- Author / Uploaded
- Merrill Skolnik
Radar Handbook, Third Edition
ii ABOUT THE EDITOR IN CHIEF Merrill Skolnik was Superintendent of the Radar Division at the U.S. Naval Research Labora
6,699 2,710 16MB
Pages 1352 Page size 498 x 767.25 pts Year 2009
Recommend Papers
File loading please wait...
Citation preview
ii
ABOUT THE EDITOR IN CHIEF Merrill Skolnik was Superintendent of the Radar Division at the U.S. Naval Research Laboratory for over 30 years. Before that he was involved in advances in radar while at the MIT Lincoln Laboratory, the Institute for Defense Analyses, and the Research Division of Electronic Communications, Inc. He is the author of the popular McGraw-Hill textbook Introduction to Radar Systems, now in its third edition, the editor of Radar Applications, as well as being a former editor of the Proceedings of the IEEE. He earned the Doctor of Engineering Degree from The Johns Hopkins University, where he also received the B.E and M.S.E degrees in electrical engineering. He is a member of the U.S. National Academy of Engineering, a Fellow of the IEEE, and the first recipient of the IEEE Dennis J. Picard Medal for Radar Technologies and Applications.
iii
RADAR HANDBOOK Merrill I. Skolnik Editor in Chief Third Edition
New York Chicago San Francisco Lisbon London Madrid Mexico City Milan New Delhi San Juan Seoul Singapore Sydney Toronto
iv
Cataloging-in-Publication Data is on file with the Library of Congress McGraw-Hill books are available at special quantity discounts to use as premiums and sales promotions, or for use in corporate training programs. To contact a representative, please visit the Contact Us pages at www.mhprofessional.com. Radar Handbook, Third Edition Copyright © 2008 by The McGraw-Hill Companies. All rights reserved. Printed in the United States of America. Except as permitted under the Copyright Act of 1976, no part of this publication may be reproduced or distributed in any form or by any means, or stored in a database or retrieval system, without the prior written permission of publisher. 1 2 3 4 5 6 7 8 9 0 DOC DOC 0 1 9 8 ISBN 978-0-07-148547-0 MHID 0-07-148547-3 Sponsoring Editor Wendy Rinaldi Editorial Supervisor Janet Walden Project Editor LeeAnn Pickrell Acquisitions Coordinator Mandy Canales Copy Editor LeeAnn Pickrell Proofreader Susie Elkind Production Supervisor Jean Bodeaux Composition International Typesetting & Composition Illustration International Typesetting & Composition Art Director, Cover Jeff Weeks Cover Designer Mary McKeon Information has been obtained by McGraw-Hill from sources believed to be reliable. However, because of the possibility of human or mechanical error by our sources, McGraw-Hill, or others, McGraw-Hill does not guarantee the accuracy, adequacy, or completeness of any information and is not responsible for any errors or omissions or the results obtained from the use of such information.
v
CONTENTS Contributors Preface Chapter 1 An Introduction and Overview of Radar Merrill Skolnik 1.1 Radar in Brief /
xiii xv 1.1 1.1
1.2 Types of Radars /
1.5
1.3 Information Available from a Radar /
1.7
1.4 The Radar Equation /
1.10
1.5 Radar Frequency Letter-band Nomenclature /
1.13
1.6 Effect of Operating Frequency on Radar /
1.14
1.7 Radar Nomenclature /
1.18
1.8 Some Past Advances in Radar /
1.19
1.9 Applications of Radar /
1.20
1.10 Conceptual Radar System Design /
1.22
Chapter 2 MTI Radar William W. Shrader and Vilhelm Gregers-Hansen 2.1 Preface /
2.1 2.1
2.2 Introduction to MTI Radar /
2.2
2.3 Clutter Filter Response to Moving Targets /
2.9
2.4 Clutter Characteristics /
2.10
2.5 Definitions /
2.19
2.6 Improvement Factor Calculations /
2.23
2.7 Optimum Design of Clutter Filters /
2.25
2.8 MTI Clutter Filter Design /
2.33
2.9 MTI Filter Design for Weather Radars /
2.46
2.10 Clutter Filter Bank Design /
2.52
2.11 Performance Degradation Caused by Receiver Limiting /
2.59
2.12 Radar System Stability Requirements /
2.65
2.13 Dynamic Range and A/D Conversion Considerations /
2.78
2.14 Adaptive MTI /
2.80
2.15 Radar Clutter Maps /
2.83
2.16 Sensitivity-velocity Control (SVC) /
2.87
2.17 Considerations Applicable to MTI Radar Systems /
2.91
vi
Chapter 3 Airborne MTI James K. Day and Fred M. Staudaher 3.1 Systems Using Airborne MTI Techniques /
3.1 3.1
3.2 Coverage Considerations /
3.2
3.3 Airborne MTI Performance Drivers /
3.3
3.4 Platform Motion and Altitude Effects on MTI Performance /
3.3
3.5 Platform-motion Compensation Abeam /
3.10
3.6 Scanning-motion Compensation /
3.14
3.7 Simultaneous Platform Motion and Scan Compensation /
3.18
3.8 Platform-motion Compensation, Forward Direction /
3.21
3.9 Space-time Adaptive Motion Compensation /
3.23
3.10 Effect of Multiple Spectra /
3.31
3.11 Example AMTI Radar System /
3.32
Chapter 4 Pulse Doppler Radar John P. Stralka and William G. Fedarko 4.1 Characteristics and Applications /
4.1 4.1
4.2 Pulse Doppler Clutter /
4.14
4.3 Dynamic-range and Stability Requirements /
4.24
4.4 Range and Doppler Ambiguity Resoluton /
4.31
4.5 Mode and Waveform Design /
4.35
4.6 Range Performance /
4.39
List of Abbreviations /
4.48
Chapter 5 Multifunctional Radar Systems for Fighter Aircraft David Lynch, Jr. and Carlo Kopp 5.1 Introduction /
5.1 5.1
5.2 Typical Missions and Modes /
5.10
5.3 A-A Mode Descriptions & Waveforms /
5.16
5.4 A-S Mode Descriptions & Waveforms /
5.28
Chapter 6 Radar Receivers Michael E. Yeomans 6.1 The Configuration of a Radar Receiver /
6.1 6.1
6.2 Noise and Dynamic-range Considerations /
6.4
6.3 Bandwidth Considerations /
6.9
6.4 Receiver Front End /
6.10
6.5 Local Oscillators /
6.14
6.6 Gain Control /
6.22
6.7 Filtering /
6.24
6.8 Limiters /
6.29
6.9 I/Q Demodulators /
6.31
6.10 Analog-to-Digital Converters /
6.35
6.11 Digital Receivers /
6.40
6.12 Diplex Operation /
6.46
6.13 Waveform Generation and Upconversion /
6.47
vii
Chapter 7 Automatic Detection, Tracking, and Sensor Integration W. G. Bath and G. V.Trunk 7.1 Introduction /
7.1 7.1
7.2 Automatic Detection /
7.1
7.3 Automatic Tracking /
7.22
7.4 Networked Radars /
7.46
7.5 Unlike-sensor Integration /
7.49
Chapter 8 Pulse Compression Radar Michael R. Ducoff and Byron W. Tietjen 8.1 Introduction / 8.2 Pulse Compression Waveform Types /
8.1 8.1 8.2
8.3 Factors Affecting Choice of Pulse Compression Systems /
8.26
8.4 Pulse Compression Implementation and Radar System Examples /
8.28
Appendix / Chapter 9 Tracking Radar Dean D. Howard 9.1 Introduction / 9.2 Monopulse (Simultaneous Lobing) /
8.36 9.1 9.1 9.3
9.3 Scanning and Lobing /
9.16
9.4 Servosystems for Tracking Radar /
9.17
9.5 Target Acquisition and Range Tracking /
9.20
9.6 Special Monopulse Techniques /
9.24
9.7 Sources of Error /
9.26
9.8 Target-caused Errors (Target Noise) /
9.26
9.9 Other External Causes of Error /
9.37
9.10 Internal Sources of Error /
9.42
9.11 Summary of Sources of Error /
9.43
9.12 Error Reduction Techniques /
9.46
Chapter 10 The Radar Transmitter Thomas A. Weil and Merrill Skolnik 10.1 Introduction /
10.1
10.2 Linear-beam Amplifiers /
10.1 10.4
10.3 Magnetron /
10.14
10.4 Crossed-field Amplifiers /
10.16
10.5 Gyrotrons /
10.17
10.6 Transmitter Spectrum Control /
10.19
10.7 Grid-controlled Tubes /
10.21
10.8 Modulators /
10.23
10.9 Which RF Power Source to Use? /
10.25
viii
Chapter 11 Solid id-State Transmitters Michael T. Borkowski 11.1 Introduction /
11.1 11.1
11.2 Advantages of Solid State /
11.1
11.3 Solid-state Devices /
11.5
11.4 Designing for the Solid-state Bottle Transmitter /
11.17
11.5 Designing for the Solid-state Phased Array Transmitter /
11.24
11.6 Solid-state System Examples /
11.37
Chapter 12 Reflector Antennas Michael E. Cooley and Daniel Davis 12.1 Introduction /
12.1 12.7
12.2 Basic Principles and Parameters /
12.3
12.3 Reflector Antenna Architectures /
12.16
12.4 Reflector Feeds /
12.25
12.5 Reflector Antenna Analysis /
12.37
12.6 Mechanical Design Considerations /
12.35
Acknowledgments / Chapter 13 Phased Array Radar Antennas Joe Frank and John D. Richards 13.1 Introduction / 13.2 Array Theory /
12.47 13.1 13.7 13.9
13.3 Planar Arrays and Beam Steering /
13.15
13.4 Aperture Matching and Mutual Coupling /
13.20
13.5 Low-sidelobe Phased Arrays /
13.28
13.6 Quantization Effects /
13.34
13.7 Bandwidth of Phased Arrays /
13.38
13.8 Feed Networks (Beamformers) /
13.46
13.9 Phase Shifters /
13.57
13.10 Solid-state Modules /
13.53
13.11 Multiple Simultaneous Receive Beams /
13.54
13.12 Digital Beamforming /
13.56
13.13 Radiation Pattern Nulling /
13.57
13.14 Calibration of Active Phased Array Antennas /
13.60
13.15 Phased Array Systems /
13.62
Chapter 14 Radar Cross Section Eugene F. Knott 14.1 Introduction /
14.1 14.1
14.2 The Concept of Echo Power /
14.4
14.3 RCS Prediction Techniques /
14.16
14.4 RCS Measurement Techniques /
14.27
14.5 Radar Echo Suppression /
14.36
ix
Chapter 15 Sea Clutter Lewis B. Wetzel 15.1 Introduction /
15.1 15.1
15.2 The Sea Surface /
15.3
15.3 Empirical Behavior of Sea Clutter /
15.7
15.4 Theories and Models of Sea Clutter /
15.27
15.5 Summary and Conclusions /
15.37
Chapter 16 Ground Echo Richard K. Moore 16.1 Introduction /
16.1 16.1
16.2 Parameters Affecting Ground Return /
16.4
16.3 Theoretical Models and Their Limitations /
16.7
16.4 Fading of Ground Echoes /
16.12
16.5 Measurement Techniques for Ground Return /
16.19
16.6 General Models for Scattering Coefficient (Clutter Models) /
16.29
16.7 Scattering Coefficient Data /
16.35
16.8 Polarimetry /
16.46
16.9 Scattering Coefficient Data Near Grazing /
16.52
16.10 Imaging Radar Interpretation /
16.55
Chapter 17 Synthetic Aperture Radar Roger Sullivan 17.1 Basic Principle of SAR /
17.1 17.1
17.2 Early History of SAR /
17.2
17.3 Types of SAR /
17.2
17.4 SAR Resolution /
17.6
17.5 Key Aspects of SAR /
17.10
17.6 SAR Image Quality /
17.16
17.7 Summary of Key SAR Equations /
17.21
17.8 Special SAR Applications /
17.22
Chapter 18 Space-Based Remote Sensing Radars R. Keith Raney 18.1 Perspective / 18.2 Synthetic Aperture Radar (SAR) /
18.1 18.1 18.5
18.3 Altimeters /
18.29
18.4 Planetary Radars /
18.43
18.5 Scatterometers /
18.53
18.6 Radar Sounders /
18.59
x
Chapter 19 Meteorological Radar R. Jeffrey Keeler and Robert J. Serafin 19.1 Introduction /
19.1 19.1
19.2 The Radar Equation for Meteorological Targets /
19.3
19.3 Design Considerations /
19.6
19.4 Signal Processing /
19.19
19.5 Operational Applications /
19.25
19.6 Research Applications /
19.33
Chapter 20 HF Over-the-Horizon Radar James M. Headrick and Stuart J. Anderson 20.1 Introduction /
20.1
20.2 The Radar Equation /
20.5
20.3 Factors Influencing Skywave Radar Design /
20.7
20.4 The Ionosphere and Radiowave Propagation /
20.13
20.5 Waveforms for HF Radar /
20.21
20.6 The Transmitting System /
20.23
20.7 Radar Cross Section /
20.26
20.8 Clutter: Echoes from the Environment /
20.29
20.9 Noise, Interference, and Spectrum Occupancy /
20.40
20.10 The Receiving System /
20.45
20.11 Signal Processing and Tracking /
20.49
20.12 Radar Resource Management /
20.54
20.13 Radar Performance Modeling /
20.55
Appendix: HF Surface Wave Radar /
20.70
Chapter 21 Ground Penetrating Radar David Daniels 21.1 Introduction / 21.2 Physics of Propagation in Materials /
20.1
21.1 21.1 21.6
21.3 Modeling /
21.13
21.4 Properties of Materials /
21.18
21.5 GPR Systems /
21.20
21.6 Modulation Techniques /
21.21
21.7 Antennas /
21.24
21.8 Signal and Image Processing /
21.30
21.9 Applications /
21.35
21.10 Licensing /
21.39
Chapter 22 Civil Marine Radar Andy Norris 22.1 Introduction /
22.1 22.1
22.2 The Challenges /
22.3
22.3 International Standards /
22.7
22.4 Technology /
22.10
22.5 Target Tracking /
22.17
xi
22.6 User Interface /
22.19
22.7 Integration with AIS /
22.23
22.8 Radar Beacons /
22.25
22.9 Validation Testing /
22.28
22.10 Vessel Tracking Services /
22.29
Appendix The Early Days of CMR /
22.31
List of Maritime Radar-related Abbreviations /
22.33
Acknowledgments /
22.34
Chapter 23 Bistatic Radar Nicholas J. Willis 23.1 Concept and Definitions /
23.1 23.1
23.2 Coordinate Systems /
23.3
23.3 Bistatic Radar Equation /
23.4
23.4 Applications /
23.9
23.5 Bistatic Doppler /
23.14
23.6 Target Location /
23.17
23.7 Target Cross Section /
23.19
23.8 Surface Clutter /
23.22
23.9 Unique Problems and Requirements /
23.26
Chapter 24 Electronic Counter-Countermeasures Alfonso Farina 24.1 Introduction /
24.1 24.1
24.2 Terminology /
24.2
24.3 Electronic Warfare Support Measures /
24.2
24.4 Electronic Countermeasures /
24.5
24.5 Objectives and Taxonomy of ECCM Techniques /
24.8
24.6 Antenna-related ECCM /
24.10
24.7 Transmitter-related ECCM /
24.31
24.8 Receiver-related ECCM /
24.32
24.9 Signal-processing-related ECCM /
24.33
24.10 Operational-deployment Techniques /
24.36
24.11 Application of ECCM Techniques /
24.37
24.12 ECCM and ECM Efficacy /
24.54
Acronym List /
24.56
Acknowledgments /
24.58
Chapter 25 Radar Digital Signal Processing James J. Alter and Jeffrey O. Coleman 25.1 Introduction /
25.1 25.1
25.2 Receive Channel Processing /
25.2
25.3 Transmit Channel Processing /
25.20
25.4 DSP Tools /
25.22
25.5 Design Considerations /
25.34
25.6 Summary /
25.37
Acknowledgments /
25.38
xii
Chapter 26 The Propagation Factor, Fp, in the Radar Equation Wayne L. Patterson 26.1 Introduction /
26.1 26.1
26.2 The Earth’s Atmosphere /
26.2
26.3 Refraction /
26.3
26.4 Standard Propagation /
26.4
26.5 Anomalous Propagation /
26.6
26.6 Propagation Modeling /
26.13
26.7 EM System Assessment Programs /
26.18
26.8 AREPS Radar System Assessment Model /
26.23
26.9 AREPS Radar Displays /
26.25
Index
1.1
xiii
CONTRIBUTORS James J. Alter Naval Research Laboratory (CHAPTER 25) Stuart J. Anderson Australian Defense Science and Technology Organisation (CHAPTER 20) W. G. Bath The Johns Hopkins University Applied Physics Laboratory (CHAPTER 7) Michael T. Borkowski Raytheon Company (CHAPTER 11) Jeffrey O. Coleman Naval Research Laboratory (CHAPTER 25) Michael E. Cooley Northrop Grumman, Electronic Systems (CHAPTER 12) David Daniels ERA Technology (CHAPTER 21) Daniel Davis Northrop Grumman Corporation (CHAPTER 12) James K. Day Lockheed Martin Corporation (CHAPTER 3) Michael R. Ducoff Lockheed Martin Corporation (CHAPTER 8) Alfonso Farina SELEX Sistemi Integrati (CHAPTER 24) William G. Fedarko Northrop Grumman Corporation (CHAPTER 4) Joe Frank The Johns Hopkins University Applied Physics Laboratory (CHAPTER 13) Vilhelm Gregers-Hansen Naval Research Laboratory (CHAPTER 2) James M. Headrick Naval Research Laboratory, retired (CHAPTER 20) Dean D. Howard Consultant to ITT Industries, Inc. (CHAPTER 9) R. Jeffrey Keeler National Center for Atmospheric Research (CHAPTER 19) Eugene F. Knott Tomorrow’s Research (CHAPTER 14) Carlo Kopp Monash University (CHAPTER 5) David Lynch, Jr. DL Sciences, Inc. (CHAPTER 5) Richard K. Moore The University of Kansas (CHAPTER 16) Andy Norris Consultant in Navigation Systems (CHAPTER 22) Wayne L. Patterson Space and Naval Warfare Systems Center (CHAPTER 26) Keith Raney The Johns Hopkins University Applied Physics Laboratory (CHAPTER 18) John D. Richards The Johns Hopkins University Applied Physics Laboratory (CHAPTER 13) Robert J. Serafin National Center for Atmospheric Research (CHAPTER 19) William W. Shrader Shrader Associates (CHAPTER 2) Merrill Skolnik (CHAPTERS 1 and 10) Fred M. Staudaher Naval Research Laboratory, retired (CHAPTER 3)
xiv
John P. Stralka Northrop Grumman Corporation (CHAPTER 4) Roger Sullivan Institute for Defense Analyses (CHAPTER 17) Byron W. Tietjen Lockheed Martin Corporation (CHAPTER 8) G. V. Trunk The Johns Hopkins University Applied Physics Laboratory (CHAPTER 7) Thomas A. Weil (CHAPTER 10) Lewis B. Wetzel Naval Research Laboratory, retired (CHAPTER 15) Nicholas J. Willis Technology Service Corporation, retired (CHAPTER 23) Michael E. Yeomans Raytheon Company (CHAPTER 6)
xv
PREFACE Radar is an important example of an electrical engineering system. In university engineering courses, the emphasis usually is on the basic tools of the electrical engineer such as circuit design, signals, solid state, digital processing, electronic devices, electromagnetics, automatic control, microwaves, and so forth. But in the real world of electrical engineering practice, these are only the techniques, piece parts, or subsystems that make up some type of system employed for a useful purpose. In addition to radar and other sensor systems, electrical engineering systems include communications, control, energy, information, industrial, military, navigation, entertainment, medical, and others. These are what the practice of electrical engineering is all about. Without them there would be little need for electrical engineers. However, the practicing engineer who is involved in producing a new type of electrical engineering system often has to depend on acquiring knowledge that was not usually covered in his or her engineering courses. The radar engineer, for example, has to understand the major components and subsystems that make up a radar, as well as how they fit together. The Radar Handbook attempts to help in this task. In addition to the radar system designer, it is hoped that those who are responsible for procuring new radar systems, those who utilize radars, those who maintain radar systems, and those who manage the engineers who do the above, also will find the Radar Handbook to be of help in fulfilling such tasks. The third edition of the Radar Handbook is evidence that the development and application of radar for both civilian and military purposes continue to grow in both utility and in improved technology. Some of the many advances in radar since the previous edition include the following: - The extensive use of digital methods for improved signal processing, data processing, decision making, flexible radar control, and multifunction radar - Doppler weather radar - Ground moving target indication, or GMTI - An extensive experimental database describing low-angle land clutter, as obtained by MIT Lincoln Laboratory, that replaced the previously widely used clutter model that dated back to World War II - The realization that microwave sea echo at low grazing angles is due chiefly to what are called “sea spikes” - The active-aperture phased array radar system using solid-state modules, also called active electronically scanned arrays (AESA), which is attractive for some multifunction radar applications that need to manage both power and spatial coverage - Planetary exploration with radar - Computer-based methods for predicting radar propagation performance in realistic environments
xvi
- Operational use of HF over-the-horizon radar - Improved methods for detecting moving targets in clutter, including space-time adaptive processing - Operational use of inverse synthetic aperture radar for target recognition - Interferometric synthetic aperture radar, or InSAR, to obtain the height of a resolved scatterer or to detect moving ground targets as well as provide a SAR image of a scene - High precision space-based altimeters, with accuracy of a few centimeters, to measure the Earth’s geoid - Ultrawideband radar for ground penetrating and similar applications - Improved high power, wide bandwidth klystron power sources based on clustered cavity resonators, as well as the multiple-beam klystron - The appearance of wide bandgap semiconductors that allow better performance because of high power and high operating temperatures - The availability of high-power millimeter-wave generators based on the gyroklystron - Nonlinear FM pulse compression with low sidelobe levels - The replacement, by the computer, of the operator as information extractor and decision maker The above are not listed in any particular order, nor should they be considered a complete enumeration of radar developments since the appearance of the previous edition. There were also some radar topics in previous editions of the Radar Handbook that are of lesser interest and so were not included in this edition. The chapter authors, who are experts in their particular field, were told to consider the reader of their chapter as being knowledgeable in the general subject of radar and even an expert in some other particular area of radar, but not necessarily knowledgeable about the subject of the particular chapter the author was writing. It should be expected that with a book in print as long as the Radar Handbook has been, not all chapter authors from the previous editions would be available to do the third edition. Many of the previous authors have retired or are no longer with us. Sixteen of the twenty-six chapters in this edition have authors or coauthors who were not involved in the previous editions. The hard work of preparing these chapters was done by the individual expert authors of the various chapters. Thus the value of the Radar Handbook is the result of the diligence and expertise of the authors who contributed their time, knowledge, and experience to make this handbook a useful addition to the desk of radar system engineers and all those people vital to the development, production, and employment of radar systems. I am deeply grateful to all the contributing authors for their fine work and the long hours they had to apply to their task. It is the chapter authors who make any handbook a success. My sincere thanks to them all. As stated in the Preface of the previous edition, readers who wish to reference or quote material from the Radar Handbook are asked to mention the names of the individual chapter authors who produced the material. MERRILL SKOLNIK Baltimore, Maryland
#HAPTER
ÊÌÀ`ÕVÌÊ>`Ê "ÛiÀÛiÜÊvÊ,>`>À
iÀÀÊ-
£°£Ê , ,Ê Ê , 2ADAR IS AN ELECTROMAGNETIC SENSOR FOR THE DETECTION AND LOCATION OF REFLECTING OBJECTS)TSOPERATIONCANBESUMMARIZEDASFOLLOWS 4HERADARRADIATESELECTROMAGNETICENERGYFROMANANTENNATOPROPAGATEINSPACE 3OME OF THE RADIATED ENERGY IS INTERCEPTED BY A REFLECTING OBJECT USUALLY CALLED ATARGET LOCATEDATADISTANCEFROMTHERADAR 4HEENERGYINTERCEPTEDBYTHETARGETISRERADIATEDINMANYDIRECTIONS 3OMEOFTHERERADIATEDECHO ENERGYISRETURNEDTOANDRECEIVEDBYTHERADARANTENNA !FTERAMPLIFICATIONBYARECEIVERANDWITHTHEAIDOFPROPERSIGNALPROCESSING A DECISIONISMADEATTHEOUTPUTOFTHERECEIVERASTOWHETHERORNOTATARGETECHO SIGNALISPRESENT!TTHATTIME THETARGETLOCATIONANDPOSSIBLYOTHERINFORMATION ABOUTTHETARGETISACQUIRED
L
L
L
L
L
!COMMONWAVEFORMRADIATEDBYARADARISASERIESOFRELATIVELYNARROW RECTAN GULAR LIKEPULSES!NEXAMPLEOFAWAVEFORMFORAMEDIUM RANGERADARTHATDETECTS AIRCRAFT MIGHT BE DESCRIBED AS A SHORT PULSE ONE MILLIONTH OF A SECOND IN DURATION ONEMICROSECOND THETIMEBETWEENPULSESMIGHTBEONEMILLISECONDSOTHATTHE PULSEREPETITIONFREQUENCYISONEKILOHERTZ THEPEAKPOWERFROMTHERADARTRANSMIT TERMIGHTBEONEMILLIONWATTSONEMEGAWATT ANDWITHTHESENUMBERS THEAVERAGE POWERFROMTHETRANSMITTERISONEKILOWATT!NAVERAGEPOWEROFONEKILOWATTMIGHT BELESSTHANTHEPOWEROFTHEELECTRICLIGHTINGUSUALLYFOUNDINAhTYPICALvCLASSROOM 7EASSUMETHISEXAMPLERADARMIGHTOPERATEINTHEMIDDLEOFTHEMICROWAVEoFRE QUENCYRANGESUCHASFROMTO'(Z WHICHISATYPICALFREQUENCYBANDFORCIVIL
4HISCHAPTERISABRIEFOVERVIEWOFRADARFORTHOSENOTTOOFAMILIARWITHTHESUBJECT&ORTHOSEWHOAREFAMILIARWITH RADAR ITCANBECONSIDEREDAREFRESHER o-ICROWAVESARELOOSELYDEFINEDASTHOSEFREQUENCIESWHEREWAVEGUIDESAREUSEDFORTRANSMISSIONLINESANDWHERE CAVITIESORDISTRIBUTEDCIRCUITSAREUSEDFORRESONANTCIRCUITSRATHERTHANLUMPED CONSTANTCOMPONENTS-ICROWAVE RADARSMIGHTBEFROMABOUT-(ZTOABOUT'(Z BUTTHESELIMITSARENOTRIGID
£°£
£°Ó
2!$!2(!.$"//+
AIRPORT SURVEILLANCERADARS)TSWAVELENGTHMIGHTBEABOUTCMROUNDINGOFF FOR SIMPLICITY 7ITHTHEPROPERANTENNASUCHARADARMIGHTDETECTAIRCRAFTOUTTORANGESp OFTONMI MOREORLESS4HEECHOPOWERRECEIVEDBYARADARFROMATARGETCAN VARYOVERAWIDERANGEOFVALUES BUTWEARBITRARILYASSUMEAhTYPICALvECHOSIGNAL FORILLUSTRATIVEPURPOSESMIGHTHAVEAPOWEROFPERHAPS WATTS)FTHERADIATED POWERISWATTSONEMEGAWATT THERATIOOFECHOSIGNALPOWERFROMATARGETTOTHE RADARTRANSMITTERPOWERINTHISEXAMPLEISn ORTHERECEIVEDECHOISD"LESS THANTHETRANSMITTEDSIGNAL4HATISQUITEADIFFERENCEBETWEENTHEMAGNITUDEOFTHE TRANSMITTEDSIGNALANDADETECTABLERECEIVEDECHOSIGNAL 3OMERADARSHAVETODETECTTARGETSATRANGESASSHORTASTHEDISTANCEFROMBEHIND HOMEPLATETOTHEPITCHERSMOUNDINABASEBALLPARKTOMEASURETHESPEEDOFAPITCHED BALL WHILEOTHERRADARSHAVETOOPERATEOVERDISTANCESASGREATASTHEDISTANCESTOTHE NEARESTPLANETS4HUS ARADARMIGHTBESMALLENOUGHTOHOLDINTHEPALMOFONEHAND ORLARGEENOUGHTOOCCUPYTHESPACEOFMANYFOOTBALLFIELDS 2ADAR TARGETS MIGHT BE AIRCRAFT SHIPS OR MISSILES BUT RADAR TARGETS CAN ALSO BE PEOPLE BIRDS INSECTS PRECIPITATION CLEARAIRTURBULENCE IONIZEDMEDIA LANDFEATURES VEGETATION MOUNTAINS ROADS RIVERS AIRFIELDS BUILDINGS FENCES AND POWER LINE POLES SEA ICE ICEBERGS BUOYS UNDERGROUND FEATURES METEORS AURORA SPACECRAFT ANDPLANETS)NADDITIONTOMEASURINGTHERANGETOATARGETASWELLASITSANGULARDIREC TION ARADARCANALSOFINDTHERELATIVEVELOCITYOFATARGETEITHERBYDETERMININGTHE RATEOFCHANGEOFTHERANGEMEASUREMENTWITHTIMEORBYEXTRACTINGTHERADIALVELOCITY FROMTHEDOPPLERFREQUENCYSHIFTOFTHEECHOSIGNAL)FTHELOCATIONOFAMOVINGTARGETIS MEASUREDOVERAPERIODOFTIME THETRACK ORTRAJECTORY OFTHETARGETCANBEFOUNDFROM WHICHTHEABSOLUTEVELOCITYOFTHETARGETANDITSDIRECTIONOFTRAVELCANBEDETERMINED ANDAPREDICTIONCANBEMADEASTOITSFUTURELOCATION0ROPERLYDESIGNEDRADARSCAN DETERMINETHESIZEANDSHAPEOFATARGETANDMIGHTEVENBEABLETORECOGNIZEONETYPE ORCLASSOFTARGETFROMANOTHER "ASIC0ARTSOFA2ADAR &IGUREISAVERYELEMENTARYBASICBLOCKDIAGRAM SHOWINGTHESUBSYSTEMSUSUALLYFOUNDINARADAR4HETRANSMITTER WHICHISSHOWNHERE ASAPOWERAMPLIFIER GENERATESASUITABLEWAVEFORMFORTHEPARTICULARJOBTHERADARIS TOPERFORM)TMIGHTHAVEANAVERAGEPOWERASSMALLASMILLIWATTSORASLARGEASMEGA WATTS4HEAVERAGEPOWERISAFARBETTERINDICATIONOFTHECAPABILITYOFARADARSPERFOR MANCETHANISITSPEAKPOWER -OSTRADARSUSEASHORTPULSEWAVEFORMSOTHATASINGLE ANTENNACANBEUSEDONATIME SHAREDBASISFORBOTHTRANSMITTINGANDRECEIVING 4HEFUNCTIONOFTHEDUPLEXERISTOALLOWASINGLEANTENNATOBEUSEDBYPROTECTING THESENSITIVERECEIVERFROMBURNINGOUTWHILETHETRANSMITTERISONANDBYDIRECTINGTHE RECEIVEDECHOSIGNALTOTHERECEIVERRATHERTHANTOTHETRANSMITTER 4HEANTENNAISTHEDEVICETHATALLOWSTHETRANSMITTEDENERGYTOBEPROPAGATEDINTO SPACE AND THEN COLLECTS THE ECHO ENERGY ON RECEIVE )T IS ALMOST ALWAYS A DIRECTIVE ANTENNA ONETHATDIRECTSTHERADIATEDENERGYINTOANARROWBEAMTOCONCENTRATETHE POWERASWELLASTOALLOWTHEDETERMINATIONOFTHEDIRECTIONTOTHETARGET!NANTENNA THATPRODUCESANARROWDIRECTIVEBEAMONTRANSMITUSUALLYHASALARGEAREAONRECEIVE TO ALLOW THE COLLECTION OF WEAK ECHO SIGNALS FROM THE TARGET4HE ANTENNA NOT ONLY CONCENTRATESTHEENERGYONTRANSMITANDCOLLECTSTHEECHOENERGYONRECEIVE BUTITALSO ACTSASASPATIALFILTERTOPROVIDEANGLERESOLUTIONANDOTHERCAPABILITIES p)NRADAR RANGEISTHETERMGENERALLYUSEDTOMEANDISTANCEFROMTHERADARTOTHETARGET2ANGEISALSOUSEDHEREIN SOMEOFITSOTHERDICTIONARYDEFINITIONS
!.).42/$5#4)/.!.$/6%26)%7/&2!$!2
£°Î
&)'52% "LOCKDIAGRAMOFASIMPLERADAREMPLOYINGAPOWERAMPLIFIERASTHETRANSMITTERINTHEUPPER PORTIONOFTHEFIGUREANDASUPERHETERODYNERECEIVERINTHELOWERPORTIONOFTHEFIGURE
4HERECEIVERAMPLIFIESTHEWEAKRECEIVEDSIGNALTOALEVELWHEREITSPRESENCECAN BEDETECTED"ECAUSENOISEISTHEULTIMATELIMITATIONONTHEABILITYOFARADARTOMAKE ARELIABLEDETECTIONDECISIONANDEXTRACTINFORMATIONABOUTTHETARGET CAREISTAKEN TO INSURE THAT THE RECEIVER PRODUCES VERY LITTLE NOISE OF ITS OWN!T THE MICROWAVE FREQUENCIES WHEREMOSTRADARSAREFOUND THENOISETHATAFFECTSRADARPERFORMANCE IS USUALLY FROM THE FIRST STAGE OF THE RECEIVER SHOWN HERE IN &IGURE AS A LOW NOISEAMPLIFIER&ORMANYRADARAPPLICATIONSWHERETHELIMITATIONTODETECTIONISTHE UNWANTEDRADARECHOESFROMTHEENVIRONMENTCALLEDCLUTTER THERECEIVERNEEDSTO HAVEALARGEENOUGHDYNAMICRANGESOASTOAVOIDHAVINGTHECLUTTERECHOESADVERSELY AFFECT DETECTION OF WANTED MOVING TARGETS BY CAUSING THE RECEIVER TO SATURATE4HE DYNAMICRANGEOFARECEIVER USUALLYEXPRESSEDINDECIBELS ISDEFINEDASTHERATIOOF THEMAXIMUMTOTHEMINIMUMSIGNALINPUTPOWERLEVELSOVERWHICHTHERECEIVERCAN OPERATEWITHSOMESPECIFIEDPERFORMANCE4HEMAXIMUMSIGNALLEVELMIGHTBESET BYTHENONLINEAREFFECTSOFTHERECEIVERRESPONSETHATCANBETOLERATEDFOREXAMPLE THESIGNALPOWERATWHICHTHERECEIVERBEGINSTOSATURATE ANDTHEMINIMUMSIGNAL MIGHTBETHEMINIMUMDETECTABLESIGNAL4HESIGNALPROCESSOR WHICHISOFTENINTHE )&PORTIONOFTHERECEIVER MIGHTBEDESCRIBEDASBEINGTHEPARTOFTHERECEIVERTHAT SEPARATESTHEDESIREDSIGNALFROMTHEUNDESIREDSIGNALSTHATCANDEGRADETHEDETEC TIONPROCESS3IGNALPROCESSINGINCLUDESTHEMATCHEDFILTERTHATMAXIMIZESTHEOUT PUTSIGNAL TO NOISERATIO3IGNALPROCESSINGALSOINCLUDESTHEDOPPLERPROCESSINGTHAT MAXIMIZESTHESIGNAL TO CLUTTERRATIOOFAMOVINGTARGETWHENCLUTTERISLARGERTHAN RECEIVERNOISE ANDITSEPARATESONEMOVINGTARGETFROMOTHERMOVINGTARGETSORFROM CLUTTERECHOES4HEDETECTIONDECISIONISMADEATTHEOUTPUTOFTHERECEIVER SOATARGET ISDECLAREDTOBEPRESENTWHENTHERECEIVEROUTPUTEXCEEDSAPREDETERMINEDTHRESHOLD )FTHETHRESHOLDISSETTOOLOW THERECEIVERNOISECANCAUSEEXCESSIVEFALSEALARMS)F THETHRESHOLDISSETTOOHIGH DETECTIONSOFSOMETARGETSMIGHTBEMISSEDTHATWOULD OTHERWISEHAVEBEENDETECTED4HECRITERIONFORDETERMININGTHELEVELOFTHEDECISION THRESHOLDISTOSETTHETHRESHOLDSOITPRODUCESANACCEPTABLEPREDETERMINEDAVERAGE RATEOFFALSEALARMSDUETORECEIVERNOISE !FTERTHEDETECTIONDECISIONISMADE THETRACKOFATARGETCANBEDETERMINED WHERE ATRACKISTHELOCUSOFTARGETLOCATIONSMEASUREDOVERTIME4HISISANEXAMPLEOFDATA PROCESSING4HEPROCESSEDTARGETDETECTIONINFORMATIONORITSTRACKMIGHTBEDISPLAYED TOANOPERATORORTHEDETECTIONINFORMATIONMIGHTBEUSEDTOAUTOMATICALLYGUIDEA
£°{
2!$!2(!.$"//+
MISSILE TO ATARGET OR THE RADAR OUTPUT MIGHT BE FURTHER PROCESSED TO PROVIDE OTHER INFORMATIONABOUTTHENATUREOFTHETARGET4HERADARCONTROLINSURESTHATTHEVARIOUS PARTS OF A RADAR OPERATE IN A COORDINATED AND COOPERATIVE MANNER AS FOR EXAMPLE PROVIDINGTIMINGSIGNALSTOVARIOUSPARTSOFTHERADARASREQUIRED 4HE RADAR ENGINEER HAS AS RESOURCES TIME THAT ALLOWS GOOD DOPPLER PROCESSING BANDWIDTHFORGOODRANGERESOLUTION SPACETHATALLOWSALARGEANTENNA ANDENERGYFOR LONGRANGEPERFORMANCEANDACCURATEMEASUREMENTS%XTERNALFACTORSAFFECTINGRADAR PERFORMANCEINCLUDETHETARGETCHARACTERISTICSEXTERNALNOISETHATMIGHTENTERVIATHE ANTENNAUNWANTEDCLUTTERECHOESFROMLAND SEA BIRDS ORRAININTERFERENCEFROMOTHER ELECTROMAGNETICRADIATORSANDPROPAGATIONEFFECTSDUETOTHEEARTHSSURFACEANDATMO SPHERE4HESEFACTORSAREMENTIONEDTOEMPHASIZETHATTHEYCANBEHIGHLYIMPORTANTIN THEDESIGNANDAPPLICATIONOFARADAR 2ADAR4RANSMITTERS 4HERADARTRANSMITTERMUSTNOTONLYBEABLETOGENERATETHE PEAKANDAVERAGEPOWERSREQUIREDTODETECTTHEDESIREDTARGETSATTHEMAXIMUMRANGE BUTALSOHASTOGENERATEASIGNALWITHTHEPROPERWAVEFORMANDTHESTABILITYNEEDEDFOR THEPARTICULARAPPLICATION4RANSMITTERSMAYBEOSCILLATORSORAMPLIFIERS BUTTHELATTER USUALLYOFFERMOREADVANTAGES 4HEREHAVEBEENMANYTYPESOFRADARPOWERSOURCESUSEDINRADAR#HAPTER 4HEMAGNETRONPOWEROSCILLATORWASATONETIMEVERYPOPULAR BUTITISSELDOMUSED EXCEPTFORCIVILMARINERADAR#HAPTER "ECAUSEOFTHEMAGNETRONSRELATIVELY LOWAVERAGEPOWERONEORTWOKILOWATTS ANDPOORSTABILITY OTHERPOWERSOURCES AREUSUALLYMOREAPPROPRIATEFORAPPLICATIONSREQUIRINGLONG RANGEDETECTIONOFSMALL MOVINGTARGETSINTHEPRESENCEOFLARGECLUTTERECHOES4HEMAGNETRONPOWEROSCIL LATOR IS AN EXAMPLE OF WHAT IS CALLED A CROSSED FIELD TUBE4HERE IS ALSO A RELATED CROSSED FIELDAMPLIFIER#&! THATHASBEENUSEDINSOMERADARSINTHEPAST BUTIT ALSOSUFFERSLIMITATIONSFORIMPORTANTRADARAPPLICATIONS ESPECIALLYFORTHOSEREQUIR INGDETECTIONOFMOVINGTARGETSINCLUTTER4HEHIGH POWERKLYSTRONANDTHETRAVELING WAVETUBE474 AREEXAMPLESOFWHATARECALLEDLINEARBEAMTUBES!TTHEHIGH POWERSOFTENEMPLOYEDBYRADARS BOTHTUBESHAVESUITABLYWIDEBANDWIDTHSASWELL ASGOODSTABILITYASNEEDEDFORDOPPLERPROCESSING ANDBOTHHAVEBEENPOPULAR 4HESOLID STATEAMPLIFIER SUCHASTHETRANSISTOR HASALSOBEENUSEDINRADAR ESPE CIALLY IN PHASED ARRAYS!LTHOUGH AN INDIVIDUAL TRANSISTOR HAS RELATIVELY LOW POWER EACHOFTHEMANYRADIATINGELEMENTSOFANARRAYANTENNACANUTILIZEMULTIPLETRANSISTORS TOACHIEVETHEHIGHPOWERNEEDEDFORMANYRADARAPPLICATIONS7HENSOLID STATETRAN SISTORAMPLIFIERSAREUSED THERADARDESIGNERHASTOBEABLETOACCOMMODATETHEHIGH DUTYCYCLEATWHICHTHESEDEVICESHAVETOOPERATE THELONGPULSESTHEYMUSTUSETHAT REQUIREPULSECOMPRESSION ANDTHEMULTIPLEPULSESOFDIFFERENTWIDTHSTOALLOWDETEC TIONATSHORTASWELLASLONGRANGE4HUSTHEUSEOFSOLID STATETRANSMITTERSCANHAVEAN EFFECTONOTHERPARTSOFTHERADARSYSTEM!TMILLIMETERWAVELENGTHSVERYHIGHPOWER CANBEOBTAINEDWITHTHEGYROTRON EITHERASANAMPLIFIERORASANOSCILLATOR4HEGRID CONTROLVACUUMTUBEWASUSEDTOGOODADVANTAGEFORALONGTIMEIN5(&ANDLOWER FREQUENCYRADARS BUTTHEREHASBEENLESSINTERESTINTHELOWERFREQUENCIESFORRADAR !LTHOUGH NOT EVERYONE MIGHT AGREE SOME RADAR SYSTEM ENGINEERSIF GIVEN A CHOICEWOULD CONSIDER THE KLYSTRON AMPLIFIER AS THE PRIME CANDIDATE FOR A HIGH POWERMODERNRADARIFTHEAPPLICATIONWERESUITABLEFORITSUSE 2ADAR !NTENNAS 4HE ANTENNA IS WHAT CONNECTS THE RADAR TO THE OUTSIDE WORLD #HAPTERSAND )TPERFORMSSEVERALPURPOSES CONCENTRATESTHERADIATEDENERGY
!.).42/$5#4)/.!.$/6%26)%7/&2!$!2
£°x
ONTRANSMITTHATIS ITISDIRECTIVEANDHASANARROWBEAMWIDTH COLLECTSTHERECEIVED ECHOENERGYFROMTHETARGET PROVIDESAMEASUREMENTOFTHEANGULARDIRECTIONTOTHE TARGET PROVIDESSPATIALRESOLUTIONTORESOLVEORSEPARATE TARGETSINANGLEAND ALLOWS THEDESIREDVOLUMEOFSPACETOBEOBSERVED4HEANTENNACANBEAMECHANICALLYSCANNED PARABOLICREFLECTOR AMECHANICALLYSCANNEDPLANARPHASEDARRAY ORAMECHANICALLYSCANNED END FIREANTENNA)TCANBEANELECTRONICALLYSCANNEDPHASEDARRAYUSINGASINGLETRANSMIT TERWITHEITHERACORPORATEFEEDORASPACE FEEDCONFIGURATIONTODISTRIBUTETHEPOWERTO EACHANTENNAELEMENTORANELECTRONICALLYSCANNEDPHASEDARRAYEMPLOYINGATEACHANTENNA ELEMENTASMALLSOLID STATEhMINIATUREvRADARALSOCALLEDANACTIVEAPERTUREPHASEDARRAY %ACHTYPEOFANTENNAHASITSPARTICULARADVANTAGESANDLIMITATIONS'ENERALLY THELARGERTHE ANTENNATHEBETTER BUTTHERECANBEPRACTICALCONSTRAINTSTHATLIMITITSSIZE
£°ÓÊ /9* -Ê"Ê, ,!LTHOUGHTHEREISNOSINGLEWAYTOCHARACTERIZEARADAR HEREWEDOSOBYMEANSOF WHATMIGHTBETHEMAJORFEATURETHATDISTINGUISHESONETYPEOFRADARFROMANOTHER 0ULSERADAR4HISISARADARTHATRADIATESAREPETITIVESERIESOFALMOST RECTANGULAR PULSES)TMIGHTBECALLEDTHECANONICALFORMOFARADAR THEONEUSUALLYTHOUGHTOF ASARADARWHENNOTHINGELSEISSAIDTODEFINEARADAR (IGH RESOLUTIONRADAR(IGHRESOLUTIONCANBEOBTAINEDINTHERANGE ANGLE ORDOP PLERVELOCITYCOORDINATES BUTHIGHRESOLUTIONUSUALLYIMPLIESTHATTHERADARHASHIGH RANGERESOLUTION3OMEHIGH RESOLUTIONRADARSHAVERANGERESOLUTIONSINTERMSOF FRACTIONSOFAMETER BUTITCANBEASSMALLASAFEWCENTIMETERS 0ULSECOMPRESSIONRADAR4HISISARADARTHATUSESALONGPULSEWITHINTERNALMODU LATIONUSUALLYFREQUENCYORPHASEMODULATION TOOBTAINTHEENERGYOFALONGPULSE WITHTHERESOLUTIONOFASHORTPULSE #ONTINUOUSWAVE#7 RADAR4HISRADAREMPLOYSACONTINUOUSSINEWAVE)TALMOST ALWAYSUSESTHEDOPPLERFREQUENCYSHIFTFORDETECTINGMOVINGTARGETSORFORMEASUR INGTHERELATIVEVELOCITYOFATARGET &- #7RADAR4HIS#7RADARUSESFREQUENCYMODULATIONOFTHEWAVEFORMTOALLOW ARANGEMEASUREMENT 3URVEILLANCERADAR!LTHOUGHADICTIONARYMIGHTNOTDEFINESURVEILLANCETHISWAY A SURVEILLANCERADARISONETHATDETECTSTHEPRESENCEOFATARGETSUCHASANAIRCRAFTOR ASHIP ANDDETERMINESITSLOCATIONINRANGEANDANGLE)TCANALSOOBSERVETHETARGET OVERAPERIODOFTIMESOASTOOBTAINITSTRACK -OVINGTARGETINDICATION-4) 4HISISAPULSERADARTHATDETECTSMOVINGTARGETS IN CLUTTER BY USING A LOW PULSE REPETITION FREQUENCY 02& THAT USUALLY HAS NO RANGEAMBIGUITIES)TDOESHAVEAMBIGUITIESINTHEDOPPLERDOMAINTHATRESULTIN SO CALLEDBLINDSPEEDS 0ULSEDOPPLERRADAR4HEREARETWOTYPESOFPULSEDOPPLERRADARSTHATEMPLOYEITHER AHIGHORMEDIUM02&PULSERADAR4HEYBOTHUSETHEDOPPLERFREQUENCYSHIFTTO EXTRACTMOVINGTARGETSINCLUTTER!HIGH02&PULSEDOPPLERRADARHASNOAMBIGUI TIESBLINDSPEEDS INDOPPLER BUTITDOESHAVERANGEAMBIGUITIES!MEDIUM02& PULSEDOPPLERRADARHASAMBIGUITIESINBOTHRANGEANDDOPPLER
£°È
2!$!2(!.$"//+
4RACKINGRADAR4HISISARADARTHATPROVIDESTHETRACK ORTRAJECTORY OFATARGET 4RACKINGRADARSCANBEFURTHERDELINEATEDAS344 !$4 473 ANDPHASEDARRAY TRACKERSASDESCRIBEDBELOW 3INGLE4ARGET4RACKER344 4RACKSASINGLETARGETATADATARATEHIGHENOUGH TOPROVIDEACCURATETRACKINGOFAMANEUVERINGTARGET!REVISITTIMEOFS DATA RATE OF MEASUREMENTS PER SECOND MIGHT BE hTYPICALv )T MIGHT EMPLOYTHEMONOPULSETRACKINGMETHODFORACCURATETRACKINGINFORMATIONIN THEANGLECOORDINATE !UTOMATICDETECTIONANDTRACKING!$4 4HISISTRACKINGPERFORMEDBYASUR VEILLANCERADAR)TCANHAVEAVERYLARGENUMBEROFTARGETSINTRACKBYUSINGTHE MEASUREMENTSOFTARGETLOCATIONSOBTAINEDOVERMULTIPLESCANSOFTHEANTENNA )TSDATARATEISNOTASHIGHASTHE3442EVISITTIMESMIGHTRANGEFROMONETO SECONDS DEPENDINGONTHEAPPLICATION 4RACK WHILE SCAN473 5SUALLYARADARTHATPROVIDESSURVEILLANCEOVERANAR ROW REGION OF ANGLE IN ONE OR TWO DIMENSIONS SO AS TO PROVIDE AT A RAPID UPDATERATELOCATIONINFORMATIONONALLTARGETSWITHINALIMITEDANGULARREGION OFOBSERVATION)THASBEENUSEDINTHEPASTFORGROUND BASEDRADARSTHATGUIDE AIRCRAFT TO A LANDING IN SOME TYPES OF WEAPON CONTROL RADARS AND IN SOME MILITARYAIRBORNERADARS 0HASEDARRAYTRACKER!NELECTRONICALLYSCANNEDPHASEDARRAYCANALMOST hCON TINUOUSLYv TRACK MORE THAN ONE TARGET AT A HIGH DATA RATE )T CAN ALSO SIMULTA NEOUSLYPROVIDETHELOWERDATARATETRACKINGOFMULTIPLETARGETSSIMILARTOTHAT PERFORMEDBY!$4 )MAGINGRADAR4HISRADARPRODUCESATWO DIMENSIONALIMAGEOFATARGETORASCENE SUCHASAPORTIONOFTHESURFACEOFTHEEARTHANDWHATISONIT4HESERADARSUSUALLY AREONMOVINGPLATFORMS 3IDELOOKINGAIRBORNERADAR3,!2 4HISAIRBORNESIDELOOKINGIMAGINGRADARPRO VIDESHIGHRESOLUTIONINRANGEANDOBTAINSSUITABLERESOLUTIONINANGLEBYUSINGA NARROWBEAMWIDTHANTENNA 3YNTHETICAPERTURERADAR3!2 3!2ISACOHERENT IMAGINGRADARONAMOVING VEHICLETHATUSESTHEPHASEINFORMATIONOFTHEECHOSIGNALTOOBTAINANIMAGEOFA SCENEWITHHIGHRESOLUTIONINBOTHRANGEANDCROSS RANGE(IGHRANGERESOLUTIONIS OFTENOBTAINEDUSINGPULSECOMPRESSION )NVERSESYNTHETICAPERTURERADAR)3!2 )3!2ISACOHERENTIMAGINGRADARTHATUSES HIGHRESOLUTIONINRANGEANDTHERELATIVEMOTIONOFTHETARGETTOOBTAINHIGHRESOLU TIONINTHEDOPPLERDOMAINTHATALLOWSRESOLUTIONINTHECROSS RANGEDIMENSIONTO BEOBTAINED)TCANBEONAMOVINGVEHICLEORITCANBESTATIONARY 7EAPONCONTROLRADAR4HISNAMEISUSUALLYAPPLIEDTOASINGLE TARGETTRACKERUSED FORDEFENDINGAGAINSTAIRATTACK 'UIDANCE RADAR 4HIS IS USUALLY A RADAR ON A MISSILE THAT ALLOWS THE MISSILE TO hHOMEIN vORGUIDEITSELF TOATARGET 7EATHERMETEOROLOGICAL OBSERVATION3UCHRADARSDETECT RECOGNIZE ANDMEASURE PRECIPITATION RATE WIND SPEED AND DIRECTION AND OBSERVE OTHER WEATHER EFFECTS
#OHERENTIMPLIESTHATTHEPHASEOFTHERADARSIGNALISUSEDASANIMPORTANTPARTOFTHERADARPROCESS
!.).42/$5#4)/.!.$/6%26)%7/&2!$!2
£°Ç
IMPORTANT FOR METEOROLOGICAL PURPOSES 4HESE MAY BE SPECIAL RADARS OR ANOTHER FUNCTIONOFSURVEILLANCERADARS $OPPLERWEATHERRADAR4HISISAWEATHEROBSERVATIONRADARTHATEMPLOYSTHEDOP PLERFREQUENCYSHIFTCAUSEDBYMOVINGWEATHEREFFECTSTODETERMINETHEWINDTHE WINDSHEARWHENTHEWINDBLOWSINDIFFERENTDIRECTIONS WHICHCANINDICATEA DANGEROUSWEATHERCONDITIONSUCHASATORNADOORADOWNBURSTOFWINDASWELLAS OTHERMETEOROLOGICALEFFECTS 4ARGETRECOGNITION)NSOMECASES ITMIGHTBEIMPORTANTTORECOGNIZETHETYPEOFTARGET BEINGOBSERVEDBYRADAREG ANAUTOMOBILERATHERTHANABIRD ORTORECOGNIZETHEPAR TICULARTYPEOFTARGETANAUTOMOBILERATHERTHANATRUCK ORASTARLINGRATHERTHANASPAR ROW ORTORECOGNIZEONECLASSOFTARGETFROMANOTHERACRUISESHIPRATHERTHANATANKER 7HENUSEDFORMILITARYPURPOSES ITISUSUALLYCALLEDANONCOOPERATIVETARGETRECOG NITION.#42 RADAR ASCOMPAREDTOACOOPERATIVERECOGNITIONSYSTEMSUCHAS)&& IDENTIFICATIONFRIENDORFOE WHICHISNOTARADAR7HENTARGETRECOGNITIONINVOLVES SOMEPARTOFTHENATURALENVIRONMENT THERADARISUSUALLYKNOWNASAREMOTESENS INGOFTHEENVIRONMENT RADAR -ULTIFUNCTIONRADAR)FEACHOFTHEABOVERADARSWERETHOUGHTOFASPROVIDINGSOME RADARFUNCTION THENAMULTIFUNCTIONRADARISONEDESIGNEDTOPERFORMMORETHANONE SUCHFUNCTIONUSUALLYPERFORMINGONEFUNCTIONATATIMEONATIME SHAREDBASIS 4HEREAREMANYOTHERWAYSTODESCRIBERADARS INCLUDINGLAND SEA AIRBORNE SPACE BORNE MOBILE TRANSPORTABLE AIR TRAFFIC CONTROL MILITARY GROUND PENETRATING ULTRA WIDEBAND OVERTHEHORIZON INSTRUMENTATION LASERORLIDAR BYTHEFREQUENCYBANDAT WHICHTHEYOPERATE5(& , 3 ANDSOON BYTHEIRAPPLICATION ANDSOFORTH
£°ÎÊ ", /" Ê6 Ê," ÊÊ, , $ETECTIONOFTARGETSISOFLITTLEVALUEUNLESSSOMEINFORMATIONABOUTTHETARGETISOBTAINED ASWELL,IKEWISE TARGETINFORMATIONWITHOUTTARGETDETECTIONISMEANINGLESS 2ANGE 0ROBABLYTHEMOSTDISTINGUISHINGFEATUREOFACONVENTIONALRADARISITSABILITY TODETERMINETHERANGETOATARGETBYMEASURINGTHETIMEITTAKESFORTHERADARSIGNALTO PROPAGATEATTHESPEEDOFLIGHTOUTTOTHETARGETANDBACKTOTHERADAR.OOTHERSENSORCAN MEASURETHEDISTANCETOAREMOTETARGETATLONGRANGEWITHTHEACCURACYOFRADARBASICALLY LIMITEDATLONGRANGESBYTHEACCURACYOFTHEKNOWLEDGEOFTHEVELOCITYOFPROPAGATION !TMODESTRANGES THEPRECISIONCANBEAFEWCENTIMETERS4OMEASURERANGE SOMESORT OF TIMING MARK MUST BE INTRODUCED ON THE TRANSMITTED WAVEFORM! TIMING MARK CAN BEASHORTPULSEANAMPLITUDEMODULATIONOFTHESIGNAL BUTITCANALSOBEADISTINCTIVE MODULATIONOFTHEFREQUENCYORPHASE4HEACCURACYOFARANGEMEASUREMENTDEPENDS ONTHERADARSIGNALBANDWIDTHTHEWIDERTHEBANDWIDTH THEGREATERTHEACCURACY4HUS BANDWIDTHISTHEBASICMEASUREOFRANGEACCURACY 2ADIAL6ELOCITY 4HERADIALVELOCITYOFATARGETISOBTAINEDFROMTHERATEOFCHANGE OFRANGEOVERAPERIODOFTIME)TCANALSOBEOBTAINEDFROMTHEMEASUREMENTOFTHEDOP PLERFREQUENCYSHIFT!NACCURATEMEASUREMENTOFRADIALVELOCITYREQUIRESTIME(ENCE TIMEISTHEBASICPARAMETERDESCRIBINGTHEQUALITYOFARADIALVELOCITYMEASUREMENT4HE SPEEDOFAMOVINGTARGETANDITSDIRECTIONOFTRAVELCANBEOBTAINEDFROMITSTRACK WHICH CANBEFOUNDFROMTHERADARMEASUREMENTSOFTHETARGETLOCATIONOVERAPERIODOFTIME
£°n
2!$!2(!.$"//+
!NGULAR$IRECTION /NEMETHODFORDETERMININGTHEDIRECTIONTOATARGETISBY DETERMININGTHEANGLEWHERETHEMAGNITUDEOFTHEECHOSIGNALFROMASCANNINGANTENNA ISMAXIMUM4HISUSUALLYREQUIRESANANTENNAWITHANARROWBEAMWIDTHAHIGH GAIN ANTENNA !NAIR SURVEILLANCERADARWITHAROTATINGANTENNABEAMDETERMINESANGLEIN THISMANNER4HEANGLETOATARGETINONEANGULARDIMENSIONCANALSOBEDETERMINEDBY USINGTWOANTENNABEAMS SLIGHTLYDISPLACEDINANGLE ANDCOMPARINGTHEECHOAMPLI TUDERECEIVEDINEACHBEAM&OURBEAMSARENEEDEDTOOBTAINTHEANGLEMEASUREMENT INBOTHAZIMUTHANDELEVATION4HEMONOPULSETRACKINGRADARDISCUSSEDIN#HAPTERIS AGOODEXAMPLE4HEACCURACYOFANANGLEMEASUREMENTDEPENDSONTHEELECTRICALSIZE OFTHEANTENNAIE THESIZEOFTHEANTENNAGIVENINWAVELENGTHS 3IZEAND3HAPE )FTHERADARHASSUFFICIENTRESOLUTIONCAPABILITYINRANGEORANGLE IT CAN PROVIDE A MEASUREMENT OF THE TARGET EXTENT IN THE DIMENSION OF HIGH RESOLU TION2ANGEISUSUALLYTHECOORDINATEWHERERESOLUTIONISOBTAINED2ESOLUTIONINCROSS RANGEGIVENBYTHERANGEMULTIPLIEDBYTHEANTENNABEAMWIDTH CANBEOBTAINEDWITH VERYNARROWBEAMWIDTHANTENNAS(OWEVER THEANGULARWIDTHOFANANTENNABEAMIS LIMITED SOTHECROSS RANGERESOLUTIONOBTAINEDBYTHISMETHODISNOTASGOODASTHE RANGERESOLUTION6ERYGOODRESOLUTIONINTHECROSS RANGEDIMENSIONCANBEOBTAINED BYEMPLOYINGTHEDOPPLERFREQUENCYDOMAIN BASEDON3!2SYNTHETICAPERTURERADAR OR)3!2INVERSESYNTHETICAPERTURERADARSYSTEMS ASDISCUSSEDIN#HAPTER4HERE NEEDS TO BE RELATIVE MOTION BETWEEN THE TARGET AND THE RADAR IN ORDER TO OBTAIN THE CROSS RANGERESOLUTIONBY3!2OR)3!27ITHSUFFICIENTRESOLUTIONINBOTHRANGEAND CROSS RANGE NOTONLYCANTHESIZEBEOBTAINEDINTWOORTHOGONALCOORDINATES BUTTHE TARGETSHAPECANSOMETIMESBEDISCERNED 4HE)MPORTANCEOF"ANDWIDTHIN2ADAR "ANDWIDTHBASICALLYREPRESENTSINFOR MATIONHENCE ITISVERYIMPORTANTINMANYRADARAPPLICATIONS4HEREARETWOTYPESOF BANDWIDTHENCOUNTEREDINRADAR/NEISTHESIGNALBANDWIDTH WHICHISTHEBANDWIDTH DETERMINEDBYTHESIGNALPULSEWIDTHORBYANYINTERNALMODULATIONOFTHESIGNAL4HE OTHERISTUNABLEBANDWIDTH'ENERALLY THESIGNALBANDWIDTHOFASIMPLEPULSEOFSINE WAVEOFDURATIONSISS0ULSECOMPRESSIONWAVEFORMS DISCUSSEDIN#HAPTER CAN HAVEMUCHGREATERBANDWIDTHTHANTHERECIPROCALOFTHEIRPULSEWIDTH ,ARGEBAND WIDTHISNEEDEDFORRESOLVINGTARGETSINRANGE FORACCURATEMEASUREMENTOFRANGETO ATARGET ANDFORPROVIDINGALIMITEDCAPABILITYTORECOGNIZEONETYPEOFTARGETFROM ANOTHER(IGHRANGERESOLUTIONALSOCANBEUSEFULFORREDUCINGTHEDEGRADINGEFFECTS OFWHATISKNOWNASGLINTINATRACKINGRADAR FORMEASURINGTHEALTITUDEOFANAIRCRAFT BASEDONTHEDIFFERENCEINTIMEDELAYRANGE BETWEENTHETWO WAYDIRECTSIGNALFROM RADARTOTARGETANDTHETWO WAYSURFACE SCATTEREDSIGNALFROMRADARTOSURFACETOTARGET ALSO CALLED MULTIPATH HEIGHT FINDING AND IN INCREASING THE TARGET SIGNAL TO CLUTTER RATIO)NMILITARYSYSTEMS HIGHRANGERESOLUTIONMAYBEEMPLOYEDFORCOUNTINGTHE NUMBEROFAIRCRAFTFLYINGINCLOSEFORMATIONANDFORRECOGNIZINGANDTHWARTINGSOME TYPESOFDECEPTIONCOUNTERMEASURES 4UNABLEBANDWIDTHOFFERSTHEABILITYTOCHANGETUNE THERADARSIGNALFREQUENCY OVERAWIDERANGEOFTHEAVAILABLESPECTRUM4HISCANBEUSEDFORREDUCINGMUTUALINTER FERENCEAMONGRADARSTHATOPERATEINTHESAMEFREQUENCYBAND ASWELLASINATTEMPTING TO MAKE HOSTILE ELECTRONIC COUNTERMEASURES LESS EFFECTIVE4HE HIGHER THE OPERATING FREQUENCYTHEEASIERITISTOOBTAINWIDESIGNALANDWIDETUNABLEBANDWIDTH !LIMITATIONONTHEAVAILABILITYOFBANDWIDTHINARADARISTHECONTROLOFTHESPECTRUM BYGOVERNMENTREGULATINGAGENCIESINTHE5NITED3TATES THE&EDERAL#OMMUNICATION
!.).42/$5#4)/.!.$/6%26)%7/&2!$!2
£°
#OMMISSION ANDINTERNATIONALLY THE)NTERNATIONAL4ELECOMMUNICATIONS5NION !FTER THESUCCESSOFRADARIN7ORLD7AR)) RADARWASALLOWEDTOOPERATEOVERABOUTONE THIRDOFTHEMICROWAVESPECTRUM4HISSPECTRUMSPACEHASBEENREDUCEDCONSIDERABLY OVERTHEYEARSWITHTHEADVENTOFMANYCOMMERCIALUSERSOFTHESPECTRUMINTHEAGEOF hWIRELESSvANDOTHERSERVICESREQUIRINGTHEELECTROMAGNETICSPECTRUM4HUS THERADAR ENGINEERISINCREASINGLYEXPERIENCINGSMALLERAVAILABLESPECTRUMSPACEANDBANDWIDTH ALLOCATIONSTHATCANBEVITALFORTHESUCCESSOFMANYRADARAPPLICATIONS 3IGNAL TO .OISE2ATIO 4HEACCURACYOFALLRADARMEASUREMENTS ASWELLASTHE RELIABLEDETECTIONOFTARGETSDEPENDSONTHERATIO%.O WHERE%ISTHETOTALENERGY OFTHERECEIVEDSIGNALTHATISPROCESSEDBYTHERADARAND.OISTHENOISEPOWERPER UNITBANDWIDTHOFTHERECEIVER4HUS%.OISANIMPORTANTMEASUREOFTHECAPABILITY OFARADAR /PERATIONWITH-ORE4HAN/NE&REQUENCY 4HEREMAYBEIMPORTANTBENEFITS WHENARADARISABLETOOPERATEATMORETHANONEFREQUENCY&REQUENCYAGILITYUSUALLY REFERSTOTHEUSEOFMULTIPLEFREQUENCIESONAPULSE TO PULSEBASIS&REQUENCYDIVERSITY USUALLYRELATESTOTHEUSEOFMULTIPLEFREQUENCIESTHATAREWIDELYSEPARATED SOMETIMESIN MORETHANONERADARBAND&REQUENCYDIVERSITYMIGHTOPERATEATEACHFREQUENCYSIMUL TANEOUSLY OR ALMOST SIMULTANEOUSLY )T HAS BEEN USED IN ALMOST ALL CIVILIAN AIR TRAFFIC CONTROLRADARS0ULSE TO PULSEFREQUENCYAGILITY HOWEVER ISNOTCOMPATIBLEWITHTHEUSE OFDOPPLERPROCESSINGTODETECTMOVINGTARGETSINCLUTTER BUTFREQUENCYDIVERSITYCAN BECOMPATIBLE4HEFREQUENCYRANGEINBOTHAGILITYANDINDIVERSITYOPERATIONSISMUCH GREATERTHANTHEINHERENTBANDWIDTHOFAPULSEOFWIDTHS %LEVATION.ULL&ILLING /PERATIONOFARADARATASINGLEFREQUENCYCANRESULTINA LOBEDSTRUCTURETOTHEELEVATIONPATTERNOFANANTENNADUETOTHEINTERFERENCEBETWEEN THEDIRECTSIGNALRADARTOTARGET ANDTHESURFACE SCATTEREDSIGNALRADARTOEARTHSSUR FACETOTARGET "YALOBEDSTRUCTURE WEMEANTHATTHEREWILLBEREDUCEDCOVERAGEAT SOMEELEVATIONANGLESNULLS ANDINCREASEDSIGNALSTRENGTHATOTHERANGLESLOBES ! CHANGEINFREQUENCYWILLCHANGETHELOCATIONOFTHENULLSANDLOBESSOTHATBYOPERATING OVERAWIDEFREQUENCYRANGE THENULLSINELEVATIONCANBEFILLEDIN ANDTHERADARWILL BELESSLIKELYTOLOSEATARGETECHOSIGNAL&OREXAMPLE MEASUREMENTSWITHAWIDEBAND EXPERIMENTAL RADAR KNOWN AS 3ENRAD WHICH COULD OPERATE FROM TO -(Z SHOWEDTHATWHENONLYASINGLEFREQUENCYWASUSED THEBLIP SCANRATIOTHEEXPERI MENTALLYMEASUREDSINGLE SCANPROBABILITYOFDETECTION WASFOUNDTOBEUNDERA PARTICULARSETOFOBSERVATIONS7HENTHERADAROPERATEDATFOURDIFFERENTWIDELYSEPA RATEDFREQUENCIES THEBLIP SCANRATIOWASAHIGHLYSIGNIFICANTINCREASEDUETO FREQUENCYDIVERSITY )NCREASED4ARGET$ETECTABILITY 4HERADARCROSSSECTIONOFACOMPLEXTARGETSUCH ASANAIRCRAFTCANVARYGREATLYWITHACHANGEINFREQUENCY!TSOMEFREQUENCIES THE RADARCROSSSECTIONWILLBESMALLANDATOTHERSITWILLBELARGE)FARADAROPERATESATA SINGLEFREQUENCY ITMIGHTRESULTINASMALLTARGETECHOAND THEREFORE AMISSEDDETEC TION"YOPERATINGATANUMBEROFDIFFERENTFREQUENCIES THECROSSSECTIONWILLVARYAND CANBESMALLORLARGEBUTASUCCESSFULDETECTIONBECOMESMORELIKELYTHANIFONLYA SINGLEFREQUENCYWEREUSED4HISISONEREASONTHATALMOSTALLAIR TRAFFICCONTROLRADARS OPERATEWITHTWOFREQUENCIESSPACEDWIDEENOUGHAPARTINFREQUENCYTOINSURETHAT TARGETECHOESAREDECORRELATEDAND THEREFORE INCREASETHELIKELIHOODOFDETECTION
£°£ä
2!$!2(!.$"//+
2EDUCED%FFECTIVENESSOF(OSTILE#OUNTERMEASURES !NYMILITARYRADARTHATISSUC CESSFULCANEXPECTAHOSTILEADVERSARYTOEMPLOYCOUNTERMEASURESTOREDUCEITSEFFEC TIVENESS /PERATING OVER A WIDE RANGE OF FREQUENCIES MAKES COUNTERMEASURES MORE DIFFICULTTHANIFOPERATIONISATONLYONEFREQUENCY!GAINSTNOISEJAMMING CHANGING FREQUENCYINANUNPREDICTABLEMANNEROVERAWIDERANGEOFFREQUENCIESCAUSESTHEJAM MERTOHAVETOSPREADITSPOWEROVERAWIDEFREQUENCYRANGEANDWILL THEREFORE REDUCE THEHOSTILEJAMMINGSIGNALSTRENGTHOVERTHEBANDWIDTHOFTHERADARSIGNAL&REQUENCY DIVERSITYOVERAWIDEBANDALSOMAKESITMOREDIFFICULTBUTNOTIMPOSSIBLE FORAHOSTILE INTERCEPTRECEIVERORANANTIRADIATIONMISSILETODETECTANDLOCATEARADARSIGNAL 4HE $OPPLER 3HIFT IN 2ADAR 4HE IMPORTANCE OF THE DOPPLER FREQUENCY SHIFT BEGAN TO BE APPRECIATED FOR PULSE RADAR SHORTLY AFTER 7ORLD 7AR )) AND BECAME AN INCREASINGLY IMPORTANT FACTOR IN MANY RADAR APPLICATIONS -ODERN RADAR WOULD BE MUCHLESSINTERESTINGORUSEFULIFTHEDOPPLEREFFECTDIDNTEXIST4HEDOPPLERFREQUENCY SHIFTFDCANBEWRITTENAS
FD VR L V COS Q L
WHEREVR VCOSPISTHERELATIVEVELOCITYOFTHETARGETRELATIVETOTHERADAR INMS VIS THEABSOLUTEVELOCITYOFTHETARGETINMS KISTHERADARWAVELENGTHINM ANDPISTHE ANGLEBETWEENTHETARGETSDIRECTIONANDTHERADARBEAM4OANACCURACYOFABOUTPER CENT THEDOPPLERFREQUENCYINHERTZISAPPROXIMATELYEQUALTOVRKT DIVIDEDBYKM 4HE DOPPLER FREQUENCY SHIFT IS WIDELY USED TO SEPARATE MOVING TARGETS FROM STATIONARYCLUTTER ASDISCUSSEDIN#HAPTERSTHROUGH3UCHRADARSAREKNOWNAS-4) MOVINGTARGETINDICATION !-4)AIRBORNE-4) ANDPULSEDOPPLER!LLMODERNAIR TRAFFICCONTROLRADARS ALLIMPORTANTMILITARYGROUND BASEDANDAIRBORNEAIR SURVEILLANCE RADARS ANDALLMILITARYAIRBORNEFIGHTERRADARSTAKEADVANTAGEOFTHEDOPPLEREFFECT9ETIN 77)) NONEOFTHESEPULSERADARAPPLICATIONSUSEDDOPPLER4HE#7CONTINUOUSWAVE RADARALSOEMPLOYSTHEDOPPLEREFFECTFORDETECTINGMOVINGTARGETS BUT#7RADARFOR THISPURPOSEISNOTASPOPULARASITONCEWAS4HE(&/4(RADAR#HAPTER COULDNOT DOITSJOBOFDETECTINGMOVINGTARGETSINTHEPRESENCEOFLARGECLUTTERECHOESFROMTHE EARTHSSURFACEWITHOUTTHEUSEOFDOPPLER !NOTHERSIGNIFICANTAPPLICATIONOFRADARTHATDEPENDSONTHEDOPPLERSHIFTISOBSER VATIONOFTHEWEATHER ASINTHE.EXRADRADARSOFTHE53.ATIONAL7EATHER3ERVICE #HAPTER MENTIONEDEARLIERINTHISCHAPTER "OTHTHE3!2AND)3!2CANBEDESCRIBEDINTERMSOFTHEIRUSEOFTHEDOPPLERFRE QUENCYSHIFT#HAPTER 4HEAIRBORNEDOPPLERNAVIGATORRADARISALSOBASEDONTHE DOPPLERSHIFT4HEUSEOFDOPPLERINARADARGENERALLYPLACESGREATERDEMANDSONTHE STABILITYOFTHERADARTRANSMITTER ANDITINCREASESTHECOMPLEXITYOFTHESIGNALPROCESS INGYETTHESEREQUIREMENTSAREWILLINGLYACCEPTEDINORDERTOACHIEVETHESIGNIFICANT BENEFITSOFFEREDBYDOPPLER)TSHOULDALSOBEMENTIONEDTHATTHEDOPPLERSHIFTISTHEKEY CAPABILITYOFARADARTHATCANMEASURESPEED ASBYITSDILIGENTUSEBYTRAFFICPOLICEFOR MAINTAININGVEHICLESPEEDLIMITSANDINOTHERVELOCITYMEASURINGAPPLICATIONS
£°{Ê / Ê, ,Ê +1/" 4HERADARRANGEEQUATIONORRADAREQUATION FORSHORT NOTONLYSERVESTHEVERYUSEFUL PURPOSEOFESTIMATINGTHERANGEOFARADARASAFUNCTIONOFTHERADARCHARACTERISTICS
!.).42/$5#4)/.!.$/6%26)%7/&2!$!2
£°££
BUTALSOISQUITEUSEFULASAGUIDEFORDESIGNINGARADARSYSTEM4HESIMPLEFORMOFTHE RADAREQUATIONMAYBEWRITTENAS
0R
0T 'T S r r !E P 2 P 2
4HERIGHT HANDSIDEHASBEENWRITTENASTHEPRODUCTOFTHREEFACTORSTOREPRESENTTHE PHYSICAL PROCESSES THAT TAKE PLACE4HE FIRST FACTOR ON THE RIGHT IS THE POWER DENSITY ATADISTANCE2FROMARADARTHATRADIATESAPOWER0TFROMANANTENNAOFGAIN'T4HE NUMERATOR R OFTHESECONDFACTORISTHERADARCROSSSECTIONOFTHETARGET)THASTHEUNIT OFAREAFOREXAMPLE SQUAREMETERS ANDISAMEASUREOFTHEENERGYREDIRECTEDBYTHE TARGETBACKINTHEDIRECTIONOFTHERADAR4HEDENOMINATOROFTHESECONDFACTORACCOUNTS FORTHEDIVERGENCEOFTHEECHOSIGNALONITSRETURNPATHBACKTOTHERADAR4HEPRODUCT OFTHEFIRSTTWOFACTORSREPRESENTSTHEPOWERPERUNITAREARETURNEDTOTHERADARANTENNA .OTETHATTHERADARCROSSSECTIONOFATARGET R ISDEFINEDBYTHISEQUATION4HERECEIVING ANTENNAOFEFFECTIVEAREA!ECOLLECTSAPORTION0ROFTHEECHOPOWERRETURNEDTOTHERADAR )FTHEMAXIMUMRADARRANGE 2MAX ISDEFINEDASOCCURRINGWHENTHERECEIVEDSIGNALIS EQUALTOTHEMINIMUMDETECTABLESIGNALOFTHERADAR 3MIN THESIMPLEFORMOFTHERADAR EQUATIONBECOMES
2MAX
0T 'T !E S
P 3MIN
'ENERALLY MOSTRADARSUSETHESAMEANTENNAFORBOTHTRANSMITTINGANDRECEIVING&ROM ANTENNATHEORY THEREISARELATIONBETWEENTHEGAIN'TOFTHEANTENNAONTRANSMITAND ITSEFFECTIVEAREA!EONRECEIVE WHICHIS'T P !E L WHEREKISTHEWAVELENGTHOF THERADARSIGNAL3UBSTITUTINGTHISINTO%QPROVIDESTWOOTHERUSEFULFORMSOFTHE RADAREQUATIONNOTSHOWNHERE ONETHATREPRESENTSTHEANTENNAONLYBYITSGAINAND THEOTHERTHATREPRESENTSTHEANTENNAONLYBYITSEFFECTIVEAREA 4HESIMPLEFORMOFTHERADAREQUATIONISINSTRUCTIVE BUTNOTVERYUSEFULSINCEIT LEAVESOUTMANYTHINGS4HEMINIMUMDETECTABLESIGNAL 3MIN ISLIMITEDBYRECEIVER NOISEANDCANBEEXPRESSEDAS
3MIN K4O "&N 3 .
)NTHISEXPRESSION K4O "ISTHESO CALLEDTHERMALNOISEFROMANIDEALOHMICCONDUC TOR WHEREK "OLTZMANNSCONSTANT 4OISTHESTANDARDTEMPERATUREOF+ AND" RECEIVERBANDWIDTHUSUALLYTHATOFTHE)&STAGEOFTHESUPERHETERODYNERECEIVER 4HE PRODUCTK4OISEQUALTOr 7(Z4OACCOUNTFORTHEADDITIONALNOISEINTRODUCED BYAPRACTICALNONIDEAL RECEIVER THETHERMALNOISEEXPRESSIONISMULTIPLIEDBYTHE NOISEFIGURE&NOFTHERECEIVER DEFINEDASTHENOISEOUTOFAPRACTICALRECEIVERTOTHE NOISEOUTOFANIDEALRECEIVER&ORARECEIVEDSIGNALTOBEDETECTABLE ITHASTOBELARGER THAN THE RECEIVER NOISE BY A FACTOR DENOTED HERE AS 3. 4HIS VALUE OF SIGNAL TO NOISERATIO3. ISTHATREQUIREDIFONLYONEPULSEISPRESENT)THASTOBELARGEENOUGH TOOBTAINTHEREQUIREDPROBABILITYOFFALSEALARMDUETONOISECROSSINGTHERECEIVER THRESHOLD ANDTHEREQUIREDPROBABILITYOFDETECTIONASCANBEFOUNDINVARIOUSRADAR TEXTS 2ADARS HOWEVER GENERALLY PROCESS MORE THAN ONE PULSE BEFORE MAKING A DETECTIONDECISION7EASSUMETHERADARWAVEFORMISAREPETITIVESERIESOFRECTANGULAR LIKEPULSES4HESEPULSESAREINTEGRATEDADDEDTOGETHER BEFOREADETECTIONDECISION
£°£Ó
2!$!2(!.$"//+
ISMADE4OACCOUNTFORTHESEADDEDSIGNALS THENUMERATOROFTHERADAREQUATIONIS MULTIPLIEDBYAFACTORN%IN WHERE%IN ISTHEEFFICIENCYINADDINGTOGETHERNPULSES 4HISVALUECANALSOBEFOUNDINSTANDARDTEXTS 4HEPOWER0TISTHEPEAKPOWEROFARADARPULSE4HEAVERAGEPOWER 0AV ISABETTER MEASUREOFTHEABILITYOFARADARTODETECTTARGETS SOITISSOMETIMESINSERTEDINTOTHE RADAREQUATIONUSING0T 0AV FPS WHEREFPISTHEPULSEREPETITIONFREQUENCYOFTHEPULSE RADARANDSISTHEPULSEDURATION4HESURFACEOFTHEEARTHANDTHEEARTHSATMOSPHERECAN DRASTICALLYAFFECTTHEPROPAGATIONOFELECTROMAGNETICWAVESANDCHANGETHECOVERAGEAND CAPABILITIESOFARADAR)NTHERADAREQUATION THESEPROPAGATIONEFFECTSAREACCOUNTEDFOR BYAFACTOR& INTHENUMERATOROFTHERADAREQUATION ASDISCUSSEDIN#HAPTER7ITH THEABOVESUBSTITUTEDINTOTHESIMPLEFORMOFTHERADAREQUATIONWEGET
2MAX
0AV '!ES N%I N &
P K4O &N F P 3 . ,S
)NTHEABOVEEQUATION ITWASASSUMEDINITSDERIVATIONTHAT"Sy WHICHISGENERALLY APPLICABLEINRADAR!FACTOR,SGREATERTHANUNITY CALLEDTHESYSTEMLOSSES HASBEEN INSERTEDTOACCOUNTFORTHEMANYWAYSTHATLOSSCANOCCURINARADAR4HISLOSSFACTOR CANBEQUITELARGE)FTHESYSTEMLOSSISIGNORED ITMIGHTRESULTINAVERYLARGEERRORIN THEESTIMATEDRANGEPREDICTEDBYTHERADAREQUATION!LOSSOFFROMD"TOMAYBE D"ISNOTUNUSUALWHENALLRADARSYSTEMLOSSFACTORSARETAKENINTOACCOUNT %QUATIONAPPLIESFORARADARTHATOBSERVESATARGETLONGENOUGHTORECEIVEN PULSES-OREFUNDAMENTALLY ITAPPLIESFORARADARWHERETHETIMEONTARGETTOISEQUAL TONFP!NEXAMPLEISATRACKINGRADARTHATCONTINUOUSLYOBSERVESASINGLETARGETFOR ATIMETO4HISEQUATION HOWEVER NEEDSTOBEMODIFIEDFORASURVEILLANCERADARTHAT OBSERVESANANGULARVOLUME7WITHAREVISITTIMETS!IRTRAFFICCONTROLRADARSMIGHT HAVEAREVISITTIMEOFFROMTOS 4HUS ASURVEILLANCERADARHASTHEADDITIONAL CONSTRAINT THAT IT MUST COVER AN ANGULAR VOLUME 7 IN A GIVEN TIME TS 4HE REVISIT TIMETSISEQUALTOTO77O WHERETO NFPAND7O THESOLIDBEAMWIDTHOFTHEANTENNA STERADIANS ISAPPROXIMATELYRELATEDTOTHEANTENNAGAIN'BY' O7O4HEREFORE WHEN NFP IN %Q IS REPLACED WITH ITS EQUAL OTS '7 THE RADAR EQUATION FOR A SURVEILLANCERADARISOBTAINEDAS
2MAX
0AV !ES %I N & T r S P K4O &N 3 . ,S 7
4HERADARDESIGNERHASLITTLECONTROLOVERTHEREVISITTIMETSORTHEANGULARCOVERAGE 7 WHICHAREDETERMINEDMAINLYBYTHEJOBTHERADARHASTOPERFORM4HERADARCROSS SECTIONALSOISDETERMINEDBYTHERADARAPPLICATION)FALARGERANGEISREQUIREDOF ASURVEILLANCERADAR THERADARMUSTHAVETHENECESSARYVALUEOFTHEPRODUCT0AV !E &ORTHISREASON ACOMMONMEASUREOFTHECAPABILITYOFASURVEILLANCERADARISITS POWER APERTUREPRODUCT.OTETHATTHERADARFREQUENCYDOESNOTAPPEAREXPLICITLY IN THE SURVEILLANCE RADAR EQUATION 4HE CHOICE OF FREQUENCY HOWEVER WILL ENTER IMPLICITLYINOTHERWAYS *USTASTHERADAREQUATIONFORASURVEILLANCERADARISDIFFERENTFROMTHECONVENTIONAL RADAREQUATIONOF%QORTHESIMPLERADAREQUATIONOF%Q EACHPARTICULARAPPLICA TIONOFARADARGENERALLYHASTOEMPLOYARADAREQUATIONTAILOREDTOTHATSPECIFICAPPLICA TION7HENTHERADARECHOESFROMLAND SEA ORWEATHERCLUTTERAREGREATERTHANTHERECEIVER NOISE THERADAREQUATIONHASTOBEMODIFIEDTOACCOUNTFORCLUTTERBEINGTHELIMITATIONTO
!.).42/$5#4)/.!.$/6%26)%7/&2!$!2
£°£Î
DETECTIONRATHERTHANRECEIVERNOISE)TCANHAPPENTHATTHEDETECTIONCAPABILITYOFARADAR MIGHTBELIMITEDBYCLUTTERINSOMEREGIONSOFITSCOVERAGEANDBELIMITEDBYRECEIVER NOISEINOTHERREGIONS4HISCANRESULTINTWODIFFERENTSETSOFRADARCHARACTERISTICS ONE OPTIMIZEDFORNOISEANDTHEOTHEROPTIMIZEDFORCLUTTERANDCOMPROMISESUSUALLYHAVETO BEMADEINRADARDESIGN!DIFFERENTTYPEOFRADAREQUATIONISALSOREQUIREDWHENTHERADAR CAPABILITYISLIMITEDBYHOSTILENOISEJAMMING
£°xÊ , ,Ê, +1 9Ê // , Ê " /1, )TISNOTALWAYSCONVENIENTTOUSETHEEXACTNUMERICALFREQUENCYRANGEOVERWHICHA PARTICULARTYPEOFRADAROPERATES7ITHMANYMILITARYRADARS THEEXACTOPERATINGFRE QUENCYRANGEOFARADARISUSUALLYNOTDISCLOSED4HUS THEUSEOFLETTERSTODESIGNATE RADAR OPERATING BANDS HAS BEEN VERY HELPFUL 4HE )%%% )NSTITUTE OF %LECTRICAL AND %LECTRONIC%NGINEERS HASOFFICIALLYSTANDARDIZEDTHERADARLETTER BANDNOMENCLATURE ASSUMMARIZEDIN4ABLE #OMMENTS ON THE TABLE 4HE )NTERNATIONAL 4ELECOMMUNICATIONS 5NION )45 ASSIGNS SPECIFIC PORTIONS OF THE ELECTROMAGNETIC SPECTRUM FOR RADIOLOCATION RADAR USEASSHOWNINTHETHIRDCOLUMN WHICHAPPLIESTO)452EGIONTHATINCLUDES.ORTH AND 3OUTH!MERICA 3LIGHT DIFFERENCES OCCUR IN THE OTHER TWO )45 2EGIONS4HUS AN , BANDRADARCANONLYOPERATEWITHINTHEFREQUENCYRANGEFROM-(ZTO-(Z ANDEVENWITHINTHISRANGE THEREMAYBERESTRICTIONS3OMEOFTHEINDICATED)45BANDS ARERESTRICTEDINTHEIRUSAGEFOREXAMPLE THEBANDBETWEENAND'(ZISRESERVED
4!",% )%%%3TANDARD,ETTER$ESIGNATIONSFOR2ADAR &REQUENCY"ANDS
"AND$ESIGNATION
.OMINAL&REQUENCY2ANGE
(& 6(&
-(Zn-(Z n-(Z
5(&
n-(Z
, 3
n'(Z n'(Z
#
n'(Z
8 +U
n'(Z n'(Z
+
n'(Z
+A 6 7
n'(Z n'(Z n'(Z
3PECIFIC&REQUENCY2ANGESFOR2ADAR"ASED ON)45&REQUENCY!SSIGNMENTS FOR2EGION n-(Z n-(Z n-(Z n-(Z n-(Z n'(Z n'(Z n'(Z n'(Z n'(Z n'(Z n'(Z n'(Z n'(Z n'(Z n'(Z n'(Z n'(Z
£°£{
2!$!2(!.$"//+
WITHFEWEXCEPTIONS FORAIRBORNERADARALTIMETERS4HEREARENOOFFICIAL)45ALLOCATIONS FORRADARINTHE(&BAND BUTMOST(&RADARSSHAREFREQUENCIESWITHOTHERELECTROMAG NETICSERVICES4HELETTER BANDDESIGNATIONFORMILLIMETERWAVERADARSISMM ANDTHERE ARESEVERALFREQUENCYBANDSALLOCATEDTORADARINTHISREGION BUTTHEYHAVENOTBEEN LISTEDHERE!LTHOUGHTHEOFFICIAL)45DESCRIPTIONOFMILLIMETERWAVESISFROMTO '(Z INREALITY THETECHNOLOGYOFRADARSAT+ABAND ISMUCHCLOSERTOTHETECHNOLOGY OFMICROWAVEFREQUENCIESTHANTOTHETECHNOLOGYOF7BAND4HEMILLIMETERWAVERADAR FREQUENCIESAREOFTENCONSIDEREDBYTHOSEWHOWORKINTHISFIELDTOHAVEALOWERBOUND OF'(ZRATHERTHANTHEhLEGALvLOWERBOUNDOF'(ZINRECOGNITIONOFTHESIGNIFICANT DIFFERENCEINTECHNOLOGYANDAPPLICATIONSTHATISCHARACTERISTICOFMILLIMETERWAVERADAR -ICROWAVESHAVENOTBEENDEFINEDINTHISSTANDARD BUTTHISTERMGENERALLYAPPLIESTO RADARSTHATOPERATEFROM5(&TO+ABAND4HEREASONTHATTHESELETTERDESIGNATIONSMIGHT NOTBEEASYFORTHENON RADARENGINEERTORECOGNIZEISTHATTHEYWEREORIGINALLYSELECTED TODESCRIBETHERADARBANDSUSEDIN7ORLD7AR))3ECRECYWASIMPORTANTATTHATTIMESO THELETTERSSELECTEDTODESIGNATETHEVARIOUSBANDSMADEITHARDTOGUESSTHEFREQUENCIES TOWHICHTHEYAPPLY4HOSEWHOWORKAROUNDRADAR HOWEVER SELDOMHAVEAPROBLEM WITHTHEUSAGEOFTHERADARLETTERBANDS /THERLETTERBANDSHAVEBEENUSEDFORDESCRIBINGTHEELECTROMAGNETICSPECTRUMBUT THEYARENOTSUITABLEFORRADARANDSHOULDNEVERBEUSEDFORRADAR/NESUCHDESIGNATION USESTHELETTERS! " # ETC ORIGINALLYDEVISEDFORCONDUCTINGELECTRONICCOUNTERMEASURE EXERCISES4HE)%%%3TANDARDMENTIONEDPREVIOUSLYSTATESTHATTHESEhARENOTCONSISTENT WITHRADARPRACTICEANDSHALLNOTBEUSEDTODESCRIBERADAR FREQUENCYBANDSv4HUS THERE MAYBE$ BANDJAMMERS BUTNEVER$ BANDRADARS
£°ÈÊ /Ê"Ê"* ,/ ÊÊ , +1 9Ê" Ê, , 2ADARSHAVEBEENOPERATEDATFREQUENCIESASLOWAS-(ZJUSTABOVETHE!-BROAD CASTBAND ANDASHIGHASSEVERALHUNDRED'(ZMILLIMETERWAVEREGION -OREUSU ALLY RADARFREQUENCIESMIGHTBEFROMABOUT-(ZTOOVER'(Z4HISISAVERYLARGE EXTENTOFFREQUENCIES SOITSHOULDBEEXPECTEDTHATRADARTECHNOLOGY CAPABILITIES AND APPLICATIONS WILL VARY CONSIDERABLY DEPENDING ON THE FREQUENCY RANGE AT WHICH A RADAROPERATES2ADARSATAPARTICULARFREQUENCYBANDUSUALLYHAVEDIFFERENTCAPABILI TIESANDCHARACTERISTICSTHANRADARSINOTHERFREQUENCYBANDS'ENERALLY LONGRANGE ISEASIERTOACHIEVEATTHELOWERFREQUENCIESBECAUSEITISEASIERTOOBTAINHIGH POWER TRANSMITTERS AND PHYSICALLY LARGE ANTENNAS AT THE LOWER FREQUENCIES /N THE OTHER HAND ATTHEHIGHERRADARFREQUENCIES ITISEASIERTOACHIEVEACCURATEMEASUREMENTSOF RANGEANDLOCATIONBECAUSETHEHIGHERFREQUENCIESPROVIDEWIDERBANDWIDTHWHICH DETERMINESRANGEACCURACYANDRANGERESOLUTION ASWELLASNARROWERBEAMANTENNAS FORAGIVENPHYSICALSIZEANTENNAWHICHDETERMINESANGLEACCURACYANDANGLERESOLU TION )NTHEFOLLOWING THEAPPLICATIONSUSUALLYFOUNDINTHEVARIOUSRADARBANDSARE BRIEFLYINDICATED4HEDIFFERENCESBETWEENADJACENTBANDS HOWEVER ARESELDOMSHARP INPRACTICE ANDOVERLAPINCHARACTERISTICSBETWEENADJACENTBANDSISLIKELY
4HEWAVELENGTHSOF+ABANDRANGEFROMMMTOMM WHICHQUALIFIESTHEMUNDERTHEhLEGALvDEFINITIONOF MILLIMETERS BUTJUSTBARELY
!.).42/$5#4)/.!.$/6%26)%7/&2!$!2
£°£x
(&TO-(Z 4HEMAJORUSEOFTHE(&BANDFORRADAR#HAPTER ISTO DETECTTARGETSATLONGRANGESNOMINALLYOUTTONMI BYTAKINGADVANTAGEOFTHE REFRACTIONOF(&ENERGYBYTHEIONOSPHERETHATLIESHIGHABOVETHESURFACEOFTHEEARTH 2ADIOAMATEURSREFERTOTHISASSHORT WAVEPROPAGATIONANDUSEITTOCOMMUNICATEOVER LONGDISTANCES4HETARGETSFORSUCH(&RADARSMIGHTBEAIRCRAFT SHIPS ANDBALLISTIC MISSILES ASWELLASTHEECHOFROMTHESEASURFACEITSELFTHATPROVIDESINFORMATIONABOUT THEDIRECTIONANDSPEEDOFTHEWINDSTHATDRIVETHESEA 6(&TO-(Z !TTHEBEGINNINGOFRADARDEVELOPMENTINTHES RADARSWEREINTHISFREQUENCYBANDBECAUSETHESEFREQUENCIESREPRESENTEDTHEFRONTIER OFRADIOTECHNOLOGYATTHATTIME)TISAGOODFREQUENCYFORLONGRANGEAIRSURVEILLANCE OR DETECTION OF BALLISTIC MISSILES!T THESE FREQUENCIES THE REFLECTION COEFFICIENT ON SCATTERING FROM THE EARTHS SURFACE CAN BE VERY LARGE ESPECIALLY OVER WATER SO THE CONSTRUCTIVEINTERFERENCEBETWEENTHEDIRECTSIGNALANDTHESURFACE REFLECTEDSIGNALCAN INCREASESIGNIFICANTLYTHERANGEOFA6(&RADAR3OMETIMESTHISEFFECTCANALMOSTDOU BLETHERADARSRANGE(OWEVER WHENTHEREISCONSTRUCTIVEINTERFERENCETHATINCREASES THERANGE THERECANBEDESTRUCTIVEINTERFERENCETHATDECREASESTHERANGEDUETOTHEDEEP NULLSINTHEANTENNAPATTERNINTHEELEVATIONPLANE,IKEWISE THEDESTRUCTIVEINTERFER ENCECANRESULTINPOORLOW ALTITUDECOVERAGE$ETECTIONOFMOVINGTARGETSINCLUTTER ISOFTENBETTERATTHELOWERFREQUENCIESWHENTHERADARTAKESADVANTAGEOFTHEDOPPLER FREQUENCYSHIFTBECAUSEDOPPLERAMBIGUITIESTHATCAUSEBLINDSPEEDS AREFARFEWER ATLOWFREQUENCIES6(&RADARSARENOTBOTHEREDBYECHOESFROMRAIN BUTTHEYCANBE AFFECTEDBYMULTIPLE TIME AROUNDECHOESFROMMETEORIONIZATIONANDAURORA4HERADAR CROSSSECTIONOFAIRCRAFTAT6(&ISGENERALLYLARGERTHANTHERADARCROSSSECTIONATHIGHER FREQUENCIES6(&RADARSFREQUENTLYCOSTLESSCOMPAREDTORADARSWITHTHESAMERANGE PERFORMANCETHATOPERATEATHIGHERFREQUENCIES !LTHOUGHTHEREAREMANYATTRACTIVEADVANTAGESOF6(&RADARSFORLONG RANGESUR VEILLANCE THEYALSOHAVESOMESERIOUSLIMITATIONS$EEPNULLSINELEVATIONANDPOOR LOW ALTITUDECOVERAGEHAVEBEENMENTIONED4HEAVAILABLESPECTRALWIDTHSASSIGNEDTO RADARAT6(&ARESMALLSORANGERESOLUTIONISOFTENPOOR4HEANTENNABEAMWIDTHSARE USUALLYWIDERTHANATMICROWAVEFREQUENCIES SOTHEREISPOORRESOLUTIONANDACCURACY INANGLE4HE6(&BANDISCROWDEDWITHIMPORTANTCIVILIANSERVICESSUCHAS46AND&- BROADCAST FURTHERREDUCINGTHEAVAILABILITYOFSPECTRUMSPACEFORRADAR%XTERNALNOISE LEVELSTHATCANENTERTHERADARVIATHEANTENNAAREHIGHERAT6(&THANATMICROWAVE FREQUENCIES0ERHAPSTHECHIEFLIMITATIONOFOPERATINGRADARSAT6(&ISTHEDIFFICULTYOF OBTAININGSUITABLESPECTRUMSPACEATTHESECROWDEDFREQUENCIES )NSPITEOFITSLIMITATIONS THE6(&AIRSURVEILLANCERADARWASWIDELYUSEDBYTHE 3OVIET5NIONBECAUSEITWASALARGECOUNTRY ANDTHELOWERCOSTOF6(&RADARSMADE THEMATTRACTIVEFORPROVIDINGAIRSURVEILLANCEOVERTHELARGEEXPANSEOFTHATCOUNTRY 4HEY HAVE SAID THEY PRODUCED A LARGE NUMBER OF 6(& AIR SURVEILLANCE RADARS SOMEWEREOFVERYLARGESIZEANDLONGRANGE ANDMOSTWEREREADILYTRANSPORTABLE )TISINTERESTINGTONOTETHAT6(&AIRBORNEINTERCEPTRADARSWEREWIDELYUSEDBYTHE 'ERMANSIN7ORLD7AR))&OREXAMPLE THE,ICHTENSTEIN3. AIRBORNERADAROPER ATEDFROMABOUTTOOVER-(ZINVARIOUSMODELS2ADARSATSUCHFREQUENCIES WERENOTAFFECTEDBYTHECOUNTERMEASURECALLEDCHAFFALSOKNOWNASWINDOW 5(&TO-(Z -ANYOFTHECHARACTERISTICSOFRADAROPERATINGINTHE 6(®IONALSOAPPLYTOSOMEEXTENTAT5(&5(&ISAGOODFREQUENCYFOR!IRBORNE -OVING4ARGET)NDICATION!-4) RADARINAN!IRBORNE%ARLY7ARNING2ADAR!%7 ASDISCUSSEDIN#HAPTER)TISALSOAGOODFREQUENCYFORTHEOPERATIONOFLONG RANGE
£°£È
2!$!2(!.$"//+
RADARSFORTHEDETECTIONANDTRACKINGOFSATELLITESANDBALLISTICMISSILES!TTHEUPPER PORTIONOFTHISBANDTHERECANBEFOUNDLONG RANGESHIPBOARDAIR SURVEILLANCERADARS ANDRADARSCALLEDWINDPROFILERS THATMEASURETHESPEEDANDDIRECTIONOFTHEWIND 'ROUND0ENETRATING2ADAR'02 DISCUSSEDIN#HAPTER ISANEXAMPLEOFWHAT ISCALLEDANULTRAWIDEBAND57" RADAR)TSWIDESIGNALBANDWIDTHSOMETIMESCOV ERSBOTHTHE6(&AND5(&BANDS3UCHARADARSSIGNALBANDWIDTHMIGHTEXTEND FORINSTANCE FROMTO-(Z!WIDEBANDWIDTHISNEEDEDINORDERTOOBTAIN GOODRANGERESOLUTION4HELOWERFREQUENCIESARENEEDEDTOALLOWTHEPROPAGATIONOF RADARENERGYINTOTHEGROUND%VENSO THELOSSINPROPAGATINGTHROUGHTYPICALSOIL ISSOHIGHTHATTHERANGESOFASIMPLEMOBILE'02MIGHTBEONLYAFEWMETERS 3UCH RANGESARESUITABLEFORLOCATINGBURIEDPOWERLINESANDPIPELINES ASWELLASBURIED OBJECTS)FARADARISTOSEETARGETSLOCATEDONTHESURFACEBUTWITHINFOLIAGE SIMILAR FREQUENCIESARENEEDEDASFORTHE'02 ,BANDTO'(Z 4HISISTHEPREFERREDFREQUENCYBANDFORTHEOPERATION OF LONG RANGE OUT TO NMI AIR SURVEILLANCE RADARS 4HE!IR 2OUTE 3URVEILLANCE 2ADAR!232 USEDFORLONGRANGEAIR TRAFFICCONTROLISAGOODEXAMPLE!SONEGOES UPINFREQUENCY THEEFFECTOFRAINONPERFORMANCEBEGINSTOBECOMESIGNIFICANT SOTHE RADARDESIGNERMIGHTHAVETOWORRYABOUTREDUCINGTHEEFFECTOFRAINAT, BANDAND HIGHERFREQUENCIES4HISFREQUENCYBANDHASALSOBEENATTRACTIVEFORTHELONG RANGE DETECTIONOFSATELLITESANDDEFENSEAGAINSTINTERCONTINENTALBALLISTICMISSILES 3BANDTO'(Z 4HE!IRPORT3URVEILLANCE2ADAR!32 THATMONITORS AIRTRAFFICWITHINTHEREGIONOFANAIRPORTISAT3BAND)TSRANGEISTYPICALLYTO NMI)FA$RADARISWANTEDONETHATDETERMINESRANGE AZIMUTHANGLE ANDELEVATION ANGLE ITCANBEACHIEVEDAT3BAND )TWASSAIDPREVIOUSLYTHATLONG RANGESURVEILLANCEISBETTERPERFORMEDATLOWFRE QUENCIESANDTHEACCURATEMEASUREMENTOFTARGETLOCATIONISBETTERPERFORMEDATHIGH FREQUENCIES)FONLYASINGLERADAROPERATINGWITHINASINGLEFREQUENCYBANDCANBEUSED THEN3BANDISAGOODCOMPROMISE)TISALSOSOMETIMESACCEPTABLETOUSE#BANDASTHE CHOICEFORARADARTHATPERFORMSBOTHFUNCTIONS4HE!7!#3AIRBORNEAIR SURVEILLANCE RADARALSOOPERATESAT3BAND5SUALLY MOSTRADARAPPLICATIONSAREBESTOPERATEDINA PARTICULARFREQUENCYBANDATWHICHTHERADARSPERFORMANCEISOPTIMUM(OWEVER IN THEEXAMPLEOFAIRBORNEAIR SURVEILLANCERADARS !7!#3ISFOUNDAT3BANDANDTHE53 .AVYS%!%7RADARAT5(&)NSPITEOFSUCHADIFFERENCEINFREQUENCY ITHASBEENSAID THATBOTHRADARSHAVECOMPARABLEPERFORMANCE4HISISANEXCEPTIONTOTHEOBSERVATION ABOUTTHEREBEINGANOPTIMUMFREQUENCYBANDFOREACHAPPLICATION 4HE.EXRADWEATHERRADAROPERATESAT3BAND)TISAGOODFREQUENCYFORTHEOBSER VATION OF WEATHER BECAUSE A LOWER FREQUENCY WOULD PRODUCE A MUCH WEAKER RADAR ECHOSIGNALFROMRAINSINCETHERADARECHOFROMRAINVARIESASTHEFOURTHPOWEROF THEFREQUENCY ANDAHIGHERFREQUENCYWOULDPRODUCEATTENUATIONOFTHESIGNALASIT PROPAGATESTHROUGHTHERAINANDWOULDNOTALLOWANACCURATEMEASUREMENTOFRAINFALL RATE4HEREAREWEATHERRADARSATHIGHERFREQUENCIES BUTTHESEAREUSUALLYOFSHORTER RANGETHAN.EXRADANDMIGHTBEUSEDFORAMORESPECIFICWEATHERRADARAPPLICATION THANTHEACCURATEMETEOROLOGICALMEASUREMENTSPROVIDEDBY.EXRAD #BANDTO'(Z 4HISBANDLIESBETWEEN3AND8BANDSANDHASPROPERTIES INBETWEENTHETWO/FTEN EITHER3OR8BANDMIGHTBEPREFERREDTOTHEUSEOF#BAND ALTHOUGHTHEREHAVEBEENIMPORTANTAPPLICATIONSINTHEPASTFOR#BAND
!.).42/$5#4)/.!.$/6%26)%7/&2!$!2
£°£Ç
8 BAND TO '(Z 4HIS IS A RELATIVELY POPULAR RADAR BAND FOR MILITARY APPLICATIONS)TISWIDELYUSEDINMILITARYAIRBORNERADARSFORPERFORMINGTHEROLESOF INTERCEPTOR FIGHTER ANDATTACKOFGROUNDTARGETS ASDISCUSSEDIN#HAPTER)TISALSO POPULARFORIMAGINGRADARSBASEDON3!2AND)3!28BANDISASUITABLEFREQUENCY FORCIVILMARINERADARS AIRBORNEWEATHERAVOIDANCERADAR AIRBORNEDOPPLERNAVIGATION RADARS ANDTHEPOLICESPEEDMETER-ISSILEGUIDANCESYSTEMSARESOMETIMESAT8BAND 2ADARSAT8BANDAREGENERALLYOFACONVENIENTSIZEANDARE THEREFORE OFINTERESTFOR APPLICATIONSWHEREMOBILITYANDLIGHTWEIGHTAREIMPORTANTANDVERYLONGRANGEISNOT AMAJORREQUIREMENT4HERELATIVELYWIDERANGEOFFREQUENCIESAVAILABLEAT8BANDAND THE ABILITY TO OBTAIN NARROW BEAMWIDTHS WITH RELATIVELY SMALL ANTENNAS IN THIS BAND AREIMPORTANTCONSIDERATIONSFORHIGH RESOLUTIONAPPLICATIONS"ECAUSEOFTHEHIGHFRE QUENCYOF8BAND RAINCANSOMETIMESBEASERIOUSFACTORINREDUCINGTHEPERFORMANCE OF8 BANDSYSTEMS +U + AND+A"ANDSTO'(Z !SONEGOESTOHIGHERRADARFREQUENCY THEPHYSICALSIZEOFANTENNASDECREASE ANDINGENERAL ITISMOREDIFFICULTTOGENERATE LARGETRANSMITTERPOWER4HUS THERANGEPERFORMANCEOFRADARSATFREQUENCIESABOVE 8BANDISGENERALLYLESSTHANTHATOF8BAND-ILITARYAIRBORNERADARSAREFOUNDAT+U BANDASWELLASAT8BAND4HESEFREQUENCYBANDSAREATTRACTIVEWHENARADAROFSMALLER SIZEHASTOBEUSEDFORANAPPLICATIONNOTREQUIRINGLONGRANGE4HE!IRPORT3URFACE $ETECTION%QUIPMENT!3$% GENERALLYFOUNDONTOPOFTHECONTROLTOWERATMAJOR AIRPORTSHASBEENAT+UBAND PRIMARILYBECAUSEOFITSBETTERRESOLUTIONTHAN8BAND)N THEORIGINAL+BAND THEREISAWATER VAPORABSORPTIONLINEAT'(Z WHICHCAUSES ATTENUATIONTHATCANBEASERIOUSPROBLEMINSOMEAPPLICATIONS4HISWASDISCOVERED AFTERTHEDEVELOPMENTOF+ BANDRADARSBEGANDURING7ORLD7AR)) WHICHISWHYBOTH +UAND+ABANDSWERELATERINTRODUCED4HERADARECHOFROMRAINCANLIMITTHECAPABIL ITYOFRADARSATTHESEFREQUENCIES -ILLIMETER 7AVE 2ADAR !LTHOUGH THIS FREQUENCY REGION IS OF LARGE EXTENT MOST OF THE INTEREST IN MILLIMETER WAVE RADAR HAS BEEN IN THE VICINITY OF '(Z WHERE THERE IS A MINIMUM CALLED A WINDOW IN THE ATMOSPHERIC ATTENUATION !WINDOWISAREGIONOFLOWATTENUATIONRELATIVETOADJACENTFREQUENCIES4HEWIN DOWAT'(ZISABOUTASWIDEASTHEENTIREMICROWAVESPECTRUM !SMENTIONED PREVIOUSLY FOR RADAR PURPOSES THE MILLIMETER WAVE REGION IN PRACTICE GENERALLY STARTSAT'(ZOREVENATHIGHERFREQUENCIES4HETECHNOLOGYOFMILLIMETERWAVE RADARSANDTHEPROPAGATIONEFFECTSOFTHEENVIRONMENTARENOTONLYDIFFERENTFROM MICROWAVERADARS BUTTHEYAREUSUALLYMUCHMORERESTRICTING5NLIKEWHATISEXPERI ENCEDATMICROWAVES THEMILLIMETERRADARSIGNALCANBEHIGHLYATTENUATEDEVENWHEN PROPAGATING IN THE CLEAR ATMOSPHERE!TTENUATION VARIES OVER THE MILLIMETER WAVE REGION4HEATTENUATIONINTHE'(ZWINDOWISACTUALLYHIGHERTHANTHEATTENU ATION OF THE ATMOSPHERIC WATER VAPOR ABSORPTION LINE AT '(Z 4HE ONE WAY ATTENUATIONINTHEOXYGENABSORPTIONLINEAT'(ZISABOUTD"PERKM WHICH ESSENTIALLYPRECLUDESITSAPPLICATION!TTENUATIONINRAINCANALSOBEALIMITATIONIN THEMILLIMETERWAVEREGION )NTERESTINMILLIMETERRADARHASBEENMAINLYBECAUSEOFITSCHALLENGESASAFRONTIER TOBEEXPLOREDANDPUTTOPRODUCTIVEUSE)TSGOODFEATURESARETHATITISAGREATPLACEFOR EMPLOYINGWIDEBANDWIDTHSIGNALSTHEREISPLENTYOFSPECTRUMSPACE RADARSCANHAVE HIGHRANGE RESOLUTIONANDNARROWBEAMWIDTHSWITHSMALLANTENNASHOSTILEELECTRONIC COUNTERMEASURES TO MILITARY RADARS ARE DIFFICULT TO EMPLOY AND IT IS EASIER TO HAVE
£°£n
2!$!2(!.$"//+
AMILITARYRADARWITHLOWPROBABILITYOFINTERCEPTATTHESEFREQUENCIESTHANATLOWER FREQUENCIES)NTHEPAST MILLIMETERWAVETRANSMITTERSWERENOTCAPABLEOFANAVERAGE POWER MORE THAN A FEW HUNDRED WATTSAND WERE USUALLY MUCH LESS!DVANCES IN GYROTRONS#HAPTER CANPRODUCEAVERAGEPOWERMANYORDERSOFMAGNITUDEGREATER THAN MORE CONVENTIONAL MILLIMETER WAVE POWER SOURCES 4HUS AVAILABILITY OF HIGH POWERISNOTALIMITATIONASITONCEWAS ,ASER2ADAR ,ASERSCANPRODUCEUSABLEPOWERATOPTICALFREQUENCIESANDINTHE INFRAREDREGIONOFTHESPECTRUM4HEYCANUTILIZEWIDEBANDWIDTHVERYSHORTPULSES ANDCANHAVEVERYNARROWBEAMWIDTHS!NTENNAAPERTURES HOWEVER AREMUCHSMALLER THAN AT MICROWAVES!TTENUATION IN THE ATMOSPHERE AND RAIN IS VERY HIGH AND PER FORMANCEINBADWEATHERISQUITELIMITED2ECEIVERNOISEISDETERMINEDBYQUANTUM EFFECTSRATHERTHANTHERMALNOISE&ORSEVERALREASONS LASERRADARHASHADONLYLIMITED APPLICATION
£°ÇÊ , ,Ê " /1, -ILITARYELECTRONICEQUIPMENT INCLUDINGRADAR ISIDENTIFIEDBYTHE*OINT%LECTRONICS 4YPE$ESIGNATION3YSTEM*%4$3 ASDESCRIBEDIN53-ILITARY3TANDARD-), 34$ $ 4HE LETTER PORTION OF THE DESIGNATION CONSISTS OF THE LETTERS !. A SLANT BAR ANDTHREEADDITIONALLETTERSAPPROPRIATELYSELECTEDTOINDICATEWHERETHEEQUIPMENTIS INSTALLED THETYPEOFEQUIPMENT ANDITSPURPOSE&OLLOWINGTHETHREELETTERSAREADASH ANDANUMERAL4HENUMERALISASSIGNEDINSEQUENCEFORTHATPARTICULARCOMBINATIONOF LETTERS4ABLESHOWSTHELETTERSTHATHAVEBEENUSEDFORRADARDESIGNATIONS !SUFFIXLETTER! " # x FOLLOWSTHEORIGINALDESIGNATIONFOREACHMODIFICATION OFTHEEQUIPMENTWHEREINTERCHANGEABILITYHASBEENMAINTAINED4HELETTER6INPAREN THESES ADDED TO THE DESIGNATION INDICATES VARIABLE SYSTEMS THOSE WHOSE FUNCTIONS MAYBEVARIEDTHROUGHTHEADDITIONORDELETIONOFSETS GROUPS UNITS ORCOMBINATIONS THEREOF 7HENTHEDESIGNATIONISFOLLOWEDBYADASH THELETTER4 ANDANUMBER THE EQUIPMENTISDESIGNEDFORTRAINING)NADDITIONTOTHE5NITED3TATES THESEDESIGNA TIONSCANALSOBEUSEDBY#ANADA !USTRALIA .EW:EALAND ANDTHE5NITED+INGDOM 3PECIALBLOCKSOFNUMBERSARERESERVEDFORTHESECOUNTRIES&URTHERINFORMATIONCAN BEFOUNDONTHE)NTERNETUNDER-), 34$ $ 4HE53&EDERAL!VIATION!GENCY&!! USESTHEFOLLOWINGTODESIGNATETHEIRAIR TRAFFICCONTROLRADARS !32 !232 !3$% 4$72
L
L
L
L
!IRPORT3URVEILLANCE2ADAR !IR2OUTE3URVEILLANCE2ADAR !IRPORT3URFACE$ETECTION%QUIPMENT 4ERMINAL$OPPLER7EATHER2ADAR
4HENUMERALFOLLOWINGTHELETTERDESIGNATIONINDICATESTHEPARTICULARRADARMODEL INSEQUENCE 7EATHERRADARSDEVELOPEDBYTHE537EATHER3ERVICE./!! EMPLOYTHEDES IGNATION7324HENUMBERFOLLOWINGTHEDESIGNATIONISTHEYEARTHERADARWENTINTO SERVICE4HUS732 $ISTHE.EXRADDOPPLERRADARTHATFIRSTENTEREDSERVICEIN 4HELETTER$INDICATESITISADOPPLERWEATHERRADAR
!.).42/$5#4)/.!.$/6%26)%7/&2!$!2
£°£
4!",% *%4$3,ETTER$ESIGNATIONSTHAT0ERTAINTO2ADAR
)NSTALLATIONFIRSTLETTER !0ILOTEDAIRCRAFT "5NDERWATERMOBILE SUBMARINE $0ILOTLESSCARRIER &&IXEDGROUND
4YPEOF%QUIPMENT SECONDLETTER ,#OUNTERMEASURES 02ADAR 33PECIALOR COMBINATION 7!RMAMENT PECULIARTOARMAMENT NOTOTHERWISECOVERED
''ENERALGROUNDUSE +!MPHIBIOUS --OBILEGROUND 00ORTABLE 37ATERSHIP 44RANSPORTABLEGROUND 5'ENERALUTILITY
0URPOSETHIRDLETTER ""OMBING $$IRECTIONFINDER RECONNAISSANCE ANDSURVEILLANCE '&IRECONTROL ..AVIGATION
13PECIALORCOMBINATION 22ECEIVING 3$ETECTINGRANGEAND BEARING SEARCH 44RANSMITTING 7!UTOMATICFLIGHTORREMOTE CONTROL 8)DENTIFICATIONANDRECOGNITION 93URVEILLANCEANDCONTROL BOTHFIRECONTROLANDAIRCONTROL
66EHICULARGROUND 77ATERSURFACEAND UNDERWATERCOMBINED :0ILOTED PILOTLESSAIRBORNE VEHICLESCOMBINED
£°nÊ -" Ê*-/Ê 6
-Ê Ê, , !BRIEFLISTINGOFSOMEOFTHEMAJORADVANCESINTECHNOLOGYANDCAPABILITYOFRADAR IN THE TWENTIETH CENTURY IS GIVEN IN SOMEWHAT CHRONOLOGICAL BUT NOT EXACT ORDER ASFOLLOWS 4HE DEVELOPMENT OF6(& RADAR FOR DEPLOYMENT ON SURFACE SHIP AND AIRCRAFT FOR MILITARYAIRDEFENSEPRIORTOANDDURING7ORLD7AR)) 4HEINVENTIONOFTHEMICROWAVEMAGNETRONANDTHEAPPLICATIONOFWAVEGUIDETECH NOLOGYEARLYIN77))TOOBTAINRADARSTHATCOULDOPERATEATMICROWAVEFREQUENCIES SOTHATSMALLERANDMOREMOBILERADARSCOULDBEEMPLOYED 4HE MORE THAN DIFFERENT RADAR MODELS DEVELOPED AT THE -)4 2ADIATION ,ABORATORYINITSFIVEYEARSOFEXISTENCEDURING77))THATPROVIDEDTHEFOUNDATION FORMICROWAVERADAR -ARCUMSTHEORYOFRADARDETECTION 4HEINVENTIONANDDEVELOPMENTOFTHEKLYSTRONAND474AMPLIFIERTUBESTHATPRO VIDEDHIGHPOWERWITHGOODSTABILITY
L
L
L
L
L
£°Óä
2!$!2(!.$"//+
4HEUSEOFTHEDOPPLERFREQUENCYSHIFTTODETECTMOVINGTARGETSINTHEPRESENCEOF MUCHLARGERECHOESFROMCLUTTER 4HEDEVELOPMENTOFRADARSSUITABLEFORAIR TRAFFICCONTROL 0ULSECOMPRESSION -ONOPULSETRACKINGRADARWITHGOODTRACKINGACCURACYANDBETTERRESISTANCETOELEC TRONICCOUNTERMEASURESTHANPRIORTRACKINGRADARS 3YNTHETICAPERTURERADAR WHICHPROVIDEDIMAGESOFTHEGROUNDANDWHATISONIT !IRBORNE -4) !-4) FOR LONG RANGE AIRBORNE AIR SURVEILLANCE IN THE PRESENCE OFCLUTTER 3TABLE COMPONENTS AND SUBSYSTEMS AND ULTRALOW SIDELOBE ANTENNAS THAT ALLOWED HIGH 02&PULSEDOPPLERRADAR!7!#3 WITHLARGEREJECTIONOFUNWANTEDCLUTTER (&OVER THE HORIZONRADARTHATEXTENDEDTHERANGEOFDETECTIONOFAIRCRAFTANDSHIPS BYANORDEROFMAGNITUDE $IGITALPROCESSING WHICHHASHADAVERYMAJOREFFECTONIMPROVINGRADARCAPABILI TIESEVERSINCETHEEARLYS !UTOMATICDETECTIONANDTRACKINGFORSURVEILLANCERADARS 3ERIALPRODUCTIONOFELECTRONICALLYSCANNEDPHASEDARRAYRADARS )NVERSESYNTHETICAPERTURERADAR)3!2 THATPROVIDEDANIMAGEOFATARGETASNEEDED FORNONCOOPERATIVETARGETRECOGNITIONOFSHIPS $OPPLERWEATHERRADAR 3PACERADARSSUITABLEFORTHEOBSERVATIONOFPLANETSSUCHAS6ENUS !CCURATECOMPUTERCALCULATIONOFTHERADARCROSSSECTIONOFCOMPLEXTARGETS -ULTIFUNCTIONAIRBORNEMILITARYRADARTHATARERELATIVELYSMALLANDLIGHTWEIGHTTHATFIT INTHENOSEOFAFIGHTERAIRCRAFTANDCANPERFORMALARGENUMBEROFDIFFERENTAIR TO AIR ANDAIR TO GROUNDFUNCTIONS
L
L
L
L
L
L
L
L
L
L
L
L
L
L
L
L
)TISALWAYSAMATTEROFOPINIONWHATTHEMAJORADVANCESINRADARHAVEBEEN/THERS MIGHTHAVEADIFFERENTLIST.OTEVERYMAJORRADARACCOMPLISHMENTHASBEENINCLUDED INTHISLISTING)TCOULDHAVEBEENMUCHLONGERANDCOULDHAVEINCLUDEDMULTIPLEEXAM PLESFROMEACHOFTHEOTHERCHAPTERSINTHISBOOK BUTTHISLISTINGISSUFFICIENTTOINDICATE THETYPEOFADVANCESTHATHAVEBEENIMPORTANTFORIMPROVEDRADARCAPABILITIES
£°Ê ** /" -Ê"Ê, , -ILITARY!PPLICATIONS 2ADARWASINVENTEDINTHESBECAUSEOFTHENEED FORDEFENSEAGAINSTHEAVYMILITARYBOMBERAIRCRAFT4HEMILITARYNEEDFORRADARHAS PROBABLY BEEN ITS MOST IMPORTANT APPLICATION AND THE SOURCE OF MOST OF ITS MAJOR DEVELOPMENTS INCLUDINGTHOSEFORCIVILIANPURPOSES 4HECHIEFUSEOFMILITARYRADARHASBEENFORAIRDEFENSEOPERATINGFROMLAND SEA ORAIR)THASNOTBEENPRACTICALTOPERFORMSUCCESSFULAIRDEFENSEWITHOUTRADAR)NAIR DEFENSE RADARISUSEDFORLONG RANGEAIRSURVEILLANCE SHORT RANGEDETECTIONOFLOW ALTITUDE hPOP UPv TARGETS WEAPON CONTROL MISSILE GUIDANCE NONCOOPERATIVE TARGET RECOGNITION ANDBATTLEDAMAGEASSESSMENT4HEPROXIMITYFUZEINMANYWEAPONSIS
!.).42/$5#4)/.!.$/6%26)%7/&2!$!2
£°Ó£
ALSOANEXAMPLEOFARADAR!NEXCELLENTMEASUREOFTHESUCCESSOFRADARFORMILITARY AIRDEFENSEISTHELARGEAMOUNTSOFMONEYTHATHAVEBEENSPENTONMETHODSTOCOUNTER ITSEFFECTIVENESS4HESEINCLUDEELECTRONICCOUNTERMEASURESANDOTHERASPECTSOFELEC TRONICWARFARE ANTIRADIATIONMISSILESTOHOMEONRADARSIGNALS ANDLOWCROSS SECTION AIRCRAFT AND SHIPS 2ADAR IS ALSO USED BY THE MILITARY FOR RECONNAISSANCE TARGETING OVERLANDORSEA ASWELLASSURVEILLANCEOVERTHESEA /NTHEBATTLEFIELD RADARISASKEDTOPERFORMTHEFUNCTIONSOFAIRSURVEILLANCEINCLUD INGSURVEILLANCEOFAIRCRAFT HELICOPTERS MISSILES ANDUNMANNEDAIRBORNEVEHICLES CONTROLOFWEAPONSTOANAIRINTERCEPT HOSTILEWEAPONSLOCATIONMORTARS ARTILLERY AND ROCKETS DETECTIONOFINTRUDINGPERSONNEL ANDCONTROLOFAIRTRAFFIC 4HEUSEOFRADARFORBALLISTICMISSILEDEFENSEHASBEENOFINTERESTEVERSINCETHE THREATOFBALLISTICMISSILESAROSEINTHELATES4HELONGERRANGES HIGHSUPERSONIC SPEEDS ANDTHESMALLERTARGETSIZEOFBALLISTICMISSILESMAKETHEPROBLEMCHALLENGING 4HEREISNONATURALCLUTTERPROBLEMINSPACEASTHEREISFORDEFENSEAGAINSTAIRCRAFT BUTBALLISTICMISSILESCANAPPEARINTHEPRESENCEOFALARGENUMBEROFEXTRANEOUSCON FUSIONTARGETSANDOTHERCOUNTERMEASURESTHATANATTACKERCANLAUNCHTOACCOMPANY THEREENTRYVEHICLECARRYINGAWARHEAD4HEBASICBALLISTICMISSILEDEFENSEPROBLEM BECOMES MORE OF A TARGET RECOGNITION PROBLEM RATHER THAN DETECTION AND TRACKING 4HENEEDFORWARNINGOFTHEAPPROACHOFBALLISTICMISSILESHASRESULTEDINANUMBEROF DIFFERENTTYPESOFRADARSFORPERFORMINGSUCHAFUNCTION3IMILARLY RADARSHAVEBEEN DEPLOYEDTHATARECAPABLEOFDETECTINGANDTRACKINGSATELLITES !RELATEDTASKFORRADARTHATISNOTMILITARYISTHEDETECTIONANDINTERCEPTIONOFDRUG TRAFFIC4HEREARESEVERALTYPESOFRADARSTHATCANCONTRIBUTETOTHISNEED INCLUDINGTHE LONG RANGE(&OVER THE HORIZONRADAR 2EMOTE3ENSINGOFTHE%NVIRONMENT 4HEMAJORAPPLICATIONINTHISCATEGORY HASBEENWEATHEROBSERVATIONRADARSUCHASTHE.EXRADSYSTEMWHOSEOUTPUTISOFTEN SEENONTHETELEVISIONWEATHERREPORT4HEREALSOEXISTVERTICAL LOOKINGWIND PROFILER RADARSTHATDETERMINEWINDSPEEDANDDIRECTIONASAFUNCTIONOFALTITUDE BYDETECTING THEVERYWEAKRADARECHOFROMTHECLEARAIR,OCATEDAROUNDAIRPORTSARETHE4ERMINAL $OPPLER7EATHER2ADAR4$72 SYSTEMSTHATWARNOFDANGEROUSWINDSHEARPRODUCED BYTHEWEATHEREFFECTKNOWNASTHEDOWNBURST WHICHCANACCOMPANYSEVERESTORMS 4HEREISUSUALLYASPECIALLYDESIGNEDWEATHERAVOIDANCERADARINTHENOSEOFSMALLAS WELLASLARGEAIRCRAFTTOWARNOFDANGEROUSORUNCOMFORTABLEWEATHERINFLIGHT !NOTHERSUCCESSFULREMOTE SENSINGRADARWASTHEDOWNWARD LOOKINGSPACEBORNE ALTIMETERRADARTHATMEASUREDWORLDWIDETHEGEOIDTHEMEANSEALEVEL WHICHISNOT THE SAME ALL OVER THE WORLD WITH EXCEPTIONALLY HIGH ACCURACY 4HERE HAVE BEEN ATTEMPTSINTHEPASTTOUSERADARFORDETERMININGSOILMOISTUREANDFORASSESSINGTHE STATUSOFAGRICULTURECROPS BUTTHESEHAVENOTPROVIDEDSUFFICIENTACCURACY)MAGING RADARSINSATELLITESORAIRCRAFTHAVEBEENUSEDTOHELPSHIPSEFFICIENTLYNAVIGATENORTH ERNSEASCOATEDWITHICEBECAUSERADARCANTELLWHICHTYPESOFICEAREEASIERFORASHIP TOPENETRATE !IR 4RAFFIC#ONTROL 4HEHIGHDEGREEOFSAFETYINMODERNAIRTRAVELISDUEINPART TOTHESUCCESSFULAPPLICATIONSOFRADARFORTHEEFFECTIVE EFFICIENT ANDSAFECONTROLOF AIRTRAFFIC-AJORAIRPORTSEMPLOYAN!IRPORT3URVEILLANCE2ADAR!32 FOROBSERVING THEAIRTRAFFICINTHEVICINITYOFTHEAIRPORT3UCHRADARSALSOPROVIDEINFORMATIONABOUT NEARBYWEATHERSOAIRCRAFTCANBEROUTEDAROUNDUNCOMFORTABLEWEATHER-AJORAIRPORTS ALSOHAVEARADARCALLED!IRPORT3URFACE$ETECTION%QUIPMENT!3$% FOROBSERVING
£°ÓÓ
2!$!2(!.$"//+
ANDSAFELYCONTROLLINGAIRCRAFTANDAIRPORTVEHICLETRAFFICONTHEGROUND&ORCONTROLOF AIRTRAFFICENROUTEFROMONETERMINALTOANOTHER LONG RANGE!IR2OUTE3URVEILLANCE 2ADARS!232 AREFOUNDWORLDWIDE4HE!IR4RAFFIC#ONTROL2ADAR"EACON3YSTEM !4#2"3 ISNOTARADARBUTISACOOPERATIVESYSTEMUSEDTOIDENTIFYAIRCRAFTINFLIGHT)T USESRADAR LIKETECHNOLOGYANDWASORIGINALLYBASEDONTHEMILITARY)&&)DENTIFICATION &RIENDOR&OE SYSTEM /THER !PPLICATIONS ! HIGHLY SIGNIFICANT APPLICATION OF RADAR THAT PROVIDED INFORMATIONNOTAVAILABLEBYANYOTHERMETHOD WASTHEEXPLORATIONOFTHESURFACE OFTHEPLANET6ENUSBYANIMAGINGRADARTHATCOULDSEEUNDERTHEEVER PRESENTCLOUDS THATMASKTHEPLANET/NEOFTHEWIDESTUSEDANDLEASTEXPENSIVEOFRADARSHASBEEN THECIVILMARINERADARFOUNDTHROUGHOUTTHEWORLDFORTHESAFENAVIGATIONOFBOATSAND SHIPS3OMEREADERSHAVEUNDOUBTEDLYBEENCONFRONTEDBYTHEHIGHWAYPOLICEUSING THE#7DOPPLERRADARTOMEASURETHESPEEDOFAVEHICLE'ROUNDPENETRATINGRADAR HASBEENUSEDTOFINDBURIEDUTILITYLINES ASWELLASBYTHEPOLICEFORLOCATINGBURIED OBJECTSANDBODIES!RCHEOLOGISTSHAVEUSEDITTODETERMINEWHERETOBEGINTOLOOK FORBURIEDARTIFACTS2ADARHASBEENHELPFULTOBOTHTHEORNITHOLOGISTANDENTOMOLOGIST FORBETTERUNDERSTANDINGTHEMOVEMENTSOFBIRDSANDINSECTS)THASALSOBEENDEM ONSTRATEDTHATRADARCANDETECTTHEGASSEEPAGETHATISOFTENFOUNDOVERUNDERGROUND OILANDGASDEPOSITS
£°£äÊ "
*/1 Ê, ,Ê-9-/ Ê - 4HEREAREVARIOUSASPECTSTORADARSYSTEMDESIGN"UTBEFOREANEWRADARTHATHASNOT EXISTEDPREVIOUSLYCANBEMANUFACTURED ACONCEPTUALDESIGNHASTOBEPERFORMEDTO GUIDETHEACTUALDEVELOPMENT!CONCEPTUALDESIGNISBASEDONTHEREQUIREMENTSFOR THERADARTHATWILLSATISFYTHECUSTOMERORUSEROFTHERADAR4HERESULTOFACONCEPTUAL DESIGNEFFORTISTOPROVIDEALISTOFTHERADARCHARACTERISTICSASFOUNDINTHERADAREQUA TIONANDRELATEDEQUATIONSANDTHEGENERALCHARACTERISTICSOFTHESUBSYSTEMSTRANSMIT TER ANTENNA RECEIVER SIGNALPROCESSING ANDSOFORTH THATMIGHTBEEMPLOYED4HE RADAREQUATIONISUSEDASANIMPORTANTGUIDEFORDETERMININGTHEVARIOUSTRADEOFFSAND OPTIONSAVAILABLETOTHERADARSYSTEMDESIGNERSOASTODETERMINEASUITABLECONCEPTTO MEETTHEDESIREDNEED4HISSECTIONBRIEFLYSUMMARIZESHOWARADARSYSTEMSENGINEER MIGHTBEGINTOAPPROACHTHECONCEPTUALDESIGNOFANEWRADAR4HEREARENOFIRMLY ESTABLISHED PROCEDURES TO CARRY OUT A CONCEPTUAL DESIGN %VERY RADAR COMPANY AND EVERYRADARDESIGNENGINEERDEVELOPSHISORHEROWNSTYLE7HATISDESCRIBEDHEREISA BRIEFSUMMARYOFONEAPPROACHTOCONCEPTUALRADARDESIGN 'ENERAL'UIDELINE )TSHOULDBEMENTIONEDTHATTHEREAREATLEASTTWOWAYSBY WHICHANEWRADARSYSTEMMIGHTBEPRODUCEDFORSOMEPARTICULARRADARAPPLICATION/NE METHODISBASEDONEXPLOITINGTHEADVANTAGESOFSOMENEWINVENTION NEWTECHNIQUE NEW DEVICE OR NEW KNOWLEDGE4HE INVENTION OF THE MICROWAVE MAGNETRON EARLY IN 7ORLD7AR))ISANEXAMPLE!FTERTHEMAGNETRONAPPEARED RADARDESIGNWASDIFFERENT FROMWHATITHADBEENBEFORE4HEOTHER ANDPROBABLYMORECOMMONMETHODFORCON CEPTUALRADARSYSTEMDESIGN ISTOSTARTWITHWHATTHENEWRADARHASTODO EXAMINETHE VARIOUSAPPROACHESAVAILABLETOACHIEVETHEDESIREDCAPABILITY CAREFULLYEVALUATEEACH APPROACH ANDTHENSELECTTHEONETHATBESTMEETSTHENEEDSWITHINTHEOPERATIONALAND FISCALCONSTRAINTSIMPOSED)NBRIEF ITMIGHTCONSISTOFTHEFOLLOWINGSTEPS
!.).42/$5#4)/.!.$/6%26)%7/&2!$!2
£°ÓÎ
$ESCRIPTIONOFTHENEEDORPROBLEMTOBESOLVED 4HISISFROMTHEVIEWPOINTOFTHECUSTOMERORTHEUSEROFTHERADAR )NTERACTIONBETWEENTHECUSTOMERANDTHESYSTEMSENGINEER 4HISISFORTHEPURPOSEOFEXPLORINGTHETRADEOFFS WHICHTHECUSTOMERMIGHTNOT BEAWAREOF THATMIGHTALLOWTHECUSTOMERTOBETTEROBTAINWHATISWANTEDWITH OUTEXCESSIVECOSTORRISK5NFORTUNATELY INTERACTIONBETWEENTHEPOTENTIALUSER OFTHERADARANDTHERADARSYSTEMSENGINEERISNOTALWAYSDONEINCOMPETITIVE PROCUREMENTS )DENTIFICATIONANDEXPLORATIONOFPOSSIBLESOLUTIONS 4HISINCLUDESUNDERSTANDINGTHEADVANTAGESANDLIMITATIONSOFTHEVARIOUSPOS SIBLESOLUTIONS 3ELECTIONOFTHEOPTIMUMORNEAROPTIMUMSOLUTION )N MANY ENGINEERING ENDEAVORS OPTIMUM DOES NOT MEAN THE BEST SINCE THE BEST MIGHTNOTBEAFFORDABLEORACHIEVABLEINTHEREQUIREDTIME/PTIMUM ASUSEDHERE MEANSTHEBESTUNDERAGIVENSETOFASSUMPTIONS%NGINEERINGOFTENINVOLVESACHIEV INGANEAR OPTIMUM NOTTHEOPTIMUM3ELECTINGTHEPREFERREDSOLUTIONSHOULDBE BASEDONAWELL DEFINEDCRITERION $ETAILEDDESCRIPTIONOFTHESELECTEDAPPROACH 4HIS IS IN TERMS OF THE CHARACTERISTICS OF THE RADAR AND THE TYPE OF SUBSYSTEMS TO BEEMPLOYED !NALYSISANDEVALUATIONOFTHEPROPOSEDDESIGN 4HISISTOVERIFYTHECORRECTNESSOFTHESELECTEDAPPROACH
L
L
L
L
L
L
!SONEPROCEEDSTHROUGHTHISPROCESS ONEMIGHTREACHAhDEADENDvANDHAVETO STARTOVERSOMETIMESMORETHANONCE(AVINGTOSTARTOVERISNOTUNUSUALDURINGA NEWDESIGNEFFORT /NECANNOTDEVISEAUNIQUESETOFGUIDELINESFORPERFORMINGTHEDESIGNOFARADAR )FTHATWEREPOSSIBLE RADARDESIGNCOULDBEDONEENTIRELYBYCOMPUTER"ECAUSEOFTHE USUALLACKOFCOMPLETEINFORMATION MOSTENGINEERINGDESIGNREQUIRES ATSOMEPOINT THEJUDGMENTANDEXPERIENCEOFTHEDESIGNENGINEERINORDERTOSUCCEED 4HE2ADAR%QUATIONIN#ONCEPTUAL$ESIGN 4HERADAREQUATIONISTHEBASIS FORCONCEPTUALRADARSYSTEMDESIGN3OMEPARAMETERSOFTHERADAREQUATIONAREDETER MINEDBYWHATTHERADARISREQUIREDTODO/THERSMAYBEDECIDEDUPONUNILATERALLYBY THECUSTOMERBUTTHATSHOULDBEDONEWITHCAUTION4HECUSTOMERUSUALLYSHOULDBE THEONEWHOSTATESTHENATUREOFTHERADARTARGET THEENVIRONMENTINWHICHTHERADAR ISTOOPERATE RESTRICTIONSONSIZEANDWEIGHT THEUSETOWHICHTHERADARINFORMATION ISTOBEPUT ANDANYOTHERCONSTRAINTSTHATHAVETOBEIMPOSED&ROMTHISINFORMATION THERADARSYSTEMSENGINEERDETERMINESWHATISTHERADARCROSSSECTIONOFTHETARGET THERANGEANDANGLEACCURACIESNEEDEDTOMEETTHERADARUSERSNEEDS ASWELLASTHE ANTENNAREVISITTIME3OMEPARAMETERS SUCHASANTENNAGAIN MIGHTBEAFFECTEDBY MORE THAN ONE NEED OR REQUIREMENT &OR INSTANCE A PARTICULAR ANTENNA BEAMWIDTH MIGHTBEINFLUENCEDBYTHETRACKINGACCURACY RESOLUTIONOFNEARBYTARGETS THEMAXI MUMSIZETHEANTENNACANBEFORAPARTICULARAPPLICATION THENEEDFORADESIREDRADAR RANGE ANDTHECHOICEOFRADARFREQUENCY4HERADARFREQUENCYISUSUALLYAFFECTEDBY MANYTHINGS INCLUDINGTHEAVAILABILITYOFALLOWEDFREQUENCIESATWHICHTOOPERATE 4HERADARFREQUENCYMIGHTBETHELASTPARAMETEROFTHERADARTOBESELECTEDAFTER MANYOTHERCOMPROMISESHAVEBEENMADE
£°Ó{
2!$!2(!.$"//+
, ,
)%%%3TANDARD$ICTIONARYOF%LECTRICALAND%LECTRONIC4ERMS TH%D.EW9ORK)%%% -)3KOLNIK ',INDE AND+-EADS h3ENRADANADVANCEDWIDEBANDAIR SURVEILLANCERADAR v )%%%4RANS VOL!%3 PPn /CTOBER -)3KOLNIK )NTRODUCTIONTO2ADAR3YSTEMS .EW9ORK-C'RAW (ILL &IG &%.ATHANSON 2ADAR$ESIGN0RINCIPLES .EW9ORK-C'RAW (ILL &IG 4HISTABLEHASBEENDERIVEDFROM)%%%3TANDARD,ETTER$ESIGNATIONSFOR2ADAR &REQUENCY"ANDS )%%%3TD 3PECIFICRADIOLOCATIONFREQUENCYRANGESMAYBEFOUNDINTHEh&##/NLINE4ABLEOF&REQUENCY !LLOCATIONS v#&2e h0ERFORMING ELECTRONIC COUNTERMEASURES IN THE 5NITED 3TATES AND #ANADA v 53 .AVY /0.!6).34 " /CTOBER 3IMILAR VERSIONS ISSUED BY THE 53 !IR &ORCE !&2 53!RMY !2 AND53-ARINE#ORPS -#/ ! :ACHEPITSKY h6(& METRIC BAND RADARS FROM .IZHNY .OVGOROD 2ESEARCH 2ADIOTECHNICAL )NSTITUTE v)%%%!%33YSTEMS-AGAZINE VOL PPn *UNE !NONYMOUS h!7!#3VS%#BATTLEASTANDOFF v%7-AGAZINE P -AY*UNE -3KOLNIK $(EMENWAY AND*0(ANSEN h2ADARDETECTIONOFGASSEEPAGEASSOCIATEDWITHOIL ANDGASDEPOSITS v)%%%4RANS VOL'23 PPn -AY
#HAPTER
/Ê,>`>À 7>Ê7°Ê-
À>`iÀ 3HRADER!SSOCIATES )NC
6
iÊÀi}iÀÃ>Ãi .AVAL2ESEARCH,ABORATORY
Ó°£Ê *,
4HIS CHAPTER ADDRESSES SURFACE BASED RADARS EG RADARS SITED ON LAND OR INSTALLED ONBOARDSHIPS&ORAIRBORNERADAR RAPIDPLATFORMMOTIONHASASIGNIFICANTEFFECTON DESIGNANDPERFORMANCEASDISCUSSEDIN#HAPTERS ANDOFTHIS(ANDBOOK 4HEFUNDAMENTALTHEORYOFMOVINGTARGETINDICATION-4) RADAR ASPRESENTEDINTHE PREVIOUSEDITIONSOFTHE2ADAR(ANDBOOK HASNOTMATERIALLYCHANGED4HEPERFORMANCE OF-4)RADAR HOWEVER HASBEENGREATLYIMPROVED DUEPRIMARILYTOFOURADVANCES INCREASEDSTABILITYOFRADARSUBSYSTEMSSUCHASTRANSMITTERS OSCILLATORS ANDRECEIVERS INCREASED DYNAMIC RANGE OF RECEIVERS AND ANALOG TO DIGITAL CONVERTERS !$ FASTERANDMOREPOWERFULDIGITALPROCESSINGAND BETTERAWARENESSOFTHELIMITA TIONS ANDTHEREFOREREQUISITESOLUTIONS OFADAPTING-4)SYSTEMSTOTHEENVIRONMENT4HESE FOURADVANCESHAVEMADEITPRACTICALTOUSESOPHISTICATEDTECHNIQUESTHATWERECONSIDERED ANDSOMETIMESTRIED MANYYEARSAGOBUTWEREIMPRACTICALTOIMPLEMENT%XAMPLESOF EARLYCONCEPTSTHATWEREWELLAHEADOFTHEAVAILABLETECHNOLOGYWERETHEVELOCITYINDICAT INGCOHERENTINTEGRATOR6)#) ANDTHECOHERENTMEMORYFILTER#-& !LTHOUGH THESE IMPROVEMENTS HAVE ENABLED MUCH IMPROVED -4) CAPABILITIES THEREARESTILLNOPERFECTSOLUTIONSTOALL-4)RADARPROBLEMS ANDTHEDESIGNOFAN-4) SYSTEMISSTILLASMUCHOFANARTASITISASCIENCE%XAMPLESOFCURRENTPROBLEMSINCLUDE THEFACTTHATWHENRECEIVERSAREBUILTWITHINCREASEDDYNAMICRANGE SYSTEMINSTABILITY LIMITATIONSWILLCAUSEINCREASEDCLUTTERRESIDUERELATIVETOSYSTEMNOISE THATCANCAUSE FALSEDETECTIONS#LUTTERMAPS WHICHAREUSEDTOPREVENTFALSEDETECTIONSFROMCLUTTER RESIDUE WORKQUITEWELLONFIXEDRADARSYSTEMS BUTAREDIFFICULTTOIMPLEMENTON FOR EXAMPLE SHIPBOARDRADARS BECAUSEASTHESHIPMOVES THEASPECTANDRANGETOEACH CLUTTERPATCHCHANGES CREATINGINCREASEDRESIDUESAFTERTHECLUTTERMAP!DECREASEIN THERESOLUTIONOFTHECLUTTERMAPTOCOUNTERTHERAPIDLYCHANGINGCLUTTERRESIDUEWILL PRECLUDEMUCHOFTHEINTERCLUTTERVISIBILITYSEELATERINTHISCHAPTER WHICHISONEOF THELEASTAPPRECIATEDSECRETSOFSUCCESSFUL-4)OPERATION -4)RADARMUSTWORKINTHEENVIRONMENTTHATCONTAINSSTRONGFIXEDCLUTTER BIRDS BATS ANDINSECTS WEATHER AUTOMOBILES ANDDUCTING4HEDUCTING ALSOREFERREDTOASANOMA LOUSPROPAGATION CAUSESRADARRETURNSFROMCLUTTERONTHESURFACEOFTHE%ARTHTOAPPEAR Ó°£
Ó°Ó
2!$!2(!.$"//+
ATGREATLYEXTENDEDRANGES WHICHEXACERBATESTHEPROBLEMSWITHBIRDSANDAUTOMOBILES ANDCANALSOCAUSETHEDETECTIONOFFIXEDCLUTTERHUNDREDSOFKILOMETERSAWAY 4HE CLUTTER MODELS CONTAINED IN THIS CHAPTER ARE APPROXIMATIONS OF THE TYPES OF CLUTTERTHATMUSTBEADDRESSED4HEEXACTQUANTITATIVEDATA SUCHASPRECISESPECTRUM ANDAMPLITUDEOFEACHTYPEOFCLUTTER ORTHEEXACTNUMBEROFBIRDSORPOINTREFLECTORS EG WATERTOWERSOROIL WELLDERRICKS PERUNITAREA ISNOTIMPORTANT BECAUSETHE-4) RADARDESIGNERMUSTCREATEAROBUSTSYSTEMTHATWILLFUNCTIONWELLNOMATTERTHEACTUAL DEVIATIONFROMTHECLUTTERMODELSOFREALCLUTTERENCOUNTERED -4)RADARSMAYUSEROTATINGANTENNASORFIXEDAPERTURESWITHELECTRONICBEAMSCAN NINGPHASEDARRAYS 4HEROTATINGANTENNAMAYUSEACONTINUOUSWAVEFORMPROCESSED THROUGHEITHERAFINITE IMPULSE RESPONSE&)2 FILTERORANINFINITE IMPULSE RESPONSE ))2 FILTER ORMAYUSEABATCHWAVEFORMCONSISTINGOFCOHERENTPROCESSINGINTERVALS #0)S THATAREPROCESSEDIN&)2FILTERSINGROUPSOF.PULSES4HETERM-4)FILTER USEDOFTENINTHISCHAPTER ISAGENERICNOMENCLATURETHATINCLUDESBOTH&)2AND))2 FILTERS 4HEFINITETIME ON TARGETDICTATESTHENEEDFORABATCHPROCESSINGAPPROACH 4HEREAREMANYDIFFERENTCOMBINATIONSOFSUCCESSFUL-4)TECHNIQUES BUTANYSPE CIFIC-4)RADARSYSTEMMUSTBEATOTALCONCEPTBASEDONTHEPARAMETERSOFTHEANTENNA TRANSMITTER WAVEFORM SIGNALPROCESSING ANDTHEOPERATIONALENVIRONMENT ! NUMBER OF PLAN POSITION INDICATOR 00) PHOTOGRAPHS TAKEN YEARS AGO ARE INCLUDEDINTHISCHAPTERTOPROVIDEABETTERUNDERSTANDINGOFTHEENVIRONMENTTHATIS DIFFICULTTOAPPRECIATEWITHMANYMODERNRADARS4HESEPHOTOGRAPHSSHOW-4)OPERA TION BIRDS INSECTS ANDDUCTINGBETTERTHANCANBEDESCRIBEDINWORDS !TTENTIONISESPECIALLYDIRECTEDTOTHEFINALSECTIONINTHISCHAPTER h#ONSIDERATIONS !PPLICABLETO-4)2ADAR3YSTEMS vWHICHPROVIDESINSIGHTINTOBOTHHARDWAREAND ENVIRONMENTALLESSONSLEARNEDDURINGMANYDECADESOF-4)SYSTEMDEVELOPMENT
Ó°ÓÊ /," 1 /" Ê/"Ê /Ê, , 4HEPURPOSEOF-4)RADARISTOREJECTRETURNSFROMFIXEDORSLOW MOVINGUNWANTED TARGETS SUCHASBUILDINGS HILLS TREES SEA ANDRAIN ANDRETAINFORDETECTIONORDISPLAY SIGNALSFROMMOVINGTARGETSSUCHASAIRCRAFT&IGURESHOWSAPAIROFPHOTOGRAPHS OFA00) WHICHILLUSTRATESTHEEFFECTIVENESSOFSUCHAN-4)SYSTEM4HEDISTANCEFROM THECENTERTOTHEEDGEOFTHE00)ISNMI4HERANGEMARKSAREAT NMIINTERVALS 4HEPICTUREONTHELEFTISTHENORMALVIDEODISPLAY SHOWINGMAINLYTHEFIXED TARGET RETURNS4HEPICTUREONTHERIGHTSHOWSTHEEFFECTIVENESSOFTHE-4)CLUTTERREJECTION 4HECAMERASHUTTERWASLEFTOPENFORTHREESCANSOFTHEANTENNATHUS AIRCRAFTSHOWUP ASASUCCESSIONOFTHREERETURNS-4)RADARUTILIZESTHEDOPPLERSHIFTIMPARTEDONTHE REFLECTEDSIGNALBYAMOVINGTARGETTODISTINGUISHMOVINGTARGETSFROMFIXEDTARGETS)N APULSERADARSYSTEM THISDOPPLERSHIFTAPPEARSASACHANGEOFPHASEOFRECEIVEDSIG NALSBETWEENCONSECUTIVERADARPULSES#ONSIDERARADARTHATTRANSMITSAPULSEOFRADIO FREQUENCY2& ENERGYTHATISREFLECTEDBYBOTHABUILDINGFIXEDTARGET ANDANAIRPLANE MOVINGTARGET APPROACHINGTHERADAR4HEREFLECTEDPULSESRETURNTOTHERADARACERTAIN TIMELATER4HERADARTHENTRANSMITSASECONDPULSE4HEREFLECTIONFROMTHEBUILDING OCCURSINEXACTLYTHESAMEAMOUNTOFTIME BUTTHEREFLECTIONFROMTHEMOVINGAIRCRAFT OCCURSINLESSTIMEBECAUSETHEAIRCRAFTHASMOVEDCLOSERTOTHERADARINTHEINTERVAL BETWEENTRANSMITTEDPULSES4HEPRECISETIMETHATITTAKESTHEREFLECTEDSIGNALTOREACH THERADARISNOTOFFUNDAMENTALIMPORTANCE7HATISSIGNIFICANTISWHETHERTHETIME CHANGESBETWEENPULSES4HETIMECHANGE WHICHISOFTHEORDEROFAFEWNANOSECONDS FORANAIRCRAFTTARGET ISDETERMINEDBYCOMPARINGTHEPHASEOFTHERECEIVEDSIGNALWITH
-4)2!$!2
Ó°Î
&)'52% A .ORMALVIDEOANDB -4)VIDEO4HESE00)PHOTOGRAPHSSHOWHOWEFFECTIVEAN-4) SYSTEMCANBE!IRCRAFTAPPEARASTHREECONSECUTIVEBLIPSINTHERIGHT HANDPICTUREBECAUSETHECAMERASHUTTER WASOPENFORTHREEREVOLUTIONSOFTHEANTENNA4HE00)RANGEISNMI
THEPHASEOFAREFERENCEOSCILLATORINTHERADAR)FTHETARGETMOVESBETWEENPULSES THE PHASEOFTHERECEIVEDPULSECHANGES &IGURESHOWSASIMPLIFIEDBLOCKDIAGRAMOFACOHERENT-4)SYSTEM4HE2& OSCILLATOR FEEDS THE PULSED AMPLIFIER WHICH TRANSMITS THE PULSES4HE 2& OSCILLATOR
&)'52% 3IMPLIFIEDBLOCKDIAGRAMOFACOHERENT-4)SYSTEM
Ó°{
2!$!2(!.$"//+
ISALSOUSEDASAPHASEREFERENCEFORDETERMININGTHEPHASEOFREFLECTEDSIGNALS4HE PHASEINFORMATIONISSTOREDINAPULSEREPETITIONINTERVAL02) MEMORYFORTHEPERIOD 4 BETWEENTRANSMITTEDPULSES ANDISSUBTRACTEDFROMTHEPHASEINFORMATIONFROMTHE CURRENTRECEIVEDPULSE4HEREISANOUTPUTFROMTHESUBTRACTORONLYWHENAREFLECTION HASOCCURREDFROMAMOVINGTARGET -OVING 4ARGET)NDICATOR-4) "LOCK$IAGRAM !MORECOMPLETEBLOCKDIA GRAMOFAN-4)RADARISSHOWNIN&IGURE4HISBLOCKDIAGRAMISREPRESENTATIVEOFA MODERNAIRTRAFFICCONTROLRADAROPERATINGAT,OR3BANDWITHATYPICALINTERPULSEPERIOD OFnMSANDA#7PULSELENGTHOFAFEWMSWHENTHETRANSMITTEREMPLOYSAVACUUM TUBEAMPLIFIERSUCHAS FOREXAMPLE AKLYSTRON ORTENSOFMSFORAPULSECOMPRESSION WAVEFORMWHENASOLID STATETRANSMITTERISUSED4HERECEIVEDSIGNALSAREAMPLIFIEDIN ALOW NOISEAMPLIFIER,.! ANDSUBSEQUENTLYDOWNCONVERTEDTHROUGHONEORMORE INTERMEDIATEFREQUENCIES)& BYMIXINGWITHSTABLELOCALOSCILLATORS!BANDPASS)& LIMITERATTHERECEIVEROUTPUTPROTECTSTHE!$CONVERTERFROMDAMAGEBUTALSOPREVENTS LIMITINGFROMTAKINGPLACEINTHE!$CONVERTER)NEARLY-4)SYSTEMS THE)&LIM ITERSERVEDTHEPURPOSEOFDELIBERATELYRESTRICTINGTHEDYNAMICRANGETOREDUCECLUTTER RESIDUESATTHE-4)OUTPUT4HERECEIVEDSIGNALSARETHENCONVERTEDINTOIN PHASEAND QUADRATURECOMPONENTS)1 THROUGHTHE!$CONVERTER EITHERUSINGAPAIROFPHASE DETECTORSORTHROUGHDIRECTSAMPLINGASDISCUSSEDIN3ECTION4HEIN PHASE) AND QUADRATURE1 OUTPUTSAREAFUNCTIONOFTHEAMPLITUDEANDPHASEOFTHE)&SIGNALAND
&)'52% -4)SYSTEMBLOCKDIAGRAM
-4)2!$!2
Ó°x
&)'52% "IPOLARVIDEORETURNFROMSINGLETRANSMITTERPULSE
HAVEINTHEPASTBEENREFERREDTOASBIPOLARVIDEOS BUTAMORECORRECTTERMINOLOGYIS THATOFTHECOMPLEXENVELOPEOFTHERECEIVEDSIGNALS!NEXAMPLEOFSUCHABIPOLAR VIDEOEITHER)OR1 RECEIVEDFROMASINGLETRANSMITTEDPULSEANDINCLUDINGBOTHCLUT TERANDPOINTTARGETSISSKETCHEDIN&IGURE)FTHEPOINTTARGETSAREMOVING THESUPER IMPOSEDBIPOLARVIDEOFROMSEVERALTRANSMITTEDPULSESWOULDAPPEARASIN&IGURE 4HEREMAINDEROFTHEBLOCKDIAGRAMIN&IGURESHOWSTHEREMAININGPROCESS INGREQUIREDSOTHATTHEMOVINGTARGETSCANBEDISPLAYEDONA00)ORSENTTOANAUTO MATICTARGETEXTRACTOR4HEIN PHASEANDQUADRATUREOUTPUTSFROMTHE!$CONVERTERARE STOREDINA02)MEMORYANDALSOSUBTRACTEDFROMTHEOUTPUTFROMTHEPREVIOUSTRANS MITTEDPULSE4HISIMPLEMENTATIONREPRESENTSTHEMOSTBASICTWO PULSE-4)CANCELER IMPLEMENTEDASAFINITEIMPULSERESPONSE&)2 FILTER!SDISCUSSEDIN3ECTION -4) CANCELERS USED IN PRACTICAL RADARS USE HIGHER ORDER FILTERS AND THESE ARE SOMETIMES IMPLEMENTEDASINFINITEIMPULSERESPONSE))2 FILTERS 4HEOUTPUTOFTHESUBTRACTORSISAGAINABIPOLARSIGNALTHATCONTAINSMOVINGTAR GETS SYSTEMNOISE ANDASMALLAMOUNTOFCLUTTERRESIDUEIFTHECLUTTERCANCELLATION ISNOTPERFECT4HEMAGNITUDESOFTHEIN PHASEANDQUADRATURESIGNALSARETHENCOM PUTED ) 1 ANDCONVERTEDTOANALOGVIDEOINADIGITAL TO ANALOG$! CON VERTERFORDISPLAYONA00)4HEDIGITALSIGNALMAYALSOBESENTTOAUTOMATICTARGET DETECTIONCIRCUITRY4HEDYNAMICRANGEPEAKSIGNALTORMSNOISE ISLIMITEDTOABOUT D"FORA00)DISPLAY !KEYDISTINCTION SOMETIMESLOSTINTHECOMPLEXITIESOFTHESYSTEMSTHATFOLLOW IS THATAN-4)RADARSYSTEMELIMINATESFIXEDCLUTTERBECAUSETHEPHASEOFSIGNALSRETURNED FROMCONSECUTIVETRANSMITTEDPULSESDONOTAPPRECIABLY CHANGE4HEFIXEDCLUTTERIS REMOVEDAFTERASFEWASTWOTRANSMITTEDPULSESBYTHESUBTRACTIONPROCESSDESCRIBED
&)'52% "IPOLARVIDEOFROMCONSECUTIVETRANSMITTEDPULSES
Ó°È
2!$!2(!.$"//+
ABOVE EVENIFEACHTRANSMITTEDPULSEHASFREQUENCYMODULATIONOROTHERARTIFACTS AS LONGASTHEARTIFACTSAREIDENTICALPULSE TO PULSE4HEPOINTBEINGMADEHEREISTHAT-4) SYSTEMOPERATIONDOESNOTDEPENDONTHEFREQUENCYRESOLUTIONOFTARGETSFROMCLUTTER 4OPROVIDEFREQUENCYRESOLUTIONWOULDREQUIREMUCHLONGERDWELLTIMESONTARGETTHAN TWOPULSESSEPARATEDBYASINGLE02)3UCHEXTENDEDDWELLTIMESISONEOFTHEFUNDA MENTALCHARACTERISTICSOFTHEMOVINGTARGETDETECTOR -OVING 4ARGET $ETECTOR -4$ "LOCK $IAGRAM 0ROGRESS IN DIGITAL SIGNAL PROCESSINGTECHNOLOGYBYTHEMID SMADEITPRACTICALFORTHEFIRSTTIMETOIMPROVE THEPERFORMANCEOFTHECLASSICAL-4)BY IMPLEMENTINGAPARALLELBANKOF&)2FILTERS TOINCREASETHEOUTPUTSIGNAL TO CLUTTERRATIOAND REPLACINGTHE)&LIMITERUSEDIN THEPASTWITHAHIGH RESOLUTIONCLUTTERMAPFOREFFECTIVEFALSEALARMCONTROL!LTHOUGH THESE CONCEPTS HAD BEEN EXPLORED MANY YEARS EARLIER USING THE 6ELOCITY )NDICATING #OHERENT)NTEGRATOR6)#) ORTHE#OHERENT-EMORY&ILTER#-& TOIMPLEMENTA DOPPLERFILTERBANK ANDSTORAGETUBESORMAGNETICDRUMMEMORYTOIMPLEMENTCLUT TERMAPS ITWASTHEWORKATTHE-)4,INCOLN,ABORATORYTOIMPROVETHEPERFORMANCE OF AIRPORT SURVEILLANCE RADARS THAT RESULTED IN ONE OF THE FIRST WORKING EXAMPLES OF WHATHASBECOMEKNOWNASTHE-OVING4ARGET$ETECTION-4$ RADAR 4HETHEORY ANDEXPECTEDBENEFITSOFTHISAPPROACHWEREDESCRIBEDINTWOREPORTSIN WHICH PROVIDEDTHEMATHEMATICALFOUNDATIONFORTHEUNDERSTANDINGANDTHEPRACTICALIMPLE MENTATIONOFTHE-4$CONCEPT 4HEPREDICTEDSUBCLUTTERVISIBILITYIMPROVEMENTFORTHE!32 AIRPORTSURVEILLANCE RADAR WHEN THE THREE PULSE -4) PROCESSOR WAS REPLACED BY THE SECOND GENERATION -4$))PROCESSOR ISSHOWNIN&IGURE
! " #
#
&)'52% 3UBCLUTTERVISIBILITYCOMPARISONBETWEENTHREE PULSE-4)AND-4$))
-4)2!$!2
Ó°Ç
0ART OF THIS IMPROVEMENT WAS DUE TO THE USE OF DOPPLER FILTER DESIGNS UTILIZING EIGHTPULSES INSTEADOFJUSTTHREEFORTHE-4) ANDPARTWASTHERESULTOFALLOWINGA LARGERDYNAMICRANGEINTOTHE-4$PROCESSORANDRELYINGONACLUTTERMAPTOSUPPRESS RESIDUESINREGIONSWHERETHECLUTTERLEVELEXCEEDSTHEMAXIMUMCLUTTERSUPPRESSION OFTHERADAR 4HEBLOCKDIAGRAMOFTHE-4$))SIGNALPROCESSORISSHOWNIN&IGURE0ARALLEL PROCESSINGCHANNELSAREPROVIDEDFORMOVINGTARGETSTHROUGHTHETWO PULSE-4)CAN CELER AND THE SEVEN PULSE DOPPLER FILTER BANK AND FOR NONMOVING hZERO DOPPLERv TARGETSTHROUGHTHE 6ELOCITY&ILTER!HIGHRESOLUTIONCLUTTERMAPISBUILTFROMTHE h 6ELOCITY&ILTERvOUTPUT ANDTHECLUTTERMAPCONTENTISUSEDFORTHRESHOLDINGINTHE TWOPROCESSINGCHANNELS)NTHEMOVINGTARGETCHANNEL THETHRESHOLDOBTAINEDFROM THECLUTTERMAPCONTENTISSCALEDDOWNBYTHEEXPECTEDCLUTTERATTENUATION)NADDITION TOTHECLUTTERMAPTHRESHOLDING CONVENTIONALCONSTANTFALSEALARMRATETHRESHOLDING IS UTILIZED AGAINST MOVING CLUTTER RAIN AND INTERFERENCE $ETECTION OUTPUTS NAMED 0RIMITIVE4ARGET/UTPUTS AREOBTAINEDTHROUGHTHISPROCESSINGFOREACHINDIVIDUALPRO CESSED#0)&IGURESHOWSTHEADDITIONALPROCESSINGREQUIREDTOGENERATECENTROIDED 4ARGET2EPORTSANDTHEPROCESSINGOFTHESE4ARGET2EPORTSTOOBTAINTRACKOUTPUTSFOR DISPLAYTOTHEAIRTRAFFICCONTROLSYSTEM 4HE-4$RADARTRANSMITSAGROUPOF.PULSESATACONSTANTPULSEREPETITIONFRE QUENCY 02& AND AT A FIXED RADAR FREQUENCY4HIS SET OF PULSES IS USUALLY REFERRED TOASTHECOHERENTPROCESSINGINTERVAL#0) ORPULSEBATCH3OMETIMESONEORTWO ADDITIONALFILLPULSESAREADDEDTOTHE#0)INORDERTOSUPPRESSRANGE AMBIGUOUSCLUTTER RETURNS ASMIGHTOCCURDURINGPERIODSOFANOMALOUSPROPAGATION4HERETURNSRECEIVED DURINGONE#0)AREPROCESSEDINTHEBANKOF. PULSEFINITE IMPULSE RESPONSE&)2 FILTERS4HENTHERADARMAYCHANGEITS02&ANDOR2&FREQUENCYANDTRANSMITANOTHER #0)OF.PULSES3INCEMOSTSEARCHRADARSAREAMBIGUOUSINDOPPLER THEUSEOFDIFFERENT
&)'52% "LOCKDIAGRAMOF-4$))SIGNALPROCESSOR
Ó°n
2!$!2(!.$"//+
&)'52% 0ROCESSINGOF0RIMITIVE4ARGETDETECTIONSAND2ADAR4ARGET2EPORTSIN-4$))
02&SONSUCCESSIVECOHERENTDWELLSWILLCAUSETHETARGETRESPONSETOFALLATDIFFERENT FREQUENCIESOFTHEFILTERPASSBANDONTHESUCCESSIVEOPPORTUNITIESDURINGTHETIMEON TARGET THUSELIMINATINGBLINDSPEEDS %ACH DOPPLER FILTER IS DESIGNED TO RESPOND TO TARGETS IN NONOVERLAPPING PORTIONS OFTHEDOPPLERFREQUENCYBANDANDTOSUPPRESSSOURCESOFCLUTTERATALLOTHERDOPPLER FREQUENCIES4HISAPPROACHMAXIMIZESTHECOHERENTSIGNALINTEGRATIONINEACHDOPPLER FILTERANDPROVIDESCLUTTERATTENUATIONOVERALARGERRANGEOFDOPPLERFREQUENCIESTHAN ACHIEVABLE WITH A SINGLE -4) FILTER4HUS ONE OR MORE CLUTTER FILTERS MAY SUPPRESS MULTIPLECLUTTERSOURCESLOCATEDATDIFFERENTDOPPLERFREQUENCIES!NEXAMPLEOFTHE USEOFAN-4$DOPPLERFILTERBANKAGAINSTSIMULTANEOUSLANDANDWEATHERCLUTTER7X ISILLUSTRATEDIN&IGURE)TCANBESEENTHATFILTERSANDWILLPROVIDESIGNIFICANT SUPPRESSIONOFBOTHCLUTTERSOURCES 4HEOUTPUTOFEACHDOPPLERFILTERISENVELOPE DETECTEDANDPROCESSEDTHROUGHACELL AVERAGINGCONSTANTFALSEALARMRATE#! #&!2 PROCESSORTOSUPPRESSRESIDUESDUETO RANGE EXTENDEDCLUTTERTHATMAYNOTHAVEBEENFULLYSUPPRESSEDBYTHEFILTER !SWILLBEDISCUSSEDLATERINTHISCHAPTER THECONVENTIONAL-4)DETECTIONSYSTEM OFTEN RELIES ON A CAREFULLY CONTROLLED DYNAMIC RANGE IN THE )& SECTION OF THE RADAR RECEIVERTOENSURETHATCLUTTERRESIDUESATTHE-4)OUTPUTARESUPPRESSEDTOTHELEVELOF THERECEIVERNOISEORBELOW4HISLIMITEDDYNAMICRANGE HOWEVER HASTHEUNDESIRABLE EFFECTOFCAUSINGADDITIONALCLUTTERSPECTRALBROADENING ANDTHEACHIEVABLECLUTTERSUP PRESSIONISCONSEQUENTLYREDUCED
-4)2!$!2
Ó°
&)'52% 3UPPRESSIONOFMULTIPLECLUTTERSOURCESBYUSINGADOPPLERFILTERBANK
)N THE -4$ ONE OR MORE HIGH RESOLUTION CLUTTER MAPS ARE USED TO SUPPRESS THE CLUTTERRESIDUES AFTERDOPPLERFILTERING TOTHERECEIVERNOISELEVELOR ALTERNATIVELY TO RAISETHEDETECTIONTHRESHOLDABOVETHELEVELOFTHERESIDUES 4HISINTURNELIMINATES THENEEDTORESTRICTTHE)&DYNAMICRANGE WHICHCANTHENBESETTOTHEMAXIMUMVALUE SUPPORTED BY THE!$ CONVERTERS4HUS A SYSTEM CONCEPT IS OBTAINED THAT PROVIDES ACLUTTERSUPPRESSIONCAPABILITYTHATISLIMITEDONLYBYTHERADARSYSTEMSTABILITY THE DYNAMICRANGEOFTHERECEIVER PROCESSOR ANDTHESPECTRUMWIDTHOFTHERETURNSFROM CLUTTER4HECONCEPTOFAHIGH RESOLUTIONDIGITALCLUTTERMAPTOSUPPRESSCLUTTERRESIDUES ISRELATEDTOEARLIEREFFORTSTOCONSTRUCTANALOGAREA-4)SYSTEMSUSING FOREXAMPLE STORAGETUBES !LSO INCLUDED IN THE -4$ IMPLEMENTATION ARE hxAREA THRESHOLDS MAINTAINED TO CONTROL EXCESSIVE FALSE ALARMS PARTICULARLY FROM BIRD FLOCKS %ACH AREA OF ABOUT SQUARENAUTICALMILESISDIVIDEDINTOSEVERALVELOCITYREGIONS4HETHRESHOLDINEACH REGIONISADJUSTEDONEACHSCANTOACHIEVETHEDESIREDLIMITONFALSEALARMSWITHOUT RAISINGTHETHRESHOLDSOHIGHTHATSMALLAIRCRAFTAREPREVENTEDFROMBEINGPLACEDIN TRACKSTATUSv )NSUBSEQUENTSECTIONS SPECIFICASPECTSOFTHEDESIGNOFAN-4$SYSTEMWILLBE DISCUSSED4HUS 3ECTION WILL DISCUSS THE DESIGN AND PERFORMANCE OF DOPPLER FILTER BANKS AND A DETAILED DISCUSSION OF CLUTTER MAPS WILL FOLLOW IN 3ECTION 3INCETHEORIGINALWORKAT,INCOLN,ABORATORYTODEVELOPTHE-4$CONCEPT ANUMBER OF-4$SYSTEMSHAVEBEENDEVELOPEDTHATVARYINDETAILFROMTHEORIGINALCONCEPT !LSO THEUSEOFCLUTTERMAPSTOINHIBITEXCESSIVECLUTTERRESIDUE INSTEADOFCONTROL LINGCLUTTERRESIDUEWITHINTENTIONALLYRESTRICTEDDYNAMICRANGE HASBEENADOPTEDIN NEWER-4)SYSTEMS
Ó°ÎÊ 1// ,Ê / ,Ê, -*" - ÊÊ /"Ê "6 Ê/, /4HERESPONSEOFAN-4)SYSTEMTOAMOVINGTARGETVARIESASAFUNCTIONOFTHETARGETS RADIALVELOCITY&ORTHE-4)SYSTEMDESCRIBEDABOVE THERESPONSE NORMALIZEDFOR UNITY NOISE POWER GAIN IS SHOWN IN &IGURE .OTE THAT THERE IS ZERO RESPONSE TOSTATIONARYTARGETSANDALSOTOTARGETSATo o o KNOTS4HESESPEEDS KNOWN AS BLIND SPEEDS ARE WHERE THE TARGETS MOVE WAVELENGTHS BETWEEN CONSECUTIVE TRANSMITTED PULSES 4HIS RESULTS IN THE RECEIVED SIGNAL BEING
Ó°£ä
2!$!2(!.$"//+
&)'52% -4)SYSTEMRESPONSEFOR -(ZRADAROPERATINGATPPS
SHIFTEDPRECISELYORMULTIPLESTHEREOFBETWEENPULSES WHICHRESULTSINNOCHANGE INTHEPHASE DETECTOROUTPUT4HEBLINDSPEEDSCANBECALCULATED
6" K
L FR
K o
WHERE6"ISTHEBLINDSPEED INMETERSPERSECONDKISTHETRANSMITTEDWAVELENGTH IN METERSANDFRISTHE02& INHERTZ!CONVENIENTSETOFUNITSFORTHISEQUATIONIS
6" KNOTS K
FR F'(Z
K o
WHEREFRISTHE02&PULSEREPETITIONFREQUENCY INHERTZANDF'(ZISTHETRANSMITTED FREQUENCY INGIGAHERTZ.OTEFROMTHEVELOCITYRESPONSECURVETHATTHERESPONSETO TARGETSATVELOCITIESMIDWAYBETWEENTHEBLINDSPEEDSISGREATERTHANTHERESPONSEFOR ANORMALRECEIVER 4HEABSCISSAOFTHEVELOCITYRESPONSECURVECANALSOBELABELEDINTERMSOFDOPPLER FREQUENCY4HEDOPPLERFREQUENCYOFTHETARGETCANBECALCULATEDFROM
FD
62
L
WHEREFDISTHEDOPPLERFREQUENCY INHERTZ62ISTHETARGETRADIALVELOCITY INMETERS PER SECOND AND K IS THE TRANSMITTED WAVELENGTH IN METERS )T CAN BE SEEN FROM &IGURETHATTHEDOPPLERFREQUENCIESFORWHICHTHESYSTEMISBLINDOCCURATMUL TIPLESOFTHEPULSEREPETITIONFREQUENCY
Ó°{Ê 1// ,Ê , / ,-/ 4HECLUTTERSUPPRESSIONNEEDEDFROMAN-4)OR-4$RADARDEPENDSONTHECHARACTER ISTICSOFTHECLUTTERENVIRONMENT THESPECIFICRADARTARGETDETECTIONREQUIREMENTS AND THEMAJORRADARDESIGNCHARACTERISTICSSUCHASRANGEANDANGLERESOLUTIONASWELLAS OPERATINGFREQUENCY4HEABILITYOFARADARTOSUPPRESSCLUTTERISDETERMINEDBYRADAR
-4)2!$!2
Ó°££
WAVEFORMANDPROCESSING AVAILABLEDYNAMICRANGE ANDTHEOVERALLRADARSYSTEMSTA BILITY)NTHISSECTION SOMEOFTHEKEYCHARACTERISTICSOFRADARCLUTTERANDITSINFLUENCE ON-4)RADARDESIGNWILLBESUMMARIZED 3PECTRAL#HARACTERISTICS 4HESPECTRALCHARACTERISTICSOFCLUTTER ASDISCUSSEDIN MOSTREFERENCES IMPLICITLYASSUMESTHATTHERADARTRANSMITSACONTINUOUS CONSTANT02& WAVEFORM4HESPECTRUMOFTHEOUTPUTOFAPULSEDTRANSMITTERUSINGASIMPLERECTANGULAR PULSEOFLENGTHSISSHOWNIN&IGURE4HESPECTRALWIDTHOFTHESIN5 5ENVELOPE ISDETERMINEDBYTHETRANSMITTEDPULSEWIDTH THEFIRSTNULLSOCCURRINGATAFREQUENCYOF FoS4HEINDIVIDUALSPECTRALLINESARESEPARATEDBYAFREQUENCYEQUALTOTHE02& 4HESESPECTRALLINESFALLATPRECISELYTHESAMEFREQUENCIESASTHENULLSOFTHE-4)FILTER RESPONSESHOWNIN&IGURE4HUS ACANCELERWILL INTHEORY FULLYREJECTCLUTTERWITH THISIDEALLINESPECTRUM)NPRACTICE HOWEVER THESPECTRALLINESOFTHECLUTTERRETURNSARE BROADENEDBYMOTIONOFTHECLUTTERSUCHASWINDBLOWNTREESORWAVESONTHESEASURFACE ASWELLASBYTHEMOTIONOFTHEANTENNAINASCANNINGRADARORDUETOPLATFORMMOTION 4HISSPECTRALSPREADPREVENTSPERFECTCANCELLATIONOFCLUTTERINAN-4)SYSTEM /FTEN INTHEPAST THEASSUMPTIONHASBEENMADETHATTHERETURNSFROMCLUTTERHAVEA GAUSSIANPOWERSPECTRALDENSITY WHICHMAYBECHARACTERIZEDBYITSSTANDARDDEVIATION RVANDMEANVELOCITYMV BOTHINUNITSOFMS5SINGTHISGAUSSIANMODEL EACHOFTHE SPECTRALLINESIN&IGUREWILLBECONVOLVEDWITHTHESPECTRUM
3' F
¤ F M F ³
EXP ¥ S F ´µ PS F ¦
4HISSPECTRUMISNORMALIZEDTOHAVEUNITPOWER ANDTHEVELOCITYPARAMETERSHAVE BEENCONVERTEDTO(ZUSINGTHEDOPPLEREQUATION MF
MV L
S V SF L
&)'52% 0ULSETRANSMITTERSPECTRUM
Ó°£Ó
2!$!2(!.$"//+
WHEREKISTHERADARWAVELENGTH)NSTEADOFTHESTANDARDDEVIATIONS F THEPOWERSPEC TRUMCANBEDEFINEDBYITS D"WIDTH" ASFOLLOWS
3' F
¤ LN F ³ LN EXP ¥ ´µ " ¦ P "
WHERE
" LN S F S F
4HEEARLYEXPERIMENTALRESULTSTHATLEDTOTHEGENERALADOPTIONOFTHEGAUSSIANMODEL WERE OBTAINED WITH RADAR EQUIPMENT OF LIMITED STABILITY AND THE SPECTRAL SHAPE WAS SOMETIMESDERIVEDFROMVIDEOSPECTRACOMPUTEDUSINGSQUARE LAWDETECTEDRETURNS "YTHEMID S NEWEXPERIMENTALRESULTSWEREOBTAINED WHICHSHOWEDTHAT THE SPECTRUM FALL OFF WAS SLOWER THAN PREDICTED BY THE GAUSSIAN MODEL4HIS LED TO NEWMODELSBASEDONPOLYNOMIALREPRESENTATIONSOFTHESPECTRUMUSINGANEQUATION OFTHEFORM
¤P³ N SIN ¥ ´ ¦ Nµ 30/,9 F P "
¤ \ F \³ ¥ ¦ " ´µ
N
4HESPECTRUMSHAPEISDETERMINEDBYTHEINTEGERN WHICHMUSTBEORLARGERIN ORDERFORTHETWOFIRSTSPECTRALMOMENTSTOEXIST!TYPICALVALUEUSEDFORTHISSPECTRUM ISN WHICHRESULTSIN
30/,9 F
P "
¤ \ F \³ ¥ ´ ¦ " µ
4HERELATIONSHIPBETWEENTHESTANDARDDEVIATIONOFTHISSPECTRUMANDITS D"WIDTH ISGIVENBY " S F
!POTENTIALISSUEWITHTHISMODELISTHATTHESKIRTSOFTHESPECTRUMCORRESPONDTO VERYLARGERADIALVELOCITYCOMPONENTSOFTHECLUTTERINTERNALMOTION $URINGTHES ANEXTENSIVEMEASUREMENTPROGRAMCONDUCTEDATTHE-)4,INCOLN ,ABORATORY OBTAINED MORE ACCURATE DATA ON LAND CLUTTER SPECTRA USING A VERY STABLE RADAREQUIPMENTANDDATAWASCOLLECTEDUNDERWELL CONTROLLEDCONDITIONS4HESENEW RESULTSLEDTOTHEFOLLOWINGEXPONENTIALMODELFORLANDCLUTTERSPECTRA
3%80 F
LN ¤ LN ³ EXP ¥ \ F \´ " " ¦ µ
(ERETHE D"SPECTRUMWIDTHCANBEEXPRESSEDINTERMSOFTHESTANDARDDEVIATIONBY
" LN S F S F
-4)2!$!2
Ó°£Î
"ILLINGSLEY USED THE PARAMETERS G VC AND A RESPECTIVELY FOR THE GAUSSIAN THE POLYNOMIAL ANDTHEEXPONENTIALSPECTRUMMODELS)NADDITION THEEXPONENTNISNEEDED FOR THE POLYNOMIAL MODEL4HESE PARAMETERS WERE CHOSEN TO SIMPLIFY THE FUNCTIONAL DESCRIPTIONOFTHESPECTRUMSHAPE)NTERMSOFTHESTANDARDDEVIATIONOFTHESPECTRAL WIDTHINMS THESEPARAMETERSCANBEDEFINEDASFOLLOWS G
S V
VC LN S V
B
SV
GAUSSIAN SPECTRRUM
POLYNOMIAL SPECTRUM WITH N
EXPONENTIAL SPECTRUM
!SSUMINGAVALUEOFS V MS CORRESPONDINGTOWINDYCONDITION THETHREE CLUTTERSPECTRUMMODELSARECOMPAREDIN&IGURE!SNOTEDIN"ILLINGSLEYALLTHREE MODELSAREINREASONABLEAGREEMENTFORTHEUPPERnD"OFTHEIRRANGEBUTDIFFER APPRECIABLYATTHELOWERVALUESOFCLUTTERSPECTRALDENSITY %STIMATEDVALUESOFTHESPECTRALSPREADOFLANDCLUTTERFROMFORESTEDREGIONSAND FORDIFFERENTWINDSPEEDSARESHOWNIN4ABLE4HEVALUESINTHETABLEAREBASED ON"ILLINGSLEYSPARAMETERA BUTCOLUMNSHAVEBEENADDEDWITHTHECORRESPONDING RMSSPECTRALSPREADINMS!NEXAMPLEOFAMEASUREDLANDCLUTTERSPECTRUMISSHOWN IN&IGURE4HESPECTRALSHAPEPARAMETERACANBEESTIMATEDASTHESLOPEOFTHE UPPER SKIRT OF THE SPECTRUM IN D" PER MS DIVIDED BY LN 4HESE VALUES OF AWEREADDEDINTHISFIGURE
&)'52% #OMPARISONOFGAUSSIAN EXPONENTIAL ANDPOLYNOMIALSPECTRAFORANRMS SPECTRALSPREADOFRV MS
Ó°£{
2!$!2(!.$"//+
4!",% -EASURED3PECTRAL3PREADFOR$IFFERENT7IND#ONDITIONSAFTER*""ILLINGSLEY
Ú7ILLIAM!NDREW0UBLISHING)NC
7IND #ONDITIONS ,IGHTAIR "REEZY 7INDY 'ALEFORCEEST
7IND3PEED MPH n n n n
%XPONENTIALAC3HAPE 0ARAMETERAMS 4YPICAL
2-33PECTRAL 7IDTHRVMS
7ORST#ASE
4YPICAL
7ORST#ASE
4HE VALUES OF RMS SPECTRAL SPREAD OF LAND CLUTTER AS DERIVED FROM THE DATA IN "ILLINGSLEYAGREEQUITEWELLWITHPREVIOUSSTUDIES)TCANPROBABLYSAFELYBESTATED THAT THE POLYNOMIAL MODEL OF LAND CLUTTER SPECTRA IS FAR TOO PESSIMISTIC AT SPECTRAL VALUESBELOWnD"ANDSHOULDBEAVOIDEDFORRADARANALYSISREQUIRINGALARGECLUTTER ATTENUATIONVALUE 4HECASEFORTHEEXPONENTIALMODEL ASPRESENTEDBY"ILLINGSLEY ISQUITECONVINC ING AND THIS MODEL HAS BEEN WIDELY ACCEPTED AS BEING THE MOST ACCURATE FOR RADAR PERFORMANCEPREDICTIONS
$&
(* +,
#' &)" 0 0 0
#' .
(#+
* /.
#!",#*
())% * %( #,.-&+ &)'52% -EASURED SPECTRA OF CLUTTER FROM FOREST 3EVERAL WIND SPEEDSANDANESTIMATEDVALUEOFAHAVEBEENADDEDAFTER*""ILLINGSLEY Ú7ILLIAM!NDREW0UBLISHING)NC
-4)2!$!2
Ó°£x
!COMPARISONBETWEENTHEGAUSSIANANDTHEEXPONENTIALMODELSONALINEARSCALE ASSHOWNIN&IGURE INDICATESTHATTHEDIFFERENCEINSPECTRALWIDTHATEVENVERY LOWLEVELSnD" ISNOMORETHANABOUTAFACTOROF&ORMANYANALYSES THISWOULD MOSTLIKELYBEINSIGNIFICANTCOMPAREDTOTHEADDEDCLUTTERSPECTRALSPREADINGCAUSEDBY SCANNINGMODULATION4HUS INMANYCASES THESIMPLEGAUSSIANMODELCANCONTINUETO BEUSEDIN-4)AND-4$PERFORMANCEANALYSIS)NCASEOFDOUBT THESPECTRALSPREAD OFTHEGAUSSIANMODELCOULDBEDOUBLEDTOASSESSTHEAVAILABLEMARGIN .ATHANSONAND2EILLYHAVESHOWNTHATTHECLUTTERSPECTRALWIDTHOFRAINISPRI MARILYDUETOATURBULENCEANDWINDSHEARCHANGEINWINDVELOCITYWITHALTITUDE -EASUREMENTS SHOW A TYPICAL AVERAGE VALUE OF RVT MS FOR TURBULENCE AND RVS MSKM FORWINDSHEAR!CONVENIENTEQUATIONIS S VS 2 Q EL MS FORTHEEFFECTOFWINDSHEAR PROVIDEDTHERAINFILLSTHEVERTICALBEAM(ERE2ISTHE RANGE TO THE WEATHER IN NAUTICAL MILES AND Q EL IS THE ONE WAY HALF POWER VERTI CALBEAMWIDTH INDEGREES4HUS FOREXAMPLE RVSOFRAINVIEWEDATNMIWITHA VERTICALBEAMWIDTHOFWOULDBERVS MS4HETOTALSPECTRALSPREADISTHEN S V S VT S VS MS2AINANDCHAFFALSOHAVEANAVERAGEVELOC ITY INADDITIONTOTHESPECTRALSPREADNOTEDABOVE WHICHMUSTBETAKENINTOACCOUNT WHENDESIGNINGAN-4)SYSTEM 4HECLUTTERSPECTRALWIDTHINMETERSPERSECONDISINDEPENDENTOFTHERADARFREQUENCY 4HESTANDARDDEVIATIONOFTHECLUTTERPOWERSPECTRUMRF INHERTZ IS S V (Z L WHERE K IS THE TRANSMITTED WAVELENGTH IN METERS AND RV IS THE CLUTTER STANDARD DEVIATION INMETERSPERSECOND
SF
&)'52% #OMPARISONOFGAUSSIANANDEXPONENTIALSPECTRAONLINEARVELOCITYSCALE
Ó°£È
2!$!2(!.$"//+
!NTENNASCANNINGALSOCAUSESASPREADOFTHECLUTTERPOWERSPECTRUMDUETOTHE AMPLITUDEMODULATIONOFTHEECHOSIGNALSBYTHETWO WAYANTENNAPATTERN4HERESULT INGCLUTTERSTANDARDDEVIATIONIS LN FR F R (Z P N N WHEREFRISTHE02&ANDNISTHENUMBEROFHITSBETWEENTHEONE WAY D"POINTSOFTHE ANTENNAPATTERN4HISEQUATIONWASDERIVEDFROMAGAUSSIANBEAMSHAPEBUTISESSEN TIALLYINDEPENDENTOFTHEACTUALBEAMSHAPEORAPERTUREILLUMINATIONFUNCTIONUSED 4HECLUTTERSPECTRALSPREADDUETOSCANNING NORMALIZEDTOTHE02& IS
SF
S F4
N
WHERE4 02&ISTHEINTERPULSEPERIOD 4HECOMBINEDSPECTRALEFFECTSOFINTERNALCLUTTERMOTIONANDANTENNASCANNINGMODU LATIONMUSTBEOBTAINEDASTHECONVOLUTIONOFTHEINDIVIDUALSPECTRA7HENBOTHSPECTRA AREGAUSSIANINSHAPE THERESULTINGSPECTRUMREMAINSGAUSSIANWITHASTANDARDDEVIATION THATISTHESQUARE ROOTOFTHESUMOFTHESQUARESOFTHEINDIVIDUALSTANDARDDEVIATIONS "YINTEGRATINGTHETWO SIDEDTAILSOFTHEGAUSSIANANDEXPONENTIALSPECTRA OUTSIDE A MULTIPLE K OF THE STANDARD DEVIATION OF THE SPECTRA A ROUGH BUT CONSERVATIVE ESTIMATECANBEFOUNDOFHOWWIDETHE-4)NOTCHMUSTBETOACHIEVEAREQUIRED IMPROVEMENT FACTOR ) 3UCH A CURVE IS SHOWN IN &IGURE BASED ON THE CLUTTER SPECTRASHOWNIN&IGURE!LTHOUGHTHISAPPROACHWOULDONLYBESTRICTLYCORRECT FORANIDEAL-4)FILTERWITHASTEP FUNCTIONPASSBAND ITCANSERVEASAPRELIMINARY GUIDELINEFORTHE-4)FILTERDESIGN
&)'52% #LUTTERPOWERINTWO SIDEDTAILSOFSPECTRUMVSMULTIPLEOFSTANDARDDEVIATION
-4)2!$!2
Ó°£Ç
!MPLITUDE#HARACTERISTICS 4OPREDICTTHEPERFORMANCEOFAN-4)SYSTEM THE POWEROFTHECLUTTERRETURNSWITHWHICHATARGETMUSTCOMPETESHOULDBEKNOWN4HE AMPLITUDEOFTHECLUTTERRETURNSDEPENDSONTHESIZEOFTHERESOLUTIONCELLOFTHERADAR THEFREQUENCYOFTHERADAR ANDTHEREFLECTIVITYOFTHECLUTTER4HEEXPECTEDRADARCROSS SECTIONOFCLUTTERCANBEEXPRESSEDASTHEPRODUCTOFAREFLECTIVITYFACTORANDTHEVOLUME ORAREAOFTHERESOLUTIONCELL &ORSURFACECLUTTER ASVIEWEDBYASURFACE BASEDRADAR
S !C S 2 P AZ
C T S
WHERES ISTHEAVERAGERADARCROSSSECTION INSQUAREMETERS!CISTHEAREAOFCLUTTER ILLUMINATED INSQUAREMETERS2ISTHERANGETOCLUTTER INMETERSPAZISTHEONE WAY HALF POWERAZIMUTHALBEAMWIDTH INRADIANSCISTHESPEEDOFPROPAGATION MILLION MSSISTHEHALF POWERRADARPULSELENGTHAFTERTHEMATCHEDFILTER INSECONDSANDR ISTHEAVERAGECLUTTERREFLECTIVITYFACTOR INSQUAREMETERSPERSQUAREMETER &ORVOLUMETRICCLUTTER SUCHASCHAFFORRAIN THEAVERAGECROSSSECTIONIS C T H WHERE6CISTHEVOLUMEOFCLUTTERILLUMINATEDM ANDGISTHECLUTTERREFLECTIVITYFACTOR MM 4HEVOLUME6CISCOMPUTEDFROMTHEHEIGHTEXTENTOFCLUTTER(METERS THE AZIMUTHEXTENTOFTHECLUTTER2 P AZ ANDTHERADARRANGERESOLUTIONCELLS)FTHECLUTTER COMPLETELYFILLSTHEVERTICALBEAM THEN ( 2 P EL WHEREP EL ISTHEELEVATIONBEAM WIDTH2ISTHERANGETOTHECLUTTERMETERS ANDCISTHESPEEDOFPROPAGATION )TSHOULDBENOTEDTHATFORLANDCLUTTERRCANVARYCONSIDERABLYFROMONERESOLU TION CELL TO THE NEXT! TYPICAL DISTRIBUTION OF R TAKEN FROM "ARTON IS SHOWN IN &IGURE4YPICALVALUESFORRANDGFROMTHESAMEREFERENCEAREGIVENIN4ABLE !DDITIONALRESULTSFORCLUTTERREFLECTIVITYAREFOUNDIN"ILLINGSLEY
S 6C H 2 P AZ P EL (
4!",% 4YPICAL6ALUESOF#LUTTER2EFLECTIVITY
#LUTTER0ARAMETERSFOR 4YPICAL#ONDITIONS #LUTTER ,ANDEXCLUDING POINTCLUTTER
2EFLECTIVITY K M G M n L WORSTPERCENT R M
S
#ONDITIONS
3EASTATE 3EA"EAUFORTSCALE RD" +" FTWAVES +" ANGLE% SIN% D" KD" ROUGH % #HAFFFORFIXED WEIGHTPERUNIT G r K VOLUME G r RK 2AIN MATCHED R MMH FORRATERMMH POLARIZATION 0OINTCLUTTER
&ROM"ARTON
"AND K M
,
3
#
8
RD"
n
n
n
n
RM
RD"
n
n
n
n
GMn rn rn rn
n
GMn rn rn rn rn
Ó°£n
2!$!2(!.$"//+
&)'52% $ISTRIBUTIONOFREFLECTIVITYFORGROUNDCLUTTERTYPICALOFHEAVYCLUTTERAT3BAND AFTER$+"ARTONÚ)%%%
"ECAUSEOFTHEIMPRECISIONINPREDICTINGRANDG THESEEQUATIONSDONOTINCLUDE ANANTENNABEAM SHAPEFACTOR&ORTHEMEASUREMENTOFTHEREFLECTIVITYOFRAIN REFER ENCESONRADARMETEOROLOGYPRESENTMOREPRECISEEQUATIONS )N ADDITION TO DISTRIBUTED CLUTTER TARGETS THERE ARE MANY TARGETS THAT APPEAR AS POINTS SUCHASRADIOTOWERS WATERTANKS ANDBUILDINGS4HESEPOINTTARGETSTYPICALLY HAVEARADARCROSSSECTIONOFTOMWITHTYPICALDENSITIESASSHOWNLATERIN &IGURE4HISGRAPHISFROM"ILLINGSLEYANDTHEADDITIONALPOINTSINDICATEDBYAN ASTERISKAREFROM7ARD &IGUREASHOWSA00)DISPLAYOFALLCLUTTEROBSERVEDWITHASURVEILLANCERADARWITH ABY MSRESOLUTIONCELLINTHEMOUNTAINOUSREGIONOF,AKEHEAD /NTARIO #ANADA 4HE00)RANGEISSETFORNMI #LUTTERTHATEXCEEDSTHEMINIMUM DISCERNIBLESIGNAL -$3 LEVELOFTHERADARBYD"ISSHOWNIN&IGUREB
&)'52% 00)DISPLAY NMIRANGEOFA ALLCLUTTERATAMOUNTAINOUSSITEANDB CLUTTERTHATEXCEEDS THESYSTEMNOISELEVELBYD"
-4)2!$!2
Ó°£
) ' $ ,% )' $$*( )#% -"+!* "**
)&"+ #%
',&+"&* "+ #%
,)$ ) + ' "+ * )"',* ))"&.( * #%
% &)'52% 4YPICALDENSITIESOFPOINTCLUTTERSCATTERERSAFTER*""ILLINGSLEY 7ILLIAM!NDREW0UBLISHING)NC
.OTE THAT THE CLUTTER IN &IGURE B IS VERY SPOTTY IN CHARACTER INCLUDING THE STRONGFIXED POINTTARGETSANDRETURNSFROMEXTENDEDTARGETS)TISSIGNIFICANTTHATTHE EXTENDEDTARGETSARENOLONGERVERYEXTENDED4HEFACEOFAMOUNTAINATMIFROM TOOCLOCKISONLYALINE)FTHE-4)SYSTEMWEREINCAPABLEOFDISPLAYINGANAIR CRAFTWHILEITWASOVERTHEMOUNTAINFACE ITWOULDDISPLAYTHEAIRCRAFTONTHENEXTSCAN OFTHEANTENNABECAUSETHEAIRCRAFTWOULDHAVEMOVEDEITHERFARTHERORNEARER4HE 00)DOESNOTHAVEARESOLUTIONTHATAPPROACHESTHERESOLUTIONOFTHESIGNALPROCESSING CIRCUITSOFTHISRADAR4HUS THEAPPARENTEXTENDEDCLUTTERHASMANYWEAKAREASNOT VISIBLE INTHESEPHOTOGRAPHS WHERETARGETSCOULDBEDETECTEDBYVIRTUEOFAN-4) RADARSINTERCLUTTERVISIBILITYDEFINEDIN3ECTION
Ó°xÊ /" 4HE )%%% 3TANDARD 2ADAR $EFINITIONS PROVIDE USEFUL DEFINITIONS FOR MANY OF THE QUANTITIES NEEDED TO QUANTIFY -4) AND -4$ PERFORMANCE BUT IN SOME CASES THE VAGUENESSOFTHEORIGINALDEFINITIONANDTHELACKOFDISTINCTIONBETWEENPERFORMANCE AGAINSTDISTRIBUTEDCLUTTERVERSUSPOINTCLUTTERRETURNSHAVELEDTOAMBIGUOUSINTERPRE TATIONSOFSEVERALTERMS)NTHISSECTION THEMAJORDEFINITIONSWILLBEREVIEWEDAND ANNOTATEDTOATTEMPTTOCLARIFYSOMEOFTHESEPOTENTIALAMBIGUITIES&OREACHTERM THE )%%%DEFINITION WHENAVAILABLE WILLBEQUOTEDALONGWITHASUBSEQUENTDISCUSSION )MPROVEMENT&ACTOR 4HE)%%%DEFINITIONOF)MPROVEMENT&ACTORREADS MOVING TARGET INDICATION-4) IMPROVEMENTFACTOR4HESIGNAL TO CLUTTERPOWERRATIOAT THEOUTPUTOFTHECLUTTERFILTERDIVIDEDBYTHESIGNAL TO CLUTTERPOWERRATIOATTHEINPUTTOTHE CLUTTERFILTER AVERAGEDUNIFORMLYOVERALLTARGETRADIALVELOCITIESOFINTEREST3YNONYMCLUTTER IMPROVEMENTFACTOR
Ó°Óä
2!$!2(!.$"//+
4HIS DEFINITION ASSUMES THAT CLUTTER IS DISTRIBUTED HOMOGENEOUSLY ACROSS MANY RANGECELLS)NTHISCASE THEABOVEDEFINITIONISEQUALLYVALIDBEFOREANDAFTERPULSE COMPRESSION!GAINSTPOINTCLUTTERTHISDEFINITIONONLYAPPLIESAFTERPULSECOMPRESSION ANDMAYRESULTINADIFFERENTVALUEOFTHEIMPROVEMENTFACTOR4HEREALDIFFICULTYWITH THISDEFINITIONIS HOWEVER THELACKOFAPRECISEDEFINITIONOFTHEDOPPLERVELOCITYINTER VAL WHICHISTOBEUSEDFORTHEREQUIREDhUNIFORMvAVERAGING/RIGINALLY THISAVERAG INGWASASSUMEDTOINVOLVEMULTIPLE02&INTERVALSBASEDONCLASSICALLOW02&RADARS USINGASINGLE-4)FILTER)TWASFORTHISREASONTHATTHE-4))MPROVEMENT&ACTORDEFI NITION) PROVIDEDINTHENDEDITIONOFTHIS2ADAR(ANDBOOKUSEDTHENOISEGAINOF THEDOPPLER-4) FILTERASTHENORMALIZINGFACTOR4HEINCREASEDUSEOFPULSEDOPPLER FILTERBANKSINMODERNRADARHAS HOWEVER LEDTOAUSEOFTHE)%%%DEFINITIONWHERE THEAVERAGINGOFTHESIGNAL TO CLUTTERRATIOIMPROVEMENTISPERFORMEDONLYACROSSA NARROWREGIONAROUNDTHEPEAKOFTHEDOPPLERFILTERRESPONSE)NTHISCASE THECOHERENT INTEGRATIONGAINOFTHEDOPPLERFILTERISAUTOMATICALLYADDEDTOTHECONVENTIONAL-4) IMPROVEMENTFACTORVALUEANDMUCHBETTERRADARPERFORMANCEISINDICATED 3INCEADEFINITIONOFCLUTTERSUPPRESSIONISOFTENNEEDED WHICHQUANTIFIESTHEINHER ENTRADARSTABILITYLIMITATIONS APARTFROMANYADDITIONALCOHERENTGAIN ITISSOMETIMES PREFERABLETOUSETHE)%%%DEFINITIONOFCLUTTERATTENUATION)NTHISCHAPTER IMPROVEMENT FACTORANDCLUTTERATTENUATIONWILLBEUSEDSYNONYMOUSLY7HENTHECOHERENTGAINOFTHE DOPPLERFILTERISINCLUDED THETERMSIGNAL TO CLUTTERRATIOIMPROVEMENTWILLBEUSED #LUTTER!TTENUATION 4HE)%%%DEFINITIONREADS CLUTTER ATTENUATION #! )N MOVING TARGET INDICATION -4) OR DOPPLER RADAR THE RATIO OF THECLUTTER TO NOISERATIOATTHEINPUTTOTHEPROCESSOR TOTHECLUTTER TO NOISERATIOATTHEOUT PUT.OTE)N-4) ASINGLEVALUEOF#!WILLBEOBTAINED WHILEINDOPPLERRADARTHEVALUE WILLGENERALLYVARYOVERTHEDIFFERENTTARGETDOPPLERFILTERS)N-4) #!WILLBEEQUALTO-4) IMPROVEMENTFACTORIFTHETARGETSAREASSUMEDUNIFORMLYDISTRIBUTEDINVELOCITY3EEALSO-4) IMPROVEMENTFACTOR
(ERE ITWILLBEASSUMEDTHAThPROCESSORvREFERSTOTHE-4)FILTERORASINGLEDOPPLER FILTERINAPULSEDOPPLERFILTERBANK"ASEDONTHISDEFINITION THECLUTTERATTENUATIONIS GIVENBY
#!
0#). 0./54
0#/54 0.).
WHERE0#).AND0#/54ARETHECLUTTERPOWERATTHEINPUTANDOUTPUTOFTHE-4)FILTER RESPECTIVELY AND0.).AND0./54ARETHECORRESPONDINGNOISEPOWERS!SNOTEDINTHE )%%%DEFINITION THEVALUEOF#!WILLMOSTLIKELYDIFFERFROMFILTERTOFILTERINADOPPLER FILTERBANKDUETOSPECIFICCLUTTERANDFILTERRESPONSECHARACTERISTICS )NTHEDISCUSSIONABOVE THEASSUMPTIONWASIMPLICITLYMADETHATCLUTTERRETURNSARE STATIONARYANDDISTRIBUTEDINRANGE4HEABOVEDEFINITIONSWILLBEEQUALLYVALIDBEFORE ANDAFTERPULSECOMPRESSION&ORASINGLEPIECEOFPOINTCLUTTER ASOFTENUSEDINACTUAL RADARSTABILITYMEASUREMENTS THEDEFINITIONOFCLUTTERATTENUATIONWOULDHAVETOBE CHANGEDASFOLLOWSTOPROVIDEIDENTICALRESULTS CLUTTERATTENUATION#! POINTCLUTTER)NMOVING TARGETINDICATION-4) OR$OPPLERRADAR THERATIOOFTHETOTALENERGYINTHERECEIVEDPOINTCLUTTERRETURNATTHEINPUTTOTHEPROCESSOR TOTHETOTALENERGYINTHEPOINTCLUTTERRESIDUEATTHEOUTPUTOFTHEPROCESSOR MULTIPLIEDBYTHE NOISEGAINOFPROCESSOR
-4)2!$!2
Ó°Ó£
4HECLUTTERATTENUATIONAGAINSTPOINTCLUTTERBASEDONTHISDEFINITIONWILLBETHESAME BEFOREORAFTERPULSECOMPRESSIONANDWILLALSOBEIDENTICALTOTHEVALUEOF#!OBTAINED AGAINSTDISTRIBUTEDCLUTTERWITHIDENTICALSPECTRALCHARACTERISTICS &ORTHEPRACTICALMEASUREMENTOF#!AGAINSTASINGLEPIECEOFPOINTCLUTTERIE CORNERREFLECTOR THETOTALENERGYMUSTBEINTEGRATED PERTHEABOVEDEFINITION ATTHE INPUTANDOUTPUTOFEACHDOPPLERFILTER4HECALCULATIONOFTHEENERGYISBESTPERFORMED PRIORTOPULSECOMPRESSIONSINCETHEPRECISEDURATIONOFTHEUNCOMPRESSEDPULSE AND THEREFORETHEINTEGRATIONWINDOW ISACCURATELYKNOWN)FDONEAFTERPULSECOMPRES SION UNCERTAINTIESINTHEINTEGRATIONOFENERGYMAYARISEDUETOTHETRANSIENTRESPONSE OFTHEPULSECOMPRESSIONFILTER 3IGNAL TO #LUTTER2ATIO)MPROVEMENT)3#2 &ORASYSTEMEMPLOYINGMUL TIPLEDOPPLERFILTERS SUCHASTHE-4$ EACHDOPPLERFILTERWILLALSOHAVEACOHER ENTGAIN '#F WHICHATTHEFILTERPEAKHASAVALUE'# MAX4HECOHERENTGAINOF A DOPPLER FILTER IS EQUAL TO THE INCREASE IN SIGNAL TO THERMAL NOISE RATIO BETWEEN THEINPUTANDTHEOUTPUTOFTHEFILTERDUETOTHECOHERENTSUMMATIONOFINDIVIDUAL TARGETRETURNS!GAINTHESECOHERENTGAINVALUESWOULDUSUALLYDIFFERFROMFILTERTO FILTERDUETOPOTENTIALLYDIFFERENTDOPPLERFILTERCHARACTERISTICS4HESECOHERENTGAIN VALUESWILLINCLUDETHEFILTERMISMATCHLOSSBUTNOTTHESTRADDLINGLOSSESBETWEEN ADJACENTFILTERS4HEPRODUCTOFTHECLUTTERATTENUATION #!I ANDTHECOHERENTGAIN '#MAX I FORTHEITHDOPPLERFILTERBECOMESTHEDEFINITIONOFTHESIGNAL TO CLUTTERRATIO 3#2 IMPROVEMENT )3#2 I #!I '# MAX I
4HISQUANTITYWASNOTINCLUDEDINTHE)%%%$ICTIONARY BUTTHEFOLLOWINGDEFINI TIONISCOMMONLYUSED SIGNAL TO CLUTTERRATIOIMPROVEMENT)3#2 4HERATIOOFTHESIGNAL TO CLUTTERRATIOOBTAINED ATTHEOUTPUTOFTHEDOPPLERFILTERBANKTOTHESIGNAL TO CLUTTERRATIOATTHEINPUTTOTHEFILTERBANK COMPUTEDASAFUNCTIONOFTARGETDOPPLERFREQUENCY
4HIS DEFINITION DOES NOT INCLUDE ANY DOPPLER AVERAGING ACROSS THE INDIVIDUAL FILTERS ANDTHEDEFINITIONDOESNOTPROVIDEASINGLEFIGUREOFMERITFORARADARDOP PLERPROCESSORBECAUSEEACHFILTERMAYHAVEDIFFERENTVALUESOFCLUTTERATTENUATION ANDCOHERENTGAIN 3INCEEACHDOPPLERFILTERHASACOHERENTGAINTHATISAFUNCTIONOFTARGETDOPPLER AN AVERAGEVALUEOFSIGNAL TO CLUTTERIMPROVEMENTCANBEDEFINEDBYAVERAGINGALLFILTERS OVERITSRESPECTIVERANGEOFTARGETDOPPLERS
)3#2
F § F ¶ ¨¯ #! '# F DF ¯ #! '# F DF · · F ¨¨ F · F . F ¨ F. · ¨ #!. '# . F DF · ¯ ¨ · F . © ¸
4HESPECIFICFREQUENCIESCOULDLOGICALLYBECHOSENASTHECROSSOVERBETWEENINDI VIDUALDOPPLERFILTERS4HISCALCULATIONWILLNOWINCLUDETHEEFFECTOFATARGETDOPPLER
Ó°ÓÓ
2!$!2(!.$"//+
STRADDLINGLOSSANDWOULDREPRESENTASINGLEFIGURE OF MERITFORADOPPLERPROCESSOR 4OSIMPLIFYTHISCALCULATIONTHEAVERAGESIGNAL TO CLUTTERIMPROVEMENTMAYBEDEFINED ASTHEFINITESUM
)3#2
.
.
£ #!I '# MAX I
I
TOWHICHTHEDOPPLERSTRADDLINGLOSSWOULDHAVETOBEADDED 3UBCLUTTER6ISIBILITY3#6 4HE)%%%DEFINITIONOFSUBCLUTTERVISIBILITYIS 3UBCLUTTERVISIBILITY4HERATIOBYWHICHTHETARGETECHOPOWERMAYBEWEAKERTHANCOINCIDENT CLUTTERECHOPOWERANDSTILLBEDETECTEDWITHSPECIFIEDDETECTIONANDFALSE ALARMPROBABILITIES .OTE4ARGETANDCLUTTERPOWERSAREMEASUREDONASINGLEPULSERETURNANDALLTARGETVELOCITIES AREASSUMEDEQUALLYLIKELY
4HESUBCLUTTERVISIBILITY3#6 OFARADARSYSTEMISAMEASUREOFITSABILITYTODETECT MOVING TARGET SIGNALS SUPERIMPOSED ON CLUTTER SIGNALS! RADAR WITH D" 3#6 CAN DETECTANAIRCRAFTFLYINGOVERCLUTTERWHOSESIGNALRETURNISTIMESSTRONGER.OTETHAT ITISIMPLICITLYASSUMEDINTHEABOVEDEFINITIONTHATSIGNALANDCLUTTERAREBOTHOBSERVED AFTERPULSECOMPRESSION4HE3#6OFTWORADARSCANNOTNECESSARILYBEUSEDTOCOMPARE THEIRPERFORMANCEWHILEOPERATINGINTHESAMEENVIRONMENT BECAUSETHETARGET TO CLUTTER RATIOSEENBYEACHRADARISPROPORTIONALTOTHESIZEOFTHERADARRESOLUTIONCELLANDMAY BEAFUNCTIONOFFREQUENCY4HUS ARADARWITHA MSPULSELENGTHANDABEAMWIDTH WOULDNEEDD"MORESUBCLUTTERVISIBILITYTHANARADARWITHA MSPULSEANDA BEAMWIDTHFOREQUALPERFORMANCEINADISTRIBUTEDCLUTTERENVIRONMENT 4HE SUBCLUTTER VISIBILITY OF A RADAR WHEN EXPRESSED IN DECIBELS IS LESS THAN THE IMPROVEMENTFACTORBYTHECLUTTERVISIBILITYFACTOR6OCSEEDEFINITIONBELOW )NTERCLUTTER6ISIBILITY)#6 4HE)%%%DEFINITIONIS INTERCLUTTERVISIBILITY4HEABILITYOFARADARTODETECTMOVINGTARGETSTHATOCCURINRESOLUTION CELLSAMONGPATCHESOFSTRONGCLUTTERUSUALLYAPPLIEDTOMOVINGTARGETINDICATION-4) OR PULSED $OPPLERRADARS.OTE4HEHIGHERTHERADARRANGEANDORANGLERESOLUTION THEBETTERTHE INTERCLUTTERVISIBILITY
4HEINTERCLUTTERVISIBILITY)#6 OFARADARISAMEASUREOFITSCAPABILITYTODETECT TARGETSBETWEENPOINTSOFSTRONGCLUTTERBYVIRTUEOFTHEABILITYOFTHERADARTORESOLVE THE AREAS OF STRONG AND WEAK CLUTTER! RADAR WITH HIGH RESOLUTION MAKES AVAILABLE REGIONSBETWEENPOINTSOFSTRONGCLUTTERWHERETHETARGET TO CLUTTERRATIOWILLBESUF FICIENTFORTARGETDETECTIONEVENTHOUGHTHE3#6OFTHERADARBASEDONAVERAGECLUTTER MAY BE RELATIVELY LOW4O ACHIEVE )#6 A MECHANISM MUST BE FURNISHED TO PROVIDE #&!2 OPERATION AGAINST THE RESIDUE FROM STRONG CLUTTER4HIS #&!2 IS PROVIDED IN OLDER-4)SYSTEMBY)&LIMITINGAND INTHE-4$IMPLEMENTATION THROUGHTHEUSEOF HIGH RESOLUTIONCLUTTERMAPS!QUANTITATIVEDEFINITIONOFINTERCLUTTERVISIBILITYHASNOT YETBEENFORMULATED &ILTER-ISMATCH,OSS 4HE)%%%DEFINITIONIS FILTERMISMATCHLOSS4HELOSSINOUTPUTSIGNAL TO NOISERATIOOFAFILTERRELATIVETOTHESIGNAL TO NOISERATIOFROMAMATCHEDFILTER
-4)2!$!2
Ó°ÓÎ
4HE MAXIMUM SIGNAL TO NOISE RATIO AVAILABLE FROM AN . PULSE FILTER IS . TIMES THE SIGNAL TO NOISE RATIO OF A SINGLE PULSE ASSUMING ALL PULSES HAVE EQUAL AMPLI TUDE7HENWEIGHTINGISAPPLIEDTOREJECTCLUTTERANDCONTROLTHEFILTERSIDELOBES THE PEAKOUTPUTSIGNAL TO NOISERATIOISREDUCED4HEFILTERMISMATCHLOSSISTHEAMOUNT BYWHICHTHEPEAK OUTPUTSIGNAL TO NOISERATIOISREDUCEDBYTHEUSEOFWEIGHTING !THREE PULSE-4)FILTERUSINGBINOMIALWEIGHTSHASAFILTERMISMATCHLOSSOFD" 4HEMISMATCHLOSSFORTHEBINOMIAL WEIGHTEDFOUR PULSECANCELERISD" #LUTTER6ISIBILITY&ACTOR6OC 4HE)%%%DEFINITIONIS CLUTTER DETECTABILITY FACTOR 4HE PREDETECTION SIGNAL TO CLUTTER RATIO THAT PROVIDES STATED PROBABILITYOFDETECTIONFORAGIVENFALSEALARMPROBABILITYINANAUTOMATICDETECTIONCIRCUIT .OTE)N-4)SYSTEMS ITISTHERATIOAFTERCANCELLATIONORDOPPLERFILTERING
4HECLUTTERVISIBILITYFACTORISTHERATIOBYWHICHTHETARGETSIGNALMUSTEXCEEDTHE CLUTTER RESIDUE SO THAT TARGET DETECTION CAN OCCUR WITHOUT HAVING THE CLUTTER RESIDUE RESULTINFALSE TARGETDETECTIONS4HESYSTEMMUSTPROVIDEATHRESHOLDTHATTHETARGETS WILLCROSSANDTHECLUTTERRESIDUEWILLNOTCROSS
Ó°ÈÊ *,"6 /Ê /",Ê 1 /" 5SING "ARTONS APPROACH THE MAXIMUM IMPROVEMENT FACTOR ) AGAINST ZERO MEAN CLUTTERWITHAGAUSSIAN SHAPEDSPECTRUMFORDIFFERENTIMPLEMENTATIONSOFTHEFINITE IMPULSE RESPONSEBINOMIAL WEIGHT-4)CANCELERSEE3ECTION IS
¤ F ³ ) y ¥ R ´ ¦ PS F µ
¤ F ³ ) y ¥ R ´ ¦ PS F µ
) y
¤ FR ³ ¥¦ PS F ´µ
WHERE)ISTHE-4)IMPROVEMENTFACTORFORTHESINGLE DELAYCOHERENTCANCELER)ISTHE -4)IMPROVEMENTFACTORFORTHEDUAL DELAYCOHERENTCANCELER)ISTHE-4)IMPROVE MENTFACTORFORTHETRIPLE DELAYCOHERENTCANCELERRFISTHERMSFREQUENCYSPREADOF THEGAUSSIANCLUTTERPOWERSPECTRUM INHERTZANDFRISTHERADARREPETITIONFREQUENCY INHERTZ7HENTHEVALUESOFRFFORSCANNINGMODULATIONIN%QARESUBSTITUTEDIN THEABOVEEQUATIONSFOR) THELIMITATIONON)DUETOSCANNINGIS
N N ) y N ) y ) y
Ó°Ó{
2!$!2(!.$"//+
&)'52% 4HEORETICAL-4)IMPROVEMENTFACTORDUETOSCANMODULATIONGAUSSIANANTENNAPATTERNN NUMBEROFPULSESWITHINTHEONE WAYHALF POWERBEAMWIDTH
4HESERELATIONSHIPSARESHOWNGRAPHICALLYIN&IGURE4HISDERIVATIONASSUMESA LINEARSYSTEM4HATIS ITISASSUMEDTHATTHEVOLTAGEENVELOPEOFTHEECHOSIGNALS ASTHE ANTENNASCANSPASTAPOINTTARGET ISIDENTICALTOTHETWO WAYANTENNAVOLTAGEPATTERN 4HISASSUMPTIONOFALINEARSYSTEMMAYBEUNREALISTICFORSOMEPRACTICAL-4)SYSTEMS WITHRELATIVELYFEWHITSPERBEAMWIDTH HOWEVER ASDISCUSSEDIN3ECTION 4HE SCANNING LIMITATION DOES NOT APPLY TO A SYSTEM THAT CAN STEP SCAN SUCH AS APHASEDARRAY.OTE HOWEVER THATSUFFICIENTPULSESMUSTBETRANSMITTEDTOINITIAL IZETHEFILTERBEFOREUSEFULOUTPUTSMAYBEOBTAINED&OREXAMPLE WITHATHREE PULSE BINOMIAL WEIGHTCANCELER THEFIRSTTWOTRANSMITTEDPULSESINITIALIZETHECANCELER ANDA USEFULOUTPUTISNOTAVAILABLEUNTILAFTERTHETHIRDPULSEHASBEENTRANSMITTED&EEDBACK ORINFINITEIMPULSERESPONSE))2 FILTERSWOULDNOTBEUSEDWITHASTEP SCANSYSTEM BECAUSEOFTHELONGTRANSIENTSETTLINGTIMEOFTHEFILTERS 4HELIMITATIONON)DUETOINTERNAL CLUTTERFLUCTUATIONSCANBEDETERMINEDBYSUB STITUTING THE APPROPRIATE VALUE OF RF INTO %QS TO "Y LETTING RF RVK WHERERVISTHERMSVELOCITYSPREADOFTHECLUTTER THELIMITATIONON)CANBEPLOTTED FORDIFFERENTTYPESOFCLUTTERASAFUNCTIONOFTHEWAVELENGTHKANDTHEPULSEREPETITION FREQUENCYFR4HISISDONEFORONE TWO ANDTHREE DELAYBINOMIAL WEIGHTCANCELERS IN&IGURE &IGURE AND&IGURE4HEVALUESOF6"GIVENARETHEFIRSTBLIND SPEEDOFTHERADARORWHERETHEFIRSTBLINDSPEED6"WOULDBEFORASTAGGERED02& SYSTEMIFSTAGGERINGWERENOTUSED 4HEIMPROVEMENTFACTORSHOWNINTHESEFIGURES FORRAINANDCHAFFISBASEDONTHEASSUMPTIONTHATTHEAVERAGEVELOCITYOFTHERAIN ANDCHAFFHASBEENCOMPENSATEDFORSOTHATTHERETURNSARECENTEREDINTHECANCELER REJECTIONNOTCH5NLESSSUCHCOMPENSATIONISPROVIDED THE-4)OFFERSLITTLEORNO IMPROVEMENTFORRAINANDCHAFF 4WOFURTHERLIMITATIONSON)ARETHEEFFECTOFPULSE TO PULSEREPETITION PERIODSTAG GERINGCOMBINEDWITHCLUTTERSPECTRALSPREADFROMSCANNINGANDINTERNAL CLUTTERMOTION
-4)2!$!2
Ó°Óx
&)'52% -4) IMPROVEMENT FACTOR AS A FUNCTION OF THE RMS VELOCITY SPREAD OF CLUTTER FOR ATWO PULSEBINOMIAL WEIGHTCANCELER
4HESELIMITATIONS PLOTTEDIN&IGUREAND&IGURE APPLYTOALLCANCELERS WHETHER SINGLEORMULTIPLE4HEDERIVATIONOFTHESELIMITATIONSANDAMEANSOFAVOIDINGTHEM BY THE USE OF TIME VARYING WEIGHTS ARE GIVEN IN h3TAGGER $ESIGN 0ROCEDURESv IN 3ECTION
Ó°ÇÊ "*/ 1 Ê - Ê"Ê 1// ,Ê / ,4HESTATISTICALTHEORYOFDETECTIONOFSIGNALSINGAUSSIANNOISEPROVIDESTHEREQUIRED FRAMEWORKFORTHEOPTIMUMDESIGNOFRADARCLUTTERFILTERS3UCHTHEORETICALRESULTS AREIMPORTANTTOTHEDESIGNEROFAPRACTICAL-4)OR-4$SYSTEM INTHATTHEYESTAB LISH UPPER BOUNDS ON THE ACHIEVABLE PERFORMANCE IN A PRECISELY SPECIFIED CLUTTER ENVIRONMENT)TSHOULDBENOTED HOWEVER THATOWINGTOTHEEXTREMEVARIABILITYOF THECHARACTERISTICSOFREALCLUTTERRETURNSPOWERLEVEL DOPPLERSHIFT SPECTRUMSHAPE SPECTRALWIDTH ETC ANYATTEMPTTOACTUALLYAPPROXIMATETHEPERFORMANCEOFSUCH OPTIMUM FILTERS FOR THE DETECTION OF TARGETS IN CLUTTER REQUIRES THE USE OF ADAPTIVE METHODS 4HE ADAPTIVE METHODS MUST ESTIMATE THE UNKNOWN CLUTTER STATISTICS AND
Ó°ÓÈ
2!$!2(!.$"//+
&)'52% -4)IMPROVEMENTFACTORASAFUNCTIONOFTHERMSVELOCITYSPREADOFCLUTTERFOR ATHREE PULSEBINOMIAL WEIGHTCANCELER
SUBSEQUENTLYIMPLEMENTTHECORRESPONDINGOPTIMUMFILTER!NEXAMPLEOFSUCHAN ADAPTIVE-4)SYSTEMISDISCUSSEDIN3ECTION &ORASINGLERADARPULSEWITHADURATIONOFAFEWMICROSECONDS THEDOPPLERSHIFT DUETOAIRCRAFTTARGETMOTIONISASMALLFRACTIONOFTHESIGNALBANDWIDTH ANDCONVEN TIONAL-4)ANDPULSEDOPPLERPROCESSINGARENOTAPPLICABLE)TISWELLKNOWNTHATTHE CLASSICALSINGLE PULSEhMATCHEDvFILTERPROVIDESOPTIMUMRADARDETECTIONPERFORMANCE WHENUSEDINAWHITE NOISEBACKGROUND!GAINSTCLUTTERRETURNSTHATHAVETHESAME SPECTRUMASTHETRANSMITTEDRADARPULSE THEMATCHEDFILTERISNOLONGEROPTIMUM BUT THEPOTENTIALIMPROVEMENTINTHEOUTPUTSIGNAL TO CLUTTERRATIOBYDESIGNINGAMODIFIED OPTIMIZEDFILTERISUSUALLYINSIGNIFICANT 7HENTHEDURATIONOFTHETRANSMITTEDRADARSIGNAL WHETHER#7ORAREPETITIVETRAIN OF.IDENTICALPULSES ISCOMPARABLEWITHORGREATERTHANTHERECIPROCALOFANTICIPATED TARGETDOPPLERSHIFTS THEDIFFERENCEBETWEENACONVENTIONALWHITE NOISEMATCHEDFIL TERORCOHERENTINTEGRATOR ANDAFILTEROPTIMIZEDTOREJECTTHEACCOMPANYINGCLUTTER BECOMESSIGNIFICANT4HECHARACTERISTICSOFTHECLUTTERARECHARACTERIZEDBYTHECOVARI ANCEMATRIX&#OFTHE.CLUTTERRETURNS)FTHEPOWERSPECTRUMOFTHECLUTTERISDENOTED
-4)2!$!2
Ó°ÓÇ
&)'52% -4) IMPROVEMENT FACTOR AS A FUNCTION OF THE RMS VELOCITY SPREAD OF CLUTTER FOR AFOUR PULSEBINOMIAL WEIGHTCANCELER
3#F ANDTHECORRESPONDINGAUTOCORRELATIONFUNCTIONIS2#TInTJ THENTHEELEMENTS OF&#AREGIVENBY
& IJ 2# TI T J
WHERETIISTHETRANSMISSIONTIMEOFTHEITHPULSE&OREXAMPLE FORAGAUSSIAN SHAPED CLUTTERSPECTRUMWEHAVE
3# F 0#
§ F FD ¶ EXP ¨ · P S F ¨© S F ·¸
WHERE0#ISTHETOTALCLUTTERPOWER RFISTHESTANDARDDEVIATIONOFTHECLUTTERSPECTRAL WIDTH ANDFDISTHEAVERAGEDOPPLERSHIFTOFTHECLUTTER4HECORRESPONDINGAUTOCOR RELATIONFUNCTIONIS
2# T 0# EXP PS F T EXP J P FDT
WHERESISTHESEPARATIONINTIMEOFTWOCONSECUTIVECLUTTERRETURNS
Ó°Ón
2!$!2(!.$"//+
&)'52% !PPROXIMATE-4)IMPROVEMENTFACTORLIMITATIONDUETOPULSE TO PULSEREPETITION PERIOD STAGGERINGANDSCANNINGALLCANCELERFIGURATIONS )D" LOG;NF =F MAXIMUMPERIOD MINIMUMPERIOD
&ORTWOPULSESSEPARATEDINTIMEBYTHEINTERPULSEPERIOD4 THECOMPLEXCORRELATION COEFFICIENTBETWEENTWOCLUTTERRETURNSIS
R4 EXP PS F 4 EXP J P FD4
4HESECONDFACTORINTHISEXPRESSIONREPRESENTSTHEPHASESHIFTCAUSEDBYTHEDOPPLER SHIFTOFTHECLUTTERRETURNS &ORAKNOWNTARGETDOPPLERSHIFT THERECEIVEDTARGETRETURNCANBEREPRESENTEDBY AN. DIMENSIONALVECTOR
S !3 F
WHERE!3ISTHESIGNALAMPLITUDEANDTHEELEMENTSOFTHEVECTORFAREFI EXP;JOFSTI= /NTHEBASISOFTHISDESCRIPTIONOFSIGNALANDCLUTTER ITHASBEENSHOWNTHATTHEOPTI MUMDOPPLERFILTERWILLHAVEWEIGHTSGIVENBY
W /04 & # S
-4)2!$!2
Ó°Ó
&)'52% !PPROXIMATE-4)IMPROVEMENTFACTORLIMITATIONDUETOPULSE TO PULSESTAGGERING AND INTERNAL CLUTTER MOTION ALL CANCELER CONFIGURATIONS )D" LOG ;K FFRRV = F MAXIMUMPERIODMINIMUMPERIOD
ANDTHECORRESPONDINGSIGNAL TO CLUTTERIMPROVEMENTIS
)3#2
W4OPT S S4 W OPT
W4OPT & # W OPT
WHERETHEASTERISKDENOTESCOMPLEXCONJUGATIONANDSUPERSCRIPT4ISTHETRANSPOSITION OPERATOR!NEXAMPLEWHERETHEOPTIMUMPERFORMANCEISDETERMINEDFORTHECASEOF CLUTTERATZERODOPPLERHAVINGAGAUSSIAN SHAPEDSPECTRUMWITHANORMALIZEDWIDTH OFRF4 ISSHOWNIN&IGURE)NTHISCASE ACOHERENTPROCESSINGINTERVALOF #0) NINEPULSESWASASSUMED ANDTHELIMITATIONDUETOTHERMALNOISEWASIGNORED BYSETTINGTHECLUTTERLEVELATD"ABOVENOISE )TSHOULDBEKEPTINMINDTHAT%QFORTHEOPTIMUMWEIGHTSWILLYIELDADIF FERENTRESULTFOREACHDIFFERENTTARGETDOPPLERSHIFT SOTHATALARGENUMBEROFPARALLEL FILTERSWOULDBENEEDEDTOAPPROXIMATETHEOPTIMUMPERFORMANCEEVENWHENTHECLUTTER CHARACTERISTICSAREKNOWNEXACTLY!SANEXAMPLE THERESPONSEOFTHEOPTIMUMFILTER DESIGNEDFORONEPARTICULARTARGETDOPPLERFREQUENCYLABELEDASPOINT!IN&IGURE ISSHOWNINABROKENLINE!TAPPROXIMATELYoFROMTHEDESIGNDOPPLER THEPERFOR MANCESTARTSTOFALLSIGNIFICANTLYBELOWTHEOPTIMUM
Ó°Îä
2!$!2(!.$"//+
&)'52% /PTIMUM SIGNAL TO CLUTTER RATIO IMPROVEMENT )3#2 FOR GAUSSIAN SHAPED CLUTTER SPECTRUMANDA#0)OFNINEPULSESCLUTTER TO NOISERATIO D"
!LSO SHOWN IN &IGURE IS A HORIZONTAL LINE LABELED hAVERAGE 3#2 IMPROVE MENTv 4HIS INDICATES THE LEVEL CORRESPONDING TO THE AVERAGE OF THE OPTIMUM 3#2 CURVEACROSSONEDOPPLERINTERVALANDMAYBECONSIDEREDASAFIGUREOFMERITFORA MULTIPLE FILTERDOPPLERPROCESSOR SOMEWHATANALOGOUSTOTHE-4)IMPROVEMENTFAC TORDEFINEDFORASINGLEDOPPLERFILTER)N&IGURE THEOPTIMUMAVERAGE)3#2HAS BEENCOMPUTEDFORSEVERALDIFFERENTVALUESOFTHE#0)ASAFUNCTIONOFTHENORMALIZED SPECTRUMWIDTH4HESERESULTSMAYBEUSEDASAPOINTOFREFERENCEFORPRACTICALDOPPLER
&)'52% 2EFERENCE CURVE OF OPTIMUM AVERAGE 3#2 IMPROVEMENT FOR AGAUSSIAN SHAPEDCLUTTERSPECTRUM
-4)2!$!2
ӰΣ
PROCESSORDESIGNSASDISCUSSEDIN3ECTION.OTETHATFORRF4yTHEAVERAGE3#2 IMPROVEMENTISDUEONLYTOTHECOHERENTINTEGRATIONOFALLTHEPULSESINTHE#0) !N-4)FILTERCANALSOBEDESIGNEDBASEDONTHECRITERIONOFMAXIMIZINGTHESIGNAL TO CLUTTERIMPROVEMENTATASPECIFICTARGETDOPPLER(OWEVER SUCHADESIGNWILLUSUALLY PROVIDESUBOPTIMUMPERFORMANCEATALLOTHERTARGETDOPPLERS4HESINGLEEXCEPTIONISTHE TWO PULSE-4)CANCELER WHICHPROVIDESOPTIMUMPERFORMANCEFORALLTARGETDOPPLERS ! MORE ATTRACTIVE APPROACH FOR DESIGNING AN OPTIMUM -4) FILTER IS TO MAXIMIZE ITSIMPROVEMENTFACTORORCLUTTERATTENUATION 4ODESIGNANOPTIMUM-4)FILTERUSING IMPROVEMENTFACTORASTHECRITERION THECOVARIANCEMATRIXOFTHECLUTTERRETURNS ASGIVEN BY%Q ISAGAINTHESTARTINGPOINT!SSHOWNBY#APON THEWEIGHTSOFTHEOPTI MUM-4)FILTERAREFOUNDASTHEEIGENVECTORCORRESPONDINGTOTHESMALLESTEIGENVALUE OFTHECLUTTERCOVARIANCEMATRIXANDTHE-4)IMPROVEMENTFACTORISEQUALTOTHEINVERSE OFTHESMALLESTEIGENVALUE4HEOPTIMUMIMPROVEMENTFACTORFORTHETHREEMODELSFOR THESPECTRUMOFLANDCLUTTERINTRODUCEDIN3ECTIONHAVEBEENCOMPUTEDBASEDONTHIS ABOVEAPPROACH &ORTHEGAUSSIANCLUTTERSPECTRUM THEOPTIMUMIMPROVEMENTFACTORISSHOWNIN &IGUREASAFUNCTIONOFTHERMSRELATIVESPECTRUMWIDTH ASSUMINGZEROMEANFOR THESPECTRUM#ALCULATIONSARESHOWNFOR-4)CANCELERSOFORDER. THROUGH &ORTHEPOLYNOMIALCLUTTERSPECTRUM THEOPTIMUMIMPROVEMENTFACTORISSHOWNIN &IGURE AGAINASAFUNCTIONOFTHE2-3RELATIVESPECTRUMWIDTHASSUMINGZERO MEANFORTHESPECTRUM &INALLY FORTHEEXPONENTIALCLUTTERSPECTRUMMODEL THEOPTIMUMIMPROVEMENTFAC TORISSHOWNIN&IGURE AGAINASAFUNCTIONOFTHE2-3RELATIVESPECTRUMWIDTH ASSUMINGZEROMEANFORTHESPECTRUM
&)'52% /PTIMUMIMPROVEMENTFACTORFORGAUSSIANSPECTRUMMODEL
Ó°ÎÓ
2!$!2(!.$"//+
&)'52% /PTIMUMIMPROVEMENTFACTORFORPOLYNOMIALCLUTTERSPECTRUMMODEL
&)'52% /PTIMUMIMPROVEMENTFACTORFOR"ILLINGSLEYSEXPONENTIALSPECTRUMMODEL
-4)2!$!2
Ó°ÎÎ
&)'52% #OMPARISONOF-4)IMPROVEMENTFACTOROFBINOMIAL WEIGHT -4)ANDOPTIMUM-4)AGAINSTAGAUSSIAN SHAPEDCLUTTERSPECTRUM
)N &IGURE THE IMPROVEMENT FACTOR OF AN -4) USING THE OPTIMUM WEIGHTS IS COMPARED WITH THE BINOMIAL COEFFICIENT -4) FOR DIFFERENT VALUES OF THE RELATIVE CLUTTERSPECTRALSPREADANDSHOWNASAFUNCTIONOFTHENUMBEROFPULSESINTHE#0) 4HESERESULTSAGAINASSUMEAGAUSSIAN SHAPEDCLUTTERSPECTRUM&ORTYPICALNUMBERS OFPULSESINTHE-4)THREETOFIVE THEBINOMIALCOEFFICIENTSAREREMARKABLYROBUST ANDPROVIDEAPERFORMANCEWHICHISWITHINAFEWDECIBELSOFTHEOPTIMUM!GAIN IT SHOULDBENOTEDTHATANYATTEMPTTOIMPLEMENTAN-4)CANCELER WHICHPERFORMSCLOSE TOTHEOPTIMUM WOULDREQUIRETHEUSEOFADAPTIVETECHNIQUESTHATESTIMATETHECLUTTER CHARACTERISTICSINREALTIME)FTHEESTIMATEISINERROR THEACTUALPERFORMANCEMAYFALL BELOWTHATOFTHEBINOMIAL WEIGHT-4)CANCELER
Ó°nÊ /Ê 1// ,Ê / ,Ê - 4HE-4)BLOCKDIAGRAMSINTRODUCEDBY&IGURESANDANDWHOSERESPONSEWAS DISCUSSEDINDETAILIN3ECTION CONSIDEREDASINGLE DELAY CANCELER)TISPOSSIBLE TOUTILIZEMORETHANONEDELAYANDTOINTRODUCEFEEDBACKANDORFEEDFORWARDPATHS AROUNDTHEDELAYSTOCHANGETHE-4)SYSTEMRESPONSETOTARGETSOFDIFFERENTVELOCITIES &ILTERSWITHONLYFEEDFORWARDPATHSARECALLEDFINITEIMPULSERESPONSE&)2 FILTERS ANDFILTERSTHATINCORPORATEFEEDBACKARECALLEDINFINITEIMPULSERESPONSE))2 FILTERS ORRECURSIVEFILTERS-ULTIPLE DELAYCANCELERSHAVEWIDERCLUTTERREJECTIONNOTCHESTHAN SINGLE DELAYCANCELERS4HEWIDERREJECTIONNOTCHENCOMPASSESMOREOFTHECLUTTER SPECTRUM AND THUS INCREASES THE -4) IMPROVEMENT FACTOR ATTAINABLE WITH A GIVEN CLUTTERSPECTRALDISTRIBUTION
$ELAYISUSEDHERETOREPRESENTANINTERPULSEMEMORYFORAN-4)FILTER!N&)2FILTERWITHONEDELAYISATWO PULSE FILTER&ORFEEDBACK))2 FILTERS ITISINAPPROPRIATETOCALLTHEMTWO PULSEORTHREE PULSE ETC FILTERSBECAUSETHEY REQUIREANUMBEROFPULSESTOREACHSTEADY STATE
Ó°Î{
2!$!2(!.$"//+
&)'52% $IRECT&ORMORCANONICALFORMOFANY-4)FILTERDESIGN
!GENERALBLOCKDIAGRAMMODELAPPLICABLETOANY-4)FILTERISSHOWNIN&IGURE 4HISMODELHASBEENDENOTEDTHEh$IRECT&ORM vORTHECANONICALFORM INTHETERMINOL OGYSURVEYPRESENTEDIN2ABINERETAL )TCANBESHOWNTHATAN-4)FILTERASSHOWNIN&IGURECANBEDIVIDEDINTOA CASCADEOFSECONDORDERSECTIONSASSHOWNIN&IGURE 7HEN A NUMBER OF SINGLE DELAY FEEDFORWARD CANCELERS ARE CASCADED IN SERIES THEOVERALLFILTERVOLTAGERESPONSEISKNSINNOFD4 WHEREKISTHETARGETAMPLITUDE NISTHENUMBEROFDELAYS FDISTHEDOPPLERFREQUENCY AND4ISTHEINTERPULSEPERIOD 4HECASCADEDSINGLE DELAYCANCELERSCANBEREARRANGEDASATRANSVERSALFILTER ANDTHE WEIGHTSFOREACHPULSEARETHEBINOMIALCOEFFICIENTSWITHALTERNATINGSIGN FOR TWOPULSES FORTHREEPULSES FORFOURPULSES ANDSOON#HANGES OFTHEBINOMIALFEEDFORWARDCOEFFICIENTSANDORTHEADDITIONOFFEEDBACKMODIFYTHE
&)'52% -4)SHOWNASCASCADEDFORMOFSECONDORDERSECTIONA ISFOREVENORDERANDB ISFOR ODDORDERWITHFIRSTORDERSECTIONATEND
-4)2!$!2
Ó°Îx
&)'52% .THORDER&)2-4)CANCELERBLOCKDIAGRAM
FILTERCHARACTERISTICS7ITHINTHISCHAPTER REFERENCETOBINOMIAL WEIGHTCANCELERSREFERS TOCANCELERSWITHTHENSINNOFD4 TRANSFERFUNCTION4HEBLOCKDIAGRAMOFTHISTYPEOF -4)CANCELERISSHOWNIN&IGURE &IGURETO&IGUREREPRESENTTYPICALVELOCITYRESPONSECURVESOBTAINABLEFROM ONE TWO ANDTHREE DELAYCANCELERS3HOWNALSOARETHECANCELERCONFIGURATIONSASSUMED WITHCORRESPONDING: PLANEPOLE ZERODIAGRAMS4HE:PLANEISTHECOMB FILTEREQUIVALENT OFTHE3PLANEWITHTHELEFT HANDSIDEOFTHE3PLANETRANSFORMEDTOTHEINSIDEOFTHEUNIT CIRCLECENTEREDAT: :EROFREQUENCYISAT: J4HESTABILITYREQUIREMENTISTHAT THEPOLESOFTHE:TRANSFERFUNCTIONLIEWITHINTHEUNITCIRCLE:EROSMAYBEANYWHERE
&)'52% /NE DELAYCANCELER
Ó°ÎÈ
2!$!2(!.$"//+
&)'52% 4WO DELAYCANCELER
4HESE VELOCITY RESPONSE CURVES ARE CALCULATED FOR A SCANNING RADAR SYSTEM WITH HITSPERONE WAY D"BEAMWIDTH!NANTENNABEAMSHAPEOFSIN5 5 TERMI NATEDATTHEFIRSTNULLS WASASSUMED4HESHAPEOFTHESECURVES EXCEPTVERYNEARTHE BLINDSPEEDS ISESSENTIALLYINDEPENDENTOFTHENUMBEROFHITSPERBEAMWIDTHORTHE ASSUMEDBEAMSHAPE 4HEORDINATELABELEDhRESPONSEvREPRESENTSTHESINGLE PULSESIGNAL TO NOISEOUTPUT OFTHE-4)RECEIVERRELATIVETOTHESIGNAL TO NOISERESPONSEOFANORMALLINEARRECEIVER FORTHESAMETARGET4HUS ALLTHERESPONSECURVESARENORMALIZEDWITHRESPECTTOTHE NOISEPOWERGAINFORTHEGIVENCANCELERCONFIGURATION4HEINTERSECTIONATTHEORDINATE REPRESENTS THE NEGATIVE DECIBEL VALUE OF ) THE -4) IMPROVEMENT FACTOR FOR A POINT CLUTTERTARGETPROCESSEDINALINEARSYSTEM
-4)2!$!2
Ó°ÎÇ
&)'52% 4HREE DELAYCANCELER
"ECAUSETHESECURVESSHOWTHESIGNAL TO NOISERESPONSEFOREACHOUTPUTPULSEFROM THE-4)CANCELER THEINHERENTLOSSINCURREDINASCANNINGRADARWITH-4)PROCESSING DUETOTHEREDUCTIONOFTHEEFFECTIVENUMBEROFINDEPENDENTPULSESINTEGRATEDISNOT APPARENT4HISLOSSISD"FORA PULSECANCELERANDD"FORA PULSECANCELER ASSUMINGALARGENUMBEROFPULSES)FQUADRATURE-4)CHANNELSSEE3ECTION ARE NOTEMPLOYED THEREISANADDITIONALLOSSOF TOD" 4HEABSCISSAOFTHESECURVES 66" REPRESENTSTHERATIOOFTARGETVELOCITY6TOTHE BLINDSPEED6" KFR WHEREKISTHERADARWAVELENGTHANDFRISTHEAVERAGE02&OF THERADAR4HEABSCISSACANALSOBEINTERPRETEDASTHERATIOOFTHETARGETDOPPLERFRE QUENCYTOTHEAVERAGE02&OFTHERADAR 4HECANCELERCONFIGURATIONSSHOWNARENOTTHEMOSTGENERALFEEDFORWARD FEEDBACK NETWORKSPOSSIBLE0AIRSOFDELAYSAREREQUIREDTOLOCATEZEROSANDPOLESELSEWHERE
Ó°În
2!$!2(!.$"//+
THANONTHEREALAXISOFTHE: PLANE)NTHECONFIGURATIONSSHOWN THEZEROSARECON STRAINEDTOTHEUNITCIRCLE4OMOVETHEZEROSOFFOFTHEUNITCIRCLE WHICHMAYBEDONE TOCONTROLTHEFLATNESSOFTHEFILTERPASSBANDRESPONSE REQUIRESACONFIGURATIONSIMILAR TOTHEELLIPTICFILTERCONFIGURATIONSHOWNIN&IGURELATERINTHISCHAPTER4HETRIPLE CANCELERCONFIGURATIONSHOWNISSUCHTHATTWOOFTHEZEROSCANBEMOVEDAROUNDTHE UNITCIRCLEINTHE:PLANE-OVINGTHEZEROSCANPROVIDEAORD"INCREASEINTHE-4) IMPROVEMENTFACTORFORSPECIFICCLUTTERSPECTRALSPREADS ASCOMPAREDWITHKEEPINGALL THREEZEROSATTHEORIGIN .OTETHEWIDTHOFTHEREJECTIONNOTCHESFORTHEDIFFERENTBINOMIAL WEIGHTCANCELER CONFIGURATIONS)FTHE D"RESPONSERELATIVETOAVERAGERESPONSEISUSEDASTHEMEA SURINGPOINT THEREJECTIONISOFALLTARGETDOPPLERSFORTHESINGLECANCELER FOR THE DUAL CANCELER AND FOR THE TRIPLE CANCELER #ONSIDER THE DUAL CANCELER %LIMINATINGOFTHEDOPPLERSMEANSLIMITINGTHESYSTEMTOALONG TERMAVERAGEOF SINGLE SCANPROBABILITYOFDETECTION&EEDBACKCANBEUSEDTONARROWTHEREJECTION NOTCHWITHOUTMUCHDEGRADATIONOF))FFEEDBACKISUSEDTOINCREASETHEIMPROVEMENT FACTOR THESINGLE SCANPROBABILITYOFDETECTIONBECOMESWORSE &IGURESHOWSTHEIMPROVEMENTFACTORLIMITATIONDUETOSCANNINGFORCANCELERS WITHFEEDBACK4HESECURVESWERECALCULATEDASSUMINGASIN5 5ANTENNAPATTERN TERMINATEDATTHEFIRSTNULLS 4HENO FEEDBACKCURVESSHOWNIN&IGUREAREALMOSTINDISTINGUISHABLEFROM THETHEORETICALCURVESDERIVEDFORAGAUSSIANPATTERNSHOWNIN&IGURE/NEOFTHE CURVESSHOWINGTHEEFFECTOFFEEDBACKONTHETRIPLECANCELERISNOTSTRAIGHTBECAUSETWO OFTHETHREEZEROSARENOTATTHEORIGINBUTHAVEBEENMOVEDALONGTHEUNITCIRCLETHE OPTIMUMAMOUNTFORHITSPERBEAMWIDTH4HUS ATHITSPERBEAMWIDTH THESETWO ZEROSARETOOFARREMOVEDFROMTHEORIGINTOBEVERYEFFECTIVE
&)'52% )MPROVEMENTFACTORLIMITATIONDUETOSCANNINGFORCANCELERSWITHFEEDBACK
-4)2!$!2
Ó°Î
)NTHEORY ITISPOSSIBLETOSYNTHESIZEALMOSTANYVELOCITYRESPONSECURVEWITHDIGI TAL FILTERS!S MENTIONED EARLIER FOR EACH PAIR OF POLES AND PAIR OF ZEROS ON THE: PLANE TWODELAYSECTIONSAREREQUIRED4HEZEROSARECONTROLLEDBYTHEFEEDFORWARD PATHSANDTHEPOLESBYTHEFEEDBACKPATHS 6ELOCITY RESPONSE SHAPING CAN BE ACCOMPLISHED BY THE USE OF FEEDFORWARD ONLY WITHOUT THE USE OF FEEDBACK 4HE PRINCIPAL ADVANTAGE OF NOT USING FEEDBACK IS THE EXCELLENTTRANSIENTRESPONSEOFTHECANCELER ANIMPORTANTCONSIDERATIONINAPHASED ARRAYORWHENPULSEINTERFERENCENOISEISPRESENT)FAPHASEDARRAYRADARSHOULDUSEA FEEDBACKCANCELER MANYPULSESWOULDHAVETOBEGATEDOUTAFTERTHEBEAMHASBEEN REPOSITIONED BEFORE THE CANCELER TRANSIENT RESPONSE HAS SETTLED TO A TOLERABLE LEVEL !NINITIALIZATIONTECHNIQUEHASBEENPROPOSEDTOALLEVIATETHISPROBLEM BUTITPRO VIDESONLYPARTIALREDUCTIONINTHETRANSIENTSETTLINGTIME)FFEEDFORWARDONLYISUSED ONLYTHREEORFOURPULSESHAVETOBEGATEDOUTAFTERMOVINGTHEBEAM4HEDISADVAN TAGEOFUSINGFEEDFORWARDFORVELOCITYRESPONSESHAPINGISTHATANADDITIONALDELAY AND THEREFORE AN ADDITIONAL TRANSMIT PULSE MUST BE PROVIDED FOR EACH ZERO USED TO SHAPETHERESPONSE&IGURESHOWSTHEVELOCITYRESPONSEAND: PLANEDIAGRAMOFA FEEDFORWARD ONLY SHAPED RESPONSE FOUR PULSECANCELER!LSOSHOWNARETHEVELOCITY RESPONSESOFAFIVE PULSEFEEDFORWARDCANCELERANDATHREE PULSEFEEDBACKCANCELER &ORTHECANCELERSSHOWN THEIMPROVEMENTFACTORCAPABILITYOFTHETHREE PULSECANCELER ISABOUTD"BETTERTHANTHESHAPED RESPONSEFOUR PULSEFEEDFORWARDCANCELER INDE PENDENTOFCLUTTERSPECTRALSPREAD 4HEFIVE PULSECANCELERRESPONSESHOWNISALINEAR PHASE-4)FILTERDESCRIBEDBY :VEREV4HEFOURZEROSARELOCATEDONTHE: PLANEREALAXISAT AND -UCHOFTHELITERATUREONFILTERSYNTHESISDESCRIBESLINEAR PHASEFILTERS BUT FOR -4) APPLICATIONS LINEAR PHASE IS OF NO IMPORTANCE !LMOST IDENTICAL FILTER RESPONSESCANBEOBTAINEDWITHNONLINEAR PHASEFILTERSTHATREQUIREFEWERPULSES AS SHOWNIN&IGURE"ECAUSEONLYAFIXEDNUMBEROFPULSESISAVAILABLEDURINGTHE TIMEONTARGET NONESHOULDBEWASTED4HUS ONESHOULDCHOOSETHENONLINEAR PHASE FILTERTHATUSESFEWERPULSES 3TAGGER$ESIGN0ROCEDURES 4HEINTERVALBETWEENRADARPULSESMAYBECHANGED TOMODIFYTHETARGETVELOCITIESTOWHICHTHE-4)SYSTEMISBLIND4HEINTERVALMAY BE CHANGED ON A PULSE TO PULSE DWELL TO DWELL EACH DWELL BEING A FRACTION OF THE BEAMWIDTH OR SCAN TO SCAN BASIS %ACH APPROACH HAS ADVANTAGES 4HE ADVANTAGES OFTHESCAN TO SCANMETHODARETHATITISEASIERTOBUILDASTABLETRANSMITTER ANDMUL TIPLE TIME AROUNDCLUTTERISCANCELEDINAPOWERAMPLIFIER-4)SYSTEM4HETRANSMIT TERSTABILIZATIONNECESSARYFORGOODOPERATIONOFANUNSTAGGERED-4)ISASIGNIFICANT CHALLENGE4OSTABILIZETHETRANSMITTERSUFFICIENTLYFORPULSE TO PULSEORDWELL TO DWELL STAGGEROPERATIONISCONSIDERABLYMOREDIFFICULT4YPICALLY PULSE TO PULSESTAGGERING ISUSEDWITH-4)PROCESSING WHEREASDWELL TO DWELLSTAGGERINGISUSEDWITH-4$ FILTERBANK PROCESSING &ORMANY-4)APPLICATIONSPULSE TO PULSEORDWELL TO DWELLSTAGGERINGISPREF ERABLETOSCAN TO SCANSTAGGERINGo&OREXAMPLE IFABINOMIAL WEIGHTEDTHREE PULSE CANCELERTHATHAS WIDEREJECTIONNOTCHESISEMPLOYEDANDIFSCAN TO SCANPULSE STAGGERINGISUSED OFTHEDESIREDTARGETSWOULDBEMISSINGONEACHSCANOWING TO DOPPLER CONSIDERATION ALONE 4HIS MIGHT BE INTOLERABLE FOR SOME APPLICATIONS o4HECHOICEBETWEENPULSE TO PULSESTAGGERINGANDDWELL TO DWELL-4$ OPERATIONISASYSTEMCONCEPTDECISION BOTHAPPROACHESHAVETHEIRADVANTAGES&OREXAMPLE PULSE TO PULSESTAGGERINGWILLNOTPROVIDECANCELINGOFCLUTTERIN THEAMBIGUOUSRANGEINTERVALS7ITHDWELL TO DWELLSTAGGERING ANEXTRATRANSMITTERPULSEALSOKNOWNASAFILLPULSE WILLENABLECANCELINGOFSECONDRANGEINTERVALCLUTTER
Ó°{ä
2!$!2(!.$"//+
&)'52% 3HAPED VELOCITY RESPONSE FEEDFORWARD CANCELERS COMPARED WITH THREE PULSE FEEDBACKCANCELER3EETEXTFORFIVE PULSECANCELERPARAMETERS
7ITHPULSE TO PULSESTAGGERING GOODRESPONSECANBEOBTAINEDONALLDOPPLERSOF INTERESTONEACHSCAN)NADDITION BETTERVELOCITYRESPONSECANBEOBTAINEDATSOME DOPPLERS THAN EITHER PULSE INTERVAL WILL GIVE ON A SCAN TO SCAN BASIS 4HIS IS SO BECAUSE PULSE TO PULSE STAGGERING PRODUCES DOPPLER COMPONENTS IN THE PASSBAND OFTHE-4)FILTER0ULSE TO PULSESTAGGERINGMAYDEGRADETHEIMPROVEMENTFACTOR ATTAINABLE ASSHOWNIN&IGUREAND&IGURE BUTTHISDEGRADATIONMAYNOTBE SIGNIFICANT ORITCANBEELIMINATEDBYTHEUSEOFTIME VARYINGWEIGHTSASDESCRIBED BELOW /NE FURTHER ADVANTAGE OF PULSE TO PULSE STAGGERING IS THAT IT MAY PERMIT ELIMINATINGTHEUSEOFFEEDBACKINTHECANCELERSUSEDTONARROWTHEBLIND SPEED NOTCHES WHICHELIMINATESTHETRANSIENTSETTLINGPROBLEMOFTHEFEEDBACKFILTERS 4HE OPTIMUM CHOICE OF THE STAGGER RATIO DEPENDS ON THE VELOCITY RANGE OVER WHICHTHEREMUSTBENOBLINDSPEEDSANDONTHEPERMISSIBLEDEPTHOFTHEFIRSTNULL
-4)2!$!2
Ó°{£
&)'52% 6ELOCITYRESPONSECURVEDUALCANCELER NOFEEDBACK PULSE INTERVALRATIO
INTHEVELOCITYRESPONSECURVE&ORMANYAPPLICATIONS AFOUR PERIODSTAGGERRATIOIS BEST ANDAGOODSETOFSTAGGERRATIOSCANBEOBTAINEDBYADDINGTHEFIRSTBLINDSPEED IN66" TOTHENUMBERS OR 4HUS IN&IGUREp WHERE THE FIRST BLIND SPEED OCCURS AT ABOUT 66" THE STAGGER RATIO IS e ALTERNATING THE LONG AND SHORT PERIODS KEEPS THE TRANSMITTER DUTY CYCLE AS NEARLY CONSTANT AS POSSIBLE AS WELL AS ENSURING GOOD RESPONSE AT THE FIRST NULL WHERE 6 6" &IGURESANDSHOWTWOOTHER PERIODVELOCITYRESPONSECURVES)F USINGFOURINTERPULSEPERIODSMAKESTHEFIRSTNULLTOBETOODEEP THENFIVEINTERPULSE PERIODSMAYBEUSED WITHTHESTAGGERRATIOOBTAINEDBYADDINGTHEFIRSTBLINDSPEED TOTHENUMBER &IGURESHOWSAVELOCITYRESPONSECURVEFOR FIVEPULSEINTERVALS4HEDEPTHOFTHEFIRSTNULLCANBEPREDICTEDFROM&IGURE WHICHISDISCUSSEDLATER &ORARADARSYSTEMWITHRELATIVELYFEWHITSPERBEAMWIDTH ITISNOTADVANTAGEOUSTO USEMORETHANFOURORFIVEDIFFERENTINTERVALSBECAUSETHENTHERESPONSETOANINDIVIDUAL TARGETWILLDEPENDONWHICHPARTOFTHEPULSESEQUENCEOCCURSASTHEPEAKOFTHEBEAM PASSESTHETARGET2ANDOMVARIATIONOFTHEPULSEINTERVALSISNOTDESIRABLEUNLESSUSED AS AN ELECTRONIC COUNTER COUNTERMEASURE FEATURE BECAUSE IT PERMITS THE NULLS TO BE DEEPERTHANTHEOPTIMUMCHOICEOFFOUR ORFIVE PULSEINTERVALS 7HENTHERATIOOFPULSEINTERVALSISEXPRESSEDASASETOFRELATIVELYPRIMEINTEGERS IE ASETOFINTEGERSWITHNOCOMMONDIVISOROTHERTHAN THEFIRSTTRUEBLINDSPEED OCCURSAT
2 2 2 ! 2. 6
6" .
p!LLVELOCITYRESPONSECURVESPLOTTEDHEREINPRESENTTHEAVERAGEPOWERRESPONSEOFTHEOUTPUTPULSESOFTHECANCELER FORTHEDURATIONOFTHETIMEONTARGETFORASCANNINGRADAR)FSTAGGERINGWEREUSEDWITHBATCHPROCESSING SUCHASINA PHASEDARRAY THESECURVESWOULDNOTAPPLYFORASINGLEOUTPUT&OREXAMPLE IFTHESTAGGERRATIOWASANDA THREE PULSE&)2FILTERISUSED ITWOULDBENECESSARYTOTRANSMITSIXPULSES WITHINTERPULSESPACINGSOF ANDSUMTHEPOWEROUTPUTFROMTHEFILTERAFTERTHELASTFOURPULSESWERETRANSMITTEDTOGETTHEEQUIVALENTRESPONSE SHOWNINTHESECURVES e.OTETHATTHEFIRSTDIFFERENCESBETWEENALLCOMBINATIONSOFTHEINTEGERS ANDARE 4HIShPERFECT DIFFERENCESETvFORTHESTAGGERSEQUENCEISTHEKEYTOTHERELATIVEFLATNESSOFTHERESPONSECURVES
Ó°{Ó
2!$!2(!.$"//+
&)'52% 6ELOCITYRESPONSECURVETHREE PULSEBINOMIALCANCELER PULSE INTERVALRATIO
&)'52% 6ELOCITYRESPONSECURVETHREE PULSEBINOMIALCANCELER PULSE INTERVALRATIO
&)'52% 6ELOCITYRESPONSECURVETHREE PULSEBINOMIALCANCELER PULSE INTERVALRATIO4HISRESPONSECURVECONTINUESTO66" WITHNODIPSBELOWD"4HEFIRST BLINDSPEEDISAT66"
-4)2!$!2
Ó°{Î
WHERE2 2 2 2. ARETHESETOFINTEGERSAND6"ISTHEBLINDSPEEDCORRESPOND INGTOTHEAVERAGEINTERPULSEPERIOD4HEVELOCITYRESPONSECURVEISSYMMETRICALABOUT ONE HALFOFTHEVALUEFROM%Q &EEDBACK AND 0ULSE TO 0ULSE 3TAGGERING 7HEN PULSE TO PULSE STAGGERING IS EMPLOYED THE EFFECT OF FEEDBACK IS REDUCED 3TAGGERING CAUSES A MODULATION OF THESIGNALDOPPLERATORNEARTHEMAXIMUMRESPONSEFREQUENCYOFTHECANCELER4HE AMOUNTOFTHISMODULATIONISPROPORTIONALTOTHEABSOLUTETARGETDOPPLERSOTHAT FORAN AIRCRAFTFLYINGAT6" THECANCELERRESPONSEISESSENTIALLYINDEPENDENTOFTHEFEEDBACK EMPLOYED&IGURESHOWSAPLOTOFTHEEFFECTSOFFEEDBACKONADUAL CANCELERSYS TEMWITHHITSPERBEAMWIDTHANDARATIOOFSTAGGERINTERVALSOF4HEFEED BACKVALUESEMPLOYEDARESEVERALOFTHOSEUSEDFORTHEUNSTAGGEREDVELOCITYRESPONSE PLOTIN&IGURE)FSCAN TO SCANPULSE INTERVALSTAGGERINGHADBEENUSEDINSTEADOF PULSE TO PULSE THENO FEEDBACKRMSRESPONSEFORTHREESCANSATATARGETVELOCITYOF6" WOULDBE D"4HECOMPOSITERESPONSEFORPULSE TO PULSESTAGGERING HOWEVER IS ONLY D"AT6" THUSILLUSTRATINGTHEADVANTAGEOFPULSE TO PULSESTAGGERING )MPROVEMENT&ACTOR,IMITATIONS#AUSEDBY3TAGGERING 7HENPULSE TO PULSE STAGGERING IS USED IT LIMITS THE ATTAINABLE IMPROVEMENT FACTOR OWING TO THE UNEQUAL TIMESPACINGOFTHERECEIVEDCLUTTERSAMPLES4HECURVESIN&IGUREAND&IGURE WHICHHAVEBEENREFERREDTOSEVERALTIMES GIVETHEAPPROXIMATELIMITATIONON)CAUSED BY PULSE TO PULSE STAGGERING AND EITHER ANTENNA SCANNING OR INTERNAL CLUTTER MOTION 4HEYHAVEBEENDERIVEDASEXPLAINEDBELOW !TWO DELAYCANCELERWILLPERFECTLYCANCELALINEARWAVEFORM 6T C AT IF ITISSAMPLEDATEQUALTIMEINTERVALSINDEPENDENTOFTHECONSTANTCORTHESLOPEA !DDITIONALDELAYCANCELERSPERFECTLYCANCELADDITIONALWAVEFORMDERIVATIVESEG A THREE DELAYCANCELERWILLPERFECTLYCANCEL6T C AT BT !STAGGERSYSTEMWITH TWOPULSEINTERVALSSAMPLESTHELINEARWAVEFORMATUNEQUALINTERVALS ANDTHEREFORE
&)'52% %FFECTOFFEEDBACKONTHEVELOCITYRESPONSECURVEDUALCANCELER PULSE INTERVALRATIO
Ó°{{
2!$!2(!.$"//+
THEREWILLBEAVOLTAGERESIDUEFROMTHECANCELERSTHATISPROPORTIONALTOTHESLOPE AANDINVERSELYPROPORTIONALTOF WHEREFISTHERATIOOFTHEINTERVALS4HEAPPAR ENTDOPPLERFREQUENCYOFTHERESIDUEWILLBEATONE HALFTHEAVERAGEREPETITIONRATE OFTHESYSTEMANDTHUSWILLBEATTHEFREQUENCYOFMAXIMUMRESPONSEOFABINOMIAL WEIGHTCANCELER 4HERATEOFCHANGEOFPHASEORAMPLITUDEOFCLUTTERSIGNALSINASCANNINGRADARIS INVERSELYPROPORTIONALTOTHEHITSPERBEAMWIDTH N4HUS WITHTHEUSEOFACOMPUTER SIMULATIONTODETERMINETHEPROPORTIONALITYCONSTANT THELIMITATIONON)DUETOSTAG GERINGISAPPROXIMATELY ¤ N ³ ) y LOG ¥ D" ¦ G ´µ
WHICHISPLOTTEDIN&IGURE 4HESECURVES WHICHAPPLYTOALLMULTIPLE DELAYCANCELERS GIVEANSWERSTHATARE FAIRLYCLOSETOTHEACTUALLIMITATIONTHATWILLBEEXPERIENCEDFORMOSTPRACTICALSTAGGER RATIOS!NEXAMPLEOFTHEACCURACYISASFOLLOWS!SYSTEMWITHHITSPERBEAM WIDTH AFOUR PULSEBINOMIALWEIGHTCANCELER ANDAPULSE INTERVALRATIOHASAN IMPROVEMENTFACTORLIMITATIONOFD"DUETOSTAGGERING4HECURVEGIVESALIMITA TIONOFD"FORTHISCASE"UTIFTHESEQUENCEOFPULSEINTERVALSWERETOBECHANGED FROMTO THEACTUALLIMITATIONWOULDBED" WHICHISD"LESS THANTHATINDICATEDBYTHECURVE4HISOCCURSBECAUSETHEPRIMARYMODULATIONWITHA PULSE INTERVALRATIOLOOKSLIKEATARGETATMAXIMUM RESPONSESPEED WHEREAS THEPRIMARYMODULATIONWITHAPULSE INTERVALRATIOLOOKSLIKEATARGETATONE HALFTHESPEEDOFMAXIMUMRESPONSE"ECAUSEITISDESIRABLETOAVERAGETHETRANSMITTER DUTYCYCLEOVERASSHORTAPERIODASPOSSIBLE THEPULSE INTERVALRATIOWOULD PROBABLYBECHOSENFORAPRACTICALSYSTEM /NCE%QFORTHELIMITATIONON)DUETOSCANNINGANDSTAGGERINGISOBTAINED ITISPOSSIBLETODETERMINETHELIMITATIONON)DUETOINTERNAL CLUTTERMOTIONANDSTAG GERING)F
N
N L FR LF r R P SV SV
FROM%QSAND ISSUBSTITUTEDINTO%Q
¤ L FR ³ ¤ L FR ³ ) LOG ¥ r ´µ LOG ¥¦ G S ´µ SV ¦G V
WHEREKISTHEWAVELENGTH FRISTHEAVERAGEPULSEREPETITIONFREQUENCY ANDRVISTHE RMSVELOCITYSPREADOFSCATTERINGELEMENTS4HISISPLOTTEDIN&IGUREFORRAINAND FORWOODEDHILLSWITHAKNOTWIND4HISLIMITATIONONTHE-4)IMPROVEMENTFACTOR ISINDEPENDENTOFTHETYPEOFCANCELEREMPLOYED 4IME 6ARYING7EIGHTS 4HEIMPROVEMENTFACTORLIMITATIONCAUSEDBYPULSE TO PULSESTAGGERINGCANBEAVOIDEDBYTHEUSEOFTIME VARYINGWEIGHTSINTHECANCELER FORWARDPATHSINSTEADOFBINOMIALWEIGHTS4HEUSEOFTIME VARYINGWEIGHTSHASNO APPRECIABLEEFFECTONTHE-4)VELOCITYRESPONSECURVE7HETHERTHEADDEDCOMPLEX ITY OF UTILIZING TIME VARYING WEIGHTS IS DESIRABLE DEPENDS ON WHETHER THE STAGGER
-4)2!$!2
Ó°{x
LIMITATION IS PREDOMINANT &OR TWO DELAY CANCELERS THE STAGGER LIMITATION IS OFTEN COMPARABLE WITH THE BASIC CANCELER CAPABILITY WITHOUT STAGGERING &OR THREE DELAY CANCELERS THESTAGGERLIMITATIONUSUALLYPREDOMINATES #ONSIDER THE TRANSMITTER PULSE TRAIN AND THE CANCELER CONFIGURATIONS SHOWN IN &IGURE$URINGTHEINTERVAL4.WHENTHERETURNSFROMTRANSMITTEDPULSE0.ARE BEINGRECEIVED THETWO DELAYCANCELERWEIGHTSSHOULDBE !
#
4.
4.
" # ANDTHETHREE DELAYCANCELERWEIGHTSSHOULDBE !
#
4. 4. 4.
" # $ 4HESEWEIGHTSHAVEBEENDERIVEDBYASSUMINGTHATTHECANCELERSSHOULDPERFECTLY CANCELALINEARWAVEFORM6T C AT SAMPLEDATTHESTAGGERRATE INDEPENDENTOFTHE VALUESOFTHECONSTANTCORTHESLOPEA!SMENTIONEDATTHEBEGINNINGOFTHISSECTION A MULTIPLE DELAYCANCELERWITHBINOMIALWEIGHTSINANUNSTAGGEREDSYSTEMWILLPERFECTLY CANCEL6T C AT 4HECHOICEOF! INBOTHCASESISARBITRARY)NTHETHREE DELAYCANCELER SETTING $ ELIMINATESTHEOPPORTUNITYFORASECOND ORDERCORRECTIONTOCANCELTHEQUADRATIC TERMBT WHICHCOULDBEOBTAINEDIF$WEREALSOTIME VARYING#OMPUTERCALCULATIONS HAVESHOWNTHATITISUNNECESSARYTOVARY$INMOSTPRACTICALSYSTEMS
&)'52% 5SEOFTIME VARYINGWEIGHTSA PULSETRAIN B TWO DELAYCANCELER ANDC THREE DELAYCANCELER
Ó°{È
2!$!2(!.$"//+
&)'52% !PPROXIMATEDEPTHOFNULLSINTHEVELOCITYRESPONSECURVEFORPULSE TO PULSE STAGGERED-4)
$EPTHOF&IRST.ULLIN6ELOCITY2ESPONSE 7HENSELECTINGSYSTEMPARAMETERS IT IS USEFUL TO KNOW THE DEPTH OF THE FIRST FEW NULLS TO BE EXPECTED IN THE VELOCITY RESPONSE CURVE!S DISCUSSED EARLIER THE NULL DEPTHS ARE ESSENTIALLY UNAFFECTED BY FEEDBACK 4HEY ARE ALSO ESSENTIALLY INDEPENDENT OF THE TYPE OF CANCELER EMPLOYED WHETHERSINGLE DUAL ORTRIPLE OROFTHENUMBEROFHITSPERBEAMWIDTH&IGURE SHOWSAPPROXIMATELYWHATNULLDEPTHSCANBEEXPECTEDVERSUSTHERATIOOFMAXIMUM TOMINIMUMINTERPULSEPERIOD
Ó°Ê /Ê / ,Ê - Ê",Ê7 / ,Ê, ,-4)FILTERSAREUSEDATTHELOWERELEVATIONANGLESINWEATHERRADARSTOPREVENTWEATHER ESTIMATESFROMBEINGCONTAMINATEDWITHGROUNDCLUTTERRETURNS)TIS HOWEVER ALSO VERYIMPORTANTTOPRESERVEANACCURATEMEASUREMENTOFWEATHERINTENSITYANDPRECIPI TATIONRATE4OMEETTHISDUALOBJECTIVE -4)FILTERSWITHNARROWFIXEDCLUTTERREJECTION NOTCHESANDFLATPASSBANDSARENEEDED5SEOFAVERYNARROWCLUTTERNOTCHEVENPERMITS MEASURINGWEATHERPRECIPITATIONRATESWITHAMEANRADIALVELOCITYOFZERO ALBEITWITH SOMEBIAS 3UCHMEASUREMENTISPOSSIBLEBECAUSEWEATHERUSUALLYHASAWIDESPEC TRALSPREADTYPICALLYTOMSWHEREASFIXEDCLUTTERHASAMUCHNARROWERSPECTRAL SPREADTYPICALLYLESSTHANMS
"IASASUSEDHEREINREFERSTOTHEERRORINMEASURINGRADARREFLECTIVITYDUETOTHECLUTTERNOTCHANDLACKOFFLATNESS OFTHE-4)FILTERS7HENWEATHERHASAWIDESPECTRALSPREADANDTHECLUTTERNOTCHOFTHEFILTERSISNARROW THEREIS MINIMALMEASUREMENTERRORINDUCEDBYTHE-4)FILTERS#ONVERSELY WHENTHEWEATHERSPECTRALWIDTHISNARROWAND THERADIALVELOCITYOFTHEWEATHERISNEARZERO SIGNIFICANTERRORINTHEWEATHERREFLECTIVITYMEASUREMENTWILLEXIST 4HEREAREOTHERCAUSESOFERRORBETWEENRADARESTIMATESOFPRECIPITATIONRATESANDRAINGAUGEMEASUREMENTSTHATARE NOTADDRESSEDHEREIN SUCHASTHESPATIALANDTEMPORALDISTRIBUTIONOFRAIN
-4)2!$!2
Ó°{Ç
%XAMPLESOFWEATHERRADARAPPLICATIONSFORWHICH-4)FILTERSAREUSED 7EATHER$OPPLER2ADARS.%82!$732 2ADARSWITHROTATINGANTENNASTHAT MEASUREPRECIPITATIONRATE DOPPLERVELOCITY ANDTURBULENCE-EASURESTOTALRAINFALL ANDPROVIDESTORNADOWARNINGS 4ERMINAL $OPPLER 7EATHER 2ADARS 4$72 2ADARS WITH ROTATING ANTENNAS DESIGNEDTODETECTSEVEREWINDSHEARINAIRCRAFTAPPROACHANDDEPARTUREPATHSCLOSE TOAIRPORTS !IRPORT 3URVEILLANCE 2ADARS 2ADARS WITH ROTATING ANTENNAS DESIGNED FOR AIR TRAFFIC CONTROL FUNCTIONS IN THE TERMINAL AREA BUT WITH A SECONDARY FUNCTION OF DETECTINGANDMONITORINGSEVEREWEATHERANDWINDSHEARINAIRCRAFTAPPROACHAND DEPARTUREPATHS 0HASED!RRAY2ADARS 2ADARSWITHFIXEDELECTRONICALLYSCANNEDANTENNASDESIGNED FORMANYFUNCTIONSSUCHASMISSILEDETECTIONANDAIRTRAFFICCONTROL ANDUSEDCON CURRENTLYFORMEASURINGPRECIPITATIONRATES !S AN EXAMPLE THE DESIGN OF ELLIPTIC -4) FILTERS AS USED IN THE4$72 WILL BE DESCRIBED 4$72 IS A # BAND RADAR USED AT AIRPORTS FOR DETECTION OF DOWNBURSTS MICROBURSTS AND PREDICTION OF WIND DIRECTION %LLIPTIC FILTERS ARE INFINITE IMPULSE RESPONSE))2 FILTERSTHATHAVETHESHARPESTPOSSIBLETRANSITIONFROMREJECTIONNOTCHTO PASSBANDFORASPECIFIEDLEVELOFTHECLUTTERREJECTIONNOTCHWIDTHANDDEPTH RIPPLEIN THEPASSBAND ANDNUMBEROFDELAYSECTIONSSEE/PPENHEIMAND3CHAFER 4HEELLIP TICFILTERSCANBEFOLLOWEDWITHPULSE PAIRPROCESSINGFORESTIMATIONOFWEATHERMEAN VELOCITYANDSPECTRALWIDTHTURBULENCE 4HEREARETWODRAWBACKSOFELLIPTICFILTERS &IRST THELONGTRANSIENTSETTLINGTIME&ORASCANNINGWEATHERRADAR ITTAKESABOUTFOUR BEAMWIDTHSOFSCANNINGAFTERTHETRANSMITTERSTARTSPULSINGBEFORECLUTTERATTENUATION REACHESTOD"3ECOND IFTHEINPUTCLUTTERSIGNALREACHESTHELIMITLEVELINTHE )&RECEIVER THEREWILLBEASIGNIFICANTTRANSIENTINCREASEOFCLUTTERRESIDUE/NEOFTHE ELLIPTICFILTERSEMPLOYEDINTHEORIGINAL4$72RADARISUSEDASANEXAMPLE 4$72OPERATESAT#BAND '(Z 4HEANTENNAROTATESATRPMAND HASAONE WAYBEAMWIDTH4HE02&IS(Z4HEELLIPTICFILTERDESIGNEDFOR THESEPARAMETERSHASANIMPROVEMENTFACTOROFD"("7HITSPERONE WAY D" BEAMWIDTH ARE4HESPECIFICATIONSFORTHEELLIPTICFILTERFORTHEABOVEPARAMETERS ARE NORMALIZED STOPBAND EDGE RF4 PASSBAND EDGE RF4 STOP BAND ATTENUATION D" BELOW PEAK FILTER RESPONSE AND PASSBAND RIPPLE D" 4OMEETTHESEREQUIREMENTS THEFILTERREQUIRES DELAYSECTIONS WHICHCANBEIMPLE MENTEDASTWOCASCADED DELAYSECTIONS ASSHOWNIN&IGURE
&)'52% &OUR DELAYELLIPTICFILTERUSEDIN4$72
Ó°{n
2!$!2(!.$"//+
4HEFILTERCOEFFICIENTSARE A A B B
A A B B
4HECALCULATEDIMPROVEMENTFACTORFORTHISFILTERAGAINSTLANDCLUTTERWITH("7IS D" ANDTHEBIASFORWEATHERRETURNSWITHSPECTRALSPREADSOFANDMSECISnD" ANDnD" RESPECTIVELY WHENTHERADIALVELOCITYOFTHEWEATHERRETURNSISV MS &IGURESHOWSTHEELLIPTICFILTER#7RESPONSEANDITSRESPONSEFORWEATHERWITH MSANDMSRMSSPECTRALSPREAD4HEUNAMBIGUOUSDOPPLERINTERVALCORRESPONDING TOFD4 ISMSFORTHEPARAMETERSUSEDTOCALCULATETHISRESPONSE &IGURESHOWSTHETIME DOMAINRESPONSESFORTHISFILTERASTHEANTENNASCANS PASTAPOINTOFCLUTTER SUCHASAWATERTOWER4HISFIGURESHOWSTHEINPUTTOTHEELLIPTIC FILTERANDTHERESIDUEOUTPUT!GAUSSIANANTENNAPATTERNISASSUMEDINTHISFIGURE4HE CALCULATEDIMPROVEMENTFACTORFORTHESEQUENCESHOWNTOTALCLUTTERPOWERINTOTHE FILTERDIVIDEDBYTOTALRESIDUEPOWEROUTOFTHEFILTER NORMALIZEDBYTHENOISEGAINOF THEFILTER ISD" !SINX XANTENNAPATTERNISASSUMEDFORTHEFOLLOWINGTHREEFIGURES BUTTHELESSONS TOBEGAINEDFROMTHESEFIGURESISESSENTIALLYINDEPENDENTOFTHEASSUMEDBEAMSHAPE &IGURESHOWSTHEFILTERRESPONSEIFTHETRANSMITTERSTARTSRADIATINGJUSTASANULLOF THEANTENNAPATTERNPASSESTHEPOINTOFCLUTTER4HEINDIVIDUALSAMPLESOFRESIDUEARE ORMORED"BELOWTHEPEAKCLUTTERRETURN4HEIMPROVEMENTFACTORFORTHISSEQUENCE ISD"
"#! !
$ !! " $ !! "! ! $ !! " $ !! "! ! ! ! ! !
"#
&)'52% %LLIPTIC FILTER #7 RESPONSE AND RESPONSE TO WEATHER WITH R AND MS RMS SPECTRALSPREAD
-4)2!$!2
Ó°{
" "
!!
" "
&)'52% 4IME DOMAIN CLUTTER INPUT AND OUTPUT RESIDUE AS ANTENNA SCANS PAST APOINTTARGET
&IGURESHOWSTHERESIDUEIFTHETRANSMITTERSTARTSRADIATINGASTHEPEAKOFTHE BEAMPASSESTHEPOINTCLUTTER&ORTY NINEPULSESAFTERTHETRANSMITTERSTARTSRADIATING THERESIDUEHASDECAYEDONLYD")TWOULDTAKEATLEASTANOTHERPULSESFORTHE RESIDUETODECAYTO D"&ORTHISREASON WHENTHETRANSMITTERSTARTSPULSING ASET TLINGTIMEOFATLEASTPULSESMUSTBEALLOWEDBEFOREUSEFULDATAISCOLLECTED
&)'52% #LUTTERINPUTANDRESIDUEFROMELLIPTICFILTER2ADARSTARTSRADIATINGATPULSE NUMBER
Ó°xä
2!$!2(!.$"//+
&)'52% #LUTTERINPUTANDRESIDUEFROMELLIPTICFILTER2ADARSTARTSRADIATINGATPULSE NUMBER
&IGURESHOWSTHEEFFECTOFTHERETURNEDSIGNALIFTHEPOINTCLUTTEREXCEEDSTHE )&LIMITLEVELBYD"7HENTHESIGNALREACHESTHELIMITLEVEL THEREISASTEPINCREASE OFRESIDUEOFABOUTD"4$72USESCLUTTERMAPSTONORMALIZETHERESIDUEFROMTHE STRONGPOINTSOFCLUTTERTHATEXCEEDTHELIMITLEVEL 4HEWEATHERMODEOF!IRPORT3URVEILLANCE2ADARSISDEMONSTRATEDBYFIVE PULSE FINITE IMPULSE RESPONSE &)2 FILTERS USED IN THE!32 AN 3 BAND RADAR USED FOR AIRTRAFFICCONTROLATAIRPORTS4HEDESIGNOFTHEFILTERSISPRIMARILYFOR-OVING4ARGET $ETECTOR-4$ DETECTIONOFAIRCRAFT BUTSPECIALATTENTIONISGIVENTOPROVIDINGFLAT PASSBAND RESPONSE FOR ACCURATE WEATHER REFLECTIVITY ESTIMATION4HE FILTER BANK FOR ("7 ISPICTUREDIN&IGUREANDTHECOEFFICIENTSARESHOWNIN4ABLE
&)'52% %FFECTOFLIMITINGONELLIPTICFILTERRESPONSE
-4)2!$!2
Ó°x£
4!",% !32#OEFFICIENTSOF!32 0ULSE,OW 02&&IR&ILTERS
&),4%2
#OEFFICIENT
#OEFFICIENT
#OEFFICIENT
#OEFFICIENT
#OEFFICIENT
D" D" D" D" D" D"
n n n n n n
n n
n n n
n n n
3ELECTIONOFFILTERSISBASEDONCLUTTERAMPLITUDEINFORMATIONSTOREDINACLUTTERMAP 4HEFILTERSARESELECTEDONARANGE CELLBY#0)BASIS 4HESE&)2CLUTTERFILTERSHAVETHENARROWESTREJECTIONNOTCHESTHATCANBEOBTAINED WITH FIVE PULSES AND THE INDICATED LEVEL OF FIXED CLUTTER REJECTION (OWEVER THE NOTCHES ARE SIGNIFICANTLY WIDER THAN THOSE OF THE ELLIPTIC FILTERS THUS THEY WILL HAVEGREATERBIASFORMEASUREMENTOFWEATHERINTENSITYWHENTHEWEATHERRADIAL VELOCITYISZERO &ORPHASEDARRAYRADARS &)2FILTERSSIMILARTOTHOSEDESCRIBEDFORTHE!32 ARE APPLICABLE4HEFILTERSCANBEDESIGNED IFTHETIMEBUDGETOFTHEPHASEDARRAYRADAR ALLOWS TOUTILIZEMORETHANTHEFIVEPULSESPERCOHERENTPROCESSINGINTERVAL#0) USED BYTHE!32 RADAR5SINGMOREPULSESMAKESPOSSIBLENARROWERREJECTIONNOTCHES ANDTHUSLESSBIASFORESTIMATESOFPRECIPITATIONWITHZERORADIALVELOCITY
&)'52% 2ESPONSEOF!32 &)2FILTERSLOW 02&FR PPS FILTERSOPERATINGAGAINSTFIXEDCLUTTER WITH("7 4HEUNAMBIGUOUSDOPPLERINTERVALF4 ISMSFORTHEPARAMETERSUSEDTOCALCULATE THISRESPONSE
Ó°xÓ
2!$!2(!.$"//+
Ó°£äÊ 1// ,Ê / ,Ê Ê - !SDISCUSSEDIN3ECTION THE-4$USESAWAVEFORMCONSISTINGOFCOHERENTPRO CESSINGINTERVALS#0)S OF.PULSES ALLATTHESAME02&AND2&FREQUENCY4HE02& ANDPOSSIBLYTHE2&ARECHANGEDFROMONE#0)TOTHENEXT7ITHTHISCONSTRAINT ONLY FINITE IMPULSE RESPONSE&)2 FILTERDESIGNSAREREALISTICCANDIDATESFORTHEFILTERBANK DESIGN&EEDBACKFILTERSREQUIREANUMBEROFPULSESTOSETTLEAFTEREITHERTHE02&OR THE2&ISCHANGEDANDTHUSWOULDNOTBEPRACTICAL 4HENUMBEROFPULSESAVAILABLEDURINGTHETIMEWHENASURVEILLANCERADARBEAM ILLUMINATESAPOTENTIALTARGETPOSITIONISDETERMINEDBYSYSTEMPARAMETERSANDREQUIRE MENTSSUCHASBEAMWIDTH 02& VOLUMETOBESCANNED ANDTHEREQUIREDDATAUPDATE RATE'IVENTHECONSTRAINTONTHENUMBEROFPULSESONTARGET ONEMUSTDECIDEHOW MANY#0)SSHOULDOCCURDURINGTHETIMEONTARGETANDHOWMANYPULSESPER#0)4HE COMPROMISEISUSUALLYDIFFICULT/NEWISHESTOUSEMOREPULSESPER#0)TOENABLETHE USEOFBETTERFILTERS BUTONEALSOWISHESTOHAVEASMANY#0)SASPOSSIBLE-ULTIPLE #0)SATDIFFERENT02&SANDPERHAPSATDIFFERENT2&FREQUENCIES IMPROVEDETECTION ANDCANPROVIDEINFORMATIONFORTRUERADIALVELOCITYDETERMINATION 4HEDESIGNOFTHEINDIVIDUALFILTERSINTHEDOPPLERFILTERBANKISACOMPROMISEBETWEEN THEFREQUENCYSIDELOBEREQUIREMENTANDTHEDEGRADATIONINTHECOHERENTINTEGRATIONGAIN OFTHEFILTER4HENUMBEROFDOPPLERFILTERSREQUIREDFORAGIVENLENGTHOFTHE#0)MUSTBE BALANCEDBETWEENHARDWARECOMPLEXITYANDTHESTRADDLINGLOSSATTHECROSSOVERBETWEEN FILTERS&INALLY THEREQUIREMENTOFPROVIDINGAHIGHDEGREEOFCLUTTERSUPPRESSIONATZERO DOPPLERLANDCLUTTER SOMETIMESINTRODUCESSPECIALDESIGNCONSTRAINTS 7HEN THE NUMBER OF PULSES IN A #0) IS LARGE q THE SYSTEMATIC DESIGN PRO CEDURE AND EFFICIENT IMPLEMENTATION OF THE FAST &OURIER TRANSFORM &&4 ALGORITHM ISPARTICULARLYATTRACTIVE4HROUGHTHEUSEOFAPPROPRIATEWEIGHTINGFUNCTIONSOFTHE TIME DOMAINRETURNSINASINGLE#0) THERESULTINGFREQUENCYSIDELOBESCANBEREADILY CONTROLLED&URTHER THENUMBEROFFILTERSEQUALTOTHEORDEROFTHETRANSFORM NEEDED TOCOVERTHETOTALDOPPLERSPACEEQUALTOTHERADAR02& CANBECHOSENINDEPENDENTLY OFTHE#0) ASDISCUSSEDBELOW !S THE #0) BECOMES SMALLER a IT BECOMES IMPORTANT TO CONSIDER SPECIAL DESIGNSOFTHEINDIVIDUALFILTERSTOMATCHTHESPECIFICCLUTTERSUPPRESSIONREQUIREMENTS ATDIFFERENTDOPPLERFREQUENCIESINORDERTOACHIEVEBETTEROVERALLPERFORMANCE7HILE SOMESYSTEMATICPROCEDURESAREAVAILABLEFORDESIGNING&)2FILTERSSUBJECTTOSPECIFIC PASSBAND AND STOPBAND CONSTRAINTS THE STRAIGHTFORWARD APPROACH FOR SMALL #0)S IS TOUSEANEMPIRICALAPPROACHINWHICHTHEZEROSOFEACHFILTERAREADJUSTEDUNTILTHE DESIREDRESPONSEISOBTAINED!NEXAMPLEOFSUCHFILTERDESIGNSISPRESENTEDNEXT %MPIRICAL&ILTER$ESIGN !NEXAMPLEOFANEMPIRICALFILTERDESIGNFORASIX PULSE #0)FOLLOWS4HESIXPULSESPER#0)MAYBEDRIVENBYSYSTEMCONSIDERATIONS SUCHAS TIME ON TARGET "ECAUSETHEFILTERWILLUSESIXPULSES ONLYFIVEZEROSAREAVAILABLEFOR THEFILTERDESIGNTHENUMBEROFZEROSAVAILABLEISTHENUMBEROFPULSESMINUSONE4HE FILTERDESIGNPROCESSCONSISTSOFPLACINGTHEZEROSTOOBTAINAFILTERBANKRESPONSETHAT CONFORMSTOTHESPECIFIEDCONSTRAINTS4HEEXAMPLETHATFOLLOWSWASPRODUCEDWITHAN INTERACTIVECOMPUTERPROGRAMWITHWHICHTHEZEROSCOULDBEMOVEDUNTILTHEDESIRED RESPONSEWASOBTAINED4HEASSUMEDFILTERREQUIREMENTSAREASFOLLOWS L
0ROVIDEARESPONSEOF D"INTHECLUTTERREJECTIONNOTCHRELATIVETOTHEPEAKTARGET RESPONSE OFTHEMOVING TARGETFILTERS
-4)2!$!2
L
L
L
Ó°xÎ
0ROVIDEARESPONSEOF D"FORCHAFFREJECTIONATVELOCITIESBETWEENoOFTHE AMBIGUOUSDOPPLERFREQUENCYRANGE )NTHISDESIGN ONLYFIVEFILTERSWILLBEIMPLEMENTED 4HREEOFTHEFIVEFILTERSWILLREJECTFIXEDCLUTTERANDRESPONDTOMOVINGTARGETS4WO FILTERSWILLRESPONDTOTARGETSATZERODOPPLERANDITSAMBIGUITIES7ITHGOODFIXED CLUTTER REJECTION FILTERS IT TAKES TWO OR MORE COHERENT FILTERS TO COVER THE GAP IN RESPONSEATZEROVELOCITY
7ITHTHEABOVECONSIDERATIONS AFILTERBANKCANBECONSTRUCTED &IGUREASHOWSTHEFILTERDESIGNEDTORESPONDTOTARGETSINTHEMIDDLEOFTHE DOPPLER PASSBAND4HE SIDELOBES NEAR ZERO VELOCITY ARE D" DOWN FROM THE PEAK THUSPROVIDINGGOODCLUTTERREJECTIONFORCLUTTERWITHINOFZERODOPPLER4HE D" SIDELOBEPROVIDESCHAFFREJECTIONTOo"ECAUSEOFTHECONSTRAINTOFHAVINGONLYFIVE ZEROSAVAILABLE THISFILTERCOULDNOTPROVIDE D"REJECTIONTOo &IGUREBSHOWSTHEFILTERTHATRESPONDSTOTARGETSASNEARASPOSSIBLETOZERO DOPPLER WHILEHAVINGAZERO DOPPLERRESPONSEOF D"4WOZEROSAREPLACEDNEAR PROVIDING D"RESPONSETOCLUTTERAT4HEFILTERSIDELOBESBETWEENAND DOPPLERPROVIDETHESPECIFIEDCHAFFREJECTIONOFD"!MIRRORIMAGEOFTHISFILTERIS USEDFORTHETHIRDMOVINGDOPPLERFILTER4HEMIRROR IMAGEFILTERHASCOEFFICIENTSTHAT ARECOMPLEXCONJUGATESOFTHEORIGINALFILTERCOEFFICIENTS &IGURE C SHOWS THE FIRST FILTER DESIGNED FOR RESPONSE AT ZERO DOPPLER #ONSIDERATIONSHEREARETHATTHEDOPPLERSTRADDLINGLOSSOFTHEFILTERBANKBEMINIMIZED
&)'52% 3IX PULSEFILTERSFORTARGETSATA F4 B &T F4 ANDC COMBINEDRESPONSE OFCOMPLETEBANKOFFIVESIX PULSEFILTERS
Ó°x{
2!$!2(!.$"//+
THIS DICTATES THE LOCATION OF THE PEAK THAT THE RESPONSE TO CHAFF AT DOPPLER BE DOWND" ANDTHATTHEMISMATCHLOSSBEMINIMIZED-INIMIZINGTHEMISMATCHLOSS ISACCOMPLISHEDBYPERMITTINGTHEFILTERSIDELOBESBETWEENANDTORISEASHIGH ASNEEDEDLOWERSIDELOBESINTHISRANGEINCREASETHEMISMATCHLOSS 4HESECONDZERO DOPPLERFILTERISTHEMIRRORIMAGEOFTHISONE &IGUREDSHOWSTHECOMPOSITERESPONSEOFTHEFILTERBANK.OTETHATTHEFILTER PEAKSAREFAIRLYEVENLYDISTRIBUTED4HEDIPBETWEENTHEFIRSTZERO DOPPLERFILTERAND THEFIRSTMOVINGDOPPLERFILTERISLARGERTHANTHEOTHERS PRIMARILYBECAUSE UNDERTHE CONSTRAINTS ITISIMPOSSIBLETOMOVETHEFIRSTDOPPLERFILTERNEARERTOZEROVELOCITY #HEBYSHEV&ILTER"ANK &ORALARGERNUMBEROFPULSESINTHE#0) AMORESYSTEM ATICAPPROACHTOFILTERDESIGNISDESIRABLE)FADOPPLERFILTERDESIGNCRITERIONISCHOSEN THATREQUIRESTHEFILTERSIDELOBESOUTSIDETHEMAINRESPONSETOBEBELOWASPECIFIEDLEVEL IE PROVIDINGACONSTANTLEVELOFCLUTTERSUPPRESSION WHILESIMULTANEOUSLYMINIMIZ INGTHEWIDTHOFTHEFILTERRESPONSE AFILTERDESIGNBASEDONTHE$OLPH #HEBYSHEVDIS TRIBUTIONPROVIDESTHEOPTIMUMSOLUTION0ROPERTIESANDDESIGNPROCEDURESBASEDON THE$OLPH #HEBYSHEVDISTRIBUTIONCANBEFOUNDINTHEANTENNALITERATURE!NEXAMPLE OFAFILTERDESIGNFORA#0)OFPULSESANDASIDELOBEREQUIREMENTOFD"ISSHOWNIN &IGURE4HEPEAKFILTERRESPONSECANBELOCATEDARBITRARILYINFREQUENCYBYADDING ALINEAR PHASETERMTOTHEFILTERCOEFFICIENTS 4HETOTALNUMBEROFFILTERSIMPLEMENTEDTOCOVERALLDOPPLERFREQUENCIESISADESIGN OPTIONTRADINGSTRADDLINGLOSSATTHEFILTERCROSSOVERFREQUENCIESAGAINSTIMPLEMENTA TIONCOMPLEXITY!NEXAMPLEOFACOMPLETEDOPPLERFILTERBANKIMPLEMENTEDWITHNINE UNIFORMLYSPACEDFILTERSISSHOWNIN&IGURE4HEPERFORMANCEOFTHISDOPPLERFILTER BANKAGAINSTTHECLUTTERMODELCONSIDEREDIN&IGUREISSHOWNIN&IGURE4HIS GRAPHSHOWSTHESIGNAL TO CLUTTERRATIOIMPROVEMENTAGAINSTCLUTTERATZERODOPPLERAS AFUNCTIONOFTARGETDOPPLERFREQUENCY/NLYTHERESPONSEOFTHEFILTERPROVIDINGTHE GREATESTIMPROVEMENTISPLOTTEDATEACHTARGETDOPPLER &ORCOMPARISONTHEOPTIMUMCURVEFROM&IGUREISSHOWNBYABROKENLINEAND THUSPROVIDESADIRECTASSESSMENTOFHOWWELLTHE#HEBYSHEVFILTERDESIGNPERFORMS AGAINSTAGIVENCLUTTERMODEL!LSOSHOWNISTHEAVERAGE3#2IMPROVEMENTFORBOTH THEOPTIMUMANDTHE#HEBYSHEVFILTERBANK
&)'52% #HEBYSHEV&)2FILTERDESIGNWITHD"DOPPLERSIDELOBES
-4)2!$!2
Ó°xx
&)'52% $OPPLERFILTERBANKOFD"#HEBYSHEVFILTERS #0) PULSES
&INALLY &IGURESHOWSTHEAVERAGE3#2IMPROVEMENTOFTHED"#HEBYSHEV DOPPLER FILTER BANK AS WELL AS THE OPTIMUM CURVE FROM &IGURE AS A FUNCTION OF THE RELATIVE SPECTRUM SPREAD OF THE CLUTTER /WING TO THE FINITE NUMBER OF FILTERS IMPLEMENTEDINTHEFILTERBANK THEAVERAGE3#2IMPROVEMENTWILLCHANGEBYASMALL AMOUNTIFADOPPLERSHIFTISINTRODUCEDINTOTHECLUTTERRETURNS4HISEFFECTISILLUSTRATED BYTHECROSS HATCHEDREGION WHICHSHOWSUPPERANDLOWERLIMITSONTHEAVERAGE3#2 IMPROVEMENTFORALLPOSSIBLECLUTTERDOPPLERSHIFTS&ORASMALLERNUMBEROFFILTERSIN THEDOPPLERFILTERBANK THISVARIATIONWOULDBEGREATER &AST&OURIER4RANSFORM&ILTER"ANK &ORALARGENUMBEROFPARALLELDOPPLER FILTERS HARDWAREIMPLEMENTATIONCANBESIMPLIFIEDSIGNIFICANTLYTHROUGHTHEUSEOF THE&&4ALGORITHM4HEUSEOFTHISALGORITHMCONSTRAINSALLFILTERSINTHEFILTERBANKTO
&)'52% 3#2 IMPROVEMENT OF D" #HEBYSHEV DOPPLER FILTER BANK COMPARED WITH THEOPTIMUM
Ó°xÈ
2!$!2(!.$"//+
&)'52% !VERAGE3#2IMPROVEMENTFORTHED"#HEBYSHEVFILTERBANKSHOWN IN&IGURE#0) PULSES/PTIMUMISFROM&IGURE
HAVEIDENTICALRESPONSES ANDTHEFILTERSWILLBEUNIFORMLYSPACEDALONGTHEDOPPLER AXIS4HENUMBEROFFILTERSIMPLEMENTEDFORAGIVENSIZEOFTHE#0)CAN HOWEVER BEVARIED&OREXAMPLE AGREATERNUMBEROFFILTERSCANBEREALIZEDBYEXTENDINGTHE RECEIVEDDATAWITHEXTRAZEROVALUESALSOKNOWNASZEROPADDING AFTERTHERECEIVED RETURNS HAVE BEEN APPROPRIATELY WEIGHTED IN ACCORDANCE WITH THE DESIRED FILTER RESPONSEEG #HEBYSHEV &ILTER "ANK $ESIGNS 5SING #ONSTRAINED /PTIMIZATION 4ECHNIQUES &OR A GREATERNUMBERSOFPULSESINTHE#0) ANDWHENTHEECONOMYOFTHE&&4IMPLEMENTA TIONOFADOPPLERFILTERBANKCANBEREPLACEDBYA&)2IMPLEMENTATION MOREDESIRABLE &)2FILTERRESPONSESCANBEREALIZEDTHROUGHTHEUSEOFAPPROPRIATENUMERICALDIGITAL FILTERDESIGNTECHNIQUES4HEGOALISSIMILARTOTHATPURSUEDWITHTHEEMPIRICALFILTER DESIGNSDISCUSSEDEARLIERBUTFILTERSWITHALARGENUMBEROFTAPSCANBEDESIGNEDTO EXACTINGSPECIFICATIONS !SANEXAMPLE CONSIDERTHEDESIGNOFADOPPLERFILTERBANKFORAN3BAND'(Z RADARUSINGA#0)OF. PULSESUSINGA02&OFK(Z!SSUMETHATTHERADARREQUIRE MENTSCALLFORASUPPRESSIONOFSTATIONARYLANDCLUTTERBYD"ANDASUPPRESSIONOF MOVINGCLUTTERRAIN BYD"&ORTHEFILTERDESIGN ACLUTTERATTENUATIOND"BELOW THESEREQUIREMENTSWILLBENEEDEDTOKEEPTHESENSITIVITYLOSSDUETOTHECLUTTERRESIDUE BELOWD"ANDALSOBECAUSEEACHDOPPLERFILTERWILLHAVEACOHERENTGAINOFAROUND LOG D" THISMUSTBEADDEDTOTHEFILTERDESIGNSPECIFICATIONASWELL4HE TOTAL3 BANDDOPPLERSPACEFORTHEABOVERADARPARAMETERSISMS ANDASSUMINGTHAT THELANDCLUTTERSUPPRESSIONREGIONHASTOBEoMSANDTHATTHEMOVINGCLUTTERSUPPRES SIONREGIONHASTOBEoMS THECONSTRAINTFORALLDOPPLERFILTERDESIGNSNORMALIZEDTO THEIRPEAKISASSHOWNIN&IGURE 5SINGASIGNALPROCESSINGTOOLBOXDEVELOPEDBY$R$AN03CHOLNIKOFTHE.AVAL 2ESEARCH,ABORATORY ADOPPLERFILTERBANKMEETINGTHEABOVECONSTRAINTSWASDESIGNED 4HEFIRSTFILTER WHICHHASITSPEAKLOCATEDASCLOSEASPOSSIBLETOTHELEFTEDGEOFTHE CONSTRAINTBOXISSHOWNIN&IGURE WITHTHEABSCISSANORMALIZEDTOTHETOTALAVAIL ABLEDOPPLERSPACE
-4)2!$!2
Ó°xÇ
" $
#$!
&)'52% $OPPLERFILTERDESIGNCONSTRAINTS
4HEMISMATCHLOSSOFTHISFILTERIS,M D" WHICHISWELLBELOWTHATOFAD" $OLPH #HEBYSHEVFILTERBANK,M D" &ORTHEREMAININGFILTERS ARELATIVESPAC ING OF $ WAS USED BUT THIS COULD BE REDUCED IN ORDER TO MINIMIZE DOPPLERSTRADDLINGLOSSES4HETHIRDFILTERINTHEFILTERBANKISSHOWNIN&IGURE
' % #! #(
# $ ##
$ & !! "( &)'52% ,EFTMOST&)2FILTERINDOPPLERFILTERBANKDESIGN
Ó°xn
2!$!2(!.$"//+
' % #! #(
# $ ##
$ & !! "( &)'52% 4HIRD&)2FILTERINDOPPLERFILTERBANKDESIGN
4HEMISMATCHLOSSHASNOWBEENREDUCEDTOD"&INALLY THECOMPLETEDOPPLER FILTERBANKISSHOWNIN&IGURE4HISFILTERBANKCOULDBEAUGMENTEDWITHADDI TIONALFILTERSAROUNDZERODOPPLER BUTTHESEWOULDNOTMEETTHEDESIGNCONSTRAINTS DISCUSSED ABOVE 4HE MAIN BENEFIT OF A CUSTOMIZED DOPPLER FILTER BANK DESIGN AS
$" %
!# % &)'52% #OMPLETEDOPPLERFILTERBANKDESIGN
-4)2!$!2
Ó°x
DESCRIBEDHERE ISITSREDUCEDMISMATCHLOSS&ORTHEFILTERSINTHEABOVEDESIGN THEAVERAGEMISMATCHLOSSIS ,M D" ASAVINGSOFD"ASCOMPAREDTOTHE ALTERNATIVEOFAD"WEIGHTED$OLPH #HEBYSHEVFILTERBANK
Ó°££Ê * ,",
Ê , /" ÊÊ
1- Ê 9Ê,
6 ,Ê / %LSEWHEREINTHISCHAPTER3ECTIONSAND PARTICULARLY )&BANDPASSLIMITERS HAVEBEENDISCUSSEDAS AMEANSOFPREVENTINGRECEIVEDCLUTTERSIGNALSFROMEXCEED INGTHERANGEOFTHE!$CONVERTERS NORMALIZING-4)CLUTTERRESIDUECAUSEDBY SYSTEMINSTABILITIES AND NORMALIZINGRESIDUEDUETOTHESPECTRALSPREADOFhFIXED CLUTTERvCAUSEDBYEITHERSCANNINGORWIND BLOWNMOTION4HEREAREOCCASIONALCLUTTER RESIDUESPIKESWHENCLUTTEREXCEEDSTHELIMITLEVEL ANDINTHEPAST THEENERGYFROM THESE SPIKES OF RESIDUE HAS BEEN SUPPRESSED BY FURTHER REDUCTION OF THE LIMIT LEVEL 7HENLIMITERSHAVEBEENUSEDTONORMALIZETHEENERGYOFCLUTTERRESIDUESPIKES THE AVERAGEIMPROVEMENTFACTOROFTHE-4)SYSTEMSDRASTICALLYDETERIORATES4HEEQUA TIONSFOR)IMPROVEMENTFACTOR OFASCANNINGRADARIN3ECTIONAREBASEDONLINEAR THEORY&IELDMEASUREMENTS HOWEVER HAVESHOWNTHATMANYSCANNINGMULTIPLE DELAY -4)RADARSYSTEMSFALLCONSIDERABLYSHORTOFTHEPREDICTEDPERFORMANCE4HISOCCURS BECAUSETHE)&BANDPASSLIMITERSHAVEBEENUSEDTOSUPPRESSTHEENERGYOFTHERESIDUE SPIKESTHATARECAUSEDBYTHELIMITINGACTION,ATERINTHISSECTION ITISSHOWNTHATTHE USEOFABINARYDETECTIONSCHEME INSTEADOFADRASTICREDUCTIONOFTHELIMITLEVEL CAN BEUSEDTOMAINTAINACLUTTERREJECTIONPERFORMANCECLOSETOLINEARTHEORYPREDICTIONIN THERESOLUTIONCELLSWHERECLUTTERLIMITINGOCCUR !NEXAMPLEOFHOWLIMITINGTHEDYNAMICRANGEADJUSTSTHERESIDUEISSHOWNINTHE -4) 00) PHOTOGRAPHS SHOWN IN &IGURE 4HE RANGE RINGS ARE AT MI INTERVALS
&)'52% %FFECTOFLIMITERSA D"IMPROVEMENTFACTOR D"INPUTDYNAMICRANGE AND B D"IMPROVEMENTFACTOR D"INPUTDYNAMICRANGE
Ó°Èä
2!$!2(!.$"//+
!NUMBEROFBIRDSARESHOWNONTHEDISPLAY4HERESIDUEFROMCLUTTERINTHELEFTPHOTO GRAPHISSOLIDOUTTONMIANDTHENDECREASESUNTILITISALMOSTENTIRELYGONEATNMI 4HE-4)IMPROVEMENTFACTORINBOTHPICTURESISD" BUTTHEINPUTDYNAMICRANGE PEAKSIGNAL TO RMSNOISE TOTHECANCELERWASCHANGEDFROMTOD"BETWEENTHE TWOPICTURES!NAIRCRAFTFLYINGOVERTHECLUTTERINTHEFIRSTMIINTHELEFT HANDPICTURE COULDNOTBEDETECTED NOMATTERHOWLARGEITSRADARCROSSSECTION)NTHERIGHT HANDPIC TURE THEAIRCRAFTCOULDBEDETECTEDIFTHETARGET TO CLUTTERCROSS SECTIONRATIOWERESUF FICIENT!LTHOUGHTHISEXAMPLEISFROMMANYYEARSAGO THEPRINCIPLEISSTILLTHESAME EVENTHOUGHCURRENT-4)IMPROVEMENTFACTORSAREBETTERBYTENSOFD"S2ESTRICTION OFTHE)&DYNAMICRANGEISSTILLAVERYEFFICIENTWAYOFNORMALIZINGCLUTTERRESIDUEDUE TOSYSTEMINSTABILITIESORCLUTTERSPECTRALSPREADTOSYSTEMNOISE4HISISTRUEWHETHER ORNOTTHERADARUSESPULSECOMPRESSION 0RIOR TO THE DEVELOPMENT OF MODERN CLUTTER MAPS FOR CONTROLLING FALSE ALARMS CAUSEDBYCLUTTERRESIDUE ORTHEMORERECENTSUGGESTIONTHATBINARYINTEGRATIONCAN MITIGATEIMPULSE LIKERESIDUE THEUSEOF)&LIMITINGWASESSENTIALFORFALSE ALARM CONTROLINAN-4)RADAR3UCHLIMITING HOWEVER SERIOUSLYAFFECTSTHEMEANIMPROVE MENTFACTOROBTAINABLEWITHASCANNING LIMITED MULTIPLE DELAYCANCELERBECAUSEOF THEINCREASEDSPECTRALSPREADOFTHECLUTTERTHATEXCEEDSTHELIMITLEVEL0ARTOFTHE ADDITIONAL CLUTTER SPECTRAL COMPONENTS COMES FROM THE SHARP DISCONTINUITY IN THE ENVELOPEOFRETURNSASTHECLUTTERREACHESTHELIMITLEVEL!TIME DOMAINEXAMPLE OFTHISPHENOMENONISSHOWNIN&IGUREFORARADARWITH. HITSPERBEAM WIDTH/NTHELEFTISAPOINTTARGETTHATDOESNOTEXCEEDTHELIMITLEVELONTHERIGHT ISAPOINTTARGETTHATEXCEEDSTHELIMITLEVELBYD".OTETHAT FORTHISEXAMPLE )DEGRADESBYD"FORTHEDUALCANCELERANDBYD"FORTHETRIPLECANCELER 4HEEXACTRESULTOFTHISCALCULATIONDEPENDSONTHEASSUMEDSHAPEOFTHEANTENNA PATTERNFORTHISEXAMPLE A SINU PATTERNTERMINATEDATTHEFIRSTNULLSWASASSUMED U 4HEREISACOMPARABLEIMPROVEMENTFACTORDEGRADATIONDUETOSPECTRALSPREADINGOF LIMITEDDISTRIBUTEDCLUTTER &IGURES ANDSHOWTHEEXPECTEDMEAN IMPROVEMENTFACTORFORTWO THREE ANDFOUR PULSECANCELERSASAFUNCTIONOFR, THERATIOOFTHERMSCLUTTERAMPLITUDETOTHELIMITLEVEL(ITSPERONE WAYHALF POWER BEAMWIDTHAREINDICATEDBY. !N EXAMPLE OF CLUTTER RESIDUE FROM SIMULATED HARD LIMITED DISTRIBUTED CLUTTER IS TAKENFROM(ALLAND3HRADER&IGURESHOWSAPOLARPLOTOFPARTOFALINEARCLUT TERSEQUENCEFORASCANNINGRADARWITH. HITSPERBEAMWIDTH4HISLINEARCLUTTER SEQUENCEISCONSECUTIVECOMPLEXVOLTAGERETURNSFROMONERANGECELLOFDISTRIBUTED CLUTTER&IGURESHOWSTHEPHASEANDAMPLITUDEOFTHISSEQUENCE )FTHISCLUTTERSEQUENCEWERED"STRONGERANDPASSEDTHROUGHA6)&LIMITER ONLYTHEPHASEINFORMATIONWOULDREMAIN%ACHPULSEWOULDHAVEA6AMPLITUDE 7HENTHERESULTINGLIMITEDCLUTTERSEQUENCEISPASSEDTHROUGHATHREE PULSECANCELER COEFFICIENTS n THEOUTPUTRESIDUEAPPEARSASIN&IGUREA4HECORRESPOND INGPULSE TO PULSEIMPROVEMENTFACTORISSHOWN&IGUREB 4HE EXPECTED THREE PULSE CANCELER IMPROVEMENT FACTOR FROM EQUATION FOR ALINEARSYSTEMWITH. IS) N D")N&IGUREB ITISSEENTHAT THISLEVELOF)ISACHIEVEDFORMOSTOFTHEPULSES WITHONLYTWOPULSESHAVINGVERY LOWVALUESOF)4HESTATISTICSFORTHEDISTRIBUTIONOF)FORTHETHREE PULSECANCELERFOR HARD LIMITEDDISTRIBUTEDCLUTTERARESHOWNIN&IGURE .OTETHATFOR. LESSTHATOFTHEHARD LIMITEDSAMPLESHAVEANIMPROVEMENT FACTORLESSTHAND" WHEREASALMOSTOFTHESAMPLESEXCEEDTHE)EXPECTEDFOR ALINEARSYSTEM
-4)2!$!2
Ó°È£
&)'52% )MPROVEMENTFACTORRESTRICTIONCAUSEDBYALIMITER
4HETIME DOMAINILLUSTRATIONSHOWNPREVIOUSLYIN&IGURELEADSTOTHECONCLU SIONOF(ALLAND3HRADERTHATUSINGAN-OUTOF.BINARYDETECTORATTHEOUTPUTOFAN -4)FILTERWILLPRECLUDEFALSEALARMSFROMTHECLUTTERRESIDUESCAUSEDBYLIMITING &IGURESHOWS INADDITIONTOCLUTTERRESIDUE THERETURNSFROMATARGETTHATWAS SUPERIMPOSEDONTHEDISTRIBUTEDCLUTTERPRIORTOTHECLUTTER PLUS TARGETSEQUENCEPASS ING THROUGH THE )& LIMITING PROCESS /NE CAN SEE THAT MANY OF THE INDIVIDUAL PULSE RETURNSFROMTHETARGETEXCEEDTHEDETECTIONTHRESHOLD WHEREASONLYFOUROFTHECLUTTER RESIDUEPULSESEXCEEDTHETHRESHOLD 4OSUMMARIZE 4HE-4)IMPROVEMENTFACTORINAMAJORITYOFLIMITINGCLUTTER CELLSEXCEEDSTHEAVERAGEIMPROVEMENTFACTOROBTAINEDWITHLINEARPROCESSING CELLS WITHPOOR-4)IMPROVEMENTFACTORCANBEREJECTEDWITHBINARYDETECTIONPROCESSING AND THEREFORE EXCELLENT-4)PERFORMANCECANBEOBTAINEDEVENINREGIONSOFCLUTTER THATEXCEEDTHE)&DYNAMICRANGE
Ó°ÈÓ
2!$!2(!.$"//+
&)'52% -EAN IMPROVEMENT FACTOR RESTRICTION VERSUS AMOUNT OF LIMITING AND CLUTTER SPECTRALSPREADFORATWO PULSECANCELERAFTER4-(ALLAND773HRADERÚ)%%%AND (27ARDAND773HRADERÚ)%%%
&)'52% -EAN IMPROVEMENT FACTOR RESTRICTION VERSUS AMOUNT OF LIMITING AND CLUTTER SPECTRALSPREADFORATHREE PULSECANCELERAFTER4-(ALLAND773HRADERÚ)%%% AND(27ARDAND773HRADERÚ)%%%
-4)2!$!2
'
$&
$*
Ó°ÈÎ
) $&$*
!% *$,!%+**!)(! *) % $ *# "
&)'52% -EANIMPROVEMENTFACTORRESTRICTIONVERSUSAMOUNTOFLIMITINGAND CLUTTERSPECTRALSPREADFORAFOUR PULSECANCELERAFTER4-(ALLAND773HRADER Ú)%%%AND(27ARDAND773HRADERÚ)%%%
.OTETHATTHISDISCUSSIONOFBINARYDETECTIONISADDRESSEDTOTHESPECTRALDISTRIBUTION OFREALCLUTTER THAT WHENVIEWEDINTHETIMEDOMAINBEFORELIMITING HASASMOOTHLY VARYINGCHANGEOFTHEAMPLITUDEANDPHASEOFTHECLUTTERVECTOR4HISISDISTINCTFROM CLUTTER VARIATIONS DUE TO SYSTEM INSTABILITIES THAT ARE NOISE LIKE WHEREIN THE SYSTEM DYNAMICRANGESHOULDBELIMITEDTOPREVENTTHEINSTABILITYRESIDUEFROMEXCEEDINGTHE SYSTEMNOISELEVEL
&)'52% 0OLARREPRESENTATIONOFALINEARCLUTTERSEQUENCE FORHITSPERBEAMWIDTHAFTER4-(ALLAND773HRADER Ú)%%%
Ó°È{
2!$!2(!.$"//+
&)'52% ,INEAR CLUTTER SEQUENCE AMPLITUDE AND PHASE FOR HITS PERBEAMWIDTHAFTER4-(ALLAND773HRADERÚ)%%%
&)'52% A 4HREE PULSE CANCELER RESIDUE AND B IMPROVEMENT FACTOR FOR HARD LIMITEDCLUTTERSEQUENCEFOR. HITSPERBEAMWIDTHAFTER4-(ALLAND773HRADER Ú)%%%
-4)2!$!2
$" &) &% ' # % $%% ! (! '"
Ó°Èx
!
!
!
! &!')#& ) * !
&!') ) #%#+
&)'52% $ISTRIBUTION OF ) AND MEAN OF ) FOR HARD LIMITED CLUTTER FOR DIFFERENT NUMERS OF SCAN NINGHITSPERBEAMWIDTH&ORREFERENCE THEMEANOF)ISALSOSHOWNFORLINEARPROCESSING)REFERSTOTHE IMPROVEMENTFACTOROFATHREE PULSE-4)CANCELER AFTER4-(ALLAND773HRADERÚ)%%%
# "# !
"!! "
&)'52% !FTER -4) PROCESSING OF THE HARD LIMITED DISTRIBUTED CLUTTER SEQUENCE. ANDATARGETSUPERIMPOSEDONTHECLUTTERSEQUENCE THERESIDUE SPIKESAREDISTINCTLYDIFFERENTFROMTHETARGETRETURNS!BINARY- OF .DETECTOR WILLREJECTTHERESIDUEANDKEEPTHETARGETAFTER4-(ALLAND773HRADER Ú)%%%
Ó°£ÓÊ , ,Ê-9-/ Ê-/ /9Ê , +1, /3YSTEM)NSTABILITIES .OTONLYDOTHEANTENNAMOTIONANDCLUTTERSPECTRUMAFFECT THEIMPROVEMENTFACTORTHATISATTAINABLE BUTSYSTEMINSTABILITIESALSOPLACEALIMITON -4)PERFORMANCE4HESEINSTABILITIESCOMEFROMTHESTALOANDCOHO FROMTHETRANS MITTERPULSE TO PULSEFREQUENCYCHANGEIFAPULSEDOSCILLATORANDFROMPULSE TO PULSE
Ó°ÈÈ
2!$!2(!.$"//+
PHASECHANGEIFAPOWERAMPLIFIER FROMTHEINABILITYTOLOCKTHECOHOPERFECTLYTOTHE PHASEOFTHEREFERENCEPULSE FROMTIMEJITTERANDAMPLITUDEJITTERONTHEPULSES AND FROMQUANTIZATIONNOISEOFTHE!$CONVERTER 0HASEINSTABILITIESWILLBECONSIDEREDFIRST)FTHEPHASESOFCONSECUTIVERECEIVED PULSESRELATIVETOTHEPHASEOFTHECOHODIFFERBY SAY RAD ALIMITATIONOFD" ISIMPOSEDON)4HE RADCLUTTERVECTORCHANGEWOULDBEEQUIVALENTTOATARGET VECTOR D"WEAKERTHANTHECLUTTER BEINGSUPERIMPOSEDONTHECLUTTER ASSHOWN IN&IGURE )N THE POWER AMPLIFIER -4) SYSTEM SHOWN IN &IGURE PULSE TO PULSE PHASE CHANGES IN THE TRANSMITTED PULSE CAN BE INTRODUCED BY THE PULSED AMPLIFIER 4HE MOSTCOMMONCAUSEOFAPOWERAMPLIFIERINTRODUCINGPHASECHANGESISRIPPLEONTHE HIGH VOLTAGEPOWERSUPPLY/THERCAUSESOFPHASEINSTABILITYINCLUDEACVOLTAGEONA TRANSMITTERTUBEFILAMENTANDUNEVENPOWERSUPPLYLOADING SUCHASTHATCAUSEDBY PULSE TO PULSESTAGGER )N THE PULSED OSCILLATOR SYSTEM SHOWN IN &IGURE PULSE TO PULSE FREQUENCY CHANGES RESULT IN PHASE RUN OUT DURING THE TRANSMITTED PULSE 0HASE RUN OUT IS THE CHANGEOFTHETRANSMITTEDPULSEPHASEDURINGTHEPULSEDURATIONWITHRESPECTTOTHE PHASEOFTHEREFERENCEOSCILLATOR)FTHECOHOLOCKEDPERFECTLYTOTHEENDOFTHETRANS MITTEDPULSE ATOTALPHASERUN OUTOFRADDURINGTHETRANSMITTEDPULSEWOULDTHEN PLACEANAVERAGELIMITATIONOFD"ONTHEIMPROVEMENTFACTORATTAINABLE0ULSE TO PULSEFREQUENCYCHANGEINMICROWAVEOSCILLATORSISPRIMARILYCAUSEDBYHIGH VOLTAGE POWERSUPPLYRIPPLE)NTHEPULSEDOSCILLATORSYSTEM APULSE TO PULSEPHASEDIFFERENCE OFRADINLOCKINGTHECOHORESULTSIN)LIMITATIONOFD"!SNOTEDELSEWHERE FREQUENCYCHANGEDURINGAPULSEFROMAPULSEDOSCILLATORDOESNOTLIMIT)IFITREPEATS PRECISELYPULSETOPULSE 4HELIMITATIONSONTHEIMPROVEMENTFACTORTHATAREDUETOEQUIPMENTINSTABILITIESIN THEFORMOFFREQUENCYCHANGESOFTHESTALOANDCOHOBETWEENCONSECUTIVETRANSMITTED PULSESAREAFUNCTIONOFTHERANGEOFTHECLUTTER4HESECHANGESARECHARACTERIZEDIN TWOWAYS!LLOSCILLATORSHAVEANOISESPECTRUM)NADDITION CAVITYOSCILLATORS USED BECAUSETHEYAREREADILYTUNABLE AREMICROPHONIC ANDTHUSTHEIRFREQUENCYMAYVARY ATANAUDIORATE4HELIMITATIONONTHEIMPROVEMENTFACTORDUETOFREQUENCYCHANGES IS THE DIFFERENCE IN THE NUMBER OF RADIANS THAT THE OSCILLATOR RUNS THROUGH BETWEEN THETIMEOFTRANSMISSIONANDTHETIMEOFRECEPTIONOFCONSECUTIVEPULSES4HUS THE IMPROVEMENT FACTOR WILL BE LIMITED TO D" IF O$F4 RAD WHERE $F IS THE OSCILLATOR FREQUENCY CHANGE BETWEEN TRANSMITTED PULSES AND4 IS THE TRANSIT TIME OF THEPULSETOANDFROMTHETARGET
&)'52% 0HASEINSTABILITY
-4)2!$!2
Ó°ÈÇ
&)'52% 0OWERAMPLIFIERSIMPLIFIEDBLOCKDIAGRAM
4OEVALUATETHEEFFECTSOFOSCILLATORPHASENOISEON-4)PERFORMANCE THEREAREFOUR STEPS&IRST DETERMINETHESINGLE SIDEBANDPOWERSPECTRALDENSITYOFTHEPHASENOISEAS AFUNCTIONOFFREQUENCYFROMTHECARRIER 3ECOND INCREASETHISSPECTRALDENSITYBY D"4HISACCOUNTSFORA D"INCREASEBECAUSEBOTHSIDEBANDSOFNOISEAFFECTCLUT TERRESIDUE ANDA D"INCREASEBECAUSETHEOSCILLATORCONTRIBUTESNOISEDURINGBOTH TRANSMITTING AND RECEIVING4HIRD ADJUST THE OSCILLATOR PHASE NOISE SPECTRAL DENSITY DETERMINEDABOVEDUETOTHEFOLLOWINGTHREEEFFECTSA THESELF CANCELLATIONOFPHASE NOISEBASEDONCORRELATIONRESULTINGFROMTHETWO WAYRANGEDELAYOFTHECLUTTEROF INTEREST B NOISE REJECTIONDUE TO THEFREQUENCY RESPONSEOF THECLUTTER FILTERS AND C NOISEREJECTIONDUETOTHEFREQUENCYRESPONSEOFTHERECEIVERPASSBAND&INALLY AS THEFOURTHSTEP INTEGRATETHEADJUSTEDSPECTRALDENSITYOFTHEPHASENOISEACROSSTHE ENTIREPASSBAND4HERESULTISTHELIMITATIONON)DUETOTHEOSCILLATORNOISE 2ATHERTHANPERFORMINGTHISINTEGRATIONOFTHERESIDUALNOISENUMERICALLY AMUCH SIMPLERANALYSISCANBECARRIEDOUTIFBOTHTHEOSCILLATORPHASENOISECHARACTERISTICAND ALLOFTHEADJUSTMENTSTOPHASENOISEAREAPPROXIMATEDBYSTRAIGHTLINESONADECIBEL VERSUS LOGFREQUENCYPLOT4HISPROCEDUREBECOMESPARTICULARLYSIMPLEWHENA-4) &)2FILTERUSINGBINOMIALCOEFFICIENTSISASSUMED4HELOCATIONSALONGTHEFREQUENCY AXIS WHERE THE STRAIGHT LINES INTERSECT ARE CALLED BREAK FREQUENCIES 4HIS SIMPLIFIED PROCEDURE WHICH IS SIMILAR TO THAT PRESENTED IN6IGNERI ET AL IS DESCRIBED IN THE FOLLOWINGPARAGRAPHS 4HE FIRST OF THE THREE ADJUSTMENTSOSCILLATOR NOISE SELF CANCELLATION DUE TO THE RANGEOFTHECLUTTEROFINTERESTREDUCESNOISEATTHELOWFREQUENCIESBYD"PER DECADEBELOWTHEBREAKFREQUENCYOF F 42 P (ERE42 2 CISTHETIME
&)'52% 0ULSEDOSCILLATORSIMPLIFIEDBLOCKDIAGRAM
Ó°Èn
2!$!2(!.$"//+
&)'52% 3TRAIGHT LINEAPPROXIMATIONTOTWO DELAYBINOMIAL-4)
DELAYOFTHECLUTTERRETURN 2ISTHECLUTTERRANGE ANDCISTHESPEEDOFLIGHT&ORTHE SECONDADJUSTMENTDUETOTHEFREQUENCYRESPONSEOFTHECLUTTERFILTERS WHICHASSTATED PREVIOUSLY ARE ASSUMED TO BE &)2 CANCELERS WITH BINOMIAL WEIGHTS IT IS NOTED THAT THERESPONSEATVERYLOWFREQUENCIESFALLOFFATD"PERDECADEFORONEDELAY D" PER DECADE FOR TWO DELAYS D" PER DECADE FOR THREE DELAYS ETC!S AN EXAMPLE THEAPPROXIMATIONUSEDFORATWO DELAY-4)FILTERISSHOWNIN&IGURE4HE-4) RESPONSEHASAPEAKVALUEOF y D" RESULTINGINANAVERAGENOISEGAINOF UNITY ANDTHESTRAIGHTLINEAPPROXIMATIONFOLLOWSTHELOWFREQUENCYASYMPTOTEUPTO THED"LEVEL WHICHOCCURSATF4 ANDSTAYSCONSTANTATTHED"LEVELATALL HIGHERFREQUENCIES4HEJUSTIFICATIONFORTHED"APPROXIMATIONATTHEHIGHERFREQUEN CIESISTHATTHEOSCILLATORSPECTRALDENSITYISMORENEARLYCONSTANTANDTHEAVERAGEOVER ONEPERIODOFTHE-4)RESPONSEISUNITY&OROTHERBINOMIALCOEFFICIENT-4)CANCELERS THEBREAKFREQUENCIESFORTHESTARTOFTHERESPONSEFALLOFFAREF4 FORONEDELAY FORTWODELAYS FORTHREEDELAYS ANDFORFOURDELAYS &OR EXAMPLE CONSIDER AN OSCILLATOR WITH SINGLE SIDEBAND PHASE NOISE SPECTRAL DENSITYASSHOWNIN&IGURE!LLOSCILLATORNOISECONTRIBUTIONSAREASSUMEDTOBE COMBINEDINTOTHISONECURVE4HESINGLE SIDEBANDNOISEISINCREASEDBYD"BECAUSE BOTHSIDEBANDSAFFECTSYSTEMSTABILITY ANDTHEPOWERINTEGRATIONISONLYCARRIEDOUT FORPOSITIVEFREQUENCIESANDBYANADDITIONALD"BECAUSETHEOSCILLATORINTRODUCES NOISEINBOTHTHEUPCONVERSIONTOTHETRANSMITTEDSIGNALANDINTHERECEIVERDOWNCON VERSIONPROCESS &IGURESHOWSTHESPECTRALMODIFICATIONSDUETOTHESYSTEMRESPONSESA 4HE FIRST MODIFICATION ACCOUNTS FOR CORRELATION DUE TO THE RANGE TO THE CLUTTER OF INTEREST ;ASSUMEDCLUTTERRANGEISyNMIKM THUS THEBREAKFREQUENCYIS(Z= B 3ECOND ATHREE PULSEBINOMIAL WEIGHTEDCANCELERISASSUMEDWITHTHERADAROPERAT INGATA02&OF(Z4HUS THEBREAKFREQUENCYISr (ZC 4HIRD THERECEIVERPASSBANDISASSUMEDTOEXTENDFROM K(ZTO K(ZWITHRESPECT TOTHE)&CENTERFREQUENCY-(:TOTALPASSBAND ATTHE D"POINTSANDDETERMINED BYATWO POLEFILTER4HUS THERECEIVERPASSBANDRESPONSEFALLSOFFATD"PERDECADE FROMTHEBREAKFREQUENCYATK(ZASSHOWN
-4)2!$!2
Ó°È
&)'52% 3INGLE SIDEBANDPHASE NOISESPECTRALDENSITYOFAMICROWAVEOSCILLATORANDTHEEFFECTIVE NOISEDENSITY
4HEADJUSTEDPHASE NOISESPECTRALDENSITYISSHOWNIN&IGURE4HETOTALNOISE POWERWITHRESPECTTOTHECARRIERISDETERMINEDBYINTEGRATIONOFTHENOISEPOWERUNDER THECURVE4HEEQUATIONFORTHEPOWERSPECTRALDENSITYOFANYONESEGMENTASAFUNC TIONOFFREQUENCYIS
¤ 3 F 3 ¥ ¦
F³ F ´µ
A
F a F a F
(ERE F AND F ARE THE START AND END FREQUENCIES OF THE SEGMENT RESPECTIVELY 3(Zn ISTHEPHASENOISESPECTRALDENSITYRELATIVETOTHECARRIERATTHEBEGINNINGOF THESEGMENTAND@ISTHESLOPEOFTHESEGMENTINLOG UNITSPERDECADE.OTETHATTHE
&)'52% !DJUSTMENTS BASEDONSYSTEMPARAMETERSSEETEXT TOTHEPHASENOISEOFAMICROWAVE OSCILLATOR
Ó°Çä
2!$!2(!.$"//+
&)'52% #OMPOSITEADJUSTMENTSANDADJUSTEDPHASE NOISESPECTRALDENSITY
D"C(Z VALUES IN &IGURE CORRESPOND TO LOG 3 &URTHER DENOTING THE PHASE NOISESPECTRALDENSITYRELATIVETOTHECARRIERATTHEENDOFTHESEGMENTAS3(Zn THE SLOPEISDEFINEDBY
A
LOG 3 3
LOG F F
4HESLOPEIND"DECADEISEQUALTO A 4HENOISEPOWERCONTRIBUTIONCORRESPOND INGTOTHISSEGMENTISFOUNDAS ª 3 A A ALL A w F A A §© F F ¶¸ 0 «
3 ;LNN F LN F = A ¬ FA
4ABLEGIVESTHEINTEGRATIONFORTHEEXAMPLE7HENTHEINTEGRATEDPOWERSFORALL SEGMENTSHAVEBEENCALCULATED THEYARESUMMEDANDTHENCONVERTEDBACKTOD"C4HE FINALANSWER D"C ISTHELIMITON)THATRESULTSFROMOSCILLATORNOISE4HELIMIT ON)3#2D" IS)D" PLUSTARGETINTEGRATIONGAIND" 4!",% )NTEGRATIONOFTHE0HASE .OISE3PECTRAL$ENSITYOF&IGUREWITH!DJUSTMENTSOF
&IGUREAS3HOWNIN&IGURE
3EGMENT F (Z
E E E
F (Z E E E
3LOPE 3LOPE D"DEK @ 3D"C(Z n n n n
n n n n
n n n n n n
3D"C(Z
)NTEGRATED POWER
)NTEGRATED POWER D"C
n n n n n n
E E E E E E
n n n n n n
E
n
4OTALINTEGRATEDNOISEPOWER
-4)2!$!2
Ó°Ç£
4IMEJITTEROFTHETRANSMITTEDPULSESRESULTSINDEGRADATIONOF-4)SYSTEMS4IME JITTERRESULTSINFAILUREOFTHELEADINGANDTRAILINGEDGESOFTHEPULSESTOCANCEL THE AMPLITUDEOFEACHUNCANCELLEDPARTBEING$TS WHERE$TISTHETIMEJITTERANDSISTHE TRANSMITTEDPULSELENGTH4HETOTALRESIDUEPOWERIS$TS ANDTHEREFORETHELIMITA TIONONTHEIMPROVEMENTFACTORDUETOTIMEJITTERIS) LOG;T $ T = D" 4HIS LIMITONTHEIMPROVEMENTFACTORISBASEDONA#7TRANSMITTERPULSEANDONTHEASSUMP TIONTHATTHERECEIVERBANDWIDTHISMATCHEDTOTHEDURATIONOFTHETRANSMITTEDPULSE)N APULSECOMPRESSIONSYSTEM THERECEIVERBANDWIDTHISWIDERBYTHETIME BANDWIDTH "S PRODUCT THUS THE CLUTTER RESIDUE POWER AT EACH END OF THE PULSE INCREASES IN PROPORTIONTOTHE"SPRODUCT4HELIMITON)FORACHIRPPULSECOMPRESSIONSYSTEMIS THEN) LOG;T $ T " T =&ORPULSECOMPRESSIONSYSTEMSEMPLOYINGPHASE CODEDWAVEFORMS THEFACTORINTHEPRECEDINGEQUATIONSHOULDBEMULTIPLIEDBYTHE NUMBEROFSUBPULSESINTHEWAVEFORM4HUS FOREXAMPLE THELIMITON)FORA PULSE "ARKERCODEIS
) LOG ;T r $ T = D"
0ULSE WIDTHJITTERRESULTSINONE HALFTHERESIDUEOFTIMEJITTER AND
) LOG
T D" $07 "T
WHERE$07ISPULSE WIDTHJITTER !MPLITUDEJITTERINTHETRANSMITTEDPULSEALSOCAUSESALIMITATIONOF
) LOG
! D" $!
WHERE!ISTHEPULSEAMPLITUDEAND$!ISTHEPULSE TO PULSECHANGEINAMPLITUDE4HIS LIMITATIONAPPLIESEVENTHOUGHTHESYSTEMUSESLIMITINGBEFORETHECANCELERBECAUSE THERE IS ALWAYS MUCH CLUTTER PRESENT THAT DOES NOT REACH THE LIMIT LEVEL7ITH MOST TRANSMITTERS HOWEVER THEAMPLITUDEJITTERISINSIGNIFICANTAFTERTHEFREQUENCY STABILITY ORPHASE STABILITYREQUIREMENTSHAVEBEENMET *ITTERINTHESAMPLINGTIMEINTHE!$CONVERTERALSOLIMITS-4)PERFORMANCE )FPULSECOMPRESSIONISDONEPRIORTOTHE!$ORIFTHEREISNOPULSECOMPRESSION THISLIMITIS
) LOG
T D" * "T
WHERE * IS THE TIMING JITTER S IS TRANSMITTED PULSE LENGTH AND "S IS THE TIME BANDWIDTHPRODUCT)FPULSECOMPRESSIONISDONESUBSEQUENTTOTHE!$CONVERTER THENTHELIMITATIONIS
) LOG
T D" *"T
4HE LIMITATIONS ON THE ATTAINABLE -4) IMPROVEMENT FACTOR ARE SUMMARIZED IN 4ABLE4HISDISCUSSIONHASASSUMEDTHATTHEPEAK TO PEAKVALUESOFTHESEINSTA BILITIES OCCUR ON A PULSE TO PULSE BASIS WHICH IS OFTEN THE CASE IN PULSE TO PULSE STAGGERED-4)OPERATION)FITISKNOWNTHATTHEINSTABILITIESARERANDOM THEPEAK
Ó°ÇÓ
2!$!2(!.$"//+
4!",% )NSTABILITY,IMITATIONS
0ULSE TO 0ULSE)NSTABILITY
,IMITON)MPROVEMENT&ACTOR
/SCILLATORPHASENOISE 3EEDISCUSSIONINTEXT 4RANSMITTERFREQUENCY ) LOG;O$FS = 3TALOORCOHOFREQUENCY ) LOG;O$F4 = 4RANSMITTERPHASESHIFT ) LOG$E #OHOLOCKING ) LOG$E 0ULSETIMING ) LOG ;T $T "T = 0ULSEWIDTH ) LOG ;T $07 "T = 0ULSEAMPLITUDE ) LOG!$! !$JITTER ) LOG ;T * "T = !$JITTERWITHPULSECOMPRESSIONFOLLOWING!$ ) LOG ;T *"T = WHERE $F INTERPULSEFREQUENCYCHANGE S TRANSMITTEDPULSELENGTH 4 TRANSMISSIONTIMETOANDFROMTARGET $E INTERPULSEPHASECHANGE $T TIMEJITTER * !$SAMPLINGTIMEJITTER "S TIME BANDWIDTHPRODUCTOFPULSECOMPRESSION SYSTEM"S UNITYFOR#7PULSES $07 PULSE WIDTHJITTER ! PULSEAMPLITUDE 6 $! INTERPULSEAMPLITUDECHANGE
VALUESSHOWNINTHESEEQUATIONSCANBEREPLACEDBYTHERMSPULSE TO PULSEVALUES WHICHGIVESRESULTSESSENTIALLYIDENTICALTO3TEINBERGSRESULTS )FTHEINSTABILITIESOCCURATSOMEKNOWNFREQUENCY EG HIGH VOLTAGEPOWERSUP PLY RIPPLE THE RELATIVE EFFECT OF THE INSTABILITY CAN BE DETERMINED BY LOCATING THE RESPONSEONTHEVELOCITYRESPONSECURVEFORTHE-4)SYSTEMFORATARGETATANEQUIVA LENTDOPPLERFREQUENCY)F FORINSTANCE THERESPONSEISD"DOWNFROMTHEMAXIMUM RESPONSE THELIMITATIONON)ISABOUTD"LESSSEVERETHANINDICATEDINTHEEQUATIONS IN4ABLE )F ALL SOURCES OF INSTABILITY ARE INDEPENDENT AS WOULD USUALLY BE THE CASE THEIRINDIVIDUALPOWERRESIDUESCANBEADDEDTODETERMINETHETOTALLIMITATION ON-4)PERFORMANCE )NTRAPULSEFREQUENCYORPHASEVARIATIONSDONOTINTERFEREWITHGOOD-4)OPERATION PROVIDEDTHEYREPEATPRECISELYFROMPULSETOPULSE4HEONLYCONCERNISALOSSOFSEN SITIVITYIFPHASERUN OUTDURINGTHETRANSMITTEDPULSEORMISTUNINGOFTHECOHOORSTALO PERMITSTHERECEIVEDPULSESTOBESIGNIFICANTLYDETUNEDFROMTHEINTENDED)&FREQUENCY )FA RADPHASERUN OUTDURINGTHEPULSEISPERMITTED THESYSTEMDETUNINGMAYBEAS LARGEASOS (ZWITHNODEGRADATIONOF-4)PERFORMANCE 4OGIVEANEXAMPLEOFINTERPULSESTABILITYREQUIREMENTS CONSIDERA -(Z RADAR TRANSMITTING A #7 PULSE OF DURATION S MS AND THE REQUIREMENT THAT NO SINGLESYSTEMINSTABILITYWILLLIMITTHE-4)IMPROVEMENTFACTORATTAINABLEATARANGE OF NMI TO LESS THAN D" A VOLTAGE RATIO OF 4HE RMS PULSE TO PULSE TRANSMITTERFREQUENCYCHANGEIFAPULSEDOSCILLATOR MUSTBELESSTHAN
$F
(Z PT
WHICHISASTABILITYOFABOUTPARTSIN
-4)2!$!2
Ó°ÇÎ
4HERMSPULSE TO PULSETRANSMITTERPHASE SHIFTCHANGEIFAPOWERAMPLIFIER MUST BELESSTHAN
$F
RAD
4HESTALOORCOHOFREQUENCYCHANGEINTHEINTERPULSEPERIODMUSTBELESSTHAN
$F
(Z P r r
WHICHISASTABILITYOFPARTINFORTHESTALOATABOUT'(Z ANDPARTINFOR THECOHOASSUMINGA -(Z)&FREQUENCY 4HECOHOLOCKINGIFAPULSEDOSCILLATORSYSTEM MUSTBEWITHIN
$F
RAD
4HEPULSETIMINGJITTERMUSTBELESSTHAN
$T
T
r r S
4HEPULSE WIDTHJITTERMUSTBELESSTHAN
$07
r T r S
4HEPULSEAMPLITUDECHANGEMUSTBELESSTHAN
$! PERCENT !
4HE!$SAMPLINGTIMEJITTERMUSTBELESSTHAN
*
r T r S
/F THE ABOVE REQUIREMENTS OSCILLATOR PHASE NOISE MAY DOMINATE (OWEVER IN SYSTEMSWITHLARGEBANDWIDTHSSHORTCOMPRESSEDPULSES THETIMINGJITTERREQUIRE MENTSBECOMESIGNIFICANTANDMAYREQUIRESPECIALCLOCKREGENERATIONCIRCUITRYATKEY SYSTEMLOCATIONS %FFECT OF 1UANTIZATION .OISE ON )MPROVEMENT &ACTOR 1UANTIZATION NOISE INTRODUCED IN THE !$ CONVERTER LIMITS THE ATTAINABLE -4) IMPROVEMENT FACTOR #ONSIDER A CONVENTIONAL VIDEO -4) SYSTEM AS SHOWN IN &IGURE "ECAUSE THE PEAKSIGNALLEVELISCONTROLLEDBYTHELINEAR LIMITINGAMPLIFIER THEPEAKEXCURSIONOF THEPHASE DETECTOROUTPUTISKNOWN ANDTHE!$CONVERTERISDESIGNEDTOCOVERTHIS EXCURSION)FTHE!$CONVERTERUSES.BITSANDTHEPHASE DETECTOROUTPUTISFROM TO THEQUANTIZATIONINTERVALIS. 4HERMSVALUEOFTHESIGNAL LEVELDEVIATION
Ó°Ç{
2!$!2(!.$"//+
&)'52% $IGITAL-4)CONSIDERATION
INTRODUCEDBYTHE!$CONVERTERIS ; . =4HELIMITONTHE-4)IMPROVE MENTFACTORTHATTHISIMPOSESONASIGNALREACHINGTHEFULLEXCURSIONOFTHEPHASEDETEC TORISFOUNDBYSUBSTITUTINGINTHEFOLLOWINGEQUATIONFROM4ABLE ) LOG
ª ¹ ! LOG « . LOG ; . =
º $! ¬; = »
"ECAUSETWOQUADRATURECHANNELSCONTRIBUTEINDEPENDENT!$NOISE THEAVERAGE LIMITONTHEIMPROVEMENTFACTOROFAFULL RANGESIGNALIS § ¶ ) LOG ¨ . LOG ; . = · © ¸
)FTHESIGNALDOESNOTREACHTHEFULLEXCURSIONOFTHE!$CONVERTER WHICHISNORMALLY THECASE THENTHEQUANTIZATIONLIMITON)ISPROPORTIONATELYMORESEVERE&OREXAMPLE IFTHESYSTEMISDESIGNEDSOTHATTHEMEANLEVELOFTHESTRONGESTCLUTTEROFINTERESTIS D"BELOWTHE!$CONVERTERPEAK THELIMITON)WOULDBE LOG ; . = 4HISISTABULATEDIN4ABLE 4HIS DISCUSSION OF!$ QUANTIZATION NOISE HAS ASSUMED PERFECT!$ CONVERTERS -ANY!$CONVERTERS PARTICULARLYUNDERHIGH SLEW RATECONDITIONS ARELESSTHANPER FECT4HIS INTURN LEADSTOSYSTEMLIMITATIONSMORESEVERETHANPREDICTEDHERESEE 3ECTION
4!",% 4YPICAL,IMITATIONON)$UETO!$1UANTIZATION
.UMBEROF"ITS .
,IMITON-4))MPROVEMENT&ACTOR) D"
-4)2!$!2
Ó°Çx
0ULSE#OMPRESSION#ONSIDERATIONSo 7HENAN-4)SYSTEMISUSEDWITHPULSE COMPRESSION THE SYSTEM TARGET DETECTION CAPABILITY IN CLUTTER MAY BE AS GOOD AS A SYSTEMTRANSMITTINGTHEEQUIVALENTSHORTPULSE ORTHEPERFORMANCEMAYBENOBETTER THANASYSTEMTRANSMITTINGTHESAMELENGTH#7PULSE4HEKINDOFCLUTTERENVIRONMENT THESYSTEMINSTABILITIES ANDTHESIGNALPROCESSINGUTILIZEDDETERMINEWHERETHESYSTEM PERFORMANCEWILLFALLBETWEENTHEABOVETWOEXTREMES5NLESSPROVISIONISINCORPO RATEDFORCOPINGWITHSYSTEMINSTABILITIESANDCLUTTERSPECTRALSPREAD THE-4)PULSE COMPRESSIONSYSTEMMAYFAILTOWORKATALLINACLUTTERENVIRONMENT )DEALLY A PULSE COMPRESSION RECEIVER COUPLED WITH AN -4) WOULD APPEAR AS IN &IGUREAp)FTHEPULSECOMPRESSIONSYSTEMWASPERFECT THECOMPRESSEDPULSE WOULDLOOKASIFTHERADARHADTRANSMITTEDANDRECEIVEDASHORTPULSE AND-4)PRO CESSINGCOULDPROCEEDASIFTHEPULSECOMPRESSIONHADNOTEXISTED)NPRACTICE THE COMPRESSEDPULSEWILLHAVETIMESIDELOBESFROMTHREEBASICCAUSES4HEFIRSTISWAVE FORM AND SYSTEM DESIGN WHICH INCLUDES COMPONENTS THAT MAY BE NONLINEAR WITH FREQUENCY ETC4HESESIDELOBESWILLBESTABLE4HATIS THEYSHOULDREPEATPRECISELYON APULSE TO PULSEBASISANDTHUSWILLCANCELINTHE-4)CANCELER)TISASSUMEDTHATTHE RADARSYSTEMISFULLYCOHERENTASREQUIREDBYRULEIN3ECTION4HESECONDCAUSE OFPULSECOMPRESSIONSIDELOBESISSYSTEMINSTABILITIES SUCHASNOISEONLOCALOSCIL LATORS TRANSMITTERTIMEJITTER TRANSMITTERTUBENOISE AND!$CONVERTERJITTER4HESE SIDELOBESARENOISE LIKEANDAREPROPORTIONALTOTHECLUTTERAMPLITUDE4HEYWILLNOT CANCELINTHE-4)CANCELER4HETHIRDSOURCEOFSIDELOBESISHIGH FREQUENCYRIPPLEIN THETRANSMITTERPOWERSUPPLY )F THE TRANSMITTER POWER SUPPLY INCORPORATES HIGH FREQUENCY AC DC ANDOR DC DC CONVERTERS AND IF THE CONVERTER FREQUENCY COMPONENTS ARE NOT SUFFICIENTLY FILTERED THEREWILLBEDISCRETETIMESIDELOBES OFFSETFROMTHECLUTTERINRANGE ASPREDICTEDBY PAIRED ECHOTHEORY4HEPAIRED ECHOSIDELOBESWILLALSOHAVEADOPPLERFREQUENCY EQUALTOTHECONVERTERFREQUENCY4HISFREQUENCYFCONV WILLALIASINTOTHE02&FR DOPPLERINTERVALATTHEFREQUENCYFDOP ;FDOP MODULOFCONV FR = 4HESESIDELOBESWILL NOTCANCELUNLESSTHEHIGH FREQUENCYCONVERTERSARESYNCHRONIZEDTOAMULTIPLEOFTHE 02& INWHICHCASEFDOP !SSUMETHATTHENOISE LIKECOMPONENTOFTHESIDELOBESISDOWND"FROMTHE PEAKTRANSMITTEDSIGNALS4HISNOISE LIKECOMPONENTWILLNOTCANCELINTHE-4)SYS TEM ANDTHEREFORE FOREACHCLUTTERAREATHATEXCEEDSTHESYSTEMTHRESHOLDBYD" ORMORE THERESIDUEWILLEXCEEDTHEDETECTIONTHRESHOLD)FTHECLUTTEREXCEEDSTHE THRESHOLD BY D" THE RESIDUE FROM THE -4) SYSTEM WILL EXCEED THE DETECTION THRESHOLDBYD" ELIMINATINGTHEEFFECTIVENESSOFTHE-4)&IGUREBSHOWSA SKETCHOFTHISEFFECT 4OENSURETHATTHENOISE LIKEPULSE COMPRESSIONSIDELOBESWILLNOTEXCEEDTHESYSTEM NOISEAFTERTHE-4)CANCELER THESYSTEMSTABILITYBUDGETMUSTENSURETHATTHEINSTABILITY SIDELOBELEVELISLOWERTHANTHEDYNAMICRANGEOFTHERECEIVINGSYSTEM4HERECEIVING SYSTEMDYNAMICRANGEISULTIMATELYDETERMINEDINAWELL DESIGNEDSYSTEM BYTHE)&
o!LLSIGNALPROCESSINGFOLLOWINGTHE!$DETECTORISDONEDIGITALLY)TISMOREMEANINGFUL HOWEVER TODESCRIBEAND DEPICTTHEPROCESSINGINANANALOGMANNER p4HE)&BANDPASSLIMITER;2ADAR(ANDBOOK ND%D PPn=SHOWNINTHISANDSUBSEQUENTDIAGRAMSHASAN AMPLITUDEOUTPUTCHARACTERISTICTHATISLINEARFORINPUTSIGNALVOLTAGESFROMNOISELEVELTOWITHIND"OFTHELIMITER OUTPUTMAXIMUMVOLTAGEANDTHENTRANSITIONSSMOOTHLYTOTHEMAXIMUMOUTPUTVOLTAGE4HEPHASEOFTHEINPUT SIGNALISPRECISELYPRESERVED4HESELIMITERCHARACTERISTICSEXISTWHETHERTHEFILTERISIMPLEMENTEDINANALOGCIRCUITRY ORADIGITALALGORITHM
Ó°ÇÈ
2!$!2(!.$"//+
&)'52% 0ULSECOMPRESSIONWITH-4)A IDEALBUTDIFFICULT TO ACHIEVECOMBINATION ANDB EFFECTOFOSCILLATORONTRANSMITTERINSTABILITIES
BANDPASSLIMITERTHATPRECEDESTHE!$CONVERTER)FSYSTEMINSTABILITIESCANNOTBECON TROLLEDTOBELESSTHANTHESYSTEMDYNAMICRANGE THENTHESYSTEMDYNAMICRANGESHOULD BEDECREASED!NALTERNATIVETODECREASINGTHEDYNAMICRANGEISTODEPENDONACELL AVERAGINGCONSTANTFALSEALARMRATE#! #&!2 PROCESSORAFTERTHESIGNALPROCESSING TOPROVIDEATHRESHOLDTHATRIDESOVERTHERESIDUENOISE BUTTHEEFFICACYOFTHISMETHOD DEPENDSONTHERESIDUENOISEBEINGCOMPLETELYNOISE LIKE WHICHISUNLIKELY !FTERADDRESSINGTHEUNSTABLEPULSE COMPRESSIONSIDELOBES ITISSTILLNECESSARYTO CONTROLDETECTIONSFROMRESIDUECAUSEDBYTHESPECTRALSPREADOFTHECLUTTERORBYLOW FREQUENCYTRANSMITTERPOWERSUPPLYRIPPLE4HISCANBEACCOMPLISHEDBYLIMITINGTHE MAXIMUMSIGNALAMPLITUDEATTHEINPUTTOTHECANCELER4HEPROCESSDESCRIBEDABOVE ISDEPICTEDIN&IGURE /NE APPROACH THAT HAS BEEN SUCCESSFUL IN ACHIEVING THE MAXIMUM -4) SYSTEM PERFORMANCEATTAINABLEWITHINTHELIMITSIMPOSEDBYSYSTEMANDCLUTTERINSTABILITIES
&)'52% 0RACTICAL-4)PULSE COMPRESSIONCOMBINATION
-4)2!$!2
Ó°ÇÇ
ISSHOWNIN&IGURE4RANSMITTERNOISEWILLBEUSEDINTHEFOLLOWINGDISCUSSION TOREPRESENTALLPOSSIBLESYSTEMINSTABILITIESTHATCREATENOISE LIKEPULSE COMPRESSION TIMESIDELOBES ,IMITERISSETTOLIMITTHESYSTEMDYNAMICRANGETOTHERANGEBETWEENPEAKCLUTTER ANDCLUTTERINSTABILITYNOISE,IMITERISSETSOTHATTHEDYNAMICRANGEATITSOUTPUTIS EQUALTOTHEEXPECTED-4)IMPROVEMENTFACTORASLIMITEDBYCLUTTERSPECTRALSPREAD OR LOW FREQUENCY TRANSMITTER POWER SUPPLY RIPPLE 4HESE LIMITER SETTINGS CAUSE THE RESIDUEDUETOTRANSMITTERNOISEANDTHERESIDUEDUETOOTHERINSTABILITIES SUCHASQUAN TIZATIONNOISEANDINTERNAL CLUTTERMOTION EACHTOBEEQUALTOFRONT ENDTHERMALNOISE ATTHECANCELEROUTPUT4HISALLOWSMAXIMUMSENSITIVITYWITHOUTANEXCESSIVEFALSE ALARMRATE,IMITERISAVERYEFFICIENTCONSTANT FALSE ALARM RATEDEVICEAGAINSTSYSTEM INSTABILITIESBECAUSEITSUPPRESSESTHEINSTABILITYNOISEINDIRECTPROPORTIONTOTHECLUTTER SIGNALSTRENGTHBUTDOESNOTSUPPRESSATANYTIMEWHENTHECLUTTERSIGNALISNOTSTRONG !LTHOUGHTHELIMITERSCAUSEPARTIALORCOMPLETESUPPRESSIONOFSOMEDESIREDTARGETSIN THECLUTTERAREAS NOTARGETSARESUPPRESSEDTHATCOULDOTHERWISEHAVEBEENDETECTEDIN THEPRESENCEOFCLUTTERRESIDUEATTHESYSTEMOUTPUTIFTHELIMITERSHADNOTBEENUSED !SASPECIFICEXAMPLE CONSIDERASYSTEMWITHAPULSE COMPRESSIONRATIOOFABOUT D" AND SYSTEM INSTABILITY NOISE APPROXIMATELY D" BELOW THE CARRIER POWER !SSUMETHATTHE-4)CANCELERIMPROVEMENTFACTORISD" LIMITEDBYCLUTTERSPEC TRAL SPREAD7ITH THE ABOVE SYSTEM PARAMETERS A RECEIVER SYSTEM THAT WILL PROVIDE THEMAXIMUMOBTAINABLEPERFORMANCEISSHOWNIN&IGURE!TTHEOUTPUTOFTHE PULSE COMPRESSIONNETWORK THESYSTEMINSTABILITYNOISEWILLBEEQUALTOORLESSTHAN THERMALNOISEFOREITHERDISTRIBUTEDCLUTTERORPOINTCLUTTER ANDTHEPEAKCLUTTERSIGNALS WILLVARYFROMABOUTD"ABOVETHERMALNOISEFOREVENLYDISTRIBUTEDCLUTTERTOD" ABOVETHERMALNOISEFORSTRONGPOINTCLUTTER "ECAUSETHE-4)CANCELERISEXPECTEDTOATTENUATECLUTTERBYD" THESECONDLIM ITERISPROVIDEDTOPREVENTTHERESIDUEFROMSTRONGCLUTTERFROMEXCEEDINGTHETHRESHOLD 7ITHOUTTHESECONDLIMITER ASTRONG POINTREFLECTORTHATWASD"ABOVENOISEATTHE CANCELERINPUTWOULDHAVEARESIDUED"ABOVENOISEATTHECANCELEROUTPUT4HIS WOULDBEINDISTINGUISHABLEFROMANAIRCRAFTTARGET )TTHETRANSMITTERNOISEWERED"LESSTHANASSUMEDABOVE THEFIRSTLIMITERWOULD BESETD"ABOVETHERMALNOISEANDMUCHLESSTARGETSUPPRESSIONWOULDOCCUR4HUS TARGETDETECTABILITYWOULDIMPROVEINANDNEARTHESTRONGCLUTTERAREASEVENTHOUGHTHE -4)IMPROVEMENTFACTORWASSTILLLIMITEDTOD"BYINTERNAL CLUTTERMOTION )N SUMMARY THE NOISE LIKE PULSE COMPRESSION SIDELOBES AND THE DURATION OF THE UNCOMPRESSEDPULSEDICTATEHOWEFFECTIVEAPULSE COMPRESSION-4)SYSTEMCANBE 3YSTEMS HAVE BEEN BUILT IN WHICH TRANSMITTER NOISE AND LONG UNCOMPRESSED PULSES COMBINEDTOMAKETHESYSTEMSINCAPABLEOFDETECTINGAIRCRAFTTARGETSINORNEARLAND CLUTTER3OMEEXISTINGPULSE COMPRESSIONSYSTEMSHAVENOTDELIBERATELYPROVIDEDTHE
&)'52% -4)WITHPULSECOMPRESSION
Ó°Çn
2!$!2(!.$"//+
TWOSEPARATELIMITERSDESCRIBEDABOVE BUTTHESYSTEMSWORKBECAUSEDYNAMICRANGEIS SUFFICIENTLYRESTRICTEDBYCIRCUITCOMPONENTS/THERSYSTEMS SUCHASTHOSETHATDELIB ERATELY HARD LIMIT BEFORE PULSE COMPRESSION FOR #&!2 REASONS DO NOT HAVE CLUTTER RESIDUEPROBLEMSBUTSUFFERFROMSIGNIFICANTTARGETSUPPRESSIONINTHECLUTTERAREAS !N ALTERNATIVE TO THE USE OF LIMITERS IS THE USE OF CLUTTER MAPS IN CONJUNCTION WITHTHE#! #&!2#LUTTERMAPSWORKWELLFORSTATIONARYRADARSOPERATINGATFIXED FREQUENCIES BUTARELESSEFFECTIVEFOROTHERRADARS4HE#! #&!2ISUSEFUL EVEN FORASYSTEMWITH)&LIMITERS BECAUSETHEREWILLBESMALLVARIATIONSONTHEORDEROF AFEWD" INTHECOMBINATIONOFCLUTTERRESIDUEANDSYSTEMNOISE4OREEMPHASIZE HOWEVER WITHOUTTHELIMITERS THEREMAYBETENSOFD"SDIFFERENCEBETWEENCLUTTER RESIDUEANDSYSTEMNOISE
Ó°£ÎÊ 9 Ê, Ê ÊÉ Ê " 6 ,-" Ê
" - ,/" 4HE ACCURATE CONVERSION OF THE RADAR )& SIGNAL INTO A DIGITAL REPRESENTATION OF THE COMPLEXENVELOPEISANIMPORTANTSTEPINTHEIMPLEMENTATIONOFAMODERNDIGITALSIG NALPROCESSOR4HISANALOG TO DIGITAL!$ CONVERSIONMUSTPRESERVETHELINEARITYOF AMPLITUDEANDPHASEOVERTHEREQUIREDDYNAMICRANGE HAVEASMALLEFFECTONOVERALL RADARSYSTEMNOISETEMPERATURE ANDBEFREEFROMUNDESIREDSPURIOUSRESPONSES !DVANCESIN!$CONVERTERTECHNOLOGYISNOWMAKINGITPOSSIBLETODIRECTLYCON VERTANANALOG)&SIGNALINTOACORRESPONDINGDIGITALCOMPLEXREPRESENTATION RATHER THANGOINGTHROUGHTHEINTERMEDIATESTEPOFFIRSTDOWNCONVERTINGTHE)&SIGNALINTO BASEBANDIN PHASE) ANDQUADRATURE1 COMPONENTSANDSUBSEQUENTLYUSINGASEPA RATE!$CONVERTERINEACHOFTHESETWOCHANNELS !FLOWCHARTOFADIRECT)&!$CONVERTERISILLUSTRATEDIN&IGUREALONGWITH SPECTRALREPRESENTATIONSOFTHESIGNALTHROUGHOUTTHECONVERSIONPROCESS4HE)&INPUT CENTERED AT THE FREQUENCY F)& IS FIRST PASSED THROUGH A BANDPASS FILTER TO ENSURE THAT NEGLIGIBLEALIASINGWILLOCCURDURINGTHESUBSEQUENT!$CONVERSIONPROCESS/NTHE RIGHTIN&IGURE THETOPGRAPHSHOWSTHEPOSITIVEANDNEGATIVEPARTSOFTHESIGNAL SPECTRUMATTHE)&FILTEROUTPUT4HEPOSITIVEPARTOFTHISSPECTRUMCORRESPONDSTOTHE COMPLEXENVELOPE WHICHNEEDSTOBETRANSLATEDINTOTHEDIGITAL)AND1REPRESENTATION 4HISFILTEROUTPUTBECOMESTHEINPUTTOTHE!$CONVERTEROPERATINGATASAMPLINGRATE OFF!$4HESPECTRUMOFTHE!$CONVERTEROUTPUTISAGAINSHOWN ANDITISOBTAINED SIMPLYBYREPLICATINGTHEORIGINAL)&SPECTRUMFROMMINUSINFINITYTOPLUSINFINITYWITH APERIODOFF!$)NTHISEXAMPLE AN!$CONVERSIONRATEOF F!$ F)& ISASSUMED4HE OPTIMUMCHOICEOFTHE!$CONVERTERSAMPLINGRATEENSURESTHATTHENEGATIVEPARTOF THESPECTRUMHASTHESMALLESTPOSSIBLEOVERLAPWITHTHEPOSITIVEPARTOFTHESPECTRUM 4HESMALLESTPOSSIBLEOVERLAPOCCURSWHENTHE!$SAMPLINGRATEISRELATEDTOTHE RADAR)&FREQUENCYASFOLLOWS
F!$
F)& -
WHERE-ISANINTEGERGREATERTHAN4HUS OPTIMUMSAMPLINGRATESAREF)& F)& F)& F)& xETC4HECORRESPONDINGMAXIMUMUNALIASEDOR.YQUIST BANDWIDTH IS".1 F!$ 4HISVALUEIS THEREFORE THEMAXIMUMALLOWABLECUTOFFBANDWIDTHOF THE)&BANDPASSFILTERATTHEINPUTTOTHE!$CONVERTER)TISNOTSTRICTLYNECESSARYTOUSE
-4)2!$!2
0 0 0 "
Ó°Ç
#$+ )
#) + %($#&! ( +),% "# + ( +' )'
!+#- ( +),% ,(() **
/
#%+ /
'%($ .&- $'( %($
&)'52% )MPLEMENTATIONOF!$CONVERSIONUSINGDIRECTSAMPLINGOFTHE)&SIGNAL
AN!$CONVERTERSAMPLINGRATEASGIVENBY%Q BUTOTHERVALUESWILLRESULTINAN AVAILABLE .YQUIST BANDWIDTH LESS THAN F!$ 4HIS IS SHOWN IN &IGURE WHERE THENORMALIZED.YQUISTBANDWIDTHISSHOWNASAFUNCTIONOFTHERELATIVE!$CONVERTER SAMPLINGRATE&ROMTHISFIGURE ITISSEENTHATTHEDIRECTCONVERSIONAPPROACHWILLFAIL WHENEVERAVALUEOF- WHICHISLOCATEDHALFWAYBETWEENTHEOPTIMUMVALUES ISUSED !TTHE!$CONVERTEROUTPUT THESIGNALSAMPLESARESTILLREALVALUED4OBEABLE TOEXTRACTTHECOMPLEXENVELOPECORRESPONDINGTOTHEPOSITIVEPARTOFTHESPECTRUM ! F F)& IT IS NECESSARY TO SHIFT THE SPECTRUM AT THE !$ CONVERTER OUTPUT DOWN IN FREQUENCY BYPTHE AMOUNT F)& 4HIS CORRESPONDS TO A MULTIPLICATION BY THE TIMESERIES UI E JI %QUIVALENTLY THECOMPLEXENVELOPESPECTRUMBELOWZERO FREQUENCYCANBESHIFTEDUPTOZEROFREQUENCYBYMULTIPLICATIONWITHTHETIMESERIES P UI E JI 4HIS RESULTS IN THE SPECTRUM SHOWN WHERE THE DESIRED SPECTRUM CORRE SPONDINGTOTHECOMPLEXENVELOPEISCENTEREDATZEROFREQUENCY BUTTHESIGNALSTILL CONTAINSTHEUNWANTEDNEGATIVESPECTRALCOMPONENTSLIGHTSHADING !SARESULTOF THISFREQUENCYTRANSLATION THESIGNALHASNOWBECOMECOMPLEX!DIGITAL&)2BAND PASSFILTERWITHANEARLYRECTANGULARRESPONSEISTHENAPPLIEDTOREJECTTHENEGATIVE FREQUENCYCOMPONENTSASSHOWNINTHEFINALGRAPHONTHERIGHT4HEDESIREDSAMPLED COMPLEXENVELOPEREPRESENTATIONHASNOWBEENREALIZED BUTATTHEORIGINALSAMPLING RATEOFF!$)FDESIRED THEOVERSAMPLINGCANFINALLYBEREMOVEDTHROUGHDECIMATION BYAFACTOROFASSHOWNINTHELASTSTEPINTHEFIGURE
Ó°nä
2!$!2(!.$"//+
"$& #!" %"'
"$ ! "' &)'52% !VAILABLE.YQUISTBANDWIDTHVS!$CONVERTERSAMPLINGRATE
!$ CONVERTERS ARE TYPICALLY CHARACTERIZED BY THEIR SIGNAL TO NOISE RATIO 3.2 PERFORMANCEREFERREDTOABANDWIDTHEQUALTOTHE!$SAMPLINGRATE/FTENTHIS3.2 IS NOT AS HIGH AS ONE WOULD EXPECT BASED ON THE NUMBER OF BITS USED BY THE!$ CONVERTER3OMETIMESTHEACTUALPERFORMANCEOFAN!$CONVERTERISCHARACTERIZEDBY ANEFFECTIVENUMBEROFBITS SMALLERTHANTHEACTUALNUMBEROFBITSANDCORRESPOND INGTOTHEACHIEVABLE3.24HE3.2OFAN!$CONVERTERSETSANUPPERLIMITONTHE ACHIEVABLEIMPROVEMENTFACTOR
Ó°£{Ê */6 Ê / 7HENTHEDOPPLERFREQUENCYOFTHERETURNSFROMCLUTTERISUNKNOWNATTHERADARINPUT SPECIALTECHNIQUESAREREQUIREDTOGUARANTEESATISFACTORYCLUTTERSUPPRESSION!SDIS CUSSEDIN3ECTION THEDOPPLERFILTERBANKWILLUSUALLYBEEFFECTIVEAGAINSTMOVING CLUTTER4HISREQUIRESTHATTHEINDIVIDUALFILTERSBEDESIGNEDWITHALOWSIDELOBELEVEL INTHEREGIONSWHERECLUTTERMAYAPPEARANDTHATEACHFILTERBEFOLLOWEDBYAPPROPRI ATE #&!2 PROCESSING CIRCUITS TO REJECT UNWANTED CLUTTER RESIDUE7HEN CLUTTER SUP PRESSIONISTOBEIMPLEMENTEDWITHASINGLE-4)FILTER ITISNECESSARYTOUSEADAPTIVE TECHNIQUESTOENSURETHATTHECLUTTERFALLSINTHE-4)REJECTIONNOTCH!NEXAMPLEOF SUCHANADAPTIVE-4)IS4!##!2 ORIGINALLYDEVELOPEDFORAIRBORNERADARS)NMANY APPLICATIONS THE ADAPTIVE -4) WILL FURTHER HAVE TO TAKE INTO ACCOUNT THE SITUATION WHEREMULTIPLECLUTTERSOURCESWITHDIFFERENTRADIALVELOCITIESAREPRESENTATTHESAME RANGEANDBEARING 5SUALLYTHEDOPPLERSHIFTOFCLUTTERRETURNSISCAUSEDBYTHEWINDFIELD ANDEARLY ATTEMPTSOFCOMPENSATINGINTHE-4)HAVEVARIEDTHECOHOFREQUENCYSINUSOIDALLYASA FUNCTIONOFAZIMUTHBASEDONTHEAVERAGEWINDSPEEDANDDIRECTION4HISAPPROACHIS
-4)2!$!2
Ó°n£
UNSATISFACTORYBECAUSETHEWINDFIELDRARELYISHOMOGENEOUSOVERALARGEGEOGRAPHICAL AREAANDBECAUSETHEWINDVELOCITYUSUALLYISAFUNCTIONOFALTITUDEDUETOWINDSHEAR IMPORTANTFORRAINCLUTTERANDCHAFF !GAINSTASINGLECLUTTERSOURCE ANIMPLEMENTA TIONISREQUIREDTHATPERMITSTHE-4)CLUTTERNOTCHTOBESHIFTEDASAFUNCTIONOFRANGE !NEXAMPLEOFSUCHANADAPTIVE-4)IMPLEMENTATIONISSHOWNIN&IGURE4HE PHASE ERRORCIRCUITCOMPARESTHECLUTTERRETURNFROMONESWEEPTOTHENEXT4HROUGH A CLOSED LOOP WHICH INCLUDES A SMOOTHING TIME CONSTANT THE ERROR SIGNAL CONTROLS APHASESHIFTERATTHECOHOOUTPUTSUCHTHATTHEDOPPLERSHIFTFROMPULSETOPULSEIS REMOVED)TSHOULDBENOTEDTHATSINCETHEFIRSTSWEEPENTERINGTHE-4)ISTAKENASA REFERENCE ANYPHASESHIFTRUN OUTASAFUNCTIONOFRANGEWILLINCREASEPROPORTIONALLY TOTHENUMBEROFSWEEPS5LTIMATELYTHISRUN OUTWILLEXCEEDTHESPEEDOFRESPONSE OFTHECLOSEDLOOP ANDTHE-4)MUSTBERESET4HISTYPEOFCLOSED LOOPADAPTIVE-4) MUST THEREFORE BEOPERATEDFORAFINITESETBATCH OFPULSESTOENSURETHATTHISWILLNOT HAPPEN3UCHBATCH MODEOPERATIONISALSOREQUIREDIFACOMBINATIONOF-4)OPERATION ANDFREQUENCYAGILITYISDESIRED )FABIMODALCLUTTERSITUATIONISCAUSEDBYTHESIMULTANEOUSPRESENCEOFRETURNSFROM LANDCLUTTERANDWEATHERORCHAFF ANADAPTIVE-4)CANBEIMPLEMENTEDFOLLOWINGA FIXED CLUTTER NOTCH -4) SECTION AS ILLUSTRATED IN &IGURE 4HE NUMBER OF ZEROS USEDINTHEFIXED ZERODOPPLER CLUTTER NOTCHSECTIONOFTHE-4)ISDETERMINEDBYTHE REQUIREDIMPROVEMENTFACTORANDTHESPECTRALSPREADOFTHELANDCLUTTER4YPICALLY THE FIXED NOTCH-4)WOULDUSETWOORTHREEZEROS&ORTHEADAPTIVEPORTIONOFTHE-4) AFULLYDIGITALIMPLEMENTATIONISSHOWNINWHICHTHEPULSE TO PULSEPHASESHIFTOFTHE CLUTTEROUTPUTFROMTHEFIRSTCANCELERISMEASUREDANDAVERAGEDOVERAGIVENNUMBEROF RANGECELLS4HISESTIMATEDPHASESHIFTISADDEDTOTHEPHASESHIFT WHICHISAPPLIEDTOTHE DATAONTHEPREVIOUSSWEEP ANDTHISNEWPHASESHIFTISAPPLIEDTOTHECURRENTDATA 4HERANGEAVERAGINGMUSTBEPERFORMEDSEPARATELYONTHE)AND1COMPONENTSOF THEMEASUREDPHASEINEACHRANGECELLDUETOTHEOAMBIGUITYOFTHEPHASEREPRESENTA TIONITSELF4HEACCUMULATIONOFTHEAPPLIEDPHASESHIFTFROMSWEEPTOSWEEP HOWEVER MUSTBEPERFORMEDDIRECTLYONTHEPHASEANDISCOMPUTEDMODULOO4HENUMBEROF ZEROSOFTHEADAPTIVE-4)SECTIONISAGAINDETERMINEDBYTHEREQUIREDIMPROVEMENT FACTORANDTHEEXPECTEDSPECTRALSPREADOFTHECLUTTER4HEPHASESHIFTISAPPLIEDTOTHE INPUTDATAINTHEFORMOFACOMPLEXMULTIPLY WHICHAGAINREQUIRESTHETRANSFORMATION OF THE PHASE ANGLE INTO RECTANGULAR COORDINATES 4HIS TRANSFORMATION CAN EASILY BE PERFORMEDBYATABLELOOKUPOPERATIONINAREAD ONLYMEMORY
&)'52% "LOCKDIAGRAMOFCLOSED LOOPADAPTIVEDIGITAL-4)
Ó°nÓ
2!$!2(!.$"//+
&)'52% /PEN LOOPADAPTIVE-4)FORCANCELLATIONOFSIMULTANEOUSFIXEDANDMOVINGCLUTTER
7HENDOPPLERSHIFTSAREINTRODUCEDBYDIGITALMEANSASDESCRIBEDABOVE THEACCU RACY OF THE ) AND 1 REPRESENTATION OF THE ORIGINAL INPUT DATA BECOMES AN IMPORTANT CONSIDERATION!NYDCOFFSET AMPLITUDEIMBALANCE QUADRATUREPHASEERROR ORNONLIN EARITYWILLRESULTINTHEGENERATIONOFUNDESIREDSIDEBANDSTHATWILLAPPEARASRESIDUE ATTHECANCELEROUTPUT!DISCUSSIONOF!$CONVERSIONCONSIDERATIONSWASPRESENTED IN3ECTION )NTHEADAPTIVE-4)IMPLEMENTATIONDESCRIBEDABOVE THENUMBEROFZEROSALLO CATEDTOEACHOFTHETWOCANCELERSWASFIXED BASEDONANAPRIORIASSESSMENTOFTHE CLUTTERSUPPRESSIONREQUIREMENT4HEONLYVARIATIONPOSSIBLEWOULDBETOCOMPLETELY BYPASSONEORBOTH OFTHE-4)CANCELERSIFNOLANDCLUTTERORWEATHERORCHAFFRETURNS ARERECEIVEDONAGIVENRADIAL!MORECAPABLESYSTEMCANBEIMPLEMENTEDIFTHENUM BEROFZEROSCANBEALLOCATEDDYNAMICALLYTOEITHERCLUTTERSOURCEASAFUNCTIONOFRANGE 4HISLEADSTOAFULLYADAPTIVE-4)IMPLEMENTATIONUSINGAMORECOMPLEXADAPTATION ALGORITHM AS DISCUSSED BELOW 3UCH AN ADAPTIVE -4) MAY PROVIDE A PERFORMANCE CLOSETOTHEOPTIMUMDISCUSSEDIN3ECTION )NORDERTOILLUSTRATETHEDIFFERENCEINPERFORMANCEBETWEENSUCHCANDIDATE-4) IMPLEMENTATIONS ASPECIFICEXAMPLEISCONSIDEREDNEXT&ORTHISEXAMPLE LANDCLUTTER RETURNSAREPRESENTATZERODOPPLERWITHANORMALIZEDSPECTRALSPREADOFRF4 AND CHAFFRETURNSAREPRESENTATANORMALIZEDDOPPLEROFFSETOFFD4 WITHANORMALIZED SPECTRALSPREADOFRF4 4HEPOWERRATIOOFTHELANDCLUTTERTOTHATOFTHECHAFFIS DENOTED1D" 4HERMALNOISEISNOTCONSIDEREDINTHISEXAMPLE)NBOTHCASES THE TOTALNUMBEROFFILTERZEROSISASSUMEDTOBEEQUALTO&ORTHEADAPTIVE-4)WITHA FIXEDALLOCATIONOFZEROS TWOZEROSARELOCATEDATZERODOPPLERANDTHEREMAININGZERO ISCENTEREDONTHECHAFFRETURNS)NTHEOPTIMUM-4) THEZEROLOCATIONSARECHOSEN SOTHATTHATOVERALLIMPROVEMENTFACTORISMAXIMIZED4HERESULTSOFTHISCOMPARISON AREPRESENTEDIN&IGURE WHICHSHOWSTHEIMPROVEMENTFACTORFORTHEOPTIMUM ANDTHEADAPTIVE-4)ASAFUNCTIONOFTHEPOWERRATIO1D" 7HEN1ISSMALLSOTHAT CHAFF RETURNS DOMINATE A SIGNIFICANT PERFORMANCE IMPROVEMENT CAN BE REALIZED BY USINGALL-4)FILTERZEROSTOCANCELTHECHAFFRETURNS4HEPERFORMANCEDIFFERENCEFOR LARGEVALUESOF1ISARESULTOFANASSUMPTIONMADETHATTHELOCATIONOFTHETHIRDZERO REMAINSFIXEDATTHECHAFFDOPPLERFREQUENCY)NREALITY THEADAPTIVE-4)WOULDMOVE
-4)2!$!2
&)'52% )MPROVEMENT FACTOR COMPARISON OF OPTIMUMANDADAPTIVE-4)AGAINSTFIXEDANDMOVING CLUTTEROFRATIO1
Ó°nÎ
&)'52% ,OCATIONOFTHETHREEFILTERZEROS FORANOPTIMUM-4)USEDAGAINSTFIXEDANDMOV INGCLUTTER
ITSTHIRDZEROTOTHELANDCLUTTERASTHELANDCLUTTERRESIDUESTARTSTODOMINATETHEOUTPUT OFTHEFIRSTCANCELER4HEZEROLOCATIONSOFTHEOPTIMUM-4)ARESHOWNIN&IGURE ANDCANBESEENTOMOVEBETWEENTHELANDCLUTTERATZERODOPPLERTOWARDTHEDOPPLER OFTHECHAFFRETURNSASTHERELATIVELEVELOFTHELANDCLUTTERBECOMESSMALL
Ó°£xÊ , ,Ê 1// ,Ê *)NMANY-4)RADARAPPLICATIONS THECLUTTER TO NOISERATIOINTHERECEIVERWILLEXCEEDTHE IMPROVEMENTFACTORLIMITOFTHESYSTEMEVENWHENTECHNIQUESSUCHASSENSITIVITYTIME CONTROL34# IMPROVEDRADARRESOLUTION ANDREDUCEDANTENNAGAINCLOSETOTHEHORIZON AREUSEDTOREDUCETHELEVELOFCLUTTERRETURNS4HERESULTINGCLUTTERRESIDUESAFTERTHE-4) CANCELERMUST THEREFORE BEFURTHERSUPPRESSEDTOPREVENTSATURATIONOFTHE00)DISPLAY ANDORANEXCESSIVEFALSE ALARMRATEINANAUTOMATICTARGETDETECTION!4$ SYSTEM !GAINSTSPATIALLYHOMOGENEOUSSOURCESOFCLUTTERSUCHASRAIN SEACLUTTER ORCORRI DORCHAFF ACELL AVERAGINGCONSTANT FALSE ALARM RATE#! #&!2 PROCESSORFOLLOWING THE-4)FILTERWILLUSUALLYPROVIDEGOODSUPPRESSIONOFTHECLUTTERRESIDUES3PECIAL FEATURESARESOMETIMESADDEDTOTHE#! #&!2 SUCHASGREATEST OF SELECTIONORTWO PARAMETERSCALEANDSHAPE NORMALIZATIONLOGIC INORDERTOIMPROVEITSEFFECTIVENESS AT CLUTTER BOUNDARIES IF THE PROBABILITY DISTRIBUTION OF THE CLUTTER AMPLITUDE IS NON GAUSSIAN(OWEVER WHENTHECLUTTERRETURNSARESIGNIFICANTLYNONHOMOGENEOUS ASIS THECASEFORTYPICALLANDCLUTTERRETURNS THEPERFORMANCEOFTHECELL AVERAGING#&!2 WILLNOTBESATISFACTORYANDOTHERMEANSMUSTBEIMPLEMENTEDTOSUPPRESSTHEOUTPUT RESIDUESTOTHENOISELEVEL 4HETRADITIONALSOLUTIONTOTHISPROBLEMHASBEENTODELIBERATELYREDUCETHERECEIVER DYNAMIC RANGE PRIOR TO THE -4) FILTER TO THE SAME VALUE AS THE MAXIMUM SYSTEM IMPROVEMENTFACTOR4HEORETICALLY THEN THEOUTPUTRESIDUESHOULDBEATORBELOWTHE NORMALRECEIVERNOISELEVEL ANDNOFALSEALARMSWOULDBEGENERATED)NPRACTICE THE INTRODUCTIONOF)&LIMITINGAGAINSTTHEGROUNDCLUTTERRETURNSWILLRESULTINANADDITIONAL
Ó°n{
2!$!2(!.$"//+
IMPROVEMENT FACTOR RESTRICTION AS DISCUSSED IN 3ECTION #ONSEQUENTLY FOR THE LIMITED)&DYNAMICRANGETOHAVETHEDESIREDEFFECTONTHEOUTPUTRESIDUES THELIMIT LEVELMUSTBESETTOD"BELOWTHEIMPROVEMENTFACTORLIMITOFTHELINEARSYSTEM 4HENETRESULTISTHATSOMEOFTHECLUTTERSUPPRESSIONCAPABILITYOFTHE-4)RADARMUST BESACRIFICEDINEXCHANGEFORCONTROLOFTHEOUTPUTFALSE ALARMRATE 3INCERETURNSFROMLANDCLUTTERSCATTERERSUSUALLYARESPATIALLYFIXEDAND THEREFORE APPEARATTHESAMERANGEANDBEARINGFROMSCANTOSCAN ITHASLONGBEENRECOGNIZED THATASUITABLEMEMORYCIRCUITCOULDBEUSEDTOSTORETHECLUTTERRESIDUESANDREMOVE THEMFROMTHEOUTPUTRESIDUEONSUBSEQUENTSCANSBYEITHERSUBTRACTIONORGAINNOR MALIZATION4HISWASTHEBASICPRINCIPLEOFTHESO CALLEDAREA-4) ANDMANYATTEMPTS HAVEBEENMADETOIMPLEMENTANEFFECTIVEVERSIONOFTHISCIRCUITOVERANEXTENDEDSPAN OFTIME4HEMAINHINDRANCETOITSSUCCESSHASBEENTHELACKOFAPPROPRIATEMEMORY TECHNOLOGY SINCETHESTORAGETUBELONGTHEONLYVIABLECANDIDATE LACKSINRESOLUTION REGISTRATIONACCURACY SIMULTANEOUSREAD AND WRITECAPABILITY ANDSTABILITY4HEDEVEL OPMENTOFHIGH CAPACITYSEMICONDUCTORMEMORIESISTHETECHNOLOGICALBREAKTHROUGH THATHASMADETHEDESIGNOFAWORKINGAREA-4)AREALITY4HEAREA-4)ISBETTERKNOWN TODAYASACLUTTERMAP BUTBOTHTERMSAREUSED 4HECLUTTERMAPMAYBECONSIDEREDASATYPEOF#&!2WHERETHEREFERENCESAMPLES WHICHARENEEDEDTOESTIMATETHELEVELOFTHECLUTTERORCLUTTERRESIDUE ARECOLLECTED IN THE CELL UNDER TEST ON A NUMBER OF PREVIOUS SCANS 3INCE AIRCRAFT TARGETS USUALLY MOVESEVERALRESOLUTIONCELLSFROMONESCANTOTHENEXT ITISUNLIKELYTHATTHEREFERENCE SAMPLESWILLBECONTAMINATEDBYATARGETRETURN!LTERNATIVELY BYMAKINGTHEAVERAG INGTIMEINTERMSOFPASTSCANS LONG THEEFFECTOFANOCCASIONALTARGETRETURNCANBE MINIMIZED!LTHOUGHTHEPRIMARYPURPOSEOFTHECLUTTERMAPISTOPREVENTFALSEALARMS DUETODISCRETECLUTTERORCLUTTERRESIDUESTHATAREATAFIXEDLOCATION ITMAYALSOBE NECESSARYTOCONSIDERSLOWLYMOVINGPOINTCLUTTERINTHECLUTTERMAPDESIGN EITHERTO SUPPRESSBIRDRETURNSORBECAUSETHERADARISONAMOVINGPLATFORMEG ASHIP 4HEMEMORYOFACLUTTERMAPISUSUALLYORGANIZEDINAUNIFORMGRIDOFRANGEAND AZIMUTH CELLS AS ILLUSTRATED IN &IGURE %ACH MAP CELL WILL TYPICALLY HAVE TO BITSOFMEMORYSOTHATITWILLHANDLETHEFULLDYNAMICRANGEOFSIGNALSATITSINPUT WHICHMAKESITPOSSIBLETODETECTASTRONGTARGETFLYINGOVERAPOINTOFCLUTTERSOME TIMESREFERREDTOASSUPERCLUTTERVISIBILITY 4HEDIMENSIONSOFEACHCELLAREACOMPRO MISEBETWEENTHEREQUIREDMEMORYANDSEVERALPERFORMANCECHARACTERISTICS4HESEARE THEMINIMUMTARGETVELOCITYTHATWILLNOTBESUPPRESSEDBYTHEMAPSO CALLEDCUTOFF VELOCITY ITSTRANSIENTRESPONSE ANDTHELOSSINSENSITIVITYCAUSEDBYTHECLUTTERMAP SIMILARTOA#&!2LOSS 4HEMINIMUMCELLSIZEWILLBECONSTRAINEDBYTHESIZEOFTHE RADARRESOLUTIONCELL
&)'52% #LUTTERMAPCELLDEFINITION
-4)2!$!2
Ó°nx
%ACHMAPCELLISUPDATEDBYTHERADARRETURNSORRESIDUES FALLINGWITHINITSBORDERS ORINITSVICINITY ONSEVERALPREVIOUSSCANS4OSAVEMEMORY THECELLSAREUSUALLY UPDATEDBYUSINGASIMPLERECURSIVESINGLE POLE FILTEROFTHEFORM
YI A YI A XI
WHEREYI ISTHECLUTTERMAPAMPLITUDEFROMTHEPREVIOUSSCAN YI ISTHEUPDATED CLUTTERMAPAMPLITUDE XI ISTHERADAROUTPUTONTHEPRESENTSCAN ANDTHECONSTANT @DETERMINESTHEMEMORYOFTHERECURSIVEFILTER4HETESTFORDETECTINGATARGETBASED ONTHEOUTPUTXI IS
XI q K4 YI
WHERE THE THRESHOLD CONSTANT K4 IS SELECTED TO GIVE THE REQUIRED FALSE ALARM RATE !LTERNATIVELY THE RADAR OUTPUT CAN BE NORMALIZED ON THE BASIS OF THE CLUTTER MAP XI CONTENTTOOBTAINANOUTPUT ZI Y I WHICHCANBEPROCESSEDFURTHERIFREQUIRED !NALOGOUSLYTOTHEIMPLEMENTATIONOFTHECELL AVERAGING#&!2PROCESSOR THEAMPLI TUDEXI CANBEOBTAINEDUSINGALINEAR SQUARE LAW ORLOGARITHMICDETECTOR 4HELOSSINDETECTABILITYDUETOTHECLUTTERMAPISANALOGOUSTOTHE#&!2LOSSANA LYZEDINTHELITERATUREFORMANYDIFFERENTCONDITIONS!NANALYSISOFTHECLUTTERMAPLOSS FORSINGLE HITDETECTIONUSINGASQUARE LAWDETECTORHASBEENPRESENTEDBY.ITZBERG 4HESEANDOTHERRESULTSCANBESUMMARIZEDINTOASINGLEUNIVERSALCURVEOFCLUTTERMAP LOSS ,#- ASAFUNCTIONOFTHECLUTTERMAPRATIOX,EFF ASSHOWNIN&IGURE WHERE X DEFINES THE REQUIRED FALSE ALARM PROBABILITY ACCORDING TO 0F X AND ,EFF IS THE EFFECTIVENUMBEROFPASTOBSERVATIONSAVERAGEDINTHECLUTTERMAPDEFINEDAS
,EFF
A A
&OREXAMPLE FOR0F AND@ THECLUTTERMAPLOSSIS,#- D"SINCE X AND,EFF FORTHISCASE!LSOSHOWNIN&IGUREISTHECURVEFORTHECONVEN TIONAL#! #&!2 WHEREALLREFERENCESAMPLESAREEQUALLYWEIGHTED)FMORETHANONE NOISEANDORCLUTTERAMPLITUDEISUSEDTOUPDATETHECLUTTERMAPCONTENTONEACHSCAN THEVALUEOF,EFFSHOULDBEINCREASEDPROPORTIONALLY)TSHOULDALSOBENOTEDTHATMOST RADARSBASETHEIRTARGETDETECTIONONMULTIPLEHITSUSINGSOMEFORMOFVIDEOINTEGRA TION ANDTHATACLUTTERMAPLOSSBASEDONTHESINGLE HITRESULTSOF&IGURECOULDBE MUCHTOOLARGE !NANALYSISOFTHEPERFORMANCEOFTYPICALIMPLEMENTATIONSOFCLUTTERMAPSHASBEEN DISCUSSED IN +HOURY AND (OYLE &ROM THIS REFERENCE A TYPICAL TRANSIENT RESPONSE CURVEISSHOWNIN&IGUREFORASINGLEPOINTCLUTTERSOURCED"ABOVETHERMAL NOISE THAT FLUCTUATES FROM SCAN TO SCAN ACCORDING TO A 2AYLEIGH PROBABILITY DENSITY FUNCTION AFILTERINGCONSTANTOF@ ANDASSUMINGFOURRETURNSNONCOHERENTLY INTEGRATEDINEACHCLUTTERMAPCELL4HEABSCISSAISINRADARSCANS ANDTHEORDINATEIS PROBABILITYOFDETECTIONOFTHEPOINTCLUTTERSOURCE3INCETHECLUTTERPOINTHASTHESAME AMPLITUDESTATISTICSASTHERMALNOISE THEOUTPUTFALSE ALARMRATEAPPROACHES0F ASYMPTOTICALLY !GAINSTASLOWLYMOVINGSOURCEOFCLUTTEREG BIRDS THEPROBABILITYOFDETECTION MAYINCREASEASTHECLUTTERSOURCECROSSESTHEBOUNDARYBETWEENTWOCLUTTERMAPCELLS 4OPREVENTTHIS ASPREADINGTECHNIQUECANBEUSED THROUGHWHICHEACHCLUTTERMAP CELLWILLBEUPDATEDNOTONLYWITHRADARRETURNSFALLINGWITHINITSBOUNDARIES BUTALSO
Ó°nÈ
2!$!2(!.$"//+
&)'52% 5NIVERSALCURVEFORDETERMININGDETECTABILITYLOSSCAUSEDBYTHE CLUTTERMAP
BYUSINGRADARRETURNSINADJACENTCELLSINRANGEANDAZIMUTH4HROUGHTHEUSEOFSUCH SPREADING ANADDITIONALDEGREEOFCONTROLOVERTHECLUTTERMAPVELOCITYRESPONSECAN BEACHIEVED !NEXAMPLEOFTHEVELOCITYRESPONSEOFACLUTTERMAPINCLUDINGSUCHSPREADINGIS SHOWNIN&IGURE4HERANGEEXTENTOFTHECLUTTERMAPCELLISMS THERADARRESO LUTIONCELLISMS N PULSESARENONCOHERENTLYINTEGRATED THEFILTERINGCONSTANTIS @ THEUPDATEINTERVALISS ANDTHE3.2 D"/NEACHSCAN THECLUTTER MAPCELLISUPDATEDWITHTHERADARAMPLITUDESINTHEFIVERANGECELLSFALLINGWITHIN THECLUTTERMAPCELLANDWITHTHEAMPLITUDEFROMONEADDITIONALRADARRESOLUTIONCELL BEFOREANDAFTERTHECLUTTERMAPCELL
&)'52% 4RANSIENT RESPONSE OF CLUTTER MAP DUE TO 3WERLING#ASEPOINTCLUTTERMODEL
-4)2!$!2
Ó°nÇ
&)'52% 6ELOCITYRESPONSEOFCLUTTERMAP
)TISSEENFROM&IGURETHATTHEVELOCITYRESPONSECHARACTERISTICOFTHECLUTTER MAPFROMSTOPBANDTOPASSBANDISSOMEWHATGRADUALINTHISPARTICULARIMPLEMENTATION 4HISISPARTLYDUETOTHELARGESIZEOFTHECLUTTERMAPCELLRELATIVETOTHERADARRESOLU TION!FINER GRAINMAPWITHADDITIONALSPREADINGWOULDHAVEAMUCHBETTERVELOCITY RESPONSECHARACTERISTIC !POTENTIALPROBLEMWITHTHETYPEOFAMPLITUDECLUTTERMAPDESCRIBEDINTHISSEC TIONISTHEFACTTHATALARGETARGETFLYINGINFRONTOFASMALLERTARGETMAYCAUSEENOUGH BUILDUPINTHEMAPTOSUPPRESSTHESMALLTARGET/NEWAYTOOVERCOMETHISPROBLEMIN ASYSTEMTHATINCLUDESAUTOMATICTRACKINGWOULDBETOUSETHETRACKPREDICTIONGATETO INHIBITUPDATINGOFTHECLUTTERMAPWITHNEWTARGET AMPLITUDES
Ó°£ÈÊ - -/6/96 " /9Ê " /," Ê-6 ® )NTHEMID S SEVERALRADARRESEARCHERSHADREALIZEDTHATSIGNALPROCESSINGALGO RITHMSTOESTIMATETHEUNAMBIGUOUSRADIALVELOCITYOFATARGETUSINGMULTIPLE02& DWELLSDURINGTHETIMEOFTARGETWEREBECOMINGPRACTICAL4HESERADIALVELOCITYESTI MATESCOULDBEUSEDFORIMPROVEDFALSE ALARMCONTROLAGAINSTSLOW MOVINGTARGETS SUCH AS BIRDS 7HEN SUCH RADIAL VELOCITY MEASUREMENTS ARE PAIRED WITH CORRE SPONDINGCROSSSECTIONESTIMATESAPOWERFULDISCRIMINANTFORDISTINGUISHINGBETWEEN SLOW MOVING BIRDS AND LOW CROSS SECTION MISSILES BECOMES POSSIBLE USING THE SO CALLEDSENSITIVITYVELOCITYCONTROL36# ALGORITHM 4HE36##ONCEPT 3ENSITIVITYVELOCITYCONTROL36# ISUSEDWHENARADARMUST DETECT AIRCRAFT AND MISSILE TARGETS IN THE PRESENCE OF RETURNS FROM UNWANTED TARGETS SUCHASLARGEBIRDSORBIRDFLOCKS4HECRITERIATOACCEPTORREJECTTARGETSISBASEDONA COMBINATIONOFTHERADIALVELOCITYANDAPPARENT2#3RADARCROSSSECTION OFTHETARGET RETURNS4HEDESIREDTARGETSMAYHAVEAN2#3SMALLERTHANASINGLEBIRD ORPOSSIBLY
Ó°nn
2!$!2(!.$"//+
$" ""$
" " "
" %$ !$"
%# %#
"#
##
$%
#$%
$& $# &)'52% )LLUSTRATIVEACCEPTANCEREJECTIONCRITERIAOF36#
ABIRDFLOCKINASINGLERADARRESOLUTIONCELL 4HUS DISCRIMINATIONREQUIRESAPARAME TERINADDITIONTOTHETARGET2#34HEAVAILABLEPARAMETERISTARGETRADIALVELOCITY"IRDS TYPICALLYFLYATKNOTSORLESS WHEREASTARGETSOFCONCERNUSUALLYHAVEAIRSPEEDSOF KNOTSORMORE)FTHERADARCANMAKEUNAMBIGUOUSRADARDOPPLERMEASUREMENTS OF EG o KNOTS WITH A SINGLE #0) COHERENT PROCESSING INTERVAL THE RADAR CAN DETERMINETHETRUERADIALVELOCITYOFEACHRADARECHOFROMRETURNSOFTHREEORMORE CONSECUTIVE#0)SATDIFFERENT02&S 4HEACCEPTANCECRITERIAOFTHE36#ALGORITHMRELATESTOTHETYPEOFTARGETAIRCRAFT MISSILE BIRD ETC BEINGACCEPTEDORREJECTED)NGENERAL THECRITERIAACCEPTSLARGETAR GETSHAVINGLOWTOHIGHRADIALVELOCITIES4HESMALLERTHEAPPARENTRADARCROSSSECTION OFTHETARGET THEHIGHERTHETRUERADIALVELOCITYMUSTBEFORACCEPTANCE4HETRUERADIAL VELOCITYVERSUSAPPARENTRADARCROSSSECTIONPROFILEISINTENDEDTOACCEPTAIRCRAFTAND MISSILESBUTREJECTBIRDS4HEREFORE THREATENINGTARGETSTHATHAVEHIGHRADIALVELOCI TIES BUTVERYSMALL2#3 CANBEINSTANTLYIDENTIFIED WHEREASRETURNSFROMBIRDS WITH THEIRSLOWRADIALVELOCITIES CANBECENSORED!TYPICAL3#6ACCEPTREJECTALGORITHMIS DEPICTEDIN&IGURE 4OOBTAINTHEDOPPLERSPACEOFoKNOTS AMBIGUOUSRANGE02&SMUSTBEUSED 4HIS REQUIRES APPROXIMATE 02&S OF (Z AT , BAND (Z AT 3 BAND AND (ZAT8BANDUNAMBIGUOUSRANGES RESPECTIVELY NMI NMI ANDNMI 4HE TRADEOFF FOR SELECTING 02&S IS THAT IN A DENSE TARGET ENVIRONMENT WHEN TRY INGTORESOLVETRUERADIALVELOCITYUSINGDIFFERENT02&S hGHOSTSveMAYBECREATED
eh'HOSTSvOCCURWHENTARGETSORNOISEPEAKS ATDIFFERENTUNAMBIGUOUSRANGESFOLDINTOTHESAME BUTINCORRECT TRUERANGECELL4HEVELOCITYRESOLUTIONALGORITHMTHENGIVESANINCORRECTRESULT ANDTHEGHOSTSMAYBEDECLAREDAS THREATENINGTARGETS
-4)2!$!2
Ó°n
)NADDITIONTOTHEhGHOSTvPROBLEM MULTIPLERANGEAMBIGUITIESLEADTOTARGETSHAVING TOCOMPETEWITHCLUTTERATALLRANGES)NPARTICULAR TARGETSATLONGDISTANCESHAVETO COMPETEWITHSTRONGCLUTTERRETURNSINTHEFIRST ORSEVERAL RANGEINTERVALS "ECAUSE OF THE GHOSTING PROBLEM IN ORDER TO MINIMIZE RANGE AMBIGUITIES WHILE RETAINING ADEQUATE DOPPLER SPACE 2& FREQUENCIES OF -(Z OR LOWER ARE BEST SUITEDFORTHE36#UNWANTEDTARGETDISCRIMINATIONTECHNIQUE 2ANGE AND2ANGE2ATE!MBIGUITY2ESOLUTION 4OAPPLYTHE36#ALGORITHM TRUERANGEANDRADIALVELOCITYRANGE RATE MUSTBEDETERMINEDFROMTHERANGE AMBIG UOUS AND DOPPLER AMBIGUOUS WAVEFORM4HIS REQUIRES MULTIPLE DETECTIONS FROM THE SAMETARGET!SSUMEADOPPLERFILTERBANKOFN PULSE&)2FILTERSANDASSUMEAPROCESS INGDWELLTHATCONSISTSOFTHREE#0)S4HE#0)SMUSTUSEDIFFERENT02&SANDMAYALSO EMPLOYDIFFERENT2&FREQUENCIES4HEDIFFERENT2&FREQUENCIESCHANGETARGET2#3 STATISTICSFROM3WERLINGTO3WERLING ANDTHUSLESSRADARENERGYISREQUIREDFORHIGH PROBABILITYOFDETECTION 4HE#0)SMUSTHAVE SUFFICIENTTRANSMITTEDPULSESSOTHAT NRETURNSENOUGHTOFILLANN PULSEFILTER WILLBERECEIVEDFROMTHEMOSTDISTANTTARGET OFINTERESTANDTHEMOSTDISTANTCLUTTERAND ONEADDITIONALPULSETOENABLEVELOCITY DETERMINATIONMOREONTHISLATER 4RUE2ANGE$ETERMINATION 4HEMOSTSTRAIGHTFORWARDWAYTODETECTATARGETAND SIMULTANEOUSLYDETERMINEITSTRUERANGEISTODETERMINE ONEACH#0) ALLhPRIMITIVEv DETECTIONSATTHEOUTPUTOFTHEDOPPLERFILTERBANK&ORTHIS ITISASSUMEDTHATEACH DOPPLER FILTER OUTPUT IS PROCESSED THROUGH AN APPROPRIATE CLUTTER MAP THRESHOLD AND CELL AVERAGING#&!2TOCONTROLTHEFALSE ALARMRATE&OREACHPEAKDETECTION ADJACENT AMPLITUDESWILLBEUSEDTOOBTAINANACCURATEAMBIGUOUSRANGEESTIMATEDENOTED R}I WHERETHESUBSCRIPTREFERSTOTHE#0)NUMBER!LSO FROMTHESPECIFICDOPPLERFILTER CORRESPONDINGTOTHEPEAKDETECTIONDESCRIBEDABOVE THEPHASEPI OFTHERETURNIS SAVED)NADDITION ACORRESPONDINGPHASEP I OBTAINEDFROMANIDENTICALSECONDDOP PLERFILTERBANKTRAILINGORLEADING THEDETECTIONFILTERBANKBYONEPULSEREPETITION INTERVAL02) ISSAVED4HISEXPLAINSWHYA#0)OFN PULSESISNEEDEDTOIMPLEMENT THE36#CONCEPT&OREACHPRIMITIVEDETECTIONINA#0) CALCULATETHESETOFALLPOSSIBLE TARGETRANGESOUTTOTHEMAXIMUMINSTRUMENTEDRANGE2MAX
2} I R}I M 202) I
M MMAX
WHERE MMAX INT 2MAX 202) I
I
WHERE202) I ISTHEAMBIGUOUSRANGEINTERVALCORRESPONDINGTOTHEITH#0)!FTERTHE PRIMITIVEDETECTIONSFROMALL#0)SINTHEPROCESSINGDWELLHAVEBEENPROCESSED THE VALUESOF 2} I FROMALL#0)SARESORTEDINTOASINGLELIST!FINALRANGEDETECTIONAND ITSTRUERANGEISTHENFOUNDASACLUSTEROFTHREEPRIMITIVEDETECTIONSHAVINGPOSSIBLE RANGES WITHIN AN ERROR WINDOW OF TWO TO THREE TIMES THE STANDARD DEVIATION OF THE AMBIGUOUSRANGEESTIMATE 4RUE2ADIAL6ELOCITY$ETERMINATION &OREACHTRUETARGETDETECTION ANUNAM BIGUOUS RADIAL VELOCITY ESTIMATE MUST NEXT BE DETERMINED USING A SIMILAR PROCE DURE TO THAT DESCRIBED ABOVE FOR RANGE &OR THIS AN ACCURATE ESTIMATE F}D I OF THE AMBIGUOUS TARGET RADIAL VELOCITY MUST BE OBTAINED AT THE RANGE CORRESPONDING TO THE AMBIGUOUS PRIMITIVE TARGET DETECTION ON EACH #0)4HIS FREQUENCY ESTIMATION PROBLEM HAS BEEN STUDIED BY MANY AUTHORS WITH THE BEST APPROACH BEING DEFINED
Ó°ä
2!$!2(!.$"//+
BY THE MAXIMUM LIKELIHOOD ESTIMATE &OR A SINGLE PULSE SIGNAL TO NOISE RATIO 3 ANDNPULSESINA#0) THE#RAMER 2AOLOWERBOUNDFORTHEACCURACYOFTHEDOPPLER FREQUENCYESTIMATEIS
SF 02& P 3 N N
3 N N
3INCE THE MAXIMUM LIKELIHOOD ESTIMATION PROCEDURE TENDS TO REQUIRE A TEDIOUS COMPUTATIONALBURDEN ASIMPLIFIEDAPPROACHFORESTIMATINGTHEDOPPLERFREQUENCYIS HIGHLYDESIRABLE/NESUCHAPPROACHUSINGPHASEMEASUREMENTSOFTHEDOPPLERFILTER OUTPUTATTIMESSEPARATEDBYONEINTERPULSEPERIOD WASPRESENTEDIN-C-AHONAND "ARRETT4HENORMALIZEDDOPPLERFREQUENCYESTIMATEIS FD I Q Q I
I 02& P
ANDTHECORRESPONDINGRADIALVELOCITYIS
V}I
FD I L
)NMOSTCASESOFINTEREST THEACCURACYOFTHISESTIMATEOFDOPPLERFREQUENCYISAS GOODASTHEMAXIMUMLIKELIHOODPROCEDURE%XPRESSEDINTERMSOFTHENUMERATOROF %Q WHICH WILL BE DENOTED BY K A SIMULATION OF THE PHASE DIFFERENCE ESTIMA TOR USING DIFFERENT WEIGHTING FUNCTIONS FOR THE DOPPLER FILTER BANK ARE SUMMARIZED IN &IGURE )T IS NOTED THAT THE PERFORMANCE OF THE PHASE DIFFERENCE ESTIMATION PROCEDUREISBESTWHENMODERATE4AYLORWEIGHTINGFUNCTIONSAREUSED&ORUNIFORM WEIGHTING THEPROCEDUREWOULDBESUBSTANTIALLYINFERIORTOTHEMAXIMUMLIKELIHOOD APPROACH4HEINCREASEINTHECONSTANTKFORTHEMORESEVEREWEIGHTINGCASESISTHE RESULTOFTHE3.2LOSSRESULTINGFROMTHEUSEOFWEIGHTING 5SINGANAPPROACHSIMILARTOTHATUSEDTORESOLVETHERANGEAMBIGUITY ALLPOSSIBLE RADIAL VELOCITIES ARE THEN ENUMERATED TO THE MAXIMUM NEGATIVE AND POSITIVE RADIAL VELOCITYOFINTERESTONEACHOFTHE#0)S
6}I V}I M 6" I
M MMAX MMAX MMAX
WHERE MMAX INT6MAX 6" I
I
)N THIS EQUATION 6" I 02&I L IS THE BLIND VELOCITY FOR THE ITH #0)4HE POS SIBLETARGETRADIALVELOCITIESFORALL#0)SARETHENSORTEDINTOASINGLELIST ANDTHEMOST LIKELYTRUERADIALVELOCITYISFOUNDWHEREATLEASTTWOPOSSIBLEVELOCITIESFALLWITHINAN INTERVALLESSTHANTWOORTHREETIMESTHESTANDARDDEVIATIONOFTHEDOPPLERFREQUENCY ESTIMATE4HETIGHTNESSOFTHECLUSTEROFNEARLYIDENTICALVELOCITIESINCONJUNCTIONWITH THENUMBEROF#0)SCONTRIBUTINGTOTHECLUSTERCANBEUTILIZEDASAMEASUREOFRELIABILITY OFTHEUNAMBIGUOUSRADIALVELOCITYESTIMATE
4HISAPPROACHWASFIRSTBROUGHTTOTHEATTENTIONOFTHEAUTHORSBY$R"EN#ANTRELLOFTHE53.AVAL2ESEARCH ,ABORATORY
-4)2!$!2
Ó°£
%&&" '''%'%$()$)!
-( +, ) $ (# & ' $
.
%'#, ) $ $ !" ' $
-"%', ) $ ( !"' $ '# '% !% %*$ " "!
-
!& &)'52% 0ERFORMANCEOFPHASE DIFFERENCEDOPPLERFREQUENCYESTIMATORFORDIFFERENT WEIGHTINGFUNCTIONSOFTHEDOPPLERFILTERBANK
#OMMENTS 4HEABOVEPROCEDUREFORDETERMININGTRUERANGEANDTRUERADIALVELOC ITYHASBEENDESCRIBEDFORADWELLOFTHREE#0)SANDTHEASSUMPTIONTHATEACHTARGET WILLHAVEARETURNFOREACHOFTHETHREE#0)S)NPRACTICE THISASSUMPTIONISNOTALWAYS VALID ANDTHEACTUALIMPLEMENTATIONMAYCHOOSE FOREXAMPLE TOHAVETHEDWELLCON SISTOFFOURORFIVE#0)S WITHTHERANGEANDVELOCITYDETERMINATIONSBEINGBASEDON THEBESTGROUPINGOFTHREERETURNS4HEACTUALIMPLEMENTATIONMUSTBEBASEDONTHE PARAMETERSOFTHESYSTEMANDPERMISSIBLETIMEALLOCATEDFOREACHDWELL 4HE02&SOFTHE#0)SSHOULDBESELECTEDTOMINIMIZETHECHANCEOFFALSERADIAL VELOCITYDETERMINATIONS/NEMETHODOFSELECTING02&SISSIMILARTOSELECTINGPULSE INTERVALRATIOSFORSTAGGERED02&OPERATION ASDESCRIBEDIN3ECTION&OREXAM PLE IF OPERATING AT AN AVERAGE 2& FREQUENCY OF -(Z AT AN AVERAGE 02& OF (ZAMBIGUOUSVELOCITYOFKNOTS ANDCOVERINGAVELOCITYRANGEOFINTEREST OFoKNOTS THEREAREAPPROXIMATELYDOPPLERAMBIGUITIESTOCOVER5SINGTHE FACTORSOFn n ASUSEDIN02&STAGGERSELECTION THEINTERPULSEPERIODSOFTHE FOURDIFFERENT02&SWOULDBEINTHERATIOOF 4HEAVERAGEOFTHESERATIOS IS4HE02&SARECALCULATEDASq q q ANDq4HE02&SWOULDBEABOUT AND(Z
Ó°£ÇÊ " - ,/" -Ê** ÊÊ /"Ê /Ê, ,Ê-9-/ -4) RADAR SYSTEM DESIGN ENCOMPASSES MUCH MORE THAN SIGNAL PROCESSOR DESIGN 4HEENTIRERADARSYSTEMTRANSMITTER ANTENNA ANDOPERATIONALPARAMETERSMUSTBE KEYEDTOFUNCTIONASPARTOFAN-4)RADAR&OREXAMPLE EXCELLENT-4)CONCEPTSWILL NOTPERFORMSATISFACTORILYUNLESSTHERADARLOCALOSCILLATORISEXTREMELYSTABLEANDTHE
Ó°Ó
2!$!2(!.$"//+
TRANSMITTER HAS VERY LITTLE PULSE TO PULSE FREQUENCY OR PHASE JITTER )N ADDITION THE SYSTEMMUSTSUCCESSFULLYOPERATEINANENVIRONMENTTHATCOMPRISESMANYUNWANTED TARGETS SUCHASBIRDS INSECTS ANDAUTOMOBILES (ARDWARE#ONSIDERATIONS )NTHISSECTION RULESANDFACTSRELATINGTO-4)RADAR DESIGN ASDEVELOPEDDURINGMANYYEARSOFWORKINTHEFIELD WILLBESUMMARIZED 4HERULESAREASFOLLOWS /PERATEATCONSTANTDUTYCYCLE 3YNCHRONIZEAC DCANDDC DCPOWERCONDITIONERSoTOHARMONICSOFTHE02& $ESIGNTHESYSTEMTOBEFULLYCOHERENTp 0ROVIDE)&,IMITERSPRIORTO!$CONVERTERS "EWARYOFVIBRATIONANDACOUSTICNOISE 4HEFACTSAREASFOLLOWS 4HEBASIC-4)CONCEPTDOESNOTREQUIREALONGTIMEONTARGETTORESOLVETARGETSFROM FIXEDCLUTTER)NSTEAD -4)SYSTEMSREJECTFIXEDCLUTTERTHROUGHASUBTRACTIONPROCESS WHILERETAININGMOVINGTARGETS 4RANSMITTERINTRAPULSEANOMALIESHAVENOAFFECTON-4)PERFORMANCEIFTHEYREPEAT PRECISELYPULSE TO PULSE 2ULE /PERATEATCONSTANTDUTYCYCLE4HETRANSMITTERWHETHERTHETRANSMITTER ISASINGLELARGETUBEORADISTRIBUTEDFUNCTIONASINANACTIVEPHASEDARRAYWITHMANY TRANSMIT RECEIVE ELEMENTS SHOULD BE OPERATED AT CONSTANT DUTY CYCLE 4HIS PERMITS THETRANSMITTERPOWERSUPPLYTRANSIENTEFFECTSTOBEIDENTICALPULSETOPULSEANDALSO PARTICULARLYAPPLICABLETOSOLID STATETRANSMITDEVICES PERMITSTHEDEVICEHEATINGAND COOLINGTOBEIDENTICALFROMPULSETOPULSE3OMETIMESCONSTANTDUTYCYCLEOPERATIONIS NOTPOSSIBLE BUTTHEREAREVARIOUSTECHNIQUESTHATCANBEUSEDTOAPPROACHTHISDESIRED CONDITION#ONSIDERAN-4$WAVEFORMWHEREA#0)CONSISTINGOFNPULSESISTRANSMIT TEDWITHACONSTANT02)4HENEXT#0)USESADIFFERENT02)#ONSTANTDUTYCYCLECANBE MAINTAINEDBYCHANGINGTHETRANSMITTEDPULSELENGTHINPROPORTIONTOTHECHANGEINTHE 02))FPULSECOMPRESSIONISUSED THERANGERESOLUTIONOFTHECOMPRESSEDPULSECANBE MAINTAINEDBYCHANGINGTHEPULSECOMPRESSIONWAVEFORM)FITISNECESSARYTOUTILIZE PRECISELYTHESAMEWAVEFORMAND2&PULSELENGTHFROM#0)TO#0) WITH FOREXAMPLE AKLYSTRONTRANSMITTER THEBEAMPULSEOFTHEKLYSTRONCANBEVARIEDTOMAINTAINCON STANTBEAMDUTYCYCLEWHILETHE2&PULSELENGTHISMAINTAINEDCONSTANT4HISWASTES PARTOFTHEBEAMPULSEENERGYFORTHELONGER02)S BUTTHEAVERAGEPOWERLOADINGON THEPOWERSUPPLYREMAINSCONSTANT4HESAMETECHNIQUECANBEUTILIZEDWITHSOLID STATEDEVICESBYCHANGINGTHEDRAINVOLTAGEPULSEDURATION WHILEHOLDINGTHE2&PULSE CONSTANT! SECOND ORDER CORRECTION THAT HAS BEEN UTILIZED WHEN CHANGING BETWEEN #0)SWITHDIFFERENT02)SISTOHAVEATRANSITION02)THATISTHEAVERAGEOFTHETWO02)S 7ITHPHASEDARRAYRADARS IFTHEBEAMTRANSITIONTIMEBETWEEN#0)STAKESLONGERTHANA 02) ITISIMPORTANTTOKEEPTHETRANSMITTERPULSINGATACONSTANTDUTYCYCLEDURINGTHE TRANSITIONTIME)FCONSTANTDUTYCYCLECANNOTBEMAINTAINED ORWHENSTARTINGTORADIATE o0OWERCONDITIONERSACCEPTEITHERACORDCINPUTANDPROVIDEAREGULATEDDCOUTPUT ph&ULLYCOHERENTvISDESCRIBEDUNDERRULE
-4)2!$!2
Ó°Î
AFTERDEADTIME THETRANSMITTER POWERSUPPLY ANDHEATINGEFFECTSMUSTBEALLOWEDTO SETTLEBEFOREGOOD-4)PERFORMANCECANBEEXPECTED4HEDURATIONOFTHESETTLINGTIME DEPENDSONTHESYSTEMPARAMETERSANDTHEREQUIREMENTS 2ULE 3YNCHRONIZE AC DC AND DC DC POWER CONDITIONERS TO HARMONICS OF THE 02&7HENAC DCANDORDC DCPOWERCONDITIONERSAREUSEDFORVOLTAGESAPPLIEDTO TRANSMITTINGDEVICES THEFREQUENCYANDITSHARMONICS OFTHECONVERTERMUSTBEATTEN UATEDSUFFICIENTLYSOTHATTHEYDONOTMODULATETHEPHASEOFTHETRANSMITTEDPULSES)F THEPOWERCONDITIONERFREQUENCIESCANNOTBESUFFICIENTLYATTENUATED THEIRFREQUENCY SHOULDBESYNCHRONIZEDTOAMULTIPLEOFTHE02&OFTHE#0)SOTHATMODULATIONSREPEAT PRECISELYPULSE TO PULSEANDTHUSWILLCANCELLIKESTATIONARYCLUTTER 2ULE $ESIGNTHESYSTEMTOBEFULLYCOHERENT!LLFREQUENCIESANDTIMINGSIGNALS SHOULDBEGENERATEDFROMASINGLEMASTEROSCILLATOR$OINGTHISMAKESTHEENTIRESYS TEMCOHERENT ANDMIXERPRODUCTSWILLBEIDENTICALPULSE TO PULSEANDWILL THEREFORE CANCELINTHE-4)FILTERS7HENTHISCOHERENCEOFALLFREQUENCIESISNOTMAINTAINED CLUTTERRESIDUEWILLOCCURANDMUSTBEQUANTIFIEDTODETERMINEIFITISATANACCEPTABLE LEVEL/NEOFTHEPROMINENTPLACESINWHICHRESIDUECAUSEDBYUNSYNCHRONIZEDLOCAL OSCILLATORSHASSHOWNUPISINPULSE COMPRESSIONSIDELOBES)FTHEPULSE COMPRESSION SIDELOBESFROMFIXEDCLUTTERRETURNSVARYFROMPULSETOPULSE THEYDONOTCANCEL4HIS COHERENCYISSUEHASBEENFURTHERDISCUSSEDBY4AYLOR 2ULE 0ROVIDE)&,IMITERSPRIORTO!$CONVERTERS-4)RADARSREQUIRETHAT)& BANDPASSLIMITERSEXISTPRIORTOAN!$ANALOGDIGITALCONVERTER 4HELIMITERPREVENTS ANY CLUTTER RETURN FROM EXCEEDING THE DYNAMIC RANGE OF THE!$4HIS REQUIREMENT EXISTSFOREITHERQUADRATURE) 1IN PHASE QUADRATURE SAMPLINGORDIRECTSAMPLING WITH THE ) AND 1 DATA CONSTRUCTED AFTER THE!$ 4HE LIMITER MUST BE DESIGNED TO MINIMIZETHECONVERSIONOFAMPLITUDETOPHASENOMATTERHOWMUCHTHESIGNALLEVEL EXCEEDSTHELIMITLEVEL)FCLUTTERSATURATESTHE!$ THE) 1DATAISSIGNIFICANTLYCOR RUPTED7HENLIMITERSPREVENT!$SATURATION THESIGNALSARELIMITEDINACONTROLLED MANNERTHATSTILLENABLESGOODCLUTTERREJECTIONABOUTOFTHETIME 2ULE "EWARYOFVIBRATIONANDACOUSTICNOISE-ANY2&DEVICESARESUSCEPTIBLE TOBOTHVIBRATIONANDACOUSTICNOISE!NAIRCONDITIONERFANBLOWINGONWAVEGUIDE HAS CAUSED DEGRADATION OF IMPROVEMENT FACTOR DUE TO PHASE MODULATION OF SIGNALS 6IBRATIONSCANCAUSEPHASEMODULATIONOFANOSCILLATOR!COUSTICNOISECANORIGINATE FROM COOLING FANS AND VIBRATIONS CAN COME FROM SHIPBOARD OR AIRBORNE RADAR PLAT FORMS#OMPONENTSSUCHASKLYSTRONSANDSOLID STATEMODULESCANHAVEUNEXPECTED SUSCEPTIBILITYTOVIBRATION2&CONNECTORSMUSTBESECURE3HOCKMOUNTSCANBEUSED TOISOLATECOMPONENTSFROMTHECABINETSTRUCTURE)TISRECOMMENDEDTHATALL2&COM PONENTS INTHEIROPERATIONALCONFIGURATION BETESTEDFORPHASESTABILITYINTHEVIBRATION ENVIRONMENTINWHICHTHEYWILLBEUSED &ACT 4HEBASIC-4)CONCEPTDOESNOTREQUIRESUFFICIENTTIME ON TARGETTORESOLVE TARGETSFROMFIXEDCLUTTERUSINGALINEARTIME INVARIANTFILTER)NSTEAD -4)SYSTEMSREJECT FIXED CLUTTER THROUGH A SUBTRACTION PROCESS WHILE RETAINING MOVING TARGETS!N -4) SYSTEMUSINGATWO PULSECANCELERREQUIRESTHETRANSMITTERTOTRANSMITONLYTWOSUC CESSIVE IDENTICAL PULSES FOR THE SYSTEM TO BE ABLE TO REJECT STABLE FIXED CLUTTER4HE RADARRETURNSFROMTHESECONDPULSEARESUBTRACTEDFROMTHERETURNSFROMTHEFIRSTPULSE
Ó°{
2!$!2(!.$"//+
4HERESULTFROMTHISSUBTRACTIONPROCESSISTHATTHEFIXEDCLUTTERISREMOVED ANDMOVING TARGETSARERETAINED4HEOUTPUTFROMTHEFIRSTPULSEISNOTUSED MAKINGTHISTYPEOF-4) FILTERTIME VARIANT/FCOURSE THECLUTTERFILTERSMAYBEMORECOMPLEXTHANATWO PULSE CANCELER eBUTTHEPRINCIPLESTILLREMAINSTHATFIXEDCLUTTERISREJECTEDBYTHEZEROSIN THECANCELERTRANSFERCHARACTERISTIC4HISENABLESPHASEDARRAYRADARSTOHAVEGOODCLUT TERREJECTIONWITHSHORTDWELLS
&ACT 4RANSMITTERINTRAPULSEANOMALIESHAVENOAFFECTON-4)PERFORMANCEIF THEYREPEATPRECISELYPULSETOPULSE4RANSMITTEDPULSESSHOULDBEIDENTICAL)TDOES NOTMATTERIFTHEREISINTRAPULSEAMPLITUDEORFREQUENCYMODULATIONOFTHETRANSMITTED PULSE ASLONGASITREPEATSPRECISELYFROMPULSETOPULSE)FTHEVOLTAGEOFTHETRANS MITTERPOWERSUPPLYVARIESPULSETOPULSE THETRANSMITTEDPULSESWILLNOTBEIDENTI CAL ANDTHERESULTINGVARIATIONSMUSTBEQUANTIFIEDTODETERMINEIFTHELIMITATIONSON IMPROVEMENTFACTORFALLWITHINTHESTABILITYBUDGETFORTHESYSTEM(OWEVER IFTHEONLY DIFFERENCEBETWEENPULSESISABSOLUTEPHASENOTINTRAPULSEVARIATIONSPULSETOPULSE SOMEMITIGATIONISPOSSIBLE/NEMETHODOFCOMPENSATINGFORSMALLVARIATIONSINTHE PHASEOFTRANSMITTERPULSESFOLLOWS,INCOLN,ABORATORYCHANGEDTHEORIGINAL4$72 WAVEFORMTOAN-4$TYPEWAVEFORM4HEORIGINAL4$72WAVEFORMWASCONSTANT 02&DURINGEACHANTENNAROTATION ANDPROCESSINGWASDONEWITHELLIPTICFILTERS 4HEY THEN MODIFIED THE SYSTEM hxTO ACHIEVE D" CLUTTER SUPPRESSION USING A NEARBY WATERTOWERFORATARGETv4HE4$72USESAKLYSTRONTRANSMITTERTUBE4YPICALPHASE PUSHINGFORAKLYSTRONDUETOMODULATORVOLTAGECHANGEISFORDELTA %%4HE STABILITYBUDGETALLOCATEDA D"LIMITONIMPROVEMENTFACTORTOTHETRANSMITTER AND THISREQUIREDTHATTHERMSPULSE TO PULSEPOWERSUPPLYVOLTAGEVARIATIONBELESSTHAN PARTIN 4HETRANSMITTERPOWERSUPPLYCOULDNOTMEETTHISREQUIREMENTWHEN THERADARCHANGED02&FROM#0)TO#0) ASREQUIREDBYAN-4$WAVEFORM4HEREFORE THEACTUALPHASEOFEACHTRANSMITTEDPULSEWASMEASURED ANDTHISMEASUREDVALUEWAS USEDTOCORRECTTHEPHASEOFTHERECEIVEDSIGNALSFORTHAT02)4HISTECHNIQUECAUSES SMALLPERTURBATIONSINPHASEFROMWEATHERSIGNALSRECEIVEDFROMAMBIGUOUSRANGES BUTDOESNOTINTERFEREWITHVELOCITYESTIMATES)TDOESDEGRADETHEIMPROVEMENTFACTOR OFCLUTTERSIGNALSRECEIVEDFROMAMBIGUOUSRANGES BUTFORTHE4$72OPERATION THAT DEGRADATIONWASDEEMEDACCEPTABLE %NVIRONMENTAL#ONSIDERATIONS 4HISDISCUSSIONCONTAINSESSENTIALINFORMA TIONFORTHOSEDESIGNINGAMODERNSURVEILLANCERADARTODETECTMAN MADEAIRBORNE TARGETS4HELAWSOFPHYSICSCOMBINEDWITHTHEENVIRONMENTMAKEITIMPOSSIBLETO DESIGNAN-4)SURVEILLANCERADARTHATDOESNOTHAVECOMPROMISES4HEPROBLEMS ARE RELATED TO THE UNWANTED RETURNS FROM BIRDS INSECTS AUTOMOBILES LONG RANGE FIXED CLUTTER AND SHORT AND LONG RANGE WEATHER4HE CURRENT STATE OF THE ART OF RADARCANAMELIORATETHESEPROBLEMS BUTNOTWITHOUTSOMEUNDESIRABLESIDEEFFECTS -ANYUNWANTEDPOINTTARGETRETURNSHAVECHARACTERISTICSSIMILARTOTHERETURNSFROM WANTEDTARGETS ANDTHEUNWANTEDRETURNSMAYOUTNUMBERRETURNSFROMDESIREDTAR GETSBYTHETHOUSANDS
e4HECLUTTERFILTERSMUSTBEDESIGNEDBASEDONSYSTEMPARAMETERSTOREJECTTHERADIALSPEEDOFTHEhFIXEDvCLUTTER 3EE3ECTIONSAND
)THASBEENOBSERVEDTHATSOMEPHASEDARRAYRADARSHAVEPOORCLUTTERREJECTION WHICHISOFTENCAUSEDBYFAILURE TOFOLLOWRULE
-4)2!$!2
Ó°x
4HE PROBLEMS ARE EXACERBATED WHEN ANOMALOUS OR DUCTED PROPAGATION OCCURS ANOMALOUSPROPAGATION ASUSEDHEREIN ISWHENTHERADARENERGYFOLLOWSTHECURVATURE OFTHE%ARTH THUSCAUSINGDETECTIONOFBOTHFIXEDANDMOVINGCLUTTERATLONGRANGES &IGURE FROM 3HRADER SHOWS 00) PHOTOGRAPHS TAKEN WITH AN !232 RADAR MOUNTEDONA FTTOWERINFLATCOUNTRYNEAR!TLANTIC#ITY .EW*ERSEY7ITHNORMAL PROPAGATION THEEXPECTEDLINE OF SIGHTISABOUTNMI BUTTHECLUTTERACTUALLYGOES OUTTONMI4HEBRIDGESACROSSTHEINTRACOASTALWATERWAYCANBESEEN/NOCCASION THEUNWANTEDLONG RANGECLUTTERANDWEATHERRETURNSCOMEFROMAMBIGUOUSRANGES
&)'52% !NOMALOUS PROPAGATION DUCTING A NMI MAXIMUM RANGEANDB NMIMAXIMUMRANGE
Ó°È
2!$!2(!.$"//+
4HERADARSYSTEMMUSTHAVEFEATURESTOCOPEWITHTHESESITUATIONS&OREXAMPLE IFPULSE TO PULSESTAGGERINGISUSED THEAMBIGUOUS RANGECLUTTERWILLNOTCANCELANDEITHERTHE 02)MUSTBEINCREASEDORTHE02)MUSTBEMADECONSTANTOVERTHEAZIMUTHANGLESFROM WHICHTHEAMBIGUOUSRANGECLUTTERISRECEIVED!NDBEFOREWARNEDOFAPITFALLINTOWHICH MANYRADARDESIGNERSHAVEFALLEN&OREXAMPLE WHENPRESENTEDWITHTHEREQUIREMENT TOTRACKTARGETS THEDESIGNERMAYNOTREALIZETHATRADARRETURNSFROMTHETARGETSOF INTERESTMAYBEEMBEDDEDINSIMILARRETURNSFROMTHOUSANDSOFUNWANTEDTARGETS !TYPICALLONG RANGEAIR TRAFFIC CONTROLRADARHASSUFFICIENTSENSITIVITYTODETECTA SINGLELARGEBIRD SUCHASACROW SEAGULL ORVULTUREAPPROXIMATE2#3OFSQUARE METER ATARANGEOFMILES)FTHEREAREMANYSUCHBIRDSINTHERESOLUTIONCELLOFTHE RADAR THENTHECOMPOSITE2#3INCREASES4ENLARGEBIRDSINARESOLUTIONCELLWILLHAVE AN2#3OFSQUAREMETER7HENMULTIPATHREFLECTIONSOCCUR SUCHASOVERTHEOCEAN WHENTHERADARBEAMISCENTEREDATTHEHORIZON THERECANBEUPTOAD"ENHANCEMENT OFTHE2#3OFTHEBIRDS GIVINGANAPPARENT2#3GREATERTHANONESQUAREMETERTOTHE FLOCKOFBIRDS)FTHEREISBIRDORBIRDFLOCK PERSQUAREMILE THEREWILLBEABOUT BIRDRETURNSWITHINMILESOFTHERADAR 4ECHNIQUESUSEDTOCOUNTERUNWANTEDTARGETSAREASFOLLOWS 3ENSITIVITYTIMECONTROL34# USEDFORELIMINATINGLOW2#3TARGETSINLOW02& RADARSTHATIS RADARSTHATHAVENORANGEAMBIGUITIESUNDERNORMALOPERATION %NHANCEDHIGH ANGLEGAINANTENNAS 4WO BEAMANTENNASBEAMLIFTEDABOVETHEHORIZONFORSHORT RANGERECEPTION AND THENLOWEREDTOHORIZONFORLONGRANGE -4$TECHNIQUESUSINGCLUTTERMAPS!LSOCOUNTINGDETECTIONSINSMALLRANGE AZIMUTHSECTORSANDINCREASINGDETECTIONTHRESHOLDSINEACHSECTORIFTOOMANY DETECTIONSOCCUR 02&SHIGHENOUGHSOTHATALLTARGETSWITHRADIALVELOCITIESBELOWKNOTSCANBE CENSORED 3ENSITIVITY VELOCITY CONTROL 36# WHICH CENSORS RADIALLY SLOW SMALL TARGETS WHILEACCEPTINGRADIALLYFASTTARGETSANDLARGETARGETS #OMBINATIONSOFTECHNIQUESTHROUGHAREUSEDINMOSTAIR TRAFFIC CONTROLRADARS WHERE THE SMALLEST TARGETS OF INTEREST HAVE AN 2#3 OF ONE SQUARE METER OR GREATER 4ECHNIQUESANDAREUSEDWHENTHEDESIREDTARGETSMAYHAVERADARCROSSSECTIONS SIMILARTO ORSMALLERTHAN ABIRD 4ECHNIQUE 34#ISTHETRADITIONALMETHODOFSUPPRESSINGBIRDSANDINSECTSINA RADARWITHANUNAMBIGUOUSRANGE02&A02&LOWENOUGHSOTHATTHERANGETOTARGETS ANDCLUTTERISUNAMBIGUOUS 34#DECREASESTHESENSITIVITYOFTHERADARATSHORTRANGE ANDTHENINCREASESSENSITIVITY USUALLYUSINGAFOURTH POWERLAW ASRANGEINCREASES 4HISHASTHEEFFECTOFNOTPERMITTINGDETECTIONOFTARGETSWITHAPPARENTRADARCROSSSEC TIONSOF SAY LESSTHANSQUAREMETER&IGURESHOWSHOWEFFECTIVE34#CANBE AGAINSTBIRDS4HESE00)PHOTOSWERETAKENWITHAN,BAND!232AIR ROUTESURVEIL LANCERADAR IN/KLAHOMA.OTETHATTHEMAJORITYOFRETURNSFROMBIRDSWEREELIMI NATED BUTNOT&IGURESHOWSTHEEFFECTOF34#AGAINSTBATSANDINSECTSo o$AYTIMEBIRDRETURNSANDNIGHTTIMEBATANDINSECTRETURNSCANOFTENBESEENINREALTIMETHEEXTENTDEPENDSONTHE WEATHERANDTIMEOFYEARONTHE.%82!$732 $ WEATHERRADARIMAGESONTHE./!!)NTERNETSITES
-4)2!$!2
Ó°Ç
&)'52% 34#CANGREATLYREDUCETHENUMBEROFBIRDSDISPLAYED2ANGENMIA "IRDSSEENWITH -4)ANDB BIRDSSEENWITH-4)AND34#
&)'52% )NSECTSWITHANDWITHOUT34#ANDRANGEMILESA BATSANDINSECTSSEENWITH-4)AND B BATSANDINSECTSSEENWITH-4)AND34#
Ó°n
2!$!2(!.$"//+
4HETYPICALDOPPLERRADARIMAGESPRESENTEDBY46WEATHERFORECASTERSOFTENHAVETHE BIRDSANDBATSANDINSECTSREMOVEDBYHUMANINTERVENTION 4ECHNIQUE 34#WORKSQUITEWELLFORUNWANTEDBIOLOGICALRETURNSNEARTHEPEAK OFTHERADARBEAM BUTWHENUSEDWITHACOSECANT SQUAREDANTENNABEAMITSOLVESONE PROBLEM BUT CREATES ANOTHER IT ALSO DECREASES SENSITIVITY TO DESIRED TARGETS AT HIGH ELEVATIONANGLESWHERETHEANTENNAGAINISLOW4HESOLUTIONTOTHISPROBLEMISTOBOOST THEANTENNAGAINATHIGHELEVATIONANGLESTOBECONSIDERABLYHIGHERTHANTHEREQUIRE MENTFORTHECOSECANT SQUAREDPATTERN.OTONLYDOESTHISCOMPENSATEFORTHEUSEOF 34# BUTALSOENHANCESTHETARGET TO CLUTTERSIGNALRATIOFORTARGETSATHIGHELEVATION ANGLES THUSIMPROVING-4)PERFORMANCE4HEPENALTYFORTHISSOLUTIONISALOSSINTHE PEAKANTENNAGAINTHATCANBEACHIEVED!NILLUSTRATIONOFTHISAPPROACHISPROVIDED IN&IGURE WHICHSHOWSBOTHTHE!232 ANTENNAPATTERNANDTHECORRESPONDING FREE SPACECOVERAGE
&)'52% !NTENNAELEVATIONPATTERNFORTHE!232 ANTENNA A COMPAREDWITHTHECOSECANT SQUAREDPATTERNANDB FREE SPACE COVERAGEDIAGRAM
-4)2!$!2
Ó°
4HELOSSINPEAKGAINFORTHISEXAMPLE DUETOTHEBOOSTOFCOVERAGEATHIGHANGLES WASABOUTD"4HECOMBINATIONOF34#WITHENHANCEDHIGH ANGLECOVERAGEDOES QUITEWELLFORINSECTSANDBIRDS BUTDOESNOTELIMINATEAUTOMOBILEANDTRUCKRETURNS 6EHICLESHAVE2#3STHATEQUALOREXCEEDTHE2#3OFMANYDESIREDAIRCRAFTTARGETS 4ECHNIQUE 4HETWO BEAMTECHNIQUEREDUCESTHERETURNSFROMVERYLOWELEVA TIONANGLESWHEREVEHICLETRAFFICANDMANYBIRDS BATS ANDINSECTS ISENCOUNTERED 4HE RADAR TRANSMITS ENERGY USING THE BASIC PATTERN BUT USES A HIGHER ANGLE BEAM FORRECEPTIONATSHORTERRANGES ANDTHEBASICANTENNAPATTERNFORRECEIVINGATLONGER RANGES&IGURESHOWS UNDERNEATHTHETRANSMITTINGFEEDHORN ASECONDRECEIVE ONLYANTENNAFEEDHORNFORTHEHIGHBEAM4HEEFFECTIVETWO WAYANTENNAPATTERNSARE SHOWNIN&IGURE !S PREVIOUSLY MENTIONED THE ABOVE TECHNIQUES 34# TWO BEAM ANTENNAS AND SOME VARIATION OF -4$ ARE CURRENTLY USED ON MANY AIR TRAFFIC CONTROL RADARS4HE TWO BEAM ANTENNAS ALSO UTILIZE SOME HIGH ANGLE GAIN ENHANCEMENT TO COUNTER THE HIGH ANGLEEFFECTSOF34# 4ECHNIQUE 4HE-4$APPROACHISDESCRIBEDIN3ECTION 4ECHNIQUE ! BRUTE FORCE TECHNIQUE USED TO ELIMINATE TARGETS WITH RADIAL VELOCITIESOFLESSTHANAPPROXIMATELYoKNOTSRESULTINGINATOTALREJECTIONINTERVAL OFKNOTS4OKEEPTHISREJECTIONOFVELOCITIESTONOMORETHANOFTHEDOPPLER SPACE AVAILABLE THE AMBIGUOUS VELOCITY MUST BE ABOUT KNOTS 4HIS REQUIRES 02&SOF (ZAT,BAND (ZAT3BAND AND AT8BANDUNAMBIGUOUS RANGES RESPECTIVELY NMI NMI ANDNMI 4HEMAINCHALLENGEWITHTHISTECH NIQUEISTHATFIXEDCLUTTERRETURNSFROMMANYRANGEAMBIGUITIES ASWELLASALLTARGETS OFINTEREST FOLDINTOTHEFIRSTRANGEINTERVAL4HUS EXCELLENTCLUTTERREJECTIONMUSTBE PROVIDEDTOPREVENTFOLDEDCLUTTERFROMSUPPRESSINGTARGETSOFINTEREST WHICHMAY BEATANYTRUERANGE 4ECHNIQUE 36# ASDESCRIBEDIN3ECTION ISUSEDWHENITISNECESSARYTO DISTINGUISHVERYLOW2#3TARGETSFROMLOWVELOCITYCLUTTER SUCHASBIRDS INSECTS AND SEA3OMEWHATLOWER02&SCANBEUSEDTHANTHOSEUSEDFORTECHNIQUEBECAUSETHE
&)'52% 4WO BEAMANTENNA
Ó°£ää
2!$!2(!.$"//+
% "&$!$"%
"( #!$ % '
"( #!$ % '
#! &% $
&)'52% %XAMPLEOFCOVERAGEOBTAINEDWITHATWO BEAMANTENNA
LOGICPERMITSRETAININGMANYOFTHETARGETSWITHSMALLERRADIALVELOCITIESIFTHEIR2#3 ISLARGEENOUGH36#STILLREJECTSBIRDCLUTTER BUTRETAINS FOREXAMPLE THEFASTINCOM ING THREATENINGLOW 2#3MISSILE WHILEALSORETAININGTHELARGERCROSS SECTIONAIRCRAFT WITHLOWERRADIALVELOCITIES
, ,
3!PPLEBAUM h-ATHEMATICALDESCRIPTIONOF6)#) v'ENERAL%LECTRIC#O 3YRACUSE .9 2EPORT .O!7#3 %%- !PRIL 3-#HOW h2ANGEANDDOPPLERRESOLUTIONOFAFREQUENCY SCANNEDFILTER v0ROC)%% VOL NO PPn -ARCH # % -UEHE h.EW TECHNIQUES APPLIED TO AIR TRAFFIC CONTROL RADARS v 0ROC )%%% VOL PPn *UNE 2*0URDYETAL h2ADARSIGNALPROCESSING v,INCOLN,ABORATORY*OURNAL VOL .O 2*-C!ULAY h!THEORYFOROPTIMUM-4)DIGITALSIGNALPROCESSING v-)4,INCOLN,ABORATORY ,EXINGTON -! 2EPORTNO 0ART) 0ART)) 3UPPLEMENT) &EBRUARY %*"ARLOW h$OPPLERRADAR v0ROC)2% VOL PPn !PRIL 7 , 3IMKINS 6 # 6ANNICOLA AND * 0 2OYAN h3EEK )GLOO RADAR CLUTTER STUDY v 2OME!IR $EVELOPMENT#ENTER 2EPORT.O2EPT42 $$#!$ ! /CTOBER 7 &ISHBEIN 37 'RAVELINE AND / % 2ITTENBACH h#LUTTER ATTENUATION ANALYSIS v 53!RMY %LECTRONICS#OMMAND &ORT-ONMOUTH .* 2EPORT.O%#/- -ARCH * " "ILLINGSLEY ,OW !NGLE 2ADAR ,AND #LUTTER-EASUREMENTS AND %MPIRICAL -ODELS .ORWICH .97ILLIAM!NDREW0UBLISHING
-4)2!$!2
Ó°£ä£
&%.ATHANSONAND*02EILLY h2ADARPRECIPITATIONECHOES%XPERIMENTSONTEMPORAL SPATIAL AND FREQUENCY CORRELATION v 4HE *OHNS (OPKINS 5NIVERSITY !PPLIED 4ECHNOLOGY ,ABORATORY 2EPORT.O4ECH-EMO4' !PRIL $+"ARTON 2ADAR3YSTEM!NALYSIS %NGLEWOOD#LIFFS .*0RENTICE (ALL $+"ARTON h2ADAREQUATIONSFORJAMMINGANDCLUTTER vIN3UPPLEMENTTO)%%%4RANS!%3 %!3#/.4ECH#ONV2EV .OVEMBER PPn 2 * $OVIAK AND $ 3 :RNIC $OPPLER 2ADAR AND 7EATHER /BSERVATIONS /RLANDO &, !CADEMIC0RESS (27ARD h!MODELENVIRONMENTFORSEARCHRADAREVALUATION vIN %!3#/.#ONVENTION 2ECORD .EW9ORK PPn )%%% h)%%%3TANDARD2ADAR$EFINITIONS v2ADAR3YSTEMS0ANEL )%%%!EROSPACEAND%LECTRONICS 3YSTEMS3OCIETY 2EPORT.O)%%%3TD $+"ARTONAND773HRADER h)NTERCLUTTERVISIBILITYIN-4)SYSTEMS vIN)%%%%!3#/. 4ECH#ONV2EC .EW9ORK .9 /CTOBER PPn $+"ARTON -ODERN2ADAR3YSTEM!NALYSIS .ORWOOD -!!RTECH(OUSE PPn ,3PAFFORD h/PTIMUMRADARSIGNALPROCESSINGINCLUTTER v)%%%4RANS VOL)4 PPn 3EPTEMBER ,!7AINSTEINAND9$:UBAKOV %XTRACTIONOF3IGNALS&ROM.OISE .EW9ORK$OVER * #APON h/PTIMUM WEIGHTING FUNCTIONS FOR THE DETECTION OF SAMPLED SIGNALS IN NOISE v )2% 4RANS)NFORMATION4HEORY VOL)4 PPn !PRIL , 2 2ABINER ET AL h4ERMINOLOGY IN DIGITAL SIGNAL PROCESSING v )%%% 4RANS ON !UDIO AND %LECTROACOUSTICS VOL!5 NO PPn $ECEMBER -)3KOLNIK )NTRODUCTIONTO2ADAR3YSTEMS RD%D .EW9ORK-C'RAW (ILL P (5RKOWITZ h!NALYSISANDSYNTHESISOFDELAYLINEPERIODICFILTERS v)2%4RANS#IRCUIT4HEORY VOL#4 NO PPn *UNE 7-(ALLAND(27ARD h3IGNAL TO NOISERATIOLOSSINMOVINGTARGETINDICATOR v0ROC)%%% VOL PPn &EBRUARY 773HRADERAND6'REGERS (ANSEN h#OMMENTSON@#OEFFICIENTSFORFEED FORWARD-4)RADAR FILTERS v0ROC)%%% VOL PPn *ANUARY 7$7HITEAND!%2UVIN h2ECENTADVANCESINTHESYNTHESISOFCOMBFILTERS vIN)2%.AT #ONV2ECVOL PT .EW9ORK .9 PPn 2(&LETCHERAND$7"URLAGE h)MPROVED-4)PERFORMANCEFORPHASEDARRAYINSEVERECLUTTER ENVIRONMENTS vIN)%%%#ONF0UBL PPn !6/PPENHEIMAND273CHAFER $IGITAL3IGNAL0ROCESSING %NGLEWOOD#LIFFS .*0RENTICE (ALL )NC P ,:VEREV h$IGITAL-4)RADARFILTERS v)%%%4RANS VOL!5 PPn 3EPTEMBER ,UDLOFF AND - -INKER h2ELIABILITY OF VELOCITY MEASUREMENT BY -4$ RADAR v )%%% 4RANS VOL!%3 PPn *ULY 7 7 3HRADER h-4) 2ADAR v #HAP IN 2ADAR (ANDBOOK - ) 3KOLNIK ED .EW9ORK -C'RAW (ILL PPn 4-(ALLAND773HRADER h3TATISTICSOFCLUTTERRESIDUEIN-4)RADARSWITH)&LIMITING vIN )%%%2ADAR#ONFERENCE "OSTON -! !PRIL PPn ''RASSO h)MPROVEMENTFACTOROFANONLINEAR-4)INPOINTCLUTTER v)%%%4RANS VOL!%3 .OVEMBER (27ARDAND773HRADER h-4)PERFORMANCEDEGRADATIONCAUSEDBYLIMITING vIN%!3#/. 4ECH#ONV2EC SUPPLEMENTTO)%%%4RANSVOL!%3 .OVEMBER PPn ' 'RASSO AND 0 & 'UARGUAGLINI h#LUTTER RESIDUES OF A COHERENT -4) RADAR RECEIVER v )%%% 4RANS VOL!%3 PPn -ARCH 4!7EIL h!PPLYINGTHE!MPLITRONAND3TABILOTRONTO-4)RADARSYSTEMS vIN)2%.AT#ONV 2EC VOL PT .EW9ORK .9 PPn
Ó°£äÓ
2!$!2(!.$"//+
4! 7EIL h!N INTRODUCTION TO -4) SYSTEM DESIGN v %LECTRONIC 0ROGRESS VOL PP n -AY $",EESONAND'&*OHNSON h3HORT TERMSTABILITYFORADOPPLERRADAR2EQUIREMENTS MEASURE MENTS ANDTECHNIQUES v0ROC)%%% VOL PPn &EBRUARY (EWLETT0ACKARD0RODUCT.OTE" -ARCH 2 6IGNERI ET AL h! GRAPHICAL METHOD FOR THE DETERMINATION OF EQUIVALENT NOISE BANDWIDTH v -ICROWAVE*OURNAL VOL PPn *UNE $ 3TEINBERG h#HAPTERS v #HAPSn IN -ODERN 2ADAR !NALYSIS %VALUATION AND 3YSTEM $ESIGN 23"ERKOWITZED .EW9ORK .9*OHN7ILEYAND3ONS * 2 +LAUDER h4HE THEORY AND DESIGN OF CHIRP RADARS v "ELL 3YSTEM 4ECHNICAL *OURNAL VOL888)8 NO PPn *ULY 72ICEAND+(7U h1UADRATURESAMPLINGWITHHIGHDYNAMICRANGE v)%%%4RANS!EROSPACE AND%LECTRONIC3YSTEMS VOL!%3 NO PPn .OVEMBER 2.ITZBERG h#LUTTERMAP#&!2ANALYSIS v)%%%4RANS VOL!%3 PPn *ULY 6'REGERS(ANSEN h#ONSTANTFALSEALARMRATEPROCESSINGINSEARCHRADARS vIN2ADAR0RESENT AND&UTURE )%%#ONF0UBLNO ,ONDON 5+ /CTOBER .+HOURYAND*3(OYLE h#LUTTERMAPS$ESIGNANDPERFORMANCE vIN)%%%.AT2ADAR#ONF !TLANTA '! '64RUNKETAL h&ALSEALARMCONTROLUSINGDOPPLERESTIMATION v)%%%4RANS!EROSPACEAND %LECTRONIC3YSTEMS VOL!%3 PPn *ANUARY 773HRADER INVENTOR h3ENSITIVITY6ELOCITY#ONTROL v530ATENT *ULY #2IFEAND22"OORSTYN h3INGLE TONEPARAMETERESTIMATIONFROMDISCRETE TIMEOBSERVATIONS v )%%%4RANS)NFORMATION4HEORY VOL)4 NO PPn 3EPTEMBER $2!-C-AHONAND2&"ARRETT h!NEFFICIENTMETHODFORTHEESTIMATIONOFTHEFREQUENCYOF ASINGLETONEINNOISEFROMTHEPHASESOFDISCRETE&OURIERTRANSFORMS v3IGNAL0ROCESSING VOL PPn *74AYLOR h2ECEIVERS v#HAPIN2ADAR(ANDBOOK ND%D -)3KOLNIKED .EW9ORK -C'RAW (ILL PPn *9.#HOETAL h2ANGE VELOCITYAMBIGUITYMITIGATIONSCHEMESFORTHEENHANCEDTERMINALDOPPLER WEATHERRADAR vINST#ONFERENCEON2ADAR-ETEOROLOGY 3EATTLE 7! PPn 773HRADER h2ADARTECHNOLOGYAPPLIEDTOAIRTRAFFICCONTROL v)%%%4RANS#OMMUNICATIONS VOL NO PPn -AY 7 7 3HRADER h-4) RADAR v #HAP IN 2ADAR (ANDBOOK - ) 3KOLNIK ED .EW 9ORK -C'RAW (ILL PPn
#HAPTER
ÀLÀiÊ / >iÃÊ °Ê >Þ ,OCKHEED-ARTIN#ORPORATION
Ài`Ê °Ê-Ì>Õ`>
iÀI .AVAL2ESEARCH,ABORATORYRETIRED
ΰ£Ê -9-/ -Ê1- ÊÊ , ", Ê /Ê/ +1 !IRBORNESEARCHRADARSWEREINITIALLYDEVELOPEDFORTHEDETECTIONOFSHIPSBYLONG RANGE PATROLAIRCRAFT$URINGTHELATTERPARTOF7ORLD7AR)) AIRBORNEEARLY WARNING!%7 RADARSWEREDEVELOPEDBYTHE53.AVYTODETECTLOW FLYINGAIRCRAFTAPPROACHINGA TASKFORCEBELOWTHERADARCOVERAGEOFTHESHIPSANTENNA4HEADVANTAGEOFTHEAIR BORNEPLATFORMINEXTENDINGTHEMAXIMUMDETECTIONRANGEFORAIRANDSURFACETARGETSIS APPARENTWHENONECONSIDERSTHATTHERADARHORIZONISNMIFORA FTANTENNAMAST COMPAREDWITHAPPROXIMATELYNMIFORA FTAIRCRAFTALTITUDE 4HEAIRCRAFTCARRIERnBASED% $AIRCRAFT&IGURE USES!%7RADARASTHEPRIMARY SENSORINITSAIRBORNETACTICALDATASYSTEM4HESERADARSWITHTHEIREXTENSIVEFIELDOF VIEW ARE REQUIRED TO DETECT SMALL AIRBORNE TARGETS AGAINST A BACKGROUND OF SEA AND LANDCLUTTER"ECAUSETHEIRPRIMARYMISSIONISTODETECTLOW FLYINGAIRCRAFT THEYCANNOT ELEVATETHEIRANTENNABEAMTOELIMINATETHECLUTTER4HESECONSIDERATIONSHAVELEDTO THEDEVELOPMENTOFAIRBORNE-4)!-4) RADARSYSTEMSSIMILARTOTHOSEUSEDIN SURFACERADARS nDISCUSSEDINTHEPRECEDINGCHAPTER 4HEMISSIONREQUIREMENTSFORAN!%7RADARDRIVETHENEEDFORAZIMUTHALCOV ERAGEANDLONG RANGEDETECTIONCAPABILITY4HEAZIMUTHALCOVERAGEREQUIREMENT ISBECAUSETHE!%7RADARSYSTEMISGENERALLYREQUIREDTOPROVIDETHEFIRSTDETECTIONOF AIRBORNETARGETS WITHOUTANYAPRIORIKNOWLEDGEOFTHELOCATIONOFTHESETARGETS!%7 SYSTEMSHAVEGENERALLYBEENDEVELOPEDATLOWERFREQUENCIESTHISCANBEUNDERSTOOD BYREVIEWINGTHESURVEILLANCERADARRANGEEQUATION 2MAX
0A !E S T TS P K4 &N , 3 . 7
3ECTIONSTHROUGHANDWERETAKENPRIMARILYFROMTHESECONDEDITIONOFTHE2ADAR(ANDBOOK #HAPTER AUTHORED BY &RED 3TAUDAHER WITH REVISIONS MADE BY *AMES $AY 4HE REMAINING SECTIONS OF THE CHAPTER WERE AUTHOREDBY*AMES$AY
롣
ΰÓ
2!$!2(!.$"//+
&)'52% % $AIRBORNEEARLY WARNING!%7 AIRCRAFTSHOWINGROTODOME HOUSINGTHEANTENNA
WHERETSISTHESCANTIMEAND7ISTHESURVEILLANCEVOLUMECOVERAGEREQUIREMENTPROD UCTOFTHEAZIMUTHANDELEVATIONANGLES !SLONGASTHEBEAMWIDTHSOFTHERADARINAZIMUTHANDELEVATION ARESMALLERTHAN THE REGION TO BE SURVEILLED THIS EQUATION IS NOT DIRECTLY DEPENDENT UPON FREQUENCY (OWEVER KEYPARAMETERSINTHISEQUATIONAREDEPENDENTUPONFREQUENCY0ARTICULARLY PROPAGATIONLOSSESFORLOWALTITUDETARGETSANDTARGET2#3FORSOMETARGETTYPES ARE GENERALLYADVANTAGEOUSFORLOWERFREQUENCIES4HERESULTISTHAT!%7SYSTEMSHAVE BEENDEVELOPEDAT5(& ,BAND AND3BANDFREQUENCIES !IRBORNE-4)RADARSYSTEMSHAVEALSOBEENUTILIZEDTOACQUIREANDTRACKTARGETSIN INTERCEPTORFIRECONTROLSYSTEMS)NTHISAPPLICATION THESYSTEMSHAVETODISCRIMINATE AGAINSTCLUTTERONLYINTHEVICINITYOFAPRESCRIBEDTARGET4HISALLOWSTHESYSTEMTOBE OPTIMIZEDATTHERANGEANDANGULARSECTORWHERETHETARGETISLOCATED-4)ISALSOUSED TODETECTMOVINGGROUNDVEHICLESBYRECONNAISSANCEANDTACTICALFIGHTERAIRCRAFT 4HE ENVIRONMENT OF HIGH PLATFORM ALTITUDE MOBILITY AND SPEED COUPLED WITH RESTRICTIONSONSIZE WEIGHT ANDPOWERCONSUMPTION PRESENTAUNIQUESETOFPROBLEMS TOTHEDESIGNEROFAIRBORNE-4)SYSTEMS4HISCHAPTERWILLBEDEVOTEDTOCONSIDER ATIONSUNIQUETOTHEAIRBORNEENVIRONMENT
ΰÓÊ "6 , Ê " - ,/" 3EARCHRADARSGENERALLYREQUIREnAZIMUTHALCOVERAGE4HISCOVERAGEISDIFFICULT TOOBTAINONANAIRCRAFTSINCEMOUNTINGANANTENNAINTHECLEARPRESENTSMAJORDRAG STABILITY ANDSTRUCTURALPROBLEMS7HENEXTENSIVEVERTICALCOVERAGEISREQUIRED THE AIRCRAFTS PLANFORM AND VERTICAL STABILIZER DISTORT AND SHADOW THE ANTENNA PATTERN !NALYSIS OF TACTICAL REQUIREMENTS MAY SHOW THAT ONLY A LIMITED COVERAGE SECTOR IS REQUIRED(OWEVER THISSECTORUSUALLYHASTOBECAPABLEOFBEINGPOSITIONEDOVERTHE FULLnRELATIVETOTHEAIRCRAFTSHEADINGBECAUSEOFTHEREQUIREMENTSFORCOVERAGE
!)2"/2.%-4)
ΰÎ
&)'52% "OEING 7EDGETAILAIRCRAFTSHOWINGANTENNASMOUNTED ABOVETHEFUSELAGE
WHILEREVERSINGCOURSE LARGECRABANGLESWHENHIGHWINDSAREENCOUNTERED THENEED TOPOSITIONGROUNDTRACKINRELATIONTOWIND NONTYPICALOPERATINGSITUATIONS ANDOPERA TIONSREQUIREMENTSFORCOVERAGEWHILEPROCEEDINGTOANDFROMTHESTATION (OWEVER INTHESANDS ANUMBEROFSYSTEMSHAVEBEENDEVELOPEDTHATPRO VIDEPHASEDARRAYPERFORMANCEINANAIRBORNEPLATFORM4HE-ULTI 2OLE%LECTRONICALLY 3CANNED!RRAY-%3! RADARDEVELOPEDBY.ORTHROP'RUMMANONA"OEING FORTHE!USTRALIAN7EDGETAILPROGRAMISANEXAMPLESEE&IGURE !NALTERNATESOLU TIONTHATCOMBINESMECHANICALSCANNINGINCONJUNCTIONWITHELECTRONICSCANNINGISIN DEVELOPMENT WITH THE!.!09 RADAR FOR THE % $ AIRCRAFT FOLLOW UP TO THE 53 .AVYS% #AIRCRAFT
ΰÎÊ , ", Ê /Ê* ,",
Ê ,6 ,4HEPERFORMANCEOFAIRBORNE-4)SYSTEMSAREPRIMARILYDETERMINEDBYMOTIONEFFECTS INDUCEDONTHECLUTTERECHOESPLATFORMMOTION ANTENNASCANNINGMOTION ANDCLUTTERINTER NALMOTION THEPROCESSINGTECHNIQUESUSEDTOENHANCETARGETDETECTIONANDMAXIMIZECLUT TERCANCELLATION ANDTHEHARDWARESTABILITYLIMITATIONSOFTHERADAR4HISCHAPTERWILLDISCUSS THEMOTIONEFFECTSASWELLASTHEPERFORMANCEOFVARIOUSPROCESSINGTECHNIQUES
ΰ{Ê * /", Ê "/" Ê Ê //1 Ê
/-Ê" Ê /Ê* ,",
-4)DISCRIMINATESBETWEENAIRBORNEMOVINGTARGETSANDSTATIONARYLANDORSEACLUTTER (OWEVER INTHEAIRBORNECASE THECLUTTERMOVESWITHRESPECTTOTHEMOVINGAIRBORNE PLATFORM )T IS POSSIBLE TO COMPENSATE FOR THE MEAN CLUTTER RADIAL VELOCITY BY USING
ΰ{
2!$!2(!.$"//+
&)'52% $EFININGGEOMETRY@¼ ANTENNAPOINTINGANGLE@ LINE OF SIGHTANGLEP ANGLE FROMANTENNACENTERLINE6G AIRCRAFTGROUNDSPEED6R RADIALVELOCITYOFPOINTTARGET6" RADIAL VELOCITYALONGANTENNACENTERLINEBORESIGHT X ANTENNAAZIMUTHANGLEX AZIMUTHANGLE2 GROUNDRANGETOPOINTTARGETAND( AIRCRAFTHEIGHT
TECHNIQUES SUCH AS TIME AVERAGED CLUTTER COHERENT AIRBORNE RADAR 4!##!2 4HIS TECHNIQUEATTEMPTSTOCENTERTHELARGESTRETURNFROMMAIN BEAMCLUTTERATZERODOPPLER FREQUENCYSUCHTHATASIMPLE-4)FILTER ALSOCENTEREDATZERODOPPLERFREQUENCY WILL CANCELTHEMAIN BEAMCLUTTER !SSHOWNIN&IGURE THEAPPARENTRADIALVELOCITYOFTHECLUTTERIS6R 6GCOS@ WHERE6GISTHEGROUNDSPEEDOFTHEPLATFORMANDAISTHEANGLESUBTENDEDBETWEENTHELINE OF SIGHTTOAPOINTONTHE%ARTHSSURFACEANDTHEAIRCRAFTSVELOCITYVECTOR&IGURESHOWS THELOCIOFCONSTANTRADIALVELOCITYALONGTHESURFACE)NORDERTONORMALIZETHEFIGURE AFLAT EARTHISASSUMED ANDTHENORMALIZEDRADIALVELOCITY6N 6R6GISPRESENTEDASAFUNCTIONOF AZIMUTHANGLEXANDNORMALIZEDGROUNDRANGE2( WHERE(ISTHEAIRCRAFTSALTITUDE )NSTEAD OF A SINGLE CLUTTER DOPPLER FREQUENCY CORRESPONDING TO A CONSTANT RADIAL VELOCITY6"IN&IGURE DETERMINEDBYTHEANTENNAPOINTINGANGLE@ THERADIAL SEESACONTINUUMOFVELOCITIES4HISRESULTSINAFREQUENCYSPECTRUMATAPARTICULAR RANGEWHOSESHAPEISDETERMINEDBYTHEANTENNAPATTERNTHATINTERSECTSTHESURFACE THE REFLECTIVITYOFTHECLUTTER ANDTHEVELOCITYDISTRIBUTIONWITHINTHEBEAM&URTHERMORE SINCE6RVARIESASAFUNCTIONOFRANGEATAPARTICULARAZIMUTHX THECENTERFREQUENCY ANDSPECTRUMSHAPEVARYASAFUNCTIONOFRANGEANDAZIMUTHANGLEX 7HENTHEANTENNAISPOINTINGAHEAD THEPREDOMINANTEFFECTISTHEVARIATIONOFTHECEN TERFREQUENCYCORRESPONDINGTOTHECHANGEIN@WITHRANGE7HENTHEANTENNAISPOINTING
!)2"/2.%-4)
ΰx
&)'52% ,OCIOFCONSTANTNORMALIZEDRADIALVELOCITY6R6GASAFUNC TIONOFAIRCRAFTRANGE TO HEIGHTRATIO2(ANDAZIMUTHANGLEX
ABEAM THEPREDOMINANTEFFECTISTHEVELOCITYSPREADACROSSTHEANTENNABEAMWIDTH4HESE ARECLASSIFIEDASTHESLANT RANGEEFFECTANDTHEPLATFORM MOTIONEFFECT RESPECTIVELY %FFECTOF3LANT2ANGEON$OPPLER/FFSET 4HEANTENNABORESIGHTVELOCITY6"IS THEGROUND VELOCITYCOMPONENTALONGTHEANTENNACENTERLINEBORESIGHT ANDISGIVEN ASn6GCOS@ )FTHECLUTTERSURFACEWERECOPLANARWITHTHEAIRCRAFT THISCOMPONENT WOULDBEEQUALTO 6GCOSX ANDWOULDBEINDEPENDENTOFRANGE4HERATIOOFTHE ACTUALBORESIGHTVELOCITYTOTHECOPLANARBORESIGHTVELOCITYISDEFINEDASTHENORMAL IZEDBORESIGHT VELOCITYRATIO 6"2
COS A COS F COSY
WHEREEISTHEDEPRESSIONANGLEOFTHEANTENNACENTERLINEFROMTHEHORIZONTAL&IGURE SHOWSTHEVARIATIONOFTHENORMALIZEDBORESIGHT VELOCITYRATIOASAFUNCTIONOFSLANTRANGE FORACURVEDEARTHANDDIFFERENTAIRCRAFTALTITUDES4HEVARIATIONISFAIRLYRAPIDFORSLANT RANGESLESSTHANNMI )TISDESIRABLETOCENTERTHECLUTTERSPECTRUMINTHENOTCHIE MINIMUM RESPONSE REGION OFTHE!-4)FILTERINORDERTOOBTAINMAXIMUMCLUTTERREJECTION4HISCANBE ACCOMPLISHEDBYOFFSETTINGTHE)&OR2&FREQUENCYOFTHERADARSIGNALBYANAMOUNT EQUALTOTHEAVERAGEDOPPLERFREQUENCYOFTHECLUTTERSPECTRUM"ECAUSETHECLUTTER CENTERFREQUENCYVARIESWITHRANGEANDAZIMUTHWHENTHERADARISMOVING ITISNECES SARYFORTHEFILTERNOTCHTOTRACKTHEDOPPLER OFFSETFREQUENCY USINGANOPEN ORCLOSED LOOPCONTROLSYSTEMSUCHAS4!##!2 DESCRIBEDBELOW !N EXAMPLE OF A RECEIVED CLUTTER SPECTRUM GIVEN AN ANTENNA RESPONSE IS SHOWN IN&IGUREA4HE4!##!2FREQUENCYOFFSETTHENSHIFTSMAIN BEAMCLUTTERTOZERO DOPPLER ASSHOWNIN&IGUREB
ΰÈ
2!$!2(!.$"//+
&)'52% .ORMALIZEDBORESIGHT VELOCITYRATIO6"2ASAFUNCTIONOFTHEDIFFERENCEBETWEENSLANTRANGE 2SANDAIRCRAFTALTITUDE(FORDIFFERENTAIRCRAFTALTITUDES
4!##!2 4HE-)4,INCOLN,ABORATORYORIGINALLYDEVELOPED4!##!2TOSOLVE THE!-4)RADARPROBLEM4HEREQUIREMENTSANDTHUSTHEIMPLEMENTATIONOF4!##!2 CHANGEDEPENDINGUPONTHETYPEOFCLUTTERCANCELLATIONPROCESSINGEMPLOYED!FTER MANYOTHERAPPROACHES ITWASRECOGNIZEDTHATIFONEUSEDTHECLUTTERRETURNRATHERTHAN THETRANSMITPULSETOPHASE LOCKTHERADARTOTHECLUTTERFILTER ONECOULDCENTERTHECLUT TERINTHEFILTERSTOPBAND4HECLUTTERPHASEVARIESFROMRANGECELLTORANGECELLOWING TOTHEDISTRIBUTIONOFTHELOCATIONOFTHESCATTERERSINAZIMUTH(ENCE ITISNECESSARY TOAVERAGETHERETURNFORASLONGANINTERVALASPOSSIBLE4!##!2ISUSEDTODESCRIBE THECENTERINGOFTHERETURNEDCLUTTERSPECTRUMTOTHEZEROFILTERFREQUENCY3INCETHE TECHNIQUECOMPENSATESFORDRIFTINTHEVARIOUSSYSTEMELEMENTSANDBIASESINTHEMEAN DOPPLERFREQUENCYDUETOOCEANCURRENTS CHAFF ORWEATHERCLUTTER ITISUSEDINSHIP BOARDANDLAND BASEDRADARSASWELLASAIRBORNERADAR !FUNCTIONALBLOCKDIAGRAMOFANAIRBORNERADAREMPLOYING4!##!2ISSHOWNIN &IGURE4HECLUTTERERRORSIGNALISOBTAINEDBYMEASURINGTHEPULSE TO PULSEPHASE SHIFTVD4POFTHECLUTTERRETURN4HISPROVIDESAVERYSENSITIVEERRORSIGNAL4HEAVER AGEDERRORSIGNALCONTROLSAVOLTAGE CONTROLLEDCOHERENTMASTEROSCILLATOR#/-/ WHICH DETERMINES THE TRANSMITTED FREQUENCY OF THE RADAR 4HE #/-/ IS SLAVED TO
&)'52% #LUTTER 0OWER 3PECTRAL $ENSITY 03$ RESPONSE THROUGH ANTENNA PATTERN A WITHOUT 4!##!2FREQUENCYOFFSETANDB WITH4!##!2FREQUENCYOFFSET
!)2"/2.%-4)
롂
&)'52% "LOCKDIAGRAMOFARADARILLUSTRATINGTHESIGNALFLOWPATHOFTHE4!##!2CONTROLLOOP
THESYSTEMREFERENCEOSCILLATORFREQUENCYVIATHEAUTOMATICFREQUENCYCONTROL!&# LOOPSHOWNIN&IGURE4HISPROVIDESASTABLEREFERENCEINTHEABSENCEOFCLUTTER !NINPUTFROMTHEAIRCRAFTINERTIALNAVIGATIONSYSTEMANDTHEANTENNASERVOPROVIDEA PREDICTEDDOPPLEROFFSET4HESEINPUTSALLOWTHE4!##!2SYSTEMTOPROVIDEANARROW BANDWIDTHCORRECTIONSIGNAL "ECAUSEOFTHENOISYNATUREOFTHECLUTTERSIGNAL THENEEDTOHAVETHECONTROLSYSTEM BRIDGEREGIONSOFWEAKCLUTTERRETURN ANDTHEREQUIREMENTNOTTORESPONDTOTHEDOP PLERSHIFTOFATRUETARGET THECONTROLSYSTEMUSUALLYTRACKSTHEAZIMUTHVARIATIONOF ASPECIFICRADARRANGEINTERVAL4HEMAXIMUMRANGEOFTHISINTERVALISCHOSENSOTHAT CLUTTERWILLBETHEDOMINANTSIGNALWITHINTHEINTERVAL4HEMINIMUMRANGEISCHOSEN TOEXCLUDESIGNALSWHOSEAVERAGEFREQUENCYDIFFERSSUBSTANTIALLYFROMTHEFREQUENCY INTHEREGIONOFINTEREST !LTERNATEAPPROACHESTOPROVIDINGTHISFREQUENCYOFFSETCANBEIMPLEMENTEDWITH DIGITALEXCITERSORONRECEIVE&ORSOMEAPPLICATIONS ITMAYBENECESSARYTOUSEMULTIPLE CONTROL LOOPS EACH ONE COVERING A SPECIFIC RANGE INTERVAL OR TO VARY THE OFFSET FRE QUENCYINRANGE4HISISPOSSIBLEIFTHEFREQUENCYOFFSETISIMPLEMENTEDONRECEIVEBUT NOTONTRANSMIT !TANYPARTICULARRANGE THEFILTERNOTCHISEFFECTIVELYATONEFREQUENCY AND THE CENTER FREQUENCY OF THE CLUTTER SPECTRUM AT ANOTHER4HE DIFFERENCE BETWEEN THESEFREQUENCIESRESULTSINADOPPLER OFFSETERROR ASSHOWNIN&IGURE4HECLUTTER SPECTRUM WILL EXTEND INTO MORE OF THE FILTER PASSBAND AND THE CLUTTER IMPROVEMENT FACTORWILLBEDEGRADED4HEREQUIREDACCURACYFORTHE4!##!2CONTROLLOOPCANBE RELAXEDIFTHE-4)FILTERISANADAPTIVEFILTER SUCHASWITHSPACE TIMEADAPTIVEPROCESS INGDISCUSSEDLATERINTHISCHAPTER 4HISISBECAUSETHEADAPTIVEFILTERWILLADJUSTTOTHE RECEIVEDSIGNALSANDOPTIMIZECLUTTERCANCELLATION 7ITHOUTADAPTIVEADJUSTMENT &IGURESHOWSTHEIMPROVEMENTFACTORFORSINGLE ANDDOUBLE DELAYCANCELERSASAFUNCTIONOFTHERATIOOFTHENOTCH OFFSETERRORTOTHE PULSEREPETITIONFREQUENCY02& FORDIFFERENTCLUTTERSPECTRALWIDTHS&ORTUNATELY THE PLATFORM MOTIONSPECTRUMISNARROWINTHEFORWARDSECTOROFCOVERAGEWHEREOFFSET ERRORISMAXIMUM!NOFFSETERROROFONE HUNDREDTHOFTHE02&WOULDYIELDAD" IMPROVEMENTFACTORFORADOUBLECANCELERWITHANINPUTCLUTTERSPECTRUMWHOSEWIDTH
ΰn
2!$!2(!.$"//+
&)'52% %FFECTOFDOPPLER OFFSETERRORFR 02&
WASOFTHE02&)FTHERADARFREQUENCYWERE'(Z 02&K(Z ANDGROUNDSPEED KT THENOTCHWOULDHAVETOBEHELDWITHINKTOR6G "ECAUSEOFTHESEREQUIREMENTSANDTHEWIDTHOFTHEPLATFORM MOTIONSPECTRUM STAG GER02&SYSTEMSMUSTBECHOSENPRIMARILYONTHEBASISOFMAINTAININGTHESTOPBAND RATHERTHANFLATTENINGTHEPASSBAND3IMILARLY HIGHER ORDERDELAY LINEFILTERSWITHOR WITHOUTFEEDBACK ARESYNTHESIZEDONTHEBASISOFSTOPBANDREJECTION4HELIMITINGCASE ISTHENARROWBANDFILTERBANKWHEREEACHINDIVIDUALFILTERCONSISTSOFASMALLPASSBAND THEBALANCEBEINGSTOPBAND )MPROVEMENTFACTORISANIMPORTANTMETRIC BUTINADDITIONTOTHISAVERAGEMETRIC DEFINEDACROSSALLDOPPLERFREQUENCIES ITISOFTENIMPORTANTTOCHARACTERIZETHEPERFOR MANCEASAFUNCTIONOFDOPPLERFREQUENCY PARTICULARLYWITHCOHERENTDOPPLERFILTERING IMBEDDED IN THE PROCESSING CHAIN 7ITH PERFORMANCE CHARACTERIZED VERSUS DOPPLER
&)'52% )MPROVEMENTFACTOR)VERSUSNORMALIZEDDOPPLEROFFSETR¼ EASAFUNCTIONOFCLUTTER SPECTRUMWIDTHRC
!)2"/2.%-4)
ΰ
FREQUENCY THERADARDESIGNCANTHENBEEVALUATEDTHROUGHTHECOMPLETEDETECTIONCHAIN ANDOPTIMIZEDINCONJUNCTIONWITHANYMULTIPLE02&STAGGERWAVEFORMSUTILIZEDTO BRIDGE-4)BLINDREGIONS 0LATFORM -OTION%FFECT 4OANAIRBORNERADAR ACLUTTERSCATTERERAPPEARSTOHAVEA RADIALVELOCITYTHATDIFFERSFROMTHEANTENNA BORESIGHTRADIALVELOCITYATTHESAMERANGEBY 6E 6R 6" 6G COS A 6G COS A
6G ;COS A COSA Q = 6X SIN Q 6Y SIN
Q
FORSMALLVALUESOFPANDDEPRESSIONANGLEE WHERE6XISTHEHORIZONTALCOMPONENT OFVELOCITYPERPENDICULARTOTHEANTENNABORESIGHTAND6YISTHECOMPONENTALONGTHE ANTENNABORESIGHTPISTHEAZIMUTHALANGLEFROMTHEANTENNABORESIGHT ORTHEINTERSEC TIONOFTHEVERTICALPLANECONTAININGTHEBORESIGHTWITHTHEGROUND4HECORRESPONDING DOPPLERFREQUENCY WHEN@ISAFEWBEAMWIDTHSFROMGROUNDTRACK IS FD
6X 6 SIN Q y X Q L L
4HISPHENOMENONRESULTSINAPLATFORM MOTIONCLUTTERPOWERSPECTRUMTHATISWEIGHTED BYTHEANTENNASTWO WAYPOWERPATTERNINAZIMUTH4HETRUESPECTRUMMAYBEAPPROX IMATEDBYAGAUSSIANSPECTRUM
( F E
¤ F ³
¥ DS ´ ¦ PMµ
E
¤6 Q ³
¥ X LS ´ ¦ PMµ
y ' Q
'P THETWO WAYPOWERPATTERNOFTHEANTENNA ISWHENP PA WHEREPAIS THEHALF POWERBEAMWIDTH WHICHCANBEAPPROXIMATEDBYKA ABEINGTHEEFFECTIVE HORIZONTALAPERTUREWIDTH4HUS
E
¤6 ³
¥ X AS ´ ¦ PMµ
OR
S PM
6X A
WHERE6XANDAAREINCONSISTENTUNITS4HISVALUEISLOWERTHANONESDERIVEDBYOTHER AUTHORS (OWEVER ITAGREESWITHMOREEXACTANALYSISOFANTENNARADIATIONPATTERNS ANDEXPERIMENTALDATAANALYZEDBY&3TAUDAHER !MOREEXACTVALUEOFTHEPARAMETERRPMMAYBEOBTAINEDBYMATCHINGATWO WAY POWERPATTERNOFINTERESTWITHTHEGAUSSIANAPPROXIMATIONATASPECIFICPOINTONTHEPAT TERN DETERMININGTHESTANDARDDEVIATIONOFPBYUSINGSTATISTICALTECHNIQUESORFITTING
ΰ£ä
2!$!2(!.$"//+
&)'52% %FFECTOFPLATFORMMOTIONONTHE-4)IMPROVEMENTFACTOR ASAFUNCTIONOFTHEFRACTIONOFTHEHORIZONTALANTENNAAPERTUREDISPLACEDPER INTERPULSEPERIOD 6X4PA
THEPATTERNANDUSINGNUMERICALMETHODS4HECALCULATIONOFTHEIMPROVEMENTFACTOR CANBEPERFORMEDBYAVERAGINGTHERESULTANTRESIDUEPOWER OBTAINEDBYSUMMINGTHE SIGNALPHASORSATSPECIFICVALUESOFP FROMNULLTONULLOFTHEANTENNAPATTERN &IGURESHOWSTHEEFFECTOFPLATFORMMOTIONONTHE-4)IMPROVEMENTFACTORAS AFUNCTIONOFTHEAPERTUREDISPLACEDINTHEPLANEOFTHEAPERTUREPERINTERPULSEPERIOD4P !DISPLACEMENTREDUCESTHEDOUBLE DELAYIMPROVEMENTFACTORTOD"4HISCOR RESPONDSTOASPEEDOFKTIFTHESYSTEMHASA02&OF(ZANDA FTANTENNA APERTURE &OR A SINGLE DELAY SYSTEM THE DISPLACEMENT HAS TO BE HELD TO FOR A D"PERFORMANCELIMIT
ΰxÊ * /", "/" ÊÊ
" * -/" Ê 4HEDELETERIOUSEFFECTSOFPLATFORMMOTIONCANBEREDUCEDBYPHYSICALLYORELECTRONI CALLYDISPLACINGTHEANTENNAPHASECENTERALONGTHEPLANEOFTHEAPERTURE4HISISREFERRED TOASTHEDISPLACEDPHASECENTERANTENNA$0#! TECHNIQUEn)NADDITION SOMEFORMS OFSPACE TIMEADAPTIVEPROCESSINGAREEXPRESSLYDEVELOPEDTOIMPROVECLUTTERCANCELLA TIONWITHANADAPTIVEFILTER ELECTRONICALLYDISPLACINGTHEANTENNAPHASECENTER %LECTRONICALLY $ISPLACED 0HASE #ENTER !NTENNA &IGURE A SHOWS THE PULSE TO PULSEPHASEADVANCEOFANELEMENTALSCATTERERASSEENBYTHERADARRECEIVER
!)2"/2.%-4)
ΰ££
&)'52% 0HASOR DIAGRAM SHOWING THE RETURN FROM A POINT SCATTERER DUE TO PLATFORM MOTION
4HEAMPLITUDE%OFTHERECEIVEDSIGNALISPROPORTIONALTOTHETWO WAYANTENNAFIELD INTENSITY4HEPHASEADVANCEIS
H P FD4P
P 6X4P SIN Q L
WHERE FD DOPPLERSHIFTOFSCATTERER%Q
4P INTERPULSEPERIOD &IGUREBSHOWSAMETHODOFCORRECTINGFORTHEPHASEADVANCEG!NIDEALIZED CORRECTIONSIGNAL%CISAPPLIED LEADINGTHERECEIVEDSIGNALBYnANDLAGGINGTHENEXT RECEIVEDSIGNALBYn&OREXACTCOMPENSATION THEFOLLOWINGRELATIONWOULDHOLD
%C % TAN H £ Q TAN
P 6X4P SIN Q L
4HISASSUMESATWO LOBEANTENNAPATTERNSIMILARTOTHATINAMONOPULSETRACKING RADAR4WORECEIVERSAREUSED ONESUPPLYINGASUMSIGNAL 3P ANDTHEOTHERA DIFFERENCESIGNAL $P 4HEDIFFERENCESIGNALISUSEDTOCOMPENSATEFORTHEEFFECTS OFPLATFORMMOTION )FTHESYSTEMISDESIGNEDTOTRANSMITTHESUMPATTERN3P ANDRECEIVEBOTH3P AND ADIFFERENCEPATTERN$P THENATTHEDESIGNSPEEDTHERECEIVEDSIGNAL3P $P CANBE APPLIEDASTHECORRECTIONSIGNAL4HEACTUALCORRECTIONSIGNALUSEDTOAPPROXIMATE%CIS K3P $P WHEREKISTHERATIOOFTHEAMPLIFICATIONINTHESUMANDDIFFERENCECHANNELS OFTHERECEIVER !UNIFORMLYILLUMINATEDMONOPULSEARRAYHASTHEDIFFERENCESIGNAL$INQUADRA TUREWITHTHESUMANDHASTHEAMPLITUDERELATIONSHIP
¤ P7 ³ $Q £Q TAN ¥ SIN Q´ ¦ L µ
WHERE7ISTHEDISTANCEBETWEENTHEPHASECENTERSOFTHETWOHALVESOFTHEANTENNA (ENCE ACHOICEOF7 6X4PANDK WOULDIDEALLYRESULTINPERFECTCANCELLATION )N PRACTICE A SUM PATTERN IS CHOSEN BASED ON THE DESIRED BEAMWIDTH GAIN AND SIDELOBESFORTHEDETECTIONSYSTEMREQUIREMENTS4HENTHEDIFFERENCEPATTERN$P IS SYNTHESIZEDINDEPENDENTLY BASEDONTHERELATIONSHIPREQUIREDATDESIGNRADARPLATFORM
ΰ£Ó
2!$!2(!.$"//+
SPEEDANDALLOWABLESIDELOBES4HETWOPATTERNSMAYBEREALIZEDBYCOMBININGTHE ELEMENTSINSEPARATECORPORATE FEEDSTRUCTURES &IGURESHOWSTHEIDEALIZEDIMPROVEMENTFACTORASAFUNCTIONOFNORMALIZED APERTURE MOVEMENT FOR A DOUBLE DELAY CANCELER 4HE IMPROVEMENT FACTOR SHOWN IS THE IMPROVEMENT FACTOR FOR A POINT SCATTERER AVERAGED OVER THE NULL TO NULL ANTENNA BEAMWIDTH)NONECASE THEGAINRATIOKISOPTIMIZEDATEACHVALUEOFPULSE TO PULSE DISPLACEMENT)NTHEOTHERCOMPENSATEDCASE THEOPTIMUMGAINRATIOKISAPPROXIMATED BYTHELINEARFUNCTIONOFINTERPULSEPLATFORMMOTIONK6X !BLOCKDIAGRAMOFTHEDOUBLE DELAYSYSTEMISSHOWNIN&IGURE!SINGLE DELAY SYSTEMWOULDNOTHAVETHESECONDDELAYLINEANDSUBTRACTOR4HENORMALLYREQUIRED CIRCUITRYFORMAINTAININGCOHERENCE GAINANDPHASEBALANCE ANDTIMINGISNOTSHOWN 4HESPEEDCONTROL6XISBIPOLARANDMUSTBECAPABLEOFREVERSINGTHESIGNOFTHE$P SIGNALINEACHCHANNELWHENTHEANTENNAPOINTINGANGLECHANGESFROMTHEPORTTOTHE STARBOARDSIDEOFTHEAIRCRAFT
&)'52% -4)IMPROVEMENTFACTORFOR$0#!COMPENSATIONASA FUNCTIONOFTHEFRACTIONOFTHEHORIZONTALPHASECENTERSEPARATION7THAT THEHORIZONTALANTENNAAPERTUREISDISPLACEDPERINTERPULSEPERIOD 6X4P7 7 A WHEREAISTHEHORIZONTALAPERTURELENGTH
!)2"/2.%-4)
ΰ£Î
&)'52% 3IMPLIFIEDDOUBLE DELAY$0#!MECHANIZATION
4HEHYBRIDAMPLIFIERSHOWNHASTWOINPUTTERMINALSTHATRECEIVE3P ANDJ$P ANDAMPLIFYTHE$P CHANNELBYK6XRELATIVETOTHE3P CHANNEL4HEOUTPUTTER MINALSPRODUCETHESUMANDDIFFERENCEOFTHETWOAMPLIFIEDINPUTSIGNALS"ECAUSE $0#!COMPENSATESFORTHECOMPLEXSIGNAL BOTHAMPLITUDEANDPHASEINFORMATION MUST BE RETAINED 4HEREFORE THESE OPERATIONS USUALLY OCCUR AT 2& OR )& $IGITAL COMPENSATION CAN BE USED IF SYNCHRONOUS DETECTION AND ANALOG TO DIGITAL !$ CONVERSION ARE PERFORMED AND THE COMPONENTS ARE TREATED AS COMPLEX PHASORS &URTHERMORE THEOPERATIONSMUSTBELINEARUNTILTHESUMSIGNALANDDIFFERENCESIG NALSHAVEBEENPROCESSEDBYTHEHYBRIDAMPLIFIER!FTERTHISSINGLE PULSECOMBINA TION THE ACTUAL DOUBLE CANCELLATION CAN BE PERFORMED BY ANY CONVENTIONAL -4) PROCESSINGTECHNIQUES 0OWERINTHE!NTENNA3IDELOBES !IRBORNESYSTEMSARELIMITEDINTHEIRABILITY TO REJECT CLUTTER DUE TO THE POWER RETURNED BY THE ANTENNA SIDELOBES4HE FULL n AZIMUTHALPATTERNSEESVELOCITIESFROM 6GTO 6G4HECOMPENSATIONCIRCUITSOFFSET THEVELOCITYBYANAMOUNTCORRESPONDINGTOTHEANTENNABORESIGHTVELOCITY6" BUTTHE TOTALRANGEOFDOPPLERFREQUENCIESCORRESPONDINGTO6GISOBTAINEDBECAUSEOFECHOES RECEIVEDVIATHESIDELOBES&ORAIRBORNESYSTEMSWITHLOW02&S THESEDOPPLERFRE QUENCIESCANCOVERSEVERALMULTIPLESOFTHE02&SOTHATTHESIDELOBEPOWERISFOLDED INTOTHEFILTER4HISLIMITATIONISAFUNCTIONOFTHEANTENNAPOINTINGANGLE THE-4)FILTER RESPONSE ANDTHESIDELOBEPATTERN)FTHESIDELOBESARERELATIVELYWELLDISTRIBUTEDIN AZIMUTH AMEASUREOFPERFORMANCECANBEOBTAINEDBYAVERAGINGTHEPOWERRETURNED BYTHESIDELOBES 4HELIMITINGIMPROVEMENTFACTORDUETOSIDELOBESIS P
)SL LIMIT
+ ¯ ' Q DQ
P
¯SL ' Q DQ
WHERETHELOWERINTEGRALISTAKENOUTSIDETHEMAIN BEAMREGION-AIN BEAMEFFECTS WOULDBEINCLUDEDINTHEPLATFORM MOTIONIMPROVEMENTFACTOR4HECONSTANT+ISTHE NOISENORMALIZATIONFACTORFORTHE-4)FILTER+ FORSINGLEDELAYANDFORDOUBLE DELAY 'P ISTHETWO WAYPOWEROFTHEANTENNAINTHEPLANEOFTHEGROUNDSURFACE 4HE$0#!PERFORMANCEDESCRIBEDINTHEPRECEDINGSUBSECTIONCANBEANALYZEDON THEBASISOFRADIATIONPATTERNSORTHEEQUIVALENTAPERTUREDISTRIBUTIONFUNCTION)FTHE RADIATIONPATTERNISUSED THECOMPOSITEPERFORMANCEMAYBEOBTAINEDEITHERBYAPPLY INGTHEPATTERNFUNCTIONSOVERTHEENTIREnPATTERNORBYCOMBININGTHEIMPROVEMENT
롣{
2!$!2(!.$"//+
FACTORSFORTHE$0#!MAIN BEAMANDTHESIDELOBEREGIONSINTHESAMEMANNERASPARAL LELIMPEDANCESARECOMBINED ) TOTAL ) SL ) $0#!
)FTHEAPERTUREDISTRIBUTIONISUSED THESIDELOBEEFFECTSAREINHERENTINTHEANALYSIS #AREMUSTBETAKEN HOWEVERIFTHEARRAYORREFLECTORFUNCTIONISUSEDWITHOUTCON SIDERINGTHEWEIGHTINGOFTHEELEMENTALPATTERNORTHEFEEDDISTRIBUTION THEINHERENT SIDELOBEPATTERNCANOBSCURETHEMAIN BEAMCOMPENSATIONRESULTS !GAIN THE PERFORMANCE VERSUS DOPPLER FREQUENCY IS IMPORTANT FOR EVALUATING OVERALL RADAR DETECTION PERFORMANCE!NTENNA SIDELOBE LIMITED PERFORMANCE CAN BE APPROXIMATEDBYPERFORMINGTHELOWERINTEGRALOF%QOVERTHOSEANGLESTHATMAP INTOAGIVENDOPPLERFILTERSPASSBAND4HENOISENORMALIZATIONTERM K MUSTALSOBE MODIFIEDTOREFLECTTHECASCADEDNOISEGAINOFTHE-4)ANDDOPPLERFILTERBANKAS .
.
.
I
I
I
. G K £ 7I £ 7I 7I COS P K . £ 7I 7I COS P K .
K .
FORTHREE PULSE-4)ANDCASCADED. PULSEDOPPLERFILTERBANK WHERE7IARETHEDOP PLERFILTERWEIGHTS OR .
.
I
I
. G K £ 7I £ 7I 7I COSP K .
K .
FORTWO PULSE-4)ANDCASCADED. PULSEDOPPLERFILTERBANK
ΰÈÊ -
"/" Ê " * -/"
&IGUREASHOWSATYPICALANTENNAMAIN BEAMRADIATIONPATTERNANDTHERESPONSEOF APOINTSCATTERERFORTWOSUCCESSIVEPULSESWHENTHEANTENNAISSCANNING)TISSEENTHAT THESIGNALSRETURNEDWOULDDIFFERBY$'P 4HISRESULTSINIMPERFECTCANCELLATIONDUE TOSCANNING4HEAVERAGEEFFECTONTHEIMPROVEMENTFACTORCANBEOBTAINEDBYINTEGRAT INGTHISDIFFERENTIALEFFECT$'P OVERTHEMAINBEAMS
)SCAN
Q
Q
\ ' Q \ DQ
Q
¯ Q \ 'Q 4PQ 'Q \ DQ
FOR SINGLE DELAY CANCELLATION
)SCAN
¯
¯
Q
Q
A
\ ' Q \ DQ
Q
¯ Q \ 'Q 4PQ 'Q 'Q 4PQ \ DQ
WHERE P NULLOFMAINBEAM
'P TWO WAYVOLTAGEPATTERN
FOR DOUBLE DELAY CANCELLATIONN B
!)2"/2.%-4)
롣x
&)'52% !NTENNASCANNINGEFFECTSA ASSEENBYTHEANTENNARADIATIONPATTERN DUETOTHEAPPARENT CHANGEINAZIMUTHOFTHESCATTERER Q Q Q 4P B ASSEENBYTHEAPERTUREILLUMINATIONFUNCTION DUE TOTHEAPPARENTMOTION V XQ OFTHESCATTERERRELATIVETOTHEANTENNAATPOSITIONXANDC STEP SCAN COMPENSATIONOFTWORECEIVEDPHASORS
)N ORDER TO TREAT SCANNING MOTION IN THE FREQUENCY DOMAIN THE APPARENT CLUTTER VELOCITYSEENBYTHESCANNINGANTENNAISEXAMINEDTODETERMINETHEDOPPLERFREQUENCY %ACHELEMENTOFANARRAYORINCREMENTALSECTIONOFACONTINUOUSAPERTURECANBECON SIDEREDASRECEIVINGADOPPLER SHIFTEDSIGNALDUETOTHERELATIVEMOTIONOFTHECLUTTER 4HE POWER RECEIVED BY THE ELEMENT IS PROPORTIONAL TO THE TWO WAY APERTURE POWER DISTRIBUTIONFUNCTION&X ATTHEELEMENT )NADDITIONTOTHEVELOCITYSEENBYALLELEMENTSBECAUSEOFTHEMOTIONOFTHEPLAT FORM EACHELEMENTSEESANAPPARENTCLUTTERVELOCITYDUETOITSROTATIONALMOTION AS ILLUSTRATEDIN&IGUREB4HEAPPARENTVELOCITYVARIESLINEARLYALONGTHEAPERTURE (ENCE THETWO WAYAPERTUREDISTRIBUTIONISMAPPEDINTOTHEFREQUENCYDOMAIN4HE RESULTINGPOWERSPECTRUMDUETOTHEANTENNASCANNINGIS
¤L F³ ( F & ¥ ´ ¦ Q µ
a F a
AQ L
WHEREQ ANTENNAROTATIONRATE
A HORIZONTALANTENNAAPERTURE 4HISSPECTRUMCANBEAPPROXIMATEDBYAGAUSSIANDISTRIBUTIONWITHSTANDARDDEVIATION
S C
FR AQ Q y N QA L
WHEREKANDAAREINTHESAMEUNITS PAISTHEONE WAYHALF POWERBEAMWIDTH ANDN ISTHENUMBEROFHITSPERBEAMWIDTH4HEAPPROXIMATIONPAyKAISREPRESENTATIVEOF ANANTENNADISTRIBUTIONYIELDINGACCEPTABLESIDELOBELEVELS )TCANBESEENTHATTHEANTENNAPATTERNPULSE TO PULSEDIFFERENTIALGAINIS
$' Q
D' Q D' Q $Q Q 4P DQ DQ
ΰ£È
2!$!2(!.$"//+
4HISSUGGESTS THATACORRECTIONSIGNALINTHEREVERSESENSETO$'P BEAPPLIED ASSHOWNIN&IGUREC(ALFTHECORRECTIONISADDEDTOONEPULSEANDHALFSUBTRACTED FROMTHEOTHER SOTHAT #ORRECTION SIGNAL
$' Q Q4P D £ Q DQ
D £Q Q4P £Q DQ
WHERE3P WASSUBSTITUTEDFOR'P 4HERADARTRANSMITSASUMPATTERN3P AND RECEIVESONTHEDIFFERENCEPATTERN$P SOTHATTHERECEIVEDSIGNALISPROPORTIONALTO THEPRODUCTOFTHETWO)FTHESIGNALRECEIVEDONTHEDIFFERENCEPATTERNISUSEDASTHE CORRECTION WEHAVE
%C $P 3P
"YCOMPARING%QSAND WESEETHATFOR%CTOAPPROXIMATETHECORRECTION SIGNAL THEDIFFERENCEPATTERNSSHOULDBE
D £Q $Q Q4P DQ
4HEDERIVATIVEOFTHESUMPATTERNISSIMILARTOADIFFERENCEPATTERNINTHATITISPOSITIVE ATTHEMAIN BEAMNULL P DECREASESTOZEROONTHEANTENNACENTERLINE ANDTHENGOES NEGATIVEUNTILP 2EFERRINGTO&IGURE ONEOBSERVESTHATTHEMECHANIZATIONFORSCANCOMPENSA TIONISFUNDAMENTALLYSIMILARTOTHE$0#!MECHANIZATIONEXCEPTTHATTHEDIFFERENCE SIGNALISAPPLIEDINPHASEWITHTHESUMSIGNALANDAMPLIFIEDBYANAMOUNTDETERMINED BYTHEANTENNAROTATIONPERINTERPULSEPERIOD 4HESIGNALSREQUIRED IFTHETRANSMISSIONSIGNAL3P THATAPPEARSINEACHCHANNEL ISNEGLECTED ARE 3Q o LQ4P $Q WHERELISTHERATIOOFTHEAMPLIFICATIONINTHETWO CHANNELS CHOSEN TO MAXIMIZE THE CLUTTER REJECTION 4HE REQUIRED DIFFERENCE PATTERN SLOPEISDETERMINEDBYTHEDERIVATIVEOFTHESCANPATTERN WHICHDIFFERSFROMTHE$0#! CRITERION4HISTECHNIQUEISKNOWNASSTEP SCANCOMPENSATIONBECAUSETHESYSTEMELEC TRONICALLYPOINTSTHEANTENNASLIGHTLYAHEADOFANDBEHINDOFBORESIGHTEACHPULSESO THATALEADINGANDLAGGINGPAIRARETAKENFROMSUCCESSIVERETURNSTOOBTAINTHEEFFECTOF THEANTENNAREMAININGSTATIONARY &IGURE SHOWS THE IMPROVEMENT OBTAINED BY $ICKEY AND 3ANTA FOR SINGLE DELAYCANCELLATION #OMPENSATION 0ATTERN 3ELECTION 3ELECTION OF THE COMPENSATION PATTERN DEPENDSONTHELEVELOFSYSTEMPERFORMANCEREQUIRED THETYPEOF-4)FILTERINGUSED THE PLATFORMVELOCITY SCANRATE ANDTHECHARACTERISTICSREQUIREDBYNORMALRADARPARAMETERS SUCHASRESOLUTION DISTORTION GAIN SIDELOBES ETC&ORINSTANCE ANEXPONENTIALPATTERN AND ITS CORRESPONDING DIFFERENCE PATTERN ARE EXCELLENT FOR SINGLE DELAY CANCELLATION $0#!BUTAREUNSATISFACTORYWHENDOUBLE DELAYCANCELLATIONISUSED4HISISBECAUSE THESINGLE DELAYCANCELERREQUIRESTHEBESTMATCHBETWEENTHEACTUALPATTERNANDTHE REQUIREDPATTERNNEARBORESIGHT WHEREASDOUBLECANCELLATIONREQUIRESTHEBESTMATCH
!)2"/2.%-4)
ΰ£Ç
&)'52% -4) IMPROVEMENT FACTOR FOR A STEP SCANCOMPENSATIONOFASINGLE DELAYCANCELER ASAFUNCTIONOFTHENUMBEROFHITSPERBEAMWIDTH 4HEANTENNAPATTERNISSINX X
ONTHEBEAMSHOULDER3TEP SCANCOMPENSATIONUSUALLYREQUIRESTHEDIFFERENCE PATTERN PEAKSTOBENEARTHENULLSOFTHESUMPATTERNTOMATCH 'RISSETTIETALHAVESHOWNTHATFORSTEP SCANCOMPENSATIONTHEIMPROVEMENTFACTOR FORSINGLE DELAYCANCELLATIONINCREASESASAFUNCTIONOFTHENUMBEROFHITSATD" DECADE FOR THE FIRST DERIVATIVE
TYPE STEP SCAN COMPENSATION AT THE RATE OF D" DECADEANDWITHFIRST ANDSECOND DERIVATIVECOMPENSATION ATTHERATEOFD"DECADE (ENCE FORAGROUND BASEDSYSTEMTHATISLIMITEDBYSCANRATE ONESHOULDIMPROVETHE COMPENSATIONPATTERNRATHERTHANUSEAHIGHER ORDER-4)CANCELER(OWEVER AIRBORNE SYSTEMSAREPRIMARILYLIMITEDBYPLATFORMMOTIONANDREQUIREBOTHBETTERCANCELERSAND COMPENSATIONFOROPERATIONINALAND CLUTTERENVIRONMENT)NTHESEA CLUTTERENVIRON MENT THESYSTEMISUSUALLYDOMINATEDBYTHESPECTRALWIDTHOFTHEVELOCITYSPECTRUMOR PLATFORMMOTIONRATHERTHANSCANNING4HEAPPLICABILITYOF$0#!ORSTEP SCANCOMPEN SATIONINTHELATTERCASEISDEPENDENTONTHEPARTICULARSYSTEMPARAMETERS
4HECOMPENSATIONREQUIREDBY$'P CANBEDETERMINEDFROMA4AYLORSSERIESEXPANSIONOF'P )NTHEPRE CEDINGDISCUSSION WEUSEDTHEFIRSTDERIVATIVE5SINGHIGHER ORDERTERMSGIVESANIMPROVEDCORRECTIONSIGNAL
롣n
2!$!2(!.$"//+
ΰÇÊ - 1 / "1-Ê* /", Ê "/" ÊÊ Ê- Ê " * -/" )N!-4)SYSTEMSHAVINGMANYHITSPERSCAN SCANNINGISASECONDARYLIMITATIONFOR ANUNCOMPENSATEDDOUBLECANCELER(OWEVER THEPERFORMANCEOFA$0#!SYSTEMIS SIGNIFICANTLYREDUCEDWHENITISSCANNED4HISISDUETOTHESCANNINGMODULATIONONTHE DIFFERENCEPATTERNUSEDFORPLATFORM MOTIONCOMPENSATION 3INCETHE$0#!APPLIESTHEDIFFERENCEPATTERNINQUADRATURETOTHESUMPATTERNTO COMPENSATEFORPHASEERRORANDSTEPSCANAPPLIESTHEDIFFERENCEPATTERNINPHASETOCOM PENSATEFORAMPLITUDEERROR ITISPOSSIBLETOCOMBINETHETWOTECHNIQUESBYPROPERLY SCALINGANDAPPLYINGTHEDIFFERENCEPATTERNBOTHINPHASEANDINQUADRATURE4HESCALING FACTORSARECHOSENTOMAXIMIZETHEIMPROVEMENTFACTORUNDERCONDITIONSOFSCANNING ANDPLATFORMMOTION 4HERELATIONSHIPSFORADOUBLE DELAYTHREE PULSE !-4)ARESHOWNINTHEPHASOR DIAGRAMIN&IGURE4HEPHASEADVANCEBETWEENTHEFIRSTPAIROFPULSESFIRSTAND SECONDPULSEFORTHETHREE PULSE-4) RECEIVEDBYTHESUMPATTERN3IS H
P 4P L
§ ¤ W R 4P ³ W 4P ¤ ³¶ ¨6X ¥SIN Q SIN ´ 6Y ¥ COS R COS Q ´ · ¦ µ ·¸ µ ¨© ¦
ANDTHEPHASEADVANCEBETWEENTHESECONDPAIROFPULSESSECONDANDTHIRDPULSEFOR THETHREE PULSE-4) IS H
P 4P § ¤ W R 4P ³ W 4P ¤ ³¶ 6X ¥SIN Q SIN 6Y ¥ COS R COS Q ´ · ¨ ´ L ¨ ¦ µ ¦ µ ·¸ ©
&)'52% 0HASOR DIAGRAM FOR SIMULTANEOUS SCANNING AND MOTION COMPENSATION
!)2"/2.%-4)
롣
WHEREPISTHEDIRECTIONOFTHECLUTTERCELLWITHRESPECTTOTHEANTENNAPOINTINGANGLE WHENTHESECONDPULSEISRECEIVEDANDVRISTHEANTENNASCANRATE4HESUBSCRIPTSON THERECEIVEDSIGNALS3IAND$IINDICATETHEPULSERECEPTIONSEQUENCE 4HE DIFFERENCE PATTERN $ IS USED TO GENERATE AN IN PHASE CORRECTION FOR SCAN NINGMOTIONANDAQUADRATURECORRECTIONFORPLATFORMMOTION4HISPROCESSYIELDS THESETOFRESULTANTSIGNALS2IJ WHERETHESUBSCRIPTIDENOTESTHEPULSEPAIRANDTHE SUBSCRIPTJDENOTESTHECOMPONENTOFTHEPAIR"ECAUSEGDOESNOTEQUALG DIF FERENTWEIGHTINGCONSTANTSAREREQUIREDFOREACHPULSEPAIR4HEVALUESOFKFORTHE QUADRATURE CORRECTION OF THE FIRST PULSE PAIR K FOR THE QUADRATURE CORRECTION FOR THESECONDPULSEPAIR LFORTHEIN PHASECORRECTIONFORTHEFIRSTPULSEPAIR ANDL FORTHESECONDPULSEPAIRAREOPTIMIZEDBYMINIMIZINGTHEINTEGRATEDRESIDUEPOWER OVERTHESIGNIFICANTPORTIONOFTHEANTENNAPATTERN USUALLYCHOSENBETWEENTHEFIRST NULLSOFTHEMAINBEAM &IGURE SHOWS THE SUM AND DIFFERENCE MAIN BEAM PATTERNS FOR AN APERTURE WAVELENGTHSLONG&IGURESHOWSTHERESIDUEFORTHECASEWHENTHEFRACTION OFTHEHORIZONTALAPERTUREWIDTHATRAVELEDPERINTERPULSEPERIOD4P 6N 6X4PA IS EQUALTOANDWHENTHENUMBEROFWAVELENGTHSTHATTHEAPERTURETIPROTATESPER INTERPULSEPERIOD 7N AVR4PK ISEQUALTO4HECORRESPONDINGIMPROVEMENT FACTORISD" 4HEIMPROVEMENTFACTORISSHOWNIN&IGUREFORARANGEOFNORMALIZEDPLATFORM MOTION6NASAFUNCTIONOFNORMALIZEDSCANNINGDISPLACEMENTS7N4HENONSCANNING CASEISSHOWNAS7N 4HEIMPROVEMENTFACTORSWERECOMPUTEDFORTHE WAVE LENGTHAPERTUREPATTERNSSHOWNIN&IGURE !NDREWSHASDEVELOPEDANOPTIMIZATIONPROCEDUREFORPLATFORM MOTIONCOMPEN SATIONTHATROTATESTHEPHASORSDIRECTLYRATHERTHANBYUSINGAQUADRATURECORRECTION4HE PROCEDUREDETERMINESTHEANTENNAFEEDCOEFFICIENTSFORTWOCOMPENSATIONPATTERNS ONE OFWHICH #P ISADDEDTOTHESUMPATTERN3P ANDFEDTOTHEUNDELAYEDCANCELER
&)'52% 3UMANDDIFFERENCEPATTERNSUSEDTODETERMINE$0#!PERFORMANCE
ΰÓä
2!$!2(!.$"//+
&)'52% $0#!CLUTTERRESIDUEVERSUSANGLEFORNORMALIZEDDISPLACEMENT 6N ANDNORMALIZEDSCANNINGMOTION 7N
PATH ANDTHEOTHER #P WHICHISADDEDTOTHESUMPATTERNANDFEDTOTHEDELAYEDPATH ASSHOWNIN&IGURE4HEPROCEDUREWASDEVELOPEDFORASINGLE DELAYCANCELERAND ANONSCANNINGANTENNA!NDREWSUSEDTHEPROCEDURETOMINIMIZETHERESIDUEPOWER OVERTHEFULLANTENNAPATTERN WHICHINCLUDESTHEMAIN BEAMANDSIDELOBEREGIONS
&)'52% $0#!IMPROVEMENTFACTORVERSUSNORMALIZEDPLATFORMMOTION 6N ASAFUNCTIONOFNORMAL IZEDSCANNINGMOTION 7N
!)2"/2.%-4)
ΰӣ
&)'52% /PTIMIZED$0#!PHASECOMPENSATION
ΰnÊ * /", "/" Ê " * -/" ]Ê ",7, Ê , /" 4HE PREVIOUS SECTIONS DISCUSSED THE COMPENSATION FOR THE COMPONENT OF PLATFORM MOTION PARALLEL TO THE ANTENNA APERTURE4!##!2 REMOVES THE AVERAGE COMPONENT OFPLATFORMMOTIONPERPENDICULARTOTHEAPERTURE4HEFORMER7HEELER,ABORATORIES DEVELOPEDTHE#OINCIDENT0HASE#ENTER4ECHNIQUE#0#4 TOREMOVETHESPECTRAL SPREAD DUE TO THE VELOCITY COMPONENT PERPENDICULAR TO THE APERTURE AND DUE TO THE COMPONENTPARALLELTOTHEAPERTURE2EMOVALOFTHECOMPONENTPARALLELTOTHEAPERTURE USESTHE$0#!PATTERNSYNTHESISTECHNIQUEDESCRIBEDIN!NDERSON WHICHCREATESTWO SIMILARLYSHAPEDILLUMINATIONFUNCTIONSWHOSEPHASECENTERSAREPHYSICALLYDISPLACED 2EMOVALOFTHECOMPONENTPERPENDICULARTOTHEAPERTUREISACCOMPLISHEDBYANOVEL EXTENSIONOFTHISCONCEPT 4HEFIRSTTERMOF%QFORSPECTRALWIDTHDUETOPLATFORMMOTIONAPPROACHESZEROAS THEANTENNAPOINTSAHEAD(OWEVERTHESECONDTERMOF%QDOMINATESASTHEANTENNA APPROACHESWITHINAFEWBEAMWIDTHSOFTHEAIRCRAFTSGROUNDTRACK)NTHISREGION
FD y
6Y Q 6YQ SIN y L L
WHICHYIELDSASINGLE SIDEDSPECTRUMTHATISSIGNIFICANTLYNARROWERTHANTHESPECTRUM ABEAM&ORMODERATEPLATFORMSPEEDSANDLOWER FREQUENCY5(& RADARS THISEFFECT ISNEGLIGIBLE ANDCOMPENSATIONISNOTREQUIRED
ΰÓÓ
2!$!2(!.$"//+
7HENITISNECESSARYTOCOMPENSATEFORTHISEFFECT THEPHASECENTEROFTHEANTENNA MUSTBEDISPLACEDAHEADOFTHEAPERTUREANDBEHINDTHEAPERTUREFORALTERNATERECEIVE PULSESSOTHATTHEPHASECENTERSARECOINCIDENTFORAMOVINGPLATFORM4HISTECHNIQUE CAN BE EXTENDED TO MORE THAN TWO PULSES BY USING THE NECESSARY PHASE CENTER DIS PLACEMENTSFOREACHPULSE)NORDERTOMAINTAINTHEEFFECTIVE02& THEDISPLACEMENT MUSTCOMPENSATEFORTHETWO WAYTRANSMISSIONPATH4OACCOMPLISHTHISDISPLACEMENT NEAR FIELDANTENNAPRINCIPLESAREUTILIZED!DESIREDAPERTUREDISTRIBUTIONFUNCTIONIS SPECIFIED4HENEAR FIELDAMPLITUDEANDPHASEARECALCULATEDATAGIVENDISTANCEFROM THEORIGIN)FTHISFIELDISUSEDASTHEACTUALILLUMINATIONFUNCTION AVIRTUALAPERTUREIS CREATEDWITHTHEDESIREDDISTRIBUTIONFUNCTIONATTHESAMEDISTANCEBEHINDTHEPHYSICAL ANTENNA&IGUREASHOWSTHEPHASEANDAMPLITUDEDISTRIBUTIONREQUIREDTOFORM AUNIFORMVIRTUALDISTRIBUTIONDISPLACEDBEHINDTHEPHYSICALAPERTURE)TCANBESHOWN THATIFTHEPHASEOFTHEILLUMINATIONFUNCTIONISREVERSEDE` E THEDESIREDVIRTUAL DISTRIBUTIONFUNCTIONISDISPLACEDAHEADOFTHEAPERTURE ASSHOWNIN&IGUREB )NPRACTICE PERFORMANCEISLIMITEDBYTHEABILITYTOPRODUCETHEREQUIREDILLUMINA TIONFUNCTION!STHEDISPLACEMENTINCREASES ALARGERPHYSICALAPERTURESIZEISREQUIRED TOPRODUCETHEDESIREDVIRTUALAPERTURESIZEOWINGTOBEAMSPREADING4HISCANBESEEN IN&IGURE4HEEFFECTIVENESSOFTHECORRECTIONVARIESWITHELEVATIONANGLESINCETHE
&)'52% #0#4CONCEPTSHOWINGDISPLACEMENTOFTHEPHASECEN TERA BEHINDTHEPHYSICALAPERTUREANDB AHEADOFTHEPHYSICALAPER TURE#OURTESYOF(AZELTINE)NC
!)2"/2.%-4)
ΰÓÎ
&)'52% #0#4CANCELLATIONRATIO INDECIBELS ASAFUNCTIONOFRELATIVEINTERPULSE MOTIONANDBEAM POINTINGDIRECTION#OURTESYOF(AZELTINE)NC
ACTUALDISPLACEMENTALONGTHELINE OF SLIGHTVARIESWITHELEVATIONANGLE4HISEFFECTIS MOREPRONOUNCEDATHIGHERAIRCRAFTSPEEDSANDHIGHERRADARFREQUENCIES!CHANGEIN THEMAGNITUDEOFTHECORRECTIONFACTOROREVENTHECOMPENSATIONPATTERNWITHRANGE HEIGHT ANDVELOCITYCOULDBEUTILIZEDTORETAINPERFORMANCE &IGURE ILLUSTRATES THE THEORETICAL -4) PERFORMANCE OF A #0#4 SYSTEM AS A FUNCTIONOFBEAM POINTINGDIRECTIONANDINTERPULSEMOTIONNORMALIZEDTOTHEINTERPULSE MOTIONUSEDTODESIGNTHECOMPENSATIONPATTERN#ANCELLATIONRATIOISDEFINEDASTHE RATIOOFINPUTCLUTTERPOWERTOOUTPUTCLUTTERRESIDUEPOWER 4HEPEAKONTHEAXIS ISTYPICALOFTHEOPTIMIZED$0#!PERFORMANCEILLUSTRATEDIN&IGURE
Î°Ê -*
/ Ê */6 ÊÊ "/" Ê " * -/" )NTRODUCTION 3EVERAL METHODS HAVE BEEN DESCRIBED TO COMPENSATE FOR ANTENNA MOTION!LLTHESETECHNIQUESAREAPPLIEDINTHERADARDESIGNPHASEFORASPECIFICSETOF OPERATIONALPARAMETERS#ONTROLSUSUALLYAUTOMATIC AREPROVIDEDTOADJUSTWEIGHTS FOROPERATIONALCONDITIONSAROUNDTHEDESIGNVALUE 4HEDEVELOPMENTOFDIGITALRADARTECHNOLOGYANDECONOMICALHIGH SPEEDPROCESSORS ALLOWSTHEUSEOFDYNAMICSPACE TIMEADAPTIVEARRAYPROCESSING34!0 WHEREBY ASETOFANTENNAPATTERNSTHATDISPLACETHEPHASECENTEROFTHEARRAYBOTHALONGAND ORTHOGONALTOTHEARRAYARECONTINUALLYSYNTHESIZEDTOMAXIMIZETHESIGNAL TO CLUTTER RATIO3PATIALADAPTIVEARRAYPROCESSINGCOMBINESANARRAYOFSIGNALSRECEIVEDATTHE SAMEINSTANTOFTIMETHATARESAMPLEDATTHEDIFFERENTSPATIALLOCATIONSCORRESPONDING
ΰÓ{
2!$!2(!.$"//+
TOTHEANTENNAELEMENTS4EMPORALADAPTIVEARRAYPROCESSINGCOMBINESANARRAYOF SIGNALSRECEIVEDATTHESAMESPATIALLOCATIONEG THEOUTPUTOFAREFLECTORANTENNA THATARESAMPLEDATDIFFERENTINSTANCESOFTIME SUCHASSEVERALINTERPULSEPERIODSFOR ANADAPTIVE-4)3PACE TIMEADAPTIVEARRAYPROCESSINGCOMBINESATWO DIMENSIONAL ARRAYOFSIGNALSSAMPLEDATDIFFERENTINSTANCESOFTIMEANDATDIFFERENTSPATIALLOCATIONS 34!0 IS A FAIRLY BROAD TOPIC THAT HAS APPLICABILITY BEYOND THIS CHAPTER ON AIRBORNE -4)RADAR4HEPRIMARYMOTIVATIONFOR34!0ISTOIMPROVECLUTTERCANCELLATIONPERFOR MANCEANDTOBETTERINTEGRATEARADARSSPATIALPROCESSINGANTENNASIDELOBECONTROLAND SIDELOBEJAMMINGCANCELLATION WITHITSTEMPORALCLUTTERCANCELLATIONPROCESSING 4HEAPPLICABILITYOF34!0TOIMPROVINGCLUTTERCANCELLATIONMUSTBEASSESSEDSPE CIFICALLYINTHECONTEXTOFTHEKEYPERFORMANCELIMITERSTOAIRBORNE-4)RADARCLUT TERCANCELLATIONASDESCRIBEDATTHESTARTOFTHISCHAPTER34!0CANIMPROVEARADARS MOTIONCOMPENSATIONPERFORMANCEANDISMOREROBUSTTHANNONADAPTIVETECHNIQUES IN ADDRESSING GENERALLY NON DISPERSIVE ERRORS IN THE RADAR FRONT END 34!0 WILL NOT DIRECTLYADDRESSCLUTTERINTERNALMOTIONEFFECTS ANTENNASCANNINGMOTIONEFFECTS OR OTHERHARDWARESTABILITYIMPACTSTOCLUTTERCANCELLATIONPERFORMANCE2ADARDESIGNERS NEEDTOASSESSTHEKEYLIMITATIONSINASPECIFICAPPLICATIONBEFOREJUMPINGTOTHECON CLUSIONTHAT34!0WILLIMPROVEPERFORMANCE 34!0S ABILITY TO INTEGRATE CLUTTER CANCELLATION TEMPORAL AND SPATIAL INTERFERENCE CANCELLATIONCANBEQUITEIMPORTANTTOMANYRADARSYSTEMSWHETHERTHEYTYPICALLYHAVETO DEALWITHINTENTIONALJAMMINGINTERFERENCEORUNINTENTIONALORCASUAL ELECTROMAGNETIC INTERFERENCE%-) 34!0GETSAWAYFROMCASCADEDSOLUTIONSSUCHASANALOGSIDELOBE CANCELLERSFOLLOWEDBYDIGITAL$0#!ANDOR-4)FILTERSTHATDONOTGENERALLYCREATEAN OPTIMUMINTERFERENCECANCELLATIONSOLUTION /PTIMAL!DAPTIVE7EIGHTS-C'UFFIN 4HEOPTIMALLINEARESTIMATEISDETER MINEDBYREQUIRINGTHEADAPTEDESTIMATIONERRORBEORTHOGONALTOTHEOBSERVEDVEC TOR R3TEADY STATECONDITIONSAREASSUMEDINTHISDERIVATION THUSTHECONDITIONFOR ORTHOGONALITYIS
%[RD ]
WHERE%[]ISTHEEXPECTATION DISTHEESTIMATIONERROR AND ISTHECOMPLEXCONJUGATE 4HEADAPTIVELYWEIGHTEDESTIMATEISOBTAINEDBYWEIGHTINGTHERECEIVEDSIGNALVECTOR BYTHEESTIMATEOFTHEADAPTIVEWEIGHTS
S} W} g R
7ITH D DEFINED AS THE DESIRED SIGNAL A MAIN BEAM TARGET THE ESTIMATION ERROR IS OBTAINEDFROMTHEFOLLOWINGEQUATION4HEN SUBSTITUTING%QINTOANDSOLV INGFORTHEADAPTIVEWEIGHTESTIMATEYIELDSTHEDESIREDCONDITIONFOROPTIMALADAPTIVE WEIGHTING
E S} D W} g R D
%[R D R g W} ] %[R D ] 2R W}
OR
W} 2R %[R D ]
!)2"/2.%-4)
ΰÓx
WHERE2R %[RRg]4HEDESIREDSIGNAL D CANBEEXPRESSEDINTERMSOFS THESIGNAL VECTOROFATARGETLOCATEDINTHEMAINBEAM ANDB THEUNADAPTEDBEAMWEIGHTVECTOR D BgS4HISISTHENSUBSTITUTEDINTO%Q
W} 2R 2 S B
%QUATION IS EQUIVALENT TO THE MINIMUM MEAN SQUARE ERROR WEIGHT EQUATION GIVENBY7IDROW WHICHHASBEENSHOWN TOBETHEOPTIMUMSETTHATMAXIMIZES THESIGNAL TO INTERFERENCERATIO(OWEVER COMPLEXVARIABLESAREEMPLOYEDHERERATHER THANREALVARIABLES4HEINTERFERENCECOVARIANCEMATRIXISFURTHERDESCRIBEDINTERMSOF THEINDIVIDUALNOISE JAMMING CLUTTER ANDSIGNALCONTRIBUTIONS
2R .) +: 23
WHERE.ISRECEIVERNOISEPOWER +:ISTHECOVARIANCEMATRIXFORCLUTTERTEMPORALLYCOR RELATED PLUSJAMMINGSPATIALLYCORRELATED AND2SISTHESIGNALCOVARIANCEMATRIX 4AXONOMYOF34!0!RCHITECTURES7ARD 4HEAPPLICATIONOFTHEADAPTIVE WEIGHTEQUATIONFROM%QINARADARSYSTEMPROVIDESNUMEROUSOPTIONSANDCOM PLICATIONS4HEOPTIONSRANGEFROMAFULLYADAPTIVESOLUTIONACROSSALLAVAILABLEANTENNA ELEMENTSANDALLPULSESINACOHERENTPROCESSINGINTERVAL#0) TOREDUCEDDEGREESOF FREEDOMSOLUTIONSINORDERTOBEPRACTICAL4HEFULLYADAPTIVESOLUTIONALSOENCOUNTERS PROBLEMSINTHEREAL WORLDWHERETHEINTERFERENCEENVIRONMENTISNOTWELLBEHAVED EG HOMOGENOUSCLUTTER )NADDITION "RENNANSRULEINDICATESTHATTOACHIEVEAN ADAPTIVESOLUTIONWITHIND"OFTHEOPTIMUMANSWERREQUIRES..ISTHENUMBEROF DEGREES OF FREEDOM INDEPENDENT INTERFERENCE SAMPLES CONTRIBUTING TO THE ADAPTIVE WEIGHTESTIMATE7ITHANTENNAARRAYSIZESINTENSTOHUNDREDSOFELEMENTSAND#0) LENGTHSOFTENSTOHUNDREDSOFPULSES THENUMBEROFDEGREESOFFREEDOMCANQUICKLY GETQUITELARGE RESULTINGINNOTONLYFAIRLYCOMPLEXADAPTIVEWEIGHTPROCESSINGBUT ALSOTHEMOREDIFFICULTPROBLEMOFOBTAININGADEQUATESAMPLESUPPORTFROMCLUTTERAND JAMMINGINTERFERENCEFORAGIVENADAPTIVEWEIGHTSOLUTION !SSUCH ITISIMPORTANTTOEXPLOREVARIOUS34!0ARCHITECTUREOPTIONSIMBEDDEDINA RADARDESIGNSOLUTION4OBEGIN AFULLYADAPTIVEARRAYARCHITECTUREISSHOWNIN&IGURE 4HISISFORALINEARARRAYANTENNAWITHADISTRIBUTEDTRANSMITTERANDDIGITALRECEIVERSCON NECTEDTOEACHANTENNAELEMENT4HEADAPTIVEWEIGHTSOLUTIONISDEVELOPEDBASEDONAT LEAST¾.¾-VECTORSAMPLESR OFLENGTH-ANTENNAELEMENTS BY.PULSES 4HE ADAPTIVEWEIGHTSOLUTIONISDEVELOPEDANDAPPLIEDTOTHERECEIVEDSIGNALSFROMTHESAME ANTENNAELEMENTSANDPULSESOFDATA4HEADAPTIVEWEIGHTEDRESPONSEISTYPICALLYPRO CESSEDTHROUGHDOPPLERFILTERINGCOHERENTINTEGRATION PRIORTODETECTIONPROCESSING 7ARD DESCRIBES THE POSSIBLE 34!0 ARCHITECTURES IN THE CONTEXT OF A GENERALIZED TRANSFORMATIONMATRIXFOLLOWEDBYTHEASSOCIATED34!0PROCESSING4HEFOURCATEGORIES OF34!0ARCHITECTURESAREORGANIZEDIN&IGURE4HETRADESFORANAPPROPRIATE34!0 DESIGNSOLUTIONMUSTBEMADEINTHECONTEXTOFTHETYPEANDSIZEOFTHEANTENNAAPERTURE UNDERCONSIDERATION THEWAVEFORMSUNDERCONSIDERATIONPARTICULARLYTHENUMBEROF PULSESPER#0)ANDMOSTIMPORTANTLY THEINTERFERENCETOBECANCELLEDCLUTTERANDJAM MING )NGENERAL FORTHETRANSFORMATIONANDDEGREESOFFREEDOMREDUCTIONTOBEUSEFUL THERESULTANTDEGREESOFFREEDOMMUSTBEGREATERTHANTHEINTERFERENCERANK 0RE $OPPLER %LEMENTAL!NTENNA34!0 #ONCEPTUALLY THESIMPLESTREDUCTION IN DEGREES OF FREEDOM IS OBTAINED BY REDUCING THE NUMBER OF TEMPORAL DEGREES OF
ΰÓÈ
2!$!2(!.$"//+ ! "
# &
$ "
" $
&
" $
&
&
&
"
! "
#
#" "
""
"$ " "
%!
&)'52% 34!0RADARBLOCKDIAGRAM
&)'52% 2EDUCEDDIMENSION34!0ARCHITECTURES
!)2"/2.%-4)
ΰÓÇ
FREEDOMIN34!0WHILESTILLPROCESSINGTHEFULLAPERTURESPATIALLY4HISISSIMILARTO ACONVENTIONAL-4)OR$0#! ARCHITECTURECASCADEDWITHDOPPLERFILTERING7ECALL THISARCHITECTUREAPRE DOPPLER ELEMENTAL LEVEL34!0ARCHITECTURE&ORATHREE PULSE VERSION OF THIS ARCHITECTURE THERE ARE - DEGREES OF FREEDOM )N THIS ARCHITECTURE PLATFORMMOTIONCOMPENSATIONTAKESTHEGENERALFORMOFADJUSTINGTHEANTENNASPHASE CENTEROVERTHETHREETEMPORALLYSEPARATEDBEAMS !BASICBLOCKDIAGRAMOFARADARINCORPORATINGPRE DOPPLER ELEMENTAL LEVELSPACE TIME ADAPTIVE ARRAY PROCESSING IS SHOWN IN &IGURE !N INDIVIDUAL DUPLEXER IS PLACEDBETWEENEACHTRANSMITTERSCHANNELIZEDOUTPUTANDITSCORRESPONDINGANTENNA ELEMENT0ROVISIONCOULDBEINCLUDEDFORELECTRONICBEAMSTEERINGUSINGHIGH POWER PHASESHIFTERSORTRANSMITMODULESWITHLOW POWERBEAMSTEERING /N RECEIVE EACH DUPLEXER OUTPUT IS SENT TO ITS OWN DIGITAL RECEIVER 4HE DIGITAL RECEIVER OUTPUTS ARE PASSED THROUGH 02) DELAYS TO YIELD TEMPORALLY DISPLACED DATA SAMPLES! FULL COMPLEMENT OF ELEMENTS AND TIME DELAYED SIGNALS ARE SAMPLED AND USEDTOGENERATETHEADAPTIVEWEIGHTS6ARIOUSALGORITHMSAREPOSSIBLETOGENERATETHE ESTIMATEOFTHEADAPTIVEWEIGHTSFROM%Q4HEFAIRLYSIMPLE,EAST-EAN3QUARED ALGORITHM GENERALLY YIELDS FAIRLY SLOW CONVERGENCE RATES /THER ALGORITHMS CAN SPEEDUPTHEADAPTATIONRATE BUTAMORECOMPLEXMECHANIZATIONISREQUIRED%XAMPLES INCLUDEA2ECURSIVE,EAST3QUAREDALGORITHM 1 2DECOMPOSITIONWITH'RAM 3CHMIDT ORTHOGONALIZATION ORA(OUSEHOLDER4RANSFORMATION4HEADAPTIVEWEIGHTSARETHEN APPLIEDTOTHERECEIVEDSIGNALSANDBEAMFORMEDTOGENERATETHREESUMCHANNELDETEC TIONBEAMSUNDELAYED ONE 02)DELAYED ANDTWO 02)DELAYEDBEAMS4HESEBEAMS ARE INTURN ADDEDTOGETHERTOFORMTHEFINAL34!0WEIGHTEDDETECTIONBEAM !SIMPLISTICVIEWOFHOWTHESETHREEBEAMSPERFORMMOTIONCOMPENSATIONISILLUS TRATEDIN&IGUREFORTHECASEWHERETHEAPERTUREISPARALLELWITHTHERADARSPLATFORM VELOCITYVECTOR4HEFIRSTPULSERETURNSPHASECENTERISADVANCEDBYAPERTUREWEIGHT ING THESECONDPULSERETURNSPHASECENTERISESSENTIALLYUNCHANGEDFROMTHEQUIESCENT WEIGHTS ANDTHETHIRDPULSERETURNSPHASECENTERISRETARDEDBYAPERTUREWEIGHTING 'IVENIDEALANTENNAPATTERNS ANDANAPERTURELARGEENOUGHTOADJUSTTHEPHASECENTERS
! " # $
% ! !# !
# %!
# %!
'
'
# ! !
! " # $
#% # !# !
! #!
&"
&)'52% 34!0BLOCKDIAGRAMELEMENTSPACEPRE DOPPLERELEMENTSPACEARCHITECTURE
$# #
## !
ΰÓn
2!$!2(!.$"//+
# "
" ! !
" "
" "
&)'52% !PERTURECONTROLFORPLATFORMMOTIONCOMPENSATION
FOR THE GIVEN PLATFORM MOTION THESE THREE APERTURES APPEAR AS IF THEY ARE STATIONARY WITHRESPECTTOEACHOTHER#LUTTERCANCELLATIONACROSSTHESETHREEPULSESISNOLONGER LIMITEDBYPLATFORMMOTIONEFFECTSTHEPRIMARYGOALOFPLATFORMMOTIONCOMPENSATION TECHNIQUES /FCOURSE THISSIMPLESTCONDITIONISONLYILLUSTRATIVE ASGENERALLYTHEANTENNAELE MENTSDONOTBEHAVEEXACTLYTHESAME ANDTHEPLATFORMMOTIONCOMPENSATIONMUSTDEAL WITHMOTIONNOTONLYINTHEPLANEOFTHEAPERTUREBUTALSOORTHOGONALTOTHEAPERTURE 0RE $OPPLER "EAM 3PACE34!0 4HEFIRSTTYPEOFTRANSFORMATIONTOBECONSID EREDISSPATIALLYORIENTED RESULTINGINBEAM SPACE34!0ARCHITECTURES4HISTRANSFOR MATIONISTYPICALLYREQUIREDFORMANYLARGEAPERTURES4HETRANSFORMATIONSCANRANGE FROMSIMPLECOLUMNBEAMFORMINGTOOVERLAPPEDSUBARRAYSTOBEAM SPACETRANSFOR MATIONSSUCHASA"UTLERMATRIX4HEGENERALGOALISTOREDUCETHESPATIALDEGREESOF FREEDOM WHILESTILLPROVIDINGACCESSTOARRAYRESPONSESTHATALLOWFORADEQUATECLUTTER CANCELLATIONANDBEAMSTHATCANBEUSEDTOCANCELDIRECTIONALINTERFERENCEASWELL4HE RESULTINGBEAMRESPONSESMUSTSPANTHECLUTTERANDJAMMINGINTERFERENCESPATIALLYIN ORDERFORTHISTYPEOFTRANSFORMATIONTOBEEFFECTIVE&OREXAMPLE IFARADARSCLUT TERCANCELLATIONPERFORMANCEISDRIVENBYMAIN BEAMCLUTTERRESIDUEDUETOPLATFORM MOTION EFFECTS THE BEAM RESPONSES MUST SPAN THE RADARS MAIN BEAM AND PROVIDE DEGREESOFFREEDOMTOALLOWFORMOTIONCOMPENSATIONINTHEARRAYMAIN BEAM)NADDI TION TOCANCELDIRECTIONINTERFERENCEJAMMINGORCASUAL%-) THEBEAMRESPONSES
!)2"/2.%-4)
ΰÓ
MUST ALSO SPAN THE SPATIAL DIRECTIONS OF THAT INTERFERENCE!N EXAMPLE OF A SIMPLE TRANSFORMATIONOFTHISTYPEWOULDBESIDELOBECANCELERARCHITECTUREWHERETHEBEAM TRANSFORMATIONWOULDGENERATEASUMCHANNELMAINBEAMANDSELECTELEMENTSFROMTHE APERTUREASSIDELOBECANCELLERS 0OST $OPPLER %LEMENT !NTENNA 34!0 4HE SECOND TYPE OF TRANSFORMATION LEADSTOWHATARECALLEDPOST DOPPLER34!0ARCHITECTURES!STHENAMEIMPLIES THE ANTENNAELEMENTSIGNALSAREFIRSTDOPPLERFILTEREDANDTHENPROCESSEDTHROUGH34!0 4HEMOTIVATIONFORTHISTYPEOFARCHITECTUREISTHATTHERESULTANT34!0SOLUTIONSCAN INDEPENDENTLYADDRESSASUBSETOFTHECLUTTERINTERFERENCEPROBLEMISOLATEDTOCLUTTER THATREMAINSINASINGLEDOPPLERFILTER4HISTECHNIQUEMAYBEMOREEFFECTIVEFORRADAR SYSTEMSWHERETHECLUTTERENVIRONMENTANDWAVEFORMSELECTIONLEADTOUNAMBIGUOUS CLUTTERRETURNSWITHINTHERADARS02&4WOEXAMPLECONDITIONS THEFIRSTWITHAMBIGU OUSDOPPLERCLUTTERANDTHESECONDWITHUNAMBIGUOUSDOPPLERCLUTTER ARESHOWNIN &IGURE4HEFIGURESHOWSTHOSEANTENNAANGLESWHERETHECLUTTERDOPPLERRESPONSE REMAINSAFTERFILTERINGTHROUGHASINGLEDOPPLERFILTER&IGUREASHOWSTHERESPONSE FORANAMBIGUOUS02&OF(Z AND&IGUREBSHOWSTHERESPONSEFORANUNAM BIGUOUS02&OF(ZFORA5(&RADAR4HISFIGUREHIGHLIGHTSTHATEVENWITHDOP PLERPROCESSING AGIVENDOPPLERFILTERMAYSTILLINCLUDECLUTTERRETURNSFROMANUMBER OFDISCONTIGUOUSANGULARINTERVALS4HEADVANTAGESOFTHISTRANSFORMATIONFROM02) TODOPPLERSPACEONOVERALL34!0PERFORMANCEVERSUSAPRE DOPPLERARCHITECTUREARE MOREDRAMATICINTHEUNAMBIGUOUSDOPPLERCLUTTERCASE 02) STAGGEREDDOPPLERFILTEROUTPUTSAREREQUIREDTOMAINTAINASETOFTEMPORALDEGREES OFFREEDOMINTHISARCHITECTURE4HEBLOCKDIAGRAMISMODIFIEDTOTHATSHOWNIN&IGURE WITHMULTIPLEDOPPLERFILTERBANKSONEACHANTENNAELEMENTAND02)DELAY 0OST $OPPLER "EAM3PACE34!0 4HEFINALCATEGORYRESULTSFROMIMPLEMENT INGBOTHDOPPLERANDSPATIALTRANSFORMATIONSPRIORTO34!0PROCESSING 4HEAPPROPRIATEARCHITECTURESOLUTIONDEPENDSUPONTHERADARDESIGNCONSTRAINTS 4HENUMBEROFANTENNAELEMENTSANDBEAMFORMINGREQUIREMENTSAREKEYDRIVERSINTHE
&)'52% !NTENNAPOINTINGANGLESWHERECLUTTERDOPPLERMAPTOASINGLEDOPPLERFILTERSPASSBAND
ΰÎä
2!$!2(!.$"//+
! " #
$ "
! " #
" $
"
&
"
&
" $
"
"
"
"
#" "
""
" "$ " "
%!
&)'52% %LEMENTSPACEPOST DOPPLER34!0ARCHITECTURE
DECISIONWHETHERTOTRANSFORMFROMELEMENTSTOBEAMSORSUBARRAYS4HEWAVEFORMS ANDCLUTTERCANCELLATIONREQUIREMENTSAREKEYDRIVERSINTHEDECISIONWHETHERTOPER FORM34!0ONSIGNALSBEFOREORAFTERDOPPLERFILTERING)NADDITION THEOVERALLTRANS FORMATIONDECISIONSTOREDUCEDEGREESOFFREEDOMAREDRIVENBYTHEINTERFERENCERANK FORTHERADARPROBLEM/NECAUTIONINTHEDESIGNPROCESSISTHATIFTHETRANSFORMATION ISFIXEDINTHERADARDESIGN ITISIMPORTANTTOHAVEEXCESSDEGREESOFFREEDOMBEYOND THETOTALINTERFERENCERANK )MPLEMENTATION#ONSIDERATIONS !SDISCUSSEDABOVE TRANSFORMATIONSANDTECH NIQUESTOREDUCETHENUMBEROFDEGREESOFFREEDOMINTHE34!0SOLUTIONAREIMPORTANT NOTONLYDUETOPROCESSINGREQUIREMENTSBUTALSOBECAUSEOFTHENEEDFORSAMPLESUP PORTONTHEORDEROFTWOTIMESTHENUMBEROFDEGREESOFFREEDOMFORADEQUATE34!0 PERFORMANCE 4HEBASICHARDWAREREQUIREMENTSFORGOODCLUTTERCANCELLATIONREMAINUNCHANGED FROM CONVENTIONAL CLUTTER CANCELLATION ARCHITECTURESLOW PHASE NOISE LOW PULSE JITTER ETC 4HE REQUIREMENTS ON THE HARDWARE MAY BECOME MORE STRINGENT BECAUSE THE34!0ARCHITECTUREALLOWSTHERADARDESIGNERTOACHIEVEHIGHERTHEORETICALCLUTTER CANCELLATIONPERFORMANCELEVELS)NADDITIONTOTHEABOVETEMPORALLYBASEDHARDWARE REQUIREMENTS THEREAREALSOSECOND ORDERSPATIALLYBASEDHARDWAREREQUIREMENTS!S ILLUSTRATEDIN&IGURE PLATFORMMOTIONCOMPENSATIONRESULTSINDIFFERENTAPERTURE WEIGHTING FOR SUCCESSIVE PULSES IN A 34!0 SOLUTION!LTHOUGH GENERALLY SPEAKING WELL MATCHEDSPATIALCHANNELSANTENNAANDRECEIVER AREDRIVENBYJAMMINGCANCELLA TIONANDANTENNASIDELOBELEVELS ASECOND ORDERREQUIREMENTRESULTSFROMTHENEEDFOR
!)2"/2.%-4)
ΰΣ
PLATFORMMOTIONCOMPENSATION)FANTENNAANDRECEIVERCHANNELSARENOTWELLMATCHED THERESULTANTSUMCHANNELBEAMSFORMEDFROMDIFFERENTAPERTUREILLUMINATIONFUNCTIONS &IGURE WILLNOTBEMATCHEDWELLENOUGHTOPROVIDEMAIN BEAMANDSIDELOBE CLUTTERCANCELLATION 0ERFORMANCE#OMPARISONS 'IVENTHENUMBEROF34!0ARCHITECTURESANDCOR RESPONDINGRADARSYSTEMDESIGNSOLUTIONS GENERAL34!0PERFORMANCECOMPARISONSARE DIFFICULTTOCOMEBY)NGENERAL 34!0PROVIDESAROBUSTSOLUTIONTODEALWITHCLUTTER ANDJAMMINGINTERFERENCEANDHELPSALLEVIATEHARDWAREMISMATCHEFFECTSWITHINREA SONAMPLITUDEANDPHASEADJUSTMENTSAREAPPLIEDTOANTENNAELEMENTANDTIMEDIS PLACEDRETURNS 'ENERALLYTOADDRESSTIME DELAYADAPTIVEWEIGHTING MORECOMPLEXITY ISREQUIREDWITHATHIRDDIMENSIONFORADAPTIVEWEIGHTShFAST TIMEvORRETURNSFROM ADJACENTSAMPLEDRANGECELLS4HISEXTENSIONCANBEEXTREMELYCOMPUTATIONALLYINTEN SIVEANDFURTHERBURDENTHESAMPLESUPPORTPROBLEMALLUDEDTOPREVIOUSLY 7HENEVALUATINGARADARDESIGNANDTRADINGOFFVARIOUSWAVEFORMSAND34!0PRO CESSINGTECHNIQUES ITISIMPORTANTTOINCLUDEINTHEANALYSISKEYDRIVERSSUCHASSIGNAL BANDWIDTH CLUTTER INTERNAL MOTION PLATFORM MOTION ANTENNA SCANNING MOTION THE AMOUNTOFSAMPLESUPPORTAVAILABLEFROMNONHOMOGENOUSANDNONSTATIONARYCLUTTER ENVIRONMENTS AND OTHER EFFECTS SUCH AS LARGE TARGET SAMPLES EFFECTING THE ADAPTIVE WEIGHTSOLUTION
ΰ£äÊ /Ê"Ê 1 /* Ê-* /, !NAIRBORNESEARCH RADARSYSTEMMAYBEOPERATEDATANALTITUDESOTHATTHERADARHORI ZONISAPPROXIMATELYATTHEMAXIMUMRANGEOFINTEREST4HISRESULTSINSEAORGROUND CLUTTERBEINGPRESENTATALLRANGESOFINTEREST/THERCLUTTERSOURCESSUCHASRAINAND CHAFFMAYCOEXISTWITHTHESURFACECLUTTER)NMOSTINSTANCES THESESOURCESAREMOV INGATASPEEDDETERMINEDBYTHEMEANWINDALOFTANDHAVEAMEANDOPPLERFREQUENCY SIGNIFICANTLYDIFFERENTFROMTHATOFTHESURFACECLUTTER)FTHE-4)FILTERISTRACKINGTHE SURFACECLUTTER THESPECTRAOFTHESOURCESWITHADIFFERENTMEANDOPPLERFREQUENCYLIE INTHEPASSBANDOFTHE-4)FILTER! KTDIFFERENTIALINA5(&SYSTEMCORRESPONDS TO(Z WHICHWOULDGENERALLYBEOUTSIDEOFTHETRADITIONAL!-4)NOTCHFILTERINA (Z02&SYSTEM!SINGLE DELAYSECONDARYCANCELERCANBECASCADEDWITHEITHER A SINGLE DELAY OR A DOUBLE DELAY PRIMARY CANCELER4HE PRIMARY CANCELER TRACKS THE MEANSURFACEVELOCITYANDREJECTSSURFACECLUTTER4HESINGLE DELAYCANCELERTRACKSTHE SECONDARYSOURCEANDREJECTSIT3INCETHEPASSANDREJECTIONBANDSOFTHETWOCANCEL ERSOVERLAP THE-4)IMPROVEMENTFACTORFOREACHCLUTTERSOURCEISAFUNCTIONOFTHEIR SPECTRALSEPARATION &IGURESHOWSTHEIMPROVEMENTFACTORFORADOUBLECANCELER WHICHCONSISTSOF TWOSINGLECANCELERS EACHTRACKINGONEOFTHESPECTRA)TCANBESEENTHATASTHESEPARA TIONVARIESFROMTOOFTHE02& THEPERFORMANCEDEGRADESFROMTHATEQUIVALENTTO ADOUBLECANCELERTOTHEPERFORMANCEOFASINGLECANCELERATHALFOFTHE02& 4HETRIPLECANCELERHASADOUBLE DELAYCANCELERTRACKINGTHEPRIMARYSPECTRAANDA SINGLE DELAYCANCELERTRACKINGTHESECONDARYSPECTRA4HEPERFORMANCEOFTHEPRIMARY SYSTEMVARIESFROMTHATOFATRIPLECANCELERTOALEVELLESSTHANTHATOFADOUBLECANCELER 4HESECONDARY SYSTEMPERFORMANCEVARIESFROMTHATOFATRIPLECANCELERTOAPERFOR MANCELEVELLOWERTHANTHATOFASINGLECANCELER
ΰÎÓ
2!$!2(!.$"//+
&)'52% -4) IMPROVEMENT FACTOR FOR A DOUBLE NOTCH CANCELER TRACKING TWO SPECTRA AS A FUNCTION OF THE NORMALIZED SPECTRA SEPARATION $FFR.ORMALIZEDSPECTRALWIDTHRCFR
ΰ££Ê 8 * Ê /Ê, ,Ê-9-/ 4HE!.!09 RADAR DEVELOPEDBY,OCKHEED-ARTINFORTHE53.AVY ISANEXAMPLE OFAN!-4)RADARSYSTEMUTILIZEDFORANAIRBORNEEARLYWARNINGRADARMISSION+EY FEATURESOFTHISSYSTEMINCLUDEASOLID STATEDISTRIBUTEDTRANSMITTER AMECHANICALLYAND ELECTRONICALLY SCANNED ROTATING ANTENNA DIGITAL RECEIVERS SPACE TIME ADAPTIVE PRO CESSING DIGITALPULSECOMPRESSION ANDCOHERENTINTEGRATIONANDAUXILIARYPROCESSING AIMEDATSUPPORTINGTHE34!0SAMPLESELECTIONPROCESS 4HE!.!09 RADARADDRESSESTHE!%7RADARSURVEILLANCECOVERAGEREQUIREMENTS DISCUSSEDATTHEBEGINNINGOFTHISCHAPTER UTILIZINGAMECHANICALLYANDELECTRONICALLY STEERABLEANTENNALOCATEDINAROTODOME4HEREARETHREESCANNINGMODESOFOPERATION
!)2"/2.%-4)
ΰÎÎ
MECHANICALLYSCANNEDWITHANOPERATOR SELECTABLESCANRATE AZIMUTHELECTRONI CALLYSCANNEDWITHTHEMECHANICALBORESITEPROVIDEDASANINPUTTOTHERADAR AND MECHANICALLYSCANNEDWITHADDITIONALELECTRONICSCANNINGWITHINANOPERATOR SELECT ABLEAZIMUTHREGION 4HETRANSMITWAVEFORMINCLUDES4!##!2MODULATIONTOCENTERMAINBEAMCLUTTER ATZERODOPPLERFREQUENCY(OWEVER BECAUSETHERADARIMPLEMENTSADAPTIVECLUTTER CANCELLATION 34!0 THE REQUIREMENTS ON 4!##!2 ARE SIGNIFICANTLY LESS COMPLEX THANFORLEGACYRADARSYSTEMS4HEREISNONEEDTOINCLUDECLOSEDLOOPADJUSTMENTSTO THE4!##!2MODULATIONFREQUENCY4HEOPTIMIZATIONOFTHE!-4)CLUTTERCANCELLA TIONFILTERISACHIEVEDINTHE34!0PROCESSINGASOPPOSEDTOADJUSTINGTHELOCATIONOF MAIN BEAMCLUTTERTOFITAFIXED!-4)FILTER )NORDERTOIMPLEMENT34!0ANDELECTRONICSCANNINGINTHISRADAR ALLELEMENTS OF THE PHASED ARRAY ANTENNA ARE PROCESSED ON TRANSMIT AND RECEIVE 4HE SOLID STATE TRANSMITTERPROVIDESLOW POWERPHASESHIFTCONTROLFORELECTRONICSTEERINGFOLLOWEDBY POWERAMPLIFICATIONINEACHOFCHANNELS4HESEARECONNECTEDTOTHEELEMENTS OFTHEPHASEDARRAYTHROUGHAN CHANNELROTARYCOUPLER4HETRANSMITRECEIVEISOLA TIONONALLCHANNELSISPROVIDEDTHROUGHCIRCULATORS4HECHANNELSAREPROCESSED SEPARATELYTHROUGHRECEIVERS FINALLYFEEDINGTHE34!0SUBSYSTEMWITH DIGITAL BASEBANDSIGNALS 4HE RADAR PERFORMS PLATFORM MOTION COMPENSATION ELECTRONICALLY AS PART OF THE 34!0ARCHITECTURE4HERADARIMPLEMENTSANELEMENT SPACEPRE DOPPLER34!0ARCHI TECTURE!DAPTIVEWEIGHTSAREGENERATEDANDAPPLIEDTOTHERECEIVECHANNELS FORM INGTHREEBEAMS3UM $ELTAAZ AND/MNI BYWEIGHTINGANDSUMMINGTHERECEIVE CHANNELSOVERTHREEPULSESTOPROVIDESIMULTANEOUSCLUTTERANDJAMMINGCANCELLATION 4HEADAPTIVEWEIGHTALGORITHMISMATCHEDTOTHERADARSOPERATINGPARAMETERSANDIS AUGMENTED WITH ADAPTIVE KNOWLEDGEnAIDED SAMPLING SCHEMES TO MAXIMIZE PERFOR MANCE IN A COMPLEX HETEROGENEOUS CLUTTER AND JAMMING INTERFERENCE ENVIRONMENT $OPPLERFILTERINGISPERFORMEDAFTERDIGITALBEAMFORMING /THERFUNCTIONSDISCUSSEDINTHISCHAPTERARENOTREQUIREDFORTHISRADARAPPLICATION BECAUSETHEYDONOTLIMITPERFORMANCE%XAMPLESINCLUDESCANNINGMOTIONCOMPENSA TIONANDMULTIPLESPECTRA!-4)CLUTTERCANCELLATION
, ,
2 # %MERSON h3OME PULSED DOPPLER -4) AND!-4) TECHNIQUES v 2AND #ORPORATION 2EPT 2 $$#$OC!$ -ARCH 2EPRINTEDIN2EFERENCE 4 3 'EORGE h&LUCTUATIONS OF GROUND CLUTTER RETURN IN AIRBORNE RADAR EQUIPMENT v 0ROC )%% ,ONDON VOL PT)6 PPn !PRIL & 2 $ICKEY *R h4HEORETICAL PERFORMANCE OF AIRBORNE MOVING TARGET INDICATORS v)2%4RANS VOL0'!% PPn *UNE 2 3 "ERKOWITZ ED -ODERN 2ADAR !NALYSIS %VALUATION AND 3YSTEM $ESIGN .EW 9ORK *OHN7ILEY3ONS $+"ARTON 2ADAR3YSTEMS!NALYSIS %NGLEWOOD#LIFFS .*0RENTICE (ALL $#3CHLERERED -4)2ADAR .ORWOOD -!!RTECH(OUSE )NC & 2 $ICKEY *R AND - - 3ANTA h&INAL REPORT ON ANTICLUTTER TECHNIQUES v 'ENERAL %LECTRIC #OMPANY2EPT2%-( -ARCH $ " !NDERSON h! MICROWAVE TECHNIQUE TO REDUCE PLATFORM MOTION AND SCANNING NOISE IN AIRBORNEMOVINGTARGETRADAR v)2%7%3#/.#ONV2EC VOL PT PPn
ΰÎ{
2!$!2(!.$"//+
h&INALENGINEERINGREPORTONDISPLACEDPHASECENTERANTENNA vVOL -ARCH VOLS AND !PRIL 'ENERAL%LECTRIC#OMPANY 3CHENECTADY .9 (5RKOWITZ h4HEEFFECTOFANTENNAPATTERNSONPERFORMANCEOFDUALANTENNARADARMOVINGTARGET INDICATORS v)%%%4RANS VOL!.% PPn $ECEMBER ' . 4SANDOULIS h4OLERANCE CONTROL IN AN ARRAY ANTENNA v -ICROWAVE * PP n /CTOBER + ' 3HROEDER h"EAM PATTERNS FOR PHASE MONOPULSE ARRAYS v -ICROWAVES PP n -ARCH 23'RISSETTI --3ANTA AND'-+IRKPATRICK h%FFECTOFINTERNALFLUCTUATIONSANDSCANNING ONCLUTTERATTENUATIONIN-4)2ADAR v)2%4RANS VOL!.% PPn -ARCH '!!NDREWS h!IRBORNE RADAR MOTION COMPENSATION TECHNIQUES /PTIMUM ARRAY CORRECTION PATTERNS v.AVAL2ES,AB2EPT -ARCH !2,OPEZAND77'ANZ h#0#4ANTENNASFOR!-4)RADAR VOL4HEORETICALSTUDY v!IR &ORCE!VIONICS,AB2EPT7, !$ *UNE.OTREADILYAVAILABLE , % "RENNAN * $ -ALLETT AND ) 3 2EED h!DAPTIVE ARRAYS IN AIRBORNE -4) RADAR v )%%% 4RANS VOL!0 PPn 3EPTEMBER ! , -C'UFFIN h! BRIEF ASSESSMENT OF ADAPTIVE ANTENNAS WITH EMPHASIS ON AIRBORNE RADAR v 'ENERAL%LECTRIC#OMPANY !IRCRAFT%QUIPMENT$IVISION !UGUST " 7IDROW AND 3 $ 3TEARNS !DAPTIVE 3IGNAL 0ROCESSING .EW *ERSEY 0RENTICE (ALL )NC 30!PPLEBAUM h!DAPTIVEARRAYS v)%%%4RANS VOL!0 PPn 3EPTEMBER ,%"RENNAN %,0UGH AND)32EED h#ONTROLLOOPNOISEINADAPTIVEARRAYANTENNAS v)%%% 4RANS VOL!%3 -ARCH * 7ARD h3PACE TIME ADAPTIVE PROCESSING FOR AIRBORNE RADAR v -)4 ,INCOLN ,ABORATORY 4ECHNICAL2EPORT $ECEMBER , % "RENNAN AND & - 3TAUDAHER h3UBCLUTTER VISIBILITY DEMONSTRATION v 4ECHNICAL 2EPORT 2, 42 !DAPTIVE3ENSORS)NCORPORATED -ARCH 2!-ONZINGOAND47-ILLER )NTRODUCTIONTO!DAPTIVE!RRAYS .EW9ORK*OHN7ILEY 3ONS
#HAPTER
*ÕÃiÊ ««iÀÊ,>`>À
Ê*°Ê-ÌÀ>>Ê 7>Ê°Êi`>À .ORTHROP'RUMMAN#ORPORATION
{°£Ê , / ,-/ -Ê Ê** /" 4HEPRIMARYBENEFITOFPULSEDOPPLERRADARISITSABILITYTODETECTSMALL AMPLITUDEMOV INGTARGETRETURNSAGAINSTANOVERWHELMINGLYLARGE AMPLITUDECLUTTERBACKGROUND .OMENCLATURE 2ADARSTHATRELYONTHEDOPPLEREFFECTTOENHANCETARGETDETEC TION ARE CALLED DOPPLER RADARS 4HE DOPPLER EFFECT MANIFESTS ITSELF WHEN THERE IS ARELATIVERANGERATE ORRADIALVELOCITY BETWEENTHERADARANDTHETARGET7HENTHE RADARS TRANSMIT SIGNAL IS REFLECTEDFROMSUCHATARGET THECARRIERFREQUENCYOFTHE RETURNSIGNALWILLBESHIFTED!SSUMINGAMONOSTATICRADARIE COLLOCATEDTRANSMIT TERANDRECEIVER THEROUNDTRIPDISTANCEISTWICETHEDISTANCEBETWEENTHETRANSMITTER ANDTHETARGET4HEDOPPLERFREQUENCYSHIFTFDISAFUNCTIONOFTHECARRIERWAVELENGTH KANDTHERELATIVERADIALVELOCITYRANGERATE BETWEENTHERADARANDTHETARGET6RELATIVE ANDISWRITTENASFD 6RELATIVEK WHEREK CFISTHEWAVELENGTH CISTHESPEEDOF LIGHT ANDFISTHECARRIERFREQUENCY7HENTHETARGETISMOVINGAWAYFROMTHERADAR THERELATIVERADIALVELOCITY ORRANGERATE ISDEFINEDTOBEPOSITIVEANDRESULTSINA NEGATIVEDOPPLERSHIFT $OPPLERRADARSCANBEEITHERCONTINUOUSWAVE#7 oORPULSEDRADARS#7RADARS SIMPLY OBSERVE THE DOPPLER SHIFT BETWEEN THE CARRIER FREQUENCY OF THE RETURN SIGNAL RELATIVETOTHETRANSMITSIGNAL0ULSEDSYSTEMSMEASUREDOPPLERBYUSINGACOHERENT TRAINOFPULSESWHERETHEREISAFIXEDORDETERMINISTICPHASERELATIONSHIPOFTHECARRIER FREQUENCYBETWEENEACHSUCCESSIVERADIOFREQUENCY2& PULSE#OHERENCECONCEN TRATESTHEENERGYINTHEFREQUENCYSPECTRUMOFTHEPULSETRAINAROUNDDISTINCTSPECTRAL LINES SEPARATEDBYTHEPULSEREPETITIONFREQUENCY02& 4HISSEPARATIONINTOSPECTRAL LINESALLOWSFORDISCRIMINATIONOFDOPPLERSHIFTS $OPPLERRADARSUSINGPULSEDTRANSMISSIONSAREMORECOMPLEXTHAN#7RADARS BUT THEYOFFERSIGNIFICANTADVANTAGES-OSTIMPORTANTISTHETIMEGATINGOFTHERECEIVER
$AVID ( -OONEY AND7ILLIAM! 3KILLMAN WROTE THIS CHAPTER FOR THE FIRST EDITION 7ILLIAM ( ,ONG JOINEDTHEAUTHORSFORTHESECONDEDITION *OHN03TRALKAAND7ILLIAM'&EDARKOUPDATEDTHEMATERIAL FORTHISEDITION o4OASSISTTHEREADER ABBREVIATIONSUSEDTHROUGHOUTTHISCHAPTERAREDEFINEDINALISTATTHEENDOFTHECHAPTER
{°£
{°Ó
2!$!2(!.$"//+
4IMEGATINGALLOWSTHEBLANKINGOFDIRECTTRANSMITTERLEAKAGEINTOTHERECEIVER4HIS PERMITSTHEUSEOFASINGLEANTENNAFORTRANSMITANDRECEIVE WHICHOTHERWISEWOULD NOTBEFEASIBLEFOR#7RADARDUETOEXCESSIVETRANSMITRECEIVEISOLATIONREQUIREMENTS 0ULSEDRADARSCANALSOUSERANGEGATING ASPECIFICFORMOFTIMEGATING WHICHDIVIDES THEINTERPULSEPERIODINTOCELLSORRANGEGATES4HEDURATIONOFEACHCELLISTYPICALLY LESSTHANOREQUALTOTHEINVERSEOFTHETRANSMITPULSEBANDWIDTH2ANGEGATINGHELPS ELIMINATEEXCESSRECEIVERNOISEFROMCOMPETINGWITHTARGETRETURNSANDALLOWSRANGE MEASUREMENTWITHPULSEDELAYRANGINGIE MEASURINGTHETIMEBETWEENTRANSMISSION OFAPULSEANDRECEPTIONOFTHETARGETECHO 0ULSEDTRANSMISSIONDOPPLERRADARSHAVEHISTORICALLYBEENCATEGORIZEDASMOVING TARGETINDICATION-4) ORPULSEDOPPLER-4)TYPICALLYELIMINATESCLUTTERBYPASSING THERECEIVEDRETURNSFROMMULTIPLECOHERENTPULSESTHROUGHAFILTERWITHASTOPBAND PLACEDINSPECTRALREGIONSOFHEAVYCLUTTERCONCENTRATIONS-OVINGTARGETSWITHDOP PLER FREQUENCIES OUTSIDE THE STOPBAND ARE PASSED ONTO DETECTION PROCESSING 0ULSE DOPPLER RADARS ON THE OTHER HAND RESOLVE AND ENHANCE TARGETS WITHIN A PARTICULAR DOPPLER BAND WHILE REJECTING CLUTTER AND OTHER RETURNS OUTSIDE THE DOPPLER BAND OF INTEREST 4HIS IS TYPICALLY ACCOMPLISHED WITH A CONTIGUOUS BANK OF DOPPLER FILTERS FORMEDBETWEENTWOOFTHECOHERENTPULSETRAINSSPECTRALLINES ONEOFWHICHISTHE CENTRALLINE2ANGEGATINGPRECEDESTHEDOPPLERFILTERBANK4HEBANDWIDTHOFEACH DOPPLERFILTERISINVERSELYPROPORTIONALTOTHEDURATIONOFTHECOHERENTPULSETRAINTHAT ISPROCESSEDTOFORMTHEDOPPLERFILTERBANK4HISPROCESSFORMSAMATCHEDFILTERTO THEENTIREPULSETRAIN -4)ANDPULSEDOPPLERRADARSSHARETHEFOLLOWINGCHARACTERISTICS L
L
#OHERENTTRANSMISSIONANDRECEPTIONTHATIS EACHTRANSMITTEDPULSEANDTHERECEIVER LOCALOSCILLATORARESYNCHRONIZEDTOAFREE RUNNING HIGHLYSTABLEOSCILLATOR #OHERENTPROCESSINGTOREJECTMAIN BEAMCLUTTER ENHANCETARGETDETECTION ANDAID INTARGETDISCRIMINATIONORCLASSIFICATION
-4)RADARSCANALSOBEIMPLEMENTEDUSINGADOPPLERFILTERBANK BLURRINGTHEHISTORIC DELINEATIONBETWEEN-4)ANDPULSEDOPPLERRADARS!SARESULT THISBOOKWILLDEFINE -4)RADARSASTHOSERADARSWHOSE02&ISSUFFICIENTLYLOWENOUGHTOPROVIDEANUNAM BIGUOUSRANGEMEASUREMENT VIAPULSEDELAYRANGING OVERTHERADARSINSTRUMENTED RANGE4HEUNAMBIGUOUSRANGE2UISGIVENBYCF2 WHERECISTHESPEEDOFLIGHT ANDF2ISTHE02&2ADARSWITH02&STHATRESULTINRANGEAMBIGUITIESWITHINTHERANGE COVERAGEOFINTERESTWILLBEREFERREDTOASPULSEDOPPLERRADARSANDWILLBETHEFOCUS OFTHISCHAPTER !PPLICATIONS 0ULSE DOPPLER IS APPLIED PRINCIPALLY TO RADAR SYSTEMS REQUIRING THEDETECTIONOFMOVINGTARGETSINASEVERECLUTTERENVIRONMENT4ABLELISTSTYPI CALAPPLICATIONSANDREQUIREMENTSn4HISCHAPTERWILLDEALPRINCIPALLYWITHAIRBORNE APPLICATIONS ALTHOUGH THE BASIC PRINCIPLES CAN ALSO BE APPLIED TO THE SURFACE BASED CASE/NLYMONOSTATICRADARSWILLBECONSIDERED 02&S 0ULSEDRADARSTHATEMPLOYDOPPLERAREDIVIDEDINTOTHREEBROAD02&CAT EGORIESLOW MEDIUM ANDHIGH!LOW 02&RADARISONEINWHICHTHERANGESOFINTEREST AREUNAMBIGUOUSWHILETHERADIALVELOCITIESDOPPLERFREQUENCIES AREUSUALLYHIGHLY AMBIGUOUS!SDISCUSSEDPREVIOUSLY THISTYPEOFRADARISCALLEDMOVINGTARGETINDICA TION-4) -4)RADARSAREGENERALLYNOTCATEGORIZEDASPULSEDOPPLERRADARS ALTHOUGH THEPRINCIPLESOFOPERATIONARESIMILAR
05,3%$/00,%22!$!2
{°Î
4!",% 0ULSE $OPPLER!PPLICATIONSAND2EQUIREMENTS
2ADAR!PPLICATION
2EQUIREMENTS
!IRBORNEORSPACEBORNESURVEILLANCE
,ONGDETECTIONRANGEACCURATERANGEDATA
!IRBORNEINTERCEPTORORFIRECONTROL
-EDIUMDETECTIONRANGEACCURATERANGE VELOCITY AND ANGLEDATA
'ROUND BASEDSURVEILLANCE
-EDIUMDETECTIONRANGEACCURATERANGEDATA
"ATTLEFIELDSURVEILLANCE SLOW MOVINGTARGETDETECTION
-EDIUMDETECTIONRANGEACCURATERANGE VELOCITYDATA
-ISSILESEEKER
3HORTDETECTIONRANGEACCURATEVELOCITYANDANGLERATEDATA MAYNOTNEEDTRUERANGEINFORMATION
3URFACE BASEDWEAPONCONTROL
3HORTRANGEACCURATERANGE VELOCITYDATA
-ETEOROLOGICAL
'OODVELOCITYRESOLUTION
-ISSILEWARNING
3HORTDETECTIONRANGEVERYLOWFALSE ALARMRATE
4HECONVERSEOFALOW 02&RADARISAHIGH 02&RADARTHATCANMEASUREDOPPLER UNAMBIGUOUSLY OVER THE SPAN OF RADIAL VELOCITIES OF INTEREST BUT IS USUALLY HIGHLY AMBIGUOUS IN RANGE ! MEDIUM 02& RADAR HAS BOTH RANGE AND DOPPLER AMBIGUI TIESn!BLENDOFMEDIUMANDHIGH02& KNOWNASHIGH MEDIUM02&WHICHWILL BEDISCUSSEDLATER ISCHARACTERIZEDASHAVINGONLYASINGLE AMBIGUITYFORTHERADIAL VELOCITIESOFINTEREST&ORTHISCHAPTER APULSEDOPPLERRADARISCHARACTERIZEDASHAVING A02&ANYWHEREWITHINTHEMEDIUMTOHIGH02®IMETHATRESULTSINAMBIGUOUS RANGEMEASUREMENTSDURINGACOHERENTPROCESSINGINTERVAL !COMPARISONOF-4)ANDPULSEDOPPLERRADARSISSHOWNIN4ABLE0REVIOUSLY UNDEFINEDTERMSWILLBEDEFINEDTHROUGHOUTTHECHAPTER4HETABLEASSUMESANAIRBORNE RADARAPPLICATIONDESIGNEDTODETECTOTHERAIRCRAFT3UCHANAPPLICATIONISCOMMONLY REFERREDTOASAIR TO AIR 4!",% #OMPARISONOF-4)AND0ULSE$OPPLER2ADARSFOR!IR TO !IR
!DVANTAGES
$ISADVANTAGES
,OW02& -4) RANGEUNAMBIGUOUS DOPPLERAMBIGUOUS
#ANSORTCLUTTERFROMTARGETSONBASIS OFRANGE&RONT ENDSENSITIVITYTIME CONTROL34# SUPPRESSESSIDELOBE DETECTIONSATSHORTRANGESANDREDUCES DYNAMICRANGEREQUIREMENTS
-ULTIPLEBLINDSPEEDS5SUALLY DOESNOTMEASURERADIALTARGET VELOCITY0OORGROUND MOVING TARGETREJECTION
-EDIUM02& 0ULSE$OPPLER RANGEAMBIGUOUS DOPPLERAMBIGUOUS
0ERFORMANCEATALLTARGETASPECTS 'OODGROUND MOVINGTARGETREJECTION -EASURESRADIALVELOCITY,ESSRANGE ECLIPSINGTHANINHIGH 02&
3IDELOBECLUTTERCANLIMIT PERFORMANCE!MBIGUITY RESOLUTIONREQUIRED,OWANTENNA SIDELOBESNECESSARY2EJECTION OFSIDELOBERETURNSOFDISCRETE GROUNDTARGETSNEEDED
(IGH02& 0ULSE$OPPLER RANGEAMBIGUOUS DOPPLERUNAMBIGUOUS
!LLOWSTHERMALNOISE LIMITED DETECTIONOFTARGETSWITHHIGHRADIAL VELOCITIES3INGLEDOPPLERBLIND ZONEATZEROVELOCITY'OODGROUND MOVINGTARGETREJECTION-EASURES RADIALVELOCITY
,IMITEDLOWRADIALVELOCITYTARGET DETECTION2ANGEECLIPSING,ARGE NUMBEROFRANGEAMBIGUITIES PRECLUDEPULSEDELAYRANGING (IGHSTABILITYREQUIREMENTSDUE TORANGEFOLDING
{°{
2!$!2(!.$"//+
4!",% 4YPICAL6ALUESFORAN8 BAND'(Z !IRBORNE&IRE #ONTROL2ADAR
0ULSE$OPPLER7AVEFORM -EDIUM02& (IGH MEDIUM02& (IGH02&
02&
4RANSMIT$UTY#YCLE
K(Z K(Z K(Z
4ABLEPROVIDESTHESPANOF02&SANDCORRESPONDINGTRANSMITDUTYCYCLESRATIO OFTRANSMITPULSEWIDTHTOINTERPULSEPERIOD FORTHEVARIOUSPULSEDOPPLERWAVEFORMS USEDINA8 BANDAIRBORNEFIRE CONTROLRADAR+EEPINMINDTHATTHEOPERATINGFREQUENCY OFTHERADAR ALONGWITHITSREQUIREDRANGEANDRADIALVELOCITYCOVERAGE DETERMINES WHETHER A 02& IS CONSIDERED MEDIUM HIGH MEDIUM OR HIGH!LSO MODERN MULTI FUNCTION RADARS ARE TYPICALLY CAPABLE OF UTILIZING WAVEFORMS FROM THE VARIOUS 02& CATEGORIESINORDERTOCARRYOUTTHEIRDIVERSEMISSIONS 0ULSE$OPPLER3PECTRUM 4HETRANSMITTEDSPECTRUMOFAPULSEDOPPLERRADARCON SISTSOFDISCRETELINESATTHECARRIERFREQUENCYFANDATSIDEBANDFREQUENCIESFoIF2 WHERE F2ISTHE02&ANDIISANINTEGER4HEENVELOPEOFTHESPECTRUMISDETERMINEDBYTHEPULSE SHAPE&ORTHERECTANGULARPULSESUSUALLYEMPLOYED ASINX XSPECTRUMISOBTAINED 5SINGACONSTANT VELOCITYAIRBORNERADAR THERECEIVEDSPECTRUMFROMASTATIONARY TARGETHASLINESTHATAREDOPPLER SHIFTEDPROPORTIONALLYTOTHERADIALVELOCITYBETWEENTHE RADARPLATFORMANDTHETARGET4HETWO WAYDOPPLERSHIFTISGIVENBYFD 62K COSX WHEREKISTHERADARWAVELENGTH 62ISTHERADARPLATFORMSPEED ANDXISTHEANGLE BETWEENTHEVELOCITYVECTORANDTHELINEOFSIGHTTOTHETARGET.OTETHATTHERELATIVE RADIALVELOCITYRANGERATE TOTHESTATIONARYTARGETIS6RELATIVE 62COSX WHICHMAKES THELATEREQUATIONFORDOPPLERSHIFTCONSISTENTWITHTHEONEPRESENTEDATTHEBEGINNING OFTHECHAPTER )LLUSTRATEDIN&IGUREISTHERECEIVEDPULSEDSPECTRUMWITHRETURNS FROMDISTRIBUTEDCLUTTER SUCHASTHEGROUNDORWEATHER ANDFROMDISCRETETARGETS SUCH ASAIRCRAFT AUTOMOBILES TANKS ETC &IGURESHOWSTHEUNFOLDEDSPECTRUMIE NOSPECTRALFOLDOVERFROMADJACENT 02&LINES INTHECASEOFHORIZONTALMOTIONOFTHERADARPLATFORM WITHASPEED62 4HECLUTTER FREEREGIONISDEFINEDASTHATPORTIONOFTHESPECTRUMINWHICHNOGROUND CLUTTER CAN EXIST ! CLUTTER FREE REGION USUALLY DOES NOT EXIST WITH MEDIUM 02&S DUETODOPPLERFOLDING 4HESIDELOBECLUTTERREGION 62KINWIDTH CONTAINSGROUND CLUTTERPOWERFROMTHESIDELOBESOFTHEANTENNA ALTHOUGHTHISCLUTTERPOWERMAYBE BELOWTHENOISELEVELINPARTOFTHEREGION4HEMAIN BEAMCLUTTERREGION LOCATEDAT F 62K COSX CONTAINSTHESTRONGRETURNFROMTHEMAINBEAMOFTHEANTENNA
&)'52% #LUTTERANDTARGETFREQUENCYSPECTRUMFROMAHORIZONTALLYMOVINGPLATFORM
05,3%$/00,%22!$!2
{°x
&)'52% 5NFOLDEDSPECTRUMWITHNOCLUTTERPOSITIONING
STRIKINGTHEGROUNDATASCANANGLEOFX MEASUREDFROMTHEVELOCITYVECTOR2AINAND CHAFFCLUTTERMAYALSOBELARGEWHENTHEMAINBEAMILLUMINATESARAINORCHAFFCLOUD -OTIONDUETOWINDSMAYDISPLACEANDORSPREADTHERETURNINFREQUENCY !LTITUDE LINECLUTTERISDUETOTHERADARRETURNFROMGROUNDCLUTTERATNEARNORMAL INCIDENCEDIRECTLYBELOWTHERADARPLATFORM ANDISATZERODOPPLERIFTHEREISNOVERTICAL COMPONENTOFPLATFORMVELOCITY!DISCRETETARGETRETURNINTHEMAINBEAMISSHOWNAT F4 F 62K COSX 64K COSX4 WHERETHETARGETSPEEDIS64 WITHANANGLE X4BETWEENTHETARGETVELOCITYVECTORANDTHERADARTARGETLINEOFSIGHT4HECOMPONENTS OFTHESPECTRUMSHOWNIN&IGUREWILLALSOVARYWITHRANGE ASDISCUSSEDLATER.OTE THATTHEDIRECTIONOF64COSX4 ISASSUMEDTOBETHEOPPOSITEOF62COSX RESULTINGIN ARELATIVERANGERATEOF6RELATIVE 64COSX4 62COSX WHICHISCONSISTENTWITHTHE DEFINITIONFORDOPPLERSHIFTSTATEDATTHEBEGINNINGOFTHECHAPTER &IGUREILLUSTRATESTHEVARIOUSCLUTTERDOPPLERFREQUENCYREGIONSASAFUNCTION OF THE ANTENNA MAIN BEAM AZIMUTH AND RELATIVE RADAR AND TARGET VELOCITIES AGAIN FORANUNFOLDEDSPECTRUM4HEORDINATEISTHERADIALORLINE OF SIGHTCOMPONENTOF TARGETVELOCITYINUNITSOFRADARPLATFORMVELOCITY SOTHEMAIN BEAMCLUTTERREGION ISATZEROVELOCITYANDTHESIDELOBECLUTTERREGIONFREQUENCYBOUNDARIESVARYSINU SOIDALLYWITHANTENNAAZIMUTH4HUS THEFIGURESHOWSTHEDOPPLERREGIONSINWHICH THETARGETBECOMESCLEAROFSIDELOBECLUTTER&OREXAMPLE IFTHEANTENNAMAIN BEAM AZIMUTH ANGLE IS AT ZERO ANY HEAD ON TARGET 64COSX4 IS CLEAR OF SIDELOBE CLUTTER WHEREASIFTHERADARISINTRAILBEHINDTHETARGETX4 ANDX THE TARGETSRADIALVELOCITYHASTOBEGREATERTHANTWICETHATOFTHERADARTOBECOMECLEAR OFSIDELOBECLUTTER 4HESIDELOBECLEARANDCLUTTERREGIONSCANALSOBEEXPRESSEDINTERMSOFTHEASPECT ANGLEWITHRESPECTTOTHETARGET ASSHOWNIN&IGURE(ERE COLLISIONGEOMETRY IS ASSUMED IN WHICH THE RADAR AND TARGET AIRCRAFT FLY STRAIGHT LINE PATHS TOWARD AN INTERCEPTPOINTTHELOOKANGLEOFTHERADARXANDTHEASPECTANGLEOFTHETARGETX4ARE CONSTANTFORAGIVENSETOFRADARANDTARGETSPEEDS62AND64 RESPECTIVELY4HECENTEROF THEDIAGRAMISTHETARGET ANDTHEANGLETOTHERADARONTHECIRCUMFERENCEISTHEASPECT ANGLE4HEASPECTANGLEANDLOOKANGLESSATISFYTHEEQUATION62SINX 64SINX4
{°È
2!$!2(!.$"//+
./4% 7 IDTHOFALTITUDE LINEANDMAIN BEAMCLUTTERREGIONSVARIESWITHCONDITIONSAZIMUTHISMEASURED FROMRADARPLATFORMVELOCITYVECTORTOTHEANTENNABORESIGHTORTOTHELINEOFSIGHTTOTHETARGET HORIZONTAL MOTIONCASE &)'52% #LUTTERANDCLUTTER FREEREGIONSASAFUNCTIONOFTARGETVELOCITYANDAZIMUTH
WHICHISDEFINEDASACOLLISIONCOURSE4HETARGETASPECTANGLEISZEROFORAHEAD ON CONDITIONANDFORATAILCHASE4HEASPECTANGLECORRESPONDINGTOTHEBOUNDARY BETWEENTHESIDELOBECLUTTERREGIONANDTHESIDELOBECLEARREGIONISAFUNCTIONOFTHE RELATIVERADAR TARGETVELOCITYRATIOANDISSHOWNIN&IGUREFORFOURCASES#ASEIS WHERETHERADARANDTARGETSPEEDSAREEQUALANDTHETARGETCANBESEENCLEAROFSIDELOBE CLUTTER IN A HEAD ON ASPECT OUT TO ON EITHER SIDE OF THE TARGETS VELOCITY VECTOR 3IMILARLY #ASESTHROUGHSHOWCONDITIONSWHERETHETARGETSSPEEDIS AND TIMESTHERADARSSPEED INWHICHCASETHETARGETCANBESEENCLEAROFSIDELOBECLUT TEROVERAREGIONOFUPTOoRELATIVETOTHETARGETSVELOCITYVECTOR!GAIN THESE CONDITIONSAREFORANASSUMEDCOLLISIONCOURSE!SISEVIDENT THEASPECTANGLEOFTHE TARGETCLEAROFSIDELOBECLUTTERISALWAYSFORWARDOFTHEBEAMASPECT !MBIGUITIESAND02&3ELECTION 0ULSEDOPPLERRADARSAREAMBIGUOUSINRANGE AND POSSIBLY DOPPLER!S MENTIONED EARLIER THE UNAMBIGUOUS RANGE 2U IS GIVEN BY CF2 WHERECISTHESPEEDOFLIGHTANDF2ISTHE02& )F THE AIRBORNE TARGET RADIAL VELOCITY TO BE OBSERVED IS BETWEEN 64 MAX OPENING FOR OPENING TARGETS POSITIVE RANGE RATE AND 64 MAX CLOSING FOR CLOSING TARGETS NEGATIVE RANGERATE THENTHEMINIMUMVALUEOF02& F2MIN WHICHISUNAMBIGUOUSINVELOCITY INBOTHMAGNITUDEANDSENSE IE POSITIVEANDNEGATIVE IS
F2 MIN 64 MAX CLOSING 64 MAX OPENING 6G L
WHERE6GISTHEUPPERLIMITFORGROUNDMOVINGTARGETREJECTION6REFERSTOTHESPEED ORTHEMAGNITUDEOFTHERANGERATE
05,3%$/00,%22!$!2
{°Ç
&)'52% 3IDELOBECLUTTER CLEARREGIONSVERSUSTARGETASPECTANGLE.OTETHETARGETISATTHECENTEROFTHE PLOTWITHTHERADARPLATFORMONTHECIRCUMFERENCE
(OWEVER SOMEPULSEDOPPLERRADARSEMPLOYA02&THATISUNAMBIGUOUSINVELOC ITYMAGNITUDEONLY IE F2 MIN ;MAX64 MAX CLOSING 64 MAX OPENING 6G=K ANDRELYON DETECTIONSINMULTIPLE02&SDURINGTHETIMEONTARGETTORESOLVETHESIGNAMBIGUITYIN DOPPLER4HESERADARSCANBEDESCRIBEDASHIGH MEDIUM 02&ANDCANBECONSIDERED TOBEINTHEHIGH 02&CATEGORYIFTHEOLDERDEFINITIONOFHIGH02&NOVELOCITYAMBI GUITY ISEXTENDEDTOALLOWONEVELOCITYAMBIGUITY THATOFDOPPLERSENSE4HELOWER 02&EASESTHEMEASUREMENTOFTRUERANGEWHILERETAININGTHEHIGH 02&ADVANTAGEOF ASINGLEBLIND SPEEDREGIONNEARZERODOPPLER(IGH MEDIUM02&ISBECOMINGMORE PREVALENTINMODERNAIRBORNERADARSFORAIR TO AIRSEARCH 4HECHOICEBETWEENHIGHANDMEDIUM02&INVOLVESANUMBEROFCONSIDERATIONS SUCHASTRANSMITTERDUTYCYCLELIMIT PULSECOMPRESSIONAVAILABILITY SIGNAL PROCESSING CAPABILITY MEASUREMENT ACCURACY REQUIREMENTS ETC BUT OFTEN DEPENDS ON THE NEED FOR ALL ASPECT TARGET DETECTABILITY!LL ASPECT COVERAGE REQUIRES GOOD PERFOR MANCEINTAILCHASE WHERETHETARGETDOPPLERISINTHESIDELOBECLUTTERREGIONNEAR THE ALTITUDE LINE )N A HIGH 02& RADAR THE RANGE FOLDOVER MAY LEAVE LITTLE CLEAR REGIONINTHERANGEDIMENSION THUSDEGRADINGTARGETDETECTABILITY"YUSINGALOWER OR MEDIUM 02& THE CLEAR REGION IN RANGE IS INCREASED AT THE EXPENSE OF VELOCITY FOLDOVERFORHIGH DOPPLERTARGETSTHATAREINTHECLUTTER FREEREGIONINHIGH02&!S ANEXAMPLE &IGURESHOWSTHECLUTTER PLUS NOISE TO NOISERATIOINRANGE DOPPLER COORDINATES FOR TWO DIFFERENT 8 BAND WAVEFORMS AT SIMILAR ALTITUDES AND AIRCRAFT VELOCITIES4HERANGEDIMENSIONREPRESENTSTHEUNAMBIGUOUSRANGEINTERVAL2U AND THEFREQUENCYDIMENSIONREPRESENTSTHE02&INTERVAL WITHTHEMAIN BEAMCLUTTER ALTITUDE LINE AND SIDELOBE CLUTTER REGIONS CLEARLY DISCERNIBLE )N BOTH WAVEFORMS THEMAIN BEAMCLUTTERRETURNISPOSITIONEDTO$#THROUGHCLUTTERPOSITIONINGVIAAN
{°n
2!$!2(!.$"//+ # " !' '( ! #
!$ !('' %
# "!('' %
)!('' % % * $#
# ' (" %
!('' %$ & $ &
# "!('' %
# ' (" %
)!('' % % * $#
!' '( ! #
!' '( ! #
!$ !('' %
!' %(" % $ #'
!' %(" % $ #'
&)'52% #LUTTER PLUS NOISE TO NOISERATIOINRANGE DOPPLERSPACE
OFFSETAPPLIEDTOTHETRANSMITFREQUENCY4HEMEDIUM 02&SPECTRUM02& K(Z CONTAINSARANGE DOPPLERREGIONINWHICHTHESIDELOBECLUTTERISBELOWTHERMALNOISE ANDINWHICHGOODTAIL ASPECTTARGETDETECTABILITYCANBEACHIEVED4HEK(ZHIGH MEDIUM 02& WAVEFORM HAS A MUCH MORE SEVERE CLUTTER FOLDING AND TAIL ASPECT TARGETSWOULDCOMPETEWITHSIDELOBECLUTTERATNEARLYALLRANGES BUTTHECLUTTER FREE REGIONISMUCHLARGER "ECAUSETHECLUTTERISFOLDEDINBOTHRANGEANDDOPPLERWITHMEDIUM 02& ANUM BEROF02&SMAYBEREQUIREDTOOBTAINASATISFACTORYPROBABILITYOFSUFFICIENTDETECTIONS TORESOLVETHERANGEANDDOPPLERAMBIGUITIES4HEMULTIPLE02&SMOVETHERELATIVE LOCATIONOFTHECLEARREGIONSSOTHATALL ASPECTTARGETCOVERAGEISACHIEVED3INCETHE SIDELOBECLUTTERGENERALLYCOVERSTHEDOPPLERREGIONOFINTEREST THERATIOOFTHEREGION WITHSIDELOBECLUTTERBELOWNOISERELATIVETOTHETOTALRANGE DOPPLERSPACEISAFUNCTION OFTHERADARALTITUDE SPEED ANDANTENNASIDELOBELEVEL )F A HIGH 02& WAVEFORM IS USED THE CLEAR RANGE REGION DISAPPEARS BECAUSE THE SIDELOBECLUTTERFOLDSINRANGEINTOTHEUNAMBIGUOUSRANGEINTERVALASSUMINGTHETAR GETDOPPLERISSUCHTHATITSTILLCOMPETESWITHTHESIDELOBECLUTTER (OWEVER INTHOSE DOPPLERREGIONSFREEOFSIDELOBECLUTTER ASSHOWNIN&IGUREAND&IGURE TARGET DETECTABILITY IS LIMITED ONLY BY THERMAL NOISE INDEPENDENT OF RADAR ALTITUDE SPEED ANDSIDELOBELEVEL4HISREQUIRESSYSTEMSTABILITYSIDEBANDSTOBEWELLBELOWNOISEFOR THE WORST CASE MAIN BEAM CLUTTER4HUS ALTHOUGH MEDIUM 02& PROVIDES ALL ASPECT TARGETCOVERAGE THETARGETISPOTENTIALLYCOMPETINGWITHSIDELOBECLUTTERATALLASPECTS WHEREASWITHHIGH02& ATARGETCANBECOMECLEAROFSIDELOBECLUTTERATASPECTANGLES FORWARDOFTHEBEAMASPECT &ORTARGETSWITHSUFFICIENTRADIALVELOCITY HIGH02&ISTYPICALLYMOREEFFICIENTTHAN MEDIUM02&4HETRANSMITPULSEWIDTHISUSUALLYLIMITEDBYTHETRANSMITTERSABILITYTO PRESERVETHEPULSEAMPLITUDEANDPHASECHARACTERISTICSOVERTHEDURATIONOFTHETRANSMIT PULSE&ORAFIXEDTRANSMITPULSEWIDTHANDPEAKPOWER AWAVEFORMWITHAHIGHER02& WILLHAVEAHIGHERTRANSMITDUTYCYCLERESULTINGINAHIGHERAVERAGETRANSMITPOWER&OR AGIVENCOHERENTPROCESSINGTIME MOREENERGYISPLACEDONTHETARGET WHICHIMPROVES DETECTABILITY&ORTHISREASON HIGH02&ISUSEDFORLONG RANGESEARCHOFHIGH SPEED CLOSINGTARGETS
05,3%$/00,%22!$!2
{°
2ANGE'ATING 2ANGEGATINGDIVIDESTHETIMEBETWEENTRANSMITPULSESINTOMUL TIPLECELLSORRANGEGATES2ANGEGATINGELIMINATESEXCESSRECEIVERNOISEANDCLUTTER FROMCOMPETINGWITHTHESIGNALANDPERMITSTARGETTRACKINGANDRANGEMEASUREMENT 4HERANGEGATEISTYPICALLYMATCHEDTOTHEBANDWIDTHOFTHETRANSMITPULSE)NASURVEIL LANCERADAR ANUMBEROFRECEIVERGATESAREUSEDTODETECTTARGETSTHATMAYAPPEARAT ANYRANGEWITHINTHEINTERPULSEPERIOD&IGUREILLUSTRATESTHEGENERALCASEWHERETHE GATESPACINGSS THEGATEWIDTHSG ANDTHETRANSMITTEDPULSESTAREALLUNEQUAL3ELECTING ST SGMAXIMIZESTARGETRETURNSIGNAL TO NOISERATIOAND ASARESULT RANGEPERFORMANCE 3ELECTINGSG SSCREATESOVERLAPPEDRANGEGATESANDREDUCESTHERANGEGATESTRADDLE LOSS3ECTION BUTCANINCREASETHEPOSSIBILITYOFRANGEGHOSTSUNLESSCONTIGUOUS DETECTIONSFROMSTRADDLEDTARGETRETURNSAREhCLUMPEDvPRIORTOTHEAMBIGUITYRESOLU TION3ECTION 7ITHRANGEGATING THERANGEMEASUREMENTACCURACYISONTHEORDER OFTHERANGEGATESIZEMMS BUTTHISCANBEIMPROVEDTOAFRACTIONOFTHEGATE WIDTHBYAMPLITUDECENTROIDING 4IMELINE $EFINITIONS 0ULSE DOPPLER RADAR WORKS ON SEVERAL DIFFERENT TIME SCALES6ARIOUSORGANIZATIONSHAVETHEIROWNNOMENCLATUREFORTIME BASEDPARAMETERS 4HEREFORE THETIMELINEDEFINITIONSUSEDTHROUGHOUTTHISCHAPTERAREDEFINEDHERE &IGUREILLUSTRATESTHEDIFFERENTTIMESCALES3TARTINGATTHELOWESTLEVEL ASERIES OF COHERENT PULSES ARE TRANSMITTED AT A PULSE REPETITION FREQUENCY 02& 4HE TIME BETWEENTHEPULSESISTHEINTERPULSEPERIOD)00 WHICHISSIMPLYTHEINVERSEOFTHE 02&4HERECEIVEPORTIONOFTHE)00ISBROKENUPINTORANGEGATES4HETRANSMITDUTY CYCLEISTHETRANSMITPULSEWIDTHDIVIDEDBYTHE)004HETRAINOFPULSESISCALLEDTHE COHERENTPROCESSINGINTERVAL#0) 4HECOHERENTPROCESSINGFORMSABANKOFDOPPLER
&)'52% %XAMPLE OF RANGE GATES WITH OVERLAP EQUALLY SPACED IN THE INTERPULSE PERIOD SBREPRESENTSTHEEXTRABLANKINGTIMEAFTERTHETRANSMITPULSETOALLOWFORRECEIVERPROTECTORRECOVERY
{°£ä
2!$!2(!.$"//+
&)'52% 0ULSEDOPPLERDWELLTIMELINE
FILTERSFOREACHRANGEGATERESULTINGINARANGE DOPPLERMAPFORA#0) SIMILARTOTHAT SHOWNIN&IGURE 3EVERAL#0)SWITHTHESAME02& BUTPOSSIBLYDIFFERENTTRANSMITCARRIERFREQUEN CIES CANBENONCOHERENTLYCOMBINEDVIAPOSTDETECTIONINTEGRATION0$) )FFREQUENCY MODULATION&- RANGINGISUSED ALLTHE#0)STHATARENONCOHERENTLYINTEGRATEDMUST HAVETHESAME&-SLOPE4HEGROUPINGOF#0)SISALOOK$ETECTIONSAREDETERMINED FORTHERANGE DOPPLERCELLSINALOOK -ULTIPLELOOKSWITHDIFFERENT02&SORFREQUENCYMODULATIONSAREUSEDTORESOLVE RANGEANDORDOPPLERAMBIGUITIES4HISGROUPOFLOOKSISADWELL!DWELLISASSOCIATED WITHAPARTICULARANTENNALINE OF SIGHTORBEAMPOSITION4ARGETREPORTSAREGENERATED FOREACHDWELL !BARREFERSTOALINEOFBEAMPOSITIONSATACONSTANTELEVATION)NSEARCH AMULTI BARRASTERSCANSTHEBEAMOVERANASSIGNEDAREAORVOLUMETOCREATEAFRAME!FRAME MAYHAVEMULTIPLEBARS4YPICALLY THEANTENNAWILLVISITEVERYBEAMPOSITIONONCE DURINGASEARCHFRAME "ASIC#ONFIGURATION &IGURESHOWSAREPRESENTATIVECONFIGURATIONOFAPULSE DOPPLERRADARUTILIZINGDIGITALSIGNALPROCESSINGUNDERTHECONTROLOFAMISSIONPROCESSOR )NCLUDEDARETHEANTENNA RECEIVEREXCITER SIGNALPROCESSOR ANDDATAPROCESSOR4HE RADARSCONTROLPROCESSORRECEIVESINPUTSFROMTHEON BOARDSYSTEMS SUCHASTHEINER TIAL NAVIGATION SYSTEM ).3 AND OPERATOR CONTROLS VIA THE MISSION PROCESSOR AND PERFORMSASAMASTERCONTROLLERFORTHERADARHARDWARE #OHERENT PROCESSING REQUIRES THAT ALL FREQUENCY DOWN CONVERSIONS INCLUDING THE FINALCONVERSIONTOBASEBAND RETAINTHECOHERENTPHASERELATIONSHIPBETWEENTRANSMIT TEDANDRECEIVEDPULSES!LLTHELOCALOSCILLATORSAREPHASEREFERENCEDTOTHESAMEMASTER OSCILLATOR WHICHISALSOUSEDTOPRODUCETHETRANSMITTEDWAVEFORM4HEIN PHASE) ANDQUADRATURE1 COMPONENTSATBASEBANDREPRESENTTHEREALANDIMAGINARYPARTS RESPECTIVELY OFACOMPLEXNUMBERWHOSECOMPLEXARGUMENTINPHASORNOTATIONISTHE PHASEDIFFERENCEBETWEENTHETRANSMITTEDANDRECEIVEDPULSES4HECOMPLEXMODULUS ORMAGNITUDE ISPROPORTIONALTOTHERECEIVEDECHOSTRENGTH
%
(
(
(
&#
#! !!
#! !!
#! !!
#! !!
' !" %%!#
'
'% !
$&# %
$
* &%
$&# %
$ ""
"' ##!
&# #&($&
( !(&
"' ##!
!$
"' ##!
#!$$!#
#&($&
,#( ' -&
,# &$# -&
!)((& '( #&($&
"" "
"
(&$''$&
(!
#&( $#
(! $#(&$!'($
# * )! $"%$##('
'(& ' !!($&
% " "
(! ( !(&
$#(&$! &$''$&
$ $#(&$! '' $# &$''$&
!! !! " ! &
05,3%$/00,%22!$!2
&)'52% 4YPICALPULSEDOPPLERRADARCONFIGURATION
#! '#
)(%)( #&($&
)&
(
'# #!%%!#
$+& "%
&#'" (
$ #!&$''$&
"(& # $"%)(&
{°££
{°£Ó
2!$!2(!.$"//+
-ASTER/SCILLATOR 4HEMASTEROSCILLATORPROVIDESAFREE RUNNING STABLEREFERENCE SINUSOIDONWHICHTHESYSTEMSYNCHRONIZATIONISBASED 3YNCHRONIZER 4HESYNCHRONIZERDISTRIBUTESPRECISELYTIMEDSTROBESANDCLOCKSFOR THEVARIOUSCOMPONENTSOFTHERADARSYSTEMTOENSURETHETIMEALIGNMENTOFTRANSMIT WAVEFORMSANDTHERECEPTIONOFTHEIRCORRESPONDINGRETURNS4HESELOW JITTERTIMING SIGNALSAREUSEDTOENABLEANDDISABLETHETRANSMITPOWERAMPLIFIERTOCREATETHETRANS MITPULSETRAIN BLANKTHERECEIVERDURINGTRANSMISSION ANDFORMTHERANGEGATES 2EFERENCE'ENERATOR 4HEREFERENCEGENERATOROUTPUTSFIXEDFREQUENCYCLOCKSAND LOCALOSCILLATORS,/S 3YNTHESIZER 4HE SYNTHESIZER GENERATES THE TRANSMIT CARRIER FREQUENCY AND THE FIRSTLOCALOSCILLATOR,/ FREQUENCY&REQUENCYAGILITYISPROVIDEDTOTHETRANSMIT AND,/SIGNALS #LUTTER/FFSET'ENERATOR 4HECLUTTEROFFSETGENERATORSHIFTSTHETRANSMITCARRIER SLIGHTLY SO THAT ON RECEIVE THE MAIN BEAM CLUTTER IS POSITIONED AT ZERO DOPPLER FRE QUENCY OR$#DIRECTCURRENT AFTERBASEBANDING4HESAMEEFFECTCOULDBEOBTAINED BYSHIFTINGTHERECEIVER,/FREQUENCY7ITHTHECLUTTERAT$# THESPURIOUSSIGNALS CAUSEDBYCERTAINRECEIVERNONLINEARITIES SUCHASMIXERINTERMODULATIONPRODUCTSAND VIDEOHARMONICS ALSOFALLNEAR$#ANDCANBEFILTEREDOUTALONGWITHTHEMAIN BEAM CLUTTER 4HE FREQUENCY SHIFT APPLIED IS A FUNCTION OF THE ANTENNA MAIN BEAM LINE OF SIGHT RELATIVE TO THE PLATFORMS VELOCITY VECTOR4HIS PROCESS IS KNOWN AS CLUTTER POSITIONING /UTPUT'ENERATOR 4HEOUTPUTGENERATESTHEPULSEDRADIOFREQUENCY2& TRANSMIT SIGNAL WHICHISTHETRANSMITDRIVESIGNALTHATISAMPLIFIEDBYTHEPOWERAMPLIFIERPRIOR TOBEINGFEDTOTHETRANSMITANTENNA !NTENNA 4HE ANTENNA CAN BE MECHANICALLY OR ELECTRONICALLY SCANNED -ODERN PULSEDOPPLERRADARSHAVEMIGRATEDTOTHEUSEOFACTIVEELECTRONICALLYSCANNEDARRAYS !%3!S !%3!SCONTAINTRANSMITRECEIVE42 MODULES EACHCOMPRISINGATRANS MITPOWERAMPLIFIERANDARECEIVELOW NOISEAMPLIFIER,.! ALONGWITHANATTENUATOR ANDPHASESHIFTER ATEACHANTENNAELEMENT )FTHESAMEANTENNAISUSEDFORTRANSMITANDRECEIVE ADUPLEXERMUSTBEINCLUDED 4HIS DUPLEXER IS USUALLY A PASSIVE DEVICE SUCH AS A CIRCULATOR WHICH EFFECTIVELY SWITCHESTHEANTENNABETWEENTHETRANSMITTERANDRECEIVER#ONSIDERABLEPOWERMAY BECOUPLEDTOTHERECEIVERSINCETYPICALLYNOMORETHANTOD"OFISOLATIONMAY BEEXPECTEDFROMFERRITECIRCULATORS !NTENNASMAYFORMVARIOUSBEAMS4HETRANSMITBEAMCANBEFORMEDWITHUNIFORM APERTUREILLUMINATIONTOMAXIMIZETHEAMOUNTOFENERGYONTARGET WHEREASTHERECEIVE SUM3 BEAMISTYPICALLYFORMEDWITHALOW SIDELOBETAPERTOMINIMIZETHERETURNS FROMGROUNDCLUTTER4HE3BEAMISUSEDFORTARGETDETECTIONAND ACTINGASASPATIALFILTER ISTHEFIRSTLINEOFDEFENSEAGAINSTCLUTTERANDINTERFERENCEINTHESIDELOBEREGION4O FACILITATETARGETTRACKING ANGLEMEASUREMENTSWITHACCURACIESFINERTHANTHEANTENNA BEAMWIDTHAREUSUALLYREQUIRED!TECHNIQUETOOBTAINSUCHANGLEMEASUREMENTSOF A TARGET ON A SINGLE PULSE IS CALLED MONOPULSE -ONOPULSE CAN BE CHARACTERIZED AS AMPLITUDEORPHASE WITHPHASEBEINGPREFERABLEDUETOITSADVANTAGEINANGLEACCURACY FORAGIVENSIGNAL TO NOISERATIO0HASEMONOPULSEUSESADELTAORDIFFERENCEBEAM
05,3%$/00,%22!$!2
{°£Î
WHICHISESSENTIALLYFORMEDBYDIVIDINGTHEAPERTUREINTOTWOHALVESANDSUBTRACTING THECORRESPONDINGPHASECENTERS-ONOPULSEBEAMS DELTA AZIMUTH$!: ANDDELTA ELEVATION$%, AREFORMEDTOPROVIDEPHASEMONOPULSEAZIMUTHANDELEVATIONANGLE MEASUREMENTS3ELF CALIBRATIONROUTINESCONTROLLEDBYTHECONTROLPROCESSORENSURE THATTHEPHASEANDAMPLITUDEMATCHOFTHERECEIVERCHANNELSENABLESACCURATEMONO PULSEMEASUREMENTS!GUARDBEAMWITHANEAR OMNIDIRECTIONALPATTERNISFORMEDFOR SIDELOBEDETECTIONBLANKINGASDISCUSSEDIN3ECTION 2ECEIVER0ROTECTOR 20 4HE RECEIVERPROTECTOR IS A LOW LOSS FAST RESPONSE HIGH POWERSWITCHTHATPREVENTSTHETRANSMITTEROUTPUTFROMTHEANTENNASDUPLEXER FROMDAMAGINGTHESENSITIVERECEIVERFRONTEND&ASTRECOVERYISREQUIREDTOMINIMIZE DESENSITIZATIONINTHERANGEGATESFOLLOWINGTHETRANSMITTEDPULSE20SCANBEIMPLE MENTEDWITHAGASDISCHARGETUBE INWHICHAGASISIONIZEDBYHIGH POWER2&!DIODE LIMITERCANBEUSEDINSTEADOFORINCONJUNCTIONWITHTHEGASDISCHARGETUBE4HE20 CANBEREFLECTIVEORABSORPTIVE BUTMUSTHAVELOWINSERTIONLOSSTOMINIMIZEIMPACT ONRECEIVECHAINNOISEFIGURE #LUTTER!UTOMATIC'AIN#ONTROL#!'# 4HE#!'#ATTENUATORISUSEDBOTHFOR SUPPRESSINGTRANSMITTERLEAKAGEFROMTHE20INTOTHERECEIVERSOTHERECEIVERISNOT DRIVEN INTO SATURATION WHICH COULD LENGTHEN RECOVERY TIME AFTER THE TRANSMITTER IS TURNEDOFF ANDFORCONTROLLINGTHEINPUTSIGNALLEVELSINTOTHERECEIVER4HERECEIVED LEVELSAREKEPTBELOWSATURATIONLEVELS TYPICALLYWITHACLUTTER!'#INSEARCHANDA TARGET!'#INSINGLE TARGETTRACK TOPREVENTSPURIOUSSIGNALS WHICHDEGRADEPERFOR MANCE FROMBEINGGENERATED .OISE!UTOMATIC'AIN#ONTROL.!'# 4HE.!'#ATTENUATORISUSEDTOSETTHE THERMALNOISELEVELINTHERECEIVERTOSUPPORTTHEREQUIREDDYNAMICRANGE ASDISCUSSED IN3ECTION4HEATTENUATIONISCOMMANDEDBASEDONMEASUREMENTSOFTHENOISE DURINGPERIODICCALIBRATION $IGITAL 0REPROCESSING 4HE ADVENT OF HIGH SPEED HIGH DYNAMIC RANGE ANALOG TO DIGITALCONVERTERS!$S ALLOWS)& SAMPLINGANDDIGITALBASEBANDING4HEDIGITAL )& SAMPLEDOUTPUTOFTHERECEIVERISDOWNCONVERTEDTOBASEBAND$# VIAADIGITAL PRODUCTDETECTOR$0$ 3UPERIOR)1IMAGEREJECTIONISANADVANTAGEOFA$0$ 4HE)AND1SIGNALSAREPASSEDTHROUGHTHEDIGITALPORTIONOFTHEPULSEMATCHED FILTER4HECOMBINATIONOFTHE)&MATCHEDFILTERANDTHEDIGITALMATCHEDFILTERFORMTHE RECEIVERSSINGLE PULSEMATCHEDFILTER $IGITAL 3IGNAL 0ROCESSING &OLLOWING DIGITAL PREPROCESSING IS A DOPPLER FIL TERBANKFORMAIN BEAMCLUTTERREJECTIONANDCOHERENTINTEGRATION2&INTERFERENCE 2&) THAT IS PULSED AND ASYNCHRONOUS TO THE RADAR TIMING CAN OFTEN BE DETECTED PRIORTOTHECOHERENTINTEGRATION2ANGE )00CELLSWHERE2&)ISDETECTEDARETHEN hREPAIREDvTOPREVENTCORRUPTIONOFTHEOUTPUTSPECTRUM4HEFILTERBANKISUSUALLY REALIZEDBYUSINGTHEFAST&OURIERTRANSFORM&&4 HOWEVER THEDISCRETE&OURIER TRANSFORM $&4 CAN BE USED WHEN THE NUMBER OF FILTERS IS SMALL !PPROPRIATE WEIGHTINGISEMPLOYEDTOREDUCETHEFILTERSIDELOBES4HEAMOUNTOFWEIGHTINGCAN BECHOSENADAPTIVELYBYSENSINGTHEPEAKSIGNALLEVELSUSUALLYMAIN BEAMCLUTTER ANDSELECTINGTHEDOPPLERWEIGHTINGDYNAMICALLY )FPULSECOMPRESSIONMODULATIONISUSEDONTHETRANSMITPULSETOINCREASEENERGYON TARGET PULSECOMPRESSIONCANBEPERFORMEDDIGITALLYEITHERBEFOREORAFTERTHEDOPPLER
{°£{
2!$!2(!.$"//+
FILTERBANK4HEADVANTAGEOFPULSECOMPRESSIONAFTERTHEFILTERBANKISTHATTHEEFFECTSOF DOPPLERONPULSECOMPRESSIONCANBELARGELYREMOVEDBYTAILORINGTHEPULSECOMPRES SIONTOTHEDOPPLEROFFSETOFEACHDOPPLERFILTER(OWEVER THISINCREASESTHETOTALAMOUNT OFSIGNALPROCESSINGREQUIRED 4HEENVELOPEATTHEOUTPUTOFTHE&&4ISFORMEDWITHALINEAR ) 1 ORSQUARE LAW ) 1 DETECTOR (ISTORICALLY LINEAR DETECTORS WERE USED TO MANAGE DYNAMIC RANGEINFIXED POINTPROCESSORS3QUARE LAWDETECTORSAREPREFERREDFORSOMEMODERN FLOATING POINT PROCESSORS 0OSTDETECTION INTEGRATION 0$) MAY BE USED WHERE EACH RANGE GATE DOPPLER FILTEROUTPUTISLINEARLYSUMMEDOVERSEVERAL#0)S&OREACHRANGE DOPPLERCELLINTHE3CHANNEL THE0$)OUTPUTISCOMPAREDWITHADETECTIONTHRESHOLD DETERMINEDBYACONSTANT FALSE ALARM RATE#&!2 PROCESSn#ELLSWITHAMPLITUDES GREATERTHANTHE#&!2THRESHOLDARELABELEDASDETECTIONS 3IMILARPROCESSINGISDONEINTHE$!:AND$%,CHANNELSWITHEXCEPTIONS ASSHOWNIN &IGURE&ORTHOSERANGE DOPPLERCELLSWITHDECLAREDDETECTIONS THEIMAGINARYPART OFTHE$!:3AND$%,3RATIOSAREUSEDFORPHASECOMPARISONMONOPULSETOESTIMATETHE AZIMUTHANDELEVATIONANGLES RESPECTIVELY RELATIVETOTHECENTEROFTHE3MAINBEAM 4HEANGLEESTIMATESARECOMPUTEDFOREACHCOHERENTLOOKANDTHENAVERAGEDOVERTHE NUMBEROF#0)SNONCOHERENTLYINTEGRATEDVIA0$) 4HEGUARDCHANNELISPROCESSEDSIMILARTOTHE3CHANNEL4HEGUARDCHANNELSPUR POSEISTOBLANKSIDELOBEDETECTIONS ASDESCRIBEDIN3ECTION 0OSTPROCESSING &OLLOWINGTHE#&!2ISDETECTIONEDITING WHICHCONTAINSTHESIDE LOBEDISCRETEREJECTIONLOGIC&OLLOWINGDETECTIONEDITING RANGEANDVELOCITYAMBI GUITYRESOLVERSWORKOVERSEVERALLOOKSWITHINADWELL4HEFINALDETECTIONOUTPUTS ALONGWITHTHEIRCORRESPONDINGUNAMBIGUOUSRANGE VELOCITY ANDANGLEMEASUREMENTS ANDTHEIRESTIMATEDACCURACIES AREPASSEDTOTHEMISSIONPROCESSORFORTRACKINGAND OPERATORDISPLAY
{°ÓÊ *1 - Ê "** ,Ê 1// , 'ENERAL #LUTTERRETURNSFROMVARIOUSSCATTERERSHAVEASTRONGINFLUENCEONTHEDESIGN OFAPULSEDOPPLERRADARASWELLASANEFFECTONTHEPROBABILITYOFDETECTIONOFPOINTTARGETS #LUTTERSCATTERERSINCLUDETERRAINBOTHLANDANDSEA WEATHERRAIN SNOW ETC ANDCHAFF 3INCETHEANTENNASGENERALLYUSEDINPULSEDOPPLERRADARSHAVEASINGLE RELATIVELYHIGH GAINMAINBEAM MAIN BEAMCLUTTERMAYBETHELARGESTSIGNALHANDLEDBYTHERADARWHEN INADOWN LOOKCONDITION4HENARROWBEAMLIMITSTHEFREQUENCYEXTENTOFTHISCLUTTER TOARELATIVELYSMALLPORTIONOFTHEDOPPLERSPECTRUM4HEREMAINDEROFTHEANTENNAPAT TERNCONSISTSOFSIDELOBES WHICHRESULTINSIDELOBECLUTTER4HISCLUTTERISGENERALLYMUCH SMALLERTHANTHEMAIN BEAMCLUTTERBUTCOVERSMUCHMOREOFTHEFREQUENCYDOMAIN4HE SIDELOBECLUTTERFROMTHEGROUNDDIRECTLYBELOWTHERADAR THEALTITUDE LINE ISFREQUENTLY LARGEOWINGTOAHIGHREFLECTIONCOEFFICIENTATSTEEPGRAZINGANGLES THELARGEGEOMETRIC AREA ANDTHESHORTRANGE2ANGEPERFORMANCEISDEGRADEDFORTARGETSINTHESIDELOBECLUTTER REGIONWHEREVERTHECLUTTERISNEARORABOVETHERECEIVERNOISELEVEL-ULTIPLE02&SMAY BEUSEDTOMOVETHETARGETWITHRESPECTTOTHESIDELOBECLUTTERINTHERANGE DOPPLERMAP THUSAVOIDINGCOMPLETELYBLINDRANGESORBLINDFREQUENCIESDUETOHIGHCLUTTERLEVELS4HIS RELATIVEMOTIONOCCURSDUETOTHERANGEANDDOPPLERFOLDOVERFROMRANGEANDORDOPPLER AMBIGUITIES)FONE02&FOLDSSIDELOBECLUTTERANDATARGETTOTHESAMEAPPARENTRANGEAND DOPPLER ASUFFICIENTCHANGEOF02&WILLSEPARATETHEM
05,3%$/00,%22!$!2
{°£x
'ROUND#LUTTERINA3TATIONARY2ADAR 7HENTHERADARISFIXEDWITHRESPECT TOTHEGROUND BOTHSTATIONARYMAIN BEAMANDSIDELOBECLUTTERRETURNSOCCURATZERO DOPPLER OFFSET FROM THE TRANSMIT CARRIER FREQUENCY4HE SIDELOBE CLUTTER IS USUALLY SMALL COMPARED WITH MAIN BEAM CLUTTER AS LONG AS SOME PART OF THE MAIN BEAM STRIKESTHEGROUND4HECLUTTERCANBECALCULATEDASINAPULSEDRADAR THENFOLDEDIN RANGEASAFUNCTIONOFTHE02& 'ROUND#LUTTERINA-OVING2ADAR 7HENTHERADARISMOVINGWITHAVELOCITY 62 THECLUTTERISSPREADOVERTHEFREQUENCYDOMAINASILLUSTRATEDIN&IGUREFORTHE SPECIAL CASE OF HORIZONTAL MOTION4HEFOLDOVERINRANGEANDDOPPLERISILLUSTRATED IN&IGUREFORAMEDIUM 02&RADARWHERETHECLUTTERISAMBIGUOUSINBOTHRANGE ANDDOPPLER4HERADARPLATFORMISMOVINGTOTHERIGHTATKTWITHADIVEANGLE OF4HENARROWANNULIISO RANGECONTOURS DEFINETHEGROUNDAREATHATCONTRIBUTES TOCLUTTERINTHESELECTEDRANGEGATE4HEFIVENARROWHYPERBOLICBANDSISO DOPPLER CONTOURS DEFINE THE AREA THAT CONTRIBUTES TO CLUTTER IN THE SELECTED DOPPLER FILTER 4HE SHADED INTERSECTIONS REPRESENT THE AREA OR CLUTTER PATCHES THAT CONTRIBUTES TO THERANGE GATE DOPPLER FILTERCELL%ACHCLUTTERPATCHCONTRIBUTESCLUTTERPOWERASA FUNCTIONOFTHEANTENNAGAININTHEDIRECTIONOFTHECLUTTERPATCHANDTHEREFLECTIVITY OFTHECLUTTERPATCH 4HEMAINBEAMILLUMINATESTHEELLIPTICALAREATOTHELEFTOFTHEGROUNDTRACK3INCE THISAREALIESENTIRELYWITHINTHEFILTERAREA THEMAIN BEAMCLUTTERFALLSWITHINTHISFILTER ANDALLOTHERFILTERSRECEIVESIDELOBECLUTTER&OURRANGEANNULIAREINTERSECTEDBYTHE MAIN BEAMELLIPSE SOTHEMAIN BEAMCLUTTERINTHISRANGEGATEISTHEVECTORSUMOF THESIGNALSRECEIVEDFROMALLFOURCLUTTERPATCHES/WINGTOTHISHIGHDEGREEOFRANGE FOLDOVER ALLRANGEGATESWILLHAVEAPPROXIMATELYEQUALCLUTTER
&)'52% 0LAN VIEW OF RANGE GATE AND DOPPLER FILTER AREAS 2ADAR ALTITUDE FT VELOCITY KTTORIGHTDIVEANGLE RADARWAVELENGTH CM02& K(ZRANGEGATEWIDTH MS RANGEGATE DOPPLERFILTERATK(ZBANDWIDTH K(ZBEAMWIDTH CIRCULAR MAIN BEAMAZIMUTH DEPRESSIONANGLE
{°£È
2!$!2(!.$"//+
)F THE MAIN BEAM WERE SCANNED IN AZIMUTH WITH THE SAME RADAR PLATFORM KINEMATICS THEMAIN BEAMCLUTTERWOULDSCANINDOPPLERFREQUENCYSOTHATITWOULD APPEARINTHESELECTEDFILTERTENTIMESTWICEFOREACHHYPERBOLICBAND )NBETWEEN THEFILTERWOULDRECEIVESIDELOBECLUTTERFROMALLDARKENEDINTERSECTIONS7ITHTHEUSE OFTHEPROPERCLUTTEROFFSETWHICHWOULDVARYASAFUNCTIONOFMAIN BEAMAZIMUTH ONTHETRANSMITFREQUENCY ASDESCRIBEDIN3ECTION THEDOPPLEROFTHEMAIN BEAM CLUTTERRETURNWILLBEZEROOR$# #LUTTER 2ETURN 'ENERAL %QUATIONS 4HE CLUTTER TO NOISE RATIO FROM A SINGLE CLUTTERPATCHWITHINCREMENTALAREAD!ATARANGE2IS # .
0AV'4 '2 L S D!
P 2 ,# K4S "N
WHERE0AV AVERAGETRANSMITPOWER
'4 TRANSMITGAININPATCHDIRECTION
'2 RECEIVEGAININPATCHDIRECTION
K OPERATINGWAVELENGTH
R CLUTTERBACKSCATTERCOEFFICIENT
,# LOSSESAPPLICABLETOCLUTTER
K "OLTZMANNSCONSTANT r 7(Z+
4S SYSTEMNOISETEMPERATURE +
"N DOPPLERFILTERBANDWIDTH ,# REFERS TO LOSSES THAT APPLY TO DISTRIBUTED SURFACE CLUTTER AS OPPOSED TO DISCRETE RESOLVABLETARGETS4HESELOSSESWILLBEDISCUSSEDIN3ECTION 4HECLUTTER TO NOISERATIOFROMEACHRADARRESOLUTIONCELLISTHEINTEGRALOF%Q OVER THE DOPPLER AND RANGE EXTENT OF EACH OF THE AMBIGUOUS CELL POSITIONS ON THE GROUNDn5NDERCERTAINSIMPLIFIEDCONDITIONS THEINTEGRATIONCANBECLOSED FORM BUTINGENERAL NUMERICINTEGRATIONISREQUIRED -AIN BEAM#LUTTER 4HENETMAIN BEAMCLUTTER TO NOISEPOWERINASINGLERANGE GATEINTHERECEIVERCANBEAPPROXIMATEDFROM%QBYSUBSTITUTINGTHERANGEGATES CS INTERSECTEDAREA COS @ 2PAZ WITHINTHEMAINBEAMONTHEGROUNDFORD!ANDSUM MINGOVERALLAMBIGUITIESOFTHATRANGEGATETHATAREWITHINTHEMAINBEAM '4 '2S # 0AV L QAZ CT
£ . P ,# K4S "N 2 COSA
4HESUMMATIONLIMITSARETHELOWERANDUPPEREDGESINTHEELEVATIONDIMENSIONOFTHE SMALLEROFTHETRANSMITANDRECEIVEBEAMS WHEREPAZ AZIMUTHHALF POWERBEAMWIDTH RADIANS
S COMPRESSEDPULSEWIDTH
@ GRAZINGANGLEATCLUTTERPATCH 4HEREMAININGTERMSAREASDEFINEDFOLLOWING%Q )FTHEMAINBEAMISPOINTEDBELOWTHEHORIZON THEMAIN BEAMCLUTTERSPECTRALWIDTH $FDUETOPLATFORMMOTIONMEASUREDD"DOWNFROMTHEPEAKISAPPROXIMATELY $F
62 L
ª Q " COSF COSQ CT SIN F COSQ ¹ «Q " COSF SINQ º H COSF ¬ »
05,3%$/00,%22!$!2
{°£Ç
WHERE62 RADARGROUNDSPEED
K 2&WAVELENGTH
P" D"ONE WAYANTENNAAZIMUTHBEAMWIDTH RADIANS
E MAIN BEAMDEPRESSIONANGLERELATIVETOLOCALHORIZONTAL RADIANS
P MAIN BEAMAZIMUTHANGLERELATIVETOTHEHORIZONTALVELOCITY RADIANS
S COMPRESSEDPULSEWIDTH
H RADARALTITUDE 7HENTHEMAGNITUDEOFTHEMAIN BEAMAZIMUTHANGLEISGREATERTHANHALFOFTHEAZI MUTHBEAMWIDTH\ Q \ q Q " THEMAIN BEAMCLUTTERPOWERSPECTRALDENSITYCANBE MODELEDWITHAGAUSSIANSHAPEWITHASTANDARDDEVIATIONRC $F -AIN BEAM#LUTTER&ILTERING )NAPULSEDOPPLERRADARUTILIZINGDIGITALSIGNAL PROCESSING MAIN BEAMCLUTTERISREJECTEDBYEITHERACOMBINATIONOFADELAY LINECLUT TERCANCELER-4)FILTER FOLLOWEDBYADOPPLERFILTERBANKORBYAFILTERBANKWITHLOW FILTERSIDELOBES WHICHAREACHIEVEDVIAWEIGHTING)NEITHERCASE THEFILTERSAROUND THEMAIN BEAMCLUTTERAREBLANKEDTOMINIMIZEFALSEALARMSONMAIN BEAMCLUTTER4HIS BLANKEDREGIONINDOPPLERISKNOWNASTHEMAIN BEAMCLUTTERNOTCH 4HE CHOICE BETWEEN THESE OPTIONS IS A TRADE OFF OF QUANTIZATION NOISE AND COM PLEXITYVERSUSTHEFILTER WEIGHTINGLOSS)FACANCELERISUSED FILTERWEIGHTINGCANBE RELAXED OVER THAT WITH A FILTER BANK ALONE SINCE THE CANCELER REDUCES THE DYNAMIC RANGEREQUIREMENTSINTOTHEDOPPLERFILTERBANKIFTHEMAIN BEAMCLUTTERISTHELARGEST SIGNAL 7ITHOUTACANCELER HEAVIERWEIGHTINGISNEEDEDTOREDUCESIDELOBESTOALEVEL SOTHATTHEFILTERRESPONSETOMAIN BEAMCLUTTERISBELOWTHETHERMAL NOISELEVEL4HIS WEIGHTINGINCREASESTHEFILTERNOISEBANDWIDTHANDHENCEINCREASESTHELOSSINSIGNAL TO NOISERATIO #HOOSINGTHEPROPERWEIGHTINGISACOMPROMISEBETWEENREJECTINGMAIN BEAM CLUTTERANDMAXIMIZINGTARGETSIGNAL TO NOISERATIO4ODYNAMICALLYMAKETHISCOM PROMISE THEFILTERWEIGHTINGCANBEADAPTIVETOTHEMAIN BEAMCLUTTERLEVELBYMEA SURINGTHEPEAKRETURNLEVELUSUALLYMAIN BEAMCLUTTER OVERTHE)00S ANDSELECTING ORCOMPUTINGTHEBESTWEIGHTINGTOAPPLYACROSSTHE#0)!NOTHERTECHNIQUETHAT ISAPPLICABLETOHIGH MEDIUMANDHIGH02&ISTOGENERATEAHYBRIDFILTERWEIGHT INGBYCONVOLVINGTWOWEIGHTINGFUNCTIONS4HERESULTISAFILTERWITHSIGNIFICANTLY LESSWEIGHTINGLOSSANDLOWFAR OUTSIDELOBES BUTATACOSTOFRELATIVELYHIGHNEAR INSIDELOBES 4O EVALUATE THE EFFECT OF MAIN BEAM CLUTTER ON TARGET DETECTION PERFORMANCE THE CLUTTER TO NOISE RATIO MUST BE KNOWN FOR EACH FILTER WHERE TARGETS ARE TO BE DETECTED!GENERALMEASURETHATCANBEEASILYAPPLIEDTOSPECIFICCLUTTERLEVELSIS THEIMPROVEMENTFACTOR)7HENUSINGADOPPLERFILTERBANK ASOPPOSEDTOAN-4) FILTER THEIMPROVEMENTFACTORISDEFINEDFOREACHDOPPLERFILTERASTHERATIOOFTHE SIGNAL TO CLUTTER POWER AT THE OUTPUT OF THE DOPPLER FILTER TO THE SIGNAL TO CLUTTER POWERATTHEINPUT4HESIGNALISASSUMEDTOBEATTHECENTEROFTHEDOPPLERFILTER )NCORPORATINGTHEEFFECTOFFILTERWEIGHTING THEIMPROVEMENTFACTORFORADOPPLER FILTERISGIVENBY
) +
§. ¶ ¨£ !N · ©N ¸ . .
£ £ !N !M EXP [ §©P N M S C4 ¶¸ ] COS;P + N M .=
N M
{°£n
WHERE!I
.
RC
+
4
2!$!2(!.$"//+
)00WEIGHT aIa. NUMBEROF)00SIN#0) STANDARDDEVIATIONOFCLUTTERSPECTRUM FILTERNUMBER+ ISTHE$#FILTER INTERPULSEPERIOD
#LUTTER TRANSIENT 3UPPRESSION 7HEN THE 02& IS CHANGED FOR MULTIPLE 02&RANGING THESLOPEISCHANGEDINLINEAR&-RANGING OR THE2&CARRIERIS CHANGED THETRANSIENTCHANGEINTHECLUTTERRETURNMAYCAUSEDEGRADATIONUNLESSITIS PROPERLYHANDLED3INCETHECLUTTERISUSUALLYAMBIGUOUSINRANGEINAPULSEDOPPLER RADAR THECLUTTERPOWERINCREASESATEACHINTERPULSEPERIOD)00 ASCLUTTERRETURNIS RECEIVEDFROMTHEFARTHERAMBIGUITIES UNTILTHEHORIZONISREACHED4HISPHENOMENON ISCALLEDSPACECHARGING.OTETHATALTHOUGHANINCREASINGNUMBEROFCLUTTERRETURNS ARERECEIVEDDURINGTHECHARGINGPERIOD THEVECTORSUMMAYACTUALLYDECREASEOWING TOTHERANDOMPHASERELATIONSOFTHERETURNSFROMDIFFERENTPATCHES )F A CLUTTER CANCELER -4) FILTER IS USED THE OUTPUT CANNOT BEGIN TO SETTLE TO ITS STEADY STATE VALUE UNTIL SPACE CHARGING IS COMPLETE 3OME SETTLING TIME MUST BE ALLOWEDBEFORESIGNALSAREPASSEDTOTHEFILTERBANK4HEREFORE THECOHERENTINTEGRA TIONTIMEAVAILABLEDURINGEACH#0)ISREDUCEDFROMTHETOTAL#0)TIMEBYTHESUMOF THESPACECHARGETIMEANDTHETRANSIENTSETTLINGTIME4HECANCELERSETTLINGTIMECAN BEELIMINATEDBYPRECHARGINGTHECANCELERWITHTHESTEADY STATEINPUTVALUE4HISIS DONEBYCHANGINGTHECANCELERGAINSSOTHATALLDELAYLINESACHIEVETHEIRSTEADY STATE VALUESONTHEFIRST)00OFDATA )FNOCANCELERISUSED SIGNALSCANBEPASSEDTOTHEFILTERBANKAFTERTHESPACECHARGE ISCOMPLETE SOTHATTHECOHERENTINTEGRATIONTIMEISTHETOTAL#0)TIMEMINUSTHESPACE CHARGETIME !LTITUDE LINE#LUTTER"LANKING 4HEREFLECTIONFROMTHEEARTHDIRECTLYBENEATH AN AIRBORNE PULSE RADAR IS CALLED ALTITUDE LINE CLUTTER "ECAUSE OF SPECULAR REFLEC TIONOVERSMOOTHTERRAIN THELARGEGEOMETRICAREA ANDRELATIVELYSHORTRANGE THIS SIGNAL CAN BE LARGE )T LIES WITHIN THE SIDELOBE CLUTTER REGION OF THE PULSE DOPPLER SPECTRUM "ECAUSE IT CAN BE MUCH LARGER THAN DIFFUSE SIDELOBE CLUTTER AND USUALLY HAS A RELATIVELY NARROW SPECTRAL WIDTH ALTITUDE LINE CLUTTER IS OFTEN REMOVED EITHER BY A SPECIAL #&!2 THAT PREVENTS DETECTION OF THE ALTITUDE LINE OR BY A TRACKER BLANKER THATREMOVESTHESEREPORTSFROMTHEFINALOUTPUT)NTHECASEOFTHETRACKER BLANKER ACLOSED LOOPTRACKERISUSEDTOPOSITIONRANGEANDVELOCITYGATESAROUNDTHEALTITUDE RETURNANDBLANKTHEAFFECTEDRANGE DOPPLERREGION.OTETHATATVERYLOWALTITUDES THEANGLESTHATSUBTENDTHEFIRSTRANGEGATEONTHEGROUNDCANBEQUITEBIG ANDTHE SPECTRALWIDTHWIDENS 3IDELOBE#LUTTER 4HEENTIRECLUTTERSPECTRUMCANBECALCULATEDFOREACHRANGE GATEBY%QIFTHEANTENNAPATTERNISKNOWNINTHELOWERHEMISPHERE)NPRELIMINARY SYSTEMDESIGN THEEXACTGAINFUNCTIONMAYNOTBEKNOWN SOONEUSEFULAPPROXIMATION ISTHATTHESIDELOBERADIATIONISISOTROPICWITHACONSTANTGAINOF'3, 3IDELOBE$ISCRETES !NINHERENTCHARACTERISTICOFAIRBORNEPULSEDOPPLERRADARS ISTHATECHOESFROMLARGE RESOLVABLEOBJECTSONTHEGROUNDDISCRETES SUCHASBUILD INGS MAYBERECEIVEDTHROUGHTHEANTENNASIDELOBESANDAPPEARASTHOUGHTHEYWERE
05,3%$/00,%22!$!2
{°£
SMALLER MOVING TARGETS IN THE MAIN BEAM4HIS IS A PARTICULARLY SEVERE PROBLEM IN AMEDIUM 02&RADAR WHEREALL ASPECTTARGETPERFORMANCEISUSUALLYDESIRED SINCE THESERETURNSCOMPETEWITHTARGETSOFINTEREST)NAHIGH 02&RADAR THEREISLITTLEIFANY RANGEREGIONCLEAROFSIDELOBECLUTTER SUCHTHATTHESIDELOBECLUTTERPORTIONOFTHEDOP PLERSPECTRUMISOFTENNOTPROCESSEDSINCETARGETDETECTABILITYISSEVERELYDEGRADEDIN THISREGION &URTHER INAHIGH 02&RADAR ESPECIALLYATHIGHERALTITUDES THERELATIVE AMPLITUDESOFTHEDISTRIBUTEDSIDELOBECLUTTERANDTHEDISCRETERETURNSARESUCHTHATTHE DISCRETESARENOTVISIBLEINTHESIDELOBECLUTTER 4HEAPPARENTRADARCROSSSECTION2#3 RAPP OFASIDELOBEDISCRETEWITHAN2#3 OFRISRAPP R'3, WHERE'3,ISTHESIDELOBEGAINRELATIVETOTHEMAINBEAM4HE LARGER SIZEDISCRETESAPPEARWITHALOWERDENSITYTHANTHESMALLERONES ANDAMODEL COMMONLYASSUMEDATTHEHIGHERRADARFREQUENCIESISSHOWNIN4ABLE4HUS ASA PRACTICALMATTER MDISCRETESARERARELYPRESENT MARESOMETIMESPRESENT AND MAREOFTENPRESENT 4WOMECHANIZATIONSFORDETECTINGANDELIMINATINGFALSEREPORTSFROMSIDELOBEDIS CRETESARETHEGUARDCHANNELANDPOSTDETECTIONSENSITIVITYTIMECONTROL34# 4HESE AREDISCUSSEDINTHEPARAGRAPHSTHATFOLLOW 'UARD#HANNEL 4HEGUARDCHANNELMECHANIZATIONCOMPARESTHEOUTPUTSOF TWO PARALLEL RECEIVING CHANNELS ONE CONNECTED TO THE MAIN ANTENNA AND THE SEC ONDTOAGUARDANTENNATHE3AND'UARDCHANNELIN&IGURE RESPECTIVELY TO DETERMINEWHETHERARECEIVEDSIGNALISINTHEMAINBEAMORTHESIDELOBESn4HE GUARD CHANNEL USES A BROAD BEAM ANTENNA THAT IDEALLY HAS A PATTERN ABOVE THE MAIN ANTENNA SIDELOBES 4HE RETURNS FROM BOTH CHANNELS ARE COMPARED FOR EACH RANGE DOPPLERCELLTHATHADADETECTIONINTHEMAINCHANNEL&ORTHESERANGE DOPPLER CELLS WHENTHEGUARDCHANNELRETURNISGREATERTHANTHATOFTHEMAINCHANNEL THE DETECTIONISREJECTEDBLANKED )FTHEMAINCHANNELRETURNISHIGHER THEDETECTION ISPASSEDON !BLOCKDIAGRAMOFAGUARDCHANNELMECHANIZATIONISSHOWNIN&IGURE!FTER THE#&!2WHICHIDEALLYWOULDBEIDENTICALINBOTHCHANNELS THEREARETHREETHRESH OLDSTHEMAINCHANNEL GUARDCHANNEL ANDMAIN TO GUARD RATIOTHRESHOLDS4HEDETEC TIONLOGICOFTHESETHRESHOLDSISALSOSHOWNIN&IGURE 4HE BLANKING THAT OCCURS BECAUSE OF THE MAINGUARD COMPARISON AFFECTS THE DETECTABILITYINTHEMAINCHANNEL THEEXTENTOFWHICHISAFUNCTIONOFTHETHRESH OLD SETTINGS 4HE THRESHOLD SETTINGS ARE A TRADEOFF BETWEEN FALSE ALARMS DUE TO SIDELOBERETURNSANDDETECTABILITYLOSSINTHEMAINCHANNEL!NEXAMPLEISSHOWN IN &IGURE FOR A NONFLUCTUATING TARGET WHERE THE ORDINATE IS THE PROBABILITY OF DETECTION IN THE FINAL OUTPUT OF THE SIDELOBE BLANKER AND THE ABSCISSA IS THE SIGNAL TO NOISE RATIO 3.2 IN THE MAIN CHANNEL4HE QUANTITY " IS THE RATIO OF THEGUARDCHANNEL3.2TOTHEMAINCHANNEL3.2ANDISILLUSTRATEDIN&IGURE
4!",% $ISCRETE#LUTTER-ODEL
2ADAR#ROSS3ECTIONM
$ENSITYPERSQUAREMILE
#'$
) &&!$
#'$
) &&!$
& &$ !"" $
&$
& &$ !"" $
&$
($
'$ ($
&)'52% 4WO CHANNELSIDELOBEBLANKER
'$ &
&
!%& && ! &$& !
!%& && ! &$& !
'$
! '$ & ! $% !
! ! ! ! % % ! %
&& ! %'& ! && &&
{°Óä 2!$!2(!.$"//+
05,3%$/00,%22!$!2
&)'52% 0ROBABILITYOFDETECTIONVERSUSSIGNAL TO NOISERATIOWITHAGUARDCHANNEL
&)'52% -AINANDGUARDANTENNAPATTERNS
{°Ó£
{°ÓÓ
2!$!2(!.$"//+
"ISSMALLFORATARGETINTHEMAINBEAMANDLARGE D"ORSO FORATARGETATTHE SIDELOBEPEAKS)NTHEEXAMPLESHOWN THEREISAD"DETECTABILITYLOSSDUETO THEGUARDBLANKINGFORTARGETSINTHEMAINBEAM )DEALLY THEGUARDANTENNAGAINPATTERNEXCEEDSTHATOFTHEMAINANTENNAATALLANGLES INSPACEEXCEPTFORTHEMAINBEAM TOMINIMIZEDETECTIONSTHROUGHTHESIDELOBES)F NOT HOWEVER ASILLUSTRATEDIN&IGUREAND&IGURE RETURNSTHROUGHTHESIDELOBE PEAKSOFTHEMAINPATTERNABOVETHEGUARDPATTERNHAVEASIGNIFICANTPROBABILITYOF DETECTIONINTHEMAINCHANNELANDWOULDREPRESENTFALSEDETECTIONS 0OSTDETECTION 34# )N THE AMBIGUITY RESOLUTION AS THE OUTPUT RETURNS ARE RANGE CORRELATED THEY ARE SUBJECTED TO POSTDETECTION 34# OR 2#3 THRESHOLDING APPLIED INSIDE THE RANGE CORRELATION PROCESS 4ARGET RETURNS THAT RANGE CORRELATE INSIDETHE34#RANGE BUTFALLBELOWTHE34#THRESHOLD ARELIKELYSIDELOBEDISCRETES ANDAREBLANKEDORREMOVEDFROMTHECORRELATIONPROCESSANDKEPTFROMGHOSTING WITHOTHERTARGETS 4HEBASICLOGICISSHOWNIN&IGURE"ASICALLY THE#&!2OUTPUTDATAIS CORRELATEDRESOLVED INRANGETHREETIMES%ACHCORRELATORCALCULATESUNAMBIGUOUS RANGEUSING-OUTOFTHE.SETSOFDETECTIONDATAEG THREEDETECTIONSREQUIRED OUTOFEIGHT02&S .ODOPPLERCORRELATIONISUSEDSINCETHEDOPPLERISAMBIGUOUS 4HERESULTSOFTHEFIRSTTWOCORRELATIONSAREUSEDTOBLANKALLOUTPUTSTHATARELIKELY TOBESIDELOBEDISCRETESFROMTHEFINALRANGECORRELATOR(ERE THREERANGECORRELA TORS ARE USED IN WHICH THE FIRST THE ! CORRELATOR RESOLVES THE RANGE AMBIGUITIES WITHINSOMENOMINALRANGE SAY NM BEYONDWHICHSIDELOBEDISCRETESARENOT LIKELY TO BE DETECTED ! SECOND CORRELATOR THE " CORRELATOR RESOLVES THE RANGE AMBIGUITIESOUTTOTHESAMERANGE BUTBEFOREATARGETCANENTERTHE"CORRELATOR ITS AMPLITUDE IS THRESHOLDED BY A RANGE VARYING THRESHOLD THE 34# THRESHOLD !RANGEGATEBYRANGEGATECOMPARISONISMADEOFTHECORRELATIONSINTHE!AND" CORRELATORS ANDIFARANGEGATECORRELATESIN!ANDNOTIN" THATGATEISBLANKED OUT OF THE THIRD CORRELATOR THE # CORRELATOR4HE # CORRELATOR RESOLVES THE RANGE AMBIGUITIESWITHINTHEMAXIMUMRANGEOFINTEREST!NALTERNATIVEMECHANIZATION ISTOREPLACETHERANGE VARYING34#WITHANEQUIVALENT2#3THRESHOLDINSIDETHE RANGECORRELATIONPROCESS4HE2#3ISCOMPUTEDFOREACHPOSSIBLEUNFOLDEDRANGE STARTINGFROMTHESHORTESTRANGE ANDCOMPAREDTOTHE2#3THRESHOLD$ETECTIONS THAT RANGE CORRELATE BUT ARE BELOW THE 2#3 THRESHOLD ARE PREVENTED FROM COR RELATING WITH OTHER DETECTS AND ALL OF THEIR UNFOLDED RANGES ARE ALSO PREVENTED FROMCORRELATING 4HEPRINCIPLEBEHINDTHEPOSTDETECTION34#APPROACHISILLUSTRATEDIN&IGURE WHERETHERETURNOFATARGETINTHEMAINBEAMANDALARGEDISCRETETARGETINTHESIDE LOBESISPLOTTEDVERSUSUNAMBIGUOUSRANGETHATIS AFTERTHERANGEAMBIGUITIESHAVE BEENRESOLVED !LSOSHOWNARETHENORMAL#&!2THRESHOLDANDTHE34#THRESHOLD VERSUS RANGE! DISCRETE RETURN IN THE SIDELOBES IS BELOW THE 34# THRESHOLD AND A RETURNINTHEMAINBEAMISABOVETHETHRESHOLD SUCHTHATTHESIDELOBEDISCRETECANBE RECOGNIZEDANDBLANKEDWITHOUTBLANKINGTHETARGETINTHEMAINBEAM4HE34#ONSET RANGEREPRESENTSTHERANGEATWHICHALARGEDISCRETETARGETINTHESIDELOBESEXCEEDSTHE #&!2THRESHOLD
'+( ,
* *&(
'+( ,
* *&(
* !#* ( ! *!%
* !#* ( ! *!%
$! +&+)
* *!&%)
$! +&+)
* *!&%)
$! +&+)
* *!&%)
+%*!&%&( ( ) &#
% % &# !% & &(( #*!&%
&+**& %) *%
% % &# !% & &(( #*!&% &+**& %) *%
- . / ! & !%- / & !%- /
! - . / #%" * *) % * !(+% &# (% )
% % &# !% & &(( #*!&%& ( $!%!% * *) 05,3%$/00,%22!$!2
&)'52% 3INGLE CHANNELSIDELOBEBLANKERUSINGPOSTDETECTION34#OR2#3THRESHOLDINGTOREMOVESIDELOBEDISCRETES
'+( ,
* *&(
* !#* ( ! *!%
%$! +&+)
* *!&%)+*
{°ÓÎ
{°Ó{
2!$!2(!.$"//+
&)'52% 0OSTDETECTION34#LEVELS
{°ÎÊ 9 , Ê Ê-/ /9Ê , +1, /$OPPLER PROCESSING SEPARATES MOVING TARGETS FROM CLUTTER AND ALLOWS THEM TO BE DETECTEDWHILEONLYCOMPETINGAGAINSTTHERMALNOISE ASSUMINGTHATTHETARGETSHAVE SUFFICIENTRADIALVELOCITY 62K ANDTHE02&ISHIGHENOUGHFORANUNAMBIGUOUS CLUTTERSPECTRUM#OHERENCE THECONSISTENCYOFPHASEOFASIGNALSCARRIERFREQUENCY FROMONEPULSETOTHENEXT ISCRUCIALFORDOPPLERPROCESSING7ITHOUTCAREFULSYSTEM DESIGN AMPLITUDE AND PHASE INSTABILITIES DURING THE COHERENT INTEGRATION TIME WILL BROADENTHEMAIN BEAMCLUTTERSPECTRUMANDRAISETHENOISEFLOORTHATCLUTTER FREETAR GETS MUST COMPETE WITH FOR DETECTION .ONLINEARITIES IN THE SYSTEM CAN ALSO CAUSE DISCRETESPURIOUSSPECTRALSIGNALSTHATCANBEMISTAKENASTARGETS4HEINSTANTANEOUS DYNAMICRANGEOFTHESYSTEMGOVERNSTHESYSTEMLINEARITYANDHENCESENSITIVITYINA STRONGCLUTTERENVIRONMENT4HEDRIVINGFACTORUPONSTABILITYREQUIREMENTSISWHENTHE MAIN BEAMCLUTTERLEVELISATTHESATURATIONPOINTOFTHERECEIVER $YNAMIC2ANGE $YNAMICRANGE ASDISCUSSEDHERE CANBEREFERREDTOASINSTAN TANEOUSDYNAMICRANGEANDISTHELINEARREGIONABOVETHERMALNOISEOVERWHICHTHE RECEIVERANDSIGNALPROCESSOROPERATEBEFOREANYSATURATIONCLIPPING ORGAINLIMITING OCCURS)FSATURATIONSOCCUR SPURIOUSSIGNALSTHATDEGRADEPERFORMANCEMAYBEGENER ATED &OR EXAMPLE IF MAIN BEAM CLUTTER SATURATES SPURIOUS FREQUENCIES CAN APPEAR INTHEDOPPLERPASSBANDNORMALLYCLEAROFMAIN BEAMCLUTTER ANDTHISMAYGENERATE FALSE TARGETREPORTS!NAUTOMATICGAINCONTROL!'# FUNCTIONISOFTENEMPLOYEDTO PREVENTSATURATIONSONEITHERMAIN BEAMCLUTTERINSEARCHORTHETARGETIN3INGLE 4ARGET 4RACK MODE (OWEVER THE USE OF!'# DEGRADES THE SYSTEMS SENSITIVITY SO LARGE
05,3%$/00,%22!$!2
{°Óx
INSTANTANEOUSDYNAMICRANGEISPREFERABLE)FSATURATIONSOCCURINARANGEGATEDURING ANINTEGRATIONPERIOD ANOPTIONINAMULTIPLE RANGEGATEDSYSTEMISSIMPLYTOBLANK DETECTIONREPORTSFROMTHATGATE7HENA-4)FILTERISNOTUSED THEDOPPLERFILTERBANK FOR EACH RANGE GATE CAN BE EXAMINED TO DETERMINE IF THERE ARE ANY DETECTIONS DUE TOSPURIOUSSIGNALSFROMLARGECLUTTER WITHSUBSEQUENTEDITINGOFTHESEDETECTIONSIF THEMEASUREDCLUTTER TO NOISERATIOEXCEEDSTHEDYNAMICRANGE3IMILARLOGICCANBE APPLIEDTOSATURATEDRANGEGATESTODETERMINEIFTHELARGESTSIGNALINTHEFILTERBANKIS INTHEPASSBANDORREPRESENTSSATURATEDCLUTTERRETURNS3ATURATEDRETURNSWITHTHEPEAK SIGNALINTHEDOPPLERPASSBANDCANREPRESENTVALIDTARGETSATSHORTRANGESANDNEEDNOT BESUBJECTEDTOTHESIDELOBEBLANKINGLOGIC 4HEMOSTSTRESSINGDYNAMIC RANGEREQUIREMENTISDUETOMAIN BEAMCLUTTERWHEN SEARCHINGFORASMALL LOW FLYINGTARGETS(ERE FULLSENSITIVITYMUSTBEMAINTAINEDIN THEPRESENCEOFTHECLUTTERTOMAXIMIZETHEPROBABILITYOFDETECTINGTHETARGET 4HEDYNAMIC RANGEREQUIREMENTOFAPULSEDOPPLERRADAR ASDETERMINEDBYMAIN BEAMCLUTTER ISAFUNCTIONNOTONLYOFTHEBASICRADARPARAMETERSSUCHASPOWER ANTENNA GAIN ETC BUTOFRADARALTITUDEABOVETHETERRAINANDTHERADARCROSSSECTION2#3 OF LOW FLYINGTARGETS!SANEXAMPLE &IGURESHOWSTHEMAXIMUMCLUTTER TO NOISE RATIO#.MAX THATAPPEARSINTHEAMBIGUOUS RANGEINTERVAL IE AFTERRANGEFOLDING FOR AMEDIUM 02&RADARASAFUNCTIONOFRADARALTITUDEANDTHERANGEOFTHEINTERSECTIONOF THEPEAKOFTHEMAIN BEAMWITHTHEGROUND.OTETHATTHECLUTTER TO NOISERATIOISARMS POWERRATIOMEASUREDATTHE!$CONVERTER!PEAKPOWERRATIOWOULDBED"HIGHER
&)'52% $YNAMIC RANGEEXAMPLE
{°ÓÈ
2!$!2(!.$"//+
4HEAMPLITUDEOFCLUTTERRETURNSFLUCTUATEOVERTIMEANDAREMODELEDASASTOCHASTIC PROCESS4HECLUTTER TO NOISERATIOREPRESENTSTHEMEANVALUEOFTHISPROCESSOVERTIME &IGUREASSUMESAPENCIL BEAMANTENNAPATTERNANDACONSTANT GAMMAMODELFOR CLUTTERREFLECTIVITY4HEANTENNABEAMISPOINTEDATTHEGROUNDCORRESPONDINGTOTHE RANGEOFTHETARGET!TLONGERRANGESSMALLLOOK DOWNANGLES CLUTTERDECREASESWITH INCREASINGRADARALTITUDESINCERANGEFOLDINGISLESSSEVEREOWINGTOLESSOFTHEMAIN BEAMINTERSECTINGTHEGROUND!TSHORTERRANGES CLUTTERINCREASESWITHRADARALTITUDE SINCETHECLUTTERPATCHSIZEONTHEGROUNDINCREASES7HILE&IGUREISFORAMEDIUM 02&RADAR SIMILARCURVESRESULTFORAHIGH 02&RADAR !LSOSHOWNIN&IGUREISTHESINGLE SCANPROBABILITYOFDETECTION0DVERSUS RANGE FOR A GIVEN 2#3 TARGET IN A RECEIVER WITH UNLIMITED DYNAMIC RANGE )F IT IS DESIREDTOHAVETHELOW FLYINGTARGETREACHATLEAST SAY AN0DBEFOREANYGAIN LIMITINGIE THEUSEOF!'# OCCURS THEDYNAMIC RANGEREQUIREMENTISDRIVENBYTHE MAIN BEAMCLUTTERLEVELS#.MAXOFD"ATFT D"ATFT ANDD"AT FTFORTHISEXAMPLE4HEHIGHERTHEDESIREDPROBABILITYOFDETECTIONORTHELOWER THERADARALTITUDE THEMOREDYNAMICRANGEISREQUIRED&URTHER IFTHESPECIFIEDTARGET 2#3ISREDUCED THEDYNAMIC RANGEREQUIREMENTFORTHESAMEDESIRED0DINCREASESAS THE0D VERSUS RANGECURVEIN&IGURESHIFTSTOTHELEFT )N A PULSE DOPPLER RADAR USING DIGITAL SIGNAL PROCESSING THE!$ CONVERTERS ARE USUALLYSELECTEDTOHAVEADYNAMICRANGETHATMEETSOREXCEEDSTHEUSABLEDYNAMIC RANGESETBYTHEMAXIMUMCLUTTER TO NOISERATIO#.MAX ANDTHESYSTEMSTABILITY4HE PEAKDYNAMICRANGE DEFINEDASTHEMAXIMUMPEAKSINUSOIDALSIGNALLEVELRELATIVETO THERMSTHERMAL NOISELEVELTHATCANBEPROCESSEDLINEARLY ISRELATEDTOTHENUMBEROF AMPLITUDEBITSINTHE!$CONVERTERBY
¤ . !$ AMP ³ § 3MAX ¶
LOG ¥ ;NOISE= ´ ¨ . · QUANTA µ ¦ © ¸ D"
WHERE ;3MAX.=D" MAXIMUMINPUTPEAKSINUSOIDALLEVELRELATIVETORMSNOISE D"
.!$ AMP N UMBER OF AMPLITUDE BITS NOT INCLUDING SIGN BIT IN THE!$ CONVERTER
;NOISE=QUANTA RMSTHERMAL NOISEVOLTAGELEVELATTHE!$CONVERTER QUANTA 4HERMSTHERMAL NOISEVOLTAGELEVELATTHE!$CONVERTERISGIVENINTERMSOFQUANTA !SINGLEQUANTAREFERSTOAUNITQUANTIZATIONLEVELOFTHE!$CONVERTER &ROMTHERELATIONSHIPDESCRIBEDABOVEANDASSUMINGTHE!$CONVERTERLIMITSTHE DYNAMICRANGE THE!$CONVERTERSIZECANNOWBEDETERMINED!DDITIONALMARGINTO ALLOWFORMAIN BEAMCLUTTERFLUCTUATIONSABOVETHEMEANVALUEALSONEEDSTOBECON SIDERED3INCEMAIN BEAMCLUTTERTIMEFLUCTUATIONSTATISTICSAREHIGHLYDEPENDENTON THETYPEOFCLUTTERBEINGOBSERVED SUCHASSEACLUTTERORCLUTTERFROMANURBANAREA AND AREGENERALLYUNKNOWN AVALUEOFTOD"ABOVETHERMSVALUEISOFTENASSUMED FORTHEMAXIMUMPEAKLEVELTHISALSOINCLUDESTHED"DIFFERENCEBETWEENTHERMS ANDPEAKVALUESOFASINUSOIDALSIGNAL 4HUS THEREQUIREDNUMBEROFAMPLITUDEBITSIN THE!$CONVERTERASDETERMINEDBYTHEMAIN BEAMCLUTTERIS §;# . = § ¶¶ MAX D" ;FLUCT?MARGIN=D" LOG ©;NOISE=QUANTA ¸ . !$ AMP q #%), ¨ · ¨ · © ¸
05,3%$/00,%22!$!2
{°ÓÇ
WHERE#%),X ISTHESMALLESTINTEGERqX4HEINSTANTANEOUSDYNAMICRANGESUPPORTED BYAN!$CONVERTERIMPROVESABOUTD"PERBIT &ORTHEEXAMPLECITEDIN&IGURE WHERETHEMAXIMUM#.ISD"ATA FT RADARALTITUDEANDWITHAFLUCTUATIONMARGINOFD"ANDTHERMALNOISEATQUANTA D" THE!$CONVERTERREQUIRESATLEASTAMPLITUDEBITSPLUSASIGNBITFORATOTAL OF BITS TO ACHIEVE THE PEAK!$ DYNAMIC RANGE OF D"4HE UPPER PORTION OF &IGUREILLUSTRATESTHISCASE4HELOWERPORTIONOF&IGUREWILLBEUSEDINTHE STABILITYDISCUSSIONTOFOLLOW 3TABILITY 4O ACHIEVE THE THEORETICAL CLUTTER REJECTION AND TARGET DETECTION AND TRACKINGPERFORMANCEOFAPULSEDOPPLERSYSTEM THEREFERENCEFREQUENCIES TIMINGSIG NALS ANDSIGNALPROCESSINGCIRCUITRYMUSTBEEXTREMELYSTABLEn)NMOSTCASES THE MAJORCONCERNISWITHSHORT TERMRATHERTHANLONG TERMSTABILITY,ONG TERMSTABILITY MAINLYAFFECTSVELOCITYORRANGEACCURACYORSPURIOUSSIGNALSDUETO02&HARMONICS BUTISRELATIVELYEASYTOMAKEADEQUATE3HORT TERMSTABILITYREFERSTOVARIATIONSWITHIN THEROUND TRIPRADARECHOTIMEORDURINGTHESIGNALCOHERENTINTEGRATIONTIME4HEMOST SEVERESTABILITYREQUIREMENTSRELATETOTHEGENERATIONOFSPURIOUSMODULATIONSIDEBANDS ONTHEMAIN BEAMCLUTTER WHICHRAISETHESYSTEMNOISEFLOORORCANAPPEARASTARGETSAT THEDETECTORS4HUS THEMAXIMUMRATIOOFMAIN BEAMCLUTTERTOSYSTEMNOISEMEASURED ATTHERECEIVEROUTPUT#. INCLUDINGTHEFLUCTUATIONMARGINASDISCUSSEDABOVE ISTHE PREDOMINANTPARAMETERTHATDETERMINESSTABILITYREQUIREMENTS 4ARGETRETURNSCOMPETEWITHCLUTTERRETURNSANDNOISEFORDETECTION3UPPOSEDESIRED TARGETSHAVESUFFICIENTRADIALSPEEDSOTHATTHEYLIEINTHECLUTTER FREEREGIONOFDOPPLER FREQUENCYWHENAPULSEDOPPLERWAVEFORMISUSED4HESETARGETSNOWHAVETOCOMPETE ONLYWITHSYSTEMNOISE4HISNOISECANBEBOTHADDITIVEANDMULTIPLICATIVE!DDITIVE NOISETENDSTOMASKMULTIPLICATIVENOISEINLOW PERFORMANCERADARS !DDITIVE NOISE SOURCES CAN BE EXTERNAL TO THE RADAR SUCH AS ATMOSPHERIC NOISE SKYTEMPERATURE GROUNDNOISEBLACKBODYRADIATION ANDJAMMERS ORTHEYCANBE INTERNAL SUCHASTHERMALNOISE4HERMALNOISEISALSOKNOWNAS *OHNSONNOISEAND
'
'
" /%$! %
.!$+$ "!%)+)&! # , # * .!$+$!%)+)&! # , # * #+** ( #+ *+*!&% (&&$
' %
' '
* ) &!) &- (
($#&!) * ( !% %* (* !) ( * , #* &*# %* (*!&% !% !) ( * , # '+!( $ %*
&)'52% $YNAMICRANGEANDSTABILITYLEVELS
{°Ón
2!$!2(!.$"//+
GAUSSIANNOISE THELATTERTERMARISINGFROMTHEGAUSSIANSTATISTICSOFITSVOLTAGEPROB ABILITYDENSITYFUNCTION4HERMALNOISEISALWAYSPRESENTINTHERADARRECEIVERANDIS THEULTIMATELIMITONRADARSENSITIVITY4HEABSOLUTELEVELOFADDITIVENOISESOURCESIS DETERMINEDBYTHESOURCEANDITSRELATIONTOTHERADAR0ROPERSYSTEMDESIGNCANREDUCE THERMALNOISETOALEVELWHEREMULTIPLICATIVENOISECANBECOMESIGNIFICANTINLIMITING THERADARSENSITIVITY -ULTIPLICATIVE NOISE IS CHARACTERIZED BY EITHER A TIME VARYING AMPLITUDE AMPLI TUDEMODULATION !- ORATIME VARYINGPHASEPHASEMODULATION 0- ORFREQUENCY MODULATION &- 4HEABSOLUTELEVELDEPENDSONTHESTRENGTHOFTHESIGNALCARRIER ONWHICHTHENOISESOURCEISRIDING-ULTIPLICATIVENOISESOURCESAREFREQUENCYINSTA BILITIES POWERSUPPLYRIPPLEANDNOISE FNOISE TIMINGJITTER ANDUNWANTEDMIXER PRODUCTSDISCRETESORSPURS -ULTIPLICATIVENOISEMODULATESRADARRETURNSBYVARYING THEIRAMPLITUDEORPHASEANDISPRESENTONALLRADARRETURNSBEINGMOSTAPPARENTON LARGERETURNSSUCHASMAIN BEAMCLUTTER4HERESULTINTHESPECTRALDOMAINISSPURIOUS MODULATIONSIDEBANDS2ANDOMMULTIPLICATIVENOISEBROADENSTHESPECTRUMOFTHECAR RIERFREQUENCY$ISCRETEMULTIPLICATIVENOISESOURCESGENERATEDISCRETESPECTRALLINES THATCANCAUSEFALSEALARMS 3YSTEM STABILITY IS CHARACTERIZED BY THE OVERALL TWO WAY TRANSMIT AND RECEIVE COMPOSITESYSTEMFREQUENCYRESPONSE WHICHISTHERETURNOFANONFLUCTUATINGTARGET ASAFUNCTIONOFDOPPLERFREQUENCY3YSTEMFREQUENCYRESPONSESHOULDBEDEFINEDBY THEDOPPLERPASSBAND4HEFOCUSOFTHISSECTIONWILLBETHESTABILITYREQUIREMENTSFOR DOPPLERFREQUENCIESSEPARATEDENOUGHFROMTHECARRIERTOBEOUTSIDETHEGROUNDMOV INGTARGETNOTCH4HECONCERNINTHISREGIONISWHITEPHASENOISE WHICHDETERMINESTHE PHASENOISEFLOOR,OWFREQUENCYIE CLOSERTOTHECARRIER STABILITYISMOREAPPLICABLE TOAIR TO GROUNDPULSEDOPPLERMODESSUCHAS'-4)AND3!2 4HELOCATIONOFANINSTABILITYSOURCEWITHINTHESYSTEMWILLDETERMINEWHETHERITIS IMPARTEDUPONARETURNSIGNALVIATHETRANSMITPATH RECEIVEPATH ORBOTH)NSTABILITIES EITHERONTRANSMITORRECEIVEARECALLEDINDEPENDENT4HOSEIMPOSEDONBOTHTRANSMIT ANDRECEIVEARECOMMON !MPLITUDE INSTABILITIES CAUSED BY!- TEND TO BE CONSIDERED INDEPENDENT SINCE THE ,/S DRIVE THE MIXERS IN THE RECEIVER INTO COMPRESSION!LSO TRANSMITTERS WORK MOSTEFFICIENTLYWHENDRIVENINTOCOMPRESSIONIE WHERETHEPOWERAMPLIFIERISSATU RATEDANDPROVIDESACONSTANTOUTPUTPOWERLEVELREGARDLESSOFSMALLDEVIATIONSONTHE INPUT )NSTABILITIESDUETO0-OFWHICH&-ISASPECIALCASE TENDTODOMINATETHOSE DUETO!-!SSUCH THEFOCUSWILLBEONPHASEDISTURBANCESRANDOMPHASENOISEAND DISCRETESINUSOIDALSIGNALSSPURIOUSSIGNALS 2ANDOM 0HASE .OISE 2ANDOM PHASE NOISE RIDING ON A LARGE SIGNAL CAN MASK WEAKTARGETRETURNS4HEOBJECTISTOSPECIFYSYSTEMPHASENOISESOTHATITISWELLBELOW THE THERMAL NOISE WHEN A LARGE SIGNAL AT THE!$ SATURATION LEVEL IS PRESENT IN THE RECEIVER!SIGNALAT!$SATURATIONISTHELARGESTSIGNALTHATCANBELINEARLYPROCESSED BYTHERADARRECEIVER 4HENTHERADARSENSITIVITYISLIMITEDBYTHERMALNOISEALWAYS PRESENT PLUSASMALLINCREASEINTHETOTALNOISELEVELCAUSEDBYTHEPHASENOISE 4HEPHASENOISEOFOSCILLATORSANDOTHERCOMPONENTSISTYPICALLYSPECIFIEDASTHE MULTIPLICATIVENOISETHATRIDESONACONTINUOUSWAVEFORM OR#7PHASENOISE)NPULSE DOPPLERRADAR TRANSMITGATINGINTERRUPTSTHECONTINUOUSWAVEFORMTOPRODUCEAPULSED WAVEFORM'ATEDPHASENOISEISTHERESULTOFGATING#7PHASENOISE4HESPECTRUMOF APULSEDGATED SIGNALISDIFFERENTFROM#74HERESULTINGNOISE THEGATEDNOISE CAN BEMUCHDIFFERENTFROMTHE#7NOISE ESPECIALLYFORLOWDUTYCYCLEWAVEFORMSAND NOISECLOSETOTHECARRIER)TISPREFERABLETOMAKENOISEMEASUREMENTSONEQUIPMENT
05,3%$/00,%22!$!2
{°Ó
UNDERTHESAMEGATINGCONDITIONSTHATWILLBEUSEDINTHERADARSYSTEM3OMEDEVICES SUCH AS HIGH POWER TRANSMITTERS CANNOT OPERATE CONTINUOUSLY AND ONLY GATED NOISE MEASUREMENTSAREPOSSIBLE4HEGATEDPHASENOISESPECTRUMISTHESUMMATIONOFTHE #7PHASENOISESPECTRUMREPLICASCENTEREDATFREQUENCIESoNF2 WHEREF2ISTHE02& ANDNISANINTEGER4HETOTALGATEDPHASENOISEINTHE02&BANDWIDTHF2EQUALSTHETOTAL #7PHASENOISEINTHETRANSMITPULSEBANDWIDTH)NTERMSOFSTABILITYREQUIREMENTS THE SYSTEMREQUIREMENTSAREDERIVEDUSINGGATEDPHASENOISE WHICHINTURNISCONVERTEDTO A#7VALUEFORSPECIFYINGCOMPONENTSSUCHASOSCILLATORS4HE#7PHASENOISEFLOOR ISSMALLERBYAFACTOROFTHERATIOOFTHE02&TOTHETRANSMITBANDWIDTHWHENTHE#7 PHASENOISEISASSUMEDTOBEWHITE 3ENSITIVITYLOSSDUETOPHASENOISEISQUANTIFIEDBYTHEINCREASEINTHESYSTEMNOISE FLOORINTHEhCLUTTER FREEvDOPPLERFILTERSDUETOTHEPHASENOISESIDEBANDSONALARGE SIGNAL SUCH AS MAIN BEAM CLUTTER 3ENSITIVITY LOSS IS THE AMOUNT BY WHICH THE TOTAL NOISETHERMALPLUSPHASE EXCEEDSTHETHERMALNOISELEVEL ASSHOWNIN%Q! GATEDPHASENOISETOTHERMALNOISERATIOOF D"RESULTSINANAPPROXIMATELYD" SENSITIVITYLOSS4HISASSUMESAWORST CASESCENARIOWITHTHEMAIN BEAMCLUTTERRETURN ATTHE!$SATURATIONLEVEL#!'# DISCUSSEDIN3ECTION ISTYPICALLYUSEDTOREGU LATETHEMEANCLUTTERTOALEVELBELOW!$SATURATIONTYPICALLYBYTHEAMOUNTOFTHE EXPECTEDCLUTTERFLUCTUATIONLEVEL 7ITH#!'# SENSITIVITYLOSSWILLBELESSTHANOR EQUALTOTHECALCULATEDWORST CASEVALUE
¤ 'ATED 0HASE .OISE 0OWER $ENSITY³ ;3ENSITIVITY ,OSS=D" LOG ¥ 4HERMAL .OISE 0OWER $ENSIITY ´µ ¦
4ABLE CONTAINS A CALCULATION OF THE PHASE NOISE FLOOR REQUIREMENTS FOR AN K(Z02&WAVEFORM#LUTTERLEVELSTHATREQUIREA BITSIGNPLUSAMPLITUDE BITS !$CONVERTERAREASSUMED ASSHOWNIN&IGURE4HETRANSMITPULSEDURATION ISMS RESULTINGINATRANSMITPULSEBANDWIDTHOFAPPROXIMATELY-(ZSINCE NOPULSECOMPRESSIONISUSED4HERMSTHERMAL NOISEPOWERISTHETHERMAL NOISEFLOOR WITHINTHERECEIVEPORTIONOF)004HISPOWERLEVELISGIVENINDECIBELSWITHRESPECT TOTHECARRIERAMPLITUDED"C 4HETHERMAL NOISEDENSITYISOBTAINEDBYDIVIDINGTHIS POWERBYTHE02&BANDWIDTH4HEMAXIMUMGATEDPHASENOISEFLOORISSETTOBED" BELOWTHETHERMALNOISEFLOORFORATMOSTAD"SENSITIVITYLOSS4HE#7PHASENOISE FLOORISTHENOBTAINEDBYMULTIPLYINGBYTHE02&TOTRANSMITBANDWIDTHRATIO 4!",% #70HASE.OISE$ENSITY&LOOR#ALCULATION
0ARAMETER 4HERMAL.OISE0OWERAT!$ 02&"ANDWIDTH
6ALUE;D"=
5NITS
D"C
D"(Z
4HERMAL.OISE$ENSITY&LOORAT!$ 0HASE.OISETO4HERMAL.OISE2ATIO
D"C(Z D"
'ATED0HASE.OISE$ENSITY&LOOR 02& TO 4RANSMIT"ANDWIDTH2ATIO
D"C(Z D"
#70HASE.OISE$ENSITY&LOOR
D"C(Z
#OMMENT BIT!$SIGN BITS THERMAL NOISESETATQUANTA K(Z02&WAVEFORM -ARGINFORATMOSTD" SENSITIVITYLOSS -(ZTRANSMITPULSEBANDWIDTH MSPULSEWIDTHWNO0#
{°Îä
2!$!2(!.$"//+
4!",% .OTIONAL3UBSYSTEM0HASE.OISE!LLOCATION
!LLOCATION 3UBSYSTEM
!DJUSTMENTFOR #OMMON3OURCE;D"=
0ERCENTAGE
D"
4RANSMITTER !%XCITER 02ECIVER 3YNCHRONIZER 3YSTEM
2EQUIREMENT;D"C(Z=
4HESYSTEM LEVEL#7PHASENOISEFLOORREQUIREMENT D"C(Z ISALLOCATED TOTHECONTRIBUTINGHARDWAREUNITS4HEPERCENTAGESAREBASEDONEXPERIENCEANDNEGO TIATIONSWITHTHESUBSYSTEMDESIGNERS!POSSIBLEALLOCATIONISPROVIDEDIN4ABLE $ISCRETES 3OMESOURCESOFDISCRETESIDEBANDSARERIPPLEONPOWERSUPPLIESAND THEPICKUPOFDIGITALCLOCKS)TISDESIRABLETOKEEPTHEINTEGRATEDDISCRETESIDEBANDS BELOWNOISEATTHE#&!2INPUTTOPREVENTDETECTINGTHESEDISCRETESANDPRODUCINGFALSE ALARMS!LL COHERENT AND POSTDETECTION INTEGRATION MUST BE ACCOUNTED FOR WHEN WE SPECIFYDISCRETEPHASENOISEREQUIREMENTS #OMMON DISCRETES ARE AFFECTED BY THE TIME DELAY BETWEEN THE PORTION IMPARTED ONTHETRANSMITANDTHATONRECEIVE4HETIME DELAYCHANGESTHECORRELATIONBETWEEN THEPHASEOFTHESPURIOUSMODULATINGFREQUENCYFROMTHETRANSMITPATHWITHTHEPHASE FROMTHERECEIVEPATH4HISCANRELIEVETHECOMMONDISCRETELEVELREQUIREMENTFOR LOW 02&OR-4) WAVEFORMSTHATARERANGEUNAMBIGUOUS(OWEVER FORHIGHLYRANGE AMBIGUOUSMEDIUM 02&ANDHIGH 02&WAVEFORMS THEASSUMPTIONISMADETHATTHE NOISE COMMON TO TRANSMIT AND RECEIVE ADDS NONCOHERENTLY IN THE DOWNCONVERSION PROCESS!SARESULT THECOMMONDISCRETEPOWERINCREASESBYD" 4ABLE PROVIDES THE CALCULATION FOR THE SYSTEM REQUIREMENTS FOR INDEPENDENT ANDCOMMONDISCRETELEVELS!SIN4ABLE AMAXIMUMCLUTTERLEVELREQUIRINGA BIT!$ISASSUMEDANDTHERMSTHERMAL NOISELEVELATTHE!$CONVERTERISSET TOQUANTA4OFORMTHEDOPPLERFILTERS PULSESARECOHERENTLYINTEGRATED 4!",% $ISCRETE,EVEL2EQUIREMENT#ALCULATION
0ARAMETER 4HERMAL.OISE0OWERAT!$ .UMBEROF0ULSES #OHERENTLY)NTEGRATED 4OTAL $OPPER&ILTER7EIGHTING )NTEGRATION .UMBEROF#0)S 'AIN .ONCOHERENTLY )NTEGRATED 4HERMAL.OISE0OWERAT#&!2 $ISCRETETO4HERMAL.OISE-ARGIN )NDEPENDENT$ISCRETE2EQUIREMENT #OMMON$ISCRETE2EQUIREMENT
6ALUE;D"= 5NITS
#OMMENT
D"C BIT!$SIGN BITS THERMALNOISE SETATQUANTA
D"
)00SINTEGRATEDPER#0)
D"
D"$OLPH #HEBYSHEVWEIGHTINGLOSS
D"
0$)OF#0)SPER,OOKLOG.PDI
D"C %FFECTIVENOISELEVELAFTERINTEGRATION
D"
D"C
0ROVIDESLOW0&!DUETODISCRETES
D"C D"LESSTHAN)NDEPENDENT$ISCRETE
05,3%$/00,%22!$!2
{°Î£
4OREDUCEDOPPLERFILTERSIDELOBES AD"$OLPH #HEBYSHEVWEIGHTINGISAPPLIED WHICHREDUCESTHECOHERENTINTEGRATION3.2GAINBYABOUTD"&ORDETECTION THREE#0)SAREINTEGRATEDNONCOHERENTLYVIA0$)FORANAPPROXIMATEINTEGRATIONGAIN IND"OFLOG.0$) ORD"4HISRESULTSINATHERMAL NOISELEVELOF D"C ATTHEDETECTOR!DISCRETETOTHERMAL NOISEMARGINOF D"ISUSEDTOPROVIDEALOW 0&!DUETODISCRETES4HECOMMONDISCRETEREQUIREMENTISMADED"MORESTRINGENT RELATIVETOTHEINDEPENDENTREQUIREMENTASDISCUSSEDABOVE
{°{Ê , Ê Ê "** ,Ê 1/9Ê, -" 1/" -EDIUMANDHIGH MEDIUM02&WAVEFORMSUSUALLYUSEMULTIPLEDISCRETE02&RANGING TORESOLVERANGEAMBIGUITIES WHILELINEAR&-RANGINGISCOMMONLYEMPLOYEDWHEN HIGH 02&WAVEFORMSAREUSED -ULTIPLE $ISCRETE 02& 2ANGING 4HE TECHNIQUES FOR CALCULATING TRUE RANGE FROMSEVERALAMBIGUOUSMEASUREMENTSGENERALLYINVOLVESEQUENTIALMEASUREMENTOF THEAMBIGUOUSRANGEINEACH02& FOLLOWEDBYANUNFOLDINGANDCORRELATIONPROCESS 4HEUNFOLDINGCREATESAVECTOROFPOSSIBLERANGESFOREACHVALIDDETECTIONBYADDINGA SETOFINTEGERS;x+=TIMESTHEUNAMBIGUOUSRANGEINTERVAL
2UNFOLD 2AMBIGUOUS
C ; F2
+=
WHERETHEUNAMBIGUOUSRANGEINTERVAL CF2 WITHC SPEEDOFLIGHTANDF2 02& 4HESETOFINTEGERS;x+=AREREFERREDTOASTHERANGEAMBIGUITYNUMBERS WITH+DETER MINEDBYTHEMAXIMUMRANGEOFINTEREST+ #%),;2MAX F2C= 2ANGECORRELATION OCCURSWHENTHEUNFOLDEDDETECTIONSARESCANNEDANDACORRELATIONWINDOWISAPPLIED ACROSS LOOKS AS SHOWN IN &IGURE )N THIS EXAMPLE THE CORRELATED TARGET RANGE HASANAMBIGUITYNUMBEROFTHTIMEAROUNDECHO ON02& ANDANAMBIGUITY
! " # !% # $ $"
#!%
$ $"! "$! #" !
"
! "
!! #
&)'52% 2ANGECORRELATIONEXAMPLEWITH02&S
{°ÎÓ
2!$!2(!.$"//+
NUMBEROFON02&SAND4HE)00LENGTHSOFTENEXPRESSEDINRANGEGATESPER)00 AREUSUALLYKEPTRELATIVELYPRIMENOCOMMONFACTORSEXCEPTTHENUMBER TOPERMIT UNAMBIGUOUSRANGINGATTHEMAXIMUMPOSSIBLERANGE 4HE LOGIC FOR CORRELATION REQUIRES AT LEAST - DETECTIONS ACROSS THE . 02&S IN A DWELLTODECLAREATARGETREPORTWITH-TYPICALLYqFORMEDIUM ANDHIGH MEDIUM 02&WAVEFORMS 2ANGEGHOSTSOCCURIFTHECORRELATEDRANGEDOESNOTREPRESENTTHE TRUETARGETRANGEANDTYPICALLYOCCURWHENTHEREISMORETHANONEDETECTIONPERLOOK 2ANGEGHOSTSCANALSOOCCURIFATARGETDETECTIONONASINGLELOOKCORRELATEDWITHOTHER DISSIMILARTARGETS ORIFMULTIPLERANGECORRELATIONSOCCURREDONASETOFDETECTIONS CORRESPONDINGTOASINGLEUNIQUETARGETIE MULTIPLEUNFOLDEDRANGESFELLWITHINTHE CORRELATIONWINDOW /NE METHOD FOR EFFICIENTLY SCANNING AND CORRELATING THE UNFOLDED DETECTIONS INVOLVES COARSE BINNING AS SHOWN IN &IGURE (ERE AMBIGUOUS DETECTIONS ARE FIRST AMPLITUDE CENTROIDED AND THEN UNFOLDED AS DISCUSSED PREVIOUSLY BUT WITH THE RESULTSSTOREDINANARRAYWHOSEELEMENTSARETHECOARSEBINS4HESEBINSHAVEASIZE LESSTHANOREQUALTOTHESHORTEST)00 ANDCORRELATIONINVOLVESSCANNINGIDENTICALBINS ACROSSALLOFTHE02&SINTHEDWELLANDAPPLYINGACORRELATIONWINDOW)NTHEEXAMPLE SHOWNIN&IGURE THEBINSARESETTONINERANGEGATESSHORTEST)00LENGTH ANDTHE FIFTHCOARSEBINCONTAINSDETECTIONSACROSSTHETHREE02&STHATFALLWITHINTHECORRELA TIONWINDOWOFoRANGEGATES"LANK OREMPTY BINSOCCURWHENTHEUNFOLDEDRANGE FALLSOUTSIDEAPARTICULARCOARSEBININTERVAL+EYADVANTAGESTOTHISAPPROACHARETHE ABILITYTOCHANGETHERANGECORRELATIONWINDOWDYNAMICALLYANDPERFORMMOTIONCOM PENSATIONEASILYFORTHERANGECHANGEACROSSTHEDWELLDUETORADARPLATFORMMOTION ANDORTHETARGETSMOTIONIFTHEUNAMBIGUOUSDOPPLERHASBEENRESOLVEDPRIORTOTHIS PROCESS !DDITIONALLY THERANGEGATESIZESDONOTNEEDTOSTAYTHESAMEACROSSTHE SETOF02&SUSEDINTHEDWELLINTHISCASE THEAMBIGUOUSRANGEGATEMEASUREMENTS ONEACHLOOKAREFIRSTCONVERTEDTOCOMMONDISTANCEUNITSEG METERS PRIORTOTHE UNFOLDINGANDSCANNINGCORRELATIONPROCESSES
' (% )'! * & #!,(,*
%'$ #'*( ,)-" ',' (% )'! %%*(,+*# ( #' ! *
()* #'*#/ #** + . +" *"()+ *+
' (% )'! * & #!,(,*
()) %+#('-#' ( '! + *
' (% )'! * & #!,(,*
&)'52% 2ANGECORRELATIONUSINGCOARSEBINNINGONUNFOLDED CENTROIDEDAMBIGUOUSDETECTIONS)N THISEXAMPLE RANGEGATESIZEISTHESAMEFORALLTHREE02&S
05,3%$/00,%22!$!2
{°ÎÎ
!DDITIONALCRITERIACANBEUSEDTOREJECTRANGEGHOSTS SUCHASSELECTINGTHECORRE LATEDRANGEWITHTHEHIGHEST- OF .VALUE SELECTINGTHEDETECTIONSBASEDONTHEMINI MUM VARIANCE ACROSS THE - DETECTIONS OR USING MAXIMUM LIKELIHOOD TECHNIQUES 4HE COMPUTED RADAR CROSS SECTION 2#3 OF CORRELATIONS CAN ALSO BE USED IN THE CORRELATIONPROCESSTOREJECTSIDELOBEDISCRETEDETECTIONSASDESCRIBEDIN3ECTION POSTDETECTION34# 4HEGHOSTINGPROBLEMCANBEMITIGATEDFURTHERBYACOMBINATIONOFDOPPLERANDOR MONOPULSEBINNING2ESOLVINGTHEDOPPLERAMBIGUITIESFIRSTPRIORTORANGECORRELA TION WILLREDUCETHESETOFDETECTIONSTOTHOSEWITHINTHEDOPPLERCORRELATIONWINDOW &ORCASESWHERETHISISNOTFEASIBLEGENERALLYTHELOWERMEDIUM02&S UTILIZINGBOTH RANGEANDDOPPLERCORRELATIONWILLREDUCEGHOSTS5SINGMONOPULSEMEASUREMENTSTO SEGREGATEANDBINTARGETSTHATAREDISTINGUISHABLEINANGLECANALSOREDUCEGHOSTING WHENTHEREAREASIGNIFICANTNUMBEROFDETECTIONSINADWELL !TYPICALMEDIUM ORHIGH MEDIUM 02&PULSEDOPPLERWAVEFORMCYCLESTHROUGH .UNIQUE02&SINAPROCESSINGDWELL.TYPICALLYBEINGTO 4HEMEDIUM02&S GENERALLYCOVERNEARLYANOCTAVEINFREQUENCYFORGOODDOPPLERVISIBILITYANDGROUND MOVINGTARGETREJECTION(OWEVER HIGH MEDIUM02&SHAVEINHERENTLYGOODDOPPLER VISIBILITYSINCETHEYAREAMBIGUOUSINSIGNONLY SOTHESPANOFTHE02&SINASETOF .02&SISUSUALLYMUCHLESSTHANANOCTAVE!DDITIONALCONSTRAINTSON02&SELECTION FORBOTHWAVEFORMSINCLUDEGOODVISIBILITYINSIDELOBECLUTTERWHERESOME02&SMAY BEOBSCUREDBYCLUTTERINPORTIONSOFTHEAMBIGUOUSRANGEINTERVAL ANDMINIMIZATION OFGHOSTSINTHEAMBIGUITYRESOLUTIONPROCESSING $OPPLER!MBIGUITY2ESOLUTION 2ESOLUTIONOFTHEUNAMBIGUOUSDOPPLER VELOCITY ISNEEDEDFORMEDIUM 02&WAVEFORMS ANDITISGENERALLYDONEWITHASIMILARUNFOLDING ANDCORRELATIONTECHNIQUE ASDESCRIBEDPREVIOUSLYFORRANGEAMBIGUITIES!SSHOWNIN &IGURE VELOCITYUNFOLDINGOFDETECTIONSINVOLVESADDINGASETOFSIGNEDINTEGERS
! # !$
!$
" " # $ !
&)'52% $OPPLER VELOCITYCORRELATIONPERFORMEDONTWODETECTIONSACROSSTWOLOOKS!MBIGUOUS DETECTIONSAREUNFOLDEDOUTTOAMAXIMUMPOSITIVEANDNEGATIVEVELOCITY
{°Î{
2!$!2(!.$"//+
TIMESTHE02&VELOCITYFIRSTBLINDSPEED TOEACHMEASUREDAMBIGUOUSRADIALVELOCITY ASFOLLOWS
6UNFOLD
F2 L ¤ &CENTROID ; * ¥¦ . &&4
³ + =´ µ
WHERE F2K IS THE FIRST BLIND SPEED 02& VELOCITY &CENTROID IS THE AMPLITUDE CEN TROIDEDDOPPLERFILTERNUMBER .&&4ISTHENUMBEROFFILTERSINTHEDOPPLERFILTERBANK AND; *xx+=REPRESENTSTHESETOFDOPPLERAMBIGUITYNUMBERSCOVERINGTHE MAXIMUM NEGATIVE AND POSITIVE DOPPLER VELOCITIES FOR THE TARGETS OF INTEREST &OR CASESWHERETHEREAREONLYAFEWAMBIGUITIESINDOPPLER DOPPLERCORRELATIONMAYBE PERFORMEDPRIORTOORINCONJUNCTIONWITHRANGECORRELATIONTOMINIMIZEGHOSTING (IGH 02&2ANGING 2ANGE AMBIGUITYRESOLUTIONINHIGH02&ISPERFORMEDBY MODULATINGTHETRANSMITTEDSIGNALANDOBSERVINGTHEPHASESHIFTOFTHEMODULATION ONTHERETURNECHO-ODULATION METHODS INCLUDE VARYING THE 02& EITHER CONTINU OUSLY OR IN DISCRETE STEPS VARYING THE 2& CARRIER WITH EITHER LINEAR OR SINUSOIDAL &- OR SOME FORM OF PULSE MODULATION SUCH AS PULSE WIDTH MODULATION 07- PULSE POSITIONMODULATION00- ORPULSE AMPLITUDEMODULATION0!- /FTHESE MODULATIONTECHNIQUES 07-AND00-MAYHAVELARGEERRORSBECAUSEOFCLIPPING OFTHERECEIVEDMODULATIONBYECLIPSINGORSTRADDLINGDISCUSSEDIN3ECTION AND 0!-ISDIFFICULTTOMECHANIZEINBOTHTHETRANSMITTERANDTHERECEIVER#ONSEQUENTLY THEYWILLNOTBEFURTHERCONSIDEREDHERE ,INEAR #ARRIER&- ,INEARFREQUENCYMODULATION&- OFTHECARRIERCANBEUSED TOMEASURERANGE4HEMODULATIONANDDEMODULATIONTOOBTAINRANGEARETHESAMEAS USEDINFREQUENCY MODULATEDCONTINUOUS WAVE&- #7 RADAR BUTTHETRANSMISSION REMAINSPULSED 3UPPOSETHEDWELLTIMEISDIVIDEDINTOTWOLOOKS)NTHEFIRSTLOOK NO&-ISAPPLIED AND THE DOPPLER SHIFT OF THE TARGET IS MEASURED )N THE SECOND LOOK THE TRANSMITTER FREQUENCYISVARIEDLINEARLYATARATE F INONEDIRECTIONIE INCREASINGORDECREASING INFREQUENCY $URINGTHEROUNDTRIPTIMETOTHETARGET THELOCALOSCILLATORHASCHANGED FREQUENCYSOTHETARGETRETURNHASAFREQUENCYSHIFT INADDITIONTOTHEDOPPLERSHIFT THAT ISPROPORTIONALTORANGE4HEDIFFERENCEINTHEFREQUENCY$FOFTHETARGETRETURNBETWEEN THETWOLOOKSISFOUND ANDTHETARGETRANGECALCULATEDFROM
2
C$F
F
4HEPROBLEMWITHONLYTWO&-SEGMENTSDURINGADWELLISTHAT WITHMORETHANA SINGLETARGETINTHEANTENNABEAMWIDTH RANGEGHOSTSRESULT&OREXAMPLE WITHTWOTAR GETSPRESENTATDIFFERENTDOPPLERS THETWOFREQUENCIESOBSERVEDDURINGTHE&-PERIOD CANNOTBEUNAMBIGUOUSLYPAIREDWITHTHETWOFREQUENCIESOBSERVEDDURINGTHENO &- PERIOD4OMITIGATETHISPROBLEM ATHREE SEGMENTSCHEMEISUSEDWITHTHEFOLLOWING SEGMENTSNO &- &- UP AND&- DOWN4HERANGEISFOUNDBYSELECTINGRETURNSFROM EACHOFTHETHREESEGMENTSTHATSATISFYTHERELATIONS
F F F
F F F
05,3%$/00,%22!$!2
{°Îx
4!",% 4HREE SLOPE&-2ANGING%XAMPLE
4HEREARETWOTARGETS !AND"&-SLOPE -(ZS 4ARGET
!
"
2ANGENMI $OPPLERFREQUENCYK(Z &-SHIFTK(Z
/BSERVED&REQUENCIES F NO&-K(Z F &-UPK(Z F &-DOWNK(Z
0OSSIBLESETSTHATSATISFYTHERELATIONSSHOWNIN%QAND%QARE F
F
F
F
F F
4ARGET
2ANGENMI
9ES .O .O 9ES
WHERE F F AND F ARE THE FREQUENCIES OBSERVED DURING THE NO &- &- UP AND &- DOWNSEGMENTS RESPECTIVELY4HERANGETHENISFOUNDFROM%Q WHERE
$F F F
OR F F OR
F F
!NEXAMPLEISSHOWNIN4ABLE )FMORETHANTWOTARGETSAREENCOUNTEREDDURINGADWELLTIME GHOSTSAGAINRESULT AS ONLY. SIMULTANEOUSLYDETECTEDTARGETSCANBERESOLVEDGHOST FREEWHERE.ISTHE NUMBEROF&-SLOPES(OWEVER THISPROBLEMISNOTSEVEREINPRACTICE SINCEMULTIPLE TARGETSINASINGLEBEAMWIDTHAREUSUALLYATRANSIENTPHENOMENON 4HEACCURACYOFTHERANGEMEASUREMENTIMPROVESASTHE&-SLOPEINCREASESSINCE THEOBSERVEDFREQUENCYDIFFERENCESCANBEMOREACCURATELYMEASURED4HE&-SLOPEIS HOWEVER LIMITEDBYCLUTTER SPREADINGCONSIDERATIONS SINCEDURINGTHE&-PERIODS THE CLUTTERISSMEAREDINFREQUENCYANDCANAPPEARINFREQUENCYREGIONSNORMALLYCLEAROF CLUTTER!NO &- &- UP DOUBLE&- UPSCHEMEISRECOMMENDEDTOPREVENTDESIRED TARGETSFROMCOMPETINGWITHMAIN BEAMCLUTTER2ANGEACCURACIESONTHEORDEROFOR MILESCANBEREASONABLYACHIEVED
{°xÊ " Ê Ê76 ", Ê - -ODERNMULTIFUNCTIONPULSEDOPPLERRADARSUTILIZEVARIOUSMODESTOACCOMPLISHTASKS SUCHASSEARCHANDTRACK%ACHMODEUSESCERTAINWAVEFORMSOPTIMIZEDFORTHEDETEC TIONANDMEASUREMENTOFVARIOUSTARGETCHARACTERISTICS &OREXAMPLE THERADAROPERATORMIGHTSELECTASEARCHMODEANDSPECIFYASEARCH VOLUME THAT THE RADAR WILL RASTER SCAN AS SHOWN IN &IGURE 6ALID DETECTIONS IN SEARCH ARE THEN CONVERTED TO TRACKS IN THE RADAR COMPUTER4HESE TRACKS NEED TO BE UPDATEDBYATRACKMODEONAREGULARBASISDEPENDINGONTHETRACKACCURACYREQUIRED (IGHTRACKACCURACYISNEEDEDFORTHREATENINGTARGETSORTHOSETHATNEEDAFIRECONTROL
{°ÎÈ
2!$!2(!.$"//+
SOLUTIONINORDERTOENGAGE ASOPPOSEDTONONTHREATENINGTARGETSWHEREAGENERALSITU ATIONALAWARENESSISSUFFICIENTANDHIGHACCURACYISNOTREQUIRED 3EARCH 4HETWOPRIMARYSEARCHMODESARE!UTONOMOUS3EARCHAND#UED3EARCH )N!UTONOMOUS3EARCHTHEOPERATORSELECTSARANGE AZIMUTH ANDELEVATIONCOVERAGE ANDTHERADARSEARCHESEACHBEAMPOSITIONTHATCOVERSTHISVOLUMEONCEPERFRAME4HE TIMEITTAKESTOCOMPLETEAFRAMEISKNOWNASTHEREVISITORFRAMETIME4HEFRAMETIME SHOULDBEMINIMIZEDTOENHANCETHECUMULATIVEPROBABILITYOFDETECTIONOFTARGETS -ODERNRADARSYSTEMSCANTAKEADVANTAGEOFON ANDOFF BOARDCUESTOINCREASE THEPROBABILITYOFACQUIRINGATARGETUSING#UED3EARCH!#UED3EARCHMODEADJUSTS THE SEARCH VOLUME AND WAVEFORM SELECTION ACCORDING TO THE ACCURACY OF THE CUES PARAMETERS 2ADARSWITHELECTRONICALLYSCANNEDARRAY%3! ANTENNASCANINTERLEAVEOTHERFUNC TIONSTRACKUPDATES #UED3EARCH CALIBRATIONS ETC WITH!UTONOMOUS3EARCH4HE RADARCOMPUTERSRESOURCEMANAGERMUSTENSURETHATTHEMAXIMUMFRAMETIMEISNOT EXCEEDEDWITHTHEINCLUSIONOFTHESEOTHERFUNCTIONSDURINGASEARCHFRAME &OR AIRBORNE PULSE DOPPLER RADARS !UTONOMOUS 3EARCH CAN HAVE TWO SUBMODES &ORWARD ASPECT AND !LL ASPECT 3EARCH &ORWARD ASPECT 3EARCH IS DESIGNED TO DETECT HEAD ONENGAGEMENTTARGETSWITHHIGHCLOSINGSPEEDSTHATARENOTCOMPETINGAGAINST MAIN BEAMORSIDELOBECLUTTER&ORWARD ASPECT3EARCHUSESHIGH DUTYHIGH 02&WAVE FORMSTOMAXIMIZETHEENERGYONTARGETANDPROVIDELONGDETECTIONRANGE&ORWARD ASPECT3EARCHWAVEFORMSINCLUDE6ELOCITY3EARCH63 (IGH 02&2ANGE 7HILE 3EARCH (273 AND!LERT#ONFIRM!LL ASPECT3EARCHCANBEEITHERASINGLEHIGH MEDIUM02& WAVEFORMTHATHASACCEPTABLEPERFORMANCEFORTARGETSTHATARECOMPETINGWITHSIDELOBE CLUTTER ORTHECOMBINATIONOF&ORWARD ASPECT3EARCHHIGH 02&WAVEFORMSINTERLEAVED WITHMEDIUM 02&WAVEFORMSDESIGNEDTODETECTTARGETSCOMPETINGWITHSIDELOBECLUT TER SUCHAS-EDIUM 02&2ANGE7HILE3EARCH-273 6ELOCITY3EARCH 63ISAHIGH 02&SEARCHWAVEFORMTHATMEASURESDOPPLERFRE QUENCYUNAMBIGUOUSLYWITHTHEPOSSIBLEEXCEPTIONOFSENSE BUTDOESNOTMEASURE RANGE4HISISTHECLASSICHIGH 02&WAVEFORM4HETRANSMITDUTYCYCLEISMAXIMIZED TOINCREASEDETECTIONRANGE4HERECEIVERMAYBERANGEGATEDTOMATCHTHEBANDWIDTH OFTHETRANSMITWAVEFORM BUTRANGEMEASUREMENTISNOTATTEMPTED !63DWELLWILLCONSISTOFASINGLELOOKATAGIVEN02&4HECOHERENTINTEGRATION TIMEISMAXIMIZEDWITHINTHELIMITSOFTHEMAXIMUMEXPECTEDTARGETRADIALACCELERATION 63ISOPTIMIZEDFOR3WERLING)AND)))TARGETAMPLITUDEFLUCTUATIONSTATISTICSANDTHE CUMULATIVEPROBABILITYOFDETECTIONOFINCOMINGTARGETSOVERSEVERALSEARCHFRAMES (IGH 02& 2ANGE 7HILE 3EARCH ,IKE 63 (273 IS A HIGH 02& WAVEFORM (OWEVER LINEAR CARRIER&-RANGINGISUSEDTOOBTAINARANGEMEASUREMENT ASDESCRIBED IN3ECTION4HISRANGEMEASUREMENTCOMESATTHEEXPENSEOFFRAMETIMEWITHTHE ADDITIONOFVARIOUS&-SLOPESFOREACHDWELL4HEACCURACYOFTHISRANGEMEASUREMENT ISDEPENDENTUPONTHELINEAR&-RANGINGSLOPES !LERT#ONFIRM 4HEBEAMAGILITYOF%3! BASEDRADARSALLOWSTHEUSEOFSEQUEN TIAL DETECTION TECHNIQUES! SIMPLIFICATION OF SUCH TECHNIQUES IS KNOWN AS!LERT #ONFIRM 4HEGOALOF!LERT#ONFIRMISTOPROVIDEHIGHSENSITIVITYWHILEMANAGING FALSEALARMSANDMINIMIZINGTHESEARCHFRAMETIME"YTRANSMITTINGALONGER#ONFIRM DWELL FOR RANGING ONLY AT BEAM POSITIONS WHERE A SHORTER DWELL !LERT HAS DETECTED
05,3%$/00,%22!$!2
{°ÎÇ
TARGETS !LERT#ONFIRMPROVIDESTHERANGEMEASUREMENTOFCLASSIC(273WAVEFORMS WITHOUTTHEFRAMETIMEEXPENSEOFTRANSMITTINGLINEAR&-RANGINGDWELLSEVERYBEAM POSITION4HE#ONFIRMDWELLCANALSOBEUSEDTOCONTROLFALSEALARMS PERMITTINGTHE !LERTDWELLTOBEMORESENSITIVETHANCLASSIC63 4HE!LERTPHASEISUSEDTOSEARCHEACHBEAMPOSITIONOFTHEFRAMEFORTHEPRESENCE OFATARGET!63WAVEFORMISUSEDWITHALOWDETECTIONTHRESHOLDANDACORRESPONDING FALSEALARMTIMEONTHEORDEROFAFEWSECONDS4HELOWERDETECTIONTHRESHOLDINCREASES SENSITIVITY7HENAN!LERTDWELLDECLARESADETECTION A#ONFIRMDWELLISSCHEDULED FORTHAT!LERTDWELLSBEAMPOSITION)FMONOPULSEMEASUREMENTSAREAVAILABLEONTHE !LERTDETECTION THE#ONFIRMBEAMCANBECENTEREDONTHEDETECTIONTODECREASEBEAM SHAPE LOSS4HE #ONFIRM DWELL IS TYPICALLY A (273 WAVEFORM AND ONLY EXAMINES DOPPLERFILTERSWITHINAWINDOWCENTEREDABOUTTHEFILTEROFTHE!LERTDETECTIONCUE4HE #ONFIRMDWELLMUSTPRODUCEADETECTIONCORRESPONDINGTOTHE!LERTDETECTIONINORDER FORAVALIDDETECTIONDECLARATION4HE#ONFIRMDWELLISUSEDTOMANAGEFALSEALERTS ANDPROVIDEARANGEMEASUREMENTFORTARGETDETECTIONS4HE!LERTAND#ONFIRMDETEC TIONTHRESHOLDSAREDESIGNEDTOACHIEVEOVERALLFALSEALARMTIMEEQUALTOCONVENTIONAL SEARCHONEEVERYFEWMINUTES !LONGWITHUSINGTHESAME02&IN!LERTAND#ONFIRM THETIMEBETWEENTHESEDWELLS ORLATENCY SHOULDBEMINIMIZEDTOPREVENTAVALID!LERT DETECTIONFROMBEINGECLIPSEDDURINGTHE#ONFIRMATIONDWELL ,OW LATENCY ALSO ALLOWS THE USE OF #ORRELATED!LERT#ONFIRM (ERE A 3WERLING )TARGET2#3FLUCTUATIONMODELISASSUMED4HISIMPLIESTHATWHENTHESAME2&CAR RIERFREQUENCYISUSEDFOR!LERTAND#ONFIRM THETARGET2#3WILLBERELATIVELYCONSTANT BETWEEN THE TWO DWELLS PROVIDING ADDITIONAL RANGE ENHANCEMENT IN TERMS OF THE CUMULATIVEPROBABILITYOFDETECTION -EDIUM 02&2ANGE7HILE3EARCH !MEDIUM 02&WAVEFORMISUSEDTODETECT TARGETSCOMPETINGWITHSIDELOBECLUTTERTHATWOULDBEUNDETECTABLEIN(273-273 ALLOWSTHEDETECTIONOFNOSEASPECTTARGETSATWIDESCANANGLESTHATARECROSSINGTHE RADARLINE OF SIGHT SUCHTHATTHEIRLOWCLOSINGVELOCITYPLACESTHEMINSIDELOBECLUT TERANDTAILASPECTTARGETSINLEADPURSUITENGAGEMENTSANATTACKGEOMETRYWHERETHE NOSEOFTHEATTACKINGAIRCRAFTISPOINTEDAHEADOFTHETARGETSPRESENTPOSITION -273 PROVIDESCOMPLETESITUATIONALAWARENESSPERCEPTIONOFTHESURROUNDINGTACTICALENVI RONMENT BUTDOESNOTHAVETHEMAXIMUMDETECTIONRANGEPROVIDEDBYTHEHIGHERDUTY CYCLEOF(273FORTHERMALNOISE LIMITEDTARGETS 4HE -273 WAVEFORM USES - OF . DETECTION PROCESSING A TYPICAL WAVEFORM MIGHTBE OF %ACH-273DWELLISMADEUPOF.LOOKSEACHWITHADIFFERENT02& $ETECTIONISREQUIREDONATLEAST-LOOKSTORESOLVETARGETRANGEANDRANGERATEUNAM BIGUOUSLY4HEDETECTIONTHRESHOLDSARESETTOPROVIDEAPPROXIMATELYONEFALSEALARM PERMINUTE 4HEEFFECTIVENESSOF-273ISDEPENDENTONTHEABILITYTODETECTTARGETSATTHEREQUIRED RANGESWHILESIMULTANEOUSLYREJECTINGDISCRETECLUTTERDETECTIONS,OWTWO WAYANTENNA SIDELOBESALONGWITHTHECOMBINATIONOFTECHNIQUESDISCUSSEDIN3ECTION SUCHAS GUARD CHANNEL BLANKING AND POSTDETECTION 34# ARE USED TO MITIGATE SIDELOBE CLUTTER DISCRETEFALSEALARMS -273ALSOUSESPULSECOMPRESSIONTODECREASETHEAMOUNTOFSIDELOBECLUTTERTHAT TARGETSMUSTCOMPETEWITH4HELOWER02&REDUCESECLIPSINGANDTHEAMOUNTOFCLUT TERRANGE FOLDING4RANSMITCARRIERFREQUENCYDIVERSITYDWELL TO DWELLFORCES3WERLING )AND ))) TARGET FLUCTUATION STATISTICS AND IMPROVES CUMULATIVE PROBABILITY OF DETEC TIONPERFORMANCE&REQUENCYDIVERSITYLOOK TO LOOKWITHINADWELLPRODUCES3WERLING ))AND)6STATISTICSANDISBETTERSUITEDFORHIGHSINGLE SCANPROBABILITYOFDETECTION
{°În
2!$!2(!.$"//+
-273CANALSOBEIMPLEMENTEDWITHAHIGH MEDIUM02& WHICHISCHARACTERIZED BYTHEWAVEFORMSDOPPLERCOVERAGEBEINGUNAMBIGUOUSINDOPPLERMAGNITUDE BUT NOTDOPPLERSENSE FORTHEMAXIMUMTARGETDOPPLEROFINTEREST4HERESULTINGSINGLE BLIND SPEED DUE TO MAIN BEAM CLUTTER PERMITS AS WIDE OF A CLUTTER REJECTION NOTCH ASREQUIREDTOREJECTMAIN BEAMCLUTTERORGROUNDMOVINGTARGETSANDSTILLNOTRESULT INDOPPLERBLINDSPEEDSFORTARGETSOFINTEREST- OF .RANGINGPROVIDESBETTERRANGE MEASUREMENTACCURACYTHANLINEAR&-RANGINGUSEDIN(2734HE02&SUSEDINA DWELL MUST BE CHOSEN TO RESOLVE THE HIGH NUMBER OF RANGE AMBIGUITIES WITHIN THE INSTRUMENTEDRANGE 4RACK 4ARGETTRACKINGISDONEBYMAKINGRANGE RANGERATE ANDAZIMUTHANDELEVA TIONANGLEMEASUREMENTSONTARGETS2ANGEMEASUREMENTSAREOBTAINEDUSINGRANGEGAT INGANDCENTROIDINGONTHETARGETRETURNWITHRANGEAMBIGUITIESBEINGRESOLVEDWITHINTHE TRACKER2ANGERATEIE DOPPLER MEASUREMENTSAREFORMEDWITHACENTROIDONTHETARGETS DOPPLERRETURNINTHEFILTERBANK!NGLEMEASUREMENTSCANBEOBTAINEDUSINGMONOPULSE SEQUENTIALLOBING ORCONICALSCAN WITHMONOPULSEBEINGTHEPROMINENTCHOICEINMOD ERNRADARS4HETRACKERCREATESWINDOWS ORGROUPSOFCONTIGUOUSRANGE DOPPLERCELLS AROUNDEACHOFTHESEMEASUREMENTSINORDERTOASSOCIATEDETECTIONSWITHEXISTINGTRACKS 4HETRACKER USUALLYIMPLEMENTEDWITHANINE STATEPOSITION VELOCITY ANDACCELERATION +ALMANFILTER ESTIMATESTARGETMOTIONINANINERTIALCOORDINATESYSTEM -ULTIPLE 4ARGET 4RACKING -44 CAN BE ACCOMPLISHED IN SEVERAL WAYS /NE METHOD4RACK 7HILE 3CAN OR473 ISTOUSETHENORMALSEARCHMODEWITH&-OR MULTIPLE 02&RANGINGANDSTORETHERANGE ANGLE ANDDOPPLEROFTHEREPORTEDDETEC TIONSINTHERADARCOMPUTER4HESEDETECTIONSARETHENUSEDTOFORMANDUPDATETRACK FILES4HEANTENNASCANSINANORMALSEARCHPATTERN ANDASCAN TO SCANCORRELATIONIS MADEONTHEDETECTIONSTHATUPDATETHETRACKFILES!LTHOUGHTRACKINGACCURACIESARE LESSTHANCANBEACHIEVEDINADEDICATEDSINGLE TARGETTRACK MULTIPLETARGETSCANBE TRACKEDSIMULTANEOUSLYOVERALARGEVOLUMEOFSPACE ! SECOND METHOD OF -ULTIPLE 4ARGET 4RACKING 0AUSE 7HILE 3CAN PARTICULARLY APPLICABLE TO %3! BASED RADARS IS TO SCAN IN A NORMAL SEARCH PATTERN PAUSE ON EACHSEARCHDETECTION ANDENTERA3INGLE 4ARGET4RACKMODEFORABRIEFPERIOD4HE ADVANTAGE IS THAT THE RESULTING RANGE ANGLE AND DOPPLER MEASUREMENTS ARE MORE ACCURATETHANTHOSEMADEWITHASCANNINGANTENNA BUTTHETIMETOSEARCHAVOLUME INSPACEISINCREASED 4RANSITION TO 4RACK OR4RACK!CQUISITION ISUSEDTOCONFIRMSEARCHTARGETDETEC TIONSANDPROVIDEIMPROVEDRANGEACCURACYWHENNEEDED)FTHETARGETISSUCCESSFULLY ACQUIRED ATRACKFILEINTHERADARCOMPUTERISINITIATED4HE4RACK!CQUISITIONWAVE FORMSPARAMETERSDEPENDUPONTHETYPEOFSEARCHWAVEFORMTHATPRODUCEDTHETARGET DETECTION4HE4RACK!CQUISITIONWAVEFORMSTHRESHOLDSARESETTOREJECTFALSEALARMS ANDREDUCETHEFALSETRACKINITIATIONRATETOLESSTHANONEPERHOUR &OR4RACK!CQUISITION A SEARCH DETECTION FROM63 WOULD REQUIRE A (273 WAVE FORMTOOBTAINARANGEMEASUREMENT(273AND!LERT#ONFIRMWAVEFORMSAREFOLLOWED BYRANGEGATEDHIGH 02&DWELLSUSING- ON .RANGINGTOACHIEVETHENECESSARYRANGE ACCURACYFORSINGLE02&TRACKUPDATES4HEUNAMBIGUOUS(273RANGEMEASUREMENTOF THESEARCHDETECTIONISUSEDTOHELPRESOLVETHERANGEAMBIGUITY&OR-273DETECTIONS ANOTHER-273DWELLISUSEDFOR4RACK!CQUISITION/NCETHETRACKFILEISINITIATED SEVERAL RAPIDTRACKUPDATESAREUSEDTOFIRMLYESTABLISHTHETRACK 7HENDOING3INGLE 4ARGET4RACKUPDATES ASINGLE02&WAVEFORMCANBEUSED 4HERANGEANDORDOPPLERAMBIGUITIESARERESOLVEDINSEARCHAND IFNECESSARY INTHE 4RANSITION TO 4RACKPHASE"YUSINGTHEUNAMBIGUOUSRANGEANDVELOCITYPREDICTIONS
05,3%$/00,%22!$!2
{°Î
OFTHETARGETPROVIDEDBYTHETRACKER ASINGLE02&CANBECHOSENSUCHTHATRANGEAND DOPPLERECLIPSINGISAVOIDEDWITHHIGHPROBABILITY4HELENGTHOFTHEDWELLISADAPTED TOPROVIDESUFFICIENTENERGYONTARGETSOTHATITSRETURNSIGNAL TO NOISERATIOWILLPRO VIDE THE NECESSARY MEASUREMENT ACCURACIES REQUIRED BY THE TRACKER 4HIS ADAPTIVE TRACKUPDATEWAVEFORMALLOWSTHESEARCHREVISITTIMETOBEMAINTAINEDWHILETRACKING MULTIPLETARGETS
{°ÈÊ , Ê* ,",
4HERADARRANGEEQUATIONISUSEDTODETERMINETHEPERFORMANCEOFPULSEDOPPLERRADAR 4HERADARRANGEEQUATIONMUSTINCLUDELOSSES BOTHSYSTEMANDENVIRONMENTAL THAT WILLDEGRADETHESTRENGTHOFRETURNSIGNALSATTHEDETECTOR0ROBABILITYOFDETECTION0D DEPENDS ON TARGET SIGNAL TO NOISE RATIO AND PROBABILITY OF FALSE ALARM 0&! WHICH ITSELFISAFUNCTIONOFWAVEFORM4HEFALSEALARMPROBABILITYDETERMINESTHEDETECTION THRESHOLDANDISREFERENCEDTOANINDIVIDUALRANGE DOPPLERCELL4HISPER CELLPROBABIL ITYISDERIVEDFROMTHESPECIFIEDFALSEREPORTTIMEFORTHESYSTEM 2ADAR2ANGE%QUATION )NTHEDOPPLERREGIONWHERETHESIGNALDOESNOTFALLIN CLUTTER PERFORMANCEISLIMITEDONLYBYSYSTEMNOISE4HESIGNAL TO NOISEPOWERRATIO INTHERANGE DOPPLERCELLATTHEDETECTORPRIORTOPOSTDETECTIONINTEGRATIONFORATARGET ATRANGE2ISGIVENBY
¤2 ³ 3.2 ¥ O ´ ¦ 2µ ¤ 0 ' ' L S 4 ³ 2O ¥ AV 4 2 ¦ P K4S "N ,4 ´µ
WHERE 2O RANGEATWHICH3.2ISEQUALTO
R4 TARGETRADARCROSSSECTION
,4 LOSSESAPPLICABLETOTHETARGET 4HEREMAININGTERMSAREASDEFINEDFOLLOWING%Q4HENETLOSS,4USEDTOCOM PUTE3.2FORATARGETISGENERALLYHIGHERTHANTHENETLOSS,#USEDTOCOMPUTE#.2 IN%Q,4INCLUDESLOSSES SUCHASECLIPSINGANDRANGEGATESTRADDLE DOPPLERFILTER STRADDLE #&!2 ANDGUARDBLANKING THATAREAPPLICABLETORESOLVABLETARGETSBUTNOT TODISTRIBUTEDCLUTTER 4HETARGET3.2REPRESENTSTHEENVELOPE ) 1 FORALINEARDETECTOROR) 1 FORASQUARE LAWDETECTOR OFTHETARGETRETURNCOMPAREDTOTHATOFJUSTNOISE4HEENVE LOPEISMEASUREDAFTERTHEENTIRECOHERENTMATCHEDFILTERPROCESSIE TRANSMITPULSE MATCHEDFILTER PULSECOMPRESSION ANDCOHERENTDOPPLERFILTERING 4HEREFORE 3.2IS ASSOCIATEDWITHASINGLE#0) ,OSSES 3OMEOFTHELOSSESINHERENTIN BUTNOTNECESSARILYUNIQUETO PULSEDOP PLERRADARSTHATEMPLOYDIGITALSIGNALPROCESSINGAREDISCUSSEDBELOW3OMEOFTHE LOSSESMAYBEINCORPORATEDINTOTHEOTHERVARIABLESINTHERADARRANGEEQUATION#ARE MUSTBETAKENTOACCOUNTFORALLOFTHESYSTEMLOSSESWHILEAVOIDINGREDUNDANCIES
{°{ä
2!$!2(!.$"//+
-OST FRONT END LOSSES ARE APPLICABLE TO BOTH TARGETS AND CLUTTER ,OSSES APPLICABLE ONLYTOTARGETSWILLBEINDICATED 2&4RANSMIT,OSS 4HISLOSSACCOUNTSFOR2&OHMICLOSSESBETWEENTHETRANSMIT TER OR 2& POWER AMPLIFIER AND THE ANTENNA RADIATOR WHICH CAN INCLUDE LOSSES FROM CONNECTORS CIRCULATORS ANDRADIATINGELEMENTS 2ADOME,OSS -OSTRADARSREQUIREARADOMETOPROTECTTHEANTENNAFROMENVIRON MENTALELEMENTSANDTOCONFORMTOTHEPLATFORMSSHAPE2ADOMESWILLHAVEALOSSTHAT MAYDEPENDONTHESCANANGLEOFTHEANTENNA4HISLOSSMUSTBEACCOUNTEDFORONTRANSMIT ANDRECEIVEIE ATWO WAYLOSS 0ROPAGATION ,OSS 0ROPAGATION THROUGH THE ATMOSPHERE RESULTS IN A LOSS ESPE CIALLYATHIGHERRADARCARRIERFREQUENCIES4HISLOSSISAFUNCTIONOFRANGE ALTITUDE AND WEATHER)TISALSOATWO WAYLOSS0ROPAGATIONLOSSISMOREOFAENVIRONMENTALLOSS THANASYSTEMLOSS BUTCANBEGROUPEDWITHTHEOTHERLOSSESTHATMAKEUPNETLOSSIN THERADARRANGEEQUATION 3CAN,OSS "ROADSIDEELECTRONICALLYSCANNEDARRAYANTENNASARESUBJECTTOREDUC TIONINGAINWHENTHEMAINBEAMISSCANNEDOFFBROADSIDE4HEPROJECTEDAREAOFTHE %3!APERTUREDECREASESASBEAMSCANSFROMBROADSIDE0ROJECTEDAREADROPSASCOSINE OFSCANCONE ANGLE-UTUALCOUPLINGBETWEENRADIATINGELEMENTSFURTHERREDUCESTHE EFFECTIVEAREA3CANLOSSMUSTBEACCOUNTEDFORONTRANSMITANDRECEIVE "EAMSHAPE,OSS 4HISTARGET SPECIFICLOSSACCOUNTSFORTHELOSSINGAINWHENTHE TARGETISNOTLOCATEDATTHEPEAKOFTHEBEAM"EAMSHAPELOSSISDEFINEDASTHEINCREASE INTHEPOWERORTHE3.2REQUIREDTOACHIEVETHESAMEPROBABILITYOFDETECTIONONATAR GETSPREADUNIFORMLYOVERTHESPECIFIEDBEAMCOVERAGEASWOULDOCCURWITHATARGETAT BEAMCENTER"EAMSHAPELOSSISUSEDPRIMARILYINSEARCHDETECTIONRANGEPERFORMANCE CALCULATIONS 2&2ECEIVE,OSS 4HISLOSSISSIMILARTO2&4RANSMIT,OSSEXCEPTITACCOUNTSFOR OHMICLOSSESFROMTHEANTENNAFACETOTHEFIRSTLOW NOISEAMPLIFIER4HISLOSSMAYBE INCLUDEDINTHERECEIVESYSTEMNOISEFIGUREORSYSTEMTEMPERATUREVALUE )&-ATCHED&ILTER,OSS 4HEMATCHEDFILTERFORAPULSEDOPPLERWAVEFORMINCLUDES THEANALOG)&MATCHEDFILTERINTHERECEIVERANDANYSUBSEQUENTDIGITALINTEGRATIONOF !$SAMPLESTOMATCHTHEDURATIONOFTHETRANSMITPULSE)&MATCHEDFILTERLOSSQUANTI FIESHOWWELLTHEANALOG)&MATCHEDFILTERCOMPARESTOTHEIDEALMATCHEDFILTERFORTHAT POINTINTHERECEPTIONCHAIN 1UANTIZATION.OISE,OSS 4HISLOSSISDUETOTHENOISEADDEDBYTHE!$CONVER SIONPROCESSANDTOTRUNCATIONDUETOFINITEWORDLENGTHSINTHESIGNAL PROCESSORTHAT FOLLOW4HISLOSSCANALSOBEINCORPORATEDINTOTHERECEIVERNOISEFIGUREVALUE 0ULSE#OMPRESSION-ISMATCH,OSS 4HISISCAUSEDBYTHEINTENTIONALMISMATCH INGOFTHEPULSECOMPRESSIONFILTERTOREDUCETIMERANGE SIDELOBES %CLIPSINGAND2ANGE'ATE3TRADDLE,OSS 4HELARGEAMOUNTOFRANGEAMBIGUITY INHERENTINPULSEDOPPLERWAVEFORMSRESULTSINTHEPOSSIBLEECLIPSINGOFTARGETRETURNS
05,3%$/00,%22!$!2
{°{£
WHENTHERECEIVERISBLANKEDDURINGPULSETRANSMISSION)NAMULTIPLERANGEGATESYS TEM THERETURNSMAYALSOSTRADDLEGATESREDUCINGTHEPULSEMATCHEDFILTEROUTPUTOF ASINGLEGATE"ECAUSEOFECLIPSINGANDRANGEGATESTRADDLE THEVALUEOF2O GIVENBY %Q MAYFALLANYWHEREBETWEENZEROANDAMAXIMUMVALUE DEPENDINGONTHE EXACTLOCATIONOFTHETARGETRETURNWITHINTHEINTERPULSEPERIOD &IGUREILLUSTRATESTHEEFFECTOFECLIPSINGANDRANGEGATESTRADDLEONTHEOUTPUT OFTHEPULSEMATCHEDFILTEROVERTHE)00%ACHRANGEGATEISASSUMEDTOBEMATCHEDTO THETRANSMITPULSEBANDWIDTH WHICHFORUNMODULATEDPULSESIE NOPULSECOMPRESSION MODULATION ISTHEINVERSEOFTHEPULSEDURATION4HEREFORE REFERRINGTO&IGURE THE GATEWIDTHSGEQUALSTHETRANSMITTEDPULSEST)N&IGURE THE)00ISSG4HEPLOTSON THELEFTREPRESENTARANGEGATESPACINGOFSSEQUALTOSG2ANGEGATESTRADDLELOSSCANBE REDUCEDBYTHEUSEOFOVERLAPPINGGATESATTHEEXPENSEOFEXTRAHARDWAREANDPROCESS ING4HERIGHTMOSTPLOTSREPRESENTTHEUSEOFRANGEGATEOVERLAPSS SG 4HE MAXIMUMPULSEMATCHEDFILTEROUTPUTASAFUNCTIONOFRETURNDELAYISSHOWNINTERMSOF RELATIVEVOLTAGEANDPOWER4HEhVOLTAGEvPLOTSHOWSTHECUMULATIVEEFFECTOFCONVOLV INGTHERETURNPULSEWITHTHEMATCHEDFILTEROFEACHRANGEGATE&ORASINGLERANGEGATE THISISSIMPLYTHECONVOLUTIONOFTWORECTANGULARPULSES WHICHRESULTSINATRIANGULAR RESPONSE4O COMPUTE LOSS THE MATCHED FILTER OUTPUT IN TERMS OF POWER IE VOLTAGE SQUARED MUSTBEUSED 7HENTHE02&ISHIGH SOTHATMANYRANGEAMBIGUITIESOCCUR THETARGETRANGEDELAY MAYBECONSIDEREDTOBERANDOMFROMFRAMETOFRAME WITHAUNIFORMDISTRIBUTIONOVER THE)00!MEASUREOFPERFORMANCEREDUCTIONDUETOECLIPSINGANDRANGEGATESTRADDLE ISFOUNDBY 5SINGTHEUNECLIPSEDDETECTIONCURVE0DVS3. FORTHEWAVEFORMANDSELECT INGAPARTICULAR3.2OFINTEREST3.ALONGWITHITSCORRESPONDINGPROBABILITYOF DETECTION0D 2EDUCE 3. BY A FACTOR RELATED TO THE RELATIVE OUTPUT hPOWERv OF THE MATCHED FILTERASAFUNCTIONOFAMBIGUOUSRANGEWITHINTHE)003EETHETHIRDROWOFPLOTS IN&IGURE 7ITHTHEREDUCED3.2 DETERMINETHENEW0DASAFUNCTIONOFAMBIGUOUSRANGE WITHINTHE)00FROMTHEUNECLIPSEDDETECTIONCURVE !VERAGETHESENEW0DVALUESACROSSTHE)00 4HERESULTWILLBEANEWDETECTIONCURVEINCLUDINGTHEAVERAGEEFFECTOFECLIPSINGAND RANGEGATESTRADDLE&ORAFIXED0D THEDIFFERENCEIN3.2BETWEENTHEUNECLIPSEDAND THEECLIPSEDDETECTIONCURVESISTHEAVERAGEECLIPSINGANDRANGEGATESTRADDLELOSS4HIS DIFFERENCEREPRESENTSTHEAVERAGEINCREASEINSIGNAL TO NOISERATIOREQUIREDTOOBTAIN THE SAME PROBABILITY OF DETECTION WITH ECLIPSING AND STRADDLE AS IN THE CASE WHERE THETRANSMITPULSEISRECEIVEDBYAMATCHEDGATEWITHNOSTRADDLE3INCETHEDETECTION CURVECHANGESSHAPE THELOSSDEPENDSONTHEPROBABILITYOFDETECTIONSELECTED WHICH ISDEPICTEDIN&IGURE&ORACCURATERESULTS ECLIPSINGANDRANGEGATESTRADDLELOSS MUSTBECOMPUTEDTOGETHER !LESSACCURATEAPPROXIMATIONCOMPARESTHEAVERAGESIGNAL TO NOISERATIOOVERTHE INTERPULSEPERIODWITHTHESIGNAL TO NOISERATIOOFTHEMATCHEDCASE)NTHECASEOF. CONTINUOUSRANGEGATESSPANNINGTHEDURATIONOFTHE)00 EACHOFWHICHAREMATCHEDTO THETRANSMITPULSEWIDTH THEAPPROXIMATEAVERAGEECLIPSINGANDSTRADDLELOSSIS
APPROXIMATE ECLIPSING AND RANGE GATE STRADDLLE LOSS
. .
4IME.ORMALIZEDBY2ANGE 'ATE$URATION
.O2'/VERLAPTT TG TSTB )00 TG
4IME.ORMALIZEDBY2ANGE 'ATE$URATION
2'/VERLAPTT TG TSTB )00 TG
&)'52% #ONCEPTOFECLIPSINGANDRANGEGATESTRADDLELOSS4HETOPROWOFPLOTSSHOWSTHETRANSMITPULSEFORASINGLE)00OFAPULSEDOPPLERWAVEFORMWITHA DUTYCYCLEOF4HESECONDROWOFPLOTSSHOWSTHERELATIVEVOLTAGEOFTHEMAXIMUMPULSEMATCHEDFILTER-& OUTPUTASAFUNCTIONOFRANGE AMBIGUOUSTARGETRETURN WITHINTHE)004HETHIRDROWOFPLOTSSHOWSTHEOUTPUTINTERMSOFRELATIVEPOWER
4RANSMIT0ULSE
-&/UTPUT h6OLTAGEv
-&/UTPUT h0OWERv
4RANSMIT0ULSE -&/UTPUT h6OLTAGEv -&/UTPUT h0OWERv
{°{Ó 2!$!2(!.$"//+
05,3%$/00,%22!$!2
{°{Î
&327 ' /&* #0%3,!#0)'2
0.$#$*+*27.('2'%2*.-
5.%+*/1*-)#-& 20#&&+' 5%+*/1*-)#-& 20#&&+'//0.6 5%+*/1*-)#-& 20#&&+' 5%+*/1*-)#-& 20#&&+' 4'0+#/
"-'%+*/1'& *)-#+2. .*1' #2*.& &)'52% #OMPARISONOFDETECTIONPERFORMANCEWITHANDWITHOUTECLIPSINGANDRANGEGATE STRADDLELOSS4HEAPPROXIMATEPERFORMANCEUSING%QISALSOPROVIDED4HEPERFORMANCEWITH ECLIPSINGANDRANGEGATESTRADDLELOSSWITHTHEUSEOFOVERLAPPEDRANGEGATESISSHOWN
%QASSUMESANUNMODULATED RECTANGULARTRANSMITPULSESHAPEWITHTHERECEIVE GATEMATCHEDTOTHETRANSMITPULSEWIDTH4HEREISNORANGEGATEOVERLAP4HEFIRSTGATE OFTHE.RANGEGATESAREBLANKEDFORTHETRANSMITPULSE!SSHOWNIN&IGURE THIS APPROXIMATIONISONLYVALIDFORA0DNEAR 4HEREARESEVERALOTHERDETAILSTHATHAVENOTBEENINCLUDEDIN&IGURE!SSHOWN IN&IGURE APORTIONOFTHEFIRSTVALIDRECEIVERANGEGATEANDPOSSIBLYAPORTION OFTHELASTRANGEGATEINTHE)00 ISTYPICALLYBLANKEDTOAVOIDRECEIVINGTRANSIENTSOF THE TRANSMIT TO RECEIVE AND RECEIVE TO TRANSMIT SWITCHING!LSO IF PULSE COMPRES SIONMODULATIONISUSEDONTHETRANSMITPULSE THERANGEGATEDURATIONWILLBEREDUCED TOMATCHTHETRANSMITPULSEBANDWIDTH!LLOFTHESEEFFECTSSHOULDBEINCLUDEDWHEN COMPUTINGTHEECLIPSINGANDRANGEGATESTRADDLELOSS $OPPLER&ILTER7EIGHTING,OSS 4HISLOSSRESULTSFROMTHEINCREASEDNOISEBAND WIDTHOFTHEDOPPLERFILTERSTHATOCCURSBECAUSEOFFILTERSIDELOBEWEIGHTING4HELOSS CANALSOBEACCOUNTEDFORBYANINCREASEOFTHEDOPPLERFILTERNOISEBANDWIDTHINSTEAD OFASASEPARATELOSS $OPPLER&ILTER3TRADDLE,OSS 4HISLOSSISDUETOATARGETNOTALWAYSBEINGINTHE CENTEROFADOPPLERFILTER)TISCOMPUTEDBYASSUMINGAUNIFORMLYDISTRIBUTEDTARGETDOP PLEROVERONEFILTERSPACINGANDISAFUNCTIONOFTHEDOPPLERFILTERSIDELOBEWEIGHTING4HIS LOSSCANBEREDUCEDATTHEEXPENSEOFINCREASEDPROCESSING BYZERO PADDINGTHECOLLECTED DATAANDPERFORMINGAHIGHER POINT&&4TOFORMHIGHLYOVERLAPPEDDOPPLERFILTERS
{°{{
2!$!2(!.$"//+
#&!2,OSS 4HISLOSSISCAUSEDBYANIMPERFECTESTIMATEOFTHEDETECTIONTHRESH OLD COMPARED WITH THE IDEAL THRESHOLD4HE FLUCTUATION IN THE ESTIMATE NECESSITATES THATTHEMEANTHRESHOLDBESETHIGHERTHANTHEIDEAL HENCEALOSS)TISONLYAPPLICABLE TOTARGETS 'UARD"LANKING,OSS 4HISTARGET SPECIFICLOSSISTHEDETECTABILITYLOSSINTHEMAIN CHANNELCAUSEDBYSPURIOUSBLANKINGFROMTHEGUARDCHANNEL3EE&IGURE 0ROBABILITYOF&ALSE!LARM 2ADARDETECTIONPERFORMANCEISDETERMINEDBY THEDETECTIONTHRESHOLD WHICHINTURNISSETTOPROVIDEASPECIFIEDPROBABILITYOF FALSE ALARMn!S DESCRIBED IN 3ECTION PULSE DOPPLER RADARS OFTEN EMPLOY A MULTILOOK DETECTION CRITERION TO RESOLVE RANGE AMBIGUITIES4HIS CAN BE ACCOM PLISHEDWITHLINEAR &-RANGINGASINTHE(273WAVEFORMOR- OF .RANGINGUSED BY-2734HESEAMBIGUITYRESOLUTIONTECHNIQUESDICTATEHOWTHEPROBABILITYOF FALSEALARMPERRANGE DOPPLERCELLISCOMPUTED4HESECALCULATIONSASSUMEANOISE LIMITEDENVIRONMENT &OR(273 DIFFERENTLINEAR &-SLOPESAREAPPLIEDTOLOOKSTHROUGHMOFAM LOOK DWELL WHEREMISTYPICALLY4HE02&ISHIGHENOUGHFORATMOSTONLYADOPPLERSIGN AMBIGUITY$ETECTIONSINLOOKSTHROUGHM MUSTCORRELATEINDOPPLERWITHDETECTIONS IN THE FIRST LOOK WHICH HAS NO SLOPE! DOPPLER CORRELATION WINDOW IS SET EQUAL TO THEMAXIMUMDOPPLEROFFSETDUETOLINEAR &-RANGINGFROMATARGETATTHEMAXIMUM INSTRUMENTED RANGE &OR DOPPLER ONLY CORRELATION THE 0&! PER RANGE DOPPLER CELL TO PROVIDEASPECIFIEDFALSEREPORTTIMEIS
0&!
³ ¤ ´ 4D LN ¥ ´ ¥ . R ¥ ¤ M³ ´ M ¥¦ ¥¦ N´µ . F . &- 4&2 µ´
M
WHERE .R NUMBEROFINDEPENDENTRANGESAMPLESPROCESSEDPER)00
.F N UMBEROFINDEPENDENTDOPPLERFILTERSVISIBLEINTHEDOPPLERPASSBAND NUMBEROFUNBLANKEDFILTERS&&4WEIGHTINGFACTOR
4D TOTALDWELLTIMEOFTHEMULTIPLE02&SINCLUDINGPOSTDETECTIONINTEGRATION IFANY SPACECHANGE ANDANYDEADTIME
N NUMBEROFLOOKSINADWELLTIME
M NUMBEROFDETECTIONSREQUIREDFORATARGETREPORTFORATYPICAL(273 DWELL N ANDM ¤ M³
¥¦ N´µ BINOMIALCOEFFICIENT N;MN M =
4&2 FALSE REPORT TIME PER -ARCUMS DEFINITION WHERE THE PROBABILITY IS THATATLEASTONEFALSEREPORTWILLOCCURINTHEFALSE REPORTTIMETHIS CANBERELATEDTOTHEAVERAGETIME4!6'BETWEENFALSEREPORTSBY
4&2y4!6'LN
.&- K&- MAX2MAXC NUMBEROFINDEPENDENTDOPPLERFILTERSINTHEDOPPLER CORRELATIONWINDOW K&- MAX STEEPESTLINEAR &-SLOPEMAGNITUDE
2MAX MAXIMUMINSTRUMENTEDRANGE
05,3%$/00,%22!$!2
{°{x
!LERT#ONFIRMINCREASESSENSITIVITYBYALLOWINGMOREFALSEALARMSIN!LERTANDRELY INGON#ONFIRMTOREJECTTHOSEFALSEALERTS4HE!LERT#ONFIRMCOMBINATIONISDESIGNED TO PROVIDE THE SAME FALSE REPORT TIME 4&2 AS A CONVENTIONAL WAVEFORM! SPECIFIED FRACTIONALINCREASE&INFRAMETIMEACCOUNTSFORTHEEXECUTIONOF#ONFIRMDWELLSTO REJECTFALSE!LERTDETECTIONS&ISONTHEORDEROFn7HENUSINGA63!LERTANDA LOOK(273#ONFIRM THEPROBABILITYOFFALSEALARMPERRANGE DOPPLERCELL 0&! AAND 0&! CFOR!LERTAND#ONFIRM RESPECTIVELY IS
0&! A
4D A LN . R A . F A4&2 A
0&! C
& ³ ¤ 4D C LN r . R C ¥¦ . F CUE . && ´µ 4&2
WHERE 4D A TOTAL!LERTDWELLTIME
.R A NUMBEROFINDEPENDENTRANGESAMPLESPROCESSEDPER)00IN!LERT
.F A NUMBER OF INDEPENDENT DOPPLER FILTERS VISIBLE IN THE !LERT DOPPLER PASSBAND
4&2 A 4D C& !LERTFALSEREPORTTIME
4D C TOTAL#ONFIRMDWELLTIME
& FRACTIONALINCREASEINFRAMETIMEALLOCATEDTO#ONFIRMn
.R C NUMBEROFINDEPENDENTRANGESAMPLESPROCESSEDPER)00IN#ONFIRM
.F CUE NUMBEROFINDEPENDENTDOPPLERFILTERSINTHE#ONFIRMWINDOWCENTERED ABOUTTHEDOPPLEROFTHE!LERTDETECTIONCUE
.&- NUMBER OF INDEPENDENT DOPPLER FILTERS IN #ONFIRM LINEAR &- RANGING DOPPLERCORRELATIONWINDOW
4&2 OVERALL!LERT#ONFIRMFALSEREPORTTIME 4HE- OF .RANGINGUSEDIN-273REQUIRESCORRELATIONINRANGEANDCANBEVIEWED ASABINARYDETECTOR-273ISTYPICALLYAMEDIUM 02&WAVEFORMWITHRANGEANDDOP PLERAMBIGUITIES$OPPLERISUSEDFORCLUTTERMITIGATIONINEACHLOOK ANDTHEDOPPLER AMBIGUITYMAYNOTNEEDTOBERESOLVEDSINCETHETRACKERCANDETERMINERANGERATEFROM SUCCESSIVEDWELLS!TYPICAL-273- OF .CORRELATIONWOULDBETHREEDETECTIONSOUT OFEIGHTLOOKSIE M ANDN &ORRANGE ONLYCORRELATION THE0&!INEACHRANGE DOPPLERCELLISGIVENBY M
0&!
§ ¶ ¨¨ 4D LN ·· . F ¨¤ M³ · ¨¥¦ N´µ . RU4&2 · © ¸
WHERE .RU NUMBEROFINDEPENDENTRANGESAMPLESINTHEOUTPUTUNAMBIGUOUS RANGE INTERVALDISPLAYRANGERANGEGATESIZE
{°{È
2!$!2(!.$"//+
&ORBETTERFALSEALARMREJECTION DOPPLERCORRELATIONCANBEUSEDFOR-273)NTHE CASEWHEREBOTHRANGEANDDOPPLERCORRELATIONAREUSED THEREQUIRED0&!IS M
0&!
§ ¶ ¨ · 4D LN · ¨ ¨¤ M³ M · ¨¥¦ N´µ . FU . RU4&27 · © ¸
WHERE .FU NUMBEROFINDEPENDENTDOPPLERFILTERSINTHEUNAMBIGUOUSDOPPLERREGION
7 WIDTHINDOPPLERFILTERS OFTHECORRELATIONWINDOWAPPLIEDTODETECTIONS FOLLOWINGINITIALDETECTION 0ROBABILITYOF$ETECTION 5SINGTHE0&!PERRANGE DOPPLERCELL THEPROBABILITY OFDETECTION0D OFAGIVENLOOKCANBEDETERMINEDFORAGIVENTARGET3.2 THENUM BER OF #0)S NONCOHERENTLY INTEGRATED .PDI AND THE TARGET 2#3 FLUCTUATION MODEL ASSUMED4HEINVERSEPROBLEMOFDETERMININGTHEREQUIRED3.2FORAGIVEN0DCANBE SOLVEDVIAAPPROXIMATIONS5NIVERSALDETECTIONEQUATIONSHAVEBEENPUBLISHEDTHAT PROVIDEREASONABLYACCURATERESULTSANDAREREPRODUCEDHERE!GAIN THEASSUMPTION THATTARGETSAREINAGAUSSIANNOISE LIMITEDENVIRONMENTISMADE &ORASINGLELOOKWITH.PDI#0)SNONCOHERENTLYINTEGRATEDANDASPECIFIED0&!PER RANGE DOPPLERCELL THE0DASAFUNCTIONOF3.2FORA-ARCUMNONFLUCTUATING TARGET CANBEAPPROXIMATEDAS 0D 3.2 0&! . PDI
¤ ERFC ¥ LN; 0&! 0&! = ¦
. PDI . PDI ³
. PDI 3.2
´ µ
WHEREERFCq ISTHECOMPLEMENTARYERRORFUNCTION4HEREQUIRED3.2ASAFUNCTIONOF 0DFORA-ARCUMTARGETISAPPROXIMATEDAS
3.2 REQD 0D 0&! . PDI
H H . PDI . PDI
. PDI
WHERE
H LN; 0&! 0&! = SIGN 0D LN; 0D 0D =
&OR3WERLINGFLUCTUATINGTARGETMODELS THE0DANDREQUIRED3.2CANBEAPPROXI MATED RESPECTIVELY AS
§ ¶ ¨ + 0 . . N · E M &! PDI PDI 0D 3.2 0&! . PDI NE + M ¨ NE · . PDI ¨ · 3.2 ¨© ·¸ NE
§ + M 0D NE . PDI NE ¶ NE
3.2 0D 0&! . PDI NE ¨
· + M 0D NE ¨© ·¸ . PDI
05,3%$/00,%22!$!2
{°{Ç
WHERE ª . PDI NE « ¬ . PDI
FOR 3WERLING ) TARGGET CHI SQUARED DISTRIBUTION WITH DEGRESSS OF FREEDOM FOR 3WERLING )) TARGET CHI SSQUARED DISTRIBUTION WITH . PDI DEGRESS OF FREEDOM FOR 3WERLING ))) TARGET CHI SQUARRED DISTRIBUTION WITH DEGRESS OF FREEDOM FOR 3WERLING )6 TARGET CHI SQUARED DISTRIIBUTION WITH . PDI DEGRESS OF FREEDOM
¤ D X³ + M X D 0 ¥ ´ CHI SQUAREDDISTRIBUTIONSURVIVALFUNCTION ¦ µ + M P D INVERSECHI SQUAREDDISTRIBUTIONSURVIVALFUNCTION X
G A X 0A X ' A
¯ TA E T DT REGULARIZEDLOWERINCOMPLETEGAMMAFUNCTION c ¯ TA E T DT
4HEINTEGRALOFTHECHI SQUAREDDISTRIBUTION+MX D ANDITSINVERSE+ M P D AREOFTEN INCLUDEDINMATHEMATICALCOMPUTATIONSOFTWAREPACKAGES 7HEN- OF .DETECTIONIE BINARYDETECTION ISUSEDWITHINADWELL THEPROBABIL ITYOFDETECTIONFOREACHLOOK0D LOOK ISUSEDTOCOMPUTETHEPROBABILITYOFDETECTION FORADWELL0D DWELL 7HENADWELLREQUIRESMDETECTIONSOUTOFNLOOKSFORATARGET DECLARATION THE0D DWELLIS N
0D DWELL
¤ K³
£ ¥¦N´µ 0DK LOOK 0D LOOK N K
K M
&OR!LERT#ONFIRMDETECTIONPERFORMANCE THE0DFORTHE!LERTDWELLANDTHE0D FORTHE#ONFIRMDWELLAREINDIVIDUALLYCOMPUTEDASAFUNCTIONOF3.2#AREMUST BETAKENTONORMALIZETHE3.2TOACCOUNTFORDIFFERENCESINDOPPLERFILTERBANDWIDTH BETWEENTHE!LERTAND#ONFIRMWAVEFORMS4HEMULTIPLICATIONOFNORMALIZEDPROB ABILITYOFDETECTIONCURVEFORTHE!LERTDWELLWITHTHATOFTHE#ONFIRMDWELLRESULTS INANESTIMATEOFTHECOMPOSITE0DVS3.CURVEFOR!LERT#ONFIRM-OREACCURATE RESULTSMUSTINCLUDETHEEFFECTSOFLATENCYBETWEENTHE!LERTAND#ONFIRMDWELLS 3EARCHDETECTIONPERFORMANCEISOFTENCHARACTERIZEDBYTHECUMULATIVEPROBABIL ITYOFDETECTION 0D CUM WHICHISDEFINEDASTHEPROBABILITYTHATTHERADARWILLDETECT ACLOSINGTARGETATLEASTONCEBYTHETIMETHETARGETHASCLOSEDTOASPECIFIEDRANGE 0D CUMISONLYDEFINEDFORCLOSINGTARGETS4HECUMULATIVEPROBABILITYOFDETECTIONFOR THEKTHSCAN ORFRAME IS K
0D CUM ;K = ; 0D SS ;I== I
0D CUM ;K = 0D SS ;K = 0D CUM ;K =
WHERE0D SS;K=ISTHESINGLE SCANPROBABILITYOFDETECTIONONTHEKTHSCAN4HEACCUMULA TIONOFSINGLE SCANPROBABILITYOFDETECTIONSISSTARTEDATARANGEWHERETHETARGETS0D SS ISAPPROXIMATELY4HEREISANOPTIMALSEARCHFRAMETIMEFORCUMULATIVEDETECTION PERFORMANCE!BALANCEMUSTBEACHIEVED!SHORTFRAMETIMELIMITSTHEAMOUNTOF ENERGYPLACEDONTARGETPERDWELLANDLOWERSTHESINGLE SCAN0D!LONGFRAMETIME ALLOWSTHETARGETTOCLOSEINRANGEMOREBETWEENREVISITS THUSLOWERINGTHEBENEFIT OF THE ACCUMULATION &IGURE ILLUSTRATES THE DIFFERENCE BETWEEN SINGLE SCAN AND CUMULATIVEPROBABILITYOFDETECTION
{°{n
2!$!2(!.$"//+
! #& ##
$ $ #%
!# "" !
&)'52% 3INGLE SCAN VS CUMULATIVE 0D AS A FUNCTION OF RANGE FOR A FIXED RADIAL VELOCITYMOVINGTARGET
#LUTTER LIMITED #ASE 4HE FOREGOING DISCUSSION ASSUMED THAT THE TARGET FELL INTHENOISE LIMITEDIE CLUTTER FREE PARTOFTHEDOPPLERBAND)FTHETARGETFALLS IN THE SIDELOBE CLUTTER REGION THERANGEPERFORMANCEWILLBEDEGRADED SINCETHE TOTALINTERFERENCEPOWERSYSTEMNOISEPLUSCLUTTER AGAINSTWHICHTHETARGETMUST COMPETEISINCREASED4HEFOREGOINGDISCUSSIONCANBEAPPLIEDTOTHESIDELOBECLUT TER REGION HOWEVER BY INTERPRETING 2O AS THE RANGE WHERE THE SIGNAL IS EQUAL TO SIDELOBECLUTTERPLUSSYSTEMNOISEn 4HE#&!2LOSSMAYALSOBEHIGHEROWING TOTHEINCREASEDVARIABILITYOFTHETHRESHOLDWHENTHECLUTTERVARIESOVERTHETARGET DETECTIONREGION-OREACCURATECALCULATIONSOFDETECTIONPERFORMANCEINTHESIDE LOBECLUTTERLIMITEDCASESHOULDINCLUDETHEPROPERCLUTTER2#3FLUCTUATIONMODELS AND#&!2TECHNIQUES
-/Ê"Ê , 6/" !%3! !$ !'# !- #!'# #&!2 #.2 #0) #7 $!: $%, D"C $# $&4
ACTIVEELECTRONICALLYSCANNEDARRAY ANALOG TO DIGITAL AUTOMATICGAINCONTROL AMPLITUDEMODULATION CLUTTERAUTOMATICGAINCONTROL CONSTANTFALSEALARMRATE CLUTTER TO NOISEPOWERRATIO COHERENTPROCESSINGINTERVAL CONTINUOUSWAVE DELTA AZIMUTHANTENNABEAMUSEDFORMONOPULSEANGLEESTIMATION DELTA ELEVATIONANTENNABEAMUSEDFORMONOPULSEANGLEESTIMATION DECIBELSWITHRESPECTTOTHECARRIER DIRECTCURRENT DISCRETE&OURIERTRANSFORM
05,3%$/00,%22!$!2
{°{
$0$ DIGITALPRODUCTDETECTOR %3! ELECTRONICALLYSCANNEDARRAY &&4 FAST&OURIERTRANSFORM &- FREQUENCYMODULATION &- #7 FREQUENCY MODULATEDCONTINUOUS WAVE (273 HIGH 02&RANGE WHILE SEARCH ) INPHASE )& INTERMEDIATEFREQUENCY ).3 INERTIALNAVIGATIONSYSTEM )00 INTERPULSEPERIOD ,.! LOW NOISEAMPLIFIER ,/ LOCALOSCILLATOR -& MATCHEDFILTER -273 MEDIUM 02&RANGE WHILE SEARCH -4) MOVINGTARGETINDICATION -44 MULTIPLE TARGETTRACKING .!'# NOISEAUTOMATICGAINCONTROL 0!- PULSE AMPLITUDEMODULATION 0D PROBABILITYOFDETECTION 0# PULSECOMPRESSION 0$) POSTDETECTIONINTEGRATIONNONCOHERENTINTEGRATION 0&! PROBABILITYOFFALSEALARM 0- PHASEMODULATION 00- PULSE POSITIONMODULATION 02& PULSEREPETITIONFREQUENCY 07- PULSE WIDTHMODULATION 1 QUADRATURE 2#3 RADARCROSSSECTION 2&) RADIOFREQUENCYINTERFERENCE RMS ROOT MEAN SQUARE 2& RADIOFREQUENCY 20 RECEIVERPROTECTOR 273 RANGE WHILE SEARCH 3 SUMRECEIVEANTENNABEAMPRIMARYBEAMUSEDFORDETECTION 3," SIDELOBEBLANKER 3.2 SIGNAL TO NOISEPOWERRATIO 34# SENSITIVITYTIMECONTROL 473 TRACK WHILE SCAN 42 TRANSMITRECEIVE 63 VELOCITYSEARCH
, ,
)%%%3TANDARD2ADAR$EFINITIONS )%%%3TDn P $ # 3CHLEHER -4) AND 0ULSED $OPPLER 2ADAR .ORWOOD -! !RTECH (OUSE )NC PPIXnX &%.ATHANSON 2ADAR$ESIGN0RINCIPLES ND%D.EW9ORK-C'RAW (ILL PPn -)3KOLNIK )NTRODUCTIONTO2ADAR3YSTEMS #HAPTER RD%D.EW9ORK-C'RAW (ILL ' 7 3TIMSON )NTRODUCTION TO !IRBORNE 2ADAR #HAPTER 0ART 8 ND %D 2ALEIGH .# 3CI4ECH0UBLISHING )NC
{°xä
2!$!2(!.$"//+
0 ,ACOMME * (ARDANGE * -ARCHAIS AND % .ORMANT !IR AND 3PACEBORNE 2ADAR 3YSTEMS !N)NTRODUCTION #HAPTER .ORWICH .97ILLIAM!NDREW0UBLISHING ,,# 3!(OVANESSIAN 2ADAR3YSTEM$ESIGNAND!NALYSIS #HAPTER .ORWOOD -!!RTECH(OUSE )NC -)3KOLNIK 2ADAR!PPLICATIONS .EW9ORK)%%%0RESS 2*$OVIAK $3:RNIC AND$33IRMANS h$OPPLERWEATHERRADAR vIN 0ROCEEDINGSOFTHE )%%% VOL NO PPn 0-AHAPATRA !VIATION7EATHER3URVEILLANCE3YSTEMS!DVANCED2ADARAND3URFACE3ENSORS FOR &LIGHT 3AFETY AND !IR 4RAFFIC -ANAGEMENT ,ONDON 5+ 4HE )NSTITUTION OF %LECTRICAL %NGINEERS + # /VERMAN + ! ,EAHY 4 7 ,AWRENCE AND 2 * &RITSCH h4HE FUTURE OF SURFACE SURVEILLANCE REVOLUTIONIZING THE VIEW OF THE BATTLEFIELD v IN 2ECORD OF THE )%%% )NTERNATIONAL2ADAR#ONFERENCE -AYn PPn $EFENSE 3CIENCE "OARD &UTURE $O$ !IRBORNE (IGH &REQUENCY 2ADAR .EEDS2ESOURCES /FFICEOFTHE5NDER3ECRETARYOF$EFENSEFOR!CQUISITIONAND4ECHNOLOGY 7ASHINGTON $# !PRIL - ) 3KOLNIK )NTRODUCTION TO 2ADAR 3YSTEMS RD %D .EW 9ORK -C'RAW (ILL PPn '73TIMSON )NTRODUCTIONTO!IRBORNE2ADAR ND%D2ALEIGH .#3CI4ECH0UBLISHING )NC PPn & # 7ILLIAMS AND - % 2ADANT h!IRBORNE RADAR AND THE THREE 02&S v -ICROWAVE *OURNAL *ULY AND REPRINTED IN - ) 3KOLNIK 2ADAR !PPLICATIONS .EW9ORK )%%% 0RESS PPn $#3CHLEHER -4)AND0ULSED$OPPLER2ADAR !RTECH(OUSE )NC PPn ' -ORRIS AND , (ARKNESS !IRBORNE 0ULSED $OPPLER 2ADAR ND %D .ORWOOD -!!RTECH (OUSE )NC P 7(,ONGAND+!(ARRIGER h-EDIUM02&FORTHE!.!0' RADAR vIN0ROCEEDINGSOFTHE )%%% VOL ISSUE &EBRUARY PPn "#ANTRELL h!$#SPURIOUSSIGNALMITIGATIONINRADARBYMODIFYINGTHE,/ vIN0ROCEEDINGSOF THE)%%%2ADAR#ONFERENCE !PRILn PPn ( (OMMEL AND ( &ELDLE h#URRENT STATUS OF AIRBORNE ACTIVE PHASED ARRAY !%3! RADAR SYSTEMSANDFUTURETRENDS vIN)%%%-44 3)NTERNATIONAL-ICROWAVE3YMPOSIUM$IGEST *UNEn PPn 3-3HERMAN -ONOPULSE0RINCIPLESAND4ECHNIQUES .ORWOOD -!!RTECH(OUSE )NC , % 0ELLON h! DOUBLE .YQUIST DIGITAL PRODUCT DETECTOR FOR QUADRATURE SAMPLING v )%%% 4RANSACTIONSON3IGNAL0ROCESSING VOL ISSUE PPn *ULY ' -INKLER #&!2 4HE 0RINCIPLES OF !UTOMATIC 2ADAR $ETECTION IN #LUTTER "ALTIMORE -$ -AGELLAN"OOK#OMPANY 2.ITZBERG 2ADAR3IGNAL0ROCESSINGAND!DAPTIVE3YSTEMS #HAPTER .ORWOOD -!!RTECH (OUSE )NC -7EISS h!NALYSISOFSOMEMODIFIEDCELL AVERAGING#&!2PROCESSORSINMULTIPLE TARGETSITUA TIONS v)%%%4RANSACTIONSON!EROSPACEAND%LECTRONIC3YSTEMS VOL!%3 NO PPn *ANUARY 00'ANDHIAND3!+ASSAM h!NALYSISOF#&!2PROCESSORSINNONHOMOGENEOUSBACKGROUND v )%%%4RANSACTIONSON!EROSPACEAND%LECTRONIC3YSTEMS VOL NO *ULY * &ARRELL AND 2 4AYLOR h$OPPLER RADAR CLUTTER v )%%% 4RANSACTIONS ON !ERONAUTICAL .AVIGATIONAL%LECTRONICS VOL!.% PPn 3EPTEMBERANDREPRINTEDIN$+ "ARTON #7AND$OPPLER2ADARS 3ECTION6) 6OL.ORWOOD -!!RTECH(OUSE )NC PPn ,(ELGOSTAMAND"2ONNERSTAM h'ROUNDCLUTTERCALCULATIONFORAIRBORNEDOPPLERRADAR v)%%% 4RANSACTIONSON-ILITARY%LECTRONICS VOL-), PPn *ULYn/CTOBER
05,3%$/00,%22!$!2
{°x£
! , &RIEDLANDER AND , * 'REENSTEIN h! GENERALIZED CLUTTER COMPUTATION PROCEDURE FOR AIRBORNE PULSE DOPPLER RADARS v )%%% 4RANSACTIONS ON !EROSPACE AND %LECTRONIC 3YSTEMS VOL!%3 PPn *ANUARYANDREPRINTEDIN$+"ARTON #7AND$OPPLER2ADARS 3ECTION6) 6OL .ORWOOD -!!RTECH(OUSE )NC PPn -"2INGEL h!NADVANCEDCOMPUTERCALCULATIONOFGROUNDCLUTTERINANAIRBORNEPULSEDOPPLER RADAR vIN.!%#/.2ECORD PPnANDREPRINTEDIN$+"ARTON #7AND$OPPLER 2ADARS 3ECTION6) 6OL.ORWOOD -!!RTECH(OUSE )NC PPn 2,-ITCHELL 2ADAR3IGNAL3IMULATION #HAPTER .ORWOOD -!!RTECH(OUSE )NC *+*AOAND7"'OGGINS h%FFICIENT CLOSED FORMCOMPUTATIONOFAIRBORNEPULSEDOPPLERCLUT TER vIN0ROCEEDINGSOFTHE)%%%)NTERNATIONAL2ADAR#ONFERENCE 7ASHINGTON $# PPn 7!3KILLMAN 3)'#,543URFACEAND6OLUMETRIC#LUTTER TO .OISE *AMMERAND4ARGET3IGNAL TO .OISE2ADAR#ALCULATION3OFTWAREAND5SERS-ANUAL .ORWOOD -!!RTECH(OUSE )NC PPn $#3CHLEHER -4)AND$OPPLER2ADAR .ORWOOD -!!RTECH(OUSE )NC PPn &*(ARRIS h/NTHEUSEOFWINDOWSFORHARMONICANALYSISWITHTHEDISCRETE&OURIERTRANSFORM v IN0ROCEEDINGSOFTHE)%%% VOL NO *ANUARY PPn 7!3KILLMAN 2ADAR#ALCULATIONS5SINGTHE4) 0ROGRAMMABLE#ALCULATOR .ORWOOD -! !RTECH(OUSE )NC P 2%:IEMERAND*!:IEGLER h-4)IMPROVEMENTFACTORSFORWEIGHTED$&4S v)%%%4RANSACTIONS ON!EROSPACEAND%LECTRONIC3YSTEMS VOL!%3 PPn -AY (27ARD h$OPPLERPROCESSORREJECTIONOFAMBIGUOUSCLUTTER v)%%%4RANSACTIONSON!EROSPACE AND%LECTRONIC3YSTEMS VOL!%3 *ULYANDREPRINTEDIN$+"ARTON #7AND$OPPLER 2ADARS 3ECTION)6n 6OL.ORWOOD -!!RTECH(OUSE )NC PPn 2(&LETCHERAND$7"URLAGE h!NINITIALIZATIONTECHNIQUEFORIMPROVED-4)PERFORMANCEIN PHASEDARRAYRADAR vIN0ROCEEDINGSOFTHE)%%% VOL $ECEMBER PPn $((ARVEYAND4,7OOD h$ESIGNFORSIDELOBEBLANKINGSYSTEMS vIN0ROCEEDINGSOFTHE )%%%)NTERNATIONAL2ADAR#ONFERENCE 7ASHINGTON $# PPn ,-AISEL h0ERFORMANCEOFSIDELOBEBLANKINGSYSTEMS v)%%%4RANSACTIONSON!EROSPACEAND %LECTRONIC3YSTEMS VOL!%3 PPn -ARCH (-&INN 23*OHNSON AND0:0EEBLES h&LUCTUATINGTARGETDETECTIONINCLUTTERUSINGSID ELOBE BLANKING LOGIC v )%%% 4RANSACTIONS ON !EROSPACE AND %LECTRONIC 3YSTEMS VOL!%3 PPn -AY !&ARINA !NTENNA BASED3IGNAL0ROCESSING4ECHNIQUESFOR2ADAR3YSTEMS #HAPTER .ORWOOD -!!RTECH(OUSE )NC PPn $! 3HNIDMAN AND 3 34OUMODGE h3IDELOBE BLANKING WITH INTEGRATION AND TARGET FLUCTUA TION v)%%%4RANSACTIONSON!EROSPACEAND%LECTRONIC3YSTEMS VOL NO PPn *ULY $ ( -OONEY h0OST $ETECTION 34# IN A -EDIUM 02& 0ULSE $OPPLER 2ADAR v 53 0ATENT *UNE & % .ATHANSON 2ADAR $ESIGN 0RINCIPLES ND %D .EW 9ORK -C'RAW (ILL )NC PPn *"4SUI $IGITAL4ECHNIQUESFOR7IDEBAND2ECEIVERS ND%D 2ALEIGH .#3CI4ECH0UBLISHING #OMPANY PPn ,0'OETZAND7!3KILLMAN h-ASTEROSCILLATORREQUIREMENTSFORCOHERENTRADARSETS vIN)%%% .!3!3YMPOSIUMON3HORT4ERM&REQUENCY3TABILITY .!3! 30 .OVEMBER 232AVEN h2EQUIREMENTSFORMASTEROSCILLATORSFORCOHERENTRADAR vIN0ROCEEDINGSOFTHE)%%% VOL &EBRUARY PPnANDREPRINTEDIN$+"ARTON #7AND$OPPLER2ADARS 3ECTION6 ) 6OL !RTECH(OUSE )NC .ORWOOD -! PPn 232AVEN #ORRECTIONTOh2EQUIREMENTSFORMASTEROSCILLATORSFORCOHERENTRADAR vIN0ROCEEDINGS OFTHE)%%% VOL ISSUE !UGUST P
{°xÓ
2!$!2(!.$"//+
-'RAY &(UTCHINSON $2IDGELY &&RUGE AND$#OOKE h3TABILITYMEASUREMENTPROBLEMS ANDTECHNIQUESFOROPERATIONALAIRBORNEPULSEDOPPLERRADAR v)%%%4RANSACTIONSON!EROSPACE AND%LECTRONIC3YSTEMS VOL!%3 PPn *ULY ! %!CKER h%LIMINATING TRANSMITTED CLUTTER IN DOPPLER RADAR SYSTEMS v -ICROWAVE *OURNAL VOL PP n .OVEMBER AND REPRINTED IN $ + "ARTON #7 AND $OPPLER 2ADARS 3ECTION6 6OL.ORWOOD -!!RTECH(OUSE )NC PPn *!3CHEERAND*,+URTZ #OHERENT2ADAR0ERFORMANCE%STIMATION .ORWOOD -!!RTECH (OUSE )NC PPn 3*'OLDMAN 0HASE.OISE!NALYSISIN2ADAR3YSTEMS5SING0ERSONAL#OMPUTERS #HAPTER .EW9ORK*OHN7ILEY3ONS )NC '64RUNKAND-7+IM h!MBIGUITYRESOLUTIONOFMULTIPLETARGETSUSINGPULSE DOPPLERWAVE FORMS v)%%%4RANSACTIONSON!EROSPACEAND%LECTRONIC3YSTEMS VOL NO PPn /CTOBER & % .ATHANSON 2ADAR $ESIGN 0RINCIPLES ND %D .EW 9ORK -C'RAW (ILL )NC PPn -"2INGEL h4HEEFFECTOFLINEAR&-ONTHEGROUNDCLUTTERINANAIRBORNEPULSEDOPPLERRADAR v IN.!%#/.g2ECORD VOL $AYTON /( -AYn PPn & % .ATHANSON 2ADAR $ESIGN 0RINCIPLES ND %D .EW 9ORK -C'RAW (ILL )NC PPn '73TIMSON )NTRODUCTIONTO!IRBORNE2ADAR ND%D-ENDHAM .*3CI4ECH0UBLISHING )NC PPn 0,"OGLER 2ADAR0RINCIPLESWITH!PPLICATIONSTO4RACKING3YSTEMS .EW9ORK*OHN7ILEY 3ONS )NC PPn 2! $ANA AND $ -ORAITIS h0ROBABILITY OF DETECTING A 3WERLING ) TARGET ON TWO CORRELATED OBSERVATIONS v )%%%4RANSACTIONS ON!EROSPACE AND %LECTRONIC 3YSTEMS VOL!%3 NO PPn 3EPTEMBER 2%:IEMER 4,EWIS AND,'UTHRIE h$EGRADATIONANALYSISOFPULSEDOPPLERRADARSDUETOSIG NALPROCESSING vIN.!%#/.2ECORD PPnANDREPRINTEDIN$+"ARTON #7AND $OPPLER2ADARS 3ECTION)6 6OL .ORWOOD -!!RTECH(OUSE )NC PPn 0,ACOMME *(ARDANGE *-ARCHAIS AND%.ORMANT !IRAND3PACEBORNE2ADAR3YSTEMS!N )NTRODUCTION .ORWICH .97ILLIAM!NDREW0UBLISHING ,,# PPn *)-ARCUM h!STATISTICALTHEORYOFTARGETDETECTIONBYPULSEDRADAR v )%%%4RANSACTIONSON )NFORMATION4HEORY VOL)4 PPn !PRIL 03WERLING h0ROBABILITYOFDETECTIONFORFLUCTUATINGTARGETS v)%%%4RANSACTIONSON)NFORMATION 4HEORY VOL)4 PPn !PRIL ,&&EHLNER h4ARGETDETECTIONBYAPULSEDRADAR v2EPORT4' *OHNS(OPKINS5NIVERSITY !PPLIED0HYSICS,ABORATORY ,AUREL -$ *ULY $ 0 -EYER AND ( ! -AYER 2ADAR 4ARGET $ETECTION (ANDBOOK OF 4HEORY AND 0RACTICE .EW9ORK!CADEMIC0RESS *6$I&RANCOAND7,2UBIN 2ADAR$ETECTION .ORWOOD -!!RTECH(OUSE )NC *6$I&RANCOAND7,2UBIN 2ADAR$ETECTION .ORWOOD -!!RTECH(OUSE )NC PPn $!3HNIDMAN h$ETERMINATIONOFREQUIRED3.2VALUES v)%%%4RANSACTIONSON!EROSPACEAND %LECTRONIC3YSTEMS VOL NO PPn *ULY $+"ARTON h5NIVERSALEQUATIONSFORRADARTARGETDETECTION v)%%%4RANSACTIONSON!EROSPACE AND%LECTRONIC3YSTEMS VOL NO PPn *ULY -%VANS .(ASTINGS AND"0EACOCK 3TATISTICAL$ISTRIBUTIONS RD%D.EW9ORK *OHN7ILEY 3ONS )NC P 7 ( 0RESS 3! 4EUKOLSKY 7 4 6ETTERLING AND " 0 &LANNERY .UMERICAL 2ECIPES IN # 4HE!RTOF3CIENTIFIC#OMPUTING ND%D#AMBRIDGE 5+#AMBRIDGE5NIVERSITY0RESS PPn
05,3%$/00,%22!$!2
{°xÎ
$-OONEYAND'2ALSTON h0ERFORMANCEINCLUTTEROFAIRBORNEPULSE-4) #7DOPPLERANDPULSE DOPPLERRADAR vIN)2%#ONVENTION2ECORD VOL PART PPnANDREPRINTEDIN $+"ARTON #7AND$OPPLER2ADARS 3ECTION6) 6OL.ORWOOD -!!RTECH(OUSE )NC PPn - " 2INGEL h$ETECTION RANGE ANALYSIS OF AN AIRBORNE MEDIUM 02& RADAR v IN )%%% .!%#/.2ECORD $AYTON /( PPn 0%(OLBOURNAND!-+INGHORN h0ERFORMANCEANALYSISOFAIRBORNEPULSEDOPPLERRADAR v IN 0ROCEEDINGS OF THE )%%% )NTERNATIONAL 2ADAR #ONFERENCE 7ASHINGTON $# PPn $! 3HNIDMAN h2ADAR DETECTION PROBABILITIES AND THEIR CALCULATION v )%%% 4RANSACTIONS ON !EROSPACEAND%LECTRONIC3YSTEMS VOL NO PPn *ULY
#HAPTER
ÕÌvÕVÌ>ÊÊ ,>`>ÀÊ-ÞÃÌiÃÊÊ vÀÊ}
ÌiÀÊÀVÀ>vÌ >Û`Ê ÞV
]ÊÀ° $,3CIENCES )NC
>ÀÊ «« -ONASH5NIVERSITY
x°£Ê /," 1 /" )N SPITE OF MORE THAN A HALF CENTURY OF IMPROVEMENTS IN RADAR PERFORMANCE AND RELIABILITY THEEFFORTREQUIREDFORDEPLOYMENT OPERATION ANDMAINTENANCEOFMOST RADARSISSUBSTANTIAL&URTHERMORE THEPOWER APERTUREPRODUCTISNEVERASLARGEAS DESIRED4HEFORWARDPROJECTEDAREAASWELLASAVIONICSWEIGHTISVERYCOSTLYINMOST FIGHTER AIRCRAFT PARAMETERS 4HESE PARAMETERS HAVE MOTIVATED USERS BUYERS AND DESIGNERSTOWANTMOREFUNCTIONSINASINGLERADARANDITSCOMPLEMENTARYPROCESSING SUITE!SARESULT MOSTMODERNFIGHTERRADARSAREMULTIFUNCTIONALPROVIDINGRADAR NAVIGATION LANDINGAIDS DATALINK AND%LECTRONIC#OUNTER-EASURES%#- FUNC TIONS 4HE PRIMARY ENABLER FOR MULTIFUNCTIONAL RADAR IS SOFTWARE DEFINED SIGNAL ANDDATAPROCESSING FIRSTINTRODUCEDINTHEMIDSn3OFTWAREPROGRAMMABILITY ALLOWSMANYRADARSYSTEMMODESTOBEPERFORMEDUSINGTHESAME2&HARDWARE)N ADDITION MODERNNAVIGATIONAIDSWORKSOWELLTHATEACHRADARMODEISDEFINEDBY ITSEARTHSITUATION GEOMETRYWITHALMOSTALLWAVEFORMPARAMETERSSETBYLOCALEARTH CONDITIONS 4HEMODERNRADAROFTENISNET CENTRIC USINGANDPROVIDINGDATATOA COMMUNICATIONSNETWORKANDWHERESUITABLYEQUIPPED HASITSOWN)NTERNETPROTOCOL )0 ADDRESS -ULTIFUNCTIONALITY IS NOT DEPENDENT ON ANTENNA TYPE )N FACT THE MECHANICALLY SCANNED !.!0' AND RADARS HAVE DEMONSTRATED MULTIFUNCTIONALITY IN COMBAT(OWEVER MULTIFUNCTIONALITYISFACILITATEDBY!CTIVE%LECTRONICALLY3CANNED !NTENNA!%3! ARRAYS4HEMULTIFUNCTIONAL!%3!RADARINTHE&! %&FIGHTERIS SHOWNWITHAPROTECTIVECOVEROVERTHEARRAYIN&IGURE4HE!%3!ISSHAPEDAND CANTEDUPWARDTOAIDINSOMEMODESANDTOMINIMIZEREFLECTIONSTOENEMYRADARS
x°£
x°Ó
2!$!2(!.$"//+
&)'52% !.!0' -ULTIFUNCTIONAL!%3!2ADAR#OURTESY2AYTHEON #OMPANY
4HIS CHAPTER ADDRESSES WHAT SIGNALS ARE EMITTED AND WHY THEY ARE NEEDED IN A -ULTIFUNCTIONAL &IGHTER!IRCRAFT 2ADAR -&!2 4HE WHY BEGINS WITH TYPICAL MIS SIONS WHICHSHOWSTHEGEOMETRYTHATGIVESRISETOEACHRADARMODEANDWAVEFORM LISTSREPRESENTATIVERADARMODES ANDSHOWSTYPICALMODERNAIRBORNERADARMODEINTER LEAVINGANDTIMING4HEANSWERTOWHATISPROVIDEDBYTYPICALWAVEFORMVARIATIONS ANDAFEWEXAMPLES4HEEXAMPLESARENOTFROMANYSINGLERADARBUTAREACOMPOSITE OFMODERNRADARS4HEGENERAL-&!2IDEAISILLUSTRATEDIN&IGURE)TSHOWSTIME MULTIPLEXED OPERATIONS FOR AIR TO AIR ! ! AIR TO SURFACE ! 3 ELECTRONIC WARFARE %7 ANDCOMMUNICATIONFROMTHESAMERADIOFREQUENCY2& HARDWAREANDPROCESS INGCOMPLEXOFTENOVERMOSTOFTHEMICROWAVEBAND 3OMETIMES MULTIPLEFUNCTIONS CANBEPERFORMEDSIMULTANEOUSLYIFACOMMONWAVEFORMISUSED 4HEANTENNAAPERTUREUSUALLYHASMULTIPLEPHASECENTERSENABLINGMEASUREMENTFOR 3PACE 4IME!DAPTIVE0ROCESSING34!0 $ISPLACED0HASE#ENTER!NTENNA$0#!
&)'52% -&!2INTERLEAVES! 3 ! ! AND%7FUNCTIONSADAPTED
-5,4)&5.#4)/.!,2!$!23934%-3&/2&)'(4%2!)2#2!&4
x°Î
PROCESSING CONVENTIONALMONOPULSEANGLETRACKING JAMMERNULLING ANDOUT OF BAND ANGLE OF ARRIVAL !/! ESTIMATION 4HE OPTIMUM PLACEMENT OF PHASE CENTERS IS AN IMPORTANTDESIGNTRADEOFF!PHASECENTERISANANTENNAAPERTURECHANNEL WHICHISOFF SETINSPACEANDPROVIDESAPARTIALLYORFULLYINDEPENDENTMEASUREMENTOFANINCOMING ELECTROMAGNETICWAVEFRONT&OREXAMPLE AONE DIMENSIONALPHASEMONOPULSEHASTWO PHASECENTERS ATWO DIMENSIONALPHASEMONOPULSEHASFOURPHASECENTERS $0#!HAS TWOORMOREPHASECENTERS ARADARWITHAGUARDHORNFORSIDELOBESUPPRESSIONHASTWO PHASECENTERS ANDANADAPTIVEARRAYMAYHAVEMANYPHASECENTERSn 34!0ISAN EXTENSIONOFTHECLASSICTHEORYFORAMATCHEDFILTERINTHEPRESENCEOFNONnWHITENOISE WHICHINCLUDESBOTHTIMEANDSPACE /VERALLWEAPONSYSTEMREQUIREMENTSUSUALLYFAVOR8OR+UBANDFORTHEOPERATING FREQUENCYOFA-&!2)NADDITION THE-&!2APERTURESANDASSOCIATEDTRANSMITTERARE USUALLYTHELARGESTONANAIRCRAFTANDHENCE CANCREATETHEHIGHEST%FFECTIVE2ADIATED 0OWER%20 FORJAMMINGADVERSARYRADARSANDDATALINKS WHERETHESEAREIN BAND -ULTIFUNCTIONAL 2ADAR !RCHITECTURE !N EXAMPLE -&!2 BLOCK DIAGRAM IS SHOWNIN&IGURE4HEMODERNINTEGRATEDAVIONICSUITECONCEPTBLURSTHEBOUNDARIES BETWEENTRADITIONALRADARFUNCTIONSANDOTHERSENSORS COUNTERMEASURES WEAPONS AND COMMUNICATIONSSEE&IGURESANDLATERINTHECHAPTER 4HEREISAMICROWAVE AND2&SUITEANELECTRO OPTICAL INFRARED ULTRAVIOLET%/ SUITEASTORESMANAGEMENT SUITEACONTROLSANDDISPLAYSSUITEAMULTIPLY REDUNDANTVEHICLEMANAGEMENTSUITE ANDAMULTIPLY REDUNDANTPROCESSORCOMPLEX %ACHMICROWAVEANDOR2&APERTUREMAYHAVESOMEEMBEDDEDSIGNALCONDITIONING BUTTHENMAYBEMULTIPLEXEDTOSTANDARDIZEDCOMMONDESIGN2& FILTER FREQUENCYREF ERENCE ANALOGTODIGITALCONVERSION!$ INPUT OUTPUT)/ ANDCONTROLMODULES! SIMILARDESIGNCONCEPTISUSEDFORTHEELECTRO OPTICAL%/ SENSORS STORESMANAGEMENT
&)'52% -&!2MERGEDWITHOTHERSENSORSADAPTED
x°{
2!$!2(!.$"//+
VEHICLEMANAGEMENT PILOT VEHICLEINTERFACE ANDINTEGRATEDCORE PROCESSINGSUITE4HERE ISSUBSTANTIALDATATRAFFICBETWEENTHECOREPROCESSINGANDTHESENSORSTOPROVIDEPOINT ING CUEING TRACKING ANDMULTISENSORFUSIONOFDETECTIONS4HEAIMOFTHISAPPROACHIS TOPROVIDEASHAREDPOOLOFCOMPUTATIONALRESOURCES WHICHMAYBEFLEXIBLYALLOCATED BETWEENSENSORSANDFUNCTIONS 4HESENSORSMAYCONTAINDEDICATEDMOTIONSENSING BUTLONG TERMNAVIGATIONISPRO VIDEDBYTHEVEHICLEMANAGEMENTGLOBALPOSITIONINGSYSTEMANDINERTIALNAVIGATIONSYS TEM'03).3 4HEON RADARMOTIONSENSINGMUSTSENSEPOSITIONTOAFRACTIONOFTHE TRANSMITTEDWAVELENGTHOVERTHECOHERENTPROCESSINGINTERVAL4HISISUSUALLYDONEWITH INERTIAL SENSORS SUCH AS ACCELEROMETERS AND GYROS WITH VERY HIGH SAMPLING RATES!N INERTIALNAVIGATIONSYSTEMESTIMATESTHEPOSITIONOFTHEAIRCRAFTINAWORLDWIDECOORDINATE SPACEBYINTEGRATINGTHEOUTPUTSOFTHEGYROSANDACCELEROMETERS TYPICALLYUSING+ALMAN FILTERINGTECHNIQUES!CCUMULATEDERRORSINSUCHASYSTEMCANBECORRECTEDBYUSING'03 UPDATESASWELLASKNOWNREFERENCEPOINTSMEASUREDWITHTHERADAR OR%/SENSORS 4HEREMAYBEDOZENSORHUNDREDSOFSTOREDPROGRAMDEVICESDISTRIBUTEDTHROUGHOUT THEAVIONICS4HESELOWERLEVELFUNCTIONALSUITESARECONNECTEDBYSTANDARDIZEDBUS SES WHICHMAYBEFIBEROPTICORWIRED4HEPROGRAMMABLEDEVICESARECONTROLLEDBY SOFTWAREOPERATINGENVIRONMENTSINVOKINGPROGRAMS4HEARCHITECTUREOBJECTIVEISTO HAVESTANDARDINTERFACES FEWUNIQUEASSEMBLIES ANDSINGLE LEVELMAINTENANCE 4HE SUITE OF MICROWAVE AND 2& APERTURES IN A FIGHTER AIRCRAFT MIGHT APPEAR AS SHOWNIN&IGURE!SMANYASAPERTURESMAYBEDISTRIBUTEDTHROUGHOUTTHEVEHI CLE PERFORMINGRADAR DATALINK NAVIGATION MISSILEWARNING DIRECTIONFINDING JAM MING OROTHERFUNCTIONSOVERAFREQUENCYRANGECOVERINGSEVERALDECADES4HEREARE APERTURESDISTRIBUTEDOVERTHEAIRCRAFTTHATPOINTFORWARDANDAFT RIGHTANDLEFT ASWELL ASUPANDDOWN3OMEAPERTURESWILLBESHAREDFORCOMMUNICATIONS RADIONAVIGATION ANDIDENTIFICATION#.) ASWELLASIDENTIFICATION FRIENDORFOE)&& DUETOCOMPATIBLE FREQUENCIESANDGEOMETRIES$ATALINKSSUCHAS*4)$3,INKAND,INKCANSHARE APERTURESWITH'03AND,BANDSATELLITECOMMUNICATIONS,3!4#/- %7APERTURES MUSTBEBROADBANDBYNATUREANDCANBESHAREDWITHRADARWARNINGRECEIVERS272 RADARAUXILIARIES ANDSOMETYPESOF#.)S
&)'52% -&!22&APERTURESSHARELOW LEVEL2&ADAPTED
-5,4)&5.#4)/.!,2!$!23934%-3&/2&)'(4%2!)2#2!&4
x°x
&)'52% -&!2PROCESSINGADAPTED
4HEAPERTURESARESIGNALCONDITIONED CONTROLLED ANDINTERFACEDTHROUGHBUSSESINTHE AIRCRAFTWITHREMAININGPROCESSINGPERFORMEDEITHERINACOMMONPROCESSORCOMPLEX ASSHOWNIN&IGURE ORINFEDERATEDPROCESSORSDISTRIBUTEDTHROUGHOUTTHEAIRCRAFT /NEIMPORTANTCLASSOFSTANDARDIZEDMODULESCONTAINSBASICTIMINGANDPROGRAMMABLE EVENTGENERATORS0%' THATCREATEACCURATETIMINGFOR0ULSE2EPETITION&REQUENCIES 02&S ANALOGTODIGITALCONVERSION!$ SAMPLING PULSEANDCHIPWIDTHS BLANK INGGATES BEAMREPOINTINGCOMMANDS ANDOTHERSYNCHRONIZEDREAL TIMEINTERRUPTS! SECONDCLASSCONTAINS2&ANDINTERMEDIATEFREQUENCY)& AMPLIFICATIONANDMIXING ! THIRD CLASS CONTAINS LOW NOISE FREQUENCY SYNTHESIZERS WHICH MAY INCLUDE $IRECT $IGITAL FREQUENCY3YNTHESIS$$3 !$CONVERTERSANDCONTROLINTERFACEMODULESARE THEFINALCLASS"USSINGPROTOCOLSANDSPEEDSMUSTHAVEADEQUATERESERVESTOINSURE FAIL SAFEREAL TIMEOPERATION 4HEFUNCTIONALBLOCKDIAGRAMANDOPERATIONOFASPECIFICSENSORMODEISTHENOVER LAIDONTHISHARDWAREANDSOFTWAREINFRASTRUCTURE!SPECIFICMODEISIMPLEMENTEDINAN APPLICATIONSPROGRAMINTHESAMESENSETHATWORD PROCESSINGISONAPERSONALCOMPUTER 0# #ARRYINGTHEANALOGYFURTHER COMMONEXPERIENCEWITHTHEUNRELIABILITYOF0# HARDWAREANDSOFTWAREREQUIRESTHATASYSTEMOFTHETYPEDEPICTEDIN&IGUREMUST BEREDUNDANT ERRORCHECKING TRUSTED FAILSAFEINTHEPRESENCEOFFAULTS ANDEMBODY STRICTPROGRAMEXECUTIONSECURITY4HISISAVERYCHALLENGINGSYSTEMENGINEERINGTASK %XHAUSTIVEMATHEMATICALASSURANCEANDSYSTEMTESTINGISREQUIRED WHICHISCOMPLETELY DIFFERENTFROMCURRENTCOMMERCIALPERSONALCOMPUTERPRACTICE !NOTIONAL-&!2INTEGRATEDCOREPROCESSINGCOMPLEXWITHITSCORRESPONDINGINTER FACES SIMILAR TO THAT SHOWN IN &IGURE IS SHOWN IN &IGURE WHERE THERE ARE MULTIPLEREDUNDANTPROCESSINGARRAYSTHATCONTAINSTANDARDIZEDMODULESCONNECTEDIN ANON BLOCKINGSWITCHEDNETWORK)NTERNALANDEXTERNALBUSSESCONNECTTHEINDIVIDUAL PROCESSINGARRAYSTOEACHOTHERASWELLASTOTHEOTHERSUITES SENSORS CONTROLS AND DISPLAYS 5SUALLY THERE ARE BOTH PARALLEL ELECTRICAL SIGNAL BUSSES AS WELL AS SERIAL FIBER OPTICBUSSESDEPENDINGONSPEEDANDTOTALLENGTHINTHEAIRCRAFT4HESIGNALANDDATA PROCESSORCOMPLEXCONTAINSMULTIPLEPROCESSORANDMEMORYENTITIES WHICHMIGHTBE
x°È
2!$!2(!.$"//+
ONASINGLECHIPORONSEPARATECHIPSDEPENDINGONYIELD COMPLEXITY SPEED CACHE SIZE ANDSOON%ACHPROCESSORARRAYMAYCONSISTOFPROGRAMMABLESIGNALPROCESSORS 030 GENERALPURPOSEPROCESSORS'00 BULKMEMORY"- INPUT OUTPUT)/ AND AMASTERCONTROLUNIT-#5 4HE030SPERFORMSIGNALPROCESSINGONARRAYSOFSENSOR DATA4HE'00SPERFORMPROCESSINGINWHICHTHEREARELARGENUMBERSOFCONDITIONAL BRANCHES4HE -#5 ISSUES PROGRAMS TO 030S '00S AND "- AS WELL AS MANAGES OVERALL EXECUTION AND CONTROL4YPICAL PROCESSING SPEED IS -)03 MILLIONS OF INSTRUCTIONSPERSECOND PERCHIPBUTMIGHTBE')03BILLIONSOFINSTRUCTIONSPER SECOND INTHENEARFUTURE#LOCKFREQUENCIESARELIMITEDBYON CHIPSIGNALPROPAGA TIONBUTAREUPTO'(ZGIGAHERTZ ANDCOULDBE'(ZINTHENEARFUTURE3ENSOR PROCESSINGHASARRIVEDATTHEPOINTWHERETHECONCEPTIONOFSUCCESSFULALGORITHMSIS MOREIMPORTANTTHANTHECOMPUTATIONALHORSEPOWERNECESSARYTOCARRYTHEMOUT -&!2 3OFTWARE 3TRUCTURE )MPROPER OPERATION OF MANY FIGHTER SYSTEMS CANBEHAZARDOUS!SPREVIOUSLYMENTIONED THESOFTWAREMUSTBEEXHAUSTIVELY TESTED ERRORCHECKED MATHEMATICALLYTRUSTED FAILSAFEINTHEPRESENCEOFFAULTS ANDEMBODYSTRICTPROGRAMEXECUTIONSECURITY/NEOFTHEMOSTIMPORTANTASPECTS ISRIGIDADHERENCETOASTRUCTUREDPROGRAMARCHITECTURE!NOBJECT BASEDHIERARCHI CALSTRUCTURE WHEREEACHLEVELISSUBORDINATETOTHELEVELABOVEANDSUBPROGRAMS ARECALLEDINSTRICTSEQUENCE ISNECESSARY)TALSOREQUIRES AMONGOTHERTHINGS THAT SUBPROGRAMS NEVER CALL THEMSELVES RECURSIVE CODE OR ANY OTHERS AT THEIR EXECUTIONLEVEL3UBPROGRAMSOBJECTS ARECALLED RECEIVEEXECUTIONPARAMETERS FROMTHELEVELABOVETHEPARENT ANDRETURNRESULTSBACKTOTHECALLINGLEVEL!N EXAMPLEOFSUCHASOFTWARESTRUCTUREISSHOWNIN&IGURESAND4HESOFTWARE WOULDBEEXECUTEDINTHEHARDWARESHOWNIN&IGURE
&)'52% -&!2STRUCTUREDSOFTWARE
-5,4)&5.#4)/.!,2!$!23934%-3&/2&)'(4%2!)2#2!&4
x°Ç
&)'52% -&!2PRIORITYSCHEDULING
!N -&!2 CAN SUPPORT MANY ACTIVITIES OR MODES CONCURRENTLY BY INTERLEAVING THEIR RESPECTIVE DATA COLLECTIONS 3URVEILLANCE TRACK UPDATES AND GROUND MAPS ARE EXAMPLESOFSUCHACTIVITIES4HESOFTWARENEEDEDTOSUPPORTEACHACTIVITYISMAPPEDTO ASPECIFICCLIENTMODULE ASSHOWNIN&IGURE%ACHCLIENTMODULEISRESPONSIBLEFOR MAINTAININGITSOWNOBJECTDATABASEANDFORREQUESTINGUSEOFTHEAPERTURE2EQUESTS AREMADEBYSUBMITTINGANTENNAJOBREQUESTSTHATSPECIFYBOTHTHEWAVEFORMTOBEUSED HOWTODOIT ANDTHEPRIORITYANDURGENCYOFTHEREQUEST !SCHEDULEREXECUTESDURINGEACHDATACOLLECTIONINTERVALANDDECIDESWHATTODO NEXT BASEDONTHEPRIORITIESANDURGENCIESOFTHEANTENNAJOBREQUESTSTHATHAVEBEEN RECEIVED4HISKEEPSTHEAPERTUREBUSYANDRESPONSIVETOTHELATESTACTIVITYREQUESTS &OLLOWINGTHESELECTIONOFTHEANTENNAJOBBYTHESCHEDULER THEFRONT ENDTRANSMITAND RECEIVE HARDWAREISCONFIGURED ANDIN PHASEANDQUADRITURE)1 DATAISCOLLECTEDAND SENTTOTHESIGNALPROCESSORS4HERE THEDATAISPROCESSEDINAMANNERDEFINEDBYTHE SENSORMODE ANDTHESIGNALPROCESSINGRESULTSARERETURNEDTOTHECLIENTTHATREQUESTED THEM4HISTYPICALLYRESULTSINDATABASEUPDATESANDORNEWANTENNAJOBREQUESTSFROM THECLIENT.EWACTIVITIESCANBEADDEDATANYTIMEUSINGTHISMODULARAPPROACH !LTHOUGHTHISSTRUCTUREISCOMPLEXANDTHESOFTWAREENCOMPASSESMILLIONSOFLINES OF CODE MODERN -&!2 SOFTWARE INTEGRITY CAN BE MAINTAINED WITH STRICT CONTROL OF INTERFACES FORMALCONFIGURATIONMANAGEMENTPROCESSES ANDFORMALVERIFICATIONAND VALIDATION SOFTWARE TOOLS )N ADDITION MOST SUBPROGRAMS ARE DRIVEN BY READ ONLY TABLES ASSHOWNIN&IGURE SOTHATTHEEVOLUTIONOFAIRCRAFTTACTICS CAPABILITIES AND HARDWAREDONOTREQUIREREWRITESOFVALIDATEDSUBPROGRAMS3OFTWAREVERSIONSBUILDS AREUPDATEDEVERYYEARTHROUGHOUTTHELIFETIMEOFTHESYSTEM WHICHMAYBEDECADES %ACHSUBPROGRAMMUSTHAVETABLEDRIVENERRORCHECKINGASWELL-ANYLOWERLEVELSARE NOTSHOWNIN&IGURESANDTHEREMAYBESEVERALTHOUSANDSUBPROGRAMSINALL 2ANGE$OPPLER3ITUATION -ODERNRADARSHAVETHELUXURYOFINTERLEAVINGMOST OFTHEMODESSUGGESTEDIN&IGUREINREALTIMEANDSELECTINGTHEBESTAVAILABLETIME ORAIRCRAFTPOSITIONTOINVOKEEACHMODEASTHEMISSIONREQUIRES 4HEGEOMETRYTHATMUSTBESOLVEDEACHTIMEISSHOWNIN&IGURE4HEFIGHTER AIRCRAFTPULSEDOPPLERGEOMETRYISCENTEREDAROUNDTHEAIRCRAFTTRAVELINGATAVELOCITY 6A ANDATANALTITUDE H ABOVETHE%ARTHSSURFACE4HERADARPULSEREPETITIONFREQUENCY
x°n
2!$!2(!.$"//+
&)'52% 3TRIKEFIGHTERPULSEDOPPLERGEOMETRY
02& GIVESRISETOASERIESOFRANGE ANDDOPPLERX Y Z AMBIGUITIES AS SHOWN IN &IGURE WHICH INTERCEPT THE %ARTHS SURFACE AS RANGE hRINGSv AND ISO DOPPLERhHYPERBOLASvBECAUSETHE%ARTHISAROUGHGEOID CONSTANTRANGEANDDOPPLER CONTOURSARENOTACTUALLYRINGSORHYPERBOLAS 4HERADARANTENNAPATTERNINTERCEPTSTHE LIMBOFTHE%ARTHUSUALLYINBOTHTHEMAINBEAMANDSIDELOBES!TARGETINTHEMAIN BEAMATRANGE 2T ANDVELOCITY 6T MAYHAVETOBEOBSERVEDINTHEPRESENCEOFBOTH RANGEANDDOPPLERAMBIGUITIES/NLYTHETARGETSLINE OF SIGHTVELOCITY 6TLOS ISOBSERV ABLEONASHORTTERMBASIS4HERADARDESIGNERSPROBLEMISTOSELECTTHEBESTWAVEFORM INTHISTARGET CLUTTERGEOMETRY(ISTORICALLY THESEWAVEFORMSWERESELECTEDAHEADOF TIME AND BUILT INTO THE RADAR HARDWARE AND SOFTWARE -OST MODERN AIRBORNE RADARS SOLVETHISGEOMETRYINREALTIMEANDCONTINUOUSLYSELECTTHEBESTAVAILABLEFREQUENCY 02& PULSEWIDTH TRANSMITPOWER SCANPATTERN ETC 5NFORTUNATELY THESPECIFICSOFTHEWAVEFORMAREUNPREDICTABLEEVENTOTHERADAR WITHOUTEXACTKNOWLEDGEOFTHEAIRCRAFT TARGET EARTHVELOCITY GEOMETRYSETANDMODE OFOPERATIONREQUESTEDBYTHEOPERATORORMISSIONSOFTWARE4HISMAKESTESTINGQUITE DIFFICULTFORTUNATELY TESTEQUIPMENTHASCOMEALONGWAY(ARDWARE IN THE LOOPTEST INGUSINGREAL TIMESIMULATIONOFTHEENTIREGEOMETRYANDEXTERNALWORLDINTHERADAR INTEGRATIONLABORATORYISCOMMONLYEMPLOYED !CTIVE%LECTRONICALLY3CANNED!RRAY!%3! !LTHOUGHMULTIFUNCTIONALRADARS HAVEBEENDEPLOYEDWITHMECHANICALLYSCANNEDANDELECTRONICALLYSCANNEDANTENNAS FULLYMULTIFUNCTIONALRADARSUSE!CTIVE%LECTRONICALLY3CANNED!RRAYS!%3! WHICH CONTAINATRANSMIT RECEIVECHANNEL42 FOREACHRADIATOR4HEADVANTAGESOF!%3! ARE FAST ADAPTIVE BEAM SHAPING AND AGILITY IMPROVED POWER EFFICIENCY IMPROVED MODEINTERLEAVING SIMULTANEOUSMULTIPLEWEAPONSUPPORT ANDREDUCEDOBSERVABIL ITYn0ERHAPSHALFTHECOSTANDCOMPLEXITYOFAN!%3!ISINTHE42CHANNELS4HAT SAID HOWEVER THEFEEDNETWORK BEAMSTEERINGCONTROLLER"3# !%3!POWERSUPPLY ANDCOOLINGSUBSYSTEMAIRORLIQUID AREEQUALLYIMPORTANT
-5,4)&5.#4)/.!,2!$!23934%-3&/2&)'(4%2!)2#2!&4
x°
!MAJORENABLERFOR!%3!SISTHESTATEOFTHEARTINMICROWAVEINTEGRATEDCIRCUITS 4HISHASFOLLOWEDTHEDRAMATICCOSTANDPERFORMANCEGAINSAVAILABLEINMOSTSEMICON DUCTORTECHNOLOGIES%ACH42CHANNELHASSELF DIAGNOSISFEATURES WHICHCANDETECT FAILUREANDCOMMUNICATETHATTOTHEBEAMSTEERINGCONTROLLERFORFAILURECOMPENSATION !%3!SCANACCOMMODATEUPTOFAILURESWITHVERYLITTLEDEGRADATIONIFPROPERLY COMPENSATEDINTHE"3# &ROMAN-&!2POINTOFVIEW THEIMPORTANTPARAMETERSAREVOLUMETRICDENSITIES HIGHENOUGHTOSUPPORTLESSTHANWAVELENGTHSPACINGRADIATEDPOWERDENSITIESHIGH ENOUGH TO SUPPORT WATTS PER SQ CM RADIATED TO PRIME POWER EFFICIENCIES GREATER THANBANDWIDTHOFSEVERAL'(ZONTRANSMITANDALMOSTTWICETHATBANDWIDTHON RECEIVEPHASEANDAMPLITUDECALIBRATIONANDCONTROLADEQUATETOPROVIDEATLEASTnD" RMSSIDELOBESAMPLITUDECONTROLADEQUATETOPROVIDED"POWERMANAGEMENTNOISE PERFORMANCEADEQUATETOSUPPORTTHESUBCLUTTERVISIBILITYREQUIREMENTSANDFINALLY SUF FICIENT STORAGE AND COMPUTING TO ALLOW BEAM REPOINTINGADJUSTMENT IN A FRACTION OF MSEC&ASTBEAMADJUSTMENTREQUIRESHIGH SPEEDBUSSESTOEACH42CHANNEL /NEOFTHEPRINCIPALADVANTAGESOFAN!%3!ISTHEABILITYTOMANAGEBOTHPOWER ANDSPATIALCOVERAGEONASHORT TERMBASISSOFMSEC /FTENANOTHERADVANTAGEIS THATBOTHTHENOISEFIGUREISLOWERANDRADIATEDPOWERISHIGHERFORAGIVENAMOUNTOF PRIMEPOWER4HISISBECAUSETHE2&PATHLENGTHSCANBEMUCHSHORTER WHICHUSUALLY LEADSTOLOWERFRONT ENDLOSSES%ACHRADIATINGELEMENTISUSUALLYDESIGNEDTOBEVERY BROADBANDANDISDRIVENBYA42CHANNELINATYPICAL!%3!ARRAY4HEREARETYPI CALLYAFEWTHOUSANDCHANNELSINAN-&!2!%3!%ACHCHANNELCONTAINSFIRST LEVEL POWERREGULATION FILTERING LOGIC CALIBRATIONTABLESASWELLASTHEOBVIOUS2&FUNC TIONS3OMECHANNELSINTHEARRAYAREDEDICATEDTOOTHERFUNCTIONSSUCHASCALIBRATION JAMMER NULLING SIDELOBE BLANKING CLOSE IN MISSILE DATALINK OUT OF BAND DIRECTION FINDING ETC !LSO THEREAREUSUALLYSOMECHANNELSATTHEEDGEOFTHEARRAYTHAT AREPASSIVEANDIMPROVETHESIDELOBESAND2#3PATTERN &IGURE SHOWS THE COMPARISON BETWEEN A CONVENTIONAL MECHANICALLY SCANNED RADAR WITH THE LOW NOISE AMPLIFIER AND A HIGH POWER TRAVELING WAVE TUBE TRANSMIT TERMOUNTEDOFFTHEGIMBALVERSUSAREAL TIMEADAPTED!%3!WITHTWODIFFERENTSCAN REGIMESFORTHESAMEAMOUNTOFINPUTPRIMEPOWER!%3!PERFORMANCEFALLSOFFFOR LARGESCANCOVERAGEBECAUSEOFTHELOWERPROJECTEDAPERTUREAREAFORAFIXEDMOUNTINGAS SHOWNIN&IGURE!MECHANICALSCANHASTHESAMEPROJECTEDAREAINALLDIRECTIONSAND LARGESCANANGLESMARGINALLYREDUCERADOMELOSSES WHICHRESULTSINSLIGHTLYIMPROVED LARGEANGLEPERFORMANCE.ONETHELESS !%3!PERFORMANCEISUSUALLYSUPERIORINSIDE
&)'52% %XAMPLE!%3!MANAGEMENTCOMPARISONADAPTED
x°£ä
2!$!2(!.$"//+
A on AZIMUTH SCAN 5SUALLY A FIGHTER CANT ENGAGE AT LONG RANGE OUTSIDE THIS AZIMUTHFORKINEMATICREASONS 4HEPERFORMANCEDIFFERENCESDEPICTEDIN&IGUREARETHERESULTOFTHREEFACTORS THEINSTALLEDAPERTURECANBELARGERINNETPROJECTEDAREAATTHEAIRCRAFTIN FLIGHT HORIZONTALDUETOELIMINATIONOFGIMBALSWINGSPACE HIGHERRADIATEDPOWERDUETO LOWERLOSSESANDBETTEREFFICIENCY ANDLOWERLOSSESBEFORETHELOW NOISEAMPLI FIER4HEOTHERMAJORADVANTAGEISTHATSEARCHVOLUMECANBECHANGEDDYNAMICALLYTO FITTHEINSTANTTACTICALSITUATION ASSUGGESTEDIN&IGURE 4HE FEED NETWORK IS MUNDANE BUT CRITICALLY IMPORTANT )N SINGLE TUBE TRANSMIT TERS THEFEEDISHEAVYBECAUSEITMUSTCARRYHIGHPOWERATLOWLOSS!%3!FEEDSUSE SMALLERCOAX STRIPLINE MICROSTRIP OR2&MODULATEDLIGHTINFIBEROPTICSFORTRANSMIT ANDRECEIVE2& SINCELESSTHANWATTS2&OROPTICALISUSUALLYREQUIRED(OWEVER SIGNIFICANT$#POWERISSTILLREQUIREDFOR2&FEEDDISTRIBUTIONAMPLIFIERSBECAUSETHOU SANDSMUSTBEDRIVEN#OST WEIGHT ANDCOMPLEXITYISSTILLANISSUEBECAUSEMULTIPLE PHASECENTERSNECESSARYFORADAPTIVEARRAYPERFORMANCEREQUIREMULTIPLEMANIFOLDS 5SUALLY ONCEASUBARRAYISFORMEDINTHEMANIFOLDS ITISDIGITIZEDANDMULTIPLEXEDFOR ADAPTIVESIGNALPROCESSING !NOTHERIMPORTANTFUNCTIONISBEAMSTEERINGCONTROL"3# 4HE"3#DOESARRAY CALIBRATION FAILED ELEMENT COMPENSATION PHASE AND AMPLITUDE SETTING FOR BEAM STEERING AS WELL AS SPACE TIME ADAPTIVE OPERATIONn4HE "3# IS USUALLY REALIZED WITH A COMBINATION OF GENERAL PURPOSE PROCESSING OF THE TYPE FOUND IN A PERSONAL COMPUTERWITHVERYHIGHSPEEDINCREMENTALPHASEANDAMPLITUDECALCULATIONAND42 MODULEINTERFACEHARDWARE"OTHSCANNINGANDADAPTIVEOPERATIONREQUIREVERYLOW LATENCYIE THETIMEBETWEENTHESENSEDNEEDANDTHEFIRSTPULSEATTHETARGETISUSUALLY MSEC BEAMCONTROLINAHIGH SPEEDAIRCRAFTPLATFORM ,ASTLY THE!%3!REQUIRESAVERYSIGNIFICANTPOWERSUPPLY0OWERSUPPLIESHAVE AHISTORYOFBEINGHEAVY HOT ANDUNRELIABLE%VENTHEBESTSYSTEMSSTILLHAVEOVERALL POWEREFFICIENCIESPRIMEPOWERINTO2&OUTINSPACE INTHEnREGIONINSPITE OF YEARS OF DEVELOPMENT 4HE TYPICAL!%3! REQUIRES LOW VOLTAGE AND HIGH CURRENT ATTHE42CHANNEL4HISFORCESLARGECONDUCTORSINTHEABSENCEOFHIGHPOWERLIGHT WEIGHTSUPERCONDUCTORSNOTAVAILABLEATTHISWRITING )TALSOREQUIRESVERYLOWVOLTAGE DROPRECTIFIERSANDREGULATORS#OOLINGISGENERALLYASIGNIFICANTPERFORMANCEBURDEN 5SUALLY THEPOWERSUPPLIESAREDISTRIBUTEDTOIMPROVERELIABILITYANDFAULTTOLERANCE /FTEN POWERCONVERTERSAREOPERATEDATSWITCHINGFREQUENCIESUPTOSEVERALHUNDRED MEGAHERTZTOREDUCETHESIZEOFMAGNETICSANDFILTERCOMPONENTS ANDSOMETIMES THE SWITCHINGFREQUENCIESARESYNCHRONIZEDTOTHERADARMASTERCLOCK
x°ÓÊ /9* Ê --" -Ê Ê " !IR TO 3URFACE-ISSION0ROFILE 4HEMODESTRUCTUREOFANYMODERNFIGHTERAIR CRAFTARISESFROMMISSIONPROFILES /NETYPICALMISSIONPROFILEFORANAIR TO SURFACE ! 3 STRIKEISSHOWNIN&IGURE4HEMISSIONPROFILEBEGINSWITHATAKEOFF CON TINUESTHROUGHFLIGHTTOATARGET ANDULTIMATELYRETURNSTOTHESTARTINGPOINT!LONGTHE WAY THEAIRCRAFTUSESAVARIETYOFMODESTONAVIGATE SEARCHANDACQUIRETARGETS TRACK TARGETS DELIVERWEAPONS ASSESSBATTLEDAMAGE ENGAGEINCOUNTERMEASURES ANDMONI TORANDCALIBRATEITSPERFORMANCE!%3!SHAVEDEMONSTRATEDSIMULTANEOUSMULTIPLE WEAPONDELIVERIES
-5,4)&5.#4)/.!,2!$!23934%-3&/2&)'(4%2!)2#2!&4
x°££
&)'52% 4YPICALAIR TO SURFACEMISSIONPROFILE
!IR TO 3URFACE-ODE3UITE 4HEMISSIONNATURALLYCREATESTHENEEDFORANAIR TO SURFACEMODESUITE FORFIGHTERRADAR ASSHOWNIN&IGURE%ACHGENERALCAT EGORYOFOPERATIONCONTAINSMODESPRIMARILYFORTHATFUNCTION BUTMODESWILLOFTEN BEINVOKEDDURINGOTHERPARTSOFTHEMISSION7ITHINEACHMODESHOWNIN&IGURE THERE IS OPTIMIZATION FOR THE PARTICULAR COMBINATION OF ALTITUDE RANGE TO THE TARGET ANTENNAFOOTPRINTONTHE%ARTHSSURFACE RELATIVETARGETANDCLUTTERDOPPLER DWELLTIME AVAILABLE PREDICTEDTARGETSTATISTICALBEHAVIOR TRANSMITTEDFREQUENCY ANDDESIREDRESO LUTION/BVIOUSLY EACHMODEMUSTNOTCOMPROMISESOMEREQUIREDLEVELOFMISSION STEALTHn!MODERNFIGHTERISNET CENTRICANDEXCHANGESSUBSTANTIALINFORMATIONWITH OTHERSYSTEMS"OTHTHEFIGHTERSWINGMAN SUPPORTAIRCRAFT ANDSURFACENODESMAY EXCHANGECOMPLETEDATAANDTASKINGINREALTIMETOFACILITATEAMISSION4HEFIGHTER ANDITSWINGMANWILLCOORDINATEMODETASKINGSOTHATDURINGAHIGHRESOLUTIONGROUND MAP WHICHCOULDTAKEAMINUTETOFORM THEWINGMANMIGHTBEPERFORMINGANAIR TO AIRSEARCHANDTRACKTOPROTECTBOTHOFTHEM
&)'52% &IGHTERAIRCRAFTAIR TO SURFACERADARMODESUITE
x°£Ó
2!$!2(!.$"//+
3OMEMODESAREUSEDFORSEVERALOPERATIONALCATEGORIES SUCHASREALBEAMMAP 2"- FIXEDTARGETTRACK&44 DOPPLERBEAMSHARPENING$"3 ANDSYNTHETICAPER TURERADAR3!2 USEDNOTONLYFORNAVIGATIONBUTALSOFORACQUISITIONANDWEAPON DELIVERYTOFIXEDTARGETSn3!2MAYALSOBEUSEDTODETECTTARGETSINEARTHWORKSOR TRENCHESCOVEREDWITHCANVASANDASMALLAMOUNTOFDIRT WHICHAREINVISIBLETO%/ OR )2 SENSORS 3IMILARLY AIR TO SURFACE RANGING ! 3 2ANGE AND PRECISION VELOCITY UPDATE065 MAYBEUSEDFORWEAPONSUPPORTTOIMPROVEDELIVERYACCURACYASWELL ASNAVIGATION 4ERRAIN FOLLOWING AND TERRAIN AVOIDANCE 4&4! IS USED FOR NAVIGATION AT VERY LOWALTITUDESORINMOUNTAINOUSTERRAIN3EASURFACESEARCH333 SEASURFACETRACK 334 ANDINVERSESYNTHETICAPERTURERADAR)3!2 WHICHWILLBEDESCRIBEDLATERIN THE CHAPTER ARE USED PRIMARILY FOR THE ACQUISITION AND RECOGNITION OF SHIP TARGETS 'ROUNDMOVINGTARGETINDICATION'-4) ANDGROUNDMOVINGTARGETTRACKING'-44 AREUSEDPRIMARILYFORTHEACQUISITIONANDRECOGNITIONOFSURFACEVEHICLETARGETSBUT ALSOFORRECOGNIZINGLARGEMOVEMENTSOFSOLDIERSANDMATERIALSINABATTLE SPACE(IGH POWERJAMMING(I0WR*AM ISACOUNTERMEASUREAVAILABLEFROM!%3!SDUETOTHEIR NATURALBROADBAND BEAMAGILE HIGHGAIN ANDHIGHPOWERATTRIBUTES!%3!SALSOALLOW LONGRANGEAIR TO SURFACEDATALINKS! 3$ATA,INK THROUGHTHERADARPRIMARILYFOR MAPIMAGERY"ECAUSETHEREMAYBETHOUSANDSOFWAVELENGTHSANDAGAINOFMILLIONS THROUGHARADAR AUTOMATICGAINCONTROLANDCALIBRATION!'##!, ISUSUALLYREQUIRED FAIRLYOFTEN-ODESOPTIMIZEDFORTHISFUNCTIONAREINVOKEDTHROUGHOUTAMISSION 7AVEFORM6ARIATIONSBY-ODE !LTHOUGHTHESPECIFICWAVEFORMISHARDTOPRE DICT TYPICALWAVEFORMVARIATIONSCANBETABULATEDBASEDONOBSERVEDBEHAVIOROFA NUMBEROFEXISTING! 3RADARSYSTEMS4ABLESHOWSTHERANGEOFPARAMETERSTHAT CANBEOBSERVEDASAFUNCTIONOFRADARMODE4HEPARAMETERRANGESLISTEDARE02& PULSEWIDTH DUTYCYCLE PULSECOMPRESSIONRATIO INDEPENDENTFREQUENCYLOOKS PULSES PERCOHERENTPROCESSINGINTERVAL#0) TRANSMITTEDBANDWIDTH ANDTOTALPULSESINA 4IME /N 4ARGET4/4 /BVIOUSLY MOSTRADARSDONOTCONTAINALLOFTHISVARIATION BUTMODESEXISTINMANY FIGHTERAIRCRAFT WHICHREPRESENTAGOODFRACTIONOFTHEPARAMETERRANGE-OSTFIGHTER RADARSAREFREQUENCYAGILESINCETHEYWILLBEOPERATEDINCLOSEPROXIMITYTOSIMILAROR IDENTICALSYSTEMS4HEFREQUENCYUSUALLYCHANGESINACAREFULLYCONTROLLED COMPLETELY COHERENTMANNERDURINGA#0)4HISCANBEAWEAKNESSFORCERTAINKINDSOFJAMMING SINCETHEPHASEANDFREQUENCYOFTHENEXTPULSEISPREDICTABLE3OMETIMESTOCOUNTER ACTTHISWEAKNESS THEFREQUENCYSEQUENCEISPSEUDORANDOMFROMAPREDETERMINEDSET WITHKNOWNAUTOCORRELATIONPROPERTIES FOREXAMPLE &RANK #OSTAS 6ITERBI 0CODES !MAJORDIFFICULTYWITHCOMPLEXWIDEBANDFREQUENCYCODINGISTHATTHEPHASESHIFT ERSINAPHASESCANNEDARRAYMUSTBECHANGEDONANINTRA ORINTER PULSEBASISGREATLY COMPLICATINGBEAMSTEERINGCONTROLANDABSOLUTE42CHANNELPHASEDELAY!NOTHER CHALLENGEISMINIMIZINGPOWERSUPPLYPHASEPULLINGWHEN02&SANDPULSEWIDTHSVARY OVERMORETHANRANGE-&!2SYSTEMSNOTONLYHAVEAWIDEVARIATIONIN02& AND PULSEWIDTH BUT ALSO USUALLY EXHIBIT LARGE INSTANT AND TOTAL BANDWIDTH #OUPLED WITHTHELARGEBANDWIDTHISTHEREQUIREMENTFORLONGCOHERENTINTEGRATIONTIMES4HIS REQUIREMENTNATURALLYLEADSTOEXTREMESTABILITYMASTEROSCILLATORSANDULTRALOW NOISE SYNTHESIZERS !IR TO !IR -ISSION 0ROFILE *UST AS WITH AN AIR TO SURFACE MISSION THE MODE STRUCTUREOFAMODERNFIGHTERAIRCRAFTAIR TO AIRMISSIONARISESFROMITSPROFILE!TYPI CALMISSIONPROFILEFORAIR TO AIR! ! ISSHOWNIN&IGURE4HEMISSIONPROFILE
-5,4)&5.#4)/.!,2!$!23934%-3&/2&)'(4%2!)2#2!&4
x°£Î
4!",% 4YPICAL7AVEFORM0ARAMETERS! 3-ODES 0ULSE 7IDTH MSEC
$UTY #YCLE
&REQ ,OOKS
0ULSES 0ER#0)
4RANSMITTED "ANDWIDTH -(Z
n
n
n
n
n
n
n
n
n
n
nK
n
n
n
n
nK
n
nK
n
n
n
n
n
n
n
n
n
n
n
n
n
n
n
n
n
n
n
n
n
n
n
n
n
n
n
n
n
n
n
n
n
n
n
n
n
n
n
n
n
n
n
n
n
n
n
n
n
n
n
n
n
n
n
n
n
n
n
n
n
n
n
n
nK
n n
n n
n n
n n
n n
n KnK
2ADAR -ODES
02& K(Z
2EAL "EAM -AP
n
n
n
$OPPLER "EAM 3HARP
n
n
3!2
n
! 32ANGE
n n
n
4&4!
n
n
3EA 3URFACE 3EARCH
n
n
)NVERSE 3!2
n
n
'-4)
n
&IXED 4ARGET 4RACK
n
'-44
n
3EA 3URFACE 4RACK
n
(I0WR*AM
n
n
#AL!'# ! 3$ATA ,INK
n n
n n
065
0ULSE #OMP 2ATIO
4OTAL 0ULSES IN4/4
BEGINS WITH AN AIRFIELD OR CARRIER TAKEOFF CONTINUES THROUGH FLIGHT PENETRATING INTO AN ENEMY BATTLE SPACE SEARCHES FOR AIR TARGETS TO ATTACK AND ULTIMATELY RETURNS TO THE STARTING POINT!LONG THE WAY THE AIRCRAFT USES A VARIETY OF MODES TO NAVIGATE EXCHANGE DATA WITH COMMAND CONTROL COMMUNICATIONS INTELLIGENCE SURVEILLANCE
&)'52% 4YPICAL! !MISSIONPROFILE
x°£{
2!$!2(!.$"//+
RECONNAISSANCE#)32 ASSETSSEARCHANDACQUIREAIRBORNETARGETSTRACKANDSEPARATE BENIGNTARGETSFROMTHREATSDELIVERWEAPONSESCAPEANDENGAGEINCOUNTERMEASURES MONITORANDCALIBRATEITSPERFORMANCE ANDRETURNTOBASE !IR TO !IR-ODE3UITE 3IMILARLY THE! !MISSIONNATURALLYCREATESTHENEEDFOR ACORRESPONDINGMODESUITEFORTHERADAR ASSHOWNIN&IGURE !TTHERADARSEN SORANDAIR TO AIRMODESOFTWARELEVEL THEREISADAPTIVETASKPRIORITIZATIONTOINSURETHAT THEHIGHESTPROCESSORPRIORITIZED PILOT SELECTEDTHREATISSERVICEDFIRST0ASSIVEMODES AREINTERLEAVEDWITHACTIVEOPERATIONTOIMPROVESURVIVABILITYANDPASSIVETRACKINGAND )$%ACHMODESHOWNIN&IGUREISOPTIMIZEDINREALTIMEFORTHEPARTICULARCOMBI NATIONOFALTITUDE RANGETOTHETARGET DENSITYOFTARGETTHREATS ANTENNAFOOTPRINTONTHE %ARTHSSURFACE RELATIVETARGETANDCLUTTERDOPPLER DWELLTIMEAVAILABLE PREDICTEDTARGET STATISTICALBEHAVIOR TRANSMITTEDFREQUENCY ANDDESIREDRESOLUTION 4HEMODECATEGORYhAUTONOMOUSANDCUEDSEARCHvCONTAINSTHEMODESMOSTCOM MONLYASSOCIATEDWITHFIGHTERRADARS4HEREAREUSUALLYTWORANGE GATEDHIGHPULSEREP ETITIONFREQUENCY(02& MODESVELOCITYSEARCH63 PRIMARILYDEDICATEDTOLONGEST RANGEDETECTIONANDRANGEWHILESEARCH273 WHICHUSESSOMEFORMOF&-RANGING TOESTIMATETARGETRANGE4HEREISAMEDIUM02&-02& MODE WHICHPROVIDESALL ASPECTVELOCITY RANGESEARCH623 ATTHEEXPENSEOFPOORERLONG RANGEPERFORMANCE )NADDITION THEREARETWOPASSIVEMODESPASSIVESEARCHANDRANGING INWHICHTHE RADARDETECTSANDESTIMATESRANGEANDANGLETOANEMITTERORBISTATICALLYWINGMANOR SUPPORTAIRCRAFT ILLUMINATEDTARGETAND%3-SHAREDAPERTUREINWHICHTHE2&ANDPRO CESSORCOMPLEXDETECTS ESTIMATESWAVEFORMPARAMETERS ANDRECORDSTHEMFORFUTURE USE0ASSIVESEARCHMAYBECOMBINEDWITHCUEDBURSTRANGINGTOBETTERESTIMATEEMIT TERLOCATION%XTENDEDVOLUMESEARCHISAMODEUSEDWITHCUEINGFROMANOTHERON OR OFF BOARDSENSORINWHATNORMALLYWOULDBEANUNFAVORABLEGEOMETRY -ANYMODESANDFUNCTIONSARESHAREDINCOMMONWITH! 3 ESPECIALLYCOUNTERMEA SURESANDPERFORMANCEMONITORING%XTREMELYIMPORTANTINBOTHMODESISIMPLEMENTA TIONOFEMISSIONSCONTROLTOMINIMIZETHEABILITYOFTHEADVERSARYTODETECT TRACK AND ATTACKUSINGTHERADAREMISSION7ITHOUTCARE THESEEMISSIONSCANEASILYSERVEASA STRONGGUIDANCESIGNALFORAHOSTILEANTIRADIATIONMISSILE!2- !NTENNAAPERTURES THATHAVEMULTIPLEINDEPENDENTPHASECENTERSCANPERFORMBOTHADAPTIVECLUTTERCANCEL LATIONASWELLASJAMMERCANCELLATIONWITHSUITABLEHARDWAREANDSOFTWARE n
&)'52% ! !MODESUITE
-5,4)&5.#4)/.!,2!$!23934%-3&/2&)'(4%2!)2#2!&4
x°£x
4HESUBSUITEOFMULTI TARGETTRACK-44 CONTAINSCONVENTIONALTRACKWHILESCAN 473 PASSIVETRACKINGOFEMITTERSORECHOESFROMBISTATICILLUMINATION MISSILETRACK ING WITH OR WITHOUT A MISSILE DATALINK OR BEACON AND SEVERAL MODES TO RECOGNIZE TARGETNUMBERANDTYPERAIDASSESSMENTANDNONCOOPERATIVETARGETRECOGNITIONUSU ALLYINCORRECTLYCALLEDTARGETIDENTIFICATION 4HEFIGHTERANDWINGMANWILLCOORDINATE MODESTHROUGHTHENETSOTHATBOTHHAVESITUATIONALAWARENESSDURINGTHELONGTIME SPANREQUIREDTOPROVIDETARGETRECOGNITION !NOTHERIMPORTANTFIGHTERCATEGORYISWEAPONSUPPORT-ISSILEUPDATEISTHEMEA SUREMENTOFMISSILEANDTARGETPOSITION VELOCITYANDACCELERATIONTOALLOWSTATISTICALLY INDEPENDENTMEASUREMENTSFORTRANSFERALIGNMENT ASWELLASMISSILESTATE OF HEALTH -ISSILEUPDATEPROVIDESTHELATESTTARGETINFORMATIONANDFUTUREDYNAMICSPREDICTION BYDATALINK)2MISSILESLAVINGCO ALIGNSRADARANDSEEKER3INCEGUNEFFECTIVERANGES ARE VERY SHORT GUN RANGING CAUSES THE RADAR TO SENSE THE GUN FIELD OF FIRE PREDICTS ANGLERATE ANDMEASURESRANGETOATARGETFORTENTATIVEGUNFIRE)TMAYALSOTRACKGUN ROUNDSDURINGFIRE 4HEREARETHOUSANDSOFELECTRICALDEGREESOFPHASEBETWEENFREESPACEANDTHE!$ CONVERTERS4HECOMBINATIONOFTEMPERATURE TIME ANDMANUFACTURINGTOLERANCESGIVES RISETOTHENEEDFORSELFCALIBRATION TEST FAULTDETECTION FAILUREDIAGNOSIS ANDNEEDED CORRECTIONS WHICHAREPERFORMEDBYASUBSUITEOFPERFORMANCEMONITORSOFTWARE 4IMING3TRUCTURE 4HESIGNIFICANCEOFTHEREMAININGPARAMETERSIN4ABLES AND CAN BEST BE ILLUSTRATED WITH A TIMING STRUCTURE TYPICAL OF FIGHTER RADARS &IGURE SHOWS A MODERN RADAR TIMING STRUCTURE IN A SEQUENCE OF PROGRESSIVELY EXPANDEDTIMELINES4HEFIRSTROWOF&IGURESHOWSATYPICALSCANCYCLECOVERING THEREQUIREDVOLUMEOFINTERESTFORASPECIFICMODE4HETIMESPANFORAFULLSCANCYCLE MIGHTBETOSECONDS)NSIDETHETOTALSCANCYCLETIME THEREMAYBESEVERALBARSOF ASCANNEDREGIONOFSPACEWITHATIMESPANOFAFEWTENTHSOFASECOND!BARISASCAN SEGMENTALONGASINGLEANGULARTRAJECTORY ASSHOWNIN&IGURE LATERINTHECHAPTER
4!",% 4YPICAL7AVEFORM0ARAMETERS! !-ODES 0ULSE 7IDTH MSEC
2ADAR -ODES
02& K(Z
2ANGE 'ATED (IGH02&
n
n
-EDIUM02&
n
"URST2ANGING
n
!CTIVE4RACK
n
2AID!SSESSMENT .ON#OOP 4ARGET2EC (I0WR*AM
n
n
#AL!'#
n
n
!IR$ATA,INK
n
n
'UN2ANGING 7EATHER !VOIDANCE
n n
n n
$UTY 2ATIO
0ULSE #OMP 2ATIO
&REQ ,OOKS
0ULSES 0ER#0)
n
n
n
n
n
n
n
n
n
n
n
n
n
n
n
n
n
n
n
n
n n
n
n
n
n
n
n
n
n n
n n
n n
)NSTANT "AND 7IDTH -(Z
4OTAL 0ULSES IN4/4
n
n
n
n
n
n
n
n
n
n
n
n
n
n
n
n
n
n
n
n
n
n
n
n
nK
n
n
n
n
n
n
n n
n n
n n
x°£È
2!$!2(!.$"//+
&)'52% 4YPICAL-&!2TIMINGSEQUENCES #OURTESY3CI4ECH0UBLISHING
%ACHBARCONSISTSOFMULTIPLEBEAMPOSITIONSOFAFEWTENSOFMILLISECONDSEACH WHICH ARECOMPUTEDONTHEFLYTOOPTIMALLYCOVERTHESELECTEDVOLUME%ACHBEAMCYCLE INTURN MAYCONTAINONEORMORERADARMODESORSUBMODES SUCHASTHOSECONTAINEDIN4ABLES ORANDDEPICTEDINTHELOWESTLINEOF&IGURE4HEMODESMAYNOTBEINVOKEDEACH TIMEDEPENDINGONTHEGEOMETRYBETWEENTHEAIRCRAFTANDTHEINTENDEDTARGETSET 4HE MODE TIME IS BROKEN UP INTO COHERENT PROCESSING INTERVALS #0)S ! COHER ENTPROCESSINGINTERVALISSEGMENTED ASSHOWNINTHEBOTTOMROWOF&IGURE4HE PARTICULAREXAMPLESHOWNISTRACKINGTHATMIGHTBEUSEDIN&44 '-44 065 OR! ' 2ANGING AS SHOWN PREVIOUSLY IN &IGURE AND LATER IN &IGURES AND )T CONSISTSOFAFREQUENCYCHANGESETTLINGTIMEPASSIVERECEIVINGTOBESURETHEBANDISNT JAMMEDCALIBRATETHATDOESNTINTENTIONALLYRADIATEBUTOFTENTHEREISSOME2&LEAKAGE RADIATED AN AUTOMATIC GAIN CONTROL !'# INTERVAL IN WHICH A NUMBER OF PULSES ARE TRANSMITTEDTOSETTHERECEIVERGAINANDFINALLYTWOINTERVALSINWHICHRANGE DOPPLER AND ANGLEDISCRIMINANTSAREFORMED4HESE#0)SOFTENBUTNOTALWAYSHAVECONSTANTPOWER FREQUENCYSEQUENCE 02&SEQUENCE PULSEWIDTH PULSECOMPRESSION ANDBANDWIDTH
x°ÎÊ Ê " Ê - ,*/" -ÊEÊ76 ", !IR TO !IR3EARCH !CQUISITIONAND4RACK-EDIUM02& )TMAYBEINSTRUC TIVETOEXAMINEHOWSEVERALMODESAREGENERATEDANDPROCESSEDTOUNDERSTANDWHYTHE WAVEFORMSMUSTBETHEWAYTHEYARE-EDIUM02&TRADESLONG RANGEDETECTIONPERFOR MANCESEE&IGURE LATERINTHECHAPTER FORALLASPECTTARGETDETECTION /FTEN HIGHANDMEDIUM02&WAVEFORMSAREINTERLEAVEDONALTERNATESCANSSEE&IGURE TO IMPROVETOTALPERFORMANCE !FTERYEARSOFSEARCHINGFORANOPTIMUMSET MOST MODERNMEDIUM02&MODESHAVEDEVOLVEDTOARANGEOF02&SBETWEENANDK(Z INADETECTIONSETOFFORTHETIMEONTARGET n4HESE02&SARECHOSENTOMINIMIZE RANGEANDVELOCITYBLINDZONESWHILESIMULTANEOUSLYALLOWINGUNAMBIGUOUSRESOLU TION OF TARGET RANGE AND DOPPLER RETURNS IN A SPARSE TARGET SPACE 2ANGE BLIND ZONESARETHOSERANGESINWHICHATARGETISECLIPSEDBYTHETRANSMITTEDPULSE6ELOCITY ORDOPPLERBLINDZONESARETHOSEVELOCITIESORDOPPLERSTHATAREEXCLUDEDDUETOTHE
-5,4)&5.#4)/.!,2!$!23934%-3&/2&)'(4%2!)2#2!&4
x°£Ç
MAIN BEAM CLUTTER AND GROUND MOVING TARGET FILTER REJECTION NOTCH 4ARGET DETEC TIONREQUIRESDETECTIONSINATLEASTOFTHE02&SWITHALL02&SCLEARATMAXIMUM RANGE4HE02&SELECTIONCRITERIAUSUALLYREQUIRESTHATTHE02&SETISCLEARIN OTHERWORDS ATLEASTASPECIFIEDNUMBERTYPICALLY OF02&SMUSTHAVEANABOVE THRESHOLDRETURNECHOFORTHEMINIMUMSPECIFIEDTARGETFORTHEFULLSPECIFIEDRANGE DOPPLERCOVERAGE !TYPICALPROCESSINGBLOCKDIAGRAMISGIVENIN&IGURE%ACH02&PROCESSING INTERVALISDIFFERENT BUTTHEYAVERAGEOUTTOANOPTIMUM ASSHOWNLATERIN&IGURE "OTH MAIN AND GUARD CHANNEL PROCESSING IS REQUIRED TO REJECT FALSE TARGETS 3OME 34!0PROCESSINGMAYHAVEBEENPERFORMEDBEFORETHISPROCESS BUTTRADITIONALSIDE LOBEANDMAIN BEAMCLUTTERISLESSOFALIMITTHANGROUNDMOVINGTARGETS WHICHHAVE VERYLARGECROSSSECTIONSANDEXO DOPPLERSIE DOPPLERFARENOUGHOUTOFMAIN BEAM CLUTTERTHATDETECTIONISNOTLIMITEDBYTHECLUTTERRETURN -02&USUALLYHASASMALL AMOUNTOFPULSECOMPRESSIONTO WHICHSTILLMAYREQUIREDOPPLERCOMPEN SATION-AINANDGUARDCHANNELSAREPROCESSEDINTHESAMEWAY/BVIOUSLY THETWO SPECTRAAREQUITEDIFFERENTANDSEPARATEFALSEALARMANDNOISEENSEMBLEESTIMATESARE MADE4HISLEADSTOSEPARATETHRESHOLDSETTINGS-ULTIPLECHANNELSAREUSEDTOESTIMATE INTERFERENCE AND SELECT %##- STRATEGY -AIN CHANNEL DETECTIONS ARE EXAMINED FOR '-4SANDCENTROIDEDINRANGEANDDOPPLERBECAUSEARETURNINRANGEORDOPPLERMAY STRADDLEMULTIPLEBINS THECENTROIDOFTHOSERETURNSINMULTIPLEBINSMUSTBEESTIMATED FROMTHEAMPLITUDEINEACHBINANDTHENUMBEROFBINSSTRADDLED 4HEGUARDCHANNEL ISDETECTEDANDTHETHRESHOLDEDRESULTSAREUSEDTOGATETHEMAINCHANNELRESULTSFORTHE FINALHIT MISSCOUNT'ENUINETARGETSARERESOLVEDINRANGEANDDOPPLER PRESENTEDTOA DISPLAYANDUSEDFOR473CORRELATIONANDTRACKING &ALSEALARMSAREACRITICALISSUEINMOSTRADARMODES4HESEAREUSUALLYSUPPRESSED FORTHERMALNOISEBYCONSTANTFALSEALARMRATETHRESHOLDING COINCIDENCEDETECTION AND POST DETECTION INTEGRATION WITH FREQUENCY AGILITY #LUTTERFALSE ALARMS ARE SUP PRESSEDBYADAPTIVEAPERTURETAPERING LOW NOISEFRONT ENDHARDWARE WIDEDYNAMIC RANGE!$S CLUTTERREJECTIONFILTERINGINCLUDING34!0 PULSECOMPRESSIONSIDELOBE SUPPRESSION DOPPLERFILTERSIDELOBECONTROL GUARDCHANNELPROCESSING RADOMEREFLEC TIONLOBECOMPENSATION ANGLERATIOTESTSSEE&IGUREANDTHEhFRINGEREGIONvFOR ANEXAMPLEANGLE RATIO TEST ANDADAPTIVE02&SELECTION
&)'52% 4YPICAL-02&PROCESSINGADAPTEDCOURTESY3CI4ECH0UBLISHING
x°£n
2!$!2(!.$"//+
&)'52% -EDIUM02&RANGE VELOCITYBLINDZONES
-02& 4YPICAL2ANGE $OPPLER"LIND-AP &OREXAMPLE ATYPICAL-02&SET FOR8BANDWITHRANGE DOPPLERCOVERAGEOFKMnK(ZISSHOWNIN&IGURE 4HIS SET IS FOR A n ANTENNA BEAMWIDTH OWNSHIP IE THE RADAR CARRYING FIGHTER VELOCITYOFMS ANDANANGLEOFFTHEVELOCITYVECTOROFn4HE02&SETIS ANDK(Z(ISTORICALLY A02&SETWAS CALCULATEDDURINGDESIGNANDREMAINEDFIXEDDURINGDEPLOYMENT-ODERNMULTIFUNC TIONALRADARCOMPUTINGISSOROBUSTTHAT02&SETSCANBESELECTEDINREALTIMEBASED ONSITUATIONGEOMETRYANDLOOKANGLE4HESET WHICHGENERATED&IGURE ONTHE AVERAGEISCLEARONOUTOF02&SFORASINGLETARGET%XCEPTFORTWOSMALLDOPPLER REGIONS ALLTHE02&SARECLEARATMAXIMUMRANGE WHICHPROVIDESMAXIMUMDETEC TIONANDMINIMUMLOSSATTHEDESIGNRANGE&ORSOMEPULSECOMPRESSIONWAVEFORMS THEECLIPSINGLOSSISALMOSTLINEARANDPARTIALOVERLAPSTILLALLOWSSHORTER RANGEDETEC TION %CLIPSING LOSS IS THAT DIMINISHMENT OF RECEIVED POWER WHEN THE RECEIVER IS OFFDURINGTHETRANSMITTEDPULSE)TISOFTENTHELARGESTSINGLELOSSINHIGHDUTYRATIO WAVEFORMS4HEBADNEWSISTHATTHEAVERAGEDETECTIONPOWERLOSSISSLIGHTLYOVER D"SEE&IGURE -02&3ELECTION!LGORITHMS /BVIOUSLY SELECTING02&SINREALTIMEREQUIRES SEVERALRULESTOGETCLOSETOAFINALSET4HISISFOLLOWEDBYSMALLITERATIONSTOPICKTHE OPTIMUMSET&ORMEDIUM02& BOTHRANGEANDVELOCITYBLINDZONESAREIMPORTANT &IRST THESOFTWAREMUSTPICKACENTRAL02&ABOUTWHICHALLTHEOTHER02&SAREDEVIA TIONSTOFILLOUTTHEDESIREDVISIBILITYCRITERIA3ECOND THE02&SETSHOULDALLBECLEARAT THEMAXIMUMDESIGNRANGESOTHATDETECTIONLOSSESAREATAMINIMUM &IGURESHOWSONEEXAMPLECRITERIAFORSELECTINGTHECENTRAL02& IE THEHIGH ESTPROBABILITYOFVISIBILITY06 )NTHEEXAMPLE THEPRODUCT06 OFTHERANGE02 ANDDOPPLER0$ TARGETVISIBILITYPROBABILITIESFORASINGLE02&PEAKSATAPPROXIMATELY ANDTHUSTHEOTHER02&SMUSTFILLINTOREACHCLEARORHIGHER4HEREARESEVERAL
-5,4)&5.#4)/.!,2!$!23934%-3&/2&)'(4%2!)2#2!&4
x°£
&)'52% -EDIUM 02&CENTRAL02&SELECTIONEXAMPLE
OTHERFACTORSTOBECONSIDEREDDOPPLERANDRANGEBLINDZONESANDECLIPSINGANDSIDE LOBECLUTTER%VENWITH34!0 SIDELOBECLUTTERISAMAJORLIMITATION "OTHSIDELOBE ANDMAIN BEAMCLUTTERCANBEMINIMIZEDBYNARROWDOPPLERANDORRANGEBINSIE RESOLUTIONCELLS WHICHIMPLYLONGERDWELLTIMESANDHIGHERTRANSMITBANDWIDTH /NEEXAMPLEMETHODFORSELECTINGASETOF02&SFOR-02&ISGIVENIN%Q4HE BASICIDEAISTOFINDATIMEINTERVAL 4! REPRESENTINGTHEDESIREDMAXIMUMCLEARRANGE ANDTHENTOCHOOSEASETOF02)SINWHICHALLWILLBECLEARATMAXIMUMRANGE4HISCAN BEACHIEVEDBYDIVIDING4!BYANINTEGER TYPICALLYTO4HISSETWILLGENERALLYNOT PROVIDECLEAROVERTHERANGE DOPPLERSPACE4HEEVENDIVISOR02)SCANBEPERTURBED ITERATIVELYBYASMALLAMOUNTTOACHIEVETHEDESIREDVISIBILITY4HENORMALIZEDTARGETSIG NAL TO NOISERATIO 40 VARIESDRAMATICALLYWITHSTRADDLEANDECLIPSINGLOSSESFOREXAMPLE SEE&IGURE 4HEFUNCTIONTOBEOPTIMIZEDISATHRESHOLDEDVERSIONOF40KORJ
&)'52% %XAMPLE2'(02&ECLIPSINGANDSTRADDLENEARMAXIMUMRANGE
x°Óä
2!$!2(!.$"//+
&OREXAMPLE THETHRESHOLDSCHEMEMIGHTBED"3.2PER02)ANDOUTOF FORALL02)S/FTENMULTIPLEANDDIFFERENTTHRESHOLDSAREUSEDFOREACH#0)AND02) ,OWERTHRESHOLDSAREALLOWABLEFORHIGHERNUMBERSOFTOTALHITS)TSHOULDBENOTED THATECLIPSINGANDSTRADDLING ANDSOON HAVEMUCHLESSEFFECTATCLOSERRANGESWHERE THEREISUSUALLYMORETHANENOUGH3.2!NOTHERSERENDIPITOUSEFFECTOFTHISSELECTION TECHNIQUEISTHATASANINDIVIDUAL02)RANGECLEARREGIONGETSSMALLER THEDOPPLERCLEAR REGIONGETSLARGER FILLING INTHEBLINDZONESINBOTHDIMENSIONS 4! 4! ¤2 ³ 4! r ¥ C T P´ 02) K 02) J # r K # r J D J ¦ C µ
40K OR J F R
# ;MOD = r 2 ;MOD R 02) = 6 F 02) K BLIND OR J BLIND K OR J R
WHERE2CISMAXIMUMDESIGNCLEARRANGE CISTHEVELOCITYOFLIGHTMS SPISTRANSMITTEDPULSEWIDTH KANDJAREINDICESEGx #ISANODDINTEGEREG #ISANEVENINTEGEREG CJISASMALLPERTURBATIONEGzYIELDINGVISIBILITY 6BLINDISAFUNCTIONOFFDESCRIBINGECLIPSINGANDSTRADDLING 2BLINDISAFUNCTIONOFRDESCRIBINGECLIPSINGANDSTRADDLING #ISACONSTANTREPRESENTINGTHEREMAINDEROFTHERANGEEQUATION FISFREQUENCY RISRANGE MODISMODULOTHEFIRSTVARIABLEBYTHESECOND 2ANGE 'ATED (IGH 02& 2ANGE GATED HIGH 02& 2'(02& PERFORMANCE IS DRAMATICALLYBETTERFORDETECTIONOFHIGHERSPEEDCLOSINGTARGETS 2ANGEGATES AREOFTENSMALLERTHANRANGERESOLUTIONCELLSORBINS 2'(02&PRODUCESTHELONGEST DETECTIONRANGEAGAINSTCLOSINGLOWCROSSSECTIONTARGETS5LTRA LOWNOISEFREQUENCY REFERENCESAREREQUIREDTOIMPROVESUBCLUTTERVISIBILITYONLOW2#3TARGETSEVENUSING 34!0 2ANGE GATING DRAMATICALLY IMPROVES SIDELOBE CLUTTER REJECTION WHICH ALLOWS OPERATIONATLOWEROWNSHIPALTITUDES0RINCIPALLIMITATIONSOF2'(02&CLOSINGTARGET DETECTIONPERFORMANCEAREECLIPSINGARADARRETURNWHENTHERECEIVERISOFFDURINGTHE TRANSMITTEDPULSE ANDRANGEGATESTRADDLELOSSESTHERANGEGATESAMPLINGTIMEMISSES THEPEAKOFTHERADARRETURN &IGURESHOWS40IWITHECLIPSINGANDSTRADDLELOSSES NEARMAXIMUMRANGEFORAHIGHPERFORMANCE2'(02&4HISMODEISOPTIMIZEDFORLOW CROSSSECTIONTARGETSOUTTOJUSTBEYONDKMMAXIMUMRANGE4HEPARTICULAREXAMPLE HASOVERLAPPINGRANGEGATESTOMINIMIZESTRADDLELOSSANDTWO02&STOALLOWATLEAST ONECLEAR02&NEARMAXIMUMRANGE4HE02&SAREK(ZANDK(Z$UTY RATIOISWITHD"REQUIREDDETECTION3.2!VERAGEDOVERALLPOSSIBLETARGETPOSI TIONSANDCLOSINGDOPPLERS THELOSSESFORTHISMODEAREASURPRISINGLYSMALLD" 4HERANGE DOPPLERBLINDZONESPLOTISSHOWNIN&IGURECORRESPONDINGTOTHE &IGUREWAVEFORM#OMPAREDTOTHEMEDIUM02&PLOTSHOWNIN&IGURE THE CLEAR REGION AND CORRESPONDING LOSSES IS DRAMATICALLY BETTER 5NFORTUNATELY RANGE ISVERYAMBIGUOUS.ORMALLY A2'(02&RANGE WHILE SEARCH273 MODEISINTER LEAVED WITH THE HIGHEST PERFORMANCE VELOCITY SEARCH 63 MODE TO RANGE ON PREVI OUSLYDETECTEDTARGETS /FTEN 273IS2'(02&WITHTHREEPHASESINWHICHACONSTANTFREQUENCYANDTWO CHIRPLINEAR&- FREQUENCIESTRIANGULARUP DOWNORUP STEEPERUP AREUSEDTORESOLVE RANGE AND DOPPLER IN A SPARSE TARGET SPACE!T LOW ALTITUDES SIDELOBE CLUTTER EVEN WITH34!0PROCESSING LIMITSPERFORMANCEFORALLTARGETSBUTESPECIALLYOPENINGTARGETS
-5,4)&5.#4)/.!,2!$!23934%-3&/2&)'(4%2!)2#2!&4
x°Ó£
&)'52% 2'(02&RANGE VELOCITYBLINDZONES CORRESPONDINGTO&IGUREWAVEFORMS
4HIS LIMITATION LEADS TO THE NEED FOR ANOTHER MODE INTERLEAVED WITH 2'(02& &ORTUNATELY THETIMELINEFOROPENINGTARGETSISMUCHLONGERNETSPEEDISLESS ANDTHE ENGAGEMENTRANGEISMUCHSHORTERWEAPONCLOSURERATESARETOOSLOW /FTEN IN GENERAL SEARCH -02& 623 MEDIUM 02& VELOCITY RANGE SEARCH IS INTERLEAVEDWITH(02&63AND273 ASSHOWNIN&IGURE TOPROVIDEALLASPECT DETECTION5NFORTUNATELY BOTH273AND623HAVEPOORERMAXIMUMDETECTIONRANGE 2'(02&CANPROVIDEALLASPECTDETECTIONBUTTAILPERFORMANCEISDRAMATICALLYPOORER DUETOSIDELOBECLUTTER%VENWITH34!0 WHICHSIGNIFICANTLYIMPROVESSIDELOBECLUTTER REJECTION LOWALTITUDETAILASPECTDETECTIONFOR2'(02&ISPOORER
&)'52% (IGHANDMEDIUM02&INTERLEAVEFORALLASPECTDETECTION
x°ÓÓ
2!$!2(!.$"//+
&)'52% #OMPARISONOFHIGHANDMEDIUM02&
!NEXAMPLECOMPARISONOF(02&AND-02&ASAFUNCTIONOFALTITUDEFORAGIVEN MAXIMUMTRANSMITTERPOWER POWER APERTUREPRODUCT ANDTYPICALANTENNAANDRADOME INTEGRATEDSIDELOBERATIOISSHOWNIN&IGURE!THIGHALTITUDEANDNOSE ON THEREIS MORETHANAND"DIFFERENCECAUSEDBYBLINDZONES STRADDLE FOLDEDCLUTTER PROCESS ING ANDTHRESHOLDINGLOSSES 2'(02&3ELECTION!LGORITHMS &IRST ASINTHE-02&CASE ALL02&SSHOULDBE CLEARATTHEMAXIMUMDESIGNRANGE3ECOND ALL02&SSHOULDBECLEARTOTHEMAXIMUM DOPPLEROFINTEREST/NEPOSSIBLESELECTIONCRITERIAISGIVENIN%Q!LTHOUGHTHE DETAILSAREQUITEDIFFERENT THEBASICPHILOSOPHYIN02&SELECTIONISTOOPTIMIZELONG RANGECLEARREGIONS 4!
r 2C r L § 4 ¶ T P AND 02) ! AND ) CEIL ¨ ! · C 6A 6T © 02) ! ¸
THEN 02)
¶ §C r T P 4! AND 02) 02) r ¨ · ) © 2C ¸
WHERE2CISMAXIMUMDESIGNCLEARRANGE CISTHEVELOCITYOFLIGHTrMS SPISTRANSMITTEDPULSEWIDTH KISTRANSMITTEDWAVELENGTH CEILISTHENEXTINTEGERABOVETHEVALUEOFTHEVARIABLE 6AAND6TARETHEMAXIMUMVELOCITIESOFINTERESTFORAIRCRAFTANDTARGETRESPECTIVELY .ONCOOPERATIVE !IR 4ARGET 2ECOGNITION -&!2 TARGET RECOGNITION 4)$ RECOGNIZESTARGETTYPEBUTNOTUNIQUEIDENTIFICATION4HEREARECOOPERATIVETARGET
-5,4)&5.#4)/.!,2!$!23934%-3&/2&)'(4%2!)2#2!&4
x°ÓÎ
IDENTIFICATIONMETHODSSUCHAS*4)$3 )&& AND2&TAGGINGTHATCANBEUNIQUE4)$ DEPENDSONDETECTINGFEATURESOFTHERADARSIGNATUREINFUSIONWITHEMISSIONSAND OTHERSENSORS4HEFIVEMOSTCOMMON4)$SIGNATURESAREMONOPULSEEXTENTSIMILAR TO THE EXAMPLE SHOWN IN &IGURE RESONANCES HIGH RESOLUTION RANGE (22 PROFILES DOPPLER SPREAD STEPPED FREQUENCY WAVEFORM MODULATION OR MULTIFRE QUENCY3&7--&2 WHICHCANBETRANSFORMEDINTOARANGEPROFILE ANDINVERSE SYNTHETICAPERTURERADAR)3!2 -ONOPULSEEXTENTALLOWSESTIMATIONOFLENGTH ANDWIDTHASWELLASSEPARATIONOFCLOSELYSPACEDAIRCRAFT!HIGHRANGERESOLUTION PROFILEALSOALLOWSTHESEPARATIONOFTARGETSFLYINGINCLOSEFORMATIONASWELLASTHE SEPARATIONOFAMISSILEFROMATARGET!HIGHRANGERESOLUTIONPROFILEONASINGLE TARGET CAN ALLOW RECOGNITION ASSUMING THE TARGET ATTITUDE IS KNOWN OR HAS BEEN GUESSED,ENGTH WIDTH ANDLOCATIONOFMAJORSCATTERINGFEATURESCANBEPROJECTED INTOARANGEPROFILEIFTHEATTITUDEISKNOWN4HENUMBEROFTYPESOFMAJORCIVILIAN ANDMILITARYAIRCRAFTANDSHIPSISATMOSTAFEWTHOUSAND EASILYSTORABLEINMEMORY 5NFORTUNATELY RECOGNITION IS LIMITED TO BROAD CATEGORIES RATHER THAN -)' - VERSUS-)' 3EVENTHOUGHTHEREARESIGNIFICANTDIFFERENCESTHATAIRSHOWVISI TORSCANEASILYSEE 4HE BASIC NOTION OF DOPPLER RESONANCES STEPPED 3&7- AND MULTIFREQUENCY -&2 SIGNATURESISMODULATIONEITHERBYREFLECTIONSFROMMOVINGPARTS EG ENGINE COMPRESSOR TURBINE ROTOR ORPROPELLERBLADES ORBYINTERACTIONSFROMSCATTERERSALONG THEAIRCRAFTORVEHICLE EG FUSELAGE WING ANTENNAS ORSTORES3&7--&2SIGNA TURESARECLOSELYRELATEDTOHIGHRANGERESOLUTIONSIGNATURESA&OURIERTRANSFORMEASILY CONVERTSONETOTHEOTHER ANDTHEYSUFFERTHESAMEATTITUDEESTIMATIONLIMITATIONS4HE PRINCIPALADVANTAGETO-&2ISTHATMANYDEPLOYEDRADARSHAVEMULTIPLECHANNELSAND SWITCHINGBETWEENTHEMONASINGLETARGETISRELATIVELYEASY!SIMPLIFIEDVERSIONOF THERECOGNITIONPROCESSISSUMMARIZEDIN&IGURE $OPPLERSIGNATURESREQUIREHIGHDOPPLERRESOLUTION WHICHISUSUALLYEASILYACHIEVED ANDLIMITEDONLYBYDWELLTIME4HEINDIVIDUALSCATTERERS WHICHGIVERISETODOPPLER SPREAD ARESMALLANDSORECOGNITIONISUSUALLYLIMITEDTOAFRACTIONTYPICAL OF MAXIMUMRANGE*ETENGINEMODULATION*%- ASUBSETOFDOPPLERSIGNATURES ISAN EXCELLENTTARGETRECOGNITIONMETHOD%VENAIRCRAFT WHICHUSETHESAMEENGINETYPE OFTENHAVEVARIATIONSINTHEENGINEAPPLICATION SUCHASTHENUMBEROFCOMPRESSOR BLADESORNUMBEROFENGINES WHICHALLOWSUNIQUETYPERECOGNITION4HEREALPICTURE OF*%-ISNOTSOCLEANBECAUSEOFMULTIPLEON AIRCRAFTBOUNCES STRADDLING ANDSPEED VARIATIONS BUT CENTROIDING OF EACH LINE IMPROVES THE SIGNATURE ESTIMATE 4HE LAST METHODOF4)$ )3!2 WILLBEDEALTWITHINANOTHERSECTION)3!2WORKSWELLONBOTH AIRCRAFTANDSHIPS!TYPICALTAILHEMISPHEREAIR TO AIR)3!2ISSHOWNIN&IGURE
&)'52% .ONCOOPERATIVETARGETRECOGNITIONSUBMODES
x°Ó{
2!$!2(!.$"//+
&)'52% ! !)3!2EXAMPLE4! "
4HE FUSION OF THE RECOGNITION OF EACH OF THE SIGNATURES ABOVE PROVIDES EXCELLENT NONCOOPERATIVERECOGNITION 7EATHER !VOIDANCE -ANY AIRCRAFT HAVE SEPARATE WEATHER RADARS 7EATHER AVOIDANCEISNORMALLYINCORPORATEDINTOMODERNFIGHTERRADARS4HENORMALOPERATING FREQUENCYFORAFIGHTERRADARHASNOTBEENCONSIDEREDOPTIMUMFORWEATHERDETECTION ANDAVOIDANCEPRIMARILYDUETOLACKOFPENETRATIONDEPTHINTOASTORMANDREDUCED OPERATINGRANGE(OWEVER WITHCOMPLEXATMOSPHERICATTENUATIONCOMPENSATIONAND DOPPLERMETHODS WEATHERCANBEDETECTEDWELLENOUGHTOALLOWWARNINGANDAVOID ANCE OF STORMS 4HE PRINCIPAL CHALLENGE IS COMPENSATING FOR BACKSCATTER FROM THE LEADINGEDGEOFASTORMANDADJUSTINGFORATTENUATIONTOSEEFARENOUGHINTOASTORMTO EVALUATEITSSEVERITY4HEBACKSCATTERFROMEACHCELLISMEASURED THEPOWERREMAINING ISCALCULATED THEATTENUATIONINTHENEXTCELLISESTIMATED ANDTHENTHEBACKSCATTERIN THENEXTCELLISMEASURED ANDSOON7HENTHEPOWERINTHECELLSDROPSTOTHENOISE LEVEL THOSECELLSBEHINDITAREDECLAREDBLIND3INCEPENETRATIONRANGEINTOASTORMIS NOTGREAT THE-&!2WEATHERMODEUSUALLYHASPROVISIONSTOMARKTHELASTVISIBLEOR RELIABLERANGEONTHEWEATHERDISPLAY4HISISSOTHEPILOTDOESNOTFLYINTOADARKAREA BELIEVINGTHEREISNOWEATHER !IR $ATA ,INKS 4HE -&!2 IS PART OF A NETWORK OF SENSORS AND INFORMA TION SOURCES #)32 NET SOMETIMES CALLED THE 'LOBAL )NFORMATION 'RID ')' !MAJORUSEOFRADARANDAIRCRAFTDATALINKSISTOPROVIDETOTALSITUATIONALAWARENESS "Y USING ON BOARD AND OFF BOARD SENSOR FUSION A TOTAL AIR AND GROUND PICTURE CAN BE PRESENTED IN THE COCKPIT4HIS PICTURE CAN BE A COMBINATION OF DATA FROM
-5,4)&5.#4)/.!,2!$!23934%-3&/2&)'(4%2!)2#2!&4
x°Óx
OTHERRADARSENSORSWINGMANORSUPPORTAIRCRAFT ONSIMILARPLATFORMSTOREPORTSBY OBSERVERSWITHBINOCULARS"ECAUSETHEMODERNFIGHTERISNET CENTRIC USINGEVERYTHING AVAILABLEON ANDOFF BOARDTHEAIRCRAFT NET CENTRICOPERATIONREQUIRESDRAMATICALLY HIGHERLEVELSOFDATAEXCHANGEANDFUSIONOFDATAFORPRESENTATIONTOTHEOPERATOR 2ADARMODESCANBESCHEDULEDBETWEENMULTIPLEAIRCRAFTINREALTIMETHROUGHTHE DATALINKS 4HE TWO MAIN USES FOR DATA LINKS ASSOCIATED WITH HIGH PERFORMANCE AIRCRAFT ARE HIGHBANDWIDTHIMAGERYTRANSMISSIONFROMAWEAPONORSENSORPLATFORMTOASECOND PLATFORMORGROUNDSTATIONANDLOWBANDWIDTHTRANSMISSIONOFCONTEXT TARGETINGDATA GUIDANCE AND HOUSEKEEPING COMMANDSn 4HE LARGEST QUANTITY OF DATA LINKS ARE ASSOCIATEDWITHWEAPONS4HEWAVEFORMSELECTEDTOTRANSMITTHISANDOTHERDATAMUST NOTCOMPROMISETHESIGNATUREOFTHEPLATFORMATEITHERENDOFTHELINK n 4HEREARENUMEROUSDATALINKSONFIGHTERS4ABLESHOWSAIRDATALINKSTHATMIGHT BEONAFIGHTERPLATFORM)NSPITEOFTHISFACT THERADARORPARTOFITSAPERTUREISOFTEN USEDFORADATALINK ESPECIALLYTOMISSILESONTHEFLYANDINRESPONSETOPEACETIME AIRTRAFFICCONTROLINTERROGATIONS0ULSEAMPLITUDEINCLUDINGON OFF PULSEPOSITION PHASESHIFT ANDFREQUENCYSHIFTMODULATIONARECOMMONLYUSED,INKSMAYBEUNIDI RECTIONALORBIDIRECTIONAL3OMEMISSILESREQUIRESEMI ACTIVEILLUMINATIONASWELLAS REFERENCESIGNALSANDMIDCOURSECOMMANDDATADERIVEDFROMMISSILEANDTARGETTRACK ING4HEDATATOANDFROMTHEMISSILEISOFTENANENCRYPTEDPHASE CODEINORNEARTHE RADAROPERATINGBAND)NSOMECASES THEFREQUENCYCHANNELISRANDOMLYSELECTEDAT THEFACTORYANDHARDWIREDINTOTHEMISSILE&REQUENCYCHANNELSARETYPICALLYSELECTED ORCOMMUNICATEDTOTHERADARIMMEDIATELYBEFORELAUNCH)FTHEDATALINKFREQUENCYIS WELLBELOWTHERADARBAND USUALLYASMALLNUMBEROFRADIATORSATTHATLOWERFREQUENCY AREIMBEDDEDINTHERADARAPERTURE)FTHEFREQUENCYISCLOSEENOUGHTOTHERADARBAND THERADARAPERTUREORASEGMENTOFTHEAPERTUREISUSED 2ADAR !PERTURE $ATALINKING (ISTORICALLY DATALINK FUNCTIONS EMBEDDED IN -&!2SHAVEBEENUSEDFORTHEMIDCOURSEGUIDANCEOFMISSILES!NEMERGINGAPPLICA TIONISTHEUSEOFTHERADARAPERTUREASAHIGHPOWER HIGHGAINPRIMARYDATALINKANTENNA
4!",% !IR$ATA,INKS
,INK
&REQ"AND
$ATA2ATEKBS
%##-
!2# !2# !2# !2# 4!$), *4)$3 *4)$3,%4 *423 4!$)83 -&!2 -ILSTAR 4#$,
5(& 5(& 6(& 6(&5(& 5(& , , , 6(& 8 5(& 8 +U 5(& +U +A 8 +U
n n n n n n n
(IGH (IGH -ODERATE -ODERATEn(IGH -ODERATEn(IGH -ODERATE -ODERATE -ODERATEn(IGH -ODERATE -ODERATEn(IGH (IGH -ODERATE
x°ÓÈ
2!$!2(!.$"//+
WHEREDATALINKTRANSMISSIONANDRECEPTIONAREINTERLEAVEDWITHOTHERMODES4HEPRIN CIPALLIMITATIONOFMOSTGENERAL PURPOSEDATALINKEQUIPMENTISTHELOWPOWER APERTURE PERFORMANCEASSOCIATEDWITHOMNIDIRECTIONAL OFTENSHARED ANTENNAAPERTURESANDLIM ITEDPOWERLEVELS4HISCONSTRAINSACHIEVABLEDATATRANSFERRATES REGARDLESSOFCHANNEL BANDWIDTH!NASSOCIATEDPROBLEMISVULNERABILITYTOINTERCEPTANDJAMMINGINHERENTIN WIDEBEAMAPERTURES!N8OR+UBAND-&!2CANEMITPOWERLEVELSINTHEMULTI KILO WATTRANGEWITHMAIN BEAMBEAMWIDTHSOFAFEWDEGREES AFFORDINGHIGHDATARATESAND SIGNIFICANTRESISTANCETOJAMMINGANDINTERCEPT4RANSMITDATARATESOFOVER-BPS ANDRECEIVEDATARATESOFUPTO'BPSHAVEBEENDEMONSTRATEDUSINGAPRODUCTION!%3! ANDAMODIFIED#OMMON$ATA,INK#$, WAVEFORM-ODELINGUSINGREPRESENTATIVE -&!2PARAMETERSINDICATESTHATPERFORMANCEBOUNDSAREATSEVERAL'BPSTHROUGHPUT OVERDISTANCESINEXCESSOFNAUTICALMILES SUBJECTTO-&!2PERFORMANCE PLATFORM ALTITUDE TROPOSPHERICCONDITIONS ANDFORWARDSCATTERINGEFFECTS )MPLEMENTATIONREQUIRESACCURATEANTENNAPOINTING SINCETHEREISRELATIVEMOTION WITHRESPECTTOTHEOTHERENDOFTHELINK/NETECHNIQUEINVOLVESTHEUSEOFANOUT OF BANDDATALINKCHANNEL EG *4)$3 TOCARRY'03POSITIONUPDATES$OPPLERSHIFTING DUETOLINKGEOMETRYDYNAMICSMUSTBEACTIVELYCOMPENSATED!RELATEDISSUEISSYN CHRONIZATIONINTIMETOALLOCATETRANSMISSIONANDRECEPTIONWINDOWSANDTOSYNCHRONIZE TIMEBASES7HENEXISTINGWAVEFORMSMUSTBEUSED THISCANPRESENTCHALLENGES%XISTING APERTURESCHEDULINGALGORITHMSCANTHENALLOCATETIMEFORTRANSMISSIONORRECEPTION 4O ACHIEVE VERY HIGH THROUGHPUTS PHASE LINEARITY IN TRANSMIT AND RECEIVE PATHS ISCRITICALSINCEDATATRANSMISSIONWAVEFORMSRELYONMODULATIONTHATISEVERYBITAS COMPLEXASMANYRADARMODES4HISCANALSOIMPACTCHOICEOFTAPERFUNCTIONBECAUSE ANGULARVARIATIONSINPHASEACROSSTHEMAIN BEAMWAVEFRONTMAYINCURPERFORMANCE PENALTIES7HERETHE-&!2ISPHASESTEERED APERTUREFILLANDSIDELOBESTEERINGEFFECTS CONSTRAINUSABLEAPERTUREBANDWIDTHSIMILARTO3!2LIMITATIONS4HELATTERISBECAUSE THEELEMENTPHASEANGLESREQUIREDTOPOINTTHEMAINBEAMARENOTTHESAMEASTHOSEFOR THEOUTERSIDELOBESOFTHEMODULATIONUSED ,OWBANDWIDTHDATALINKSCANUSEALLTHERADARBANDWIDTHTOIMPROVEENCRYPTION ANDSIGNAL TO JAMRATIOS(OWEVER THEDATALINKONAWEAPONISTRAVELINGTOTHETARGET WHICHWILLINEVITABLYATTEMPTTOPROTECTITSELF7HENTHEWEAPONISNEARTHETARGET THESIGNAL TO JAMRATIOCANBEVERYUNFAVORABLE!NTENNAJAMMERNULLINGISUSUALLY REQUIREDSINCETRANSMITTINGMOREPOWERTOBURNTHROUGHMAYNOTBEPOSSIBLE#LEARLY THEDATAFROMANDTOAWEAPONMUSTALSOBESUFFICIENTLYENCRYPTEDTOPREVENTTAKE OVER OFTHEWEAPONINFLIGHT 4IMESYNCHRONIZEDWITHARADARTRANSMISSIONONADIFFERENTSETOFBEAMSANDORFRE QUENCIES MESSAGESARESENTTOONEORMOREMISSILESONTHEFLYTOTHETARGETS/BVIOUSLY ALL THE RANDOM FREQUENCY DIVERSITY SPREAD SPECTRUM AND ENCRYPTION NECESSARY FOR ROBUSTCOMMUNICATIONSHOULDBEINCORPORATEDINTOTHEMESSAGE%ACHMISSILEMAY ANSWER BACK AT A KNOWN BUT RANDOMIZED OFFSET FREQUENCY AND TIME WITH IMAGE OR HOUSEKEEPINGDATA!GAINAWAVEFORMASROBUSTASPOSSIBLEISUSED BUTSINCETHEBASE BANDDATAANDLINKGEOMETRYMAYBEQUITEDIFFERENT THEDATACOMPRESSION DIVERSITY ANDENCRYPTIONMAYBEDIFFERENT 4HEMISSILEDATALINKWAVEFORMUSUALLYMUSTBESTEALTHYANDGREATLYATTENUATEDIN THEDIRECTIONOFTHETARGETSINCEONECOUNTERMEASURESSTRATEGYISADECEPTIONREPEATER JAMMERATTHETARGET(IGHACCURACYTIMEANDFREQUENCYSYNCHRONIZATION INCLUDING RANGE OPENING AND DOPPLER EFFECTS BETWEEN BOTH ENDS OF THE LINK CAN DRAMATICALLY REDUCETHEEFFECTIVENESSOFJAMMINGBYNARROWINGTHESUSCEPTIBILITYWINDOW4IME ANDFREQUENCYSYNCHRONIZATIONALSOMINIMIZESACQUISITIONORREACQUISITIONTIME
-5,4)&5.#4)/.!,2!$!23934%-3&/2&)'(4%2!)2#2!&4
x°ÓÇ
!NAIRCRAFTUSINGADATALINKISMOVINGWITHRESPECTTOTHEOTHERENDOFTHELINK SOTHELINKGEOMETRYISCONTINUALLYCHANGINGINTIME FREQUENCY ASPECT ANDATTITUDE 4HESIGNALPROCESSORWILLGENERATEWAVEFORMSFORTRANSMISSIONBYTHESEEKERORDATA LINK)TWILLALSOMEASURETARGETRANGE ANGLE DOPPLER ANDSOON ANDPROVIDETHOSETO THEOTHERPLATFORM4HE-&!2SIGNALPROCESSORSENDSMOTIONSENSINGANDNAVIGATION ESTIMATESTOCORRECTMEASUREMENTSTOTRACK ENCODE ANDDECODEDATALINKMESSAGES ANDTOPERFORMJAMMERNULLING "EACON 2ENDEZVOUS AND 3TATION +EEPING -OST MODERN MILITARY AIRCRAFT DEPENDONIN FLIGHTREFUELINGFORMANYMISSIONS4HISREQUIRESRENDEZVOUSWITHTANKER AIRCRAFTDURINGALLWEATHERCONDITIONSASWELLASSTATIONKEEPINGUNTILAIRCRAFTCURRENTLY INLINEFORREFUELINGDEPART4HISMAYINVOLVEDETECTINGACODEDBEACONONTHETANKER SKINTRACKINGTANKERSANDOTHERAIRCRAFTATCLOSERANGE3TATIONKEEPINGRANGESCANBE BETWEENANDSOFMETERS3PECIALSHORT RANGERADARMODESAREUSUALLYUSEDFOR THISPURPOSE,OWPOWER SHORTPULSEOR&- #7WAVEFORMSAREOFTENUSED/NEMETER ACCURACYANDMETERMINIMUMRANGEISUSUALLYREQUIREDFORBLINDTANKING (IGH0OWER !PERTURE*AMMING 4HEBASICNOTIONBEHIND-&!2HIGHPOWER APERTUREJAMMINGISSUGGESTEDIN&IGURE ! THREAT EMITTER WHETHER SURFACE OR AIRBORNE IS FIRST DETECTED AND RECOGNIZED BYTHESPHERICALCOVERAGERADARWARNINGRECEIVER272 FUNCTIONPOSSIBLYJUSTAN APPLICATIONOVERLAYONTHE2&ANDPROCESSINGINFRASTRUCTURESHOWNIN&IGURE )FTHEINTERCEPTISINSIDETHERADARFIELDOFVIEW&/6 FINEANGLE OF ARRIVAL!/! ANDPOSSIBLYBURSTRANGINGAREPERFORMEDWITHTHEPRIMARYRADARAPERTURE ASSHOWN INTHETOPPORTIONOF&IGURE(IGH GAINELECTRONICSUPPORTMEASURES%3- ARE THENPERFORMEDANDRECORDEDONTHEEMITTERMAINBEAMORSIDELOBESUSINGTHENOSE APERTURE)FITISDETERMINEDFROMANON BOARDTHREATTABLE CURRENTRULESOFENGAGE MENT OR MISSION PLAN HIGH POWER DENSITY JAMMING BASED ON THE CORRESPONDING ON BOARD TECHNIQUES TABLE MAY BE INITIATED USING THE HIGH GAIN NOSE APERTURE
&)'52% -&!2%#-EXAMPLE
x°Ón
2!$!2(!.$"//+
"ECAUSETHEADVERSARYRADARMAYALSOBEA-&!2 THREATTABLESWILLBEREQUIREDTO CATEGORIZETHEMBYTHEIRAPPARENTSTATISTICALNATURE/LDSTYLEMATCHINGBY02& PULSE WIDTH AND PULSE TRAIN ENVELOPE WONT WORK VERY WELL BECAUSE WAVEFORMS VARY SO MUCH4HETYPICALNOSEAPERTURERADARnBASEDEFFECTIVERADIATEDPEAKPOWER%200 CANEASILYEXCEEDD"7 WHICHISNORMALLYMORETHANENOUGHTOPLAYHOBWITHTHREAT RADARS &OREXAMPLE ASSUMINGA'(ZIN BANDSIGNAL nD"ITHREATSIDELOBE ANDnD"7THREATSENSITIVITY AJAMMINGPULSED"ABOVEMINIMUMSENSITIVITY CANBEGENERATEDATKM/BVIOUSLY INTHENEARSIDELOBESORMAINBEAM THERANGE FORAD"PULSEWILLBEMUCHGREATER
x°{Ê -Ê " Ê - ,*/" -ÊEÊ76 ", 4ERRAIN&OLLOWING 4ERRAIN!VOIDANCE 4HENEXTEXAMPLEISTERRAINFOLLOWING TERRAINAVOIDANCE4&4! SHOWNIN&IGURE)NTERRAINFOLLOWING4& THEANTENNA SCANSSEVERALVERTICALBARSORIENTEDALONGTHEAIRCRAFTVELOCITYVECTORANDGENERATESAN ALTITUDE RANGEPROFILETHATISSOMETIMESDISPLAYEDTOTHEPILOTONAN% SCANDISPLAY $EPENDING ON THE AIRCRAFTS MANEUVERING CAPABILITIES THERE IS A CONTROL PROFILE G ACCELERATIONMANEUVERCONTROLLINESHOWNASANUPWARDCURVINGLINEINTHEUPPERRIGHT OF&IGUREn)FTHISCONCEPTUALLINEINTERCEPTSTHETERRAINANYWHEREINRANGE AN AUTOMATICUPMANEUVERISPERFORMED4HEREISALSOACONCEPTUALPUSHOVERLINE NOT SHOWNINTHEFIGURE WHICHCAUSESACORRESPONDINGDOWNMANEUVER4HECONTROLPRO FILEINMODERNAIRCRAFTISAUTOMATICBECAUSEAHUMANPILOTDOESNOTHAVETHEREFLEXES TOAVOIDALLPOSSIBLEDETECTEDOBSTACLES )NTERRAINAVOIDANCE4! THEANTENNASCANISINAHORIZONTALPLANESHOWNINTHE UPPERLEFTOF&IGURE 3EVERALALTITUDEPLANECUTSAREESTIMATEDANDPRESENTEDTO
&)'52% 4&4!MODEEXAMPLEADAPTEDCOURTESY3CI4ECH0UBLISHING
-5,4)&5.#4)/.!,2!$!23934%-3&/2&)'(4%2!)2#2!&4
x°Ó
THEPILOTONANAZIMUTH RANGEDISPLAYSHOWNINTHELOWERRIGHTOF&IGURE 4HE TERRAIN AVOIDANCE SCAN PATTERN SHOWS ALL THE TERRAIN THAT IS NEAR OR ABOVE THE FLIGHT ALTITUDEANDONECUTBELOWATASETCLEARANCEALTITUDEFTTYPICALLY &IGURE LOWERLEFTANDLOWERRIGHT SHOWSTHESITUATIONGEOMETRYOFANAIRCRAFTFLYINGTOWARD TWOHILLSANDTHECORRESPONDINGALTITUDECUTSDISPLAYEDTOTHEPILOT4HISALLOWSEITHER MANUALORAUTOMATICTURNINGFLIGHTTOMAINTAINALOWERALTITUDE 4&4!ALLOWSANAIRCRAFTTOPENETRATEATLOWALTITUDEUSINGTHETERRAINASMASKING THUSPREVENTINGEARLYDETECTION4&4!ISANIMPORTANTASPECTOFSTEALTHEVENWHENTHE ALTITUDEISNOTALLTHATLOWBECAUSELOWERALTITUDESPROVIDESOMETERRAINOBSCURATION ANDMANYOTHERCOMPETINGTARGETSWITHSIMILARCROSS SECTIONS 4ERRAIN(EIGHT%STIMATION 3OMEOFTHEFEATURESOF4&4!ARETHEREQUIREDSCAN PATTERN THENUMBEROFINDEPENDENTFREQUENCYLOOKSREQUIREDTOOBTAINAVALIDESTIMATE OFTHEHEIGHTOFAPOSSIBLYSCINTILLATINGOBJECTALONGTHEFLIGHTPATH ANDTHERANGECOV ERAGE"ECAUSETERRAINHEIGHTISESTIMATEDTHROUGHANELEVATIONMEASUREMENT ANGLE ACCURACYISCRITICAL4HERANGECOVERAGE ALTHOUGHSHORT REQUIRESMULTIPLEOVERLAPPING BEAMSANDMULTIPLEWAVEFORMS/NEMETHODFORCALCULATINGTERRAINHEIGHTISSHOWNIN &IGURE)TCONSISTSOFMEASURINGTHECENTROIDANDEXTENTOFEACHINDIVIDUALBEAM POSITIONOVERMANYPULSESANDESTIMATINGTHETOPOFTHETERRAININEACHBEAM ASSHOWN INTHEFIGURE4HECALCULATIONISSUMMARIZEDIN%Q ª£ 3I r $I ¹ 0R £ \ 3I \ POWER RECEIVED #R 2E « I º CENTROID 0R I » ¬ £ \ $I \ %R I
#R EXTENT SQUARED 4 #R r %R TERRAIN TOP ESTIMATE 0R
WHERE3IISASINGLESUMMONOPULSEMEASUREMENT $IISTHECORRESPONDINGELEVATION DIFFERENCEMONOPULSEMEASUREMENT 5SUALLYTHERANGE ELEVATIONPROFILEISMEASUREDINMULTIPLESEGMENTSWITHSEPARATE 02&SANDPULSEWIDTHS4HELOWEST02&ISUSEDTOMEASURETHELONGEST RANGEPORTION OFTHEPROFILEATTHETOPOFTHEELEVATIONSCAN)TUSESTHELARGESTPULSECOMPRESSIONRATIO n %ACHBEAMPOSITIONOVERLAPSBYASMUCHASANDMULTIPLEFREQUENCY
&)'52% 4ERRAINHEIGHTESTIMATION#OURTESY3CI4ECH0UBLISHING
x°Îä
2!$!2(!.$"//+
LOOKSINEACHBEAMCREATEASMANYASINDEPENDENTLOOKS4HESHORTESTRANGEATTHE BOTTOMOFTHEELEVATIONSCANUSESASHORTPULSEWITHNOPULSECOMPRESSIONANDAMUCH HIGHER02& BUTTHESAMENUMBEROFLOOKS4HEPULSESINA4/4AREALLTHEPULSESTHAT ILLUMINATEASINGLESPOTFROMTHEOVERLAPPINGBEAMS%ACHOVERLAPPINGBEAMMUSTBE COMPENSATEDFORTHEANTENNALOOKANGLEBEFORETHEBEAMSCANBESUMMEDFORATERRAIN HEIGHTESTIMATEFROMALLTHEBEAMS4HERADARCROSSSECTIONOFTHETERRAINCOULDBE QUITELOWEG SNOW COVEREDLEVELTREELESSTERRAIN SOSOMEPULSESMAYBEINTEGRATED COHERENTLYTOIMPROVESIGNAL TO NOISERATIOFORA#0)OFUPTOPULSES ASSHOWNINTHE 4&4!ENTRYIN4ABLE 4ERRAIN$ATABASE-ERGING &ORTHEPURPOSESOFSAFETYASWELLASSTEALTH ACTIVE RADARMEASUREMENTSAREMERGEDWITHAPRESTOREDTERRAINDATABASE&IGURESHOWS THEGENERALCONCEPTOFMERGED4&4!MEASUREMENTSWITHSTOREDDATA !CTIVERADARMEASUREMENTSAREMADEOUTTOAFEWMILES4HEINSTANTUSETERRAINDATA BASEEXTENDSOUTTOPERHAPSTENMILES4HETERRAINDATABASECANNOTBECOMPLETELYCURRENT ANDMAYCONTAINCERTAINSYSTEMATICERRORS&OREXAMPLE THEDATABASECANNOTCONTAIN THEHEIGHTOFWIRESSTRUNGBETWEENTOWERSORSTRUCTURESERECTEDSINCETHEDATABASEWAS PREPARED&ORTHELOWESTPOSSIBLEFLIGHTPROFILESWITHLESSTHANnPROBABILITYOFCRASH PERMISSION THEPRESTOREDDATAISMERGEDANDVERIFIEDWITHACTIVERADARMEASUREMENTS ,OWCRASHPROBABILITIESMAYALSOREQUIRESOMEHARDWAREANDSOFTWAREREDUNDANCY)N ADDITION ASTHEAIRCRAFTFLIESDIRECTLYOVERAPIECEOFTERRAIN COMBINEDTERRAINPROFILEIS VERIFIEDBYARADARALTIMETERFUNCTION4%2#/-4%202/- INTHE2&ANDPROCESSOR COMPLEX 5SUALLY THE PRESTORED DATA IS GENERATED AT THE REQUIRED RESOLUTION BEFORE A MISSIONFROMTHEWORLDWIDEDIGITALTERRAINELEVATIONDATABASE$4%$ 3EA3URFACE3EARCH !CQUISITION AND4RACK 3EASURFACESEARCH ACQUISITION ANDTRACKAREORIENTEDTOWARDTHREETYPESOFTARGETSSURFACESHIPS SUBMARINESSNORKEL INGORNEARTHESURFACE ANDSEARCHANDRESCUE4RACKINGMAYBEPRELIMINARYTOATTACK WITHANTISHIPWEAPONS!LTHOUGHMOSTSHIPSARELARGERADARTARGETS THEYMOVERELA TIVELYSLOWLYCOMPAREDTOLANDVEHICLESANDAIRCRAFT)NADDITION SEACLUTTEREXHIBITS BOTHCURRENTANDWIND DRIVENMOTIONASWELLAShSPIKYvBEHAVIOR4HESEFACTSOFTEN REQUIREHIGHRESOLUTIONANDMULTIPLELOOKSINFREQUENCYORTIMETOALLOWSMOOTHINGOF SEACLUTTERFORSTABLEDETECTIONANDTRACK )FTHETARGETISASIGNIFICANTSURFACEVES SEL THEN2#3MIGHTBEM ANDAMRANGERESOLUTIONMIGHTBEUSEDFORSEARCH
&)'52% 4&4!TERRAINMERGING #OURTESY3CI4ECH0UBLISHING
-5,4)&5.#4)/.!,2!$!23934%-3&/2&)'(4%2!)2#2!&4
x°Î£
&)'52% 2ANGEPROFILESHIPRECOGNITION
ANDACQUISITION)FTHETARGETISAPERISCOPEORPERSONINALIFERAFTTHENMRESOLU TIONMIGHTBEUSEDSINCETHE2#3MIGHTBELESSTHANMANDSMOOTHINGISESPECIALLY IMPORTANT$0#!ANDDOPPLERPROCESSINGISOFTENINTERLEAVEDWITHTRADITIONALBRIGHT D"ORGREATERABOVEBACKGROUND TARGETDETECTION,OWER02&SAREUSUALLYUSED WHICH IMPLY RELATIVELY HIGH PULSE COMPRESSION RATIOS AS SHOWN IN4ABLE 3CAN RATESAREOFTENSLOWWITHONEBARTAKINGSECONDS ! HIGH RANGE RESOLUTION PROFILE CAN BE USED TO RECOGNIZE A SHIP JUST AS WITH AN AIRCRAFT)TNATURALLYHASTHESAMEWEAKNESSPREVIOUSLYMENTIONED ANDTHEASPECT ORATTITUDEMUSTBEKNOWN)FTHEATTITUDEISKNOWN THENTHEMAJORSCATTERERSCANBE MAPPEDINTOARANGEPROFILEANDCORRELATEDWITHTHESHIPPOWERRETURNINEACHCELL!N EXAMPLEOFASHIPRANGEPROFILEISSHOWNIN&IGURE4HESEPROFILESAREUSUALLY GENERATEDINTRACKWHENTHEPROFILEISSTABILIZEDINRANGE 4HEWAKEOFASURFACESHIPORSUBMARINENEARTHESURFACEPROVIDESASUBSTANTIAL CROSS SECTION OVER TIME BUT REQUIRES SURFACE STABILIZED INTEGRATION OVER nS OF SECONDS %ARTHSSURFACESTABILIZEDINTEGRATIONCANBEDONEUSINGAMOTIONCOM PENSATEDDOPPLERBEAMSHARPENING$"3 MODE )NVERSE3!2 !FARMORERELIABLEMETHODOFSHIPRECOGNITIONISINVERSESYNTHETIC APERTURERADAR)3!2 4HEBASICNOTIONISTHATTHEMOTIONOFARIGIDOBJECTCANBE RESOLVEDINTOATRANSLATIONANDROTATIONWITHRESPECTTOTHELINEOFSIGHTTOTHETARGET4HE ROTATIONGIVESRISETOADIFFERENTIALRATEOFPHASECHANGEACROSSTHEOBJECT4HEPHASE HISTORYDIFFERENCESCANBEMATCHFILTEREDTORESOLVEINDIVIDUALSCATTERERSINARANGECELL #ONCEPTUALLY SUCHAMATCHEDFILTERISNODIFFERENTTHANAFILTERUSEDTOMATCHAPHASE CODEDPULSECOMPRESSIONWAVEFORM4HISISTHEBASISOFALL3!2 2#3RANGEIMAGING OBSERVEDGEOMETRICTARGETACCELERATION TURNTABLEIMAGING AND)3!2 !SHIPINOPENWATEREXHIBITSROLL PITCH ANDYAWMOTIONSABOUTITSCENTEROFGRAV ITYCG &OREXAMPLE &IGURESHOWSAROLLINGMOTIONOFonTHATMIGHTBE EXHIBITEDBYASHIPINCALMSEAS4HEROLLMOTIONMIGHTHAVEAPERIODOFSECONDS 4HEMOTIONOFALMOSTALLTHESCATTERERSONALARGECOMBATANTAREMOVINGINARCSOF CIRCLESPROJECTEDASSEGMENTSOFELLIPSESTOARADAROBSERVER&ORARADAROBSERVERTHE CHANGEINRANGE D2 ASSOCIATEDWITHAROLLMOVEMENTISAFUNCTIONOFTHEHEIGHT H
x°ÎÓ
2!$!2(!.$"//+
&)'52% )NVERSE3!2NOTION
OFTHESCATTERERABOVETHECENTEROFGRAVITY4HEAPPROXIMATERANGERATEFOREACHSCAT TERERINROLLINGPITCH YAW MOTIONATAHEIGHT H ISTHETIMEDERIVATIVEOF2SHOWNIN &IGURE&ORAGIVENDESIREDCROSSRANGERESOLUTIONWITHREASONABLESIDELOBES $RC AMUSTBEEQUALTO$RCK&ORTHEEXAMPLE FTCROSSRANGERESOLUTIONISOBTAINABLE WITHA SECONDOBSERVATIONTIME4HECORRESPONDINGDOPPLERANDDOPPLERRATESARE ALSOGIVENIN&IGURE &ORASHIPWHOSEPRINCIPALSCATTERERSARELESSTHANFTABOVETHECENTEROFGRAVITY THEDOPPLERSWILLBEINTHERANGEOFo(ZAT8BANDWITHARATEOFCHANGEOFUPTO o(ZS!SLONGASTHEIMAGERESOLUTIONISNOTTOOGREAT EACHRANGE DOPPLERBINCAN BEMATCHFILTEREDUSINGTHEHYPOTHESIZEDMOTIONFOREACHSCATTERERANDANIMAGECAN BEFORMEDONTHESHIP%ACHRANGEBINMAYCONTAINMULTIPLESCATTERERSFROMTHESHIP INAGIVENROLLPLANE ANDTHEYMAYBEDISTINGUISHEDBYTHEIRDIFFERINGPHASEHISTORY (OWEVER SCATTERERSINTHEPITCHAXISATTHESAMERANGEANDROLLHEIGHTCANNOTBESEPA RATED!LTHOUGHPITCHANDYAWMOTIONSARESLOWER THEYALSOEXISTANDALLOWSEPARATION INOTHERSIMILARPLANES 2EASONABLYGOODIMAGESCOUPLEDWITHEXPERIENCEDRADAROPERATORSALLOWRECOGNI TIONOFMOSTSURFACECOMBATANTS2ECOGNITIONAIDSUSINGPRESTOREDSHIPPROFILESALLOW IDENTIFICATIONTOHULLNUMBERINMANYCASES!NEXAMPLEOFASINGLE)3!2IMAGEOF ALANDINGASSAULTSHIPISGIVENIN&IGURE4HERADARINTHISCASEISILLUMINATING
&)'52% 3INGLE)3!2SHIPIMAGE
-5,4)&5.#4)/.!,2!$!23934%-3&/2&)'(4%2!)2#2!&4
x°ÎÎ
THESHIPFROMTHEBOWATKMANDnGRAZING4HEBRIGHTSCATTERERSEXHIBITCROSS RANGESIDELOBES WHICHCANBEPARTIALLYREDUCEDBYSENSINGLARGERETURNS THENAPPLY ING AMPLITUDE WEIGHTING AND DISPLAY COMPRESSION AS HAS BEEN DONE IN THIS IMAGE )NTEGRATIONOFMULTIPLE)3!2IMAGESDRAMATICALLYIMPROVESQUALITY !IR TO 'ROUND2ANGING !IR TO GROUNDRANGINGISUSEDMOSTOFTENFORTARGET INGOFGUNS DUMBBOMBS ANDMISSILESWITHSHORT RANGESEEKERSAGAINSTFIXEDOR SLOWMOVINGTARGETS4HETARGETISDETECTEDANDDESIGNATEDINSOMEOTHERMODE SUCHAS'-4) $"3 3!2 OR3334HEDESIGNATEDTARGETISTRACKEDINRANGEAND ANGLETOPROVIDEAMOREACCURATEDISTANCEANDANGLETOTHETARGET4HETRACKING MAYBEOPENORCLOSEDLOOP4HEESTIMATESARETHENPROVIDEDTOTHEWEAPONBEFORE ANDAFTERLAUNCH$EPENDINGONDISTANCE ANOTHERDESIGNATOR SUCHASALASER AND THERADARMAYBEALTERNATELYSLAVEDTOONEANOTHER"OTHTHERADARANDTHEOTHER DESIGNATORMAYBESUBJECTTOATMOSPHERICREFRACTION ESPECIALLYATLOWALTITUDES WHICHISSOMETIMESESTIMATEDANDCOMPENSATED 0RECISION6ELOCITY5PDATE 0RECISIONVELOCITYUPDATE065 ISUSEDFORNAVIGA TIONCORRECTIONTOANINERTIALPLATFORM!LTHOUGH'03UPDATESARECOMMONLYUSEDTO PROVIDENAVIGATIONINMANYSITUATIONS AMILITARYAIRCRAFTCANNOTDEPENDSOLELYONITS AVAILABILITY&URTHERMORE INERTIALSENSORSAREUSEDTOFILLINBETWEEN'03MEASURE MENTS EVEN UNDER THE BEST CIRCUMSTANCES )NERTIAL SENSORS ARE EXTREMELY GOOD OVER SHORT SPAN TIMES BUT VELOCITY DRIFT IS A MAJOR LONG TIME ERROR SOURCE EG KMH ACCUMULATESMERRORPERMINUTE!RADARMODEMAYREQUIREPOSITIONTOKM FORPROPEROPERATION 065 GENERALLY USES THREE OR MORE ANTENNA BEAM POSITIONS IN WHICH IT MAKES A VELOCITYMEASUREMENT ASSHOWNIN&IGURE4HISMODEDIRECTLYEMULATESDEDI CATEDRADARDOPPLERNAVIGATORS4HEREISATHREE STAGEVELOCITYMEASUREMENTPROCESS &IRST THESURFACEISAUTOMATICALLYACQUIREDINRANGE3ECOND AFINERANGEMEASUREMENT ISMADE OFTENUSINGMONOPULSEDISCRIMINANTSANDRANGECENTROIDINGSIMILARTOTHAT SHOWN IN %Q 4HIRD A LINE OF SIGHT VELOCITY MEASUREMENT 6,/3 USING DOPPLER ANDORRANGERATE ISMADEALSOUSINGCENTROIDING"ECAUSETERRAINMAYBERISINGORFALL INGATTHEILLUMINATEDPATCHESGIVINGRISETOVELOCITYERRORS TERRAINSLOPEISESTIMATED ANDUSEDTOCORRECTTHEESTIMATEDVELOCITY
&)'52% 0RECISION VELOCITY UPDATE CONCEPT
x°Î{
2!$!2(!.$"//+
!+ALMANFILTERARECURSIVEFILTERTHATADAPTIVELYCOMBINESMODELSOFTARGETMEA SUREMENTSANDOFERRORS ISEMPLOYEDTOPROVIDEABETTERESTIMATEOFAIRCRAFTVELOCITY !LTHOUGHTHISPROCEDURECANBEPERFORMEDOVERLANDORWATER SEACURRENTSMAKEOVER WATERMEASUREMENTSFARLESSACCURATE4HISVELOCITYMEASUREMENTPROVIDESIN FLIGHT TRANSFERALIGNMENTOFTHEVARIOUSINERTIALPLATFORMSAIRCRAFT WEAPONS ANDRADAR !SET OFOUTPUTSISPROVIDEDTOTHEMISSIONMANAGEMENTCOMPUTERFUNCTION INCLUDING.ORTH %AST $OWN.%$ VELOCITYERRORSANDESTIMATESOFSTATISTICALACCURACIES 3NIFF OR 0ASSIVE ,ISTENING -OST MODES HAVE A PRECURSOR SUBPROGRAM CALLED SNIFF WHICHLOOKSFORPASSIVEDETECTIONSINATENTATIVEOPERATINGCHANNELBEFOREANY RADAREMISSIONSINTHATCHANNEL4HEDETECTIONSCOULDBEAFRIENDLYINTERFEROR AJAMMER ORANINADVERTENTINTERFERORSUCHASAFAULTYCIVILIANCOMMUNICATIONSTRANSPONDER 4HISLASTEXAMPLEISTHEMOSTCOMMONINTHEAUTHORSEXPERIENCE)TISNOTUNCOMMON FORAFAULTYTRANSPONDERTOAPPEARASAMILLIONSQUAREMETERTARGET $OPPLER"EAM3HARPENING$"3 $"3ISVERYSIMILARTOSYNTHETICAPER TURERADAR3!2 SINCEBOTHUSETHEDOPPLERSPREADACROSSTHEANTENNAMAINBEAMTO CREATEHIGHERRESOLUTIONINTHECROSSBEAMDIRECTION 4HEPRINCIPALDIFFERENCEIS THEAMOUNTOFANGULARCOVERAGE BEAMSCANNING RESOLUTION DATAGATHERINGTIME AND ACCURACYOFMATCHEDFILTERINGINEACHRANGE DOPPLERCELL!$"3MAPMAYTAKEASEC ONDTOGATHEROVERANANGLEOFn$EPENDINGONTHEANGLEFROMTHEAIRCRAFTVELOCITY VECTOR A3!2MAPOFAFEWFEETRESOLUTIONMAYTAKETENSOFSECONDSTOGATHERAT8 BAND$"3AND3!2ARECOMPAREDINAQUALITATIVEWAYIN&IGURE !STHEBEAMISPOSITIONEDCLOSERTOTHEVELOCITYVECTOR THEDOPPLERSPREADISSMALLER ANDSOCOHERENTDWELLTIMESMUSTINCREASEFORTHESAMERESOLUTION5SUALLY THEREISA TRANSITIONFROMSHORTERCOHERENTPROCESSINGINTERVALS#0)S ANDLONGERPOSTDETECTION INTEGRATIONS0$)S TOLONGER#0)SANDSHORTER0$)SASTHEBEAMAPPROACHESTHEAIR CRAFTVELOCITYVECTOR.EARNOSE ONDWELLTIMESBECOMEPROHIBITIVEANDTHESCANCENTER ISFILLEDWITHREALBEAMMAPPING4HEREALBEAMUSESTHESAMERANGERESOLUTION BUT BECAUSERETURNSFROMTHEENTIREBEAMAREUSED SOMEAMPLITUDEEQUALIZATIONISREQUIRED TOPROVIDEUNIFORMCONTRASTANDBRIGHTNESSACROSSTHEWHOLEMAP3OMEEFFORTISMADE
&)'52% $OPPLERBEAMSHARPENING$"3 COMPARISONTO3!2
-5,4)&5.#4)/.!,2!$!23934%-3&/2&)'(4%2!)2#2!&4
x°Îx
&)'52% $"3PROCESSINGADAPTEDCOURTESY3CI4ECH0UBLISHING
TOMATCHFILTERBOTHINRANGECLOSUREANDPHASEHISTORY THEDOPPLERSPREADSINCEISO RANGEANDISO DOPPLERSARENOTCLOSETOORTHOGONALNEARTHEAIRCRAFTVELOCITYVECTORSEE &IGURE 3!2 ONTHEOTHERHAND ISUSUALLYFULLYMATCHEDRELATIVETOTHEDESIRED RESOLUTIONANDPHASEHISTORY INEVERYRANGE DOPPLERCELL &IGURE SHOWS THE SIGNAL PROCESSING THAT MIGHT BE FOUND IN $"3 MODE )T CONSISTSOFMULTIPLETIMEAROUNDECHO-4!% SUPPRESSION AMPLITUDEWEIGHTINGTO IMPROVE SIDELOBES PRESUMMATION AN &&4 FILTER BANK MAGNITUDE DETECTION IN EACH USABLEFILTEROUTPUT PLACEMENTOFEACHFILTEROUTPUTINTHECORRECTGROUNDSTABILIZED LOCATIONFOLLOWEDBYPOSTDETECTIONINTEGRATION ANDSCALINGFORTHEDISPLAYFORCON STANTBRIGHTNESSANDDYNAMICRANGE$EPENDINGONGRAZINGANGLE AMBIGUOUSRETURNS MAYCOMPETEWITHTHEREGIONTOBEIMAGED/FTEN ACOMBINATIONOFSENSITIVITYTIME CONTROL34# ANDPULSETOPULSEPHASECODINGISUSEDTOREJECTMULTIPLETIMEAROUND ECHOES-4!% 4HEAMOUNTOFPRESUMMATION02%35- ANDPOSTDETECTION INTEGRATION0$) ASAFUNCTIONOFBEAMPOSITIONOFFTHEVELOCITYVECTORISSHOWNINTHE LOWERRIGHTOF&IGURE&OREACHDIFFERENTANGLE THEREISADIFFERENTDOPPLERSPREAD ACROSS THE BEAM4HEREFORE IN ORDER TO MAINTAIN A CONSTANT BEAM SHARPENING RATIO DIFFERENTAMOUNTSOFPRESUMMINGMUSTBEUSEDFOREACHBEAMPOSITION0RESUMMING ISTHEFORMATIONOFANUNFOCUSSEDSYNTHETICBEAMIE THEREISLITTLEORNOATTEMPTTO MATCHTHEEXACTPHASEHISTORYOFSURFACEPOINTS INSIDETHEREALANTENNABEAMBYWHAT ISESSENTIALLYALOWPASSFILTER4HISWOULDRESULTINDIFFERENTTARGETBRIGHTNESSANDCON TRASTIFITWERENOTCOMPENSATEDBYAPPLYINGACORRESPONDINGPOSTDETECTIONINTEGRATION 0$) FOREACHANGLE ASSHOWNIN&IGURE -ULTIPLEFREQUENCYLOOKSAREUSEDTOREDUCESPECKLEINTHEIMAGEANDSOSEVERAL DIFFERENTFREQUENCIESARE0$)ED4HE#0)ISTHEPRESUMRATIOTIMESTHENUMBEROFFILTER SAMPLESnISTYPICAL %ACH#0)MAYHAVEMINORCHANGESINTHE02&TOSIM PLIFYPROCESSINGANDCOMPENSATEFORAIRCRAFTMANEUVERS4HEAIRCRAFTMAYTRAVELFT DURING THE GATHERING TIME 4HERE IS CONSIDERABLE TRANSPORT DELAY IN MOST 3!2 AND $"3PROCESSINGASARESULT PROCESSEDRETURNSMUSTBERECTIFIEDIE COMPENSATEDFOR GEOMETRICDISTORTION MOTIONCOMPENSATED ANDMAPPEDINTOTHEPROPERSPACEANGLE ANDRANGEPOSITION3INCE$"3USUALLYMAPSALARGEAREATOPROVIDEOVERALLGROUND SITUATIONALAWARENESS THETOTALRANGECOVERAGEISOFTENCOVEREDINMULTIPLEELEVATION BEAMS AND RANGE SWATHS 4HIS IS TRANSPARENT TO THE OPERATOR BUT REQUIRES DIFFERENT 02&S PULSEWIDTHS FILTERSHAPES ANDDWELLTIMES
x°ÎÈ
2!$!2(!.$"//+
!LTHOUGHAN-&!2CONTAINSAVERYSTABLETIMEREFERENCE UNCERTAINTIESINTHERATE OFCHANGEOFTERRAINHEIGHT REFRACTION WINDSALOFT ANDVERYLONGCOHERENTINTEGRATION TIMESFORCETHEMEASUREMENTOFTHECLUTTERDOPPLERERRORVERSUSPREDICTEDFREQUENCYTO MAINTAINPROPERFOCUSANDBINREGISTRATION ASSHOWNINTHEUPPERRIGHTIN&IGURE !SIMILARFUNCTIONISPERFORMEDIN3!2ASWELL 3YNTHETIC!PERTURE2ADAR !SISTHECASEFOR$"3 3!2ISAMULTIRATE FILTERING PROBLEM IE ACASCADEOFFILTERSINWHICHTHEINPUTSAMPLINGRATEISHIGHERTHANTHE OUTPUTSAMPLINGRATE ASSHOWNIN&IGURE WHICHREQUIRESVERYCAREFULATTENTIONTO RANGEANDAZIMUTHFILTERSIDELOBES4YPICALLY THESPACINGOFINDIVIDUALPULSESONTHE GROUNDISCHOSENTOBEMUCHCLOSERTHANTHEDESIREDULTIMATERESOLUTION4HISALLOWS LINEAR RANGE CLOSURE AND PHASE CORRECTION SINCE EACH POINT ON THE SURFACE MOVES A SIGNIFICANTFRACTIONOFARANGECELLPULSETOPULSE n 4HEINPUTSIGNAL POINT !IN&IGURE ISSHOWNASASPECTRUMAT! FOLDEDABOUTTHE02&ONTHELEFTIN &IGURE 3UBSEQUENTLY PRESUMMATIONISAPPLIED WHICHFORMSANUNFOCUSSEDSYNTHETICBEAM ORFILTERINSIDETHEMAIN BEAMGROUNDRETURNPOINT"IN&IGURE WHICHIMPROVES AZIMUTHSIDELOBESANDNARROWSTHESPECTRUM ASSUGGESTEDINTHECENTERGRAPHSHOWN IN&IGURE4HEPRESUMMEROUTPUTISRESAMPLEDATALOWERRATE F3 CONSISTENTWITH ACCEPTABLEFILTERALIASING4HEN RANGEPULSECOMPRESSIONISPERFORMED ASSUMINGTHE TRANSMITTEDPULSEISVERYLONGCOMPAREDTOTHERANGESWATH)FCHIRPLINEAR&- ISUSED PARTOFTHEhSTRETCHvPULSECOMPRESSIONPROCESSINGISPERFORMEDINTHERANGECOMPRES SIONFUNCTIONWITHTHEREMAINDERPERFORMEDINPOLARFORMATPROCESSING4HEDECHIRPED ANDPARTIALLYFILTEREDORCOMPRESSEDOUTPUT SHOWNATPOINT#IN&IGURE MAYBE RESAMPLEDAGAINATANEWF3 ASINDICATEDINTHERIGHTGRAPHSHOWNIN&IGURE POINT #)NANYCASE AZIMUTHVARIABLEPHASEADJUSTMENTANDBINMAPPINGWHICHCOMPEN SATES FOR CHANGES IN MEASUREMENT SPACE ANGLES AND RANGE CLOSURE SINCE SIGNIFICANT MOTIONOCCURSDURINGTHEDATAGATHERINGTIME MUSTBEPERFORMEDBEFOREAZIMUTHFILTER INGSOMETIMESCALLEDCOMPRESSIONBECAUSEITISSIMILARTOPHASEMATCHEDPULSECOM PRESSION 4HEOUTPUTOFAZIMUTHCOMPRESSIONISSHOWNATPOINT#4HECOMPLEX3!2 OUTPUTMAPMUSTBECHECKEDFORDEPTHOFFOCUSANDUSUALLYREQUIRESAUTOFOCUSSINCE BOTH ATMOSPHERIC EFFECTS AND LOCALLY RISING OR FALLING TERRAIN MAY CAUSE DEFOCUSING 3UBSEQUENTTOREFOCUSING THEMAPISMAGNITUDEDETECTEDANDHISTOGRAMAVERAGEDTO MAINTAINUNIFORMBRIGHTNESS4HEMAPISINTEGRATEDWITHOTHERLOOKS WHICHREQUIRES
&)'52% 3!2PROCESSINGADAPTEDCOURTESY3CI4ECH0UBLISHING
-5,4)&5.#4)/.!,2!$!23934%-3&/2&)'(4%2!)2#2!&4
x°ÎÇ
&)'52% 3!2-ULTIRATE&ILTERINGADAPTEDCOURTESY3CI4ECH0UBLISHING
GEOMETRICALCORRECTIONANDMOTIONCOMPENSATION4HETOTALMAPDYNAMICRANGECAN EASILYBEGREATERTHAND"4HETYPICALCOCKPITDISPLAYISLIMITEDTOnD"AND DYNAMIC RANGECOMPRESSION SUCHASCONVERTINGMAPAMPLITUDESINTOTHEIRLOGARITHMS ISOFTENPERFORMED $"3OR3!202& 0ULSE,ENGTHAND#OMPRESSION3ELECTION &OREACH3!2 OR $"3 GEOMETRY THE TRANSMITTED PULSE WIDTH PULSE REPETITION INTERVAL AND PULSE COMPRESSIONRATIOMUSTBECALCULATED/NEPOSSIBLESETOFSELECTIONCRITERIAISGIVEN IN%Q 5SUALLY THELASTRANGEAMBIGUITYBEFORETHERANGESWATHISCHOSENTOBEOUTSIDE THEMAINBEAM FARENOUGHTOBEATLEASTD"DOWN INCLUDING2EFFECTS/FTENIN 3!2 THETRANSMITTEDPULSEISMUCHLARGERTHANTHERANGESWATH 2SWATH#LEARLY IN EACH OF THE CASES THE NEAREST INTEGRAL CLOCK INTERVAL AND NEAREST CONVENIENT PULSE COMPRESSIONRATIOISSELECTEDBECAUSETHEVALUESIN%QWILLBECLOCKINTEGERSONLY BYCOINCIDENCE 0ULSE2EPETITION)NTERVAL02)
r 2 2MIN 2SWATH 2P L q 02) q
r 6A r 5 r "AZ r SINQ C 0ULSE7IDTH2Pa$UTYMAXr02)rC -INIMUM!LLOWABLE!MBIGUOUS2ANGE 2MINyHrCSCD 5r"EL 2ANGE3WATHIS'EOMETRYAND)NSTRUMENTATION$EPENDENT 2SWATHaHr;CSCD "EL CSCD "EL = AND2SWATHa2MAXSWATH
WHEREKISTRANSMITTEDWAVELENGTH HISTHEAIRCRAFTALTITUDE "AZ"ELARETHEAZIMUTHELEVATIONHALFPOWERBEAMWIDTHS PDARETHEANGLESBETWEENTHEVELOCITYVECTORANDANTENNABEAMCENTER 2ISTHEDISTANCETOTHEFIRSTRANGEBIN 6AISTHEAIRCRAFTVELOCITY 2SWATHISTHERANGESWATHLENGTH 2MAXSWATHISMAXIMUMINSTRUMENTEDRANGESWATH 2MINISTHERANGETOTHECLOSESTALLOWABLEAMBIGUITY $UTYMAXISALLOWABLEDUTYRATIO 2PISTHETRANSMITTEDPULSELENGTHINDISTANCEUNITS CISTHEVELOCITYOFLIGHT 5 5AREBEAMWIDTHMULTIPLIERSATPREDEFINEDPOWERROLLOFF
x°În
2!$!2(!.$"//+
&OREXAMPLE ASSUME6A MS K M H M P D "AZ "EL 5 5 2SWATH KM 2MIN KM DESIREDMAPPINGRANGE 2 KM $UTYMAX SELECTINGAFIRSTGUESSFOR2P MTHEN 02) MSEC 2MINISTHEEQUIVALENTOFMSEC ANDTHENEXTALLOWABLEAMBIGUITYWOULDBEPASTTHE SWATHATMSECTHEREFORE A02)OFORMSECCOULDBEUSEDWITHATRANSMITTED PULSEOFAPPROXIMATELYORMSECRESPECTIVELY 'ROUND-OVING4ARGET)NDICATION'-4) AND4RACK'-44 '-4)IS THEDETECTIONANDACQUISITIONOFGROUNDMOVINGTARGETS'-4)AND'-44RADAR MODESHAVEADIFFERENTSETOFCHALLENGES&IRST TARGETDETECTIONISUSUALLYTHEEASY PARTTHE2#3OFMOSTANTHROPOGENICOBJECTSANDMANYNATURALMOVINGTARGETSIS LARGEnM 5NFORTUNATELY THEREAREMANYSTATIONARYOBJECTSWITHMOVING PARTSSUCHASVENTILATORS FANS WATERCOURSES ANDPOWERLINESTHATLEADTOAPPARENT FALSEALARMS/FTENSLOW MOVINGVEHICLESHAVEFAST MOVINGPARTSEG HELICOP TERSANDAGRICULTURALIRRIGATORS -OSTAREASHAVELARGENUMBERSOFVEHICLESANDSCATTERERSTHATCOULDBEVEHICLES)TIS TYPICALTOHAVEUPTO BONAFIDE'-4SINTHEFIELDOFVIEW0ROCESSINGCAPACITY MUSTBEADEQUATETOHANDLEANDDISCRIMINATETHOUSANDSOFHIGH3.2THRESHOLDCROSSINGS ANDHUNDREDSOFMOVINGTARGETSOFINTEREST5SUALLYMULTI HYPOTHESISTRACKINGFILTERS WILLBEFOLLOWINGSEVERALHUNDRED'-4SOFINTERESTSIMULTANEOUSLY)NMOSTCASES ALL TARGETSMUSTBETRACKEDANDTHENRECOGNIZEDONTHEBASISOFDOPPLERSPECTRUMHELICOPTERS VSWHEELEDVEHICLESVSTRACKEDVEHICLESVSSCANNINGANTENNAS RATEOFMEASUREDLOCA TIONCHANGEVENTILATORLOCATIONSDONTCHANGE ANDCONSISTENTTRAJECTORYEG MPH WHERETHEREARENOROADSISIMPROBABLEFORASURFACEVEHICLE )NADDITION VEHICLESOF INTERESTMAYHAVERELATIVELYLOWRADIALVELOCITIESREQUIRINGENDOCLUTTERPROCESSINGIE FARENOUGHINSIDEMAIN BEAMCLUTTERTHATDETECTIONISLIMITEDFORDOPPLERONLYFILTERING ! PROCESSING BLOCK DIAGRAM FOR '-4) IS SHOWN IN &IGURE !LTHOUGH THERE AREALTERNATEWAYSTOPERFORMENDOCLUTTERPROCESSING AMULTIPLEPHASECENTERnBASED
&)'52% 'ROUND MOVING TARGET DETECTION PROCESSING ADAPTED COURTESY 3CI4ECH 0UBLISHING
-5,4)&5.#4)/.!,2!$!23934%-3&/2&)'(4%2!)2#2!&4
x°Î
PROCESSING SCHEME IS GIVEN IN &IGURE -ULTIPLE CHANNELS OR PHASE CENTERS ARE DIGITIZEDANDPULSECOMPRESSED0ERIODICCALIBRATIONSIGNALSAREUSEDTOCREATEAGAIN PHASEANDBEAMSTEERINGCORRECTIONTABLEFORALLFREQUENCIES ANTENNABEAMSTEERING ANDCHANNELS WHICHARETHENAPPLIEDTOTHEDIGITIZEDMEASUREMENTSINEACHCHANNEL -OTIONCOMPENSATIONTOAFRACTIONOFAWAVELENGTHFORPLATFORMMANEUVERSORDEVIA TIONSISAPPLIEDTOTHEDATA!COARSETWO DIMENSIONAL&&4ISPERFORMEDFOLLOWEDBY SPACE TIMEADAPTIVECALCULATIONS ANDFILTERWEIGHTINGISAPPLIEDTOREJECTSOMECLUT TER AND JAMMING (IGH RESOLUTION DOPPLER FILTERING IS PERFORMED IN A CONVENTIONAL &&4 PERHAPS WITH $0#! CLUTTER CANCELLATION $OPPLER FILTER OUTPUTS ARE USED TOFORMMAIN BEAMCLUTTERERRORDISCRIMINANTSFORPRECISELYMEASURINGDOPPLERCENTER FREQUENCYTOPROVIDEFRACTIONOFWAVELENGTHMOTIONCOMPENSATION-AIN BEAMCLUTTER ISNOTINTHESAMEFREQUENCYLOCATIONFOREACHRANGEBIN ANDSOFILTEROUTPUTORDERMUST BEADJUSTEDTOPRESENTACOMMONINPUTTOTHETHRESHOLDDETECTOR4HEDOPPLERFILTER BANKOUTPUTSALSOAREAPPLIEDTOAMULTILEVELTHRESHOLDDETECTORFORGROUNDMOVING TARGETDETECTIONSIMILARTOTHOSEDESCRIBEDINh'ROUND-OVING4ARGET4HRESHOLDINGv 3UMANDDIFFERENCEDISCRIMINANTFUNCTIONSAREFORMEDANDSTOREDINBUFFERSTORAGEFOR EACHDETECTEDMOVINGTARGETTOIMPROVETARGETTRACKINGANDGEOLOCATIONACCURACY /FTEN02&SAREAMBIGUOUSINBOTHRANGEANDDOPPLERBUTUNAMBIGUOUSINSIDE THEMAINBEAMANDNEARSIDELOBESIE THEREISONLYONERANGEORDOPPLERAMBIGU ITYINTERVALINTHEMAINBEAMANDNEARSIDELOBES 02&SELECTIONISSIMILARTO! ! -02&5SUALLYFEWER02&SAREUSEDFOURORFIVEARETYPICAL!RANGEAMBIGU ITYMAYBEINTHEMAINBEAMATLOWGRAZINGANGLES4WOOUTOFFOURORTHREEOUT OFFIVEISUSUALLYTHEFINALDETECTIONCRITERIA02&STYPICALLYAREnK(Z#ODED WAVEFORMS ARE OFTEN USED TO REJECT AMBIGUOUS RETURNS OUTSIDE THE ANTENNA MAIN BEAMTHATCOMPETEWITHTHEREGIONOFINTEREST!FTRANGECELLSIZEISOFTENUSED TOMATCHTHESMALLESTVEHICLEOFINTERESTANDTOREDUCEBACKGROUNDCLUTTER'ROUND MOVING TARGET RECOGNITION MAY REQUIRE FT RESOLUTION !NTENNA ILLUMINATION MUST BE GROUND STABILIZED SINCE THE AIRCRAFT WILL ENGAGE IN BOTH INTENTIONAL AND UNINTENTIONALMANEUVERS 'ROUND -OVING 4ARGET 4HRESHOLDING 4HE TYPICAL MULTILEVEL THRESHOLD HAS SEVERALUNIQUEFEATURES)NADDITIONTOTHEOBVIOUSALERT CONFIRMPROPERTIESADOUBLE THRESHOLDINGMETHODINWHICHALOWERFIRSTTHRESHOLDNOMINATESRADARRETURNSASPOS SIBLETARGETSTOBECONFIRMEDBYARETURNOBSERVATIONWITHAHIGHERTHRESHOLD ITALSO USESMULTIPLEPHASECENTERDISCRIMINANTSASWELLASNEARSIDELOBETHRESHOLDMULTIPLI ERS%VENWITH34!0 THENON GAUSSIANNATUREOFCLUTTERREQUIRESHIGHERTHRESHOLDSIN THEMAINBEAMANDNEARSIDELOBES4HRESHOLDCROSSINGSARECORRELATEDINRANGEAND DOPPLERANDBUFFEREDALONGWITHCORRESPONDINGPHASECENTERDISCRIMINANTS WHICHARE PRESENTEDTOTRACKINGFILTERSORACTIVITYCOUNTERS 4HEREARETHREEREGIONSOFTHRESHOLDINGMAIN BEAMCLUTTER LIMITEDDETECTION NEAR SIDELOBECLUTTER LIMITEDDETECTION ANDTHERMAL NOISE LIMITEDDETECTION.EARSURFACE TARGETSOFINTERESTWILLOFTENHAVERADIALVELOCITIESOFAFEWMILESPERHOURFORLONG PERIODSOFTIME WHICHFORCESTHEDETECTIONOFGROUNDMOVINGTARGETSWELLINTOMAIN BEAM CLUTTER 0HASE MONOPULSE $0#! OR 34!0 PROCESSING ALLOWS THE FIRST ORDER CANCELLATIONOFCLUTTERFORMANYSLOW MOVINGTARGETS5NFORTUNATELY CLUTTERDOESNOT ALWAYSHAVEWELL BEHAVEDSTATISTICALTAILS ANDTOMAINTAINACONSTANTFALSEALARMRATE THETHRESHOLDMUSTBERAISEDFORENDOCLUTTERTARGETS4HEOUTPUTOFTHEDOPPLERFILTER BANKMIGHTBETHOUGHTOFASATWODIMENSIONALRANGE DOPPLERIMAGE4HEREWILLSTILLBE PARTSOFMAIN BEAMCLUTTERTHATARECOMPLETELYDISCARDEDEXCEPTFORMOTIONCOMPENSA TIONBECAUSECLUTTERCANCELLATIONISINADEQUATE
x°{ä
2!$!2(!.$"//+
&)'52% -ULTIREGION'-4THRESHOLDING#OURTESY3CI4ECH0UBLISHING
!NEXAMPLETHRESHOLDINGSCHEMEBASEDONTHESECONCEPTSISSHOWNIN&IGURE 4HERANGE DOPPLERSPACEISBROKENUPINTOAGRIDOFRANGEBINSANDDOPPLERFILTERS AS SHOWNINTHEFIGURE%ACHCELLINTHEGRIDMIGHTBE¾RANGE DOPPLERBINSWITH GRIDCELLSTOTAL3OMEGRIDLOCATIONSCLOSETOMAIN BEAMCLUTTER-,#INFIGURE ARE USEDFORFORMINGMAIN BEAMCLUTTERDISCRIMINANTSONLYANDAREOTHERWISEDISCARDED 4HEBINSINTHEEXAMPLE INEACHGRIDCELLAREENSEMBLEAVERAGED%! INSUMAND DIFFERENCECHANNELS4HEPOWERINEACHBININAGRIDCELLINTHECLEARTHERMALNOISE LIMITED REGIONISCOMPAREDTOATHRESHOLD 04(%! WHICHISAFUNCTIONOFTHE%! INTHATGRIDCELL)NTHEENDOCLUTTERNEARSIDELOBEREGION ADISCRIMINANT #S ISFORMED ANDUSEDTOPROVIDEADDITIONALCLUTTERCANCELLATIONPRIORTOTHRESHOLDING!GAIN THE THRESHOLD 04(%! ISAFUNCTIONOFTHE%!INTHATGRIDCELLANDAPRIORIKNOWLEDGEOF THECLUTTERSTATISTICS!LTHOUGHONLYONETHRESHOLDISDESCRIBED TWOAREACTUALLYUSED BEFOREHITSANDTHEIRCORRESPONDINGDISCRIMINANTSAREPASSEDTOTHETRACKFILES!LLLOW THRESHOLDHITSAREPASSEDTOACTIVITYCOUNTERS!SCOMPLEXASTHISTHRESHOLDINGSCHEME SEEMSTOBE ITISVERYDETECTIONPOWEREFFICIENT 4YPICAL '-4 7EAPON $ELIVERY !S MENTIONED PREVIOUSLY MISSILE GUIDANCE REQUIRESTRACKINGOFBOTHTARGETSANDMISSILESALSOBULLETSINGUNLAYINGRADARGUNLAY INGISATERMINVENTEDBYTHE5+DURING77))FORRADARPOINTINGOFANTIAIRCRAFTGUNS 2ANGE ACCURACY IS AT LEAST AN ORDER OF MAGNITUDE BETTER THAN ANGLE ACCURACY 3OME METHODMUSTBEUSEDTOIMPROVEANGLEACCURACYFORWEAPONDELIVERY!NEXAMPLEPRO CESSINGDIAGRAMFOR'-4WEAPONDELIVERYISSHOWNIN&IGURE)NTHISCASE THREE DIFFERENTCLASSESOFTARGETORMISSILEARETRACKED!SINGLEWAVEFORMMAYBEUSEDTOTRACK STATIONARY ENDO ANDEXOCLUTTERMOVINGTARGETS ANDMISSILESORBULLETS%ACHCLASSOF RETURN BASEDONITSRANGEANDDOPPLERLOCATION ISSEPARATELYTRACKEDANDGEOLOCATED 4HEREARESEVERALCOMMONTYPESOFGEOLOCATIONMANYOFTHEMAREBASEDONUSING EITHER $4%$ OR CARTOGRAPHIC DATA /NE METHOD USING CARTOGRAPHIC DATA IS SHOWN
-5,4)&5.#4)/.!,2!$!23934%-3&/2&)'(4%2!)2#2!&4
x°{£
&)'52% 4YPICAL'-4WEAPONGUIDANCEADAPTEDCOURTESY3CI4ECH0UBLISHING
IN&IGURE!NERRORELLIPSEANDITSCORRESPONDINGECCENTRICITYARECALCULATEDFOR EACHTARGET)FTHEECCENTRICITYISLESSTHANSOMEARBITRARYTHRESHOLDEG RELA TIVE THEMINIMUMPERPENDICULARDISTANCEISCALCULATEDFORROADSEGMENTSINSIDETHE SIGMAELLIPSE!SSHOWNINTHEFIGURE THEPERPENDICULARINTERCEPTMAYNOTLIEINSIDE THEROADSEGMENTANDWILLBEDISCARDED4HEMINIMUMDISTANCEFORVALIDROADSEGMENT DISTANCESWILLBESELECTEDASTHE'-4LOCATION)FTHEECCENTRICITYISGREATERTHANTHE THRESHOLD THEROADSEGMENTSTHATHAVEAMAJORELLIPSEAXISINTERCEPTINSIDESIGMA ARECOMPARED ANDTHEMINIMUMDISTANCEISSELECTED/BVIOUSLY SOMEOTHERSCREENING MUSTALSOBEAPPLIED&OREXAMPLE SOMEROADSCANNOTSUPPORTHIGHSPEEDSANDTANKS DONOTHAVETOBEONROADS !COMMON3!2 -4)DISPLAYMAYBEPRESENTEDTOTHEOPERATOR)NADDITION GUID ANCECOMMANDSORERRORSAREDERIVEDFROMTHEMEASUREMENTSANDPROVIDEDTODOWN LINKS TO EITHER MISSILES ON THE FLY OR GUN DIRECTING COMPUTERS FOR THE NEXT ROUNDS 3HORT TERMCOHERENTCHANGEDETECTIONMAYBEUSEDTOSEPARATESTATIONARYTARGETSFROM SLOW MOVINGENDOCLUTTERTARGETS3HORT TERMCOHERENTCHANGEDETECTIONISAMETHODIN WHICHTWOCOHERENT3!2MAPSTAKENWITHINAFEWHOURSOFONEANOTHERATTHESAME FREQUENCYAREREGISTEREDANDCROSS CORRELATEDPIXELBYPIXEL4HEFAST MOVINGTARGET CATEGORYUSUALLYINCLUDESBOTHTARGETSANDBULLETSORMISSILES
&)'52% #ARTOGRAPHIC ASSISTED'-4GEOLOCATION
x°{Ó
2!$!2(!.$"//+
-ISSILE0ERFORMANCE!SSESSMENT 4RACK AND5PDATE -ISSILEMIDCOURSEGUID ANCEUSUALLYCONSISTSOFASSESSINGTHEMISSILEPERFORMANCE MEASUREMENTOFTHETARGET ANDMISSILELOCATION PREDICTIONOFTHEPATHOFEACH ANDUPDATINGTHERESULTINGDATATO THEMISSILEFORTHEBESTFUTUREINTERCEPTOFTHETARGET)TMAYALSOINCLUDETHEMOSTCURRENT ESTIMATEOFTHETARGETTYPEANDATTITUDEFORBESTFUZING4HEMISSILEUSUALLYSENDSDATA ABOUT ITS STATE OF HEALTH OWNSHIP MEASUREMENTS REMAINING FUEL AMOUNTS AND TARGET ACQUISITION IFANY7HENTHEMISSILEISCLOSETOTHEDATALINKAIRCRAFTWHICHMAYORMAY NOTBETHELAUNCHINGPLATFORM COMMUNICATIONISOFTENTHROUGHANAPERTUREOTHERTHANIN THEMAIN-&!2!STHEDISTANCEGETSGREATER THEPRIMARY-&!2APERTUREISUSED!STHE DATALINKAIRCRAFTMANEUVERS THEAPERTURETHATHASTHELARGESTPROJECTEDAREAINTHEDIREC TIONOFTHEMISSILEISUSED4HEBANDWIDTHTOTHEMISSILEISVERYLOWANDCANBEREDUNDANT ANDHIGHLYENCRYPTEDTOPROVIDEGOODANTIJAM!* PROTECTION)FITCONTAINSIMAGERY THEUPLINKBANDWIDTHFROMTHEMISSILEISRELATIVELYLARGEANDWILLHAVECOMPARATIVELY LOWER!*PERFORMANCE!NADAPTIVE-&!2PRIMARYAPERTURECANIMPROVEAWIDERBAND MISSILEUPLINK!*IFTHEJAMMERISOFFSETFROMTHETARGET!TTHEMISSILEEND THEMISSILE ANTENNACANHAVEJAMMERNULLINGTOIMPROVEDOWNLINK!* !'# #ALIBRATE AND 3ELF 4EST 5SUALLY AT THE BEGINNING OF A NEW MODE THE END OF EACH SCAN BAR OR ONCE PER SECOND THE CALIBRATE AND SELF TEST SUBPROGRAM IS INVOKEDBYTHEOPERATIONALFLIGHTPROGRAM/&0 EXECUTIVE!SEQUENCEOFSUBROUTINES ISEXECUTEDTHATMEASURESPHASEANDGAINUNBALANCEBETWEENCHANNELSUSINGASIGNAL INJECTEDONTHEANTENNA4HISISUSUALLYDONEOVERARANGEOFINPUTAMPLITUDES FREQUEN CIES AND!'#SETTINGSBECAUSEOFTHENONLINEARCHARACTERISTICSOFMOST2&FRONTENDS !LSO FOR MODES LIKE4&4! A FULL SET OF OFF ANGLE DIAGNOSTICS IS PERFORMED WHICH TESTSTHEINTEGRITYOFTHEENTIREMEASUREMENT PROCESSING ANDFLIGHTCONTROLCHAINOFTEN ENOUGHTOKEEPTHEPROBABILITYOFAFAILURE INDUCEDCRASHPERFLIGHTBELOWnINTHE PRESENCEOFJAMMINGORCOMPONENTFAILURES )NADDITION THEREAREINITIATEDBUILT INTESTSATTWOLEVELSANOPERATIONALREADINESS TESTPERFORMEDASPARTOFMISSIONINITIATIONANDAFAULTISOLATIONTESTPERFORMEDBYTHE MAINTENANCECREWINRESPONSETOANOPERATORDEFICIENCYREPORT"OTHTESTSTAKELONGER ANDAREMOREEXHAUSTIVE)NTHEBESTCASE THESPECIFICFLIGHTLINEORAFIRST LEVELMAIN TENANCEREPLACEABLEASSEMBLYISIDENTIFIEDWITHHIGHPROBABILITY3UCHASSEMBLIESARE THENSENTTOADEPOTFORREPLACEMENT REPAIR FAILURETRACKING ANDORRECLAMATION&OR ASSEMBLIESTHATHAVEAVERYLOWFAILURERATE ITISUSUALLYCHEAPERTOREPLACEANDRECLAIM RATHERTHANREPAIREVENWHENTHEASSEMBLYISVERYEXPENSIVE
, ,
3HORTCOURSENOTESANDOTHERPAPERSCANUSUALLYBEOBTAINEDFROMTHEAUTHORSORTHECOURSESPONSORFOR ASMALLFEE!LLOFTHEAUTHORSPAPERSREFERENCEDAREAVAILABLEIN!DOBE!CROBATFORMATSUBJECTONLY TOCOPYRIGHTRESTRICTIONSBYE MAILREQUESTDAVIDLYNCHJR IEEEORGANDCARLOKOPP IINETNETAU #+OPP h!CTIVEELECTRONICALLYSTEEREDARRAYS v HTTPWWWAUSAIRPOWERNET *OINT!DVANCED 3TRIKE4ECHNOLOGY 0ROGRAM h!VIONICS ARCHITECTURE DEFINITION v 53 $O$ PUBLICRELEASE UNLIMITEDDISTRIBUTIONANDUSE PP $%LIOTED (ANDBOOKOF$IGITAL3IGNAL0ROCESSING 3AN$IEGO #!!CADEMIC0RESS PPn n n n , 4OWER AND $ ,YNCH h0IPELINE (IGH 3PEED 3IGNAL 0ROCESSOR v 53 0ATENT
-5,4)&5.#4)/.!,2!$!23934%-3&/2&)'(4%2!)2#2!&4
x°{Î
,4OWERAND$,YNCH h3YSTEMFOR!DDRESSINGAND!DDRESS)NCREMENTINGOF!RITHMETIC5NIT 3EQUENCE#ONTROL3YSTEM v530ATENT ,4OWERAND$,YNCH h0IPELINEDMICROPROGRAMMABLECONTROLOFAREALTIMESIGNALPROCESSOR v IN)%%%-ICRO#ONFERENCE *UNE P $ ,YNCH h2ADAR SYSTEMS FOR STRIKEFIGHTER AIRCRAFT v PRESENTED AT !/# 4HIRD 2ADAR%7 #ONFERENCE0ROCEEDINGS 5NCLASSIFIEDPAPERINCLASSIFIEDPROCEEDINGSAVAILABLEFROMAUTHORBY REQUEST &EBRUARYn $ ,YNCH )NTRODUCTION TO 2& 3TEALTH 2ALEIGH .# 3CI4ECH 0UBLISHING PP n n n nn n $,YNCHETAL h!DVANCEDAVIONICSTECHNOLOGY v%VOLVING4ECHNOLOGY)NSTITUTE3HORT#OURSE .OTES .OVEMBER 33"LACKMUN -ULTIPLE4ARGET4RACKINGWITH2ADAR!PPLICATIONS $EDHAM -!!RTECH(OUSE PPn n $!&ULGHUMAND$"ARRIE h2ADARBECOMESAWEAPON v!VIATION7EEK3PACE4ECHNOLOGY PPn 3EPTEMBER )MAGE#OURTESY2AYTHEON#OMPANY CLEAREDFORPUBLICRELEASE 302 -3TREETLY 2ADARAND%LECTRONIC7ARFARE3YSTEMS n TH%D #OULSDON 3URREY 5+ *ANES)NFORMATION'ROUP PPn 2 .ITZBERG 2ADAR 3IGNAL 0ROCESSING AND !DAPTIVE 3YSTEMS .ORWOOD -!!RTECH (OUSE PPn n n 7 + 3AUNDERS h#7 AND &7 RADARv & - 3TAUDAHER h!IRBORNE -4)v 7 ( ,ONG $(-OONEY AND7!3KILLMAN h0ULSEDOPPLERRADARv2*3ERAFIN h-ETEOROLOGICALRADAR v 2ADAR(ANDBOOK ND%D -3KOLNIKED .EW9ORK-C'RAW(ILL PPn n n n 0 ,ACOMME * 0 (ARDANGE * # -ARCHAIS AND % .ORMANT !IR AND 3PACEBORNE 2ADAR 3YSTEMS !N )NTRODUCTION .ORWICH .9 7ILLIAM !NDREW 0UBLISHING PP n n n *$AVIS h3UNINTROSEIGHTnCOREPROCESSOR v%LECTRONIC.EWS 2EED%LSEVIER .OVEMBER !LTERA#ORPORATION h3TRATIX))&0'!S v.OVEMBER HTTPWWWALTERACOM $!&ULGHUM h$EEPLOOK v!VIATION7EEKAND3PACE4ECHNOLOGY *ANUARY $!&ULGHUM h&UTURERADAR v!VIATION7EEKAND3PACE4ECHNOLOGY /CTOBER -0ECKAND'7'OODMAN *R h!GILERADARBEAMS v#)32*OURNAL PPn -AY h2AYTHEONS!0' !%3!RADARFORTHE&! 3UPER(ORNETSETSANEWSTANDARDASITDELIVERS MULTIPLE*$!-SSIMULTANEOUSLYONTARGET v-ARKET7ATCH $ECEMBER -3ELINGER h53.AVYEYES@GROWTHPLANFOR3UPER(ORNETS!%3!RADAR v!EROSPACE$AILY AND$EFENSE2EPORT $ECEMBER 2 % (UDSON 3 / !+3 0 0 "OGDANOVIC AND $ $ ,YNCH h-ETHOD AND 3YSTEM FOR 2EDUCING0HASE%RRORINA0HASED!RRAY2ADAR"EAM3TEERING#ONTROLLER 530ATENT 2(ILL $+RAMER AND2-ANKINO h4ARGET$ETECTION3YSTEMINA2ADAR3YSTEM%MPLOYING -AINAND'UARD#HANNEL!NTENNAS v530ATENT 2 -ONZINGO AND4 -ILLER )NTRODUCTION TO!DAPTIVE!RRAYS .EW9ORK *OHN7ILEY 3ONS PPn 2+LEMM h!DAPTIVEAIRBORNE-4)!NAUXILIARYCHANNELAPPROACH v)%%0ROCEEDINGS VOL PART& NO P 3 !KS $ $ ,YNCH * / 0EARSON AND 4 +ENNEDY h!DVANCED MODERN RADAR v %VOLVING 4ECHNOLOGY)NSTITUTE3HORT#OURSE.OTES .OVEMBER 7ORK PERFORMED BY , 'RIFFITHS AND #4SENG h!DAPTIVE ARRAYRADAR PROJECT REVIEW v (UGHES !IRCRAFT)2$ PERFORMEDAT53# *ULY # +O h! FAST ADAPTIVE NULL STEERING ALGORITHM BASED ON OUTPUT POWER MEASUREMENTS v )%%% 4RANSACTIONSON!EROSPACEAND%LECTRONIC3YSTEMS VOL NO PPn *ULY
x°{{
2!$!2(!.$"//+
(7ANG (0ARK AND-7ICKS h2ECENTRESULTSINSPACE TIMEPROCESSING vIN)%%%.ATIONAL 2ADAR#ONFERENCE PPn *7ARD h3PACE TIMEADAPTIVEPROCESSINGFORAIRBORNERADAR v-)4,INCOLN,ABORATORY2EPORT APPROVEDFORUNLIMITEDPUBLICDISTRIBUTION .-'REENBLATT *66IRTS AND-&0HILLIPS h& %3!MEDIUM02&DESIGN v(UGHES!IRCRAFT )$#.O *ANUARY UNCLASSIFIEDREPORT $ 3CHLEHER h,OW PROBABILITY OF INTERCEPT RADARv IN )%%% )NTERNATIONAL 2ADAR #ONFERENCE P %#ARLSON h,OWPROBABILITYOFINTERCEPTTECHNIQUESANDIMPLEMENTATIONS vIN)%%%.ATIONAL 2ADAR#ONFERENCE P 'ROGER h/,0) ,0)RADARDESIGNWITHHIGH!2-RESISTANCE vIN$'/.TH2ADAR#ONFERENCE P $ ,YNCH h2EAL TIME RADAR DATA PROCESSING v PRESENTED AT )%%% 3OLID 3TATE #IRCUITS #OMMITTEE $IGITAL&ILTERING-EETING .EW9ORK /CTOBER $#RAIGAND-(ERSHBERGER h&,!-2OPERATORTARGET/!0RECOGNITIONSTUDY v(UGHES!IRCRAFT 2EPORT.O0 *ANUARY $ECLASSIFIED $#3CHLEHER %LECTRONIC7ARFAREINTHE)NFORMATION!GE .ORWOOD -!!RTECH(OUSE PPn n 3 (OVANESSIAN )NTRODUCTION TO 3YNTHETIC !RRAY AND )MAGING 2ADARS $EDHAM -! !RTECH (OUSE #HAPTER * #URLANDER AND 2 -C$ONOUGH 3YNTHETIC!PERTURE 2ADAR 3YSTEMS AND 3IGNAL 0ROCESSING .EW9ORK7ILEY3ONS PPn n *+OVALY 3YNTHETIC!PERTURE2ADAR $EDHAM -!!RTECH(OUSE PPn n n ",EWIS &2+RETSCHMER AND773HELTON !SPECTSOF2ADAR3IGNAL0ROCESSING $EDHAM -!!RTECH(OUSE PPn -2ADANT $,EWIS AND3)GLEHART h2ADARSENSORS v5#,!3HORT#OURSE.OTES *ULY $,YNCH */0EARSON AND%3HAMASH h0RINCIPLESOF-ODERNRADAR v%VOLVING4ECHNOLOGY )NSTITUTE3HORT#OURSE.OTES *UNE * &RICHEL AND & #OREY h!.!0' -ULTIMODE 2ADAR 0ROGRAM v IN )%%% .!%#/. P 2.EVIN h!.!0' MULTIMODERADARPERFORMANCEEVALUATION vIN)%%%.!%#/. P $ ,YNCH h3,/3( FILTER PROCESSING v PRESENTED AT )%%%!5 3YMPOSIUM ON $IGITAL &ILTERS (ARRIMAN .9 *ANUARY 4REFFEISENETAL h/BSTACLE#LEARANCE3YSTEMFOR!IRCRAFT v530ATENT )NTERNATIONAL $EFENSE 2EVIEW !IR $EFENSE 3YSTEMS 'ENEVA 3WITZERLAND )NTERAVIA PPn # +OPP h-ISSILES IN THE !SIA 0ACIFIC v $EFENCE 4ODAY HTTPWWWAUSAIRPOWERNET $4 -ISSILE 3URVEY -AY PDF '3TIMSON )NTRODUCTIONTO!IRBORNE2ADAR ND%D -ENDHAM .*3CI4ECH0UBLISHING PPn n n *#LARKE h!IRBORNERADARv0ARTS -ICROWAVE*OURNAL PANDP *ANUARYAND &EBRUARY %!RONOFF AND $ +RAMER h2ECENT DEVELOPMENTS IN AIRBORNE -4) RADARS v (UGHES!IRCRAFT 2EPORT PRESENTEDAT)%%%7ESCON $+RAMERAND',AVAS h2ADAR3YSTEMWITH4ARGET)LLUMINATIONBY$IFFERENT7AVEFORMS v53 0ATENT $-OONEY h0OST $ETECTION34#INA-EDIUM02&0ULSE$OPPLER2ADAR v530ATENT % &ROST AND , ,AWRENCE h-EDIUM 02& 0ULSE $OPPLER 2ADAR 0ROCESSOR FOR $ENSE 4ARGET %NVIRONMENTS v530ATENT 7 ,ONG AND + (ARRIGER h-EDIUM 02& FOR THE !.!0' RADAR v IN )%%% 0ROCEEDINGS VOL NO P
-5,4)&5.#4)/.!,2!$!23934%-3&/2&)'(4%2!)2#2!&4
x°{x
%!RONOFFAND.'REENBLATT h-EDIUM02&RADARDESIGNANDPERFORMANCE v(UGHES!IRCRAFT 2EPORT PRESENTEDAT)%%%.ATIONAL2ADAR#ONFERENCE ( %RHARDT h-02& PROCESSING FUNCTIONS ISSUE v (UGHES !IRCRAFT )$# /CTOBER UNCLASSIFIEDREPORT * +IRK h4ARGET $ETECTION 3YSTEM IN A -EDIUM 02& 0ULSE $OPPLER 3EARCH4RACK 2ADAR 2ECEIVER v530ATENT + 'ERLACH h3ECOND TIME AROUND RADAR RETURN SUPPRESSION USING 02) MODULATION v )%%% 4RANSACTIONS ON !EROSPACE AND %LECTRONIC 3YSTEMS VOL !%3 NO PP n .OVEMBER , $URFEE AND 7 $ULL h-02& )NTERPULSE 0HASE -ODULATION FOR -AXIMIZING $OPPLER #LEAR 3PACE v530ATENT 3(OVANESSIAN h!NALGORITHMFORCALCULATIONOFRANGEINMULTIPLE02&RADAR v)%%%4RANSACTIONS ON!EROSPACE%LECTRONIC3YSTEMS VOL!%3 NO -ARCH PPn '-ORRIS !IRBORNE0ULSE$OPPLER2ADAR .ORWOOD -!!RTECH(OUSE 23CHLOLTER h$IGITALREALTIME3!2PROCESSORFOR#8BANDAPPLICATIONS vIN)'!233 :URICH VOL P 2+LEMM h!IRBORNE-4)VIADIGITALFILTERING vIN)%%0ROCEEDINGS VOL PART& NO P 4ECHNOLOGY3ERVICE#ORP h!DAPTARSPACE TIMEPROCESSINGINAIRBORNERADARS v43# 0$ &EBRUARY UNCLASSIFIEDREPORT $ ,YNCH h3IGNAL PROCESSOR FOR SYNTHETIC APERTURE RADAR v PRESENTED AT 30)% 4ECHNICAL 3YMPOSIUM%AST PAPERNO *(ARMON h4RACKBEFOREDETECTPERFORMANCEFORAHIGH02&SEARCHMODE vIN)%%%.ATIONAL 2ADAR#ONFERENCE PPn *2'UERCI 3PACE 4IME!DAPTIVE0ROCESSINGFOR2ADAR .ORWOOD -!!RTECH(OUSE PP n n 0 4AIT )NTRODUCTION TO 2ADAR 4ARGET 2ECOGNITION "ODMIN #ORNWALL 5+ )%% PPn n 00EEBLES 2ADAR0RINCIPLES .EW9ORK*OHN7ILEY3ONS PPn n % %ICHBLATT 4EST AND %VALUATION OF THE 4ACTICAL -ISSILE 7ASHINGTON $# !)!! PPn n 2 -ACFADZEAN 3URFACE "ASED !IR $EFENSE 3YSTEM !NALYSIS SELF PUBLISHED PPn -2OBINAND-0OULIN $IGITAL4ELEVISION&UNDAMENTALS ND%D .EW9ORK-C'RAW (ILL PPn 70RATT $IGITAL)MAGE0ROCESSING .EW9ORK7ILEY3ONS PPn -3IMON */MURA 23CHOLTZ AND",EVITT h,OWPROBABILITYOFINTERCEPTCOMMUNICATIONS v #HAPTER IN 3PREAD 3PECTRUM #OMMUNICATIONS (ANDBOOK .EW 9ORK -C'RAW (ILL PPn 7'ABRIEL h.ONLINEARSPECTRALANALYSISANDADAPTIVEARRAYSUPERRESOLUTIONTECHNIQUES v.2, 2EPORT APPROVEDFORUNLIMITEDPUBLICDISTRIBUTION *!SENSTORFER 4#OX AND$7ILKSCH h4ACTICALDATALINKSYSTEMSANDTHE!USTRALIANDEFENSE FORCE !$& TECHNOLOGY DEVELOPMENTS AND INTEROPERABILITY ISSUES v $EFENSE 3CIENCE AND 4ECHNOLOGY/RGANISATION2EPORT $34/ 42 APPROVEDFORPUBLICRELEASE # +OPP h4HE PROPERTIES OF HIGH CAPACITY MICROWAVE AIRBORNE AD HOC NETWORKS v 0H$ DISSERTATION -ONASH5NIVERSITY -ELBOURNE !USTRALIA /CTOBER * +ATZMAN $EFENCE )NDUSTRY $AILY HTTPWWWDEFENSEINDUSTRYDAILYCOMELEC TRICKS TURNING AESA RADARS INTO BROADBAND COMLINKSINDEXPHP #.AKOS 3"AKER **$OUGLASS AND!23ARTI h(IGHSPEEDDATALINK v!USTRALIA0ATENT0#4 !5 7/ $34/4ACTICAL3URVEILLANCE3YSTEMS$IVISION 3ALISBURY !USTRALIA .OVEMBER $ ! &ULGHUM h3EE IT JAM IT KILL ITv !VIATION 7EEK 3PACE 4ECHNOLOGY PP -AY
x°{È
2!$!2(!.$"//+
$#3CHLEHER )NTRODUCTIONTO%LECTRONIC7ARFARE $EDHAM -!!RTECH(OUSE PPn n #ASE *RETAL h2ADARFOR!UTOMATIC4ERRAIN!VOIDANCE v530ATENT ( , 7ARUSZEWSKI *R h!PPARATUS AND -ETHOD FOR AN !IRCRAFT .AVIGATION 3YSTEM (AVING )MPROVED -ISSION -ANAGEMENT AND 3URVIVABILITY #APABILITIES v 53 0ATENT "ARNEYETAL h!PPARATUSAND-ETHODFOR!DJUSTING3ET#LEARANCE!LTITUDEINA4ERRAIN&OLLOWING 2ADAR v530ATENT 2*AWOROWSKI h/UTLOOKSPECIFICATIONSMILITARYAIRCRAFT v!VIATION7EEKAND3PACE4ECHNOLOGY PPn *ANUARY &(ARRISAND$,YNCH h$IGITALSIGNALPROCESSINGANDDIGITALFILTERINGWITHAPPLICATIONS v%VOLVING 4ECHNOLOGY)NSTITUTE3HORT#OURSE.OTES n PP n &EBRUARY 2&ABRIZIO h!HIGHSPEEDDIGITALPROCESSORFORREALTIME3!2IMAGING vIN)'!233 !NN !RBOR-) VOL P 4#ULLENAND#&OSSEDS *ANES,AND "ASED!IR$EFENCEn #OULSDON 3URREY 5+ *ANES)NFORMATION'ROUP PPn 2+LEMM h.EWAIRBORNE-4)TECHNIQUES vIN)NTERNATIONAL2ADAR#ONFERENCE,ONDON P h0AVE MOVER 4!7$3 DESIGN REQUIREMENTS v (UGHES!IRCRAFT 3PECIFICATION .OVEMBER UNCLASSIFIED UNLIMITEDDISTRIBUTION * 0EARSON h&,!-2 SIGNAL TO NOISE EXPERIMENTS v (UGHES !IRCRAFT 2EPORT .O 0 $ECEMBER DECLASSIFIED %/"RIGHAM 4HE&AST&OURIER4RANSFORM .EW9ORK0RENTICE(ALL PPn $,YNCH ETAL h,0)2PHASEREVIEW v(UGHES!IRCRAFT2EPORT UNCLASSIFIEDREPORT */0EARSON h-OVINGTARGETEXPERIMENTANDANALYSIS v(UGHES!IRCRAFT2EPORT.O0 PPn n $ECEMBER DECLASSIFIED +2OGERS h%NGINEERSUNLOCKMYSTERYOFCAR DOORDEVICEFAILURES v,AS6EGAS2EVIEW*OURNAL !UGUST P"
#HAPTER
,>`>ÀÊ,iViÛiÀÃ
V
>iÊ °Ê9i>Ã 2AYTHEON#OMPANY
È°£Ê / Ê " 1,/" ÊÊ "ÊÊ, ,Ê,
6 , 4HE FUNCTION OF A RADAR RECEIVER IS TO AMPLIFY FILTER DOWNCONVERT AND DIGITIZE THE ECHOESOFTHERADARTRANSMISSIONINAMANNERTHATWILLPROVIDETHEMAXIMUMDISCRIMI NATIONBETWEENDESIREDECHOSIGNALSANDUNDESIREDINTERFERENCE4HEINTERFERENCECOM PRISESNOTONLYTHESELFNOISEGENERATEDINTHERADARRECEIVERBUTALSOTHEENERGYRECEIVED FROMGALACTICSOURCES NEIGHBORINGRADARSANDCOMMUNICATIONEQUIPMENT ANDPOSSIBLY JAMMERS4HEPORTIONOFTHERADARSOWNRADIATEDENERGYTHATISSCATTEREDBYUNDESIRED TARGETSSUCHASRAIN SNOW BIRDS INSECTS ATMOSPHERICPERTURBATIONS ANDCHAFF MAY ALSOBECLASSIFIEDASINTERFERENCEANDISCOMMONLYCATEGORIZEDASCLUTTER7HEREAIR BORNERADARSAREUSEDFORALTIMETERSORMAPPING OTHERAIRCRAFTAREUNDESIREDTARGETS AND THEGROUNDISTHEDESIREDTARGET)NTHECASEOFWEATHERRADARS GROUND BUILDINGS AND AIRCRAFTARECLUTTER ANDRAINORSNOWISTHEDESIREDTARGET-ORECOMMONLY RADARSARE INTENDEDFORDETECTIONOFAIRCRAFT MISSILES SHIPS SURFACEVEHICLES ORPERSONNEL ANDTHE REFLECTIONFROMWEATHER SEA ORGROUNDISCLASSIFIEDASCLUTTERINTERFERENCE !LTHOUGHTHEBOUNDARIESOFTHERADARRECEIVERARESOMEWHATARBITRARY THISCHAPTER WILLCONSIDERTHOSEELEMENTSIDENTIFIEDIN&IGUREASTHERECEIVER4HERADAREXCITER GENERATESTHETRANSMITWAVEFORMSASWELLASLOCALOSCILLATOR,/ CLOCK ANDTIMING SIGNALS 3INCE THIS FUNCTION IS USUALLY TIGHTLY COUPLED TO A RADAR RECEIVER IT IS ALSO SHOWNIN&IGUREANDWILLBEDISCUSSEDINTHISCHAPTER4HEPURPOSEOF&IGUREIS TOILLUSTRATETHEFUNCTIONSTYPICALOFAMODERNRADARRECEIVERANDEXCITER 6IRTUALLY ALL RADAR RECEIVERS OPERATE ON THE SUPERHETERODYNE PRINCIPLE SHOWN IN &IGURE 4HROUGH THIS ARCHITECTURE THE RECEIVER FILTERS THE SIGNAL TO SEPARATE DESIRED TARGET SIGNALS FROM UNWANTED INTERFERENCE !FTER MODEST 2& AMPLIFICA TION THESIGNALISSHIFTEDTOANINTERMEDIATEFREQUENCY)& BYMIXINGWITHALOCAL OSCILLATOR ,/ FREQUENCY -ORE THAN ONE CONVERSION STAGE MAY BE NECESSARY TO REACHTHEFINAL)&WITHOUTENCOUNTERINGSERIOUSIMAGE ORSPURIOUS FREQUENCYPROB LEMSINTHEMIXINGPROCESS4HESUPERHETERODYNERECEIVERVARIESTHE,/FREQUENCYTO FOLLOWANYDESIREDTUNINGVARIATIONOFTHETRANSMITTERWITHOUTDISTURBINGTHEFILTERING AT)&4HISSIMPLIFIESTHEFILTERINGOPERATIONASTHESIGNALSOCCUPYAWIDERPERCENTAGE
4HISCHAPTERINCORPORATESMATERIALWRITTENBY*OHN74AYLOR *RFORTHEFIRSTANDSECONDEDITIONSANDUPDATED BY-ICHAEL9EOMANSFORTHISEDITION
È°£
È°Ó
2!$!2(!.$"//+
BANDWIDTHATTHE)&FREQUENCY4HESEADVANTAGESHAVEPROVENTOBESOSIGNIFICANT THATCOMPETITIVEFORMSOFRECEIVERSHAVEVIRTUALLYDISAPPEARED )N CONVENTIONAL ANTENNA SYSTEMS THE RECEIVER INPUT SIGNAL IS DERIVED FROM THE DUPLEXER WHICH PERMITS A SINGLE ANTENNA TO BE SHARED BETWEEN TRANSMITTER AND RECEIVER)NACTIVEARRAYSYSTEMS THERECEIVERINPUTISDERIVEDFROMTHERECEIVEBEAM FORMINGNETWORK!CTIVEARRAYANTENNASINCLUDELOW NOISEAMPLIFIERSPRIORTOFORMING THERECEIVEBEAMSALTHOUGHTHESEAREGENERALLYCONSIDEREDTOBEANTENNARATHERTHAN RECEIVERCOMPONENTS THEYWILLBEDISCUSSEDINTHISCHAPTER ($ !#'& #"'%#
) &$'&#'& ! ($ !! $# & & %
&&!'&"$
"$&& '%
"$&& '%
"$&& '%
"$&& '%
&&!'&"$
$& & *!& % +$
! '%
%" & '#%
&$
# "%'#% #
%' ' #")%& #"
"' &"$
&&" & ! $"%%"$ &)'52% 'ENERALCONFIGURATIONOFARADARRECEIVER
# &
# & "& ' ) '+ !#"'%# ('#!' "#"'%# ' # & '#% # %"'# & '#% " # '# ' #")%'%
2!$!22%#%)6%23
È°Î
4HE BLOCK DIAGRAM SHOWN IN &IGURE INCLUDES SENSITIVITY TIME CONTROL 34# ATTENUATION AT THE 2& INPUT !LTERNATIVELY ADJUSTABLE 2& ATTENUATION MAY BE USED %ITHER FORM PROVIDES INCREASED DYNAMIC RANGE ABOVE THAT PROVIDED BY THE ANALOG TO DIGITAL!$ CONVERTERS2&ATTENUATIONISDESCRIBEDINMOREDETAILIN3ECTION 4HE34#ATTENUATORISFOLLOWEDBYAN2&LIFIER OFTENREFERREDTOASALOW NOISE AMPLIFIER,.! 4HISAMPLIFIERPROVIDESSUFFICIENTGAINWITHALOWNOISEFIGURETO MINIMIZETHESUBSEQUENTDEGRADATIONOFTHEOVERALLRADARNOISEFIGUREBYSUBSEQUENT COMPONENTS)FSUFFICIENTGAINISPROVIDEDINTHEANTENNAPRIORTOTHERECEIVER ITMAY BEPOSSIBLETOELIMINATETHISGAINSTAGE4HE2&FILTERPROVIDESREJECTIONOFOUT OF BAND INTERFERENCE INCLUDINGREJECTIONATTHE2&IMAGEFREQUENCY!FTERDOWNCONVERSIONTO )& ABANDPASSFILTERPROVIDESREJECTIONOFUNWANTEDSIGNALSANDSETSTHERECEIVERANA LOG PROCESSINGBANDWIDTH!DDITIONALGAINISPROVIDEDAT)&TOOVERCOMELOSSESAND RAISETHESIGNALLEVELREQUIREDFORSUBSEQUENTPROCESSINGANDTOSETTHECORRECTSIGNAL LEVELINTOTHE!$CONVERTERS!N)&LIMITERPROVIDESGRACEFULLIMITINGOFLARGESIGNALS THATWOULDOTHERWISEOVERLOADTHE!$CONVERTERS 4HETWODOMINANTMETHODSOFDIGITIZATION )&SAMPLINGANDANALOG)1DEMODULA TIONWITHBASEBAND!$CONVERSION AREINCLUDEDFORILLUSTRATIONIN&IGURE THOUGH INGENERAL RECEIVERSWILLNOTINCLUDEBOTHTECHNIQUES0RIORTOTHEAVAILABILITYOFAFFORD ABLEDIGITALSIGNALPROCESSING ANUMBEROFFUNCTIONS SUCHASMONOPULSECOMPARISON CURRENTLYPERFORMEDINTHEDIGITALDOMAIN WEREPERFORMEDUSINGANALOGPROCESSING WITHINTHERECEIVER2EADERSINTERESTEDINTHEDETAILSOFTHESEANALOGPROCESSINGTECH NIQUESWILLFINDDETAILSINTHEFIRSTANDSECONDEDITIONSOFTHISHANDBOOK !LLBUTTHESIMPLESTOFRADARSREQUIREMORETHANONERECEIVERCHANNEL&IGURE SHOWSASINGLERECEIVERCHANNELTHATMAYBEREPLICATEDANYNUMBEROFTIMESDEPENDING ONTHERADARSYSTEMREQUIREMENTS-ONOPULSERADARSTYPICALLYINCLUDETHREERECEIVER CHANNELS SUM DELTAAZIMUTH ANDDELTAELEVATIONCHANNELS USEDTOPROVIDEIMPROVED ANGLEACCURACY!DDITIONALLY MANYMILITARYRADARSYSTEMSINCLUDEASIDELOBEBLANKER ORSEVERALSIDELOBECANCELERCHANNELSTOCOMBATJAMMING3INCETHEADVENTOFDIGITAL BEAMFORMINGRADARSYSTEMS THENUMBEROFRECEIVERCHANNELSREQUIREDHASINCREASED DRAMATICALLY WITH SOME SYSTEMS NOW REQUIRING HUNDREDS OF RECEIVER CHANNELS )N THESEMULTICHANNELRECEIVERSYSTEMS CLOSEMATCHINGANDTRACKINGOFGAINANDPHASEIS REQUIRED2ECEIVERCHANNELTRACKINGANDEQUALIZATIONAREDISCUSSEDIN3ECTION 4HESTABLELOCALOSCILLATOR34!,/ BLOCKPROVIDESTHELOCALOSCILLATORFREQUENCIES FORDOWNCONVERSIONINTHERECEIVERANDUPCONVERSIONINTHEEXCITER&ORTRUECOHERENT OPERATION THE34!,/ISLOCKEDTOALOWFREQUENCYREFERENCE SHOWNBYTHEREFERENCE OSCILLATORIN&IGURETHATISUSEDASTHEBASISFORALLCLOCKSANDOSCILLATORSSUCHASTHE COHERENTLOCALOSCILLATOR#/(/ WITHINTHERECEIVERANDEXCITER4HECLOCKGENERATOR PROVIDESCLOCKSTOTHE!$CONVERTERSANDTHEDIRECTDIGITALSYNTHESIZERANDPROVIDES THEBASISFORTHESIGNALSTHATDEFINETHERADARTRANSMITANDRECEIVEINTERVALS 4HEDIRECTDIGITALSYNTHESIZERIN&IGUREISUSEDTOGENERATETHETRANSMITWAVE FORMSATAN)&FREQUENCYPRIORTOUPCONVERSIONTOTHE2&OUTPUTFREQUENCY&ILTERING INTHEEXCITERISREQUIREDTOREJECTALIASEDSIGNALSFROMTHEDIRECTDIGITALSYNTHESIZERAND UNWANTEDMIXERPRODUCTS2&GAINISTYPICALLYREQUIREDTOPROVIDEASUFFICIENTDRIVE LEVELTOTHETRANSMITTERORPHASEDARRAYANTENNA !LMOSTALLMODERNRADARSYSTEMSUSEDIGITALSIGNALPROCESSINGTOPERFORMAVARIETY OFFUNCTIONS INCLUDINGPULSECOMPRESSIONANDTHEDISCRIMINATIONOFDESIREDTARGETSFROM INTERFERENCEONTHEBASISOFVELOCITYORTHECHANGEINPHASEFROMONEPULSETOTHENEXT 0REVIOUSLY PULSECOMPRESSIONWASPERFORMEDUSINGANALOGPROCESSINGWITHDISPERSIVE DELAY LINES TYPICALLY SURFACE ACOUSTIC WAVE 3!7 DEVICES!NALOG PULSE COMPRES SIONHASLARGELYBEENREPLACEDBYPULSECOMPRESSIONUSINGDIGITALSIGNALPROCESSING
È°{
2!$!2(!.$"//+
)NTHECASEOFVERYWIDEBANDWAVEFORMS ANALOGSTRETCHPROCESSINGSEE3ECTION MAY BEUSEDTOREDUCETHESIGNALBANDWIDTHBEFORESUBSEQUENTDIGITALSIGNALPROCESSING 4HERECEIVERDISCUSSEDHEREINFOCUSESONTHOSEFUNCTIONSTHATPROVIDEANALOGPRO CESSINGANDDIGITIZATIONOFTHEINDIVIDUALPULSESIGNALSWITHTHEMINIMUMOFDISTORTION ENABLING SUBSEQUENT DIGITAL SIGNAL PROCESSING TO MAXIMIZE THE PERFORMANCE OF THE RADAR4HEDIGITALSIGNALPROCESSINGFUNCTIONISNOTNORMALLYCONSIDEREDTOBEPARTOF THERECEIVER
È°ÓÊ "- Ê Ê 9 , Ê
" - ,/" 2ECEIVERSGENERATEINTERNALNOISETHATMASKSWEAKSIGNALSBEINGRECEIVEDFROMTHERADAR TRANSMISSIONS4HISNOISECONTRIBUTION WHICHCANBEEXPRESSEDASEITHERANOISETEM PERATUREORANOISEFIGURE ISONEOFTHEFUNDAMENTALLIMITATIONSONTHERADARRANGE 4HE NOISE TEMPERATURE OR NOISE FIGURE OF THE RADAR RECEIVER HAS BEEN REDUCED TOTHEPOINTTHATITNOLONGERREPRESENTSADOMINANTINFLUENCEINCHOOSINGBETWEEN AVAILABLEALTERNATIVES)TISAPARADOXTHATANOISEPARAMETERISUSUALLYTHEFIRSTCHAR ACTERISTIC SPECIFIED FOR A RADAR RECEIVER YET FEW RADARS EMPLOY THE LOWEST NOISE RECEIVER AVAILABLE BECAUSE SUCH A CHOICE REPRESENTS TOO GREAT A SACRIFICE IN OTHER PERFORMANCEPARAMETERS #OSTISRARELYACONSIDERATIONINREJECTINGALOWER NOISEALTERNATIVE!REDUCTIONIN REQUIREMENTSFORANTENNAGAINORTRANSMITTERPOWERINVARIABLYPRODUCESCOSTSAVINGS FAR IN EXCESS OF ANY ADDED COST OF A LOWER NOISE RECEIVER /THER VITAL PERFORMANCE CHARACTERISTICSTHATGENERALLYDICTATETHECHOICEOFRECEIVERFRONTENDINCLUDE L
L
L
$YNAMICRANGEANDSUSCEPTIBILITYTOOVERLOAD )NSTANTANEOUSBANDWIDTHANDTUNINGRANGE 0HASEANDAMPLITUDESTABILITY
!DIRECTCOMPROMISEMUSTBEMADEBETWEENTHENOISEFIGUREANDTHEDYNAMICRANGE OFARECEIVER4HEINTRODUCTIONOFAN2&LIFIERINFRONTOFTHEMIXERNECESSARILY INVOLVESRAISINGTHESYSTEMNOISELEVELATTHEMIXERTOMAKETHENOISECONTRIBUTIONOF THEMIXERITSELFINSIGNIFICANT%VENIFTHE2&LIFIERITSELFHASMORETHANADEQUATE DYNAMICRANGE THEMIXERDYNAMICRANGEHASBEENCOMPROMISED ASINDICATEDBELOW
2ATIOOFFRONT ENDNOISETOMIXERNOISE 3ACRIFICEINMIXERDYNAMICRANGE $EGRADATIONOFSYSTEMNOISETEMPERATUREDUE TOMIXERNOISE
%XAMPLE
%XAMPLE
%XAMPLE
D" D" D"
D" D" D"
D" D" D"
4HESAMECONSIDERATIONSAPPLYTOTHESETTINGOFTHENOISELEVELATTHEINPUTTOTHE !$CONVERTERS4RADITIONALLY THENOISECONTRIBUTIONOFTHE!$CONVERTERWASCON SIDEREDBYTHESYSTEMENGINEERSASASEPARATECONTRIBUTIONTOTHEOVERALLRADARSYSTEM NOISE DISTINCTFROMRECEIVERNOISE ANDWASACCOUNTEDFORATTHESYSTEMLEVEL4ODAY IT HASBECOMECOMMONTOINCLUDETHE!$CONVERTERNOISEASPARTOFTHEOVERALLRECEIVER NOISE#ONSEQUENTLY ITISIMPORTANTTOUNDERSTANDWHETHERORNOTTHECONTRIBUTIONOF THE!$CONVERTERISINCLUDEDINTHESPECIFICATIONFORTHENOISEFIGUREOFARECEIVER
2!$!22%#%)6%23
È°x
)N ACTIVE ARRAY ANTENNAS AND MANY CONVENTIONAL ANTENNAS LOW NOISE AMPLIFIERS ,.!S ESTABLISHTHESYSTEMNOISEFLOORPRIORTOTHERECEIVERINPUT4HENOISEFROMTHE ANTENNAISUSUALLYSETWELLABOVETHERECEIVERNOISEFLOORSUCHTHATTHERECEIVERHAS ONLYASMALLIMPACTONOVERALLSYSTEMNOISE!GAIN THETRADE OFFMUSTBEPERFORMED BETWEENSYSTEMDYNAMICRANGEANDNOISEFIGURE $EFINITIONS $YNAMIC 2ANGE REPRESENTS THE RANGE OF SIGNAL STRENGTH OVER WHICH THE RECEIVER WILL PERFORM AS EXPECTED )T REQUIRES THE SPECIFICATION OF A MINIMUMLEVEL TYPICALLYTHENOISEFLOOR THEMAXIMUMLEVELTHATCANBEHANDLED WITHSOMEALLOWABLEDEVIATIONFROMTHEIDEALRESPONSE ANDTHETYPEOFSIGNALTO BE HANDLED4HESE PARAMETERS ARE DEFINED THROUGH A VARIETY OF CHARACTERISTICS AS DESCRIBEDBELOW -ODERN RADARS SYSTEMS INCREASINGLY RELY SOLELY ON LINEAR RECEIVER CHANNELS FOL LOWED BY DIGITAL SIGNAL PROCESSING PROVIDING BOTH INCREASED FLEXIBILITY AND NEAR IDEALSIGNAL DETECTIONCHARACTERISTICS0REVIOUSLY AVARIETYOFLIMITINGORLOGARITHMIC RECEIVERAPPROACHESWEREUSEDTOPERFORMVARIOUSSIGNAL PROCESSINGFUNCTIONS4HESE RECEIVERSMUSTDEFINEANALLOWABLEERRORINTHEIROUTPUTSRELATIVETOTHEIRIDEALNONLIN EARRESPONSE 2ECEIVERSTHATINCLUDESOMEFORMOFGAINCONTROLMUSTDISTINGUISHBETWEENINSTAN TANEOUS DYNAMIC RANGE AND THE TOTAL DYNAMIC RANGE THAT IS ACHIEVED AS A RESULT OF PROGRAMMEDGAINVARIATION 2ECEIVER )NPUT .OISE ,EVEL "ECAUSE MANY RADAR SYSTEMS INCLUDE LOW NOISE AMPLIFIERSPRIORTOTHEINPUTOFTHERECEIVER ITISIMPORTANTTOUNDERSTANDANDSPECIFY THENOISELEVELATTHERECEIVERINPUT4HISNOISELEVELISSETBYTHEANTENNANOISETEM PERATUREANDITSTOTALEFFECTIVENOISEGAINORLOSS4HENOISELEVELCANBESPECIFIEDEITHER ASANRMSPOWERINASPECIFIEDBANDWIDTHORASANOISEPOWERSPECTRALDENSITY 3YSTEM.OISE 4HESYSTEMNOISELEVELISTHECOMBINEDANTENNAANDRECEIVERNOISE 4YPICALLY THERECEIVERINPUTNOISEWILLEXCEEDTHATOFTHENOISEDUETOTHERECEIVER ITSELF SOTHATTHERECEIVERHASONLYASMALLIMPACTONTHESYSTEMNOISETEMPERATUREOR NOISEFIGURE4HUS WHENDEFININGDYNAMIC RANGEPARAMETERS SUCHASSIGNAL TO NOISE RATIO ITISIMPORTANTTOSPECIFYWHETHERTHENOISELEVELBEINGREFERENCEDISTHERECEIVER NOISEORTOTALSYSTEMNOISE -INIMUM 3IGNAL OF )NTEREST -INIMUM SIGNAL DEFINITIONS SUCH AS MINIMUM DETECTABLE SIGNAL OR MINIMUM DISCERNABLE SIGNAL HAVE BEEN USED IN THE PAST HOW EVER THESEDEFINITIONSHAVEBECOMELESSCOMMONDUETOTHEEXTENSIVEUSEOFDIGITAL SIGNAL PROCESSINGTECHNIQUES$IGITALSIGNALPROCESSINGOFTHERECEIVEROUTPUTALLOWS THEDETECTIONOFSIGNALSWELLBELOWTHERECEIVERNOISEFLOORANDTHEMINIMUMDETECT ABLELEVELDEPENDSONTHENATUREOFTHEPROCESSINGPERFORMED 3IGNAL TO .OISE2ATIO3.2 3.2ISTHERATIOOFTHESIGNALLEVELTOTHATOFTHE NOISE3.2ISTYPICALLYEXPRESSEDINDECIBELSD" 4HEMAXIMUMRECEIVER3.2IS SETBYTHENOISECONTRIBUTIONANDMAXIMUMSIGNALCAPABILITYOFEVERYCOMPONENT INTHECHAINHOWEVER SINCETHELIMITINGTECHNOLOGYISOFTENTHE!NALOG TO $IGITAL !$ CONVERTER THEPRECEDINGCOMPONENTSANDGAINSTRUCTUREAREOFTENCHOSENSUCH THATTHEMAXIMUM3.2ISDRIVENBYTHEPERFORMANCEOFTHE!$CONVERTER-ORE DETAILSOFTHERELATIONSHIPBETWEEN!$CONVERTERANDRECEIVER3.2AREINCLUDEDIN 3ECTIONSAND
È°È
2!$!2(!.$"//+
3PURIOUS&REE$YNAMIC2ANGE3&$2 3&$2ISTHERATIOOFTHEMAXIMUMSIG NALLEVELTOTHATOFLARGESTSPURIOUSSIGNALCREATEDWITHINTHERECEIVER3&$2ISTYPI CALLYEXPRESSEDINDECIBELSD" 4HISPARAMETERISDETERMINEDBYAVARIETYOFFACTORS INCLUDING THE MIXER INTERMODULATION SPURIOUS DESCRIBED IN MORE DETAIL IN 3ECTION THESPURIOUSCONTENTOFTHERECEIVERLOCALOSCILLATORS THEPERFORMANCEOFTHE!$ CONVERTER ANDTHEMANYSNEAKPATHSTHATMAYRESULTINUNWANTEDSIGNALSCOUPLINGONTO THERECEIVERSIGNALPATH )NTERMODULATION$ISTORTION)-$ )NTERMODULATIONDISTORTIONISANONLINEARPRO CESSTHATRESULTSINGENERATIONOFFREQUENCIESTHATARELINEARCOMBINATIONSOFTHEFUN DAMENTALFREQUENCIESOFTHEINPUTSIGNALS3ECONDANDTHIRDORDERINTERMODULATIONARE THEMOSTCOMMONLYSPECIFIED ANDTHEPERFORMANCEOFTHERECEIVERISUSUALLYSPECIFIED INTERMSOFTWO TONESECONDANDTHIRDORDERINPUTINTERCEPTPOINTS4HEINTERCEPTPOINT ISTHEEXTRAPOLATEDLEVELATWHICHTHEPOWERINTHEINTERMODULATIONPRODUCTEQUALSTHAT OFTHETWOFUNDAMENTALSIGNALS &ORINPUTSIGNALSATFREQUENCIESFANDF SECONDORDERINTERMODULATIONDISTORTION PRODUCESSIGNALSATFREQUENCIES FnF F F FANDF4HIRDORDERINTERMODU LATIONDISTORTIONPRODUCESSIGNALSATFREQUENCIESFnF FnF F F F F F ANDF&ORNARROWBANDSIGNALS ONLYTHETHIRDORDERPRODUCTSFnFANDFnFFALL INBAND ANDCONSEQUENTLY THIRDORDERDISTORTIONISTYPICALLYTHEPRIMARYCONCERN4HE POWERLEVELSOFTHESETHIRDORDERINTERMODULATIONPRODUCTSAREGIVENBY
0 F F D"M 0F D"M 0F D"M 0)0 D"M
0 F F D"M 0F D"M 0F D"M 0)0 D"M
WHERE 0FD"M POWEROFINPUTSIGNALATFREQUENCYFIND"M
0FD"M POWEROFINPUTSIGNALATFREQUENCYFIND"M
0)0D"M THIRDORDERINTERCEPTPOINTIND"M )NTERMODULATIONCANRESULTINAVARIETYOFUNDESIRABLEEFFECTSSUCHAS L
L
L
)NTERMODULATION OF CLUTTER RETURNS CAUSING BROADENING OF CLUTTER DOPPLER WIDTH RESULTINGINTHEMASKINGOFTARGETS 5NWANTED IN BAND SIGNALS DUE TO OUT OF BAND INTERFERING SIGNALS RESULTING IN FALSETARGETS )NTERMODULATION PRODUCTS FROM IN BAND SIGNALS THAT CANNOT BE READILY CANCELLED THROUGHLINEARCANCELLATIONTECHNIQUES RESULTINGINSUSCEPTIBILITYTOJAMMERS
)NTERMODULATIONDISTORTIONOCCURSTHROUGHOUTTHERECEIVERCHAIN#ONSEQUENTLY THE RECEIVER WILL HAVE A SIGNIFICANTLY DIFFERENT INPUT INTERCEPT POINT DEPENDING ON THE SIGNALFREQUENCYRELATIVETOTHERADIOFREQUENCY2& )& ANDVIDEOFILTERBANDWIDTHS )T IS THEREFORE IMPORTANT TO DISTINGUISH BETWEEN THE REQUIREMENTS FOR IN BAND AND OUT OF BAND INTERMODULATION DISTORTION AS DIFFERENT SIGNALS HAVE DIFFERENT EFFECTS ON THERECEIVER #ROSS -ODULATION$ISTORTION #ROSS MODULATIONOCCURSASARESULTOFTHIRDORDER INTERMODULATION WHEREBYTHEAMPLITUDEMODULATION!- OFONESIGNAL TYPICALLYAN UNWANTEDINTERFERENCESIGNALINTHEOPERATING2&BANDBUTUSUALLYOUTSIDETHETUNED SIGNALBANDWIDTH ISTRANSFERREDONTOTHEDESIREDSIGNAL
2!$!22%#%)6%23
È°Ç
4HERESULTANTPERCENT!-MODULATION D ONTHEDESIREDSIGNALISGIVENBY
D U
05
0)0 05
WHERE U PERCENT!-MODULATIONOFTHEUNWANTEDSIGNAL
05 POWEROFUNWANTEDSIGNAL
0)0 THIRDORDERINTERCEPTPOINT #ROSSMODULATIONCANRESULTINTHEMODULATIONOFCLUTTERANDTARGETRETURNSDUETO LARGEAMPLITUDEMODULATEDOUT OF BANDINTERFERENCESRESULTINGINPOORCLUTTERCANCEL LATIONANDPOORRANGESIDELOBEPERFORMANCE D" #OMPRESSION 0OINT 4HE INPUT D" COMPRESSION POINT OF A RECEIVER IS A MEASURE OF THE MAXIMUM LINEAR SIGNAL CAPABILITY AND IS DEFINED AS THE INPUT POWERLEVELATWHICHTHERECEIVERGAINISD"LESSTHANTHESMALLSIGNALLINEARGAIN 2ECEIVERGAINCOMPRESSIONCANRESULTFROMCOMPRESSIONINAMPLIFIERS MIXERS AND OTHERCOMPONENTSTHROUGHOUTTHERECEIVERCHAIN4YPICALLY THERECEIVERISDESIGNED TOPROVIDECONTROLLEDGAINCOMPRESSIONTHROUGHALIMITINGSTAGEATTHEFINAL)&AS DESCRIBEDIN3ECTION !NALOG TO $IGITAL#ONVERTER&ULL3CALE 4HE!$CONVERTERFULLSCALELEVELDETER MINESTHEMAXIMUMLEVELTHATCANBEDIGITIZED2ECEIVERSTYPICALLYPROVIDECONTROLLED LIMITING3ECTION TOPREVENTTHESIGNALLEVELFROMEXCEEDINGTHEFULLSCALELEVEL OFTHE!$CONVERTER0RACTICALCONSIDERATIONSMEANTHATTHEHARDLIMITLEVELISTYPI CALLYSETD"BELOWFULLSCALETOPREVENTOVERLOADASARESULTOFCOMPONENTTOLERANCE VARIATIONS 4YPES OF 3IGNALS 6ARIOUS TYPES OF SIGNALS ARE OF INTEREST IN DETERMINING DYNAMIC RANGEREQUIREMENTSDISTRIBUTEDTARGETS POINTTARGETS WIDEBANDNOISEJAM MING ANDNARROWBANDINTERFERENCE)FTHERADAREMPLOYSAPHASE CODEDSIGNAL THE ELEMENTSOFTHERECEIVERPRECEDINGTHEDECODERWILLNOTRESTRICTTHEDYNAMICRANGE OFAPOINTTARGETASSEVERELYASTHEYWILLFORDISTRIBUTEDCLUTTERTHETIME BANDWIDTH PRODUCTOFTHECODEDPULSEINDICATESTHEADDEDDYNAMICRANGETHATTHEDECODERWILL EXTRACTFROMTHEPOINTTARGETS#ONVERSELY IFTHERADARINCORPORATESANEXCESSIVELY WIDE BANDWIDTH2&LIFIER ITSDYNAMICRANGEMAYBESEVERELYRESTRICTEDDUETO WIDEBANDNOISEINTERFERENCE 7HENLOW NOISEAMPLIFIERS,.!S AREINCLUDEDINTHEANTENNA PRIORTOFORMING THERECEIVEBEAMS THEANTENNASIDELOBELEVELSACHIEVEDAREDEPENDENTUPONTHEDEGREE TOWHICHGAINANDPHASECHARACTERISTICSARESIMILARINALL,.!S$YNAMICRANGEHAS ANEXAGGERATEDIMPORTANCEINSUCHCONFIGURATIONSBECAUSEMATCHINGNONLINEARCHAR ACTERISTICSISIMPRACTICAL4HEEFFECTOFSTRONGINTERFERENCEMOUNTAINCLUTTER OTHER RADARPULSES ORELECTRONICCOUNTERMEASURES%#- ENTERINGTHROUGHTHESIDELOBES WILLBEEXAGGERATEDIFITEXCEEDSTHEDYNAMICRANGEOFTHE,.!SBECAUSESIDELOBES WILLBEDEGRADED4HE,.!SAREWIDEBANDDEVICES VULNERABLETOINTERFERENCEOVER THEENTIRERADAROPERATINGBANDANDOFTENOUTSIDETHISBANDALTHOUGHOFF FREQUENCY INTERFERENCEISFILTEREDINSUBSEQUENTSTAGESOFTHERECEIVER STRONGINTERFERENCESIGNALS CANCAUSECLUTTERRETURNSINTHE,.!TOBEDISTORTED DEGRADINGTHEEFFECTIVENESSOF DOPPLERFILTERINGANDCREATINGFALSEALARMS4HISPHENOMENONISDIFFICULTTOISOLATEAS THECAUSEOFFALSEALARMSINSUCHRADARSOWINGTOTHENONREPETITIVECHARACTEROFMANY
È°n
2!$!2(!.$"//+
SOURCESOFINTERFERENCE)NMODERNRADARARCHITECTURESTHATEMPLOYDIGITALBEAMFORM ING NONLINEARITYATANYSTAGEOFTHERECEIVERCHANNELWILLCREATESIMILARPROBLEMS 3YSTEM CALIBRATION TECHNIQUES AND ADAPTIVE BEAMFORMING TECHNIQUES CAN COM PENSATE FOR LINEAR GAIN AND PHASE DEVIATIONS HOWEVER AS FOR THE CASE OF THE ,.! NONLINEARITIES DESCRIBED ABOVE COMPENSATION FOR NONLINEAR CHARACTERISTICS IS EITHER IMPRACTICAL OR IMPOSSIBLE WHEN THE CAUSE OF THE NONLINEAR DISTORTION IS OUTSIDE THE DIGITIZEDBANDWIDTH %VALUATION ! THOROUGH EVALUATION OF ALL ELEMENTS OF THE RECEIVER IS NEC ESSARY TO PREVENT UNANTICIPATED DEGRADATION OF NOISE FIGURE OR DYNAMIC RANGE )NADEQUATE DYNAMIC RANGE MAKES THE RADAR RECEIVER VULNERABLE TO INTERFERENCE WHICH CAN CAUSE SATURATION OR OVERLOAD MASKING OR HIDING THE DESIRED SIGNALS !TABULARFORMATFORSUCHACOMPUTATIONATYPICALEXAMPLEOFWHICHISSHOWNIN 4ABLE WILLPERMITTHOSECOMPONENTSTHATCONTRIBUTESIGNIFICANTNOISEORRESTRICT THEDYNAMICRANGETOBEQUICKLYIDENTIFIEDh4YPICALvVALUESAREINCLUDEDINTHE TABLEFORPURPOSESOFILLUSTRATION
#OMPONENT .OISE&IGURE #OMPONENT'AIN #OMPONENT/UTPUT RD/RDER)NTERCEPT #OMPONENT/UTPUTD" #OMPRESSION0OINT #UMULATIVE'AIN #UMULATIVE .OISE&IGURE #UMULATIVE/UTPUT RD/RDER)NTERCEPT #UMULATIVE/UTPUTD" #OMPRESSION0OINT 2ECEIVER.OISE,EVEL 3YSTEM.OISE,EVEL "ANDWIDTH !$3.2IN .YQUIST"7 !$#ONVERTER 3AMPLE2ATE !$&ULL3CALE,EVEL !$.OISE,EVEL 3YSTEM.OISE2ELATIVE TO!$.OISE -AXIMUM0OINT#LUTTER OR4ARGET,EVEL
D"
D" D"M
D"M
D" D"
D"M
D"M
D"M(Z
D"M(Z -(Z D" -(Z
D"M
D"M(Z D" D"M
!$#ONVERTER
,IMITER
!'#!TTENUATOR
!MPLIFIER
"ANDPASS&ILTER
-IXER
"ANDPASS&ILTER
)NPUT
!MPLIFIER
5NITS
34#!TTENUATOR
4!",% .OISEAND$YNAMIC 2ANGE#HARACTERISTICS
+
%
2!$!22%#%)6%23
È°
È°ÎÊ 7 /Ê " - ,/" $EFINITIONS 4HEINSTANTANEOUSBANDWIDTHOFACOMPONENTISTHEFREQUENCYBAND OVERWHICHTHECOMPONENTCANSIMULTANEOUSLYPROCESSTWOORMORESIGNALSTOWITHINA SPECIFIEDACCURACY7HENTHETERMINSTANTANEOUSBANDWIDTHISUSEDASARADARRECEIVER PARAMETER ITREFERSTOTHERESULTINGBANDWIDTHSETBYTHECOMBINATIONOF2& )& VIDEO ANDDIGITALFILTERINGTHATOCCURSWITHINTHERECEIVER 7HEN THE RADAR RECEIVER EMPLOYS STRETCH PROCESSING DEFINED LATER IN THIS SEC TION THE 2& PROCESSING BANDWIDTH IS SIGNIFICANTLY LARGER THAN THE )& BANDWIDTH #ONSEQUENTLY THETERMINSTANTANEOUSBANDWIDTHCANBECONFUSING#ONFUSIONCANBE AVOIDEDBYUSINGTHETERMS2&WAVEFORMBANDWIDTH ,/LINEAR&-CHIRP BANDWIDTH AND)&PROCESSINGBANDWIDTH4HERELATIONSHIPBETWEEN2& ,/ AND)&BANDWIDTHS USEDINSTRETCHPROCESSINGISEXPLAINEDINMOREDETAILLATER 4HETUNINGRANGEISTHEFREQUENCYBANDOVERWHICHTHECOMPONENTMAYOPERATE WITHOUTDEGRADINGTHESPECIFIEDPERFORMANCE4UNINGISTYPICALLYACCOMPLISHEDBY ADJUSTINGTHELOCALOSCILLATORFREQUENCYANDADJUSTINGTHE2&FILTERINGCHARACTERIS TICS4HEFREQUENCYRANGEOVERWHICHTHERADAROPERATESISOFTENREFERREDTOASTHE OPERATINGBANDWIDTH )MPORTANT #HARACTERISTICS 4HE ENVIRONMENT IN WHICH A RADAR MUST OPERATE INCLUDES MANY SOURCES OF ELECTROMAGNETIC RADIATION WHICH CAN MASK THE RELATIVELY WEAK RETURNS FROM ITS OWN TRANSMISSION 4HE SUSCEPTIBILITY TO SUCH INTERFERENCE IS DETERMINEDBYTHEABILITYOFTHERECEIVERTOSUPPRESSTHEINTERFERINGFREQUENCIESIFTHE SOURCESHAVENARROWBANDWIDTHORTORECOVERQUICKLYIFTHEYAREMORELIKEIMPULSESIN CHARACTER/NEMUSTBECONCERNEDWITHTHERESPONSEOFTHERECEIVERINBOTHFREQUENCY ANDTIMEDOMAINS 'ENERALLY THECRITICALRESPONSEISDETERMINEDINTHE)&PORTIONOFTHERECEIVERTHIS WILLBEDISCUSSEDIN3ECTION(OWEVER ONECANNOTIGNORETHE2&PORTIONOFTHE RECEIVERMERELYBYMAKINGITHAVEWIDEBANDWIDTH3ECTIONDISCUSSEDHOWEXCES SIVELY WIDE BANDWIDTH CAN PENALIZE DYNAMIC RANGE IF THE INTERFERENCE IS WIDEBAND NOISE %VEN MORE LIKELY IS AN OUT OF BAND SOURCE OF STRONG INTERFERENCE EG OTHER RADARS 46STATIONS ORMICROWAVECOMMUNICATIONLINKS THAT IFALLOWEDTOREACHTHIS POINT CAN EITHER OVERLOAD THE MIXER OR BE CONVERTED TO )& BY ONE OF THE SPURIOUS RESPONSESOFTHEMIXER )DEALMIXERSINASUPERHETERODYNERECEIVERACTASMULTIPLIERS PRODUCINGANOUTPUT PROPORTIONALTOTHEPRODUCTOFTHETWOINPUTSIGNALS%XCEPTFORTHEEFFECTOFNONLINEARI TIESANDUNBALANCE THESEMIXERSPRODUCEONLYTWOOUTPUTFREQUENCIES EQUALTOTHESUM ANDTHEDIFFERENCEOFTHETWOINPUTFREQUENCIES4HENONLINEARITIESANDIMBALANCEOF MIXERSISDESCRIBEDINMOREDETAILIN3ECTION 4HEBESTRADARRECEIVERISONEWITHTHENARROWEST2&INSTANTANEOUSBANDWIDTHCOM MENSURATEWITHTHERADIATEDSPECTRUMANDHARDWARELIMITATIONSANDWITHGOODFREQUENCY ANDIMPULSERESPONSES!WIDETUNINGRANGEPROVIDESFLEXIBILITYTOESCAPEINTERFERENCE BUTIFTHEINTERFERENCEISINTENTIONAL ASINTHECASEOFJAMMING ACHANGEIN2&FRE QUENCYONAPULSE TO PULSEBASISMAYBEREQUIREDUSINGSWITCHABLEORELECTRONICALLY TUNEDFILTERS)FTHE2&FILTERINGISLOCATEDPRIORTO2&LIFICATION THEFILTERINSERTION LOSSWILLHAVEAD"FORD"IMPACTONTHERECEIVERNOISEFIGURE ANOTHERSACRIFICEINNOISE TEMPERATURETOACHIEVEMOREVITALOBJECTIVES9TTRIUMIRONGARNET9)' FILTERSANDPIN DIODESWITCHEDFILTERSHAVEBEENUSEDTOPROVIDETHENECESSARYFREQUENCYAGILITY
È°£ä
2!$!2(!.$"//+
3TRETCH 0ROCESSING 3TRETCH PROCESSING IS A TECHNIQUE FREQUENTLY USED TO PRO CESSWIDEBANDWIDTHLINEAR&-WAVEFORMS4HEADVANTAGEOFTHISTECHNIQUEISTHATIT ALLOWSTHEEFFECTIVE)&SIGNALBANDWIDTHTOBESUBSTANTIALLYREDUCED ALLOWINGDIGITIZA TIONANDSUBSEQUENTDIGITALSIGNALPROCESSING ATMOREREADILYACHIEVABLESAMPLERATES "YAPPLYINGASUITABLYMATCHEDCHIRPWAVEFORMTOTHERECEIVERFIRST,/ COINCIDENT WITHTHEEXPECTEDTIMEOFARRIVALOFTHERADARRETURN THERESULTANT)&WAVEFORMHAS ASIGNIFICANTLYREDUCEDBANDWIDTHFORTARGETSOVERALIMITEDRANGE WINDOWOFINTER EST0ROVIDEDTHATTHELIMITED RANGEWINDOWCANBETOLERATED ASUBSTANTIALLYREDUCED PROCESSINGBANDWIDTHALLOWSMOREECONOMICAL!$CONVERSIONANDSUBSEQUENTDIGITAL SIGNALPROCESSING)TALSOALLOWSAGREATERDYNAMICRANGETOBEACHIEVEDWITHLOWER RATE!$CONVERTERSTHANWOULDBEACHIEVABLEIFDIGITIZATIONOFTHEENTIRE2&SIGNAL BANDWIDTHWEREPERFORMED )FTHE,/CHIRPRATEISSETEQUALTOTHERECEIVEDSIGNALCHIRPRATEOFAPOINTTARGET THERESULTANTOUTPUTISACONSTANTFREQUENCYTONEATTHEOUTPUTOFTHESTRETCHPROCESSOR RECEIVER WITHFREQUENCY$T"4 WHERE$TISTHEDIFFERENCEINTIMEBETWEENTHERECEIVED SIGNALANDTHE,/CHIRPSIGNAL AND"4ISTHEWAVEFORMCHIRPSLOPECHIRPBANDWIDTH PULSEWIDTH 4ARGETDOPPLERISMAINTAINEDTHROUGHTHESTRETCHPROCESSING PRODUCING ANOUTPUTFREQUENCYOFFSETEQUALTOTHEDOPPLERFREQUENCY THOUGHTHEWIDEPERCENTAGE BANDWIDTHOFTENUSEDMEANSTHATTHEDOPPLERFREQUENCYCANCHANGESIGNIFICANTLYOVER THEDURATIONOFTHEPULSE )GNORINGTHEEFFECTOFTARGETDOPPLER THEREQUIRED2&SIGNALBANDWIDTHISEQUALTO THETRANSMITTEDWAVEFORMBANDWIDTH'IVENTHE2&SIGNALBANDWIDTH"2 THERECEIVED PULSEWIDTH42 ANDTHERANGEINTERVAL$4 THEREQUIRED,/REFERENCEWAVEFORMDURA TIONISGIVENBY
4, 42 $4
THE,/REFERENCECHIRPWAVEFORMBANDWIDTHISGIVENBY
",
42 $4 "2 42
ANDTHE)&PROCESSINGBANDWIDTHISGIVENBY
")
$4 " 42 2
È°{Ê ,
6 ,Ê," /Ê #ONFIGURATION 4HERADARFRONTENDCONSISTSOFALOW NOISEAMPLIFIER,.! AND BANDPASSFILTERFOLLOWEDBYADOWNCONVERTER4HERADARFREQUENCYISDOWNCONVERTED TO AN )& WHERE FILTERS WITH SUITABLE BANDPASS CHARACTERISTICS ARE PHYSICALLY REALIZ ABLE4HEMIXERITSELFANDTHEPRECEDINGCIRCUITSAREGENERALLYRELATIVELYBROADBAND 4UNINGOFTHERECEIVER BETWEENTHELIMITSSETBYTHEPRESELECTORORMIXERBANDWIDTH ISACCOMPLISHEDBYCHANGINGTHE,/FREQUENCY/CCASIONALLY RECEIVERSWILLINCLUDE FILTERINGBEFORETHE,.!INORDERTOLIMITTHEEFFECTSOFINTERMODULATIONDISTORTIONTHAT CANOCCURINTHE,.!%VENWHENFILTERINGISINCLUDEDBEFORETHE,.! ASECONDFILTER ISOFTENSTILLREQUIREDBETWEENTHE,.!ANDTHEMIXERINORDERTOREJECTTHEAMPLIFIER NOISEATTHEIMAGEFREQUENCY7ITHOUTTHISFILTER THENOISECONTRIBUTIONOFABROADBAND ,.!WOULDBEDOUBLED
2!$!22%#%)6%23
È°££
4HERECEIVERFRONTENDMAYALSOINCLUDEALIMITER USEDTOPROTECTTHERECEIVERCIR CUITRY FROM DAMAGE DUE TO HIGH POWER THAT MAY OCCUR EITHER FROM LEAKAGE DURING TRANSMITMODEORASARESULTOFINTERFERENCEFROMANOTHERSYSTEMSUCHASARADARATCLOSE RANGE&RONT ENDLIMITERSAREDISCUSSEDINMOREDETAILIN3ECTION 4HERADARORRECEIVERFRONTENDOFTENINCLUDESSOMEFORMOFGAINORATTENUATIONCON TROLASSHOWNIN&IGURE'AINCONTROLISDESCRIBEDINMOREDETAILIN3ECTION %FFECT OF #HARACTERISTICS ON 0ERFORMANCE .ONCOHERENT PULSE RADAR PERFOR MANCEISAFFECTEDBYFRONT ENDCHARACTERISTICSINTHREEWAYS.OISEINTRODUCEDBYTHE FRONTENDINCREASESTHERADARNOISETEMPERATURE DEGRADINGSENSITIVITY ANDLIMITSTHE MAXIMUMRANGEATWHICHTARGETSAREDETECTABLE&RONT ENDSATURATIONONSTRONGSIGNALS MAYLIMITTHEMINIMUMRANGEOFTHESYSTEMORITSABILITYTOHANDLESTRONGINTERFERENCE &INALLY THEFRONT ENDSPURIOUSPERFORMANCEAFFECTSTHESUSCEPTIBILITYTOOFF FREQUENCY INTERFERENCE #OHERENTRADARPERFORMANCEISEVENMOREAFFECTEDBYSPURIOUSMIXERCHARACTERIS TICS2ANGEANDVELOCITYACCURACYISDEGRADEDINPULSEDOPPLERRADARSSTATIONARYTARGET CANCELLATIONISIMPAIREDIN-4)MOVING TARGETINDICATION RADARSANDRANGESIDELOBES ARERAISEDINHIGH RESOLUTIONPULSECOMPRESSIONSYSTEMS 3PURIOUS$ISTORTIONOF2ADIATED3PECTRUM )TISASURPRISETOMANYRADARENGI NEERS THAT COMPONENTS OF THE RADAR RECEIVER CAN CAUSE DEGRADATION OF THE RADIATED TRANSMITTERSPECTRUM GENERATINGHARMONICSOFTHECARRIERFREQUENCYORSPURIOUSDOP PLERSPECTRA BOTHOFWHICHAREOFTENREQUIREDTOBED"ORMOREBELOWTHECARRIER (ARMONICS CAN CREATE INTERFERENCE IN OTHER ELECTRONIC EQUIPMENT 3PURIOUS DOPPLER SPECTRA LEVELS ARE DICTATED BY REQUIREMENTS TO SUPPRESS CLUTTER INTERFERENCE THROUGH DOPPLERFILTERING (ARMONICS ARE GENERATED BY ANY COMPONENT THAT BECOMES NONLINEAR WHEN SUB JECTEDTOTHEPOWERLEVELCREATEDBYTHETRANSMITTERANDTHATPASSESTHOSEHARMONICSTO THEANTENNA'ASEOUSORDIODERECEIVER PROTECTORSAREDESIGNEDTOBENONLINEARDURING THETRANSMITTEDPULSEANDREFLECTTHEINCIDENTENERGYBACKTOWARDTHEANTENNA)SOLATORS ORCIRCULATORSAREOFTENEMPLOYEDTOABSORBMOSTOFTHEREFLECTEDFUNDAMENTAL BUTTHEY AREGENERALLYMUCHLESSEFFECTIVEATTHEHARMONICS-OREOVER THESEFERRITEDEVICESARE NONLINEARDEVICESANDCANGENERATEHARMONICS 3PURIOUSDOPPLERSPECTRAARECREATEDBYANYPROCESSTHATDOESNOTREOCCURIDENTI CALLYONEACHTRANSMITTEDPULSE'ASEOUSRECEIVER PROTECTORSIONIZEUNDERTRANSMITTER POWERLEVELS BUTTHEREISSOMESMALLSTATISTICALVARIATIONINTHEINITIATIONOFIONIZA TION ON THE LEADING EDGE OF THE PULSE AND IN ITS SUBSEQUENT DEVELOPMENT )N RADARS DEMANDINGHIGHCLUTTERSUPPRESSIONINEXCESSOFD" ITHASSOMETIMESBEENFOUND NECESSARYTOPREVENTTHISVARIABLEREFLECTEDPOWERFROMBEINGRADIATEDBYUSEOFBOTH ACIRCULATORANDANISOLATORINTHERECEIVEPATH 3PURIOUS2ESPONSEOF-IXERS 4HEIDEALMIXERACTSASAMULTIPLIER PRODUCINGAN OUTPUTPROPORTIONALTOTHEPRODUCTOFTHETWOINPUTSIGNALS4HEINPUT2&SIGNALATFRE QUENCYF2ISFREQUENCYSHIFTEDORMODULATEDBYTHE,/SIGNALATFREQUENCYF,"ALANCED MIXERS ARE USED TO MINIMIZE CONVERSION LOSS AND UNWANTED SPURIOUS RESPONSES )N ACTIVEMIXERS MODULATIONISPERFORMEDUSINGTRANSISTORS ANDINPASSIVEMIXERS THE MODULATION IS PERFORMED USING 3CHOTTKY BARRIER DIODES OR OTHER SOLID STATE DEVICES EG -%3&%4 WHEREINCREASEDDYNAMICRANGEISREQUIRED 4HERESULTINGOUTPUTSIGNALFREQUENCIESF, F2ANDF,nF2 ARETHESUMANDDIFFERENCE OFTHETWOINPUTFREQUENCIES)NPRACTICE ALLMIXERSPRODUCEUNWANTEDINTERMODULATION
È°£Ó
2!$!2(!.$"//+
SPURIOUSRESPONSESWITHFREQUENCIES NF, MF2WHEREMANDNAREINTEGERS ANDTHE DEGREETOWHICHTHESESPURIOUSPRODUCTSIMPACTTHERADARPERFORMANCEDEPENDSUPONTHE TYPEOFMIXERANDTHEOVERALLRADARPERFORMANCEREQUIREMENTS!NALYSISOFMIXERSPURI OUSLEVELSISNONTRIVIAL ANDTHERECEIVERDESIGNERTYPICALLYREQUIRESTABULATEDDATAGENER ATEDTHROUGHMIXERCHARACTERIZATIONMEASUREMENTSTOPREDICTMIXERSPURIOUSLEVELS !DVANCES IN MIXER TECHNOLOGY HAVE RESULTED IN A WIDE VARIETY OF COMMERCIALLY AVAILABLEDEVICESEMPLOYINGBALANCED DOUBLEBALANCED ANDDOUBLE DOUBLEBALANCED TOPOLOGIESCOVERINGAWIDERANGEOF2& ,/ AND)&FREQUENCIESANDARANGEOFPER FORMANCECHARACTERISTICS -IXER3PURIOUS %FFECTS#HART !GRAPHICALDISPLAYOFMIXERSPURIOUSCOMPO NENTSUPTOTHESIXTHORDERISSHOWNIN&IGURE4HISCHARTALLOWSIDENTIFICATIONOF THOSECOMBINATIONSOFINPUTFREQUENCIESANDBANDWIDTHSTHATAREFREEOFSTRONGLOW ORDERSPURIOUSCOMPONENTS3UCHCHARTSAREMOSTUSEFULINDETERMININGOPTIMUM)&AND ,/FREQUENCIESDURINGTHEINITIALDESIGNPHASE/NCETHEFREQUENCYPLANHASBEENDETER MINED COMPUTERANALYSISOFSPURIOUSRESPONSESISTYPICALLYUSEDTOENSURESPURIOUSFREE PERFORMANCEOVERTHEENTIRERANGEOF,/FREQUENCIESAND2&AND)&BANDWIDTHS 4HEHEAVYLINEIN&IGUREREPRESENTSTHEDESIREDSIGNALANDSHOWSTHEVARIATION OF NORMALIZED OUTPUT FREQUENCY ( n , ( WITH NORMALIZED INPUT FREQUENCY ,( !LL OTHER LINES ON THE CHART REPRESENT THE UNWANTED SPURIOUS SIGNALS 4O SIMPLIFY USEOFTHECHART THEHIGHERINPUTFREQUENCYISDESIGNATEDBY(ANDTHELOWERINPUT FREQUENCYBY,
&)'52% $OWNCONVERTERSPURIOUS EFFECTSCHART( HIGHINPUTFREQUENCY, LOW INPUTFREQUENCY
2!$!22%#%)6%23
È°£Î
3EVENPARTICULARLYUSEFULREGIONSHAVEBEENOUTLINEDONTHECHART5SEOFTHECHART ISILLUSTRATEDBYMEANSOFTHEREGIONMARKED! WHICHREPRESENTSTHEWIDESTAVAILABLE SPURIOUS FREEBANDWIDTHCENTEREDAT,( 4HEAVAILABLE2&PASSBANDISFROM TO ANDTHECORRESPONDING)&PASSBANDISFROMTO(OWEVER SPURI OUS)&FREQUENCIESOF(n, AND(n, AREGENERATEDATTHEEXTREMES OFTHE2&PASSBAND!NYEXTENSIONOFTHEINSTANTANEOUS2&BANDWIDTHWILLPRODUCE OVERLAPPING)&FREQUENCIES ACONDITIONTHATCANNOTBECORRECTEDBY)&FILTERING4HE (n,AND(n,SPURIOUSFREQUENCIES LIKEALLSPURIOUS)&FREQUENCIES ARISEFROM CUBICORHIGHER ORDERINTERMODULATION 4HEAVAILABLESPURIOUS FREEBANDWIDTHINANYOFTHEDESIGNATEDREGIONSISROUGHLY OFTHECENTERFREQUENCYOR(n, (4HUS RECEIVERSREQUIRINGAWIDEBAND WIDTHSHOULDUSEAHIGH)&FREQUENCYCENTEREDINONEOFTHESEREGIONS&OR)&FREQUEN CIESBELOW(n, ( THESPURIOUSFREQUENCIESORIGINATEFROMHIGH ORDERTERMS INTHEPOWER SERIESMODELANDARECONSEQUENTLYLOWENOUGHINAMPLITUDETHATTHEY CANOFTENBEIGNORED&ORTHISREASON ALOW)&GENERALLYPROVIDESBETTERSUPPRESSION OFSPURIOUSRESPONSES 4HESPURIOUS EFFECTSCHARTALSODEMONSTRATESSPURIOUSINPUTRESPONSES/NEOFTHE STRONGEROFTHESEOCCURSATPOINT" WHERETHE(n,PRODUCTCAUSESAMIXEROUTPUTIN THE)&PASSBANDWITHANINPUTFREQUENCYAT!LLTHEPRODUCTSOFTHEFORM.(n, PRODUCEPOTENTIALLYTROUBLESOMESPURIOUSRESPONSES4HESEFREQUENCIESMUSTBEFIL TEREDAT2&TOPREVENTTHEIRREACHINGTHEMIXER)FSUFFICIENTFILTERINGCANNOTBEAPPLIED PRIORTOTHEMIXINGPROCESS SPURIOUSPRODUCTSTHATFALLWITHINTHEOPERATINGBANDWILL NOLONGERBEFILTERABLE WHICHWILLSERIOUSLYDEGRADESYSTEMPERFORMANCE 3PURIOUSRESPONSESNOTPREDICTEDBYTHECHARTOCCURWHENTWOORMORE2&INPUTSIG NALSPRODUCEOTHERFREQUENCIESBYINTERMODULATIONTHATLIEWITHINTHE2&PASSBAND )MAGE 2EJECT -IXER ! CONVENTIONAL MIXER HAS TWO INPUT RESPONSES AT POINTS ABOVEANDBELOWTHE,/FREQUENCYWHERETHEFREQUENCYSEPARATIONEQUALSTHE)&4HE UNUSED RESPONSE KNOWN AS THE IMAGE IS SUPPRESSED BY THE IMAGE REJECT OR SINGLE SIDEBANDMIXERSHOWNIN&IGURE4HE2&HYBRIDPRODUCESAnPHASEDIFFERENTIAL BETWEENTHE,/INPUTSTOTHETWOMIXERS4HEEFFECTOFTHISPHASEDIFFERENTIALONTHE )&OUTPUTSOFTHEMIXERSISA nSHIFTINONESIDEBANDANDA nSHIFTINTHEOTHER 4HE)&HYBRID ADDINGORSUBTRACTINGANOTHERnDIFFERENTIAL CAUSESTHEHIGH SIDEBAND SIGNALSTOADDATONEOUTPUTPORTANDTOSUBTRACTATTHEOTHER7HEREWIDEBANDWIDTHS AREINVOLVED THE)&HYBRIDISOFTHEALL PASSTYPE)NPRACTICE IMAGEREJECTMIXERSOFTEN DONOTPROVIDESUFFICIENTREJECTIONOFTHEIMAGERESPONSEALONEWITHOUTFILTERING)N THISCASE THEYCANBEUSEDINCONJUNCTIONWITHANIMAGEREJECTIONFILTER REDUCINGTHE MAGNITUDEOFREJECTIONREQUIREDBYTHEFILTER
" !
&)'52% )MAGEREJECTMIXER
#
# # #
È°£{
2!$!2(!.$"//+
#HARACTERISTICSOF!MPLIFIERSAND-IXERS .OISEFIGURE AMPLIFIERGAIN MIXER CONVERSIONLOSS D"COMPRESSIONPOINT ANDTHIRDORDERINTERCEPTPOINTARETHEMOST COMMONPERFORMANCEPARAMETERSSPECIFIEDFORAMPLIFIERSANDMIXERS/CCASIONALLY A SECONDORDERINTERCEPTPOINTSPECIFICATIONISALSOREQUIREDFORVERYWIDEBANDWIDTHSIG NALS)TSHOULDBENOTEDTHATFORAMPLIFIERS COMPRESSIONPOINTANDTHIRDORDERINTERCEPT AREUSUALLYSPECIFIEDATTHEIROUTPUTWHEREASFORMIXERSTHESEPARAMETERSAREUSUALLY SPECIFIEDATTHEIRINPUT !DDITIONALSPECIFICATIONSFORMIXERSINCLUDE,/DRIVEPOWER PORT TO PORTISOLATION ANDSINGLETONEINTERMODULATIONLEVELS4HE,/DRIVEPOWERSPECIFICATIONDEFINESHOW MUCH ,/ POWER IS REQUIRED BY THE MIXER TO MEET ITS SPECIFIED PERFORMANCE LEVELS 4YPICALLY THEHIGHERTHE,/POWER THEHIGHERTHED"COMPRESSIONPOINTANDTHIRD ORDER INTERCEPT POINT 2ADAR RECEIVERS OFTEN REQUIRE HIGH ,/ DRIVE LEVEL MIXERS IN ORDERTOMEETTHECHALLENGINGDYNAMIC RANGEREQUIREMENTS4HEPORT TO PORTISOLATION ISUSEDTODETERMINETHEPOWERLEVELCOUPLEDDIRECTLYBETWEENTHEMIXERPORTSWITHOUT FREQUENCY TRANSLATION 4HE SINGLE TONE INTERMODULATION LEVELS SPECIFY THE LEVELS OF THE NF, MF2SPURIOUSSIGNALS ASDISCUSSEDPREVIOUSLY
È°xÊ " Ê"- /",&UNCTIONSOFTHE,OCAL/SCILLATOR 4HESUPERHETERODYNERECEIVERUTILIZESONE OR MORE LOCAL OSCILLATORS AND MIXERS TO CONVERT THE SIGNAL TO AN INTERMEDIATE FRE QUENCYTHATISCONVENIENTFORFILTERINGANDPROCESSINGOPERATIONS4HERECEIVERCAN BETUNEDBYCHANGINGTHEFIRST,/FREQUENCYWITHOUTDISTURBINGTHE)&SECTIONOFTHE RECEIVER3UBSEQUENTSHIFTSININTERMEDIATEFREQUENCYAREOFTENACCOMPLISHEDWITHIN THERECEIVERBYADDITIONAL,/S GENERALLYOFFIXEDFREQUENCY4HESE,/SAREGENER ALLYALSOUSEDINTHEEXCITERTOUPCONVERTMODULATEDWAVEFORMSTO2&FOROUTPUTTO THETRANSMITTER )NMANYEARLYRADARS THEONLYFUNCTIONOFTHELOCALOSCILLATORSWASCONVERSIONOF THEINPUTSIGNALFREQUENCYTOTHECORRECTINTERMEDIATEFREQUENCY-ANYMODERNRADAR SYSTEMS HOWEVER COHERENTLYPROCESSASERIESOFRETURNSFROMATARGET4HELOCALOSCIL LATORSACTESSENTIALLYASATIMINGSTANDARDBYWHICHTHESIGNALDELAYISMEASUREDTO EXTRACTRANGEINFORMATION ACCURATETOWITHINASMALLFRACTIONOFAWAVELENGTH4HE PROCESSINGDEMANDSAHIGHDEGREEOFPHASESTABILITYTHROUGHOUTTHERADAR 34!,/)NSTABILITY 4HEFIRSTLOCALOSCILLATOR GENERALLYREFERREDTOASASTABLE LOCALOSCILLATOR34!,/ TYPICALLYHASTHEGREATESTEFFECTONRECEIVER EXCITERSTABILITY HOWEVER WHENEVALUATINGTHEOVERALLPERFORMANCE OTHERCONTRIBUTIONSSHOULDNOTBE NEGLECTED!DVANCESINSTATE OF THE ART34!,/OSCILLATORPERFORMANCEANDTHESTRIN GENTCLUTTERCANCELLATIONREQUIREMENTSOFMODERNRADARSMEANSTHATTHEPHASENOISEOF ALLOSCILLATORSANDTIMINGJITTEROF!$CONVERTERAND$!CONVERTERCLOCKSAND42 STROBESMAYBESIGNIFICANT 4HESHORT TERMSTABILITYREQUIREMENTSOFTHE34!,/AREGENERALLYCHARACTERIZED BYDEVICENOISERELATIVETOCARRIERD"C SPECIFIEDINTERMSOFAPHASENOISESPECTRUM AND MEASURED IN THE FREQUENCY DOMAIN ,ONG TERM STABILITY IS TYPICALLY CHARACTER IZEDBYAGINGANDENVIRONMENTALEFFECTS SPECIFIEDINTERMSOFFREQUENCYDRIFTAND MEASUREDUSINGAN!LLAN6ARIANCETECHNIQUE2EQUIREMENTSARETYPICALLYSPECIFIED INTERMSOFANABSOLUTEFREQUENCYTOLERANCEORAMAXIMUMFREQUENCYDEVIATIONOVER SOMETIMEINTERVAL
2!$!22%#%)6%23
È°£x
)TSHOULDBENOTEDTHATMEASUREMENTSOFPHASENOISEARETYPICALLYPERFORMEDBY MEASUREMENTOFDOUBLE SIDEBANDNOISE THESUMOFTHEPOWERINBOTHTHEUPPERAND LOWERSIDEBANDS BUTMORETYPICALLYREPORTEDANDSPECIFIEDASSINGLESIDEBAND33" VALUES$OUBLE SIDEBANDNOISECANBETRANSLATEDTOASINGLE SIDEBANDVALUEBYSUB TRACTINGD"5NEQUALSIDEBANDPOWERCANONLYRESULTFROMADDITIVESIGNALSORNOISE ORCORRELATEDAMPLITUDEANDPHASENOISECOMPONENTS !MPLITUDEMODULATION!- OFTHE34!,/ISTYPICALLYNOTASIGNIFICANTFACTORAS ITISUSUALLYATALOWERLEVELTHANTHEPHASENOISEATSMALLOFFSETFREQUENCIESFROMCAR RIER ANDCANBEFURTHERREDUCEDTHROUGHLIMITING-ODERNMIXERSTYPICALLYPROVIDEA SIGNIFICANTREDUCTIONINTHEEFFECTOF34!,/AMPLITUDEMODULATIONASTHEIRCONVERSION GAINISRELATIVELYINSENSITIVETO,/POWERVARIATIONWHENOPERATEDATTHEIRSPECIFIED DRIVELEVEL &ORSYSTEMSREQUIRINGHIGHSENSITIVITY !-NOISECANBECOMEDISRUPTIVEIFUNIN TENTIONALCONVERSIONOF!-TO0-NOISEOCCURSINTHERECEIVERCHAIN4HISPROCESS CANOCCURVIASUBOPTIMUMCOMPONENTBIASTECHNIQUESWHEREHIGHAMPLITUDESIGNALS OR NOISE CREATE A PHASE SHIFT RESULTING IN ANOTHER PHASE NOISE CONTRIBUTION TO THE RECEIVERCHAIN 6IBRATION3ENSITIVITY )NADDITIONTOTHEPHASENOISEGENERATEDBYTHE34!,/IN ABENIGNENVIRONMENT SOURCESOFUNWANTEDPHASEMODULATIONINCLUDETHEEFFECTSOF POWERSUPPLYRIPPLEANDSPURIOUSSIGNALSASWELLASMECHANICALORACOUSTICVIBRATION FROM FANS MOTORS AND OTHER SOURCES4HE EFFECTS OF VIBRATION CAN BE SEVERE ESPE CIALLYINAIRBORNEENVIRONMENTSWHEREHIGHVIBRATIONLEVELSAREPRESENT4HEVIBRATION SENSITIVITYOFANOSCILLATORISSPECIFIEDBYTHEFACTIONALFREQUENCYVIBRATIONSENSITIVITY COMMONLYKNOWASTHEG SENSITIVITY4YPICALLY ASINGLECONSTANTVALUEISSPECIFIED)N PRACTICE THESENSITIVITYVARIESSIGNIFICANTLYWITHVIBRATIONFREQUENCYANDISDIFFERENT FOREACHAXIS%QUATIONCANBEUSEDTODETERMINETHEEFFECTONOSCILLATORPHASENOISE DUETORANDOMVIBRATIONINEACHAXIS
§' F G F ¶ , FV LOG ¨ I I V · D"C33"INA(ZBANDWIDTH FV ¨© ·¸
WHERE FV
F
'I FI FV
VIBRATIONFREQUENCY(Z OSCILLATORFREQUENCY(Z OSCILLATORFRACTIONALFREQUENCYVIBRATIONSENSITIVITYG INAXISI VIBRATION POWER SPECTRAL DENSITY G(Z IN AXIS I AT THE VIBRATION FREQUENCYFV
4HECOMPOSITE34!,/VIBRATIONSENSITIVITY' ISDEFINEDBYTHEROOTSUMSQUARE OFTHESENSITIVITYINEACHOFTHETHREEPRIMEAXES ASSHOWNIN%Q
\' \ ' X ' Y ' Z
2ANGE $EPENDENCE -OST MODERN RADARS USE THE 34!,/ IN BOTH THE RECEIVER FORDOWNCONVERSIONANDTHEEXCITERFORUPCONVERSION4HISDOUBLEUSEOFTHE34!,/ INTRODUCESADEPENDENCEONRANGEOFTHECLUTTERANDEXAGGERATESTHEEFFECTOFCERTAIN UNINTENTIONALPHASE MODULATIONCOMPONENTSBYD" THECRITICALFREQUENCIESBEING THOSEWHICHCHANGEPHASEBYODDMULTIPLESOFDURINGTHETIMEPERIODBETWEEN TRANSMISSIONANDRECEPTIONOFTHECLUTTERRETURNFROMASPECIFIEDRANGE
È°£È
2!$!2(!.$"//+
4HISRANGE DEPENDENTFILTERCHARACTERISTICISGIVENBY
\ &2 FM \ SIN P FM 2 C SIN P FM4
WHERE FM MODULATIONFREQUENCY(Z
2 RANGEM
C PROPAGATIONVELOCITY rMS
4 TIMEDELAY 2CS !SHORTTIMEDELAYCANTOLERATEMUCHHIGHERDISTURBANCESATLOWMODULATIONFRE QUENCIES ASILLUSTRATEDBYTHETWOCASESIN&IGURE#ONSEQUENTLY THEEFFECTSOF 34!,/STABILITYNEEDTOBECOMPUTEDFORSEVERALTIMEDELAYSORRANGESTOENSURESUF FICIENTSTABILITYEXISTSFORTHEINTENDEDAPPLICATION #LOSETOCARRIERPHASEMODULATIONISTYPICALLYDOMINATEDBYTHATOFTHEOSCILLATORS DUETOTHEINHERENTFEEDBACKPROCESSWITHINTHEOSCILLATORCIRCUITRY.OISECONTRIBU TORS WITHIN THE OSCILLATOR LOOP THAT EXHIBIT A F CHARACTERISTIC D"DECADE NOISE SLOPE AREENHANCEDBYD"VIATHEFEEDBACKMECHANISMWITHARESULTINGNETF CHARACTERISTICD"DECADE NOISESIGNATURECLOSETOCARRIER WITHINTHEOSCILLATORLOOP BANDWIDTH/UTSIDETHISLOOPBANDWIDTH THEOSCILLATORNOISESIGNATURERESUMESAF SLOPEUNTILREACHINGAFLATTHERMALNOISEFLOOR!TLARGERFREQUENCYOFFSETS SIGNIFICANT NOISECONTRIBUTIONSCANRESULTFROMOTHERCOMPONENTSSUCHASAMPLIFIERSINTHE34!,/ SIGNAL PATH $EPENDING ON THE LOCATION OF THESE AMPLIFIERS THEY MAY EITHER CREATE PHASEMODULATIONTHATISCOMMONTOBOTHTHERECEIVERANDEXCITERCORRELATEDNOISE ORADDPHASENOISETOONLYTHERECEIVEROREXCITERUNCORRELATEDNOISE 5NCORRELATED ORUNCOMMONNOISEISNOTSUBJECTTOTHERANGEDEPENDENTFACTORDESCRIBEDABOVESOIT MUSTBEACCOUNTEDFORSEPARATELY/THERSIGNIFICANTCONTRIBUTORSOFUNCOMMONNOISE ARETHENOISEONTHEEXCITERWAVEFORMBEFOREUPCONVERSION ALONGWITHAMPLIFIERSIN THERECEIVERANDEXCITERSIGNALPATHS 4HEUNDESIRED33"PHASENOISEAFTERDOWNCONVERSIONBYTHE34!,/ISTHESUMOF THEUNCOMMONPHASENOISEANDTHECOMMONPHASENOISEREDUCEDBYTHERANGEFACTOR
&)'52% %FFECTOFRANGEDELAYONCLUTTERCANCELLATION
2!$!22%#%)6%23
$("& $ ( # , )$, 2
È°£Ç
)'')(# , )$, !
# , )$, !- +)0( )(/ +,$)( !
2
( )'')(# , )$, !
%2
%2
%2
2
+ *. ( 1 &)'52% 0HASENOISECOMPONENTS
&IGUREILLUSTRATESTYPICALCOMMONANDUNCOMMONPHASENOISECOMPONENTSANDTHE RESULTINGMIXEROUTPUTPHASENOISEASCALCULATEDUSING
, g F ,# F \ &2 F \ ,5 F
WHERE ,# F 34!,/33"PHASENOISESPECTRUMCOMMONTOTHERECEIVERANDEXCITER ,5 F TOTALRECEIVER EXCITERUNCORRELATED34!,/33"PHASENOISE &2 F RANGEDEPENDENCEFACTOR 2ESIDUE0OWERAND-4))MPROVEMENT&ACTOR 3UBSEQUENTSTAGESOFTHERECEIVER ANDSIGNALPROCESSORHAVERESPONSESTHATAREFUNCTIONSOFTHEDOPPLERMODULATIONFRE QUENCY SOTHEOUTPUTSPECTRUMCANBEOBTAINEDBYCOMBININGTHERESPONSESOFTHESE FILTERSWITHTHESPECTRUMPRESENTATTHEMIXERINPUT)N-4)SYSTEMS ITISCOMMONTO DESCRIBETHEABILITYTOSUPPRESSCLUTTERINTERMSOFAN-4)IMPROVEMENTFACTOR4HE -4) IMPROVEMENT FACTOR ) IS DEFINED AS THE SIGNAL TO CLUTTER RATIO AT THE OUTPUT OF THECLUTTERFILTERDIVIDEDBYTHESIGNAL TO CLUTTERRATIOATTHEINPUTOFTHECLUTTERFILTER AVERAGEDUNIFORMLYOVERALLTARGETRADIALVELOCITIESOFINTEREST4HE-4)IMPROVEMENT FACTORLIMITATIONDUETOTHE34!,/MAYBEEXPRESSEDASTHERATIOOFTHE34!,/POWER TOTHETOTALINTEGRATEDPOWEROFTHERETURNMODULATIONSPECTRUMITCREATESATTHEOUTPUT OFTHE-4)FILTERS&IGUREILLUSTRATESTHEEFFECTOFTHEOVERALLFILTERING CONSISTINGOF -4)FILTERINGANDRECEIVERFILTERINGONTHERESIDUEPOWERSPECTRUM 4HEINTEGRATEDRESIDUEPOWERDUETOTHE34!-/PHASENOISEISGIVENBY
c
0RESIDUE ¯ \ ( F \ , ` F DF
c
WHERE ( F COMBINED RESPONSE OF RECEIVER AND DOPPLER FILTERS NORMALIZED TO D" NOISEGAIN ,g F PHASENOISEAFTERDOWNCONVERSIONASDEFINEDIN%Q
È°£n
2!$!2(!.$"//+
( $ ( ) ' $,#$#+ '( $#
$ ( + !.
!*)) ' ( *
.
!) ' (%$#(
$" # $%%! ' !) ' # + ' !) ' (%$#(
.
.
.
.
' &* #&)'52% #LUTTERRESIDUEDUETO,/PHASENOISE
AND THE LIMIT ON THE -4) IMPROVEMENT FACTOR DUE TO THE 34!,/ PHASE NOISE IS GIVENBY ) LOG 0RESIDUE
)FTHERADARUTILIZESMORETHANONEDOPPLERFILTER THEEFFECTOF34!,/INSTABILITY SHOULDBECALCULATEDFOREACHINDIVIDUALLY 0ULSE$OPPLER0ROCESSING )NPULSEDOPPLERSYSTEMS ASERIESOFPULSESARETRANS MITTED AT A FIXED PULSE REPETITION FREQUENCY 02& AND DOPPLER PROCESSING IS PER FORMEDWITHINTHEDIGITALSIGNALPROCESSOR USINGSAMPLESSEPARATEDATTHE02&RATE 4HERESULTINGSAMPLINGOFTHERECEIVEROUTPUTATTHE02&PRODUCESALIASINGOFTHEPHASE NOISESPECTRUMPERIODICALLYATTHE02&INTERVAL ASSHOWNIN&IGURE WHEREEACH CURVE REPRESENTS THE PHASE NOISE AT THE OUTPUT OF THE RECEIVER INCLUDING THE EFFECTS OF RECEIVER FILTERING AND OFFSET BY A MULTIPLE OF THE 02& FREQUENCY 4HE COMBINED PHASENOISEDUETOEACHALIASEDCOMPONENTISCALCULATEDUSING%QWITHTHERESULT ILLUSTRATEDIN&IGURE4HISSAMPLEDPHASENOISESPECTRUMPROVIDESAMETHODFOR COMPARINGDIFFERENT,/PHASENOISEPROFILESANDTHEIRRELATIVEIMPACTONTHEOVERALL PERFORMANCEOFTHESYSTEM
,} F
c
£ §©, ` F KF02& \ ( F KF02& \¶¸
K c
3INUSOIDAL-ODULATIONS 2ADARPERFORMANCEISAFFECTEDBYBOTHRANDOMANDSINU SOIDALMODULATIONS 3INUSOIDAL MODULATIONSCANHAVEASIGNIFICANTIMPACTONRADAR PERFORMANCE THOUGHTHEDEGREETOWHICHTHEYCAUSEDEGRADATIONOFTENDEPENDSON THEIRRELATIONSHIPTOTHERADAR02&ANDTHEIRMAGNITUDERELATIVETOTHERANDOMMODU LATIONS%XAMPLESOFSUCHUNDESIREDSINUSOIDALMODULATIONSAREIN BAND UNFILTERABLE MIXERPRODUCTS ORLEAKAGEDUETOINSUFFICIENTISOLATIONBETWEENSIGNALSOURCESWITHIN ARECEIVEROREXCITER)NADDITIONTOEXTERNALSOURCESOFINTERFERENCE THERADARDESIGNER
2!$!22%#%)6%23
È°£
&)'52% 0HASENOISEALIASINGINAPULSEDOPPLERSYSTEM
&)'52% 3AMPLEDPHASENOISESPECTRUMDUETOPHASENOISEALIASING
MUST BE CONCERNED WITH INTERNAL SIGNAL SOURCES -4) AND PULSE DOPPLER RADARS ARE PARTICULARLYSUSCEPTIBLETOANYSUCHINTERNALOSCILLATORSTHATARENOTCOHERENT IE THAT DONOTHAVETHESAMEPHASEFOREACHPULSETRANSMISSION4HEEFFECTOFTHESPURIOUS SIGNALISTHENDIFFERENTFOREACHRETURN ANDTHEABILITYTOREJECTCLUTTERISDEGRADED
È°Óä
2!$!2(!.$"//+
!TRULYCOHERENTRADARGENERATESALLFREQUENCIES INCLUDINGITSINTER PULSEPERIODS FROM A SINGLE FREQUENCY REFERENCE4HIS FULLY COHERENT ARCHITECTURE INSURES THAT BOTH THE DESIRED FREQUENCIES AND ALL THE INTERNALLY GENERATED SPURIOUS SIGNALS ARE COHERENT ELIMINATINGTHEDEGRADATIONOFCLUTTERREJECTION -ANY RADAR SYSTEMS ARE PSEUDO COHERENT4HE SAME OSCILLATORS ARE USED IN BOTH TRANSMITANDRECEIVEBUTNOTNECESSARILYCOHERENTWITHEACHOTHER4HERESULTISTHAT THEPHASEOFTHETARGETREMAINSCONSTANT BUTTHEPHASEOFMANYOFTHESPURIOUSSIGNALS VARIESFROMPULSETOPULSE)NTHISTYPEOFCONFIGURATION SIGNALISOLATIONANDFREQUENCY ARCHITECTUREISCRITICALTOMINIMIZETHEOCCURRENCEOFSPURIOUSSIGNALSTHATCOULDERRO NEOUSLYBEINTERPRETEDASFALSETARGETS #/(/AND4IMING)NSTABILITY 4HEMAJORITYOFTHISDISCUSSIONHASFOCUSED ON THE 34!,/ AS THE MAJOR CONTRIBUTOR TO RECEIVER STABILITY /THER CONTRIBUTORS SUCH AS THE SECOND ,/ THE COHERENT OSCILLATOR #/(/ IF USED !$ AND $! CONVERTER CLOCKS CAN ALL BECOME SIGNIFICANT !$ AND $! CONVERTER CLOCK JITTER BECOMESINCREASINGLYSIGNIFICANTASSAMPLERATESAND)&FREQUENCIESAREINCREASED 4HEEFFECTSOF!$AND$!CONVERTERCLOCKPHASENOISEANDJITTERISDESCRIBEDIN 3ECTIONSAND4HEJITTERONTIMINGSTROBESUSEDTOPERFORMTRANSMITRECEIVE 42 SWITCHINGISTYPICALLYLESSSTRINGENTTHANTHATOF!$CLOCKS ASITDOESNOTHAVE ADIRECTIMPACTONTHESIGNALPHASE(OWEVER IFCOMPONENTSSUCHASTRANSMITRECEIVE SWITCHESORPOWERAMPLIFIERSHAVEATRANSIENTPHASERESPONSEOFSIGNIFICANTDURATION TIMEJITTERONTHESWITCHINGTIMECANBETRANSLATEDINTOAPHASEMODULATIONOFTHE TRANSMITTERORRECEIVERSIGNAL 4OTAL2ADAR)NSTABILITY 4HEPRIMARYSOURCESOFRADARINSTABILITYAREUSUALLYTHE RECEIVER EXCITER COMMON PHASE NOISE RECEIVER AND EXCITER UNCOMMON PHASE NOISE ANDTHETRANSMITTERPHASENOISE)FTHESPECTRAOFTHESECOMPONENTSAREAVAILABLE EITHER THROUGHMEASUREMENTSORTHROUGHPREDICTIONSBASEDONSIMILARDEVICES THECONVOLU TIONOFRECEIVER EXCITERCOMMONPHASENOISE MODIFIEDBYTHERANGE DEPENDENTEFFECT WITHTHEOTHERCOMPONENTS PROVIDESANESTIMATEOFTHESPECTRUMOFRETURNSFROMSTABLE CLUTTER WHICHISTHENMODIFIEDBYTHERECEIVERFILTERSANDINTEGRATEDTOOBTAINTHERESI DUEPOWERCAUSEDBYTHESECONTRIBUTORS4HESEPROCEDURESAREEMPLOYEDTODIAGNOSE THESOURCEOFRADARINSTABILITYINANEXISTINGRADARORTOPREDICTTHEPERFORMANCEOFA RADARINTHEDESIGNSTAGEANDTOALLOWTHEALLOCATIONOFSTABILITYREQUIREMENTSTOCRITICAL COMPONENTSORSUBSYSTEMSWITHINTHERADAR -EASUREMENTOFTOTALRADARINSTABILITYCANBECONDUCTEDWITHTHERADARANTENNA SEARCH LIGHTINGASTABLEPOINTCLUTTERREFLECTORTHATPRODUCESASIGNALRETURNCLOSETO BUTBELOW THEDYNAMIC RANGELIMITOFTHERECEIVER3UITABLECLUTTERSOURCESAREDIF FICULTTOFINDATMANYRADARSITES ANDINTERRUPTIONOFROTATIONOFTHEANTENNATOCON DUCTSUCHATESTMAYBEUNACCEPTABLEATOTHERSINTHISCASE AMICROWAVEDELAYLINE CANBEEMPLOYEDTOFEEDADELAYEDSAMPLEOFTHETRANSMITTERPULSEINTOTHERECEIVER !LL SOURCES OF INSTABILITY ARE INCLUDED IN THIS SINGLE MEASUREMENT EXCEPT FOR ANY CONTRIBUTORSOUTSIDETHEDELAY LINELOOP)TISIMPORTANTTORECOGNIZETHATTIMINGJIT TERDOESNOTPRODUCEEQUALIMPACTONALLPARTSOFTHERETURNPULSEANDGENERALLYHAS MINIMALEFFECTONTHECENTEROFTHEPULSE SOITISESSENTIALTOCOLLECTDATASAMPLESAT AMULTIPLICITYOFPOINTSACROSSTHERETURN INCLUDINGLEADINGANDTRAILINGEDGES4HE TOTALRADARINSTABILITYISTHERATIOOFTHESUMOFTHEMULTIPLICITYOFRESIDUEPOWERSAT THEOUTPUTOFTHEDOPPLERFILTERTOTHESUMOFTHEPOWERSATITSINPUT DIVIDEDBYTHE RATIOOFRECEIVERNOISEATTHESELOCATIONS3TABILITYISTHEINVERSEOFTHISRATIOBOTHARE GENERALLYEXPRESSEDINDECIBELS
2!$!22%#%)6%23
È°Ó£
)NRADARSWITHPHASE CODEDTRANSMISSIONANDPULSECOMPRESSIONRECEIVERS RESIDUE MAYBESIGNIFICANTINTHERANGESIDELOBEREGIONASWELLASINTHECOMPRESSEDPULSE CAUSEDBYPHASEMODULATIONDURINGTHELONGTRANSMITTEDPULSERATHERTHANSOLELYFROM PULSETOPULSE-EASUREMENTOFSTABILITYOFSUCHRADARSMUSTEMPLOYAVERYLARGENUM BEROFDATAPOINTSTOOBTAINANANSWERVALIDFORCLUTTERDISTRIBUTEDINRANGE )NADDITIONTOTHEAMPLITUDEANDPHASENOISEOFTHERECEIVER EXCITERANDTHETRANS MITTER MECHANICALLYSCANNINGANTENNASPRODUCEAMODULATIONTHATISPREDOMINANTLY !-4HECOMBINEDEFFECTISTHESUMOFTHERESIDUEPOWERSPRODUCEDBYEACHCOMPO NENTINDIVIDUALLY ,OW .OISE &REQUENCY 3OURCES -ANY RADAR SYSTEMS OPERATE OVER A RANGE OF 2& FREQUENCIES REQUIRING A NUMBER OF ,/ FREQUENCIES THAT ARE TYPICALLY GENERATED USINGFREQUENCYSYNTHESIS&REQUENCYSYNTHESISISTHEPROCESSOFCREATINGONEORMORE FREQUENCIESFROMASINGLEREFERENCEFREQUENCYUSINGFREQUENCYMULTIPLICATION DIVI SION ADDITION ANDSUBTRACTIONTOSYNTHESIZETHEREQUIREDFREQUENCIES4HEFUNDAMENTAL BUILDINGBLOCKOFANYFREQUENCYSYNTHESISAPPROACHISTHEOSCILLATOR#RYSTALOSCILLATORS HAVEHISTORICALLYBEENTHEMOSTCOMMONSOURCETECHNOLOGY6(&CRYSTALOSCILLATORS EMPLOYINGDOUBLY ROTATED3# )4 ETC CRYSTALRESONATORSAREABLETOSUPPORTHIGHER POWERLEVELSTHANSINGLEAXISCRYSTALS4HISENABLESTHEMTOACHIEVELOWERPHASENOISE ANDIMPROVEDVIBRATIONIMMUNITYDUETOPROPERTIESUNIQUETOTHEPARTICULARAXISOF ROTATION&REQUENCYMULTIPLICATIONOFTHESE6(&SOURCESISOFTENUSEDTOGENERATETHE RADAR2&FREQUENCIESREQUIREDHOWEVER THISMULTIPLICATIONPROCESSRESULTSININCREASE INPHASENOISEPERFORMANCEBYLOG- D"WHERE-ISTHEMULTIPLICATIONFACTOR! VARIETYOFOTHERSOURCETECHNOLOGIES SUCHAS3URFACE!COUSTIC7AVE3!7 OSCILLA TORS HAVEBEENEXPLOITEDTOACHIEVEIMPROVEDPHASENOISEPERFORMANCE3!7OSCIL LATORSENABLELOWERFAR FROM CARRIERPHASENOISE LARGELYDUETOTHEIRHIGHERFREQUENCY OPERATIONANDTHERESULTINGLOWERFREQUENCYMULTIPLICATIONFACTORREQUIREDTOGENERATE THEEQUIVALENTRADAR2&OUTPUTFREQUENCIES 6ERYACCURATEFREQUENCYTIMINGISOFTENREQUIREDINRADARSWHERECOORDINATIONOR HAND OFFFROMONERADARTOANOTHER ORCOMMUNICATIONTOAMISSILEINFLIGHT ISREQUIRED 4HISISTYPICALLYTHECASEWHEREASEARCHRADARACQUIRESATARGETANDQUEUESAPRECI SIONTRACKINGRADAR!CCURATETIMINGFORTHESEAPPLICATIONSMAYBEACHIEVEDBYPHASE LOCKINGTHELOWPHASENOISERADAROSCILLATORSTOALOWFREQUENCYREFERENCEGENERATED FROMEITHERARUBIDIUMOSCILLATORORA'03RECEIVER)NTHISCONFIGURATION THELONG TERM STABILITYOFTHEREFERENCEOSCILLATORISSUPERIORTOTHATOFTHERADAROSCILLATOR ANDTHE SHORT TERMSTABILITYOFTHERADAROSCILLATORISSUPERIORTOTHATOFTHEREFERENCEOSCILLATOR 4HEPHASELOCKLOOP0,, ARCHITECTUREISESTABLISHEDTOEXPLOITTHESTRENGTHSOFBOTH TECHNOLOGIESBYSELECTINGA0,,BANDWIDTHATTHEOFFSETFREQUENCYWHERETHESOURCE STABILITIESCROSSOVER&ORTYPICALRADARANDREFERENCEOSCILLATORTECHNOLOGIES THISUSU ALLYOCCURSINTHE(ZTOK(ZOFFSETREGION &REQUENCY 3YNTHESIS 4ECHNIQUES 4HE MOST COMMON TECHNIQUES ARE DIRECT SYNTHESIS DIRECTDIGITALSYNTHESIS ANDFREQUENCYMULTIPLICATION$IRECTSYNTHESISIS THE PROCESS OF GENERATING FREQUENCIES THROUGH THE MULTIPLICATION AND MIXING OF A NUMBEROFSIGNALSATDIFFERENTFREQUENCIESTOPRODUCETHEREQUIREDOUTPUTFREQUENCY &REQUENCYMULTIPLICATIONANDDIRECTDIGITALSYNTHESISAREDESCRIBEDIN3ECTION #ONVENTIONAL PHASE LOCKED LOOP SYNTHESIZERS ARE OCCASIONALLY USED BUT THEIR FRE QUENCYSWITCHINGTIMESANDPHASESETTLINGRESPONSESAREGENERALLYINADEQUATETOMEET THESTRINGENTRADARRECEIVER EXCITERREQUIREMENTS0HASELOCKEDLOOPSAREMORELIKELY USEDTOLOCKFIXEDHIGH FREQUENCYOSCILLATORSTOSTABLELOW FREQUENCYREFERENCESTO
È°ÓÓ
2!$!2(!.$"//+
ENSURECOHERENCEOFALLOSCILLATORSWITHINTHERECEIVER EXCITERANDOBTAINANOPTIMUM BALANCEOFLONG ANDSHORT TERMSTABILITY #OHERENCE!FTER&REQUENCY3WITCHING ,ONGRANGERADARSOFTENTRANSMITASERIES OFPULSESBEFORERECEIVINGRETURNSFROMTHEFIRSTINTHESEQUENCE0ULSESMAYBETRANSMITTED ATANUMBEROFDIFFERENTOPERATINGFREQUENCIESREQUIRINGSWITCHINGOFTHE,/FREQUENCY BETWEENPULSES)FTARGETRETURNSAREPROCESSEDCOHERENTLY THEPHASEOFTHE,/SIGNAL MUSTBECONTROLLEDSUCHTHATEACHTIMEITSWITCHESTOAPARTICULARFREQUENCY THEPHASEOF THE,/ISTHESAMEPHASETHATITWOULDHAVEBEENHADNOFREQUENCYSWITCHINGOCCURRED 4HISREQUIREMENTDRIVESTHEARCHITECTUREUSEDTOGENERATE,/FREQUENCIES'ENERATING ALLTHEFREQUENCIESFROMASINGLEREFERENCEFREQUENCYDOESNOTGUARANTEEPHASECOHER ENCEWHENFREQUENCYSWITCHINGOCCURS4HREESOURCESOFPHASEAMBIGUITYARECOMMON FREQUENCYDIVIDERS DIRECTDIGITALSYNTHESIZERS ANDVOLTAGECONTROLLEDOSCILLATORS6#/ &REQUENCYDIVIDERSPRODUCEANOUTPUTSIGNALTHATCANHAVEANYONEOF.PHASES WHERE. ISTHEDIVIDERATIOSWITCHINGDIVIDERSCANRESULTINPHASEAMBIGUITYOFO.)FFREQUENCY DIVIDERSAREUSEDINTHEFREQUENCYSYNTHESISPROCESS THEYMUSTBEOPERATEDCONSTANTLY WITHOUT SWITCHING THE INPUT FREQUENCY OR DIVIDE RATIO TO AVOID THIS PHASE AMBIGUITY $IRECTDIGITALSYNTHESIZERS$$3S CANBEUSEDEITHERTOGENERATE,/FREQUENCIESDIRECTLY ORTOGENERATEMODULATEDWAVEFORMSPRIORTOUPCONVERSION7HENPULSE TO PULSEPHASE COHERENCEISREQUIRED THESTARTINGPHASEISRESETTOZEROATTHESTARTOFEACHPULSE)FALLTHE ,/FREQUENCIESUSEDAREMULTIPLESOFTHEPULSEREPLETIONFREQUENCY THERESULTINGPHASE WILLBETHESAMEFOREACHPULSE6#/SCANBEUSEDTOCREATEATUNABLE,/BUTAREUSUALLY PHASELOCKEDTOANOTHERSTABLESOURCEFORIMPROVEDSTABILITY4HETUNINGVOLTAGEDESIGN ANDFILTERCAPACITORTECHNOLOGYUSEDTOACHIEVEPHASELOCKMUSTBECAREFULLYDESIGNED TOENSURERAPIDVOLTAGEANDSTOREDCHARGETRANSITIONS/THERWISE THE6#/MAYPROPERLY ACQUIREANDACHIEVEPHASELOCK BUTTHERESIDUALVOLTAGEDECAYFROMTHETRANSITIONWILL MANIFESTITSELFINANINSIDIOUSPHASEAMBIGUITYCALLEDPOST TUNINGDRIFT 3TRETCH0ROCESSING )NSTRETCHPROCESSING THE,/SIGNALFREQUENCYISMODULATED WITHACHIRPWAVEFORMSIMILARTOTHATOFTHERECEIVEDSIGNALTOREDUCETHEBANDWIDTH OFTHE)&SIGNALASDESCRIBEDIN3ECTION4HEWIDEBANDCHIRPWAVEFORMISTYPICALLY GENERATEDBYPASSINGANARROWERBANDWIDTHLINEARFREQUENCYMODULATION,&- WAVE FORM THROUGH A FREQUENCY MULTIPLIER THAT INCREASES BOTH THE OPERATING FREQUENCY AND BANDWIDTHOFTHECHIRPWAVEFORM&REQUENCYMULTIPLIERSMULTIPLYTHEPHASEDISTORTION OFTHEINPUTSIGNALANDOFTENHAVESIGNIFICANTPHASEDISTORTIONTHEMSELVES$ISTORTIONOF THE,/CHIRPSIGNALPHASECANHAVEASIGNIFICANTEFFECTONTHECOMPRESSEDPULSEPERFOR MANCE EITHERDISTORTINGTHECOMPRESSEDPULSESHAPEORDEGRADINGSIDELOBEPERFORMANCE 3ECTION 0HASEERRORSCANBEMEASUREDUSINGATESTTARGETINJECTEDINTOTHERECEIVER ANDMEASURINGTHEPHASERIPPLEATTHERECEIVEROUTPUT"YPERFORMINGTHISMEASUREMENT WITHTARGETSINJECTEDATDIFFERENTSIMULATEDRANGES THEERRORSASSOCIATEDWITHTHERECEIVER ,/ANDTESTSIGNALCANBESEPARATED#ORRECTIONOFRECEIVER,/PHASEDISTORTIONCANBE READILYCORRECTEDWHENUSINGADIRECTDIGITALSYNTHESIZERASDESCRIBEDIN3ECTION
È°ÈÊ Ê " /," 3ENSITIVITY4IME#ONTROL34# 4HESEARCHRADARDETECTSRETURNSOFWIDELYDIF FERINGAMPLITUDES OFTENSOGREATTHATTHEDYNAMICRANGEOFAFIXED GAINRECEIVERWILL BEEXCEEDED$IFFERENCESINRETURNSTRENGTHARECAUSEDBYDIFFERENCESINRADARCROSS
2!$!22%#%)6%23
È°ÓÎ
SECTIONS INMETEOROLOGICALCONDITIONS ANDINRANGE4HEEFFECTOFRANGEONRADARRETURN STRENGTHOVERSHADOWSTHEOTHERCAUSESANDCANBEMITIGATEDBYATECHNIQUEKNOWNAS SENSITIVITYTIMECONTROL WHICHCAUSESTHERADARRECEIVERSENSITIVITYTOVARYWITHTIMEIN SUCHAWAYTHATTHEAMPLIFIEDRADARRETURNSTRENGTHISINDEPENDENTOFRANGE 4IMESIDELOBESOFCOMPRESSEDPULSESINRADARSTHATTRANSMITCODEDWAVEFORMSCAN BEDEGRADEDBY34#'RADUALCHANGESCANUSUALLYBETOLERATED BUTATCLOSERANGE THE RATEOFCHANGEOFATTENUATIONCANBEVERYLARGE-OSTMODERNRADARSTHATINCLUDE34# USEDIGITAL34#CONTROL WHICHCANLEADTOLARGESTEPSIZESATCLOSERANGEUNLESSHIGH DIGITIZATIONRATESAREUSED4HEPHASESTABILITYOFTHE34#ATTENUATORISALSOANIMPOR TANTCONSIDERATIONASEXCESSIVEPHASEVARIATIONASAFUNCTIONOFATTENUATIONCANHAVEA DRAMATICIMPACTONRANGESIDELOBES #LUTTER-AP!UTOMATIC'AIN#ONTROL )NSOMERADARS MOUNTAINORURBANCLUT TERCANCREATERETURNSTHATWOULDEXCEEDTHEDYNAMICRANGEOFTHERECEIVER4HESPATIAL AREAOCCUPIEDBYSUCHCLUTTERISTYPICALLYAVERYSMALLFRACTIONOFTHERADARCOVERAGE SOCLUTTERMAP!'#HASBEENUSEDASANALTERNATIVETOBOOSTINGTHE34#CURVE4HIS TECHNIQUEUSESADIGITALMAPTORECORDTHEMEANAMPLITUDEOFTHECLUTTERINEACHMAP CELLOVERMANYSCANSANDADDSRECEIVERATTENUATIONWHERENECESSARYTOKEEPTHECLUTTER RETURNSBELOWTHESATURATIONLEVELOFTHERECEIVER 0ROGRAMMABLE'AIN#ONTROL 2EDUCEDGAINMAYBEDESIRABLEINAVARIETYOF SITUATIONS SUCH AS HIGH CLUTTER OR HIGH INTERFERENCE ENVIRONMENTS OR IN SHORT RANGE MODES&IXEDATTENUATIONISOFTENPREFERABLETO34#ORCLUTTERMAPCONTROL(IGH02& PULSE DOPPLER RADARS FOR EXAMPLE CANNOT TOLERATE 34# DUE TO THE RANGE AMBIGUITY OFTARGETS!DDITIONALATTENUATIONMAYBEPROGRAMMEDEITHERMANUALLYVIAOPERATOR CONTROLORAUTOMATICALLYTOINCREASETHERECEIVERSLARGESIGNALHANDLINGCAPABILITYOR TOREDUCEITSSENSITIVITY 'AIN.ORMALIZATION 2ECEIVERGAINCANVARYDUETOCOMPONENTTOLERANCES FRE QUENCYRESPONSE VARIATIONWITHTEMPERATURE ANDAGING!CCURATERECEIVERGAINCONTROL IS REQUIRED FOR A VARIETY OF REASONS THAT INCLUDE TARGET RADAR CROSS SECTION MEASURE MENT MONOPULSEANGLEACCURACY MAXIMIZINGTHERECEIVERDYNAMICRANGE ANDNOISE LEVELCONTROL$IGITALGAINCONTROLPERMITSTHECALIBRATIONOFRECEIVERGAINBYINJECT INGTESTSIGNALSDURINGRADARDEADTIMEORDURINGSOMESCHEDULEDCALIBRATIONINTERVAL #ALIBRATIONCOEFFICIENTSCANBESTOREDASAFUNCTIONOFCOMMANDEDATTENUATION OPERAT INGFREQUENCY ANDTEMPERATUREASNEEDED-EASUREMENTSOVERTIMECANALSOBEUSED TOASSESSCOMPONENTAGINGANDPOTENTIALLYPREDICTRECEIVERFAILUREPRIORTODEGRADATION BEYONDACCEPTABLELIMITS!CCURATEGAINCONTROLISESSENTIALFORRECEIVERCHANNELSUSED TOPERFORMMONOPULSEANGLEMEASUREMENTS WHEREAMPLITUDESRECEIVEDINTWOORMORE BEAMSSIMULTANEOUSLYARECOMPAREDTOACCURATELYDETERMINETHETARGETSPOSITIONIN AZIMUTHORELEVATION2ECEIVERDYNAMICRANGEISMAXIMIZEDWITHACCURATEGAINCONTROL ASTOOLITTLEGAINCANRESULTINNOISEFIGUREDEGRADATIONANDTOOMUCHGAINRESULTSIN LARGESIGNALSEXCEEDINGTHE!$CONVERTERFULL SCALEORCREATINGUNWANTEDGAINCOM PRESSION INTERMODULATION ORCROSSMODULATIONDISTORTION !UTOMATIC .OISE ,EVEL #ONTROL !NOTHER WIDELY EMPLOYED USE FOR!'# IS TO MAINTAINADESIREDLEVELOFRECEIVERNOISEATTHE!$CONVERTER!SWILLBEDESCRIBED IN3ECTION TOOLITTLENOISERELATIVETOTHEQUANTIZATIONINCREMENTOFTHE!$CON VERTERCAUSESALOSSINSENSITIVITY3AMPLESOFNOISEARETAKENATLONGRANGE OFTENBEYOND THEINSTRUMENTEDRANGEOFTHERADARORDURINGSOMESCHEDULEDPERIOD)FTHERADARHAS
È°Ó{
2!$!2(!.$"//+
2&34#PRIORTOANYAMPLIFICATION ITCANBESETTOFULLATTENUATIONTOMINIMIZEEXTER NALINTERFERENCEWITHMINIMALANDPREDICTABLE EFFECTONSYSTEMNOISETEMPERATURE-OST RADARSEMPLOYAMPLIFIERSPRIORTO34# SOTHEYCANNOTATTENUATEEXTERNALINTERFERENCEWITH OUTAFFECTINGTHENOISELEVEL4HENOISELEVELCALIBRATIONALGORITHMMUSTBEDESIGNEDTO TOLERATEEXTERNALINTERFERENCEANDRETURNSFROMRAINSTORMSORMOUNTAINSATEXTREMERANGE !NOTHERCONCERNWITHAMPLIFICATIONPRIORTO34#ISTHATTHENOISELEVELATTHEOUTPUT OFTHE34#ATTENUATORVARIESWITHRANGE!TCLOSERANGE THENOISELEVELINTOTHE!$ CONVERTERMAYFALLBELOWTHEQUANTIZATIONINTERVAL!LSO ACONSTANTNOISELEVELASA FUNCTIONOFRANGEATTHERECEIVEROUTPUTISDESIRABLEINORDERTOMAINTAINACONSTANTFALSE ALARMRATE.OISEINJECTIONAFTERTHE34#ATTENUATORISUSEDTOOVERCOMETHISPROBLEM !NOISESOURCEANDATTENUATORAREOFTENEMPLOYEDAT)&TOINJECTADDITIONALNOISETO COMPENSATEFORTHEREDUCEDNOISEAFTERTHE34#ATTENUATOR$IGITALCONTROLOFTHENOISE INJECTIONISSYNCHRONIZEDWITHTHE34#ATTENUATIONTOPROVIDEANEFFECTIVECONSTANT NOISELEVELATTHE!$CONVERTERINPUT 'AIN#ONTROL#OMPONENTS -OSTMODERNRADARSPERFORMGAINCONTROLDIGITALLY $IGITALCONTROLPERMITSCALIBRATIONOFEACHATTENUATIONVALUETODETERMINETHEDIFFER ENCE BETWEEN THE ACTUAL ATTENUATION AND THAT COMMANDED BY INJECTING TEST SIGNALS DURINGDEADTIME )NTHEPAST GAINCONTROLLEDAMPLIFIERSWEREUSEDEXTENSIVELYTOCONTROLANDADJUST RECEIVERGAIN2ECENTLY THISAPPROACHHASLARGELYBEENREPLACEDUSINGDIGITALSWITCHED ORANALOGVOLTAGEORCURRENT CONTROLLEDATTENUATORSDISTRIBUTEDTHROUGHOUTTHERECEIVER CHAIN6ARIABLEATTENUATORSHAVEANUMBEROFADVANTAGESOVERVARIABLEGAINAMPLIFI ERSTHEYTYPICALLYPROVIDEBROADERBANDWIDTHS GREATERGAINCONTROLACCURACY GREATER PHASESTABILITY IMPROVEDDYNAMICRANGE ANDFASTERSWITCHINGSPEED 4HECHOICEBETWEENVOLTAGECONTROLLEDANDSWITCHEDATTENUATIONDEPENDSONTRADE OFFSBETWEENPERFORMANCEOFAVARIETYOFPARAMETERS3WITCHEDATTENUATORSGENERALLY PROVIDEMAXIMUMATTENUATIONACCURACY FASTERSWITCHINGSPEED IMPROVEDAMPLITUDE ANDPHASESTABILITY GREATERBANDWIDTH HIGHERDYNAMICRANGE ANDHIGHERPOWERHAN DLINGCAPABILITY6OLTAGEORCURRENTCONTROLLEDATTENUATORS CONTROLLEDVIAA$!CON VERTER TYPICALLYPROVIDEIMPROVEDRESOLUTIONANDLOWERINSERTIONLOSS 'AINCONTROLATTENUATORSAREOFTENINCORPORATEDWITHINTHERECEIVERATBOTH2&AND )&2&ATTENUATIONISUSEDTOPROVIDEINCREASEDDYNAMICRANGEINTHEPRESENCEOFLARGE TARGETRETURNS"YPLACINGTHEATTENUATIONASCLOSETOTHEFRONTENDASPOSSIBLE LARGE SIGNALSCANBEHANDLEDBYMINIMIZINGGAINCOMPRESSION INTERMODULATION ORCROSS MODULATION DISTORTION IN THE MAJORITY OF RECEIVER COMPONENTS4HE DISADVANTAGE OF USINGFRONT ENDATTENUATIONISTHATITWILLTYPICALLYHAVEALARGERIMPACTONRECEIVER NOISEFIGURETHANATTENUATIONPLACEDLATERINTHERECEIVER4HISISNOTUSUALLYANISSUE WHENTHEINTENTOFADDINGATTENUATIONISTODESENSITIZETHERECEIVERASISTHECASEFOR 34# "ACK END OR )& ATTENUATION IS OFTEN USED TO ADJUST THE GAIN OF THE RECEIVER TO COMPENSATEFORRECEIVERGAINVARIATIONSDUETOCOMPONENTVARIATIONSWHERERECEIVER NOISEFIGUREDEGRADATIONCANNOTBETOLERATED
È°ÇÊ / , &ILTERINGOFTHE%NTIRE2ADAR3YSTEM &ILTERINGPROVIDESTHEPRINCIPALMEANS BYWHICHTHERADARDISCRIMINATESBETWEENTARGETRETURNSANDINTERFERENCEOFMANY TYPES4HEFILTERINGISPERFORMEDBYAVARIETYOFFILTERSTHROUGHOUTTHERECEIVERAND
2!$!22%#%)6%23
È°Óx
INTHESUBSEQUENTDIGITALSIGNALPROCESSING-OSTRADARSTRANSMITMULTIPLEPULSESAT ATARGETBEFORETHEANTENNABEAMISMOVEDTOADIFFERENTDIRECTION ANDTHEMULTIPLE RETURNSARECOMBINEDINSOMEFASHION4HERETURNSMAYBECOMBINEDUSINGCOHERENT INTEGRATIONORVARIOUSDOPPLERPROCESSINGTECHNIQUESINCLUDING-4) TOSEPARATE DESIREDTARGETSFROMCLUTTER&ROMTHERADARSYSTEMSTANDPOINT THESEAREALLFILTER INGFUNCTIONS ANDINMODERNRADARSYSTEMS THESEFUNCTIONSAREPERFORMEDUSING DIGITALSIGNALPROCESSINGONTHERECEIVEROUTPUT)AND1DATA4HESEFUNCTIONSARE DISCUSSEDINOTHERCHAPTERSOFTHISHANDBOOK4HEPURPOSEOFTHEFILTERINGWITHIN THE RECEIVER IS TO REJECT OUT OF BAND INTERFERENCE AND DIGITIZE THE RECEIVED SIGNAL WITHTHEMINIMUMOFERRORSOTHATOPTIMUMFILTERINGCANBEPERFORMEDUSINGDIGITAL SIGNALPROCESSING -ATCHED &ILTERING !LTHOUGH MATCHED FILTERING IS TYPICALLY NOW PERFORMED WITHINTHEDIGITALSIGNAL PROCESSINGFUNCTION THECONCEPTISEXPLAINEDHEREFORCOM PLETENESS4HEOVERALLFILTERRESPONSEOFTHESYSTEMISCHOSENTOMAXIMIZETHERADAR PERFORMANCE)FTHESIGNALSPECTRUM8V INTHEPRESENCEOFWHITENOISEWITHPOWER SPECTRAL DENSITY . IS PROCESSED WITH A FILTER WITH FREQUENCY RESPONSE (V THE RESULTINGSIGNAL TO NOISERATIO3.2 ATTIME4ISGIVENBY
C
P
c
8 V ( V E JW4 DV
¯ c
c
. \ ( V \ DV P ¯
c
4HEIDEALFILTERRESPONSEFROMTHESTANDPOINTOFMAXIMIZING3.2ISTHEMATCHEDFILTER THATMAXIMIZESTHE3.2ATTIME4-WHEN
( - V 8 V E JV4-
$EVIATIONSFROMTHEIDEALMATCHEDFILTERRESPONSE(-V PRODUCEAREDUCTIONIN 3.2TERMEDMISMATCHLOSS4HISLOSSCANOCCURFORANUMBEROFREASONSSUCHASTARGET DOPPLERORBECAUSEAFILTERRESPONSEISCHOSENTHATISDIFFERENTFROMTHEMATCHEDFILTER RESPONSEINORDERTOMINIMIZEANOTHERPARAMETERSUCHASRANGESIDELOBES 2ECEIVERFILTERINGISOFTENMODIFIEDFORDIFFERENTWAVEFORMSUSED7HENRADARSYS TEMSUSEWAVEFORMSOFWIDELYVARYINGBANDWIDTHS DIFFERENT)1DATARATESMAYBE USEDTOMINIMIZETHEDIGITALSIGNAL PROCESSINGTHROUGHPUTREQUIREMENTS7ITHDIFFER ENTDATARATESCOMESTHENEEDTOADJUSTTHERECEIVERFILTERINGINORDERTOAVOIDALIASING SIGNALS BEYOND THE .YQUIST RATE!LTHOUGH THESE RADARS ADJUST THEIR FILTERING TO THE WAVEFORMBANDWIDTH THEYDONOTTYPICALLYIMPLEMENTTHEMATCHEDFILTERINGWITHINTHE RECEIVER4HISFUNCTIONISUSUALLYIMPLEMENTEDINDIGITALSIGNALPROCESSING 2ECEIVER&ILTERING &ILTERINGISREQUIREDATVARIOUSPOINTSTHROUGHOUTTHERECEIVER CHAININCLUDING2& )& BASEBANDIFUSED DIGITALFILTERINGPRIORTODECIMATIONREDUC TIONOFTHESAMPLERATE ANDASANINTEGRALPARTOF)1GENERATION 3ECTIONDESCRIBEDHOWSPURIOUSRESPONSESAREGENERATEDINTHEMIXINGPROCESS 5NWANTEDINTERFERENCESIGNALSCANBETRANSLATEDTOTHEDESIREDINTERMEDIATEFREQUENCY EVENTHOUGHTHEYAREWELLSEPARATEDFROMTHESIGNALFREQUENCYATTHEINPUTTOTHEMIXER 4HEABILITYOFTHERADARTOSUPPRESSSUCHUNWANTEDINTERFERENCEISDEPENDENTUPONTHE FILTERINGPRECEDINGTHEMIXERASWELLASONTHEQUALITYOFTHEMIXERITSELF
È°ÓÈ
2!$!2(!.$"//+
4HEPRIMARYFUNCTIONOF2&FILTERINGISTHEREJECTIONOFTHEIMAGERESPONSEDUETO THEFIRSTDOWNCONVERSION)MAGEREJECTIONFILTERINGCANBEALLEVIATEDUSINGANIMAGE REJECTMIXERHOWEVER THEMAXIMUMREJECTIONACHIEVABLEBYIMAGEREJECTMIXERSIS TYPICALLY INADEQUATE WITHOUT THE USE OF ADDITIONAL REJECTION THROUGH FILTERING 4HIS IMAGE SUPPRESSIONPROBLEMISTHEREASONWHYSOMERECEIVERSDONOTTRANSLATEFROMTHE RECEIVEDSIGNALFREQUENCYDIRECTLYTOTHEFINALINTERMEDIATEFREQUENCYINASINGLESTEP 4HEOTHERSPURIOUSPRODUCTSOFAMIXERGENERALLYBECOMEMORESERIOUSIFTHERATIO OF INPUT TO OUTPUT FREQUENCIES OF THE DOWNCONVERTER IS LESS THAN 4HE SPURIOUS EFFECTSCHART&IGURE SHOWSTHATTHEREARECERTAINCHOICESOFFREQUENCYRATIOTHAT PROVIDESPURIOUS FREEFREQUENCYBANDS APPROXIMATELYOFTHEINTERMEDIATEFRE QUENCYINWIDTH"YTHEUSEOFAHIGHFIRST)& ONECANELIMINATETHEIMAGEPROBLEM ANDPROVIDEAWIDETUNINGBANDFREEOFSPURIOUSEFFECTS&ILTERINGPRIORTOTHEMIXER REMAINSIMPORTANT HOWEVER BECAUSETHENEIGHBORINGSPURIOUSRESPONSESAREOFRELA TIVELYLOWORDERANDMAYPRODUCESTRONGOUTPUTSFROMTHEMIXER2&FILTERINGISALSO IMPORTANTASITREDUCESOUT OF BANDINTERFERENCEBEFOREITCANCAUSEINTERMODULATIONOR CROSS MODULATIONDISTORTIONWITHINTHERECEIVER )FTHERECEIVEROPERATINGBANDWIDTHISALARGEPERCENTAGEOFTHE2&FREQUENCY SOME FORMOFSWITCHEDORTUNABLE2&FILTERINGMAYBEREQUIREDSOTHATTHEIMAGERESPONSEIS REJECTEDASITMOVESTHROUGHTHEOPERATINGBANDWIDTH4HECHOICEBETWEENUSINGSWITCHED ORTUNABLEFILTERINGDEPENDSONTHESWITCHINGSPEED LINEARITY ANDSTABILITYREQUIREMENTSOF THERECEIVER3WITCHEDFILTERSPROVIDETHEFASTESTRESPONSETIME WITHEXCELLENTLINEARITYAND STABILITYBUTCANBEBULKYANDSUFFERFROMTHEADDITIONALLOSSOFTHESWITCHCOMPONENTS !NALTERNATEAPPROACHTHATISSOMETIMESUSEDWITHLARGEOPERATINGBANDWIDTHSIS TOFIRSTUPCONVERTTHEINPUT2&SIGNALTOAN)&FREQUENCYHIGHERTHANTHE2&OPERATING BAND4HISPROCESSVIRTUALLYELIMINATESTHEIMAGERESPONSEPROBLEM ALLOWINGTHEUSE OFASINGLE2&FILTERSPANNINGTHEENTIREOPERATINGBANDWIDTH.ARROWBANDWIDTHFILTER INGCANBEUSEDONTHEHIGH)&ASDEFINEDBYTHESIGNALBANDWIDTHBEFOREDOWNCONVER SIONTOALOWER)&FORDIGITIZATIONORBASEBANDCONVERSION )&FILTERINGISTHEPRIMARYFILTERINGUSEDTODEFINETHERECEIVERBANDWIDTHPRIORTO!$ CONVERSIONINRECEIVERSUSINGEITHER)&SAMPLINGORBASEBANDCONVERSION)N)&SAMPLING RECEIVERS THE)&FILTERACTSASTHEANTI ALIASINGFILTERANDLIMITSTHEBANDWIDTHOFSIGNALS ENTERINGTHE!$CONVERTER)NRECEIVERSUSINGBASEBANDCONVERSION THE)&FILTERSETSTHE RECEIVERBANDWIDTH3UBSEQUENTVIDEOFILTERINGSHOULDBEOFGREATERBANDWIDTHTOPREVENT THEINTRODUCTIONOF)1IMBALANCEDUETOFILTERDIFFERENCESBETWEEN)AND1CHANNELS )N)&SAMPLINGRECEIVERS DIGITALFILTERINGISUSUALLYTHEPRIMARYMEANSOFSETTINGTHE FINALRECEIVERBANDWIDTHANDPROVIDESANTI ALIASREJECTIONREQUIREDTOPREVENTALIASING IN THE DECIMATION OF THE )1 DATA RATE $IGITAL FILTERING CAN BE PRECISELY CONTROLLED TAILORED TO ALMOST ANY DESIRED PASSBAND AND STOP BAND REJECTION REQUIREMENTS4HE DIGITALFILTERSUSEDARETYPICALLYLINEARPHASE&)2FILTERS BUTTHEYCANALSOBETAILOREDTO COMPENSATEFORVARIATIONSINTHEPASSBANDPHASEANDAMPLITUDERESPONSESOF2&AND )&ANALOGFILTERS &ILTER #HARACTERISTICS &ILTER RESPONSES ARE CHARACTERIZED FULLY BY EITHER THEIR FREQUENCY RESPONSE (V OR THEIR IMPULSE RESPONSE HT HOWEVER THEY ARE USUALLY SPECIFIEDBYAVARIETYOFPARAMETERSASDESCRIBEDBELOW$IGITALFILTERSMAYBESPECI FIEDUSINGTHESAMEMEASURES ORBECAUSETHEYCANBESPECIFIEDEXACTLY THEYAREFRE QUENTLYSPECIFIEDBYTHEIRTRANSFERFUNCTION(Z ORIMPULSERESPONSEHN +EY PASSBAND CHARACTERISTICS ARE INSERTION LOSS BANDWIDTH PASSBAND AMPLITUDE ANDPHASERIPPLE ANDGROUPDELAY"ANDWIDTHSAREFREQUENTLYSPECIFIEDINTERMSOF A D" BANDWIDTH HOWEVER IF A LOW PASSBAND VARIATION IS REQUIRED THE SPECIFIED
2!$!22%#%)6%23
È°ÓÇ
BANDWIDTHMAYBE FOREXAMPLE SPECIFIEDASAD"ORD"BANDWIDTH0ASSBAND AMPLITUDEVARIATIONRELATIVETOTHEINSERTIONLOSSISAKEYPARAMETERTHATHASPOTENTIAL IMPACTONRANGESIDELOBESANDCHANNEL TO CHANNELTRACKING0HASERIPPLE IFSPECIFIED ISRELATIVETOABEST FITLINEARPHASEANDHASSIMILAREFFECTSASAMPLITUDERIPPLE'ROUP DELAY THERATEOFCHANGEOFPHASEVSFREQUENCY ISIDEALLYCONSTANTFORLINEARPHASE FILTERS4HEABSOLUTEVALUEOFGROUPDELAYDOESNOTIMPACTTHERANGESIDELOBEPERFOR MANCEHOWEVER THERELATIVEGROUPDELAYBETWEENCHANNELSMUSTBETIGHTLYCONTROLLED ORCOMPENSATEDINMONOPULSE SIDELOBECANCELER ANDDIGITALBEAMFORMINGSYSTEMS !LTHOUGH STOPBAND REJECTION IS CLEARLY A KEY PARAMETER FILTERS WITH FAST ROLL OFF MAYNOTPROVIDETHEREQUIREDPHASEANDIMPULSERESPONSECHARACTERISTICS&IGURE SHOWSTHEMAGNITUDERESPONSEOFSIXDIFFERENTFIFTHORDERLOW PASSFILTERSWITHEQUAL D"BANDWIDTH4HE#HEBSHEVFILTERSANDD"RIPPLE HAVEFLATPASSBAND RESPONSEANDIMPROVEDSTOPBANDREJECTIONRELATIVETOTHEREMAININGFILTERSHOWEVER ASSHOWNIN&IGUREAND&IGURE THEYHAVEINFERIORPHASEGROUPDELAY AND IMPULSERESPONSECHARACTERISTICS $IGITAL FILTERS CAN BE EITHER &INITE )MPULSE 2ESPONSE &)2 OR )NFINITE )MPULSE 2ESPONSE))2 &)2FILTERSARETYPICALLYPREFERREDASTHEIRFINITERESPONSEISDESIRABLE ALONGWITHTHEIRLINEARPHASECHARACTERISTIC0HASELINEARITYISACHIEVEDWITHTHESYM METRICIMPULSERESPONSECONDITIONDEFINEDBY%QORTHEANTI SYMMETRICIMPULSE RESPONSECONDITIONSDEFINEDBY%Q
HN H- N N x -
WHERE-ISTHELENGTHOFTHE&)2FILTERIMPULSERESPONSE
HN H- N N x -
&)'52% -AGNITUDERESPONSEOFLOWPASSFILTERS
È°Ón
2!$!2(!.$"//+
&)'52% 'ROUPDELAYRESPONSEOFLOWPASSFILTERS
&)'52% .ORMALIZEDIMPULSERESPONSEOFLOWPASSFILTERS
2!$!22%#%)6%23
È°Ó
2ANGE 3IDELOBES %RRORS IN FILTER RESPONSES CAN PRODUCE DEGRADATION IN PULSE COMPRESSIONRANGESIDELOBES4HEEFFECTOFAFILTERRESPONSEONRANGEORTIMESIDELOBES CAN BE SEEN BY TAKING THE FILTER IMPULSE RESPONSE HT AND ADDING TO THIS A DELAYED IMPULSE RESPONSE LOG@ D" BELOW THE MAIN RESPONSE TO PRODUCE THE MODIFIED RESPONSEHgT WHICHISGIVENBY
HgT HT @HT 4
5SINGTHEPROPERTYOFTIMESHIFTINGOFTHE&OURIERTRANSFORM THERESULTANTFREQUENCY RESPONSEISGIVENBY
( `V ( V @ E JV4 ( V
4HUS FORSMALLVALUESOF@ THERESULTINGMAGNITUDEANDPHASERESPONSEISTHATOFTHE ORIGINALFILTERMODIFIEDBYASINUSOIDALPHASEANDAMPLITUDEMODULATIONASGIVENHERE
\ ( `V \ \ ( V \ A COSV4
( `V ( V @ SINV 4
4HEREFORE IFTHEREARENRIPPLESACROSSTHEFILTERBANDWIDTH" THERANGESIDELOBE OCCURSATTIME4GIVENBY
4 N"
!SSUMINGACOMPRESSEDPULSEWIDTHOF" VALUESOFN WILLPUTTHERANGE SIDELOBE WITHIN THE MAIN LOBE OF THE TARGET RETURN RESULTING IN A DISTORTION OF THE MAINLOBERESPONSE #HANNEL -ATCHING 2EQUIREMENTS 2ADAR RECEIVERS WITH MORE THAN ONE RECEIVER CHANNEL TYPICALLY REQUIRE SOME DEGREE OF PHASE AND AMPLITUDE MATCHING OR TRACKING BETWEEN CHANNELS )N ORDER TO OPERATE EFFECTIVELY SIDELOBE CANCELER CHANNELSMUSTTRACKVERYCLOSELY#ONSTANTOFFSETSINGAINORPHASEDONOTDEGRADE SIDELOBECANCELERPERFORMANCE BUTSMALLVARIATIONSINPHASEANDAMPLITUDEACROSS THEBANDWIDTHCAUSESIGNIFICANTDEGRADATION&OREXAMPLE ACHIEVINGACANCELLATION RATIOOFD"REQUIRESAGAINTRACKINGOFLESSTHAND"ACROSSTHERECEIVERBAND WIDTH&ILTERSARETHEMAINSOURCEOFAMPLITUDEANDPHASERIPPLEACROSSTHESIGNAL BANDWIDTH AS OTHER COMPONENTS SUCH AS AMPLIFIERS AND MIXERS ARE TYPICALLY RELA TIVELYBROADBAND4HEDEGREEOFTRACKINGREQUIREDFORSIDELOBECANCELEROPERATION WASPREVIOUSLYACHIEVEDBYPROVIDINGMATCHEDSETSOFFILTERSWITHTIGHTLYTRACKING AMPLITUDEANDPHASERESPONSES-ODERNDIGITALSIGNALPROCESSINGALLOWSTHECORREC TIONOFTHESECHANNEL TO CHANNELVARIATIONSUSING&)2EQUALIZATION3ECTION OR CORRECTIONINTHEFREQUENCYDOMAININTHEDIGITALSIGNALPROCESSOR ALLOWINGTHEUSE OFLESSTIGHTLYCONTROLLEDFILTERS
È°nÊ / ,!PPLICATIONS ,IMITERSAREUSEDTOPROTECTTHERECEIVERFROMDAMAGEANDTOCON TROL SATURATION THAT MAY OCCUR WITHIN THE RECEIVER 7HEN RECEIVED SIGNALS SATURATE SOMESTAGEOFTHERADARRECEIVERTHATISNOTEXPRESSLYDESIGNEDTOCOPEWITHSUCHA
È°Îä
2!$!2(!.$"//+
SITUATION THEDISTORTIONSCANRESULTINSEVERELYDEGRADEDRADARPERFORMANCE ANDTHE DISTORTION OF OPERATING CONDITIONSCANPERSISTFORSOMETIMEAFTERTHESIGNALDISAP PEARS6IDEOSTAGESAREMOSTVULNERABLEANDTAKELONGERTORECOVERTHAN)&STAGES SOITISCUSTOMARYTOINCLUDEALIMITERINTHELAST)&STAGE DESIGNEDTOQUICKLYREGAIN NORMALOPERATINGCONDITIONSIMMEDIATELYFOLLOWINGTHEDISAPPEARANCEOFALIMITING SIGNAL,IMITINGPRIORTOTHE!$CONVERTERALSOPREVENTSTHEDISTORTIONTHATOCCURS WHEN SIGNALS EXCEED FULL SCALE!LTHOUGH!$ CONVERTERS CAN OFTEN HANDLE MODEST OVERLOADWITHFASTRECOVERY THEDISTORTIONTHATOCCURSDEGRADESSIGNALPROCESSINGSUCH ASDIGITALPULSECOMPRESSIONANDCLUTTERREJECTION7ITH)&LIMITING THESEHARMONICS AREFILTEREDOUTUSINGBANDPASSFILTERINGAFTERLIMITINGPRIORTO!$CONVERSION MINI MIZINGTHEDEGRADATIONDUETOLIMITING !LLRADARSYSTEMSCONTAINSOMEFORMOF4RANSMIT2ECEIVE42 DEVICETOPROTECT THERECEIVEELECTRONICSFROMTHEHIGH POWERTRANSMITSIGNAL)NMANYSYSTEMS AN2& FRONT ENDLIMITERISALSOREQUIREDINORDERTOPREVENTTHERECEIVERFROMBEINGDAMAGED BYHIGHINPUTPOWERLEVELSFROMTHEANTENNATHATMAYOCCURASARESULTOFLEAKAGEFROM THE42DEVICEDURINGTRANSMITMODEORFROMINTERFERENCEDUETOJAMMERSOROTHER RADARSYSTEMS4HESELIMITERSARETYPICALLYDESIGNEDTOLIMITWELLABOVETHEMAXIMUM SIGNALSTOBEPROCESSEDBYTHERECEIVER )N THE PAST LIMITERS WERE USED TO PERFORM A VARIETY OF ANALOG SIGNAL PROCESSING FUNCTIONS(ARDLIMITERSWITHASMUCHASD"OFLIMITINGRANGEWEREUSEDWITHSOME DESIGNEDTOLIMITON RECEIVERNOISE!PPLICATIONSTHATUTILIZEHARDLIMITING INCLUDING PHASE DETECTORSANDPHASE MONOPULSERECEIVERS AREDESCRIBEDIN3ECTIONOFTHE SECONDEDITIONOFTHISHANDBOOK-ODERNRADARSYSTEMSAREMOSTLYDESIGNEDTOMAXI MIZETHELINEAROPERATINGREGION WITHLIMITERSUSEDONLYTOHANDLEEXCESSIVELYLARGE SIGNALSTHATINEVITABLYEXISTUNDERWORSTCASECONDITIONS #HARACTERISTICS 4HE IDEAL LIMITER IS PERFECTLY LINEAR UP TO THE POWER LEVEL AT WHICHLIMITINGBEGINSFOLLOWEDBYATRANSITIONREGIONBEYONDWHICHTHEOUTPUTPOWER REMAINSCONSTANT)NADDITION THEINSERTIONPHASEISCONSTANTFORALLINPUTPOWERLEV ELS ANDRECOVERYFROMLIMITINGISINSTANTANEOUS4HEOUTPUTWAVEFORMFROMABAND PASS LIMITER IS SINUSOIDAL WHEREAS THE OUTPUT WAVEFORM FROM A BROADBAND LIMITER APPROACHESASQUAREWAVE$EVIATIONSFROMTHEIDEALCHARACTERISTICSCANDEGRADERADAR PERFORMANCEINAVARIETYOFWAYS ,INEARITY "ELOW ,IMITING /NE MAJOR DRAWBACK OF ADDING A LIMITER STAGE TO A RECEIVER CHANNEL IS THAT IT IS INHERENTLY NONLINEAR 3INCE ANY PRACTICAL LIMITER HAS A GRADUALTRANSITIONINTOLIMITING THELIMITERISOFTENTHELARGESTCONTRIBUTORTORECEIVER CHANNEL NONLINEARITY IN THE LINEAR OPERATING REGION AND CAN CAUSE SIGNIFICANT INTER MODULATIONDISTORTIONOFIN BANDSIGNALS&ORTHISREASON THEPRIMARYLIMITINGSTAGEIS USUALLYLOCATEDATTHEFINAL)&STAGEWHEREMAXIMUMFILTERINGOFOUT OF BANDINTERFER ENCEHASBEENACHIEVED4HELOWEROPERATINGFREQUENCYALSOALLOWSIMPLEMENTATIONOF ALIMITERTHATMORECLOSELYMATCHESTHEIDEALCHARACTERISTICS ,IMITING !MPLITUDE 5NIFORMITY .O SINGLE STAGE LIMITER WILL EXHIBIT A CONSTANT OUTPUT OVER A WIDE RANGE OF INPUT SIGNAL AMPLITUDES /NE CAUSE IS APPARENT IF ONE CONSIDERSTHEEFFECTOFASINGLE STAGELIMITERHAVINGAPERFECTLYSYMMETRICALCLIPPINGAT VOLTAGESo%&ORASINUSOIDALINPUT THEOUTPUTSIGNALATTHETHRESHOLDOFLIMITINGIS
V %SINVT
2!$!22%#%)6%23
ȰΣ
ANDWHENTHELIMITERISFULLYSATURATEDANDTHEOUTPUTWAVEFORMISRECTANGULAR ITIS GIVENBYTHE&OURIERSERIES
VO`
% c SIN NVT P N £ N
WHICHISANINCREASEOFLOGO D"INTHEPOWEROFTHEFUNDAMENTAL )N PRACTICE THE AMPLITUDE PERFORMANCE IS ALSO DEGRADED BY CAPACITIVE COUPLING BETWEEN INPUT AND OUTPUT OF EACH LIMITING STAGE CHARGE STORAGE IN TRANSISTORS AND DIODES AND2#TIMECONSTANTSTHATPERMITCHANGESINBIASWITHSIGNALLEVEL&ORTHESE REASONS TWOORMORELIMITERSTAGESMAYBECASCADEDWHENGOODAMPLITUDEUNIFORMITY ISREQUIREDOVERAWIDEDYNAMICRANGE 0HASE5NIFORMITY 4HECHANGEOFINSERTIONPHASEOFTHELIMITERWITHAMPLITUDEIS LESSOFACONCERNFORMODERNRADARSYSTEMSTHATOPERATEPRIMARILYINTHELINEAROPERAT INGREGION(OWEVER MAINTAININGCONSTANTINSERTIONPHASEDURINGLIMITINGPRESERVES THE PHASE OF TARGET RETURNS IN THE PRESENCE OF LIMITING CLUTTER OR INTERFERENCE 4HE CHANGEOFINSERTIONPHASEWITHSIGNALAMPLITUDEISGENERALLYDIRECTLYPROPORTIONALTO THEFREQUENCYATWHICHITISOPERATED 2ECOVERY4IME 4HERECOVERYTIMEOFALIMITERISAMEASUREOFHOWQUICKLYTHE LIMITERRETURNSTOLINEAROPERATIONAFTERTHELIMITINGSIGNALISREMOVED&ASTRECOVERYIS PARTICULARLYIMPORTANTWHENTHERADARISEXPOSEDTOIMPULSIVEINTERFERENCE
È°Ê É+Ê " 1 /",!PPLICATIONS 4HE )1 DEMODULATOR ALSO REFERRED TO AS A QUADRATURE CHANNEL RECEIVER QUADRATUREDETECTOR SYNCHRONOUSDETECTOR ORCOHERENTDETECTOR PERFORMSFRE QUENCYCONVERSIONOFSIGNALSATTHE)&FREQUENCYTOACOMPLEXREPRESENTATION ) J1 CENTEREDATZEROFREQUENCY4HEBASEBANDIN PHASE) ANDQUADRATURE PHASE1 SIGNALS AREDIGITIZEDUSINGAPAIROF!$CONVERTERSPROVIDINGAREPRESENTATIONOFTHE)&SIGNAL INCLUDINGPHASEANDAMPLITUDEWITHOUTLOSSOFINFORMATION4HERESULTINGDIGITALDATACAN THENBEPROCESSEDUSINGAWIDEVARIETYOFDIGITALSIGNAL PROCESSINGALGORITHMS DEPEND INGONTHETYPEOFRADARANDMODEOFOPERATION0ROCESSINGSUCHASPULSECOMPRESSION DOPPLERPROCESSING ANDMONOPULSECOMPARISON ALLREQUIREAMPLITUDEANDPHASEINFOR MATION4HEPREDOMINANCEOFDIGITALSIGNALPROCESSINGINMODERNRADARSYSTEMSHASLED TOALMOSTUNIVERSALNEEDFOR.YQUISTRATESAMPLEDDATA)NMANYMODERNRADARSYSTEMS DIGITAL)AND1DATAISNOWGENERATEDUSING)&SAMPLINGFOLLOWEDBYDIGITALSIGNALPRO CESSINGUSEDTOPERFORMTHEBASEBANDCONVERSIONASDESCRIBEDIN3ECTIONSAND )1DEMODULATORSARESTILLUSED THOUGHTHEIRUSEISINCREASINGLYLIMITEDTOWIDERBAND WIDTHSYSTEMSWHERE!$CONVERTERSARENOTYETAVAILABLEWITHTHEREQUIREDCOMBINATION OFBANDWIDTHANDDYNAMICRANGETOPERFORM)&SAMPLING )MPLEMENTATION &IGURESHOWSTHEBASICBLOCKDIAGRAMOFA)1DEMODUAL TOR4HE)&SIGNALDESCRIBEDBY%QISSPLITANDFEDTOAPAIROFMIXERSORANALOG MULTIPLIERS4HEMIXER,/PORTSAREFEDWITHAPAIROFSIGNALSINQUADRATURE GENERATED FROMTHEREFERENCEFREQUENCYSIGNAL ORCOHERENTOSCILLATOR#/(/ ANDREPRESENTED
È°ÎÓ
2!$!2(!.$"//+
!("$$ %# $
$
!$
$
" $ !& %!# * "!(# # )# ' # !$
!("$$ %#
&)'52% )1DEMODULATOR
INCOMPLEXFORMIN%Q)GNORINGANYMIXERINSERTIONLOSSORLOSSASSOCIATEDWITH THE)&SPLIT THECOMPLEXREPRESENTATIONOFTHEMIXEROUTPUTISGIVENBY%Q)DEAL LOW PASSFILTERINGREJECTSTHESECONDSUMFREQUENCY TERMOF%Q PRODUCINGTHE )1DEMODULATOROUTPUTASREPRESENTEDBY%Q !3 J V T P E
E J V T P J !2 §©SINV T J COSV T ¶¸ J!2 E JV T
6)& !3 SINV T P
6#/(/
6)&6#/(/
6) J61
!3 J V T P !! !! E
E J V T P !2 E JV T 3 2 E J;V V T P = 3 2 E J;V V T P =
!3 !2 ! ! ! ! COS;V V T P = J 3 2 SIN;V V T P = 3 2 E J §©V V T P ¶¸
)N IMPLEMENTING AN )1 DEMODULATOR IT IS IMPORTANT TO PROVIDE WELL BALANCED )AND1CHANNELSINORDERTOMAXIMIZEIMAGEREJECTION ASEXPLAINEDBELOW4HEMIXERS MUSTHAVE$#COUPLED)&OUTPUTPORTSANDBEPRESENTEDWITHAGOODMATCHATBOTHTHE WANTEDLOWFREQUENCYOUTPUTANDTHEUNWANTEDSUMFREQUENCY!MATCHATTHESUM FREQUENCYCANBEPROVIDEDUSINGADIPLEXERFILTER6IDEOFILTERINGISREQUIREDTOREJECT THESUMFREQUENCYMIXEROUTPUTSANDALSOPROVIDESREJECTIONOFWIDEBANDNOISEFROM THEVIDEOAMPLIFIERS WHICHWOULDOTHERWISEALIASTOBASEBANDTHROUGHTHE!$CON VERTERSAMPLINGPROCESS PRODUCINGANUNWANTEDDEGRADATIONOFRECEIVERNOISEFIGURE 6IDEOAMPLIFICATIONISOFTENREQUIREDTOINCREASETHESIGNALLEVELTOTHEFULL SCALESIGNAL LEVELOFTHE!$CONVERTERANDALSOALLOWSFORIMPEDANCEMATCHINGOFTHEMIXERAND !$CONVERTER 4HECONVENTIONFORTHE)AND1RELATIONSHIPISTHATTHE)SIGNALPHASELEADSTHE1SIG NALPHASEFORRADARSIGNALSWITHPOSITIVEDOPPLERAPPROACHINGTARGETS &REQUENCYCON VERSIONSWITHINTHERECEIVERUSING,/FREQUENCIESGREATERTHANTHE2&FREQUENCYWILL CAUSEADOPPLERFREQUENCYINVERSION SOEACHCONVERSIONMUSTBECONSIDEREDINORDER TOACHIEVETHECORRECTSENSEOF)AND1ATTHERECEIVEROUTPUT&ORTUNATELY ANINCORRECT )AND1RELATIONSHIPCANEASILYBEFIXEDEITHERINTHERECEIVERORTHESIGNALPROCESSOR BYSWITCHINGTHE)AND1DIGITALDATAORBYCHANGINGTHESIGNOFEITHER)OR1 'AINOR0HASE)MBALANCE )FTHEGAINSOFTHE)AND1CHANNELSARENOTEXACTLY EQUALORIFTHEIR#/(/PHASEREFERENCESARENOTEXACTLYDEGREESAPART ANINPUT SIGNALATFREQUENCYVWILLCREATEANOUTPUTATBOTHTHEDESIREDFREQUENCYV VAND
2!$!22%#%)6%23
È°ÎÎ
AT THE IMAGE FREQUENCY V V 4HE IMAGE SIGNALS GENERATED BY GAIN AND PHASE IMBALANCEAREGIVENBY%QAND%Q&ORSMALLERRORS IFTHERATIOOFVOLTAGE GAINSISo$ ORIFTHEPHASEREFERENCESDIFFERBYOo$ RADIANS THERATIOOFTHE SPURIOUSIMAGEAT VDTOTHEDESIREDOUTPUTOFVDIS$INVOLTAGE $INPOWER OR LOG$ INDECIBELS 6) J61 % COSV D T J $ % SINV D T ¤¥ $ ³´ %E JV D T $ %E JV D T µ ¦ ¤
$³
¤
¤ $ ³ J¥V D T ´ ¤ $ ³ J¥V D T 6) J61 % COSV D T J% SINV D T $ COS ¥ ´ %E ¦ µ SIN ¥ ´ %E ¦ ¦ µ ¦ µ
$ P ³ ´µ
(ISTORICALLY ) AND 1 PHASE AND GAIN CORRECTIONS HAVE BEEN PERFORMED USING ADJUSTMENTSINTHEANALOGSIGNALPATHS ASSHOWNIN&IGURE'AINERRORSMAY BECORRECTEDBYACHANGEINGAININTHE)&ORVIDEOSTAGESOFEITHERORBOTH)AND1 CHANNELS6IDEOGAINCONTROLMUSTBEIMPLEMENTEDWITHCAREASITCANEXAGGERATE THENONLINEARITYOFTHOSESTAGES4HESECORRECTIONSCANNOWBEIMPLEMENTEDMORE PRECISELYINTHEDIGITALDOMAIN !MEASUREMENTOFTHESIGNALSPECTRUMATTHECENTEROFTHE)&BANDWIDTHINDICATES THE DEGREE OF GAIN AND PHASE IMBALANCE COMPENSATION (OWEVER AS THE FOLLOWING DISCUSSIONWILLEXPLAIN THESUPPRESSIONOFIMAGEENERGYACROSSTHE)&BANDWIDTHMAY BESUBSTANTIALLYLESSTHANINDICATEDBYTHISMEASUREMENTAT)&CENTER 4IME $ELAY AND &REQUENCY 2ESPONSE )MBALANCE )F THE RESPONSES OF THE )AND1CHANNELSARENOTIDENTICALACROSSTHEENTIRESIGNALBANDWIDTH UNWANTEDIMAGE RESPONSESWILLOCCURTHATAREFREQUENCYDEPENDENT/PTIMUMBANDPASSFILTERINGSHOULD
#*$&& '% "
' '
, &
"$ & !#( '#% , $#*% %" +% ) %
'
&' !$
# &
"
!$
#
&'
, #*$&& '%
'
"
&)'52% )1DEMODULATORWITHGAIN PHASE $#OFFSET ANDTIME DELAYADJUSTMENTS
' '
È°Î{
2!$!2(!.$"//+
BEAT)& WHEREITAFFECTS)AND1CHANNELSIDENTICALLY NOTATBASEBAND6IDEOFILTER BANDWIDTH SHOULD BE MORE THAN HALF THE )& BANDWIDTH AND CONTROLLED BY PRECISION COMPONENTSINORDERTOMINIMIZETHECREATIONOFIMAGESIGNALS3UBSTITUTING$V FOR$ IN%QAND%QGIVESTHEIMAGECOMPONENTSFORFREQUENCYDEPENDENTGAINAND PHASEERRORS3IMILARLY SUBSTITUTINGV$4FOR$IN%QGIVESTHEIMAGECOMPONENT DUETOTIME DELAYIMBALANCEINTHE)AND1PATHS3MALLTIME DELAYIMBALANCESCAN BECORRECTEDBYADDINGTIMEDELAYTOTHE!$SAMPLECLOCK ASSHOWNIN&IGURE ,ARGETIME DELAYCORRECTIONSSHOULDBEAVOIDEDASTHEYCANCAUSEPROBLEMSALIGNING THE)AND1DIGITALDATA7HENADDINGTIMEDELAYTOTHESAMPLECLOCK CAREMUSTBE TAKENTOAVOIDADDINGJITTER WHICHCOULDDEGRADETHE!$CONVERTER3.2PERFORMANCE 4IME DELAYCORRECTIONCANALSOBEIMPLEMENTEDEFFECTIVELYINTHEDIGITALDOMAIN AND IFFREQUENCYDEPENDENTPHASEANDAMPLITUDEIMBALANCECORRECTIONISREQUIRED THISIS MOSTEASILYANDEFFECTIVELYPERFORMEDINTHEDIGITALDOMAINUSING&)2FILTERINGOFTHE )AND1DATAORBYPERFORMINGCORRECTIONSINTHEFREQUENCYDOMAINDATAASPARTOFTHE RADARSIGNALPROCESSING .ONLINEARITYIN)AND1#HANNELS #OMPONENTTOLERANCESOFTENLEADTOSOME WHATDIFFERENTNONLINEARITIESIN)AND1 WHICHCANGENERATETHEVARIETYOFSPURIOUS DOPPLERCOMPONENTS 4HEIDEALINPUTSIGNALIS
6 !E JV D T ) J1
%ACHVIDEOCHANNELRESPONSECANBEEXPRESSEDASAPOWERSERIES&ORSIMPLICITY ONLYSYMMETRICALDISTORTIONWILLBECONSIDERED4HE!$OUTPUT INCLUDINGARESIDUAL GAINIMBALANCEOF$ IS
6g)1 6g) J6g1
6g) 6) A6 ) C6 )
D61 6g1 $ 61 B61
3UBSTITUTIONOF%QSANDINTO%QYIELDSTHEAMPLITUDESOFTHESPECTRAL COMPONENTSLISTEDIN4ABLE.OTETHATIFTHENONLINEARITIESIN)AND1WEREIDENTI CALA BC D SPURIOUSCOMPONENTSAT VAND VWOULDNOTBEPRESENTANDTHE IMAGE V WOULDBEPROPORTIONALTOINPUTSIGNALAMPLITUDE3PURIOUSATZERODOPPLER ISNOTDUETODCOFFSETITISTHERESULTOFEVEN ORDERNONLINEARITIESTHATWEREOMITTED FROMTHEABOVEEQUATIONS4HENEGATIVETHIRDHARMONICISTHEDOMINANTCOMPONENT PRODUCEDBYNONLINEARITY 4!",% 3PURIOUS3IGNAL#OMPONENTS'ENERATEDBY)1.ONLINEARITY
3IGNAL&REQUENCY
!MPLITUDEOF3PECTRAL#OMPONENT
V
V
V )NPUT V V V
!C D !A B !C D !$ !A B !C D ! $ !A B !C D !A B !C D !C D
2!$!22%#%)6%23
È°Îx
$#/FFSET 3MALLSIGNALSANDRECEIVERNOISECANBEDISTORTEDBYANOFFSETIN THEMEANVALUEOFTHE!$CONVERTEROUTPUTUNLESSTHEDOPPLERFILTERSUPPRESSESTHIS COMPONENT &ALSE ALARMCONTROLINRECEIVERSWITHOUTDOPPLERFILTERSISSOMETIMESDEGRADEDBY ERRORSOFASMALLFRACTIONOFTHELEASTSIGNIFICANTBIT,3" SOCORRECTIONISPREFERABLY APPLIEDATTHEANALOGINPUTTOTHE!$$#OFFSETSCANBEMEASUREDUSINGDIGITALPRO CESSINGOFTHE!$CONVERTEROUTPUTSANDACORRECTIONAPPLIEDUSING$!CONVERTERS ASSHOWNIN&IGURE$#OFFSETCORRECTIONCANALSOBEPERFORMEDEFFECTIVELYINTHE DIGITALDOMAIN PROVIDEDTHATTHE$#OFFSETATTHEINPUTOFTHE!$CONVERTERISNOTSO LARGETHATITRESULTSINASIGNIFICANTLOSSOFAVAILABLEDYNAMICRANGE -ANYOFTHE)1DEMODULATORERRORSDESCRIBEDABOVEAREEITHERREDUCEDDRAMATI CALLY OR ELIMINATED USING )& SAMPLING 4HIS ALONG WITH THE REDUCTION OF HARDWARE REQUIRED ARE THE REASONS THAT )& SAMPLING DESCRIBED IN 3ECTIONS AND IS BECOMINGTHEDOMINANTAPPROACH
È°£äÊ "/" / Ê " 6 ,/ ,4HEHIGH SPEED!$CONVERTERISAKEYCOMPONENTINRECEIVERSOFMODERNRADARSYS TEMS4HE EXTENSIVE USE OF DIGITAL SIGNAL PROCESSING OF RADAR DATA HAS RESULTED IN A DEMANDFORCONVERTERSWITHBOTHSTATE OF THE ARTSAMPLINGRATESANDDYNAMICRANGE !NALOGTODIGITALCONVERTERSTRANSFORMCONTINUOUSTIMEANALOGSIGNALSINTODISCRETE TIMEDIGITALSIGNALS4HEPROCESSINCLUDESBOTHSAMPLINGINTHETIMEDOMAIN CONVERT INGFROMCONTINUOUSTIMETODISCRETETIMESIGNALSANDQUANTIZATION CONVERTINGFROM CONTINUOUSANALOGVOLTAGESTODISCRETEFIXED LENGTHDIGITALWORDS"OTHTHESAMPLING ANDQUANTIZATIONPROCESSPRODUCEERRORSTHATMUSTBEMINIMIZEDINORDERTOLIMITTHE RADARPERFORMANCEDEGRADATION)NADDITION AVARIETYOFOTHERERRORSSUCHASADDITIVE NOISE SAMPLINGJITTER ANDDEVIATIONFROMTHEIDEALQUANTIZATION RESULTINNON IDEAL !$CONVERSION !PPLICATIONS 4HECONVENTIONALAPPROACHOFUSINGAPAIROFCONVERTERSTODIGI TIZETHE)AND1OUTPUTSOFAN)1DEMODULATORIS INMANYCASES BEINGREPLACEDBY DIGITAL RECEIVER ARCHITECTURES WHERE A SINGLE!$ CONVERTER IS FOLLOWED BY DIGITAL SIGNALPROCESSINGTOGENERATE)AND1DATA$IGITALRECEIVERTECHNIQUESAREDESCRIBED IN3ECTION !LTHOUGHTHEDIVIDINGLINEISARBITRARYANDADVANCINGWITHTHESTATE OF THE ART RADAR RECEIVERS ARE OFTEN CLASSIFIED AS EITHER WIDEBAND OR HIGH DYNAMIC RANGE $IFFERENT RADARFUNCTIONSPUTAGREATEREMPHASISONONEORTHEOTHEROFTHESEPARAMETERS&OR EXAMPLE IMAGINGRADARSPUTAPREMIUMONWIDEBANDWIDTH WHEREASPULSEDOPPLER RADARSREQUIREHIGHDYNAMICRANGE"ECAUSERADARSAREOFTENREQUIREDTOOPERATEINA VARIETYOFMODESWITHDIFFERINGBANDWIDTHANDDYNAMICRANGEREQUIREMENTS ITISNOT UNCOMMONTOUSEDIFFERENTTYPESOF!$CONVERTER SAMPLINGATDIFFERENTRATESFORTHESE DIFFERENTMODES $ATA&ORMATS 4HEMOSTFREQUENTLYUSEDDIGITALFORMATSFOR!$CONVERTERSARE SCOMPLEMENTANDOFFSETBINARY 4HESCOMPLEMENTISTHEMOSTPOPULARMETHODOFDIGITALREPRESENTATIONOFSIGNED INTEGERSANDISCALCULATEDBYCOMPLEMENTINGEVERYBITOFAGIVENNUMBERANDADDINGONE
È°ÎÈ
2!$!2(!.$"//+
4HEMOSTSIGNIFICANTBITISREFERREDTOASTHESIGNBIT)FTHESIGNBITIS THEVALUEISPOSI TIVEIFITIS THEVALUEISNEGATIVE4HEREPRESENTATIONOFVOLTAGEINSCOMPLEMENTFORM ISGIVENBY
% K B.. B. . B. . B
WHERE % ANALOGVOLTAGE
. NUMBEROFBINARYDIGITS
BI STATEOFITHBINARYDIGIT
K QUANTIZATIONVOLTAGE /FFSETBINARYISANALTERNATECODINGSCHEMEINWHICHTHEMOSTNEGATIVEVALUEIS REPRESENTEDBYALLZEROSANDTHEMOSTPOSITIVEVALUEISREPRESENTEDBYALLONES:EROIS REPRESENTEDBYAMOSTSIGNIFICANTBIT-3" OFONEFOLLOWEDBYALLZEROS4HEREPRE SENTATIONOFVOLTAGEINOFFSETBINARYISGIVENBY
% K;B. . B. . B. . B=
4HE 'RAY CODE IS ALSO USED IN CERTAIN HIGH SPEED!$ CONVERTERS IN ORDER TO REDUCETHEIMPACTOFDIGITALOUTPUTTRANSITIONSONTHEPERFORMANCEOFTHE!$CON VERTER4HE'RAYCODEALLOWSALLADJACENTTRANSITIONSTOBEACCOMPLISHEDBYTHECHANGE OFASINGLEDIGITONLY $ELTA 3IGMA #ONVERTERS $ELTA SIGMA CONVERTERS DIFFER FROM CONVENTIONAL .YQUISTRATECONVERTERSBYCOMBININGOVERSAMPLINGWITHNOISE SHAPINGTECHNIQUESTO ACHIEVEIMPROVED3.2INTHEBANDWIDTHOFINTEREST.OISESHAPINGMAYBEEITHERLOW PASSORBANDPASSDEPENDINGONTHEAPPLICATION$ELTA SIGMAARCHITECTURESPROVIDEPOTEN TIALIMPROVEMENTSINSPURIOUS FREEDYNAMICRANGE3&$2 AND3.2OVERCONVENTIONAL .YQUISTCONVERTERSWHERETIGHTTOLERANCESAREREQUIREDTOACHIEVEVERYLOWSPURIOUS PERFORMANCE$IGITALFILTERINGANDDECIMATIONISREQUIREDTOPRODUCEDATARATESTHATCAN BEHANDLEDBYCONVENTIONALPROCESSORS4HISFUNCTIONISEITHERPERFORMEDASANINTEGRAL PARTOFTHE!$CONVERTERFUNCTIONORCANBEINTEGRATEDINTOTHEDIGITALDOWNCONVERSION FUNCTIONUSEDTOGENERATEDIGITAL)AND1DATA ASDESCRIBEDIN3ECTION 0ERFORMANCE#HARACTERISTICS 4HEPRIMARYPERFORMANCECHARACTERISTICSOF!$ CONVERTERS ARE THE SAMPLE RATE OR USABLE BANDWIDTH AND RESOLUTION THE RANGE OVER WHICHTHESIGNALSCANBEACCURATELYDIGITIZED4HERESOLUTIONISLIMITEDBYBOTHNOISE ANDDISTORTIONANDCANBEDESCRIBEDBYAVARIETYOFPARAMETERS 3AMPLE 2ATE 3AMPLING OF BAND LIMITED SIGNALS IS PERFORMED WITHOUT ALIASING DISTORTION PROVIDEDTHATTHESAMPLERATE FS ISGREATERTHAN TWICETHESIGNALBANDWIDTHANDPROVIDEDTHESIG NALBANDWIDTHDOESNOTSTRADDLETHE.YQUISTFRE QUENCY FS ORANYINTEGERMULTIPLE.FS )N CONVENTIONAL BASEBAND APPROACHES SAM PLINGISUSUALLYPERFORMEDATTHEMINIMUMRATETO MEETTHE.YQUISTCRITERIA3INCETHEBASEBAND)AND 1SIGNALSHAVEBANDWIDTHS" EQUALTOHALFTHE )&SIGNALBANDWIDTH ASAMPLERATEJUSTGREATERTHAN &)'52% "ASEBANDSAMPLING THE)&BANDWIDTHISREQUIREDSEE&IGURE
2!$!22%#%)6%23
È°ÎÇ
&)'52% )&SAMPLINGINSECOND.YQUISTREGION
&OR)&SAMPLING AFREQUENCYATLEASTTWICETHE)&BANDWIDTHISREQUIREDHOWEVER OVERSAMPLINGISTYPICALLYEMPLOYEDTOEASEALIASREJECTIONFILTERINGANDTOREDUCETHE EFFECTOF!$CONVERTERQUANTIZATIONNOISE)&SAMPLINGISOFTENPERFORMEDWITHTHE SIGNAL LOCATED IN THE SECOND .YQUIST REGION AS SHOWN IN &IGURE OR IN HIGHER .YQUISTREGIONS 3TATED 2ESOLUTION 4HE STATED RESOLUTION OF AN!$ CONVERTER IS THE NUMBER OF OUTPUTDATABITSPERSAMPLE4HEFULL SCALEVOLTAGERANGEOFA.YQUISTRATECONVERTER ISGIVENBY6&3 .1 WHERE.ISTHESTATEDRESOLUTIONAND1ISTHELEASTSIGNIFICANT BIT,3" SIZE 3IGNAL TO .OISE 2ATIO3.2 3.2ISTHERATIOOFRMSSIGNALAMPLITUDETORMS !$CONVERTERNOISEPOWER&ORANIDEAL!$CONVERTER THEONLYERRORISDUETOQUAN TIZATION0ROVIDEDTHATTHEINPUTSIGNALISSUFFICIENTLYLARGERELATIVETOTHEQUANTIZATION SIZEANDUNCORRELATEDTOTHESAMPLINGSIGNAL THEQUANTIZATIONERRORISESSENTIALLYRAN DOMANDISASSUMEDTOBEWHITE4HERMSQUANTIZATIONNOISEIS1 ANDSIGNAL TO QUANTIZATION NOISERATIO31.2 OFANIDEAL!$CONVERTERISGIVENBY
31.2D" .
0RACTICAL!$CONVERTERSHAVEADDITIONALSAMPLINGERRORSOTHERTHANQUANTIZATION INCLUDINGTHERMALNOISEANDAPERTUREJITTER0ROVIDEDTHATTHESEADDITIONALERRORSCAN BECHARACTERIZEDASWHITE THEYCANBECOMBINEDWITHTHEQUANTIZATIONNOISEWITHA RESULTING3.2LESSTHANTHETHEORETICAL3.2OFTHEIDEALCONVERTER"ECAUSEVARIOUS !$CONVERTERERRORMECHANISMSAREDEPENDENTONINPUTSIGNALLEVELANDFREQUENCY ITISIMPORTANTTOCHARACTERIZEDEVICESOVERTHEFULLRANGEOFINPUTCONDITIONSTOBE EXPECTED4HEAVAILABLESIGNAL TO NOISERATIOOFSTATE OF THE ARTHIGH SPEED!$CON VERTERSHASBEENSHOWNTOFALLOFFBYONE BITD" FOREVERYDOUBLINGOFTHESAMPLE RATE/VER SAMPLINGOFTHESIGNALFOLLOWEDBYFILTERINGANDDECIMATIONPROVIDESAN IMPROVEMENTOFONEHALF BITD" INTHEACHIEVABLESIGNAL TO NOISE RATIOFOREACH DOUBLINGOFTHESAMPLERATE4HUS FORHIGHDYNAMIC RANGEAPPLICATIONS THEBESTPER FORMANCE IS ACHIEVED USING A STATE OF THE ART!$ CONVERTER THAT HAS A MAXIMUM SAMPLERATEJUSTSUFFICIENTFORTHEAPPLICATION 3PURIOUS&REE$YNAMIC2ANGE3&$2 3&$2ISTHERATIOOFTHESINGLE TONESIG NAL AMPLITUDE TO THE LARGEST SPURIOUS SIGNAL AMPLITUDE AND IS USUALLY STATED IN D" 3IMILARTO3.2 THESPURIOUSPERFORMANCEOFAN!$CONVERTERISDEPENDENTONTHE
È°În
2!$!2(!.$"//+
INPUTSIGNALFREQUENCYANDAMPLITUDE4HEFREQUENCYOFSPURIOUSSIGNALSISALSODEPEN DENTONTHEINPUTSIGNALFREQUENCYWITHTHEHIGHESTVALUESTYPICALLYDUETOLOWORDER HARMONICSORTHEIRALIASES7HENUSING)&SAMPLINGWITHASIGNIFICANTOVER SAMPLING RATIOFS" THEWORSTSPURIOUSSIGNALSMAYBEAVOIDEDBYCHOOSINGTHESAMPLE FREQUENCY RELATIVE TO SIGNAL FREQUENCY SUCH THAT THE UNWANTED SPURIOUS SIGNALS FALL OUTSIDETHESIGNALBANDWIDTHOFINTEREST)FTHEWORSTCASESPURIOUSCANBEAVOIDED THE SPECIFIED3&$2ISLESSIMPORTANTTHANTHELEVELSOFTHESPECIFICSPURIOUSCOMPONENTS THATFALLWITHINTHEBANDWIDTHOFINTEREST!GAIN ITISIMPORTANTTOCHARACTERIZEDEVICES OVERTHERANGEOFEXPECTEDOPERATINGCONDITIONS 4HEIMPACTOF!$CONVERTERSPURIOUSSIGNALSONRADARPERFORMANCEDEPENDSONTHE TYPEOFWAVEFORMSBEINGPROCESSEDANDTHEDIGITALSIGNALPROCESSINGBEINGPERFORMED )NAPPLICATIONSUSINGCHIRPWAVEFORMSWITHLARGETIME BANDWIDTHPRODUCTS SPURIOUS SIGNALSARELESSCRITICALASTHEYAREEFFECTIVELYREJECTEDINTHEPULSECOMPRESSIONPRO CESSBECAUSETHEIRCODINGDOESNOTMATCHTHATOFTHEWANTEDSIGNAL)NPULSEDOPPLER APPLICATIONS SPURIOUS SIGNALS ARE OF MUCH GREATER CONCERN BECAUSE THEY CAN CREATE COMPONENTSWITHDOPPLERATAVARIETYOFFREQUENCIESTHATMAYNOTBEREJECTEDBYTHE CLUTTERFILTERING 3IGNAL TO .OISE AND $ISTORTION2ATIO3).!$ 3).!$ISTHERMSSIGNALAMPLI TUDETOTHERMSVALUEOFTHE!$CONVERTERNOISEPLUSDISTORTION4HENOISEPLUSDIS TORTION INCLUDES ALL SPECTRAL COMPONENTS EXCLUDING $# AND THE FUNDAMENTAL UP TO THE.YQUISTFREQUENCY3).!$ISAUSEFULFIGUREOFMERITFOR!$CONVERTERS BUTIN DIGITALRECEIVERAPPLICATIONS WHERETHEWORSTSPURIOUSCOMPONENTSMAYFALLOUTSIDEOF THEBANDWIDTHOFINTEREST ITISNOTNECESSARILYAKEYDISCRIMINATORBETWEENCOMPETING CONVERTERSFORASPECIFICAPPLICATION %FFECTIVE.UMBEROF"ITS%./" 4HETERMEFFECTIVENUMBEROFBITSISOFTENUSED TOSTATETHETRUEPERFORMANCEOFAN!$CONVERTERANDHASBEENSTATEDINTHELITERATURE INTERMSOF3).!$AND3.2 ASGIVENBELOW#ONSEQUENTLY ITISIMPORTANTTODIFFER ENTIATEBETWEENDEFINITIONSWHENUSINGTHISTERM
.EFF ;3).!$D" =
.EFF ;3.2D" =
4WO4ONE)NTERMODULATION$ISTORTION)-$ 4WOTONEINTERMODULATIONDISTORTION ISALSOIMPORTANTINRECEIVERAPPLICATIONS4ESTINGISPERFORMEDWITHTWOSINUSOIDALINPUT SIGNALSOFUNEQUALFREQUENCYANDLEVELSSETSUCHTHATTHESUMOFTHETWOINPUTSDOES NOTEXCEEDTHE!$CONVERTERFULL SCALELEVEL3IMILARTO)-$FORAMPLIFIERS THEMOST SIGNIFICANTDISTORTIONISUSUALLYSECONDORDERORTHIRDORDER)-$PRODUCTS(OWEVER DUETOTHECOMPLEXNATUREOFTHEDISTORTIONMECHANISMIN!$CONVERTERS THEAMPLITUDE OF)-$PRODUCTSISNOTEASILYCHARACTERIZEDANDPREDICTEDBYTHEMEASUREMENTOFAN INPUTINTERCEPTPOINT )NPUT .OISE ,EVEL AND $YNAMIC 2ANGE !CCURATE SETTING OF THE!$ CON VERTERINPUTNOISELEVELRELATIVETOTHE!$CONVERTERNOISEISCRITICALTOACHIEVINGTHE OPTIMUMTRADE OFFBETWEENDYNAMICRANGEANDSYSTEMNOISEFLOOR4OOHIGHALEVEL OFNOISEINTOTHE!$CONVERTERWILLDEGRADETHEAVAILABLEDYNAMICRANGETOOLOW ALEVELWILLDEGRADETHEOVERALLSYSTEMNOISEFLOOR3UFFICIENTTOTALNOISESHOULDBE APPLIEDTOTHE!$CONVERTERINPUTTORANDOMIZEORhWHITENvTHEQUANTIZATIONNOISE
2!$!22%#%)6%23
!
!
" !
È°Î
" ! $
!#
&)'52% )&SAMPLINGNOISESPECTRUMS
4HISCANBEACHIEVEDWITHRMSINPUTNOISER EQUALTOTHE,3"STEPSIZE1 )N ADDITION THEINPUTNOISEPOWERSPECTRALDENSITYSHOULDBESUFFICIENTTOMINIMIZETHE IMPACTONSYSTEMNOISEDUETOTHE!$CONVERTERNOISE4HEIMPACTONOVERALLNOISE DUETOQUANTIZATIONNOISEISGIVENBY R 1 R q1 R R
4YPICALOPERATINGPOINTSAREINTHERANGEOFR1 TOR1 WITHCORRESPONDING NOISEPOWERDEGRADATIONDUETOQUANTIZATIONOFD"ANDD" RESPECTIVELY )NPRACTICE THE3.2OFHIGH SPEEDCONVERTERSISOFTENSUCHTHATTHENOISEOFTHE !$CONVERTERISSIGNIFICANTLYGREATERTHANTHETHEORETICALQUANTIZATIONNOISE)NADDI TION THE!$CONVERTERINPUTSIGNALNOISEBANDWIDTHMAYBESIGNIFICANTLYLESSTHANTHE .YQUISTBANDWIDTH4HISISASIGNIFICANTFACTORIN)&SAMPLINGAPPLICATIONSWHERETHE )&NOISEBANDWIDTHISOFTENLESSTHANOFTHE.YQUISTBANDWIDTH)NTHISCASE THETOTAL INPUTAND!$CONVERTERNOISEMUSTBESUFFICIENTTOWHITENTHEQUANTIZATIONNOISE AND THEPOWERSPECTRALDENSITYOFTHEINPUTNOISESHOULDBESUFFICIENTLYGREATERTHANTHATOF THE!$CONVERTER ASILLUSTRATEDIN&IGURE)NSOMECASES OUT OF BANDNOISEMAY BEADDEDTOWHITENTHE!$CONVERTERQUANTIZATIONNOISEANDSPURIOUSSIGNALS4HEOUT OF BANDNOISEISTHENREJECTEDTHROUGHSUBSEQUENTDIGITALSIGNALPROCESSING 4HERESULTING3.2OFTHESYSTEMAFTERDIGITALFILTERINGWITHRECEIVERBANDWIDTH"2 ANDSAMPLERATEFSISGIVENBY
¤ F ³ 3.2393 D" 3.2!$# D" LOG ¥ 3 ´ LOG 3)& 3!$# ¦ "2 µ
WHERE3)&3!$#ISTHERATIOOFNOISEPOWERSPECTRALDENSITYOFTHE!$CONVERTERINPUT SIGNALTOTHEPOWERSPECTRALDENSITYOFTHE!$CONVERTER4HEDEGRADATIONOFOVERALL SENSITIVITYDUETOTHE!$CONVERTERNOISEISGIVENBY
,D" LOG 3!$#3)&
È°{ä
2!$!2(!.$"//+
!$ #ONVERTER 3AMPLE #LOCK 3TABILITY 4HE STABILITY OF THE SAMPLE CLOCK IS CRITICALTOACHIEVINGTHEFULLCAPABILITYOFAN!$CONVERTER3AMPLE TO SAMPLEVARIA TIONINTHESAMPLINGINTERVAL CALLEDAPERTUREUNCERTAINTYORAPERTUREJITTER PRODUCES ASAMPLINGERROR PROPORTIONALTOTHERATEOFCHANGEOFINPUTVOLTAGE&ORASINUSOIDAL INPUTSIGNAL THE3.2DUETOAPERTUREUNCERTAINTYALONEISGIVENBY
3.2D" LOGOFRJ
WHERE F INPUTSIGNALFREQUENCY
RJ RMSAPERTUREJITTER 3IMILARLY CLOSE TO CARRIERNOISESIDEBANDSPRESENTONTHESAMPLECLOCKSIGNALARE TRANSFERREDTOSIDEBANDSONTHESAMPLEDINPUTSIGNAL REDUCEDBYLOG FF3 D" &OR EXAMPLE IN AN )& SAMPLING APPLICATION WITH THE INPUT SIGNAL Ð OF THE SAMPLE FREQUENCY THECLOSE TO CARRIERPHASENOISEOFTHESAMPLECLOCKWILLBETRANSFERREDTO THEOUTPUTOFTHE!$CONVERTEROUTPUTDATASIGNAL REDUCEDBYD"
È°££Ê / Ê,
6 ,4HE AVAILABILITY OF HIGH SPEED ANALOG TO DIGITAL CONVERTERS CAPABLE OF DIRECT SAM PLING OF RADAR RECEIVER )& SIGNALS HAS RESULTED IN THE ALMOST UNIVERSAL ADOPTION OF DIGITALRECEIVERARCHITECTURESOVERCONVENTIONALANALOG)1DEMODULATION)NADIGITAL RECEIVER A SINGLE!$ CONVERTER IS USED TO DIGITIZE THE RECEIVED SIGNAL AND DIGITAL SIGNAL PROCESSING IS USED TO PERFORM THE DOWNCONVERSION TO ) AND 1 BASEBAND SIG NALS#ONTINUINGADVANCESINSAMPLINGSPEEDSARELEADINGTOSAMPLINGATINCREASING FREQUENCIES SOMETIMESELIMINATINGTHENEEDFORASECONDDOWNCONVERSION WITHTHE POSSIBILITYAPPROACHINGOFSAMPLINGDIRECTLYATTHERADAR2&FREQUENCY4HEBENEFITS OF)&SAMPLINGOVERCONVENTIONALANALOG)1DEMODULATIONARE L
L
L
L
L
L
L
6IRTUALELIMINATIONOF)AND1IMBALANCE 6IRTUALELIMINATIONOF$#OFFSETERRORS 2EDUCEDCHANNEL TO CHANNELVARIATION )MPROVEDLINEARITY &LEXIBILITYOFBANDWIDTHANDSAMPLERATE 4IGHTFILTERTOLERANCE PHASELINEARITY ANDIMPROVEDANTI ALIASFILTERING 2EDUCEDCOMPONENTCOST SIZE WEIGHT ANDPOWERDISSIPATION
4HEUSEOFAHIGH)&FREQUENCYISDESIRABLEASITEASESTHEDOWNCONVERSIONAND FILTERINGPROCESSHOWEVER THEUSEOFHIGHERFREQUENCIESPLACESGREATERDEMANDSON THEPERFORMANCEOFTHE!$CONVERTER$IRECT2&SAMPLINGISCONSIDEREDTHEULTI MATEGOALOFDIGITALRECEIVERS WITHALLTHETUNINGANDFILTERINGPERFORMEDTHROUGH DIGITALSIGNALPROCESSING4HEADVANTAGEBEINGTHEALMOSTCOMPLETEELIMINATIONOF ANALOG HARDWARE (OWEVER NOT ONLY DOES THE!$ CONVERTER HAVE TO SAMPLE THE 2& DIRECTLY BUT UNLESS IT IS PRECEDED BY TUNABLE 2& PRESELECTOR FILTERS THE!$ CONVERTER INPUT MUST HAVE THE DYNAMIC RANGE TO HANDLE ALL OF THE SIGNALS PRES ENT IN THE RADAR BAND SIMULTANEOUSLY 'ENERALLY THE INTERFERENCE POWER ENTERING THE!$CONVERTERISPROPORTIONALTOTHEBANDWIDTHOFCOMPONENTSINFRONTOFTHE
2!$!22%#%)6%23
È°{£
!$CONVERTER4HEREQUIRED!$CONVERTER3.2TOAVOIDSATURATIONONTHEINTERFER INGSIGNALSISGIVENBY
¤ 0 # ³ 3.2!$# D" LOG ¥ ) ´ ¦ . !$# µ
WHERE
0) INTERFERENCEPOWERAT!$CONVERTERINPUT
# CRESTFACTOR
.!$# !$CONVERTERNOISE 4HECRESTFACTORISTHEPEAKLEVELTHATCANBEHANDLEDWITHINTHEFULL SCALERANGE OF THE!$ CONVERTER RELATIVE TO THE RMS INTERFERENCE LEVEL )T IS SET TO ACHIEVE A SUFFICIENTLYHIGHPROBABILITYTHATFULL SCALEWILLNOTBEEXCEEDED&OREXAMPLE WITH GAUSSIANNOISE ACRESTFACTOROFSETSTHEPEAKLEVELATTHERLEVELD"ABOVE THERMSLEVEL WITHAPROBABILITYOFTHATTHEFULL SCALEISNOTEXCEEDEDON EACH!$CONVERTERSAMPLE 3ETTINGTHESYSTEMNOISELEVELPOWERSPECTRALDENSITYINTOTHE!$CONVERTER2D" ABOVETHE!$CONVERTERNOISEGIVES
¤ F. ³ 2 D" LOG ¥ S 393 ´ " . ¦ )& !$# µ
WHERE
.393 SYSTEMNOISEAT!$CONVERTERINPUTINBANDWIDTH")& #OMBINING%QANDGIVESTHEREQUIRED3.2AS
¤ 0 # ")& ³ 3.2!$# D" LOG ¥ ) 2 D" ¦ F3 . 393 ´µ
4HEGENERATIONOFBASEBAND)AND1SIGNALSFROMTHE)&SAMPLED!$CONVERTERDATA ISPERFORMEDUSINGDIGITALSIGNALPROCESSINGANDCANBEIMPLEMENTEDTHROUGHAVARIETY OFAPPROACHES4WOAPPROACHESAREDESCRIBEDNEXT $IGITAL $OWNCONVERSION 4HE DIGITAL DOWNCONVERSION APPROACH IS SHOWN IN &IGURE4HESIGNALISSAMPLEDBYTHE!$CONVERTER FREQUENCYSHIFTEDTOBASE BAND LOW PASSFILTERED ANDDECIMATEDTOPRODUCE)1DIGITALDATA4HESIGNALSPECTRUM ATEACHSTAGEOFTHEPROCESSISSHOWNIN&IGURE)NCONTINUOUS TIME&IGA FREQUENCY IS IN HERTZ AND IS REPRESENTED BY & )N DISCRETE TIME &IG BnE FRE QUENCYISINRADIANSPERSAMPLEANDISREPRESENTEDBYV4HESPECTRUMOFTHEANA LOGINPUTSIGNALXT ISSHOWNIN&IGUREA WITHTHESIGNALSPECTRUMCENTEREDAT &HERTZ4HESIGNALISSAMPLEDBYTHE!$CONVERTERATFREQUENCY&S PRODUCINGTHE W CENTEREDATFREQUENCYV WITHTHE TIMESEQUENCE X N ANDFREQUENCYSPECTRUM 8 IMAGECENTEREDAT V4HE!$CONVERTEROUTPUTSIGNALISTHENFREQUENCYSHIFTEDBY COMPLEXMULTIPLICATIONWITHTHEREFERENCESIGNALE JV N CORRESPONDINGTOAREFERENCE SIGNALROTATINGATVRADIANSPERSAMPLE CENTERINGTHESIGNALSPECTRUM 8V ABOUT ZERO4HEUNWANTEDIMAGEISRE CENTEREDAT VIFV OOR V OIFVaO 4HEUNWANTEDIMAGEISTHENREJECTEDUSINGTHE&)2FILTERWITHIMPULSERESPONSEHN PRODUCING OUTPUT X} N WITH SPECTRUM 8} V &INALLY THE SAMPLE RATE IS REDUCED BY
È°{Ó
2!$!2(!.$"//+
&)'52% $IGITALDOWNCONVERSIONARCHITECTURE
SELECTINGEVERY$THSAMPLE0ROVIDEDTHEFILTERRESPONSE(V HASSUFFICIENTREJECTION FORFREQUENCIES\V \ q P $ THEREWILLBENEGLIGIBLEALIASINGANDLOSSOFINFORMATIONIN THEDECIMATIONPROCESS
&)'52% $IGITALDOWNCONVERSIONSPECTRA
2!$!22%#%)6%23
È°{Î
&)'52% (ILBERTTRANSFORMERARCHITECTURE
(ILBERT 4RANSFORMER !N ALTERNATIVE DIGITAL RECEIVER ARCHITECTURE IS SHOWN IN &IGUREWITHTHERELEVANTSIGNALSPECTRASHOWNIN&IGURE4HE!$CONVERTER OUTPUT SIGNAL X N IS PROCESSED USING A (ILBERT TRANSFORMER COMPRISING &)2 FILTERS HN ANDHN WHERETHEFREQUENCYRESPONSESAREGIVENBY
\( V \ y \( V \ y \V V \ a "
( V ª J \ V V \ a " y
' V «¬ J \ V V \ a "
AND
4HEFILTEROUTPUTSFORMTHEDESIREDCOMPLEXVALUEDSIGNALX N CENTEREDATFREQUENCY V WHILEREJECTINGTHEIMAGECENTEREDAT V4HEFINALSTAGEISTOPERFORMAFREQUENCY SHIFTANDSAMPLERATEREDUCTIONBYDECIMATINGTHESIGNALBYSELECTINGEVERY$THSAMPLE
&)'52% 3PECTRAOF(ILBERTTRANSFORMERRECEIVER
È°{{
2!$!2(!.$"//+
)FTHESPECTRUMOF8V ISCENTEREDATFREQUENCYV OK$ K THEDECIMATION WILLCENTERTHESPECTRUM9V ABOUTZERO0ROVIDEDTHEFILTERRESPONSESHAVESUFFICIENT REJECTIONFORFREQUENCIES\VoV\qO$ THEREWILLBENEGLIGIBLEALIASINGANDLOSSOF INFORMATIONINTHEDECIMATIONPROCESS )1%RRORS $IGITAL)AND1GENERATIONDOESNOTPRODUCESIGNALSWITHOUTERROR AS IS OFTEN STATED BUT INSTEAD ALLOWS THE GENERATION OF THESE SIGNALS WITH ERRORS THAT ARE SUFFICIENTLY SMALL TO BE CONSIDERED NEGLIGIBLE 4HE PRIMARY CAUSE OF THE IMBALANCE IS THE NON IDEAL FILTER RESPONSES!N INFINITE NUMBER OF TAPS WOULD BE REQUIREDTOSETTHEPASSBANDGAINTOUNITYANDTHESTOPBANDGAINTOZEROHOWEVER FOR MOST APPLICATIONS SUFFICIENT PROCESSING RESOURCES ARE AVAILABLE TO REDUCE THE ERRORSTOINSIGNIFICANTLEVELS&INITELENGTHWORDSFORFILTERCOEFFICIENTSPRODUCENON IDEALFILTERRESPONSES4HEEFFECTONPASSBANDRESPONSEISTYPICALLYNEGLIGIBLE BUT SIGNIFICANTDISTORTIONOFTHEFILTERSTOPBANDREJECTIONCANOCCUR POTENTIALLYEFFECTING )1BALANCE $IGITAL $OWNCONVERSION 5SING -ULTIRATE 0ROCESSING AND 0OLYPHASE FILTERS 4HEREAREMANYVARIATIONSTOTHESEBASICAPPROACHES ANDSPECIFICIMPLE MENTATIONSOFTENUTILIZEEFFICIENTAPPROACHESTHATMINIMIZETHENUMBEROFCALCULA TIONS REQUIRED WITH EMPHASIS ON REDUCING THE NUMBER OF MULTIPLICATIONS AS THESE REQUIRESIGNIFICANTLYMORERESOURCESTHANADDITIONS4WOTECHNIQUESUSEDTOREDUCE THE&)2FILTERPROCESSINGBURDENAREMULTIRATEPROCESSINGANDPOLYPHASEFILTERING 4HEDIGITALDOWNCONVERSIONAPPROACHISSHOWNIN&IGUREUSINGMULTIRATEPRO CESSING4HEFIRST&)2FILTERHN PROVIDESSUFFICIENTREDUCTIONTOPREVENTALIASING INTHEFIRSTDECIMATIONBYFACTOR$ THESECONDFILTERHN PROVIDESALIASREDUCTION FORTHESECONDDECIMATIONANDCANALSOBEUSEDTOCORRECTPASSBANDRIPPLEORDROOP DUETOFILTERHN &ORLARGEDECIMATIONFACTORS MORETHANTWODECIMATIONSTAGES MAYBEUSED !POPULARFILTERFORTHEFIRSTSTAGEISTHE#ASCADED)NTEGRATOR#OMB#)# DECIMA TORFILTERTHATCANBEIMPLEMENTEDWITHOUTMULTIPLIERS4HESEFILTERSPROVIDEREJECTIONIN THESTOPBANDATFREQUENCIESTHATALIASTOTHEPASSBANDASARESULTOFDECIMATION3INCE THEY PROVIDE RELATIVELY LARGE PASSBAND DROOP AND SLOW STOPBAND REJECTION THEY ARE GENERALLYFOLLOWEDBYA&)2FILTERTHATCANBOTHCORRECTFOR#)#PASSBANDDROOPAND
&)'52% $IGITALDOWNCONVERSIONARCHITECTURE
2!$!22%#%)6%23
È°{x
PROVIDETHEDESIREDSTOPBANDREJECTIONRESPONSE4HEKTHORDER#)#FILTERFORDECIMA TIONFACTOR$HASTRANSFERFUNCTION §$ ¶ ( + Z ¨£ Z M · ©M ¸
+
+
§ Z $ ¶ ¨
· © Z ¸
!POLYPHASEFILTERISAFILTERBANKTHATSPLITSANINPUTSIGNALINTO$SUB BANDFILTERS OPERATINGATASAMPLERATEREDUCEDBYAFACTOR$ PROVIDINGACOMPUTATIONALLYEFFICIENT APPROACHTOPERFORMINGTHE&)2FILTERINGFOLLOWEDBYDECIMATIONINADIGITALRECEIVER 2ATHERTHANCOMPUTINGALLTHEFILTEROUTPUTSAMPLESANDONLYUSINGEVERY$THSAMPLE THEPOLYPHASEAPPROACHCALCULATESONLYTHOSETHATAREACTUALLYUSED&IGUREAND %QDEFINEHOWTHEFILTERWITHIMPULSERESPONSEHN FOLLOWEDWITHDECIMATION BYFACTOR$ ISIMPLEMENTEDINAPOLYPHASESTRUCTURE4HEINPUTSIGNALXN ISDIVIDED INTO$PARALLELPATHSBYTHEhCOMMUTATOR vWHICHOUTPUTSSAMPLESINTURN ROTATINGINA COUNTERCLOCKWISEDIRECTION TOEACHOFTHE&)2FILTERSOPERATINGATTHEREDUCEDSAMPLE RATE4HEOUTPUTSOFTHE&)2FILTERSARESUMMEDTOPRODUCETHEOUTPUTSIGNALYM 4HIS ARCHITECTUREISBENEFICIALASITPROVIDESANAPPROACHTHATCANBEEASILYPARALLELIZEDAT RATE&8$
PKN HK N$ K x $
N x +
-ULTI #HANNEL2ECEIVER#ONSIDERATIONS -ODERNRADARSYSTEMSRARELYCON TAINONLYONERECEIVERCHANNEL-ONOPULSEPROCESSING FOREXAMPLE REQUIRESTWO OR MORE CHANNELS TO PROCESS SUM AND DELTA SIGNALS !DDITIONALLY THE CHANNELS MUSTBECOHERENT SYNCHRONIZEDINTIME ANDWELLMATCHEDINPHASEANDAMPLITUDE $IGITAL BEAMFORMING SYSTEMS REQUIRE A LARGE NUMBER OF CHANNELS WITH SIMILAR COHERENCEANDSYNCHRONIZATIONREQUIREMENTSANDTIGHTPHASEANDAMPLITUDETRACK ING 4HE COHERENCE REQUIREMENT DICTATES THE RELATIVE PHASE STABILITY OF ,/ AND !$CONVERTERCLOCKSIGNALSUSEDFOREACHRECEIVECHANNEL4HETIMESYNCHRONIZA TION REQUIREMENT MEANS THAT!$ CONVERTER CLOCK SIGNALS FOR EACH CHANNEL MUST BEALIGNEDINTIMEANDDECIMATIONMUSTBEPERFORMEDINPHASEFOREACHCHANNEL 0HASE AND AMPLITUDE IMBALANCE BETWEEN CHANNELS IS A RESULT OF VARIATION IN THE
&)'52% $ECIMATIONUSINGPOLYPHASEFILTERS
È°{È
2!$!2(!.$"//+
ANALOGCIRCUITRYPRIORTOANDWITHINTHE!$CONVERTER)FTHE)&FILTERBANDWIDTHIS WIDERELATIVETOTHEDIGITALRECEIVERBANDWIDTH THEMAJORITYOFTHEERRORBETWEEN CHANNELSWILLBEACONSTANTGAINANDPHASEOFFSETACROSSTHERECEIVERBANDWIDTH ! SINGLE CORRECTION APPLIED AS A COMPLEX MULTIPLICATION OF )1 DATA WILL COR RECT FOR GAIN AND PHASE OFFSETS AND IS USUALLY ADEQUATE TO PROVIDE THE REQUIRED CHANNEL TRACKING FOR MONOPULSE APPLICATIONS 7HEN TIGHTER CHANNEL TRACKING IS REQUIRED SUCHASFORSIDELOBECANCELERORDIGITALBEAMFORMINGAPPLICATIONS &)2 FILTEREQUALIZATIONCANBEUSEDTOCORRECTFORFREQUENCYDEPENDENTVARIATIONSACROSS THE RECEIVER BANDWIDTH &)2 FILTER EQUALIZATION CAN BE PERFORMED EITHER SUBSE QUENTTOTHE&)2FILTERINGUSEDTOGENERATE)1DATAORCOMBINEDWITHTHESEFILTERS )T SHOULD BE NOTED THAT TO CORRECT FOR FREQUENCY AND PHASE VARIATION ACROSS THE RECEIVERBANDWIDTHREQUIRES&)2FILTERSWITHCOMPLEXCOEFFICIENTS APPLIEDEQUALLY TO)AND1DATA2EALVALUECOEFFICIENTSTYPICALLYUSEDIN)1GENERATIONPROVIDEFIL TERRESPONSESSYMMETRICALABOUTZEROFREQUENCY#ORRECTIONOF)&FILTERFREQUENCY RESPONSEERRORSWILL INGENERAL REQUIREASYMMETRICFREQUENCYCORRECTIONTHATCAN ONLYBEPROVIDEDATBASEBANDUSINGCOMPLEXCOEFFICIENTS 4HEDEGREETOWHICHTHESEMULTIPLERECEIVERCHANNELSMUSTTRACKDEPENDSONTHE SPECIFIC SYSTEM REQUIREMENTS !LTHOUGH MODERN SYSTEMS TYPICALLY INCLUDE SOME DEGREEOFCHANNELEQUALIZATIONFUNCTION AREASONABLEDEGREEOFTRACKINGBETWEENGAIN PHASE ANDTIMINGMUSTBEMAINTAINEDINORDERTOALLOWTHECHANNELEQUALIZATIONTO BEPERFORMEDUSINGDIGITALSIGNALPROCESSINGWITHOUTCONSUMINGEXCESSIVEPROCESSING RESOURCES!LSO THERELATIVESTABILITYOFTHERADARCHANNELSASAFUNCTIONOFTIMEAND TEMPERATUREMUSTBESUCHTHATTHECORRECTIONSCANMAINTAINADEQUATETRACKINGDURING THETIMEBETWEENCALIBRATIONINTERVALS $IGITALBEAMFORMINGSYSTEMSREQUIREALARGENUMBEROFRECEIVERCHANNELS)NTHESE APPLICATIONS SIZE WEIGHT POWERDISSIPATION ANDCOSTARECRITICALCONSIDERATIONS
È°£ÓÊ Ê * 8Ê"* ,/" $IPLEX"ENEFITS $IPLEXOPERATIONCONSISTSOFTWORECEIVERSTHATSIMULTANEOUSLY PROCESSRETURNSFROMTRANSMISSIONSONDIFFERENTFREQUENCIES4RANSMISSIONSAREUSU ALLYNON OVERLAPPINGINTIMETOAVOIDAD"INCREASEINPEAKPOWERANDBECAUSEMOST RADARTRANSMITTERSAREOPERATEDINSATURATIONANDSIMULTANEOUSTRANSMISSIONATMULTIPLE FREQUENCIESWOULDPRODUCESIGNIFICANTTRANSMITTEDINTERMODULATIONDISTORTION 4HESENSITIVITYBENEFITOFDIPLEXOPERATIONFORDETECTING3WERLINGTARGETSISSHOWN IN&IGURE INCREASINGWITHPROBABILITYOFDETECTION0$ &OREXAMPLE DIPLEXOPER ATIONACHIEVES0$WITHD"LESSTOTALSIGNALPOWERTHANSIMPLEX!SSUMPTIONS MADEINDERIVING&IGUREARE 2ETURNSONTHETWOFREQUENCIESAREADDEDINVOLTAGEORPOWERPRIORTOTHEDETECTION DECISIONRATHERTHANBEINGSUBJECTEDTOINDIVIDUALDETECTIONDECISIONS 3EPARATIONOFTHETWOFREQUENCIESISSUFFICIENTTOMAKETHEIR3WERLINGFLUCTUA TIONSINDEPENDENT4HISDEPENDSONTHEPHYSICALLENGTHOFTHETARGETINTHERANGE DIMENSIONK24HEMINIMUMFREQUENCYSEPARATIONIS-(ZK2M -(Z WILLMAINTAINTHEDIPLEXBENEFITFORAIRCRAFTLONGERTHANMFT %QUALENERGYISTRANSMITTEDINBOTHPULSES!IMBALANCESACRIFICESONLYD" OFTHEBENEFITAT0$
2!$!22%#%)6%23
È°{Ç
&)'52% $IPLEXOPERATIONIMPROVESTHESENSITIVITYOFTHERECEIVER
"OTHLINEARANDASYMMETRICALNONLINEAR&-PRODUCEARANGEERRORASAFUNCTION OFDOPPLERDUETORANGE DOPPLERCOUPLING4HESERANGEDISPLACEMENTSMUSTMATCHIN THETWORECEIVERSTOWITHINASMALLFRACTIONOFTHECOMPRESSEDPULSEWIDTHOTHERWISE THESENSITIVITYBENEFITSOFDIPLEXOPERATIONARENOTFULLYACHIEVEDANDRANGEACCURACY MAYBEDEGRADED )MPLEMENTATION $IPLEX OPERATION CAN BE IMPLEMENTED WITH A VARIETY OF APPROACHES#OMPLETEREPLICATIONOFTHERECEIVERCHANNELSISTYPICALLYTHEMOSTEXPEN SIVEAPPROACHANDMAYBEREQUIREDIFTHEFREQUENCYSEPARATIONISVERYLARGE!MORE COMMON APPROACH IS SEPARATION OF THE FREQUENCIES AT THE FIRST )& AS THIS DOES NOT REQUIRECOMPLETEDUPLICATIONOFTHE2&FRONTENDORTHEFIRST,/SIGNAL3EPARATESEC ONDLOCALOSCILLATOROR)1DEMODULATORREFERENCEFREQUENCIESCANBEUSEDTOPROCESS THEDIFFERENTFREQUENCIES7ITHTHEUSEOFHIGH SPEED)&SAMPLING ITISALSOPOSSIBLE TODIGITIZEBOTHSIGNALSSIMULTANEOUSLYUSINGASINGLE!$CONVERTERANDPERFORMTHE FREQUENCYSEPARATIONUSINGDIGITALSIGNALPROCESSING7HICHEVERAPPROACHISUSED CARE MUSTBETAKENTOPROVIDEADEQUATEDYNAMICRANGEANDLINEARITYTOPREVENTINTERMODULA TIONDISTORTIONFROMDEGRADINGRADARPERFORMANCE
È°£ÎÊ 76 ", Ê ,/" ÊÊ Ê1* " 6 ,-" 4HEEXCITERFUNCTIONOFWAVEFORMGENERATIONANDUPCONVERSIONISOFTENTIGHTLYCOUPLED WITHTHERECEIVERFUNCTION4HEREQUIREMENTFORCOHERENCEBETWEENTHERECEIVERAND EXCITERISAMAJORFACTORFORTHISTIGHTCOUPLINGANDTHEUSEOFTHESAME,/FREQUEN CIES WITHIN THE RECEIVER AND EXCITER USUALLY RESULTS IN HARDWARE SAVINGS 3IMILAR TO THEMIGRATIONTODIGITALRECEIVERARCHITECTURES THEEXCITERFUNCTIONALITYISINCREASINGLY BEINGIMPLEMENTEDUSINGDIGITALAPPROACHES
È°{n
2!$!2(!.$"//+
$IRECT $IGITAL 3YNTHESIZER 4HE $IRECT $IGITAL 3YNTHESIZER $$3 PRODUCES WAVEFORMSUSINGDIGITALTECHNIQUESANDPROVIDESSIGNIFICANTIMPROVEMENTSINSTABIL ITY PRECISION AGILITY ANDVERSATILITYOVERANALOGTECHNIQUES4HEMAINLIMITATIONSARE THENOISEANDSPURIOUSSIGNALSASDESCRIBEDBELOW4HEGENERAL$$3ARCHITECTUREIS SHOWNIN&IGURE4HEDOUBLEACCUMULATORARCHITECTURE COMPRISINGTHEFREQUENCY ANDPHASEACCUMULATORS ENABLESTHEGENERATIONOF#7 LINEAR&-CHIRP NONLINEAR PIECE WISELINEAR &- FREQUENCYMODULATED ANDPHASEMODULATEDWAVEFORMS#7 WAVEFORMSAREGENERATEDBYAPPLYINGACONSTANTFREQUENCYWORDDIGITIZEDFREQUENCY REPRESENTATION INPUTTOTHEPHASEACCUMULATOR CREATINGALINEARPHASESEQUENCETHATIS FIRSTTRUNCATEDTHENINPUTTOACOSINEORSINE LOOKUPTABLETHATOUTPUTSTHECORRESPOND ING SINUSOIDAL SIGNAL VALUE TO THE DIGITAL TO ANALOG $! CONVERTER4HE FREQUENCY RESOLUTIONISDEPENDENTONTHENUMBEROFBITSANDTHECLOCKFREQUENCYOFTHEPHASE ACCUMULATOR4HEOUTPUTFREQUENCYISGIVENBY
FOUT
- F FCLK .F
WHERE
-F FREQUENCYWORD INPUTTOTHEPHASEACCUMULATOR
FCLK PHASEACCUMULATORCLOCKFREQUENCY
.E NUMBEROFBITSOFPHASEACCUMULATOR ,INEAR &- OR CHIRP WAVEFORMS ARE GENERATED BY APPLYING A CONSTANT CHIRP SLOPE WORDDIGITIZEDCHIRPSLOPEREPRESENTATION TOTHEINPUTOFTHEFREQUENCYACCUMULATOR CREATINGAQUADRATICPHASESEQUENCEATTHEOUTPUTOFTHEPHASEREGISTER0IECEWISE LINEAR ORNONLINEAR&-WAVEFORMSCANBEGENERATEDBYAPPLYINGATIME VARYINGSLOPEINPUT TOTHEFREQUENCYREGISTER4HEFREQUENCYACCUMULATORMAYBECLOCKEDEITHERATTHESAME RATEASTHEPHASEACCUMULATORORATASUB MULTIPLETOPROVIDEFINERCHIRPSLOPERESOLU TION)FBOTHACCUMULATORSARECLOCKEDATTHESAMERATE THECHIRPSLOPEISGIVENBY $FOUT - 3 FCLK .F $T
WHERE
-3 CHIRPSLOPEWORD INPUTTOTHEFREQUENCYACCUMULATOR
.F NUMBEROFBITSOFFREQUENCYACCUMULATOR &REQUENCYMODULATEDANDPHASEMODULATEDWAVEFORMSCANBECREATEDAPPLYINGTIME VARYINGINPUTSTOTHEFREQUENCYMODULATION&- ANDPHASEMODULATION0- PORTS
&)'52% $IRECT$IGITAL3YNTHESIZERBLOCKDIAGRAM
2!$!22%#%)6%23
È°{
%RRORSSUCHASPHASETRUNCATIONAND$!CONVERTERQUANTIZATIONANDNONLINEARITY PRODUCE SPURIOUS SIGNALS DUE TO THEIR DETERMINISTIC NATURE4HE SPURIOUS SIGNAL FRE QUENCIESGENERATEDBYA$$3CANBEREADILYPREDICTEDASTHEYAREAFUNCTIONOFTHE DIGITALARCHITECTUREANDPROGRAMMEDFREQUENCY4HESPURIOUSSIGNALMAGNITUDESARE LESSPREDICTABLEASTHEMAGNITUDESOFTHEDOMINANTSPURIOUSSIGNALSAREAFUNCTIONOF THE$!CONVERTERNONLINEARITY 7HEN GENERATING #7 WAVEFORMS THE $! CONVERTER SEQUENCE REPEATS AFTER + SAMPLESWHERE+EQUALSTHEGREATESTCOMMONDIVISOROF.EAND-F4HUS SPURIOUS SIGNALSOCCURONLYATFREQUENCIES
FSPUR
NFCLK N +
)NTHEEXTREMECASEWHERE-FDOESNOTCONTAINTHEFACTOR THISCREATESASPURIOUSFRE QUENCYSPACINGOFFCLK.E&OREXAMPLE WITHA'(ZCLOCKAND BITFREQUENCYACCU MULATOR THESPURIOUSFREQUENCYSPACINGCANBEASCLOSEAS(Z)NMOSTCASES SUCH CLOSELYSPACEDSPURIOUSSIGNALSCANNOTBEDIFFERENTIATEDFROMNOISE#ONVERSELY CHOOS INGVALUESOF-FTHATCONTAINLARGEFACTORSOF.CREATESRELATIVELYLARGESPURIOUSSPACING &OREXAMPLE USINGA-(ZCLOCKALLOWSTHEGENERATIONOFFREQUENCIESATMULTIPLESOF -(ZWITHALLTHESPURIOUSCOMPONENTSOCCURRINGATMULTIPLESOF-(Z 4HEIMPACTOF$$3SPURIOUSSIGNALSONRADARPERFORMANCEDEPENDSONTHENATURE OFTHESPURIOUSSIGNALSANDTHETYPEOFRADARPROCESSINGINVOLVED!PPLICATIONSUSING CHIRP WAVEFORMS WITH LARGE TIME BANDWIDTH PRODUCTS ARE TYPICALLY LESS SENSITIVE TO $$3SPURIOUSSIGNALSSINCETHE$$3SPURIOUSSIGNALSCHIRPATADIFFERENTRATETOTHAT OFTHEWANTEDSIGNAL4HESPURIOUSSIGNALSARETHUSREJECTEDDURINGPULSECOMPRESSION )NPULSEDOPPLERAPPLICATIONS SPURIOUSSIGNALSAREOFMUCHGREATERCONCERNHOWEVER THEIREFFECTSCANBEMITIGATEDBYENSURINGTHATTHE$$3GENERATESEACHWAVEFORMFROM THE SAME INITIAL CONDITIONS 2ESTARTING THE $$3 FOR EVERY PULSE GUARANTEES THAT THE SAMEDIGITALSEQUENCEWILLBEINPUTTOTHE$!CONVERTERFOREACHPULSE4HERESULTISA $$3OUTPUTTHATONLYCONTAINSSPECTRALCOMPONENTSATMULTIPLESOFTHE02& 4ECHNIQUESHAVEBEENPROPOSEDORINCORPORATEDINTO$$3DEVICESTHATREDUCESPU RIOUS LEVELS BY ADDING DITHERING TO REDUCE THE EFFECTS OF LIMITED WORD LENGTHS4HE EFFECTOFTHESETECHNIQUESANDTHESPURIOUSSIGNALSTHATTHEYAREDESIGNEDTOMITIGATE SHOULDBECONSIDEREDCAREFULLYASTHEYMAYBEDETRIMENTALTORADARPERFORMANCE4HE USEOFDITHERINGWILLRANDOMIZETHESPURIOUSSIGNAL RESULTINGINPULSE TO PULSEVARIA TIONSINTHEDIGITALSEQUENCEOUTPUTTOTHE$!CONVERTER ARESULTTHATISUNDESIRABLEIN PULSEDOPPLERAPPLICATIONS 4RULYRANDOMERRORSARENOTGENERATEDBYTHEDIGITALPORTIONOFTHE$$34HEONLY NONDETERMINISTICERRORSAREARESULTOFTHE$!CONVERTERPERFORMANCEINTHEFORMOF INTERNALCLOCKJITTERORADDITIVETHERMALNOISEANDTHEEFFECTOFTHEPHASENOISEONTHE INPUTCLOCKSIGNAL )NTERNAL$!CONVERTERCLOCKJITTERPRODUCESPHASEMODULATIONOFTHEOUTPUTSIGNAL PROPORTIONALTOTHEOUTPUTFREQUENCY3IMILARLY PHASENOISEPRESENTONTHECLOCKINPUT SIGNALISTRANSFERREDTOTHEOUTPUTSIGNAL REDUCEDBYLOG FOUTFCLK D"$!CON VERTERADDITIVETHERMALNOISEISINDEPENDENTOFOUTPUTSIGNALFREQUENCYANDPRODUCES BOTHPHASEANDAMPLITUDENOISECOMPONENTS &REQUENCY-ULTIPLIERS &REQUENCYMULTIPLICATIONALLOWSSIGNALSTOBEINCREASED INBOTHFREQUENCYANDBANDWIDTH&REQUENCYMULTIPLICATIONISFREQUENTLYUSEDINGEN ERATINGLOCALOSCILLATOR#7FREQUENCIESWHEREALLFREQUENCIESARETYPICALLYBASEDONA
È°xä
2!$!2(!.$"//+
&)'52% &REQUENCYMULTIPLIEROPERATION
LOWFREQUENCYREFERENCE4HEYALSOPROVIDETHECAPABILITYFORWIDE BANDWIDTHCHIRP WAVEFORMSTHATCANNOTBEGENERATEDDIRECTLYUSINGAVAILABLE$$3DEVICES&REQUENCY MULTIPLIERS OPERATE AS SHOWN IN &IGURE BY MULTIPLYING THE PHASE OF THE INPUT SIGNALBYTHEINTEGERMULTIPLICATIONFACTOR-3INCEINPRACTICETHEPROCESSTYPICALLY INCLUDESSOMEFORMOFLIMITING THEOUTPUTAMPLITUDE!T GENERALLYHASALOWERAMPLI TUDEVARIATIONTHANTHEINPUTSIGNALAMPLITUDE!T "ECAUSETHEMULTIPLICATIONPROCESSMULTIPLIESUPTHEVARIATIONSINTHESIGNALPHASE BY FACTOR - INPUT PHASE NOISE AND SPURIOUS PHASE MODULATIONS ARE INCREASED BY LOG- D"3IMILARLY VARIATIONSINTHEPHASEOFTHESIGNALASAFUNCTIONOFFRE QUENCYAREMULTIPLIEDUP4HESEVARIATIONSAREPRODUCEDDURINGSIGNALFILTERINGAND MAYBEPRESENTONTHEINPUTSIGNAL&ORCHIRPWAVEFORMS THISCANRESULTINASIGNIFICANT DEGRADATIONINTHERANGESIDELOBEPERFORMANCE!LSO PRACTICALMULTIPLIERSMAYHAVEA SIGNIFICANTPHASEVARIATIONASAFUNCTIONOFFREQUENCY)FTHEINPUTSIGNALPHASEDISTOR TIONISGIVENBY
¤ P NF ³
E F A SIN ¥ ¦ " ´µ
WHERE
A PEAKPHASERIPPLE
" WAVEFORMINPUTBANDWIDTH
N NUMBEROFCYCLESOFPHASERIPPLE THERESULTINGOUTPUTDISTORTIONPRODUCESRANGESIDELOBESATTIMESoN-"ANDMAGNITUDE LOG-A RELATIVETOTHEMAINBEAMOFTHETARGETRETURN!SANEXAMPLE GENERAT INGACHIRPWAVEFORMTHATHASRANGESIDELOBESBETTERTHAND"USINGANrMULTIPLIER REQUIRESTHATTHEINPUTSIGNALHASLESSTHANDEGREESPEAK PEAKPHASERIPPLE &REQUENCYMULTIPLIERSCANBEIMPLEMENTEDUSINGAVARIETYOFTECHNIQUES SUCHAS USINGSTEPRECOVERYDIODEMULTIPLIERSORUSINGPHASELOCKEDLOOPS7HEREWIDEPERCENT AGEBANDWIDTHANDFASTSETTLINGISREQUIRED THEMOSTCOMMONTECHNIQUEISTOCASCADEA SERIESOFFREQUENCYDOUBLERSORLOWORDERMULTIPLIERS4HISTYPEOFMULTIPLIERCANALSO PROVIDENEARIDEALPHASENOISEPERFORMANCE BUTHASSIGNIFICANTPHASEMODULATIONASA FUNCTIONOFFREQUENCYASITCONTAINSFILTERSBETWEENEACHSTAGEOFMULTIPLICATION 0REDISTORTIONOFTHEMULTIPLIERINPUTWAVEFORMISOFTENUSEDINORDERTOPRODUCE WIDEBAND CHIRP WAVEFORMS WITH LOW RANGE SIDELOBE PERFORMANCE )F THE MULTIPLIER ISCHARACTERIZEDBYANOUTPUTPHASEDISTORTIONASAFUNCTIONOFINPUTFREQUENCYGIVEN BYEV THENAPREDISTORTIONOFTHEINPUTSIGNALBYPHASE EV -WILLEQUALIZETHE MULTIPLIERRESPONSE0REDISTORTIONCANBEPERFORMEDVERYPRECISELYBYADDINGTHEPHASE MODULATIONVIATHE$$3THATISUSEDTOGENERATETHECHIRPWAVEFORM 7AVEFORM 5PCONVERSION 5PCONVERSION OF EXCITER WAVEFORMS IS SIMILAR TO DOWNCONVERSIONWITHINTHERECEIVER!LSO SIMILARPRACTICALCONSIDERATIONSOFMIXER SPURIOUSANDIMAGEREJECTIONAPPLY4HEONESIGNIFICANTADDITIONALCHALLENGEISTHE REJECTION OF THE ,/ LEAKAGE ,/ REJECTION TYPICALLY IMPOSES TIGHT FILTER REJECTION REQUIREMENTS ON THE 2& FILTERS AND FOR WIDE TUNABLE RANGES SWITCHED FILTERS ARE OFTENREQUIRED
2!$!22%#%)6%23
È°x£
, ,
-)3KOLNIK 2ADAR(ANDBOOK ND%D .EW9ORK-C'RAW(ILL -)3KOLNIK 2ADAR(ANDBOOK ST%D .EW9ORK-C'RAW(ILL 2 %7ATSON h2ECEIVERDYNAMICRANGE0ART v7ATKINS*OHNSON #OMPANY 4ECHNICAL.OTE VOL NO *ANUARY&EBRUARY "#(ENDERSON h-IXERSINMICROWAVESYSTEMS0ART v7ATKINS*OHNSON#OMPANY 4ECHNICAL .OTE VOL NO *ANUARY&EBRUARY $7!LLAN ((ELLWIG 0+ARTASCHOFF *6ANIER *6IG '-27INKLER AND.&9ANNONI h3TANDARDTERMINOLOGYFORFUNDAMENTALFREQUENCYANDTIMEMETROLOGY vIN0ROCEEDINGSOFTHE ND!NNUAL&REQUENCY#ONTROL3YMPOSIUM "ALTIMORE -$ *UNEn PPn 02ENOULT %'IRARDET AND,"IDART h-ECHANICALANDACOUSTICEFFECTSINLOWPHASENOISEPIEZO ELECTRICOSCILLATORS vPRESENTEDAT)%%% RD!NNUAL3YMPOSIUMON&REQUENCY#ONTROL -!2ICHARDS &UNDAMENTALOF2ADAR3IGNAL0ROCESSING .EW9ORK-C'RAW (ILL !):VEREV (ANDBOOKOF&ILTER3YNTHESIS .EW9ORK*OHN7ILEYAND3ONS )NC !6/PPENHEIMAND273CHAFER $ISCRETE 4IME3IGNAL0ROCESSING .EW9ORK0RENTICE(ALL )NC 7+ESTER 4HE$ATA#ONVERSION(ANDBOOK ,ONDON%LSEVIER.EWNES 2(7ALDEN h!NALOG TO DIGITALCONVERTERSURVEYANDANALYSIS v)%%%*OURNALON3ELECTED!REAS IN#OMMUNICATIONS VOL NO PPn !PRIL ""RANNON h3AMPLEDSYSTEMSANDTHEEFFECTSOFCLOCKPHASENOISEANDJITTER v!NALOG$EVICES )NC !PPLICATION.OTE !. *'0ROAKISAND$'-ANOLAKIS $IGITAL3IGNAL0ROCESSING ND%D .EW9ORK-ACMILLAN %"(OGENAUER h!NECONOMICALCLASSOFDIGITAL&ILTERSFORDECIMATIONANDINTERPOLATION v)%%% 4RANSACTIONSON!COUSTICS 3PEECHAND3IGNAL0ROCESSING VOL!330 NO !PRIL *4IERNEY # - 2ADAR AND " 'OLD h! DIGITAL FREQUENCY SYNTHESIZER v )%%%4RANS!5 PPn -ARCH (4.ICHOLAS)))AND(3AMUELI h!NANALYSISOFTHEOUTPUTSPECTRUMOFDIRECTDIGITALFREQUENCY SYNTHESIZERSINTHEPRESENCEOFPHASE ACCUMULATORTRUNCATION v0ROCEEDINGSSTANNUAL&REQUENCY #ONTROL3YMPOSIUM 53%2!#/- &T-ONMOUTH .* -AY PPn
#HAPTER
ÕÌ>ÌVÊ iÌiVÌ]Ê /À>V}]Ê>`Ê-iÃÀÊ Ìi}À>Ì 7°Ê°Ê >Ì
Ê>`Ê°Ê6°Ê/ÀÕ 4HE*OHNS(OPKINS5NIVERSITY!PPLIED0HYSICS,ABORATORY
Ç°£Ê /," 1 /" !SDIGITALPROCESSINGHASINCREASEDINSPEEDANDDIGITALHARDWAREHASDECREASEDINCOST ANDSIZE RADARSHAVEBECOMEMOREANDMOREAUTOMATED SOTHATAUTOMATICDETECTION ANDTRACKING!$4 SYSTEMSAREASSOCIATEDWITHALMOSTALLBUTTHESIMPLESTOFRADARS )N THIS CHAPTER AUTOMATIC DETECTION AUTOMATIC TRACKING AND SENSOR INTEGRATION TECHNIQUESFORSURVEILLANCERADARSAREDISCUSSED)NCLUDEDINTHEDISCUSSIONAREVARI OUSNONCOHERENTINTEGRATORSTHATPROVIDETARGETENHANCEMENT THRESHOLDINGTECHNIQUES FORFALSEALARMSANDTARGETSUPPRESSION ANDALGORITHMSFORESTIMATINGTARGETPOSITION ANDRESOLVINGTARGETS4HEN ANOVERVIEWOFTHEENTIRETRACKINGSYSTEMISGIVEN FOL LOWEDBYADISCUSSIONOFITSVARIOUSCOMPONENTSSUCHASTRACKINITIATION CORRELATION LOGIC TRACKING FILTER AND MANEUVER FOLLOWING LOGIC &INALLY THE CHAPTER CONCLUDES WITHADISCUSSIONOFSENSORINTEGRATIONANDRADARNETTING INCLUDINGBOTHCOLOCATEDAND MULTISITESYSTEMS
Ç°ÓÊ 1/" / Ê / /" )NTHES -ARCUMAPPLIEDSTATISTICALDECISIONTHEORYTORADARANDLATER3WERLING EXTENDED THE WORK TO FLUCTUATING TARGETS 4HEY INVESTIGATED MANY OF THE STATISTICAL PROBLEMS ASSOCIATED WITH THE NONCOHERENT DETECTION OF TARGETS IN GAUSSIAN NOISE .OTE)FTHEINPHASEANDQUADRATURECOMPONENTSAREGAUSSIANDISTRIBUTED THEENVE LOPE IS 2AYLEIGH DISTRIBUTED AND THE POWER IS EXPONENTIALLY DISTRIBUTED -ARCUMS MOSTIMPORTANTRESULTWASTHEGENERATIONOFCURVESOFPROBABILITYOFDETECTION0$ VER SUSSIGNAL TO NOISERATIO3. FORADETECTORTHATSUMS.ENVELOPE DETECTEDSAMPLES EITHERLINEARORSQUARE LAW UNDERTHEASSUMPTIONOFEQUALSIGNALAMPLITUDES7HEREAS FORAPHASEDARRAY THEEQUALAMPLITUDEASSUMPTIONISVALIDFORAROTATINGRADAR THE RETURNEDSIGNALAMPLITUDEISMODULATEDBYTHEANTENNAPATTERNASTHEBEAMSWEEPSOVER
Ç°£
Ç°Ó
2!$!2(!.$"//+
THETARGET-ANYAUTHORSHAVEINVESTIGATEDVARIOUSDETECTORS COMPARINGDETECTIONPER FORMANCEANDANGULARESTIMATIONRESULTSWITHOPTIMALVALUES ANDMANYOFTHESERESULTS AREPRESENTEDLATERINTHISSECTION )NTHEORIGINALWORKONDETECTORS THEENVIRONMENTWASASSUMEDKNOWNANDHOMO GENEOUS SOTHATFIXEDTHRESHOLDSCOULDBEUSED(OWEVER AREALISTICRADARENVIRON MENTEG CONTAININGLAND SEA ANDRAIN WILLCAUSEANEXORBITANTNUMBEROFFALSE ALARMSFORAFIXED THRESHOLDSYSTEMTHATDOESNOTUTILIZEEXCELLENTCOHERENTPROCESSING 4HREEMAINAPPROACHESADAPTIVETHRESHOLDING NONPARAMETRICDETECTORS ANDCLUTTER MAPSHAVEBEENUSEDTOSOLVETHENONCOHERENT FALSE ALARMPROBLEM"OTHADAPTIVE THRESHOLDING AND NONPARAMETRIC DETECTORS ARE BASED ON THE ASSUMPTION THAT HOMO GENEITYEXISTSINASMALLREGIONABOUTTHERANGECELLTHATISBEINGTESTED4HEADAP TIVETHRESHOLDINGMETHODASSUMESTHATTHENOISEDENSITYISKNOWNEXCEPTFORAFEW UNKNOWN PARAMETERS EG THE MEAN AND THE VARIANCE 4HE SURROUNDING REFERENCE CELLSARETHENUSEDTOESTIMATETHEUNKNOWNPARAMETERS ANDATHRESHOLDBASEDONTHE ESTIMATEDDENSITYISOBTAINED.ONPARAMETRICDETECTORSOBTAINACONSTANTFALSE ALARM RATE#&!2 BYRANKINGORDERINGTHESAMPLESFROMSMALLESTTOLARGEST THETESTSAMPLE WITH THE REFERENCE CELLS 5NDER THE HYPOTHESIS THAT ALL THE SAMPLES TEST AND REFER ENCE AREINDEPENDENTSAMPLESFROMANUNKNOWNDENSITYFUNCTION THERANKOFTHETEST SAMPLEISUNIFORMANDCONSEQUENTLY ATHRESHOLDTHATYIELDS#&!2CANBESET#LUTTER MAPSSTOREANAVERAGEBACKGROUNDLEVELFOREACHRANGE AZIMUTHCELL!TARGETISTHEN DECLAREDINARANGE AZIMUTHCELLIFTHENEWVALUEEXCEEDSTHEAVERAGEBACKGROUNDLEVEL BYASPECIFIEDAMOUNT /PTIMAL $ETECTOR 4HE RADAR DETECTION PROBLEM IS A BINARY HYPOTHESIS TESTINGPROBLEMINWHICH(DENOTESTHEHYPOTHESISTHATNOTARGETISPRESENTAND( ISTHEHYPOTHESISTHATTHETARGETISPRESENT7HILESEVERALCRITERIAIE DEFINITIONSOF OPTIMALITY CANBEUSEDTOSOLVETHISPROBLEM THEMOSTAPPROPRIATEFORRADARISTHE .EYMAN 0EARSON4HISCRITERIONMAXIMIZESTHEPROBABILITYOFDETECTION0$FORAGIVEN PROBABILITYOFFALSEALARM0FABYCOMPARINGTHELIKELIHOODRATIO,DEFINEDBY%Q TOANAPPROPRIATETHRESHOLD4THATDETERMINESTHE0FA!TARGETISDECLAREDPRESENTIF
, X XN
P X XN\ ( q4 P X XN\ (
WHEREPX x XN\( ANDPX x XN\( ARETHEJOINTPROBABILITYDENSITYFUNCTIONSOF THENOBSERVATIONSXIUNDERTHECONDITIONSOFTARGETPRESENCEANDTARGETABSENCE RESPEC TIVELY&ORALINEARENVELOPEDETECTOR THESAMPLESHAVEA2AYLEIGHDENSITYUNDER( ANDA2ICEANDENSITYUNDER( ANDTHELIKELIHOODRATIODETECTORREDUCESTO N
I
¤!X ³ ) ¥ I I ´ q 4 ¦S µ
WHERE)ISTHEMODIFIED"ESSELFUNCTIONOFZEROORDER RISTHENOISEPOWER AND!IIS THETARGETAMPLITUDEOFTHEITHPULSEANDISPROPORTIONALTOTHEANTENNAPOWERPATTERN &ORSMALLSIGNALS!I R THEDETECTORREDUCESTOTHESQUARE LAWDETECTOR N
£ !I XI q 4 I
!54/-!4)#$%4%#4)/. 42!#+).' !.$3%.3/2).4%'2!4)/.
Ç°Î
ANDFORLARGESIGNALS!I R ITREDUCESTOTHELINEARDETECTOR N
£ !I XI 4
I
&ORCONSTANTSIGNALAMPLITUDEIE !I ! THESEDETECTORSWEREFIRSTSTUDIEDBY -ARCUMANDWERESTUDIEDINSUCCEEDINGYEARSBYNUMEROUSOTHERPEOPLE4HEMOST IMPORTANTFACTSCONCERNINGTHESEDETECTORSARETHEFOLLOWING 4HEDETECTIONPERFORMANCESOFTHELINEARANDSQUARE LAWDETECTORSARESIMILAR DIF FERINGONLYBYLESSTHAND"OVERWIDERANGESOF0$ 0FA ANDN "ECAUSETHESIGNALRETURNOFASCANNINGRADARISMODULATEDBYTHEANTENNAPATTERN TO MAXIMIZETHE3.WHENINTEGRATINGALARGENUMBEROFPULSESWITHNOWEIGHTINGIE !I ONLYOFTHEPULSESBETWEENTHEHALF POWERPOINTSSHOULDBEINTEGRATED ANDTHEANTENNABEAM SHAPEFACTOR!"3& ISD"4HE!"3&ISTHENUMBERBY WHICHTHEMIDBEAM3.MUSTBEREDUCEDSOTHATTHEDETECTIONCURVESGENERATEDFOR EQUALSIGNALAMPLITUDESCANBEUSEDFORTHESCANNINGRADAR 4HECOLLAPSINGLOSSFORTHELINEARDETECTORCANBESEVERALDECIBELSGREATERTHANTHE LOSSFORASQUARE LAWDETECTORSEE&IGURE 4HECOLLAPSINGLOSSISTHEADDITIONAL SIGNALREQUIREDTOMAINTAINTHESAME0$AND0FAWHENUNWANTEDNOISESAMPLESALONG WITHTHEDESIREDSIGNAL PLUS NOISESAMPLESAREINTEGRATED4HENUMBEROFSIGNALSAM PLESINTEGRATEDIS. THENUMBEROFEXTRANEOUSNOISESAMPLESINTEGRATEDIS- ANDTHE COLLAPSINGRATIOQ . - . -OSTAUTOMATICDETECTORSAREREQUIREDNOTONLYTODETECTTARGETSBUTALSOTOMAKEANGU LARESTIMATESOFTHEAZIMUTHPOSITIONOFTHETARGET3WERLINGCALCULATEDTHESTANDARD DEVIATIONOFTHEOPTIMALESTIMATEBYUSINGTHE#RAMER 2AOLOWERBOUND4HERESULTS
L
L
L
L
&)'52% #OLLAPSINGLOSSVERSUSCOLLAPSINGRATIOFORAPROBABILITYOFFALSEALARMOF ANDAPROB ABILITYOFDETECTIONOFAFTER'64RUNKÚ)%%%
Ç°{
2!$!2(!.$"//+
&)'52% #RAMER 2AOBOUNDFORANGULARESTIMATESFORFLUCTUATINGANDNONFLUCTUATINGTARGETSR ISTHESTANDARDDEVIATIONOFTHEESTIMATIONERROR AND.ISTHENUMBEROFPULSESWITHINTHE D"BEAM WIDTH WHICHISP4HE3.ISTHEVALUEATTHECENTEROFTHEBEAMAFTER03WERLINGÚ)%%%
ARESHOWNIN&IGURE WHEREANORMALIZEDSTANDARDDEVIATIONISPLOTTEDAGAINSTTHE MIDBEAM3.4HISRESULTHOLDSFORAMODERATEORLARGENUMBEROFPULSESINTEGRATED ANDTHEOPTIMALESTIMATEINVOLVESFINDINGTHELOCATIONWHERETHECORRELATIONOFTHE RETURNEDSIGNALANDTHEDERIVATIVEOFTHEANTENNAPATTERNISZERO!LTHOUGHTHISESTI MATEISRARELYIMPLEMENTED ITSPERFORMANCEISAPPROACHEDBYSIMPLEESTIMATES 0RACTICAL$ETECTORS -ANYDIFFERENTDETECTORSOFTENCALLEDINTEGRATORS AREUSED TO ACCUMULATE THE RADAR RETURNS AS THE RADAR SWEEPS BY A TARGET! FEW OF THE MOST COMMONDETECTORSARESHOWNIN&IGURE4HEFEEDBACKINTEGRATOR ANDTWO POLE FILTER AREDETECTORSTHATMINIMIZETHEDATASTORAGEREQUIREMENTS7HILETHESEDETEC TORSMAYSTILLBEFOUNDINOLDERRADARS THEYPROBABLYWOULDNOTBEIMPLEMENTEDIN NEW RADARS AND WILL NOT BE DISCUSSED IN THIS EDITION 4HOUGH ALL THE DETECTORS ARE SHOWNIN&IGUREASBEINGCONSTRUCTEDWITHSHIFTREGISTERS THEYWOULDNORMALLYBE IMPLEMENTEDWITHRANDOM ACCESSMEMORY4HEINPUTTOTHESEDETECTORSCANBELINEAR VIDEO SQUARE LAWVIDEO ORLOGVIDEO"ECAUSELINEARVIDEOISPROBABLYTHEMOSTCOM MONLYUSED THEADVANTAGESANDDISADVANTAGESOFTHEVARIOUSDETECTORSWILLBESTATED FORTHISVIDEO -OVING7INDOW 4HEMOVINGWINDOWIN&IGUREAPERFORMSARUNNINGSUMOF NPULSESINEACHRANGECELL
3I 3I XI XI N
WHERE3IISTHESUMATTHEITHPULSEOFTHELASTNPULSESANDXIISTHEITHPULSE4HEPER FORMANCEOFTHISDETECTORFORNyISONLYD"WORSETHANTHEOPTIMALDETECTOR GIVENBY%Q4HEDETECTIONPERFORMANCECANBEOBTAINEDBYUSINGAN!"3&OF D"ANDSTANDARDDETECTIONCURVESFOREQUALAMPLITUDEPULSES4HEANGULARESTIMATE THATISOBTAINEDBYEITHERTAKINGTHEMAXIMUMVALUEOFTHERUNNINGSUMORTAKINGTHE MIDPOINTBETWEENTHEFIRSTANDLASTCROSSINGSOFTHEDETECTIONTHRESHOLDHASABIASOF NPULSES WHICHISEASILYCORRECTED4HESTANDARDDEVIATIONOFTHEESTIMATIONERROROF BOTHTHESEESTIMATORSISABOUTPERCENTHIGHERTHANTHEOPTIMALESTIMATESPECIFIED
!54/-!4)#$%4%#4)/. 42!#+).' !.$3%.3/2).4%'2!4)/.
Ç°x
&)'52% "LOCKDIAGRAMSOFVARIOUSDETECTORS4HELETTER#INDICATES ACOMPARISON SISADELAY ANDLOOPSINDICATEFEEDBACKFROM'64RUNK
BYTHE#RAMER 2AOBOUND!DISADVANTAGEOFTHISDETECTORISTHATITISSUSCEPTIBLETO INTERFERENCETHATIS ONELARGESAMPLEFROMINTERFERENCECANCAUSEADETECTION4HIS PROBLEMCANBEMINIMIZEDBYUSINGSOFTLIMITING 4HEDETECTIONPERFORMANCEDISCUSSEDPREVIOUSLYISBASEDONTHEASSUMPTIONTHATTHE TARGETISCENTEREDINTHEMOVINGWINDOW)NTHEREALSITUATION THERADARSCANSOVERTHE TARGET ANDDECISIONSTHATAREHIGHLYCORRELATEDAREMADEATEVERYPULSE(ANSENANA LYZEDTHISSITUATIONFOR. ANDPULSESANDCALCULATEDTHEDETECTIONTHRESH OLDS SHOWN IN &IGURE THE DETECTION PERFORMANCE SHOWN IN &IGURE AND THE ANGULARACCURACYSHOWNIN&IGURE#OMPARING(ANSENSSCANNINGCALCULATIONWITH THESINGLE POINTCALCULATION ONECONCLUDESTHATABOUTD"OFIMPROVEMENTISOBTAINED BYMAKINGADECISIONATEVERYPULSE4HEANGULARERROROFTHEBEAM SPLITTINGPROCEDURE ISABOUTPERCENTGREATERTHANTHEOPTIMALESTIMATE&ORLARGESIGNAL TO NOISERATIOS THEACCURACYRMSERROR OFTHEBEAM SPLITTINGANDMAXIMUM RETURNPROCEDURESWILLBE LIMITEDBYTHEPULSESPACINGANDWILLAPPROACH
S Q} $Q
Ç°È
2!$!2(!.$"//+
&)'52% 3INGLE SWEEPFALSE ALARMPROBABILITY0FAVERSUSTHRESHOLDFORMOVINGWINDOW 4HENOISEIS2AYLEIGH DISTRIBUTEDWITHR AFTER6'(ANSENÚ)%%%
WHERE$PISTHEANGULARROTATIONBETWEENTRANSMITTEDPULSES#ONSEQUENTLY IFTHENUM BEROFPULSESPERBEAMWIDTHISSMALL THEANGULARACCURACYWILLBEPOOR&ORINSTANCE IF PULSES ARE SEPARATED BY BEAMWIDTH S Q} IS BOUNDED BY BEAMWIDTHS (OWEVER IMPROVEDACCURACYCANBEOBTAINEDBYUSINGTHEAMPLITUDESOFTHERADAR RETURNS!NACCURATEESTIMATEOFTHETARGETANGLEISGIVENBY
$Q N ! ! Q} Q A$Q
&)'52% $ETECTIONPERFORMANCEOFTHEANALOGMOVING WINDOWDETECTORFORTHENO FADINGCASEAFTER6'(ANSENÚ)%%%
!54/-!4)#$%4%#4)/. 42!#+).' !.$3%.3/2).4%'2!4)/.
Ç°Ç
&)'52% !NGULARACCURACYOBTAINEDWITHBEAM SPLITTINGESTIMATIONPROCEDURE FORTHENO FADINGCASE"ROKEN LINECURVESARELOWERBOUNDSDERIVEDBY3WERLING AND POINTSSHOWNARESIMULATIONRESULTSAFTER6'(ANSENÚ)%%%
WHERE
A BEAMWIDTH
AND ! AND ! ARE THE TWO LARGEST AMPLITUDES OF THE RETURNED SAMPLES AND OCCUR AT ANGLESPANDP P $P RESPECTIVELY"ECAUSETHEESTIMATESHOULDLIEBETWEENP ANDPAND%QWILLNOTALWAYSYIELDSUCHANESTIMATE Q} SHOULDBESETEQUALTOP IF Q} PAND Q} SHOULDBEEQUALTOPIF Q} P4HEACCURACYOFTHISESTIMATORISGIVEN IN&IGUREFORTHECASEOFN PULSESPERBEAMWIDTH4HISESTIMATIONPROCEDURE CANALSOBEUSEDTOESTIMATETHEELEVATIONANGLEOFATARGETINMULTIBEAMSYSTEMSWHERE PANDPARETHEELEVATION POINTINGANGLESOFADJACENTBEAMSAND!AND!ARETHE CORRESPONDINGAMPLITUDES "INARY)NTEGRATOR 4HEBINARYINTEGRATORISALSOKNOWNASTHEDUAL THRESHOLDDETEC TOR - OUT OF .DETECTOR ORRANKDETECTORSEEh.ONPARAMETRIC$ETECTORS vLATERINTHIS SECTION ANDNUMEROUSINDIVIDUALSHAVESTUDIEDITn!SSHOWNIN&IGURED THE INPUTSAMPLESAREQUANTIZEDTOOR DEPENDINGONWHETHERORNOTTHEYARELESSTHAN ATHRESHOLD44HELAST.ZEROSANDONESARESUMMEDWITHAMOVINGWINDOW AND COMPAREDWITHASECONDTHRESHOLD4 -&ORLARGE. THEDETECTIONPERFORMANCEOF THISDETECTORISAPPROXIMATELYD"LESSTHANTHEMOVING WINDOWINTEGRATORBECAUSE OFTHEHARDLIMITINGOFTHEDATA ANDTHEANGULARESTIMATIONERRORISABOUTPERCENT GREATERTHANTHE#RAMER 2AOLOWERBOUND3CHWARTZSHOWEDTHATWITHIND"THE OPTIMALVALUEOF-FORMAXIMUM0$ISGIVENBY
- .
Ç°n
2!$!2(!.$"//+
&)'52% !NGULARACCURACYFORTWOPULSESSEPARATEDBYBEAMWIDTHS
WHEN 0FA AND 0$ 4HEOPTIMALVALUEOF0N THEPROBABILITYOF EXCEEDING4WHENONLYNOISEISPRESENT WASCALCULATEDBY$ILLARDANDISSHOWNIN &IGURE4HECORRESPONDINGTHRESHOLD4IS
4 R LN0.
!COMPARISONOFTHEOPTIMALBESTVALUEOF- BINARYINTEGRATORWITHVARIOUSOTHER PROCEDURESISGIVENIN&IGURESANDFOR0$ AND RESPECTIVELY 4HEBINARYINTEGRATORISUSEDINMANYRADARSBECAUSE ITISEASILYIMPLEMENTED ITIGNORESINTERFERENCESPIKESTHATCAUSETROUBLEWITHINTEGRATORSTHATDIRECTLYUSE SIGNALAMPLITUDEAND ITWORKSEXTREMELYWELLWHENTHENOISEHASANON 2AYLEIGH DENSITY&OR. COMPARISONOFTHEOPTIMALBINARYINTEGRATOROUTOF ANOTHER BINARYINTEGRATOROUTOF ANDTHEMOVING WINDOWDETECTORINLOG NORMALINTERFER ENCEANEXAMPLEOFANON 2AYLEIGHDENSITY WHERETHELOGOFTHERETURNHASAGAUSSIAN DENSITY ISSHOWNIN&IGURE4HEOPTIMALBINARYINTEGRATORISMUCHBETTERTHAN THEMOVING WINDOWINTEGRATOR4HEOPTIMALVALUESFORLOG NORMALINTERFERENCEWERE CALCULATEDBY3CHLEHERANDARE- ANDFOR. AND RESPECTIVELY "ATCH0ROCESSOR 4HEBATCHPROCESSOR&IGUREE ISVERYUSEFULWHENALARGE NUMBEROFPULSESAREWITHINTHE D"BEAMWIDTH)F+.PULSESAREINTHE D"BEAM WIDTH +PULSESARESUMMEDBATCHED ANDEITHERAORAISDECLARED DEPENDING ONWHETHERORNOTTHEBATCHISLESSTHANATHRESHOLD44HELAST.ZEROSANDONESARE
!54/-!4)#$%4%#4)/. 42!#+).' !.$3%.3/2).4%'2!4)/.
&)'52% /PTIMUMVALUESOF0.ASAFUNCTIONOFTHESAMPLESIZENANDTHEPROBABILITYOFFALSE ALARM@2ICEANDISTRIBUTIONWITH3. D"PERPULSEAFTER'-$ILLARDÚ)%%%
&)'52% #OMPARISONOFBINARYINTEGRATOR- OUT OF . WITHOTHER INTEGRATIONMETHODS0FA 0$ AFTER-3CHWARTZ Ú)%%%
Ç°
Ç°£ä
2!$!2(!.$"//+
&)'52% #OMPARISONOFBINARYINTEGRATOR- OUT OF . WITH OTHERINTEGRATIONMETHODS0FA 0$ AFTER-3CHWARTZ Ú)%%%
SUMMEDANDCOMPAREDWITHASECONDTHRESHOLD-!NALTERNATIVEVERSIONOFTHISDETEC TORISTOPUTTHEBATCHAMPLITUDESTHROUGHAMOVING WINDOWDETECTOR 4HEBATCHPROCESSOR LIKETHEBINARYINTEGRATOR ISEASILYIMPLEMENTED IGNORESINTER FERENCESPIKES ANDWORKSEXTREMELYWELLWHENTHENOISEHASANON 2AYLEIGHDENSITY &URTHERMORE THE BATCH PROCESSOR REQUIRES LESS STORAGE DETECTS BETTER AND ESTIMATES
&)'52% #OMPARISONOFVARIOUSDETECTORSINLOG NORMALR D" INTERFERENCE. 0FA AFTER$#3CHLEHERÚ)%%%
!54/-!4)#$%4%#4)/. 42!#+).' !.$3%.3/2).4%'2!4)/.
Ç°££
ANGLESMOREACCURATELYTHANTHEBINARYINTEGRATOR&ORINSTANCE IFTHEREWEREPULSES ONTARGET ONECOULDBATCHPULSES QUANTIZETHISRESULTTOAORA ANDDECLAREATARGET WITHA OUT OF OR OUT OF BINARYINTEGRATOR4HEDETECTIONPERFORMANCEOFTHE BATCHPROCESSORFORALARGENUMBEROFPULSESINTEGRATEDISAPPROXIMATELYD"WORSE THANTHEMOVINGWINDOW4HEBATCHPROCESSORHASBEENSUCCESSFULLYIMPLEMENTEDBY THE!PPLIED0HYSICS,ABORATORYOF4HE*OHNS(OPKINS5NIVERSITY4OOBTAINANACCU RATEAZIMUTHESTIMATE Q} APPROXIMATELYPERCENTGREATERTHANTHELOWERBOUND £ "IQI Q} £ "I
ISUSED WHERE"IISTHEBATCHAMPLITUDEANDPIISTHEAZIMUTHANGLECORRESPONDINGTO THECENTEROFTHEBATCH &ALSE !LARM#ONTROL )NTHEPRESENCEOFCLUTTER IFFIXEDTHRESHOLDSAREUSEDWITH THEPREVIOUSLYDISCUSSEDINTEGRATORS ANENORMOUSNUMBEROFDETECTIONSWILLOCCURAND WILLSATURATEANDDISRUPTTHETRACKINGCOMPUTERASSOCIATEDWITHTHERADARSYSTEM&OUR IMPORTANTFACTSSHOULDBENOTED L
L
L
L
! TRACKING SYSTEM SHOULD BE ASSOCIATED WITH THE AUTOMATIC DETECTION SYSTEM THE ONLYEXCEPTIONISWHENONEDISPLAYSMULTIPLESCANSOFDETECTIONS 4HE 0FA OF THE DETECTOR SHOULD BE MATCHED TO THE TRACKING SYSTEM TO PRODUCE THE OVERALLLOWEST3.REQUIREDTOFORMATRACKWITHOUTINITIATINGTOOMANYFALSETRACKS SEE&IGURE LATERINTHISCHAPTER 2ANDOMFALSEALARMSANDUNWANTEDTARGETSEG STATIONARYTARGETS ARENOTAPROB LEMIFTHEYAREREMOVEDBYTHETRACKINGSYSTEM 3CAN TO SCANPROCESSINGCANBEUSEDTOREMOVESTATIONARYPOINTCLUTTERORMOVING TARGETINDICATION-4) CLUTTERRESIDUES
/NECANLIMITTHENUMBEROFFALSEALARMSWITHAFIXED THRESHOLDSYSTEMBYSETTING AVERYHIGHTHRESHOLD5NFORTUNATELY THISWOULDREDUCETARGETSENSITIVITYINREGIONSOF LOWNOISECLUTTER RETURN4HREEMAINAPPROACHESADAPTIVETHRESHOLD NONPARAMET RICDETECTORS ANDCLUTTERMAPSHAVEBEENUSEDTOREDUCETHEFALSE ALARMPROBLEM !DAPTIVE THRESHOLDING AND NONPARAMETRIC DETECTORS ASSUME THAT THE SAMPLES IN THE RANGECELLSSURROUNDINGTHETESTCELLCALLEDREFERENCECELLS AREINDEPENDENTANDIDENTI CALLYDISTRIBUTED&URTHERMORE ITISUSUALLYASSUMEDTHATTHETIMESAMPLESAREINDEPEN DENT"OTHKINDSOFDETECTORSTESTWHETHERTHETESTCELLHASARETURNSUFFICIENTLYLARGER THANTHEREFERENCECELLS#LUTTERMAPSALLOWVARIATIONINSPACE BUTTHECLUTTERMUSTBE STATIONARYOVERSEVERALTYPICALLYTO SCANS#LUTTERMAPSSTOREANAVERAGEBACK GROUNDLEVELFOREACHRANGE AZIMUTHCELL!TARGETISTHENDECLAREDINARANGE AZIMUTH CELLIFTHENEWVALUEEXCEEDSTHEAVERAGEBACKGROUNDLEVELBYASPECIFIEDAMOUNT !DAPTIVE4HRESHOLDING 4HEBASICASSUMPTIONOFTHEADAPTIVETHRESHOLDINGTECH NIQUEISTHATTHEPROBABILITYDENSITYOFTHENOISEISKNOWNEXCEPTFORAFEWUNKNOWN PARAMETERS4HESURROUNDINGREFERENCECELLSARETHENUSEDTOESTIMATETHEUNKNOWN PARAMETERS ANDATHRESHOLDBASEDONTHEESTIMATEDPARAMETERSISOBTAINED4HESIM PLEST ADAPTIVE DETECTOR SHOWN IN &IGURE IS THE CELL AVERAGE #&!2 CONSTANT FALSE ALARMRATE INVESTIGATEDBY&INNAND*OHNSON)FTHENOISEHASA2AYLEIGHDEN SITY PX XEXP XR R ONLYTHEPARAMETERRRISTHENOISEPOWER NEEDSTO BEESTIMATED ANDTHETHRESHOLDISOFTHEFORM4 +3XI +N P S} WHERE S} ISTHE
Ç°£Ó
2!$!2(!.$"//+
&)'52% #ELL AVERAGING#&!24HELETTER#INDICATESACOMPARISONFROM'64RUNK
ESTIMATEOFR(OWEVER SINCE4ISSETBYANESTIMATE S} ITHASSOMEERRORANDMUSTBE SLIGHTLYLARGERTHANTHETHRESHOLDTHATONEWOULDUSEIFRWEREKNOWNEXACTLYAPRIORI 4HERAISEDTHRESHOLDCAUSESALOSSINTARGETSENSITIVITYANDISREFERREDTOASA#&!2 LOSS4HISLOSSHASBEENCALCULATEDANDISSUMMARIZEDIN4ABLE!SCANBESEEN FORASMALLNUMBEROFREFERENCECELLS THELOSSISLARGEBECAUSEOFTHEPOORESTIMATEOF R#ONSEQUENTLY ONEWOULDPREFERTOUSEALARGENUMBEROFREFERENCECELLS(OWEVER IFONEDOESTHIS THEHOMOGENEITYASSUMPTIONIE ALLTHEREFERENCECELLSARESTATISTI CALLYSIMILAR MIGHTBEVIOLATED!GOODRULEOFTHUMBISTOUSEENOUGHREFERENCECELLS SOTHATTHE#&!2LOSSISBELOWD"ANDATTHESAMETIMENOTLETTHEREFERENCECELLS EXTENDOVERARANGEINTERVALTHATVIOLATESTHEHOMOGENOUSBACKGROUNDASSUMPTION 5NFORTUNATELY FORASPECIFICRADARTHISMIGHTNOTBEFEASIBLE )FTHEREISUNCERTAINTYABOUTWHETHERORNOTTHENOISEIS2AYLEIGH DISTRIBUTED ITIS BETTERTOTHRESHOLDINDIVIDUALPULSESANDUSEABINARYINTEGRATORASSHOWNIN&IGURE 4HISDETECTORISTOLERANTOFVARIATIONSINTHENOISEDENSITYBECAUSEBYSETTING+TOYIELD AWITHPROBABILITY A0FAy CANBEOBTAINEDBYUSINGA OUT OF DETECTOR 7HILENOISEMAYBENON 2AYLEIGH ITWILLPROBABLYBEVERY2AYLEIGH LIKEOUTTOTHE
4!",% #&!2,OSSFOR0FA AND0$
.UMBEROF0ULSES )NTEGRATED
,OSSFOR6ARIOUS.UMBERSOF2EFERENCE#ELLSIND"
AFTER2,-ITCHELLAND*&7ALKERÚ)%%%
c
!54/-!4)#$%4%#4)/. 42!#+).' !.$3%.3/2).4%'2!4)/.
Ç°£Î
&)'52% )MPLEMENTATION OF A BINARY INTEGRATOR 4HE LETTER # INDICATES A COMPARISON FROM'64RUNK
TENTHPERCENTILE&URTHERMORE ONECANUSEFEEDBACKBASEDONSEVERALSCANSOFDATA TOCONTROL+INORDERTOMAINTAINADESIRED0FAONEITHERASCANORASECTORBASIS4HIS DEMONSTRATESAGENERALRULETOMAINTAINALOW0FAINVARIOUSENVIRONMENTS ADAPTIVE THRESHOLDINGSHOULDBEPLACEDINFRONTOFTHEINTEGRATOR )FTHENOISEPOWERVARIESFROMPULSETOPULSEASITWOULDINJAMMINGWHENFRE QUENCYAGILITYISEMPLOYED ONEMUST#&!2EACHPULSEANDTHENINTEGRATE7HILETHE BINARYINTEGRATORPERFORMSTHISTYPEOF#&!2ACTION ANALYSIS HASVERIFIEDTHATTHE RATIODETECTORSHOWNIN&IGUREISABETTERDETECTOR4HERATIODETECTORSUMSSIGNAL TO NOISERATIOSANDISSPECIFIEDBY N
£ I
XI J M
§©XI J K XI J K ¶¸ M £ K
WHEREXIJ ISTHEITHENVELOPE DETECTEDPULSEINTHEJTHRANGECELLANDMISTHENUMBER OF REFERENCE CELLS 4HE DENOMINATOR IS THE MAXIMUM LIKELIHOOD ESTIMATE OF S I THE NOISEPOWERPERPULSE4HERATIODETECTORWILLDETECTTARGETSEVENTHOUGHONLYAFEW RETURNEDPULSESHAVEAHIGHSIGNAL TO NOISERATIO5NFORTUNATELY THISWILLALSOCAUSE THERATIODETECTORTODECLAREFALSEALARMSINTHEPRESENCEOFNARROW PULSEINTERFERENCE 4OREDUCETHENUMBEROFFALSEALARMSWHENNARROW PULSEINTERFERENCEISPRESENT THE INDIVIDUALPOWERRATIOSCANBESOFT LIMITEDTOASMALLENOUGHVALUESOTHATINTERFER ENCEWILLCAUSEONLYAFEWFALSEALARMS!COMPARISONOFTHERATIODETECTORWITHOTHER COMMONLYUSEDDETECTORSISSHOWNIN&IGURESANDFORNONFLUCTUATINGAND FLUCTUATING TARGETS! TYPICAL PERFORMANCE IN SIDELOBE JAMMING WHEN THE JAMMING LEVELVARIESBYD"PERPULSEISSHOWNIN&IGURE"YEMPLOYINGASECONDTESTTO
Ç°£{
2!$!2(!.$"//+
&)'52% 2ATIODETECTORFROM'64RUNK
IDENTIFYTHEPRESENCEOFNARROW PULSEINTERFERENCE ADETECTIONPERFORMANCEAPPROXI MATELYHALFWAYBETWEENTHELIMITINGANDNONLIMITINGRATIODETECTORSCANBEOBTAINED )FTHENOISESAMPLESHAVEANON 2AYLEIGHDENSITYSUCHASTHECHI SQUAREDENSITYOR LOG NORMALDENSITY ITISNECESSARYTOESTIMATEMORETHANONEPARAMETERANDTHEADAP TIVEDETECTORISMORECOMPLICATED5SUALLYTWOPARAMETERSAREESTIMATED THEMEAN ANDTHEVARIANCE ANDATHRESHOLDOFTHEFORM 4 M} +S} ISUSED4HESAMPLEDMEAN ISEASILYOBTAINED(OWEVER THEUSUALESTIMATEOFTHESTANDARDDEVIATION
§ ¶ S} ¨ £ XI M} · ©. ¸
WHERE
M} £ XI .
&)'52% #URVESOFPROBABILITYOFDETECTIONVERSUSSIGNAL TO NOISERATIOPERPULSEFORTHE CELL AVERAGING#&!2 RATIODETECTORS LOGINTEGRATOR ANDBINARYINTEGRATORNONFLUCTUATINGTARGET . M REFERENCECELLS AND0FA FROM'64RUNKAND0+(UGHES
!54/-!4)#$%4%#4)/. 42!#+).' !.$3%.3/2).4%'2!4)/.
Ç°£x
&)'52% #URVES OF PROBABILITY OF DETECTION VERSUS SIGNAL TO NOISE RATIO FOR THE CELL AVERAGING#&!2 RATIODETECTORS LOGINTEGRATOR ANDBINARYINTEGRATOR2AYLEIGH PULSE TO PULSE FLUCTUATINGTARGET . M REFERENCECELLS AND0FA FROM'64RUNKAND0+ (UGHES
ISSOMEWHATMOREDIFFICULTTOIMPLEMENTCONSEQUENTLY THEMEANDEVIATEDEFINEDBY
S ! £ \ XI M} \
ISSOMETIMESUSEDBECAUSEOFITSEASEOFIMPLEMENTATIONANDBECAUSEITISMOREROBUST )TSHOULDBENOTEDTHATTHE#&!2LOSSASSOCIATEDWITHATWO PARAMETERTHRESHOLDIS LARGERTHANTHOSEASSOCIATEDWITHAONE PARAMETERTHRESHOLDSEE4ABLE ANDFOR THATREASON ATWO PARAMETERTHRESHOLDISRARELYUSED
&)'52% #URVES OF PROBABILITY OF DETECTION VERSUS SIGNAL TO NOISE RATIO FOR THE CELL AVERAGING#&!2 RATIODETECTORS LOGINTEGRATOR ANDBINARYINTEGRATOR2AYLEIGH PULSE TO PULSE FLUCTUATIONS M REFERENCECELLS 0FA ANDMAXIMUMJAMMING TO NOISERATIO D" FROM'64RUNKAND0+(UGHES
Ç°£È
2!$!2(!.$"//+
)FTHENOISESAMPLESARECORRELATED NOTHINGCANBEDONETOTHEBINARYINTEGRATORTO YIELDALOW0FA4HUS ITSHOULDNOTBEUSEDINTHISSITUATION(OWEVER IFTHECORRELATION TIMEISLESSTHANABATCHINGINTERVAL THEBATCHPROCESSORWILLYIELDALOW0FAWITHOUT MODIFICATIONS 4ARGET3UPPRESSION 4ARGETSUPPRESSIONISTHELOSSINDETECTABILITYCAUSEDBYOTHER TARGETSORCLUTTERRESIDUESINTHEREFERENCECELLS"ASICALLY THEREARETWOAPPROACHESTO SOLVINGTHISPROBLEM REMOVELARGERETURNFROMTHECALCULATIONOFTHETHRESHOLDnOR DIMINISHTHEEFFECTSOFLARGERETURNSBYEITHERLIMITINGORUSINGLOGVIDEO4HETECHNIQUE THATSHOULDBEUSEDISAFUNCTIONOFTHEPARTICULARRADARSYSTEMANDITSENVIRONMENT 2ICKARDAND$ILLARDPROPOSEDACLASSOFDETECTORS$+ WHERETHE+LARGESTSAMPLES ARECENSOREDREMOVED FROMTHEREFERENCECELLS!COMPARISONOF$NOCENSORING WITH$AND$FORA3WERLINGTARGETANDASINGLESQUARE LAWDETECTEDPULSEISSHOWN IN&IGURE WHERE.ISTHENUMBEROFREFERENCECELLS AISTHERATIOOFTHEPOWEROF THEINTERFERINGTARGETTOTHETARGETINTHETESTCELL ANDTHEBRACKETEDPAIRM N INDICATES THE3WERLINGMODELSOFTHETARGETANDTHEINTERFERINGTARGET RESPECTIVELY!SSHOWN IN&IGURE WHENONEHASANINTERFERINGTARGET THE0$DOESNOTAPPROACHAS3. INCREASES!NOTHERAPPROACHTHATCENSORSSAMPLESINTHEREFERENCECELLIFTHEYEXCEED ATHRESHOLDISBRIEFLYDISCUSSEDINTHEh.ONPARAMETRIC$ETECTORvSUBSECTION &INNINVESTIGATEDTHEPROBLEMOFTHEREFERENCECELLSSPANNINGTWOCONTINUOUSDIF FERENThNOISEvFIELDSEG THERMALNOISE SEACLUTTER ETC /NTHEBASISOFTHESAMPLES HEESTIMATEDTHESTATISTICALPARAMETERSOFTHETWONOISEFIELDSANDTHESEPARATIONPOINT BETWEENTHEM4HEN ONLYTHOSEREFERENCECELLSTHATAREINTHENOISEFIELDCONTAINING THETESTCELLAREUSEDTOCALCULATETHEADAPTIVETHRESHOLD !NALTERNATIVEAPPROACHFORINTERFERINGTARGETSISTOUSELOGVIDEO"YTAKINGTHE LOG LARGESAMPLESINTHEREFERENCECELLSWILLHAVELESSEFFECTTHANLINEARVIDEOONTHE THRESHOLD4HELOSSASSOCIATEDWITHUSINGLOGVIDEO RATHERTHANLINEARVIDEO ISD"
&)'52% $ETECTION PROBABILITY VERSUS 3.2 FOR A 3WERLING #ASE PRIMARY TARGET AFTER*42ICKARDAND'-$ILLARDÚ)%%%
!54/-!4)#$%4%#4)/. 42!#+).' !.$3%.3/2).4%'2!4)/.
Ç°£Ç
&)'52% "LOCKDIAGRAMOFCELL AVERAGINGLOG #&!2RECEIVERAFTER6'(ANSEN AND*27ARDÚ)%%%
FORPULSESINTEGRATEDANDD"FORPULSESINTEGRATED!NIMPLEMENTATION OFTHELOG#&!2ISSHOWNIN&IGURE)NMANYSYSTEMS THEANTILOGSHOWNIN &IGUREISNOTTAKEN4OMAINTAINTHESAME#&!2LOSSASFORLINEARVIDEO THE NUMBEROFREFERENCECELLS-LOGFORTHELOG#&!2SHOULDEQUAL
-LOG -LIN
WHERE-LINISTHENUMBEROFREFERENCECELLSFORLINEARVIDEO4HEEFFECTOFTARGETSUPPRES SIONWITHLOGVIDEOISDISCUSSEDLATERINTHISSECTIONSEE4ABLE LATERINTHECHAPTER .ONPARAMETRIC$ETECTORS 5SUALLYNONPARAMETRICDETECTORSOBTAIN#&!2BYRANK ING THE TEST SAMPLE WITH THE REFERENCE CELLS 2ANKING MEANS THAT ONE ORDERS THE SAMPLESFROMTHESMALLESTTOTHELARGESTANDREPLACESTHESMALLESTWITHRANK THENEXT SMALLESTWITHRANK ANDTHELARGESTWITHRANKN 5NDERTHEHYPOTHESISTHAT ALLTHESAMPLESAREINDEPENDENTSAMPLESFROMANUNKNOWNDENSITYFUNCTION THETEST SAMPLEHASEQUALPROBABILITYOFTAKINGONANYOFTHENVALUES&ORINSTANCE REFERRINGTO THERANKERIN&IGURE THETESTCELLISCOMPAREDWITHOFITSNEIGHBORS3INCE INTHE SETOFSAMPLES THETESTSAMPLEHASEQUALPROBABILITYOFBEINGTHESMALLESTSAMPLEOR EQUIVALENTLYANYOTHERRANK THEPROBABILITYTHATTHETESTSAMPLETAKESONVALUES IS!SIMPLERANKDETECTORISCONSTRUCTEDBYCOMPARINGTHERANKWITHATHRESHOLD +ANDGENERATINGAIFTHERANKISLARGER AOTHERWISE4HESANDSARESUMMEDINA MOVINGWINDOW4HISDETECTORINCURSA#&!2LOSSOFABOUTD"BUTACHIEVESAFIXED 0FAFORANYUNKNOWNNOISEDENSITYASLONGASTHETIMESAMPLESAREINDEPENDENT4HIS DETECTORWASINCORPORATEDINTOTHE!243 !POSTPROCESSORUSEDINCONJUNCTIONWITHTHE &EDERAL!VIATION!DMINISTRATIONAIRPORTSURVEILLANCERADAR!32 4HEMAJORSHORTCOM INGOFTHISDETECTORISTHATITISFAIRLYSUSCEPTIBLETOTARGETSUPPRESSIONEG IFALARGE TARGETISINTHEREFERENCECELLS THETESTCELLCANNOTRECEIVETHEHIGHESTRANKS )FTHETIMESAMPLESARECORRELATED THERANKDETECTORWILLNOTYIELD#&!2!MOD IFIEDRANKDETECTOR CALLEDTHEMODIFIEDGENERALIZEDSIGNTEST-'34 MAINTAINS ALOW0FAANDISSHOWNIN&IGURE4HISDETECTORCANBEDIVIDEDINTOTHREEPARTS A RANKER AN INTEGRATOR IN THIS CASE A TWO POLE FILTER AND A THRESHOLD DECISION PROCESS !TARGETISDECLAREDWHENTHEINTEGRATEDOUTPUTEXCEEDSTWOTHRESHOLDS
Ç°£n
2!$!2(!.$"//+
&)'52% 2ANKDETECTOROUTPUTOFACOMPARATOR#ISEITHERAZEROORA ONEFROM'64RUNK
4HEFIRSTTHRESHOLDISFIXEDEQUALSL 4+IN&IGURE ANDYIELDS0FA WHEN THE REFERENCE CELLS ARE INDEPENDENT AND IDENTICALLY DISTRIBUTED4HE SECOND THRESHOLDISADAPTIVEANDMAINTAINSALOW0FAWHENTHEREFERENCESAMPLESARECOR RELATED4HEDEVICEESTIMATESTHESTANDARDDEVIATIONOFTHECORRELATEDSAMPLESWITH THE MEAN DEVIATE ESTIMATOR WHERE EXTRANEOUS TARGETS IN THE REFERENCE CELLS HAVE BEENEXCLUDEDFROMTHEESTIMATEBYUSEOFAPRELIMINARYTHRESHOLD4 4HE BASIC DISADVANTAGES OF ALL NONPARAMETRIC DETECTORS ARE THAT THEY HAVE RELATIVELY LARGE #&!2 LOSSES THEY HAVE PROBLEMS WITH CORRELATED SAMPLES AND ONE LOSES AMPLITUDE INFORMATION WHICH CAN BE A VERY IMPORTANT DISCRIMINANT BETWEENTARGETANDCLUTTER&OREXAMPLE ALARGERETURNCROSSSECTIONqM IN ACLUTTERAREAISPROBABLYJUSTCLUTTERBREAKTHROUGH3EEh2ADAR$ETECTION!CCEPTANCEv IN3ECTION #LUTTER-APPING !CLUTTERMAPUSESADAPTIVETHRESHOLDINGWHERETHETHRESHOLD ISCALCULATEDFROMTHERETURNINTHETESTCELLONPREVIOUSSCANSRATHERTHANFROMTHESUR ROUNDINGREFERENCECELLSONTHESAMESCAN4HISTECHNIQUEHASTHEADVANTAGEINTHAT FORESSENTIALLYSTATIONARYENVIRONMENTSEG LAND BASEDRADARAGAINSTGROUNDCLUTTER THERADARHASINTERCLUTTERVISIBILITYITCANSEEBETWEENLARGECLUTTERRETURNS,INCOLN ,ABORATORYINITSMOVING TARGETDETECTOR-4$ USEDACLUTTERMAPFORTHEZERO DOP PLERFILTERVERYEFFECTIVELY4HEDECISIONTHRESHOLD4FORTHEITHCELLIS
4 ! 3I
WHERETHECLUTTERISESTIMATEDUSINGASIMPLEFEEDBACKINTEGRATOR
3I + 3I 8I
!54/-!4)#$%4%#4)/. 42!#+).' !.$3%.3/2).4%'2!4)/.
Ç°£
&)'52% -ODIFIEDGENERALIZEDSIGNTESTPROCESSORAFTER'64RUNKETAL
WHERE3IISTHEAVERAGEBACKGROUNDLEVEL 8IISTHERETURNINTHEITHCELL +ISTHEFEED BACKVALUETHATDETERMINESTHEMAPTIMECONSTANT AND!ISTHECONSTANTTHATDETERMINES THE0FA)NTHE-4$USEDFORTHE!32APPLICATION +IS WHICHEFFECTIVELYAVERAGES THELASTEIGHTSCANS4HEPURPOSEOFTHECLUTTERMAPISTODETECT INCLUTTERFREEAREAS CROSSINGTARGETSTHATWOULDHAVEBEENREMOVEDBYTHEDOPPLERPROCESSING4HEMAIN UTILITYOFCLUTTERMAPSISWITHFIXED FREQUENCY LAND BASEDRADARS7HILECLUTTERMAPS CAN BE USED WITH FREQUENCY AGILE RADARS AND ON MOVING PLATFORMS EG RADARS ON SHIPS THEYARENOTNEARLYASEFFECTIVEINTHESEENVIRONMENTS 4ARGET2ESOLUTION )NAUTOMATICDETECTIONSYSTEMS ASINGLELARGETARGETWILLPROB ABLYBEDETECTEDIE CROSSADETECTIONTHRESHOLD MANYTIMES EG INADJACENTRANGE CELLS AZIMUTH BEAMS AND ELEVATION BEAMS 4HEREFORE AUTOMATIC DETECTION SYSTEMS HAVEALGORITHMSFORMERGINGTHEINDIVIDUALDETECTIONSINTOASINGLECENTROIDEDDETEC TION-OSTALGORITHMSHAVEBEENDESIGNEDSOTHATTHEYWILLRARELYSPLITASINGLETARGET INTOTWOTARGETS4HISPROCEDURERESULTSINPOORRANGERESOLUTIONCAPABILITY!MERG INGALGORITHMOFTENUSEDISTHEADJACENT DETECTIONMERGINGALGORITHM WHICHDECIDES WHETHERANEWDETECTIONISADJACENTTOANYOFTHEPREVIOUSLYDETERMINEDSETSOFADJACENT DETECTIONS)FTHENEWDETECTIONISADJACENTTOANYDETECTIONINTHESETOFADJACENTDETEC TIONS ITISADDEDTOTHESET4WODETECTIONSAREADJACENTIFTWOOFTHEIRTHREEPARAMETERS RANGE AZIMUTH AND ELEVATION ARE THE SAME AND THE OTHER PARAMETER DIFFERS BY THE RESOLUTIONELEMENTRANGECELL$2 AZIMUTHBEAMWIDTHP ORELEVATIONBEAMWIDTHF ! STUDY COMPARED THE RESOLVING CAPABILITY OF THREE COMMON DETECTION PROCE DURESLINEARDETECTORWITH 4 M} !S} LINEARDETECTORWITH 4 "M} ANDLOGDETECTOR WITH 4 # M} WHERETHECONSTANTS! " AND#AREUSEDTOOBTAINTHESAME0FAFOR ALLDETECTORS4HEESTIMATES M} AND S} OFLANDRWEREOBTAINEDFROMEITHER ALLTHE REFERENCECELLSOR THELEADINGORLAGGINGHALFOFTHEREFERENCECELLS CHOOSINGTHE
Ç°Óä
2!$!2(!.$"//+
4!",% 0ROBABILITYOF$ETECTING"OTH4ARGETSWITH,OG6IDEO7HENTHE4WO4ARGETS!RE 3EPARATEDBY OR2ANGE#ELLS3.OFTARGETISD"AND3.OFTARGETIS ORD"
4HRESHOLDING 4ECHNIQUE !LLREFERENCECELLS
2EFERENCECELLSWITH MINIMUMMEANVALUE
4ARGET 3EPARATION
3.OF4ARGETNO
AFTER'64RUNKÚ)%%%
HALFWITHTHELOWERMEANVALUE4HEFIRSTSIMULATIONINVOLVEDTWOTARGETSSEPARATEDBY ORRANGECELLSANDATHIRDTARGETRANGECELLSFROMTHEFIRSTTARGET 7HENTHETWOCLOSELYSPACEDTARGETSWEREWELLSEPARATED EITHERORRANGECELLS APART THEPROBABILITYOFDETECTINGBOTHTARGETS0$ WAS FORTHELINEARDETECTOR WITH 4 M} !S} 0$ FORTHELINEARDETECTORWITH 4 "M} AND0$ FORTHELOGDETECTOR!SECONDSIMULATION INVOLVINGONLYTWOTARGETS INVESTIGATEDTHE EFFECTOFTARGETSUPPRESSIONONLOGVIDEO ANDTHERESULTSARESUMMARIZEDIN4ABLE 4HEMAXIMUMVALUEOF0$ISOBTAINEDWHENBOTHTARGETSHAVEAN3.OFD")FONE OFTHETARGETSHASALARGER3.THANTHEOTHERTARGET SUPPRESSIONOCCURSEITHERTARGET SUPPRESSESTARGETORVICEVERSA!LSO ONENOTESANIMPROVEDPERFORMANCEFORASMALL 3.TOD" WHENCALCULATINGTHETHRESHOLDUSINGONLYTHEHALFOFTHEREFERENCE CELLSWITHTHELOWERMEANVALUE4HERESOLUTIONCAPABILITYOFTHELOGDETECTORTHATUSES ONLYTHEHALFOFTHEREFERENCECELLSWITHTHELOWERMEANISSHOWNIN&IGURE4HE PROBABILITYOFRESOLVINGTWO EQUAL AMPLITUDETARGETSDOESNOTRISEABOVEUNTILTHEY ARESEPARATEDINRANGEBYPULSEWIDTHS "YASSUMINGTHATTHETARGETISSMALLWITHRESPECTTOTHEPULSEWIDTHANDTHATTHEPULSE SHAPEISKNOWN THERESOLUTIONCAPABILITYCANBEIMPROVEDBYFITTINGTHEKNOWNPULSE SHAPETOTHERECEIVEDDATAANDCOMPARINGTHERESIDUESQUAREERRORWITHATHRESHOLD )FONLYONETARGETISPRESENT THERESIDUESHOULDBEONLYNOISEANDHENCESHOULDBE SMALL )F TWO OR MORE TARGETS ARE PRESENT THE RESIDUE WILL CONTAIN SIGNAL FROM THE REMAINING TARGETS AND SHOULD BE LARGE 4HE RESULTS OF RESOLVING TWO TARGETS WITH 3. D" ARE SHOWN IN &IGURE 4HESE TARGETS CAN BE RESOLVED AT A RESOLU TIONPROBABILITYOFWITHAFALSEALARMPROBABILITYOFATSEPARATIONSVARYING BETWEENONE FOURTHANDTHREE FOURTHSOFAPULSEWIDTH DEPENDINGONTHERELATIVEPHASE DIFFERENCEBETWEENTHETWOTARGETS-OREOVER THISRESULTCANBEIMPROVEDFURTHERBY PROCESSINGMULTIPLEPULSES !UTOMATIC$ETECTION3UMMARY 7HENONLYTOSAMPLESPULSES AREAVAIL ABLE ABINARYINTEGRATORSHOULDBEUSEDTOAVOIDFALSEALARMSDUETOINTERFERENCE7HEN AMODERATENUMBEROFPULSESTO AREAVAILABLE ABINARYINTEGRATOR OR A MOV ING WINDOWINTEGRATORSHOULDBEUSED)FTHENUMBEROFPULSESISLARGEGREATERTHAN ABATCHPROCESSORSHOULDBEUSED)FTHESAMPLESAREINDEPENDENT AONE PARAM ETERMEAN THRESHOLDCANBEUSED)FTHESAMPLESAREDEPENDENT ONECANEITHERUSE
!54/-!4)#$%4%#4)/. 42!#+).' !.$3%.3/2).4%'2!4)/.
Ç°Ó£
&)'52% 2ESOLUTION CAPABILITY OF A LOG DETECTOR THAT USED HALF OF THE REFERENCES CELLS WITH LOWERMEANAFTER'64RUNKÚ)%%%
A TWO PARAMETERMEAN ANDVARIANCE THRESHOLD ORADAPT AONE PARAMETERTHRESHOLD ONASECTORBASIS(OWEVER THESERULESSHOULDSERVEONLYASAGENERALGUIDELINE)TIS HIGHLYRECOMMENDEDTHATBEFOREADETECTORISCHOSENTHERADARVIDEOFROMTHEENVI RONMENTOFINTERESTBECOLLECTEDANDANALYZEDANDTHATVARIOUSDETECTIONPROCESSESBE SIMULATEDONACOMPUTERANDTESTEDAGAINSTTHERECORDEDDATA
&)'52% 0ROBABILITYOFRESOLUTIONASAFUNCTIONOFRANGESEPARATIONPROBABILITYOFFALSEALARM ISSAMPLINGRATE$2 SAMPLESPERPULSEWIDTHTARGETSTRENGTHS NONFLUCTUATING ! ! D"PHASEDIFFERENCES ANDAFTER'64RUNKÚ)%%%
Ç°ÓÓ
2!$!2(!.$"//+
-ANYMODERNRADARSUSECOHERENTPROCESSINGTOREMOVECLUTTER&ORTHEPURPOSEOF APPLYINGTHEPREVIOUSDISCUSSIONSONNONCOHERENTPROCESSINGTOCOHERENTPROCESSING THEINTEGRATEDOUTPUTINARANGE DOPPLERCELLOFTHEDOPPLERPROCESSORFORASINGLECOHER ENTPROCESSINGINTERVAL#0) CANBETREATEDASASINGLENONCOHERENTPULSE"ECAUSE THREEAMBIGUOUSMEASUREMENTSIE DETECTIONS AREUSUALLYREQUIREDTOREMOVETHE RANGEANDDOPPLERAMBIGUITIES TO#0)SMAYBETRANSMITTED ANDHENCE THERE AREUSUALLYTONONCOHERENTPULSESAVAILABLEFORPROCESSING
Ç°ÎÊ 1/" / Ê/, !TRACKREPRESENTSTHEBELIEFTHATAPHYSICALOBJECTORhTARGETvISPRESENTANDHASACTU ALLYBEENDETECTEDBYTHERADAR!NAUTOMATICRADARTRACKINGSYSTEMFORMSATRACKWHEN ENOUGHRADARDETECTIONSAREMADEINABELIEVABLEENOUGHPATTERNTOINDICATEATARGETIS ACTUALLYPRESENTASOPPOSEDTOASUCCESSIONOFFALSEALARMS ANDWHENENOUGHTIMEHAS PASSEDTOALLOWACCURATECALCULATIONOFTHETARGETSKINEMATICSTATEUSUALLYPOSITION ANDVELOCITY4HUS THEGOALOFTRACKINGISTOTRANSFORMATIME LAPSE DETECTIONPICTURE SHOWNIN&IGUREA CONSISTINGOFTARGETDETECTIONS FALSEALARMS ANDCLUTTER INTO ATRACKPICTURESHOWNIN&IGUREB CONSISTINGOFTRACKSONREALTARGETS OCCASIONAL FALSETRACKS ANDOCCASIONALDEVIATIONSOFTRACKPOSITIONFROMTRUETARGETPOSITIONS &IGURESAANDBALSOILLUSTRATESOMEOFTHECHALLENGESOFAUTOMATICTRACK ING$ETECTIONSAREMADEONTARGETS BUTSOMEDETECTIONSAREMISSINGBECAUSEOFTARGET FADESORMULTIPLETARGETSINTHESAMERESOLUTIONCELL WHEREASADDITIONALDETECTIONSARE PRESENTDUETOCLUTTERORNOISE
&)'52%A 4HIRTY MINUTETIMELAPSEOF!.&0. ,BAND AIRTRAFFIC CONTROL RADAR DETECTIONS OVER A Ò KM SQUARE AREA AFTER ( ,EUNG ET AL Ú)%%%
!54/-!4)#$%4%#4)/. 42!#+).' !.$3%.3/2).4%'2!4)/.
Ç°ÓÎ
&)'52% B 4HIRTY MINUTE TIME LAPSE OF TRACKS FORMED FROM DATA IN &IGURE A USING 'LOBAL .EAREST .EIGHBOR '.. 4ECHNIQUE AFTER (,EUNGETALÚ)%%%
!UTOMATICTRACKINGCANGENERALLYBEDIVIDEDINTOTHEFIVESTEPSSHOWNIN&IGURE ANDDETAILEDHERE 2ADARDETECTIONACCEPTANCEACCEPTINGORREJECTINGDETECTIONSFORINSERTIONINTOTHE TRACKINGPROCESS4HEPURPOSEOFTHISSTEPISTOCONTROLFALSETRACKRATES !SSOCIATIONOFACCEPTEDDETECTIONSWITHEXISTINGTRACKS 5PDATINGEXISTINGTRACKSWITHASSOCIATEDDETECTIONS .EWTRACKFORMATIONUSINGUNASSOCIATEDDETECTIONS 2ADARSCHEDULINGANDCONTROL 4HERESULTOFTHEAUTOMATICTRACKINGPROCESSISATRACKFILETHATCONTAINSATRACKSTATE FOREACHTARGETDETECTEDBYTHERADAR !SSHOWNIN&IGURE THEREISAFEEDBACKLOOPBETWEENALLTHESEFUNCTIONSSOTHE ABILITYTOUPDATEEXISTINGTRACKSACCURATELYNATURALLYAFFECTSTHEABILITYTOASSOCIATEDETEC TIONSWITHEXISTINGTRACKS!LSO THEABILITYTOCORRECTLYASSOCIATEDETECTIONSWITHEXISTING TRACKSAFFECTSTHETRACKSACCURACYANDTHEABILITYTOCORRECTLYDISTINGUISHBETWEENANEXIST INGTRACKANDANEWONE4HEDETECTIONACCEPTREJECTSTEPMAKESUSEOFFEEDBACKFROMTHE ASSOCIATIONFUNCTIONTHATMEASURESTHEDETECTIONACTIVITYINDIFFERENTREGIONSOFTHERADAR COVERAGE-ORESTRINGENTACCEPTANCECRITERIAAREAPPLIEDINMOREACTIVEREGIONS 4RACK&ILE 7HENATRACKISESTABLISHEDINTHECOMPUTER ITISASSIGNEDATRACKNUM BER!LLPARAMETERSASSOCIATEDWITHAGIVENTRACKAREREFERREDTOBYTHISTRACKNUMBER 4YPICALTRACKPARAMETERSARETHEFILTEREDANDPREDICTEDPOSITIONVELOCITYACCELERATION WHENAPPLICABLE TIMEOFLASTUPDATETRACKQUALITYSIGNAL TO NOISERATIOCOVARIANCE MATRICESTHECOVARIANCECONTAINSTHEACCURACYOFALLTHETRACKCOORDINATESANDALLTHE STATISTICALCROSS CORRELATIONSBETWEENTHEM IFA+ALMAN TYPEFILTERISBEINGUSEDAND
&)'52% 3TRUCTUREOFAUTOMATICTRACKINGPROCESS
Ç°Ó{ 2!$!2(!.$"//+
!54/-!4)#$%4%#4)/. 42!#+).' !.$3%.3/2).4%'2!4)/.
Ç°Óx
TRACKHISTORYIE THELASTNDETECTIONS 4RACKSANDDETECTIONSCANBEACCESSEDINVARI OUSSECTORED LINKED LIST ANDOTHERDATASTRUCTURESSOTHATTHEASSOCIATIONPROCESSCAN BEPERFORMEDEFFICIENTLY)NADDITIONTOTHETRACKFILE ACLUTTERFILEISMAINTAINED! CLUTTERNUMBERISASSIGNEDTOEACHSTATIONARYORVERYSLOWLYMOVINGECHO!LLPARAM ETERSASSOCIATEDWITHACLUTTERPOINTAREREFERREDTOBYTHISCLUTTERNUMBER!GAIN EACH CLUTTERNUMBERISASSIGNEDTOASECTORINAZIMUTHFOREFFICIENTASSOCIATION 2ADAR$ETECTION!CCEPTANCE 7HENTHERADARSYSTEMHASEITHERNOORLIMITED COHERENTPROCESSING NOTALLTHEDETECTIONSDECLAREDBYTHEAUTOMATICDETECTORAREUSED INTHETRACKINGPROCESS2ATHER MANYOFTHEDETECTIONSCONTACTS AREFILTEREDOUTIN SOFTWAREUSINGAPROCESSCALLEDACTIVITYCONTROL 4HEBASICIDEAISTOUSEDETECTION SIGNALCHARACTERISTICSINCONNECTIONWITHAMAPOFTHEDETECTIONACTIVITYTOREDUCETHE RATEOFDETECTIONSTOONETHATISACCEPTABLEFORFORMINGTRACKS4HEMAPISCONSTRUCTED BY COUNTING THE UNASSOCIATED DETECTIONS THOSE THAT DO NOT ASSOCIATE WITH EXISTING TRACKS ATTHEPOINTINTHETRACKPROCESSINGSHOWNIN&IGURE #OUNTSAREAVERAGEDOVERMANYREVISITSOFTHERADARTOACHIEVESTATISTICALSIGNIFI CANCE4HEDETECTIONSIGNALCHARACTERISTICSSUCHASAMPLITUDEORSIGNAL TO NOISE ARE THENRE THRESHOLDEDTOREDUCESENSITIVITYINREGIONSOFUNACCEPTABLYHIGHACTIVITY)N NOCIRCUMSTANCESAREDETECTIONSELIMINATEDIFTHEYFALLWITHINATRACKGATEIE AGATE CENTEREDONTHEPREDICTEDPOSITIONOFAFIRMTRACK &IGUREILLUSTRATESANEXAMPLE
&)'52% (ISTOGRAM OF DETECTION SIGNAL TO NOISE RATIO DETECTION ILLUSTRATINGTHEEFFECTIVENESSOFTHEACTIVITYCONTROLUSINGTHESIGNAL TO NOISE TESTINRAINCLUTTER5NGATEDCONTACTSGENERALLYREPRESENTCLUTTER'ATEDCON TACTSGENERALLYREPRESENTTARGETS2E THRESHOLDING INTHISCASE SUCCESSFULLY ELIMINATESLARGENUMBERSOFCLUTTERDETECTIONSWHILEPRESERVINGMOSTTARGET DETECTIONSAFTER7'"ATHETAL
Ç°ÓÈ
2!$!2(!.$"//+
OFTHISPROCESSWHENLARGENUMBERSOFRAINCLUTTERDETECTIONSAREPOTENTIALLYOVERLOAD INGTHETRACKINGPROCESS)NTHISCASE ACTIVITYCONTROLEFFECTIVELYELIMINATESMOSTOFTHE CLUTTERDETECTIONSWITHOUTELIMINATINGMANYOFTHEACTUALTARGETDETECTIONS(OWEVER BECAUSETHISPROCESSESSENTIALLYCONSTITUTESCONTROLLEDDESENSITIZATIONOFTHERADAR IT MUSTBEUSEDWITHCARE4HEMAPPINGOFTHEDETECTIONACTIVITYMUSTBEPRECISESOTHAT DESENSITIZATIONOCCURSONLYINTHOSEREGIONSREQUIRINGIT 5PDATING%XISTING4RACKSWITH!SSOCIATED$ETECTIONS 4HESIMPLESTMETHOD OFUPDATINGATRACKSTATEISTHE@ AFILTERDESCRIBEDBY
XSK XPK @;XMK XPK =
VSK VSK A;XMK XPK =4
XPK XSK VSK 4
WHEREXSK ISTHEFILTEREDPOSITION VSK ISTHEFILTEREDVELOCITY XPK ISTHEPREDICTED POSITION XMK ISTHEMEASUREDPOSITION 4ISTHETIMEBETWEENDETECTIONS AND@ A ARETHEPOSITIONANDVELOCITYGAINS RESPECTIVELY4HESELECTIONOF@ A ISADESIGN TRADEOFF3MALLGAINSMAKEASMALLCORRECTIONINTHEDIRECTIONOFEACHDETECTION!SA RESULT THETRACKINGFILTERISLESSSENSITIVETONOISEBUTISMORESLUGGISHTORESPONDTO MANEUVERSDEVIATIONFROMTHEASSUMEDTARGETMODEL#ONVERSELY LARGEGAINSPRO DUCEMORETRACKINGNOISEBUTQUICKERRESPONSETOMANEUVERS4HESEERRORSAREREADILY CALCULATEDASAFUNCTIONOF@ANDAUSINGTHEFORMULASSHOWNIN4ABLE 4OTUNETHE@ AFILTERFORRADARTRACKING ONEUSESTHERADARPARAMETERSTOCALCULATE THE TRACKING ERRORS LISTED IN 4ABLE AS A FUNCTION OF THE TRACKING GAINS @ AND A 4HENONESELECTSTHEGAINSTHATBESTMEETTHENEEDSOFTHEAPPLICATION&OREXAMPLE CONSIDER A RADAR THAT HAS METER RANGE MEASUREMENT ACCURACY AND A TWO SECOND CONSTANTUPDATEINTERVAL4HEAPPLICATIONOFTHISRADARSYSTEMISTOTRACKATARGETTHAT MOVESLINEARLYBUTWITHOCCASIONALUNPREDICTABLEMANEUVERSOFUPTOGMS
4!",% #HARACTERIZATIONOF4RACKING%RRORSASA&UNCTIONOF4RACKING'AINS@ANDA
3TEADY STATE 4RACK%RROR 3TANDARD DEVIATIONOF FILTEREDTRACKING STATE 2ADARDETECTION 3TANDARD NOISESTANDARD DEVIATION OFPREDICTED DEVIATION R TRACKINGSTATE ,AGBIAS IN #ONSTANT FILTEREDTRACK MANEUVERA STATE UNITSOFGS ,AGBIAS IN #ONSTANT PREDICTEDTRACK MANEUVERA STATE UNITSOFGS %RROR3OURCE 2ADARDETECTION NOISESTANDARD DEVIATION R
)N0OSITION
)N6ELOCITY
§ A B A ¶ S¨ · © A ; A B = ¸ § A AB B ¶ S¨ · ©A ; A B = ¸ A4 A4 B
A B
¶ B S § r¨ 4 ©A ; A B =·¸ ¶ B S § r 4 ¨©A ; A B =·¸ ¤ A ³ A4 ¥ ´ ¦ B µ ¤ A ³ A4 ¥ ´ ¦ B µ
!54/-!4)#$%4%#4)/. 42!#+).' !.$3%.3/2).4%'2!4)/.
Ç°ÓÇ
&ORSIMPLICITY ASSUMETHE"ENEDICT "ORDNERCONSTANTRELATIONSHIP;A @ @ = BETWEEN@ANDA 4HE POSITION ACCURACY OF THE FILTER CAN THEN BE CALCULATED USING THE FORMULAS IN 4ABLEANDISSHOWNIN&IGURE7HENTHETARGETISNONMANEUVERING ACCURACY ASMEASUREDBYTHESTANDARDDEVIATIONOFTHEPREDICTEDTRACKINGSTATE IMPROVESMONO TONICALLY AS THE TRACKING GAIN @ DECREASES TO #ONVERSELY WHEN THE TARGET IS PER FORMINGTHE GMANEUVER ACCURACY ASMEASUREDBYTHELAGORBIAS INTHEPREDICTED TRACKINGSTATE IMPROVESMONOTONICALLYASTHETRACKINGGAININCREASESTO4HETOTAL TRACKINGERRORCANBEDEFINEDASTHEERRORTHATISEXCEEDEDONLYOFTHETIMEDUETO THESUMOFRANDOMERRORSANDBIAS4HETOTALRANGE TRACKINGERRORISBESTINTHEREGION @ WITHAMINIMUMAROUND)FACCURACYFORMANEUVERSISTHEDOMINANT CONCERN THENONEWOULDPROBABLYTUNETHISFILTERTOTOACHIEVETHELOWESTTOTAL ERROR FOR A G ACCELERATION4HIS SAME TECHNIQUE CAN BE APPLIED TO MANY DIFFERENT RADAR TRACKINGPROBLEMSUSINGTHEEQUATIONSIN4ABLETOCALCULATEAGRAPHSUCHAS THEONESHOWNIN&IGURE &ORSIMPLETRACKINGPROBLEMS THE@ AFILTERWITHCONSTANTGAINSSELECTEDFORTHEAPPLI CATIONWILLOFTENBEADEQUATE(OWEVER MORECOMPLEXTRACKINGPROBLEMSREQUIREVARI ABLETRACKINGGAINSEG LARGERGAINSATTHEBEGINNINGOFTHETRACKANDLARGERGAINSAFTER MISSEDDETECTIONSORWHENTHERANGETOTHETRACKDECREASES MAKINGANGLENOISELESSOF ANISSUE !SYSTEMATICMETHODFORCALCULATINGTHEGAINSDEPENDINGONTHESITUATIONISTHE
&)'52% %XAMPLEOFTHETUNINGOFAN@ ARADARRANGE TRACKINGFILTERBYSELECTINGTHEGAINTHATMINI MIZESTOTALERRORRADARPARAMETERSRANGEACCURACY METERSUPDATEINTERVAL SECONDSTARGETPARAMETER GUNKNOWNACCELERATIONGAINRELATION ;A @ @ =
Ç°Ón
2!$!2(!.$"//+
+ALMANFILTER 4HE+ALMANFILTERMINIMIZESTHEMEAN SQUAREPREDICTIONERRORWHEN THERANDOMPROCESSESAREGAUSSIAN4HE+ALMANFILTERCANBEFORMULATEDFORTARGETMOTION INONE TWO ORTHREEDIMENSIONSINPOLAR #ARTESIAN OR%ARTH CENTEREDCOORDINATESAND FORTHREE DIMENSIONAL TWO DIMENSIONAL ORONE DIMENSIONALRADARMEASUREMENTS&OR SIMPLICITY ATHREE DIMENSIONALTRACKINGPROBLEMIN#ARTESIANSPACEWITHTHREEMEASURED RADARDIMENSIONSISCONSIDEREDHERE4ARGETMOTIONISDESCRIBEDBY
8TK ETK 8TK !TK !PTK
WHERE8TK ISTHETARGETSTATEATTIMETK CONSISTINGOFPOSITIONANDVELOCITYCOMPONENTS ETK ISATRANSITIONMATRIXTHATMOVESTHETARGETLINEARLYOVERANELAPSEDTIME 4K TK TK FROMTIMETKTOTIMETK !TK ISTHETARGETSTATECHANGEDUETOANUNKNOWNACCELERATION CAUSEDBYAMANEUVERORATMOSPHERICDRAGAND!PTK ISTARGETSTATECHANGEDUETOAKNOWN ACCELERATIONTHATCANBECORRECTED SUCHASGRAVITYFORAFALLINGOBJECTOR#ORIOLLISACCELERA TION4HECOMPONENTSOFTHESTATEVECTORANDTRANSITIONMATRIXFORTHISPROBLEMARE X T K u
8 T K
X T K Y T K u
Y T K Z T K u
Z T K
F T K
4K
4K
4K
4HEUNKNOWNACCELERATION!TK ISZERO MEANANDISCHARACTERIZEDBYITSCOVARIANCE MATRIX1TK )FONEVIEWSTHEUNKNOWNMANEUVERASAWHITE NOISEPROCESSWITHSPEC TRALDENSITYQG(Z THENTHEACCELERATIONISSAMPLEDBYEACHRADARDETECTIONPRODUCING ADISCRETECOVARIANCEMATRIX
4K 4K 4K 4K 4K 4K 1 T K Q 4K 4K 4K 4K 4K 4K
4HEOBSERVATIONEQUATIONRELATESTHEACTUALRADARMEASUREMENTS9KATTIMETKTOTHE TARGETSTATE
9K H8TK NK
WHERENKISTHERADARMEASUREMENTNOISEHAVINGACOVARIANCEMATRIX
S R S Q K S J S $
!54/-!4)#$%4%#4)/. 42!#+).' !.$3%.3/2).4%'2!4)/.
Ç°Ó
COMPOSEDOFTHERADARMEASUREMENTACCURACIESINRANGE AZIMUTH ELEVATION ANDDOP PLER4HEFUNCTIONHISTHECOORDINATETRANSFORMTHATRELATESTHEMEASUREMENTSTOTHE STATEATTIMETKACCORDINGTOTHECOORDINATEFRAMEDESIGNCHOICESSEE4ABLE LATERIN THECHAPTER )NORDERTOUSETHE+ALMANFILTER HISAPPROXIMATEDASALINEARFUNCTION INTHEVICINITYOFTHEPREDICTEDTRACKSTATE
H 8 H 8 TK \ TK ( ; 8 8 TK \ TK = r 8 8 TK \ TK
WHERE(ISTHEGRADIENTOFH%ACHCOORDINATEFRAMEHASITSOWNAPPROXIMATIONFOR(&OR EXAMPLE IFTHESTATECOORDINATESYSTEMISCOMPOSEDOFTHREE DIMENSIONAL#ARTESIANCOOR DINATESCENTEREDATTHERADAR THENMULTIPLICATIONBY(TRANSFORMS#ARTESIANCOORDINATES X Y Z INTOPOLARMEASUREMENTCOORDINATESRANGE AZIMUTH ELEVATION DOPPLER AND
X § ¨ R ¨ Y ¨ X Y ¨ ( ¨
XZ ¨ ¨R X Y ¨ XR XR ¨ R ©
Y R
X X Y
YZ R X Y YR YR R
Z R
X R
Y R
X Y R ZR ZR R
¶ · · · · · · · Z· · R¸
WHERE R X Y Z ISRANGE 4HE +ALMAN FILTER EQUATIONS FOR RADAR TRACKING ARE THEN SIMPLY GENERALIZATIONS OFTHE@ AFILTEREQUATIONSWHERE@ANDAVARYWITHTIME4HE+ALMANFILTERUPDATE PROCEDURECONTINUESASFOLLOWS &IRST PREDICTANEWTARGETSTATEESTIMATE 8 TK \ TK OFTHESTATE8TK ATTIMETK GIVENALLMEASUREMENTSUPTOTIMETK
8 TK \ TK F TK 8 TK !P TK
ALONGWITHITSCOVARIANCE 0K \K E¼ TK 0K\K E¼ TK 4 1TK
4HEN UPDATETHETARGETSTATEUSINGTHEK STRADARMEASUREMENT
8 TK \ TK 8 TK \ TK + K ;9K ( TK 8 TK \ TK =
ANDITSCOVARIANCE
0K \K ;( *K (TK =0K \K
Ç°Îä
2!$!2(!.$"//+
USINGTHE+ALMANGAINS
*K 0K \K (4TK ;(TK 0K \K (4TK K=
"ECAUSE THE GAINS ARE CALCULATED USING THE HISTORY OF ALL PAST UPDATE TIMES AND ACCURACIES THEGAINSAUTOMATICALLYINCREASEAFTERMISSEDDETECTIONSANDAUTOMATICALLY INCREASETOGIVEGREATERWEIGHTTOADETECTIONWHENITISKNOWNTOBEMOREACCURATE ANDTHEYAUTOMATICALLYDECREASEASTHETRACKAGES REFLECTINGTHEVALUEOFTHEDETECTIONS ALREADYFILTERED&OREXAMPLE FORAZERORANDOMACCELERATION 1K ANDACONSTANT DETECTIONCOVARIANCEMATRIX K THE@nAFILTERCANBEMADEEQUIVALENTTOTHE+ALMAN FILTERBYSETTING
A
K K K
K K
AND
B
ONTHEKTHSCAN4HUS ASTIMEPASSES @ANDAAPPROACHZERO APPLYINGHEAVYFILTERING TOTHENEWSAMPLES)NPRACTICALRADARAPPLICATIONS1K ANDSOTHETRACKINGGAINS EVENTUALLYSETTLETOANON ZEROVALUETERMEDTHESTEADY STATETRACKINGGAINS 4HETRADEOFFSFOREMPLOYINGA+ALMANFILTERFORRADARTRACKINGGENERALLYARETUNING THE FILTER FOR THE DESIRED DEGREE OF FILTERING SELECTING THE TRACKING COORDINATES AND ADAPTINGTHEFILTERTODEALWITHCHANGESINTHETARGETMOTIONEG MANEUVERS DIFFERENT PHASESOFBALLISTICFLIGHT ANDSOON 4UNINGTHE+ALMAN&ILTER 4HEGREATESTADVANTAGEOFTHE+ALMANFILTERFORRADAR TRACKINGISTHATITPROVIDESASYSTEMATICWAYOFCALCULATINGGAINS(OWEVER ADISADVAN TAGEISTHATTHISGAINCALCULATIONASSUMESLINEARTARGETMOTIONWITHRANDOMPERTURBA TIONS%Q -OSTPRACTICALRADAR TRACKINGPROBLEMSINVOLVETARGETSTHATDEVIATE FROMLINEARMOTIONINMORECOMPLEXWAYSEG COURSECORRECTIONS TERRAINFOLLOWING EVASIVEMANEUVERS ANDATMOSPHERICDRAG 4HE+ALMANFILTERISTUNEDTOAPRACTICAL RADAR TRACKINGPROBLEMTHROUGHTHESELECTIONOFTHECOVARIANCEMATRIX 1TK OFTHE UNKNOWNRANDOMMANEUVER4HEGOALOFTHISSELECTIONISTOOBTAINTHEBESTPOSSIBLE TRACKINGPERFORMANCEFORTHEMORECOMPLEXCASESOFINTERESTWHILESTILLUSINGTHESIM PLE+ALMANRANDOMPERTURBATIONMODEL&OREXAMPLE INTHESIMPLIFIEDCASEOFASINGLE DIMENSION AND CONSTANT TRACKING CONDITIONS THE MEASUREMENT COVARIANCE MATRIX IS SIMPLYASINGLE CONSTANTMEASUREMENTVARIANCE K R¼ M ANDTHETIMEBETWEENDETEC TIONSISACONSTANT2K 4)NTHISCASE THE+ALMANFILTERDESCRIBEDIN%QSTO HASGAINSTHATAREAFUNCTIONOFTHEDIMENSIONLESSTRACK FILTERINGPARAMETERFTRACK
G TRACK
Q4 S M
"ECAUSETHERADARMEASUREMENTACCURACY ASREPRESENTEDBYTHECOVARIANCEMATRIX ANDTHETIMEBETWEENDETECTIONOPPORTUNITIES 4 AREPARAMETERSOFTHERADARDESIGN ITSELF THESELECTIONOF1TK ISTHEDEGREEOFFREEDOMAVAILABLETOTHETRACKINGFILTER DESIGN4ABLESUMMARIZESTHEMETHODSFORTUNINGTHE+ALMANFILTER
-ODELNO2ANDOM CHANGEINVELOCITYATEACH MEASUREMENTINTERVAL
-ODELNO2ANDOM CHANGEINACCELERATIONAT EACHMEASUREMENTINTERVAL 3TANDARDDEVIATIONOF ACCELERATIONCHANGEISRA
-ODELNO7HITENOISE SPECTRALDENSITYQG(Z ACCELERATIONSAMPLEDBYRADAR MEASUREMENT
-ANEUVER-ODEL
S V
4K 4K 4K 4K
4K 4K 4K 4K
S A
Q
1 SUBMATRIX
Q4 S M
S A4 S M
S V4 S M
A A
G TRACK
AND
B
G TRACK
B A A
G TRACK AND
A A A AND
B
3TEADY STATE'AIN2ELATIONAND 4RACKING)NDEX
4!",% #OMPARISONOF-ETHODSOF4UNING+ALMAN&ILTERFOR0RACTICAL2ADAR4RACKING0ROBLEMS
6ARYRVTOINCREASE DECREASEGAINS ANDOBTAINDESIRED PERFORMANCEUSING EQUATIONSIN4ABLE
6ARYRATOINCREASE DECREASEGAINS ANDOBTAINDESIRED PERFORMANCEUSING EQUATIONSIN4ABLE
6ARYQTOINCREASE DECREASEGAINS ANDOBTAINDESIRED PERFORMANCEUSING EQUATIONSIN4ABLE
4UNING-ETHOD
2ESPONDSVERYWELLTO MANEUVERS BUTOPERATESAT THEEDGEOFFILTERSTABILITY (IGHERRADARMEASUREMENT RATECANACTUALLYRESULTINLESS ACCURATETRACK 6ERYCONSERVATIVEWITH RESPECTTOFILTERSTABILITY
!CCOMMODATESVARIABLE MEASUREMENTRATESWELL 2ESPONDSTOMANEUVERS BUTNOTATTHEEDGEOFFILTER STABILITY
#HARACTERISTICS
!54/-!4)#$%4%#4)/. 42!#+).' !.$3%.3/2).4%'2!4)/.
ǰΣ
-ODELNO#ONSTANT DETERMINISTICACCELERATION AG &ILTEROBJECTIVEISTO MINIMIZELAGPLUSCSTANDARD DEVIATIONS
-ODELNO#ONSTANTLY ACCELERATINGTARGETWITH AWHITENOISEJERK J;GS (Z=SAMPLEDBYRADAR MEASUREMENT*ERKISTHERATE OFCHANGEOFACCELERATION
-ANEUVER-ODEL
4K 4K 4K 4K
4K 4K
1SUBMATRIXNOT APPLICABLE)NSTEAD ASSUMECONSTANT PARABOLICMOTION AT
4K 4K J 4K
1 SUBMATRIX
J4 S M
G TRACK
AND
A 4 C S M
B A A
G TRACK
AND
3TEADY STATEGAINCALCULATIONS DESCRIBEDIN&ITZGERALD
3TEADY STATE'AIN2ELATIONAND 4RACKING)NDEX
6ARYATOINCREASE DECREASEGAINS ANDOBTAINDESIRED PERFORMANCEUSING EQUATIONSIN4ABLE
3ELECTTHISMODELWHEN TARGETISKNOWN EXPECTEDTOBE ACCELERATING
4UNING-ETHOD
4!",% #OMPARISONOF-ETHODSOF4UNING+ALMAN&ILTERFOR0RACTICAL2ADAR4RACKING0ROBLEMS#ONTINUED
&ILTERMINIMIZESERRORFOR AWORST CASEDETERMINISTIC MANEUVERVICEARANDOMONE
:EROLAGSTOCONSTANT ACCELERATIONHOWEVER NOISE ERRORSAREMUCHGREATER
#HARACTERISTICS
Ç°ÎÓ 2!$!2(!.$"//+
!54/-!4)#$%4%#4)/. 42!#+).' !.$3%.3/2).4%'2!4)/.
Ç°ÎÎ
!SSEENIN&IGURE THESELECTIONOF1TK ANDTHUSFTRACKALLOWSONETOUNIQUELY DETERMINE THE STEADY STATE TRACKING GAINS AS A FUNCTION OF FTRACK /NE CAN SEE THAT LARGEASSUMEDMANEUVERSLARGEQ @A ORA LARGERTIMEBETWEENUPDATES 4ORVERY ACCURATERADARMEASUREMENTSSMALL WILLRESULTINLARGETRACKINGGAINS4HEPOSI TION GAIN @ IS NEARLY IDENTICAL FOR THE 1TK MODELS NO AND IN4ABLE (OWEVER THE VELOCITY GAIN A DIFFERS CONSIDERABLY &OR RANDOM CHANGES IN ACCEL ERATION AT EACH MEASUREMENT INTERVAL MODEL NO THE GAINS INCREASE TO @ A ¼ ¼ WHICHISTHELIMITOFFILTERSTABILITY4HUS THISMODELPRODUCESFILTERGAINSTHAT ARETHEMOSTAGGRESSIVEATMINIMIZINGLAGSTOMANEUVERSATTHEEXPENSEOFLARGER % "(%
'! $ $(
% "%
% "(%
% "%
'! $ $ -
$*') ' (*' # $) *') ' (*' # $)
%,$ *+ '' )
$ *+ '' )
%')& ) $) '+"
%$ & ) $) '+"
&)'52% 4HERELATIONSHIPBETWEENTHESTEADY STATETRACKINGGAINS@ANDAISSHOWNFORDIFFERENT 1TK SCORRESPONDINGTODIFFERENTASSUMPTIONSABOUTTHEUNKNOWNTARGETMANEUVER-ODELNOWHITE NOISEACCELERATIONSAMPLEDATEACHMEASUREMENTINTERVALMODELNORANDOMCHANGEINACCELERATIONAT EACHMEASUREMENTINTERVALMODELNORANDOMCHANGEINVELOCITYATEACHMEASUREMENTINTERVALAND MODELNOCONSTANTDETERMINISTICACCELERATION-ODELNONOTSHOWNASITISAGAINMODEL
Ç°Î{
2!$!2(!.$"//+
TRACKINGERRORSDUETORADARMEASUREMENTNOISE&ORRANDOMCHANGESINVELOCITYAT EACHMEASUREMENTINTERVALMODELNO THEGAINSINCREASETO@ A WHICH ISVERYCONSERVATIVEFROMAFILTERSTABILITYPOINTOFVIEW&ORWHITENOISEACCELERATION SAMPLEDBYRADARMEASUREMENTSMODELNO THEGAINSAREACOMPROMISE INCREASING TO A B "ECAUSETHISMODELISASAMPLEDCONTINUOUSTIMEACCELERATION ITISPREFERREDWHENUPDATETIMESAREVARIABLEBECAUSETHETARGETDOESNOTMANEUVER MOREORLESSWHENTHEUPDATEINTERVALCHANGES 4HEEQUATIONSIN4ABLECANTHENBEUSEDTOCALCULATETHEFILTERPERFORMANCEIN TERMSOFVARIANCEREDUCTIONRATIOSANDTRACKINGLAGS!DJUSTMENTSTOPARAMETERSOFFTRACK CANBEMADETOOBTAINTHEDESIREDNOISEANDLAGTRADEOFF 3ELECTION OF 4RACKING #OORDINATES 4HE +ALMAN FILTER ASSUMES LINEAR TARGET MOTIONANDALINEARRELATIONBETWEENTHERADARDETECTIONSANDTHETARGETCOORDINATES (OWEVER RADARSMAKEDETECTIONSINPOLARCOORDINATESRANGE ANGLE DOPPLER WHILE TARGETMOTIONISMOSTLIKELYLINEARIN#ARTESIANCOORDINATESX Y Z 4HEREFORE SOME COMPROMISESMUSTGENERALLYBEMADEINSELECTINGACOORDINATESYSTEMFORFILTERING 4ABLEDESCRIBESTHEDESIGNTRADEOFFSFORDIFFERENTSELECTIONS 4HEPOLAR+ALMANFILTERISRARELYUSEDBECAUSEOFTHEPSEUDO ACCELERATIONSINTRO DUCED BY PROPAGATING THE STATE IN POLAR COORDINATES 4HE #ARTESIAN%ARTH CENTERED +ALMANFILTERCANWORKWELLBUTMAYHAVEDIFFICULTYACCOMMODATINGRADARMEASURE MENTS OF LESS THAN THREE DIMENSIONS4HE EXTENDEDDUAL COORDINATE SYSTEM +ALMAN FILTERPREVENTSPSEUDO ACCELERATIONSANDACCOMMODATESMEASUREMENTSOFANYDIMEN SIONALITY"OTHTHE#ARTESIAN%ARTH CENTERED+ALMANFILTERSINVOLVENONLINEARTRANSFOR MATIONSRESULTINGINANIMPERFECTCALCULATIONOFTHETRACKINGACCURACY7HENPREDICTION TIMESARELONGANDORWHENVERYACCURATERESULTSARENEEDED THESEIMPERFECTIONSIN THE+ALMANFILTERCOVARIANCECALCULATIONCANBESIGNIFICANT ANDTHETRACKINGERRORSCAN BEQUITENON GAUSSIAN0ARTICLEFILTERSTYPICALLYPROPAGATEALARGENUMBEROFRANDOM SAMPLESPARTICLES FROMASTATETRANSITIONPRIORDISTRIBUTIONTOESTIMATEPOSTERIORDIS TRIBUTIONSTHATARENOTREQUIREDTOBEGAUSSIANINFORM4HUS INAPARTICLEFILTER EVEN MULTI MODALDISTRIBUTIONSCANBEUSEDASPRIORANDREALIZEDASPOSTERIORDISTRIBUTIONS (OWEVER PARTICLEFILTERSREQUIREQUITEABITOFCOMPUTATION 4HEUNSCENTED+ALMANFILTERMOREEFFICIENTLYCALCULATESTHETRACKINGACCURACYBY PROPAGATINGSELECTEDCARDINALPOINTSTHROUGHTHEFILTER4HEUNSCENTED+ALMAN&ILTER APPROXIMATESTHECOVARIANCEMATRIXWITHASETOF, SAMPLEPOINTS WHERE,ISTHE NUMBEROFSTATEDIMENSIONS4HESAMPLEPOINTSAREPROPAGATEDTHROUGHANARBITRARY TRANSFORMFUNCTIONANDTHENUSEDTORECONSTRUCTAGAUSSIANCOVARIANCEMATRIX4HIS TECHNIQUE HAS THE ADVANTAGE OF REPRESENTING THE COVARIANCE ACCURATELY TO THE THIRD ORDEROFA4AYLORSERIESEXPANSION!SARESULT THECALCULATEDTRACKINGACCURACYISAT LEASTTOTHIRDORDER UNCONTAMINATEDORhUNSCENTEDv BYTHENONLINEARITY !DAPTING&ILTERTO$EALWITH#HANGESIN4ARGET-OTION 4HE+ALMANFILTER ASSUMESLINEARTARGETMOTIONPERTURBEDBYARANDOMMANEUVERMODELASAMATHEMATI CAL CONVENIENCE IN CALCULATING TRACKING GAINS (OWEVER MOST RADAR TARGETS DO NOT MOVEINARANDOMMANEUVERBUTINSTEADMOVELINEARLYATTIMESANDTHENMANEUVER UNPREDICTABLYATTIMES4HECHALLENGEINADAPTINGTHEFILTERTODEALWITHCHANGESINTHE TARGETMOTIONEG MANEUVERS BALLISTICRE ENTRY ISTOADAPTTHETARGETMOTIONMODEL FORTHE+ALMANFILTEROVERTIMESOTHATMOREACCURATETRACKINGOCCURSTHANWITHASINGLE MODEL4HESIMPLESTFORMOFADAPTATIONISAMANEUVERDETECTORTOMONITORTHETRACKING FILTERRESIDUALSDIFFERENCESBETWEENMEASUREDANDPREDICTEDPOSITION ,ARGE CORRELATED
!54/-!4)#$%4%#4)/. 42!#+).' !.$3%.3/2).4%'2!4)/.
Ç°Îx
4!",% !DVANTAGESAND$ISADVANTAGESOF%MPLOYINGTHE+ALMAN&ILTERIN$IFFERENT #OORDINATE&RAMES #OORDINATESFOR 3TATE0REDICTION %QS
-ETHODOF #OVARIANCE 0ROPAGATION
!DVANTAGES
$ISADVANTAGES
0OLAR+ALMAN 0OLAR FILTER
0OLAR
%QSTO INPOLAR COORDINATES
&ILTERCOVARIANCES ARECALCULATED EXACTLYANDSTATE ERRORSGAUSSIAN DISTRIBUTED2ADAR DETECTIONSOF LESSTHANTHREE DIMENSIONSCAN BEUSED
0SEUDO ACCELERATIONS INTRODUCED INSTATE PROPAGATION
#ARTESIAN %ARTH #ENTERED +ALMAN FILTER
#ARTESIAN %ARTH CENTERED
#ARTESIAN %ARTH CENTERED
%QSTO IN#ARTESIAN %ARTH CENTERED COORDINATES
3TATEPROPAGATION ISLINEAR NOPSEUDO ACCELERATIONS
&ILTER COVARIANCESARE NOTEXACTDUE TONONLINEAR TRANSFORMATION
%XTENDED DUAL COORDINATE +ALMAN FILTER
0OLAR
#ARTESIAN %ARTH CENTERED
%QSTO INPOLAR COORDINATES
2EQUIRES FREQUENT COORDINATE TRANSFORMS
5NSCENTED +ALMAN FILTER
0OLAROR #ARTESIAN %ARTH CENTERED
#ARTESIAN %ARTH CENTERED
#OVARIANCE INFERREDBY PROPAGATING MULTIPLESTATES
3TATEPROPAGATION ISLINEAR NOPSEUDO ACCELERATIONS 2ADARDETECTIONS OFLESSTHANTHREE DIMENSIONS CANBEEASILY ACCOMMODATED 3TATEPROPAGATION ISLINEAR NOPSEUDO ACCELERATIONS &ILTERCOVARIANCE MOREEXACT THANTRADITIONAL METHODS PARTICULARLYFOR LONGEXTRAPOLATION TIMES
+ALMAN&ILTER #OORDINATE &RAME 6ARIANTS
#OORDINATESFOR 'AIN#ALCULATION %QS ANDSTATEUPDATE %Q
-ORECOMPLEX BUTNOT NECESSARILY MORE COMPUTATION
RESIDUALS GENERALLY INDICATE A MANEUVER A DEVIATION FROM THE FILTER MODEL 5PON MANEUVERDETECTION THEMANEUVERSPECTRALDENSITY Q ISINCREASEDINTHE+ALMANFILTER MODEL RESULTINGINHIGHERTRACKINGGAINSANDBETTERFOLLOWINGOFTHEMANEUVER !MORECOMPLEXAPPROACHISTOUSEMULTIPLE+ALMANFILTERSRUNNINGSIMULTANEOUSLY WITHDIFFERENTTARGETMOTIONMODELSGENERALLY DIFFERENTQVALUESORDIFFERENTEQUA TIONSFORTARGETMOTIONEG CONSTANTACCELERATIONORCONSTANTVELOCITY &IGURE SHOWSABANKOFMULTIPLEPARALLELFILTERSALLFEDBYTHESAMESTREAMOFASSOCIATEDMEA SUREMENTS!TEACHDETECTIONTIME TK ONEOFTHESEVERALFILTEROUTPUTSMUSTBESELECTED TOBETHETRACKSTATEUSEDFORDETECTIONTOTRACKASSOCIATION !SYSTEMATICWAYOFEMPLOYINGMULTIPLETARGETMOTIONMODELSISTHE)NTERACTING -ULTIPLE-ODEL)-- APPROACHDIAGRAMMEDIN&IGURE-ULTIPLEMODELSRUN SIMULTANEOUSLYHOWEVER THEYDONOTRUNINDEPENDENTLY)NSTEAD THEREISMIXINGOF
Ç°ÎÈ
2!$!2(!.$"//+
&)'52% "ANK OF PARALLEL RADAR TRACKING FILTERS EACH EMPLOYING A DIFFERENT TARGET MOTION MODEL AFTER3"LACKMANAND20OPOLIÚ!RTECH(OUSE
&)'52% &LOWCHARTOFINTERACTINGMULTIPLEMODELSAFTER3"LACKMANAND20OPOLI Ú!RTECH(OUSE
!54/-!4)#$%4%#4)/. 42!#+).' !.$3%.3/2).4%'2!4)/.
Ç°ÎÇ
"$ !"
THEMODELSTATES4HEUPDATEEQUATIONFORTHEITHMODELDEPENDSNOTONLYONTHEITH MODELSTATEBUTALSOONTHESTATESOFALLOTHERMODELS4HESESTATESAREMIXEDUSING INFERREDPROBABILITIESOFTHETARGETTRANSITIONINGFROMONEMOTIONMODELTOANOTHER !SANEXAMPLE CONSIDERRADARTRACKINGOFABALLISTICMISSILETHATUNDERGOESDISTINCT PHASESOFFLIGHTBOOST EXO ATMOSPHERICFLIGHT ANDENDO ATMOSPHERICRE ENTRY%ACHOF THESEPHASESOFFLIGHTHASADISTINCTTARGETMODEL$URINGBOOST THETARGETISCONTINUALLY ACCELERATINGANDINCREASINGSPEED4HISACCELERATIONISUNKNOWNANDMUSTBEESTIMATED $URING EXO ATMOSPHERIC FLIGHT THE OBJECT IS FALLING WITH THE KNOWN ACCELERATION OF GRAVITY$URINGENDO ATMOSPHERICRE ENTRY THETARGETCONTINUESTOFALLBUTEXPERIENCESA DRAGACCELERATIONDUETOITSBALLISTICCOEFFICIENTANUNKNOWNTARGETPARAMETERRELATEDTO THESHAPEANDMASSOFTHETARGET !N)--FILTERCANBEUSEDTOSYSTEMATICALLYTRANSITION BETWEENTHESEDIFFERENTPHASESOFFLIGHT PROVIDINGASINGLEFILTEROUTPUT&IGURE SHOWSTHEMODELPROBABILITIESFORSUCHAN)--FILTERAPPLICATION
"$ # "
"$ " $
" " !
! &)'52% -ODEL PROBABILITIES RESULTING FROM THE APPLICATION OF AN )-- FILTER TO A BALLISTIC MISSILETRACKINGPROBLEMA PROBABILITYTHATTARGETMOTIONIShBOOSTPHASE vB PROBABILITYTHATTARGET MOTIONIShEXO ATMOSPHERICvFLIGHT C PROBABILITYTHATTARGETMOTIONIShENDO ATMOSPHERICvRE ENTRY AFTER2#OOPERMANRÚ&IFTH)NTERNATIONAL#ONFERENCEON)NFORMATION&USION VOL
Ç°În
2!$!2(!.$"//+
!SSOCIATIONOF!CCEPTED$ETECTIONWITH%XISTING4RACKS 4HEGOALOFDETECTION TO TRACKASSOCIATIONISTOCORRECTLYASSIGNRADARDETECTIONSTOEXISTINGTRACKSSOTHETRACK STATESINTHETRACKFILECANBECORRECTLYUPDATED4HEBASISFORASSIGNMENTISAMEASUREOF HOWCLOSETOGETHERTHEDETECTIONANDTRACKAREINTERMSOFMEASURABLEPARAMETERSSUCH ASRANGE ANGLE DOPPLER AND WHENAVAILABLE TARGETSIGNATURE4HESTATISTICALDISTANCE ISCALCULATEDASAWEIGHTEDCOMBINATIONOFTHEAVAILABLEDETECTION TO TRACKCOORDINATE DIFFERENCES)NTHEMOSTGENERALCASE THISISACOMPLEXQUADRATICFORM
$ 9K H 8 TK \ TK ; ( TK 0 K \ K ( 4 TK 2K = 9K H 8 TK \ TK 4
&ORMOSTSINGLERADAR TRACKINGPROBLEMS ITREDUCESTOASIMPLEWEIGHTEDSUM $
RM RP Q M Q P J M J P $M $ P S R S PR S Q S PQ S J S PJ S $ S P$
WHERERM PM IM $M ARETHEMEASUREDRANGE AZIMUTH ELEVATION ANDDOPPLERWITH ACCURACIESRR RP RI R$ RP PP IP $P ARETHERANGE AZIMUTH ELEVATION ANDDOP PLERPREDICTEDBYTHEAUTOMATICTRACKERWITHACCURACIESRPR RPP RPI RP$ 4HEPRE DICTEDACCURACIESAREABYPRODUCTOFTHERADARTRACKINGFILTER3TATISTICALDISTANCERATHER THAN %UCLIDEAN DISTANCE MUST BE USED BECAUSE THE RANGE ACCURACY IS USUALLY MUCH BETTERTHANTHEAZIMUTHACCURACY 7HENTARGETSAREWIDELYSPACEDANDINACLEARENVIRONMENT ONLYONETARGETDETECTION PAIRHASASMALL$ MAKINGTHESEASSIGNMENTSOBVIOUS4HUS THEDESIGNOFDETECTION TO TRACKASSOCIATIONISUSUALLYDOMINATEDBYTHEMOREDIFFICULTCONDITIONSOFCLOSELYSPACED TARGETSORCLOSELYSPACEDTARGETSANDCLUTTER&IGURESHOWSACOMMONSITUATIONFOR CLOSELYSPACEDTARGETSANDORCLUTTER4HREEASSOCIATIONGATESARECONSTRUCTEDAROUNDTHE PREDICTEDPOSITIONSOFTHREEEXISTINGTRACKS4HREEDETECTIONSAREMADE BUTASSIGNMENTOF THEDETECTIONSTOTHETRACKSISNOTOBVIOUSTWODETECTIONSAREWITHINGATETHREEDETEC TIONSAREWITHINGATEANDONEDETECTIONISWITHINGATE4ABLELISTSALLDETECTIONS
&)'52% %XAMPLESOFTHEPROBLEMSCAUSEDBYMULTIPLEDETECTIONSAND TRACKSINCLOSEVICINITYFROM'64RUNK
!54/-!4)#$%4%#4)/. 42!#+).' !.$3%.3/2).4%'2!4)/.
Ç°Î
4!",% !SSOCIATION4ABLEFOR%XAMPLE3HOWNIN&IGURE
4RACK.O
$ETECTION.O
$ETECTION.O c
$ETECTION.O c c
FROM'64RUNK
WITHINTHETRACKINGGATESANDTHESTATISTICALDISTANCEBETWEENTHEDETECTIONANDTRACK)F THEDETECTIONISOUTSIDETHETRACKGATE THESTATISTICALDISTANCEISSETTOINFINITY .EAREST NEIGHBOR ASSIGNMENT IS THE MOST COMMON SOLUTION TO THIS PROBLEM 4HE SIMPLESTFORMOFNEARESTNEIGHBORWORKSSEQUENTIALLYONINCOMINGDATA!SEACHNEW DETECTIONISMADE ITISASSIGNEDTOTHETRACKWITHWHICHITHASTHESMALLESTSTATISTICAL DISTANCE(ENCE IFDETECTIONNOWASRECEIVEDFIRST ITWOULDBEASSIGNEDTOTRACKNO (OWEVER ITISBETTERTODELAYTHEASSOCIATIONPROCESSSLIGHTLYSOTHATALLDETECTIONSIN ALOCALNEIGHBORHOODARERECEIVEDANDSTOREDANDANASSOCIATIONTABLE SUCHAS4ABLE GENERATED4HISHASIMPLICATIONSABOUTHOWSECTORSARESCANNEDWITHAPHASEDARRAY .EAREST NEIGHBORASSIGNMENTCANNOWBEAPPLIEDTOTHEASSOCIATIONTABLEBYFINDING THESMALLESTSTATISTICALDISTANCEBETWEENADETECTIONANDATRACK MAKINGTHATASSOCIA TION ANDELIMINATINGTHATDETECTIONANDTRACKROWANDCOLUMN FROMTHETABLE4HIS PROCESSISREPEATEDUNTILTHEREAREEITHERNOTRACKSORNODETECTIONSLEFT!PPLYINGTHIS ALGORITHMTO4ABLERESULTSINDETECTIONNOUPDATINGTRACKNO DETECTIONNO UPDATINGTRACKNO ANDTRACKNONOTBEINGUPDATED"ETTERASSIGNMENTSAREPOSSIBLE WITHMORESOPHISTICATEDPROCESSINGALGORITHMS4HETHREETYPESOFMORESOPHISTICATED ALGORITHMSMOSTFREQUENTLYUSEDARE 'LOBAL .EAREST .EIGHBOR '.. #ONSIDER THE WHOLE MATRIX OF STATISTICAL DIS TANCES SIMULTANEOUSLY AND MINIMIZE A METRIC SUCH AS THE SUM OF ALL STATISTICAL DISTANCES FOR A COMPLETE ASSIGNMENT SOLUTION 0ERFORMING THIS OPTIMIZATION CAN BE DONE USING -UNKRES ALGORITHM -UNKRES ALGORITHM IS AN EXACT SOLUTION OF THEMINIMIZATIONPROBLEMBUTISRARELYUSEDBECAUSEITISCOMPUTATIONALLYSLOW! MORECOMPUTATIONALLYEFFICIENTEXACTSOLUTIONISTHE*ONKER 6OLGENANT #ASTANON *6# ALGORITHM4HE*6#ISMUCHMOREEFFICIENTFORSPARSEASSIGNMENTMATRICES WHICHARELIKELYFORPRACTICALRADAR TRACKINGPROBLEMS 3PEEDIMPROVEMENTSOF TOTIMESHAVEBEENREPORTED!NEFFECTIVESUBOPTIMALSOLUTIONISTHE!UCTION ALGORITHM WHICH VIEWS THE TRACKS AS BEING hAUCTIONED OFFv TO THE DETECTIONS ITERATIVELY ASSIGNING HIGHER COSTS TO TRACKS COMPETED FOR BY MORE DETECTIONS &IGUREPROVIDESACOMPARISONOFTHE-UNKRES *6# AND!UCTIONALGORITHMS OPTIMIZEDFORSPARSEDATA4HE*6#AND!UCTIONALGORITHMSPROVIDEASIGNIFICANT INCREASEINCOMPUTATIONALSPEED!LTHOUGHTHE!UCTIONALGORITHMISSIMPLER REQUIR INGLESSLINESOFCODE THE*6#ALGORITHMGENERALLYREQUIRESLESSCOMPUTATIONTIME 0ROBABILISTIC $ATA !SSOCIATION 0$! !NOTHER ALTERNATIVE IS THE PROBABILISTIC DATAASSOCIATION0$! ALGORITHM WHERENOATTEMPTISMADETOASSIGNTRACKS TO DETECTIONS BUT INSTEAD TRACKS ARE UPDATED WITH ALL THE NEARBY DETECTIONS WEIGHTEDBYTHEPERCEIVEDPROBABILITYOFTHETRACKBEINGTHECORRECTASSOCIATION "ECAUSE 0$! RELIES ON ERRONEOUS ASSOCIATIONS ESSENTIALLY hAVERAGING OUT v IT IS MOSTEFFECTIVEWHENTRACKSAREFARENOUGHAPARTTHATNEARBYDETECTIONSORIGINATE FROM SPATIALLY RANDOM NOISE OR CLUTTER EXCLUSIVELY AND WHEN THE TRACKING GAINS ARESMALLIE WHENTHETRACKINGINDEXFTRACKISSMALL 4HE*OINT0ROBABILISTIC$ATA
Ç°{ä
2!$!2(!.$"//+
&)'52% !COMPARISONOFTHEEXECUTIONTIMEFOR THE-UNKRESOPTIMUM *6#OPTIMUM AND!UCTION SUBOPTIMUM ALGORITHMS SHOWS THE RAPID INCREASE IN COMPUTATION REQUIRED FOR -UNKRES AS THE NUMBER OF ROWSINTHEASSIGNMENTMATRIXINCREASES4HE*6#AND AUCTION ALGORITHMS SHOW MUCH MORE GRADUAL GROWTH AFTER)+ADARETALÚ30)%
!SSOCIATION *0$! IS AN EXTENSION OF 0$! THAT HANDLES MORE CLOSELY SPACED TARGETS)N*0$! DETECTIONSAREWEIGHTEDLESSWHENTHEYARENEARANOTHERTRACK -ULTIPLE(YPOTHESIS!LGORITHMS 4HEMOSTSOPHISTICATEDALGORITHMSAREMULTIPLE HYPOTHESISALGORITHMSINWHICHALLORMANY POSSIBLETRACKSAREFORMEDANDUPDATED WITHEACHPOSSIBLEDETECTION )N4ABLE TRACKNOWOULDBECOMETHREE TRACKSORHYPOTHESES CORRESPONDINGTOUPDATINGWITHDETECTIONNO DETECTION NO ANDNODETECTION%ACHOFTHESETRACKSWOULDUNDERGOA+ALMANFILTERUPDATE ANDBEELIGIBLEFORASSOCIATIONWITHTHENEXTSETOFDETECTIONS4RACKSAREPRUNED AWAY IN A SYSTEMATIC MANNER LEAVING ONLY THE MOST PROBABLE &IGURE ILLUS TRATESTHETRACKINGOFASINGLETARGETUSINGMULTIPLEHYPOTHESISTECHNIQUES)NTHIS EXAMPLE MANYHYPOTHESESAREFORMEDAND OVERSUCCESSIVEMEASUREMENTINTERVALS SUCCESSFULLYPRUNEDAWAYLEAVINGONLYONECORRECTTRACK 4HEREGIONOFAPPLICABILITYFORTHEMORESOPHISTICATEDALGORITHMSISDETERMINEDBYTWO PARAMETERSTHEDENSITYOFEXTRANEOUSDETECTIONSKDETECTIONSPERUNITAREAORVOLUME
&)'52% %XAMPLE OF THE USE OF MULTIPLE HYPOTHESIS TRACKING ON SCANS OF SIMULATED RADAR DATA CONTAININGASINGLETARGETANDMANYFALSEALARMSA SHOWSALLHYPOTHESESFORMSANDB SHOWSTHESINGLE HYPOTHESISSELECTED0RUNEDHYPOTHESESAREGRAYEDOUT AFTER7+OCHÚ)%%%
!54/-!4)#$%4%#4)/. 42!#+).' !.$3%.3/2).4%'2!4)/.
Ç°{£
&)'52% 4HEAPPLICABILITYOFDIFFERENTDETECTION TO TRACKASSOCIATIONALGORITHMS ISDETERMINEDBYTHEDENSITYOFFALSEALARMSANDTHEDIMENSIONLESSTRACKINGPARAMETER FTRACKAFTER$*3ALMONDÚ30)%
ANDTHEDIMENSIONLESSTRACKFILTERINGPARAMETERFTRACK&IGUREBOUNDSTHISREGION OFAPPLICABILITY7HENKANDFTRACKARESMALL THENTHEREISNONEEDFORANYMORETHAN SIMPLE NEAREST NEIGHBOR TRACKING AND INDEED MOST TRACKING SYSTEMS STILL USE THIS APPROACH!SKINCREASES THEREISGREATERRISKOFFALSEASSOCIATIONDECISIONSHOWEVER THEEFFECTOFTHISISREDUCEDIFFTRACKISSMALL!TTHEOTHEREXTREME WHENKANDFTRACKARE LARGE THETRACKINGPROBLEMISESSENTIALLYUNSOLVABLEWITHOUTBASICCHANGESTOTHERADAR DESIGNPARAMETERSTOREDUCETHEM4HEREISANINTERMEDIATEREGIONWHERESOPHISTICATED ASSOCIATIONHASVALUE4HEWIDTHOFTHISREGIONISVERYSPECIFICTOTHEPARTICULARPROB LEM7HENFTRACKISLARGEANDVERYLITTLEDELAYINTHEOUTPUTCANBETOLERATED THENTHE REGIONOFAPPLICABILITYISFAIRLYSMALLANDVERYSIMPLEMULTIPLEHYPOTHESISAPPROACHES SPLITTINGTRACKSINTOATMOSTONEORTWOHYPOTHESES ARETHENTHEBESTANSWER 7HENFTRACKISSMALL THEN0$!*0$!CANBEUSEDTOOPERATEATSIGNIFICANTLYHIGHER FALSEALARMDENSITIES7HENSIGNIFICANTDELAYCANBETOLERATEDINTHEOUTPUT THENMANY HYPOTHESESCANBEFORMEDASIN&IGURE ANDORDERSOFMAGNITUDEMOREDETECTIONS HANDLED"LACKMANAND0OPOLIPROVIDEAGOODSURVEYOFCOMPARATIVESTUDIESINTHIS AREA/NESTUDYUSINGDATARECORDEDFROMFLIGHTSOFCLOSELYSPACEDAIRCRAFTSHOWED VERYLITTLEDIFFERENCEBETWEEN'.. *0$! AND-(4(OWEVER THEORETICALPREDIC TIONSCANSHOWDIFFERENCESOFORDERSOFMAGNITUDEINTHEDENSITYOFCLUTTERDETECTIONS THATCANBEHANDLED .EW4RACK&ORMATION 4HEREARETWOCLASSESOFTRACKFORMATIONALGORITHMS &ORWARD TRACKINGALGORITHMSBASICALLYPROPAGATEONEHYPOTHESISFORWARDINTIME RECURSIVELYCHECKINGFORhTARGET LIKEvMOTION$ETECTIONSTHATDONOTCORRELATEWITH CLUTTER POINTS OR TRACKS ARE USED TO INITIATE NEW TRACKS )F THE DETECTION DOES NOT CONTAIN DOPPLER INFORMATION THE NEW DETECTION IS USUALLY USED AS THE PREDICTED POSITIONINSOMEMILITARYSYSTEMS ONEASSUMESARADIALLYINBOUNDVELOCITY AND ALARGECORRELATIONREGIONMUSTBEUSEDFORTHENEXTOBSERVATION4HECORRELATION REGIONMUSTBELARGEENOUGHTOCAPTURETHENEXTDETECTIONOFTHETARGET ASSUMING THAT IT COULD HAVE THE MAXIMUM VELOCITY OF INTEREST! COMMON TRACK INITIATION
Ç°{Ó
2!$!2(!.$"//+
CRITERIONISFOUROUTOFFIVE ALTHOUGHONEMAYREQUIREONLYTHREEDETECTIONSOUTOF FIVEOPPORTUNITIESINREGIONSWITHALOWFALSE ALARMRATEANDALOWTARGETDENSITY (OWEVER ONEMAYREQUIREAMUCHLARGERNUMBEROFDETECTIONSWHENTHERADARHAS THEFLEXIBILITYOFANELECTRONICSCANTHATCANPLACEMANYDETECTIONOPPORTUNITIESIN ASHORTTIMEINTERVAL "ACKWARD TRACKINGORhBATCHvALGORITHMSCONSIDERALLTHEDETECTIONSSIMULTANE OUSLY ATTEMPTINGTOMATCHTHEDETECTIONSTOAhTARGET LIKEvPATTERN4HISCANBEDONE BYACTUALLYCONSTRUCTINGALARGENUMBEROFMATCHEDFILTERS ASINRETROSPECTIVEPRO CESSINGSEE&IGURE ORBYUSINGAFORWARD TRACKINGPROCESSWITHMULTIPLE HYPOTHESISFORMEDANDPROPAGATED *UST AS AUTOMATIC RADAR DETECTION IS A TRADEOFF BETWEEN PROBABILITY OF DETECTION ANDPROBABILITYOFFALSEALARM NEWTRACKFORMATIONISATRADEOFFBETWEENTHESPEEDAT WHICHATRACKISFORMEDANDTHEPROBABILITYOFERRONEOUSLYFORMINGAFALSETRACKTHAT DOESNOTREPRESENTAPHYSICALOBJECTOFINTEREST4HEREARETWOTYPESOFFALSETRACKS 4RACKSONREALOBJECTSTHATARESIMPLYNOTOFINTEREST&OREXAMPLE IFTHETARGETSOF INTERESTAREAIRPLANES THENAFALSETRACKCOULDBEATRACKONABIRD 4RACKSCOMPOSED OFUNRELATEDDETECTIONSFROMDIFFERENTOBJECTSTHATTHEAUTOMATICTRACKINGPROCESSHAS MISTAKENLYASSOCIATEDTOGETHER&OREXAMPLE AFALSETRACKCOULDBECOMPOSEDOFDETEC TIONSFROMSEVERALDIFFERENTSTATIONARYCLUTTERPOINTSTHATHAVEBEENASSOCIATEDTOGETHER OVERTIMETOCREATEAFALSEMOVINGTRACK 4HEAPPROACHFORPREVENTINGFALSETRACKSONOBJECTSNOTOFINTERESTISTOACTUALLY DEVELOPTRACKSONALLOFTHEMBUTTHENOBSERVETHEMLONGENOUGHTOCLASSIFYTHEMAS UNWANTED)NTHECASEOFTHEBIRD ONEWOULDGATHERENOUGHDETECTIONSTOIMPROVETHE VELOCITYACCURACYOFTHETRACKSOTHATITISCLEARWHETHERTHETRACKISOFINTERESTORNOT 4HUS ONEDESIRESTODELAYTHEDISCLOSUREOFATRACKUNTILENOUGHTIMEHASPASSEDTO CLASSIFYITACCURATELY4HISACCURACYCANBEDETERMINEDBY4OBS THEAMOUNTOFTIMEOVER WHICHTHEOBJECTISOBSERVEDANDBYBASICPARAMETERSOFTHERADAR 4 THETIMEBETWEENSUCCESSIVEDETECTIONS R THEACCURACYINAPARTICULARDIMENSIONOFINTEREST - THENUMBEROFDETECTIONSUSEDINFORMINGTHETRACK . 4OBS4 WHICHISTHENUMBEROFDETECTIONOPPORTUNITIES 4HEVELOCITYACCURACYISGIVENBYTHEFOLLOWINGEQUATION
SV
S § . ¶ r 4OBS ¨© . . ·¸
4HEDOMINANTDESIGNPARAMETERSINTHEEQUATIONARETHEACCURACYOFTHERADARAND THEOBSERVATIONTIME"ETTERACCURACYORLONGEROBSERVATIONTIMEALLOWSMOREACCURATE MEASUREMENTOFVELOCITY -AKINGMOREDETECTIONSINTHEOBSERVATIONTIMEIMPROVES THEACCURACYBUTONLYINASQUARE ROOTSENSE 4HE APPROACH TO PREVENTING FALSELY COMPOSED TRACKS FROM DIFFERENT OBJECTS IN A CLUTTERREGION ' ISTOREQUIREENOUGHDETECTIONSINATIGHTENOUGHPATTERNTOMAKE %;.&4= THEEXPECTEDNUMBEROFFALSETRACKS SMALL7HENTHEREISANAVERAGEOF.# DETECTIONSINA$ DIMENSIONALREGION' THEN
- %;.&4= K&rK¼ $ . - P r.#rF¼
!54/-!4)#$%4%#4)/. 42!#+).' !.$3%.3/2).4%'2!4)/.
Ç°{Î
&)'52% 4HERETROSPECTIVEPROCESSA ASINGLESCANOFDATA B EIGHTSCANSOFDATA ANDC EIGHT SCANSOFDATAWITHTRAJECTORYFILTERSAPPLIEDAFTER0RENGAMANETALÚ)%%%
Ç°{{
2!$!2(!.$"//+
WHEREK&ISTHERATIOOFTHESIZEOFTHEPOSSIBLESPACEATARGETCANTRAVELINONEDETECTION INTERVALTOTHESIZEOFENTIRECLUTTERREGION'
L&
6-!8 $ '
ANDK0ISTHERATIOOFTHESIZEOFARADARRESOLUTIONCELLTOTHESIZEOFTHEENTIRECLUTTER REGION'
L0
T T $ '
$ . - BEINGTHECOM SIBEINGTHERESOLUTIONhDISTANCEvINTHEITHDIMENSION ANDF¼ BINATORIALTERM
¤ . ³ $ - G $ . - . $ ¥ ¦ - ´µ
&IGUREGIVESANEXAMPLEOFTHEAPPLICATIONOF%QSTOTOARADAR WITHK0 ANDK0 )NCREASINGTHENUMBEROFDETECTIONSREQUIREDTOFORM
&)'52% 6ARIATIONOFTHEEXPECTEDNUMBEROFFALSETRACKSWITHTHETRACKFORMATION- OUT OF .CRITE RIONAFTER7'"ATHETAL
!54/-!4)#$%4%#4)/. 42!#+).' !.$3%.3/2).4%'2!4)/.
Ç°{x
ATRACKFROMTHREEOUTOFFIVE TOFIVEOUTOFEIGHT INCREASESTHEDENSITYOFFALSE ALARMS THAT CAN BE TOLERATED BY MORE THAN AN ORDER OF MAGNITUDE &ORWARD AND BACKWARD TRACKING ALGORITHMS PRODUCE SIMILAR NUMBERS OF FALSE TRACKS (OWEVER THEBACKWARD TRACKINGALGORITHMSCANOPERATEINMOREAMBIGUOUSSITUATIONSWHERE THEDENSITYOFFALSEALARMS K ISCOMPARABLETOORGREATERTHANK&ORK0 5NDERTHESE AMBIGUOUS CIRCUMSTANCES THE FORWARD TRACKER WILL HAVE MULTIPLE DETECTIONS IN A TRACKFORMATIONORPROMOTIONGATEANDWILLREQUIREMULTIPLEHYPOTHESISTORELIABLY FORMTRACKS 4HEDESIGNOFTHETRACKFORMATIONPROCESSANDTHEAUTOMATICDETECTIONPROCESS SHOULDBECONSIDEREDTOGETHER!LONGERTIMEALLOWEDFORTRACKFORMATIONHIGHER -. ALLOWSTHERADARDETECTIONPROCESSTOUSELOWERDETECTIONTHRESHOLDS RESULT ING IN BETTER RADAR SENSITIVITY &OR ANY GIVEN SET OF RADAR PARAMETERS -. TRACK FORMATIONCRITERION ANDPROBABILITYDISTRIBUTIONOFCLUTTERAMPLITUDES THEREEXISTS ANOPTIMUMFALSE ALARMRATETHATMINIMIZESTHESIGNAL TO NOISERATIOREQUIREDTO DETECTTARGETS&IGUREILLUSTRATESTHISOPTIMIZATIONFORANEIGHT SCANTRACKFOR MATIONPROCESS
&)'52% /VERALLSENSITIVITYOFANAUTOMATICDETECTIONANDAUTOMATIC TRACKING PROCESS WORKING TOGETHER 4HE SINGLE SCAN FALSE ALARM PROBABILITY CANBEOPTIMIZEDTOPROVIDETHELOWESTREQUIREDSIGNAL TO NOISERATIOFORVARI OUS PROBABILITY DISTRIBUTIONS OF CLUTTER AMPLITUDE AFTER 0RENGAMAN ET AL Ú)%%%
Ç°{È
2!$!2(!.$"//+
6ERYLOWSINGLE SCANFALSE ALARMPROBABILITIESALLOWTRACKSTOBEFORMEDQUICKLY (OWEVER IFALONGERDELAYISTOLERABLE THENDETECTIONTHRESHOLDSCANBELOWER RESULT INGINBETTERSENSITIVITYINNON GAUSSIANCLUTTER 2ADAR3CHEDULINGAND#ONTROL 4HEINTERACTIONOFTHERADAR TRACKINGSYSTEM WITHTHESCHEDULINGANDCONTROLFUNCTIONOFTHERADARISMINORFORMECHANICALROTATING RADARSBUTMAJORFORPHASEDARRAYRADARS&ORMECHANICALLYROTATINGRADARS ALLTHATIS USUALLYDONEISTHATTHETRACKINGGATESAREFEDBACKTOTHESIGNALPROCESSOR4HETRACKING GATESAREALWAYSUSEDTOFACILITATETHEASSOCIATIONPROCESSANDMAYBEUSEDTOLOWER THEDETECTIONTHRESHOLDWITHINTHEGATEANDORMODIFYTHECONTACTENTRYLOGICWITHINTHE GATEEG MODIFYRULESGOVERNINGCLUTTERMAPS 4HEINTERACTIONOFTHETRACKINGSYSTEMWITHAPHASEDARRAYRADARISMUCHMORESIG NIFICANT4HEMAJORBENEFITOFAPHASEDARRAYWITHRESPECTTOTRACKINGISINTHEAREAOF TRACKINITIATION 0HASEDARRAYSUSEACONFIRMATIONSTRATEGYTOINITIATETRACKSRAPIDLY 4HATIS AFTERTHEASSOCIATIONPROCESS ALLUNASSOCIATEDDETECTIONSGENERATECONFIRMATION DWELLSTOCONFIRMTHEEXISTENCEOFANEWTRACK4HEINITIALCONFIRMATIONDWELLUSESTHE SAMEWAVEFORMFREQUENCYAND02& IFAPULSE DOPPLERWAVEFORM BUTMAYINCREASETHE ENERGY!NALYSISHASSHOWNTHATA D"INCREASEINTHETRANSMITTEDCONFIRMATIONENERGY ADDITIONALENERGYISALSOAVAILABLEBYPLACINGTHETARGETINTHECENTEROFTHECONFIRMA TION BEAM CAN SIGNIFICANTLY INCREASE THE PROBABILITY OF CONFIRMATION &URTHERMORE THECONFIRMATIONDWELLSHOULDBETRANSMITTEDASSOONASPOSSIBLETOMAINTAINA3WERLING )FLUCTUATIONMODEL4HATIS IFTHETARGETWASORIGINALLYDETECTEDWHENTHETARGETFLUC TUATIONPRODUCEDALARGERETURN THECONFIRMATIONDWELLWILLSEETHISSAMELARGERETURN !FTERCONFIRMATION ASERIESOFINITIALTRACKMAINTENANCEDWELLSOVERSEVERALSECONDSIS USED TO DEVELOP AN ACCURATE STATE VECTOR! COMPLETE DISCUSSION OF PRIORITY ASSOCIATED WITHTRACKINGWITHINTHESCHEDULEROFAPHASEDARRAYISBEYONDTHESCOPEOFTHISBRIEF DISCUSSION(OWEVER ITISWORTHWHILENOTINGTHESEGENERALRULES #ONFIRMATIONDWELLS SHOULDHAVEAPRIORITYHIGHERTHANALLOTHERFUNCTIONSEXCEPTTHOSEASSOCIATEDWITHWEAPON CONTROL LOWPRIORITYTRACKSEG TRACKSATLONGRANGE CANBEUPDATEDUSINGSEARCH DETECTIONSAND HIGHPRIORITYTRACKSSHOULDHAVEAPRIORITYHIGHERTHANVOLUMESURVEIL LANCE4HEUPDATERATEFORHIGHPRIORITYTRACKSSHOULDBESUCHTHATASINGLETRACKINGDWELLIS SUFFICIENTTOUPDATETHETRACK4HEACTUALUPDATERATEWILLDEPENDONMANYFACTORSINCLUD INGA MAXIMUMTARGETSPEEDANDMANEUVERCAPABILITY B RADARBEAMWIDTHBEAMCOULD BESPOILED C RANGEOFTHERADARTRACK ANDD ACCURACYOFPREDICTEDPOSITION)FAPULSE DOPPLERDWELLISREQUIREDTOUPDATETHETRACKINCLUTTER THEWAVEFORMSHOULDBESELECTEDTO PLACETHETARGETNEARTHECENTEROFTHEAMBIGUOUSRANGE DOPPLERDETECTIONSPACE&INALLY THETRACKCANBEUPDATEDWITHTHEAMBIGUOUSRANGE DOPPLERDETECTIONBECAUSETHETRACK STATE VECTORCANBEUSEDTOREMOVETHEAMBIGUITY
Ç°{Ê
/7", Ê, ,-
)DEALLY ASINGLERADARCANRELIABLYDETECTANDTRACKALLTARGETSOFINTEREST(OWEVER THE ENVIRONMENTANDTHELAWSOFPHYSICSOFTENWILLNOTPERMITTHIS)NGENERAL NOSINGLE RADARCANPROVIDEACOMPLETESURVEILLANCEANDTRACKINGPICTURE2ADARNETWORKINGCAN BEAGOODSOLUTIONTOTHISPROBLEMAND INSOMECASES MAYBEMORECOSTEFFECTIVETHAN SOLVINGTHEPROBLEMTHROUGHONEVERYHIGHPERFORMANCERADAR2ADARNETWORKINGSYSTEMS AREGENERALLYCHARACTERIZEDBYWHATRADARDATAARESHAREDANDHOWTHEYARECORRELATED ANDFUSED4HETWOMOSTCOMMONWAYSOFCOMBININGRADARDATAAREASFOLLOWS
!54/-!4)#$%4%#4)/. 42!#+).' !.$3%.3/2).4%'2!4)/.
Ç°{Ç
$ETECTION TO TRACKFUSIONSEE&IGURE UPPERHALF ASSOCIATESEACHDETECTIONTO THENETWORKEDTRACK CALCULATEDPOTENTIALLYUSINGDETECTIONSFROMALLRADARS4HUS THEENTIRESTREAMOFDETECTIONSUPTOTHEPRESENT ISPOTENTIALLYAVAILABLETOCALCU LATETHETRACKSTATEUSEDFORTHEASSOCIATIONDECISIONONTHEMOSTRECENTDETECTION 4RACK TO TRACKFUSIONSEE&IGURE LOWERHALF ASSOCIATESEACHDETECTIONTOA SINGLERADARTRACKSTATECALCULATEDUSINGONLYDETECTIONSFROMTHATRADAR4HESINGLE RADARTRACKSTATESARETHENGROUPEDWITHEACHOTHERTOPRODUCEANETTEDTRACKSTATE 4HEDESIGNDECISIONASTOWHICHAPPROACHISBETTERFORGROUPINGDATADEPENDSONTHE RADARSANDTARGETSINVOLVED/NECASEWHEREDETECTION TO TRACKASSOCIATIONISCLEARLYBET TERISWHENTHERADARSHAVEAREDUCEDPROBABILITYOFDETECTIONSOTHEREAREPOTENTIALGAPS INTHEDATASTREAMORPERIODSWHERETHEDATASTREAMISSPARSE)NTHESECASES AMUCHMORE ACCURATETRACKSTATECANBECALCULATEDUSINGMULTIPLEDATASTREAMSTHANUSINGONLYONE BECAUSEMULTIPLESTREAMSWILLTENDTOFILLINTHEGAPSINDETECTIONANDRESTOREAHIGHCON SISTENTDATARATEDURINGPERIODSOFREDUCEDPROBABILITYOFDETECTION&IGUREILLUSTRATES THESENSITIVITYTOTARGETFADESBYPLOTTINGTHETRACKREGIONOFUNCERTAINTY2/5 VERSUSTHE PROBABILITYOFDETECTIONFORSINGLERADARTRACKINGANDMULTIPLERADARTRACKING4HE2/5IS DEFINEDASTHEDISTANCETHATCONTAINSTHEERRORWITHPERCENTPROBABILITYANDIS 2/5 TRACKINGERRORDUETODETECTIONNOISE TRACKINGERRORDUETOMANEUVER 4HISCANBECALCULATEDFORANYCASEOFINTERESTUSINGTHEFORMULASIN4ABLE
&)'52% 4HEREARETWOCOMMONMETHODSOFFUSIONDATAINRADARNETWORKINGDETECTION TO TRACKAND TRACK TO TRACKAFTER7"ATHÚ)%%
Ç°{n
2!$!2(!.$"//+
&)'52% #OMPARISONOFDETECTION TO TRACKANDTRACK TO TRACKASSOCIATION&ORFAD INGTARGETS0D DETECTION TO TRACKISPREFERRED&ORLARGESENSORBIASESANDNON FADING TARGETS TRACK TO TRACKISPREFERREDAFTER7"ATHÚ)%%
7HENTHEPROBABILITYOFDETECTIONISMUCHLESSTHANUNITY THEMEASUREMENT TO TRACK FUSIONISCONSIDERABLYMOREACCURATE4HISISEASILYEXPLAINEDBYTHEFACTTHATTHEPROB ABILITYOFASIGNIFICANTOUTAGEOFDATAISMUCHREDUCEDIFTWOSOURCESAREAVAILABLE7ITH AMOREACCURATETRACK TIGHTERASSOCIATIONCRITERIACANBEUSEDFORDETECTIONS )FTHEBIASESCANNOTBEEFFECTIVELYREMOVED THENTHEREMAYBEANADVANTAGETOASSO CIATINGTOASINGLERADARTRACKWHICHBYDEFINITIONISUNBIASEDWITHRESPECTTOITSELF )FBIASESCANNOTBEKEPTSMALLERTHANTHE2/5 THENATHIGHPROBABILITIESOFDETECTION ONEPREFERSSINGLERADARASSOCIATIONFOLLOWEDBYTRACK TO TRACKASSOCIATION )TISPOSSIBLETOMAKESIMPLECOMPARISONSBETWEENTHEACCURACYOFDETECTIONFUSION ASOPPOSEDTOTRACKFUSIONFOREQUIVALENTUSEOFDATABANDWIDTHTOEXCHANGERADARDATA 7HEN2/5ISPLOTTEDASAFUNCTIONOFTHEPOSITIONGAIN@ ITHASTHEhBATHTUBvSHAPE SHOWNBYTHESINGLERADARCURVEIN&IGURE4HELEFT HANDSIDEOFTHEhBATHTUBvIS DOMINATEDBYTHELAGCOMPONENT WHILETHERIGHT HANDSIDEISDOMINATEDBYTHERADAR MEASUREMENTNOISECOMPONENT"ECAUSETHEGAINSHORIZONTALAXIS ARETHEDESIGNERS CHOICE THESINGLERADAR2/5ISTHEMINIMUMOFTHEhBATHTUBvCURVE .OWCONSIDERTHEFUSIONOFTWORADARSINAPARTICULARDIMENSION)FONERADARHASONE TENTHTHE2/5OFTHEOTHERINTHISDIMENSION THENTHEMOREACCURATERADARINTHISDIMENSION WILLDOMINATEANDESSENTIALLYDETERMINETHERESULT!TLEASTINSTEADYSTATE ITISRELATIVELY EASYTOPRODUCETHISDOMINANCEBYANYOFTHEFUSIONMETHODS/FMOREINTERESTISTHECASE WHERETHERADARSARECOMPARABLEINTERMSOFACCURACYANDUPDATERATE PRODUCINGCOMPA RABLE2/5S4HISCASEMORECLEARLYSHOWSTHEDIFFERENCEINTHEFUSIONMETHODS &OR EXAMPLE WHEN TWO IDENTICAL RADARS ARE COMBINED BY DETECTION FUSION THEN THEUPDATERATEISESSENTIALLYDOUBLED4HISREDUCESTHELAGBYAFACTOROF ALLOWINGA SMALLERGAINTOBESELECTEDOPTIMIZATIONMORETOTHELEFTOFTHEhBATHTUBv REDUCING THETRACKINGERRORSDUETOMEASUREMENTNOISE4HENETRESULTISTHEMOVEMENTFROMTHE SINGLERADARCURVETOTHEDETECTIONFUSIONCURVEIN&IGURE
!54/-!4)#$%4%#4)/. 42!#+).' !.$3%.3/2).4%'2!4)/.
Ç°{
&)'52% #OMPARISONOFDETECTIONFUSIONANDTRACKFUSIONAPPROACHES&ORAIR BREATHINGTARGETS DETECTIONFUSIONPRODUCESTHEMOSTACCURATETRACKSMALLEST2/5 AFTER7"ATHÚ)%%
7HENTWOIDENTICALRADARSARECOMBINEDBYTRACKFUSION THEUPDATERATEFOREACH TRACKINGPROCESSDOESNOTCHANGE ANDSOTHELAGDOESNOTCHANGE(OWEVER THESTAN DARDDEVIATIONOFTHETRACKINGERRORSDUETOMEASUREMENTNOISEISREDUCEDBYTHESQUARE ROOTOF ALLOWINGALARGERGAINTOBESELECTEDOPTIMIZATIONMORETOTHERIGHTOFTHE BATHTUB REDUCINGTHELAG4HENETRESULTISTHEMOVEMENTFROMTHESINGLERADARCURVE TOTHETRACKFUSIONCURVEIN&IGURE )FTHEREISANYSIGNIFICANTMANEUVERPOSSIBLE THEFACTOROFINLAGWILLHAVEAMORE SIGNIFICANTEFFECTTHANTHEFACTOROFTHESQUAREROOTOFINTHESQUAREROOTOFTHETRACKING ERRORSDUETOMEASUREMENTNOISE4HUS ONECANSEETHEDETECTIONFUSIONCURVEACHIEVES ASIGNIFICANTLYLOWERMINIMUMTHANTHETRACKFUSIONCURVE 4OCOMBINEDATAFROMMULTIPLERADARS THEDATAMUSTBEPLACEDINACOMMONCOOR DINATESYSTEM4HISPROCESSISCALLEDGRIDLOCKINGANDINVOLVESSPECIFYINGTHELOCATION OFTHERADARSANDESTIMATINGRADARBIASESINRANGEANDANGLE4HEPREVIOUSDIFFICULT PROBLEMOFRADARLOCATIONISSOLVEDTRIVIALLYBYTHEGLOBALPOSITIONINGSYSTEM!NESTI MATEOFRADARBIASESBETWEENTWORADARSCANBEOBTAINEDFROMALONG TERMAVERAGEOF THEDIFFERENCEBETWEENPREDICTEDANDMEASUREDCOORDINATESONALLTRACKSTHATHAVEA SUBSTANTIALNUMBEROFDETECTIONSFROMBOTHRADARS
Ç°xÊ 1 - -",Ê / ,/" !NUMBEROFSENSORSCANBEINTEGRATEDRADAR IDENTIFICATIONFRIENDORFOE)&& THE AIRTRAFFICCONTROLRADARBEACONSYSTEM!4#2"3 INFRARED OPTICAL ANDACOUSTIC4HE SENSORSTHATAREMOSTEASILYINTEGRATEDARETHEELECTROMAGNETICSENSORS IE RADAR )&& ANDSTROBEEXTRACTORSOFNOISESOURCESOREMITTERS
Ç°xä
2!$!2(!.$"//+
)&&)NTEGRATION 4HEPROBLEMOFINTEGRATINGRADARANDMILITARY)&&DATAISLESS DIFFICULT THAN THAT OF INTEGRATING TWO RADARS 4HE QUESTION OF WHETHER DETECTIONS OR TRACKSSHOULDBEINTEGRATEDISAFUNCTIONOFTHEAPPLICATION)NAMILITARYSITUATION BY INTEGRATINGDETECTIONSONECOULDINTERROGATETHETARGETONLYAFEWTIMES IDENTIFYIT ANDTHENASSOCIATEITWITHARADARTRACK&ROMTHENON THEREWOULDBELITTLENEEDFOR RE INTERROGATINGTHETARGET(OWEVER INANAIRTRAFFICCONTROLSITUATIONUSING!4#2"3 TARGETS WOULD BE INTERROGATED AT EVERY SCAN AND CONSEQUENTLY EITHER DETECTIONS OR TRACKSCOULDBEINTEGRATED 2ADARn$& "EARING 3TROBE )NTEGRATION #ORRELATING RADAR TRACKS WITH $& DIRECTIONFINDING BEARINGSTROBESONEMITTERSHASBEENCONSIDEREDBY#OLEMANAND LATERBY4RUNKAND7ILSON 4RUNKAND7ILSONCONSIDEREDTHEPROBLEMOFASSOCI ATINGEACH$&TRACKWITHEITHERNORADARTRACKORONEOFMRADARTRACKS)NTHEIRFOR MULATION THEREWERE+$&ANGLETRACKS EACHSPECIFIEDBYADIFFERENTNUMBEROF$& DETECTIONSANDSIMILARLY MRADARTRACKS EACHSPECIFIEDBYADIFFERENTNUMBEROFRADAR DETECTIONS"ECAUSEEACHTARGETCANCARRYMULTIPLEEMITTERSIE MULTIPLE$&TRACKS CANBEASSOCIATEDWITHEACHRADARTRACK EACH$&TRACKASSOCIATIONCANBECONSIDERED BY ITSELF RESULTING IN + DISJOINT ASSOCIATION PROBLEMS #ONSEQUENTLY AN EQUIVALENT PROBLEMISGIVENA$&TRACKSPECIFIEDBYN$&BEARINGDETECTIONS ONECANASSOCIATE THE$&TRACKWITHNORADARTRACKORWITHONEOFMRADARTRACKS THEJTHRADARTRACKBEING SPECIFIEDBYMJRADARDETECTIONS5SINGACOMBINATIONOF"AYESAND.EYMAN 0EARSON PROCEDURES AND ASSUMING THAT THE $& DETECTION ERRORS ARE USUALLY INDEPENDENT AND GAUSSIAN DISTRIBUTEDWITHZEROMEANANDCONSTANTVARIANCERBUTWITHOCCASIONALOUT LIERSIE LARGEERRORSNOTDESCRIBEDBYTHEGAUSSIANDENSITY 4RUNKAND7ILSONARGUED THATTHEDECISIONSHOULDBEBASEDONTHEPROBABILITY
0J PROBABILITY:qDJ
WHERE:HASACHI SQUAREDENSITYWITHNJDEGREESOFFREEDOMANDDJISGIVENBY NJ
D J £ MIN[ ;Q E TI Q J TI = S ] I
J M
WHERENJISTHENUMBEROF$&DETECTIONSOVERLAPPINGTHETIMEINTERVALFORWHICHTHE JTHRADARTRACKEXISTSPETI ISTHE$&DETECTIONATTIMETIPJTI ISTHEPREDICTEDAZIMUTH OFRADARTRACKJFORTIMETIANDTHEFACTORLIMITSTHESQUAREERRORTORTOACCOUNTFOR $&OUTLIERS"YUSINGTHETWOLARGEST0JS DESIGNATED0MAXAND0NEXT ANDTHRESHOLDS 4, 4( 4- AND2 THEFOLLOWINGDECISIONSANDDECISIONRULESWEREGENERATED &IRMCORRELATION $&SIGNALGOESWITHRADARTRACKHAVINGLARGEST0JIE 0MAX WHEN0MAXq4(AND0MAXq0NEXT 2 4ENTATIVECORRELATION $&SIGNALPROBABLYGOESWITHRADARTRACKHAVINGLARGEST0J IE 0MAX WHEN4( 0MAXq4-AND0MAXq0NEXT 2 4ENTATIVECORRELATIONWITHSOMETRACK $&SIGNALPROBABLYGOESWITHSOMERADAR TRACKBUTCANNOTDETERMINEWHICH WHEN0MAXq4-BUT0MAX 0NEXT 2 4ENTATIVELYUNCORRELATED $&SIGNALPROBABLYDOESNOTGOWITHANYRADARTRACK WHEN4- 0MAX 4, &IRMLYUNCORRELATED $&SIGNALDOESNOTGOWITHANYRADARTRACKWHEN4,q0MAX
!54/-!4)#$%4%#4)/. 42!#+).' !.$3%.3/2).4%'2!4)/.
Ç°x£
4HELOWERTHRESHOLD4,DETERMINESTHEPROBABILITYTHATTHECORRECTRADARTRACKIE THEONEASSOCIATEDWITHTHE$&SIGNAL WILLBEINCORRECTLYREJECTEDFROMFURTHERCONSID ERATION)FTHEDESIREDREJECTIONRATEFORTHECORRECTTRACKIS02 ONECANOBTAINTHISBY SETTING4, 024HETHRESHOLD4(ISSETEQUALTO0FA DEFINEDASTHEPROBABILITYOFFALSELY ASSOCIATINGARADARTRACKWITHA$&SIGNALWHENTHE$&SIGNALDOESNOTBELONGWITH THERADARTRACK4HETHRESHOLD4(ISAFUNCTIONOFTHEAZIMUTHDIFFERENCELBETWEENTHE TRUE$& POSITIONANDTHERADARTRACKUNDERCONSIDERATION4HETHRESHOLD4(WASFOUND FORL RANDL RBYSIMULATIONTECHNIQUES ANDTHERESULTSFOR0FA ARE SHOWNIN&IGURE"ETWEENTHEHIGHANDLOWTHRESHOLDS THEREISATENTATIVEREGION 4HEMIDDLETHRESHOLDDIVIDESTHEhTENTATIVEvREGIONINTOATENTATIVELYCORRELATEDREGION ANDATENTATIVELYUNCORRELATEDREGION4HERATIONALEINSETTINGTHETHRESHOLDISTOSETTHE TWOASSOCIATEDERRORPROBABILITIESEQUALFORAPARTICULARSEPARATION4HETHRESHOLD4- WASFOUNDBYUSINGSIMULATIONTECHNIQUESANDISALSOSHOWNIN&IGURE 4HEPROBABILITYMARGIN2ENSURESTHESELECTIONOFTHEPROPER$&RADARASSOCIATION AVOIDINGRAPIDLYCHANGINGDECISIONS WHENTHEREARETWOORMORERADARTRACKSCLOSE TOONEANOTHER4HECORRECTSELECTIONISREACHEDBYPOSTPONINGADECISIONUNTILTHETWO HIGHESTASSOCIATIONPROBABILITIESDIFFERBY24HEVALUEFOR2ISFOUNDBYSPECIFYINGA PROBABILITYOFANASSOCIATIONERROR0EACCORDINGTO0E 00MAXq0NEXT 2 WHERE 0MAXCORRESPONDSTOANINCORRECTASSOCIATIONAND0NEXTCORRESPONDSTOTHECORRECT ASSOCIATION4HEPROBABILITYMARGIN2ISAFUNCTIONOF0EANDTHESEPARATIONLOFTHE RADARTRACKS4HEPROBABILITYMARGIN2WASFOUNDFORL R R ANDRBY USINGSIMULATIONTECHNIQUES ANDTHERESULTSFOR0E ARESHOWNIN&IGURE
&)'52% (IGH THRESHOLD SOLID LINES AND MIDDLE THRESHOLD DASHED LINES VERSUS NUMBER OF SAMPLES FOR TWO DIFFERENT SEPARATIONS AFTER '6 4RUNK AND *$ 7ILSONÚ)%%%
Ç°xÓ
2!$!2(!.$"//+
&)'52% 0ROBABILITY MARGIN VERSUS NUMBER OF $& DETECTIONS FOR THREE DIFFERENT TARGET SEPARATIONS 4HE OS XS AND $S ARE THE SIMULATION RESULTSFORL L ANDL RESPECTIVELYAFTER'64RUNKAND *$7ILSONÚ)%%%
"ECAUSETHECURVESCROSSONEANOTHER ONECANENSURETHAT0EaFORANYLBYSETTING 2EQUALTOTHEMAXIMUMVALUEOFANYCURVEFOREACHVALUEOFN 4HEALGORITHMWASEVALUATEDBYUSINGSIMULATIONSANDRECORDEDDATA7HENTHE RADARTRACKSARESEPARATEDBYSEVERALSTANDARDDEVIATIONSOFTHEDETECTIONERROR COR RECTDECISIONSAREMADERAPIDLY(OWEVER IFTHERADARTRACKSARECLOSETOONEANOTHER ERRORSAREAVOIDEDBYPOSTPONINGTHEDECISIONUNTILSUFFICIENTDATAAREACCUMULATED!N INTERESTINGEXAMPLEWITHRECORDEDDATAISSHOWNIN&IGURESAND&IGURE SHOWSTHERADARAZIMUTH DETECTIONSOFTHECONTROLAIRCRAFT THERADARDETECTIONSOFFOUR AIRCRAFTOFOPPORTUNITYINTHEVICINITYOFTHECONTROLAIRCRAFT ANDTHE$&DETECTIONSON THERADARONTHECONTROLAIRCRAFT4HEASSOCIATIONPROBABILITIES WITHANDWITHOUTLIMIT INGIN%Q ARESHOWNIN&IGURE)NITIALLY ANAIRCRAFTOFOPPORTUNITYHASTHE HIGHESTASSOCIATIONPROBABILITYHOWEVER AFIRMDECISIONISNOTMADEBECAUSE0MAX DOES NOT EXCEED 0NEXT BY THE PROBABILITY MARGIN!FTER THE TH $& DETECTION THE EMITTERISFIRMLYCORRELATEDWITHTHECONTROLAIRCRAFT(OWEVER ATTHETH$&DETEC TION AVERYBADDETECTIONOUTLIER ISMADE ANDTHEFIRMCORRELATIONISDOWNGRADED TOATENTATIVECORRELATIONIFLIMITINGISNOTUSED)FLIMITINGISEMPLOYED HOWEVER THE CORRECTDECISIONREMAINSFIRM )NACOMPLEXENVIRONMENTWHERETHEREAREMANYRADARTRACKSAND$&SIGNALSOURCES ITISQUITEPOSSIBLETHATMANY$&SIGNALSWILLBEASSIGNEDTHECATEGORYTHATTHE$& SIGNALPROBABLYGOESWITHSOMERADARTRACK4OREMOVEMANYOFTHESEAMBIGUITIES MULTISITE$&OPERATIONCANBECONSIDERED4HEEXTENSIONOFTHEPREVIOUSPROCEDURES
!54/-!4)#$%4%#4)/. 42!#+).' !.$3%.3/2).4%'2!4)/.
Ç°xÎ
&)'52% 2ADARDETECTIONSOAND$&DETECTIONSCOLLECTEDONTHECONTROLAIRCRAFT4HEOS $S S ANDXSARERADARDETECTIONSONFOURAIRCRAFTOFOPPORTUNITYINTHEVICINITYOFTHECONTROL AIRCRAFTAFTER'64RUNKAND*$7ILSONÚ)%%%
&)'52% !SSOCIATIONPROBABILITIESFOREXPERIMENTALDATA4HEBOLDLINESAREPROBABILITIESFOR THECONTROLAIRCRAFTTHESOLIDLINE FORLIMITINGTHEDASHEDLINE FORNOLIMITINGTHETHINLINE THEASSO CIATIONPROBABILITYFORTHEAIRCRAFTOFOPPORTUNITYANDTHETHINDASHEDLINES THETHRESHOLDS4-AND4( AFTER'64RUNKAND*$7ILSONÚ)%%%
Ç°x{
2!$!2(!.$"//+
TOMULTISITEOPERATIONISSTRAIGHTFORWARD3PECIFICALLY IFPETI ANDPETK ARETHE$& ANGLE DETECTIONS WITH RESPECT TO SITES AND AND IF PJTI AND PJTK ARE THE ESTI MATEDANGULARPOSITIONSOFRADARTRACKJWITHRESPECTTOSITESAND THENTHEMULTISITE SQUAREDERRORISSIMPLY N J
[
N J
]
[
]
D J £ MIN ;Q E TI Q J TI = S £ MIN ;Q E TK Q J TK = S I
K
4HE PREVIOUSLY DESCRIBED PROCEDURE CAN THEN BE USED WITH DJ BEING DEFINED BY %QINSTEADOF%Q
, ,
* ) -ARCUM h! STATISTICAL THEORY OF TARGET DETECTION BY PULSED RADAR v )2%4RANS VOL )4 PPn !PRIL 03WERLING h0ROBABILITYOFDETECTIONFORFLUCTUATINGTARGETS v)2%4RANS VOL)4 PPn !PRIL *.EYMANAND%30EARSON h/NTHEPROBLEMSOFTHEMOSTEFFICIENTTESTSOFSTATISTICALHYPOTH ESES v0HILOS4RANS23OC,ONDON VOL SER! P ,6"LAKE h4HEEFFECTIVENUMBEROFPULSESPERBEAMWIDTHFORASCANNINGRADAR v0ROC)2% VOL PPn *UNE ' 6 4RUNK h#OMPARISON OF THE COLLAPSING LOSSES IN LINEAR AND SQUARE LAW DETECTORS v 0ROC )%%% VOL PPn *UNE 03WERLING h-AXIMUMANGULARACCURACYOFAPULSEDSEARCHRADAR v0ROC)2% VOL PPn 3EPTEMBER '64RUNK h3URVEYOFRADAR!$4 v.AVAL2ES,AB2EPT *UNE '64RUNK h#OMPARISONOFTWOSCANNINGRADARDETECTORS4HEMOVINGWINDOWANDTHEFEEDBACK INTEGRATOR v)%%%4RANS VOL!%3 PPn -ARCH '64RUNK h$ETECTIONRESULTSFORSCANNINGRADARSEMPLOYINGFEEDBACKINTEGRATION v)%%%4RANS VOL!%3 PPn *ULY '64RUNKAND"(#ANTRELL h!NGULARACCURACYOFASCANNINGRADAREMPLOYINGA POLEINTEGRA TOR v)%%%4RANS VOL!%3 PPn 3EPTEMBER "(#ANTRELLAND'64RUNK h#ORRECTIONSTO@ANGULARACCURACYOFASCANNINGRADAREMPLOYING ATWO POLEFILTER v)%%%4RANS VOL!%3 PPn .OVEMBER $##OOPERAND*72'RIFFITHS h6IDEOINTEGRATIONINRADARANDSONARSYSTEMS v*"RIT)2% VOL PPn -AY 6'(ANSEN h0ERFORMANCEOFTHEANALOGMOVINGWINDOWDETECTION v)%%%4RANS VOL!%3 PPn -ARCH 03WERLING h4HE@DOUBLETHRESHOLDMETHODOFDETECTION v0ROJECT2AND2ES-EM2- $ECEMBER *6(ARRINGTON h!NANALYSISOFTHEDETECTIONOFREPEATEDSIGNALSINNOISEBYBINARYINTEGRATION v )2%4RANS VOL)4 PPn -ARCH -3CHWARTZ h!COINCIDENCEPROCEDUREFORSIGNALDETECTION v)2%4RANS VOL)T PPn $ECEMBER $(#OOPER h"INARYQUANTIZATIONOFSIGNALAMPLITUDESEFFECTFORRADARANGULARACCURACY v)%%% 4RANS VOL!NE PPn -ARCH ' - $ILLARD h! MOVING WINDOW DETECTOR FOR BINARY INTEGRATION v )%%% 4RANS VOL )4 PPn *ANUARY
!54/-!4)#$%4%#4)/. 42!#+).' !.$3%.3/2).4%'2!4)/.
Ç°xx
$#3CHLEHER h2ADARDETECTIONINLOG NORMALCLUTTER vIN)%%%)NT2ADAR#ONF 7ASHINGTON $# PPn h2ADAR PROCESSING SUBSYSTEM EVALUATION v VOL *OHNS (OPKINS 5NIVERSITY !PPL 0HYS ,AB 2EPT&0 4 .OVEMBER (-&INNAND23*OHNSON h!DAPTIVEDETECTIONMODEWITHTHRESHOLDCONTROLASAFUNCTIONOF SPACIALLYSAMPLEDCLUTTER LEVELESTIMATES v2#!2EV VOL PPn 3EPTEMBER 2,-ITCHELLAND*&7ALKER h2ECURSIVEMETHODSFORCOMPUTINGDETECTIONPROBABILITIES v)%%% 4RANS VOL!%3 PPn *ULY '64RUNKAND*$7ILSON h!UTOMATICDETECTORFORSUPPRESSIONOFSIDELOBEINTERFERENCE vIN )%%%#ONF$ECISION#ONTROL $ECEMBERn PPn '64RUNKAND0+(UGHES)) h!UTOMATICDETECTORSFORFREQUENCY AGILERADAR vIN)%%)NT 2ADAR#ONF ,ONDON PPn '64RUNK "(#ANTRELL AND&$1UEEN h-ODIFIEDGENERALIZEDSIGNTESTPROCESSORFOR $ RADAR v)%%%4RANS VOL!%3 PP 3EPTEMBER *42ICKARDAND'-$ILLARD h!DAPTIVEDETECTIONALGORITHMSFORMULTIPLE TARGETSITUATIONS v )%%%4RANS VOL!%3 PPn *ULY (-&INN h!#&!2DESIGNFORAWINDOWSPANNINGTWOCLUTTERFIELDS v)%%%4RANS VOL!%3 PPn -ARCH "! 'REEN h2ADAR DETECTION PROBABILITY WITH LOGARITHMIC DETECTORS v )2% 4RANS VOL )4 -ARCH 6'(ANSENAND*27ARD h$ETECTIONPERFORMANCEOFTHECELLAVERAGELOG#&!2RECEIVER v )%%%4RANS VOL!%3 PPn 3EPTEMBER '-$ILLARDAND#%!NTONIAK h!PRACTICALDISTRIBUTION FREEDETECTIONPROCEDUREFORMULTIPLE RANGE BINRADARS v)%%%4RANS VOL!%3 PPn 3EPTEMBER 6'(ANSENAND"!/LSEN h.ONPARAMETRICRADAREXTRACTIONUSINGAGENERALIZEDSIGNTEST v )%%%4RANS VOL!%3 3EPTEMBER 7'"ATH ,!"IDDISON 3&(AASE AND%#7ETZLAR h&ALSEALARMCONTROLINAUTOMATED RADARSURVEILLANCESYSTEMS vIN)%%)NT2ADAR#ONF ,ONDON PPn #%-UEHE ,#ARTLEDGE 7($RURY %-(OFSTETTER -,ABITT 0"-C#ORISON AND6* 3FERRINO h.EWTECHNIQUESAPPLIEDTOAIR TRAFFICCONTROLRADARS v0ROC)%%% VOL PPn *UNE '64RUNK h2ANGERESOLUTIONOFTARGETSUSINGAUTOMATICDETECTORS v)%%%4RANS VOL!%3 PPn 3EPTEMBER '64RUNK h2ANGERESOLUTIONOFTARGETS v)%%%4RANS VOL!%3 PPn .OVEMBER '64RUNKAND3-"ROCKETT h2ANGEANDVELOCITYAMBIGUITYRESOLUTION vIN)%%%.ATIONAL 2ADAR#ONF "OSTON PPn '64RUNKAND-+IM h!MBIGUITYRESOLUTIONOFMULTIPLETARGETSUSINGPULSE DOPPLERWAVE FORMS v)%%%4RANS VOL!%3 PP /CTOBER (,EUNG :(U AND-"LANCHETTE h%VALUATIONOFMULTIPLERADARTARGETTRACKERSINSTRESSFUL ENVIRONMENTS v )%%% 4RANS !EROSPACE AND %LECTRONIC 3YSTEMS VOL NO PP n "(#ANTRELL '64RUNK AND*$7ILSON h4RACKINGSYSTEMFORTWOASYNCHRONOUSLYSCANNING RADARS v.AVAL2ES,AB2EPT 7$3TUCKEY h!CTIVITYCONTROLPRINCIPLESFORAUTOMATICTRACKINGALGORITHMS vIN)%%%2ADAR #ONFERENCE PPn 42"ENEDICTAND'7"ORDNER h3YNTHESISOFANOPTIMALSETOFRADARTRACK WHILE SCANFILTERING EQUATIONS v)2%4RANS VOL!# PPn 2%+ALMAN h!NEWAPPROACHTOLINEARFILTERINGANDPREDICTIONPROBLEMS v*"ASIC%NG!3-% 4RANS SER$ VOL PPn 2%+ALMANAND23"UCY h.EWRESULTSINLINEARFILTERINGANDPREDICTIONTHEORY v*"ASIC%NG !3-%4RANS SER$ VOL PPn
Ç°xÈ
2!$!2(!.$"//+
3"LACKMANAND20OPOLI $ESIGNAND!NALYSISOF-ODERN4RACKING3YSTEMS "OSTON!RTECH 2!3INGER h%STIMATINGOPTIMALTRACKINGFILTERPERFORMANCEFORMANNEDMANEUVERINGTARGETS v )%%%4RANS VOL!%3 PPn "&RIEDLAND h/PTIMUMSTEADYSTATEPOSITIONANDVELOCITYESTIMATIONUSINGNOISYSAMPLEDPOSI TIONDATA v)%%%4RANSVOL!%3 P 0+ALATA h4HETRACKINGINDEX!GENERALIZEDPARAMETERFOR@ AAND@ A FTARGETTRACKERS v )%%%4RANS!EROSPACEAND%LECTRONIC3YSTEMS !%3 PPn 7$"LAIRAND9"AR 3HALOM h4RACKINGMANEUVERINGTARGETSWITHMULTIPLESENSORS$OESMORE DATA ALWAYS MEAN BETTER ESTIMATES v )%%% 4RANS !EROSPACE AND %LECTRONIC 3YSTEMS VOL PP &2#ASTELLA h!NALYTICALRESULTSFORTHEX Y+ALMANTRACKINGFILTER v)%%%4RANS!EROSPACEAND %LECTRONIC3YSTEMS .OVEMBER VOL PP 2 & &ITZGERALD h3IMPLE TRACKING FILTERS 3TEADY STATE FILTERING AND SMOOTHING PERFORMANCE v )%%%4RANS!EROSPACEAND%LECTRONIC3YSTEMS VOL!%3 PPn '*0ORTMANN *-OORE AND7'"ATH h3EPARATEDCOVARIANCEFILTERING vIN2EC)%%% )NTERNATIONAL2ADAR#ONFERENCE PPn 0-OOKERJEEAND&2EIFLER h2EDUCEDSTATEESTIMATORFORSYSTEMSWITHPARAMETRICINPUTS v)%%% 4RANS!EROSPACEAND%LECTRONIC3YSTEMS VOL NO PPn !3'ELB !PPLIED/PTIMAL%STIMATION #AMBRIDGE -!-)40RESS & 2 #ASTELLA h-ULTISENSOR MULTISITE TRACKING FILTER v )%% 0ROC 2ADAR 3ONAR .AVIGATION VOL ISSUE PPn %!7AN 2VANDER-ERWE AND!4.ELSON h$UALESTIMATIONANDTHEUNSCENTEDTRANSFORMA TION vIN!DVANCESIN.EURAL)NFORMATION0ROCESSING3YSTEMS #AMBRIDGE-)40RESS PPn '!7ATSONAND7$"LAIR h)--ALGORITHMFORTRACKINGTARGETSTHATMANEUVERTHROUGHCOORDI NATEDTURNS v30)% 3IGNALAND$ATA0ROCESSINGOF3MALL4ARGETS VOL PPn 2 #OOPERMAN h4ACTICAL BALLISTIC MISSILE TRACKING USING THE INTERACTING MULTIPLE MODEL ALGORITHM v IN 0ROC &IFTH )NTERNATIONAL #ONFERENCE ON )NFORMATION &USION VOL PPn #,-OREFIELD h!PPLICATIONOFnINTEGERPROGRAMMINGTOMULTI TARGETTRACKINGPROBLEMS v )%%%4RANS VOL!# PPn 2*ONKERAND!6OLGENANT h!SHORTESTAUGMENTINGPATHALGORITHMFORDENSEANDSPARSELINEAR ASSIGNMENTPROBLEMS v#OMPUTING VOL NO PPn $"ERTSEKAS h4HEAUCTIONALGORITHMFORASSIGNMENTANDOTHERNETWORKFLOWPROBLEMS!TUTO RIAL v)NTERFACES VOL PPn )+ADAR %%ADAN AND2'ASSNER h#OMPARISONOFROBUSTIZEDASSIGNMENTALGORITHMS v30)% VOL PPn 9"AR 3HALOMAND%4SE h4RACKINGINACLUTTEREDENVIRONMENTWITHPROBABILISTICDATAASSOCIA TION v!UTOMATICA VOL PPn 3"#OLEGROVEAND*+!YLIFFE h!NEXTENSIONOFPROBABILISTICDATAASSOCIATIONTOINCLUDE TRACKINITIATIONANDTERMINATION vINTH)2%%)NT#ONV$IG -ELBOURNE !USTRAILIA PPn 3"#OLEGROVE !7$AVIS AND*+!YLIFFE h4RACKINITIATIONANDNEARESTNEIGHBORSINCORPO RATEDINTOPROBABILISTICDATAASSOCIATION v*%LEC%LECTRON%NG!USTRALIA )%!USTAND)2%% !UST VOL PPn 9"AR 3HALOMAND4&ORTMANN 4RACKINGAND$ATA!SSOCIATION /RLANDO &,!CADEMIC0RESS 273ITTLER h!NOPTIMALASSOCIATIONPROBLEMINSURVEILLANCETHEORY v)%%%4RANS VOL-), PPn **3TEINAND33"LACKMAN h'ENERALIZEDCORRELATIONOFMULTI TARGETTRACKDATA v)%%%4RANS VOL!%3 PPn
!54/-!4)#$%4%#4)/. 42!#+).' !.$3%.3/2).4%'2!4)/.
Ç°xÇ
'64RUNKAND*$7ILSON h4RACKINITIATIONOFOCCASIONALLYUNRESOLVEDRADARTARGETS v)%%% 4RANS VOL!%3 PPn 7+OCH h/N"AYESIAN-(4FORWELLSEPARATEDTARGETSINDENSELYCLUTTEREDENVIRONMENT vIN 0ROC)%%%)NTERNATIONAL2ADAR#ONFERENCE PPn $*3ALMOND h-IXTUREREDUCTIONALGORITHMSFORTARGETTRACKINGINCLUTTER v30)% 3IGNALAND $ATA0ROCESSINGOF3MALL4ARGETS VOL PPn 2*0RENGAMAN 2%4HURBER AND7'"ATH h!RETROSPECTIVEDETECTIONALGORITHMFOREXTRAC TIONOFWEAKTARGETSINCLUTTERANDINTERFERENCEENVIRONMENTS vIN)%%%)NT2ADAR#ONF ,ONDON PPn .,EVINE h!NEWTECHNIQUEFORINCREASINGTHEFLEXIBILITYOFRECURSIVELEASTSQUARESSMOOTHING v "ELL3YSTEM4ECHNICAL*OURNAL PPn 7'"ATH -%"ALDWIN AND7$3TUCKEY h#ASCADEDSPATIALCORRELATIONPROCESSESFORDENSE CONTACTENVIRONMENTS vIN0ROC2!$!2 PPn 2*0RENGAMAN 2%4HURBER AND7'"ATH h!RETROSPECTIVEDETECTIONALGORITHMFOREXTRAC TIONOFWEAKTARGETSINCLUTTERANDINTERFERENCEENVIRONMENTS vIN)%%%)NT2ADAR#ONF ,ONDON PPn %2"ILLAM h0ARAMETEROPTIMISATIONINPHASEDARRAYRADAR vIN2ADAR "RIGHTON 5+ n /CTOBER PPn '64RUNK *$7ILSON AND0+(UGHES )) h0HASEDARRAYPARAMETEROPTIMIZATIONFORLOW ALTITUDETARGETS vIN)%%%)NTERNATIONAL2ADAR#ONFERENCE -AYPPn 7"ATH h4RADEOFFSINRADARNETWORKING vIN0ROC)%%2!$!2 PPn *2-OOREAND7$"LAIR h0RACTICALASPECTSOFMULTISENSORTRACKING vIN-ULTITARGET -ULTISENSOR 4RACKING!PPLICATIONSAND!DVANCES 6OL))) "OSTON!RTECH(OUSE */#OLEMAN h$ISCRIMINANTSFORASSIGNINGPASSIVEBEARINGOBSERVATIONSTORADARTARGETS vIN )%%%)NT2ADAR#ONF 7ASHINGTON $# PPn '64RUNKAND*$7ILSON h!SSOCIATIONOF$&BEARINGMEASUREMENTSWITHRADARTRACKS v)%%% 4RANS VOL!%3 PPn '64RUNKAND*$7ILSON h#ORRELATIONOF$&BEARINGMEASUREMENTSWITHRADARTRACKS vIN )%%%)NT2ADAR#ONF ,ONDON PPn
#HAPTER
*ÕÃiÊ «ÀiÃÃÊ,>`>À V
>iÊ,°Ê ÕVvvÊ ÞÀÊ7°Ê/iÌi ,OCKHEED-ARTIN-3
n°£Ê /," 1 /"
!PULSECOMPRESSIONRADARTRANSMITSALONGPULSEWITHPULSEWIDTH4ANDPEAKPOWER 0T WHICH IS CODED USING FREQUENCY OR PHASE MODULATION TO ACHIEVE A BANDWIDTH "THATISLARGECOMPAREDTOTHATOFANUNCODEDPULSEWITHTHESAMEDURATION4HE TRANSMIT PULSEWIDTH IS CHOSEN TO ACHIEVE THE SINGLE PULSE TRANSMIT ENERGY GIVEN BY %T 0T4 THAT IS REQUIRED FOR TARGET DETECTION OR TRACKING4HE RECEIVED ECHO ISPROCESSEDUSINGAPULSECOMPRESSIONFILTERTOYIELDANARROWCOMPRESSEDPULSE RESPONSEWITHAMAINLOBEWIDTHOFAPPROXIMATELY"THATDOESNOTDEPENDONTHE DURATIONOFTHETRANSMITTEDPULSE &IGURESHOWSABLOCKDIAGRAMOFABASICPULSECOMPRESSIONRADAR4HECODED PULSEISGENERATEDATALOWPOWERLEVELINTHEWAVEFORMGENERATORANDAMPLIFIEDTOTHE REQUIREDPEAKTRANSMITPOWERUSINGAPOWERAMPLIFIERTRANSMITTER4HERECEIVEDSIGNAL ISMIXEDTOANINTERMEDIATEFREQUENCY)& ANDAMPLIFIEDBYTHE)&LIFIER4HESIG NALISTHENPROCESSEDUSINGAPULSECOMPRESSIONFILTERTHATCONSISTSOFAMATCHEDFILTER TOACHIEVEMAXIMUMSIGNAL TO NOISERATIO3.2 !SDISCUSSEDBELOW THEMATCHED FILTERISFOLLOWEDBYAWEIGHTINGFILTERIFREQUIREDFORREDUCTIONOFTIMESIDELOBES4HE OUTPUTOFTHEPULSECOMPRESSIONFILTERISAPPLIEDTOANENVELOPEDETECTOR AMPLIFIEDBY THEVIDEOAMPLIFIER ANDDISPLAYEDTOANOPERATOR 4HE RATIO OF THE TRANSMIT PULSEWIDTH TO THE COMPRESSED PULSE MAINLOBE WIDTH IS DEFINEDASTHEPULSECOMPRESSIONRATIO4HEPULSECOMPRESSIONRATIOISAPPROXIMATELY 4" OR4" WHERE4"ISDEFINEDASTHETIME BANDWIDTHPRODUCTOFTHEWAVEFORM 4YPICALLY THEPULSECOMPRESSIONRATIOANDTIME BANDWIDTHPRODUCTARELARGECOMPARED TOUNITY 4HE USE OF PULSE COMPRESSION PROVIDES SEVERAL PERFORMANCE ADVANTAGES 4HE INCREASEDDETECTIONRANGECAPABILITYOFALONG PULSERADARSYSTEMISACHIEVEDWITH PULSE COMPRESSION WHILE RETAINING THE RANGE RESOLUTION CAPABILITY OF A RADAR THAT USESANARROWUNCODEDPULSE4HEREQUIREDTRANSMITTEDENERGYCANBEESTABLISHEDBY
4HE AUTHORS WOULD LIKE TO ACKNOWLEDGE THE USE OF MATERIAL PREVIOUSLY PREPARED BY %DWARD # &ARNETT AND 'EORGE(3TEVENSFORTHEh0ULSE#OMPRESSION2ADARvCHAPTERINTHESECONDEDITIONOFTHE2ADAR(ANDBOOK EDITEDBY-ERRILL)3KOLNIK
n°£
n°Ó
2!$!2(!.$"//+
!
"# !
"
&)'52% "LOCKDIAGRAMOFABASICPULSECOMPRESSIONRADAR
INCREASINGTHEWAVEFORMPULSEWIDTHWITHOUTEXCEEDINGCONSTRAINTSONTRANSMITTERPEAK POWER4HEAVERAGEPOWEROFTHERADARMAYBEINCREASEDWITHOUTINCREASINGTHEPULSE REPETITIONFREQUENCY02& AND HENCE DECREASINGTHERADARSUNAMBIGUOUSRANGE)N ADDITION THERADARISLESSVULNERABLETOINTERFERINGSIGNALSTHATDIFFERFROMTHECODED TRANSMITTEDSIGNAL 4HEMAINLOBEOFTHECOMPRESSEDPULSEATTHEOUTPUTOFTHEMATCHEDFILTERHASTIME ORRANGE SIDELOBESTHATOCCURWITHINTIMEINTERVALSOFDURATION4 BEFOREANDAFTERTHE PEAK OF THE PEAK OF THE COMPRESSED PULSE4HE TIME SIDELOBES CAN CONCEAL TARGETS WHICHWOULDOTHERWISEBERESOLVEDUSINGANARROWUNCODEDPULSE)NSOMECASES SUCH ASPHASE CODEDWAVEFORMSORNONLINEARFREQUENCYMODULATIONWAVEFORMS MATCHED FILTERPROCESSINGALONEACHIEVESACCEPTABLETIMESIDELOBELEVELS(OWEVER FORTHECASE OFALINEARFREQUENCYMODULATIONWAVEFORM THEMATCHEDFILTERISGENERALLYFOLLOWED BYAWEIGHTINGFILTERTOPROVIDEAREDUCTIONINTIMESIDELOBELEVELS)NTHISCASE THE WEIGHTINGFILTERRESULTSINASIGNAL TO NOISERATIOLOSSCOMPAREDTOTHATOFMATCHEDFILTER PROCESSINGALONE
n°ÓÊ *1 - Ê " *, --" Ê76 ", Ê/9* 4HEFOLLOWINGSECTIONSDESCRIBETHECHARACTERISTICSOFTHELINEARANDNONLINEARFRE QUENCYMODULATIONWAVEFORMS PHASE CODEDWAVEFORMS ANDTIME FREQUENCYCODED WAVEFORMS4HEAPPLICATIONOFSURFACEACOUSTICWAVE3!7 DEVICESFORLINEARFRE QUENCY MODULATION ,&- WAVEFORM PULSE COMPRESSION IS DISCUSSED7AVEFORM SIGNAL ANALYSIS TECHNIQUES MATCHED FILTER PROPERTIES AND THE WAVEFORM AUTOCOR RELATIONANDAMBIGUITYFUNCTIONDEFINITIONSUSEDARESUMMARIZEDINTHE!PPENDIX ATTHEENDOFTHISCHAPTER
05,3%#/-02%33)/.2!$!2
n°Î
,INEAR &REQUENCY -ODULATION 4HE LINEAR FREQUENCY MODULATION OR CHIRP WAVEFORM HAS A RECTANGULAR AMPLITUDE MODULATION WITH PULSEWIDTH 4 AND A LINEAR FREQUENCY MODULATION WITH A SWEPT BANDWIDTH " APPLIED OVER THE PULSE4HE TIME BANDWIDTHPRODUCTOFTHE,&-WAVEFORMISEQUALTO4" WHERE4"ISTHEPRODUCTOF PULSEWIDTHANDSWEPTBANDWIDTH4HE D"WIDTHOFTHECOMPRESSEDPULSEATTHEOUT PUTOFTHEMATCHEDFILTERISS " FORLARGEVALUESOFTIME BANDWIDTHPRODUCT 4HEPEAKTIMESIDELOBELEVELOFTHECOMPRESSEDPULSEISnD" !S DISCUSSED IN 3ECTION A FREQUENCY DOMAIN WEIGHTING FILTER IS GENERALLY REQUIREDFOLLOWINGTHEMATCHEDFILTERTOPROVIDEREDUCEDTIMESIDELOBELEVELS ATTHE COST OF REDUCED 3.2 AND AN INCREASE IN THE WIDTH OF THE COMPRESSED PULSE!S AN EXAMPLE THEUSEOF D"4AYLORWEIGHTINGREDUCESTHEPEAKTIMESIDELOBELEVELFROM nD"TOnD"ANDINTRODUCESAD"LOSSIN3.24HE D"WIDTHOFTHECOM PRESSEDPULSEWITHWEIGHTINGINCREASESFROMS "TOS " 4HE ,&- WAVEFORM HAS A KNIFE EDGE AMBIGUITY FUNCTION WITH CONTOURS THAT ARE APPROXIMATELYELLIPTICALWITHAMAJORAXISDEFINEDBYTHELINEV @S WHERE@ o"4 ISTHE,&-SLOPE4HISPROPERTYINTRODUCESRANGE DOPPLERCOUPLINGATTHEMATCHEDFILTER OUTPUTCAUSINGTHEMATCHEDFILTEROUTPUTPEAKTOOCCUREARLIERINTIMEFORATARGETWITHA POSITIVEDOPPLERFREQUENCYCOMPAREDTOASTATIONARYTARGETATTHESAMERANGE ASSUMING APOSITIVELINEARFREQUENCYMODULATIONSLOPEANDLATERINTIMEFORANEGATIVESLOPE 4HECOMPRESSEDPULSESHAPEAND3.2ARETOLERANTTODOPPLERSHIFTFORTHE,&- WAVEFORM!SARESULT ITISNOTNECESSARYTOIMPLEMENTMULTIPLEMATCHEDFILTERSTO COVERTHERANGEOFEXPECTEDTARGETDOPPLERSHIFTS ,&-7AVEFORM$EFINITION 4HE,&-WAVEFORMISASINGLE PULSEBANDPASSSIGNAL DEFINEDAS
XT !RECTT4 COS;O FT O@T=
WHERE4ISTHEPULSEWIDTH FISTHECARRIERFREQUENCY @ISTHE,&-SLOPE ANDTHERECT FUNCTIONISDEFINEDAS
ª \ X \
RECTX « ¬ \ X \
4HE,&-SLOPEISGIVENBY@ o"4 WHERETHEPLUSSIGNAPPLIESFORAPOSITIVE ,&-SLOPETERMEDANUP CHIRP ANDTHEMINUSSIGNFORANEGATIVE,&-SLOPEADOWN CHIRP 4HEAMPLITUDEMODULATIONISAT !RECTT4 ANDTHEPHASEMODULATIONISA QUADRATICFUNCTIONOFTIME
ET O@T
4HEFREQUENCYMODULATION DEFINEDASTHEINSTANTANEOUSFREQUENCYDEVIATIONFROM THECARRIERFREQUENCYF ISEXPRESSEDINTERMSOFTHEPHASEMODULATIONBY
FI T
DF
P DT
4HEFREQUENCYMODULATIONFORAN,&-WAVEFORMISLINEARWITHSLOPEEQUALTO@
FI T A T o " 4 T \ T \ a 4
n°{
2!$!2(!.$"//+
WHERETHEPLUSSIGNAPPLIESFORAPOSITIVE,&-SLOPEANDTHEMINUSSIGNFORANEGATIVE SLOPE 4HE COMPLEX ENVELOPE OF THE ,&- WAVEFORM IS EXPRESSED IN TERMS OF THE AMPLITUDEANDPHASEMODULATIONFUNCTIONSAS
UT !RECTT4 EJO@T
&IGURESHOWSANEXAMPLEOFAN,&-BANDPASSSIGNALWITHAPULSEWIDTH4 §S SWEPTBANDWIDTH" -(ZANDTIME BANDWIDTHPRODUCTEQUALTO4" 4HE,&- SLOPEIS"4 -(Z§S4HEINSTANTANEOUSFREQUENCYOFTHE,&-WAVEFORMVARIES BETWEENAND-(ZOVERTHEPULSEDURATION ASINDICATEDBYTHEREDUCTIONINTHE SPACINGOFSUCCESSIVEPOSITIVE GOINGZEROCROSSINGSOFTHESIGNALo ,&-7AVEFORM3PECTRUM 4HESPECTRUMOFTHE,&-WAVEFORMHASASIGNIFI CANTAMPLITUDEVARIATIONVERSUSFREQUENCYFORSMALLTIME BANDWIDTHPRODUCTS&ORLARGE VALUESOFTIME BANDWIDTHPRODUCT THEMAGNITUDEOFTHESPECTRUMAPPROACHESRECTF" UT
RECTT 4 E JPA T 4
\ 5 F \ y RECT F " FOR 4" 4HE,&-SPECTRUMISEXPRESSEDINTERMSOFTHECOMPLEX&RESNELINTEGRAL ANDTHE AMPLITUDEVARIATIONPRESENTFORLOWVALUESOF4"ISTERMEDTHE&RESNELRIPPLE ,&-7AVEFORM!MBIGUITY&UNCTION 4HEWAVEFORMAUTOCORRELATIONFUNCTIONAND AMBIGUITYFUNCTIONFORAN,&-WAVEFORMAREGIVENBY
C U T FD ; \ T 4 \= SINC; FD AT 4 \ T 4 \ = REECT T 4 E JP FDT
9U T FD ; \ T 4 \= SINC ; FD AT 4 \ T 4 \ = RECTT 4
WHERETHESINCFUNCTIONISDEFINEDAS
SINCX SINOX OX
4HEMATCHEDFILTERTIMERESPONSEFORATARGETWITHDOPPLERSHIFTFDISOBTAINEDBYTHE SUBSTITUTIONT nTINTHEAUTOCORRELATIONFUNCTION
YT C U T FD ; \ T 4 \= SINC; FD A T 4 \ T 4 \ = RECTT 4 E JP FD T
,&-2ANGE DOPPLER#OUPLING 4HE,&-WAVEFORMEXHIBITSRANGE DOPPLERCOU PLINGWHICHCAUSESTHEPEAKOFTHECOMPRESSEDPULSETOSHIFTINTIMEBYANAMOUNT PROPORTIONALTOTHEDOPPLERFREQUENCY4HEPEAKOCCURSEARLIERINTIMEATT nFD4"FOR APOSITIVE,&-SLOPE COMPAREDTOPEAKRESPONSEFORASTATIONARYTARGET4HEPEAKOF THEAMBIGUITYFUNCTIONISSHIFTEDTOS FD4"FORAPOSITIVE,&-SLOPE 4IME$ELAYAND2ANGE2ESOLUTION7IDTHS 4HETIME DELAYRESOLUTIONWIDTHISEQUAL TOTHEWIDTHOFTHEAMBIGUITYFUNCTIONATASPECIFIEDLEVELRELATIVETOTHEPEAKVALUE o,OWVALUESOFCARRIERFREQUENCYANDTIME BANDWIDTHPRODUCTHAVEBEENUSEDTOILLUSTRATETHEVARIATIONOFINSTANTA NEOUSFREQUENCYOVERTHEPULSEIN&IGURE
05,3%#/-02%33)/.2!$!2
n°x
&)'52% ,&-BANDPASSSIGNALEXAMPLESHOWNFOR4 §S " -(Z F -(Z
&ORTHECASEOFALARGETIME BANDWIDTH THEMAGNITUDEOFTHEAUTOCORRELATIONFUNCTION MEASUREDALONGTHERELATIVETIMEDELAYAXISISGIVENBY
\ C U T \ y \SINC"T \ \T \ 4
4HEX D"TIMEDELAYRESOLUTIONISMEASUREDBETWEENTHEVALUESOFTFORWHICH
LOG\SINC"S \ XD"
4HE RANGE RESOLUTION IS EQUAL TO C TIMES THE CORRESPONDING TIME DELAY RESOLUTION WHERECISTHESPEEDOFLIGHT4ABLECONTAINSASUMMARYOFTHERESOLUTIONWIDTHS FORTHE,&-WAVEFORM ,&-7AVEFORM%XAMPLES &IGURESHOWSTHEMAGNITUDEOFTHEAUTOCORRELA TIONFUNCTIONASAFUNCTIONOFRELATIVETIMEDELAYTFORDOPPLERSHIFTSpOFn-(Z AND-(Z PULSEWIDTH4 §S SWEPTBANDWIDTH" -(Z AND,&-SLOPE @ "4 -(Z§S!DOPPLERSHIFTOFFD " -(ZCAUSESTHEPEAKOFTHE CORRELATIONFUNCTIONTOMOVETOS FD4" §S&IGURESHOWSTHERESULTWHEN THEPULSEWIDTHISINCREASEDTO§STOYIELDAWAVEFORMWITHAN,&-SLOPEEQUAL 4!",% ,&-7AVEFORM4IME$ELAYAND2ANGE2ESOLUTION7IDTHS
-AINLOBE7IDTH D" D" D" D"
4IME$ELAY2ESOLUTIONS S " S " S " S "
2ANGE2ESOLUTIONM $2 C" $2 C" $2 C" $2 C"
p4HESEVALUESOFDOPPLERSHIFTARELARGEFORMICROWAVERADARSANDWERESELECTEDTOSHOWTHEEFFECTOFRANGE DOPPLER COUPLING
n°È
2!$!2(!.$"//+
&)'52% ,&- WAVEFORM AUTOCORRELATION FUNCTION 4 §S " -(Z 4"
TO-(Z§S)NTHISCASE ADOPPLERSHIFTOF-(ZSHIFTSTHEPEAKOFAUTOCOR RELATIONFUNCTIONTOS §S ANINCREASEOFAFACTOROFTENCOMPAREDTOTHERESULT FORA §SPULSEWIDTH
&)'52% ,&- WAVEFORM AUTOCORRELATION FUNCTION 4 §S " -(Z 4"
05,3%#/-02%33)/.2!$!2
n°Ç
&REQUENCY $OMAIN7EIGHTING FOR ,&- 4IME 3IDELOBE 2EDUCTION ! FREQUENCY DOMAINWEIGHTINGFILTERISUSEDFOLLOWINGTHEMATCHEDFILTERFORTIMESIDELOBEREDUCTION 4AYLORWEIGHTINGPROVIDESAREALIZABLEAPPROXIMATIONTOTHEIDEAL$OLPH #HEBYSHEV WEIGHTING WHICHACHIEVESTHEMINIMUMMAINLOBEWIDTHFORAGIVENVALUEOFPEAK TIMESIDELOBELEVEL4HEFREQUENCYRESPONSEOFTHEEQUIVALENTLOWPASSFILTERFORTHE 4AYLORWEIGHINGFILTERIS
N ¤ MF ³ 7 F £ &M COS ¥ P ´ "µ ¦ M
WHERE&MISTHE4AYLORCOEFFICIENTANDN ISTHENUMBEROFTERMSINTHEWEIGHTINGFUNC TION4HECOMPRESSEDPULSERESPONSEATTHEOUTPUTOFTHEWEIGHTINGFILTERISGIVENBY N
YO T SINC"T £ &M ;SINC"T M SINC"T M =
M
!SDISCUSSEDBELOW THECOMPRESSEDPULSERESPONSE%Q ISBASEDONTHEASSUMP TIONTHATTHETIME BANDWIDTHPRODUCTOFTHE,&-WAVEFORMISMUCHGREATERTHANUNITY 4" 4HEFILTERMATCHINGLOSSFOR4AYLORWEIGHTINGISGIVENBY+LAUDERETALAS N
,M £ &M
M
&IGURE SHOWS A COMPARISON OF THE COMPRESSED PULSE RESPONSE FOR THREE FRE QUENCYDOMAINWEIGHTINGTYPES#URVE!ISFORUNIFORMWEIGHTINGWHERE7F
&)'52% #OMPARISON OF COMPRESSED PULSE SHAPES FOR THREE FREQUENCY DOMAIN WEIGHTINGFUNCTIONS
n°n
2!$!2(!.$"//+
MATCHEDFILTERPROCESSING #URVE#ISFOR4AYLORWEIGHTINGWITHnD"PEAKTIME SIDELOBELEVELN AND#URVE"ISFOR(AMMINGWEIGHTINGWHERE ¤ MF ³ 7 F & COS ¥ P ´ "µ ¦
&
4HE4AYLORCOEFFICIENTSFORn D"4AYLORWEIGHTINGN ARELISTEDHERE
& & & & &
4ABLE SHOWS THE PEAK TIME SIDELOBE LEVEL D" AND D" COMPRESSED PULSE WIDTHS ANDFILTERMATCHINGLOSSFORTHETHREEWEIGHTINGFUNCTIONTYPES4HEAPPLICATION OFn D"4AYLORWEIGHTINGREDUCESTHEPEAKTIMESIDELOBELEVELFROMnD"TO nD"ANDINCREASESTHEFILTERMATCHINGLOSSFROMD"TOD"4HE D"COM PRESSED PULSEMAINLOBEWIDTHINCREASESFROM"TO"WHENn D"4AYLOR WEIGHTINGISUSED4HE D"AND D"MAINLOBEWIDTHSANDFILTERMATCHINGLOSSFOR (AMMINGWEIGHTINGAREAPPROXIMATELYTHESAMEASFORn D"4AYLORWEIGHTING 4HESE RESULTS ASSUME THAT THE TIME BANDWIDTH PRODUCT OF THE ,&- WAVEFORM IS MUCHGREATERTHANUNITYSOTHATTHETIMESIDELOBEPERFORMANCEISNOTLIMITEDBYTHE &RESNELAMPLITUDERIPPLEINTHESPECTRUMOFTHE,&-WAVEFORM#OOKAND0AOLILLO AND#OOKAND"ERNFELDHAVEANALYZEDTHEEFFECTOFTHE&RESNELAMPLITUDERIPPLEAND PULSERISE TIMEANDFALL TIMEONTIMESIDELOBELEVELS!PHASEPREDISTORTIONTECHNIQUE IS DESCRIBED BY #OOK AND 0AOLILLO WHICH REDUCES THE &RESNEL AMPLITUDE RIPPLE TO ALLOW LOW TIME SIDELOBES TO BE ACHIEVED FOR ,&- WAVEFORMS WITH RELATIVELY SMALL TIME BANDWIDTHPRODUCTS 2ADAREQUIPMENTDISTORTIONSOURCESALSOESTABLISHLIMITATIONSONACHIEVABLETIME SIDELOBE LEVELS AND ARE DISCUSSED BY +LAUDER ET AL AND #OOK AND "ERNFELD 4HE METHODOFPAIRED ECHOANALYSISISUSEDTOEVALUATETHEEFFECTOFAMPLITUDEANDPHASE DISTORTION ON THE TIME SIDELOBE LEVELS &REQUENCY DOMAIN AMPLITUDE AND PHASE DIS TORTIONISTYPICALLYCAUSEDBYFILTERSANDTRANSMISSIONLINEREFLECTIONS4IMEDOMAIN AMPLITUDEANDPHASEDISTORTION TERMEDMODULATIONDISTORTIONBY#OOKAND"ERNFELD CANRESULTFROMPOWERSUPPLYRIPPLEINHIGH POWERTRANSMITTERAMPLIFIERS
4!",% #OMPARISONOF,&-7EIGHTING&ILTERS
7EIGHTING &UNCTION
0EAK4IME3IDELOBE ,EVELD"
D"-AINLOBE 7IDTH S
D"-AINLOBE 7IDTH S
&ILTER-ATCHING ,OSSD"
5NIFORM 4AYLOR D" N (AMMING
" "
" "
"
"
05,3%#/-02%33)/.2!$!2
n°
4AYLOR 6ERSUS #OSINE 3QUARED 0LUS 0EDESTAL 7EIGHTING &IGURE A PLOTS THE TAPER COEFFICIENT & AND PEDESTAL HEIGHT ( VERSUS THE PEAK TIME SIDELOBE LEVEL FOR COSINE SQUARED PLUS PEDESTALWEIGHTING&ORAGIVENPEAKTIMESIDELOBELEVEL 4AYLOR WEIGHTINGOFFERSTHEORETICALADVANTAGESINRANGERESOLUTIONAND3.2PERFORMANCE AS ILLUSTRATEDIN&IGUREBAND&IGUREC
&)'52% A 4APERCOEFFICIENTANDPEDESTALHEIGHTVERSUSPEAKTIMESIDELOBE LEVEL B #OMPRESSED PULSE WIDTH VERSUS PEAK TIME SIDELOBE LEVEL C 3.2 LOSS VERSUSPEAKTIMESIDELOBELEVEL
n°£ä
2!$!2(!.$"//+
3!7 $EVICES FOR ,&- 0ULSE #OMPRESSION ! 3URFACE !COUSTIC 7AVE 3!7 DEVICECONSISTSOFANINPUTTRANSDUCERANDANOUTPUTTRANSDUCERMOUNTEDONAPIEZO ELECTRICSUBSTRATE4HESETRANSDUCERSAREUSUALLYIMPLEMENTEDASINTERDIGITALDEVICES THATCONSISTOFAMETALFILMDEPOSITEDONTHESURFACEOFTHEACOUSTICMEDIUM4HISMETAL FILMISMADEOFFINGERSSEE&IGURE THATDICTATETHEFREQUENCYCHARACTERISTICOFTHE UNIT4HEINPUTTRANSDUCERCONVERTSANELECTRICALSIGNALINTOASOUNDWAVEWITHOVER OFTHEENERGYTRAVELINGALONGTHESURFACEOFTHEMEDIUM4HEOUTPUTTRANSDUCER TAPSAPORTIONOFTHISSURFACESOUNDWAVEANDCONVERTSITBACKINTOANELECTRICSIGNAL 4HE3!7DEVICE HASUNIQUEFEATURESTHATDICTATEITSUSEFULNESSFORAGIVENRADAR APPLICATION)TREPRESENTSONEOFTHEFEWANALOGPROCESSINGDEVICESUSEDINMODERN RADAR4HEADVANTAGESOFTHE3!7DEVICEAREITSCOMPACTSIZE THEWIDEBANDWIDTHS THATCANBEATTAINED THEABILITYTOTAILORTHETRANSDUCERSTOAPARTICULARWAVEFORM THE ALL RANGECOVERAGEOFTHEDEVICE ANDTHELOWCOSTOFREPRODUCINGAGIVENDESIGN4HE MAJORSHORTCOMINGSOFTHE3!7APPROACHARETHATTHEWAVEFORMLENGTHISRESTRICTED 3INCESOUNDTRAVELSABOUTTOMM§SONTHESURFACEOFA3!7DEVICE AMM QUARTZ DEVICE ABOUT THE LARGEST AVAILABLE HAS A USABLE DELAY OF ABOUT §S FOR A SINGLEPASS!LSO BECAUSEEACH3!7DEVICEISWAVEFORMSPECIFIC EACHWAVEFORM REQUIRESADIFFERENTDESIGN 3!7PULSECOMPRESSIONDEVICESDEPENDONTHEINTERDIGITALTRANSDUCERFINGERLOCA TIONSORTHESURFACE ETCHEDGRATINGTODETERMINEITSBANDPASSCHARACTERISTICS&IGURE SHOWSTHREETYPESOFFILTERDETERMINATIONAPPROACHES!WIDEBANDINPUTTRANSDUCERAND AFREQUENCY SELECTIVEDISPERSIVE OUTPUTTRANSDUCERAREUSEDIN&IGUREA7HENAN IMPULSEISAPPLIEDTOTHEINPUT THEOUTPUTSIGNALISINITIALLYALOWFREQUENCYTHATINCREASES BASEDONTHEOUTPUTTRANSDUCERFINGERSPACINGS ATLATERPORTIONSOFTHEPULSE4HISRESULTS
&)'52% 3!7 TRANSDUCER TYPES A DISPERSIVE OUTPUT B BOTH INPUT AND OUTPUT DISPERSIVE AND C DISPERSIVEREFLECTIONS
05,3%#/-02%33)/.2!$!2
n°££
INANUP CHIRPWAVEFORMTHATWOULDBEAMATCHEDFILTERFORADOWN CHIRPTRANSMITTED WAVEFORM)N&IGUREBBOTHTHEINPUTTRANSDUCERANDTHEOUTPUTTRANSDUCERAREDIS PERSIVE WHICHWOULDRESULTINTHESAMEIMPULSERESPONSEASTHATSHOWNIN&IGUREA &ORAGIVENCRYSTALLENGTHANDMATERIAL THEWAVEFORMDURATIONFORTHEAPPROACHESIN &IGUREAAND&IGUREBWOULDBETHESAMEANDISLIMITEDTOTHETIMETHATITTAKES ANACOUSTICWAVETOTRAVERSETHECRYSTALLENGTH&IGURECSHOWSAREFLECTION ARRAY COMPRESSION2!# APPROACHTHATESSENTIALLYDOUBLESTHEACHIEVABLEPULSELENGTHFOR THESAMECRYSTALLENGTH)NAN2!# THEINPUTANDOUTPUTTRANSDUCERSHAVEABROADBAND WIDTH!FREQUENCY SENSITIVEGRATINGISETCHEDONTHECRYSTALSURFACETOREFLECTAPORTION OFTHESURFACE WAVESIGNALTOTHEOUTPUTTRANSDUCER4HISGRATINGCOUPLINGDOESNOTHAVEA SIGNIFICANTIMPACTONTHESURFACE WAVEENERGY%XCEPTFORAINCREASEINTHEWAVEFORM DURATION THEIMPULSERESPONSEOFTHE2!#ISTHESAMEASFORTHEAPPROACHESSHOWNIN &IGUREAANDB4HUS THESETHREEAPPROACHESYIELDASIMILARIMPULSERESPONSE &IGURE SHOWS A SKETCH OF A 3!7 PULSE COMPRESSION DEVICE WITH DISPERSIVE INPUTANDOUTPUTTRANSDUCERS!STHEENERGYINA3!7DEVICEISCONCENTRATEDINITSSUR FACEWAVE THE3!7APPROACHISMUCHMOREEFFICIENTTHANBULK WAVEDEVICES WHERE THEWAVETRAVELSTHROUGHTHECRYSTAL4HEPROPAGATIONVELOCITYOFTHESURFACEWAVEIS INTHERANGEOFTOMS DEPENDINGONTHECRYSTALMATERIAL ANDALLOWSALARGE DELAYINACOMPACTDEVICE!COUSTICABSORBERMATERIALISREQUIREDATTHECRYSTALEDGES TO REDUCE THE REFLECTIONS AND HENCE THE SPURIOUS RESPONSES 4HE UPPER FREQUENCY LIMITDEPENDSONTHEACCURACYTHATCANBEACHIEVEDINTHEFABRICATIONOFTHEINTERDIGITAL TRANSDUCER4HE 3!7 DEVICE MUST PROVIDE A RESPONSE THAT IS CENTERED ON A CARRIER ASTHELOWESTFREQUENCYOFOPERATIONISABOUT-(ZANDISLIMITEDBYTHECRYSTAL ! MATCHED FILTER 3!7 PULSE COMPRESSION DEVICE CAN USE VARIABLE FINGER LENGTHS TO ACHIEVEFREQUENCYWEIGHTING ANDTHISINTERNALWEIGHTINGCANCORRECTFORTHE&RESNEL AMPLITUDERIPPLESINTHE&-SPECTRUM7ITHTHISCORRECTION nD"TIMESIDELOBE LEVELSCANBEACHIEVEDFORALINEAR &-WAVEFORMWITH4"ASLOWAS4HELEVELOF SIDELOBESUPPRESSIONDEPENDSUPONTHETIMEBANDWIDTHPRODUCT THEWEIGHTINGFUNC TIONAPPLIED ANDFABRICATIONERRORSINTHE3!7DEVICE4IMESIDELOBELEVELSOFnD" HAVEBEENACHIEVEDFOR4"BETWEENAND4"PRODUCTSOFUPTOHAVEBEEN ACHIEVEDWITHTIMESIDELOBESBETTERTHANnD"$YNAMICRANGEISLIMITEDBYNON LINEARITIESINTHECRYSTALMATERIAL BUTDYNAMICRANGESOVERD"HAVEBEENACHIEVED 4HEMOSTCOMMON3!7MATERIALSAREQUARTZ LITHIUMNIOBATE ANDLITHIUMTANTALITE
&)'52% 3URFACE WAVEDELAYLINE
n°£Ó
2!$!2(!.$"//+
.ONLINEAR &REQUENCY -ODULATION 7AVEFORMS 4HE NONLINEAR &- WAVE FORMHASSEVERALDISTINCTADVANTAGESOVER,&- )TREQUIRESNOFREQUENCYDOMAIN WEIGHTINGFORTIMESIDELOBEREDUCTIONBECAUSETHE&-MODULATIONOFTHEWAVEFORMIS DESIGNEDTOPROVIDETHEDESIREDSPECTRUMSHAPETHATYIELDSTHEREQUIREDTIMESIDELOBE LEVEL 4HIS SHAPING IS ACCOMPLISHED BY INCREASING THE RATE OF CHANGE OF FREQUENCY MODULATIONNEARTHEENDSOFTHEPULSEANDDECREASINGITNEARTHECENTER4HISSERVES TOTAPERTHEWAVEFORMSPECTRUMSOTHATTHEMATCHEDFILTERRESPONSEHASREDUCEDTIME SIDELOBES4HUS THELOSSINSIGNAL TO NOISERATIOASSOCIATEDWITHFREQUENCYDOMAIN WEIGHTINGASFORTHE,&-WAVEFORM ISELIMINATED )FASYMMETRICAL&-MODULATIONISUSED&IGUREA WITHTIME DOMAINAMPLITUDE WEIGHTINGTOREDUCETHEFREQUENCYSIDELOBES THENONLINEAR &-WAVEFORMWILLHAVEA THUMBTACK LIKEAMBIGUITYFUNCTION&IGURE !SYMMETRICALWAVEFORMTYPICALLY HAS A FREQUENCY THAT INCREASES OR DECREASES WITH TIME DURING THE FIRST HALF OF THE PULSEANDDECREASESORINCREASES DURINGTHELASTHALFOFTHEPULSE!NONSYMMETRICAL WAVEFORM IS OBTAINED BY USING ONE HALF OF A SYMMETRICAL WAVEFORM &IGURE B (OWEVER THENONSYMMETRICALWAVEFORMRETAINSSOMEOFTHERANGE DOPPLERCOUPLING OFTHELINEAR &-WAVEFORM /NEOFTHEPRIMARYDISADVANTAGESOFTHENONLINEAR &-WAVEFORMISTHATITISLESS DOPPLERTOLERANTTHANTHE,&-)NTHEPRESENCEOFDOPPLERSHIFT THETIMESIDELOBES OF THE PULSE COMPRESSED .,&- TEND TO INCREASE COMPARED TO THOSE OF THE ,&- &IGURE SHOWNLATERINTHISSECTION AND4ABLEILLUSTRATETHISBEHAVIORFORATYPICAL .,&-PULSE 4HISCHARACTERISTICOFTHE.,&-WAVEFORMSOMETIMESNECESSITATESPROCESSINGUSING MULTIPLEMATCHEDFILTERSOFFSETINDOPPLERSHIFTTOACHIEVETHEREQUIREDTIMESIDELOBE LEVEL"ECAUSEOFTHEDOPPLERSENSITIVITYOFTHEAMBIGUITYFUNCTION THENONLINEARFRE QUENCYMODULATIONWAVEFORMISUSEFULINATRACKINGSYSTEMWHERERANGEANDDOPPLER FREQUENCYAREAPPROXIMATELYKNOWN ANDTHETARGETDOPPLERSHIFTCANBECOMPENSATEDIN THEMATCHEDFILTER4HENONSYMMETRICAL.,&-WAVEFORMISUSEDINTHE--2SYSTEM FOREXAMPLE WHICHDETECTSANDTRACKSORDNANCESUCHASMORTARS ARTILLERY ANDROCKETS 4O ACHIEVE A n D" 4AYLOR COMPRESSED PULSE RESPONSE FOR EXAMPLE THE FRE QUENCY VERSUS TIME FREQUENCY MODULATION FUNCTION OF A NONSYMMETRICAL .,&- WAVEFORMOFBANDWIDTH"IS
¤T P NT ³ F T " ¥ £ + N SIN 4 4 ´µ ¦ N
&)'52% 3YMMETRICALANDNONSYMMETRICALNONLINEAR &-WAVEFORMS
05,3%#/-02%33)/.2!$!2
n°£Î
&)'52% !MBIGUITYFUNCTIONOFAN,&-WAVEFORMCOMPAREDTOASYMMETRICAL.,&-WAVEFORM
WHERETHECOEFFICIENTSARE
+ + + + + + +
/THER .,&- WAVEFORMS THAT HAVE BEEN UTILIZED IN RADAR INCLUDE THE NONSYM METRICALSINE BASEDANDTANGENT BASEDWAVEFORMSe&ORTHESINE BASEDWAVEFORM THE RELATIONSHIPBETWEENTIMEANDFREQUENCYMODULATIONISGIVENAS
T F K SIN P F " 4 " P
FOR " a F a "
WHERE4ISTHEPULSEWIDTH "ISTHESWEPTBANDWIDTH ANDKISATIMESIDELOBELEVEL CONTROLFACTOR 4YPICALKVALUESAREAND WHICHYIELDTIMESIDELOBELEVELSOFnD"AND nD" RESPECTIVELY&IGUREISAPLOTOFPEAKTIMESIDELOBELEVELASAFUNCTIONOFTHE TIMESIDELOBECONTROLFACTORK FORVARIOUS4"PRODUCTS FORTHIS.,&-WAVEFORM e#OURTESYOF%DWIN-7ATERSCHOOT ,OCKHEED-ARTIN-ARITIMEAND3ENSOR3YSTEMS 3YRACUSE .9
n°£{
2!$!2(!.$"//+
&)'52% 0EAKTIMESIDELOBELEVELFORASINE BASED.,&-WAVEFORMAS A FUNCTION OF K FACTOR #OURTESY OF $R 0ETER ( 3TOCKMANN ,OCKHEED -ARTIN -ARITIMEAND3ENSOR3YSTEMS 3YRACUSE .9
4HEFREQUENCYMODULATION VERSUS TIMEFUNCTIONFORATANGENT BASEDWAVEFORMIS GIVENAS
F T " TAN B T 4 TAN B FOR 4 a T a 4
WHERE4ISTHEPULSEWIDTH "ISTHESWEPTBANDWIDTH ANDAISDEFINEDAS
B TAN A a A c
WHERE@ISATIMESIDELOBELEVELCONTROLFACTOR 7HEN @ IS ZERO THE TANGENT BASED .,&- WAVEFORM REDUCES TO AN ,&- WAVE FORM (OWEVER @ CANNOT BE MADE ARBITRARILY LARGE BECAUSE THE COMPRESSED PULSE TENDSTODISTORT#OLLINSAND!TKINSDISCUSSANEXTENSIONOFTHETANGENT BASED.,&- FORWHICHTHEFREQUENCYMODULATIONFUNCTIONISAWEIGHTEDSUMOFTANGENT BASEDAND LINEARFREQUENCYMODULATIONTERMS &IGURE SHOWS THE FREQUENCY MODULATION VERSUS TIME FUNCTIONS FOR A SINE BASED.,&-WAVEFORMWITHK ATANGENT BASED.,&-WAVEFORMWITH@ ANDAN,&-WAVEFORM 4HESENSITIVITYOFA.,&-WAVEFORMTODOPPLERSHIFTCANBESEENIN&IGURE WHICHSHOWSTHEMATCHEDFILTEROUTPUTFORASINE BASED.,&-WAVEFORMINTHEPRES ENCEOFDOPPLERSHIFT 4HEAMBIGUITYFUNCTIONOFA.,&-SINE BASEDWAVEFORMISSHOWNIN&IGURE )TCANBENOTEDTHATTHISAMBIGUITYFUNCTIONISMORETHUMBTACK LIKEINNATURETHANFOR AN,&-WAVEFORM INDICATINGTHATTHISWAVEFORMISMOREDOPPLERSENSITIVETHANTHE ,&-WAVEFORM 4ABLE PROVIDES A COMPARISON OF .,&- WAVEFORMS WITH WEIGHTED AND UNWEIGHTED ,&- FOR DIFFERENT VALUES OF THE TARGET RADIAL VELOCITY IN TERMS OF PEAK ANDAVERAGETIMESIDELOBELEVELSAND3.2LOSS4HE.,&-WAVEFORMSHOWSBETTER
05,3%#/-02%33)/.2!$!2
n°£x
&)'52% &REQUENCY MODULATION VERSUS TIME FOR SINE BASED .,&- TANGENT BASED .,&- AND,&-WAVEFORMS
PERFORMANCEINTERMSOF3.2LOSSANDPEAKTIMESIDELOBELEVEL43, THANTHE,&- WAVEFORM4HE43,LEVELDOESNOTDEGRADEAPPRECIABLYFORTHE,&-WAVEFORMFOR HIGHERRADIALVELOCITIES DEMONSTRATINGTHEHIGHERDOPPLERTOLERANCEOF,&-
&)'52% -ATCHED FILTER OUTPUT OF 3 BAND §S PULSEWIDTH -(Z BAND WIDTH.,&-SINE BASEDWAVEFORMWITHMSRADIALVELOCITY#OURTESYOF%DWIN- 7ATERSCHOOT ,OCKHEED-ARTIN-ARITIMEAND3ENSOR3YSTEMS 3YRACUSE .9
n°£È
2!$!2(!.$"//+
&)'52% !MBIGUITYFUNCTIONOFASINE BASEDSYMMETRICAL.,&-WAVEFORM
0HASE #ODED7AVEFORMS )NPHASE CODEDWAVEFORMS THEPULSEISSUBDIVIDED INTOANUMBEROFSUBPULSESEACHOFDURATIONC 4.WHERE4ISTHEPULSEWIDTHAND. ISTHENUMBEROFSUBPULSES0HASE CODEDWAVEFORMSARECHARACTERIZEDBYTHEPHASE MODULATIONAPPLIEDTOEACHSUBPULSE "INARY0HASE#ODES !PHASE CODEDWAVEFORMTHATEMPLOYSTWOPHASESIS CALLED BINARY OR BIPHASE CODING! BINARY PHASE CODED WAVEFORM IS CONSTANT INMAGNITUDEWITHTWOPHASEVALUES nORn4HEBINARYCODECONSISTSOFA SEQUENCEOFEITHERSANDSOR SAND S4HEPHASEOFTHESIGNALALTERNATES
4!",% #OMPARISONOF,INEAR&-AND.ONLINEAR&-7AVEFORM0ERFORMANCE
7EIGHTING ,&-UNWEIGHTED ,&-UNWEIGHTED ,&-WITHnD" 4AYLORWEIGHTING ,&-WITHnD" 4AYLORWEIGHTING 3INE BASED.,&- WITHK 3INE BASED.,&- WITHK
4ARGET2ADIAL 6ELOCITYMS
0EAK43,D"
!VERAGE 43,D"
&ILTER-ATCHING ,OSSD"
o
o
o
!N3 BANDRADARWITH §STRANSMITPULSEWIDTHAND -(ZBANDWIDTHWASUSEDINTHISCOMPARISON 4HEDOPPLERSHIFTEXPRESSEDIN(ZISFD K 6R 6RWHERE6RISTHERADIALVELOCITYEXPRESSEDIN MS6R FORANOUT BOUNDTARGET
!VERAGEOF43,POWERRATIO
05,3%#/-02%33)/.2!$!2
n°£Ç
BETWEEN n AND n IN ACCORDANCE WITHTHESEQUENCEOFELEMENTS SAND SOR SAND S INTHEPHASECODE ASSHOWNIN&IGURE"ECAUSETHE FREQUENCYISNOTUSUALLYAMULTIPLEOF THERECIPROCALOFTHESUBPULSEWIDTH THECODEDSIGNALISGENERALLYDISCON TINUOUS AT THE PHASE REVERSAL POINTS 4HIS DOES NOT IMPACT ITS TIME SIDE LOBES BUT DOES CAUSE SOME INCREASE &)'52% "INARYPHASE CODEDSIGNAL INTHESPECTRUMSIDELOBELEVELS 5PON RECEPTION THE COMPRESSED PULSE IS OBTAINED BY MATCHED FILTER PROCESSING 4HEWIDTHOFTHECOMPRESSEDPULSEATTHEHALF AMPLITUDEPOINTISNOMINALLYEQUALTO THESUBPULSEWIDTH4HERANGERESOLUTIONISHENCEPROPORTIONALTOTHETIMEDURATIONOF ONEELEMENTOFTHECODEONESUBPULSE 4HETIME BANDWIDTHPRODUCTANDPULSECOM PRESSIONRATIOAREEQUALTOTHENUMBEROFSUBPULSESINTHEWAVEFORMIE THENUMBER OFELEMENTSINTHECODE /PTIMAL"INARY#ODES /PTIMALBINARYCODESAREBINARYSEQUENCESWHOSEPEAK SIDELOBEOFTHEAPERIODICAUTOCORRELATIONFUNCTIONISTHEMINIMUMPOSSIBLEFORAGIVEN CODELENGTH#ODESWHOSEAUTOCORRELATIONFUNCTION ORZERO DOPPLERRESPONSE EXHIBIT LOWSIDELOBESAREDESIRABLEFORPULSECOMPRESSIONRADARS2ESPONSESDUETOMOVING TARGETSWILLDIFFERFROMTHEZERO DOPPLERRESPONSE)FTHEMATCHEDFILTERISBASEDONLY ONTHEZERO DOPPLERRESPONSE ANINCREASEINTHETIMESIDELOBESWILLRESULT5LTIMATELY IFTHEDOPPLERSHIFTBECOMESVERYLARGE THEMATCHEDFILTERRESPONSEWILLDEGRADE4HIS CANBEALLEVIATEDBYUTILIZINGABANKOFMATCHEDFILTERS COVERINGTHEEXPECTEDRANGEOF DOPPLERSHIFTS"ECAUSETHISISMORECOMPUTATIONALLYINTENSIVETHANASINGLEMATCHED FILTER OLDERRADARSYSTEMSTENDNOTTOEMPLOYBANKSOFFILTERS4HEINCREASEINCOMPU TATIONALCAPACITYOFMODERNRADARSYSTEMS HOWEVER CANMAKETHISMOREATTRACTIVE "ARKER#ODES !SPECIALCLASSOFBINARYCODESISTHE"ARKERCODES"ARKERCODES AREBINARYCODESWITHPEAKTIMESIDELOBELEVELSEQUALTOnLOG. WHERE.ISTHE LENGTHOFTHECODE4HEENERGYINTHESIDELOBEREGIONISMINIMUMANDUNIFORMLYDIS TRIBUTED4HE"ARKERCODEISTHEONLYUNIFORMPHASECODETHATREACHESTHISLEVEL !LLTHEKNOWNBINARY"ARKERCODESARELISTEDIN4ABLE/NLYBINARY"ARKERCODES OFLENGTHS ANDHAVEBEENFOUNDn ! PULSE COMPRESSION RADAR USING "ARKER CODES WOULD BE LIMITED TO A MAXIMUM TIME BANDWIDTH PRODUCT OF &IGURE SHOWS THE AUTOCORRELATION FUNCTION OF
4!",% +NOWN"INARY"ARKER#ODES
,ENGTH
#ODE
n°£n
2!$!2(!.$"//+
&)'52% 3UPERPOSITIONOFTHEAUTOCORRELATIONFUNCTIONSFORALL POSSIBLE BITCODESEQUENCESWITHTHE"ARKER#ODEHIGHLIGHTEDDARK SHOWNFORZERODOPPLERSHIFT
ALENGTH"ARKERCODEFORZERODOPPLERSHIFTSUPERIMPOSEDUPONALLPOSSIBLEAUTO CORRELATIONFUNCTIONSOF BITBINARYSEQUENCES)TCANBESEENTHATTHE"ARKERCODE PROVIDESTHELOWESTTIMESIDELOBELEVELSOFALLPOSSIBLECODES
!LLOMORPHIC&ORMS !BINARYCODEMAYBEREPRESENTEDINANYONEOFFOURALLO MORPHICFORMS ALLOFWHICHHAVETHESAMECORRELATIONCHARACTERISTICS4HESEFORMSARE THECODEITSELF THEINVERTEDCODETHECODEWRITTENINREVERSEORDER THECOMPLEMENTED CODESCHANGEDTOSANDSTOS ANDTHEINVERTEDCOMPLEMENTEDCODE&ORSYM METRICALCODES THECODEANDITSINVERSEAREIDENTICAL -AXIMAL ,ENGTH3EQUENCES -AXIMAL LENGTHSEQUENCESHAVEASTRUCTURESIMI LARTORANDOMSEQUENCESAND THEREFORE POSSESSDESIRABLEAUTOCORRELATIONFUNCTIONS 4HEY ARE OFTEN CALLED PSEUDORANDOM NOISE 02. SEQUENCES (ISTORICALLY THESE SEQUENCESWEREGENERATEDUSINGNSTAGESOFSHIFTREGISTERSWITHSELECTEDOUTPUTTAPS USED FOR FEEDBACK SEE &IGURE 7HEN THE FEEDBACK CONNECTIONS ARE PROPERLY CHOSEN THEOUTPUTISASEQUENCEOFMAXIMALLENGTH WHICHISTHEMAXIMUMLENGTH OFASEQUENCEOFSANDSTHATCANBEFORMEDBEFORETHESEQUENCEISREPEATED4HE LENGTHOFTHEMAXIMALSEQUENCEIS. N WHERENISTHENUMBEROFSTAGESINTHE SHIFT REGISTERGENERATOR 4HE FEEDBACK CONNECTIONS THAT PROVIDE THE MAXIMAL LENGTH SEQUENCES MAY BE DETERMINEDFROMASTUDYOFPRIMITIVEANDIRREDUCIBLEPOLYNOMIALS!NEXTENSIVELISTOF THESEPOLYNOMIALSISGIVENBY0ETERSONAND7ELDON !LTHOUGHMAXIMAL LENGTHSEQUENCESHAVESOMEDESIRABLEAUTOCORRELATIONCHAR ACTERISTICS AMAXIMUMLENGTHSEQUENCEDOESNOTGUARANTEELOWESTTIMESIDELOBES WHENCOMPAREDTOOTHERBINARYCODES!NEXAMPLEOFTHISISPROVIDEDFORA BIT SEQUENCE&IGUREAISAHISTOGRAMOFTHEPEAKTIMESIDELOBELEVELFORTHEAUTO CORRELATIONOFEVERYPOSSIBLECOMBINATIONOFA BITCODE&IGUREBISTHESAME BUTFORONLYMAXIMALLENGTHSEQUENCESOF LENGTHCODEASUBSETOF&IGUREA &IGUREASHOWSALOWESTTIMESIDELOBE LEVELOFnD"4HELOWESTSIDELOBEFOR THEMAXIMALLENGTHSEQUENCEISSEENFROM &IGUREBTOBEONLYnD" &)'52% 3HIFT REGISTERGENERATOR
05,3%#/-02%33)/.2!$!2
,$ )& (, % *
#+!- ) (, %/
n°£
"!$ ! #& - #*
"!$ ! #& - #*
##'&**!# !+* (, % *
!+.!$# % + (, % *
&)'52% (ISTOGRAM OF PEAK TIME SIDELOBE LEVELS FOR BIT SEQUENCES A ALL POSSIBLE BIT SEQUENCESANDB BITMAXIMALLENGTHSEQUENCES
-INIMUM0EAK3IDELOBE#ODES "INARYCODESTHATPROVIDEMINIMUMPEAKTIMESIDE LOBELEVELSBUTEXCEEDTHETIMESIDELOBELEVELSACHIEVEDBY"ARKERCODESnLOG. ARE TERMEDMINIMUMPEAKSIDELOBECODES4HESECODESAREUSUALLYFOUNDUSINGCOMPUTER SEARCHTECHNIQUES3KOLNIKAND,EVANONAND-OZESONPROVIDETHESECODESFORVARIOUS SEQUENCELENGTHS ALONGWITHTHERESULTINGTIMESIDELOBELEVELS #OMPLEMENTARY3EQUENCES #OMPLEMENTARYSEQUENCESCONSISTOFTWOSEQUENCES OFTHESAMELENGTH.WHOSEAPERIODICAUTOCORRELATIONFUNCTIONSHAVESIDELOBESEQUAL INMAGNITUDEBUTOPPOSITEINSIGN4HESUMOFTHETWOAUTOCORRELATIONFUNCTIONSHAS APEAKOF.ANDASIDELOBELEVELOF)NAPRACTICALAPPLICATION THETWOSEQUENCES MUSTBESEPARATEDINTIME FREQUENCY ORPOLARIZATION WHICHRESULTSINDECORRELATIONOF RADARRETURNSSOTHATCOMPLETESIDELOBECANCELLATIONMAYNOTOCCUR(ENCE THEYHAVE NOTBEENWIDELYUSEDINPULSECOMPRESSIONRADARS 0OLYPHASE#ODES 7AVEFORMSCONSISTINGOFMORETHANTWOPHASESMAYALSOBE USED0OLYPHASECODESCANBECONSIDEREDASCOMPLEXSEQUENCESWHOSEELEMENTSHAVE AMAGNITUDEOFONE BUTWITHVARIABLEPHASE4HEPHASESOFTHESUBPULSESALTERNATE AMONGMULTIPLEVALUESRATHERTHANJUSTTHEnANDnOFBINARYPHASECODES4HESE CODESTENDTOBEDISCRETEAPPROXIMATIONSTO,&-WAVEFORMS ANDHENCEPOSSESSSIMI LARAMBIGUITYFUNCTIONSANDDOPPLERSHIFTCHARACTERISTICS4HEAUTOCORRELATIONFUNCTIONS ARESIMILAR WITHAPEAKTOSIDELOBERATIOOFABOUT . &RANK#ODES 4HE&RANKCODECORRESPONDSTOASTEPPED PHASEAPPROXIMATIONOF AN,&-WAVEFORM(ERE THEPULSEISBROKENUPINTO-GROUPS EACHOFWHICHIS FURTHERBROKENUPINTO-SUBPULSES(ENCE THETOTALLENGTHOFTHE&RANKCODE IS- WITHACORRESPONDINGCOMPRESSIONRATIOOF-4HE&RANKPOLYPHASECODESDERIVETHE SEQUENCEOFPHASESFORTHESUBPULSESBYUSINGAMATRIXTECHNIQUEASFOLLOWS
§ ¨ ¨ ¨ " " ¨" ¨ - - ©
! ¶ ! - · · ! - · " " · ! - ·¸
n°Óä
2!$!2(!.$"//+
4HEMATRIXELEMENTSREPRESENTTHEMULTIPLYINGCOEFFICIENTSOFABASICPHASESHIFT O- WHERE-ISANINTEGER4HEPHASESHIFTCORRESPONDINGTOTHEELEMENTM NOFTHE MATRIXCANBEWRITTENAS
FM N
P M N M - N - -
!NEXAMPLEOFA&RANK#ODEMATRIXFOR- ISGIVENHERE
§ P ¨ ¨ ¨ ©¨
¶ § · P ¨ · ¨ · ¨ ·¸ ¨©
¶ ¶ § C C ¨ · C· · · ¨ · ¨ C C · ¸· ¨© C C C ·¸
#ONCATENATINGTHEROWSOFTHISMATRIXYIELDSTHEPHASEFOREACHOFTHESUBPULSES &IGURESHOWSTHEPHASEMODULATIONCHARACTERISTICOFTHE&RANK#ODEFORTHEABOVE EXAMPLE .OTE HOW THE PHASE STEP BETWEEN SUBPULSES INCREASES BETWEEN SUBPULSE GROUPSWITHALENGTHEQUALTOFOUR4HISCHARACTERISTICCANBEREGARDEDASASTEPPED PHASEAPPROXIMATIONTOQUADRATICPHASEMODULATION !S - INCREASES THE PEAK SIDELOBEnVOLTAGE RATIO APPROACHES O- 4HIS COR RESPONDS TO APPROXIMATELY A D" IMPROVEMENT OVER PSEUDORANDOM SEQUENCES OFSIMILARLENGTH4HEAMBIGUITYFUNCTIONGROSSLYRESEMBLESTHEKNIFE EDGERIDGE CHARACTERISTIC ASSOCIATED WITH ,&- WAVEFORMS AS CONTRASTED WITH THE THUMBTACK CHARACTERISTICOFPSEUDORANDOMSEQUENCES&IGURE (OWEVER FORSMALLRATIOSOF DOPPLERSHIFTTOWAVEFORMBANDWIDTH AGOODDOPPLERRESPONSECANBEOBTAINEDFOR REASONABLETARGETVELOCITIES ,EWISAND+RETSCHMER#ODES0 0 0 0 ,EWISAND+RETSCHMERHAVESTUD IEDTHE0 0 0 AND0POLYPHASECODES 4HESECODESARESTEPAPPROXIMATIONS TOTHE,&-PULSECOMPRESSIONWAVEFORMS HAVELOW RANGESIDELOBES ANDHAVETHE
&)'52% 0HASE VERSUS TIME RELATIONSHIP FOR &RANK CODE OF LENGTH-
05,3%#/-02%33)/.2!$!2
n°Ó£
&)'52% !MBIGUITYFUNCTIONOFA&RANKCODEOFLENGTH-
DOPPLERTOLERANCEOFTHE,&-CODES4HE0AND0CODESAREMODIFIEDVERSIONSOF THE&RANKCODEWITHTHE$#FREQUENCYTERMATTHECENTEROFTHEPULSEINSTEADOFATTHE BEGINNING4HEYAREMORETOLERANTOFRECEIVERBAND LIMITINGPRIORTOPULSECOMPRESSION ENCOUNTEREDINDIGITALRADARSYSTEMS4HE0CODESCONTAINS-ELEMENTSASDOESTHE &RANKCODE BUTTHERELATIONSHIPOFTHEITHELEMENTTOTHEJTHGROUPISEXPRESSEDAS
FI J P - ; - J =; J - I =
WHEREIANDJAREINTEGERSRANGINGFROMTO- 0CODESARESIMILAR BUTTHEPHASEISSYMMETRICWITHTHEFOLLOWINGCHARACTERISTIC
FI J [P ; - - = P - I J ]; - J=
4HE0AND0CODESAREDERIVEDBYESSENTIALLYCONVERTINGAN,&-WAVEFORMTO BASEBAND4HESETENDTOBEMOREDOPPLERTOLERANTTHANTHE&RANK 0 OR0CODES AND ARE ALSO MORE TOLERANT OF PRECOMPRESSION BANDWIDTH LIMITATIONS THAT APPEAR IN RADARSYSTEMS4HEPHASEOFTHE0CODEISGIVENAS
JN
P N x .n N .
4HE0CODEPHASERELATIONSHIPISSIMILAR
FN
P N
P K aNa. .
4ABLESUMMARIZESTHEPHASEANDAUTOCORRELATIONCHARACTERISTICSOFTHE&RANK CODEANDTHE,EWISAND+RETSCHMER0THROUGH0POLYPHASECODES
n°ÓÓ
2!$!2(!.$"//+
4!",% 3UMMARYOF0HASEAND!UTOCORRELATION#HARACTERISTICSOF&RANKAND,EWISAND +RETSCHMER0OLYPHASE#ODES
0OLYPHASE #ODE 0HASE
&RANK
P I J . I x. J x.
P 0
0
0
0HASEVS4IME#HARACTERISTIC !UTOCORRELATIOND" . %XAMPLE . %XAMPLE
; - J =
s;J - I = FORITHELEMENTIN THEJTHGROUP
[P ; - - =
P - I J ] ; ; - J= FORITHELEMENTIN THEJTHGROUP
P N . N x.n
0
P N
PK . aNa.
0N K 0OLYPHASE#ODES 7HEREASTHEPREVIOUSLYDISCUSSEDPOLYPHASECODESARE DERIVEDFROM,&-WAVEFORMS 0N K CODESAREDERIVEDFROMSTEPAPPROXIMATIONSOF THEPHASECHARACTERISTICOFTHEWEIGHTINGFUNCTIONOF.,&-WAVEFORMS4HEWEIGHT INGFUNCTIONISGIVENBY
¤P F ³ 7 F K K COSN ¥ ´ ¦ "µ
WHEREKANDNAREPARAMETERSOFTHEWEIGHTINGFUNCTION "ISTHESWEPTBANDWIDTHOF THEWAVEFORM ANDn"aFa"4HISISACOSNWEIGHTINGONAPEDESTALOFHEIGHTK &IGURE (AMMINGWEIGHTINGISACHIEVEDFORN ANDK
05,3%#/-02%33)/.2!$!2
n°ÓÎ
N
&)'52% COS ONPEDESTALWEIGHTINGFUNCTIONSHOWNFORN
&ORTHECASEWHEREN THEWEIGHTINGFUNCTIONCANBEINTEGRATEDTOOBTAINTHEFOLLOWING RELATIONSHIPBETWEENTIMEANDFREQUENCY
T F A SIN P F " WHEREA nK K 4 "
WHICHISSIMILARTOTHESINE BASED.,&-DISCUSSEDEARLIER4HISPARTICULARCODEIS CALLED0HASEFROM.ONLINEAR&REQUENCY0., ANDITSAUTOCORRELATIONFUNCTIONIS SHOWNIN&IGUREFORA §SPULSEWIDTH -(ZBANDWIDTHWAVEFORMWITH A ANDFD 4HETIMESIDELOBELEVELSARESEENTOBEBELOWnD" 4HE AMBIGUITY FUNCTION IS SIMILAR TO THAT PROVIDED IN THE DISCUSSION OF .,&- WHICHISEXPANDEDIN&IGURETOSHOWINMOREDETAILTHEIMPACTOFDOPPLERSHIFTON THEPULSECOMPRESSEDWAVEFORMFORPRACTICALVALUESOFDOPPLERSHIFTS
&)'52% §S0.,PULSEAUTOCORRELATIONFUNCTIONFOR4" A ANDFD
n°Ó{
2!$!2(!.$"//+
&)'52% %XPANDEDVIEWOF0.,AMBIGUITYDIAGRAMFOR §SPULSE A AND " -(Z
!STHEDOPPLERSHIFTMOVESAWAYFROMZERO THEPEAKDECREASESANDTHECLOSE IN TIMESIDELOBELEVELSONONESIDEORTHEOTHERBEGINTOINCREASE.OTETHATANF"RATIO OFCORRESPONDSTOADOPPLERSHIFTASSOCIATEDWITHAPPROXIMATELYA-ACHTARGET ATA3BANDCARRIERFREQUENCY )NGENERALFOR0N K WAVEFORMS THEINTEGRALOFTHEWEIGHTINGFUNCTIONPROVIDES THERELATIONSHIPBETWEENTIMEANDFREQUENCYMODULATIONASSHOWNIN%Q PF
T " ;K K COSN X = DX 4 P ¯ P
3INCEFREQUENCYMODULATIONISPROPORTIONALTOTHETIMEDERIVATIVEOFPHASE PHASE ISOBTAINEDBYINTEGRATINGTHEFREQUENCYWITHRESPECTTOTIME4HEEXPRESSIONFORFRE QUENCY HOWEVER ISNOTSTRAIGHTFORWARD ANDISUSUALLYOBTAINEDTHROUGHNUMERICAL EVALUATION 1UADRIPHASE#ODES 1UADRIPHASECODESAREANEXAMPLEOFAPHASE CODEDWAVE FORM WITHOUT PHASE DISCONTINUITIES 1UADRIPHASE CODES ARE BASED ON THE USE OF SUBPULSES WITH A HALF COSINE SHAPE AND PHASE CHANGES BETWEEN ADJACENT SUBPULSES OFMULTIPLESOFon4HECOSINEWEIGHTINGPROVIDESFASTERSPECTRUMROLL OFF LOWER FILTERMATCHINGLOSS ANDSMALLERRANGESAMPLINGLOSSWHENCOMPAREDTORECTANGULAR SUBPULSEPHASE CODEDWAVEFORMS4ABLE
4!",% 1UADRIPHASE7AVEFORM0ERFORMANCE3UMMARY
2ADIATED3PECTRUM D"7IDTH &ALLOFFC SUBPULSEDURATION 2ANGE3AMPLING,OSS &ILTER-ATCHING,OSS
1UADRIPHASE#ODE
2ECTANGULAR 3UBPULSE#ODE
C D"/CTAVE D" D"
C D"/CTAVE D" D"
05,3%#/-02%33)/.2!$!2
n°Óx
&)'52% 4IME FREQUENCY CODEDWAVEFORM
4IME &REQUENCY #ODED 7AVEFORMS ! TIME FREQUENCY CODED WAVEFORM &IGURE CONSISTSOFATRAINOF.PULSESWITHEACHPULSEATADIFFERENTFREQUENCY 'ENERALLY THEFREQUENCIESAREEQUALLYSPACED ANDTHEPULSESAREOFTHESAMEAMPLI TUDE4HEAMBIGUITYFUNCTIONFORAPERIODICWAVEFORMOFTHISTYPECONSISTSOFACENTRAL SPIKEPLUSMULTIPLESPIKESORRIDGESDISPLACEDINTIMEANDFREQUENCY!LTHOUGHITIS UNACHIEVABLEINPRACTICE THEOBJECTIVEISTOCREATEAHIGH RESOLUTION THUMBTACK LIKE CENTRALSPIKEWITHACLEARAREAAROUNDIT-EASUREMENTISTHENPERFORMEDONTHEHIGH RESOLUTIONCENTRALSPIKE4HERANGERESOLUTIONORCOMPRESSED PULSEWIDTHISDETERMINED BYTHETOTALBANDWIDTHOFALLTHEPULSES ANDTHEDOPPLERRESOLUTIONISDETERMINEDBYTHE RECIPROCALOFTHEWAVEFORMDURATION4&OREXAMPLE ATYPICALWAVEFORMINTHISCLASS HAS.CONTIGUOUSPULSESOFWIDTHTWHOSESPECTRAOFWIDTHSAREPLACEDSIDEBYSIDE INFREQUENCYTOELIMINATEGAPSINTHECOMPOSITESPECTRUM3INCETHEWAVEFORMBAND WIDTHISNOW.S THENOMINALCOMPRESSED PULSEWIDTHISS.4HESERELATIONSHIPSARE SUMMARIZEDIN4ABLE 3HAPINGOFTHEHIGH RESOLUTIONCENTRALSPIKEAREAASWELLASTHEGROSSSTRUCTUREOFTHE AMBIGUITYSURFACECANBEACCOMPLISHEDBYVARIATIONSOFTHEBASICWAVEFORMPARAM ETERS SUCHASAMPLITUDEWEIGHTINGOFTHEPULSETRAIN STAGGERINGOFTHEPULSEREPETITION INTERVAL ANDFREQUENCYORPHASECODINGOFTHEINDIVIDUALPULSES #OSTAS #ODES #OSTAS CODES ARE A CLASS OF FREQUENCY CODED WAVEFORMS THAT HAVENEARIDEALRANGEANDDOPPLERSIDELOBEBEHAVIOR )NOTHERWORDS THEIRAMBI GUITYFUNCTIONAPPROACHESTHEIDEALTHUMBTACK PROVIDINGBOTHDOPPLERANDRANGE INFORMATION &IGURE !LL SIDELOBES EXCEPT FOR A FEW NEAR THE ORIGIN HAVE ANAMPLITUDEOF-!FEWSIDELOBESCLOSETOTHEORIGINAREABOUTTWICEASLARGE ORABOUT- WHICHISCHARACTERISTICOF#OSTASCODES4HECOMPRESSIONRATIOOFA #OSTASCODEISABOUT- 4HE#OSTASCODEISABURSTOF-CONTIGUOUSUNCODEDPULSEWAVEFORMS EACHWITHA DIFFERENTFREQUENCYSELECTEDFROMAFINITESETOF-EQUALLYSPACEDFREQUENCIESTHATARE 4!",% .0ULSES#ONTIGUOUSIN4IMEAND&REQUENCY
7AVEFORMDURATION 4 7AVEFORMBANDWIDTH " 4IME BANDWIDTHPRODUCT 4" #OMPRESSEDPULSEWIDTH " $OPPLERRESOLUTION 4
.S .S . S. S. .S
n°ÓÈ
2!$!2(!.$"//+
&)'52% #OMPARISONOFAMBIGUITYFUNCTIONSFOR. STEPPEDLINEARAND#OSTASSEQUENCESHOWING THEIMPACTOFFREQUENCYORDER
PROCESSEDCOHERENTLY4HEORDERINWHICHTHEFREQUENCIESAREGENERATEDGREATLYINFLU ENCESTHENATUREOFTHEAMBIGUITYFUNCTIONOFTHEBURST)FTHEFREQUENCIESAREMONOTONI CALLYINCREASINGORDECREASING THEWAVEFORMISSIMPLYASTEPPEDAPPROXIMATIONTOAN ,&- WHICHHASARIDGEINITSAMBIGUITYFUNCTION&IGURE )NORDERTOAPPROACHA THUMBTACK LIKEAMBIGUITYFUNCTION THEORDEROFTHEFREQUENCIESNEEDSTOBEMORERAN DOMINNATURE4HEORDEROFFREQUENCIESISTHECODE ANDITISGENERATEDVIAASPECIALCLASS OF-¾-#OSTASARRAYS#OSTAS SUGGESTEDATECHNIQUEFORSELECTINGTHEORDEROFTHESE FREQUENCIESTOPROVIDEMORECONTROLLEDRANGEANDDOPPLERSIDELOBES!NEXAMPLEOFA #OSTASCODEOFLENGTHISSHOWNIN&IGURE ASITCOMPARESTOTHESTEPPED,&- 4ABLESSHOWINGTHESEQUENCEORDERFOREACHWAVEFORMAREALSOPROVIDED
n°ÎÊ /",-Ê / Ê "
Ê"ÊÊ *1 - Ê " *, --" Ê-9-/ 4HECHOICEOFAPULSECOMPRESSIONSYSTEMINVOLVESTHESELECTIONOFTHETYPEOFWAVE FORMANDTHEMETHODOFGENERATIONANDPROCESSING-ETHODSOFGENERATINGANDPROCESS INGPULSECOMPRESSIONWAVEFORMSAREDISCUSSEDINTHESECTIONONPULSECOMPRESSION IMPLEMENTATION IN THIS CHAPTER $ISCUSSIONS HERE WILL CONCENTRATE ON THE WAVEFORM ITSELF4HEPRIMARYFACTORSINFLUENCINGTHESELECTIONOFAPARTICULARWAVEFORMAREUSU ALLYTHERADARREQUIREMENTSOFDOPPLERTOLERANCEANDTIMESIDELOBELEVELS 4ABLESUMMARIZESTHESEFACTORSFORTHREE&-TYPES,&- .,&- ANDPHASE CODED WAVEFORMS4HESYSTEMSARECOMPAREDONTHEASSUMPTIONTHATINFORMATIONISEXTRACTEDBY PROCESSINGASINGLEWAVEFORMASOPPOSEDTOMULTIPLE PULSEPROCESSING4HESYMBOLS" AND4DENOTETHEBANDWIDTHANDTHEPULSEWIDTHOFTHEWAVEFORM RESPECTIVELY )NCASESWHEREANINSUFFICIENTDOPPLERSHIFTOCCURS SUCHASWITHASTATIONARYOR TANGENTIALTARGET RANGERESOLUTIONISTHECHIEFMEANSFORSEEINGATARGETINCLUTTER
05,3%#/-02%33)/.2!$!2
n°ÓÇ
4!",% #OMPARISONSOF0ERFORMANCE#HARACTERISTICSFOR,&- .,&- AND0HASE #ODED
7AVEFORMS &ACTOR
,INEAR&-
$OPPLER TOLERANCE
3UPPORTSDOPPLER !DEQUATEINSENSITIVITY (IGHERSENSITIVITYTO (IGHESTSENSITIVITY SHIFTSUPTOo" TODOPPLERTOALLOWUSE DOPPLERSHIFT4IME TODOPPLERSHIFT 4IMESHIFTOFFD4" GENERALLYUPTO-ACH SIDELOBESINCREASE 4IMESIDELOBES INCREASEWHILE ISINTRODUCEDBY 4IMESHIFTOFFD4"IS WHILEMAINLOBE RESPONSEDECREASES MAINLOBERESPONSE RANGE DOPPLER INTRODUCEDBYRANGE COUPLING DOPPLERCOUPLINGFORA FORHIGHERDOPPLER DECREASESFOR HIGHERDOPPLER 4IMESIDELOBE NONSYMMETRICAL.,&- CHARACTERISTIC CHARACTERISTICOF PERFORMANCE WAVEFORM#OMMON OFATHUMBTACK ATHUMBTACK LIKE LIKEAMBIGUITY REMAINSEXCELLENT THEREFORE IN!4# AMBIGUITYFUNCTION FORLARGEDOPPLER RADARS-ULTIPLETUNED FUNCTION 5SED 5SED THEREFORE FOR THEREFORE FOR SHIFTS PULSECOMPRESSORS LOW SPEEDTARGET REQUIREDFORHIGH SPEED LOW SPEEDTARGET APPLICATIONSAND APPLICATIONSAND TARGETS WITHSMALL4" WITHSMALL4" PRODUCTS,ONGER PRODUCTS PHASE CODED WAVEFORMSAREMORE SENSITIVETODOPPLER SHIFTSTHANTHE SHORTERONES "ETTERTIMESIDELOBES 'OODTIME &ORNONSYMMETRICAL !DEQUATE SIDELOBESTHATARE THANBINARYPHASE .,&- EXCELLENT WEIGHTING HIGH CODEDWAVEFORMS DETERMINEDBY 4"PRODUCT AND TIMESIDELOBESIF CODING THEREISADEQUATE LOWAMPLITUDE ANDPHASEERRORS .,&-PHASECODING ARENECESSARYTO AHIGH4"PRODUCT ACHIEVEGOODTIME ANDSUFFICIENTLYLOW AMPLITUDEANDPHASE SIDELOBES ERRORS)NCREASING .,&-PHASECODE WEIGHTINGINTRODUCES INCREASEDRADIAL VELOCITYSENSITIVITY
4IME SIDELOBE LEVEL
'ENERAL
/FTENUSEDFOR HIGH SPEED TARGETCAPABILITY -ACH %XTREMELYWIDE BANDWIDTHS ACHIEVABLE
.ONLINEAR&-
"INARY0HASE#ODED 0OLYPHASE#ODED
'ENERALLYFOUNDIN 'ENERALLYFOUNDIN 5SEISGENERALLY RESTRICTEDTOAPPLICATIONS LOWDOPPLERSHIFT LOWDOPPLERSHIFT APPLICATIONS APPLICATIONS WHEREPRIMARY TARGETRADIALVELOCITIES -ACH-ULTIPLE TUNEDMATCHEDFILTERS AREGENERALLYNOT COMPUTATIONALLY PRACTICAL
#LUTTERREJECTIONWITHPULSECOMPRESSIONWAVEFORMSISDUETOTHEGREATERRANGERESO LUTION ACHIEVABLE OVER UNCODED WAVEFORMS "ECAUSE THE RANGE RESOLUTION IS PRO PORTIONAL TO THE RECIPROCAL OF THE BANDWIDTH WIDER BANDWIDTH PULSE COMPRESSION WAVEFORMSCANOFFERGREATERCLUTTERREJECTION
n°Ón
2!$!2(!.$"//+
n°{Ê *1 - Ê " *, --" Ê * //" Ê Ê, ,Ê-9-/ Ê 8 * 4HISSECTIONDESCRIBESTHEGENERATIONANDPROCESSINGOFPULSECOMPRESSIONWAVEFORMS ANDPROVIDESEXAMPLESOFRADARSYSTEMSTHATUTILIZETHESEPROCESSINGTECHNIQUES-AJOR ADVANCESARECONTINUALLYBEINGMADEINTHEDEVICESANDTECHNIQUESUSEDINPULSECOM PRESSIONRADARS3IGNIFICANTADVANCESAREEVIDENTINTHEDIGITALAND3!7TECHNIQUES THATALLOWTHEIMPLEMENTATIONOFAVARIETYOFPULSECOMPRESSIONWAVEFORMTYPES4HE DIGITAL APPROACH HAS BLOSSOMED BECAUSE OF THE MANIFOLD INCREASE IN COMPUTATIONAL SPEEDANDALSOBECAUSEOFTHESIZEREDUCTIONANDTHESPEEDINCREASEOFTHEMEMORY UNITS3!7TECHNOLOGYHASEXPANDEDBECAUSEOFTHEINVENTIONOFTHEINTERDIGITALTRANS DUCER WHICHPROVIDESEFFICIENTTRANSFORMATIONOFANELECTRICALSIGNALINTOACOUSTIC ENERGYANDVICEVERSA $IGITAL7AVEFORM'ENERATION &IGURESHOWSADIGITALAPPROACHFORGEN ERATINGTHERADARWAVEFORM4HEPHASECONTROLELEMENTSUPPLIESDIGITALSAMPLESOFTHE IN PHASECOMPONENT)ANDTHEQUADRATURECOMPONENT1 WHICHARECONVERTEDTOTHEIR ANALOGEQUIVALENTS4HESEPHASESAMPLESMAYDEFINETHEBASEBANDCOMPONENTSOFTHE DESIREDWAVEFORM ORTHEYMAYDEFINETHEWAVEFORMCOMPONENTSONALOW FREQUENCY CARRIER)FTHEWAVEFORMISONACARRIER THEBALANCEDMODULATORISNOTREQUIRED ANDTHE FILTEREDCOMPONENTSWOULDBEADDEDDIRECTLY4HESAMPLE AND HOLDCIRCUITREMOVES THETRANSIENTSDUETOTHENONZEROTRANSITIONTIMEOFTHEDIGITAL TO ANALOG$! CON VERTER4HELOW PASSFILTERSMOOTHESORINTERPOLATES THEANALOGSIGNALCOMPONENTS BETWEENWAVEFORMSAMPLESTOPROVIDETHEEQUIVALENTOFAMUCHHIGHERWAVEFORM SAMPLINGRATE4HE)T COMPONENTMODULATESAnCARRIERSIGNAL ANDTHE1T COMPO NENTMODULATESAnPHASE SHIFTEDCARRIERSIGNAL4HEDESIREDWAVEFORMISTHESUMOF THEn MODULATEDCARRIERANDTHEn MODULATEDCARRIER!SMENTIONEDEARLIER WHEN THEDIGITALPHASESAMPLESINCLUDETHECARRIERCOMPONENTS THE)AND1COMPONENTSARE CENTEREDONTHISCARRIERFREQUENCYANDTHELOW PASSFILTERCANBEREPLACEDWITHABAND PASSFILTERCENTEREDONTHE)&CARRIER 7HENALINEAR &-WAVEFORMISDESIRED THEPHASESAMPLESFOLLOWAQUADRATICPAT TERNANDCANBEGENERATEDBYTWOCASCADEDDIGITALINTEGRATORS4HEINPUTDIGITALCOM MANDTOTHEFIRSTINTEGRATORDEFINESTHISQUADRATICPHASEFUNCTION4HEDIGITALCOMMAND TO THE SECOND INTEGRATOR IS THE OUTPUT OF THE FIRST INTEGRATOR PLUS THE DESIRED CARRIER FREQUENCY4HISCARRIERMAYBEDEFINEDBYTHEINITIALVALUEOFTHEFIRSTINTEGRATOR4HE DESIREDINITIALPHASEOFTHEWAVEFORMISTHEINITIALVALUEOFTHESECONDINTEGRATORORELSE MAYBEADDEDTOTHESECOND INTEGRATOROUTPUT 7ITHADVANCESINDIGITALTECHNOLOGY ITHASBECOMEPOSSIBLEANDPRACTICALTOGENERATE WAVEFORMSDIRECTLYAT)&OR2&CARRIERFREQUENCIESONASINGLEINTEGRATEDCIRCUITCHIP4HIS TECHNIQUEISCALLED$IRECT$IGITAL3YNTHESIS OR$$3 ANDINVOLVESGENERATINGWAVEFORMSAT
&)'52% $IGITALWAVEFORMGENERATIONBLOCKDIAGRAM
05,3%#/-02%33)/.2!$!2
n°Ó
HIGHSAMPLINGRATESANDFILTERINGTHEOUTPUT4HESEDEVICESGENERATETHEWAVEFORMBYACCU MULATINGPHASEINFORMATION WHICHISTHENUSEDTOLOOKUPVALUESOFTHEWAVEFORMUSUALLY ASINEWAVE 4HISISCONVERTEDTOANANALOGSIGNALWITHADIGITAL TO ANALOGCONVERTER$!# OR$!CONVERTER ANDFILTERED!VARIETYOFWAVEFORMTYPESEG ,&- .,&- AND#7 WAVEFORMS CANBEGENERATEDINTHISWAYBYUSINGTHEAPPROPRIATEPHASEMODULATIONCHAR ACTERISTIC!SANEXAMPLE THE!NALOG$EVICES!$$IRECT$IGITAL3YNTHESIZERUSESA BIT$!#OPERATINGATUPTOA '(ZINTERNALCLOCKSPEED$!#UPDATERATE $IGITAL 0ULSE #OMPRESSION n $IGITAL PULSE COMPRESSION TECHNIQUES ARE ROUTINELYUSEDFORMATCHEDFILTERINGOFRADARWAVEFORMS4HEMATCHEDFILTERMAYBE IMPLEMENTEDBYUSINGADIGITALCONVOLUTIONFORANYWAVEFORMORELSEBYUSEOFSTRETCH PROCESSINGFORALINEAR &-WAVEFORM $IGITAL PULSE COMPRESSION HAS DISTINCT FEATURES THAT DETERMINE ITS ACCEPTABILITY FORAPARTICULARRADARAPPLICATION$IGITALMATCHEDFILTERINGUSUALLYREQUIRESMULTIPLE OVERLAPPEDPROCESSINGUNITSFOREXTENDEDRANGECOVERAGE4HEADVANTAGESOFTHEDIGI TAL APPROACH ARE THAT LONG DURATION WAVEFORMS PRESENT NO PROBLEM THE RESULTS ARE EXTREMELYSTABLEUNDERAWIDEVARIETYOFOPERATINGCONDITIONS ANDTHESAMEIMPLEMEN TATIONCOULDBEUSEDTOHANDLEMULTIPLEWAVEFORMTYPES !NALOGPRODUCTDETECTORSUSEDTOEXTRACT)AND1BASEBANDCOMPONENTSHAVEBEEN REPLACEDINMANYSYSTEMSBYDIGITALDOWN CONVERSIONTECHNIQUES)NTHISAPPROACH THE COMPLEXENVELOPESEQUENCEISEVALUATEDBYDIGITALSIGNALPROCESSINGOF!$CONVERTER SAMPLESATTHEFINAL)&OUTPUTOFTHERECEIVER RATHERTHANBYSEPARATE!$CONVERSIONOF BASEBANDANALOG)AND1COMPONENTSn$IGITALDOWN CONVERSIONISADVANTAGEOUS BECAUSEPERFORMANCEISNOTLIMITEDBYAMPLITUDEANDPHASEIMBALANCESTHATEXISTIN ANALOGPRODUCT DETECTIONHARDWARE &IGUREILLUSTRATESTWODIGITALSIGNAL PROCESSINGAPPROACHESTOPROVIDINGTHE MATCHEDFILTERFORAPULSECOMPRESSIONWAVEFORM)NBOTHCASES THEINPUTSIGNALISTHE COMPLEXENVELOPESEQUENCEASFORMEDUSINGEITHERDIGITALDOWN CONVERSIONORANALOG #!
!
! $ #!
!
!
" %
&)'52% A 4IME DOMAIN DIGITAL PULSE COMPRESSION PROCESSOR AND B FREQUENCY DOMAIN DIGITAL PULSECOMPRESSIONPROCESSOR
n°Îä
2!$!2(!.$"//+
PRODUCTDETECTIONFOLLOWEDBY!$CONVERSIONINEACHBASEBANDCHANNEL&IGUREA SHOWSADIGITALIMPLEMENTATIONOFATIME DOMAINCONVOLUTIONPROCESSORTHATWILLPRO VIDEMATCHED FILTERPERFORMANCEFORANYRADARWAVEFORM)NTHISCASE DISCRETE TIME CONVOLUTIONISDONEINTHETIMEDOMAINBYCONVOLUTIONOFTHECOMPLEXENVELOPEINPUT SEQUENCEFOLLOWINGDIGITALDOWN CONVERSIONWITHTHEMATCHEDFILTERIMPULSERESPONSE SEQUENCE"ECAUSETIME DOMAINCONVOLUTIONCANBECOMPUTATIONALLYINTENSIVE AMORE ECONOMICALAPPROACHFROMACOMPUTATIONALSTANDPOINTISSHOWNIN&IGUREB IN WHICHFREQUENCY DOMAINPROCESSINGISUSEDTOIMPLEMENTTHECONVOLUTION 4HEFREQUENCY DOMAINDIGITALPULSECOMPRESSIONPROCESSOROPERATESONTHEPRINCI PLETHATTHEDISCRETE&OURIERTRANSFORM$&4 OFTHETIMECONVOLUTIONOFTWOSEQUENCES ISEQUALTOTHEPRODUCTOFTHEDISCRETE&OURIERTRANSFORMSOFEACHOFTHESEQUENCES)F -RANGESAMPLESARETOBEPROVIDEDBYONEPROCESSOR THELENGTHOFTHE$&4MUST EXCEED-PLUSTHENUMBEROFSAMPLESINTHEREFERENCEWAVEFORMMINUSONETOACHIEVE ANAPERIODICCONVOLUTION4HESEADDED-SAMPLESAREFILLEDWITHZEROSINTHEREFER ENCEWAVEFORM$&4&OREXTENDEDRANGECOVERAGE REPEATEDPROCESSINGOPERATIONSARE REQUIREDWITHRANGEDELAYSOF-SAMPLESBETWEENADJACENTOPERATIONSUSINGTHEOVER LAP SAVECONVOLUTIONTECHNIQUE 4HISPROCESSORCANBEUSEDWITHANYWAVEFORM ANDTHEREFERENCEWAVEFORMCANBEOFFSETINDOPPLERFREQUENCYTOACHIEVEAMATCHED FILTERATTHISDOPPLERFREQUENCY 0ULSE#OMPRESSION2ADAR%XAMPLES 4HEREAREMANYRADARSUNDERDEVELOP MENTORDEPLOYEDTHATUTILIZESOMEOFTHEPULSECOMPRESSIONWAVEFORMSPREVIOUSLYDIS CUSSED!DVANCESINDIGITALSIGNAL PROCESSINGTECHNOLOGYHAVEENABLEDAWIDERVARIETY OFWAVEFORMIMPLEMENTATIONS&OREXAMPLE RADARSYSTEMSARENOLONGERLIMITEDTOTHE ,&-WAVEFORMINSTEAD RADARSYSTEMCAPABILITIESCANBEEXTENDEDTOTAKEADVANTAGE OFTHEMORECOMPLEXPROCESSINGASSOCIATEDWITHTHENONLINEAR&-WAVEFORM !.403 AND !.&03 3URVEILLANCE 2ADARS 4HE !.403 AND !. &03 ARE A FAMILY OF , BAND LONG RANGE SURVEILLANCE RADARS THAT EMPLOY ,&- WAVEFORMS4HE ANTENNA IS MECHANICALLY ROTATED IN AZIMUTH AND ELECTRONIC PENCIL BEAMSCANNINGISPERFORMEDINELEVATION4HETRANSMISSIONUTILIZESTWOTIME SEQUENCED ,&-PULSESOFDIFFERENTFREQUENCIESINORDERTOCREATE3WERLING#ASETARGETSTATISTICS "OTHRADARSEMPLOYFREQUENCY DOMAINDIGITALPULSECOMPRESSIONPROCESSING !IR 3URVEILLANCE AND 0RECISION !PPROACH 2ADAR 3YSTEM 4HE!IR 3URVEILLANCE AND0RECISION!PPROACH2ADAR3YSTEM!30!2#3 ISINTENDEDTOPROVIDETHENEXT GENERATIONAIRTRAFFICCONTROL!4# RADAR ASPARTOFTHE-ULTI -ISSION3URVEILLANCE 2ADAR--32 FAMILYOF!4#RADARSBUILTBY,OCKHEED-ARTIN#O.ONLINEAR&- WAVEFORMSAREUSEDBECAUSETHETARGETSOFINTERESTHAVERELATIVELYLOWDOPPLERSHIFTS LESSTHAN-ACH ,IKETHE!.&03 RADAR THISSYSTEMIMPLEMENTSFREQUENCY DOMAINDIGITALPULSECOMPRESSIONPROCESSING -ULTI -ISSION2ADAR 4HE-ULTI -ISSION2ADAR--2 ISDESIGNEDTODETECTAND TRACKMORTARS ARTILLERY ANDROCKETS4HISRADARUSESANONLINEAR&-SINE BASEDWAVE FORM$IGITALFREQUENCY DOMAINPULSECOMPRESSIONPROCESSINGISPERFORMED !32 .EXT 'ENERATION3OLID 3TATE!IR4RAFFIC#ONTROL2ADAR 4HE!32 TER MINALAIRPORTSURVEILLANCERADARTRANSMITSA §SPULSEWITHPEAKPOWEROFK7TO PROVIDEASINGLE PULSETRANSMITENERGYOF*.ONLINEARFREQUENCYMODULATIONIS USEDWITHAPULSECOMPRESSIONRATIOOFTOACHIEVERANGE RESOLUTIONEQUIVALENTTO ANUNCODED §SPULSE4HEFILTERMATCHINGLOSSISLESSTHAND"ANDTYPICALTIME
05,3%#/-02%33)/.2!$!2
n°Î£
SIDELOBELEVELSMEASUREDONPRODUCTIONHARDWAREAREnD"$IGITALPULSECOMPRES SIONISUSED!NUNCODED §SPULSEISUSEDTOPROVIDECOVERAGEFORTARGETSWITHIN THERANGEINTERVALFROMTONMI 3TRETCH0ULSE#OMPRESSIONn 3TRETCHPULSECOMPRESSIONISATECHNIQUEFOR PERFORMING,&-PULSECOMPRESSIONOFWIDEBANDWAVEFORMSUSINGASIGNALPROCESSOR WITHBANDWIDTHTHATISMUCHSMALLERTHANTHEWAVEFORMBANDWIDTH WITHOUTLOSSOF SIGNAL TO NOISERATIOORRANGERESOLUTION3TRETCHPULSECOMPRESSIONISUSEDFORASINGLE TARGETORFORMULTIPLETARGETSTHATARELOCATEDWITHINARELATIVELYSMALLRANGEWINDOW CENTEREDATASELECTEDRANGE &IGURE SHOWS A BLOCK DIAGRAM OF A STRETCH PULSE COMPRESSION SYSTEM4HE ,&-WAVEFORMHASASWEPTBANDWIDTH" PULSEWIDTH4 AND,&-SLOPEA4HEREFER ENCEWAVEFORMISGENERATEDWITHTIMEDELAYS2 SWEPTBANDWIDTH"2 PULSEWIDTH42 AND,&-SLOPE@24HEREFERENCEWAVEFORMTIMEDELAYISTYPICALLYDERIVEDBYRANGE TRACKINGOFASELECTEDTARGETWITHINTHERANGEWINDOW4HECORRELATIONMIXER #- IN&IGUREPERFORMSABANDPASSMULTIPLICATIONOFTHERECEIVEDSIGNALBYTHEOUTPUT OFTHEREFERENCEWAVEFORMGENERATOR4HELOWERSIDEBANDATTHE#-OUTPUTISSELECTED BYABANDPASSFILTER"0& 3PECTRUMANALYSISISPERFORMEDWHENTHE,&-SLOPESOFTHETRANSMITANDREFERENCE WAVEFORMSAREEQUAL@ @2 2EDUCED BANDWIDTHPULSECOMPRESSIONPROCESSINGIS PERFORMEDIFTHEREFERENCEWAVEFORM,&-SLOPEISLESSTHANTHETRANSMITWAVEFORM ,&-SLOPE@2 @ )NBOTHCASES THEREQUIREDPROCESSINGBANDWIDTH"PISMUCH SMALLERTHANTHEWAVEFORMBANDWIDTH &IGURESHOWSTHEPRINCIPLEOFSTRETCHPULSECOMPRESSIONFORTHECASEWHERETHE ,&-SLOPESOFTHETRANSMITANDREFERENCEWAVEFORMSAREEQUAL4HEINSTANTANEOUSFRE QUENCYISPLOTTEDASAFUNCTIONOFTIMEATTHREEPOINTSINTHESTRETCHPULSECOMPRESSION SYSTEMBLOCKDIAGRAM CORRELATIONMIXERINPUT CORRELATIONMIXER,/REFERENCE WAVEFORM GENERATOR OUTPUT AND CORRELATION MIXER OUTPUT OUTPUT OF BANDPASS FILTER 4HREE,&-TARGETSIGNALSARESHOWNATTHECORRELATIONMIXERINPUTTARGETISAT ZEROTIMEOFFSETRELATIVETOTHEREFERENCEWAVEFORMTARGETISEARLIERINTIMETHANTHE REFERENCEWAVEFORMANDTARGETISLATERINTIME)NEACHCASE THE,&-SLOPEFORTHE TARGETSIGNALSIS"44HEREFERENCEWAVEFORMAPPLIEDTOTHE,/PORTOFTHE#-HAS ,&-SLOPEEQUALTO"242 "4 4HE INSTANTANEOUS FREQUENCY AT THE CORRELATION MIXER OUTPUT IS THE DIFFERENCE BETWEENTHEINSTANTANEOUSFREQUENCIESATTHE#-INPUTAND,/PORTS!SARESULT THE #-OUTPUTSIGNALSFORTHETHREETARGETSIGNALSAREUNCODEDPULSESPULSED#7SIGNALS WITHFREQUENCYOFFSETFROMTHEMIXER)&OUTPUTF)&GIVENBY ¤ "³ D F ¥ ´ TD ¦4µ
!
$
$ $
$
!% !# !
"
&)'52% 3TRETCHPULSECOMPRESSIONSYSTEMBLOCKDIAGRAM
!
! !
n°ÎÓ
2!$!2(!.$"//+
"# $# ! % !
! $ &
#
#
"# $# $#
&)'52% #ORRELATIONMIXERSIGNALSINSTRETCHPULSECOMPRESSIONAFTER2OTHETAL
WHERETDISTHETIMEDELAYOFTHEMIDPOINTOFTHESIGNALMEASUREDRELATIVETOTHEMID POINTOFTHEREFERENCEWAVEFORM&ORTHECASESHOWN WHERETHE2&CARRIERFREQUENCY ISABOVETHECARRIERFREQUENCYOFTHEREFERENCEWAVEFORM APOSITIVETIMEDELAYRESULTS IN A NEGATIVE FREQUENCY OFFSET4HE SIGNALS AT THE CORRELATION MIXER OUTPUT ARE THEN RESOLVEDINTHEFREQUENCYDOMAINBYSPECTRALANALYSISPROCESSING ! TYPICAL IMPLEMENTATION FOR THE SPECTRAL ANALYSIS PROCESSING INCLUDES A SECOND FREQUENCYCONVERSIONFOLLOWINGTHE#-TOAFINALINTERMEDIATEFREQUENCY)& ANTI ALIASINGFILTERING DIRECTSAMPLINGATTHEFINAL)&USINGANANALOG TO DIGITALCONVERTER !$# DIGITALDOWNCONVERSION$$# TOACOMPLEXENVELOPESEQUENCE TIME DOMAIN WEIGHTING ANDSPECTRALANALYSISUSINGAN&&4PADDEDWITHZEROS0REVIOUSIMPLE MENTATIONSUSEDANALOGPRODUCTDETECTORSTOEXTRACT)AND1BASEBANDSIGNALS WITH SEPARATE!$#SINTHE)AND1BASEBANDCHANNELS #ORRELATION-IXER/UTPUT3IGNAL!NALYSIS 4HERECEIVEDSIGNALATTHE#-INPUT PORTFROMAPOINTTARGETIS
¤T T³ XIN T ! RECT ¥ COS;P F FD T T PA T T = ¦ 4 ´µ
WHERE!ISTHEAMPLITUDE 4ISTHETRANSMITPULSEWIDTH FISTHECARRIERFREQUENCY FD ISTHEDOPPLERFREQUENCY SISTHESIGNALTIMEDELAY AND@ISTHE,&-SLOPEFORTHE TRANSMITWAVEFORM4HEREFERENCEWAVEFORMAPPLIEDTOTHE,/PORTIS
¤T T2³ X 2 T RECT ¥ COS;P F2 T T 2 PA 2 T T 2 = ¦ 42 ´µ
WHERE42ISTHEPULSEWIDTH F2ISTHECARRIERFREQUENCY S2ISTHEREFERENCEWAVEFORM TIMEDELAY AND@2ISTHE,&-SLOPEFORTHEREFERENCEWAVEFORM@2a@
05,3%#/-02%33)/.2!$!2
n°ÎÎ
4HECORRELATIONMIXERACTSASABANDPASSMULTIPLIERWITHOUTPUTXINT X2T 4HE)& OUTPUTOFTHECORRELATIONMIXERISEVALUATEDUSINGTHEIDENTITY
COSXCOSY COSX Y COSX Y
WHERETHEFIRSTTERMONTHERIGHT HANDSIDEOFTHEEQUATIONCORRESPONDSTOTHEUPPER SIDEBANDANDTHESECONDTOTHELOWERSIDEBANDATTHEMIXEROUTPUT4HEUPPERSIDEBAND ISREJECTEDBYTHEBANDPASSFILTERTOYIELD ¤T T2³ ¤T T³ X)& T ! RECT ¥ RECT ¥ ¦ 4 ´µ ¦ 42 ´µ COS;P F)& T T P FD T T PA 2 T 2 T T T P A A 2 T T F =
WHEREF)& F F2ISTHE)&CARRIERFREQUENCYF F2ISASSUMED ANDTHECARRIERPHASE SHIFTIS
F P F2 T T 2 PA 2 T T 2
4HE)&SIGNALISAN,&-WAVEFORMWITHREDUCEDSLOPE@ @2THEFACTORTHATMULTI PLIESTHEQUADRATICTERMINTHEARGUMENTOFTHECOSINE ANDAFREQUENCYOFFSETRELATIVE TOTHE)&CARRIERFREQUENCYF)&GIVENBY
D F FD A 2 T 2 T
4HEDURATIONOFTHEREFERENCEWAVEFORMISREQUIREDTOEXCEEDTHETRANSMITPULSE WIDTHTOAVOIDALOSSIN3.2CAUSEDBYTARGETECHOESTHATARENOTCONTAINEDWITHINTHE REFERENCEWAVEFORM %QUAL4RANSMIT AND 2EFERENCE7AVEFORM ,&- 3LOPES &OR THE CASE WHERE THE TRANSMITANDREFERENCEWAVEFORM,&-SLOPESAREEQUAL@ @2 THE)&SIGNALISAN UNCODEDPULSEWITHFREQUENCYOFFSETGIVENBY
D F FD A T 2 T
4HEFREQUENCYOFFSETISMEASUREDUSINGSPECTRUMANALYSISANDCONVERTEDTOTARGET TIMEDELAYANDRANGERELATIVETOTHEREFERENCEWAVEFORMBY $T T T 2
DF A
$R 2 2
C $T
WHERE2 CS2ISTHERANGECORRESPONDINGTOTHETIMEDELAYOFTHEREFERENCEWAVEFORM +ELLOG DESCRIBES ADDITIONAL CONSIDERATIONS FOR APPLICATION OF TIME DOMAIN WEIGHTINGINSTRETCHPROCESSINGANDPROVIDESDETAILSONCOMPENSATIONTECHNIQUESFOR HARDWAREERRORS4HEEFFECTOFTIMEMISMATCHBETWEENTHESIGNALANDTHEWEIGHTING FUNCTIONISANALYZEDBY4EMES
n°Î{
2!$!2(!.$"//+
5NEQUAL 4RANSMIT AND 2EFERENCE 7AVEFORM 3LOPES ! STRETCH PROCESSOR WITH UNEQUALFREQUENCY SLOPEWAVEFORMSREQUIRESPULSECOMPRESSIONOFTHERESIDUALLINEAR &-ATTHEOUTPUTOFTHECORRELATIONMIXER!LINEAR&-SIGNALWITHASLOPEOF@IN @2 OCCURSATTHETARGETRANGE WHICHISOFFSETINFREQUENCYFROMTHE)&CARRIERFREQUENCY BY@2S2 S 7ITHTHERANGE DOPPLERCOUPLINGOFTHE,&-WAVEFORM THEAPPARENT TIMEDELAYOFTHISTARGETWILLBE
SAPP @2S2 S @ @2
4HISRESULTCANBEINTERPRETEDASYIELDINGATIME EXPANSIONFACTOROF@2@@2 FOR THE COMPRESSED PULSE!S FOR THE CASE OF EQUAL ,&- SLOPES THE RANGE WINDOW WIDTHDEPENDSONTHEACHIEVABLEPROCESSINGBANDWIDTH 3TRETCH 0ROCESSING 2ANGE 2ESOLUTION7IDTH 4HE D" FREQUENCY RESOLUTION WIDTH FORSPECTRALANALYSISUSINGARECTANGULARWINDOWOFTIMEDURATIONEQUALTOTHETRANSMIT PULSEWIDTHIS
$F
4
4HE D"TIMEDELAYRESOLUTIONWIDTHOBTAINEDBYSTRETCHPROCESSINGISOBTAINEDBY DIVIDING$FBY\@\TOCONVERTTOUNITSOFTIMEDELAY
T
$F " 4 "
#ONSEQUENTLY THE D"RESOLUTIONWIDTHACHIEVEDBYSTRETCHPROCESSINGISTHESAME ASTHATACHIEVEDBYTHEMATCHEDFILTERFORTHE,&-WAVEFORM4HE D"RANGERESOLU TIONWIDTHIS
$2
C "
4IME DOMAIN WEIGHTING IS UTILIZED IN THE SPECTRAL ANALYSIS PROCESSING TO REDUCE THETIMESIDELOBESOFTHECOMPRESSEDPULSEANDIMPROVETHERESOLUTIONPERFORMANCE WHENMULTIPLETARGETSAREPRESENTWITHINTHERANGEWINDOW!SANEXAMPLE THEUSEOF (AMMINGTIME DOMAINWEIGHTINGREDUCESTHEPEAKTIMESIDELOBELEVELFROMnD" TOnD"WITHANINCREASEINTHE D"FREQUENCYRESOLUTIONWIDTHTO$F 4 4HE D"RANGERESOLUTIONWIDTHFOR(AMMINGWEIGHTINGIS
$2
C (AMMING7EIGHTING "
2ANGE7INDOW7IDTH 4HEWIDTHOFTHERANGEWINDOWISESTABLISHEDBYTHEBAND WIDTHOFTHESPECTRALANALYSISANDTHE,&-SLOPEOFTHETRANSMITWAVEFORM!SSUMEATIME WINDOWOFWIDTH$TANDASTRETCHPROCESSINGBANDWIDTH"P!TARGETATTHEEDGEOFTHETIME WINDOWYIELDSAFREQUENCYOFFSETEQUALTOONE HALFOFTHEPROCESSINGBANDWIDTH
OR
" $T " P 4 $T 4
"P "P
" " 4
05,3%#/-02%33)/.2!$!2
n°Îx
4HERANGEWINDOWWIDTHIS
$R
C4 " P C "P " " 4
3TRETCH 0ULSE #OMPRESSION 2ADAR %XAMPLES 4HIS SECTION DESCRIBES THREE EXAMPLESOFRADARSTHATEMPLOYSTRETCHPULSECOMPRESSIONSYSTEMS ,ONG2ANGE)MAGING2ADAR 4HE,ONG2ANGE)MAGING2ADAR,2)2 ISAN 8 BANDRADARWITHSTRETCHPROCESSINGBANDWIDTHSOF -(Z AND-(Z4HE WIDEBANDWAVEFORMHASASWEPTBANDWIDTHOF-(Z TOAPULSEWIDTHOFAPPROXI MATELY§S ANDA,&-SLOPE"4y-(Z§S -(Z§S4HERANGE WINDOWWIDTHFORTHE-(ZPROCESSINGBANDWIDTHIS
$R
M MS r -(Z C "P M " 4 -(Z MS
-ILLIMETER7AVE2ADAR 4HESTRETCHPROCESSINGIMPLEMENTATIONFORTHE-ILLIMETER 7AVE RADAR --7 LOCATED AT +WAJALEIN !TOLL IS DESCRIBED BY !BOUZAHARA AND !VENT4HE--7RADAROPERATESATACARRIERFREQUENCYOF'(ZUSINGWAVEFORMS WITHAMAXIMUMSWEPTBANDWIDTHOF-(ZANDPULSEWIDTHOF§S4HE,&- SLOPEFORTHETRANSMITWAVEFORMIS
A
" -(Z -(ZMS 4 MS
4HESTRETCHPROCESSINGBANDWIDTHIS"P -(Z4HEWIDTHOFTHESTRETCHPROCESSING TIMEWINDOWIS
$T
-(Z MS -(Z MS
4HEREFERENCEWAVEFORMPULSEWIDTHIS42 §STOAVOIDALOSSIN3.2 FORTARGETSATTHEEDGESOFTHERANGEWINDOW4HESWEPTBANDWIDTHOFTHEREFERENCE WAVEFORMANDTHERANGEWINDOWWIDTHARE
"2 -(ZMS r MS -(Z C $R $T M MS r MS M
4HE D" RANGE RESOLUTION WIDTH WITH (AMMING WEIGHTING APPLIED OVER THE §S PULSEWIDTHINTHESPECTRALANALYSISPROCESSINGIS
$2
C M MS
M " -(Z
#OBRA$ANE7IDEBAND0ULSE#OMPRESSION3YSTEM 4HECHARACTERISTICSOFTHE WIDEBAND PULSE COMPRESSION SYSTEM DEVELOPED FOR THE #OBRA $ANE RADAR ARE SUM MARIZEDIN4ABLE
n°ÎÈ
2!$!2(!.$"//+
4!",% #OBRA$ANE7IDEBAND0ULSE#OMPRESSION3YSTEM#HARACTERISTICSADAPTEDFROM&ILER AND(ARTTÚ)%%%
#HARACTERISTIC
6ALUE
4RANSMIT,&-BANDWIDTH 2EFERENCE,&-BANDWIDTH 4RANSMITWAVEFORMSWEPTBANDWIDTH " 2EFERENCEWAVEFORMSWEPTBANDWIDTH "REF 4RANSMITPULSEWIDTH 4 2EFERENCEPULSEWIDTH 4REF 4RANSMITWAVEFORM,&-SLOPE #OMPRESSEDPULSEWIDTHnD" S 4IME BANDWIDTHPRODUCT 4" 4IMESIDELOBELEVEL 4ARGETRANGEWINDOW .UMBEROFRANGESAMPLES 2ANGESAMPLESPACING &IRST)&ATOUTPUTOFCORRELATIONMIXER 3ECOND)& 3TRETCHPROCESSINGBANDWIDTH "P !$CONVERTERSAMPLINGFREQUENCY
TO-(Z TO-(Z
-(Z -(Z
§S §S
-(Z§SUP CHIRP FT nD" FT FT -(Z -(Z K(Z -(ZIN)AND1BASEBANDCHANNELS
%XCLUDESPULSEWIDTHANDSWEPTBANDWIDTHEXTENSIONDUETO FTRANGEWINDOW
** 8 3IGNAL!NALYSIS3UMMARYn 4ABLEISASUMMARYOFSIGNALANALYSISDEFI NITIONSANDRELATIONSHIPS4ABLESHOWS7OODWARDS&OURIERTRANSFORMRULESAND PAIRS 4HESERELATIONSHIPSSIMPLIFYTHEAPPLICATIONOFSIGNALANALYSISTECHNIQUES)N MOSTCASES ITWILLNOTBENECESSARYTOEXPLICITLYPERFORMANINTEGRATIONTOEVALUATETHE &OURIERTRANSFORMORINVERSE&OURIERTRANSFORM
4!",% 3IGNAL!NALYSIS$EFINITIONSAND2ELATIONSHIPS
&OURIERTRANSFORMSPECTRUM OF SIGNALXT
c
8 F
¯ XT E J P FT DT
c
)NVERSE&OURIERTRANSFORMOF SPECTRUM8F
c
X T
¯ 8 F E J P FT DF
c
#ONVOLUTIONOFSIGNALSXT ANDYT
Y T X T H T c
c
&ILTERFREQUENCYRESPONSE %ULERSIDENTITY
( F 9 F 8 F
c
¯ XT HT T DT ¯ XT T HT DT
E JQ COS Q J SIN Q
c
05,3%#/-02%33)/.2!$!2
n°ÎÇ
4!",% 3IGNAL!NALYSIS$EFINITIONSAND2ELATIONSHIPS#ONTINUED
#OSINEANDSINEFUNCTIONSEXPRESSED INTERMSOFCOMPLEXEXPONENTIALS
COS Q E JQ E JQ SIN Q E JQ E JQ J
0ARSEVALSTHEOREM SUPERSCRIPTASTERISKINDICATES COMPLEXCONJUGATE
c
c
¯ XT Y T DT
¯ 8 F 9 F DF
c c
c
c
¯ \ XT \ DT ¯ \ 8 F \ DF
c
c
RECTFUNCTION
ª \ T \ RECTT « ¬ \ T \
SINCFUNCTION
SINC F SINP F P F
2EPETITIONOPERATOR
c
REP4 ; XT =
£ XT N4
N c
#OMBOPERATOR
c
COMB & ; 8 F =
£ 8 N& D F N&
N c
3AMPLINGPROPERTYOFDELTAFUNCTION
c
¯ XT D T T DT XT
c
#AUCHY 3CHWARZINEQUALITY
c
¯ F X G X DX
c
c
c
a ¯ \ F X \ DX ¯ \ G X \ DX
c
c
WITH EQUALITY IF AND ONLY IF F X KG X
2ADAR4RANSMIT7AVEFORMS n 4HETRANSMITTEDWAVEFORMSUSEDINRADAR AREBANDPASSSIGNALSTHATCANBEEXPRESSEDINTHEFORM
XT AT COS;P FT F T =
WHEREAT ISTHEAMPLITUDEMODULATION6 ET ISTHEPHASEMODULATIONRAD AND FISTHECARRIERFREQUENCY(Z 4HEAMPLITUDEANDPHASEMODULATIONFUNCTIONSVARY SLOWLYCOMPAREDTOTHEPERIODOFTHECARRIERF #ONSEQUENTLY XT ISANARROWBAND WAVEFORMWITHABANDWIDTHTHATISSMALLCOMPAREDTOTHECARRIERFREQUENCY #OMPLEX%NVELOPE 4HECOMPLEXENVELOPEOFXT ISGIVENBY
UT AT E JF T
A
n°În
2!$!2(!.$"//+
4!",% &OURIER4RANSFORM2ULESAND0AIRS
XT YT
REP4 ; XT =
#OMMENTS &OURIERTRANSFORMPAIR ,INEARITY 3IGNALTIMEREVERSAL #ONJUGATEOFSIGNAL 4IMEDOMAINDIFFERENTIATION &REQUENCYDOMAINDIFFERENTIATION 3IGNALTIMESHIFT 3IGNALFREQUENCYSHIFT 4IMESCALING 4IMEDOMAINCONVOLUTION 4IMEDOMAINMULTIPLICATION 8 F 9 F \ 4 \ COMB 4 ; 8 F = 7OODWARDSREPETITIONOPERATOR
COMB4 ; XT =
\ 4 \ REP 4 ; 8 F =
7OODWARDSCOMBOPERATOR
8T CT RECTT SINCT EXPnPT
XnF CF SINCF RECTF EXPnPF
4IME FREQUENCYINTERCHANGEDUALITY $ELTAFUNCTIONINTIME $ELTAFUNCTIONINFREQUENCY RECTFUNCTIONINTIME RECTFUNCTIONINFREQUENCY 'AUSSIANTIMEFUNCTION
3IGNAL XT !XT "UT X T X T DXDT
JPTXT XT S XT EXPJPFT XT4
X T Y T
3PECTRUM 8F !8F "5F 8 F 8 F JPF8F D8DF 8F EXP JPFS 8F F \4\8F4 8F 9F
4HEBANDPASSSIGNALISEXPRESSEDINTERMSOFTHECOMPLEXENVELOPEBY
UT 2E; XT E J P FT =
B
#OMPLEX%NVELOPE2EPRESENTATIONOF2ADAR%CHOES 4HERADARECHOSIGNAL FROMAPOINTTARGETIS
SR T !R AT TD COS;P F FD T TD F T TD =
WHERE!RISADIMENSIONLESSAMPLITUDESCALEFACTOR TDISTHETARGETTIMEDELAYS FDIS THETARGETDOPPLERSHIFT(Z AT ISTHEAMPLITUDEMODULATION6 ET ISTHEPHASE MODULATIONRAD ANDFISTHETRANSMITCARRIERFREQUENCY(Z 4HECOMPLEXENVELOPE OFSRT IS
UR T !R E J P FTD UT TD E J P FD T TD
4HETERMUTnTD ISTHECOMPLEXENVELOPEOFTHETRANSMITWAVEFORMDELAYEDINTIME BYTD4HECOMPLEXEXPONENTIALEXP;JOFDTnTD =REPRESENTSALINEARPHASEMODULATION VERSUSTIMETHATISIMPRESSEDONTHERECEIVEDECHOSIGNALBYTHEDOPPLERSHIFTFD4HE CARRIERPHASESHIFTISPC nOFTD 4HETIMEDELAYANDDOPPLERSHIFTAREEXPRESSEDINTERMSOFTARGETRANGEANDRANGE RATEBYTD 2CS ANDFD nK 6R(Z WHERE2ISTHETARGETRANGEM 6R D2DT
05,3%#/-02%33)/.2!$!2
n°Î
ISTHERANGE RATENEGATIVEFORANINCOMINGTARGET CISTHESPEEDOFLIGHT ANDK CF M ISTHECARRIERWAVELENGTH -ATCHED&ILTERS !MATCHEDFILTERACHIEVESMAXIMUMOUTPUTSIGNAL TO NOISE RATIOFORASIGNALRECEIVEDINWHITENOISE4HEMATCHEDFILTERFREQUENCYRESPONSEFOR ASIGNALUT IS
( MF F K5 F E J P FT
WHEREKISANARBITRARYCOMPLEXCONSTANTAND5F ISTHESPECTRUMOFUT 4HETIME DELAYTISREQUIREDTOEXCEEDTHEDURATIONOFUT TOACHIEVEACAUSALIMPULSERESPONSE THATISZEROFORNEGATIVETIME4HEMATCHEDFILTERIMPULSERESPONSEIS
HMF T KU T T
4HEPEAKSIGNAL TO NOISETOMEAN NOISE POWERRATIOATTHEOUTPUTOFAFILTERWITH FREQUENCYRESPONSE(F ISDEFINEDAS
3 . O
!
S NO
WHERE!OISTHEMATCHEDFILTEROUTPUTSIGNALAMPLITUDEATTHEPEAKOFTHESIGNALANDRNO ISTHEMATCHEDFILTEROUTPUTNOISEPOWER4HEMATCHEDFILTEROUTPUT3.2ISGIVENBY
3 . MF
%
.
WHERE%ISTHEENERGYOFTHERECEIVEDBANDPASSSIGNALATTHEMATCHEDFILTERINPUT* AND.ISTHEONE SIDEDNOISEPOWERSPECTRUMATTHEMATCHEDFILTERINPUT7(Z &ILTER-ATCHING,OSS &ILTERMATCHINGLOSS,MISTHELOSSIN3.2THATRESULTSWHEN ASIGNALISNOTPROCESSEDUSINGAMATCHEDFILTER4HEFILTERMATCHINGLOSSISDEFINEDAS
,M
3 . MF
3 . O
WHERE 3. O IS THE 3.2 AT THE OUTPUT OF A FILTER WITH FREQUENCY RESPONSE (F AND 3. MFISTHEMATCHEDFILTER3.24HEFILTERMATCHINGLOSSCANALSOBEEXPRESSEDAS
,M
% .
3 . O
WHERETHEMATCHEDFILTER3.2ISGIVENBY3. MF %. 4HEFILTERMATCHINGLOSSIS q WHERE,M FORTHEMATCHEDFILTER4HEFILTERMATCHINGLOSSEXPRESSEDINDECIBELS IS,MD" LOG,M ANDEQUALSD"FORTHEMATCHEDFILTER
!NALTERNATEDEFINITIONOFSIGNAL TO NOISERATIOISALSOUSEDINTHELITERATUREINWHICHTHESIGNALPOWERATTHEPEAKOF THEWAVEFORMISAVERAGEDOVERONECYCLEOFTHECARRIER )NTHISCASE THEAVERAGESIGNALPOWERISONE HALFOFTHE PEAKSIGNALPOWERANDTHEMATCHED FILTEROUTPUT3.2IS%.
n°{ä
2!$!2(!.$"//+
!MBIGUITY &UNCTIONS n 4HE AUTOCORRELATIONo FUNCTION FOR A TRANSMIT WAVEFORMWITHCOMPLEXENVELOPEUT ISDEFINEDAS
c
C U T FD ¯ UT U T T E J P FD T DT
c
WHERESISTHERELATIVETIMEDELAYANDFDISDOPPLERSHIFT4HERELATIVETIMEDELAYIS POSITIVEFORATARGETFURTHERINRANGETHANAREFERENCETARGET ANDDOPPLERFREQUENCYIS POSITIVE FOR AN INCOMING TARGET NEGATIVE RANGE RATE 4HE COMPLEX ENVELOPE UT ISNORMALIZEDTOUNITENERGY c
¯ \ UT \ DT
c
4HEAMBIGUITYFUNCTIONOFUT ISDEFINEDASTHESQUAREMAGNITUDEOFTHEAUTOCORRELATION FUNCTION
9U T FD \ C U T FD \
4HEAMBIGUITYFUNCTIONISINTERPRETEDASASURFACEABOVETHEDELAY DOPPLERSnFD PLANE4HEMAXIMUMVALUEOFTHEAMBIGUITYFUNCTIONISUNITYATTHEORIGINS FD
9 U T FD a 9 U
4HEVOLUMEUNDERTHEAMBIGUITYSURFACEISUNITYFORANYWAVEFORMUT c
c
¯ ¯ 9 U T FD DT DFD
c c
)NTHEGENERALCASE WHERETHEENERGYOFTHECOMPLEXENVELOPEISNOTNORMALIZED TOUNITY THEVALUEOFTHEAMBIGUITYFUNCTIONATTHEORIGINISEQUALTO% WHERE% ISTHEENERGYOFTHEBANDPASSSIGNALCORRESPONDINGTOUT ANDTHEVOLUMEUNDERTHE AMBIGUITYFUNCTIONISALSOEQUALTO% 4HENORMALIZATIONCONDITIONISEQUIVALENTTO THEASSUMPTIONTHATTHEENERGYOFTHEBANDPASSTRANSMITWAVEFORMEQUALS* -ATCHED&ILTER4IME2ESPONSE 4HEMATCHEDFILTERTIMERESPONSETOATARGET WITHDOPPLERSHIFTFD CANBEEXPRESSEDINTERMSOFTHEAUTOCORRELATIONFUNCTION4HE MATCHEDFILTERIMPULSERESPONSEWITHK ANDT IS
HMF T U T
4HEMATCHEDFILTERINPUTSIGNALISASSUMEDTOHAVEZEROTIMEDELAYANDADOPPLER SHIFTFD
ST UT E J P FD T
o4HETERMINOLOGYFORTHISFUNCTIONISNOTSTANDARDIZEDINTHELITERATURE7OODWARDUSESTHETERMCORRELATIONFUNC TION4HETERMTIME FREQUENCYAUTOCORRELATIONFUNCTIONISUSEDBY3PAFFORD4HESIGNSASSOCIATEDWITHSANDFD WITHINTHEINTEGRANDALSODIFFERINTHELITERATURE4HESTANDARDIZEDDEFINITIONPROPOSEDBY3INSKYAND7ANGIS USEDINTHISCHAPTER
05,3%#/-02%33)/.2!$!2
n°{£
4HE MATCHED FILTER OUTPUT SIGNAL YT IS FOUND BY CONVOLUTION OF ST WITH THE MATCHEDFILTERIMPULSERESPONSEHMFT c
YT
¯ UT ` U T ` T E J P F T ` DT ` D
c
#OMPARISONOFTHISRESULTWITHTHEDEFINITIONOFTHEAUTOCORRELATIONFUNCTIONSHOWS THATTHEMATCHEDFILTERRESPONSECANBEEXPRESSEDAS
YT 8U T FD
!SARESULT THEMATCHEDFILTERTIMERESPONSEFORATARGETWITHDOPPLERFREQUENCYFD ISATIME REVERSEDVERSIONOFTHEAUTOCORRELATIONFUNCTION #ONDITIONSFOR4ARGET2ESOLUTIONIN4IME$ELAYAND$OPPLER&REQUENCY !SSUMETHATTWOTARGETSWITHEQUALRADARCROSSSECTIONSAREPRESENTATTHESAMEANGULAR POSITION4HEFIRSTTARGETTERMEDTHEREFERENCETARGET ISLOCATEDATTHEORIGINOFTHE DELAY DOPPLERPLANEWITHZERORELATIVETIMEDELAYANDZERODOPPLERFREQUENCY ANDTHE SECONDTARGETISATRELATIVETIMEDELAYSANDDOPPLERFREQUENCYFD4HERELATIVETIMEDELAY ISPOSITIVEWHENTHESECONDTARGETISFARTHERINRANGETHANTHEREFERENCETARGETANDTHE DOPPLERFREQUENCYISPOSITIVEFORANINCOMINGTARGET4HEMATCHED FILTEROUTPUTPOWER FORTHEREFERENCETARGETISPROPORTIONALTOTHEAMBIGUITYFUNCTIONANDISGIVENBY
0REF 9U
4HEMATCHEDFILTEROUTPUTPOWERFORTHESECONDTARGET EVALUATEDATTHEPEAKOFTHE REFERENCETARGET IS
0 9US FD
4HESECONDTARGETISUNRESOLVEDFROMTHEREFERENCETARGETATLOCATIONSINTHEDELAY DOPPLERPLANEWHERE9US FD y
, ,
*2+LAUDER !#0RICE 3$ARLINGTON AND7*!LBERSHEIM h4HETHEORYANDDESIGNOFCHIRP RADARS v"ELL3YST4ECH* VOL PPn *ULY # % #OOK AND - "ERNFIELD 2ADAR SIGNALS !N )NTRODUCTION TO 4HEORY AND !PPLICATION .EW9ORK!CADEMIC0RESS # % #OOK AND * 0AOLILLO h! PULSE COMPRESSION PREDISTORTION FUNCTION FOR EFFICIENT SIDELOBE REDUCTIONINAHIGH POWERRADAR v0ROC)%%% PPn !PRIL 4 4 4AYLOR h$ESIGN OF LINE SOURCE ANTENNAS FOR NARROW BEAMWIDTH AND LOW SIDELOBES v )2% 4RANS VOL!0 PPn *ANUARY 2#(ANSEN h!PERTURETHEORY vIN-ICROWAVE3CANNING!NTENNAS VOL) 2#(ANSENED .EW9ORK!CADEMIC0RESS CHAP ('AUTIERAND04OURNOIS h3IGNALPROCESSINGUSINGSURFACE ACOUSTIC WAVEANDDIGITALCOMPO NENTS v)%%%0ROC VOL PT& PPn !PRIL ! * 3LOBODNIK *R h3URFACE ACOUSTIC WAVES AND 3!7 MATERIALS v 0ROC )%%% VOL PPn -AY 47"RISTOL h!COUSTICSURFACE WAVE DEVICEAPPLICATIONS v-ICROWAVE* VOL PPn *ANUARY
n°{Ó
2!$!2(!.$"//+
*7!RTHUR h-ODERN3!7 BASEDPULSECOMPRESSIONSYSTEMSFORRADARAPPLICATIONS v%LECTRONICS #OMMUNICATIONS%NGINEERING*OURNAL $ECEMBER 2#7ILLIAMSON h0ROPERTIESANDAPPLICATIONSOFREFLECTIVE ARRAYDEVICES v0ROC)%%% VOL PPn -AY '7*UDD h4ECHNIQUEFORREALIZINGLOWTIMESIDELOBELEVELSINSMALLCOMPRESSIONRATIOCHIRP WAVEFORMS v0ROC)%%%5LTRASONICS3YMP PPn !0OHL #0OSCH &3EIFERT AND,2EINDL h7IDEBANDCOMPRESSIVERECEIVERWITH3!7CONVOLVER v )%%%5LTRASONICS3YMPOSIUM PPn 83HOU *8U (7ANG AND18U h3!7PULSECOMPRESSIONSYSTEMSWITHLOWERSIDELOBES v !SIA0ACIFIC-ICROWAVE#ONFERENCE PPn 4-URAKAMI h/PTIMUMWAVEFORMSTUDYFORCOHERENTPULSEDOPPLER v2#!&INAL2EPT PREPARED FOR/FFICEOF.AVAL2ESEARCH #ONTRACT.ONR X !$ &EBRUARY 4#OLLINSAND0!TKINS h.ONLINEARFREQUENCYMODULATIONCHIRPSFORACTIVESONAR v)%%0ROC 2ADAR 3ONAR.AVIG VOL NO PPn $ECEMBER ,26ARSCHNEYAND$4HOMAS h3IDELOBEREDUCTIONFORMATCHEDRANGEPROCESSING v)%%% 2ADAR#ONFERENCE PPn .,EVANONAND%-OZESON 2ADAR3IGNALS .EW9ORK)%%%0RESS *OHN7ILEY3ONS )NC PP 2 ( "ARKER h'ROUP SYNCHRONIZATION OF BINARY DIGITAL SYSTEMS v IN #OMMUNICATION 4HEORY 7*ACKSONED .EW9ORK!CADEMIC0RESS PPn 0*%DMONSON #+#AMPBELL AND3&9UEN h3TUDYOF3!7PULSECOMPRESSIONUSING¾ "ARKERCODESWITHQUADRIPHASE)$4GEOMETRIES v)%%%5LTRASONICS3YMPOSIUM PPn 4 &ELHAUER h$ESIGN AND ANALYSIS OF NEW 0N K POLYPHASE PULSE COMPRESSION CODES v )%%% 4RANSACTIONSON!EROSPACEAND%LECTRONICS3YSTEMS VOL NO PPn *ULY 2 4URYN AND * 3TOVER h/N BINARY SEQUENCES v 0ROC !M -ATH 3OC VOL PP n *UNE $',UENBURGER h/N"ARKERCODESOFEVENLENGTH v0ROC)%%% VOL PPn *ANUARY 24URYN h/N "ARKER CODES OF EVEN LENGTH v 0ROC )%%% CORRESPONDENCE VOL P 3EPTEMBER ,"OMERAND-!NTWEILER h0OLYPHASE"ARKERSEQUENCES v%LECTRONICS,ETTERS VOL NO PPn .OVEMBER (-EIKLE -ODERN2ADAR3YSTEMS .ORWOOD -!!RTECH(OUSE P " , ,EWIS h2ANGE TIME SIDELOBE REDUCTION TECHNIQUE FOR &- DERIVED POLYPHASE 0# CODES v )%%%4RANSACTIONSON!EROSPACEAND%LECTRONICS3YSTEMS VOL NO PPn *ULY 770ETERSONAND%*7ELDON *R %RROR#ORRECTING#ODES #AMBRIDGE-)40RESS APP# -)3KOLNIK )NTRODUCTIONTO2ADAR3YSTEMS RD%D .EW9ORK-C'RAW(ILL P .,EVANONAND%-OZESON 2ADAR3IGNALS .EW9ORK)%%%0RESS *OHN7ILEY3ONS )NC PPn ,"MERAND-!NTWEILER h0OLYPHASE"ARKERSEQUENCES v%LECTRONICS,ETTERS VOL NO PPn .OVEMBER 7 $ 7IRTH 2ADAR 4ECHNIQUES 5SING !RRAY !NTENNAS )%% 2ADAR 3ONAR .AVIGATION AND !VIONICS3ERIES ,ONDON4HE)NSTITUTIONOF%LECTRICAL%NGINEERS 2 , &RANK h0OLYPHASE CODES WITH GOOD NONPERIODIC CORRELATION PROPERTIES v )%%% 4RANS VOL)4 PPn *ANUARY ",,EWISAND&&+RETSCHMER *R h!NEWCLASSOFPOLYPHASEPULSECOMPRESSIONCODESAND TECHNIQUES v)%%%4RANS VOL!%3 PPn -AY3EECORRECTION )%%%4RANS VOL!%3 P -AY " , ,EWIS h2ANGE TIME SIDELOBE REDUCTION TECHNIQUE FOR &- DERIVED POLYPHASE 0# CODES v )%%%4RANSACTIONSON!EROSPACEAND%LECTRONICS3YSTEMS VOL NO PPn *ULY
05,3%#/-02%33)/.2!$!2
n°{Î
",,EWISAND&&+RETSCHMER *R h,INEAR&REQUENCY-ODULATION$ERIVED0OLYPHASE0ULSE #OMPRESSION #ODES v )%%% 4RANS ON !EROSPACE AND %LECTRONICS 3YSTEMS !%3 NO PPn 3EPTEMBER * 7 4AYLOR AND ( * "LINCHIKOFF h1UADRIPHASE CODE A RADAR PULSE COMPRESSION SIGNAL WITH UNIQUE CHARACTERISTICS v )%%%4RANS!EROSPACE AND %LECTRONIC 3YSTEMS VOL NO PPn -ARCH (*"LINCHIKOFF h2ANGESIDELOBEREDUCTIONFORTHEQUADRIPHASECODES v)%%%4RANS!EROSPACE AND%LECTRONIC3YSTEMS VOL NO !PRIL PPn .,EVANON h3TEPPED FREQUENCYPULSE TRAINRADARSIGNAL v)%%0ROC 2ADAR3ONAR.AVIGATION VOL NO $ECEMBER !72IHACZEK 0RINCIPLESOF(IGH 2ESOLUTION2ADAR .EW9ORK-C'RAW (ILL"OOK#OMPANY CHAP *0$ONOHUEAND&-)NGELS h!MBIGUITYFUNCTIONPROPERTIESOFFREQUENCYHOPPEDRADARSONAR SIGNALS v0ROCOFTHE3OUTHEASTCON SESSION" PPn *0#OSTAS h!STUDYOFACLASSOFDETECTIONWAVEFORMSHAVINGNEARLYIDEALRANGE DOPPLERAMBI GUITYPROPERTIES v0ROCOFTHE)%%% VOL NO !UGUST "2-AHAFZA 2ADAR3YSTEMS!NALYSISAND$ESIGNUSING-!4,!" "OCA2ATON#HAPMAN (ALL#2# " - 0OPVIK h.EW CONSTRUCTION OF #OSTAS SEQUENCES v %LECTRONIC ,ETTERS VOL NO *ANUARY -)3KOLNIK )NTRODUCTIONTO2ADAR3YSTEMS RD%D .EW9ORK-C'RAW(ILL PPn $0-ORGAN h3URFACEACOUSTICWAVEDEVICESANDAPPLICATIONS v5LTRASONICS VOL PPn ,/%BERAND((3OULE *R h$IGITALGENERATIONOFWIDEBAND,&-WAVEFORMS v)%%%)NT 2ADAR#ONF2EC PPn !$ '303DIRECTDIGITALSYNTHESIZERDATASHEET 2EV! !NALOG$EVICES .ORWOOD -!AVAILABLEATWWWANALOGCOM *+(ARTTAND,&3HEATS h!PPLICATIONOFPIPELINE&&4TECHNOLOGYINRADARSIGNALANDDATA PROCESSING v%!3#/.2EC PPnREPRINTEDIN$AVID+"ARTON 2ADARS VOL !NN!RBOR"OOKSON$EMAND5-) 0 % "LANKENSHIP AND % - (OFSTETTER h$IGITAL PULSE COMPRESSION VIA FAST CONVOLUTION v )%%% 4RANS ON !COUSTICS 3PEECH AND 3IGNAL 0ROCESSING VOL!330 NO PP n !PRIL , 7 -ARTINSON AND 2 * 3MITH h$IGITAL MATCHED FILTERING WITH PIPELINED FLOATING POINT FAST &OURIER TRANSFORMS &&4S v )%%% 4RANS ON !COUSTICS 3PEECH AND 3IGNAL 0ROCESSING VOL!330 NO PPn !PRIL ,%0ELLON h!DOUBLE.YQUISTDIGITALPRODUCTDETECTORFORQUADRATURESAMPLING v)%%%4RANS ON3IGNAL0ROCESSING VOL NO PPn '! 3HAW AND 3 # 0OHLIG h)1 BASEBAND DEMODULATION IN THE 2!330 3!2 BENCHMARK v 0ROJECT2EPORT2!330 -ASSACHUSETTS)NSTITUTEOF4ECHNOLOGY ,INCOLN,ABORATORY !UGUST HTTPWWWLLMITEDULLRASSPDOCUMENTSHTML - ! 2ICHARD h$IGITAL )1 v 3ECTION IN &UNDAMENTALS OF 2ADAR 3IGNAL 0ROCESSING .EW9ORK-C'RAW (ILL , 2 2ABINER AND " 'OLD 4HEORY AND!PPLICATION OF $IGITAL 3IGNAL 0ROCESSING %NGLEWOOD #LIFFS .*0RENTICE (ALL )NC CHAP **'OSTIN h4HE'%SOLID STATERADAR v)%%%%!3#/. PPn %, #OLE 0!$E#ESARE -*-ARTINEAUS 23"AKER AND3-"USWELL h!32 !NEXT GENERATIONSOLID STATEAIRTRAFFICCONTROLRADAR v)%%%2ADAR#ONFERENCE PPn 7*#APUTI *R h3TRETCH!TIME TRANSFORMATIONTECHNIQUE v)%%%4RANS VOL!%3 PPn -ARCH 7*#APUTI h!TECHNIQUEFORTHETIME TRANSFORMATIONOFSIGNALSANDITSAPPLICATIONTODIRECTIONAL SYSTEMS v4HE2ADIOAND%LECTRONIC%NGINEER PPn -ARCH
n°{{
2!$!2(!.$"//+
7*#APUTI h3WEPT HETERODYNEAPPARATUSFORCHANGINGTHETIME BANDWIDTHPRODUCTOFASIGNAL v 530ATENT .OVEMBER 7*#APUTI h0ULSE TYPEOBJECTDETECTIONAPPARATUS v530ATENT .OVEMBER +22OTH -%!USTIN $*&REDIANI '(+NITTEL AND!6-RSTIK h4HE+IERNANREENTRY MEASUREMENTSSYSTEMON+WAJALEIN!TOLL v4HE,INCOLN,ABORATORY4ECHNICAL*OURNAL VOL NO $2"ROMAGHIMAND*00ERRY h!WIDEBANDLINEARFMRAMPGENERATORFORTHELONG RANGEIMAG INGRADAR v)%%%4RANS -ICROWAVE4HEORYAND4ECHNIQUES VOL-44 NO PPn -AY '2!RMSTRONGAND-!XELBANK h$ESCRIPTIONOFTHELONG RANGEIMAGINGRADAR v0ROJECT2EPORT 03) -ASSACHUSETTS)NSTITUTEOF4ECHNOLOGY ,INCOLN,ABORATORY .OVEMBER -$!BOUZAHRAAND2+!VENT h4HE K7MILLIMETER WAVERADARATTHE+WAJALEIN!TOLL v )%%%!NTENNASAND0ROPAGATION-AGAZINE VOL NO PPn !PRIL 7#+ELLOG h$IGITALPROCESSINGRESCUESHARDWAREPHASEERRORS v-ICROWAVES2& PPn .OVEMBER # ,4EMES h3IDELOBE SUPPRESSION IN A RANGE CHANNEL PULSE COMPRESSION RADAR v )2%4RANS VOL-), PPn !PRIL %&ILERAND*(ARTT h#/"2!$!.%WIDEBANDPULSECOMPRESSIONSYSTEM v)%%%%!3#/. PP !n - 3 3TEIN AND * * *ONES h-ODERN #OMMUNICATION 0RINCIPLES WITH !PPLICATION TO $IGITAL 3IGNALING v.EW9ORK-C'RAW (ILL 0 - 7OODWARD 0ROBABILITY AND )NFORMATION 4HEORY WITH !PPLICATION TO 2ADAR 0ERGAMON 0RESS $"RANDWOOD h&OURIER4RANSFORMS vIN2ADARAND3IGNAL0ROCESSING "OSTON!RTECH(OUSE '7$ELEY h7AVEFORMDESIGN vIN2ADAR(ANDBOOK -)3KOLNIKED ST%D .EW9ORK -C'RAW (ILL ! ) 3INSKY h7AVEFORM SELECTION AND PROCESSINGv IN 2ADAR 4ECHNOLOGY % "ROOKNER ED "OSTON!RTECH(OUSE #HAP #7(ELSTROM 3TATISTICAL4HEORYOF3IGNAL$ETECTION ND%D 0ERGAMON0RESS ' , 4URIN h!N INTRODUCTION TO MATCHED FILTERS v )2% 4RANS )NFORM 4HEORY VOL )4 PPn *UNE $+"ARTON -ODERN2ADAR3YSTEM!NALYSISAND-ODELING #ANTON -!!RTECH(OUSE)NC #HAP P &%.ATHANSON *02EILLY AND-.#OHEN 2ADAR$ESIGN0RINCIPLES3IGNAL0ROCESSINGAND THE%NVIRONMENT ND%D.EW9ORK-C'RAW (ILL CHAP P !72IHACZEK h2ADARSIGNALDESIGNFORTARGETRESOLUTION v0ROC)%%% VOL PPn &EBRUARY !)3INSKYAND#07ANG h3TANDARDIZATIONOFTHEDEFINITIONOFTHEAMBIGUITYFUNCTION v)%%% 4RANS!EROSPACEAND%LECTRONIC3YSTEMS PPn *ULY )%%%STANDARDRADARDEFINITIONS )%%%3TD 4HE)NSTITUTIONOF%LECTRICALAND%LECTRONIC %NGINEERS .EW9ORK .9 4HEAMBIGUITYFUNCTIONISDEFINEDONPAGEUSINGTHESTANDARD IZEDDEFINITIONGIVENBY3INSKYAND7ANG ,*3PAFFORD h/PTIMUMRADARSIGNALPROCESSINGINCLUTTER v)%%%4RANS)NFORMATION4HEORY VOL)4 NO PPn 3EPTEMBER
#HAPTER
/À>V}Ê,>`>À i>Ê °ÊÜ>À` #ONSULTANTTO)44)NDUSTRIES )NC
°£Ê /," 1 /" 4YPICALTRACKINGRADARSHAVEAPENCILBEAMTORECEIVEECHOESFROMASINGLETARGETAND TRACK THE TARGET IN ANGLE RANGE ANDOR DOPPLER )TS RESOLUTION CELLDEFINED BY ITS ANTENNABEAMWIDTH TRANSMITTERPULSELENGTHEFFECTIVEPULSELENGTHMAYBESHORTER WITHPULSECOMPRESSION ANDORDOPPLERBANDWIDTHISUSUALLYSMALLCOMPAREDWITH THATOFASEARCHRADARANDISUSEDTOEXCLUDEUNDESIREDECHOESORSIGNALSFROMOTHER TARGETS CLUTTER ANDCOUNTERMEASURES%LECTRONICBEAM SCANNINGPHASEDARRAYRADARS MAYTRACKMULTIPLETARGETSBYSEQUENTIALLYDWELLINGUPONANDMEASURINGEACHTARGET WHILEEXCLUDINGOTHERECHOORSIGNALSOURCES "ECAUSEOFITSNARROWBEAMWIDTH TYPICALLYFROMAFRACTIONOFnTOORn TRACKING RADARSUSUALLYDEPENDUPONINFORMATIONFROMASURVEILLANCERADAROROTHERSOURCEOF TARGETLOCATIONTOACQUIRETHETARGET IE TOPLACEITSBEAMONORINTHEVICINITYOFTHE TARGETBEFOREINITIATINGATRACK3CANNINGOFTHEBEAMWITHINALIMITEDANGLESECTORMAY BENEEDEDTOACQUIRETHETARGETWITHINITSBEAMANDCENTERTHERANGE TRACKINGGATESON THEECHOPULSEPRIORTOLOCKINGONTHETARGETORCLOSINGTHETRACKINGLOOPS4HEGATEACTS LIKEAFAST ACTINGON OFFSWITCHTHATTURNSTHERECEIVERhONvATTHELEADINGEDGEOFTHE TARGETECHOPULSEANDhOFFvATTHEENDOFTHETARGETECHOPULSETOELIMINATEUNDESIRED ECHOES4HERANGE TRACKINGSYSTEMPERFORMSTHETASKOFKEEPINGTHEGATECENTEREDON THETARGETECHO ASDESCRIBEDIN3ECTION 4HE PRIMARY OUTPUT OF TRACKING RADAR IS THE TARGET LOCATION DETERMINED FROM THE POINTINGANGLESOFTHEBEAMANDPOSITIONOFITSRANGE TRACKINGGATES4HEANGLELOCA TION IS THE DATA OBTAINED FROM SYNCHROS AND ENCODERS ON THE ANTENNA TRACKING AXES ORDATAFROMABEAM POSITIONINGCOMPUTERONANELECTRONIC SCANPHASEDARRAYRADAR )NSOMECASES TRACKINGLAGISMEASUREDBYCONVERTINGTRACKING LAG ERRORVOLTAGESFROM THETRACKINGLOOPSTOUNITSOFANGLE4HISDATAISUSEDTOADDTOORSUBTRACTFROMTHE ANGLESHAFTPOSITIONDATAFORREAL TIMECORRECTIONOFTRACKINGLAG 4HEREAREALARGEVARIETYOFTRACKING RADARSYSTEMS INCLUDINGSOMETHATACHIEVE SIMULTANEOUSLY BOTH SURVEILLANCE AND TRACKING FUNCTIONS ! WIDELY USED TYPE OF TRACKINGRADARANDTHEONEDISCUSSEDINDETAILINTHISCHAPTERISAGROUND BASEDSYS TEMCONSISTINGOFAPENCIL BEAMANTENNAMOUNTEDONAROTATABLEPLATFORMWITHSERVO MOTORDRIVEOFITSAZIMUTHANDELEVATIONPOSITIONTOFOLLOWATARGET&IGUREA %RRORS IN POINTING DIRECTION ARE DETERMINED BY SENSING THE ANGLE OF ARRIVAL OF THE ECHOWAVEFRONTANDCORRECTEDBYPOSITIONINGTHEANTENNATOKEEPTHETARGETCENTERED °£
°Ó
2!$!2(!.$"//+
INTHEBEAM-ODERNREQUIREMENTSFORSIMULTANEOUSPRECISIONTRACKINGOFMULTIPLE TARGETS HAS DRIVEN THE DEVELOPMENT OF THE ELECTRONIC SCAN ARRAY MONOPULSE RADAR WITHTHECAPABILITYTOSWITCHITSBEAMPULSE TO PULSEAMONGMULTIPLETARGETS4HE !.-03 SHOWNIN&IGUREBISANEXAMPLEOFAHIGHLYVERSATILEELECTRONICSCAN MONOPULSEMISSILE RANGEINSTRUMENTATIONRADAR 4HE PRINCIPAL APPLICATIONS OF PRECISION TRACKING RADAR ARE WEAPON CONTROL AND MISSILE RANGEINSTRUMENTATION)NBOTHAPPLICATIONS AHIGHDEGREEOFPRECISIONANDAN ACCURATEPREDICTIONOFFUTUREPOSITIONOFTHETARGETAREGENERALLYREQUIRED4HEEARLIEST USEOFTRACKINGRADARWASGUNFIRECONTROL4HEAZIMUTHANGLE ELEVATIONANGLE ANDTHE RANGETOTHETARGETWEREMEASURED ANDFROMTHERATEOFCHANGEOFTHESEPARAMETERS THE VELOCITYVECTOROFTHETARGETSPEEDANDDIRECTION WASCOMPUTEDANDITSFUTUREPOSITION PREDICTED4HISINFORMATIONWASUSEDTOMOVETHEGUNTOLEADTHETARGETANDSETTHEFUZE DELAY4HETRACKINGRADARPERFORMSASIMILARROLEINPROVIDINGGUIDANCEINFORMATION ANDSTEERINGCOMMANDSFORMISSILECONTROL )NMISSILE RANGEINSTRUMENTATION THETRACKING RADAROUTPUTISUSEDTOMEASURETHE TRAJECTORYOFTHEMISSILEANDTOPREDICTFUTUREPOSITION4RACKINGRADARSAREUSEDTOCOM PUTETHEIMPACTPOINTOFALAUNCHEDMISSILECONTINUOUSLYDURINGTHELAUNCHPHASEINCASE OFMISSILEFAILUREFORRANGESAFETY)FTHEIMPACTPOINTAPPROACHESAPOPULATEDOROTHER CRITICALAREA THEMISSILEISDESTROYED-ISSILE RANGEINSTRUMENTATIONRADARSARENORMALLY USEDWITHABEACONPULSEREPEATER TOPROVIDEAPOINT SOURCEECHOUSUALLYITSPULSE ISDELAYEDTOSEPARATEITFROMTHETARGETECHOANDWITHHIGHSIGNAL TO NOISERATIO TO ACHIEVEPRECISIONTRACKINGONTHEORDEROFMILINANGLEANDMINRANGE
A
B
&)'52% A !.&01 # BAND MONOPULSE PRECISION TRACKING RADAR INSTALLATION AT THE .!3! 7ALLOPS)SLAND3TATION 6!)THASA FT DIAMETERDISHANDASPECIFIEDTRACKINGPRECISIONOFMRADRMS B !.-03 # BAND ELECTRONIC SCAN PHASED ARRAY -ULTI /BJECT4RACKING 2ADAR -/42 INSTALLED AT THE7HITE3ANDS-ISSILE2ANGE0HOTOOFTHE!.-03 COURTESYOFTHE7HITE3ANDS-ISSILE2ANGEAND ,OCKHEED-ARTIN
42!#+).'2!$!2
°Î
4HISCHAPTERDESCRIBESTHEMONOPULSESIMULTANEOUSLOBINGWITHEITHERPHASECOM PARISONORAMPLITUDECOMPARISON CONICAL SCAN ANDSEQUENTIALLOBINGTRACKING RADAR TECHNIQUESWITHTHEMAINEMPHASISONTHEAMPLITUDE COMPARISONMONOPULSESIMUL TANEOUSLOBING RADAR
°ÓÊ " "*1 - Ê- 1 / "1-Ê " ® 4HE SUSCEPTIBILITY OF CONICAL SCANNING AND SEQUENTIAL LOBING TRACKING TECHNIQUES TO ECHO AMPLITUDE FLUCTUATIONS AND AMPLITUDE JAMMING AS DESCRIBED IN 3ECTION WASTHEMAJORREASONFORTHEDEVELOPMENTOFTRACKINGRADARTHATPROVIDESSIMULTANE OUSLY ALL THE NECESSARY LOBES FOR ANGLE ERROR SENSING 4HIS REQUIRED THAT THE OUTPUT FROMTHELOBESBECOMPAREDSIMULTANEOUSLYONASINGLEPULSE ELIMINATINGTHEEFFECTS OFECHOAMPLITUDECHANGEWITHTIME4HETECHNIQUETOACCOMPLISHTHISWASINITIALLY CALLEDSIMULTANEOUSLOBING WHICHWASDESCRIPTIVEOFTHETECHNIQUE,ATER THETERM MONOPULSEWASCOINED REFERRINGTOTHEABILITYTOOBTAINANGLEERRORINFORMATIONON ASINGLEPULSE)THASBECOMETHECOMMONLYUSEDNAMEFORTHISTRACKINGTECHNIQUE EVENTHOUGH THELOBESAREGENERATEDSIMULTANEOUSLYANDMONOPULSETRACKINGCANBE PERFORMEDWITH#7RADAR 4HEORIGINALMONOPULSETRACKINGRADARSSUFFEREDINANTENNAEFFICIENCYANDCOM PLEXITYOFMICROWAVECIRCUITRYBECAUSEWAVEGUIDESIGNAL COMBININGCIRCUITRYWASA RELATIVELYNEWART4HESEPROBLEMSWEREOVERCOMEANDMONOPULSERADAR WITHMOD ERNCOMPACTOFF THE SHELFPROCESSINGCIRCUITRY CANREADILYOUTPERFORMSCANNINGAND LOBINGSYSTEMS4HEMONOPULSETECHNIQUEALSOHASANINHERENTCAPABILITYFORHIGH PRECISIONANGLEMEASUREMENTBECAUSEITSFEEDSTRUCTUREISCOMPACTWITHSHORTSIGNAL PATHSANDRIGIDLYMOUNTEDWITHNOMOVINGPARTS4HISHASMADEPOSSIBLETHEDEVEL OPMENTOFPENCIL BEAMTRACKINGRADARSTHATMEETMISSILE RANGEINSTRUMENTATION RADAR REQUIREMENTSOFnANGLE TRACKINGPRECISION 4HISCHAPTERISDEVOTEDTOTRACKINGRADAR BUTMONOPULSETECHNIQUESAREUSEDIN OTHERSYSTEMSINCLUDINGHOMINGDEVICES DIRECTIONFINDERS ANDSOMESEARCHRADARS (OWEVER MOSTOFTHEBASICPRINCIPLESANDLIMITATIONSOFMONOPULSEAPPLYFORALLAPPLI CATIONS-OREGENERALCOVERAGEISFOUNDIN3HERMANAND,EONOVAND&ORMICHEV !MPLITUDE #OMPARISON-ONOPULSE !METHODFORVISUALIZINGTHEOPERATIONOF ANAMPLITUDE COMPARISONRECEIVERISTOCONSIDERTHEECHOSIGNALATTHEFOCALPLANEOF ANANTENNA4HEECHOISFOCUSEDTOAFINITESIZEhSPOTv4HEhSPOTvISCENTEREDONTHE FOCALPLANEWHENTHETARGETISONTHEANTENNAAXISANDMOVESOFFCENTERWHENTHETAR GETMOVESOFFAXIS4HEANTENNAFEEDISLOCATEDATTHEFOCALPOINTTORECEIVEMAXIMUM ENERGYFROMATARGETONAXIS 4HEAMPLITUDE COMPARISONFEEDISDESIGNEDTOSENSEANYFEEDPLANEDISPLACEMENT OFTHESPOTFROMTHECENTEROFTHEFOCALPLANE!MONOPULSEFEEDUSINGTHEFOUR HORN SQUARE FOR EXAMPLE WOULD BE CENTERED AT THE FOCAL PLANE )T PROVIDES SYMMETRY SOTHATWHENTHESPOTISCENTERED EQUALENERGYFALLSONEACHOFTHEFOURHORNS4HE RADARSENSESTARGETDISPLACEMENTFROMTHEANTENNAAXISTHATSHIFTSTHESPOTOFFOFTHE CENTEROFTHEFOCALPLANEBYMEASURINGTHERESULTANTUNBALANCEOFENERGYRECEIVED INTHEFOURHORNS4HISISACCOMPLISHEDBYUSEOFMICROWAVEWAVEGUIDEHYBRIDSTO SUBTRACTOUTPUTSOFPAIRSOFHORNS PROVIDINGASENSITIVEDEVICETHATGIVESSIGNALOUT PUTWHENTHEREISANUNBALANCECAUSEDBYTHETARGETBEINGOFFAXIS4HE2&CIRCUITRY FOR A CONVENTIONAL FOUR HORN SQUARE FEED SEE &IGURE SUBTRACTS THE OUTPUT OF
°{
2!$!2(!.$"//+
&)'52% -ICROWAVE COMPARATOR CIRCUITRY USED WITH A FOUR HORN MONOPULSEFEED
THELEFTPAIRFROMTHEOUTPUTOFTHERIGHTPAIRTOSENSEANYUNBALANCEINTHEAZIMUTH DIRECTION)TALSOSUBTRACTSTHEOUTPUTOFTHETOPPAIRFROMTHEOUTPUTOFTHEBOTTOM PAIRTOSENSEANYUNBALANCEINTHEELEVATIONDIRECTION)NADDITION THECIRCUITRYADDS THEOUTPUTOFALLFOURHORNSFORASUMSIGNALFORDETECTION MONOPULSEPROCESSING ANDRANGETRACKING 4HECOMPARATORSHOWNIN&IGUREISTHECIRCUITRYTHATPERFORMSTHEADDITIONAND SUBTRACTIONOFTHEFEEDHORNOUTPUTSTOOBTAINMONOPULSESUMANDDIFFERENCESIGNALS)T ISILLUSTRATEDWITHHYBRID 4ORMAGIC 4 WAVEGUIDECOMPONENTS4HESEAREFOUR PORT DEVICESTHAT INBASICFORM HAVETHEINPUTSANDOUTPUTSLOCATEDATRIGHTANGLESTOEACH OTHER(OWEVER THEMAGIC4SHAVEBEENDEVELOPEDINCONVENIENThFOLDEDvCONFIGU RATIONSFORAVERYCOMPACTCOMPARATOR4HEPERFORMANCEOFTHESEANDOTHERSIMILAR FOUR PORTDEVICESISDESCRIBEDIN#HAPTEROF3HERMAN 4HESUBTRACTOROUTPUTSARECALLEDDIFFERENCESIGNALS WHICHAREZEROWHENTHETARGET ISONAXIS INCREASINGINAMPLITUDEWITHINCREASINGDISPLACEMENTOFTHETARGETFROMTHE ANTENNAAXIS4HEDIFFERENCESIGNALSALSOCHANGEnINPHASEFROMONESIDEOFCENTER TOTHEOTHER4HESUMOFALLFOUR HORNOUTPUTSPROVIDESAREFERENCESIGNALTOCONTROL ANGLE TRACKINGSENSITIVITYVOLTSPERDEGREEOFERROR TOREMAINCONSTANT EVENTHOUGH THETARGETECHOSIGNALMAYVARYOVERALARGEDYNAMICRANGE4HISISACCOMPLISHEDBY AUTOMATICGAINCONTROL!'# TOKEEPTHESUMSIGNALOUTPUTANDANGLE TRACKINGLOOP GAINSCONSTANTFORSTABLEAUTOMATICANGLETRACKING &IGUREISABLOCKDIAGRAMOFTYPICALMONOPULSERADARS4HESUMSIGNAL ELEVA TIONDIFFERENCESIGNAL ANDAZIMUTHDIFFERENCESIGNALAREEACHCONVERTEDTOINTERMEDI ATEFREQUENCY)& USINGACOMMONLOCALOSCILLATORTOMAINTAINRELATIVEPHASEAT)& 4HE)&SUM SIGNALOUTPUTISDETECTEDANDPROVIDESTHEVIDEOINPUTTOTHERANGETRACKER 4HERANGETRACKERMEASURESANDTRACKSTHETIMEOFARRIVALOFTHEDESIREDTARGETECHO ANDPROVIDESGATEPULSESTHATTURNONTHERADARRECEIVERCHANNELSONLYDURINGTHEBRIEF PERIODWHENTHEDESIREDECHOISEXPECTED4HEGATEDVIDEOISUSEDTOGENERATETHEDC
42!#+).'2!$!2
°x
&)'52% "LOCKDIAGRAMOFACONVENTIONALMONOPULSETRACKINGRADAR
VOLTAGEPROPORTIONALTOTHEMAGNITUDEOFTHE3SIGNALOR¨3¨FORTHE!'#OFALLTHREE)& AMPLIFIERCHANNELS4HE!'#MAINTAINSCONSTANTANGLE TRACKINGSENSITIVITYVOLTSPER DEGREEERROR EVENTHOUGHTHETARGETECHOSIGNALVARIESOVERALARGEDYNAMICRANGE BY CONTROLLINGGAINORDIVIDINGBY¨3¨!'#ISNECESSARYTOKEEPTHEGAINOFTHEANGLE TRACKINGLOOPSCONSTANTFORSTABLEAUTOMATICANGLETRACKING3OMEMONOPULSESYSTEMS SUCHASTHETWO CHANNELMONOPULSE CANPROVIDEINSTANTANEOUS!'#ORNORMALIZING BYUSEOFLOGDETECTORSASDESCRIBEDLATERINTHISSECTION 4HESUMSIGNALATTHE)&OUTPUTALSOPROVIDESAREFERENCESIGNALTOPHASEDETECTORS THATDERIVEANGLE TRACKING ERRORVOLTAGESFROMTHEDIFFERENCESIGNALS4HEPHASEDETEC TORSAREESSENTIALLYDOT PRODUCTDEVICESPRODUCINGTHEOUTPUTVOLTAGE
E
\3\ \$\ COS Q \ 3 \ \ $\
OR
E
$ COS Q \3\
WHERE E ANGLE ERROR DETECTOROUTPUTVOLTAGE
¨3 ¨ MAGNITUDEOFSUMSIGNAL
¨$ ¨ MAGNITUDEOFDIFFERENCESIGNAL
P PHASEANGLEBETWEENSUMANDDIFFERENCESIGNALS 4HEDOT PRODUCTERRORDETECTORISONLYONEOFAWIDEVARIETYOFMONOPULSEANGLE ERROR DETECTORSDESCRIBEDIN#HAPTEROF3HERMAN .ORMALLY PISEITHERnORnWHENTHERADARISPROPERLYADJUSTED ANDTHEONLY PURPOSEOFTHEPHASE SENSITIVECHARACTERISTICISTOPROVIDEAPLUSORMINUSPOLARITYCOR RESPONDINGTOP nANDP n RESPECTIVELY GIVINGA ORnPOLARITYTOTHEANGLE ERROR DETECTOROUTPUTTOINDICATETOTHESERVOWHICHDIRECTIONTODRIVETHEPEDESTAL )NAPULSEDTRACKINGRADAR THEANGLE ERROR DETECTOROUTPUTISBIPOLARVIDEOTHAT IS ITISAVIDEOPULSEWITHANAMPLITUDEPROPORTIONALTOTHEANGLEERRORANDWHOSE POLARITYPOSITIVEORNEGATIVE CORRESPONDSTOTHEDIRECTIONOFTHEERROR4HISVIDEO IS TYPICALLY PROCESSED BY A SAMPLE AND HOLD CIRCUIT THAT CHARGES A CAPACITOR TO THE PEAKVIDEO PULSEVOLTAGEANDHOLDSTHECHARGEUNTILTHENEXTPULSE ATWHICHTIMETHE CAPACITORISDISCHARGEDANDRECHARGEDTOTHENEWPULSELEVEL7ITHMODERATELOW PASS FILTERING THISGIVESTHEDCERRORVOLTAGEOUTPUTTOTHESERVOAMPLIFIERTOCORRECTTHE ANTENNAPOSITION
°È
2!$!2(!.$"//+
4HE THREE CHANNEL AMPLITUDE COMPARISON MONOPULSE TRACKING RADAR IS THE MOST COMMONLY USED MONOPULSE SYSTEM (OWEVER THE THREE SIGNALS MAY SOMETIMES BE COMBINEDINOTHERWAYSTOPERFORMWITHATWO CHANNELRECEIVERSYSTEMASDESCRIBED LATERINTHISSECTION USEDINSOMECURRENTSURFACE TO AIRMISSILE3!- SYSTEMS -ONOPULSE !NTENNA&EED4ECHNIQUES -ONOPULSE RADARFEEDSMAYHAVEANYOF AVARIETYOFCONFIGURATIONS3INGLEAPERTURESAREALSOEMPLOYEDBYUSEOFHIGHER ORDER WAVEGUIDEMODESTOEXTRACTANGLE ERROR SENSINGDIFFERENCESIGNALS4HEREAREMANY TRADEOFFSINFEEDDESIGNBECAUSEOPTIMUMSUMANDDIFFERENCESIGNALS LOWSIDELOBE LEVELS SELECTABLEPOLARIZATIONCAPABILITY ANDSIMPLICITYCANNOTALLBEFULLYSATISFIED SIMULTANEOUSLY4HETERMSIMPLICITYREFERSNOTONLYTOCOSTSAVINGSBUTALSOTOTHEUSE OFNONCOMPLEXCIRCUITRY WHICHISNECESSARYTOPROVIDEABROADBANDSYSTEMWITHGOOD BORESIGHTSTABILITYTOMEETPRECISION TRACKINGREQUIREMENTS"ORESIGHTISTHEELECTRICAL AXISOFTHEANTENNAORTHEANGULARLOCATIONOFASIGNALSOURCEWITHINTHEANTENNABEAM ATWHICHTHEANGLE ERROR DETECTOROUTPUTSGOTOZERO 3OMEOFTHETYPICALMONOPULSEFEEDSAREDESCRIBEDTOSHOWTHEBASICRELATIONSAND TRADEOFFS INVOLVED IN THE VARIOUS PERFORMANCE FACTORS AND HOW THE MORE IMPORTANT FACTORSCANBEOPTIMIZEDBYAFEEDCONFIGURATIONBUTATTHEPRICEOFLOWERPERFORMANCE INOTHERAREAS-ANYNEWTECHNIQUESHAVEBEENADDEDSINCETHEORIGINALFOUR HORN SQUAREFEEDINORDERTOPROVIDEGOODOREXCELLENTPERFORMANCEINALLDESIREDFEEDCHAR ACTERISTICSINAWELL DESIGNEDMONOPULSERADAR 4HEORIGINALFOUR HORNSQUAREMONOPULSEFEEDISINEFFICIENTBECAUSETHEOPTIMUM FEEDSIZEAPERTUREFORTHEDIFFERENCESIGNALSISAPPROXIMATELYTWICETHEOPTIMUMSIZE FORTHESUMSIGNAL#ONSEQUENTLY ANINTERMEDIATESIZEISTYPICALLYUSEDWITHASIGNIFI CANTCOMPROMISEFORBOTHSUMANDDIFFERENCESIGNALS4HEOPTIMUMFOUR HORNSQUARE FEED WHICHISSUBJECTTOTHISCOMPROMISE DESCRIBEDIN3HERMAN ISBASEDONMINI MIZINGTHEANGLEERRORCAUSEDBYRECEIVERTHERMALNOISE(OWEVER IFSIDELOBESAREA PRIMECONSIDERATION ASOMEWHATDIFFERENTFEEDSIZEMAYBEDESIRED 4HELIMITATIONOFTHEFOUR HORNSQUAREDFEEDISTHATTHESUM ANDDIFFERENCE SIGNAL %FIELDSCANNOTBECONTROLLEDINDEPENDENTLY)FINDEPENDENTCONTROLCOULDBEPROVIDED THEIDEALWOULDBEAPPROXIMATELYASDESCRIBEDIN&IGURE WITHTWICETHEDIMENSION FORTHEDIFFERENCESIGNALSINTHEPLANEOFERRORSENSINGTHANFORTHESUMSIGNAL !TECHNIQUEUSEDBYTHE-)4,INCOLN,ABORATORYTOAPPROACHTHEIDEALISA HORN FEED &IGURE 4HE OVERALL FEED AS ILLUSTRATED IS DIVIDED INTO SMALL PARTS AND THE MICROWAVECIRCUITRYSELECTSTHEPORTIONSNECESSARYFORTHESUMANDDIFFERENCESIGNALSTO APPROACHTHEIDEAL/NEDISADVANTAGEISTHATTHISFEEDREQUIRESAVERYCOMPLEXMICROWAVE CIRCUIT!LSO THEDIVIDEDFOUR HORNPORTIONSOFTHEFEEDAREEACHFOURELEMENTARRAYSTHAT GENERATELARGEFEEDSIDELOBESINTHE( PLANE BECAUSEOFTHEDOUBLE PEAK%FIELD!NOTHER CONSIDERATIONISTHATTHE HORNFEEDISNOT PRACTICAL FOR FOCAL POINT FED PARABOLAS OR REFLECTARRAYS BECAUSE OF ITS SIZE ! FOCAL POINT FEED IS USUALLY SMALL TO PRODUCE A BROADPATTERNANDMUSTBECOMPACTTOAVOID BLOCKAGEOFTHEANTENNAAPERTURE)NSOME CASES THE SMALL OPTIMUM SIZE REQUIRED IS BELOW WAVEGUIDE CUTOFF AND DIELECTRIC LOADINGOFTHEHORNAPERTURESBECOMESNEC &)'52% !PPROXIMATELYIDEALFEED APERTURE ESSARYTOAVOIDCUTOFF % FIELDDISTRIBUTIONFORSUMANDDIFFERENCESIGNALS
42!#+).'2!$!2
°Ç
&)'52% 4WELVE HORNFEED
!PRACTICALAPPROACHTOMONOPULSEFEEDDESIGNUSESHIGHER ORDERWAVEGUIDEMODES RATHER THAN MULTIPLE HORNS FOR INDEPENDENT CONTROL OF SUM AND DIFFERENCE SIGNAL %FIELDS4HISALLOWSMUCHGREATERSIMPLICITYANDFLEXIBILITY!TRIPLE MODETWO HORN FEEDUSEDBY2#! RETRACTSTHE% PLANESEPTATOALLOWBOTHTHE4%AND4%MODES TOBEEXCITEDANDPROPAGATEINTHEDOUBLE WIDTHSEPTUMLESSREGION ASILLUSTRATEDIN &IGURE!TTHESEPTUM THEDOUBLE HUMPED%FIELDISREPRESENTEDBYTHECOMBINED 4% AND 4% MODES SUBTRACTING AT THE CENTER AND ADDING AT THE 4% MODE OUTER PEAKS(OWEVER BECAUSETHETWOMODESPROPAGATEATDIFFERENTVELOCITIES APOINTIS REACHEDFARTHERDOWNTHEDOUBLE WIDTHGUIDEWHERETHETWOMODESADDINTHECENTER ANDSUBTRACTATTHEOUTERHUMPSOFTHE4%MODE4HERESULTISASUM SIGNAL%FIELD CONCENTRATED ASDESIRED TOWARDTHECENTEROFTHEFEEDAPERTURE 4HIS SHAPING OF THE SUM SIGNAL % FIELD IS ACCOMPLISHED INDEPENDENTLY OF THE DIFFERENCE SIGNAL%FIELD4HEDIFFERENCESIGNALISTWO4% MODESIGNALS SIDEBYSIDE ARRIVINGATTHESEPTUMOF&IGUREOUTOFPHASE!TTHESEPTUM ITBECOMESTHE4% MODE WHICHPROPAGATESTOTHEHORNAPERTUREANDUSESTHEFULLWIDTHOFTHEHORNAS DESIRED4HE4% MODE HAS ZERO % FIELD IN THE CENTER OF THE WAVEGUIDE WHERE THE SEPTUMISLOCATEDANDISUNAFFECTEDBYTHESEPTUM !FURTHERSTEPINFEEDDEVELOPMENTISTHEFOUR HORNTRIPLE MODEFEEDILLUSTRATEDIN &IGURE4HISFEEDUSESTHESAMEAPPROACHASDESCRIBEDABOVEBUTWITHTHEADDI TIONOFATOPANDBOTTOMHORN4HISALLOWSTHE% PLANEDIFFERENCESIGNALTOCOUPLETO ALLFOURHORNSANDUSESTHEFULLHEIGHTOFTHEFEED4HESUMSIGNALUSESONLYTHECENTER TWO HORNS TO LIMIT ITS % FIELD IN THE % PLANE AS DESIRED FOR THE IDEAL FIELD SHAPING
°n
2!$!2(!.$"//+
&)'52% 5SEOFRETRACTEDSEPTUMTOSHAPETHESUM SIGNAL%FIELD
4HE USE OF SMALLER TOP AND BOTTOM HORNS IS A SIMPLER METHOD OF CONCENTRATING THE % FIELDTOWARDTHECENTEROFTHEFEED WHERETHEFULLHORNWIDTHISNOTNEEDED 4HEFEEDSDESCRIBEDTHUSFARAREFORLINEAR POLARIZATIONOPERATION7HENCIRCULAR POLARIZATIONISNEEDEDINAPARABOLOID TYPEANTENNA SQUAREORCIRCULARCROSS SECTION HORN THROATS ARE USED 4HE VERTICAL AND HORIZONTAL COMPONENTS FROM EACH HORN ARE
&)'52% &OUR HORNTRIPLE MODEFEEDAFTER07(ANNANÚ)%%%
42!#+).'2!$!2
°
SEPARATED AND COMPARATORS PROVIDED FOR EACH POLARIZATION4HE SUM AND DIFFERENCE SIGNALSFROMTHECOMPARATORSARECOMBINEDWITHRELATIVEPHASETOOBTAINCIRCULAR POLARIZATION 5SE OF THE PREVIOUSLY DESCRIBED FEEDS FOR CIRCULAR POLARIZATION WOULD REQUIRETHEWAVEGUIDECIRCUITRYTOBEPROHIBITIVELYCOMPLEX#ONSEQUENTLY AFIVE HORN FEEDHASBEENUSEDASILLUSTRATEDIN&IGURE 4HEFIVE HORNFEEDISSELECTEDBECAUSEOFTHESIMPLICITYOFTHECOMPARATORTHAT REQUIRESONLYTWOMAGICORHYBRID 4SFOREACHPOLARIZATION4HESUMANDDIFFER ENCE SIGNALS ARE PROVIDED FOR THE TWO LINEAR POLARIZATION COMPONENTS AND IN AN !.&01 RADAR ARE COMBINED IN A WAVEGUIDE SWITCH FOR SELECTING POLARIZATION 4HESWITCHSELECTSEITHERTHEVERTICALORTHEHORIZONTALINPUTCOMPONENTORCOMBINES THEMWITHA RELATIVEPHASEFORCIRCULARPOLARIZATION4HISFEEDDOESNOTPROVIDE OPTIMUMSUM ANDDIFFERENCE SIGNAL%FIELDSBECAUSETHESUMHORNOCCUPIESSPACE DESIREDFORTHEDIFFERENCESIGNALS'ENERALLY ANUNDERSIZEDSUM SIGNALHORNISUSED ASACOMPROMISE(OWEVER THEFIVE HORNFEEDISAPRACTICALCHOICEBETWEENCOM PLEXITYANDEFFICIENCY)THASBEENUSEDINSEVERALINSTRUMENTATIONRADARSINCLUDING THE!.&01 !.&01 !.401 AND!.-03 ANDINTHE!.401 TACTICALPRECISION TRACKINGRADAR 4HEMULTIMODEFEEDTECHNIQUECANBEEXPANDEDTOOTHERHIGHER ORDERMODESFOR ERRORSENSINGAND% FIELDSHAPING 4HEDIFFERENCESIGNALSARECONTAINEDINUNSYM METRICALMODESSUCHASTHE4%MODEFOR( PLANEERRORSENSINGANDCOMBINED4% AND4-MODESFOR% PLANEERRORSENSING4HESEMODESPROVIDETHEDIFFERENCESIG NALS ANDNOCOMPARATORSAREUSED'ENERALLY MODECOUPLINGDEVICESCANGIVEGOOD PERFORMANCEINSEPARATINGTHESYMMETRICALANDUNSYMMETRICALMODESWITHOUTSIGNIFI CANTCROSS COUPLINGPROBLEMS
&)'52% &IVE HORNFEEDWITHCOUPLINGTOBOTHLINEAR POLARIZATIONCOMPONENTS WHICHARE COMBINEDBYTHESWITCHMATRIXTOSELECTHORIZONTAL VERTICAL ORCIRCULARPOLARIZATION
°£ä
2!$!2(!.$"//+
-ULTIBANDMONOPULSEFEEDCONFIGURATIONSAREPRACTICALANDINUSEINSEVERALSYS TEMS! SIMPLE EXAMPLE IS A COMBINED 8 BAND AND +A BAND MONOPULSE PARABOLOID ANTENNARADAR3EPARATECONVENTIONALFEEDSAREUSEDFOREACHBAND WITHTHE+A BAND FEEDASA#ASSEGRAINFEEDANDTHE8 BANDFEEDATTHEFOCALPOINT4HE#ASSEGRAINSUB DISHISAHYPERBOLIC SHAPEDHIGHLYEFFICIENTGRIDOFWIRESREFLECTIVETOPARALLELPOLARIZA TIONANDTRANSPARENTTOORTHOGONALPOLARIZATION)TISORIENTEDTOBETRANSPARENTTOTHE 8 BANDFOCAL POINTFEEDBEHINDITANDREFLECTIVETOTHEORTHOGONALLYPOLARIZED+A BAND FEEDEXTENDINGFROMTHEVERTEXOFTHEPARABOLOID -ONOPULSEFEEDHORNSATDIFFERENTMICROWAVEFREQUENCIESCANALSOBECOMBINED WITHCONCENTRICFEEDHORNS4HEMULTIBANDFEEDCLUSTERSWILLSACRIFICEEFFICIENCYBUT CANSATISFYMULTIBANDREQUIREMENTSINASINGLEANTENNA !'#!UTOMATIC'AIN#ONTROL 4OMAINTAINASTABLECLOSED LOOPSERVOSYSTEMFOR ANGLE TRACKING THE RADAR MUST MAINTAIN ESSENTIALLY CONSTANT LOOP GAIN INDEPENDENT OF TARGETECHOSIZEANDRANGE4HEPROBLEMISTHATMONOPULSEDIFFERENCESIGNALSFROMTHE ANTENNAAREPROPORTIONALTOBOTHTHEANGLEDISPLACEMENTOFTHETARGETFROMTHEANTENNAAXIS ANDTHEECHOSIGNALAMPLITUDE&ORAGIVENTRACKINGERROR THEERRORVOLTAGEWOULDCHANGE WITHECHOAMPLITUDEANDTARGETRANGECAUSINGACORRESPONDINGCHANGEINLOOPGAIN !'#ISUSEDTOREMOVETHEANGLE ERROR DETECTOR OUTPUTDEPENDENCEONECHOAMPLI TUDEANDRETAINCONSTANTTRACKINGLOOPGAIN!TYPICAL!'#TECHNIQUEISILLUSTRATEDIN &IGUREFORAONE ANGLECOORDINATETRACKINGSYSTEM4HE!'#SYSTEMDETECTSTHE PEAKVOLTAGEOFTHESUMSIGNALANDPROVIDESANEGATIVEDCVOLTAGEPROPORTIONALTOTHE PEAKSIGNALVOLTAGE4HENEGATIVEVOLTAGEISFEDTOTHE)&LIFIERSTAGE WHEREITIS USEDTODECREASEGAINASTHESIGNALINCREASES!HIGHGAININTHE!'#LOOPISEQUIVALENT TODIVIDINGTHE)&OUTPUTBYAFACTORPROPORTIONALTOITSAMPLITUDE )NATHREE CHANNELMONOPULSERADAR ALLTHREECHANNELSARECONTROLLEDBYTHE!'# VOLTAGE WHICHEFFECTIVELYPERFORMSADIVISIONBYTHEMAGNITUDEOFTHESUMSIGNALOR ECHOAMPLITUDE#ONVENTIONAL!'#ESSENTIALLYHOLDSCONSTANTGAINDURINGTHEPULSE REPETITIONINTERVAL!LSO THE!'#OFTHESUMCHANNELNORMALIZESTHESUMECHOPULSE AMPLITUDETOSIMILARLYMAINTAINASTABLERANGE TRACKINGSERVOLOOP 4HEANGLE ERRORDETECTOR ASSUMEDTOBEAPRODUCEDETECTOR HASANOUTPUT \E\ K
$3 COS Q \3 \ \ 3\
WHERE\E\ISTHEMAGNITUDEOFTHEANGLE ERRORVOLTAGE0HASESAREADJUSTEDTOPROVIDE ORONAPOINT SOURCETARGET4HERESULTANTIS \E\ o K
$
\3\
&)'52% !'#INMONOPULSETRACKING
42!#+).'2!$!2
°££
#OMPLEXTARGETSCANCAUSEOTHERPHASERELATIONSASAPARTOFTHEANGLESCINTILLATION PHENOMENON 4HE ABOVE ERROR VOLTAGE PROPORTIONAL TO THE RATIO OF THE DIFFERENCE SIGNALDIVIDEDBYTHESUMSIGNAL ISTHEDESIREDANGLE ERROR DETECTOROUTPUT GIVINGA CONSTANTANGLEERRORSENSITIVITY 7ITHLIMITED!'#BANDWIDTH SOMERAPIDSIGNALFLUCTUATIONSMODULATE¨E¨BUTTHE LONG TIME AVERAGE ANGLE SENSITIVITY IS CONSTANT4HESE FLUCTUATIONS ARE LARGELY FROM RAPIDCHANGESINTARGETREFLECTIVITY RT THATAREFROMTARGETAMPLITUDESCINTILLATION 4HERANDOMMODULATIONOF¨E¨CAUSESANADDITIONALANGLENOISECOMPONENTTHATAFFECTS THECHOICEOF!'#BANDWIDTH 4HE!'#PERFORMANCEINCONICAL SCANRADARSPROVIDESSIMILARCONSTANTANGLEERROR SENSITIVITY /NE MAJOR LIMITATION IN CONICAL SCAN RADARS IS THAT THE!'# BANDWIDTH MUSTBESUFFICIENTLYLOWERTHANTHESCANFREQUENCYTOPREVENTTHE!'#FROMREMOVING THEMODULATIONCONTAININGTHEANGLEERRORINFORMATION 0HASE #OMPARISON-ONOPULSE !SECONDMONOPULSETECHNIQUEISTHEUSEOFMUL TIPLEANTENNASWITHOVERLAPPINGNONSQUINTED BEAMSPOINTEDATTHETARGET)NTERPOLATING TARGETANGLESWITHINTHEBEAMISACCOMPLISHED ASSHOWNIN&IGURE BYCOMPARING THEPHASEOFTHESIGNALSFROMTHEANTENNASFORSIMPLICITYASINGLE COORDINATETRACKER IS DESCRIBED )F THE TARGET WERE ON THE ANTENNA BORESIGHT AXIS THE OUTPUTS OF EACH
&)'52% A 7AVEFRONTPHASERELATIONSHIPSINAPHASECOMPARISONMONOPULSERADARANDB BLOCK DIAGRAMOFAPHASECOMPARISONMONOPULSERADARONEANGLECOORDINATE
°£Ó
2!$!2(!.$"//+
INDIVIDUALAPERTUREWOULDBEINPHASE!S THE TARGET MOVES OFF AXIS IN EITHER DIREC TION THERE IS A CHANGE IN RELATIVE PHASE 4HEAMPLITUDESOFTHESIGNALSINEACHAPER TUREARETHESAMESOTHATTHEOUTPUTOFTHE ANGLE ERROR PHASE DETECTOR IS DETERMINED BYTHERELATIVEPHASESEE&IGURE 4HE PHASE DETECTOR CIRCUIT IS ADJUSTED WITH A PHASESHIFTONONECHANNELTOGIVEZERO OUTPUT WHEN THE TARGET IS ON AXIS AND AN OUTPUTINCREASINGWITHINCREASINGANGULAR DISPLACEMENTOFTHETARGETWITHAPOLARITY CORRESPONDINGTOTHEDIRECTIONOFERROR 4YPICALFLAT FACECORPORATE FEDPHASED ARRAYSCOMPARETHEOUTPUTOFHALVESOFTHE APERTURE AND FALL INTO THE CLASS OF PHASE &)'52% A 2& PHASE COMPARISON MONO COMPARISON MONOPULSE (OWEVER THE PULSE SYSTEM WITH SUM AND DIFFERENCE OUTPUTS AND BASICSIGNALPROCESSINGOFAMPLITUDE AND B VECTORDIAGRAMOFTHESUMANDDIFFERENCESIGNALS PHASE COMPARISON MONOPULSE IS SIMILAR BUT THE CONTROL OF AMPLITUDE DISTRIBUTION ACROSS AN ARRAY APERTURE FOR THE SUM AND DIFFERENCESIGNALSMAINTAINSEFFICIENCYANDLOWERSIDELOBES &IGURESHOWSTHEANTENNAANDRECEIVERFORONEANGULAR COORDINATETRACKINGBY PHASECOMPARISONMONOPULSE!NYPHASESHIFTSOCCURRINGINTHEMIXERAND)&LI FIERSTAGESCAUSESASHIFTINTHEBORESIGHTOFTHESYSTEM4HEDISADVANTAGESOFPHASE COMPARISONMONOPULSEWITHSEPARATEAPERTURESCOMPAREDWITHAMPLITUDE COMPARISON MONOPULSEARETHERELATIVEDIFFICULTYINMAINTAININGAHIGHLYSTABLEBORESIGHTANDTHE DIFFICULTYINPROVIDINGTHEDESIREDANTENNAILLUMINATIONTAPERFORBOTHSUMANDDIF FERENCE SIGNALS 4HE LONGER PATHS FROM THE ANTENNA OUTPUTS TO THE COMPARATOR CIR CUITRYMAKETHEPHASE COMPARISONSYSTEMMORESUSCEPTIBLETOBORESIGHTCHANGEDUE TOMECHANICALLOADINGSAG DIFFERENTIALHEATING ETC ! TECHNIQUE GIVING GREATER BORESIGHT STABILITY COMBINES THE TWO ANTENNA OUT PUTSAT2&WITHPASSIVECIRCUITRYTOYIELDSUMANDDIFFERENCESIGNALS ASSHOWNIN &IGURE4HESESIGNALSMAYTHENBEPROCESSEDLIKEACONVENTIONALAMPLITUDE COMPARISONMONOPULSERECEIVER4HESYSTEMSHOWNIN&IGUREWOULDPROVIDE A RELATIVELY GOOD DIFFERENCE CHANNEL TAPER HAVING SMOOTHLY TAPERED % FIELDS ON EACHANTENNA(OWEVER ASUM SIGNALEXCITATIONWITHTHETWOANTENNASPROVIDESA TWO HUMPEDIN PHASE% FIELDDISTRIBUTIONTHATCAUSESHIGHSIDELOBESSINCEITLOOKS LIKEATWO ELEMENTARRAY4HISPROBLEMMAYBEREDUCEDBYALLOWINGSOMEAPERTURE OVERLAPBUTATTHEPRICEOFLOSSOFANGLESENSITIVITYANDANTENNAGAIN %LECTRONIC3CAN0HASED!RRAY-ONOPULSE 4RACKINGRADARSDEDICATEDTOSINGLE TARGETTRACKINGCANPROVIDEVERYHIGHPRECISIONLONGRANGEPERFORMANCE SUCHASTHE !.&01 &IGURE A WITH A SPECIFIED PRECISION OF MILLIRADIAN 7ITH HIGHPOWERANDAHIGHGAINANTENNAD" ANDSPECIALTRACKINGTECHNIQUES THEYARE THE WORKHORSE FOR PRECISION TRACKING OF SATELLITES AND SIMILAR TASKS (OWEVER MOST MODERNTASKSREQUIREPRECISIONSIMULTANEOUSTRACKINGOFMULTIPLESIMULTANEOUSTARGETS WHEREUSEOFMULTIPLESINGLETARGETTRACKINGRADARSARENOTCOSTEFFECTIVE4HEDEVELOP MENTOFELECTRONICSCANPHASEDARRAYTECHNOLOGYHASRESULTEDINVERSATILEHIGHPRECI SIONMONOPULSETRACKINGWITHTHECAPABILITYOFSIMULTANEOUSMULTITARGETTRACKINGBY SWITCHINGITSBEAMTOEACHOFSEVERALTARGETSONAPULSE TO PULSEBASISORBYGROUPS
42!#+).'2!$!2
°£Î
OF PULSES -ONOPULSE TRACKING IS NECESSARY TO OBTAIN ANGLE DATA ON EACH PULSE TO MAINTAINADEQUATEDATARATESWHENSHARINGPULSESANDPOWERAMONGSEVERALTARGETS! DETAILEDDISCUSSIONOFELECTRONICSCANPHASEDARRAYSISGIVENIN#HAPTERHOWEVER SOMECHARACTERISTICSOFTHEARRAYSREQUIRESPECIALCONSIDERATIONFORTHEANGLETRACKING PERFORMANCEOFTRACKINGRADARSUSINGMONOPULSEPHASEDARRAYANTENNAS /PTICAL FEED-ONOPULSE%LECTRONIC3CAN!RRAYS /PTICAL FEEDMONOPULSEARRAYS INCLUDETHELENSARRAYANDREFLECTARRAY#HAPTER THATAREOPTICALLYFEDBYACONVEN TIONALMONOPULSEFEED4HE!.-01 &IGUREB ISANEXAMPLEOFANOPTICALLY FEDARRAYLENSWITHTHEANTENNAMOUNTEDONATWO AXISPEDESTAL4YPICALINSTANTANEOUS ELECTRONICANGLECOVERAGEISoTOANALMOSToCONEFIELD OF VIEWTHATMAYBE MOVEDBYPEDESTALDRIVETOCENTERONAMULTITARGETEVENTORFOLLOWANEVENTPROGRESS INGTOADIFFERENTAREA3OMEMILITARYSYSTEMSSUCHASTHE0ATRIOTWITHTHEoCONE OFINSTANTANEOUSVIEWISFIXEDONITSVEHICLEWITHOUTAPEDESTALANDISDEPENDENTON MOVEMENT OF ITS VEHICLE TO CHANGE THE REGION OF ANGULAR COVERAGE AS NEEDED 4HE ADVANTAGESOFSPACEFEDARRAYSARE #ONVENTIONALMONOPULSEMICROWAVEHORNFEEDSAREUSED !RRAYELEMENTSAREAVAILABLEWITHSELECTABLEPOLARIZATIONOFTHERADIATEDENERGYWHEN FEDBYANOPTIMIZEDLINEARPOLARIZEDMONOPULSEFEEDSUCHASIN&IGURE ANDSELECT ABLERECEIVE POLARIZATIONASWELL4HISAVOIDSTHETYPICALCOMPROMISEANDGREATERCOM PLEXITYOFAPOLARIZATION CONTROLLEDMONOPULSEFEEDASDESCRIBEDIN&IGURE %LECTRONICSCANARRAYLENSESCANALSOREFOCUSFROMATRANSMITFEEDHORNTOANADJACENT RECEIVEFEEDHORNONRECEPTIONTOALLOWHIGHPOWERTRANSMISSIONTHROUGHASIMPLE SINGLEHORNFEEDTOSIMPLIFYISOLATIONOFTHERECEIVERFROMTHETRANSMITPOWER !RRAYSALLOWGREATERFLEXIBILITYTOOPTIMIZEAMPLITUDEDISTRIBUTIONOFTHERADIATED ENERGYACROSSTHEARRAYTOREDUCESIDELOBES
L
L
L
L
-OSTOFTHEELECTRONICSCANPHASEDARRAYDISADVANTAGESAREDESCRIBEDIN#HAPTER AND INCLUDE LOSSES IN THE ARRAY PHASE SHIFTING ELEMENTS LIMITATION OF INSTANTANEOUS BANDWIDTH WITH CONVENTIONAL PHASE CONTROL ELEMENTS IMPROVED WITH SPECIAL TRUE TIME DELAY PHASE SHIFTING PHASE QUANTIZATION ERRORS #HAPTER RESULTING FROM PHASESHIFTINGINSTEPS RESTRICTIONTOASINGLERFBANDMULTIBANDARRAYSREQUIRESPECIAL TECHNIQUESWITHMAJORCOMPROMISES ANDGRADUALDEGRADATIONOFPERFORMANCEASTHE BEAM IS SCANNED FROM THE NORMAL TO THE ARRAY4HE QUANTIZATION ERRORS FROM PHASE SHIFTINGINSTEPSAREOFCONCERNTOMONOPULSERADARBECAUSEITRESULTSINCORRESPONDING RANDOMERRORSTEPSINTHEELECTRONICAXISOFTHEARRAY!SDESCRIBEDIN#HAPTER THE QUANTIZATIONERRORSAREINVERSELYPROPORTIONALTOTHENUMBEROFPHASESHIFTINGELEMENTS AND0WHERE0ISTHENUMBEROFBITSOFPHASECONTROLINEACHELEMENT#ONSEQUENTLY THEHIGHPRECISIONTRACKINGRADARSWITHTYPICALLYTOPHASESHIFTERSANDFOUR ORMOREPHASESHIFTBITSHAVESMALLRESULTANTELECTRICALAXISERRORSTEPSONTHEORDEROF MILLIRADIANSORLESS4HEELECTRICALAXISERRORSAREESSENTIALLYRANDOMANDCANBE FURTHERREDUCEDBYAVERAGING)NTENTIONALDITHEROFPHASESTEPSMAYBEINTRODUCEDTO AIDINAVERAGING 4HEOPTICALLYFEDTECHNIQUERESULTSINFEEDENERGYSPILLOVERAROUNDTHEAPERTURE HOWEVER THESERESULTANTSPILLOVERSIDELOBESCANBEELIMINATEDBYANABSORBINGCONE BETWEENTHEFEEDANDTHEARRAYAPERTURE4HEABSORBINGCONEISOBSERVEDINTHE!. -01 &IGUREB (OWEVER COOLINGISALSONECESSARYANDPROVIDED ASOBSERVED BYTHECOOLINGCOILSAROUNDTHEABSORBINGCONE
°£{
2!$!2(!.$"//+
/FFURTHERCONCERNTOHIGHPRECISIONMONOPULSEAPPLICATIONSISDRIFTOFTHEELEC TRONICAXISTHATCAUSESVARIATIONSINPHASEANDTEMPERATUREVARIATIONACROSSTHEARRAY SURFACE THAT CAUSES DISTORTION OF THE LENS 3IGNIFICANT VARIATION OF HEAT DISTRIBUTION ACROSSTHEARRAYFACECANRESULTFROMHIGHPOWERTRANSMITTEDTHROUGHTHEPHASESHIFTING ELEMENTSASWELLASTHEELECTRONICPHASECONTROL#ONSEQUENTLY WHEREHIGHPRECISION TRACKINGISREQUIRED SPECIALCOOLINGTECHNIQUESMAYBENECESSARYTOMAINTAINCONSTANT TEMPERATUREACROSSTHEAPERTURE #ORPORATE&EED-ONOPULSE%LECTRONIC3CAN0HASED!RRAY 4HECORPORATEFEED ARRAYISFEDBYDIVIDINGANDSUBDIVIDINGTHETRANSMITSIGNALTHROUGHTRANSMISSIONLINES TYPICALLYTOSUBARRAYSOFMULTIPLEARRAYRADIATINGELEMENTS4HISTECHNIQUE ALTHOUGH TYPICALLY RESULTING IN HEAVIER AND HIGHER COST IMPLEMENTATION OFFERS THE ADVANTAGE OFFLEXIBILITYOFCONTROLOFTHESIGNALPATHSTHROUGHTHEARRAYSTRUCTURE ASDESCRIBED IN#HAPTER!NOTHERADVANTAGEISTHECAPABILITYTOTRANSMITVERYHIGHPEAKPOWER WITHOUTTHELIMITATIONSOFFULLPEAKPOWERPROPAGATINGTHROUGHASINGLETRANSMISSION LINE4HISISACCOMPLISHEDINTHECORPORATEFEEDARRAYBYPLACINGHIGHPOWERAMPLIFIERS WHERETHEPOWERDIVIDESTOTHESUBARRAYS ALLOWINGTHESUMOFTHEHIGHPEAKPOWER AMPLIFIEROUTPUTSTOADDINSPACETOMEETREQUIREMENTSFORLONG RANGETRACKINGAND POWERSHARINGBETWEENMULTIPLESIMULTANEOUSTARGETS 4HE PARALLEL POWER AMPLIFIER CONFIGURATION ALSO PROVIDES A PRACTICAL MEANS FOR OVERCOMING THE NARROW INSTANTANEOUS BANDWIDTH OF TYPICAL PHASED ARRAYS AT WIDE SCANANGLES&ULLARRAYINSTANTANEOUSBANDWIDTHREQUIRESEQUALPATHLENGTHSBETWEEN EACHARRAYELEMENTANDTHETARGET REQUIRINGMANYWAVELENGTHSOFPHASECONTROLORTHE EQUIVALENTTIMEDELAYINARRAYELEMENTSATWIDEANGLESCANS(OWEVER THISCONTROLHAS PROHIBITIVELYHIGHLOSSFORTYPICALPHASEDARRAYRADIATINGELEMENTSCONSEQUENTLY TYPI CALPHASEDARRAYELEMENTSPROVIDEONLYSUFFICIENTPHASECONTROLOFUPTOORTOONE WAVELENGTH LIMITEDTOTOLERABLELOSS TOCAUSETHESIGNALFROMEACHELEMENTTOARRIVE APPROXIMATELYINPHASEATTHETARGET5NFORTUNATELY THISSHORTCUTISADEQUATEFORONLY ANARROWINSTANTANEOUSBANDWIDTH4HEPARALLELPOWERAMPLIFIERS ASDESCRIBEDABOVE PROVIDE A LOW POWER AMPLIFIER DRIVE STAGE WHERE THE HIGH LOSS OF THE DESIRED TIME DELAYCONTROLCANBETOLERATEDTOGAINWIDEINSTANTANEOUSBANDWIDTH ASDESCRIBEDIN #HAPTER4HETIMEDELAYMAYBECONTROLLEDSIMILARTOTHEDIODEPHASESHIFTERSUSED INRADIATINGELEMENTSTHATSWITCHBETWEENDIFFERENTLINELENGTHSTOADJUSTPHASE,ONGER TIMEDELAYTRANSMISSIONLINECOULDBESIMILARLYCONTROLLEDBYDIODESWITCHINGTOPRO VIDETHEWIDEINSTANTANEOUSBANDWIDTHTOALLOW FOREXAMPLE USEOFWIDEBANDNARROW PULSESTOPROVIDETHERANGERESOLUTIONREQUIREMENTSFORTRACKINGRADARAPPLICATIONS 4WO #HANNEL-ONOPULSE -ONOPULSERADARSMAYBEDESIGNEDWITHFEWERTHANTHE CONVENTIONALTHREE)&CHANNELS4HISISACCOMPLISHED FOREXAMPLE BYCOMBININGTHESUM ANDDIFFERENCESIGNALSINTWO)&CHANNELSANDTHESUMANDTWODIFFERENCESIGNALOUTPUTS ARETHENINDIVIDUALLYRETRIEVEDATTHEOUTPUT4HESETECHNIQUESPROVIDESOMEADVANTAGES IN!'#OROTHERPROCESSINGTECHNIQUESBUTATTHECOSTOFREDUCED3.2 REDUCEDANGLE DATARATE ANDPOTENTIALFORCROSSCOUPLINGBETWEENAZIMUTHANDELEVATIONINFORMATION !TWO CHANNELMONOPULSERECEIVERCOMBINESTHESUMANDDIFFERENCESIGNALS AT2& ASSHOWNIN&IGURE4HEMICROWAVERESOLVERISAMECHANICALLYROTATED 2&COUPLINGLOOPINCYLINDRICALWAVEGUIDE4HEAZIMUTHANDELEVATIONDIFFERENCE SIGNALS ARE EXCITED IN THIS GUIDE WITH % FIELD POLARIZATION ORIENTED AT O 4HE ENERGY IN THE COUPLER CONTAINS BOTH DIFFERENCE SIGNALS COUPLED AS THE COSINE ANDSINEOFTHEANGULARPOSITIONOFTHECOUPLER VST WHEREVS ISTHEANGULARRATE OF ROTATION 4HE HYBRID ADDS THE COMBINED DIFFERENCE SIGNALS $ AT THE ANGULAR
42!#+).'2!$!2
°£x
&)'52% "LOCKDIAGRAMOFATWO CHANNELMONOPULSERADARSYSTEMFROM23.OBLIT
RATEOFROTATION4HE3 $AND3n$OUTPUTSEACHLOOKLIKETHEOUTPUTOFACONICAL SCAN TRACKER EXCEPT THAT THEIR MODULATION FUNCTION DIFFERS BY )N CASE ONE CHANNELFAILS THERADARCANBEOPERATEDASASCAN ON RECEIVE ONLYCONICAL SCANRADAR WITHESSENTIALLYTHESAMEPERFORMANCEASACONICAL SCANRADAR4HEADVANTAGEOFTWO CHANNELSWITHOPPOSITE SENSEANGLE ERRORINFORMATIONONONECHANNELWITHRESPECTTO THEOTHERISTHATSIGNALAMPLITUDEFLUCTUATIONSINTHERECEIVEDSIGNALARECANCELEDINTHE POST DETECTIONSUBTRACTIONATTHE)&OUTPUTTHATRETRIEVESTHEANGLE ERRORINFORMATION 4HELOG)&PERFORMSESSENTIALLYASANINSTANTANEOUS!'# GIVINGTHEDESIREDCONSTANT ANGLE ERRORSENSITIVITYOFTHEDIFFERENCESIGNALSNORMALIZEDBYTHESUMSIGNAL4HE DETECTED$INFORMATIONISABIPOLARVIDEOWHERETHEERRORINFORMATIONISCONTAINEDIN THESINUSOIDALENVELOPE4HISSIGNALISSEPARATEDINTOITSTWOCOMPONENTS AZIMUTH ANDELEVATION ERRORINFORMATION BYANANGLEDEMODULATION4HEDEMODULATOR USING A REFERENCE FROM THE DRIVE ON THE ROTATING COUPLER EXTRACTS THE SINE AND COSINE COMPONENTSFROM$TOGIVETHEAZIMUTH ANDELEVATION ERRORSIGNALS4HEMODULATION CAUSEDBYTHEMICROWAVERESOLVERISOFCONCERNININSTRUMENTATIONRADARAPPLICATIONS BECAUSEITADDSSPECTRALCOMPONENTSINTHESIGNAL COMPLICATINGTHEPOSSIBLEADDITION OFPULSEDOPPLERTRACKINGCAPABILITYTOTHERADAR 4HISSYSTEMPROVIDESINSTANTANEOUS!'#OPERATIONWITHONLYTWO)&CHANNELSAND OPERATION WITH REDUCED PERFORMANCE IN CASE OF FAILURE OF EITHER CHANNEL (OWEVER THEREISALOSSOF D"3.2ATTHERECEIVERINPUTS ALTHOUGHTHISLOSSISPARTLYREGAINED BYCOHERENTADDITIONOFTHE3 SIGNALINFORMATION4HEDESIGNOFTHEMICROWAVERESOLVER MUSTMINIMIZELOSSTHROUGHTHEDEVICE ANDPRECISELYMATCHED)&CHANNELSAREREQUIRED TOMINIMIZECROSSCOUPLINGBETWEENTHEAZIMUTHANDELEVATIONCHANNELS)NSOMEMOD ERNSYSTEMS THERESOLVERPERFORMANCEISIMPROVEDBYUSEOFFERRITESWITCHINGDEVICES TOREPLACETHEMECHANICALROTATINGCOUPLER #ONOPULSE #ONOPULSEALSOCALLEDSCANWITHCOMPENSATION ISARADARTRACKING TECHNIQUETHATISACOMBINATIONOFMONOPULSEANDCONICALSCAN !PAIROFANTENNA
°£È
2!$!2(!.$"//+
BEAMSISSQUINTEDINOPPOSITEDIRECTIONSFROMTHEANTENNAAXISANDROTATEDLIKEAPAIR OFCONICAL SCAN RADARBEAMS3INCETHEYEXISTSIMULTANEOUSLY MONOPULSEINFORMATION CANBEOBTAINEDFROMTHEPAIROFBEAMS4HEPLANEINWHICHMONOPULSEINFORMATION IS MEASURED ROTATES #ONSEQUENTLY ELEVATION AND AZIMUTH INFORMATION IS SEQUENTIAL ANDMUSTBESEPARATEDFORUSEINEACHTRACKINGCOORDINATE#ONOPULSEPROVIDESTHE MONOPULSE ADVANTAGE OF AVOIDING ERRORS CAUSED BY AMPLITUDE SCINTILLATION AND IT REQUIRES ONLY TWO RECEIVERS (OWEVER IT HAS THE DISADVANTAGE OF LOWER ANGLE DATA RATESANDTHEMECHANICALCOMPLEXITYOFPROVIDINGANDCOUPLINGTOAPAIROFROTATING ANTENNAFEEDHORNS
°ÎÊ -
Ê Ê "
4HEFIRSTTECHNIQUEUSEDFORRADARANGLETRACKINGWASTODISPLACETHEANTENNABEAM ABOVEANDBELOWTHETARGETINELEVATIONANDSIDETOSIDEOFTHETARGETINAZIMUTHTO COMPAREBEAMAMPLITUDESSIMILARTOMONOPULSERADARSIMULTANEOUSLOBINGBUTDIFFER INGBYBEINGINATIMESEQUENCE4HISWASPERFORMEDBYACONTINUOUSCONICALBEAM SCAN ASILLUSTRATEDIN&IGUREORBYSEQUENTIALLYLOBINGUPDOWNANDRIGHTLEFT ANDOBSERVINGTHEDIFFERENCEBETWEENAMPLITUDESASAMEASUREOFDISPLACEMENTOFTHE ANTENNAAXISFROMTHETARGET4HESIGNALOUTPUTFORACONICAL SCANRADAR ILLUSTRATEDIN &IGURE ISTYPICALLYASINUSOIDAMPLITUDEMODULATIONOFTHERECEIVEDTARGETECHO PULSES4HEAMPLITUDEOFTHEMODULATIONISAMEASUREOFTHEMAGNITUDEOFTHEANGLE ERROR ANDTHEPHASE RELATIVETOTHESCANNING BEAMROTATIONANGLE INDICATESTHEPORTION OFTHEERRORCAUSEDBYEACHTRACKINGAXIS 4HEPERFORMANCEOFSCANNINGANDLOBINGRADARRELATIVETOTHEBEAMOFFSETANGLEIS DESCRIBEDIN"ARTON!NOPTIMUMBEAMOFFSETISDESCRIBEDASACOMPROMISEBETWEEN THELOSSOFANTENNAGAINANDTHEINCREASEINSENSITIVITYTOTARGETANGLEDISPLACEMENT FROM THE ANTENNA AXIS AS BEAM OFFSET IS INCREASED4HE OPTIMUM OFFSET IS TYPICALLY CHOSENTOPROVIDETHEMINIMUMRMSANGLE TRACKINGERRORASAFFECTEDBYTHESIGNAL TO NOISERATIOANDTRACKINGSENSITIVITY3PECIALTRACKINGRADARAPPLICATIONSWITHNONTYPICAL REQUIREMENTSCOULDARRIVEATADIFFERENTOPTIMUMBEAMOFFSET !MAJORLIMITATIONOFSCANNINGANDLOBINGRADARISTHESUSCEPTIBILITYTOTARGETAMPLI TUDEFLUCTUATIONSTHATOCCURDURINGTHETIMETHEBEAMISMOVEDFROMSIDETOSIDEORUP ANDDOWN)TISALSOSUSCEPTIBLETOFALSEMODULATIONONSIGNALSFROMCOUNTERMEASURES 4HEECHOFLUCTUATIONSNOTRELATEDTOANTENNABEAMPOSITIONCAUSEFALSETARGETANGLE TRACKINGERRORS
&)'52% #ONICAL SCANTRACKING
42!#+).'2!$!2
°£Ç
&)'52% A !NGLEERRORINFORMATIONCONTAINEDINTHEENVELOPE OFTHERECEIVEDPULSESINACONICAL SCANRADARANDB REFERENCESIGNAL DERIVEDFROMTHEDRIVEOFTHECONICAL SCANFEED
-ONOPULSERADARWASDEVELOPEDTOPROVIDESIMULTANEOUSOFFSETANTENNABEAMSFOR COMPARISONOFTARGETECHOAMPLITUDESONASINGLEPULSEINDEPENDENTOFECHOSIGNAL AMPLITUDEFLUCTUATIONS(OWEVER FEWMICROWAVEDEVICESANDCOMPONENTSWEREINI TIALLYAVAILABLE ANDTHEFIRSTMONOPULSESYSTEMSWERECOMPLEXANDRESULTEDINCUM BERSOMEANDINEFFICIENTANTENNAS!TPRESENT MODERNMONOPULSERADARS ASDESCRIBED IN3ECTION PROVIDEHIGHLYSTABLEANDEFFICIENTANTENNASWITHHIGHPRECISIONPERFOR MANCEANDHAVEGENERALLYDISPLACEDSCANNINGANDLOBINGTRACKINGRADARSFORMEETING THEINCREASINGDEMANDSFORHIGHPRECISIONANDHIGHDATARATEOFANGLEINFORMATIONON EACHPULSE(OWEVER SPECIALRADARTRACKINGREQUIREMENTSMAYEXISTWHEREAPRACTICAL IMPLEMENTATIONOFCONICALSCANORLOBINGTRACKINGRADARMAYMOREEFFECTIVELYPROVIDE ADEQUATEPERFORMANCE
°{Ê - ,6"-9-/ -Ê",Ê/, Ê, , 4HESERVOSYSTEMOFATRACKINGRADARISTHESUBSYSTEMOFTHERADARTHATRECEIVESASITS INPUTTHETRACKING ERRORVOLTAGEANDPERFORMSTHETASKOFMOVINGTHEANTENNABEAMINA DIRECTIONTHATWILLREDUCETOZEROTHEALIGNMENTERRORBETWEENTHEANTENNAAXISANDTHE TARGET&ORTWO AXISTRACKINGWITHAMECHANICAL TYPEANTENNAPEDESTAL THEREARETYPI CALLYSEPARATEAXESOFROTATIONFORAZIMUTHANDELEVATIONANDSEPARATESERVOSYSTEMSTO MOVETHEANTENNAABOUTEACHAXIS!CONVENTIONALSERVOSYSTEMISCOMPOSEDOFAMPLI FIERS FILTERS ANDAMOTORTHATMOVESTHEANTENNAINADIRECTIONTOMAINTAINTHEANTENNA AXIS ON THE TARGET 2ANGE TRACKING IS ACCOMPLISHED BY A SIMILAR SYSTEM TO MAINTAIN RANGEGATESCENTEREDONTHERECEIVEDECHOPULSES4HISMAYBEACCOMPLISHEDBYANALOG TECHNIQUESORBYDIGITAL COUNTERREGISTERSTHATRETAINNUMBERSCORRESPONDINGTOTARGET RANGETOPROVIDEACLOSEDRANGE TRACKINGLOOPDIGITALLY 3ERVOSYSTEMS MAY USE HYDRAULIC DRIVE MOTORS CONVENTIONAL ELECTRIC MOTORS GEAREDDOWNTODRIVETHEANTENNA ORDIRECT DRIVEELECTRICMOTORSWHERETHEANTENNA MECHANICAL AXIS SHAFT IS PART OF THE ARMATURE AND THE MOTOR FIELD IS BUILT INTO THESUPPORTCASE4HEDIRECTDRIVEISHEAVIERFORAGIVENHORSEPOWERBUTELIMINATES
°£n
2!$!2(!.$"//+
GEARBACKLASH"ACKLASHMAYALSOBEREDUCEDWITHCONVENTIONALMOTORSBYDUPLICATE PARALLEL DRIVES WITH A SMALL RESIDUAL OPPOSING TORQUE WHEN NEAR ZERO ANGLE RATE !MPLIFIERGAINANDFILTERCHARACTERISTICSASWELLASMOTORTORQUEANDINERTIADETER MINETHEVELOCITYANDACCELERATIONCAPABILITYORTHEABILITYTOFOLLOWTHEHIGHER ORDER MOTIONOFTHETARGET )TISDESIREDTHATTHEANTENNABEAMFOLLOWTHECENTEROFTHETARGETASCLOSELYASPOS SIBLE WHICHIMPLIESTHATTHESERVOSYSTEMSHOULDBECAPABLEOFMOVINGTHEANTENNA QUICKLY4HECOMBINEDVELOCITYANDACCELERATIONCHARACTERISTICSOFASERVOSYSTEMCAN BEDESCRIBEDBYTHEFREQUENCYRESPONSEOFTHETRACKINGLOOP WHICHACTSESSENTIALLYLIKE ALOW PASSFILTER)NCREASINGTHEBANDWIDTHINCREASESTHEQUICKNESSOFTHESERVOSYS TEMANDITSABILITYTOFOLLOWASTRONG STEADYSIGNALCLOSELY(OWEVER ATYPICALTARGET CAUSESSCINTILLATIONOFTHEECHOSIGNAL GIVINGERRONEOUSERROR DETECTOROUTPUTS ANDAT LONGRANGE THEECHOISWEAK ALLOWINGRECEIVERNOISETOCAUSEADDITIONALRANDOMFLUC TUATIONSONTHEERRORDETECTOROUTPUT#ONSEQUENTLY AWIDESERVOBANDWIDTH WHICH REDUCESLAGERRORS ALLOWSTHENOISETOCAUSEGREATERERRONEOUSMOTIONSOFTHETRACKING SYSTEM4HEREFORE FORBESTOVERALLPERFORMANCE ITISNECESSARYTOLIMITTHESERVOBAND WIDTH TO THE MINIMUM NECESSARY TO MAINTAIN A REASONABLY SMALL TRACKING LAG ERROR 4HERE IS AN OPTIMUM BANDWIDTH THAT MAY BE CHOSEN TO MINIMIZE THE AMPLITUDE OF THETOTALERRONEOUSOUTPUTSINCLUDINGBOTHTRACKINGLAGANDRANDOMNOISE DEPENDING UPONTHETARGET ITSTRAJECTORY ANDOTHERRADARPARAMETERS 4HEOPTIMUMBANDWIDTHFORANGLETRACKINGISRANGE DEPENDENT!TARGETWITHTYPICAL VELOCITYATLONGRANGEHASLOWANGLERATESANDALOW3.2 ANDANARROWERSERVOPASSBAND WILLFOLLOWTHETARGETWITHREASONABLYSMALLTRACKINGLAGWHILEMINIMIZINGTHERESPONSE TORECEIVERTHERMALNOISE!TCLOSERANGE THESIGNALISSTRONG OVERRIDINGRECEIVERNOISE BUTTARGETANGLESCINTILLATIONERRORSPROPORTIONALTOTHEANGULARSPANOFTHETARGETARELARGE !WIDERSERVOBANDWIDTHISNEEDEDATCLOSERANGETOKEEPTRACKINGLAGWITHINREASONABLE VALUES BUTITMUSTNOTBEWIDERTHANNECESSARYORTHETARGETANGLESCINTILLATIONERRORS WHICHINCREASEINVERSELYPROPORTIONALTOTARGETRANGE MAYBECOMEEXCESSIVE 4HELOW PASSCLOSED LOOPCHARACTERISTICOFASERVOSYSTEMISUNITYATZEROFREQUENCY TYPICALLYREMAININGNEARTHISVALUEUPTOAFREQUENCYNEARTHELOW PASSCUTOFF WHERE ITMAYPEAKUPTOHIGHERGAIN ASSHOWNIN&IGUREA4HEPEAKINGISANINDICATION OFSYSTEMINSTABILITYBUTISALLOWEDTOBEASHIGHASTOLERABLE TYPICALLYTOABOUTD" ABOVEUNITYGAINTOOBTAINMAXIMUMBANDWIDTHFORAGIVENSERVOMOTORDRIVESYSTEM 3YSTEM!IN&IGUREAISACASEOFEXCESSIVEPEAKINGOFABOUTD"4HEEFFECTOF THEPEAKINGISOBSERVEDBYAPPLYINGASTEPERRORINPUTTOTHESERVOSYSTEM4HEPEAKING OFTHELOW PASSCHARACTERISTICRESULTSINANOVERSHOOTWHENTHEANTENNAAXISMOVESTO ALIGNWITHTHETARGET(IGHPEAKINGCAUSESALARGEOVERSHOOTANDARETURNTOTHETARGET WITH ADDITIONAL OVERSHOOT )N THE EXTREME AS IN SYSTEM! SHOWN IN &IGURE B THE ANTENNA ZEROS IN ON THE TARGET WITH A DAMPED OSCILLATION!N OPTIMUM SYSTEM COMPROMISE BETWEEN SPEED OF RESPONSE AND OVERSHOOT AS IN SYSTEM " ALLOWS THE ANTENNATOMAKEASMALLOVERSHOOTWITHREASONABLYRAPIDEXPONENTIALMOVEMENTBACK TOTHETARGET4HISCORRESPONDSTOABOUTD"PEAKINGOFTHECLOSED LOOPLOW PASS CHARACTERISTIC 4HE RESONANT FREQUENCY OF THE ANTENNA AND SERVOSYSTEM STRUCTURE INCLUDING THE STRUCTUREFOUNDATION WHICHISACRITICALITEM MUSTBEKEPTWELLABOVETHEBANDWIDTH OF THE SERVOSYSTEM OTHERWISE THE SYSTEM CAN OSCILLATE AT THE RESONANT FREQUENCY !FACTOROFATLEASTISDESIRABLEFORTHERATIOOFSYSTEMRESONANCEFREQUENCYTOSERVO BANDWIDTH(IGHRESONANTFREQUENCYISDIFFICULTTOOBTAINWITHALARGEANTENNA SUCH AS THE!.&01 RADAR WITH A FT DISH BECAUSE OF THE LARGE MASS OF THE SYSTEM
42!#+).'2!$!2
°£
&)'52% A #LOSED LOOP FREQUENCY RESPONSE CHARACTERISTICS OF TWO SERVOSYSTEMSANDB THEIRCORRESPONDINGTIMERESPONSETOASTEPINPUT
4HERATIOWASPUSHEDTOAVERYMINIMUMOFABOUTTOOBTAINSERVOSYSTEMBANDWIDTH OFTHESPECIFIED(Z!SMALLERRADARWITHA FTDISH FOREXAMPLE CANPROVIDEA SERVOSYSTEMBANDWIDTHUPTOOR(ZWITHCONVENTIONALDESIGN ,OCKE DESCRIBES METHODS FOR CALCULATING ANGLE TRACKING LAG FOR A GIVEN TARGET TRAJECTORY VERSUS TIME AND SET OF SERVOSYSTEM CHARACTERISTICS 2ANGE TRACKING LAGS MAYBESIMILARLYCALCULATED BUTWITHTYPICALINERTIALESSELECTRONICTRACKINGSYSTEMS TRACKINGLAGSAREUSUALLYNEGLIGIBLE %LECTRONICALLY STEERABLE ARRAYS PROVIDE A MEANS FOR INERTIALESS ANGLE TRACKING (OWEVER BECAUSEOFTHISCAPABILITY THESYSTEMCANTRACKMULTIPLETARGETSBYRAPIDLY SWITCHINGFROMONETOANOTHERRATHERTHANCONTINUOUSLYTRACKINGASINGLETARGET 4HETRACKERSIMPLYPLACESITSBEAMATTHELOCATIONWHERETHETARGETISEXPECTED CORRECTSFORTHEPOINTINGERRORBYCONVERTINGERRORVOLTAGESWITHKNOWNANGLE ERROR SENSITIVITY TOUNITSOFANGLE ANDMOVESTOTHENEXTTARGET4HESYSTEMDETERMINES WHERETHETARGETWASAND FROMCALCULATIONSOFTARGETVELOCITYANDACCELERATION PRE DICTSWHEREITSHOULDBETHENEXTTIMETHEBEAMLOOKSATTHETARGET4HELAGERROR IN THISCASE ISDEPENDENTONMANYFACTORS INCLUDINGTHEACCURACYOFTHEVALUEOFANGLE SENSITIVITY USED TO CONVERT ERRORVOLTAGESTOANGULARERROR THESIZEOFTHEPREVIOUS TRACKINGERROR ANDTHETIMEINTERVALBETWEENLOOKS
°Óä
2!$!2(!.$"//+
°xÊ /, /Ê +1-/" Ê Ê, Ê/, 2ANGETRACKINGISACCOMPLISHEDBYCONTINUOUSLYMEASURINGTHETIMEDELAYBETWEEN THETRANSMISSIONOFAN2&PULSEANDTHEECHOSIGNALRETURNEDFROMTHETARGET ANDCON VERTINGTHEROUNDTRIPDELAYTOUNITSOFDISTANCE4HERANGEMEASUREMENTISTHEMOST PRECISEPOSITION COORDINATEMEASUREMENTOFTHERADARTYPICALLY WITHHIGH3.2 ITCAN BEWITHINAFEWMETERSATHUNDREDS OF MILESRANGE2ANGETRACKINGUSUALLYPROVIDES THE MAJOR MEANS FOR DISCRIMINATING THE DESIRED TARGET FROM OTHER TARGETS ALTHOUGH DOPPLERFREQUENCYANDANGLEDISCRIMINATIONAREALSOUSED BYPERFORMINGRANGEGAT INGTIMEGATING TOELIMINATETHEECHOOFOTHERTARGETSATDIFFERENTRANGESFROMTHE ERROR DETECTOROUTPUTS4HERANGE TRACKINGCIRCUITRYISALSOUSEDFORACQUIRINGADESIRED TARGET2ANGETRACKINGREQUIRESNOTONLYTHATTHETIMEOFTRAVELOFTHEPULSETOANDFROM THETARGETBEMEASUREDBUTALSOTHATTHERETURNISIDENTIFIEDASATARGETRATHERTHANNOISE ANDARANGE TIMEHISTORYOFTHETARGETBEMAINTAINED !LTHOUGHTHISDISCUSSIONISFORTYPICALPULSE TYPETRACKINGRADARS RANGEMEASURE MENTMAYALSOBEPERFORMEDWITH#7RADARSUSING&- #7 AFREQUENCY MODULATED #7THATISTYPICALLYALINEAR RAMP&-4HETARGETRANGEISDETERMINEDBYTHERANGE RELATEDFREQUENCYDIFFERENCEBETWEENTHEECHO FREQUENCYRAMPANDTHEFREQUENCYOF THERAMPBEINGTRANSMITTED4HEPERFORMANCEOF&- #7SYSTEMS WITHCONSIDERATION OFTHEDOPPLEREFFECT ISDESCRIBEDIN3HERMAN !CQUISITION 4HE FIRST FUNCTION OF THE RANGE TRACKER IS ACQUISITION OF A DESIRED TARGET!LTHOUGHTHISISNOTATRACKINGOPERATION ITISANECESSARYFIRSTSTEPBEFORERANGE TRACKINGORANGLETRACKINGMAYTAKEPLACEINATYPICALRADAR3OMEKNOWLEDGEOFTARGET ANGULARLOCATIONISNECESSARYFORPENCIL BEAMTRACKINGRADARSTOPOINTTHEIRTYPICALLY NARROWANTENNABEAMSINTHEDIRECTIONOFTHETARGET4HISINFORMATION CALLEDDESIGNA TIONDATA MAYBEPROVIDEDBYSURVEILLANCERADARORSOMEOTHERSOURCE)TMAYBESUF FICIENTLYACCURATETOPLACETHEPENCILBEAMONTHETARGET ORITMAYREQUIRETHETRACKER TOSCANALARGERREGIONOFUNCERTAINTY4HERANGE TRACKINGPORTIONOFTHERADARHASTHE ADVANTAGEOFSEEINGALLTARGETSWITHINTHEBEAMFROMCLOSERANGEOUTTOTHEMAXIMUM RANGEOFTHERADAR)TTYPICALLYBREAKSTHISRANGEINTOSMALLINCREMENTS EACHOFWHICH MAYBESIMULTANEOUSLYEXAMINEDFORTHEPRESENCEOFATARGET7HENBEAMSCANNINGIS NECESSARY THERANGETRACKEREXAMINESTHEINCREMENTSSIMULTANEOUSLYFORSHORTPERIODS SUCHASS MAKESITSDECISIONABOUTTHEPRESENCEOFATARGET ANDALLOWSTHEBEAMTO MOVETOANEWLOCATIONIFNOTARGETISPRESENT4HISPROCESSISTYPICALLYCONTINUOUSFOR MECHANICAL TYPETRACKERSTHATMOVETHEBEAMSLOWLYENOUGHTHATATARGETWILLREMAIN WELLWITHINTHEBEAMFORTHESHORTEXAMINATIONPERIODOFTHERANGEINCREMENTS 4ARGETACQUISITIONINVOLVESCONSIDERATIONOFTHE3.THRESHOLDANDINTEGRATIONTIME NEEDED TO ACCOMPLISH A GIVEN PROBABILITY OF DETECTION WITH A GIVEN FALSE ALARM RATE SIMILARTOSURVEILLANCERADAR(OWEVER HIGHFALSE ALARMRATES ASCOMPAREDWITHVALUES USEDFORSURVEILLANCERADARS AREUSEDBECAUSETHEOPERATORKNOWSTHATTHETARGETISPRES ENT ANDOPERATORFATIGUEFROMFALSEALARMSWHENWAITINGFORATARGETISNOTINVOLVED /PTIMUMFALSE ALARMRATESARESELECTEDONTHEBASISOFPERFORMANCEOFELECTRONICCIR CUITSTHATOBSERVEEACHRANGEINTERVALTODETERMINEWHICHINTERVALHASTHETARGETECHO !TYPICALTECHNIQUEISTOSETAVOLTAGETHRESHOLDSUFFICIENTLYHIGHTOPREVENTMOST NOISE PEAKS FROM CROSSING THE THRESHOLD BUT SUFFICIENTLY LOW THAT A WEAK SIGNAL MAY CROSS!NOBSERVATIONISMADEAFTEREACHTRANSMITTERPULSEASTOWHETHER INTHERANGE INTERVALBEINGEXAMINED THETHRESHOLDHASBEENCROSSED4HEINTEGRATIONTIMEALLOWSTHE RADARTOMAKETHISOBSERVATIONSEVERALTIMESBEFOREDECIDINGIFTHEREISATARGETPRESENT
42!#+).'2!$!2
°Ó£
4HEMAJORDIFFERENCEBETWEENNOISEANDATARGETECHOISTHATNOISESPIKESEXCEEDINGTHE THRESHOLDARERANDOM BUTIFATARGETISPRESENT THETHRESHOLDCROSSINGSAREMOREREGULAR /NETYPICALSYSTEMSIMPLYCOUNTSTHENUMBEROFTHRESHOLDCROSSINGSOVERTHEINTEGRATION PERIOD ANDIFCROSSINGSOCCURFORMORETHANHALFTHENUMBEROFTIMESTHATTHERADARHAS TRANSMITTED ATARGETISINDICATEDASBEINGPRESENT)FTHERADARPULSEREPETITIONFREQUENCY IS(ZANDTHEINTEGRATIONTIMEISS THERADARWILLOBSERVETHRESHOLDCROSSINGS IFTHEREISASTRONGANDSTEADYTARGET(OWEVER BECAUSETHEECHOFROMAWEAKTARGET COMBINEDWITHNOISEMAYNOTALWAYSCROSSTHETHRESHOLD ALIMITMAYBESET SUCHAS CROSSINGS THATMUSTOCCURDURINGTHEINTEGRATIONPERIODFORADECISIONTHATATARGETIS PRESENT&OREXAMPLE PERFORMANCEONANON SCINTILLATINGTARGETHASAPROBABILITY OFDETECTIONATAD" PER PULSE3.2ANDAFALSEALARMPROBABILITYOFn4HE!. &03 AND!.&01 INSTRUMENTATIONRADARSUSETHESEDETECTIONPARAMETERSWITH CONTIGUOUSRANGEGATESOFYDEACHFORACQUISITION4HEGATESGIVECOVERAGEOFA NMIRANGEINTERVALATTHERANGEWHERETHETARGETISEXPECTED POSSIBLYFROMCOARSERANGE DESIGNATIONFROMSEARCHRADAR 2ANGE4RACKING /NCEATARGETISACQUIREDINRANGE ITISDESIRABLETOFOLLOWTHE TARGETINTHERANGECOORDINATETOPROVIDEDISTANCEINFORMATIONORSLANTRANGETOTHETAR GET!PPROPRIATETIMINGPULSESPROVIDERANGEGATINGSOTHEANGLE TRACKINGCIRCUITSAND !'#CIRCUITSLOOKATONLYTHESHORTRANGEINTERVAL ORTIMEINTERVAL WHENTHEDESIRED ECHO PULSE IS EXPECTED 4HE RANGE TRACKING OPERATION IS PERFORMED BY CLOSED LOOP TRACKINGSIMILARTOTHEANGLETRACKER%RRORINCENTERINGTHERANGEGATEONTHETARGET ECHOPULSEISSENSED ERRORVOLTAGESAREGENERATED ANDCIRCUITRYISPROVIDEDTORESPOND TOTHEERRORVOLTAGEBYCAUSINGTHEGATETOMOVEINADIRECTIONTORECENTERONTHETARGET ECHOPULSE 4HERANGE TRACKINGERRORMAYBESENSEDINMANYWAYS4HEMOSTCOMMONLYUSED METHODISTHEEARLY ANDLATE GATETECHNIQUESEE&IGURE 4HESEGATESARETIMED SOTHATTHEEARLYGATEOPENSATTHEBEGINNINGOFTHEMAINRANGEGATEANDCLOSESATTHE CENTEROFTHEMAINGATE4HELATEGATEOPENSATTHECENTERANDCLOSESATTHEENDOF THEMAINRANGEGATE4HEEARLYANDLATEGATESEACHALLOWTHETARGETVIDEOTOCHARGE CAPACITORSDURINGTHETIMEWHENTHEGATESAREOPEN4HECAPACITORSACTASINTEGRATORS 4HEEARLY GATECAPACITORCHARGESTOAVOLTAGEPROPORTIONALTOTHEAREAOFTHEFIRSTHALF OFTHETARGETVIDEOPULSE ANDTHELATE GATECAPACITORCHARGESNEGATIVELYPROPORTION ALLYTOTHELATEHALFOFTHETARGETVIDEO7HENTHEGATESAREPROPERLYCENTEREDABOUTA SYMMETRICALVIDEOPULSE THECAPACITORSAREEQUALLYCHARGED3UMMINGTHEIRCHARGE VOLTAGESYIELDSAZEROOUTPUT 7HEN THE GATES ARE NOT CENTERED ABOUT THE TARGET VIDEO SO THAT THE EARLY GATE EXTENDS PAST THE CENTER OF THE TARGET VIDEO THE EARLY GATE CAPACITOR CHARGED POSI TIVELYRECEIVESAGREATERCHARGE4HELATEGATESEESONLYASMALLPORTIONOFTHEPULSE RESULTINGINASMALLERNEGATIVECHARGE3UMMINGTHECAPACITORVOLTAGESRESULTSINA NEGATIVEOUTPUT/VERARANGEOFERRORSOFAPPROXIMATELYoOFTHETARGET VIDEO PULSEWIDTH THEVOLTAGEOUTPUTISESSENTIALLYALINEARFUNCTIONOFTIMINGERRORAND OFAPOLARITYCORRESPONDINGTOTHEDIRECTIONOFERROR$URINGACQUISITION THETARGET ISCENTEREDINTHEYDACQUISITIONGATEBYRANGE TRACKINGTECHNIQUESDESCRIBED ASFOLLOWS ANDTHEGATEISREDUCEDTOAPPROXIMATELYTHEWIDTHOFTHERADARTRANSMIT PULSEFORNORMALTRACKING -ANYRADARRANGE TRACKINGSYSTEMSUSEHIGHSPEEDSAMPLINGCIRCUITRYTOTAKETHREE TOFIVESAMPLESINTHEVICINITYOFTHEECHOVIDEOPULSE4HEAMPLITUDESOFTHESAMPLES ONTHELEADINGANDLAGGINGHALVESOFTHEPULSEARECOMPAREDFORRANGE ERRORSENSING SIMILARTOTHECOMPARISONOFAMPLITUDESINTHEEARLY LATE GATESRANGETRACKER
°ÓÓ
2!$!2(!.$"//+
&)'52% %ARLY ANDLATE GATERANGE ERROR SENSINGCIRCUIT
)NSOMECASES LEADING ORLAGGING EDGERANGETRACKINGISDESIRED4HISHASBEEN ACCOMPLISHEDINSOMEAPPLICATIONSBYSIMPLYADDINGABIASTOMOVETHEERROR SENSING GATESEITHERTOLEADORLAGTHECENTEROFTHETARGET4HISPROVIDESSOMEREJECTIONBYTHE GATESOFUNDESIREDRETURNSTHATMIGHTOCCURNEARTHETARGET SUCHASTHEECHOESFROM OTHER NEARBY TARGETS 4HRESHOLD DEVICES ARE ALSO USED AS LEADING OR LAGGING EDGE TRACKERS BY OBSERVING WHEN THE TARGET VIDEO EXCEEDS A GIVEN THRESHOLD LEVEL 4HE POINTOFCROSSINGTHETHRESHOLDISUSEDTOTRIGGERGATINGCIRCUITSTOREADOUTATARGET RANGEFROMTIMINGDEVICESORTOGENERATEASYNTHETICTARGETPULSE 4HERANGE TRACKINGLOOPISCLOSEDBYUSINGTHERANGE ERROR DETECTOROUTPUTTOREPO SITIONRANGEGATESANDCORRECTRANGEREADOUT/NETECHNIQUEUSESAHIGH SPEEDDIGITAL COUNTER DRIVEN BY A STABLE OSCILLATOR4HE COUNTER IS RESET TO ZERO AT THE TIME OF THE TRANSMITPULSE4ARGETRANGEISREPRESENTEDBYANUMBERSTOREDINADIGITALREGISTER AS SHOWNIN&IGURE!COINCIDENCECIRCUITSENSESWHENTHEDIGITALCOUNTERREACHESTHE NUMBERINTHERANGEREGISTERANDGENERATESTHERANGEGATE ASINDICATEDINTHEBLOCKDIA GRAMSHOWNIN&IGURE!RANGEERRORSENSEDBYTHERANGEERRORDETECTORRESULTSINAN ERRORVOLTAGETHATDRIVESAVOLTAGE CONTROLLEDVARIABLE FREQUENCYOSCILLATORTOINCREASE ORDECREASETHECOUNTINTHERANGEREGISTER DEPENDINGONTHEPOLARITYOFTHEERRORVOLT AGE4HISCHANGESTHENUMBERINTHERANGEREGISTERTOWARDTHEVALUECORRESPONDINGTO THERANGEOFTHETARGET2ANGEREADOUTISACCOMPLISHEDBYREADINGTHENUMBERINTHE REGISTER WHERE FOREXAMPLE EACHBITMAYCORRESPONDTOA YDRANGESTEP
42!#+).'2!$!2
°ÓÎ
&)'52% $IGITALRANGETRACKEROPERATION
!NOTHERTECHNIQUEISTOUSEAPAIROFOSCILLATORSONECONTROLLINGTHETRANSMITTER TRIGGERANDTHEOTHERCONTROLLINGTHERANGEGATE4HERANGERATEISCONTROLLEDBYTHE BEATFREQUENCYBETWEENTHEOSCILLATORS WHEREONEISFREQUENCY CONTROLLEDBYTHERANGE
&)'52% "LOCKDIAGRAMOFADIGITALRANGETRACKER
°Ó{
2!$!2(!.$"//+
ERROR DETECTOR OUTPUTVOLTAGE4HEBEATFREQUENCYISASMALLFRACTIONOFONE(ZANDIS BETTERVISUALIZEDASAPHASERATEBETWEENTHETRANSMITPULSECYCLEANDCYCLEOFTHERANGE GATE4HECHANGINGPHASECAUSESTHERANGEGATETOFOLLOWAMOVINGTARGET 4HEELECTRONICRANGETRACKERISINERTIALESS ALLOWINGANYDESIREDSLEWSPEED ANDPRO VIDESFLEXIBILITYFORCONVENIENTLYGENERATINGACQUISITIONGATESFORAUTOMATIC DETECTION CIRCUITRYASWELLASTRANSMITTERTRIGGERANDPRE TRIGGERPULSES4RACKINGBANDWIDTHISUSU ALLYLIMITEDTOTHATNECESSARYFORTRACKINGTOMINIMIZELOSSOFTRACKTOFALSETARGETSAND COUNTERMEASURES-ANYOTHERELECTRONICRANGE TRACKINGTECHNIQUESALSOOFFERINGMOSTOF THESEADVANTAGESAREUSED NTH 4IME !ROUND 4RACKING 4O EXTEND UNAMBIGUOUS RANGE BY REDUCING THE 02&INCREASESTHEACQUISITIONTIMEANDREDUCESTHEDATARATE!SOLUTIONTOTHISPROB LEMISCALLEDNTH TIME AROUNDTRACKING WHICHAVOIDSTRANSMITTINGATTHETIMETHATAN ECHOISEXPECTEDTOARRIVEANDCANRESOLVETHERANGEAMBIGUITY4HISALLOWSTHERADAR TOOPERATEATHIGH02&ANDTRACKUNAMBIGUOUSLYTOLONGRANGESWHERESEVERALPULSES MAYBEPROPAGATINGINSPACETOANDFROMTHETARGET4HETECHNIQUEISUSEFULONLYWHEN ATARGETISBEINGTRACKED$URINGACQUISITION THERADARMUSTLOOKATTHEREGIONBETWEEN TRANSMITTERPULSES ANDUPONINITIALACQUISITION ITCLOSESTHERANGE ANDANGLE TRACK INGLOOPSWITHOUTRESOLVINGTHERANGEAMBIGUITY4HENEXTSTEPISTOFINDWHICHRANGE INTERVAL ORBETWEENWHICHPAIROFTRANSMITPULSES THETARGETISLOCATED4HEZONENIS DETERMINEDBYCODINGATRANSMITPULSEANDCOUNTINGHOWMANYPULSESRETURNBEFORE THECODEDPULSERETURNS )NSTRUMENTATIONRADARSPROVIDENTH TIME AROUNDTRACKINGCAPABILITYBECAUSEBEA CONSAREUSEDONROCKETSANDSPACEVEHICLESTOPROVIDESUFFICIENTSIGNALLEVELATVERY LONGRANGES 4OPREVENTTHETARGETECHOFROMBEINGBLANKEDBYATRANSMITPULSE ITISNECESSARY TOSENSEWHENTHETARGETISAPPROACHINGANINTERFERENCEREGIONANDSHIFTTHEREGION 4HISISACCOMPLISHEDBYCHANGINGTHE02&ORALTERNATELYDELAYINGGROUPSOFPULSES EQUALTOTHENUMBEROFPULSESINPROPAGATION4HISCANBEPERFORMEDAUTOMATICALLY TOPROVIDEANOPTIMUM02&SHIFTORTOALTERNATELYDELAYPULSEGROUPSOFTHECORRECT NUMBEROFPULSES
°ÈÊ -* Ê " "*1 - Ê/ +1 $UAL "AND -ONOPULSE $UAL BAND MONOPULSE CAN BE EFFICIENTLY ACCOMMO DATEDONASINGLEANTENNATOCOMBINETHECOMPLEMENTARYFEATURESOFTWO2&BANDS !USEFUL COMBINATION OF BANDS IS 8 BAND '(Z AND +A BAND '(Z 4HE 8 BANDOPERATIONPROVIDESTHEEXPECTEDMICROWAVEPERFORMANCEOFGOODRADARRANGE ANDPRECISETRACKING)TSWEAKNESSISTHELOW ANGLEMULTIPATHREGIONANDTHEAVAILABIL ITYOFELECTRONICCOUNTERMEASURESINTHEBAND4HE+ABAND ALTHOUGHATMOSPHERIC AND RAIN ATTENUATION LIMITED PROVIDES MUCH GREATER TRACKING PRECISION IN THE LOW ANGLE MULTIPATHREGIONANDASECONDANDMOREDIFFICULTBANDTHATTHEELECTRONIC COUNTERMEA SURESTECHNIQUESMUSTCOVER !.AVAL2ESEARCH,ABORATORYSYSTEMCALLED42!+84RACKING2ADAR!T+AAND 8BANDS WASDESIGNEDFORINSTRUMENTATIONRADARAPPLICATIONSFORMISSILEANDTRAINING RANGES )TSPURPOSEWASTOADDPRECISIONTRACKINGONTARGETS ESSENTIALLYTOhSPLASHv ANDPROVIDEPRECISIONTRACKINGAT+ABANDINANENVIRONMENTOF8 BANDCOUNTERMEA SUREEXPERIMENTS
42!#+).'2!$!2
°Óx
!SIMILAR8 AND+A BANDSYSTEMWASDEVELOPEDBY(OLLANDSE3IGNAALAPPARATENOF THE.ETHERLANDSFORTACTICALAPPLICATION4HELAND BASEDVERSIONCALLED&,9 #!4#(%2 ISPARTOFAMOBILEANTI AIR WARFARESYSTEM!NOTHERVERSION '/!, +%%0%2 ISFOR ASHIPBOARDANTI AIR WARFAREAPPLICATIONFORTHEFIRECONTROLOF'ATLINGGUNS"OTH SYSTEMSTAKEFULLADVANTAGEOFTHETWOBANDSTOPROVIDEPRECISIONTRACKINGINMULTIPATH ANDELECTRONIC COUNTERMEASURESENVIRONMENTS -IRROR 3CANNED!NTENNA)NVERSE#ASSEGRAIN !NANTENNATECHNIQUETHAT USESAMOVABLE2&MIRRORFORSCANNINGTHEBEAM CALLEDAMIRROR SCANNEDANTENNAOR INVERSE#ASSEGRAIN PROVIDESUSEFULAPPLICATIONSTOMONOPULSERADAR4HETECHNIQUE USESARADOME SUPPORTEDWIRE GRIDPARABOLOIDTHATREFLECTSPARALLEL POLARIZEDFEED ENERGY4HEBEAM POLARIZEDPARALLELTOTHEGRID ISCOLLIMATEDBYTHEPARABOLOIDAND ISREFLECTEDBYAFLATMOVEABLEPOLARIZATIONROTATINGMIRROR4HEBASICPOLARIZATION ROTATINGMIRRORISAFLATMETALSURFACEWITHAGRIDOFWIRESLOCATEDAQUARTERWAVE LENGTHABOVETHEMETALSURFACEANDORIENTEDATRELATIVETOTHE2&ENERGYREFLECTED FROM THE PARABOLOID 4HE 2& ENERGY MAY BE VISUALIZED AS BEING COMPOSED OF A COMPONENTPARALLELTOANDREFLECTINGFROMTHEGRIDANDACOMPONENTPERPENDICULAR TOANDPASSINGTHROUGHTHEGRIDTOREFLECTFROMTHEMETALMIRRORSURFACEBELOW"Y TRAVELINGTHEQUARTERWAVESPACETWICE THISCOMPONENTISSHIFTEDBYINPHASE 7HENADDEDTOTHEREFLECTIONFROMTHEGRID ITRESULTSINACHANGEINPOLARIZA TION4HETOTALREFLECTEDENERGYFROMTHEMIRRORROTATEDBYWILLEFFICIENTLYPASS THROUGHTHEWIRE GRIDPARABOLOID4HEADVANTAGESAREASFOLLOWS 4HEMIRRORAND ITSDRIVEMECHANISMARETHEONLYMOVINGPARTSFORBEAMMOVEMENT4HEFEEDAND RADOME SUPPORTEDPARABOLOIDREMAINFIXED 4HEBEAMMOVEMENTISBYSPECULAR REFLECTION TWICETHEANGLEOFTHEMIRRORTILT4HISPROVIDESACOMPACTSTRUCTUREFOR AGIVENANGLECOVERAGEREQUIREMENT 4HENORMALLYLIGHTWEIGHTMIRRORANDTHE BEAM DISPLACEMENT VERSUS MIRROR TILT ALLOW REDUCED SIZE AND VERY RAPID BEAM SCANWITHLOWSERVODRIVEPOWER 4HECOMPACTNESSANDLIGHTNESSAREPARTICULARLYATTRACTIVEFORAIRBORNEAPPLICATIONS SUCHASTHE4HOMPSON #3&!GAVERADARINTHE3UPER%NTENDARDS WHICHDETERMINES TARGETRANGEANDDESIGNATIONDATAFORTHE%XOCETMISSILE)TISACOMPACTMONOPULSE ROLL ANDPITCH STABILIZEDRADARWITHAZIMUTHANDELEVATIONSCAN4HE)SRAELI %LTASUBSIDIARYOF)SRAELI!IRCRAFT)NDUSTRIESALSODEVELOPEDANAIRBORNETRACKINGRADAR USINGTHISANTENNATECHNOLOGYFORAIR TO AIRCOMBATANDGROUNDWEAPONDELIVERY ! GROUND OR SHIPBOARD BASED EXPERIMENTAL MIRROR ANTENNA SYSTEM CONCEPT WAS DEVELOPEDWITHDUAL BANDMONOPULSECAPABILITY'(ZAND'(ZBANDS 4HE OBJECTIVE INCLUDED HIGH SPEED BEAM MOVEMENT FOR HIGH DATA RATE $ SURVEILLANCE ANDMULTITARGETPRECISIONTRACKING$UAL BANDPOLARIZATION TWISTMIRRORDESIGNWAS ACCOMPLISHEDWITHATWO LAYERMIRRORGRIDCONFIGURATION /N !XIS4RACKING 4HEBESTRADARTRACKINGPERFORMANCEISUSUALLYACCOMPLISHED WHEN THE TARGET IS ESSENTIALLY ON THE RADAR ANTENNA AXIS 4HEREFORE FOR MAXIMUM PRECISIONTRACKING ITISDESIRABLETOMINIMIZELAGANDOTHERERRORSOURCESAFFECTING THEBEAMPOINTING!TECHNIQUECALLEDON AXISTRACKINGWASDEVELOPEDTOMINIMIZE RADARAXISDEVIATIONFROMTHETARGETBYPREDICTIONANDOPTIMUMFILTERINGWITHINTHE TRACKINGLOOP 4HETECHNIQUEISPARTICULARLYEFFECTIVEWHENTHETARGETTRAJECTORYIS KNOWNAPPROXIMATELY SUCHASWHENTRACKINGSATELLITESINORBITORABALLISTICTARGET! COMPUTERINTHETRACKINGLOOPCANCAUSETHERADARTOFOLLOWANESTIMATEDSETOFORBITAL PARAMETERS FOR EXAMPLE )T ALSO PERFORMS OPTIMUM FILTERING OF RADAR ANGLE ERROR DETECTOROUTPUTTOGENERATEANERRORTRENDFROMWHICHITCANUPDATETHEASSUMEDSET
°ÓÈ
2!$!2(!.$"//+
OF ORBITAL PARAMETERS TO CORRECT THE RADAR BEAM MOVEMENT TO UPDATE THE ORIGINAL SETOFORBITALPARAMETERS ANDBYTHISMEANS THERADARANTENNAAXISCANBEHELDON TARGETWITHMINIMUMERROR )MPROVEDTRACKINGCANALSOBEPROVIDEDONOTHERTARGETSWHERETHEAPPROXIMATE TRAJECTORY CAN BE ANTICIPATED (OWEVER PERFORMANCE OF ON AXIS TRACKING IS LIMITED WHENTRACKINGTARGETSWITHUNANTICIPATEDMANEUVERS
°ÇÊ -"1,
-Ê"Ê ,,", 4HEREAREMANYSOURCESOFERRORINRADAR TRACKINGPERFORMANCE&ORTUNATELY MOSTARE INSIGNIFICANTEXCEPTFORVERYHIGH PRECISIONTRACKING RADARAPPLICATIONSSUCHASRANGE INSTRUMENTATION WHERETHEANGLEPRECISIONREQUIREDMAYBEOFTHEORDEROFMRAD MRAD ORMILLIRADIAN ISONETHOUSANDTHOFARADIAL ORTHEANGLESUBTENDEDBY M CROSS RANGEAT MRANGE -ANYSOURCESOFERRORCANBEAVOIDEDORREDUCEDBY RADARDESIGNORMODIFICATIONOFTHETRACKINGGEOMETRY#OSTISAMAJORFACTORINPROVID INGHIGH PRECISION TRACKINGCAPABILITY4HEREFORE ITISIMPORTANTTOKNOWHOWMUCH ERRORCANBETOLERATED WHICHSOURCESOFERRORAFFECTTHEAPPLICATION ANDWHATISTHE MOSTCOST EFFECTIVEMEANSTOSATISFYTHEACCURACYREQUIREMENTS "ECAUSETRACKINGRADARSTRACKTARGETSNOTONLYINANGLEBUTALSOINRANGEANDSOME TIMESINDOPPLER THEERRORSINEACHOFTHESETARGETPARAMETERSMUSTBECONSIDEREDON MOSTERRORBUDGETS4HERESTOFTHISCHAPTERWILLPROVIDEAGUIDEFORDETERMININGTHE SIGNIFICANTERRORSOURCESANDTHEIRMAGNITUDES )T IS IMPORTANT TO RECOGNIZE WHAT THE ACTUAL RADAR INFORMATION OUTPUT IS &OR A MECHANICALLYMOVEDANTENNA THEANGLE TRACKINGOUTPUTISUSUALLYOBTAINEDFROMTHE SHAFT POSITION OF THE ELEVATION AND AZIMUTH ANTENNA AXES!BSOLUTE TARGET LOCATION RELATIVETOEARTHCOORDINATES WILLINCLUDETHEACCURACYOFTHESURVEYOFTHEANTENNA PEDESTALSITE 0HASED ARRAY INSTRUMENTATION RADAR SUCH AS THE -ULTI OBJECT 4RACKING 2ADAR -/42 PROVIDEELECTRONICBEAMMOVEMENTOVERALIMITEDSECTOROFABOUToO TO APPROXIMATELYoOPLUSMECHANICALMOVEMENTOFTHEANTENNATOMOVETHECOVERAGE SECTORn 4HEOUTPUTWILLBEMECHANICALSHAFTPOSITIONSLOCATINGTHENORMALTOTHE ARRAYPLUSDIGITALANGLEINFORMATIONFROMTHEELECTRONICBEAMSCANFOREACHTARGET
°nÊ /, / 1- Ê ,,",-Ê/, /Ê "- ® 2ADARTRACKINGOFTARGETSISPERFORMEDBYUSEOFTHEECHOSIGNALREFLECTEDFROMATARGET ILLUMINATED BY THE RADAR TRANSMIT PULSE4HIS IS CALLED SKIN TRACKING TO DIFFERENTIATE ITFROMBEACONTRACKING WHEREABEACONORATRANSPONDERTRANSMITSITSSIGNALTOTHE RADARANDUSUALLYPROVIDESASTRONGERPOINT SOURCESIGNAL"ECAUSEMOSTTARGETS SUCH ASAIRCRAFT ARECOMPLEXINSHAPE THETOTALECHOSIGNALISCOMPOSEDOFTHEVECTORSUM OFAGROUPOFSUPERIMPOSEDECHOSIGNALSFROMTHEINDIVIDUALPARTSOFTHETARGET SUCHAS THEENGINES PROPELLERS FUSELAGE ANDWINGEDGES4HEMOTIONSOFATARGETWITHRESPECT TO THE RADAR CAUSES THE TOTAL ECHO SIGNAL TO CHANGE WITH TIME RESULTING IN RANDOM FLUCTUATIONSINTHERADARMEASUREMENTSOFTHEPARAMETERSOFTHETARGET4HESEFLUCTUA TIONSCAUSEDBYTHETARGETONLY EXCLUDINGATMOSPHERICEFFECTSANDRADARRECEIVERNOISE CONTRIBUTIONS ARECALLEDTARGETNOISE
42!#+).'2!$!2
°ÓÇ
4HISDISCUSSIONOFTARGETNOISEISBASEDLARGELYONAIRCRAFT BUTITISGENERALLYAPPLI CABLETOANYTARGET INCLUDINGLANDTARGETSOFCOMPLEXSHAPETHATARELARGEWITHRESPECT TOAWAVELENGTH4HEMAJORDIFFERENCEISINTHETARGETMOTION BUTTHEDISCUSSIONSARE SUFFICIENTLYGENERALTOAPPLYTOANYTARGETSITUATION 4HEECHORETURNFROMACOMPLEXTARGETDIFFERSFROMTHATOFAPOINTSOURCEBYTHE MODULATIONSTHATAREPRODUCEDBYTHECHANGEINAMPLITUDEANDRELATIVEPHASEOFTHE RETURNS FROM THE INDIVIDUAL ELEMENTS4HE WORD MODULATIONS IS USED IN PLURAL FORM BECAUSEFIVETYPESOFMODULATIONOFTHEECHOSIGNALTHATARECAUSEDBYACOMPLEXTARGET AFFECTRADARS4HESEAREAMPLITUDEMODULATION PHASEFRONTMODULATIONGLINT POLAR IZATIONMODULATION DOPPLERMODULATION ANDPULSETIMEMODULATIONRANGEGLINT 4HE BASICMECHANISMBYWHICHTHEMODULATIONSAREPRODUCEDISTHEMOTIONOFTHETARGET INCLUDINGYAW PITCH ANDROLL WHICHCAUSESTHECHANGEINRELATIVERANGEOFTHEVARIOUS INDIVIDUALELEMENTSWITHRESPECTTOTHERADAR !LTHOUGHTHETARGETMOTIONSMAYAPPEARSMALL ACHANGEINRELATIVERANGEOFTHE PARTS OF A TARGET OF ONLY ONE HALF WAVELENGTH BECAUSE OF THE TWO WAY RADAR SIGNAL PATH CAUSESAFULLCHANGEINRELATIVEPHASE!T8BAND THISISABOUTCM WHICH ISSMALLEVENCOMPAREDWITHTHEFLEXUREBETWEENPARTSOFANAIRCRAFT 4HEFIVETYPESOFMODULATIONCAUSEDBYACOMPLEXTARGETAREDISCUSSEDNEXT !MPLITUDE.OISE !MPLITUDENOISEISTHECHANGEINECHOSIGNALAMPLITUDECAUSED BYACOMPLEX SHAPEDTARGET EXCLUDINGTHEEFFECTSOFCHANGINGTARGETRANGE)TISTHE MOST OBVIOUS OF THE VARIOUS TYPES OF ECHO SIGNAL MODULATION BY A COMPLEX SHAPED TARGETANDISREADILYVISUALIZEDASTHEFLUCTUATINGSUMOFMANYSMALLVECTORSCHANGING RANDOMLYINRELATIVEPHASE!LTHOUGHITISCALLEDNOISE ITMAYINCLUDEPERIODICCOMPO NENTS!MPLITUDENOISETYPICALLYFALLSINTOALOWFREQUENCYANDHIGHFREQUENCYREGION OFINTEREST4HESECATEGORIESOVERLAPINSOMERESPECTS BUTITISCONVENIENTTOSEPARATE THENOISEINTHESETWOFREQUENCYRANGESBECAUSETHEYAREGENERATEDBYDIFFERENTPHE NOMENA ANDTHEYAREEACHSIGNIFICANTTODIFFERENTFUNCTIONSOFTHERADAR ,OW &REQUENCY!MPLITUDE.OISE 4HELOW FREQUENCYAMPLITUDENOISEISTHETIME VARIATIONOFTHEVECTORSUMOFTHEECHOESFROMALLTHEREFLECTINGSURFACESOFTHETARGET 4HETIMEVARIATIONISVISUALIZEDBYCONSIDERINGTHETARGETASARELATIVELYRIGIDBODY WITHNORMALYAW PITCH ANDROLLMOTIONS4HESMALLCHANGESINRELATIVERANGEOFTHE REFLECTORSCAUSEDBYTHISMOTIONRESULTINCORRESPONDINGhRANDOMvCHANGEINTHERELA TIVEPHASES#ONSEQUENTLY THEVECTORSUMFLUCTUATESRANDOMLY4YPICALLY TARGETRAN DOMMOTIONISLIMITEDTOSMALLASPECTCHANGESSUCHTHATTHEAMPLITUDESOFTHEECHOES FROMTHEINDIVIDUALREFLECTORSVARYLITTLEOVERAPERIODOFAFEWSECONDS ANDCHANGEIN RELATIVEPHASEISTHEMAJORCONTRIBUTOR%XCEPTIONSARELARGEFLATSURFACESWITHNARROW REFLECTIONPATTERNS !NEXAMPLEOFATARGETCONFIGURATIONISADISTRIBUTIONOFREFLECTINGSURFACESTHAT CHANGEINRELATIVERANGEWITHTARGETMOTION!TYPICALPULSEAMPLITUDETIMEFUNCTIONIS ASLOWLYVARYINGECHOAMPLITUDE4HELOW FREQUENCYAMPLITUDENOISECONTRIBUTESTHE LARGESTPORTIONOFTHENOISEMODULATIONDENSITYANDISCONCENTRATEDMAINLYBELOWABOUT (ZAT8BAND4HEAMPLITUDE NOISESPECTRUMISSIMILARFORBOTHLARGEANDSMALL TARGETS4HISISBECAUSETHERATEOFRELATIVERANGECHANGEISAFUNCTIONOFBOTHANGULAR YAWANDDISTANCEFROMTHECENTEROFGRAVITYOFTHEAIRCRAFT4HUS ALARGERAIRCRAFTWITH SLOWYAWRATESBUTGREATERWINGSPANGENERATESALOW FREQUENCYNOISESPECTRUMSIMI LARTOTHATOFASMALLAIRCRAFTWITHHIGHYAWRATESBUTSMALLERWINGSPAN(OWEVER THE LARGERAIRCRAFTTYPICALLYHASTHEBROADERNOISESPECTRUMBECAUSEOFTHEDIFFERENCEIN DISTRIBUTIONOFDOMINANTREFLECTORS
°Ón
2!$!2(!.$"//+
4HE RADAR FREQUENCY AFFECTS THE LOW FREQUENCY AMPLITUDE NOISE SPECTRUM SHAPE WHERETHESPECTRUMWIDTHISCLOSELYPROPORTIONALTOTHERADARFREQUENCYIFTHETARGET SPANISASSUMEDTOBEATLEASTSEVERALWAVELENGTHS 4HEREASONFORTHISDEPENDENCE ISTHATTHERELATIVEPHASEOFTHEINDIVIDUALECHOSIGNALSISAFUNCTIONOFTHENUMBEROF WAVELENGTHSOFCHANGEINRELATIVERANGECAUSEDBYTHETARGETSRANDOMMOTION4HUS WITH SHORTER WAVELENGTHS A GIVEN RELATIVE RANGE CHANGE WILL SUBTEND MORE WAVE LENGTHS CAUSINGHIGHERPHASERATE RESULTINGINHIGHER FREQUENCYNOISECOMPONENTS 4HERATEOFAMPLITUDEFLUCTUATIONSOFTHEENVELOPEOFTHEECHOPULSESISAPPROXIMATELY PROPORTIONALTOTHERADARFREQUENCY ! MATHEMATICAL MODEL OF LOW FREQUENCY AMPLITUDE NOISE OF A TYPICAL AIRCRAFT IS GIVENBY
! F
"
" F
WHERE! F FRACTIONALMODULATION (Z
" HALF POWERBANDWIDTH (Z
F FREQUENCY (Z 4HEVALUEOF"FALLSTYPICALLYBETWEEN(ZAND(ZAT8BAND WITHTHELARGER AIRCRAFTATTHEHIGHERVALUESBECAUSEOFTHELARGERREFLECTORS SUCHASENGINES SPREAD OUT ALONG THE WINGS4HESE REFLECTORS WITH THE GREATER SEPARATION CONTRIBUTE TO THE HIGHERFREQUENCIESBECAUSETHEIRRELATIVERANGECHANGEISLARGEFORAGIVENANGULAR MOVEMENTOFTHETARGET! F ISTHEMODULATIONPOWERDENSITYSUCHTHATTHESPECTRUM MAYBEINTEGRATEDOVERANYFREQUENCYRANGETOFINDTHETOTALNOISEPOWERWITHINA FREQUENCYBANDOFINTEREST4AKINGTHESQUAREROOTOFTHEVALUEOFTHEINTEGRALGIVES THERMSMODULATION (IGH &REQUENCY !MPLITUDE .OISE (IGH FREQUENCY AMPLITUDE NOISE CONSISTS OF BOTHRANDOMNOISEANDPERIODICMODULATION4HERANDOMNOISEISLARGELYARESULTOF THEVIBRATIONANDMOVINGPARTSOFTHEAIRCRAFTPRODUCINGARELATIVELYFLATNOISESPEC TRUMSPREADOUTTOAFEWHUNDRED(Z DEPENDINGONTHETYPEOFAIRCRAFT4HERMSNOISE DENSITYISTYPICALLYAFEWPERCENTOFMODULATIONPER (Z 4HE PERIODIC MODULATION APPEARING AS SPIKES IN THE &IGURE SPECTRUM ARE CAUSEDBYRAPIDLYROTATINGPARTSOFANAIRCRAFT SUCHASTHEPROPELLERS!STHEECHO FROMAPROPELLERBLADECHANGESWITHASPECTWHENITROTATES APERIODICMODULATION
&)'52% 4YPICALAMPLITUDESPECTRALVOLTAGEDISTRIBUTIONSHOWINGTHEPROPELLERMODULATIONMEASURED ONAPROPELLER DRIVENAIRCRAFTINFLIGHT&IGUREFROM$UNN (OWARD AND+ING¡)2%
42!#+).'2!$!2
°Ó
ISPRODUCED4HEBACKGROUNDNOISEFROMTHEAIRFRAMEISALSOOBSERVED4HESPIKES INTHESPECTRUMRESULTFROMAFUNDAMENTALMODULATIONFREQUENCYRELATEDTOTHEPRO PELLER REVMIN AND NUMBER OF BLADES 3INCE IT IS NOT USUALLY SINUSOIDAL THERE ARE HARMONICFREQUENCIESSPREADTHROUGHOUTTHESPECTRUM ASSHOWNIN&IGUREFOR THE3." ASMALLAIRCRAFTWITHTWOPROPELLERENGINES4HELOCATIONOFTHESESPIKES ISNOTDEPENDENTON2&FREQUENCY ASINTHECASEOFLOW FREQUENCYAMPLITUDENOISE BECAUSE THE TARGET CONTROLS THE PERIODICITY OF THE MODULATION WHICH IS DEPENDENT ONLYONTHEAIRCRAFTPROPELLERROTATIONRATEANDNUMBEROFBLADES*ETAIRCRAFTMAYALSO CAUSEECHOAMPLITUDEMODULATIONOFRADARSIGNALSREFLECTEDFROMROTATINGFANBLADES FROMWITHINTHEJETENGINES4HEJETENGINECAUSEDMODULATIONISCALLED*ET%NGINE -ODULATION*%- SPECTRALMODULATIONLINES4HEHIGH FREQUENCY NOISEMODULATION AFFECTSSCAN TYPETRACKINGRADARS ASDESCRIBEDLATER ANDGIVESSOMEINFORMATIONAS TOTHETYPEOFAIRCRAFT %FFECTS OF !MPLITUDE 3CINTILLATION ON 2ADAR 0ERFORMANCE !MPLITUDE NOISE TO SOMEEXTENT AFFECTSALLTYPESOFRADARSINPROBABILITYOFDETECTIONANDTRACKINGRADAR ACCURACYn/NEEFFECTONALLTYPESOFTRACKINGRADARSISTHEINTERRELATIONBETWEENTHE LOW FREQUENCYSPECTRUMOFAMPLITUDENOISE THE!'#CHARACTERISTICSWHICHDETERMINE TOWHATEXTENTTHESLOWFLUCTUATIONSARESMOOTHED ANDTHEANGLENOISE4HEEFFECTSON ANGLENOISEAREDESCRIBEDLATERINTHISSECTION WHEREITISDESCRIBEDWHYAFAST ACTING !'#ISGENERALLYTHEPREFERREDCHOICEFORMAXIMIZINGOVERALLTRACKINGACCURACY (IGH FREQUENCYAMPLITUDENOISECAUSESERRORSONLYINCONICAL SCANORSEQUENTIALLOB ING TRACKING RADARS BECAUSE THE EFFECTS ARE ELIMINATED BY THE MONOPULSE TECHNIQUES #ONICALSCANORSEQUENTIALLOBING TOSENSETARGETDIRECTION DEPENDUPONMEASURINGTHE AMPLITUDEOFTHESIGNALFORATLEASTTWODIFFERENTANTENNABEAMPOSITIONSFOREACHTRACKING AXIS)NAZIMUTHTRACKING FOREXAMPLE THEANTENNABEAMISDISPLACEDTOTHELEFTOFTHE TARGETANDTHENTOTHERIGHT)FTHETARGETWEREONTHEANTENNAAXIS THESIGNALWOULDDROP THESAMEAMOUNTWHENTHEBEAMASSUMEDTOBESYMMETRICAL ISMOVEDANEQUALAMOUNT INEITHERDIRECTION4HEAMPLITUDESFOREACHBEAMPOSITIONARESUBTRACTEDINANANGLEERROR DETECTORHENCE THEOUTPUTISZEROIFTHETARGETISONTHEANTENNAAXISANDBECOMESFINITE INCREASINGPOSITIVELYORNEGATIVELYASTHETARGETMOVESOFFAXISTOTHERIGHTORLEFT (IGH FREQUENCYNOISECANCAUSETHEAMPLITUDETOCHANGEDURINGTHETIMETAKENTO MOVETHEANTENNABEAMFROMONEPOSITIONTOTHENEXT%VENIFTHETARGETISONAXIS HIGH FREQUENCY NOISE CAN CAUSE THE AMPLITUDE AT THE TWO BEAM POSITIONS TO DIFFER THUSCAUSINGANERRONEOUSINDICATIONTHATTHETARGETISOFFAXIS4HISEFFECTISAVERAGED OUTEXCEPTFORTHENOISESPECTRALENERGYNEARTHESCANRATE&OREXAMPLE APERIODIC MODULATIONSPIKENEARTHESCANRATEWILLCAUSETHETRACKINGRADARTODRIVEITSANTENNA INACIRCULARMOTIONAROUNDTHETARGETATARATEEQUALTOTHEDIFFERENCEINFREQUENCY BETWEENTHESCANRATEANDTHEFREQUENCYOFTHESPECTRALLINE4HEDIRECTION CLOCKWISE ORCOUNTERCLOCKWISE DEPENDSUPONWHETHERTHESPECTRALLINEISABOVEORBELOWTHE SCAN RATE AND WHETHER THE SCAN IS CLOCKWISE OR COUNTERCLOCKWISE4HE SERVOSYSTEM FILTERSOUTALLFREQUENCIESOUTSIDETHEFREQUENCYRANGEBETWEENTHESCANRATEPLUSTHE SERVOBANDWIDTHANDTHESCANRATEMINUSTHESERVOBANDWIDTH ANDANANGLESENSITIVITY CONSTANTTHATCONVERTSRMSMODULATIONTORMSANGLEERROR !NEQUATIONUSINGTHISRELATIONTOCALCULATERMSNOISEINSCANNINGANDLOBING TYPE TRACKINGRADARSCAUSEDBYHIGH FREQUENCYAMPLITUDENOISEIS
SS
Q" KS
! FS B
°Îä
2!$!2(!.$"//+
WHERE RS RMSANGLEERRORINSAMEANGULARUNITSASP"
! FS RMS FRACTIONAL MODULATIONNOISEDENSITYINVICINITYOFSCANRATE
KS CONICAL SCANERRORSLOPEKS FORSYSTEMOPTIMUM
P" ONE WAYANTENNABEAMWIDTH
A SERVOBANDWIDTH (Z !SAMPLECALCULATIONFORANFSOF(Z WHERE!FS FROMMEASUREDDATATAKENONA LARGEJETAIRCRAFTISAPPROXIMATELY (Z P"ISMILS ANDAIS(Z GIVESARS OFMILRMS )NTHECASEOFAPERIODICMODULATION WHEREASPECTRALLINEFALLSWITHINTHEBAND FSoA THERMSNOISEISRS P"! FS WHERE! FS ISTHERMSFRACTIONALMODULATION CAUSEDBYTHESPECTRALLINE4HERESULTANTRMSTRACKINGERRORRSWILLBEPERIODICATTHE FREQUENCYFS FTWHEREFTISTHEFREQUENCYOFTHESPECTRALLINE 4HEEFFECTSOFAMPLITUDENOISEONTARGETDETECTIONANDACQUISITIONAREOFCONCERNIN ALLTYPESOFRADARS PARTICULARLYATLONGRANGESWHERETHESIGNALISWEAK4HEAMPLITUDE FLUCTUATIONSCANCAUSETHESIGNALTODROPBELOWTHENOISELEVELFORSHORTPERIODSOFTIME THUSAFFECTINGTHECHOICEOFTHRESHOLDS ACQUISITIONSCANRATE ANDDETECTIONLOGICn !NGLE .OISE 'LINT !NGLE NOISE CAUSES A CHANGE WITH TIME IN THE APPARENT LOCATIONOFTHETARGETWITHRESPECTTOAREFERENCEPOINTONTHETARGET4HISREFERENCE POINTISUSUALLYCHOSENASTHECENTEROFhGRAVITYvOFTHEREFLECTIVITYDISTRIBUTIONALONG THETARGETCOORDINATEOFINTEREST4HECENTEROFGRAVITYISTHELONG TIME AVERAGEDTRACK INGANGLEONATARGET4HETERMGLINTISSOMETIMESUSEDFORANGLENOISE BUTITGIVES THEFALSEIMPRESSIONTHATTHEWANDERINTHEAPPARENTPOSITIONOFATARGETALWAYSFALLS WITHINTHETARGETSPAN)TWASORIGINALLYEXPECTEDTHATANGLEFLUCTUATIONSCAUSEDINA MONOPULSERADARBYATARGETWOULDBESIMPLEVARIATIONSINTHECENTEROFGRAVITYOF THEREFLECTINGAREASHOWEVER MUCHLARGERANGLEERRORSWEREOBSERVED4HEAPPARENT ANGULARLOCATIONOFATARGETCANFALLATAPOINTCOMPLETELYOUTSIDETHEEXTREMITIESOF THETARGET4HISCANBEDEMONSTRATEDBOTHEXPERIMENTALLYANDTHEORETICALLY !PAIR OFSCATTERERSCANBEAPPROPRIATELYSPACEDTOCAUSEATRACKINGRADARWITHCLOSED LOOP TRACKINGTOALIGNITSANTENNAAXISATAPOINTMANYTIMESTHESCATTERERSPACINGAWAY FROMTHESCATTERERS)FTHESCATTERERSARESTATIONARY THERADARANTENNAWILLSTAYPOINTING INTHEERRONEOUSDIRECTION&IGURESHOWSEXPERIMENTALDATADEMONSTRATINGTHIS PHENOMENONWITHATWO REFLECTORTARGET 4HEANGLENOISEPHENOMENONAFFECTSALLTYPESOFTRACKINGRADARSBUTISMAINLYOF CONCERNFORTRACKINGRADARSWHEREPRECISIONTARGETLOCATIONISNEEDED4OAIDINVISU ALIZINGWHYANGLENOISEAFFECTSANYRADAR TYPEANGULAR DIRECTION SENSINGDEVICE THE ECHOSIGNALPROPAGATINGINSPACEWASANALYZED SHOWINGTHATTHEANGLENOISEISPRES ENTINTHISPROPAGATINGENERGYASADISTORTIONOFTHEPHASEFRONT4HEORETICALPLOTSOF ADISTORTEDPHASEFRONTFROMDUALSOURCESCOMPAREVERYCLOSELYWITHPHOTOGRAPHSOF THEPHASEFRONTOFTHERADIATINGSURFACERIPPLESINTHERIPPLE TANKEXPERIMENTWITHDUAL VIBRATINGPROBES!LLRADARANGLE SENSINGDEVICESSENSE BYONEMEANSORANOTHER THE PHASEFRONTOFTHESIGNALANDINDICATETHETARGETTOBEINADIRECTIONNORMALTOTHEPHASE FRONT4HUS THEPHASE FRONTDISTORTIONSAFFECTALLTYPESOFANGLE SENSINGRADARS -ANYMEASUREMENTSOFANGLENOISEHAVEBEENMADEONAVARIETYOFAIRCRAFT AND THE RESULTS OF THEORETICAL STUDIES HAVE BEEN VERIFIED4HE THEORY AND MEASUREMENTS SHOWTHATANGLENOISEEXPRESSEDINLINEARUNITSOFDISPLACEMENT SUCHASMETERS OFTHE APPARENTPOSITIONOFTHETARGETFROMTHECENTEROFGRAVITYOFTHETARGETISINDEPENDENT OFRANGEEXCEPTFORVERYSHORTRANGES 4HEREFORE RMSANGLENOISERANGISEXPRESSEDIN
42!#+).'2!$!2
°Î£
% % %
!"#!!$
&)'52% !PPARENTLOCATIONOFADUAL SOURCETARGETASAFUNCTIONOFRELATIVEPHASEEFORDIFFERENT VALUESOFRELATIVEAMPLITUDEAMEASUREDWITHATRACKINGRADAR&IGUREFROM(OWARD
UNITSOFMETERSOFERRORMEASUREDATTHETARGETLOCATION4HERESULTSSHOWTHATTHERMS VALUEOFANGLENOISERANGISEQUALTO2O WHERE2OISTHERADIUS OF GYRATION TAKEN ALONGTHEANGULARCOORDINATEOFINTEREST OFTHEDISTRIBUTIONOFTHEREFLECTINGAREASOFTHE TARGET&OREXAMPLE IFATARGETSREFLECTINGAREASHAVEACOSO@, SHAPEDDISTRIBU TION WHERE@ISAVARIABLEANDTHETARGETSPANISFROM ,TOn, CALCULATIONOFTHE RADIUSOFGYRATIONDIVIDEDBY GIVESAVALUEOFRANGOF,4YPICALVALUESOFRANG ONACTUALAIRCRAFTFALLBETWEEN,AND, DEPENDINGUPONTHEDISTRIBUTIONOFTHE MAJORREFLECTINGAREASSUCHASENGINES WINGTANKS ANDSOON!SMALLAIRCRAFT NOSE ONVIEW WITHASINGLEENGINEANDNOSIGNIFICANTREFLECTORSATTACHEDTOTHEWINGSWILL HAVEARANGOFAPPROXIMATELY, WHEREASLARGERAIRCRAFTWITHANOUTBOARDENGINEAND POSSIBLYWINGTANKSWILLHAVEARANGAPPROACHINGTHEVALUEOF,4HEAIRCRAFTSIDE VIEWALSOTENDSTOWARDTHEVALUEOF,BECAUSEOFAMORECONTINUOUSDISTRIBUTION OFREFLECTINGAREAS%STIMATIONOFANGLESCINTILLATIONRMSERRORINUNITSOFTARGETSPAN CANBEMADEBYRELATINGTHEAPPROXIMATETARGETDISTRIBUTIONIN&IGUREWITHACTUAL AIRCRAFTCONFIGURATIONS 4HEVALUEOFRANGFORACOMPLEXTARGETISESSENTIALLYAFIXEDVALUEREGARDLESSOF2& FREQUENCY IFATARGETSPANOFATLEASTSEVERALWAVELENGTHSISASSUMEDANDISINDEPENDENT OFTHERATEOFRANDOMMOTIONOFTHETARGET(OWEVER ASDESCRIBEDLATER THESPECTRAL DISTRIBUTIONOFANGLE NOISEPOWERISDIRECTLYAFFECTEDBYRADARFREQUENCY ATMOSPHERIC TURBULENCE ANDOTHERPARAMETERS
2ADIUS OF GYRATIONISCALCULATEDASSUMINGTHEhWEIGHTvOFTHESCATTERERSISTHEIREFFECTIVERADARSCATTERINGCROSSSECTION
°ÎÓ
2!$!2(!.$"//+
! " !
! $!
" % !
!!
!# !
!# ! !
&)'52% 2-3ANGLESCINTILLATIONBASEDONTHETHEORETICALRELATIONTOTHERADIUS OF GYRATIONOFTHE DISTRIBUTIONOFREFLECTINGAREASOFTHETARGET
4ARGETANGLENOISEISTYPICALLYGAUSSIAN DISTRIBUTED!NEXAMPLEOFTHEMEASURED DISTRIBUTION OF THE APPARENT TARGET ANGLE OF A SMALL TWO ENGINE AIRCRAFT IS SHOWN IN &IGURE!RELATIVELYLONGTIMESAMPLEISNEEDED SINCESHORTTIMESAMPLESOFDATA CANDEPARTFROMTHEGAUSSIANSHAPE5NUSUALTARGETSMAYALSODEPARTFROMGAUSSIAN DISTRIBUTED ANGLE NOISE $ELANO GIVES DATA FROM TWO AIRCRAFT IN FORMATION THAT ARE GAUSSIAN DISTRIBUTED WHEN COMPLETELY UNRESOLVED BUT CHANGE SHAPE AT CLOSE RANGE WHERETHEANTENNABEGINSTORESOLVETHETWOAIRCRAFTASDESCRIBEDIN3ECTION
&)'52% !MPLITUDEPROBABILITYDISTRIBUTIONOFANGLESCINTILLATIONMEASUREDONASMALL TWO ENGINEAIRCRAFT
42!#+).'2!$!2
°ÎÎ
!LTHOUGHTHERMSVALUEOFANGLENOISEISESSENTIALLYACONSTANTFORAGIVENTARGETAND ASPECT THESPECTRALDISTRIBUTIONOFTHISENERGYISDEPENDENTONRADARFREQUENCYANDTHE RANDOMTARGETMOTION!TYPICALSPECTRUMSHAPEIS
. F S ANG
"
P " F
WHERE. F SPECTRALNOISEPOWERDENSITY POWER(Z
" NOISEBANDWIDTH (Z
F FREQUENCY (Z 4HEVALUESOF"AREPROPORTIONALTORADARFREQUENCYANDDEPENDENTUPONAIRTUR BULENCEEFFECTSONTARGETMOTIONANDTARGETASPECT!NEXAMPLEOFAMEASUREDANGLE SCINTILLATIONSPECTRUMISSHOWNIN&IGURE4YPICALVALUESOF"AT8BAND INRELA TIVELYTURBULENTAIR RANGEFROMABOUT(ZFORSMALLAIRCRAFTTOABOUT(ZFORLARGER AIRCRAFT"CHANGESINPROPORTIONTORADARFREQUENCYPROVIDEDTHATTHETARGETSPANISAT LEASTAFEWWAVELENGTHS!GAIN LONGTIMESAMPLESARENECESSARYTOOBTAINARELATIVELY SMOOTHSPECTRUMFROMMEASUREDDATA&ORTHEABOVEVALUESOF" ABOUTMINUTESOF DATAWASNECESSARYTOREACHESSENTIALLYTHELONG TIME AVERAGEDCHARACTERISTIC4HISIS AREFERENCEPOINTABOUTWHICHTHEREWILLBECONSIDERABLEVARIATIONFORATYPICALTIME PERIODOFINTEREST&OREXAMPLE WITHONLYMINUTEOFDATATHENOISEPOWERRANGWOULD VARY OVER TO TIMES THE LONG TIME AVERAGED RANG!T LOWER RADAR FREQUENCIES ANDINLESSTURBULENTATMOSPHERE "MAYBESMALLER ANDPROPORTIONATELYLONGERTIME SAMPLESARENECESSARYTHUS FORSHORTTIMESAMPLESOFRADARPERFORMANCE SIGNIFICANT STATISTICALVARIATIONSMUSTBEEXPECTED 4OCONVERTRANGEXPRESSEDINLINEARUNITSMEASUREDATTHETARGETTOANGULARUNITSFOR ARADARATRANGER THEFOLLOWINGRELATIONMAYBEUSED RANGANGULARMILS RANGM RKM "ECAUSE THE ANGULAR ERRORS CAUSED BY ANGLE NOISE ARE INVERSELY PROPORTIONAL TO RANGE ANGLE NOISE IS OF CONCERN MAINLY AT MEDIUM AND CLOSE RANGES4HE RESULTANT TRACKINGNOISECANBEREDUCEDBYLOWERINGTHESERVOBANDWIDTHTOREDUCETHERADARS ABILITYTOFOLLOWTHEHIGHER FREQUENCYCOMPONENTSOFTHENOISE4HEAMOUNTOFNOISE REDUCTIONMAYBEESTIMATEDBYCOMPARINGTHEAREAUNDERASPECTRAL POWER DENSITYPLOT OFANGLENOISEBELOWTHEFREQUENCYCORRESPONDINGTOTHERADARSERVOBANDWIDTHWITH THETOTALAREAUNDERTHEPOWER DENSITYPLOT4HESPECTRAL POWER DENSITYPLOTMAYBE OBTAINEDBYSQUARINGTHEORDINATEVALUESOFASPECTRAL DISTRIBUTIONPLOTSUCHASSHOWN IN&IGURE 4HECHOICEOF!'#CHARACTERISTICSALSOAFFECTSTHEAMOUNTOFANGLENOISEFOLLOWED BYATRACKINGANTENNA4HE!'#VOLTAGEISGENERATEDFROMTHESUMSIGNALANDFOL LOWSTHEECHO SIGNAL AMPLITUDEFLUCTUATION4HEREISADEGREEOFCORRELATIONBETWEEN THE ANGLE NOISE MAGNITUDE AND ECHO SIGNAL MAGNITUDE SUCH THAT ANGLE NOISE PEAKS AREGENERALLYACCOMPANIEDBYADIPORFADEINAMPLITUDE!SLOW!'#SYSTEMTHAT DOESNOTMAINTAINCONSTANTSIGNALLEVELDURINGRAPIDCHANGESALLOWSTHESIGNALLEVEL TODROPDURINGARAPIDFADE REDUCINGSENSITIVITYVOLTSPERDEGREEANGLEERROR DURING THELARGEANGLE NOISEPEAKS4HISRESULTSINASMALLERRMSTRACKINGNOISEWITHASLOW !'#SYSTEM (OWEVER THISREASONINGNEGLECTSANADDITIONALNOISETERM CAUSEDBYTHELACKOF FULL!'#ACTION WHICHISPROPORTIONALTOTRACKINGLAG!TRACKINGLAGCAUSESADCERROR
°Î{
2!$!2(!.$"//+
&)'52% 3PECTRAL ENERGY DISTRIBUTION OF ANGLE SCINTILLATION MEASURED ON THE NOSE ASPECTOFASMALLTWO ENGINEAIRCRAFT
VOLTAGE IN THE ANGLE ERROR DETECTOR OUTPUT EQUAL TO ANGLE ERROR TIMES THE ANGLE SEN SITIVITY!SLOW!'#ALLOWSTHEAMPLITUDENOISETOMODULATETHETRUETRACKING ERROR VOLTAGE CAUSINGADDITIONALNOISEINANGLETRACKING4HUS THEREWILLBEANADDITIONAL RMS ANGLE ERROR PROPORTIONAL TO TRACKING LAG AND DEPENDENT ON THE!'# TIME CON STANT ASILLUSTRATEDIN&IGURE )NGENERAL AFAST!'#ISRECOMMENDEDBECAUSEITREDUCESTHEADDITIONALNOISE TERMALLOWEDBYSLOW!'#ANDTHEPOSSIBILITYOFLARGERRMSTRACKINGERRORS WHICH CAN BE CONSIDERABLY GREATER THAN THE ANGLE NOISE WITH A FAST!'#!S PREVIOUSLY DISCUSSED ANGLENOISEISSIGNIFICANT MAINLYATMEDIUMANDCLOSERANGEWHERETARGET ANGLERATESAREGREATEST!SSEENIN&IGUREATRACKINGLAGOFONLYONE HALFTHE
42!#+).'2!$!2
°Îx
&)'52% !NGLE SCINTILLATIONNOISEPOWERASAFUNCTIONOFTRACKING ERRORFORTHREEDIFFERENT!'#BANDWIDTHSFROM$UNN (OWARD AND+ING ¡)2%
TARGETSPANWILLRESULTINGREATERTRACKINGNOISEINASLOW!'#SYSTEM WITHTHEDANGER OFMUCHHIGHERNOISEWITHGREATERLAG4HEREFORE FOROVERALLPERFORMANCE AFAST!'# ISRECOMMENDED 2ANGE.OISE2ANGE'LINT 2ANGENOISE ORRANDOMTRACKINGERRORSINTHERANGE COORDINATECAUSEDBYCOMPLEXTARGETS ISASIGNIFICANTBASICLIMITATIONINRANGETRACKING !CQUISITIONOFADESIREDSPECTRALLINEBYADOPPLERFREQUENCYTRACKINGSYSTEMISALSO LIMITEDBYRANGENOISE#OARSEVELOCITYINFORMATIONISOBTAINEDBYDIFFERENTIATIONOF RANGETODETERMINETHEDESIREDSPECTRALLINE2ANGENOISEISAMAJORLIMITATIONTOTHE ACCURACYOFVELOCITYOBTAINEDFROMRANGERATEANDCANPREVENTSELECTIONOFTHEDESIRED SPECTRALLINE 4HERANGE TRACKINGERRORSCAUSEDBYAFINITE SIZETARGETANDBYMULTIPATHALSOCAUSE SIGNIFICANT ANGLE TRACKING ERRORS IN MULTILATERATION TRACKING SYSTEMS THAT TRIANGULATE USINGHIGH PRECISIONRANGEMEASUREMENTSFROMMULTIPLELOCATIONSTOCALCULATETARGET ANGLELOCATION-ULTILATERATIONSYSTEMS SUCHASTHE0ACIFIC-ISSILE2ANGE%XTENDED !REA4RACKING3YSTEM%!43 DEPENDUPONVERYPRECISERANGEMEASUREMENTS3MALL RANGE TRACKINGERRORSCAUSESIGNIFICANTERRORSINCALCULATEDTARGETANGLEBASEDONTHE RANGEMEASUREMENTS4HESEERRORSMUSTBEFULLYUNDERSTOODTOASSESSTHEPERFORMANCE OFMULTILATERATIONSYSTEMS 4ARGET CAUSED RANGE TRACKING ERRORS SIMILAR TO TARGET CAUSED ANGLE ERRORS ARE GREATERTHANTHEWANDEROFTHETARGETCENTEROFGRAVITYANDCANFALLOUTSIDETHETARGET SPAN&IGURESHOWSTYPICALSAMPLESOFSPECTRAL ENERGYDISTRIBUTIONSANDPROB ABILITYDENSITYFUNCTIONSFORDIFFERENTTARGETCONFIGURATIONS4HERANGENOISEMEASURE MENTSWEREMADEONSMALLANDLARGEAIRCRAFTANDMULTIPLEAIRCRAFTUSINGTHESPLITVIDEO RANGEERRORDETECTOR4HECHARACTERISTICSFOLLOWVERYCLOSELYTOTHERELATIONSOFTARGET ANGLENOISETOTHETARGETCONFIGURATIONRADIUS OF GYRATIONALONGTHEANGLECOORDINATE
°ÎÈ
2!$!2(!.$"//+
&)'52% 4YPICALSPECTRAL ENERGYDISTRIBUTIONSFORTHETHREEVIEWSOFTHE3."AIRCRAFTA NOSEVIEW B SIDEVIEW C TAILVIEW ANDD SIDEVIEWOFTWOSMALLTWO ENGINEAIRCRAFTFLYINGINFORMATION
&ORRANGETRACKING ITISNECESSARYTORELATERANGENOISETOTHETARGETREFLECTIVITYDISTRI BUTIONALONGTHERANGECOORDINATE)NGENERAL THELONG TIME AVERAGEVALUEOFTHERMS RANGEERRORMAYBECLOSELYESTIMATEDBYTAKINGTIMESTHERADIUS OF GYRATIONOFTHE DISTRIBUTIONOFTHEREFLECTINGAREASINTHERANGEDIMENSIONBASEDONMANYMEASURE MENTSOFSMALL LARGE ANDMULTIPLEAIRCRAFT4YPICALLY INTERMSOFTARGETSPANALONG THE RANGE COORDINATE THE RMS VALUE WILL FALL BETWEEN AND TIMES THE TARGET SPANBEINGCLOSETOTHEMULTIPLIER FORTHETAILVIEWANDNOSEVIEW AND FOR THESIDEVIEW4HESPECTRALSHAPEMAYBECLOSELYESTIMATEDBYUSINGTHESAMEFUNCTION OFFREQUENCYASDESCRIBEDFORANGLENOISEANDTHESAMEVALUEOFBANDWIDTH4HEERROR ASAFUNCTIONOFRELATIVEPHASEANDAMPLITUDEOFTHETARGETREFLECTORSISSIMILARTOTHE ANGLENOISEPHENOMENON !BEACONONACOOPERATIVETARGETCANPROVIDEAPOINTSOURCESINGLE PULSERESPONSE TOELIMINATERANGEERRORCAUSEDBYTHETARGET(OWEVER VERYSTABLECIRCUITRYISREQUIRED TOAVOIDPULSEJITTERANDDRIFT $OPPLER 3CINTILLATION AND 3PECTRAL ,INES $OPPLER SCINTILLATION AND SPECTRAL LINESCAUSEDBYACOMPLEXTARGETMAYBEDIVIDEDINTOTWOPHENOMENA SPECTRAL LINESCAUSEDBYPARTSOFTHEAIRCRAFTSUCHASPROPELLERSANDJETTURBINEBLADES AND A CONTINUOUSDOPPLERSPECTRUMSPREADBYTHEMOTIONOFANAIRCRAFTINFLIGHTSYMMETRICALLY
42!#+).'2!$!2
°ÎÇ
ABOVEANDBELOWTHEAVERAGEDOPPLEROFTHETARGET!TARGETTYPICALLYHASASIGNIFICANT RANDOMYAW PITCH ANDROLLMOTIONEVENONAhFIXEDvHEADING4IMEPLOTSOFTYPICAL AIRCRAFTHEADINGFORANAIRCRAFTFLYINGAhSTRAIGHTCOURSEvAREOBSERVEDTOHAVETYPICAL RANDOMYAWMOTIONTHATCAUSESSMALLCHANGESINTHEDOPPLERFROMEACHOFTHESCATTERING SURFACESOFTHEAIRCRAFTSRIGIDSTRUCTURE2ELATIVETOTHEAVERAGEDOPPLEROFTHEAIRCRAFT THESCATTERINGSURFACESLOCATEDAWAYFROMTHEAIRCRAFTCENTERWILLHAVEASMALLINCREASING ANDDECREASINGRELATIVEDOPPLERFREQUENCYASTHEAIRCRAFTYAWSRIGHTANDLEFT4HISCAUSES A SPECTRAL SPREAD OF THE DOPPLER OF THE ECHO FROM THE RIGID BODY OF THE AIRCRAFT AND ISACCOMPANIEDBYSPECTRALLINESCAUSEDBYMOVINGPARTSONTHEAIRCRAFT #OMPONENTSOFTHETARGETECHOFROMROTATINGORMOVINGPARTSOFTHETARGETCAUSE DOPPLERLINESATFREQUENCIESDISPLACEDFROMTHEAIRFRAMEDOPPLERSPECTRUM4HEPERIODIC AMPLITUDEMODULATIONCAUSESPAIRSOFDOPPLERLINESSYMMETRICALABOUTTHEDOPPLEROF THEAIRFRAMEVELOCITY-OVINGPARTSCANALSOCAUSEPUREFREQUENCYMODULATIONTHATWILL RESULTINASINGLESETOFDOPPLERLINESONONESIDEOFTHEAIRFRAMEDOPPLERSPECTRUM !MAJORSIGNIFICANCEOFTHEDOPPLERMODULATIONISITSEFFECTONDOPPLER MEASURING RADARS!DOPPLERTRACKINGSYSTEMTHATAUTOMATICALLYTRACKSTHEFREQUENCYOFASPECTRAL LINEOFTHEECHOISSUBJECTEDTOTWOPROBLEMS THEREISTHEPOSSIBILITYOFLOCKINGON AFALSELINECAUSEDBYMOVINGPARTSOFTHETARGETAND WHENPROPERLYLOCKEDONTO THEAIRFRAMEDOPPLERSPECTRUM THEDOPPLERREADINGWILLBENOISYASDEFINEDBYTHE RANDOMFLUCTUATIONININSTANTANEOUSFREQUENCYASOBSERVEDBYTHESPREADOFTHEDOP PLERSPECTRUM#OHERENTBEACONSWHICHRECEIVE AMPLIFY ANDTRANSMITRECEIVEDRADAR PULSES CANPROVIDEADOPPLER SHIFTEDRESPONSEFREEOFTARGET CAUSEDSPECTRALSPREAD ANDPERIODICMODULATIONS!DELAYTIMEISPROVIDEDTOSEPARATETHEBEACONRESPONSE FROMTHETARGETECHO 4ARGETDOPPLERSCINTILLATIONALSOOFFERSUSEFULINFORMATIONABOUTTHETARGETCONFIGURA TION.ORMALTARGETMOTIONWILLRESULTINDIFFERENTDOPPLERSHIFTSFOREACHMAJORSCAT TEREROFARIGID BODYTARGET ANDTHESHIFTSWILLBEAFUNCTIONOFTHEDISPLACEMENTOFTHE SCATTERERFROMAREFERENCEPOINTSUCHASTHECENTEROFROTATIONOFTHETARGETSRANDOM MOTIONS4HEREFORE AHIGH RESOLUTIONDOPPLERSYSTEMCANRESOLVEMAJORREFLECTORSAND LOCATETHEMINCROSSRANGEASAFUNCTIONOFTHEDOPPLERDIFFERENCEFROMTHEREFERENCE REFLECTOR4HISTECHNIQUE CALLEDINVERSESYNTHETICAPERTURERADAR)3!2 USESTHETARGET MOTIONFORTHENEEDEDASPECTCHANGE INSTEADOFRADARMOTIONASUSEDINCONVENTIONAL SYNTHETICAPERTURERADAR TOOBTAINDETAILEDCROSS RANGETARGETIMAGEINFORMATION
°Ê "/ ,Ê 8/ , Ê 1- -Ê"Ê ,,", -ULTIPATH -ULTIPATHANGLEERRORSRESULTFROMREFLECTIONSOFTHETARGETECHO FROM OBJECTS OR SURFACES CAUSING ECHO PULSES TO ARRIVE BY OTHER THAN THE DIRECT PATHTOTHERADARBEAMINADDITIONTOTHE DIRECTPATH4HESEERRORSARESOMETIMES CALLED LOW ANGLE TRACKING ERRORS WHEN APPLIED TO TRACKING OF TARGETS AT SMALL ELEVATION ANGLES OVER THE %ARTH OR OCEAN SURFACEn -ULTIPATH ERRORS ARE TYPICALLY A SPECIAL DUAL SOURCE CASE OF 'EOMETRYOFTHERADARMULTIPATH ANGLENOISERESULTINGFROMTHEGEOMETRY &)'52% TRACKING CONDITION WHERE THE REFLECTION FROM A AS DESCRIBED IN &IGURE WHERE THE SURFACE APPEARS TO THE RADAR AS AN IMAGE BELOW TARGET AND ITS IMAGE REFLECTED FROM A THESURFACE
°În
2!$!2(!.$"//+
SURFACETOTHERADARBEAMARETHETWOSOURCES/VERASMOOTHOCEANSURFACE THEY ARE SEPARATED ONLY IN THE ELEVATION COORDINATE SO THAT MOST OF THE ERROR APPEARS INTHEELEVATION TRACKINGCHANNEL3EVEREELEVATIONERRORSMAYCAUSESOMECROSS COUPLING OF THE ERROR TO THE AZIMUTH CHANNEL 2OUGH SURFACES CAUSE DIFFUSE SCATTERING WHICHCANCONTRIBUTEERRORSTOBOTHAZIMUTHANDELEVATIONTRACKING $IFFERENT PATH GEOMETRIES SUCH AS NON FLAT LAND OR A BUILDING MAY ALSO CAUSE A SIGNIFICANTERRORTOAPPEARINTHEAZIMUTH TRACKINGCHANNEL 4HEMAJORDIFFICULTYWITHLOW ANGLETRACKINGISTHATTHETARGETANDITSIMAGEARE ESSENTIALLYCOHERENTANDTHEIRRELATIVEPHASECHANGESSLOWLYANDTHEANGULARERRORIT CAUSES IS READILY FOLLOWED BY AN ANGLE TRACKING SYSTEM &URTHERMORE THE PATHS ARE ALMOST EQUAL AND IN MOST CASES THEY CANNOT BE RESOLVED BY HIGH RANGE RESOLUTION TECHNIQUES,ONGTIMEAVERAGESOFTHEDATADONOT INPRACTICE GIVETARGETELEVATION THUS THEMULTIPATHANGLEERRORHASNOSIMPLESOLUTIONANDISGENERALLYMINIMIZEDBY USINGNARROW BEAMANTENNAS 7HENTHETARGETISATLOWALTITUDE THEMULTIPATHERRORSARESEVERE ASOBSERVEDIN THEMEASUREDDATASHOWNIN&IGURE4HISDATAISTHEMULTIPATHERROROFA BEAMWIDTH3BAND '(Z TRACKINGRADARTHATISTRACKINGANAIRCRAFTTARGETWITHA BEACONAT FTALTITUDE!N!.&03 TRACKINGRADARWITHABEAMWIDTHAT # BAND '(Z WAS USED TO SIMULTANEOUSLY TRACK WITH ITS NARROW BEAM WHICH REMAINEDABOVETHESEASURFACEWITHOUTSIGNIFICANTMULTIPATHERROR TOPROVIDEATRUE TARGETALTITUDEREFERENCEFORTHEDATAIN&IGURE4HEREISAMEASUREMENTBIASERROR OBSERVEDIN&IGURE OFABOUT 4HE TRACKING DATA FROM A RADAR TRACKING A TARGET WITH A BEACON IS PLOTTED IN &IGURE SHOWINGATYPICALMULTIPATHERRORILLUSTRATINGTHEPHENOMENONFROMTHE REGIONWHERETHEIMAGEENTERSTHESIDELOBESTOTHEREGIONWHEREITENTERSTHEMAIN BEAM 4HERE ARE THREE METHODS USED FOR PREDICTING MULTIPATH ERRORS DEPENDING UPONWHERETHEREFLECTEDTARGETIMAGEENTERSTHEANTENNAPATTERN!TTHEFARRANGE
&)'52% -EASUREDELEVATION TRACKINGERROROFAN3 BANDRADARUSINGAN!.&03 RADARFORATARGET ELEVATIONREFERENCE
42!#+).'2!$!2
°Î
THEIMAGEENTERSTHEANTENNAMAINBEAM ANDTHEERRORISESSENTIALLYTHATOFATWO REFLECTORTARGETGLINTERRORFOLLOWINGAPPROXIMATELYTHEEQUATION
WHERE E
Q
H
E
E H
R R COS F R R COS F
ERROR SAMEUNITSASH MEASUREDATTHETARGETRANGERELATIVETOTHETARGET MAGNITUDEOFSURFACEREFLECTIONCOEFFICIENT HEIGHTOFTARGET RELATIVE PHASE DETERMINED BY GEOMETRY OF DIRECT AND SURFACE REFLECTED SIGNALPATHS ASSHOWNIN&IGURE
!LTHOUGHTHEFLUCTUATIONSINQANDEALTERTHEACTUALTRACKINGFROMTHETHEORETICAL THE EQUATIONGIVESAGOODINDICATIONOFTHEERRORSTOBEEXPECTEDWHENTRACKINGAPOINT SOURCESUCHASABEACON(OWEVER SKINTRACKINGOFANAIRCRAFTATLOWELEVATIONMAY RESULTINADEPARTUREFROMTHECLASSICPERIODICERRORVERSUSELEVATION ASILLUSTRATEDIN &IGURE BECAUSEOFANINTERACTIONBETWEENTARGETANGLESCINTILLATIONANDMULTIPATH ERRORTHATCANCHANGETHECHARACTERISTICSOFTHEMULTIPATHERROR 7HEN TRACKING A POINT SOURCE TARGET AT CLOSE RANGE THE RADAR MAIN BEAM IS ABOVE THE IMAGE BUT THE IMAGE IS SEEN BY THE DIFFERENCE PATTERN SIDELOBES4HE MULTIPATHERRORSTHATRESULTARECYCLIC ALMOSTSINUSOIDAL WITHANRMSVALUEPRE DICTEDBYTHEEQUATION
S%
RQ "
'SE PEAK
WHERE R% RMSELEVATIONANGLEMULTIPATHERROR SAMEUNITSASP"
P" ONE WAYANTENNABEAMWIDTH
Q REFLECTIONCOEFFICIENT AND'SEPEAK ISTHEPOWERRATIOOFTHETRACKING ANTENNASUM PATTERNPEAKTOTHEERROR PATTERNPEAKSIDELOBELEVELATTHEANGLEOFARRIVALOFTHEIMAGESIGNAL 4HECYCLICRATEMAYBEAPPROXIMATEDBYTHEEQUATION
WHERE FM
H
K
%
FM
H% L
FREQUENCYOFCYCLICMULTIPATHERROR RADS HEIGHTOFRADARANTENNA WAVELENGTH SAMEUNITSASH RATEOFTARGETELEVATIONCHANGEASSEENBYRADAR RADS
4HE INTERMEDIATE RANGE IS BETWEEN THE SHORT RANGE REGION WHERE THE IMAGE APPEARSINTHESIDELOBES ANDTHELONG RANGEREGION WHERETHEIMAGEAPPEARSWITHIN THEHALF POWERBEAMWIDTH4HEERRORISDIFFICULTTOCALCULATEINTHISREGIONBECAUSE ITFALLSINTHENONLINEARERROR SENSINGPORTIONOFTHEANTENNAPATTERNS ANDTHERADAR RESPONSEISSTRONGLYDEPENDENTUPONTHESPECIFICFEEDDESIGNANDERROR PROCESSING TECHNIQUE(OWEVER &IGURE PROVIDESAPRACTICALMEANSFORAPPROXIMATING MULTIPATH ERROR VALUES IN THIS REGION 4HE CURVES ARE CALCULATED MULTIPATH ERRORS BASEDONANASSUMEDGAUSSIAN SHAPEDSUMPATTERNANDDERIVATIVEOFTHESUMPATTERN
°{ä
2!$!2(!.$"//+
&)'52% #ALCULATED RMS MULTIPATH ERROR R% VERSUS TARGET ELEVATION %T BOTH NORMALIZED TO RADAR BEAMWIDTHP"
ASTHEMONOPULSEDIFFERENCEPATTERN&IGURESHOWSTYPICALSIDELOBEMULTIPATH ERRORS FOR HIGHER ELEVATION TARGETS AND THE LINEARLY DECREASING ERROR VERSUS TARGET ELEVATION PREDICTEDBYTHEABOVEEQUATION FORVERYLOW ELEVATIONTARGETS4HEGRAPH ISNORMALIZEDTORADARBEAMWIDTHONBOTHAXESFORCONVENIENTUSEWITHAWIDEVARI ETYOFRADARS4HEDASHEDPORTIONSOFTHECURVESAREREGIONSOFUNCERTAINTYBECAUSE OFSIGNIFICANTVARIATIONSOFREFLECTIONFORAGIVENSEASTATE )N THE INTERMEDIATE REGION THE ERROR INCREASES TO A PEAK AT TARGET ELEVATIONS OF ABOUTBEAMWIDTH4HEPEAKVALUEISDEPENDENTONSEVERALFACTORSINCLUDINGSURFACE ROUGHNESSWHICH INPART DETERMINESTHEVALUEOFQ SERVOBANDWIDTH ANDANTENNA CHARACTERISTICSINTHEREGION4HEERRORSARESEVERE ANDWITHUN SMOOTHEDTRACKWIDE SERVOBANDWIDTH THERADARCANBREAKLOCKANDLOSETRACKOFTHETARGET 7HENTHESURFACEISROUGH CORRESPONDINGTOAREFLECTIONCOEFFICIENTOFABOUT THECHARACTERISTICOFTHEERRORVERSUSELEVATIONCHANGESISOBSERVEDIN&IGURE4HE ROUGHSURFACECAUSESSIGNIFICANTDIFFUSESCATTERINGRATHERTHANAMIRRORREFLECTION4HIS CHANGESTHESHAPEOFTHEERRORCURVEANDRESULTSINSOMERESIDUALELEVATION ANGLEERROR WHENTHETARGETELEVATIONGOESTOZERO)TALSOCAUSESSOMESIGNIFICANTAZIMUTHERROR #ROSSTALK#AUSEDBY#ROSS 0OLARIZED%NERGY 4ARGETECHOENERGYCROSS POLAR IZEDTOTHERADARANTENNACAUSESCROSSTALKCROSSCOUPLING INRADARSIE THEAZIMUTH ERRORCAUSESOUTPUTFROMTHEELEVATION ERRORDETECTOR ANDTHEELEVATIONERRORCAUSES OUTPUTFROMTHEAZIMUTH ERRORDETECTOR'ENERALLY THISEFFECTISNEGLIGIBLEBECAUSETHE CROSS POLARIZEDENERGYISUSUALLYASMALLFRACTIONOFTHERECEIVEDPOLARIZATIONFROM TYPICAL TARGETS AND IT IS NORMALLY REDUCED BY ABOUT D" BY THE ANTENNA DESIGN (OWEVER INSPECIALCASES THERESULTANTCROSSTALKCANBEVERYHIGHANDMAYCAUSEA LARGETRACKINGERRORANDPOSSIBLELOSSOFTRACK&OREXAMPLE POLARIZATIONOFALINEARLY POLARIZEDBEACONONATARGETCOULDROTATEWITHTARGETASPECTCHANGEAND INTHEWORST CASE APPROACHACROSS POLARIZEDCONDITION
42!#+).'2!$!2
°{£
4HEORETICALLY THECOUPLINGTOCROSS POLARIZEDENERGYISZEROWHENTHESOURCEISPRE CISELYONAXISANDINCREASESWITHDISPLACEMENTFROMTHEAXIS4HECROSS POLARIZATION ERRORINATRACKINGRADARSYSTEMISPURECROSSTALKSOTHATASMALLTRUETRACKINGERRORIN ONETRACKINGCOORDINATECAUSESTHEANTENNATOMOVEINTHEOTHERCOORDINATE4HEERROR INTHESECONDCOORDINATETHENCAUSESTHEANTENNATOMOVEFARTHERFROMTHESOURCEINTHE FIRSTCOORDINATE7HENTHEREISNORETARDINGEFFECT THECROSS POLARIZEDENERGYCAUSES THEANTENNATODRIVEOFFTARGETINONEOFTHEQUADRANTSOFTHETWO AXISANGLE TRACKING COORDINATESYSTEM DEPENDINGUPONTHEDIRECTIONOFTHEINITIALERRORTHATMOVEDTHE SOURCEOFFTHEPRECISEON AXISPOSITION ! SOLUTION USED WITH MISSILE RANGE INSTRUMENTATION RADAR WHERE TARGET ASPECT CHANGESCANCAUSEALINEARLYPOLARIZEDBEACONTOROTATETOACROSS POLARIZEDASPECT ISTOPROVIDEACIRCULARPOLARIZATIONTRACKINGCAPABILITY#OUPLINGALINEARLYPOLARIZED SIGNALTOACIRCULARLYPOLARIZEDANTENNARESULTSINAD"SIGNALLOSS BUTITISINDEPEN DENTOFTHEDIRECTIONOFTHELINEARPOLARIZATIONWHENROTATEDABOUTALINEINTHEDIRECTION TOWARDTHERADAR 4ROPOSPHERE 0ROPAGATION 4HE TROPOSPHERE IS TYPICALLY A NONHOMOGENEOUS MEDIUMFORPROPAGATIONANDWILLCAUSERANDOMBEAMBENDING&IGUREILLUSTRATES THEAPPROXIMATERELATIONOFRMSANGLEERRORTOVARIOUSATMOSPHERICCONDITIONS4HE WORST CASE IS HEAVY CUMULUS CLOUDS WHICH CAUSE COLUMNS OF AIR SHADED FROM THE SUN BY THE CLOUDS THAT ARE COOLER THAN THE SURROUNDING AIR AND CONSEQUENTLY OF A DIFFERENT DIELECTRIC CONSTANT 4HE RESULT IS TYPICALLY A RANDOM BEAM BENDING AS THE RADIATEDENERGYPASSESTHROUGHTHESECOLUMNS&IGUREAPPLIESONLYFORTHEPORTION
&)'52% !NGLE FLUCTUATION VERSUS PATH LENGTH FOR DIFFERENT TROPOSPHERES FROM &INAL 2EPORT )NSTRUMENTATION 2ADAR !.&03 8. BY2#!UNDERCONTRACT"U!ER./AS C
°{Ó
2!$!2(!.$"//+
OFTHEBEAMTHATISWITHINTHETROPOSPHERE/NCETHEBEAMGOESABOVETHETROPOSPHERE TYPICALLYABOUTTOKM THEREISNOFURTHERBEAMBENDING 4HETROPOSPHEREALSOAFFECTSTARGETRANGEMEASUREMENT BUTTHEERRORSARESMALL INTHEORDEROFTOMMAXIMUM(OWEVER EVENSMALLERRORSOFTHISMAGNITUDE WILLCAUSESIGNIFICANTERRORSINMULTILATERATIONSYSTEMSTHATDETERMINETARGETANGLEBY CALCULATIONSUSINGPRECISERANGEMEASUREMENTSFROMSEPARATELOCATIONS
°£äÊ / , Ê-"1,
-Ê"Ê ,,", 2ECEIVER4HERMAL.OISE 4HEANGLEERRORCAUSEDBYRECEIVERTHERMALNOISEINA MONOPULSETRACKINGSYSTEMIS
ST
KM
Q"
"T 3 . FR BN
WHERE KM IS THE ANGLE ERROR DETECTOR SLOPE 4HE VALUE OF KM IS DETERMINED BY THE STEEPNESSOFTHEANTENNADIFFERENCEPATTERNS ANDAVARIETYOFVALUESCANBEOBTAINED DEPENDING ON THE TYPE OF FEED USED 4HE VALUES VARY FROM FOR THE ORIGINAL FOUR HORN SQUARE FEED TO A MAXIMUM OF FOR THE -)4 HORN FEED (OWEVER AS DESCRIBED IN THE DISCUSSION ON FEEDS THE HORN FEED GIVES A LOWER ANTENNA EFFICIENCY THANANOPTIMUMMULTIMODEMONOPULSEFEED WHICHCANAPPROACH ANEFFICIENCYOF ALTHOUGHITSANGLESENSITIVITYISLESS TYPICALLYHAVINGAVALUE OF4HEREFORE THEREISATRADEOFFBETWEENSLOPEANDEFFICIENCY!SLOPEFORMONO PULSERADARSISDEPENDENTUPONFEEDDESIGNANDISTYPICALLYFORAGOODMODERN FOUR HORNMULTIMODEFEEDDESIGN 7HENTHEREISASIGNIFICANTTRACKINGLAGORDELIBERATEBEAMOFFSETFROMTHETARGET THEERRORRTO DUETORECEIVERNOISEFORAGIVEN3.2 ISGIVENBYTHEEQUATION
S T S T ,; K Q , Q " =
WHERE P, LAGANGLE SAMEUNITSASP"
, ANTENNASUM PATTERNLOSSATANGLEP, !SIMILARRANGE TRACKINGERRORRRTRESULTSFROMRECEIVERNOISE4HEEQUATIONRELATING THEERRORTOTHE3.2ANDSYSTEMPARAMETERSIS
S RT
T KR 3 . FR BN
FT RMS
WHERE S PULSELENGTHINFT
KR R ANGE ERROR DETECTOR SENSITIVITY MAXIMUM VALUE OF FOR A RECEIVER WHERE"
3. SIGNAL TO NOISERATIO
AN SERVOBANDWIDTH /THER)NTERNAL3OURCESOF%RROR 4HEREAREMANYOTHERSOURCESOFINTERNALERRORS THATARESMALLINWELL DESIGNEDTRACKINGRADARS4HESEINCLUDECHANGESINRELATIVEPHASE ANDAMPLITUDEBETWEENMONOPULSERECEIVERCHANNELSASAFUNCTIONOFSIGNALSTRENGTH
42!#+).'2!$!2
°{Î
4!",% )NVENTORYOF2ANGE %RROR#OMPONENTS
#OMPONENT
"IAS
.OISE
2ADAR DEPENDENT TRACKINGERRORS
:ERORANGESETTING 2ANGEDISCRIMINATORSHIFT SERVOUNBALANCE 2ECEIVERDELAY
2ECEIVERTHERMALNOISE -ULTIPATH 3ERVOELECTRICALNOISE 3ERVOMECHANICALNOISE 6ARIATIONINRECEIVERDELAY 2ANGERESOLVERERROR )NTERNALJITTER $ATAGEARNONLINEARITYANDBACKLASH $ATATAKEOFFNONLINEARITYANDGRANULARITY 2ANGEOSCILLATORINSTABILITY $YNAMICLAG 'LINT 3CINTILLATION "EACONJITTER )RREGULARITIESINTROPOSPHERICREFRACTION )RREGULARITIESINIONOSPHERICREFRACTION
2ADAR DEPENDENT 2ANGEOSCILLATORFREQUENCY TRANSLATIONERRORS $ATATAKEOFFZEROSETTING
4ARGET DEPENDENT TRACKINGERRORS
$YNAMICLAG "EACONDELAY
0ROPAGATIONERROR
!VERAGETROPOSPHERICREFRACTION !VERAGEIONOSPHERICREFRACTION
&ROM$+"ARTONINh-ODERN2ADAR v23"ERKOWITZED .EW9ORK*OHN7ILEY3ONS CHAP P
2&FREQUENCY DETUNING ANDTEMPERATURE!LSO PEDESTALBENDINGFROMSOLARHEATING NONORTHOGONALITYOFPEDESTALAXES GEARINGBACKLASH BEARINGWOBBLE GRANULARITYOF DATAREADOUT ANDMANYOTHERFACTORSCONTRIBUTETOERRORS4ABLELISTSTHEMAGNITUDE OFTHESEERRORSFORTHEPRECISIONINSTRUMENTATIONRADAR!.&03 #ALIBRATION IS IMPORTANT TO MINIMIZE ERRORS 7HEN MAXIMUM PERFORMANCE IS REQUIRED TIMELYACCURATECALIBRATIONMUSTBEPERFORMED4HEPROCEDUREMAYREQUIRE UPTOFOURHOURSTOFULLYSTABILIZETHERADARSYSTEM&ORINSTRUMENTATIONRADAR WHERE THETIMEOFATRACKINGEVENTISKNOWN FINALCALIBRATIONISPERFORMEDJUSTPRECEDINGTHE EVENTTOMINIMIZEDRIFTERRORS
°££Ê -1 ,9Ê"Ê-"1,
-Ê"Ê ,,", !NGLE -EASUREMENT %RRORS !N INVENTORY OF ANGLE MEASUREMENT ERRORS IS GIVENIN4ABLE4HISINCLUDESSEVERALSOURCESOFERRORTHATSHOULDBECONSIDEREDIN ADDITIONTOTHERADAR RELATEDSOURCES &IGUREISANEXAMPLEOFTHEMEASUREDTRACKINGPERFORMANCEOFAN!.&03 RADARTRACKINGA INMETALSPHERETHATPROVIDESAPOINTSOURCETARGETTOELIMINATE TARGET CAUSED ERRORS 4HE DATA ILLUSTRATES WHICH ERROR SOURCES DOMINATE AT DIFFERENT REGIONSOFTHERADARRANGEANDTHEIRCHARACTERISTICSVERSUSRANGE 4HE TARGET CAUSED ERRORS DISCUSSED IN 3ECTION INCLUDE THE USUAL TRACKING EVENTSWHERETHETARGETEXTENTISWITHINTHE D"BEAMWIDTHOFTHERADAR(OWEVER ALARGETARGETSUCHASANAIRCRAFTFORMATIONMAYEXTENDBEYONDTHELINEARANGLE ERROR REGIONOFTHEANTENNAPATTERNSANDEVENTUALLYREACHTHEPOINTOFRESOLUTIONOFONE OFTHEAIRCRAFT4HERESULTANTANGLE TRACKINGERRORFORLARGETARGETSISILLUSTRATEDBY THEEXAMPLEIN&IGURE)N&IGUREA THETYPICALGAUSSIAN LIKEGLINTERROR DISTRIBUTIONISOBSERVED7ITHTHEWIDERSEPARATIONOFTHEAIRCRAFT THETRACKING ERROR
°{{
2!$!2(!.$"//+
4!",% )NVENTORYOF!NGLE %RROR#OMPONENTS
#OMPONENT
"IAS
.OISE
2ADAR DEPENDENT TRACKINGERRORS DEVIATIONOFANTENNA FROMTARGET
"ORESIGHTAXISCOLLIMATION !XISSHIFTWITH 2&AND)&TUNING 2ECEIVERPHASESHIFT 4ARGETAMPLITUDE 4EMPERATURE 7INDFORCE !NTENNAUNBALANCE 3ERVOUNBALANCE ,EVELINGOFPEDESTAL.ORTH ALIGNMENT 3TATICFLEXUREOFPEDESTAL ANDANTENNA /RTHOGONALITYOFAXESSOLAR HEATING
2ECEIVERTHERMALNOISE -ULTIPATHELEVATIONONLY 7INDGUSTS 3ERVOELECTRICALNOISE 3ERVOMECHANICALNOISE
2ADAR DEPENDENT TRANSLATIONERRORS ERRORSINCONVERTING ANTENNAPOSITIONTO ANGULARCOORDINATES
4ARGET DEPENDENT TRACKINGERRORS
0ROPAGATIONERRORS
$YNAMICLAG
!VERAGEREFRACTIONOF TROPOSPHERE !VERAGEREFRACTIONOF IONOSPHERE 4ELESCOPEORREFERENCE !PPARENTOR INSTRUMENTATIONERRORS INSTRUMENTSTABILITY FOROPTICALREFERENCE &ILMEMULSIONANDBASE STABILITY /PTICALPARALLAX
$YNAMICDEFLECTIONOFPEDESTAL ANDANTENNA "EARINGWOBBLE $ATAGEARNONLINEARITY ANDBACKLASH $ATATAKEOFFNONLINEARITY ANDGRANULARITY 'LINT $YNAMICLAGVARIATION 3CINTILLATION "EACONMODULATION )RREGULARITIESINTROPOSPHERIC REFRACTION )RREGULARITIESINIONOSPHERIC REFRACTION 4ELESCOPE CAMERA ORREFERENCE INSTRUMENTVIBRATION &ILM TRANSPORTJITTER 2EADINGERROR 'RANULARITYERROR 6ARIATIONINOPTICALPARALLAX
&ROM$+"ARTONINh-ODERN2ADAR v23"ERKOWITZED .EW9ORK*OHN7ILEY3ONS CHAP P
DISTRIBUTIONCHANGESSHAPE BECOMINGSOMEWHATRECTANGULARWITHASEPARATIONOF AIRCRAFTASIN&IGUREB!TTHEWIDESTSEPARATION WHERETHEAIRCRAFTAREALMOST RESOLVED ASIN&IGUREC THERADARWILLTRACKONEAIRCRAFTUNTILITFADESANDTHE OTHER AIRCRAFT BLOSSOMS IN AMPLITUDE4HEN THE RADAR TRACKING POINT WILL MOVE TO THEOTHERAIRCRAFT4HEDWELLONEACHTARGETWITHRANDOMSWITCHINGBETWEENTHETWO AIRCRAFTCAUSESTHEDOUBLE HUMPEDDISTRIBUTIONOFERROR 2ANGE -EASUREMENT %RRORS 4HE MAJOR SOURCES OF TARGET RANGE ERROR MEASUREMENT ERRORS ARE GIVEN IN4ABLE 4YPICAL BIAS AND NOISE OF TARGET RANGE MEASUREMENT ERRORS IN A PRECISION RANGING RADAR ARE EQUAL TO A TOTAL RMS VALUE OF M RMS &URTHER DETAILS OF RANGE ERROR SOURCES AND THEIR MAGNITUDE ARE GIVE IN 3ECTIONOF"ARTON ,IMITATIONS OF 0ERFORMANCE -ITCHELL ET AL DESCRIBE BASIC PERFORMANCE LIMITATIONS OF THE!.&01 HIGH PRECISION TRACKING RADAR MEASURED UNDER IDEAL
42!#+).'2!$!2
°{x
&)'52% !ZIMUTH TRACKING NOISE VERSUS RANGE USING A IN METAL SPHERETARGETSUPPORTEDINSIDEABALLOONTOMINIMIZETARGETMOTIONESTIMATED ATINRMS AN SERVOBANDWIDTH
CONDITIONSWITHACAREFULLYDESIGNEDBORESIGHTINGFACILITY4HISTASKPROVIDEDMEA SUREDDATAVERIFYINGTHEANTICIPATEDPERFORMANCEOFTHEHIGHESTPRECISIONTRACKING RADARATTHATTIME 4!",% )NVENTORYOF2ANGE %RROR#OMPONENTS
#OMPONENT
"IAS
.OISE
2ADAR DEPENDENT TRACKINGERRORS
:ERORANGESETTING 2ANGEDISCRIMINATORSHIFT SERVOUNBALANCE 2ECEIVERDELAY
2ADAR DEPENDENT TRANSLATIONERRORS
2ANGEOSCILLATORFREQUENCY $ATATAKEOFFZEROSETTING
4ARGET DEPENDENT TRACKINGERRORS
$YNAMICLAG "EACONDELAY
0ROPAGATIONERROR
!VERAGETROPOSPHERICREFRACTION !VERAGEIONOSPHERICREFRACTION
2ECEIVERTHERMALNOISE -ULTIPATH 3ERVOELECTRICALNOISE 3ERVOMECHANICALNOISE 6ARIATIONINRECEIVERDELAY 2ANGERESOLVERERROR )NTERNALJITTER $ATAGEARNONLINEARITYANDBACKLASH $ATATAKEOFFNONLINEARITYANDGRANULARITY 2ANGEOSCILLATORINSTABILITY $YNAMICLAG 'LINT 3CINTILLATION "EACONJITTER )RREGULARITIESINTROPOSPHERICREFRACTION )RREGULARITIESINIONOSPHERICREFRACTION
&ROM$+"ARTONINh-ODERN2ADAR v23"ERKOWITZED .EW9ORK*OHN7ILEY3ONS CHAP P
°{È
2!$!2(!.$"//+
&)'52% 0ROBABILITYDISTRIBUTIONOFRADARPOINTINGWHENTRACKING TWOTARGETSWHERETHELEFTTARGETISAPPROXIMATELYD"LARGERTHANTHE RIGHTTARGET 4HREEDIFFERENTANGULARSEPARATIONSOFTHETARGETSAREA ANTENNA BEAMWIDTH B ANTENNA BEAMWIDTH AND C ANTENNA BEAMWIDTH
°£ÓÊ ,,",Ê, 1 /" Ê/ +1 -ULTIPATH %RROR2EDUCTION 6ERY LOW ALTITUDETARGETSCAUSESEVEREELEVATION ANGLETRACKINGERRORS ASDESCRIBEDIN3ECTION WHICHMAYRESULTINUSELESSELEVATION TRACKING DATA AND POSSIBLE LOSS OF TRACKING OF THE TARGET ! VARIETY OF TECHNIQUES HAVE BEEN DEVELOPED TO REDUCE THESE ERRORS OR THEIR EFFECTS ON RADAR TRACKINGn /NESIMPLEAPPROACHTOAVOIDLOSSOFTRACKINGINELEVATIONISTOOPENTHEELEVATION TRACKING SERVO LOOP AND PLACE THE ANTENNA BEAM AT ABOUT A HALF BEAMWIDTH ABOVE THE HORIZON!ZIMUTH CLOSED LOOP TRACKING MAY CONTINUE!LTHOUGH THE ELEVATION ANGLE ERROR DETECTOROUTPUTHASLARGEINDICATEDANGLEERRORS ITISMONITOREDTOOBSERVE WHETHERORNOTTHETARGETISMANEUVERINGUPWARDTHROUGHTHEBEAM!TARGETRISING THROUGHTHEBEAMWILLCAUSEAPOSITIVEANGLE TRACKINGERRORINDICATIONANDTHECLOSED LOOPELEVATIONTRACKINGRESUMES !VERYEFFECTIVEANDDIRECTAPPROACHTOMULTIPATH ERRORREDUCTIONISTOUSEAVERY NARROWBEAM USUALLYACCOMPLISHEDBYOPERATINGATSHORTWAVELENGTHSSUCHASAN MM '(ZOR+ABAND REGIONWITHTHEUSUALMICROWAVE TRACKINGAPERTURESIZE
42!#+).'2!$!2
°{Ç
4HISAPPROACHCANREDUCEERRORSBYTWOEFFECTS&IRST ASOBSERVEDIN&IGURE THE MAGNITUDEOFTHEELEVATIONMULTIPATHERRORREDUCESINDIRECTPROPORTIONTOTHEBEAM WIDTH4HESECONDADVANTAGEOFSHORTERWAVELENGTHSISTHATEVENARELATIVELYSMOOTH SEA SUCHASSEASTATE HASWAVEHEIGHTSOFMANYWAVELENGTHSANDAPPEARSROUGH RESULTINGINASMALLERREFLECTIONCOEFFICIENT4HISISOBSERVEDIN&IGURETOGIVE SMALL MULTIPATH ERRORS 4HE MM WAVELENGTH MONOPULSE CAPABILITY MAY BE EFFEC TIVELY COMBINED WITH A LOWER MICROWAVE BAND AS DESCRIBED IN 3ECTION TO TAKE ADVANTAGEOFTHECOMPLEMENTARYFEATURESOFBOTHBANDS 4ARGET!NGLEAND2ANGE3CINTILLATION'LINT 2EDUCTION 4ARGET CAUSEDERRORS INANGLEANDRANGETRACKINGMAYBEREDUCEDBYFILTERING SUCHASREDUCINGTRACKING SERVO BANDWIDTH (OWEVER SUFFICIENT SERVO BANDWIDTH MUST BE RETAINED TO FOLLOW TARGETTRAJECTORIES5NFORTUNATELY TARGETANGLEANDRANGESCINTILLATIONPOWERDENSITYIS NORMALLYCONCENTRATEDBELOWABOUTTO(ZWHENOPERATINGATMICROWAVEBANDSAND FALLSWITHINNORMALLYREQUIREDBANDWIDTHS 4ARGET SCINTILLATION TOTAL NOISE POWER IS RELATIVELY INDEPENDENT OF FREQUENCY BUT THE SPECTRAL ENERGY TENDS TO SPREAD UPWARD IN FREQUENCY AS WAVELENGTH IS REDUCED RESULTINGINLOWERNOISEPOWERDENSITYINTHESERVOPASSBAND4HEREFORE OPERATINGATA SHORTERWAVELENGTHWILLRESULTINLOWERTARGETNOISEEFFECTSONCLOSED LOOPTRACKING $IVERSITYTECHNIQUES WHICHCANPROVIDESTATISTICALLYINDEPENDENTSAMPLESOFTARGET SCINTILLATION OFFERAMEANSFORREDUCINGTARGETSCINTILLATIONEFFECTS4HEMOSTPRACTICAL TECHNIQUEISFREQUENCYDIVERSITYUSINGPULSE TO PULSERADARFREQUENCYCHANGE WHICH WILLALTERTHEPHASERELATIONSBETWEENTHEECHOESFROMDOMINANTREFLECTINGSURFACES OFTHETARGETn4HEFREQUENCYCHANGEMUSTBESUFFICIENTTOCAUSEENOUGHCHANGEIN RELATIVEPHASESOFTHEREFLECTORSTORESULTINSTATISTICALLYINDEPENDENTSAMPLESOFTARGET SCINTILLATION AT EACH NEW FREQUENCY!N APPROXIMATE RULE IS A MINIMUM FREQUENCY CHANGEOFS WHERESISTHERADARRANGEDELAYTIMEBETWEENTHELEADINGANDLAGGING EXTREMITIES OF THE TARGET 4HE REDUCTION IN RMS ANGLE AND RANGE TARGET SCINTILLATION MAYBEAPPROXIMATEDBYDIVIDINGBYTHESQUAREROOTOFN WHERENISTHENUMBEROF FREQUENCYSTEPSPROVIDED 2EDUCTIONOF)NTERNALLY#AUSED%RRORS !NGLEERRORSCAUSEDBYRECEIVERTHER MAL NOISE AS WELL AS TARGET SCINTILLATION ARE MINIMIZED BY MAINTAINING THE TARGET AS CLOSELY AS POSSIBLE TO THE TRACKING AXES 4HE TECHNIQUE CALLED ON AXIS TRACKING DESCRIBED IN 3ECTION IS A MEANS OF PLACING A COMPUTER IN THE TRACKING LOOP TO MINIMIZELAGANDPROVIDEOPTIMUMANGLE ERRORFILTERING !CCURATESYSTEMCALIBRATIONALSOGREATLYREDUCESINTERNALSOURCESOFERROR&REQUENT CALIBRATIONCORRECTSFORDRIFTINCOMPONENTGAINANDPHASEANDPEDESTALFLEXURE/THER INTERNALSOURCESOFERRORWITHKNOWNCHARACTERISTICSCANBEAUTOMATICALLYCORRECTEDTO MINIMIZETHEIRCONTAMINATIONOFTHEOUTPUTDATA
, ,
3-3HERMAN -ONOPULSE0RINCIPLESAND4ECHNIQUES .ORWOOD -!!RTECH(OUSE !),EONOVAND+)&ORMICHEV -ONOPULSE2ADAR v.ORWOOD -!!RTECH(OUSE *($UNNAND$$(OWARD h0RECISIONTRACKINGWITHMONOPULSERADAR v%LECTRONICS VOL PPn !PRIL 0:0EEBLES *R h3IGNAL0ROCESSORANDACCURACYOFTHREE BEAMMONOPULSETRACKINGRADAR v)%%% 4RANS VOL!%3 PPn *ANUARY
°{n
2!$!2(!.$"//+
0 7 (ANNAN h/PTIMUM FEEDS FOR ALL THREE MODES OF A MONOPULSE ANTENNA ) 4HEORY )) 0RACTICE v)%%%4RANS VOL!0 PPn 3EPTEMBER h&INAL REPORT ON INSTRUMENTATION RADAR !.&03 8. v 2ADIO #ORPORATION OF !MERICA UNPUBLISHEDREPORT.4)3 PP n $ + "ARTON h2ECENT DEVELOPMENTS IN RADAR INSTRUMENTATION v !STRON !EROSP %NG VOL PPn *ULY * 4 .ESSMITH h2ANGE INSTRUMENTATION RADARS v )%%% 4RANS VOL !%3 PP n .OVEMBER *!$I#URCIO h!.401 PRECISIONTRACKINGRADAR vIN)%%%)NT2ADAR#ONF2EC !RLINGTON 6! PPn $$(OWARD h3INGLE!PERTUREMONOPULSERADARMULTI MODEANTENNAFEEDANDHOMINGDEVICE v IN0ROC)%%%)NT#ONV-IL%LECTRON#ONF 3EPTEMBERn PPn 0-IKULICH 2$OLUSIC #0ROFERA AND,9ORKINS h(IGHGAINCASSEGRAINMONOPULSEANTENNA v IN)%%%' !0)NT!NTENNA0ROPAG3YMP2EC 3EPTEMBER 2#*OHNSONAND(*ASIK !NTENNA%NGINEERING(ANDBOOK ND%D .EW9ORK-C'RAW (ILL "OOK#OMPANY #HAP $#ROSS $(OWARD -,IPKA !-AYS AND%/RNSTEIN h42!+8!DUAL FREQUENCYTRACKING RADAR v-ICROWAVE* VOL PPn 3EPTEMBER 67(AMMONDAND+(7EDGE h4HEAPPLICATIONOFPHASED ARRAYINSTRUMENTATIONRADARINTEST ANDEVALUATIONSUPPORT vIN%LECTRON.AT3ECURITY#ONF2EC 3INGAPORE *ANUARYn *7"ORNHOLDT h)NSTRUMENTATIONRADARS4ECHNICALEVALUATIONANDUSE vIN0ROC)NT4ELEMETRY #OUNCIL .OVEMBER 7"-ILWAY h-ULTIPLETARGETINSTRUMENTATIONRADARSFORMILITARYTESTANDEVALUATION vIN0ROC )NT4ELEMETRY#ONFVOL88) 2,3TEGALL h-ULTIPLEOBJECTTRACKINGRADAR3YSTEMENGINEERINGCONSIDERATIONS vIN0ROC)NT 4ELEMETRY#OUNCIL 2 3 .OBLIT h2ELIABILITY WITHOUT REDUNDANCY FROM A RADAR MONOPULSE RECEIVER v-ICROWAVES PPn $ECEMBER (3AKAMOTOAND0:0EEBLES *R h#ONOPULSERADAR v)%%%4RANS VOL!%3 PPn *ANUARY 0!"AKUTAND)3"OLSHAKOV 1UESTIONSOFTHE3TATISTICAL4HEORYOF2ADAR VOL)) -OSCOW 3OVETSKOYE 2ADIO #HAPS AND 4RANSLATION AVAILABLE FROM .4)3 !$ *UNE - ) 3KOLNIK )NTRODUCTION TO 2ADAR 3YSTEMS ND %D .EW 9ORK -C'RAW (ILL "OOK #OMPANY $+"ARTON 2ADAR3YSTEMS!NALYSIS .ORWOOD -!!RTECH(OUSE !3,OCKE 'UIDANCE 0RINCTON .*$6AN.OSTRAND#OMPANY #HAP $##ROSS h,OWJITTERHIGHPERFORMANCEELECTRONICRANGETRACKER vIN)%%%)NT2ADAR#ONF 2EC PPn $,-ALONE h&,9#!4#(%2 v.AT$EF PPn *ANUARY (OLLANDSE3IGNAALAPPARATEN"6ADVERTISEMENT $EF%LECTRON VOL P !PRIL %DITOR h)NSIDE THE %XOCET &LIGHT OF A SEA SKIMMER v $EF %LECTRON VOL PP n !UGUST %DITOR h3PECIALSERIES)SRAELI!VIONICS v!VIAT7EEK3PACE4ECHNOL PPn !PRIL $ # #ROSS $ $ (OWARD AND * 7 4ITUS h-IRROR ANTENNA RADAR CONCEPT v -ICROWAVE * VOL PPn -AY $$(OWARDAND$##ROSS h-IRRORANTENNADUAL BANDLIGHTWEIGHTMIRRORDESIGN v)%%% 4RANS VOL!0 PPn -ARCH %03CHELONKA h!DAPTIVECONTROLTECHNIQUEFORON AXISRADAR vIN)NT2ADAR#ONF2EC PPn
42!#+).'2!$!2
°{
)$/LINAND&$1UEEN h$YNAMICMEASUREMENTOFRADARCROSSSECTION v0ROC)%%% VOL PPn !UGUST *($UNN $$(OWARD AND!-+ING h0HENOMENAOFSCINTILLATIONNOISEINRADAR TRACKING SYSTEMS v0ROC)2% VOL PPn -AY -)3KOLNIK )NTRODUCTIONTO2ADAR3YSTEMS .EW9ORK-C'RAW (ILL"OOK#OMPANY #HAP $+"ARTON -ODERN2ADAR3YSTEM!NALYSIS .ORWOOD -ASS!RTECH(OUSE P ' -ERRILL $ * 0OVEJSIL 2 3 2AVEN AND 0 7ATERMAN !IRBORNE 2ADAR "OSTON "OSTON 4ECHNICAL0UBLISHERS PPn $$(OWARD h2ADARTARGETANGULARSCINTILLATIONINTRACKINGANDGUIDANCESYSTEMSBASEDON ECHOSIGNALPHASEFRONTDISTORTION vIN0ROC.AT%LECTRON#ONF VOL /CTOBER 2($ELANO h!THEORYOFTARGETGLINTORANGLESCINTILLATIONINRADARTRACKING v0ROC)2% VOL PPn $ECEMBER 2($ELANOAND)0FEFFER h4HEEFFECTSOF!'#ONRADARTRACKINGNOISE v0ROC)2% VOL PPn *UNE *($UNNAND$$(OWARD h4HEEFFECTSOFAUTOMATICGAINCONTROLPERFORMANCEONTHETRACK INGACCURACYOFMONOPULSERADARSYSTEMS v0ROC)2% VOL PPn -ARCH $ # #ROSS AND * % %VANS h4ARGET GENERATED RANGE ERRORS v IN )%%% )NT 2ADAR #ONF 2EC !RLINGTON 6! !PRILn PPn $*0OVEJSIL 232AVEN AND07ATERMAN !IRBORNE2ADAR 0RINCETON .*$6AN.OSTRAND #OMPANY PPn 2(YNESAND2%'ARDNER h$OPPLERSPECTRAOF3BANDAND8BANDSIGNALS v)%%%4RANS3UPPL VOL!%3 PPn .OVEMBER !!!USHERMAN !+OZMA *,7ALKER (-*ONES AND%#0OGGIO h$EVELOPMENTINRADAR IMAGING v)%%%4RANS VOL!%3 PPn *ULY '$IKE 27ALLENBERG AND*0OTENZA h)NVERSE3!2ANDITSAPPLICATIONTOAIRCRAFTCLASSIFICA TION vIN)%%%)NT2ADAR#ONF2EC PPn $ + "ARTON h4HE LOW ANGLE TRACKING PROBLEM v PRESENTED AT )%% )NT 2ADAR #ONF ,ONDON /CTOBERn $ + "ARTON AND ( 2 7ARD (ANDBOOK OF 2ADAR -EASUREMENT %NGLEWOOD #LIFFS .* 0RENTICE (ALL $+"ARTON h,OW ANGLERADARTRACKING v0ROC)%%% VOL PPn *UNE $+"ARTON 2ADAR2ESOLUTIONAND-ULTIPATH%FFECTSINVOLOF2ADARS .ORWOOD -!!RTECH (OUSE $$(OWARD *.ESSMITH AND3-3HERMAN h-ONOPULSETRACKINGERRORDUETOMULTIPATH #AUSESANDREMEDIES vIN%!3#/.2EC PPn % - 4 *ONES h0ARABOLOID REFLECTOR AND HYPERBOLOID LENS ANTENNA v )2% 4RANS VOL !0 PPn *ULY 2-ITCHELLETAL h-EASUREMENTSOFPERFORMANCEOF-)0)2-ISSILE0RECISION)NSTRUMENTATION 2ADAR3ET!.&01 v&INAL2EPT .AVY#ONTRACT./7 D 2#! -ISSILEAND3URFACE 2ADAR$IVISION -OORESTOWN .* $ECEMBER 0 2 $AX h!CCURATE TRACKING OF LOW ELEVATION TARGETS OVER THE SEA WITH A MONOPULSE RADAR v IN )%% 2ADAR #ONF 0UBL 2ADAR0RESENT AND &UTURE ,ONDON /CTOBER n PPn $$(OWARD h)NVESTIGATIONANDAPPLICATIONOFRADARTECHNIQUESFORLOW ALTITUDETARGETTRACK ING vIN)%%)NT2ADAR#ONF2EC ,ONDON /CTOBERn $$(OWARD h%NVIRONMENTALEFFECTSONPRECISIONMONOPULSEINSTRUMENTATIONTRACKINGRADARAT '(Z vIN)%%%%!3#/.2EC /CTOBER 2 * -C!ULAY AND 4 0 -C'ARTY h-AXIMUM LIKELIHOOD DETECTION OF UNRESOLVED TARGETS AND MULTIPATH v)%%%4RANS VOL!%3 PPn .OVEMBER
°xä
2!$!2(!.$"//+
7$7HITE h4ECHNIQUESFORTRACKINGLOW ALTITUDERADARTARGETSINTHEPRESENCEOFMULTIPATH v )%%%4RANS VOL!%3 PPn .OVEMBER 0 : 0EEBLES *R h-ULTIPATH ERROR REDUCTION USING MULTIPLE TARGET METHODS v )%%% 4RANS VOL!%3 PPn .OVEMBER & % .ATHANSON 2ADAR $ESIGN 0RINCIPLES .EW 9ORK -C'RAW (ILL "OOK #OMPANY P ',INDE h2EDUCTIONOFRADARTRACKINGERRORSWITHFREQUENCYAGILITY v)%%%4RANS VOL!%3 PPn -AY ',INDE h!SIMPLEAPPROXIMATIONFORMULAFORGLINTIMPROVEMENTWITHFREQUENCYAGILITY v)%%% 4RANS !%3 PPn .OVEMBER $ + "ARTON &REQUENCY !GILITY AND $IVERSITY IN 6OL OF 2ADARS .ORWOOD -!!RTECH (OUSE
#HAPTER
/
iÊ,>`>ÀÊ/À>ÃÌÌiÀ /
>ÃÊ°Ê7iÊ>`Ê iÀÀÊ-
£ä°£Ê /," 1 /" 2OLE OF THE 4RANSMITTER IN 2ADAR )F A RADAR SYSTEMS DESIGNER COULD ASK FOR ANYTHINGHEORSHEWANTEDINARADARTRANSMITTER THATWISHMIGHTBESOMETHINGLIKE THEFOLLOWING 0ROVIDE THE NECESSARY TRANSMITTED ENERGY WITH THE NEEDED AVERAGE AND PEAK POWER ASWELLASTHEREQUIREDSTABILITYANDLOWNOISEFORGOODDOPPLERPROCESS ING OPERATE WITH HIGH EFFICIENCY HAVE WIDE BANDWIDTH AND BE EASILY TUNABLE BEREADILYMODULATEDINAMPLITUDE FREQUENCY ORPHASEASNECESSARYHAVEHIGH RELIABILITYANDLONGLIFEREQUIREMINIMUMMAINTENANCEHAVENODANGEROUS8 RAY EMISSIONSREQUIRENOPERSONNELTOOPERATEBEOFANAFFORDABLEPRICEANDBEOF REASONABLESIZEANDWEIGHTFORTHEDESIREDAPPLICATION /FCOURSE NOTALLOFTHESEDESIRABLEATTRIBUTESCANBEACHIEVEDINANYGIVENRADARTRANS MITTERAPPLICATION#OMPROMISESNEEDTOBEMADEDEPENDINGONTHEAPPLICATION 4HERADAREQUATIONFORASURVEILLANCERADARONETHATHASTOCOVERAFIXEDVOLUME OFSPACEONAREGULARBASIS INDICATESTHATTHEMAXIMUMRANGEOFSUCHARADARISPRO PORTIONALTO0AV! WHERE0AVISTHEAVERAGEPOWEROFTHETRANSMITTERAND!ISTHE AREAOFTHEANTENNAAPERTURE!FUNDAMENTALMEASUREOFTHERADARRANGEPERFORMANCE IS THEREFORE THE POWER APERTURE PRODUCT /NE CAN OBTAIN A LONG RANGE BY HAVING A LARGEANTENNA ALARGETRANSMITTER ORACOMBINATIONOFBOTH)TISNOTUSUAL UNDERMOST CIRCUMSTANCES FORARADARTOHAVEAHUGE COSTLYANTENNAANDASMALL INEXPENSIVE TRANSMITTER ORVICEVERSA4HEREHASTOBEAREASONABLEBALANCEBETWEENTHESETWO MAJORSUBSYSTEMSOFARADAR)NASURVEILLANCERADAR STRAIGHTFORWARDCALCULUSWILL SHOWTHATUNDERSIMPLEASSUMPTIONSTHEMINIMUMTOTALCOSTOFARADAROCCURSWHEN THECOSTOFTHETRANSMITTEREQUALSTHECOSTOFTHEANTENNABUTTHISISTRUEONLYWHEN THEREARENOCRITERIA OTHERTHANMINIMUMCOST THATHAVETOBESATISFIEDANDTHERE AREUSUALLYOTHERCRITERIATHATNEEDTOBECONSIDERED !SISWELLKNOWNINRADAR THEDOPPLEREFFECTISEXTENSIVELYUSEDTODETECTMOVING TARGETSINTHEPRESENCEOFLARGECLUTTERECHOES)TISTHEBASISFORSEVERALOFTHECHAPTERS INTHIS(ANDBOOK3OMETRANSMITTERTYPES HOWEVER AREFARBETTERTHANOTHERSWHENTHE RADARHASTOEMPLOYTHEDOPPLER SHIFTEDSIGNALTODETECTMOVINGTARGETSINTHEMIDSTOF HEAVYCLUTTERECHOES %XAMINATIONOFTHEBASICRADAREQUATIONFORDETECTIONOFTARGETSATLONGRANGEINDI CATESTHATTHEAVERAGEPOWERISFARMOREIMPORTANTTHANTHEPEAKPOWERASAMEASURE
£ä°£
£ä°Ó
2!$!2(!.$"//+
OFTHERADARSCAPABILITY!VACUUMTUBE WITHAGIVENAVERAGEPOWERCANUSUALLYBE DESIGNEDTOHANDLETHEHIGHVOLTAGESASSOCIATEDWITHALARGEPEAKPOWERWITHOUTBREAK DOWN!SOLID STATETRANSMITTERCANNOT)NTHEPAST AVERAGEPOWERSOFRADARTRANSMIT TERSHAVEBEENFROMASMALLFRACTIONOFAWATTTOTHEORDEROFAMEGAWATT 4YPESOF2ADAR4RANSMITTERS 4HEVERYFIRSThRADARS vSUCHASTHOSEUSEDBY (EINRICH (ERTZ THE FIRST RADAR SCIENTIST IN THE LATE S AND THE SHIPBOARD RADAR INVENTEDBY#HRISTIAN(ULSMEYERTHEFIRSTRADARENGINEER INTHEEARLYSUSEDTHE SPARKGAPASTHETRANSMITTER)TWASAVERYPOORTRANSMITTER BUTTHATISNOTUNUSUALINTHE EARLYDAYSOFANEWANDDIFFERENTDEVELOPMENT4HE$E&ORESTGRID CONTROLLEDVACUUM TUBETRIODE WASINVENTEDSHORTLYTHEREAFTER ANDBYTHEEARLYS ITHADBEENWELL DEVELOPEDTOWHEREITWASSUCCESSFULLYANDEXTENSIVELYUSEDINTHOSECOUNTRIESTHAT BUILTTHEFIRST6(&AND5(&RADARSUSEDFORAIRDEFENSEEARLYIN7ORLD7AR))3OME 5(&RADARSEFFECTIVELYUSEDTHEGRID CONTROLLEDVACUUMTUBEWELLINTOTHEEARLYPARTOF THECURRENTCENTURY)THASBEENAVERYCOMPETITIVEPOWERSOURCEFOR5(&RADARAPPLI CATIONS4HEDRAWBACKOFTHEGRID CONTROLLEDVACUUMTUBEISTHATTRANSIT TIMEEFFECTS LIMITITSAPPLICATIONATMICROWAVEFREQUENCIES BUTVARIANTSOFGRID CONTROLLEDVACUUM TUBESHAVEBEENSUCCESSFULLYUSEDUPTOABOUT-(Z 4HEBARRIEROFTRANSITTIMEEFFECTSWASOVERCOMEWITHTHEINVENTIONOFTHEMICRO WAVECAVITYMAGNETRONEARLYIN7ORLD7AR))INBYTHE5NITED+INGDOM5+ 4HE INTRODUCTION OF THE MAGNETRON ALLOWED HIGH POWER RADAR TO BE SUCCESSFULLY DEVELOPED FOR USE AT THE HIGHER FREQUENCIES WHERE SMALLER SIZE ANTENNAS COULD BE USED)TISOFINTERESTTONOTETHATTHE*APANESEINVENTEDTHEMAGNETRONBEFORETHE 5+DID AND3OVIET5NIONENGINEERSPUBLISHEDAPAPERDESCRIBINGTHEIRMAGNETRON INTHE-ARCHISSUEOF0ROCEEDINGSOFTHE)NSTITUTEOF2ADIO%NGINEERS NOWTHE 0ROCEEDINGSOFTHE)%%%BUTTHEWARTIMECHAOSINTHEMILITARYDEVELOPMENTSOFBOTH THE3OVIET5NIONAND*APANWASSUCHTHATTHESEINVENTIONSWERENOTFULLYEXPLOITED BYTHESETWOCOUNTRIESDURING77)) 4HEINVENTIONOFTHEMAGNETRONWASIMPORTANT BECAUSEITALLOWEDRADARTOBEDEVELOPEDFORUSEATMICROWAVEFREQUENCIESRATHERTHAN BELIMITEDTO6(&AND5(&FREQUENCIES)TCAUGHTTHE'ERMANELECTRONICCOUNTER MEASURESEFFORTOFFGUARDBECAUSETHEYHADNOIDEATHATTHE5NITED+INGDOMANDTHE 5NITED3TATESCOULDPRODUCEMICROWAVERADAR4HESUCCESSOFTHEMAGNETRONWASA LARGEFACTORINTHEEFFECTIVEAPPLICATIONOFMILITARYRADARBYTHE5NITED3TATESANDTHE 5NITED+INGDOMDURING7ORLD7AR)) 4HEMAGNETRONISANEXAMPLEOFWHATISCALLEDACROSSED FIELDTUBEINTHATITEMPLOYS AMAGNETICFIELDANDANELECTRICFIELDTHATAREORTHOGONALTOONEANOTHER4HEMAGNETRON ISANOSCILLATORBUTTHEGRID CONTROLLEDVACUUMTUBECOULDBEOPERATEDASEITHERANOSCIL LATORORANAMPLIFIER4HEOTHERELECTRONICTUBESMENTIONEDINTHISCHAPTERAREUSUALLY OPERATEDASAMPLIFIERS!MPLIFIERSATMICROWAVEFREQUENCIESHAVEGENERALLYPRODUCED HIGHER POWERS THAN OSCILLATORS BUT PROBABLY MORE IMPORTANT THEY ALLOW THE USE OF STABLE MODULATEDWAVEFORMSNEEDEDFORWAVEFORMSINRADARSTHATDEPENDONTHEUSEOF PULSECOMPRESSIONANDFORTHEDOPPLEREFFECTTODETECTMOVINGTARGETSINCLUTTER 4HE MICROWAVE KLYSTRON AMPLIFIER WAS INVENTED BEFORE THE MAGNETRON AND WAS DESCRIBED IN A PAPER IN THE -AY ISSUE OF THE *OURNAL OF !PPLIED 0HYSICS &ORTHEMOSTPART THEKLYSTRONAMPLIFIERWASIGNOREDDURING77))ANDDIDNTATTRACT
)NTHE5NITED3TATES THEDEVICETHATGENERATESTHE2&POWERISCALLEDATUBE BUTINTHE5NITED+INGDOM ITISCALLED AVALVE!BOOKONMICROWAVEPOWERSOURCESSUGGESTSTHATTHESEDEVICESBECALLEDMICROWAVEVACUUMELECTRONIC DEVICES-6%$ )NTHISCHAPTER HOWEVER THENAMETUBEWILLBERETAINED
4(%2!$!242!.3-)44%2
£ä°Î
THEATTENTIONOFRADARENGINEERSUNTILTHEANNOUNCEMENTINAPAPERINTHE.OVEMBER 0ROCEEDINGSOFTHE)%%%BY3TANFORD5NIVERSITYENGINEERSOFTHEDEVELOPMENT OFAN3 BANDMULTICAVITYKLYSTRONCAPABLEOF-7PEAKPOWERANDK7AVERAGE POWERFORUSEINALINEARACCELERATOR4HISWASAGREATACCOMPLISHMENTINITSTIME4HE HIGHPOWER HIGHEFFICIENCY GOODSTABILITY ANDWIDEBANDWIDTHATHIGHPOWER OFTHE MICROWAVEKLYSTRONAMPLIFIERHAVECAUSEDSOMERADARDESIGNENGINEERSTOSAYTHATTHE KLYSTRONSHOULDBETHEFIRSTMICROWAVEPOWERSOURCETOCONSIDERWHENDESIGNINGANEW HIGH PERFORMANCERADAR4HEREWAS ATONETIME ASINGLE CAVITYKLYSTRONOSCILLATOR CALLEDTHEREFLEXKLYSTRONTHATWASOFLOWPOWERANDMAINLYUSEDASARECEIVERLOCAL OSCILLATOR BUTITHASGENERALLYBEENREPLACEDBYSOLID STATEDEVICESANDISNOTDISCUSSED FURTHERINTHISCHAPTER 4HEKLYSTRONISANEXAMPLEOFALINEAR BEAMTUBEBECAUSETHEDIRECTIONOFTHEDC ELECTRICFIELDTHATACCELERATESTHEELECTRONBEAMCOINCIDESWITHTHEAXISOFTHEMAGNETIC FIELDTHATFOCUSESANDCONFINESTHEBEAM)TGENERATESAHIGHLYCONCENTRATEDHIGH ENERGY LINEARBEAMOFELECTRONSTHATINTERACTSWITHTHEMICROWAVESTRUCTURETWOORMOREMICRO WAVECAVITIES TOACHIEVEAMPLIFICATION!NOTHEREXAMPLEOFTHELINEAR BEAMTUBEISTHE TRAVELINGWAVETUBE474 AMPLIFIER)TGENERALLYCANDOALMOSTWHATAKLYSTRONCAN DO BUTITISCAPABLEOFVERYWIDEBANDWIDTHATLOWPOWERS WHICHTHEKLYSTRONISNOT 4HE474USUALLYHASSLIGHTLYLESSGAINTHANAKLYSTRONANDLESSSTABILITY)TSHOULDBE NOTED HOWEVER THATASTHEPOWEROFA474INCREASES ITSBANDWIDTHDECREASESANDAS THEPOWEROFAKLYSTRONAMPLIFIERINCREASES ITSBANDWIDTHINCREASES4HUS ATTHEHIGH POWERSNEEDEDFORMANYRADARAPPLICATIONS THEBANDWIDTHSOFTHESETWOTYPESOFLINEAR BEAMTUBESAREAPPROXIMATELYCOMPARABLE 4HEREALSOHAVEBEENHYBRIDSOFTHEKLYSTRONANDTHE474THATHAVEBEENOFINTEREST FORRADARAPPLICATIONS ANDWHICHHAVEINTERESTINGCHARACTERISTICS 4HECROSSED FIELDAMPLIFIER LIKETHEMAGNETRON ISACROSSED FIELDTUBETHATEMPLOYS AMAGNETICFIELDORTHOGONALTOTHEELECTRICFIELD)TISCAPABLEOFWIDEBANDWIDTHAND GENERALLYISOFSMALLERSIZEANDDOESNOTREQUIRETHEVERYHIGHVOLTAGESOFTHELINEAR BEAMTUBE!LTHOUGHITHASSOMEADVANTAGESNOTFOUNDINOTHERTUBES ITHASLOWER GAINTHANLINEAR BEAMAMPLIFIERSSOMULTIPLESTAGESOFAMPLIFICATIONAREREQUIRED ANDITSNOISELEVELISHIGHERTHANTHELINEAR BEAMTUBE WHICHMAKESITLESSCAPABLE FORDETECTINGMOVINGTARGETSINCLUTTER 4HEGYROTRON WHICHCANBEEITHERANOSCILLATORORANAMPLIFIER ISAN2& POWER SOURCE THAT CAN PRODUCE VERY HIGH POWER AT MILLIMETER WAVELENGTHS #ONVENTIONAL MICROWAVEPOWERSOURCESUTILIZERESONANTSTRUCTURESINWHICHTHEPHASEVELOCITYOFTHE ELECTROMAGNETICFIELDPROPAGATINGALONGTHE2&STRUCTUREISSLOWEDSOASTOBECLOSETO THEELECTRONBEAMVELOCITY4HUS THEYAREKNOWNASSLOW WAVETUBES4HECHARACTERISTIC SIZEOFTHEINCREMENTSOFTHE2&STRUCTUREOFSLOW WAVETUBESISTYPICALLYAFRACTION OFAWAVELENGTH4HEYBECOMESMALLERASTHEFREQUENCYISINCREASEDWAVELENGTHIS DECREASED 3MALLER SIZE MEANS THAT A TUBE CANNOT DISSIPATE HEAT AS WELL AS A LARGER TUBE SOTHATTHEPOWERCAPABILITYOFMICROWAVEPOWERTUBESDECREASESAPPROXIMATELY INVERSELYASTHESQUAREOFTHEFREQUENCY4HEGYROTRON ONTHEOTHERHAND DOESNOTHAVE THISTYPEOFFREQUENCYDEPENDENCESINCEITUSESWHATISCALLEDAFAST WAVESTRUCTURE 4HISISUSUALLYASMOOTHWAVEGUIDEORALARGERESONATOR.OATTEMPTISMADETOREDUCE THEPROPAGATIONVELOCITYOFTHEELECTROMAGNETICWAVEWITHINTHISSTRUCTURE4HEELECTRON BEAMISNOTCLOSETOTHE2&STRUCTURESOITISNOTASLIMITEDINSIZEASARETHESTRUCTURESOF
)NELECTRICALENGINEERING 2&STANDSFORRADIOFREQUENCY BUTINRADAR ITISOFTENUSEDTOMEANTHERADARFREQUENCY
£ä°{
2!$!2(!.$"//+
SLOW WAVETUBES4HELARGERSIZEOFTHEFAST WAVETUBEMEANSTHATITCANHANDLELARGER POWERATTHEHIGHERFREQUENCIES4HEGYROTRONHASMAINLYBEENOFSIGNIFICANCEFORHIGH POWERAPPLICATIONSATMILLIMETER WAVEFREQUENCIES 4HESOLID STATETRANSISTORAMPLIFIERHASBEENOFINTERESTFORRADARAPPLICATIONS3UCH INTERESTINSOLIDSTATEHASALSOBEENDUE INPART TOITSCOMPLETELYREPLACINGVACUUM TUBESINRECEIVERANDCOMPUTERAPPLICATIONS4HESOLID STATETRANSMITTERISDISCUSSEDIN #HAPTER ANDABRIEFCOMPARISONOFITWITHTHEVACUUMTUBETRANSMITTERISGIVENAT THEENDOFTHISCHAPTER4HECHIEFADVANTAGESOFASOLID STATERADARTRANSMITTERARETHAT ITCANOPERATEWITHWIDEBANDWIDTHSITHASTHEPOTENTIALFORLONGLIFEANDITISFAVORED BYSOMEBUYERSOFRADAR)TCANNOT HOWEVER EMPLOYHIGHPEAK POWERWAVEFORMS4HE LIMITATIONONPEAKPOWERINASOLID STATETRANSMITTERRESULTSINCOMPROMISESTHATHAVE TOBEMADEINTHEDESIGNOFTHEOVERALLRADARSYSTEM /SCILLATOR6ERSUS!MPLIFIER 4HEPOWERAMPLIFIERISOFTENPREFERREDOVERTHE POWER OSCILLATOR AS THE TRANSMITTER POWER SOURCE IN HIGH POWER HIGH PERFORMANCE RADARSYSTEMS)NANAMPLIFIER THESIGNALTOBETRANSMITTEDISPRECISELYGENERATEDAT A LOW POWER LEVEL AND IS THEN AMPLIFIED TO ACHIEVE THE REQUIRED POWER TO BE RADI ATEDFROMTHEANTENNA!MPLIFIERSHAVETHEADVANTAGEOFBEINGABLETOPROVIDESTABLE WAVEFORMS CODEDORFREQUENCYMODULATEDPULSECOMPRESSIONWAVEFORMS FREQUENCY AGILITY ASWELLASCOMBININGANDARRAYING 4HEMAGNETRONISANOSCILLATORTHATHASLESSFLEXIBILITYANDISUSUALLYNOISIERTHAN ALINEAR BEAMAMPLIFIER%ACHTIMEAPULSEISTRANSMITTED ITSPHASEISDIFFERENTFROM THE PHASE OF PREVIOUS PULSES4HAT IS ITS PHASE IS RANDOM FROM PULSE TO PULSE4O DETECTTHEDOPPLERFREQUENCYSHIFTFOR-4)PROCESSING THEPHASECANNOTCHANGEINA RANDOMMANNERATTHERECEIVERFROMPULSETOPULSE4HISLIMITATIONISOVERCOMEBY TAKINGASAMPLEOFTHERANDOMPHASEOFEACHTRANSMITTEDPULSEANDUSINGITTORESET THEPHASEOFTHELOCALOSCILLATORINTHERECEIVERTOMATCHTHEPHASEOFTHETRANSMITTED SIGNAL4HISISSOMETIMESCALLEDCOHERENTONRECEIVE'ENERALLY THE-4)IMPROVE MENTFACTORTHATCANBEOBTAINEDWITHAMAGNETRONISNOTASGOODASCANBEOBTAINED WITHALINEAR BEAMAMPLIFIER )NTHEPAST THEREMIGHTHAVEBEENDEBATEASTOWHETHERTOUSEANOSCILLATORORAN AMPLIFIERFORAHIGH PERFORMANCERADARTRANSMITTER4HEREISUSUALLYNOQUESTIONTHAT THEAMPLIFIERISUSUALLYTHEPREFERREDCHOICE EXCEPTINSITUATIONSWHERETHELOWCOSTOF AMAGNETRONTRANSMITTERISMOREIMPORTANTTHANTHELOWER-4)IMPROVEMENTFACTORIT PROVIDESCOMPAREDTOALINEAR BEAMTRANSMITTER4HEMAGNETRONOSCILLATOR HOWEVER HASBEENUSEDINSOMESHORTORMEDIUMRANGERADARSANDINTHEWIDELYPOPULARCIVIL MARINERADAR#HAPTER WHICHREQUIRESONLYASMALLPOWERTRANSMITTERANDHASNO NEEDFOR-4)CAPABILITY
£ä°ÓÊ , Ê * ,- Ó 4HEKLYSTRON 474 ANDHYBRIDSOFTHETWOHAVEBEENIMPORTANTSOURCESOF2&POWERFOR MANYSUCCESSFULRADARSYSTEMS4HEELECTRONSEMITTEDFROMTHECATHODEAREFORMEDINTO ALONGCYLINDRICALBEAMTHATRECEIVESTHEFULLPOTENTIALENERGYOFTHEELECTRICFIELDBEFORE THEBEAMENTERSTHEMICROWAVEINTERACTIONREGION4HEELECTRONBEAM GENERATEDBYAN hELECTRONGUN vESSENTIALLYFLOWSINASTRAIGHTLINEINLINEAR BEAMTUBESTOINTERACTWITH AMICROWAVECIRCUITTOPRODUCEAMPLIFICATIONOFANINPUTSIGNAL4HEMAJORDIFFERENCE AMONGTHESEVERALTYPESOFLINEAR BEAMTUBESISTHETYPEOFMICROWAVECIRCUITEMPLOYED
4(%2!$!242!.3-)44%2
£ä°x
ANDTHENATUREOFTHEINTERACTIONTHATPRODUCESAMPLIFICATION4RANSIT TIMEEFFECTS WHICH LIMITTHEHIGHFREQUENCYPERFORMANCEOFGRID CONTROLLEDTUBES ARETAKENADVANTAGEOFIN LINEAR BEAMTUBESTOVELOCITYMODULATETHEUNIFORMELECTRONBEAMTOCREATEBUNCHESOF ELECTRONSFROMWHICH2&ENERGYCANBEEXTRACTEDATTHEOUTPUTOFTHETUBE,INEAR BEAM TUBESASAMPLIFIERSCANPRODUCEHIGHPOWERWITHGOODEFFICIENCYANDHIGHGAINANDWITH WIDEBANDWIDTH4HEYHAVEBEENCAPABLEOFPRODUCINGAVERAGEPOWERSOFAMEGAWATT AS WELL AS AVERAGE POWERS OF MANY KILOWATTS IN A SIZE SUITABLE FOR USE IN A MILITARY FIGHTERATTACKAIRCRAFT +LYSTRON 4HE KLYSTRON AMPLIFIER HAS BEEN AN IMPORTANT 2& POWER SOURCE FOR MANYRADARAPPLICATIONS!SMENTIONED ITISCAPABLEOFHIGHAVERAGEANDHIGHPEAK POWER HIGHGAIN GOODEFFICIENCY STABLEOPERATION LOWINTERPULSENOISE LARGEBAND WIDTH AT HIGH POWER AND BEING AN AMPLIFIER IT CAN WORK WELL WITH THE FREQUENCY ANDPHASEMODULATEDWAVEFORMSNEEDEDFORPULSECOMPRESSION+LYSTRONSHAVEOPER ATEDATFREQUENCIESFROM5(&TOMILLIMETERWAVELENGTHSANDHAVEFOUNDUSEINSUCH DIVERSEAPPLICATIONSASAIRPORTSURVEILLANCERADARSWHERETHEAVERAGEPOWERSMIGHTBE MORETHANONEKILOWATT INAIRBORNEMILITARYAIRCRAFTWHERETHEAVERAGEPOWERMIGHTBE OFTHEORDEROFK7ORMORE ANDINLONGRANGEDETECTIONOFINTERCONTINENTALBALLISTIC MISSILESWHERETHEAVERAGEPOWERPERTUBECANBEGREATERTHANK7 &IGUREDEPICTSTHEPRINCIPALPARTSOFATHREE CAVITYKLYSTRON!TTHELEFTISTHE HEATERTHATHEATSTHECATHODEANDTHECATHODETHATEMITSASTREAMOFELECTRONSTHATARE COLLIMATEDINTOANARROWCYLINDRICALBEAMOFHIGHELECTRONDENSITY4HEELECTRONGUN THATGENERATESTHEBEAMCONSISTSOFTHECATHODE THEMODULATINGANODEALSOCALLED THEBEAMCONTROLGRID ANDTHEANODE4HEMODULATINGANODEPROVIDESTHEMEANSTO PULSETHEELECTRONBEAMONANDOFF4HE2&CAVITIESARETHEMICROWAVEEQUIVALENTOF ARESONANTCIRCUIT%LECTRONSARENOTINTENTIONALLYCOLLECTEDATTHEANODEASTHEYARE INGRID CONTROLLEDTUBESANDCROSSED FIELDTUBES BUTINTHECOLLECTOR SHOWNATTHE RIGHT HANDSIDEOFTHEILLUSTRATION AFTERTHEELECTRONBEAMHASGIVENUPITS2&ENERGY ATTHEOUTPUTCAVITY!LOW POWERSIGNALISAPPLIEDTOTHEINPUTOFTHEFIRSTCAVITYAND APPEARS AT THE INTERACTION GAP4HOSE ELECTRONS IN THE BEAM THAT ARRIVE AT THE FIRST INTERACTION GAP WHEN THE INPUT SIGNAL VOLTAGE IS AT A MAXIMUM THE POSITIVE PEAK OFTHESINEWAVE ARESPEEDEDUPCOMPAREDTOTHOSEELECTRONSTHATARRIVEATTHEGAP WHENTHEINPUTSIGNALVOLTAGEISAMINIMUMTHENEGATIVETROUGHOFTHESINEWAVE
&)'52% 2EPRESENTATIONOFTHEPRINCIPALPARTSOFATHREE CAVITYKLYSTRONAMPLIFIER
£ä°È
2!$!2(!.$"//+
)NTHEFIRSTDRIFTSPACE THOSEELECTRONSSPEEDEDUPDURINGTHEPEAKOFONECYCLECATCH UPTOTHOSETHATWERESLOWEDDOWNDURINGTHEMINIMUMOFTHEPREVIOUS2&CYCLE 4HERESULTISTHATTHEELECTRONSBECOMEhBUNCHEDvPERIODICALLY4HISBUNCHINGCAN BE THOUGHT OF AS PRODUCING A MODULATION OF THE DENSITY OF ELECTRONS4HE BUNCHES PASSTHROUGHTHEINTERACTIONSPACEOFTHESECONDCAVITY WHICHREINFORCESTHEDENSITY MODULATION TO ENHANCE THE BUNCHING 4HIS PROCESS OF IMPRESSING A TIME VARIATION INVELOCITYTHATRESULTSINBUNCHINGOFTHEELECTRONSOFANINITIALLYUNIFORMELECTRON BEAMISCALLEDVELOCITYMODULATION4HREEORMORE2&CAVITIESMIGHTBEUSED4HE INTERACTIONGAPOFTHEOUTPUTCAVITYISPLACEDATTHEPOINTOFMAXIMUMBUNCHINGSO THATTHE2&POWERCANBEEXTRACTEDFROMTHEDENSITYMODULATEDELECTRONBEAMBYA COUPLINGLOOPINALOWERPOWERTUBEORBYAWAVEGUIDENOTSHOWN INAHIGHPOWER TUBE)NESSENCE THEDCENERGYOFTHEELECTRONBEAMATTHEFIRSTCAVITYISCONVERTED TO2&ENERGYATTHEOUTPUTCAVITYBYTHEVELOCITYMODULATIONPROCESS4HELARGERTHE NUMBEROFCAVITIESTHEGREATERCANBETHEGAINOFTHEKLYSTRON4HEGAINOFAFOUR CAV ITYKLYSTRONCANBEMORETHAND" DEPENDINGONTHEBANDWIDTH!FTERTHEBUNCHED ELECTRONSDELIVERTHEIR2&POWERTOTHEOUTPUT THESPENTELECTRONSAREREMOVEDBYTHE COLLECTORELECTRODE !NAXIALMAGNETICFIELDIS EMPLOYED TO COUNTERACT THE MUTUAL REPULSION OF THE ELECTRONS THAT FORM THE ELECTRON BEAM 4HE MAGNETIC FIELD CONFINES THE ELECTRONS TOARELATIVELYLONG THINBEAMANDPREVENTSTHEMFROMDISPERSING)TCANBEGENER ATEDBYALONGSOLENOIDTHATHASIRONSHIELDINGAROUNDITSOUTSIDEDIAMETER ORBYA LIGHTERWEIGHTPERIODIC PERMANENT MAGNETIC00- SYSTEMTHATCONSISTSOFASERIES OFMAGNETICLENSES ! MULTICAVITY KLYSTRON CAN HAVE ITS BANDWIDTH INCREASED BY STAGGER TUNING THE CAVITIES SIMILAR TO THE MANNER IN WHICH STAGGER TUNING IS DONE IN AN )& AMPLIFIER OFASUPERHETERODYNERECEIVERTOOBTAINBROADERBANDWIDTH)TISMORECOMPLICATED HOWEVER TODOTHISINTHEKLYSTRONSINCETHEVELOCITYMODULATIONTHATAPPEARSATEACH INTERACTIONGAPCONTRIBUTESACOMPONENTTOTHEEXCITINGCURRENTATTHESUCCEEDINGGAPS SOMETHINGTHATDOESNOTOCCURINAN)&LIFIER4HEEARLY6! FOUR CAVITY3 BAND KLYSTRONHADA-(ZBANDWIDTHANDAGAINOFD"WHENITSFOURCAVITIESWERE SYNCHRONOUSLYTUNED BUTWHENSTAGGER TUNED ITSBANDWIDTHWAS-(Z AND AGAINOFD" 4HEORYSHOWSTHATTHEBANDWIDTHOFAKLYSTRONCANBESIGNIFICANTLYINCREASEDBY INCREASINGITSCURRENTANDTHUSITSPOWER!-7PEAKPOWERKLYSTRON FOREXAMPLE CANHAVEANBANDWIDTHASCOMPAREDTOAK7TUBE WHICHMIGHTHAVEA BANDWIDTH ANDAK7TUBEHAVINGONLYABANDWIDTH(IGH POWERMULTICAV ITYKLYSTRONSCANBEDESIGNEDWITHBANDWIDTHSASLARGEASTO4HEKLYSTRONIS SOMETIMESTHOUGHTOFASHAVINGANARROWBANDWIDTHANDTHETRAVELINGWAVETUBEIS THOUGHTOFASHAVINGWIDEBANDWIDTHBUTATTHEHIGHPOWERLEVELSNEEDEDFORLONG RANGERADARS THEIRBANDWIDTHSARECOMPARABLE)TISSOMETIMESUNFORTUNATETHATTHIS FACTISNOTALWAYSUNDERSTOOD 4HE KLYSTRON AS AN EXAMPLE OF A LINEAR BEAM TUBE IS CAPABLE OF HIGH POWER BECAUSETHEGENERATIONOFTHEELECTRONBEAM ITSINTERACTIONWITHTHEELECTROMAGNETIC FIELD ANDTHECOLLECTIONOFTHESPENTELECTRONSAREPERFORMEDINSEPARATEPARTSOFTHE TUBEWHERETHEGENERATEDHEATCANBEDISSIPATEDEFFECTIVELY 4HE KLYSTRON AND OTHER LINEAR BEAM TUBES CAN HAVE LONG LIFE 'ILMOUR REPORTS THAT THE MEAN TIME BETWEEN FAILURES -4"& OF DIFFERENT APPLICATIONS OF KLYS TRONSINRADARSYSTEMSVARIEDFROM HOURSTO HOURS WITHANAVERAGEOF HOURSFORALLAPPLICATIONS4HEREARE HOURSINAYEAR 4HE6!
4(%2!$!242!.3-)44%2
£ä°Ç
HIGH POWERKLYSTRONTUBEUSEDINTHEORIGINAL"ALLISTIC-ISSILE%ARLY7ARNING3YSTEM HADADEMONSTRATEDLIFEINEXCESSOF HOURS3YMONSREPORTSTHATONEOFTHE "-%73 TUBES THAT HE DESIGNED WAS STILL OPERATING AFTER HOURS WHEN THE RADARIN'REENLANDWASREPLACEDBYTHESOLID STATE0AVE0AWSRADAR4HE6! % WASALSOAHIGH POWER5(&KLYSTRONTHATHADA-7PEAKPOWER -(ZD" BANDWIDTH D"GAIN ANDANAVERAGEPOWEROFK7ATADUTYCYCLEOFAND A§SPULSEWIDTH 4HE6! %ORIGINALLYDEVELOPEDBY6ARIAN!SSOCIATES )NC ISA CAVITY3 BAND PULSEKLYSTRONTHATOPERATESFROMTO'(Z PRODUCESAPEAKPOWEROFFROM TO-7 ANAVERAGEPOWERUPTOK7 HASAGAINOFABOUTD" ANEFFICIENCY BETWEENAND ANDAD"BANDWIDTHOF-(Z)THASDEMONSTRATEDAMEAN TIME BETWEEN FAILURESOF HOURS)TWASUSEDINTHE!32 AIRPORTSURVEILLANCE RADARANDINTHE732 $.EXRADDOPPLERWEATHERRADARWHEREITSOPERATINGBANDIS FROMTO'(Z ASWELLASINOTHERRADARS 6ERYHIGH POWERKLYSTRONSAREEMPLOYEDINLINEARACCELERATORSSUCHASFOUNDATTHE 3TANFORD,INEAR!CCELERATOR#ENTER+LYSTRONSFORTHISAPPLICATION FOREXAMPLE MIGHT HAVE-7PEAKPOWERWITHEFFICIENCYUSINGSOLENOIDMAGNETSORn-7 PEAKPOWERWITHEFFICIENCYUSINGPERIODICPERMANENTMAGNETS )MPROVEMENTSTOTHEKLYSTRONASARADARPOWERSOURCEAREDISCUSSEDLATERINTHE SUBSECTIONONHYBRIDS OFWHICHTHECLUSTERED CAVITYKLYSTRONISAGOODEXAMPLEOF WHATCANBEPROVIDEDINTHEWAYOFHIGHPOWERANDWIDEBANDWIDTH -ULTIPLE "EAM+LYSTRON-"+ 4HEKLYSTRONAMPLIFIERISANIMPORTANTTUBE FOR HIGH POWER HIGH PERFORMANCE RADAR APPLICATIONS (OWEVER IT REQUIRES A LARGE VOLTAGEWHENHIGHPOWERISNEEDED(IGHVOLTAGERESULTSINGREATERSIZEANDTHENEED FORSHIELDINGFROMTHE8 RAYSTHATAREGENERATED)NAKLYSTRON THEPOWERAVAILABLEFOR CONVERSIONOFTHEDCPOWEROFTHEELECTRONBEAMTO2&POWEROFANELECTROMAGNETIC WAVEISGIVENBYTHEPRODUCTOFTHEBEAMCURRENTANDTHEBEAMVOLTAGE!LTHOUGH KLYSTRONSHAVEBEENOPERATEDATVERYHIGHVOLTAGES ITISUSUALLYPREFERREDTOOPERATEIT ATALOWERVOLTAGE IFPOSSIBLE BECAUSELOWERVOLTAGESGENERALLYMAKETHEPOWERSUP PLIESSIMPLER LIGHTER ANDMORERELIABLE!REDUCTIONOFBEAMVOLTAGEINACONVENTIONAL KLYSTRONMEANSANINCREASEOFTHEBEAMCURRENTINORDERTOMAINTAINTHESAMEPOWER !N INCREASE IN BEAM CURRENT HOWEVER RESULTS IN AN INCREASE IN THE CURRENT DENSITY WHERESPACECHARGEEFFECTSMAYNOTBENEGLIGIBLE ANDTHEREPULSIVEFORCESTHATOCCUR AMONGTHEELECTRONSAREINCREASEDANDCANCAUSETHEELECTRONDENSITYBUNCHESTOLOSE COHERENCE4HERESULTISADECREASEINEFFICIENCY(IGHERCURRENTDENSITIESALSOREQUIRE STRONGERMAGNETSTOKEEPTHEELECTRONBEAMCONFINED LEADINGTOLARGERVOLUMEAND WEIGHT4HUS SIMPLYLOWERINGTHEBEAMVOLTAGEANDINCREASINGTHECURRENTDENSITY DOESNOTUSUALLYPROVIDEANETADVANTAGE 4HELIMITATIONSOFLOWERBEAMVOLTAGE HOWEVER CANBEOVERCOMEBYSEPARATING THESINGLEELECTRONBEAMINTOANUMBEROFSMALLERBEAMS CALLEDBEAMLETS SOTHATEACH OFTHEBEAMLETSHASALOWENOUGHCURRENTDENSITYTOAVOIDTHEUNDESIRABLEREPULSIVE EFFECTSOFAHIGHCURRENT DENSITYBEAM!CCORDINGTO.USINOVICHETAL EACHBEAMLET ISTRANSPORTEDDOWNITSOWNINDIVIDUALDRIFTCHANNELAMETALLIC WALLEDTUBE PARALLEL TO BUTISOLATEDFROM THEOTHERBEAMLETS4HEYAREALLOWEDTOINTERACTONLYOVERTHE SMALL AXIAL EXTENT OF THE CAVITY GAP!FTER PASSING BY THE CAVITY GAP THE BEAMLETS REENTER THEIR INDIVIDUAL DRIFT CHANNELS AND PROPAGATE IN ISOLATION FROM ONE ANOTHER 3UCHKLYSTRONSARECALLEDMULTIPLE BEAMKLYSTRONS OR-"+)THASBEENSAIDTHATTHE NUMBEROFBEAMLETSINAN-"+MIGHTBEFROMTO
£ä°n
2!$!2(!.$"//+
4HECHIEFMOTIVATIONFORTHEMULTIPLE BEAMKLYSTRONISTHEEFFICIENTGENERATIONOF HIGH2&POWERATALOWERVOLTAGETHANINACONVENTIONALKLYSTRON"ECAUSEOFITSLOWER VOLTAGETWOORTHREETIMESLOWER AN-"+CANBEMORECOMPACT HAVEALOWERMAGNET WEIGHTUPTOTENTIMESLESS BEOFLOWERWEIGHTANDVOLUME GENERATELESS8 RAYS HAVE HIGHELECTRONICEFFICIENCYUPTOPERCENT ANDHAVETHEPOTENTIALFORAHIGHERINSTAN TANEOUS BANDWIDTH THAN DOES A CONVENTIONAL KLYSTRON 4HE LOWER VOLTAGES AT WHICH THEYOPERATERESULTINPOWERSUPPLIESTHATCANBESIMPLER LIGHTER CHEAPER ANDMORE RELIABLE4HE -"+ CAN HAVE A HIGH OUTPUT POWER TO WEIGHT RATIO THAT MIGHT BE TWO TOTHREETIMESGREATERTHANTHATOFANEQUIVALENTSINGLE BEAMKLYSTRON4HEYCANALSO HAVEREDUCEDNOISEANDLESSPHASESENSITIVITYTODEVIATIONSINVOLTAGE WHICHAIDSINTHE DETECTIONOFLOWCROSS SECTIONMOVINGTARGETSINCLUTTER#OMPAREDTOACROSSED FIELD AMPLIFIER THEYHAVEALARGERDYNAMICRANGE#OMPAREDTOA474 THEYARECAPABLEOF HIGHERPEAKANDAVERAGEPOWERS ANDTHEYARELESSSENSITIVETOVIBRATIONS 4HE 2USSIAN COMPANY KNOWN AS &EDERAL 3TATE 5NITARY %NTERPRISE 20# )STOK USUALLY SHORTENED TO )STOK HAS BEEN PRODUCTIVE IN THE DEVELOPMENT OF -"+S FOR RADAR!T 8 BAND THEY REPORT AN -"+ WITH BEAMLETS PRODUCING K7 PEAK POWER K7AVERAGEPOWER BANDWIDTH ANANODEVOLTAGEOFK6 WITHAMAG NETWEIGHINGKG!T3BAND ONEOFTHEIRTUBESWITHBEAMSHADAPEAKPOWER OFK7 K7AVERAGEPOWER OPERATEDWITHK6ANODEVOLTAGE HADA BANDWIDTH ANDAWEIGHTWITHOUTMAGNETOFKG !NAPPARENTEXTENSIONOFTHEMULTIPLEBEAMCONCEPTISTOEMPLOYASHEETELECTRON BEAM WHICHISASTHINANDASWIDEANDHASASMUCHCURRENTASCANBEACHIEVEDCON SISTENTWITHOTHERCONSTRAINTS)THASBEENCONSIDEREDFORVERYHIGH POWERKLYSTRONS -7PEAKPOWERANDPERIODICPERMANENTMAGNETIC OR00- FOCUSING DESIGNED FORAVERYLARGELINEARACCELERATOR)TISCLAIMEDTHATTHEBEAMCURRENTDENSITYANDTHE FOCUSINGMAGNETICFIELDCANBEREDUCED BEMADEWITHFEWERPARTS MIGHTBEMORERELI ABLE ANDCANHAVELOWERACQUISITIONANDOPERATINGCOSTS/NEPOSSIBLEDISADVANTAGE ISTHATSHEET BEAMKLYSTRONSMIGHTNOTBEWIDEBAND 4HEPRINCIPLEOFTHEMULTIPLE BEAMLINEAR BEAMTUBEHASALSOBEENCONSIDEREDFOR THETRAVELINGWAVETUBE BUTITISNOTOBVIOUSWHETHERITHASANYSIGNIFICANTADVANTAGES OVERTHE-"+ 4RAVELING 7AVE 4UBE 474 4HE 474 LINEAR BEAM TUBE IS SIMILAR TO THE KLYSTRONINTHATTHECATHODE 2&CIRCUIT ANDCOLLECTORAREALLSEPARATEFROMONEANOTHER 4HEREIS HOWEVER CONTINUOUSINTERACTIONOFTHEELECTRONBEAMANDTHE2&FIELDOVER THEENTIRELENGTHOFTHEMICROWAVEPROPAGATINGSTRUCTUREOFTHE474ASCOMPARED TOTHEKLYSTRONWHERETHEINTERACTIONOCCURSONLYATTHEGAPSOFARELATIVELYFEWRESO NANTCAVITIES4HE474WASORIGINALLYCONCEIVEDWITHAHELIXASTHESLOW WAVE2& STRUCTURE ASINTHEILLUSTRATIONSHOWNIN&IGURE4HEELECTRONBEAMISSIMILARTO
&)'52% 2EPRESENTATIONOFTHEPRINCIPLEPARTSOFATRAVELINGWAVETUBE SHOWINGAHELIXSLOW WAVECIRCUITSHOWNFORSIMPLICITY
4(%2!$!242!.3-)44%2
£ä°
THATOFTHEKLYSTRON ANDTHEYBOTHUSETHEPROCESSOFVELOCITYMODULATIONTOCAUSETHE ELECTRONBEAMTOBEPERIODICALLYBUNCHEDDENSITYMODULATION 4HEELECTRONBEAM PASSESTHROUGHTHE2&INTERACTIONCIRCUIT)NTHEEXAMPLESHOWNIN&IGURE WHERE AHELIXISSHOWNASTHESLOW WAVESTRUCTURE THE2&SIGNALISSLOWEDDOWNBYTHE HELIXSOTHATITSFORWARDVELOCITYISVERYNEARLYEQUALTOTHATOFTHEVELOCITYOFTHE ELECTRONBEAM4HISNEARMATCHOFVELOCITIESISWHATCAUSESTHECUMULATIVEINTERAC TIONTHATTRANSFERSDCENERGYFROMTHEELECTRONBEAMTOAMPLIFYTHEELECTROMAGNETIC WAVEPROPAGATINGONTHEHELIX!FTERDELIVERINGITSENERGYTOTHE2&FIELD THESPENT ELECTRONSAREREMOVEDBYTHECOLLECTOR USUALLYAMULTISTAGEDEPRESSEDCOLLECTOR!N AXIALMAGNETICFIELDKEEPSTHEELECTRONBEAMFROMDISPERSINGASITTRAVELSDOWNTHE TUBE JUSTASINTHEKLYSTRON 4HEHELIX474ISCAPABLEOFBANDWIDTHINEXCESSOFANOCTAVETO WHICHIS MUCHHIGHERTHANOTHERRADARTUBES4HE474ISOFTENTHOUGHTOFASAVERYBROADBAND TUBE BUTTHEBROADBANDWIDTHOFAHELIX474ISNOTOFGREATSIGNIFICANCEINRADAR APPLICATIONSSINCETHEHELIX474ISLIMITEDINITSPEAKPOWERTOAFEWK74HISMEANS THATTHEHELIX474ISBESTUSEDIN#7ORHIGHDUTYCYCLERADARAPPLICATIONS IFATALL !LSO SUCHBROADBANDWIDTHSARESELDOMAVAILABLEFORRADARAPPLICATIONSBECAUSEOF REGULATORYRESTRICTIONSINTHEUSEOFTHEELECTROMAGNETICSPECTRUM4OACHIEVEHIGH POWER IN A 474 OTHER TYPES OF SLOW WAVE STRUCTURES HAVE TO BE EMPLOYED AND THESEUSUALLYPROVIDELESSBANDWIDTHTHANTHEHELIX3UCHSTRUCTURESARETHECOUPLED CAVITYOFWHICHTHECLOVERLEAFISANEXAMPLE RING BAR ANDTHESO CALLEDLADDER NETWORK4HEBANDWIDTHOFACOUPLED CAVITY474CANBETO4HERING BAR HAS BROADER BANDWIDTH AND HIGHER EFFICIENCY THAN THE COUPLED CAVITY CIRCUIT BUT ITISNOTCAPABLEOFASHIGHAPOWERASTHECOUPLEDCAVITY4HUS THEBANDWIDTHOFA 474DECREASESASITSPOWERINCREASES/NTHEOTHERHAND ASMENTIONEDPREVIOUSLY THEBANDWIDTHOFAKLYSTRONINCREASESWITHINCREASINGPOWER SOTHATTHEBANDWIDTHS OF THE 474 AND THE KLYSTRON ARE GENERALLY COMPARABLE FOR MANY HIGH POWER RADARAPPLICATIONS "OTHFORWARDANDBACKWARDWAVESMAYPROPAGATEALONGTHEMICROWAVESTRUCTURE OF A 474 LEADING TO A POSSIBILITY OF BACKWARD WAVE OSCILLATIONS )N &IGURE ATTENUATIONISSHOWNALONGTHEHELIXSOASTOPREVENTOSCILLATIONDUETOREFLECTIONS AT THE OUTPUT AND THE INPUT OF THE STRUCTURE4HE ATTENUATION MAY BE DISTRIBUTED OR LUMPED BUTITISUSUALLYFOUNDINTHEMIDDLETHIRDOFTHETUBE!LTHOUGHOSCILLATION CAN BE PREVENTED BY DISTRIBUTING LOSS ALONG THE STRUCTURE IT RESULTS IN LOWER EFFI CIENCYSOMETHING UNATTRACTIVE IN HIGH POWER TUBES )NSTEAD OSCILLATIONS MAY BE PREVENTEDBYTHEUSEOFDISCONTINUITIESCALLEDSEVERS WITHONESEVERFOREVERYTO D" OF TUBE GAIN!T EACH SEVER THE POWER TRAVELING IN THE REVERSE DIRECTION IS DISSIPATEDINTHESEVERLOADSWITHOUTSERIOUSLYAFFECTINGTHEPOWERTRAVELINGINTHE FORWARDDIRECTION4HESEVERLOADSMAYBEPLACEDEXTERNALTOTHETUBETOREDUCEDIS SIPATIONWITHINTHE2&STRUCTUREITSELF4HEEFFICIENCYOFA474ISUSUALLYLESSTHAN THATOFAKLYSTRONBECAUSEOFTHELOSSDUETOTHEATTENUATIONOFTHESEVERS ASWELLAS BYTHEPRESENCEOFRELATIVELYHIGH2&POWEROVERANAPPRECIABLEPARTOFTHEENTIRE STRUCTURE! TECHNIQUE FOR IMPROVING THE EFFICIENCY OF HIGH POWER474S IS CALLED VELOCITYTAPERING4HISTECHNIQUECONSISTSOFTAPERINGTHELENGTHOFTHELASTFEWSEC TIONS OF THE SLOW WAVE CIRCUIT TO TAKE INTO ACCOUNT THE SLOWING DOWN OF THE BEAM ASTHEENERGYISEXTRACTEDFROMIT6ELOCITYTAPERINGPERMITSEXTRACTINGMOREOFTHE ENERGYFROMTHEBEAMANDSIGNIFICANTLYIMPROVESTHEPOWER BANDWIDTHPERFORMANCE OFTHETUBE.EVERTHELESS HIGH POWER474SGENERALLYSHOWANAPPRECIABLEFALLOFFOF POWEROUTPUTTOWARDTHEBANDEDGES SOTHATTHERATEDBANDWIDTHDEPENDSVERYMUCH ONHOWMUCHPOWERFALLOFFCANBETOLERATEDBYTHESYSTEM
£ä°£ä
2!$!2(!.$"//+
)FA474USINGACOUPLED CAVITYCIRCUITISCATHODE PULSED3ECTION THEREIS ANINSTANTDURINGTHERISEANDFALLOFVOLTAGEWHENTHEBEAMVELOCITYBECOMESSYNCHRO NOUSWITHTHECUTOFFFREQUENCYTHESO CALLEDOMODE OFTHEMICROWAVECIRCUIT AND THETUBECANGENERATEOSCILLATIONS4HESEOSCILLATIONSATTHELEADINGANDTRAILINGEDGES OFTHE2&OUTPUTPULSEHAVEACHARACTERISTICAPPEARANCEONAPOWER TIMEPRESENTATION THATHASGIVENTHEMTHENAMERABBITEARS/NLYINRARECASESHASITBEENPOSSIBLETOSUP PRESSTHESEOSCILLATIONSCOMPLETELY(OWEVER SINCETHISPARTICULAROSCILLATIONDEPENDS ONELECTRONVELOCITY WHICHINTURNDEPENDSONBEAMVOLTAGE THEPROBLEMISAVOIDEDBY THEUSEOFMOD ANODEORGRIDPULSING3ECTION )NTHISCASE ITISONLYNECESSARY TOBESURENOTTOLETTHEMODULATORBEGINPULSINGTHEBEAMCURRENTDURINGTURN ONOFTHE HIGH VOLTAGEPOWERSUPPLYUNTILTHEVOLTAGEISSAFELYABOVETHEOSCILLATIONRANGE WHICH ISTYPICALLYSOMEWHEREBETWEENANDOFFULLOPERATINGVOLTAGE !MODIFICATIONOFTHEHELIXSLOW WAVESTRUCTUREISTHERING BARCIRCUIT WHICHCANBE USED IF THE PEAK POWER IS LESS THAN TO K74HE 2AYTHEON 1+7 ! IS AN EXAMPLE WITHAPEAKPOWEROFK7 DUTYCYCLE ANDD"GAIN)TOPERATESAT ,BANDFROMTO-(Z4HE53!IR&ORCE#OBRA$ANE OPERATINGFROMTO -(Z ISALONGRANGERADARLOCATEDINTHE!LEUTIAN)SLANDSTHATUSESRING BAR474S 1+7 EACHWITHAPEAKPOWEROFK7ANDAVERAGEPOWEROFK7 4HE3BAND6! !474AMPLIFIEREMPLOYSACLOVERLEAFCOUPLEDCAVITYMICRO WAVESLOW WAVESTRUCTURE7ITHTHEUSEOFLIQUIDCOOLING ITISCAPABLEOF-7PEAK POWEROVERA-(ZBANDWIDTH)TSDUTYCYCLEIS WITHAGAINOFD" ANDA §SPULSEWIDTH4HIS474WASORIGINALLYDESIGNEDTOBEUSEDINTERCHANGEABLYWITH THEPOPULAR6! KLYSTRON EXCEPTTHATTHE6! !474HASAWIDERBANDWIDTHTHAN THE6! KLYSTRON)TALSOREQUIRESAGREATERPOWERINPUTSIGNALBECAUSEOFITSLOWER GAINTHANTHEKLYSTRON7HENHIGHPOWERISREQUIRED THEKLYSTRONTENDSTOBEPREFERRED OVERTHE474SINCEITDOESNTEXPERIENCETHESTABILITYPROBLEMSOFTHE474 'ILMOURGIVESTHEMEANTIMEBETWEENFAILURES-4"& FORNINEDIFFERENTTYPES OFCOUPLED CAVITY474SASVARYINGFROM HOURSTO HOURS WITHANAVER AGEOF HOURSFORALLNINECLASSESOFTUBES(EALSOSAYSTHAT474SFORSPACE APPLICATION WHICHAREOFLOWERPOWERTHANRADAR474S HAVE-4"&SOFTHEORDEROF ONEMILLIONHOURS $EPRESSED#OLLECTOR 4HEEFFICIENCYOFA474ORAKLYSTRONCANBEIMPROVED BYTHEUSEOFASO CALLEDDEPRESSEDCOLLECTOR 7ITHASINGLECOLLECTOR ASIGNIFICANT FRACTIONOFTHEPOWERINPUTTOTHETUBEISDISSIPATEDASHEATINTHECOLLECTOR)FTHEVOLT AGEONTHECOLLECTORISREDUCEDDEPRESSED BELOWTHEBODYVOLTAGE THEVELOCITYOFTHE ELECTRONSSTRIKINGTHECOLLECTORISREDUCEDANDSOISTHEHEATGENERATEDINTHECOLLECTOR 4HUS THECOLLECTORRECOVERSSOMEOFTHEPOWERINTHESPENTELECTRONBEAM4HEUSEOF MULTIPLEDEPRESSEDCOLLECTORSATINTERMEDIATEVOLTAGES RATHERTHANASINGLECOLLECTOR ALLOWSCATCHINGEACHSPENTELECTRONATAVOLTAGENEAROPTIMUM5PTOTENCOLLECTORSEC TIONSHAVEBEENUSEDINSOMECOMMUNICATIONTUBES BUTTHREESECTIONSAREMORETYPICAL FOR HIGH POWER 474S FOR RADAR SYSTEMS 4HE SEVERAL DIFFERENT VOLTAGES NEEDED FOR THEDEPRESSEDCOLLECTORSADDCOMPLEXITYTOTHEHIGH POWERVOLTAGESUPPLY BUTTHESE VOLTAGESNEEDNOTBEASWELLREGULATEDASTHEMAIN BEAMVOLTAGE)TISUSUALLYEASIER TODESIGNADEPRESSEDCOLLECTORFORA474THANFORAKLYSTRONSINCETHESPENTELECTRON BEAMOFA474MIGHTHAVEASPREADINVELOCITY BUTTHEKLYSTRONMIGHTHAVEA VELOCITYSPREADOFALMOST"ECAUSETHEEFFICIENCYINACONVENTIONAL474IS USUALLYLOWERTHANTHATOFAKLYSTRON THEINCREASEINEFFICIENCYINTHE474PROVIDED BYADEPRESSEDCOLLECTORHASAGREATERRELATIVEEFFECTTHANWITHAKLYSTRON
4(%2!$!242!.3-)44%2
£ä°££
6ARIANTSOFTHE+LYSTRONANDTHE474 )TWASMENTIONEDTHATTHEBANDWIDTHOF AKLYSTRONINCREASESASITSPOWERISINCREASED4HEBANDWIDTHCANALSOBEINCREASEDBY COMBININGTHEBESTFEATURESOFTHEKLYSTRONANDTHETRAVELINGWAVETUBETOOBTAINBETTER BANDWIDTH EFFICIENCY ANDGAINFLATNESSTHANEITHERTHECONVENTIONALKLYSTRONORTHE 474)NTHESETUBES THEBASICSTRUCTUREISTHATOFAKLYSTRON BUTINSTEADOFANUMBER OFSINGLECAVITIESBEINGUSED THESINGLECAVITYISREPLACEDBYAMORECOMPLEXMULTIPLE CAVITY4HREE SUCH VARIANTS ARE THE 4WYSTRON EXTENDED INTERACTION KLYSTRON AND THE CLUSTEREDCAVITYKLYSTRON-OSTHIGH PERFORMANCERADARKLYSTRONSTENDTOEMPLOYTHE MOREINTRICATECAVITYSTRUCTUREBECAUSEOFTHEBETTERPERFORMANCEITPROVIDES #OMPARISON OF6ARIOUS ,INEAR "EAM 4UBE 3TRUCTURES &IGURE ILLUSTRATES THEBASICSTRUCTUREOFTHE2&CIRCUITSTHATCHARACTERIZETHEVARIOUSTYPESOFLINEAR BEAMTUBES 4WYSTRON 4HE BANDWIDTH OF A CONVENTIONAL KLYSTRON IS LIMITED PRIMARILY BY THEBANDWIDTHOFTHEOUTPUTRESONANTCAVITY)FACOUPLEDCAVITYSLOW WAVECIRCUIT AS IS USED IN THE 474 IS SUBSTITUTED FOR THE OUTPUT RESONANT CAVITY OF A KLYSTRON &IGURED THEBANDWIDTHOFTHEKLYSTRONCANBEINCREASEDSIGNIFICANTLY ANDTHERE ISASLIGHTINCREASEINEFFICIENCY4HISREQUIRESTHATTHEINTERMEDIATECAVITIESANDTHE INPUTCAVITYOFSUCHATUBEBESTAGGER TUNEDTOACCOMMODATETHEINCREASEDBANDWIDTH OFFEREDBYTHEOUTPUTCIRCUIT"ECAUSETHISTYPEOFTUBEISPARTKLYSTRONANDPART474 ITWASNAMED4WYSTRON4HE6! 3 BAND4WYSTRONHASABANDWIDTHOFWITH AEFFICIENCY D"GAINATMIDBAND PEAKPOWEROF-7 ANDAVERAGEPOWER OFK7 %XTENDED)NTERACTION+LYSTRON%)+ )NTHE%)+ THESINGLE GAPRESONANTCAVITIES OFTHEKLYSTRONAREREPLACEDBYARESONATEDSLOW WAVE474 LIKECIRCUITTHATCONTAINSTWO ORMOREINTERACTIONGAPS&IGUREC 3UCHCAVITIESCANBEUSEDFORTHEPRIORCAVITIES ASWELLASTHEOUTPUTCAVITY4HISALLOWSWIDERBANDWIDTHANDGREATERPOWERTHANTHE CONVENTIONALKLYSTRONAMPLIFIER3TAPRANSETAL STATETHATTHEHIGH POWER6! # %)+OPERATEDOVERAFREQUENCYRANGEFROMTO-(ZBANDWIDTH WITHA PEAKPOWEROF-7ANDANAVERAGEPOWEROFK7 ANDANEFFICIENCYOF %)+DEVICESHAVEBEENOFINTERESTFORMILLIMETER WAVEAPPLICATIONS!CCORDINGTO THE#OMMUNICATIONS0OWER)NDUSTRIES#0) BROCHURE ITS6+"MILLIMETER WAVE%)+WHENOPERATINGATACENTERFREQUENCYOF'(ZWITHA'(ZBANDWIDTH HASAPEAKPOWEROFK7 AVERAGEPOWEROF7 ABOUTDUTYCYCLE GAIN OFD" PULSEWIDTHOF§S ANDISLIQUIDCOOLED)THASMUCHLOWERPOWERTHANA GYROKLYSTRONDISCUSSEDLATER ATTHISFREQUENCY BUTITSCMBYCMDIAMETER SIZE ISCONSIDERABLYSMALLERANDITCOSTSCONSIDERABLYLESSTHANAGYROKLYSTRON !SIMILAR%)+ ALSOBUILTBY#0) HASBEENUSEDINTHE.!3!#LOUD3ATSPACEBORNE RADARTHATPROVIDESTHEVERTICALPROFILEOFCLOUDSFORUNDERSTANDINGCLOUDEFFECTSON BOTHTHEWEATHERANDCLIMATE)TOPERATESATACENTERFREQUENCYOF'(ZWITHA -(ZBANDWIDTH K7PEAKPOWER §SPULSEDURATION (ZPRF ANDAN EFFICIENCYOF)TISCONDUCTIONCOOLED%ACHCAVITYISASHORTPIECEOFRESONANT SLOW WAVESTRUCTUREBASEDONLADDERGEOMETRY4HETUBEWEIGHSKGANDCANOPER ATEOVERATEMPERATURERANGEFROM TO O#)TWASPREDICTEDTHATTHIS%)+WOULD BECAPABLEOFTWOYEARSOFCONTINUOUSOPERATIONWITHACONFIDENCELEVEL4WO %)+SWEREEMPLOYEDIN#LOUD3ATONEPRIME ONEREDUNDANT SOASTOACHIEVEA CONFIDENCEOFMEETINGTHETWO YEARLIFEREQUIREMENT
£ä°£Ó
2!$!2(!.$"//+
0 ). 'UN
)NTERACTION STRUCTURE
0 /UT #OLLECTOR
)NTERACTION )MPEDANCE $ISTANCE A
:
)MPEDANCE B
)MPEDANCE C )NPUT
/UTPUT LOAD
)MPEDANCE D &)'52% "ASIC STRUCTURE OF SEVERAL TYPES OF LINEAR BEAMTUBESA KLYSTRON B COUPLED CAVITY474 C EXTENDED INTERACTIONKLYSTRON ANDD 4WYSTRONAFTER!3TAPRANSETAL Ú)%%%
#LUSTERED #AVITY+LYSTRONS 4HISISAGOODEXAMPLEOFTHETECHNIQUEOFGROUPING CAVITIESTOIMPROVETHEOPERATIONOFAKLYSTRON4HEINDIVIDUALINTERMEDIATECAVITIESOF AMULTICAVITYKLYSTRONAREEACHREPLACEDBYACLUSTEROFTWOORTHREEARTIFICIALLYLOADED LOW 1 CAVITIES WITH 1S OF ONE HALF TO ONE THIRD OF THE SINGLE CAVITY THEY REPLACE &IGURE COMPARES SCHEMATICALLY THE BASIC DIFFERENCE BETWEEN THE CONVENTIONAL STAGGER TUNEDKLYSTRONANDTHECLUSTERED CAVITYKLYSTRON)THASBEENSAIDFORAGIVEN
4(%2!$!242!.3-)44%2
£ä°£Î
&)'52% #OMPARISON OF THE STRUCTURES OF A CONVENTIONAL STAGGER TUNED KLYSTRON TOP ANDCLUSTERED CAVITYKLYSTRONBOTTOM #OURTESYOFTHE)%%%
GAIN BANDWIDTHPRODUCT THISFORMOFSTRUCTURECANPRODUCEATUBEOFMUCHSHORTER LENGTHSOTHATTHERECANBESUBSTANTIALSAVINGSINMAGNETWEIGHTANDPOWER3YMONS THEINVENTOROFTHECLUSTERED CAVITYKLYSTRON STATESTHATONEOFTHESEWIDEBANDWIDTH TUBESCANBEUSEDTOREPLACETHETWONARROWER BANDKLYSTRONSINTHE!7!#3RADAR 7HENEACHOFTHETWONARROW BANDTUBESISREPLACEDBYAWIDEBANDCLUSTERED CAVITY TUBE REDUNDANTOPERATIONCANBEPROVIDEDWITHHIGHERRELIABILITYANDWITHOUTALARGE WEIGHTPENALTYBECAUSEEITHEROFTHESECLUSTERED CAVITYKLYSTRONSPROVIDEFULLOPERA TIONAL CAPABILITY SIMILAR TO THE REDUNDANCY COMMONLY EMPLOYED IN &!! AIR TRAFFIC CONTROLRADARS -ICROWAVE0OWER-ODULE-0- !NOVELVARIANTOFTHELINEAR BEAMTUBEIS THEMICROWAVEPOWERMODULE WHICHISANAMPLIFIERTHATEMPLOYSASOLID STATEMICRO WAVEINTEGRATED CIRCUITAMPLIFIERTODRIVEAMODERATE POWERHELIXTRAVELINGWAVETUBE ALONGWITHANINTEGRATEDCIRCUITPOWERCONDITIONER ALLINALIGHTWEIGHTPACKAGE)TCAN PROVIDEHIGHEFFICIENCY WIDEINSTANTANEOUSBANDWIDTH LOWNOISE ANDAVERAGEPOWER LEVELSFROMSEVERALTENSTOSEVERALHUNDREDSOFWATTS)TISSAIDTOBESMALLERANDLIGHTER THANCOMPARABLE474ANDSOLID STATEPOWERSOURCES ANDISCAPABLEOFOPERATINGAT HIGHAMBIENTTEMPERATURES4HEGAINOFAN-0-MIGHTBENOMINALLYD"ANDIS DIVIDEDBETWEENTHESOLID STATEDRIVERANDTHE474POWERBOOSTERINTHERATIOSFROM TO4HE-0-SEEMSBESTSUITEDFORTHEHIGHERMICROWAVEFREQUENCIES PERHAPSFROMTO'(Z !SERIOUSCONSTRAINTOFTHE-0-FORRADARAPPLICATIONSISTHATTHEHELIX474LIMITS ITSUSETO#7ORHIGHDUTYCYCLETRANSMISSIONSPREFERABLYGREATERTHAN )TALSO ISOFRELATIVELYMODESTPOWERFORMANYRADARAPPLICATIONS
£ä°£{
2!$!2(!.$"//+
£ä°ÎÊ /," 5NLIKE LINEAR BEAM TUBES THAT ARE NORMALLY OPERATED AS AMPLIFIERS THE MAGNETRON ISANOSCILLATOR!SEXAMPLEOFACOMMONLYUSEDEARLYMAGNETRONWASTHE* AN , BANDTUBETHATWASMECHANICALLYTUNABLEFROMTO-(Z)TCOULDOPERATE WITHAPEAKPOWEROFK7 A§SPULSEWIDTH ANDAPULSEREPETITIONFREQUENCYOF (ZTHATPROVIDEDANAVERAGEPOWEROF7)TSEFFICIENCYWASTYPICALFOR MAGNETRONSATTHATTIME4HECOMPACTSIZEANDEFFICIENTOPERATIONOFTHEMAGNETRON ATMICROWAVEFREQUENCIESALLOWEDRADARSIN7ORLD7AR))TOBESMALLENOUGHTOFLYIN MILITARYAIRCRAFTANDTOBEMOBILEFORGROUNDWARFARE-AGNETRONS HOWEVER SEEMTO BELIMITEDTOABOUTAFEWKILOWATTSOFAVERAGEPOWER WHICHCANRESTRICTTHEIRUTILITY 4HEYALSOHAVELIMITATIONSINSTABILITYAND THEREFORE INTHE-4)IMPROVEMENTFACTOR THEYCANACHIEVE ANDTHEYOFTENHAVEASHORTERLIFETHANLINEAR BEAMTUBES "ECAUSETHEMAGNETRONISANOSCILLATORRATHERTHANANAMPLIFIER THESTARTINGPHASE OF EACH PULSE IS RANDOM FROM PULSE TO PULSE4HIS RANDOM CHANGE OF PHASE CAN BE ACCOMMODATEDINA-4)RADARRECEIVERBYUSEOFACOHERENTOSCILLATORCOHO ASTHE REFERENCESIGNALINTHEPHASE DETECTORSTAGEOFTHERECEIVER/NEACHPULSE THEPHASE OFTHEMAGNETRONPULSESETSTHEPHASEOFTHECOHO)NTHISMANNER THERECEIVEDSIGNAL APPEARSTOBECOHERENTPULSETOPULSE4HISISSOMETIMESCALLEDCOHERENTONRECEIVE 4HE-4)IMPROVEMENTFACTOROBTAINEDWITHAMAGNETRONANDACOHERENT ON RECEIVE OPERATIONUSUALLYISNOTASGOODASCANBEOBTAINEDWITHAN-4)SYSTEMTHATUSESA POWERAMPLIFIERASTHETRANSMITTER !UTOMATICFREQUENCYCONTROL!&# ISOFTENEMPLOYEDTOKEEPTHERECEIVERTUNED TO THE FREQUENCY OF THE TRANSMITTER SINCE THE MAGNETRON FREQUENCY CAN SLOWLY DRIFT WITHCHANGESINAMBIENTTEMPERATUREANDSELF HEATING4HE!&#CANBEAPPLIEDTOTHE MAGNETRONITSELFTOKEEPITOPERATINGONITSASSIGNEDFREQUENCY WITHINTHELIMITSOFTHE ACCURACYOFTHETUNINGMECHANISM !MAGNETRONCANBEMECHANICALLYCHANGEDINFREQUENCYOVERATOFREQUENCY RANGEAND INSOMECASES ASMUCHAS2APIDMECHANICALTUNINGCANBEACHIEVED WITHASLOTTEDDISKSUSPENDEDABOVETHEANODECAVITIES7HENROTATED ITALTERNATELY PROVIDESINDUCTIVEANDCAPACITIVELOADINGOFTHECAVITIESTORAISEANDLOWERTHEFRE QUENCY3UCHAROTARY TUNEDMAGNETRONCANPROVIDEVERYFASTTUNINGRATES&OREXAM PLE ATAROTATIONRATEOFRPM AMAGNETRONWITHCAVITIESCANTUNEACROSSABAND TIMESPERSECOND #OAXIAL-AGNETRON !SIGNIFICANTIMPROVEMENTINTHEPOWER EFFICIENCY STA BILITY ANDLIFEOFTHEORIGINALFORMOFTHEMAGNETRONOCCURREDWITHTHEINTRODUCTIONOF THECOAXIALMAGNETRON4HEKEYDIFFERENCEISTHEINCORPORATIONOFASTABILIZINGCAVITY SURROUNDINGTHECONVENTIONALMAGNETRONCAVITIES WITHTHESTABILIZINGCAVITYCOUPLED TO THE MAGNETRON CAVITIES SO AS TO PROVIDE BETTER STABILIZATION 4HE FREQUENCY OF A COAXIAL MAGNETRON CAN BE CHANGED BY MECHANICALLY MOVING ONE OF THE END PLATES CALLEDATUNINGPISTON OFTHESTABILIZINGCAVITY4HETUNINGPISTONCANBEPOSITIONED MECHANICALLYFROMTHEOUTSIDEOFTHEVACUUMBYMEANSOFAVACUUMBELLOWS )NTHECOAXIALMAGNETRON THEOUTPUTOFEVERYOTHERRESONANTCAVITYISCOUPLEDTOTHE STABILIZINGCAVITYTHATSURROUNDSTHEANODESTRUCTURE4HEOUTPUTPOWERISTHENCOUPLED FROMTHESTABILIZINGCAVITY O-ODEOF/PERATION !MAGNETRON WHETHERCONVENTIONALORCOAXIAL CANOSCIL LATEATANUMBEROFDIFFERENT CLOSELYSPACEDFREQUENCIESDUETOVARIOUSPOSSIBLECON FIGURATIONSOFTHE2&FIELDTHATCANEXISTBETWEENTHECATHODEANDTHERESONANTCAVITIES
4(%2!$!242!.3-)44%2
£ä°£x
4HESEDIFFERENT2&FIELDCONFIGURATIONS ALONGWITHCOUPLINGAMONGTHECAVITYRESO NATORSOFTHEMAGNETRON RESULTINDIFFERENTMODESOFOSCILLATION4HEMAGNETRONCAN SHIFT ALMOSTUNPREDICTABLY FROMONEMODETOANOTHERWHICHMEANSTHEFREQUENCY SHIFTSUNPREDICTABLY ASTHEVOLTAGECHANGESORASTHEINPUTIMPEDANCETHATTHEMAG NETRONEXPERIENCESCHANGES4HESHIFTFROMONEMODETOANOTHER OFTENCALLEDMODING ISESPECIALLYBADSINCEITCANOCCURWHENTHERADARANTENNASCANSANDVIEWSDIFFERENT ENVIRONMENTS)TISIMPORTANTTOAVOIDMODING 4HEPREFERREDMAGNETRONMODEOFOPERATIONISTHESO CALLED OMODETHATOCCURS WHENTHE2&FIELDCONFIGURATIONISSUCHTHATTHE2&PHASEALTERNATESOORADIANS BETWEENADJACENTCAVITIES4HEADVANTAGEOFTHEOMODEISTHATITSFREQUENCYCANBE MOREREADILYSEPARATEDFROMTHEFREQUENCIESOFTHEOTHERPOSSIBLEMODES!N. CAVITY MAGNETRONCANHAVE.POSSIBLEMODES4HEOMODEOSCILLATESATASINGLEFREQUENCY BUTTHEOTHERMODESCANOSCILLATEATTWODIFFERENTFREQUENCIESSOTHATTHEMAGNETRON CANOSCILLATEAT. DIFFERENTFREQUENCIES #OAXIAL-AGNETRON,IFE 4HEPOWERTHATCANBEPRODUCEDBYAMAGNETRONDEPENDS ON ITS SIZE! LARGER SIZE MEANS MORE RESONATORS WHICH MAKES IT MORE DIFFICULT TO SEPARATETHEVARIOUSMODESOFOSCILLATIONINACONVENTIONALMAGNETRON4HECOAXIAL MAGNETRON HOWEVER WITHSTABILIZATIONCONTROLLEDBYTHEOUTERCAVITY PERMITSSTABLE OPERATIONWITHALARGERNUMBEROFCAVITIES ANDTHUSWITHGREATERPOWER4HEANODE ANDCATHODESTRUCTURESOFACOAXIALMAGNETRONCANALSOBEBIGGER WHICHFURTHERALLOWS OPERATIONATHIGHERPOWER4HELARGERSTRUCTURESPERMITMORECONSERVATIVEDESIGN WITH THERESULTTHATITHASLONGERLIFEANDBETTERRELIABILITYTHANCONVENTIONALMAGNETRONS ASWELLASMORESTABLEOPERATION4HEOPERATINGLIFEOFACOAXIALMAGNETRONHASBEEN SAIDTOBEBETWEEN AND HOURS WHICHISAFIVE TOTWENTYFOLDINCREASE COMPAREDTOCONVENTIONALHIGH POWERMAGNETRONS ,IMITATIONSOF-AGNETRONS 7HENTHEMAGNETRONWASFIRSTINTRODUCED ITPRO VIDEDACAPABILITYNOTAVAILABLEWITHTHEGRID CONTROLLEDTUBESUSEDFOREARLYRADARS !STIMEPASSED THEDEMANDSFORIMPROVEDRADARPERFORMANCEOUTRANTHECAPABILITIES AVAILABLEFROMTHEMAGNETRON&ORTUNATELY OTHERTUBETYPESWEREINVENTEDTHATOVER CAMETHELIMITATIONSOFTHEMAGNETRON !LTHOUGHTHEMAGNETRONHASHADIMPORTANTAPPLICATIONSINTHEPAST ITHASALSOHAD SERIOUSLIMITATIONSTHATCONSTRAINITSUSEFULNESSFORRADAR)TSMAJORLIMITATIONSAREITS POORSTABILITYWHICHLIMITSTHEABILITYTODETECTMOVINGTARGETSINCLUTTER ITSRELATIVELY MODESTAVERAGEPOWER ANDITSSIGNALCANNOTBEREADILYMODULATEDFORPULSECOMPRES SION4HESEANDOTHERSAREDISCUSSEDNEXT 4HE USE OF THE DOPPLER FREQUENCY SHIFT TO DETECT MOVING TARGETS IN THE MIDST OF LARGE CLUTTER ECHOES REQUIRES THAT THE TRANSMITTER PRODUCE A STABLE SIGNAL WITH LITTLE EXTRANEOUSNOISE"ECAUSEOFTHEIRPOORSTABILITYANDNOISYTRANSMISSIONS MAGNETRONS ARELIMITEDINTHEAMOUNTOF-4))MPROVEMENT&ACTORTHEYCANACHIEVETOABOUTOR PERHAPSD"-ANYRADARAPPLICATIONSREQUIREGREATER-4))MPROVEMENT&ACTORS 3OMERADARSALSOREQUIRETHEUSEOFPULSE COMPRESSIONWAVEFORMSTOOBTAINTHERESO LUTIONOFASHORTPULSEWITHTHEENERGYOFALONGPULSE)TISDIFFICULTTOPHASEORFRE QUENCYMODULATETHEWAVEFORMOFAMAGNETRON ASISNEEDEDFORPULSECOMPRESSION 4HUS POWERAMPLIFIERSAREALMOSTALWAYSUSEDFORPULSECOMPRESSIONAPPLICATIONS -AGNETRONSARENOTSTABLEENOUGHTOBESUITABLEFORVERYLONGPULSESEG §S AND STARTINGJITTERLIMITSTHEIRUSEATVERYSHORTPULSEWIDTHSEG §S ESPECIALLYATHIGH POWERANDATTHELOWERFREQUENCYBANDS)TSMAXIMUMAVERAGEPOWERISOFTHEORDER OFSEVERALKILOWATTS WHICHISLESSTHANTHATREQUIREDFORSOMEMILITARYAPPLICATIONS
£ä°£È
2!$!2(!.$"//+
3INCETHEMAGNETRONISANOSCILLATORWITHARANDOMSTARTINGPHASEONEACHPULSE ITCAN NOTBEUSEDTOELIMINATESECOND TIME AROUNDCLUTTERECHOESASCANANAMPLIFIERTRANS MITTER3IMILARLY COMBININGTHEPOWEROUTPUTSOFMULTIPLEMAGNETRONSHASNOTBEEN ATTRACTIVE-AGNETRONSCANPRODUCECONSIDERABLEELECTROMAGNETICINTERFERENCEACROSS ABANDWIDTHMUCHWIDERTHANTHESIGNALBANDWIDTHCOAXIALMAGNETRONSARESOMEWHAT BETTERINTHISRESPECT !LSO MAGNETRONSDONOTHAVEPRECISEFREQUENCYCONTROLNORARE THEYABLETOPERFORMPRECISEFREQUENCYJUMPING )NSPITEOFITSMANYUNFAVORABLECHARACTERISTICS THEMAGNETRONISATUBETHATCANBE CONSIDEREDFORLESSDEMANDINGRADARTASKS&ORALONGTIME ITWASTHETRANSMITTEROF CHOICEFORUSEINTHECIVILMARINERADAR ONEOFTHEMOSTWIDELYUSEDRADARS ASBRIEFLY DISCUSSEDNEXT #IVIL -ARINE 2ADAR -AGNETRONS 4HE MAGNETRON HAS BEEN WELL SUITED FOR APPLICATIONINCIVILMARINERADARSUSEDONSMALLPLEASUREBOATSORLARGECOMMERCIAL SHIPS )TS SUCCESS HAS BEEN DUE IN PART TO THE RADAR NEEDING ONLY SMALL TRANSMITTER POWER ANDTHERADARDOESNOTREQUIREDOPPLERPROCESSINGTOSEPARATEMOVINGTARGETS FROMLARGEFIXEDCLUTTERECHOES4HUS MANYOFTHEPROBLEMSTHATOCCURWITHMAGNE TRONSWHENUSEDINOTHERAPPLICATIONSARENOTFOUNDISTHISAPPLICATION!LSOIMPORTANT ISTHATTHECIVILMARINERADARBUSINESSISVERYCOMPETITIVEBECAUSEOFTHELARGEWORLD WIDENEEDFORSUCHRADARS4HISHASRESULTEDINTHEDEVELOPMENTOFLOW COST HIGHLY RELIABLEMAGNETRONSFORTHISIMPORTANTRADARAPPLICATION 4HESEMAGNETRONSGENERATEPEAKPOWERSFROMTOK7ANDHAVERELATIVELYLOW AVERAGEPOWERSOFAFEWWATTSTOAFEWTENSOFWATTS!NEXAMPLEOFAMAGNETRONFOR ACIVILMARINERADARISTHE-'MANUFACTUREDBY%%9OF#HELMSFORD %NGLAND )TISANCAVITY8 BANDMAGNETRONTHATOPERATESATAFIXEDFREQUENCYWITHINTHE BANDFROMTO-(ZWITHAPEAKPOWEROFK7ANDANEFFICIENCYOF )TOPERATESWITHANANODEVOLTAGEOFK6ANDANANODECURRENTOFAMPS 4YPICALLY ITSPULSEWIDTHMIGHTBE§SWITHADUTYCYCLEOF4HEMANUFAC TURERCLAIMSANEXPECTEDTYPICALLIFEOFOVER HOURSANDGUARANTEESAMINIMUM LIFEOF HOURS )TMIGHTALSOBEMENTIONEDTHATTHEMAGNETRONHASHADOUTSTANDINGSUCCESSASTHE POWERSOURCEFORTHEMICROWAVEOVEN/VERTHEYEARS ITHASDEVELOPEDINTOAVERY LOWCOSTANDHIGHLYRELIABLEGENERATOROFMICROWAVEPOWERTHATISWELL SUITEDFORTHIS APPLICATION
£ä°{Ê ,"-- Ê * ,- Ón 4HECROSSED FIELDAMPLIFIER OR#&! LIKETHEMAGNETRON HASAMAGNETICFIELDTHATIS ORTHOGONALTOTHEELECTRICFIELD BUTITISANAMPLIFIERRATHERTHANANOSCILLATOR)TIS SIMILARINAPPEARANCETOAMAGNETRONEXCEPTTHATTHE2&CIRCUITISINTERRUPTEDTOPRO VIDETHEINPUTANDOUTPUTCONNECTIONSASNEEDEDFORANAMPLIFIER#&!SMIGHTHAVE ANEFFICIENCYFROMTO USEALOWERVOLTAGETHANLINEAR BEAMTUBES ARELIGHTER INWEIGHTANDSMALLERINSIZE ANDHAVEBEENFOUNDFROM5(&TO+BAND(OWEVER THEYHAVERELATIVELYLOWGAINANDTHEIRSTABILITYANDNOISEARENOTASGOODASFOUNDIN LINEAR BEAMTUBES SOTHEIRAPPLICATIONFOR-4)RADARHASBEENLIMITED"ECAUSEOFTHE #&!SLOWGAIN THECROSSED FIELDAMPLIFIERTRANSMITTERNEEDSMORETHANONESTAGEOF 2&LIFICATION EACHWITHITSOWNPOWERSUPPLY MODULATOR ANDCONTROLS!LLTHESE STAGESMUSTBESTABLETOACHIEVEGOOD-4)PERFORMANCE
4(%2!$!242!.3-)44%2
£ä°£Ç
"ECAUSETHE#&!HASRELATIVELYLOWGAIN ITISSOMETIMESUSEDONLYINONEORTWO OFTHEHIGHEST POWERSTAGESOFANAMPLIFIERCHAIN WHEREITMAYOFFERANADVANTAGEIN EFFICIENCY OPERATINGVOLTAGE SIZEANDORWEIGHTCOMPAREDTOOTHERTUBES4HEOUTPUT STAGE#&!MIGHTBEPRECEDEDBYAMEDIUM POWER474THATPROVIDESMOSTOFTHEGAIN OFTHETOTALAMPLIFIERCHAIN7HENCOMPARINGTHE#&!WITHTHELINEAR BEAMTUBE THE ENTIRETRANSMITTERSYSTEMNEEDSTOBECOMPAREDANDNOTJUSTTHETUBEITSELF 4HE#&! HASALSOBEENCONSIDEREDASAMEANSTOBOOSTTHEPOWEROUTPUTOFPREVIOUSLYEXISTING RADARSYSTEMSTHATEMPLOYEDMAGNETRONS4HEREHAVEBEENBOTHBACKWARD WAVEAND FORWARDWAVE#&!S4HEBACKWARD WAVE#&!ISALSOKNOWNASTHE!MPLITRON )TISPOSSIBLETOPULSESOME#&!S WHICHHAVECOLDCATHODES TOEMPLOYWHATIS CALLED$#OPERATION WHERETHETRANSMITTERISTURNEDONANDOFFTOGENERATEAPULSE WAVEFORMWITHOUTTHENEEDFORAHIGH POWERMODULATOR)NDCOPERATIONTHEHIGHVOLT AGEISCONTINUOUSLYPRESENTBETWEENANODEANDCATHODE ANDTHECURRENTISTURNEDON BYAPPLYINGTHE2&DRIVEANDTURNEDOFFBYPULSINGTHECONTROLELECTRODE4HECONTROL ELECTRODECONSISTSOFASEGMENTOFTHECATHODESTRUCTUREINTHEDRIFTREGION 4OPREVENT THETUBEFROMSTARTINGWITHOUT2&DRIVE THECATHODEMUSTBEKEPTCOOLENOUGHTOPRE VENTTHERMIONICEMISSION4HECONTROLELECTRODENEEDSONLYASHORT MEDIUM POWER PULSE TYPICALLYONE THIRDOFTHEANODEVOLTAGEANDONE THIRDOFTHEANODEPEAKCURRENT 3INCE THE CONTROL ELECTRODE IS INSULATED AND SINCE SOME ENERGY IS DISSIPATED ON THE CONTROLELECTRODE ITCANBEDIFFICULTTOCOOL4HISCANLIMITTHEMAXIMUMPULSEREPETI TIONFREQUENCYTHATCANBEUSED)NSPITEOFITREQUIRINGNOMODULATOR DCOPERATIONHAS SELDOMBEENUSEDBECAUSEOFITSMANYLIMITATIONS #ROSSED FIELDAMPLIFIERSHAVEBEENUSEDINRADARSINTHEPAST BUTTHEYHAVESIGNIFI CANTDISADVANTAGES ASWASDESCRIBEDINTHESECONDEDITIONOFTHIS2ADAR(ANDBOOK THATMAKEITLESSLIKELYTHEYWILLBEWIDELYUSEDINTHEFUTURE
£ä°xÊ 9,"/," - Σ]ÎÓ]ÎÎ )T HAS BEEN NOTED PREVIOUSLY THAT THE POWER HANDLING CAPABILITY OF THE MICROWAVE POWERTUBESDISCUSSEDTHUSFARINTHISCHAPTERDECREASESASTHEFREQUENCYISINCREASED 4HISRESULTSBECAUSETHERESONANTSTRUCTURESOFTHESLOW WAVEMICROWAVECIRCUITRYOF THESETUBESBECOMESMALLERWITHINCREASINGFREQUENCY4HESMALLERTHEDEVICETHEMORE DIFFICULTITISTODISSIPATETHEHEATTHATISGENERATED4HUS THEPOWEROUTPUTDECREASES APPROXIMATELYINVERSELYASTHESQUAREOFTHERADARFREQUENCY 4HEGYROTRON2&POWERGENERATOR HOWEVER DOESNOTHAVETHISLIMITATIONBECAUSE ITDOESNOTEMPLOYSLOW WAVERESONANTMICROWAVESTRUCTURES4HESEDEVICESEMPLOYA FAST WAVESTRUCTURE SUCHASASMOOTHCIRCULARTUBE ONEWHERETHEPHASEVELOCITYOFTHE ELECTROMAGNETICWAVEISGREATERTHANTHEVELOCITYOFLIGHT7ITHASLOW WAVEDEVICE THEPHASEVELOCITYISLESSTHANTHEVELOCITYOFLIGHT 4HEDIAMETEROFTHEGYROTRONCIRCUIT CANBEMANYWAVELENGTHS ANDTHEELECTRONBEAMNEEDNOTBEPLACEDCLOSETODELICATE 2&STRUCTURES"ECAUSEAFAST WAVESTRUCTURERATHERTHANASLOW WAVESTRUCTUREISUSED THEYDONOTHAVETHESIZELIMITATIONSOFOTHERMICROWAVEPOWERSOURCESASTHEFREQUENCY ISINCREASED4HUS THEYCANGENERATEGREATERPOWERATTHEHIGHERFREQUENCIESTHANCAN OTHER2&POWERSOURCES SOMETHINGESPECIALLYATTRACTIVEATMILLIMETERWAVELENGTHS
4UBEISUSEDHEREASBEINGAhHOLLOWELONGATEDCYLINDERv
£ä°£n
2!$!2(!.$"//+
4HEMAGNETICFIELDINAGYROTRONSERVESADIFFERENTFUNCTIONFROMTHEMAGNETICFIELD INASLOW WAVEDEVICE)NTHESLOW WAVEDEVICE THEMAGNETICFIELDKEEPSTHEELECTRONIC BEAMCOLLIMATED)NTHEFAST WAVEDEVICE HOWEVER THEMAGNETICFIELDDETERMINESTHE FREQUENCY BUT THE FREQUENCY OF A CONVENTIONAL SLOW WAVE DEVICE IS DETERMINED BY THECIRCUITDIMENSIONS!NELECTRONINANAPPLIEDAXIALMAGNETICFIELD"OWILLROTATEAT WHATISCALLEDTHEELECTRONCYCLOTRONFREQUENCY WHICHISGIVENBYVC E"OMG WHERE E ELECTRONCHARGE M ELECTRONRESTMASS ANDGISTHERELATIVISTICFACTOR WHICHIS ; EMC 6O= WHEREC VELOCITYOFLIGHTAND6O BEAMVOLTAGE4HEBEAMVOLTAGE ANDTHECORRESPONDINGELECTRONVELOCITYINAGYROTRONAREHIGHENOUGHTOCAUSERELATIV ISTICEFFECTS4HEELECTRONSFOLLOWHELICALPATHSAROUNDTHEMAGNETICFIELDLINESWHENIN THEPRESENCEOFANELECTROMAGNETICWAVEWITHATRANSVERSECOMPONENTOFELECTRICFIELD %LECTRONSTHATLOSEENERGYTOTHEELECTROMAGNETICWAVEBECOMELIGHTERANDACCUMULATE PHASELEADANDTHENCATCHUPWITHTHEELECTRONSTHATGAINENERGYANDBECOMEHEAVIER ANDACCUMULATEPHASELAG4HUS ELECTRONSBECOMEPHASE BUNCHEDINTHEIRCYCLOTRON ORBITSASARESULTOFTHERELATIVISTICMASSCHANGEOFTHEELECTRONS4HEGYROTRONBUNCHING OPERATIONALSOCANBEOBTAINEDATHARMONICSOFTHECYCLOTRONFREQUENCY BUTTHERECAN BEPROBLEMSWITHHIGHERCIRCUITLOSSESANDCOMPETITIONWITHMODESOPERATINGATLOWER HARMONICSSOTHATMOSTHIGH POWERGYROTRONSOPERATEATTHEFUNDAMENTALFREQUENCYOR ITSSECONDHARMONIC "ECAUSE THE FREQUENCY OF A GYROTRON IS DETERMINED BY THE MAGNETIC FIELD AND NOTBYTHESIZEOFTHEFAST WAVESTRUCTURE THESTRUCTURECANBELARGE ANDITISTHEN POSSIBLE TO GENERATE QUITE HIGH POWER AT MILLIMETER WAVE FREQUENCIES 4HE LARGE MAGNETICFIELDSNEEDEDFORMILLIMETER WAVEGYROTRONSOFTENHAVETOBEGENERATEDBY SUPERCONDUCTINGMAGNETS 4HEGYROTRONWITHASINGLECAVITYOPERATESASANOSCILLATOR)TISSOMETIMESCALLED AGYRO OSCILLATORTODIFFERENTIATEITFROMAGYRO AMPLIFIERTHATUTILIZESSEVERALRESONANT CAVITIESORATRAVELINGWAVECIRCUITTOOPERATEASANAMPLIFIER4HEGYRO AMPLIFIERTHAT EMPLOYSSEVERALRESONANTCAVITIESISCALLEDAGYROKLYSTRON ANDWHENATRAVELING WAVE CIRCUITISUSED ITISCALLEDAGYRO TRAVELING WAVE TUBE OR MORECOMMONLY GYRO 474 4HEREISALSOAGYROTWYSTRONWITHTHERESONANTOUTPUTCAVITYREPLACEDBYA474CIR CUITSOASTOACHIEVEGREATERBANDWIDTHTHANCANBEOBTAINEDWITHARESONANTCAVITY !LTHOUGHGYRO OSCILLATORSHAVEBEENCAPABLEOFGREATERPOWERTHANGYRO AMPLIFIERS THEGYRO AMPLIFIERHASUSUALLYBEENPREFERREDFORRADARAPPLICATIONSFORTHESAMEREA SONTHEAMPLIFIERHASBEENPREFERREDATMICROWAVEFREQUENCIES ESPECIALLYWHENDOP PLERPROCESSINGISIMPORTANT !N EXAMPLE OF A HIGH POWER GYROKLYSTRON FOR RADAR APPLICATIONS IS THE 6'" THATWASUSEDINTHEEXPERIMENTAL7 BANDRADARKNOWNAS7ARLOCATTHE53 .AVAL2ESEARCH,ABORATORY)THADFIVECAVITIES OPERATEDOVERA-(ZBANDWIDTH CENTEREDAT'(ZWITHANAVERAGEPOWEROFK7 APEAKPOWEROFK7 DUTYCYCLE ANDEFFICIENCYWITHAK6 !ELECTRONBEAM)TUSEDASUPER CONDUCTING MAGNET WITH A CLOSED CYCLE COOLING SYSTEM SO THAT NO LIQUID CRYOGENS WEREREQUIRED )TPROVIDEDAMAGNETICFIELDOFK'4HEFIVE CAVITYGYROKLYSTRON COULDACHIEVEABANDWIDTHOF-(ZATANAVERAGEPOWEROFK74HERADARUSED AFTDIAMETERANTENNATHATPROVIDEDABEAMWIDTHOF4HIS7 BAND7ARLOCWAS INSTALLEDINAVANANDWASUSEDFORVARIOUSEXPERIMENTS4HE7ARLOCRADARWASABOUT THREEORDERSOFMAGNITUDEMORECAPABLETHANMOSTPREVIOUSRADARSUSEDFORMILLIME TER WAVERADAR4HISEXPERIMENTAL7ARLOCRADARWASEMPLOYEDTODEMONSTRATEAT7 BANDTHE)3!2IMAGINGOFMOVINGTARGETS CLOUDSTRUCTURE LOW ANGLEOPERATION AND UNUSUALATMOSPHERICRESEARCHINCLUDINGWHATHAVEBEENCALLEDhAIRSPIKESv
4(%2!$!242!.3-)44%2
£ä°£
4HEABOVEDISCUSSIONWASMAINLYABOUTTHEGYROTRONAMPLIFIER4HEGYROTRONHAS ALSOBEENOPERATEDASANOSCILLATORTOPRODUCEVERYHIGHPOWER BUTTHEOSCILLATORVER SIONHASNOTBEENASPOPULARASTHEAMPLIFIERFORRADARAPPLICATIONS4HISMIGHTBEDUE TOTHEAMPLIFIERBEINGBETTERABLETOPRODUCETHEDESIREDRADARWAVEFORMS
£ä°ÈÊ /, - // ,Ê-* /,1 Ê " /," 4HE INCREASING DEMAND FOR ELECTROMAGNETIC SPECTRUM FOR BOTH CIVILIAN AND MILITARY APPLICATIONS HAS ACCENTUATED THE NEED TO CONTROL THE SPECTRUM OF RADAR TRANSMITTERS TO AVOID INTERFERENCE WITH USERS OF THE ELECTROMAGNETIC SPECTRUM OPERATING AT OTHER FREQUENCIES4HEASPECTSOFCONCERNHEREARETHOSETHATAFFECT2&TUBESELECTIONAND ACHIEVEMENTOFMINIMUMSPECTRUMOCCUPANCYBYTHETRANSMITTERSDISCUSSEDPREVIOUSLY INTHISCHAPTER 2EDUCTIONOF3PURIOUS/UTPUTS 2&TUBESPURIOUSOUTPUTSMAYBEGROUPEDINTO THREEKINDSHARMONICS ADJACENT BAND ANDIN BAND !LL2&TUBESPRODUCESOMEHARMONICOUTPUT)NGENERAL LITTLECANBEDONEINTUBE DESIGN TO REDUCE HARMONIC OUTPUTS BUT IT IS FEASIBLE TO FILTER OUT HARMONICS TO D"REDUCTION WITHHIGH POWERFILTERS !DJACENT BANDSPURIOUSOUTPUTCANALSOOCCURINSOMECATHODE PULSED474SAND #&!S!DJACENT BANDSPURIOUSOUTPUTISAFFECTEDBYTUBEANDMODULATORSELECTION BUT ITCANBEFILTEREDBYAHIGH POWERMICROWAVEFILTERIFNECESSARY !LL2&TUBESPRODUCESOMEIN BANDBACKGROUNDNOISELEVEL)NA -(ZBANDWIDTH THISNOISEMIGHTBETOD"DOWNINCONVENTIONAL#&!S TOD"DOWNINTHE LOW NOISE HIGH GAIN #&! AND D" DOWN OR BETTER IN LINEAR BEAM TUBES )N BAND SPURIOUSCANNOTNORMALLYBEIMPROVEDWITHFILTERSBECAUSEITOCCURSWITHINTHESAME FREQUENCYRANGEASTHEDESIREDSIGNALSPECTRUM!TTEMPTSTOUSENOISEDEGENERATIONTO REDUCETHEINHERENT2&TUBENOISELEVELSARESUBJECTTOLIMITATIONS)N BANDSPURIOUS SIGNALSCANALSORESULTFROMPOWERSUPPLYANDMODULATORINSTABILITIES 2EDUCTION OF 3PECTRUM !MPLITUDE %XCEEDING SIN X X 4HE SPECTRUM OF A PERFECTLYRECTANGULARPULSEHASTHEFAMILIARSINX XFORM WHEREXISO FO F S FOIS THERADARCARRIERFREQUENCY ANDSISTHEPULSEWIDTH)FS ISCALLEDTHENOMINALBAND WIDTHOFTHESIGNAL THEENVELOPEOFTHESPECTRUMPEAKSFALLSOFFATTHERATEOFD" PEROCTAVEOFBANDWIDTH ANDTHISREDUCTIONWILLCONTINUEUNTILTHEENVELOPEREACHES THEINHERENTNOISEOUTPUTLEVELOFTHETRANSMITTER4HISRATEOFSPECTRUMFALLOFFISTOO SLOWTOMEETMOSTSYSTEMREQUIREMENTS.EVERTHELESS WITHOUTSPECIALCARETHEACTUAL SPECTRUMENVELOPEMIGHTBEEVENWORSETHANTHIS DEPENDINGONTUBECHARACTERISTICS ASARESULTOFPHASEMODULATIONDURINGTHEFINITERISEANDFALLOFPRACTICALMODULATOR AND2&DRIVEPULSESHAPES)NTHESECASES EITHERTHELEADINGANDTRAILINGEDGESMUST BEAPPROPRIATELYTAILORED ORELSEINLINEAR BEAMTUBES THE2&DRIVEMAYBEWITHHELD DURINGTHERISEANDFALLTIME!LTHOUGHTHISMAYSLIGHTLYREDUCEAPPARENTEFFICIENCY IT SHOULDBENOTEDTHATENERGYOUTSIDETHEAPPROXIMATELYSGENERATEDDURINGRISEAND FALLWITHTHE2&DRIVEPRESENTISNOTUTILIZEDBYTHERECEIVERANYWAY )MPROVEMENTBY-EANSOF3HAPED0ULSES 3INCETHEENERGYINTHESPECTRUM BEYOND PLUS OR MINUS S FROM FO IS NOT USED BY THE RECEIVER IT IS DESIRABLE FOR
£ä°Óä
2!$!2(!.$"//+
ELECTROMAGNETIC COMPATIBILITY PURPOSES TO AVOID TRANSMITTING ENERGY BEYOND THOSE LIMITS4HISOBJECTIVEMAYBEAPPROACHEDBYUSINGAPULSESHAPEDIFFERENTFROMTHE CONVENIENT AND CONVENTIONAL RECTANGULAR PULSE (IGHLY SHAPED PULSES HAVE NOT BEENUSEDOFTENINRADARSYSTEMSBECAUSEOFTHELOSSOFEFFICIENCYTHATRESULTS4HESE LIMITATIONS HOWEVER DO NOT APPLY WHEN USING THE GRID CONTROLLED TUBES KNOWN AS THE#ONSTANT%FFICIENCY!MPLIFIERORTHE)NDUCTIVE /UTPUT4UBE ASDISCUSSEDLATERIN 3ECTION !NOTHERAPPROACHTOSPECTRUMIMPROVEMENTISTOSHAPETHERISEANDFALLOFARECT ANGULARPULSE4HISATTENUATESTHESPECTRUMOFFREQUENCIESFARFROMFO WHILETHEFLAT TOPPEDPORTIONOFTHEPULSERETAINSTHEHIGHTRANSMITTEREFFICIENCYFORMOSTOFTHEPULSE DURATION3INCEARECTANGULARPULSEHASTHEBESTTRANSMITTEREFFICIENCYBUTHASHIGH SPECTRALENERGYATFREQUENCIESFARFROMTHECENTERFREQUENCY WHEREASAHIGHLYSHAPED PULSEHASLESSFAR OUTSPECTRALENERGYBUTPOORTRANSMITTEREFFICIENCY THEFRACTIONOF THEPULSELENGTHTOBEUSEDFORTHESHAPEDRISEANDFALLISACRUCIALDECISION !LTHOUGHTHEIMPROVEMENTATTAINABLEINPRACTICEISLIMITEDBYPHASEMODULATIONIN THETRANSMITTERDURINGTHERISEANDFALL SIGNIFICANTIMPROVEMENTSCANBEOBTAINED )N A LINEAR BEAM TUBE TRANSMITTER WITH PROPERLY SHAPED 2& DRIVE FOR EXAMPLE THE SPECTRUMWIDTHATD"DOWNCANUSUALLYBENARROWEDBYABOUTANORDEROFMAGNI TUDEATACOSTOFABOUTD"INTRANSMITTEREFFICIENCY !MPLIFIERCHAINRADARSYSTEMS WHETHERTUBEORSOLIDSTATE OFTENUSESOMESHAPING OFTHEEDGESOFTHETRANSMITTED2&PULSETOREDUCETHE2&SPECTRUMWIDTH4HISCANBE DONEBYSIMPLYSLOWINGTHERISEANDFALLTIMESOFTHEEXCITERSIGNALTOTHETRANSMITTER ANDTHISAPPROACHGENERALLYHASBEENADEQUATETOSATISFY-ILITARY3TANDARDSANDRELATED SYSTEMREQUIREMENTS 3PECTRAL.OISEIN$OPPLER2ADARS 4HEDOPPLERFREQUENCYSHIFTISWIDELYUSED TODETECTMOVINGTARGETECHOSIGNALSINTHEPRESENCEOFLARGECLUTTERECHOES(OWEVER IFTHERADARTRANSMITTERGENERATESNOISEORITSPULSEWAVEFORMHASSIGNIFICANTSPEC TRALENERGYATTHEDOPPLERFREQUENCIESEXPECTEDFROMMOVINGTARGETS THISUNWANTED NOISEORSPECTRAWILLDEGRADETHEDETECTIONOFDESIREDTARGETS4HETRANSMITTERNOISE IS REFLECTED BACK FROM THE CLUTTER AND ENTERS THE RECEIVER AND IS SOMETIMES CALLED hTRANSMITTEDCLUTTERv3OMETYPESOFMICROWAVETUBESAREMOREOFAPROBLEMTHAN OTHERS%XTRANEOUSNOISEINAMICROWAVEAMPLIFIERTUBEATTHEFREQUENCIESEXPECTED FROMDOPPLER SHIFTEDTARGETECHOESCANBEPRODUCEDBYIONOSCILLATIONS!CCORDING TO!!!CKER hTHESEAREPERIODICINSTABILITIESTHATCANOCCURINTHEELECTRONBEAM AT VIDEO FREQUENCIES RESULTING IN SIGNALS OTHER THAN THE CARRIER FREQUENCY CAUSING SEVEREPROBLEMSTODOPPLERRADARPERFORMANCEv!CKERALSOSTATESTHATIONOSCILLATIONS REQUIREAFINITETIMETODEVELOPSOTHATIFATUBEISOPERATEDWITHLESSTHANA§SPULSE WIDTH IONNOISEISUSUALLYNOTOFCONCERN !DVANCESINDIGITALTECHNOLOGYHAVEALLOWEDAMETHODTOREDUCEINTRA PULSETRANS MITTERNOISEANDPOWERSUPPLYINSTABILITIESTHATAFFECTRADARPERFORMANCEBYTHEPRESENCE OFSTRONGCLUTTERECHOES4HETECHNIQUE KNOWNAS4RANSMITTER.OISE#OMPENSATION 4.# CAPTURESANDPROCESSESANACCURATEREPLICAOFEACHTRANSMITTEDPULSE"YMEANS OFPULSE TO PULSECOMPARISONS THEMEASUREDTRANSMITTERERRORSAREUSEDTODERIVEA DIGITAL FILTER THAT COMPENSATES FOR THE TRANSMITTER NOISE THAT ARRIVES IN THE RECEIVER DIGITAL SIGNAL PROCESSOR4.# COMPENSATES FOR INTRA PULSE TRANSMITTER NOISE AS WELL AS POWER SUPPLY INSTABILITIES!LTHOUGH 4.# WORKS ONLY IN A SINGLE UNAMBIGUOUS RANGE INTERVAL IT IS SAID THAT IT SHOULD BE ABLE TO OPERATE WITH SOME MEDIUM 02& RADARSIFSIGNIFICANTCLUTTERISNOTLIKELYTOEXTENDOVERMORETHANONE02&INTERVAL
4(%2!$!242!.3-)44%2
£ä°Ó£
!N EXPERIMENTAL IMPLEMENTATION USING DATA COLLECTED ON AN OPERATIONAL RADAR WITH A#&!TRANSMITTERSHOWEDTHAThTHE4.#TECHNIQUECANIMPROVERADARDETECTIONOF TARGETSINCLUTTERBYD"ORMOREv
£ä°ÇÊ , " /," Ê/1 4HEGRID CONTROLLEDTUBEISAMODERNVERSIONOFTHECLASSICALTRIODEORTETRODEVACUUM TUBETHATDATESBACKTOTHEEARLYYEARSOFTHETHCENTURY4HESEDEVICESEMPLOYA CATHODETOGENERATEELECTRONS ONEFORATRIODE ORTWOFORATETRODE CONTROLGRIDS ANDANANODETOCOLLECTTHEELECTRONS!SMALLVOLTAGEAPPLIEDTOTHECONTROLGRIDACTSTO CONTROLTHENUMBEROFELECTRONSTRAVELINGFROMCATHODETOANODE4HEPROCESSBYWHICH THEELECTRONDENSITYOFTHEELECTRONSTREAMISMODULATEDBYTHESIGNALONTHECONTROL GRIDTOPRODUCEAMPLIFICATIONISCALLEDDENSITYMODULATION)NTHELATTERHALFOFTHETH CENTURY GRID CONTROLLED TUBES WERE SUCCESSFULLY EMPLOYED IN SUCH IMPORTANT RADAR APPLICATIONSAS(&OVER THE HORIZONRADAR 6(&AND5(&AIRCRAFTSURVEILLANCERADARS ANDSATELLITESURVEILLANCERADARS'RID CONTROLLEDTUBESARECAPABLEOFHIGHPOWER WIDE BANDWIDTH GOODEFFICIENCY ANDINHERENTLONGLIFE BUTTHEYAREOFLOWORMODERATE GAIN4HEIRCHIEFLIMITATIONISTHATTHEYARENOTCAPABLEOFOPERATINGATHIGHERFREQUEN CIES BUTTHEYARECAPABLEUPTOFREQUENCIESAPPROACHING'(Z'RID CONTROLLEDTUBES HAVEBEENOPERATEDAT5(&ANDHIGHERFREQUENCIESBYUSINGMICROWAVETECHNIQUESIN THEIRCONSTRUCTION ASWASDONEINTHE#OAXITRON4HEYCANALSOBEMADETOOPERATEWITH CONSTANTEFFICIENCYWHENSHAPINGOFTHEPULSEAMPLITUDEISUSEDTOREDUCEINTERFERENCE CAUSEDBYITSFAR OUTSPECTRUM SOMETHINGNOTASPRACTICALTODOWITHOTHERTYPESOF MICROWAVETUBES #OAXITRON 4HEPERFORMANCEOFCONVENTIONALGRID CONTROLTUBESATTHEHIGHERFRE QUENCIESISLIMITEDBYTHETIMEITTAKESFORTHEELECTRONSTOTRANSITFROMTHECATHODETO THEANODEOFTHETUBE4HISTRANSITTIMEMUSTBESMALLCOMPAREDTOTHEPERIODOFTHE2& SIGNALTOBEAMPLIFIED4OMINIMIZETHEUNDESIREDTRANSIT TIMEEFFECTS THECOMPLETE2& INPUTANDOUTPUTCIRCUITANDTHEELECTRICALINTERACTIONSYSTEMCANBEPLACEDWITHINTHE VACUUMENVELOPE3UCHAGRID CONTROLLEDTUBEISCALLEDA#OAXITRON)NONEEMBODI MENT OF THE #OAXITRON THE ELECTRON INTERACTION STRUCTURE CONSISTED OF A CYLINDRICAL ARRAYOFESSENTIALLYINDEPENDENTGROUNDED GRIDUNITTRIODES 4HE SO CALLED!& #OAXITRON DESCRIBED IN 6INGST ET AL OPERATED OVER A FREQUENCYRANGEFROMTO-(ZWITHAPEAKPOWEROF-7 APULSEWIDTH OF§S ADUTYCYCLEOF ANAVERAGEPOWEROFJUSTUNDERK7 ANDAPLATE EFFICIENCYOF4HE#OAXITRONHASBEENSUCCESSFULLYEMPLOYEDFOR5(&RADARS INCLUDINGAIRBORNE #ONSTANT %FFICIENCY !MPLIFIER #%! )T HAS BEEN SAID THAT hA CONSTANT EFFICIENCY AMPLIFIER HAS BEEN A GOAL FOR TRANSMITTER ENGINEERS EVER SINCE ,EE $E&ORESTAND!MBROSE&LEMINGINVENTEDTHEFIRSTELECTRONICAMPLIFIERSv4HISGOAL SEEMSTOHAVEBEENACHIEVEDBYTHE#%!GRID CONTROLLEDTUBE )T IS CUSTOMARY TO THINK OF THE SHAPE OF A CONVENTIONAL RADAR PULSE AS BEING RECTANGULAR )T IS SELDOM HOWEVER PERFECTLY RECTANGULAR WITH VERY SHORT RISE AND FALLTIMESBECAUSESUCHAWAVEFORMHASAVERYLARGEBANDWIDTH ASONECANOBSERVE FROMITS&OURIERTRANSFORM%VENIFALARGEBANDWIDTHWEREAVAILABLETOSUPPORTA
£ä°ÓÓ
2!$!2(!.$"//+
RECTANGULARPULSE ALARGEBANDWIDTHWOULDLIKELYCAUSEINTERFERENCETOOTHERRADARS ANDOTHERELECTROMAGNETICSYSTEMS&ORTHISREASON GOVERNMENTFREQUENCYALLOCATION AGENCIESUSUALLYREQUIRETHATTHEFREQUENCYSPECTRUMFROMARADARNOTCONTAINLARGE ENERGYATOTHERFREQUENCIES4HISISBECOMINGMOREIMPORTANTASTHEOCCUPANCYOFTHE ELECTROMAGNETICSPECTRUMISINCREASINGLYCROWDEDWITHTRANSMITTERS4HECLASSICAL WAY TO REDUCE THE FAR OUT SPECTRUM FROM A RADAR TRANSMITTER IS TO SHAPE OR TAPER ITSWAVEFORM SUCHASBYUSINGATRAPEZOIDALSHAPE AGAUSSIAN LIKEPULSESHAPE A TRUNCATEDGAUSSIAN PERHAPSACOSINEONAPEDESTAL OROTHERTYPEOFNONRECTANGULAR SHAPE4HEPROBLEMWITHUSINGCONVENTIONALTRANSMITTERSSUCHASDISCUSSEDINTHIS CHAPTERISTHATWHENUSINGASHAPEDWAVEFORMSOMELOSSINEFFICIENCYRESULTS4HUS ITISSELDOMTHATARADARDESIGNERWOULDWANTTOUSEAHIGHLYSHAPEDPULSEWAVEFORM IN ORDER TO REDUCE THE SPECTRUM RADIATED OUTSIDE OF THE RADARS NORMAL OPERATING SIGNALBANDWIDTH4HE#%! HOWEVER ISAN2&POWERSOURCETHATDOESNOTHAVEITS EFFICIENCYDECREASEDWHENANONRECTANGULAR ORSHAPED WAVEFORMISUSED4HE#%! HASBEENWIDELYUSEDFORCOMMERCIAL46TRANSMITTERSTHATHAVEHIGHLYMODULATED NONCONSTANTAMPLITUDEWAVEFORMS 4HE#%!ISBASEDONAGRID CONTROLLEDTUBEKNOWNASAN)NDUCTIVE/UTPUT4UBE OR)/44HE#%!ISSIMILARTOSOMETHINGCALLEDA+LYSTRODEEXCEPTTHATTHE#%! EMPLOYSTHE)/4WITHAMULTISTAGEDEPRESSEDCOLLECTORSIMILARTOTHATUSEDINKLYS TRONSAND474S )NTHE)/4 THEWIREGRIDOFAGRID CONTROLLEDTUBEISREPLACED WITHANAPERTURETHATDOESNOTINTERCEPTTHEELECTRONS ANDITHASACOAXIALMAGNETIC FIELDTHATCONFINESTHEELECTRONSTREAMASINAKLYSTRONORA474!LTHOUGHAN2& CAVITYISUSEDINAN)/4 THEBEAMISDENSITYMODULATED ORBUNCHED WITHAGRID SIMILARTOHOWITISMODULATEDINATRIODEORTETRODEGRID CONTROLLEDTUBE4HISMAKES ITSMALLERANDLIGHTERTHANACOMPARABLEKLYSTRON4HEDENSITYMODULATEDELECTRONS THUS FORM BUNCHES AND 2& ENERGY IS EXTRACTED BY PASSING THE BEAM THROUGH THE RESONANTCAVITY4HE#%!HASBEENWIDELYUSEDFOR5(& 46TRANSMITTERS AHIGHLY COMPETITIVEINDUSTRYCONCERNEDWITHCOST)THASBEENSAIDTHATIN5(& 46 THEUSE OFA#%!REDUCESTHEREQUIREDPRIMEPOWERBYONE HALFCOMPAREDTOACONVENTIONAL TUBE TRANSMITTER AND BY ONE THIRD OF THE PRIME POWER OF A SILICON CARBIDE SOLID STATETRANSMITTER4HE#%!ACHIEVESTHESEEFFICIENCIESSINCETHEREISNOLOSSOFEFFI CIENCYWHENUSINGSHAPEDPULSEWAVEFORMS ASTHEREISWITHOTHERMICROWAVETUBES 4HISISANIMPORTANTREASONFORITSUSEFOR5(& 46WITHITSTIME VARYING AMPLITUDE WAVEFORM)TALSOSHOULDBEANADVANTAGEFORRADARAPPLICATIONSTHATREQUIRESHAPED WAVEFORMSATFREQUENCIESUPTO-(Z WHENITISREQUIREDTOREDUCETHEFAR OUT SPECTRALENERGY !#%! SUCHASMANUFACTUREDBY, #OMMUNICATIONS CANOPERATEWITHINTHE 5(& 46BANDFROMTO-(ZWITHAN-(ZBANDWIDTHTHESPECTRALWIDTH OFA46CHANNEL K7PEAKPOWERATEFFICIENCY ANDANAVERAGEPOWEROF K7ORGREATER4HESINGLEINPUTCAVITYCANBEMADETOTUNEOVERTHEENTIREBAND WITHLOW6372 4HUS THECONSTANTEFFICIENCYAMPLIFIERISAGRID CONTROLLEDTUBE OPERATINGASCLASS !" THATCONSISTSOFANINDUCTIVE OUTPUTTUBEWITHAMULTISTAGEDEPRESSEDCOLLECTOR)T ISALINEARAMPLIFIERWHOSEPRIMEPOWERCANBEPROPORTIONALTOTHEOUTPUTPOWER PRO VIDINGCONSTANTEFFICIENCYOVERAWIDERANGEOFOUTPUTPOWERS4HE#%!SEEMSTOBE THEPREFERREDTUBEFOR5(& 46TRANSMITTERS RATHERTHANOTHERTYPESOFGRID CONTROLLED TUBES SOLID STATE ORKLYSTRONS)TWOULDSEEMTHATTHE#%!OUGHTTOBEOFINTERESTFOR RADAR APPLICATIONS AT FREQUENCIES AS HIGH AS -(Z WHEN HIGHLY SHAPED PULSES NEEDTOBEUSED
4(%2!$!242!.3-)44%2
£ä°ÓÎ
!PPLICATIONOF'RID #ONTROLLED4UBES 4HEREHASBEENIMPORTANTAPPLICATIONOF THEGRID CONTROLLEDTUBEFORRADARSINTHEPASTAT(& 6(& AND5(&)TISSTILLOFVALUEFOR APPLICATIONSINTHESEFREQUENCYREGIONSANDSHOULDBECONSIDEREDASACANDIDATEWHEN DESIGNINGARADARTOOPERATEATTHELOWERFREQUENCIES4HECONSTANTEFFICIENCYAMPLI FIERSHOULDBEOFINTERESTBECAUSEOFITSHIGHEREFFICIENCYWHENSHAPEDWAVEFORMSARE NEEDEDFORCONTROLOFTHERADIATEDSPECTRUM
£ä°nÊ " 1 /",4HISSECTIONBRIEFLYREVIEWSTHEMODULATOR SOMETIMESCALLEDTHEPULSER WHICHISTHE DEVICETHATTURNSTHETRANSMITTERTUBEONANDOFFTOGENERATETHEDESIREDPULSEWAVE FORM4HOSEDESIRINGMOREINFORMATIONMIGHTEXAMINE#HAPTERIN,3IVANSBOOK ONTRANSMITTERS THECHAPTERBY4!7EILINTHESECONDEDITIONOF2ADAR(ANDBOOK THE #ONFERENCE 2ECORDS OF THE )NTERNATIONAL 0OWER -ODULATOR 3YMPOSIA AND THE #ONFERENCE0ROCEEDINGSOFTHE)%%%0ULSE0OWER#ONFERENCES 4HE TYPE OF TUBE DETERMINES TO SOME EXTENT THE TYPE OF MODULATOR! MODULA TORBASICALLYCONSISTSOFANENERGYSTORAGEDEVICE WHICHMAYBEACAPACITANCEORA PULSE FORMING NETWORK AND A SWITCH FOR TRIGGERING THE DC PULSE4HE SWITCH IN THE PASTMIGHTHAVEBEENAVACUUMTUBE THYRATRON IGNITRON SILICON CONTROLLEDRECTIFIER 3#2 REVERSE SWITCHINGRECTIFIER SPARKGAP ORMAGNETIC(OWEVER THESOLID STATE SWITCHSEEMSTOBETHESWITCHINGMECHANISMTHATSHOULDBECONSIDEREDINITIALLYWHEN DESIGNINGATRANSMITTERMODULATOR-ODULATORSCANBECLASSEDASEITHERLOWPOWEROR HIGHPOWER DEPENDINGONHOWTHETUBEISMODULATED )FTHETUBEHASAGRID ASMALLANDRELATIVELYINEXPENSIVETYPEOFMODULATORCANBE USED BUTGRIDSUSUALLYARENOTFEASIBLEWITHHIGHPOWERTUBES!WIDELYUSEDSWITCHING ELEMENTFORLOW POWERMODULATORSISTHE-/3&%4TRANSISTOR ,OW POWERMODULATORSCANBEUSEDWITHTUBESTHATEMPLOYAMODULATINGANODE ASDOESTHELINEAR BEAMAMPLIFIER4HEMODULATINGANODEINALINEAR BEAMTUBEISPART OF THE ELECTRON GUN AND IS SEPARATED FROM THE BODY OF THE TUBE4HE VOLTAGE OF THE MODULATINGANODEISVARIEDOVERALARGERANGEINORDERTOVARYTHEELECTRON BEAMCUR RENT BUTTHEPOWERNEEDEDTODRIVETHEMODULATINGANODEISSMALLBECAUSETHECURRENT INTERCEPTEDBYTHEMODULATINGANODEISVERYSMALL 6ERYHIGH POWERTUBESCANNOTUSEAMODULATINGANODEBECAUSETHECONTROLELECTRODE MIGHT NOT BE ABLE TO HANDLE THE POWER 7HEN THIS OCCURS A HIGH POWER MODULATOR CALLEDACATHODEPULSERMIGHTHAVETOBEUSEDTOSWITCHTHETUBEONANDOFF#ATHODE PULSERSMUSTSWITCHTHEFULLBEAMVOLTAGEANDCURRENTSIMULTANEOUSLY WHICHINVOLVES HIGHINSTANTANEOUSPOWERS4HEYMUSTCONTROLTHEFULLBEAMPOWEROFTHE2&TUBE EITHER DIRECTLYORTHROUGHACOUPLINGCIRCUIT4HEENERGYSTORAGEDEVICEMIGHTBEMADEUPOF CAPACITORS INDUCTORS ORSOMECOMBINATIONOFTHETWOASINPULSE FORMINGNETWORKS 4HEENERGYINTHEENERGYSTORAGEDEVICEISDISCHARGEDBYAVERYCAPABLESWITCH 4HELINE TYPEMODULATORUSESADELAYLINEORAPULSE FORMINGNETWORK0&. ASTHE ENERGYSTORAGEELEMENT!SWITCHINITIATESTHEDISCHARGEOFTHEENERGYSTOREDINTHE 0&.4HESHAPEANDDURATIONOFTHEPULSEAREDETERMINEDBYTHEPASSIVEELEMENTSOF THE0&.4HESWITCHHASNOCONTROLOVERTHEPULSESHAPE OTHERTHANTOINITIATEIT4HE PULSEENDSWHENTHE0&.HASDISCHARGEDSUFFICIENTLY!DISADVANTAGEOFTHISACTIONIS THATTHETRAILINGEDGEOFTHEPULSEISUSUALLYNOTSHARPSINCEITDEPENDSONTHEDISCHARGE CHARACTERISTICSOFTHE0&.)THASBEENWIDELYUSEDINTHEPASTFORMAGNETRONPULSING
£ä°Ó{
2!$!2(!.$"//+
)NANACTIVE SWITCHMODULATOR THESWITCHHASTOBETURNEDOFFASWELLASTURNEDON /RIGINALLY THESWITCHWASAVACUUMTUBEANDTHEMODULATORWASCALLEDAHARD TUBE MODULATORTODISTINGUISHITFROMTHEGAS TUBESWITCHOFTENUSEDINALINE TYPEMODULATOR 3INCEOTHERTHANVACUUMTUBESCANBEUSEDASTHESWITCHINANACTIVE SWITCHMODULATOR THEhHARD TUBEvDESIGNATIONMEANINGAVACUUMTUBE MIGHTNOTALWAYSAPPLY5NLIKE THE LINE TYPE MODULATOR THE SWITCH IN THE ACTIVE SWITCH MODULATOR CONTROLS BOTH THE BEGINNING AND END OF THE PULSE 3INCE THE ENERGY STORAGE DEVICE IS A CAPACITOR THE PULSECANDROOP SOMETHINGTHATCANBEPREVENTEDBYEXTRACTINGONLYASMALLFRACTION OFTHESTOREDENERGYFROMTHECAPACITOR4HISREQUIRESALARGECAPACITANCE WHICHMAY BEOBTAINEDWITHACOLLECTIONOFCAPACITORSCALLEDACAPACITORBANK4HEACTIVE SWITCH MODULATORPERMITSGREATERFLEXIBILITYANDPRECISIONTHANTHELINE TYPEMODULATOR)TCAN PROVIDEEXCELLENTPULSESHAPE VARYINGPULSEDURATIONS ANDPULSEREPETITIONFREQUEN CIES INCLUDINGMIXEDPULSELENGTHSANDBURSTSOFPULSESWITHCLOSEPULSESPACINGS -ICROWAVE TUBES AND THEIR HIGH VOLTAGE SWITCHES CAN SOMETIMES PRODUCE AN UNWANTEDARCDISCHARGETHATEFFECTIVELYPLACESASHORTCIRCUITACROSSTHEPOWERSUP PLYANDORMODULATORDELIVERINGPOWERTOTHETUBE3INCE*OFENERGYCANUSUALLY CAUSEDAMAGETOAN2&TUBEORTHESWITCHINGDEVICE ANDSINCETHECAPACITORBANK FORANACTIVE SWITCHMODULATORMUSTOFTENSTOREFARMORETHAN*TOPREVENTEXCES SIVEDROOP SOMEMEANSMUSTBEPROVIDEDTODIVERTTHESTOREDENERGYWHENANARC DISCHARGEOCCURS3UCHADEVICEISTHECROWBAR SOCALLEDBECAUSEITISEQUIVALENTTO PLACINGAHEAVYCONDUCTORLIKEACROWBAR DIRECTLYACROSSTHEPOWERSUPPLYTODIVERT THEENERGYANDTHUSPREVENTTHEENERGYFROMDISCHARGINGTHROUGHTHETUBEANDCAUS INGSERIOUSDAMAGE!CROWBARIS THEREFORE NEEDEDFORAHIGH POWERACTIVE SWITCH MODULATORBECAUSEOFTHELARGEAMOUNTOFENERGYSTOREDINITSCAPACITORBANK/NTHE OTHERHAND CROWBARSARENOTUSUALLYNEEDEDWITHLINE TYPEMODULATORS WHICHSTORE LESSENERGYINTHEIRPULSE FORMINGNETWORK #ERTAINCROSSED FIELDAMPLIFIERSCANBEPULSEDBYMEANSOFACONTROLELECTRODE LOCATED IN THE TUBES DRIFT REGION WITHOUT A SEPARATE FULL POWER PULSE MODULATOR 4HISISCALLEDDCOPERATION%VENTHOUGHDCOPERATIONAVOIDSAHIGHPOWERMODULA TOR ITHASSELDOMBEENUSEDBECAUSEITREQUIRESAMUCHLARGERCAPACITORBANKTOLIMIT DROOP ANARCINTHETUBEREQUIRESACROWBARTHATINTERRUPTSOPERATIONFORAFEWSECONDS INSTEADOFONLYFORASINGLEPULSE ANDTHEADJACENTRADARSMIGHTINJECTENOUGH2& POWERINTOTHERADARANTENNAANDBACKTOTHETRANSMITTERTOTURNONADCOPERATED#&! ATTHEWRONGTIMES4HEREHASBEENATLEASTONEEXAMPLEINTHEPASTWHEREAMAJOR RADARSYSTEMORIGINALLYDESIGNEDWITH#&!SBASEDONDCOPERATIONHADTOHAVEITSDC OPERATED#&!SREPLACEDDURINGTHEMIDDLEOFITSDEVELOPMENTWITH#&!STHATUSED CONVENTIONALPULSEMODULATORS !TTHEBEGINNINGOFTHETHCENTURY THESOLID STATEMODULATORWASDEVELOPEDAND BEGANTOBEUSEDFORRADARTRANSMITTERSASEITHERCATHODEPULSEDORMODULATINGANODE PULSEDMODULATORS ASWELLASGRIDPULSED3OLID STATEMODULATORSOFFERIMPROVEDTRANS MITTER PERFORMANCE BY ALLOWING A WIDE VARIATION IN PARAMETERS PULSE WIDTH PULSE REPETITIONFREQUENCY PULSEAGILITY ANDPULSE TO PULSECONSISTENCY 4HEYALSOPROVIDE COSTSAVINGSTHATRESULTFROMTHEINHERENTRELIABILITYOFTHESESWITCHMODULESCOMPARED TOCONVENTIONALSWITCHTUBES ANDTHEELIMINATIONOFNUMEROUSAUXILIARYCOMPONENTS NEEDEDFORTHEOPERATIONOFSWITCHTUBES ,OWEROPERATINGCOSTSANDSMALLERCOOL INGREQUIREMENTSOCCURBECAUSEOFTHEIRHIGHERCONVERSIONEFFICIENCY4HEYAREALSO SAIDTOHAVEHIGHERRELIABILITYWITHLONGERCOMPONENTLIFE4HEABILITYOFTHESOLID STATE SWITCHTOOPENQUICKLYLESSTHANONEMICROSECOND WHENAFAULTISDETECTEDELIMINATES THENEEDFORACROWBAR4HEENERGY STORAGEDEVICEDOESNOTDISCHARGEDURINGANARC SOWHENTHEFAULTHASCLEARED THETRANSMITTERCANRESUMEOPERATIONINMICROSECONDS
4(%2!$!242!.3-)44%2
£ä°Óx
!SOLID STATECATHODEMODULATORCANPROVIDEPULSEWIDTHSVARYINGFROMNSTOhDCv ONAPULSE TO PULSEBASISANDCANSUPPORTPULSEREPETITIONFREQUENCIESUPTOK(Z 4HEHIGHVOLTAGESOLID STATESWITCHESAREBUILTFROMMODULESTHATMIGHTCONTAINFROM TOINDIVIDUALTRANSISTORSCONNECTEDINSERIESTOPROVIDETHEREQUIREDTRANSMITTER CATHODEVOLTAGE2ISETIMESCANBEASLOWASNS
£ä°Ê 7 Ê,Ê*"7 ,Ê-"1,
Ê/"Ê1- ¶ 4HEREISNOGOOD SIMPLEANSWERTOTHISQUESTION BUTINTHISSECTIONWESHALLATTEMPT TODISCUSSSOMEOFTHEVARIOUSISSUESTHATMIGHTBEINVOLVED 4HISCHAPTERHASBRIEFLYDESCRIBEDTHEVARIOUSVACUUMTUBESTHATHAVEBEENUSEDOR CONSIDEREDFORRADARAPPLICATIONS ANDTHENEXTCHAPTERDISCUSSESTHESOLID STATETRANSMIT TER WHICHHASALSOBEENWIDELYUSEDINRADAR!QUESTIONTHATNATURALLYARISESISWHICH 2&POWERSOURCESHOULDBEUSEDFORSOMEPARTICULARRADARAPPLICATION2ADARSYSTEM DESIGNUSUALLYINVOLVESMAKINGCHOICESAMONGTHEVARIOUSPOSSIBILITIESAVAILABLE7HEN TRYINGTODETERMINEWHICH2&POWERSOURCETOUSE ACHOICECANBEMADEBYDOINGA SEPARATESYSTEMDESIGNWITHEACH2&POWERSOURCETHATSEEMSPROMISING4HEDECISION ASTOWHICHTOUSECANBEBASEDONHOWWELLEACHSYSTEMDESIGNPERFORMSTHEDESIRED TASKACCORDINGTOSOMEPRE ESTABLISHEDCRITERIA4HIS UNFORTUNATELY ISSELDOMDONE)T ISSUSPECTEDTHATSOMETIMESTHEDECISIONASTOWHICH2&POWERSOURCETOUSEISDETER MINEDBYWHATTHERADARSYSTEMDESIGNERTHINKSTHEBUYERORCUSTOMER OFTHERADAR DESIRES3OMETIMESTHEBUYERWILLACTUALLYSPECIFYTHETYPEOFTRANSMITTERTOBEDELIVERED -ANUFACTURINGAPRODUCTBASEDONWHATTHEBUYERTHINKSHEORSHEWANTSMAYBEAGOOD MARKETINGSTRATEGYFORMANYPRODUCTS BUTINSOMETHINGLIKEARADAR ITMIGHTBEBETTER FORACUSTOMERTOCLEARLYSPECIFYWHATPERFORMANCEISWANTEDANDTHENLEAVETHEDECISION ASTOWHAT2&POWERSOURCESHOULDBEUSEDTOTHERADARSYSTEMDESIGNER)TISUSUALLY BETTERIFTHERADARDESIGNCANBEDETERMINEDBYTHERADARSYSTEMDESIGNERANDNOTBYTHE MANUFACTURERSMARKETINGDEPARTMENT4HEGOALSOFTHERADARDESIGNERANDTHEMARKET INGDEPARTMENTARENOTALWAYSTHESAME)TISAPPRECIATED HOWEVER THATSOMETIMESTHE MARKETINGMANAGERSOPINIONHASTOPREVAILIFTHECOMPANYISTOREMAININBUSINESS !NUMBEROFDIFFERENT2&POWERSOURCESHAVEBEENCONSIDEREDTHAT ATONETIMEOR OTHER HAVEBEENEMPLOYEDINRADAR.OTALLMIGHTBEPOPULARORDESIREDATSOMEPARTIC ULARTIMEBUTMOSTSHOULDBECONSIDERED EVENIFBRIEFLY BYTHERADARSYSTEMDESIGNER WHENTRYINGTODETERMINEANEWRADARSYSTEMDESIGNORANUPGRADEOFSOMEEXISTING SYSTEM/PINIONSABOUTTHEUTILITYOFTHEVARIOUSVACUUMTUBETRANSMITTERSMENTIONED HEREWILLBEBRIEFLYGIVENNEXT WITHTHESUGGESTIONTOTHEREADERTOKEEPINMINDTHAT CIRCUMSTANCESCANCHANGEANDTHESEOPINIONSCANCHANGEASWELL4HESEOPINIONSARE NOThWRITTENINSTONE vANDARENOTLIKELYTOBEUNIVERSALLYAGREEDTOBYALLTHOSEWHO WORKINRADAR"UTTHATISTHENATUREOFANYENGINEERINGENDEAVOR "RIEF/PINIONS!BOUTTHE5TILITYOF6ARIOUS2ADAR6ACUUM4UBES 4HETYPES OF2&POWERSOURCESAREMENTIONEDBELOWINNOPARTICULARORDER 'RID #ONTROLLED4UBE !LTHOUGHSOMEMIGHTTHINKTHESESHOULDHAVEDISAPPEARED ALONGWITHTHEOLDRADIOVACUUMTUBE THEREHAVEBEENMANY(& 6(& AND5(&RADARS THATSUCCESSFULLYOPERATEDWITHGRID CONTROLTUBES/FTENWITHSUCHRADARS ITWOULDCOST MORETOREPLACETHEMWITHSOLID STATETRANSMITTERS ANDTHEREMIGHTBELITTLEGAINEDBY DOINGSO4HEGRID CONTROLLEDTUBEKNOWNASTHECONSTANTEFFICIENCYAMPLIFIER#%!
£ä°ÓÈ
2!$!2(!.$"//+
ANDITSPREDECESSORSTHE)/4ANDTHE+LYSTRODE ARETHEONLY2&POWERSOURCESTHAT CANOPERATEEFFICIENTLYWHENAMPLITUDESHAPEDWAVEFORMSAREDESIREDFORMINIMIZING OUT OF BANDINTERFERENCETOOTHERRADARS4HUS THE#%!PROBABLYSHOULDBEACANDIDATE WHENCONSIDERINGANYNEW5(&RADARSYSTEM ASWELLASRADARSATLOWERFREQUENCIES ESPECIALLYIFMUTUALINTERFERENCEISAPOTENTIALPROBLEM -AGNETRON )T WAS MENTIONED THAT THE MAGNETRON WAS WHAT MADE MICROWAVE RADARPOSSIBLEINTHES4HEMAGNETRONISSTILLAVALIDCANDIDATEFORSMALL NON DOPPLERRADARSSUCHASCIVILMARINERADARS ALTHOUGHSUCHRADARSALSOHAVEBEENMANU FACTUREDWITHSOLID STATETRANSMITTERS)TISNOTLIKELYTHATMAGNETRONSWILLBEUSEDIN HIGHPERFORMANCERADARS ESPECIALLYTHOSETHATREQUIREAVERAGEPOWERSMORETHANONE OR TWO KILOWATTS OR WHERE -4) IMPROVEMENT FACTORS HAVE TO BE GREATER THAN TO D"&OREXAMPLE DURINGTHEPROCUREMENTOFTHE.EXRADDOPPLERWEATHERRADARIN THEMID S THEMAGNETRONWASCONSIDERED BUTITCOULDNOTMEETTHECLUTTERCAN CELLATIONSPECIFICATIONS WHICHISWHY.EXRADEMPLOYSAKLYSTRON)NTHEPAST SOME LONG RANGE!IR4RAFFIC#ONTROL!IR2OUTE3URVEILLANCE2ADARSUSEDAMAGNETRON BUT THEKLYSTRONSEEMSTOBETHEPREFERREDCHOICEFORTHISAPPLICATION #ROSSED &IELD!MPLIFIER !LTHOUGH THESE TUBES WERE EMPLOYED FOR SOME MAJOR RADARAPPLICATIONSBECAUSETHEYHAVEGOODEFFICIENCY REQUIRERELATIVELYLOWVOLTAGE ANDHAVEWIDEBANDWIDTHABOUT THEYARELESSLIKELYTOBEUSEDBECAUSETHEYARE NOISYWHICHAFFECTSTHEIRDOPPLER PROCESSINGPERFORMANCE THEYAREOFRELATIVELYLOW GAINWHICHREQUIRESTHETRANSMITTERTOHAVEMULTIPLESTAGES ANDBECAUSETHEKLYSTRON ISUSUALLYABETTEROVERALLCHOICE +LYSTRON 4HEORIGINALKLYSTRONSEMPLOYEDRESONANTCAVITIESTHATRESTRICTEDTHEIR BANDWIDTH4HEBANDWIDTHOFAKLYSTRON HOWEVER INCREASESASITSPOWERINCREASES 2ESONANTCAVITIESWERELATERREPLACEDBYWIDER BANDCIRCUITS WHICHWERERELATEDTO THETYPEOFCIRCUITSUSEDIN474S3UCHKLYSTRONSAREKNOWNASTHE#LUSTERED#AVITY +LYSTRON %XTENDED)NTERACTION+LYSTRON ANDTHE4WYSTRON7HENCONSIDERINGATRANS MITTERFORHIGH PERFORMANCERADAR THESEVARIANTSOFTHEKLYSTRONARELIKELYTOBEHIGHLY FAVOREDFORMANYAPPLICATIONS4HEKLYSTRONHASGOODSTABILITYANDLOWNOISESOASTO ENABLELARGER-4)IMPROVEMENTFACTORSTOBEOBTAINEDWHENUSINGTHEDOPPLERSHIFT TODETECTMOVINGTARGETSINCLUTTER!THIGHPOWER HIGHVOLTAGESHAVETOBEUSEDAND PROTECTIONFROM8 RAYSGENERATEDBYTHEHIGHVOLTAGEMUSTBEEMPLOYED(OWEVER THE-"+MULTIPLE BEAMKLYSTRON VERSIONOFTHEKLYSTRONCANBEUSEDTOACHIEVEHIGH POWERWITHLOWERVOLTAGE 4RAVELING7AVE4UBE !SMENTIONED THE474ANDTHEKLYSTRONCANHAVECOMPA RABLEBANDWIDTHSWHENTHETUBEPRODUCESHIGHPOWER4HEPERFORMANCEOFA474IS SIMILARTOTHATOFAWIDEBANDKLYSTRON EXCEPTTHATITMIGHTNOTBEASSTABLEASTHEKLYSTRON ANDHAVESLIGHTLYLESSGAIN4HEMICROWAVEPOWERMODULE-0- WHICHISACOMBINA TIONOFHELICAL474ANDSOLID STATEDEVICE HASNOTHADSIGNIFICANTAPPLICATIONINRADAR 'YROTRONS )F VERY HIGH POWER IS NEEDED AT MILLIMETER WAVE FREQUENCIES THE GYROTRONAMPLIFIEROROSCILLATORISTHEONLY2&POWERSOURCEAVAILABLE&ORLOW POWER RADARAPPLICATIONSATMILLIMETERWAVES THE%)+CANBEUSED 3OLID 3TATE!MPLIFIERSFOR2ADAR4RANSMITTERS 3OLID STATETRANSMITTERSAND VACUUM TUBE TRANSMITTERS HAVE SIGNIFICANT DIFFERENCES YET THEY ARE BOTH EMPLOYED
4(%2!$!242!.3-)44%2
£ä°ÓÇ
INRADAR3OMEOFTHESEDIFFERENCESAREMENTIONEDIN3ECTIONOF#HAPTERh3OLID 3TATE4RANSMITTERSv"RIEFLY PROPONENTSOFSOLIDSTATEMIGHTSAYTHATTHEYDONOTNEED AHOTCATHODEASDOESAVACUUMTUBE DONOTREQUIREHIGHVOLTAGESORMAGNETS DONOT PRODUCE8 RAYRADIATIONSASSOMEVACUUMTUBESDO HAVEhGRACEFULDEGRADATION vAND THATMAINTAINABILITYISITSKEYASSET/NTHEOTHERHAND PROPONENTSOFVACUUMTUBES MIGHTSAYTHATRADARSUSINGSOLID STATETRANSMITTERSHAVELIMITEDPEAKPOWERANDTHUS NEED TO OPERATE WITH A LONG PULSE AND A HIGH DUTY CYCLE WHICH REQUIRE THE USE OF PULSECOMPRESSION4HELONGPULSECANMASKORECLIPSETARGETECHOESATSHORTRANGESO THATANADDITIONALSHORTPULSETRANSMISSIONISNEEDEDTOUNMASKTHEECLIPSEDECHOES AT SHORT RANGES7HEN 3ENSITIVITY4IME #ONTROL WHICH HAS A VARYING RECEIVER GAIN WITHRANGE ISUSEDWITHALONGPULSEANDPULSECOMPRESSION DISTORTIONCANRESULTIN THECOMPRESSEDPULSE)THASALSOBEENSAIDTHATSOLID STATETRANSMITTERSAREOFTENLESS EFFICIENT THEY MIGHT BE HEAVIER AND THEIR COST MIGHT BE GREATER THAN AN EQUIVALENT VACUUMTUBERADARSYSTEM4HEABOVEHAVEALLBEENSAIDATONETIMEORANOTHER BUT THEREISNOTUNIVERSALAGREEMENTABOUTTHEIMPORTANCEOFTHESECHARACTERISTICSFORALL RADARAPPLICATIONS 4HERADARENGINEERSHOULDNOTSIMPLYCOMPARETHEPARTICULARDIFFERENCESBETWEEN ASOLID STATETRANSMITTERANDAVACUUMTUBETRANSMITTERWHENDETERMININGWHATTYPE OF2&POWERSOURCETOUSEINANYPARTICULARAPPLICATION4HECHOICEBETWEENTHETWO SHOULDBEMADEBYCOMPARINGARADARSYSTEMDESIGNEDTOEFFECTIVELYUSESOLIDSTATE ANDARADARSYSTEMDESIGNEDTOEFFECTIVELYUSEVACUUMTUBES!SSUMINGTHESOLIDSTATE ANDVACUUMTUBERADARSAREDESIGNEDTOPROVIDEIDENTICALPERFORMANCEFORTHEDESIRED APPLICATION THENTHECHOICESHOULDBEBASEDONCOMPARINGCOST SIZE WEIGHT RELIABIL ITY MAINTAINABILITY ANDANYOTHERSYSTEMREQUIREMENTTHATISIMPORTANTFORDECISION MAKING5NFORTUNATELY THISISNOTALWAYSDONE"UYERSOFRADARSSHOULDBEENCOUR AGEDNOTTOINSISTTHATTHERADARDESIGNERUSESOMEPARTICULARTECHNOLOGYBECAUSEITIS CONSIDEREDTHEFASHIONABLETHINGTODOATTHETIME4HEYMIGHTNOTALWAYSBEGETTING THEBESTRADARFORTHEPARTICULARAPPLICATION 4HEREHAVEBEENATLEASTTHREEWAYSTOAPPLYSOLID STATETRANSMITTERSTOHIGH PERFOR MANCERADARS ASAREPLACEMENTFORAVACUUMTUBETRANSMITTERINANALREADYEXIST INGRADAR ASTHETRANSMITTERFORANEWRADARDESIGNAND ASANACTIVEAPERTURE PHASEDARRAYRADAR !N EXAMPLE OF REPLACING AN EXISTING VACUUM TUBE TRANSMITTER WITH A SOLID STATE TRANSMITTERISTHE53.AVYS!.303 ARELATIVELYMODESTCAPABILITY5(&RADAR FORAIRSURVEILLANCE4HISRADARWASCHOSENFORHAVINGITSVACUUMTUBETRANSMITTER REPLACEDWITHASOLID STATETRANSMITTERUSINGTRANSISTORAMPLIFIERSBECAUSEITALREADY USEDALONGPULSEWAVEFORMWITHAHIGHDUTYCYCLEANDPULSECOMPRESSION WHICHIS WHATSOLID STATERADARSUSUALLYREQUIRE4HESOLID STATETRANSMITTERWASPUTINTOPRODUC TIONANDINSTALLEDINEXISTINGRADARS)TDIDTHEJOBITWASSUPPOSEDTODO BUTITISNOT OBVIOUSTHATTHESOLID STATETRANSMITTERHADANETADVANTAGEOVERTHETUBETRANSMITTER 4HESOLID STATETRANSMITTERWASSUPPOSEDTOOCCUPYTHESAMEFLOORSPACEASTHEVACUUM TUBETRANSMITTER BUTITOCCUPIEDABOUTTHESAMEFLOORSPACEASTHEENTIRE!.303 RADAR WHICHUSEDAVACUUMTUBE!LSOTHESOLID STATETRANSMITTERCOSTMORETHANTHE TUBEVERSION/NEHIGHLYSIGNIFICANTADVANTAGEOFTHESOLID STATEVERSIONOFTHE303 HOWEVER WASTHATITCOULDINCLUDESPARESOLID STATEMODULESASPARTOFTHETRANSMITTER ITSELF SOTHATTIMETOREPAIRWASREDUCED !NEXAMPLEOFTHESECONDAPPROACHTOACHIEVINGASOLID STATERADARTRANSMITTERIS THE!32 AIRPORTSURVEILLANCERADAR)NTHEMID S THE!32 AIRSURVEILLANCE RADAR AT 3 BAND WAS DEVELOPED BY .ORTHROP 'RUMMAN THEN7ESTINGHOUSE FOR USE AT MAJOR AIRPORTS TO CONTROL LOCAL AIR TRAFFIC )T WAS AN EXCELLENT RADAR THAT USED A
£ä°Ón
2!$!2(!.$"//+
WELL TESTEDKLYSTRONAMPLIFIERVACUUMTUBE ANDITWASINSTALLEDTHROUGHOUTTHE5NITED 3TATES4HESAMETUBEISUSEDINTHE.EXRADDOPPLERWEATHERRADAR (OWEVER INTHE LATESSOLID STATETECHNOLOGYHADADVANCEDSUFFICIENTLYSOTHAT.ORTHROP'RUMMAN DEVELOPEDTHE!32 ALSOAT3BAND USINGASOLID STATETRANSMITTER)TSOVERALLRADAR PERFORMANCEWASSIMILARTOTHE!32 BUTITWASNOTJUSTAREPLACEMENTOFTHETRANSMIT TERBUTANEWDESIGNTOUSESOLID STATETRANSMITTERSEFFECTIVELY)TALSOTOOKIMPORTANT ADVANTAGEOFADVANCESINDIGITALRECEIVERSANDDIGITALPROCESSINGTHATOCCURREDSINCETHE DEVELOPMENTOFTHE!32 TOSIGNIFICANTLYIMPROVEWHATCOULDBEACCOMPLISHEDWITH THISRADAR!SMENTIONED SOLID STATETRANSMITTERSREQUIRETHEUSEOFLONGPULSES4HE !32 EMPLOYEDA§SPULSEDURATIONATAPEAKPOWEROFK74HISMEANSTHAT TARGETSOUTTOARANGEOFABOUTNMIWOULDBEMASKED ORECLIPSED BYTHELONGPULSE ANDMIGHTNOTBEDETECTED4ODETECTTARGETSATRANGESMASKEDBYTHELONGPULSE ASEC ONDSHORT PULSE§SINDURATION ANDATADIFFERENTFREQUENCYFROMTHELONGPULSE WAS TRANSMITTEDALMOSTIMMEDIATELYAFTERTHELONGPULSE)TDETECTSTARGETSWITHINTHERANGE FROMNMIORLESSTOARANGEOFABOUTNMI4HELONGPULSEEMPLOYSNONLINEAR&- PULSECOMPRESSIONWITHAPULSECOMPRESSIONRATIOTOACHIEVEARANGERESOLUTIONOF LESSTHANNMIASREQUIREDFORANAIR TRAFFICCONTROLRADAR4YPICALTIME SIDELOBESWITH THENONLINEAR&-WAVEFORMWERED"BELOWTHEPEAKRESPONSE)TMIGHTBENOTEDTHAT #OLEETALSTATETHATINORDERhTOENSURECONTINUEDAVAILABILITYOFTHEPOWERTRANSISTORS REQUIREDTOPRODUCETHEPOWERAMPLIFIERPANELS .ORTHROP'RUMMANHASDEVELOPEDAN IN HOUSEMANUFACTURINGCAPABILITYFORHIGH POWER3 BANDTRANSISTORSv 4HETHIRDAPPROACHTOEMPLOYINGSOLID STATETRANSMITTERSISTHEACTIVEAPERTUREPHASED ARRAYRADAR!TEACHELEMENTOFAPHASEDARRAYRADARANTENNAISASOLID STATEMODULE KNOWNASA42MODULE THATCONTAINSATRANSMITTER RECEIVER ANDDUPLEXER4HEVACUUM TUBEISNOTUSUALLYCOMPETITIVEFORTHISAPPLICATION)N#HAPTER h-ULTIFUNCTIONAL2ADAR 3YSTEMSFOR&IGHTER!IRCRAFT vTHEACTIVEAPERTURERADARISCALLEDAN!CTIVE%LECTRONICALLY 3CANNED!NTENNA!%3! 4HESUBSECTIONENTITLEDh!CTIVE%LECTRONIC3CANNED!RRAY !%3! vIN3ECTION DESCRIBESQUITEWELLTHEMILITARYAIRBORNEAPPLICATIONOFSOLID STATERADAR ANDENUMERATESITSADVANTAGESANDWHYITISIMPORTANT4HEREITISSTATED THAThONEOFTHEPRINCIPALADVANTAGESOFAN!%3!ISTHEABILITYTOMANAGEBOTHPOWER ANDSPATIALCOVERAGEONASHORT TERMBASISSOFMS v)TISALSOSAIDTHAThBANDWIDTH OFSEVERAL'(ZONTRANSMITvISREQUIRED ANDTHISISWITHINTHECAPABILITYOFSOLID STATE TRANSMITTERS4HEREADERISREFERREDTO3ECTION #HAPTER AND3ECTIONFOR FURTHERINFORMATIONABOUTTHISIMPORTANTAPPLICATIONOFSOLID STATE !LTHOUGHANYOFTHE2&POWERSOURCESMENTIONEDHERECOULDBEUSEDINFUTURE RADARSYSTEMS ITSEEMSLIKELYTHATTHELINEAR BEAMAMPLIFIER PARTICULARLYONEOFTHE VARIANTSOFTHEKLYSTRON MIGHTBETHEFIRST2&POWERSOURCETOCONSIDERFORAHIGH PERFORMANCEMICROWAVERADARTHATEMPLOYSAMECHANICALLYSTEEREDANTENNAORACON VENTIONAL PHASED ARRAY RADAR THAT DOES NOT EMPLOY THE ACTIVE APERTURE &OR ACTIVE APERTUREPHASEDARRAYRADARS ITISLIKELYTHATTHESOLID STATETRANSISTORAMPLIFIERWILL BETHECHOICE
, ,
-)3KOLNIK )NTRODUCTIONTO2ADAR3YSTEMS .EW9ORK-C'RAW (ILL P !3'ILMOUR *R -ICROWAVE4UBES .ORWOOD -!!RTECH(OUSE 7*$ODDS 4-ORENO AND7*-C"RIDE *R h-ETHODSFORINCREASINGTHEBANDWIDTHOFHIGH POWERMICROWAVEAMPLIFIERS v)2%7%3#/.#ONV2EC PT PPn
4(%2!$!242!.3-)44%2
£ä°Ó
2*"ARKERETAL -ODERN-ICROWAVEAND-ILLIMETER 7AVE0OWER%LECTRONICS .EW9ORK)%%% 0RESSAND7ILLEY)NTERSCIENCE P !3'ILMOUR *R 0RINCIPLESOF4RAVELING7AVE4UBES "OSTON -!!RTECH(OUSE 3EC 233YMONS h4UBES3TILLVITALAFTERALLTHESESYEARS v)%%%3PECTRUM VOL PPn !PRIL 2-0HILLIPSAND$73PREHN h(IGH POWERKLYSTRONSFORTHENEXTLINEARCOLLIDER v0ROC)%%% VOL PPn -AY 2(!BRAMS ",EVUSH !!-ONDELLI AND2+0ARKER h6ACUUMELECTRONICSFORTHEST CENTURY v)%%%-ICROWAVE-AGAZINE PPn 3EPTEMBER '3.USINOVICH ",EVUSH AND$!BEh!REVIEWOFTHEDEVELOPMENTOFMULTIPLE BEAM KLYSTRONS AND 474S v .AVAL 2ESEARCH ,ABORATORY 7ASHINGTON $# -2 -ARCH 2(!BRAMS ",EVUSH !!-ONDELLI AND2+0ARKER h6ACUUMELECTRONICSFORTHEST CENTURY v)%%%-ICROWAVE-AGAZINE PPn 3EPTEMBER !.+OROLYOV %!'ELVICH 96:HARY !$:AKURDAYEV AND6)0OOGNIN h-ULTIPLE BEAM KLYSTRONAMPLIFIERSPERFORMANCEPARAMETERSANDDEVELOPMENTTRENDS v)%%%4RANS VOL03 PPn *UNE 2*"ARKERETAL -ODERN-ICROWAVEAND-ILLIMETER 7AVE0OWER%LECTRONICS .EW9ORK)%%% 0RESSAND7ILLEY)NTERSCIENCE 3EC 7(9OCOM h(IGHPOWERTRAVELINGWAVETUBES4HEIRCHARACTERISTICSANDSOMEAPPLICATIONS v -ICROWAVE* VOL PPn *ULY ! 3 'ILMOUR *R 0RINCIPLES OF 4RAVELING 7AVE 4UBES "OSTON -! !RTECH (OUSE 3EC ( ' +OSMAHL h-ODERN MULTISTAGE DEPRESSED COLLECTORS! 2EVIEW v 0ROC )%%% VOL PPn .OVEMBER !3'ILMOUR *R -ICROWAVE4UBES .ORWOOD -!!RTECH(OUSE 3EC -*3MITHAND'0HILLIPS 0OWER+LYSTRONS4ODAY .EW9ORK*OHN7ILEY 3EC ! % 3TAPRANS 7 -C#UNE AND * ! 2UETZ h(IGH POWER LINEAR BEAM TUBES v 0ROC )%%% VOL PPn -ARCH !3'ILMOUR *R -ICROWAVE4UBES .ORWOOD -!!RTECH(OUSE 3EC !2OITMAN $"ERRY AND"3TEER h3TATE OF THE ART7 BANDEXTENDEDINTERACTIONKLYSTRONFOR THE#LOUD3ATPROGRAM v)%%%4RANS VOL%$ PPn -AY 233YMONSAND*2-6AUGHAN h4HELINEARTHEORYOFTHECLUSTEREDCAVITYKLYSTRON v)%%% 4RANS VOL03 PPn /CTOBER 233YMONS h4UBES3TILLVITALAFTERALLTHESEYEARS v)%%%3PECTRUM VOL PPn !PRIL 2(!BRAMS *R h4HEMICROWAVEPOWERMODULE!@SUPERCOMPONENTvFORRADARTRANSMITTERS v 2ECORDOFTHE)%%%.ATIONAL2ADAR#ONF !TLANTA '! PPn #23MITH #-!RMSTRONG AND*$UTHIE h4HEMICROWAVEPOWERMODULE!VERSATILEBUILDING BLOCKFORHIGH POWERTRANSMITTERS v0ROC)%%% VOL PPn -AY -)3KOLNIK )NTRODUCTIONTO2ADAR3YSTEMS RD%D .EW9ORK-C'RAW (ILL 3EC . "UTLER h4HE MICROWAVE TUBE RELIABILITY PROBLEM v -ICROWAVE * VOL PP n -ARCH 0 $ , 7ILLIAMS #IVIL MARINE RADAR ,ONDON )NSTITUTION OF %LECTRICAL %NGINEERS 3EC - ) 3KOLNIK )NTRODUCTION TO 2ADAR 3YSTEMS RD %D .EW9ORK -C'RAW (ILL #OMPANIES 3EC !3'ILMOUR *R -ICROWAVE4UBES .ORWOOD -!!RTECH(OUSE 3EC ,,#LAMPITT h3 "ANDAMPLIFIERCHAIN v2AYTHEON#OMPANY 7ALTHAM-! PRESENTEDAT.!4/ #ONF-ICROWAVE4ECHNIQUES 0ARIS -ARCH 6,'RANATSTEINAND)!LEXOFF (IGH0OWER-ICROWAVE3OURCES "OSTON!RTECH(OUSE !3'ILMOUR *R -ICROWAVE4UBES .ORWOOD -!!RTECH(OUSE #HAP
£ä°Îä
2!$!2(!.$"//+
+,&ELCHETAL h#HARACTERISTICSANDAPPLICATIONSOFFAST WAVEGYRODEVICES v0ROC)%%% VOL PPn -AY -"LANKETAL h$EVELOPMENTANDDEMONSTRATIONOFHIGH AVERAGEPOWER7 BANDGYRO AMPLIFIERS FORRADARAPPLICATIONS v)%%%4RANSVOL03 PPn *UNE '*,INDEETALPRIVATECOMMUNICATION h7ARLOC!HIGH POWERCOHERENT'(ZRADARv *0-URRAY h%LECTROMAGNETICCOMPATIBILITY v#HAPIN2ADAR(ANDBOOK ST%D PPTO 4 ! 7EIL h%FFICIENT SPECTRUM CONTROL FOR PULSED RADAR TRANSMITTERS v #HAP IN 2ADAR 4ECHNOLOGY %"ROOKNERED .ORWOOD -!!RTECH(OUSE *0-URRAY h%LECTROMAGNETICCAPABILITY v#HAPIN2ADAR(ANDBOOK ST%D -3KOLNIK ED .EW9ORK-C'RAW (ILL % "ROOKNER AND 2 * "ONNEAU h3PECTRA OF ROUNDED TRAPEZOIDAL PULSES HAVING AN!-0- MODULATION AND ITS APPLICATION TO OUT OF BAND RADIATION v -ICROWAVE * VOL PP n $ECEMBER !!!CKER h%LIMINATINGTRANSMITTEDCLUTTERINDOPPLERRADARSYSTEMS v-ICROWAVE* VOL .O PPn .OVEMBER - 4 .GO 6 'REGERS (ANSEN AND ( 2 7ARD h4RANSMITTER NOISE COMPENSATION! SIGNAL PROCESSINGTECHNIQUEFORIMPROVINGCLUTTERSUPPRESSION v0ROC)%%%#ONFERENCEON2ADAR n!PRIL PPn 4%6INGST $2#ARTER *!%SHLEMAN AND*-0AWLIKOWSKI h(IGH POWERGRIDDEDTUBES v0ROC)%%% VOL PPn -ARCH 233YMONS h4UBES3TILLVITALAFTERALLTHESEYEARS v)%%%3PECTRUM VOL PPn !PRIL 6,'RANATSTEIN 2+0ARKER AND#-!RMSTRONG h6ACUUMELECTRONICSATTHEDAWNOFTHE TWENTY FIRSTCENTURY v0ROC)%%% VOL PPn -AY 233YMONS h4HECONSTANTEFFICIENCYAMPLIFIER v.!""ROADCAST%NGR#ONF0ROC PPn 233YMONSETAL h4HECONSTANTEFFICIENCYAMPLIFIER!PROGRESSREPORT vPRESENTEDAT.!" "ROADCAST%NGR#ONF0ROC , 3IVAN h4HE MODULATOR v #HAP IN -ICROWAVE 4UBE 4RANSMITTERS ,ONDON #HAPMAN (ALL 4!7EIL h4RANSMITTERS v#HAPIN2ADAR(ANDBOOK ND%D .EW9ORK-C'RAW (ILL 3EC h0ULSEMODULATORSv 4!7EIL h4RANSMITTERS v#HAPIN2ADAR(ANDBOOK ND%D .EW9ORK-C'RAW (ILL PPTO - 0 * 'AUDREAU ET AL h3OLID STATE RADAR MODULATORS v PRESENTED AT TH )NTERNATIONAL 0OWER-ODULATOR3YMPOSIUM *UNE!VAILABLEFROM$IVERSIFIED4ECHNOLOGIES )NC WWWDIVTECSCOM -'AUDREAUETAL h3OLID STATEUPGRADEFORTHE#/"2!*5$93 BANDPHASEDARRAYRADAR vPRE SENTEDAT)%%%2ADAR#ONFERENCE!VAILABLEFROM$4))NTERNETSITEWWWDIVTECSCOM -'AUDREAUETAL h(IGHPERFORMANCE SOLID STATEHIGHVOLTAGERADARMODULATORS vPRESENTEDAT 0ULSED0OWER#ONFERENCE!VAILABLEFROM$4))NTERNETSITEWWWDIVTECSCOM + * ,EE # #ORSON AND ' -OLS h! K7 SOLID STATE !.303 RADAR TRANSMITTER v -ICROWAVE* VOL PPn *ULY *74AYLOR *RAND'"RUNNIS h$ESIGNOFANEWAIRPORTSURVEILLANCERADAR!32 v 0ROC )%%% VOL PPn &EBRUARY % , #OLE ET AL h!32 ! NEXT GENERATION SOLID STATE AIR TRAFFIC CONTROL RADAR v 0ROC FOR 2!$!2#/. )%%%2ADAR#ONFERENCE n-AY PPn
#HAPTER
-`-Ì>ÌiÊ/À>ÃÌÌiÀÃ V
>iÊ/°Ê ÀÜÃ 2AYTHEON#OMPANY
££°£Ê /," 1 /" &ORCOMMERCIALAPPLICATIONS THETRANSISTORHASALLBUTREPLACEDVACUUMTUBETECHNOL OGYINTRANSMITTERSOPERATINGAT6(&ANDBELOW3INCETHES THEPOWEROUTPUT CAPABILITYAMONGVARIOUSSOLID STATETECHNOLOGIESHASINCREASEDTOTHEPOINTWHERETHEY AREACTIVELYPURSUEDASREPLACEMENTSFORSOMEVACUUMELECTRONICSINRADARTRANSMITTERS THISISNOT HOWEVER AUNIVERSALLYATTRACTIVESOLUTION4HETRANSITIONFROMHIGH POWER KLYSTRONS TRAVELINGWAVETUBES474S CROSSED FIELDAMPLIFIERS#&!S ANDMAGNE TRONS TOSOLID STATEELECTRONICSHASACTUALLYBEENVERYGRADUALBECAUSETHEPOWEROUTPUT OFINDIVIDUALSOLID STATEDEVICESISQUITELIMITEDCOMPAREDTOTYPICALRADARREQUIREMENTS .EVERTHELESS TRANSMITTERDESIGNERSHAVELEARNEDTHATTHEREQUIREDHIGHERPOWERLEVELS FORRADARTRANSMITTERSCANBEACHIEVEDWITHASOLID STATETECHNOLOGYBECAUSETRANSIS TORSANDTRANSISTORAMPLIFIERMODULESCANBEREADILYCOMBINEDINPARALLELTOACHIEVE ACOMPOSITEHIGHEREQUIVALENTPOWEROUTPUT!SDEPICTEDIN&IGURE THISDESIGN ATTRIBUTEHELPSTOEXTENDTHESOLID STATEPERFORMANCEENVELOPEWELLINTOTHEREGIONTHAT HADPREVIOUSLYBEENDOMINATEDBYONLYVACUUMELECTRONICS )TISNOTTHEINTENTOFTHIS CHAPTER TO DELINEATE THE RELATIVE MERITS OF THESE SOMETIMES COMPETING TECHNOLOGIES BUTRATHERTODESCRIBETHELIMITS DESIGNPRACTICES ANDCHARACTERISTICSOFTHESOLID STATE TECHNOLOGYFORUSEINTHECOMMONRADARFREQUENCYRANGES4HEADVANTAGESOFSOLID STATETECHNOLOGIESWILLBEDESCRIBEDSOMEOFTHEKEYSEMICONDUCTORTECHNOLOGIESAND DEVICESWILLBEDISCUSSEDANDSOMEEXAMPLESOFSOLID STATECOMPONENTANDTRANSMITTER DESIGNWILLBEPRESENTED
££°ÓÊ 6 / -Ê"Ê-" Ê-// !LTHOUGH THE GAP IN PERFORMANCE CAPABILITIES BETWEEN THE SOLID STATE AND VACUUM ELECTRONICSTECHNOLOGIESCANBEWIDE THERESTILLEXISTRELEVANTTRADESINVOLVINGCOST MAINTAINABILITY ANDRELIABILITY ANDTHISDESIGNTRADESPACECANBEVERYCOMPLICATED 3OMEPOINTTOTHECONTINUEDMATURATIONOFVACUUMELECTRONICSANDSUGGESTTHATBOTH VACUUMTUBESANDSOLID STATEDEVICESWILLBEAPPEALINGINHIGHPERFORMANCERADARSFOR MANYYEARSTOCOME/THERSNOTESTILLTHATTHEBESTVALUEINELECTRONICEQUIPMENTISPRO VIDEDWHENTHEhAPPROPRIATETECHNOLOGYvISAPPLIEDTOAFFORDABLEMILITARYELECTRONICS RECOGNIZINGTHATTUBESANDSOLIDSTATEMAYREMAINASCOMPLEMENTARYDESIGNSOLUTIONS ££°£
££°Ó
2!$!2(!.$"//+
&)'52% "YCOMBININGTHEOUTPUTSOFTHOUSANDSOFTRANSISTORAMPLIFIERS THECUMULATIVEAVERAGEPOWEROUTPUTOFSOLID STATETECHNOLOGIESCANEFFECTIVELY COMPETEWITHTHEPERFORMANCECAPABILITIESOFVACUUMTUBETECHNOLOGY ASSHOWN INTHECENTEROVERLAPREGIONWHERECOMPETINGAMPLIFIERSOLUTIONSCOEXIST
FORFUTURESYSTEMREQUIREMENTS&OREXAMPLE MICROWAVEPOWERTUBESCONTINUETOPRO VIDESIGNIFICANTLYHIGHERPOWEROUTPUTANDEFFICIENCIESTHANSOLID STATEPOWERAMPLI FIERSFORHIGHPERFORMANCEMILLIMETER WAVERADARS#OMPAREDWITHTUBES SOLID STATE DEVICESOFFERTHEFOLLOWINGADVANTAGES .OHOTCATHODESAREREQUIREDTHEREFORE THEREISNOWARMUPDELAY NOWASTEDHEATER POWER ANDVIRTUALLYNOLIMITONTRANSISTOROPERATINGLIFE5NDERCERTAINOPERATING CONDITIONS THEPREDICTIONOFTHEMEDIANTIMETOFAILURE-44& FORSOME2&TRANSIS TORSCANEXCEED YEARS 4RANSISTORAMPLIFIERSOPERATEATMUCHLOWERVOLTAGESTHEREFORE POWERSUPPLYVOLT AGESAREONTHEORDEROFVOLTSRATHERTHANKILOVOLTSTOAVOIDTHENEEDFORLARGESPAC INGS OILFILLING ORENCAPSULATION#OMPAREDWITHAHIGH VOLTAGEPOWERSUPPLY A LOW VOLTAGESUPPLYUSESFEWERNONSTANDARDPARTSANDISGENERALLYLESSEXPENSIVE 4RANSMITTERSDESIGNEDWITHSOLID STATEDEVICESEXHIBITIMPROVEDMEANTIMEBETWEEN FAILURES -4"& IN COMPARISON WITH TUBE TYPE TRANSMITTERS !MPLIFIER MODULE -4"&S GREATER THAN HOURS HAVE BEEN EXTRAPOLATED FROM ACCELERATED LIFE TESTING!FACTOROFIMPROVEMENTINTRANSMITTERSYSTEM-4"&HASBEENREPORTED FORAN3BANDSOLID STATETRANSMITTERREPLACINGAKLYSTRONTRANSMITTER 'RACEFULDEGRADATIONOFSYSTEMPERFORMANCEOCCURSWHENINDIVIDUALMODULESFAIL 0OWEROUTPUTDEGRADESBY LOGnA ASDEVICESFAIL WHEREAISTHEFRACTIONOF FAILEDDEVICES4HISRESULTSBECAUSEALARGENUMBEROFSOLID STATEDEVICESMUSTBE COMBINEDTOPROVIDETHEPOWERFORARADARTRANSMITTER ANDTHEYAREEASILYCOMBINED INWAYSTHATDEGRADEGRACEFULLYWHENINDIVIDUALUNITSFAIL 4HEABILITYTODEMONSTRATEWIDEBANDWIDTHISASIGNIFICANTCHARACTERISTICOFSOLID STATEDEVICES7HILEHIGH POWERMICROWAVERADARTUBESCANACHIEVETOBAND WIDTH SOLID STATETRANSMITTERMODULESCANACHIEVEUPTOBANDWIDTHORMORE WITHACCEPTABLEEFFICIENCY
L
L
L
L
L
3/,)$ 34!4%42!.3-)44%23
££°Î
&LEXIBILITYCANBEREALIZED!MODULEWITHBOTHTRANSMITANDRECEIVEPATHAMPLIFIERS 42MODULE CANBEASSOCIATEDWITHEVERYANTENNAELEMENTINPHASEDARRAYSYS TEMS2&DISTRIBUTIONLOSSESTHATNORMALLYOCCURINATUBE POWEREDSYSTEMBETWEEN APOINT SOURCETUBEAMPLIFIERANDTHEFACEOFTHEARRAYARETHUSELIMINATED)NADDI TION PHASESHIFTINGFORBEAMSTEERINGCANBEIMPLEMENTEDATLOWPOWERLEVELSONTHE INPUTFEEDSIDEOFANACTIVEARRAYMODULETHISAVOIDSTHEHIGH POWERLOSSESOFTHE PHASESHIFTERSATTHERADIATINGELEMENTSANDRAISESOVERALLEFFICIENCY!LSO PEAK2& POWERLEVELSATANYPOINTARERELATIVELYLOWBECAUSETHEOUTPUTSARECOMBINEDONLY INSPACE&URTHERMORE AMPLITUDETAPERINGCANBEACCOMPLISHEDBYTURNINGOFFOR ATTENUATINGINDIVIDUALACTIVEARRAYAMPLIFIERS&ORPHASEDARRAYSYSTEMSWITHMODEST POWERLEVELS THESOLID STATESOLUTIONOFFERSADVANTAGESTHATMAKEITATTRACTIVEASTHE BASISFORARADARTRANSMITTER
L
4HEGENERALREPLACEMENTOFHIGH POWERMICROWAVETUBESBYSOLID STATEDEVICESHAS NOTBEENSTRAIGHTFORWARD!TTEMPTSTOREPLACEEXISTINGTUBE TYPETRANSMITTERSWITHASOLID STATERETROFITHAVEBEENHINDEREDBYTHEREQUIREMENTTOBEAFORM FIT FUNCTIONALREPLACE MENTFORTHEINCUMBENTHARDWARE2ADARTRANSMITWAVEFORMSTHATPREVIOUSLYHADBEEN ARCHITECTEDTOMAKEOPTIMUMUSEOFTHEHIGHPEAKPOWERANDLOWDUTYCYCLECAPABILITY OFTHETUBENOLONGERFAVORTHESOLID STATETRANSMITTER!LOWDUTYCYCLEENVIRONMENTIS NOTTHEMOSTCOST EFFECTIVESOLUTIONFORSOLID STATEDEVICESBECAUSETRANSISTORSEXHIBIT MUCHSHORTERTHERMALTIMECONSTANTSTHANTHEREPLACEMENTTUBEANDAREMOREEFFICIENTLY OPERATEDUSINGALOWERCOMPOSITEPEAKPOWERATAHIGHERDUTYCYCLE!SANEXAMPLEOF THEDILEMMA AN, BANDMICROWAVETRANSISTORTHATISCAPABLEOFPERHAPSWATTS7 AVERAGEPOWERCANNOTPROVIDEMUCHMORETHANWATTSOFPEAKPOWERWITHOUTOVER HEATINGDURINGTHEPULSE4HESHORTPULSELENGTHSANDLOWDUTYCYCLESTYPICALOFOLDER TUBE TYPERADARSTHUSMAKEVERYINEFFICIENTUSEOFTHEAVERAGEPOWERCAPABILITIESOF MICROWAVE TRANSISTORS4O REPLACE THE OLD WELL PROVEN * , BAND MAGNETRON THAT DEVELOPS7OFAVERAGE2&POWERATTYPICAL DUTYCYCLEWOULDREQUIRE TOOFTHE WATTTRANSISTORSJUSTDESCRIBED(OWEVER WITHADUTYCYCLETHE WATTAVERAGEPOWERREQUIREMENTCOULDBEPROVIDEDBYONLYTOOFTHE WATT TRANSISTORS)NOTHERWORDS MICROWAVETRANSISTORSAREMUCHMORECOST EFFECTIVEWHEN THEREQUIREDRADARSYSTEMAVERAGEPOWERCANBEPROVIDEDBYALOWERPEAKPOWERATA HIGHERDUTYCYCLE!SARESULT THEREHAVEBEENRELATIVELYFEWDIRECTREPLACEMENTSOF OLDERLOWDUTYCYCLETRANSMITTERSBYSOLID STATETRANSMITTERS3OMEINITIATIVES SUCHAS THESOLID STATE!.303 REPLACEMENTTHATWASMOTIVATEDBYTHEATTRACTIVERELIABILITY MAINTAINABILITY ANDAVAILABILITYCHARACTERISTICSOFAMODULARSOLID STATESYSTEM HAVE NOTSEENTHESUCCESSONCEENVISIONEDDUETOTHEACQUISITIONCOSTOFSOLID STATEREPLACE MENTTRANSMITTERS&ORNEWRADARSYSTEMS SYSTEMDESIGNERSHAVEBEENMOTIVATEDBY THESECONSIDERATIONSTOCHOOSEASHIGHADUTYCYCLEASPOSSIBLE BOTHTOREDUCETHEPEAK POWERREQUIREDANDTOPERMITUSINGSOLID STATEDEVICESATAREASONABLECOST 4HEDECISIONTOUSEAHIGHTRANSMITTERDUTYCYCLE HOWEVER HASSIGNIFICANTIMPACT ONTHERESTOFTHERADARSYSTEM/PERATIONATAHIGHDUTYCYCLEGENERALLYREQUIRESTHE USEOFPULSECOMPRESSIONTOPROVIDETHEDESIREDUNAMBIGUOUSRANGECOVERAGETOGETHER WITHREASONABLYSMALLRANGERESOLUTION/THERCONSEQUENCESFOLLOWINTURNTHEWIDE TRANSMITTEDPULSEUSEDWITHPULSECOMPRESSIONBLINDSTHERADARATSHORTRANGES SOA hFILL INvPULSEMUSTALSOBETRANSMITTEDANDPROCESSED4OPREVENTPOINTSOFSTRONGCLUT TERFROMMASKINGSMALLMOVINGTARGETS THESIGNALPROCESSORMUSTACHIEVELOWPULSE COMPRESSIONTIMESIDELOBESANDHIGHCLUTTERCANCELLATIONRATIO!SARESULT ITISMUCH EASIERTODESIGNASOLID STATETRANSMITTERASPARTOFANEWSYSTEMTHANITISTORETROFITONE INTOANOLDSYSTEMTHATUSUALLYDOESNOTHAVEALLTHESEFEATURES
££°{
2!$!2(!.$"//+
4HEUSEOF SOLID STATEDOES NOTELIMINATEALLTHEPROBLEMSOF TRANSMITTERDESIGN 4HE2&COMBININGNETWORKSMUSTBEDESIGNEDWITHGREATCAREANDSKILLTOMINIMIZE COMBININGLOSSESINORDERTOKEEPTRANSMITTEREFFICIENCYHIGH3UITABLEISOLATIONFROM EXCESSIVEVOLTAGE STANDING WAVERATIO6372 MUSTBEPROVIDEDTOPROTECTTHEMICRO WAVETRANSISTORSFROMUNDESIREDOPERATIONALSTRESSES ANDTHEIRHARMONICPOWEROUTPUT MUSTBEPROPERLYFILTEREDTOMEET-), 34$ ANDOTHERSPECIFICATIONSON2&SPEC TRUMQUALITY!LSO JUSTASINTUBE TYPETRANSMITTERS ENERGYMANAGEMENTISSTILLCRUCIAL %ACHDCPOWERSUPPLYMUSTHAVEACAPACITORBANKLARGEENOUGHTOSUPPLYTHEENERGY DRAWNBYITSSOLID STATEMODULESDURINGANENTIREPULSE ANDEACHPOWERSUPPLYMUST RECHARGEITSCAPACITORBANKSMOOTHLYBETWEENPULSESWITHOUTDRAWINGANEXCESSIVE CURRENTSURGEFROMTHEPOWERLINE !S A RESULT OF UNAVOIDABLE LOSSES IN COMBINING THE OUTPUTS OF MANY SOLID STATE DEVICES ITISESPECIALLYTEMPTINGTOAVOIDCOMBININGBEFORERADIATING SINCECOMBINING INSPACEISESSENTIALLYLOSSLESS&ORTHISREASON MANYSOLID STATETRANSMITTERSCONSIST OFAMPLIFIERMODULESTHATFEEDEITHERROWS COLUMNS ORSINGLEELEMENTSOFANARRAY ANTENNA%SPECIALLYINTHELAST NAMEDCASE ITISNECESSARYTOBUILDTHEMODULESAND USUALLYTHEIRPOWERSUPPLIES INTOTHEARRAYSTRUCTURE'ENERALLY SOLID STATEDEVICES ORMODULESARECOMBINEDINONEOFTHREEFUNDAMENTALCONFIGURATIONSTOGENERATETHE REQUIRED TRANSMITTER POWER LEVELS &IGURE SHOWS THAT THIS MAY INVOLVE EITHER THECOMBINATIONOFAMPLIFIEROUTPUTSTOASINGLEPORTTOFEEDAMECHANICALLYROTATING ANTENNAORSOMECOMBINATIONOFELECTRONICPHASESTEERINGANDAMPLIFICATIONDISTRIB UTEDAMONGMANYFIXEDELEMENTSOFAPLANARTWO DIMENSIONALARRAY "ECAUSEOFTHELARGENUMBEROFINDIVIDUALMODULESINATYPICALSOLID STATETRANS MITTER FAILUREOFANINDIVIDUALORAFEWMODULESHASLITTLEEFFECTONOVERALLTRANSMITTER PERFORMANCE4HEMODULEOUTPUTSADDASVOLTAGEVECTORS SOTHELOSSOFOFTHE MODULES FOREXAMPLE RESULTSINAREDUCTIONTOOFVOLTAGEOUTPUT WHICHIS OFPOWEROUTPUT%VENTHISISONLYA D"REDUCTIONTHEDIFFERENCEBETWEENAND OFTHEPOWERENDSUPINTHECOMBINERLOADSORINSIDELOBESIFTHECOMBININGIS INSPACE !SARESULTOFTHIShGRACEFULDEGRADATION vOVERALLRELIABILITYOFSOLID STATE TRANSMITTERSISVERYHIGHEVENIFMAINTENANCEISDELAYEDUNTILCONVENIENTSCHEDULED PERIODSHOWEVER THISADVANTAGESHOULDNOTBEABUSED#ONSIDERACASEWHERE OFMODULESAREALLOWEDTOFAILBEFOREOUTPUTPOWERFALLSBELOWREQUIREMENTS ANDASSUMETHATMAINTENANCEOCCURSATSCHEDULEDTHREE MONTHINTERVALS)NTHISCASE MODULE-4"&NEEDONLYBE HTOPROVIDECONFIDENCETHATTHETRANSMITTER
&)'52% #OMMONSOLID STATETRANSMITTERCONFIGURATIONSMAYCOMBINEMANYAMPLIFIERSINPARALLEL TOASINGLEANTENNAPORTA ORMAYUSEPHASE SHIFTELEMENTSTOELECTRONICALLYSTEERABEAMB ORMAYUTILIZE TRANSMITRECEIVEMODULESWITHPHASE SHIFTCAPABILITYATEVERYELEMENTTOSTEERABEAMC
3/,)$ 34!4%42!.3-)44%23
££°x
WILLNOThFAILvINLESSTHANTHREEMONTHSHOWEVER THECOSTOFREPLACEMENTMODULESAND LABORWOULDBEVERYUNATTRACTIVEBECAUSENEARLYOFTHETRANSMITTERWOULDHAVETO BEREPLACEDEVERYYEAR(IGHER-4"&SARETHUSESSENTIALTOENSURETHATTHETRANSMITTER ISNOTONLYAVAILABLEBUTALSOAFFORDABLE&ORTUNATELY SOLID STATEMODULERELIABILITYHAS PROVENTOBEEVENBETTERTHANTHE-), ($"+ PREDICTIONS!.&03 0!6% 0!73 FOREXAMPLE HASGROWNTO HOURS WHICHISTIMESTHEPREDICTED VALUE4HISINCLUDESTHEACTUAL42MODULE-4"& ALONGWITHTHERECEIVERTRANSMIT RECEIVER 42 SWITCHES AND PHASE SHIFTERS AS WELL AS THE POWER AMPLIFIERS )N FACT -4"&FORTHEOUTPUTPOWERTRANSISTORSMEASURESBETTERTHANMILLIONHOURS
££°ÎÊ -" -// Ê 6
!LTHOUGH THE 2& POWER GENERATING CAPABILITY OF SINGLE TRANSISTORS IS SMALL WITH RESPECTTOTHEOVERALLPEAKANDAVERAGEPOWERREQUIREMENTSOFARADARTRANSMITTER TRANSISTORS ARE USED QUITE EFFECTIVELY BY COMBINING THE OUTPUTS OF MANY IDENTICAL SOLID STATEAMPLIFIERS4HEPOWEROUTPUTLEVELFROMAPARTICULARDEVICEISAFUNCTION OFNOTONLYTHECHOSENTECHNOLOGY BUTALSOTHEFREQUENCYANDOTHERCONDITIONS SUCH ASPULSEWIDTH DUTYCYCLE AMBIENTTEMPERATURE OPERATINGVOLTAGE ANDTHEPRESENTED LOADIMPEDANCE 4ECHNOLOGIES AND #ONSTRUCTION 3EMICONDUCTING MATERIALS USED IN THE FABRI CATION OF TRANSISTORS ARE CONSIDERED TO BE THOSE MATERIALS THAT ARE TYPICALLY NEITHER CONDUCTORS NOR INSULATORS 4HE CHARGE CARRYING PROPERTIES OF THESE SEMICONDUCTING MATERIALSCANBEMODIFIEDDRAMATICALLYTHROUGHTHESUBSTITUTIONOFMINUTEAMOUNTS OFIMPURITYIONSORTHROUGHCRYSTALLATTICEDEFECTS EITHEROFWHICHACTTOMODULATETHE FLOWOFELECTRONS3EMICONDUCTORMATERIALSFROMWHICHTRANSISTORSAREFABRICATEDFOR USEINSOLID STATERADARTRANSMITTERSHAVEGENERALLYBEENEITHERSILICONORONEOFTHE SO CALLEDCOMPOUNDSEMICONDUCTORS SUCHASGALLIUMARSENIDE'A!S INDIUMPHOS PHIDE)N0 SILICONCARBIDE3I# GALLIUMNITRIDE'A. ORSILICONGERMANIUM3I'E 3EMICONDUCTORS LIKE SILICON OR GALLIUM ARSENIDE HAVE FOUND EARLY WIDE ACCEPTANCE BECAUSEITHASPROVENPRACTICALTOCONTROLTHEIRCRYSTALLATTICEDEFECTSACCURATELYAND REPEATABLY DURING TRANSISTOR MANUFACTURING 3OME SEMICONDUCTORS SUCH AS GALLIUM NITRIDE'A. ORSILICONCARBIDE3I# AREREFERREDTOASWIDEBANDGAPSEMICONDUC TORS3EMICONDUCTORSTHATEXHIBITLARGEBANDGAPVALUESAREESPECIALLYCAPABLEOFPRO DUCINGVERYHIGHOUTPUTPOWERLEVELSWITHACCEPTABLEGAINATTHEFREQUENCIESUSEDIN MOSTRADARAPPLICATIONS 4RANSISTORSARETHREE TERMINALDEVICESANDARECLASSIFIEDASEITHERBIPOLARORUNIPOLAR &IGUREHELPSTOPORTRAYTHECONSTRUCTIONDIFFERENCESAMONGCOMMONMICROWAVE THREE TERMINALDEVICES ANDTHISFIGUREISREFERENCEDMULTIPLETIMESINSUCCEEDINGSEC TIONS4HEBIPOLARJUNCTIONTRANSISTOR"*4 ISSONAMEDBECAUSETHECONDUCTIONPATH THROUGHTHETRANSISTORMAKESUSEOFBOTHMAJORITYANDMINORITYCHARGECARRIERSTOESTAB LISHCURRENTFLOWINTHESEMICONDUCTOR)TISACURRENT CONTROLLEDDEVICEWITHTHECOLLEC TORCURRENTMODULATEDBYTHECURRENTFLOWINGBETWEENTHEBASE EMITTERJUNCTION4HIS COMPARESTOTHEOPERATIONOFAFIELDEFFECTTRANSISTOR&%4 ORAUNIPOLARDEVICE WHERE CHARGEISCARRIEDWITHONLYONETYPEOFCHARGECARRIER4HEREMAININGTRANSISTORCONSTRUC TIONSIN&IGUREAREALLVARIANTSOFA&%4!NEXTERNALVOLTAGE APPLIEDTOTHEGATE TERMINALOFA&%4 CONTROLSTHEWIDTHOFTHEDEPLETIONREGIONBELOWTHEGATETERMINAL!S THEWIDTHOFTHEDEPLETIONREGIONISVARIED SOTOOISTHEEQUIVALENTRESISTANCEBETWEEN
££°È
2!$!2(!.$"//+
&)'52% 4RANSISTORS ARE THREE TERMINAL SEMICONDUCTOR DEVICES THAT ALLOW A SMALL VOLTAGE OR CURRENTTOCONTROLALARGERVOLTAGEORCURRENT3OMECROSSSECTIONSOFCOMMONTRANSISTORTYPESUSEDIN THEDESIGNOFRADARTRANSMITTERSARETHEA 'A!S-%3&%4 B 'A!S0(%-4 C 3ILICON-/3&%4 D 3ILICON,$-/3&%4 E 3ILICON"*4 AND F 'A.(%-4ON3I#3UBSTRATE
THEDRAINANDSOURCECONTACTS ALLOWINGTHECURRENTFLOWINGBETWEENTHEDRAINANDSOURCE TOBEMODULATEDACCORDINGLYHENCE &%4SAREREFERREDTOASVOLTAGECONTROLLEDDEVICES 4HERE EXIST NUMEROUS &%4 VARIANTS DUE TO SOMETIMES SUBTLE CONSTRUCTION OR MATE RIAL DIFFERENCES!MONG THESE ARE THE -/3&%4 -ETAL /XIDE 3EMICONDUCTOR &%4 -%3&%4-ETAL3EMICONDUCTOR&%4 AND(&%4(ETEROSTRUCTURE&%4 4HECOMMON (&%4DEVICESAREREFERREDTOASTHE(%-4(IGH%LECTRON-OBILITY4RANSISTOR AND 0(%-40SEUDOMORPHIC(IGH%LECTRON-OBILITY4RANSISTOR 4OBEUSEFULINARADARTRANSMITTERAMPLIFIER THETRANSISTORMUSTBECAPABLEOFOPER ATING AT THE APPROPRIATE HIGH FREQUENCY WITH GOOD EFFICIENCY WHILE DEMONSTRATING USEFULPOWERGAINWITHADEQUATETHERMALMANAGEMENTPROPERTIESTOENSUREHIGHRELI ABILITY4HEREISNOTONETRANSISTORTYPEORONESEMICONDUCTORMATERIALTHATISUNIVER SALLYUSEFULACROSSALLTHECOMMONRADARBANDSFROM5(&THROUGH7BAND)NFACT AMONGTHERADARBANDS THEREISOFTENADIFFERENTDOMINANTDEVICETYPE ALONGWITHITS ATTENDANTDESIGNANDFABRICATIONMETHODOLOGIES THATOFFERSTHEOPTIMUMPERFORMANCE FORTHATBAND ! FIRST ORDER APPROXIMATION OF THE POWER OUTPUT FROM A SINGLE STAGE SOLID STATE AMPLIFIERUSINGA&%4ASTHESEMICONDUCTORDEVICEISGIVENBYTHERELATIONSHIP
02&-!8 )-!8 6$'" \60\ 6+
3/,)$ 34!4%42!.3-)44%23
££°Ç
)NTHISRELATIONSHIP )-!8ISTHEMAXIMUMOPENCHANNELCURRENT 6$'"ISTHEGATE DRAINBREAKDOWNVOLTAGE 60ISTHEPINCHOFFVOLTAGE AND6+ISTHEKNEEVOLTAGE4HESE TRANSISTOR PARAMETERS DEFINE THE TRANSFER CHARACTERISTICS IN THE ) 6 CURRENT VOLTAGE PLANE ANDTHEBOUNDARIESOFTHE) 6PLANEDEFINETHEPEAKPOWERPERFORMANCEENVE LOPEOFTHETRANSISTOR!LSO THEREISANOPTIMUMLOADIMPEDANCETHATWILLMAXIMIZETHE POWEROUTPUTTHATCANBEDELIVEREDFROMANAMPLIFIERANDTOAFIRSTORDERESTIMATE THAT LOADIMPEDANCEISREPRESENTEDBYTHELINETHATTRANSVERSELYCUTSACROSSTHE) 6PLANE FROMTHEREGIONOFTHEBREAKDOWNVOLTAGETOTHEREGIONOFTHEKNEEVOLTAGE ASSHOWN IN&IGURE4HEABILITYOFATRANSISTORTODEMONSTRATEGAINATHIGHFREQUENCIESIS IMPACTEDBYTHEMOBILITYANDSATURATEDVELOCITYOFCHARGECARRIERSINTHESEMICONDUC TOR4HEABILITYOFATRANSISTORTODEMONSTRATEHIGHPOWEROUTPUTISIMPACTEDBYTHE BREAKDOWNVOLTAGE THECURRENTCAPABILITY ANDTHEKNEEVOLTAGEOFTHETRANSISTOR 3ILICON DEVICE TYPES COST EFFECTIVELY SATISFY THE REQUIREMENTS OF RELIABILITY ELEC TRICAL PERFORMANCE PACKAGING COOLING AVAILABILITY AND MAINTAINABILITY AT LOWER RADAR BAND FREQUENCIES TYPICALLY 5(& , BAND AND INTO 3 BAND 4HESE DEVICES ARE USUALLY MANUFACTURED AS DISCRETELY PACKAGED TRANSISTORS AND REQUIRE EXTERNAL IMPEDANCE MATCHINGCIRCUITRYINORDERTOFUNCTIONAPPROPRIATELYINANAMPLIFIER(IGH PERFORMANCE TRANSISTORS AT HIGHER FREQUENCIES THAN 3 BAND ARE USUALLY BUILT USING COMPOUNDSEMICONDCTORS3UCHTRANSISTORSCANRESULTINHIGHCUTOFFFREQUENCIESAND DEMONSTRATEGAINATFREQUENCIESMUCHHIGHERTHANSILICON&OREXAMPLE ELECTRONSIN GALLIUMARSENIDE'A!S TRAVELAPPROXIMATELYTWICEASFASTASTHEYDOINSILICON)THAS AHIGHERSATURATEDELECTRONVELOCITYANDHIGHERELECTRONMOBILITY ALLOWINGITTOFUNC TIONATFREQUENCIESINTOTHE7BAND'A!STRANSISTORSGENERATELESSNOISETHANSILICON DEVICESWHENOPERATEDATHIGHFREQUENCYSOTHEYALSOMAKESUPERIORLOW NOISEAMPLI FIERS!KEYATTRIBUTETHATMAKES'A!SANATTRACTIVETECHNOLOGYISTHATTHE'A!S&%4 CANBEFULLYINTEGRATEDWITHTHEPASSIVECIRCUITRYTHATISNECESSARYTOPROVIDETHEBIAS ING LOADING FILTERING ANDSWITCHINGFUNCTIONSTHATARENECESSARYFORMULTISTAGE42 MODULEDESIGNS5NLIKETHESILICONPOWERTRANSISTORS THE'A!S&%4ANDITSASSOCIATED
&)'52% 4YPICALTRANSISTORCURRENT VOLTAGECONTINUUM) 6PLANE SHOWING KEY &%4 DC PERFORMANCE LIMITS WITH OPTIMUM LOAD LINE FOR POWER OUTPUT SHOWN (IGHER POWER OUTPUT IS ACHIEVED WHEN THE MAXI MUMCHANNELCURRENT)-!8 ANDTHEBREAKDOWNVOLTAGE6$'" AREBOTH INCREASED/PTIMUMAMPLIFIERDESIGNPLACESTHELOADLINEASINDICATED
££°n
2!$!2(!.$"//+
4!",% +EY3EMICONDUCTOR#HARACTERISTICSOFTHE0RIMARY3EMICONDUCTORS5SEDFOR0OWER
'ENERATIONIN3OLID STATE4RANSMITTERS4HEHIGHSATURATEDVELOCITY BREAKDOWNFIELD ANDTHERMAL CONDUCTIVITYOF3I#AND'A.MAKETHEMATTRACTIVEFORHIGH POWER AMPLIFIERAPPLICATIONS
"ANDGAP%NERGY 2&0OWER$ENSITY $IELECTRIC#ONSTANT "REAKDOWN&IELD 4HERMAL#ONDUCTIVITY %LECTRON-OBILITY 3ATURATED6ELOCITY
5NITS
3ILICON
'A!S
)N0
3I#
'A.
E6 7MM 6CM 7M# CM6SEC CMSEC
n
n
n
n
n
BATCH PROCESSEDMONOLITHICMICROWAVEINTEGRATEDCIRCUITRY--)# FABRICATIONTECH NOLOGYALLOWFORCIRCUITFUNCTIONSTOBEPROCESSEDINTOVERY VERYSMALL CONVENIENTLY PACKAGEDCHIPS4HEWIDEBANDGAPSEMICONDUCTORS SUCHAS3I#AND'A. AREALSO COMPATIBLE WITH --)# PROCESSING BUT ARE ALSO CAPABLE OF VERY HIGH POWER OUTPUT LEVELS4HESE SEMICONDUCTORS HAVE MATERIAL PROPERTIES THAT LEAD TO HIGH BREAKDOWN VOLTAGEWITHCOMMENSURATELYHIGHCHANNELCURRENTSANORDEROFMAGNITUDEHIGHER POWEROUTPUTTHAN'A!S4ABLE &OR THE UPPER END OF THE SOLID STATE MICROWAVE SPECTRUM IE THE MILLIMETER WAVERANGE THESINGLE PORTMICROWAVEDIODECANBEUSEDASALOW POWEROSCILLATOR 5NFORTUNATELY THEPOWEROUTPUTANDEFFICIENCYOFTHESEDEVICESARE INGENERAL VERY LOWINFACT THEEFFICIENCYISSIGNIFICANTLYLOWERTHANTHATOFTHEIRTUBECOUNTERPARTS (OWEVER #7ANDPULSEDPOWEROUTPUTAREATTAINABLEUPTO'(Z 0EAKAND!VERAGE0OWER,IMITATIONS !FIRST ORDERLIMITONTHE2&POWEROUT PUTCAPABILITYOFATRANSISTORISITSBREAKDOWNVOLTAGEANDMAXIMUMCURRENTHANDLING CAPABILITY7ITHINTHATLIMIT THEMAXIMUMPRACTICALLEVELOFPOWEROUTPUTTHATCANBE OBTAINEDFROMASINGLETRANSISTOROVERAGIVENBANDWIDTHISGOVERNEDBYTHETHERMAL DISSIPATIONLIMITOFTHEDEVICE!SDEVICESBECOMELARGERANDTHEDISSIPATIVEHEATFLUX FROMTHETOPSURFACEOFTHETRANSISTORCHIPTOTHEBOTTOMLAYEROFTHETRANSISTORCHIP INCREASES THEJUNCTIONTEMPERATUREINCREASESTOTHEPOINTWHERETHETRANSISTORBECOMES THERMALLYLIMITED2EGARDLESSOFTHESEMICONDUCTORUSED THEELECTRICALPERFORMANCE ANDOPERATINGLIFETIMEDEGRADEATINCREASINGLYHIGHERTEMPERATURES 4HEREISACOMPOSITETHERMALTIMECONSTANTASSOCIATEDWITHTHENUMEROUSTHERMALLY RESISTIVELAYERSBETWEENTHETRANSISTORJUNCTIONANDTHEHEATSINKORCOLDPLATETOWHICH THEDEVICEISATTACHED4HISOCCURSBECAUSEEACHLAYERSEMICONDUCTOR CERAMICSUB STRATE METALBASE ETC EXHIBITSBOTHATHERMALRESISTANCEANDATHERMALCAPACITANCE 4HEN THEREEXISTSANEQUIVALENTTHERMALTIMECONSTANTS FOREACHPACKAGINGMATERIAL LAYER4HISTHERMALTIMECONSTANTHASBEENAPPROXIMATEDEDAS
S &Q#+4(
WHERE&ISTHICKNESSCM QISDENSITYGMCC #ISSPECIFICHEAT7SECGMn# AND +4(ISTHERMALCONDUCTIVITY7CMn# &OREXAMPLE &IGURESHOWSTHATWHENTHE PULSEWIDTHANDDUTYCYCLEFORAGIVEN'A!STRANSISTORISINCREASEDFROM§SAND TO§SAND RESPECTIVELY THEREISAn#INCREASEINTHEOVERALLJUNCTIONTEM PERATURE!LTHOUGHTHETRANSISTORMAYOPERATERELIABLYATADESIREDOUTPUTPOWERLEVEL FORTHESHORTERPULSEWIDTH ITWOULDSUFFERFROMADECREASEINLONG TERMRELIABILITY IFOPERATEDATTHESAMEPOWERLEVELFORTHELONGERPULSEWIDTH4HUS IFREQUIREDTO
3/,)$ 34!4%42!.3-)44%23
££°
+$" ,#% -( )*" !"* ,#% -( +" ,#%
+ +" -( +" -( +" +(."*&) * '+$"', "&)"* ,-*" "+)('+" +" !-,/
+(."*&) * '+$"', "&)"* ,-*" "+)('+" +" !-,/
"&)"* ,-*"
"&)"* ,-*"
$&"+"
$&"+"
&)'52% /NE LIMIT OF TRANSISTOR CAPABILITY IS DETERMINED BY THE MAXIMUM JUNCTION TEMPERATURE WHICHINTURNISDETERMINEDBYTHETHERMALTIMECONSTANT ANDTHISRESULTSINVERYDIFFERENTCAPABILITIESASA FUNCTIONOFOPERATINGPULSEWIDTHANDDUTYCYCLE
MAINTAINLONG TERMRELIABILITYATTHELONGERPULSEWIDTH THEDISSIPATIONINTHETRANSIS TORWOULDHAVETOBEREDUCEDTOBRINGTHEJUNCTIONTEMPERATUREDOWNTOANACCEPTABLE LEVEL$E RATINGTHEINHERENTSHORT PULSECAPABILITYBYLOWERINGTHEDISSIPATEDPOWER INTHETRANSISTOR PERHAPSBYREDUCINGTHEOPERATINGVOLTAGEANDPOWEROUTPUT ISONE METHODOFACHIEVINGTHEDESIREDRELIABILITY!NOTHERMETHODMAYINVOLVETHEREDUCTION INAMBIENTTEMPERATUREWITHTHEUSEOFCHILLEDFLUIDINTHEAMPLIFIERHEAT SINK4HESE ARENOTALWAYSPRACTICALSOLUTIONSANDONEFINDSTHATTHELAYOUTOFTHETRANSISTORITSELF ISOFTENOPTIMIZEDFORAPARTICULARPULSEWIDTHANDDUTYCYCLEINORDERTOACHIEVETHE OPTIMUMPERFORMANCEANDRELIABILITYATTHELOWESTOPERATINGTEMPERATURE 4HEACTIVETRANSISTORAREAONTHESURFACEOFTHECHIPTHECHIPISSOMETIMESCALLED THEDIE ISTYPICALLYDIVIDEDINTOMANAGEABLEUNITSCELLS WHERETHECELLSIZEISOFTEN OPTIMIZEDFORAPARTICULARAPPLICATIONORRANGEOFAPPLICATIONS)NADDITIONTOFREQUENCY CONSIDERATIONS PULSEWIDTHANDDUTYCYCLEOR ASARESULT THEPEAKANDAVERAGEDIS SIPATED POWER ARE THE PARAMETERS THAT DETERMINE THE CELL SIZE AND ARRANGEMENT OF CELLSONACHIP4HEULTIMATEOPERATINGJUNCTIONTEMPERATUREOFTHETRANSISTORISLARGELY DEPENDENTONTHETRANSIENTHEATINGTHATWILLBEENCOUNTEREDANDTHELAYOUTANDAREAOF THEINDIVIDUALCELLS&ORDEVICESTHATAREDESIGNEDTOOPERATEFORLONGPULSESOR#7 AN INCREASEINTHEAVERAGEPOWERCAPABILITYOFTHETRANSISTORCANBEACHIEVEDBYDIVIDING THEACTIVEAREAOFATRANSISTORINTOSMALL THERMALLYISOLATEDCELLAREAS 3INCETHEOVERALLTHERMALTIMECONSTANTFORATYPICALPOWERTRANSISTORDIEITSELFMAY BEONTHEORDEROFn§S THETRADEOFFBETWEENPEAKANDAVERAGEPOWERVERSUS DEVICESIZECANBESIGNIFICANTFORSOLID STATERADARSUSINGPULSECOMPRESSIONWITHPULSE WIDTHSINTHETO§SRANGE!SANEXAMPLE THETHERMALTIMECONSTANTOFASILICON DIEWITHATHICKNESSOFMILSISAPPROXIMATELY§SWHEREASAGALLIUMARSENIDEDIE WITHATHICKNESSOFMILSISAPPROXIMATELY§S4HUS FORANOPERATINGPULSEWIDTH
££°£ä
2!$!2(!.$"//+
REPRESENTATIVEOFASOLID STATERADARWITHPULSECOMPRESSION^§S THETEMPERA TURERISEACROSSTHESILICONDIEHASREACHEDOFITSSTEADY STATEVALUE BUTFORAN OPERATINGPULSEWIDTHREPRESENTATIVEOFASHORTERRANGEFIRECONTROLRADAR^§S THE TEMPERATURERISEACROSSTHESILICONDIEHASONLYREACHEDOFITSSTEADY STATEVALUE )FTHEVOLTAGEANDCURRENTTHRESHOLDOFTHETRANSISTORHASNOTBEENREACHED THESHORTER PULSEWIDTHOPERATIONCOULDALLOWFORSIGNIFICANTLYLARGERPOWERCAPABILITYTOBEDEM ONSTRATED5SUALLY AVERYDETAILEDTHERMALANALYSISUSINGTHEFINITEELEMENTMETHODIS REQUIREDTOQUANTIFYTHESERELATIONSHIPSDURINGTRANSISTORANDAMPLIFIERDESIGN "ACKGROUNDANDDESCRIPTIONSOFTHECOMMONTHREE TERMINALDEVICETYPESANDTHEIR ASSOCIATEDTECHNOLOGIESASUTILIZEDFORTHECOMMONRADARBANDSAREDESCRIBEDINTHE FOLLOWINGSECTIONS 3ILICON "IPOLAR *UNCTION 4RANSISTOR 4HE SILICON BIPOLAR JUNCTION TRANSISTOR "*4 WASTHEEARLIESTOFTHEMICROWAVEPOWERDEVICESANDFOUNDITSWAYINTOTUBE REPLACEMENTTRANSMITTERSANDPHASEDARRAYAPPLICATIONSSTARTINGINTHELATES!T LOWERFREQUENCIES ESPECIALLYBELOW'(Z THE3I"*4HASBEENSHOWNTOBECAPABLE OFVERYHIGHPOWERLEVELSFORTRANSISTORS!MPLIFIERDESIGNISREALIZABLEFORFREQUENCIES UPTHROUGH3BAND WHERETHETRADEOFFBETWEENDEVICEPERFORMANCEANDOVERALLSYS TEMCOSTBEGINSTOREACHAPOINTOFDIMINISHINGRETURNS4HESILICONBIPOLARTRANSISTOR TECHNOLOGYISNOWVERYMATURE BUTTHEDEMANDFORTHESEHIGHPERFORMANCEDEVICES ISLOWBECAUSETHEPRODUCTIONQUANTITIESREQUIREDFORRADARSYSTEMSISSMALLRELATIVE TOCOMMERCIALSILICONELECTRONICPRODUCTS4HUS THERETENDSTOBEASMALLNUMBEROF MANUFACTURERSWHOPROVIDEQUALITYDEVICESFORUSEINAMPLIFIERDESIGNS 3ILICON BASED MICROWAVE POWER TRANSISTORS CAN ACTUALLY BE CONSIDERED HYBRID MICROELECTRONIC CIRCUITS AND ARE GENERALLY SINGLE CHIP OR MULTICHIP TRANSISTORS COM BINEDINPARALLELWITHINAFLANGEDHERMETICPACKAGE3OMEFORMOFINTERNALIMPEDANCE PREMATCHINGCIRCUITRYISOFTENINCLUDEDINORDERTOPRESERVETHEINTRINSICBANDWIDTHOF THESEMICONDUCTORCHIPANDTOMAKETHETASKOFEXTERNALIMPEDANCEMATCHINGEASIER 4HEINTERNALMATCHINGALSOINCREASESTHETERMINALIMPEDANCESOFTHEPACKAGEDDEVICE TOALEVELWHERETHECOMPONENTLOSSESOFTHECIRCUITRYEXTERNALTOTHETRANSISTORBECOME LESSCRITICAL&IGUREISANEXAMPLEOFA WATTINTERNALLYMATCHEDPOWERTRAN SISTORHYBRIDUSINGTHE3I"*4SEMICONDUCTORTECHNOLOGY)TSHOWSTHETRANSISTORDIE ALONGWITHTHECAPACITORSANDWIRESTHATAREUSEDASLOW PASSANDHIGH PASSIMPEDANCE MATCHINGCOMPONENTSTOACHIEVEANACCEPTABLELEVELOFIMPEDANCEPREMATCHING 4HEMICROWAVEPOWER3I"*4ISINVARIABLYAN.0.STRUCTURE&IGUREE WITH A VERTICAL DIFFUSION PROFILE IE THE COLLECTOR CONTACT FORMS THE BOTTOM LAYER OF THE CHIP4HE 0 TYPE BASE REGION HAS BEEN DIFFUSED OR IMPLANTED INTO THE COLLECTOR THE . TYPEEMITTERHASBEENDIFFUSEDORIMPLANTEDINTOTHEBASE ANDBOTHBASEANDEMITTER REGIONSAREACCESSIBLEFROMTHETOPSURFACEOFTHECHIP4HECOLLECTORREGIONCONSISTS OFAN. DOPED LOW RESISTIVITYEPITAXIALLAYERTHATISGROWNONAVERYLOWRESISTIVITY SILICONSUBSTRATE4HECHARACTERISTICSOFTHEEPITAXIALLAYER IE THICKNESSANDRESISTIV ITY CANDETERMINETHEUPPERLIMITOFPERFORMANCEOFTHEDEVICEINTERMSOFRUGGEDNESS EFFICIENCY ANDSATURATEDPOWEROUTPUT 4HEFUNDAMENTALLIMITATIONONHIGH FREQUENCY3I"*4PERFORMANCEISTHEOVERALL COLLECTOR TO EMITTERDELAYTIME)FASIGNALISINTRODUCEDTOEITHERTHEBASEORTHEEMIT TER FOURSEPARATEREGIONSOFATTENUATIONORTIMEDELAYAREENCOUNTEREDTHEEMITTER BASE JUNCTION CAPACITY CHARGING TIME THE BASE TRANSIT TIME THE COLLECTOR DEPLETION LAYER TRANSMITTIME ANDTHECOLLECTORCAPACITANCE RESISTANCECHARGINGTIME(IGH FREQUENCY TRANSISTORDESIGNISCONCERNEDWITHOPTIMIZINGTHEPHYSICALPARAMETERSTHATCONTRIBUTE TOTHETIME DELAYCOMPONENTS
3/,)$ 34!4%42!.3-)44%23
££°££
&)'52% ! WATT, BANDLONG PULSEANDHIGH DUTY CYCLE SILICON BIPOLAR POWER TRANSISTOR IN A CUSTOM HERMETIC DUAL LEADED LOW INDUCTANCEPACKAGEHASANOVERALLFOOTPRINTOF r0HOTOGRAPHCOURTESYOF2AYTHEON#OMPANY
4HEDESIGNCHALLENGEFORHIGH POWER3I"*4SISTOMAINTAINAUNIFORMHIGHCURRENT DENSITYOVERALARGEEMITTERAREAWITHAMINIMUMTEMPERATURERISE(IGH FREQUENCY DEVICES REQUIRE SHALLOW NARROW HIGH RESISTANCE BASE REGIONS UNDER THE EMITTER REGION CAUSING MOST OF THE CURRENT CARRIED IN THE DEVICE TO BE CROWDED ALONG THE PERIPHERYOFTHEEMITTER4HUS INORDERTOMAXIMIZETHECURRENT HANDLINGCAPABILITYOF THEDEVICEAND HENCE THEPOWEROUTPUTCAPABILITYOFTHEDEVICE THEEMITTERPERIPHERY IS MAXIMIZED "ECAUSE THE CAPACITANCE OF THE COLLECTOR BASE JUNCTION APPEARS AS A DELETERIOUSPARASITICELECTRICALCOMPONENT THEEMITTER PERIPHERYTOBASE AREARATIO OR%P"A ISMAXIMIZEDWHEREPOSSIBLE'ENERALLY HIGHER FREQUENCYDEVICESEXHIBIT HIGHER%P"ARATIOSANDTOOBTAINAHIGH%P"ARATIOVERYFINELINEGEOMETRIESARE REQUIRED WHERETHETERMGEOMETRYREFERSTOTHESURFACECONSTRUCTIONDETAILSOFTHE TRANSISTORDICE 3ILICON ,$-/3 &%4 4HE SILICON ,ATERALLY $IFFUSED -ETAL /XIDE 3EMI CONDUCTOR,$-/3 TRANSISTORISBEGINNINGTOSUPERSEDETHESILICONPOWER"*4AS AREPLACEMENTDEVICE ESPECIALLYATTHE6(& 5(& AND, BANDFREQUENCIES)NPAR TICULAR THECOMMERCIALCOMMUNICATIONSINDUSTRYHASFOUNDTHATTHE3I,$-/3&%4 DOMINATESASACELLPHONEBASE STATIONPOWERAMPLIFIERBECAUSEOFTHEHIGHERGAIN LINEARITY ANDEFFICIENCYTHATITDEMONSTRATESCOMPAREDTOTHESILICON"*4!LTHOUGHIT ISA&%4 ITSCONSTRUCTIONCHARACTERISTICS PACKAGING ANDDESIGNCHALLENGESAREVERY SIMILARTOTHEDESIGNCHALLENGESOFTHE3I"*4
££°£Ó
2!$!2(!.$"//+
4HESILICON,$-/3&%4&IGURED ISPROCESSEDONP MATERIALWITHALIGHTLY DOPEDP TYPEEPITAXIALLAYER ANDJUSTLIKETHESILICON"*4 MULTIPLEIMPURITYIMPLANTS FORMTHEVARIOUSJUNCTIONS)TISSTILLCONSIDEREDASLOWERDEVICETHANOTHERSEMICONDUC TORS SUCHAS'A!S BECAUSETHEMOBILITYINSILICON-/3&%4CHANNELSISRELATIVELYLOW !LTHOUGHTHEBULKMOBILITYOFSILICONISLOWERTHAN'A!S ITDOESNOTPRECLUDETHESILI CON,$-/3&%4ASAHIGHFREQUENCYPOWERTRANSISTOR4HECONTINUOUSPROCESSFABRICA TIONIMPROVEMENTINTHESILICON#-/3INDUSTRYHASRESULTEDINSUB MICRONPRODUCTION TRANSISTORFEATURESIZES ANDTHESMALLERFEATURESIZESALLOWFORACOMPENSATEDINCREASE INHIGHERFREQUENCYOPERATIONTHATIS ITCANEXHIBITUSABLEGAININTO3BAND)NPARTICU LAR THE,$-/3STRUCTUREENABLESASHORTCHANNELASARESULTOFTHELATERALDIFFUSIONOF THEP TYPEIMPLANT4HERESULTINGSHORTCHANNELCONTRIBUTESTOIMPROVEDHIGHFREQUENCY RESPONSEINSPITEOFTHELOWERMOBILITYOFSILICON4HEMEASUREDBREAKDOWNVOLTAGES CANBEINEXCESSOF6 SOOPERATIONATHIGHERVOLTAGESISPOSSIBLE ORCONVERSELY A HIGHERLEVELOFMARGININRUGGEDNESSCANBEACHIEVEDFORAGIVENOPERATINGVOLTAGETHE LATTERISAKEYADVANTAGEFORHIGH RELIABILITYPOWERAMPLIFIERAPPLICATIONS 4HEUNDERSIDEOFTHE,$-/3TRANSISTORDICEISTHESOURCECONNECTIONTHUS THECHIP CANBEMOUNTEDDIRECTLYTOAMETALPACKAGEBASE4HISISUNLIKETHE3I"*4WHERETHE HIGHVOLTAGECOLLECTORCONTACTISTHEUNDERSIDEOFTHECHIP!SARESULTOFNOTHAVINGTO ELECTRICALLYISOLATETHEUNDERSIDEOFTHE,$-/3CHIP THEREISNONEEDTOUSETHEPOTEN TIALLYTOXICBERYLLIUMOXIDEBASEDPACKAGESTHATPERMEATETHE3I"*4PRODUCTLINES 4HELOWERSOURCEINDUCTANCEACHIEVEDWITHDIRECTATTACHMENTTOTHEMETALFLANGEOFA PACKAGEBASEENABLESHIGHERGAINSTOBEDEMONSTRATEDFORCOMPARABLE3I"*4POWER LEVELSATFREQUENCIESBELOW'(Z BUTTHESEDEVICESAREPRESENTLYNOTATTRACTIVEAT FREQUENCIESABOVE3BAND !PRIMARYADVANTAGEOFTHE,$-/3DEVICEISTHERMALSTABILITY4HEDRAINCURRENT HAS A NEGATIVE TEMPERATURE COEFFICIENT THEREFORE THE ,$-/3 &%4 IS NOT SUSCEP TIBLETOTHERMALRUNAWAYANDDOESNOTREQUIRETHEAMOUNTOFGAIN DEGRADINGRESISTIVE EMITTERBALLASTINGTHATISCOMMONLYREQUIREDINA3I"*4TOHELPNORMALIZEJUNCTION TEMPERATURES!MORETHERMALLYSTABLEDEVICEALLOWSFORTHEMOREEFFICIENTPOWERCOM BININGOFTRANSISTORCELLSWITHINAPACKAGE4HISCONTRIBUTESTOALOWERPERFORMANCE SENSITIVITYTOLOADMISMATCHAPROBLEMTHATHASCOMPLICATEDTHEDESIGNPROCESSFOR THE3I"*4&IGUREAND&IGURESUMMARIZETHEPERFORMANCEENVELOPEFORCOM MERCIALLYAVAILABLESILICONBIPOLARJUNCTIONTRANSISTORSANDSILICON,$-/3&%4SFOR GIVENTRANSMITWAVEFORMSn 'A!S0(%-4 4HE'A!S0SEUDOMORPHIC(IGH%LECTRON-OBILITY4RANSISTOR 0(%-4 ISACTUALLYAHETEROSTRUCTUREMATERIAL&IGUREB CONSISTINGOFSLIGHTLY STRAIN MISMATCHEDCRYSTALLAYERS!VERYSIMPLIFIEDDESCRIPTIONPORTRAYSAN!L'A!S LAYER OVER AN )N'A!S CHANNEL ON A 'A!S SUBSTRATE FORMING A HIGH QUALITY TWO DIMENSIONALELECTRONGASLAYER OFTENREFERREDTOASTHE$%'4HIS$%'EXHIBITS SUPERIOR ELECTRON TRANSPORT PROPERTIES RESULTING IN A VERY CONFINED CHANNEL WITH FEWEROPPORTUNITIESFORCHARGECARRIERCOLLISIONS4HISALLOWSFORAVERYHIGH QUALITY TRANSISTORTHATCANBEMADEWITHUSEFULGAINBEYOND7BAND(IGHERMOBILITYAND ELECTRONVELOCITYCANBEENGINEEREDBYINCREASINGTHEPERCENTAGECONTENTOFINDIUM INTHECHANNELOFTHE&%44HISCANBEACCOMPLISHEDUPTOAPOINT WHEREBEYOND APPROXIMATELYINDIUMCONTENT THELATTICESTRAINDIFFERENTIALRESULTSINDEGRADING PERFORMANCEANDRELIABILITY4HESETECHNIQUESCANRESULTINTRANSISTORSWITHBIGGER BANDGAPDIFFERENCESTHANOTHERWISEPOSSIBLEFORTHECHOSENMATERIALS4HEFABRICATION OFTHESETRANSISTORSEMPLOYSTHEUSEOFADVANCEDSEMICONDUCTORPROCESSINGSUCHAS -OLECULAR"EAM%PITAXY-"% OR-OLECULAR/RGANIC#HEMICAL6APOR$EPOSITION
3/,)$ 34!4%42!.3-)44%23
££°£Î
&)'52% 0ERFORMANCESPACEOFCOMMERCIALLYAVAILABLESILICONPOWERTRANSISTORS
-/#6$ FABRICATIONTECHNIQUESTOACHIEVETHEHIGHPERFORMANCECHARACTERISTICS 4HESE ARE CAPITAL INTENSIVE SEMICONDUCTOR PROCESSING STEPS THAT ARE REQUIRED IN ORDERTOACHIEVETHEHIGHQUALITYCHANNELCHARACTERISTICSTHATDEFINEAMICROWAVEOR MILLIMETER WAVE POWER TRANSISTOR /PTIMIZING THE MOLECULAR CONTENT OF THE &%4 CHANNELFORBESTPERFORMANCEISSOMETIMESREFERREDTOASBANDGAPENGINEERING4HE CHALLENGEFORTHEDEVICEENGINEERISTODEVELOPATRANSISTORTHATSUPPORTSTHEHIGHEST VOLTAGECURRENTOPERATIONWHILEDEMONSTRATINGTHEBESTHIGHFREQUENCYGAIN
&)'52% 0ERFORMANCESPACEOFCOMMERCIALLYAVAILABLESILICONPOWERTRANSISTORS
££°£{
2!$!2(!.$"//+
4HE COMPLICATION IN POWER TRANSISTOR DESIGN EXTENDS BEYOND THE EXOTIC MATERIAL FABRICATIONTECHNOLOGIESTHATAREUSEDTODEFINETHEBASIC&%44AILOREDCONSTRUCTION TECHNIQUESAREUSEDTOCONTROLTHEELECTRICFIELDINTENSITYANDIMPROVETHEBREAKDOWN VOLTAGEENHANCEMENTSSUCHASTHEFIELDPLATE DOUBLEGATERECESS ORAUTOMATIC ETCHSTOPLAYERSAREFABRICATIONANDDESIGNTECHNIQUESTHATAREUSEDTOOPTIMIZETHE 0(%-4 PERFORMANCE FOR A GIVEN OPERATING FREQUENCY RANGE TO BRING HIGHER VALUE PERFORMANCE ORRELIABILITYTOTHESEMICONDUCTORFABRICATIONPROCESS 4HEFUNDAMENTALTHREE FINGERED&%4STRUCTUREDRAIN GATE SOURCE SHOWNASA'A!S 0(%-4&%4INCROSS SECTIONIN&IGURE HASPOWERPERFORMANCELIMITATIONSTHAT AREMITIGATEDBYEMPLOYINGASTRUCTUREDDESIGNAPPROACHFORACHIEVINGHIGHPOWER OUTPUTLEVELS!SSHOWNIN&IGURE THESMALLESTPHYSICALCONSTRUCTIONDIMENSION OFTHEGATEELECTRODEISCALLEDTHEGATELENGTHTHELONGEROFTHEDIMENSIONSISCALLED THEGATEWIDTH4HECURRENTCARRYINGCAPABILITYANDHENCETHEPOWERCAPABILITY OFTHE &%4ISINCREASEDASTHEGATEWIDTHISINCREASED4HEREISALIMITASTOHOWLONGTHEGATE WIDTHCANBEINCREASEDBEFOREPHASEDIFFERENTIALANDSIGNALATTENUATIONALONGTHELONGER DIMENSIONOFTHEGATEWIDTHBEGINTOHAVEADELETERIOUSIMPACTONAMPLIFIERPERFOR MANCE)NPRACTICE THEMAXIMUMGATEWIDTHCANBEFOUNDTOAPPROACHAPPROXIMATELY §M §M OR§MFOR3BAND 8BAND OR+ABANDFREQUENCIES RESPECTIVELY 7ITH A LIMITATION ON MAXIMUM GATE WIDTH ADDITIONAL CURRENT AND HENCE POWER CAPABILITYCANONLYBEACHIEVEDBYCOMBININGMULTIPLEGATEELECTRODESINPARALLEL'ATE ELECTRODES ORFINGERSASTHEYAREOFTENREFERREDTO AREGENERALLYGROUPEDINLOGICALLY CONVENIENTSUBSTRUCTURESCELLS THATARESTEPPEDANDREPEATEDTOFORMASYMMETRICCOR PORATEHIERARCHYOFCOMBINEDTRANSISTORS4HEOUTPUTSOFALLFINGERSAREREQUIREDTOBE COMBINEDINPHASEANDTHENIMPEDANCE MATCHEDTOTHEAPPROPRIATELEVEL!NINDUSTRY WIDEFIGURE OF MERITFORCAPABILITYOFTHESEMICONDUCTORANDTHEUNIT&%4ISTHEPOWER OUTPUTDENSITY ANDTHISISGIVENINUNITSOFWATTSMMOFTOTAL&%4GATEWIDTHORGATE PERIPHERY&OROPERATINGVOLTAGESOFnVOLTS ANORMALIZEDPOWEROUTPUTDENSITYOF n7MMSHOULDBEEXPECTEDFORMOREADVANCED'A!S0(%-4STRUCTURESOPER ATINGATnVOLTS ONECANEXPECTTODELIVERn7MMOFNORMALIZEDPOWER OUTPUTDENSITY4HUS TOACHIEVEAPOWERLEVELOFWATTSAT'(Z WHENOPERATING FROMVOLTS APPROXIMATELYGATEFINGERSMUSTSOMEHOWBECOMBINEDINPARALLELTO
&)'52% #ROSS SECTION OF A §M DOUBLE GATEnRECESSED 'A!S 0(%-4 TRANSISTOR SHOWING GATE DRAIN AND SOURCE METALS 0HOTOGRAPH COURTESYOF2AYTHEON#OMPANY
3/,)$ 34!4%42!.3-)44%23
££°£x
&)'52% 4YPICALTWO STAGE'A!S--)#POWERAMPLIFIERWITHINSERT SHOWING MULTIPLE PARALLELED GATE FINGERS IN FINAL STAGE UNIT CELL 0HOTOGRAPH COURTESYOF2AYTHEON#OMPANY
DELIVERTHEPOWER(IGHERNUMBERSOFPARALLELEDFINGERSNECESSARILYLEADTODECREASING INPUTANDOUTPUTIMPEDANCES FURTHERCOMPLICATINGTHEABILITYTOPROVIDETHEDESIRED IMPEDANCE MATCH OVER THE DESIRED BANDWIDTH (IGHER IMPEDANCE TRANSFORMATION RATIOS AND WIDER BANDWIDTHS INVARIABLY CONTRIBUTE TO ADDITIONAL LOSS IN THE MATCH INGNETWORKS WHETHERTHESENETWORKSAREHYBRIDCONSTRUCTIONOR--)#CONSTRUCTION !DDITIONALLOSSESDEGRADETHEINHERENTPOWER GAIN ANDEFFICIENCYCHARACTERISTICSOFTHE INTRINSIC&%44HEMOSTAPPROPRIATEAMPLIFIERDESIGNFORAGIVENAPPLICATIONREQUIRES OPTIMIZATIONOFTHETRANSISTOR ANDTHEVARIABLESTHATAFFECTTHATOPTIMIZATION SUCHAS UNIT GATE LENGTH GATE WIDTH NUMBER OF GATE FINGERS CELL CONSTRUCTION IMPEDANCE MATCHINGCIRCUITS ANDBIASNETWORKS ALLREQUIREDETAILEDATTENTIONDURINGTHEDESIGN OFTHEAMPLIFIER%XCELLENTCOMPILATIONSOFINDUSTRYPERFORMANCEHAVEBEENPUBLISHED FORFURTHERINSIGHT 4HESEREFERENCESOUTLINESTATE OF THE ARTPOWEROUTPUTDENSITY ANDEFFICIENCIESOFCOMPOUNDSEMICONDUCTORSFROMTHROUGH'(Z 7IDE "ANDGAP 3EMICONDUCTORS 3INCE THE INCEPTION OF SOLID STATE :OLPER DRAWS HISTORICAL REFERENCE TO THE FIRST SECOND AND THIRD GENERATION OF SEMICONDUC TOR MATERIALS AS SILICON GALLIUM ARSENIDE OR INDIUM PHOSPHIDE AND THE SO CALLED WIDE BANDGAP SEMICONDUCTORS 7"'3 4HE LATTER ARE DOMINATED BY THE SILICONCARBIDE3I# -%3&%4ANDTHEGALLIUMNITRIDE!L'A.'A. HETEROJUNCTION FIELDEFFECTTRANSISTOR(&%4 4HEADVENTOFTHETHIRDSEMICONDUCTORGENERATIONOPENS ENORMOUSNEWPOSSIBILITIESINTHEAREAOFHIGHPOWERAMPLIFIERSFORUSEINSOLID STATE 4HE7"'3MATERIALSAREABLETOPRODUCEVERYHIGHPOWER OUTPUTLEVELSnWMM
££°£È
2!$!2(!.$"//+
FROMHIGHBUSVOLTAGESnVOLTS WHILEMAINTAININGTRANSISTOR LIKEPROPERTIESAT HIGHEROPERATINGTEMPERATURESTHAN3IOR'A!S4HEYAREFINDINGAPPLICATIONINTHE 3BAND # BAND OR 8 BAND FREQUENCY RANGES4HE INTEREST IN DEVELOPMENT IS BEING FUELED BY BOTH THE MILITARY FOR HIGH PERFORMANCE SENSORS AND ALSO BY COMMERCIAL INTERESTSFORHIGH POWERWIRELESSBASE STATIONAMPLIFIERS)NPARTICULAR THE'A.(&%4 DEVICEDEMONSTRATESPHYSICALPROPERTIESTHATMAKEITUSEFULASAHIGHGAINDEVICEWITH VERYHIGHPOWEROUTPUTCAPABILITYINTOTHE7BAND4HE3I#-%3&%4WILLLIKELYBE COMPETITIVEATTHELOWERFREQUENCYRANGESOF,BANDTHROUGH#BAND 4HE THERMAL CONDUCTIVITY OF THE 3I# SUBSTRATE IS SUPERIOR TO 'A!S BY NEARLY AN ORDEROFMAGNITUDE ANDTHENORMALIZEDPOWEROUTPUTSAREMUCH MUCHHIGHERINTHE WIDEBANDGAPSEMICONDUCTORSTHANCURRENTLYBEINGACHIEVEDUSING'A!SATANYVOLT AGE4HEHIGHERTHERMALCONDUCTIVITYOF3I#ENABLESMOREEFFICIENTTHERMALMANAGE MENT#OUPLEDWITHTHEHIGHBREAKDOWNVOLTAGEANDCHANNELCURRENTCAPABILITYOFTHE 3I#-%3&%4 MEASUREDRESULTSOFWATTSOF#7POWEROUTPUTWITHAND"ASSOCI ATEDLEVELOFLARGESIGNALGAINAT'(ZFROMA6DRAINSUPPLYVOLTAGEHAVEBEEN REPORTEDFROMASINGLETRANSISTORCELL %LECTRONMOBILITYINTHE'A.(%-4ATSATURATEDDRIFTVELOCITIESISHIGHENOUGHTHAT HIGHGAINWITHSIMULTANEOUSHIGHPOWEROUTPUTANDHIGHEFFICIENCIESCANBEACHIEVED WITHVOLTAGESASLOWASTOVOLTS7ITHA'A.EPITAXIALLAYERPROCESSEDONA3I# SUBSTRATE THECURRENTSTATE OF THE ARTFORTRANSISTORPERFORMANCEISDEFINEDONSEVERAL FRONTSINTHESEMICONDUCTORINDUSTRYBYTHEFOLLOWINGPERFORMANCES PULSEDPOWER ADDED EFFICIENCY 0!% OF AT 6 AND '(Z ON A MM &%4 AND #7 POWEROF7AT6AND'(ZONASINGLEMMTRANSISTOR POWERDENSITY OF7MMAT'(Z LESSTHAND"POWERDEGRADATIONAFTER HOURS 2&OPERATIONAT6WITHCHANNELTEMPERATURESOFn#0OWER ADDEDEFFICIENCY ISACIRCUITDESIGNERSTERMANDISDEFINEDBY 0!% 0/ 0) 0$#
WHERE 0/ IS THE 2& POWER OUTPUT 0) IS THE 2& POWER INPUT AND 0$# IS THE TOTAL DCPOWERINPUT &IGUREAND&IGUREILLUSTRATETHEADVANTAGESOF'A.AT'(ZWHEN COMPAREDWITHTHEPHYSICALGEOMETRYOFANIDENTICALLYSIZED'A!S0(%-4TRANSISTOR
*#) ,#+ " -#') $' $ 0%%
''. ),+(,+ !!# # & / & #&
#&
' %
)#- %
&)'52% 4YPICAL '(Z PERFORMANCE CURVES FOR A MM PERIPHERY 'A!S 0(%-4 &%4 OPERATING AT 6 USING A #7 DUTY WAVEFORM
3/,)$ 34!4%42!.3-)44%23
££°£Ç
$* ,$+ !# -$(* %( !% 0&&
((.!*,+),+ ""$ $!' / ' $'
*$-! &
$'
( &
&)'52% 4YPICAL '(Z PERFORMANCE CURVES FOR A MM PERIPHERY 'A. (%-4 &%4 OPERATING AT 6 USING A #7 DUTY WAVEFORM
)NTHISEXAMPLE A'A!S0(%-4WITHMMOFTOTALGATEPERIPHERY&IGURE IS COMPAREDWITHANIDENTICALMM'A.(%-4&IGURE 4HESEFIGURESPORTRAY THEPOWEROUTPUT0O POWER ADDEDEFFICIENCY0!% ANDGAIN'N 0ERFORMANCEFOR EACHISREFERENCEDTO'(ZFOR#7OPERATION4HE'A!S0(%-4OPERATESAT6 THE'A.(%-4OPERATESAT6&ROMTHESEPERFORMANCECURVES ONESEESTHATTHE SMALLSIGNALGAINSARENEARLYIDENTICALINTHEnD"RANGE ASARETHELARGESIGNAL EFFICIENCIES BUTTHEPOWEROUTPUTCAPABILITYOFTHE'A.(%-4ISD"GREATERTHAN FORTHE'A!S0(%-4OFTHESAMESIZE
££°{Ê - Ê",Ê/ Ê-" -// ÊÊ "// Ê/, - // , 2ADAR TRANSMITTER DESIGN INVARIABLY REQUIRES SIGNIFICANT RADIATED POWER FROM THE ANTENNAINORDERTOPROJECTTOTHEMINIMUMRANGEREQUIREMENTWHILEMAINTAININGSOME MINIMUMSIGNAL TO NOISERATIOONRECEIVE4HEIMPACTOFTHEREQUIREMENTFORHIGHRADI ATEDPOWERISFUNDAMENTALTOTHEDESIGNOFSOLID STATETRANSMITTERSHIGHPOWERMUST BEACHIEVEDBYCOMBININGTHEOUTPUTSOFLOWER POWERAMPLIFIERSINORDERTODEVELOP THE REQUIRED RADIATED LEVELS 4RANSISTOR FINGERS ARE COMBINED INTO --)# AMPLIFI ERSAMPLIFIERSARECOMBINEDINTOMODULESANDMODULESARECOMBINEDINTOSYSTEMS 'ENERALLY THE COMBINING TAKES ON ONE OF TWO DIFFERENT CONFIGURATIONS USING EITHER SPACE COMBINEDORCORPORATE COMBINEDARCHITECTURES4HEPHASEDARRAYISACOMMON EXAMPLE OF THE SPACE COMBINED CONFIGURATION WHEREIN EACH RADIATING ANTENNA ELE MENTISFEDBYANAMPLIFIERMODULEANDTHEWAVEFRONTISFORMEDINSPACE4HECOM MONEXAMPLEOFTHECORPORATE COMBINEDDESIGNISTHEhSOLID STATEBOTTLE vWHEREINA MECHANICALLYROTATINGANTENNAISFEDFROMASINGLEPORT ANDTHEPOWERATTHEPORTIS THESUMMATIONOFTHEOUTPUTSOFMANYAMPLIFIERMODULES4HOSEMODULESMIGHTBE PHYSICALLYLOCATED FOREXAMPLE BELOWDECKONASHIPAWAYFROMTHEANTENNA3OLID STATETRANSMITTERDESIGNSHAVEBEENBUILTAROUNDEACHOFTHESEGENERICFORMS ANDTHE COMPONENTSTHATAREREQUIREDINTHEIMPLEMENTATIONOFEACHSHARESIMILARCHARACTER ISTICSANDDEVICES
££°£n
2!$!2(!.$"//+
)NTHECORPORATE COMBINEDSOLID STATEBOTTLE HIGHPOWERLEVELSAREGENERATEDATA SINGLEPOINTBYCOMBININGTHEOUTPUTSOFMANYPOWERAMPLIFIERMODULES)NGENERAL APOWERAMPLIFIERMODULE ASSHOWNIN&IGURE CONSISTSOFANUMBEROFIDENTICAL AMPLIFIERSTHATAREPARALLEL COMBINEDANDISOLATEDFROMONEANOTHERTHROUGHTHEUSE OFMICROWAVECOMBININGANDISOLATINGTECHNIQUES$RIVEPOWERFORTHISPARALLELGROUP ISOBTAINEDFROMDRIVERORPREDRIVERSTAGES USINGPHASE ANDAMPLITUDE MATCHEDMIR ROR IMAGEDMICROWAVEPOWERDIVIDERS!CIRCULATORATTHEMODULEOUTPUTPORTISCOM MONLYUSEDTOPROTECTTHEAMPLIFIERFROMTHEDAMAGINGEFFECTSOFHIGH LOAD6372 MOSTNOTABLYFROMTHEANTENNA!LSO ANCILLARYCIRCUITRYSUCHASENERGYSTORAGECAPACI TANCEFORPULSEDOPERATION BUILT IN TEST")4 SENSORS ORADAPTIVECONTROLCOMPONENTS MAYBEINCLUDED !MPLIFIER -ODULE $ESIGN 3OLID STATE AMPLIFIERS FOR USE IN TRANSMITTER DESIGNAREOFTENREFERENCEDBYTHEIRCLASSOFOPERATION!MPLIFIERSAREDESIGNATED ASOPERATINGEITHER#LASS ! " !" # $ % & OR '#LASS ! !" " AND
#GENERALLYREFERTOANALOGAMPLIFIERSWHEREAS#LASS $ % & AND 'GENERALLY REFERTOSWITCHING MODEAMPLIFIERS%ACHCLASSOFOPERATIONFORTHEANALOGMODES ISDEFINEDBYTHEMANNERINWHICHTHETRANSISTORISBIASEDEACHCLASSOFOPERATION
&)'52% 3OLID STATEPOWERAMPLIFIERMODULECOMBINESMANYSINGLESTAGEAMPLIFIERSTOGETHERWITH MATCHEDPHASEANDAMPLITUDEUSINGRESISTIVELYISOLATINGCOMBININGTECHNIQUES
3/,)$ 34!4%42!.3-)44%23
££°£
FORTHESWITCHINGMODESISDEFINEDBYTHEMANNERINWHICHTHETRANSISTORISBIASED ANDHOWTHEWAVESHAPEOFCURRENTANDVOLTAGEISMANIPULATED&OREXAMPLE CURRENT SWINGINANAMPLIFIERTHATISBIASED#LASS !REPLICATESEXACTLYTHEINPUTSIGNALUP TOTHEPOINTWHERETHETRANSISTORVOLTAGEANDCURRENTLIMITSAREREACHED)NPRACTICE #LASS !AMPLIFIERSARETHEMOSTLINEARASWELLASTHELEASTEFFICIENT(IGHDYNAMIC RANGELINEARRECEIVEAMPLIFIERSAREBIASED#LASS ! ANDAUDIOAMPLIFIERSMAYBEALSO BEBIASED#LASS !TOPRESERVETHELINEARITYOFTHEINPUTSIGNAL#LASS "AMPLIFIERS AREBIASEDSUCHTHATCONDUCTINGCURRENTINTHETRANSISTORFLOWSFOREXACTLYONEHALF OFTHEINPUTSIGNALVOLTAGESWING0USH PULLAMPLIFIERSMAYBEBIASEDINTHISFASHION SUCHTHATONETRANSISTOROPERATESOVERTHEPOSITIVEINPUTSIGNALSWING ANDTHESEC ONDTRANSISTOROPERATESOVERTHENEGATIVEINPUTSIGNALSWING(IGHEREFFICIENCYBUT HIGHERDISTORTIONISEXPERIENCEDWHENCOMPAREDWITHA#LASS !DESIGN4HE#LASS !"OPERATEDAMPLIFIERISBIASEDJUSTABOVECONDUCTIONUSINGATRICKLEQUIESCENT CURRENTANDISALSOCOMMONLYUSEDASAPUSH PULLAMPLIFIER#LASS #AMPLIFIERSARE BIASEDSUCHTHATCONDUCTINGCURRENTINTHETRANSISTORFLOWSFORLESSTHANOFTHE INCIDENTINPUTVOLTAGESIGNAL4HISALLOWSFORTHEHIGHESTEFFICIENCYATTHEEXPENSE OF POWER GAIN AND WITH THE HIGHEST LEVEL OF NONLINEAR OPERATION #LASS # BIASED TRANSISTORSAREACTUALLYhOFFvWITHOUTTHEPRESENCEOFAN2&SIGNALONTHEINPUT&OR USEINRADARTRANSMITTERAMPLIFIERS THE#LASS #AMPLIFIEROFFERSHIGHEREFFICIENCY OVER#LASS ! " OR !")NPRACTICE THEYCANBEMADETOBEhSELF BIASINGvAND HAVEBEENTHEPREFERREDCLASSOFOPERATIONFORTHESILICONBIPOLARTRANSISTORSUSEDAT 5(& ,BAND AND3BAND"ECAUSETHISCLASSOFOPERATIONISINHERENTLYNONLINEAR AS THETRANSISTORMODULATESBETWEENBEINGOFFANDSATURATEDTHROUGHEACH2&CYCLE THE HARMONICCONTENTISHIGH ANDAPPROPRIATEFILTERINGOFUNDESIREDHIGHERORDERSPEC TRALCONTENTMUSTBEAPPLIEDATTHEOUTPUTOFTHETRANSMITTER4HEAMPLIFIER#LASS $
% & AND 'AREHIGHEFFICIENCYSWITCHINGAMPLIFIERCONFIGURATIONSTHATREQUIRE SPECIALIZEDTERMINATIONOFTHESIGNALHARMONICSFILTERING INORDERTOMAXIMIZETHE AMPLIFIEREFFICIENCY4HESECANBECOMPLICATEDHARDWAREIMPLEMENTATIONSBUTMAY BE WARRANTED WHERE INCREMENTAL IMPROVEMENT IN EFFICIENCY BRINGS BENEFIT TO THE TRANSMITTERSYSTEM 3ILICON"*4STHATOPERATEINTHE(&THROUGH3 BANDFREQUENCYRANGESARECOMMONLY BIASED EITHER #LASS " OR #LASS # #LASS # OPERATION IS THE PREFERRED MODE BECAUSE THE2&OUTPUTPOWEROFTHEAMPLIFIERISMAXIMIZEDFORAGIVENPRIMEPOWERINPUT)N GENERAL THEBASE EMITTERJUNCTIONISREVERSE BIASED ANDCOLLECTORCURRENTISDRAWNFOR LESSTHANHALFOFAN2&CYCLE#OLLECTORCURRENTISDRAWNONLYWHENTHEINPUTVOLTAGE EXCEEDSTHEREVERSEBIASACROSSTHEINPUTANDTHEOUTPUTVOLTAGEISDEVELOPEDACROSSA RESONANT TUNEDLOAD4HENETRESULTISHIGHAMPLIFIEREFFICIENCY4HEPRACTICALIMPLICA TIONSOFA#LASS # BIASEDAMPLIFIERSTAGEAREASFOLLOWS .OQUIESCENTDCCURRENTISDRAWNWHILETHEDEVICEISNOTBEINGDRIVEN SUCHASIN THERADARRECEIVEMODE(ENCE THEREISNOPOWERDISSIPATIONINTHEAMPLIFIERWHILE THETRANSMITTERISOPERATINGINTHISMODE /NLYONEPOWERSUPPLYVOLTAGEISNECESSARYFORTHECOLLECTORTERMINALOFTHETRANSIS TOR4HE#LASS #OPERATIONISASELF BIAS WHEREINTHETRANSISTORDRAWSCOLLECTORCUR RENTONLYWHENTHE2&VOLTAGESWINGONTHEINPUTEXCEEDSTHEBUILT INPOTENTIALOF THEEMITTER BASEJUNCTION!DDITIONALREVERSEBIASINGMAYBEINTRODUCEDASARESULT OFTHEVOLTAGEDROPINDUCEDBYCURRENTFLOWACROSSPARASITICRESISTANCEOFTHEBASE OREMITTER BIASRETURN ANDINCOMMONBASEOPERATION THISWILLRESULTINDEGRADED POWERGAIN
L
L
££°Óä
2!$!2(!.$"//+
#LASS # BIASED AMPLIFIERS ARE VERY SENSITIVE TO ANY DEVIATIONS FROM THE NOMINAL OPERATINGPOINT#LASS # BIASEDAMPLIFIERSEXHIBITSENSITIVITYTO2&DRIVELEVELAND LOAD IMPEDANCE THAT MAY DEGRADE THE OUTPUT PULSE CHARACTERISTICS! SINGLE STAGE #LASS #BIASED"*4AMPLIFIERWILLTYPICALLYEXHIBITAVERYNARROWhLINEARvTRANSFER CHARACTERISTICTHELINEARREGIONMAYEXISTOVERONLYANARROW TO D"WINDOWOF 2&INPUTDRIVE4HISBECOMESSTRIKINGLYCRITICALWHENSEVERAL#LASS # BIASEDSTAGES ARECASCADEDINSERIES ASISCOMMONINMOSTAMPLIFIERCONFIGURATIONS4HEFINALTIER OFOUTPUTTRANSISTORSINASERIALAMPLIFIERCHAINMUSTBEDRIVENINTOSATURATIONBYTHE PRECEDINGSTAGES ANDTHEDRIVELEVELMUSTBEHELDRELATIVELYCONSTANTASAFUNCTION OFTIMEANDTEMPERATURE3INCETHESEDEVICESEXHIBITTHISNARROWOPERATINGRANGE SMALLDECREASESINTHEINPUT2&DRIVELEVELTOAMULTISTAGEAMPLIFIERMAYBRINGTHE FINALTIEROFDEVICESOUTOFSATURATION&AILURETOCONTROLTHESECONDITIONSACCURATELY CANRESULTINUNACCEPTABLYDEGRADEDOUTPUTPULSEFIDELITY
L
)NAVERYSIMPLESENSE THEDESIGNOFANAMPLIFIERMODULECONSISTSOFMATCHINGTHE POWERTRANSISTORSTOTHEPROPERIMPEDANCELEVELANDTHENCOMBININGTHEPOWERLEVELS ATTHESEIMPEDANCES!TYPICALPACKAGEDPOWERTRANSISTORHASLOWINPUTANDOUTPUT IMPEDANCESTHATMUSTBETRANSFORMEDUPTOHIGHERLEVEL USUALLYOHMS4HUS THE TYPICAL AMPLIFIER DESIGN TASK MUST ADDRESS BOTH LOW LOSS AND INEXPENSIVE REACTIVE IMPEDANCE TRANSFORMINGNETWORKSTHATCANPROVIDETHEPROPERSOURCEANDLOADIMPED ANCESTOTHETRANSISTOR4HECOMMONMEDIUMFORPROVIDINGTHISFUNCTIONISAMICROSTRIP TRANSMISSION LINE -ICROSTRIP IS A QUASI 4%- MODE TRANSMISSION LINE MEDIUM THAT REQUIRESPHOTOLITHOGRAPHICALLYDEFINEDLINESONALOW LOSS HIGH QUALITYDIELECTRICSUB STRATE2EACTIVECOMPONENTSTHATARENECESSARYASIMPEDANCE MATCHINGELEMENTSCAN BEAPPROXIMATEDINTHEMICROSTRIPFORMAT!NINEXPENSIVEREACTIVEMATCHINGNETWORK CANBEFORMEDBYUSINGANINTERCONNECTEDPATTERNOFMICROSTRIPELEMENTS3HUNT AND SERIES CONNECTEDINDUCTIVEREACTANCESASWELLASSHUNTCAPACITIVEREACTANCES ARETHE MOSTEASILYFABRICATEDANDMOSTFREQUENTLYUSEDMATCHINGELEMENTS 0OWER#OMBINING !POWERCOMBINERCOHERENTLYADDSTOGETHERTHE2&OUTPUT VOLTAGESOFINDIVIDUALAMPLIFIERSANDDELIVERSTHESUMTOTALOFTHEMODULESOUTPUT POWER MINUSTHELOSSESOFTHECOMBINER TOASINGLEPORT4HEOUTPUTSOFIDENTICAL SINGLE STAGEPOWERAMPLIFIERSARECOMMONLYSUMMEDBYUSINGWELL DOCUMENTED SPLITTING AND COMBINING TECHNIQUES &IGURE 4HESE TECHNIQUES ALSO ADDRESS ISOLATION BETWEEN PARALLELED AMPLIFIERS (AVING ISOLATION BETWEEN ADJACENT PORTS MEANSTHATIFONEDEVICEFAILS THEPOWERCOMBINERPROVIDESAFIXEDLOADIMPEDANCE TOTHEREMAININGDEVICEHOWEVER HALFTHEPOWEROFTHEREMAININGACTIVEDEVICEWILL BEDISSIPATEDINTHEISOLATIONRESISTOROFTHECOMBINER)NORDERTOACHIEVETHEMOST EFFICIENT COMBINING OF PARALLEL AMPLIFIER STAGES THE PHASE AND AMPLITUDE BALANCE OFINDIVIDUALSTAGESSHOULDBEASSIMILARASPOSSIBLE!NYDEVIATIONSFROMIDENTICAL PHASEANDAMPLITUDEBALANCERESULTINPOWEROUTPUTLOSTTOTHERESISTIVETERMINATING PORTOFTHECOMBINER4HEPOWERLOSTTOSIMILARITYDIFFERENCES FROMEITHERPHASEOR AMPLITUDE ISDICTATEDBYVECTORADDITIONANDISGIVENBY
0,/34 LOG31240 0 0 0 #/3P 0 0
WHEREPISTHEPHASEDIFFERENCEINDEGREESBETWEENTWOAMPLIFIERSTHATARESUMMED TOGETHER 3124INDICATESTHEhSQUAREROOTOF v AND0AND0ARETHEPOWERLEVELSOF EACHAMPLIFIERINWATTS&IGUREQUANTIFIESTHEIMPACTOFLOSTPERFORMANCEDUETO PHASEORAMPLITUDEIMBALANCE
3/,)$ 34!4%42!.3-)44%23
££°Ó£
&)'52% #OMMONMICROWAVEPOWER COMBININGCIRCUITTOPOLOGIESTHATAREUSEDTOPROVIDE ISOLATIONAMONGADJACENTPARALLELAMPLIFIERSINACORPORATECOMBININGSTRUCTURE
#ONTOURSOF6ECTORAL0OWER,OST
0HASE)MBALANCEDEG
D" D" D" D" D" D" D" D" D" D"
D"
D"
!MPLITUDE)MBALANCED" &)'52% #ONTOURSOFPOWERLOSTTOTHEISOLATIONLOADRESISTOROFANISOLATEDPOWERCOM BINERFORARANGEOFAMPLITUDEANDPHASEIMBALANCESBETWEENTWOCOMBINEDAMPLIFIERS7ITHAN AMPLITUDEIMBALANCEOFD"ANDAPHASEIMBALANCEOFn APPROXIMATELYD"OFPOWERWILL BELOSTTOTHEISOLATINGTERMINATIONOFTHEPOWERCOMBINER
££°ÓÓ
2!$!2(!.$"//+
)NGENERAL THEREQUIREMENTSFORAPOWERCOMBINERARE 4HECOMBINERSHOULDHAVELOWINSERTIONLOSSTOMAXIMIZETRANSMITTEREFFICIENCY 4HECOMBINERSHOULDHAVE2&ISOLATIONAMONGPORTS SUCHTHATFAILEDMODULESDONOT AFFECTTHELOADIMPEDANCESORCOMBININGEFFICIENCYFORTHEREMAININGFUNCTIONING MODULES 4HECOMBINERSHOULDPROVIDEACONTROLLED2&IMPEDANCETOTHEAMPLIFIERMODULES SUCHTHATTHEAMPLIFIERCHARACTERISTICSARENOTDEGRADED 4HEDISSIPATEDPOWERCAPABILITYOFTHEPOWERCOMBINERTERMINATIONSSHOULDBESUF FICIENTTOACCOMMODATEANYCOMBINATIONOFPOWERAMPLIFIERFAILURES 4HE MECHANICAL PACKAGING OF THE POWER COMBINER SHOULD ALLOW MODULES TO BE REPAIREDEASILY4HEPACKAGINGSHOULDALSOPROVIDESHORT EQUALPHASEANDLOW LOSS INTERCONNECTIONSBETWEENTHEAMPLIFIERMODULESANDTHECOMBINER
L
L
L
L
L
0OWERCOMBINERSMAYBEEITHERISOLATIVEORREACTIVEDESIGNS)NISOLATIVEDESIGNS ANY IMBALANCE OR DIFFERENCE BETWEEN THE PHASE AND AMPLITUDE OF THE VOLTAGES THAT AREBEINGCOMBINEDISDIRECTEDTOARESISTIVETERMINATION4HENETRESULTISTHATACON STANTLOADIMPEDANCEISPRESENTEDTOTHEAMPLIFIERUNDERALLCONDITIONSEVENWHENAN ADJACENTAMPLIFIERINACOMBININGTIERHASFAILED)NAREACTIVECOMBINERDESIGN ANY IMBALANCEINPOWERORPHASEBETWEENTWOINPUTSIGNALSRESULTSINREFLECTEDPOWERAND INCREASED6372TOTHEMODULEDRIVINGIT(IGHERTHANDESIREDFREQUENCY DEPENDENT PHASEANDAMPLITUDERIPPLEMAYRESULTFROMIMPROPERUSEOFTHISCONFIGURATION ! SPLITTER AND COMBINER NETWORK MAY ALSO PROVIDE SERIAL ISOLATION AMONG CAS CADEDAMPLIFIERSTAGESASWELLASPARALLELISOLATION&OREXAMPLE WHENA#LASS # BIASEDTRANSISTORISPULSED ITPASSESTHROUGHITSCUTOFF LINEAR ANDSATURATIONREGIONS #ONSEQUENTLY THE INPUT AND OUTPUT IMPEDANCES ARE DYNAMICALLY VARYING AND THE INPUTIMPEDANCECHANGESVERYDRAMATICALLY4HEDRAMATICALLYCHANGINGINPUTIMPED ANCEWILLPRESENTANUNDESIRABLELOADTOTHEPRECEDINGAMPLIFIERSTAGESUPPLYINGTHE 2&DRIVEPOWER4HISMAYVERYWELLSENDTHEPREVIOUSSTAGEINTOUNWANTEDOSCIL LATION(OWEVER AQUADRATURESPLITTERNETWORK IE APOWERDIVIDERTHATPROVIDESA D"SPLITASWELLASAnPHASEOFFSET CANBEUSEDTOPROVIDEACONSTANTIMPEDANCE ATTHEINPUTTOTHESPLITTERREGARDLESSOFTHEINDIVIDUALAMPLIFIERINPUTIMPEDANCES &IGURE 4HISENSURESTHATADRIVERAMPLIFIERSTAGEISPRESENTEDWITHAWELL MATCHEDLOAD 4YPICAL 2& TRANSMISSION MEDIA THAT ARE USED IN THE CONSTRUCTION OF HIGH POWER COMBINERS INCLUDE COAXIAL TRANSMISSION LINES MICROSTRIP OR STRIPLINE TRANSMISSION LINES OR WAVEGUIDE4HE CHOICE OF TRANSMISSION MEDIUM IS GENERALLY A FUNCTION OF MANY PARAMETERS INCLUDING PEAK AND AVERAGE POWER HANDLING CAPABILITY OPERAT INGFREQUENCYANDBANDWIDTH MECHANICALPACKAGINGCONSTRAINTS AND OFCOURSE THE OVERALLLOSSTHATCANBETOLERATED-OREOFTENTHANNOT ACOMBINERDESIGNUTILIZESA HIERARCHYOFCASCADEDDESIGNSTOSUMTHEOUTPUTSOFMANYMODULESHOWEVER UNIQUE CONFIGURATIONSTHATSUMMANYPORTSTOASINGLEPORTHAVEBEENBUILT !MPLITUDE AND 0HASE 3ENSITIVITIES 4HE PHASE AND AMPLITUDE SENSITIVITY OF TRANSISTORAMPLIFIERSTOPOWERSUPPLYRIPPLEMAYIMPACTTHE-4)IMPROVEMENTFACTOR THATCANBEATTAINED)NAMULTISTAGEAMPLIFIER THEPHASEERRORSDUETOPOWERSUPPLY SENSITIVITYOFSERIALLYCASCADEDSTAGESWILLADD)NADDITION CAREFULDESIGNMUSTTAKE INTO ACCOUNT INTERACTIONS THAT CAN OCCUR AS A RESULT OF THE MANY CASCADED STAGES OF SOLID STATEAMPLIFICATION4HESEINCLUDETHEFOLLOWING
3/,)$ 34!4%42!.3-)44%23
££°ÓÎ
&)'52% 0OWER AMPLIFIER COMBINING CONFIGURATIONS THAT PROVIDE MINIMUM INPUT PORT REFLECTEDPOWERA QUADRATURE COUPLEDAMPLIFIERPAIRANDB SPLIT 4AMPLIFIERPAIRWITHAnOFFSET 4HE AMPLIFIER INPUT VOLTAGE REFLECTION COEFFICIENT IS GIVEN AS ' AND THE AMPLIFIER VOLTAGE GAIN AS !2EPRINTEDWITHPERMISSIONFROM%$/STROFFETAL 3OLID 3TATE4RANSMITTERS .ORWOOD -!!RTECH (OUSE
0HASE ERRORS IN CASCADED STAGES SIMPLY ADD (OWEVER IT MAY ALSO BE POSSIBLE TO ARRANGE THEM TO CANCEL BY PROPER PHASING OF POWER SUPPLY RIPPLES FOR DIFFERENT STAGES 3IMILARLY IN A STAGE WITH . MODULES IN PARALLEL EACH WITH ITS OWN HIGH FREQUENCYPOWER CONDITIONEDPOWERSUPPLY THEOVERALLPHASERIPPLECANUSUALLYBE ASSUMEDTOBEREDUCEDBYAFACTOREQUALTOTHESQUAREROOTOF.IFTHEPOWERSUPPLY CLOCKSAREPURPOSELYNOTSYNCHRONIZED "ECAUSEOFSATURATIONEFFECTS AMPLITUDEERRORSINCASCADEDSTAGESDONOTSIMPLYADD (OWEVER AMPLITUDEERRORSINDRIVINGSTAGESWILLCAUSEDRIVE INDUCEDPHASEVARIA TIONSINTHEFOLLOWINGSTAGES ASNOTEDABOVE ALLOFWHICHMUSTBECOUNTED 4IMEJITTERINCASCADEDSTAGESSIMPLYADDSUNLESSTHESTAGESAREARRANGEDTOCANCELOR TOBEROOT SUM SQUARED)NADDITION AMPLITUDEFLUCTUATIONSINTHE2&DRIVEWILLALSO CAUSEDRIVE INDUCEDJITTER WHICHMAYEVENEXCEEDPOWER SUPPLY RIPPLE INDUCEDJITTER SOTHISFACTORMUSTBECAREFULLYMEASURED
L
L
L
3PECTRAL%MISSIONS 7HENARECTANGULAR2&DRIVEPULSEISAPPLIEDTOASINGLE MODULE THE AMPLIFIER WILL TYPICALLY SHOW RISE AND FALL TIMES THAT ARE ON THE ORDER OFNANOSECONDS4HEOUTPUTSIGNALSPECTRUMOFTHISPULSESHAPEMAYNOTMEETSPEC TRALEMISSIONSREQUIREMENTS ANDITMAYBENECESSARYTOSLOWTHERISEANDFALLTIMES (OWEVER THE AMPLIFIER OPERATING REGION OF OPTIMUM EFFICIENCY OCCURS AS THE TRAN SISTOR IS DRIVEN INTO SATURATION AND FOR A LARGE TRANSMITTER THERE MAY BE NUMEROUS TIERSOFCASCADEDSATURATEDAMPLIFIERS7ITHSOMANYCASCADEDSATURATINGAMPLIFIERS IT BECOMESVERYDIFFICULTTOCONTROLTHERISEANDFALLTIMESASARESULTOFTHENONLINEARITY THATISINTRODUCEDINTOTHEPOWERTRANSFERFUNCTIONFORTHETRANSMITTER#ONSEQUENTLY ANINPUTPULSESHAPEWITHVERYEXAGGERATEDSLOWRISEANDFALLTIMESMAYBENECESSARY TOACHIEVETHEDESIREDOUTPUT PULSESPECTRALCOMPOSITION
££°Ó{
2!$!2(!.$"//+
££°xÊ - Ê",Ê/ Ê-" -// Ê *- Ê,,9Ê/, - // , )NCONTRASTTOTHEDESIGNOFTHESOLID STATEBOTTLETRANSMITTERWHERESIGNIFICANTLOSSESCAN ACCRUEINTHECOMBININGCIRCUITRY THESOLID STATEPHASEDARRAYANTENNAUSESINDIVIDUAL TRANSMITRECEIVE42 MODULESWITHINTERNALPHASESHIFTCAPABILITY%ACH42MODULE ISLOCATEDBEHINDANASSOCIATEDRADIATINGELEMENTINATWO DIMENSIONALARRAY)NTHIS FASHION THEBEAMISMOREEFFICIENTLYFORMEDINSPACEANDONEAVOIDSTHELOSSESTHAN CANACCUMULATEINCORPORATECOMBINING4HETRANSMITRECEIVE42 MODULE REGARD LESS OF COMPLEXITY HAS FIVE FUNDAMENTAL FUNCTIONS TO PROVIDE GAIN AND POWER OUTPUTINTHETRANSMITMODE TOPROVIDEGAINANDLOW NOISEFIGUREINTHERECEIVE MODE TOSWITCHBETWEENTRANSMITANDRECEIVESTATES TOPROVIDEPHASESHIFTFOR BEAMSTEERINGFORBOTHTRANSMITANDRECEIVEPATHS AND TOPROVIDESELF PROTECTION FORTHELOW NOISEAMPLIFIER 4HEFIRST42MODULEWASDEVELOPEDBY4EXAS)NSTRUMENTSINTHEMID SAS PARTOFTHE-OLECULAR%LECTRONICSFOR2ADAR!PPLICATIONS-%2! PROGRAMINITI ATEDBYTHE53!IR&ORCETODETERMINETHEFEASIBILITYOFUSING8 BAND42MODULES INASOLID STATEPHASEDARRAYRADAR!SARESULTOFCONTINUOUSDEVELOPMENT PHASED ARRAYSAREUSEDINMULTIPLEMILITARYANDCOMMUNICATIONSSYSTEMS4HEADVANTAGES OFAPHASEDARRAYTRANSMITTERINCLUDE THEABILITYTOHAVEMULTIPLEINDEPENDENTLY STEEREDBEAMSFROMASINGLEAPERTURE THESPEEDOFELECTRONICVERSUSMECHANI CALBEAMLOCATIONS AND THEEFFICIENCYOFUTILIZINGSPACECOMBININGINSTEADOF PERFORMINGTHEPOWERCOMBININGBEFORETHEANTENNA"LOCKDIAGRAMSOFREPRESEN TATIVE42MODULEFUNCTIONSARESHOWNIN&IGURE&UNCTIONALLY THESEAREALL EQUIVALENT BUTTHEPARTITIONINGOFCIRCUITFUNCTIONSISDEPENDENTONTHECAPABILITY OFTHE--)#SUSED ANDDIFFERENTIMPLEMENTATIONSMAYBEREQUIREDTOADDRESSA KEYRELIABILITYREQUIREMENTORAKEYPERFORMANCEPARAMETER&OREXAMPLE THEUSE OFASINGLEHIGHPERFORMANCEPOWERAMPLIFIERMAYOBVIATETHENEEDFORCOMBIN INGTWOLESSERPOWERAMPLIFIERSTOGETHERTOACHIEVETHESAMEPERFORMANCE4HESE REPRESENT COST CAPABILITY AND AVAILABILITY TRADES THAT MIGHT BE EXERCISED BY THE 42MODULEARCHITECT -ICROWAVE -ONOLITHIC )NTEGRATED #IRCUITS --)#S $URING THE S IT WASTHEREDUCTION TO PRACTICEOFTHEMICROWAVEMONOLITHICINTEGRATEDCIRCUIT--)# THAT ENABLED MOST HIGH FREQUENCY PHASED ARRAYS TO BE REALIZED --)# USE IN 42 MODULEDESIGNHASENABLEDBOLDNEWMODULECONFIGURATIONS ANDHENCEPHASEDARRAY SYSTEMS TOBEENVISIONED"ECAUSESOMEOFTHEMORECOMPLEXFUNCTIONSINTHEGENERIC 42MODULEBLOCKDIAGRAMCANBEFABRICATEDBYUSING--)#TECHNOLOGY THECOM PONENTSTHATCANBEREALIZEDTHROUGHTHEUSEOFTHISTECHNOLOGYCANBEEMPLOYEDTO CREATESYSTEMARCHITECTURESTHATAREDIFFICULT IFNOTIMPRACTICAL TODESIGNWITHOTHER LESSINTEGRATEDTECHNOLOGIES4HE--)#DESIGNAPPROACHUTILIZESACTIVEANDPASSIVE DEVICESTHATHAVEBEENMANUFACTUREDBYUSINGASINGLEPROCESS!CTIVEANDPASSIVECIR CUITELEMENTSAREFORMEDONASEMI INSULATINGSEMICONDUCTORSUBSTRATETHROUGHVARI OUSDEPOSITIONSCHEMES4HEMONOLITHICAPPROACHTOCIRCUITDESIGNINHERENTLYOFFERS SEVERALADVANTAGES ,OW COSTCIRCUITRY #OMPONENTASSEMBLYISELIMINATEDBECAUSECOMPLEXCIRCUIT CONFIGURATIONSUSINGBOTHACTIVEANDPASSIVECOMPONENTSAREBATCHPROCESSEDONTHE SAMESUBSTRATE
L
3/,)$ 34!4%42!.3-)44%23
££°Óx
&)'52% #OMMON 42 MODULE CONFIGURATIONS MAKE USE OF POWER AMPLIFIERS LOW NOISEAMPLIFIERS DUPLEXERS SWITCHES ANDCONTROLSTOENABLEON FACEBEAMSTEERINGINAPHASEDARRAYANTENNA!RCHITECTUREVARIATIONSMAYRESULT FROM COMPONENT CAPABILITY DIFFERENCES AS WELL AS PERFORMANCE AND PACKAGING CONSTRAINTS
)NCREASEDRELIABILITY "ATCH PROCESSEDCOMPONENTSLEADTOAREDUCEDNUMBEROF PARTSFROMTHERELIABILITYSTANDPOINTANDHENCETOINCREASEDOPERATINGLIFETIMES )NCREASEDREPRODUCIBILITY #IRCUITRYTHATISBATCH PROCESSEDORCIRCUITSTHATORIGI NATEFROMTHESAMEWAFEREXHIBITCONSISTENTELECTRICALCHARACTERISTICSFROMCOMPONENT TOCOMPONENT 3MALL SIZE AND WEIGHT )NTEGRATION OF ACTIVE AND PASSIVE COMPONENTS ONTO A SINGLECHIPRESULTSINHIGH DENSITYCIRCUITRYWITHMULTIPLEFUNCTIONSONASINGLE CHIP /VERALL THE 42 MODULE CAN BE MADE MUCH SMALLER THAN WITH DISCRETE COMPONENTS
L
L
L
4HEPARTITIONINGOF42MODULECIRCUITFUNCTIONSONTOMONOLITHICCHIPSUSUALLYREP RESENTSATRADEOFFAMONGSEVERALDESIGNISSUES ANDTHERESULTANTCIRCUITCONFIGURATIONS REPRESENTACOMPROMISEAMONGTHEGOALSOFOPTIMUM2&PERFORMANCE HIGHLEVELSOF INTEGRATION ANDFABRICATIONYIELDSTHATARECONSISTENTWITHPROCESSINGCAPABILITIESOF 'A!S--)#S!MONGTHESINGLE CHIPCIRCUITDESIGNSTHATHAVEBEENREPORTEDFROM 5(&THROUGHMILLIMETER WAVEFREQUENCIESAREPOWERAMPLIFIERS LOW NOISEAMPLIFI ERS WIDEBANDAMPLIFIERS PHASESHIFTERS ATTENUATORS 42SWITCHES ANDOTHERSPECIAL FUNCTION DESIGNS .OTEWORTHY DESIGN CONSIDERATIONS FOR THESE --)# FUNCTIONS ARE DESCRIBEDNEXT
££°ÓÈ
2!$!2(!.$"//+
0OWER!MPLIFIERS 4HEAREACONSUMEDBYCOMBININGINPARALLELTHETOTALNUM BEROFGATEFINGERSIE TOTALGATEPERIPHERY ISUSUALLYATAPREMIUM&ORHIGH POWER DESIGN THE LOAD IMPEDANCE PRESENTED TO THE FINAL DEVICE MUST BE CAREFULLY CHOSEN SUCHTHATPOWEROUTPUTANDEFFICIENCYAREMAXIMIZED!LSO TOOMUCHGATEPERIPHERY MAY INCREASE THE CHIP AREA SUCH THAT COST OF THE COMPONENT BECOMES UNATTRACTIVE ,OSSESINTHEOUTPUTCIRCUITOFTHEFINALSTAGECANSIGNIFICANTLYREDUCEPOWEROUTPUT ANDEFFICIENCY/FF CHIPMATCHINGMAYBENECESSARYTOMAXIMIZEPOWEROUTPUTFORA GIVENDESIGN 'A!SISAPOORTHERMALCONDUCTOR0OWER&%4DESIGNTHATADDRESSES THERMALMANAGEMENTISREQUIRED!DEQUATEHEATSINKINGOFTHECHIPISMANDATORYAND MAYBECOMEALIMITINGFACTORINHIGHPERFORMANCEDESIGNS #AREFULATTENTIONMUST BE PAID TO UNPLANNED VOLTAGE STRESSES ON THE POWER AMPLIFIER EITHER FROM TRANSIENT INDUCED EFFECTS OR LOAD IMPEDANCE VARIATIONS IN ORDER TO MAINTAIN THE DESIRED RELI ABILITY &OREFFICIENTMULTIPLE STAGEDESIGNS ITISNECESSARYTHATTHEFINALSTAGEOF THEAMPLIFIERREACHSATURATIONBEFORETHEPRECEDINGSTAGES4HISMUSTBEADDRESSEDIN THECIRCUITDESIGN ,OW .OISE!MPLFIIERS -ULTIPLESTAGELINEARDESIGNSREQUIREPROPERDEVICE SIZING OF SUCCESSIVE STAGES IN ORDER TO MAINTAIN LOW INTERMODULATION DISTORTION PRODUCTS #IRCUITLOSSESONTHEINPUT BEFORETHEFIRSTSTAGE DEGRADETHENOISE FIGUREOFTHEDESIGNTHEREFORE SOMEDESIGNSUTILIZEOFF CHIPMATCHING 4HEBEST NOISE FIGURE USUALLY REQUIRES A BIASCONDITIONTHATISCLOSERTOTHE PINCH OFFVOLTAGEOFTHE&%4THAN FORAPOWERAMPLIFIER4HEPINCH OFF VOLTAGE IS THE VOLTAGE THAT WHENAPPLIEDTOTHEGATETERMINAL CAUSES THE CURRENT IN THE TRAN SISTOR CHANNEL TO STOP FLOWING 4HUS THE TRANSISTOR IS hPINCHED OFFv AND VARIABILITY AROUND THIS OPERATING POINT CAN CAUSE LARGE CIRCUITPERFORMANCEVARIABILITYIF DESIGNED POORLY "OTH GAIN AND NOISE FIGURES ARE HIGHLY DEPEN DENT ON THE PINCH OFF VOLTAGE WHEN THE &%4 IS BIASED CLOSE TO PINCH OFF "ECAUSE THE PINCH OFF VOLTAGE CAN VARY AMONG DEVICES FROM THE SAME WAFER THE BIAS CONDITION MUST BE CHOSEN CARE FULLY'AINANDNOISEFIGURESARE USUALLYTRADEDOFFAGAINSTREPEAT ABLE PERFORMANCE %XAMPLES OF AN ,BAND TWO STAGE LOW NOISE AMPLIFIER 'A!S --)# AND AN , BANDLOW NOISEAMPLIFIER--)#3HOWN 8 BAND POWER AMPLIFIER 'A!S &)'52% HEREARETHESPIRALINDUCTORS METAL NITRIDE METALCAPACITORS --)#ARESHOWNIN&IGURE ANDVIA HOLECONNECTIONSTOGROUND0HOTOGRAPHCOURTESYOF AND&IGURE RESPECTIVELY 2AYTHEON#OMPANY
3/,)$ 34!4%42!.3-)44%23
££°ÓÇ
&)'52% 8 BANDTWO STAGEPOWERAMPLIFIER--)#SHOWINGPARAL LELCOMBINATIONOF&%4CELLSINTHEOUTPUTSTAGE4HISEXAMPLEWASFABRI CATEDON§M THICK'A!SSUBSTRATE4HE2&LINESAREMICROSTRIP FORMAT 4%- MODETRANSMISSIONLINES0HOTOGRAPHCOURTESYOF2AYTHEON#OMPANY
4RANSMIT2ECEIVE 3WITCHING &OR SWITCHING APPLICATIONS THE &%4 DESIGN SHOULDBECHOSENSUCHTHATTHERATIOOF/&& /.RESISTANCEOFTHE&%4ISKEPTASHIGHAS POSSIBLE4HECHANNELLENGTHLARGELYDETERMINESTHE/.RESISTANCEANDHENCETHEINSER TIONLOSSOFTHEDEVICE4HETRADEOFFBETWEENSHORTGATELENGTHTHUSLOWERPROCESSING YIELD ANDINSERTIONLOSSMUSTBEEXAMINED 4HEVALUEOFTHEPARASITICDRAIN SOURCE CAPACITANCEWILLAFFECTTHE/&& STATEISOLATIONOFTHEDEVICE4HISCAPACITANCEDEPENDS LARGELY ON THE SOURCE DRAIN SPACING OF THE &%4 GEOMETRY #RITICAL APPLICATIONS ARE USUALLYONLYTHEFRONT ENDSWITCHINGCONFIGURATIONSINA42MODULE IE BEFORETHE RECEIVELOW NOISEAMPLIFIERORAFTERTHETRANSMITAMPLIFIER 0HASE 3HIFTERS $IGITALLY CONTROLLED PHASE SHIFTER DESIGNS GENERALLY UTI LIZE EITHER A SWITCHED LINE OR A LOADED LINE CIRCUIT CONFIGURATION USING EITHER DISTRIBUTEDTRANSMISSION LINECOMPONENTSORLUMPED ELEMENTEQUIVALENTCIRCUITS TOACHIEVEMULTIPLE BITPHASESHIFTING3WITCHED LINECONFIGURATIONSRELYON&%4 SWITCHESTOSWITCHLENGTHSOFTRANSMISSIONLINEINANDOUTOFTHECIRCUITANDARE TYPICALLYUSEDFORHIGHERFREQUENCIESWHERELESSCHIPAREAISNEEDED,OADED LINE CONFIGURATIONSUSETHESWITCHED&%4PARASITICSASCIRCUITELEMENTSTOINTRODUCETHE NECESSARYPHASECHANGES 4HETYPICALPROCESSINGANDCONSTRUCTIONSEQUENCEFORA--)#CHIPISFAIRLYSIMILAR AMONGTHE'A!SFOUNDRIES&IGURE )NTHISFIGURE THEACTIVECHANNELREGION
££°Ón
2!$!2(!.$"//+
%0)4!8)!,,!9%23
-%3!%4#(!.$/89'%. )-0,!.4&/2)3/,!4)/. /(-)#-%4!,0!44%2.).' $%0/3)4)/.!.$!,,/9
% "%!-/2/04)#!,,9 $%&).%'!4%0!44%2. '!4%2%#%33 !.$'!4% -%4!,$%0/3)4)/. 0(%-4%0)4!8)!,,!9%23
'A!S35"342!4%
/(-)#-%4!,
$%&).%#!0!#)4/2 "/44/-0,!4%-%4!,
$%0/3)43I.0!33)6!4)/. &/,,/7%$"94A.4().&),2%3)34/23
.)42)
%$#APACITOR
0,!3-!%4#( 4!.4!,5-.)42)
%$
0,!3-!%4#( 3),)#/..)42)
%$'A!S
'!4%-%4!,
2ESISTOR
4!.4!,5-
&%4
4()#+-%4!,
.)42)
%$
4!.4!,5MM
#!0"/44/-
$%&).%!)2"2)$'%0),,/73 0!44%2.!.$$%0/3)4 4()#+-%4!, 2%-/6%!)2 "2)$'%0),,/73 !.$$/ &).!,&2/.43)$%$#4%34 #!0"/44/MM
-/5.47!&%2/.#!22)%2 '2).$%4#(4/MM -!3+!.$%4#(6)!3
0,!4%506)!3 $%&).%'2)$ $)#% !.$$)3-/5.4 $%&).%!)2"2)$'%3 4()#+-%4!, %,%#42)#!,4%34 7!8 3!00()2%
&)'52% 'A!S--)#PROCESSINGMAKESUSEOFDEPOSITIONANDETCHINGTECHNIQUES TOFIRSTDEFINETHEACTIVECHANNELREGIONOFTHETRANSISTORn FOLLOWEDBYTHEDEPOSITIONOF METALS DIELECTRICLAYERS ANDRESISTIVELAYERSFORMINGTHEPASSIVECOMPONENTSn 4HEN THICKMETALINTERCONNECTS AREINTRODUCED FOLLOWEDBYBACKSIDEPROCESSINGTOCONNECT2& GROUNDTOTHETOPSIDECOMPONENTSn
3/,)$ 34!4%42!.3-)44%23
££°Ó
OFA&%4ISDELINEATEDBYANYOFSEVERALPATTERNINGTECHNIQUESONASEMI INSULATING 'A!SSUBSTRATESUCHASIONIMPLANTATIONORMOLECULARBEAMEPITAXY/NCETHE&%4 HASBEENDEFINED ACOMBINATIONOFDEPOSITEDDIELECTRICFILMSANDMETALLAYERSISUSED TOFORMTHEPASSIVECOMPONENTSSUCHASMETAL INSULATOR METALCAPACITORS ANDALSO TOINTERCONNECTALLTHEELEMENTSOFTHECIRCUIT3TANDARDLIBRARIESOFCIRCUITELEMENTS MAYINCLUDE&%4SUSEDASLINEARAMPLIFIERS LOW NOISEAMPLIFIERS SATURATINGPOWER AMPLIFIERS OR SWITCHES RESISTORS CAPACITORS INDUCTORS DIODES TRANSMISSION LINES INTERCONNECTS ANDPLATEDGROUNDVIAS 4RANSMIT2ECEIVE-ODULE#HARACTERISTICS 4HEIMPACTOFANTENNAARRAYELEC TRICALREQUIREMENTSONTHEPACKAGINGOF--)#COMPONENTSINTOA42MODULEISFUN DAMENTAL4HEPERIODICNATUREOFDIGITALPHASESHIFTINGATEACHRADIATINGELEMENTCAN CREATEMULTIPLEDISTINCTLOCATIONSINSPACEWHEREPARASITICBEAMSGRATINGLOBES CAN OCCUR)NARRAYDESIGN THISISAVOIDEDIFTHERADIATINGELEMENTSPACINGD ISLESSTHAN THATDESCRIBEDBY D K SINP
"
7HEREDISTHESPACINGBETWEENADJACENTRADIATINGELEMENTS KISTHEWAVELENGTHOF THEHIGHESTOPERATINGFREQUENCY ANDPISTHEMAXIMUMSCANANGLEOFTHEARRAY&OR HEMISPHERICAL PHASED ARRAY COVERAGE THE MAXIMUM SCAN ANGLE CAN BE UPWARDS OF on DEPENDINGONTHENUMBEROFARRAYFACESUSEDINTHESYSTEMCONFIGURATION4HUS FORAN8 BANDARRAYTHATREQUIRESSCANNINGTOLARGEANGLES THESPACINGBETWEENRADIAT INGELEMENTS ANDBYIMPLICATION THEMAXIMUMSPACINGAVAILABLEFOR42MODULES WHENTHEYAREALIGNEDBEHINDTHERADIATINGELEMENTSMUSTBEONTHEORDEROFINCHES ORLESS!LLEVIATIONSINPACKAGINGMAYBEALLOWABLEIFTHESCANVOLUMEISNOTREQUIRED TOEXTENDTOAFULLFIELDOFVIEW6ALUESOFELEMENTSPACINGTHATSATISFY%QARE SHOWNASAFUNCTIONOFSCANANGLEFORSOMEOFTHECOMMONRADARFREQUENCYBANDS THROUGHMM WAVEFREQUENCIESIN&IGURE4HEIMPLICATIONOFTHISGRAPHISTHAT FULL42MODULEFUNCTIONALITYMUSTBEPACKAGEDINTOTHESPACEANDVOLUMEBEHINDTHE PLANARARRAY ANDTHISREQUIREMENTCANPOSEVERYDIFFICULTCHALLENGESTOTHE42MODULE
" $!%
# &'
&)'52% -AXIMUMOPERATINGFREQUENCYANDWORST CASESCAN ANGLEDEFINETHEMAXIMUMALLOWABLEDISTANCEAMONGADJACENTRADIAT INGELEMENTS42MODULESFITTINGBEHINDEACHELEMENTARECONSTRAINED BYTHESESPACINGS
££°Îä
2!$!2(!.$"//+
DESIGNER IN ORDER TO SATISFY THE 2& ELECTRICAL DC ELECTRICAL THERMAL AND RELIABILITY REQUIREMENTS0ACKAGINGOF--)#COMPONENTSINTOTHE42MODULEMUSTTAKEINTO CONSIDERATION MULTIPLEELEMENTSASTHEYIMPACTTHEELECTRICALPERFORMANCE 0OWER #ONDITIONING #ONSIDERATIONS 0ULSED TRANSMIT AMPLIFIERS CAN CONSUME VERY HIGH DC CURRENTS AND SPECIAL DESIGN ATTENTION MUST BE PAID TO PARASITIC INDUC TANCETHATCANGENERATEVERYHIGHVOLTAGESPIKESANDCAUSEDAMAGETO--)#POWER AMPLIFIERS)NADDITION THEDCPOWERSOURCEMUSTINCLUDEAPPROPRIATEENERGYSTORAGE SOMETIMESLOCALLYINTHEMODULE INORDERTOSUPPORTTHEMINIMUMVOLTAGEPULSEDROOP ASAFUNCTIONOFTIME %NVIRONMENTAL0ROTECTION#ONSIDERATIONS --)#COMPONENTSUTILIZETHIN FILM METALDEPOSITIONTECHNIQUESTODELINEATETHEVERYFINEFEATURESTHATMAKEUPTHEMICRO WAVECIRCUITRY4HESEFEATURESARESUSCEPTIBLETOPOTENTIALSHORT TERMFAILUREDUETO CORROSION METALMIGRATION ANDDENDRITICGROWTHIFTHEREAREVOLTAGESONTHECIRCUITRY WHENEXPOSEDTOANATMOSPHERETHATCAUSESMOISTURETOCONDENSEONTHECIRCUITRY 4HUS AHERMETICPACKAGEWITHADRY NITROGEN FILLEDINTERIORISUSUALLYEMPLOYEDTO ENSURELONG TERMRELIABILITY(ERMETICPACKAGINGALSOBRINGSWITHITTHEUNDESIRABLE EFFECT OF TRAPPING INSIDE THE HOUSING ANY MOLECULAR CONTENT THAT OUTGASES INTO THE INTERIORCAVITY)NPARTICULAR HYDROGENCANBEPRESENTINTHEINTERIORMETALPLATINGAND HAS BEEN KNOWN TO CAUSE LONG TERM RELIABILITY CONCERNS IN SOME 'A!S AMPLIFIERS /NESOLUTIONINVOLVESTHEUSEOFANINTERNALHYDROGENGETTERTOCOUNTERBALANCETHE RELIABILITY IMPACT! GETTER IS A MATERIAL INCLUDED IN THE MODULE HOUSING TO ABSORB RESIDUALHYDROGEN -ECHANICAL0ACKAGING#ONSIDERATIONS 4HE42MODULEHOUSINGMUSTBEMADE OF MATERIALS THAT PROVIDE FOR ADEQUATE THERMAL MANAGEMENT AND LONG TERM RELIABIL ITY-ATERIALSTHATSIMULTANEOUSLYSUPPORTEXPOSURETOSHOCK VIBRATION TEMPERATURE CYCLING ANDADEQUATETHERMALMANAGEMENTMUSTBEUSED-ATERIALSTHATMATCHVERY CLOSELYTHECOEFFICIENTOFTHERMALEXPANSION#4% OFTHESEMICONDUCTORMATERIALMUST BEUSEDINTHEDESIGNOFTHEHOUSINGSUCHTHATCRACKINGOFTHESEMICONDUCTORDEVICES DOESNOTOCCURDURINGTHERMALCYCLINGTHATHAPPENSDURINGNORMALOPERATIONORDURING TEMPERATURECHANGESDURINGASSEMBLYANDTEST %LECTRICAL)NTERCONNECTION#ONSIDERATIONS 4HEINTERCONNECTIONOF--)#CHIPS WITHINTHE42MODULEMUSTUTILIZECONTROLLEDIMPEDANCETRANSMISSIONLINESWITHLOW INSERTIONLOSS4HUS SOMECOMBINATIONOFHIGH QUALITYMICROWAVEDIELECTRICMATERIAL MUSTBEINTEGRALTOTHEMICROWAVEELECTRICALANDMECHANICALDESIGNOFTHEMODULE !TTENTION TO THE COEFFICIENT OF THERMAL EXPANSION AND MANUFACTURABILITY ISSUES WILL IMPACTTHECHOICEOFUSABLEMATERIALS42MODULESALSOGENERALLYREQUIREASMANYAS nCONTROLORBIASCONNECTIONSINORDERTOINTERFACEWITHAMPLIFIERS CONTROLCIRCUITRY ANDPHASESHIFTERS4HEINTERCONNECTIONDENSITY ESPECIALLYATHIGHERFREQUENCIES CAN BECOMEAPACKAGINGDESIGNCHALLENGE!TFREQUENCIESABOVE'(Z THEUSEOFCON VENTIONAL CONNECTORS IS USUALLY PROHIBITIVE DUE TO THE SMALL WIDTH AVAILABLE IN FULL FIELD OF VIEWARRAYS -ANUFACTURABILITY#ONSIDERATIONS "YDEFINITION THEUSEOF--)#COMPONENTS INVOKESAMICROELECTRONICASSEMBLY TEST ANDHANDLINGMANUFACTURINGINFRASTRUCTURE 4HEMANUFACTURINGOFLOW COST42MODULESISPARAMOUNTTOBEINGABLETOEFFECTIVELY PRODUCE AFFORDABLE ARRAYS $ESIGN METHODOLOGIES SUCH AS STATISTICAL PERFORMANCE
3/,)$ 34!4%42!.3-)44%23
££°Î£
REPRESENTATION AREOFTENEXPLOITEDTOMAXIMIZEFUNCTIONALYIELD4HEINTEGRATIONOF DESIGNANDMANUFACTURINGPROCESSESISAKEYCOMPONENTTOSUCCESSFULEXECUTIONOF PRODUCTMANUFACTURING
££°ÈÊ -" -// Ê-9-/ Ê 8 * 0!6%0!735(&%ARLY7ARNING2ADAR 4HE0!6%0!73!.&03 SYSTEMISA5(&SOLID STATEACTIVEAPERTUREPHASEDARRAYRADARTHATWASBUILTFORTHE %LECTRONIC3YSTEMS$IVISIONOFTHE53!IR&ORCEBYTHE%QUIPMENT$IVISIONOFTHE 2AYTHEON#OMPANYDURINGTHELATES4HERADARISALONG RANGESYSTEMWITHA PRIMARY MISSION TO DETECT AND TRACK SEA LAUNCHED BALLISTIC MISSILES 4HE TWO FACED RADARUSESACTIVE42MODULESPERFACE ANDEACHMODULEINTERFACESWITHADIPOLE ANTENNAELEMENT%XTRAELEMENTSANDANARROWBEAMAREUSEDONRECEIVE ANDUPGRADE CAPABILITYHASBEENINCLUDEDFORTHEFUTUREINSTALLATIONOFUPTO42MODULESPER ARRAYFACE4HEPEAKPOWEROUTPUTFROMEACHFACE WHENPOPULATEDWITHMODULES ISK7 ANDTHEAVERAGEPOWEROUTPUTISK7 !MONGTHEMODULESPERFACE GROUPSOF42MODULESAREOPERATEDASA SUBARRAY)NTRANSMIT AHIGH POWERARRAYPREDRIVERISUSEDTODRIVESUBARRAYDRIVER AMPLIFIERS%ACHOFTHESEPOWERAMPLIFIERSPROVIDESENOUGH2&DRIVEFORALLMOD ULESINONESUBARRAY)NRECEIVE THESIGNALFROMEACHOFTHESUBARRAYSISFEDINTOA RECEIVEBEAMFORMINGNETWORK 4HE42MODULECONTAINSPREDRIVER DRIVER ANDFINALTRANSMITAMPLIFIERS TRANSMIT RECEIVESWITCHING LOW NOISEAMPLIFIERS LIMITER PHASESHIFTERS ANDLOGICCONTROL4HE 42MODULEBLOCKDIAGRAMISSHOWNIN&IGURE ANDAPHOTOGRAPHISSHOWNIN
&)'52% "LOCKDIAGRAMOFTHE0!6%0!73TRANSMITRECEIVEMODULESHOWSA TRANSISTOR DRIVINGCONFIGURATIONFORTHETRANSMITAMPLIFIERANDAQUADRATURESPLITTERONTHEOUTPUTTOGENERATEAPOLAR IZEDFEEDTOTHERADIATINGELEMENT
££°ÎÓ
2!$!2(!.$"//+
&)'52% 0!6%0!735(&42MODULECONSISTSOFTRANSMITMODULEANDRECEIVE MODULE IN A NESTED CONFIGURATION OF CAST ALUMINUM HOUSINGS 0HOTOGRAPH COURTESY OF 2AYTHEON#OMPANY
&IGURE4HETRANSMITTERPORTIONOFTHE42MODULECONTAINSSEVENSILICONBIPO LARPOWERTRANSISTORS OPERATED#LASS #FROMA6DCPOWERSUPPLY4HETRANSMIT AMPLIFIERCHAINCONSISTSOFAPREDRIVERTRANSISTORFEEDINGTWODRIVERTRANSISTORS INTURN FEEDINGFOURFINALTRANSISTORS IE A CONFIGURATION%ACHOFTHEFOURFINALSTAGES DELIVERS 7 PEAK FOR MS PULSE WIDTHS AT DUTY CYCLES UP TO -ORE THAN TRANSISTORSHAVEBEENBUILTINTOMORETHAN MODULES&UTUREUPGRADESOF THISDESIGNINTHE"-%73ARRAYSWILLUSETHEMOREPOWERFULANDEFFICIENT3I,$-/3 &%4TECHNOLOGYFORENHANCEDPERFORMANCECAPABILITIES !.303 3HIPBOARD3EARCH2ADAR 4HE!.303 WASANEXISTING5(& TUBE TYPE LONG RANGE $SHIPBOARDSEARCHRADARSYSTEM FORWHICHANEWSOLID STATE TRANSMITTERWASBUILTDURINGTHESTOREPLACETHETUBE4HESOLID STATETRANSMITTER WASBUILTFORTHE.AVAL3EA3YSTEMS#OMMANDBYTHETHEN 7ESTINGHOUSE%LECTRIC #ORPORATION4HEEXISTINGWAVEFORMFROMTHEORIGINALTRANSMITTERWASNOTCHANGED ANDTHESOLID STATEUNITWASINSTALLEDASADIRECTRETROFIT4HISWASNOTQUITEASDIFFICULT ASUSUAL BECAUSETHETUBE TYPESYSTEMALREADYUSEDLONGPULSESANDPULSECOMPRES SIONWITHADUTYCYCLEOFNEARLY WHICHISMUCHHIGHERTHANOLDERDUTYCYCLE SYSTEMS!LTHOUGHITMAYHAVEBEENDESIRABLETOGOTOAHIGHERDUTYCYCLEANDLOWER PEAKPOWERTOMAKETHESOLID STATERETROFITEASIER THE.AVYPREFERREDNOTTOHAVETO MODIFYTHERESTOFTHESYSTEM 4HE K7PEAKPOWERTRANSMITTERUSEDATOTALOFHIGH POWERAMPLIFIERMOD ULES WHICH ALONGWITHPOWERCOMBINING PREDRIVERS DRIVERS ANDCONTROLCIRCUITRY WEREHOUSEDINTHREESEPARATECABINETS4HEREWEREFINALPOWEROUTPUTMODULES ARRANGEDINTWOGROUPSOF%ACHMODULE&IGURE PRODUCED7PEAKAND 7AVERAGEFORA §SPULSEWIDTHATADUTYCYCLE$RIVEPOWERFORTHETWO
3/,)$ 34!4%42!.3-)44%23
££°ÎÎ
&)'52% !.303 TRANSMITTER AMPLIFIER MODULE 0HOTOGRAPH COURTESY OF 7ESTINGHOUSE%LECTRIC#ORPORATION
BANKSOFFINALOUTPUTMODULES K7 WASPROVIDEDFROMTHECOMBINEDOUTPUTSOF MOREIDENTICALMODULESINTHEDRIVERGROUP0REDRIVERSANDAREDUNDANTPREAMPLIFIER WEREUSEDASPRECEDINGDRIVESTAGES 4HEPOWERAMPLIFIERMODULECONSISTEDOFTENIDENTICALSILICONBIPOLARPOWERTRAN SISTORSARRANGEDINA DRIVING AMPLIFIERCONFIGURATIONTODEVELOPMORETHAN7 PEAKPOWEROUTPUTOVERTHETO-(ZFREQUENCYBANDWIDTH%ACHTRANSISTORWAS A7PEAK POWERDEVICETHATWASOPERATEDINABALANCEDPUSH PULLCIRCUITDESIGN "YUSINGAPUSH PULLCONFIGURATION THECIRCUITDESIGNERSALLEVIATEDSOMEOFTHELOW IMPEDANCE MATCHINGPROBLEMSNORMALLYASSOCIATEDWITHVERYHIGHPOWERTRANSISTORS 4HE2&INPUTDRIVETOTHEMODULEWAS7PEAKANDWASUSEDTODRIVETWODEVICES !COMBINEDPOWERLEVELOFGREATERTHAN7WASSPLITEIGHTWAYSTODRIVETHEEIGHT IDENTICALOUTPUTSTAGES,OSSESINTHEOUTPUTCIRCULATOR FINALPOWERCOMBINING ANDTHE FAULTDETECTIONCIRCUITRYREDUCEDTHECOMBINEDPOWERLEVELTO7/UTPUTMODULES WERELIQUID COOLEDFORNORMALOPERATION BUTANEMERGENCYBACKUPFORCED AIRCOOLING WAS PROVIDED IN THE EVENT OF A PRIMARY COOLING SYSTEM FAILURE4HE DISSIPATED HEAT COULDBETOLERATEDBECAUSETHESYSTEMOPERATEDATALOWDUTYCYCLE 4HEPOWERCOMBININGFOREACHOUTPUTCABINETCONSISTEDOFCOMBINERS4HE REACTIVE POWER COMBINER CONSISTED OF SEVEN GROUPS OF COMBINERS FABRICATED IN AIR STRIPLINE USING IN GROUND PLANE SPACING 4HE SEVEN OUTPUTS WERE COMBINED BY USING A SINGLE AIR STRIPLINE COMBINER WITH IN GROUND PLANE SPACING4HE K7 OUTPUTS OF THE TWO COMBINERS WERE COMBINED IN A SINGLE ISOLATED HYBRID THAT WAS MANUFACTURED BY USING A COAXIAL TRANSMISSION LINE4HE ADVERTISED LOSSESOFTHEANDCOMBINERSWERED"ANDD" RESPECTIVELY 2!-0, "AND!IR4RAFFIC#ONTROL4RANSMITTER 4HE2ADAR-ODERNIZATION 0ROJECT2!-0 RADARSYSTEMISAN,BANDSYSTEMBUILTBYTHE2AYTHEON#OMPANYDUR INGTHELATESTOREPLACETHEEARLIERPRIMARYANDSECONDARYSURVEILLANCERADARSUSED FORAIRTRAFFICCONTROLBY#ANADAS-INISTRYOF4RANSPORT 4HEPRIMARYSURVEILLANCE RADARCONSISTSOFAROTATINGREFLECTOR HORN FEDBYASOLID STATETRANSMITTER ANDINTERFAC INGWITHREDUNDANTRECEIVECHANNELSWITHRECEIVER EXCITERSANDSIGNALPROCESSORS4HE PRIMARYSURVEILLANCERADAROPERATESBETWEENAND-(ZWITHA K7PEAK
££°Î{
2!$!2(!.$"//+
&)'52% 2!-0 TRANSMITTER AMPLIFIER MODULE 0HOTOGRAPH COURTESY OF 2AYTHEON #OMPANY
POWEROUTPUTANDPROVIDESRADARCOVERAGETONMIANDTOANALTITUDEOF FTWITH ANPROBABILITYOFDETECTIONFORAMTARGETWITHAZIMUTHANDRANGERESOLUTIONTO nANDNMI RESPECTIVELY4HERECEIVER EXCITEREFFICIENTLYUTILIZESTHETRANSMIT TERSOLID STATEDEVICESWITHAHIGHDUTY CYCLEWAVEFORM!PAIROFPULSESISUSEDINTHE FREQUENCY AGILESYSTEM ANDTARGETRETURNSAREPROCESSEDBYAMOVING TARGETDETECTOR 4HEPULSEPAIRCONSISTSOFA §SSINGLE TONEPULSETHATPROVIDESCOVERAGETONMIAND A §SNONLINEARCHIRPPULSETHATPROVIDESCOVERAGETONMI4HE §SPULSEIS COMPRESSEDTO§SSUCHTHATHIGHDUTYCYCLEISACHIEVEDWITHOUTCOMPROMISINGRANGE RESOLUTION4HETRANSMITTERCONSISTSOFMODULES EACHCAPABLEOF7POWEROUT PUT&IGURE THATARECOMBINEDTOPRODUCETHEGREATERTHANK7PEAKPOWER LEVEL4WOMODULESANDA6DCPOWERSUPPLYMAKEUPASINGLETRANSMITTINGGROUP 4HEMODULECONSISTSOFA DRIVING DRIVING TRANSISTOR AMPLIFIERCONFIGURA TIONOFSILICONBIPOLARPOWERDEVICES4HETWOFINALOUTPUTDEVICESANDTHEEIGHTDRIVER DEVICES ARE 7 TRANSISTORS CAPABLE OF OPERATING UP TO A DUTY CYCLE OVER THE -(Z BANDWIDTH AT COLLECTOR EFFICIENCIES GREATER THAN %ACH MODULE IS AIR COOLED ANDTHEMEASUREDEFFICIENCYISGREATERTHANWHENTHEMODULEISOPERATING ATANAVERAGEDUTYCYCLE-ODULEPOWERGAINISGREATERTHAND"!CIRCULATORIS USEDONTHEOUTPUTPORTTOPROTECTTHE7DEVICESFROMANTENNA GENERATEDREFLECTIONS ANDCONTROLCIRCUITRYHASBEENINCLUDEDTOSWITCHOFFMODULESINTHEEVENTOFCOOLING SYSTEMFAILURE!HIGH POWERREPLICATEDCOMBINERBUILTBYUSINGACOMBINATIONOF REACTIVEANDRESISTIVEPOWER COMBININGTECHNIQUESINAIR DIELECTRICSTRIPLINE ISEMPLOYED TOSUMTHEMODULEOUTPUTSTOTHEK7LEVEL
, ,
--ETH h)NDUSTRIALASSESSMENTOFTHEMICROWAVEPOWERTUBEINDUSTRY v$EPARTMENTOF$EFENSE 2EPORT !PRIL P 6'RANATSTEIN 20ARKER AND#!RMSTRON h3CANNINGTHETECHNOLOGY6ACUUMELECTRONICSATTHE DAWNOFTHESTCENTURY v0ROCEEDINGSOFTHE)%%% VOL NO PPn -AY
3/,)$ 34!4%42!.3-)44%23
££°Îx
6 'REGERS (ANSEN h2ADAR SYSTEMS TRADE OFFS VACUUM ELECTRONICS VS SOLID STATE v IN TH )NTERNATIONAL6ACUUM%LECTRONICS#ONFERENCE !PRILn PPn 2 3YMONS h-ODERN MICROWAVE POWER SOURCES v )%%% !%33 3YSTEMS -AGAZINE PP n *ANUARY 4 3ERTIC h)DIOSYNCRASIES OF 474 AMPLIFIERS v PRESENTED AT 4HE &UTURE OF %LECTRONIC $EVICES #ONFERENCE )NSTITUTEOF0HYSICS -ARCH -(ANCZORAND-+UMAR h K73 BANDSOLID STATETRANSMITTERFORMODERNRADAR3934%-3 v )%%% 4RANSACTIONS ON -ICROWAVE 4HEORY AND 4ECHNIQUES VOL NO PP n $ECEMBER $2UTLEDGE .#HENG 29ORK 27EIKLE AND-$E,ISIO h&AILURESINPOWERCOMBININGARRAYS v )%%%4RANSACTIONSON-ICROWAVE4HEORYAND4ECHNIQUES VOL NO PPn *ULY ,"7ALKER (IGH0OWER'A!S&%4!MPLIFIERS .ORWOOD -!!RTECH(OUSE P (EWLETT 0ACKARD !PPLICATION .OTES (IGH &REQUENCY 4RANSISTOR 0RIMER 0ART 4HERMAL 0ROPERTIES P ( #OOKE h-ICROWAVE TRANSISTORS THEORY AND DESIGN v 0ROCEEDINGS OF THE )%%% VOL PPn !UGUST 6ENDORTRANSISTORDATASHEET )NTEGRA4ECHNOLOGIES )NC WWWINTEGRATECHCOM 6ENDORTRANSISTORDATASHEET 4YCO%LECTRONICS -! #/- WWWMACOMCOM 6ENDORTRANSISTORDATASHEET 34-ICROELECTRONIC WWWSTCOM 6ENDORTRANSISTORDATASHEET 0HILIPS WWWDATASHEETCATALOGCOM . 3AKURA + -ATSUNAGE + )SHIKURA ) 4AKENAKE + !SANO . )WATA - +ANAMORI AND -+UZUHARA h7 , BAND 'A!S POWER &0 (&%4 OPERATED AT 6 v IN )%%% -ICROWAVE 4HEORYAND4ECHNIQUES3YMPOSIUM$IGEST PPn 4 7INSLOW h0OWER DEPENDENT INPUT IMPEDANCE OF FIELD PLATE -%3&%4S v #OMPOUND 3EMICONDUCTOR)NTEGRATED#IRCUIT$IGEST PPn * (UANG ' *ACKSON 3 3HANFIELD ! 0LATZKER 0 3ALEDAS AND # 7EICHERT h!N!L'A!S )N'A!SPSEUDOMORPHICHIGHELECTRONMOBILITYTRANSISTORWITHIMPROVEDBREAKDOWNVOLTAGEFOR 8 AND+U BANDPOWERAPPLICATIONS v)%%%4RANSACTIONSON-ICROWAVE4HEORYAND4ECHNIQUES VOL NO PPn -AY +!LAVI 3 /GUT 0 ,YMNA AND - "ORKOWSKI h! HIGHLY UNIFORM AND HIGH THROUGHPUT DOUBLESELECTIVE0(%-4PROCESSUSINGANALLWETETCHCHEMISTRY vPRESENTEDAT'A!S-A4ECH #ONFERENCE # 3NOWDEN h2ECENT DEVELOPMENT IN COMPOUND SEMICONDUCTOR MICROWAVE POWER TRANSISTOR TECHNOLOGY v)%%0ROC #IRCUITS$EVICES3YST VOL NO PPn *UNE $ -ILLER AND - $RINKWINE h(IGH VOLTAGE MICROWAVE DEVICES!N OVERVIEW v PRESENTED AT )NTERNATIONAL#ONFERENCEON#OMPOUND3EMICONDUCTOR-FG *:OLPER h3CANNINGTHESPECIALISSUE SPECIALISSUEONWIDEBANDGAPSEMICONDUCTORDEVICES v 0ROCEEDINGSOFTHE)%%% VOL NO PPn *UNE 5-ISHRA 00ARIKH AND97U h!L'A.'A.(%-4S!NOVERVIEWOFDEVICEOPERATIONAND APPLICATIONS v0ROCEEDINGSOFTHE)%%% VOL NO PPn *UNE 24REW h3I# AND 'A. TRANSISTORS)S THERE ONE WINNER FOR MICROWAVE POWER APPLICATIONS v 0ROCEEDINGSOFTHE)%%% VOL NO PPn *UNE 3!LLEN 2 3ADLER 4!LCORN * 0ALMOUR AND # #ARTER h3ILICON CARBIDE -%3&%4S FOR HIGH POWER3 BANDAPPLICATIONS vIN)%%%-44 3)NTERNATIONAL-ICROWAVE3YMPOSIUM *UNE PPn 4HOMAS+AZIORPERSONALCOMMUNICATION 2AYTHEON2&#OMPONENTS !UGUST 97UAND00ARIKH h(IGH POWER'A.(%-4SBATTLEFORVACUUM TUBETERRITORY v#OMPOUND 3EMICONDUCTOR-AGAZINE *ANUARY&EBRUARY #OLIN7HELANPERSONALCOMMUNICATION 2AYTHEON2&#OMPONENTS !UGUST ((OWE 3TRIPLINE#IRCUIT$ESIGN .ORWOOD -!!RTECH(OUSE PPn $ -C1UIDDY 2 'ASSNER 0 (ULL 0 * -ASON AND * "EDINGER h4RANSMITRECEIVE MODULE TECHNOLOGYFOR8 BANDACTIVEARRAYRADAR v0ROCEEDINGSOFTHE)%%% VOL NO PPn -ARCH
££°ÎÈ
2!$!2(!.$"//+
'*ERINICAND-"ORKOWSKI h-ICROWAVEMODULEPACKAGING vIN)%%%-ICROWAVE4HEORYAND 4ECHNIQUES3YMPOSIUM$IGEST PPn " +OPP - "ORKOWSKI AND ' *ERINIC h4RANSMITRECEIVE MODULES v )%%% 4RANSACTIONS ON -ICROWAVE4HEORYAND4ECHNIQUES VOL NO PPn -ARCH " +OPP # -OORE AND 2 #OFFMAN h4RANSMITRECEIVE MODULE PACKAGING %LECTRICAL DESIGN ISSUES v*OHNS(OPKINS!0,4ECHNICAL$IGEST VOL NO PPn $(OFT h3OLID STATETRANSMITRECEIVEMODULEFORTHE0!6%0!73PHASEDARRAYRADAR v-ICROWAVE *OURNAL PPn /CTOBER +,EE ##ORSON AND'-OLS h!K7SOLID STATE!.303 RADARTRANSMITTER v-ICROWAVE *OURNAL VOL PPn *ULY *$YCKAND(7ARD h2!-0SNEWPRIMARYSURVEILLANCERADAR v-ICROWAVE*OURNAL P $ECEMBER ( 7ARD h4HE 2!-0 032 A SOLID STATE SURVEILLANCE RADAR v PRESENTED AT )%% )NTERNATIONAL 2ADAR#ONFERENCE ,ONDON /CTOBER
#HAPTER
,iviVÌÀÊÌi>Ã V
>iÊ °Ê iÞÊ>`Ê >iÊ >ÛÃ %LECTRONIC3YSTEMS .ORTHROP'RUMMAN#ORPORATION
£Ó°£Ê /," 1 /" 2OLE OF THE 2ADAR 2EFLECTOR !NTENNA 2ADAR REFLECTOR ANTENNAS PROVIDE THE MEANSBYWHICHTHETRANSMITRECEIVE ENERGYANDITSASSOCIATEDWAVEFORMISRADIATED INTOCOUPLEDFROM FREESPACE)NTRANSMITMODE THEANTENNALAUNCHESAGUIDEDWAVE FROMTHETRANSMITTERINTOFREESPACEANDTYPICALLYFOCUSESTHISRADIATEDENERGYOVERA LIMITEDANGULARRANGEORBEAMWIDTH)NRECEIVEMODE THEREFLECTORANTENNAOPERATESIN ARECIPROCALMANNER RECEIVINGREFLECTEDRADARTARGETENERGY IE ECHOES FROMALIMITED ANGULARRANGE4HESERECEIVEDECHOESARETHENCONVERTEDINTOGUIDEDWAVESTHATARE AMPLIFIEDANDSUBSEQUENTLYPROCESSEDINTHERADARRECEIVER 4YPICALLY THERADARREFLECTORANTENNAMUSTBEDESIGNEDTOENABLEBEAMSCANNING OVERTHEFIELD OF VIEW&/6 VIAEITHERMECHANICALORELECTRONICMEANSORSOMECOM BINATIONOFBOTH )N3ECTION METHODSOFELECTRONICBEAMSCANNINGLIMITED&/6 USING ARRAY FEEDS ARE DISCUSSED4HUS THE RADAR REFLECTOR ANTENNA PERFORMS SEVERAL IMPORTANTFUNCTIONS )TCONVERTSTHEGUIDEDWAVEFROMTHETRANSMITTERTOARADIATED WAVEORVICEVERSAONRECEIVE )TCONCENTRATESORCOLLIMATESTHERADIATEDENERGY INTO A DIRECTIVEBEAM OF SPECIFIEDGAIN ANDBEAMWIDTH )T COLLECTS THEREFLECTED ENERGYSCATTEREDFROMTHERADARTARGETAND )TSUPPORTSBEAMSCANNINGVIAEITHER ELECTRONICORMECHANICALMEANSORBOTH !NTENNA "EAM 3CANNING &OR MOST RADAR APPLICATIONS THE TRADE OR CHOICE BETWEENAREFLECTORANTENNAANDADIRECTRADIATINGPHASEDARRAYISTYPICALLYDRIVENBY FACTORSRELATINGTOSCANRATE SCANVOLUME ANDCOST2EFLECTORANTENNASARETYPICALLY EMPLOYEDINARADARWHEN SLOWERSCANRATESARESUFFICIENTANDMECHANICALSCAN NINGSUFFICES ANDOR AVERYHIGHGAINELECTRICALLYLARGE APERTUREISREQUIREDANDA PHASEDARRAY IE ANELECTRONICSCANNINGARRAY%3! ISCOSTPROHIBITIVE ANDOR THE REQUIREDSCANVOLUMEISLIMITEDANDCANBESATISFIEDVIAUSEOFANARRAY FEDREFLECTOR $URINGTHESANDS PHASESHIFTERAND42MODULETECHNOLOGYGREATLYMATURED AND%3!COSTSDROPPEDDRAMATICALLY4HESEADVANCESHAVERESULTEDININCREASEDINTER ESTANDUTILIZATIONOF%3!SFORWIDESCANRADARAPPLICATIONS ANDARRAY FEDREFLECTORS WHERELIMITEDELECTRONICSCANSUFFICES !DVANTAGESAND!PPLICATIONSOFTHE2ADAR2EFLECTOR!NTENNA )NTHEPREVIOUS PARAGRAPH THEPROLIFERATIONOF%3!ANTENNASINMODERNRADARSYSTEMSISLINKEDTOTHE £Ó°£
£Ó°Ó
2!$!2(!.$"//+
DRAMATIC42MODULECOSTREDUCTIONSANDTECHNOLOGYIMPROVEMENTS4HEIMPROVEDPER FORMANCEOF%3!RADARSISCITEDASAREASONFORDECREASEDUTILIZATIONOFREFLECTORANTENNAS INMANYOFTODAYSRADARSYSTEMDESIGNS (OWEVER THEREARESTILLAPPLICATIONSWHERETHEREFLECTORANTENNAISWELLSUITEDTORADAR APPLICATIONSANDWILLCONTINUETOFINDAPPLICATIONSINTHEFUTURE4HREERELEVANTEXAMPLESOF RADARAPPLICATIONSWELLSUITEDTOTHEUSEOFREFLECTORANTENNASAREBRIEFLYDESCRIBEDBELOW ,OW#OST2ADAR &ORVERYCOST CONSTRAINEDAPPLICATIONSWHEREMECHANICALSCAN RATESSUFFICE REFLECTORANTENNASARESTILLTHEDOMINANTCHOICE/NESUCHNICHEISCOM MERCIALWEATHERRADAR EG .%82!$AND4$72 6ERY(IGH 'AIN ,ONG 2ANGE2ADAR &ORVERYHIGH GAINRADARAPPLICATIONS THECOST OFAN%3!ISTYPICALLYSTILLPROHIBITIVE ANDTHEREFLECTORPROVIDESANECONOMICALMEANSOF REALIZINGSUCHHIGHGAINS4WOEXAMPLESOFLONG RANGERADARAPPLICATIONSGENERALLYREQUIR INGVERYHIGHANTENNAGAINSARE MISSILEDEFENSERADARAND SPACE BASEDRADAR ,IMITED3CAN2ADARS 3OMERADARSOPERATEOVERALIMITEDFIELD OF VIEWANDORTHE REQUIREMENTSDICTATEFASTELECTRONICSCANNINGOVERASMALL&/6ANDSLOWERMECHANICAL SCANNINGOVERALARGERFIELDOFVIEW%3! FEDREFLECTORARCHITECTURESAREWELLSUITEDFOR SUCHAPPLICATIONSANDAREDESCRIBEDINGREATERDETAILIN3ECTION4HREERELEVANTEXAM PLESARE MISSILEDEFENSERADAR SPACE BASEDRADAR AND GROUND BASEDSEARCHAND TRACKRADAR$AZIMUTHELECTRONICSCANNINGSUFFICESFORSOMEOFTHESEAPPLICATIONS #LASSIFICATIONOF2EFLECTOR!NTENNAS 2ADARREFLECTORANTENNASCANBECLASSIFIEDIN VARIOUSWAYS/NEUSEFULCLASSIFICATIONCRITERIAISELECTRICALDESIGN IE THEREFLECTOROPTICS CONFIGURATION4ABLEPROVIDESASUMMARYLEVELCOMPARISONOFSOMECOMMONRADAR
4!",% #OMPARISONOF+EY&EATURESOF2EFLECTOR!RCHITECTURES
3INGLE2EFLECTOR 0ARABOLIC
%LECTRONIC s ,IMITEDINBOTH !ZIMUTHAND 3CANNING %LEVATION %SCAN s !CHIEVEDVIA &EEDSWITCHING
#YLINDRICAL 2EFLECTOR
$UAL2EFLECTOR #ASSEGRAINOR 'REGORIAN
#ONFOCAL 0ARABOLOIDS
3PHERICALAND 4ORUS
s ,IMITEDINBOTH s 5SESPLANAR s 0OTENTIALFOR s 7IDE$ VERYWIDE$ %3!SOURCE !ZIMUTHAND SCANNING SCANNINGTORUS s 4YPICALLY %LEVATION s 5SES%3! OR$3CANNING LIMITED BUT LINESOURCE s !CHIEVEDVIA SPHERICAL TRADABLE FEEDSWITCHING FORWIDE$ s !CHIEVEDVIA BYVARYING SCANNING MAGNIFICATION FEEDSWITCHING
s -ODESTTOLOW s (IGH !PERTURE s -EDIUMTOHIGH s -EDIUMTO s (IGH s 3 WITCHED s $%3! s . OESCAN OESCAN3INGLE HIGH %FFICIENCY s . BEAMARRAYON PLANARSOURCE s $%3!LINE 3INGLEHORN HORN &EED CIRCULARARC s %SCAN!RRAY SOURCE s %SCAN!RRAY 4YPES TORUSREFLECTOR SWITCHEDFEEDS SWITCHEDFEEDS ORSPHERICAL ARCSPHERICAL REFLECTOR "LOCKAGE #ONCERNS
s -ITIGATEFEED BLOCKAGEVIA OFFSETGEOMETRY
s -ITIGATEFEED s -ITIGATEFEED s -ITIGATEFEED s 3ERIOUS CONCERNFOR BLOCKAGE BLOCKAGEVIA BLOCKAGE VERYWIDESCAN VIAOFFSET OFFSETGEOMETRY VIAOFFSET CONFIGURATIONS GEOMETRY s #ANMOVEFEED GEOMETRY BEHINDREFLECTOR
2%&,%#4/2!.4%..!3
£Ó°Î
REFLECTORARCHITECTURESFROMTHISPERSPECTIVE-OREDETAILEDDISCUSSIONSOFTHECHARACTERIS TICSOFTHESEARCHITECTURESAREINCLUDEDIN3ECTIONWHEREINEACHOFTHESEARCHITECTURES ISAFFORDEDADEDICATEDSUBSECTION!NOTHERMEANSOFCLASSIFICATIONISVIAPLATFORMVEHI CLE ORSITEGROUND BASED SHIP BASED AIRBORNE ORSPACE BORNE 4HEPLATFORMFREQUENTLY DRIVESMECHANICALANDENVIRONMENTALREQUIREMENTSANDOFTENEITHERENABLESORCONSTRAINS THEREFLECTORSIZE)N3ECTION REFLECTORARCHITECTURESAREDISCUSSEDANDCOMPARED AND IN3ECTION MECHANICALANDENVIRONMENTALDESIGNCONSIDERATIONSAREADDRESSED #HAPTER 3YNOPSIS 4HE BALANCE OF THIS CHAPTER IS DIVIDED INTO FIVE SECTIONS 3ECTIONSUMMARIZESTHEBASICDESIGNPRINCIPLESANDPARAMETERSGOVERNINGREFLEC TORANTENNADESIGN3ECTIONPROVIDESABRIEFOVERVIEWOFCONICSECTIONSANDCLASSES OF REFLECTOR SYSTEMS AND ASSOCIATED OPTICS 3ECTION DISCUSSES VARIOUS TYPES OF REFLECTORFEEDSANDRELATEDDESIGNPRINCIPLES3ECTIONDESCRIBESREFLECTORANALYSIS ANDSYNTHESISMETHODSANDASSOCIATEDDESIGNSOFTWAREPACKAGES&INALLY 3ECTION BRIEFLYREVIEWSMECHANICALDESIGNISSUESANDCONSIDERATIONS
£Ó°ÓÊ - Ê*, * -Ê Ê*, / ,&UNDAMENTALLY REFLECTORS ARE ANTENNAS THAT WORK ON OPTICAL PRINCIPLES ON RECEIVE FOCUSINGENERGYTOAFOCALPOINTASALENSDOESFORLIGHT/NTRANSMIT POWEREMANAT INGSPHERICALLYFROMALOWGAIN BROAD PATTERNEDFEEDISREFLECTEDANDENERGYISCOL LIMATEDTOFORMAPLANEWAVETHEREBYPROVIDINGINCREASEDANTENNAGAINANDANARROWER BEAMWIDTH)NDISCUSSINGANTENNAS ONECANUSEEITHERTRANSMITORRECEIVEARGUMENTS BECAUSEANTENNASARERECIPROCALDEVICES4HISMEANSTHATBOTHTHETRANSMITANDRECEIVE PERFORMANCEOFAPASSIVEANTENNA EG PATTERNS GAIN LOSSES ETC CANBEPREDICTED USINGBASICAPERTUREANTENNAPRINCIPLES)NTHISSECTION THESEBASICREFLECTORDESIGN PRINCIPLESAREREVIEWEDVIAUSEOFACANONICALEXAMPLE #ONSIDERAPARABOLIC SHAPEDREFLECTORFORMINGACIRCULARAPERTURE FEDBYAHORNAT ACENTRALFOCALPOINT4HISSIMPLEREFLECTORCONFIGURATIONHASASURFACESHAPEDEFINED BYTHEEQUATION Z
X Y
F F
WHEREFISTHEFOCALLENGTHANDTHEVERTEXISLOCATEDATZ F4HERESULTANTANTENNA BEAMPATTERNPOINTSINTHEPOSITIVEZ DIRECTION&ORAROUNDREFLECTOROFDIAMETER$ THE EDGEORRIMISACIRCLEANDTHEEDGEDIMENSIONSAREONTHISCIRCLEDEFINEDBY
XEDGE YEDGE
$
4HISREFLECTORISSHOWNIN&IGURE /NEFREQUENTLYISINTERESTEDINTHEANGLE@FROMTHEZ AXISTOPOINTSONTHEREFLECTOR SURFACE
¤ X Y ³ A ARCTAN ¥ ´ ¦ F µ
£Ó°{
2!$!2(!.$"//+
&)'52% 0ARABOLICREFLECTORINX ZPLANE
4HUS THEEDGEANGLEFORAROUNDREFLECTORIS
¤ $³ A EDGE ARCTAN ¥ ´ ¦ Fµ
!NOTHERUSEFULPARAMETERISTHEDISTANCERFROMTHEFOCALPOINTTOAPOINTONTHEREFLECTOR R F
X Y F
!PERTURE'AINAND,OSSES 4HEGAINOFTHEREFLECTORANTENNAISONEOFITSMOST IMPORTANTPARAMETERS)TISCONVENIENTTODESCRIBETHEREFLECTORANTENNAGAINWITHREF ERENCETOTHEFUNDAMENTALGAINLIMITANAPERTUREOFAREA!4HISLIMIT APPLICABLETO APERTUREANTENNASOFSUFFICIENTELECTRICALSIZEAPPROXIMATELYSQUAREWAVELENGTHS ORGREATER ISTHESO CALLEDAPERTUREGAIN'AP
'AP
P ! L
2%&,%#4/2!.4%..!3
£Ó°x
WHERE K IS THE WAVELENGTH &OR A ROUND REFLECTOR OF DIAMETER $ THIS APERTURE GAIN LIMITIS ¤ P $³ 'AP ¥ ¦ L ´µ
)N PRACTICE IT IS SOMETIMES USEFUL TO DESCRIBE REFLECTOR GAIN BY DECREMENTING THE APERTURE GAIN BY SUBTRACTING VARIOUS APERTURE RADIATION LOSSES SUCH AS SPILLOVER TAPER EFFICIENCY FEEDBLOCKAGE REFLECTORLEAKAGE SURFACEDISTORTION STRUTBLOCKAGE FEEDALIGN MENT ETC FROM'AP4HESELOSSFACTORSAREDESCRIBEDINDETAILLATERWITHINTHISSECTION $IRECTIVE'AINAND&EED,OSSES $IRECTIVEGAINORDIRECTIVITYISAMEASUREOF THEPEAKPOWERRELATIVETOTHEAVERAGEPOWERRADIATEDBYANISOTROPICRADIATOR IE A RADIATORTHATRADIATESENERGYEQUALLYINALLDIRECTIONS$IRECTIVEGAINCONSIDERSONLYTHE RADIATEDPOWERTHUS ANTENNALOSSESSUCHASFEEDMISMATCH FEEDLOSS ANDWAVEGUIDE ANDOR CABLE LOSSES MUST ALSO BE CONSIDERED (OWEVER THE RADAR ENGINEER TYPICALLY TABULATESTHESELOSSESSEPARATELYFORUSEINOTHERRADARCALCULATIONS!NTENNADIRECTIV ITYISANIMPOSINGCALCULATIONREQUIRINGVOLUMEINTEGRALS BUTTYPICALREFLECTORPATTERN COMPUTATIONCODESEXPRESSTHEPATTERNINTERMSOFDIRECTIVITY ANDTHEANTENNALOSSES AREGENERALLYACCOUNTEDFORSEPARATELY)NTHETEXTTHATFOLLOWS REFLECTORDIRECTIVITYIS DESCRIBEDBASEDUPONAVAILABLEhAPERTUREGAINvANDASSOCIATEDRADIATIONLOSSES4HIS APPROACHSHOULDBEINTUITIVETOTHERADARENGINEER !PERTURE &IELD -ETHOD OF !NALYSIS 4HE APERTURE FIELD REFLECTOR ANALYSIS METHODISBASEDUPONRAY TRACINGPRINCIPLESANDWORKSWELLFORSYMMETRIC CENTER FED PARABOLICREFLECTORS7ITHTHISMETHOD THEAPERTUREFIELDDISTRIBUTIONISCALCULATEDINAN X YPLANEATZ &IGURE BYASSUMINGCOHERENTREFLECTIONOFSPHERICALRADIATION FROMAFEEDATTHEFOCALPOINT4HEFIELDDISTRIBUTIONISTHENUSEDTOCOMPUTETHEFAR FIELDRADIATIONPATTERN&ORMORECOMPLEXGEOMETRIES EG OFFSET FEDREFLECTORS THIS METHODDOESNOTWORKASWELLASTHEMORERIGOROUSPHYSICALOPTICS0/ METHODTHAT ISDESCRIBEDIN3ECTION &ORTHESIMPLECENTER FEDFOCALFEEDEXAMPLESHOWNIN&IGURE THESIMPLER APERTURE FIELDMETHODOFANALYSISISACCURATEANDITSAPPLICATIONISSIMPLEANDSTRAIGHT FORWARDANDMAKESTHEDISCUSSIONOFTHERADIATIONLOSSESEASIERTOFOLLOW5SINGTHIS METHODOFANALYSIS THEFIELDAMPLITUDEONANX YGRID &GRID INTHEAPERTUREPLANEIS EASILYDETERMINEDFROMTHEFEEDANDSPACETAPERING &GRID X Y &FEED X Y Z
F &FEED X Y Z R X Y F
WHERE&FEEDISTHEFEEDRADIATIONPATTERN&ORTHISCASE WITHTHEFEEDATTHEFOCALPOINT THETOTALDISTANCETRAVELEDFROMTHEFEEDTOTHEREFLECTORANDBACKTOTHEAPERTURE PLANE ISEQUAL4HISEXPRESSIONISDECEPTIVELYSIMPLEANDACCURATELYACCOUNTSFORTHEFEED REFLECTORTRANSFORMATIONSANDAREAPROJECTIONS 4HE RESULTANT APERTURE FIELD & V} IS THEN TRANSFORMED TO THE FAR FIELD USING THE SPATIALTRANSFORMATION & V} £ &GRID X Y E
X Y
J
P L
X I} Y I} X
Y
u V}
£Ó°È
2!$!2(!.$"//+
WHERE V} ISAUNITVECTORINTHEDIRECTIONOFINTEREST.OTETHAT%QISASIMPLE$ SPATIALSUMMATIONANALOGOUSTOTHATUSEDFORARRAYANTENNAPATTERNCALCULATIONS 4APER%FFICIENCY )NANTENNADESIGN APERTURETAPERISUSEDTOLOWERSIDELOBES 4HE MODEST RESULTANT LOSS AND INCREASED BEAMWIDTH IS THE PRICE AND ONE IS USUALLY WILLINGTOPAYTOOBTAINTHEDESIREDSIDELOBELEVEL4HELOSSASSOCIATEDWITHAPERTURE TAPERISACCOUNTEDFORINTHETAPEREFFICIENCY(OWEVER THETAPEREFFICIENCYISNOTAN OHMICLOSSWHEREENERGYISDISSIPATED BUTISAREDISTRIBUTIONOFENERGY)NTHECASEOF AREFLECTORFEDBYAHORN THETAPERDISTRIBUTIONISDETERMINEDBYTHEFEEDHORNPATTERN THEDISTANCETOTHEREFLECTOR ANDTHEPROJECTEDAREAINTHEDIRECTIONOFPEAKRADIATION &ORARADIALLYSYMMETRICFEEDANDREFLECTOR WHERETHEFIELDISRADIALLYSYMMETRICAND &GRIDX Y GR THEEFFICIENCY G ISCOMPUTEDAS
¯ GR P R DR H ¯ G R P R DR ¯ P R DR
3PILLOVER,OSS 3PILLOVERLOSSREFERSTOFEEDPOWERTHATMISSES ORSPILLSOVER THE EDGESOFTHEREFLECTOR)NTHERADARREFLECTORDESIGNPROCESS ONETYPICALLYADJUSTSTHE EDGE ILLUMINATION TO ACHIEVE A DESIRED TAPER AND SIDELOBE LEVEL RESULTING IN MODEST SPILLOVER LOSS 3PILLOVER LOSS IS THE FEED POWER THAT IS LOST VIA RADIATION BEYOND THE EDGESOFTHEREFLECTOR4HISLOSSCANBECOMPUTEDAS ¤ &EED 0OWER )NCIDENT ON 2EFLECTOR ³ 3PILLOVER ,OSS 4OTAL &EED 0OWER ¥ ´µ 4OTAL &EED 0OWER ¦
&ORARADIALLYSYMMETRICFEEDANDREFLECTOR THISCALCULATIONISSTRAIGHTFORWARD %DGE DIFFRACTION AND RESULTANT ANTENNA BACKLOBES ARE A RELATED CONSEQUENCE OF FEEDSPILLOVERANDEDGETAPER&ORANYGIVENREFLECTORDESIGN EDGEILLUMINATIONOFTHE REFLECTORWILLPRODUCERADIATIONBEHINDTHEREFLECTORDUETODIFFRACTION4HISDIFFRACTION MAYBETHOUGHTOFASRE RADIATIONFROMTHEEDGEOFTHEREFLECTORTHATCAUSESRADIATION LOBESBEHINDTHEREFLECTOR&ORACENTER FEDREFLECTORSUCHASTHATSHOWNIN&IGURE APRIMARYBACKLOBEWILLARISEDIRECTLYBEHINDTHEREFLECTORDUETOCOHERENTADDITIONOF THEEDGEDIFFRACTIONCURRENTS/NECOMMONMEANSOFSPECIFYINGTHISBACKLOBELEVELIS VIATHEFRONT TO BACK&"RATIO IE THERATIOOFTHEMAINBEAMANDBACKLOBEGAINS4HE ANALYSISOFTHESEREFLECTOREDGEDIFFRACTIONEFFECTSANDASSOCIATED&"RATIOSFORSOME COMMONREFLECTORGEOMETRIESAREDESCRIBEDBY+NOP &EED "LOCKAGE -ANY REFLECTOR SYSTEMS SUFFER FEED ANDOR FEED SUPPORT BLOCKAGETOSOMEDEGREE&ORCENTER FEDGEOMETRIES THEREWILLDEFINITELYBEBLOCK AGEBECAUSETHEFEEDISWITHINTHE&/6OFTHEREFLECTOR!CONSEQUENCEOFBLOCKAGE ISHIGHERSIDELOBES THELEVELSOFWHICHDEPENDUPONTHEBLOCKAGEAREA!NOTHERCON SEQUENCEISLOSSDUETOBLOCKAGEANDDEPENDSUPONTHEBLOCKEDELECTRICFIELDTOMAIN ELECTRICFIELDRATIO %B%M WHICH INTURN ISDETERMINEDFROMTHERATIOOFBLOCKEDPOWER TOTOTALPOWERONTHEMAINREFLECTOR 0B0M ANDRATIOOFTHEGAINOFTHEBLOCKINGOBJECT TOTHEGAINOFTHEMAINREFLECTOR 'B'M
0B ¤ %B ³ ¥¦ % ´µ 0 M M
'B 'M
2%&,%#4/2!.4%..!3
£Ó°Ç
&)'52% 'RAPHICAL REPRESENTATION OF SPILL OVERLOSS
2EFLECTORTAPERISOFTENAPPROXIMATEDBYARADIALAMPLITUDEDISTRIBUTION
GR R
WHERERISTHERADIALDISTANCENORMALIZEDTOTHEREFLECTORRADIUSANDGR DROPSTOZERO ATTHEEDGE4HEUSEOFTHISTAPERFUNCTIONLEADSTOASIMPLEBLOCKAGELOSSEQUATION
0B G ¯ P R DR $B 0M $ ¯ G R P R DR M
$B 'B 'M H $M
WHEREGISTHEEFFICIENCY ASGIVENIN%Q5SING%QAND%QLEADS TOTHESIMPLEEXPRESSIONFORBLOCKAGELOSSTYPICALLYFOUNDINTHELITERATURE %B $ B %M $M
¤ % ³ $ ³ ¤ "LOCKAGE ,OSS ¥ B ´ ¥ B ´ $M µ ¦ %M µ ¦
WHERE$BAND$MARETHEDIAMETEROFTHEBLOCKAGEANDREFLECTOR RESPECTIVELY 4HEEFFECTIVEFEEDHORNDIMENSIONSCAUSINGBLOCKAGEMAYBEDIFFERENTFROMTHE PHYSICALDIMENSIONS)FTHEWALLSARENOTTAPERED SUCHASSHOWNIN&IGURE THE EFFECTIVE SIZE OF THE BLOCKAGE HOLE CAN BE LARGER THAN THE PROJECTED OBSTACLE AREA
£Ó°n
2!$!2(!.$"//+
&)'52% #APACITIVELOADINGTOREDUCEFEEDHORNBLOCKAGE
&ORFEEDSWITHCONDUCTINGWALLS THEEFFECTIVE( PLANEWIDTH Wg ISATLEASTKAND INCREASESWITHDEPTH$
[
W ` W MAX L L $
]
WHEREMAXINDICATESTAKINGTHELARGEROFTHETWOVALUES4HEINCREASEINEFFECTIVEWIDTH CANSOMETIMESBEREDUCEDBYADDINGCAPACITIVELOADING WHICHCANCONSTRAINTHEEFFEC TIVEWIDTHTOABOUTAQUARTERWAVELENGTHWIDERTHANTHEPHYSICALWIDTH4HEEFFECTIVE % PLANEDIMENSIONISTHESAMEASTHEACTUALDIMENSION 'AIN/PTIMIZATION 4HREEOFTHEPRINCIPALREFLECTORANTENNALOSSES TAPEREFFI CIENCY LOSS SPILLOVER AND BLOCKAGE HAVE BEEN EXPLAINED IN DETAIL ABOVE 4HESE DESIGNPARAMETERSLOSSFACTORS AFFECTONEANOTHERANDAREOFTENTRADEDTOOPTIMIZE ANTENNAPERFORMANCE EG GAIN SIDELOBES ETC/THERTYPICALREFLECTORLOSSES DESCRIBED LATERINTHISSECTION ARERESISTIVELOSSFACTORSTHATSIMPLYREDUCETHEANTENNAGAIN 4HE DESIGN TRADES ASSOCIATED WITH TAPER EFFICIENCY SPILLOVER AND BLOCKAGE ARE ILLUSTRATED BY USE OF AN EXAMPLE #OMPUTED LOSSES ARE SHOWN IN &IGURE FOR A WAVELENGTH DIAMETER CENTER FED CIRCULAR REFLECTOR WITH A WAVELENGTH FOCAL LENGTH ANDAGAUSSIANFEEDHORNAHORNWITHARADIATIONPATTERNDESCRIBEDBYAGAUSS IANFUNCTION 4HEGAUSSIANFEEDUSEDINTHISSAMPLEANALYSISISAHYPOTHETICALFEED WITHARADIALLYSYMMETRICPATTERNANDVERYLOWSPILLOVER ANDMOSTTYPICALFEEDHORN PATTERNSAREWELLAPPROXIMATEDBYAGAUSSIANFEEDMODEL4HEFEEDSIZEDETERMINESTHE EDGETAPER IE THELARGERTHEFEED THEGREATERTHEEDGETAPER4HEPLOTIN&IGURE SHOWSHOWTHETHREELOSSTERMS ANDTHETOTALLOSS VARYASAFUNCTIONOFFEEDPATTERN EDGETAPER THATIS THEFEEDPOWERDIRECTEDATTHEEDGEOFTHEREFLECTOR RELATIVETOTHE FEEDPATTERNPEAK4HISISUSEDHEREBECAUSETHEFEEDPATTERNISMEASUREDINDEPENDENT OFTHEREFLECTOR7HENTHEEDGETAPERISLOW VIRTUALLYALLTHEPOWERSTRIKESTHEREFLECTOR ANDTHELOSSISINSIGNIFICANT!STAPERDECREASES THEREISMORESPILLOVER ANDFEEDPOWER MISSESTHEREFLECTOR INCREASINGTHELOSS/NTHEOTHERHAND WITHTOOMUCHTAPER THE TAPEREFFICIENCYISPOORBECAUSETHEREFLECTORISUNDERILLUMINATED
2%&,%#4/2!.4%..!3
£Ó°
!
"
&)'52% 4APEREFFICIENCY SPILLOVER BLOCKAGE ANDTOTALLOSSVSFEEDPATTERNEDGETAPER
&IGUREDEMONSTRATESTHEGAINOPTIMIZATIONPROCESSWITHAHYPOTHETICALFEED PATTERN BLOCKAGE ETC ANDTHETOTALLOSSISD"EFFICIENCY WHENA D" EDGETAPERISIMPLEMENTED!LTHOUGHTHEPLOTOF&IGUREINCLUDESTAPER BLOCKAGE ANDSPILLOVERLOSSES THEREAREADDITIONALLOSSESTHATMUSTBEINCLUDEDWHENASSESSING THEOVERALLAPERTUREEFFICIENCY4HESELOSSES EG FEEDBLOCKAGE SURFACEREFLECTION FEEDMISMATCH ANDRESISTIVELOSSES ETC VARYFROMSYSTEMTOSYSTEM BUTD"IS TYPICAL7ITHTHESEADDITIONALLOSSES THEOVERALLLOSSBECOMESD"ORAPERTURE EFFICIENCYTYPICALFORASINGLEREFLECTORSYSTEM 3IDELOBEREQUIREMENTSMUSTALSOBECONSIDERED!SSHOWNIN&IGURE FORTHE SAMECENTER FEDREFLECTORSYSTEM THESIDELOBELEVELCANBEREDUCEDBYINCREASINGTHE FEEDPATTERNEDGETAPER
! !
&)'52% 3IDELOBE LEVELS WITH AND WITHOUT BLOCKAGE VS FEED PATTERN EDGETAPER
£Ó°£ä
2!$!2(!.$"//+
&)'52% 5NPERTURBEDFIELDANDFIELDINCLUDINGFEEDBLOCKAGE
&IGUREALSOSHOWSTHATFEEDBLOCKAGEINCREASESTHESIDELOBELEVELFOREXAMPLE WITHAnD"EDGETAPER ONEOBTAINSnD"SIDELOBESRATHERTHAN D"SIDE LOBES&IGURESANDFURTHERILLUSTRATETHISIMPACT4HISBLOCKAGEEFFECTCANBE MODELEDASAhHOLEvINTHEAPERTURETHATCANBEREPRESENTEDBYABROADPATTERNWITH LESSGAIN4HISBLOCKAGEPATTERNISSUBTRACTEDFROMUNPERTURBEDUNBLOCKED APERTURE FIELDS ASSHOWNIN&IGURE 4HEASSOCIATEDPATTERNS WITHANDWITHOUTBLOCKAGE ARESHOWNIN&IGURE4HE ALTERNATINGLARGE SMALL LARGE ANDSOON SIDELOBEPROGRESSIONISCHARACTERISTICOFA BLOCKEDAPERTURE 3URFACE,EAKAGE,OSS -ANYREFLECTORSURFACESAREDESIGNEDWITHAGRID AWIRE MESH ORMETALIZEDFABRICSURFACEINORDERTOMINIMIZEWINDRESISTANCE REDUCEWEIGHT ANDORENABLESTOWAGEDEPLOYMENT3OMECOMMONREFLECTORMESHSURFACEPATTERNSARE
&)'52% 5NPERTURBEDPATTERNANDPATTERNINCLUDINGBLOCKAGE
2%&,%#4/2!.4%..!3
£Ó°££
&)'52% #OMMONREFLECTORSURFACEMATERIALSFORREDUCEDWINDRESISTANCEA TUBING B EXPANDED METAL C RECTANGULAR D DOUBLELAYER ANDE SCREEN
SHOWNIN&IGURE4HEMESHOPENINGSIZEISGENERALLYCHOSENTOBEASLARGEASPOS SIBLE BUTTHEGAP S BETWEENCONDUCTORSMUSTBESUBSTANTIALLYLESSTHANKTOCUTOFF ANDPREVENTSIGNIFICANTTRANSMISSIONOFELECTROMAGNETICENERGYTHROUGHTHESURFACE 4HEATTENUATION INDECIBELS THROUGHTHEPASSAGEDEPTHTISAPPROXIMATELYTS PLUS FRINGINGLOSSES WHICHAREAPPROXIMATELYKS 4HEPOWERPASSINGTHROUGHTHEREFLECTOR ORTRANSMISSIONLOSS CANBEDETERMINED USINGAHANDYNOMOGRAPH/NESELECTSTHEGRIDSPACINGANDTHREADRADIUSTOACHIEVE THETRANSMISSIONLOSSREQUIRED4HERESULTINGLOSSINANTENNAGAINISTERMEDLEAKAGE LOSS AND THE RELATIONSHIP BETWEEN LEAKAGE LOSS AND TRANSMISSION LOSS IS PLOTTED IN &IGUREFORACONDUCTIVEREFLECTORNOOHMICLOSSES 4HELEAKAGELOSSVSSPACING RELATIONSHIPFOR&IGUREACANALSOBECOMPUTEDUSINGANEQUIVALENTCIRCUIT WITH SHUNTSUSCEPTANCE B DEVELOPEDBY-UMFORD THESOURCEOFTHENOMOGRAPH B
L ¤ ³ S LN ¥ ¦ E P D S ´µ
,EAKAGE ,OSS
B
£Ó°£Ó
2!$!2(!.$"//+
&)'52% 2EFLECTORLEAKAGELOSSVSTRANSMISSIONLOSS
4HISNOMOGRAPHISFREQUENTLYUSEDFORTHESIMPLECONFIGURATIONSIN&IGUREA&OR OTHERCONFIGURATIONSANDTHREADFORMS THESAMEEQUATIONCANBEUSEDBYCOMPUTING ANEQUIVALENTRADIUSBYMATCHINGTHECROSSSECTIONALAREAS /NE SIGNIFICANT SOURCE OF RADIATION IN THE BACK HEMISPHERE IS LEAKAGE THROUGH THEREFLECTOR4HISRADIATIONLEVELISDETERMINEDFROMTHEDIFFERENCEBETWEENPRIMARY FEEDHORN ANDSECONDARYREFLECTOR GAINSANDTHELEAKAGELOSS RADIATIONTHROUGH THEMESH 4HEREARETWOCONSIDERATIONSREGARDINGTHEREFLECTORSURFACELEAKAGE4HELEAKAGE LOSSAFFECTSTHEREFLECTORGAINDIRECTLY4HERADIATIONLEVELINTHEBACKHEMISPHEREISA FUNCTIONOFTHEFEEDGAIN REDUCEDBYTHETRANSMISSIONLOSSTHROUGHTHEREFLECTOR4HUS THEREFLECTORDESIGNERMUSTCONSIDERBOTHTHELEAKAGELOSSANDTHETRANSMISSIONLOSS &IGURE 4HEREARE HOWEVER ADDITIONALBACKLOBESTHATAREDISTINCTFROMTHEBACKRADIATIONDUE TOSURFACELEAKAGE4HESEADDITIONALLOBESAREDUETOREFLECTOREDGEDIFFRACTIONTHATADDS COHERENTLYANDTYPICALLYCAUSESARELATIVELYSTRONGMAINBACKLOBEBEHINDTHEREFLECTOR #ENTER FEDGEOMETRIES IE THOSEWITHREFLECTOREDGESEQUIDISTANTFROMTHEFEED ENABLE COHERENTADDITIONOFTHEDIFFRACTEDENERGYDIRECTLYTOTHEREAROFTHEREFLECTOR&ORTHESE GEOMETRIES THEBACKLOBELEVELISDIRECTLYRELATEDTOTHEEDGEILLUMINATIONLEVEL 3URFACE2OUGHNESS,OSS !LLRADARREFLECTORANTENNAS ESPECIALLYTHOSETHATARE MECHANICALLYSCANNEDORDEPLOYED REQUIRECAREFULCONSIDERATIONOFMECHANICALDESIGN DETAILS&IRST THEREFLECTINGSURFACEMUSTBEDESIGNEDANDBUILTSOTHATITREMAINSWITHIN CLOSETOLERANCESTYPICALLYoK EVENUNDERDYNAMICOPERATINGANDENVIRONMENTAL CONDITIONS!LSO THEFEEDMUSTBEACCURATELYALIGNEDWITHRESPECTTOTHEREFLECTOR4HE FEED SUPPORT STRUCTURE AND THE REFLECTOR STIFFENING STRUCTURE MUST MAINTAIN THE FEED LOCATIONANDSURFACEDIMENSIONSWHILETHEANTENNAISBEINGROTATED4HISDIMENSIONAL STABILITYMUSTBEMAINTAINEDTHROUGHWINDLOADING TEMPERATUREVARIATIONS OROTHER ENVIRONMENTALFACTORSTOENSURETHATPATTERNPERFORMANCEISMAINTAINED
2%&,%#4/2!.4%..!3
£Ó°£Î
&)'52% 3URFACEROUGHNESS DK VSLOSS
2EFLECTORANTENNAGAINLOSSDUETOSURFACEROUGHNESSHASBEENDISCUSSEDBY*OHN 2UZE USINGASTATISTICALPOINTOFVIEW4HELOSSOFGAINDUETOSMALLROUGHNESSERRORS ISAPPROXIMATELY
' ¤ P E ³ y D ¥ ' ¦ L ´µ
WHERE D ISTHEMEANSQUAREPHASEERROR DISTHEEFFECTIVERMSSURFACEERROR KISTHE WAVELENGTH 'ISTHEGAINWITHOUTPHASEERROR AND'ISTHEGAINWITHPHASEERROR 4HE ROUGHNESS LOSS EFFECTS EMBODIED IN %Q ARE CAPTURED IN &IGURE WHEREGAINLOSSVSSURFACEROUGHNESSINLIEUOFPHASE ERROR ISPLOTTED4HEPLOTSHOWSTHATFORD"GAIN LOSS THERMSSURFACEERRORMUSTBELESSTHANK4O MAINTAINMODESTLOSSES SURFACEERRORSMUSTBETIGHTLY CONTROLLED !NOTHERCONSIDERATIONINMESHREFLECTORSISSYSTEM ATIC SURFACE DEFORMATION &OR MANY REFLECTORS A MESH IS ATTACHED TO A METAL OR COMPOSITE BACKING STRUCTURE &ORSPACEBORNEDEPLOYABLEREFLECTORS THEMESHISTYPI CALLYAVERYSHEERFABRIC LIKEMEMBRANETHATISSTRETCHED ACROSS THE SURFACE AND ATTACHED AT A FINITE NUMBER OF POINTS TO FORM THE REFLECTING SURFACE )N EITHER CASE THEREARESURFACEDISTORTIONSBETWEENTHEPRECISELYCON TROLLEDMOUNTINGPOINTS4HISSETSUPASYSTEMATICERROR INTHEFORMOFPERIODICCUSPSSEE&IGURE 4HESE ERRORSTYPICALLYCAUSEPATTERNGRATINGLOBESBECAUSETHESE &)'52% 3YSTEMATICDIS ERROR CUSPS ARE NORMALLY SEVERAL WAVELENGTHS APART PLACEMENTBETWEEN SUPPORTSWITH 4HEGRATINGLOBESAREEASILYRECOGNIZABLEBASEDONTHEIR ACUSPBETWEENSUPPORTS
£Ó°£{
2!$!2(!.$"//+
WELL DEFINEDANGULARSPACING&ORAGRIDWITHSUPPORTS ANDASSOCIATEDERRORS ADISTANCE SAPART THEGRATINGLOBEAPPEARSAT
P ARCSINSK
4HEGRATINGLOBEAMPLITUDEDEPENDSONTHEDEPTHOFTHEDISTORTION&IGURE ANDISTYPICALLY
¤ P E ³ 'RATING ,OBE ¥ ¦ L ´µ
WHEREDISTHEDEPTHOFTHECUSP &EED $ISPLACEMENT 4HE PERMISSIBLE TOTAL ERROR IN THE OVERALL FEED REFLECTOR SYSTEM ALIGNMENTn IS GENERALLY RESTRICTED TO K OR oK /N THE BASIS OF THIS CRITERION THE RESULTANT MAXIMUM DEVIATION FROM THE PARABOLIC CONDITION FEED AT FOCUS WOULDBEoK$ISPLACEMENTOFTHEFEEDALONGTHEFOCALAXISTHEZ AXISIN &IGURE PRODUCESANEVEN ORDERPHASEERRORONTHEAPERTUREILLUMINATION4HIS RESULTSINMODESTBEAMBROADENINGANDSOMEFILLINGOFTHEFIRSTNULL BUTISNORMALLY NOTTOODETRIMENTAL $ISPLACEMENTOFTHEFEEDNORMALTOTHEZ AXISPRODUCESANODD ORDERPHASEERRORIN THEAPERTUREANDCAUSESHIGHERSIDELOBESONONESIDEOFTHEBEAM&URTHERMORE SUCH DISPLACEMENT WILL CAUSE THE BEAM TO MISPOINT )F THE DISPLACEMENT IS SMALL FIXED AND KNOWN ONE CAN TYPICALLY CALIBRATE OUT THE FIXED MISPOINTING BIAS (OWEVER IF THEDISPLACEMENTISRANDOM SAYCAUSEDBYVIBRATION THEBEAMPOINTINGERRORCANBE APROBLEM4HEREFLECTORBEAMWILLBESTEEREDBYPRADIANSIFTHEFEEDISDISPLACEDOFF AXISBYANAMOUNTD
P ARCTANDF RADIANS
WHERE F IS THE FOCAL LENGTH 3O IF THE LATERAL FEED DISPLACEMENT ERROR IS D THE BEAM POINTINGERROR $P IS $Q
E F RADIANS E F
3TRUT"LOCKAGE 3TRUTSAREUSEDTOSUPPORTTHEFEED ANDFORCENTER FEDREFLEC TORS TYPICALLYFORMATRIPOD ASSHOWNIN&IGURE3TRUTSCATTERINGISACOMPLEX PHENOMENATHATDEPENDSONSTRUTSIZE STRUTGEOMETRY FIELDPOLARIZATION ANDOTHERFAC TORS(OWEVER INGENERAL STRUTINTERFERENCESCATTERINGWILLLIEWITHINACONICALREGION ABOUTTHESTRUTAXIS4HESTRUTISILLUMINATEDBYAPLANARWAVEFRONTANDONEEDGEOFTHE SCATTERINGCONELIESONTHEREFLECTORAXISSEE&IGURE )FTHESTRUTTILTSATTO THEAXIS THESCATTERINGCONEMAXIMUMANGLEISTWICETHETILTANGLE OR4HUS THE SCATTERINGFROMTHREESTRUTSFORMSINTERSECTINGRINGS ASSHOWNIN&IGURE4HIS CAUSESTHEMOSTBLOCKAGEATTHEPATTERNPEAKWHERETHETHREERINGSINTERSECT 0OLARIZATIONPLAYSASIGNIFICANTROLEINSTRUTSCATTERING&ORTHEEXAMPLESHOWNIN &IGURE STRUTISPARALLELTOTHE% FIELDANDITSBLOCKAGEAREAISLARGERTHANITS ACTUALPHYSICALCROSSSECTION(OWEVER THELOWERSTRUTS AND ARETILTEDWITH RESPECTTOTHE% FIELD ANDTHEREFOREAPPEARSMALLERTHANTHEIRPHYSICALCROSSSECTION
2%&,%#4/2!.4%..!3
£Ó°£x
&)'52% #ENTER FEDREFLECTORWITHTRIPODSTRUTS SIDEVIEW ANDAXIALVIEW
&)'52% 3TRUTANDMAXIMUMSCATTERINGCONE
&)'52% !XIALVIEWOFTRIPODSTRUTBLOCKAGEINTERFERENCE PATTERNS
£Ó°£È
£Ó°ÎÊ , /",Ê /
2!$!2(!.$"//+
Ê, / /1, -
2EFLECTORANTENNASAREBUILTINAWIDEVARIETYOFSHAPESANDSIZESWITHACORRESPONDING VARIETYOFFEEDSYSTEMSTOILLUMINATETHESURFACES EACHSUITEDTOITSPARTICULARAPPLI CATION&IGUREILLUSTRATESTHEMOSTCOMMONOFTHESEREFLECTORS EACHOFWHICHIS DESCRIBEDINSOMEDETAILINTHEFOLLOWINGSUBSECTIONS4HEPARABOLOIDIN&IGUREA COLLIMATESRADIATIONFROMAFEEDATTHEFOCUSINTOAPENCILBEAM PROVIDINGHIGHGAINAND MINIMUMBEAMWIDTH4HEPARABOLICCYLINDERIN&IGUREBPERFORMSTHISCOLLIMA TIONINONEPLANEBUTALLOWSTHEUSEOFALINEARARRAYINTHEOTHERPLANE THEREBYALLOWING FLEXIBILITYINEITHERSTEERINGORSHAPINGOFTHEBEAMINTHATPLANE)FBEAMSHAPINGNOT SCANNING ISTHEGOAL ANALTERNATIVEMETHODUSINGASINGLEFEED INLIEUOFALINEARARRAY ISSHOWNIN&IGUREC3HAPINGOFTHESURFACEALONGTHEVERTICALAXISISUSEDTOSPOIL THEBEAMSHAPEINTHISPLANE BUTBECAUSEONLYTHEPHASEOFTHEWAVEACROSSTHEAPERTURE ISCHANGED THEREISLESSCONTROLOVERTHEBEAMSHAPETHANINTHEPARABOLICANDORPHASE CYLINDERSHOWNIN&IGUREBWHEREINTHELINEARARRAYMAYBEADJUSTEDINAMPLITUDE 6ERYOFTENTHERADARDESIGNERNEEDSMULTIPLEBEAMSTOPROVIDEINCREASEDCOVERAGE ORTODETERMINEANGLE&IGUREDSHOWSHOWMULTIPLEDISCRETEFEEDLOCATIONSPRO DUCEASETOFSECONDARYBEAMSATDISTINCTANGLES4HEADDITIONALFEEDSMUSTBEOFFSET FROMTHEFOCUS ANDTHERESULTANTSECONDARYBEAMSWILLSUFFERSOMEGAINLOSSANDDIS TORTIONCOMMENSURATEWITHTHEASSOCIATEDFEEDDISPLACEMENT)FAN%3!FEEDISUSED THEREFLECTORSYSTEMCANBEDESIGNEDTOENABLEELECTRONICBEAMSCANNING ALBEITOVER ALIMITED&/64HEUSEOFMODERN%3!AND%3! LIKEREFLECTORFEEDSTOACHIEVEELEC TRONICSCANNINGISDISCUSSEDFURTHERIN3ECTION!NESPECIALLYCOMMONMULTIPLE BEAMDESIGNISTHEMONOPULSEANTENNAIN&IGUREE USEDFORANGLEDETERMINATION ONASINGLEPULSE ASTHENAMEIMPLIES)NTHISINSTANCE THESECONDBEAMISNORMALLYA DIFFERENCEBEAMWITHITSNULLATTHEPEAKOFTHEFIRSTBEAM
&)'52% #OMMONREFLECTORANTENNATYPESA PARABOLOID B PARABOLICCYLINDER C SHAPED D STACKEDBEAM E MONOPULSE ANDF #ASSEGRAIN
2%&,%#4/2!.4%..!3
£Ó°£Ç
-ULTIPLE REFLECTOR SYSTEMS TYPIFIED BY THE #ASSEGRAIN ANTENNA SHOWN IN &IGUREF OFFERONEMOREDEGREEOFFLEXIBILITYBYSHAPINGTHEPRIMARYBEAMAND OR ALLOWING THE FEED SYSTEM TO BE CONVENIENTLY LOCATED BEHIND THE MAIN REFLECTOR 4HESYMMETRICALARRANGEMENTSHOWNHASSIGNIFICANTBLOCKAGE BUTOFFSETGEOMETRIES MITIGATEFEEDBLOCKAGE )N MODERN REFLECTOR ANTENNA DESIGN COMBINATIONS AND VARIATIONS OF THESE BASIC TYPESAREWIDESPREADHOWEVER DESIGNGOALSGENERALLYSTRESSBEAMGAINS SHAPES LOCATIONS ETC WHILESTIPULATINGMINIMALLOSSESANDLOWSIDELOBELEVELS 0ARABOLOIDAL2EFLECTOR!NTENNAS 4HETHEORYANDDESIGNOFPARABOLOIDALREFLEC TORANTENNASAREEXTENSIVELYDISCUSSEDINTHELITERATUREn!BASICGEOMETRYISSHOWN IN&IGUREA WHICHASSUMESAPARABOLICREFLECTORSURFACEOFFOCALLENGTHFWITH AFEEDATTHEFOCALPOINT)TCANBESHOWNFROMGEOMETRICALOPTICSCONSIDERATIONSTHAT A SPHERICAL WAVE EMERGING FROM THE FOCAL POINT & AND INCIDENT ON THE REFLECTOR IS TRANSFORMED AFTER REFLECTION INTO A PLANE WAVE TRAVELING IN THE POSITIVE Z DIRECTION &IGUREB !LTHOUGHREFLECTORSARECOMMONLYILLUSTRATEDWITHAROUNDOUTLINEORRIMANDACEN TRALFEEDPOINT AVARIETYOFREFLECTORAPERTURESHAPESAREUSEDINPRACTICE ASSHOWNIN &IGURE/FTEN THEAZIMUTHANDELEVATIONBEAMWIDTHREQUIREMENTSDIFFER REQUIR INGANOBLONGAPERTURE ASSHOWNIN&IGUREB E )FLOWSIDELOBELEVELSAREREQUIRED FEEDBLOCKAGEMAYBECOMEINTOLERABLE REQUIR INGTHEUSEOFANOFFSETFEED&IGUREC 4HEFEEDISSTILLGENERALLYLOCATEDATTHE FOCALPOINT BUTTHEREFLECTORISREALIZEDVIAUSEOFADIFFERENTPORTIONOFTHEPARABOLA &OROFFSET FEDREFLECTORCONFIGURATIONS THEFOCALAXISGENERALLYDOESNOTINTERSECTTHE REFLECTOR SURFACE &EEDS FOR OFFSET FED REFLECTORS ARE GENERALLY AIMED CLOSE TO BUT SLIGHTLYBEYOND THECENTEROFTHEREFLECTORAREATOACCOUNTFORTHELARGERSPACETAPER SPREADING LOSS ON THE FAR SIDE OF THE REFLECTOR4HIS GENERALLY RESULTS IN A SLIGHTLY UNSYMMETRICALAPERTUREILLUMINATION 4HE CORNERS OF MOST PARABOLOIDAL REFLECTORS ARE FREQUENTLY ROUNDED NOT SHOWN OR MITERED &IGURE D TO REDUCE EXTRANEOUS SURFACE AREA ANDOR MINIMIZE THE TORQUEREQUIREDTOTURNTHEANTENNA"ECAUSETHESECORNERREGIONSAREGENERALLYWEAKLY
&)'52% 'EOMETRICALREPRESENTATIONOFAPARABOLOIDALREFLECTORA GEOMETRYANDB OPERATION
£Ó°£n
2!$!2(!.$"//+
&)'52% 0ARABOLOIDALREFLECTORAPERTURESHAPESORRIMSA ROUNDOUTLINERIM B OBLONG C OFFSETFEED D MITEREDCORNER E SQUARECORNER ANDF STEPPEDCORNER
ILLUMINATEDBYTHEFEED THEIRREMOVALGENERALLYHASLITTLEIMPACTONTHEGAIN(OWEVER CIRCULARANDELLIPTICALOUTLINESRIMSWILLPRODUCEMODESTSIDELOBESINBOTHPRINCIPALAND NONPRINCIPALPLANES)FVERYLOWSIDELOBESARESPECIFIEDINNONPRINCIPALPLANES ITMAYBE NECESSARYTOMAINTAINSQUARECORNERS ASSHOWNINTHEUPPERPARTOF&IGUREE 0ARABOLIC #YLINDER!NTENNA )T ISQUITECOMMONTHATEITHERTHEBEAMMUST BESTEERABLEORSHAPEDINONLYONEPLANE EITHER AZIMUTH OR ELEVATION ! PARABOLIC CYLINDRICAL REFLECTOR FED BY A LINEAR ARRAY FEED CAN ACCOMPLISH THIS AT MODERATELY HIGHERCOST 4HEPARABOLICCYLINDERANTENNACANBE APPLIEDTOACHIEVEAPRECISELYSHAPEDBEAM FROMACOMMONAPERTURE4HE!.403 &IGURE USESAVERTICALARRAYTOPRO VIDE FINE CONTROL OF THE ELEVATION PATTERN WITHASINGLEELEVATIONCOLUMNFEEDARRAY AND SO IS VERY COST EFFECTIVE 4HE ELEVA TION BEAM SHAPING INCORPORATES A STEEP BEAM SLOPE AT THE HORIZON TO ALLOW RADAR OPERATIONATLOWELEVATIONANGLESWITHOUT DEGRADATION FROM GROUND REFLECTIONS4HE 403 PRODUCESAMUCHSHARPERSLOPEAT THEHORIZONTHANASHAPEDREFLECTOROFEQUAL HEIGHT4HEARRAYFEEDENABLESSUPERPOSI TIONOFBEAMSCLOSETOTHEAPERTURENORMAL THEREBYENABLINGVERYHIGHTAPEREFFICIENCY NEARFULLAPERTUREGAIN
&)'52% !.403 PARABOLIC CYLINDER ANTENNA#OURTESY.ORTHROP'RUMMAN#ORPORATION
2%&,%#4/2!.4%..!3
£Ó°£
4HE BASIC PARABOLIC CYLINDER GEOMETRY IS SHOWN IN &IGURE 4HE REFLECTOR SURFACEISDEFINEDAS Z
Y
F F
WHEREZISTHEDISTANCEFROMTHEFOCALPLANE FISTHEFOCALLENGTHOFTHECYLINDRICAL REFLECTOR ANDYISTHEHORIZONTALDIMENSION&ORTHEPARABOLICCYLINDER THESURFACEDOES NOTVARYWITHX THEHEIGHT4HEFEEDISGENERALLYONTHEFOCALLINE ANDINMANYWAYS THEDESIGNOFPARABOLICCYLINDERREFLECTORSISSIMILARTOTHATOFPARABOLOIDALREFLECTORS /NE SIGNIFICANT DIFFERENCE IS THAT THE FEED ENERGY DIVERGES CYLINDRICALLY RATHER THAN SPHERICALLY ANDSOTHEFEEDPOWERDENSITYFALLSOFFASQRATHERTHANQ 4HEHEIGHTOFTHEPARABOLICCYLINDER&IGUREA MUSTALLOWFORBEAMWIDTH SHAPING ANDSTEERINGOFTHELINEARFEEDARRAY7HENTHELINESOURCESTEERSATANGLEP FROMBROADSIDE THEPRIMARYBEAMFROMTHESOURCELIESONACONIC ANDTHEINTERCEPTS ATTHEUPPERRIGHTANDLEFTCORNERSOFTHEREFLECTORAREFARTHERUPTHANINTHECENTER AS SHOWN IN &IGURE B4HEREFORE THE CORNERS OF PARABOLIC CYLINDER REFLECTORS ARE SELDOMROUNDEDINPRACTICE 3HAPED2EFLECTORS &ANBEAMSWITHASPECIFIEDSHAPEAREREQUIREDFORAVARIETYOF REASONS!COMMONELEVATIONSHAPEDBEAMREQUIREMENTISTOPROVIDEEQUALECHOSIGNAL POWERONTARGETSATCONSTANTALTITUDE)FTHETRANSMITANDRECEIVEBEAMSAREIDENTICAL ANDIFSECONDARYEFFECTSAREIGNORED THISCANBEACHIEVEDWITHAPOWERRADIATIONPAT TERNPROPORTIONALTOCSCP WHEREPISTHEELEVATIONANGLE)NPRACTICE THEWELL KNOWN COSECANT SQUAREDPATTERNISTYPICALLYMODIFIEDTOACCOUNTFORTHECURVATUREOFTHEEARTH ANDTHECHARACTERISTICSOFSENSITIVITYTIMECONTROL34#
&)'52% 0ARABOLICCYLINDERA GEOMETRYANDB SURFACEEXTENSIONENABLESLINE SOURCESTEERING
£Ó°Óä
2!$!2(!.$"//+
&)'52% 2EFLECTORSHAPING
!RELATIVELYSIMPLEWAYTOSHAPETHEBEAMISTOSHAPETHEREFLECTOR AS&IGURE ILLUSTRATES%ACHPORTIONOFTHEREFLECTORISDESIGNEDTOREFLECTAPORTIONOFTHEINCI DENTENERGYINADIFFERENTDIRECTION ANDTOTHEEXTENTTHATGEOMETRICOPTICSISVALID THEPOWERDENSITYATTHATANGLEISTHEINTEGRATEDSUMOFTHEPOWERDENSITYFROMTHE FEEDACROSSTHATPORTIONOFTHEREFLECTOR3ILVERGRAPHICALLYDESCRIBESAPROCEDUREFOR DETERMININGTHEREFLECTORCONTOURFORACOSECANT SQUAREDBEAM(OWEVER COMPUTER SOFTWAREPACKAGESNOWEXISTTHATENABLESYNTHESISOFARBITRARYBEAMSHAPESVIAAPPLI CATIONOFITERATIVEOPTIMIZATIONTECHNIQUESINCONJUNCTIONWITHPHYSICALOPTICSnBASED PATTERNCOMPUTATIONS4HESEANALYSISMETHODSANDSOFTWAREPACKAGESARESUMMARIZED IN3ECTION /FFSET FEDPARABOLICREFLECTORSAREOFTENUSEDTOMITIGATEFEEDBLOCKAGE(OWEVER REFLECTORSHAPINGCANALSOBEUSEDTOMITIGATEBLOCKAGEANDISSOMETIMESAPPLIEDTO REDIRECTTHEREFLECTEDENERGYAWAYFROMTHEFEED ASSHOWNIN&IGURE&IGURE ILLUSTRATESHOWSHAPINGCANBEAPPLIEDTOVIRTUALLYELIMINATEBLOCKAGEEVENTHOUGHTHE FEEDAPPEARSTOBEWITHINTHE&/6OFTHEREFLECTOR 4HE!32 ANTENNA&IGURE FOUNDATMAJORAIRPORTS TYPIFIESSHAPEDREFLEC TOR ANTENNA DESIGN 4HE ELEVATION BEAM SHAPE IS TAILORED USING A COMPUTER AIDED DESIGNPROCESS ANDAZIMUTHSIDELOBESARELOWEREDBYOFFSETTINGTHEFEEDSOTHEREISNO BLOCKAGE4WOLINEARORCIRCULARLYPOLARIZEDELEVATIONBEAMSAREPRODUCEDBYUSING TWOFEEDHORNS/NEBEAMISCLOSETOTHEHORIZONFORCLOSEINTARGETS ANDTHESECONDIS HIGHERINELEVATION SOITRECEIVESLESSGROUNDCLUTTERFORLONGRANGETARGETS /NE TYPICAL CHARACTERISTIC OF SHAPED REFLECTORS IS LOWER APERTURE EFFICIENCY 'ENERALLY THE SURFACE SHAPING PROCESS SPOILS THE APERTURE PHASE AND BROADENS THE BEAMTHEREBYINHERENTLYREDUCINGTHEAPER TURE EFFICIENCY (OWEVER THIS SACRIFICE IN APERTUREEFFICIENCYISGENERALLYACCEPTEDBY THE RADAR DESIGNER WHEN BEAM SHAPING IS DESIREDORREQUIRED 4HE SECOND ANTENNA ATOP THE !32 REFLECTOR &IGURE PROVIDES AN INDE PENDENTTRACKINGSYSTEM)TISAN!IR4RAFFIC #ONTROL2ADAR"EACON3YSTEMARRAYANTENNA THATTRANSMITSANDRECEIVESNARROWAZIMUTH SUM DIFFERENCE ANDGUARDBEAMS ALLSHAPED INELEVATION)TREQUIRESATRANSPONDERABOARD &)'52% %LIMINATIONOFBLOCKAGE THEAIRCRAFTSTARGETED ASITHASLOWGAIN
2%&,%#4/2!.4%..!3
£Ó°Ó£
&)'52% !32 SHAPED REFLECTOR WITH OFFSET FEED !IR 4RAFFIC #ONTROL 2ADAR "EACON 3YSTEM !4#2"3 ARRAY IS MOUNTED ON TOP #OURTESY .ORTHROP 'RUMMAN #ORPORATION
-ULTIPLE 2EFLECTOR !NTENNASn 4HERE ARE BOTH DIFFICULTIES AND ADVANTAGES ASSOCIATEDWITHADDINGASECONDARY ORSUBREFLECTOR TOAPARABOLOIDALREFLECTORSYSTEM 4HESHAPEOFTHESUBREFLECTORDETERMINESHOWTHEPOWERWILLBEDISTRIBUTEDACROSSTHE PRIMARY REFLECTOR AND THEREBY PROVIDES SOME CONTROL OVER AMPLITUDE IN ADDITION TO PHASEINTHEAPERTURE MAKINGITPOSSIBLETOPRODUCEVERYLOWSPILLOVERORTOPRODUCE ASPECIFICLOW SIDELOBEDISTRIBUTION"YSUITABLECHOICEOFSHAPE THEAPPARENTFOCAL LENGTHCANBEENLARGEDSOTHATTHEFEEDSIZEISPRACTICALOREVENFEASIBLE4HISISSOME TIMESNECESSARYFORMONOPULSEOPERATION 4HE#ASSEGRAINDUALREFLECTORANTENNA&IGURE DERIVEDFROMOPTICALTELE SCOPEDESIGNS ISTHEMOSTPREVALENTDUALREFLECTORCONFIGURATION&IGUREASHOWS ASMALLSUBREFLECTORBETWEENTHEFEEDANDPARABOLICMAINREFLECTOR4HEFEEDILLUMI NATESTHEHYPERBOLOIDALSUBREFLECTOR WHICHINTURNILLUMINATESTHEPARABOLOIDALMAIN REFLECTOR4HEFEEDISPLACEDATONEFOCUSOFTHEHYPERBOLOID ANDTHEPARABOLOIDFOCUS ISCOINCIDENTWITHTHESECONDFOCUSOFTHEHYPERBOLOID4HEUSEOFASUBREFLECTORALSO ALLOWSTHEFEEDTOBELOCATEDBEHINDTHEMAINREFLECTORANDCLOSERTOTHETRANSMITTER ANDRECEIVERINORDERTOMINIMIZETRANSMISSIONLINELOSSES&URTHERMORE IFTHEFEEDIS LOCATEDBEHINDTHEMAINREFLECTOR THECENTEROFGRAVITYWILLBEBIASEDCLOSERTOTHEMAIN REFLECTORVERTEXTHEREBYSIMPLIFYINGTHEDESIGNOFBOTHTHESTRUCTUREANDTHEGIMBAL PRECISIONMECHANICALPOSITIONINGSYSTEM 4HE'REGORIANDUALREFLECTORANTENNASYSTEMNOTSHOWNIN&IGURE ISSIMILAR TOTHE#ASSEGRAIN BUTITUSESANELLIPSOIDALSUBREFLECTORINLIEUOFAHYPERBOLOIDRESULT INGINALENGTHENINGOFTHEREFLECTORSYSTEMALONGTHEFOCALAXIS 4HEPARAMETERSOFTHE#ASSEGRAINREFLECTORARERELATEDBYTHEFOLLOWINGEXPRESSIONS
TANXV $MFM
TANXV TANXR FC$S
E ,VFC
£Ó°ÓÓ
2!$!2(!.$"//+
&)'52% #ASSEGRAINDUALREFLECTORANTENNASYSTEMSTHELARGERSURFACEISTHEMAINREFLECTOR ANDTHESMALLERSURFACEISTHESUBREFLECTOR A RAYOPTICSB TYPICALAXIALCONFIGURATION ANDC OFFSETCONFIGURATION
WHERETHEECCENTRICITYEOFTHEHYPERBOLOIDISGIVENBY
E SIN;XV XR =SIN;XV XR =
4HEEQUIVALENT PARABOLOIDCONCEPTISACONVENIENTMETHODOFANALYZINGTHERADIA TIONCHARACTERISTICSUSINGASINGLEREFLECTORhEQUIVALENTvMODEL4HISMETHODUTILIZES APARABOLOIDOFEQUALDIAMETER BUTALARGERFOCALLENGTHTOMODELTHEDUAL REFLECTOR #ASSEGRAINSYSTEM4HEEQUATION
FC $MTANXR
DEFINESTHEEQUIVALENTFOCALLENGTH ANDTHEFOCALLENGTHRATIOORMAGNIFICATIONMIS GIVENBY
M FCFM E E
2%&,%#4/2!.4%..!3
£Ó°ÓÎ
4HEMAGNIFICATIONMISAUSEFULMETRICINTHATITPROVIDESAMEASUREOFTHEREDUCTIONIN SIZELENGTHALONGTHEFOCALAXISTHATISENABLEDBYUSEOFTHE#ASSEGRAINREFLECTORSYSTEM INLIEUOFASINGLEPARABOLICREFLECTORSYSTEM4HEFEEDISDESIGNEDTOPRODUCESUITABLE ILLUMINATIONWITHINSUBTENDEDANGLESoXRASSOCIATEDWITHTHELONGERFOCALLENGTHFC !PERTUREBLOCKINGCANBELARGEFORCENTER FED#ASSEGRAINANTENNAS4HEBLOCKAGE CANBEMINIMIZEDBYCHOOSINGTHEDIAMETEROFTHESUBREFLECTORTOBEEQUALTOTHATOF THEFEED4HISOCCURSWHEN
$3 FM L K
WHEREKISTHERATIOOFTHEFEED APERTUREDIAMETERTOITSEFFECTIVEBLOCKINGDIAMETER /RDINARILYKISSLIGHTLYLESSTHAN&ORLINEARLYPOLARIZEDRADARAPPLICATIONS APERTURE BLOCKING CAN BE SIGNIFICANTLY REDUCED BY USING A POLARIZATION TWIST REFLECTOR AND A SUBREFLECTORMADEOFPARALLELWIRES4HISTWISTREFLECTORDESIGNENABLESAROTATION OFTHEPOLARIZATIONSUCHTHATTHEPOLARIZATIONOFTHEBEAMUPONREFLECTIONFROMTHEMAIN REFLECTORISORTHOGONALANDTRANSPARENTTOTHEGRIDDEDSUBREFLECTOR "LOCKAGECANALSOBEELIMINATEDBYOFFSETTINGBOTHTHEFEEDANDTHESUBREFLECTOR &IGURE C 7ITH BLOCKAGE AND SUPPORTING STRUTS AND SPILLOVER VIRTUALLY ELIMI NATED THISGEOMETRYISUSEFULFORVERYLOWSIDELOBEAPPLICATIONS !S DESCRIBED EARLIER THE APERTURE EFFICIENCY OF SINGLE REFLECTOR SYSTEMS IS MAXI MIZEDBYBALANCINGTHEFEEDTAPERANDTHEFEEDSPILLOVERANDMINIMIZINGOTHERLOSSES BUTISTYPICALLYn(OWEVER DUALREFLECTORSYSTEMSEG #ASSEGRAIN HAVEAN ADDITIONALDEGREEOFFREEDOMANDSURFACESHAPINGCANBEAPPLIEDTODECREASETHETAPER LOSSANDENABLEAPERTUREEFFICIENCIESINEXCESSOF !DIFFERENTTYPEOFDUALREFLECTORSYSTEMTHATISPARTICULARLYWELL SUITEDTOAPPLICA TIONSWHERELIMITEDELECTRONICSCANNINGISREQUIREDISTHESO CALLEDCONFOCALREFLECTOR SYSTEMnSHOWNIN&IGURE4HISSYSTEMEMPLOYSTWOPARABOLICREFLECTORS A MAINANDASUB THATSHAREACOMMONFOCALPOINT4HEOPTICSOFTHISSYSTEMISDESIGNED SUCH THAT A PLANE WAVE SOURCE SAY FROM AN ARRAY IS FIRST CONVERTED TO A SPHERICAL WAVEATTHESUBREFLECTOR4HEN UPONREFLECTIONFROMTHESUBREFLECTOR THEFEEDENERGY CONVERGESATTHECOMMONFOCUSANDDIVERGESAGAINASASPHERICALWAVEBEFOREFINALLY REFLECTINGFROMTHEMAINREFLECTOR 4HECONFOCALSYSTEMHASSEVERALINTERESTINGPROPERTIES TIEDTOTHEMAGNIFICATION FACTOR-
- F-F3
WHEREF-ANDF3ARETHEFOCALLENGTHSOFMAINANDSUBREFLECTORS RESPECTIVELY4HEFIRST PROPERTYSHOWSTHATTHESYSTEMISESSENTIALLYAFEEDSOURCEMAGNIFIER4HEREFLECTOR GAIN 'R ISDESCRIBEDBY
'Ry'Fr-rCOSPR
WHERE'FISTHEGAINOFTHEFEEDARRAYANDPRISTHESCANANGLEOFTHEREFLECTORSECOND ARY BEAM4HESECONDPROPERTYDEFINESTHESCANNING4HEREFLECTORSCANANGLE PR IS DEFINEDBYTHEFOLLOWINGEQUATION
PRyPF-
WHEREPFISTHEFEEDSCANANGLE&OREXAMPLE IFTHEMAGNIFICATIONFACTORISANDTHE %3!FEEDARRAYISSCANNED THEREFLECTORBEAMWILLSCANAPPROXIMATELY
£Ó°Ó{
2!$!2(!.$"//+
0ARABOLIC -AIN2EFLECTOR A2EF A!%3!-AG
$MAIN
#OMMON &OCUS
FMAIN
FSUB
0HASED !RRAY&EED
-AG
$SUB
FMAIN FSUB
A!%3!
0ARABOLIC 3UBREFLECTOR
&)'52% #ONFOCALDUALREFLECTORANTENNA
3CANABERRATIONSLEADTOMODERATELYHIGHERSCANLOSSESANDSLIGHTBEAMSCANANGLE DEVIATIONSFROMTHOSEPREDICTEDBY%QSANDWHENIDEAL%3!PLANEWAVE EXCITATIONS IE LINEAR PHASE SLOPE ARE APPLIED (OWEVER THE AMPLITUDE AND PHASE CONTROLSINTHE%3!ALLOWFORSCANABERRATIONCOMPENSATIONVIACONJUGATEMATCHING OFTHEAPERTUREFIELDS4HUS THEUSEOFAN%3!FEEDENABLESRECOVERYOFSCANLOSSES RESULTINGFROMABERRATIONSINTHESYSTEM #ONFOCAL REFLECTOR ARCHITECTURES HAVE BEEN THE SUBJECT OF STUDY AND ANALYSIS FOR MANY YEARS AND NUMEROUS DEMONSTRATION SYSTEMS HAVE ALSO BEEN DEVELOPEDn !LTHOUGH CONFOCAL REFLECTORS HAVE NOT BEEN ADOPTED FOR SIGNIFICANT USAGE IN OPERA TIONALSYSTEMS THESEREFLECTORSYSTEMSARELIKELYTOBEPARTOFSOMENEXT GENERATION RADARSDUETOTHERELATIVELYRECENTMATURATIONOFENABLING%3!TECHNOLOGY 3PHERICAL2EFLECTORS n 4HESPHERICALREFLECTORISSOMETIMESUSEDFORAPPLI CATIONSREQUIRINGSCANNINGORMULTIPLEBEAMSOVERVERYWIDEANGLES)TSDESIGNISBASED UPONTHEFACTTHAT OVERLIMITEDANGULARREGIONS ASPHERICALSURFACEVIEWEDFROMANY POINTHALFWAYBETWEENTHECENTEROFASPHEREANDITSSURFACEISNEARLYPARABOLIC4HIS MEANSTHATIFAFEEDISMOVEDALONGANINNERSPHERICALSURFACEOFCONSTANTRADIUS2 WHERE2ISTHERADIUSOFTHESPHERICALREFLECTOR THESECONDARYBEAMCANBESTEERED4HE RANGEOFBEAMSTEERINGISLIMITEDBYTHESIZEOFTHESPHERICALREFLECTOR IE THEPORTION OFAFULLSPHEREREALIZEDBYTHEREFLECTOR4HESCANNINGCAPABILITYCANBEIMPLEMENTED VIAUSEOFEITHERASINGLEMOVABLEFEEDORANARRAYWITHSWITCHABLEFEEDS 3ELF BLOCKAGEREFLECTORBLOCKINGITSELF ISANOTHERPOTENTIALLIMITINGFACTORINSPHER ICALREFLECTORSYSTEMS(OWEVER OFAZIMUTHSTEERINGCANBEACCOMPLISHEDVIA APOLARIZATIONDESIGNSCHEMESIMILARTOTHEPOLARIZATIONTWISTSUBREFLECTORDESCRIBED
2%&,%#4/2!.4%..!3
£Ó°Óx
ABOVEFORTHE#ASSEGRAINSYSTEM)NTHISDESIGN THEFEEDPOLARIZATIONISTILTEDAND THEREFLECTORISFORMEDOFCONDUCTINGSTRIPSPARALLELTOTHEPOLARIZATION(OWEVER THE CONDUCTINGSTRIPSONOPPOSINGSIDESOFTHEREFLECTORARETWISTED THEREBYENABLING TRANSMISSIONOFTHEREFLECTEDENERGY4HISTYPEOFANTENNAISKNOWNASAHELISPHERE )FWIDEANGLESCANNINGINONLYONEPLANE IE AZIMUTHORELEVATION ISREQUIRED ASIM ILARDESIGNCALLEDTHEPARABOLICTORUSISMOREAPPLICABLE4HEPARABOLICTORUSREFLECTORIS ASURFACETHATISSPHERICALINONEPLANEAZIMUTHORELEVATION ANDPARABOLICINTHEOTHER PLANE4HISDESIGNTAKESADVANTAGEOFBOTHTHEWIDESCANNINGENABLEDBYTHESPHERICAL SHAPINGANDTHEHIGHAPERTUREEFFICIENCYENABLEDBYTHEPARABOLICSHAPING4HEHEIGHT ELEVATION DIMENSIONOFTHEREFLECTORISSETBYTHEREQUIREDELEVATIONBEAMWIDTH 4HEPARABOLICTORUSHASSEENAPPLICATIONINVARIOUSRADARSINCLUDINGTHEORIGINAL "-%73SYSTEMANDTHE303 AND301 "SYSTEMS
£Ó°{Ê , /",Ê
7HEREASPHASEDARRAYANTENNASAREFREQUENTLYCHOSENFORRADARSYSTEMDESIGNS REFLEC TORANTENNASWEREONCETHEDOMINANTANTENNADESIGNCHOICEFORMEDIUM TOHIGH GAIN RADARAPERTURES/BVIOUSLY THECOSTOFASINGLEFEEDHORNANDMETALREFLECTORISMUCHLESS THANTHESAMESIZEARRAYWITHMANYINDIVIDUALELEMENTSANDASSOCIATEDPHASESHIFTERS AMPLIFIERS RECEIVERS ETC#ONSEQUENTLY MANYRADARSCURRENTLYINTHEFIELDUSEREFLEC TORANTENNAS&URTHERMORE REFLECTORANTENNADESIGNSAREUSEDINMODERNRADARDESIGNS WHEREMODERATESCANRATESANDSCANVOLUMESAREREQUIREDORLOWCOSTISESSENTIAL -ANYLEGACYRADARSEMPLOYREFLECTORANTENNASWITHSINGLEFEEDELEMENTSORACLUSTER OFFEEDSIE ANARRAY WITHAFIXEDBEAM2&COMBINERORDIVIDERNETWORK&IGURE SHOWS SOME TYPICAL SINGLE FEED REFLECTOR CONFIGURATIONS UTILIZING HORN WAVEGUIDE AND DIPOLE FEEDS &IGURE SHOWS A FEW COMMON TYPES OF FLARED HORN FEEDS
&)'52% 3OMETYPICALREFLECTORANTENNACONFIGURATIONS
£Ó°ÓÈ
2!$!2(!.$"//+
&)'52% 6ARIOUSTYPESOFHORNFEEDSFORREFLECTORANTENNAS
/THERTYPESOFFEEDSSUCHASDIPOLES MICROSTRIPPATCHES NOTCHES ETC ARESOMETIMES USED BUT FOR SINGLE FEED REFLECTOR IMPLEMENTATIONS FLARED WAVEGUIDE HORNS ARE THE MOSTCOMMON4HEFEEDINCONJUNCTIONWITHTHEREFLECTOR MUSTALSOSATISFYTHEANTENNA POLARIZATIONREQUIREMENTSANDHANDLEREQUIREDPEAKANDAVERAGEPOWERLEVELSUNDER ALLOPERATIONALENVIRONMENTS/THERFEEDDESIGNCONSIDERATIONSINCLUDETHEOPERATING BANDWIDTH AND THE POTENTIAL IMPLEMENTATION OF ANY ADDITIONAL MODESPATTERNS EG DIFFERENCEORSQUINTEDBEAMS &ORSINGLE FEEDRADARREFLECTORANTENNASSUCHASTHOSEDEPICTEDIN&IGURES MECHANICALSCANNINGISGENERALLYACHIEVEDVIAAGIMBALAPRECISIONMECHANICALPOINT ING SYSTEM 2ADAR ANTENNA GIMBAL DESIGNS VARY GREATLY DEPENDING UPON SCAN RATE &/6 TRACKINGREQUIREMENTS ANTENNASIZE MASS ETC "ASIC &EEDS &OR RADARS REQUIRING A SIMPLE PENCIL BEAM BASIC SINGLE MODE WAVEGUIDEHORNFEEDSSUCHASPYRAMIDAL4%MODE ANDCONICAL4%MODE HORNSARE WIDELYUSED3INGLE MODE FLAREDHORNSWILLPROVIDELINEARLYPOLARIZEDPENCILBEAMSAND WILL GENERALLY HANDLE HIGH POWER &OR MORE DEMAND INGAPPLICATIONSREQUIRINGTRACKINGMODES POLARIZATION DIVERSITY HIGHBEAMEFFICIENCY ORULTRA LOWSIDELOBES FEED DESIGNS BECOME CORRESPONDINGLY MORE COMPLEX &ORSUCHAPPLICATIONS SEGMENTED FINNED MULTIMODE ANDORCORRUGATEDHORNS ASILLUSTRATEDIN&IGURE AREOFTENUSED-ULTIMODEFEEDSENABLEREALIZATIONOF DIFFERENCEMODEPATTERNSWITHACOMPACT SINGLEFEED HORN AND AS SUCH ARE ESPECIALLY USEFUL FOR TRACKING APPLICATIONS -ONOPULSE&EEDS n -ONOPULSEISFREQUENTLY USED IN RADAR TRACKING AND SURVEILLANCE SYSTEMS TO EITHERKEEPTHEBEAMPOINTEDONTHETARGETTRACKING ORTOACCURATELYMEASURETHEANGLETOTHETARGETSUR VEILLANCE n !MPLITUDE COMPARISON MONOPULSE SYSTEMS ILLUS TRATED IN &IGURE USE THE SUM OF THE TWO FEED
&)'52% !MPLITUDE COM PARISONMONOPULSEANTENNASHOWING SUMANDDIFFERENCEBEAMS
2%&,%#4/2!.4%..!3
£Ó°ÓÇ
OUTPUTSTOFORMAHIGH GAINLOW SIDELOBEBEAMANDTHEDIFFERENCEOFTHETWOSQUINTED BEAMSTOFORMAPRECISE DEEPNULLATBORESIGHT4HESUMBEAMISUSEDONBOTHTRANS MITANDRECEIVETODETECTTHETARGET4HEDIFFERENCEBEAMISRECEIVEONLYANDPROVIDES ANGLEDETERMINATION)NMOSTAPPLICATIONS BOTHAZIMUTHANDELEVATIONDIFFERENCEBEAM PORTS ARE IMPLEMENTED &IGURE ILLUSTRATES THE CONCEPT OF AMPLITUDE COMPARI SONMONOPULSE!FEEDBACKLOOPMINIMIZESTHERECEIVEDDIFFERENCEBEAMSIGNALBY MECHANICALLYSTEERINGTHEANTENNATOKEEPTHENULLANDTHECORRESPONDINGSUMBEAM PEAK ONTARGET 4HEREARENUMEROUSWAYSTOREALIZEAMPLITUDEMONOPULSEBEAMSINAREFLECTOR ANTENNADESIGN BUTMOSTDESIGNSGENERALLYFALLINTOTWOCLASSES MULTIFEEDAND MULTIMODE-ULTIFEEDDESIGNSUSECOMBININGNETWORKSTOGENERATEDIFFERENTIAL FEEDDISTRIBUTIONS)NITSSIMPLESTFORM ANAZEL MULTIFEEDMONOPULSEFEEDARRAY CANBEREALIZEDASAFOUR ELEMENTFEED ASSHOWNIN&IGURE(OWEVER SOME APPLICATIONS USE MORE FEED ELEMENTS TO FURTHER TAILOR THE DISTRIBUTION TO IMPROVE EFFICIENCYANDORDIFFERENCEBEAMSLOPE )FTHEREFLECTORISILLUMINATEDWITHASIMPLEFOUR ELEMENTFEED ACONFLICTGENERALLY ARISESBETWEENTHEGOALSOFHIGHSUM BEAMEFFICIENCYANDHIGHDIFFERENCE BEAMSLOPE FROMTHEMONOPULSECOMPARATOR4HEFORMERREQUIRESASMALLOVERALLFEEDSIZE WHEREAS THE LATTER REQUIRES LARGE INDIVIDUAL FEEDS &IGURE .UMEROUS DESIGN METHODS HAVEBEENDEVISEDTOOVERCOMETHISPROBLEM ASWELLASTHEASSOCIATEDHIGHDIFFERENCE PATTERNSIDELOBES4HESEMETHODSEITHERUSEDIFFERENTSETSOFFEEDELEMENTSFORTHESUM ANDDIFFERENCEBEAMSORAPPLYDIFFERENTARRAYAMPLITUDEPHASEWEIGHTINGSFOREACHOF THE BEAMS )F HORN FEED ELEMENTS ARE USED ONE APPROACH IS TO OVERSIZE THE FEEDS TO ENABLEMULTIMODEEXCITATIONFORTHESUMBEAMASDESCRIBEDBY(ANNAN!COMPARISON OFSOMECOMMONMONOPULSEFEEDCONFIGURATIONSISINCLUDEDIN4ABLE
, "))"&%( &' $& (*$ #)# % #) .#*( (% "%*( ( %&) #)"+ !( (% /" '- ' (
&)'52% &OUR ELEMENTMONOPULSEFEEDWITHDUM DELTAAZ ANDDELTAELPORTS
£Ó°Ón
2!$!2(!.$"//+
&)'52% 0LOTSOFSUM BEAMEFFICIENCYANDDIFFERENCE BEAMSLOPE ASAFUNCTIONOFASSOCIATEDEDGETAPERS( PLANESHOWN
!RRAY&EEDS !SINGLEFEEDATTHEFOCALPOINTOFAPARABOLAFORMSABEAMPARALLEL TOTHEFOCALAXIS!DDITIONALFEEDSDISPLACEDFROMTHEFOCALPOINTFORMADDITIONALBEAMS ATANGLESFROMTHEAXISSEE%Q 4HUS ONECANEMPLOYAMULTIPLEFEEDARRAYWITH APPROPRIATEELECTRONICSTOFEEDAREFLECTORANDPROVIDEEITHERMULTIPLEDISPLACEDBEAMS ORELECTRONICBEAMSWITCHING IE BEAMSCANNINGTODISCRETEANGLES!REFLECTORSYSTEM SUCHASTHISCANEFFECTIVELYPROVIDEELECTRONICSCANNINGOVERANARROW&/6(OWEVER THISTYPEOFARRAY FEDREFLECTORARCHITECTUREDOESSUFFERFROMONEDRAWBACK!PARABOLA CONVERTSASPHERICALWAVEINTOAPUREPLANEWAVEONLYWHENTHESOURCEFEED ISATTHE FOCUS)FTHESOURCEFEED ISDISPLACEDFROMTHEFOCUS THEREFLECTEDWAVEISSOMEWHAT DISTORTEDANDTHISRESULTSINGAINLOSSANDBEAMSHAPEDISTORTION&IGURESHOWS THEEFFECTOFTHISDISTORTIONONTHEPATTERNOFATYPICALCENTER FEDREFLECTORASTHEFEEDIS MOVEDOFF AXIS 4!",% -ONOPULSE&EEDHORN0ERFORMANCE
(PLANE
3IDELOBES D"
%PLANE
4YPEOF(ORN
%FFICIENCY
3LOPE
3LOPE
3UM
$IFFERENCE
3IMPLEFOUR HORN
4WO HORNDUAL MODE
4WO HORNTRIPLE MODE
4WELVE HORN
&OUR HORNTRIPLE MODE
&EEDSHAPE
2%&,%#4/2!.4%..!3
£Ó°Ó
&)'52% 0ATTERNSFOROFF AXISFEEDS
! PHASED ARRAY %3! TYPE FEED COVERING THE FOCAL REGION PLANAR OR CURVED IN SHAPE SUCHASTHATSHOWNIN&IGUREB CANPROVIDEIMPROVEDCAPABILITY)TOFFERS TWOENHANCEMENTSTHATEXTENDTHECAPABILITYABOVEANDBEYONDTHATOFAMULTIPLEFEED ARRAY WITH SWITCHED BEAMS 4HE PHASED ARRAY FED REFLECTOR CAN TRANSMIT OR RECEIVE BEAMS OVER CONTINUOUS ANGLES WITHIN THE &/6 WHEREAS THE MULTIPLE FEED ARRAY IS LIMITEDTODISCRETEBEAMPOSITIONS)TALSOPROVIDESGREATERAPERTUREEFFICIENCYBECAUSE ITALLOWSFORADJUSTMENTOFTHEELEMENTAMPLITUDESANDPHASESTOREDUCESCANLOSSES DUETOABERRATIONS)FWEVIEWTHEREFLECTORASACOLLECTOROFPARALLELRAYSFROMARANGE OFANGLESCOVERINGTHE&/6ANDEXAMINETHECONVERGINGRAYPATHS&IGUREA IT ISEVIDENTTHATANAPPROPRIATELYSIZEDFEEDREGIONCANBEFOUNDTHATINTERCEPTSMOSTOF THEENERGY)FTHEPHASED ARRAYFEEDARRAYISAPPROPRIATELYDESIGNED BEAMDISTORTION ANDSCANLOSSESSUCHASTHOSESHOWNIN&IGURE CANBEEFFECTIVELYELIMINATED 4HISSORTOFDESIGNAPPROACHWHEREINTHEFEEDARRAYAMPLITUDEPHASEDISTRIBUTIONIS hMATCHEDvTOTHEFOCALPLANEFIELDSISOFTENREFERREDTOASCONJUGATEFIELDMATCHING
£Ó°Îä
2!$!2(!.$"//+
&)'52% %XTENDEDFEEDREGIONIMPROVESSIDELOBESOFOFFSETFEEDUSEDON !232 A RAYGEOMETRYANDB CURVEDFEED
&EED ARRAYS SUCH AS THAT ILLUSTRATED IN THE!232 REFLECTOR ANTENNA SHOWN IN &IGURESAND HAVEALSOBEENUSEDTOENABLESHAPEDBEAMSANDLOWSIDE LOBEPATTERNS0ASSIVECOMBINERNETWORKSAREUSEDTOGENERATEMULTIPLERECEIVEBEAMS STACKEDINELEVATIONANDASINGLETRANSMITBEAM4HERECEIVEBEAMSREQUIRELOWAZI MUTH SIDELOBES! CONVENTIONAL BEAMFORMING APPROACH WOULD INCORPORATE AN ARRAY AT THE FOCAL PLANE WITH A SINGLE BEAM PERFEEDHOWEVER THEASSOCIATEDPHASE DISTORTION DUE TO DISPLACEMENT CAUSES POOR AZIMUTH SIDELOBES 4O CORRECT THIS PROBLEM THE FEED ARRAY IS PLACED FORWARD OF THE AZIMUTH FOCAL POINT ENABLING COMPENSATION AND SIDELOBE IMPROVEMENTSVIAUSEOFMULTIPLEFEEDS PERBEAMWITHAPPROPRIATEFEEDPHASING &IGUREA 4WO DIFFERENT FOCAL LENGTHSAREUSEDINTHEREFLECTOR ONEFOR ELEVATIONANDALONGERONEFORAZIMUTH 4HE FEED IS ON A CURVED SURFACE OPTI MIZEDVIARAYTRACING ANDISFORWARDOF THEAZIMUTHFOCALPOINT&OREACHROW THEAMPLITUDEANDPHASEISOPTIMIZEDFOR ABEAMWITHLOWAZIMUTHSIDELOBES4HE ELEVATION PATTERNS FOR EACH SINGLE ROW HAVE POOR SIDELOBES BUT SEVERAL ROWS AREUSEDFOREACHRECEIVEBEAMTHEREBY IMPROVINGTHEELEVATIONSIDELOBES&OR TRANSMIT ALLROWSTHEWHOLEARRAY &)'52% !232 LOW SIDELOBE REFLECTOR AREUSED/NRECEIVE GROUPSOFROWS WITH OFFSET ARRAY FEED #OURTESY .ORTHROP 'RUMMAN AREUSEDTOFORMRECEIVEBEAMS #ORPORATION
2%&,%#4/2!.4%..!3
£Ó°xÊ , /",Ê /
£Ó°Î£
Ê 9--
2EFLECTORANTENNAANALYSISMETHODSCANGENERALLYBELUMPEDINTOTHREECLASSESORCATEGO RIES 0HYSICAL/PTICS0/ ORINDUCEDCURRENTMETHODS 'EOMETRICAL/PTICS'/ METHODS WITHANDWITHOUTDIFFRACTIONTERMS AND RIGOROUS ORFULL WAVE METHODS 0HYSICAL /PTICS 0/ 2EFLECTOR !NALYSIS 4HE 0HYSICAL /PTICS 0/ METHOD ISCOMMONLYEMPLOYEDFORTHEMOSTRIGOROUSREFLECTORANALYSISDUETOITSACCURACY )TINCORPORATESTHEFIELDPROPERTIESOFTHEFEED ANDMODELSTHERESULTANTFIELDSFROM THE REFLECTOR THUS ENABLING THE COMPUTATION OF THE CROSS POLARIZATION PROPERTIES &URTHERMORE THEMETHODISMOREACCURATEFORFEEDSTHATARENOTATTHEFOCALPOINTAND REFLECTORSTHATARENOTPARABOLIC4HEREAREMANYGOODREFERENCESTHATDESCRIBETHETHE ORYBEHINDTHEMETHODANDHOWITISAPPLIEDTOTHEANALYSISOFREFLECTORANTENNASn 0/ISAVERYGENERALhHIGHFREQUENCYvANALYSISMETHODTHATGENERALLYPROVIDESHIGH FIDELITYPATTERNPREDICTIONSFORMOSTREFLECTORSYSTEMSASLONGASTHEREFLECTORDIMEN SIONSARELARGE SAY GREATERTHANABOUTFIVEWAVELENGTHSINBOTHDIMENSIONS!NOVER VIEWOF0/ISPROVIDEDHERETOENABLEANUNDERSTANDINGOFTHEFUNDAMENTALSOFTHE METHOD4HE0/METHODCANBEBROKENINTOTWOSTEPS THECALCULATIONOFINDUCED REFLECTORSURFACECURRENTS AND THEINTEGRATIONOFTHESECURRENTSWITHANAPPROPRIATE FREESPACEVECTOR'REENSFUNCTIONKERNEL TODETERMINETHEFAR FIELDPATTERNS &IRST CONSIDERTHECALCULATIONOFTHEREFLECTORSURFACECURRENTS)TISASSUMEDTHAT THE FIELD FROM THE FEED THAT IS INCIDENT ON THE REFLECTOR HAS A SPHERICAL WAVEFRONT WITHAMPLITUDETAPERINGDEFINEDBYTHEFEEDPATTERN3O ASAFIRSTSTEP THEFEEDIS MATHEMATICALLYMODELEDTODETERMINETHEINCIDENTFIELDAMPLITUDEANDPHASEATTHE REFLECTORSURFACE$IFFERENTMODELSAREAPPLIEDDEPENDINGONTHECHOICEOFFEEDUSED INTHEDESIGNEXAMPLESINCLUDEWAVEGUIDEFEEDHORNS MICROSTRIPPATCHES DIPOLES ETC3OMETIMESTHEFEEDMODELWILLINSTEADEMPLOYMEASUREDFEEDPATTERNSIFSUCH DATAISAVAILABLE!LLMODELSMUSTBENORMALIZEDTOSOMEPRESCRIBEDRADIATEDPOWER LEVEL EG WATT&IGURESHOWSATYPICALWAVEGUIDEFEEDHORNMODELANDITS ASSOCIATEDLOCALCOORDINATESYSTEM "ASED ON AN APPROPRIATE APPLICATION OF EQUIVALENCE PRINCIPLE AND THE INDUCTION THEOREM nTHECURRENTSINDUCEDONTHEREFLECTORCANBEDETERMINEDFROMTHEFEED
&)'52% 7AVEGUIDE FEED HORN MODEL ANDCOORDINATESYSTEM
£Ó°ÎÓ
2!$!2(!.$"//+
( FIELDINCIDENTATTHESURFACEOFTHEREFLECTOR4HEKEYPREMISEOFTHEEQUIVALENCE PRINCIPLE IS THAT FIELDS FROM A SCATTERER EG A REFLECTOR CAN BE REPRESENTED BY AN hEQUIVALENTvELECTRICCURRENT* ANDMAGNETICCURRENT- THATAREDIRECTLYRELATEDTOTHE INCIDENT%AND(FIELDSVIA
* N} r (
- N} r %
WHERE N} IS THE NORMAL TO THE REFLECTOR SURFACE 4HE APPLICATION OF THE EQUIVALENCE PRINCIPLETO0/ BASEDREFLECTORANALYSESASSHOWNHEREISASPECIALIZEDCASEWHEREIN THEREFLECTORISANELECTRICCONDUCTOR ANDCONTRIBUTIONSFROMSURFACECURRENTSONTHE BACKSIDEOFTHEREFLECTORAREDEEMEDNEGLIGIBLE!NAPPROPRIATEAPPLICATIONOFIMAGE THEORYnIMPOSESAZEROTANGENTIAL% FIELD%Q ANDDOUBLESTHEELECTRICCUR RENT * %Q RESULTINGINANEQUIVALENTSURFACECURRENTREPRESENTEDBY
* N} r (
.OWCONSIDERAGENERALIZEDREFLECTORSURFACEASSHOWNIN&IGURE4HESUR FACEISDIVIDEDINTORECTANGULARGRIDREGIONSOFAREAD!THATINTERCEPTTHEINCIDENTFEED FIELD)FTHEFEEDFAR FIELD( FIELDPATTERNIS ( V} POLARIZEDINTHEDIRECTION V} THENTHE INCIDENT( FIELDATTHEREFLECTORIS
( ( V} V} N} E JKR D! P R
#OMBINING%QSANDYIELDSTHEEQUIVALENTSURFACECURRENT * ATAREAD!
* N} r ( V} V} N} E JKR D! P R
WHERE N} ISTHENORMALTOTHESURFACE S} ISTHEOBSERVATIONDIRECTION&IGURE RIS THEDISTANCEFROMTHEFEEDTOTHEREFLECTINGSURFACE K OK IE THEWAVENUMBER RTERMACCOUNTSFORTHEPROPAGATIONPHASEANDSPACELOSSFROMTHEFEED ANDTHEE JKRO¼ TOTHEREFLECTORSURFACE
&)'52% 'ENERALIZEDREFLECTORGEOMETRY
2%&,%#4/2!.4%..!3
£Ó°ÎÎ
4HEFINALSTEPINTHE0/ BASEDPATTERNSOLUTIONISTOCALCULATETHEREFLECTORFARFIELDS VIAAVECTORINTEGRATIONOFTHEPRODUCTOFTHESURFACECURRENTANDTHEFREESPACE'REENS FUNCTION4HEMAGNETICVECTORPOTENTIAL!ISDEFINEDBYTHEEQUATION
! ¯¯¯
* E JK\R R ` \ DR ` P \ R R ` \
4HE VECTOR % AND ( FIELDS ARE RELATED TO ! VIA SIMPLE DERIVATIVES ANDOR VECTOR MULTIPLICATIONS)NPRACTICE %QISCOMPUTEDASASUMMATIONOFNUMERICALINTE GRATIONS0ROPERCONVERGENCEOFTHEFIELDSOLUTIONANDRESULTINGPATTERNSISAFUNCTIONOF THEGRIDSIZE ANDTHISISGENERALLYACHIEVEDANDVERIFIEDBYINCREMENTALLYDECREASINGTHE GRIDSIZEUNTILTHESOLUTIONSTABILIZES!CHIEVINGSUFFICIENTCONVERGENCEINREFLECTOR0/ COMPUTATIONSWITHINREASONABLECOMPUTERRUNTIMESAFEWMINUTESORLESS ISRARELYA PROBLEMWITHMODERNCOMPUTERS 'EOMETRICAL/PTICS'/ 2EFLECTOR!NALYSIS )NCLUDING'4$54$ 4HEREARE AVARIETYOF'/ BASEDPATTERNREFLECTORANALYSISMETHODS ALLOFWHICHAREROOTEDINRAY TRACINGANDSOMEOFWHICHAREAUGMENTEDWITHDIFFRACTIONTERMSFORIMPROVEDACCURACY !LTHOUGHTHESIMPLE'/METHODNODIFFRACTIONTERMS WORKSREASONABLYWELL ITISNOT GENERALLYASACCURATEAS0/(OWEVER TWOOFTHEMORECOMMONENHANCEDMETHODS 'EOMETRICAL4HEORYOF$IFFRACTION'4$ AND5NIFORM4HEORYOF$IFFRACTION54$ INCLUDEEDGEDIFFRACTIONANDAREMUCHMOREACCURATE54$ISESSENTIALLYANENHANCE MENTOF'4$WHEREINLOCALIZED'4$SINGULARITIESARECORRECTED4HEDIFFRACTIONTERMSIN 54$INCREASETHEACCURACYOFTHEBASIC'/SOLUTIONANDWILLPROPERLYPREDICTTHEPATTERN ASYMMETRIESOFMOREGENERALIZEDREFLECTORGEOMETRIES,IKE0/ '4$54$METHODS WILL GENERALLY PROVIDE HIGH FIDELITY PATTERN PREDICTIONS FOR MOST REFLECTOR SYSTEMS CENTER FED OFFSET SINGLE DUAL ETC ASLONGASTHEREFLECTORSIZEISAPPROXIMATELYKOR LARGER-OREDETAILEDDESCRIPTIONSOF'4$54$CANBEFOUNDINVARIOUSREFERENCES &ULL 7AVE2EFLECTOR!NALYSIS-ETHODS 2IGOROUSORFULL WAVEMETHODSINCLUDE FOREXAMPLE THEMETHODOFMOMENTS-/- THEFINITEELEMENTMETHOD&%- AND THEFINITEDIFFERENCETIMEDOMAIN&$4$ METHOD!LTHOUGHTHESEMETHODSAREVERY RIGOROUS AND HIGHLY ACCURATE THEY ARE NOT GENERALLY EMPLOYED FOR REFLECTOR DESIGN ANALYSIS BECAUSE THEY TEND TO BE TOO COMPUTATIONALLY INTENSIVE4HESE METHODS ARE MORE TYPICALLY APPLIED FOR PRECISION ANALYSIS OF MICROWAVE DEVICES OR ELECTRICALLY hSMALLERvANTENNAS EG RADIATORSANDFEEDS THATARENOMORETHANAFEWWAVELENGTHS IN SIZE )N RECENT YEARS HYBRID METHODS INCORPORATING 0/ OR '/'4$ ALONG WITH -/- &%- OR&$4$HAVEBEENDEVELOPED4HESEMETHODSENABLEENHANCEDREFLEC TORFEEDMODELING IE INTEGRATEDWITHREFLECTORANALYSIS ANDRIGOROUSMODELINGOF ELECTRICALLYSMALLSCATTERERS EG SMALLSUBREFLECTORSORFEEDSUPPORTSTRUTS #OMPUTER#ODESFOR2EFLECTOR$ESIGNAND!NALYSIS !NUMBEROFCOMMER CIALANDUNIVERSITYCODESHAVEBEENDEVELOPEDFORTHEANALYSISANDDESIGNOFREFLEC TOR SYSTEMS 4WO OF THE MORE WELL KNOWN AND COMMONLY USED CODES ARE '2!30 ANDTHE3!4#/-7ORKBENCHWITHITS.%# 2%&MODULE'2!30ISACOMMERCIALLY AVAILABLE0/ BASEDREFLECTORDESIGNANDSCATTERINGANALYSISCODEDEVELOPEDBY4)#2! #OPENHAGEN $ENMARK 4HE3!4#/-7ORKBENCHWASDEVELOPEDBY4HE/HIO3TATE 5NIVERSITY %LECTRO3CIENCE ,ABORATORY /35 %3, AND IS A USER FRIENDLY CODE THAT INCORPORATESAWIDEVARIETYOFSOFTWAREMODULES SOMEOFWHICHAREBASEDUPONLEGACY
£Ó°Î{
2!$!2(!.$"//+
/35CODESSUCHAS.%# 2%&/352EFLECTOR#ODE 4HE3!4#/-7ORKBENCHIS AVAILABLETOMEMBERSOFTHE53!3ATELLITE)NDUSTRY#ODE#ONSORTIUM 4)#2!'2!30ISAGENERALIZED0/ BASEDCODEINTENDEDFORBOTHREFLECTORSYSTEM DESIGNANALYSIS AND SCATTERING ANALYSES '2!30 HAS POPULAR '5) VERSIONS THAT RUN ON-ICROSOFT0# BASED7INDOWSOPERATINGSYSTEMS .4 80 ASWELLAS ,).58!LTHOUGHTHE'2!30CODEIS0/ BASED ITALSOINCLUDESA0HYSICAL4HEORYOF $IFFRACTION04$ OPTIONASWELLASA'EOMETRICAL/PTICS'/ 5NIFORM'EOMETRICAL 4HEORYOF$IFFRACTION5'4$ OPTIONTHATCANBETURNEDONWHENNEEDED4HECODE ISVERYGENERALINTHATITCANMODELSTANDARDCONICSECTION BASEDREFLECTORSASWELLAS ARBITRARILYSHAPEDSURFACESORSCATTERERSIFDESIRED)TALSOHASASUITEOFFEEDMODELSTO DRAWUPONANDHASTOOLSTOENABLEFEEDARRAYMODELING&IGURESHOWSASNAPSHOT OFTHE'2!30'5)WINDOW INCLUDINGARENDERINGOFANARRAY FEDREFLECTORANDITS ASSOCIATEDBEAMROSETTA IE ANOVERLAYOFBEAMSASSOCIATEDWITHEACHOFTHEINDI VIDUALARRAYFEEDS3OMEOTHERNOTABLEFEATURESOFTHE'2!30CODEINCLUDESCATTERING MODELSFORMESH FREQUENCYSELECTIVEORLOSSYREFLECTORSURFACES ANDASPHERICALWAVE EXPANSION37% FEATUREFORMODELINGOFSYSTEMSWHEREINTHEREFLECTORORSCATTERERIS INTHENEARFIELDOFTHEFEEDSOURCE&INALLY THEREAREVARIOUSOTHERANTENNASOFTWARE MODULES AVAILABLE FROM4)#2! THAT CAN BE USED IN CONJUNCTION WITH '2!30 /NE NOTABLE EXAMPLE IS 0HYSICAL /PTICS 3HAPER 0/3 AN OPTIMIZER MODULE FOR SHAPED REFLECTORSYNTHESISANDORFEEDARRAYAMPLITUDEPHASEWEIGHTSYNTHESIS-OREINFORMA TIONISAVAILABLEATWWWTICRACOM 4HE/35 %3,3!4#/-7ORKBENCHISA-ICROSOFT7INDOWSnBASEDMODULAR SOFTWARE PACKAGE FOR 0# PLATFORMS RUNNING 7INDOWS 80 )T CONTAINS AVARIETYOFMODULESORSO CALLEDWIZARDSINADDITIONTOTHEGENERALIZED'/'4$ BASED REFLECTORSCATTERING CODE BACKBONE 4HE CORE '/'4$ REFLECTORSCATTERING
&)'52% 4)#2!'2!30'5) MULTIBEAMARRAY FEDREFLECTORMODELANDPATTERNS
2%&,%#4/2!.4%..!3
£Ó°Îx
-AXIMUM
-AGNITUDED"
Y
X
Z
4HETA
&)'52% /35 %3,3!4#/-7ORKBENCH'5) OFFSET'REGORIANREFLECTORMODELANDPATTERN
CODEPORTIONOFTHE3!4#/-7ORKBENCHISBASEDUPONTHELEGACY.%# 2%&AND .%# "3#CODES4HE%-7ORKBENCH LIKE'2!30 ISVERYGENERALINITSCAPABILI TIES IE ITCANHANDLEADIVERSITYOFREFLECTORSCATTERERSHAPESANDCOMBINATIONSAND ALSOHASVARIOUSFEEDMODELSTODRAWUPON)TALSOHASFEEDANDARRAYWIZARDSTHAT EMPLOYFULL WAVE%-MODELSTHATCANBEUSEDASSOURCESFORREFLECTORANDSCATTER INGDESIGNANALYSES&IGURESHOWSASNAPSHOTOFTHE7ORKBENCH'5)WINDOW INCLUDINGARENDERINGOFANOFFSET FEDREFLECTORANDITSASSOCIATEDBEAMPATTERN-ORE INFORMATIONISAVAILABLEATESLENGOHIO STATEEDU
£Ó°ÈÊ Ê - Ê " - ,/" 2EFLECTOR MECHANICAL DESIGN IS A DETAILED DISCIPLINE UNTO ITSELF WITH A MULTITUDE OF FACTORS TO CONSIDER &URTHERMORE DESIGNS VARY SIGNIFICANTLY DEPENDING UPON MANY FACTORS INCLUDINGPLATFORM REFLECTORSIZE ENVIRONMENT FREQUENCYOFOPERATION SCAN &/6 ANDCOSTCONSTRAINTS!LTHOUGHITISNOTWITHINTHESCOPEOFTHISCHAPTERTOADDRESS MECHANICALDESIGNINDETAIL ABRIEFSURVEYOFDESIGNFACTORSANDCONSIDERATIONSPRO VIDESSOMEUSEFULINSIGHTS 4HEPLATFORM IE VEHICLE ORINSTALLATIONSITEISASIGNIFICANTDRIVERFORRADARSEN SORS IN GENERAL INCLUDING THE ANTENNA 0LATFORM IS A GENERIC TERM REFERRING TO THE VEHICLE WHERE THE RADAR AND ANTENNA ARE INSTALLED 4YPICAL RADAR PLATFORMS INCLUDE PEDESTALFIXEDSITE GROUNDVEHICLES SHIPS AIRPLANES 5!6S ANDSPACECRAFTSATELLITES 4HEFOLLOWINGSHORTSECTIONISDEVOTEDTOPLATFORMIMPACTSANDSOMEKEYASSOCIATED DESIGNDRIVERS4HESEINCLUDEMASS VOLUMESTOWAGEDEPLOYMENT GIMBALSPRECISION MECHANICALPOSITIONINGSYSTEMS MATERIALS ANDMECHANICALTOLERANCES&INALLY THERE ISABRIEFDISCUSSIONOFENVIRONMENTALDESIGNCONSIDERATIONSANDRADOMES
£Ó°ÎÈ
2!$!2(!.$"//+
)NSTALLATION)SA3IGNIFICANT-ECHANICAL$ESIGN$RIVER 4HEPLATFORMISGEN ERALLY A DOMINANT MECHANICAL DESIGN DRIVER BECAUSE IT DETERMINES THE ENVIRONMENT THERMAL VIBRATION ETC ANDITTYPICALLYDRIVESTHEAVAILABLESIZE WEIGHT ANDPOWER 37!0 FORTHERADARANDTHEREFLECTORANTENNA4ABLEPROVIDESAQUALITATIVECOM PARISON OF TYPICAL DESIGN REQUIREMENTS AND FEATURES FOR RADAR REFLECTOR ANTENNAS ON GROUND BASED SHIP BASED AIRBORNE ANDSPACEBORNEPLATFORMS -ASS 6OLUME 3TOWAGE $EPLOYMENT AND'IMBALING 4HEDEGREETOWHICH THESEFIVEFACTORS MASS VOLUME STOWAGE DEPLOYMENT ANDGIMBALINGDRIVETHEREFLEC TORDESIGNVARYINACCORDANCEWITHTHEREFLECTORSYSTEMANDTHEPLATFORM(OWEVER 4!",% -ECHANICAL$ESIGN$RIVERSFOR2EFLECTOR!NTENNA3YSTEMSASA&UNCTIONOF0LATFORM 0,!4&/2-$2)6%32%&,%#4/2!.4%..!-%#(!.)#!,$%3)'. 'ROUND BASED -ASS
6OLUME
4HERMAL
6IBRATION
3HIP BASED
!IRBORNE
3PACEBORNE
s !MAJORDRIVERLAUNCH s 4YPICALLYNOTAMAJOR s 4YPICALLYNOTA s 4YPICALLYA COSTSAREVERYHIGHAND MAJORDRIVER SIGNIFICANTDRIVER DRIVER AREDRIVENBYAVAILABLE s #OULDBEAMAJOR s -AYBEADRIVERIF VOLUMEANDMASSFOR DRIVERDEPENDING FIELDDEPLOYMENTIS ONSIZEOFANTENNA RADARPAYLOAD REQUIRED s 5SEOFLIGHTWEIGHT ANDPLATFORM MATERIALSISIMPORTANT s !MAJORDRIVERLAUNCH s 4YPICALLYA s 4YPICALLYNOTAMAJOR s $EPENDS A COSTSAREVERYHIGHAND SIGNIFICANTDRIVER DRIVERINSOME DRIVER AREDRIVENBYAVAILABLE s #OULDBEAMAJOR CASES s -AYBEADRIVERIF VOLUMEANDMASSFOR DRIVERDEPENDING FIELDDEPLOYMENTIS ONSIZEOFANTENNA RADARPAYLOAD REQUIRED s /NCEINSPACE ANDPLATFORM ANTENNADEPLOYMENTS ARETYPICALLYNEEDED EG UNFOLDING ETC s !MAJORDRIVER NEED s #ANBEAMAJOR s #ANBEAMAJOR s #ANBEAMAJOR SOPHISTICATEDMODELING DRIVER DRIVER DRIVER TOPREDICTSOLARHEATING s 2ADARSARE s 2ADARSARETYPICALLY s 2ADARSARE THROUGHOUTORBIT TYPICALLYHIGH TYPICALLYHIGH HIGHPOWER s 0ASSIVECOOLINGSYSTEMS POWER s (IGHPOWERDENSITIES POWER AREGENERALLYEMPLOYED s (IGHPOWER ATFEEDORFEEDARRAY s (IGHPOWER EG HEATPIPES DENSITIESATFEED DENSITIESAT ARECOMMON ORFEEDARRAYARE FEEDORFEED s #OOLINGSYSTEM COMMON ARRAYARE DESIGNTOMAINTAIN s #OOLINGSYSTEM COMMON FEEDTEMPCANBEA s #OOLINGSYSTEM DESIGNTOMAINTAIN CHALLENGE FEEDTEMPCANBEA DESIGNTO CHALLENGE MAINTAINFEED TEMPCANBEA CHALLENGE s 4YPICALLYNOTAMAJOR s 4YPICALLYNOTA s 4YPICALLYAMAJOR s 4YPICALLYAMAJOR MAJORDRIVER DRIVER DRIVER DRIVENBYLAUNCH DRIVER VEHICLEROCKET s (OWEVER MUST CONSIDERVIBRATION DURINGTRANSPORT TRUCK AIRPLANE OTHER
2%&,%#4/2!.4%..!3
£Ó°ÎÇ
4!",% -ECHANICAL$ESIGN$RIVERSFOR2EFLECTOR!NTENNA3YSTEMSASA&UNCTIONOF0LATFORM
#ONTINUED 0,!4&/2-$2)6%32%&,%#4/2!.4%..!-%#(!.)#!,$%3)'. 'ROUND BASED 3TOWAGE $EPLOYMENT
s #ANBEADRIVER IFSYSTEMIS TRANSPORTABLE
/THER
s )STRANSPORTABILITY AREQUIREMENT !RETHEREMULTIPLE ENVIRONMENTSTO WHICHTHERADAR ANTENNAWILLBE EXPOSED
3HIP BASED
!IRBORNE
3PACEBORNE
s 4YPICALLYREQUIRED GENERALLYAMAJOR DESIGNDRIVER s 2ELIABILITYOF DEPLOYMENTISAMAJOR CONCERNMISSION DEPENDSONIT s 7HEREONTHE s 6OLUMEISAMAJOR s 3PECIALIZED ENVIRONMENTS SHIPISTHERADAR CONSTRAINT NOT s ,AUNCHDRIVES MUCHROOMFOR ANTENNA )SIT VIBRATIONAND COVEREDWITHA ANTENNAAPERTURES ACOUSTICLOADS RADOME 7ILLIT s 2ADIATIONADRIVERAT BEEXPOSEDTO SOMEORBITS WATERORWAVE s 4HERMALEXTREMES SLAP INCLUDINGGRADIENTS AREACONCERN s 4YPICALLYNOTA s 4YPICALLYNOT REQUIREMENT AREQUIREMENT BUTTHEREARE EXCEPTIONS
MASSANDVOLUMECONSTRAINTSGENERALLYHAVEASIGNIFICANTIMPACTONTHEREFLECTORSYSTEM DESIGN&URTHERMORE SOMESORTOFSTOWAGEANDDEPLOYMENTOFTHEREFLECTORISSOME TIMESREQUIRED ESPECIALLYFORLARGERREFLECTORS4HESECONSIDERATIONSANDCONSTRAINTS DRIVETHECHOICESOFMATERIALS STRUCTURALDESIGNS PASSIVEANDACTIVEMECHANISMS ETC )TISBEYONDTHESCOPEOFTHISCHAPTERTOADDRESSTHISTOPICINDETAIL(OWEVER ITSUSEFUL TOSHOWACOUPLEEXAMPLESFORILLUSTRATION #ONSIDER FIRST AGROUND BASEDDUAL REFLECTORDESIGNWITHA METERMAINREFLECTOR APERTURE4HISREFLECTOR SHOWNIN&IGURE ISUSEDFORAN3 BANDMETEOROLOGICAL RADARAPPLICATION4HEPANELIZEDALUMINUMREFLECTORISMECHANICALLYSCANNEDVIAUSE OFAGIMBALNOTSHOWN 4HEFEED ADUAL POLARIZEDWAVEGUIDEHORN ISALSOSHOWNIN &IGURE4HESTRUCTURALDESIGNOFTHISLARGEREFLECTORWASASIGNIFICANTTASKDRIVEN BYTHENEEDTOMAINTAINLOWREFLECTORSURFACEDISTORTIONLESSTHANMILS WITHSEVERE WINDANDGRAVITY LOADINGFORCESANDTHERMALGRADIENTS 4HE SECOND EXAMPLE IS A SPACE BASED DEPLOYABLE REFLECTOR 4HE MESH REFLECTOR SHOWNINBOTHSTOWEDANDDEPLOYEDCONFIGURATIONSIN&IGURE ISANOFFSETREFLEC TORWITHAMETERCIRCULARPROJECTEDAPERTURE4HIS, BANDDESIGN DEVELOPEDBY .ORTHROP 'RUMMAN3PACE4ECHNOLOGIES!STRO!EROSPACEGROUP HASBEENSUCCESSFULLY LAUNCHEDANDDEPLOYEDANDISCURRENTLYINUSEONSEVERALCOMMUNICATIONSATELLITES !TOTALOFFIVEREFLECTORSOFAPERTUREDIAMETERSMETERS METERS ANDMETERS HAVEBEENFLOWN3TUDIESHAVEADDRESSEDTHEPOTENTIALUSAGEOFTHISREFLECTORTECHNOL OGYFORVARIOUSSPACE BASEDRADARAPPLICATIONS INCLUDINGWEATHERSENSINGMONITORING .%82!$ ANDPLANETARY3!2MAPPINGMISSIONSLUNARAND-ARS 3IGNIFICANTFEA TURESOFTHISREFLECTORINCLUDEITSPRECISESURFACEACCURACY HIGHSTIFFNESSANDSTABILITY LOW MASS ANDRELIABLEDEPLOYMENT&OREXAMPLE FORTHEREFLECTORSHOWNIN&IGURE AN 2-3SURFACEACCURACYOFLESSTHANMILSFROMALLERRORSOURCESINCLUDINGIN ORBITTHER MALGRADIENTSWASACHIEVEDVIAPRUDENTMATERIALCHOICESANDMATCHINGOFTHEASSOCIATED MATERIALCOEFFICIENTSOFTHERMALEXPANSION#4%S 0OINTINGPRECISIONDUETOECLIPSE THERMALSNAPHASBEENMEASUREDINORBITATLESSTHANDEGREES
£Ó°În
2!$!2(!.$"//+
&)'52% 'ROUND BASED 3 BAND METER DUAL REFLECTOR AND DUAL POL FEED A PHOTO OF SYSTEM B MECHANICAL#!$RENDERINGSHOWINGPANELIZEDREFLECTORSURFACEANDSUPPORTSTRUCTUREANDC DUAL POLARIZED WAVEGUIDEFEEDHORN#OURTESY'ENERAL$YNAMICS#3YSTEMS
&)'52% 3PACE BASEDDEPLOYABLE, BAND!342/-ESHREFLECTORWITHMETER CIRCULARPROJECTEDAPERTURE#OURTESY.ORTHROP'RUMMAN#ORPORATION
2%&,%#4/2!.4%..!3
£Ó°Î
$EPLOYABLESPACE BASEDREFLECTORSHAVEALSOBEENDEVELOPEDBYTHE(ARRIS#ORPO RATIONFORVARIOUSSPACE BASEDCOMMUNICATIONSAPPLICATIONS3EEWWWHARRISCOMFOR MOREDETAILS "ECAUSEMOSTREFLECTORDESIGNSHAVEATBESTLIMITEDELECTRONICSCANCAPABILITY A GIMBALISTYPICALLYNEEDEDTOEXTENDTHEMECHANICAL &/6FORTHERADAR4HEKEY FACTORSORSPECIFICATIONSTHATTYPICALLYDRIVETHEDESIGNORPROCUREMENTOFTHEGIMBAL ARESCANRATE SLEWREQUIREMENTS ACCELERATIONDECELERATIONREQUIREMENTS TORQUEAND LOADREFLECTORMASS REQUIREMENTS POWERREQUIREMENTS ETC)TISIMPORTANTFORTHE RADAR SYSTEM ENGINEER TO UNDERSTAND THESE FACTORS AND ASSOCIATED PRACTICAL GIMBAL DESIGNLIMITS %NVIRONMENTAL&ACTORSAND#ONSIDERATIONS 4HEIMPACTOFENVIRONMENTALFAC TORSVARIESWIDELY BUTSOMEOFTHEFACTORSTHATARETYPICALLYSIGNIFICANTINCLUDETHERMAL VIBRATION ANDEXPOSUREEG SALT SAND WATER RADIATION ETC 4HERMALEFFECTS IE SPATIALORTEMPORALTEMPERATUREVARIATIONS AREOFPARTICULARCONCERNFORSPACEBORNE SENSORSTHATOFTENSEEVERYSIGNIFICANTTEMPERATURECHANGESGREATERTHAN#TEM PORALORSPATIALVARIATIONISNOTUNCOMMON 6IBRATIONISANOTHERCONCERN ESPECIALLY FOR AIRBORNE AND SPACEBORNE REFLECTORS 2EFLECTORS ON THESE PLATFORMS GENERALLY SEE PARTICULARLY STRESSING VIBRATION LEVELS DRIVEN BY AIRPLANE OR LAUNCH VEHICLE ROCKET ENVIRONMENTS0OTENTIALEXPOSURETOSALT SAND WATER ETC ISHIGHLYDEPENDENTUPON PLATFORM USEOFRADOMEORNOT ETC BUTMUSTBECONSIDEREDINTHEDESIGN 2ADOMES 2ADOMES ARE USED WHEN IT IS NECESSARY TO PROTECT ANTENNAS FROM ADVERSEENVIRONMENTALEFFECTS)DEALLY ARADOMESHOULDBEPERFECTLYTRANSPARENTTOTHE 2&RADIATIONFROMORTO THEANTENNAANDYETBEABLETOWITHSTANDSUCHENVIRONMENTAL EFFECTSASWIND RAIN HAIL SNOW ICE SAND SALTSPRAY LIGHTNING ANDINTHECASEOF HIGH SPEEDAIRBORNEAPPLICATIONS THERMAL EROSION ANDOTHERAERODYNAMICEFFECTS)N PRACTICE THESEENVIRONMENTALFACTORSDETERMINETHEMECHANICALDESIGNOFTHERADOME ANDTHEDESIREFORIDEAL2&TRANSPARENCYMUSTBECOMPROMISEDBECAUSEMECHANICAL ANDELECTRICALREQUIREMENTSAREOFTENINCONFLICT 2ADOMESCAUSEFOURMAJORELECTRICALEFFECTSONANTENNAPERFORMANCE"EAMDEFLEC TIONISTHESHIFTOFTHEELECTRICALAXIS WHICHISCRITICALFORTRACKINGRADAR4RANSMISSION LOSSISTHEMEASUREOFENERGYLOSTBYREFLECTIONANDABSORPTION4HEREFLECTEDPOWER CAUSESANTENNAMISMATCHINSMALLRADOMESANDSIDELOBESINLARGERRADOMES 2ADOMEDESIGNISASPECIALIZEDART ANDMANYBOOKS AREDEVOTEDTOITSINTRICATE DETAILS4HISSECTIONMAKESNOATTEMPTTOPROVIDERADOMEDESIGNINFORMATIONASSUCH BUTINSTEADISAIMEDATMAKINGTHERADARSYSTEMDESIGNERAWAREOFTHEBASICCONCEPTS BEHINDTHETYPESOFRADOMESAVAILABLEFORVARIOUSAPPLICATIONS 4HREE GENERAL CLASSES OF RADOME ARE OF INTEREST FOR REFLECTOR ANTENNA APPLICA TIONSFEEDCOVERS WHICHOFTENHAVETOENDUREPRESSURE HIGHVOLTAGE ANDHEATING COVERS ATTACHED TO THE REFLECTOR WHICH ALTER THE PATTERN IN A FIXED MANNER AND EXTERNALRADOMES WITHINWHICHTHEANTENNAMOVES%XTERNALRADOMESARETHEMOST COMMONANDWILL THEREFORE BEEMPHASIZED7ITHINEACHCLASS AVARIETYOFSKIN AND SKIN SUPPORTING DESIGNS IS AVAILABLE TO MINIMIZE THE ELECTRICAL EFFECTS UNDER THECONSTRAINTSOFTHEENVIRONMENT4HERADOMESKINMAYBERIGID SUPPORTEDBYA FRAMEWORK ORAIR SUPPORTED 4HEMOSTCOMMONRIGIDRADOME WALLSTRUCTURESARESHOWNIN&IGUREANDARE KNOWNASHOMOGENEOUSSINGLELAYER ! SANDWICH " SANDWICH # SANDWICH MULTIPLE LAYERSANDWICH ANDDIELECTRICSWITHMETALINCLUSIONS
£Ó°{ä
2!$!2(!.$"//+
&)'52% #OMMON RADOME WALL CROSS SECTIONS A SINGLE LAYER B ! SANDWICH C " SANDWICH D # SANDWICH E MULTIPLE LAYERSAND WICH ANDF DIELECTRICSWITHMETALINCLUSIONS
3INGLE ,AYER 4HE HOMOGENEOUS SINGLE LAYER RADOME HAS BEEN USED IN MANY RADOMEAPPLICATIONS-ATERIALSFORTHISTYPEHAVEINCLUDEDFIBERGLASS REINFORCEDPLAS TICS CERAMICS ELASTOMERS ANDMONOLITHICFOAM4HEOPTIMUMTHICKNESSFORASINGLE LAYERISAMULTIPLEOFAHALFWAVELENGTHINTHEDIELECTRICMATERIALATTHEAPPROPRIATE INCIDENCEANGLE BUTMANYSINGLE LAYERRADOMESARESIMPLYTHIN WALLAPPROXIMATIONS TOTHEZERO THICKNESSCASE ! 3ANDWICH ! COMMONLY USED RADOME WALL CROSS SECTION IS THE ! SANDWICH WHICHCONSISTSOFTWORELATIVELYDENSETHINSKINSANDATHICKERLOW DENSITYCORE4HIS CONFIGURATIONEXHIBITSHIGHSTRENGTH TO WEIGHTRATIOS4HESKINSAREGENERALLYFIBERGLASS REINFORCEDPLASTICS ANDTHECOREISAFOAMORHONEYCOMB)NORGANICSKINANDCORESAND WICHESALSOHAVEBEENDEVELOPEDFORHIGH TEMPERATUREAPPLICATIONS!SARULE THESKINS OFTHESANDWICHAREMADESYMMETRICALOROFEQUALTHICKNESSTOALLOWMIDBANDCANCEL LATIONOFREFLECTIONS " 3ANDWICH )NCONTRASTTOTHE! SANDWICH THE" SANDWICHISATHREE LAYERCON FIGURATIONWHOSESKINSHAVEADIELECTRICCONSTANTLOWERTHANTHATOFTHECOREMATERIAL 4HISWALLCROSSSECTIONISHEAVIERTHANTHATOFTHE! SANDWICHBECAUSEOFTHERELATIVELY DENSECORE4HE" SANDWICHISNOTCOMMONLYUSEDBECAUSETHECOREDIELECTRICCONSTANT ISQUITEHIGHFORAPROPERMATCH # 3ANDWICH 4HE# SANDWICHISAFIVE LAYERDESIGNCONSISTINGOFOUTERSKINS A CENTERSKIN ANDTWOINTERMEDIATECORES4HESYMMETRICAL# SANDWICHCANBETHOUGHT OFASTWOBACK TO BACK! SANDWICHES4HISCONFIGURATIONISUSEDWHENTHEORDINARY ! SANDWICHWILLNOTPROVIDESUFFICIENTSTRENGTH ORFORCERTAINELECTRICALPERFORMANCE CHARACTERISTICS ORWHENONELAYERISTOSERVEASAWARM AIRDUCTFORDEICING -ULTIPLE ,AYER3ANDWICH -ULTIPLE LAYERSANDWICHESOF ORMORELAYERS ARE SOMETIMES CONSIDERED WHEN GREAT STRENGTH GOOD ELECTRICAL PERFORMANCE AND LIGHTWEIGHT ARE REQUIRED 3OME OF THESE DESIGNS HAVE USED THIN LAYERS OF FIBERGLASS
2%&,%#4/2!.4%..!3
£Ó°{£
LAMINATESANDLOW DENSITYCORESTOATTAINHIGHTRANSMISSIONPERFORMANCEOVERLARGE FREQUENCYBANDS $IELECTRIC,AYERSWITH-ETAL)NCLUSIONS -ETALINCLUSIONSHAVEBEENCONSIDERED FOR USE WITH DIELECTRIC LAYERS TO ACHIEVE FREQUENCY FILTERING BROAD FREQUENCY BAND PERFORMANCE ORREDUCED THICKNESSRADOMES4HINLAYERSOFMETALINCLUSIONSEXHIBIT THECHARACTERISTICSOFLUMPEDCIRCUITELEMENTSSHUNTEDACROSSATRANSMISSIONLINE&OR EXAMPLE A GRID OF PARALLEL METAL WIRES EXHIBITS THE PROPERTIES OF A SHUNT INDUCTIVE SUSCEPTANCE 4HEREAREMANYADDITIONALRADOMEDESIGNISSUESANDAPPLICATIONSPECIFICCONSIDER ATIONSANDDESIGNDRIVERS BUTTHESEAREBEYONDTHESCOPEOFTHISCHAPTER
"7 /4HEAUTHORSWISHTOACKNOWLEDGEANDTHANK(ELMUT3CHRANK 'ARY%VANS AND$ANIEL $AVISALSOCO AUTHOROFTHISCHAPTER FOR#HAPTER h2EFLECTOR!NTENNAS vINTHESECOND EDITIONOFTHISHANDBOOK7EAREGRATEFULFORTHEIRCONTRIBUTIONSANDPORTIONSOF THESECONDEDITIONCHAPTERHAVEBEENRETAINED 0ORTIONS OF THE MATERIAL IN THE h2ADOMEv SUBSECTION WERE ADAPTED FROM #HAPTER h2ADOMES v IN THE FIRST EDITION OF THIS HANDBOOK WHICH WAS AUTHOREDBY6INCENT*$I#AUDO
, ,
*$+RAUS !NTENNAS ND%D .EW9ORK-C'RAW (ILL"OOK#OMPANY 3EC 7,3TUTZMANAND'!4HIELE !NTENNA4HEORYAND$ESIGN #HAPTER .EW9ORK*OHN7ILEY AND3ONS # - +NOP h/N THE FRONT TO BACK RATIO OF A PARABOLIC DISH ANTENNA v )%%%4RANS!NTENNAS 0ROPAG VOL PPn *ANUARY 7642USCH h3CATTERINGFROMAHYPERBOLOIDALREFLECTORINACASSEGRAINFEEDSYSTEM v)%%% 4RANS VOL!0 PPn *ULY #,'RAY h%STIMATINGTHEEFFECTOFFEEDSUPPORTMEMBERBLOCKINGONANTENNAGAINANDSIDELOBE LEVEL v-ICROWAVE* PPn -ARCH -ICROWAVE%NGINEERS(ANDBOOKAND"UYERS'UIDE .EW9ORK(ORIZON(OUSE P 77-UMFORD h3OMETECHNICALASPECTSOFMICROWAVERADIATIONHAZARDS v0ROC)2% PPn &EBRUARY *2UZE h4HEEFFECTOFAPERTUREERRORSONTHEANTENNARADIATIONPATTERN v.UOVO#IMENTO 3UPPL VOL NO PPn *2UZE h!NTENNATOLERANCETHEORY!REVIEW v0ROC)%%% VOL PPn !PRIL 3 3ILVER ED -ICROWAVE !NTENNA 4HEORY AND $ESIGN -)4 2ADIATION ,ABORATORY 3ERIES VOL .EW9ORK-C'RAW (ILL"OOK#OMPANY 9 4 ,O h/N THE "EAM $EVIATION &ACTOR OF A 0ARABOLIC 2EFLECTOR v )2% 4RANS VOL !0 PPn -AY 0 $ 0OTTER h!PPLICATION OF SPHERICAL WAVE THEORY TO #ASSEGRAINIAN FED PARABOLOIDS v )%%% 4RANS VOL!0 PPn .OVEMBER 2#*OHNSONAND(*ASIKEDS !NTENNA%NGINEERING(ANDBOOK ND%D .EW9ORK-C'RAW (ILL "OOK#OMPANY PPn n
£Ó°{Ó
2!$!2(!.$"//+
94,OAND37,EEEDS !NTENNA(ANDBOOK4HEORY !PPLICATIONSAND$ESIGN 2EFLECTOR !NTENNAS #HAPTER .EW9ORK6AN.OSTRAND2EINHOLD#O)NC #*3LETTEN h4HETHEORYOFREFLECTORANTENNAS v!IR&ORCE#AMBRIDGE2ES,AB !, 0HYS3CI2ES 0APER +3+ELLEHERAND(0#OLEMAN h/FF AXISCHARACTERISTICSOFTHEPARABOLOIDALREFLECTOR v.AVAL 2ES,AB2EPT ! 7 2UDGE AND .!!DATIA h/FFSET PARABOLIC REFLECTOR ANTENNAS! REVIEW v 0ROCEEDINGS )%%% VOL NO PPn $ECEMBER $'+IELSY h0ARABOLICCYLINDERAERIALS v7IRELESS%NG VOL PPn -ARCH 2,&ANTEETAL h!PARABOLICCYLINDERANTENNAWITHVERYLOWSIDELOBES v)%%%4RANS VOL!0 PPn *ANUARY 0 7 (ANNAN h-ICROWAVE ANTENNAS DERIVED FROM THE CASSEGRAIN TELESCOPE v )2% 4RANS VOL!0 PPn -ARCH 0$0OTTER h!PERTUREILLUMINATIONANDGAINOFA#ASSEGRAINIANSYSTEM v)%%%4RANS VOL!0 PPn -AY 7642USCH h3CATTERINGFROMAHYPERBOLOIDALREFLECTORINA#ASSEGRAINIANFEEDSYSTEM v)%%% 4RANS VOL!0 PPn *ULY %*7ILKINSONAND!*!PPLEBAUM h#ASSEGRAINSYSTEMS v)2%4RANS VOL!0 PPn *ANUARY # * 3LETTEN ET AL h/FFSET DUAL REFLECTOR ANTENNAS FOR VERY LOW SIDELOBES v -ICROWAVE * PPn -AY 76 2USCH h4HE CURRENT STATE OF THE REFLECTOR ANTENNA ART v )%%%4RANS!NTENNAS 0ROPAG VOL!0 NO PPn !PRIL 4 (AEGER AND * * ,EE h#OMPARISONS BETWEEN A SHAPED AND NONSHAPED SMALL CASSEGRAIN ANTENNA v)%%%4RANS!NTENNAS0ROPAG VOL NO $ECEMBER 2!0EARSON %%LSHIRBINI AND-33MITH h%LECTRONICBEAMSCANNINGUSINGANARRAY FEDDUAL OFFSETREFLECTORANTENNA v)%%%!0 3)NT3YMP$IG PPn *UNE %0%KELMANAND"3,EE h!NARRAY FED DUAL REFLECTORANTENNASYSTEMOFOFFSETCONFOCAL PARABOLOIDS FORSATELLITEANTENNAAPPLICATIONS v)%%%3YMP!NTENNAS0ROPAG PPn (+3CHUMANAND$20FLUG h!PHASEDARRAYFEED DUALOFFSETREFLECTORANTENNAFORTESTING ARRAYCOMPENSATIONTECHNIQUES v)%%%3YMP!NTENNAS0ROPAG PPn 7 $ &ITZGERALD h,IMITED ELECTRONIC SCANNING WITH A NEAR FIELD #ASSEGRAINIAN SYSTEM v 4ECHNICAL2EPORT -)4,INCOLN,ABORATORY 3EPTEMBER 4,EE h!STUDYOFSPHERICALREFLECTORSASWIDEANGLESCANNINGANTENNAS v)%%%4RANS!NTENNAS 0ROPAG VOL PPn *ULY 4 #HU AND 0 0 )ANNONE h2ADIATION PROPERTIES OF A PARABOLIC TORUS REFLECTOR v )%%% 4RANS !NTENNAS0ROPAG VOL NO *ULY -3KOLNIK h!LONGRANGERADARWARNINGSYSTEMFORTHEDETECTIONOFINTERCONTINENTALBALLISTIC MISSILES v-)4,INCOLN,ABORATORY42 !UGUST -3KOLNIK )NTRODUCTIONTO2ADAR3YSTEMS RD%D .EW9ORK-C'RAW (ILL PP #!"ALANIS !NTENNA4HEORY!NALYSISAND$ESIGN #HAPTERSAND .EW9ORK*OHN7ILEY AND3ONS !7,OVEED %LECTROMAGNETIC(ORN!NTENNAS .EW9ORK)%%%0RESS 7#OHENAND#-3TEINMETZ h!MPLITUDEANDPHASESENSINGMONOPULSESYSTEMPARAMETERS v -ICROWAVE* PPn /CTOBER $22HODES )NTRODUCTIONTO-ONOPULSE .EW9ORK-C'RAW (ILL"OOK#OMPANY , * 2ICARDI AND , .IRO h$ESIGN OF A TWELVE HORN MONOPULSE FEED v )2% )NT #ONV 2EC PART -ARCH PPn 07(ANNANAND0!,OTH h!MONOPULSEANTENNAHAVINGINDEPENDENTOPTIMIZATIONOFTHESUM ANDDIFFERENCEMODES v)2%)NT#ONV2EC PART -ARCH PPn
2%&,%#4/2!.4%..!3
£Ó°{Î
"3AKAAND%9AZGAN h0ATTERNOPTIMIZATIONOFAREFLECTORANTENNAWITHPLANAR ARRAYFEEDSAND CLUSTERFEEDS v)%%%4RANS!NTENNAS0ROPAGAT VOL NO *ANUARY 2&(ARRINGTON 4IME(ARMONIC%LECTROMAGNETIC&IELDS .EW9ORK-C'RAW (ILL PPn ,$IAZAND4-ILLIGAN !NTENNA%NGINEERING5SING0HYSICAL/PTICS0RACTICAL#!$4ECHNIQUES AND3OFTWARE "OSTON!RTECH(OUSE PPn #!"ALANIS h'REENSFUNCTIONSvIN!DVANCED%NGINEERING%LECTROMAGNETICS #HAPTER .EW 9ORK*OHN7ILEYAND3ONS 0(0ATHAK h(IGHFREQUENCYTECHNIQUESFORANTENNAANALYSIS v0ROCOFTHE)%%% VOL NO *ANUARY 94,OAND37,EEEDS !NTENNA(ANDBOOK4HEORY !PPLICATIONSAND$ESIGN 4ECHNIQUES FOR(IGH&REQUENCY0ROBLEMS #HAPTER .EW9ORK6AN.OSTRAND2EINHOLD#O)NC '&0AYNTER 4(,EE AND7$"URNSIDE h%XPANSIONOFEXISTING%-7ORKBENCHFORMULTIPLE COMPUTATIONAL ELECTROMAGNETICS CODES v )%%% !NTENNAS AND 0ROPAGATION -AGAZINE VOL NO *UNE $"RUNKOW 6."RINGI 0#+ENNEDY 3!2UTLEDGE 6#HANDRASEKAR %!-UELLER AND 2+"OWIE h!DESCRIPTIONOFTHE#35 #(),,.ATIONAL2ADAR&ACILITY v*!TMOS/CEAN 4ECH PPn - 4HOMSON h4HE ASTROMESH DEPLOYABLE REFLECTOR v )%%% 3YMP !NTENNAS AND 0ROPAG PPn -4HOMSON h!STROMESH$EPLOYABLE2EFLECTORSFOR+UAND+A "AND3ATELLITES v!)!!3YMP PPn *+(,IN (&ANG %)M AND5/1UIJANO h#ONCEPTSTUDYOFAMSPHERICALREFLECTOR SYSTEM FOR .%82!$ IN SPACE APPLICATION v PRESENTED AT TH!)!!!3-%!3#%!(3!3# 3TRUCTURES 3TRUCTURAL$YNAMICS AND-ATERIALS#ONFERENCE .EWPORT 2) -AYn 2&OWELLAND7ANG ( h0RECISIONPOINTINGOFTHE4HURAYASATELLITEvPRESENTEDATTH!!3 'UIDANCEAND#ONTROL#ONFERENCE "RECKENRIDGE #/ &EBRUARYn 2#(ANSEN -ICROWAVE3CANNING!NTENNAS .EW9ORK!CADEMIC0RESS .EW9ORK ,OS !LTOS #!0ENINSULA0UBLISHING *$7ALTON *RED 2ADOME%NGINEERING(ANDBOOK .EW9ORK-ARCEL$EKKER -3KOLNIKED 2ADAR(ANDBOOK ND%D .EW9ORK-C'RAW (ILL -3KOLNIKED 2ADAR(ANDBOOK ST%D .EW9ORK-C'RAW (ILL
#HAPTER
*
>Ãi`ÊÀÀ>ÞÊÊ ,>`>ÀÊÌi>Ã iÊÀ> *OHNS(OPKINS5NIVERSITY!PPLIED0HYSICS,ABORATORY
Ê °Ê,V
>À`Ã *OHNS(OPKINS5NIVERSITY!PPLIED0HYSICS,ABORATORY
£Î°£Ê /," 1 /"
0HASED!RRAY2ADARS %ARLYRADARSYSTEMSUSEDANTENNAARRAYSFORMEDBYTHE COMBINATIONOFINDIVIDUALRADIATORS3UCHANTENNASDATEBACKTOTHETURNOFTHETWEN TIETHCENTURY !NTENNACHARACTERISTICSAREDETERMINEDBYTHEGEOMETRICPOSITIONOF THE RADIATORS AND THE AMPLITUDE AND PHASE OF THEIR EXCITATION!S RADARS PROGRESSED TOSHORTERWAVELENGTHS ARRAYSWEREDISPLACEDBYSIMPLERANTENNASSUCHASPARABOLIC REFLECTORS&ORMODERNRADARAPPLICATIONS THEADVENTOFELECTRONICALLYCONTROLLEDPHASE SHIFTERS SWITCHES ANDTRANSMITRECEIVEMODULESHASONCEMOREDIRECTEDATTENTIONTO ARRAY ANTENNAS 4HE APERTURE EXCITATION MAY NOW BE MODULATED BY CONTROLLING THE PHASEOFTHEINDIVIDUALELEMENTSTOGIVEBEAMSTHATARESCANNEDELECTRONICALLY4HE DRAMATICADVANTAGEOFELECTRONICALLYSTEEREDPHASEDARRAYSASCOMPAREDTOREFLECTORS ISPROVIDEDBYTHETIMEREQUIREDTOSTEERBEAMSANDTHEFLEXIBILITYINSTEERING7HILE PRIORRADARSTOOKSECONDSTOSTEERTOANEWLOCATION PHASEDARRAYSTAKEMICROSECONDS )NADDITION THENEWLOCATIONCANBEANYWHEREINAHEMISPHERE4HISCHAPTERWILLBE DEVOTEDTOARRAYSOFTHISTYPE -ULTIFUNCTION2ADAR 4HECAPABILITYOFRAPIDLYANDACCURATELYSWITCHINGBEAMS PERMITSMULTIPLERADARFUNCTIONSTOBEPERFORMED INTERLACEDINTIME!NELECTRONICALLY STEEREDARRAYRADARMAYTRACKAGREATMULTIPLICITYOFTARGETS ILLUMINATEANUMBEROF TARGETSWITH2&ENERGYANDGUIDEMISSILESTOWARDTHEM ANDPERFORMCOMPLETEHEMI SPHERICALSEARCHWITHAUTOMATICTARGETSELECTIONANDHANDOVERTOTRACKING)TMAYEVEN ACTASACOMMUNICATIONSYSTEM DIRECTINGHIGH GAINBEAMSTOWARDDISTANTRECEIVERSAND TRANSMITTERS#OMPLETEFLEXIBILITYISPOSSIBLESEARCHANDTRACKRATESMAYBEADJUSTED TOBESTMEETPARTICULARSITUATIONS ALLWITHINTHELIMITATIONSSETBYTHETOTALUSEOFTIME
0ORTIONS OF THIS CHAPTER THAT APPEARED IN EARLIER EDITIONS OF THE 2ADAR (ANDBOOK WERE WRITTEN BY THE LATE 4HEODORE##HESTON APIONEERINPHASEDARRAYANTENNAS
£Î°£
£Î°Ó
2!$!2(!.$"//+
4HEANTENNABEAMWIDTHMAYBECHANGEDTOSEARCHSOMEAREASMORERAPIDLYWITHLESS GAIN&REQUENCYAGILITYISPOSSIBLEWITHTHEFREQUENCYOFTRANSMISSIONCHANGINGATWILL FROMPULSETOPULSEOR WITHCODING WITHINAPULSE6ERYHIGHPOWERSMAYBEGENER ATEDFROMAMULTIPLICITYOFAMPLIFIERSDISTRIBUTEDACROSSTHEAPERTURE%LECTRONICALLY CONTROLLEDARRAYANTENNASCANGIVERADARSTHEFLEXIBILITYNEEDEDTOPERFORMALLTHEVARI OUSFUNCTIONSINAWAYBESTSUITEDFORTHESPECIFICTASKATHAND4HEFUNCTIONSMAYBE PROGRAMMEDADAPTIVELYTOTHELIMITOFONESCAPABILITYTOEXERCISEEFFECTIVEAUTOMATIC MANAGEMENTANDCONTROL 0HASEDARRAYTHEORYWASSTUDIEDINTENSIVELYINTHES4ECHNOLOGYADVANCED AND LED TO A SERIES OF OPERATIONAL SYSTEMS IN THE S MANY PUBLICATIONS BECAME AVAILABLEn )N TERMS OF PERFORMANCE IMPROVEMENT ULTRALOW SIDELOBES LESS THAN
D" WEREDEMONSTRATEDFIRSTINTHESBY7ESTINGHOUSE%LECTRIC#ORPORATIONS !7!#3!IRBORNE7ARNINGAND#ONTROL3YSTEM ANDBROUGHTABOUTTIGHTTOLERANCESIN CONSTRUCTIONANDPHASESETTINGS4HEADVENTOFMOREANDBETTERCOMPUTERMODELINGAND SOPHISTICATEDTESTEQUIPMENTSUCHASNETWORKANALYZERSHASLEDTOIMPROVEDMETHODS OFDESIGNINGWELL MATCHEDAPERTURES"ETTERCOMPONENTSSUCHASRADIATINGELEMENTS PHASE SHIFTERS AND POWER DIVIDERS ARE NOW AVAILABLE -ORE ECONOMICAL SOLID STATE DEVICESANDMEMORYCHIPSHAVELEDTOPRECISIONAPERTUREPHASECONTROLWITHCORREC TIONSFORFREQUENCYANDTEMPERATUREVARIATIONS3OLID STATEMICROWAVEDEVICESHOLD GREATPROMISEFORFUTURESYSTEMSWHEREASOLID STATEMODULEISASSOCIATEDWITHEACH RADIATING ELEMENT IMPROVEMENTS IN TERMS OF APERTURE CONTROL RELIABILITY AND EFFI CIENCYCONTINUE0HASEDARRAYSCANBECONTROLLEDADAPTIVELY PARTICULARLYFORSIDELOBE CANCELLATION4HISISANAREAWHERETHEORYANDUNDERSTANDINGHAVEADVANCEDMUCH !LSO GREAT PROGRESS HAS BEEN MADE WITH INDOOR NEAR FIELD ANTENNA RANGES WHERE COMPUTER CONTROLLEDPRECISIONTWO DIMENSIONALRADIATIONPATTERNSAREDERIVEDATMUL TIPLEFREQUENCIESANDWITHSCANNING 0HASEDARRAYSAREVERYEXPENSIVE!STECHNOLOGYADVANCES COSTSAREEXPECTEDTOBE REDUCED!TTHESAMETIME THEQUESTFORBETTERPERFORMANCEWITHLOWERSIDELOBESAND WIDERBANDWIDTHKEEPSTHECOSTSHIGH 0HASED!RRAY!NTENNAS 4HEPHASEDARRAYANTENNAHASANAPERTURETHATISASSEM BLEDFROMAGREATMANYSIMILARRADIATINGELEMENTS SUCHASSLOTS DIPOLES ORPATCHES EACHELEMENTBEINGINDIVIDUALLYCONTROLLEDINPHASEANDAMPLITUDE!CCURATELYPRE DICTABLERADIATIONPATTERNSANDBEAM POINTINGDIRECTIONSCANBEACHIEVED 4HE GENERAL PLANAR ARRAY CHARACTERISTICS ARE READILY OBTAINED FROM A FEW SIMPLE EQUATIONSTHATAREGIVENHEREBUTDISCUSSEDLATERINGREATERDETAIL7ITHTHEELEMENTS SPACEDBYKK WAVELENGTH TOAVOIDTHEGENERATIONOFMULTIPLEBEAMSGRATING LOBES THENUMBEROFRADIATINGELEMENTS.FORAPENCILBEAMISAPPROXIMATELYRELATED TOTHEBEAMWIDTHBY
.y
P "
. WHEREP"ISTHE D"BEAMWIDTHINDEGREES4HECORRESPONDINGANTENNAGAIN WHENTHE BEAMPOINTSBROADSIDETOTHEAPERTURE IS
P" y
'yO.GyO.G,GA
0(!3%$!22!92!$!2!.4%..!3
£Î°Î
WHEREGACCOUNTSFORANTENNALOSSESG, ANDREDUCTIONINGAINDUETOUNEQUALWEIGHT INGOFTHEELEMENTSWITHANONUNIFORMAMPLITUDEGA 7HENSCANNINGTOANANGLEIS P THEGAINOFAPLANARARRAYISREDUCEDTOTHATOFTHEPROJECTEDAPERTURE
'P yO.GCOSP
3IMILARLY THE SCANNED BEAMWIDTH IS INCREASED FROM THE BROADSIDE BEAMWIDTH EXCEPTINTHEVICINITYOFENDFIRE P n
P " SCANNED y
P " BROADSIDE
COS P
4HE TOTAL NUMBER OF BEAMS - WITH BROADSIDE BEAMWIDTH AND SQUARE STACKING THATFITINTOASPHEREISAPPROXIMATELYEQUALTOTHEGAINANDWITHGyISTHUSSIMPLY RELATEDTO.BY
-yO.
!NARRAYWHERETHEELEMENTSAREFEDINPARALLELSEE3ECTION ANDSCANNEDBY PHASESHIFT MODULOO HASLIMITEDBANDWIDTHFORWIDEBANDOPERATION CONSTANTPATH LENGTHSRATHERTHANCONSTANTPHASESAREREQUIRED4HELIMITISGIVENBY
"ANDWIDTH yBEAMWIDTHn 4HISISEQUIVALENTTOLIMITATIONSGIVENBY
0ULSELENGTH rAPERTURESIZE
7ITHTHESECRITERIA THESCANNEDRADIATIONPATTERNATnISSTEEREDBYoONE FOURTH OFTHEBEAMWIDTHATTHEANGLEOFSCANASTHEFREQUENCYISCHANGEDOVERTHEBAND)FALL THEFREQUENCIESINTHEBANDAREUSEDWITHEQUALWEIGHTING THENTWICETHEBANDWIDTH HALFTHEPULSELENGTH BECOMESACCEPTABLE!TASCANANGLEP THEBEAMSTEERSWITH FREQUENCYTHROUGHANANGLECPSOTHAT
DP y
DF TAN P F
RAD
&ORWIDERBANDWIDTHS TIME DELAYNETWORKSHAVETOBEINTRODUCEDTOSUPPLEMENT THEPHASESHIFTERS #ONFORMAL !RRAYS 0HASED ARRAYS MAY CONFORM TO CURVED SURFACES AS REQUIRED FOREXAMPLE FORFLUSH MOUNTINGONAIRCRAFTORMISSILES)FTHESURFACEHASA LARGERADIUSOFCURVATURESOTHATALLTHERADIATINGELEMENTSPOINTINSUBSTANTIALLYTHE SAME DIRECTION THEN THE CHARACTERISTICS ARE SIMILAR TO THOSE OF A PLANAR ARRAY EVEN THOUGHTHEEXACT$POSITIONOFTHEELEMENTHASTOBETAKENINTOACCOUNTTOCALCULATE THEREQUIREDPHASE!SMALLRADIUSOFCURVATUREISFOUNDWITHCYLINDRICALORSPHERICAL ARRAYSUSEDFORnCOVERAGE%LEMENTSARESWITCHEDTOAVOIDSECTIONSOFTHEANTENNA WHERETHEYPOINTAWAYFROMTHEDESIREDBEAMDIRECTION$IFFICULTIESMAYBEENCOUN TEREDINMATCHINGTHERADIATINGELEMENTSANDINMAINTAININGPOLARIZATIONPURITY4HE DISCUSSIONINTHISCHAPTERWILLCONCENTRATEONPLANARPHASEDARRAYS RATHERTHANCON FORMALARRAYS
£Î°{
2!$!2(!.$"//+
$6OLUMETRIC3EARCH 4HREE DIMENSIONAL$ VOLUMETRICRADARSEARCHISPOS SIBLEWITHELECTRONICSCANNINGINBOTHAZIMUTHANDELEVATIONIMPORTANTREGIONSEG THEHORIZON MAYBEEMPHASIZEDATWILLANDSEARCHEDMOREFREQUENTLY4HERADARMAY OPERATE WITH A HIGHER THAN NORMAL FALSE ALARM RATE SINCE TARGETS CAN EASILY BE CON FIRMEDBYADDITIONALDWELLS0HASECONTROLALLOWSBEAMSTOBEWIDENED FOREXAMPLE TOREDUCESEARCHTIMEFORTHEMOREELEVATEDREGIONS WHEREREDUCEDRANGESNEEDLESS ANTENNAGAIN!SEPARATEROTATINGSURVEILLANCERADARSYSTEMMAYBEADDEDFOREXTRA COVERAGEATASECONDFREQUENCY ANDTOALLOWTHE$RADARMORETIMEFORTRACKING -ONOPULSE4RACK 0HASED ARRAY RADARS ARE WELL SUITED FOR MONOPULSE TRACKING 4HERADIATINGELEMENTSOFTHEARRAYCANBECOMBINEDINTHREEDIFFERENTWAYSTOGIVETHE SUMPATTERNANDTHEAZIMUTHANDELEVATIONDIFFERENCEPATTERNS#ONTRADICTORYREQUIRE MENTSINOPTIMUMAMPLITUDEDISTRIBUTIONFORSUMANDDIFFERENCEPATTERNSEXIST BUT ASWITHOTHERANTENNASYSTEMS THEYMAYBEINDEPENDENTLYSATISFIED4HESUMANDDIF FERENCEPATTERNSARESCANNEDSIMULTANEOUSLY 4HE DIFFERENCE PATTERN NULL IN A PHASED ARRAY SYSTEM GIVES GOOD BEAM POINTING ACCURACY !BSOLUTE BEAM POINTING ACCURACIES TO WITHIN LESS THAN ONE FIFTIETH OF A SCANNED BEAMWIDTH HAVE BEEN MEASURED WITH SCANS UP TO n4HE ACCURACY IS LIMITED BY PHASE AND AMPLITUDE ERRORS 3INCE PHASE SHIFT RATHER THAN TIME DELAY IS USED ASTHEFREQUENCYISCHANGED THEDIRECTIONOFTHENULLOFTHESCANNEDBEAMISALSO CHANGED ANDTHEBEAMMOVESTOWARDBROADSIDEWITHANINCREASEINFREQUENCY 3HAPED"EAMS 4HERADIATIONPATTERNOFANARRAYMAYBESHAPEDBYMODIFYING THEAPERTUREDISTRIBUTION'OODPATTERNAPPROXIMATIONSCANBEOBTAINEDBYUSINGPHASE ONLY)NPARTICULAR THEBEAMMAYBEBROADENEDBYAPPLYINGASPHERICALPHASEDISTRIBU TIONTOTHEAPERTUREORBYAPPROXIMATINGITWITHAGABLETRIANGULAR PHASEDISTRIBUTION "EAMSOFTHISTYPEAREOFPARTICULARINTERESTBECAUSETHEYAREEASILYGENERATED4HEY MAYBEUSEDFORTRANSMISSIONINASYSTEMWHERETHERECEIVINGANTENNAHASACLUSTEROF SIMULTANEOUSBEAMS OR ASPREVIOUSLYDISCUSSED THEYMAYBEUSEDINASEARCHSYSTEM TOREDUCETHENUMBEROFANGULARCELLSINREGIONSOFSHORTERRANGE -ONITORING %LECTRONICALLYSCANNEDARRAYSARECOMPOSEDOFVERYMANYPARTSAND INCLUDEELECTRONICCIRCUITRYTODRIVETHEPHASESHIFTERSORSWITCHESTHATSTEERTHEBEAM 4HE OVERALL RELIABILITY OF SUCH ARRAYS CAN BE GREAT GRACEFUL DEGRADATION HAS BEEN CLAIMEDBECAUSETHEFAILUREOFASMUCHASOFTHECOMPONENTSLEADSTOALOSSIN GAINOFONLYD"4HEREIS HOWEVER ADEGRADATIONOFLOW SIDELOBES.EVERTHELESS THEFUNCTIONINGOFTHEANTENNAISCOMPLEX ANDTHEREISNEEDFORPROVIDINGTESTORMON ITORINGCIRCUITRY4HEDECISIONTOPOINTABEAMINACERTAINDIRECTIONISMADESOME WHEREINTHERADARCONTROLSYSTEMANDISNORMALLYDEFINEDBYTWODIRECTIONCOSINES ! TEST OR MONITORING CIRCUIT SHOULDESTABLISHTHECORRECTFUNCTIONING OF ALL COMPO NENTS INCLUDINGALLBEAM POINTINGCOMPUTATIONS ELECTRONICDRIVERSANDPHASESHIFTERS ORSWITCHES ANDALLTHEIRINTERCONNECTIONS&REQUENTINDICATIONSTHATTHEANTENNASYS TEMISFUNCTIONINGORISCAPABLEOFFUNCTIONINGSHOULDBEAVAILABLE)NONEPOSSIBLE METHOD THEPHASESHIFTERSAREPROGRAMMEDTOFOCUSONANEARBYMONITORPROBEAND SCANPASTIT4HISWILLYIELDACLOSEAPPROXIMATIONOFTHECOMPLETERADIATIONPATTERN WHEREGAINANDSIDELOBESCANBEMEASUREDANDCOMPAREDWITHPREVIOUSRESULTS4HE COMBINATIONOFINDIVIDUALELEMENTSANDTHEIRPHASESHIFTERSANDDRIVERS CANALSOBE CHECKEDWITHTHISCONFIGURATION4HEPHASEATEACHELEMENTISSEQUENTIALLYROTATEDAT SOMELOWFREQUENCYTHEAMPLITUDEANDPHASEOFTHISMODULATIONASRECEIVEDBYTHE PROBERELATEDIRECTLYTOBOTHTHERELATIVEAMPLITUDEEXCITATIONOFTHEELEMENTANDITS
0(!3%$!22!92!$!2!.4%..!3
£Î°x
RELATIVEPHASESETTING/THERMETHODSHAVEBEENPROPOSEDWHEREMEASUREMENTS ARECOMPAREDWITHPREVIOUSLYRECORDEDONES $EPLOYMENTOF!PERTURES 7ITHPLANARARRAYS SCANNINGISLIMITEDBYTHELOSSIN GAINANDTHEINCREASEINBEAMWIDTHCORRESPONDINGTOTHEREDUCTIONOFTHEAPERTURETO ITSPROJECTEDAREA0RACTICALEXTREMEVALUESOFSCANNINGARETHEREFOREINTHEREGIONOF TOn!MINIMUMOFTHREEPLANARARRAYAPERTURESISTHENNECESSARYFORHEMISPHERICAL COVERAGE4HEANTENNASMAYBEPOSITIONEDASSHOWNIN&IGURE PERMITTINGAVIEW THATISUNIMPEDEDBYTHECENTRALSUPERSTRUCTURE4HEAPERTURESWOULDNORMALLYBETILTED BACKFROMTHEVERTICALTOBALANCETHESCANANGLES 2ADIATING %LEMENTS 4HE MOST COMMONLY USED RADIATORS FOR PHASED ARRAYS ARE DIPOLES SLOTS OPEN ENDEDWAVEGUIDESORSMALLHORNS ANDPRINTED CIRCUIThPATCHESv ORIGINALLYCALLED#OLLINGSRADIATORAFTERTHEIRINVENTOR 4HEELEMENTHASTOBESMALL ENOUGHTOFITINTHEARRAYGEOMETRY THEREBYLIMITINGTHEELEMENTTOANAREAOFALITTLE MORE THAN K )N ADDITION MANY RADIATORS ARE REQUIRED AND THE RADIATING ELEMENT SHOULDBEINEXPENSIVEANDRELIABLEANDHAVEIDENTICALCHARACTERISTICSFROMUNITTOUNIT "ECAUSETHEIMPEDANCEANDPATTERNOFARADIATORINANARRAYAREDETERMINEDPRE DOMINANTLYBYTHEARRAYGEOMETRY3ECTION THERADIATINGELEMENTMAYBECHOSEN TOSUITTHEFEEDSYSTEMANDTHEPHYSICALREQUIREMENTSOFTHEANTENNA&OREXAMPLE IF THERADIATORISFEDFROMASTRIPLINEPHASESHIFTER ASTRIPLINEDIPOLEWOULDBEALOGICAL CHOICE)FAWAVEGUIDEPHASESHIFTERISUSED ANOPEN ENDEDWAVEGUIDEORASLOTMIGHT BE CONVENIENT!T THE LOWER FREQUENCIES WHERE COAXIAL COMPONENTS ARE PREVALENT DIPOLESHAVEBEENFAVORED!GROUNDPLANEISUSUALLYPLACEDABOUTKBEHINDANARRAY OFPARALLELDIPOLESSOTHATTHEANTENNAFORMSABEAMINONLYONEHEMISPHERE &ORLIMITEDSCANNINGSAY LESSTHANn ITISPOSSIBLETOUSEDIRECTIVERADIATORS HAVINGDIMENSIONSOFHEIGHTANDWIDTHOFSEVERALWAVELENGTHS7ITHSUCHSEPARATION THEMUTUALCOUPLINGEFFECTSSEE3ECTION CANBESMALL ANDTHEPATTERNANDIMPED ANCEOFANELEMENTINTHEARRAYAPPROACHTHOSEOFTHEISOLATEDELEMENT
&)'52% 'UIDED MISSILE CRUISER SHOWING TWO OUT OF FOUR PHASED ARRAY ANTENNAS #OURTESYOF)NGALLS3HIPBUILDING$IVISIONOF,ITTON
£Î°È
2!$!2(!.$"//+
4HEELEMENTMUSTBECHOSENTOGIVETHEDESIREDPOLARIZATION USUALLYVERTICALOR HORIZONTAL4HESPECIALCASEOFCIRCULARPOLARIZATIONISDISCUSSEDBELOW )FPOLARIZATIONDIVERSITYISREQUIREDORIFANARRAYISREQUIREDTOTRANSMITONEPOLAR IZATION AND RECEIVE THE ORTHOGONAL OR BOTH POLARIZATIONS EITHER CROSSED DIPOLES OR CIRCULAR OR SQUARE RADIATORS SEEM SUITABLE 7ITH APPROPRIATE FEED SYSTEMS BOTH ARE CAPABLEOFPROVIDINGVERTICALANDHORIZONTALPOLARIZATIONINDEPENDENTLYANDMAYBE COMBINED TO PROVIDE ANY DESIRED POLARIZATION INCLUDING CIRCULAR 3UCH POLARIZATION DIVERSITYADDSCONSIDERABLECOMPLEXITY REQUIRINGTWOFEEDSYSTEMSORSWITCHESATTHE RADIATINGELEMENTLEVEL #IRCULAR0OLARIZATION &ROMTHEPOINTOFVIEWOFTHEANTENNADESIGNER CIRCULAR POLARIZATIONISPOSSIBLE THOUGHDIFFICULTIESMAYBEENCOUNTEREDINMATCHINGFORLARGE SCANANGLES/NSCANNING ACOMPONENTOFTHEUNDESIREDORTHOGONALPOLARIZATIONWILL BEGENERATED ANDSOMEPROVISIONSHOULDBEMADETOABSORBTHATENERGY7ITHA CONVENTIONALCIRCULARLYPOLARIZEDANTENNA SUCHASAPARABOLICDISHWITHACIRCULARLY POLARIZED FEED GOOD CIRCULARITY MAY BE OBTAINED OVER PART OF THE MAIN BEAM WITH RAPIDDETERIORATIONOVERTHERESTOFTHEPATTERN7ITHAPLANARARRAY THERELEVANTBEAM WIDTHISTHEBEAMWIDTHOFTHEELEMENTINTHEARRAYRATHERTHANTHEARRAYBEAMWIDTH 7ITHCIRCULARPOLARIZATION THESIGNALRETURNEDFROMASINGLE BOUNCETARGETIE A SPHEREORFLATPLATE WILLREQUIREANANTENNAMATCHEDTOTHEOPPOSITESENSEOFCIRCULAR POLARIZATION FROM THAT TRANSMITTED )F THE SAME ANTENNA IS USED THEN SINGLE BOUNCE TARGETSAREREJECTED3UCHASYSTEMCAN THEREFORE GIVEAMEASUREOFSUPPRESSIONOF RAINECHOES IDEALLYAMOUNTINGTO
LOGE E D"
WHEREEISTHEVOLTAGE ELLIPTICITYRATIO!NEARLYMODELOFA2AYTHEONREFLECTARRAYGAVE ANELLIPTICITYRATIOOFLESSTHAND"WITHSCANSUPTOn CORRESPONDINGTOATHEORETICAL RAINREJECTIONOFATLEASTD"!TTHESAMETIME ANAIRCRAFTTARGETWOULDTYPICALLYLOSE APPROXIMATELYD" LEAVINGARELATIVENETIMPROVEMENTOFD"OFRAINREJECTION 0HASED!RRAYSWITH6ERY7IDE"ANDWIDTH !RADARSYSTEMTHATHASTHECAPABIL ITYOFCHANGINGFREQUENCYOVERAVERYWIDEBANDWIDTHCAN WITHADVANTAGE ADAPTITS TRANSMISSIONTOTAKEINTOACCOUNTFREQUENCY DEPENDENTMULTIPATHCHARACTERISTICS TAR GETRESPONSE ENVIRONMENTALCONDITIONS INTERFERENCE ANDJAMMING&URTHER WIDEBAND PROCESSINGCANGIVEFINERANGERESOLUTION 0HASEDARRAYSHAVETHEPOTENTIALOFOPERATINGOVERVERYWIDEBANDWIDTHS4HE HIGH END OF THE FREQUENCY BAND IS LIMITED BY THE PHYSICAL SIZE OF THE ELEMENTS WHICHMUSTBESPACEDCLOSEENOUGHINTHEARRAYTOAVOIDTHEGENERATIONOFGRATING LOBES SEE 3ECTION &OR WIDE INSTANTANEOUS BANDWIDTH RATHER THAN TUNABLE BANDWIDTH TIMEDELAYSHAVETOBEADDEDTOPREVENTTHEBEAMFROMBEINGSCANNED ASTHEFREQUENCYISCHANGED 4HE IMPEDANCE OF THE RADIATING ELEMENT AT THE APERTURE WITH CLOSELY SPACED ELEMENTS IS APPROXIMATELY INDEPENDENT OF FREQUENCY BUT THE ELEMENT MUST BE MATCHED OVER THE WIDE BANDWIDTH 4HIS IS DIFFICULT TO ACHIEVE WITHOUT EXCITING HARMFULSURFACEWAVESWHENSCANNING.EVERTHELESS MATCHINGWITHOCTAVEBAND WIDTHFORSCANNINGTOonHASBEENACHIEVED ,IMITED3CANNING )FSCANNINGISLIMITEDTOASMALLANGULARVOLUME CONSIDERABLE SIMPLIFICATIONSBECOMEPOSSIBLE4HETOTALNUMBEROFACTIVECONTROLSCANBEREDUCEDTO
0(!3%$!22!92!$!2!.4%..!3
£Î°Ç
ABOUTEQUALTHETOTALNUMBEROFBEAMS3UBARRAYSSEE3ECTION MAYBEFORMED EACHWITHONLYONEPHASECONTROLOFASIZESUCHTHATTHESUBARRAYBEAMWIDTHINCLUDES ALL THE SCAN ANGLES!LTERNATIVELY A SMALL PHASED ARRAY COULD BE PLACED IN THE FOCAL REGIONOFALARGEREFLECTORTOSCANTHENARROWBEAMWIDTHOFTHEREFLECTOROVERALIMITED SCANANGLE 3CANNINGOF!RRAYS 0HASE 3CANNING 4HE BEAM OF AN ANTENNA POINTS IN A DIRECTION THAT IS NORMAL TOTHERADIATEDPHASEFRONT)NPHASEDARRAYS THISPHASEFRONTISADJUSTEDTOSTEERTHE BEAMBYINDIVIDUALCONTROLOFTHEPHASEOFEXCITATIONOFEACHRADIATINGELEMENT4HIS ISINDICATEDIN&IGUREA4HEPHASESHIFTERSAREELECTRONICALLYACTUATEDTOPERMIT RAPIDSCANNINGANDAREADJUSTEDINPHASETOAVALUEBETWEENANDORAD7ITHAN INTERELEMENTSPACINGS THEINCREMENTALPHASESHIFTXBETWEENADJACENTELEMENTSFORA SCANANGLEPISX OK SSINP)FTHEPHASEXISCONSTANTWITHFREQUENCY THESCAN ANGLEPISFREQUENCY DEPENDENT 4IME $ELAY3CANNING 0HASESCANNINGWASSEENTOBEFREQUENCY SENSITIVEHOW EVER TIME DELAYSCANNINGISINDEPENDENTOFFREQUENCY$ELAYLINESAREUSEDINSTEADOF PHASESHIFTERS ASSHOWNIN&IGUREB PROVIDINGANINCREMENTALDELAYFROMELEMENT TOELEMENTOFS SC SINP WHEREC VELOCITYOFPROPAGATION)NDIVIDUALTIME DELAY CIRCUITS3ECTION ARENORMALLYTOOCUMBERSOMETOBEADDEDTOEACHRADIATINGELE MENT!REASONABLECOMPROMISEMAYBEREACHEDBYADDINGONETIME DELAYNETWORKTO AGROUPOFELEMENTSSUBARRAY WHEREEACHELEMENTHASITSOWNPHASESHIFTER &REQUENCY 3CANNING &REQUENCY RATHER THAN PHASE MAY BE USED AS THE ACTIVE PARAMETER TO EXPLOIT THE FREQUENCY SENSITIVE CHARACTERISTICS OF PHASE SCANNING &IGURECSHOWSTHEARRANGEMENT!TONEPARTICULARFREQUENCY ALLRADIATORSAREIN PHASE!STHEFREQUENCYISCHANGED THEPHASEACROSSTHEAPERTURETILTSLINEARLY ANDTHE BEAM IS SCANNED &REQUENCY SCANNING ARRAYS ARE RELATIVELY SIMPLE AND INEXPENSIVE
&)'52% 'ENERATIONOFSCANNEDBEAMSA PHASEDARRAY B TIME DELAYARRAY C FREQUENCY SCANNED ARRAY ANDD "LASS TYPEARRAY
£Î°n
2!$!2(!.$"//+
TOIMPLEMENT4HEYHAVEBEENDEVELOPEDANDDEPLOYEDINTHEPASTTOPROVIDEELEVATION ANGLE SCANNING IN COMBINATION WITH MECHANICAL HORIZONTAL ROTATION FOR $ RADARS !CHAPTERINTHEFIRSTEDITIONOFTHISHANDBOOKWASDEVOTEDTOTHISAPPROACH WHICH SINCETHENHASRECEIVEDMUCHLESSATTENTIONFREQUENCYISTOOIMPORTANTAPARAMETER FORACHIEVINGHIGH RANGERESOLUTION ELECTRONICCOUNTER COUNTERMEASURES ANDMULTIPLE RADAR OCCUPANCY TO GIVE IT UP FOR ANTENNA SCANNING &REQUENCY SCANNING IS SELDOM USEDANYMORE )&3CANNING &ORRECEIVING THEOUTPUTFROMEACHRADIATINGELEMENTMAYBEHET ERODYNEDMIXED TOANINTERMEDIATEFREQUENCY)& !LLTHEVARIOUSMETHODSOFSCAN NING ARE THEN POSSIBLE INCLUDING THE BEAM SWITCHING SYSTEM DESCRIBED BELOW AND CANBECARRIEDOUTAT)& WHEREAMPLIFICATIONISREADILYAVAILABLEANDLUMPEDCONSTANT CIRCUITSMAYBEUSED $IGITAL"EAMFORMINGn &ORRECEIVING THEOUTPUTFROMEACHRADIATINGELEMENT MAYBEAMPLIFIEDANDDIGITIZED4HESIGNALISTHENTRANSFERREDTOACOMPUTERFORPRO CESSING WHICH CAN INCLUDE THE FORMATION OF MULTIPLE SIMULTANEOUS BEAMS FORMED WITHAPPROPRIATEAPERTUREILLUMINATIONWEIGHTING ANDADAPTIVELYDERIVEDNULLSINTHE BEAM PATTERNS TO AVOID SPATIAL INTERFERENCE OR JAMMING ,IMITATIONS ARE DUE TO THE AVAILABILITYANDCOSTOFANALOG TO DIGITAL!$ CONVERTERSANDTOTHEIRFREQUENCYAND DYNAMIC RANGECHARACTERISTICS0ARTIALIMPLEMENTATIONISPOSSIBLEBYDIGITIZINGATSUB ARRAYLEVELSONLY "EAM3WITCHING 7ITHPROPERLYDESIGNEDLENSESORREFLECTORS ANUMBEROFINDE PENDENTBEAMSMAYBEFORMEDBYFEEDSATTHEFOCALSURFACE%ACHBEAMHASSUBSTAN TIALLYTHEGAINANDBEAMWIDTHOFTHEWHOLEANTENNA!LLENHASSHOWNTHATTHEREARE EFFICIENTEQUIVALENTTRANSMISSIONNETWORKSTHATUSEDIRECTIONALCOUPLERSANDHAVETHE SAMECOLLIMATINGPROPERTY!TYPICALFORM AFTER"LASS ISSHOWNIN&IGURED 4HE GEOMETRY CAN BE ADJUSTED TO PROVIDE EQUAL PATH LENGTHS THUS PROVIDING FRE QUENCY INDEPENDENTTIME DELAYSCANNING!NOTHERPOSSIBLECONFIGURATIONPROVIDING MULTIPLEBROADBANDBEAMSUSESPARALLELPLATESCONTAININGAWIDE ANGLEMICROWAVE LENS %ACHPORTCORRESPONDSTOASEPARATEBEAM4HELENSPROVIDESAPPROPRIATE TIME DELAYS TO THE APERTURE GIVING FREQUENCY INVARIANT SCANNING 4HE BEAMS MAY BE SELECTED THROUGH A SWITCHING MATRIX REQUIRING - SINGLE POLEnDOUBLE THROW 30$4 SWITCHESTOSELECTONEOUTOF-BEAMS4HEBEAMSARESTATIONARYINSPACE ANDOVERLAPATAPPROXIMATELYTHED"POINTS4HISISINCONTRASTTOTHEPREVIOUSLY DISCUSSEDMETHODSOFSCANNING WHERETHEBEAMCANBESTEEREDACCURATELYTOANYPOSI TION4HEBEAMSALLLIEINONEPLANE4HESYSTEMMAYBECOMBINEDWITHMECHANICAL ROTATION OF THE ANTENNA GIVING VERTICAL SWITCHED SCANNING FOR $ COVERAGE -UCH GREATERCOMPLEXITYISREQUIREDFORASYSTEMSWITCHINGBEAMSINBOTHPLANES -ULTIPLE3IMULTANEOUS"EAMS )NSTEADOFSWITCHINGTHEBEAMS ASDESCRIBEDIN THEPRECEDINGPARAGRAPH ALLTHEBEAMSMAYBECONNECTEDTOSEPARATERECEIVERS GIVING MULTIPLESIMULTANEOUSRECEIVEBEAMS4HETRANSMITTERRADIATIONPATTERNWOULDNEEDTO BEWIDETOCOVERALLTHERECEIVEBEAMS3UCHMULTIBEAMSYSTEMSHAVEFOUNDAPPLICA TIONINCOMBINATIONWITHMECHANICALROTATIONFOR$COVERAGE -ULTIPLE )NDEPENDENTLY 3TEERED "EAMS )NDEPENDENT MULTIPLE BEAMS MAY BE GENERATEDWITHASINGLEBEAMFORMERBYMODIFYINGBOTHAMPLITUDEANDPHASEATTHE APERTURE4HISCANBESEENFROM&IGURE WHERE FOREXAMPLE TWOINDEPENDENT
0(!3%$!22!92!$!2!.4%..!3
£Î°
&)'52% !PERTUREDISTRIBUTIONGIVINGTWOBEAMS
BEAMS ARE GENERATED "OTH BEAMS HAVE THE SAME AMPLITUDE VOLTAGE DISTRIBUTION &X BUTDIFFERENTLYINCLINEDLINEARPHASEDFRONTS4HETOTALAPERTUREEXCITATIONWITH BOTHBEAMSIS
X¶ § & X Y & X E J Y X A & X E J Y X A & X COS ¨Y Y · E J Y Y X A A¸ ©
4HAT IS THE APERTURE AMPLITUDE DISTRIBUTION REQUIRED FOR TWO SEPARATE BEAMS VARIES COSINUSOIDALLY ANDTHEPHASEDISTRIBUTIONISLINEARANDHASTHEAVERAGEINCLINATION )N MOST PHASED ARRAY SYSTEMS ONLY THE PHASE CAN BE CONTROLLED )GNORING THE REQUIREDAMPLITUDEVARIATIONSSTILLLEADSTOGOODAPPROXIMATIONSFORFORMINGMULTIPLE BEAMS BYSUPERIMPOSINGTHEVARIOUSREQUIREDPHASE SHIFTERSETTINGSMODULOO )N THECASEOFTWOBEAMS THEAPERTUREPHASESLOPEHASTHEAVERAGEINCLINATIONANDVARIES PERIODICALLYFROMTOO 6ERTICAL3CAN/NLY !GREATLYSIMPLIFIEDPHASEDARRAYSYSTEMBECOMESPOSSIBLE IFTHEREISNONEEDFORMULTIFUNCTIONCAPABILITIES INCLUDINGFIRECONTROL WHEREABEAM MAYHAVETOBEPOINTEDINANYGIVENDIRECTIONATANYTIME4HEARRAYISSCANNEDINTHE VERTICALPLANEONLYANDMECHANICALLYROTATEDTOGIVEAZIMUTHCOVERAGE4HENUMBER OFPHASECONTROLPOINTSISTHENREDUCEDTOTHENUMBEROFHORIZONTALROWS)NTHECASE OFASHIPSSURVEILLANCERADAR THEANTENNASHOULDBEPOSITIONEDASHIGHASPOSSIBLETO AVOIDSHADOWINGBYTHESUPERSTRUCTURE BUTTHEPEDESTALNEEDNOTBESTABILIZEDSINCE STABILIZATIONCANBEACHIEVEDBYELECTRONICBEAMSTEERING3CANNINGCANBEINTHEFORM OFPHASESCANNINGORMULTIPLESIMULTANEOUSBEAMSMAYBEUSEDONRECEIVEWITHAWIDE ANTENNAPATTERNONTRANSMIT
£Î°ÓÊ ,,9Ê/ ",9 !RRAYWITH4WO%LEMENTS &IGURESHOWSTWOISOTROPICRADIATORSTHATARE SPACEDBYADISTANCESANDEXCITEDWITHEQUALAMPLITUDEANDPHASE7ITHUNITYINPUT
£Î°£ä
2!$!2(!.$"//+
&)'52% 2ADIATIONPATTERNOFTWOISOTROPICRADIATORS
POWER THEVECTORSUMOFTHEIRCONTRIBUTIONS ADDEDATAGREATDISTANCEASAFUNCTIONOF P ISTHERADIATIONPATTERN
%A P
J P L S SINP ;E E J P L S SINP =
WHEREPISMEASUREDFROMTHEBROADSIDEDIRECTION.ORMALIZING TOGETUNITYAMPLI TUDEWHENP ANDSIMPLIFYINGGIVE § S ¶ %A P COS ¨P SIN P · © L ¸ 4HEABSOLUTEVALUEOF%AP ISPLOTTEDIN&IGUREASAFUNCTIONOFOSK SINP )F THE PLOT HAD BEEN IN TERMS OF THE ANGLE P THE LOBES WOULD HAVE BEEN FOUND TO INCREASEINWIDTHAS\P\INCREASED4HEMAINBEAMOCCURSWHENSINP 4HEOTHER LOBESHAVETHESAMEAMPLITUDEASTHEMAINBEAMANDAREREFERREDTOASGRATINGLOBES
0(!3%$!22!92!$!2!.4%..!3
£Î°££
4HEYOCCURATANGLESGIVENBYSINP o;MSK = WHEREMISANINTEGER&ORTHEHALF SPACEGIVENBY n P n THEREAREM`GRATINGLOBES WHEREM`ISTHELARGEST INTEGERSMALLERTHANSK)FS K GRATING LOBEMAXIMADONOTOCCUR ANDTHEVALUEAT onISCOSOSK 4HISVALUEISFORISOTROPICRADIATORSANDISREDUCEDIFTHERADIATORS HAVEDIRECTIVITY ,INEAR!RRAY 7ITHALINEARARRAYOF.ISOTROPICRADIATORS EXCITEDWITHEQUAL AMPLITUDESANDPHASEANDSEPARATEDBYDISTANCESS ASSHOWNIN&IGURE THECON DITION FOR THE OCCURRENCE OF GRATING LOBES IS UNCHANGED FROM THE SIMPLER CASE JUST CONSIDERED4HEYOCCURFORTHESAMEVALUESOFOSK SINP BUTTHEWIDTHOFTHELOBES ISREDUCED ANDTHEYARESEPARATEDBYMINORLOBES3UMMINGTHEVECTORCONTRIBUTIONS FROMALLELEMENTS WITHELEMENTASPHASEREFERENCE GIVES N . J P L NS SIN P £ E . N 4HEFACTOR . SHOWSTHATEACHELEMENTISENERGIZEDWITH.OFTHEUNITY INPUT POWER.ORMALIZINGTHEGAINTOUNITYATBROADSIDE P GIVESTHEPATTERN
%A P
%A P
SIN; .P S L SIN P = . SIN ;P S L SIN P =
%AP GIVES THE RADIATION PATTERN FOR ISOTROPIC RADIATORS AND IS KNOWN AS THEARRAY FACTOR )T IS SHOWN IN &IGURE FOR . 4HIS PATTERN IS REPETITIVE AND THE LOCATIONSOFTHEADJACENTGRATINGLOBESATANGLESPANDPARESEPARATEDBYOSK SINP SINP O
&)'52% ,INEARARRAYWITH.RADIATORSUNIFORMLYSPACEDBYADISTANCES
£Î°£Ó
2!$!2(!.$"//+
&)'52% !RRAYFACTORWITH. ELEMENTS
4HERADIATINGELEMENTSARENOTISOTROPICBUTHAVEARADIATIONPATTERN%EP KNOWN ASTHEELEMENTFACTORORELEMENTPATTERNTHENTHECOMPLETERADIATIONPATTERN%P IS THEPRODUCTOFTHEARRAYFACTORANDTHEELEMENTPATTERN
% P %E Q %A P %E P
SIN ; .P S L SINP = . SIN;P S L SINP =
!NAPPROXIMATIONTOTHEPATTERNOF%QISINTHEFORM
% P
SIN ;P A L SIN P = P A L SIN P
WHERETHEEFFECTIVEAPERTUREISA .S WHICHEXTENDSBYSBEYONDTHECENTERSOF THEENDELEMENTS)NCONTRASTTOTHEARRAYFACTOR THISPATTERNHASONLYONEMAXIMUM ANDISNONREPETITIVE)TISTHEWELL KNOWN&OURIERTRANSFORMOFACONTINUOUSCONSTANT AMPLITUDEDISTRIBUTION&ORUNIFORMILLUMINATION THEBEAMWIDTHIS
P"
RAD n AL AL
4HEFIRSTSIDELOBEISD"DOWNFROMTHEPEAKOFTHEMAINBEAM &OR LARGER VALUES OF P THE PATTERN OF A CONTINUOUS APERTURE IS MODIFIED FROM %QBYTHEOBLIQUITYFACTOR COSP 4HISGIVES
% P
COSP
SIN;P A L SIN P = P A L SINP
&ORCLOSELYSPACEDELEMENTS THEOBLIQUITYFACTORISVERYSIMILARTOTHEAMPLITUDE PATTERN OF A WELL DESIGNED MATCHED RADIATING ELEMENT COSP FOR VALUES UP TO SOMEORn!TGREATERANGLES THEELEMENTPATTERNHASVALUESTHATAREGREATERTHAN THOSEGIVENBY COSP ANDTHATAREAFUNCTIONOFTHETOTALNUMBEROFELEMENTS 3CANNED,INEAR!RRAYS 4HEPATTERNOFTHEARRAYMAYBESTEEREDTOANANGLEP BYAPPLYINGLINEARLYPROGRESSIVEPHASEINCREMENTSFROMELEMENTTOELEMENTSOTHAT THEPHASEBETWEENADJACENTELEMENTSDIFFERSBYOSK SINP%QUATIONISTHEN MODIFIED GIVINGTHENORMALIZEDARRAYFACTOROFAUNIFORMLYILLUMINATEDARRAYSAS
0(!3%$!22!92!$!2!.4%..!3
SIN .P S L SINP SINP
. SIN P S L SINP SINP
%A P
£Î°£Î
ANDTHEPATTERNIS
% P %E P
SIN .P S L SINP SINP
. SIN;P S L SINP SINP =
%QUATIONDESCRIBESTHEFUNDAMENTALRESPONSEOFASCANNEDARRAYSYSTEM4HE ARRAYWILLHAVEONLYONESINGLEMAJORLOBE ANDGRATING LOBEMAXIMAWILLNOTOCCUR FOR n P nASLONGAS
S \ SIN P SIN P \ P L
P
OR S
L \ SINP \
WHICHISALWAYSTRUEIFSK 7HENSCANNINGISLIMITED THEVALUEOFSKMAYBE INCREASED FOREXAMPLE TOSK FORSCANNINGTOAMAXIMUMOFnORSK FORSCANNINGTOAMAXIMUMOFon &ORLARGERVALUESOFSK GRATINGLOBESOCCURATANGLESP GIVENBY
SIN Q SIN Q o
N SL
WHENNISANINTEGER )NTHELIMIT THEINEQUALITY%Q DOESALLOWAGRATING LOBEPEAKTOOCCURAT nWHENSCANNINGTOP%VENTHOUGHTHEGRATINGLOBEISREDUCEDWHENMULTIPLIED BYTHEELEMENTPATTERN ITMAYBEPRUDENTTOSPACETHEELEMENTSSUCHTHATTHEFIRSTNULL OFTHEGRATINGLOBE RATHERTHANTHEPEAK OCCURSATn7ITH.ELEMENTSTHISMORE RESTRICTIVECONDITIONISGIVENBY S .
r L . \ SIN P \
%QUATIONMAYAGAINBEAPPROXIMATEDBYTHE&OURIERTRANSFORMOFTHEILLUMINA TIONACROSSTHECONTINUOUSAPERTURE
% P
COS P
SIN P A L SIN P SINP
P A L SIN P SIN P
4HE &OURIER TRANSFORM SOLUTIONS FOR CONTINUOUS APERTURES MAY BE USED TO APPROXIMATE PATTERNS FOR PRACTICAL AMPLITUDE AND PHASE DISTRIBUTIONS AS LONG AS THE ELEMENT TO ELEMENTSPACINGISSMALLENOUGHTOSUPPRESSGRATINGLOBES-ONOPULSE DIFFERENCEPATTERNSMAYBEAPPROXIMATEDINTHESAMEWAYFROMTHE&OURIERTRANSFORMS OFTHECORRESPONDINGCONTINUOUSODDAPERTUREDISTRIBUTIONS %LEMENT&ACTORAND'AINOF0LANAR!RRAYS 4HEMAXIMUMGAINOFAUNIFORMLY ILLUMINATEDANDLOSSLESSAPERTUREOFAREA! WITHABROADSIDEBEAM IS 'MAX P ! L
£Î°£{
2!$!2(!.$"//+
7ITHANONUNIFORMAPERTUREDISTRIBUTIONANDWITHLOSSESPRESENT THEGAINISREDUCED BYTHEEFFICIENCYTERMGTO ! H L )FTHEAPERTUREISCONSIDEREDASAMATCHEDRECEIVER THENTHEAMOUNTOFENERGYARRIV INGFROMADIRECTIONPISPROPORTIONALTOITSPROJECTEDAREA4HEGAINWITHSCANNING THEREFORE IS
'MAX P
' P P
! COS P H L
)FTHEAPERTUREISMADEUPOF.EQUALRADIATINGELEMENTSANDISMATCHEDTOACCEPT THE INCIDENT POWER THEN THE CONTRIBUTION TO THE OVERALL GAIN IS THE SAME FROM ALL ELEMENTS HENCE
'P .'EP G
WHERE'EISTHEGAINPERELEMENT)TFOLLOWSFROM%QTHATTHEMATCHEDELEMENT POWERPATTERNIS ! COS P .L ANDTHENORMALIZEDRADIATIONAMPLITUDEPATTERNOFTHEMATCHED ELEMENTORMATCHED ELEMENTPATTERNIS
'E P P
%E P COS P
&ORAGIVENELEMENTSPACINGS THETOTALNUMBEROFRADIATORS.INTHEAREA!IS. !S AND%QGIVES
§S¶ 'E P P ¨ · COS P ©L ¸
7HENTHEELEMENTSPACINGISS K THENTHEPOWERPATTERNOFANELEMENTTHATIS PERFECTLYMATCHEDATALLSCANANGLESIS
'EP OCOSP
!NDTHEPEAKANTENNAGAININTHEDIRECTIONOFSCAN P IS
'P O.GCOSP
WHERETHEEFFICIENCYTERMGACCOUNTSFORLOSSESANDFORANONUNIFORMAPERTUREDISTRI BUTION&ORABROADSIDEBEAMP AND
' O.G
ANDTHEELEMENTGAINIS'E O &IGURESHOWSATHEORETICALEXAMPLEOFTHEARRAYANDELEMENTFACTORSANDTHE RESULTINGPATTERNFORA ELEMENTARRAY WITHELEMENTSPACINGS K SCANNEDTOn
0(!3%$!22!92!$!2!.4%..!3
£Î°£x
&)'52% 4EN ELEMENTLINEARARRAYSCANNEDTOnELEMENTSPACINGS K
4HEPATTERNMAXIMUMISNOTEDTOOCCURATLESSTHANnBECAUSETHEGAINOFTHEELEMENT PATTERNINCREASESTOWARDBROADSIDE4HEELEMENTPATTERNVALUEATnISCOSn INPOWERORINAMPLITUDE RELATIVETOTHEMAXIMUMATBROADSIDE ASEXPECTED 4HESIDELOBESINTHEGENERALREGIONOFBROADSIDEARENOTREDUCEDBECAUSEINTHATREGION THEELEMENTPATTERNISAPPROXIMATELYUNITY2ELATIVETOTHEBEAMMAXIMUM THEREFORE THE SIDELOBESNEARBROADSIDEAREINCREASEDBYAPPROXIMATELYD"
£Î°ÎÊ * ,Ê,,9-Ê Ê Ê-/
, 0LANAR !RRAYS ! PLANAR ARRAY IS CAPABLE OF STEERING THE BEAM IN TWO DIMEN SIONS )N A SPHERICAL COORDINATE SYSTEM THE TWO COORDINATES P AND E DEFINE POINTS ONTHESURFACEOFAUNITHEMISPHERE!SSHOWNIN&IGURE PISTHEANGLEOFSCAN MEASUREDFROMBROADSIDEANDEISTHEPLANEOFSCANMEASUREDFROMTHEXAXIS6ON !ULOCKHASPRESENTEDASIMPLIFIEDMETHODFORVISUALIZINGTHEPATTERNSANDTHEEFFECT OFSCANNING(ECONSIDERSTHEPROJECTIONOFTHEPOINTSONAHEMISPHEREONTOAPLANE &IGURE THEAXESOFTHEPLANEARETHEDIRECTIONCOSINESCOS@X COS@Y&ORANY DIRECTIONONTHEHEMISPHERE THEDIRECTIONCOSINESARE
COS A X SIN P COS F
COS A Y SIN P SIN F
4HEDIRECTIONOFSCANISINDICATEDBYTHEDIRECTIONCOSINESCOS@XS COS@YS(ERE THEPLANEOFSCANISDEFINEDBYTHEANGLEEMEASUREDCOUNTERCLOCKWISEFROMTHECOS @XAXISANDISGIVENBY
F TAN
COS A YS
COS A XS
4HEANGLEOFSCANPISDETERMINEDBYTHEDISTANCEOFTHEPOINTCOS@XS COS@YS FROM THEORIGIN4HISDISTANCEISEQUALTOSINP&ORTHISREASON AREPRESENTATIONOFTHISSORTIS CALLEDSINPSPACE!FEATUREOFSINPSPACEISTHATTHEANTENNAPATTERNSHAPEISINVARIANT
£Î°£È
2!$!2(!.$"//+
&)'52% 0LANAR ARRAY ELEMENTGEOMETRYANDPHASING
TOTHEDIRECTIONOFSCAN!STHEBEAMISSCANNED EVERYPOINTONTHEPLOTISTRANSLATEDIN THESAMEDIRECTIONANDBYTHESAMEDISTANCEASISTHEBEAMMAXIMUM 4HEREGIONINSIDETHEUNITCIRCLEWHERE
COS A X COS A Y a
&)'52% 0ROJECTIONOFPOINTSONAHEMISPHEREONTOTHEPLANE OFTHEARRAY
0(!3%$!22!92!$!2!.4%..!3
£Î°£Ç
ISDEFINEDASREALSPACE THEHEMISPHEREINTOWHICHENERGYISRADIATED4HEINFINITE REGIONOUTSIDETHEUNITCIRCLEISREFERREDTOASIMAGINARYSPACE!LTHOUGHNOPOWERIS RADIATEDINTOIMAGINARYSPACE THECONCEPTISUSEFULFOROBSERVINGTHEMOTIONOFGRAT INGLOBESASTHEARRAYISSCANNED)NADDITION THEPATTERNINIMAGINARYSPACEREPRESENTS STOREDENERGYANDCONTRIBUTESTOTHEELEMENTIMPEDANCEINTHEARRAY 4HEMOSTCOMMONELEMENTLATTICESHAVEEITHERARECTANGULARORATRIANGULARGRID !SSHOWNIN&IGURE THEMNTHELEMENTISLOCATEDATMDX NDY 4HETRIANGULARGRID MAYBETHOUGHTOFASARECTANGULARGRIDWHEREEVERYOTHERELEMENTHASBEENOMITTED 4HEELEMENTLOCATIONSCANBEDEFINEDBYREQUIRINGTHATM NBEEVEN #ALCULATIONS FOR THE ELEMENT STEERING PHASES ARE GREATLY SIMPLIFIED BY THE ADOP TIONOFTHEDIRECTIONCOSINECOORDINATESYSTEM)NTHISSYSTEM THELINEAR PHASETAPERS DEFINEDBYTHEBEAM STEERINGDIRECTIONCOS@XS COS@YS MAYBESUMMEDATEACHELE MENTSOTHATTHEPHASINGATTHEMNTHELEMENTISGIVENBY
Y MN M4XS N4YS
WHERE 4XS O K DXCOS@XS ELEMENT TO ELEMENTPHASESHIFTINTHEXDIRECTION
4YS O K DYCOS@YS ELEMENT TO ELEMENTPHASESHIFTINTHEYDIRECTION 4HEARRAYFACTOROFATWO DIMENSIONALARRAYMAYBECALCULATEDBYSUMMINGTHE VECTORCONTRIBUTIONOFEACHELEMENTINTHEARRAYATEACHPOINTINSPACE&ORANARRAY SCANNEDTOADIRECTIONGIVENBYTHEDIRECTIONCOSINESCOS@XSANDCOS@YS THEARRAYFAC TOROFAN-r.RECTANGULARARRAYOFRADIATORSMAYBEWRITTEN - .
%A COS A XS COS A YS
£ £
\ !MN \ E J; M 4X 4XS N4Y 4YS =
M N
WHERE 4X OK DXCOS@X
4Y O K DYCOS@Y
!MN AMPLITUDEOFMNTHELEMENT !NARRAYMAYBEVISUALIZEDASHAVINGANINFINITENUMBEROFGRATINGLOBESONLYONE OFWHICHNAMELY THEMAINBEAM ISDESIREDINREALSPACE)TISCONVENIENTTOPLOTTHE POSITIONOFTHEGRATINGLOBESWHENTHEBEAMISPHASEDFORBROADSIDEANDOBSERVETHE MOTIONOFTHESELOBESASTHEBEAMISSCANNED&IGURESHOWSTHEGRATING LOBE LOCATIONSFORBOTHRECTANGULARANDTRIANGULARSPACING&ORARECTANGULARARRAY THEGRAT INGLOBESARELOCATEDAT COS A XS COS A X o
L P DX
L Q DY P Q
COS A YS COS A Y o
4HELOBEATP Q ISTHEMAINBEAM!TRIANGULARGRIDISMOREEFFICIENTFOR SUPPRESSINGGRATINGLOBESTHANARECTANGULARGRID SOTHATFORAGIVENAPERTURESIZE
£Î°£n
2!$!2(!.$"//+
&)'52% 'RATING LOBE POSITIONS FOR A RECTANGULAR AND B TRIANGULAR GRIDS SHOWINGTHEMOTIONOFTHELOBESASTHEBEAMISSCANNEDATANGLEP
FEWERELEMENTSAREREQUIRED)FTHETRIANGULARLATTICECONTAINSELEMENTSATMDX NDY WHEREM NISEVEN THEGRATINGLOBESARELOCATEDAT COS A XS COS A X o
L P DX
COS A YS COS A Y o
L Q DY
WHEREP QISEVEN
0(!3%$!22!92!$!2!.4%..!3
£Î°£
"ECAUSE ONLY ONE MAIN BEAM IS NORMALLY DESIRED IN REAL SPACE AN APPROPRIATE DESIGNWILLPLACEALLBUTONEMAXIMUMINIMAGINARYSPACEFORALLANGLESOFSCAN7ITH SCANNING LOBESTHATWEREORIGINALLYINIMAGINARYSPACEMAYMOVEINTOREALSPACEIF THEELEMENTSPACINGISGREATERTHANK!STHEARRAYISSCANNEDAWAYFROMBROADSIDE EACHGRATINGLOBEINSINPSPACE WILLMOVEADISTANCEEQUALTOTHESINEOFTHEANGLEOF SCANANDINADIRECTIONDETERMINEDBYTHEPLANEOFSCAN4OENSURETHATNOGRATINGLOBES ENTERREALSPACE THEELEMENTSPACINGMUSTBECHOSENSOTHATFORTHEMAXIMUMSCAN ANGLEPM THEMOVEMENTOFAGRATINGLOBEBYSINPMDOESNOTBRINGTHEGRATINGLOBEINTO REALSPACE)FASCANANGLEOFnFROMBROADSIDEISREQUIREDFOREVERYPLANEOFSCAN NOGRATINGLOBESMAYEXISTWITHINACIRCLEOFRADIUS SINPM 4HESQUAREGRID THATMEETSTHISREQUIREMENTHAS
L L OR D X D Y L DX DY
(ERE THEAREAPERELEMENTIS D X D Y L L
&ORANEQUILATERAL TRIANGULARARRAY THEREQUIREMENTISSATISFIEDBY
L DY
L OR D Y L D X L DX
"ECAUSEELEMENTSARELOCATEDONLYATEVERYOTHERVALUEOFMN THEAREAPERELEMENTIS
D X D Y L L L
&OR THE SAME AMOUNT OF GRATING LOBE SUPPRESSION THE SQUARE GEOMETRY REQUIRES APPROXIMATELYMOREELEMENTS %LEMENT 0HASING#ALCULATIONS !COMPUTERISUSUALLYREQUIREDTOPERFORMTHE STEERINGCOMPUTATIONSFORAPHASEDARRAYANTENNA)TCANCOMPENSATEFORMANYOFTHE KNOWNPHASEERRORSCAUSEDBYTHEMICROWAVECOMPONENTS THEOPERATINGENVIRON MENT ANDTHEPHYSICALPLACEMENTOFTHEELEMENTS&OREXAMPLE IFTHEINSERTIONAND DIFFERENTIALPHASEVARIATIONSWHICHMAYOCCURFROMPHASESHIFTERTOPHASESHIFTER AREKNOWN THEYMAYBETAKENINTOACCOUNTINTHECOMPUTATIONS+NOWNTEMPERATURE VARIATIONSACROSSTHEARRAYTHATWOULDINDUCEPHASEERRORSMAYBECOMPENSATEDFOR &INALLY MANYFEEDSEG OPTICALANDSERIESFEEDS DONOTPROVIDEEQUALPHASEEXCITA TIONATTHEINPUTTOEACHPHASESHIFTER4HERELATIVEPHASEEXCITATIONCAUSEDBYTHESE FEEDSISAKNOWNFUNCTIONOFFREQUENCY)NTHESECASES THECOMPUTERMUSTPROVIDE ACORRECTIONBASEDONTHELOCATIONOFTHEELEMENTINTHEARRAYANDONTHEFREQUENCY OFOPERATION &OR A LARGE ARRAY WITH THOUSANDS OF ELEMENTS MANY CALCULATIONS ARE REQUIRED TO DETERMINE THE PHASING OF THE ELEMENTS 4HESE CALCULATIONS MUST BE PERFORMED IN A SHORTPERIODOFTIME4HEUSEOFTHEORTHOGONALPHASECOMMANDSM4XS N4YSHELPSTO MINIMIZETHESECALCULATIONS/NCETHEELEMENT TO ELEMENTPHASEINCREMENTS4XS 4YS HAVEBEENCOMPUTEDFORAGIVENBEAM POINTINGDIRECTION THEINTEGRALMULTIPLESOF4YS MAYBEUSEDTOSTEERTHECOLUMNS&IGURE
£Î°Óä
2!$!2(!.$"//+
£Î°{Ê * ,/1, Ê / ÊÊ Ê 1/1 Ê "1* Ê{x 3IGNIFICANCEOF!PERTURE-ATCHING !NANTENNAISADEVICETHATACTSASATRANS FORMER TO PROVIDE A GOOD MATCH BETWEEN A SOURCE OF POWER AND FREE SPACE )F THE ANTENNAISNOTMATCHEDTOFREESPACE POWERWILLBEREFLECTEDBACKTOWARDTHEGENERA TOR RESULTINGINALOSSINRADIATEDPOWER)NADDITION AMISMATCHPRODUCESSTANDING WAVESONTHEFEEDLINETOTHEANTENNA4HEVOLTAGEATTHEPEAKSOFTHESESTANDINGWAVES IS \'\ TIMESGREATERTHANTHEVOLTAGEOFAMATCHEDLINE WHERE'ISTHEVOLTAGE REFLECTIONCOEFFICIENT4HISCORRESPONDSTOANINCREASEDPOWERLEVELTHATIS \'\ TIMESASGREATASTHEACTUALINCIDENTPOWER4HEREFORE WHILETHEANTENNAISRADIATING LESSPOWER INDIVIDUALCOMPONENTSMUSTBEDESIGNEDTOHANDLEMOREPEAKPOWER7ITH ANTENNASTHATDONOTSCAN THEMISMATCHMAYOFTENBETUNEDOUTBYCONVENTIONALTECH NIQUES PREFERABLYATAPOINTASCLOSETOTHESOURCEOFTHEMISMATCHASPOSSIBLE )N A SCANNING ARRAY THE IMPEDANCE OF A RADIATING ELEMENT VARIES AS THE ARRAY IS SCANNED ANDTHEMATCHINGPROBLEMISCONSIDERABLYMORECOMPLICATED5NLIKEACONVEN TIONALANTENNA WHEREMISMATCHAFFECTSONLYTHELEVELOFTHEPOWERRADIATEDANDNOTTHE SHAPEOFTHEPATTERN SPURIOUSLOBESINTHESCANNINGARRAYMAYAPPEARASACONSEQUENCE OFTHEMISMATCH&URTHER THEREARECONDITIONSWHEREANANTENNATHATISWELLMATCHEDAT BROADSIDEMAYHAVESOMEANGLEOFSCANATWHICHMOSTOFTHEPOWERISREFLECTED 4HEVARIATIONINELEMENTIMPEDANCEANDELEMENTPATTERNISAMANIFESTATIONOFTHE MUTUALCOUPLINGBETWEENRADIATINGELEMENTSTHATAREINCLOSEPROXIMITYTOONEANOTHER &ORAPRACTICALDESIGN TWOEMPIRICALTECHNIQUESAREOFGREATVALUE 7AVEGUIDESIMULATORSPROVIDEAMEANSFORDETERMININGTHEELEMENTIMPEDANCE INANINFINITEARRAYWITHTHEUSEOFONLYAFEWELEMENTS4HEEFFECTIVENESSOFA MATCHINGSTRUCTUREBASEDONTHESEMEASUREMENTSMAYALSOBEDETERMINEDINTHE SIMULATOR !SMALLARRAYISTHEBESTTECHNIQUEFORDETERMININGTHEACTIVEELEMENTPATTERN4HE ACTIVEELEMENTPATTERN OBTAINEDBYEXCITINGONEELEMENTANDTERMINATINGITSNEIGH BORS ISTHEBESTOVERALLMEASUREOFARRAYPERFORMANCEOTHERTHANTHEFULLARRAYITSELF )FALARGEREFLECTIONOCCURSATSOMEANGLEOFSCAN ITCANBERECOGNIZEDBYANULLIN THEELEMENTPATTERN4HESMALLARRAYCANALSOPROVIDEDATAONTHECOUPLINGBETWEEN ELEMENTS4HISDATACANBEUSEDTOCALCULATETHEVARIATIONINIMPEDANCEASTHEARRAY ISSCANNED "OTHTHESETECHNIQUESWILLBEDISCUSSEDLATERINTHISSECTION %FFECTSOF-UTUAL#OUPLING 7HENTWOANTENNASORELEMENTS AREWIDELYSEPA RATED THEENERGYCOUPLEDBETWEENTHEMISSMALLANDTHEINFLUENCEOFONEANTENNAON THECURRENTEXCITATIONANDPATTERNOFTHEOTHERANTENNAISNEGLIGIBLE!STHEANTENNAS AREBROUGHTCLOSERTOGETHER THECOUPLINGBETWEENTHEMINCREASES)NGENERAL THEMAG NITUDEOFTHECOUPLINGISINFLUENCEDBYTHEDISTANCEBETWEENTHEELEMENTS THEPATTERN OF THE ELEMENTS AND THE STRUCTURE IN THE VICINITY OF THE ELEMENTS &OR EXAMPLE THE RADIATIONPATTERNOFADIPOLEHASANULLINTHEP onDIRECTIONANDISOMNIDIRECTIONAL INTHEP nPLANE4HEREFORE ITCANBEEXPECTEDTHATDIPOLESINLINEWILLBELOOSELY COUPLEDANDPARALLELDIPOLESWILLBETIGHTLYCOUPLED7HENANELEMENTISPLACEDINAN ARRAYOFMANYELEMENTS THEEFFECTSOFCOUPLINGARESUFFICIENTLYSTRONGTHATTHEPATTERN ANDIMPEDANCEOFTHEELEMENTSINTHEARRAYAREDRASTICALLYALTERED
0(!3%$!22!92!$!2!.4%..!3
£Î°Ó£
4HE TERMS ACTIVE ELEMENT PATTERN AND ELEMENT IMPEDANCE REFER TO AN ELEMENT IN ITSOPERATINGENVIRONMENTIE INANARRAYWITHITSNEIGHBORINGELEMENTSEXCITED )N THE ARRAY EACH EXCITED ELEMENT COUPLES TO EVERY OTHER ELEMENT4HE COUPLING FROM SEVERALELEMENTSTOATYPICALCENTRALELEMENT ELEMENT ISSHOWNIN&IGURE 4HE#MN PQAREMUTUAL COUPLINGCOEFFICIENTSRELATINGTHEVOLTAGEAMPLITUDEANDPHASE INDUCEDINTHEMNTHELEMENTTOTHEVOLTAGEEXCITATIONATTHEPQTHELEMENT4HECOUPLED SIGNALSADDVECTORIALLYTOPRODUCEAWAVETRAVELINGTOWARDTHEGENERATOROFELEMENT THATAPPEARSTOBEAREFLECTIONFROMTHERADIATOROFELEMENT!STHEPHASESOF THENEIGHBORINGELEMENTSAREVARIEDTOSCANTHEBEAM THEVECTORSUMOFTHECOUPLED SIGNALSCHANGESANDCAUSESANAPPARENTCHANGEINTHEIMPEDANCEOFELEMENT&OR SOMESCANANGLES THECOUPLEDVOLTAGESTENDTOADDINPHASE CAUSINGALARGEREFLECTION ANDPOSSIBLYTHELOSSOFTHEMAINBEAM,ARGEREFLECTIONSOFTENOCCURATSCANANGLES JUSTPRIORTOTHEEMERGENCEOFAGRATINGLOBEINTOREALSPACE BUTINSOMEINSTANCESSUCH REFLECTIONSMAYOCCURATSMALLERSCANANGLES 4HEDESCRIPTIONOFTHEIMPEDANCEVARIATIONGIVENABOVEMADENOREFERENCETOTHE FEEDNETWORKORTHEPHASESHIFTERSANDASSUMEDTHATTHEONLYCOUPLINGBETWEENELE MENTSISVIATHERADIATINGAPERTURE4HECOUPLINGCOEFFICIENTSWOULDBEMEASURED AND BY SUPERPOSITION THE PHASED VOLTAGE CONTRIBUTIONS FROM EVERY ELEMENT IN THE ARRAY ORATLEASTTHOSEINTHEIMMEDIATEVICINITY WOULDBEADDEDVECTORIALLYTOPRODUCE THEVOLTAGEREFLECTEDBACKTOWARDTHEGENERATOR)NAPRACTICALARRAY THEIMPEDANCE VARIATIONDEPENDSUPONTHEFEEDSYSTEMANDTHEPHASESHIFTER)FTHESEARETAKENINTO ACCOUNT THEIMPEDANCEVARIATIONMAYBEDIFFERENTFROMWHATTHEABOVEMODELMIGHT PREDICT)NMOSTANALYSES ONLYTHECOUPLINGATTHEAPERTUREISCONSIDERED4HISDESCRIP TIONPROVIDESINSIGHTINTOTHEINTRINSICIMPEDANCEVARIATIONOFTHEAPERTUREWHENITIS ISOLATEDFROMOTHEREFFECTS ASINTHECASEWHEREEACHELEMENTHASANINDEPENDENTFEED EG ITSOWNGENERATORANDISOLATOR )NTHISCASEIT ISASIMPLEMATTERTOMEASURETHE VOLTAGE STANDING WAVERATIO6372 INANYLINEANDDETERMINEEXACTLYTHEEXTENTOF THEIMPEDANCEANDMISMATCHVARIATION&ORMANYFEEDSYSTEMS THISISNOTPOSSIBLE ANDAMEASUREMENTOFTHEREFLECTEDENERGYWILLPROVIDEERRONEOUSINFORMATIONANDA
&)'52% #OUPLEDSIGNALSTOACENTRALELEMENTFROMNEIGHBORINGELEMENTS
£Î°ÓÓ
2!$!2(!.$"//+
FALSESENSEOFSECURITY5NLESSALLTHEREFLECTIONSARECOLLIMATEDBACKATSOMECENTRAL POINTORINDEPENDENTFEEDSAREUSED SOMEOFTHEREFLECTEDENERGYWILLGENERALLYBE RE REFLECTEDANDCONTRIBUTETOUNDESIRABLESIDELOBES &ORLARGEARRAYS THEIMPEDANCEOFANELEMENTLOCATEDNEARTHECENTEROFTHEARRAY ISOFTENTAKENASTYPICALOFTHEIMPEDANCEOFEVERYELEMENTINTHEARRAY!SMIGHT BEEXPECTED THISELEMENTISMOSTSTRONGLYINFLUENCEDBYELEMENTSINITSIMMEDIATE VICINITY7HENTHEARRAYISSCANNED THEINFLUENCEOFELEMENTSSEVERALWAVELENGTHS DISTANTISALSOSIGNIFICANT&ORDIPOLESABOVEAGROUNDPLANE THEMAGNITUDEOFTHE COUPLINGBETWEENELEMENTSDECAYSRAPIDLYWITHDISTANCE&ORAREASONABLEINDICATION OFARRAYPERFORMANCE ANELEMENTINTHECENTEROFA BY ARRAYMAYBETAKENAS TYPICALOFANELEMENTINALARGEARRAY&ORDIPOLESWITHNOGROUNDPLANETHECOUPLING BETWEENELEMENTSDOESNOTDECAYSORAPIDLY ANDA BY ARRAYAPPEARSREASONABLE &ORANARRAYOFOPEN ENDEDWAVEGUIDES A BY ARRAYSHOULDSUFFICE)FACCURATE PREDICTION OF THE ARRAY PERFORMANCE IS REQUIRED MANY MORE ELEMENTS ARE NEEDED THANAREINDICATEDABOVE )TISOFTENCONVENIENTTOASSUMETHATTHEARRAYISINFINITEINEXTENTANDHASAUNIFORM AMPLITUDEDISTRIBUTIONANDALINEAR PHASETAPERFROMELEMENTTOELEMENT)NTHISMAN NER EVERYELEMENTINTHEARRAYSEESEXACTLYTHESAMEENVIRONMENT ANDTHECALCULATIONS FORANYELEMENTAPPLYEQUALLYTOALL4HESEASSUMPTIONSPROVIDEASIGNIFICANTSIMPLIFI CATIONINTHECALCULATIONOFTHEELEMENTIMPEDANCEVARIATIONS)NADDITION IMPEDANCE MEASUREMENTSMADEINSIMULATORSCORRESPONDTOTHEELEMENTIMPEDANCEINANINFINITE ARRAY)NSPITEOFTHEASSUMPTIONS THEINFINITE ARRAYMODELHASPREDICTEDWITHGOOD ACCURACY THE ARRAY IMPEDANCE AND THE IMPEDANCE VARIATIONS %VEN ARRAYS OF MOD ESTPROPORTIONSLESSTHANELEMENTS HAVEBEENINREASONABLEAGREEMENTWITHTHE RESULTSPREDICTEDFORANINFINITEARRAY %LEMENT0ATTERN &ROMENERGYCONSIDERATIONS THEDIRECTIONALGAINOFAPERFECTLY MATCHEDARRAYWITHCONSTANTAMPLITUDEDISTRIBUTIONG WILLVARYASTHEPROJECTED APERTUREAREAFROM%Q
' P
P ! COS P L
)FITISASSUMEDTHATEACHOFTHE.ELEMENTSINTHEARRAYSHARESTHEGAINEQUALLY THE GAINOFASINGLEELEMENTISFROM%Q
'E P
P ! COS P .L
)FTHEELEMENTISMISMATCHED HAVINGAREFLECTIONCOEFFICIENT'P E THATVARIESAS AFUNCTIONOFSCANANGLE THEELEMENTGAINPATTERNISREDUCEDTO
'E P
P ! COS P ; \ ' Q F \ = .L
4HE ELEMENT PATTERN IS SEEN TO CONTAIN INFORMATION PERTAINING TO THE ELEMENT IMPEDANCEn4HEDIFFERENCEBETWEENTHETOTALPOWERRADIATEDINTHEELEMENTPAT TERNANDTHEPOWERDELIVEREDTOTHEANTENNATERMINALSMUSTEQUALTHEREFLECTEDPOWER )N TERMS OF THE RADIATION PATTERN OF THE SCANNING ARRAY THIS MEANS THAT SINCE THE SCANNED ANTENNA PATTERNS TRACE OUT THE ELEMENT PATTERN IT FOLLOWS THAT THE AVERAGE POWER LOST FROM THE SCANNED PATTERN IS EQUAL TO THE POWER LOST FROM THE ELEMENT
0(!3%$!22!92!$!2!.4%..!3
£Î°ÓÎ
PATTERN BECAUSE OF REFLECTIONS )T IS NOT ENOUGH TO MATCH ONE ELEMENT IN THE PRES ENCEOFALLITSTERMINATEDNEIGHBORS4HEELEMENTWILLDELIVERPOWERTOITSNEIGHBORS AND THIS LOSS IN POWER CORRESPONDS TO THE AVERAGE POWER LOST WHEN SCANNING!N IDEAL ALTHOUGHNOTNECESSARILYREALIZABLEELEMENTPATTERN WOULDPLACEALLTHERADIATED POWERINTOTHESCANREGION GIVINGAPATTERNLIKEACOSINEONAPEDESTALANDTHEREBY PROVIDINGMAXIMUMANTENNAGAINFORTHENUMBEROFELEMENTSUSED 4HINNED!RRAYS 4HENUMBEROFRADIATINGELEMENTSINANARRAYMAYBEREDUCED TOAFRACTIONOFTHOSENEEDEDCOMPLETELYTOFILLTHEAPERTUREWITHOUTSUFFERINGSERIOUS DEGRADATIONINTHESHAPEOFTHEMAINBEAM(OWEVER AVERAGESIDELOBESAREDEGRADED INPROPORTIONTOTHENUMBEROFELEMENTSREMOVED4HEELEMENTDENSITYMAYBETHINNED SOASTOTAPERTHEAMPLITUDEDISTRIBUTIONEFFECTIVELY ANDTHESPACINGISSUCHTHATNO COHERENTADDITIONCANOCCURTOFORMGRATINGLOBES!THINNEDAPERTURE WHEREELEMENTS HAVE BEEN REMOVED RANDOMLY FROM A REGULAR GRID IS SHOWN IN &IGURE 4HE GAINISTHATDUETOTHEACTUALNUMBEROFELEMENTS.'EP BUTTHEBEAMWIDTHISTHAT
&)'52% A 4HINNED ARRAY WITH A ELEMENT GRID CONTAINING ELEMENTS B 0ATTERN FOR A THINNED ARRAY 3! IS THE AVERAGE SIDELOBE LEVEL AFTER 2%7ILLEYÚ)2%#OURTESYOF"ENDIX2ADIO
£Î°Ó{
2!$!2(!.$"//+
OFTHEFULLAPERTURE&OREXAMPLE IFTHEARRAYHASBEENTHINNEDSOTHATONLYOF THEELEMENTSAREUSED THEGAINOFTHEARRAYWILLDROPBYD"(OWEVER BECAUSETHE MAINBEAMISVIRTUALLYUNCHANGED ABOUTOFTHEPOWERISDELIVEREDTOTHESIDELOBE REGION4HINNEDARRAYSARESELDOMUSED )FTHEREMOVEDELEMENTSINAREGULARTHINNEDARRAY AREREPLACEDWITHELEMENTS WITHMATCHEDLOADS THEELEMENTPATTERNISIDENTICALTOTHATOFONEINTHEREGULARARRAY WITHALLELEMENTSEXCITED4HEELEMENTPATTERNISINDEPENDENTOFTHEARRAYEXCITATION ANDTHESAMEFRACTIONALAMOUNTOFPOWERWILLBELOSTBECAUSEOFMISMATCH WHETHER THE ARRAY IS THINNED TAPERED OR UNIFORMLY ILLUMINATED )T SHOULD BE NOTED THAT THE CONCEPTOFANELEMENTPATTERNTHATAPPLIESEQUALLYTOEVERYELEMENTISVALIDONLYWHEN ISOLATINGFEEDSAREUSEDANDEDGEEFFECTSAREIGNORED ! THINNED ARRAY MAY ALSO BE IMPLEMENTED WITH AN IRREGULAR ELEMENT SPACING ALTHOUGHTHISISNOTCOMMON)NTHISCASE THEELEMENTGAINANDIMPEDANCE WILLVARY FROMELEMENT DEPENDINGUPONTHEENVIRONMENTOFAGIVENELEMENT4OOBTAINTHEGAIN OFTHEARRAY ITISNECESSARYTOSUMALLTHEDIFFERENTELEMENTGAINS'ENP 4HUS
' P £ 'EN P N
)MPEDANCE6ARIATIONOF&REE3PACE )TISOFINTERESTTOEXAMINETHECASEOFA LARGECONTINUOUSAPERTURETHATMAYBECONSIDEREDTOBETHELIMITINGCASEOFANARRAY OF MANY VERY SMALL ELEMENTS 4HE FREE SPACE IMPEDANCE %( VARIES AS COS P FOR SCANNINGINTHE%PLANEANDASSECPFORSCANNINGINTHE(PLANE4HEIMPEDANCEOF A MEDIUM IS THUS DEPENDENT UPON THE DIRECTION OF PROPAGATION AND THE IMPEDANCE VARIATION OF A SCANNING APERTURE IS A NATURAL CONSEQUENCE OF THIS DEPENDENCE 4HE CONTINUOUSAPERTUREAPPEARSTOREPRESENTALOWERLIMITTOTHEIMPEDANCEVARIATIONWITH SCANNING4HISISINDICATEDBY!LLENSRESULTSWHEREIMPEDANCEVARIATIONWITHSCAN NINGWASCALCULATEDFORDIPOLESABOVEAGROUNDPLANE)NSPITEOFINCREASEDMUTUALCOU PLING ORPERHAPSBECAUSEOFIT THEMORECLOSELYTHEDIPOLESWERESPACED THESMALLER THEIMPEDANCEVARIATIONWITHSCANNING!LTHOUGHTHEIMPEDANCEVARIATIONDECREASED THEABSOLUTEIMPEDANCEOFTHEDIPOLESALSODECREASED MAKINGTHEMMOREDIFFICULTTO MATCHATBROADSIDE)TISEXPECTEDTHATTOOBTAINANIMPEDANCEVARIATIONSMALLERTHAN THATOFFREESPACESOMEIMPEDANCECOMPENSATIONMUSTBEEMPLOYED -UTUAL#OUPLINGAND3URFACE7AVES 4HEMUTUALCOUPLINGBETWEENTWOSMALL ISOLATEDDIPOLESSHOULDDECREASEASRINTHE(PLANEANDRINTHE%PLANE%AND (PLANESAREINTERCHANGEDFORSLOTS #OUPLINGMEASUREMENTSHAVESHOWNTHATINTHE ARRAYENVIRONMENTTHERATEOFDECAYISSLIGHTLYGREATERTHANPREDICTEDABOVE INDICATING THATSOMEOFTHEENERGYISDELIVEREDTOOTHERELEMENTSINTHEARRAYANDMAYBEDIS SIPATEDANDRERADIATEDFROMTHESEELEMENTS4HESAMEMEASUREMENTSHAVESHOWNTHAT THEPHASEDIFFERENCEOFTHEENERGYCOUPLEDTOELEMENTSISDIRECTLYPROPORTIONALTOTHEIR DISTANCEFROMTHEEXCITEDELEMENTS INDICATIVEOFASURFACEWAVETRAVELINGALONGTHE ARRAY LEAKINGENERGYTOEACHOFTHEELEMENTS&ORBESTPERFORMANCE THEVELOCITYOF THESURFACEWAVESHOULDBEVERYCLOSETOTHATOFFREESPACE)FTHEARRAYCONTAINSWAVE GUIDESORHORNSLOADEDWITHDIELECTRIC THEVELOCITYWILLDECREASESLIGHTLY&URTHER IF THEDIELECTRICPROTRUDESFROMTHERADIATORSORIFADIELECTRICSHEETISUSEDINFRONTOFTHE ARRAY THEVELOCITYOFTHESURFACEWAVEMAYDECREASEDRAMATICALLY4HISSURFACEWAVE ISIMPORTANTBECAUSEITCANCAUSEALARGEREFLECTIONANDANACCOMPANYINGLOSSOFTHE BEAM FORSOMEANGLESOFSCAN4HISCANBESTBESEENBYEXAMININGTHECONDITIONOF
0(!3%$!22!92!$!2!.4%..!3
£Î°Óx
PHASINGFORWHICHTHECOUPLINGSFROMMANYELEMENTSWILLADDIN PHASETOCAUSEALARGE REFLECTIONINATYPICALELEMENT #ONSIDERANARRAYINWHICHTHEVELOCITYOFTHESURFACEWAVEISTHATOFFREESPACE 4HEDIFFERENCEINTHEPHASEOFTHEVOLTAGESCOUPLEDFROMANADJACENTPAIROFELEMENTS TOELEMENTEIN&IGURE ISRELATEDTOTHESCANANGLEBY
P S P S P S SIN P SIN P L L L 4HECOUPLINGSWILLBEINPHASEWHEN$X OORWHEN
S
L SIN P
4HISISSEENTOBEEXACTLYTHESAMECONDITIONSASPREVIOUSLYDETERMINEDFORTHEEMER GENCEOFAGRATINGLOBEINTOREALSPACE4HEREFORE ITMAYBEEXPECTEDTHATWHENAGRAT INGLOBEISABOUTTOEMERGEINTOREALSPACE THECOUPLEDVOLTAGESTENDTOADDINPHASE ANDCAUSEALARGEMISMATCH !RRAY3IMULATORS !GOODDEALOFEFFORTHASGONEINTOMATCHINGARADIATORIN THEPRESENCEOFANARRAYOFRADIATORS4HEUSEOFWAVEGUIDESIMULATORSASDEVELOPED BY 7HEELER ,ABORATORIES HAS MADE IT POSSIBLE TO DETERMINE THE MATCHING STRUCTURE EXPERIMENTALLYWITHOUTNEEDINGTOBUILDANARRAY!WAVEGUIDE OPERATINGINA4% MODE MAYBECONSIDEREDTOCONTAINTWOINCLINEDnPLANEWAVESPROPAGATINGDOWNTHE GUIDE4HEANGLETHATEACHOFTHEPLANEWAVESMAKESWITHTHELONGITUDINALDIRECTION &IGURE ISDETERMINEDBYTHE(DIMENSIONOFTHEWAVEGUIDEANDSIMULATESTHE ANGLEOFSCANOFANINFINITEARRAY
SIN Q
L LC
WHERE P SCANANGLE
K FREE SPACEWAVELENGTH
KC CUTOFFWAVELENGTHOFGUIDE
&)'52% 4WOADJACENTELEMENTSCOUPLINGTO ANOTHERELEMENTINTHESAMEROW
£Î°ÓÈ
2!$!2(!.$"//+
&)'52% !RRAYSIMULATORTERMINATEDWITHTWODUMMYELEMENTS
!DDITIONALSCANANGLESMAYBESIMULATEDBYEXCITINGOTHERMODES4HEWAVEGUIDE DIMENSIONSARECHOSENSOTHATARADIATINGELEMENTORELEMENTPLACEDINTHEWAVEGUIDE SEESMIRRORIMAGESINTHEWALLSOFTHEWAVEGUIDETHATAPPEARTOBEATTHESAMESPACING ASTHEARRAYTOBESIMULATED"OTHRECTANGULARANDTRIANGULARARRAYSMAYBESIMULATED ASSHOWNIN&IGURE4HEIMPEDANCEMEASUREMENTSAREMADEBYLOOKINGINTO A WAVEGUIDE SIMULATOR THAT IS TERMINATED WITH DUMMY ELEMENTS4HIS IS EQUIVALENT TOLOOKINGATANINFINITEARRAYFROMFREESPACEATASCANANGLEGIVENBY%Q! MATCHINGSTRUCTURE DESIGNEDFROMTHESIMULATORIMPEDANCEDATA MAYBEPLACEDINTO THESIMULATORTOMEASUREITSEFFECTIVENESS3EVERALSIMULATORDESIGNS RESULTS ANDA COMPLETEDISCUSSIONOFTHETOPICHAVEBEENPRESENTEDBY(ANNANAND"ALFOUR4HE TECHNIQUEISLIMITEDINTHATONLYDISCRETESCANANGLESCANBESIMULATED3EVERALSCAN ANGLESINBOTHPLANESOFSCANGIVEAGENERALIDEAOFTHEARRAYIMPEDANCE
&)'52% 2ECTANGULAR ANDTRIANGULAR ARRAYGEOMETRIES WITHSIMULATORBOUNDARIESSUPERIMPOSEDA SQUAREARRAYWITH SIMULATORSUPERIMPOSEDANDB TRIANGULARARRAYWITHSIMULATOR SUPERIMPOSED
0(!3%$!22!92!$!2!.4%..!3
£Î°ÓÇ
#OMPENSATIONFOR3CANNED)MPEDANCE6ARIATION 4HEIMPEDANCEOFANELE MENTINANARRAYHASBEENDISCUSSEDANDHASBEENSHOWNTOVARYASTHEARRAYISSCANNED !NARRAYTHATISMATCHEDATBROADSIDECANBEEXPECTEDTOHAVEATLEASTA6372AT AnANGLEOFSCAN4OCOMPENSATEFORTHEIMPEDANCEVARIATION ITISNECESSARYTOHAVE ACOMPENSATIONNETWORKTHATISALSODEPENDENTONSCANNING 3MALL !RRAYS 4HE ELEMENT PATTERN IS THE BEST SINGLE INDICATOR OF IMPEDANCE MATCHINGINASCANNINGARRAY/NEWAYOFDETERMININGTHEELEMENTPATTERNISTOBUILD ASMALLARRAY!CENTRALELEMENTISEXCITED ANDALLOTHERELEMENTSARETERMINATED4HE PATTERNOFTHISCENTRALELEMENTISTHEACTIVEELEMENTPATTERN$IAMONDHASEXAMINED THENUMBEROFELEMENTSREQUIREDINASMALLARRAYTOPROVIDEAREASONABLEAPPROXIMA TIONTOANELEMENTINANINFINITEARRAY(ECONCLUDESTHATTOELEMENTSAREREQUIRED TOPROVIDEAGOODINDICATION&IGURESHOWSTHECHANGEINTHEMEASUREDACTIVE ELEMENTPATTERNASTHENUMBEROFELEMENTSISINCREASED&ORA ELEMENTARRAY THE NULLISVERYPRONOUNCED%VENFORTHE ELEMENTARRAY ITISCLEARTHATTHEGAINVARIA TIONWITHSCANNINGISDRAMATICALLYGREATERTHANCOSP 4HESMALLARRAYCANALSOBEUSEDTOMEASURECOUPLINGCOEFFICIENTSASDEMONSTRATED BY&IGURE4HESECOUPLINGCOEFFICIENTSCANBEUSEDTOCALCULATETHEIMPEDANCE VARIATIONASTHEARRAYISSCANNED'ROVE -ARTIN AND0EPEHAVENOTEDTHATFORTHEELE MENTTOBEMATCHEDINITSOPERATINGENVIRONMENTTHESELF COUPLINGMUSTEXACTLYCANCEL THECOUPLINGFROMALLOTHERELEMENTS4HEYHAVEUSEDTHISTECHNIQUETOPROVIDEAGOOD MATCHONANULTRALOW SIDELOBEWIDEBANDPHASEDARRAY 4HE COMBINATION OF WAVEGUIDE SIMULATORS AND SMALL ARRAYS PROVIDES POWERFUL EMPIRICALTOOLSTOSUPPLEMENTTHEANALYTICALTECHNIQUES%XPERIENCEHASDEMONSTRATED THATALARGEANTENNASHOULDNOTBEBUILTUNTILTHEELEMENTPATTERNHASBEENVERIFIEDWITH ASMALLARRAY
&)'52% %XPERIMENTAL ( PLANE PATTERNS OF THE CENTER ELEMENTS OF WAVEGUIDES ARRAYS AFTER",$IAMONDÚ!RTECH(OUSE
£Î°Ón
2!$!2(!.$"//+
£Î°xÊ "7- " Ê*- Ê,,9,OWSIDELOBESHAVELONGBEENOFINTERESTTOANTENNADESIGNERS4HISINTERESTHASBEEN HEIGHTENEDBYTHEJAMMINGTHATTHREATENSMOSTMILITARYRADARS4HEREQUIREMENTFOR LOWSIDELOBESFORCLUTTERREJECTIONINTHE!7!#3RADARRESULTEDINTECHNOLOGYTHATNOW SUPPORTSSIDELOBELEVELSOFMORETHAND"BELOWTHEMAIN BEAMPEAK 4HEPRICE THATMUSTBEPAIDTOACHIEVETHESELOWSIDELOBESINCLUDES AREDUCTIONINGAIN AN INCREASEINBEAMWIDTH INCREASEDTOLERANCECONTROL INCREASEDCOST AND THE NEEDTOOPERATEINANENVIRONMENTFREEFROMOBSTRUCTIONSTHATCANREADILYINCREASETHE SIDELOBES)NSPITEOFTHESEDRAWBACKS THETRENDTOLOW SIDELOBEANTENNASHASACCEL ERATEDSINCELOWSIDELOBESPROVIDEACOUNTERTOELECTRONICCOUNTERMEASURES%#- !NTENNASIDELOBESCANBECONTROLLEDBYTHEAPERTUREAMPLITUDEDISTRIBUTION&OR PHASED ARRAYS THE AMPLITUDE OF EACH ELEMENT MAY BE CONTROLLED INDIVIDUALLY AND THEREFORE GOODSIDELOBECONTROLCANBEACHIEVED4HEPROCESSOFDESIGNINGALOW SIDELOBEANTENNACANBECONSIDEREDINTWOPARTS #HOOSETHECORRECTILLUMINATIONFUNCTIONTOACHIEVETHEDESIREDDESIGNERROR FREE SIDELOBES #ONTROLTHEPHASEANDAMPLITUDEERRORSTHATCONTRIBUTETOTHERANDOMSIDELOBES /F THE TWO CONTROLLING ERRORS FUNDAMENTALLY LIMITS SIDELOBE PERFORMANCE 4HE EFFECTSOFILLUMINATIONFUNCTIONANDERRORSAREDISCUSSEDBELOW )LLUMINATION &UNCTIONS 4HE RELATION BETWEEN APERTURE ILLUMINATION AND THE FAR FIELD PATTERN HAS BEEN STUDIED EXTENSIVELY AND IS WELL DOCUMENTED IN THE LITERA TUREn&ORACONTINUOUSAPERTURE THEFAR FIELDPATTERNISTHE&OURIERTRANSFORMOF THEDISTRIBUTIONACROSSTHEAPERTURE&ORANARRAY SAMPLESARETAKENOFTHECONTINUOUS DISTRIBUTIONATEACHOFTHEDISCRETELOCATIONS3OMETYPICALILLUMINATIONFUNCTIONSARE GIVENIN4ABLE)TISSEENTHATUNIFORMILLUMINATIONCONSTANTAMPLITUDE RESULTS INTHEHIGHESTGAINANDTHENARROWESTBEAMWIDTHBUTATTHECOSTOFHIGHSIDELOBES!S THEAMPLITUDEISTAPERED THEGAINDROPS THEBEAMBROADENS ANDTHESIDELOBESMAY BEREDUCED)TISIMPORTANTFORTHEANTENNADESIGNERTOCHOOSEANEFFICIENTANDREALIZ ABLEILLUMINATIONFUNCTIONTHATPROVIDESLOWSIDELOBESATAMINIMUMLOSSINGAIN&OR LOW SIDELOBERADARS THE4AYLORILLUMINATION FORTHESUMPATTERNSANDTHE"AYLISS ILLUMINATIONFORTHEDIFFERENCEPATTERNSHAVEALMOSTBECOMEANINDUSTRYSTANDARD 4HE4AYLORILLUMINATIONISSOMEWHATSIMILARTOACOSINESQUAREDONAPEDESTALAND ISREADILYIMPLEMENTED4HE"AYLISSILLUMINATIONISADERIVATIVEFORMOFTHE4AYLOR ILLUMINATIONANDISALSOREADILYIMPLEMENTED)TSHOULDBENOTEDTHATINMANYPHASED ARRAYSTHESIDELOBEPERFORMANCEFORTHEDIFFERENCEPATTERNISCOMPARABLETOTHATOFTHE SUMPATTERN&ORBOTHSUMANDDIFFERENCEPATTERNS THESIDELOBESAREREFERENCEDTOTHE PEAKOFTHESUMPATTERN4HEBEAMWIDTHFACTORPROVIDESTHEBEAMWIDTH INDEGREES OF ANAPERTUREWITHLENGTHA &IGUREGIVESTHEAPPROXIMATELOSSINGAINANDTHEBEAMWIDTHFACTORFORTHE 4AYLOR ILLUMINATION AS THE SIDELOBES CHANGE &OR A MORE COMPREHENSIVE TREATMENT SEE"ARTONAND7ARD4HESIDELOBESPREDICTEDBY4ABLEAREFORANTENNASTHAT HAVEPERFECTPHASEANDAMPLITUDEACROSSTHEAPERTURE4OALLOWFORERRORS APERTURE ILLUMINATIONSAREOFTENCHOSENTOPROVIDEPEAKSIDELOBESBELOWTHOSEREQUIRED&OR EXAMPLE IFTHEANTENNASPECIFICATIONCALLSFOR D"SIDELOBES A4AYLORILLUMINATION THATPROVIDES D"DESIGNSIDELOBESMIGHTBECHOSEN4HETERMINOLOGY N INDICATES THATTHEFIRSTNSIDELOBESAREHELDTOTHESPECIFIEDLEVEL
0(!3%$!22!92!$!2!.4%..!3
£Î°Ó
4!",% )LLUMINATION&UNCTIONS
)LLUMINATION&UNCTION
%FFICIENCY G
0EAK3IDELOBE D"
"EAMWIDTH &ACTOR K
,INEARILLUMINATIONFUNCTIONSBEAMWIDTH KKADEGREES A LENGTHOFANTENNA 5NIFORM #OSINE #OSINESQUARE(ANNING #OSINESQUAREDOND"PEDESTAL #OSINESQUAREOND"PEDESTAL (AMMING 4AYLOR N 4AYLOR N 4AYLOR N
#IRCULARILLUMINATIONFUNCTIONSBEAMWIDTH KK$DEGREES $ DIAMETEROFANTENNA 5NIFORM 4AYLOR N 4AYLOR N 4AYLOR N
)T SHOULD BE NOTED THAT FOR A RECTANGULAR ARRAY A DIFFERENT ILLUMINATION MAY BE CHOSEN FOR EACH PLANE4HIS IS APPROPRIATE IF THE SIDELOBE REQUIREMENTS IN EACH OF THEPLANESAREDIFFERENT4HERESULTANTLOSSINGAINISTHENTHESUMINDECIBELS OFTHE LOSSESINEACHPLANE
&)'52% 4AYLORILLUMINATIONLOSSANDBEAMWIDTHFACTOR
£Î°Îä
2!$!2(!.$"//+
%FFECTOF%RRORS 7HENERRORSOCCURINPHASEORAMPLITUDE ENERGYISREMOVED FROMTHEMAINBEAMANDDISTRIBUTEDTOTHESIDELOBES)FTHEERRORSAREPURELYRANDOM THEY CREATE RANDOM SIDELOBES THAT ARE CONSIDERED TO BE RADIATED WITH THE GAIN AND PATTERN OF THE ELEMENT7HEN THE ERRORS ARE CORRELATED THE SIDELOBE ENERGY WILL BE LUMPEDATDISCRETELOCATIONSINTHEFARFIELD4HECORRELATEDERRORSWILL THEREFORE PRO VIDEHIGHERSIDELOBES BUTONLYATALIMITEDNUMBEROFLOCATIONS"OTHCORRELATEDAND RANDOMSIDELOBESAREOFCONCERNTOANTENNADESIGNERS#ORRELATEDERRORSAREDISCUSSED IN3ECTION !NALYSES OF THE FAR FIELD EFFECT OF ERRORS ARE BASED ON THE FACT THAT ANTENNAS ARE LINEARDEVICES4HATIS THEFAR FIELDPATTERNISTHESUMOFTHEVOLTAGEAMPLITUDEAND PHASE OFEACHRADIATINGELEMENTINTHEANTENNA&ORTHISREASON THEFAR FIELDVOLTAGE PATTERNCANBECONSIDEREDTOBETHESUMOFTHEDESIGNPATTERNPLUSTHEPATTERNCREATED SOLELYBYTHEERRORS
%4 P F %DESIGN P F %ERROR P F
)N GENERAL THREE REGIONS WILL BE RECOGNIZED IN THE TOTAL RESULTANT PATTERN A LOW NOISEFLOORGENERATEDBYRANDOMERRORSTHATFOLLOWTHEELEMENTPATTERN AFEWPEAK SIDELOBESDUETOCORRELATEDERRORS ANDTHEMAINBEAMWITHITSSIDELOBESDUETOTHE DESIGNDISTRIBUTION 2ANDOM%RRORS !LLENAND2UZEHAVEMADEDETAILEDANALYSESOFTHEEFFECTS OFRANDOMERRORSONANTENNAS4HISDISCUSSIONWILLFOLLOWTHEANALYSISPERFORMEDBY !LLEN!S PREVIOUSLY MENTIONED AMPLITUDE AND PHASE ERRORS TAKE A FRACTION OF THE ENERGYFROMTHEMAINBEAMANDDISTRIBUTETHISENERGYTOTHESIDELOBES4HISFRACTION IS FORSMALLINDEPENDENTRANDOMERRORS
S 4 S F S !
WHERE RE RMSPHASEERROR RAD
R! RMSAMPLITUDEERROR VOLTSVOLT66 4HIS ENERGY IS RADIATED INTO THE FAR FIELD WITH THE GAIN OF THE ELEMENT PATTERN 4ODETERMINETHEMEAN SQUARED SIDELOBELEVEL-33, ITISNECESSARYTOCOMPARE THISENERGYWITHTHEPEAKOFTHEPATTERNOFANARRAYOF.ELEMENTSSOTHATTHEMEAN SQUARED SIDELOBELEVELIS
-33,
S 4
HA . S 4
.OTE THAT IN THE DENOMINATOR OF THIS EXPRESSION THE GAIN DUE TO THE ARRAY FACTOR .ISREDUCEDBYTHEAPERTUREEFFICIENCYGAANDBYTHEERRORPOWERLOSTFROMTHEMAIN BEAM S 4 !SANEXAMPLE CONSIDERANARRAYOFELEMENTSWITHANAPERTURE EFFICIENCYOF RA VV ANDRE RAD4HEN S 4
-33,
S 4 r D" H . S 4
4HERESULTISTHATTHISARRAYHASAMEANFLOOROFRANDOMSIDELOBESTHATONTHEAVERAGE ISD"BELOWTHEPEAKOFTHEBEAM)TALSOILLUSTRATESTHATTOACHIEVELOWSIDELOBES
0(!3%$!22!92!$!2!.4%..!3
£Î°Î£
VERYTIGHTTOLERANCESAREREQUIRED4HEAMPLITUDEOFVVISEQUIVALENTTOATOTAL AMPLITUDE STANDARD DEVIATION OF D" RMS4HE TOTAL RMS PHASE ERROR IS n )T SHOULDBENOTEDTHATTHEREARENUMEROUSSOURCESOFPHASEANDAMPLITUDEERRORSTHAT AREINDUCEDBYTHEPHASESHIFTERS THEFEEDNETWORK THERADIATINGELEMENTS ANDTHE MECHANICALSTRUCTURE4HETASKOFBUILDINGALOW SIDELOBEANTENNAISONEOFREDUCING EACHOFTHEAMPLITUDEERRORSTOAFEWTENTHSOFADECIBELANDTHEPHASEERRORSTOAFEW DEGREES4HEFEWERTHENUMBEROFELEMENTSUSED THETIGHTERTHETOLERANCEBECOMES 4HEINDIVIDUALEFFECTSOFPHASEANDAMPLITUDEERRORSANDFAILEDELEMENTSARESUM MARIZEDIN&IGURE4HERESULTANTRMSSIDELOBESAREREFERENCEDTOTHEGAINOFA SINGLEELEMENTSOTHATTHECURVECANBEUSEDFORANYNUMBEROFELEMENTSWITHINDEPEN DENTERRORS&OREXAMPLE AnRMSPHASEERRORWILLPRODUCEANRMSSIDELOBELEVELTHAT ISAPPROXIMATELYD"BELOWTHEGAINOFANELEMENT)FELEMENTSD" ARE USED THERMSSIDELOBELEVELISD"BELOWTHEGAINOFTHEARRAY4HISISTHEEFFECTOF ONLYTHERANDOMPHASEERRORS4HEEFFECTSDUETOAMPLITUDEERRORSANDFAILEDELEMENTS MUSTALSOBEINCLUDED 4HEPREVIOUSDISCUSSIONAPPLIESTOTHERMSSIDELOBELEVEL4HISANALYSISHASBEEN EXTENDEDBY!LLENTOAPPLYTHEPROBABILITYOFKEEPINGASINGLESIDELOBEBELOWAGIVEN
&)'52% 2ANDOMERRORSANDRMSSIDELOBES
£Î°ÎÓ
2!$!2(!.$"//+
LEVELANDTHENTHEPROBABILITYOFKEEPINGANUMBEROFSIDELOBESBELOWAGIVENLEVEL"Y IGNORINGTHEELEMENTPATTERN THE-33,INCLUDINGFAILEDELEMENTSISGIVENBY
-33,
0 S ! 0S F
HA 0.
WHERE 0 PROBABILITYOFAFAILEDELEMENT.OTETHATIF0 NOFAILEDELEMENTS THISEQUATIONBECOMES
-33,
S ! S F S 4 HA . HA .
4HISISTHESAMEAS%QEXCEPTFOR S 4 INTHEDENOMINATOR WHICHISNOT SIGNIFICANTFORLOW SIDELOBEANTENNAS&ORTHECASEINWHICHTHEDESIGNSIDELOBESARE WELLBELOWTHESIDELOBESCAUSEDBYERRORS !LLENHASDEVELOPEDTHESETOFCURVESSHOWN IN&IGURE!NEXAMPLEWILLILLUSTRATETHEUSEOFTHESECURVES)FYOUDESIRETOHOLD THESIDELOBEATAGIVENPOINTINSPACETOLESSTHAND"BELOWTHEPEAKOFTHEBEAM WITHAPROBABILITYOF DRAWAVERTICALLINEFROM D"ONTHEABSCISSAUNTILIT INTERSECTSTHECURVE&ROMTHISINTERSECTION DRAWAHORIZONTALLINEANDREADTHE VALUEOF-33, INTHISCASE D"4HEN
-33, D"
OR
-33, r
0 S ! 0S F
HA 0.
&)'52% 3IDELOBELEVELTOBEHELDWITHPROBABILITY0AFTER*,!LLEN
0(!3%$!22!92!$!2!.4%..!3
£Î°ÎÎ
&ORA ELEMENTARRAY
0 S ! 0S F
HA 0
&ORGA THISARRAYCANTOLERATE0 ORR! D" ORRE n.ATURALLY EACHTYPEOFERRORMUSTBEANTICIPATED ANDONEMUSTALLOWABUDGETFORFAILEDELE MENTS AMPLITUDEERRORS ANDPHASEERRORS &ORANUMBEROFINDEPENDENTSIDELOBES THEPROBABILITYTHATNSIDELOBESCANBEKEPT BELOWAGIVENLEVEL24ISEQUALTOTHEPRODUCTOFTHEPROBABILITIESTHATEACHSIDELOBE CANBEHELDBELOWTHISLEVEL N
0 ;N SIDELOBES 24 = 0 ; 2P I 24 =
2P I SIDELOBE LEVEL AT P I
I
!SSUMINGTHESAMESIDELOBEREQUIREMENTATEACHPI
0;NSIDELOBES 24= [ 0;ONESIDELOBE 24=]N
ANDFOR0;ONESIDELOBE 24=
0;NSIDELOBES 24= N0;ONESIDELOBE 24=
!SIMPLEEXAMPLEWILLILLUSTRATETHEPROCESS)FITISNECESSARYTOKEEPALLSIDELOBES INASECTORBELOW D"WITHAPROBABILITYOF DETERMINETHEREQUIREDPROBABILITYON ANYONEGIVENSIDELOBE
0;SIDELOBES D"=
4HEN
0;ONEGIVENSIDELOBE D"=
0;ONEGIVENSIDELOBE D"=
0;ONEGIVENSIDELOBE D"=
4HATIS TOKEEPALLSIDELOBESBELOW D"WITHAPROBABILITYOF ITISNECESSARY TOKEEPANYGIVENSIDELOBEBELOW D"WITHAPROBABILITYOF4HEPROCESSOF CONTROLLINGEACHANDEVERYSIDELOBEISTHUSSEENASFORMIDABLE SINCETHETOTALNUM BEROFSIDELOBESISAPPROXIMATELYEQUALTOTHENUMBEROFELEMENTSINAPHASEDARRAY &ORA ELEMENTARRAYANDAPROBABILITYOFTHATASINGLESIDELOBEWILLNOT EXCEED24ATANYSINGLELOCATION ITWILLSTILLBEEXPECTEDTHATSIDELOBESWILLEXCEED 24WHENALLSIDELOBELOCATIONSARETAKENINTOACCOUNT &ORVERYLOWSIDELOBEARRAYS ITISREASONABLETOALLOWAFEWSIDELOBESTOEXCEED THE-33,VALUEBYASMUCHASTOD"TOACCOUNTFORRANDOMVARIATIONS4HIS CANBESEENFROM&IGUREASTHEDIFFERENCEBETWEEN0 AND0 OR0 )FTHISALLOWANCEISNOTGRANTED THEANTENNAWILLBEOVERDESIGNED )TISWORTHWHILETODOSOMEPROBABILITYCALCULATIONSBEFORESPECIFYINGTHEEXACT SIDELOBEREQUIREMENTS
£Î°Î{
2!$!2(!.$"//+
£Î°ÈÊ +1 /`>ÀÊ ÀÃÃÊ-iVÌ
Õ}iiÊ°Ê ÌÌ 4OMORROWS2ESEARCH
£{°£Ê /," 1 /" !RADARDETECTSORTRACKSATARGET ANDSOMETIMESCANCLASSIFYIT ONLYBECAUSETHERE ISANECHOSIGNAL)TIS THEREFORE CRITICALINTHEDESIGNANDOPERATIONOFRADARSTOBE ABLE TO QUANTIFY OR OTHERWISE DESCRIBE THE ECHO ESPECIALLY IN TERMS OF SUCH TARGET CHARACTERISTICSASSIZE SHAPE ANDORIENTATION&ORTHATPURPOSE THETARGETISASCRIBED ANEFFECTIVEAREACALLEDTHERADARCROSSSECTION OR2#34HE2#3ISTHEPROJECTEDAREA OFAMETALSPHERETHATWOULDRETURNTHESAMEECHOSIGNALASTHETARGET HADTHESPHERE BEENSUBSTITUTEDFORIT 5NLIKETHEECHOOFTHESPHERE HOWEVER WHICHISINDEPENDENTOFTHEVIEWINGANGLE THEECHOESOFALLBUTTHESIMPLESTTARGETSVARYSIGNIFICANTLYWITHORIENTATION!SWILLBE SHOWNLATER THISVARIATIONCANBEQUITERAPID ESPECIALLYFORTARGETSMANYWAVELENGTHS INSIZE 4HEECHOCHARACTERISTICSDEPENDINSTRONGMEASUREONTHESIZEANDNATUREOFTHE TARGETSURFACESEXPOSEDTOTHERADARBEAM4HEVARIATIONISSMALLFORELECTRICALLYSMALL TARGETSTARGETSLESSTHANAWAVELENGTHORSOINSIZE BECAUSETHEINCIDENTWAVELENGTHIS TOOLONGTORESOLVETARGETDETAILS/NTHEOTHERHAND THEFLAT SINGLYCURVEDANDDOUBLY CURVEDSURFACESOFELECTRICALLYLARGETARGETSALLGIVERISETODIFFERENTECHOCHARACTERISTICS 2EENTRANT STRUCTURES SUCH AS JET ENGINE INTAKES AND EXHAUSTS GENERALLY HAVE LARGE ECHOES ANDEVENTHETRAILINGEDGESOFAIRFOILSCANBESIGNIFICANTECHOSOURCES 4HERADARCROSSSECTIONSOFSIMPLEBODIESCANBECOMPUTEDEXACTLYBYASOLUTIONOF THEWAVEEQUATIONINACOORDINATESYSTEMFORWHICHACONSTANTCOORDINATECOINCIDES WITHTHESURFACEOFTHEBODY4HEEXACTSOLUTIONREQUIRESTHATTHEELECTRICANDMAGNETIC FIELDSJUSTINSIDEANDJUSTOUTSIDETHESURFACESATISFYCERTAINCONDITIONSTHATDEPENDON THEELECTROMAGNETICPROPERTIESOFTHEMATERIALOFWHICHTHEBODYISMADE 7HILETHESESOLUTIONSCONSTITUTEINTERESTINGACADEMICEXERCISESANDCAN WITHSOME STUDY REVEALTHENATUREOFTHESCATTERINGMECHANISMSTHATCOMEINTOPLAY THEREARENO KNOWNTACTICALTARGETSTHATFITTHESOLUTIONS4HUS EXACTSOLUTIONSOFTHEWAVEEQUA TIONARE ATBEST GUIDELINESFORGAUGINGOTHERAPPROXIMATE METHODSOFCOMPUTING SCATTEREDFIELDS !NALTERNATIVEAPPROACHISTHESOLUTIONOFTHEINTEGRALEQUATIONSGOVERNINGTHEDIS TRIBUTIONOFINDUCEDFIELDSONTARGETSURFACES4HEMOSTUSEFULAPPROACHTOASOLUTION ISKNOWNASTHEMETHODOFMOMENTS INWHICHTHEINTEGRALEQUATIONSAREREDUCEDTO ASYSTEMOFLINEARHOMOGENEOUSEQUATIONS4HEATTRACTIONOFTHISMETHODISTHATTHE SURFACEPROFILEOFTHEBODYISUNRESTRICTED ALLOWINGTHECOMPUTATIONOFTHESCATTERING £{°£
£{°Ó
2!$!2(!.$"//+
FROMTRULYTACTICALOBJECTS!NOTHERISTHATORDINARYMETHODSOFSOLUTIONMATRIXINVER SIONANDGAUSSIANELIMINATION FOREXAMPLE MAYBEEMPLOYEDTOEFFECTASOLUTION4HIS METHODISLIMITEDBYCOMPUTERMEMORYANDEXECUTIONTIME HOWEVER TOOBJECTSAFEW DOZENWAVELENGTHSINSIZEATBEST !LTERNATIVESTOTHESEEXACTSOLUTIONSARESEVERALAPPROXIMATEMETHODSTHATMAYBE APPLIED WITH REASONABLE ACCURACY TO ELECTRICALLY LARGE TARGET FEATURES 4HEY INCLUDE THETHEORIESOFGEOMETRICALANDPHYSICALOPTICS THEGEOMETRICALANDPHYSICALTHEORIES OFDIFFRACTION ANDTHEMETHODOFEQUIVALENTCURRENTS4HESEAPPROXIMATIONSAREDIS CUSSEDIN3ECTION/THERAPPROXIMATEMETHODSNOTDISCUSSEDHEREAREEXPLOREDIN DETAILINSOMEOFTHEREFERENCESLISTEDATTHEENDOFTHISCHAPTER 4HEPRACTICALENGINEERCANNOTRELYENTIRELYONPREDICTIONSANDCOMPUTATIONS AND MUSTEVENTUALLYMEASURETHEECHOCHARACTERISTICSOFSOMETARGETS4HISMAYBEDONEBY USINGFULL SCALETESTOBJECTSORSCALEMODELSTHEREOF3MALLTARGETSOFTENMAYBEMEASURED INDOORS BUTLARGETARGETSMUSTUSUALLYBEMEASUREDONANOUTDOORTESTRANGE4HECHAR ACTERISTICSOFTYPICALINDOORANDOUTDOORTESTFACILITIESAREDESCRIBEDIN3ECTION #ONTROLOFTHEECHOCHARACTERISTICSOFSOMETARGETSISOFVITALTACTICALIMPORTANCE NAMELYSTEALTH4HEREAREONLYTWOPRACTICALWAYSOFREDUCINGTHEECHOTHROUGHSHAP INGANDRADARABSORBERS3HAPINGISTHESELECTIONORDESIGNOFSURFACEPROFILESSOTHAT LITTLEORNOENERGYISREFLECTEDBACKTOWARDTHERADAR"ECAUSETARGETCONTOURSAREDIF FICULTTOCHANGEONCETHETARGETHASBECOMEAPRODUCTIONITEM SHAPINGISBESTIMPLE MENTEDINTHECONCEPTDEFINITIONSTAGEBEFOREPRODUCTIONDECISIONSHAVEBEENMADE 2ADAR ABSORBING MATERIALS ACTUALLY SOAK UP RADAR ENERGY ALSO REDUCING THE ENERGY REFLECTEDBACKTOTHERADAR(OWEVER THEAPPLICATIONOFABSORBERSISALWAYSEXPENSIVE WHETHER GAUGED IN TERMS OF NONRECURRING ENGINEERING COSTS LIFETIME MAINTENANCE OR REDUCED MISSION CAPABILITIES4HE TWO METHODS OF ECHO CONTROL ARE DISCUSSED IN 3ECTION ANDACOLLECTIONOFFOURSTEALTHYPLATFORMSISSURVEYEDTHERE 3EVEN"ASIC%CHO-ECHANISMS &IGUREILLUSTRATESSEVENBASICECHOSOURCES THATMIGHTBEFOUNDONATYPICALAIRBORNETARGET!LLDEPENDINVARYINGDEGREEONTHE
&)'52% %XAMPLESOFSEVENBASICECHO SOURCEMECHANISMSAFTER%&+NOTTÚ!MERICAN )NSTITUTEOF!ERONAUTICSAND!STRONAUTICS
2!$!2#2/333%#4)/.
£{°Î
TARGETASPECTANGLEASSEENFROMTHERADAR3OMEAREDOMINANTSCATTERINGMECHANISMS WHEREASOTHERSAREWEAK.OTALLARESIGNIFICANTONOTHERKINDSOFPLATFORMS SUCHAS WARSHIPSORMILITARYGROUNDVEHICLES7EBRIEFLYDISCUSSTHESEVENINDESCENDINGORDER OFSIGNIFICANCE 2EENTRANT 3TRUCTURES 4HE ONLY REENTRANT STRUCTURE APPEARING ON THE HYPOTHETI CALMISSILEIN&IGUREISITSEXHAUSTDUCTATTHEREAR BUTJETINTAKEDUCTSBEHAVE MUCHTHESAMEWAY4HEECHOESFROMCAVITIESSUCHASINTAKEDUCTS EXHAUSTDUCTS AND COCKPITSARELARGEANDTENDTOPERSISTOVERASPECTANGLESASWIDEASnORn4HISIS BECAUSEMOSTOFTHEINTERNALDUCTSURFACESIE COMPRESSORSTAGESANDTURBINEFACES AREMETALLIC ANDANYRADARWAVETHATFINDSITSWAYINTOTHESTRUCTUREWILLLIKELYFIND ITSWAYBACKOUTTOWARDTHERADAR4HISISALSOTRUEOFINTERNALREFLECTIONSFROMWITHIN COCKPITCANOPIES 3PECULAR3CATTERERS !SPECULARSCATTERERISANYTARGETSURFACETHATISORIENTEDPER PENDICULARTOTHELINEOFSIGHTTOTHERADAR&LATSURFACESOFFERPARTICULARLYLARGEECHOES INTHESPECULARDIRECTION BUTTHEECHOESDROPOFFSHARPLYAWAYFROMTHATDIRECTION4HE SPECULARECHOESFROMSINGLYANDDOUBLYCURVEDSURFACESCYLINDRICALANDSPHEROIDAL SURFACES ARESOMEWHATLOWERTHANTHOSEFROMFLATSURFACES BUTAREMOREPERSISTENT WITHCHANGESINASPECTANGLE 4RAVELING WAVE%CHOES 7HENTHEANGLEOFINCIDENCEISASMALLGRAZINGANGLEOFF THESURFACE ASURFACETRAVELINGWAVECANBEINDUCED4HESURFACEWAVETENDSTOBUILD UPTOWARDTHEREAROFTHEBODYANDISUSUALLYREFLECTEDBACKTOWARDTHEFRONTBYANY DISCONTINUITYATTHEREAR4RAVELING WAVEECHOESATLOWGRAZINGANGLESARENEARLYAS SIGNIFICANTASSPECULARECHOESATNORMALINCIDENCE 4IP %DGE AND#ORNER$IFFRACTION 3CATTERINGFROMTIPS EDGES ANDCORNERSISLESS SIGNIFICANTTHANSPECULARECHOESANDTHUSAREWORRISOMETOTHEDESIGNERONLYWHEN MOSTOTHERSOURCESOFECHOHAVEBEENSUPPRESSED4HEECHOESFROMTIPSANDCORNERS ARELOCALIZEDANDTENDTOINCREASEWITHTHESQUAREOFTHEWAVELENGTH NOTTHESIZEOF ANYSURFACEFEATURE4HUS THEYBECOMEPROGRESSIVELYLESSIMPORTANTASTHERADARFRE QUENCYRISES 3URFACE$ISCONTINUITIES -OSTAIRFRAMESHAVESLOTSORGAPSWHERECONTROLSURFACES MEETTHESTATIONARYAIRFRAME3LOTS GAPS ANDEVENRIVETHEADSCANREFLECTENERGYBACK TOTHERADAR"ECAUSETHESETENDTOBESMALLEFFECTS ITISNOTEASYTOISOLATEANDCHAR ACTERIZETHEM #REEPING7AVES !CREEPINGWAVEISONETHATGETSBOUNDTOASMOOTH SHADEDSUR FACE ISGUIDEDAROUNDTHEREAROFASMOOTHBODY ANDISTHENLAUNCHEDBACKTOTHERADAR WHENITREAPPEARSATTHESHADOWBOUNDARYONTHEOPPOSITESIDE!SSHOWNINTHENEXT SECTION THECREEPINGWAVECAUSESTHEECHOESFROMSMALLSPHERESTOVARYWITHSPHERE SIZE4HEMECHANISMCANALSOBEPRESENTFOROTHERSMOOTHBODIES SUCHASTHEGENERIC MISSILEDEPICTEDIN&IGURE4HECREEPINGWAVEMECHANISMISNEVERASIGNIFICANT ONEFORMILITARYANDCIVILIANTARGETS )NTERACTIONS 2ELATIVELYSTRONGECHOESCANOCCURWHENAPAIROFTARGETSURFACESARE ORIENTEDFORAFAVORABLEBOUNCEFROMONESURFACETOANOTHERANDTHENBACKTOTHERADAR ASINTHEINTERACTIONBETWEENTHEFUSELAGEANDTHETRAILINGEDGEOFTHERIGHTWINGSHOWN
£{°{
2!$!2(!.$"//+
IN&IGURE3IMILARINTERACTIONSOCCURFORSHIPTARGETSWHENBULKHEADS RAILINGS MASTS ANDOTHERTOPSIDEFEATURESBECOMEMIRROREDINTHEMEANSEASURFACE .OTALLOFTHESEMECHANISMSAREREVEALEDINTHECHARACTERISTICSOFTHESELECTIONOF SIMPLEANDCOMPLEXTARGETS ASSHOWNINTHENEXTSECTION
£{°ÓÊ / Ê "
*/Ê"Ê "Ê*"7 , $EFINITION OF 2#3 !N OBJECT EXPOSED TO AN ELECTROMAGNETIC WAVE DISPERSES INCIDENTENERGYINALLDIRECTIONS4HISSPATIALDISTRIBUTIONOFENERGYISCALLEDSCATTER ING ANDTHEOBJECTITSELFISOFTENCALLEDASCATTERER4HEENERGYSCATTEREDBACKTOTHE SOURCEOFTHEWAVECALLEDBACKSCATTERING CONSTITUTESTHERADARECHOOFTHEOBJECT4HE INTENSITYOFTHEECHOISDESCRIBEDEXPLICITLYBYTHERADARCROSSSECTIONOFTHEOBJECT FOR WHICHTHEACRONYM2#3HASBEENGENERALLYRECOGNIZED%ARLYPAPERSONTHESUBJECT CALLEDITTHEECHOAREAORTHEEFFECTIVEAREA TERMSSTILLFOUNDOCCASIONALLYINCONTEM PORARYTECHNICALLITERATURE 4HEFORMALDEFINITIONOFRADARCROSSSECTIONIS
\ % \ R LIM P 2 S \ % \ 2lc
WHERE%ISTHEELECTRIC FIELDSTRENGTHOFTHEINCIDENTWAVEIMPINGINGONTHETARGETAND %SISTHEELECTRIC FIELDSTRENGTHOFTHESCATTEREDWAVEATTHERADAR4HEDERIVATIONOFTHE EXPRESSIONASSUMESTHATATARGETEXTRACTSPOWERFROMANINCIDENTWAVEANDTHENRADI ATESTHATPOWERUNIFORMLYINALLDIRECTIONS!LTHOUGHTHEVASTMAJORITYOFTARGETSDO NOTSCATTERENERGYUNIFORMLYINALLDIRECTIONS THEDEFINITIONASSUMESTHATTHEYDO4HIS PERMITSONETOCALCULATETHESCATTEREDPOWERDENSITYONTHESURFACEOFALARGESPHERE OFRADIUS2CENTEREDONTHESCATTERINGOBJECT2ISTYPICALLYTAKENTOBETHERANGEFROM THERADARTOTHETARGET 4HESYMBOLRHASBEENWIDELYACCEPTEDASTHEDESIGNATIONFORTHE2#3OFANOBJECT ALTHOUGHTHISWASNOTSOATFIRST 4HE2#3ISTHEPROJECTEDAREAOFAMETALSPHERETHAT ISLARGECOMPAREDWITHTHEWAVELENGTHANDTHAT IFSUBSTITUTEDFORTHEOBJECT WOULD SCATTERIDENTICALLYTHESAMEPOWERBACKTOTHERADAR(OWEVER THE2#3OFALLBUTTHE SIMPLESTSCATTERERSFLUCTUATESGREATLYWITHTHEORIENTATIONOFTHEOBJECT SOTHENOTION OFANEQUIVALENTSPHEREISNOTVERYUSEFUL 4HELIMITINGPROCESSIN%QISNOTALWAYSANABSOLUTEREQUIREMENT)NBOTHMEA SUREMENTANDANALYSIS THERADARRECEIVERANDTRANSMITTERAREUSUALLYTAKENTOBEINTHE FARFIELDOFTHETARGETDISCUSSEDIN3ECTION ANDATTHATDISTANCE THESCATTEREDFIELD %SDECAYSINVERSELYWITHTHEDISTANCE24HUS THE2TERMINTHENUMERATOROF%Q ISCANCELEDBYANIDENTICALBUTIMPLICIT2TERMINTHEDENOMINATOR#ONSEQUENTLY THE DEPENDENCEOFTHE2#3ON2 ANDTHENEEDTOFORMTHELIMIT USUALLYDISAPPEARS 4HERADARCROSSSECTIONIS THEREFORE ACOMPARISONOFTHESCATTEREDPOWERDENSITYAT THERECEIVERWITHTHEINCIDENTPOWERDENSITYATTHETARGET!NEQUALLYVALIDDEFINITIONOF THE2#3RESULTSWHENTHEELECTRIC FIELDSTRENGTHSIN%QAREREPLACEDWITHTHEINCI DENTANDSCATTEREDMAGNETIC FIELDSTRENGTHS)TISOFTENNECESSARYTOMEASUREORCALCU LATETHEPOWERSCATTEREDINSOMEOTHERDIRECTIONTHANBACKTOTHETRANSMITTER ABISTATIC SITUATION!BISTATIC2#3MAYBEDEFINEDFORTHISCASEASWELLASFORBACKSCATTERING PROVIDEDITISUNDERSTOODTHATTHEDISTANCE2ISMEASUREDFROMTHETARGETTOTHERECEIVER
2!$!2#2/333%#4)/.
£{°x
&ORWARDSCATTERINGISASPECIALCASEOFBISTATICSCATTERINGINWHICHTHEBISTATICANGLEIS nWHENCETHEDIRECTIONOFINTERESTISALONGTHESHADOWZONEBEHINDTHETARGET 4HESHADOWITSELFCANBEREGARDEDASTHESUMOFTWOFIELDSOFNEARLYEQUALSTRENGTH BUTnOUTOFPHASE/NEISTHEINCIDENTFIELD ANDTHEOTHERISTHESCATTEREDFIELD 4HEFORMATIONOFTHESHADOWIMPLIESTHATTHEFORWARDSCATTERINGISLARGE WHICHIS INDEEDTHECASE4HEFIELDSBEHINDTHETARGETAREHARDLYEVERPRECISELYZERO HOWEVER BECAUSE SOME ENERGY USUALLY LEAKS INTO THE SHADOW ZONE VIA DIFFRACTION FROM THE SIDESOFTHETARGET %XAMPLESOF2#3#HARACTERISTICS 4HEDISCUSSIONOFRADARCROSSSECTIONCHAR ACTERISTICSWILLFIRSTCONSIDERSIMPLETARGETS OFWHICHTHESPHEREISACLASSICEXAMPLE 4HISWILLBEFOLLOWEDBYCOMPLEXOBJECTS OFWHICHANAIRCRAFTISAGOODEXAMPLE 3IMPLE /BJECTS "ECAUSE OF ITS PURE RADIAL SYMMETRY THE PERFECTLY CONDUCTING SPHEREISTHESIMPLESTOFALLTHREE DIMENSIONALSCATTERERS$ESPITETHESIMPLICITYOFITS GEOMETRICALSURFACE HOWEVER ANDTHEINVARIANCEOFITSECHOWITHORIENTATION THE2#3 OFTHESPHEREVARIESCONSIDERABLYWITHELECTRICALSIZE4HEEXACTSOLUTIONFORTHESCATTER INGBYACONDUCTINGSPHEREISKNOWNASTHE-IESERIESANDISSHOWNIN&IGURE .OTETHATTHECHARTISSPLITROUGHLYINTOTHREEREGIONS)NTHE2AYLEIGHREGIONBELOW KA THE2#3RISESWITHTHEFOURTHPOWEROFTHESPHERERADIUS ANECHODEPENDENCE CHARACTERISTIC OF ELECTRICALLY SMALL BODIES WHETHER SPHERICAL OR NOT )N THIS REGION THEINCIDENTWAVECANNOTACCURATELYRESOLVEBODYLENGTH TO WIDTHVARIATIONS)NTHE OPTICSREGIONABOVEKA OPTICSFORMULASFORPREDICTINGTHE2#3OFTHEMETALBODY GENERALLYWORKREASONABLYWELL3ANDWICHEDBETWEENTHE2ALEIGHREGIONBELOWAND THEOPTICSREGIONABOVEISTHERESONANCEREGION WHERETWOORMOREMECHANISMSMAY COMBINEINANDOUTOFPHASEWITHEACHOTHERTOPRODUCETHEUNDULATIONSINTHE2#3 )NTHECASEOFTHESPHERE THEUNDULATIONSINTHERESONANCEREGIONAREDUETOTWO DISTINCTCONTRIBUTIONSTOTHEECHO ONEASPECULARREFLECTIONFROMTHEFRONTOFTHESPHERE ANDTHEOTHERACREEPINGWAVETHATCIRCLESAROUNDITSSHADOWEDSIDE4HETWOGOINAND OUTOFPHASEASTHESPHEREGROWSLARGERBECAUSETHEDIFFERENCEINTHELENGTHSOFTHEIR ELECTRICALPATHFROMSOURCETORECEIVERINCREASESCONTINUOUSLYWITHINCREASINGKA4HE UNDULATIONSBECOMEWEAKERWITHINCREASINGKABECAUSETHECREEPINGWAVELOSESMORE ENERGYTHELONGERTHEELECTRICALPATHAROUNDTHESHADOWEDSIDE
&)'52% 2ADARCROSSSECTIONOFAPERFECTLYCONDUCTINGSPHERE NORMALIZEDTOTHEOPTICSVALUEOA4HEPARAMETERKA OAKISTHE CIRCUMFERENCEOFTHESPHEREEXPRESSEDINWAVELENGTHS
£{°È
2!$!2(!.$"//+
)FONLYTHESPECULARREFLECTIONISSIGNIFICANT THEOPTICS REGION2#3OFTHEPERFECTLY CONDUCTINGSPHEREISSIMPLY
R OA
WHEREAISTHERADIUSOFTHESPHERE"UTTHE2#3OFPERMEABLEDIELECTRIC BODIESIS MORECOMPLICATEDTHANTHISBECAUSEENERGYCANENTERTHEBODYANDRATTLEAROUNDINSIDE BEFORECOMINGBACKOUT!NEXAMPLEISTHEDIELECTRICSPHEREWHOSE2#3ISPLOTTEDIN &IGURE"ECAUSETHEDIELECTRICMATERIALISSLIGHTLYLOSSY ASINDICATEDBYTHENON ZEROIMAGINARYCOMPONENTOFTHEINDEXOFREFRACTION THE2#3OFTHESPHEREDECAYS GRADUALLYWITHINCREASINGELECTRICALSIZE!TLASETALWENTEVENFURTHERBYCOMPARING THEMEASUREDANDTHEORETICAL2#3OF0LEXIGLASSPHERESINTHEIRATTEMPTSTOUNDERSTAND THESCATTERINGBYHAILSTONES 4HE2#3OFVERYSLENDERDIELECTRICBODIESDOESNOTEXHIBITTHISCOMPLEXITY HOW EVER BECAUSETHESOURCESOFREFLECTIONFRONTANDBACKSIDESOFADIELECTRICCYLINDER FOR EXAMPLE ARETOOCLOSETOEACHOTHERTOBERESOLVABLEBYTHEINCIDENTWAVE!NEXAMPLE ISTHEBROADSIDE2#3OFATHINSTRINGSHOWNIN&IGURE4HESTRINGWASANGLEDn ACROSSTHETESTZONEOFALARGEINDOORTESTCHAMBER ANDTHE2#3WASMEASUREDASA FUNCTIONOFFREQUENCYFORFOURTRANSMIT RECEIVEPOLARIZATIONCOMBINATIONS/NLYTHE COPOLARIZED66ANDCROSS POLARIZED6(TRACESARESHOWNBECAUSETHE((AND(6 MEASUREMENTSCLOSELYTRACKTHE66AND6(DATA4HEMEASUREDDATAARETHERAPIDLY VARYINGTRACESANDWEREFITTEDSTATISTICALLYTOTHESMOOTHLYVARYINGTRACESREPRESENTING THEEXACTSOLUTIONOFTHETWO DIMENSIONALWAVEEQUATIONFORDIELECTRICCYLINDERS 4HESTRINGDIAMETERWASINCHANDITSILLUMINATEDLENGTHWASESTIMATEDTOBE ABOUTFT"ASEDONAMEANSEPARATIONBETWEENTHEMEASURED66AND6(DATAOF D" THEEFFECTIVEDIELECTRICCONSTANTOFTHESTRINGWASESTIMATEDTOBEDR 4HIS MAY BE THE FIRST TIME THAT 2#3 MEASUREMENTS WERE EVER USED TO ESTIMATE THE DIELECTRICCONSTANTOFASTRING3TRINGSAREOFINTERESTAT2#3TESTFACILITIESBECAUSETHEY SOMETIMESAREUSEDAShINVISIBLEvTARGETSUPPORTS
&)'52% 2#3OFALOSSYDIELECTRICSPHEREWITHN IAFTER*2HEINSTEIN Ú)%%%
2!$!2#2/333%#4)/.
£{°Ç
&)'52% -EASURED AND PREDICTED BROADSIDE 2#3 OF A STRING STRETCHED ACROSS THE TEST ZONE OF AN INDOOR TEST CHAMBER AT n ANGLE Ú (ORIZON (OUSE2EPRINTEDWITHPERMISSION
4HEBEHAVIOROFSHORTWIREDIPOLESISMARKEDLYDIFFERENTFROMTHATOFLONGDIELECTRIC STRINGS!SSHOWNIN&IGURE THEBROADSIDEECHOOFAMETALWIREEXHIBITSRESO NANCESATODDMULTIPLESOFAHALFWAVELENGTH WITHPLATEAUSOFNEARLYCONSTANTRETURN BETWEEN THE RESONANT PEAKS 4HESE PLATEAUS RISE WITH INCREASING DIPOLE LENGTH AND BECOMELESSDISTINCTASTHEDIPOLEBECOMESTHICKERANDLONGER4HEYEVENTUALLYDISAP PEARWHENTHEDIPOLEBECOMESFATENOUGHANDLONGENOUGH 4HE2#3CANRISETOSIGNIFICANTLEVELSATEND ONASPECTS ASWELLASINTHEBROADSIDE REGIONS OFBODIESBOTHFATANDTHIN4HESENEAR END ONECHOESAREATTRIBUTABLETOSUR FACETRAVELINGWAVESTHATRADIATEPOWERINTHEBACKWARDDIRECTION!NEXAMPLEISTHE OGIVE ASPINDLE SHAPEDOBJECTFORMEDBYROTATINGANARCOFACIRCLEABOUTITSCHORD
&)'52% -EASUREDBROADSIDERETURNSOFATHINDIPOLE#OURTESYOF 5NIVERSITYOF-ICHIGAN2ADIATION,ABORATORY
£{°n
2!$!2(!.$"//+
&IGUREISTHE2#3PATTERNOFAKLONG nHALF ANGLEOGIVERECORDEDFORHORI ZONTALPOLARIZATIONINCIDENTELECTRICFIELDINTHEPLANEOFTHEOGIVEAXISANDTHELINEOF SIGHT 4HELARGELOBEATTHERIGHTSIDEOFTHEPATTERNISASPECULARECHOINTHEBROADSIDE SECTOR ANDTHESEQUENCEOFPEAKSATTHELEFTSIDEISTHECONTRIBUTIONOFTHESURFACETRAV ELINGWAVENEAREND ONINCIDENCE.OTETHATTHE2#3ISEXTREMELYSMALLNOTMEASUR ABLEINTHISCASE ATPRECISELYEND ONINCIDENCE4HEORETICALPREDICTIONSINTHEEND ON REGIONCLOSELYMATCHTHEMEASUREDPATTERNFORTHISPARTICULARBODY !METALPLATEISAMOREELEMENTARYSTRUCTURETHANTHEOGIVESHOWNIN&IGURE BUTITS2#3PATTERNISNOLESSCOMPLEX3AMPLEPATTERNSAREREPRODUCEDIN&IGURE FORFOURDIFFERENTINCIDENTANDRECEIVEDPOLARIZATIONCOMBINATIONS4HETRACESFOR(( DOTS AND(6SHORTDASHES AREEACHSHIFTEDDOWNBYD"FORCLARITY WHEREASTHOSE FORTHE66LONGDASHES AND6(SOLID AREhASISvNOTSHIFTED 4HEPLATEWASROTATED ABOUT A VERTICAL AXIS PARALLEL TO ONE EDGE OF THE PLATE AND THE INCIDENT OR RECEIVED POLARIZATIONWASEITHERPARALLELTO6 ORPERPENDICULARTO( THATAXIS RESPECTIVELY
&)'52% -EASURED2#3PATTERNOFAK nHALF ANGLEMETALOGIVEAFTER,0ETERS Ú)%%%
2!$!2#2/333%#4)/.
£{°
&#'$ !& (
%"
( "'&
&)'52% 2#3OFASQUAREFLATPLATE INALONGASIDEMEASUREDAT-(Z4HE(( AND(6PATTERNSHAVEBEENARTIFICIALLYLOWEREDD"FORCLARITY#OURTESYOF307EIETAL THE"OEING#OMPANY/RIGINALDATACOURTESYOFTHE"OEING#OMPANY 3EATTLE 7ASHINGTON
4HEPLATEISPRESENTEDBROADSIDETOTHEINCIDENTWAVEATTHECENTEROFTHECHARTn ANDISSEENEDGE ONATTHELEFTANDRIGHTSIDESn 4HELARGESPECULARRETURNFROMTHE PLATEATTHECENTEROFTHECHARTISPREDICTEDWITHQUITEGOODACCURACYBYTHEFLAT PLATE FORMULAGIVENIN4ABLE LATERINTHISSECTION4HEEDGE ONRETURNFOR66POLARIZA TIONISWELLPREDICTEDBYTHESTRAIGHT EDGEFORMULA ALSOGIVENIN4ABLE 4HESEUNDULATINGPLATEPATTERNSFOLLOWASINXXVARIATIONQUITECLOSELYFORASPECT ANGLESOUTTOABOUTn"EYONDTHATANGLE THETWOPATTERNSDIFFERBYPROGRESSIVELY WIDERMARGINS4HESINXXBEHAVIORISCHARACTERISTICOFAUNIFORMLYILLUMINATEDAPER TURE BUTUNLIKETHEONE WAYILLUMINATIONFUNCTIONENCOUNTEREDINANTENNAWORK THE ARGUMENTXFORTHEFLATPLATEINCLUDESATWO WAYROUND TRIP ILLUMINATIONFUNCTION 4HUS THEBEAMWIDTHOFTHEECHORESPONSEOFAFLATPLATEISHALFTHEBEAMWIDTHOFAN ANTENNAAPERTUREOFTHESAMESIZE4HEPROMINENTLOBEINTHEHORIZONTALPATTERNINTHE REGIONBETWEENnANDnISDUETOASURFACETRAVELINGWAVE )NCONTRASTTOTHEPATTERNOFAFLATPLATE THE2#3PATTERNOFACORNERREFLECTORISQUITE BROAD4HISISBECAUSETHECORNERREFLECTORISAREENTRANTSTRUCTURE ANDNOMATTERWHAT ITSORIENTATIONWITHINLIMITS OFCOURSE INTERNALLYREFLECTEDWAVESAREDIRECTEDBACK TOWARDTHESOURCEOFTHEINCIDENTWAVE!CORNERREFLECTORISFORMEDBYTWOORTHREEFLAT PLATESINTERSECTINGATRIGHTANGLES ANDWAVESIMPINGINGONTHEFIRSTFACEAREREFLECTED ONTOTHESECONDIFTHEREISATHIRDFACE ITRECEIVESWAVESREFLECTEDBYTHEFIRSTTWO FACES4HEMUTUALORTHOGONALITYOFTHEFACESENSURESTHATTHEDIRECTIONTAKENBYWAVES UPONFINALREFLECTIONISBACKTOWARDTHESOURCE 4HEINDIVIDUALFACESOFTHECORNERREFLECTORMAYBEOFARBITRARYSHAPE BUTTHEMOST COMMON IS AN ISOSCELES TRIANGLE FOR THE TRIHEDRAL CORNER DIHEDRAL CORNERS TYPICALLY HAVERECTANGULARFACES4HE2#3OFACORNERREFLECTORSEENALONGITSAXISOFSYMMETRY
£{°£ä
2!$!2(!.$"//+
4!",% 2#3!PPROXIMATIONSFOR3IMPLE3CATTERING&EATURES
3CATTERING&EATURE #ORNERREFLECTOR &LATPLATE 3INGLYCURVEDSURFACE $OUBLYCURVEDSURFACE 3TRAIGHTPLATEEDGE #URVEDEDGE #ONETIP !CUTEFLATMETALCORNER !CUTEFLATMETALCORNER
/RIENTATION
!PPROXIMATE2#3
.OTES
!XISOFSYMMETRYALONG,/3 3URFACEPERPENDICULARTO,/3 3URFACEPERPENDICULARTO,/3 3URFACEPERPENDICULARTO,/3 ,/3PERPENDICULARTOFRONTEDGE AND%INPLANEOFPLATE %DGEELEMENTPERPENDICULARTO,/3 !XIALINCIDENCE ,/3PERPENDICULARTOREAREDGEAND %INPLANEOFPLATE ,/3ALONGCORNERBISECTORAND% INPLANEOFPLATE
O!EFFK
O! K OA,K OAA ,O
AK KSIN@ K
K
./4%3 ,/3 LINEOFSIGHT !EFF EFFECTIVEAREACONTRIBUTINGTOMULTIPLEINTERNALREFLECTIONS ! ACTUALAREAOFTHEPLATE A MEANRADIUSOFCURVATURE, LENGTHOFSLANTEDSURFACE A A PRINCIPALRADIIOFSURFACECURVATUREINORTHOGONALPLANES , EDGELENGTH A RADIUSOFEDGECONTOUR @ HALFANGLEOFTHECONE %MPIRICALVALUESREPORTEDBY+NOTT 3HAEFFER AND4ULEY
ISIDENTICALTOTHATOFAFLATPLATEWHOSEPHYSICALAREAMATCHESTHEEFFECTIVEAREAOFTHE CORNERREFLECTOR4HEMAGNITUDEOFTHEECHOMAYBEDETERMINEDBYFINDINGTHEPOLYGO NALAREASONEACHFACEOFTHECORNERRECEIVINGWAVESREFLECTEDBYTHEOTHERFACESAND FROMWHICHTHEFINALREFLECTIONISBACKTOWARDTHESOURCE4HEEFFECTIVEAREAISDETER MINEDBYSUMMINGTHEPROJECTIONSOFTHEAREASOFTHOSEPOLYGONSONTHELINEOFSIGHT THE2#3ISTHENFOUNDBYSQUARINGTHATAREA MULTIPLYINGBYO ANDDIVIDINGBYK &IGURE IS A COLLECTION OF 2#3 PATTERNS OF A TRIHEDRAL CORNER REFLECTOR WITH TRIANGULAR FACES 4HE REFLECTOR WAS FABRICATED OF THREE TRIANGULAR PLYWOOD PANELS METALLIZEDTOENHANCETHEIRSURFACEREFLECTIVITIES4HEAPERTUREEXPOSEDTOTHERADAR WAS THEREFORE ANEQUILATERALTRIANGLE ASSHOWNIN&IGURE4HEEIGHTPATTERNSIN &IGUREWEREMEASUREDWITHTHEPLANEOFTHEAPERTURETILTEDABOVEORBELOWTHE LINEOFSIGHTBYTHEANGLEE 4HEBROADCENTRALPARTOFTHESEPATTERNSISDUETOATRIPLE BOUNCEMECHANISM BETWEENTHETHREEPARTICIPATINGFACES WHILETHEhEARSvATTHESIDESOFTHEPATTERNS AREDUETOTHESINGLE BOUNCE FLAT PLATESCATTERINGFROMTHEINDIVIDUALFACES!LONG THEAXISOFSYMMETRYOFTHETRIHEDRALREFLECTORIN&IGUREP n E n THE 2#3 IS O,K WHERE , IS THE LENGTH OF ONE OF THE EDGES OF THE APERTURE .OT SHOWNARETHEECHOREDUCTIONSOBTAINEDWHENTHETRIHEDRALFACESARENOTPERPEN DICULARTOEACHOTHER4HOSEREDUCTIONSDEPENDONTHESIZEOFTHEFACESEXPRESSED INWAVELENGTHS 4HE2#3OFMOSTOFTHESIMPLESCATTERINGFEATURESDISCUSSEDINTHISSECTIONMAYBE ESTIMATEDBYUSINGTHESIMPLEFORMULASLISTEDIN4ABLE4HE2#3OFSOMECOM PLICATEDTARGETSMAYBEESTIMATEDBYREPRESENTINGTHETARGETASACOLLECTIONOFFEATURES LIKETHOSELISTEDIN4ABLE CALCULATINGTHEINDIVIDUALCONTRIBUTIONSANDTHENSUM MINGTHECONTRIBUTIONSCOHERENTLYORNONCOHERENTLY ASGOVERNEDBYTHEOBJECTIVEOF THECALCULATIONS
2!$!2#2/333%#4)/.
£{°££
&)'52% 2#3 PATTERNS OF A TRIHEDRAL CORNER REFLECTOR %DGE OF APERTURE IN K CM 3 3 2OBERTSON Ú !44 2EPRINTEDWITHPERMISSIONFROM!444ECHNICAL*OURNAL
#OMPLEX/BJECTS /BJECTSSUCHASINSECTS BIRDS AIRPLANES SHIPS ANDANTENNAS CANBEMUCHMORECOMPLEXTHANTHOSEJUSTDISCUSSED EITHERBECAUSEOFTHEMULTIPLIC ITYOFSCATTERERSONTHEMORBECAUSEOFTHECOMPLEXITYOFTHEIRSURFACEPROFILESAND DIELECTRICCONSTANTS)NSECTSAREEXAMPLESOFTHELATTER -EASURED VALUES FOR A DOZEN SPECIES OF INSECTS ARE LISTED IN4ABLE 4HE BUGSWEREALIVEFORTHEMEASUREMENTSBUTHADTOBEDRUGGEDTOIMMOBILIZETHEM &IGURESHOWSTHERELATIONSHIPBETWEENTHE2#3ANDTHEMASSOFANINSECT WITHTHEVARIATIONOFAWATERDROPLETSHOWNFORCOMPARISON4ABLELISTSTHE 2#3OFAMANASREPORTEDBY3CHULTZETAL/THERCOMPARISONSHAVEBEENMADE FORBOTHBIRDSANDINSECTS
&)'52% #OORDINATESYSTEMFORTHE2#3PATTERNSIN &IGURE332OBERTSON Ú!442EPRINTEDWITH PERMISSIONFROM!444ECHNICAL*OURNAL
£{°£Ó
2!$!2(!.$"//+
4!",% -EASURED)NSECT2#3AT'(Z
)NSECT
,ENGTH MM
7IDTH MM
"ROADSIDE 2#3 D"SM
%ND ON 2#3 D"SM
"LUE WINGEDLOCUST !RMYWORMMOTH !LFALFACATERPILLARBUTTERFLY (ONEYBEEWORKER #ALIFORNIAHARVESTERANT 2ANGECRANEFLY 'REENBOTTLEFLY 4WELVE SPOTTEDCUCUMBERBEETLE #ONVERGENTLADYBEETLE 3PIDERUNIDENTIFIED
./4%/RIGINALVALUESREPORTEDINSQUARECENTIMETERSHAVEBEENCONVERTEDHERETOD"SM WHICHISDECIBELS RELATIVETOASQUAREMETER
4!",% -EASURED2#3OFA-AN
&REQUENCY '(Z
2#3 M n n n n n
&)'52% 3AMPLE OF MEASURED 2#3 OF INSECTS AS A FUNCTION OF INSECT MASS AT '(Z BASED ON 2ILEYS SUMMARY 4HE DASHED LINE IS THE CALCULATED 2#3 OF WATER DROPLETSFORCOMPARISONAFTER*22ILEYÚ)%%%
2!$!2#2/333%#4)/.
£{°£Î
&)'52% -EASURED2#3PATTERNOFA" BOMBERATAFREQUENCYOF'(Z
%XAMPLESOF2#3PATTERNSFORAIRCRAFTARESHOWNIN&IGURESAND4HE " PATTERNIN&IGUREWASMEASUREDATAFREQUENCYOF'(Z4HEPOLARFORMAT ISUSEFULFORDISPLAYPURPOSESBUTISNOTASCONVENIENTFORDETAILEDCOMPARISONSASIS ARECTANGULARFORMATLIKETHEONEUSEDIN&IGURE4HATRECTANGULARPATTERNISOF AONE THIRDSCALEMODEL# AIRCRAFTANDWASDISPLAYEDINTHEEARLYSONA53 !IR&ORCEWEBSITE4HE# ISAMILITARYVERSIONOFTHE2AYTHEON(AWKER80 MID SIZEBUSINESSJET 4HE!IR&ORCEWEBSITEREVEALSVERYLITTLETECHNICALDETAILABOUTTHETESTCONDITIONS ATTENDINGTHEDATACOLLECTION SUCHASTHEFREQUENCYANDPOLARIZATIONOFTHEMEASURE MENTS NOTEVENTHEUNITSINWHICHTHE2#3DATAAREDISPLAYED(OWEVER EVENIFWEDO NOTKNOWTHETESTFREQUENCYORPOLARIZATION WEDOKNOWTHATTHEFULL SCALE2#3WILL BELOGr D"HIGHERTHANTHOSECHARTEDINTHEFIGUREIE HIGHERBYTHE SQUAREOFTHEINVERSESCALEFACTOR 7ESUSPECTTHATNOSE ONINCIDENCEISATTHECENTER OFTHEPATTERNANDTHATTHECHARTED2#3DATAAREINDECIBELSABOVEASQUAREMETERAT THETESTFREQUENCY &IGURECHARTSTHE2#3OFASHIPMEASUREDATAND'(ZATHORIZONTAL POLARIZATION4HEDATAWERECOLLECTEDBYASHORE BASEDRADARINSTRUMENTATIONCOMPLEX ASTHESHIPSTEAMEDINALARGECIRCLEON#HESAPEAKE"AY4HETHREETRACESINTHESECHARTS ARETHE ANDPERCENTILELEVELSOFTHESIGNALSCOLLECTEDOVERASPECTANGLEhWIN DOWSvnWIDE4HEPATTERNSARENOTSYMMETRICAL ESPECIALLYATTHEHIGHERFREQUENCY .OTETHATTHE2#3CANEXCEEDMID"SM
£{°£{
2!$!2(!.$"//+
&)'52% -EASURED2#3OFAONE THIRDSCALEMODEL# MILITARYAIRCRAFT
!NEMPIRICALFORMULAFORTHE2#3OFANAVALSHIPIS
R F
$
WHEREdISTHERADARFREQUENCYINMEGAHERTZAND$ISTHEFULL LOADDISPLACEMENTOF THEVESSELINKILOTONS 4HERELATIONSHIPISBASEDONMEASUREMENTSOFSEVERALSHIPS ATLOWGRAZINGANGLESANDREPRESENTSTHEAVERAGEOFTHEMEDIAN2#3INTHEPORTAND STARBOARDBOWANDQUARTERASPECTS BUTEXCLUDINGTHEBROADSIDEPEAKS4HESTATISTICS INCLUDEDATACOLLECTEDATNOMINALWAVELENGTHSOF ANDCMFORSHIPDIS PLACEMENTSRANGINGFROMTOKILOTONS &IGURE SUMMARIZES THE GENERAL 2#3 LEVELS OF THE WIDE VARIETY OF TARGETS DISCUSSEDINTHISSECTION WITHTHE2#3OFAMETALLICSPHERESHOWNASAFUNCTIONOFITS VOLUMEFORCOMPARISON4HEORDINATEISTHE2#3INSQUAREMETERS ANDTHEABSCISSAIS THEVOLUMEOFTHETARGETINCUBICFEET"ECAUSETHECHARTISINTENDEDONLYTODISPLAYTHE WIDERANGEIN2#3THATMAYBEENCOUNTEREDINPRACTICE THELOCATIONSOFTARGETSONTHE CHARTAREAPPROXIMATEATBEST7ITHINGIVENTARGETCLASSES THE2#3MAYBEEXPECTED TOVARYBYASMUCHASORD" DEPENDINGONFREQUENCY ASPECTANGLE ANDSPECIFIC TARGET CHARACTERISTICS 2EADERS SEEKING MORE EXPLICIT DETAIL THAN THIS SHOULD CONSULT REFERENCEDMATERIALATTHEENDOFTHISCHAPTER
2!$!2#2/333%#4)/.
£{°£x
&)'52% -EASURED2#3OFALARGENAVALAUXILIARYSHIPFORHORIZONTALINCIDENTPOLARIZATION4HE UPPERPATTERNA ISFOR'(Z ANDTHELOWERPATTERNB ISFOR'(Z3HOWNARETHE AND PERCENTILELEVELSBASEDONTHESTATISTICSOFTHEDATAOVERnASPECTANGLEWINDOWS
£{°£È
2!$!2(!.$"//+
&)'52% 3UMMARYOF2#3LEVELSOFTARGETSDISCUSSED INTHISSECTION4HELOCATIONSOFTARGETSONTHECHARTAREGENERAL INDICATIONSONLY
£{°ÎÊ , -Ê*, /" Ê/ +1 !SSHOWNIN&IGURE SCATTERINGOBSTACLESAREGENERALLYSORTEDINTOTHREEDIFFERENT REGIMESBASEDONTHEIRBODYSIZEINWAVELENGTHS6ERYLOOSELY THESETHREEREGIONSARE L
L
L
2AYLEIGHREGIONTYPICALBODYSIZE K 2ESONANCEREGIONK TYPICALBODYSIZE K /PTICSREGIONK TYPICALBODYSIZE
4HEBOUNDARIESSEPARATINGTHETHREEREGIMESAREDIFFUSEATBEST4HEUTILITYOFOUR 2#3ESTIMATIONANDCOMPUTATIONMETHODSDEPENDSINLARGEMEASUREONWHEREINTHIS SIZESCHEMEWEFINDOURTARGET !LTHOUGHTHECOMPLEXITYANDSIZEOFMOSTSCATTERINGOBJECTSPRECLUDETHEAPPLICA TION OF EXACT METHODS OF RADAR CROSS SECTION PREDICTION EXACT SOLUTIONS FOR SIMPLE BODIES PROVIDE VALUABLE CHECKS FOR APPROXIMATE METHODS 4HE EXACT METHODS ARE RESTRICTEDTORELATIVELYSIMPLEORRELATIVELYSMALLOBJECTSINTHE2AYLEIGHANDRESONANT REGIONS WHEREASMOSTOFTHEAPPROXIMATEMETHODSHAVEBEENDEVELOPEDFORTHEOPTICS REGION ALSOCALLEDTHEHIGH FREQUENCYREGION4HEREAREEXCEPTIONSTOTHESEGENERAL LIMITATIONS OFCOURSE4HEEXACTSOLUTIONSFORMANYOBJECTSCANBEUSEDFORLARGEBOD IESWELLINTOTHEOPTICSREGIONIFONEUSESARITHMETICOFSUFFICIENTPRECISION ANDMANY OPTICS APPROXIMATIONS CAN BE EXTENDED TO BODIES OF MODEST ELECTRICAL SIZE INTO THE RESONANCEREGION,OW FREQUENCYAPPROXIMATIONSDEVELOPEDFORTHE2AYLEIGHREGION CANEXTENDUPWARDINTOTHERESONANCEREGION %XACT-ETHODS 4HEEXACTMETHODSAREBASEDONEITHERTHEINTEGRALORDIFFEREN TIALFORMOF-AXWELLSEQUATIONS
2!$!2#2/333%#4)/.
£{°£Ç
$IFFERENTIAL %QUATIONS -AXWELLS FOUR DIFFERENTIAL EQUATIONS CONSTITUTE A SUC CINCTSTATEMENTOFTHERELATIONSHIPBETWEENELECTRICANDMAGNETICFIELDSPRODUCEDBY CURRENTSANDCHARGESANDBYEACHOTHER4HEFOUREQUATIONSMAYBEMANIPULATEDFOR ISOTROPICSOURCE FREEREGIONSTOGENERATETHEWAVEEQUATION
& K &
WHERE & REPRESENTS EITHER THE VECTOR ELECTRIC FIELD OR THE VECTOR MAGNETIC FIELD %QUATIONISASECOND ORDERDIFFERENTIALEQUATIONTHATMAYBESOLVEDASABOUNDARY VALUEPROBLEMWHENTHEFIELDSONTHESURFACEOFTHESCATTERINGOBSTACLEARESPECIFIED 4HEFIELDSARETYPICALLYREPRESENTEDASTHESUMOFKNOWNANDUNKNOWNCOMPONENTS INCIDENTANDSCATTEREDFIELDS ANDTHEBOUNDARYCONDITIONSARETHEKNOWNRELATION SHIPSTHATMUSTBESATISFIEDBETWEENTHEFIELDSBOTHELECTRICANDMAGNETIC JUSTINSIDE ANDJUSTOUTSIDETHESURFACEOFTHEOBSTACLE4HOSEBOUNDARYCONDITIONSAREPARTICULARLY SIMPLEFORSOLIDCONDUCTINGORDIELECTRICOBJECTS 4HE BOUNDARY CONDITIONS INVOLVE ALL THREE COMPONENTS OF THE VECTOR FIELDS AND THESURFACEOFTHEBODYMUSTCOINCIDEWITHACOORDINATEOFTHEGEOMETRICALSYSTEMIN WHICHTHEBODYISDESCRIBED&OREXAMPLE THECOORDINATER CONSTANTCOULDREPRESENT ASPHERICALSURFACE4HESOLUTIONOFTHEWAVEEQUATIONISMOSTUSEFULFORTHOSESYSTEMS INWHICHTHEEQUATIONISSEPARABLEINTOORDINARYDIFFERENTIALEQUATIONSINEACHOFTHE VARIABLES4HESCATTEREDFIELDSARETYPICALLYEXPRESSEDINTERMSOFINFINITESERIES THE COEFFICIENTSOFWHICHARETOBEDETERMINEDINTHEACTUALSOLUTIONOFTHEPROBLEM/NCE OBTAINED THESOLUTIONALLOWSTHEFIELDSTOBECALCULATEDATANYPOINTINSPACE WHICH IN2#3PROBLEMSISTHELIMITASTHEDISTANCEFROMTHEOBSTACLEBECOMESINFINITE4HE SOLUTIONOFTHEWAVEEQUATIONMAYTHENBEUSEDIN%QTODETERMINETHESCATTERING CROSSSECTION !SIDEFROMAFEWVERYSIMPLEOBJECTS SUCHASTHESPHEREANDTHEINFINITECIRCULAR CYLINDER THESOLUTIONFOR%QISMOREACADEMICTHANPRACTICAL4HESOLUTIONFOR OTHERSTRUCTURES SUCHASINFINITEPARABOLICANDELLIPTICCYLINDERS AREDIFFICULTATBEST ANDFORMANYSTRUCTURESWHOSESURFACESMAYCOINCIDEWITHACOORDINATESYSTEM THERE ISNOCONVENIENTMETHODOFSOLUTION 4HEMOSTUSEFULANDPRACTICALOFTHEEXACTSOLUTIONSAVAILABLEISTHATOFTHEPER FECTLYCONDUCTINGSPHERE SHOWNEARLIERIN&IGURE-ETALSPHERESAREUSEDROU TINELY AS CALIBRATION TARGETS FOR 2#3 MEASUREMENTS BECAUSE AN EXACT SOLUTION IS AVAILABLEMETALSPHERESARENOTVERYHARDTOBUILDANDEFFICIENTCOMPUTERCODESARE AVAILABLEFOROBTAININGTHEEXACTSOLUTION.OOTHERSCATTERINGBODYAFFORDSALLTHESE CONVENIENCES )NTEGRAL%QUATIONS -AXWELLSEQUATIONSMAYALSOBEMANIPULATEDTOGENERATEA PAIROFINTEGRALEQUATIONSKNOWNASTHE3TRATTON #HUEQUATIONS
%S u ¯ [IK: N r ( 9 N r % r 9 N ; % 9] D3
(S u ¯ [ IK9 N r % 9 N r ( r 9 N ; % 9] D3
WHERENISTHEUNITSURFACENORMALERECTEDATTHESURFACEPATCHD3ANDYISTHE'REENS FUNCTION
9 EIKR P R
£{°£n
2!$!2(!.$"//+
4HEDISTANCERIN%QISMEASUREDFROMTHESURFACEPATCHD3TOTHEPOINTAT WHICHTHESCATTEREDFIELDSAREDESIRED WHICHCOULDBEANOTHERSURFACEPATCH4HESE EXPRESSIONSSTATETHATIFTHETOTALELECTRICANDMAGNETICFIELDDISTRIBUTIONSAREKNOWN OVER A COMPLETELY CLOSED SURFACE 3 AS INDICATED BY THE LITTLE CIRCLE ON THE INTEGRAL SIGN THEFIELDSANYWHEREINSPACEMAYBECOMPUTEDBYSUMMINGINTEGRATING THOSE SURFACEFIELDDISTRIBUTIONSOVERTHEENTIRESURFACE4HISSCATTERINGPROBLEMRELIESON THESAMETWOEQUATIONS BUTINSTEADOFMEASURINGTHETOTALFIELDSOVERACLOSEDSURFACE SURROUNDINGTHEBODY ONEDETERMINESTHEFIELDSINDUCEDONTHEBODYSURFACESTHEM SELVESBYTHEINCIDENTWAVEANDTHENSOLVESASYSTEMOFLINEAREQUATIONS4HESESURFACE FIELDSBECOMEUNKNOWNSTOBEDETERMINED4HETWOEQUATIONSARECOUPLEDBECAUSETHE UNKNOWNSAPPEARONBOTHSIDESOFBOTHEQUATIONS4HEMETHODOFSOLUTIONISKNOWNAS THEMETHODOFMOMENTS-/- WHICHREDUCESTHEINTEGRALEQUATIONSTOACOLLECTION OFHOMOGENEOUSLINEAREQUATIONSTHATMAYBESOLVEDBYMATRIXTECHNIQUES /NCETHEBOUNDARYCONDITIONSHAVEBEENSPECIFIED THESURFACE3ISSPLITINTOACOL LECTIONOFDISCRETEPATCHES ASSUGGESTEDIN&IGURE4HEPATCHESMUSTBESMALL ENOUGHTYPICALLYLESSTHANK THATTHEUNKNOWNCURRENTSANDCHARGESOVEREACHPATCH ARECONSTANTORATLEASTCANBEDESCRIBEDBYSIMPLEFUNCTIONS!WEIGHTINGFUNCTIONMAY BEASSIGNEDTOEACHPATCH ANDTHEPROBLEMISESSENTIALLYSOLVEDWHENTHEAMPLITUDE ANDPHASEOFTHOSEFUNCTIONSHAVEBEENDETERMINED )FTHEPOINTOFOBSERVATIONISFORCEDDOWNTOAGENERALSURFACEPATCH THEFIELDSON THELEFTSIDESOF%QSANDARETHOSEDUETOTHECONTRIBUTIONSOFTHEFIELDSONALL OTHERPATCHES PLUSTHEINCIDENTFIELDSANDAhSELF FIELDv4HESELF FIELDORSELF CURRENTOR SELF CHARGE ISMOVEDTOTHERIGHTSIDEOFTHEEQUATIONS LEAVINGONLYTHEKNOWNINCIDENT FIELDONTHELEFTSIDE7HENTHEPROCESSISREPEATEDFOREACHPATCHONTHESURFACE ASYS TEMOFNLINEARHOMOGENEOUSEQUATIONSINNUNKNOWNSISGENERATED)FTHEBOUNDARY CONDITIONSPERMITTHEDECOUPLINGOFTHEEQUATIONS THENUMBEROFUNKNOWNSMAYBE HALVEDTONEQUATIONSINNUNKNOWNS 4HE COEFFICIENTS OF THE RESULTING MATRIX INVOLVE ONLY THE ELECTRICAL DISTANCES INWAVELENGTHS BETWEENALLPATCHESTAKENBYPAIRS ANDTHEORIENTATIONOFPATCH SURFACE NORMALS 4HE UNKNOWN FIELDS MAY BE FOUND BY INVERTING THE RESULTING MATRIX AND MULTIPLYING THE INVERTED MATRIX BY A COLUMN MATRIX REPRESENTING THE INCIDENTFIELDATEACHPATCH4HESURFACEFIELDSARETHENSUMMEDININTEGRALSSIMILAR TO%QSANDTOOBTAINTHESCATTEREDFIELD WHICHTHENMAYBEINSERTEDIN %QTOCOMPUTETHE2#3
&)'52% 4HEMETHODOFMOMENTSDIVIDESTHEBODYSURFACEINTOACOLLECTIONOFDISCRETEPATCHES4HIS PLANFORMOFTHE53!IR&ORCE" 3PIRITSTEALTHBOMBERUSESTRIANGULARPATCHES
2!$!2#2/333%#4)/.
£{°£
&)'52% !ZIMUTH PLANE -/- PREDICTED EDGE ON 2#3OFAFLATPLATEHAVINGTHEPLANFORMSHOWNIN&IGURE FORWINGLEADINGEDGESKINLENGTH4HEINCIDENTELECTRICFIELD WASINTHEPLANEOFTHEPLATE
4HEMETHODOFMOMENTSHASBECOMEAPOWERFULTOOLINTHEPREDICTIONANDANALYSIS OF ELECTROMAGNETIC SCATTERING WITH APPLICATIONS FOR ANTENNA DESIGN AS WELL AS 2#3 PREDICTION4HISMETHODHASTHREELIMITATIONS HOWEVER &IRST BECAUSECOMPUTERMEMORYANDPROCESSINGTIMEBOTHINCREASERAPIDLYWITH THEELECTRICALSIZEOFTHEOBJECT THEREMIGHTBEANECONOMICLIMITFORTHEMAXIMUM TARGETELECTRICALSIZEINWAVELENGTHS FORWHICH-/-CANBEUSED3ECOND -/- YIELDSNUMBERS NOTFORMULAS ANDISTHEREFOREANUMERICALEXPERIMENTALTOOL(OWEVER TRENDSMAYBEESTABLISHEDBYRUNNINGTHESENUMERICALEXPERIMENTSREPEATEDLYFORPARA METRICCHANGESINTHEGEOMETRYORCONFIGURATIONOFANOBJECT ORINTHEANGLEOFARRIVAL OROFTHEFREQUENCY OFTHEINCIDENTWAVE4HIRD THESOLUTIONSFORSOMEOBJECTSMAY CONTAINSPURIOUSRESONANCESTHATDONOTACTUALLYEXIST THEREBYREDUCINGTHECONFIDENCE ONEMAYHAVEINAPPLYINGTHEMETHODTOARBITRARYSTRUCTURES &IGURE SHOWS A -/- CODE PREDICTION OF THE EDGE ON 2#3 PATTERN OF A LARGE FLATMETALPLATEOFZEROTHICKNESSHAVINGTHEPLANFORMOF&IGURE&OR THEPURPOSEOFILLUSTRATION WECHOSEASIMULATIONFREQUENCYSUCHTHATTHELEADING EDGESOFTHEWINGSWEREKLONG4HEINCIDENTPOLARIZATIONANDTHEDIRECTIONOFTHE INCIDENTWAVEWEREBOTHINTHEPLANEOFTHEPLATE.OSE ONINCIDENCELIESATZERO DEGREEASPECTATTHECENTEROFTHECHART ANDTHETAIL ONASPECTLIESATnATBOTH SIDESOFTHECHART !SSHOWNIN4ABLE THEAPPROXIMATE2#3OFASTRAIGHTEDGEOFLENGTH,PRE SENTEDPERPENDICULARTOTHEINCIDENTWAVEISR ,O(OWEVER THISESTIMATEISSOME D" LOWER THAN THE PEAK AMPLITUDE ATTAINED IN &IGURE BY THE LEADING EDGE ECHOES EITHER SIDE OF NOSE ON INCIDENCE %VIDENTLY THERE ARE OTHER MORE SUBTLE ECHOSOURCESTHATCONTRIBUTETOTHE2#3ATTHESEASPECTS POSSIBLYSURFACETRAVELING WAVECONTRIBUTIONS !PPROXIMATE -ETHODS !PPROXIMATE METHODS FOR COMPUTING SCATTERED FIELDS AREAVAILABLEINBOTHTHE2AYLEIGHANDTHEOPTICSREGIONS2AYLEIGH REGIONAPPROXIMA TIONSMAYBEDERIVEDBYEXPANDINGTHEWAVEEQUATION%Q INAPOWERSERIESOF THEWAVENUMBERK(IGHER ORDERTERMSOFTHEEXPANSIONBECOMEPROGRESSIVELYMORE DIFFICULTTOOBTAIN4HE2#3PATTERNOFA2AYLEIGHSCATTERERISVERYBROAD ESPECIALLYIF THEOBJECTHASSIMILARTRANSVERSEANDLONGITUDINALDIMENSIONS4HEMAGNITUDEOFTHE ECHOISPROPORTIONALTOTHESQUAREOFTHEVOLUMEOFTHEOBJECTANDVARIESASTHEFOURTH
£{°Óä
2!$!2(!.$"//+
POWEROFTHEFREQUENCYOFTHEINCIDENTWAVE"ECAUSETHEMETHODOFMOMENTSIS QUITE WELL SUITED TO THE SOLUTION OF 2AYLEIGH REGION PROBLEMS ANALYTICAL 2AYLEIGH REGION EXPANSIONS FOR PREDICTING THE 2#3 OF ELECTRICALLY SMALL OBJECTS HAVE LAPSED INTODISUSE 3EVERALAPPROXIMATEMETHODSHAVEBEENDEVISEDFORTHEOPTICSREGION EACHWITHITS PARTICULARADVANTAGESANDLIMITATIONS4HEMOSTMATUREOFTHEMETHODSAREGEOMETRIC OPTICS AND PHYSICAL OPTICS WITH LATER METHODS ATTACKING THE PROBLEM OF DIFFRACTION FROMEDGESANDFROMSHADOWBOUNDARYFIELDDISCONTINUITIES7HILETHEGENERALACCU RACYOFTHEOPTICSREGIONAPPROXIMATIONSIMPROVESASTHESCATTERINGOBSTACLEBECOMES ELECTRICALLYLARGER SOMEOFTHEMGIVEREASONABLYACCURATERESULTSWITHINORD" FOROBJECTSASSMALLASAWAVELENGTHORSO 'EOMETRIC/PTICS 4HETHEORYOFGEOMETRICOPTICS'/ ISBASEDONTHECONSERVA TIONOFENERGYWITHINASLENDERFICTITIOUSTUBECALLEDARAY4HEDIRECTIONOFPROPAGATION ISALONGTHETUBE ANDCONTOURSOFEQUALPHASEAREPERPENDICULARTOIT)NALOSSLESS MEDIUM ALLTHEENERGYENTERINGTHETUBEATONEENDMUSTCOMEOUTTHEOTHEREND BUT ENERGYLOSSESWITHINTHEMEDIUMMAYALSOBEACCOUNTEDFOR!NINCIDENTWAVEMAYBE REPRESENTEDASACOLLECTIONOFALARGENUMBEROFRAYS ANDWHENARAYSTRIKESASURFACE PARTOFTHEENERGYISREFLECTEDANDPARTISTRANSMITTEDACROSSTHESURFACE4HEAMPLITUDE ANDPHASEOFTHEREFLECTEDANDTRANSMITTEDRAYSDEPENDONTHEPROPERTIESOFTHEMEDIA ONEITHERSIDEOFTHESURFACE4HEREFLECTIONISPERFECTIFTHESURFACEISPERFECTLYCON DUCTING ANDNOENERGYISTRANSMITTEDACROSSTHEBOUNDARYINTOTHEBODY7HENENERGY CANPASSTHROUGHTHESURFACE TRANSMITTEDRAYSAREBENTTOWARDTHESURFACENORMALIN CROSSINGASURFACEINTOANELECTRICALLYDENSERMEDIUMHIGHERINDEXOFREFRACTION AND AWAYFROMTHESURFACENORMALINTOALESSDENSEMEDIUM4HISBENDINGOFRAYSISKNOWN ASREFRACTION $EPENDINGONSURFACECURVATUREANDBODYMATERIAL REFLECTEDANDTRANSMITTED RAYSMAYDIVERGEFROMONEANOTHERORTHEYMAYCONVERGETOWARDEACHOTHER4HIS DEPENDENCEISTHEBASISFORTHEDESIGNOFLENSESANDREFLECTORSATRADARWAVELENGTHS ASWELLASATOPTICALWAVELENGTHS4HEREDUCTIONININTENSITYASTHERAYSDIVERGE SPREADAWAY FROMTHEPOINTOFREFLECTIONCANBECALCULATEDFROMTHECURVATURES OFTHEREFLECTINGSURFACEANDTHEINCIDENTWAVEATTHESPECULARPOINT WHICHISTHAT POINTONTHESURFACEWHERETHEANGLEOFREFLECTIONEQUALSTHEANGLEOFINCIDENCE 4HE PRINCIPAL RADII OF CURVATURE OF THE SURFACE ARE MEASURED IN TWO ORTHOGONAL PLANESATTHESPECULARPOINT ASSHOWNIN&IGURE7HENTHEINCIDENTWAVEIS PLANARANDTHEDIRECTIONOFINTERESTISBACKTOWARDTHESOURCE THEGEOMETRICOPTICS 2#3ISSIMPLY
R P AA
WHEREAANDAARETHERADIIOFCURVATUREOFTHEBODYSURFACEATTHESPECULARPOINT 4HISFORMULABECOMESEXACTINTHEOPTICALLIMITOFVANISHINGWAVELENGTHSANDIS PROBABLYACCURATETOORPERCENTFORRADIIOFCURVATUREASSMALLASKORK)T ASSUMES THAT THE SPECULAR POINT IS NOT CLOSE TO AN EDGE7HEN APPLIED TO DIELECTRIC OBJECTS THEEXPRESSIONSHOULDBEMULTIPLIEDBYTHESQUAREOFTHEVOLTAGEREFLECTION COEFFICIENTASSOCIATEDWITHTHEMATERIALPROPERTIESOFTHEOBJECT)NTERNALREFLECTIONS MAYALSOBEACCOUNTEDFOR ANDTHEPHASEOFINTERNALLYREFLECTEDRAYSSHOULDBEADJUSTED ACCORDINGTOTHEELECTRICALPATHLENGTHSTRAVERSEDWITHINTHEBODYMATERIAL4HENET 2#3SHOULDTHENBECOMPUTEDASTHECOHERENTSUMOFTHESURFACEREFLECTIONPLUSALL SIGNIFICANTINTERNALREFLECTIONS%QUATIONFAILSWHENONEORBOTHSURFACERADIIOF
2!$!2#2/333%#4)/.
£{°Ó£
&)'52% 4HEGEOMETRICOPTICS2#3OFADOUBLYCURVEDSURFACEDEPENDS ONTHEPRINCIPALRADIIOFCURVATUREATTHESPECULARPOINT4HESPECULARPOINTISWHERE THESURFACENORMALPOINTSTOWARDTHERADAR
CURVATUREATTHESPECULARPOINTBECOMEINFINITE YIELDINGINFINITE2#3 WHICHISOBVI OUSLYWRONG4HISOCCURSFORFLATANDSINGLYCURVEDSURFACES 0HYSICAL /PTICS 4HE THEORY OF PHYSICAL OPTICS 0/ IS A SUITABLE ALTERNATIVE FORBODIESWITHFLATANDSINGLYCURVEDSURFACEFEATURES4HETHEORYISBASEDONTWO APPROXIMATIONSINTHEAPPLICATIONOF%QSAND BOTHOFWHICHAREREASONABLY EFFECTIVEINAHOSTOFPRACTICALCASES4HEFIRSTISTHEFAR FIELDAPPROXIMATION WHICH ASSUMESTHATTHEDISTANCEFROMTHESCATTERINGOBSTACLETOTHEPOINTOFOBSERVATIONIS LARGECOMPAREDWITHANYDIMENSIONOFTHEOBSTACLEITSELF4HISALLOWSUSTOREPLACETHE GRADIENTOF'REENSFUNCTIONWITH
Y IKY OS
Y O E IKR r S E IK2O P 2O
WHERERISTHEPOSITIONVECTOROFINTEGRATIONPATCHD3ANDSISAUNITVECTORPOINTING FROMANORIGININORNEARTHEOBJECTTOTHEFAR FIELDOBSERVATIONPOINT USUALLYBACK TOWARDTHERADAR2OISTHEDISTANCEFROMTHEORIGINOFTHEOBJECTTOTHEFAR FIELDOBSER VATIONPOINT 4HESECONDISTHETANGENTPLANEAPPROXIMATION INWHICHTHETANGENTIALFIELDCOM PONENTSNr%ANDNr(AREAPPROXIMATEDBYTHEIRGEOMETRICOPTICSVALUES4HATIS ATANGENTPLANEISPASSEDTHROUGHTHESURFACECOORDINATEATTHEPATCHD3 ANDTHETOTAL SURFACEFIELDSARETAKENTOBEPRECISELYTHOSETHATWOULDHAVEEXISTEDHADTHESURFACE ATD3BEENINFINITEANDPERFECTLYFLAT)NESSENCE WEDONOTKNOWTHESEFIELDS BUTWE TAKEOURBESTGUESSASTOWHATTHEYAREANDINSERTTHATESTIMATEINTOEITHEROFTHETWO INTEGRALS4HATDONE THEESTIMATEOFTHEUNKNOWNFIELDSINTHEINTEGRALSOF%QS ANDMAYBEEXPRESSEDENTIRELYINTERMSOFTHEKNOWNINCIDENTFIELDVALUES4HE PROBLEMTHENBECOMESONEOFEVALUATINGTHECHOSENINTEGRALANDSUBSTITUTINGTHERESULT INTO%QTOOBTAINTHE2#3
£{°ÓÓ
2!$!2(!.$"//+
)FTHESURFACEISAGOODCONDUCTOR THETOTALTANGENTIALELECTRICFIELDISVIRTUALLYZERO ANDTHETOTALTANGENTIALMAGNETICFIELDISTWICETHEAMPLITUDEOFTHEINCIDENTTANGENTIAL MAGNETICFIELD N r%
ªN r (I Nr( « ¬N
ILLUMINATED SURFACES SHADED SURFACEES
.OTETHATTHETANGENTIALCOMPONENTSOFBOTHTHEELECTRICANDTHEMAGNETICFIELDS ARESETTOZEROOVERTHOSEPARTSOFTHESURFACESHADEDFROMTHEINCIDENTFIELDBYOTHER BODYSURFACES/THERAPPROXIMATIONSMAYBEDEVISEDFORNONCONDUCTINGSURFACES)F THEINCIDENTWAVELENGTHISLONGENOUGH FOREXAMPLE THESURFACEOFASOAPBUBBLEOR THELEAFOFATREEMAYBEMODELEDASATHINMEMBRANE OVERWHICHNEITHERTHEELECTRIC NORMAGNETICFIELDSAREZERO 4HEPHYSICAL OPTICSINTEGRALISEASYTOEVALUATEFORFLATMETALLICPLATESBECAUSETHE PHASEISTHEONLYQUANTITYWITHINTHEINTEGRALTHATVARIES ANDITVARIESLINEARLYACROSS THESURFACE7HENAPPLIEDTOARECTANGULARMETALPLATE THEINTEGRALEVALUATIONLEADS TOTHE2#3
R P
! COSP K
;
SIN K@ SINP COSE SIN KW SINP SIN E
; K@ SINP COSE KW SINP SIN E
WHERE! @WISTHEPHYSICALAREAOFTHEPLATE PISTHEANGLEBETWEENTHESURFACE NORMALOFTHEPLATEANDTHEDIRECTIONTOTHERADAR EISTHEANGLEBETWEENTHEPLANE CONTAININGTHELINEOFSIGHTANDTHEEDGEWHOSELENGTHIS@ ANDWISTHEWIDTHOFTHE PLATE!MOREGENERALPHYSICALOPTICSFORMULAISAVAILABLEFORTHEBISTATICSCATTERING FROMANYPOLYGONALPLATE )FWESETE nORn WEOBTAINAPRINCIPALPLANE2#3PATTERNINCIDENCEINA PLANEPERPENDICULARTOAPAIROFEDGES 7HENE n %QBECOMES
R P
! COSP K
;
SIN K@ SINP K@ SINP
)FWESETE nINSTEADOFE n WEGETNEARLYTHESAMEANSWER EXCEPTTHATK@ IN%QBECOMESKW4HEPHYSICALOPTICSINTEGRALISNOTDEPENDENTONTHEPOLAR IZATIONOFTHEINCIDENTWAVEANDISUNRELIABLEFORANGLESMUCHGREATERTHANnFROM BROADSIDEINCIDENCE "YWAYOFCOMPARISON THEPHYSICALOPTICSFORMULAFORTHE2#3OFACIRCULARMETAL DISKIS
R P
! COSP K
;
* KD SINP KD SINP
WHERE!ISTHEPHYSICALAREAOFTHEDISK DISITSDIAMETER AND*X ISTHE"ESSELFUNC TIONOFTHEFIRSTKINDOFORDER%QUATIONSTHROUGHALLREDUCETOTHEVALUE LISTEDIN4ABLEFORNORMALINCIDENCE&ORFURTHERCOMPARISON THE0/PATTERNSOF TWOSQUAREPLATESANDACIRCULARDISKAREPLOTTEDIN&IGURE
2!$!2#2/333%#4)/.
£{°ÓÎ
&)'52% 0/ PATTERNS OF THE 2#3 OF A SQUARE PLATE ADISK ANDSECONDSQUAREPLATE
4HETHREEPATTERNSEACHCOVERAnSECTORFROMBROADSIDETOEDGE ONANDAREPLACED SIDE BY SIDEFORCLARITY4HEAREASOFALLTHREEPLATESWEREFIXEDATK HENCEALLTHREE PATTERNSRISETOTHESAMEAMPLITUDEATBROADSIDEINCIDENCEZEROASPECT 4HECENTER PATTERNISFORTHEDISK WHILETHEFIRSTANDTHIRDAREBOTHFORASQUAREPLATE(OWEVER THESQUAREPLATEWASORIENTEDFORAPRINCIPAL PLANEPATTERNINTHELEFTMOSTCHARTANDLIKE ADIAMONDE n INTHERIGHTMOSTCHART4HEAMOUNTOFSURFACEDISTRIBUTEDTOWARD THESIDESOFTHEPLATESINFLUENCESTHESIDELOBELEVELS 4HE 0/ INTEGRAL IS SOMEWHAT MORE COMPLICATED TO EVALUATE WHEN THE SURFACE IS SINGLYORDOUBLYCURVED!NEXACTEVALUATIONCANBEPERFORMEDFORACIRCULARCYLINDER ANDASPHERICALCAPVIEWEDALONGTHEAXISOFSYMMETRY BUTNOTFORATRUNCATEDCONEOR ASPHERICALCAPSEENALONGOTHERTHANTHEAXISOFSYMMETRY%VENSO THEEXACTEVALU ATIONFORTHECYLINDERINCLUDESFICTITIOUSCONTRIBUTIONSFROMTHESHADOWBOUNDARIESAT THESIDESOFTHECYLINDERTHATDONOTAPPEARINASTATIONARYPHASEAPPROXIMATION 4HEAMPLITUDEOFTHEELEMENTALSURFACECONTRIBUTIONSCHANGESSLOWLYOVERTHESURFACE OFINTEGRATIONWHEREASTHEPHASECHANGESMUCHMORERAPIDLY!SSUCH THENETCONTRIBU TIONINREGIONSOFRAPIDPHASECHANGEISESSENTIALLYZEROANDMAYBEIGNORED!STHESPEC ULARREGIONSAREAPPROACHED ONTHEOTHERHAND THEPHASEVARIATIONSLOWSDOWNANDTHEN REVERSESASTHESPECULARPOINTISCROSSED4HISRESULTSINANONZEROSPECULARCONTRIBUTION TOTHEINTEGRAL4HEPHASEVARIATIONNEARTHESHADOWBOUNDARIESISRAPID HENCE SURFACE CONTRIBUTIONSTHEREAREIGNOREDINASTATIONARYPHASEEVALUATION BUTANEXACTEVALUATION INCLUDESTHEMBECAUSETHESHADOWBOUNDARIESARETHELIMITSOFINTEGRATION"ECAUSETHE ACTUALSURFACEFIELDDISTRIBUTIONSDONOTSUDDENLYDROPTOZEROASTHESHADOWBOUNDARYIS CROSSED ASASSUMEDBYTHETHEORY THESHADOWBOUNDARYCONTRIBUTIONSARESPURIOUS 4HUS ASTATIONARYPHASEAPPROXIMATIONOFTHEPHYSICALOPTICSINTEGRALOVERCLOSEDCURVED SURFACESTENDSTOBEMORERELIABLETHANANEXACTEVALUATIONOFTHEINTEGRAL 7ITHTHISINMIND THESTATIONARYPHASERESULTFORACIRCULARCYLINDERIS
R KA@
SIN K@ SINP
K@ SINP
WHEREAISTHERADIUSOFTHECYLINDER @ISITSLENGTH ANDPISTHEANGLEOFFBROADSIDE INCIDENCE%QUATIONINCLUDESONLYTHECONTRIBUTIONFROMTHECURVEDSIDEOFTHE
£{°Ó{
2!$!2(!.$"//+
CYLINDER AND NOT ITS FLAT ENDS WHICH MAY BE INCLUDED BY USING THE PRESCRIPTION OF %Q%QUATIONMAYALSOBEUSEDTOESTIMATETHE2#3OFATRUNCATEDRIGHT CIRCULARCONEIFTHERADIUSAISREPLACEDBYTHEMEANRADIUSOFTHECONEAND@ISREPLACED BYTHELENGTHOFTHESLANTEDSURFACE !LTHOUGHTHETHEORYOFPHYSICALOPTICSOFFERSASIGNIFICANTIMPROVEMENTOVERGEO METRIC OPTICS FOR FLAT AND SINGLY CURVED SURFACES IT SUFFERS OTHER DRAWBACKS %VEN THOUGH WE OBTAIN THE PROPER RESULT FOR MOST OF THE ILLUMINATED SURFACE THE PHYSI CALOPTICSINTEGRALYIELDSFALSECONTRIBUTIONSFROMTHESHADOWBOUNDARIES ASALREADY NOTED -OREOVER PHYSICAL OPTICS SHOWS NO DEPENDENCE ON THE POLARIZATION OF THE INCIDENTWAVEANDYIELDSDIFFERENTRESULTSWHENTHERECEIVERANDTHETRANSMITTERARE INTERCHANGED4HESEEFFECTSCONTRADICTOBSERVEDBEHAVIOR&INALLY ITERRSBYWIDERMAR GINSASTHEDIRECTIONOFOBSERVATIONMOVESFARTHERAWAYFROMTHESPECULARDIRECTION +ELLERSGEOMETRICALTHEORYOFDIFFRACTION'4$ OFFERSANIMPROVEMENTINBOTHTHE POLARIZATIONDEPENDENCEANDTHEPREDICTEDVALUESINTHEWIDE ANGLEREGIONS 'EOMETRIC4HEORYOF$IFFRACTION '4$ISARAY TRACINGMETHODTHATASSIGNSAN AMPLITUDEANDPHASETOFIELDSDIFFRACTEDATSMOOTHSHADOWBOUNDARIESANDATSURFACE DISCONTINUITIES"ECAUSETHELATTERAREMUCHMORESIGNIFICANTINBACKSCATTERINGCOM PUTATIONSTHANTHEFORMER WEFOCUSHEREONEDGEDIFFRACTION4HETHEORYASSUMESTHAT ARAYSTRIKINGANEDGEEXCITESACONEOFDIFFRACTEDRAYS ASIN&IGURE4HEHALF ANGLEOFTHISDIFFRACTIONCONEISEQUALTOTHEANGLEBETWEENTHEINCIDENTRAYANDTHE EDGE5NLESSTHEPOINTOFOBSERVATIONLIESONTHEDIFFRACTIONCONE NOVALUEISASSIGNED THEDIFFRACTEDFIELD4HESCATTERINGDIRECTIONINBACKSCATTERINGPROBLEMSISTHEREVERSE OFTHEDIRECTIONOFINCIDENCE WHENCETHEDIFFRACTIONCONEBECOMESADISK ANDTHESCAT TERINGEDGEELEMENTISPERPENDICULARTOTHELINEOFSIGHT 4HEAMPLITUDEOFTHEDIFFRACTEDFIELDISGIVENBYTHEPRODUCTOFADIFFRACTIONCOEFFI CIENTANDADIVERGENCEFACTOR ANDTHEPHASEDEPENDSONTHEPHASEOFTHEEDGEEXCITATION ANDONTHEDISTANCEBETWEENTHEOBSERVATIONPOINTANDTHEDIFFRACTINGEDGEELEMENT 4WOCASESARERECOGNIZED DEPENDINGONWHETHERTHEINCIDENTFIELDISPOLARIZEDPARALLEL ORPERPENDICULARTOTHEEDGE 4HEDIFFRACTEDFIELDISGIVENBYTHEFORMULA
%D
'E IKS EIP 8 A 9 P KS SIN A
WHERE'ISADIVERGENCEFACTOR 8AND9AREDIFFRACTIONCOEFFICIENTS AISTHEANGLE BETWEENTHEINCIDENTRAYANDTHEEDGE ANDSISTHEDISTANCETOTHEOBSERVATIONPOINT FROM THE POINT OF DIFFRACTION4HE DIFFERENCE OF THE TWO DIFFRACTION COEFFICIENTS IS
&)'52% 4HE+ELLERCONEOFDIFFRACTEDRAYS
2!$!2#2/333%#4)/.
£{°Óx
USEDWHENTHEINCIDENTELECTRICFIELDISPARALLELTOTHEEDGE4-POLARIZATION ANDTHE SUMWHENTHEINCIDENTMAGNETICFIELDISPARALLELTOTHEEDGE4%POLARIZATION 4HEDIVERGENCEFACTORACCOUNTSFORTHEDECAYINAMPLITUDEASTHERAYSSPREADAWAY FROMTHEEDGEELEMENTANDINCLUDESTHEEFFECTSOFTHERADIUSOFTHEEDGEIFITISCURVED ASATTHEENDOFATRUNCATEDCYLINDER ANDTHERADIUSOFCURVATUREOFTHEINCIDENTPHASE FRONT4HEDIVERGENCEFACTORFORATWO DIMENSIONALEDGEOFINFINITELENGTH ILLUMI NATEDBYAPLANEWAVEIS' S4HEDIFFRACTIONCOEFFICIENTSARE
8
SINP N N
COSP N COS;EI ES N=
9
SINP N N
COSP N COS;EI ES N=
WHEREEIANDESARETHEANGLESOFTHEPLANESOFINCIDENCEANDSCATTERING ASMEASURED FROMONEFACEOFTHEWEDGESAY THEILLUMINATEDONE ANDNISTHEEXTERIORWEDGEANGLE NORMALIZEDWITHRESPECTTOO7HENTHESEEXPRESSIONSAREEVALUATEDFORTHECASEOFA FLATMETALEDGEVIEWEDEDGE ONWITHTHEINCIDENTPOLARIZATIONINTHEPLANEOFTHEPLATE THEYYIELDTHEEDGE ONFORMULAR ,OLISTEDIN4ABLE +ELLERSDIFFRACTIONCOEFFICIENTSAREBASEDONANAPPROXIMATIONOFTHEEXACTSOLUTION FORANINFINITETWO DIMENSIONAL METALWEDGEASAPPLIEDTOATHREE DIMENSIONALPROB LEM!LTHOUGHTHISADAPTATIONOFATWO DIMENSIONALSOLUTIONTOTHETHREE DIMENSIONAL WORLD IS REASONABLY EFFECTIVE MOST OF THE TIME THE DIFFRACTION COEFFICIENTS INCONVE NIENTLYBLOWUPJUSTWHENNEEDEDMOST!CURSORYEXAMINATIONOF%QSAND WILLSHOWWHY 4HEDENOMINATORSOFBOTHEXPRESSIONSCONTAINTHEDIFFERENCEOFTWOCOSINETERMS THATBECOMEEQUALINTWODIFFERENTCASES7HENTHESCATTERINGDIRECTIONESISALIGNED ALONGTHESHADOWBOUNDARYWHEREEI ES O THEDIFFRACTIONCOEFFICIENT8IN%Q BECOMES SINGULAR A MEANINGLESS RESULT7HEN THE SCATTERING DIRECTION ES IS ALIGNED ALONGTHESPECULARDIRECTIONWHERETHELOCALANGLEOFREFLECTIONISEQUALTOTHELOCAL ANGLEOFINCIDENCE THENEI ES O)NTHISCASE ITISTHEDIFFRACTIONCOEFFICIENT9IN %QTHATBECOMESSINGULAR ASIMILARLYMEANINGLESSRESULT.OTETHATTHESETWO SINGULARITIESDONOTDEPENDONBODYGEOMETRY BUTONLYONTHERELATIVEDISPOSITIONSOF THEINCIDENCEANDSCATTERINGDIRECTIONS 0HYSICAL 4HEORY OF $IFFRACTION 4HE SINGULARITIES IN '4$ ARE OVERCOME IN THE PHYSICAL THEORY OF DIFFRACTION 04$ FORMULATED BY 0 )A 5FIMTSEV !LTHOUGH THESEPUBLICATIONSMAYBEDIFFICULTTOFIND WECITETHEMHEREFORCOMPLETENESS.OTE FROMTHEEDITOR4HEREADERINTERESTEDINTHISSUBJECTMIGHTALSOSEETHE5FIMTSEVPAPER h#OMMENTSON$IFFRACTION0RINCIPLESAND,IMITATIONSOF2#32EDUCTION4ECHNIQUES v 0ROC)%%% VOL PPn $ECEMBER ,IKE+ELLER 5FIMTSEVRELIED ONTHEAPPROXIMATEWIDE ANGLE SOLUTIONOFTHETWO DIMENSIONALWEDGEPROBLEM BUT HEDISTINGUISHEDBETWEENhUNIFORMvANDhNONUNIFORMvINDUCEDSURFACECURRENTS4HE UNIFORMCURRENTSWERENONEOTHERTHANTHESURFACECURRENTSOFPHYSICALOPTICS WHEREAS THENONUNIFORMCURRENTSWERETAKENTOBEUNDEFINEDFILAMENTARYCURRENTSALONGTHE EDGEITSELF5FIMTSEVNEVERATTEMPTEDTOWORKOUTHISFILAMENTARYFRINGECURRENTS BUT INSTEADTRACEDTHEIREFFECTDIRECTLYTOTHEFARSCATTEREDFIELD 2ECOGNIZINGTHATTHEFAR FIELD0/CONTRIBUTIONTOTHEFARFIELDWASTHEPARTOFTHE '4$PRESCRIPTIONGIVINGRISETOSINGULARITIESINTHE8AND9OF%QSAND 5FIMTSEVDEVISEDAMODIFIEDSETOFDIFFRACTIONCOEFFICIENTSBYSIMPLYSUBTRACTINGAWAY
£{°ÓÈ
2!$!2(!.$"//+
THE OFFENSIVE 0/ DIFFRACTION COEFFICIENTS FROM THE TIME HONORED WIDE ANGLE WEDGE SOLUTION4HIS GENERATED A NEW SET OF DIFFRACTION COEFFICIENTS THAT RETAINED ONLY THE EDGETERMS THEREFOREEXCLUDINGANYSURFACETERMS5FIMTSEVS04$COEFFICIENTSWERE WELLBEHAVEDINALMOSTALLDIRECTIONSINSPACE BUTSUFFEREDONEDISADVANTAGEINORDER TOCALCULATETHE2#3OFANARBITRARYEDGEDBODY ONEHADTOSUMALLTHE04$EDGE CONTRIBUTIONS PLUSALLTHE0/AND'/SURFACECONTRIBUTIONS(OWEVER THEPROCEDURE ISVIABLEANDHASBEENWELLDOCUMENTED )NCREMENTAL ,ENGTH $IFFRACTION #OEFFICIENT '4$ AND 04$ ARE BOTH BASED ON THEEXACTSOLUTIONOFTHETWO DIMENSIONALWEDGEPROBLEM FORWHICHTHEDIRECTIONS OFINCIDENCEANDSCATTERINGAREPERPENDICULARTOTHEEDGE7HENEXTENDEDTOTHECASE OFOBLIQUEINCIDENCE THEDIRECTIONOFOBSERVATIONMUSTLIEALONGAGENERATOROFTHE +ELLERCONEDEPICTEDIN&IGURE)FTHEEDGEISSTRAIGHTANDOFFINITELENGTH AS INTHETHREE DIMENSIONALWORLD %QOF+NOTTPROVIDESANAPPROXIMATIONOFTHE 2#3)FTHEEDGEISCURVED ITMAYBEREGARDEDASACOLLECTIONOFINFINITESIMALLYSHORT SEGMENTSBUTTEDTOGETHER ANDTHESCATTEREDFIELDSMAYBECOMPUTEDVIAANINTEGRATION OFINCREMENTALFIELDSDIFFRACTEDBYEACHELEMENTOFTHEEDGE4HISISTHECONCEPTINTRO DUCEDBY-ITZNER ANDTHESUMMATIONOFTHEFIELDSDIFFRACTEDBYTHEEDGEELEMENTS IMPLIESANINTEGRALAROUNDTHEEDGECONTOUR -ITZNER HOWEVER SOUGHTTHEFIELDSSCATTEREDINARBITRARYDIRECTIONS NOTJUSTTHOSE ALONGTHELOCAL+ELLERCONES ANDFORTHISPURPOSEHEDEVELOPEDHISINCREMENTALLENGTH DIFFRACTION COEFFICIENT ),$# %XTENDING THE EXAMPLE PROVIDED BY 5FIMTSEV HE DEVISEDASETOFDIFFRACTIONCOEFFICIENTSFORARBITRARYDIRECTIONSOFINCIDENCEANDSCAT TERING.OTUNEXPECTEDLY THOSECOEFFICIENTSAREMORECOMPLICATEDTHANTHE8SAND9S APPEARINGIN%QSAND -ITZNER EXPRESSED HIS RESULT AS THE DIFFRACTED ELECTRIC FIELD COMPONENTS PARALLEL ANDPERPENDICULARTOTHEPLANEOFSCATTERINGINTERMSOFTHECOMPONENTSOFTHEINCI DENTELECTRICFIELDPARALLELANDPERPENDICULARTOTHEPLANEOFINCIDENCE!SSUCH THE DIFFRACTIONCOEFFICIENTSMAYBEEXPRESSEDASTHREESEPARATEPAIRSREPRESENTINGPARAL LEL PARALLEL PERPENDICULAR PERPENDICULAR AND PARALLEL PERPENDICULAR OR PERPENDICU LAR PARALLEL COMBINATIONS/NEMEMBEROFEACHPAIRISDUETOTHETOTALSURFACECURRENT ON THE DIFFRACTING EDGE INCLUDING THE ASSUMED FILAMENTARY EDGE CURRENTS AND THE OTHERISDUETOTHEUNIFORMPHYSICALOPTICSCURRENTS-ITZNERSUBTRACTEDONEMEMBER OFEACHPAIRFROMTHEOTHER THEREBYRETAININGTHECONTRIBUTIONSFROMTHEFILAMENTARY EDGECURRENTSALONE 4HE RESULTS HAVE THE IDENTICAL FORM OF 5FIMTSEVS EXPRESSIONS IN WHICH THE 0/ COEFFICIENTS ARE SUBTRACTED FROM THE NON 0/ COEFFICIENTS 4HUS -ITZNERS EXPRES SIONFORTHESCATTEREDFIELDCONTAINSONLYTHECONTRIBUTIONSFROMTHEFILAMENTARYEDGE CURRENTS)NAPPLYINGHISTHEORYTOSCATTERINGOBJECTS THEREFORE THECONTRIBUTIONSOF NONFILAMENTARY INDUCEDSURFACECURRENTSMUSTBEACCOUNTEDFORSEPARATELY JUSTASIN 5FIMTSEVS04$7HENTHEDIRECTIONSOFINCIDENCEANDSCATTERINGBECOMEPERPENDICU LAR TO AN EDGE THE PERPENDICULAR PARALLEL TERMS DISAPPEAR AND -ITZNERS DIFFRACTION COEFFICIENTSTHENREDUCEIDENTICALLYTO5FIMTSEVS -ETHOD OF %QUIVALENT #URRENTS 5NDERTAKING WHAT HE CALLED A MORE RIGOROUS EVALUATION OF THE FIELDS INDUCED ON A WEDGE -ICHAELI DUPLICATED -ITZNERS RESULT FORTHETOTALSURFACECURRENTS CONFIRMING-ITZNERSPRIORDEVELOPMENT BUTHEDIDNOT EXPLICITLYREMOVETHE0/SURFACE CURRENTCONTRIBUTIONS 4HUS LIKE+ELLERS8AND 9 -ICHAELISDIFFRACTIONCOEFFICIENTSBECOMESINGULARINTHETRANSITIONREGIONSALONG
2!$!2#2/333%#4)/.
£{°ÓÇ
THEREFLECTIONANDSHADOWBOUNDARYDIRECTIONS-ICHAELILATERINVESTIGATEDTHEREMOVAL OFTHESINGULARITIES THECLEVERESTOFWHICHWASTHEUSEOFASKEWEDCOORDINATESYSTEM ALONGTHEWEDGESURFACES 7HILETHESEMETHODSOFEVALUATINGTHEFIELDSSCATTEREDBYEDGEELEMENTSMAYBE APPLICABLE TO SMOOTH UNBOUNDED EDGES THEY DO NOT ACCOUNT FOR THE DISCONTINUITIES ATCORNERSWHERETHEEDGESTURNABRUPTLYINOTHERDIRECTIONS!NATTACKONTHECORNER PROBLEMHASBEENSUGGESTEDBY3IKTAETAL
£{°{Ê , -Ê -1, /Ê/ +1 2#3MEASUREMENTSMAYBEREQUIREDFORANYOFSEVERALREASONS RANGINGFROMSCIENTIFIC INQUIRYTOVERIFICATIONOFCOMPLIANCEWITHPRODUCTSPECIFICATIONS4HEREARENOFORMAL STANDARDS GOVERNING INSTRUMENTATION AND MEASUREMENT METHODS BUT INFORMAL STAN DARDSOFGOODMEASUREMENTPRACTICEHAVEBEENRECOGNIZEDFORDECADES$EPENDING ONTHESIZEOFTHETESTOBJECT THEFREQUENCIESTOBEUSED ANDOTHERTESTREQUIREMENTS MEASUREMENTSMAYBEMADEININDOORTESTFACILITIESORONOUTDOORRANGES"ECAUSEONE ISSELDOMINTERESTEDINTHE2#3OFANOBJECTFORONLYONEASPECTANGLE ALLSTATICTEST RANGESUSETURNTABLESORROTATORSTOVARYTHETARGETASPECTANGLE!LTHOUGHTHEPURPOSE OFTESTINGOFTENGOVERNSHOWTHEMEASUREMENTSWILLBEMADE -ACKAND$YBDALPRO VIDEGOODOVERALLGUIDESFORROUTINE2#3TESTING 'ENERAL 2EQUIREMENTS 4HE MOST IMPORTANT REQUIREMENT FOR 2#3 MEASURE MENTS IS THAT THE TEST OBJECT BE ILLUMINATED BY A RADAR WAVE OF ACCEPTABLY UNIFORM AMPLITUDEANDPHASE'OODPRACTICEDICTATESTHATTHEAMPLITUDEOFTHEINCIDENTWAVE DEVIATEBYNOMORETHAND"OVERTHETRANSVERSEANDLONGITUDINALEXTENTOFTHETAR GETANDTHATTHEPHASEDEVIATIONBELESSTHAN)TISSTANDARDPRACTICEATSOMETEST RANGESTOPHYSICALLYPROBETHEINCIDENTFIELDATTHEONSETOFATESTPROGRAMTOVERIFYTHE AMPLITUDEUNIFORMITYOFTHEINCIDENTWAVE 4HEPHASEREQUIREMENTISTHEBASISOFTHEFAR FIELDRANGECRITERION
2 $K
WHERE2ISTHEDISTANCEBETWEENTHEINSTRUMENTATIONRADARANDTHETESTOBJECTAND$IS THEMAXIMUMTARGETDIMENSIONTRANSVERSETOTHELINEOFSIGHT!LLOTHERERRORSOURCES BEINGFIXED COMPLIANCEWITHTHEFAR FIELDREQUIREMENTISGENERALLYFELTTOYIELDDATA WITHANACCURACYOFD"ORBETTER&IGUREILLUSTRATESTHEFAR FIELDREQUIREMENT FORAVARIETYOFFREQUENCIESANDTARGETSIZES %RRORSATTRIBUTABLETORADARINSTRUMENTATIONSHOULDBEHELDTOD"ORLESS WHICH REQUIRESCAREFULDESIGNANDSELECTIONOFCOMPONENTS4HEDRIFTINSYSTEMSENSITIVITY SHOULDNOTEXCEEDTHISVALUEFORTHETIMEITTAKESTORECORDASINGLE2#3PATTERN WHICH SOMETIMESMAYAPPROACHANHOUR4HEDYNAMICRANGEOFTHESYSTEMSHOULDBEATLEAST D" WITHD"PREFERRED,INEARITYOVERTHISRANGESHOULDBED"ORBETTER AND IFNOT STEPSSHOULDBETAKENTOCORRECTMEASUREDDATAVIACALIBRATIONOFTHERECEIVER TRANSFERFUNCTIONGAINCHARACTERISTICS 2#3 MEASUREMENTS SHOULD BE CALIBRATED BY THE SUBSTITUTION METHOD IN WHICH AN OBJECTOFKNOWNSCATTERINGCHARACTERISTICSISSUBSTITUTEDFORTHETARGETUNDERTEST'IVEN THEKNOWNMEASUREDORCALIBRATED RECEIVERGAINCHARACTERISTICS THISESTABLISHESTHECON STANTBYWHICHARECEIVEROUTPUTINDICATIONMAYBECONVERTEDTOANABSOLUTE2#3VALUE
£{°Ón
2!$!2(!.$"//+
&)'52% 4HE FAR FIELD DISTANCE 2EPRINTED WITH PERMISSION OF 3CI4ECH0UBLISHING )NC
#OMMONCALIBRATIONTARGETSINCLUDEMETALSPHERES RIGHTCIRCULARCYLINDERS FLATPLATES AND CORNERREFLECTORS4HERADARCROSSSECTIONSOFTHESEOBJECTSMAYBECALCULATEDBYUSINGTHE EXPRESSIONSGIVENIN3ECTION "ECAUSE RESIDUAL BACKGROUND REFLEC TIONS CONTAMINATE THE DESIRED TARGET ECHO SIGNAL THEYSHOULDBEMINIMIZEDBYCAREFUL RANGEDESIGNANDOPERATION)NTERIORWALLSIN INDOORTESTCHAMBERSMUSTBECOVEREDWITH HIGH QUALITY RADAR ABSORBING MATERIAL AND THESURFACEOFTHEGROUNDONOUTDOORRANGES SHOULD BE SMOOTH AND FREE OF VEGETATION 4ARGETSUPPORTSTRUCTURESSHOULDBEDESIGNED SPECIFICALLYFORLOWECHOCHARACTERISTICS 4HEEFFECTSOFUNDESIREDBACKGROUNDSIG NALSAREILLUSTRATEDIN&IGURE"ECAUSE THE RELATIVE PHASE BETWEEN THE BACKGROUND SIGNALANDTHETARGETSIGNALISUNKNOWN TWO CURVESARESHOWNTHEYCORRESPONDTOPERFECT IN PHASEANDOUT OF PHASECONDITIONS)FTHE BACKGROUNDSIGNALISEQUALTOTHETARGETSIGNAL RATIOOFD" ANDTHETWOAREINPHASE THE TOTALRECEIVEDPOWERISFOURTIMESTHEPOWER DUETOEITHERONE4HISISTHEVALUESHOWNAT THEUPPERLEFTOFTHECHARTD" )FTHETWO AREOUTOFPHASE THEYCANCELEACHOTHER AND &)'52% -EASUREMENTERRORASAFUNC THEREISNOSIGNALATALLOFFTHELOWERLEFTOF TIONOFTHERELATIVEBACKGROUNDPOWERLEVEL
2!$!2#2/333%#4)/.
£{°Ó
THECHART 4HECHARTSHOWSTHATIFTHEERRORDUETOBACKGROUNDSIGNALSISTOBED"OR LESS THEBACKGROUNDMUSTBEATLEASTD"BELOWTHESIGNALBEINGMEASURED 4HREEDIFFERENTKINDSOFSUPPORTSTRUCTURESHAVEBEENDEMONSTRATEDTOBEUSEFULIN 2#3MEASUREMENTS4HEYARETHELOW DENSITYPLASTICFOAMCOLUMN THESTRINGSUSPEN SIONHARNESS ANDTHESLENDERMETALPYLON4HEECHOFROMAPLASTICFOAMCOLUMNARISES FROMTWOMECHANISMS/NEISACOHERENTSURFACEREFLECTION ANDTHEOTHERISANONCO HERENTVOLUMECONTRIBUTIONFROMTHETHOUSANDSOFINTERNALCELLSCOMPRISINGTHEFOAM MATERIAL 4HECOLUMNSHOULDBEDESIGNEDSOTHATITSSURFACESARENEVERCLOSERTHAN TOTOTHELINEOFSIGHTTOTHERADARDEPENDINGONFREQUENCY THEREBYMINIMIZ INGTHEEFFECTOFTHESURFACEREFLECTION4HENONCOHERENTVOLUMERETURNISIRREDUCIBLE HOWEVER ANDISNOTINFLUENCEDBYTHEORIENTATIONOFTHECOLUMN4HEVOLUMERETURN OFSUITABLEFOAMCOLUMNSUPPORTMATERIALSISOFTHEORDEROFr MPERFTOF EXPOSEDCOLUMNAT'(Z 3TRINGSUSPENSIONMETHODSAREBESTIMPLEMENTEDINDOORS WHEREANOVERHEADSUP PORTPOINTISNORMALLYAVAILABLE ALTHOUGHONEDOCUMENTEDDESIGNWASSERIOUSLYCON SIDEREDFOROUTDOORUSE/NEOFTHREECONFIGURATIONSMAYBESELECTED ALLREQUIRING ACUSTOM MADESLINGORHARNESSTOSUPPORTTHETARGET4HEFIRSTUSESASINGLEOVERHEAD SUPPORTPOINTANDGUYLINESTOAFLOOR MOUNTEDTURNTABLETOROTATETHETARGET4HESEC ONDCONFIGURATIONSUSPENDSTHETARGETFROMANOVERHEADTURNTABLE REDUCINGTHEGUY LINESANDSTRINGLOADSATTHEEXPENSEOFAMORECOSTLYINSTALLATION4HETHIRDCONFIGURA TIONISTHEMOSTCOSTLY USINGAPAIROFTURNTABLESSLAVEDTOGETHER ONEINTHECEILINGAND ONEONTHEFLOOR 4HEECHOSIGNALFROMASTRINGDEPENDSONTHELENGTHANDDIAMETEROFTHESTRING ITSTILTANGLEWITHRESPECTTOTHEINCIDENTWAVE ANDITSDIELECTRICCONSTANT.OMATTER WHATTHETILTOFTHESTRING ITWILLBEPRESENTEDNORMALTOTHELINEOFSIGHTTWICEINA COMPLETEROTATIONOFTHETARGETANDMAYCAUSEASPIKEINTHE2#3PATTERNTHATCOULDBE ERRONEOUSLYATTRIBUTEDTOTHETARGETUNLESSOTHERWISEACCOUNTEDFOR4HE2#3OFASTRING RISESWITHTHEFOURTHPOWEROFITSDIAMETERINTHE2AYLEIGHREGIONSEE&IGURE ANDFORAGIVENTENSILESTRENGTH THEDIAMETERRISESONLYASTHESQUAREROOTOFTHELOAD TOBESUPPORTED4HUS BECAUSETHEECHOSIGNALINCREASESWITHTHESQUAREOFTHELOAD CARRYINGCAPACITY STRINGSUSPENSIONTECHNIQUESAREBESTSUITEDFORMEASUREMENTSOF LIGHTOBJECTSATLOWFREQUENCIES 4HEMETALTARGETSUPPORTPYLONWASFIRSTSUGGESTEDIN BUTAPRACTICALIMPLE MENTATIONOFTHECONCEPTDIDNOTAPPEARUNTIL4HECONFIGURATIONOFTHEPYLONIS SHOWNIN&IGURE ANDITOWESITSELECTROMAGNETICPERFORMANCETOTHESHARPNESSOF ITSLEADINGEDGEANDITSTILTTOWARDTHERADARTOTHELEFTINTHEDIAGRAM 0YLONSASTALL ASFTHAVEBEENBUILT ANDITISCUSTOMARYTOTREATTHEMWITHRADAR ABSORBINGMATERIAL TOSUPPRESSTHEECHOESFROMTHELEADINGANDTRAILINGEDGES 4HEOBVIOUSADVANTAGEOFTHEMETALPYLONISITSSUPERIORWEIGHT CARRYINGCAPABIL ITY COMPARED WITH THAT OF STRINGS AND PLASTIC FOAM COLUMNS (OWEVER BECAUSE THE TOPOFTHEPYLONISSMALL THEROTATIONMECHANISMNEEDEDTOVARYTHEASPECTANGLEOF THETARGETMUSTBEEMBEDDEDINTHETARGETITSELF4HISUSUALLYDESTROYSTHEOPERATIONAL VALUEOFTHETARGET-OSTOFTHEROTATORSFORTHESEPYLONSAREDUAL AXIS AZIMUTH OVER ELEVATIONDESIGNS7HENMEASUREMENTSAREMADEWITHTHEAZIMUTHROTATIONANGLETILTED BACKAWAYFROMTHERADAR PARTSOFTHETARGETMAYSWEEPTHROUGHTHESHADOWCAST BYTHETOPOFTHEPYLON POSSIBLYDEGRADINGTHEMEASUREMENTS/NEWAYTOAVOIDTHIS ISTOINVERTTHETARGETANDTILTTHEROTATIONAXISTOWARDTHERADARINSTEADOFAWAYFROM IT4HISREQUIRESTHEINSTALLATIONOFTHEROTATORINTHETOPOFTHETARGETASWELLASINTHE BOTTOM4HEUNUSEDINTERNALCAVITIESCREATEDFORSUCHINSTALLATIONSMUSTBECONCEALED BYCOVERSORSHIELDS
£{°Îä
2!$!2(!.$"//+
&)'52% 4HEMETALSUPPORTPYLON4HEDESIGN ISFORANINCIDENTWAVEARRIVINGFROMTHELEFT2EPRINTED WITHPERMISSIONOF3CI4ECH0UBLISHING )NC
)T IS OFTEN NECESSARY TO MEASURE SCALE MODELS WHICH REQUIRES THE APPLICATION OF SCALINGLAWS"ECAUSENONCONDUCTINGMATERIALSMUSTBESCALEDDIFFERENTLYTHANGOOD CONDUCTORS ITISNOTPOSSIBLETOSATISFYALLTHESCALINGREQUIREMENTSFORARBITRARYTARGETS COMPOSEDOFCONDUCTINGANDNONCONDUCTINGMATERIALS-OSTTARGETSREQUIRINGSCALE MODELTESTING HOWEVER AREDOMINANTLYMETALLIC FORWHICHTHEPERFECTLYCONDUCTING SCALINGLAWISGENERALLYREGARDEDASADEQUATE 7HENNORMALIZEDWITHRESPECTTOTHESQUAREOFTHEWAVELENGTH THE2#3PATTERNS OFTWOPERFECTLYCONDUCTINGOBJECTSOFIDENTICALSHAPEBUTDIFFERENTSIZEWILLBEIDENTI CALIFTHEOBJECTSARETHESAMENUMBEROFWAVELENGTHSINSIZE)FAMODELISONE TENTH OFFULLSCALE FOREXAMPLE ITSHOULDBEMEASUREDATONE TENTHOFTHEFULL SCALEWAVE LENGTHTENTIMESTHEFULL SCALEFREQUENCY 4HE2#3OFTHEFULL SCALETARGETMAYBE OBTAINEDFROMTHESCALE MODELMEASUREMENTSBYMULTIPLYINGTHESCALE MODEL2#3 BYTHESQUAREOFTHERATIOOFTHETWOFREQUENCIES)NTHISEXAMPLE THATFACTORIS ORD" /UTDOOR4EST2ANGES /UTDOORTESTRANGESAREREQUIREDWHENTESTTARGETSARETOO LARGETOBEMEASUREDINDOORS4HEFAR FIELDCRITERIONOFTENREQUIRESTHATTHERANGETO THETARGETBESEVERALTHOUSANDFEETSEE&IGURE "ECAUSETHETYPICALTARGETHEIGHT ABOVETHEGROUNDISAFEWDOZENFEETATBEST THEELEVATIONANGLETOTHETARGETASSEEN FROMTHERADARISATMOSTANDOFTENLESS!TSUCHLOWGRAZINGANGLES THEGROUNDIS STRONGLYILLUMINATEDBYTHEANTENNAS ANDUNLESSTHEGROUNDBOUNCECANBESUPPRESSED THE TARGET WILL BE ILLUMINATED BY A MULTIPATH FIELD )N THE DESIGN OF AN OUTDOOR TEST RANGE THEREFORE ADECISIONMUSTBEMADEWHETHERTOEXPLOITTHEGROUNDBOUNCEORTO ATTEMPTTODEFEATIT)TISGENERALLYEASIERTOEXPLOITITTHANTOELIMINATEIT
2!$!2#2/333%#4)/.
£{°Î£
4ESTRANGESDESIGNEDTOEXPLOITTHEMULTIPATHEFFECTMAYBEASPHALTEDTOIMPROVE THEGROUNDREFLECTION ALTHOUGHMANYRANGESAREOPERATEDOVERNATURALSOIL0AVINGTHE RANGEENSURESUNIFORMITYINTHECHARACTERISTICSOFTHEGROUNDPLANEFROMDAYTODAYAND EXTENDSITSOPERATIONALUSEFULNESSTOHIGHERFREQUENCIESTHANMIGHTOTHERWISEBEPOS SIBLE!CONDUCTINGSCREENEMBEDDEDINTHEASPHALTMAYIMPROVETHEREFLECTION0AVING ALSOREDUCESMAINTENANCEOFTHEGROUNDPLANE SUCHASMIGHTBEREQUIREDBYPERIODI CALLYREMOVINGVEGETATIONANDSMOOTHINGOUTWINDBLOWNRIDGESINUNSTABLESOIL 4HEANGLEOFINCIDENCEANDTHEDIELECTRICPROPERTIESOFASPHALTANDNATURALSOILARE SUCH THAT THE PHASE OF THE VOLTAGE REFLECTION COEFFICIENT IS WITHIN A FEW DEGREES OF 4HISBEINGTHECASE ONECANUSUALLYCHOOSEACOMBINATIONOFTARGETANDANTENNA HEIGHTSSUCHTHATTHEWAVEREFLECTEDBYTHEGROUNDARRIVESATTHETARGETINPHASEWITH THEWAVEPROPAGATEDDIRECTLYFROMTHEANTENNAS4HERESULTISTHEFOLLOWINGRULEFOR SELECTINGTHEANTENNAANDTARGETHEIGHTS
HA HT L 2
WHEREHAANDHTARETHEANTENNAANDTARGETSHEIGHTS RESPECTIVELY AND2ISTHERANGETO THETARGET "ECAUSEMOSTTESTRANGESHAVETURNTABLESORTARGETPYLONSINSTALLEDATAFEWFIXED LOCATIONSRELATIVETOAPERMANENTRADARCOMPLEX THERANGE2ISUSUALLYRESTRICTEDTOA FEWPRESETVALUES4HETARGETISINSTALLEDATAHEIGHTHTHIGHENOUGHTOMINIMIZESPURI OUSINTERACTIONSWITHTHEGROUND YETLOWENOUGHTOMINIMIZETHESIZEANDCOMPLEX ITYOFTHETARGETSUPPORTSTRUCTURE4HEREFORE ITISTHEANTENNAHEIGHTHATHATISMOST READILYCONTROLLEDANDADJUSTEDTOOPTIMIZETHELOCATIONOFTHEFIRSTLOBEINTHEVERTI CALMULTIPATHINTERFERENCEPATTERN4HISISEASILYACCOMPLISHEDBYMOUNTINGTHERADAR ANTENNASONCARRIAGESTHATCANBERAISEDORLOWEREDALONGRAILSINSTALLEDONTHESIDEOF ABUILDINGORATOWER 4HEIDEALGROUNDPLANEOFFERSATHEORETICALSENSITIVITYENHANCEMENTOFD"OVER IDENTICALMEASUREMENTSMADEINFREESPACE4HEACTUALENHANCEMENTISUSUALLYLESS THANTHIS PRIMARILYBECAUSEOFTHEDIRECTIVITYOFTHEANTENNASANDIMPERFECTIONSINTHE GROUNDPLANE!NTENNADIRECTIVITYPRECLUDESTHETARGETEVERBEINGSQUARELYALIGNEDON THEBORESIGHTSOFBOTHTHEREALANTENNAANDITSIMAGEINTHEGROUNDPLANEATTHESAME TIME ANDTHEREFLECTIONCOEFFICIENTOFTYPICALGROUNDPLANESVARIESFROMTOASLOW ASORLESS&ORALLEXCEPTVERYHIGHANDVERYLOWFREQUENCIESMILLIMETERWAVE LENGTHSAND6(& TYPICALSENSITIVITIESAREOFTHEORDEROFTOD"ABOVEFREESPACE INSTEADOFTHEIDEALD" 7HENTHERANGETOTHETARGETISRELATIVELYSHORTANDTESTSMUSTBEPERFORMEDOVER A WIDE RANGE OF FREQUENCIES IT IS SOMETIMES ADVANTAGEOUS TO ATTEMPT TO DEFEAT THE GROUND PLANEEFFECT/NEOPTIONISTOINSTALLABERMSHAPEDLIKEANINVERTED6RUNNING BETWEENTHERADARANDTHETARGET4HEPURPOSEOFTHEBERMSSLANTEDTOPISTODEFLECT THEGROUND REFLECTEDWAVEOUTOFTHETARGETZONE!NOTHEROPTIONISTOINSTALLASERIES OFLOWRADARFENCESACROSSTHERANGE4HEDESIGNOBJECTIVEISTOBLOCKGROUND REFLECTED RAYSFROMREACHINGTHETARGETFROMTHERADAR ANDVICEVERSA BYSHIELDINGTHESPECULAR ZONEONTHEGROUNDFROMBOTH4HENEARSIDESOFTHEFENCESSHOULDBESLANTEDTODEFLECT ENERGYUPWARDOUTOFTHETARGETTESTZONE ANDMAYBECOVEREDWITHABSORBINGMATE RIAL)TISDIFFICULT HOWEVER TOPREVENTDIFFRACTIONOFRADARENERGYFROMTHETOPOFTHE FENCESFROMREACHINGTHETARGETORTOPREVENTTARGET DIFFRACTEDSIGNALSFROMREACHING THERADARRECEIVERVIATHESAMEKINDOFMECHANISM "ECAUSEOFTHELARGEDISTANCESFROMTHERADARTOTHETARGETONOUTDOORRANGES INSTRU MENTATIONRADARSATONETIMEDEVELOPEDPEAKSIGNALPOWERSRANGINGFROMTOK7
£{°ÎÓ
2!$!2(!.$"//+
4HEHIGH POWERINSTRUMENTATIONOFYESTERYEARHASBEENLARGELYREPLACEDONSTATICTEST RANGESWITHCOHERENTSTEPPED FREQUENCYRADARSTHATAREFARMOREVERSATILE BUTHIGH POWERSYSTEMSREMAINUSEFULFORDYNAMICTESTINGOFTARGETSFLYINGORSAILINGPASTTHEM ON DYNAMIC TEST RANGES 3TEPPED AND SWEPT FREQUENCY INSTRUMENTATION SYSTEMS ON STATICRANGESCANCOLLECT2#3PATTERNSATHUNDREDSOFFREQUENCIESFORASINGLEROTATION OFTHETESTTARGET4HESIGNAL TO NOISERATIOCANBEIMPROVEDWHENNECESSARYBYMEANS OF MULTISWEEP OR MULTISTEP SIGNAL INTEGRATION SCHEMES4HE PRICE PAID FOR MUCH OF THISVERSATILITYISTHEREQUIREMENTFORMOREACTIVETESTTIMEPERTARGETROTATION THEREBY INCREASINGMEASUREMENTCOSTS )NDOOR4EST2ANGES )NDOORTESTRANGESOFFERPROTECTIONFROMWEATHERANDTHERE FOREMOREPRODUCTIVETESTING BUTUNLESSAVERYLARGEFACILITYISAVAILABLE MAXIMUM TARGETSIZESARELIMITEDTOONEORTWODOZENFEET"ECAUSEOFTHEIRPROXIMITY THEWALLS FLOOR ANDCEILINGMUSTBECOVEREDWITHHIGH QUALITYABSORBINGMATERIAL4HELOWERTHE INTENDEDFREQUENCYOFOPERATION THEMOREEXPENSIVETHEABSORBERBECOMES!BSORBER REFLECTIVITY RATINGS OF D" ARE COMMON AMONG THE MATERIALS USED 4HIS PERFOR MANCEISUSUALLYACHIEVABLEONLYWITHTHEPYRAMIDALDESIGN %ARLYINDOORCHAMBERSWERERECTANGULARINSHAPE ANDDESPITETHEINSTALLATIONOF GOOD ABSORBENT MATERIALS ON THE WALLS 2#3 MEASUREMENTS COULD BE CONTAMINATED BYWALLREFLECTIONS4HEMOSTSENSITIVEPARTOFTHEANECHOICCHAMBERISTHEREARWALL WHICHRECEIVESTOPERCENTOFTHEPOWERRADIATEDBYTHERADARHENCE THEBEST ABSORBERSHOULDBERESERVEDFORTHEREARWALL4HEFLOOR CEILING ANDSIDEWALLSALSO CONTRIBUTEERRORS VIAAQUADRUPLETOFREFLECTIONSNOTUNLIKETHOSEDUETOTHEGROUND PLANEOFOUTDOORRANGES!REMEDYISTHETAPEREDANECHOICCHAMBER WHICHELIMINATES MOSTOFTHESIDEWALLREFLECTIONSPURELYBYTILTINGPORTIONSOFTHEWALLS FLOOR ANDCEIL INGAWAYFROMTHECHAMBERCENTERLINE %VENTARGETSOFMODESTSIZECANNOTBEMEASUREDATTHEFAR FIELDDISTANCEININDOOR FACILITIESBECAUSEMOSTCHAMBERSARENOTMUCHMORETHANFTORSOINLENGTH)TIS POSSIBLE HOWEVER TOPROVIDETHENECESSARYUNIFORMITYOFILLUMINATIONBYCOLLIMATING THERADIATEDBEAM4HISCANBEDONEBYINSERTINGALENSBETWEENTHERADARANDTHETAR GET ORBYREFLECTINGTHERADARBEAMOFFACOLLIMATINGREFLECTOR4HISLATTERCONCEPT ISKNOWNASTHECOMPACTRANGEBECAUSEABEAMOFPARALLELRAYSCANBEGENERATEDINA MUCHSHORTERDISTANCETHANWOULDBEPOSSIBLEWITHOUTTHECOLLIMATINGDEVICE 4HEREFLECTOROFFERSADIFFERENTWAYTOCOLLIMATEABEAM)NCONTRASTTOTHELENS WHICHISPLACEDBETWEENTHERADARANDTHETESTOBJECT THERADARANDTHETESTOBJECT REMAINONTHESAMESIDEOFTHEREFLECTOR ASSHOWNIN&IGURE4HEREFLECTORIS TYPICALLYANOFFSETPARABOLOID MEANINGTHEPARABOLOIDALSURFACEDOESNOTINCLUDETHE VERTEXOFTHEGENERATINGPARABOLA4HISPERMITSTHEFEEDTHATEXCITESTHEREFLECTORTOBE PLACEDOUTOFTHEBEAMREFLECTEDTOWARDTHETARGET)FTHETESTOBJECTISHELDWITHINONE ORTWOFOCALLENGTHSOFTHEREFLECTORANDIFTHEREFLECTORISEXCITEDBYASUITABLYDESIGNED FEED THEREFLECTEDWAVEISSENSIBLYPLANAR (OWEVER UNLESSTHEEDGESOFTHEREFLECTORARECAREFULLYDESIGNED THEINCIDENTFIELD INTHETARGETZONEWILLBECONTAMINATEDBYUNDESIREDFIELDSDIFFRACTEDFROMTHEEDGES OFTHEREFLECTOR4HEDIFFRACTIONCAUSESRIPPLESINBOTHTHEAMPLITUDEANDTHEPHASEOF THEFIELDDISTRIBUTIONINTHETARGETZONE)NSOMECASES THEEFFECTISSMALLENOUGHTO BE IGNORED BUT IN HIGH QUALITY INSTALLATIONS THE RIPPLE MAY BE OBJECTIONABLY LARGE 2OLLED EDGECONFIGURATIONS SUCHASTHEONEONTHEUPPEREDGEOFTHEMAINREFLECTOR IN&IGURE CANBEDESIGNEDTOMINIMIZEEDGEDIFFRACTION (OWEVER THEPRICE PAID FOR THIS IMPROVEMENT IN PERFORMANCE IS A MUCH LARGER AND MORE COMPLICATED REFLECTORSTRUCTURE
2!$!2#2/333%#4)/.
£{°ÎÎ
&)'52% !COMPACTRANGEUSINGANOFFSETPARABOLOIDALREFLECTOR
4HESINGLE REFLECTORDESIGNSHOWNIN&IGUREWORKEDTOLERABLYWELLFORSMALL TESTTARGETS BUTITSOONBECAMEAPPARENTTHATTHEREFLECTORHADTOBECONSIDERABLYLARGER FORMANYTARGETSOFVITALMILITARYINTEREST4HISCOULDBEACCOMPLISHEDBYDOUBLINGOR TRIPLINGTHESIZEOFTHEREFLECTOR BUTTHATBROUGHTONAROUNDOFOTHERPROBLEMS MAINLY THEINCREASEDFOCALLENGTHOFTHEREFLECTOR7HILETHEFOCALDISTANCECOULDBESHORTENED TOCOMFORTABLYFITAXIALSPACELIMITATIONSALONGTHEBORESIGHTOFTHEREFLECTOR ITWAS THENHARDERTOCONTROLTHEFIELDAMPLITUDETAPERACROSSTHEREFLECTORDUETOTHEPROXIM ITYOFTHEFEEDHORN4HESOLUTIONWASTOADDASMALLERSUBREFLECTORINASUBTERRANEAN GALLERYBUILTESPECIALLYFORIT ASSUGGESTEDIN&IGURE 4HESUBREFLECTORHADTHEEFFECTOFGREATLYINCREASINGTHEFOCALLENGTHOFTHEMAIN REFLECTOR MAKINGITEASIERTOOPTIMIZEITSILLUMINATION4HISPARTICULARCONFIGURATION ISKNOWNASA'REGORIANSYSTEM CHARACTERIZEDBYAFOCUSBETWEENTHETWOREFLECTORS
&)'52% 'ENERICDUAL REFLECTORCOMPACTRANGECONFIGURATION
£{°Î{
2!$!2(!.$"//+
WHEREMOSTOFTHERAYSBETWEENTHETWOREFLECTORSCONVERGE)NASECONDCONFIGURA TIONKNOWNASTHE#ASSEGRAIN THEFOCUSISAVIRTUALONELYINGBEHINDTHESUBREFLECTOR 4HE'REGORIANCONFIGURATIONPERMITSTHECONSTRUCTIONOFASMALLERAPERTUREBETWEENTHE MAINCHAMBERANDTHESUBREFLECTORGALLERYTHANDOESTHE#ASSEGRAINCONFIGURATION ,ARGECOMPACTRANGESSUCHASTHEONESHOWNIN&IGUREAREVERYCOSTLYAND CANBEAFFORDEDBYONLYTHELARGESTOFCOMPANIESORTHEGOVERNMENT THUSRANGETIME ISPREMIUM3OMECOMPANIESKEEPTHEIRCOMPACTRANGESBUSYHOURSPERDAY 4ARGETSMEASUREDINDOORSAREPLACEDMUCHCLOSERTOTHERADARTHANTHOSEMEASURED OUTDOORS ANDUSEFULMEASUREMENTSMAYBEMADEBYUSINGMUCHLESSRADIATEDPOWER %ARLYINDOORINSTRUMENTATIONRADARSRELIEDONSIMPLE#7SOURCES ANDUNDESIREDCHAM BERREFLECTIONSWERESUPPRESSEDBYACANCELLATIONPROCESS4HEPROCEDUREISTOPREPARE THECHAMBERFORAMEASUREMENTINEVERYRESPECTEXCEPTFORTHEINSTALLATIONOFTHETARGET ONITSSUPPORTFIXTURE!SMALLSAMPLEOFTHETRANSMITTEDSIGNALISPASSEDTHROUGHAVARI ABLEATTENUATORANDAVARIABLEPHASESHIFTERANDCOMBINEDWITHTHERECEIVEDSIGNAL4HE AMPLITUDEANDPHASEOFTHESIGNALSAMPLEARETHENADJUSTEDSOASTOCANCELTHESIGNAL RECEIVEDINTHEABSENCEOFTHETARGET 4HE AVAILABILITY OF LOW COST PHASE LOCKED FREQUENCY SYNTHESIZED SOURCES NOW MAKES IT ATTRACTIVE TO COLLECT WIDEBAND 2#3 DATA WHICH CONTAIN FAR MORE TARGET SCATTERING INFORMATION THAN #7 MEASUREMENTS MADE AT SINGLE FREQUENCIES 7HEN COHERENT2#3SCATTERINGDATAARESUITABLYPROCESSED ITISPOSSIBLETOGENERATE)3!2 IMAGERY ORTWO DIMENSIONALMAPSOFTHEECHOSOURCESOFTESTOBJECTS &IGUREISANEXAMPLEOFSUCHANIMAGE)NTHISCASE THEPROCESSINGREQUIRED TOGENERATETHISIMAGEISADOUBLE&OURIERTRANSFORMATION ONEFROMTHEFREQUENCY DOMAINTOTHETIMEDOMAINANDTHEOTHERFROMTHEANGLEDOMAINTOTHECROSS RANGE DOMAIN4HEFREQUENCY TIMEDOMAINPROCESSINGMAYBEPERFORMEDVIRTUALLYINREAL TIMEASECONDORTWOFORPROCESSINGANDDISPLAYONAVIDEOSCREEN BUTTHECONVERSION
&)'52% 2ADARIMAGEOFASMALLDRONEAIRCRAFT0LANFORM OUTLINE HAS BEEN ADDED FOR CLARITY #OURTESY $ , -ENSA 53 .AVY0ACIFIC-ISSILE4EST#ENTER
2!$!2#2/333%#4)/.
£{°Îx
FROM THE ANGLE DOMAIN TO THE CROSS RANGE DOMAIN MUST BE PERFORMED OFFLINE IN THIS EXAMPLE4HE FAST &OURIER TRANSFORM &&4 IS INVARIABLY EXPLOITED TO EXPEDITE THEPROCESSING 4HEIMAGEDATAPRESENTEDIN&IGUREWERECOLLECTEDFORASTEPPED FREQUENCY SIGNALWITHABANDWIDTHOF'(ZCENTEREDAT'(Z4HEASPECTANGLEWASVARIED OVERASECTORnWIDECENTEREDONTHENOSE ONASPECT4HECHARTEDIMAGECONTOURSARE D"APARTANDTHETOTALAMPLITUDEVARIATIONISD" 4HE RESOLUTION OF THE PROCESSED IMAGE IN THE TIME RANGE DOMAIN IS INVERSELY PROPORTIONALTOTHEBANDWIDTHOFTHEEMITTEDWAVEFORM4HERESOLUTIONINTHECROSS RANGE DOMAIN IS INVERSELY PROPORTIONAL TO THE ASPECT ANGLE WINDOW OVER WHICH THE DATAARECOLLECTED4HUS THEOPERATINGCHARACTERISTICSOFTHEINSTRUMENTATIONSYSTEM ANDTHEAZIMUTHALDATASAMPLINGRATEMUSTBEDECIDEDBEFORETHEDATAARECOLLECTED "ECAUSETHECROSS RANGECOORDINATEOFTHERESULTINGIMAGEISPERPENDICULARTOTHEAXIS OFROTATIONOFTHETARGET ITMAYBENECESSARYTOMULTIPLYTHATCOORDINATEBYASCALEFACTOR THATEFFECTIVELYREGISTERSTHEGENERATEDIMAGEWITH SAY APLANVIEWOFTHETARGET 4HERESULTINGDATAMAYBEPRESENTEDINTHEFORMOFACONTOURMAP ASIN&IGURE ORINACOLOR CODEDORGRAYSCALEPIXELFORMAT(ERE THETARGETOUTLINEHASBEENSUPER POSEDONTHEIMAGEDATAFORDIAGNOSTICANALYSIS ANDTHEPARTICULARATTITUDESHOWNIS FORNOSE ONINCIDENCE3IMILARIMAGESCANBEGENERATEDFOROTHERANGLESOFINCIDENCE PROVIDEDTHETARGETISROTATEDTHROUGHASECTORWIDEENOUGHTOYIELDTHEDESIREDCROSS RANGE RESOLUTION AND SAMPLED AT A SUFFICIENT NUMBER OF ANGLES OVER THAT SECTOR )N PRACTICE THETARGETISROTATEDCONTINUOUSLYWHILETHESWEPT ORSTEPPED FREQUENCYDATA ARECOLLECTED!RULEOFTHUMBISTHATTHEANGULARSPEEDBESLOWENOUGHTHATTHEPHASE OFTHERETURNATTHEENDOFAFREQUENCYSWEEPDUETOTARGETMOTIONNOTBEMORETHAN FROMWHATITWOULDHAVEBEENHADTHETARGETNOTMOVED .OTETHATTHENOSESECTIONOFTHEDRONEISSPECKLEDWITHHEAVYCONCENTRATIONSOF SCATTERINGCENTERS POSSIBLYDUETOCONTRIBUTIONSFROMINTERNALSTRUCTURALFEATURES4HE REAREDGESOFTHEFORWARDCANARDSSEEMTOBESTRONGERSCATTERERSTHANTHELEADINGEDGES !TTHENOSE ONASPECTANGLEFORWHICHTHEIMAGEDATAWERECOLLECTED THELEADINGEDGES OFTHEWINGSAREVIRTUALLYINVISIBLE(OWEVER NOTEAFEWECHOSOURCESALONGALINE PARALLELTO ANDSLIGHTLYFORWARDOF THEWINGTRAILINGEDGES)FTHETARGETROTATIONHAD BEENCENTEREDONANASPECTANGLEPERPENDICULARTOONEOFTHEWINGS THELEADINGEDGE OFTHATONEWINGWOULDHAVEhLITUPv )NTHEREGIONOFTHEMAINWINGROOTS WESEEHEAVYCONCENTRATIONSOFECHOSOURCES 3OMEOFTHEMLIEFORWARDOFANYWINGSURFACE!LTHOUGHWEMAYCONCEIVEOFAPPARENT SOURCESBEINGSTRUNGOUTBEHINDANYPHYSICALSCATTERINGOBSTACLEDUETOTIMEDELAYSOF MULTIPLEREFLECTIONS ITISHARDTORECONCILETHEMBEINGSTRUNGOUTINFRONTOFTHEBODY 7EDOSEESEVERALCLUSTERSOFAPPARENTSCATTERINGCENTERSPOSITIONEDAFTOFTHETAILOF THEAIRCRAFT BUTLACKINGANYDETAILEDDESCRIPTIONOFTHETESTOBJECT WECANNOTINTERPRET THEIRMEANING 4HESEhGHOSTvSCATTERERSOWETHEIREXISTENCETOTHEWAYINWHICHTHEDATA PROCESSING SYSTEMSORTSTHERANGEANDCROSS RANGELOCATIONSOFSCATTERERS$OWN RANGELOCATIONS ARESORTEDACCORDINGTOTHEIRPROCESSEDTIMEDELAYSANDCROSS RANGELOCATIONSACCORD INGTOTHEIRTIME DELAYRATES WHETHERDUETOREALSCATTERERSORTOINTERACTIONSBETWEEN SCATTERERS %VEN THOUGH THE CONTRIBUTIONS OF SOME SCATTERING CENTERS MAY INVOLVE PROPAGATIONINDIRECTIONSOTHERTHANALONGTHELINEOFSIGHTFROMTHERADAR THESYSTEM HASNOWAYOFDISCERNINGTHATFACT4HEREFORE DESPITETHEPOWERFULDIAGNOSTICVALUEOF IMAGESLIKETHESE ONEMUSTALWAYSBEAWARETHATMULTIPLEINTERACTIONSBETWEENTARGET ELEMENTSCANCREATESCATTERINGSOURCESTHATARENOTWHERETHEYAPPEARTOBE
£{°ÎÈ
2!$!2(!.$"//+
£{°xÊ , ,Ê "Ê-1**, --" 4HEPROBABILITYOFBEINGDETECTEDBYHOSTILERADARSCANBEREDUCEDBYDECREASINGTHE TARGETSRADARCROSSSECTION4HEMAJORMETHODSTOREDUCETHE2#3AREBYSHAPINGOF THETARGETANDTHEUSEOFABSORBERS"YSHAPING WEMEANTHEINTENTIONALSELECTIONOF TARGETSURFACESANDFEATURESSOASTOMINIMIZETHEAMOUNTOFENERGYSCATTEREDBACKTO THERADAR3HAPINGINCLUDESSPECIFICDESIGNCONFIGURATIONS SUCHASTHEPLACEMENTOF ENGINEINTAKES WHICHCANHAVELARGERADARECHOES WHERETHEYMAYBESHIELDEDFROM THEINCIDENTWAVEBYOTHERPARTSOFTHETARGET4HEPURPOSEOFRADAR ABSORBINGMATERIALS 2!- ISTOABSORBTHEINCIDENTRADARENERGYSOASTOMINIMIZETHEENERGYSCATTERED BACKTOTHERADAR"OTHMETHODSHAVEADVANTAGESANDDISADVANTAGES 2ADAR!BSORBERS 4HE PURPOSE OF THE RADAR ABSORBER IS TO ATTENUATE INCIDENT ENERGYANDTHEREBYREDUCETHEENERGYSCATTEREDORREFLECTEDBACKTOTHERADAR-OST ABSORBERSAREDESIGNEDTOREDUCESPECULARREFLECTIONSFROMMETALLICSURFACES BUTSTEALTH TECHNOLOGYHASSPAWNEDTHEDEVELOPMENTOFNONSPECULARABSORBERSINTENDEDPRIMARILY TOSUPPRESSECHOESDUETOSURFACETRAVELINGWAVES 4HE SIMPLEST SPECULAR ABSORBER IS THE 3ALISBURY SCREEN WHICH IS A THIN RESISTIVE SHEET MOUNTED A QUARTER WAVELENGTH ABOVE THE METAL SURFACE TO BE HIDDEN FROM A RADAR4HEDESIGNWORKSBESTFORINCIDENCENORMALTOTHESHEET ANDIFITCANBEMANU FACTUREDWITHARESISTIVITYOFOHMSPERSQUARETHEIMPEDANCEOFFREESPACE ALLTHE POWERINTHEINCIDENTWAVEISTRANSFERREDTOTHESHEETANDNONEISREFLECTED(OWEVER THESINGLE SHEET3ALISBURYSCREENSUFFERSSEVERALLIMITATIONS)TSTHINSHEETSANDLOW LOSSSPACERSAREFRAGILE ITS D"BANDWIDTHISBARELY ANDITSPERFORMANCEDETE RIORATESPROGRESSIVELYASTHEANGLEOFINCIDENCEMOVESAWAYFROMNORMALINCIDENCE )TISDIFFICULTTOOVERCOMETHEFRAGILITYPROBLEMWITHROBUSTMATERIALS BUTTHEBAND WIDTHCANBEIMPROVEDBYCASCADINGSEVERALSHEETS ASSHOWNIN&IGURE4HIS CREATESWHATISKNOWNASA*AUMANNABSORBER4HEBANDWIDTHRISESWITHTHENUMBER OFLAYERSANDCANATTAINARESPECTABLEFORAFOUR SHEETDESIGN ASSUGGESTEDIN &IGURE4HEPRICEPAIDFORTHISBANDWIDTHEXPANSIONISAMUCHTHICKER BULKIER MATERIALTHATTENDSTOBEIMPRACTICALFORTACTICALMILITARYTARGETS ,IKETHE3ALISBURYSCREEN THE$ØLLENBACHLAYERISALSOASIMPLEABSORBER4HEMATE RIALISUNIFORMTHROUGHOUTITSVOLUMEANDISAMIXTUREOFCOMPOUNDSDESIGNEDTOHAVE ASPECIFIEDINDEXOFREFRACTION4HATDESIGNMAYINCLUDEMATERIALSWITHMAGNETICLOSSES ASWELLASCARBONPARTICLESRESPONSIBLEFORELECTRICLOSSES4HEREFORE THEELECTRICAND MAGNETIC SUSCEPTANCES RELATIVE PERMITTIVITY AND RELATIVE PERMEABILITY HAVE IMAGI NARYCOMPONENTS RESULTINGINANINDEXOFREFRACTIONWITHANIMAGINARYCOMPONENT
&)'52% 4HE*AUMANNABSORBERISACASCADEDCOLLECTIONOF THINRESISTIVESHEETSSTACKEDINFRONTOFAMETALBULKHEAD SPACEDK APART WHERE + SPACER DIELECTRIC CONSTANT 4HE CLASSIC 3ALISBURY SCREENISTHEDEGENERATIVECASEOFASINGLESHEET
2!$!2#2/333%#4)/.
£{°ÎÇ
&)'52% 0ERFORMANCE OF *AUMANN ABSORBERS WITHASMANYASFOURSHEETS!LLFOUROFTHESETRACESWERE OPTIMIZEDFORMAXIMUMBANDWIDTHATTHEnD"LEVEL 4HESHEETRESISTIVITIESMUSTINCREASEFROMALOWVALUEAT THEINNERSHEETTOAHIGHVALUEATTHEOUTERSHEET
4HERESULTINGIMAGINARYPARTOFTHEPROPAGATIONCONSTANTATTENUATESWAVESTRAVELING THROUGHTHEMATERIAL -OSTOFTHECOMMERCIALVERSIONSOF$ØLLENBACHABSORBERSAREFLEXIBLEANDCANBE APPLIEDTOMODESTLYCURVEDSURFACES4HEDIELECTRICABSORBERSARETYPICALLYMADEOFA RUBBERYFOAM SOMETIMESURETHANE IMPREGNATEDWITHCARBONPARTICLES)MPREGNATION MAYBEPERFORMEDBYDIPPINGACOMPRESSEDSLABOFMATERIALINAGRAPHITESUSPENSION BATH THENWRINGINGITOUTANDDRYINGIT-AGNETIC$ØLLENBACHLAYERSCANBEROLLEDFROM AMIXTUREOFNATURALORSYNTHETICRUBBERLOADEDWITHCARBONYLIRONORFERRITEPOWDERS 4HELOWERTHEPOWDERCONTENT THEMOREFLEXIBLETHESHEETBUTTHELESSEFFECTIVEITSELEC TROMAGNETICPERFORMANCE$IELECTRICANDMAGNETIC$ØLLENBACHLAYERSTYPICALLYRANGE FROMABOUTMMTOCMINTHICKNESS4HEMAGNETICVERSIONSAREASHEAVYLBFT MAKINGTHEMIMPRACTICALFORMOSTTACTICALAPPLICATIONS 4HEFRONTFACEANDTHEMETALBACKINGOFTHE$ØLLENBACHLAYERAREITSONLYSOURCES OFREFLECTION4HEUSEOFPHYSICALLYREALIZABLEMATERIALSMAKESITIMPOSSIBLETOFORCE EITHER REFLECTION TO ZERO4HE DESIGN OBJECTIVE THEREFORE IS TO CHOOSE THE ELECTRICAL PROPERTIESOFTHELAYERSOTHATTHEFRONT FACEANDMETAL BACKREFLECTIONSTENDTOCANCEL EACHOTHER)FTHEMATERIALPROPERTIESAREDOMINATEDBYELECTRICEFFECTS THEOPTIMUM LAYER THICKNESS IS CLOSE TO K AS MEASURED IN THE MATERIAL )F THEY ARE DOMINANTLY MAGNETIC THELAYERCANBEMUCHTHINNER !SWITHTHESIMPLE3ALISBURYSCREEN $ØLLENBACHLAYERSCANBECASCADEDINATTEMPTS TOEXPANDBANDWIDTH PRODUCINGWHATISKNOWNASGRADEDABSORBERS&OROPTIMUM PERFORMANCE THEINTRINSICIMPEDANCEOFEACHLAYERTYPICALLYGETSSMALLERTHECLOSER THELAYERISTOTHEMETALBULKHEADORBACKINGLAYER&IVEORMORELAYERSHAVEBEENUSED INTHECOMMERCIALPRODUCTIONOFGRADEDDIELECTRICABSORBERS BUTCOMMERCIAL GRADED MAGNETICABSORBERSAPPEARTOHAVEBEENLIMITEDTOTHREELAYERS)TISIMPORTANTINTHE DESIGNPROCESSTOACCOUNTFORTHEACTUALTHICKNESSANDELECTRICALPROPERTIESOFTHEADHE SIVEFILMSUSEDTOBONDTHELAYERSTOEACHOTHER4HESEMATERIALSARETOOFLIMSYORTOO HEAVYFORMOSTMILITARYAPPLICATIONS 4HE PYRAMIDAL ABSORBER USED TO SUPPRESS WALL REFLECTIONS IN INDOOR CHAMBERS REPRESENTSAPARTICULARLYEFFECTIVEMETHODOFVARYINGTHEEFFECTIVEIMPEDANCEhSEENv
£{°În
2!$!2(!.$"//+
BYANINCIDENTWAVE4HEABSORBERISMADEOFFLEXIBLE CARBON IMPREGNATEDPLASTIC FOAMCUTINTHEFORMOFPYRAMIDS)TEXHIBITSOPTIMUMPERFORMANCEWHENTHEPYRA MIDSAREPOINTEDTOWARDTHEDIRECTIONOFTHEINCIDENTWAVE ANDTHEPYRAMIDSSHOULD BEOFTHEORDEROFTOWAVELENGTHSDEEP&IRE RETARDANTPAINTISUSUALLYAPPLIEDTO PYRAMIDALABSORBERSTOSATISFYSAFETYREQUIREMENTS BUTATHIGHFREQUENCIES THEPAINT TENDSTODEGRADETHEPERFORMANCEOFTHEMATERIAL.EVERTHELESS PYRAMIDALABSORBERS OFSUFFICIENTDEPTHCONSISTENTLYTURNINPERFORMANCESBETTERTHANLESSTHAN D" "ECAUSETHESEABSORBERSDONOTRELYONTHECANCELLATIONOFAFRONT FACEREFLECTIONBY AREAR FACEREFLECTION THEYEXHIBITGREATBANDWIDTH)NGENERAL APYRAMIDALABSORBER WITH SHARP TIPS AND UNIFORM BULK LOSS CHARACTERISTICS CAN HAVE A BANDWIDTH THAT EXCEEDS .ONSPECULARABSORBERSNEEDNOTHAVETHEGREATTHICKNESSCHARACTERIZEDBYSPECU LARABSORBERS)NTENDEDPRIMARILYFORSUPPRESSIONOFSURFACETRAVELING WAVEECHOES NONSPECULARMATERIALSHAVETHEOPPORTUNITYTOREDUCETHEBUILDUPOFSURFACECUR RENTSOVERSEVERALWAVELENGTHSALONGTHESURFACE4HEYAREABLETOREGISTERQUITE RESPECTABLE PERFORMANCES THEREFORE SIMPLY BECAUSE A THIN LAYER ATTACHED TO A METALLICSURFACENEEDNOTBEVERYHEAVY)NTHISRESPECT THESURFACETRAVELING WAVE CONTRIBUTIONDUETOLONG SMOOTHSURFACESISONEOFTHEEASIESTTOSUPPRESS%VEN SO THETHICKNESSANDGEOMETRICDISTRIBUTIONOFSURFACE WAVEABSORBERSSHOULDBE VARIEDFOROPTIMUMPERFORMANCE "YTHISPOINT ITSHOULDBEAPPARENTTHATTHEAPPLICATIONOFRADARABSORBINGMATERI ALS TO VULNERABLE TARGETS IS NOT A VERY EFFECTIVE WAY TO ENHANCE THEIR SURVIVABILITY 4HESEMATERIALSAREHEAVY DEMANDUNDUESURFACECAREANDMAINTENANCE SUFFERLIMITED BANDWIDTH ANDNOTLEAST ARECOSTLY!FARMOREVIABLEOPTION TARGETSHAPING ISUSUALLY AVAILABLEIFONEISWILLINGTOCONSIDERITATTHEONSETOFSYSTEMDEVELOPMENT 3HAPING 3HAPING IS THE RESULT OF JUDICIOUSLY ORIENTING TARGET SURFACES AND EDGESINAWAYTHATMINIMIZESTHEIRCONTRIBUTIONSTOTHETOTALRADARECHO4HISOFTEN MEANS SELECTING AIRFRAME SHAPES AND NAVAL HULL PROFILES THAT INITIALLY OUTRAGE AIR FRAME DESIGNERS AND NAVAL ARCHITECTS "UT THERE IS NO POINT IN CONSIDERING SHAPE CONTROLUNLESSASPECIFICTHREATDIRECTIONCANBEIDENTIFIEDINAZIMUTHORELEVATION ORBOTH)FALLDIRECTIONSAREEQUALLYLIKELY THENTHEADVANTAGEOFCHOOSINGFAVOR ABLESURFACEORIENTATIONSFORONETHREATDIRECTIONISCANCELEDBYANACCOMPANYING ENHANCEMENTINANOTHER)NMANYSITUATIONS HOWEVER THEGENERALDIRECTIONOFTHE THREATCANBEFORECAST &IGUREILLUSTRATESTHE2#3REDUCTIONAVAILABLETHROUGHSHAPING4HEPLOTTED CURVESAREBASEDONTHEORYANDMEASUREMENTSANDSHOWHOWTHENOSE ONAXIAL 2#3 VARIESWITHTHEELECTRICALSIZEOFEACHOFTHESIXROTATIONALLYSYMMETRICALMETALLICBOD IESSHOWNIN&IGURE4HEDIAMETERSANDPROJECTEDAREASOFTHEOBJECTSAREIDENTI CAL ANDTHEIRVOLUMESDIFFERATMOSTBYAFACTOROF%XCEPTFORTHESPHERE WHOSE GEOMETRIC OPTICS2#3ISSHOWNBYTHEUPPERMOSTTRACE ALLTHEOBJECTSHAVETHESAME NOSEANGLE ANDOFTHESIXSHAPES THEOGIVEEXHIBITSTHELOWEST2#34HUS AT LEASTALONGTHEAXESOFTHESEPARTICULARBODIES THE2#3CANBEMINIMIZEDBYSELECTING THEAPPROPRIATESURFACEPROFILE (OWEVER THE ATTAINMENT OF LOW ECHOES OVER A RANGE OF ASPECT ANGLES IS USUALLY ACCOMPANIEDBYHIGHERECHOLEVELSATOTHERANGLES4HUS THESELECTIONOFANOPTIMUM SHAPESHOULDALWAYSINCLUDEANEVALUATIONOFTHEVARIATIONOFTHE2#3OVERARANGEOF ASPECTSWIDEENOUGHTOCOVERTHEANTICIPATEDTHREATDIRECTIONS4HISIMPLIESTHECAPA BILITYTOMEASURETHE2#3PATTERNSOFACOLLECTIONOFOBJECTSWITHCANDIDATESURFACE PROFILESORTHECAPABILITYTOPREDICTTHOSEPATTERNS ORBOTH
2!$!2#2/333%#4)/.
£{°Î
&)'52% 2#3OFACOLLECTIONOFBODIESOFREVOLUTIONOFSIMILARSIZEAND PROJECTEDAREAAFTER7%"LOREÚ)%%%
4WO APPROACHES MAY BE TAKEN IN THE APPLICATION OF SHAPING /NE IS TO REPLACE FLATSURFACESWITHCURVEDSURFACESANDTHEREBYELIMINATENARROWBUTINTENSESPECULAR LOBES4HISISNOTVERYEFFECTIVEBECAUSEITINCREASESTHEGENERALECHOLEVELSATNEARBY ASPECT ANGLES4HE SECOND APPROACH IS TO EXTEND FLAT AND SINGLY CURVED SURFACES SO ASTOFURTHERNARROWTHESPECULARLOBEEVENIFTHISINCREASESITSINTENSITY4HELOGICOF THISAPPROACHISTHATTHEPROBABILITYOFDETECTIONISPROPORTIONALTOTHEAVERAGE2#3 OVER A RANGE OF SOLID ANGLES OF OBSERVATION AND IF THE WIDTH OF THE LOBE IS NARROW ENOUGH ITSCONTRIBUTIONTOTHEAVERAGE2#3MAYBELESSTHANIFITWEREAWIDERBUT LESSINTENSELOBE4HEREQUIRED2#3PATTERNLEVELSOFSPECIFICVEHICLECONCEPTSSHOULD BEESTABLISHEDBYMEANSOFMISSIONANALYSESBEFOREDECIDINGWHICHSHAPINGCRITERION ISAPPLICABLE 3HAPINGISUSUALLYDIFFICULTTOEXPLOITOREXPENSIVETOIMPLEMENTFORVEHICLESOR OBJECTSALREADYINPRODUCTIONBECAUSETHEVEHICLECONFIGURATIONANDPROFILEHAVEBEEN SELECTEDANDOPTIMIZEDFORSPECIFICMISSIONOBJECTIVES#HANGESINTHECONFIGURATION AFTERPRODUCTION THEREFORE ARELIKELYTOIMPAIRTHEMISSIONCAPABILITIESOFTHEVEHICLE )FCONSIDEREDANOPTIONINTHECONTROLOF2#3 SHAPINGMUSTBEINCLUDEDINTHECONCEP TUALDESIGNOFTHEVEHICLEWELLBEFOREANYPRODUCTIONDECISIONSAREMADE&URTHERMORE SHAPINGISNOTVERYEFFECTIVEFORBODIESTHATARENOTELECTRICALLYLARGE ,OW2ADAR#ROSS3ECTION6EHICLES 4HEFOLLOWINGARESOMEEXAMPLESOFLOW CROSSSECTIONVEHICLESFROMTHEEARLYDAYSOFLOWCROSS SECTIONVEHICLEDEIGN 4HE 32 4HE DESIGN OF LOW CROSS SECTION VEHICLES PROBABLY BEGAN WHEN #LARENCE h+ELLYv *OHNSON ,OCKHEEDS FAMOUS DESIGNER UNDERTOOK DEVELOPMENT
£{°{ä
2!$!2(!.$"//+
&)'52% 4HEOBJECTSWHOSERADARCROSSSECTIONS AREPLOTTEDIN&IGURE
OFTHE! ANEARLYPROTOTYPEOFTHE32 "LACKBIRDRECONNAISSANCEPLATFORM!T ,OCKHEEDSFABLED3KUNK7ORKS HERECOGNIZEDTHEIMPORTANCEOFBRINGINGTHE2#3 DESIGNENGINEERINTOTHEINNER CIRCLEDESIGNTEAM4HE! DEVELOPMENTCONTRACTWAS AWARDEDIN ANDBYEARLYTHE! WASFLYINGMISSIONSAROUNDTHEWORLD 4HEINFLUENCEOF*OHNSONSRADARSIGNATURESPECIALISTSISEVIDENTIN&IGURE 4HEMOSTREMARKABLEFEATUREOFTHE32 ISTHECHINETHATRUNSFROMTHENOSETOTHE ROOT OF THE DELTA WING )N THE NOSE ON SECTOR THE RADAR ECHO WILL BE DOMINATED BY RETURNS FROM THE ENGINE INLETS WHERE THE CHINE CONTRIBUTION IS NO DOUBT NEGLIGIBLE 7HENSEENFROMTHEBROADSIDEASPECTS THECHINEREDUCESTHESPECULARECHOTHATWOULD HAVECOMEFROMTHEOTHERWISEROUNDEDSIDESOFTHEFORWARDFUSELAGE.OTETHATTHETAIL FINSARECANTEDINWARD THEREBYDEFLECTINGINCIDENTRADARWAVESUPWARDAWAYFROM THERADAR WHENSEENFROMTHESIDE4HISDESIGNGREATLYREDUCESTHE32 SECHOINA NARROWBROADSIDESECTOROFANGLES 4HE& 4HELARGESTECHOSOURCEINTHE32 NOSE ONREGIONISPROBABLYTHE ENGINEINTAKESBECAUSETHEYARETHRUSTWELLFORWARDOFTHEWINGLEADINGEDGES4HE INTAKESOFTHE& .IGHTHAWK BYCONTRAST AREINSTALLEDABOVETHEWINGANDWELLAFT OFTHELEADINGEDGETHEYARETHELITTLEBLACKDIAMONDSSEENINTHENOSE ONVIEWOFTHE & SHOWNIN&IGURE!SSUCH THEINTAKESARESHIELDEDFROMGROUND BASED
2!$!2#2/333%#4)/.
£{°{£
&)'52% ,OCKHEEDS32 "LACKBIRD
RADARSWHENTHE& ISINLEVELFLIGHT%VENSO THE& DEVELOPERSCONTRIVEDAN EGG CRATECOVERINGFORTHEINTAKESTHAT INTHEORY PREVENTSAPPROACHINGRADARWAVES FROMENTERINGTHEINLETDUCTS WHERETHEYRATTLEAROUNDANDEVENTUALLYCOMEBACKOUT AGAIN HEADINGDIRECTLYBACKTOTHERADAR "ECAUSETHEEGG CRATEGRILLWORKREDUCEDAIRFLOW THEINTAKEHADTOBEENLARGEDTO RESTORENORMALFLOW!NDTHEDESIGNERSLATERDISCOVEREDTHATTHEGRILLWORKTENDEDTO ICEUP WHICHTHEYOVERCAMEWITHANELECTRICALHEATINGSYSTEM4HEMOSTREMARKABLE FEATURESOFTHE& AREITSFACETTEDAERODYNAMICALLYPOOR SURFACEPROFILEANDITS
&)'52% ,OCKHEEDS& .IGHTHAWKFIGHTER
£{°{Ó
2!$!2(!.$"//+
SHARPLYSWEPTTAILFINS4HETAILFINSARECANTEDOUTASWELLASBEINGSWEPTAFT ANDTHE WINGSAREALSOSHARPLYSWEPT!LTHOUGH,OCKHEEDMANAGEDTOPRODUCEASUPERSONIC 32 AIRFRAMEUSINGEXOTICMATERIALS THELOW2#3DEMANDEDOFTHE& REQUIRED ASUBSONICAIRFRAME4HEAIRFRAMEISCOVEREDWITHTHINABSORBINGMATERIALWHOSEEDGES ARESERRATEDTOREDUCEREFLECTIONSWHEREHATCHESANDCOVERSFITINTOTHEFUSELAGE " 3PIRIT"OMBER .ORTHROP THEPRIMECONTRACTORFORTHE" 3PIRIT FACEDTHE SAMEPROBLEMWITHENGINEPLACEMENTTHAT,OCKHEEDDIDWITHTHE& .IGHTHAWK 4HESOLUTIONWASTHESAMEEMBEDTHEENGINESINTAKESINTHETOPSIDEOFTHEAIRFRAME 0OSSIBLYBECAUSETHE" HADADIFFERENTMISSIONTHANTHE& DID .ORTHROPDID NOTINSTALLEGG CRATEGRILLWORKOVERTHEENGINEINTAKES)NDEED .ORTHROPDESIGNERS DEVISEDHINGEDCOWLINGSTHATOPENUPATLANDINGANDTAKEOFFSPEEDSTOINCREASEAIR FLOWINTOTHEENGINES4HECOWLINGSARETHENRETRACTEDATCRUISINGSPEEDFOROPTIMUM THRUSTANDEFFICIENCY )NTHEINTERESTOFLOWERINGTHEAIRFRAMESRADARECHO .ORTHROPSDESIGNTEAMDELIB ERATELYBUILTTHE" WITHOUTATAILFIN!SIDEFROMTHIS ITISINTERESTINGTHATTHE& AND" SHARESOMECOMMONFEATURES/NEISTHEROUNDEDWINGTIPS WHICHTENDTO REDUCETIP SPAWNEDREFLECTIONSOFSURFACETRAVELINGWAVESTHATMIGHTBUILDUPALONG THEWINGSLEADINGEDGES!NOTHERISTHEUSEOFTHINABSORBERCOATINGSTHATARESERRATED AROUNDTHEEDGESOFHATCHES COVERS ANDCANOPIESTOSUPPRESSREFLECTIONSFROMEDGE DISCONTINUITIES9ET ANOTHER IS THE FACT THAT THE " LIKE THE & HAS A SUBSONIC AIRFRAME4HISSUGGESTSTHATALTHOUGHTHECHINECONCEPTMAYHAVEWORKEDFORTHEFUSE LAGEOFTHEFABLED-ACH 32 ITISBYNOMEANSAVIABLEAPPROACHFORREDUCINGTHE ECHOESFROMWINGLEADINGEDGES )NDEED THEDESIGNERSOFTHE" AIRFRAMEAPPARENTLYRECOGNIZEDEARLYINTHEDESIGN WORKTHATITWOULDBENEARLYIMPOSSIBLETOREDUCETHELEADINGEDGE2#3OFTHEIRSUB SONIC AIRFRAME TO ACCEPTABLE LEVELS 4HAT BEING THE CASE THEY DECIDED TO ANGLE ALL LEADINGANDTRAILINGEDGESATACOMMONSWEEPANGLEn4HEIRPHILOSOPHYWASTHAT IFTHEYCOULDNTSUPPRESSTHEEDGERETURNS THENEXTBESTOPTIONWOULDBETOANGLETHEM ALLINTOFOURCOMMONDIRECTIONSINSPACE4HUS ALLTRAILINGEDGESINTHE" AREPARALLEL TOLEADINGEDGES 8 # 5NMANNED #OMBAT 6EHICLE 4HE "OEING #OMPANY UNVEILED A MOCKUP OF THE h#v VERSION OF ITS UNMANNED COMBAT VEHICLE IN THE MID S LESS THAN A DECADE AFTER THE PROJECT WAS FUNDED BY THE $EFENSE !DVANCED 2ESEARCH 0ROJECTS !DMINISTRATION$!20! !N!SSOCIATED0RESSPHOTOOFTHEAIRCRAFTMOCKUPISSHOWN IN&IGURE4HEAIRFRAMEISFTWIDEANDFTLONG 4HENOSEANGLEOFTHEPLANFORMISNEARLYDOUBLETHATOFTHE& YETBARELYHALF THATOFTHE" SOTHEPLANFORMNOSEANGLESEEMSTOBEACOMPROMISEBETWEENTHETWO .OTETHATTHEABSENCEOFACOCKPITIMPROVESTHESTEALTHINESSOFTHEAIRFRAME)NDEED THEENGINEINLETCOWLINGREPLACESTHECOCKPIT ANDEVENTHELIPSOFTHEINLETAREBROADLY SERRATEDTOREDUCETHEIRCONTRIBUTIONTOTHERADARECHO4HELACKOFANYTAILFINANDTHE CONTOUROFTHETRAILINGEDGESOFTHEPLANFORMREVEALSTRONGINFLUENCESFROMTHE" DESIGNPHILOSOPHY ,OW#ROSS3ECTION3HIPS #ONVENTIONALSHIPSUSUALLYHAVEVERYLARGESTRUCTURES WITHMANYHORIZONTALANDVERTICALREFLECTINGSURFACESTHATMEETATRIGHTANGLES FORM INGCORNERREFLECTORSWITHSTRONGECHOES4HEYALSOCANHAVEMANYINDIVIDUALSCAT TERERSTHATCANCONTRIBUTETOALARGERADARCROSSSECTION4OACHIEVELOWRADARCROSS SECTION THEHORIZONTALVERTICALDESIGNPLANISCHANGEDSOASTOEMPLOYTILTEDSURFACES
2!$!2#2/333%#4)/.
£{°{Î
&)'52% "OEINGS MOCKUP OF ITS 8 # UNMANNED COMBAT VEHICLE #OURTESYOFTHE!SSOCIATED0RESS
THAT SPOIL THE CORNER REFLECTOR EFFECT 3URFACE TILTING ALSO MOVES THE RADAR ANGLE OF INCIDENCE WELL INTO THE FAR SIDELOBES OF MOST SURFACES ON THE VESSEL4HUS VERTICAL BULKHEADSOFTENARETILTEDINBOARD
, ,
%&+NOTT h2ADAROBSERVABLES vIN4ACTICAL-ISSILE!ERODYNAMICS'ENERAL4OPICS 6OL -*(EMSCH ED 7ASHINGTON $#!MERICAN)NSTITUTEOF!ERONAUTICSAND!STRONAUTICS #HAP %'3CHNEIDER h2ADAR v0ROC)2% VOL PPn !UGUST 3$2OBERTSON h4ARGETSFORMICROWAVENAVIGATION v"ELL3YST4ECH* VOL PPn * ! 3TRATTON %LECTROMAGNETIC 4HEORY .EW 9ORK -C'RAW (ILL "OOK #OMPANY PPn n * 2HEINSTEIN h"ACKSCATTER FROM SPHERES ! SHORT PULSE VIEW v )%%% 4RANS VOL !0 PPn *ANUARY $!TLAS ,*"ATTAN 7'(ARPER "-(ERMAN -+ERKER AND%-ATIJEVIC h"ACK SCATTERBY DIELECTRICSPHERESREFRACTIVEINDEX^ v)%%%4RANS VOL!0 PP *ANUARY %&+NOTT !72EED AND0307EI h"ROADSIDEECHOESFROMWIRESANDSTRINGS v-ICROWAVE *OURNAL PPETSEQ *ANUARY 33#HANGAND66,IEPA h-EASUREDBACKSCATTERINGCROSSSECTIONOFTHINWIRES 5NIVERSITYOF -ICHIGAN 2AD,AB2EPT 4 -AY , 0ETERS *R h%ND FIRE ECHO AREA OF LONG THIN BODIES v )2% 4RANS VOL!0 PP n *ANUARY 0307EI !72EED #.%RICKSEN AND-$"USHBECK h3TUDYOF2#3MEASUREMENTSFROM ALARGEFLATPLATE vIN0ROCTH!-4!#ONFERENCE !NTENNA-EASUREMENT4ECHNIQUES!SSOCIATION 3YMPOSIUM .EWPORT 2) /CTOBER PPn %&+NOTT h!TOOLFORPREDICTINGTHERADARCROSSSECTIONOFANARBITRARYCORNERREFLECTOR vIN )%%%0UBL )%%%3OUTHEASTCON#ONFERENCE #( (UNTSVILLE !, !PRILn PPn
£{°{{
2!$!2(!.$"//+
% & +NOTT h2#3 REDUCTION OF DIHEDRAL CORNERS v )%%% 4RANS VOL !0 PP n -AY 7 #!NDERSON h#ONSEQUENCES OF NON ORTHOGONALITY ON THE SCATTERING PROPERTIES OF DIHEDRAL REFLECTORS v)%%%4RANS VOL!0 PPn /CTOBER %&+NOTT *&3HAEFFER AND-44ULEY 2ADAR#ROSS3ECTION 2ALEIGH .#3CI4ECH0UBLISHING )NC P 2'(AJOVSKY !0$EAM AND!(,A'RONE h2ADARREFLECTIONSFROMINSECTSINTHELOWER ATMOSPHERE v)%%%4RANS VOL!0 PPn -ARCH &63CHULTZ 2#"URGENER AND3+ING h-EASUREMENTSOFTHERADARCROSSSECTIONOFAMAN v 0ROC)2% VOL PPn &EBRUARY #26AUGHN h"IRDSANDINSECTSASRADARTARGETS!REVIEW v0ROC)%%% VOL PPn &EBRUARY *22ILEY h2ADARCROSSSECTIONOFINSECTS v0ROC)%%% VOL PPn &EBRUARY , . 2IDENOUR ED 2ADAR 3YSTEM %NGINEERING -)4 2ADIATION ,ABORATORY 3ERIES 6OL .EW9ORK-C'RAW (ILL"OOK#OMPANY P 53!IR&ORCEWEBSITE $ECEMBER HTTPWWWWRSAFRLAFMILOTHERMMFCOMPRESHTM -)3KOLNIK )NTRODUCTIONTO2ADAR3YSTEMS .EW9ORK-C'RAW (ILL"OOK#OMPANY P -)3KOLNIK h!NEMPIRICALFORMULAFORTHERADARCROSSSECTIONOFSHIPSATGRAZINGINCIDENCE v )%%%4RANS VOL!%3 P -ARCH 32AMOAND*27HINNERY &IELDSAND7AVESIN-ODERN2ADIO ND%D .EW9ORK*OHN7ILEY 3ONS PPn *!3TRATTON 2EF PPn 2 & (ARRINGTON &IELD #OMPUTATION BY -OMENT -ETHODS .EW 9ORK -ACMILLAN #OMPANY 2%+LEINMAN h4HE2AYLEIGH2EGION v0ROC)%%% VOL PPn !UGUST *7#RISPIN *RAND+-3IEGEL EDS -ETHODSOF2ADAR#ROSS3ECTION!NALYSIS .EW9ORK !CADEMIC0RESS PPn %&+NOTT h!PROGRESSIONOFHIGH FREQUENCY2#3PREDICTIONTECHNIQUES v0ROC)%%% VOL PPn &EBRUARY %&+NOTTETAL 2EF P %&+NOTTETAL 2EF PPn 4"!3ENIOR h!SURVEYOFANALYTICALTECHNIQUESFORCROSS SECTIONESTIMATION v0ROC)%%% VOL PPn !UGUST ) * 'UPTA AND 7 $ "URNSIDE h0HYSICAL OPTICS CORRECTION FOR BACKSCATTERING FROM CURVED SURFACES v)%%%4RANS VOL!0 PPn -AY *"+ELLER h$IFFRACTIONBYANAPERTURE v*!PPL0HYS VOL PPn !PRIL *"+ELLER h'EOMETRICALTHEORYOFDIFFRACTION v*/PT3OC!M VOL PPn 2'+OUYOUMJIANAND0(0ATHAK h!UNIFORMTHEORYOFDIFFRACTIONFORANEDGEINAPERFECTLY CONDUCTINGSURFACE v0ROC)%%% VOL PPn .OVEMBER **"OWMAN 0,%5SLENGHI AND4"!3ENIOREDS %LECTROMAGNETICAND!COUSTIC3CATTERING BY3IMPLE3HAPES !MSTERDAM.ORTH (OLLAND P 0)A5FIMTSEV h!PPROXIMATECOMPUTATIONOFTHEDIFFRACTIONOFPLANEELECTROMAGNETICWAVESAT CERTAINMETALBOUNDARIES 0ART)$IFFRACTIONPATTERNSATAWEDGEANDARIBBON v:H4EKHN&IZ 5332 VOL NO PPn 0)A5FIMTSEV h!PPROXIMATECOMPUTATIONOFTHEDIFFRACTIONOFPLANEELECTROMAGNETICWAVESAT CERTAINMETALBOUNDARIES 0ART))4HEDIFFRACTIONBYADISKANDBYAFINITECYLINDER v:H4EKHN &IZ5332 VOL NO PPn 0)A5FIMTSEV h-ETHODOFEDGEWAVESINTHEPHYSICALTHEORYOFDIFFRACTION v53!IR&ORCE 3YSTEMS#OMMAND &OREIGN4ECHNOLOGY$IVISION$OC&4$ (# 4RANSLATED FROMTHE2USSIANVERSIONPUBLISHEDBY-OSCOW3OVIET2ADIO0UBLICATION(OUSE
2!$!2#2/333%#4)/.
£{°{x
%&+NOTTETAL 2EF PPn +--ITZNER h)NCREMENTALLENGTHDIFFRACTIONCOEFFICIENTS v.ORTHROP#ORPORATION !IRCRAFT$IV 4ECH2EPT!&!, 42 !PRIL %&+NOTT h4HERELATIONSHIPBETWEEN-ITZNERS),$#AND-ICHAELISEQUIVALENTCURRENTS v)%%% 4RANS VOL!0 PPn *ANUARY;)NTHELASTTERMOF%Q INTHISREFERENCE THEDOTPRECEDINGTHEMINUSSIGNSHOULDBEDELETEDANDASHOULDBEREPLACEDBYSINAIN%Q THESIGNOFTHEFIRSTTERMONTHERIGHTSIDEMUSTBEREVERSED= ! -ICHAELI h%QUIVALENT EDGE CURRENTS FOR ARBITRARY ASPECTS OF OBSERVATION v )%%% 4RANS VOL!0 PPn -ARCH3EEALSOCORRECTION VOL!0 P &EBRUARY !-ICHAELI h%LIMINATIONOFINFINITESINEQUIVALENTEDGECURRENTS 0ART)&RINGECURRENTCOMPO NENTS v)%%%4RANS VOL!0 PPn *ULY !-ICHAELI h%LIMINATIONOFINFINITIESINEQUIVALENTEDGECURRENTS 0ART))0HYSICALOPTICSCOM PONENTS v)%%%4RANS VOL!0 PPn !UGUST &! 3IKTA 7 $ "URNSIDE 4 4 #HU AND , 0ETERS *R h&IRST ORDER EQUIVALENT CURRENT AND CORNERDIFFRACTIONSCATTERINGFROMFLATPLATESTRUCTURES v)%%%4RANS VOL!0 PPn *ULY 2 " -ACK h"ASIC DESIGN PRINCIPLES OF ELECTROMAGNETIC SCATTERING MEASUREMENT FACILITIES v 2OME!IR$EVELOPMENT#ENTER2EPT2!$# 42 -ARCH 2 " $YBDAL h2ADAR CROSS SECTION MEASUREMENTS v 0ROC )%%% VOL PP n !PRIL 2'+OUYOUMJIANAND,0ETERS *R h2ANGEREQUIREMENTSINRADARCROSSSECTIONMEASUREMENTS v 0ROC)%%% VOL PPn !UGUST %&+NOTTETAL 2EF P -!0LONUS h4HEORETICALINVESTIGATIONOFSCATTERINGFROMPLASTICFOAMS v)%%%4RANS VOL!0 PPn *ANUARY 4"!3ENIOR -!0LONUS AND%&+NOTT h$ESIGNINGFOAMED PLASTICMATERIALS v-ICROWAVES PPn $ECEMBER %&+NOTTAND4"!3ENIOR h3TUDIESOFSCATTERINGBYCELLULARPLASTICMATERIALS v5NIVERSITYOF -ICHIGAN 2AD,AB2EPT & !PRIL ##&REENY h4ARGETSUPPORTPARAMETERSASSOCIATEDWITHRADARREFLECTIVITYMEASUREMENTS v0ROC )%%% VOL PPn !UGUST %&+NOTTETAL 2EF P 7(%MERSON h%LECTROMAGNETICWAVEABSORBERSANDANECHOICCHAMBERSTHROUGHTHEYEARS v )%%%4RANS VOL!0 PPn *ULY ,3OLOMON h2ADARCROSSSECTIONMEASUREMENTS(OWACCURATEARETHEY v%LECTRONICS VOL PPn *ULY 7(%MERSONAND("3EFTON *R h!NIMPROVEDDESIGNFORINDOORRANGES v0ROC)%%% VOL PPn !UGUST (%+ING &)3HIMABUKURO AND*,7ONG h#HARACTERISTICSOFATAPEREDANECHOICCHAMBER v )%%%4RANS VOL!0 PPn -AY 2"$YBDALAND#/9OWELL h6(&TO%(&PERFORMANCEOFA FOOTQUASI TAPEREDANECHOIC CHAMBER v)%%%4RANS VOL!0 PPn *ULY 2#*OHNSON (!%CKER AND2!-OORE h#OMPACTRANGETECHNIQUESANDMEASUREMENTS v )%%%4RANS VOL!0 PPn 3EPTEMBER 7$"URNSIDE -#'ILREATH "-+ENT AND',#LERICI h#URVEDEDGEMODIFICATIONOF COMPACTRANGEREFLECTOR v)%%%4RANS VOL!0 PPn &EBRUARY 2#2UDDUCK -#,IANG 7$"URNSIDE AND*39Uh&EASIBILITYOFCOMPACTRANGESFOR NEAR ZONEMEASUREMENTS v)%%%4RANS VOL!0 PPn -ARCH 7 $ "URNSIDE #7 0ISTORIUS AND - # 'ILREATH h! DUAL CHAMBER 'REGORIAN SUBREFLECTOR FOR COMPACT RANGE APPLICATIONS v 0ROC OF THE !NTENNA -EASUREMENT 4ECHNIQUES !SSOCIATION 3EPTEMBERn/CTOBER PPn
£{°{È
2!$!2(!.$"//+
% & +NOTT 2ADAR #ROSS 3ECTION -EASUREMENTS .EW 9ORK 6AN .OSTRAND 2EINHOLD PPn $,-ENSA (IGH2ESOLUTION2ADAR)MAGING .ORWOOD -!!RTECH(OUSE 7 7 3ALISBURY h!BSORBENT "ODY FOR %LECTROMAGNETIC 7AVES v 53 0ATENT *UNE 7%"LORE h4HERADARCROSSSECTIONOFOGIVES DOUBLE BACKEDCONES DOUBLEROUNDEDCONES AND CONESPHERES v)%%%4RANS VOL!0 PPn 3EPTEMBER -$/,EARYAND%RIC3CHULZINGER 32 )NSIDE,OCKHEEDS"LACKBIRD /SEOLA 7)-OTORBOOKS )NTERNATIONAL0UBLISHERS7HOLESALERS " 3WEETMAN AND * 'OODALL ,OCKHEED & ! /SEOLA 7) -OTORBOOKS )NTERNATIONAL 0UBLISHERS7HOLESALERS % & +NOTT h2#32 'UIDELINES (ANDBOOK v &INAL 4ECHNICAL 2EPORT ON %%3')4 0ROJECT ! v%NGINEERING%XPERIMENT3TATION 'EORGIA)NSTITUTEOF4ECHNOLOGY !PRIL
#HAPTER
-i>Ê ÕÌÌiÀ iÜÃÊ °Ê7iÌâi .AVAL2ESEARCH,ABORATORYRETIRED
£x°£Ê /," 1 /" &OR AN OPERATIONAL RADAR BACKSCATTER OF THE TRANSMITTED SIGNAL BY ELEMENTS OF THE SEASURFACEOFTENPLACESSEVERELIMITSONTHEDETECTABILITYOFRETURNSFROMSHIPS AIR CRAFT ANDMISSILES NAVIGATIONBUOYS ANDOTHERTARGETSSHARINGTHERADARRESOLUTION CELLWITHTHESEASURFACE4HESEINTERFERINGSIGNALSARECOMMONLYREFERREDTOASSEA CLUTTER ORSEAECHO4HESEARCHFORAUSEFULUNDERSTANDINGOFTHISIMPORTANTRADAR CONTAMINANTBEGANWITHTHECOLLECTIONANDANALYSISOFCLUTTERDATAFROMOPERATING RADARS WITHTHEGOALOFESTABLISHINGTHERELATIONSHIPBETWEENCLUTTERSIGNALSANDTHE PARAMETERS OF BOTH THE RADAR AND THE SEA ENVIRONMENT -UCH OF THE EARLIEST WORK TOOKPLACEDURING77))AND CAN BE FOUND IN ONE OF THE COMPREHENSIVE SERIES OF 2!$,!"VOLUMESDOCUMENTINGTHERADARRESEARCHTHATWASDONEATTHATTIME"UT MOSTOFTHECLUTTERDATAFROMTHISPERIOD ANDEVENINTOTHES WASCOLLECTEDIN BITSANDPIECESFROMISOLATEDEXPERIMENTS OFTENWITHPOOR INCOMPLETE ORMISLEAD INGDESCRIPTIONSOFTHESEASURFACE )T WOULD SEEM A SIMPLE MATTER TO REFINE THESE RESULTS BY USING INSTRUMENTATION RADARSOPERATINGOVERTHEWIDEVARIETYOFRADARANDENVIRONMENTALPARAMETERSENCOUN TEREDINPRACTICE"UTWHILETHEPARAMETERSRELATINGTOTHERADARSYSTEMANDITSCONFIGU RATION SUCHASFREQUENCY CELLSIZE POLARIZATION GRAZINGANGLEATTHESURFACE ETC CAN BESPECIFIED SELECTINGANDQUANTIFYINGTHEENVIRONMENTALPARAMETERSISQUITEANOTHER MATTER&IRST ITHASNOTALWAYSBEENCLEARWHICHENVIRONMENTALPARAMETERSAREIMPOR TANT &OR EXAMPLE WIND SPEED CERTAINLY SEEMS TO AFFECT CLUTTER LEVELS BUT THE COR RELATIONOFCLUTTERWITH SAY ASHIPSANEMOMETERREADINGSISOFTENINCONSISTENT!ND ALTHOUGHTHESTATEOFAGITATIONOFTHESEASURFACESEASTATE APPEARSTOHAVEASTRONG EFFECT IT IS A SUBJECTIVE MEASURE AND ITS RELATION TO PREVAILING LOCAL WINDS IS OFTEN UNCERTAIN -OREOVER IT HAS BEEN FOUND THAT THE TEMPERATURES OF THE AIR AND THE SEA SURFACECANAFFECTTHEWAYINWHICHMEASUREDWINDSPEEDISRELATEDTOTHEGENERATION OF CLUTTER PRODUCING WAVES YET THE IMPORTANCE OF THESE EFFECTS WERE UNAPPRECIATED OVERMOSTOFTHEHISTORYOFSEACLUTTERMEASUREMENTS SOAIRANDSEATEMPERATURESWERE SELDOMRECORDED&INALLY EVENIFTHEIMPORTANCEOFANENVIRONMENTALPARAMETERHAS BEENRECOGNIZED ITISOFTENDIFFICULTORTOOEXPENSIVE TOMEASUREITACCURATELYINTHE FIELDUNDERREALSEACONDITIONS 7HILE MANY ASPECTS OF SEA CLUTTER THUS REMAINED FRUSTRATINGLY ILL DEFINED THE EARLIER WORK DID DISCLOSE SOME GENERAL TRENDS SUCH AS THE TENDENCY OF AVERAGE CLUTTERSIGNALSTRENGTHSATLOWTOINTERMEDIATEGRAZINGANGLESTOINCREASEWITHTHE £x°£
£x°Ó
2!$!2(!.$"//+
GRAZING ANGLE AND THE WIND SPEED OR SEA STATE AND GENERALLY TO BE GREATER FOR VERTICAL POLARIZATION AND IN UPWINDDOWNWIND DIRECTIONS &OR OTHER REVIEWS OF SEA CLUTTER AND ITS HISTORY SEE 3KOLNIK .ATHANSON AND ,ONG 3EA CLUTTER IS HOWEVER ACOMPLEXPHENOMENON PRESENTINGVARIOUSFACESDEPENDINGONTHEWAY THERADARVIEWSTHESCENE&OREXAMPLE ITISCOMMONLYNOTEDTHATWHENVIEWEDON AN!SCOPESIGNALAMPLITUDEVERSUSRANGE THEAPPEARANCEOFSEACLUTTERDEPENDS STRONGLY ON THE SIZE OF THE RESOLUTION CELL OR RADAR FOOTPRINT &OR LARGE CELLS IT APPEARSDISTRIBUTEDINRANGEANDMAYBECHARACTERIZEDBYASURFACE AVERAGEDCROSS SECTIONWITHRELATIVELYMODESTFLUCTUATIONSABOUTAMEANVALUE!STHESIZEOFTHE RESOLUTIONCELLISREDUCED CLUTTERINCREASINGLYAPPEARSTOCONTAINSEQUENCESOFISO LATED TARGET LIKE OR DISCRETE RETURNS THAT VARY IN TIME!T THE HIGHER RESOLUTIONS THE DISCRETE RETURNS TEND TO STAND WELL OUT OF THE BACKGROUND OCCURRING FOR BOTH POLARIZATIONSBUTMOSTCLEARLYEVIDENTWITHHORIZONTALPOLARIZATIONATSMALLGRAZING ANGLES4HESEISOLATEDRETURNSARECALLEDSEASPIKESANDAREACOMMONCLUTTERCOM PONENTINTHISRADAROPERATINGREGIME1UITECLEARLY ANUNDERSTANDINGOFSEACLUTTER INALLITSASPECTSWILLBEACONSIDERABLEUNDERTAKING&ORTUNATELY ACLOSERELATION SHIPBETWEENRADARANDOCEANOGRAPHYHASGROWNUPINTHEFIELDSOFREMOTESENSING LEADINGTOTHEACCUMULATIONOFALARGEAMOUNTOFINFORMATION BOTHEXPERIMENTAL ANDTHEORETICAL ABOUTHOWSCATTERINGATRADARFREQUENCIESRELATESTOOCEANOGRAPHIC VARIABLES)NMANYWAYS THISINFORMATIONSERVESASTHEBASISOFMUCHOFOURCURRENT UNDERSTANDINGOFSEACLUTTER )NMODELINGSEACLUTTER THEREISADIFFERENCEBETWEENATHEORY WHICHRELATESTHE PHYSICALSCATTERINGPROPERTIESOFTHESEASURFACETOTHERECEIVEDSIGNAL ANDACHARAC TERIZATION WHICHPROVIDESADESCRIPTIONOFTHESEACLUTTERDATAINTERMSOFASTATISTICAL MODELEG 2AYLEIGH LOGNORMAL 7EIBULL AND+ DISTRIBUTION THAT ALTHOUGHSOME TIMESSUGGESTIVEOFPHYSICALPROCESSESINTHEUNDERLYINGSCATTERING ISOFGREATERDIRECT INTEREST TO THE RADAR SYSTEM DESIGNER IN PROVIDING DETECTION PROBABILITIES AND FALSE ALARMRATES (ISTORICALLY ATTEMPTSTOPROVIDEATHEORETICALEXPLANATIONOFTHEOBSERVEDBEHAV IOROFCLUTTERSIGNALSTRACEESSENTIALLYFROMTHEWORKPURSUEDDURING7ORLD7AR)) ANDDESCRIBEDINTHEWELL KNOWN-)42ADIATION,ABORATORYBOOKMENTIONEDABOVE 5NFORTUNATELY THESCATTERINGMODELSDEVELOPEDDURINGTHISPERIOD ALONGWITHMOST OFTHOSEPUBLISHEDOVERTHEFOLLOWINGDECADE FAILEDTOACCOUNTINANYCONVINCING WAYFORTHEBEHAVIOROFSEABACKSCATTER)N HOWEVER #ROMBIEOBSERVEDTHATAT HIGH FREQUENCY(& WAVELENGTHSTENSOFMETERS SCATTERINGAPPEAREDTOARISEFROM ARESONANTINTERACTIONWITHSEAWAVESOFONE HALFOFTHEINCIDENTWAVELENGTH IE TO BEOFTHE"RAGGTYPE2EINFORCEDBYTHETHEORETICALIMPLICATIONSOFVARIOUSSMALL WAVEHEIGHT APPROXIMATIONS AND WAVE TANK MEASUREMENTS UNDER IDEALIZED CONDI TIONS THE"RAGGMODELWASINTRODUCEDINTOTHEMICROWAVEREGIMEBYMANYWORKERS IN THE MID Sn 4HIS PRODUCED A REVOLUTION IN THINKING ABOUT THE ORIGINS OF SEACLUTTERBECAUSEITINVOLVEDTHESEAWAVESPECTRUM THUSFORGINGALINKBETWEEN CLUTTERPHYSICSANDOCEANOGRAPHYINWHATBECAMETHEFIELDOFRADIOOCEANOGRAPHY (OWEVER FUNDAMENTAL CONCEPTUAL PROBLEMS IN APPLYING THE "RAGG HYPOTHESIS IN MICROWAVESCATTERING ALONGWITHITSINABILITYTOADDRESSSIGNIFICANTASPECTSOFMEA SUREDSEACLUTTER HAVELEDTHROUGHTHEYEARSTOCONTINUINGINQUIRYINTOTHEPHYSICAL ORIGINSOFSEASCATTERANDHOWBESTTOMODELITn4HISBEINGTHECASE SPECULATION ABOUTPHYSICALMODELSWILLBEKEPTTOAMINIMUMINTHESECTIONSONTHEEMPIRICAL BEHAVIOROFSEACLUTTER4HEPROBLEMOFMODELINGSEASCATTERWILLBEDISCUSSEDSEPA RATELYINALATERSECTION
3%!#,544%2
£x°Î
£x°ÓÊ / Ê- Ê-1,
#LOSE OBSERVATION OF THE SEA SURFACE DISCLOSES A VARIETY OF FEATURES DESCRIBABLE AS WEDGES CUSPS WAVES FOAM TURBULENCE ANDSPRAY ASWELLASBREAKINGEVENTSOFALL SIZESANDMASSESOFFALLINGWATER!NYORALLOFTHESEMIGHTCONTRIBUTETOTHESCATTER ING OF ELECTROMAGNETIC WAVES RESPONSIBLE FOR SEA CLUTTER 4HE BASIC OCEANOGRAPHIC DESCRIPTOROFTHESEASURFACE HOWEVER ISTHEWAVESPECTRUM WHICHSAYSLITTLEABOUT THE DETAILS OF THESE FEATURES BUT CONTAINS A GREAT DEAL OF INFORMATION ABOUT THE SEA SURFACEINGENERALANDISCENTRALTOTHEAPPLICATIONOFTHE"RAGGSCATTERINGHYPOTHESIS !CCORDINGLY SOMETUTORIALMATERIALDESCRIBINGTHESPECTRALCHARACTERIZATIONOFTHESEA SURFACEISINCLUDEDINTHISSECTION ALONGWITHABRIEFDISCUSSIONOFSURFACEEVENTSSUCH ASWAVEBREAKINGANDOTHERSURFACEEFFECTSTHOUGHTTOCONTRIBUTETOTHEPRODUCTIONOF SEASPIKES 4HEREAREBASICALLYTWOTYPESOFSURFACEWAVES CAPILLARYANDGRAVITY DEPENDING ONWHETHERSURFACETENSIONORGRAVITYISTHEDOMINANTRESTORINGFORCE4HETRANSITION BETWEENONEANDTHEOTHERTAKESPLACEATAWAVELENGTHOFABOUTCM SOTHESMALLER CAPILLARY WAVES SUPPLY THE SURFACE FINE STRUCTURE WHILE GRAVITY WAVES MAKE UP THE LARGERANDMOSTVISIBLESURFACESTRUCTURES3EAWAVESHAVETHEIRORIGINPRIMARILYINTHE WIND BUTTHISDOESNOTMEANTHATTHEhLOCALvWINDISAPARTICULARLYGOODINDICATOROF WHATTHEWAVESTRUCTUREBENEATHITWILLBE)NORDERTOAROUSETHESURFACETOITSFULLY DEVELOPEDOREQUILIBRIUMSTATE THEWINDMUSTBLOWFORASUFFICIENTTIMEDURATION OVERASUFFICIENTDISTANCEFETCH 4HATPARTOFTHEWAVESTRUCTUREDIRECTLYPRODUCED BYTHESEWINDSISCALLEDSEA"UTWAVESPROPAGATE SOEVENINTHEABSENCEOFLOCAL WIND THERECANBESIGNIFICANTLOCALWAVEMOTIONDUETOWAVESARRIVINGFROMFARAWAY PERHAPSFROMADISTANTSTORM7AVESOFTHISTYPEARECALLEDSWELL ANDSINCETHESURFACE OVERWHICHTHEWAVESTRAVELACTSASALOW PASSFILTER SWELLCOMPONENTSOFTENTAKETHE FORMOFLONG CRESTEDLOW FREQUENCYSINUSOIDS 4HE 7AVE 3PECTRUM 4HE OCEAN WAVE SPECTRUM DESCRIBING THE SEA SURFACE APPEARSINSEVERALFORMS)FTHETIMEHISTORYOFTHESURFACEELEVATIONISMONITOREDATA FIXEDPOINT THERESULTINGTIMESERIESMAYBEPROCESSEDTOPROVIDEAFREQUENCYSPECTRUM 3F OFTHESURFACEELEVATION WHERE3F DFISAMEASUREOFTHEENERGYIE SQUARE OFTHEWAVEHEIGHT OFTHEWAVESINTHEFREQUENCYINTERVALBETWEENFANDF DF7AVE SPECTRAHAVEBEENMEASUREDINTHEOPENOCEANPRIMARILYFORGRAVITYWAVESDOWNTO WAVELENGTHSOFABOUTM/PEN OCEANMEASUREMENTSOFCAPILLARYWAVESPECTRAARE ESPECIALLYDIFFICULTTOPERFORM &ORAGRAVITYWAVE THEFREQUENCYFANDTHEWAVENUMBER+ARERELATEDBYTHEDIS PERSIONRELATION
F O G+
WHEREGISTHEACCELERATIONOFGRAVITYAND+ O, WITH,BEINGTHEWAVELENGTH !LTHOUGHEACHINDIVIDUALGRAVITYWAVEOBEYSTHISRELATION THEWAVESATAPOINTON THESEASURFACECOULDCOMEFROMANYDIRECTIONSOTHEYARECHARACTERIZEDBYATWO DIMENSIONALPROPAGATIONVECTORWITHORTHOGONALCOMPONENTS+XAND+Y WHERETHE+ TOBEUSEDIN%QISTHEMAGNITUDE+ +X +Y 4HEWAVENUMBERSPECTRUM ASSOCIATEDWITH3F ISAFUNCTIONOFTHETWOCOMPONENTSOF+ANDISCOMMONLYWRIT TENAS7+X +Y 4HISISCALLEDTHEDIRECTIONALWAVESPECTRUMANDEXPRESSESTHEASYM METRIESASSOCIATEDWITHWINDS CURRENTS REFRACTION ISOLATEDSWELLCOMPONENTS ETC
£x°{
2!$!2(!.$"//+
&OR A GIVEN SOURCE OF ASYMMETRY SUCH AS THE WIND VARIOUS PARTS OF THE SPECTRUM WILLDISPLAYDIFFERENTDIRECTIONALBEHAVIORS&OREXAMPLE INAFULLYDEVELOPEDSEA THE LARGER WAVES WILL TEND TO MOVE IN THE DIRECTION OF THE WIND WHILE THE SMALLER WAVESWILLBEMOREISOTROPIC$IRECTIONALSPECTRAAREMOREDIFFICULTTOMEASUREAND AREOBTAINEDBYAVARIETYOFEXPERIMENTALMETHODS SUCHASANARRAYOFWAVESTAFFS TOMEASURESURFACEHEIGHTSOVERAMATRIXOFPOINTS AMULTIAXISACCELEROMETERBUOY STEREO PHOTOGRAPHY AND EVEN BY PROCESSING RADAR BACKSCATTER SIGNALS (OWEVER A FREQUENCYSPECTRUMMEASUREDATAPOINTCANCONTAINNOKNOWLEDGEOFWAVEDIRECTION SOAWAVENUMBERSPECTRUM7+ ISOFTENDEFINEDINTERMSOFTHEFREQUENCYSPECTRUM 3F BYTHERELATION
7+ 3F+ DFD+
WITHTHERELATIONBETWEENFAND+GIVENBY%Q4OACCOUNTFORTHEWINDDIRECTION 7+ ISSOMETIMESMULTIPLIEDBYANEMPIRICALFUNCTIONOF+ANDDIRECTIONERELATIVE TOTHEUP WINDDIRECTION /CEANOGRAPHERSHAVENOTALWAYSBEENINCOMPLETEAGREEMENTABOUTTHEFORMOF THEFREQUENCYSPECTRUM.ONEQUILIBRIUMWAVECONDITIONS INADEQUATESAMPLINGTIMES POOR GROUND TRUTH ETC CAN CONTAMINATE THE DATA SET FROM WHICH EMPIRICAL SPECTRA AREDERIVED(OWEVER BYCAREFULSELECTIONOFDATAFROMMANYSOURCES ENSURINGTHAT ONLYEQUILIBRIUMFULLYDEVELOPED SEACONDITIONSWEREREPRESENTEDANDTHEWINDWAS ALWAYSMEASUREDATTHESAMEREFERENCEHEIGHTUSUALLYTAKENASMETERS 0IERSON AND-OSKOWITZESTABLISHEDASIMPLEEMPIRICALSPECTRUMTHATHASPROVENPOPULARAND USEFUL)THASTHEFORM
3F !F E "FMF
WHEREGISTHEACCELERATIONOFGRAVITY ANDFM GO5 CORRESPONDINGTOTHEFREQUENCY OFAWAVEMOVINGWITHAVELOCITYEQUALTOTHEWINDSPEED5!AND"AREEMPIRICAL CONSTANTS 4HIS SPECTRUM IS ILLUSTRATED IN &IGURE FOR SEVERAL WIND SPEEDS 4HE EFFECTOFINCREASINGWINDSPEEDISSIMPLYTOMOVETHELOW FREQUENCYCUTOFFTOLOWER FREQUENCIESALONGTHEHIGH FREQUENCYF ASYMPTOTE)TSHOULDBENOTEDTHATMOSTOF THEOCEANOGRAPHERSSPECTRAAREBASEDONMEASUREMENTSATRELATIVELYLOWFREQUENCIES ANDSOCANNOTBETAKENSERIOUSLYATFREQUENCIESABOVEABOUT(Z.EVERTHELESS THESE SPECTRALFORMSAREOFTENUSEDUPTO(ZORGREATERINPREDICTINGRADARCLUTTERUNDER THE"RAGGHYPOTHESIS #ONVERTING THIS FREQUENCY SPECTRUM INTO AN ISOTROPIC WAVENUMBER SPECTRUM THROUGH%QRESULTSINASPECTRUMOFSIMILARFORM ONLYWITHA+ ASYMPTOTE 0HILLIPSDERIVEDTHISASYMPTOTICBEHAVIORONDIMENSIONALGROUNDS ANDAWIDELYUSED SIMPLIFICATION OBTAINEDBYREPLACINGTHESMOOTHPEAKIN&IGUREBYASHARPCUTOFF ISGENERALLYREFERREDTOASTHE0HILLIPS3PECTRUM
7+ + + G5
+ G5
WHERETHECUTOFFWAVENUMBERCORRESPONDSTOTHEFREQUENCYFMOFTHEPEAKIN%Q /PPOSEDTOTHISHIGHLYSIMPLIFIEDFORMAREINCREASINGLYCOMPLEXSPECTRABASEDONMORE CAREFULEMPIRICALSTUDIESASWELLASMORESOPHISTICATEDTHEORETICALCONSIDERATIONS )NDISCUSSINGTHECHARACTERIZATIONOFTHESEASURFACEBYITSSPECTRUM ITMUSTBEKEPT INMINDTHATTHESPECTRUMISAHIGHLYAVERAGEDDESCRIPTIONOFHOWTHEENERGYOFTHESUR FACEISDISTRIBUTEDAMONGTHEWAVENUMBERS ORFREQUENCIES OFTHEWAVESPRESENTONIT
3%!#,544%2
£x°x
&)'52% 3EAWAVEFREQUENCYSPECTRAOFTHE0IERSON -OSKOWITZ TYPE REPRESENTING FULLY DEVELOPED SEAS AFTER 7 * 0IERSON AND ,-OSKOWITZÚ!MERICAN'EOPHYSICAL5NION
3INCETHEPHASESOFTHESEWAVESARELOST THESPECTRUMGIVESNOINFORMATIONABOUTTHE DETAILEDMORPHOLOGYOFTHESURFACEITSELF IE ABOUTTHECOMPLEXSURFACEFEATURESTHAT ARERESPONSIBLEFORTHESCATTEREDFIELD4HISPOINTWILLBERAISEDAGAINASWEGOALONG 'ENERAL3EA$ESCRIPTORS 4HESHAPEOFTHECURVESIN&IGUREINDICATESTHAT THESEAWAVESYSTEMISSHARPLYPEAKED SOITSHOULDBEPOSSIBLETOGETAROUGHIDEAOF THEBEHAVIOROFTHEMAJORWAVESONTHESURFACEBYTAKINGTHEVALUESOFPERIODF ANDWAVELENGTHO+ DEFINEDATTHESPECTRALPEAK4HESEVALUESAREASSIGNEDTOA WAVESATISFYINGTHEDISPERSIONRELATION%QANDHAVINGAPHASEVELOCITY# OF+ EQUALTOTHEWINDSPEED5"YUSING%Q THEPERIOD4`ANDWAVELENGTH,`THEREBY DEFINEDTAKETHEFORM
4` 5 ,` 5
WHERE5ISINMETERSPERSECOND&OREXAMPLE THELARGESTWAVESINAFULLYDEVELOPED SEAFORAKTMS WINDWILLHAVEAWAVELENGTHOFABOUTFTM WITHA PERIODOFS 4HESTATISTICALDISTRIBUTIONOFWAVEHEIGHTSONTHEOCEANSURFACEISQUITECLOSETO GAUSSIAN WITH A MEAN SQUARE HEIGHT THAT CAN BE OBTAINED BY INTEGRATING THE WAVE HEIGHTSPECTRUMOVERALLFREQUENCIESORWAVENUMBERS &ORSPECTRARESEMBLINGTHOSE IN&IGURE THERMSWAVEHEIGHTISGIVENAPPROXIMATELYBY
HRMS 5 M
£x°È
2!$!2(!.$"//+
4HERMSWAVEHEIGHTCONTAINSCONTRIBUTIONSFROMALLTHEWAVESONTHESURFACE BUT VERYOFTENITISTHEPEAK TO TROUGHHEIGHTFORTHEHIGHERWAVESTHATISOFMAJORINTEREST 4HISISCERTAINLYTHECASEFORASHIPINASEAWAYORINTHESHADOWINGOFTHESURFACEATLOW RADARGRAZINGANGLES4HESIGNIFICANTHEIGHT ORPEAK TO TROUGHHEIGHTOFTHEONE THIRD HIGHESTWAVES PROVIDESSUCHAMEASURE)TISDENOTEDBY(ANDISTAKENTOBEABOUT SIXTIMESTHESPECTRALRMSAMPLITUDESEE EG +INSMAN &IG &ORA KTWIND THISISONLYABOUTFT BUTFORGALE FORCEWINDSOFKT ITRISESTOALMOSTFT WHICH ISARATHERFORMIDABLESEA ,OOKINGATTHESEA ANOBSERVERMIGHTDESCRIBEWHATISSEENINTERMSOFASUBJECTIVE STATEOFTHESEA EG hSMOOTH vhROUGH vORhTERRIFYINGv)FTHESEDESCRIPTIONSARELISTED INORDEROFSEVERITYANDASSIGNEDNUMBERS THESENUMBERSDEFINEASEASTATE!SIMILAR NUMERICALSCALEEXISTSFORWINDSPEEDS THE"EAUFORTWINDSCALE WITHNUMBERSABOUT ANINTEGERHIGHERTHANTHECORRESPONDINGSEASTATE"UTITISSELDOMUSEDINREFERENCE TOSEACLUTTER 4HEREARE THEN TWONUMBERSCOMMONLYUSEDTOINDICATETHEACTIVITYOFTHESEA SURFACEASUBJECTIVESEASTATEANDAMEASUREDWINDSPEED/NLYWHENTHEWINDHAS SUFFICIENTFETCHANDDURATIONTOEXCITEAFULLYDEVELOPEDSEA CANAWAVEHEIGHTBEUNAM BIGUOUSLYASSOCIATEDWITHIT4HESURFACEDESCRIPTORSGENERALLYUSEDINCONNECTIONWITH SEA CLUTTERSEA STATE WIND SPEED AND ITS ASSOCIATED EQUILIBRIUM WAVEHEIGHTARE GIVENIN4ABLE WITHTHEWINDSPEEDINKNOTS THESIGNIFICANTWAVEHEIGHTINFEET ANDTHEDURATIONFETCHREQUIREDFORAFULLYDEVELOPEDSEAINHOURSNAUTICALMILE)TIS OFINTERESTTONOTETHATTHEMEDIANWINDSPEEDOVERTHEWORLDSOCEANSISABOUTKT CORRESPONDINGTOSEASTATE "REAKING7AVESAND/THER3URFACE$ISTURBANCES 4HEOBSERVABLEFEATURESOF THESEASURFACETHATBESTSUGGESTANORIGINFORTHESHARPLOCALIZEDRADARRETURNSCALLEDSEA SPIKESARESURFACEEVENTSTHATARETHEMSELVESSHARPLYLOCALIZED EVENTSINCLUDINGBREAK INGWAVESOFALLSIZES INDUCEDEITHERBYTHEWINDORBYNONLINEARINTERACTIONSAMONG WAVE SYSTEMS ,ARGE SCALE BREAKING WAVES DISPLAY TWO CHARACTERISTIC BEHAVIORS SPILLING INWHICHANUNSTABLEWAVEPEAKUNRAVELS ANDPLUNGING WHERETHEPEAKCURLS OVERONITSELFANDCRASHESONTOTHEFRONTFACEASACASCADEOFWATERMASSES ENDINGINA CHAOTICJUMBLE!NOTHERDIFFERENTEVENTISTHEMICROBREAKER ASMALL TRANSIENTSHOCK FRONTINDUCEDBYAPUFFOFWINDORANOTHERWAVE!SNOTEDEARLIER HIGHLYAVERAGEDWAVE SPECTRA CANNOT DISCLOSE THE MORPHOLOGY OF SUCH SURFACE FEATURES AND UNFORTUNATELY PHYSICALOCEANOGRAPHYISSTILLUNABLETOPROVIDEAGENERALLYSATISFACTORYDESCRIPTIONOR CHARACTERIZATIONOFWAVEBREAKING.EVERTHELESS THEREARETWOUSEFULHEURISTICPARAM ETERSRELATINGELEMENTSOFABREAKINGWAVESCENETOWINDSPEED7HITECAPDENSITYISA VISIBLETRACEROFBREAKINGWAVEACTIVITYANDHASAPOWER LAWDEPENDENCEONWINDSPEED 4!",% 3EA 3URFACE$ESCRIPTORS
3EA3TATE SMOOTH SLIGHT MODERATE ROUGH VERYROUGH HIGH VERYHIGH
7IND3PEED KT
7AVEHEIGHT( FT
$URATIONFETCH HNMI
n n n n n n
n n n n n n
3%!#,544%2
£x°Ç
GIVENBYQWB^54HEAVERAGELENGTHOFABREAKINGWAVEFRONTMOVINGATSPEEDCALSO DEPENDSONWINDSPEEDANDISGIVENBYAPARAMETER,C 4HESEPARAMETERSWILLAPPEAR AGAINLATERWHENWEDISCUSSSOMEOFTHEMORERECENTMODELSFORSEACLUTTER!NADDITIONAL FEATUREOFSMALL SCALEBREAKING OROTHERSTRONGLYNONLINEAREVENTS ISTHEAPPEARANCEOF hPARASITICvORhBOUNDvCAPILLARIESATTACHEDTOTHEEVENTANDMOVINGWITHIT 4HEYTEND TOBESMALL AMPLITUDEFEATURES LOCALIZEDANDNARROW BAND
£x°ÎÊ *, Ê 6",Ê"Ê- Ê 1// , 3EACLUTTERISAFUNCTIONOFMANYPARAMETERS SOMEOFTHEMSHOWINGACOMPLICATED INTERDEPENDENCE SO WE EMPHASIZE AGAIN THAT IT IS NOT AN EASY TASK TO ESTABLISH ITS DETAILED BEHAVIOR WITH A GREAT DEAL OF CONFIDENCE OR PRECISION &OR EXAMPLE IN A PROPERSEACLUTTERMEASUREMENT THEPOLARIZATION RADARFREQUENCY GRAZINGANGLE AND RESOLUTIONCELLSIZEWILLHAVEBEENSPECIFIED4HENTHEWINDSPEEDANDDIRECTIONMUST BEMEASUREDATAREFERENCEALTITUDE ANDIFTHERESULTSARETOBECOMPAREDWITHTHOSE OFOTHEREXPERIMENTERS THEPROPERDURATIONANDFETCHSHOULDBEAVAILABLETOENSURE STANDARDIZATIONTOEQUILIBRIUMSEACONDITIONS3INCETHESEMEASUREDWINDSARERELATED TOTHEWINDSTRUCTUREATTHESURFACETHROUGHTHEATMOSPHERICBOUNDARYLAYER THESHAPE OFTHISLAYERMUSTBEDETERMINEDBYMEASURINGTHEAIRANDSEATEMPERATURES4OCOM PLICATETHEPICTURESTILLFURTHER ITHASBEENFOUNDTHATSEACLUTTERCANBEDEPENDENTON THEDIRECTIONOFTHELONGWAVES WHICHINCLUDESSWELLINTHEMEASUREMENTAREA SO IDEALLYTHEDIRECTIONALWAVESPECTRUMSHOULDBEMEASUREDASWELL/BVIOUSLY ITIS UNLIKELYTHATALLOFTHESEENVIRONMENTALPARAMETERSWILLBERECORDEDWITHPRECISIONIN EVERYOREVENANY SEACLUTTERMEASUREMENTSOCONSIDERABLEVARIABILITYINTHEBASIC CONDITIONSUNDERWHICHSEACLUTTERDATAARECOLLECTEDBYDIFFERENTEXPERIMENTERSCAN BEEXPECTED)TISOFINTERESTTONOTETHATINMANYOFTHEREPORTEDMEASUREMENTSOFSEA CLUTTER PARTICULARLYINTHEOLDERLITERATURE WIDEINCONSISTENCIESBETWEENWINDSPEED ANDWAVEHEIGHTMAYBEFOUND&OREXAMPLE AWINDSPEEDOFKTMIGHTBEREPORTED WITH WAVEHEIGHTS OF FT OR KT WINDS WITH FT WAVES 4HESE PAIRINGS ARE NOT CONSISTENTWITHTHEVALUESFORANEQUILIBRIUMSEADESCRIBEDIN4ABLEANDINDICATE THEUNNOTICEDORUNRECORDEDPRESENCEOFHEAVYSWELLORHIGHLYNONEQUILIBRIUMWIND CONDITIONSORBOTH%VENWITHALLTHEVARIABLESPROPERLYSPECIFIED RECORDEDCLUTTER DATACANBESPREADOVERAWIDEDYNAMICRANGE ESPECIALLYATLOWGRAZINGANGLES 3INCESEACLUTTERISGENERALLYVIEWEDASASURFACE DISTRIBUTEDPROCESS THEBASICCLUTTER PARAMETERISTAKENTOBETHENORMALIZEDRADARCROSSSECTION.2#3 R OFTHESURFACE COMMONLYREFERREDTOASSIGMAZEROANDEXPRESSEDINDECIBELSRELATIVETOMM)TIS OBTAINEDEXPERIMENTALLYBYDIVIDINGTHEMEASUREDRADARCROSSSECTIONOFANILLUMINATED PATCHOFTHESURFACEBYANORMALIZINGAREA SODIFFERENCESINTHEDEFINITIONOFTHISAREA CANLEADTOINCONSISTENCIESAMONGVARIOUSREPORTSOF.2#3MEASUREMENTS3CATTERING FROMANYDISTRIBUTEDTARGETINVOLVESTHEPRODUCTOFTHETRANSMITTINGANDRECEIVINGSYS TEMFOOTPRINTSINTEGRATEDOVERTHETARGET4HESEFOOTPRINTSCOVEREXACTLYTHESAMEAREA FORAMONOSTATICRADARANDWILLDEPENDONTHEPULSE ANDBEAMWIDTHS THERANGE AND THEGRAZINGANGLE)FTHEFOOTPRINTSAREASSUMEDTOBEOFTHECOOKIE CUTTERTYPECONSTANT AMPLITUDEFALLINGSHARPLYTOZEROATTHEHALF POWERPOINTS THENTHERELATIONBETWEENTHE ACTUALRADARCLUTTERCROSSSECTIONRC ASINFERREDFROMTHERECEIVEDPOWERVIATHERADAR EQUATION ANDTHE.2#3RISGIVENBY
R RC!F
£x°n
2!$!2(!.$"//+
WHERE FOR A RADAR WITH AN ANTENNA BEAMWIDTH " AND RECTANGULAR PULSE OF LENGTH S VIEWINGTHESURFACEATRANGE2ANDGRAZINGANGLEX THEAREA!FISEITHER
!F O"2 SINX
FORBEAM LIMITEDCONDITIONSEG CONTINUOUS WAVE#7 ORLONG PULSERADARATHIGH GRAZINGANGLES OR
!F CS "2COSX
FORPULSE WIDTH LIMITEDCONDITIONSEG SHORT PULSERADARATLOWGRAZINGANGLES 2EALRADARSDONOTPRODUCECOOKIE CUTTERFOOTPRINTS HOWEVER SINCETHEANTENNA BEAMWILLHAVEACOMPLEXPROFILEANDTHEPULSEMIGHTBESHAPED&ORTHISREASON ANEFFECTIVE!MUSTBEOBTAINEDFROMASURFACEINTEGRATIONOFTHEACTUALAMPLITUDE PROFILEOFTHEFOOTPRINT WHICHWILLTENDTORESULTINASMALLERVALUEOF!THANTHAT DEFINEDBY%QOR%Q4HISWILLPRODUCELARGERVALUESOFRASDERIVED FROM MEASURED VALUES OF RC BY %Q -OST EXPERIMENTERS USE THE HALF POWER BEAMWIDTHIN%Q OR%Q WITHANERRORTHATISUSUALLYONLYORD" #LUTTER3TATISTICS 3UMMARIESOFCLUTTERMEASUREMENTSMADEBEFOREABOUT MAYBEFOUNDINSEVERALOFTHESTANDARDREFERENCEBOOKSONRADAR ANDRADARCLUTTER !MONG THE PROGRAMS OF THIS PERIOD THE MOST AMBITIOUS WAS THAT PURSUED IN THE LATE S AT THE .AVAL 2ESEARCH ,ABORATORY .2, IN WHICH AN AIRBORNE FOUR FREQUENCYRADAR&2 OPERATINGWITHBOTHHORIZONTALANDVERTICALPOLARIZATIONSAT 5(&-(Z ,BAND-(Z #BAND-(Z AND8BAND-(Z MADECLUTTERMEASUREMENTSUPWIND DOWNWIND ANDCROSSWINDINWINDSFROMTO KTFORGRAZINGANGLESBETWEENAND4HESYSTEMWASCALIBRATEDAGAINSTSTAN DARD METAL SPHERES DROPPED FROM AIRCRAFT AND WIND SPEEDS AND WAVEHEIGHTS WERE RECORDEDINTHEMEASUREMENTAREASFROMSHIPINSTRUMENTS 4YPICALLY SAMPLESOFRFORAGIVENSETOFRADARANDENVIRONMENTALPARAMETERSARE SCATTEREDOVERAWIDERANGEOFVALUESANDINTHE.2,MEASUREMENTSWEREORGANIZED INTOPROBABILITYDISTRIBUTIONSOFTHETYPESHOWNIN&IGURE4HEDATA REPRESENTED BYTHESOLIDLINE AREPLOTTEDONNORMALPROBABILITYPAPERWITH2AYLEIGHANDLOG NORMAL DISTRIBUTIONSSHOWNFORCOMPARISONDASHEDLINES 4HEORDINATEISTHEPERCENTOFTIME FORWHICHTHEABSCISSAISEXCEEDED ANDTHEABSCISSAISTHEVALUEOFRASDEFINEDBY %Q WITH!TAKENFROM%QOR%QASAPPROPRIATE4HISPARTICULARDISTRI BUTIONISREPRESENTATIVEOFCLUTTERFROMARELATIVELYLARGERADARFOOTPRINTPULSELENGTH ABOUTLSECORMETERS MEASUREDATINTERMEDIATEGRAZINGANGLESTO FOR MODERATEWINDSPEEDSABOUTKT )TIS2AYLEIGH LIKEBUTSHOWSATENDENCYTOWARD LOG NORMALBEHAVIORFORTHELARGERCROSSSECTIONS&ROMADETAILEDSTATISTICALANALYSIS OFTHE.2,&2DATA 6ALENZUELAAND,AINGCONCLUDEDTHAT FORTHISDATAATLEAST THE DISTRIBUTIONSOFSEACLUTTERCROSSSECTIONSWEREINTERMEDIATEBETWEENTHE2AYLEIGHAND LOG NORMALDISTRIBUTIONS /RGANIZINGTHEDATASAMPLESINTOPROBABILITYDISTRIBUTIONSMAKESTHEMEDIAN VALUEACONVENIENTSTATISTICALMEASUREOFTHECLUTTERCROSSSECTION"UTMANYINVES TIGATORS PROCESS THEIR DATA TO PROVIDE THE MEAN VALUE AND BECAUSE THE CONVERSION OFAMEDIANTOAMEANREQUIRESKNOWLEDGEOFTHEPROBABILITYDISTRIBUTIONFUNCTION CAREMUSTBETAKENTOAVOIDAMBIGUITYINCOMPARINGTHEMEASUREMENTSOFDIFFERENT EXPERIMENTERS 4HE ORIGINAL ANALYSIS OF THE .2, &2 DATA WAS BASED ON MEDIAN CROSSSECTIONSANDTHEASSUMPTIONSOFTHECOOKIE CUTTERANTENNABEAMEMBODIEDIN %QSANDn)NLATERPRESENTATIONSOFTHISDATA THEMEDIANVALUESOFR
3%!#,544%2
£x°
&)'52% !N EXAMPLE OF THE PROBABILITY DISTRIBUTION OF SEA CLUTTERDATAFROM*#$ALEYETAL
WEREREPLACEDBYMEANS RAISINGTHEMBYABOUTD" ANDTHEAREA!IN%Q WASREDEFINEDINTERMSOFAMOREREALISTICTAPEREDFOOTPRINT ADDINGANOTHERTOD" 4HISMEANSTHATTHERECANBEADIFFERENCEOFTOD"BETWEENTHEEARLIERANDLATER PRESENTATIONSOFTHESAMEDATA ANDSINCETHESERESULTSHAVEBEENWIDELYUSEDAND QUOTED ITISIMPORTANTTOENSURETHATTHEPROPERDEFINITIONOFRISBEINGUSEDWHEN COMPARINGTHEMWITHCLUTTERDATATHATHASBEENTAKENBYOTHEREXPERIMENTERSORIN
USINGTHESERESULTSINCLUTTERPREDICTIONS &IGURESHOWSTHATEVENFORINTERMEDIATEGRAZINGANGLESINTHERANGEn THESEACLUTTERDISTRIBUTIONDEPARTSFROMSTRICTLY2AYLEIGH!TLOWERGRAZINGANGLES AND PARTICULARLYFORNARROWPULSEWIDTHS THEPRESENCEOFSEASPIKESOROTHERNON GAUSSIAN BEHAVIORMAYBEACCOMMODATEDBYONEOFTHEMULTIPARAMETERORCOMPOUNDDISTRIBU TIONSTHATEXPRESSANEXCESSOFHIGHERRETURNS SUCHASTHE7EIBULLAND+ DISTRIBUTIONS 4HELATTERWASINTRODUCEDTOCHARACTERIZETHEPARTICULARBEHAVIOROFLOW GRAZING ANGLE CLUTTERSEENINAMARINEENVIRONMENT)TSSUCCESSISVERYLIKELYDUETOITSRELATIONTO THE 2ICE DISTRIBUTION WHICH DESCRIBES THE STATISTICS OF STEADY SIGNALS IN NOISE THUS REFLECTINGTHESTATISTICSOFhTARGET LIKEvSEASPIKERETURNSINA2AYLEIGHBACKGROUND
£x°£ä
2!$!2(!.$"//+
'ENERAL4RENDS "EINGTHEFIRSTREALLYCOMPREHENSIVECOLLECTIONOFCLUTTERDATA OVERAWIDERANGEOFRADARFREQUENCIES THE&2PROGRAMPRODUCEDMANYPLOTSSHOW ING THE DEPENDENCE OF SEA CLUTTER ON GRAZING ANGLE FREQUENCY POLARIZATION WIND DIRECTION ANDWINDSPEED(OWEVER COMPARISONOFTHESEPLOTSWITHOTHERSMADEBOTH EARLIERANDLATERSHOWSTHEEXTENTOFTHEVARIATIONSTOBEFOUNDINSEACLUTTERMEASURE MENTSREPORTEDBYDIFFERENTINVESTIGATORSFOREXACTLYTHESAMESETOFPARAMETERS4HIS ISSEENCLEARLYIN&IGUREAANDB WHICHCOMPARESTHEGRAZING ANGLEDEPENDENCE OF8 BANDCLUTTERDATAFORWINDSPEEDSINTHENEIGHBORHOODOFKTOBTAINEDFROM FOURSOURCES.2,&2THESEAREMEANRESULTSFORUPWINDDIRECTIONSANDINCLUDE THEANTENNACORRECTIONSMENTIONEDABOVE AIRCRAFTMEASUREMENTSBY-ASUKOETAL ALSOINTHEUPWINDDIRECTION AND SUMMARIES OF DATA TAKEN FROM BOOKS ON RADAR SYSTEMSBY3KOLNIKAND.ATHANSON4HEDISCREPANCIESBETWEENTHEDIFFERENTDATA SETSCANBEACCOUNTEDFOR ATLEASTINPART ASFOLLOWS4HEOLDERDATASUMMARIESWERE BASEDONPUBLISHEDMEASUREMENTSFROMVARIOUSSOURCESINWHICHTHEREISNOSPECI FICATIONOFWINDDIRECTION)TMAY THEREFORE BEASSUMEDTHATTHESEDATAREPRESENT SOMEKINDOFAVERAGEOFUPWIND DOWNWIND ANDCROSSWINDDIRECTIONS!SWILLBE SEEN THISAVERAGEISABOUTTOD"SMALLERTHANTHEUPWINDRETURNS-OREOVER THE EARLY.2,&2DATAWASUSEDLIBERALLYINTHEOLDERDATASUMMARIES ANDITWASNOTED ABOVETHATTHEREISADIFFERENCEOFTOD"BETWEENTHEEARLYANDLATERPRESENTATIONS OFTHESAME.2,&2DATA THELATTERBEINGUSEDIN&IGUREAANDB7ITHTHESE CORRECTIONS THECURVESMIGHTSHOWCLOSERAGREEMENT.EVERTHELESS ITISCLEARTHAT UNCRITICALUSEOFPUBLISHEDCLUTTERDATACOULDLEADRADARSYSTEMSDESIGNERSTOCHOOSE SEACLUTTERESTIMATESMANYD"APARTFORTHESAMECONDITIONS 4HE.2,&2DATASETISUNIQUEINTHATNOOTHERPROGRAMHASREPORTEDMEASURE MENTSMADEOVERSOWIDEARANGEOFFREQUENCIES GRAZINGANGLES ANDWINDSPEEDSATTHE SAMETIME&IGURESHOWSTHETRENDSFORBOTHVERTICALLYANDHORIZONTALLYPOLARIZED
&)'52% #OMPARISONOF8 BANDCLUTTERDATAFROMDIFFERENTSOURCESFORANOMINALWINDSPEEDOF KNA VERTICALPOLARIZATIONANDB HORIZONTALPOLARIZATIONBASEDONDATAFROM(-ASUKOETAL .2,&2 -)3KOLNIK AND&%.ATHANSON
3%!#,544%2
£x°££
SEACLUTTEROVERARANGEOFGRAZINGANGLESDOWNTOn4HECURVESREPRESENTTHECENTERS OFoD"BANDSTHATCONTAINTHEMAJORRETURNSFORTHETHREEHIGHERFREQUENCIES, # AND8BANDSTHE5(&RETURNSWEREAFEWDECIBELSLOWER ANDWINDSPEEDSABOVE ABOUTKT4HEMAJORDIFFERENCESINSEACLUTTERFORTHETWOPOLARIZATIONSARESEENTO LIEINTHERANGEOFGRAZINGANGLESBETWEENABOUTnANDn WHERETHEHORIZONTALLY POLARIZEDRETURNSARESMALLER4HISDIFFERENCEISFOUNDTOBEEMPHASIZEDATBOTHLOWER WINDSPEEDSANDLOWERFREQUENCIES4HECROSSSECTIONSAPPROACHEACHOTHERATHIGH ANGLES n AND FORTHEHIGHERMICROWAVEFREQUENCIES ATLOWANGLES n ASWELL )NFACT FORGRAZINGANGLESLESSTHANAFEWDEGREESANDMODERATETOSTRONGWINDSPEEDS OBSERVERSHAVEREPORTEDTHATAT8BANDANDATTHEHIGHERSEASTATESTHEHORIZONTALLY POLARIZEDRETURNSCANEXCEEDTHEVERTICALLYPOLARIZEDRETURNS 4HE.2,&2SYSTEMPERMITTEDTRANSMISSIONANDRECEPTIONONORTHOGONALPOLAR IZATIONSSOTHATDATACOULDBECOLLECTEDFORCROSS POLARIZEDSEACLUTTER4HESERETURNS TENDEDTOHAVEAWEAKDEPENDENCEONGRAZINGANGLEANDWEREALWAYSSMALLERTHAN EITHER OF THE LIKE POLARIZED RETURNS LYING IN THE CROSS HATCHED REGION SHOWN ON &IGURE )T IS INFORMATIVE TO COMPARE MEASUREMENTS AT DIFFERENT FREQUENCIES BY DIFFERENT INVESTIGATORSINDIFFERENTPARTSOFTHEWORLDUNDERSIMILARWINDCONDITIONS&IGURE DISPLAYSMEASUREMENTSOFVERTICALLYPOLARIZEDSEACLUTTERDOWNTOAGRAZINGANGLEOF FORWINDSPEEDSOFABOUTKTFROMTHREEINDEPENDENTEXPERIMENTSUSINGAIRBORNE RADARSAT# 8 AND+ BANDFREQUENCIES !LTHOUGHTHEREISNOASSURANCETHAT
&)'52% 'ENERAL TRENDS IN CLUTTER BEHAVIOR FOR AVERAGE WINDSPEEDSABOUTKT BASEDON.2,&2DATA0LOTSREPRESENT , # AND8 BANDDATAWITHINoD"
£x°£Ó
2!$!2(!.$"//+
&)'52% &REQUENCY DEPENDENCE OF SEA CLUTTER FOR WIND SPEEDSOFABOUTKT'(Z &EINDT'(Z 3CHROEDER AND'(Z -ASUKO
ALLTHESEMEASUREMENTSWEREMADEOVERFULLYDEVELOPEDSEAS ITISCLEARTHATTHEREIS A RATHER STRONG CONSISTENCY AMONG THEM WHICH REINFORCES THE OBSERVATION MADE IN REFERENCETO&IGURETHATTHEFREQUENCYDEPENDENCEOFSEACLUTTERATINTERMEDIATE GRAZINGANGLESISWEAKATMICROWAVEFREQUENCIESFROM,TO+BAND $EPENDENCE ON 7IND 3PEED AND $IRECTION %XPERIMENTALLY THE RELATION BETWEENSEACLUTTERANDWINDSPEEDISCOMPLEXANDUNCERTAIN ITHAVINGBEENFOUND TO DEPEND ON ALMOST ALL OF THE PARAMETERS THAT CHARACTERIZE SEA CLUTTER FREQUENCY GRAZINGANGLE POLARIZATION THESTATEOFTHESEASURFACE THEDIRECTIONANDSPEEDOF THEWINDITSELF ANDEVENONWHETHERTHEMEASUREMENTSAREMADEFROMANAIRCRAFTOR ATOWERPLATFORM !COMMONWAYTOORGANIZECLUTTERDATAISTOSEEKTHEBESTSTRAIGHT LINEFITLINEAR REGRESSION BETWEENCLUTTERCROSSSECTIONSINDECIBELSANDTHELOGOFTHEWINDSPEED ORSOMEOTHERPARAMETER 4HIS OFCOURSE IMPOSESAPOWER LAWRELATIONBETWEEN THEVARIABLESR^5N WHERENISDETERMINEDBYTHESLOPEOFTHELINE!NEXAMPLEIS SHOWNIN&IGURE/NTHEOTHERHAND WHILETHETOTALITYOFTHE.2,&2RESULTS APPEAREDTOSHOWSATURATIONFORWINDSPEEDSABOVEABOUTKT THEHIGHANDLOW TO MODERATEWIND SPEEDDATAWERECOLLECTEDATDIFFERENTTIMESINDIFFERENTPLACESUNDER DIFFERENTCONDITIONSOFSEA SURFACEDEVELOPMENT ANDDISCREPANCIESBETWEENTHETWO DATA SETS FOR COMMON WIND SPEEDS HAVE WEAKENED THE EVIDENCE FOR SATURATION /THERINVESTIGATORSDENYTHATITISEVENPOSSIBLETOEXPRESSWINDDEPENDENCEINTHE FORM OF A POWER LAW PROPOSING THE EXISTENCE OF A KIND OF THRESHOLD WIND SPEED BELOWWHICHCLUTTERVIRTUALLYVANISHESANDABOVEWHICHTHECLUTTERLEVELRISESRAPIDLY TOWARDASATURATIONVALUE4HISISINDICATEDBYTHECURVESIN&IGURE WHERE THESTRAIGHTLINESCORRESPONDTOVARIOUSPOWERLAWSANDTHECURVEDLINESDERIVEFROM
3%!#,544%2
£x°£Î
&)'52% 3EA CLUTTER FROM A TOWER PLATFORM WITH POWER LAW WIND SPEED DEPENDENCE DEFINED BY LINEAR REGRESSION ANGLE OF INCIDENCE GRAZINGANGLE AFTER!(#HAUDHRYAND2+-OORE Ú)%%%
WAVESPECTRUMCONSIDERATIONS)TISPOSSIBLETOFINDEXAMPLESOFDATATHATAPPEAR TOFOLLOWSUCHBEHAVIORWHILEATTHESAMETIMEBEINGEXPRESSEDASAPOWERLAWBY BRUTELINEARREGRESSION ASILLUSTRATEDINTHETOWERDATASHOWNIN&IGURE4HIS BEHAVIORISNOTUNCOMMON
&)'52% ! HYPOTHETICAL WIND SPEED DEPENDENCE OF SEA CLUTTER CURVED TRACES COMPARED WITH VARIOUS POWER LAWS STRAIGHT LINES DERIVEDFROM7*0IERSONAND-!$ONELANÚ!MERICAN 'EOPHYSICAL5NION
£x°£{
2!$!2(!.$"//+
&)'52% %XAMPLEOFFORCINGAPOWER LAWFITCOMPAREDATAPOINTSWITH THOSEIN&IGURE AFTER!(#HAUDHRYAND2+-OOREÚ)%%%
.EVERTHELESS THEIMPOSITIONOFAPOWER LAWRELATIONPROVIDESACONVENIENTWAY TOVISUALIZETRENDSINTHEBEHAVIOROFSEACLUTTERWITHWINDSPEED4HEVARIOUSAIR CRAFTMEASUREMENTSREFERREDTOABOVE AUGMENTEDBYDATAFROMATOWERINTHE .ORTH3EA WEREUSEDASTHEBASISOFTHEPOWER LAWPLOTSOFRASFUNCTIONSOF WINDSPEEDANDGRAZINGANGLESHOWNIN&IGUREA B4HESEPLOTSSUGGESTHOWSEA CLUTTER FOR A GIVEN FREQUENCY 8 BAND WIND DIRECTION UPWIND AND POLARIZATION BEHAVESWITHWINDSPEEDANDGRAZINGANGLE(OWEVER EXAMINATIONOFTHEACTUALDATA POINTSUNDERLYINGTHESELINEARREGRESSIONSSHOWPOINTSCATTERTHATSOMETIMESRESEM BLES &IGURE SOMETIMES &IGURE AND SOMETIMES NEITHER SO THESE STRAIGHT LINES COVER UP CONSIDERABLE UNCERTAINTY )N FACT IT APPEARS THAT THERE IS NO SIMPLE FUNCTIONALDEPENDENCEOFSEACLUTTERONWINDSPEEDTHATCANBEESTABLISHEDWITHANY CONFIDENCE FROM EXISTING DATA ALTHOUGH MOST INVESTIGATORS WOULD PROBABLY AGREE THATTHEBEHAVIOROFMICROWAVESEACLUTTERWITHWINDSPEEDATINTERMEDIATEGRAZING ANGLESCANBEROUGHLYDESCRIBEDASFOLLOWSFORLIGHTWINDSLESSTHANTOKT SEA CLUTTERISWEAK VARIABLE ANDILLDEFINEDFORINTERMEDIATEWINDSABOUTTOKT ITCANBEDESCRIBEDROUGHLYBYAPOWERLAWOFTHETYPEFOUNDIN&IGUREANDFOR STRONGWINDSABOVEABOUTKT THEREISATENDENCYFORITTOLEVELOFF)NFACT THE CONVERGENCEOFTHELINESIN&IGUREA BWITHINCREASINGWINDSPEEDSUGGESTSTHAT THEREFLECTIVITYOFTHESEASURFACEISTENDINGTOWARD,AMBERTSLAW FORWHICHTHERE IS NO DEPENDENCE ON GRAZING ANGLE FREQUENCY OR POLARIZATION BUT ONLY ON SURFACE ALBEDO ORAVERAGEREFLECTIVITY )NSEVERALOFTHEEXPERIMENTSREFERENCEDABOVE THEDEPENDENCEOFSEABACKSCATTER ONANGLERELATIVETOTHEWINDDIRECTIONWASFOUNDBYRECORDINGTHERADARRETURNFROMA SPOTONTHESURFACEWHILEFLYINGAROUNDITINACIRCLE&IGUREA BGIVESANEXAMPLE OFTHISBEHAVIORFORGRAZINGANGLESOFABOUTANDWINDSPEEDSCLOSETOKT4HE FIGURESCONTAINRESULTSOBTAINEDINDEPENDENTLYBYTHREEDIFFERENTGROUPS4HEBEHAVIOR SHOWNHEREISREPRESENTATIVEOFTHATFOUNDGENERALLYSEACLUTTERISSTRONGESTVIEWED UPWIND WEAKESTVIEWEDCROSSWIND ANDOFINTERMEDIATESTRENGTHVIEWEDDOWNWIND THETOTALVARIATIONBEINGABOUTD"/THERSTUDIESCORROBORATETHISBEHAVIOR
3%!#,544%2
£x°£x
&)'52% !REPRESENTATIONOF8BAND UPWINDCLUTTERBEHAVIORWITHWINDSPEEDANDGRAZINGANGLE A VERTICALPOLARIZATIONANDB HORIZONTALPOLARIZATION
&)'52% $EPENDENCE OF CLUTTER ON WIND DIRECTION NOMINAL WIND SPEED KT GRAZING ANGLE ABOUT UPWIND AND DOWNWIND AFTER ( -ASUKO ET AL Ú!MERICAN 'EOPHYSICAL 5NION
£x°£È
2!$!2(!.$"//+
3EA#LUTTERAT(IGH'RAZING!NGLES 4HETOPLINESIN&IGUREA BCORRE SPONDTOCLUTTERATAGRAZINGANGLEOF THATIS FORARADARLOOKINGSTRAIGHTDOWN /N A STRICTLY EMPIRICAL BASIS THE CLUTTER CROSS SECTION AT THIS ANGLE IS ONLY WEAKLY DEPENDENT ON FREQUENCY HAS A MAXIMUM OF ABOUT D" AT ZERO WIND SPEED AT LEASTFORTHEANTENNABEAMWIDTHSANDEXPERIMENTALCONFIGURATIONSREPORTED ANDFALLS OFFGRADUALLYASTHEWINDPICKSUP3CATTERINGATHIGHGRAZINGANGLESISCOMMONLY REGARDEDASAFORMOFSPECULARSCATTERINGFROMTILTEDFACETSOFTHESURFACE SOITISOF INTERESTTONOTETHATTHEREAPPEARSTOBEASMALLRANGEOFANGLESINTHENEIGHBORHOOD OF FORWHICHTHECROSSSECTIONISALMOSTCOMPLETELYINDEPENDENTOFWINDSPEED 3INCETHESEANGLESCORRESPONDTOCOMPLEMENTSOFTHECOMMONRMSSEASLOPEANGLES OFABOUT ITMIGHTBEARGUEDTHATASTHEWINDINCREASES THECLUTTERDECREASEDUE TOINCREASINGSURFACEROUGHNESSISBALANCEDBYACLUTTERINCREASEDUETOANINCREASING POPULATIONOFSCATTERINGFACETS4HISLINECOULD THEREFORE BEREGARDEDASTHEBOUND ARYSEPARATINGTHESPECULARREGIME WHERETHECROSSSECTIONISDECREASEDBYSURFACE ROUGHNESS FROM THE ROUGH SURFACE REGIME WHERE THE CROSS SECTION INCREASES WITH SURFACEROUGHNESS)TSHOULDFURTHERBENOTEDTHATCLUTTERMEASUREMENTSATTHESEHIGH GRAZINGANGLESWILLBERELATIVELYSENSITIVETOTHEAVERAGINGEFFECTSOFWIDEANTENNA BEAMWIDTHS WHICHCOULDBECOMEASOURCEOFAMBIGUITYINAIRCRAFTMEASUREMENTSAT THELOWERRADARFREQUENCIES !T,OW'RAZING!NGLES !TLOWGRAZINGANGLES BELOWMEANSEASLOPEANGLES OFABOUT SEACLUTTERTAKESONADIFFERENTCHARACTER4HESHARPTARGET LIKECLUTTER PEAKS KNOWN AS SEA SPIKES BEGIN TO APPEAR ON! SCOPE PRESENTATIONS AND THEPROBABILITYDISTRIBUTIONSASSUMEADIFFERENTFORM &IGUREAANDBSHOW THEPRESENCEOFSEASPIKESIN SECONDTIMEHISTORIESOFRETURNSFROMAFIXEDSPOT MEASUREDOFFTHECOASTOF&LORIDAWITHAVARIABLE RESOLUTION8 BANDRADARLOOKING INTOMODERATEA ANDCALMB SEASATAGRAZINGANGLE.OTICETHATTHEAPPEAR ANCEOFTHESEASPIKESISVERYSIMILARFORBOTHMODERATEANDWEAKWINDCONDITIONS ALTHOUGHTHEAMPLITUDESDIFFERBYALMOSTD" ANDTHEVERTICALLYPOLARIZEDRETURNS APPEARTOBESOMEWHATBROADER WHILETHEHORIZONTALLYPOLARIZEDRETURNSAREMORE SPIKY PARTICULARLYFORSHORTPULSESINCALMSEAS4HESEAREALLCHARACTERISTICSOFSEA CLUTTERATLOWGRAZINGANGLES 4HE PROBABILITY DISTRIBUTIONS OF LOW GRAZING ANGLE SEA CLUTTER CHANGE WITH WIND SPEED%XAMPLESMAYBEFOUNDINTHEMEASUREMENTSBY4RIZNAOFLOW ANGLESEACLUT TERUSINGHIGH RESOLUTION NS SHIPBOARDRADARINBOTHTHE!TLANTICANDTHE0ACIFIC OCEANS4HEPROBABILITYDISTRIBUTIONSOFTHECLUTTERCROSSSECTIONSWEREPLOTTEDINTHE MANNERSHOWNIN&IGURE WHICHSHOWSTHEDISTRIBUTIONSOFHORIZONTALLYPOLAR IZED8 BANDDATAATAGRAZINGANGLEFORLOW MEDIUM ANDHIGHWINDSPEEDSINORDER FROM LEFT TO RIGHT 4HE LOW WIND TRACE CORRESPONDS TO A 2AYLEIGH DISTRIBUTION THE OTHERSEGMENTEDTRACESARETWO PARAMETER7EIBULLDISTRIBUTIONSDEFINEDBYDIFFERENT PARAMETERPAIRS)TISCLEARTHATTHEBEHAVIORISDIFFERENTANDCONSIDERABLYMORECOM PLEXTHANTHATSHOWNIN&IGUREFORHIGHERGRAZINGANGLESANDWIDERPULSES&ROM THECHARACTEROFTHEDATA 4RIZNAINTERPRETSTHESETHREE SEGMENTTRACESASSHOWINGPRI MARILYRECEIVERNOISEINTHELOWESTBRANCH DISTRIBUTEDSPATIALLYHOMOGENEOUS CLUTTER IN THE MIDDLE BRANCH AND GENUINE SEA SPIKES IN THE BRANCH CONTAINING THE HIGHEST CROSSSECTIONS SOMEOFWHICHEXCEEDM&ORTHEHIGHERWINDSPEEDSANDFULLY DEVELOPEDSEASENCOUNTEREDINTHE.ORTH!TLANTIC THEPERCENTAGEOFSEASPIKESINTHIS POPULATIONWASFOUNDTOGROWASTHETHPOWEROFTHEWINDSPEED WHICH INTEREST INGLY ISTHESAMEWIND SPEEDDEPENDENCESHOWNBYTHEPERCENTAGEOFWHITECAPSSEEN ONTHESURFACE WHICH ASNOTEDIN3ECTION ARETRACERSFORBREAKINGWAVES
3%!#,544%2
£x°£Ç
&)'52% 3EASPIKESAT8BAND GRAZINGANGLE ANDVARIOUSPULSEWIDTHSA SEASTATEAND B SEASTATE.OTEEQUALAMPLITUDESATTHETWOPOLARIZATIONSANDAD"DIFFERENCEINCLUTTERSTRENGTH BETWEENMODERATEANDWEAKWINDSFROM*0(ANSENAND6&#AVALERI
&)'52% %XAMPLESOFCLUTTERPROBABILITYDISTRIBUTIONS ATLOWGRAZINGANGLESAFTER$4RIZNA
£x°£n
2!$!2(!.$"//+
)N COMPARING STATISTICAL RESULTS IT SHOULD BE KEPT IN MIND THAT TO THE EXTENT THAT THESEASURFACEMAYBEVIEWEDASASTATIONARYHOMOGENEOUSPROCESS ASITGENERALLY ISOVERTHEDURATIONANDSPATIALEXTENTOFANYPARTICULAREXPERIMENTALEVENT THESCAT TERINGCROSSSECTIONMAYBESAIDTOBEERGODIC WHICHMEANSTHATTHESTATISTICALRESULTS OBTAINEDBYTIMEAVERAGINGFROMASMALLCELLAREEQUIVALENTTOANENSEMBLEAVERAGE FROM A LARGER CELL PROVIDED THAT THE NUMBER OF hSAMPLESv IS THE SAME IN THE TWO CASES&ORTHISREASON THESTATISTICALIMPLICATIONSOFEXPERIMENTALDATACANBEPROP ERLYCOMPAREDONLYIFTHEDETAILSOFTHESAMPLINGPROCEDUREARESPECIFIED(OWEVER THENUMBEROFSAMPLESINMOSTOFTHEEXPERIMENTALRESULTSSHOWNTHUSFARHAVEBEEN SUFFICIENTLYLARGETHATTHEDIFFERENCESBETWEEN FOREXAMPLE &IGURESAND MAYBECONSIDEREDREALANDRELATEDTODIFFERENCESINGRAZINGANGLERATHERTHANINRESO LUTIONCELLSIZE)NFACT DISTRIBUTIONSCLOSELYRESEMBLINGTHOSEIN&IGUREWERE OBTAINED MUCH EARLIER FROM SIMILAR MEASUREMENTS WITH CONSIDERABLY BROADER PULSE WIDTHS/THERMEASUREMENTSHAVECONTINUEDTOCONFIRMTHEDIFFERENCESTHATEMERGE IN! SCOPEAPPEARANCEANDSTATISTICALDESCRIPTIONOFTHECLUTTERINTHISREGIMEOFLOW GRAZINGANGLES 3OMEATTEMPTSTODESCRIBETHEPHYSICALORIGINOFTHESEPHENOMENA WILLBEDISCUSSEDIN3ECTIONBELOW !T6ERY,OW'RAZING!NGLES 4HEREISSOMEEVIDENCETHATSEACLUTTERMIGHT DROPOFFMORESHARPLYBELOWACRITICALANGLEINTHENEIGHBORHOODOFADEGREEORSO 4HISCRITICALANGLE ORCRITICALRANGEFORARADARATAFIXEDHEIGHT HASBEENOBSERVED FROMTIMETOTIMESINCEFIRSTNOTEDINEARLYOBSERVATIONSOFSEACLUTTER4HECRITICAL ANGLEHASBEENASCRIBEDTOINTERFERENCEBETWEENDIRECTANDPERFECTLY REFLECTEDRAYSAT THESCATTERINGTARGETSRESPONSIBLEFORTHECLUTTERSIGNAL ALTHOUGHTHESETARGETSREMAIN UNSPECIFIED!LTHOUGHTHISSIMPLEPICTURECOULDPRODUCETHE2nDECAYTHATISSOME TIMESOBSERVED ACRITICALANGLEOFTENFAILSTOMATERIALIZE ANDWHENITDOES ITNEED NOT SHOW AN 2n DECREASE WITH RANGE EQUIVALENT TO A FOURTH POWER DEPENDENCE ON GRAZINGANGLE !NALTERNATIVEEXPLANATIONFORTHISBEHAVIOR APPLICABLEATTHEHIGHER MICROWAVEFREQUENCIES HASBEENSUGGESTEDBASEDONATHRESHOLD SHADOWINGMODEL FORUPWINDANDDOWNWINDDIRECTIONS 4HISMODELIMPLIESASHARPDECREASEINTHE AVERAGECROSSSECTIONFORGRAZINGANGLESBELOWAFEWDEGREES)NCROSSWINDDIRECTIONS WITHTHERADARLOOKINGALONGTHETROUGHSOFTHEMAJORWAVES AMUCHMILDERSHADOW INGFUNCTIONWILLAPPLY SOTHERESHOULDBEACLEARDISTINCTIONBETWEENTHEUPWIND DOWNWINDANDCROSSWINDBEHAVIOROFSEACLUTTERATVERYLOWGRAZINGANGLES %XAMPLESOFCLUTTERBEHAVIORATTHESEVERYLOWANGLESMAYBEFOUNDININDEPENDENT MEASUREMENTSATRELATIVELYHIGHWINDSPEEDSBY(UNTERAND3ENIOROFFTHESOUTHCOAST OF%NGLANDANDBY3ITTROPOFFTHEWESTCOASTOF.ORWAY4HEIRRESULTSFORORTHOGONAL DIRECTIONSRELATIVETOTHEWINDARESHOWNIN&IGURE ALONGWITHTHEPREDICTIONSOF ACONVENTIONALSHADOWINGFUNCTIONANDTHETHRESHOLD SHADOWINGFUNCTION)TWOULD APPEARTHATACOMBINATIONOFCONVENTIONALSHADOWINGWHICHGOESASTHEFIRSTPOWER OFTHEGRAZINGANGLE ACROSSTHEWIND ANDTHRESHOLDSHADOWINGINUPWINDANDDOWN WINDDIRECTIONS CANACCOUNTFORTHEOBSERVEDBEHAVIOROFTHISVERYLOW ANGLECLUTTER QUITEWELL4HEDECAYLAWFORVERYLOW ANGLECLUTTERSHOULD THEREFORE DEPENDONTHE VIEWINGANGLERELATIVETOTHEWINDDIRECTION SOITMIGHTOCCURWITHPOWERSBETWEEN THEFIRSTANDTHEFOURTH4HISISJUSTWHATHASBEENOBSERVED)TSHOULDBEREMARKED HOWEVER THATSHADOWINGATLOWGRAZINGANGLESISACOMPLEXPHENOMENONSEEBELOW ANDTHEPHYSICALORIGINOREVENTHEEXISTENCEOFACRITICALANGLEISSTILLOPENTOQUES TION-OREOVER THEREISRELATIVELYLITTLEGOODDATAONVERYLOW ANGLECLUTTERFOROTHER THAN8 BANDFREQUENCIES SOTHEGENERALBEHAVIOROFSEACLUTTERINTHISANGULARREGIME REMAINSUNCERTAIN
3%!#,544%2
£x°£
&)'52% $IFFERENTIALBEHAVIOROFVERYLOW ANGLECLUTTERFORORTHOGONALWINDDIRECTIONS 3CISACONVENTIONALSHADOWINGFUNCTION34ISATHRESHOLD SHADOWINGFUNCTIONAFTERDATAFROM )-(UNTERAND3ENIORÚ)%%%AND(3ITTROP
!T(&AND-ILLIMETER 7AVE&REQUENCIES !LLTHEMEASUREMENTSDESCRIBED ABOVEWEREMADEATMICROWAVEFREQUENCIESBETWEEN5(&-(Z AND+ABAND '(Z (IGH FREQUENCY (& RADARS USUALLY OPERATE IN THE FREQUENCY RANGE BETWEENABOUTAND-(Z CORRESPONDINGTOWAVELENGTHSBETWEENANDM RESPECTIVELY 3INCE THE OPERATION OF SUCH RADARS TAKES PLACE EITHER BY THE GROUND WAVEOROVERIONOSPHERICSKY WAVE PATHSSPANNINGGREATRANGES THEGRAZINGANGLES TENDTOBESMALLBETWEENAND &ORTHESEWAVELENGTHSANDGRAZINGANGLES MEASUREMENTSBY#ROMBIEINDICATETHATTHESCATTERINGFROMTHESEASURFACEWASTHE RESULTOFSCATTERINGFROMSEAWAVESOFONE HALFTHERADARWAVELENGTH IE h"RAGGv SCATTER )N THE YEARS SINCE THESE EARLY MEASUREMENTS THERE HAS BEEN CONSIDERABLE ACTIVITY IN THE FIELD OF (& RADAR AND (& CLUTTER AND THE RESULTS CAN BE SUM MARIZED AS FOLLOWS &OR VERTICAL POLARIZATION THE MAJOR ENERGY OF THE (& CLUTTER SIGNALAPPEARSINSPECTRALLINESDISPLACEDTOEITHERSIDEOFTHECARRIERFREQUENCYBY THEFREQUENCYOFSEAWAVESHAVINGAWAVELENGTHEQUALTOHALFTHE(&WAVELENGTHK INMETERS 4HERELATIVESTRENGTHSOFTHEPLUSANDMINUSLINESAREDETERMINEDBYTHE PROPORTIONOFADVANCINGANDRECEDING"RAGG RESONANTWAVECOMPONENTSINTHECLUT TERCELL0ROVIDEDTHEWINDSPEEDISGREATERTHANABOUT L KTWITHKINMETERS AND THESEAISFULLYDEVELOPED THECLUTTERCROSSSECTIONRISABOUTnD"ANDISRELA TIVELYINDEPENDENTOFWINDSPEEDANDFREQUENCY4HEDEFINITIONOFRIN(&RADAR IS COMPLICATED BY PROBLEMS IN PROPERLY DEFINING ANTENNA GAINS FOR GROUND WAVE ANDSKY WAVEPATHSANDBYPROPAGATIONEFFECTSDUETOTHEIONOSPHERE 4HECLUTTER SPECTRUM TENDS TO FILL IN AROUND AND BETWEEN THE LINES AS THE WIND PICKS UP &OR HORIZONTALPOLARIZATIONWHICHISPOSSIBLEONLYFORSKY WAVEPATHSOVERWHICHTHE PLANEOFPOLARIZATIONCANBEROTATEDBYTHE%ARTHSMAGNETICFIELD THECROSSSECTION ISMUCHSMALLERANDSHOWSTHECHARACTERISTICFOURTH POWERDECAYWITHADECREASING GRAZINGANGLE&ORTHESE(&WAVELENGTHSOFTENSOFMETERS THESEAISRELATIVELYFLAT ANDTHESCATTERINGLAWSARESIMPLE!DETAILEDDISCUSSIONOF(&RADARMAYBEFOUND IN#HAPTER
£x°Óä
2!$!2(!.$"//+
!TTHEOTHERENDOFTHEPOTENTIALLYUSEFULRADARSPECTRUM INTHEMILLIMETER WAVE BAND THE FEW PUBLISHED MEASUREMENTS OF RADAR CLUTTER LEAD TO THE CONCLUSION THAT MILLIMETER WAVEBACKSCATTERBEHAVESINMUCHTHESAMEMANNERASBACKSCATTERATTHE LOWERMICROWAVEFREQUENCIES4HISWASSUGGESTEDBYTHE+ BANDCURVESSHOWNIN &IGUREFORMODERATEWINDSPEEDSANDFURTHERSUPPORTEDBYSOMEOLDERSHIPBOARD DATA AT FREQUENCIES BETWEEN AND '(Z )T SHOULD BE NOTED THAT FOR MARITIME RADARS CLUTTER SIGNAL PATHS LIE CLOSE TO THE SEA SURFACE WHERE THE ATMOSPHERIC AND WATER VAPOR DENSITIES ARE HIGHEST 4HIS MEANS THAT AT THESE HIGHER FREQUENCIES THE CLUTTERSIGNALWILLBESTRONGLYAFFECTEDBYATMOSPHERICABSORPTIONEFFECTS ANDCONSE QUENTLYTHESURFACE RELATEDCROSSSECTIONINFERREDFROMTHERECEIVEDSIGNALSTRENGTHIN ANYGIVENMEASUREMENTWILLDEPENDUPONTHEPATHLENGTH-OREOVER THEROLEOFSEA SPRAYINBOTHSCATTERINGANDABSORPTIONWILLCERTAINLYBEMOREIMPORTANTTHANATTHE LOWERMICROWAVEFREQUENCIES )TISDIFFICULTTOFINDCLUTTERDATAATFREQUENCIESABOVE+ABAND ALTHOUGH( AND 6 POLARIZED RETURNS AT '(Z AT A GRAZING ANGLE OF WERE REPORTED BOTH WITH VALUESCLOSETOnD" 4HE3PECTRUMOF3EA#LUTTER 4HESCATTERINGFEATURESPRODUCINGSEACLUTTERARE ASSOCIATEDWITHASURFACESUBJECTTOSEVERALTYPESOFMOTION4HEFEATURESTHEMSELVES MAYBEMOVINGWITHSMALLGROUPORPHASEVELOCITIESOVERTHISSURFACEWHILETHESURFACE ITSELFISMOVED INTURN BYTHEORBITALVELOCITIESOFTHELARGERWAVESPASSINGACROSSIT ORTHEFEATUREMAYBEADVECTEDATTHEVELOCITYOFTHEWAVESYSTEMSUPPORTINGIT4HE SCATTERERSMIGHTEVENBEDETACHEDFROMTHEUNDERLYINGSURFACE ASINTHEPLUMESEMIT TEDATTHECRESTSOFBREAKINGWAVES ANDMOVEATSPEEDSGREATERTHANTHEWAVESYSTEM ITSELF!THIGHERRADARFREQUENCIESANDINSTRONGWINDS THEPOSSIBILITYOFSCATTERING FROMSPRAYCARRIEDBYTHEWINDFIELDABOVETHESURFACEMUSTBECONSIDERED!LLOFTHIS COMPLEXMOTIONSHOWSUPINADOPPLERSHIFTIMPARTEDTOTHESCATTEREDELECTROMAGNETIC WAVE5NFORTUNATELY THEREISASYETLITTLEDETAILEDPHYSICALUNDERSTANDINGOFTHECOM PLICATEDPHENOMENOLOGYOFSEACLUTTERSPECTRA -EASUREMENTSOFMICROWAVECLUTTERSPECTRAFORREALSEASHAVEBEENREPORTEDINTHE LITERATURE FOR AIRCRAFT MEASUREMENTS OF THE SPECTRAL SHAPE ALONE FIXED SITE SHORE MEASUREMENTSSHOWINGASHIFTINTHESPECTRALPEAK ANDMEASUREMENTSFROMSHIPS ATINTERMEDIATEGRAZINGANGLES/THERMEASUREMENTSOFSEACLUTTERSPECTRAINCLUDE THOSEMADEATMUCHLOWERFREQUENCIESINTHE(&BAND ASDESCRIBEDINTHELASTSECTION THOSEMADEUNDERARTIFICIALCONDITIONSINWAVETANKS WHOSEAPPLICATIONTOREAL SEA CONDITIONSISUNCERTAINANDTHOSEFROMOTHERFIXED SITESATHIGHRESOLUTIONANDSHORT AVERAGINGTIMES TOBEDISCUSSEDLATER !SITTURNSOUT MICROWAVESEACLUTTERSPECTRAHAVEARATHERSIMPLEFORMATTHELOWER GRAZINGANGLES&IGUREILLUSTRATESTYPICALSPECTRALBEHAVIORATTHETWOPOLARIZA TIONS BASEDONDATACOLLECTEDBY0IDGEONFOR# BANDCLUTTERLOOKINGUPWINDATAFEW DEGREESGRAZING 4HEPEAKFREQUENCYOFTHEUPWINDSPECTRUMAPPEARSTOBEDETERMINEDBYTHEPEAK ORBITALVELOCITYOFTHELARGESTSEAWAVES PLUSAWIND DEPENDENTVELOCITYINCREMENT CONTAINING BUTNOTENTIRELYEXPLAINEDBY WIND INDUCEDSURFACECURRENTS4HISPEAK ORBITALVELOCITYISTAKENTOBETHATOFTHEMAJORWAVESANDMAYBEOBTAINEDINTERMSOF THESIGNIFICANTHEIGHT(ANDPEAKPERIOD4`3ECTION FROMTHEEXPRESSION
6ORB O(4` 5MS
4HEAPPROXIMATEDEPENDENCEONWINDSPEED5WASFOUNDBYSUBSTITUTING( HRMS FROM%Q ASSUMINGAFULLYDEVELOPEDSEA AND4`FROM%Q4OTHIS THEREMUST
3%!#,544%2
£x°Ó£
&)'52% 1UALITATIVE BEHAVIOR OF DOPPLER SPECTRAOFSEACLUTTERLOOKINGUPWINDATLOWGRAZING ANGLESAFTER# BANDMEASUREMENTSBY670IDGEON Ú!MERICAN'EOPHYSICAL5NION
BEADDEDAWIND DRIFTVELOCITYOFABOUTOF5ANDAFIXEDSCATTERERVELOCITYWHICH APPEARSTOBEABOUTMSINTHE8 AND# BANDMEASUREMENTS 3UMMINGTHESE COMPONENTSYIELDSTHEVIRTUALDOPPLERVELOCITYATTHEPEAKOFTHECLUTTERSPECTRUMFOR THEPARTICULARCASEOFAVERTICALLYPOLARIZED8 OR# BANDRADARLOOKINGUPWINDATLOW GRAZINGANGLES
6VIR 5MS
!SNOTEDEARLIER CAREMUSTBETAKENWHENEVERWINDSPEEDISUSEDTOPARAMETERIZE APROCESSTHATDEPENDSONWAVEHEIGHT4HEREISANUNAMBIGUOUSRELATIONONLYFORA FULLYDEVELOPEDSEAINTHEABSENCEOFSWELL 4HEREMAININGPROPERTIESOFTHECLUTTER SPECTRUMCANNOWBEDISCUSSEDINTERMSOF6ORBAND6VIR&OREXAMPLE THESPECTRAL PEAKFORHORIZONTALPOLARIZATIONFOLLOWSASIMILARLINEARDEPENDENCEON5 ONLYWITH ACOEFFICIENTLYINGSOMEWHEREBETWEENAND ASMAYBENOTEDINTHESKETCH SHOWNIN&IGURE4HEREASONSFORTHEDIFFERENCESBETWEENTHESPECTRAFORTHETWO POLARIZATIONSARENOTASYETCLEAR ALTHOUGHTHETENDENCYOFTHE( POLARIZATIONSPECTRA TOLIEATAHIGHERFREQUENCYISLIKELYDUETOTHEPREFERENTIALSOURCEOF( POLARIZATION RETURNSINFASTER MOVINGWAVESTRUCTURES 4HE HALF POWER WIDTH $ OF THE CLUTTER VELOCITY SPECTRUM IS QUITE VARIABLE DEPENDINGONSUCHTHINGSASRADARPOLARIZATIONANDSEACONDITIONS)TSEEMSMOST CLOSELYRELATEDTOTHEPEAKORBITALVELOCITYGIVENBY%Q.ATHANSONSHOWS APLOTCONTAININGSPECTRALWIDTHSATBOTHPOLARIZATIONSFROMSEVERALINVESTIGATORS OVER A WIDE ASSORTMENT OF UNSPECIFIED SEA CONDITIONS 4HE POINTS ARE WIDELY SCATTERED BUTTHEDEPENDENCEONWINDSPEEDISGIVENROUGHLY WITHARATHERLARGE VARIANCE BYTHEEXPRESSION$^5MS WHICHISJUSTTHEORBITALVELOCITYIN %QWITHACOEFFICIENTABOUTHALFWAYBETWEENTHEVALUESFORVERTICAL^ AND HORIZONTAL ^ POLARIZATION &OR LOOK DIRECTIONS AWAY FROM UPWIND THE PEAKDOPPLERFOLLOWSACOSINEDEPENDENCEQUITECLOSELY GOINGTOZEROATCROSSWIND ASPECTSANDTURNINGNEGATIVEDOWNWIND4HEWIDTHOFTHESPECTRUMAPPEARSTO REMAINRELATIVELYCONSTANT
£x°ÓÓ
2!$!2(!.$"//+
4HEDETAILSOFTHECLUTTERSPECTRUMSHOWLITTLEDEPENDENCEONEITHERTHERADARFRE QUENCYORTHEGRAZINGANGLE ATLEASTFORANGLESLESSTHANABOUT)NREVIEWINGTHE RESULTSOFMEASUREMENTSATFOURFREQUENCIES5(& , # AND8BANDS6ALENZUELA AND,AINGNOTEDARELATIVELYWEAKTENDENCYOFCLUTTERBANDWIDTHTODECREASEWITH INCREASESINFREQUENCYBETWEENTHE5(&AND8BANDSANDGRAZINGANGLESBETWEEN AND3INCEBOTHOFTHESEVARIATIONSCANLIKELYBEACCOMPANIEDBYACHANGEINTHE SIZEOFTHERADARFOOTPRINTONTHESURFACE THEYMIGHTBEDUETOADEPENDENCEONRESOLU TIONCELLDIMENSIONS ALTHOUGHTHEOTHERWORKERSFOUNDTHATTHEPULSELENGTHHADLITTLE EFFECTONCLUTTERBANDWIDTHFORVALUESBETWEENABOUTAND§SEC 3PECTRA OBTAINED WITH SHORT AVERAGING TIMES DISCLOSE SOMETHING OF THE ORIGINS OFTHECLUTTERSPECTRUM&IGUREISASEQUENCEOFSECONDSPECTRAOBTAINED BY+ELLERETALWITHACOHERENTVERTICALLYPOLARIZED8 BANDRADAROPERATINGATA GRAZINGANGLEOFANDARESOLUTIONCELLSIZEOFABOUTM4HEZERO DOPPLERREF ERENCEINTHISFIGUREWASLOCATEDARBITRARILYATn(Z4HESPREADALONGEACHLINE
&)'52% 3HORT TIMEAVERAGEDDOPPLERSPECTRAAT8BANDFORAN INTERMEDIATEGRAZINGANGLEOFSPECTRACOMPUTEDATSECINTERVALS SHALLOW WATERDATAISFROMAFIXEDSITEONAPIER FROM7#+ELLER ETAL
3%!#,544%2
£x°ÓÎ
ISDUETOTHESMALL SCALEWAVEMOTIONSONTHESURFACE WHILETHELARGERMEANDERSARE INDUCEDBYTHEVELOCITIESOFLARGEWAVESMOVINGTHROUGHTHEMEASUREMENTCELL4HE WINDSPEEDWASABOUTMS ANDADOPPLERSHIFTOF(ZCORRESPONDSTOARADIAL VELOCITYOFMS4HEAVERAGECLUTTERSPECTRUMEXPECTEDFORTHISWINDSPEEDAND GRAZINGANGLE WITHBANDWIDTHESTIMATEDFROM%Q ISINCLUDEDINTHESKETCH SHOWNIN&IGURE4HELARGESPECTRALSPIKEAPPEARINGINTHECENTEROFTHEDISPLAY ISNODOUBTDUETOAWAVEBREAKINGINORCLOSETOTHEMEASUREMENTCELL4HEDOPPLER VELOCITY FOR THIS SPIKE SUGGESTS A PEAK SCATTERER VELOCITY ABOUT EQUAL TO THE WIND SPEED WHICHWOULDCORRESPONDTOTHEVELOCITYOFTHELONGESTWAVESONTHESURFACE !LTHOUGHSUCHEVENTSARERELATIVELYRAREINAFIXEDAREAOFM THEYSHOULDOCCUR QUITEFREQUENTLYWITHINALARGESURVEILLANCECELLANDMIGHTOFTENHAVELARGESCATTER INGCROSSSECTIONSASSOCIATEDWITHTHEM3IMILARRECORDSMAYBEFOUNDINREFERENCE 7ARDETAL /THER%NVIRONMENTAL%FFECTS 2AIN %ARLYEVIDENCEOFTHEEFFECTOFRAINONSEACLUTTERWASMAINLYANECDOTALFOR EXAMPLE RADAROPERATORSWOULDREPORTTHATSEACLUTTERTENDSTODECREASEWHENITSTARTS TORAIN(OWEVER THEREHASBEENLITTLEINTHEWAYOFRELIABLE QUANTITATIVEEXPERIMENTAL INFORMATIONABOUTTHEINTERACTIONBETWEENRAINANDWIND DRIVENSEACLUTTERINTHEOPEN OCEAN,ABORATORYMEASUREMENTSBY-OOREETALWITHARTIFICIALhRAINvSUGGESTEDTHAT FORLIGHTWINDSTHEBACKSCATTERLEVELINCREASEDWITHTHERAINRATE WHILEFORHEAVYWINDS RAIN MADE LITTLE DIFFERENCE %XTENSIVE MEASUREMENTS AT +U BAND IN THE OPEN OCEAN TENDEDTOCONFIRMTHISBEHAVIOR )NMEASUREMENTSINNATURALRAINOVER#HESAPEAKE"AY (ANSENFOUNDTHATEVEN ALIGHTRAINMMH CHANGESTHESPECTRALCHARACTEROFSEACLUTTERATMODERATEWIND SPEEDS MS BY INTRODUCING A SIGNIFICANT HIGH FREQUENCY COMPONENT (E ALSO FOUND SOME EVIDENCE IN SUPPORT OF THE RADAR OPERATORS AT LEAST FOR THE LOW GRAZ INGANGLESANDHORIZONTALPOLARIZATIONSWITHWHICHMOSTSHIPBOARDRADARSOPERATE &IGURECOMPARESTHECORRELATIONFUNCTIONOFSEACLUTTER8BAND LOWGRAZING ANGLE (POLARIZATION WITHANDWITHOUTRAINFORA KTWINDSPEEDANDARAINRATE OFMMH4HESHARPDECREASEINCORRELATIONTIMEINTHEPRESENCEOFRAINREFLECTS THEBROADENINGOFTHECLUTTERSPECTRUM ALTHOUGHGENERALLYTHEREAPPEARSTOBELITTLE QUANTITATIVEINFORMATIONABOUTTHEEFFECTOFRAINONTHESPECTRUMOFSEACLUTTER
&)'52% %FFECTOFRAINONTHECORRELATIONFUNCTIONOFWIND DRIVENSEA CLUTTER8BAND HORIZONTALPOLARIZATION WINDSPEEDKT RAINRATEMMH FROM*0(ANSEN
£x°Ó{
2!$!2(!.$"//+
4HEPRODUCTIONOFSEACLUTTERBYRAINFALLINGONAhCALMvSURFACEINTHEABSENCE OFWINDWASALSOINVESTIGATEDBY(ANSEN WITHTHERESULTSSHOWNIN&IGURE !HIGH RESOLUTION8 BANDRADAR NSPULSE BEAMWIDTH OPERATINGATAGRAZING ANGLEOFABOUT VIEWEDTHEBACKSCATTERFROMAFIXEDSPOTONTHEWINDLESSSURFACEOF #HESAPEAKE"AYASTHERAINSTEADILYINCREASEDFROMTOMMH4HECROSSSECTIONSFOR VERTICALANDHORIZONTALPOLARIZATIONSWEREQUITEDIFFERENTFORLOWRAINRATESBUTTENDED TOMERGEATARAINRATEOFABOUTMMH4HEMAGNITUDEOFTHISSPLASHCROSSSECTIONROSE TOAROFABOUTnD" CORRESPONDINGTOHIGHLYAVERAGEDWIND INDUCEDCROSSSEC TIONSATTHISGRAZINGANGLEFORWINDSOFABOUTKT&URTHERLABORATORYANDTHEORETI CALSTUDIESHAVESHOWNTHATTHEMAJORSCATTERINGFEATUREUNDERTHESECONDITIONSISTHE VERTICALSTALKTHATEMERGESSHORTLYAFTERDROPIMPACT-OREOVER THESESTUDIESSUGGEST THATTHE6 POLARIZEDRETURNSFROMRAINDROPSPLASHESSHOULDBEONLYMILDLYSENSITIVETO THERAINRATE WHILETHE( POLARIZEDRETURNSSHOULDSHOWASTRONGDEPENDENCEONBOTH THERAINRATEANDTHEDROP SIZEDISTRIBUTION3OMETHINGOFTHISBEHAVIORMAYBESEEN INTHEDATAIN&IGURE/PENOCEANMEASUREMENTSAT+UBANDANDATMUCHHIGHER GRAZING ANGLES SHOW SUFFICIENT VARIABILITY WITH WIND SPEED RAIN RATE AND GRAZING ANGLETOLEAVETHEUNCERTAINTIESTHATOPENEDTHISSECTIONLARGELYUNRESOLVED )NADDITIONTOSCATTERINGFROMTHERAINDROPIMPACTS THEDISTRIBUTIONOFRAINDROPS INTHEVOLUMEOFTHEATMOSPHEREABOVETHESURFACECANHAVETWOADDITIONALEFFECTS ONSEACLUTTERASANABSORBERSCATTEREROVERTHERADARPROPAGATIONPATH WHICHIS WELL UNDERSTOOD ANDASAMASS ADDITIVETOTHEWIND AFFECTINGMOMENTUMTRANSFER TO THE SURFACE AND THUS THE EXCITATION OF WIND WAVES THEMSELVES WHICH IS LESS WELL UNDERSTOOD !TMOSPHERIC$UCTING !NOTHERTOPICINSEACLUTTERTHATHASBEENLITTLEEXPLORED IS THE ROLE PLAYED BY PROPAGATION EFFECTS WITHIN THE ATMOSPHERIC BOUNDARY LAYER LYINGOVERTHESEASURFACE4HEEFFECTSOFATMOSPHERICABSORPTIONHAVEBEENNOTED ABOVEINCONNECTIONWITHMILLIMETER WAVECLUTTER BUTATVERYLOWGRAZINGANGLES THE RAY PATHS JOINING THE RADAR TO THE SURFACE BECOME VERY SENSITIVE TO REFRACTIVE INHOMOGENEITIESINTHEATMOSPHERICBOUNDARYLAYER/VERDISTANCESAPPROACHINGAND
&)'52% 3EA CLUTTER PRODUCED BY RAIN SPLASHES ALONE ON A CALM SURFACE D"CORRESPONDSTOABOUTR D" FROM(ANSEN
3%!#,544%2
£x°Óx
BEYONDTHECONVENTIONALOPTICALHORIZON SUCHPERTURBATIONSCOULDPRODUCESTRONG FOCUS DEFOCUSVARIATIONSALONGTHESURFACEILLUMINATIONPROFILE ORAGENERALRISE INTHELOCALGRAZINGANGLE&IGUREGIVESANEXPERIMENTALEXAMPLEOFTHEEFFECT OFDUCTINGONVERYLOW ANGLESEACLUTTER4HEGRAZINGANGLEGIVENASTHEABSCISSA ISACTUALLYAPLOTOFINVERSERANGE SOTHELIFTINGOFTHECROSSSECTIONBYDUCTINGOVER ANORDER OF MAGNITUDESPANOFRANGESISVERYLIKELYDUETOARISEINTHELOCALGRAZING ANGLEPRODUCEDBYREFRACTIONINTHEEVAPORATIVELAYERFIRSTMETERSORSOABOVE THESURFACE 3UCHEFFECTSSHOULDBESUSPECTEDWHENEVERTHERADARPROPAGATIONPATH EXTENDSBEYONDTHEOPTICALHORIZON 3HADOWING 4HEPOSSIBILITYOFSHADOWINGMUSTBECONSIDEREDSERIOUSLYWHENEVER THESEAISVIEWEDATGRAZINGANGLESSMALLERTHANTHERMSSLOPEANGLEOFTHESEASURFACE 3OMEEXAMPLESWEREDISCUSSEDEARLIERINCONNECTIONWITHTHEBEHAVIOROFSEACLUTTERAT LOWGRAZINGANGLESIN&IGURE)NFACT THESHARPFALLOFFOFTHENONDUCTINGDATAIN &IGUREMIGHTBEFURTHEREVIDENCEOFTHETHRESHOLDSHADOWINGMENTIONEDEARLIER (OWEVER THECOMMONIDEAOFSHADOWINGDERIVESFROMTHEGEOMETRICALOPTICSCONCEPT OFASHARPTRANSITIONBETWEENLIGHTANDDARKNESS"YCONSIDERINGTHEIMPLICATIONSOF DIFFRACTIONATTHEWAVEPEAKS ITISPOSSIBLETODETERMINETHEDOMAINOFRADARFREQUEN CIESANDWINDSPEEDSOVERWHICHTHECONCEPTSOFGEOMETRICALOPTICSMAYBEAPPLIED 4HISWASDONEIN7ETZEL WHEREITISSHOWNHOWDIFFRACTION RATHERTHANGEOMETRICAL SHADOWING CONTROLSPROPAGATIONINTOANDOUTOFTHETROUGHSOFTHEWAVESUNDERMANY OFTHEUSUALFREQUENCIESANDWINDSPEEDSENCOUNTEREDINPRACTICALRADAROPERATIONSAT LOWGRAZINGANGLES&OREXAMPLE SHADOWINGWILLTAKEPLACEAT+ABANDFORANYWINDS ABOVEKT YETWILLHARDLYEVEROCCURAT, BANDFREQUENCIES,ATERANALYTICALSOLU TIONSBASEDONNUMERICALMETHODSEXPLOREDANDEXPANDEDTHEIDEAOFSHADOWINGOVER THESEASURFACEUNDERHIGHLYIDEALIZED ANDMOREGENERALCONDITIONS 3URFACE#URRENTS 4HEMOSTOBVIOUSEFFECTOFACURRENTONSEACLUTTERWOULDBE ASHIFTINTHEPEAKOFTHEDOPPLERSPECTRUM ANALOGOUSTOTHECONTRIBUTIONOFTHE WIND DRIFTCURRENTMENTIONEDINCONNECTIONWITH%Q!NOTHEREFFECTISRELATEDTO
&)'52% %FFECTOFDUCTINGONLOW ANGLECLUTTERWINDSPEED ABOUTKTAFTER&"$YERAND.##URRIEÚ)%%%
£x°ÓÈ
2!$!2(!.$"//+
THEFACTTHATTHEEXCITATIONOFTHESURFACE WAVESYSTEMDEPENDSONTHELOCALAPPARENT WINDATTHESURFACE SOTHERECANBESIGNIFICANTDIFFERENCESINWAVEHEIGHTACCORDING TOWHETHERTHEWINDISBLOWINGWITHORAGAINSTTHECURRENT!CCORDINGTO%Q WAVEHEIGHTISPROPORTIONALTOTHESQUAREOFTHEWINDSPEED SOINTHE'ULF3TREAM FOREXAMPLE WITHACURRENTOFKTFLOWINGNORTH A KTNORTHERLYBLOWINGAGAINST THECURRENTWILLRAISEASEATHREETIMESASHIGHASA KTSOUTHERLYBLOWINGWITHTHE CURRENT%VENWITHNOWIND THEPRESENCEOFSTRONGCURRENTSHEARSCANPRODUCEHIGHLY AGITATEDSURFACES3HIPBOARDOBSERVERSHAVEREPORTEDBANDSOFROARINGBREAKERSPASS INGBYONANOTHERWISE SMOOTHSURFACE PRESUMABLYPRODUCEDBYPOWERFULSURFACE CURRENTSHEARSASSOCIATEDWITHLARGE AMPLITUDEINTERNALWAVES)NAMORESUBTLEWAY MODULATED CURRENTS ARE HELD RESPONSIBLE FOR SYNTHETIC APERTURE RADAR 3!2 IMAGES THATCONTAINTHEEXPRESSIONOFBOTTOMTOPOGRAPHYPRODUCEDBYTHE"ERNOULLI%FFECTIN SHALLOWWATERS)NEACHOFTHEEXAMPLESCITEDABOVE THECURRENTPRODUCESACHANGE INTHESURFACEROUGHNESS WHICHCANBEEXPECTEDTOGIVERISETOACHANGEINSEACLUTTER CROSSSECTION #ONTAMINANTS 4HEIDEAOFPOURINGOILONTROUBLEDWATERSISAFAMILIARONETHE ANGRYSURFACEWILLSMOOTHANDSUBSIDE)NANOTHERAGE THESURVIVAL GEARLOCKEROF EVERYSAILINGSHIPWOULDCONTAINABOTTLEOFOILTOQUIETTHESEAINASTORM!LTHOUGH THEEFFECTIVENESSOFTHISPROCEDUREHASALWAYSBEENSOMEWHATCONTROVERSIAL THERE ISNOQUESTIONTHATOILCANPRODUCEASLICKOFSMOOTHWATERATRELATIVELYLOWWIND SPEEDS)NFACT BIOLOGICALOILS PRODUCEDBYBACTERIA ALGAE ANDPLANKTON CANBE FOUND EVERYWHERE ON THE WORLDS OCEANS AND FORM NATURAL SLICKS IN THOSE REGIONS THATCOMBINETHEGREATESTOILCONCENTRATIONWITHTHELOWESTWINDSPEEDS EG CLOSE TOCONTINENTALSHORELINES-AN MADECONTAMINANTSCAN OFCOURSE HAVETHESAME EFFECT!LAYEROFOILONLYONEMOLECULETHICKWILLSIGNIFICANTLYAFFECTTHEABILITYOF THESURFACETOSUPPORTWAVEMOTIONS BUTTHISLAYERMUSTBECONTINUOUS4HEADJA CENTMOLECULESTHENSENSEEACHOTHERANDFORMAFILMTHATISRESISTANTTOHORIZONTAL COMPRESSION4HESURFACEELASTICITYISCHANGED ATYPEOFLONGITUDINALVISCOSITYIS INTRODUCED ANDTHESURFACEBECOMESSTABILIZEDAGAINSTTHEGROWTHOFSHORTWAVESUP TOSEVERALINCHESINLENGTH 4OTHEEXTENTTHATRADARSEACLUTTERISPRODUCEDBYSMALL SCALESURFACEROUGHNESSAT GRAZINGANGLESLESSTHANABOUT THEPRESENCEOFOILONTHESURFACESHOULDLEADTO AMEASURABLEDECREASEINCLUTTERCROSSSECTION"UT ASNOTEDABOVE THEREDUCTIONOF SMALLWAVEMOTIONSREQUIRESTHEEXISTENCEOFACONTINUOUSMONOLAYERSLICKFORMATION ISAGOnNO GOPROCESS ANDSOSLICKSWILLTENDTOHAVERELATIVELYSHARPBOUNDARIES)N OPERATINGTHE.2,&2SYSTEMASASYNTHETICAPERTURERADARTOOBTAINIMAGESOFTHE SLICKSPRODUCEDBYOILSPILLS 'UINARDFOUNDTHATTHESLICKSWEREWELLDEFINED THATIT TOOKVERYLITTLEOILTOMAINTAINAVISIBLESLICK THATVERTICALPOLARIZATIONPROVIDEDMUCH GREATERCONTRASTTHANDIDHORIZONTAL ANDTHATTHESLICKSWEREQUENCHEDBYWINDSAND CURRENTS!LTHOUGHSIGNALSTRENGTHWASNOTRECORDEDINTHISIMAGINGEXPERIMENT LATER MEASUREMENTSAT8AND,BANDSBYOTHERSINDICATEDTHATATTHEHIGHERGRAZINGANGLES ABOUT THE CLUTTER REDUCTION PRODUCED BY THE TYPES OF OIL OCCURRING IN NATURAL SLICKSWASRATHERSMALL ONTHEORDEROFAPERCENT3INCESLICKSAREDISPERSEDBYTHE WINDANDASSOCIATEDWAVEACTIONATWINDSPEEDSGREATERTHANABOUTKT THEEFFECTOF NATURALSLICKSONCLUTTERMAYNOTBECLEARBECAUSETHEYTENDTOOCCURINTHEREGIMEOF LOWWINDSPEEDSWHERETHESEASURFACEISALREADYILLDEFINED 4HECELEBRATEDSUNGLITTERMEASUREMENTSBY#OXAND-UNKGAVEAQUANTITATIVE MEASUREOFTHEEFFECTOFCONTAMINANTSONTHESURFACESLOPESINOPENWATER SHOWING THATTHEWIND GENERATEDCOMPONENTOFTHERMSSLOPEOFhOILEDvWATERSISSIGNIFICANTLY
3%!#,544%2
£x°ÓÇ
SMALLERTHANTHATOFhCLEANvWATER4HEHEAVYCOMMERCIALOILSUSEDINTHEIREXPERIMENT WERE EFFECTIVE IN SUPPRESSING SMALL SCALE WAVES OVER A RANGE OF WIND SPEEDS WELL BEYONDTHOSEWHICHWOULDNORMALLYDISPERSETHELIGHTERNATURALOILS SOTHEEFFECTOFOIL SPILLSONSEACLUTTERSHOULDBEEXPECTEDTOEXTENDTOTHEHIGHERWINDSPEEDS)NFACT AT THESEHIGHERWINDSPEEDS THEDEPRESSIONOFRADARBACKSCATTERBYSUCHOILSAT8AND+A BANDSCANREACHTOD"ATINTERMEDIATEGRAZINGANGLESBETWEENAND
£x°{Ê / ", -Ê Ê " -Ê"Ê- Ê 1// , )NADDITIONTOPROVIDINGANINTELLECTUALBASISFORhUNDERSTANDINGvSEACLUTTERPHENOM ENA ACOMPLETETHEORYOFSEACLUTTERSHOULDIDEALLYPROVIDEACCURATEAPRIORIPREDIC TIONSOFALLASPECTSOFCLUTTERBEHAVIORUNDERALLPOSSIBLEENVIRONMENTALCONDITIONS)N SPITEOFOVERYEARSOFEFFORT THETHEORYOFSEACLUTTERDOESNEITHEROFTHESETASKSVERY WELL ASWEWILLSEEINTHISSECTION )N THE DEVELOPMENT OF MODELS OF SEA SCATTER BASED ON PHYSICAL THEORY THERE ARE ESSENTIALLYTWOBASICANDDISTINCTAPPROACHES(ISTORICALLY THEFIRSTAPPROACHASSUMED SEASCATTERTOHAVEITSORIGININSCATTERINGFEATURES OROBSTACLES ACTUALLYPRESENTONOR NEARTHESEASURFACE%ARLYSCATTERINGMODELSINCLUDEDRAINTOMODELSPRAY SMOOTH CIRCULARMETALLICDISKS ARRAYSOFSEMI INFINITEPLANES ANDFIELDSOFHEMISPHERI CALBOSSES TONAMEAFEW/BVIOUSLY THECHOICEOFTHESESCATTERINGOBSTACLESRELATED MORETOTHEPREEXISTENCEOFCONVENIENTSCATTERINGSOLUTIONSFORTHESESHAPESTHANTO INSIGHTSGAINEDFROMOBSERVINGTHESEA3INCETHEN FEATUREMODELSHAVESOUGHTGREATER REALITYBYCONSIDERINGWEDGESHAPES ASSUGGESTEDBYTHESHARPCRESTSOF3TOKESWAVES OBSERVEDONMOSTNATURALWATERSURFACES ANDTHESHOCKSANDPLUMESSUGGESTED BYTHEPROPERTIESOFWAVEGROUPSANDTHEHYDRODYNAMICSOFBREAKINGWAVES 4HE OTHER APPROACH TO THEORETICAL MODELING DERIVES THE SCATTERED FIELD FROM A GLOBALBOUNDARY VALUEPROBLEM'"60 INWHICHTHESEAASAWHOLEISCONSIDEREDA BOUNDARYSURFACEWHOSECORRUGATIONSAREDESCRIBEDBYSOMEKINDOFSTATISTICALPRO CESS!N ENORMOUS LITERATURE IS DEVOTED TO THE THEORY OF SURFACE SCATTER FROM THIS POINTOFVIEW STEMMINGFROMTHEIMPORTANCENOTONLYOFRADARSEASCATTER BUTALSO RADARGROUNDSCATTERANDSONARREVERBERATIONTHEACOUSTICEQUIVALENTOFRADARCLUTTER FROMBOTHTHESURFACEANDTHEBOTTOMOFTHESEA"ECAUSETHE'"60APPROACHLEADS TOTHEANALYTICALEXPRESSIONOFTHE"RAGGSCATTERINGHYPOTHESISTHATHASDOMINATEDTHE THEORYOFSEASCATTERSINCETHELATES ABRIEFEXPLANATIONOFSOMEOFTHECENTRAL IDEASISINCLUDEDBELOW 4HEORIES"ASEDON'LOBAL"OUNDARY 6ALUE0ROBLEMS 'ENERALFORMULATIONS OFTHE'"60 THOUGHELEGANT AREOFLITTLEPRACTICALVALUE ANDSOMEKINDOFAPPROXI MATIONISNECESSARYTOOBTAINUSEFULQUANTITATIVERESULTSFROMTHEM4HEMETHODSOF APPROXIMATIONRELATETOTHETWOMETHODSOFFORMULATINGTHE'"60 3MALL AMPLITUDE APPROXIMATIONS SEA WAVEHEIGHTS MUCH SMALLER THAN THE RADAR WAVELENGTH AREUSEDABINITIOWITH2AYLEIGHSHYPOTHESIS INWHICHTHESURFACE BOUNDARYCONDITIONSAREEMPLOYEDTOMATCHANANGULARSPECTRUMOFOUTGOINGPLANE WAVESTOTHEINCIDENTFIELDn ! GENERAL INTEGRAL FORMULATION BASED ON 'REENS THEOREM IS PURSUED EITHER IN A SMALL AMPLITUDE APPROXIMATION OR UNDER THE ASSUMPTIONS OF PHYSICAL OPTICS SURFACECURVATURESMUCHGREATERTHANTHERADARWAVELENGTH n
£x°Ón
2!$!2(!.$"//+
)NFORMULATION SOMETIMESCALLEDTHESMALL PERTURBATIONMETHOD30- ANDASSO CIATED MOST OFTEN WITH THE WORK OF 2ICE THE SURFACE DISPLACEMENTS ARE ASSUMED EVERYWHERETOBEMUCHSMALLERTHANTHERADARWAVELENGTH SOTHEMETHODISDIRECTLY APPLICABLEONLYTOSUCHCASESAS(&SCATTERINGWITHWAVELENGTHSOFTENSOFMETERS ATLOWTOINTERMEDIATEWINDSPEEDS ANDWITHWAVEHEIGHTSOFAFEWMETERSATMOST 4HESOLUTIONISINTHEFORMOFAPOWERSERIESINTHERATIOOFSEAWAVEHEIGHTTORADAR WAVELENGTH ANDITPREDICTSTHEFIRST ORDER"RAGGLINESANDSECOND ORDERSPECTRALFILLING AROUNDTHELINESTHATWEREMENTIONEDINTHEEARLIERSECTIONON(&SEACLUTTER /NTHEOTHERHAND THEVARIOUSINTEGRALFORMULATIONSREFERENCEDABOVEUSUALLYBEGIN WITHAVERYGENERALEXPRESSIONFORTHEFIELDSSCATTEREDFROMTHESEASURFACE WHICHARE SQUARED AND ENSEMBLE AVERAGED OVER REALIZATIONS OF THE SEA SURFACE TO PROVIDE THE AVERAGEPOWERRETURNEDTOTHERADARANTENNA ANDTHENNORMALIZEDTOTHEILLUMINATED AREAASIN%Q$ESPITETHEGENERALITYOFTHEINITIALFORMULATIONS MOSTOFTHEFINAL EXPRESSIONSFORREITHERAPPEARIN ORCANBEPUTINTO AFORMREPRESENTEDSCHEMATI CALLY BY THE FOLLOWING SIMPLIFIED ONE DIMENSIONAL EXPRESSION SEE (OLIDAY ET AL "ECHMANNAND3PIZZICHINO &UNGAND0AN AND6ALENZUELA FOREXAMPLE c
; # Y =
S Y !K &P Y ¯ DY EI KY ;E K H
E K H =
c
WHERE!ISACONSTANTK KCOSXANDK KSINXWHEREKISTHERADARWAVE NUMBER OK &PX IS A FUNCTION OF POLARIZATION P GRAZING ANGLE X AND THE ELECTRICALPROPERTIESOFSEAWATERHISTHERMSSEAWAVEHEIGHTAND#Y ISTHESURFACE CORRELATION COEFFICIENT /F COURSE THE REDUCTION OF A COMPLICATED BOUNDARY VALUE PROBLEMTOSOSIMPLEAFORMREQUIRESASSUMPTIONSABOUTBOTHTHESURFACEFIELDSAND THEDISTRIBUTIONOFTHESEAHEIGHTSWHICHISGAUSSIANTOAGOODAPPROXIMATION "UT WHILETHE30-APPROACHMENTIONEDABOVEREQUIRESTHERATIOSHKTOBESMALLRIGHTAT THESTART '"60THEORIESDERIVEDFROMEXPRESSIONSRESEMBLING%QHAVENOA PRIORIRESTRICTIONSONSURFACEHEIGHTS 4HE STATISTICAL PROPERTIES OF THE SEA SURFACE ENTER THROUGH THE CORRELATION COEFFI CIENT#Y APPEARINGUNDERTHEINTEGRALSIGNINTHEEXPONENTIALINTHEBRACKETS ANDBY EXPANDINGTHISEXPONENTIALIN%Q ITMAYBEWRITTEN
S Y !K &P Y E
K H
c
£
N
K N 7 N K N
WHERE c
7 N K ¯ DT EI KT ;H # T =N
c
3MALL AMPLITUDE!PPROXIMATION )NTHELIMITOFSMALLRATIOSOFRMSWAVEHEIGHTTO RADARWAVELENGTHOR MORESPECIFICALLY
KH
ONLYTHEFIRSTTERMINTHESERIESIN%QSURVIVES ANDTHECROSSSECTIONASSUMES THEVERYSIMPLEFORM
S Y P K &P` Y 7 K COSY
3%!#,544%2
£x°Ó
WHERETHECONSTANT!HASBEENMADEEXPLICITAND&PHASABSORBEDASINTERMFROMTHE SERIES7 ISTHE&OURIERTRANSFORMOFTHESURFACECORRELATIONFUNCTION WHICHMAKES ITTHESEAWAVENUMBERSPECTRUMDISCUSSEDIN3ECTION EVALUATEDATTWICETHE SURFACE PROJECTED RADARWAVENUMBER WHICHDEFINESA"RAGGORHALF WAVELENGTH RESONANCE%XCEPTPOSSIBLYFORTHEDETAILSOFTHEANGLEFACTOR&P %QISEQUIVA LENTTOTHERESULTOBTAINEDBYTHE30-DISCUSSEDABOVE ANDALTHOUGHITISSOMETIMES FELT THAT ITS DERIVATION FROM A SURFACE INTEGRAL PROVIDES SOME POTENTIAL FOR GREATER GENERALIZATION ITCARRIESWITHITALLOFTHESAMERESTRICTIONS "EFOREPROCEEDINGFURTHER ITISINSTRUCTIVETOLOOKALITTLEMORECLOSELYATTHEIMPLI CATIONSOFTHEMATHEMATICALEXPRESSIONSINTHESEFORMULATIONS.OTETHATIN%Q THEEXPRESSIONINTHEBRACKETSUNDERTHEINTEGRALISTHEONLYPLACEATWHICHTHESURFACE WAVEPROPERTIESOFTHESEAAPPEAR4HATIS THECROSSSECTIONISSIMPLYPROPORTIONALTO THE&OURIERTRANSFORMOFASEA SURFACEFUNCTIONAL SOTHERADARACTSASAFILTERTUNEDTO THEhSPATIALFREQUENCYvKCOSX EXTRACTINGTHATLINEFROMTHESPECTRUMOFWHATEVER ASSORTMENTOFSCATTERERSTHESEASURFACEFUNCTIONALEXPRESSES WHETHERTHEYBELONG SWELLCOMPONENTS SHORT WAVELENGTHNOISE LOCALIZEDSCATTERINGFEATURES ORACHAOTIC TUMBLEOFWATERBALLS/NLYUNDERQUITESPECIALCIRCUMSTANCESWILLTHEREACTUALLYBE ANIDENTIFIABLESURFACE WAVEATTHAThFREQUENCYvTHATWOULDJUSTIFYTHETERM"RAGG RESONANCEINITSORIGINALSENSE WHICH AFTERALL WASARESONANCEINANORDEREDCRYSTAL LATTICEOFDISCRETESCATTERERS!LTHOUGHAUTHORSOFTENREFERTOhFREE"RAGGWAVES vSUCH OBJECTSAREFOUNDPRIMARILYAMONGTHEPARASITICCAPILLARIESREFERREDTOIN3ECTION ORAMONGTHERINGWAVESPROPAGATINGOUTFROMTHEIMPACTOFAFALLINGDROP4HISRAISES A QUESTION ABOUT THE MEANING OF SUCH OFTEN USED TERMS AS "RAGG WAVELETS "RAGG PATCHES ANDSOON ASIFSUCHTHINGSHADAREALEXISTENCEOUTSIDEOFTHEIREMERGENCE ASANARTIFACTOFAFILTEROPERATION4HISCONFUSIONOFCONCEPTSMIGHTBEAVOIDEDBY VISUALIZINGTHERADARASEXTRACTINGTHEh"RAGGLINEvFROMTHESPECTRALCOMPOSITIONSOF THOSESURFACEFEATURESTHATCONTAINAWAVEOFLENGTHKCOSXINTHEIR&OURIERREPRE SENTATION INDEPENDENTOFTHEEXISTENCEOFSUCHAWAVEASAREALOBJECT .EVERTHELESS THISDIRECTLINEARRELATIONBETWEENRADARCROSSSECTIONANDTHEOCEAN OGRAPHERSDESCRIPTOROFTHESEASURFACEHASHADAPOWERFULINFLUENCEONTHINKINGABOUT THEPHYSICALORIGINSOFSEACLUTTER)TISAPPEALINGINITSSIMPLICITY ANDITSUGGESTSA DIRECTWAYBOTHTOPREDICTRADARCLUTTERFROMMEASUREMENTSORFORECASTSOFTHESEASPEC TRUMAND INVERSELY TOUSERADARBACKSCATTERMEASUREMENTSTOPROVIDEREMOTESENSING OFTHESEASURFACEFOROCEANOGRAPHICANDMETEOROLOGICALAPPLICATIONSPROVIDED OF COURSE THATITCORRECTLYDESCRIBESTHISRELATIONSHIP !LTHOUGH%QSUCCESSFULLYPREDICTSTOST ORDER THECLUTTERRETURNSAT(& FREQUENCIES AT MICROWAVE FREQUENCIES THE SMALL WAVEHEIGHT ASSUMPTION ON WHICH THISMODELRESTSISVIOLATEDONANYREALSEASURFACE4HESMALL WAVEHEIGHTCONDITION EXPRESSEDBY%QMEANSTHATAT8BAND FOREXAMPLE THEMAXIMUMDEPARTUREOF THESEASURFACEFROMAFLATPLANEMUSTBEMUCHSMALLERTHANMM /THER#ALCULATIONAL3TRATEGIES )NSTEADOFEXPANDINGTHEEXPONENTIALINTHEINTE GRANDOF%Q ITSHOULDBEPOSSIBLE ATLEASTINPRINCIPLE TOREPLACE#Y DIRECTLY BYTHE&OURIERTRANSFORMOF7+ THEINVERSEOF%QFORN THUSPROVIDING ADIRECTFUNCTIONALRELATIONSHIPBETWEENTHERADARCROSSSECTIONANDTHESEAWAVESPEC TRUMWITHOUTTHERESTRICTIONSOFASMALL AMPLITUDEAPPROXIMATION4HISCUMBERSOME APPROACHINVOLVESEXTENSIVECOMPUTATIONSEVENTOOBTAINLIMITEDRESULTSININDIVIDUAL CASES ASSHOWNINWORKBY(OLLIDAYETAL )NANOTHERLIMITINGCASE THEBASICINTEGRALFORMULATIONOFTHE'"60ISSOLVEDIN THEOPTICALAPPROXIMATIONLARGEK RESULTINGINANEXPRESSIONCOMMONLYCALLEDTHE
£x°Îä
2!$!2(!.$"//+
SPECULARRETURN BECAUSEITSORIGINMAYBETRACEDTOPIECESOFTHESURFACETHATPROVIDE AREFLECTIONPOINTFORTHEINCIDENTWAVE 4HISEXPRESSIONISWRITTENFORAGAUSSIAN SEASURFACEINTHEFORM
S Y \ 2 \ S CSC Y EXP; COT Y S =
WHERESISTHERMSSURFACESLOPEAND2ISTHEFLAT SURFACEREFLECTIONCOEFFICIENTFORNOR MALINCIDENCE4HISISTHETYPEOFSCATTERINGALLUDEDTOINCONNECTIONWITHTHEHIGHGRAZ INGANGLERETURNSDISCUSSEDIN3ECTIONTHETENDENCYOFRTOLEVELOFFFORGRAZING ANGLESCLOSETOSEE&IGURESAND MAYBEASCRIBEDTOTHISMECHANISM &ROMWHATHASBEENSAIDTHUSFAR ITCANBESEENTHATSTRICTANALYTICALSOLUTIONSVIA THE'"60APPROACHAPPEARTORUNINTODEADENDSINTRACTABLEFORMALEXPRESSIONSINTHE FORMOF%Q SMALL AMPLITUDEAPPROXIMATIONSINTHEFORMOF%QTHATMAKE LITTLESENSEFORMICROWAVESCATTERINGFROMREALSEASURFACES OROPTICALLIMITSSUCHAS %QTHATRELATETOTHEPROBABILITYDENSITIESOFSPECULARLYREFLECTINGSURFACESLOPES )TAPPEARS THEREFORE THATTHEUSEOFINTEGRALFORMULATIONSINTHEPRACTICALSOLUTIONOF THESEACLUTTERPROBLEMATMICROWAVEFREQUENCIESWILLREQUIRESOMETHINGMORE #OMPOSITE 3URFACE(YPOTHESES 3INCEITISNOTCLEARHOWTOEXTENDSTRAIGHTFOR WARD'"60SOLUTIONSBEYONDTHELIMITINGAPPROXIMATIONSDESCRIBEDABOVE AHEURISTIC MODELWASDEVELOPEDTHATVIEWEDTHESEAASACARPETOF"RAGGSCATTERINGhWAVELETSv MODULATEDBYTHEMOTIONSOFTHELARGERWAVESONTHESURFACEn4HISCOMPOSITE SURFACEMODELISOFTENREFERREDTOASTHETWO SCALEMODEL INWHICHITISIMAGINEDTHAT THESURFACE WAVESPECTRUMCANSOMEHOWBESEPARATEDINTOTWOPARTS ONECONTAINING LOW AMPLITUDEh"RAGGSCATTERINGWAVELETSvWHOSEINTEGRATEDRMSWAVEHEIGHTSATISFIES THECONDITIONSOF%QANDANOTHERTHATCONTAINSONLYTHELONGERWAVESTHATTILT ANDSTRETCHANDOTHERWISEMODULATETHE"RAGGWAVES AFFECTINGTHE"RAGGSCATTERERS THROUGHAMODULATIONTRANSFERFUNCTION ASWELLASPROVIDINGASPECULARCOMPONENT RESEMBLING%Q/THERASSUMPTIONSINCLUDETHAT THECORRELATIONLENGTHSOF THESHORT"RAGGWAVESBELONGENOUGHTHATARESONANTINTERACTIONISPOSSIBLE BUTSHORT ENOUGHTHATADJACENTAREASONTHESURFACECONTRIBUTETOTHETOTALSIGNALINRANDOMPHASE NOTEHOWh"RAGGWAVESvAREVIEWEDHEREASPHYSICALOBJECTS AND THELONGWAVES THATTILTANDMODULATETHESHORTWAVESHAVERADIIOFCURVATURESUFFICIENTLYLARGETHATTHE CURVATUREOVERTHECORRELATIONLENGTHOFTHEh"RAGGPATCHESvISSMALLINSOMESENSE)N ITSSIMPLESTANDMOSTCOMMONLYUSEDhTILTvFORM ITINTERPRETSRX IN%Q AS THECROSSSECTIONOFAPATCHWITHLOCALGRAZINGANGLEX R @ WHERE@ISTHELOCAL WAVESLOPEANDXISTHEMEANGRAZINGANGLE&ORTHESIMPLEONE DIMENSIONALCASE THISQUANTITYISAVERAGEDOVERTHESEASLOPEANGLEDISTRIBUTIONP@ YIELDING c
S Y ¯ S Y A PA DA
c
&ORAMOREGENERALTWO DIMENSIONALSEA THELOCALGRAZINGANGLEISAFUNCTIONOFTHE SLOPESINANDNORMALTOTHEPLANEOFINCIDENCE SOFOREACHPOLARIZATIONP THEANGLE FUNCTION&PX INRX BECOMESACOMPLEXMIXTUREOFTHEANGLEFUNCTIONSOFBOTH POLARIZATIONS0LANTPROVIDESACOMPREHENSIVEDISCUSSIONOFTHISMODEL%XTENSIONS OFTHISMODELINTOWHATMIGHTBECALLEDATHREE SCALEMODELAREGUIDEDBYTHESAME IDEASTHATLEDTOTHETWO SCALEMODEL !NADDITIONALADHOCSPECTRALPARTITIONIS INTRODUCEDBETWEENTHELONGESTANDSHORTESTWAVECOMPONENTSOFTHESEASPECTRUM BUT THISPRODUCEDONLYMODESTIMPROVEMENT
3%!#,544%2
£x°Î£
!LTHOUGHSUCHCOMPOSITE SURFACEMODELSMAYLEAVETHEIMPRESSIONTHATTHEYHAVE EMERGEDASARIGOROUSPRODUCTOFANINTEGRALFORMULATIONOFTHE'"60 ITISCLEARTHAT THEYARENOTREALLYSCATTERINGTHEORIES BUTINSTEADSCATTERINGPICTURESASSEMBLEDFROM AGROUPOFMOREORLESSPLAUSIBLEASSUMPTIONS"UTWITHTHEFAILUREOFTHEMOREFORMAL '"60THEORIESTOPROVIDEAGENERALFRAMEWORKFORPREDICTINGANDUNDERSTANDINGSEA CLUTTER THESEMODELSHAVEBECOMETHEBASISFORMOSTANALYTICALAPPROACHESTOMICRO WAVESCATTERINGFROMTHESEA &IGURE COMPARES A SAMPLE OF .2, &2 DATA TAKEN AT HIGH WIND SPEEDS KN WITHTHEPREDICTIONSOFTHEPURE30-"RAGGMODELINTHEFORMOF%Q FOR6 POLARIZATIONANDTHETWO SCALEMODELINTHEFORMOF%Q FOR( POLARIZATION 4HE WAVE SPECTRUM USED WAS THE 0HILLIPS SPECTRUM GIVEN IN %Q (ISTORICALLY COMPARISONSOFTHISTYPEHAVEBEENUSEDOFTENTOPROVIDESUPPORTFORTHE"RAGGSCAT TERING HYPOTHESIS AND THE AGREEMENT OFTEN LOOKS GOOD ESPECIALLY FOR VERTICAL POLARIZATIONATTHEHIGHERWINDSPEEDS9ETWHYTHISISSOREMAINSAPUZZLINGCURIOSITY )NTHISEXAMPLE THEWINDSPEEDSAREHIGHSOTHESEAWILLBEROUGH BUTITWASNOTED ABOVETHATTHE30-APPROXIMATIONUSEDIN&IGUREREQUIRESWAVEHEIGHTSMUCH LESSTHANACENTIMETER SOTHISAPPROXIMATIONISTOTALLYINVALIDFORTHESEDATA-OREOVER THE0HILLIPSSPECTRUMWASUSEDASTHESEASURFACESPECTRUM BUTTHEREISNOEVIDENCE THATTHISSPECTRUMHOLDSDOWNTOTHEREQUIREDCAPILLARYWAVELENGTHOFABOUTCM )NFACT THENATUREOFTHESEASPECTRUMINTHISRANGEREMAINSUNCERTAINANDHASBEEN REFERREDTOAShONEOFTHEMOSTEXCITINGUNSOLVEDPROBLEMSOFTHESEASURFACEv4HE PRIMARYEFFECTOFTHETWO SCALEMODELISSIMPLYTORAISETHEINAPPLICABLE30-VALUES FOR( POLARIZATION WHICHAREDROPPINGSHARPLYWITHGRAZINGANGLE BYINCLUDINGHIGHER LOCALANGLESVIA%Q4HEREWOULDBELITTLESENSIBLEEFFECTONTHEMORECONSTANT VERTICALRETURNS&INALLY THEPOLARIZATIONDIFFERENCESTHEMSELVESHAVEBEENSHOWNTO DERIVEENTIRELYFROMTHEBEHAVIOROFTHEREFLECTIONCOEFFICIENTSATTHEUNDERLYINGSURFACE SEE FOREXAMPLE 7RIGHTAND7ETZEL ANDSOARENOTANINTRINSICPARTOFTHE"RAGG HYPOTHESIS AND WOULD APPLY TO ANY SMALL PERTURBATION ON THE SURFACE .EVERTHELESS AGREEMENTBETWEENMEASUREMENTANDPREDICTIONOFTHETYPEILLUSTRATEDIN&IGURE
&)'52% #OMPARISONOFTHEPREDICTIONSOFTHE"RAGGHYPOTHESISWITH.2, &2 DATA HEAVY LINES FOR HIGHER WIND SPEEDS KT DASH DOTTED LINES 30- "RAGG DASHED LINE TWO SCALE MODEL FOR ( POLARIZATION ONLY ASSUMING MEAN SEASLOPESAFTER6ALENZUELA
£x°ÎÓ
2!$!2(!.$"//+
HASKEPTALIVECREDIBILITYINTHE"RAGGSCATTERINGHYPOTHESISINSPITEOFTHECLEARVIOLA TIONSOFCONDITIONSANDNONSEQUITURSNOTEDABOVE ASWELLASTHELACKOFAPROPERTHEORY ARGUEDFROMFIRSTPRINCIPLES 4HEFAILUREOFTHISMODELTOACCOUNTFORSEASPIKESANDOTHERNON 2AYLEIGHRETURNS NOTEDIN3ECTIONHASLEDTOANAUGMENTATIONOFTHETWO SCALECOMPOSITESURFACETO INCLUDEBREAKINGWAVES APRESUMEDSOURCEOFTHESERETURNS/NEOFTHELATESTOFTHESE TWO SCALE PLUS MODELS MAY BE FOUND IN +UDRYAVTSEV ET AL WHERE BREAKING WAVEEFFECTSAREINCORPORATEDANALYTICALLYTHROUGHTHE0HILLIPSEXPRESSIONFORTHE DENSITY OF BREAKING FRONTS AS A FUNCTION OF WIND SPEED THE PARAMETER ,C NOTED IN3ECTION WITHTHESCATTERINGBEHAVIORBASEDON7ETZELSPLUMEMODELSEE h3CATTERING BY 3URFACE &EATURESv 4HE RESULT IS A SIGNIFICANT IMPROVEMENT IN SEA SCATTERPREDICTIONS EMPHASIZINGTHEIMPORTANCEOFBREAKINGINTHESCATTERINGSCENE !NEXAMPLEOFTHISIMPROVEMENTISSHOWNIN&IGURE WHEREEXPERIMENTALDATA FORTHEPOLARIZATIONRATIORELATIVETOWINDDIRECTIONWASOBTAINEDFROMTHE0OLRAD PROGRAM/NEOFTHEMAJORCLAIMSFOR"RAGGMODELSHASBEENTHEIRAPPARENTABIL ITYTOAGREELOOSELYWITHTHEOBSERVEDPOLARIZATIONRATIOSOFSEACLUTTERRETURNS AND IN&IGURE ASIN&IGURE THEDATAWERECOMPAREDTOTHEPREDICTIONSOFTHE 30-PURE "RAGGMODELANDTHETWO SCALEMODEL WHILEADDINGTHETWO SCALE PLUS MODEL WHICH INCORPORATES THE EFFECTS OF BREAKING WAVES )N THIS CASE THE "RAGG MODELANDTHETWO SCALEMODELDERIVEDFROMITCLEARLYFAILTODESCRIBETHEOBSERVED BEHAVIOROFTHEPOLARIZATIONRATIO WHILETHEINCLUSIONOFBREAKINGWAVESFULLMODEL PROVIDES A SURPRISINGLY FAITHFUL REPRODUCTION OF THE DATA EVEN AT THE HIGH GRAZING ANGLE OF 4HE 8 BAND DATA ILLUSTRATED PREVIOUSLY IN &IGURE A B CAN ALSO BESHOWNTOCORROBORATETHEPREDICTIONSOFTHISMODELFORASIMILARWINDSPEEDAND GRAZINGANGLE THUSFURTHERSUPPORTINGTHESUSPICIONTHATBREAKING WAVEEVENTSWILL CONTRIBUTEIMPORTANTLYTOSEACLUTTEROVERMOSTOFTHEhROUGHSURFACEvREGIMEOFGRAZ INGANGLESATTHESEWINDSPEEDS
&)'52% 0OLARIZATION RATIO VERSUS WIND DIRECTION FOR 8 BAND RADAR AT GRAZING ANGLE AND WIND ABOUT KT 0OINTS EXPERIMENTAL DATA FROM 0OLRADEXPERIMENTDASHEDLINEPURE30-"RAGGDASHED DOTTEDLINETWO SCALE"RAGGSOLIDLINETWO SCALE PLUSMODELINCLUDINGBREAKINGWAVESAFTER +UDRYATSEVETALÚ4HE!MERICAN'EOPHYSICAL5NION
3%!#,544%2
£x°ÎÎ
3CATTERINGBY3URFACE&EATURES !BREAKINGWAVE WITHPLUMESOFWATERCAS CADINGDOWNITSFACEANDPERHAPSAHALOOFSPRAYABOVE ISONLYONEOFTHERICHASSORT MENTOFSCATTERINGELEMENTSAPPEARINGONTHESEASURFACEINCLUDINGWEDGES CUSPS MICROBREAKERS HYDRAULICSHOCKS PATCHESOFTURBULENCE ANDGRAVITY CAPILLARYWAVES BOTHWIND DRIVENANDPARASITIC ANYORALLOFWHICHCOULDCONTRIBUTETOTHESCATTERED CLUTTERSIGNAL &OREXAMPLE THECOMMON3TOKESWAVEHASAQUASI TROCHOIDALSTRUCTURETHATRESEM BLESAWEDGEONTHESURFACE SOWEDGESCATTERMIGHTDESCRIBEANIMPORTANTASPECTOFSEA CLUTTER 4HESCATTERINGMODELISUSUALLYSOMEVARIANTOFTHEFAMILIARGEOMETRICAL THEORYOFDIFFRACTION'4$ WHICHISSTRICTLYAPPLICABLETOTHEBACKSCATTERPROBLEM ONLYWHENTHEEDGEOFTHEWEDGEISNORMALTOTHEPLANEOFINCIDENCE.EVERTHELESS THE CROSSSECTIONPREDICTIONSATTHELOWERGRAZINGANGLESFORBOTHPOLARIZATIONSSHOWTRENDS SIMILARTOTHEPREDICTIONSOFTHE"RAGGORCOMPOSITE SURFACEMODELS /NEMAJORPROBLEMWITHALLMODELSBASEDONSCATTERINGFEATURESIMULATIONSISTHE LACKOFRELIABLEINFORMATIONABOUTTHESHAPES SIZES ORIENTATIONS SPEEDS LIFETIMES AND STATISTICS OF THE FEATURES THEMSELVES 4HUS ALTHOUGH THERE IS OFTEN GUIDANCE FROMEITHEROBSERVATIONORTHEORY THEPREDICTIONSOFSUCHMODELSWILLBEBASEDON UNCERTAINASSUMPTIONSABOUTTHESECRUCIALPARAMETERS!SANEXAMPLE WATERSURFACE STABILITYARGUMENTSPREVENTTHEINTERIORANGLEOFASHARPENINGWAVECRESTFROMFALL INGBELOW WHICHTHENBECOMESACONVENIENTMEASUREOFTHEWEDGEANGLEIN WEDGE SCATTERINGMODELS)N&IGURE THEOVERALLSCALEOFWEDGESCATTERINGAS CALCULATEDBYTHE'4$WASADJUSTEDTOLOCATETHECLUSTEROFCROSSSECTIONSATTHELEVEL OFTHEEXPERIMENTALVALUES7EDGESAPPEARTOMODELTHEQUALITATIVEBEHAVIORWITH BOTHPOLARIZATIONSFAIRLYWELLATTHELOWERGRAZINGANGLES &IGUREALSOINCLUDESTWOADDITIONALSIMPLESCATTERINGMODELSFORCOMPARISON ,AMBERTSLAW MENTIONEDINCONNECTIONWITH&IGUREA B EXPRESSESTHECROSSSEC TIONINTHEFORMR !SINX WHERE!ISTHESURFACEALBEDO#HOOSING! D" AREASONABLEVALUEFORMICROWAVEFREQUENCIES GIVESAFAIRLYGOODMATCHTOTHEVERTI CALLYPOLARIZEDRETURNSOVERAWIDERANGEOFGRAZINGANGLES4HEFACETMODEL EXPRESSED
&)'52% #OMPARISON OF SEVERAL AD HOC FEATURE MODELS WITH .2, &2 DATA DATATHESAMEASSHOWNIN&IGURE
£x°Î{
2!$!2(!.$"//+
BY%QANDTHOUGHTTODESCRIBECLUTTERATTHEHIGHERGRAZINGANGLES ISSHOWN FORKTSEAS4HEGENERALBEHAVIORDESCRIBEDBYTHESETWOMODELSSEEMSTOAGREE ABOUTASWELLASANYOTHER ALTHOUGHTHEYTOOMUSTEMPLOYARBITRARYASSUMPTIONSTO OBTAINREASONABLEFITSTOTHEDATA SOTHESIGNIFICANCEOFTHISAGREEMENTISDIFFICULTTO ASSESS(OWEVER ONEMIGHTDEDUCEFROM&IGURETHATSHARPTHINGSLIKEWEDGES DOMINATETHECLUTTERATSMALLGRAZINGANGLES FLATTHINGSLIKEFACETS ATLARGEANGLES ANDGENERALLYROUGHTHINGSATTHEINTERMEDIATEANGLES 4HE THEORY OF SCATTERING FROM BREAKING WAVES REFERENCED IN CONNECTION WITH &IGURE WAS ORIGINALLY MOTIVATED BY AN ATTEMPT TO EXPLAIN THE COMPLEX BEHAVIOROFSEASPIKESATLOWGRAZINGANGLESOBSERVEDBY,EWISAND/LIN4HIS THEORY WAS BASED ON THE PLUME MODEL OF THE MOST COMMON SPILLING BREAKER IN WHICH A WATER PLUME IS EMITTED AT THE SPILLING CREST AND MOVES DOWN THE FRONT FACETHESCATTERINGBEHAVIORWASSUPPLIEDBYMULTIPATHILLUMINATIONINVOLVING REFLECTIONSFROMTHEFACEOFTHEWAVE4HEELABORATIONOFTHISMODELEXPLAINED MUCHOFTHECOMPLEXBEHAVIOROFTHEOBSERVEDSEASPIKESHOWEVER LIKEALLOTHER MODELSBASEDONSCATTERINGFEATURES ITWASNECESSARYTOMAKEASSUMPTIONSABOUT THESIZES SHAPES ANDLIFETIMESOFTHESCATTERINGPLUMES4HESEPARAMETERSWEREALL INFERREDFROMOBSERVATIONOFREALSEASURFACES ANDTHERESULTINGPREDICTIONSWERE SURPRISINGLYGOOD!DDITIONALLY ITSSUCCESSINTHETWO SCALE PLUSMODELMENTIONED ABOVEPROVIDESFURTHERCREDIBILITY !LTHOUGH SCATTERING FEATURES HAVE BEEN INTRODUCED MAINLY IN CONNECTION WITH LOW GRAZING ANGLE SEA CLUTTER SEE 7ETZEL FOR A DETAILED DISCUSSION THERE IS EVI DENCE ASNOTEDABOVE TOBELIEVETHATFEATURESCATTERINGOPERATESATALLGRAZINGANGLES #ONSIDERINGTHEFAILUREOFSCATTERINGTHEORIESFORMULATEDASA'"60TOPROVIDEANY PREDICTIONSBEYONDTHOSEINCERTAINLIMITING CASEAPPROXIMATIONSANDTHEPRECARIOUS NATUREOFTHELOGICALINFRASTRUCTUREOFTHE"RAGGHYPOTHESISINMICROWAVESCATTERING FROMANATURALSEA ITISQUITEPOSSIBLETHATFURTHERCAREFULCONSIDERATIONOFTHEACTUAL SCATTERINGFEATURESPRESENTONTHESEASURFACEWILLIMPROVEOURUNDERSTANDINGOFSEA CLUTTERINTHEFUTURE )MPLICATIONS OF 3URFACE 'EOMETRY 4HE APPROXIMATIONS TO THE '"60 DIS CUSSEDABOVEWEREALLFORMULATEDINTHEFREQUENCYDOMAIN BUTATIME DOMAINMODEL FORSEASCATTERPOINTSTOAPOSSIBLEGENERALSURFACE GEOMETRICORIGINFORTHESURFACE RETURNS 4HE MODEL INTRODUCES THE IDEA THAT THE BASIC SCATTERING ELEMENTS OF A SURFACEARELOCALIZEDATPOINTSOFHIGHSURFACECURVATURE ASATTHESHARPTIPSOFSMALL 3TOKESWAVESORATTHECORNEROFAPLUMEINTERSECTINGTHEFRONTFACEOFABREAKING WAVE5SINGAC FUNCTIONASAPROBINGPULSE ANAPPROXIMATEEXPRESSIONFORTHESCAT TERINGCROSSSECTIONWASFOUNDASAFUNCTIONOFSURFACECURVATURE#RTO WHERETOIS THEROUND TRIPTIMEFROMTHERADARTOAPOINTRTO ONTHESURFACE
RTO "X S TO # CTOCOSX
WITH " A COMPLICATED TRIGONOMETRIC FUNCTION OF GRAZING ANGLE X SURFACE SLOPE S ANDTO4HEFACTOR"PEAKSATPOINTSOFSPECULARREFLECTION SO%QEXPRESSESTHE EFFECTSOFSPECULARGLINTSASWELLASSHARPCURVATURES!LTHOUGHTHEORIGINALTHEORY ISBASEDONAPHYSICALOPTICSFORMULATIONFORASCALARFIELDSEE3ANGSTONFORTHE VECTORFORM SOMESUPPORTFORITSIMPLICATIONSCANBEGAINEDFROMAPLOTOFTHESQUARE OFSURFACECURVATUREOVERAREALSEASURFACE&IGUREASHOWSTHESURFACESLOPE MEASUREDOVERASHORTSEGMENTOFSURFACEINTHE'ULF3TREAM WITHTHECORRESPOND INGCURVATURE SQUAREDPROFILEBELOW4HECLUTTERCROSS SECTIONDEFINEDFORTHISPROFILE
3%!#,544%2
£x°Îx
#%# ! #$
!#!& #"
$!%#$!
! $!
-ETERS
4IMES
A
B
&)'52% A -EASUREDSLOPETOPCURVE OVERASAMPLEDSURFACEINTHE'ULF3TREAM WITHTHECOR RESPONDINGSQUAREOFTHESURFACECURVATUREBELOWB 7AVE TANKMEASUREMENTOFRADARSCATTERINGFROMAN EVOLVINGBREAKINGWAVE CORRELATEDWITHWAVESURFACEHEIGHTVARIATIONSFROM-!3LETTENAND*#7EST Ú4HE!MERICAN'EOPHYSICAL5NION
BY%QCLEARLYBEARSARESEMBLANCETOSOMEOFTHEHIGHRESOLUTIONRETURNSSHOWN IN&IGURE-OREOVER THESESPIKYRETURNSARECORRELATEDWITHJUSTTHEKINDOF SURFACE BUMPS AND WRINKLES AND SLOPE DISCONTINUITIES THAT HAVE BEEN IDENTIFIED AS SOURCESOFSEASPIKESINLABORATORYTANKMEASUREMENTS !NEXAMPLEISSHOWN IN &IGURE B WHERE AN ULTRA HIGH RESOLUTION RADAR LOOKS AT THE RETURN FROM A BREAKINGWAVEWHOSESURFACEISEVOLVINGASPLOTTEDABOVETHERADARSIGNAL7ESEE THATTHESPIKESAPPEARATTHEPOINTSOFMAXIMUMSURFACECURVATURE ALTHOUGHTHELARGE SIGNALPEAKISPROBABLYASPECULARREFLECTIONFROMTHEINITIALBREAKINGFRONT )TISOFTENOVERLOOKEDTHATTHEPRESUMEDORIGINOFSEASCATTERISSUGGESTEDBYTHE KINDOFMEASURINGINSTRUMENTBEINGUSED WHICHINTURNDETERMINESTHEMOSTAPPRO PRIATETHEORETICALBASISIE THEhTHEORYOFTHEEXPERIMENTv)FYOUGOTOSEAWITH A#7RADARANhAVERAGINGWAVESPECTROMETERvYOUWILLBESELECTINGASPECTRAL LINE BY LONG INTEGRATION TIMES AND INTERPRET THE ORIGIN AS A WAVE EFFECT NAMELY A h"RAGG RESONANCEv /N THE OTHER HAND IF YOU USE A HIGH RESOLUTION PROBEA RADARMICROSCOPETHECLUTTERSCENEWILLBEPOPULATEDBYHIGHLYLOCALIZEDSCATTER INGEVENTS ORSEASPIKES ISOLATEDBYASHORT PULSE WIDE BANDWIDTHSIGNAL)NTHIS CASE THEMOSTAPPROPRIATEhTHEORYOFTHEEXPERIMENTvISTHETIME DOMAINFORMALISM DESCRIBEDABOVE /THERWAYSOFVIEWINGSEACLUTTERINTERMSOFSURFACEGEOMETRYCHARACTERIZETHESEA ANDTHECLUTTERASFRACTALPROCESSES ORSEEKPARAMETERSDESCRIBINGITSCOMPLEXITYBY DEFININGAhSTRANGEATTRACTORv5NFORTUNATELY THESESTUDIESDONOTSEEMTOCONTAIN ANYUSEFULINSIGHTSINTOTHEPHYSICALSCATTERINGPROCESSESATTHESURFACE EXCEPT PER HAPS TOCONCLUDETHATSEACLUTTERARISESFROMMULTIPLESOURCES WHICHWEALREADYKNOW /NTHEOTHERHAND THEIDENTIFICATIONOFCHANGESINTHECHARACTERISTICMEASURESOFTHESE PROCESSESEG FRACTALDIMENSIONANDEMBEDDINGDIMENSION HAVEBEENPROPOSEDASA WAYTOIDENTIFYTHEPRESENCEOFTARGETSINCLUTTER
£x°ÎÈ
2!$!2(!.$"//+
.UMERICAL -ETHODS 7ITH RAPID INCREASES IN COMPUTER SPEED IT HAS BECOME PRACTICAL TO SOLVE CERTAIN SCATTERING PROBLEMS BY NUMERICAL METHODS THEREBY SIDE STEPPINGTHEINTRODUCTIONOFTHEAPPROXIMATIONSREQUIREDBYTHEANALYTICALSOLUTIONS DESCRIBEDABOVE)NSURFACESCATTERING PARTICULARLYFORTHECONTINUOUSSEASURFACE THE METHODOFCHOICEAPPEARSTOBESOMEVARIANTOFTHE-ETHODOF-OMENTS!NEXACT INTEGRALEQUATIONFORTHESURFACECURRENTSEXCITEDBYANILLUMINATINGFIELDISSOLVED NUMERICALLYOVERAGRIDOFPOINTS WHERETHEFLEXIBILITYANDACCURACYOFTHESOLUTION DEPENDS ESSENTIALLY ONTHEGRIDSPACING THESIZEOFTHESURFACEFEATURESCOMPAREDTO THEILLUMINATINGWAVELENGTH THEEXTENTOFTHESURFACEOVERWHICHTHEGRIDISLAID AND THEEFFICIENCYOFTHECOMPUTINGALGORITHMSUSEDINWHATAREEXTENSIVECALCULATIONS /NCEFOUNDFORANENSEMBLEOFSURFACEREALIZATIONS THESECURRENTSCANBEUSEDINA SCATTERINGINTEGRALOVEREACHOFTHESURFACESTOGENERATEANENSEMBLEOFSCATTEREDFIELDS WHICHAREFINALLYAVERAGEDINTOASURFACESCATTERINGCROSSSECTION!LTHOUGHTHESE METHODSAREOFTENVIEWEDASTHEhGOLDSTANDARDvFORDOINGSCATTERINGCALCULATIONS THEIR COMPLEXITYANDDIFFICULTYGENERALLYRESTRICTTHEIRAPPLICATIONTOIDEALIZEDORLABORATORY SURFACESTRUCTURES WHERETHEYSIMPLYCONFIRMTHAT-AXWELLSEQUATIONSCONTINUETO BEVERIFIEDINSCATTERINGEXPERIMENTS.EVERTHELESS SUCHNUMERICALSIMULATIONSCANBE INFORMATIVEINIDENTIFYINGTHESOURCEOFPARTICULARSCATTERINGEVENTS SUCHASSEASPIKES ALONGWITHTHEIRDEPENDENCEONSUCHRADARPARAMETERSASGRAZINGANGLE POLARIZATION ANDFREQUENCY 2OLEOF,ABORATORY3TUDIES 4HESEASURFACEISANATURALSYSTEMCONTROLLEDBY THELAWSOFHYDRODYNAMICS"UTSOISABOWLOFSOUPORATANKOFWATERORARUSHING STREAMALL OF WHICH MIGHT SHARE CERTAIN BEHAVIORS WITH A SEA SURFACE WHILE PRE SENTINGAVENUEMUCHMOREAMENABLETOTHECOMFORTABLEINVESTIGATIONOFSCATTERING PHENOMENOLOGY7HILETHEREISTHEOBVIOUSMATTEROFSCALE ONEMIGHTENTERTAINTHE NOTIONTHATWHATISFOUNDTOHOLDINTHESMALLCOMPASSOFALABORATORYWAVETANKMIGHT TRANSFERWITHLITTLEALTERATIONTOTHEOPENOCEAN"UTTHISCERTAINLYCANNOTBETRUETHE SEASURFACEISSTRUCTUREDBYLARGE SCALEWINDSYSTEMS IMPOSSIBLETODUPLICATEUNDER LABORATORYCONDITIONS4HEREFORE THELABORATORYISUSEDALMOSTEXCLUSIVELYTOSTUDYIN DETAILHOWANELECTROMAGNETICWAVEINTERACTSWITHSOMERESTRICTEDANDWELL CONTROLLED ASPECTOFSURFACEPHENOMENOLOGYTHATISTHOUGHTTOBEINVOLVEDINTHEOPENSEA 4HEREISAVASTLITERATUREEXTENDINGOVERALMOSTYEARSREPORTINGAWIDEVARIETYOF LABORATORYEXPERIMENTSONMICROWAVESCATTERINGFROMADISTURBEDWATERSURFACE4HE EARLIESTAPPEARTOBECAREFULSMALL SCALEEXPERIMENTSINTHEMID STOCONFIRMTHE EXISTENCEOF"RAGGSCATTERATCENTIMETERWAVELENGTHS WHILEATTHEOTHERENDOFTHE EXPERIMENTALSCALE THECHAOSOFAFULL SCALEBREAKERWASSIMULATEDBYSUBMERGINGA HYDROFOILACROSSAMETERWIDECIRCULATINGWATERCHANNELDRIVENBYMEGAWATTSOF TURBINEPOWER"UTMOSTLABORATORYEXPERIMENTSAREMOREMODEST INVOLVINGALONG WAVETANK PERHAPSAMETERORTWOACROSS WITHTHEWAVESYSTEMPRODUCEDBYEITHERA CONTROLLEDWINDORAPROGRAMMEDWAVEMAKER 4OILLUSTRATEAFEWOFTHEEXPERIMENTSANDTHEIRRESULTS+WOHAND,AKEMEASURED 8 BANDRETURNSFROMGENTLEBREAKINGWAVESINAWAVETANKANDFOUNDTHATSPECULAR AND CURVATURE SCATTERING APPEARED TO DOMINATE OVER "RAGG SCATTERING FOR SUCH SUR FACES+ELLERETAL MEASURED8 BANDRETURNSANDSURFACESPECTRUMSIMULTANEOUSLY INAWAVETANKANDFOUND"RAGG BASEDTHEORIESMIGHTHAVECREDENCEATINTERMEDIATE GRAZINGANGLESANDSTRONGWINDS BUTWEREUNABLETOACCOUNTFORSCATTERINGBEHAVIOR UNDEROTHERCONDITIONS3LETTENAND7EST MADEATWO PRONGEDAPPROACHTOBREAK INGWAVESCATTER CONSTRUCTINGAMETALLICMODELOFABREAKINGWAVE COMPARINGITS
3%!#,544%2
£x°ÎÇ
SCATTERINGPROPERTIESWITHNUMERICALCALCULATIONS ANDTHENGOINGTOTHEWAVETANK TOVERIFYTHESCATTERINGBEHAVIORFORREALWATERWAVES%RICSONETALGENERATEDA STATIONARYBREAKERINASMALLFLOWTUNNELANDCOMPAREDITSSCATTERINGPROPERTIESWITH ASPECULARPOINTCALCULATION#OAKLEYETALSETUPAHYDROFOILINAPOWERFULWATER CHANNEL GENERATINGALARGEBREAKINGWAVEFRONTTHATPRODUCEDRADARRETURNSCONSISTENT WITH,AMBERTS,AW ALONGWITHTHEPOLARIZATIONRATIOSIMPLIEDBYMULTIPATHREFLEC TIONSFROMTHEUNDISTURBEDFRONTFACE4HESEINVESTIGATORS ALONGWITHMANYOTHERS HAVEBEENEXPLORINGRADARSCATTERINGFROMWATERSURFACESINWAYSTHATCANBEEXPECTED TOCONTRIBUTESIGNIFICANTLYTOOURGROWINGUNDERSTANDINGOFSEACLUTTER
£x°xÊ -1 ,9Ê Ê " 1-" )NTHEEARLYDAYSOFRADAR THEIMPORTANCEOFKNOWINGTHESEACLUTTERENVIRONMENTLED TOMANYEXPERIMENTSUNDERAVARIETYOFCONDITIONS6ARIATIONSINQUALITYANDCOMPLETE NESS OF GROUND TRUTH CALIBRATION OF THE EQUIPMENT AND THE EXPERIMENTERS EXPERI ENCELEDTORESULTSTHATOFTENSHOWEDCONSIDERABLEINCONSISTENCYANDSUGGESTEDCLUTTER BEHAVIORTHATWASSOMETIMESMOREAFUNCTIONOFTHEVAGARIESOFTHEEXPERIMENTTHANOF THEPHYSICSOFTHECLUTTER!SDATAOFINCREASINGLYBETTERQUALITYACCUMULATED ITMIGHT HAVEBEENEXPECTEDTHATTHEBEHAVIOROFSEACLUTTERWOULDBEESTABLISHEDWITHINCREAS INGCONFIDENCE4HISHASNOTALWAYSBEENSO LEAVINGOURGENERALKNOWLEDGEABOUT SEACLUTTERTOBESUMMARIZEDROUGHLYASFOLLOWS&ORTHEHIGHEROFWINDSPEEDS ENCOUNTEREDOVERTHEWORLDSOCEANSGREATERTHANABOUTKT MICROWAVESEACLUT TERATINTERMEDIATETOHIGHGRAZINGANGLESHASLITTLEDEPENDENCEONFREQUENCY ANDTHE EFFECTSOFWINDSPEEDAREUNCERTAIN SEEMINGTODEPENDONPOLARIZATION WINDDIRECTION ANDGRAZINGANGLEINOFTENCONFUSINGWAYS9ETVARIOUSEMPIRICALDESCRIPTIONSANDSTA TISTICALCHARACTERIZATIONSAREAVAILABLETHATALLOWMUCHOFTHEUSEFULSEACLUTTERREGIME TOBEDESCRIBEDINWAYSTHATCANBEOFPRACTICALVALUETOTHERADARCOMMUNITY PROVIDED THATSOMECAREISTAKENINDEFININGANDOBSERVINGTHEPERTINENTPARAMETERS(OWEVER THEREAREMAJORAREASOFUNCERTAINTYPRESENTATANYWINDSPEED WHENEVERTHEGRAZING ANGLEGOESBELOWAFEWDEGREESANDTHESURFACEILLUMINATIONBEGINSTOFEELTHEEFFECTS OFREFRACTIONANDDIFFRACTION ANDATANYGRAZINGANGLE WHENEVERTHEWINDSPEEDIS LESSTHANABOUTKT WHEREPECULIARITIESANDUNCERTAINTIESINTHEGENERATIONOFSURFACE ROUGHNESSBEGINTOEMERGEMOSTSTRONGLY!TTHELOWGRAZINGANGLESENCOUNTEREDIN MARITIMERADAROPERATIONS SEACLUTTERBECOMESSPIKYANDINTERMITTENT REQUIRINGSPE CIALATTENTIONTOSIGNALPROCESSINGANDTHEINTERPRETATIONOFTHERADARSIGNAL-OREOVER FEATURESOFTHESEAENVIRONMENTSUCHASRAIN CURRENTS SLICKS ANDREFRACTIVEANOMALIES CANCONFUSETHERELIABLESEPARATIONOFTARGETRETURNSFROMCLUTTERARTIFACTS 4HEQUESTIONOFMICROWAVESEACLUTTERTHEORYREMAINSUNSETTLED4HEMOSTPOP ULAR MODEL THE TWO SCALE "RAGG MODEL IS ACTUALLY AN ASSEMBLAGE OF ASSUMPTIONS SUPPORTED BY CIRCUMSTANTIAL EVIDENCE THERE IS STILL NO CLEAR REASON WHY IT SHOULD WORKWHENITDOES)NFACT THEREISINCREASINGEVIDENCEFROMBOTHTHETANKANDTHE OPENOCEANTHATTHISMODELFAILSTOACCOUNTFORMANYASPECTSOFMEASUREDSEASCATTER BEHAVIOR!UGMENTINGITWITHATERMEXPRESSINGTHEEFFECTOFBREAKINGWAVESINACTIVE SEAS HAS IMPROVED PREDICTIONS BUT STILL PERPETUATES THE AD HOC CHARACTER OF COM POSITE SURFACEMODELS4HEORIESBASEDONSCATTERINGBYSURFACEFEATURESHAVEBEGUN TOSHOWPROMISE ANDATLEASTONEOFTHESEFEATURESTHEBREAKINGWAVEATVARIOUS SCALES MACRO TO MICROIS INCREASINGLY RECOGNIZED AS AN IMPORTANT CONTRIBUTOR TO
£x°În
2!$!2(!.$"//+
SEACLUTTERFORLOWGRAZINGANGLESANDSHORTPULSESINPARTICULAR4HEMAJORPROBLEM OFCHARACTERIZINGTHESEFEATURESINAMANNERUSEFULTOQUANTITATIVEPREDICTIONSISSTILL BEINGADDRESSED0ERHAPSTHEEXPRESSIONOFTHESCATTERINGPROPERTIESOFTHESURFACEIN TERMSOFANINTRINSICSURFACEPROPERTYLIKEITSFINE SCALECURVATUREMIGHTINTRODUCEAN ORGANIZINGPRINCIPLEFORTHEMANYBITSANDPIECESTHATPRESENTLYMAKEUPTHETHEORY OFSEASCATTER )NTHELASTEDITIONOFTHIS(ANDBOOK THEFINALSTATEMENTINTHISCHAPTERWAS h)TWILLBEINTERESTINGTOSEEWHATPROGRESSWILLHAVEBEENMADEINTHETHEORYOFSEA CLUTTER BY THE PUBLICATION OF THE NEXT EDITION OF THIS HANDBOOKv )T APPEARS THAT THE ANSWER ISNOT MUCH "UT THERE IS SOME EVIDENCE THAT THE THEORY OF SEA SCATTER IS GRADUALLYBEINGFREEDFROMTHEPARALYZINGMONOTHEISMOF"RAGGSCATTER SOTHEREIS HOPEFORTHEFUTURE
, ,
$%+ERR 0ROPAGATIONOF3HORT2ADIO7AVES .EW9ORK-C'RAW (ILL"OOK#OMPANY - ) 3KOLNIK )NTRODUCTION TO 2ADAR 3YSTEMS RD %D .EW 9ORK -C'RAW (ILL "OOK #OMPANY &%.ATHANSON 2ADAR$ESIGN0RINCIPLES ND%D .EW9ORK-C'RAW (ILL"OOK#OMPANY -7 ,ONG 2ADAR 2EFLECTIVITY OF ,AND AND 3EA RD %D .ORWOOD -!!RTECH (OUSE $#ROMBIE h$OPPLERSPECTRUMOFSEAECHOAT-CS v.ATURE VOL PPn *77RIGHT h!NEWMODELFORSEACLUTTER v)%%%4RANS VOL!0 PPn & ' "ASS ) - &UKS ! ) +ALMYKOV ) % /STRUVSKY AND! $ 2OSENBERG h6ERY HIGH FREQUENCY RADIO WAVE SCATTERING BY A DISTURBED SEA SURFACE v )%%% 4RANS VOL !0 PPn $"ARRICKAND10EAKE h!REVIEWOFSCATTERINGFROMSURFACESWITHDIFFERENTROUGHNESSSCALES v 2ADIO3CI VOL PPn $!TLAS 2 # "EAL 2! "ROWN 0 $E -EY 2 + -OORE # ' 2APLEY AND # 4 3WIFT h0ROBLEMSANDFUTUREDIRECTIONSINREMOTESENSINGOFTHEOCEANSANDTROPOSPHEREAWORKSHOP REPORT v*'EOPHYS2ES VOL# PPn $(OLIDAY '3T #YR AND.%7OODS h!RADAROCEANIMAGINGMODELFORSMALLTOMODERATE INCIDENCEANGLES v)NT*2EMOTE3ENSING VOL PPn $3+WOHAND"-,AKE h!DETERMINISTIC COHERENT ANDDUAL POLARIZEDLABORATORYSTUDY OFMICROWAVEBACKSCATTERINGFROMWATERWAVES PART3HORTGRAVITYWAVESWITHOUTWIND v )%%%*/CEANIC%NG VOL/% PPn ,"7ETZEL h%LECTROMAGNETICSCATTERINGFROMTHESEAATLOWGRAZINGANGLES vIN3URFACE7AVES AND&LUXES#URRENT4HEORYAND2EMOTE3ENSING CHAP ','EERNAERTAND7*0LANTEDS $ORDRECHT .ETHERLAND2EIDEL ,"7ETZEL h!TIMEDOMAINMODELFORSEASCATTER v2ADIO3CI VOL NO PPn -ARCHn!PRIL $-IDDLETONAND(-ELLIN h7IND GENERATEDSOLUTIONS !POTENTIALLYSIGNIFICANTMECHANISM INOCEANSURFACEWAVEGENERATIONANDWAVESCATTERING v)%%%*/CEANIC%NG VOL/% PPn 34ANGAND/(3HEMDIN h-EASUREMENTOFHIGH FREQUENCYWAVESUSINGAWAVEFOLLOWER v *'EOPHYS2ES VOL PPn 7*0IERSONAND,-OSKOWITZ h!PROPOSEDSPECTRALFORMFORFULLYDEVELOPEDSEASBASEDONTHE SIMILARITYTHEORYOF3!+ITAIGORODSKII v*'EOPHYS2ES VOL PPn
3%!#,544%2
£x°Î
/ - 0HILLIPS h3PECTRAL AND STATISTICAL PROPERTIES OF THE EQUILIBRIUM RANGE IN WIND GENERATED GRAVITYWAVES v*&LUID-ECH VOL PPn *ULY 7*0IERSON *RAND-!$ONELAN h2ADARSCATTERINGANDEQUILIBRIUMRANGESINWIND GENERATED WAVESWITHAPPLICATIONTOSCATTEROMETRY v*'EOPHYS2ES VOL# PPn 3!+ITAIGORODSKII h/NTHETHEORYOFTHEEQUILIBRIUMRANGEINTHESPECTRUMOFWIND GENERATED GRAVITYWAVES v*0HYS/CEANOGR VOL PPn "+INSMAN 7IND7AVES %NGLEWOOD#LIFFS .*0RENTICE (ALL /-0HILLIPS &,0OSNER AND*0(ANSEN h(IGHRANGERESOLUTIONRADARMEASUREMENTSOFTHE SPEEDDISTRIBUTIONOFBREAKINGEVENTSINWINDGENERATEDWAVES3URFACEIMPULSEANDWAVEENERGY DISSIPATIONRATES v*0HYS/CEANOG VOL * 7U h6ARIATIONS OF WHITECAP COVERAGE WITH WIND STRESS AND WATER TEMPERATURE v * 0HYS /CEANOGR VOL PPn /CTOBER /-0HILLIPS h2ADARRETURNSFROMTHESEASURFACEn"RAGGSCATTERINGANDBREAKINGWAVES v *0HYS/CEANOGR VOL PPn 700LANT h!NEWINTERPRETATIONOFSEASURFACESLOPEPROBABILITYDENSITYFUNCTIONS v*'EOPHYS 2ES VOL NO# P *#$ALEY *42ANSONE *!"URKETT AND*2$UNCAN h3EACLUTTERMEASUREMENTSONFOUR FREQUENCIES v.AVAL2ES,AB2EPT .OVEMBER '26ALENZUELAAND2,AING h/NTHESTATISTICSOFSEACLUTTER v.AVAL2ES,AB2EPT $ECEMBER .7'UINARD *42ANSONE *R AND*#$ALEY h6ARIATIONOFTHE.2#3OFTHESEAWITHINCREAS INGROUGHNESS v*'EOPHYS2ES VOL PPn *#$ALEY h7INDDEPENDENCEOFRADARSEARETURN v*'EOPHYS2ES VOL PPn +$7ARD #*"AKER AND37ATTS h-ARITIMESURVEILLANCERADAR0ART2ADARSCATTERINGFROM THEOCEANSURFACE v)%%0ROC VOL 0T& NO !PRIL 37ATTS +$7ARD AND24!4OUGH h4HEPHYSICSANDMODELINGOFDISCRETESPIKESINRADAR SEACLUTTER vPRESENTEDAT)%%%)NTERNATIONAL2ADAR#ONFERENCE (-ASUKO +/KAMOTO -3HIMADA AND3.IWA h-EASUREMENTOFMICROWAVEBACKSCATTERING SIGNATURESOFTHEOCEANSURFACEUSING8BANDAND+ABANDAIRBORNESCATTEROMETERS v*'EOPHYS 2ES VOL# PPn !)+ALMYKOVAND660USTOVOYTENKO h/N0OLARIZATIONFEATURESOFRADIOSIGNALSSCATTEREDFROM THESEASURFACEATSMALLGRAZINGANGLES v*'EOPHYS2ES VOL PPn )+ATZAND,-3PETNER h0OLARIZATIONANDDEPRESSIONANGLEDEPENDENCEOFRADARTERRAINRETURN v *2ES.AT"UR3TAND 3EC$VOL $ PPn &&EINDT 67ISMANN 7!LPERS AND7#+ELLER h!IRBORNEMEASUREMENTSOFTHEOCEANRADAR CROSSSECTIONAT'(ZASAFUNCTIONOFWINDSPEED v2ADIO3CI VOL PPn ,#3CHROEDER 023CHAFFNER *,-ITCHELL AND7,*ONES h!!&%2!$3#!4 '(Z MEASUREMENTS AND ANALYSIS 7IND SPEED SIGNATURE OF THE OCEAN v )%%% * /CEANIC %NG VOL/% PPn '0DE,OORAND0(OOGEBOOM h2ADARBACKSCATTERMEASUREMENTSFROM0LATFORM.OORDWIJK INTHE.ORTH3EA v)%%%*/CEANIC%NG VOL/% PPn *ANUARY !(#HAUDHRYAND2+-OORE h4OWER BASEDBACKSCATTERMEASUREMENTSOFTHESEA v)%%% */CEANIC%NG VOL/% PPn $ECEMBER & 4 5LABY 2 + -OORE AND! + &UNG -ICROWAVE 2EMOTE 3ENSING !CTIVE AND 0ASSIVE 6OL))) 2EADING -!!DDISON 7ESLEY0UBLISHING#OMPANY 3EC "3PAULDING $(ORTON AND0(UONG h7IND!SPECT&ACTORIN3EA#LUTTER-ODELING vPRESENTED AT)%%%)NTERNATIONAL2ADAR#ONFERENCE " , ,EWIS AND ) $ /LIN h%XPERIMENTAL STUDY AND THEORETICAL MODEL OF HIGH RESOLUTION BACKSCATTERFROMTHESEA v2ADIO3CI VOL PPn *0(ANSENAND6&#AVALERI h(IGHRESOLUTIONRADARSEASCATTER EXPERIMENTALOBSERVATIONSAND DISCRIMINANTS v.AVAL2ESEARCH,ABORATORY2EPORT.O
£x°{ä
2!$!2(!.$"//+
$4RIZNA h-EASUREMENTANDINTERPRETATIONOF.ORTH!TLANTIC/CEAN-ARINE2ADAR3EA3CATTER v .AVAL2ES,AB2EPT -AY 0"ECKMANN 0ROBABILITYIN#OMMUNICATION%NGINEERING .EW9ORK(ARCOURT "RACEAND7ORLD )NC 3ECT ' 6 4RUNK h2ADAR PROPERTIES OF NON 2AYLEIGH SEA CLUTTER v )%%% 4RANS VOL !%3 PPn 0(9,EE *$"ARTER +,"EACH #,(INDMAN "-,AKE (2UNGALDIER *#3HELTON ! " 7ILLIAMS 29EE AND ( #9UEN h8 BAND MICROWAVE SCATTERING FROM OCEAN WAVES v *'EOPHYS2ES VOL NO# PPn &EBRUARY -+ATZIN h/NTHEMECHANISMSOFRADARSEACLUTTER v0ROC)2% VOL PPn *ANUARY ,"7ETZEL h!MODELFORSEABACKSCATTERINTERMITTENCYATEXTREMEGRAZINGANGLES v2ADIO3CI VOL PPn ) - (UNTER AND 4 "! 3ENIOR h%XPERIMENTAL STUDIES OF SEA SURFACE EFFECTS ON LOW ANGLE RADARS v0ROC)%% VOL PPn ( 3ITTROP h8 AND +U BAND RADAR BACKSCATTER CHARACTERISTICS OF SEA CLUTTER v IN 0ROC 523) #OMMISSION )) 3PECIALIST -EETING ON -ICROWAVE 3CATTERING FROM THE %ARTH % 3CHANDA ED "ERN "'3MITH h'EOMETRICALSHADOWINGOFTHERANDOMROUGHSURFACE v)%%%4RANS VOL!0 PPn & " $YER AND . # #URRIE h3OME COMMENTS ON THE CHARACTERIZATION OF RADAR SEA ECHO v IN $IG)NT)%%%3YMP!NTENNAS0ROPAGAT *ULYn $ % "ARRICK * - (EADRICK 2 7 "OGLE AND $ $ #ROMBIE h3EA BACKSCATTER AT (& )NTERPRETATIONANDUTILIZATIONOFTHEECHO v0ROC)%%% VOL ##4EAGUE ',4YLER AND2(3TEWART h3TUDIESOFTHESEAUSING(&RADIOSCATTER v)%%% */CEANIC%NG VOL/% PPn *#7ILTSE 303CHLESINGER AND#-*OHNSON h"ACK SCATTERINGCHARACTERISTICSOFTHESEAIN THEREGIONFROMTO+-# v0ROC)2% VOL PPn '7%WELL --(ORST AND-44ULEY h0REDICTINGTHEPERFORMANCEOFLOW ANGLEMICRO WAVE SEARCH RADARS4ARGETS SEA CLUTTER AND THE DETECTION PROCESS v 0ROC /#%!.3 PPn 7+2IVERS h,OW ANGLERADARSEARETURNAT MMWAVELENGTH v&INAL4ECH2EPT 'EORGIA )NSTITUTE OF 4ECHNOLOGY %NGINEERING %XPERIMENT 3TATION #ONTRACT . # .OVEMBER , " 7ETZEL h/N MICROWAVE SCATTERING BY BREAKING WAVES v IN 7AVE $YNAMICS AND 2ADIO 0ROBINGOFTHE/CEAN3URFACE #HAP /-0HILLIPSAND+(ASSELMANNEDS .EW9ORK 0LENUM0RESS PPn ",(ICKS .+NABLE *+OVALY '3.EWELL *02UINA AND#73HERWIN h4HESPEC TRUM OF 8 BAND RADIATION BACKSCATTERED FROM THE SEA SURFACE v * 'EOPHYS 2ES VOL PPn '26ALENZUELAAND2,AING h3TUDYOFDOPPLERSPECTRAOFRADARSEAECHO v*'EOPHYS2ES VOL PPn 670IDGEON h$OPPLERDEPENDENCEOFSEARETURN v*'EOPHYS2ES VOL PPn 95-ELNICHUKAND!!#HERNIKOV h3PECTRAOFRADARSIGNALSFROMSEASURFACEFORDIFFERENT POLARIZATIONS v)ZV!TMOS/CEANIC0HYS VOL PPn *77RIGHT AND7 # +ELLER h$OPPLER SPECTRA IN MICROWAVE SCATTERING FROM WIND WAVES v 0HYS&LUIDS VOL PPn $ 4RIZNA h! MODEL FOR DOPPLER PEAK SPECTRAL SHIFT FOR LOW GRAZING ANGLE SEA SCATTER v )%%% */CEANIC%NG VOL/% PPn 0(9,EE *$"ARTER +,"EACH %#APONI #,(INDMAN "-,AKE (2UNGALDIER AND*#3HELTON h0OWERSPECTRALLINESHAPESOFMICROWAVERADIATIONBACKSCATTEREDFROMSEA SURFACESATSMALLGRAZINGANGLES v)%%0ROC 2ADAR 3ONAR.AVIG VOL NO PPn /CTOBER &%.ATHANSON LOCCIT 3EC
3%!#,544%2
£x°{£
7#+ELLER 7*0LANT AND'26ALENZUELA h/BSERVATIONOFBREAKINGOCEANWAVESWITHCOHER ENTMICROWAVERADAR vIN7AVE$YNAMICSAND2ADIO0ROBINGOFTHE/CEAN3URFACE CHAP /-0HILLIPSAND+(ASSELMANNEDS .EW9ORK0LENUM0RESS PPn 2+-OORE 939U !+&UNG $+ANEKO '*$OME AND2%7ERP h0RELIMINARYSTUDY OF RAIN EFFECTS ON RADAR SCATTERING FROM WATER SURFACES v )%%% * /CEANIC %NG VOL /% PPn 2&#ONTRERAS 7*0LANT 7 #+ELLER +(AYES AND*.YSTUEN h%FFECTSOFRAINON+UBAND BACKSCATTERFROMTHEOCEAN v*'EOPHYS2ES VOL NO# PPn *0(ANSEN h(IGHRESOLUTIONRADARBACKSCATTERFROMARAINDISTURBEDSEASURFACE vPRESENTEDAT )3.2 2EC 4OKYO /CTOBERn * 0 (ANSEN h! SYSTEM FOR PERFORMING ULTRA HIGH RESOLUTION BACKSCATTER MEASUREMENTS OF SPLASHES vIN0ROC)NT-ICROWAVE4HEORY4ECHNIQUES3YMP "ALTIMORE ,"7ETZEL h/NTHETHEORYOFELECTROMAGNETICSCATTERINGFROMARAINDROPSPLASH v2ADIO3CI VOL .O PPn 22OMEISER !3CHMIDT AND7!LPERS h!THREE SCALECOMPOSITESURFACEMODELFORTHEOCEAN WAVE RADARMODULATIONTRANSFERFUNCTION v*'EOPHYS2ES VOL PPn " ,E-EHAUTE AND 4 +HANGAONKAR h$YNAMIC INTERACTION OF INTENSE RAIN WITH WATER WAVES v *0HYS/CEANOG VOL $ECEMBER ,"7ETZEL h/NTHEORIGINOFLONG PERIODFEATURESINLOW ANGLESEABACKSCATTER v2ADIO3CI VOL PPn 0 'ERSTOFT , 4 2OGERS 7 3 (ODGKISS AND , * 7AGNER h2EFRACTIVITY ESTIMATION USING MULTIPLEELEVATIONANGLES v)%%%*OF/CEANIC%NG VOL NO PPn *ULY $%"ARRICK h.EAR GRAZINGILLUMINATIONANDSHADOWINGOFROUGHSURFACES v2ADIO3CI VOL NO PPn -AY *UNE * - 3TURM AND * # 7EST h.UMERICAL STUDY OF SHADOWING IN ELECTROMAGNETIC SCATTERING FROMROUGHDIELECTRICSURFACES v)%%%4RANIN'EOSCIAND2EMOTE3ENSING VOL NO 3EPTEMBER 2"0ERRYAND'23CHIMKE h,ARGE AMPLITUDEINTERNALWAVESOBSERVEDOFFTHENORTHWESTCOAST OF3UMATRA v*'EOPHYS2ES VOL PPn 7!LPERSAND)(ENNINGS h!THEORYOFTHEIMAGINGMECHANISMOFUNDERWATERBOTTOMTOPOGRAPHY BYREALANDSYNTHETICAPERTURERADAR v*'EOPHYS2ES VOLPPn 7 'ARRETT h0HYSICOCHEMICAL EFFECTS OF ORGANIC FILMS AT THE SEA SURFACE AND THEIR ROLE IN THE INTERPRETATIONOFREMOTELYSENSEDIMAGERY vIN/.2,7ORKSHOP0ROC2OLEOF3URFACTANT&ILMS ONTHE)NTERFACIAL0ROPERTIESOFTHE3EA3URFACE &,(ERRAND*7ILLIAMSEDS .OVEMBER PPn ((UHNERFUSS 7!LPERS 7$'ARRETT 0!,ANGE AND33TOLTE h!TTENUATIONOFCAPILLARY ANDGRAVITYWAVESATSEABYMONOMOLECULARORGANICSURFACEFILMS v*'EOPHYS2ES VOL PPn *#3COTT h3URFACEFILMSINOCEANOGRAPHY vIN/.2,7ORKSHOP0ROC2OLEOF3URFACTANT&ILMS ONTHE)NTERFACIAL0ROPERTIESOFTHE3EA3URFACE &,(ERRAND*7ILLIAMSEDS .OVEMBER PPn .7'UINARD h2ADARDETECTIONOFOILSPILLS vPRESENTEDAT*OINT#ONF3ENSINGOF%NVIRONMENTAL 0OLLUTANTS !)!!0APn 0ALO!LTO #! .OVEMBERn ( (ÓHNERFUSS 7 !LPERS ! #ROSS 7 $ 'ARRETT 7 # +ELLER 0 ! ,ANGE 7 * 0LANT &3CHLUDE AND$,3CHULER h4HEMODIFICATIONOF8AND,BANDRADARSIGNALSBYMONOMOLECULAR SEASLICKS v*'EOPHYS2ES VOL PPn #3#OXAND7(-UNK h3TATISTICSOFTHESEASURFACEDERIVEDFROMSUNGLITTER v*-AR2ES VOL PPn 7!LPERSAND((ÓHNERFUSS h2ADARSIGNATURESOFOILFILMSFLOATINGONTHESEASURFACEANDTHE -ARANGONIEFFECT v*'EOPHYS2ES VOL PPn !PRIL (-ASUKOAND()NOMATA h/BSERVATIONSOFARTIFICIALSLICKSBY8AND+ABANDAIRBORNESCAT TEROMETERS v IN 0ROC )NT 'EOSCIENCE AND 2EMOTE 3ENSING 3YMP )'!233 %DINBURGH 3EPTEMBER n PP n 0UBLISHED BY .OORDWIJK .ETHERLANDS %UROPEAN 3PACE!GENCY %34%#
£x°{Ó
2!$!2(!.$"//+
( 'OLDSTEIN h&REQUENCY DEPENDENCE OF THE PROPERTIES OF SEA ECHO v 0HYS 2EV VOL PPn ! ( 3CHOOLEY h3OME LIMITING CASES OF RADAR SEA CLUTTER NOISE v 0ROC )2% VOL PPn 73!MENT h&ORWARDANDBACKSCATTERINGBYCERTAINROUGHSURFACES v4RANS)2% VOL!0 PPn 6 4WERSKY h/N THE SCATTERING AND REFLECTION OF ELECTROMAGNETIC WAVES BY ROUGH SURFACES v 4RANS)2% VOL!0 PPn $2,YZENGA !,-AFFETT AND2!3CHUCHMAN h4HECONTRIBUTIONOFWEDGESCATTERINGTO THERADARCROSSSECTIONOFTHEOCEANSURFACE v)%%%4RANSVOL'% PPn , "7ETZEL h! MINIMALIST APPROACH TO SEA BACKSCATTERTHE WEDGE MODEL v IN 523) /PEN 3YMP7AVE0ROPAGAT2EMOTE3ENSINGAND#OMMUNICATION 5NIVERSITYOF.EW(AMPSHIRE $URHAM PREPRINTVOLUME *ULYn!UGUST PPn 3 / 2ICE h2EFLECTION OF ELECTROMAGNETIC WAVES FROM SLIGHTLY ROUGH SURFACES v #OMMUN 0URE!PPL-ATH VOL PPn 7 ( 0EAKE h4HEORY OF RADAR RETURN FROM TERRAIN v IN )2% .AT #ONV 2EC VOL PPn ' 2 6ALENZUELA h$EPOLARIZATION OF %- WAVES BY SLIGHTLY ROUGH SURFACES v )%%% 4RANS VOL!0 PPn & ' "ASS AND ) - &UKS 7AVE 3CATTERING FROM 3TATISTICALLY 2OUGH 3URFACES .EW 9ORK 0ERGAMON0RESS # %CKART h4HE SCATTERING OF SOUND FROM THE SEA SURFACE v * !COUST 3OC !M VOL PPn 0"ECKMANNAND!3PIZZICHINO 4HE3CATTERINGOF%LECTROMAGNETIC7AVESFROM2OUGH3URFACES .EW9ORK-ACMILLAN#OMPANY ,"7ETZEL h(&SEASCATTERANDOCEANWAVESPECTRA vPRESENTEDAT523)3PRING-EET .ATIONAL !CADEMYOF3CIENCES 7ASHINGTON !PRIL ! + &UNG AND ' 7 0AN h! SCATTERING MODEL FOR PERFECTLY CONDUCTING RANDOM SURFACES )MODELDEVELOPMENT v)NT*2EMOTE3ENSING VOL NO PPn ' 2 6ALENZUELA h4HEORIES FOR THE INTERACTION OF ELECTROMAGNETIC AND OCEANIC WAVESA REVIEW v"OUNDARY ,AYER-ETEOROL VOL PPn " & +URYANOV h4HE 3CATTERING OF SOUND AT A ROUGH SURFACE WITH TWO TYPES OF IRREGULARITY v 3OV0HYS!COUST VOL PPn 7 * 0LANT h"RAGG SCATTERING OF ELECTROMAGNETIC WAVES FROM THE AIRSEA INTERFACE v IN 3URFACE7AVESAND&LUXES#URRENT4HEORYAND2EMOTE3ENSING CHAP ','EERNAERT AND7*0LANTEDS $ORDRECHT .ETHERLANDS2EIDEL ! 3CHMIDT 6 7ISMANN 2 2OMEISER AND 7!LPERS h3IMULTANEOUS MEASUREMENTS OF THE OCEANWAVERADARMODULATIONTRANSFERFUNCTIONAT, #AND8BANDSFROMTHERESEARCHPLATFORM .ORDSEE v*'EOPHYS2ES VOL PPn 7 0 0LANT h! STOCHASTIC MULTISCALE MODEL OF MICROWAVE BACKSCATTER FROM THE OCEAN v *'EOPHYS2ES VOL NO# P 6+UDRYAVTSEV $(AUSER '#AUDAL AND"#HAPRON h!SEMIEMPIRICALMODELOFTHENORMAL IZEDRADARCROSS SECTIONOFTHESEASURFACE"ACKGROUNDMODEL v*'EOPHYS2ES VOL NO# 6+UDRYAVTSEV $(AUSER '#AUDAL AND"#HAPRON h!SEMIEMPIRICALMODELOFTHENORMAL IZEDRADARCROSS SECTIONOFTHESEASURFACE2ADARMODULATIONTRANSFERFUNCTION v*'EOPHYS 2ES VOL NO# %&+NOTT *&3HAEFFER AND-44ULEY 2ADAR#ROSS3ECTION ND%D "OSTON!RTECH (OUSE -3,ONGUET (IGGINSAND*34URNERh!N@ENTRAININGPLUMEMODELOFASPILLINGBREAKER v *&LUID-ECH VOL PPn
3%!#,544%2
£x°{Î
+ * 3ANGSTON h4OWARD A THEORY OF ULTRAWIDEBAND SEA SCATTER v IN )%%% .ATIONAL 2ADAR #ONFERENCE -AYn PPn $4RIZNAPRIVATECOMMUNICATION *#7ESTAND-!3LETTEN h-ULTIPATH%-SCATTERINGFROMBREAKINGWAVESATGRAZINGINCI DENCE v2ADIO3CI VOL NO PPn -!3LETTENAND*#7EST h2ADARINVESTIGATIONSOFBREAKINGWATERWAVESATLOWGRAZINGANGLES WITHSIMULTANEOUSHIGH SPEEDOPTICALIMAGERY v2ADIO3CI VOL NO P *#HEN 4,O *,ITVA AND(,EUNG h3CATTERINGOFELECTROMAGNETICWAVESFROMATIME VARYING FRACTALSURFACE v-ICROWAVEAND/PTICAL4ECH,ETT VOL NO P 3 (AYKIN h2ADAR CLUTTER ATTRACTOR IMPLICATIONS FOR PHYSICS SIGNAL PROCESSING AND CONTROL v )%%0ROC2ADAR3ONAR.AVIG VOL NO P !UGUST 2(ARRINGTON 4IME (ARMONIC%LECTROMAGNETIC&IELDS .EW9ORK-C'RAW (ILL $ * $ONOHUE ( # +U $ 2 4HOMPSON AND * 3ADOWSKI h$IRECT NUMERICAL SIMULATION OFELECTROMAGNETICROUGHSURFACEANDSEASCATTERINGBYANIMPROVEDBANDEDMATRIXITERATIVE METHOD h*OHNS(OPKINS!0,4ECH$IGEST VOL NO PPn # , 2INO AND ( $ .GO h.UMERICAL SIMULATION OF LOW GRAZING ANGLE OCEAN MICROWAVE BACKSCATTERANDITSRELATIONTOSEASPIKES v)%%%0'!0 VOL NO n *#7EST *-3TURM AND! **A,OW 'RAZING3CATTERINGFROM"REAKING7ATER7AVES5SING AN)MPEDANCE"OUNDARY--'4$!PPROACH )%%%4RANS!NTENNAS0ROPAGAT VOL NO PPn *ANUARY $"#OAKLEY 0-(ALDEMAN $'-ORGAN +2.ICOLAS $20ENNDORF ,"7ETZEL AND#37ELLER h%LECTROMAGNETICSCATTERINGFROMLARGESTEADYBREAKINGWAVES v%XPERIMENTS IN&LUIDS VOL NO PPn -AY -2+ELLER ",'OTWOLS 7*0LANT AND7#+ELLER h#OMPARISONOFOPTICALLY DERIVED SPECTRAL DENSITIES AND MICROWAVE CROSS SECTIONS IN A WIND WAVE TANK v * 'EOPHYS 2ES VOL NO# PPn %!%RICSON $2,YZENGA AND$47ALKER h2ADARBACKSCATTERFROMSTATIONARYBREAKING WAVES v*'EOPHYS2ES VOL )SSUE# P 9 ' 4ROKHIMOVSKI h'RAVITYnCAPILLARY WAVE CURVATURE SPECTRUM AND MEAN SQUARE SLOPE RETRIEVEDFROMMICROWAVERADIOMETRICMEASUREMENTSCOASTALOCEANPROBINGEXPERIMENT v *F!TMOSPH/CEANIC4ECH VOL NO PPn
#HAPTER
ÀÕ`Ê V
,V
>À`Ê °Ê Ài 4HE5NIVERSITYOF+ANSAS
£È°£Ê /," 1 /" 2ADARGROUNDRETURNISDESCRIBEDBYR THEDIFFERENTIALSCATTERINGCROSSSECTION OR SCATTERINGCOEFFICIENTSCATTERINGCROSSSECTIONPERUNITAREA RATHERTHANBYTHETOTAL SCATTERINGCROSSSECTIONRUSEDFORDISCRETETARGETS3INCETHETOTALCROSSSECTIONROF APATCHOFGROUNDVARIESWITHTHEILLUMINATEDAREATHATISDETERMINEDBYTHEGEOMETRIC RADARPARAMETERSPULSEWIDTH BEAMWIDTH ETC RWASINTRODUCEDTOOBTAINACOEF FICIENTINDEPENDENTOFTHESEPARAMETERS 5SEOFADIFFERENTIALSCATTERINGCROSSSECTIONIMPLIESTHATTHERETURNFROMTHEGROUND ISCONTRIBUTEDBYALARGENUMBEROFSCATTERINGELEMENTSWHOSEPHASESAREINDEPENDENT 4HISISPRIMARILYBECAUSEOFDIFFERENCESINDISTANCETHAT ALTHOUGHSMALLFRACTIONSOF TOTALDISTANCE AREMANYWAVELENGTHS3UPERPOSITIONOFPOWERISPOSSIBLEFORTHECOM PUTATIONOFAVERAGERETURNS)FTHISCONDITIONISNOTAPPLICABLETOAPARTICULARGROUND TARGET THEDIFFERENTIAL SCATTERINGCROSS SECTIONCONCEPTHASNOMEANINGFORTHATTARGET &OREXAMPLE AVERYFINE RESOLUTIONRADARMIGHTBEABLETORESOLVEAPARTOFACARTHE SMOOTH SURFACES ON THE CAR WOULD NOT BE PROPERLY REPRESENTED BY R /N THE OTHER HAND ACOARSERRADARMIGHTLOOKATMANYCARSINALARGEPARKINGLOT ANDAVALIDRFOR THEPARKINGLOTCOULDBEDETERMINED )FAREGIONILLUMINATEDATONETIMEBYARADARCONTAINSNSCATTERINGELEMENTSANDTHE ABOVECRITERIONISSATISFIEDSOTHATPOWERMAYBEADDED THERADAREQUATIONFORAVERAGE POWERBECOMES N
0R £ I
N 0TI'TI !RIS I 0TI'TI !RI S I $!I $!I
£ P 2I P 2I I
(ERE $!IISANELEMENTOFSURFACEAREAAND0TI POWERTRANSMITTEDTOWARDPOINTI 'TIGAININDIRECTIONOFPOINTI AND!RIRECEIVINGEQUIVALENTAPERTUREINDIRECTIONOF POINTI AREVALUESOF0T 'T AND!RAPPROPRIATEFORANELEMENTATTHELOCATIONOF$!I 4HEFACTORINPARENTHESESINTHENUMERATOROFTHERIGHT HANDEXPRESSIONISTHEINCRE MENTALSCATTERINGCROSSSECTIONFORELEMENTI BUTTHISCONCEPTISMEANINGFULONLYINAN AVERAGE4HUS THEAVERAGEPOWERRETURNEDISGIVENBY N
0R £ I
0TI'TI !RIS $ !I
P 2I £È°£
£È°Ó
2!$!2(!.$"//+
(ERE RHASBEENUSEDTODENOTETHEAVERAGEVALUEOFRI$!I)NTHISFORMULATION WEMAYPASSINTHELIMITFROMTHEFINITESUMTOTHEINTEGRALGIVENBY
0R
P
0' T T !RS D! ¯)LLUMINATED AREA 2
4HISINTEGRALISNOTREALLYCORRECT FORTHEREISAMINIMUMSIZEFORREAL INDEPENDENT SCATTERINGCENTERS.EVERTHELESS THECONCEPTISWIDELYUSEDANDISAPPLICABLEASLONG ASTHEILLUMINATEDAREAISLARGEENOUGHTOCONTAINMANYSUCHCENTERS &IGUREILLUSTRATESTHEGEOMETRYASSOCIATEDWITH%Q.OTETHATFORARECTAN GULARPULSE 0TISEITHERZEROORTHEPEAKTRANSMITTERPOWERBUTFOROTHERPULSESHAPES THE VARIATION WITH T OR 2 IS SIGNIFICANT!CTUAL PULSES ARE OFTEN APPROXIMATED BY RECTANGULARPULSESWITHWIDTHSEQUALTOTHEIRHALF POWERWIDTHS2EALPULSESCANNOTBE RECTANGULARAFTERPASSINGTHROUGHREALTRANSMITTER ANTENNA ANDRECEIVERBANDWIDTHS 4HE TRANSMITTING ANTENNA GAIN AND RECEIVING ANTENNA APERTURE ARE FUNCTIONS OF THE ELEVATIONANDAZIMUTHANGLES
'T 'TP E !R !RP E
A
4HEDIFFERENTIALSCATTERINGCROSSSECTIONITSELFISAFUNCTIONOFBOTHLOOKANGLEP E ANDGROUNDLOCATION
R RP E LOCATION
B
4HEINTEGRALOF%QMUSTBEINVERTEDWHENR ISMEASURED7ITHNARROWBEAMS ANDSHORTPULSES THEINVERSIONISRELATIVELYEASY BUTWITHTHEWIDERBEAMSANDLON GER PULSES USED IN MANY MEASUREMENTS THE VALUES OBTAINED ARE SOMETIMES POORLY DEFINED 3OMEAUTHORSUSEASCATTERINGCROSSSECTIONPERUNITPROJECTEDAREARATHERTHAN PER UNIT GROUND AREA &IGURE ILLUSTRATES BY USING A SIDE VIEW THE DIFFERENCE
&)'52% 'EOMETRYOFTHERADAREQUATION
'2/5.$%#(/
£È°Î
&)'52% 'ROUNDAREAANDPROJECTEDAREA
BETWEENGROUNDAREAANDPROJECTEDAREA4HEGROUNDAREAISPROPORTIONALTO$Q AND THEPROJECTEDAREAISSMALLER4HUS
S ! G D PROJECTED AREA G COSQ D! OR
S G COSQ
3INCEBOTHFANDRARECALLEDSCATTERINGCOEFFICIENTS READERSOFTHELITERATUREMUSTBE ESPECIALLYCAREFULTODETERMINEWHICHISBEINGUSEDBYAPARTICULARAUTHOR 2ADARASTRONOMERSUSEADIFFERENTR
TOTAL RETURN POWER FROM ENTIRE SURFACE
POWER RETURNNED FROM PERFECT ISOTROPICSPHERE OF SAME RADIUS
4HERESULTINGVALUEFORRISUSUALLYMUCHSMALLERTHANRFORTHEPLANETATVERTICAL INCIDENCEANDISLARGERTHANTHEVALUESOFRNEARGRAZINGINCIDENCERETURNFROMTHE LIMBOFTHEPLANET 2ELATIVE)MPORTANCEOF4HEORYAND%MPIRICISM 4HETHEORYOFRADARGROUND RETURNHASBEENTHESUBJECTOFMANYPUBLICATIONS 4HEVARIOUSTHEORIES INSOFARAS THEYCANBECONFIRMEDBYEXPERIMENT PROVIDEBASESFORJUDGINGTHEEFFECTSOFVARIA TIONSINTHEDIELECTRICPROPERTIESOFTHEGROUND OFTHEROUGHNESSOFTHEGROUNDAND NATUREOFVEGETATIVEORSNOWCOVER OFRADARWAVELENGTH ANDOFANGLEOFINCIDENCE 6IEWEDASAIDSTOINSIGHT RADARGROUND RETURNTHEORIESCANBEEXTREMELYUSEFUL 4HEVALIDITYOFANYGROUND RETURNTHEORYMUSTDEPENDONTHEMATHEMATICALMODEL USED TO DESCRIBE THE SURFACE AS WELL AS ON THE APPROXIMATIONS REQUIRED TO OBTAIN ANSWERS%VENTHESIMPLESTGROUNDSURFACE THESEA ISEXTREMELYDIFFICULTTODESCRIBE ACCURATELY IT IS HOMOGENEOUS TO BEYOND THE SKIN DEPTH CONTAINS RELATIVELY MODEST SLOPES ANDEXCEPTFORSPRAY HASNOPARTABOVEANOTHERPARTOFTHESURFACE!TGRAZING ANGLES SHADOWINGOFONEWAVEBYANOTHERMIGHTOCCUR,ANDSURFACESAREMUCHMORE DIFFICULTTODESCRIBE)MAGINEANADEQUATEMATHEMATICALDESCRIPTIONOFTHESHAPEOFA FORESTWHENEVERYLEAFANDPINENEEDLEMUSTBEDESCRIBED &URTHERMORE LANDSURFACES ARESELDOMHOMOGENEOUSEITHERHORIZONTALLYORWITHDEPTH 3INCEATRUEMATHEMATICALDESCRIPTIONOFTHEGROUNDSURFACEAPPEARSOUTOFTHEQUES TION EMPIRICALMEASUREMENTSARENECESSARYTODESCRIBETHERADARRETURNFROMNATURAL SURFACES4HEROLEOFTHEORYISTOAIDININTERPRETINGTHESEMEASUREMENTSANDTOSUGGEST HOWTHEYMAYBEEXTRAPOLATED
£È°{
2!$!2(!.$"//+
!VAILABLE 3CATTERING )NFORMATION 0RIOR TO THE LACK OF COORDINATED RESEARCHPROGRAMSOVERTHENECESSARYLONGPERIODRESULTEDINONLYONEREALLYUSABLE SET OF MEASUREMENTS DEVELOPED AT /HIO 3TATE 5NIVERSITY 3INCE THAT TIME EXTEN SIVEMEASUREMENTSHAVEBEENMADEFROMTRUCKSANDHELICOPTERSBYTHE5NIVERSITYOF +ANSAS GROUPS IN THE .ETHERLANDS AND SEVERAL GROUPS IN &RANCE 4HESE MEASUREMENTSCONCENTRATEDESPECIALLYONVEGETATION WITHTHE+ANSASMEASUREMENTS ALSOINCLUDINGSOMEWORKONSNOWANDEXTENSIVEWORKONSEAICE-OSTOFTHESEMEA SUREMENTSWEREINTHETORANGEOFINCIDENCEANGLES-EASUREMENTSNEARVERTI CALARESCARCER 7ELL CONTROLLEDEXPERIMENTSNEARGRAZINGAREALSOSCARCEEXCEPTFOR AMAJOR,INCOLN,ABORATORYPROGRAM !IRBORNEMEASUREMENTSARENECESSARYTOMAKELARGERSCATTERINGAREASACCESSIBLE !LTHOUGHAIRBORNEPROGRAMSFORSPECIALPURPOSESHAVEBEENLEGION CURVESOFSCATTER INGCOEFFICIENTVERSUSANGLEFORAKNOWNHOMOGENEOUSAREAARESCARCE4HEWORKAT THE-)42ADIATION,ABORATORYWASEARLY7ORKBY0HILCO#ORPORATION 'OODYEAR !EROSPACE#ORPORATION 'ENERAL0RECISION,ABORATORY ANDTHE53.AVAL2ESEARCH ,ABORATORY .2, n PROGRAMS WERE IMPORTANT EARLY ON 4HE #ANADA #ENTRE FOR 2EMOTE3ENSING##23 HASMADENUMEROUSAIRBORNEANDGROUND BASEDSCATTEROM ETERMEASUREMENTS ESPECIALLYOVERSEAICE4HE%NVIRONMENTAL2ESEARCH)NSTITUTE OF -ICHIGAN %2)- ##23 THE %UROPEAN 3PACE !GENCY %3! AND THE *ET0ROPULSION,ABORATORY*0, USEDIMAGINGSYNTHETICAPERTURERADARS3!2S FOR SOMESCATTERINGMEASUREMENTS BUTMOSTWERENOTWELLCALIBRATED3INCETHEADVENT OFSPACEBORNE3!2S3)2! " AND#%23AND2ADARSAT%NVISAT*%23 AND OTHERS HUNDREDSOFPAPERSHAVEAPPEAREDDEALINGWITHMEASUREMENTSOFSCATTERING AND RADAR APPLICATIONS -OREOVER THE *0,!)23!2 HAS FLOWN AROUND THE WORLD ANDSEVERALOTHERAIRBORNE3!2SFORREMOTESENSINGHAVEAPPEAREDINVARIOUSCOUN TRIES WITHHUNDREDSOFRESULTINGPAPERS4HEREADERSHOULDSEARCHTHELITERATUREFOR THESERESULTS WHICHAREFARTOONUMEROUSTOREFERENCEHERE-ANYOFTHEMORERECENT 3!2SnALSOPROVIDEINFORMATIONONPOLARIMETRICRESPONSES 2ESULTS OF MOST OF THESE MEASUREMENTS ARE SUMMARIZED IN 5LABY -OORE AND &UNG AND5LABYAND$OBSON-ORECOMPLETESUMMARIESOFTHEEARLIERWORKAND NEAR GRAZINGSTUDIESAREIN,ONG ANDINTHEWORKOF"ILLINGSLEY -ANYAPPLICA TIONSUMMARIESAREALSOINTHE-ANUALOF2EMOTE3ENSING 2EADERSREQUIRINGMORE DETAILEDINFORMATIONSHOULDCONSULTTHESEBOOKS
£È°ÓÊ *, / ,-Ê / ÊÊ ,"1 Ê, /1, 2ADARRETURNDEPENDSUPONACOMBINATIONOFSYSTEMPARAMETERSANDGROUNDPARAMETERS 2ADARSYSTEMPARAMETERS%QSANDAANDB 7AVELENGTH 0OWER )LLUMINATEDAREA $IRECTIONOFILLUMINATIONBOTHAZIMUTHANDELEVATION 0OLARIZATIONINCLUDINGTHEFULLPOLARIZATIONMATRIXWHENAVAILABLE 'ROUNDPARAMETERS #OMPLEXPERMITTIVITYCONDUCTIVITYANDPERMITTIVITY 2OUGHNESSOFSURFACE )NHOMOGENEITY OF SUBSURFACE OR COVER TO DEPTH WHERE ATTENUATION REDUCES WAVESTONEGLIGIBLEAMPLITUDE
'2/5.$%#(/
£È°x
$IFFERENTWAVELENGTHSARESENSITIVETODIFFERENTELEMENTSONTHESURFACE/NEOFTHE EARLIESTKNOWNANDMOSTSTRIKINGDIRECTIONALEFFECTSISTHECARDINAL POINTEFFECTINRETURNS FROMCITIES2ADARSLOOKINGINDIRECTIONSALIGNEDWITHPRIMARYSTREETGRIDSOBSERVESTRON GERREGULARRETURNSTHANRADARSATOTHERANGLES(ORIZONTALLYPOLARIZEDWAVESAREREFLECTED BETTER BY HORIZONTAL WIRES RAILS ETC THAN ARE VERTICALLY POLARIZED WAVES 6ERTICALLY POLARIZEDWAVESAREREFLECTEDBETTERFROMVERTICALSTRUCTURESSUCHASTREETRUNKS ATLEAST WHENTHEWAVELENGTHISCOMPARABLEORLARGERTHANTHETRUNKDIAMETER )F THE GEOMETRY OF TWO RADAR TARGETS WERE THE SAME THE RETURNS WOULD BE STRONGER FROMTHETARGETWITHHIGHERCOMPLEXPERMITTIVITYBECAUSELARGERCURRENTSDISPLACEMENTOR CONDUCTION WOULDBEINDUCEDINIT"ECAUSEIDENTICALGEOMETRIESWITHDIFFERINGPERMIT TIVITIESDONOTOCCURINNATURE THISDISTINCTIONISNOTEASYTOMEASURE%FFECTIVEPERMITTIV ITYFORGROUNDTARGETSISVERYSTRONGLYINFLUENCEDBYMOISTURECONTENTSINCETHERELATIVE PERMITTIVITYOFLIQUIDWATERISFROMABOUTAT8BANDTOABOUTAT3BANDANDLONGER WAVELENGTHS WHEREASMOSTDRYSOLIDSHAVEPERMITTIVITIESLESSTHAN!TTENUATIONISALSO STRONGLY INFLUENCED BY MOISTURE SINCE WET MATERIALS USUALLY HAVE HIGHER CONDUCTIVITY THANTHESAMEMATERIALSDRY&IGURESANDSHOWTHEEFFECTOFMOISTURECONTENTON PROPERTIESOFPLANTSANDOFSOIL4HEHIGHPERMITTIVITYOFPLANTSWITHMUCHMOISTUREMEANS THATRADARRETURNFROMCROPSVARIESASTHEPLANTSMATURE EVENWHENGROWTHISNEGLECTED
&)'52% -EASURED MOISTURE DEPENDENCE OF THE DIELECTRIC CONSTANTOFCORNLEAVESAT AND'(Z3ISTHESALINITYOFWATER CONTENT IN PARTS PER THOUSAND DV DV JDVp IS THE COMPLEX DIELECTRIC CONSTANTIN&M ANDMVISTHEVOLUMETRICMOISTURECONTENTINKGM AFTER&45LABY 2+-OORE AND!+&UNG
£È°È
2!$!2(!.$"//+
&)'52% !PPARENT RELATIVE DIELECTRIC CONSTANT VERSUS MOISTURECONTENT2ICHFIELDSLITLOAM AFTER*2,UNDIEN
4HEROUGHNESSOFSURFACESESPECIALLYNATURALONES ISDIFFICULTTODESCRIBEMATH EMATICALLYBUTEASYTOUNDERSTANDQUALITATIVELY4HUSITISEASYTOSEETHATAFRESHLY PLOWEDFIELDISROUGHERTHANTHESAMEFIELDAFTERRAINANDWINDHAVEBEENATWORK ONIT!FORESTISINHERENTLYROUGHERTHANEITHERAFIELDORACITY)TISHARDERTOSEETHE DIFFERENCEBETWEENTHEROUGHNESSOFNATURALAREASANDTHEROUGHNESSOFACITYTHATHAS FLATWALLSINTERSPERSEDWITHWINDOWSILLSANDWITHCURBS CARS ANDSIDEWALKS 3URFACESTHATARERELATIVELYSMOOTHTENDTOREFLECTRADIOWAVESINACCORDANCEWITH THE&RESNEL REFLECTIONDIRECTION SOTHEYGIVESTRONGBACKSCATTERONLYWHENTHELOOK ANGLE IS NEARLY NORMAL TO THE SURFACES 2OUGH SURFACES ON THE OTHER HAND TEND TO RERADIATENEARLYUNIFORMLYINALLDIRECTIONS ANDSOTHEYGIVERELATIVELYSTRONGRADAR RETURNSINANYDIRECTION 4HE PROBLEM OF RADAR SCATTER IS COMPLICATED BECAUSE WAVES PENETRATE SIGNIFICANT DISTANCESINTOMANYSURFACESANDVEGETATIONCANOPIES ANDINTERNALREFLECTIONANDSCATTER CONTRIBUTETOTHERETURN-EASUREMENTSOFATTENUATIONFORFIELDCROPS ANDGRASSES SHOWTHATMOSTOFTHERETURNISFROMTHEUPPERLAYERS WITHSOMECONTRIBUTIONBYTHESOIL ANDLOWERLAYERSIFTHEVEGETATIONISNOTVERYDENSE!T#BANDANDHIGHERFREQUENCIES MOSTOFTHESIGNALRETURNEDFROMTREESISUSUALLYFROMTHEUPPERANDMIDDLEBRANCHES WHENTHETREESAREINLEAF nALTHOUGHINWINTERTHESURFACEISAMAJORCONTRIBUTORTO THESIGNAL!T,BAND ANDESPECIALLYAT6(& THESIGNALPENETRATESFARTHER SOTRUNKSAND THEGROUNDCANBEMAJORCONTRIBUTORSEVENWHENTHETREESARELEAFEDOUT !DDITIONALPROBLEMSOCCURNEARGRAZINGINCIDENCE "ECAUSEOFTHELOWANGLE WITHTHESURFACE SHADOWINGFREQUENTLYOCCURSSOMEPARTSOFTHETARGETAREOBSCURED BYINTERVENINGPROJECTIONSSUCHASHILLSANDBUILDINGS0ARTSOFTHEAREATHATARESOME WHATELEVATEDHAVETHESIGNALMODIFIEDBYTHEEFFECTOFMULTIPATHINTERFERENCEBETWEEN
!NGLEOFREFLECTIONEQUALSANGLEOFINCIDENCE
'2/5.$%#(/
£È°Ç
THEDIRECTRAYANDONEREFLECTEDOFFTHEGROUND3INCETHESCATTERINGFROMRELATIVELY LEVELSURFACESISVERYSMALL ANYPROJECTIONMAYGIVEARETURNMUCHSTRONGERTHANTHE BACKGROUND THEREBYSKEWINGTHESTATISTICSSOA2AYLEIGHDISTRIBUTIONNOLONGERAPPLIES TOTHEAVERAGESIGNAL/BJECTSSUCHASTREES BUILDINGS FENCEPOSTS ANDPOWERLINES GIVELOCALIZEDECHOESSTRONGRELATIVETOTHEIRSURROUNDINGS -OREOVER THE SIGNAL FROM SURFACES WITHOUT PROJECTIONS FALLS OFF VERY RAPIDLY FORDEPRESSIONANGLESWITHINAFEWDEGREESOFGRAZING4HISMEANSTHATTHEEFFECT OFSMALLLOCALSLOPESCANBEVERYSIGNIFICANTINMODULATINGTHERETURNSIGNAL NOT JUSTINSHADOWING
£È°ÎÊ / ", / Ê " -ÊÊ Ê/ ,Ê //" $ESCRIPTIONSOFA3URFACE -ANYTHEORETICALMODELSFORRADARRETURNFROMTHE GROUNDASSUMEAROUGHBOUNDARYSURFACEBETWEENAIRANDANINFINITEHOMOGENEOUS HALF SPACE 3OME INCLUDE EITHER VERTICAL OR HORIZONTAL HOMOGENEITIES IN THE GROUND PROPERTIESANDINVEGETATIVEORSNOWCOVERS 3URFACEDESCRIPTIONSSUITABLEFORUSEINMATHEMATICALMODELSARENECESSARILYGREATLY IDEALIZED&EWNATURALGROUNDSARETRULYHOMOGENEOUSINCOMPOSITIONOVERVERYWIDE AREAS$ESCRIPTIONSOFTHEIRDETAILEDSHAPEMUSTBESIMPLIFIEDIFTHEYARETOBEHANDLED ANALYTICALLY ALTHOUGH COMPUTERS PERMIT THE USE OF TRUE DESCRIPTIONS6ERY FEW SUR FACESHAVEEVERBEENMEASUREDTOTHEPRECISIONAPPROPRIATEFORCENTIMETER WAVELENGTH RADARSEVENFORTHESE THEREISNOASSURANCETHATSCATTERINGBOUNDARIESDONOTEXIST WITHINASKINDEPTHBENEATHTHESURFACE3URFACESCONTAININGVEGETATIONANDCONGLOM ERATEROCKSALMOSTCOMPLETELYDEFYDESCRIPTION 3TATISTICALDESCRIPTIONSOFSURFACESAREUSEDFORMOSTTHEORIES SINCEATHEORYSHOULD BE REPRESENTATIVE OF SOME KIND OF SURFACE CLASS RATHER THAN OF A PARTICULAR SURFACE ANDSINCEEXACTDESCRIPTIONISSODIFFICULT4HESTATISTICALDESCRIPTIONSTHEMSELVESMUST BE OVERSIMPLIFIED HOWEVER -ANY THEORIES ASSUME ISOTROPIC STATISTICS CERTAINLY NOT APPROPRIATE FOR PLOWED FIELDS OR GRIDDED CITIES -OST THEORIES ASSUME SOME KIND OF MODELINVOLVINGONLYTWOORTHREEPARAMETERSSTANDARDDEVIATION MEANSLOPE CORRELA TIONDISTANCE ETC WHEREASNATURALORHUMAN MADE SURFACESSELDOMARESOSIMPLY DESCRIBED4HETHEORIESFORVEGETATIONANDOTHERVOLUMESCATTERSHAVEMOREPARAMETERS &ORNEAR GRAZINGCONDITIONS THEMODELSMUSTACCOUNTFORSHADOWING 3IMPLIFIED-ODELS %ARLYRADARTHEORIESFORGROUNDRETURNASSUMED ASINOPTICS THATMANYTARGETSCOULDBEDESCRIBEDBYA,AMBERT LAWVARIATIONOFINTENSITYTHATIS THEDIFFERENTIALSCATTERINGCOEFFICIENTVARIESASCOSP WITHPBEINGTHEANGLEOFINCI DENCE4HIShPERFECTLYROUGHvASSUMPTIONWASSOONFOUNDWANTING ALTHOUGHITISA FAIRAPPROXIMATIONFORTHERETURNFROMMANYVEGETATEDSURFACESOVERTHEMIDRANGEOF ANGLESOFINCIDENCE #LAPP DESCRIBED THREE MODELS INVOLVING ASSEMBLIES OF SPHERES WITH DIFFERENT SPACINGS AND EITHER WITH OR WITHOUT A REFLECTING GROUND PLANE 4HESE MODELS YIELD VARIATIONS FROM R INDEPENDENT OF ANGLE THROUGH R s COSP TO R s COSP 3INCE THESPHEREMODELSAREHIGHLYARTIFICIAL ONLYTHERESULTINGSCATTERLAWSNEEDBECONSID ERED-OSTTARGETSGIVERETURNSTHATVARYMORERAPIDLYOVERPARTOFTHEINCIDENCE ANGLE REGIMETHANTHESEMODELS ALTHOUGHFORESTSANDSIMILARROUGHTARGETSOFSOMEDEPTH SOMETIMESGIVESUCHSLOWLYVARYINGRETURNS
£È°n
2!$!2(!.$"//+
3INCE THESE ROUGH SURFACE MODELS USUALLY FAIL TO EXPLAIN THE RISE IN RETURN NEAR VERTICALINCIDENCE OTHERSIMPLIFIEDMODELSCOMBINE,AMBERTSLAWANDOTHERROUGH SURFACESCATTERINGMODELSWITHSPECULARREFLECTIONATVERTICALINCIDENCE ANDASMOOTH CURVEISDRAWNBETWEENTHESPECULARVALUEANDTHEROUGH SURFACEPREDICTION 3PECULAR REFLECTION IS DEFINED AS REFLECTION FROM A SMOOTH PLANE AND OBEYS THE &RESNELREFLECTIONLAWS!TNORMALINCIDENCE THESPECULAR REFLECTIONCOEFFICIENTIS THEREFORE
'2
HG H
HG H
WHEREGANDGGARETHEINTRINSICIMPEDANCESOFAIRANDEARTH RESPECTIVELY4HEFRACTION OFTOTALINCIDENTPOWERSPECULARLYREFLECTEDFROMAROUGHSURFACEIS
E PS H L
WHERERH STANDARDDEVIATIONOFSURFACEHEIGHTVARIATIONS AND
K WAVELENGTH 3INCE THIS PROPORTION IS DOWN TO WHEN RH K O AND TO WHEN S H L P SIGNIFICANTSPECULARREFLECTIONISSELDOMFOUNDFORTHECENTIMETER WAVELENGTHSGENERALLYUSEDFORRADAR.EVERTHELESS ASIMPLIFIEDMODELLIKETHISIS CONVENIENTFORSOMEPURPOSES /BSERVATIONOFREFLECTEDSUNLIGHTFROMRIPPLEDWATER FROMROADS ANDFROMOTHER SMOOTHSURFACESLEADSTOTHEPOSTULATIONOFAFACETTHEORY 4HEONLYSUNLIGHTREACH INGTHEOBSERVERFROMSMOOTHSURFACESSUCHASWATERISTHATFROMFACETSFORWHICHANGLE OFINCIDENCEEQUALSANGLEOFREFLECTION4HUS THEOBSERVEDLIGHTMAYBEDESCRIBEDBY METHODSOFGEOMETRICOPTICS 7HENGEOMETRICOPTICSISUSEDTODESCRIBERADARSCATTER THESURFACEOFTHEGROUND ISREPRESENTEDBYSMALLFLAT PLANESEGMENTS2ADARRETURNISASSUMEDTOOCCURONLYFOR FACETSORIENTEDNORMALTOTHERADARNORMALORIENTATIONISREQUIREDFORBACKSCATTERSOTHAT THEREFLECTEDWAVERETURNSTOTHESOURCE 4HUS IFTHESLOPEDISTRIBUTIONOFSUCHFACETSIS KNOWN THEFRACTIONNORMALTOAGIVENDIVERGINGBEAMCANBEESTABLISHED ANDFROMTHIS THERETURNCANBEOBTAINED'EOMETRICOPTICSASSUMESZEROWAVELENGTH ANDSOTHERESULTS OFSUCHATHEORYAREWAVELENGTH INDEPENDENT CLEARLYNOTINACCORDWITHOBSERVATION 4HE FACET MODEL FOR RADAR RETURN IS EXTREMELY USEFUL FOR QUALITATIVE DISCUSSIONS ANDSOMODIFICATIONTOMAKEITFITBETTERWITHOBSERVATIONISAPPROPRIATE4WOKINDS OFMODIFICATIONMAYBEUSED SEPARATELYORJOINTLYCONSIDERINGTHEACTUALRERADIATION PATTERNOFFINITE SIZEFACETSATFINITEWAVELENGTHSANDCONSIDERINGTHEEFFECTOFWAVE LENGTHONESTABLISHINGTHEEFFECTIVENUMBEROFFACETS4HUS THESCATTERFROMAFACET MAYACTUALLYOCCURINDIRECTIONSOTHERTHANTHATREQUIRINGTHATANGLEOFINCIDENCEEQUAL ANGLEOFREFLECTION&IGUREILLUSTRATESTHIS&ORLARGEFACETSCOMPAREDWITHWAVE LENGTH MOSTOFTHERETURNOCCURSALMOSTATNORMALINCIDENCE WHEREASFORSMALLFACETS THEORIENTATIONMAYBEOFFNORMALBYACONSIDERABLEAMOUNTWITHOUTGREATREDUCTION INSCATTER!STHEWAVELENGTHISINCREASED THECATEGORYOFAGIVENFACETCHANGESFROM LARGETOSMALLEVENTUALLYTHEFACETISSMALLERTHANAWAVELENGTH ANDITSRERADIATION PATTERN SHAPE REMAINS ALMOST ISOTROPIC FROM THAT POINT -ANY FACETS THAT WOULD BE SEPARATEAT SAY A CMWAVELENGTHARECOMBINEDATA MWAVELENGTHTHERESULTMAY BEATRANSITIONFROMROUGH TOSMOOTH SURFACEBEHAVIOR&IGUREASHOWSANUMBER OFFACETSOFDIFFERENTSIZESCONTRIBUTINGTOARADARRETURN
'2/5.$%#(/
£È°
&)'52% .ORMAL INCIDENCERERADIATIONPATTERNSOFFACETS
0HYSICAL /PTICS -ODELS 4HEORIES BASED ON APPLICATIONS OF THE +IRCHHOFF (UYGENSPRINCIPLEHAVEBEENTHOROUGHLYDEVELOPED n4HE+IRCHHOFFAPPROXI MATIONISTHATTHECURRENTFLOWINGATEACHPOINTINALOCALLYCURVEDORROUGH SURFACE ISTHESAMEASWOULDFLOWINTHESAMESURFACEIFITWEREFLATANDORIENTEDTANGENTTOTHE ACTUALSURFACE4HISASSUMPTIONPERMITSCONSTRUCTIONOFSCATTEREDFIELDSBYASSUMING THATTHECURRENTOVERAROUGHPLANESURFACEHASTHESAMEMAGNITUDEASIFTHESURFACE WERESMOOTH BUTWITHPHASEPERTURBATIONSSETBYTHEDIFFERINGDISTANCESOFINDIVIDUAL
&)'52%A &ACETMODELOFARADARRETURN
£È°£ä
2!$!2(!.$"//+
POINTS FROM THE MEAN PLANE &OR SURFACES ASSUMED TO BE AZIMUTHALLY ISOTROPIC THE USUALAPPROACHYIELDSINTEGRALSOFTHEFORM E KS H COSQ ; R X =* KX COSQ X DX COS Q ¯
WHERE QX
P
RH
K
*
SPATIALAUTOCORRELATIONFUNCTIONOFSURFACEHEIGHTS ANGLEWITHVERTICAL STANDARDDEVIATIONOFSURFACEHEIGHTS O K FIRST ORDER FIRST KIND"ESSELFUNCTION
4HEAUTOCORRELATIONFUNCTIONOFHEIGHTWITHDISTANCEISSELDOMKNOWNFORTERRAIN ALTHOUGHITCANBEDETERMINEDONALARGESCALEBYANALYSISOFCONTOURMAPS ANDIT HASBEENFOUNDFORSOMEAREASBYCAREFULCONTOURINGATCLOSEINTERVALSANDSUBSEQUENT ANALYSIS"ECAUSEOFLACKOFKNOWLEDGEOFACTUALAUTOCORRELATIONS MOSTTHEORYHAS BEENDEVELOPEDWITHARTIFICIALFUNCTIONSTHATARECHOSENMOREFORTHEIRINTEGRABILITY THANFORTHEIRFITWITHNATURESELECTIONAMONGTHEMHASBEENONTHEBASISOFWHICHONES YIELDTHEBESTFITBETWEENTHEORETICALANDEXPERIMENTALSCATTERCURVES 4HECORRELATIONFUNCTIONFIRSTUSEDWASGAUSSIAN
QX E X ,
WHERE,ISTHECORRELATIONLENGTH.OTONLYISTHISAFUNCTIONTHATMAKESTHEINTEGRAL ANALYTICALLYTRACTABLE BUTITALSOGIVESEXACTLYTHESAMERESULTSASGEOMETRICOPTICS 3INCEITFAILS LIKEGEOMETRICOPTICS TOEXPLAINFREQUENCYVARIATION ITCANNOTBEATRULY REPRESENTATIVECORRELATIONFUNCTION ALTHOUGHITGIVESASCATTERINGCURVETHATFITSSEVERAL EXPERIMENTALCURVESNEARTHEVERTICAL4HENEXTMOSTFREQUENTLYUSEDFUNCTIONISTHE EXPONENTIAL
RX E \X\ ,
4HISHASSOMEBASISINCONTOUR MAPANALYSISTHERESULTSFITBOTH%ARTHANDLUNAR RADARRETURNOVERAWIDERRANGEOFANGLESTHANTHEGAUSSIAN BUTSOMETIMESNOT ASWELLNEARVERTICAL &URTHERMORE ITHASTHEMERITTHATITEXHIBITSFREQUENCYDEPEN DENCE 2ESULTING EXPRESSIONS FOR POWER SCATTERING COEFFICIENT VARIATIONS APPEAR IN 4ABLE
4!",% 3CATTERING#OEFFICIENT6ARIATION
#ORRELATIONCOEFFICIENT
E X
,
E \X\ ,
0OWER%XPRESSION
2EFERENCE
+ , S H TAN Q E SIN Q
$AVIES
¤ +Q SIN Q ³ ! ¥ COS Q ´µ COS Q SIN Q ¦
6ORONOVICH
'2/5.$%#(/
£È°££
3MALL 0ERTURBATIONAND4WO 3CALE-ODELS 2ECOGNITIONTHATEXISTINGMODELS WEREINADEQUATEFORDESCRIBINGOCEANSCATTERLEDTORECOGNITIONTHATRESONANCEOFTHE SIGNALWITHSMALLSTRUCTURESONTHESURFACEHASAPOWERFULINFLUENCEONTHESTRENGTH OFTHESIGNALRECEIVED 4HUSASMALL PERTURBATIONMETHODORIGINALLYPROPOSEDBY 2ICEBECAMETHEMOSTPOPULARWAYTODESCRIBEOCEANSCATTER)TSAPPLICATIONTOLAND SCATTERWASNOTFARBEHIND 4HETERM"RAGGSCATTERISOFTENUSEDTODESCRIBETHEMECHANISMFORTHESMALL PERTURBATIONMODEL4HEIDEACOMESFROMTHECONCEPTILLUSTRATEDIN&IGUREB !SINGLESINUSOIDALCOMPONENTOFACOMPLEXSURFACEISSHOWNWITHANINCOMING RADAR WAVE AT ANGLE OF INCIDENCE P4HE RADAR WAVELENGTH IS K AND THE SURFACE COMPONENT WAVELENGTH IS , 7HEN THE SIGNAL TRAVELS AN EXTRA DISTANCE K $2 BETWEENTHESOURCEANDTWOSUCCESSIVEWAVECRESTS THEPHASEDIFFERENCEBETWEEN THEECHOESFROMSUCCESSIVECRESTSISSOTHEECHOSIGNALSALLADDINPHASE)F THISCONDITIONISSATISFIEDFORAPARTICULAR,ANDP ITFAILSTOBESATISFIEDFOROTHERS 4HUS THISISARESONANTSELECTIONFORAGIVENPOFAPARTICULARCOMPONENTOFTHE SURFACE,4HESTRENGTHOFTHERECEIVEDSIGNALISPROPORTIONALTOTHEHEIGHTOFTHIS COMPONENTANDTOTHENUMBEROFCRESTSILLUMINATEDBYTHERADAR)FTHESURFACEHAS ANUNDERLYINGCURVATURE THENUMBEROFILLUMINATEDCRESTSSATISFYINGTHERESONANCE CRITERIONMAYBELIMITEDBYTHELENGTHOFTHEESSENTIALLYFLATREGIONOTHERWISE ITIS LIMITEDBYTHERADARRESOLUTION 4HETHEORETICALEXPRESSIONFORTHESCATTERINGCOEFFICIENTIS
S PQ K S COS Q \ A PQ \ 7 K SIN Q
WHERE P Q POLARIZATIONINDICES(OR6
K O KTHERADARWAVENUMBER
@(( 2&RESNELREFLECTIONCOEFFICIENTFORHORIZONTALPOLARIZATION
A 66 E R
SIN Q E R SIN Q
;E R COSQ E R SIN Q =
WHEREDRISTHERELATIVEPERMITTIVITYD ` JD pAND@6( @(6 7KSINP ISTHE NORMALIZEDROUGHNESSSPECTRUMTHE&OURIERTRANSFORMOFTHESURFACEAUTOCORRELATION FUNCTION )TMAYBEWRITTENAS7+ WHERE+ISTHEWAVENUMBERFORTHESURFACE )NTERMSOFTHEWAVELENGTHONTHESURFACE,
+ O,
&)'52%B )N PHASEADDITIONFOR"RAGGSCATTERING$2 NK
£È°£Ó
2!$!2(!.$"//+
4HUS THECOMPONENTOFTHESURFACETHATSATISFIESTHE"RAGGRESONANCECONDITIONIS
, KSINP
4HISMEANSTHATTHEMOSTIMPORTANTCONTRIBUTORTOASURFACERETURNISTHECOMPONENTOF SURFACEROUGHNESSWITHWAVELENGTH,%VENTHOUGHOTHERCOMPONENTSMAYBEMUCH LARGER THE"RAGGRESONANCEMAKESTHISCOMPONENTMOREIMPORTANT/NTHEOCEAN THIS MEANSTHATTINYRIPPLESAREMOREIMPORTANTTHANWAVESTHATAREMETERSHIGHTHESAME APPLIESFORLAND SURFACESCATTER !SORIGINALLYDEVELOPED THISTHEORYWASFORPERTURBATIONSTOHORIZONTALFLATSUR FACES BUT IT WAS SOON MODIFIED TO HANDLE SURFACES WITH LARGE SCALE ROUGHNESS4HE LARGE SCALEROUGHNESSWASASSUMEDTOCAUSEATILTINGOFTHEFLATSURFACETOWHICHTHE SMALL PERTURBATIONTHEORYCOULDBEAPPLIED4HEPRINCIPALPROBLEMWITHTHISAPPROACH ISDECIDINGWHEREINTHESURFACESPECTRUMLIESTHEBOUNDARYBETWEENTHELARGERCOMPO NENTSTHATDOTHETILTINGANDSMALLERCOMPONENTSTHATARE"RAGG RESONANT-ANYPAPERS HAVEBEENWRITTENTODESCRIBETHEEVOLUTIONOFTHISTHEORYFORACOMPLETESUMMARY THE READERISREFERREDTO&UNGSDEVELOPMENT /THER-ODELS 4HETHEORYFORVOLUMESCATTERHASLEDTOMANYPAPERSANDCON TINUESTOEVOLVE&ORAREVIEWOFSOMEOFTHEAPPROACHES THEREADERSHOULDCONSULT &UNGSSUMMARYANDPAPERSBY+ONG ,ANG &UNG AND4SANG4HESEMODELSHAVE BEENUSEDREASONABLYSUCCESSFULLYTODESCRIBESCATTERFROMVEGETATION SNOW AND SEAICE-ODELSOFSTRAIGHTVEGETATIONSUCHASWHEATINTERMSOFCYLINDERSHAVEHAD SOMESUCCESS #ORNER REFLECTOREFFECTSHAVEBEENUSEDTODESCRIBESTRONGRETURNS FROM BUILDINGS AT NON NORMAL INCIDENCE ANGLES /THER SPECIALIZED MODELS HAVE BEENUSEDFORPARTICULARPURPOSES ,ATERTHEORETICALWORKFORSURFACESINVOLVESSOLVINGINTEGRALEQUATIONSFORTHESCAT TEREDFIELDS4HISHASBEENUSEDBOTHTOVALIDATEOTHERMODELSANDTOBETTERDESCRIBE THETRUESCATTERINGFROMAKNOWNROUGHSURFACE4HISMETHODTENDSTOBECOMPUTATION ALLYEXTENSIVE.UMERICALSCATTERINGCOMPUTATIONSAREALSOINVOGUE 2EGARDLESS OF THE MODEL USED AND THE APPROACH APPLIED TO DETERMINING THE FIELD STRENGTH THEORETICALWORKONLYGUIDESUNDERSTANDING!CTUAL%ARTHSURFACESARETOOCOM PLEXTOBEDESCRIBEDADEQUATELYINANYOFTHEMODELS ANDTHEEFFECTSOFSIGNALSTHATPEN ETRATETHEGROUNDANDARESCATTEREDTHEREINARETOOLITTLEKNOWNTOPERMITITSEVALUATION
£È°{Ê Ê"Ê,"1 Ê " 4HE AMPLITUDE OF GROUND ECHOES RECEIVED BY RADARS ON MOVING VEHICLES FLUCTUATES WIDELYBECAUSEOFVARIATIONSINPHASESHIFTFORRETURNFROMDIFFERENTPARTSOFTHEILLUMI NATEDAREA)NFACT EVENFIXEDRADARSFREQUENTLYOBSERVEFLUCTUATIONSINGROUNDECHOES BECAUSEOFMOTIONSOFVEGETATION WIRESBLOWINGINTHEWIND ETC4HISFLUCTUATIONIS REFERREDTOASFADING &ADINGISSIGNIFICANTFORTHERADARENGINEERBECAUSEONEMUSTACCOUNTFORTHEFACT THATASINGLESAMPLEOFTHERADARRETURNMAYVARYWIDELYFROMTHEMEANDESCRIBEDBY R4HUS THESYSTEMMUSTBEABLETOHANDLETHEDYNAMICRANGEOFFADING WHICHMAY EXCEEDD" 2EGARDLESS OF THE MODEL USED TO DESCRIBE A GROUND SURFACE SIGNALS ARE IN FACT RETURNEDFROMDIFFERENTPOSITIONSNOTONAPLANE!SARADARMOVESPASTAPATCHOFGROUND
'2/5.$%#(/
£È°£Î
WHILEILLUMINATINGIT THELOOKANGLECHANGES ANDTHISCHANGESTHERELATIVEDISTANCESTO DIFFERENTPARTSOFTHESURFACETHERESULTISTHATRELATIVEPHASESHIFTISCHANGED4HISISTHE SAMEKINDOFRELATIVE PHASE SHIFTCHANGEWITHDIRECTIONTHATISPRESENTFORANANTENNA ARRAYANDRESULTSINTHEANTENNAPATTERN&ORGROUNDECHO THEDISTANCEISDOUBLED SOTHE PATTERNOFANECHOINGPATCHOFLENGTH,HASLOBESOFWIDTHK,4HISCOMPARESWITHK, FORANANTENNAOFTHESAMECROSS RANGELENGTH"ECAUSETHEEXCITATIONOFTHEELEMENTSOF THESCATTERINGARRAYISRANDOM THESCATTERINGPATTERNINSPACEISALSORANDOM 4HISFADINGPHENOMENONISUSUALLYDESCRIBEDINTERMSOFTHEDOPPLERSHIFTOFTHE SIGNAL3INCEDIFFERENTPARTSOFTHETARGETAREATSLIGHTLYDIFFERENTANGLES THESIGNALS FROMTHEMEXPERIENCESLIGHTLYDIFFERENTDOPPLERSHIFTS4HEDOPPLERSHIFT OFCOURSE ISSIMPLYTHERATEOFCHANGEOFPHASEDUETOMOTION4HUS THETOTALRATEOFCHANGEOF PHASEFORAGIVENTARGETIS
W W C W DI
DFI D W CT K2I DT DT
WHERE VC CARRIERANGULARFREQUENCY
VDI DOPPLERANGULARFREQUENCYFORITHTARGET
EI PHASEFORITHTARGET
2I RANGEFROMRADARTOITHTARGET 4HEDOPPLERSHIFTCANBEEXPRESSEDINTERMSOFTHEVELOCITYVECTORVAS
W DI K
D2I 2 KV I KV COS V 2 I DT 2I
WHEREBOLD FACEDLETTERSAREVECTORS(ENCE THETOTALFIELDISGIVENBY
T ª § ¶¹ 2 % £ !I EXP « J ¨W C T ¯ K V I DT K2I ·º 2I ·¸» I ¬ ¨©
WHERE!IISTHEFIELDAMPLITUDEOFTHEITHSCATTERERAND2IISTHERANGEATTIMEZERO 4HE ONLY REASON THE SCALAR PRODUCT VARIES FOR DIFFERENT SCATTERERS IS THE DIFFERENT ANGLEBETWEENTHEVELOCITYVECTORANDTHEDIRECTIONTOTHESCATTERER4HISRESULTSINA SEPARATEDOPPLERFREQUENCYFOREACHSCATTERER)FWEASSUMETHELOCATIONSTOBERANDOM ASMOSTTHEORIESDO THERECEIVEDSIGNALISTHESAMEASONECOMINGFROMASETOFOSCIL LATORSWITHRANDOMPHASESANDUNRELATEDFREQUENCIES4HISSAMEMODELOFAGROUPOF RANDOMLYPHASED DIFFERENT FREQUENCYOSCILLATORSISUSEDTODESCRIBENOISETHUS THE STATISTICSOFTHEFADINGSIGNALANDTHESTATISTICSOFRANDOMNOISEARETHESAME 4HISMEANSTHATTHEENVELOPEOFTHERECEIVEDSIGNALISARANDOMVARIABLEWITHITS AMPLITUDE DESCRIBED BY A 2AYLEIGH DISTRIBUTION 3UCH DISTRIBUTIONS HAVE BEEN MEA SUREDFORMANYGROUND TARGETECHOES!LTHOUGHTHEACTUALDISTRIBUTIONSVARYWIDELY NOBETTERDESCRIPTIONCANBEGIVENFORRELATIVELYHOMOGENEOUSTARGETS7ITHA2AYLEIGH DISTRIBUTION THERANGEOFFADINGISABOUTD" SOANINDIVIDUALPULSERETURNMAY BEANYWHEREINTHISRANGE 7HENATARGETISDOMINATEDBYONELARGEECHOSUCHASAMETALROOFORIENTEDTOGIVE ASTRONGRETURN THEDISTRIBUTIONISBETTERDESCRIBEDBYTHATFORASINEWAVEINNOISE )FTHELARGEECHOISCONSIDERABLYSTRONGERTHANTHEMEANOFTHEREMAININGCONTRIBUTORS TOTHERETURN THISAPPROACHESANORMALDISTRIBUTIONABOUTTHEVALUEFORTHELARGEECHO 4HISSITUATIONISPARTICULARLYCOMMONFORNEAR GRAZINGCONDITIONS
£È°£{
2!$!2(!.$"//+
&ORREFERENCE THETWODISTRIBUTIONSAREGIVEN
P V DV
V V Y E DV Y
2AYLEIGH
P V DV
V V A Y ¤ AV ³ E ) ¥ ´ Y ¦Y µ
SINE WAVE 2AYLEIGH
WHERE V ENVELOPEVOLTAGE
X MEANSQUAREVOLTAGE
! SINE WAVEPEAKVOLTAGE
)X "ESSELFUNCTION FIRSTKIND ZEROORDER IMAGINARYARGUMENT )NPRACTICE THEDISTRIBUTIONFROMLARGETARGETSMAYBEMORECOMPLICATEDTHANEITHER OFTHESIMPLEMODELSDESCRIBED)NDEED PARTICULARLYNEARGRAZINGINCIDENCE THESIGNAL ISOFTENDESCRIBEDBYA+ A7EIBULL ORALOG NORMALDISTRIBUTIONn4HESEDISTRIBU TIONSAREMOREOFTENUSEDTODESCRIBETHEVARIATIONSBETWEENDIFFERENTRETURNSFROMAN AREA RATHERTHANFADING4HEYMAYBETHOUGHTOFASDESCRIBINGWHATHAPPENSWHEN THE AREA CONTAINS DIFFERENT R S AND THE DISTRIBUTION FOR EACH IS 2AYLEIGH "ECAUSE OFTHIS THERANGEOFVARIABILITYMAYBEEVENGREATERTHANTHED"FORA2AYLEIGH DISTRIBUTION &ADING 2ATE#OMPUTATIONS $OPPLERFREQUENCYCALCULATIONISTHEEASIESTWAY TOFINDFADINGRATES4OCOMPUTETHESIGNALAMPLITUDERETURNEDWITHAPARTICULARRANGE OFDOPPLERSHIFTS ALLSIGNALSHAVINGSUCHSHIFTSMUSTBESUMMED4HISREQUIRESKNOW INGTHECONTOURSOFCONSTANTDOPPLERSHIFTISODOPS ONTHESCATTERINGSURFACE4HESE CONTOURS MUST BE ESTABLISHED FOR EACH PARTICULAR GEOMETRIC ARRANGEMENT! SIMPLE EXAMPLEISPRESENTEDHEREHORIZONTALMOTIONOVERAPLANEEARTH4HISISTYPICALOFAN AIRCRAFTINORDINARYCRUISINGFLIGHT #ONSIDER TRAVEL IN THE Y DIRECTION WITH Z VERTICAL AND THE ALTITUDE FIXED Z H 4HEN
V Y V
2 X X Y Y Z H WHEREX Y Z AREUNITVECTORS(ENCE
VR V
2 2
VY
X Y H
WHERE VR IS THE RELATIVE SPEED #URVES OF CONSTANT RELATIVE SPEED ARE ALSO CURVES OF CONSTANTDOPPLERSHIFT4HEEQUATIONOFSUCHACURVEIS
X Y
V VR H VR
4HIS IS A HYPERBOLA4HE LIMITING CURVE FOR ZERO RELATIVE SPEED IS A STRAIGHT LINE PERPENDICULARTOTHEVELOCITYVECTOR&IGURESHOWSSUCHASETOFCONSTANT DOPPLER SHIFTCONTOURS
'2/5.$%#(/
£È°£x
&)'52% #ONTOURS OF CONSTANT DOPPLER FREQUENCYSHIFTONAPLANEEARTHDUETOHORIZONTAL MOTION
4HESPECTRUMOFFADINGCANBECALCULATEDBYASLIGHTREARRANGEMENTOFTHERADAR EQUATION%Q 4HUS IF7R FD ISTHEPOWERRECEIVEDBETWEENFREQUENCIESFDAND FD DFD THERADAREQUATIONBECOMES
7R FD DFD
P
AREAA ¯)LLUMINATED BETWEEN F AND F DF D
D
D
DFD 0' T T !R S D! 2 P
¯
0' T T !R S 2
¤ D! ³ ¥¦ DF ´µ D
4HISISANINTEGRALINWHICHTHEAREAELEMENTBETWEENFDANDFD DFDISEXPRESSED INTERMSOFCOORDINATESALONGANDNORMALTOTHEISODOPS3UCHCOORDINATESMUSTBE ESTABLISHEDFOREACHPARTICULARCASE &IGURESHOWSTHEGEOMETRYFORHORIZONTALTRAVEL4HECOORDINATEWISALONGTHE ISODOP ANDGISNORMALTOIT7ECANEXPRESS%QINTERMSOFTHESECOORDINATESAS
7R FD
DH § L ¶ DFD ¨© P ·¸
§ 0' S DX ¶ T · 2 ¸
¯STRIPP ¨©
.OTETHAT0T THETRANSMITTEDPOWER ISNON ZERO IN THE INTEGRAL ONLY FOR THE TIME IT ILLU MINATESTHEGROUND)NPULSERADARS ONLYTHAT PARTOFTHEGROUNDAREAPROVIDINGSIGNALSBACK TO THE RADAR AT A PARTICULAR TIME CAN BE CON SIDEREDTOHAVEFINITE0T ANDSOTHERANGEOF FREQUENCIESTHATCANBEPRESENTISLIMITEDBY THEPULSE ASWELLASBYTHEANTENNASANDTHE MAXIMUMVELOCITY !NOTHEREXAMPLEISSHOWNIN&IGURE 4HISISTHESMALLILLUMINATEDAREAFORANARROW BEAM SHORT PULSE SYSTEM WITH THE ANTENNA POINTED STRAIGHT AHEAD (ERE WE CAN MAKE LINEARAPPROXIMATIONSWITHOUTTOOMUCHERROR
&)'52% 'EOMETRY OF COMPLEX FADING CALCULATIONSAFTER&45LABY 2+-OORE AND !+&UNG
£È°£È
2!$!2(!.$"//+
&)'52% 'EOMETRYOFDOPPLER SHIFTCALCULA TIONSFORANAIRBORNESEARCHRADAR
!PULSEOFLENGTHSISTRANSMITTEDFROMANANTENNAOFBEAMWIDTHE7EMAYSIMPLIFY THEPROBLEMBYASSUMINGARECTANGULARILLUMINATEDAREA 2ECSSINP &URTHERMORE THECURVATUREOFTHEISODOPSMAYBENEGLECTED SOTHEDOPPLERFREQUENCYISASSUMEDTO BETHESAMEFORALLMAXIMUM RANGEPOINTSANDTHESAMEFORALLMINIMUM RANGEPOINTS 7ITHTHISASSUMPTION FD MAX
FD MIN
V SIN Q MAX L
V SIN Q MIN L
4HUS THETOTALWIDTHOFTHEDOPPLERSPECTRUMIS
$ FD
V SIN Q MAX SIN Q MIN L
&ORSHORTPULSESANDANGLESAWAYFROMVERTICAL THISIS
$ FD y
V $Q COSQ L
)NTERMSOFPULSELENGTH ITBECOMES VCT COS Q HL SIN Q )FTHEANGULARDIFFERENCEACROSSTHEILLUMINATEDRECTANGLEISSMALLENOUGHSOTHATR ISESSENTIALLYCONSTANT THEDOPPLERSPECTRUMISARECTANGLEFROMFMINTOFMAX
$ FD
'2/5.$%#(/
£È°£Ç
)NPRACTICE ANTENNABEAMSARENOTRECTANGULAR4HERESULTISTHATTHEDOPPLERSPEC TRUMFORASIDE LOOKINGRADARLIKETHATSHOWNINTHEEXAMPLEISNOTRECTANGULARBUT RATHERHASTHESHAPEOFTHEANTENNAALONG TRACKPATTERN4HUS IFTHEANTENNAPATTERNIN THEALONG TRACKDIRECTIONIS' ' A WITHATHEANGLEOFFTHEBEAMCENTER WECAN EXPRESSAINTERMSOFTHEDOPPLERFREQUENCYFDAS A FDKV
ANDTHESPECTRUMIS
7 FD
L 0TS RX § L FD ¶ ' ¨ · P 2 © V ¸
WHERERXISTHEHORIZONTALRESOLUTIONINTHERANGEDIRECTION/FCOURSE THEHALF POWER BEAMWIDTHMAYBEUSEDASANAPPROXIMATION RESULTINGINTHEBANDWIDTHGIVENBY %Q %FFECTOF$ETECTION 4HEEFFECTOFDETECTINGNARROWBANDNOISEHASBEENTREATED EXTENSIVELY IN THE LITERATURE (ERE IT IS NECESSARY ONLY TO SHOW THE POSTDETECTION SPECTRUM OF THE PRECEDING EXAMPLE AND TO CONSIDER THE NUMBER OF INDEPENDENTLY FADING SAMPLES PER SECOND &IGURE SHOWS THE SPECTRUM BEFORE AND AFTER SQUARE LAWDETECTION&ORSQUARE LAWDETECTION THEPOST DETECTIONSPECTRUMISTHE SELF CONVOLUTIONOFTHEPREDETECTIONSPECTRUM/NLYTHEPARTTHATPASSESTHELOW PASS FILTERSINADETECTORISSHOWNINTHEFIGURE4HERECTANGULAR2&SPECTRUMHASBECOME ATRIANGULARVIDEOSPECTRUM 4HISSPECTRUMDESCRIBESTHEFADINGOFTHEDETECTOROUTPUTFORA#7RADAR&ORA PULSERADAR THESPECTRUMISSAMPLEDBYTHEPULSEREPETITIONFREQUENCY02& )FTHE 02&ISHIGHENOUGHSOTHATTHEENTIRESPECTRUMCANBEREPRODUCEDTHE02&ISHIGHER THANTHE.YQUISTFREQUENCY $FD THEDIAGRAMINDICATEDISTHATOFTHESPECTRUMOFTHE SAMPLESOFARECEIVEDPULSEATAGIVENRANGE&IGURESHOWSASERIESOFACTUAL PULSESFROMAMOVINGRADAR FOLLOWEDBYASERIESOFSAMPLESATRANGE24HESPECTRUM SHOWNIN&IGUREISTHESPECTRUMOFTHEENVELOPEOFSAMPLESAT2AFTERLOW PASS FILTERING 4HESPECTRUMOFFADINGATANOTHERRANGEORVERTICALANGLE ISDIFFERENT IN ACCORDWITH%Q &ORMANYPURPOSES THENUMBEROFINDEPENDENTSAMPLESISIMPORTANTBECAUSETHESE MAYBETREATEDBYUSINGTHEELEMENTARYSTATISTICSOFUNCORRELATEDSAMPLES&ORCONTINU OUSINTEGRATION THEEFFECTIVENUMBEROFINDEPENDENTSAMPLEIS
&)'52% 3PECTRUM OF FADING FROM A HOMOGENEOUS SMALL PATCH A BEFOREANDB AFTERDETECTION
£È°£n
2!$!2(!.$"//+
&)'52% &ADINGFORSUCCESSIVEPULSES OFAMOVINGRADARWITHGROUNDTARGET
'2/5.$%#(/
.
0E4
4§ X¶ ¯ ¨ · 2SF X DX © 4¸
£È°£
WHERE0E ISTHEMEANENVELOPEPOWER 4ISTHEINTEGRATIONAVERAGING TIME AND2SFT ISTHEAUTOCOVARIANCEFUNCTIONFORTHEDETECTEDVOLTAGE&ORMANYPRACTICALPURPOSES IF.ISLARGE ITMAYBEAPPROXIMATEDBY
.y"4
WHERE " IS THE EFFECTIVE )& BANDWIDTH &OR THE EFFECT OF SHORT INTEGRATION TIME SEE 5LABYETAL &ADINGSAMPLESCAN OFCOURSE ALSOBEINDEPENDENTBECAUSEMOTIONOFTHEVEHICLE CAUSESTHEBEAMTOILLUMINATEADIFFERENTPATCHOFGROUND4HUS INAPARTICULARCASE THE INDEPENDENT SAMPLERATEMAYBEDETERMINEDEITHERBYTHEMOTIONOFTHEILLUMINATED PATCHOVERTHEGROUNDORBYTHEDOPPLEREFFECTORBYSOMECOMBINATIONOFTHETWO 4HE NUMBER OF INDEPENDENT SAMPLES DETERMINES THE WAY IN WHICH THE 2AYLEIGH OROTHERDISTRIBUTIONSMAYBEAPPLIED4HUS IFPULSESGIVEONLYINDEPENDENT SAMPLES THEVARIANCEOFTHEMEANOBTAINEDBYINTEGRATINGTHESEPULSESISMUCHGREATER THANWOULDBETRUEIFALLPULSESWEREINDEPENDENT $OPPLER BASEDSYSTEMS SUCHASDOPPLERNAVIGATORS MOVING TARGETINDICATORS AND SYNTHETIC APERTURERADARSYSTEMS DEPENDONTHEPREDETECTIONSPECTRUMFORTHEIROPERA TION BECAUSETHEYARECOHERENTANDDONOTUSEAMPLITUDEORSQUARE LAWDETECTION -OVING 4ARGET3URFACES 3OMETIMESCLUTTERHASINTERNALMOTION4HISCANOCCUR WHENFIXEDRADARSAREUSEDTOOBSERVEMOVEMENTOFTHESEAANDTHELAND/NLAND CLUTTER MOTION IS USUALLY DUE TO MOVING VEGETATION ALTHOUGH MOVING ANIMALS AND MACHINESCREATESIMILAREFFECTS4HERADARRETURNFROMANASSEMBLYOFSCATTERERSLIKE THOSESHOWNIN&IGURECANCHANGEBECAUSEOFMOTIONOFTHEINDIVIDUALSCATTERERS JUSTASITCHANGESBECAUSEOFMOTIONOFTHERADAR4HUS IFEACHSCATTERERISATREE THE WAVINGOFTHETREESASTHEWINDBLOWSCAUSESRELATIVEPHASESHIFTSBETWEENTHESEPARATE SCATTERERSTHERESULTISFADING&ORAFIXEDRADAR THISMAYBETHEONLYFADINGOBSERVED EXCEPTFORVERYSLOWFADINGDUETOCHANGESINREFRACTION)FTHESURFACEELEMENTSARE STIFF THEYMAYNOTMOVEENOUGHTOGETSIGNIFICANTDOPPLERSPREADING ANDTHEFADING DISTRIBUTIONMAYNOTBECLOSETO2AYLEIGH3EE"ILLINGSLEYANDOTHERPAPERSBYHIM FORMOREDISCUSSIONOFTHESITUATIONFORFIXEDRADARSOBSERVINGGROUNDTARGETS&ORA MOVINGRADAR THISMOTIONOFTHETARGETCHANGESTHERELATIVEVELOCITIESBETWEENTARGET ELEMENTANDRADARSOTHATTHESPECTRUMISDIFFERENTFROMTHATFORAFIXEDSURFACE4HE WIDTH OF THE SPECTRUM DUE TO VEHICLE MOTION DETERMINES THE ABILITY OF THE RADAR TO DETECTTHISTARGETMOTION
£È°xÊ -1, /Ê/ +1 -ÊÊ ",Ê,"1 Ê, /1, 3PECIAL PURPOSEINSTRUMENTATIONRADARSANDMODIFIEDSTANDARDRADARSMAYBEUSEDTO DETERMINETHEGROUNDRETURN3INCETHEGROUNDRETURNISALMOSTINVARIABLYDUETOSCATTER ING THESESYSTEMSARETERMEDSCATTEROMETERS3UCHSYSTEMSMAYUSE#7SIGNALSWITH ORWITHOUTDOPPLERPROCESSING BUTTHEYMAYALSOUSEBOTHPULSEAND&-TECHNIQUES
£È°Óä
2!$!2(!.$"//+
3CATTEROMETERSCAPABLEOFMEASURINGRESPONSEOVERAWIDERANGEOFFREQUENCIESARE CALLEDSPECTROMETERS6ARIOUSANTENNAPATTERNSFROMPENCILBEAMSTOFANBEAMSMAY BEUSED3YSTEMSTOMEASURETHEFULLPOLARIZATIONMATRIXMUSTUSEVERYCAREFULANTENNA DESIGNSSOTHATTHEPHASESOFTHEDIFFERENTTRANSMITTEDANDRECEIVEDPOLARIZATIONSARE WELLCONTROLLED ANDLEAKAGEBETWEENPOLARIZATIONSISTHOROUGHLYSUPPRESSED #7AND&- #73YSTEMS 4HESIMPLESTSCATTEROMETERUSESASTATIONARY#7 RADAR3UCHSYSTEMSARENOTVERYFLEXIBLE BUTTHEYAREDISCUSSEDHEREINSOMEDETAILTO ILLUSTRATECALIBRATIONTECHNIQUESTHATALSOAPPLYTOTHEMORECOMPLEXSYSTEMS 4HE#7SCATTEROMETERISSHOWNINBLOCKFORMIN&IGURE4OEVALUATERTHE RATIOOFTRANSMITTEDTORECEIVEDPOWERISREQUIRED4HESYSTEMDEPICTEDIN&IGUREA MEASURESTRANSMITTERPOWERANDRECEIVERSENSITIVITYSEPARATELY4HETRANSMITTERFEEDSAN ANTENNATHROUGHADIRECTIONALCOUPLERSOTHATAPORTIONOFTHEENERGYMAYBEFEDTOA POWERMETER4HERECEIVEROPERATESFROMASEPARATEANTENNAELECTRICALLYISOLATED 4HE OUTPUTOFTHERECEIVERISDETECTED AVERAGED ANDDIGITALLYRECORDED)TSSENSITIVITYMUST BECHECKEDBYUSEOFACALIBRATIONSOURCE4HECALIBRATEDSIGNALMAYBEFEDTHROUGHTHE RECEIVERATATIMEWHENTHETRANSMITTERISOFF&IGUREBSHOWSASIMILARARRANGE MENTINWHICHTHESIGNALFROMTHETRANSMITTERISATTENUATEDAKNOWNAMOUNTANDUSEDTO CHECKTHERECEIVERGAIN"YCOMPARINGTHEOUTPUTFROMTHEATTENUATEDTRANSMITTERSIGNAL WITH THAT RECEIVED FROM THE GROUND THE SCATTERING CROSS SECTION MAY BE DETERMINED WITHOUTACTUALLYKNOWINGTHETRANSMITTEDPOWERANDTHERECEIVERGAIN 4HE CALIBRATIONS SHOWN IN &IGURE ARE INCOMPLETE WITHOUT KNOWING THE ANTENNAPATTERNSANDABSOLUTEGAINS3INCEACCURATEGAINMEASUREMENTSAREDIFFICULT ABSOLUTECALIBRATIONSMAYBEMADEBYCOMPARINGRECEIVEDSIGNALSWITHPROPERRELA TIVECALIBRATION FROMTHETARGETBEINGMEASUREDANDFROMASTANDARDTARGET3TANDARD TARGETSMAYBEMETALSPHERES ,UNEBURG LENSREFLECTORS METALPLATES CORNERREFLECTORS ORACTIVERADARCALIBRATORS!2#SACTUALLYREPEATERS /FTHEPASSIVECALIBRATORS THE,UNEBURG LENSREFLECTORISBESTBECAUSEITHASALARGECROSSSECTIONFORITSVOLUME ANDHASAVERYWIDEPATTERNSOTHATALIGNMENTISNOTCRITICAL,UNEBURG LENSREFLECTORS AREUSEDFORMAKINGSTRONGRADARTARGETSOFSMALLVESSELS ANDTHEYMAYBEOBTAINED
&)'52% #7 SCATTEROMETER SYSTEM BLOCK DIAGRAM A SEPARATE TRANSMITTER AND RECEIVER CALIBRATIONANDB CALIBRATIONOFTHERATIOOFRECEIVEDTOTRANSMITTEDPOWER
'2/5.$%#(/
£È°Ó£
FROMCOMPANIESTHATSUPPLYTHATMARKET&OR DISCUSSIONOFTHERELATIVEMERITSOFDIFFERENT PASSIVECALIBRATIONTARGETS SEE5LABYETAL 4HEIDEALRECEIVERWOULDRESPONDLINEARLY TO ITS INPUT SO THAT A SINGLE CALIBRATION AT ONEINPUTLEVELWOULDSUFFICEFORALLLEVELS 4HEUSUALRECEIVER HOWEVER HASSOMENON LINEARITIESDUETODETECTORPROPERTIESANDTO SATURATIONOFITSAMPLIFIERSBYLARGESIGNALS &IGURE SHOWS A TYPICAL INPUT OUTPUT CURVEFORARECEIVER4WOEQUALINCREMENTS ININPUTSIGNAL$I ASSHOWN PRODUCEDIF FERENT INCREMENTS IN OUTPUT BECAUSE OF THE &)'52% 4YPICALRECEIVERINPUT OUTPUT NONLINEARITY OF THIS CURVE &OR THIS REASON CURVE)LLUSTRATEDISTHEEFFECTOFNONLINEARITY RECEIVERCALIBRATIONMUSTBEPERFORMEDOVER ARANGEOFINPUTLEVELS ANDTHENONLINEARI TIESMUSTBECOMPENSATEDFORINTHEDATAPROCESSING #7SCATTEROMETERSDEPENDONANTENNABEAMSTODISCRIMINATEDIFFERENTANGLESOF INCIDENCEANDDIFFERENTTARGETS5SUALLYASSUMPTIONSAREMADETHATTHEANTENNAPAT TERNHASCONSTANTGAINWITHINTHEACTUALD"POINTSANDZEROGAINOUTSIDE BUTTHIS CLEARLYISNOTANACCURATEDESCRIPTION)FLARGETARGETSAPPEARINTHELOCATIONSILLUMI NATEDBYTHESIDEOFTHEMAINBEAMORTHEMINORLOBES THEIRSIGNALSMAYCONTRIBUTE SO MUCH TO THE RETURN THAT ITISSIGNIFICANTLYCHANGED3INCETHISCHANGEDSIGNALIS CHARGEDTOTHEDIRECTIONOFTHEMAJORLOBEBYTHEDATAREDUCTIONPROCESS THERESULTING VALUEFORRISINERROR2ESPONSESATVERTICALINCIDENCEFREQUENTLYCAUSETROUBLE FOR VERTICAL INCIDENCESIGNALSAREUSUALLYFAIRLYSTRONG4HUSTHEANTENNAPATTERNMUSTBE ACCURATELYKNOWNANDTAKENINTOACCOUNTINTHEDATAANALYSIS!PATTERNWITHSTRONG MINORLOBESMAYBESIMPLYINADMISSIBLE 4HESCATTERINGCOEFFICIENTISDETERMINEDBYAPPLYING
0R
0T L P
¯)LLUMINATED AREA
'TS D!
2
4HEINTEGRATIONISOVERWHATEVERAREAISILLUMINATEDSIGNIFICANTLY INCLUDINGTHEREGIONS HITBYTHEMINORLOBES4HEUSUALASSUMPTIONISTHATRISCONSTANTOVERTHEILLUMINATED AREA SOTHAT
0R
0T L S P
¯)LLUMINATED AREA
'T D! 2
4HISASSUMPTIONWOULDBETRUEONLYIFTHEANTENNACONFINEDTHERADIATEDENERGYTO A VERY SMALL SPREAD OF ANGLES AND TO A FAIRLY HOMOGENEOUS REGION 4HE RESULTING EXPRESSIONIS
S
P 0R
0T L ¯)LLUMINATED 'T 2 D! AREA
£È°ÓÓ
2!$!2(!.$"//+
.OTETHATONLYTHERATIOOFTRANSMITTEDTORECEIVEDPOWERISREQUIRED SOTHETECH NIQUESHOWNIN&IGUREBISJUSTIFIED3OMETIMES2 'T ORBOTHAREASSUMEDCON STANT OVER THE ILLUMINATED AREA BUT SUCH AN APPROXIMATION TO %Q SHOULD BE ATTEMPTEDONLYAFTERCHECKINGITSVALIDITYFORAPARTICULARPROBLEM )FTHERESULTOFAPPLYINGTHETECHNIQUEOF%QTOASETOFMEASUREMENTSINDI CATESTHATRPROBABLYDIDVARYACROSSTHESIGNIFICANTLYILLUMINATEDAREA THISVARIATION MAYBEUSEDASAFIRSTAPPROXIMATIONTODETERMINEAFUNCTIONFP DESCRIBINGTHEP VARIATIONOFR ANDANEXT ORDERAPPROXIMATIONTHENBECOMES
S
P 0R 0T L ¯)LLUMINATED §© F Q 'T 2 ¶¸ D!
AREEA
0ROPERSCATTERINGMEASUREMENTSDEMANDANACCURATEANDCOMPLETEMEASUREMENTOF ANTENNAGAIN'T4HISCANBEAVERYTIME CONSUMINGANDEXPENSIVEPROCESS PARTICU LARLYWHENTHEANTENNAISMOUNTEDONANAIRCRAFTOROTHERMETALLICOBJECT.EVERTHELESS COMPLETEPATTERNSAREAMUSTFORGOODSCATTERMEASUREMENTS 2ANGE -EASURING 3YSTEMS 2ADARS ABILITY TO SEPARATE RETURNS FROM DIFFERENT RANGESCANBEUSEDADVANTAGEOUSLYALONGWITHDIRECTIVEANTENNABEAMSTOSIMPLIFYTHE SCATTERINGMEASUREMENTS-OSTRANGINGSCATTEROMETERSUSEEITHERPULSEMODULATIONOR &- ALTHOUGHMOREEXOTICMODULATIONSCOULDALSOBEUSED4HEDISCUSSIONHERETREATS PULSESYSTEMS BUTSINCEALLOTHERRANGE MEASURINGSYSTEMSCANBEREDUCEDTOEQUIVA LENTPULSESYSTEMS MOSTRESULTSAREGENERAL &IGURE SHOWS THE WAY IN WHICH PULSE MEASUREMENT OF RANGE IS USED &IGUREASHOWSACIRCULARPENCILBEAM!TANGLESNEARGRAZING THEILLUMI NATEDPATCHSETBYTHECIRCULARANTENNAPATTERNBECOMESRATHERLONGTHEPATCHISAN ELLIPSE ANDUSEOFTHEPULSELENGTHTOCONFINEILLUMINATIONTOAPARTOFTHEPATCH ISHELPFUL)NDEED FORANGLESVERYNEARGRAZING THISISTHEONLYSATISFACTORYWAYTO RESOLVESMALLREGIONS-ANYSYSTEMSTHATUSEBEAMWIDTHTOSETTHEMEASUREDAREA NEARVERTICALUSERANGERESOLUTIONFORANGLESBEYOND SAY
&)'52% 2ANGE RESOLUTION APPLIED TO SCATTEROMETRY A IMPROVING ONE DIMENSION OF A CIRCULAR BEAMILLUMINATIONPATTERNANDB USEWITHAFANBEAM
'2/5.$%#(/
£È°ÓÎ
&IGUREBSHOWSANANTENNAPATTERNTHATTAKESBETTERADVANTAGEOFTHEPOSSIBILI TIESOFRANGEMEASUREMENT!FANBEAMISUSEDTOILLUMINATEANARROWSTRIPALONGTHE GROUND ANDTHERANGERESOLUTIONPERMITSSEPARATINGTHERETURNSFROMDIFFERENTANGLES BYTHETIMETHEYRETURN4HISTECHNIQUEISESPECIALLYEFFECTIVEATANGLESAWAYFROMTHE VERTICAL FORTHERESOLUTIONNEARTHEVERTICALISMUCHPOORERTHANNEARGRAZING )FWEASSUMETHATRISESSENTIALLYCONSTANT THEGAINISCONSTANT THEPULSEISRECTAN GULAR ANDTHEDIFFERENCEINRANGEACROSSARESOLUTIONELEMENTISNEGLIGIBLE THEEXPRES SIONFORRBECOMES
S
0R P 2 SIN Q
0T L 'FR2
WHERER2ISTHESHORT RANGERESOLUTION *ANZAHASREPORTEDDETAILSOFCALIBRATIONPROBLEMSWITHARANGE MEASURINGPULSED RADARSCATTEROMETER #7 $OPPLER3CATTEROMETERS !CONVENIENTWAYFORANAIRBORNEMEASUREMENT ISTOMEASURETHESCATTERINGCOEFFICIENTATMANYANGLESSIMULTANEOUSLYWITHA#7SYS TEMINWHICHTHERELATIVEVELOCITIESCORRESPONDINGTODIFFERENTANGLESARESEPARATEDBY SEPARATINGTHEIRDOPPLERFREQUENCIES4HEUSEOFAFANBEAMWITHSUCHASYSTEMPERMITS THESIMULTANEOUSMEASUREMENTOFSCATTERINGCOEFFICIENTSATPOINTSAHEADOFANDBEHIND THEAIRCRAFTCARRYINGTHERADAR&IGURESHOWSTHIS4HEPATTERNOFTHEANTENNAILLU MINATIONONTHEGROUNDISSHOWNINTERSECTEDBYTWOISODOPSLINESOFCONSTANTDOPPLER FREQUENCY WITHTHEWIDTHOFTHESPECTRUMBETWEENTHEMSHOWNONTHEDIAGRAM4HE DISTANCEBETWEENTHEMCANBESEENTOBE $R 2SIN Q SIN Q
AND
$FD
V SIN Q SIN Q L
4HUS THEWIDTHOFTHEELEMENTONTHEGROUNDISRELATEDTOTHEDOPPLERFREQUENCY BANDWIDTHBY
$R
2L $FD V
&)'52% 2ESOLUTIONINAFAN BEAM#7 DOPPLERSCATTEROMETER
£È°Ó{
2!$!2(!.$"//+
WHERETHISTECHNIQUEISAPPLIEDTOTHERADAREQUATIONANDTHEFOLLOWINGAREASSUMED RCONSTANTINTHEILLUMINATEDAREA !NTENNAGAINCONSTANTOVERITSBEAMWIDTH&ANDZEROELSEWHERE 2ANGEVARIATIONACROSSTHESMALLILLUMINATEDAREANEGLIGIBLE
0R
0T L ' S D! 0T L S ' &$FD
P ¯ 2 V2
0R V2 0T L ' &$FD
ANDSO
S
$OPPLER SCATTEROMETERS NEED NOT USE FORE AND AFT BEAMS 4HE 3EASAT AND .3#!44 SPACEBORNE DOPPLER SCATTEROMETERS WERE DESIGNED WITH BEAMS POINTED SQUINTED AHEADANDBEHINDTHENORMALTOTHEGROUNDTRACK )NDEPENDENT 3AMPLES 2EQUIRED FOR -EASUREMENT !CCURACY 4HE 2AYLEIGH DISTRIBUTIONDESCRIBESTHEFADINGSIGNALFAIRLYWELL)FWEASSUMEA2AYLEIGHDISTRIBUTION OFFADING THENUMBEROFINDEPENDENTSAMPLESREQUIREDFORAGIVENACCURACYISSHOWNIN &IGURE4HERANGEDEFINEDINTHISFIGUREISTHERANGEOFMEANVALUESLYINGBETWEEN ANDOFPOINTSONTHEDISTRIBUTION4HISACCURACYRANGEISINDEPENDENTOFANYACCU RACYPROBLEMSASSOCIATEDWITHCALIBRATIONANDKNOWLEDGEOFTHEANTENNAPATTERN 4HEPRECISIONOFTHEMEASUREMENTDEPENDSUPONTHENUMBEROFINDEPENDENTSAM PLES NOTONTHETOTALNUMBEROFSAMPLES4HENUMBEROFINDEPENDENTSAMPLESCANBE FOUNDFROM%QOR%QAFTERSUITABLEANALYSIS4HISANALYSISASSUMESTHAT ONLYDOPPLERFADINGCONTRIBUTESTOINDEPENDENCEBUTMOTIONFROMONECELLTOANOTHER ALSOADDSINDEPENDENTSAMPLES4HUS THETOTALNUMBEROFSUCHSAMPLESISAPPROXI MATELYTHEPRODUCTOFTHENUMBERCALCULATEDFROM%QANDTHENUMBEROFGROUND CELLSAVERAGED&IGURESHOWSSOMEEXAMPLESOFTHEEFFECTOFTHEANGLEOFINCI DENCEONTHENUMBEROFINDEPENDENTSAMPLESFORAHORIZONTALLYTRAVELINGSCATTEROMETER WITHAFORWARD POINTEDBEAM 3TUDY OF THE RESULTS OBTAINED IN THIS TYPE OF ANALYSIS INDICATES THAT IN REGIONS WHERETHESCATTERINGCOEFFICIENTDOESNOTCHANGERAPIDLYWITHANGLE THEWIDESTPOS SIBLEANGULARWIDTHOBTAINEDBYALONGERPULSEORAWIDERFILTERFORA#7 DOPPLER SYSTEM GIVES THE MAXIMUM NUMBER OF INDEPENDENT SAMPLES FOR A GIVEN DISTANCE TRAVELEDALONGTHEGROUND
&)'52% !CCURACYOFAVERAGESFORFADING SIGNALS
'2/5.$%#(/
£È°Óx
&)'52% %XAMPLESOFTHEVARIATIONWITHANGLEOFINCIDENCE OFTHENUMBEROFINDEPENDENTSAMPLESFORASCATTEROMETER
.EAR 6ERTICAL0ROBLEM -OSTPUBLISHEDRADARRETURNDATAPURPORTINGTOINCLUDE VERTICAL INCIDENCE GIVE VERTICAL INCIDENCE SCATTERING COEFFICIENTS THAT ARE TOO SMALL 4HISISACONSEQUENCEOFAFUNDAMENTALPROBLEMINMEASURINGNEARTHEVERTICALWITH AFINITEBEAMWIDTHORPULSELENGTH.EAR VERTICALRADARRETURNSFROMMOSTTARGETSDROP OFFRAPIDLYASTHEANGLEWITHTHEVERTICALISINCREASED4HUS THEMEASURINGBEAMWIDTH ORPULSEWIDTHUSUALLYENCOMPASSESSIGNALSFROMREGIONSHAVINGVALUESFORRMANY DECIBELSAPART3INCETHESCATTERINGCOEFFICIENTVARIESMUCHMORERAPIDLYNEARTHEVERTI CALTHANATANGLESBEYONDORFROMTHEVERTICAL THEPROBLEMISMUCHMORESEVERE ATTHEVERTICAL&URTHERMORE THEPROBLEMISCOMPLICATEDATTHEVERTICALBYTHEFACTTHAT THEANGULARSCALETERMINATESTHERE SOTHATABEAMCENTEREDATTHEVERTICALILLUMINATES WEAKERTARGETSR ONBOTHSIDESOFITSPATTERN WHEREASABEAMAWAYFROMTHEVERTICAL ILLUMINATESSTRONGERSIGNALSONONESIDEANDWEAKERSIGNALSONTHEOTHER &IGURESHOWSWHATHAPPENSFORASTEEPLYDESCENDINGCURVEOFRVERSUSP 4HERADARRETURNINTEGRALFROM%QISACONVOLUTIONINTEGRALTHEFIGURESHOWSTHE CONVOLUTIONOFTHEBEAMPATTERNWITHTHERCURVE#LEARLY THEAVERAGEATTHEVERTICAL ISLOWERTHANITSHOULDBETOINDICATEPROPERLYTHEVARIATIONOFRNEARTHEVERTICAL &IGURESHOWSANEXAMPLEBASEDONTHETHEORETICALSCATTERINGCOEFFICIENTFOR THESEADERIVEDFROMTHESPECTRAREPORTEDBYTHE3TEREO7AVE/BSERVATION0ROJECT 4HEEFFECTOFDIFFERENTBEAMWIDTHSISCLEARLYSHOWN 7ITHAPULSEOROTHERRANGE MEASURINGSYSTEM REPORTEDVALUESAREALWAYSINERROR BECAUSE ASINDICATEDABOVE ITISALMOSTIMPOSSIBLETORESOLVEANARROWRANGEOFANGLES NEARTHEVERTICAL&ORSHORTRANGES ONECANCONFIGURETHEANTENNASOTHATAPLANEWAVE IMPINGESONTHESURFACE7HENTHISISDONE THENEAR VERTICALSCATTERINGCOEFFICIENTCAN HAVEITSANGULARVARIATIONPROPERLYDESCRIBED
£È°ÓÈ
2!$!2(!.$"//+
&)'52% (OWFINITEBEAMWIDTHCAUSESANEAR VERTICALERRORINMEASURING THESCATTERINGCOEFFICIENT
'ROUND AND (ELICOPTER 3CATTEROMETERS AND 3PECTROMETERS -ANY GROUND SCATTERING MEASUREMENTS HAVE BEEN MADE WITH SYSTEMS MOUNTED ON BOOM TRUCKS ANDHELICOPTERS-OSTOFTHESEARE&- #7SYSTEMS THATUSEWIDEBANDWIDTHTO OBTAINEXTRAINDEPENDENTSAMPLESRATHERTHANFORFINERESOLUTION3OMEUSEVERYWIDE BANDWIDTHTOOBTAINFINERANGERESOLUTIONTOLOCATESOURCESOFSCATTERING-OSTHAVE MULTIPLE POLARIZATION CAPABILITY AND SOME ARE CAPABLE OF POLARIMETRY BECAUSE THE PHASEOFTWORECEIVEDSIGNALSWITHORTHOGONALPOLARIZATIONCANBEMEASURED 4HEBASICELEMENTSOFAN&- #7SCATTEROMETERARESHOWNIN&IGURE4HE SWEPTOSCILLATORMUSTPRODUCEALINEARSWEEPTHISISEASYWITHYTTRIUM IRON GARNET 9)' nTUNED OSCILLATORS BUT REQUIRES LINEARIZING CIRCUITS IF TUNING USES A VARACTOR
'2/5.$%#(/
£È°ÓÇ
&)'52% %FFECT OF ANTENNA BEAMWIDTH ON THEMEASUREDSCATTERINGCOEFFICIENTASAFUNCTIONOF ANGLEOFINCIDENCE
-ANY SYSTEMS USE DIGITAL WAVEFORM SYNTHESIS TO OBTAIN THE SWEPT WAVEFORM )F DUALANTENNASAREUSEDASSHOWN THEOVERLAPOFTHEBEAMSMUSTBECONSIDERED 3INGLE ANTENNA SYSTEMS ARE SOMETIMES USED WITH A CIRCULATOR ISOLATING TRANSMITTER ANDRECEIVERTHEIRPERFORMANCEISSOMEWHATPOORERTHANTHATOFDUAL ANTENNASYSTEMS BECAUSEOFINTERNALREFLECTIONSANDLEAKAGETHROUGHTHECIRCULATOR &IGURESHOWSTHEKINDOFSYSTEMTHATMAYBEUSEDTOMEASURESCATTERINGFROM WITHINAVOLUME"YDETERMININGTHESPECTRUMOFTHERETURN THEUSERCANESTABLISHTHE SCATTERINGFROMDIFFERENTRANGES4HISSYSTEMHASBEENUSEDINDETERMININGTHESOURCES OFSCATTERINVEGETATIONnANDSNOW 5LTRASONICWAVESINWATERCANBEUSEDTOSIMULATEELECTROMAGNETICWAVESINAIRn "ECAUSEOFTHEDIFFERENCEINVELOCITYOFPROPAGATION ANACOUSTICFREQUENCYOF-(Z CORRESPONDSWITHAWAVELENGTHOFMM3UCHAWAVELENGTHISOFACONVENIENTSIZE FORMANYMODELINGMEASUREMENTS AND OFCOURSE EQUIPMENTINTHE -(ZREGIONIS INMANYWAYSEASIERTOOPERATETHANEQUIPMENTINTHEMICROWAVEREGIONCERTAINLYIT ISMUCHEASIERTOOPERATEANDLESSEXPENSIVETHANMICROWAVEEQUIPMENTOPERATINGAT A MMWAVELENGTH !COUSTICPLANEWAVESANDELECTROMAGNETICPLANEWAVESSATISFYTHESAMEBOUNDARY CONDITIONS7HENTHESCATTERINGSURFACESARENOTPLANEANDWHENANGLESOFINCIDENCE ARERATHEROBLIQUE THEANALOGYBETWEENACOUSTICANDELECTROMAGNETICWAVESISLESS VALID/FCOURSE ACOUSTICSYSTEMSCANNOTSIMULATECROSS POLARIZATION
£È°Ón
2!$!2(!.$"//+
&)'52% "ASICBLOCKDIAGRAMOFAN&- #7SCATTEROMETER2&SECTION
3CATTERING #OEFFICIENTS FROM )MAGES 2ADAR IMAGES PRODUCED BY REAL OR SYNTHETIC APERTURE RADARS CAN BE USED FOR SCATTERING COEFFICIENT MEASUREMENT 5NFORTUNATELY MOSTSUCHSYSTEMSAREUNCALIBRATEDORPOORLYCALIBRATED SOTHERESULTS ARESOMEWHATDUBIOUS EVENONARELATIVEBASIS WHENIMAGESAREPRODUCEDONDIF FERENTDAYS2ELATIVECALIBRATIONHASBEENINTRODUCEDINTOSOMESYSTEMS n !BSOLUTECALIBRATION WHICHALSOSERVESASRELATIVECALIBRATIONINSOMECASES CANBE ACHIEVED BY USING STRONG REFERENCE TARGETS WITH THE ACTIVE RADAR CALIBRATOR !2# REPEATERSESPECIALLYSUITABLE !NOTHERAPPROACHTHATHASBEENUSEDISTOMEASURE SCATTERINGFROMREFERENCEAREASWITHAGROUND BASEDORHELICOPTERSYSTEMTHATISWELL CALIBRATEDANDTOCOMPARETHEIMAGESTOTHESEMEASUREDVALUES
&)'52% "ASICBLOCKDIAGRAMOFAN&- #7RANGE DISCRIMINATINGSCATTEROMETERCONTROLAND DATA HANDLINGSYSTEM
'2/5.$%#(/
£È°Ó
"ISTATIC-EASUREMENTS -EASUREMENTSOFGROUNDRETURNWHENTHERECEIVERAND TRANSMITTERARESEPARATEDARECOMPARATIVELYRARE4HESEMEASUREMENTSAREVERYDIFFICULT TOMAKEFROMAIRCRAFTBECAUSEITISNECESSARYTHATBOTHTRANSMITTERANDRECEIVERANTEN NASLOOKATTHESAMEGROUNDPOINTATTHESAMETIMEANDTHATTHESIGNALBECORRELATED WITHKNOWNANTENNALOOKANGLES&URTHERMORE ITISDIFFICULTTOKNOWTHEPOLARIZATION ANDTHEEXACTSIZEANDSHAPEOFTHECOMMONAREAILLUMINATEDBYTHEANTENNABEAMS ARESOMETIMESDIFFICULTTODETERMINE&ORTHISREASON FEWBISTATICMEASUREMENTSFROM AIRCRAFTHAVEBEENREPORTEDINTHELITERATURE ,ABORATORY BISTATIC MEASUREMENTS HAVE BEEN MADE BY BOTH THE 7ATERWAYS %XPERIMENT3TATIONAND4HE/HIO3TATE5NIVERSITY GROUPSUSINGELECTROMAGNETIC WAVESANDBYTHE5NIVERSITYOF+ANSASGROUPUSINGACOUSTICWAVES"ISTATICMEA SUREMENTSOFLASERRADIATIONHAVEBEENMADEAT"ELL4ELEPHONE,ABORATORIES AND # BANDMEASUREMENTSOFBUILDINGSHAVEBEENMADEATTHE5NIVERSITYOF+ANSAS /THERSURFACE BASEDMEASUREMENTSHAVEALSOBEENREPORTED "ISTATIC MEASUREMENTS CALL FOR COMPLICATIONS WHEN MADE OUTSIDE THE LABORATORY BECAUSEANABSOLUTEREFERENCEFORBOTHTRANSMITTERPOWERANDRECEIVERSENSITIVITYMUST BEUSED)NTHELABORATORY HOWEVER ITISPOSSIBLETOUSETECHNIQUESSIMILARTOTHOSEFOR MONOSTATICMEASUREMENTS
£È°ÈÊ , Ê " -Ê",Ê- // , Ê
" /Ê 1// ,Ê " -® 3CATTER MEASUREMENTS MADE DURING THE S ALLOWED THE GENERATION OF MOD ELS FOR AVERAGE BACKSCATTER FROM LARGE AREAS )N PARTICULAR THESE INCLUDED MEA SUREMENTS WITH THE 3KYLAB RADIOMETER SCATTEROMETER 2!$3#!4 AND WITH TRUCK MOUNTED MICROWAVE ACTIVE SPECTROMETERS -!3 BY THE 5NIVERSITY OF+ANSAS4WODIFFERENTMODELSWEREDEVELOPEDBASEDONTHESAMEDATA ONEA LINEARMODELANDONEAMORECOMPLICATEDFORMULATION(EREWEPRESENTONLYTHE LINEARMODEL4HESEMODELSAREFORAVERAGES ANDTHEMODELSDONOTINCLUDEVARIA TIONSABOUTTHEAVERAGE(OWEVER ANALYSISOF3HUTTLE)MAGING2ADAR3)2 DATA PERMITSSOMEESTIMATESTOBEMADEOFTHEVARIABILITYTOBEEXPECTEDFORDIFFERENT SIZESOFILLUMINATEDFOOTPRINT 4HEGENERALCHARACTERISTICSOFRADARBACKSCATTEROVERTHERANGEOFANGLESOFINCI DENCEHAVEBEENKNOWNFORDECADES&IGURESHOWSTHESE&ORLIKE POLARIZED WAVES ONE CAN BREAK SCATTER INTO THREE ANGULAR REGIMES NEAR VERTICAL THE QUASI SPECULARREGION INTERMEDIATEANGLESFROMTOABOUTTHEPLATEAUREGION AND NEAR GRAZING THE SHADOW REGION #ROSS POLARIZED SCATTER DOES NOT HAVE SEPARATE QUASI SPECULARANDPLATEAUREGIONSTHEPLATEAUEXTENDSTOVERTICAL ANDTOOLITTLEIS KNOWNTOESTABLISHWHETHERASHADOWREGIONEXISTS &ORNEARLYEVERYTYPEOFTERRAIN THEMEASUREDDATAFITSCLOSELYTOTHEFORM
OR
S !I E Q QI
A
S D" LOG !I Q QI
B
WHERE!IANDPIARECONSTANTSTHATDIFFERFORTHENEAR VERTICALANDMIDRANGEREGIONS &IGURESHOWSANEXAMPLEOFTHISVARIATION.OTHEORYGIVESEXACTLYTHISRESULT
£È°Îä
2!$!2(!.$"//+
&)'52% 'ENERALCHARACTERISTICSOFSCATTERINGCOEFFICIENTVARIATION WITHANGLEOFINCIDENCEAFTER&45LABY 2+-OORE AND!+&UNG
BUT NEARLY ALL MEASUREMENTS FIT SUCH A MODEL CLOSELY AND THE MODEL APPROXIMATES MOSTTHEORETICALCURVESWELLOVERTHERELEVANTREGIONS4HISSIMPLERESULTMEANSTHAT SIMPLECLUTTERMODELSMAYBEDEVELOPEDANDUSED ALTHOUGHMORECOMPLEXMODELS MAYBENECESSARYFORSOMEREMOTE SENSINGAPPLICATIONS
&)'52% 2EGRESSION OF AVERAGE OF ALL '(Z CROPLAND DATA FOR TWO YEARS OBTAINED WITH A MICROWAVE ACTIVE SPECTROMETER AFTER 2 + -OORE + ! 3OOFI AND 3-0URDUSKIÚ)%%%
'2/5.$%#(/
£È°Î£
4HEBASISFORTHELINEARMODELISACOMBINATIONOFTHE3KYLABRESULTSOVER.ORTH !MERICAANDTHOSEFROM+ANSASCROPLANDMEASUREMENTSOVERTHREECOMPLETESEASONS WITHTHEMICROWAVEACTIVESPECTROMETER-!3 4HE '(Z3KYLAB2!$3#!4 HADAGROUNDFOOTPRINTOFA KMCIRCLEATVERTICALTOANELLIPSEOFBYKMAT 4HE-!3HADFOOTPRINTSATRANGINGFROMBYMAT'(ZTOBYM AT'(Z BUTMILLIONSOFMEASUREMENTSWEREAVERAGEDFORTHEMODEL"ECAUSETHE 3KYLABDATAWASATONLYONEFREQUENCYANDTHERESPONSESFORTHETWOEXPERIMENTSWERE ESSENTIALLY THE SAME AT THAT FREQUENCY THE FREQUENCY RESPONSE SHOWN IN THE MODEL DEPENDSENTIRELYONTHE-!3MEASUREMENTS 4HESUMMER3KYLABOBSERVATIONSINCLUDEDDESERTS GRASSLAND CROPLAND ANDFORESTS WHEREASTHE+ANSASMEASUREMENTSWEREONLYOFCROPLAND(OWEVER EARLYANDLATEINTHE GROWINGSEASON THECROPLANDWASESSENTIALLYBARE SIMILARTOTHESUMMERDESERTEXCEPT FORSOILMOISTURECONTENT$URINGTHEHEIGHTOFTHEGROWINGSEASON THECROPSWEREDENSE ENOUGHSOTHATSCATTERWASSIMILARTOTHATFROMFORESTS4HUS THEOVERALLMODELSEEMS REPRESENTATIVEOFSUMMERCONDITIONSAVERAGEDOVERALLOF.ORTH!MERICA 4HEMODELTAKESTHEFORM S D" F Q ! "Q #F $F Q
n a Q a n
A
WHERE! " # AND$TAKEONDIFFERENTVALUESFORDIFFERENTPOLARIZATIONSABOVEANDBELOW '(Z4HEFREQUENCYRESPONSEBELOW'(ZISMUCHMORERAPIDTHANABOVE'(Z -OREOVER ATFREQUENCIESABOVE'(ZTHEFREQUENCYRESPONSEISINDEPENDENTOFANGLE SOTHAT$ &ORLOWERFREQUENCIES THEFREQUENCYRESPONSEISANGLE DEPENDENT &ORANGLESLESSTHAN ONLYTWOPOINTSWEREAVAILABLE AND SOSEPARATE FREQUENCYREGRESSIONSWERERUNATEACHOFTHESEANGLES4HEMODELFORTHESEANGLESIS
S D" F Q - Q . Q F
Q n n
B
4HEFREQUENCYRESPONSESBELOW'(ZDIFFEREDFORTHETWOYEARS SOTHEMOD ELSHAVESEPARATEVALUESOFTHECONSTANTSFORAND4HEYEARWAS VERYDRYIN+ANSASTHEREFORE THEVALUESAREPROBABLYMOREREPRESENTATIVE BUTBOTHAREGIVENHERE6ALUESOFTHECONSTANTSAREIN4ABLE&IGURE SHOWSTHECLUTTERMODELFORTHEMIDRANGEOFANGLESASAFUNCTIONOFFREQUENCY 4!",% #ONSTANTSFOR,INEAR3CATTERING-ODEL3UMMER
&REQUENCY 2ANGE '(Z
!NGLE &REQUENCY #ONSTANT 3LOPE" 3LOPE# !OR- D" OR. D" D"'(Z
3LOPE #ORRECTION$ D"¾'(Z
%Q
0OLARIZATION
!NGULAR 2ANGE
A
6 6 6 ( ( (
n n n n n n
n n n n n n
B
6AND( 6AND( 6AND( 6AND( 6AND( 6AND(
n n n n n n
!FTER2+-OORE +!3OOFI AND3-0URDUSKIÚ)%%%
£È°ÎÓ
2!$!2(!.$"//+
&)'52% 'ENERAL LAND SCATTERING CLUTTER MODEL VERTICAL POLARIZATION (ORIZONTALPOLARIZATIONISVERYSIMILARAFTER2+ -OORE +!3OOFI AND3-0URDUSKIÚ)%%%
4HE FIGURE IS ONLY FOR VERTICAL POLARIZATION BECAUSE RESULTS ARE SO SIMILAR FOR VERTICALANDHORIZONTAL 5LABY DEVELOPED A DIFFERENT MORE COMPLEX MODEL FROM THE +ANSAS VEGETATION DATA4HISMODELFITSCURVESRATHERTHANSTRAIGHTLINESTOTHEMEASUREDDATA&ORMOST PURPOSES THESTRAIGHT LINEMODELISADEQUATE ANDITISMUCHEASIERTOUSE ! STRAIGHT LINE MODEL FOR SNOW COVERED GRASSLAND SIMILAR TO THAT FOR VEGETATION DEPENDSONAMORELIMITEDDATASET 4HEDATAWASFORONLYONESEASONIN#OLORADO WHENTHESNOWWASONLYABOUTCMDEEP4HISMEANSTHATTHESIGNALPROBABLYPENE TRATEDTOTHEGROUNDSURFACEATFREQUENCIESBELOWABOUT'(Z.EVERTHELESS THEMODEL INDICATESTHEKINDOFRESULTSTOBEEXPECTEDFORTHISIMPORTANTSITUATION4ABLEGIVES THERESULTINGCONSTANTSTOUSEIN%QA 4!",% 2EGRESSION2ESULTSFOR'ROUND "ASED-EASUREMENTSOF3NOW #OVERED'ROUND
4IMEOF $AY $AY $AY $AY $AY .IGHT .IGHT .IGHT .IGHT
0OLARIZATION
&REQUENCY #ONSTANT 2ANGE '(Z ! D"
&REQUENCY !NGLE3LOPE 3LOPE# " D" D"'(Z
3LOPE#ORRECTION $ D" r'(Z
6 6 ( ( 6 6 ( (
n n n n n n n n
n
!FTER2+-OORE +!3OOFI AND3-0URDUSKI¡)%%% ./4%P TOn6ALUESOFCOEFFICIENTSINTHISTABLEAREALSOCONSIDEREDTHOSEOFTHEMODEL
'2/5.$%#(/
3NOW SCATTER DEPENDS STRONGLY ON THE FREE WATER CONTENT OF THE UPPER LAYER OF SNOW SO SCATTER IS MUCH LOWER FROM THE WET DAYTIME SNOWWHERESOLARMELTINGHASCOM MENCED THAN FOR THE DRY NIGHTTIME SNOW (ENCE DIFFERENT MODELS MUST BE USED FOR DAY AND NIGHT COMPARE THE DAY AND NIGHT MEASUREMENTS SHOWN IN &IGURE 4HE DIFFER ENCE BETWEEN DAY AND NIGHT SCATTER FROMSNOWISEVENMOREPRONOUNCED AT '(Z BUT THE MODEL DOES NOT INCLUDE '(Z BECAUSE NO DATA EXISTSBETWEENAND'(Z !LTHOUGH NO SPECIFIC CLUTTER MODELHASBEENDEVELOPEDFORFORESTS RESULTS FROM THE 3KYLAB 2!$3#!4 AND 3EASAT SCATTEROMETER SHOW THAT THE !MAZON RAINFOREST SCATTERS ALMOST INDEPENDENTLY OF THE ANGLE OF INCIDENCE EVEN NEAR VERTICAL 4HEMEANMEASUREDVALUEATWAS
o D" AT '(Z 3IMILAR RESULTS WERE FOUND AT #BAND /BSERVATIONS WITH 3)2 " 3)2 # AND *%23 INDICATED THAT THIS LACK OF ANGULAR VARIATION OF R ALSO IS PRESENTAT'(Z 4HE MODELS DESCRIBED ABOVE ARE BASED ON AVERAGES OVER VERY LARGE AREAS &OR THIS SITUATION THE VARI ABILITY FROM PLACE TO PLACE IS SMALL PARTICULARLYINTHEMIDRANGEOFANGLES &IGURE SHOWS THE MEAN AND UPPER AND LOWER DECILE VALUES MEA SUREDBYTHE3KYLAB2!$3#!4OVER .ORTH !MERICA 4HE LARGE VARIATION NEAR VERTICAL APPARENTLY RESULTS FROM THE EFFECT OF NEARLY SPECULAR REFLEC TION FROM WATER BODIES 7HEN THE FOOTPRINT IS SMALLER MORE VARIABILITY OCCURS4HISISSHOWNIN&IGURE FROMASTUDYOFTHEVARIATIONOFSCAT TEROBSERVEDBY3)2 "WITHAVERAGES OVER DIFFERENT SIZED FOOTPRINTS &OR SMALL FOOTPRINTS THE SCATTER VARIES OVERAWIDERANGE ANDSYSTEMDESIGN ERSMUSTACCOUNTFORTHIS
£È°ÎÎ
&)'52% 2EGRESSIONSFORVERTICAL POLARIZATION CLUTTERMODELFORSNOWA DAYANDB NIGHT.OTETHE LARGE DIFFERENCES (ORIZONTAL POLARIZATION IS SIMILAR AFTER2+-OORE +!3OOFI AND3-0URDUSKI Ú)%%%
£È°Î{
2!$!2(!.$"//+
&)'52% !NGULAR PATTERNS OF THE MEAN UPPER DECILE AND LOWER DECILE OF 3KYLAB SCATTEROMETER OBSERVATIONS OVER .ORTH!MERICA DURING THE SUMMER SEASON FROM -OORE ET AL 5NIVERSITYOF+ANSAS2EMOTE3ENSING,ABORATORY4ECHNICAL2EPORT
&)'52% RANGEOFPIXELAMPLITUDEVERSUSRESOLUTION
'2/5.$%#(/
£È°Îx
£È°ÇÊ - // , Ê " /Ê / .UMEROUS PROGRAMS TO GATHER SCATTERING COEFFICIENT DATA EXISTED PRIOR TO BUT SIZABLE DATA COLLECTIONS WITH ACCOMPANYING hGROUND TRUTHv WERE RARE 3INCE HOWEVER SEVERALMAJORPROGRAMSHAVECHANGEDTHESITUATIONSOTHATMUCHINFORMATION ISNOWAVAILABLE)NDEED THISINFORMATIONISSOWIDESPREADTHATANADEQUATESUMMARY OF THE LITERATURE IS IMPOSSIBLE (ENCE THIS SECTION CAN ONLY GIVE HIGHLIGHTS OF THE RESULTSANDMAJORPROGRAMS4HEREADERSHOULDCONSULTTHETHREEMAJORCOMPENDIAOF SUCHDATAFORMOREINFORMATIONBOTHONRESULTSANDONBIBLIOGRAPHY NOTETHAT INFORMATIONISSPREADTHROUGHMANYCHAPTERSOFTHESEVOLUMES 3OMEEARLYSCATTERING COEFFICIENT MEASUREMENTPROGRAMSWORTHMENTIONINGINCLUDE THOSEOFTHE.AVAL2ESEARCH,ABORATORY 'OODYEAR!EROSPACE#ORPORATION 3ANDIA #ORPORATIONNEAR VERTICALDATA ANDPARTICULARLY4HE/HIO3TATE5NIVERSITY &ROM TO THE LARGEST PROGRAM WAS AT THE 5NIVERSITY OF +ANSAS %XTENSIVE PROGRAMS WERE ALSO IN &RANCE #ENTRE .ATIONAL D%TUDES 3PATIALES #ENTRE.ATIONALD%TUDESDES4£L£COMMUNICATIONS 5NIVERSIT£0AUL3ABATIER THE .ETHERLANDS #ANADA#ENTREFOR2EMOTE3ENSING##23ESPECIALLYSEAICE AND3WITZERLANDAND!USTRIASNOW -ANYOFTHERESULTSFROMTHESEPROGRAMS APPEAR IN DIGESTS OF THE )NTERNATIONAL 'EOSCIENCE AND 2EMOTE 3ENSING 3YMPOSIA )'!233 )%%% 'EOSCIENCE AND 2EMOTE 3ENSING 3OCIETY AND JOURNALS SUCH AS )%%%4RANSACTIONSON'EOSCIENCEAND2EMOTE3ENSINGANDON/CEAN%NGINEERING )NTERNATIONAL *OURNAL OF 2EMOTE 3ENSING 2EMOTE 3ENSING OF %NVIRONMENT AND 0HOTOGRAMMETRIC%NGINEERINGAND2EMOTE3ENSING !LTHOUGHCALIBRATIONSFORSOMEOFTHEOLDERDATAWEREDOUBTFUL SUMMARYPRESEN TATIONSARENOTAVAILABLEFORNEWERDATA!CCORDINGLY &IGURESHOWSANEARLIER SUMMARYBASEDMOSTLYON8 BANDDATA/NESHOULDBECAUTIOUSINUSINGTHISDATA BUT THEFIGUREGIVESAFEELFORTHEOVERALLVARIATIONS&IGUREISASIMILARPRESENTATION FORNEAR VERTICALDATA#ALIBRATIONOFTHESYSTEMSWASGOOD BUTTHEANTENNAEFFECT DISCUSSEDIN3ECTIONMAKESTHEVALUESFROMTOLOW %FFECTS OF 2OUGHNESS -OISTURE #ONTENT AND 6EGETATION #OVER 3CATTERING FALLSOFFMORERAPIDLYWITHANGLESFORSMOOTHSURFACESTHANFORROUGHSURFACES3INCE THEROUGHNESSTHATAFFECTSRADARMUSTBEMEASUREDINWAVELENGTHUNITS ASURFACESMOOTH ATLONGWAVELENGTHSMAYBEROUGHATSHORTERONES4HISISILLUSTRATEDIN&IGURE WHICH SHOWS THESE EFFECTS WITH MEASUREMENTS FROM PLOWED FIELDS!T '(Z THE SIGNALCHANGEDD"BETWEENANDFORTHESMOOTHESTFIELDANDONLYD"FORTHE ROUGHEST!T'(ZTHESMOOTHESTFIELDWASROUGHENOUGHTOREDUCETHEVARIATION TOD" &ORMOSTSURFACES CROSS POLARIZEDSCATTERISLOWERTHANLIKE POLARIZEDSCATTER OFTEN BYABOUTD"#ROSS POLARIZEDSCATTERFROMSMOOTHSURFACESISMUCHLESSNEARVERTI CAL THAN ELSEWHERE &IGURE SHOWS THIS EFFECT #ROSS POLARIZED RETURNS FROM VOLUMESCATTERERSWITHELEMENTSTHATARELARGECOMPAREDWITHAWAVELENGTHARESTRON GERTHANFORSURFACES SOMETIMESBEINGONLYD"DOWN 3CATTERDEPENDSONTHEDIELECTRICCONSTANT WHICHDEPENDSONMOISTURECONTENT4HUS SCATTERFROMWETSOILSATANGLESOFFVERTICALISUSUALLYMUCHHIGHERTHANFROMDRYSOILS &IGURESHOWSTHIS4HEEFFECTCANBEMANYDECIBELSD"INTHEFIGURE 6EGETATIONCANOPIESOVERSOILCANCONTRIBUTETOSCATTERINTHEVARIOUSWAYSSHOWN IN &IGURE &IGURE SHOWS AN EXAMPLE -OST OF THE SCATTER FROM THEENTIREPLANTCAMEFROMTHETOPLEAVES WITHENOUGHATTENUATIONTHERETOREDUCE
£È°ÎÈ
2!$!2(!.$"//+
&)'52% "OUNDARIESOFMEASUREDRADARDATAA HORIZONTALPOLAR IZATIONANDB VERTICALPOLARIZATION#OURTESYOF)+ATZ
THE SCATTER FROM STEM BOTTOM LEAVES AND SOIL TO MEASURABLE BUT NEGLIGIBLE SIZE 7HENTHOSELEAVESWEREABSENT THESIGNALSSCATTEREDFROMTHESOILANDLOWERPARTS OFTHEPLANTWEREABOUTEQUALTOEACHOTHERANDWEREMUCHLARGERTHANWHENLEAVES WEREPRESENT
'2/5.$%#(/
£È°ÎÇ
&)'52% "OUNDARIES OF MEASURED RADAR RETURN NEAR VERTICAL INCIDENCE BASED ON 3ANDIA #ORPORATION DATA FROM & * *ANZA 2 + -OORE AND " $ 7ARNER
&)'52% !NGULARRESPONSEOFTHESCATTERINGCOEFFICIENTFORFIVEMOISTFIELDSWITHDIFFERENTROUGHNESSAT A '(Z B '(Z ANDC '(ZAFTER&45LABY 2+-OORE AND!+&UNG
£È°În
2!$!2(!.$"//+
&)'52% !NGULAR DEPENDENCE OF THE DEPOLARIZATION RATIO OF A SMOOTHSURFACEAFTER&45LABY 2+-OORE AND!+&UNG
&)'52% -EASUREDSCATTERINGCOEFFICIENTRLEFTSCALE ASAFUNCTION OF SOIL MOISTURE CONTENT FOR THREE SURFACE ROUGHNESSES4HE SOLID CURVE IS THE REFLECTIVITY'RIGHTSCALE CALCULATEDONTHEBASISOFDIELECTRICMEASUREMENTS AFTER4,E4OANÚ)%%%
'2/5.$%#(/
&)'52% #ONTRIBUTIONS TO BACKSCATTER FROM A VEGETATION CANOPY OVERASOILSURFACE DIRECTBACKSCATTERINGFROMPLANTS DIRECTBACKSCAT TERINGFROMSOILINCLUDESTWO WAYATTENUATIONBYCANOPY AND PLANT SOIL MULTIPLESCATTERINGAFTER&45LABY 2+-OORE AND!+&UNG
&)'52% &- #7PROBINGSCATTEROMETERMEASUREMENTSOFA CORNPLANTAT4HESOLIDCURVEISTHEFULLPLANTTHEDOT DASHCURVE LEAF REMOVED THE DOTTED CURVE LEAF REMOVED AFTER , + 7U ETAL
£È°Î
£È°{ä
2!$!2(!.$"//+
"ECAUSE VOLUME SCATTER DOMINATES FOR DENSE VEGETATION ESPECIALLY TREES R IS NEARLYINDEPENDENTOFTHEANGLEOFINCIDENCE&IGURESHOWSTHISWITHRESULTS FROM8 BANDIMAGINGOFAFOREST4HEFIGUREISAPLOTOFFRATHERTHANRF RCOSP !TLOWFREQUENCIESSUCHAS6(& THISCONDITIONCHANGESBECAUSETHEATTENUATIONTHROUGH THELEAVESANDBRANCHESISLESS 3OIL-OISTURE &IGURESHOWSTHESIZEOFTHEEFFECTOFSOILMOISTUREONR 3OILMOISTUREEFFECTSDIFFERFORDIFFERENTSOILS$OBSONAND5LABYSHOWEDTHATTHIS USEOFMOISTUREEXPRESSEDINPERCENTOFFIELDCAPACITYIMPROVEDTHEFITBETWEENRAND MOISTURECONTENT&IELDCAPACITYISAMEASUREOFHOWTIGHTLYTHESOILPARTICLESBINDTHE WATERTHEUNBOUNDWATERAFFECTSDMORE!NEMPIRICALEXPRESSIONFORFIELDCAPACITY &# IS
&# 3 #PERCENTBYWEIGHT
WHERE3AND#ARETHEPERCENTAGESBYWEIGHT OFSANDANDCLAYINTHESOIL4HESOIL MOISTURECONTENTINTERMSOFFIELDCAPACITYIS
MF MG &#PERCENT
WITHMGTHEPERCENTMOISTUREINTHESOILBYWEIGHT7HENWEUSETHISMEASURE THERELA TIONBETWEENRIND"ANDMFISLINEAREVENINTHEPRESENCEOFMODERATEVEGETATIONCOVER ASSHOWNIN&IGURE4HESLOPEOFTHISCURVEISSOMEWHATDIFFERENTWITHVEGETA TIONCOVERTHANITISWITHOUT HOWEVER!LTHOUGHMFISAPPARENTLYATLEASTASGOODASTHE VOLUMETRICMOISTURECONTENTFORRELATINGTOR ITSUSEHASBEENQUESTIONED 3OIL MOISTURE CAN AFFECT A RADAR IMAGE AS HAS BEEN DEMONSTRATED IN IMAGERY OBTAINEDFROMTHE3EASAT, BAND3!2!SIMULATIONEXPERIMENTSHOWEDTHATONE CANESTIMATESOILMOISTUREWITHINFOROFTHEPIXELSINANIMAGE-OREOVER ITSHOWEDTHATRESOLUTIONSBETWEENANDMWERESUPERIORTOFINERRESOLUTIONS
&)'52% -EASURED SCATTERING VARIATION OF A FOREST PARCEL OF OLD BEECH TREES .OTE USE OF F WITH AN ARBITRARY REFERENCE INSTEAD OF R FOR THE ORDINATE AFTER$((OEKMAN
'2/5.$%#(/
£È°{£
&)'52% '(ZSCATTERINGCOEFFICIENTVERSUSSOILMOISTUREPERCENTOFFIELDCAPACITY FOR VEGETATION COVEREDSOILAFTER&45LABYETAL
FORTHISPURPOSE-OSTOFTHESPACEBORNE3!2STHATFOLLOWED3EASATHAVEBEENUSEDIN SOIL MOISTURESTUDIES 6EGETATION "ACKSCATTERFROMVEGETATIONDEPENDSONMANYPARAMETERSANDVAR IESWIDELY4HUS ALTHOUGHWECANDEVELOPAVERAGEMODELSLIKETHOSEDESCRIBEDIN 3ECTION DETAILSAREMUCHMORECOMPLEX4HERVARIESWITHSEASON MOISTURE CONTENT STATEOFGROWTH ANDTIMEOFDAY &IGURESHOWSTHESEASONALVARIATIONFORCORNCOMPAREDWITHAMODEL PRESENTEDINTHEREFERENCE4HEMUCHLARGERVARIATIONATRAPPARENTLYRESULTSFROM THELARGEREFFECTATVERTICALOFTHESOILANDCONSEQUENTLYITSMOISTURECONTENT4HE RAPIDD"SWINGBETWEEN-AYAND*UNERESULTSFROMDRYINGOFTHESOIL%VEN AT WHERE ATTENUATION THROUGH THE CANOPY MASKS THE SOIL EFFECT THE SEASONAL VARIATION EXCEEDS D" $IURNAL VARIATIONS ARE RELATIVELY SMALL BUT FINITE 4HEY RESULTBOTHFROMPLANTMOISTURECHANGESANDFROMMORPHOLOGICALCHANGESACORN PLANTACTUALLYLIFTSITSLEAVEShTOMEETTHESUNvMORNINGGLORIESCLOSETHEIRFLOWERS ATNIGHT -OSTCROPSAREPLANTEDINROWS4HISCAUSESANAZIMUTHALVARIATIONOFR ASSHOWN IN&IGURE4HEMODULATIONSHOWNISTHERATIOOFRLOOKINGPARALLELTOTHEROWS MOREVEGETATION TOTHATLOOKINGNORMAL4HISPHENOMENONISMUCHMOREPRONOUNCED ATTHELOWERFREQUENCIES 3OMEGENERALPROPERTIESOFVEGETATIONSCATTERAREVISIBLEIN&IGURE!TLOW FREQUENCIES THEDECAYWITHPISRAPIDOUTTOABOUTANDTHENMOREGRADUALMOST OFTHESTEEPPARTRESULTSFROMSURFACEECHO!THIGHERFREQUENCIES THEPLANTATTENU ATIONPREVENTSASIGNIFICANTSURFACEECHO SOTHEANGULARVARIATIONISMOREUNIFORM
£È°{Ó
2!$!2(!.$"//+
&)'52% 4IMEVARIATIONOFSCATTERFROMA CORNANDB ALFALFAATINCIDENCEANGLESOFVERTICAL ANDAFTER%!TTEMAAND&45LABY
#ROSS POLARIZED SIGNALS AT VERTICAL ARE NEGLIGIBLE SO EVEN AT LOW FREQUENCIES THE CROSS POLARIZED R VARIES UNIFORMLY!T BOTH HIGH AND LOW FREQUENCIES IT IS ABOUT D"BELOWTHELIKE POLARIZEDR 3NOW 7HEN SNOW COVERS THE GROUND MUCH OF THE SCATTER IS FROM THE SNOW RATHERTHANTHEUNDERLYINGGROUND3NOWISBOTHAVOLUME SCATTERINGANDANATTENUAT INGMEDIUM7HENTHESNOWISDRY SCATTERCOMESFROMALARGEVOLUMEWHENITIS WET THESCATTERINGVOLUMEISMUCHLESSBECAUSEOFHIGHERATTENUATION!SARESULT
'2/5.$%#(/
£È°{Î
&)'52% &REQUENCYRESPONSEOFTHELOOK DIRECTIONMODULATION RATIOFORASOYBEANFIELDWITHHORIZONTALPOLARIZATIONATINCIDENCEANGLES OF ANDAFTER&45LABY 2+-OORE AND!+&UNG
RDECREASESRAPIDLYASTHESUNMELTSTHETOPLAYER&IGUREILLUSTRATESHOWFAST THISCANBEANDALSOSHOWSTHATTHEEFFECTISMUCHGREATERATTHEHIGHERFREQUENCIES WHEREATTENUATIONISGREATER&IGURESHOWSTHEANGULARVARIATIONSEENFOR SNOW COVEREDGROUND/FF VERTICALSCATTERINGISMUCHGREATERATHIGHERFREQUENCIES &ORTHE CMDEPTHSHOWN MUCHOFTHESCATTERATAND'(ZISPROBABLYFROM THEUNDERLYINGSURFACE 3OME REPORTS STATE THAT THERE ARE RADAR HOT SPOTS IN SNOW COVER PARTICULARLY AT '(Z4HESEREPORTSRESULTFROMIMPROPERINTERPRETATIONOFVARIATIONSTHATAREDUE TONORMAL2AYLEIGHFADINGOFTHESIGNAL3CATTERFROMSNOWCOMESFROMMANYCEN TERS WITHIN THE ILLUMINATED VOLUME SO THE CONDITIONS FOR 2AYLEIGH FADING ARE MET
£È°{{
2!$!2(!.$"//+
&)'52% #OMPARISON OF MODEL CALCULATIONS WITH MEASUREMENTS AT A '(Z AND B '(ZAFTER(%OMAND!+&UNG
-EASUREMENTSWITHSUITABLEAVERAGINGINFREQUENCYORILLUMINATIONANGLEDEMONSTRATE THATSNOW COVEREDSURFACESSCATTERESSENTIALLYUNIFORMLYEXCEPTFORTHEEFFECTSOFTHE MULTIPATHFADING 3EA )CE 3EA ICE IS A VERY COMPLEX MEDIUM )CE OBSERVERS CHARACTERIZE IT IN MANYDIFFERENTCATEGORIESTHATDEPENDONTHICKNESS AGE ANDHISTORYOFFORMATION (ENCE ONECANNOTCHARACTERIZEITSRADARRETURNINANYSIMPLEWAYINTHISSENSE ITIS LIKEVEGETATION4HEMOSTIMPORTANTICETYPESFROMARADARPOINTOFVIEWAREFIRST YEAR &9TOMTHICK MULTIYEAR-9 MTHICK ANDACONGLOMERATIONOFTHINNER TYPES MTHICK ,IKESNOW SEAICEINFLUENCEDBYSOLARMELTINGANDABOVEFREEZINGTEMPERATURES SCATTERSMICROWAVESVERYDIFFERENTLYFROMTHEMORENORMALCOLD SURFACEICE)NWIN TER THECOLD-9ICESCATTERSMUCHMORETHANCOLD&9ICE)NSUMMER RFOR-9ICE DECREASESTOABOUTTHESAMELEVELASTHATOF&9ICE&IGURESHOWSTHISANDTYPI CALANGULARRESPONSES4HESECURVESAREFOR'(Z BUTTHERESULTSWOULDBESIMILAR ATANYFREQUENCYDOWNTO3BAND&IGURESHOWSTHEFREQUENCYVARIATIONOFR FORVARIOUSKINDSOFICE3HORE FASTICEISGROUNDEDTOTHEBOTTOMATTHESHORELINEIN THISCASE ITISPROBABLY-9'RAYICEISONEOFTHETYPESTHINNERTHAN&9 +IMDEVELOPEDATHEORYTHATEXPLAINSAWIDERANGEOFSEA ICERMEASUREMENTS &ROMTHISANDEXTENSIVEDATAFROMTHELITERATUREONICEPROPERTIES &IGURE SHOWS THE RANGES OF &9 AND -9 SCATTERING UNDER WINTER CONDITIONS #LEARLY HIGHERFREQUENCIESAREBETTERFORIDENTIFYINGICETYPESTHANLOWERFREQUENCIES AND
'2/5.$%#(/
£È°{x
&)'52% $IURNALPATTERNSOFRANDLIQUID WATERCONTENT FORSNOWATSEVERALFREQUENCIES.OTETHEEXTREMEVARIATIONOFTHE +ABANDASTHESUNSTARTSTOMELTTHESURFACEAFTER7(3TILESAND &45LABY
DISCRIMINATIONISNOTPOSSIBLEBELOWABOUT'(Z!T,BANDANDBELOW THEDIFFER ENCESBETWEEN-9AND&9ICEARESMALLEVENINWINTER4HISMEANSTHATIMAGING RADARSCANEASILYDISTINGUISHICETYPESBYINTENSITYALONEATTHEHIGHERFREQUENCIES INWINTERBUTNOTINSUMMER4HISFACTISTHEBASISFOROPERATIONALICE MONITORING SYSTEMSBYTHE3OVIET5NION;USINGTHE4OROS+U BANDSIDE LOOKINGAIRBORNERADAR 3,!2 =AND#ANADAUSINGAMODIFIED8 BAND!03 3,!2ANDTHE34!2 8 BAND3!2 !PRIMEMOTIVATIONFORTHE#ANADIAN2ADARSAT3!2WASMONITOR INGOFSEAICE WHICHTHESYSTEMHASBEENDOINGSUCCESSFULLYSINCE 4HE 2USSIAN8 BANDREAL APERTURERADARSINTHE/KEANSERIESHAVEBEENUSEDFORSIMILAR PURPOSESn 3NOWCOVERONICECANMASKICESCATTERITSELFASWITHSNOWONLAND3INCETHEARCTIC ISRELATIVELYDRY MOSTAREASHAVELITTLESNOW BUTSNOWDOESMAKEDISTINGUISHINGICE TYPESDIFFICULTATTIMES4HISISPARTICULARLYTRUEINTHE!NTARCTIC WHERESNOWISMORE PREVALENTONTHESEAICE
£È°{È
2!$!2(!.$"//+
&)'52% !NGULAR RESPONSE OF R OF DRY SNOW AT DIFFERENT FREQUENCIES2APIDFALLOFFATLOWERFREQUENCIESAPPARENTLYRESULTSFROM PENETRATIONTOTHESMOOTHGROUNDSURFACEAFTER7(3TILESETAL
0ROGRAMSTOLEARNMICROWAVEPROPERTIESOFSEAICEHAVEBEENNUMEROUSBECAUSE OFTHEIMPORTANCEOFARCTICOPERATIONSANDMETEOROLOGY-ICROWAVEREMOTESENSING IS NECESSARY TO MONITOR ICE PROPERTIES IN THE ARCTIC OWING TO THE LONG WINTER NIGHT FREQUENTCLOUDCOVER ANDINACCESSIBILITY
£È°nÊÊ *" , /,9 3EVERAL SYNTHETIC APERTURE IMAGING RADARS ARE CAPABLE OF MEASURING THE FULL COM PLEXPOLARIZATIONMATRIX0ROBABLYTHEFIRSTOFTHESEWASANAIRBORNESYSTEMBUILTBY .!3!S *ET 0ROPULSION ,ABORATORY4HE FIRST ONE IN SPACE WAS THE 3HUTTLE )MAGING 2ADARn#3)2 # !LTHOUGHUSEOFMULTIPLEPOLARIZATIONSDATESFROMTHEEARLYDAYSOF IMAGINGRADARS THEMEASUREMENTOFPHASEBETWEENTHERECEIVEDSIGNALWITHDIFFERENT POLARIZATIONSISMORERECENT DATINGFROMTHELATES&EW IFANY FULL POLARIMETRIC DATASETSEXISTOFTHETYPEDESCRIBEDABOVEFORSINGLEPOLARIZATIONS&ORMORECOMPLETE DISCUSSIONSOFRADARPOLARIMETRY CONSULTREFERENCES5LABYAND%LACHI 3LETTENAND -C,AUGHLIN ANDVAN:YLAND+IM 3INCE POLARIMETRIC RADARS USE DEFINED PHASES FOR BOTH TRANSMIT AND RECEIVE THE SIGNALSMUSTBEDESCRIBEDINTHEFORMUSEDFORELLIPTICALPOLARIZATION4HISISILLUSTRATED IN&IGURE
'2/5.$%#(/
£È°{Ç
&)'52% #OMPARISON OF SEA ICE SCATTERING AT '(ZINSUMMERANDWINTERAFTER!,'RAYETAL Ú)%%%
7HEN B THE POLARIZATION IS LINEAR WITH THE % VECTOR IN THE DIRECTION GIVEN BYX7HENB on THEPOLARIZATIONISCIRCULAR WITH nFORLEFT HANDAND n FORRIGHT HAND7HEN \B\ n THEPOLARIZATIONISELLIPTICAL !NALYTICALLY THEELECTRICFIELDMAYBEDESCRIBEDAS
% %HH %VV
WHEREHANDVAREUNITVECTORSINTHEHANDVDIRECTIONS4HEINSTANTANEOUSFIELDSARE GIVENBY%Q WHERETHEDSSHOWTHEDIFFERENTPHASESFORTHECOMPONENTSOF% ANDKISTHEWAVENUMBER
EH T 2E %H E J WT KX D H
A
£È°{n
2!$!2(!.$"//+
&)'52% %XAMPLEOFFREQUENCYRESPONSEOFRFORDIFFERENTKINDSOFSEAICE FROM93+IM
AND EV T 2E %V J WT KZ D V
B
)NCOMPLEXFORMAT
%H %H E JD H AND %V %V E JD V )FWETAKEC CVnCHANDSETCV ASAREFERENCE WECANWRITE
% %H E JD %V V
4HUS FORASINGLEWAVE WENEEDONLYHAVETHREEINDEPENDENTPARAMETERS)NRADAR WE MUSTCONSIDERBOTHTRANSMITTEDANDRECEIVEDPOLARIMETRICSIGNALS SOTHENEEDFORFOUR MAGNITUDESANDTWOPHASES !NOTHER WAY TO DESCRIBE POLARIMETRIC SIGNALS IS TO USE THE MATRIX OF 3TOKES PARAMETERS
§ ¶ §) ¶ ¨ %H %V · ¨1· ¨ · & ¨ · ¨ %H %V · 5
¨ · ¨ 2E %H %V · ©¨6 ¸· ¨ )M % % · H V ¸ ©
4HEINDIVIDUAL3TOKESPARAMETERS) 1 5 AND6AREDEFINEDASSHOWNIN%Q
'2/5.$%#(/
£È°{
&)'52% -EASUREMENT BASEDTHEORETICALRVARIATIONSFORFIRST YEARAND MULTIYEARSEAICE2ANGESAREDETERMINEDBYUSINGKNOWNVARIATIONSOFICECHARAC TERISTICSAFTER93+IMETAL
3OMEOFTHERETURNSIGNALSFROMARESOLUTIONCELLMAINTAINTHEIRPOLARIZATIONCHARAC TERISTICSOVERTIMEANDSPACE WHEREASOTHERSHAVEARANDOMPOLARIZATION4HISOCCURS AS FORSUNLIGHT WHENTHEPOLARIZATIONELLIPSECHANGESITSPROPERTIESRANDOMLYANDRAPIDLY WITHTIMEORWITHSMALLDIFFERENCESINANGLE7HENBOTHTHEPERSISTENTANDRANDOMPARTS
&)'52% 0OLARIMETRIC ELLIPSE B IS THEELLIPTICITYANGLE ANDXISTHEORIENTATION ANGLE4HEELLIPSEISTHELOCUSOFTHEENDOF THE%VECTORTHROUGHOUTACYCLE
£È°xä
2!$!2(!.$"//+
AREPRESENT THETARGETISSAIDTOBEPARTIALLYPOLARIZEDWHENNORANDOMCOMPONENTIS PRESENT THETARGETISFULLYPOLARIZED2ADARSIGNALSAREFREQUENTLYONLYPARTIALLYPOLARIZED ESPECIALLYWHEREMULTIPLEBOUNCESOCCURWITHINTHETARGETAREA &ORTHENONRANDOMPART WEMUSTDEFINEA3TOKESVECTORUSINGANENSEMBLEAVERAGE OFEACHCOMPONENTTHEAVERAGINGMAYBEOVERTIMEORLOOKANGLE4HUSWEHAVE § ¨ ¨ & ¨ ¨ ¨ ¨ ©
%H %V ¶ · · %H %V · · 2E%H %V · )M%H %V ·¸
WHENTHEWAVEISCOMPLETELYPOLARIZED
) 1 5 6
) 1 5 6
BUTWHENITISPARTIALLYPOLARIZED
)NFACT WHENTHEWAVEISCOMPLETELYUNPOLARIZEDSUNLIGHT FOREXAMPLE %VAND%H AREUNCORRELATED SO5AND6AREBOTHZERO 7AVESOFTHISTYPEAREUSEDINPOLARIMETRICRADARHOWEVER TOSEEHOWTHESCATTER INGCOEFFICIENTWORKS WENEEDTOCONSIDERBOTHTHEINCIDENTANDSCATTEREDWAVE !TTHISPOINT WEMUSTINTRODUCETHESCATTERINGMATRIX3 4HERECEIVEDFIELDMAY BEREPRESENTEDBY
JK2 %R E 3 %T 2
WHERE
§% T ¶ §% R ¶ % R ¨ VR · AND %T ¨ VT · ©%H ¸ ©%H ¸
AND
§3 3 ¨ VV ©3HV
3VH ¶ 3HH ·¸
)NTHEUSUALRECIPROCALMEDIA 3VH 3HV3INCETHECHOICEOFAPHASEREFERENCEIS ARBITRARY THEREARETHENTHREEINDEPENDENTMAGNITUDES\3VV\ \3HH\ \3HV\ BUTONLYTWO INDEPENDENTPHASES3HH 3HV 4HESEQUANTITIESCANBEUSEDTODESCRIBETHEPROPER TIESOFTHEPOLARIZEDPARTOFTHEECHOFROMATARGET 7ECANALSODESCRIBETHESCATTERINGUSINGTHE-UELLERMATRIXTHATISRELATEDTOTHE 3TOKESMATRIX4HEREADERISREFERREDTOTHELITERATUREFORFURTHERDESCRIPTIONSOFTHE -UELLERMATRIX
'2/5.$%#(/
£È°x£
4HEUSUALWAYTOOBTAINPOLARIZEDRESPONSESISTOTRANSMITALTERNATEVERTICALLYAND HORIZONTALLYPOLARIZEDPULSES0RESUMINGTHEREISALMOSTNOCHANGEINTHETARGETDUR INGTHEINTERPULSEINTERVAL THERESPONSESMAYBECOMBINEDTOPRODUCETHESCATTERING MATRIXOR-UELLERMATRIX"YCOMBININGTHESIGNALSINPROCESSING THISMETHODPERMITS SYNTHESIZINGEQUIVALENTTRANSMITTEDPOLARIZATIONSWITHANYELLIPTICITYANDORIENTATION !COMMONLYUSEDWAYTODESCRIBETHEPOLARIZATIONCHARACTERISTICSOFATARGETISTHE POLARIZATIONSIGNATURE4HISCONSISTSOFTWOTHREE DIMENSIONALGRAPHS&ORTHEFIRST GRAPH CALLEDCOPOLARIZED ONEUSESTHECOMPONENTSOFTHERECEIVEDSIGNALTHATARETHE SAMEASTHETRANSMITTED SIGNALPOLARIZATION4HESECONDGRAPHUSESCOMPONENTSOFTHE RECEIVEDSIGNALTHATAREORTHOGONALTOTHETRANSMITTEDSIGNAL &IGUREGIVESAWIDELYQUOTEDEXAMPLEOFTHISTYPEOFDISPLAYFORIMAGESOF 3AN &RANCISCO4HE AXES IN THE HORIZONTAL PLANE ARE THE ORIENTATION ANGLE FOR THE SYNTHESIZEDTRANSMITTEDSIGNALXTANDITSELLIPTICITYANGLEBT4HEVERTICALAXISISRELATIVE POWER6ALUESOFXT nANDnAREHORIZONTALPOLARIZATION WHEREASXT nISVER TICALPOLARIZATION,INEARPOLARIZATIONOCCURSWHENBT n ANDRIGHTANDLEFTCIRCULAR POLARIZATIONSOCCURWHENBT on7HENTHEMINIMUMISABOVEZERO THEPEDESTAL BENEATHITCORRESPONDSTOTHEUNPOLARIZEDSIGNAL 4HEOCEANIMAGEIN&IGUREASHOWSTHATTHEPOLARIZATIONISESSENTIALLYLIN EAR WITH THE66 SIGNAL STRONGER THAN THE ((4HE CROSS POLARIZED RESPONSE SHOWS ESSENTIALLYNOCROSS POLARIZEDSIGNALFORLINEARTRANSMISSION BUTSOMEFORCIRCULARLY POLARIZEDTRANSMISSION &ORTHEPARKSHOWNIN&IGUREB THEVERTICALLYPOLARIZEDLINEARSIGNALISSLIGHTLY HIGHERTHANTHEHORIZONTALLYPOLARIZEDONE4HEREISSOMECROSS POLARIZEDRESPONSEFOR THELINEARSIGNALANDSOMEUNPOLARIZEDSIGNAL&ORTHEURBANAREASHOWN THESTRONGEST RESPONSESARETILTEDINORIENTATIONINBOTHTHECOPOLARIZEDANDCROSS POLARIZEDCASES !# )"+! %,!' %'"-%$) # !')" # ) "' *# ' ) "$! '
! !() # *$&%# '"-!
&)'52% 3ELECTIONOFPOLARIZATIONSIGNATURESFROM3!2IMAGEOF 3AN&RANCISCOA ANOCEANAREA B ALARGEPARK ANDC ONEOFSEVERAL URBANAREASAFTER$,%VANSÚ)%%%
£È°xÓ
2!$!2(!.$"//+
4HEACTUALNUMBERSFORTHECOPOLARIZEDRESPONSEFORTHISCASEAREB n66 AND X n4HEREFERENCEPRESENTSSIMILARPLOTSSHOWINGSEPARATELYTHEPOLARIZEDAND UNPOLARIZEDRESPONSES "ECAUSEOFTHECOMPLEXITYOFTHISREPRESENTATIONANDOTHERSFORPOLARIMETRICSIGNALS ONECANNOTASREADILYPROVIDECURVESOFRESPONSEASFORSINGLE POLARIZATIONIMAGES (ENCE WEDONOTFINDMANYCATALOGSOFPOLARIMETRICSCATTERINGRESPONSES .EVERTHELESS MANYAUTHORSHAVEDESCRIBEDTHEUSEOFPOLARIMETRICIMAGES3OMEOF THEPAPERSUSINGTHETERMPOLARIMETRICREALLYREFERTOTHEUSEOFJUST(( 66 AND(6 POLARIZATIONSWITHOUTREGARDFORTHEPHASE)NTHISSENSE THEYAREUSINGTHESEIMAGESIN THEWAYTHATLIKE ANDCROSS POLARIZEDIMAGESHAVEBEENUSEDSINCETHESTARTOFIMAGING RADARS/THERS HOWEVER TAKEFULLADVANTAGEOFTHEFULLPOLARIZATIONMATRIX /NEWAYTOUSETHEFULLMATRIXISTOSYNTHESIZEPOLARIZATIONSTHATEITHEREMPHASIZE ORSUPPRESSPARTICULARCLASSESOFTARGETS&OREXAMPLE IN&IGUREC ONECOULDSYN THESIZEAnORIENTATIONANGLEFORALINEARPOLARIZATIONTOEMPHASIZETHISCLASSORUSE VERTICALPOLARIZATIONTOSUPPRESSTHEDOMINANTCLASSINTHEIMAGE6ARIOUSAUTHORS HAVESHOWNTHATONECANSYNTHESIZEANELLIPTICALPOLARIZATIONTHATINCREASESTHETARGET TO CLUTTERRATIOWHERETHETARGETIS FOREXAMPLE AMANMADEOBJECT3WARTZETAL FOUNDAPOLARIZATIONTHATGAVEAD"TARGET TO CLUTTERRATIOWHERETHETARGETWASAN URBANAREAANDTHECLUTTERWASREPRESENTEDBYAPARKINTHE3AN&RANCISCOIMAGEUSED TO PRODUCE &IGURE (E FOUND THIS WAS OBTAINED WITH TRANSMITTER POLARIZATION HAVINGXE BT n n ANDRECEIVERPOLARIZATIONOFXE BT 4HISCOMPARESWITHTHEBESTRESULTUSINGLIKE ANDCROSS POLARIZATIONSWITHOUTPHASE COHERENCEOFD" /THERSUSETHETHREEINDEPENDENTMAGNITUDESOFTHESCATTERINGMATRIXANDTHEPHASE ANGLEDBETWEENTHE((AND66RESPONSES2ESEARCHHASSHOWNTHEREISLITTLEUSEFUL INFORMATIONINTHEPHASEANGLERELATING((TOCROSSPOLARIZATION!COMMONUSEOF THESEDATAISINPRODUCINGSTATEVECTORSTOEMPLOYINDISCRIMINATIONOFTARGETAREAS WITHTHECOMPONENTSOFTHEVECTORSBEINGTHETHREEMAGNITUDESANDTHEPHASEANGLES FOREACHFREQUENCYUSED4HESEVECTORSARETHENUSEDINVARIOUSSTATISTICALALGORITHMS TOIDENTIFYDIFFERENTTARGETCLASSES 4HISAPPROACHHASALSOBEENUSEDINOTHER FORESTS AGRICULTURALAREAS SEAICE ANDSNOW ANDTOIDENTIFYSURFACE CLASSESOFGEOLOGICSIGNIFICANCE !N EXAMPLE OF THE USE OF PHASE DIFFERENCE IN DISCRIMINATING SURFACE CLASSES IN THE!MAZON BASIN IS ILLUSTRATED IN &IGURE .OTE THE SIGNIFICANT DIFFERENCES BETWEEN#AND8BANDFOR-ACROPHYTEAND&LOODEDFOREST4HESEDIFFERENCESCOULD BEUSEDASDISCRIMINATORSTOIDENTIFYTHESECLASSES BUTNORMALLYTHEYWOULDSIMPLYBE ADDITIONALELEMENTSINTHESTATEVECTORSUSEDINSTATISTICALALGORITHMS
£È°Ê - // , Ê " /ÊÊ /Ê ,Ê,`>À
,}iÀÊ-ÕÛ> )NSTITUTEFOR$EFENSE!NALYSES
-OST OF THE DISCUSSION IN THIS (ANDBOOK CONCERNS REAL APERTURE RADAR 2!2 WHERETHEANTENNAISAPHYSICALOBJECTTHATFIRSTEMITS ANDTHENCOLLECTS THERADIA TION7ETURNOURATTENTIONTOTHECASEWHERETHEANTENNAMOVESTOCOVERASYN THETICAPERTURE THUSPRODUCINGSYNTHETICAPERTURERADAR3!2 4HISOVERVIEWIS BASEDON3ULLIVANAND#UTRONAoMOREDETAILEDTREATMENTSAREALSOPROVIDEDIN THELITERATUREn
£Ç°£Ê - Ê*, * Ê"Ê-, &ORAIRBORNEORSPACEBORNEGROUND MAPPINGRADAR THEREHASBEENCONTINUOUSDESIRE TOACHIEVEFINERRESOLUTION7ESHALLUSETHETERMRANGERESOLUTIONTOMEANTHERESOLU TIONALONGTHELINE OF SIGHT,/3 FROMTHERADARTOTHETARGETREGIONANDCROSSRANGE RESOLUTIONTOMEANTHERESOLUTIONALONGTHEDIRECTIONPERPENDICULARTOTHE,/3AND PARALLELTOTHEGROUND4HEFORMERISALSOFREQUENTLYTERMEDDOWNRANGERESOLUTIONTO EMPHASIZETHATITISALONGTHE,/3#ROSSRANGERESOLUTIONISALSOFREQUENTLYCALLEDAZI MUTHRESOLUTION SINCEITISMEASUREDALONGALINEOBTAINEDBYHOLDINGRANGECONSTANT ANDVARYINGTHEAZIMUTHASMEASUREDFROMTHEPHYSICALANTENNA OFTHE,/3)FAND ONLYIF THE,/3REMAINSPERPENDICULARTOTHEDIRECTIONOFFLIGHT RANGERESOLUTIONIS SOMETIMESCALLEDCROSS TRACKRESOLUTION ANDCROSSRANGERESOLUTIONISSOMETIMESCALLED ALONG TRACKRESOLUTION 7ITHRESPECTTO3!2RESOLUTION THEPREFERREDTERMSAREFINEANDCOARSE"ETTER RESOLUTION IS FINER NOT GREATER POORER RESOLUTION IS COARSER NOT LESS )N THIS WAY AMBIGUITY IN TERMINOLOGY CAN BE AVOIDED /F COURSE IN PRACTICE THE TERMS HIGH RESOLUTION FINE RESOLUTION AND LOW RESOLUTION COARSE RESOLUTION ARE OFTEN USED WITHOUTAMBIGUITY #ROSSRANGERESOLUTIONWASINITIALLYACHIEVEDBYUSEOFANARROWBEAM4HEBEAM WIDTHINRADIANS P"OFANAPERTUREANTENNAISGIVENAPPROXIMATELYBYTHEWAVELENGTH
4HEPRESENTCHAPTERDRAWSSIGNIFICANTLYFROM$R3ULLIVANSBOOK 2ADAR&OUNDATIONSFOR)MAGINGAND!DVANCED #ONCEPTS 2ALEIGH .# 3CI4ECH 0UBLISHING $R 3ULLIVAN IS GRATEFUL TO 3CI4ECH FOR PERMISSION TO QUOTE CONSIDERABLEMATERIALFROMTHECHAPTERSON3!2(EISALSOGRATEFULTO-R-ICHAEL4ULEY)NSTITUTEFOR$EFENSE !NALYSES FORREVIEWINGTHEMANUSCRIPTPRIORTOPUBLICATIONANDSUGGESTINGMANYIMPROVEMENTS o)NTHEFIRSTTWOEDITIONSOFTHIS(ANDBOOK THECHAPTERON3!2WASWRITTENBY$R,OUIS*#UTRONA WHOISNOW DECEASED )N $R 3ULLIVAN HAD THE PRIVILEGE OF WORKING WITH $R #UTRONA AT THE %NVIRONMENTAL 2ESEARCH )NSTITUTEOF-ICHIGAN !NN!RBORNOW'ENERAL$YNAMICS 9PSILANTI ANDISGRATEFULFORHAVINGLEARNEDMUCHFROM HIMCONCERNING3!2
£Ç°£
£Ç°Ó
2!$!2(!.$"//+
KDIVIDEDBYTHEAPERTUREDIAMETERP"yK$4HECORRESPONDINGLINEARCROSSRANGE RESOLUTIONATRANGE2ISTHEN
D CR y
2L REALAPERTURE $
&OREXAMPLE IFK CM8BAND AND$ M P"yRADIANS!TARANGEOF2 KM THECROSSRANGERESOLUTIONWOULDBE2P"yKM HARDLYFINEENOUGHTORESOLVE SUCHTARGETSASBUILDINGSANDVEHICLES(OWEVER BYUSINGAPPROPRIATECOHERENTPROCESS ING ANAPERTUREOFMODESTSIZEMAYBEMOVEDEG BYANAIRCRAFTORSPACECRAFTREFERRED TOASTHEPLATFORM ALONGAPATHINSPACEASYNTHETICAPERTUREANDMAYACHIEVECROSS RANGERESOLUTIONCOMPARABLETOWHATWOULD INPRINCIPLE BEACHIEVEDBYAREALAPERTURE WITHALENGTHEQUALTOTHEPATHLENGTHSYNTHETICAPERTURE ,3!
D CR y
2L L y SYNTHETICAPERTURE ,3! $P
WHERE $P IS THE SYNTHETIC APERTURE ANGLE IE THE ANGLE SUBTENDED BY THE SYNTHETIC APERTUREASSEENFROMTHETARGETAREA4HEADDITIONALFACTOROFTWOINTHEDENOMINATOR COMPAREDWITH%Q OCCURSBECAUSEOFTHE3!2PROCESSINGANDWILLBEDISCUSSED &OREXAMPLE FORAPATHLENGTHOFKM THECROSSRANGERESOLUTIONFORTHECASEDISCUSSED ABOVEWOULDBEyCM CLEARLYASUPERBIMPROVEMENTOVERTHEREAL APERTURECASE
£Ç°ÓÊ , 9Ê-/",9Ê"Ê-, 4HEORIGINALCONCEPTOF3!2WASFIRSTDESCRIBEDBY#ARL7ILEYOF'OODYEARIN (ECALLEDITDOPPLERBEAMSHARPENING$"3 ,ATER THEDOPPLERBEAMSHARPENINGMODE OF3!2WASINTRODUCEDASTHENAMEFORAVARIABLESQUINTANGLEMODETHATPRODUCEDA PARTIAL PLAN POSITION INDICATOR 00) DISPLAY4HUS $"3 REALLY HAS TWO MEANINGS IN 3!2 THENAMEFOR3!2INVENTEDBY7ILEYBEFOREITWASCALLED3!2AND THE NAMEFORA00) LIKEMODEBASEDONSQUINTED3!2 )N THE5NIVERSITYOF)LLINOISDEMONSTRATEDTHE3!2CONCEPT)N DURING ASUMMERSTUDYTHATLAUNCHEDAPROGRAMKNOWNAS0ROJECT-ICHIGAN IDEASRELATED TOSYNTHETICAPERTURESWEREDISCUSSEDBY,*#UTRONAOFTHE5NIVERSITYOF-ICHIGAN 7ILLOW2UN,ABORATORIES #73HERWINOFTHE5NIVERSITYOF)LLINOIS 7(AUSZOF 'ENERAL%LECTRIC AND*+OEHLEROF0HILCO#ORPORATION4HISRESULTEDINASUCCESSFUL 3!2PROGRAMBYTHE-ICHIGANGROUP4HE)LLINOISGROUPALSODEMONSTRATEDSUCCESS FUL3!2IMAGING4HEWORKOF#UTRONAETALAND3HERWINETAL PLUSMANYOTHER EARLY 3!2 PAPERS ARE COMPILED IN A VERY USEFUL BOOK BY +OVALY -ORE DETAILED HISTORIESOF3!2DEVELOPMENTAREGIVENBY#URLANDERAND-C#ONOUGH *ACKSONAND !PEL AND!USHERMANETAL
£Ç°ÎÊ /9* -Ê"Ê-, 7HEN WE REFER TO 3!2 WE USUALLY MEAN FOCUSED 3!2 THE TERM INDICATES THAT THE PHASE INFORMATION HAS BEEN OPTIMALLY PROCESSED TO PRODUCE RESOLUTION COMPARABLE TO THE THEORETICAL LIMIT )N THE DEVELOPMENT OF 3!2 SEVERAL INTERESTING TECHNIQUES
39.4(%4)#!0%2452%2!$!2
£Ç°Î
PRECEDEDTHEDEVELOPMENTOFFOCUSED3!24HESETECHNIQUESAREDISCUSSEDINORDEROF PROGRESSIVELYFINERRESOLUTION 0RECURSORSTO&OCUSED3!2 3IDE ,OOKING!IRBORNE2ADAR3,!2 3,!2CONSISTEDOFANAIRCRAFT MOUNTED 2!2 POINTED PERPENDICULAR TO THE DIRECTION OF FLIGHT HENCE hSIDE LOOKINGv WITH CROSSRANGERESOLUTION^2K$ $OPPLER"EAM3HARPENING$"3 !SPREVIOUSLYMENTIONED WHEN7ILEYFIRST CONCEIVEDOFTHECONCEPTTHATWENOWCALL3!2 HETERMEDITDOPPLERBEAMSHARP ENING7ILEYEXPLAINEDITASFOLLOWSh)HADTHELUCKTOCONCEIVEOFTHEBASICIDEA WHICH ) CALLED $OPPLER "EAM 3HARPENING $"3 RATHER THAN 3YNTHETIC!PERTURE 2ADAR3!2 ,IKEALLSIGNALPROCESSING THEREISADUALTHEORY/NEISAFREQUENCY DOMAINEXPLANATION4HISIS$OPPLER"EAM3HARPENING)FONEPREFERS ONECANANA LYZETHESYSTEMINTHETIMEDOMAININSTEAD4HISIS3!24HEEQUIPMENTREMAINSTHE SAMEnJUSTTHEEXPLANATIONCHANGES#ONCEPTIONWASREPORTEDINA'OODYEAR!IRCRAFT REPORTINv 3UBSEQUENTLY ASDESCRIBEDIN3ECTIONOF3CHLEHER $"3CAMETOREFERTOAN AIRBORNESCANNINGMODEINWHICHTHEECHOESFROMTHESCANNINGREALBEAMAREDOPPLER PROCESSEDTOPRODUCECROSSRANGERESOLUTIONFINERTHANTHATPROVIDEDBYTHEREALBEAM ALONEBROADSIDECROSSRANGERESOLUTIONISy2K,$"3 WHERE,$"3ISTHESYNTHETICAPER TURELENGTHGENERATEDDURINGATARGETDWELL3TIMSONEXPLAINSh4YPICALLY THEANTENNA CONTINUOUSLYSCANSTHEREGIONOFINTEREST"ECAUSETHEINTEGRATIONTIMEISLIMITEDTO THELENGTHOFTIMEAGROUNDPATCHISINTHEANTENNABEAMOR IFYOUPREFER THELENGTH OFTHEARRAYTHATCANBESYNTHESIZEDISSOLIMITEDTHERESOLUTIONISCOARSERTHANCANBE ACHIEVEDWITHANON SCANNINGANTENNAvP 5NFOCUSED3!2 4HISTYPEOFEARLY3!2ISDESCRIBEDBY#UTRONAASFOLLOWSh4HE COHERENTSIGNALSRECEIVEDATTHESYNTHETICARRAYPOINTSAREINTEGRATED WITHNOATTEMPT MADETOSHIFTTHEPHASESOFTHESIGNALSBEFOREINTEGRATION4HISLACKOFPHASEADJUST MENTIMPOSESAMAXIMUMUPONTHESYNTHETICANTENNALENGTHTHATCANBEGENERATED 4HISMAXIMUMSYNTHETICANTENNALENGTHOCCURSATAGIVENRANGEWHENTHEROUND TRIP DISTANCEFROMARADARTARGETTOTHECENTEROFTHESYNTHETICARRAYDIFFERSBYKFROMTHE ROUND TRIPDISTANCEBETWEENTHERADARTARGETANDTHEEXTREMITIESOFTHEARRAYv#UTRONA SHOWSTHATTHECROSSRANGERESOLUTIONISAPPROXIMATELY K2 5NFOCUSED3!2ISTYPICALLYNOTUSEDTODAYANDISINCLUDEDHEREONLYFORHISTORICAL REASONS)TWASUSEDINTHEEARLYDAYSOF3!2SINCETHETECHNOLOGYOFTHATTIMEDIDNOT SUPPORTFOCUSED3!2 4YPESOF&OCUSED3!2 )NFOCUSED3!2 APHASECORRECTIONISMADEFOREACH RETURNINGPULSEECHO4HISESSENTIALLYRESULTSINTHETHEORETICALCROSSRANGERESOLUTION OF%Q 3TRIPMAP3!2 3TRIPMAP3!2ORhSTRIPv3!2 ISALSOSOMETIMESCALLEDhSEARCHv 3!2 SINCEITISUSEFULFORIMAGINGLARGEAREASATRELATIVELYCOARSERESOLUTION)NSTRIP MAP3!2 THEBEAMREMAINSNORMALTOTHEFLIGHTPATHTHELATTERISASSUMEDTOBEA STRAIGHTLINEATCONSTANTALTITUDE ANDCONTINUOUSLYOBSERVESASWATHORSTRIP OFTERRAIN PARALLELTOTHEFLIGHTPATHEXTENDINGFROMSOMEMINIMUMRANGE2MINTOSOMEMAXIMUM RANGE2MAXFROMTHEFLIGHTPATH
£Ç°{
2!$!2(!.$"//+
&ORSTRIPMAP3!2 THESYNTHETICAPERTUREANGLE$PISESSENTIALLYEQUALTOTHEREAL APERTUREBEAMWIDTHP"
$P y P " y
L $
4HUS
D CR y
L $ y $P
5NDERIDEALCONDITIONS ASLONGAS$KANDSIGNAL TO NOISERATIO3.2 THENTHESMALLERTHEPHYSICALANTENNA THEFINERTHECROSSRANGERESOLUTION INDEPENDENT OFRANGE !S THE PHYSICAL ANTENNA MOVES ALONG THE SYNTHETIC APERTURE THE RETURN FROM A POINTTARGETATAPARTICULARRANGEWILLEXHIBITAQUADRATICPHASEBEHAVIORIE PHASE VARIESASTHESQUAREOFTHETIMEREFERENCEDTOTHECLOSESTAPPROACH THATISUNIQUETO THETARGETSLOCATIONONTHEGROUND 3OMESTRIPMAP3!2SUSEAFILTERINGAPPROACH TOTAKEADVANTAGEOFTHISPHENOMENON)NFACT FORTHEECHOFROMAPOINTTARGETIN THESCENE ACLOSEANALOGYEXISTSBETWEENITSQUADRATICPHASEVARIATIONDURINGASINGLE PULSEFROMALINEAR&-;,&-=PULSEECHO ANDITSQUADRATICPHASEVARIATIONOVER MANYPULSESDUETOPLATFORMMOTION3TIMSON P /THERSTRIPMAP3!2SDIVIDE THESTRIPINTOSUBPATCHESANDUSESPOTLIGHT 3!2PROCESSINGNEXTSECTION FOREACH SUBPATCHSEEALSO3ECTIONOF!USHERMANETAL 4HENEWER2ANGE-IGRATION!LGORITHM2-! SEE#HAPTEROF#ARRARAETAL ORIGINALLYDEVELOPEDFORSEISMICAPPLICATIONS PROVIDESTHEMOSTTHEORETICALLYCORRECT SOLUTIONTOTHESTRIPMAPIMAGEPROBLEM)TDOESNOTMAKEAFAR FIELDAPPROXIMATIONBUT TREATSTHEWAVEFRONTSASSPHERICAL)TISPARTICULARLYAPPLICABLETO3!2WITHVERYWIDE FRACTIONAL BANDWIDTH ANDOR WIDE SYNTHETIC APERTURE ANGLE 2-! INVOLVES SUBSTAN TIAL COMPUTATIONAL COMPLEXITY HOWEVER AS PROCESSORS BECOME MORE SOPHISTICATED THISLIMITATIONISDISAPPEARING!SIMPLER FASTERVERSIONOF2-!ISTHE#HIRP 3CALING !LGORITHM#3! SEE#HAPTEROF#ARRARAETAL 3QUINTED 3TRIPMAP 3!2 )N THIS CASE THE ANTENNA BORESIGHT IS NOT NORMAL TO THE FLIGHT PATH!S SEEN FROM A TOP VIEW THE SQUINT ANGLE PSQ IS THE ANGLE BETWEEN THEANTENNABORESIGHTANDTHENORMALTOTHEFLIGHTPATHTHUS FORABROADSIDEBEAM PSQ ANDCCR $-OREGENERALLY
$P
D CR
P!
L $P
L $ COSP SQ $ COSP SQ
)TISASSUMEDHERETHATTHESYNTHETICAPERTURELENGTH,3!2ANDPSQISESSENTIALLY CONSTANTDURINGADATACOLLECTION$EPENDINGONDETAILS THISCONDITIONISVALIDONLYFOR PSQLESSTHANABOUT SINCE FORAGIVENCROSSRANGERESOLUTION ASPSQ INCREASES ,3! INCREASES ANDTHECONDITIONBECOMESNOLONGERVALID 3POTLIGHT3!2 3POTLIGHT3!2SOMETIMESCALLEDhSPOT3!2v ISUSEDTOOBTAIN A RELATIVELY FINE RESOLUTION IMAGE OF A KNOWN LOCATION OR TARGET OF INTEREST!S THE
39.4(%4)#!0%2452%2!$!2
£Ç°x
PLATFORMPASSESBYTHETARGET THEBEAMDIRECTIONMOVESTOKEEPPOINTINGATTHETARGET )NTHISWAY $PMAYBEMADECONSIDERABLYGREATERTHANP" ANDCCRSPOTLIGHT CCR STRIPMAP 7EMAYWISHTOMAKEACORRECTIONFORTHEVARIATIONINRECEIVEDPOWER ^2 ASTHERANGETOTHETARGETVARIESSLIGHTLYOVERTHESYNTHETICAPERTURE4HISIS USUALLYNEGLIGIBLEFORMOSTSPOTLIGHT3!2APPLICATIONSBUTMIGHTNOTBENEGLIGIBLE WHEN COLLECTION ANGLES ARE LARGE SUCH AS FOR THE CASE OF FOLIAGE PENETRATION 3!2 3ECTION 4HESYNTHETICAPERTURETIMET!REQUIREDTOCOLLECTTHEDATAFORASPOTLIGHT3!2IMAGE ISFOUNDASFOLLOWS
D CR y
L L2 L2 y $P ,3! COSP SQ 6T ! COSP SQ
T! y
L2 6D CR COSP SQ
WHERE6ISTHEPLATFORMSPEED )NTERFEROMETRIC 3!2 )NTERFEROMETRIC 3!2 )N3!2 SOMETIMES ALSO CALLED h)&3!2v REFERSTOTHEUSEOFTWOANTENNASWHOSESIGNALSARECOMBINEDCOHERENTLY )N3!2 WAS ORIGINALLY DEVELOPED BY THE *ET 0ROPULSION ,ABORATORY *0, TO DETECT OCEANCURRENTSORMOVINGTARGETS 4HETWOANTENNASWEREDISPLACEDHORIZONTALLY ONTHEPLATFORMALONGALINEPARALLELTOTHEGROUND SOTHATTHERECEIVEDECHOESFROM A MOVING TARGET WOULD BE DIFFERENT FROM THE CORRESPONDING ECHOES FROM FIXED TAR GETS ANDTHUSMOVERSCOULDBEDETECTEDANDANALYZED,ATERRESEARCHERSEG !DAMS ETAL USEDTWOANTENNASDISPLACEDVERTICALLYONTHEPLATFORMSOTHATTHERECEIVED ECHOES FROM A TARGET ABOVE THE SURFACE ASSUMED FLAT WOULD BE DIFFERENT FROM THE CORRESPONDINGECHOESFROMATARGETONTHESURFACE ANDTHUSTARGETHEIGHTCOULDBEESTI MATED"OTHTYPESOF)N3!2AREDISCUSSEDIN3ECTION4HEFORMERISDISCUSSEDIN h)NTERFEROMETRIC3!2FOR-OVING4ARGET)NDICATION-4) vANDTHELATTERISDISCUSSED INh)NTERFEROMETRIC3!2FOR4ARGET(EIGHT-EASUREMENTv )NVERSE3!2 3KOLNIKPRESENTSADISCUSSIONOF)NVERSE3!2)3!2 (ESTATES h)N3!2 THETARGETISASSUMEDSTATIONARYANDTHERADARISINMOTION)N)3!2 THE TARGETMOTIONPROVIDESTHECHANGESINRELATIVEVELOCITYTHATCAUSEDIFFERENTDOPPLER SHIFTSTOOCCURACROSSTHETARGETvPPn 3KOLNIKALSOINCLUDESADISCUSSION OF)3!2IMAGESOFSHIPSOBTAINEDBYTHE53.AVAL2ESEARCH,ABORATORY.2, -USMANETAL !NAIRBORNERADAROBTAINSASERIESOFIMAGESOFASHIPTHATISEXPE RIENCINGPITCHROLLYAWINTHEWAVES ANDTHEUSERISABLETOIDENTIFYTHESHIPTYPEAND CHARACTERISTICS-USMANETALDISCUSSFEATUREEXTRACTION MULTIFRAMEPROCESSING AND ACAPABILITYFORAUTOMATICTARGETRECOGNITION!42 OFSHIPS)3!2ISALSOWIDELYUSED FORDIAGNOSTICMEASUREMENTSONINDOORANDOUTDOORRADARCROSSSECTION2#3 RANGES +NOTTETAL P )MPROVEMENTSIN3!22ESOLUTION 4HEFOLLOWINGEXAMPLEILLUSTRATESHOW3!2 CROSSRANGERESOLUTIONHASIMPROVEDASTHEPRECEDINGTYPESOFAIRBORNEMAPPINGRADAR WEREDEVELOPED,ETUSASSUMETHATK M8BAND $ APERTUREDIAMETER M 2 KM PSQ 6 MSEC ,$"3 MCORRESPONDINGTOANANGULAR SCANRATEOFSEC ANDSPOTLIGHTSYNTHETICAPERTURELENGTH KM$PyDEG
£Ç°È
2!$!2(!.$"//+
4HENCROSSRANGERESOLUTIONISAPPROXIMATELYASFOLLOWSFORTHEDIFFERENTMODESDIS CUSSEDPREVIOUSLY 3,!2M $"3M 5NFOCUSEDSTRIPMAP3!2M 3TRIPMAP3!2M 3POTLIGHT3!2M
£Ç°{Ê -,Ê, -" 1/" )NTHISSECTION WEDISCUSS3!2RESOLUTIONINMOREDETAIL"YhRESOLUTION vINKEEPINGWITH COMMONUSAGE WEMEANTHEPRECISIONTOWHICHWECANMEASURETHELOCATIONOFAPOINT TARGETANDNOTNECESSARILYTHEABILITYTORESOLVETWOPOINTTARGETS&ORADISCUSSIONOFTHIS ISSUE SEE7OLFEAND:ISSIS (OWWEDOTHISWILLBEDISCUSSEDINMOREDETAILBELOW 3INCE FINE RANGE RESOLUTION IS TYPICALLY ACHIEVED WITH A SINGLE PULSE THE CORRE SPONDING PROCESSING IS OFTEN TERMED FAST TIME PROCESSING /N THE OTHER HAND FINE CROSSRANGERESOLUTIONREQUIRESMULTIPLEPULSES ANDTHECORRESPONDINGPROCESSINGIS THEREFORE OFTENTERMEDSLOW TIMEPROCESSING#ARRARA 2ICHARDS AND+LEMM 2ANGE 2ESOLUTION 3TRICTLY SPEAKING 3!2 REFERS TO A METHOD FOR IMPROVING CROSSRANGERESOLUTION NOTRANGERESOLUTION(OWEVER BECAUSEFINERANGERESOLUTIONIS SONECESSARYTOASUCCESSFUL3!2 ANDALSOBECAUSEOFANANALOGYBETWEENRANGEAND CROSSRANGERESOLUTION WEDISCUSSRANGERESOLUTIONBRIEFLYHERE &INERANGERESOLUTIONISACHIEVEDBYTRANSMITTINGANDRECEIVINGRADARWAVESCHAR ACTERIZEDBYAFAIRLYWIDEBANDWIDTH"!SANEXAMPLE CONSIDERACARRIERFREQUENCY F '(ZANDABANDWIDTH" '(Z/NEWAYTOACHIEVETHISBANDWIDTHNOT THEBESTWAY INGENERAL BUTAWAYTHATISEASYTODESCRIBE ISTOUSEASTEP FREQUENCY WAVEFORMCONSISTINGOFASERIESOFhSINGLE FREQUENCYvPULSES EACHWITHAFREQUENCY SOMEWHATGREATERTHANTHATOFTHEPREVIOUSPULSE"YAhSINGLE FREQUENCYvPULSE WE MEAN A PULSE CONSISTING OF A PURE SINUSOIDAL TONE MULTIPLIED BY A RECTANGULAR FUNCTION OF DURATION hWIDTHv S MUCH LONGER THAN THE PERIOD OF THE TONE 3UCH A PULSEISNOTTRULYSINGLE FREQUENCYBUTHASABANDWIDTHOFyS&OREXAMPLE IFS MICROSECOND "PULSE -(Z4HISISFARLESSTHANTHEBANDWIDTHOFTHEOVERALL STEP FREQUENCYWAVEFORM EQUALTOTHEDIFFERENCEBETWEENTHEFREQUENCIESOFTHELAST ANDFIRSTPULSESINTHESEQUENCE WHICHISTYPICALLYHUNDREDSOF-(Z 3TEP FREQUENCYPULSECOMPRESSIONHASNOTPROVENSUCCESSFULINAIRBORNEORSPACE BORNEAPPLICATIONS ASCOMPAREDTOTHELINEAR &-,&- WAVEFORMSEE3ECTION OF#ARRARA ANDISSELDOMUSED,INEAR &-,&- ISACOMMONWAVEFORMUSEDIN OPERATIONALHIGH POWERRADARS BECAUSE EACHPULSECONTAINSTHEFULLBANDWIDTH THEREBY ENABLING THE FULL BANDWIDTH TO BE TRANSMITTED AND RECEIVED MUCH MORE QUICKLY THAN WITH STEP FREQUENCYA GREAT ADVANTAGE WHEN THE RADAR IS MOVING SUCHASFOR3!2AND THEHARDWAREISRELATIVELYINEXPENSIVEANDMATURE,&- HASBEENSUCCESSFULLYEMPLOYEDOPERATIONALLYEG INTHE53.AVY!.!03 AND!.!03 SINCETHES4HEONLYAPPARENTLYSUCCESSFULAPPLICATIONOF STEP FREQUENCY HAS BEEN IN GROUND BASED INSTRUMENTATION RADARS WHERE IT IS LESS EXPENSIVETOIMPLEMENTANDMORETIMEISAVAILABLEFORDATACOLLECTION+NOTTETAL PP .EVERTHELESS FORTHEMOMENT WEASSUMETHESTEP FREQUENCYWAVEFORMBECAUSE ITPROVIDESAMUCHSIMPLEREXAMPLEFOREXPLAININGTHEPRINCIPLEOFRANGERESOLUTION
39.4(%4)#!0%2452%2!$!2
£Ç°Ç
,ETUSASSUMETHATTHERADARTRANSMITSASTEP FREQUENCYWAVEFORMCONSISTINGOFIDEN TICALGROUPSOFPULSES EACHGROUPCONSISTINGOF. hSINGLE FREQUENCYvPULSES OFWIDTHS7ITHINAPULSEGROUP THEFREQUENCYOFAPULSEIS$FGREATERTHANTHATOF THEPREVIOUSPULSE ANDTHERADARTRANSMITS02& .GROUPSPERSECOND WHERE02& ISTHEPULSEREPETITIONFREQUENCY4HEWAVEFORMBANDWIDTHIS. $FS4HE PHASEANDAMPLITUDEOFEACHPULSEECHOISDIGITALLYRECORDEDBYTHERADAR!SSHOWN IN&IGUREA ADISCRETE&OURIERTRANSFORM$&4 TYPICALLYAFAST &OURIERTRANS FORM&&4 ISAPPLIEDTOTHISSETOF.COMPLEXSAMPLESOFFREQUENCY DOMAINDATA RESULTINGINASETOF.COMPLEXNUMBERSINTHETIME DOMAINCORRESPONDINGTOECHOES MAGNITUDEANDPHASE THATWOULDBERETURNEDFROMAVERYSHORTPULSEOFWIDTHy" SAMPLEDATTIMEINTERVALS$T "4HISISASIMPLEEXAMPLEOFPULSECOMPRESSION 3INCE AN INCREMENTAL DELAY $T CORRESPONDS TO AN INCREMENTAL DOWNRANGE DISTANCE $R C$T WEMULTIPLYTHE$&4OUTPUTBYCANDOBTAINTHEECHOESCORRESPONDING TOASETOFDOWNRANGEDISTANCESSEPARATEDBYAPIXELWIDTHOFC$T C"4HUS THE RANGERESOLUTIONSTRICTLYSPEAKING PIXELSEPARATION OFASTEP FREQUENCYWAVEFORM OFBANDWIDTH"IS
D R C "
!LTHOUGHITISBEYONDTHESCOPEOFTHISCHAPTER ITCANBESHOWNTHATSUCHARANGE RESOLUTIONOFyC"MAYBEOBTAINEDUSINGAWIDEVARIETYOFWAVEFORMTYPES ASLONG ASTHEOVERALLTRANSMITTEDBANDWIDTHIS"&OREXAMPLE 3ECTIONOF3ULLIVANSHOWS THATTHISISTRUEFORTHE,&-WAVEFORM #ROSSRANGE2ESOLUTION ,ETUSNOWASSUMETHATTHEAIRBORNEORSPACEBORNE 3!2 ISOBSERVINGASCENEONTHE%ARTHSSURFACECONSISTINGOFAFEWPOINTTARGETSANDTHATIT TRANSMITSANDRECEIVES.IDENTICALPULSESEACHOFBANDWIDTH"PRESUMABLY THOUGHNOT NECESSARILY VIATHE,&-WAVEFORM ANDDETERMINESTHEDOWNRANGEPOSITIONOFEACH
"
!#
!
$
$
!
"
!# $ $
#
$ $
&)'52% 2ANGEANDCROSSRANGERESOLUTION3IMILARDISCRETE&OURIERTRANSFORM$&4 PROCESSESMAY BEUSEDTOOBTAINRANGEANDCROSSRANGERESOLUTION
£Ç°n
2!$!2(!.$"//+
TARGETWITHARANGERESOLUTIONOFC",ETUSALSOASSUMETHATTHE3!2ISMOVINGINA STRAIGHTLINEATACONSTANTALTITUDE(ANDCONSTANTSPEED6FORATIME4ALONGADIRECTION NORMALTOTHE,/34HESYNTHETICAPERTURE,3! 64ISASSUMEDSMALLCOMPAREDWITH THERANGE2TOTHECENTEROFTHETARGETREGION!SVIEWEDFROMTHETARGETREGIONALSO ASSUMEDSMALLCOMPAREDTO2 THESYNTHETICAPERTURESUBTENDSTHESYNTHETICAPERTURE ANGLEy,3!2 642!STHERADARMOVESTHROUGHITSSYNTHETICAPERTURE ITVIEWSTHE SCENEFROMSLIGHTLYDIFFERENTANGLES&ORSIMPLICITY LETUSASSUMETHATDURINGTHISTIME THETARGETSDONOTLEAVETHEIRhRANGEBINSvOFWIDTHC"4HISASSUMPTIONWILLBEDIS CUSSEDIN3ECTION h2ANGE-IGRATIONv &ROM THE VIEWPOINT OF THE 3!2 THE SCENE APPEARS TO BE ROTATING WITH ANGULAR VELOCITY7 62$URINGTHEDATACOLLECTION THETOTALANGLETHROUGHWHICHTHESCENE APPEARSTOROTATEIS$P 74 642!SPECIFICPOINTTARGETAPPEARSTOHAVEA,/3 VELOCITYOF7RRELATIVETOTHE3!2 WHERERISTHECROSSRANGEDISTANCEOFTHETARGET FROMTHE,/34HESEAPPARENT,/3VELOCITIESWILLRESULTINDOPPLERFREQUENCIESIN ABSOLUTEVALUE OFVAPPARENT K 7RK WHEREKISTHEWAVELENGTHCORRESPONDING TOTHECARRIERFREQUENCY &OREACHRANGEBIN WENOWHAVE.COMPLEXNUMBERSCORRESPONDINGTODIFFERENT RADAR ECHOES IN THE TIME DOMAIN!S SHOWN IN &IGURE B THESE . TIME DOMAIN ECHOESMAYBEPROCESSEDUSINGA$&4TOPRODUCEASETOF.FREQUENCY DOMAINRETURNS 4HE FREQUENCY INTERVAL BETWEEN SUCCESSIVE RETURNS IS $F 4 AND THE OVERALL FRE QUENCYINTERVALIS. 4y.4 02& F27EASSUMEOPERATIONATBASEBAND AND THUSTHEFREQUENCYINQUESTIONISTHEAPPARENTDOPPLERFREQUENCYOFTHETARGETS7E CONVERTTHISTOCROSSRANGEBYMULTIPLYINGBYK7 K26
D CR y
L L L2 L2
y 74 $P ,3! 64
.OTETHATOURASSUMPTIONTHAT264PERMITSTHEUSEOFSMALL ANGLEAPPROXIMA TIONSFORSMALL$P7HEN$PISNOTSMALL %QMUSTBEAPPROPRIATELYMODIFIED 3UMMARYOF3!22ESOLUTION 7EHAVE THEREFORE NOWDERIVEDTHETWOBASIC FORMULASFOR3!2RESOLUTION
D R C "
D CR
L L2 y P ,3! $P
2ANGE 2ESOLUTION
#ROSSRANGE 2ESOLUTION
4HEPROCESSINGDESCRIBEDPRODUCESATWO DIMENSIONALARRAYOFCOMPLEXNUMBERS IE EACHCONSISTSOFAMAGNITUDEANDAPHASE4HISORDEREDARRAYOFCOMPLEXNUMBERS ASAFUNCTIONOFDOWNRANGEANDCROSSRANGEPRODUCESACOMPLEXRADARIMAGE IE EACH PIXELCONSISTSOFAMAGNITUDEANDAPHASE4YPICALLYTHEMAGNITUDESQUAREDREPRESENT INGPIXELENERGY ISDISPLAYED !SSHOWNIN#HAPTEROF3ULLIVAN APOINTTARGETINTHESCENETRANSFORMSTOATWO DIMENSIONALPOINT SPREADFUNCTION03& INTHERADARIMAGE SO CALLEDBECAUSEAPOINT TARGETISDISPLAYEDINTHEIMAGEASSOMEWHAThSPREADOUTv4HIS03&ISCHARACTERIZEDBY AMAINLOBEANDSIDELOBESINBOTHRANGEANDCROSSRANGE5SUALLYWEIGHTINGALSOCALLED TAPERINGORAPODIZATION ISAPPLIEDINTHEPROCESSING RESULTINGINCONSIDERABLYLOWERSIDE LOBES BUTATTHEEXPENSEOFASOMEWHATBROADERMAINLOBE APRICETHATTHEUSERISTYPICALLY WILLINGTOPAY-ANYTYPESOFWEIGHTINGEXIST)FNOWEIGHTINGISAPPLIED THE03&ISA SINC FUNCTIONOFTHEFORMSINX X )NTHATCASE THEFORMULASABOVEFOR3!2RESOLUTION
39.4(%4)#!0%2452%2!$!2
£Ç°
REPRESENTTHEDISTANCEFROMTHEMAINLOBEPEAKTOTHEFIRSTNULL.OTETHATTHISDEFINITIONOF 3!2RESOLUTIONISDIFFERENTFROMTHEMORECOMMONDEFINITIONOFTHEHALF POWERWIDTHOF THEMAINLOBE7ITHNOWEIGHTING THELATTERIS TIMESTHEVALUESGIVENABOVETHUS THETWODEFINITIONSARENOTVERYDIFFERENT7EPREFERTHEFORMERDEFINITIONBECAUSE FORNO WEIGHTING ITRESULTSINASIMPLERFORMULAWITHOUTTHEINTRODUCTIONOFTHEFACTOROF -OREDETAILSCONCERNINGWEIGHTINGAREGIVENIN3ECTION 4HEREAREATLEASTTWOMATHEMATICALLYEQUIVALENTWAYSOFCONSIDERING3!2!SWEHAVE DEVELOPEDTHECONCEPTSOFAR THECROSSRANGERESOLUTIONMAYBECONSIDEREDTORESULTFROMTHE DOPPLERSHIFTSRESULTINGFROMTHEDIFFERENTAPPARENTLINE OF SIGHTVELOCITIESOFDIFFERENTPARTS OFTHESCENE(OWEVER THECROSSRANGERESOLUTIONMAYALSOBECONSIDEREDTORESULTFROMTHE LARGESYNTHETICAPERTURE MUCHASFINECROSSRANGERESOLUTIONWOULDALSORESULTFROMALARGE REALAPERTURE0ER%Q THECROSSRANGERESOLUTIONPEAK TO FIRSTNULL OFA3!2ISFINER BYAFACTOROFTWOTHANTHERESOLUTIONFORA2!2OFEQUALAPERTURE!NINTUITIVEEXPLANATION FORTHISINTERESTINGRESULTISTHATFOR2!2 THEECHORECEIVEDATAPARTICULARAPERTURELOCATION RESULTSFROMENERGYTRANSMITTEDFROMALLLOCATIONSINTHEAPERTURE WHEREASFOR3!2 THE ECHORECEIVEDATAPARTICULARAPERTURELOCATIONRESULTSFROMENERGYTRANSMITTEDFROMTHAT KNOWN LOCATIONINTHEAPERTUREIE MOREINFORMATIONISRECEIVED#ARRARAETAL P 3TIMSONPROVIDESADETAILEDEXPLANATIONFORTHISRESULTPPn &IGUREPRESENTSACOMPARISONOF2!2AND3!2
&)'52% #OMPARISONOF2!2AND3!24HECROSSRANGERESOLUTIONPEAK TO FIRST NULLOFANTENNAPATTERN OFA3!2ISONE HALFTHATOFAREALAPERTURERADAR 2!2 OFTHESAMEAPERTUREDIAMETER#OURTESYOF3CI4ECH0UBLISHING )NC
£Ç°£ä
2!$!2(!.$"//+
4HESIDELOBESAREALSODIFFERENTFOR2!2AND3!2&ORA2!2WITHANUNWEIGHTED APERTURE FUNCTION THE TRANSMITTED INTENSITY AT THE PEAK OF THE FIRST ANGULAR SIDELOBE IS REDUCED BY n D" AND THE RECEIVED INTENSITY FROM A TARGET IN THAT DIRECTION IS THUSREDUCEDBYnD"&ORA3!2 TYPICALLYTHEENTIREREGIONOFTHEIMAGEISINTHE MAINBEAMDURINGTHEDATACOLLECTION ANDTHEREARENOEFFECTSFROMTHESIDELOBESOF THEPHYSICALANTENNA4HESIDELOBESRESULTSOLELYFROMTHEPROCESSING ANDWITHNO WEIGHTING THEFIRSTSIDELOBEISREDUCEDBYnD"RELATIVETOTHEMAINBEAM
£Ç°xÊ 9Ê-* /-Ê"Ê-, 2ANGEAND6ELOCITY#ONTOURS 5SINGFINERANGERESOLUTION ARADARCANDISTIN GUISH BETWEEN TARGETS AT DIFFERENT RANGES! PARTICULAR TARGET MAY BE DETERMINED TO BE LOCATED ON A CONSTANT RANGE CONTOUR )N $ SPACE THESE CONTOURS ARE CONCENTRIC SPHERESWITHTHERADARATTHECENTER&IGUREA 3IMILARLY USINGDOPPLERPROCESSING THERADARCANDISTINGUISHBETWEENTARGETSOF DIFFERENTAPPARENTVELOCITIES)F6ISTHEPLATFORMVELOCITYANDPISTHEANGLEBETWEEN6 ANDTHE,/3TOASTATIONARYTARGET THENTHEAPPARENT,/3SPEEDOFTHETARGETIS6,/3
6COSP&IGUREB )N$SPACE SURFACESOFCONSTANT6,/3ARECIRCULARCONESWITH AXIS6ANDGENERATINGANGLEP WITHTHERADARATTHEVERTEX4HENEGATIVESIGNOCCURS
&)'52% 2ANGE AND VELOCITY CONTOURS IN $ SPACE A #ONSTANT RANGE CON TOURSARECONCENTRICSPHERESWITHTHERADARATTHECENTERB #ONSTANT APPARENT VELOCITY CONTOURSARECIRCULARCONESWITHTHERADARATTHEVERTEXANDTHEAXISALONGTHEPLATFORM VELOCITYVECTOR#OURTESYOF3CI4ECH0UBLISHING )NC
39.4(%4)#!0%2452%2!$!2
£Ç°££
BECAUSEWEDEFINE,/3VELOCITYASD2DT WHERE2ISTHERANGETOTHETARGET4HUS A POSITIVED2DTCORRESPONDSTOARECEDINGTARGETANDRESULTSINANEGATIVEDOPPLERFRE QUENCYSHIFT ANDANEGATIVED2DTCORRESPONDSTOANINCOMINGTARGETANDRESULTSINA POSITIVEDOPPLERFREQUENCYSHIFT #ONSIDERANAIRBORNERADARWITHANISOTROPICANTENNAPATTERN WITHCONSTANTVELOCITY ALONGASTRAIGHTLINEPARALLELTOAFLATGROUND&IGUREA /NTHEGROUND THECON STANT RANGECONTOURSARETHEINTERSECTIONSOFCONCENTRICSPHERESWITHTHEGROUNDASET OFCONCENTRICCIRCLESWITHTHESUBRADARPOINTATTHECENTER&IGUREB 4HECONTOURS OFCONSTANT,/3VELOCITYCALLEDISODOPS CORRESPONDTOTHEINTERSECTIONSBETWEENTHE SETOFCONESANDTHEFLATGROUNDASETOFNESTEDHYPERBOLAS&IGUREC &IGURED SHOWSTHECOMBINATIONOFCONSTANT RANGECIRCLESANDTHEISODOPS4HEhNADIRLINEvSHOWN IN&IGUREISTHELOCUSOFSUBRADARPOINTSASTHEPLATFORMFLIESALONGITSPATH
&)'52% 2ANGEANDVELOCITYCONTOURSONTHE%ARTHSSURFACEA #OLLECTIONGEOMETRYB #ONSTANT RANGECONTOURSARECONCENTRICCIRCLESWITHTHESUBRADARPOINTATTHECENTERhNADIRLINEvREFERSTOTHELOCUSOF SUBRADARPOINTSC #ONSTANT APPARENT VELOCITYCONTOURShISODOPSv ARECONFOCALHYPERBOLASWITHTHEAXIS PARALLELTOTHEPLATFORMVELOCITYVECTORD 3ETOFINTERSECTINGCONCENTRICCIRCLESANDCONFOCALHYPERBOLAS #OURTESYOF3CI4ECH0UBLISHING )NC
£Ç°£Ó
2!$!2(!.$"//+
4HROUGH APPROPRIATE RANGE DOPPLER PROCESSING RETURNS FROM EACH INTERSECTION CELL MAY BE DISTINGUISHED /VER A SMALL ANGLE ABOUT THE BROADSIDE DIRECTION THE RANGECONTOURSANDTHEISODOPSAREESSENTIALLYORTHOGONALTOEACHOTHER4HERESULT INGRADARRETURNSMAYBEDISPLAYEDTOYIELDANIMAGEOFTHEGROUND!TANONZERO SQUINTANGLE THEISODOPSARENOTORTHOGONALTOTHERANGECONTOURSHOWEVER ADDI TIONAL PROCESSING CORRECTIONS CAN STILL USUALLY RESULT IN AN ESSENTIALLY UNDISTORTED GROUNDIMAGE -OTION#OMPENSATION 4HEBASICTHEORYOF3!2RELIESONTHEASSUMPTIONTHAT THEPLATFORM ANDTHEREFORETHE3!2ANTENNA ISTRAVELINGALONGASTRAIGHT LINEFLIGHT PATHATCONSTANTVELOCITYPARALLELTOTHEGROUNDATCONSTANTALTITUDE4HISISNOTEXACTLY TRUE ANDFORSUCCESSFUL3!2IMAGING ITISNECESSARYTHATTHEDEVIATIONSOFTHEANTENNA FROMTHISNOMINALFLIGHTPATHBEMEASURED RECORDED ANDCOMPENSATEDFORINTHEPRO CESSING 4HIS PROCEDURE IS KNOWN AS MOTION COMPENSATION SOMETIMES ABBREVIATED MOCOMP &OREXAMPLE ATAPARTICULARMOMENT ASAPARTICULARFREQUENCYISTRANSMIT TED IFTHEANTENNAISESTIMATEDTOHAVEDEVIATEDADISTANCEDAWAYFROMTHENOMINAL FLIGHTPATHALONGTHE,/3 THEPHASECORRECTION
$F
P D P DF L C
WITHAPPROPRIATESIGN ISADDEDTOTHEMEASUREDPHASEATTHEFREQUENCYFTOPRODUCE THEBESTESTIMATEOFWHATTHERECORDEDPHASEWOULDHAVEBEENIFTHEPLATFORMHADNOT DEVIATEDFROMTHENOMINALFLIGHTPATH3IMILARLY IFTHEPLATFORMSPEEDISNOTCONSTANT THERECEIVEDDATAAREINTERPOLATEDTOPRODUCETHEBESTESTIMATEOFWHATTHEYWOULDHAVE BEENIFTHESPEEDHADBEENCONSTANT 7HEN THE PLATFORM IS AN AIRCRAFT AN ON BOARD )NERTIAL .AVIGATION 3YSTEM ).3 USESACCELEROMETERSANDGYROSCOPESTOMEASURETHEDEVIATIONS3OMETIMESASMALLER )NERTIAL-EASUREMENT5NIT)-5 RELYINGONTHESAMEGENERALPRINCIPLESIShSTRAPPED DOWNvVERYNEARTHEANTENNA7ITHOUTANABSOLUTEREFERENCEFRAME THEOUTPUTSOFANY ).3OR)-5WILLDRIFTWITHTIMEASERRORSACCUMULATE!NABSOLUTEFRAMEFORPOSITION ANDVELOCITYMAYBEOBTAINEDFROMTHEGLOBALPOSITIONINGSYSTEM'03 ACONSTELLA TIONOFATLEASTSATELLITESINPOLAR%ARTHORBITPROVIDINGCONTINUOUSREFERENCESIGNALS FORDETERMINATIONOFPRECISEPOSITIONANDVELOCITY 3LANTAND'ROUND0LANES 7HENA3!2IMAGEISINITIALLYPRODUCED THERANGE PIXELSIZECRISUSUALLYACONSTANT)TISGENERALLYCHOSENTOBESOMEWHATLESSTHANC" EG C" TOENSUREADEQUATESAMPLING !SILLUSTRATEDIN&IGURE THEACTUAL GROUNDLOCATIONSTHATCORRESPONDTOTHESERANGESAMPLESARENOTSPACEDATCONSTANT INTERVALSINGROUNDRANGE.EARTHESCENECENTER THEYARESPACEDAT
CG CRCOSX
WHEREXISTHEGRAZINGANGLE!TGROUNDRANGESCLOSERTOTHERADAR THEYARESPACEDSTILL FARTHERAPARTBECAUSEOFTHESPHERICALRANGECONTOURS.EARTHESCENECENTER THEIMAGE CORRESPONDSTOTHEPROJECTIONOFTHEGROUNDONTOASLANTPLANETHISPLANEISDETERMINED BYTHE,/3ANDITSPERPENDICULARINTHEGROUNDPLANE7EOFTENREFERTOTHISTYPEOF IMAGEASASLANT PLANEIMAGE"YAPPROPRIATEINTERPOLATIONANDRESAMPLING AGROUND PLANEIMAGEWITHCG CONSTANT CCRMAYBEPRODUCED'ROUND PLANEIMAGERYWITH MINIMALDISTORTIONISNECESSARYIFCOMPARISONISTOBEMADEWITHMAPSORWITHIMAGING TAKENFROMOTHERSENSORS SUCHASOPTICALSENSORSOROTHER3!2S
39.4(%4)#!0%2452%2!$!2
£Ç°£Î
&)'52% 3LANTANDGROUNDPLANES4HESLANTPLANEISDETERMINED BY THE RADAR LINE OF SIGHT AND ITS PERPENDICULAR IN THE GROUND PLANE 'ROUND PLANERANGERESOLUTIONISCOARSERTHANSLANT PLANERANGERESOLU TION#OURTESYOF3CI4ECH0UBLISHING )NC
0ULSE 2EPETITION &REQUENCY 02& 2EQUIREMENTS FOR 3!2 &OR BROADSIDE OPERATION THEAPPARENTANGULARVELOCITYOFTHESCENEROTATIONIS
7
6 2
7ITHRESPECTTOTHERADAR THERELATIVEVELOCITYOFPOINT!SEE&IGURE ATTHE FIRSTNULLOFTHEMAINBEAMIS
L6 ¤ 6 ³ ¤ L 2³ V! 7R ¥ ´ ¥ ´
$ ¦ 2µ ¦ $ µ
&)'52% -INIMUM 02& FOR 3!24HE APPARENT LINE OF SIGHT VELOCITY OF POINT! IS TOWARD THE RADAR WHEREAS THE APPARENT LINE OF SIGHT VELOCITY OF POINT " IS AWAY FROM THERADAR4HESEDETERMINETHEMINIMUM02&OF6$ WHERE6 PLATFORMSPEEDAND$ ANTENNAPHYSICALDIAMETER#OURTESYOF3CI4ECH0UBLISHING )NC
£Ç°£{
2!$!2(!.$"//+
3IMILARLY THERELATIVEVELOCITYOFPOINT"ONTHEOPPOSITESIDEOFTHEBEAMIS ¤ 6 ³ ¤ L 2 ³ L6 V" 7R ¥ ´ ¥ ´
¦ 2µ ¦ $ µ $
4HUS THERANGEOFRELATIVEVELOCITIESINTHESCENEIS
$V 7R 7R 7R
L6
$
4HERANGEOFDOPPLERFREQUENCIESRECEIVEDFROMTHESCENEIS
$FD
L6 6 L $ $
4HUS TOAVOIDVELOCITYAMBIGUITY THE02&MUSTBEATLEAST6$7RITING
F2 MIN
6 $ T 2 MAX
$
WEHAVE
6T 2 MAX
4HUS THEDISTANCETRAVELEDBYTHEPLATFORMDURINGTHETIMEBETWEENPULSEST2 MUST BENOMORETHAN$ ANDTHE3!2MUSTTRANSMITATLEASTTWOPULSESASITSPHYSICAL ANTENNAPASSESASTATIONARYPOINTINSPACE 7EALSOFREQUENTLYWANTRANGE UNAMBIGUOUSOPERATION WHICHIMPLIES
6 C a F2 $ 2
&OREXAMPLE IF6 MSyKTS $ M AND2 KM THEN(Z F2 (Z %QISREALLYTWOEQUATIONS7EUSE FORTHESECONDEQUATIONINSTEADOFa BECAUSEWHENTHEEQUALITYISUSED APULSEISBEINGTRANSMITTEDJUSTASTHEECHOFROM THEPREVIOUSPULSEISBEINGRECEIVED RESULTINGINECLIPSINGANDCONSEQUENTLOSSOFTHE RECEIVEDINFORMATION 3KOLNIKPP n POINTS OUT THAT SINCE FOR STRIPMAP 3!2 THE CROSSRANGE RESOLUTIONCCR $%Q %QBECOMES
6 C a F2 D CR 2
4HISLEADSTOTHECONDITION
2 C a D CR 6
4HUS THEUNAMBIGUOUSRANGE2UANDTHERESOLUTIONOFASTRIPMAP3!2CANNOTBE SELECTEDINDEPENDENTLYOFONEANOTHER3KOLNIKFURTHERPOINTSOUT QUOTING"AYMAAND -C)NNES THATMORESOPHISTICATEDREASONINGLEADSTOTHECONDITION
2U C
a D CR 6
39.4(%4)#!0%2452%2!$!2
£Ç°£x
3KOLNIKCONTINUES h7HENA3!2IMAGESTHEGROUNDFROMANELEVATEDPLATFORM THEUNAMBIGUOUSRANGECANCORRESPONDTOTHEDISTANCEBETWEENTHEFORWARDEDGEAND THEFAREDGEOFTHEREGIONTOBEMAPPED4HISREQUIRESTHATTHEELEVATIONBEAMWIDTHBE TAILOREDTOILLUMINATEONLYTHESWATH3THATISTOBEIMAGEDBYTHERADAR4HESWATH3IS OFTENMUCHSMALLERTHANTHEMAXIMUMRANGESOTHATTHE02&CANBEINCREASEDTOALLOW THEUNAMBIGUOUSRANGE2UTOENCOMPASSTHEDISTANCE3COSX WHEREXISTHEGRAZING ANGLEvP &ORASTRIPMAP3!2 %QTHENBECOMES 3 C
a D CR 6 COSY
2ANGE-IGRATION !SWEHAVESEEN A3!2MAYOBTAINRANGERESOLUTIONOFCR C" WHERE" SIGNALBANDWIDTH ANDOBTAINCROSS RANGERESOLUTIONTHROUGHDOPPLER PROCESSING WITHCCR K$P)FWEWISHTOPREVENTRANGEMIGRATIONMOVEMENTOFA POINTTARGETFROMONERANGEBINTOTHENEXTDURINGTHETIMEREQUIREDTOCOLLECTTHEDATA FORIMAGEFORMATION WEWOULDREQUIRETHAT$2 THEVARIATIONOFRANGEDURINGTHEDATA COLLECTIONOVERTHESYNTHETICAPERTURE BELESSTHANCR 7ECONSIDERTHEFORMATIONOFA3!2IMAGEAFTERCOLLECTINGDATAOVERANAPERTURE TIMET!4HE3!2FLIGHTPATHISASTRAIGHTLINEATCONSTANTSPEEDANDALTITUDEOVERAFLAT GROUND&ROM,EVANONWEHAVE
2MAX
2
6 T ! 2
2MIN 2
WHERE2 DISTANCEFROMTHERADARTOTHESCENECENTERINTHEMIDDLEOFTHEDATACOLLEC TIONINTERVAL AND2MAX DISTANCEFROMTHERADARTOTHESCENECENTERATTHEBEGINNING ANDENDOFTHEDATACOLLECTIONINTERVAL4HEN
$2 2MAX 2MIN
6T ! ,3! 2 $Q 2 L DR 2 2 D CR
4HELASTINEQUALITYISNECESSARYFORTHECONDITIONOFNORANGEMIGRATION&OREXAM PLE PARAMETERSFORA3!2MIGHTBE2 KM K M ANDCR CCR MTHEN $2 M CR ANDTHECONDITIONISNOTSATISFIED4HUS THEPROCESSORMUSTUSUALLY CORRECTFORRANGEMIGRATION(OWEVER THISISTYPICALLYACCOMPLISHEDBYMODERN3!2 PROCESSINGMETHODS&ORSPOTLIGHT3!2 THEPOLARFORMATALGORITHM ISOFTENUSED TOACCOMPLISHTHISCORRECTION /THER0ROCESSING&UNCTIONS #URLANDERETALPROVIDEADETAILEDDISCUSSIONOF SEVERALKEYOPTIONSFOR3!2PROCESSINGBEYONDSIMPLEIMAGEFORMATION L
L
L
L
#LUTTERLOCK #URLANDER ET AL #HAPTER REFERS TO THE USE OF INFORMATION IN THE RECEIVED SIGNALS TO ASCERTAIN THE CENTER FREQUENCY OF THE ECHOES FROM THE GROUND CLUTTER ANDCOMPENSATEFORSIDEWAYSDRIFTOFTHEPLATFORM !UTOFOCUS #URLANDER ET AL #HAPTER DESCRIBES THE USE OF INFORMATION IN THE COMPLEX IMAGEITSELFTOESTIMATEANDCORRECTPHASEERRORS ANDTHENREPROCESSAND SHARPENTHEIMAGESEEALSO#ARRARAETAL #ALIBRATION#URLANDERETAL #HAPTER REFERSTOTHEUSEOFTARGETSOFKNOWNRADAR CROSSSECTION2#3 INTHESCENETOOBTAINTHEABSOLUTELEVELOF2#3PERPIXELAND THUSR THEGROUND2#3PERUNITAREA 'EOLOCATION#URLANDERETAL #HAPTER ISTHEPROCESSOFDETERMININGTHEABSOLUTE LATITUDEANDLONGITUDEOFPIXELSINTHE3!2IMAGE TYPICALLYUSINGINFORMATIONFROM THE'03
£Ç°£È
2!$!2(!.$"//+
£Ç°ÈÊ -,Ê Ê+1 /9 )TISCLEARLYIMPORTANTFORA3!2TOPRODUCEHIGH QUALITYIMAGERY)MAGEQUALITYIS TYPICALLYMEASUREDUSINGSEVERALIMAGE QUALITYMETRICS)1-S DESCRIBEDINTHEFOL LOWINGSECTIONS-OREDETAILEDDISCUSSIONOF3!2IMAGERYISGIVENBY(ENDERSONAND ,EWISAND/LIVERAND1UEGAN 0OINT 3PREAD&UNCTION03& !POINTTARGETMAYBECONSIDEREDANIMPULSEINPUT TOA3!2PROCESSOR ANDTHE03&INTHEIMAGEMAYBEREGARDEDASANIMPULSERESPONSE )02 4HEPRIMARY)1-FORMOST3!2SISTHEWIDTHMETERS OFTHE03&MAINLOBEAT ITShHALF POWERPOINTS vORPOINTSWHERETHEINTENSITYPOWER PROPORTIONALTOVOLTAGE SQUARED IS ONE HALF OR D" RELATIVE TO THE MAINLOBE PEAK4HIS )1- IS TYPICALLY REFERREDTOASTHEh D"WIDTHv 4OOBTAINFINERESOLUTIONINEITHERRANGEORCROSSRANGE A&OURIERTRANSFORM&4 IS PERFORMEDONASETOFCOLLECTEDDATA3INCEALLDATASAMPLESHAVEESSENTIALLYTHESAME MAGNITUDE FOR EITHER RANGE OR CROSSRANGE WE ESSENTIALLY PERFORM A &4 ON A RECT ANGULARFUNCTION WHICHPRODUCESASINC FUNCTIONSINX X WITHA D"WIDTH OF CPNWHERECPN PEAK TO FIRST NULLINTERVAL ANDAFIRSTSIDELOBEnD" BELOWTHEPEAK !SMENTIONEDIN3ECTION WHENATAPERING ORWEIGHTING FUNCTIONMULTI PLIESTHERECTANGULARINPUT THERESULTISTYPICALLYAFUNCTIONWITHBROADERMAINLOBE AND LOWER SIDELOBES THAN THE SINC SEE 3ECTION OF 3ULLIVAN ! TYPICAL WEIGHTING FUNCTION USED IN 3!2 PROCESSING IS 4AYLOR WEIGHTING WITH THE FIRST SIDELOBE CONSTRAINED TO BE n D" BELOW THE PEAK AND hNBAR v SEE 3ECTION $OF#ARRARAETAL WHICHPRODUCESAWIDENEDMAINBEAMOF D")02VALUE L CPN!NOTHERCHOICEIS(ANNORh(ANNINGv WEIGHTING WHICHRESULTSINAN EVENWIDERMAINBEAMOF CPNTHEFIRSTSIDELOBEISnD"BELOWTHEPEAK AND THE FAR SIDELOBES ARE VERY LOW COMPARED WITH UNIFORM OR4AYLOR WEIGHTING !NEXCELLENTDISCUSSIONOFOVERWEIGHTINGFUNCTIONSNOTINCLUDING4AYLOR IS GIVENBY(ARRIS 3IGNAL 4O .OISE2ATIO3.2 &ORAREALRADAR FORWHICHTHEEXACTPHASEOFTHE TARGETECHOCANNEVERBEKNOWNINADVANCE THEGREATESTACHIEVABLESIGNAL TO NOISE RATIO3.2 IS3ULLIVAN 3ECTION
3.2
%
K4 &
% 02X AVGT !
WHERE% COLLECTEDENERGYK "OLTZMANNSCONSTANT ¾nJOULE+ELVIN 4 STANDARDTEMPERATURE+ & hNOISEFIGURE vWHICHISTYPICALLYABOUT 02X AVG AVERAGE RECEIVED POWER AND T! TIME TO FORM THE SYNTHETIC APERTURE 4HEDENOMINATOROF%QISCORRECTONLYIFTHETEMPERATUREOFTHERADARIS THESAMEASTHATOFTHESCENE WHICHWEASSUMESEE#HAPTERAND3ECTION OF3ULLIVAN
%
04X AVG' L S 04X AVG !H S T! T! P 2 ,OSS P 2 L ,OSS
39.4(%4)#!0%2452%2!$!2
£Ç°£Ç
WHERE04X AVG AVERAGETRANSMITTEDPOWER ' ANTENNAGAIN R TARGETRADARCROSS SECTION2#3 ! ANTENNAAPERTUREAREA G ANTENNAEFFICIENCY ANDTHERADARLOSSES AREREPRESENTEDBY,OSS &OR3!2 ATPSQ FROM%Q
T!
L2 6D CR
4HUS
3.2
04X AVG' L S 04X AVG !H S
P 2K4 & ,OSS 6D CR P 2L K4 & ,OSS 6D CR
)FAFLATGROUNDISBEINGOBSERVED THEN
S S D CRD R COSY
WHERERCHARACTERIZESTHEGROUND2#3PERUNITAREAANDCR PIXELWIDTHINSLANT RANGE4HENTHESIGNAL TO NOISERATIO3.2 IS
3.2
04X AVG !H S D R 04X AVG' L S D R P 2K4 & ,OSS 6 COSY P 2L K4 & ,OSS 6 COSY
4HISAGREESWITH3KOLNIK %Q AND#URLANDERETAL %Q )TISVERYUSEFULTOCONSIDERTHENOISE EQUIVALENTSIGMA ZERO.%R DEFINEDASTHE LEVELOFRTHATPRODUCESARECEIVEDPOWEREQUALTOTHETHERMALNOISEPOWER IE AN 3.2OFUNITY7ESET3.2 ANDHAVE
.%S
P 2K4 & ,OSS 6 COSY P 2L K4 & ,OSS 6 COSY 04X AVG' L D R 04X AVG !H D R
&OREXAMPLE IF2 KM 4 + & ,OSS 6 MS X O 0AVG 7 ' D" K M8BAND ANDCR M THEN.%R D" !CLEAR3!2IMAGEMUSTHAVEAN3.2GREATERTHANABOUTD"&ROM"ARTONAND SUMMARIZEDIN3ECTIONOF3ULLIVAN WESEETHATTHISEXAMPLE3!2COULDIMAGE hWOODEDHILLS vIE Ry D" WITH3.2yD" BUTCOULDNOTIMAGEhFLATLANDv PERHAPSDESERT ATRy D" SINCE3.2y D" )NTEGRATED3IDELOBE2ATIO)3,2 !NACTUAL03&TYPICALLYRESEMBLESTHETHEO RETICAL03&BUTISSOMEWHATDIFFERENTFROMIT ESPECIALLYINTHESIDELOBES DUETOPHASE NOISE MOTIONCOMPENSATIONIMPERFECTIONS ANDOTHERhREAL WORLDvEFFECTS!USEFUL FIGUREOFMERITISTHEINTEGRATEDSIDELOBERATIO)3,2 DEFINEDAS
)3,2
)NTEGRAL OVER 03& 3IDELOBES )NTEGRAL OVEER 03& -AINLOBE
)3,2ISUSUALLYMEASUREDIND"ATYPICALVALUEMIGHTBE D",OW)3,2IS CLEARLYDESIRED -ULTIPLICATIVE.OISE2ATIO-.2 4HERMALNOISEGENERALLYINTERNALWHENTHE RADARISA3!2 ISOFTENREFERREDTOASADDITIVENOISE SINCEITADDSTOTHESCENEINDE PENDENTOFTHESCENECONTENT!NOTHERTYPEOFUNWANTEDBACKGROUNDINA3!2IMAGE
£Ç°£n
2!$!2(!.$"//+
ISOFTENCALLEDMULTIPLICATIVENOISENOTREALLYNOISEINTHESTRICTSENSE WHICHISPRO PORTIONALTOTHEAVERAGESCENEINTENSITY #ARRARAETALDEFINEMULTIPLICATIVENOISEASFOLLOWSh4HEPRINCIPALCONTRIBUTORSTO MULTIPLICATIVENOISEARETHEINTEGRATEDSIDELOBESOFTHESYSTEMIMPULSERESPONSE THE ENERGYPRESENTINTHESCENEASARESULTOFRANGEANDAZIMUTHAMBIGUITIES ANDDIGITAL ;IE FROMQUANTIZATIONINTHEANALOG TO DIGITALCONVERTER=NOISEvP 4HEMULTIPLICATIVENOISERATIO-.2 OFA3!2IMAGEISDEFINEDASTHERATIOOFTHE IMAGEINTENSITYINNO RETURNAREA.2! NOTINCLUDINGTHERMALNOISE DIVIDEDBYTHE AVERAGEIMAGEINTENSITYINARELATIVELYBRIGHTSURROUNDINGAREAINPRINCIPLENOTINCLUD INGTHERMALNOISE !N.2!ISANAREAWITHESSENTIALLYZERORETURNFOREXAMPLE A SHADOWAREA AVERYSMOOTHAREASUCHASACALMLAKE ORASPECIALLYCONSTRUCTEDLARGE SHEETOFALUMINUM !NOTHER SIMILAR 3!2 IMAGE QUALITY METRIC )1- IS THE CONTRAST RATIO #2 DEFINEDASTHERATIOOFTHEAVERAGEINTENSITYOFATYPICALBRIGHTREGIONINA3!2IMAGE TOTHEINTENSITYOFAN.2!)FTHERMALNOISEISNEGLIGIBLE THEN#2 -.2 #OMPARISON OF 3!2 )MAGERY AND /PTICAL )MAGERY 4HE HUMAN EYE IS OF COURSE ASYSTEMFORPRODUCINGIMAGESUSINGVISIBLELIGHT4HELIGHTHITSTHELENSANDIS FOCUSEDUPONTHERETINA ANDTHERESULTINGIMAGEISTRANSMITTEDTOTHEBRAIN/VERMANY MILLENNIA HUMANSHAVEBECOMEFULLYACCUSTOMEDTOSEEINGANDPROCESSINGTHISVIS IBLEIMAGERY4HEREFORE UPONSEEINGA3!2IMAGE WEMAYINSTINCTIVELYASSUMETHAT ITHASCERTAINPROPERTIESOFAVISIBLEIMAGE WHICH INFACT ITDOESNOTPOSSESS/PTICAL IMAGERYISBASEDONANhANGLE ANGLEvPRINCIPLE WHEREAS3!2IMAGERYISBASEDONA VERYDIFFERENThRANGE CROSSRANGEvPRINCIPLE 4HETOPILLUSTRATIONIN&IGUREILLUSTRATESTHEAPPEARANCEOFAFLATLANDSCAPETO THEHUMANEYEORACAMERA 4HETERRAINISILLUMINATEDBYSUNLIGHT ATLEASTPARTIALLY DIFFUSEDTHROUGHTHEATMOSPHERE!TTHEEYE EACHPIXELSUBTENDSTHESAMEAZIMUTHAND ELEVATIONANGLES4HUS PIXELSFARTHERFROMTHEEYEARELARGERCOARSERRESOLUTION IN BOTHDOWNRANGEANDCROSSRANGE THANPIXELSCLOSERTOTHEEYE 4HEBOTTOMILLUSTRATIONIN&IGURESHOWSTHAT FORA3!2IMAGE THESITUATIONIS QUITEDIFFERENTASSUMINGADEQUATE3.2 4HERANGEPIXELSIZECRIS
DR
C
" COS Y
0IXELSFARTHERFROMTHE3!2ARESMALLERINRANGESMALLERGRAZINGANGLEANDFINER DOWNRANGE RESOLUTION THAN PIXELS CLOSER TO THE 3!2 AND CROSSRANGE RESOLUTION IS INDEPENDENTOFRANGE 7HENWEDISPLAYA3!2IMAGE ESPECIALLYOFALARGELANDSCAPE ITISUSUALLYMOST SATISFYINGTODISPLAYITWITHTHE3!2DIRECTIONATTHETOP4HEFINERRESOLUTIONPIXELSARE ATTHEBOTTOM JUSTASTHEYAREWITHANATURALLYORIENTEDOPTICALIMAGE4HISORIENTATION TENDSTOLOOKMOSTNATURALTOAHUMANOBSERVER "ECAUSE 3!2 IMAGERY AND OPTICAL IMAGERY ARE COLLECTED USING ENTIRELY DIFFERENT PHYSICALPRINCIPLES WESHOULDNOTBESURPRISEDIFTHEYLOOKDIFFERENT!GOODEXAMPLE OF THIS IS PROVIDED IN A 3!2 IMAGE OF THE7ASHINGTON -ONUMENT COURTESY OF THE %NVIRONMENTAL2ESEARCH)NSTITUTEOF-ICHIGAN NOW'ENERAL$YNAMICS 9PSILANTI -) 4HETOPILLUSTRATIONIN&IGUREILLUSTRATESTHECOLLECTIONGEOMETRYANDTHESCHE MATICRESULT OFOPTICALIMAGERYOFTHE7ASHINGTON-ONUMENTWITHTHE-ONUMENTS SHADOWPOINTEDTOWARDTHEOBSERVER7EASSUMETHATTHESUNISTOTHESOUTHOFTHE -ONUMENTANDTHEOBSERVERISTOTHENORTH4HEIMAGESHOWSASHADOWONTHENORTH
39.4(%4)#!0%2452%2!$!2
£Ç°£
&)'52% #OMPARISONOF3!2ANDOPTICALIMAGERY/PTICALIMAGERYISBASEDON AN hANGLE ANGLEv PRINCIPLE 3!2 IMAGERY IS BASED ON A hRANGE CROSSRANGEv PRINCIPLE /FTENOPTICALAND3!2IMAGESOFTHESAMETARGETREGIONDONOTLOOKTHESAMETOAHUMAN OBSERVER#OURTESYOF3CI4ECH0UBLISHING )NC
SIDECASTBYTHESUN4HEPORTIONOFTHE-ONUMENTVISIBLEINTHEIMAGEISTHENORTH SIDE ILLUMINATEDBYDIFFUSELYSCATTEREDSUNLIGHT)NCOMPARISON THEBOTTOMILLUSTRATION IN&IGURESHOWSTHEGEOMETRYANDRESULTOF3!2IMAGERY AGAINWITHTHESHADOW ONTHENORTHSIDE4HISTIMETHESHADOWISCASTBYTHE3!2ITSELF4HEPORTIONOFTHE MONUMENTVISIBLEINTHEIMAGEISTHESOUTHSIDE&IGURESHOWSTHE3!2IMAGE)T DOESNOTLOOKENTIRELYLIKEANOPTICALIMAGE NORSHOULDIT !NOTHERDIFFERENCEBETWEEN3!2ANDOPTICALIMAGESISTHEPRESENCEOFSPECKLE SEE3ECTION IN(ENDERSONAND,EWIS INTHEFORMER,ETUSCONSIDERAPARTICU LARPIXELOFACOMPLEXIMAGEOFCOMPLICATEDTERRAIN SUCHASVEGETATION"YhPIXELv WEMEANTHECOMPLEXNUMBERMAGNITUDEANDPHASETHAT AFTER3!2PROCESSING CORRESPONDSTOAPARTICULARLOCATIONONTHEGROUND )FONLYONESCATTERERWEREINTHE REGIONOFGROUNDREPRESENTEDBYTHEPIXEL THENTHEPIXELMAGNITUDEANDPHASEWOULD BEAFUNCTIONOFTHESCATTERERSEXACTPOSITION3INCETHEREGIONREPRESENTEDBYTHE PIXELTYPICALLYCONTAINSMANYSCATTERERS THECOMPLEXPIXELVALUEISTHESUMOFTHE
£Ç°Óä
2!$!2(!.$"//+
&)'52% 0RINCIPLES OF IMAGING THE 7ASHINGTON -ONUMENT &OR THE GEOMETRY SHOWN THEOPTICALIMAGESHOWSTHESIDEOFTHE-ONUMENTONTHESAMESIDEASTHESHADOW WHEREAS THE 3!2 IMAGE SHOWS THE SIDE OF THE -ONUMENT ON THE OPPOSITE SIDE OF THE SHADOW#OURTESYOF3CI4ECH0UBLISHING )NC
COMPLEX NUMBERS THAT EACH RESULTS FROM ONE OF THE SCATTERERS4HUS WHEN TERRAIN ESPECIALLYVEGETATION ISIMAGED THEAMPLITUDEVOLTAGE OFAPARTICULARPIXELISTHE MAGNITUDEOFTHECOMPLEXSUMOFTHECOHERENTRETURNSFROMMANYSCATTERERSWITHIN THEPIXEL)NANOTHERNEARBYPIXEL EVENIFTHETERRAINISNOMINALLYTHESAMEASINTHE FIRSTPIXEL THECOHERENTRETURNSWILLADDDIFFERENTLYANDTHEPIXELMAGNITUDEWILLBE SOMEWHAT DIFFERENT 4HIS PHENOMENON CHARACTERISTIC OF COHERENT IMAGERY CAUSES 3!2IMAGERYOFTERRAINTOEXHIBITMOREPIXEL TO PIXELFLUCTUATIONSPECKLE THANCOR RESPONDINGOPTICALIMAGERY 3TIMSONPOINTSOUT h3OMETIMESTHEBEAMOFTHEREALANTENNAMAYBEWIDEENOUGH TOENABLETHESAMEAREATOBEMAPPEDSEVERALTIMESWITHOUTCHANGINGTHEANTENNAS LOOKANGLE4HISISCALLEDMULTILOOKMAPPING7HENTHEMAPSARESUPERIMPOSEDIE WHEN;THEMAGNITUDESOF=SUCCESSIVERETURNSFROMEACHRESOLUTIONCELLAREAVERAGED THEEFFECTSOFSCINTILLATION;IE SPECKLE=AREREDUCEDvP
39.4(%4)#!0%2452%2!$!2
£Ç°Ó£
&)'52% 3!2IMAGEOFTHE7ASHINGTON-ONUMENT4HE3!2IMAGESHOWSTHESIDEOFTHE-ONUMENT THATISONTHEOPPOSITESIDEOFTHESHADOW WHICHMAYAPPEARCOUNTERINTUITIVETOAHUMANOBSERVER#OURTESY OF'ENERAL$YNAMICS 9PSILANTI -ICHIGAN
£Ç°ÇÊ -1 ,9Ê"Ê 9Ê-,Ê +1/" !REVIEWOFTHEBASICEQUATIONSOF3!2FOLLOWS 2ANGERESOLUTION CR C"C SPEEDOFLIGHT " PULSEBANDWIDTH #ROSSRANGERESOLUTION CCR K$P K WAVELENGTH $P ANGLESUBTENDEDBYSYNTHETICAPERTURE 0HYSICALBEAMWIDTH K$$ ANTENNADIAMETER
L
L
L
£Ç°ÓÓ L
2!$!2(!.$"//+
#ROSSRANGERESOLUTIONFORSTRIPMAP3!2
L
L
L
D CR y
6 C a F2 $ 2
)MAGE#OLLECTION4IMET! K26CCRCOSPSQ 02&F2 02&q6$6 PLATFORMVELOCITY 02&LIMITSFORUNAMBIGUOUSRANGE F2 C2
L
$ L L y $Q L $
&ORSTRIPMAP3!2
3 C
a D CR 6 COSY
3IGNAL TO NOISERATIO 3.2
04X AVG !H S D R 04X AVG' L S D R P 2 K4 & ,OSS 6 COSY P 2 L K4 & ,OSS 6 COSY
£Ç°nÊ -* Ê-,Ê** /" )NTHISSECTION WEBRIEFLYDISCUSSSEVERALSPECIFICASPECTSOF3!2 SPECIFICALLYPOLARI METRIC3!2 MOVINGTARGETS VIBRATINGTARGETS MEASUREMENTOFOBJECTHEIGHT ANDFOLI AGE PENETRATION3!2 0OLARIMETRIC3!2 5SUALLYWHENARADARTRANSMITSAPULSEATAPARTICULARPOLARIZA TIONEG HORIZONTAL( ITRECEIVESTHEECHOESATTHESAMEPOLARIZATION3OMERADARS ARE CAPABLE OF TRANSMITTING AT ONE POLARIZATION AND RECEIVING AT TWO ORTHOGONAL POLAR IZATIONSEG HORIZONTAL;(=ANDVERTICAL;6=ORRIGHT CIRCULAR;2=ANDLEFT CIRCULAR;,= &URTHERMORE SOMERADARSCANTRANSMITATEITHEROFTWOORTHOGONALPOLARIZATIONSANDRECEIVE ATEITHEROFTHETRANSMITTEDPOLARIZATIONSANDTHECHOICEOFTRANSMITTEDANDRECEIVEDPOLAR IZATIONSCANBEVARIEDFROMPULSETOPULSE)FTHEPHASESASWELLASTHEMAGNITUDESOFTHE ECHOESAREOBTAINED THENSUCHARADARISFULLYPOLARIMETRIC7EMAYDESIGNATETHECHOICE OFPOLARIZATIONSASFOLLOWS(6IShTRANSMIT( RECEIVE6 vANDSOFORTH &ULLYPOLARIMETRIC3!2SHAVEBEENDEMONSTRATED3ULLIVANETALAND(ELDETAL &OREXAMPLE 3ULLIVANETALINCLUDES((AND(68 BAND3!2IMAGESTAKENOFTHE SAMESCENEATTHESAMETIMEUSING((AND(6MODESINTERLEAVEDONAPULSE TO PULSE BASIS4HE3!2DESCRIBEDCOULD USINGPULSE TO PULSEINTERLEAVING TRANSMITRECEIVEFIRST (( THEN(6 THEN6( ANDTHEN66DATA ANDPRODUCEFOURCORRESPONDINGSIMULTANE OUSLYCOLLECTEDCOMPLEXIMAGES SUCHTHATTHEPHASESOFTHECORRESPONDINGPIXELSINTHE FOURIMAGESBEARASPECIFICRELATIONSHIPTOEACHOTHER DEPENDINGONTHETARGETTYPE .OVAKETALDEVELOPEDANOPTIMALPOLARIMETRICWHITENINGFILTERFORENHANCEDTAR GETDETECTIONINSUCHSETSOFFULLY POLARIMETRIC3!2IMAGES5SINGFULLYPOLARIMETRIC DATAFROMA '(Z3!2 THEYSHOWEDTHATDIHEDRALREFLECTORSLOOKQUITEDIFFERENT FROM TRIHEDRAL REFLECTORS IN FULLY POLARIMETRIC 3!2 IMAGERY &EW DIHEDRALS EXIST IN +A BANDNATURALCLUTTERTHUS IFAPORTIONOFA3!2IMAGECORRESPONDSCLOSELYTOA DIHEDRAL THENTHEREGIONISLIKELYTOCONTAINCULTURALHUMAN MADE OBJECTS
39.4(%4)#!0%2452%2!$!2
£Ç°ÓÎ
-OVING4ARGETSINA3!2)MAGE $ISPLACEMENT OF A -OVING 4ARGET 4HE BASIC THEORY OF 3!2 ASSUMES THAT THE GROUNDSCENE ISSTATIONARY!MOVINGTARGETINTHESCENEWILLHAVEAhWRONGvRELA TIONSHIPBETWEENITSLOCATIONANDITSLINE OF SIGHTVELOCITY)FTHETARGETMOTIONISINA STRAIGHTLINEATCONSTANTSPEED THETARGETIMAGEWILLBEDISPLACEDINCROSSRANGEBY
RDISPL
6,/3 6,/3 2 6 7
WHERE7ISTHEAPPARENTROTATIONRATEOFTHESCENERELATIVETOTHERADARAND6,/3ISTHETARGET VELOCITYCOMPONENTALONGTHERADARLINE OF SIGHT)NGENERAL COMPLICATEDMOTIONOFATAR GETDURINGA3!2DATACOLLECTIONPREVENTSFORMATIONOFACLEAR3!2IMAGEOFTHETARGET $ETECTIONOF-OVING4ARGETSIN3!2)MAGES 6ARIOUSPROCESSINGMETHODSHAVE BEENDEVELOPEDTODETECTANDREPOSITIONMOVINGTARGETS 3INGLE !PERTURE-OVING 4ARGET)NDICATION-4) 3!2 7ITHRESPECTTOCON VENTIONALSINGLE APERTURE3!2 KEYRESULTSHAVEBEENOBTAINEDBYSEVERALAUTHORS INCLUDING2ANEY &REEMAN &REEMANAND#URRIE AND7ERNESSET AL )FTHE 02&ISGREATERTHANTHEMINIMUMNECESSARYTOPRODUCEA3!2IMAGE THENFURTHER DOPPLERBANDSAREAVAILABLE4HESEBANDSCANBEUSEDFORADDITIONALINFORMATION AND PROCESSING RESULTS FOR MOVING TARGETS WILL BE DIFFERENT FROM THOSE FOR FIXED TARGETS&REEMANPRESENTSASUMMARYOFPOTENTIALRESULTSFORMOVINGTARGETS COV ERING SUCH ISSUES AS AZIMUTH SHIFT RANGE WALK AND AZIMUTH DEFOCUS h0ROBABLY THEWORSTDEFECTWILLBEDISPLACEMENTOFMOVINGTARGETSINTHEAZIMUTHDIRECTION AWAY FROM THEIR TRUE POSITION ON THE GROUND4HE PREFILTER WE HAVE DESCRIBED IS OPTIMISED FOR TARGETS TRAVELING RADIALLY3UCH TARGETS WILL APPEAR AT THEIR CORRECT POSITIONINTHE-4)IMAGEv )NTERFEROMETRIC 3!2 )N3!2 FOR -OVING 4ARGET )NDICATION -4) !S MENTIONED IN 3ECTION )NTERFEROMETRIC 3!2 )N3!2 SOMETIMES ALSO CALLED )&3!2 REFERSTOTHEUSEOFTWOANTENNASWHOSESIGNALSARECOMBINEDCOHERENTLY 4HETWOANTENNASAREDISPLACEDHORIZONTALLYALONGALINEPARALLELTOTHEGROUND TO DETECT AND ANALYZE MOVING TARGETS AND ARE DISPLACED VERTICALLY TO ESTIMATE TERRAINHEIGHT"OTHTYPESOF)N3!2AREDISCUSSEDHEREIN4HEFORMERISDISCUSSED INTHISSECTIONANDTHELATTERISDISCUSSEDLATERINh)NTERFEROMETRIC3!2)N3!2 FOR 4ARGET(EIGHT-EASUREMENTv )N3!2 TO DETECT MOVING TARGETS WAS ORIGINALLY DEVELOPED BY THE *ET 0ROPULSION ,ABORATORY*0, TODETECTOCEANCURRENTS ANDHASBEENIMPROVEDBYSEVERAL AUTHORS /NE OF THE MOST SOPHISTICATED TECHNIQUES HAS BEEN DEVELOPED FOR THE *OINT34!23AIRCRAFTANDUSESANINTERESTINGCOMBINATIONOF3!2AND-4)TECH NIQUESTODETECTANDEVALUATEMOVINGTARGETS 4HE*OINT34!233!2MODEINVOLVESACLASSICALSINGLE RECEIVER CHANNELSPOTLIGHT 3!2THATDWELLSONADESIGNATEDGROUND REFERENCEDCOORDINATEFORADURATIONTHAT RESULTS IN A NOMINALLY SQUARE POINT SPREAD FUNCTION IE DOWNRANGE RESOLUTION CROSSRANGERESOLUTION 4HE-4)MODEISCAPABLEOFDETECTINGANDACCURATELYGEO LOCATINGBOTHEXOCLUTTERIE TARGETMOVINGFASTERTHANAPPARENTTERRAINMOTION AND ENDOCLUTTERIE TARGETMOVINGMORESLOWLYTHANAPPARENTTERRAINMOTION RETURNS FROMMOVINGTARGETSTHAT INGENERAL HAVERADARCROSSSECTIONSTHATARESMALLERTHAN
£Ç°Ó{
2!$!2(!.$"//+
THECORRESPONDINGMAIN BEAMCLUTTER ONLYCELLS)TACCOMPLISHESTHISBYTRANSMITTING ACOHERENTBURSTOFPULSESTHATARESUBSEQUENTLYRECEIVEDBYEACHOFTHREELINEARLYDIS PLACEDSUBARRAYSORINTERFEROMETERPORTS )NEACHCHANNEL THEPULSESAREFAST TIME ANDSLOW TIMEPROCESSEDINTOASETOFRANGEANDDOPPLERCELLSWHOSEINTENSITIESMAY BECONSIDEREDASA3!2IMAGEOFTHESCENEALTHOUGHNOTASFINEINRANGEORDOPPLER RESOLUTIONASINTHE3!2MODEANDGENERALLYNOTWITHANOMINALLYSQUARE03& %ACH OFTHEINTERFEROMETERPORTSPRODUCESACOMPLEX VALUED RANGE DOPPLERhIMAGEvTHAT COULDBECALLEDAh3!2vIMAGE SINCEITWASFORMEDFROMACOHERENTSEQUENCEOF PULSES ANDTHESUBSEQUENTCOMPLEXPAIR WISECOMBININGOFTHESEIMAGESWITHTHE PROPERRELATIVECOMPLEXWEIGHTINGTONULLTHECLUTTERCANBECONSIDEREDASAN)N3!2 PROCESS/NTHEOTHERHAND TOAVOIDCONFUSIONWITHTHETYPEOFINTERFEROMETRIC3!2 THATISUSEDFORTARGETHEIGHTMEASUREMENT THE*OINT34!23TEAMTYPICALLYREFERSTO THEIRPROCESSASh#LUTTER3UPPRESSION)NTERFEROMETRYvORSIMPLYh#3)vp "ARBAROSSAAND&ARINASHOWTHAT BYUSINGMULTIPLESUBAPERTURES DETECTIONAND REPOSITIONINGOFMOVINGTARGETSCANBECONSIDERABLYIMPROVED INANEXTENSIONOFTHE REAL BEAM$ISPLACED0HASE #ENTER!NTENNA$0#! TECHNIQUE3TAUDAHER 4HEY DEVELOPEDAPROCEDUREFOR3!2PROCESSINGUSINGANARBITRARYNUMBEROFSUBAPER TURES SEPARATEDHORIZONTALLY TOCANCELGROUNDCLUTTERANDIMAGEAMOVINGTARGET 4HEIRAPPROACHISACOMBINATIONOFSPACE TIMEPROCESSINGSEETHELITERATURE FORADISCUSSIONOF3PACE 4IME!DAPTIVE0ROCESSINGOR34!0 ANDTIME FREQUENCY PROCESSING &IGUREASHOWSASIMULATEDPOINT SPREADFUNCTION03& OFA MOVINGPOINTTARGETAFTERCLUTTERCANCELLATION AND&IGUREBSHOWSTHEFINALSIMU LATED03&AFTERRANGEMIGRATIONCOMPENSATION 4HEAUTHORSSTATEh4HE;POINT=TARGETISSUPPOSEDMOVINGONTHETERRAINSHADOW INGEFFECTSHAVEBEENNEGLECTED ATACONSTANTVELOCITY INADIRECTIONOBLIQUEWITH RESPECTTOTHERADARMOTION4HEVELOCITYPARAMETERSHAVEBEENCHOSENINORDERTO MAKEEVIDENTTHEPRESENCEOFRANGEMIGRATIONANDOFCROSS RANGESMEARINGOFTHETAR GETIMAGE4HEGROUNDREFLECTIVITYHASBEENASSUMEDEQUALTOTHETARGETREFLECTIVITY THISISQUITEAPESSIMISTICASSUMPTION BECAUSEINMANYCASESOFPRACTICALINTEREST THETARGETREFLECTIVITYISHIGHER !RECEIVERTHERMALNOISE D"BELOWTHETARGET RETURN HASALSOBEENSUMMEDTOTHERECEIVEDSIGNAL4HEGROUNDECHOISFIRSTCAN CELED BYUSINGATWO ELEMENTANTENNAANDTWOTIMESAMPLES4HETWOANTENNASARE SEPARATEDBYD V4;V PLATFORMSPEED 4 PULSEREPETITIONINTERVAL=!3!2IMAGE ISTHENFORMEDBYCONVENTIONALTECHNIQUES4HERESULTISSHOWNIN&IGURE;A= 4HESMEARINGOFTHEMOVINGPOINTLIKETARGETISEVIDENT'IVENTHEMOTIONPARAM ETERS THETARGETHASMIGRATEDOVERSIXRANGECELLS4HISISTHECAUSEFORTHEBROADEN INGOFTHETARGETIMAGEEVENINRANGE ASWELLASINCROSSRANGE4HETARGETECHO CAUSES A DETECTION AND INITIALIZES THE MOTION ESTIMATION CHANNEL4HE HIGH ;FINE= RESOLUTIONDATAAREINITIALLYSMOOTHEDINRANGETODECREASE;COARSEN=THERANGERESO LUTION4HENTHEPROCESSORLOOKSFORTHERANGECELLWITHTHEMAXIMUMENERGYCONTENT ANDCOMPUTESTHE76$;7IGNER 6ILLE$ISTRIBUTION=OFTHATCELLONLY4HEPHASE HISTORYISTHENUSEDFORCOMPENSATINGTHERANGEMIGRATIONANDTHEPHASESHIFTON THEHIGH;FINE=RESOLUTIONRANGEDATA4HEFINALIMAGEISSHOWNIN&IGURE;B= 4HESHARPENINGOFTHETARGETIMAGEISQUITEEVIDENTv"ARBAROSSAAND&ARINAASSUMED APOINTTARGETINTHEIRSIMULATION4HEYOBTAINAPRECISELOCATIONOFASIMULATEDMOV INGPOINTTARGET BUTDONOTCLAIMTOHAVEPRODUCEDASIMULATEDIMAGEOFANEXTENDED MOVINGTARGET SUCHASAVEHICLE p0ARAGRAPHCOURTESYOF$R-ARSHALL'REENSPAN .ORTHROP 'RUMMAN#ORPORATION
39.4(%4)#!0%2452%2!$!2
£Ç°Óx
&)'52% 3!2 IMAGE OF A MOVING TARGET USING MULTIPLE SUBAPERTURES FOR CLUTTER CANCELLATIONSIMULATEDDATA A ADAPTIVEPROCESSINGANDB ADAPTIVEPROCESSINGPLUS3!2 AFTER3"ARBAROSSAAND!&ARINAÚ)%%%
'UARINO AND )BSEN DESCRIBE AN EXPERIMENT USING THE!.!0' RADAR h4HE RADAR PROVIDES A UNIQUE SIMULTANEOUS 3!2'-4) ;'ROUND -OVING 4ARGET )NDICATIONSCANNINGREALAPERTURERADAR=MODEINWHICHDETECTEDTARGETSAREDIS PLAYEDONTHE3!2MAPASMOVINGTARGETSYMBOLS4HESYMBOLSAREACCURATELY LOCATEDATTHEIRTRUEAZIMUTHPOSITIONRELATIVETOTHEMAPCENTER4HE;3!2=MAP ONWHICHTHEMOVINGTARGETSYMBOLISDISPLAYEDISCOLLECTEDANDPROCESSEDSIMUL TANEOUSLYWITHTHE'-4)v4HEAUTHORSALSOMAKECLEARTHAT'LOBAL0OSITIONING 3YSTEM'03 INPUTSWEREESSENTIALTOTHEIRACCURATELOCATIONOFTARGETSFIXEDTAR GETSWEREGEOLOCATEDTOANABSOLUTEACCURACYOFBETTERTHANMETERS ANDMOVING TARGETVEHICLESTOANABSOLUTEACCURACYOFABOUTMETERS3TIMSONALSODISCUSSES THESE!.!0' RESULTSPP )MAGINGOF-OVING4ARGETSIN3!2)MAGES 0ERRYETALHAVEDEVELOPEDAMETHOD FOR3!2IMAGINGOFGROUND MOVINGTARGETSTHATHAVEUNKNOWNSTRAIGHT LINE CONSTANT SPEEDMOTION4HEYPROCESSTHERECEIVEDPHASEHISTORYWITHAhKEYSTONEFORMATTINGv PROCEDURETHATELIMINATESTHEEFFECTSOFLINEARRANGEMIGRATIONFORALLGROUND MOVING TARGETS REGARDLESSOFTHEIRUNKNOWNVELOCITY4HEPROCESSINGPROCEDURETHENAUTOMATI CALLYFOCUSESTHEMOVINGTARGETS&IGUREASHOWSACONVENTIONALLYPROCESSED3!2 IMAGECONTAININGTHREEMOVINGTARGETSAMILITARYTRUCKTYPE- ATRACTOR TRAILER TRUCK ANDASURROGATEIE AFULL SIZEREPLICA OFAMISSILETRANSPORTER ERECTOR LAUNCHER 4%, &IGUREBSHOWSTHEFOCUSEDIMAGEOFTHETRACTOR TRAILERRESULTINGFROMTHE PROCESSING4HETWO FOOTRESOLUTIONCLEARLYSHOWSTHEOUTLINEOFTHECABANDTRAILEROF THETRUCK 6IBRATING4ARGETSINA3!2)MAGE #ONSIDERA3!2OBSERVINGASCENETHATCON TAINSAPOINTTARGETWHOSEPOSITIONISOSCILLATINGSINUSOIDALLYVIBRATING SEE3ECTION OF#ARRARAETAL 4HECOMPONENTOFTHEVIBRATIONAMPLITUDETHATISPARALLELTOTHELINE OF SIGHT,/3 ISD4HEVARIABLECOMPONENTOFTHERADAR TARGETDISTANCEISTHEN
$2TGTT DSINOFVIBT
WHEREFVIBISTHEVIBRATIONFREQUENCY ,ETTHENORMALIZEDCOMPLEXECHOCORRESPONDINGTOASTATIONARYPIXELBE E J P FD T WHEREFDISTHEDOPPLERFREQUENCYCHARACTERISTICOFTHEPIXEL7EASSUMELOWFRACTIONAL BANDWIDTH INWHICHCASETHISISEQUIVALENTTOTHEDOPPLERFREQUENCYCORRESPONDING TOTHECENTERFREQUENCYOFTHETRANSMITTEDBANDWIDTHSEE3ECTIONOF3ULLIVAN
£Ç°ÓÈ
2!$!2(!.$"//+
!
&)'52% )MAGINGAMOVINGTARGETINA3!2IMAGEA #ONVENTIONAL3!2IMAGEREALDATA SHOWING BLURREDMOVINGVEHICLESAN-MILITARYTRUCK ATRACTOR TRAILERTRUCK ANDASURROGATEMOCKUP OFAMISSILE TRANSPORTER ERECTOR LAUNCHERB )MAGEOFTRACTOR TRAILERTRUCKUSINGhKEYSTONEvPROCESSINGTHETRUCKSCABIS ATTHEBOTTOMANDTHETRAILERISABOVEITAFTER200ERRYETALÚ)%%%
)NADDITIONTOTHISECHO THEPIXELCONTAININGTHETARGETWILLPRODUCEANADDITIONALECHO WITHAPERIODICPHASEERROR
FE
P D SIN P FVIBT FO SIN P FVIBT L
7EASSUMEODK THUSEO4HENORMALIZEDCOMPLEXECHOCORRESPONDING TOTHEPHASEERRORIS
E JFE E JF SIN P FVIBT
y JF SIN P FVIBT
F E J P FVIBT E J P FVIBT 4HE NORMALIZED COMPLEX ECHO CORRESPONDING TO THE VIBRATING TARGET IS THEN THE COMPLEXPRODUCTOFTHEECHOCORRESPONDINGTOTHESTATIONARYPIXELANDTHEECHOCOR RESPONDINGTOTHEPHASEERROR
E JFDOP E J P FD T E JFE
AND
E JFDOP E J P FD T
FO J P T FD FVIB E
E J P T FD FVIB
)NTHE3!2IMAGE THEVIBRATINGPOINTTARGETWILLAPPEARINTHREECROSSRANGELOCATIONS -OSTOFTHETARGETENERGYSTILLAPPEARSATTHECORRECTLOCATION WHEREASASMALLFRACTION OFTHEENERGYWILLAPPEARINEACHOFTWOPIXELSSEPARATEDINCROSSRANGEBYFVIBINDOPPLER FREQUENCY4HUS AVIBRATINGTARGETCANGIVERISETOAPAIROFDISTINCTIVEECHOES
39.4(%4)#!0%2452%2!$!2
£Ç°ÓÇ
4HE CORRESPONDING VELOCITY SEPARATION IS $V o FVIB K AND THE CROSSRANGE DISPLACEMENTISTHEN
$R
FVIBLAVG 2 $V $V 2 o
6 6 7
WHEREKAVG AVERAGEWAVELENGTHASSUMINGLOWFRACTIONALBANDWIDTH 4HERELATIVE AMPLITUDEOFEACHOFTHEPAIREDECHOESIS
6OLTAGE
FO P D
LAVG
¤ P D ³ F
0OWER ¤¥ O ³´ ¥ ¦ µ ¦ LAVG ´µ
4HUS THEAMPLITUDEOFTHEPAIREDECHOESISPROPORTIONALTOTHESQUAREOFTHEVIBRA TIONAMPLITUDE ANDCROSSRANGEDISPLACEMENTISPROPORTIONALTOTHEVIBRATIONFREQUENCY SEE3ECTIONOF3ULLIVAN &ORBRIGHT POINT LIKETARGETS ORFORTARGETSSUCHTHATODISNOTSMALLCOMPARED TOK ADDITIONALTERMSSHOULDBERETAINEDIN%Q DESCRIBINGTHEFACTTHATASERIES OFPAIREDECHOES OFDECREASINGAMPLITUDE MAYAPPEARINCROSSRANGE &IGURESHOWSA3!2IMAGEOFASCENEINCLUDINGAVIBRATINGTARGETATRUCK WITHITSENGINERUNNING4HEIMAGECONTAINSTWOSETSOFPAIREDECHOES CORRESPONDINGTO TWOVIBRATIONFREQUENCIESCHARACTERISTICOFTHEPARTICULARTRUCKUSEDFORTHEOBSERVATION -EASUREMENT OF /BJECT (EIGHT 4HE BASIC THEORY OF 3!2 ASSUMES THAT THE SCENEISFLAT4OTHEEXTENTTHATTHESCENEISNOTFLAT DISTORTIONSINTHE3!2IMAGEWILL RESULT)NSOMECASES THEYCANBEUSEDTOMEASURETHEHEIGHTOFELEVATEDOBJECTSABOVE AFLATTERRAIN
&)'52% 3!2SCENECONTAININGVIBRATINGTARGET#ROSSRANGEISHORI ZONTALRANGEISVERTICAL4HEPAIREDECHOESINCROSSRANGEARECHARACTERISTICOFA VIBRATINGTARGETTRUCKWITHENGINERUNNING INA3!2IMAGE4HEFREQUENCIES (ZAND(Z AREPECULIARTOTHESPECIFICTRUCKTHATWASIMAGED#OURTESY OF.ORTHROP 'RUMMAN#ORPORATION
£Ç°Ón
2!$!2(!.$"//+
3HADOWS 4HESIMPLESTMETHODOFMEASURINGOBJECTHEIGHTISTOOBSERVETHELENGTH ,SHADOWOFTHESHADOWOFTHEOBJECTCASTBYTHE3!2ANDCALCULATETHEOBJECTHEIGHTH FROMTHEKNOWN3!2ALTITUDE(ANDGROUNDRANGE2G
H ,SHADOW
( 2G
4HISEXPRESSIONASSUMESFLAT EARTH ANDMAYBEGENERALIZEDTOCURVED EARTHIF2GIS RELATIVELYLARGESEE3ECTIONOF3ULLIVAN(OWEVER THESHADOWMETHODWORKSONLY FORANISOLATED RELATIVELYHIGHOBJECTONESSENTIALLYFLATTERRAINEG &IGURE ,AYOVER 3!2PROCESSINGSORTSTARGETRETURNSINTOBINSPIXELS DEPENDINGONTHE RANGE2ANDVELOCITYVOFTHETARGETRELATIVETOTHEPLATFORM)FTWOORMORETARGETSHAVE THESAME2ANDV THENTHEYWILLBEPLACEDATTHESAMELOCATIONINTHE3!2IMAGE 7ESHALLDEFINEALAYOVERCONTOURASTHELOCUSOFPOINTSIN$SPACESUCHTHATAN OBJECTATANYOFTHEPOINTSWILLBEASSIGNEDTOTHESAMELOCATIONINA3!2IMAGE !SSHOWNIN&IGURE ALAYOVERCONTOURISTHEINTERSECTIONOFACONSTANT RANGE SPHEREOFRANGE2ANDACONSTANTVELOCITYCONEOFGENERATINGANGLEA COSnV6 WITHAXISALONGTHEPLATFORMDIRECTION IE ACIRCLEOFRADIUS2SINAAHEADOFTHE PLATFORMA nCORRESPONDSTOTARGETSBEHINDTHEPLATFORM 7ESHALL THERE FORE CALLTHECONTOURTHELAYOVERCIRCLE)FTHETOPOFANELEVATEDOBJECT SUCHASA TOWER ISONTHELAYOVERCIRCLEANDIFTHEGROUNDISFLAT THENTHETOPOFTHETOWER WILLAPPEARINTHE3!2IMAGEATTHESAMEPOSITIONASAPOINTONTHEGROUNDWHERE THELAYOVERCIRCLEINTERSECTSTHEGROUND4HETOWERWILLBEhLAIDOVER vHENCETHE NOMENCLATURE !SSHOWNIN&IGURE LETUSCONSIDERAPLATFORMINSTRAIGHT LINE CONSTANT SPEED MOTIONATALTITUDE(OVERAFLATEARTHFORMINGA3!2IMAGE THECENTEROFWHICHISAT SLANTRANGE2S(ANDSQUINTANGLEPSQ3UPPOSETHATATOWEROFHEIGHTHH( ISINTHEAREATHATISIMAGED7EDESCRIBELOCATIONSWITHINTHEIMAGEBYACOORDINATE SYSTEMX Y )FTHEBASEOFTHETOWERISATX Y WEWISHTOASCERTAINTHEIMAGE COORDINATESOFTHETOPOFTHETOWER &IGUREAILLUSTRATESAPERSPECTIVEVIEW"ECAUSE2G( THEISODOPYnAXIS MAKESANANGLEPSQWITHTHEY AXIS4HEIMAGECENTERISADISTANCE3 2GCOSPSQFROM THEX AXIS WHERE2G GROUNDRANGE&IGUREBSHOWSAVIEWFROMTHE X AXIS INDICATINGTHELAYOVERCIRCLENORMALTOTHEX AXISANDSHOWINGTHATTHEIMAGELOCATION OFTHETOWERTOPISLOCATEDADISTANCETHELAYOVERDISTANCE D H(2GCOSPSQ FROM THEIMAGELOCATIONOFTHETOWERBASE&IGURECTHENDEPICTSTHEVIEWINIMAGE COORDINATESX Y 4HEIMAGECOORDINATESOFTHETOWERTOPARE
X X DSINPSQ Y Y DCOSPSQ
&OREXAMPLE IF2G KM ( KM H M ANDPSQ THEND M X X ANDY YnM4HETOWERTOPAPPEARSINTHEIMAGEMCLOSERTOTHERADAR THANTHETOWERBASE4HISPRINCIPLEMAYSOMETIMESBEUSEDTOESTIMATETHEHEIGHTOF ISOLATED TOWER LIKESTRUCTURESONRELATIVELYLEVELGROUND
H
D2G COSQSQ
(
4HEINTERSECTIONOFTHECONSTANT VELOCITYCONEANDTHEGROUNDISAHYPERBOLA)F (ISNOT2 THEISODOPDIRECTIONWILLNOTBEPARALLELTOTHEDOWN RANGEDIRECTION
39.4(%4)#!0%2452%2!$!2
£Ç°Ó
&)'52% ,AYOVERA 0ERSPECTIVEVIEW B VIEWALONGPLATFORMFLIGHTPATH ANDC VIEW INCOORDINATESYSTEMOF3!2IMAGE#OURTESYOF3CI4ECH0UBLISHING )NC
4HEGEOMETRYISMORECOMPLICATEDBUTLAYOVERDISTANCEANDOBJECTHEIGHTMAYSTILL BEESTIMATED 3TEREO3!2 4WO3!2IMAGESOFTHESAMESCENEMAYBEOBTAINEDFROMSOMEWHAT DIFFERENTLOCATIONSSEE3ECTIONIN#ARRARAETAL .ONCOHERENTCOMPARISON
£Ç°Îä
2!$!2(!.$"//+
OFTHETWOTHESTEREOTECHNIQUEMAYENABLEESTIMATIONOFOBJECTHEIGHT4HETECH NIQUE IS ANALOGOUS TO THE METHOD BY WHICH WE HUMANS USE OUR TWO EYES TO HELP ESTIMATETHEDISTANCEOFTHEOBJECTSTHATWESEE)NFACT THETWO3!2IMAGESMAYBE PRINTED ON THE SAME PAGE USING TWO DIFFERENT COLORS WITH THE VIEWER USING SPECIAL GLASSESSOTHATTHELEFTEYESEESONLYONEIMAGEANDTHERIGHTEYEONLYTHEOTHERANDTHE BRAINPROCESSINGTHETWOTOGETHERSOTHATTHESCENEISPERCEIVEDIN$ )NTERFEROMETRIC3!2)N3!2 FOR4ARGET(EIGHT-EASUREMENT )NTERFEROMETRIC3!2 )N3!2 ALSOCALLED)&3!2SEE3ECTIONOF#ARRARAETALAND!DAMSETAL WHENUSEDFORTERRAINHEIGHTMEASUREMENT INVOLVESTWO3!2IMAGESTAKENFROMANTEN NASATSLIGHTLYDIFFERENTALTITUDESANDCOMPAREDCOHERENTLYTOOBTAINFINE RESOLUTIONINFOR MATIONREGARDINGTHEHEIGHTOFTERRAINORTARGETSINTHEIMAGE)NTHISCASE ITISSOMETIMES CALLED)&3!2% WHERE%EMPHASIZESELEVATIONMEASUREMENT )N3!2MAYBEPERFORMED USINGASINGLEPLATFORMWITHTWOANTENNASSINGLE PASS)N3!2 ORBYTHESAMEPLATFORM MAKINGTWOPASSESOVERTHESAMETERRAINTWO PASS)N3!2 !LLENGIVESSEVERALEXAM PLESOFFIELDEDSYSTEMSUSINGEACHTYPE)TISESSENTIALTHATTHERELATIVELOCATIONSOFTHETWO ANTENNASBERATHERPRECISELYKNOWN!DVANTAGESANDDISADVANTAGESOFTHETWOTYPESOF )N3!2AREASFOLLOWS 4WO PASS)N3!2 L
L
L
L
L
.OSPECIALHARDWAREISREQUIREDACONVENTIONAL3!2MAYBEFLOWNTWICEOVERTHE DESIGNATEDTERRAIN -OTIONCOMPENSATIONISCHALLENGINGTHEPOSITIONOFTHEANTENNAVERSUSTIMEINEACH PASSMUSTBEKNOWNWITHGREATPRECISION ! LONG BASELINE VERTICAL DISTANCE BETWEEN ANTENNA PATHS PROVIDES FINE VERTICAL RESOLUTIONBUTCHALLENGINGAMBIGUITIES 4HESCENEMAYCHANGEBETWEENPASSESDUETOWIND ETC %XAMPLE RESULTS ARE GIVEN BY 3CHULER ET AL WHO PERFORM hTERRAIN TOPOGRAPHY MEASUREMENTUSINGMULTIPASSPOLARIMETRIC3!2v
3INGLE PASS)N3!2 "ASELINEISRELATIVELYWELLKNOWN PROVIDINGCONSISTENCYTHROUGHOUTSYNTHETICAPERTURE 3CENEISSAMEFORBOTHIMAGESSINCEDATAFOREACHARECOLLECTEDSIMULTANEOUSLY /N BOARD REAL TIMEPROCESSINGISAPOSSIBILITY -ORE SOPHISTICATED EXPENSIVE HARDWARE IS REQUIRED TWO ANTENNAS TWO RECEIVER CHANNELS ANDTWOSETSOFANALOG TO DIGITAL!$ CONVERTERS %XAMPLERESULTSAREGIVENBY!DAMSETAL WHOINCLUDEAN)N3!2IMAGEOF THE STADIUM AT THE 5NIVERSITY OF -ICHIGAN IN!NN!RBOR VIEWABLE WITH TWO COLORGLASSES
L
L
L
L
L
4OUNDERSTANDTHETHEORYOF)N3!2 WEFIRSTCONSIDERTWOANTENNAS !AND" SEPARATED VERTICALLYBYABASELINE, OBSERVINGAPOINTTARGETATHATISONAFLATGROUNDATRANGE2 THERADARLINE OF SIGHT,/3 INTERSECTSTHEFLATGROUNDATGRAZINGANGLEX&IGURE 7ECONSIDERTWOPOSSIBILITIES ONEANTENNATRANSMITSANDEACHRECEIVESN AND ANTENNA!TRANSMITSANDTHENRECEIVESTHENANTENNA"TRANSMITSANDTHENRECEIVESN
39.4(%4)#!0%2452%2!$!2
£Ç°Î£
&)'52% )N3!2 VERTICALANTENNASEPARATION6ERTICALANTENNASEPARATIONENABLESESTIMATIONOFTHE HEIGHTOFATARGETABOVETHEAVERAGEGROUNDHEIGHTOR MOREGENERALLY TERRAINHEIGHTVERSUSLOCATION#OURTESY OF3CI4ECH0UBLISHING )NC
&ORAhSINGLE FREQUENCYvPULSEOFWAVELENGTHK THEDIFFERENCEINTHEPHASESOFTHEECHOES RECEIVEDFROMTHEPOINTTARGETOBSERVEDBYTHETWOANTENNASISFROM&IGURE
$F
P NS P N, SIN Y L L
7ENOWCONSIDERTHESAMEANTENNAS!AND"OBSERVINGASECONDPOINTTARGETBTHAT ISADISTANCEHABOVETHEFLATGROUNDALSOATRANGE2THERADARLINE OF SIGHT,/3 INTER SECTSTHEPARALLELTOTHEFLATGROUNDATGRAZINGANGLEX4HEDIFFERENCEINTHEPHASESOF THEECHOESRECEIVEDFROMTHEPOINTTARGETOBSERVEDBYTHETWOANTENNASISNOW
$F
P N, SIN Y L
7ECONSIDERTHEQUANTITY
$F x \ $F $F \
P N, \SIN Y SIN Y \ L
7EASSUMETHATH2ANDTHUSXyXyX X X4HEN WHERE$X \X X\ FROM&IGURE
$F y
P N, P N, H P N,H COSY$Y COSY
L L 2 COSY L2
£Ç°ÎÓ
2!$!2(!.$"//+
7ENOWCONSIDER\C$E \ THECHANGEIN$EDUETOACHANGEINHGIVENBY\CH\
\D $F \
P N, \D H\ L2
!NTENNAS!AND"MAYBECONSIDEREDASSEPARATEDINVERTICALDISTANCEONANAIRCRAFT 4HERELATIONSHIPBETWEENC$E ANDAVARIATIONINTERRAINALTITUDECHIS
\D H\
L 2 \D $F \ ANTENNASSEPARATEDVERTICALLY P N,
)N3!2FORTERRAINELEVATIONMEASUREMENTCANALSOBEPERFORMEDBYANAIRCRAFTWITH TWOANTENNASSEPARATEDHORIZONTALLYPERPENDICULARTOTHEFLIGHTPATH BY,4HEAIRCRAFT ISBANKINGATANGLEF ANDCOLLECTINGDATAFROMTHEFLATGROUNDATGRAZINGANGLEX &IGURE 4HENTHEEFFECTIVEAPERTUREPERPENDICULARTOTHE,/3 IS,SINX F INSTEADOF,COSX&ROM&IGURE WEHAVE
\D H\
L 2 \D $F \ COSY ANTENNASSEPARATEDHORIZONTALLY P N, SINY G
)N EITHER GEOMETRY SINCE BOTH CHANNELS ARE NOISY THE EXPECTED ACCURACY IN THE PHASEDIFFERENCE SIGMA ISGIVENBY,EVANON
D $F
3.2
WHERE3.2 SIGNAL TO NOISERATIOSEE3ECTION 4HUS THETHEORETICALACCURACY FORTERRAINALTITUDEMEASUREMENTIS 6ERTICALANTENNASEPARATIONNOBANKING
DH
L2
P N, 3.2
&)'52% )N3!2 HORIZONTAL ANTENNA SEPARATION !S LONG AS THE TWO APERTURESDONOTBOTHLIEONTHESAMELINEOFSIGHTTOTHETARGETAREA ANESTIMATEOF TERRAINHEIGHTMAYBEMADE BYCOMPARINGTHEPHASESOFECHOESRECEIVEDBYTHETWO APERTURES#OURTESYOF3CI4ECH0UBLISHING )NC
39.4(%4)#!0%2452%2!$!2
£Ç°ÎÎ
(ORIZONTALANTENNASEPARATION
DH
L 2 COSY
P N, SINY G 3.2
&URTHERMORE WHENTHEPHASEMOVESTHROUGHANINTERVALOFO ANAMBIGUITYOCCURS INTERRAINALTITUDEMEASUREMENT4HECORRESPONDINGALTITUDEDIFFERENCEISCOMPUTEDBY REPLACINGC$E BYOIN%QSAND 6ERTICALANTENNASEPARATIONNOBANKING
L2 N,
L 2 COSY
N, SINY G
$H AMBIG (ORIZONTALANTENNASEPARATION
$H AMBIG
!LTHOUGHWEHAVEDERIVEDTHESERELATIONSHIPSFORASINGLEMONOCHROMATICPULSE THEY CANBESHOWNSEE3ECTIONOF3ULLIVANAND3ECTIONSANDOF#ARRARAETAL TOBETRUEFOR3!2PIXELSALSO WITHKREPLACEDBYCFAVG 4HE.ATIONAL!ERONAUTICSAND3PACE!DMINISTRATION.!3! PERFORMEDSUCCESSFUL 8# BANDSINGLE PASSPOLARIMETRIC)N3!2SINGLE PASS FORTHE3PACE3HUTTLE2ADAR 4OPOGRAPHY-ISSION324- USINGANTENNASONTHESHUTTLEITSELFANDONTHESHUTTLES MANEUVERABLEARMTOPRODUCEACOMPLETE$MAPOFTHE%ARTHSSURFACEBETWEENn .LATITUDEANDn3LATITUDENEARLYOFTHESURFACE WITHBESTVERTICALACCURACY OFMETERSONA METERHORIZONTALGRID &OLIAGE 0ENETRATION &/0%. 3!2 !LTHOUGH HIGHER FREQUENCY GREATER THAN APPROXIMATELY'(Z MICROWAVESDONOTPENETRATEFOLIAGEWELL LOWERFREQUENCYMICRO WAVESDO&LEISCHMANETALSEEALSO3ECTION OF5LABYETAL &OREXAMPLE FOR#BAND THEATTENUATIONOFATYPICALFORESTCANOPYVARIESFROMyD"TOyD" THEPROBABILITYTHATTHEATTENUATIONISLESSTHAND"ISABOUT/NTHEOTHERHAND FOR 5(&RADIATION ATTENUATIONVARIESFROMTOyD"HALFTHETIMEITISLESSTHANyD" 4HUS FOR &/0%. 5(& RADIATION IS NECESSARY SHORTER WAVES WILL NOT PENETRATE THE FOLIAGE WHEREASFORAIRBORNEAPPLICATIONS LONGERWAVESWOULDREQUIREPROHIBITIVELY LARGEANTENNAS3PECIFICVALUESOFATTENUATION;D"METER=VARYWITHGRAZINGANGLE TREE TYPE LEAFDENSITY ANDMOISTURECONTENTHOWEVER THEPREVIOUSSTATEMENTISAGENERAL SUMMARYOFTHESERESULTSFURTHERDETAILSAREGIVENIN&LEISHMANETAL 4HEAPERTURETIMET!REQUIREDTOCOLLECTSUFFICIENTDATAFORA3!2IMAGEISFOUNDFROM %Q&OREXAMPLE LETUSASSUME2 KM 6 MSECKTS PSQ ANDCCR M&ORF '(Z8BAND K M T! SEC ANDTHEFRACTIONALBANDWIDTH"FO /NTHEOTHERHAND FORFO '(Z5(& K M T! SEC MINAND "FO 3UCHAHIGHFRACTIONALBANDWIDTHANULTRA WIDEBAND3!2 PRESENTSCHALLENGES INDESIGNINGHARDWARECOMPONENTS SUCHASANTENNAS THATAREREASONABLYLINEAROVERTHE FULLFREQUENCYRANGE&URTHERMORE THELONGAPERTURETIMEPRESENTSMOTION COMPENSA TIONCHALLENGES ANDTHEWIDEREAL BEAMANGLEADDSTOPROCESSINGDIFFICULTIES VERYLIKELY REQUIRING2ANGE -IGRATION!LGORITHM2-! PROCESSING3ECTION )NADDITION FOR CALCULATINGCROSSRANGERESOLUTION THESMALL ANGLEAPPROXIMATIONNOLONGERHOLDS
£Ç°Î{
2!$!2(!.$"//+
! ! !
&)'52% #ONVENTIONAL AND &/0%. 3!2 IMAGES )N THE CONVENTIONAL IMAGE TARGET VEHICLES CANNOTREADILYBESEEN WHEREASINTHE&/0%.IMAGETHEYAREQUITEPROMINENT3OURCEHTTPWWWDARPA MIL$!20!4ECH0RESENTATIONSSPO?PDF-OYER##4"7PDF
! NUMBER OF AUTHORS REPORT SUCCESSFUL RESULTS WITH &/0%. 3!2 USING SUCH 3!2S AS THE %NVIRONMENTAL 2ESEARCH )NSTITUTE OF -ICHIGAN 0 3!2 THE 3WEDISH.ATIONAL$EFENSE2ESEARCH%STABLISHMENT#!2!"!3SENSOR ANDTHE32) )NTERNATIONAL 5LTRA 7IDEBAND 3!2 &URTHERMORE -OYER PRESENTS IMAGES FROM CONVENTIONALAND&/0%.3!2SSHOWINGTHATVEHICLESUNDERTREESMAYBEIMAGED SIGNIFICANTLYBETTERWITH&/0%.3!2THANWITHCONVENTIONAL3!2EXAMPLEIMAGERY ISGIVENIN&IGURE
, ,
2*3ULLIVAN 2ADAR&OUNDATIONSFOR)MAGINGAND!DVANCED#ONCEPTS 2ALEIGH .#3CI4ECH PREVIOUSLYPUBLISHEDAS-ICROWAVE2ADAR)MAGINGAND!DVANCED#ONCEPTS .ORWOOD -!!RTECH(OUSE ,*#UTRONA h3YNTHETICAPERTURERADAR vIN-3KOLNIK 2ADAR(ANDBOOK ND%D .EW9ORK -C'RAW (ILL ST%D .EW9ORK-C'RAW (ILL 7 ' #ARRARA 2 3 'OODMAN AND 2 - -AJEWSKI 3POTLIGHT 3YNTHETIC !PERTURE 2ADAR .ORWOOD -!!RTECH(OUSE *#URLANDERAND2-C$ONOUGH 3YNTHETIC!PERTURE2ADAR .EW9ORK*OHN7ILEYAND3ONS '73TIMSON )NTRODUCTIONTO!IRBORNE2ADAR ND%D -ENDHAM .*3CI4ECH #**AKOWATZ *R $%7AHL 0(%ICHEL $#'HIGLIA AND0!4HOMPSON 3POTLIGHT -ODE 3!2!3IGNAL 0ROCESSING!PPROACH "OSTON+LUWER!CADEMIC0UBLISHERS 3 ! (OVANESSIAN )NTRODUCTION TO 3YNTHETIC !RRAY AND )MAGING 2ADARS .ORWOOD -! !RTECH(OUSE
39.4(%4)#!0%2452%2!$!2
£Ç°Îx
2 / (ARGER 3YNTHETIC !PERTURE 2ADAR 3YSTEMS 4HEORY AND $ESIGN .EW 9ORK!CADEMIC 0RESS 2"IRK 7#AMUS %6ALENTI AND7-C#ANDLESS h3YNTHETICAPERTURERADARIMAGINGSYSTEMS v )%%%!%3-AGAZINE PP .OVEMBER #*ACKSONAND*!PELDECEASEDTHEBOOKISDEDICATEDTOHIM 3YNTHETIC!PERTURE2ADAR-ARINE 5SERS-ANUAL 7ASHINGTON $#$EPARTMENTOF#OMMERCE .ATIONAL/CEANICAND!TMOSPHERIC !DMINISTRATION./!! $!USHERMAN !+OZMA *7ALKER (*ONES AND%0OGGIO h$EVELOPMENTSINRADARIMAGING v )%%%4RANSACTIONSON!EROSPACEAND%LECTRONIC3YSTEMS VOL!%3 NO *ULY #7ILEY h3YNTHETICAPERTURERADARS v)%%%4RANSACTIONS!EROSPACEAND%LECTRONIC3YSTEMS VOL!%3 PPn -AY , * #UTRONA 7 % 6IVIAN % . ,EITH AND ' / (ALL h! HIGH RESOLUTION RADAR COMBAT SURVEILLANCESYSTEM v)2%4RANSACTIONSON-ILITARY%LECTRONICS VOL-), NO PPn !PRIL2EPRINTEDIN+OVALY #73HERWIN *02UINA AND2$2AWLIFFE h3OMEEARLYDEVELOPMENTSINSYNTHETICAPER TURERADARSYSTEMS )2%4RANSACTIONSON-ILITARY%LECTRONICS VOL-), NO PPn !PRIL2EPRINTEDIN+OVALY **+OVALY 3YNTHETIC!PERTURE2ADAR .ORWOOD -!!RTECH(OUSE 4HISISACOLLECTION OFEARLYCLASSICPAPERSCONCERNING3!2 $#3CHLEHER -4)AND0ULSED$OPPLER2ADAR .ORWOOD -!!RTECH(OUSE .,EVANON 2ADAR0RINCIPLES .EW9ORK7ILEY )NTERSCIENCE 2 - 'OLDSTEIN AND ( ! :EBKER h)NTERFEROMETRIC RADAR MEASUREMENT OF OCEAN CURRENTS v .ATURE VOL PPn 2-'OLDSTEIN (!:EBKER AND40"ARNETT h2EMOTESENSINGOFOCEANCURRENTS v3CIENCE VOL PPn '&!DAMSETAL h4HE%2)-INTERFEROMETRIC3!2)&3!2 vIN0ROCEEDINGSOFTHE)%%% .ATIONAL 2ADAR #ONFERENCE PP 2EPRINTED IN )%%% !%3 3YSTEMS -AGAZINE $ECEMBER -3KOLNIK )NTRODUCTIONTO2ADAR3YSTEMSST%D .EW9ORK-C'RAW (ILL ND%D .EW9ORK-C'RAW (ILL RD%D .EW9ORK-C'RAW (ILL 3 -USMAN $ +ERR AND # "ACHMANN h!UTOMATIC RECOGNITION OF )3!2 SHIP IMAGES v )%%% 4RANSACTIONSON!EROSPACEAND%LECTRONIC3YSTEMS VOL NO PPn /CTOBER 7,7OLFEAND':ISSISEDS 4HE)NFRARED(ANDBOOK REVED !NN!RBOR -)%NVIRONMENTAL 2ESEARCH)NSTITUTEOF-ICHIGANNOW'ENERAL$YNAMICS 9PSILANTI -) -2ICHARDS &UNDAMENTALSOF2ADAR3IGNAL0ROCESSING .EW9ORK-C'RAW (ILL 2+LEMM 0RINCIPLESOF3PACE 4IME!DAPTIVE0ROCESSING v,ONDON)%% % & +NOTT * & 3HAEFFER AND - 4 4ULEY 2ADAR #ROSS 3ECTION ND %D 2ALEIGH .# 3CI4ECH %/"RIGHAM 4HE&AST&OURIER4RANSFORMAND)TS!PPLICATIONS %NGLEWOOD#LIFFS .*0RENTICE (ALL % $ +APLAN 5NDERSTANDING '03 0RINCIPLES AND !PPLICATIONS .ORWOOD -! !RTECH (OUSE 27"AYMAAND0!-C)NNES h!PERTURESIZEANDAMBIGUITYCONSTRAINTSFORASYNTHETICAPERTURE RADAR vIN0ROC)NTERNATIONAL2ADAR#ONFERENCE PPn2EPRINTEDIN+OVALY & - (ENDERSON AND ! * ,EWIS EDS 0RINCIPLES AND !PPLICATIONS OF )MAGING 2ADAR .EW9ORK7ILEY # /LIVER AND 3 1UEGAN 5NDERSTANDING 3YNTHETIC !PERTURE 2ADAR )MAGES .ORWOOD -! !RTECH(OUSE &*(ARRIS h/NTHEUSEOFWINDOWSFORHARMONICANALYSISWITHTHEDISCRETE&OURIERTRANSFORM v 0ROCEEDINGSOFTHE)%%% VOL NO PP *ANUARY $"ARTON 2ADAR3YSTEMS!NALYSISAND-ODELING .ORWOOD -!!RTECH(OUSE
£Ç°ÎÈ
2!$!2(!.$"//+
2*3ULLIVAN !$.ICHOLS 2&2AWSON #7(ANEY &0$AREFF AND**3CHANNE *R h0OLARIMETRIC8,# BAND3!2 vIN0ROCEEDINGSOFTHE)%%%.ATIONAL2ADAR#ONFERENCE PP $.(ELD 7%"ROWN AND47-ILLER h0RELIMINARYRESULTSFROMTHE.!3!*0,MULTIFRE QUENCY MULTIPOLARIZATION3!2 vIN0ROCEEDINGSOFTHE)%%%.ATIONAL2ADAR#ONFERENCE PP 3EE ALSO 0! 2OSEN ET AL h5!63!2 .EW .!3! AIRBORNE 3!2 SYSTEM FOR RESEARCH v )%%% !EROSPACE AND %LECTRONIC 3YSTEMS -AGAZINE VOL NO PP n .OVEMBER ,-.OVAK -#"URL AND77)RVING h/PTIMALPOLARIMETRICPROCESSINGFORENHANCEDTARGET DETECTION v)%%%4RANSACTIONSON!EROSPACEAND%LECTRONIC3YSTEMS VOL NO PPn *ANUARY ,-.OVAK 3$(ALVERSEN '*/WIRKA AND-(IETT h%FFECTSOFPOLARIZATIONANDRESOLU TION ON 3!2!42 v )%%% 4RANSACTIONS ON !EROSPACE AND %LECTRONIC 3YSTEMS VOL NO PP *ANUARY 2 + 2ANEY h3YNTHETIC APERTURE IMAGING RADAR AND MOVING TARGETS v )%%% 4RANSACTIONS OF !EROSPACEAND%LECTRONIC3YSTEMS VOL!%3 NO PP ! &REEMAN h3IMPLE -4) USING SYNTHETIC APERTURE RADAR v IN 0ROCEEDINGS OF )'!233 3YMPOSIUM %3!30 !&REEMANAND!#URRIE h3YNTHETICAPERTURERADAR3!2 IMAGESOFMOVINGTARGETS v'%#* 2ES VOL NO PPn 37ERNESS 7#ARRARA ,*OYCE AND$&RANCZAK h-OVINGTARGETALGORITHMSFOR3!2DATA v )%%%4RANSACTIONSON!EROSPACEAND%LECTRONIC3YSTEMS VOL!%3 NO PPn #4!LLEN h)NTERFEROMETRICSYNTHETICAPERTURERADAR v)%%%'233OCIETY.EWSLETTER PPn .OVEMBER 3 "ARBAROSSA AND! &ARINA h3PACE TIME FREQUENCY PROCESSING OF SYNTHETIC APERTURE RADAR SIGNALS v)%%%4RANSACTIONSON!EROSPACEAND%LECTRONIC3YSTEMS VOL NO PPn !PRIL &-3TAUDAHER h!IRBORNE-4) v#HAPTERIN2ADAR(ANDBOOK -3KOLNIKED ND%D .EW9ORK-C'RAW (ILL *7ARD 3PACE 4IME!DAPTIVE0ROCESSINGFOR!IRBORNE2ADAR 4ECHNICAL2EPORT ,EXINGTON -!,INCOLN,ABORATORY -ASSACHUSETTS)NSTITUTEOF4ECHNOLOGY *'UERCI 3PACE 4IME!DAPTIVE0ROCESSINGFOR2ADAR .ORWOOD -!!RTECH(OUSE 6##HENAND(,ING 4IME &REQUENCY4RANSFORMSFOR2ADAR)MAGINGAND3IGNAL!NALYSIS .ORWOOD -!!RTECH(OUSE , #OHEN h4IME FREQUENCY DISTRIBUTIONSnA REVIEW v 0ROCEEDINGS OF THE )%%% VOL NO *ULY 2'UARINOAND0)BSEN h)NTEGRATED'03).33!2'-4)RADARPRECISIONTARGETINGFLIGHTTEST RESULTS vIN0ROCEEDINGS)NSTITUTEOF.AVIGATION'03 #ONFERENCE PPn 200ERRY 2#$I0IETRO AND2,&ANTE h3!2IMAGINGOFMOVINGTARGETS v)%%%4RANSACTIONS ON!EROSPACEAND%LECTRONIC3YSTEMS VOL NO PPn *ANUARY *2ODRIGUEZAND*--ARTIN h4HEORYANDDESIGNOFINTERFEROMETRICSYNTHETICAPERTURERADAR v )%%0ROCEEDINGS 0ART& VOL PPn !PRIL 2 "AMLER AND 0 (ARTL h3YNTHETIC APERTURE RADAR INTERFEROMETRY v )NVERSE 0ROBLEMS VOL PP 2 TO 2 !UGUST 3EE ALSO & 'INI AND & ,OMBARDINI h-ULTIBASELINE CROSS TRACK 3!2INTERFEROMETRY!SIGNAL PROCESSINGPERSPECTIVE v)%%%!EROSPACEAND%LECTRONIC3YSTEMS -AGAZINE VOL NO 0ART4UTORIALS PPn !UGUST-!2ICHARDS h!BEGINNERS GUIDETOINTERFEROMETRIC3!2CONCEPTSANDSIGNALPROCESSING v)%%%!EROSPACEAND%LECTRONIC 3YSTEMS-AGAZINE VOL NO 0ART4UTORIALS PPn 3EPTEMBER $,3CHULER * 3,EE 4,!INSWORTH AND-2'RUNES h4ERRAINTOPOGRAPHYMEASUREMENT USINGMULTIPASSSYNTHETICAPERTURERADARDATA v2ADIO3CIENCE VOL NO -AYn*UNE PPn 7 " 3COTT h&LIGHT TO RADAR MAP %ARTH FROM SPACE v !VIATION 7EEK AND 3PACE 4ECHNOLOGY PP 3EPTEMBER #OVER3TORY
39.4(%4)#!0%2452%2!$!2
£Ç°ÎÇ
* ' &LEISCHMAN 3!YASLI % -!DAMS $ 2 'OSSELIN - & 4OUPS AND -! 7ORRIS h&OLIAGE PENETRATION EXPERIMENT v SERIES OF THREE PAPERS )%%% 4RANSACTIONS ON !EROSPACE AND%LECTRONIC3YSTEMS VOL NO PP *ANUARY4HISSERIESOFPAPERSWAS AWARDEDTHE-"ARRY#ARLTON!WARDSEE)%%%4RANSACTIONSON!EROSPACEAND%LECTRONIC 3YSTEMS VOL NO P /CTOBER &45LABY 2+-OORE AND!+&UNG -ICROWAVE2EMOTE3ENSING 6OLUMES .ORWOOD -! !RTECH(OUSE %,!YERS *-2ALSTON 20-AHONEY 0'4OMLINSON AND*-C#ORKLE h!NTENNAMEA SURESOFMERITFORULTRA WIDESYNTHETICAPERTURERADAR vIN0ROCEEDINGSOFTHE)%%%2ADAR #ONFERENCE PP .6ANDENBERG $23HEEN 33HACKMAN AND$7ISEMAN h0 ULTRAWIDEBAND3!23YSTEM APPLICATIONSTOFOLIAGEPENETRATION v0ROCEEDINGS30)% VOL PPn -&4OUPS ,"ESSETTE AND"4"INDER h&OLIAGEPENETRATIONDATACOLLECTIONSANDINVESTIGA TIONSUTILIZINGTHE0 57"3!2v 0ROCEEDINGS30)% VOL Pn ,-(5LANDERAND0/&ROLIND h0RECISIONPROCESSINGOF#!2!"!3(&6(& BAND3!2 DATA v 0ROCEEDINGS )%%% 'EOSCIENCE 2EMOTE 3ENSING 3YMPOSIUM )'!233 (AMBURG 'ERMANY VOL Pn!LSOSEE,-5LANDERETAL h$ETECTIONOFCONCEALEDGROUND TARGETS IN #!2!"!3 3!2 IMAGES USING CHANGE DETECTION v 0ROCEEDINGS 30)% VOL Pn !LGORITHMSFOR3YNTHETIC!PERTURE2ADAR)MAGERY6) %':ELNIOED %-7INTER -*3CHLANGEN AND#2(ENDRIKSON h#OMPARISONSOFTARGETDETECTIONINCLUT TERUSINGDATAFROMTHE&/0%.EXPERIMENTS v0ROCEEDINGS30)% VOL Pn !LGORITHMSFOR3YNTHETIC!PERTURE2ADAR)MAGERY $!'IGLIOED ,-OYER h#OUNTERCONCEALEDTARGETTECHNOLOGIES vPRESENTEDAT$!20!4ECH HTTPWWW DARPAMIL$!20!4ECH0RESENTATIONSSPO?PDF-OYER##4"7PDF
#HAPTER
-«>Vi >Ãi`Ê,iÌiÊ -iÃ}Ê,>`>ÀÃ ,°Ê iÌ
Ê,>iÞ *OHNS(OPKINS5NIVERSITY!PPLIED0HYSICS,ABORATORY
£n°£Ê * ,-* /6 -OTIVATION 7ORLDWIDE THERATEOFINVESTMENTINSPACE BASEDRADAR3"2 DUR INGTHETIMETHERADARSINTHISCHAPTERWEREOPERATINGWASONTHEORDEROFONEBILLION DOLLARSPERYEAR3PACE BASEDSYNTHETICAPERTURERADAR3!2 SYSTEMSCAPABLEOF M RESOLUTIONHAVEBECOMETHENORM WITHSYSTEMSUNDERDEVELOPMENTORALREADYLAUNCHED BYATLEASTSEVENCOUNTRIES!SEXPANDEDINTHEAPPROPRIATESECTIONSOFTHISCHAPTER THERANGE MEASUREMENTPRECISIONOFSURFACEHEIGHTCHANGEISNOWONTHEORDEROF MILLIMETERPERYEAR ASESTABLISHEDBYTWODIFFERENTCLASSESOF%ARTH OBSERVING3"2S 3!2SANDRADARALTIMETERS 3EVERALNATIONSARESPONSORINGRADARSFOREXPLORATIONAT THE-OONANDBEYOND3"2 RELATEDPATENTAPPLICATIONSCONTINUEAPACE)NSHORT 3"2 ISANEXCITING EXACTING EXTENSIVE ANDEXPANDINGTOPIC 3PACE BASEDRADARSYSTEMSFACEFUNDAMENTALCHALLENGES4HEPERMISSIBLEOPTIONS FOR THE VALUE OF SEVERAL PARAMETERS SUCH AS PULSE REPETITION FREQUENCY ARE MORE RESTRICTED FOR 3"2 THAN FOR AIRBORNE SYSTEMS ,IKEWISE THE HARDWARE ENVIRONMENT IMPOSESMORERIGOROUSCONSTRAINTSONIMPLEMENTATION AND3"2SYSTEMSDONOTENJOY THE LUXURIES OF HANDS ON MAINTENANCE NOR IN FIELD PARTS REPLACEMENT (OWEVER THE PAYOFFFROMRADARSINSPACEMORETHANCOMPENSATESFORTHESECHALLENGES SINCESPACE OFFERS A UNIQUE PERSPECTIVE FOR %ARTH OBSERVATION AND IS AN ESSENTIAL VIEWPOINT FOR LUNARORPLANETARYEXPLORATION #OVERED AND /MITTED 4OPICS 4HIS CHAPTER INTRODUCES SPACE BASED REMOTE SENSINGRADARS4HEFOCUSISON4YPE))3"2S ASOUTLINEDINTHEPREVIOUSEDITIONOF THIS(ANDBOOK INCLUDINGBOTH%ARTH ORBITINGANDPLANETARYSYSTEMS4HEMATERIALIN THISCHAPTERISDESIGNEDTOBEREASONABLYCOMPLETEATASURVEYLEVELTHEDISCUSSION ZOOMS IN ON SELECTED CASE EXAMPLES TO ILLUSTRATE APPLICATION SPECIFIC IMPLEMENTA TIONSORTECHNOLOGICALINNOVATIONS!NOUTSTANDINGEARLYEXAMPLEISTHE3EASATSATEL LITELAUNCHEDIN&IGURE WHICHASITSNAMESUGGESTS WASDESIGNEDFOR OCEANICOBSERVATIONS4HREEOFITSSENSORSWERE3"2SASYNTHETICAPERTURERADAR AN ALTIMETER ANDASCATTEROMETER!STHEREADERWILLDISCOVERINTHISCHAPTER THESETHREE 3EASATINSTRUMENTSESTABLISHEDTHEINITIALPARADIGMFORVIRTUALLYALLSUBSEQUENTRADARS OFTHEIRRESPECTIVECLASSES
£n°£
£n°Ó
2!$!2(!.$"//+
&)'52% 4HE3EASATSATELLITE FEATUR INGTHEANTENNASOFITSTHREERADARS#OURTESY OF.!3!
4HIS CHAPTER DOES NOT COVER THE 4YPE ) SHORT RANGE SPECIALIZED 3"2 SYSTEMS REVIEWEDINEARLIEREDITIONS SUCHASTERMINALGUIDANCEORRENDEZVOUSRADARS!LSONOT COVEREDARE4YPE)))3"2S SUCHASMULTI SPACECRAFTSYSTEMSFORSPACE BASEDRADAR SURVEILLANCEOFTHE%ARTHSSURFACEORAIRSPACE!LTHOUGHTHESELARGE3"2CONCEPTSARE INTERESTINGINPRINCIPLE THEIRIMPLIEDCOSTSREMAINADISINCENTIVE PARTICULARLYIFTHEIR ERSTWHILESPONSORSEXPECTTHEIRPERFORMANCETOAPPROACHTHECURRENTSTATE OF THE ARTIN AIRBORNESEARCHORSURVEILLANCERADARS %XCEPTFORTHEMENTIONOFAFEWBASICCONCEPTS THISCHAPTERDOESNOTDELVEINTOTHEEXTENSIVESUBJECTSOFORBITOLOGY IMPLEMENTATION OFSPACE QUALIFIEDHARDWARE NORSYSTEMINTEGRATIONANDTEST FORWHICHTHEINTERESTED READERISDIRECTEDTOSTANDARDREFERENCES "ASIC/RBIT#HARACTERISTICS 5NLIKEANAIRBORNEPLATFORMTHATCANGOANYWHERE ATANYTIMESUBJECTTOFUELANDAIR SPACELIMITATIONS ASATELLITESPOSITIONANDVELOC ITYWHENINORBITABOUTAPLANETARYBODYARERIGIDLYGOVERNEDBYORBITALDYNAMICS SUMMARIZEDCOMPACTLYBY+EPLERSLAWS&URTHER ACCESSBYAN3"2TOAGIVENAREA OFINTERESTDEPENDSONTHEROTATIONRATEOFTHEPLANET ASWELLASTHESATELLITESPOSITION ALONGITSORBITANDTHERADARSVIEWINGGEOMETRY4HUS THEPRIMARYPARAMETERSTOBE INCLUDEDIN3"2MISSIONDESIGNINCLUDEORBITALALTITUDE SPACECRAFTON ORBITVELOCITY ANDHENCEPERIOD ORBITINCLINATION ANDTHEROTATIONRATEOFTHEPLANET %ARTH OBSERVING 3"2S SUCH AS 3!2S TEND TO OPERATE FROM SPACECRAFT IN NEAR CIRCULARLOW %ARTHORBITS,%/ 4YPICAL,%/ALTITUDESSPANKMTOKM,OWER ALTITUDESINCURLARGERATMOSPHERICDRAG WHEREASHIGHERALTITUDESIMPLYHIGHERRADIA TIONLEVELSANDLONGERRADARRANGES NEITHEROFWHICHAREDESIRABLEINMOSTSITUATIONS 3PACECRAFTVELOCITIESATTHESE,%/ALTITUDESAREONTHEORDEROFKMSTHEIRCOR RESPONDINGPERIODSAREABOUTMINUTES%ARTHROTATIONATARATEOF^DEGREE MIN SHIFTSTHESUB SATELLITEPOINTATTHEEQUATORBY^KMORBIT TO ORBIT4HEORBIT ALTITUDENORMALLYMAYBECHOSENTOTUNETHEPERIODAND%ARTHROTATIONRATESOTHATAN EXACT REPEATPATTERNDEVELOPSTHATHASASTIPULATEDNUMBEROFDAYS4HEREPEATPERIOD
30!#% "!3%$2%-/4%3%.3).'2!$!23
£n°Î
OFTEN IS AN INTEGRAL NUMBER SUCH AS THE DAY REPEAT OF 2!$!23!4 ALTHOUGH A NON INTEGRALPERIODMAYBEPREFERRED SUCHASTHE DAYREPEATOFTHE4/0%8 0OSEIDONRADARALTIMETER/RBITPARAMETERSSUCHASREPEATPERIODMUSTBEMAINTAINED REQUIRINGSMALLBOOSTSFROMSPACECRAFTTHRUSTERMANEUVERS TYPICALLYAPPLIEDEVERY SEVERALWEEKSFOR,%/MISSIONS4HEREVISITTIMEOFAGIVEN3"2ASSETDEPENDSONTHE RANGESWATHWIDTHCOVEREDBYTHERADARINQUESTION ASWELLASTHEORBITSEXACT REPEAT PERIODANDTHELATITUDEOFTHESITEOFINTEREST4HEOFF NADIR LOOKANGLEOFCERTAIN3"2S CANBEADJUSTEDTOINCREASETHEEFFECTIVEREVISITRATE.OTETHATORBITMANEUVERSARENOT APRACTICALMEANSTOIMPROVETHEFREQUENCYOFSITECOVERAGE SINCEALARGECHANGEIN ALTITUDEHENCEVELOCITY ORESPECIALLYANYCHANGEOFORBITINCLINATIONTHEANGLEOF THEINERTIALORBITPLANEWITHRESPECTTOTHE%ARTHSEQUATOR WOULDREQUIREASUBSTANTIAL EXPENDITUREOFPRECIOUSONBOARDFUELRESOURCES 4HE%ARTHISFLATTENEDATTHEPOLES DUEPRIMARILYTOITSRELATIVELYRAPIDROTATION4HE RESULTING LACK OF SPHERICAL SYMMETRY IN THE GRAVITY FIELD AT ORBITAL ALTITUDE IMPOSES SMALLLATERALFORCESONANINCLINEDORBITPLANE WHICHCONSEQUENTLYPRECESSESININERTIAL SPACE4HEAMOUNT DIRECTION ANDRATEOFORBITPRECESSIONCANBECONTROLLEDBYCHOICE OFTHEINCLINATIONANDTHEMEANALTITUDEOFTHEORBIT-ANYSATELLITEPLATFORMSUSETHIS DEGREEOFFREEDOMTOGENERATEASUN SYNCHRONOUSORBIT WHICHISONETHATMAINTAINSA CONSTANTANGLEOFITSORBITPLANERELATIVETOSOLARILLUMINATIONOVERTHEENTIREYEAR4HE %UROPEAN3PACE!GENCYS%NVISATSPACECRAFTISAGOODEXAMPLEOFASUN SYNCHRONOUS ,%/ HAVING ^n INCLINATIONo AND KM ALTITUDE 3UN SYNCHRONOUS SPACECRAFT THATHOSTOPTICALINSTRUMENTSSUCHAS*APANS!,/3 CHOOSETHEPHASEOFTHESUNANGLE TOFAVORILLUMINATIONOFTHESURFACE WHICHUSUALLYLEADSTOAMIDDAYORBITFROMWHICH MOSTOFTHE%ARTHSSURFACEISVIEWEDATABOUTTHESAMELOCALTIME NEARMIDDAY3UCH ORBITSIMPLYTHATTHESPACECRAFTMUSTPASSTHROUGHTHE%ARTHSSHADOWABOUTHALFTHE TIME WHICHHASCONSEQUENCESONTHEDESIGNOFTHETHERMALANDPOWERSUBSYSTEMSIN PARTICULAR )N CONTRAST SPACECRAFT THAT CARRY ONLY RADARS SUCH AS 2!$!23!4 TEND TOWARDFAVORABLEILLUMINATIONOFTHESPACECRAFT4HENATURALRESULTINTHISCASEISTHESO CALLEDDAWN DUSKORBIT INWHICHTHESATELLITEANDITSSOLAR PANEL DEPENDENTPOWER SYSTEMAVOIDSTHESHADOWOFTHE%ARTHALMOSTALWAYSFORALMOSTALLSEASONS #ERTAINAPPLICATIONSAREPARTICULARLYWELL SERVEDBYEXACT REPEATORBITS&OREXAM PLE IFAGROUPOFORBITALTRAJECTORIESFALLSWITHINASMALLRADIUSOFEACHOTHERWHENOVER AN AREA OF INTEREST THEN RADAR MEASUREMENTS FROM SEVERAL ORBITS MAY BE COMPARED COHERENTLY THUSPOTENTIALLYSENSITIVEATTHEORDEROFAWAVELENGTHTOCHANGESINTHE SCENEBETWEENOBSERVATIONS3UCHCOHERENTCHANGEDETECTIONISASTANDARDTECHNIQUEIN THEFIELDOFSPACE BASED3!2INTERFEROMETRY REVIEWEDINTHEFOLLOWINGSECTION%XACT REPEATORBITSARESTANDARDFORMOSTRADARALTIMETERS BUTFORGEOPHYSICALREASONS NOT FORMUTUALCOHERENCY3UN SYNCHRONICITYPRESENTSITSOWNPROBLEMSFOROCEAN SENSING ALTIMETERS4HESECOMMENTSAREELABORATEDIN3ECTION !SDISCUSSEDINSEVERALCHAPTERSOFTHISBOOK THEPERFORMANCEOFDOPPLER SENSITIVE RADARSISCONDITIONALUPONTHEVELOCITYOFTHEIRHOSTPLATFORM4HEVELOCITYOFASPACE CRAFTINORBITATALTITUDEHABOVEAPLANETOFRADIUS20ANDMASS-0ISGIVENBY
63# - 0 ' 20 H
.ADIRISTHEPOINTBELOWTHESPACECRAFTONTHESURFACEINTERSECTEDBYTHERADIUSVECTORFROMTHE%ARTHSCENTERTO THESPACECRAFT o)NCLINATIONSGREATERTHANnARERETROGRADEBECAUSETHEIR% 7VELOCITYCOMPONENTINTHEASCENDINGPASSISCONTRARY TOTHEDIRECTIONOFTHE%ARTHSROTATION INCONTRASTTOPROGRADEORBITSWHOSEINCLINATIONSARELESSTHANn
£n°{
2!$!2(!.$"//+
4!",% 3PACECRAFT6ELOCITIES
"ODY %ARTH 6ENUS -ARS 'ANYMEDE #ALISTO -OON %UROPA
-ASSKG
2ADIUSKM
!LTITUDEHKM
63#MS
H63#KMS
r r r r r r r
WHERE'ISTHEUNIVERSALGRAVITYCONSTANTprn.MKGn4ABLELISTSREP RESENTATIVESPACECRAFTVELOCITIESFORBODIESINTHESOLARSYSTEMTHATHAVEBEENVISITED ORARELIKELYTOBEOBSERVED BYRANGE DOPPLERRADARS&EASIBLESATELLITEALTITUDESARE LIMITED BELOW BY THE PREVAILING ATMOSPHERIC DENSITY4HE FINAL COLUMN OF THE TABLE LISTSTHEALTITUDE VELOCITYPRODUCTH63#CORRESPONDINGTOEACHENTRY4HISPRODUCTISA SCALINGFACTORTHATCHARACTERIZESTHERANGE DOPPLERSPACECONFRONTINGAN3"2INTENDED TOBEDEPLOYEDINTHATENVIRONMENT4HEREISAPPROXIMATELYA FOLDSPREADINTHE VALUEOFTHISPARAMETER FROMTHE%ARTHTO*UPITERSMOON%UROPA)TFOLLOWSTHATRADAR DESIGNSTHATWORKINONESITUATIONMAYNOTBEATALLAPPROPRIATEIFMIGRATEDTOADIFFER ENTPLANETARYBODY )T IS OFTEN SAID THAT RADAR IS hALL WEATHER v BUT THIS GENERALIZATION CLEARLY IS NOT UNIVERSALLYTRUE ESPECIALLYFOR3"2S&ROMSPACE THEIONOSPHEREANDORATMOSPHERE MAYCORRUPTOREVENPREVENTRADARPROPAGATION4HEIONOSPHEREMAYINDUCE&ARADAY ROTATION e THUS DEGRADING OR DESTROYING THE POLARIZATION PROPERTIES OF THE TRANSMIT TEDANDRECEIVEDSIGNALS4HE&ARADAYROTATIONAOFALINEARLY POLARIZED% VECTORIS PROPORTIONALTO2-K WHERETHEROTATIONMEASURE2-ISAFUNCTIONOFIONOSPHERIC ELECTRONDENSITY4HEIONOSPHEREALSOINTRODUCESDISPERSIONAND UNDERCERTAINUNFA VORABLE CIRCUMSTANCES EFFECTIVELY CUTS OFF PROPAGATION4HUS FOR EXAMPLE IT WAS NOTPOSSIBLEFORTHE -(Z-!23)3RADARSOUNDERTOPROBETHE-ARTIANSURFACEDUR INGDAYLIGHTHOURS BECAUSETHECUTOFFFREQUENCYUNDERTHOSECONDITIONSINCREASEDTO ABOUT-(Z4HUS -!23)3WORKEDASASURFACESOUNDERDURINGDARKHOURSAND ASANIONOSPHERICSOUNDERDURINGDAYLIGHTHOURS-OREONTHE-!23)3RADARMAYBE FOUNDIN3ECTION4HE CMWAVELENGTHOFTHE-AGELLAN6ENUSRADARREVIEWED IN3ECTION WASCHOSENINRESPONSETOTHETRADE OFFBETWEENPROPAGATIONTHROUGH 6ENUSVERYDENSEATMOSPHEREFORWHICHLONGERWAVELENGTHSWOULDBEBETTER AND SYNTHETICAPERTURERADARSYSTEMCONSIDERATIONSFORWHICHSHORTERWAVELENGTHSWOULD BEBETTER 0ROPAGATIONSPEEDISRETARDEDALONGTHEPATHLENGTHFROMANOCEAN VIEWING ALTIMETERTOTHE%ARTHBYAVERYSMALLFRACTIONOFTHESPEEDOFLIGHT BUTSUFFICIENTNEV ERTHELESSTOIMPOSERANGEMEASUREMENTERRORSOFMANYMETERS4HESEERRORSMUSTBE ESTIMATEDANDCOMPENSATEDBEFORETHEREQUIREDCM LEVELACCURACYCANBEACHIEVED ASSUMMARIZEDIN3ECTION #OMMENTS ON (ARDWARE /N A POPULAR!MERICAN CHILDRENS TELEVISION PRO GRAM ONE IS TOLD THAT h)T IS NOT EASY BEING GREENv ,IKEWISE IT IS NOT EASY BEING p.ISTHESTANDARDSYMBOLFOR.EWTON FORCE WITHTHEUNITSMKGSn e4HEPLANEOFPOLARIZATIONOFAN%-WAVEISPERTURBEDBYINTERACTIONWITHTHEMAGNETICFIELDTHROUGHWHICHITPASSES ANEFFECTDISCOVEREDBY&ARADAY
30!#% "!3%$2%-/4%3%.3).'2!$!23
£n°x
ARADAR ESPECIALLYABOARDASPACECRAFT"ECAUSEARADARBYDEFINITIONMUSTTRANSMIT ITSNEAR FIELDRADIATIONISAPOTENTIALTHREATTOALLOTHERINSTRUMENTSANDSUBSYSTEMS OFTHEHOSTSPACECRAFTANDITSPAYLOAD/NCEHAVINGGOTPASTTHERISKORPARANOIA OF NEAR FIELDRADIATION NORMALSPACECRAFTDESIGNPRINCIPLESKICKIN4HEFIRSTORDERCON SIDERATIONSONHARDWARETHATARECHARACTERISTICOFANDESSENTIALLYUNIQUETO THESPACE ENVIRONMENT INCLUDE RADIATION AND ENERGETIC PARTICLES VIBRATION ESPECIALLY DURING THE LAUNCH PHASE HARSH AND CONTRASTING THERMAL ENVIRONMENTS OFTEN CHALLENGING MASSLIMITATIONS ANDAPREMIUMONPAYLOADPOWER)N%ARTHORBITAND PERHAPSSUR PRISINGLY ALSO AT THE -OON A SPACE BASED RADAR MUST COMPLY WITH INTERNATIONALLY AGREEDSPECTRALALLOCATIONS4HESELIMITBOTHTHEAVAILABLEBANDSANDTHEBANDWIDTHS WHICHIMPACTSYSTEMDESIGNANDMAYCONSTRAINCERTAINPERFORMANCEOBJECTIVES SUCH ASRESOLUTION 3INCEITISEXPENSIVETOGETTOORBIT 3"2S LIKEOTHERSPACE BASEDSYSTEMS MUSTBE DESIGNEDTOMINIMIZEMASSANDTOMAXIMIZEEFFICIENCYANDLONGEVITY-ASS POWER AND LIFETIME EMERGE AS DRIVING THEMES THAT DICTATE CONSERVATIVE DESIGN GENEROUS MARGINSDURINGSYSTEMIMPLEMENTATION ANDREDUNDANCYOFTENREALIZEDBYDUAL STRING HARDWAREINMOSTIFNOTALLSUBSYSTEMSOTHERTHANTHEANTENNA /RGANIZATIONOFTHE#HAPTER 4HECHAPTERSECTIONSAREORGANIZEDBYMEASURE MENTTHEME TAKENINABROADSENSE4HESETHEMESARE%ARTH ORBITINGSYNTHETICAPERTURE RADAR3!2 RADARALTIMETRYWHICHINTHE3"2CONTEXTALMOSTALWAYSIMPLIESOBSER VATIONOFTHE%ARTHSOCEANSANDLARGERSURFACEWATERBODIES PLANETARYRADARSWHERE hPLANETvINCLUDESPLANETOIDSSUCHASLARGEMOONS SCATTEROMETERSWHOSEDATAASSOCI ATEAGEOPHYSICALPARAMETERSUCHASOCEANICWINDSPEEDTOTHEOBSERVEDCALIBRATED RADARBACKSCATTERPROPERTIESOFTHEILLUMINATEDSURFACE ANDSOUNDERSWHICHINCLUDES BOTHATMOSPHERICANDSUBSURFACERADARSYSTEMS %ACHSECTIONINCLUDESANOVERVIEWOF ALLRELEVANT3"2S NOTINGKEYTURNINGPOINTSORWATERSHEDINNOVATIONSINTHETHEMES HISTORY3ELECTEDEXAMPLESHAVEBEENCHOSENFORMOREIN DEPTHREVIEW/NLINEWEB SITESARESUGGESTEDFOREACHCITEDINSTRUMENTTHESEWEBSITESWEREACCESSIBLEATTHE DATEOFPUBLICATIONOFTHISBOOK
£n°ÓÊ -9 / / Ê* ,/1, Ê, ,Ê-,® )N ITS MOST GENERAL FORM ANIMAGING RADAR IS ADEVICE DESIGNED TO PROVIDEA TWO DIMENSIONALPORTRAYALOFTHERADARBACKSCATTERRETURNINGFROMTHEFIELDILLUMINATED INRANGEANDAZIMUTH3PACE BASEDMICROWAVEIMAGERSARESYNTHETICAPERTURERADARS WITHTHEEXCEPTIONOFCERTAINEARLY3OVIETOCEAN OBSERVINGREAL APERTURESYSTEMS !SWITHALLIMAGINGSYSTEMS 3!2IMAGEPRODUCTSARERATEDACCORDINGTOTHEIRRESOLU TION WHEREhHIGHERvIShBETTERv(IGHERRESOLUTIONALWAYSIMPLIESWIDERBANDWIDTHIN BOTHRANGEANDAZIMUTH!ZIMUTHBANDWIDTHDERIVESFROMTHEDOPPLERSIGNATURESSET UPBYTHEMOTIONOFTHERADARWITHRESPECTTOTHEILLUMINATEDFIELD2ESOLUTIONBYITSELF ISNOTSUFFICIENTTODETERMINETHEIMAGEQUALITYOFIMPORTANCETOMOSTAPPLICATIONS
4HEFIELDOFSPACE BASEDREMOTESENSINGRADARSISSUBJECTTORAPIDCHANGE4HISCHAPTERPROVIDESTHEVIEWFROM THE EARLY ST CENTURY 2EADERS ARE ENCOURAGED TO SEEK CURRENTLY TOPICAL INFORMATION THROUGH ONLINE RESOURCES +EYWORDS SUCHASTHENAMESOFTHEMISSION NATIONALITY ANDRADAR AREUSUALLYSUFFICIENTTOLOCATESEVERALREFER ENCES!LERT.OTALLONLINERESOURCESAREACCURATETHEREADERISADVISEDTOSEEKOUTMORETHANONEANDTOVERIFY INFORMATIONBYCROSS COMPARISON
£n°È
2!$!2(!.$"//+
3!2IMAGESAREDEGRADEDBYAMULTIPLICATIVESELF NOISEKNOWNASSPECKLE WHICHIS ADIRECTCONSEQUENCEOFTHECOHERENCEREQUIREDBYTHERADAR PROCESSORCOMBINATION TO FORM THE SYNTHETIC APERTURE AND THE RESULTING ENHANCED RESOLUTION 3PECKLE CAN BEREDUCEDONLYTHROUGHSUPPLEMENTALINCOHERENTPROCESSING MULTI LOOKINGIN3!2 JARGON!DDITIONALLOOKSREQUIREPROPORTIONALLYMOREBANDWIDTH)TFOLLOWSTHATLARGE TWO DIMENSIONALBANDWIDTHRANGEANDAZIMUTH ISTHEDRIVINGREQUIREMENTFORTHIS CLASSOFRADAR 3PACE BASED3!2SYSTEMSHAVEMOTIVATEDFRUITFULSPECIALIZATIONSINQUANTITATIVE APPLICATIONSINAWIDEVARIETYOFAREAS COMPREHENSIVELYREVIEWEDINTHE0RINCIPLES AND!PPLICATIONSOF)MAGING2ADAR4OPICSSUCHAS3POT3!2 3CAN3!2 POLARIMETRY ANDINTERFEROMETRYTHATHAVEINFLUENCEDRADARSYSTEMANDMISSIONDESIGNAREOUTLINED INCLOSINGPARAGRAPHSOFTHISSECTION &LIGHT3YSTEMS 4HECONCEPTOF3!2 INTRODUCEDINBY#ARL7ILEY WAS REDUCEDTOPRACTICEINSUBSEQUENTYEARS FIRSTTHROUGHSIMULATIONS THENTHROUGHAIR BORNEPROOF OF CONCEPTSYSTEMS1UILL THEFIRSTSPACE BASED3!2SEE4ABLE WASLAUNCHEDONLYADECADELATER4HATWASAREMARKABLEACHIEVEMENT CONSIDERING THATINTHEMODERNERA ITOFTENTAKESNEARLYYEARSTOGOFROMCONCEPTTOLAUNCHOF ANEW3!2 EVENTHOUGHTHEPRINCIPLESANDTECHNOLOGYFORTHESE3"2SAREBYNOW WELLESTABLISHED 1UILLWASRUDIMENTARY BUTDIDSUCCEEDINGENERATINGDATASUFFICIENT TO FORM IMAGES 4HE NOMINAL M RESOLUTION WAS SPECTACULAR FOR ITS TIME GIVEN THAT THE BEST RESOLUTION THAT COULD BE EXPECTED FROM AN OTHERWISE COMPARABLE REAL APERTURE3"2WOULDBEONTHEORDEROFKILOMETERS.EVERTHELESS THERESULTSDIDNOT MEETTHENEEDSOFTHESPONSOR ANDSOTHENOTIONALSECONDANDTHIRDMISSIONSWERE NEVERLAUNCHED1UILLWASTHEONLY!MERICAN3"2WHOSEDATAWEREOPTICALLYRECORDED ONBOARD EVENTUALLY RETURNED TO %ARTH BY EJECTED CAPSULE AND THEN COLLECTED BY AN AIRBORNERETRIEVALMANEUVER 4!",% 3YNTHETIC!PERTURE2ADARS%ARTH VIEWING
3ATELLITE3!2 1UILL 3EASAT 3)2!" 3)2# +OSMOS !LMAZ %23 * %23 2!$!23!4 %23 0RIRODA 324%.6)3!4 )'3 " 0!,3!2 *IAN"ING 4ERRA3!2 8 2!$!23!4 #/3-/ 4EC3!2
52, #OUNTRY
,AUNCH
2ESM
"AND
53! M 8 53! , 53! @ ^ , 53!' ) @ ^ ,#8 5332 n 3 5332 n 3 %3! # *APAN , #ANADA # %3! # 2USSIA5KRAINE 3 , 53!' ) ^ # 8 %3! # *APAN 8 *APAN n , #HINA n , 'ERMANY 8 #ANADA # )TALY 8 )SRAEL n 8
0OLARIZATION (( (( 6ARIOUSTOQUAD(( (( (( 66 (( (( 66 (( 66 (( 66 66OR(( DUAL -ULTIMODE 6ARIOUSTO1UAD -ULTI POLARIMETRIC 6ARIOUS 6ARIOUSTO1UAD -ULTI POLARIMETRIC -ULTIMODE
30!#% "!3%$2%-/4%3%.3).'2!$!23
£n°Ç
4!",% 3YNTHETIC!PERTURE2ADARS%ARTH VIEWING #ONTINUED
3ATELLITE3!2 +ONDOR % (* # 3!2 ,UPE !RKON 2)3!4 4ANDEM 8 2ADARSAT # -!03!2 3ENTINEL
52,
#OUNTRY ,AUNCH 2USSIA #HINA 'ERMANY 2USSIA )NDIA 'ERMANY #ANADA n "RAZIL'ERMANY n %UROPE n
2ESM n n n n
"AND 3 3 8 3 , 0 # 8 # , #,
0OLARIZATION -ULTIMODE -ULTIMODE -ULTIMODE -ULTIMODE 6ARIOUSTO1UAD 6ARIOUSTO1UAD 6ARIOUSTO1UAD 3INGLE DUAL QUAD 6ARIOUSTO1UAD
HTTPWWWSKYROCKETDESPACEINDEX?FRAMEHTM HTTPWWWSKYROCKETDESPACESAT?MIL?USAHTM HTTPWWWASTRONAUTIXCOMCRAFTSEASATHTM HTTPDIRECTORYEOPORTALORGPRES?3)23HUTTLE)MAGING2ADAR-ISSIONSHTML HTTPSOUTHPORTJPLNASAGOV HTTPWWWASTRONAUTIXCOMCRAFTALMAZTHTM HTTPWWWRUSSIANSPACEWEBCOMALMAZTHTML HTTPEARTHESAINTERS HTTPWWWNASDAGOJPPROJECTSSATJERSINDEX?EHTML HTTPWWWSPACEGCCAASCENGSATELLITESRADARSAT HTTPENWIKIPEDIAORGWIKI3PACE "ASED?2ADAR HTTPWWWASTRONAUTIXCOMCRAFTPRIRODAHTM HTTPWWWJPLNASAGOVSRTM HTTPENVISATESAINTOBJECTINDEXCFM FOBJECTID HTTPWWWSPACECOMSPACENEWSARCHIVESPYARCH?HTML HTTPWWWEORCJAXAJP!,/3ABOUTPALSARHTM HTTPWWWSINODEFENCECOMSTRATEGICSPACECRAFTJIANBINGASP HTTPWWWCAFDLRDETSXSTART?ENHTM HTTPWWWSPACEGCCAASCENGSATELLITESRADARSATINF?OVERASP HTTPDIRECTORYEOPORTALORGPRES?#/3-/3KY-ED#ONSTELLATIONOF3!23ATELLITESHTML HTTPWWWIAICOIL$EFAULTASPX DOC)$ &OLDER)$ LANG ENRES POS HTTPWWWNPOMASHRUSPACEENSPACEHTM H TTPWWWEOHANDBOOKCOMEOHBPDFSMISSIONS?ALPHABETICALPDFSEARCH #HINA(* # SATELLITERADAR HTTPDIRECTORYEOPORTALORGPRES?3!2,UPE#ONSTELLATIONHTML HTTPINDUSTRYESAINT!44!#(%-%.43!NFM?PDFSEARCH *APANSPACERADAR)' 3 2 HTTPDIRECTORYEOPORTALORGINFO?2)3!42ADAR)MAGING3ATELLITEHTML HTTPDIRECTORYEOPORTALORGINFO?4AN$%-84ERRA3!28ADDONFOR$IGITAL%LEVATION-EASUREMENTHTML HTTPWWWMDACORPORATIONCOMNEWSPRPRHTM HTTPELIBDLRDE HTTPWWWGMESINFO
3EASAT 4HEGENERALLYACKNOWLEDGEDSPACE BASEDSYNTHETICAPERTURERADARPIO NEER WAS THE 3EASAT 3!2 &IGURE 4HAT , BAND SYSTEM PERSISTS AS THE DESIGN PARADIGM FOR %ARTH OBSERVING SPACE BASED 3!2S 3EASAT ILLUSTRATES SEVERAL CHARACTERISTICSOFMANYCIVILIAN%ARTH OBSERVING3!2S INCLUDINGTHESIZEANDASPECT RATIOOFTHEANTENNAMBYM ITSRELATIVELYSTEEPANGLEOFINCIDENCE^n ITSSWATHWIDTHKM ANDUSEOFALINEAR&-CHIRP MODULATEDPULSEWAVEFORM COMPRESSIONRATIO 3EASAT3!2SAVERAGERADIATEDPOWERWASRELATIVELYSMALL 7 ALTHOUGHITSPEAKPOWERWASAPPRECIABLEK7 4HEANTENNAWASPASSIVE CONSISTINGOFEIGHTFLATMICROSTRIPPANELS RADIATINGANDRECEIVING((POLARIZATION 4HEREWASNOONBOARDRECORDER SODATAWEREDOWNLINKED BUTONLY OFCOURSE WHEN INRADIOVISIBILITYOFONEOFTHEFOURGROUNDSTATIONSINTHE5NITED3TATES #ANADA AND THE 5NITED +INGDOM THAT WERE EQUIPPED TO RECEIVE THE DATA 4ELEMETRY WAS
£n°n
2!$!2(!.$"//+
ANALOG-(Z OFFSETVIDEO TOBECONVERTEDONTHEGROUNDTOEITHEROPTICALMEDIA TRANSPARENTFILMSTRIPS ORDIGITIZED BITQUANTIZATION )MAGERYWASGENERATEDBUT NOTIMMEDIATELYo BYEITHEROPTICALORDIGITALPROCESSINGMETHODS4HE3EASATSATEL LITESUFFEREDAMASSIVESHORTCIRCUITINITSPRIMARYPOWERSYSTEMINTHESOLARPANEL SLIP RINGASSEMBLY WHICHENDEDITSMISSIONIN/CTOBERAFTERONLYTHREEMONTHS OFOPERATION 3)2 3!2 3ERIES 4HE 3HUTTLE IMAGING RADARS 3)2 ! WHICH FLEW ON THE FIRST 3HUTTLE THAT CARRIED A SCIENCE PAYLOAD 3)2 " AND 3)2 #8 3!2 WERE ESSENTIALLY TECHNOLOGYANDSCIENCE DEMONSTRATIONSMISSIONS EACHLASTINGABOUTONEWEEKOR LESS)NSEQUENCE THESERADARSHADINCREASINGLYMORECAPABILITYINTERMSOFINCIDENCE FREQUENCY ANDPOLARIZATION3)2 #8 3!2OPERATEDATTHREEBANDS#AND,53! AND8CONTRIBUTEDTHROUGHANINTERNATIONALPARTNERSHIPWITH'ERMANYAND)TALY $ATA FROM3)2 #CONTINUESINDEMAND THANKSTOITSFULLYPOLARIMETRICMULTIBANDCOVERAGE OF A WIDE VARIETY OF SCENES4HE 3HUTTLE 2ADAR4ERRAIN -APPER 324- WAS AN OUTGROWTHOF3)2 # USINGASMALLRECEIVINGANTENNAAT8AND#BAND MOUNTEDON A MLONGEXTENDABLESTRUT TOCOLLECTSIMULTANEOUSBACKSCATTERSUBSEQUENTLYPRO CESSEDINTOTOPOGRAPHICMAPS4HISWASTHEFIRSTDEMONSTRATIONOFSINGLE PASSSPACE BASEDINTERFEROMETRIC3!2CAPABILITY)N3!2 $ATAWERECOLLECTEDOVERAVERYLARGE FRACTIONOFTHEGLOBALLANDMASS +OSMOS !LTHOUGHNOTCLASSIFIEDINTHESTRICTSENSE +OSMOSCAMETOVIEWLARGELY AFTERTHELAUNCHOFITSTECHNICALSUCCESSOR !LMAZ2USSIANAND!RABICFORDIAMONDIN THEROUGH 0RECEDINGTHESE3OVIET3!2SWEREASERIESOFREAL APERTURERADARS KNOWN AS/KEANANDBYOTHERNAMES !LMAZWASAVERYINTERESTINGRADAR INTHATITPROVIDED UNIQUE3 BAND3"2IMAGERYOFTHE%ARTHSSURFACE4HETECHNOLOGYBEHINDTHISAND RELATED2USSIANSYSTEMSCONTINUEDTOBEDEVELOPED CULMINATINGINTHE+ONDOR %RADAR AND THROUGHABILATERALTECHNOLOGYEXCHANGEPROGRAM THE(* #3!2OF#HINA "OTHOFTHESERADARSUSETHE MPARABOLICREFLECTORDEVELOPEDORIGINALLYFOR0RIRODA THE FINAL MODULE FOR THE 2USSIAN -)2 COMPLEX 4RAVERS THE RADAR ABOARD 0RIRODA WASANEXPERIMENTALDEMONSTRATIONMISSION4HEREAREATLEASTTHREEMEMBERSOFTHE 8 BANDNATIONALASSET3!2FLEET INCLUDING4EC3!2)SRAEL ANDTHE)'3 2SERIES *APAN 4HEFIRST)'3 2WASLAUNCHEDIN4HELAUNCHOFASEQUELFAILED %23 AND%23 4HE# BAND3!2SFROMTHE%UROPEAN3PACE!GENCY%3! INTRODUCED OPERATIONAL SPACE BASED 3!2 CAPABILITY 3INCE THE LAUNCH OF THE FIRST %UROPEAN2ADAR3ATELLITE%23 %3!3!2SHAVEMAINTAINEDACONTINUOUSRECORD OFOUTSTANDINGPERFORMANCE%23 ANDITSFOLLOWERSHAVEHADONBOARDDATARECORDING CAPABILITY%23 AND%23 HADINCOMMON^ MRESOLUTIONATLOOKS KMSWATH WIDTH AND^nINCIDENCE ALLINTHEPATTERNOFTHE3EASAT3!24HETWO%233!2SWERE VIRTUALLYIDENTICAL%23 AND%23 ENJOYEDABOUTONEYEAROFSIMULTANEOUSOPERA TION ORGANIZEDBY%3!TOCHASEEACHOTHERSOTHATTHEIRJOINTREPEATVISITWASONLYONE DAY4HISLEADTOTHEACCUMULATIONOFAUNIQUEDATASET ESPECIALLYVALUABLEFORCOHERENT CHANGEDETECTIONMEASUREMENTSTWO PASS)N3!2 4HE%233!2INSTRUMENTWAS ASUBSETOFACOMBINEDRADARGROUP THE!CTIVE-ICROWAVE)NSTRUMENT!-) COM PRISEDOFASCATTEROMETERANDAWINDWAVEMINI 3!2MODE ASWELLASTHE3!2ITSELF o4HEFIRSTDIGITALLYPROCESSEDIMAGESFROMTHE3EASAT3!2REQUIREDHOURSFORAQUARTER FRAMEKMSQUARE ONAMAINFRAMECOMPUTER
30!#% "!3%$2%-/4%3%.3).'2!$!23
£n°
4HESCATTEROMETERMODEISDESCRIBEDIN3ECTION 4HEWINDWAVEMODE BASED ONTHE3!2 WASDESIGNEDTOGRAB KMSQUARESNAPSHOTIMAGESOFTHEOCEANSURFACE WHICHCOULDBEPROCESSEDONBOARDORLATERINAGROUNDFACILITY TOESTIMATEWINDSPEED ANDDIRECTIONFROMTHERADARBRIGHTNESSANDWAVEPATTERNINTHEDATA4HISMODEWAS MOTIVATEDBYAREQUIREMENTTOGATHER3!2 QUALITYDATAOVERALARGEAREAWITHINTIGHT DATAVOLUMELIMITS/NECONSEQUENCEOFTHEOCEAN VIEWINGREQUIREMENTSWASTHAT66p EMERGED AS THE FAVORED POLARIZATION SINCE VERTICALLY POLARIZED OCEANIC BACKSCATTER TENDSTOBELARGERAT#BANDATSTEEPINCIDENCEeTHANHORIZONTALLYPOLARIZEDOCEANIC BACKSCATTER%23 AND ALSOCARRIEDRADARALTIMETERS3ECTION 4HE%3!SERIES OFSATELLITESUSEMIDDAYSUN SYNCHRONOUSORBITSBECAUSETHEIRPAYLOADSINCLUDEOPTICAL SENSORS4HERESULTINGHALF ORBITECLIPSECONTRIBUTESTOTHEIRPER ORBIT3!2OPERATIONAL LIMITOFTENMINUTES * %23 4HE 3!2 ABOARD THE *APANESE %ARTH 2ESOURCES 3ATELLITE * %23 WASSIMILARTO3EASAT BEINGAT,BAND WITHAN( POLARIZEDMBYMANTENNA )TSnINCIDENTANGLE WHICHISLARGERTHANTHATOF3EASAT WASENABLEDBYITSLOWER ALTITUDEANDLARGERANTENNAAPERTURE)TSK7PEAKPOWERWASCOMPARABLETOTHATOF 3EASAT/NECONSEQUENCEOFTHELARGERANTENNAVERTICALDIMENSIONISTHE KMSWATH WHICHISNARROWERTHANTHATOF3EASAT* %23 WASCRIPPLEDBYANTENNAANDCONNEC
TORPROBLEMS SOTHATITSSENSITIVITYNOISE EQUIVALENTSIGMA ZERO.%QR WASONLY nD" D"SHYOFITSnD"DESIGN!SARESULT * %23 IMAGEPRODUCTSWEREFAR NOISIERTHANTHOSEOF3EASAT WHOSESENSITIVITYWASnD")NSPITEOFTHATHANDICAP HOWEVER * %23 DATAAT CMWAVELENGTH PROVIDEDTHEFIRSTSYNOPTICCOVERAGE OFTHETROPICALFORESTSOF"RAZILANDNEIGHBORINGCOUNTRIES4HESEDATAESTABLISHEDAN EARLYhGOLDSTANDARDvFORTROPICALFORESTSURVEYS SINCE,BANDISSOMUCHBETTERSUITED TOTHISAPPLICATIONTHANSHORTERWAVELENGTHS* %23 HAD MRESOLUTIONATLOOKS ABOUThBETTERvTHAN3EASAT BASEDONCOMPARISONOFTHEIRRESPECTIVE3!2IMAGE QUALITYFACTORS3ECTION * %23 OPERATEDFOREIGHTYEARS CONSIDERABLYLONGER THANITSTWO YEARDESIGNLIFE 2!$!23!4 3HOWNIN&IGURE 2!$!23!4 MARKEDAMAJORMILESTONE INSPACE BASED3!2)TWASTHEFIRSTSYSTEMTOOFFERTHEUSERACHOICEOFRESOLUTIONS INCIDENT ANGLES AND SWATH WIDTHS4HE EVOLUTION OF THESE CHARACTERISTICS MERITS A BRIEFREVIEW4HE#ANADIANREQUIREMENTSSPANNEDAVARIETYOFAPPLICATIONS FROMOCE ANICSURVEILLANCEVESSELSANDOILPLATFORMSASWELLASSEASTATE LAND ANDSEA ICE AGRICULTURE AND FORESTS AMONG MANY OTHERS 4HE SEA ICE APPLICATION HAD HIGH PRI ORITY WHICH DROVE THE CHOICE OF POLARIZATION (ORIZONTAL WAS CHOSEN BECAUSE THAT
p)TISCOMMONINRADARREMOTESENSINGTHATTHEIRPOLARIZATIONSAREABBREVIATEDASANALPHABETICPAIR INTHISCASE INDICATINGVERTICALPOLARIZATIONONBOTHTRANSMITANDRECEIVE e3PACE BASED3!2STENDTOLOOKTOWARDTHESURFACEATANGLESTHATAREMUCHCLOSERTOVERTICALTHANDOAIRBORNE3!2S 4HEMOSTCOMMONLYUSEDTERMINOLOGYISINCIDENCETHEANGLEATTHEILLUMINATEDSURFACEBETWEENTHELOCALVERTICAL ANDTHEINCOMINGILLUMINATION 4HEANGLEOFINCIDENCEISTHECOMPLEMENTOFTHEGRAZINGANGLE THECUSTOMARY NOMENCLATUREFORAIRBORNERADARS)NCIDENCEDIFFERSFROMELEVATIONTHEANGLEATTHESPACECRAFTBETWEENVERTICALAND THEDIRECTIONFROMTHESPACECRAFTTOTHESCENE WHERETHEDIFFERENCEISDUETOTHE%ARTHSCURVATURE
!LERT4HE*APANESE3!2SUSUALLYSPECIFYTHELOOKANGLEASTHEELEVATIONANGLEATTHESPACECRAFT ALTHOUGHCALLING THATANGLEhINCIDENCEv4HUS MOSTOFTHELITERATURECITESnFOR* %23 SINCIDENCE WHICHCANLEADTOCONFUSION IFTHEVALUEOFTHISPARAMETERISIMPORTANTINAGIVENAPPLICATION4HESAMECAVEATAPPLIESTO0!,3!2 DESCRIBED INASUBSEQUENTPARAGRAPH
£n°£ä
2!$!2(!.$"//+
&)'52% 2!$!23!4 IS OUTWARDLY SIMILAR TO ITS PREDECESSOR4HE SOLAR PANELS ARE PARALLEL TO THE ALONG TRACK AXIS OF THE ANTENNA INDICATIVE OF ADAWN DUSKSUN SYNCHRONOUSORBIT#OURTESYOFTHE#ANADIAN3PACE!GENCY
OFFEREDANADVANTAGEWHENATTEMPTINGTODISTINGUISHNEWICEFROMCALMSEAAT#BAND ANDMODERATEINCIDENCE4HEAPPLICATIONSDIVERSITYIMPLIEDASPANOFPREFERREDINCI DENCEFROM^nTOMORETHANn)NRESPONSE THEANTENNAWASREQUIREDTOSTEERITS BEAMINELEVATION WHICHEVOLVEDINTOSEVENDIFFERENTSTANDARDELEVATIONBEAMPAT TERNS ELECTRONICALLYSTEEREDANDSHAPED!SMIGHTBEEXPECTED NOAPPLICATIONSTHEME WOULDACCEPTDEGRADEDRESOLUTION4OSATISFYTHATDEMAND THERADARDESIGNADOPTED THREEBANDWIDTHS SOTHATTHENOMINALGROUND RANGERESOLUTIONWOULDBEMAINTAINED AT ^M OVER ALL BASELINE INCIDENT ANGLES!S A COROLLARY THE WIDER BANDWIDTH AT SHALLOWERINCIDENCEWOULDRESULTINFINERRANGERESOLUTION4HEANTENNADESIGNWAS BASED ON HORIZONTAL RUNS OF WAVEGUIDES EACH CENTER FED &ERRITE PHASE SHIFTERS ONEFOREACHWAVEGUIDE CONTROLLEDTHETRANSMITANDRECEIVEBEAMSHAPEANDBORESIGHT IN ELEVATION 4HE ELECTRONIC BEAM SELECTION ENABLED 2!$!23!4 TO INCORPORATE 3CAN3!2o4HUS THERESOLUTIONOPTIONSFOR2!$!23!4 RANGEFROMMBYM SINGLELOOK KMSWATHSFINEMODE TOMBYMLOOKS KMSWATHS 3CAN3!27IDE )NCIDENCERANGESFROMnTOn INCLUDINGTHEEXTENDEDMODES 4HEREARESEVENSTANDARDMODES EACHHAVINGITSOWNELEVATIONBEAMTHESEMODES HAVENOMINALLYMBYMLOOKS KMSWATHS4HE.%QRISnD"OR BETTERANDMODE DEPENDENT "Y THE END OF 2!$!23!4 HAD COMPLETED ITS TH YEAR LOGGING MORE THAN ORBITSANDCOLLECTINGENOUGHDATATOMAPTHEENTIRESURFACEOFTHE%ARTH ANEQUIVALENTOFTIMES4HE#ANADIAN)CE3ERVICERELIESON2!$!23!4 DATA FORITSROUTINEOPERATIONS WHICHREQUIREMORETHANFRAMESOFDATAPERYEAR3INCE THE 3!2 IS THE ONLY 2!$!23!4 PAYLOAD INSTRUMENT A SUN SYNCHRONOUS DAWN DUSK ORBIT WAS CHOSEN TO MAXIMIZE ILLUMINATION OF THE SOLAR PANELS WHICH ALLOWS MINUTESOF3!2OPERATIONPERORBIT2!$!23!4 LOOKSTOTHERIGHTSIDEOFTHE ORBITPLANE WHICHGIVESITACCESSTOTHE#ANADIAN!RCTICUPTOTHE.ORTH0OLE4WICE DURINGITSMISSION THESPACECRAFTWASYAWEDnFORSEVERALWEEKS WHICHENABLED FULL COVERAGE OF!NTARCTICA4HE RESULTING DATA WERE MERGED TO YIELD THE FIRST HIGH RESOLUTION IMAGERY OF THE WHOLE CONTINENT AND OVER SEVERAL REGIONS REPEAT PASS COVERAGESUPPORTEDINTERFEROMETRIC3!2MEASUREMENTOF!NTARCTICGLACIALFLOWRATES 2!$!23!4 ISANENHANCEDVERSIONOF2!$!23!4 4ABLECHARTSASUM MARYOFITSMANYMODES
o$ISCUSSEDLATERINTHISSECTION
30!#% "!3%$2%-/4%3%.3).'2!$!23
£n°££
4!",% 2SAT -ODES
-ODE
7IDTH7
!CCESS
2ESOLUTION
,OOKS
13!2
713!2
KM
KM n n n n n
M 2Gr!Z r r r r r
2Gr!Z r r r r r
n n
r r
r r
n n
r r
r r
n n
r r
r r
r
r
3ELECTIVEPOLARIZATION 3TANDARD 7IDE &INE 3CAN3!27IDE 3CAN3!2.ARROW 3INGLEPOLARIZATION ,OWINCIDENCE (IGHINCIDENCE 0OLARIMETRY 3TANDARD1UAD0OL &INE1UAD0OL 3ELECTIVE3INGLE0OL -ULTI LOOK&INE 5LTRA &INE %XPERIMENTAL -/$%8'-4) 6ERY(IGH2ESOLUTION
%.6)3!4 4HE ADVANCED 3!2 !3!2 ABOARD %3!S %NVISAT TAKES 2!$!23!4 SVERSATILITYONESTEPFURTHER WITHTHEADDITIONOFTWOPOLARIZATIONS (AND6 ONEITHERTRANSMITORRECEIVE)TSMBYMACTIVEARRAYANTENNACOM PRISES TRANSMITRECEIVE MODULES )N OTHER REGARDS ITS MODES REFLECT THE BASIC 2!$!23!4 DESIGNDUE INLARGEPART TOTHEPARTICIPATIONBYKEYRADARSPECIALISTS FROM#ANADAAMEMBEROF%3!S%ARTH/BSERVATION0ROGRAM"OARDONTHE!3!2 CONCEPTUALDESIGNTEAM 4HETRANSMITANDRECEIVEPOLARIZATIONSAREINDEPENDENTOF EACHOTHER SOTHATATFULLRESOLUTION THEPOLARIZATIONCHOICESARE(( 66 OR(6.OTE THAT THIS DUAL POLARIZATION MODE IS ACTUALLY ALTERNATING POLARIZATION IN WHICH THE POLARIZATIONSTATESARESWITCHEDBETWEENTRANSMISSIONSORRECEPTIONS BUTTHEPULSE REPETITION FREQUENCY IS NOT INCREASED 3UCH A hDUAL POLARIZEDv PAIR BY DEFINITION CANNOTBEMUTUALLYCOHERENTSINCEITCORRESPONDSTOINTERLEAVEDSAMPLESOFTHEBACK SCATTER TIME MULTIPLEXEDATLESSTHANTHE.YQUISTRATE!SACONSEQUENCE THEPHASE DIFFERENCEBETWEENCOMPLEXSAMPLESATEACHPIXELISNOTAVAILABLE4HE!3!2ALTER NATINGPOLARIZATIONMODEPROVIDESDUAL POLARIZEDIMAGESTHATARESIMILARTOTHOSETHAT HAVEBEENAVAILABLEFROMMANYAIRBORNESYSTEMSFORDECADES ALTHOUGHNOTAVAILABLE FROMAN3"2EXCEPTFOR3)2 "AND3)2 # UNTIL%.6)3!4 0!,3!2 )NCONTRASTTOTHEINCOHERENTPOLARIMETRICOPTIONSOF!3!2 THE0HASED !RRAY, BAND3YNTHETIC!PERTURE2ADAR0!,3!2 ABOARD*APANS!,/3pLAUNCHED IN *ANUARY INCLUDES FULL QUADRATUREe POLARIMETRY 4HE 0!,3!2 MODES INCLUDESTANDARDSINGLE POLARIZATIONMAPPINGMODES A3CAN3!2MODE AVARIETYOF DUAL ANDQUADRATURE POLARIZEDMODES ANDEXPERIMENTALMODES INCLUDING3POT3!2 %ARLYMISSIONCALIBRATIONANDVALIDATIONSTUDIESVERIFIEDTHATTHERADARISPERFORMING ASINTENDED-OREON0!,3!2APPEARSLATERINTHISSECTION p!DVANCED,AND/BSERVATION3ATELLITE *!8! *APAN e$ISCUSSEDLATERINTHISSECTION
£n°£Ó
2!$!2(!.$"//+
*IAN"ING +NOWN ALTERNATIVELY AS 2EMOTE 3ENSING 3ATELLITE *IANBING IS#HINASFIRSTSYNTHETICAPERTURERADARMISSION4HESPACECRAFTMASSISKG LAUNCHEDINTOASUN SYNCHRONOUSORBITAT^KMALTITUDE-ISSIONOBJECTIVESINCLUDE POLARIMETRICDIVERSITYANDINTERFEROMETRY4HETWOBASELINEMULTI LOOKRESOLUTIONSARE M KMSWATH ANDM KMSWATH OVERAVARIETYOFINCIDENTANGLES)TS ANTENNAISANACTIVEPHASEDARRAY 4ERRA3!2 8 4ERRA3!2 8 IS THE FIRST CIVILIAN DEDICATED SPACE BASED 3!2 AT 8BAND)TSMBYMANTENNAISATWO DIMENSIONALACTIVEARRAYOF42 MODULES)THASAVARIETYOFMODES FROM3CAN3!2 MRESOLUTIONOVER KM SWATHS TO3POT3!2 MRESOLUTIONOVERA KMBY KMIMAGEFRAME )TSSTRIP MAPPING MODE IS BASELINED AT M RESOLUTION ACROSS KM SWATHS 4HE ARRAY IS PARTITIONEDINTHEALONG TRACKDIRECTION WHICHCANBEEXERCISEDINATWO APERTURE ALONG TRACKINTERFEROMETRICMODEFOR'-4)EXPERIMENTS AMONGOTHERAPPLICATIONS &ULLQUADRATUREPOLARIZATIONISONEOFTHEMODEOPTIONS4HEONLYPAYLOADINSTRUMENT ISTHERADAR SOTHESPACECRAFTISDESIGNEDFORASUN SYNCHRONOUSDAWN DUSKORBIT DAYREPEAT3EVERALYEARSAFTERTHELAUNCHOF4ERRA3!2 8 ITWILLBEJOINEDBYA COMPANION 4ANDEM 8 WHICHISMEANTTOBEAFUNCTIONALCOPY4HESETWOWILLCO ORBITASACLOSELYCOORDINATEDPAIRTOSUPPORTAVARIETYOFBISTATICANDINTERFEROMETRIC APPLICATIONS /THER 3PACE BASED 3!2S 3PACE BASED 3!2 CONTINUES TO UNDERGO CONSID ERABLE EXPANSION ON AN INTERNATIONAL FRONT 4HIS SECTION PROVIDES AN OVERVIEW OF PROGRAMSKNOWNATTHETIMEOFPUBLICATIONOFTHIS(ANDBOOK TOHAVEPROGRESSED THROUGH0HASE! WHICHISEVIDENCEOFFUNDINGTHATISSUFFICIENTLYSERIOUSTHATMOST ARE LIKELY TO CULMINATE IN THE LAUNCH AND OPERATION OF A FLIGHT SYSTEM4HE ARCHI TECTUREOFTHESEEMERGINGSYSTEMSISDOMINATEDBYONEOFTWOANTENNAPARADIGMS ACTIVETWO DIMENSIONALPHASEDARRAYSORREFLECTORS-OSTMISSIONSAREMULTIMODEIN RESOLUTIONHENCESWATHANDCOVERAGE ANDPOLARIMETRYRANGINGFROMINCOHERENT DUAL POLARIZATION TO FULL QUADRATURE POLARIMETRY !T LEAST FOUR OF THESE INITIATIVES IMPLYSEVERALSATELLITES EITHERINCONSTELLATIONORINSERIES!LLTOGETHER SOMETHING INEXCESSOFNEW3!2SAREBEINGLAUNCHEDINTHEFIRSTDECADEOFTHESTCENTURY FROM AT LEAST EIGHT DIFFERENT COUNTRIES (IGHLIGHTS OF SEVERAL OF THESE SYSTEMS ARE SUMMARIZEDINTHEFOLLOWINGPARAGRAPHS #/3-/ 3KY-ED )TALY HAS A SERIES OF FOUR #/3-/ 3KY-ED 8 BAND 3!2 SATELLITES4HE#/3-/3!2SHAVEMULTIPOLARIZATIONACTIVEPHASED ARRAYANTENNAS THATSUPPORTAVARIETYOFMODESINCLUDING M3POT3!2 STRIPMAP 3CAN3!2 AND KMWIDESWATH4HE#/3-/BUSISBASEDONTHEDESIGNBUILTANDFLIGHT PROVEN FOR#ANADAS2!$!23!4 4EC3!2 4HEFIRSTSPACE BASED3!2FROM)SRAEL 4EC3!2ISAFEATUREDELEMENT OF THEIR NATIONAL SATELLITE TECHNOLOGY DEVELOPMENT PROGRAM ,AUNCHED BY )NDIA 4EC3!2S NOMINAL STRIP MAP MODE IS MULTI LOOK M RESOLUTION AT 8 BAND -AJOR ADDITIONAL OBJECTIVES INCLUDE LARGE AREA COVERAGE AS WELL AS HIGH RESOLUTION WHICH IMPLY 3CAN3!2 AND 3POT3!2 MODES RESPECTIVELY 4HE M 3POT3!2 RESOLUTION CONSTRAINSTHEDESIGN ONECONSEQUENCEOFWHICHISTHESYMMETRICALBODY MOUNTED MDIAMETERUMBRELLA STYLEMESHREFLECTORKG DRIVENBYONEOFTENFEEDHORNS SLIGHTLYOFFSETFROMTHEFOCALPOINT4HISUNITY ASPECTRATIOANTENNAISANOTABLEDEPAR TUREFROMTHERECTANGULARANTENNASSOTYPICALOFMOSTSPACE BASED3!2PRECEDENTS
30!#% "!3%$2%-/4%3%.3).'2!$!23
£n°£Î
&)'52% 4EC3!2 FEATURES A SYMMETRICAL REFLECTOR ANTENNA INCONTRASTTOTHECLASSICHIGHASPECT RATIOhBILLBOARDv STYLEPIONEEREDBY3EASAT#OURTESYOF)!) )SRAEL
3CAN3!2COVERAGE MRESOLUTION KMSWATH TO MRESOLUTION KMSWATH INCIDENCE DEPENDENT ISEXECUTEDBYSEQUENTIALSELECTIONOFTHEAPPROPRIATEFEEDS4HE FEEDHORNSARE( OR6 POLARIZED SOTHATPOLARIMETRICDIVERSITYISALSOSUPPORTEDBYTHIS ARRANGEMENT-ISSIONDESIGNINCLUDESSPACECRAFTSTEERINGTOSUPPORTSQUINTEDASPECTS RELATIVE TO THE REFERENCE SIDE LOOKING ORTHOGONAL VIEWING 4HE HIGH POWER STAGE IS COMPRISED OF TEN CHANNELED 474!S EIGHT OF WHICH ARE REQUIRED IN COMBINATION LEAVINGTWOASREDUNDANTBACKUP4HERADARMASSISKGINCLUDINGTHEREFLECTOR ANDFEEDS SATELLITEDRYMASSINCLUDINGTHERADARIS^KG WHICHATTHETIMESETTHE STANDARDASTHESMALLEST3!2SATELLITEIN%ARTHORBIT4HEPOWERSUBSYSTEMDELIVERS UP TO K7 DURING IMAGING OPERATIONS 4HE SPACECRAFT ORBIT IS n INCLINATION ^KMALTITUDE DAYREPEATPERIOD3INCETHISISNOTASUN SYNCHRONOUSORBITAND SINCETHEANTENNAPATTERNTOFIRSTORDER ISSYMMETRIC THESPACECRAFTMAYBEROTATED ABOUTTHERADARSLINE OF SIGHTTOHELPSUSTAINNEAR FULLILLUMINATIONOFTHETWOSOLAR PANELARRAYSINALLSUN ORBITPLANECONFIGURATIONS2ADARDATAARERECORDEDINA'BIT SOLID STATEUNITFOLLOWING TO BLOCK FLOATING POINTQUANTIZATION3PACECRAFTDESIGN LIFEISFIVEYEARS (* # (* # IS THE FIRST OF FIVE 3!2 SATELLITES IN #HINAS SMALL SATELLITE PROGRAMANNOUNCEDINFORENVIRONMENTANDDISASTERMONITORING4HEARCHI TECTUREOFTHESESYSTEMSISCLOSELYPARALLELTO2USSIAS+ONDOR %SERIES SINCETHEY AREBOTHOUTGROWTHSOFABILATERALDEVELOPMENTPROGRAMBASEDONTHEARCHITECTURE OFTHE0RIRODA3BANDRADAR4HE(* #SANTENNAISAREFLECTORTHATHASANEFFEC TIVEAPERTUREOFMBYMFOLLOWINGDEPLOYMENT)NSTRIP MAPMODE THE(* #HASAMULTI LOOK MRESOLUTIONOVERA KMSWATH AND MRESOLUTIONIN 3CAN3!2MODEAT KMSWATHWIDTH3POT3!2MODEISSUPPORTEDBYCONTROLLED YAWMANEUVERSOFTHESPACECRAFT!LLOFTHESPACECRAFTINTHESERIESFIVERADARSAND SIXOPTICALSYSTEMS USESUN SYNCHRONOUSORBITSAT^KMALTITUDE4HERADARS MASSIS^KG 3!2 ,UPE 'ERMANY HAS FIVE IDENTICAL 8 BAND SATELLITES DISTRIBUTED IN THREE KMHIGHORBITS INCLINEDATABOUTn4HEASPECTRATIOOFTHEIRMBYM
4RAVELING WAVETUBEAMPLIFIER3EE#HAPTERFORMOREDISCUSSION
£n°£{
2!$!2(!.$"//+
ANTENNASSUGGESTSTHATTHEDOMINANTOBJECTIVEISFINERESOLUTION WHICHNECESSITATESA RELATIVELYNARROWRANGESWATH0UBLISHEDSPECIFICATIONSNOTETHATTHEINTENDEDRESO LUTIONINTHESLIP 3!2oMODEISMOVERAKMBYKMIMAGEFRAME4HESE INNOVATIVE3"2SARERELATIVELYSMALL ATLEASTBY%ARTH OBSERVINGSATELLITE3!2STAN DARDS4HEIRKGMASSTOTALDRYMASSOFTHESPACECRAFTANDTHERADAR ISLESSTHAN THEMASSOF2!$!23!4 SANTENNA4HE3!2 ,UPEDESIGNALSOISCOST CONSCIOUS BASED ON RIGID NONDEPLOYED REFLECTOR ANTENNAS hBORROWEDv FROM A COMMERCIAL COMMUNICATIONSSATELLITEPRODUCTIONLINE THATAREINHERENTLYMOREEFFICIENTANDLESS MASSIVE THAN AN ACTIVE ARRAY 4HE RADAR ELECTRONICS ARE DIRECTLY DESCENDED FROM A COMMERCIALPRODUCTLINE 2)3!4 4HE 2ADAR )MAGING 3ATELLITE OR 2)3!4 IS )NDIAS FIRST SPACE BASED 3!2 FOLLOWINGEXTENSIVEPROGRAMSINOPTICALREMOTESENSINGSATELLITESANDAIRBORNE IMAGINGRADARDEVELOPMENT2)3!4SDEPLOYABLEANTENNAMBYM ISANACTIVE PHASEDARRAYCOMPRISEDOF# BAND'HZ 42MODULES EACHCAPABLEOF7 PEAKPOWER4HEAVERAGEOUTPUTPOWER7 REQUIRESANAVERAGEINPUTDCPOWER OFK7%ACH42MODULEISCONNECTEDTOSEPARATEDISTRIBUTIONNETWORKSFEEDING ( AND6 POLARIZEDELEMENTS WHICHSUPPORTPOLARIZATIONDIVERSITYASWELLASELEVA TIONBEAMSTEERING4HEREARETWOPARALLELRECEIVECHANNELSDEDICATEDTOTHE( AND 6 POLARIZEDANTENNAELEMENTS 2)3!4HASFIVEMODES EACHOFWHICHMAYOPERATEAT AVARIETYOFINCIDENTANGLES4HEMODESAREFINE RESOLUTIONSTRIP MAP MRESOLU TION KM SWATH DUAL POLARIZATION FINE RESOLUTION STRIP MAP M AT KM QUADRATURE POLARIZATION MEDIUMRESOLUTION3CAN3!2MATKM DUAL POLAR IZATION COARSERESOLUTION3CAN3!2MATKM DUAL POLARIZATION ANDHIGH RESOLUTION3POT3!2BETTERTHANM KMSQUAREIMAGEFRAME DUAL POLARIZATION 4HE3POT3!2MODEREQUIRESYAWPITCHSTEERINGOFTHESPACECRAFTTOon#OVERAGE TOEITHERSIDEOFTHEGROUNDTRACKREQUIRESAROLLMANEUVEROFTHESPACECRAFTTODIRECT THEANTENNAPATTERNTOTHEOPPOSITESIDEOFNADIR ANAPPROACHTHATISSIMILARTOTHATOF 2!$!23!4 4HEVARIETYOFRESOLUTIONSISSUPPORTEDBYFOURBANDWIDTHS-(Z -(Z -(Z AND-(Z THROUGHAPROGRAMMABLEDIGITALCHIRPGENERATOR 4HERECEIVEDDATAAREDOWNCONVERTEDTOBASEBAND DIGITIZEDTOBITS)AND1 AND QUANTIZEDBYBLOCK FLOATINGPOINTMEANS TOFEWERBITSTO ATTHEUSERSOPTION WITHINMODE DEPENDENTLIMITS!LLSUBSYSTEMSSAVEFORTHEANTENNA AREDUAL REDUN DANT.OMINAL02&IS(Zo(Z$ATARATESSPAN-BITSSTO-BITSS DEPENDINGONMODE4HEON ORBITMASSOFTHESPACECRAFTWILLBE^KG OFWHICH THE3!2PAYLOADINCLUDINGTHEANTENNA CLAIMS^KG/NBOARDDATASTORAGECAPAC ITYIS'BITSDOWNLINKMAXIMUMDATARATEIS-BITSS8BAND DUALCIRCULARLY POLARIZED 4HE2)3!4ORBITISSUN SYNCHRONOUS DAWN DUSK AT^KMALTITUDE AND DAYREVISITPERIOD -!03!2 4HE -ULTI !PPLICATION 0URPOSE 3!2 IS A JOINT "RAZILIAN 'ERMAN ENTERPRISE AIMED PRIMARILY AT ASSESSING AND MONITORING "RAZILS NATURAL RESOURCES !FTERSEVERALYEARSOFTRADESTUDIES ,BANDWASSELECTED'HZ 4HERADARISBUILT AROUNDANEAR SYMMETRICALREFLECTORMBYM WITHTENFEEDS OFFSETFROMTHE FOCALPOINTSOTHATTHEBEAMCANBEELECTRONICALLYSCANNEDINELEVATION3PATIALRESOLU TIONANDSWATHSPANMTOM ANDKMTOKM RESPECTIVELY MODE DEPENDENT o3LIP 3!2ISAMODIFIED3CAN3!2MODE INWHICHTHEANTENNAPATTERNISDRAGGEDALONGTHESURFACEATASLOWERRATE THANINTHECONVENTIONALSTRIP MAPMODE4HERESULTISLARGERDOPPLERBANDWIDTH HENCEENHANCEDAZIMUTHRESOLU TION ANDALSOAWIDERIMAGEDAREATHANAPURE3POT3!2CANSUPPORT
30!#% "!3%$2%-/4%3%.3).'2!$!23
£n°£x
4HEHIGH RESOLUTIONSPECIFICATIONRESULTSFROMANEXTERNALCONSTRAINT THEMAXIMUM -(ZBANDWIDTHSTIPULATEDBYINTERNATIONALSPECTRALALLOCATIONAGREEMENTS4HERE ISPROVISIONFORALLPOLARIMETRICCONFIGURATIONS4HESUN SYNCHRONOUSORBITWILLBECON TROLLEDTOASSURERELIABLE DAYREVISITBASELINESTOSUPPORTINTERFEROMETRY.OMINAL INSTRUMENTMASSISKG 0!,3!2 !LTHOUGHBASEDON* %23 HERITAGE 0!,3!2ISANEXCELLENTEARLY EXAMPLEOFMULTIMODESPACE BASED3!2S0!,3!2SMODES&IGURE INCLUDE STANDARDSINGLE POLARIZATIONMAPPING 3CAN3!2 AVARIETYOFDUAL ANDQUADRATURE POLARIZED MODES p AND EXPERIMENTAL OR DEMONSTRATION MODES INCLUDING 3POT3!2 4HE,BANDCM BASELINEFREQUENCY-(Z HASTWOBANDWIDTHS -(Z FINE BEAMSINGLE POLARIZATIONMODE AND-(ZDUAL QUAD POL AND3CAN3!2 MODES 4HESPANOFMID SWATHINCIDENTANGLESISnnn .OTETHATTHE*APANESE USUALLYCITETHESEANGLESAShOFF NADIRvnnn WHICHREFERSTOTHEIRELEVATION WITHRESPECTTOVERTICALINSPACECRAFTCOORDINATES RATHERTHANTHEIRINTERSECTIONRELA TIVETOALOCALVERTICALATTHE%ARTHSMEANOBLATESPHEROIDALSURFACE
"
(' !! ' %
"
"
#$
# &$!(' $#$ ) $!% " '% $ )
&)'52% /VERVIEWOF0!,3!2SVIEWINGGEOMETRIES%ACHOFTHESEBEAMPOSITIONSSUPPORTSA VARIETYOFPOLARIZATIONCOMBINATIONS LEADINGTOAVERYLARGENUMBEROFAVAILABLEMODES4HESOLARPANEL IS ORTHOGONAL TO THE ORBIT PLANE INDICATIVE OF A MIDDAY SUN SYNCHRONOUS ORBIT $IAGRAM COURTESY OF *!8! *APAN
p4HE SEVERAL FORMS OF POLARIMETRIC DIVERSITY COMMON IN REMOTE SENSING SYSTEMS ARE REVIEWED LATER IN THISSECTION
£n°£È
2!$!2(!.$"//+
-ODERN SPACE BASED 3!2S OWE THEIR LARGE MODE VARIETY TO ACTIVE ELECTRONIC STEERED ANTENNA ARRAYS 0!,3!2S ANTENNA CONSISTS OF SOLID STATE 42 MODULES DISTRIBUTEDONFOURPANELSWHOSEDEPLOYEDDIMENSIONSAREMBYM VERTICAL ANDHORIZONTAL RESPECTIVELY3PACECRAFTVELOCITYANDANTENNALENGTHDICTATEALOWER BOUND ON PULSE REPETITION FREQUENCY WHICH FOR 0!,3!2 SPANS K(Zn K(Z DEPENDINGONMODE0EAKTRANSMITTEDPOWERIS^K7 TWICETHATOFTHE3EASAT3!2 4HERESULTINGSENSITIVITYNOISE EQUIVALENTSIGMA ZERO ISVERYGOOD nD"ORBETTER FORMOSTMODES0!,3!2SHOST!,/3SPACECRAFTISYAW STEEREDTOMAINTAINAZIMUTH ANTENNA BORESIGHT POINTING AT ZERO DOPPLER WHICH INCREASES THE LIKELIHOOD OF PASS TO PASSINTERFEROMETRICCOHERENCEANDSIMPLIFIESSOMEWHAT 3!2IMAGEFORMATION PROCESSING4HENOMINALDATARATEINMOSTMODESIS-BITS WHICHISDOWNLINKED VIA*APANS$ATA2ELAY4EST3ATELLITE$243 4HE3CAN3!2MODEREQUIRESONLYHALF THATRATE -BITS WHICHCANBEDOWNLINKEDDIRECTLYTOGROUNDSTATIONS!,/3HAS ANONBOARD'BYTESOLID STATERECORDERTOBUFFERDATAOUTPUTFROMTHERADAR ASWELL ASFROMTHERESTOFTHEPAYLOAD 0!,3!2SVOLUMINOUSVARIETYOFMODESISACURSEASWELLASABLESSING-ISSION MANAGEMENTMUSTCOPEWITHDATACOLLECTIONINEACHOFTHESEMODES ASWELLASPHAS INGTHERESULTINGDATABURDENTOSHARETHECOMMUNICATIONSLINKWITHTHETWOOTHERHIGH DATA RATEINSTRUMENTSINTHE!,/3PAYLOAD4HESTANDARDPOLICYFORTHEEARLYYEARSOF 0!,3!2SON ORBITSCHEDULINGISTOFOCUSONSIXhDEFAULTvMODESFOURhOPERATIONALv AND TWO hSEMI OPERATIONALv 4HE RESULTING TERMS ARE FIXED hSTANDARDv OFF NADIR ANGLE OF n FOR A GREAT MAJORITY OF THE DATA TAKES POLARIZATION OPTIONS TO BE SINGLE POL((ANDDUAL POL(( (6 QUAD POLATnOFF NADIR FOR2$DEM ONSTRATIONSOVERPRESELECTEDhSUPERSITESvAND FIVE BEAM3CAN3!2IN((POLARIZA TION)NADDITION THEFOLLOWINGCONSTRAINTSAPPLYONLYONEMODEISEXERCISEDDURING ONE DAYREPEATCYCLEPREFERREDOPERATIONSAREDURINGTHEHOURSOFDARKNESSINTHE ASCENDINGPASSESFORMOSTMODES EXCEPTINGLOWERDATA RATE3CAN3!2DATATAKESDUR INGDESCENDINGPASSESINCOORDINATIONWITHTHEOPTICALSENSORS ANDALSOEXCEPTING EXTRAORDINARY)N3!2ANDMARINEAPPLICATIONSATNONSTANDARDINCIDENCEANDRECURRENT REPEAT PASSCOVERAGEOFSELECTEDSITESINGROUPSOFEIGHTORMORE DAYCYCLESINSUP PORTOF)N3!2OBJECTIVES 3PACE BASED3!2$ESIGN)SSUES 4HEOPTIONSFORSPACE BASED3!2DESIGN AREMORELIMITEDTHANFORAIRBORNESYSTEMS DUEPRIMARILYTOTHECONSTRAINTSIMPOSED BYVIABLEORBITS INCLUDINGESPECIALLYSENSORVELOCITY RADARRANGE2 ANDSYSTEMCOST 4HEFOLLOWINGPARAGRAPHSREVIEWTHEMAJORTHEMES 02&#ONSTRAINTS 4HERULESTHATGOVERNTHEPULSEREPETITIONFREQUENCY02& OF ASPACE BASED3!2ARETHESAMEASTHOSEAPPLICABLETOAIRBORNESYSTEMS ALTHOUGH THEY PLAY OUT RATHER DIFFERENTLY 4HE FUNDAMENTAL REQUIREMENT IS THAT THE 02& FP BESUFFICIENTLYHIGHTOSAMPLEUNAMBIGUOUSLYTHEDOPPLERSPECTRUMOFWIDTH"$OP AND ALSO SUFFICIENTLY LOW SO THAT THERE IS TIME BETWEEN TRANSMISSIONS TO RECEIVE THEDATABACKSCATTEREDFROMTHEINTENDEDSWATHOFSLANTRANGETIME DOMAIN WIDTH 424HUS
"$OP F0 42
)NPRACTICE SUFFICIENTMARGINMUSTBEINCLUDEDINBOTHTHEUPPERANDLOWERLIMITSTO ACCOUNTFORTHELENGTHOFTHETRANSMITTEDPULSE ANDFORTHEFACTTHATNEITHERTHEDOPPLER SPECTRUMNORTHEANTENNASELEVATIONPATTERNHAVESHARPCUTOFFS
30!#% "!3%$2%-/4%3%.3).'2!$!23
£n°£Ç
4HELOWERBOUNDOFTENISRECASTAS
"$OP
B63# 63# F0 $!Z L
WHICHSTATESTHATTHE02&MUSTBESUFFICIENTLYHIGHSUCHTHATTHEREARETWOTRANSMIS SIONSPERANTENNAAPERTURELENGTH$!ZASTHERADARMOVESALONGITSTRAJECTORY(ERE 63# IS SPACECRAFT VELOCITY ALONG ITS ORBIT A IS THE WIDTHe OF THE AZIMUTH ANTENNA PATTERN ANDKISTHERADARWAVELENGTH 4HISFORMISINTUITIVELYSATISFYING SINCETHE SINGLE LOOKAZIMUTHRESOLUTIONISAPPROXIMATELYONE HALFOFTHEANTENNASALONG TRACK WIDTH HENCETHISINEQUALITYREQUIRESTHATEACHRESOLVEDALONG TRACKRANGELINEMUST BESAMPLEDATLEASTONCE5SUALLYTHE02&LOWERBOUNDISSETSOTHATTHEREISAMARGIN OFORMOREWITHRESPECTTOTHISCONSTRAINT )NANAIRBORNE3!2 THE02&CONSTRAINTISDERIVEDTOSATISFYTHEDOPPLERBANDWIDTH FROMWHICHFOLLOWSTHEMAXIMUMRANGETHATTHERADARCANOPERATEWITHOUTINTRODUC ING AMBIGUITIES (OWEVER BY DEFAULT THE MINIMUM RANGE FOR A SPACE BASED 3!2 IS ITS ORBITAL ALTITUDE USUALLY KM OR HIGHER4HE TYPICAL SLANT RANGE TO THE INTENDED SCENEMAYBEKMANDMORE4HUS THEUPPERBOUNDONTHE02&SHOULDNOTBESET BYTHERANGETOTHESCENE BUTRATHERBYTHERANGEWIDTHOFTHEAREATOBEIMAGED!SA CONSEQUENCE THERESULTINGHIGH02&WILLGENERATEASEQUENCEOFPULSESATANYMOMENT THATAREDISTRIBUTEDBETWEENTHERADARANDTHESCENE4HESPACEBETWEENPULSESMUSTBE LARGER THAN THE INTENDED SWATH WIDTH &OR EXAMPLE IN CERTAIN MODES 2!$!23!4 GENERATESSEVENPULSEShINFLIGHTvSIMULTANEOUSLY!TTHEBEGINNINGOFSUCHADATACOL LECTION BACKSCATTERFROMTHEINTENDEDSCENEWOULDARRIVEONLYAFTERTHESEVENTHPULSE HADBEENTRANSMITTED )N MANY AIRBORNE SYSTEMS THE 02& IS CHOSEN TO BE RATHER HIGHER THAN THE LIMIT IMPOSEDBYTHERANGETOTHEINTENDEDTARGETSPACE)NSUCHCASES THEEXTRA02&CON TRIBUTES TO IMPROVED 3.2 BUT AT THE COST OF INCREASED AVERAGE DATA RATE $ATA RATE CANBEDECREASEDBYhPRE SUMMINGvCOHERENTLYADDINGNADJACENTRETURNS4HECON SEQUENCE OFCOURSE ISTHATTHEEFFECTIVE02&ISREDUCEDBYTHESAMEFACTORN4HIS PRACTICEISSELDOMACCEPTABLEFORSPACE BORNE3!2S BECAUSEITLEADSTOAZIMUTHAMBI GUITIESUNLESSTHEDOPPLERSPECTRUMISLIMITEDPRIORTO02&REDUCTION !MBIGUITIES 4HE 02& GENERATES A TWO DIMENSIONALLY SAMPLED SPACE WHEN THE DATAAREDECOMPOSEDINTOhSLOWTIMEvINTHEAZIMUTHDIRECTION ANDhFASTTIMEvINTHE RANGEDIRECTION )NAZIMUTH THE02&CREATESALIASEDVERSIONSOFTHEDATAILLUMINATED BYTHEMAINBEAMOFTHEANTENNA4HESPECTRAOFTHESEALIASESARELOCATEDATMULTIPLES OFTHE02&TOEITHERSIDEOFTHEDOPPLERCENTROIDOFTHEMAINBEAM/FCOURSE WHEN SAMPLEDTHEYAREFOLDEDBACKINTOTHE.YQUISTPASSBAND4HESEALIASESAREAZIMUTH AMBIGUITIES WHICH ARE SUPPRESSEDHENCE NOT VISIBLEIN A WELL DESIGNED SYSTEM SUPPORTEDBYAWELL TUNEDPROCESSOR7HENTHEYDOAPPEAR AZIMUTHAMBIGUITIESARE RELATIVELYEASYTOIDENTIFY&IGURE BECAUSETHEYAREWEAKERGHOST DUPLICATESOF IMAGEFEATURESTHATWERECOLLECTEDTHROUGHTHEMAINBEAMAND THEREFORE ATEARLIEROR LATERPOSITIONSALONGTHEIMAGESTRIP4HEAZIMUTHSHIFTOFTHEAMBIGUITIESRELATIVETO THECENTRALIMAGEISANINTEGRALMULTIPLEOF $8 2L F0 63# WHICHISTHESPATIAL
e&ORAUNIFORMLYILLUMINATEDAPERTURE THE D"BEAMWIDTHISA K$ )TISCUSTOMARYFORANALYSISOF3!2 !Z SYSTEMSTOAPPROXIMATETHISEXPRESSIONBYA^K$!ZANDTOINTERPRETAASTHEWIDTHOFTHERECTANGLETHATHASTHE SAMEPEAKVALUEANDAREAASTHEANTENNAPATTERN
£n°£n
2!$!2(!.$"//+
OFFSETCORRESPONDINGTOTHE02&!ZIMUTHAMBIGUITIES ESPECIALLYFROMPOINTTARGETS HAVETHESAMEDOPPLER&-RATEASSCATTERERSWITHINTHEMAINBEAM ANDSOTHEIRFOCUS ISPRESERVEDTHROUGHTHEPROCESSOR )NTHERANGEDIRECTION ONEOFTHECONSEQUENCESOFHAVINGMANYPULSESINFLIGHTAT ONCEISTHATTHEREAREECHOESFROMSEVERALDIFFERENTRANGESTHATARRIVEBACKATTHERADARAT THESAMERELATIVEDELAYWITHINTHERANGEGATEASTHEREFLECTIONSFROMTHEINTENDEDSWATH )FTHESEEXTRAECHOESARESUFFICIENTLYSTRONG THERESULTINGIMAGEARTIFACTSARERANGEAMBI GUITIES2ANGEAMBIGUITIESARENOTASEASYTOIDENTIFYASAZIMUTHAMBIGUITIES BECAUSE THEYARISEFROMRANGESOUTSIDEOFTHENOMINALSWATH HENCENOTOTHERWISEIMAGED2ANGE AMBIGUITIESBYDEFINITIONARISEFROMRANGESTHATAREDIFFERENTFROMTHOSEFORWHICHTHE PROCESSORISSET SOTHATRANGE AMBIGUOUSPOINTTARGETSTENDTOBEDEFOCUSED 4HE PRINCIPAL MEANS OF SUPPRESSING AMBIGUITIES IS TO CONFINE THE MAIN BEAM OF THEANTENNASOTHATTHEPOTENTIALSOURCESOFAZIMUTHORRANGEAMBIGUITIESARENOTILLU MINATED OR AT LEAST ARE ILLUMINATED ONLY VERY WEAKLY 4HIS REQUIREMENT IMPOSES A MINIMUM AREA CONSTRAINT ON THE 3!2S ANTENNA 4HE LOWER AND UPPER BOUND 02& CONSTRAINTSOF"$OPAND42LEADTO
$%L $!Z 263# L C TANP )NC
WHERETHEANTENNAAREAISTHEPRODUCTOFITSLENGTH$!ZANDHEIGHT$%L ANDP)NCISTHE MEANINCIDENTANGLEINTHEIMAGEDSWATH4HERANGE VELOCITYPRODUCTINTHISEXPRES SIONISDETERMINEDBYTHEPARAMETERSPECULIARTOTHEPARTICULARPLANETORMOON ABOUT WHICHTHE3!2ISTOOPERATE4ABLE !SACONSEQUENCE ANANTENNAOFAREAM ATTHE-OONWOULDHAVEBEM FORTHESAMERADARAT-ARSANDNEARLYM FOR OPERATIONIN%ARTHORBIT )TALWAYSISTEMPTINGTOPUSHTHISCONSTRAINT SINCEMOSTSPACE BASED3!2SUSEAS MUCHOFTHEAMBIGUITY FREESPACEASCANBETOLERATED)NPRACTICE THEANTENNAAREA USUALLYISCHOSENTOBEATLEASTAFACTOROFTWOLARGERTHANTHISMINIMUMWOULDSUG GEST!MBIGUITIESAREPROPORTIONALTOTHESTRENGTHOFTHEOFFENDINGBACKSCATTER ANDAS SUCH THEYCONTRIBUTETOTHEMULTIPLICATIVENOISE RATIO-.2 OFTHESYSTEM!NTENNA SIDELOBES AND AMBIGUITIES ARE FURTHER SUPPRESSED BY APPROPRIATE WEIGHTING IN THE PROCESSOR4HETRADE OFFISLOWER-.2 ATTHEEXPENSEOFBROADERIMPULSERESPONSE WIDTH )27 4YPICAL DESIGNS PROVIDE ^ EXCESS RANGE AND DOPPLER BANDWIDTH RELATIVE TO THOSE IMPLIED BY THE REQUIRED RANGE AND AZIMUTH RESOLUTIONS TO ACCOM MODATESUCHWEIGHTING .ADIR2ETURN !POTENTIALLYTROUBLESOMERANGEAMBIGUITYARISESFROMTHESURFACE DIRECTLYBELOWTHESPACECRAFT4HISNADIRRETURNISALWAYSRELATIVELYSTRONG PARTICULARLY IFTHEREARESPECULARBACKSCATTERINGCOMPONENTS3INCEANYREALISTICANTENNAPATTERN HASANON ZEROSIDELOBEDIRECTEDTOWARDNADIR THERESULTINGREFLECTIONCOULDAPPEARIN THEIMAGE4HEMAINSTRATEGYISTOAVOIDTHEAMBIGUITYBYCHOOSINGTHE02&SOTHATTHE NADIRRETURNARRIVESATTHESAMETIMETHATTHERADARISTRANSMITTING4HISTIMINGPLACES AFURTHERCONSTRAINTONTHEPULSEREPETITIONFREQUENCY)TTURNSOUTTHATTHENADIRRETURN MAY NOT BE AVOIDABLE IF OTHER CONSTRAINTS OVERRIDE THE AVAILABLE 02& OPTIONS4HIS OCCURS FOREXAMPLE IFTHEDRIVINGREQUIREMENTIS3CAN3!2 WHICHHASITSOWNSETOF CONSTRAINTSON02&
-ULTIPLICATIVENOISE ASTANDARDSPECIFICATIONINSYNTHETICAPERTURERADAR INCLUDESUNWANTEDCONTRIBUTIONSSUCHAS AMBIGUITIESANDQUANTIZATIONNOISETHATAREPROPORTIONALTOTHESTRENGTHOFTHERECEIVEDSIGNAL
30!#% "!3%$2%-/4%3%.3).'2!$!23
£n°£
&)'52% %XAMPLEOFARTIFACTSASTHEYAPPEAREDINEARLY2!$!23!4 FOUR SUB SWATH3CAN3!2IMAGERY4HEDIRECTIONOFFLIGHTISVERTICALINTHISPRESENTATION NEAR EDGERANGEATTHELEFTOFTHEFRAME#OURTESYOFTHE#ANADIAN3PACE!GENCY ANDTHE#ANADA#ENTREFOR2EMOTE3ENSING
!NTENNASAND4RANSMITTERS !NTENNASFORTHEPIONEERINGSPACE BASED3!2SYS TEMSWEREEXCLUSIVELYPASSIVE SUCHASTHE, BANDPATCHARRAYON3EASATORTHESLOT TED WAVEGUIDE ARRAYS USED ON %23 AND!LMAZ4HE FIRST EXCEPTION TO THIS RULE WAS2!$!23!4 DESIGNEDAROUNDANARRAYOFHORIZONTALSLOTTEDWAVEGUIDES EACHOFWHICHWASCENTER FEDTHROUGHAPHASESHIFTERSOTHATTHEELEVATIONBEAMPAT TERNCOULDBESELECTEDANDSHAPEDELECTRONICALLY-OREAMBITIOUSREADhMASSIVEAND EXPENSIVEv SYSTEMSTENDTOUSETWO DIMENSIONALLYACTIVEELECTRONICSCANNEDARRAYS %3!S 4HESEAREPOPULATEDBYTRANSMITRECEIVE42 MODULES OFTENINCORPORATING TWOPOLARIZATIONS(AND6 %XAMPLESINCLUDE2!$!23!4 %.6)3!4S!3!2 0!,3!2 #/3-/ 4ERRA3!2 8 AND2)3!4)TISARGUEDTHATACTIVEARRAYSSETTHE STAGEFORhGRACEFULFAILUREvSINCETHELOSSOFAFEW42ELEMENTSWOULDHAVELITTLEEFFECT ONTHENETPERFORMANCEOFTHESYSTEM)NPARALLEL ANALTERNATIVE3!2ANTENNAPARADIGM STRESSESSIMPLICITYANDLOWERMASSANDLOWERCOST OVERTWO DIMENSIONALELECTRONIC BEAMSTEERING4HESEAREREFLECTORS OFWHICH#HINAS(* # 'ERMANYS3!2 ,UPE )SRAELS4EC3!2 AND"RAZILS-AP3!2AREGOODEXAMPLES)FAREFLECTORISDRIVENBY MULTIPLEFEEDS THENONEMAYSTILLEFFECTBEAMSTEERING ALTHOUGHWITHRATHERLESSBEAM SHAPEVARIETYANDCONTROLTHANTHROUGHAN%3! 3PACE BASEDRADARTRANSMITTERSNATURALLYFALLINTOTWOCLASSES INTIMATELYCOUPLEDWITH THEANTENNASARCHITECTURE)FTHEANTENNAISACTIVE THENTHETRANSMITTERASWELLASTHEFRONT ENDOFTHERECEIVER ISDISTRIBUTEDOVERTHEARRAY)NTHISCASE SEVERALHUNDRED42ELE MENTS OFAFEWWATTSPEAKPOWEREACH ADDUPTOMANYHUNDREDSOFPEAKRADIATEDPOWER 0HASECONTROLOFTHEELEMENTSISACRITICALPARAMETER USUALLYREQUIRINGADAPTIVETEMPERA TURECOMPENSATIONTOASSURECOHERENCYOFTHERADIATEDWAVEFRONT4HEALTERNATIVEISALMOST ALWAYSLIMITEDTOTRAVELINGWAVETUBEAMPLIFIERS474!S ALTHOUGHRECENTDEVELOPMENTS INHIGH POWERSOLID STATEDEVICESISINFLUENCING3"23!2DESIGN2ADARSBUILTAROUND 474!S HAVE ESTABLISHED IMPRESSIVE LONGEVITY RECORDS WITNESS 2!$!23!4 AND %23 BOTHOFWHICHREMAINEDINOPERATIONFORMORETHANTENYEARS
£n°Óä
2!$!2(!.$"//+
$ATA2ATE $ATARATEISPROPORTIONALTOTHEPRODUCTOFPULSEREPETITIONFREQUENCY F0 THENUMBEROFRANGESAMPLES.2 WHICHISPROPORTIONALTOSLANT RANGESWATH PLUS THE UNCOMPRESSED PULSE LENGTH AND INVERSELY PROPORTIONAL TO RANGE RESOLUTION THE NUMBEROFQUANTIZATIONBITS.3RETAINEDINEACHSAMPLEOFTHEDATA ANDAFACTOROFTHAT ACCOUNTSFORTHEIN PHASE) ANDQUADRATURE1 COMPONENTSSINCEBOTHTHEAMPLITUDE ANDTHEPHASEOFTHESIGNALSTREAMAREREQUIRED/NCERESOLUTIONANDSWATHAREESTAB LISHED THENUMBEROFBITSPERSAMPLEISTHEONLYPARAMETEROPENTOCHOICE%XCELLENT RESULTSMAYBEOBTAINEDFOR.3 ASSMALLASBITSPER)ANDPER1 BYADAPTINGTHE QUANTIZATIONTHRESHOLDSTOTHEMEANSIGNALLEVEL2EFERTO3ECTIONFORMOREON THISTOPIC 1UANTIZATIONNOISE WHICHISLARGERFORFEWERBITS ISPROPORTIONALTOSIGNAL STRENGTHHENCEITISAFACTORINTHE-.2BUDGET%XACTINGAPPLICATIONSSUCHASINTERFER OMETRYAREBETTERSERVEDBYMOREBITSPERSAMPLE SUBJECTTOTHERATEANDVOLUMELIMITS OFTHEDATAHANDLINGSUBSYSTEMS 0ROCESSING !LTHOUGH SIMILAR IN PRINCIPLE TO AIRBORNE SYSTEMS PROCESSING FOR SPACE BASED3!2SDIFFERSINSEVERALKEYREGARDS4HEHIGHLIGHTSAREREVIEWEDHERE &ORMORECOMPLETECOVERAGE SEETHESTANDARDREFERENCES !SIMPLIFIEDINTRODUC TIONTOTHEKEYPARAMETERSMAYBEHELPFUL 4HE NATURAL STARTING POINT IS THE RANGE EQUATION FROM WHICH SEVERAL PROPERTIES EMERGETHATAREUNIQUETOTHESPHERICALGEOMETRYOFRADARSINORBIT)NTHENARROW BEAM SIDE LOOKINGCASE ANDNEGLECTINGTHEEFFECTSOF%ARTHROTATION THERADAR TO TARGETRANGE VARIATIONGENERATESAPHASETIME HISTORYOVERASYNTHETICAPERTURELENGTHOF4SECONDS FROMAPOINTREFLECTORATMINIMUMSLANTRANGE2
1T
P ¤ T ³ 2 6 6
3# "EAM L ¥¦ 2 ´µ
WHERE6"EAMISTHEVELOCITYONTHESURFACEOFTHEILLUMINATINGFOOTPRINTOFTHEAZIMUTH ANTENNAPATTERN4HETIMEDERIVATIVEOFTHEPHASEYIELDSTHESCATTERERSDOPPLERHISTORY
F$ T
63#6"EAM T L 2
IN WHICH THE &- RATE IS PROPORTIONAL TO THE EFFECTIVE VELOCITY 6%FF 63# 6"EAM 4HISISINCONTRASTTOTHEAIRBORNECASEFORWHICHTHE&-RATEOFTHEAZIMUTHDOPPLER MODULATIONISPROPORTIONALTOTHESQUAREOFTHEAIRCRAFTVELOCITY7HYTHEDIFFERENCE 2ATHERTHANASTRAIGHTLINE WHICHISTHEBASELINESITUATIONFORANAIRBORNESYSTEM THE SYNTHETICAPERTUREOFASPACE BORNE3!2ISFORMEDALONGANARC4HISIMPOSESASMALL BUTSIGNIFICANTINCREASEINTHEEFFECTIVELENGTHOFTHESYNTHETICAPERTUREANDALSOMODI FIESTHE&-RATE!SACONSEQUENCE THENOMINALSINGLE LOOKAZIMUTHRESOLUTIONFROM ASPACE BASED3!2ISR!Z 6"EAM 63# $!Z RATHERTHANTHEFAMOUShONEHALFOFTHE APERTURELENGTHvOFAIRBORNE3!2S.OTETHAT6"EAMISALWAYSSMALLERTHANTHESPACE CRAFT VELOCITY AND DECREASES WITH INCREASING SPACECRAFT ALTITUDE AND INCIDENT ANGLE !LERT)NCERTAIN3!2PROCESSINGLITERATURE THEEFFECTIVEVELOCITYFORTHEORBITALCASEIS DENOTEDhRADARVELOCITY vARATHERMISLEADINGANDINAPPROPRIATETERM 4HE AVERAGE DATA RATE FROM SPACE BASED 3!2S IN %ARTH ORBIT IS ON THE ORDER OF -BS MEGABITSPERSECOND WITHHIGHERRESOLUTIONANDPOLARIZATIONDIVERSITYSYS TEMSGENERATINGSEVERALTIMESTHAT4HEDRIVERSARETHESPACECRAFTVELOCITY^KMS RANGERESOLUTION ANDSWATHWIDTH-ANYUSERSWOULDLIKETOHAVEIMMEDIATEACCESS TO PROCESSED DATA WHICH LEADS TO THE QUESTION OF ONBOARD PROCESSING 3PACE BASED
30!#% "!3%$2%-/4%3%.3).'2!$!23
£n°Ó£
3!2SYSTEMSASARULEDONOTIMPLEMENTIMAGEFORMATIONONBOARDFORSEVERALREASONS INCLUDINGHIGHDATARATES0ROCESSINGFROMRAW3!2DATATOIMAGERYINCREASESDATA VOLUMESUBSTANTIALLY THUSINCREASINGTHEDOWNLINKDATATRANSFERBURDEN0ERHAPSMORE PERSUASIVE ONCEPROCESSEDINTODETECTEDIMAGES THEOPTIONSARELIMITEDFORSPECIAL IZEDAPPLICATION SPECIFICPOSTPROCESSING )NCONTRASTTOAIRBORNESYSTEMS THEDYNAMICSOFMOSTSPACECRAFTARESUCHTHATNO MOTIONCOMPENSATIONISREQUIREDFORSPACE BASED3!2SUNLESSEXTREMELYFINERESOLU TIONISTOBEGENERATED (OWEVER DETERMININGTHEDOPPLERCENTROIDOFTHEAZIMUTH SPECTRUMWITHRESPECTTOZERODOPPLEREMERGESASADOMINANTISSUE)FTHEAZIMUTH ANTENNABORESIGHTISPERFECTLYORTHOGONALTOTHEINERTIALORBITPLANE THE%ARTHSROTA TIONIMPOSESADOPPLERSHIFTONTOTHERECEIVEDDATA&ROMLOW%ARTHORBIT,%/ THE MAGNITUDEOFTHISSHIFTISONTHEORDEROFn ANDTOFIRSTORDER VARIESSINUSOIDALLY WITHLATITUDE WITHMAXIMUMMAGNITUDEATTHEEQUATOR ANDWITHZEROATTHEEXTREME .AND3LATITUDES4HEEFFECTCANBEOFFSETBYYAW STEERINGTHESPACECRAFTSOTHATTHE ANTENNASBORESIGHTISALWAYSDIRECTEDTOWARDZERODOPPLER4HISORIENTSTHEVERTICAL PLANEOFTHEAZIMUTHBORESIGHTTOBEORTHOGONALTOTHENADIRTRACKONTHESURFACE RATHER THANTOTHEORBITPLANE7HEREAS3!2DATAFROMBOTHARRANGEMENTSCANBEPROCESSED INTOSATISFACTORYIMAGERY MOREDEMANDINGAPPLICATIONSSUCHASRADARINTERFEROMETRY AREBETTERSERVEDBYYAW STEEREDSYSTEMS9AWSTEERINGIMPOSESNEGLIGIBLEADDITIONAL DEMANDSONTHESPACECRAFTATTITUDECONTROLSYSTEM SINCEITREQUIRESMANEUVERSOFONLY onOVEREACHORBITALPERIOD.OTETHATA3!2LOOKSDOWNASWELLASTOTHESIDE SO THATVERTICALVELOCITYCOMPONENTSINTHESATELLITESORBITALSOLEADTODOPPLERSHIFTSIN THEDATA)NPRINCIPLE ADOPPLERSHIFTFROMAVERTICALVELOCITYCOMPONENTALSOCOULDBE OFFSETBYATTITUDEADJUSTMENTSOFTHESPACECRAFT ALTHOUGHTHISSTRATEGYISNOTINGENERAL PRACTICE$OPPLERCENTROIDESTIMATIONISACENTRALFUNCTIONIMPLEMENTEDINALLPROCESS INGALGORITHMSFOR3"23!2DATA $ATA0RODUCTS 4HENOTIONALDATAPRODUCTFROMASPACE BASED3!2ISIMAG ERY USUALLYVISUALIZEDASABLACK AND WHITEMAPPINGOFTHESCENEILLUMINATEDBY THERADAR"YDEFINITION THEDIGITALNUMBERSATEACHPIXELINSUCHANIMAGEARRAY AREREALANDNON NEGATIVE)NTHEORY THESENUMBERSCORRESPONDTOTHEMAGNITUDE SQUARED OF THE FOCUSED AND DETECTED BACKSCATTERED FIELD )N PRACTICE MOST IMAGE PRODUCTSSUCHASTHOSEFROMTHE%UROPEAN3PACE!GENCYS3!2S USEMAGNITUDE BECAUSETHERESULTINGIMAGERYHASANACCEPTABLEAPPEARANCEANDTHESIZEOFTHEDATA FILEISSMALLERTHANIFIN\MAGNITUDE\)FSEVERALDATASETSOVERTHESAMESCENEARE COMBINED OFTEN THESE ARE INDIVIDUALLY COLOR CODED LEADING TO MULTICOLOR IMAGE PRODUCTS%ACHCONSTITUENTDATASETMIGHTBEFROMADIFFERENTPOLARIZATION WAVE LENGTH OROBSERVATIONTIME )TISCOMMONPARLANCETOREFERTOIMAGERYASMAPPINGSOFTHENORMALIZEDBACKSCAT TERPOWERRX Y !LERT)NFACT THISISSELDOMIFEVERTRUE"ACKSCATTEREDPOWERIS PROPORTIONALTO\MAGNITUDE\ NOTMAGNITUDE(ENCE THEUSERMUSTASSURETHATTHEDATA AREINDEEDMAGNITUDE SQUAREDBEFOREAPPLYINGTOOLS SUCHASSPECKLEFILTERS THATARE DESIGNEDFORRDIMENSIONALITY3ECOND RIMPLIESTHATTHEDATAARECALIBRATED NOT ONLYWITHRESPECTTOTHERADIOMETRICPARAMETERSOFTHERADARANDPROCESSOR BUTALSO WITHRESPECTTOTHELOCALINCIDENTANGLEATTHEPIXELLOCATIONX Y !LTHOUGHDATAFROM %23 ARECORRECTEDTOACCOUNTFORTHEMEANINCIDENCEWITHINTHEIMAGEDSWATH THEREISNOATTEMPTTOCORRECTFORSLOPESLOCALLYWITHINTHESWATHTOTHEPIXELLEVEL!N ALTERNATIVEISTODENOTETHEMAGNITUDE SQUARED DIGITALNUMBERSASA WHICHINDICATES SIMPLYRADARPOWERPERPIXEL4HISHASBECOMESTANDARDPRACTICEWITH2!$!23!4 DATA FOREXAMPLE
£n°ÓÓ
2!$!2(!.$"//+
3TANDARDIMAGEPRODUCTSUSUALLYAREhMULTI LOOKv)NJARGONCOMMONINTHESPACE BASED3!2FIELD hLOOKSvREFERTOSTATISTICALLYINDEPENDENTVERSIONSOFTHESAMESCENE 7HEN THESE ARE ADDED TOGETHER THE NET RESULT IS TO REDUCE THE SPECKLE NOISE WHILE REINFORCINGTHEIMAGEDFEATURES%ACHSUCHLOOKISFORMEDFROMASPECTRALBANDTHAT DOES NOT OVERLAP SPECTRA CORRESPONDING TO THE OTHER LOOKS4HUS FOR A GIVEN BAND WIDTH INCREASINGTHENUMBEROFLOOKSREDUCESSPECKLE BUTATTHECOSTOFCOMPROMISING RESOLUTION-OREONTHISTRADE OFFMAYBEFOUNDIN3ECTION )NCONTRASTTOCONVENTIONALPOST DETECTIONIMAGERY FOCUSED3!2DATAMAYBEPRE SENTEDASSINGLE LOOKCOMPLEX3,# PRODUCTS4HESEDATARETAINTHEFULLRESOLUTIONOF THERADAR ANDMOSTIMPORTANT RETAINTHERELATIVEPHASEOFTHEBACKSCATTEREDFIELD"Y DEFINITION 3,#FILESAREINAMPLITUDEANDPHASE OFTENREPRESENTEDASANARRAYOFIN PHASE) ANDQUADRATURE1 SIGNEDNUMBERPAIRS ATEACHPIXEL3,#DATAAREREQUIRED FOR3!2INTERFEROMETRY POLARIMETRY ANDCOHERENTCHANGEDETECTION 0USHING!MBIGUITY,IMITS 4HEBASELINESINGLE LOOK3!2AZIMUTHRESOLUTION ISPROPORTIONALTOONEOVERTHEDOPPLERBANDWIDTHGENERATEDBYTHEAZIMUTHBEAM WIDTHOFTHESIDE LOOKINGANTENNA4HECORRESPONDINGLENGTHOFTHESYNTHETICAPERTURE ISEQUIVALENTTOTHEALONG TRACKSPREADOFTHEANTENNAPATTERN WHICH OFCOURSE IS PROPORTIONAL TO RANGE ,ET THIS BE THE CANONICAL CASE!ZIMUTH RESOLUTION MAY BE SHARPENEDONLYBYINCREASINGDOPPLERBANDWIDTH WHICHCANBEDONEINONEOFTWO WAYSINCREASINGTHEANTENNASBEAMWIDTHORINCREASINGTHESPREADOFASPECTANGLES WITHINWHICHTHEANTENNAILLUMINATESAGIVENPORTIONOFTHESCENE4HELATTERISTHE BASISFOR3POTLIGHT3!2 oINWHICHTHEANTENNAISSTEEREDTODWELLONTHEINTENDEDAREA ASTHERADARPASSES THUSCREATINGAWIDERTOTALDOPPLERBANDWIDTHANDALONGERSYN THETICAPERTURE 4HETRADE OFFISTHATADJACENTAREASALONG TRACKMAYNOTBEIMAGED AT ALL )NCREASING AZIMUTH RESOLUTION BY BROADENING THE ANTENNA PATTERN EITHER BY REDUCINGTHEAPERTURELENGTHORSPOILINGTHEBEAM HASTHEDISADVANTAGEOFREDUCING THEANTENNASGAIN WHICHUSUALLYISNOTDESIRABLEFORSPACE BASED3!2S)NADDITION THE02&MUSTBELARGERTHANTHEINSTANTANEOUSDOPPLERBANDWIDTH THUSREDUCINGTHE ALLOWABLEUNAMBIGUOUSRANGESWATH 'OINGTHEOTHERDIRECTIONSMALLERDOPPLERBANDWIDTHLEADSTOMORECOARSEAZI MUTHRESOLUTION4HEDOPPLERBANDWIDTHOFTHEORIGINALSIGNALHISTORYFROMAGIVEN BACKSCATTERER MAY BE REDUCED BY THE SIMPLE EXPEDIENT OF GENERATING A SHORTER SYN THETICAPERTURETHANTHECANONICALCASE4HISLOGICLEADSTOTHEhBURSTMODE vWHICH FIGURESPROMINENTLYINTWOFORMSINSPACE BASED3!2S"URSTMODEALONGASINGLE IMAGEDSWATHIMPLIESAREDUCEDDATARATE WHICHMAYBENECESSARYTOMEETTHESTRIN GENTDATA RATEREQUIREMENTSCONFRONTINGPLANETARYORLUNARMISSIONS!LTERNATIVELY THE INTERVALSBETWEENBURSTSMAYBEUSEDTOILLUMINATESEVERALDIFFERENTRANGESWATHS THUS EXPANDINGTHEAREATHATMAYBEIMAGEDUNAMBIGUOUSLY4HISISTHEPRINCIPLEBEHIND THE3CAN3!2MODE !MBIGUITY3PACE4RADE OFFS )TISEASYTOSHOWTHATTHESERESOLUTIONANDCOVERAGE OPTIONSARECONSISTENTWITHTHEPRINCIPLESTHATGOVERNRANGEANDAZIMUTHAMBIGUITIES 4HEFUNDAMENTALRULEISTHATTHEIMAGESPACEILLUMINATEDBYTHEANTENNA MUSTBE hUNDERSPREADvIFAMBIGUITIESARETOBEAVOIDED4HEUNDERSPREADCONDITIONISTHAT
o!LTERNATIVELYKNOWNAS3POT3!2
42 "$OP
30!#% "!3%$2%-/4%3%.3).'2!$!23
£n°ÓÎ
WHERE42ISTHESLANT RANGESWATHDEPTHOFTHEANTENNAPATTERNAND"$OPISTHECOR RESPONDINGDOPPLERBANDWIDTH4OFIRSTORDER THEAZIMUTHRESOLUTIONISGIVENBY
R!Z
A 2. , 3 !Z "$OP
WHEREAISTHEAZIMUTHBEAMWIDTH 2ISSLANTRANGE .,ISTHENUMBEROFLOOKSHERE ASSUMED TO BE TAKEN IN THE AZIMUTH DOMAIN AND 4!Z "$OP IS THE AZIMUTH TIME BANDWIDTHPRODUCT COMPRISEDOFTHEILLUMINATIONTIMEOFTHETARGET ANDITSDOPPLER BANDWIDTH3UBSTITUTINGFORDOPPLERBANDWIDTHINTHEUNDERSPREADCONDITIONLEADSTO THECONSTRAINT
42 A 2. , 3 !Z R!Z
WHICHSHOWSHOWRESOLUTIONANDTARGETILLUMINATIONTIMEMAYBETRADEDAGAINSTEACH OTHERWHILESTILLRESPECTINGTHEFUNDAMENTALAMBIGUITYCONSTRAINT4HEFOLLOWINGFOUR CASESAREIMPORTANTINPRACTICE 3TRIP-AP 4HESTANDARDAPPROACHISSTRIPMAPPING INWHICHTHEAMBIGUITY FREE SPACEISNEARLY FILLEDWITHTHEALLOWABLESWATH RESOLUTION ANDNUMBEROFLOOKS/F COURSE AZIMUTH RESOLUTIONCANBEINCREASEDWITHINTHEALLOWEDSPACEATNOLOSSOF SWATHWIDTHIFTHENUMBEROFLOOKSISDECREASEDINPROPORTION 3POT3!2 )F AZIMUTH RESOLUTION IS THE DRIVING OBJECTIVE THEN R!Z MAY BE REDUCEDASLONGASTHEINTEGRATIONTIME4!ZISINCREASEDINPROPORTION'IVENTHATTHE BEAMWIDTHOFTHEANTENNAISFIXED THEINTEGRATIONTIMECANBEINCREASEDONLYIFTHE BEAM IS POINTED TO MAINTAIN ILLUMINATION OF THE DESIRED TARGET MUCH AS A SPOTLIGHT FROMAMOVINGVEHICLEDWELLSONANAREAOFINTEREST4HEUSUALCONSEQUENCEOFFINE RESOLUTIONIN3POT3!2MODEISSMALLERRANGESWATHANDANAZIMUTHSIZETHATISLIMITED ABOVEBYTHEWIDTHOFTHEANTENNASFOOTPRINT4HEREQUIREDSTEERINGRATEISRELATIVELY SLOW TYPICALLYAFEWDEGREESOVERAFEWSECONDS IMPLEMENTEDEITHERBYMOVINGTHE ANTENNABEAMORBYYAW STEERINGTHESPACECRAFT.OTETHATTHERADARS02&NEEDSTO BEONLYABOVETHE.YQUISTLIMITSETBYTHEANTENNABEAMWIDTH NOTBYTHETOTALSPAN OFDOPPLERFREQUENCIESCOLLECTED2ANGERESOLUTIONISIMPROVEDINTHEUSUALWAY BY INCREASINGTHERADARSBANDWIDTH FORWHICHTHE3TRETCHTECHNIQUEISOFTENHELPFUL! VARIATIONOFTHISMODE3LIP3!2 ISTODRAGTHEANTENNAFOOTPRINTRATHERTHANTOSTAREAT ONEAREA THUSTRADINGPOORERAZIMUTHRESOLUTIONTHANAPURE3POT3!2WOULDDELIVER TOGAININCREASEDAZIMUTHALCOVERAGE (OW FAR CAN THIS BE PUSHED 5NDER THE ASSUMPTION THAT A TARGETS SCATTERING IS COHERENTOVERAFULLnSECTOR ITCANBESHOWNTHATTHEULTIMATEAZIMUTHRESOLU TIONISK"YTHEWAY SUCHPHENOMENALRESULTSHAVEBEENAPPROACHEDINTHEFIELD OFSEISMOLOGY "URST-ODE )FAVERAGEDATARATEISTHEDRIVINGCONSIDERATION THENTHEINTEGRA TIONTIME4!ZMAYBEREDUCEDBELOWTHECANONICALLIMITSETBYTHEAZIMUTHANTENNA BEAMWIDTH4HISISACCOMPLISHEDBYTURNINGOFFTHETRANSMITTERAFTERENOUGHPULSES HAVEBEENCOLLECTEDTOSATISFYTHEAZIMUTHRESOLUTIONREQUIREMENT%ACHSUCHBURSTHAS ANINSTANTANEOUSDOPPLERCORRESPONDINGTOTHEANTENNABEAMWIDTHWHICHDETERMINES THE.YQUIST02&LIMIT BUTASHORTERSYNTHETICAPERTURELENGTH"URSTMODEISSTANDARD
£n°Ó{
2!$!2(!.$"//+
OPERATINGPROCEDUREFORPLANETARYORLUNARRADARS FORWHICHHIGHIMAGERESOLUTIONIS NOTREQUIREDANDTHESPACECRAFT TO %ARTHDATALINKISSEVERELYLIMITED7HILEINBURST MODE ITISCUSTOMARYTOUSEEACHBURSTASASINGLE LOOKDATATAKE SETTINGTHEBURSTREP ETITIONFREQUENCYSOTHATTHEDESIREDNUMBEROFLOOKSISCOLLECTEDDURINGTHESYNTHETIC APERTURELENGTHOFTHEAZIMUTHBEAMPATTERN4HECHALLENGEISTOCALIBRATETHEANTENNA PATTERNSUCHTHATTHEFRAMELETSFROMALLBURSTSMAYBECOMBINEDTOASSEMBLEACONTINU OUS IMAGE ALONG TRACK -ISMATCHES APPEAR AS hSCALLOPINGvSYSTEMATIC BRIGHTNESS MODULATIONSATBOUNDARIESBETWEENEACHOFTHEFRAMELETS 3CAN3!2n )FSWATHWIDTHISTHEDRIVINGREQUIREMENT THENAZIMUTHRESOLUTION CANBETRADEDFORRANGECOVERAGE4HETRICKISTOMULTIPLEXSEVERALBURST MODEDATA SETS WHEREEACHSETOFBURSTSCORRESPONDSTOADIFFERENTRANGESUB SWATH)NTHISFORM OFBURSTMODE THETRANSMITTERISALWAYShONvTHEBURSTRANGESUB SWATHALLOCATION BURDENFALLSONTOTHEANTENNA3CAN3!2REQUIRESRAPIDELEVATIONBEAMSTEERING SUCH ASTHROUGHAPHASEDARRAYEG 4ERRA3!2 8 ORSELECTIONOFONEAMONGSEVERALRANGE OFFSETFEEDSFACINGAREFLECTOREG (* # )NADDITIONTOSUPPRESSINGSCALLOPING GOOD3CAN3!2IMAGERYREQUIRESTHATTHESEVERALRANGESUB SWATHSBEKNITTEDTOGETHER SUCH THAT THE CROSSOVERS BETWEEN ANTENNA PATTERNS ARE NOT EVIDENT 2!$!23!4 WASTHEFIRSTMISSIONTOIMPLEMENTTHENTOPERFECT OPERATIONAL3CAN3!2 WHICHHAS BEENADOPTEDASASTANDARDMODEONMANYSPACE BASED3!2S3WATHWIDTHSACHIEVED AREASMUCHASFIVETIMESTHENOMINALSTRIP MAPWIDTH WHICHISCONSIDERABLYLARGER THANTHECONVENTIONALAMBIGUITYCONSTRAINTWOULDALLOW.ORMALLY THETRADE OFFIN AZIMUTHRESOLUTIONISBALANCEDWITHACORRESPONDINGCOMPROMISEINRANGERESOLUTION LEAVINGEXCESSRANGEBANDWIDTHTHATMAYBECONVERTEDINTOLOOKS3TARTINGFROMA KMSWATH Mr M LOOKSYSTEM AREASONABLE3CAN3!2MODECOULDBE KMSWATH Mr Mr LOOKS WITHNOINCREASEINAVERAGEDATARATEOR TRANSMITTEDPOWER .OTE THAT ALL OF THESE AMBIGUITY SPACE TRADES START WITH THE CANONICAL CASE 4HE TRADE OFFS ARE RELATIVE TO THAT STARTING POSITION! RADAR HAVING AN INHERENTLY SMALL RANGESWATH FOREXAMPLE WOULDREQUIRE3CAN3!2TOEXPANDTHERANGESWATHTOAFEW TENSOFKM WHICHMAYSTILLBEMUCHLARGERTHANTHESAMERADARCOULDCOVERWITHOUT AMBIGUITIESINASTRIP MAPMODE -ULTIPLE #HANNELS )NTERFEROMETRY AND 0OLARIZATION 0HASE COMPARISON BETWEENTWOORMOREMUTUALLYCOHERENTDATASETSLEADSTORICHNEWPOSSIBILITIES ESPE
CIALLY INCLUDING INTERFEROMETRY AND POLARIMETRY 4HIS IS PARTICULARLY RELEVANT TO SPACE BASED3!2S WHICHHAVEBEENANDWILLCONTINUETOBERICHSOURCESOFQUANTITA TIVEMICROWAVEMEASUREMENTSOFAWIDEVARIETYOFSURFACEFEATURES ENABLEDBYTHESE MULTICHANNELCAPABILITIES4HEFOLLOWINGPARAGRAPHSPROVIDEONLYAGLIMPSEINTOTHESE TOPICSTHEDISCUSSIONISMEANTTOWHETTHEAPPETITEOFTHEREADERANDTOPROVIDELEADS TOTHEVOLUMINOUSLITERATURE )NTERFEROMETRY )NTERFEROMETRYBYRADAR&IGURE IMPLIESMEASUREMENTSTHAT AREBASEDONPHASEDIFFERENCESSENSEDTHROUGHTWODIFFERENTOBSERVATIONSOFTHESAME PHENOMENAn0HASEDIFFERENCESARISEFROMMICROWAVE SCALECHANGESTHATAREDUE EITHERTODIFFERENTIALVIEWINGASPECTORTOELEMENTSOFMOTIONINTHESCENE)NGENERAL TERMS THESENSITIVITYOFPHASEMEASUREMENTSDEPENDSTOFIRSTORDERON THERADARS WAVELENGTH THE SPATIAL OR TEMPORAL BASELINE OF THE CONTRIBUTING DATA SETS AND THESCALEOFSPATIALORTEMPORALDIFFERENTIALSIGNALS4HEINTERFEROMETRICBASELINE INCREASESWITHRANGEANDWITHPLATFORMVELOCITY)TFOLLOWSTHATFORSPACE BASEDRADARS
30!#% "!3%$2%-/4%3%.3).'2!$!23
£n°Óx
&)'52% 2ADARINTERFEROMETRYEXPRESSESTHEINTERFERENCECREATEDBETWEENTWOMUTUALLY COHERENTBACKSCATTEREDFIELDS4HEPHASEDIFFERENCEINTERFEROGRAMMODULOO CORRESPONDSTO THERELATIVEELEVATIONOFTHEILLUMINATEDTERRAINAFTERREMOVALOFTHESYSTEMATICSLANT RANGEAND %ARTH CURVATURESIGNATURES
CONVENTIONALINTERFEROMETRIC3!2MEASUREMENTSFROMONESPACECRAFTPLATFORMUSUALLY ARENOTPRACTICAL SINCETHEIMPLIEDSPATIALORTEMPORALSEPARATIONSOFTHEMEASUREMENTS AREMUCHLARGERTHANONESATELLITECOULDSUPPORT!NALERTREADERMAYNOTETHEOBVIOUS EXCEPTIONTOTHISRULE 324-DESCRIBEDPREVIOUSLY WHICHMOUNTEDITSSECONDINTER FEROMETRICANTENNAONA MEXTENDABLESTRUT 3ATELLITEORBITSTENDTOBEWELL KNOWN ANDFOLLOWVERYSIMILARTRAJECTORIESOVER SUBSEQUENT REPEAT PERIODS )T FOLLOWS THAT THE SPACE BASED ENVIRONMENT OFFERS AN ATTRACTIVEALTERNATIVEREPEAT PASSINTERFEROMETRY ORIGINALLYSUGGESTEDBY'OLDSTEIN )FTHEPASS TO PASSOBSERVATIONSARESEPARATEDINTHEVERTICALPLANE THENINTERFEROM ETRY LEADS TO RELATIVE TERRAIN HEIGHT ESTIMATION )F TWO OBSERVATIONS HAVE A TIME DELAYCORRESPONDINGTOTHEREPEATPERIODOFTHEORBITTYPICALLYTODAYS THEN SUB WAVELENGTHMOVEMENTSINTHELINE OF SIGHTDIRECTIONOFTHERADAR MAYBEMEA SURED4HETECHNIQUECANBEEXTENDEDTOMULTIPLEPASSESWITHPROPORTIONATEINCREASE INTHETEMPORALBASELINE LEADINGTOQUITEREMARKABLERESULTS2EPEAT PASSTECHNIQUES AREWELLSUITEDTOMAPPINGTOPOGRAPHICRELIEFANDTOLONG TERMCOHERENTCHANGEDETEC TIONFORMAPPINGGLACIERMOVEMENTORTERRESTRIALSUBSIDENCE)FSHORTERTIMESCALES AREOFINTEREST TODETECTMOVINGVEHICLES FOREXAMPLE'-4) THENASHORTERINTER FEROMETRICBASELINEISREQUIRED WHICHIMPLIESTWOORMORE 3"2SINRELATIVELYTIGHT CO ORBITINGFORMATION 4HE BASIC 3!2 INTERFEROMETRIC ENVIRONMENT IS ONE IN WHICH THERE IS A PAIR OF MUTUALLYCOHERENTIMAGESTHATHAVEEMBEDDEDPHASESTHATDEPENDONTHEDETAILSOF VIEWINGGEOMETRYANDSCENESTRUCTURE4HECOHERENTLYCOMBINEDIMAGESAREKNOWN AS AN INTERFEROGRAM WHICH TYPICALLY CONTAINS FRINGES THAT EXPRESS THE INTERACTIONS BETWEEN THE PHASE STRUCTURE OF THE TWO DATA SETS 3IGNAL PROCESSING IS DESIGNED TO ESTIMATETHESEPHASEDIFFERENCES ANDTODEDUCEGEOPHYSICALPARAMETERSOFINTEREST FROMTHERESULTINGMEASUREMENT 4HEINTERFEROMETRICSIGNALMODELISSIMPLEINCONCEPT&ORANYNEIGHBORHOODINTHE SCENE THEINPUTSIGNALPAIRMAYBEDESCRIBEDBY
S T ' A EXP; JJ =
£n°ÓÈ
2!$!2(!.$"//+
AND
S T ' A EXP; JJ J$J R T T =
WHERETHESUBSCRIPTSONTHEREFLECTIVITY'SUGGESTTHATTHETWOSIGNALSMAYBEOBTAINED ATTWODIFFERENTPOINTSINTIMEASWELLASFROMTWODIFFERENTSPATIALPERSPECTIVES4HE OBJECTIVEISTOESTIMATETHERELATIVEPHASEDIFFERENCE$I USUALLYFOUNDTHROUGHTHE CROSS CORRELATION
%;S T S T = 2 T T A EXP; J$J R T T =
WHICHISPRESENTEDASITWOULDBECALCULATEDUSINGCOMPLEXIMAGEDATA(ERE %;=IS THEEXPECTATIONAVERAGING OPERATOR4HEPHASEDIFFERENCE$IMAYBEDUEEITHERTO GEOMETRICORTOTEMPORALDIFFERENCESBETWEENTHETWOOBSERVATIONS3UCCESSFULINTER FEROMETRYDEPENDSONTHECROSSCORRELATION2T T OFTHESCATTERINGFUNCTIONS'TAND 'T4HENORMALIZEDCROSS CORRELATIONFUNCTIONISTHEMUTUALCOHERENCEFUNCTION
G T T
2 T T %;\S \ = %;\S \ =
INPARALLELTOTHATENCOUNTEREDINPHYSICALOPTICS'AMMAISAQUANTITATIVEMAPPING OFTHECOHERENCEBETWEENTHETWOOBSERVATIONS)NGENERAL SCENECOHERENCEDECREASES WITHSHORTERWAVELENGTHANDLONGERTIMEBETWEENOBSERVATIONS -UTUAL COHERENCE IS AN ESSENTIAL INGREDIENT FOR RADAR INTERFEROMETRY #OHERENCE IMPLIESTWOCONSTRAINTSSPATIALANDTEMPORAL4HESPATIALCONSTRAINTAPPLIESTOTHESPAC INGBETWEENTHEORBITALPASSES)DEALLY THERADARWAVELENGTHPROJECTEDONTOEACHAREA OFTHESURFACEMUSTBETHESAMEFROMBOTHORBITS3INCETHETWOORBITSARESEPARATED EACHAREAISOBSERVEDATASLIGHTLYDIFFERENTINCIDENTANGLE4HISIMPLIESTHATTHEEFFEC TIVEWAVELENGTHPROJECTEDONTOTHEGROUNDPLANEISSLIGHTLYDIFFERENTFORTHETWOCASES )NTERFERENCEISSUPPORTEDONLYIFTHERANGEBANDWIDTHOFTHERADARSIGNALISSUFFICIENTTO SPANTHEPROJECTEDWAVELENGTHS WHICHBECOMESMOREDEMANDINGASTHEORBITSEPARA TIONINCREASES&ORTUNATELY THERANGEPULSEHASSUFFICIENTBANDWIDTHUSUALLYMORE THAN-(Z SOTHATMUTUALLYCOHERENTRANGEBANDWIDTHSCANBECHOSENFROMTHEDATA ATTHETIMEOFPROCESSING,OSSOFMUTUALCOHERENCETHROUGHINCREASINGORBITSPACING ISKNOWNASBASELINEDECORRELATION/NEMAYSHOWFORREASONABLYLEVELTERRAINTHAT THEUPPERBOUNDCONSTRAINTONTHEDIFFERENCE$P2ADINELEVATIONANGLEBETWEENTHETWO ORBITSIS $P 2AD L TANP 2AD R2 WHERER2ISSLANTRANGERESOLUTION WHICHISINVERSELY PROPORTIONAL TO RANGE BANDWIDTH !LERT )N THE 3!2 INTERFEROMETRIC LITERATURE IT IS CUSTOMARYTOUSEELEVATIONANGLE DEFINEDASTHEANGLEBETWEENTHERADARLINEOFSIGHT ANDTHE%ARTHRADIUSVECTOR ASSEENFROMTHERADAR &ORTYPICALLARGETIME BANDWIDTH PRODUCTSIGNALS THEELEVATIONANGLECONSTRAINTIMPLIESTHATCORRELATIONOFTHEPAIROF RETURNSIGNALSISMAINTAINEDFORORBITALSEPARATIONSONTHEORDEROFAKILOMETER&OR ABSOLUTEELEVATIONMAPSTOBEDERIVED HOWEVER PRECISEKNOWLEDGETOTHELEVELOFONE METERISREQUIREDOFTHESPATIALSEPARATIONBETWEENOBSERVATIONTRACKS 4EMPORALCOHERENCEAPPLIESPRIMARILYTOTHESCENE)NORDERFORTHETWOSIGNALSTO ACTASANINTERFEROMETRICPAIR THEIRRESPECTIVEPHASESTRUCTURESMUSTBERELATIVELYSTABLE OVERTHETIMEINTERVALBETWEENSATELLITEOBSERVATIONS)NSHORT THEREMUSTEXISTMUTUAL COHERENCEBETWEENTHETWOSCATTERINGSIGNALS EVENTHOUGHTHEYAREOBSERVEDATDIFFER ENTTIMES4HISREQUIREMENTISREADILYSATISFIEDFORSHORTINTEROPPORTUNITYINTERVALS SUCH
30!#% "!3%$2%-/4%3%.3).'2!$!23
£n°ÓÇ
ASFROMTHETHREE DAYREPEATORBITFIRSTUSEDWITH3EASATDATATOPROVETHECONCEPTAND FORSTABLETERRAINFEATURES SUCHASUNVEGETATEDROCKYMOUNTAINSLOPES)TISNOTNECES SARILYSATISFIEDFORSCENES SUCHASICEORVEGETATION THATMAYUNDERGOCHANGESINTHE DETAILSOFREFLECTIONANDSCATTERINGBETWEENOBSERVATIONS )NCERTAINNATURALANDMOSTURBANSCENES THEREWILLBEMANYCORNER REFLECTOR SHAPED FEATURESWHOSEPHASEREMAINSSTABLEOVERVERYLONGTIMESCALES4HESESO CALLEDPER MANENTORPERSISTENT SCATTERERSSUPPORTDIFFERENTIALINTERFEROMETRICMEASUREMENTS THATMAYSPANMANYREPEATVISITSOFTHERADAR LEADINGTOREMARKABLESENSITIVITYTOSLOW MOTION PHENOMENA &OR EXAMPLE MULTIFRAME $)N3!2p ANALYSIS OF 2!$!23!4 DATAHASLEDTOMAPSOF.EW/RLEANSSUBSIDENCERATES WHICHVARYFROM^MMYTO MORETHANMMY WITHASENSITIVITYONTHEORDEROFMMY !NYAPPROACHTOPHASEDIFFERENCEMEASUREMENTISSUBJECTTOTHEFUNDAMENTALO AMBIGUITYCHARACTERISTICOFPHASEESTIMATIONALGORITHMS )NMANYRADARSITUATIONS KNOWLEDGEOFTHEPHYSICALCONSTRAINTSOFTHESITUATION COUPLEDWITHPHASEUNWRAPPING ALGORITHMS ISSUFFICIENTFORTHEPURPOSE 0OLARIMETRY &ORANYGIVENPOLARIZATIONOFTHETRANSMITTEDWAVE THEREFLECTIVITY PROCESSINGENERALWILLGIVERISETOADIVERSITYOFPOLARIZATIONSINTHEBACKSCATTERED WAVE4OOBSERVETHESE THERADARMUSTBEDUAL POLARIZED3IMILARLY THEREFLECTIVITY ISAFUNCTIONOFTHEPOLARIZATIONOFTHETRANSMITTEDWAVE4HUS IFTHESCATTERINGFUNC TIONITSELFISTOBEFULLYCHARACTERIZED TWOORTHOGONALPOLARIZATIONSMUSTBETRANSMIT TEDASWELL)NCREASINGLY POLARIMETRICDIVERSITYISBEINGIMPLEMENTEDINSPACE BASED 3!2S )MPLEMENTATIONOFAFULLYPOLARIMETRICRADARALWAYSIMPLIESGREATERDATA CHANNELCAPACITY MORETRANSMITTEDPOWER ANDLESSRANGESWATHCOVERAGE/FCOURSE THEANTENNATHERADARShPOLARIZATIONGATEWAYvMUSTBEABLETORECEIVE ANDPOS SIBLYALSOTOTRANSMIT ONMORETHANONEPOLARIZATION )N GENERAL TERMS THERE ARE FOUR OPTIONS AVAILABLE FOR POLARIMETRIC DIVERSITY IN A SPACE BASED3!24HESEARE 3INGLE MONOSTATIC POLARIZATION 4YPICAL OF ALL DEDICATED SPACECRAFT 3!2S UNTILTHELAUNCHOF%.6)3!4 WITHEITHER((OR66POLARIZATIONS4HISCUSTOM ARYNOTATIONINDICATESHORIZONTALORVERTICALLINEAR POLARIZATIONSONBOTHTRANS MISSIONANDRECEPTIONFORTHESESINGLE POLARIZEDRADARS $UALPOLARIZATION 4HETRADITIONALDEFINITIONISTRANSMISSIONONONEPOLARIZATION USUALLY LINEAR SUCH AS ( AND RECEPTION ON THE LIKE POLARIZED AND THE CROSS POLARIZEDCOMPONENTSSUCHAS(AND6 )NATRADITIONALDUAL POLARIZEDRADAR THE RELATIVEPHASEBETWEENTHETWOPOLARIZEDDATASETSISDISCARDED)N%ARTH ORIENTED REMOTE SENSING RADARS TYPICAL COMBINATIONS INCLUDE (( AND (6 FOR EXAMPLE OR((AND66WHICHREQUIRESTWOSEPARATETRANSMITPOLARIZATIONS 4HE!3!2 ABOARD %.6)3!4 IS THE FIRST SPACE BASED EXAMPLE OF THIS TYPE OF POLARIZATION DIVERSITY )F THE FOUR LINEAR POLARIZATION POSSIBILITIES ARE EXPLOITED NONCOHER ENTLY THENTHEBACKSCATTERINGFUNCTIONOFTHESCENEMAYBECHARACTERIZEDBYTHE THREEBACKSCATTERCOEFFICIENTSR(( R6( R66 WHICH OFCOURSE AREDEVOIDOF PHASE.OTETHATRECIPROCITYIMPLIESTHATR(6 R6( #OHERENT DUAL POLARIZATION ! DUAL POLARIZED RADAR THAT RETAINS THE RELATIVE PHASE BETWEEN THE TWO RECEIVED POLARIZATIONS IS A SIGNIFICANT DEPARTURE FROM TRADITIONALDUAL POLARIZEDSYSTEMS4HEMODIFIERhCOHERENTvHELPSTODISTINGUISH p$IFFERENTIALINTERFEROMETRICSYNTHETICAPERTURERADAR
£n°Ón
2!$!2(!.$"//+
SUCHRADARSFROMTHEIRMORECOMMONCOUNTERPARTSDESCRIBEDINTHEPRECEDING PARAGRAPH#OHERENTDUALPOLARIZATIONHASNOTBEENEXPLOITEDINORBITAL3!2S ALTHOUGHITISSTANDARDPRACTICEIN%ARTH BASEDRADARASTRONOMYTHROUGHFACILI TIESSUCHASTHE!RECIBORADARTELESCOPE %XPERIENCEHASSHOWNTHATTHEREIS RELATIVELYLITTLEADDEDVALUEINTHEPHASEBETWEENTHELIKE POLARIZEDANDCROSS POLARIZEDRETURNSUNDERTHECONDITIONOF(OR6TRANSMITPOLARIZATION(OWEVER ANINNOVATIVEALTERNATIVEISTOTRANSMITCIRCULARPOLARIZATIONANDRECEIVECOHER ENTLYTWOORTHOGONALLINEARLYPOLARIZEDCOMPONENTS3EE3ECTIONFORFUR THERDISCUSSION &ULLORQUADRATUREPOLARIZATION 4HISISTHERICHESTOPTIONBECAUSEITALLOWSFULL CHARACTERIZATIONOFTHECOMPLEXMATRIXOFTHEBACKSCATTERATALLRESOLVEDPOINTSIN THESCENE)THASBEENDEVELOPEDEXTENSIVELYINTHEORYANDINPRACTICEWITHDATA FROMAIRBORNESYSTEMSAND3)2 #*APANS0!,3!2ISTHEFIRSTOPERATIONALSPACE BASEDSYSTEMTOINCORPORATEAQUAD POLMODE 0RIMARYINTERESTINFULLYPOLARIMETRICRADARSDERIVESFROMTHEENRICHEDSCATTERING OBSERVATIONPOSSIBILITIESREVEALEDTHROUGHREPLACEMENTOFTHESCALARFORMOFREFLECTIV ITYBYITSCOMPLEXVECTORCOUNTERPART 4HUS WHENEITHER(OR6POLARIZATIONSARE INCIDENTONASCATTERINGELEMENT BOTHPOLARIZATIONSAREBACKSCATTEREDACCORDINGTO
§%(" ¶ §3(( ¨% " · ¨3 © 6 ¸ © 6(
3(6 ¶ §%(4 ¶
366 ·¸ ¨©%64 ·¸
WHERETHESUPERSCRIPT"DENOTESTHEFIELDCOMPONENTSREFLECTEDBACKTOWARDTHERADAR 4HENEWTERMSOFINTERESTREPRESENTTHESCENESrSCATTERINGMATRIX ANARRAYOFFOUR COMPLEXNUMBERS%ACHELEMENTINTHISBACKSCATTERINGMATRIXEXPRESSESTHEMAGNI TUDEANDPHASEIMPOSEDONTOTHEBACKSCATTEREDFIELDSUPERSCRIPT" INRESPONSETOTHE ILLUMINATIONFROMTHETRANSMITTEDFIELDSUPERSCRIPT4 ACCORDINGTOTHEIRRESPECTIVE POLARIZATIONS4HUS THESCATTERINGMATRIXISAQUANTITATIVEDESCRIPTIONOFTHETRANSFOR MATIONOFPOLARIZATIONSTATEUPONREFLECTION ASWELLASTHEMAGNITUDEANDPHASEOF EACHREFLECTIONCOEFFICIENT)TISOFTENTRUETHATTHEFIELDPOLARIZATIONSARENOTCHANGED DURINGPROPAGATION THEIRROTATIONALASSUMPTION)NTHISCASE THEPOLARIZATIONSOFTHE BACKSCATTERED WAVES ARE EQUIVALENT TO THOSE THAT ARRIVE AT THE RADAR 4HIS PROPERTY CHARACTERIZESMOSTOFTHEPOLARIMETRYLITERATURE ATLEASTINREMOTESENSINGAPPLICATIONS ANDISREFLECTEDINTHESEPARAGRAPHS4HEPRINCIPALEXCEPTIONTOTHISRULEIS&ARADAY ROTATION WHICHMAYBEASIGNIFICANTFACTORFORLONGERWAVELENGTHSYSTEMS SUCHAS0 BANDANDTOALESSEREXTENT,BAND &ORIRROTATIONALPROPAGATION THEPORTIONOFTHEBACKSCATTEREDFIELDCAPTUREDBYTHE
RADARISDETERMINEDBYTHEPOLARIZATIONVECTOROFTHERECEIVINGANTENNA ;% 2=4HESIG NALVOLTAGEVRECENTERINGTHESYSTEMMAYBEWRITTENINVECTOR MATRIXFORMAS
VREC §©%(2
§% " ¶ %62 ¶¸ ¨ (" · ©%6 ¸
4HISISTHESTARTINGPOINTFOR3!2QUADRATUREPOLARIMETRY%SSENTIALLY AQUAD POL 3!2ISMANAGEDSOTHATTHETRANSMITTERGENERATESBOTHORTHOGONALPOLARIZATIONS4HE RESULTINGQUAD POLDATASETCANBETRANSFORMEDTOREPRESENTALLPOSSIBLECOMBINATIONS OFTRANSMITANDORRECEIVEPOLARIZATIONS0ITFALLSAWAITTHEUNWARY HOWEVER INCLUDING TRICKYCOORDINATECONVENTIONS ANINITIALLYCONFUSINGVARIETYOFhSTANDARDvFORMSFOR
30!#% "!3%$2%-/4%3%.3).'2!$!23
£n°Ó
REPRESENTINGTHEDATA ANDSEVERALALTERNATIVEMETHODSFORDATAANALYSIS/NCEMAS TERED HOWEVER QUAD POL 3!2 DATA IS THE UNDOUBTED GOLD STANDARD FOR QUANTITATIVE SCENECHARACTERIZATIONBYANIMAGINGRADAR !SPACE BASEDQUAD POLCAPABILITYIMPLIESASIGNIFICANTCOST4HEDRIVINGREQUIRE MENTISTHATTHEDATAMUSTBEMUTUALLYCOHERENT4HATISRELATIVELYEASYFORTHERECEIVER WHICH ONLY NEEDS TO HAVE TWO CHANNELS THAT CAPTURE SIMULTANEOUSLY THE PHASE AND AMPLITUDE OF TWO ORTHOGONAL POLARIZATIONS OF THE BACKSCATTERED FIELD /N THE OTHER HAND ONLYONEPOLARIZATIONCANBETRANSMITTEDATATIME)LLUMINATINGTHESCENEWITH TWOPOLARIZATIONSREQUIRESTHETRANSMITTERTOBETOGGLEDBETWEENORTHOGONALPOLARIZA TIONSTATES4HISMULTIPLEXEDTRANSMISSIONSCHEMEIMPLIESTHATTHERADARS02&MUSTBE DOUBLEDTOSATISFYTHEMINIMUM.YQUISTSAMPLINGRATESIMULTANEOUSLYFOREACHPAIROF TRANSMISSIONS$OUBLED02&IMPLIESTHATTHEAVERAGERADIATEDPOWERMUSTBEDOUBLED ANDTHEUNAMBIGUOUSRANGESWATHISHALVED BOTHINCOMPARISONTOTHESTANDARDCASE OFTRANSMITTINGONLYONEPOLARIZATION.OTETHATTHEAVERAGEDATARATEISTHESAMEASTHE DUAL POLARIZEDCASE SINCETWICEASMUCHDATAARECOLLECTEDBYAQUAD POLMODEFOR EACHRESOLVEDPOINTINTHESCENE BUTTHESWATHWIDTHISSMALLERBYAFACTOROFTWO #ONSIDERABLEPROGRESSCONTINUESTOBEMADEINTHEDEVELOPMENTOFTOOLSFORQUANTI TATIVEANALYSISOFPOLARIMETRIC3!2DATA7HENINCOMBINATIONWITHINTERFEROMETRIC DATA THEFIELDISKNOWNAS0OL)N3!2 FORWHICHDEDICATEDSPECIALISTMEETINGSARE CONVENED FREQUENTLY!N IMPORTANT METHODOLOGY IS TARGET DECOMPOSITION THROUGH WHICH SPECIFIC BACKSCATTER CLASSES SUCH AS DOUBLE BOUNCE "RAGG OR VOLUME OF A SCENEMAYBESEPARATEDFROMOTHERTYPES THENCESUBJECTEDTOINTERFEROMETRICANALYSIS 5SINGSUCHTECHNIQUES ITISPOSSIBLETOESTIMATETHETOPOGRAPHYOFTHESURFACEBENEATH AVEGETATEDCANOPY FOREXAMPLE !PPLICATIONS 3!2SARETHELARGESTCLASSOFSPACE BASEDREMOTE SENSINGRADARS PRIMARILY AS A RESULT OF THEIR PRACTICAL UTILITY -ANY APPLICATIONS ARE ENERGIZED BY RADARSNATURALABILITYTOOPERATEATNIGHTORTHROUGHCLOUD FOG SMOKE ANDHAZE AND ITSINHERENTSENSITIVITYTOCHANGESWITHINTHESCENEATWAVELENGTHSCALES2ADARIMAG ERYHASPROVENTOBEVALUABLEFORAWIDEVARIETYOFAPPLICATIONS FROMOCEANOGRAPHIC OBSERVATIONS THE THEME THAT MOTIVATED 3EASAT TO MEASUREMENT OF MILLIMETER SCALE DISPLACEMENTSUCHASTHESUBSIDENCEOFURBANAREASORTHESWELLINGOFVOLCANOESPRIOR TOTHEIRERUPTION #ANADASREQUIREMENTTOMAINTAINNEAR CONTINUOUSMONITORINGOFITS NORTHERNANDCOASTALICEISMETPRIMARILYBYTHOUSANDSOFFRAMESOF2!$!23!4DATA PERYEAR)NDIAISTHESECONDLARGESTCONSUMEROFSPACE BASEDIMAGINGRADARDATA USED FORAGRICULTUREANDFORESTMANAGEMENT ANDFORMEASURINGCHANGESINITSALPINEGLA CIERS#OUNTRIESSUCHAS"RAZILGRACEDWITHTROPICALFORESTSRELYONSPACE BASEDRADAR IMAGERY TO MAINTAIN SURVEILLANCE AND TO COMPILE ANNUAL STATISTICS OF DEFORESTATION 3INCERADARIMAGERYISARELIABLEMETHODOFMAPPINGSLICKSONTHEOCEANSSURFACE IT ISTHEPRINCIPALMEANSOFMONITORINGOILSPILLSTHATMAYRESULTFROMAGROUNDEDTANKER ORAVESSELILLEGALLYPUMPINGITSBILGESINACOASTALAREA4HEIMAGINGRADARREFERENCE CITEDEARLIERPROVIDESANEXCELLENTREVIEWOFMANYOFTHESEAPPLICATIONS
£n°ÎÊ / / ,)NITSMOSTGENERALFORM ANALTIMETERISARADARDEVICEDESIGNEDTOMEASURETHEVERTI CALDISTANCEBETWEENTHERADARANDTHESURFACEBELOW)NAIRBORNEAPPLICATIONS THE RESULTINGhALTITUDEvISAMEASUREOFTHECLEARANCEBENEATHTHEAIRCRAFT7HEREASTHE
£n°Îä
2!$!2(!.$"//+
MAIN OBJECTIVE OF A SPACE BASED ALTIMETER IS ALSO TO MEASURE THE DISTANCE BETWEEN THERADARANDTHESURFACE THEMOSTCOMMONAPPLICATIONISDETERMINATIONOFTHELOCAL SEALEVELRELATIVETOTHE%ARTHSGEOID eRATHERTHANTHEHEIGHTOFTHESPACECRAFT4HE REFERENCEFORTHISMEASUREMENTTHEORBITALHEIGHTOFTHESPACECRAFTMUSTBEKNOWN BYOTHERMEANSTOWITHINAFEWCENTIMETERS3EA SURFACEHEIGHTISAFUNCTIONOFMANY GEOPHYSICALPARAMETERS SUCHASCURRENTFLOW AN%L.I¶OEVENT ANDVARIATIONSINTHE OCEANS DEPTH 2ELATIVELY SMALL CHANGES ON THE ORDER OF CM IN MEAN SEA SURFACE HEIGHT MAY CORRESPOND TO SUBSTANTIAL DIFFERENCES IN THE CORRESPONDING GEOPHYSICAL PARAMETERS)TFOLLOWSTHATRANGEMEASUREMENTACCURACYANDPRECISIONARETHEDRIVING REQUIREMENTSFORTHISCLASSOFRADAR4HEACCURACYOFANALTIMETERSHEIGHTMEASUREMENT DEPENDSTOFIRSTORDERONKNOWLEDGEOFTHESPACECRAFTSHEIGHTALONGITSORBITANDON CORRECTIONOFTHEPROPAGATIONDELAYSSUFFEREDBYTHERADARSROUND TRIPWAVEFORM4HE PRECISIONOFANOCEAN VIEWINGALTIMETERISPROPORTIONALTOTHERADARSRANGERESOLUTION ANDINVERSELYPROPORTIONALTOTHESQUAREROOTOFTHENUMBEROFSTATISTICALLYINDEPENDENT MEASUREMENTS LOOKS COMBINED FOR EACH DATA POINT /CEAN VIEWING ALTIMETERS IN GENERAL HAVELARGE3.24HUS BANDWIDTHANDLOOKSBECOMETHEDRIVINGREQUIREMENTS ONSYSTEMDESIGN4HEEMPHASISINTHISSECTIONISONALTIMETERPRECISION 3EA SURFACEHEIGHTMEASUREMENTSHAVEBECOMEESSENTIALFORAWIDEVARIETYOFAPPLI CATIONSINOCEANOGRAPHY GEODESY GEOPHYSICS ANDCLIMATOLOGY7ITHTHEEXCEPTION OFNEAR POLARICE %ARTH ORBITINGOCEANOGRAPHICALTIMETERSHAVESEENRELATIVELYLITTLE APPLICATIONOVERNONAQUATICSURFACES ! SATELLITE BASED ALTIMETER SYSTEMATICALLY CIRCLES THE %ARTH GENERATING SURFACE HEIGHTMEASUREMENTSALONGITSNADIRTRACK4HESEMEASUREMENTSACCUMULATE PROVID INGUNIQUESYNOPTICDATATHATHAVEREVOLUTIONIZEDOURKNOWLEDGEANDUNDERSTANDING OFBOTHGLOBALANDLOCALPHENOMENA FROM%L.I¶OTOBATHYMETRY3"2ALTIMETERDATA ALSOPROVIDEMEASUREMENTSOFSIGNIFICANTWAVEHEIGHTANDWINDSPEED!LTHOUGHONE MIGHT CONSIDER ALTIMETERS TO BE RELATIVELY SIMPLE ONE DIMENSIONAL RANGE MEASURE MENT INSTRUMENTS THEIRPHENOMENALACCURACYANDPRECISIONREQUIRESELEGANTMICRO WAVEIMPLEMENTATIONANDINNOVATIVESIGNALPROCESSING /VERVIEW 4HESURFACE HEIGHTMEASUREMENTOBJECTIVESOFSPACE BASEDALTIMETERS CANBEGROUPEDINTOFOURBROADCATEGORIESLARGE SCALEDYNAMICSEA SURFACETOPOGRA
PHY DYNAMICMESOSCALE OCEANICFEATURES STATICMESOSCALESEA SURFACETOPOGRAPHY ANDICESEAICEASWELLASCONTINENTALICESHEETS%ACHOFTHESEMEASUREMENTTHEMES IMPLIESNARROWEDCONSTRAINTSONCHOICEOFORBITANDONTHETOP LEVELINSTRUMENTAND MISSIONDESIGN3ATELLITEALTIMETERSDEDICATEDTODETERMININGTHEOCEANSLARGE SCALE DYNAMICSURFACETOPOGRAPHYARECHARACTERIZEDBYABSOLUTESEA SURFACEHEIGHT33( SEC AVERAGED MEASUREMENT ACCURACY ON THE ORDER OF CENTIMETERS ALONG TRACKS OF MORETHANKM ANDORBITSTHATRETRACETHEIRSURFACETRACKSEVERYTODAYS )NCONTRAST MESOSCALEMISSIONSFOCUSONSEA SURFACEHEIGHTSIGNALSOFLESSTHAN^ KM IN LENGTH 2ATHER THAN ABSOLUTE 33( ACCURACY THESE SHORTER SCALE APPLICATIONS REQUIRE PRECISION SUFFICIENT TO SUSTAIN SURFACE SLOPE MEASUREMENT ACCURACY ON THE ORDEROFMICRORADIANONEMMSEA LEVELCHANGEOVERA KMDISTANCE &ORGEODETIC SIGNALS THAT ARE EXPRESSED THROUGH STATIC SEA SURFACE TOPOGRAPHIC VARIATIONS ORBITS AREREQUIREDTHATGENERATEDENSETRACK TO TRACKSPACING/BSERVATIONOFOCEANICAND e4HEAVERAGESEALEVELINTHEABSENCEOFDYNAMICPERTURBATIONSOFTHESURFACEELEVATIONDUETOTIDESANDCURRENTS
)NTHEFIELDOFOCEANOGRAPHY MESOSCALEFEATURESHAVESCALESOFSEVERALHUNDREDKILOMETERS ASOPPOSEDTOTHEMUCH LARGERBASINSCALETHE.ORTH!TLANTICOCEAN FOREXAMPLE
30!#% "!3%$2%-/4%3%.3).'2!$!23
£n°Î£
POLARICESHEETSREQUIRESTHATTHEALTIMETERHAVEROBUSTRANGEANDSPATIALRESOLUTION ACCURACY ANDPRECISIONREGARDLESSOFTHENON ZEROAVERAGESURFACESLOPEINBOTHTHE ALONG TRACKANDCROSS TRACKDIRECTIONOFTHECONTINENTALGLACIERS3UITABLEORBITSFOR ICESHEETMISSIONSMUSTHAVENEAR POLARINCLINATIONANDMULTIYEARRELATIVEACCURACY OFAFEWCENTIMETERS 7HEREASTHEMETHODOLOGYOFTHESEINSTRUMENTSISTODETERMINETHEDISTANCEBETWEEN THE RADAR AND THE SURFACE LIKE ANY RADAR AN ALTIMETER ACTUALLY MEASURES ROUND TRIP DELAY NOTDISTANCE!TTHEACCURACYREQUIREDOFASPACE BASEDOCEANOGRAPHICALTIMETER THEDECEPTIVELYSIMPLEPROPORTIONALITYOFRANGETODELAY TIMEMUSTTAKEINTOACCOUNT THESMALLBUTSIGNIFICANTRETARDATIONOFTHERADARSMICROWAVESASTHEYPROPAGATE4HE CM LEVEL33(ACCURACYREQUIREDOFTHESEINSTRUMENTSISMUCHSMALLERTHANTHERANGING ERRORSINTRODUCEDBYDELAYSTHROUGHTHEIONOSPHEREANDTHEATMOSPHERE4HEDELAYS IMPOSEDBYTHEIONOSPHEREAREAFUNCTIONOFFREQUENCY)NPRACTICE THESECANBEESTI MATEDANDTHENCORRECTEDIFTHEALTIMETERMEASURESROUND TRIPRANGEATTWODIFFERENT FREQUENCIES4HEDELAYSIMPOSEDBYTHEATMOSPHEREARECOMPRISEDOFTWOCOMPONENTS THEDRYATMOSPHEREANDWATER VAPOR4HEDRYATMOSPHERECOMPONENTISWELL KNOWN AND STABLE AT LONG SPATIAL SCALES IN PRACTICE THE RESULTING DELAY IS COMPENSATED BY RECOURSETOMODELPREDICTIONS$ELAYSDUETOWATER VAPORINTHEATMOSPHEREAREVARI ABLEDOWNTOSCALESOFSEVERALHUNDREDKILOMETERSANDMUCHSMALLERWHENTRAVERSING ASTORMFRONT 3TANDARDPRACTICEISTOMEASURETHEINTEGRATEDWATERVAPORCONTRIBUTION INTHEVERTICALCOLUMNBELOWTHEALTIMETERBYAMICROWAVERADIOMETER FORWHICHTWO ORTHREEFREQUENCIESAREREQUIRED -EASUREMENTERRORSAREDOMINATEDBYTHEACCURACYOFORBITHEIGHTDETERMINATION ANDBYTHEINTRINSICPRECISIONOFTHEINSTRUMENT&IGURESHOWSASUMMARYHISTORY OFTHESEFACTORS4HEDATASHOWTHAT CMINSTRUMENTACCURACYISTHESTATE OF THE ART FORCONVENTIONALALTIMETERS4HEDELAY DOPPLERINSTRUMENTSEEBELOW WOULDFURTHER IMPROVEINSTRUMENTPRECISIONTOCM
!
&)'52% (ISTORYOFPRECISIONORBITDETERMINATION0/$ ANDINTRIN SICINSTRUMENTPRECISIONOFTHELEADINGRADARALTIMETERSOFTHEPASTYEARS 6ERTICAL AXIS IN CM -ODERN 0/$ ACCURACY RELIES ON '03 AND THE &RENCH $/2)3 SYSTEM 0RECISION IS LIMITED BY THE ALTIMETERS DEGREES OF FREEDOM INCOHERENT WAVEFORM AVERAGING AFTER $UDLEY #HELTON /REGON 3TATE 5NIVERSITY PERSONALCOMMUNICATION
£n°ÎÓ
2!$!2(!.$"//+
#ENTIMETER SCALE RANGE ACCURACY IS SUPPORTED IN THE OCEANOGRAPHIC APPLICATION BYAVERAGINGOVERTHERANGERESPONSEOFMANYRETURNS4HERANGERESOLUTIONOFEACH RETURNWAVEFORMISTYPICALLYONTHEORDEROFMETERS4HESEWAVEFORMSAREACCU MULATED AND AVERAGED PULSE TO PULSE WHOSE SHAPE CONVERGES ON THE FLAT SURFACE IMPULSE RESPONSE &IGURE 3EA SURFACE HEIGHT 33( IS DERIVED FROM THE TIME DELAY TO THE MIDPOINT OF THE WAVEFORMS LEADING EDGE RISE /NE THOUSAND OR MORESUCHWAVEFORMSAVERAGEDOVERONESECONDCORRESPONDTOAMEANRANGEESTI MATE WHOSE STANDARD DEVIATION IS ON THE ORDER OF CENTIMETERS WHICH IN PRACTICE DEGRADESWITHINCREASINGSIGNIFICANTWAVEHEIGHT /NE SECONDAVERAGESARESTANDARD FOROPERATIONALALTIMETERS WHICHIMPLIESANALONG TRACKRESOLUTIONONTHEORDEROF KILOMETERS DETERMINEDPRIMARILYBYSATELLITEVELOCITY!VERAGINGIShTHENAMEOF THEGAMEvINRADARALTIMETRY&OREXAMPLE GLOBALDATASETSFROMINSTRUMENTSSUCH AS4/0%8AND*ASON HAVEBEENANALYZEDTOESTIMATETHERATEOFMEANSEA LEVELRISE TOANACCURACYOFMILLIMETERPERYEAR )NADDITIONTOSEA SURFACEHEIGHT THESATELLITERADARALTIMETERSWAVEFORMSUPPORTS TWOOTHEROCEANOGRAPHICMEASUREMENTSSIGNIFICANTWAVEHEIGHT37( ANDSURFACE WIND SPEED 73 /VER A QUASI FLAT SEA A PULSE LIMITED ALTIMETERS IDEALIZED MEAN
"
!
"
"
!! &)'52% A 4HEALTIMETERSPULSETYPICALLYMLONGAFTER COMPRESSION SEQUENTIALLYENCOUNTERSOCEANICSURFACEWAVESOFHEIGHT UPTOMORMORE B 3EA SURFACEHEIGHT33( CORRESPONDSTOTHE MIDPOINT OF THE WAVEFORMS LEADING EDGE SIGNIFICANT WAVE HEIGHT 37( TOTHESLOPEOFTHELEADINGEDGE ANDWINDSPEED73 TOTHE INVERSE BACKSCATTEREDPOWER4HEWAVEFORMSDEPICTEDHEREAREIDEAL IZED USEFUL hSMOOTHNESSv REQUIRES OR MORE INCOHERENTLY AVER AGEDRADARRETURNS
30!#% "!3%$2%-/4%3%.3).'2!$!23
£n°ÎÎ
WAVEFORMISASTEPFUNCTION WHOSERISETIMEISEQUALTOTHECOMPRESSEDPULSELENGTH ANDWHOSEPOSITIONONTHETIME DELAYAXISISDETERMINEDBYTHEALTIMETERSHEIGHT)F THESEASURFACEISMODULATEDBYWAVES THEALTIMETRICDEPTHOFTHESURFACEINCREASES WHICHREDUCESTHESLOPEOFTHEWAVEFORMSLEADINGEDGE(ENCE 37(ISPROPORTIONAL TOTHEWAVEFORMRISETIME)FTHESEASURFACEISDISTURBEDBYTHEWIND THERESULTING FINE SCALEROUGHNESSDECREASESTHEPOWEROFTHEPULSEREFLECTEDBACKTOTHEALTIMETER (ENCE FORWINDSPEEDSOFMORETHANABOUTTWOKNOTS 73ISINVERSELYRELATEDTOMEAN WAVEFORM POWER )N PRACTICE THE INFLECTIONS OF THE IDEALIZED FLAT SURFACE RESPONSE FUNCTIONWAVEFORMARESOFTENEDBYTHEPULSEWEIGHTING ANDTHEWAVEFORMISATTENU ATEDOVERTIMEBYTHEWEIGHTINGOFTHEANTENNAPATTERN 4OEXTRACT37(AND73FROMWAVEFORMDATA FINELYTUNEDALGORITHMSHAVEBEEN DEVELOPED AND VALIDATED AGAINST IN SITU BUOY MEASUREMENTS &OR EXAMPLE THE 4/0%8+UBANDALTIMETERMEASURES37(TOWITHINoMUPTOMORETHANMAND 73WITHINoMSUPTOMORETHANMS4HESEFIGURESCORRESPONDTOAVERAGESOVER SECOND ORABOUTKM ALONGTHESUB SATELLITEPATHOFTHEALTIMETERSFOOTPRINT WHICH TYPICALLYISKMnKMWIDE DETERMINEDBYMEANSEASTATE &LIGHT 3YSTEMS +EY ATTRIBUTES OF SATELLITE RADAR ALTIMETERS ARE SUMMARIZED IN 4ABLE 3INCE OCEANIC HEIGHT MEASUREMENT ACCURACY HAS IMPROVED DUE PRIMARILY TO MORE EFFECTIVE MEANS OF ESTIMATING AND CORRECTING SYSTEMATIC ERRORS 0ERFORMANCE ALSO HAS BENEFITED FROM INNOVATIVE ONBOARD HARDWARE AND ALGORITHMS AND MORE PRECISE DETERMINATION OF THE RADIAL COMPONENT OF THE ORBIT 4HE *ASON ALTIMETER REPRESENTS THE STATE OF THE ART IN ABSOLUTE SEA SURFACE HEIGHT MEASUREMENT ACCURACYASOFTHEYEAR 3 AND '%/3 4HE FIRST SATELLITE RADAR ALTIMETER WAS THE PROOF OF CONCEPT 3 INSTRUMENTTHATFLEWONTHREE3KYLABMISSIONS)TSOBJECTIVESWERETOVERIFY PREDICTEDWAVEFORMRESPONSETOWINDANDWAVES TOMEASURETHERADARCROSSSECTION OFTHESEAATVERTICALINCIDENCE TOMEASUREINTER PULSECORRELATIONPROPERTIES ANDTO OBSERVETHEEFFECTOFOFF NADIRANTENNAORIENTATIONASCATTEROMETEREXPERIMENT 'EOS PROVIDEDTHEFIRSTGEODETICANDGEOPHYSICALRESULTSOFSIGNIFICANCEWITHINTHE.ATIONAL 'EODETIC 3ATELLITE 0ROGRAM INCLUDING THE FIRST MAPS OF SEA LEVEL VARIABILITY AND THE 4!",% !LTIMETERS
3PACECRAFT #OUNTRY 3KYLAB '%/3 3EASAT 'EOSAT %23 4/0%8 0OSEIDON %23 '&/ *ASON %NVISAT *ASON !LTIKA #RYO3AT 3ENTINEL
9EAR
2EPEAT
DAYS 53! .O 53! n .O 53! ^ 53! n '- %3! n 53! n &RANCE %3! n 53! n &RANCE n %3! n &RANCE )NDIA&R %3! %UROPE
)NCLINATION !LTITUDE 3PACING DEGREES ^
KM
KM NA ^ ^
NA
(/ "AND CORRECTION !CCURACY +U +U +U +U +U # +U +U +U +U # +U 3 +U # +U +A +U # +U
n n 9ES n 9ES 9ES 9ES 9ES 9ES 9ES 9ES 9ES n 9ES
CM M
£n°Î{
2!$!2(!.$"//+
MARINEGEOID'EOS ANDTHE3 ALTIMETERSUSEDCONVENTIONALPULSE COMPRESSION TECHNIQUES!SSUGGESTEDINTHETABLE NEITHEROFTHESETWOEARLYALTIMETERSINCLUDEDA WATER VAPORRADIOMETER ANDEACHUSEDONLYONEFREQUENCY SOTHATTHEYHADNOIN BUILT MEANSTOCORRECTFORIONOSPHERICORATMOSPHERICPROPAGATIONDELAYS 3EASATS!LTIMETER 3EASATS WAS THE FIRST TO USE FULL DERAMPo PULSE COMPRESSION WHICHOPENEDTHEWAYFORTHEVERYSMALLRANGERESOLUTIONREQUIREDFORMANYOCEANOGRAPHIC APPLICATIONS4HEDERAMPTECHNIQUEDESCRIBEDBELOW HASBEENADOPTEDBYALLRADARALTIM ETERSSINCETHEN3EASATWASDESIGNEDTOMEASUREGLOBALOCEANDYNAMICTOPOGRAPHY ASWELL ASWAVEHEIGHTANDSURFACEWINDSPEED 'EOSAT 4HISALTIMETERSDESIGNWASPATTERNEDCLOSELYAFTERTHATOFTHE3EASAT ALTIMETER 'EOSAT WAS A 53 .AVY MILITARY SATELLITE WHOSE PRIMARY MISSION WAS TO MAP THE %ARTHS MARINE GEOID TO THEN UNPRECEDENTED ACCURACY FOR WHICH A NON REPEATORBITWASREQUIRED3INCEITSPUBLICRELEASEIN THEDATASETFROMTHEFIRST MONTH GEODETIC MISSION HAS BECOME THE BACKBONE OF THE GLOBAL BATHYMETRIC CHARTTHATISTHEINDUSTRYSTANDARD 'EOSATS SECONDARY MISSION WAS TO OBSERVE DYNAMIC MESOSCALE OCEANO GRAPHICPHENOMENA FORWHICHITWAS MANEUVEREDINTOANEXACTREPEATORBIT PERIOD DAYS 'EOSATS GEO DETIC MISSION AND EXACT REPEAT MIS SION ARE KNOWN AS '- AND %2- RESPECTIVELY!S A SPACECRAFT 'EOSAT WAS ONE OF THE FEW %ARTH OBSERVING MISSIONSTORELYONTHEPURELYPASSIVE GRAVITY GRADIENTMEANSOFATTITUDECON TROL AS EVIDENCED BY THE EXTENDED VERTICAL BOOM IN &IGURE 4HE ATTITUDEWASSTABLETOLESSTHANn TO WHICH THE ALTIMETERS PULSE LIMITED RANGEMEASUREMENTWASROBUST 'EOSAT&OLLOW /N'&/ '&/ WAS DESIGNED TO REPLICATE AS MUCH AS POSSIBLE THE 'EOSAT EXACT REPEAT MISSION IN SUPPORT OF OPERATIONAL REQUIREMENTSFORTHE53.AVY'&/ REPRESENTS THE CURRENT STATE OF THE ARTINSMALLDEDICATEDRADARALTIMETER MISSIONS)TINCLUDESADUAL FREQUENCY WATER VAPORRADIOMETER762 AT AND '(Z DATA FROM WHICH ARE USED TO REDUCE THE CORRESPONDING PROPAGATION UNCERTAINTY TO CM
&)'52% 4HE'EOSATRADARALTIMETER4HENADIR DIRECTED ANTENNA A REFLECTOR IS HIDDEN INSIDE OF THE SOLAR ARRAYS 4HIS SPACECRAFT MAINTAINED VERTICALITY BY GRAVITY GRADIENT HENCE THE LONG BOOM AND COUNTER WEIGHT 4HEDATAWEREIMPERVIOUSTORANDOMLYORIENTED YAWANGLESABOUTTHEVERTICALAXIS )MAGECOURTESYOF *OHNS(OPKINS5NIVERSITY!PPLIED0HYSICS,ABORATORY
o&ULLDERAMPORSIMPLYDERAMP ISSTANDARDTERMINOLOGYINSPACE BASEDRADARALTIMETRY)TISKNOWNMORECOMMONLY TOMOSTRADARENGINEERSASTHE3TRETCHTECHNIQUE
30!#% "!3%$2%-/4%3%.3).'2!$!23
£n°Îx
4HERADARSMASSISKGINCLUDINGFULLREDUNDANCYANDTHE762 ITSPRIMEPOWER CONSUMPTIONISLESSTHAN74OTALSPACECRAFTDRYMASSpISABOUTKG 4/0%80OSEIDON )NTHELATES PROGRAMPLANNINGFORSATELLITERADARALTIM ETERMISSIONSSPLITINTOTWOTHEMES DETERMINEDBYTHERELATIVEPRIORITYOFTHEIRMEA SUREMENTS )F THE ALTIMETER WERE THE PRIME PAYLOAD INSTRUMENT THEN THE ORBIT AND MISSIONDESIGNCOULDBEOPTIMIZEDACCORDINGLY4HISTHEMEWASFOLLOWEDBY4/0%8 0OSEIDON40 AJOINT5NITED3TATES.!3! AND&RENCH#.%3 MISSION4/0%8 WASDESIGNEDTOMEASUREANDMAPTHEDYNAMICOCEANTOPOGRAPHYWITHSUFFICIENTACCU RACYTODETERMINELARGE SCALECIRCULATIONPATTERNS4/0%8MOSTFAMOUSCONTRIBUTION ISEARLYOBSERVATIONANDNEAR REAL TIMEMONITORINGOF%L.I¶OEVENTS WHOSEHEIGHT SIGNATUREOVERTHEEQUATORIALEASTERN0ACIFICOCEANTYPICALLYISANINCREASEONTHEORDER OFnCMWITHRESPECTTOTHEMEAN0OSEIDON CONTRIBUTEDBY&RANCE WASASMALL PROOF OF CONCEPTINSTRUMENTTHATHADASOLID STATETRANSMITTER0OSEIDONWASTHEPRE CURSOROFTHE*ASONALTIMETERSANDTHE3)2!,INSTRUMENTABOARD#RYO3AT 4HE40ORBITREPEATPERIODWASCHOSENCAREFULLYTOSATISFYADEQUATEOBSERVATIONOF THEDOMINANTALIASEDTIDALCONSTITUENTS!LLSOLARTIDALCONSTITUENTSWOULDBEAMBIGU OUSWITHOTHERHEIGHTSIGNALSIFTHEREPEATPERIODWEREANINTEGRALNUMBEROFDAYS&OR 40 THETIMEOFDAYFOREACHSUBSEQUENTOBSERVATIONSLIPSBYABOUTTWOHOURS4HE 40REPEATPASSFOOTPRINTLOCATIONACCURACYISBETTERTHANoKM AREQUIREMENTTHATIS BOUNDEDBYTHECROSS TRACKGRADIENTOFTHEOCEANICGEOID4HE40INSTRUMENTPACK AGEINCLUDEDATHREE FREQUENCYRADIOMETER4/0%8WASTHEFIRSTALTIMETERTOUSETWO FREQUENCIESTIME MULTIPLEXED TOESTIMATEANDCOMPENSATEFORPROPAGATIONDELAYS IMPOSEDBYIONOSPHERICELECTRONS$ESIGNEDFORANINITIALTHREE YEARMISSION SUBSE QUENTLYSTRETCHEDTOFIVEYEARS 40PROVIDEDVALUABLEDATAFORANIMPRESSIVETHIRTEEN YEARS40WASFORMALLYDECOMMISSIONEDIN$ECEMBER !SISTRUEFORMOSTRADARS THERECEIVEDWAVEFORMPRODUCEDBYANINDIVIDUALPULSE FROM4/0%8WASCORRUPTEDBYCOHERENTSELF NOISEKNOWNASSPECKLE4HESTANDARD DEVIATIONOFSPECKLEISREDUCEDBYSUMMINGAVERAGING MANYSTATISTICALLYINDEPENDENT WAVEFORMSTOGETHER3TATISTICALINDEPENDENCEBETWEENSEQUENTIALRETURNSOBSERVEDBY ARADARALTIMETERDEPENDSPRIMARILYONTHERADARPULSEREPETITIONRATE THEANTENNASIZE THESPACECRAFTVELOCITY ANDONTHESEASURFACECONDITIONS4HEANTENNAWASA M REFLECTOR THAT SERVED BOTH ALTIMETER BANDS AND ALSO THE RADIOMETER 3ELECTED PARAM ETERSASSOCIATEDWITHTHEALTIMETERSDESIGNARELISTEDIN4ABLE4HEPULSE TO PULSE 4!",% 4/0%80ARAMETERS
0ARAMETER
6ALUE
5NITS
,&-RATE 0ULSEDURATION 0ULSE"7RADIATED 4IMErBANDWIDTH 0ULSERESOLUTION #ARRIER+UBAND #ARRIER#BAND )&FREQUENCY 3TRETCHBANDWIDTH 2ANGETIMESPAN
-(Z§S §S -(Z DIMENSIONLESS M '(Z '(Z -(Z -(Z NS
p4OTALMASS NOTINCLUDINGCONSUMABLESSUCHASFUELFORPROPULSIONORATTITUDECONTROL
£n°ÎÈ
2!$!2(!.$"//+
STATISTICALINDEPENDENCEREQUIREMENTEVALUATEDFORTHE4/0%8INDICATESTHATTHEMAXI MUM02&SHOULDBEK(Z YETITWASK(ZINPRACTICE4HEPULSERATEABOVETHE THRESHOLDIMPROVEDTHEADDITIVE3.2 BUTDIDNOTCONTRIBUTETOSPECKLEREDUCTION4HE 02&STATISTICALINDEPENDENCELIMITDECREASESWITHINCREASINGSIGNIFICANTWAVEHEIGHT *ASON *ASON FOLLOWEDINTHEFOOTSTEPSOF4/0%8 FIGURATIVELYANDLITERALLY !FTERTHELAUNCHOF*ASON INTOTHE40ORBIT 4/0%8WASMANEUVEREDINTOAhTAN DEMvPHASINGSOTHATTHEMEASUREMENTSOFTHETWOALTIMETERSCOULDBECROSS CALIBRATED *ASON ISESSENTIALLYIDENTICALTO*ASON %23 %23 AND%.6)3!4 )FTHEALTIMETERISNOTTHEPRIMARYPAYLOAD THEN THERESULTINGMISSIONANDORBITARELIKELYTOBEDETERMINEDBYOTHERREQUIREMENTS WHICHMAYCOMPROMISEALTIMETRY4HE%UROPEAN3PACE!GENCYSSATELLITEALTIMETERS ON %23 AND %23 AS WELL AS THE ADVANCED RADAR ALTIMETER 2! ON %3!S %.6)3!4 ARE OF SECOND PRIORITY WITH RESPECT TO THE OTHER INSTRUMENTS ON THEIR RESPECTIVESPACECRAFT4HEIRSUN SYNCHRONOUSORBITSARELESSTHANOPTIMUMFORMOST ALTIMETRIC APPLICATIONS DUE PRIMARILY TO THE FACT THAT FOUR OF THE EIGHT DOMINANT TIDAL CONSTITUENTS ARE SUN SYNCHRONOUS 4HESE ORBITS ARE ALSO AT LOWER ALTITUDES THANTHE40ORBIT WHICHIMPLIESTHATORBITMAINTENANCEMANEUVERSMUSTBEMORE FREQUENT THUSCOMPROMISINGPRECISIONORBITDETERMINATION$URINGAPORTIONOFITS MISSION THEORBITOF%23 WASREPHASEDTOALONGREPEATPERIODDAYS 4HAT LONG REPEAT PERIOD GENERATED A RELATIVELY DENSE SURFACE SAMPLING GRID USEFUL FOR ESTIMATINGSEAICECOVER GEODESY ANDBATHYMETRY4HE%23 MISSIONDIDNOTVARY ITSREPEATPERIOD4HECONSEQUENCEOFTHESEORBITPROPERTIESISTHATTHERESULTINGDATA ARE NOT WELL SUITED TO MEASURING THE ANNUAL RATE OF SEA LEVEL RISE WHICH IS A KEY CLIMATE RELATEDVARIABLE #RYO3AT 4HISWASTHEFIRST%ARTH%XPLORER/PPORTUNITY-ISSIONS WHICHWASPART OF THE %UROPEAN 3PACE!GENCYS ,IVING 0LANET 0ROGRAMME4HE MISSION CONCEPT WASSELECTEDINANDSUBSEQUENTLYLAUNCHEDIN/CTOBER5NFORTUNATELY THE LAUNCHVEHICLEMALFUNCTIONED%3!ANDITSMEMBERSTATESAUTHORIZEDAREPLACEMENT 4HE#RYO3ATORBITHASAHIGH INCLINATIONn ANDALONG REPEATPERIODDAYS WITH A DAYSUBCYCLE DESIGNEDTOPROVIDEDENSEINTERLOCKINGCOVERAGEOVERTHEPOLAR REGIONS)TSAIMISTOSTUDYPOSSIBLECLIMATEVARIABILITYANDTRENDSBYDETERMININGTHE VARIATIONSINTHICKNESSOFTHE%ARTHSCONTINENTALICESHEETSANDMARINESEAICECOVER #RYO3ATISDESCRIBEDINMOREDETAILINASUBSEQUENTSECTION !LTI+A !LTI+A DIFFERS FROM OTHER OCEAN VIEWING ALTIMETERS IN THIS SECTION DUE PRIMARILYTOITSUSEOF+ABAND'(Z RATHERTHAN+UBAND4HEFIRSTINSTRUMENT FROM&RANCE ISPARTOFTHEPAYLOADON)NDIAS/CEANSAT !LTI+AISSINGLE FREQUENCY SINCEAT+ABANDTHERETARDATIONDUETOTHEIONOSPHEREISSUFFICIENTLYSMALLTHATITDOES NOT HAVE TO BE MEASURED AND COMPENSATED (OWEVER THE ^ CM WAVELENGTH IS VULNERABLETOATMOSPHERICMOISTUREITISPREDICTEDTHATASMUCHASOFTHEDATA WILLBECOMPROMISEDBYRAIN4HEKGINSTRUMENTREQUIRESANINPUTPOWEROF7 4HEOFFSET FEDREFLECTORANTENNAISMINDIAMETER RESULTINGINABEAMWIDTHLESSTHAN HALFTHATOFITS+U BANDCOUNTERPARTS3EVERALADVANTAGESARECLAIMEDFORTHESMALLER BEAMWIDTH INCLUDINGOPERATIONCLOSERTOLAND/NTHEOTHERHAND THENARROWERBEAM IMPLIES THAT THE WAVEFORM IS MORE SENSITIVE TO SPACECRAFT ATTITUDE ERRORS !LTI+AS -(ZBANDWIDTHLEADSTOAPULSE LIMITEDFOOTPRINTABOUTSMALLERTHANUSUAL
30!#% "!3%$2%-/4%3%.3).'2!$!23
£n°ÎÇ
4HE02&ISK(Z APPROXIMATELYTWICETHATOFMOSTCONVENTIONALALTIMETERS SLIGHTLY LARGERTHANTHEPULSE TO PULSESTATISTICALINDEPENDENCECONDITIONOFK(Z /RBIT #ONSIDERATIONS 'IVEN AN ARBITRARILY GOOD RADAR ALTIMETER ITS ORBIT BECOMES THE DOMINANT FACTOR THAT MAY LIMIT SEA SURFACE HEIGHT MEASUREMENT ACCU RACY/RBITSELECTIONFORANOCEANALTIMETERREQUIRESCONSIDERATIONOFTHEIMPACTOFAN ORBITSINCLINATION REPEATPERIOD ANDALTITUDE&OREXAMPLE IFTHEOBJECTIVEISABSOLUTE SEA SURFACE HEIGHT ACCURACY OVER LARGER SPATIAL SCALES AND LONG TIME SCALES THEN A HIGHERALTITUDEORBITHAVINGARELATIVELYMODERATEPROGRADEINCLINATION ANDRELATIVELY SHORTNON SUN SYNCHRONOUSREPEATPERIODISTHEONLYSENSIBLESTARTINGPOINT !NALTIMETERSREVISITPERIODISTENDAYSORMORE INCONTRASTTOTIDESWITHAPPROXI MATELYORCYCLESPERDAYDRIVENPRIMARILYBYLUNARANDSOLARGRAVITY!SARESULT ALLTIDALSIGNALSSENSEDBYANALTIMETERAREUNDERSAMPLED!LTIMETRICDATARETAINTHE RESULTINGALIASES WHICHOVERTHECOURSEOFAYEARORSOCANBEIDENTIFIED QUANTIFIED ANDCALIBRATEDOUT!NALTIMETERSORBITMUSTBECHOSENSOTHATTHETIDALALIASESDONOT GETCONFUSEDWITHSIGNALSOFGEOPHYSICALINTEREST 4HE40/RBIT 4HESTATE OF THE ARTATLEASTINACCURACYANDLARGE SCALECIRCULATION STUDIES IS*ASON OPERATINGINTHEORBITORIGINALLYDESIGNEDFOR4/0%80OSEIDON 4HEORBITPARAMETERSINCLUDEREPEATPERIODCALENDARDAYSUNFORTUNATELY OFTEN STATEDASDAYS INCLINATIONnREPEATTRACKSEPARATIONATTHEEQUATORKM AND ALTITUDEKM4HERADIALCOMPONENTOFPRECISIONORBITDETERMINATION0/$ ISON THEORDEROFCMFOR40 AND*ASON RESULTSSHOW0/$TOALEVELOFCM!LTHOUGH THESEPARAMETERSREFLECTTHEFRUITSOFMULTIPLEYEARSOFTRADESTUDIESBYMANYINDIVIDU ALS ATLEASTONEUNWANTEDCHARACTERISTICREMAINS4HE+TIDALALIASISVERYNEARLYTWO CYCLESPERYEAR THUSAPPEARINGCLOSETOGEOPHYSICALSIGNALSASSOCIATEDWITHSEASONAL EFFECTS+CANNOTBEIGNORED ASITISTHELARGESTDIURNALCONSTITUENTANDISSECONDIN MAGNITUDEONLYTOTHEDOMINANTLUNARCONSTITUENT 4HECONSTRAINTONTHEEXACTNESSOFANORBITSREPEATINGGROUNDTRACKISDETERMINEDTO FIRSTORDERBYTHEFINESTRUCTUREINTHELOCALGEOIDEXPRESSEDATTHEOCEANSSURFACE&OR EXAMPLE CROSS TRACKSURFACESLOPESGRADIENTS INTHEGEOIDMAYBEASLARGEASrn NEARTHEDEEPEROCEANICTRENCHES)NSUCHANEXTREMECASE ACROSS TRACKDRIFTOFONLY KMWOULDGIVERISETOA CMCHANGEINSEA SURFACEHEIGHT33( )NRESPONSE ALGO RITHMSHAVEBEENDEVELOPEDTHATCORRECT33(DATAFORTHEEFFECTSOFTHELARGERCROSS TRACKGEOIDGRADIENTS)TALSOISSTANDARDPRACTICETOCONSTRAINANALTIMETERSCROSS TRACK DRIFTTOLESSTHANKM2EPEATTOLERANCEUSUALLYISTHECONDITIONTHATMOTIVATESACTIVE ORBITMAINTENANCEMANEUVERS .ON 2EPEAT/RBIT 4HEPRECEDENTFORTHISIS'EOSATITSFIRSTMONTHSWERE DEVOTEDTOGEODESYFORWHICHANON REPEATORBITISOPTIMAL'EODETICMISSIONSMAP GRAVITYANOMALIESREFLECTEDINSUBTLELOCALTILTSOFTHEMEANOCEANSURFACE4HESEARE STATICMESOSCALEFEATURESOFSPATIALSCALESLESSTHANABOUTKM DETERMINEDBYTHE TOPOGRAPHICFEATURES COMPOSITIONOFTHESEABOTTOM ANDSTATIONARYOCEANICCURRENTS $ATAFROM'EOSATHAVEBEENUSEDTODERIVETHESTANDARDBATHYMETRICCHARTSAVAILABLE FORTHEGLOBALOCEANS 'EOSAT%2-/RBIT 4HEONLYOTHERFAMILYOFDEDICATEDMISSIONSISTHATINTHE 'EOSAT n %XACT 2EPEAT -ISSION %2- ORBIT THE SAME ORBIT USED BY '&/4HISORBITHASAPERIODOFCALENDARDAYSSOMETIMESINAPPROPRIATELY
£n°În
2!$!2(!.$"//+
ABBREVIATEDTODAYS nINCLINATION CONSEQUENTLYKMTRACK TO TRACKSPAC INGATTHEEQUATOR ANDKMALTITUDEe&ROMTHE'EOSATORBIT HALFOFTHEPRINCI PALTIDALCONSTITUENTSALIASINTOUNWANTEDFREQUENCIESNEARZERO ONE ORTWOCYCLES PERYEAR )NPARTICULAR THEDOMINANTTIDALCONSTITUENT THECOMMONTWICE DAILYLUNAR TIDE IS ALIASED TO DAYS WHICH IS CLOSE TO THE ANNUAL CYCLE 0RECISION ORBIT DETERMINATIONISGOODTOONLYABOUTCM WHICHISRELATIVELYLARGE DUEINNOSMALL MEASURETOFAILUREOFTHEPRIMARYONBOARD'03NAVIGATIONSUBSYSTEM 3UN 3YNCHRONOUS /RBITS 3UN SYNCHRONOUS SATELLITES HOST %UROPEAN 3PACE !GENCY%3! ALTIMETERSON%23 %23 AND2! ON%.6)3!4!LLSHARETHE
SAME ORBIT CALENDAR DAYS REPEAT PERIOD n INCLINATION AND KM MEAN EQUATORIALALTITUDE2ADIALKNOWLEDGEOFTHESESUN SYNCHRONOUSORBITSISGOODTOABOUT CM BASED ON THE $ELFT MODEL!S SUN SYNCHRONOUS ALTIMETERS THE LARGEST SOLAR CONSTITUENTTWICEDAILY ALIASESTOZERO ANDALLTIDALCONSTITUENTSTHATAREPRIMARILY DEPENDENTONSOLARFORCESALIASTOFREQUENCIESCLOSETOZERO 4HEORETICAL&OUNDATIONS 4HEFOLLOWINGPARAGRAPHSPROVIDEASUMMARYOFTHE KEY CHARACTERISTICS OF A SPACE BASED RADAR ALTIMETER %XAMPLES ARE DRAWN FROM THE DESIGNOF4/0%8 0ULSE LIMITED !LTIMETERS &IGURE ILLUSTRATES THE PULSE LIMITED CONDITION 4HERADIUSR0OFTHEAREADELIMITEDONAQUASI FLATSURFACEBYAPULSEOFLENGTHSSEC ONDSONTHE%ARTHOFMEANRADIUS2%SEENFROMARELATIVEALTITUDEOFHKILOMETERSIS
R0 CT H A 2
WHERE@2 2% H 2%ISACONSEQUENCEOFTHESPHERICALOBSERVATIONGEOMETRY&OR TYPICALSATELLITERADARALTIMETERS THEPULSE LIMITEDFOOTPRINTOVERAQUASI FLATSURFACEIS ONTHEORDEROFTWOKILOMETERSINDIAMETER4HEPULSE LIMITEDAREA!PIS
!0 P R0 P CT H A 2
!STHEPULSECONTINUESTOIMPINGEANDSPREADOVERTHESURFACE THERESULTINGPULSE LIMITEDANNULIALLHAVEAREASEQUALTOTHATOFTHEINITIALPULSE LIMITEDFOOTPRINT(ENCE THERECEIVEDPOWERTENDSTOMAINTAINTHELEVELCORRESPONDINGTOTHEPEAKOFTHEINITIAL RESPONSE &IGURE 4HE PULSE LIMITED AREAS EXPAND IN RESPONSE TO INCREASING LARGE SCALE SURFACE ROUGHNESS WHICH IN THE OCEANOGRAPHIC CONTEXT IS EXPRESSED AS SIGNIFICANTWAVEHEIGHT37( 4HEHEIGHTACCURACYOFAPULSE LIMITEDALTIMETERIS MUCHLESSSENSITIVETOSMALL ANGULARPOINTINGERRORSTHANISTHECASEFORABEAM LIMITEDALTIMETER !DAPTIVE4RACKING !SATELLITE BASEDRADARALTIMETERNEEDSTOMEASURETHEDIS TANCEACCURATELY BUTONLYFORANESSENTIALLYPLANARSURFACE ORIENTEDORTHOGONALLYTO THERADARSLINE OF SIGHT#ONSERVATIVEDESIGNSUGGESTSTHATTHEMEASUREMENTSHOULD BECONCENTRATEDNEARTHEREFLECTIONFROMTHATSURFACE(ENCE OCEAN VIEWINGALTIM ETERSHAVEASMALLRANGEWINDOWWHOSEPOSITIONTRACKSTHEDELAYANDSTRENGTHOFTHE
e4HE'EOSAT%2-ORBITWASCHOSENFORPOLITICALASMUCHASFORTECHNICALREASONS)TFOLLOWEDTHE3EASATORBIT THATHADESTABLISHEDAWELL KNOWNPRECEDENT
30!#% "!3%$2%-/4%3%.3).'2!$!23
£n°Î
!
! !
!
!
! !
" # &)'52% 4HEPULSE LIMITEDCONDITION/VERANOMINALLYLEVELFLAT SURFACE THEALTIMETERSSHORTPULSEA REFLECTSFIRSTFROMANAREATHATMAYBE MUCHSMALLERTHANTHEFOOTPRINTILLUMINATEDBYTHEANTENNAPATTERNB
SURFACEREFLECTION4HEOCEANSSURFACEHASASIGNIFICANTWAVEHEIGHTOFLESSTHAN MORSO2ADARBACKSCATTERISPRIMARILYSPECULAR TYPICALLYSPANNINGD"TOD" TO CITE PARAMETERS USED IN THE TESTING OF THE 4/0%8 ALTIMETER )N PRACTICE RANGE GATEDELAYANDBACKSCATTERTRACKINGAREMETWITHTWOSERVO REGULATORFEEDBACKLOOPS &IGURE 4HE FIRST LOOP IS A SECOND ORDER HEIGHT TRACKER CONSISTING OF RANGE POSITIONALPHATRACKER ANDRANGERATEBETATRACKER 4HESECONDLOOPISTHERECEIVER GAIN CONTROL !'# !LTIMETER HEIGHT MEASUREMENT IS GIVEN BY THE SETTING OF THE
£n°{ä
2!$!2(!.$"//+
#!'
#! "# !!
% !
! "" !
$!#$! &!"
#
' ! (! !
!"#
! &!
!
#!
&)'52% !GENERICSIGNALFLOWDIAGRAMFORANOCEAN VIEWING RADAR ALTIMETER 0RINCIPAL FEEDBACK LOOPS INCLUDE RANGE GATE TRACKING BOTHCOARSETHEALPHALOOP ANDFINERANGE RATETRACKINGTHEBETALOOP ANDMEANSIGNALPOWERTHE!'#LOOP
RANGEDELAYCOARSEANDFINEVALUES CORRECTEDBYTHEREMAININGHEIGHTERRORMEASURED FROMTHEWAVEFORMSPOSITIONINTHETRACKER3URFACEWINDSPEEDANDSIGNIFICANTWAVE HEIGHTAREDERIVEDFROMTHE!'#VALUESANDTHEWAVEFORMSSHAPE RESPECTIVELY 4HEPRECISIONOFANINDIVIDUALHEIGHTMEASUREMENTISDETERMINEDBYTHECOMBINATION OFRANGERESOLUTIONANDINCOHERENTWAVEFORMAVERAGING)FASINGLESIMPLESHORTPULSE WERETRANSMITTED THENTHEHEIGHTRESOLUTIONWOULDEQUALTHEPULSELENGTH4HEPRINCIPAL DISADVANTAGEOFASHORTPULSEISTHATITCONTAINSLITTLEENERGY4HEINHERENTRESOLUTIONOFA PULSEISINVERSELYPROPORTIONALTOITSBANDWIDTH3PACE BASEDRADARALTIMETERSUSESOME FORMOFMODULATIONONTHETRANSMITTEDSIGNALTOMAINTAINALARGEBANDWIDTHWITHINA LONGERPULSE THUSINCREASINGTHETRANSMITTEDENERGYATNOLOSSOFRESOLUTION $ERAMPON2ECEIVE 3ATELLITE BASEDRADARALTIMETERSPRESENTANELEGANTEMBODI MENTOFTHE3TRETCHTECHNIQUE WHICHISKNOWNASFULLDERAMPINTHEFIELDOFSPACE BASEDRADARALTIMETRY4HISMETHODWASFIRSTEMPLOYEDBY-AC!RTHURINTHE3EASAT ALTIMETER ANDHASBEENADOPTEDASTHESTANDARDTECHNIQUESINCETHENFORTHISTYPEOF RADAR4HEDISTINGUISHINGFEATUREOFTHISTECHNIQUEISACLEVERTRADEBETWEENTHETWOKEY
30!#% "!3%$2%-/4%3%.3).'2!$!23
£n°{£
PARAMETERSINALARGETIME BANDWIDTHPRODUCT4"0 SIGNAL!FTERRECEPTION DEMODU LATIONISAPPLIEDTHATTRANSFORMSTHEhSHORTTIME LARGEBANDWIDTHvNATUREOFTHEORIGI NALPULSETOhLONGTIME SMALLBANDWIDTHvSIGNALS3INCETHESAME4"0ISMAINTAINED THEORIGINALRESOLUTIONISPRESERVED4HEMETHODISIDEALFORALTIMETRY SINCETHERANGE DEPTHOFTHEOCEANSSURFACEISVERYMUCHSMALLERTHANTHETIMEAVAILABLEINTHEPULSE REPETITIONPERIOD#LEARLY THEFULLDERAMPTECHNIQUEOFFERSACONSIDERABLESAVINGSIN SYSTEMBANDWIDTHATALLSUBSEQUENTSTAGESANDATNOCOSTINRANGERESOLUTION4HEFIG URESCITEDIN4ABLESHOWTHATTHERATIOOFWAVEFORMBANDWIDTHTO2&BANDWIDTH FOR4/0%8ISONTHEORDEROF4HE4/0%8ALTIMETERDESIGNISDESCRIBEDMORE COMPLETELYINTHEOPENLITERATURE 'EOSAT 'EODETIC -ISSION 2ADAR ALTIMETRIC DATA ARE THE BASIS FOR STATE OF THE ART GRAVIMETRIC VARIATIONS EXPRESSED AT THE OCEANS SURFACE AND CONSEQUENTLY OCEANICBATHYMETRY 4HEPRINCIPALOBJECTIVEOFAGEODETICSATELLITERADARALTIMETER ISTOMEASURETHEALONG TRACK SLOPEOFTHESEASURFACECAUSEDBYGRAVITYDEFLECTIONS OVER SPATIAL SCALES LESS THAN A FEW HUNDREDS OF KILOMETERS &IGURE 4HESE SLOPESAREDERIVEDFROMTHE33(MEASUREMENTSSUMMARIZEDABOVE BUTTHISAPPLICA TIONHASITSOWNUNIQUEIMPLICATIONSFORSYSTEMDESIGN4HEHIGHLIGHTSAREREVIEWED INTHEFOLLOWINGPARAGRAPHS 3EA SURFACESLOPEISDERIVEDBYTAKINGTHEDIFFERENCEBETWEENTWONEIGHBORING HEIGHTMEASUREMENTS WHERETHESLOPETANGENTEQUALShRISEOVERRUNv4HEKEYWORD FORTHESEMEASUREMENTSISPRECISIONTHESTANDARDDEVIATIONNOISE OFTHESEA SURFACE HEIGHT MEASUREMENT ABOUT ITS MEAN VALUE (EIGHT MEASUREMENT PRECISION IS DETER MINED BY THE RADAR ALTIMETERS POST PROCESSING RANGE RESOLUTION AND BY THE AMOUNT OFAVERAGINGAVAILABLEFOREACHESTIMATE.OTETHATAPRECISIONMEASUREMENTMAYSTILL HAVEPOORACCURACY IFITSMEANVALUEISBIASEDAWAYFROMTHECORRECTVALUE7HEN COMPARINGTWONEIGHBORINGHEIGHTMEASUREMENTS ANYCONSTANTBIASISCANCELLEDBY SUBTRACTIONASLONGASTHEERRORISTHESAMEFORBOTHMEASUREMENTS4HESEA SURFACE SLOPEMEASUREMENTPROBLEMISCHALLENGINGBECAUSETHEDESIREDSLOPESIGNALSAREAS SMALLASONEMICRORADIAN EQUIVALENTTOAMMHEIGHTDIFFERENTIALRISE FOREACHKM ALONG TRACKSEPARATIONRUN )N ADDITION TO HEIGHT PRECISION GEODETIC ALTIMETRY REQUIRES SMALLER ALONG TRACK RESOLUTIONTHANACONVENTIONALALTIMETERANDANORBITTHATACCUMULATESDENSECROSS TRACKCOVERAGE4HEALTIMETERSFOOTPRINTRESOLUTIONSHOULDBESMALLERTHANABOUTKM
&)'52% 7HEN AVERAGED AND STRIPPED OF DYNAMIC CURRENT DRIVEN FEATURES THE MEAN OCEAN SURFACEISADIRECTEXPRESSIONOFTHELOCALGRAVITYGRA DIENT 3TATE OF THE ART RADAR ALTIMETERS CAN MEASURE THERESULTINGSLOPESTOA MICRORADIANPRECISION
,ITERALLY MEASUREMENTOFTHEDISTANCEBETWEENTHEMEANOCEANSURFACEANDTHELOCALSEAFLOOR
£n°{Ó
2!$!2(!.$"//+
WHICHCORRESPONDSTOTHEMINIMUMHALF WAVELENGTHSCALEOFTHEOBSERVABLEPERTUR BATIONSINTHEOCEANSMEANSURFACEDUETOSPATIALVARIATIONSINTHE%ARTHSGRAVITY 4HE ORBIT SHOULD NOT REPEAT FOR ^ YEARS TO YIELD AN AVERAGE GROUND TRACK SPAC INGOFKM AGAININRESPECTOFTHEGRAVITYSIGNALATTHEOCEANSSURFACE4HEORBITS INCLINATION SHOULD BE NEAR nnn TO RESOLVE NORTH AND EAST SLOPES NEARLY EQUALLY ANDTOCOVERTHELOWERLATITUDESWHEREEXISTINGDATAAREINADEQUATE.OTETHATOCEANO GRAPHICRADARALTIMETERMISSIONS4/0%80OSEIDON *ASON %23 %.6)3!4 AND 'EOSAT%2-'&/ ARENORMALLYPLACEDINTOEXACT REPEATORBITSTODAYS AND ASACONSEQUENCE HAVEWIDELYSPACEDKMTOKM GROUNDTRACKS3UCHORBITS CANNOTRESOLVETHESHORT WAVELENGTHTWO DIMENSIONALSURFACESLOPESREQUIREDFORUSE FULGEODESY 3INCE ABSOLUTE HEIGHT ACCURACY IS NOT REQUIRED GEODETIC RADAR ALTIMETERS CAN BE RELATIVELYBASICINSTRUMENTS4HEYDONOTNEEDTOCOMPENSATEFORPROPAGATIONDELAYS HENCETHEYNEEDONLYONEFREQUENCY ANDTHEYDONOTNECESSARILYNEEDAWATERVAPOR RADIOMETER762 )NDEED ASIMPLEINSTRUMENTISPREFERREDITHASBEENSHOWNTHAT EFFORTSTOCORRECTFORPATHDELAYSUSUALLYADDNOISETOSLOPEESTIMATES'EODETICMEA SUREMENTSPROVIDEDBYTHE'EOSATAND%23 BOTHSINGLE FREQUENCYALTIMETERSWITH NO762 FURNISHEDTHEBESTRESOLUTIONOCEANICGEODESYANDBATHYMETRYAVAILABLEUP THROUGHATLEASTFORTHEOPENOCEAN4HEIRRESULTINGBATHYMETRICRESOLUTIONISLIM ITEDTOABOUTKMNORTH SOUTHANDPOORERRESOLUTIONOFEAST WESTSLOPECOMPONENTS 4HESERESULTSREFLECTTHELESS THAN OPTIMUMRESOLUTION WAVEFORMPRECISION ANDORBIT INCLINATIONOFTHOSETWOALTIMETERS'EODETICRESOLUTIONATTHEOCEANSSURFACECANBE NOFINERTHANABOUTKMHALFAWAVELENGTH ALIMITTHATISDETERMINEDBYTHEAVERAGE DEPTHOFTHEOCEAN #RYO3AT)CE3HEET-ISSION 0ULSE LIMITEDSPACE BASEDRADARALTIMETERSWORK BESTOVERRELATIVELYMILDTOPOGRAPHICRELIEFOFMEANSLOPEZERO SUCHASTHEOCEANS SURFACE/VERICESHEETSORTERRESTRIALSURFACES PERFORMANCEISDEGRADED5NWANTED CHARACTERISTICSINCLUDEFOOTPRINTDILATIONOVERROUGHERTERRAIN HEIGHTERRORSINPROPOR TIONTOSURFACEMEANSLOPE ANDTHETENDENCYOFTHEMINIMUMRANGEMEASUREMENTTO HOPFROMONEELEVATEDREGIONTOANOTHERWITHOUTTHECONTROLORKNOWLEDGEOFTHEDATA ANALYST "EAM LIMITEDTECHNIQUES OFWHICHLASERALTIMETERSAREEXTREMEEXAMPLES CIRCUMVENTTHESEPROBLEMS BUTMAYIMPLYTHEIROWNSETOFDISADVANTAGES !MAJORPOTENTIALAPPLICATIONOFRADARALTIMETRYISTOMONITORTHEHEIGHTOFEXTENSIVE ICESHEETS ASFOUNDIN'REENLANDOR!NTARCTICA!PPROXIMATELYOFTHESELAND ICE SURFACESHAVESLOPESLESSTHAN^n WHICH ALTHOUGHSMALL ISSUFFICIENTTOTRICKACON VENTIONALALTIMETERINTOVERYLARGEHEIGHTERRORS&OREXAMPLE ANUNKNOWNnSLOPE WOULDLEADTOA MSURFACEHEIGHTERROR WHICHISUNACCEPTABLEIFCM LEVELINTER ANNUALCHANGESARETHEOBJECTIVE 4HE#RYO3ATALTIMETERISTHEFIRSTSPACE BASEDRADARALTIMETERDESIGNEDTOOPER ATEOVERICE&IGURE )TSPAYLOADINSTRUMENTISTHE3!2)NTERFEROMETRIC2ADAR !,TIMETER3)2!, WHICHHASTHREEMODES#ONVENTIONAL 3!2 AND)NTERFEROMETRIC 4HE#ONVENTIONALMODEPULSE LIMITED DESCRIBEDINTHEFORGOINGPARAGRAPHS REFLECTS ITS 0OSEIDON HERITAGE4HE 3!2 MODE IS BASED ON THE DELAY DOPPLER ARCHITECTURE WHICHOFFERSADVANTAGESINPRECISION RESOLUTION ANDALONG TRACKSURFACESLOPETOLER ANCE4HE)NTERFEROMETRICMODEISDESIGNEDTOMEASURETHECROSS TRACKSURFACESLOPE COMPONENT"OTHOFTHESEADVANCEDALTIMETERMODESHAVEBEENDEMONSTRATEDWITHTHE $0AIRBORNEALTIMETER 5NLIKE PREVIOUS RADAR ALTIMETER MISSIONS #RYO3AT WILL DOWNLINK ALL ALTIMETRIC DATAWITHESSENTIALLYNOONBOARDPROCESSING$ATAFROMEACHOFTHETHREEMODESARE
30!#% "!3%$2%-/4%3%.3).'2!$!23
£n°{Î
&)'52% 4HE#RYO3ATSATELLITEANDITS3)2!,ALTIMETER4HE TWOANTENNAS)NTERFEROMETRICMODE AREATHWARTTHEVELOCITYVECTOR SOTHATTHEDIFFERENTIALPHASEMODULOO OFTHEFIRSTRETURNINDICATES THE CROSS TRACK POSITION OF THE MINIMUM RANGE REFLECTING SURFACE WHICH IN EFFECT IS A MEASURE OF THE CROSS TRACK COMPONENT OF THE MEANSURFACEGRADIENT#OURTESYOF%UROPEAN3PACE!GENCY
PROCESSEDINGROUND BASEDFACILITIES SINCETHEMORECOMPLICATEDWAVEFORMSFROMICY SURFACESREQUIREITERATIVEDEVELOPMENTOFSUITABLEPROCESSINGALGORITHMSBYINVESTIGA TORSPRIORTORETRIEVINGTHEDESIREDINFORMATION4HECONVENTIONALMODEISUSEDFORTHE OPENOCEANFORCALIBRATIONANDSEA SURFACEHEIGHTREFERENCEPURPOSES ANDTHECENTRAL CONTINENTALICESHEETSTHATARERELATIVELYLEVEL4HEINTERFEROMETRICMODEISRESERVED FORTHEMORESTEEPLYSLOPINGMARGINSOFTHEICESHEETS4HESYNTHETICAPERTUREMODE ISUSEDPRIMARILYOVERSEAICE WHEREITSSHARPERSPATIALRESOLUTIONANDPRECISIONSUP PORTMEASURINGTHEDIFFERENCEBETWEENTHESEALEVELANDTHETOPSURFACEOFFLOATING ICEFREEBOARD "ECAUSETHEDENSITYOFICEISRELATIVELYWELL KNOWN SUCHFREEBOARD MEASUREMENTSCANBEINVERTEDTOESTIMATEICETHICKNESS
£n°{Ê * /,9Ê, ,4HEHISTORYOFPLANETARYIMAGINGRADARSISSUMMARIZEDIN4ABLE6ENUSHASBEEN THEMOSTPOPULARDESTINATION LARGELYBECAUSEITISCLOUD COVEREDHENCEITSSURFACEIS NOTOBSERVABLEBYOPTICALMEANS ITSMASSANDSIZEARESIMILARTOTHOSEOF%ARTH AND SPECTRALOBSERVATIONSHAVESHOWNTHATITSATMOSPHEREIS^#/ SUGGESTINGTHATA GREENHOUSEEFFECTCOULDHAVEOVERWHELMEDWHATMIGHTHAVEBEENAMOREHOSPITABLE PLANET!POPULARTHEMEFORPLANETARYEXPLORATIONBYRADARISTHESEARCHFOREVIDENCE OF WATER ESPECIALLY WATER ICE $ATA FROM RADAR MISSIONS ARE AVAILABLE THROUGH .!3!S0LANETARY$ATA3YSTEM &LIGHT 3YSTEMS 6ENERA PERFORMED THE FIRST SIMPLE RADAR MEASUREMENTS OF 6ENUS FROM A SPACECRAFT 6ENERA CARRIED A PULSE MODULATED RADAR ALTIMETER WHICH RETURNEDREADINGSDURINGITSDESCENTFROMORBITTOITSDEMISEONTHESURFACEOF6ENUS
£n°{{
2!$!2(!.$"//+
4!",% 0LANETARY2ADARS
-ISSION
52, 0LANET
9EAR
6ENERA 5332 0IONEER6ENUS/RBITER 06/ 53! 6ENERA5332 -AGELLAN53!
6ENUS 6ENUS
n
6ENUS 6ENUS
n n
#LEMENTINE53! #ASSINI53!
-OON 4ITAN
#HANDRAYAAN )NDIA
-OON
,UNAR2ECONNAISSANCE /RBITER,2/53!
-OON
2ADAR 2ADARALTIMETRY /2!$!LTIMETERALSOCOARSEIMAGERY CM 3!2ANDALTIMETER CMWAVELENGTH 3!2CMM MPIXELS COVERAGE "ISTATICSCATTEROMETEREXPERIMENTCM 42-CM 3!2RESOLUTIONnKM ANDALTIMETER &ORERUNNER-INI 2&53! CM3!2 SCATTEROMETER -INI 2&3!2CMANDCM IMAGER ANDINTERFEROMETER
HTTPWWWMENTALLANDSCAPECOM6?2ADAR-APPINGHTM HTTPHEASARCNASAGOVDOCSHEASARCMISSIONSPVOHTMLINSTRUMENTATION HTTPENWIKIPEDIAORGWIKI6ENERA? HTTPWWWJPLNASAGOVMAGELLAN HTTPFILERCASEEDU^SJRADVANCEDTH?CLOSE?CLEMENTINEHTML HTTPSATURNJPLNASAGOVSPACECRAFTINSTRUMENTS CASSINI RADARCFM HTTPWWWLPIUSRAEDUMEETINGSLPSCPDFPDFSEARCH CHANDRAYAAN RADAR HTTPLUNARGSFCNASAGOVMISSIONSSCANDINSTHTML
4HE CAPSULES TRAJECTORY WAS ESTIMATED BY DOPPLER RADIO READINGS AND AERODYNAMIC CALCULATIONS AND BY SUBTRACTING THIS FROM THE ABSOLUTE RADAR ALTITUDE READINGS A GROUNDPROFILECOULDBEMEASURED2EADINGSSPANAVERTICALRANGEOFKMDOWN TOKM DURINGWHICHTIMETHECAPSULEDRIFTEDHORIZONTALLYFORADISTANCEOFABOUT KM!NALYSISOFTHERETURNPULSESYIELDEDESTIMATESOFELEVATIONVARIATIONSOFTHE OVER FLOWNSURFACE6ENERA DEMONSTRATEDTHEFIRSTBISTATICPLANETARYRADAR OBSERVATIONS4HE6ENERA ORBITERSMAPPEDSTRIPSOFTHESURFACEOF6ENUS RANG INGFROMnKMLONGANDnKMWIDE! CMWAVELENGTHRADIOWAVE WASBEAMEDATTHESURFACEBYTHETELEMETRYANTENNA ANDBOTHTHEDIRECTANDREFLECTED SIGNALSWERERECORDEDBY%ARTH BASEDRECEIVERS4HEFIRSTANALYSISOFTHESEDATAGAVE ONE DIMENSIONALMEASUREMENTSOFTERRAINSHAPE WITHARESOLUTIONOFnKM 0IONEER6ENUSWASHOSTTOEXPERIMENTSWITHATOTALMASSOFKG INCLUDINGA RADARALTIMETER/2!$ WHICHALSOPRODUCEDRUDIMENTARYSURFACEMAPSASTHERADAR BEAMWASSCANNEDINTHEPLANEORTHOGONALTOTHEORBITBYTHESPACECRAFTS20-SPIN STABILIZATION4HERADARPACKAGEREQUIREDANAVERAGE7INPUTPOWERANDHADAMASS OFKG0EAKTRANSMITTEDPOWERWAS74HE8BANDAND3BANDCOMMUNICATIONS SYSTEMUSEDADESPUNANTENNA^MDIAMETERDISH 4HERADARALTIMETERPROVIDEDMANY YEARSOFDATAWITHAHEIGHTACCURACYOFM WHICHWASTHEBESTAVAILABLEINFORMATION ON6ENUSSURFACEFIGUREUNTIL-AGELLAN4HEALTIMETERSWAVEFORMSTRENGTHANDSHAPE WERE ANALYZED TO ESTIMATE SURFACE ELECTRICAL CONDUCTIVITY AND METER SCALE ROUGHNESS PROPERTIES4HESPACECRAFTS HOURORBITWASHIGHLYELLIPTICAL^KMPERIAPSIS AND^ KMAPOAPSISoFORMOSTOFTHEMISSION 2ADARDATAWERECOLLECTEDONLY BELOWKMALTITUDES WITHARESOLVEDFOOTPRINTONTHESURFACEOFKMALONGTRACK ANDKMACROSSTRACK o0ERIAPSISANDAPOAPSISARE RESPECTIVELY THEPOINTSALONGANELLIPTICALORBITTHATARECLOSESTTOANDFARTHESTFROMTHE GRAVITATIONALCENTEROFTHESYSTEM
30!#% "!3%$2%-/4%3%.3).'2!$!23
£n°{x
6ENERA SIMULTANEOUShTWINvMISSIONS WERETHEFIRSTSPACE BASED3!2MAP PERSOFANOTHERPLANET4HEYIMAGEDTHEAREAFROMTHENORTHPOLEDOWNTOABOUTn. LATITUDEOVERMONTHSOFOPERATIONS4HEIRRADARSHADTWOMODES IMAGINGANDALTIM ETRY OPERATING AT CM WAVELENGTHS )MAGING RESOLUTION WAS ^ KM %ACH KG SPACECRAFT WAS A CYLINDER M IN LENGTH4HE SYNTHETIC APERTURE RADAR ANTENNA WAS A rMETERPARABOLICCYLINDERREFLECTOR POWEREDBYAN WATTTRAVELINGWAVETUBE AMPLIFIER2ATHERTHANPULSEORCHIRPMODULATION 6ENERAUSEDACONTINUOUSTRANSMISSION MODULATEDBYACODEDSEQUENCEOFnPHASESHIFTS4HERECEIVEDSIGNALWASDIGITIZED INTOCOMPLEXNUMBERSBITS) BITS1 !RADARLOOKWASTAKENEVERYSECONDS ANDSTOREDINA2!-MEMORYBUFFER4OKEEPUPWITHTHISDATARATE RECORDINGALTERNATED BETWEEN TWO ONBOARD TAPE RECORDERS $ATA WERE DOWNLINKED EACH ORBIT ^ -"YTES ANDTHENPROCESSEDINGROUND BASEDFACILITIES%ACHIMAGINGPASSGENERATEDRADAR IMAGESTHATWERECOMBINEDINTOASURVEYSTRIPOFKMWIDEBYKMLONG4HESE WERESUBSEQUENTLYCOMBINEDINTOMOSAICS4HESPACECRAFTINCLUDEDA MDIAMETERPARA BOLICDISHANTENNAFORTHERADARALTIMETER!FTERTHEORBITSWEREACCURATELYDETERMINED THEALTIMETERSWERESWITCHEDTOHIGH RESOLUTIONMODE! ELEMENTPHASEMODULATION WASUSED WITHAHEIGHTAMBIGUITYOFKM)NLATERPHASESOFPROCESSING DOPPLER FREQUENCYANALYSISNARROWEDTHEEFFECTIVEFOOTPRINTTOKMBYKM4HEALTIMETER OPERATIONSINTERLEAVEDWITHTHOSEOFTHEIMAGER RESULTEDINTHEFIRSTRADARALTIMETRICMAP OFTHENORTHERN OF6ENUSCOMPRISEDOFMORETHAN INDIVIDUALMEASUREMENTS 4HE COMMUNICATIONS SYSTEM USED A DEDICATED M RADIO DISH ANTENNA4HE6ENERA SPACECRAFT WERE IN APPROXIMATELY ^ HOUR POLAR ORBITS WITH A PERIAPSIS ^ KM ATn.LATITUDE ANDAPOAPSIS^ KM -AGELLANMAPPEDOVEROFTHESURFACEOF6ENUS&IGURE WITHIMAG ING RESOLUTION AN ORDER OF MAGNITUDE BETTER THAN THE EARLIER 6ENERA MISSIONS
&)'52% 4HEIMPACTCRATER'OLUBKINAONTHESURFACEOF6ENUSIMAGED BY -AGELLAN 3 BAND (( POLARIZED 4HE KM MILE DIAMETER CRATER IS CHARACTERIZEDBYTERRACEDINNERWALLSANDACENTRALPEAK TYPICALOFLARGEIMPACT CRATERS ON %ARTH THE -OON AND -ARS 2OUGH EJECTA GIVE RISE TO STRONG RADAR RETURN ABLESSINGFORTHOSEINTERESTEDINPLANETARYGEOLOGY#OURTESYOF.!3!
£n°{È
2!$!2(!.$"//+
!LTIMETRYANDRADIOMETRYDATAALSOMEASUREDTHESURFACETOPOGRAPHYANDELECTRI CALCHARACTERISTICS-AGELLANSELLIPTICALORBITWASINCLINEDATn WHICHALLOWED VIRTUALLYFULLACCESSTOTHESURFACEBYTHESIDE LOOKING3!2"YTHEENDOFTHEMIS SION -AGELLANHADRETURNEDMOREDATATHANALLPRIORPLANETARYMISSIONSCOMBINED 4HERADAROPERATEDINTHREEMODESIMAGER ALTIMETER ANDRADIOMETERINTERLEAVED DURINGEACHPASS4HE8BANDDATADOWNLINKSUPPORTEDDATARATESOFKBITSOR KBITS4HE MDIAMETERHIGH GAINANTENNAWASUSEDFORBOTHTHERADARAND FORTELECOMMUNICATIONS3PACECRAFTMASSWASKGTHERADARMASSWASKG )NPUT POWER WAS 7 AT 6$# -AGELLAN OPERATED AT 3 BAND 'HZ RADIATINGAPEAKPOWEROF7.OMINALPULSELENGTHWAS§SEC WITH02& (Zn (Z SELECTABLE TO ACCOMMODATE THE WIDE VARIATIONS IN RANGE AND INCIDENCENECESSITATEDBYTHEELLIPTICALORBIT)TACHIEVED MRESOLUTIONIN3!2 MAPPINGMODE MHEIGHTRESOLUTIONINALTIMETERMODE ANDn#INRADIOMETER MODE!LL-AGELLANDATAAREAVAILABLETHROUGHTHE0LANETARY$ATA3YSTEM #ASSINI A MULTIMODE RADAR MAPPER LEVERAGED FROM -AGELLANS HERITAGE WAS INCLUDED IN THE INSTRUMENT PAYLOAD OF THE #ASSINI (UYGENS -ISSION WHICH WAS LAUNCHEDIN/CTOBERANDSTARTEDITSFOUR YEARTOUROF3ATURNANDITSMOONSIN *ULY4HEMOTIVATIONFORTHE#ASSINIMAPPERWASTHESAMEASTHATFOR-AGELLAN NAMELY TOMAKEMEASUREMENTSOFTHESURFACEOF4ITANTHROUGHITSDENSECLOUDCOVER $URINGITSEXTENSIVETOUROFTHE3ATURNIANSYSTEM THE#ASSINI (UYGENSMISSIONWAS TOCOMPLETEFLYBYSOF4ITAN OFWHICHWILLBEATTHECLOSESTAPPROACHOFLESSTHAN KM OFWHICHWILLHAVEMINIMUMALTITUDESOF^KM4HEFIRSTCLOSEFLYBY WASIN.OVEMBER FROMWHICHTHEFIRSTRADARIMAGESOFTHESURFACEWERECOL LECTED4HERADARANTENNAUSESTHEM( POLARIZEDHIGH GAINTELECOMMUNICATIONS ANTENNA ASTRATEGYSIMILARTOTHATPIONEEREDON-AGELLAN3EVENBEAMS EACHATDIF FERENTFREQUENCY WIDTH ANDBORESIGHTORIENTATION AREREQUIREDTOSUPPORTMULTIPLEXED ALTIMETRYANDSCATTEROMETRYASWELLASIMAGINGANDRADIOMETRY4HERADARSMASSIS ^KG ANDITSINPUTPOWERREQUIREMENTIS^70EAKDATARATESAREONTHEORDER OFKBITS!LLMODESOPERATEAT+UBAND'(Z )NITSMOSTFAVORABLELOWER ALTITUDEIMAGINGGEOMETRY GROUNDRANGEANDAZIMUTHRESOLUTIONSAREONTHEORDEROF KM ATLOOKS!THIGHERALTITUDES MORELOOKSAREGATHEREDTOPARTIALLYOFFSETTHE DEGRADEDRESOLUTION4HERADARSNOISE EQUIVALENTRRANGESFROM^ D"ATLOW ALTITUDE TO^ D"ATKMALTITUDE)NCONTRASTTOTHESCHEMEUSEDON-AGELLAN SMALLERANGLESOFINCIDENCEANDLOWERBANDWIDTHAREUSEDFORTHEHIGHERALTITUDES4HE LOWERBANDWIDTHHELPSTOREDUCETHEMEANNOISELEVEL WHEREASTHESHALLOWERINCIDENT ANGLEHELPSTOMAINTAINRANGERESOLUTIONWITHSMALLERRADIATEDPULSEBANDWIDTH #LEMENTINE ONEOFTHEFIRSThFASTERBETTERCHEAPERvMISSIONS HADPRIMARYOBJECTIVES INCLUDINGLASERALTIMETRYANDOPTICALSURFACEMAPPINGOFTHE-OONASWELLASTECHNOL OGYDEMONSTRATION4HEMAINPAYLOADINSTRUMENTATIONWASCOMPRISEDOFFOUROPTICAL CAMERAS INCLUDINGONEWITHALASERALTIMETER-AJORNEWINFORMATIONABOUTTHE-OON WASPROVIDEDFROM#LEMENTINESDATACOLLECTEDDURINGITSDAYSINLUNARORBIT #LEMENTINEISRELEVANTTOTHISCHAPTERBECAUSEOFAUNIQUEBISTATICRADAREXPERIMENT CONDUCTEDWITHTHE3BANDCM 2&DATASYSTEM4HELUNARSOUTHPOLEWASILLU MINATEDBY#LEMENTINESCOMMUNICATIONSANTENNAWATTS CIRCULARLYPOLARIZED AND THEREFLECTIONSFROMTHESPECULARPOINTWERETRACKEDBYANANTENNAOFTHE$EEP3PACE .ETWORK$3. OVERFOURPASSES4HEOBSERVEDREFLECTEDSIGNALCHARACTERISTICSWERE CONSISTENTWITHNORMALLUNARREGOLITHpONTHREEPASSES BUTDATAFROMTHEFOURTHPASS p&OUND VIRTUALLY EVERYWHERE ON THE -OONS SURFACE REGOLITH IS A LAYER OF GRANULAR ROCKY MATERIAL COVERING SOLIDROCK
30!#% "!3%$2%-/4%3%.3).'2!$!23
£n°{Ç
SEEMEDTOSHOWANENHANCEDSTRENGTHTHATCORRESPONDEDTOTHESPECULARPOINTPASS INGACROSSTHEFLOOROFTHECRATER3HACKELTON3UCHENHANCEDREFLECTIONS ESPECIALLY INTHEhUNEXPECTEDvSENSEOFCIRCULARPOLARIZATION AREINDICATIVEOFVOLUMETRICRADAR RESPONSEFROMVERYCOLDFROZENVOLATILESSUCHASWATER ICE BESTILLUSTRATEDBY%ARTH BASEDRADAROBSERVATIONSOF*UPITERSICYMOONS4HESUBSEQUENTCLAIMTHATWATER ICE HADBEENDISCOVEREDATTHE-OONPRECIPITATEDWIDEINTEREST7HENINDEPENDENTANALY SESOFTHE#LEMENTINEDATAFAILEDTOREPRODUCETHEORIGINALRESULT CONSIDERABLE CONTROVERSYWASGENERATEDASWELL$ISCOVERYANDORVERIFICATIONOFPOLARICEDEPOSITS ONTHE-OONEMERGEDASAMAJOROBJECTIVEOF.!3!SEXPLORATIONPROGRAM ANDIF PROVEN WOULDBEANESSENTIALRESOURCEFORHABITABLEOUTPOSTSATTHE-OON 2ADAR%XPLORATIONFOR0LANETARY)CE 6OLUMETRICICEGIVESRISETOTWOUNUSUAL RADAR RESPONSES7HEN ILLUMINATED BY A CIRCULARLY POLARIZED FIELD THE PREDOMINANT BACKSCATTERFROMMOSTNATURALSURFACESHASTHEOPPOSITESENSEOFCIRCULARPOLARIZATION )NTHECASEOFVOLUMETRICICE HOWEVER THEBACKSCATTERHASTHESAMESENSEOFCIRCU LARPOLARIZATION4HECLASSICALMEASUREOFTHISEFFECTISTHECIRCULAR POLARIZATIONRATIO #02 R3#R/# ORhSAMESENSEOVEROPPOSITESENSEvCIRCULARLYPOLARIZEDBACKSCATTER STRENGTHS4HETOTALREFLECTEDPOWERFROMVOLUMETRICICEISRELATIVELYSTRONG ATLEAST FORhCLEANvDEPOSITS"OTHTHEPOLARIZATIONANDRADARBRIGHTNESSEFFECTSAREEXPLAINED BYTHECOHERENTOPPOSITIONBACKSCATTEREFFECT#/"% 7ATER ICEWASPREDICTEDMANYYEARSAGOTOHAVEACCUMULATEDOVERSOMETWOBILLION YEARSINTHEFLOOROFLUNARCRATERSOROTHERFEATURESWHOSEDEPTHANDLATITUDEKEPTTHEM INPERMANENTSOLARSHADOW4HEONLYSOURCEOFHEATFORTHOSEREGIONSWOULDBEBACK GROUNDSTARLIGHTANDENERGYFROMTHE-OONSINTERIOR SOTHATTHEAMBIENTTEMPERATURE WOULDBENOMORETHAN^+!SWATER ICEENTERSSUCHACOLDSPACEFROMCOMETS IT ACCUMULATES4HISPROCESSGENERALLYISACCEPTEDASANEXPLANATIONOFTHERADAR BRIGHT RESPONSEFROM-ERCURYSPOLARCRATERS FOREXAMPLE ASOBSERVEDBY%ARTH BASEDRADAR TELESCOPES$UETOTHESMALLAXIALTILTOFTHE-OON HOWEVER RADARTELESCOPESSUCHAS !RECIBOHAVENOSIMILAROPPORTUNITYTOEXPLORETHEFLOORSOFTHELUNARPOLARCRATERS 4HEPROBLEMISTHATRELATIVELYLARGE#02ISNOTUNIQUETOVOLUMETRICICEDEPOSITS $IHEDRALTWO DIMENSIONAL CORNERSALSOREFLECTMOSTSTRONGLYINTHESAMESENSEASTHE INCIDENTCIRCULARPOLARIZATION.ATURALLYOCCURRINGDIHEDRALS SUCHASROUGHROCKFOR MATIONSCREATEDBYALARGEIMPACT COULDGENERATEFALSEWATER ICESIGNATURES4OREDUCE THEPOTENTIALAMBIGUITYOF#02ANDBRIGHTNESSMEASUREMENTS THERADAROBSERVATIONS MUSTBEREPEATABLEANDSHOULDBECORRELATEDWITHOTHERINDICATORS #HANDRAYAAN AND THE ,UNAR 2ECONNAISSANCE /RBITER ,2/ INCLUDE IN EACH OF THEIRPAYLOADSAh-INI 2&vRADAR4HEVERSIONFOR#HANDRAYAAN ISAT3 BAND CM WAVELENGTH WITH MRESOLUTIONATLOOKS4HE-INI 2&FOR,2/HASTWOFREQUEN CIES 3BANDCM AND8BANDCM ANDTWORESOLUTIONS MATLOOKS AND MATLOOKS4HE,2/RADARALSOINCLUDESANINTERFEROMETRICMODE WHICHREQUIRES A CONTINUOUS 02& IN CONTRAST TO THE BURST PLAN USED FOR THE OTHER MODES "OTH HAVE MODERATEINCIDENTANGLES^DEGREES MODERATESWATHWIDTHSKMTOKM AND OPERATEFROMLOWALTITUDESKMANDKM RESPECTIVELY 'IVENTHEAPPLICABLESMALL
RANGE VELOCITYPRODUCT4ABLE THEANTENNAAREANEEDSTOBEONLY^M TOSATISFY THEMINIMUMAREACONSTRAINT%Q 4HESERADARSAREINDEEDLOWMASS ATABOUTKG ANDKG RESPECTIVELY INCLUDINGINEACHCASETHEIRANTENNA !MAJOROBJECTIVEFORBOTHOFTHESERADARSISTOLOOKFOREVIDENCEOFICEDEPOSITS INTHEPERMANENTLYSHADOWEDAREASOFTHE-OONSPOLARREGIONS4HISREQUIRESTHAT THEYMUSTMEASURETHECIRCULARPOLARIZATIONRATIO#02 (ENCE THEYTRANSMITCIRCULAR POLARIZATION ANDTHEYAREDUAL POLARIZEDONRECEIVE4HEIRANTENNASARECOMPRISED OFPASSIVEARRAYSOF( AND6 POLARIZEDELEMENTS DRIVENSIMULTANEOUSLYnOUTOF
£n°{n
2!$!2(!.$"//+
PHASESOTHATTHERADIATEDPOLARIZATIONISCIRCULAREITHERLEFTORRIGHT 4HERECEIVED LINEARPOLARIZATIONSAREMAINTAINEDTHROUGHTHEREMAINDEROFTHESYSTEMTOTHEIMAGE
PROCESSOR OUTPUT PRODUCTS4HIS RESULTS IN THE HYBRID POLARITY ARCHITECTURE THAT IS OUTLINEDBELOW -AGELLAN)NNOVATIVE6ENUS-APPER -AGELLAN&IGURE HADTOFACEUP TOTWODRIVINGMISSIONRESTRAINTSCOSTANDDATARATE4HEFIRSTWASSETBY.!3!ANDTHE 53GOVERNMENTBUDGETAUTHORITIES4HESECONDWASSETBYPHYSICS CONDITIONALUPON THEDATA RATECAPABILITIESOFTHE$EEP3PACE.ETWORK4HELESSON OFCOURSE ISTHAT ITISNOTENOUGHTODOGOODREADhBIGBUDGET 3"2 BASEDv SCIENCE ITMUSTBEDONE EFFICIENTLYANDRELATIVELYPATIENTLY)NTHECASEOF-AGELLAN HOWEVER THESETOP LEVEL RESTRAINTSMOTIVATEDASUPERBINNOVATIVERADARDESIGN #OST 4HERE WERE SEVERAL CONSEQUENCES TO THE SEVERE REDUCTION IN APPROVED FUNDS RELATIVE TO FUNDS REQUESTED FOR THE ORIGINAL 6ENUS /RBITING )MAGING 2ADAR 6/)2 MISSION2ATHERTHANACONVENTIONALCIRCULARORBIT -AGELLANWASREDESIGNED FORANELLIPTICALORBIT&IGURE WHICHHADCONSIDERABLYLESSASSOCIATEDCOSTS AND RISK!LSO RATHER THAN THE ORIGINAL LARGE HIGH ASPECT RATIO ANTENNA TYPICAL OF SPACE BASED3!2S -AGELLANWASOBLIGEDTOUSEASPARECIRCULARCOMMUNICATIONS ANTENNALEFTOVERFROMAPREVIOUSMISSION7HEREASTHESEMAYSOUNDLIKEBENIGN IFNOTTRIVIALMODIFICATIONS THEYNECESSITATEDPARADIGM SHIFTINGINNOVATIONSBYTHE 3!2DESIGNTEAM !NTENNA 4HE KEY ELEMENT IN ANY SPACE BASED 3!2 DESIGN IS THE ANTENNA )T DETERMINESRANGESWATHCOVERAGEANDREQUIREDMINIMUMTRANSMITTERPOWER ANDHASA MAJORINFLUENCEONRESOLUTIONANDDATARATE4HE-AGELLANANTENNA A MDIAMETER DISH WASASIGNIFICANTDEPARTUREFROMTHECONVENTIONALHIGHLYASYMMETRICRECTANGULAR ANTENNASTHATWERETHENINFAVORFOR3!2S
&)'52% !RTISTSIMPRESSIONOF-AGELLANOBSERVINGTHESURFACE OF6ENUS BACKLITBYTHESUN FEATURINGTHERADARANDHIGH GAINCOMMUNI CATIONS ANTENNAANDTHESMALLERHORNANTENNAFORTHEALTIMETER#OURTESY OF.!3!
30!#% "!3%$2%-/4%3%.3).'2!$!23
£n°{
&)'52% $ETAILSOF-AGELLANSELLIPTICALORBIT DOMINATEDBY^MINUTESOF DATA TAKE AND HOURS OF DATA DOWNLINK DURING EACH HOUR ORBIT PERIOD 'RAPHIC COURTESYOF.!3!
4HEVERTICALDIMENSIONOFTHEANTENNATOGETHERWITHRANGE INCIDENCE ANDWAVE LENGTH DETERMINEDTHEWIDTHOFTHEILLUMINATEDSWATHONTHESURFACE4HISPROVIDEDAN UPPERBOUNDONTHEIMAGEDSWATHWIDTH WHICH INTHECASEOF-AGELLAN WASLESSTHAN THESWATHACTUALLYILLUMINATED4HEIMAGEDSWATHWIDTHWASCHOSENTOBESOMEWHAT WIDERTHANTHEORBIT TO ORBITTRANSLATIONOF6ENUSSURFACEDUETOPLANETROTATION4HE PERIODOFTHEELLIPTICALORBITWASSELECTEDTOBEABOUTTHREEHOURS SOTHATINSUCCESSION EACHIMAGINGPASSOVERLAPPEDANDEXTENDEDTHESURFACEIMAGEDONPREVIOUSPASSES )NTHEALONG TRACKDIRECTION THEANTENNASIZEHADFAR REACHINGCONSEQUENCES4HE THEORETICALSINGLE LOOK AZIMUTHRESOLUTIONAVAILABLEFROMTHE-AGELLANANTENNACOULD BEABOUTMETERS3ECTION 4HISISONTHEORDEROFTIMESSMALLERTHANTHESCI ENCEREQUIREMENTOFMETERSAZIMUTHRESOLUTION)TFOLLOWEDTHATSINGLE LOOK M DATACOULDBECOLLECTEDBYOPERATINGTHERADARONLYOFTHETIME)F.,LOOKSWERE REQUIRED THENTHEIMPLIEDOPERATINGDUTYFACTORWOULDBE., LARGERBYAFACTOROF .,4HERESULTISTHEBURSTMODE3ECTION INWHICHTHERADAROPERATESATMUCHLESS THANOFTHETIME"URSTMODEISASTANDARDSTRATEGYFOR3!2SDESIGNEDTOEXPLORE THE-OONOROTHERPLANETARYBODIES USINGANTENNASWHOSEALONG TRACKDIMENSIONIS MUCHSMALLERTHANTHEAZIMUTHRESOLUTIONREQUIREDOFTHEDATA4HELOOKSPARAMETER., DESERVESSPECIALCOMMENTINTHE3"2CONTEXT SUMMARIZEDBELOW 4HE -AGELLAN ANTENNA WAS USED AS THE HIGH GAIN ANTENNA FOR DATA DOWNLINK AS WELLASFORTHE3!2$URINGTHEHIGH ALTITUDESEGMENTOFEACHORBIT THESPACECRAFT WASORIENTEDTOPOINTTHEANTENNATOWARD%ARTH4HEANTENNAHADTWOFEEDS ONEAT3 BAND(( POLARIZATIONFORTHERADAR AND8BANDCIRCULAR POLARIZATIONFORTELEMETRY !FTEREACHPOLE TO POLEDATACOLLECTION THETELEMETRYTRANSFERREDTHEACCUMULATEDDATA TOONEOFTHETHREE$EEP3PACE.ETWORK$3. RECEIVINGSTATIONS SOTHAT INCONSE QUENCE THEDATADUMPKEPTPACEWITHTHEDATATAKE PERORBIT /RBIT &ORREASONSDIRECTLYATTRIBUTABLETOPRINCIPLESOFORBITALMECHANICS ITWAS MUCHLESSCOSTLYTOGOINTOANELLIPTICALORBITAT6ENUSRATHERTHANACIRCULARONE4HE FACTTHATITWOULDBECONSIDERABLYMOREDIFFICULTTOGETDECENTIMAGERYSUCCESSFULLY
£n°xä
2!$!2(!.$"//+
FROMANELLIPTICALORBITWASOFLITTLECONCERNTOTHEBUDGET MASTERS ALTHOUGHTHEELLIP TICALORBITCONSTRAINTATTRACTEDMORETHANALITTLEATTENTIONFROMTHE3!2DESIGNTEAM 4HE-AGELLANRADARHADTOADAPTTOVARIATIONSINRELATIVEALTITUDEFROMAPPROXIMATELY KMNEARTHEEQUATOR TOMORETHANKMOVERTHEPOLES 1UITEREASONABLY ONEMIGHTEXPECTTHATTHERESULTINGIMAGERYLETALONETHEIMPLIEDTIMINGANDSCAL INGISSUESWOULDSUFFERASACONSEQUENCE4HANKSTOTHEMISSIONDESIGN HOWEVER -AGELLANIMAGEQUALITYISSURPRISINGLYCONSISTENT POLETOPOLE4HEREASONSPROVIDE ANIMPORTANTOBJECTLESSON 3INCETHE-AGELLANRADARWASOPERATEDINBURSTMODE ITWASCONVENIENTASWELL ASNECESSARY PRIORTOEACHBURSTTOSETTHEMODEPARAMETERS WHICH INGENERAL VARIED FROMBURSTTOBURST#RITICALPARAMETERSINCLUDED02& RANGEGATE BURSTLENGTH BURST PERIOD ANDSPACECRAFTROLL4HEPARAMETERFILESWEREPREPAREDINADVANCE BASEDONTHE DATACOLLECTIONGEOMETRY ANDTURNEDINTOCOMMANDSTOBEGENERATEDBYTHERADARMAP PINGSEQUENCINGSOFTWARE4HERESULTWASASETOFABOUTUNIQUECONFIGURATIONS EACHTIEDTOSPECIFICSEGMENTSOFTHEORBIT)NOPERATION SUITABLECOMMANDSWEREPRE LOADEDINTOTHEONBOARD3!2CONTROLPROCESSORFOREACHTHREE DAYMAPPINGINTERVAL )NORDERTOOFFSETTHETENFOLDALTITUDECHANGEON3!2IMAGEQUALITY THE3!2OPER ATINGPROFILEWASDESIGNEDTOEXPLOITAVARIETYOFINCIDENTANGLES!TTHESTARTOFEACH IMAGING PASS AT HIGH ALTITUDE THE INCIDENCE WAS SLEWED FROM STEEP NEAR THE POLE TOSHALLOWINTHENEIGHBORHOODOFTHEEQUATOR BACKTOSTEEPWHENAPPROACHINGTHE OPPOSITEPOLE4HISINCIDENCEVARIATIONHELPEDTOOFFSETTHELARGECHANGEINRADARRANGE TOTHEIMAGEDSWATH BUTITMEANTALSOTHATTHERANGERESOLUTIONASEXPRESSEDONTHE SURFACE VARIED AS A FUNCTION OF LATITUDE &OR A CONSTANT RADAR BANDWIDTH THE EFFEC TIVESURFACERANGERESOLUTIONATSHALLOWERINCIDENCEISIMPROVEDOVERTHATACHIEVEDAT STEEPERINCIDENCE&ORTUNATELY ATSTEEPERINCIDENCE ANDHENCEATLONGERRANGES THERE WASMORETIMEAVAILABLETOGATHERMORELOOKS )MAGE1UALITY ,OOKSANDRESOLUTIONWORKTOGETHERTODETERMINETHEIMAGEQUAL ITY READ hGEOPHYSICAL INFORMATION POTENTIALv OF 3!2 IMAGERY OVER NATURAL TERRAIN COMPOSEDOFDISTRIBUTEDSCATTERERS4HEGOVERNINGEXPRESSIONISTHE3!2IMAGEQUAL ITYPARAMETER
13!2
., R2GR!Z
WHERE.,ISTHENUMBEROFSTATISTICALLYINDEPENDENT LOOKS ANDR2G ANDR!Z ARETHE RANGEANDAZIMUTHRESOLUTION RESPECTIVELY ONTHESURFACE(ERETHEIMPORTANTGENERAL IZABLELESSONISTHATANINCREASEINNUMBEROFLOOKSCANBEAPPLIEDTOOFFSETADECREASE INRANGERESOLUTIONWITHINREASONANDINTHISKINDOFEXPLORATORYSPACE BASED3!2 DATA .OTE THAT BOTH LOOKS AND RESOLUTION REQUIRE SUPPORT IN BANDWIDTH )T FOLLOWS THAT13!2ISPROPORTIONALTOTHEPRODUCTOFTHERANGEANDAZIMUTHBANDWIDTHS HENCE PROPORTIONALTOTHETWO DIMENSIONAL INFORMATIONCAPACITYOFTHERADARINTHE3HANNON SENSE4HIS PRINCIPLE WAS APPLIED WITH GREAT PROFIT TO THE -AGELLAN 3!2 DESIGN ASILLUSTRATEDBY4ABLE&ROMTHATTABLE ONECANVERIFYTHATTHEIMAGEQUALITYOF -AGELLANDATAVARIEDBYNOMORETHAN^oPOLETOPOLE INSPITEOFLARGEVARIATIONS INRADARRANGE INCIDENTANGLE ANDGROUNDRANGERESOLUTION $ATA2ATE -AGELLAN3!2DATAWERERELAYEDFROM6ENUSTO%ARTHVIATHE$3. 4HISMAJORCOMMUNICATIONSYSTEMIMPOSEDAWORKINGLIMITOFABOUTKBITSON THE 3!2 DATA TELEMETRY 7HEREAS THIS MAY SEEM RATHER LARGE IT IS MINUSCULE BY
30!#% "!3%$2%-/4%3%.3).'2!$!23
£n°x£
4!",% )MAGE1UALITY-AGELLAN2ESOLUTIONAND,OOKS
!LTITUDEKM
)NCIDENCE DEGREES
R2M
R!M
,OOKS.,
13!2.,R2R!
rn rn rn rn rn
SPACE BASED3!2STANDARDS&OREXAMPLE THEDIGITALDATARATEFORTHE%23 AND 2!$!23!4 %ARTH OBSERVING 3!2S IS ON THE ORDER OF -BITS .EWER DESIGNS CLAIMUPTO-BITS3INCETHE-AGELLANOBJECTIVEWASTOIMAGEASUBSTANTIALPOR TIONOFTHESURFACEOFTHEENTIREPLANETAT MRESOLUTIONWITHINTHELENGTHOFTHE PRIMARYMISSION THE$3.DATA RATECAPABILITYEMERGEDASTHETOUGHESTREQUIREMENT ONTHEENTIRESYSTEM 2AW3!2DATARATEISPROPORTIONALTOTHEIMAGEQUALITYFACTOR SWATHWIDTH SPACE CRAFTVELOCITY ANDTHENUMBEROFDIGITALBITSPERDATASAMPLE/FCOURSE MEANDATA RATECANBERELAXEDIFTHEDATAFROMANYGIVENPASSCANBECOLLECTEDANDTHENPLAYED BACKATASLOWERRATE!LTHOUGHTHISSTRATEGYWASEXPLOITEDBYTHE-AGELLANDESIGN TOLERANCEFORWHICHWASSETUPBYTHEELLIPTICALORBIT ITWASNOTSUFFICIENTTOSOLVETHE LIMITEDDATA RATEPROBLEM 4HEONLYDEGREEOFFREEDOMREMAININGINTHEDATA RATEBUDGETWASTHENUMBEROF BITSRETAINEDFOREACHSAMPLEINTHERAW3!2DATASTREAM7ORKINGBACKTHROUGHTHE $3.CONSTRAINT ITTURNEDOUTTHATTHEREWEREONLYTWOBITSAVAILABLEFOR-AGELLANS RAW3!2DATA 9ESA BIT3!2!NDAGAIN THEUNIQUECHARACTERISTICSOFANORBITAL3!2MADE THISANACCEPTABLESOLUTIONFORTHE-AGELLANDESIGN4HEKEYREQUIREMENTSFORTHIS PARADIGMARETWO ANEFFECTIVESIGNALENCODINGTHATISVERYLARGEAND ANIMAG ING ENVIRONMENT THAT IS DENSE AND DOMINATED BY DISTRIBUTED RANDOM BACKSCATTER 0LANETARY3!2SANDMANY%ARTH OBSERVINGSPACE BASEDRADARS EASILYSATISFYTHESE REQUIREMENTS/NEMEASUREOFANIMAGINGRADARSEXTENSIVESIGNALENCODINGISTHE PRODUCTOFITSRANGEANDAZIMUTHTIME BANDWIDTHPRODUCTS OREQUIVALENTLY ITSPOTEN TIALTWO DIMENSIONALCOMPRESSIONRATIO)NTHECASEOF3!2DATA THISRATIOISGIVEN BY THE AREA OF THE INSTANTANEOUS PULSE FOOTPRINT ANTENNA WIDTH BY PROJECTED PULSE LENGTH DIVIDEDBYTHERESOLVEDCELLAREATHEPRODUCTOFAZIMUTHANDRANGERESOLU TION 4HISRATIOVARIEDBYMODEFOR-AGELLAN BUT INGENERAL WASWELLINEXCESSOF WHICHTURNSINTOAGAININDYNAMICRANGEFROMTHESIGNALDOMAINTOTHEIMAGE DOMAINOFD" 4HEh BITMETHODvWASBASEDONA"LOCK !DAPTIVE1UANTIZER"!1 4HISIN EFFECTIMPLEMENTEDANAUTOMATICGAINCONTROL!'# THATSELECTEDTHEMOSTINFLUENTIAL DIGITALSAMPLESBITS FROMTHERAW3!2DATASTREAM!SDESIGNEDFOR-AGELLAN THE DATAWEREDIGITIZEDINTOBITS IN PHASEANDQUADRATURE)1 4HEANALOG TO DIGITAL STAGEWASFOLLOWEDBYTHE"!1OPERATION WHICHSELECTEDTHETWOMOSTSIGNIFICANTBITS INEACH)1 DATAPAIR RELATIVETOAMEANSIGNALLEVELTHATHADBEENESTABLISHEDFROM THEPREVIOUSBURSTOFRECEIVEDDATA4HEMEANSIGNALLEVELVARIEDVERYSLOWLYBURST TOBURSTSINCEADJACENTBURSTSCOVEREDESSENTIALLYTHESAMESCENEELEMENTS4HEMEAN SIGNALLEVEL!'#SETTING WASINCLUDEDINTHEHEADERFOREACHBURSTSDATARECORDTO BEUSEDINSUBSEQUENT3!2IMAGEFORMATION
£n°xÓ
2!$!2(!.$"//+
!LTHOUGHTHEDYNAMICRANGEOFTHERAW3!2DATAOUTOFA"!1OPERATORISSEVERELY LIMITED THEPOTENTIALDYNAMICRANGEOFTHERESULTINGIMAGEDATAISMUCHLARGERITIS BOUNDEDABOVEBYTHEPRODUCTOFTHEINPUTDYNAMICRANGEANDTHETWO DIMENSIONAL COMPRESSIONRATIOOFTHE3!2DATA4HUS THEDYNAMICRANGECAPACITYAFTERPROCESSING FOR-AGELLANIMAGERYWASINEXCESSOFD"4HISWASWELLILLUSTRATEDINTHEMANY THOUSANDSOFIMAGEFRAMESFORMEDFROM-AGELLANS3!2DATA (YBRID POLARITY !RCHITECTURE ! LEADING HIGH LEVEL OBJECTIVE OF A RADAR DES TINEDFORTHE-OON -ARS ORANYOTHERPLANETARYBODYISTOMAXIMIZEITSMEASUREMENT POTENTIAL WHILEALSOMINIMIZINGITSRESOURCEDEMANDSPRINCIPALLYPOWERANDMASS )F SENSITIVITYTOFROZENVOLATILESISAREQUIREMENTLEVIEDONAPLANETARYEXPLORATORYRADAR THENTHESYSTEMSHOULDBEDUAL POLARIZEDANDMUSTTRANSMITCIRCULARPOLARIZATION!S REVIEWEDIN3ECTION ADUAL POLARIZEDRADARMAXIMIZESITSMEASUREMENTCAPABILI TIESONLYIFITRETAINSTHERELATIVEPHASEASWELLASTHEMAGNITUDESOFTHETWORECEIVED AMPLITUDES SUCHAS%(AND%6INTHELINEARPOLARIZATIONBASIS)THASBEENKNOWNSINCE THATAQUASI MONOCHROMATIC%-FIELDCANBEFULLYCHARACTERIZEDBYTHEFOUR3TOKES PARAMETERS)NTERMSOFLINEARLYPOLARIZEDRECEIVEDDATA THE3TOKESPARAMETERSARE 3 \ %( \ \ %6 \
3 \ %( \ \ %6 \
3 2E %( %6
3 )M %( %6
WHERE DENOTESCOMPLEXCONJUGATE ANDTHECARATS INDICATEANAVERAGETAKENOVER SEVERALSAMPLES#LEARLY THERELATIVEPHASEBETWEENTHETWOPOLARIZATIONSISANESSENTIAL FACTORFORTWOOFTHEFOUR3TOKESPARAMETERS$ATAEXPRESSEDTHROUGHTHE3TOKESPARAM ETERSAREWELL SUITEDTOBEINGEXPLOITEDBYMATRIXDECOMPOSITIONMETHODOLOGY &OR A GIVEN TRANSMITTED POLARIZATION THE VALUES OF THESE 3TOKES PARAMETERS ARE INVARIANTWITHRESPECTTOTHEPOLARIZATIONBASISOFTHERECEIVER)TFOLLOWSTHATTHEOPTI MUMARCHITECTUREISHYBRID POLARITYCIRCULARLYPOLARIZEDONTRANSMITANDLINEARLY DUAL POLARIZED ON RECEIVE &IGURE 4HIS ARCHITECTURE REQUIRES LESS MASS AND OFFERSGREATEREFFICIENCYTHANALTERNATIVES WHILECAPTURINGALLOFTHEPOTENTIALINFORMA TIONINTHEBACKSCATTEREDFIELD !NANTENNACOMPRISEDOFTWOLINEARARRAYSSUCHAS(AND6 WILLRADIATEACIRCULARLY POLARIZEDFIELDIFTHESETSOFELEMENTSAREDRIVENSIMULTANEOUSLYANDnOUTOFPHASE ASSHOWNIN&IGURE)NPRACTICE THEAMPLITUDEWEIGHTINGANDRELATIVEPHASING OFTHEARRAYSWILLSELDOMBEPERFECT!SARESULT THERADIATEDFIELDWILLBESOMEWHAT ELLIPTICAL RATHERTHANPURELYCIRCULAR4HEHYBRID POLARITYARCHITECTUREISSELF CALIBRATING AND THEREFORE RELATIVELYROBUSTINRESPONSETOSUCHIMPERFECTIONS)NBRIEF UNDERTHE CONDITIONTHATR(( R66 THEMEANSIGNALLEVELINTHETWORECEIVECHANNELSSHOULDBE EQUAL)NTERMSOFTHE3TOKESPARAMETERS 3 4HE(AND6BACKSCATTERCOEFFICIENTS WILLALWAYSBEEQUIVALENTWHENTHERADARSILLUMINATIONISPERPENDICULARTOTHESURFACE (ENCE ANYHYBRID POLARITYRADARCANSETUPTHISCONDITIONBYTHESIMPLEEXPEDIENTOF LOOKINGDOWNONAHORIZONTALSURFACEDURINGACALIBRATIONEXERCISE$ISCREPANCIESIN EITHERAMPLITUDEORPHASEWILLBEEVIDENTFROMSUCHDATACOLLECTEDOVERARANDOMDIS TRIBUTEDSCENE4HEREISNONEEDFORAKNOWNPOINT TARGETREFERENCEINTHEFIELDOFVIEW 4HE3TOKESPARAMETERSTHATCORRESPONDTOSUCHMEASUREMENTSARESUFFICIENTTOCHARAC TERIZETHERELATIVE(6PHASEOFTHETRANSMITTEDFIELD ASWELLASTHATOFTHERECEIVERS
30!#% "!3%$2%-/4%3%.3).'2!$!23
£n°xÎ
&)'52% 4HE HYBRID POLARITY 3!2 ARCHITECTURE FIRST USED BY THE -INI 2& LUNAR RADARS ON #HANDRAYAAN AND,2/
£n°xÊ - // ," / ,3PACE BASEDREMOTESENSINGSCATTEROMETERSMEASURETHENORMALIZEDBACKSCATTERWITH SUFFICIENTPRECISIONANDACCURACYTODEDUCETHEVALUEOFONEORMOREPARAMETERSOF GEOPHYSICALSIGNIFICANCE&OREXAMPLE THEPOWERREFLECTEDFROMTHEOCEANBACKTOA RADARISAFUNCTIONOFSURFACEROUGHNESSATTHESCALEOFTHERADARSWAVELENGTH WHICH INTURN ISAFUNCTIONOFTHELOCALWIND%STIMATIONOFWINDSPEEDANDDIRECTIONOVER THEOPENOCEANISTHEMOSTCOMMONAPPLICATIONFORTHESEINSTRUMENTS!WINDSCAT TEROMETERWASADOPTEDBY%5-%43!4INTHEEARLYSASAREQUIREDOPERATIONAL CAPABILITY WITHOPERATIONALACCURACIESOFoMSINWINDSPEEDANDonINDIRECTION )NADDITIONTOOPENOCEANOBSERVATIONS CALIBRATEDDATAFROMTHISCLASSOF3"2HAVE BEENAPPLIEDTOAVARIETYOFLARGE AREASURFACEFEATURES SUCHASDETERMINATIONOFSEA ICECOVERAGE MAPPINGTHEBOUNDARIESBETWEENTHEPRINCIPALICEZONESOF'REENLAND ORGLOBALESTIMATIONOFTROPICALDEFORESTATION)NALLSUCHAPPLICATIONS THEEMPHASISIS ONMEASUREMENTOFMEANREFLECTIVITYOVERLARGEAREAS RATHERTHANMAPPINGFINESPATIAL DETAIL4HESERADARSTYPICALLYHAVERESOLUTIONSONTHESCALEOFSOFKILOMETERS SUP PORTEDOVERSWATHSOFKILOMETERSORMORE )NTHEOCEANAPPLICATION RELATIVELYSMALLCHANGESINRADARBACKSCATTERMAYCOR RESPONDTOSUBSTANTIALDIFFERENCESINTHERETRIEVEDWINDINFORMATIONe )TFOLLOWS THATTHEDOMINANTREQUIREMENTFORTHISCLASSOFRADARISTHEACCURACYANDPRECISION OFTHERECEIVEDPOWERMEASUREMENT (OWEVER THENEXTSTEP VECTORWINDRETRIEVALS TRANSFORMING THE RADAR BACKSCATTERED POWER INTO ACCURATE ESTIMATES OF WIND SPEED AND DIRECTIONIS FAR FROM TRIVIAL )NDEED THE TECHNIQUE FAILS FOR THE VERY LOW WINDSPEEDSTHATDONOTGENERATEWAVELENGTH SCALESURFACEROUGHNESS)NTHELIMIT
eHTTPWWWEUMETSATINTGROUPSOPSDOCUMENTSDOCUMENTPDF?TM?REV SCATTEROMETER WPDF
.OTETHATBOTHACCURACYANDPRECISIONAREREQUIRED2ADARBACKSCATTERBYITSVERYNATUREISAQUANTITYHAVINGALARGE STANDARDDEVIATIONTHATCANBEREDUCEDONLYBYEXTENSIVEAVERAGING"ECAUSETHEGEOPHYSICALINTERPRETATIONOFSCAT TEROMETRICDATAOFTENDEPENDSONDISTINGUISHINGBETWEENTWOSIMILARVALUESOFR THERESULTSDEPENDCRITICALLYON REDUCINGTHEUNCERTAINTYINTHEESTIMATEDVALUEASWELLASGETTINGTHEAVERAGEVALUERIGHT
£n°x{
2!$!2(!.$"//+
AN OBLIQUE VIEWING RADAR SUCH AS A SCATTEROMETER WILL GENERATE VIRTUALLY NO BACK SCATTERFROMTHESEASURFACEINTHEABSENCEOFWIND DRIVENWAVES EVENIFTHEREISA SUBSTANTIALSWELLINTHEREGION 6ECTOR7IND2ETRIEVAL 4HENORMALIZEDBACKSCATTERCOEFFICIENTRFROMAWIND ROUGHENEDOCEANICSURFACEDEPENDSFOREMOSTONTHERADARSWAVELENGTH THELOCALANGLE OFINCIDENCE ANDTHEPOLARIZATION RESPECTIVELY4HEWINDPARAMETERSTOBEESTIMATED AREITSSPEED THERELATIVEANGLEINTHEHORIZONTALPLANEBETWEENTHEWINDDIRECTION ANDTHERADARLINE OF SIGHT4HEOCEANSREFLECTIVITYISALSOAFUNCTIONOFOTHERFACTORS INCLUDINGSURFACTANTSSUCHASOILSLICKS EITHERNATURALORANTHROPOGENIC THEAIR SEA TEMPERATUREDIFFERENCE ORTHEPRESENCEOFLARGEWAVESSUCHASOCEANICSWELL BUTTHESE AREOFLESSSIGNIFICANCEFORTHEPRESENTDISCUSSION 4HE REFLECTION COEFFICIENT R IS NONLINEAR WITH RESPECT TO THE WIND PARAMETERS &IGUREILLUSTRATESTHERESPONSEFORONEPOLARIZATION WHERETHEHORIZONTALAXIS ISTHERELATIVEWINDDIRECTION ANDTHEVERTICALAXISISTHENORMALIZEDRADARCROSSSEC TION4HESEVERALCURVESEACHCORRESPONDTOASPECIFICWINDSPEED)NGENERAL UPWIND ANDDOWNWINDASPECTSPROVIDESTRONGERBACKSCATTERTHANCROSS WIND ANDTHEUPWIND ASPECTUSUALLYISABITSTRONGERTHANDOWNWIND7INDVECTORDATAHAVEBEENCOLLECTED BYAIRBORNESCATTEROMETERSFLYINGINCIRCLESLITERALLY OVERINSTRUMENTEDTESTSITES 4HEREHAVEBEENMANYATTEMPTSOVERTHEYEARSTOCONVERGEONASUITABLEMATHEMATI CALMODELFORTHISBEHAVIOR WITHREASONABLESUCCESS4HEREARESEVERALVECTORWIND RETRIEVALMETHODSINCURRENTUSE INCLUDING#-/$ ANDANEURALNETWORKMODEL 4HEDATACLEARLYSHOWTHATMEASUREMENTOFRADARBACKSCATTERATONLYONEASPECT ANGLEISNOTSUFFICIENTTODETERMINEWINDSPEEDANDDIRECTION4HE3EASATSCATTEROMETER USEDTWOLOOKANGLESSEPARATEDBYn BUTTHERESULTINGRETRIEVALSHADASMANYAS
&)'52% 4YPICAL BACKSCATTER STRENGTH VERTICAL AXIS FROM A WIND DRIVENSEASURFACE ASAFUNCTIONOFWINDSPEEDMODELEDDATA AND THEWINDDIRECTIONRELATIVETOTHERADARSLOOKDIRECTIONHORIZONTALAXIS 3IMILARFAMILIESOFCURVESCORRESPONDTOTHERADARSPOLARIZATIONUSUALLY ((OR66 ANDANGLEOFINCIDENCE#URVESSUCHASTHESEAREDERIVEDFROM AMODELSUCHAS#-/$ SUBSEQUENTLYVERIFIEDBYEXTENSIVEAIRBORNE MEASUREMENTS
30!#% "!3%$2%-/4%3%.3).'2!$!23
£n°xx
FOURPOTENTIALSOLUTIONS WHICHPRESENTEDASDIRECTIONALAMBIGUITIES3PACE BASED WIND SCATTEROMETERS ARE CHARACTERIZED BY DIFFERING VIEWING GEOMETRIES EACH MOTI VATEDBYTHENEEDTOSUPPRESSDIRECTIONALAMBIGUITIES WITHINTHECONSTRAINTOFAPHYSI CALLYORFINANCIALLY FEASIBLEIMPLEMENTATION -EASUREMENT0RECISION #LEARLY RMUSTBEMEASUREDWITHANACCURACYAND PRECISIONOFLESSTHAND"IFUSEFULWINDRETRIEVALSARETOBEDERIVED!CCURACYDEPENDS ONTHERADARSSTABILITYANDITSCALIBRATION4HECHALLENGEFORSPACE BORNESCATTEROMETRY ISTODESIGNTHERADARSUCHTHATTHEPRECISIONTHENORMALIZEDSTANDARDDEVIATIONOFTHE RMEASUREMENTSISSUFFICIENTLYSMALL)NTHESTANDARDTERMINOLOGYOFSCATTEROMETRY THECLASSICALPARAMETERIS+0 THENORMALIZEDSTANDARDDEVIATIONOFTHEMEASUREMENT )NTHECASEOFAFAN BEAMSCATTEROMETERTHATEMPLOYSDOPPLERFILTERING THEGOVERNING EXPRESSIONIS
+0
3.2 3.2
.4"
WHERE.ISTHENUMBEROFSTATISTICALLYINDEPENDENTPULSESSUMMEDINTOEACHRMEA SUREMENT 4ISTHETRANSMITTEDPULSELENGTH "ISTHEDOPPLERBANDWIDTHOFTHEMEA SUREMENTCELL AND3.2ISTHESIGNAL TO NOISERATIO+0USUALLYISCITEDASAPERCENT WHEREVALUESOFORBETTERARETHEOBJECTIVE.OTEFORHIGH3.2THAT+0CONVERGES TO .4" !TLOWERWINDSPEEDS+0DEPENDSON3.2ASWELLASONTHENUMBEROF STATISTICALLYINDEPENDENTLOOKS4HEDETAILSOFANYEXPRESSIONSUCHASTHISDEPENDON THEUNDERLYINGSTATISTICALMODEL WHICHISGAUSSIANINTHISCLASSICEXPRESSION(OWEVER THEGENERALPRINCIPLEISTHATTHESCATTEROMETERMUSTPROVIDEMANYINDEPENDENTLOOKS TOREDUCETHESTANDARDDEVIATIONOFTHERMEASUREMENT REGARDLESSOFTHESTATISTICAL DISTRIBUTIONOFTHEOCEANSBACKSCATTER 4RENDS 6ECTOR WIND DATA HAVE BEEN ADOPTED BY OPERATIONAL METEOROLOGICAL AGENCIES SUCH AS %5-%43!4 )T IS LIKELY THAT SPACE BASED MICROWAVE ASSETS WILL CONTINUETOBEUSEDFORTHEFORESEEABLEFUTURETOPROVIDETHESEDATA4HESUCCESSOF 3EA7INDSDISCUSSEDLATERINTHISSECTION SUGGESTSTHATTHECONICALSCANPARADIGMWILL BETHEBASISFORFUTUREVECTORWINDSCATTEROMETERDESIGN 4HATSAID THEREARETWOSPACE BASEDALTERNATIVESFORMEASURINGVECTORWINDSBY MICROWAVEMEANS ACTIVEANDPASSIVE2ADARSOFTENAREUNPOPULARONSPACECRAFTTHAT HOSTOTHERINSTRUMENTS OFWHICHSOMEMAYBECOMPROMISEDBYRADIOFREQUENCYINTER FERENCE2&) GENERATEDBYANEARBYMICROWAVETRANSMITTER2ADARSALSOREQUIREMORE POWERFROMTHEIRHOSTSPACECRAFTTHANPASSIVESYSTEMS4HESEANDRELATEDCONSIDER ATIONS MOTIVATED THE DEVELOPMENT OF 7IND3AT A PASSIVE INSTRUMENT THAT ESTIMATES NEAR SURFACEVECTORWINDSBY3TOKESPARAMETERANALYSISOFTHEMICROWAVEEMISSIVITY FROMTHEOCEANSURFACE7IND3ATISONEOFTWOINSTRUMENTSABOARDTHE#ORIOLISSATEL LITE LAUNCHEDIN4HEOPERATIONALRELIABILITYOFPASSIVE VECTORWINDDATARELATIVE TOSCATTEROMETRICMEASUREMENTSREMAINSANOPENISSUE 3CATTEROMETRICDATAAREBEINGEXPLOITEDFORMANYPURPOSESOTHERTHANOCEANICVEC TORWINDS!LTHOUGHTHEhIMAGESvGENERATEDBYASPACE BASEDSCATTEROMETERMAYHAVE ONLY KMRESOLUTION THEIRWIDESWATHANDFREQUENTREVISITINTERVALSAREWELLSUITEDTO SYNOPTICCOVERAGEOFGLOBAL SCALEPHENOMENA4HEMULTI YEARHISTORYOFSCATTEROMET RICRADARSPROVIDESANIMPORTANTDATASETFORCLIMATECHANGESTUDIESASWELLASMONI TORINGSEASONALVARIATIONS3UITABLEAPPLICATIONSINCLUDESEAICECOVER LARGEICEBERGS CONTINENTALICESHEETS VEGETATION ANDSOILMOISTUREn
£n°xÈ
2!$!2(!.$"//+
&LIGHT3YSTEMS 2AD3CAT4ABLE WASTHENAMEGIVENTOTHERADIOMETER SCATTEROMETERPORTIONOFTHE3 +UBANDINSTRUMENTABOARD3KYLAB4HETOP LEVEL OBJECTIVESOFTHISEXPERIMENTWERE TOPROVIDETHENEAR SIMULTANEOUSMEASUREMENT OF MICROWAVE BACKSCATTER AND EMISSIVITY OF LAND AND OCEAN ON A GLOBAL SCALE AND TOPROVIDEENGINEERINGDATAFORUSEINDESIGNINGSPACERADARALTIMETERS4HEEQUIP MENTSHAREDACOMMONGIMBALEDANTENNA4HESCATTEROMETERMEASUREDTHENORMALIZED BACKSCATTERCOEFFICIENTOFOCEANANDTERRAINASAFUNCTIONOFINCIDENCERANGINGFROM nTOn!LTHOUGHONLYSPARSECOVERAGEOFSELECTEDSITESWASPOSSIBLE THEDATAWERE SUFFICIENTTODEMONSTRATETHEPOTENTIALOFSPACE BASEDRADARMEASUREMENTOFSURFACE WINDVECTORSOVERTHEOCEAN4HE3 ZONEOFACCESSWASFORWARDANDTO EITHERSIDEOFTHESPACECRAFTGROUNDTRACK&ORSELECTEDMEASUREMENTS THEBEAMWAS POINTEDINTHEALONG TRACKDIRECTIONTOFIXEDANGLESOF AND WITHSUFFICIENTDWELLTIMEATEACHANGLETOPERMITAVERAGINGTOACHIEVEAPPROXIMATELY PRECISION2AD3CATDATACOLLECTEDOVERTHE!MAZONRAINFORESTSUGGESTEDTHATTHE UNIFORMITY OF THE OBSERVED BACKSCATTER WOULD BE A STABLE CALIBRATION REFERENCE FOR SPACE BASEDRADARS WHICHHASSINCEBEENVALIDATEDASASTANDARDTECHNIQUE 3!33 THE 3EASAT ! 3ATELLITE 3CATTEROMETER WAS THE FIRST SPACE BASED RADAR DESIGNEDSPECIFICALLYTOMEASUREOCEANICWINDS)TWASAMULTI FAN BEAMINSTRUMENT COMPRISEDOFTWOSETSOFTWODUAL POLARIZEDANTENNAS((AND66 EACH^ MIN LENGTH WHOSE FAN SHAPED BEAMS POINTED TO n AND n TO EITHER SIDE OF THE ORBIT PLANE )NCIDENCE SPANNED n TO n COVERING A KM WIDE SWATH ON EACH SIDE #ALIBRATIONDATATAKENOVERTHERAINFORESTWEREUSEDTOREDUCEANTENNAGAINUNCER TAINTYTOLESSTHAND"3INCE3EASATWASNOTYAW STEERED THEFOREANDAFTFOOTPRINTS WERE MISREGISTERED DUE TO %ARTH ROTATION WHICH REDUCED THE USEFUL SWATH AT LOWER LATITUDESTOABOUTKM4HEVALUEOF+PVARIEDFROMTOOVERTHEOCEANUNDER MODERATETOHIGHSEASTATES BUTDEGRADEDTOFORLOWERWINDSPEEDSANDTO FOR VERY LOW BACKSCATTER FROM NON OCEANIC SURFACES4HE ACCURACIES OF WIND SPEED ANDDIRECTIONOVERnMSWEREoMSANDoO RESPECTIVELY4HEDATAWERENOT SUFFICIENTTOAVOIDDIRECTIONALAMBIGUITIES HOWEVER.OMINALRESOLUTIONWASKM DETERMINEDBYTHEINTERSECTIONOFTHEANTENNAPATTERNANDISO DOPPLERCONTOURS4HE RADAROPERATEDAT'(Z RADIATINGAPEAKPOWEROF7ATDUTYFACTORFROM A TRAVELING WAVE TUBE AMPLIFIER 474! 4HE WAVEFORM WAS MODULATED #7 4HE RECEIVERFRONTENDWASATUNNELDIODEAMPLIFIER WHICHMAINTAINEDTHENOISEFIGURETO BELESSTHAND"ATALLOPERATINGTEMPERATURES-EANINPUTPOWERWAS7DC THEINSTRUMENTMASSWASKG
4!",% 3CATTEROMETERS
.AME
3PACECRAFT
#OUNTRY
9EAR
!NTENNA
"AND
0OLARIZATION
2AD3CAT 3!33 %3#!4 %3#!4 .3#!4 3EA7INDS 3EA7INDS #.3#!4 !3#!4 3CAT
3KYLAB 3EASAT %23 %23 !$%/3) 1UIK3#!4 !$%/3)) 3: -ET/P !QUARIUS
53! 53! %UROPE %UROPE 53*APAN 53 53*APAN #HINA %UROPE 53!
n n n
0ENCILBEAM &ANBEAMS &ANBEAMS &ANBEAMS &ANBEAMS #ONICALSCAN #ONICALSCAN CONICALSCAN &ANBEAMS BEAMPUSH
+U +U # # +U +U +U +U # ,
66 (( 66 (( 66 66 66 (( 66 (( 66 (( 66 (( 66 66 6( (6 ((
30!#% "!3%$2%-/4%3%.3).'2!$!23
£n°xÇ
73ABOARDTHE%23 AND%23 SPACECRAFTOF%3!DENOTESTHESCATTEROMETERMODE EMBEDDEDINTHEIR#BAND!-)RADARINSTRUMENTATION4HESESCATTEROMETERSUSEDTHREE
FAN BEAMANTENNAS WHOSEFOOTPRINTSWEREORIENTEDATn n ANDn WITHRESPECTTO THESATELLITETRACK4HETWOOUTERANTENNASARE MLONG.OTETHATTHESPACECRAFTHADTO BEYAW STEEREDTOMAINTAINTHISFOOTPRINTGEOMETRYOVERTHEROTATING%ARTH4HE#BAND OPERATINGFREQUENCY ALTHOUGHADEPARTUREFROMSPACE BASEDPRECEDENT RESULTEDFROM USEOFTHESAME2&HARDWAREASTHE3!2MODE!SACONSEQUENCE SIMULTANEOUS3!2 ANDSCATTEROMETEROPERATIONSWERENOTPOSSIBLE)NCONTRASTTO+UBAND THE#BANDDATA WERELESSDEGRADEDBYRAINANDPROVEDTOBEMORERELIABLEFORHIGHERWINDSPEEDS 4HEANTENNASWATHSSPANNEDKM FROMWHICHTHEAVERAGEDDATAFROMTHETHREE LOOK DIRECTIONSWERECOLOCATEDINTO KMRESOLUTIONCELLS POSTEDONA KMGRID !3#!4 THE!DVANCED3CATTEROMETERABOARD-ET/P ISESSENTIALLYANIMPROVED VERSIONOFTHE%23 INSTRUMENTS)TISASTAND ALONERADARDESIGNEDFOROPERATIONAL USEITDOESNOTHAVETOTIME SHAREONBOARDELECTRONICSASWASTHECASEWITHTHESCAT TEROMETERINTHE!-)SUITE)TCOVERSSWATHSONBOTHSIDESOFTHESATELLITEGROUNDTRACK 4HENEAREDGEOFTHESE KMSWATHSAREOFFSETKMFROMNADIR SPANNINGnnn nINCIDENCE4HED"RADIOMETRICALLYACCURATEDATAAREAVERAGEDTOACHIEVE+P FROM HIGH UP WIND SPEED TO LOW SPEED CROSS WIND ASPECT 4HE RESULT INGVECTORSFORNEAR SURFACEWINDSCOVERnMSWITHACCURACYoMSANDon 4HERADAROPERATESAT'(Z RADIATINGMSLINEARFREQUENCY MODULATED,&- PULSESAT7PEAKPOWERFROMCOMBINED'A!S&%4DEVICES/NLYONEANTENNAIS ACTIVEFORS ATATIMETHEOPERATIONCYCLESAROUNDTHESIXANTENNASINSEQUENCE 4HEINSTRUMENTMASSISKGINPUTPOWERREQUIREDIS74HANKSTOONBOARD PROCESSING THEINHERENTDATARATEISREDUCEDFROM-BITSTOANAVERAGEOFKBITS TOTHE-ET/P PAYLOADDATA HANDLINGSYSTEM .3#!4 THE.!3!3CATTEROMETER PROVIDEDTO*APANASPARTOFTHE!DVANCED%ARTH /BSERVING 3ATELLITE !$%/3 PAYLOAD WAS AN UPGRADED VERSION OF 3!33 .3#!4 USEDSIXDUAL POLARIZEDSTICKANTENNASMLONG FOUROFWHICHWEREAIMEDATon
( POLARIZED AND on 6POLARIZED FROM THE SURFACE TRACK AND THE TWO MIDBEAM
ANTENNAPATTERNSWEREALIGNEDATn ANDnEACH(AND6POLARIZED 4HETHIRDBEAM ONEACHSIDEHELPEDTOREMOVETHEFOURFOLDDIRECTIONALAMBIGUITIESTHATPLAGUED3!33 WINDRETRIEVALS4WO KMWIDESWATHSWERECOVERED AT KMRESOLUTION)NORDER TOSUPPORT KMALONG TRACKRESOLUTION THERADARSSEQUENCERHADTOCYCLETHROUGHALL ANTENNAPATTERNSWITHINS RESULTINGINAMAXIMUMDWELLTIMEOFMSWITHIN EACHOFTHEEIGHTFOOTPRINTS#ROSS BEAMRESOLUTIONWASDETERMINEDBYDOPPLERANALYSIS (OWEVER SINCETHEMEANDOPPLEROFFSETWASAFUNCTIONOFANTENNAORIENTATIONASWELL ASINCIDENCE THERETURNFROMEACHDIRECTIONNEEDEDITSOWN,/OFFSET4HEANTENNAS PEAKGAINWASD" DIRECTEDTOWARDMAXIMUMRANGE.3#!4SMASSWASKG REQUIREDINPUTPOWERWAS74HE2&SYSTEMWASBUILTAROUNDREDUNDANT474!S TRANSMITTINGMODULATED MSPULSESATA02&OF(Z PEAKPOWER7 3EA7INDSMARKSASIGNIFICANTDEPARTUREFROMTHEhSTICKANTENNASvOFPRIORWIND SCATTEROMETERS RELYINGINSTEADONADISHANTENNAROTATINGAT20-TOSWEEPITSTWO BEAMSOVERANADIR CENTEREDSWATH KMWIDE&IGURE 4HEFIRST3EA7INDS MISSIONWASABOARD1UIK3#!4 MOBILIZEDBY.!3!ANDLAUNCHEDIN*UNEASA RAPIDRESPONSETOTHEPREMATURELOSSOF!$%/3IN*UNE4HESECOND3EA7INDS WASEMBARKEDON*APANS!$%/3 ))"OTHINSTRUMENTSOPERATEAT+UBANDK(Z RADIATING7 MSPULSESAT(Z02& SPLITEQUALLYBETWEENTHETWOANTENNA BEAMS4HETRANSMITTERISA474! BASEDON.3#!4HERITAGE4HEMODULATEDPULSE BANDWIDTH IS K(Z WHICH IS MAINTAINED WITHIN AN K(Z FILTER IN THE RECEIVER 4HE RECEIVED DATA MUST BE COMPENSATED TO OFFSET THE DOPPLER SHIFT WHICH VARIES
£n°xn
2!$!2(!.$"//+
&)'52% 4HE 3EAWINDS SCATTEROMETER AS EMBARKED ON *APANS !$%/3 )) SPACECRAFT 4HE RADAR DRIVES THE CONICALLY SCANNED REFLECTOR ANTENNA WHICHTAKESUPMOSTOFTHEREALESTATEON THE%ARTH VIEWINGFACEOFTHESATELLITE
SINUSOIDALLY OVER -(Z DURING EACH ANTENNA ROTATION )NSTRUMENT MASS IS KG REQUIREDINPUTPOWERIS74HESENUMBERSILLUSTRATETHEPRINCIPALADVANTAGESOF THEARCHITECTURE PROVIDINGGREATERCOVERAGEWITHLESSMASSANDPOWER INCONTRASTTO THE STICK ANTENNA ARCHITECTURE 3YSTEM SENSITIVITY ACCOMMODATES R IN THE RANGE nD"TOnD"4HEANTENNAISA MREFLECTORGAIN^D" WITHTWOFEEDS RESULT INGINAPAIROFPENCILBEAMSATn(POLARIZATION ANDnINCIDENCE6POLARIZATION 4HEILLUMINATIONGEOMETRYALSOISADVANTAGEOUSBECAUSETHEINCIDENCEISTHESAMEFOR ALL ASPECT ANGLES 4HE BEAM LIMITED FOOTPRINTS ARE APPROXIMATELY KM BY KM &OLLOWINGONBOARDPROCESSING THEAVERAGEDATARATEISKBITSS3EA7INDSPERFOR MANCEISATLEASTCOMPARABLETOOTHERWINDSCATS WINDSPEEDANDDIRECTIONACCURACY BEING MS TO MS AT MS AND n RESPECTIVELY .OMINAL SURFACE RESOLUTION IS KMADVANCEDPROCESSINGREDUCESTHISTO^KM!LTHOUGHTHESWATHISKM WIDE THEVARIETYOFASPECTANDPOLARIZATIONCOVERAGELIMITSTHESCIENCE COMPLIANTWIND VECTORRETRIEVALSTOSTRIPSFROMKMTOKMEITHERSIDEOFTHEGROUNDTRACK !QUARIUS 4HE !QUARIUS MISSION IS DESIGNED TO MAP SEA SURFACE SALINITY FOR WHICH,BANDRADIOMETRICSENSINGOFTHEOCEANSEMISSIVITYISTHEPRIMARYMEASURE MENT(OWEVER EMISSIVITYISAFUNCTIONOFTHEROUGHNESSOFTHESURFACE ASWELLAS ITSTEMPERATUREANDDIELECTRICCONSTANT WHICHISTHEVARIABLEOFINTEREST4HE!QUARIUS PAYLOADINCLUDESAN,BAND-(Z SCATTEROMETERTOMEASURESURFACEROUGHNESS 4HESCATTEROMETERANDRADIOMETERSHARETHESAME MDIAMETERREFLECTORILLUMINATED BYTHREEOFFSETFEEDS WHICHGENERATETHREESIDE LOOKINGBEAMSATn n ANDn INCIDENCE THUS SWEEPING OUT STRIPS OF COVERAGE AS THE SPACECRAFT MOVES ALONG ITS ORBIT4HESCATTEROMETERISFULLYPOLARIZED(( (6 6( AND66 0EAKTRANSMITTED POWERIS^7 PULSELENGTHISMS SUFFICIENTTOSUPPORTSEASURFACEROVERTHE RANGED"TOnD"2ESOLUTIONISMODEST AT^KM4HESCATTEROMETERANDRADI OMETERSHAREELECTRONICS#OMBINEDINSTRUMENTMASSIS^KG ANDREQUIREDPRIME POWERIS^7
30!#% "!3%$2%-/4%3%.3).'2!$!23
£n°x
£n°ÈÊ , ,Ê-"1 ,)NITSMOSTGENERALFORM ARADARSOUNDERISADEVICEWHOSETRANSMISSIONSAREDESIGNED TOPENETRATETHEVOLUMEOFATARGETMEDIUM FROMWHICHTHEWAVEFORMOFTHERESULTING BACKSCATTER INDICATES VARIATIONS IN DIELECTRIC CONTRASTS AS A FUNCTION OF DEPTHo!S A SOUNDERPASSESOVERANILLUMINATEDREGION THESEQUENCEOFRANGINGWAVEFORMSGENER ATESAPROFILE WHICHISATWO DIMENSIONALREFLECTIVITYCROSSSECTIONOFTHESURVEYED VOLUME0ENETRATIONDEPTHINGENERALINCREASESWITHWAVELENGTHANDALSOWITHRADIATED POWER /N THE OTHER HAND REFLECTIVITY DEPENDS ON THE DIELECTRIC CONTRASTS BETWEEN INTERNAL LAYERS A MATERIALS DIELECTRIC CONSTANT IS ALSO A FUNCTION OF WAVELENGTH )T FOLLOWSTHATSPACE BASEDRADARSOUNDERSMUSTCHOOSEAFREQUENCYANDBANDWIDTHTHAT BALANCETHEOFTENCONFLICTINGREQUIREMENTSOFPENETRATION REFLECTIVITY ANDRESOLUTION UNDERTHECONSTRAINTSOFAVAILABLEPOWERANDANTENNAAPERTURE 4HESPACE BASEDRADARSOUNDERSHIGHLIGHTEDIN4ABLEFALLNATURALLYINTOTWO GROUPS SUBSURFACE AND ATMOSPHERICIONOSPHERIC )T IS EVIDENT THAT THE SUBSURFACE SOUNDERSALLAREATRELATIVELYLOWFREQUENCY INCONTRASTTOTHEATMOSPHERICSOUNDERSAT MUCHHIGHERFREQUENCY4HEIONOSPHERICSOUNDINGMODEOF-!23)3ISASPECIALCASE ELABORATEDBELOW 3UBSURFACE 3OUNDINGnFLIGHT 3YSTEMS 3UBSURFACE SOUNDING FROM A SPACE BASED RADAR IS CONSIDERABLY MORE CHALLENGING THAN FROM A SURFACE MOUNTED '02 #HAPTER ORAVERYLOWALTITUDEAIRCRAFT/FCOURSE ONCERADARSIGNALSPENETRATE THESURFACE THEUSUALVOLUMETRICATTENUATIONSANDREFLECTIONSOCCUR!SWITHANY'02 LARGE DYNAMIC RANGE IS REQUIRED SINCE THE SIGNALS OF INTEREST MAY BE WEAKER THAN COMPETINGRETURNSBYD"ORMORE2ADARSOUNDINGTOAPPRECIABLEDEPTHISPOSSIBLE ONLYINDRYMATERIALSSUCHASLUNARREGOLITHORINVERYCOLDLOW LOSSICE 4!",% 2ADAR3OUNDERS
)NSTRUMENT
52,
!,3% -!23)3 3(!2!$ ,23 02 -!23)3 #02 $02
3PACECRAFT
9EARS
/BJECTIVE
&REQUENCY
!POLLO -ARS%XPRESS -2/ 3%,%.% 42--ARS%XPRESS #LOUD3AT '0-
n n n n n
,UNARSUBSURFACE -ARSSUBSURFACE -ARSSUBSURFACE ,UNARSUBSURFACE 2AIN -ARSIONOSPHERE %ARTHCLOUDPROFILES 2AIN
-(Z -(Z -(Z -(Z '(Z n-(Z '(Z '(Z
HTTPNSSDCGSFCNASAGOCDATABASE-ASTER#ATALOG SC !EX HTTPSCIESAINTSCIENCE EWWWAREAINDEXCFM FAREAID HTTPMARSJPLNASAGOVMROOVERVIEW HTTPWWWJSFWSINFOSELENE?SYMPOENTEXTOVERVIEWHTML HTTPTRMMGSFCNASAGOV HTTPSCIESAINTSCIENCE EWWWAREAINDEXCFM FAREAID HTTPCLOUDSATATMOSCOLOSTATEEDU HTTPGPMGSFCNASAGOVDPRHTML
o4HETERMSOUNDERUSUALLYASSOCIATEDWITHACOUSTICECHOSOUNDING DERIVESFROMMANYCENTURIESOFOCEANICDEPTH MEASUREMENTSUSINGLEADLINESANDTHELIKE4HELOGICALEXTENSIONFROMACOUSTICTOELECTROMAGNETICMETHODOLOGY ISASMALLSTEPINCOMPARISON
£n°Èä
2!$!2(!.$"//+
)NADDITIONTOTHEUSUAL'02CONSIDERATIONS TWOSPACE SPECIFICISSUESARISE NEITHER OFWHICHCANBESOLVEDBYTHEUSUALEXPEDIENTOFINCREASINGTHERADARSTRANSMITTED POWER4HEFIRSTPROBLEMISCLUTTER&ROMORBITALALTITUDE SCATTERERSONTHESURFACEFAR FROMNADIRMAYGENERATESTRONGBACKSCATTERTHATAPPEARSATTHESAMERADARRANGEAS THESIGNALSREFLECTEDFROMDEPTH ASSUGGESTEDIN&IGURE4HEPROBLEMISCOM POUNDEDWITHINCREASINGALTITUDEANDBYTHEFACTTHATATTHELONGWAVELENGTHSREQUIRED FORDEEPERPENETRATION THESIZECONSTRAINTSONASPACECRAFT MOUNTEDANTENNADICTATE THATTHEILLUMINATIONPATTERNWILLHAVELITTLEORNODIRECTIVITY0ROCESSINGOVERGROUPS OF RETURNS TO REDUCE THE EFFECTIVE WIDTH OF THE BEAM CAN BE HELPFUL $OPPLER BASED TECHNIQUES ARE APPLICABLE TO THE ALONG TRACK DIRECTION (OWEVER THE ORBITS ALTI TUDE VELOCITYPARAMETER4ABLE MAYBESOLARGETHATTHEAVAILABLEAMBIGUITY FREE RANGE DOPPLERWINDOWISTOOSMALLTOBEUSEFUL.ARROWINGTHEEFFECTIVEANTENNAPAT TERNINTHECROSS TRACKDIRECTIONPRESENTSEVENMOREOFACHALLENGE 4HESECONDPROBLEMISRANGESIDELOBES&ROMORBITALALTITUDESANDFROMAREALISTIC SPACECRAFT ITISNOTFEASIBLETOTRANSMITASIMPLESHORTPULSETHATHASSUFFICIENTENERGY TOGENERATEUSEFULREFLECTIONSFROMDEPTH,ONGMODULATEDPULSESARETHEONLYPRACTICAL METHOD5NFORTUNATELY THESPECULARCOMPONENTOFSURFACEREFLECTIONUSUALLYISVERY STRONGATTHELONGWAVELENGTHSREQUIREDFORSUBSURFACESOUNDING0ULSECOMPRESSION OFTHESURFACERETURNGENERATESRANGESIDELOBESWHICHAPPEARATDEPTHSTHATCOULDEASILY OVERWHELMTHEWEAKERREFLECTIONSFROMTHEINTERNALSTRUCTURE4HESTANDARDSTRATEGY TOMITIGATETHISPROBLEMISRIGOROUSSIDELOBECONTROL REQUIRINGSEVEREPULSEAMPLITUDE WEIGHTINGANDSTRICTCONTROLOFPHASEANDAMPLITUDELINEARITY $UETOTHELARGEFOOTPRINTOFASPACE BASEDSOUNDER ANDTHENEEDTOSALVAGEALL POSSIBLECONTRIBUTIONSOFSIGNALSFROMDEPTH ITISSTANDARDPRACTICETOASSUMETHATTHE DOMINANTINSITURETURNSARISEFROMSPECULARSCATTERING HENCEFROMEXTENDEDHORIZONTAL LAYERS4HECONTRIBUTINGAREAISDETERMINEDBYTHERADIUSR&OFTHEFIRST&RESNELZONE R& HL INFREESPACE WHEREHISTHEALTITUDEOFTHERADARABOVETHESURFACE4HE RADIUSISSOMEWHATLARGERWITHINTHEMEDIUM SINCETHESPHERICALWAVEFRONTISFLAT TENEDDUETOTHESLOWERSPEEDOFINSITUPROPAGATION !,3% 4HE!POLLO,UNAR3OUNDER%XPERIMENT WASACOMBINATIONIMAGER ANDSOUNDER OPERATINGATWAVELENGTHSOFM M ANDM4HE!,3%SOUNDER
&)'52% 4WO PROBLEMS THAT CHALLENGE SPACE BASED SUB SURFACESOUNDINGARE RANGE COINCIDENTCOMPETITIONBETWEENTHE DESIREDRETURNFROMDEPTHANDSURFACECLUTTERAND RANGESIDELOBES FROMTHEVERYSTRONGRETURNFROMTHETOPSURFACEATNADIR
30!#% "!3%$2%-/4%3%.3).'2!$!23
£n°È£
MODEWASDESIGNEDTOMEASURESUBSURFACEHORIZONSINTHELUNARDIELECTRICCONSTANT INBOTHSIDE LOOKINGANDDOWN LOOKINGVIEWINGGEOMETRY4HEINSTRUMENTWASBASED ON SYNTHETIC APERTURE RADAR 3!2 PRINCIPLES4HE DATA WERE RECORDED DIRECTLY ONTO MM PHOTOGRAPHIC FILM WHICH WAS PROCESSED THROUGH A COMBINATION OF OPTICAL ANDDIGITALMEANSFOLLOWINGRETURNOF!POLLOTO%ARTH/PTICALPROCESSINGWASTHE STATE OF THE ARTBACKINFOR3!2DATA 0ENETRATIONDEPTHSPROVEDTOBEAPPROXI MATELYPROPORTIONALTOWAVELENGTH4HERADARSWAVEFORMWASCONSTRAINEDSOTHATALL SIDELOBESWEREATLEASTD"BELOWTHEMAIN BEAMPEAKFORALLRESPONSESBEYONDTHREE IMPULSE WIDTHS OF THE COMPRESSED SIGNAL!MPLITUDE AND PHASE LINEARITY WERE CON STRAINEDTOBEBETTERTHANANDRADIAN RESPECTIVELY4HETRANSMITTEDPULSES WERELINEAR&- ATBANDWIDTHINALLTHREEBANDS.OMINALFREE SPACERESOLUTIONS WEREM M ANDM!NTENNAGAINSWERE D" D" AND D" 4HESELOWNUMBERSFOLLOWFROMTHEPOORDIRECTIVITYOFTHEANTENNA4RANSMITTEDAVER AGEPOWERWAS7 7 AND70ENETRATIONDEPTHSWEREPREDICTEDTOBEM M ANDM WHICHTURNEDOUTTOBECONSISTENTWITH!,3%SPERFORMANCE -!23)3 4HE %UROPEAN 3PACE!GENCYS -ARS %XPRESS SPACECRAFT INCLUDES THE -ARS!DVANCED 2ADAR FOR 3UBSURFACE AND )ONOSPHERIC 3OUNDING INSTRUMENT THE FIRSTORBITALSOUNDERTOFLYSINCE!,3%-!23)3ISAMULTIFREQUENCYDOWN LOOKING RADARTHATRADIATES -(ZPULSESINONEOFFOURBANDSCENTEREDONTHEFREQUENCIESCITED IN4ABLE-ARS%XPRESSISINANELLIPTICALORBITSUBSURFACESOUNDINGOPERATIONS ARERESTRICTEDTOTHELOWERKMTOKMALTITUDES3OUNDINGISFURTHERLIMITED BYTHEIONOSPHERE WHICHPREVENTSEFFECTIVERADIOWAVEPROPAGATIONTOTHESURFACEAT FREQUENCIESBELOWTHEPLASMAFREQUENCYF WHICHAT-ARSIS^-(ZONTHESUNLITSIDE AND^-(ZONTHEDARKSIDE4HEIONOSPHEREINDUCESAFREQUENCY DEPENDENTTIME DELAYONTHESIGNALACCORDINGTOTHEINDEXOFREFRACTIONN WHEREN ; F F = 4HERESULTINGDISPERSIONDISTORTSTHERADARMODULATION WHICHMUSTBECOMPENSATED BEFOREPULSECOMPRESSION4HE MDIPOLEANTENNAORIENTEDORTHOGONALTOTHEORBIT PLANEISONLYWEAKLYDIRECTIVE WITHAD"GAIN4HETWO MLONGELEMENTSWERE NOTUNFURLEDUNTILTWOYEARSINTOTHEMISSION DUETOCONCERNSABOUTTHEIRPOTENTIAL FOR DAMAGING THE SPACECRAFT DURING DEPLOYMENT4HE EFFECTIVE CROSS TRACK FOOTPRINT ISONTHEORDEROFKM4HEALONG TRACKFOOTPRINTISABOUTKM WHICHISTHERESULT OFONBOARDCOHERENTDOPPLERPROCESSING4HISSTRATEGYREDUCESTHEIMPACTOFOFF NADIR CLUTTERARISINGFROMSOURCESINTHEALONG TRACKDIRECTION4HETECHNIQUEIMPROVESTHE SUBCLUTTERVISIBILITYBYD"ORMORE4HERADARSMASSANDINPUTPOWERAREKGAND 70EAKRADIATEDPOWERIS74HESYSTEMNOISEFLOORISABOUTD"BELOWTHE MEANSURFACERETURN WHICHESTABLISHESTHEDYNAMICRANGETHATLIMITSDEPTHOFPENETRA TION-!23)3HASPERFORMEDASINTENDED WITHEARLYRESULTSFROMTHEPOLARLAYERED DEPOSITS FOREXAMPLE 3(!2!$ 4HE3HALLOW2ADARSOUNDERWASDESIGNEDTOCOMPLEMENT-!23)3 )NGENERALTERMS ITHASHIGHERRESOLUTIONATAHIGHERFREQUENCY DESIGNEDTOPROVIDE SHARPER DIFFERENTIATION OF THE UPPER SEVERAL HUNDRED METERS OF THE SURFACE OF -ARS 3(!2!$TRANSMITSA -(ZLINEAR&-SIGNALCENTEREDAT-(Z4HEORETICALVERTI CALRESOLUTIONISMINMATERIALHAVINGAPERMITTIVITYOF4HE MDIPOLEANTENNA HASAFREQUENCY DEPENDENTTWO WAYGAINOF D"TO D"4HEEFFECTIVEBEAM FOOTPRINTAFTERDOPPLERPROCESSING IS^KMALONGTRACKAND^KMACROSSTRACK .OMINAL3.2WITHRESPECTTOTHESURFACERETURNISINEXCESSOFD")NSTRUMENTMASS IS^KG INPUTPOWERIS^73(!2!$MEASUREMENTSSTARTEDLATEONLYWHEN THE-2/ORBITWASCIRCULARIZEDAFTERSIXMONTHSOFAEROBRAKING
£n°ÈÓ
2!$!2(!.$"//+
3%,%.% 4HE *APANESE LUNAR MISSION 3%,%.% INCLUDES A -(Z ,UNAR 2ADAR 3OUNDER ,23 AS ONE OF ITS PAYLOAD INSTRUMENTS4HE ORBIT IS CIRCULAR AT KMALTITUDE4HERADARTRANSMITS§SECLINEAR&-SIGNALSTHATAREDEMODU LATEDUSINGTHESTRETCHTECHNIQUE SIMILARTORADARALTIMETERS%ACHPULSEISAMPLITUDE WEIGHTEDBYASINEFUNCTION O TOSUPPRESSSIDELOBESBY^D"FROMTHESURFACE RETURNTHATOTHERWISEWOULDMASKTHEDESIREDRETURNSFROMDEPTH4HEINSITURESOLUTION ISNOMINALLY^MWITHINAMEDIUMOFPERMITTIVITY^4HERADARDYNAMICRANGEIS ^ D" TO PERMIT OBSERVATION OF SUBSURFACE PROFILES TO A DEPTH OF SEVERAL KM4HE ANTENNAISCOMPRISEDOFTWOSETSOFDIPOLES MTIP TO TIP WITHANEFFECTIVEFOOTPRINT OFSEVERALTENSOFKM0EAKOUTPUTPOWERIS7)NSTRUMENTMASSISKGANDINPUT POWER7 !TMOSPHERIC)ONOSPHERIC3OUNDINGn&LIGHT3YSTEMS 4HEOBJECTIVEOFTHIS CLASSOFRADARSOUNDERSISTOGENERATEACROSS SECTIONPROFILE OFTHEWATERORELEC TRONDENSITYINTHEORBITPLANEBENEATHTHESPACECRAFT!TMOSPHERICSOUNDINGBYRADAR REQUIRES SENSITIVITY TO RELATIVELY WEAK BACKSCATTER EFFECTIVE SUPPRESSION OR AVOID ANCE OFTHESTRONGRETURNFROMNADIR MODESTRANGERESOLUTION ANDRELATIVELYNARROW FIELDSOFVIEW4HESEREQUIREMENTSLEADTOHIGHPOWERRADARSAT+U BANDORABOVE A SIMPLEPULSEWAVEFORM ANDSUBSTANTIALANTENNAAREA 2ADARSOUNDERSSHOULDNOTBECONFUSEDWITHPASSIVE MICROWAVERADIOMETERS ALSO CALLED SOUNDERS UNFORTUNATELYTHAT ARE USED BY OPERATIONAL METEOROLOGICAL SATELLITES TO ESTIMATE ATMOSPHERIC WATER DISTRIBUTION ! MULTIFREQUENCY RADIOMETER GENERATESCOARSEWATERVAPORDENSITYPROFILESFORWHICHALTITUDEISAFUNCTIONOFFRE QUENCY0ASSIVEMICROWAVESOUNDINGUNITSHAVEMASSANDPOWERREQUIREMENTSONTHE ORDEROFKGAND7 MUCHLESSTHANTHEIRACTIVERADARCOUNTERPARTS 42-- 4HE 4ROPICAL 2AINFALL -EASURING -ISSION WAS A JOINT UNDERTAKING BETWEEN.!3!ANDTHE*APANESE!EROSPACE%XPLORATION!GENCY*!8! 4HEFIVE INSTRUMENTPAYLOADINCLUDESTHE0RECIPITATION2ADAR02 WHICHWASDESIGNEDAND BUILTBY*!8!THEN.!3$! ANDWASTHEFIRSTOFITSKINDONASPACE BASEDPLATFORM )TSPRECESSING KMORBIT INCLINEDATn SUPPORTSTEMPORALLYANDSPATIALLYSPARSE ATMOSPHERICCOVERAGEOVERTROPICALLANDANDSEA4HERADARPROVIDESATHREE DIMEN SIONALSTRUCTUREOFRAINFALLFROMTHESURFACETOANALTITUDEOFKM7HENCOMBINED WITHDATAFROMTHEPASSIVEMICROWAVERADIOMETER4-) 02DATASUPPORTIMPROVED ACCURACYOFRAINFALLRETRIEVALS4HERADARS+UBAND^CM FREQUENCYISABOUTTHREE TIMES HIGHER THAN MOST SURFACE BASED METEOROLOGICAL RADARS BUT WAS SELECTED TO ACHIEVEAREASONABLYNARROWn BEAMWIDTHFROMANANTENNAAREACONSTRAINEDBY SPACECRAFTACCOMMODATIONTOBENOMORETHANMBYM(ORIZONTALRESOLUTION ATNADIRISABOUTKM4HEANTENNA A ELEMENTSLOTTEDWAVEGUIDEPHASEDARRAY WITHD"GAIN ISELECTRONICALLYSCANNEDOVERonACROSSTRACK COVERINGASWATH KM WIDE CENTERED AT NADIR 0EAK TRANSMITTED POWER IS 7 GENERATED FROM SOLID STATEPOWERAMPLIFIERS330!S ONEFOREACHWAVEGUIDE4HE MRANGE RESOLUTIONISSETBYTHEUNITYTIME BANDWIDTH PRODUCT§SECPULSE4HERADARHAS SUFFICIENTSENSITIVITYTORESPONDTORAINRATESASSMALLASMMHR)NSTRUMENTMASSIS KGREQUIREDINPUTPOWERIS7 4HEIONOSPHERICSOUNDINGMODEON-!23)3DESCRIBEDABOVE ISAIMEDPRIMAR ILYATCHARACTERIZATIONOFTHE-ARTIANIONOSPHEREDURINGDAYLIGHTCONDITIONSFROM ALTITUDESBELOWKM4HERADARISOPERATEDASASTEPPED FREQUENCYINSTRUMENT SWEEPINGK(ZTO-(ZINK(ZINTERVALS OVERSECONDS&ROM KM THENOMINAL3.2ISD" INCREASINGTOD"AT-(Z
30!#% "!3%$2%-/4%3%.3).'2!$!23
£n°ÈÎ
#LOUD3AT ,AUNCHED IN !PRIL #LOUD3AT INCLUDES AS ITS PRIMARY PAYLOAD THE#LOUD0ROFILING2ADAR#02 #LOUD3ATFLIESINASUN SYNCHRONOUSORBITIN CLOSEFORMATIONWITH#!,)03/ WHICHCARRIESACLOUD PROFILINGLIDAR ANDINSOME WHATLOOSERFORMATIONWITH!QUA !URA 4ERRA AND0!2!3/,4AKENTOGETHER THESE SIXENVIRONMENTALSATELLITESCONSTITUTETHESO CALLED! 4RAIN4HEAVERAGESEPARATION BETWEEN#LOUD3ATAND#!,)03/ISABOUTKM WHICHCORRESPONDSTOAONE MINUTE DELAYBETWEENTHERADARANDLIDARCLOUDPROFILINGMEASUREMENTS4HE#02WASDEVEL OPEDJOINTLYBY.!3!ANDTHE#ANADIAN3PACE!GENCY)TISA'(ZNADIR VIEWING REALAPERTURERADAR TRANSMITTING§SECPULSESATA02&OFK(ZTOFILLAWINDOW FROMTHESURFACETOKMALTITUDEWITH MVERTICALRESOLUTIONSOUNDINGDATA4HE ANTENNA DIAMETER LIMITED BY THE LAUNCH VEHICLE SHROUD IS M WHICH SUPPORTS ACROSS TRACKANDALONG TRACKRESOLUTIONSOFKMANDKM RESPECTIVELY4HELARGER ALONG TRACKRESOLUTIONREFLECTSTHE SECINTEGRATIONTIMEOFTHERETURNS!NTENNAGAIN ISD"!VERAGEDATARATEISKBITSS$YNAMICRANGEISD"MINIMUMDETECTABLE VOLUMETRICRETURNISnD":4HE02MASSISKGINPUTPOWERREQUIREDIS7 0EAKPOWERTRANSMITTEDISK7 4HE #02S HIGH POWER AMPLIFIER (0! IS THE FIRST OF ITS KIND FOR A SPACE BASED RADAR ANEXTENDEDINTERACTIONKLYSTRON4HEKLYSTRONISDRIVENBYM7SIGNALS FROMASOLID STATEPREAMPLIFIER4HEKLYSTRONREQUIRESK6 PROVIDEDBYAHIGH VOLTAGE POWERSUPPLYSYSTEMTHATALSOISASPACEFIRST4HE(0!ISFULLYREDUNDANT $02 4HE DUAL FREQUENCY PRECIPITATION RADAR IS THE ACTIVE MICROWAVE INSTRU MENTFORTHE'LOBAL0RECIPITATION-EASUREMENT'0- #ORE/BSERVATORY$02IS BASEDONA+UBANDINSTRUMENT+U02 SIMILARTOITSPREDECESSORON42-- AUGMENTED BYA+A BAND'(Z RADAR+A02 4HEIRTWOPHASEDARRAYSLOTTEDWAVEGUIDE ANTENNASARESIZEDANDORIENTEDSOTHATTHEIRFOOTPRINTSARETHESAME4HEIRRESPECTIVE STEEREDBEAMSARESYNCHRONIZEDSOTHATFORTHECENTRAL KMSWATHWITHINWHICHTHEY BOTHHAVECOVERAGE THEIRVERTICALPROFILESARENEAR SIMULTANEOUS4HE+U02AND+A02 ANTENNASARESIZEDATMrMANDMrM RESPECTIVELY EACHCOMPRISED OF SLOTTED WAVEGUIDES DRIVEN BY INDIVIDUAL SOLID STATE POWER AMPLIFIERS 0EAK TRANSMITTEDPOWERSARE7AND7-ASSANDINPUTPOWEROFTHETWORADARSARE KGANDKGAND7AND74HEONLYOTHERINSTRUMENTINTHEPAYLOAD ISAMICROWAVERADIOMETER4OPROVIDECOVERAGEATMORELATITUDES THESPACECRAFTHAS AHIGHERINCLINATIONORBITTHAN42--Sn4HEMAINADVANTAGESOFTHESECONDFRE QUENCYANDINCREASEDPOWERARETODISTINGUISHBETWEENRAINANDSNOWANDTOINCREASE SENSITIVITYTORAINRATESASLOWASMMHR
, ,
$ % "ARRICK AND #4 3WIFT h4HE 3EASAT MICROWAVE INSTRUMENTS IN HISTORICAL PERSPECTIVE v )%%%*OURNALOF/CEANIC%NGINEERING VOL/% PPn $,%VANS 7!LPERS !#AZENAVE #%LACHI 4&ARR $'LACKIN "(OLT ,*ONES 74,IU 7-C#ANDLESS 9-ENARD 2-OORE AND%.JOKU h3EASATn! YEARLEGACYOFSUCCESS v2EMOTE 3ENSINGOF%NVIRONMENT VOL PPn - $ 'RIFFIN AND * 2 &RENCH 3PACE6EHICLE $ESIGN !MERICAN )NSTITUTE OF!ERONAUTICS AND !STRONAUTICS 6*0ISACANE &UNDAMENTALSOF3PACE3YSTEMS ND%D /XFORD/XFORD5NIVERSITY0RESS & - (ENDERSON AND ! * ,EWIS EDS 0RINCIPLES AND !PPLICATIONS OF )MAGING 2ADAR .EW9ORK*7ILEY3ONS)NC
£n°È{
2!$!2(!.$"//+
# ! 7ILEY h3YNTHETIC !PERTURE 2ADARS! PARADIGM FOR TECHNOLOGY EVOLUTION v )%%% 4RANSACTIONSON!EROSPACEAND%LECTRONIC3YSTEMS VOL!%3 PPn (*ENSEN ,#'RAHAM ,*0ORCELLO AND%.,EITH h3IDE LOOKINGAIRBORNERADAR v3CIENTIFIC !MERICAN VOL PPn 2 , *ORDAN h4HE 3EASAT ! SYNTHETIC APERTURE RADAR SYSTEM v )%%% *OURNAL OF /CEANIC %NGINEERING VOL/% PPn 2 , *ORDAN " , (UNEYCUTT AND - 7ERNER h4HE 3)2 #8 3!2 SYNTHETIC APERTURE RADAR SYSTEM v0ROCEEDINGSOFTHE)%%% VOL PPn ! &REEMAN - !LVES " #HAPMAN * #RUZ 9 +IM 3 3HAFFER * 3UN % 4URNER AND + 3ARABANDI h3)2 # DATA QUALITY AND CALIBRATION RESULTS v )%%%4RANSACTIONS ON 'EOSCIENCE AND2EMOTE3ENSING VOL PPn "2ABUS -%INEDER !2OTH AND2"AMLER h4HESHUTTLETOPOGRAPHYMISSIONANEWCLASSOF DIGITALELEVATIONMODELSACQUIREDBYSPACEBORNERADAR v0HOTOGRAMMETRYAND2EMOTE3ENSING VOL PPn 79IRONG :-INHUI AND(7EN h3!2ACTIVITIESIN02#HINA vIN0ROCEEDINGS TH%UROPEAN #ONFERENCEON3YNTHETIC!PERTURE2ADAR $RESDEN 'ERMANY 6$%6ERLAG 93HARAYAND5.AFTALY h4%#3!2DESIGNCONSIDERATIONSANDPROGRAMMESTATUS v)%%0ROC 2ADAR3ONAR.AVIGATION VOL PPn %07!TTEMA h4HEACTIVEMICROWAVEINSTRUMENTON BOARDTHE%23 SATELLITE v0ROCEEDINGS OFTHE)%%% VOL PPn 2"AMLER -%INEDER "+AMPES (2UNGE AND.!DAM h324-ANDBEYOND#URRENTSITU ATIONANDNEWDEVELOPMENTSINSPACEBORNE)N3!2 vIN0ROCEEDINGS )30237ORKSHOPON(IGH 2ESOLUTION-APPINGFROM3PACE (ANOVER 'ERMANY 9 .EMOTO ( .ISHINO - /NO ( -IZUTAMARI + .ISHIKAWA AND + 4ANAKA h*APANESE EARTH RESOURCES SATELLITE SYNTHETIC APERTURE RADAR v 0ROCEEDINGS OF THE )%%% VOL PPn 2+2ANEY !0,USCOMBE %*,ANGHAM AND3!HMED h2!$!23!4 v0ROCEEDINGSOFTHE )%%% VOL PPn +#*EZEK +&ARNESS 2#ARANDE 87U AND.,ABELLE (AMER h2!$!23!4 SYNTHETIC APERTURERADAROBSERVATIONSOF!NTARCTICA-ODIFIED!NTARCTIC-APPING-ISSION v2ADIO 3CIENCE VOL PP !!LI )"ARNARD 0!&OX 0$UGGAN 2'RAY 0!LLAN !"RAND AND23TE -ARI h$ESCRIPTION OF 2!$!23!4 SYNTHETIC APERTURE RADAR DESIGN v #ANADIAN * 2EMOTE 3ENSING VOL PPn 0!&OX !0,USCOMBE AND!!4HOMPSON h2!$!23!4 3!2MODESDEVELOPMENTAND UTILIZATION v#ANADIAN*2EMOTE3ENSING VOL PPn # :ELLI h%.6)3!4 2! !DVANCED RADAR ALTIMETER )NSTRUMENT DESIGN AND PRE LAUNCH PERFORMANCEASSESSMENTREVIEW v!CTA!STRONAUTICA VOL PPn 32#LOUDE '+RIEGER AND+00APATHANASSIOU h!FRAMEWORKFORINVESTIGATINGSPACE BORNE POLARIMETRICINTERFEROMETRYUSINGTHE!,/3 0!,3!2SENSOR vIN0ROCEEDINGS)%%%'EOSCIENCE AND2EMOTE3ENSING3YMPOSIUM)'!233 !LASKA )%%% -3HIMADA -7ATANABE 4-ORIYAMA AND44ADONO h0!,3!2CHARACTERIZATIONANDINITIAL CALIBRATION v IN 0ROCEEDINGS )%%% )NTERNATIONAL 'EOSCIENCE AND 2EMOTE 3ENSING 3YMPOSIUM )'!233 $ENVER #/ )%%% ! -OREIRA ' +RIEGER $ (OUNAM - 7ERNER 3 2IEGGER AND % 3ETTELMEYER h4AN$%- 8!4ERRA3!2 8ADD ONSATELLITEFORSINGLE PASS3!2INTERFEROMETRY vIN0ROC )NTERNATIONAL'EOSCIENCEAND2EMOTE3ENSING3YMPOSIUM)'!233 !NCHORAGE !LASKA )%%% 2,EVY .ATHANSOHNAND5.AFTALY h/VERVIEWOFTHE4%#3!2SATELLITEMODESOFOPERATION v IN0ROCEEDINGS TH%UROPEAN#ONFERENCEON3YNTHETIC!PERTURE2ADAR $RESDEN 'ERMANY 6$% 6ERLAG 97U -:HU AND7(ONG h3!2ACTIVITIESIN02#HINA vIN0ROCEEDINGSOF%53!2 $RESDEN 'ERMANY )4'6$%
30!#% "!3%$2%-/4%3%.3).'2!$!23
£n°Èx
4-ISRA 332ANA 6("ORA .-$ESAI #6.2AO AND.2AJEEVJYOTHI h3!2PAYLOADOF RADARIMAGINGSATELLITE2)3!4 OF)32/ vIN0ROCEEDINGS TH%UROPEAN#ONFERENCEON3YNTHETIC !PERTURE2ADAR $RESDEN 'ERMANY 6$%6ERLAG 23CHROEDER *0ULS &*OCHIM * ,"UESO "ELLO ,$ATASHVILI ("AIER --1UINTINODA 3ILVE AND70ARADELLA h4HE-!03!2MISSION/BJECTIVES DESIGN ANDSTATUS vIN0ROCEEDINGS OF%53!2 $RESDEN 'ERMANY )4'6$% ( +IMURA AND . )TOH h!,/3 0!,3!2 4HE *APANESE SECOND GENERATION SPACEBORNE 3!2 ANDITSAPPLICATION v0ROC3OCIETYOF0HOTO OPTICAL)NSTRUMENTATION%NGINEERS30)% VOL PPn *##URLANDERAND2.-C$ONOUGH 3YNTHETIC!PERTURE2ADAR3YSTEMSAND3IGNAL0ROCESSING .EW9ORK*OHN7ILEY3ONS )NC 2 + 2ANEY h2ADAR FUNDAMENTALS TECHNICAL PERSPECTIVE v IN 0RINCIPLES AND !PPLICATIONS OF )MAGING 2ADAR & (ENDERSON AND ! ,EWIS EDS .EW 9ORK 7ILEY )NTERSCIENCE PPn ' &RANCESCHETTI AND 2 ,ANARI 3YNTHETIC !PERTURE 2ADAR 0ROCESSING "OCA 2ATON &, #2# 0RESS 2 + 2ANEY h#ONSIDERATIONS FOR 3!2 IMAGE QUANTIFICATION UNIQUE TO ORBITAL SYSTEMS v )%%% 4RANSACTIONS'EOSCIENCEAND2EMOTE3ENSING VOL PPn 0 % 'REEN *R h2ADAR MEASUREMENTS OF TARGET SCATTERING PROPERTIES v )N 2ADAR !STRONOMY *6%VANSAND4(AGFORSEDS .EW9ORK-C'RAW (ILL 7'#ARRARA 23'OODMAN AND2--AJEWSKI 3POTLIGHT3YNTHETIC!PERTURE2ADAR3IGNAL 0ROCESSING!LGORITHMS "OSTON!RTECH(OUSE # 6 *AKOWATZ $ % 7AHL 0 ( %ICHEL $ # 'HIGLIA AND 0 ! 4HOMPSON 3POTLIGHT -ODE 3YNTHETIC !PERTURE 2ADAR ! 3IGNAL 0ROCESSING !PPROACH "OSTON +LUWER!CADEMIC 0UBLISHERS 2 "AMLER h/PTIMUM LOOK WEIGHTING FOR BURST MODE AND SCAN3!2 PROCESSING v )%%% 4RANSACTIONSON'EOSCIENCEAND2EMOTE3ENSING VOL PPn +4OMIYASU h#ONCEPTUALPERFORMANCEOFASATELLITE BORNE WIDESWATHSYNTHETICAPERTURERADAR v )%%%4RANSACTIONSON'EOSCIENCEAND2EMOTE3ENSING VOL PPn 2+-OORE *0#LAASEN AND9(,IN h3CANNINGSPACEBORNESYNTHETICAPERTURERADARWITH INTEGRATEDRADIOMETER v)%%%4RANSACTIONSON!EROSPACEAND%LECTRONIC3YSTEMS VOL!%3 PPn !,USCOMBE !4HOMPSON 0*AMES AND0&OX h#ALIBRATIONTECHNIQUESFORTHE2!$!23!4 3!2SYSTEM vIN0ROCEEDINGSOF%53!2 $RESDEN 'ERMANY 6$%6ERLAG 7-"OERNER (-OTT %,UNEBURG #,IVINGSTONE ""RISCO 2*"ROWN AND*30ATERSON h0OLARIMETRYINRADARREMOTESENSINGBASICANDAPPLIEDCONCEPTS vIN0RINCIPLESAND!PPLICATIONSOF )MAGING2ADAR &-(ENDERSONAND!*,EWISEDS .EW9ORK*OHN7ILEY3ONS )NC ,'RAHAM h3YNTHETICINTERFEROMETERSFORTOPOGRAPHICMAPPING v0ROC)%%% VOL PPn 2'ENSAND*VAN'ENDEREN h2EVIEWARTICLE3!2INTERFEROMETRYISSUES TECHNIQUES APPLICA TIONS v)NT*2EMOTE3ENSING VOL PPn 02OSEN 3(ENSLEY )*OUGHIN &,I 3-ADSEN %2ODRIGUEZ AND2'OLDSTEIN h3YNTHETIC APERTURERADARINTERFEROMETRY v0ROC)%%% VOL PPn 2 & (ANSSEN 2ADAR )NTERFEROMETRY $ORDRECHT 4HE .ETHERLANDS +LEWER !CADEMIC 0UBLISHERS (:EBKERAND2'OLDSTEIN h4OPOGRAPHICMAPPINGFROMINTERFEROMETRICSYNTHETICAPERTURERADAR OBSERVATIONS v*'EOPHYS2ES VOL PPn 3-ADSEN (:EBKER AND*-ARTIN h4OPOGRAPHICMAPPINGUSINGRADARINTERFEROMETRY v)%%% 4RANS'EOSCIENCEAND2EMOTE3ENSING VOL PPn ! 'ABRIEL 2 'OLDSTEIN AND ( :EBKER h-APPING SMALL ELEVATION CHANGES OVER LARGE AREAS $IFFERENTIALRADARINTERFEROMETRY v*'EOPHYS2ES VOL PPn $-ASSONNETAND+&EIGL h2ADARINTERFEROMETRYANDITSAPPLICATIONTOCHANGESINTHE%ARTHS SURFACE v2EV'EOPHYSICS VOL PPn
£n°ÈÈ
2!$!2(!.$"//+
-"ORNAND%7OLF 0RINCIPLESOF/PTICS .EW9ORK0ERGAMON0RESS -ACMILLAN &'ATELLI !'UARNIERI &0ARIZZI 00ASQUALI #0RATI AND&2OCCA h4HEWAVENUMBERSHIFTIN 3!2INTERFEROMETRY v)%%%4RANS'EOSCIENCEAND2EMOTE3ENSING VOL PPn ( :EBKER AND * 6ILLASENOR h$ECORRELATION IN INTERFEROMETRIC RADAR ECHOES v )%%% 4RANS 'EOSCIENCEAND2EMOTE3ENSING VOL PPn !&ERRETTI #0RATI AND&2OCCA h.ONLINEARSUBSIDENCERATEESTIMATIONUSINGPERMANENTSCAT TERERSINDIFFERENTIAL3!2INTERFEROMETRY v)%%%4RANS'EOSCIENCEAND2EMOTE3ENSING VOL PPn 4 ( $IXON & !MELUNG ! &ERRETTI & .OVALI & 2OCCA 2 $OKKA ' 3ELLA 3 7 +IM 37DOWINSKI AND $7HITMAN h3PACE GEODESY 3UBSIDENCE AND FLOODING IN .EW /RLEANS v .ATURE VOL PPn $'HIGLIAAND-0RITT 4WO DIMENSIONAL0HASE5NWRAPPING4HEORY !LGORITHMS AND3OFTWARE .EW9ORK7ILEY 2 'OLDSTEIN AND # 7ERNER h2ADAR INTERFEROGRAM FILTERING FOR GEOPHYSICAL APPLICATIONS v 'EOPHYSICAL2ES,ETTERS VOL PPnn **VAN:YL (!:EBKER AND#%LACHI h)MAGINGRADARPOLARIZATIONSIGNATURES4HEORYAND OBSERVATION v2ADIO3CIENCE VOL PPn 0 % 'REEN *R h2ADAR MEASUREMENTS OF TARGET SCATTERING PROPERTIES v IN 2ADAR !STRONOMY *6%VANSAND4(AGFORSEDS .EW9ORK-C'RAW (ILL"OOK#OMPANY PPn ! 'UISSARD h-EULLER AND +ENNAUGH MATRICES IN RADAR POLARIMETRY v )%%% 4RANSACTIONS ON 'EOSCIENCEAND2EMOTE3ENSING VOL PPn #,OPEZ -ARTINEZ %0OTTIER AND32#LOUDE h3TATISTICALASSESSMENTOF%IGENVECTOR BASED TARGET DECOMPOSITION THEOREMS IN RADAR POLARIMETRY v )%%% 4RANS 'EOSCIENCE AND 2EMOTE 3ENSING VOL PPn 3 2 #LOUDE AND + 0 0APATHANASSIOU h0OLARIMETRIC 3!2 INTERFEROMETRY v )%%% 4RANS 'EOSCIENCEAND2EMOTE3ENSING VOL PPn 3 2 #LOUDE AND % 0OTTIER h!N ENTROPY BASED CLASSIFICATION SCHEME FOR LAND APPLICATIONS OF POLARIMETRIC3!2 v)%%%4RANS'EOSCIENCEAND2EMOTE3ENSING VOL PPn , , &U AND ! #AZANAVE EDS 3ATELLITE !LTIMETRY AND THE %ARTH 3CIENCES 3AN $IEGO !CADEMIC0RESS *2*ENSENAND2+2ANEY h$ELAY$OPPLERRADARALTIMETER"ETTERMEASUREMENTPRECISION v IN 0ROCEEDINGS )%%% 'EOSCIENCE AND 2EMOTE 3ENSING 3YMPOSIUM )'!233g 3EATTLE 7! )%%% PPn 2+-OOREAND#37ILLIAMS *R h2ADARRETURNATNEAR VERTICALINCIDENCE v0ROCEEDINGSOF THE)2% VOL PPn ' 3 "ROWN h4HE AVERAGE IMPULSE RESPONSE OF A ROUGH SURFACE AND ITS APPLICATIONS )%%% !NTENNASAND0ROPAGATION VOL PPn % * 7ALSH h0ULSE TO PULSE CORRELATION IN SATELLITE RADAR ALTIMETRY v 2ADIO 3CIENCE VOL PPn *4-C'OOGAN ,3-ILLER '3"ROWN AND'3(AYNE h4HE3 RADARALTIMETEREXPERI MENT v0ROCEEDINGSOFTHE)%%% VOL PPn '3(AYNE h2ADARALTIMETERMEANRETURNWAVEFORMSFROMNEAR NORMALINCIDENCEOCEANSURFACE SCATTERING v)%%%!NTENNASAND0ROPAGATION VOL!0 PPn *,-AC!RTHUR ##+ILGUS #!4WIGG AND06+"ROWN h%VOLUTIONOFTHESATELLITERADAR ALTIMETER v*OHNS(OPKINS!0,4ECHNICAL$IGEST VOL PPn /CTOBERn$ECEMBER *,-AC!RTHUR 0#-ARTH AND*'7ALL h4HE'%/3!4RADARALTIMETER v*OHNS(OPKINS !0,4ECHNICAL$IGEST VOL PPn 7(&3MITHAND$43ANDWELL h"ATHYMETRICPREDICTIONFROMDENSESATELLITEALTIMETRYAND SPARSESHIPBOARDBATHYMETRY v*'EOPHYS2ES VOL PPn $43ANDWELLAND7(&3MITH h"ATHYMETRICESTIMATION vIN3ATELLITE!LTIMETRYAND%ARTH 3CIENCES , ,&UAND!#AZENAVEEDS .EW9ORK!CADEMIC0RESS PPn !0, 3PECIALSECTIONS h'EOSATSCIENCEANDALTIMETERTECHNOLOGY v*OHNS(OPKINS!0,4ECHNICAL $IGEST VOL
30!#% "!3%$2%-/4%3%.3).'2!$!23
£n°ÈÇ
$ " #HELTON * # 2IES " * (AINES , , &U AND 0 3 #ALLAHAN h3ATELLITE ALTIMETRY v IN 3ATELLITE!LTIMETRYAND%ARTH3CIENCES , ,&UAND!#AZANAVEEDS 3AN$IEGO!CADEMIC 0RESS PPn * 'OLDHIRSH AND * 2 2OWLAND h! TUTORIAL ASSESSMENT OF ATMOSPHERIC HEIGHT UNCERTAINTIES FOR HIGH PRECISION SATELLITE ALTIMETER MISSIONS TO MONITOR OCEAN CURRENTS v )%%% 4RANSACTIONS 'EOSCIENCEAND2EMOTE3ENSING VOL PPn $*7INGHAM L0HALIPPOU #-AVROCORDATOS AND$7ALLIS h4HEMEANECHOANDECHO CROSS PRODUCT FROM A BEAMFORMING INTERFEROMETRIC ALTIMETER AND THEIR APPLICATION TO ELE VATION MEASUREMENTS v )%%% 4RANSACTIONS ON 'EOSCIENCE AND 2EMOTE 3ENSING VOL PPn 06INCENT .3TEUNOU %#AUBET ,0HALIPPOU ,2EY %4HOUVENOT AND*6ERRON h!LTI+A A+A BANDALTIMETERYPAYLOADANDSYSTEMFOROPERATIONALALTIMETRYDURINGTHE'-%3PERIOD v 3ENSORS VOL PPn -%0ARKE 2(3TEWART $,&ARLESS AND$%#ARTWRIGHT h/NTHECHOICEOFORBITSFOR AN ALTIMETRIC SATELLITE TO STUDY OCEAN CIRCULATION AND TIDES v *OURNAL OF 'EOPHYSICAL 2ESEARCH VOL PPn /CTOBER $43ANDWELLAND7(&3MITH h-ARINEGRAVITYANOMALYFROM'EOSATAND%23 SATELLITE ALTIMETRY v*'EOPHYS2ES VOL PPn 2$2AY h!PPLICATIONSOFHIGH RESOLUTIONOCEANTOPOGRAPHYTOOCEANTIDES vIN2EPORTOFTHE (IGH 2ESOLUTION/CEAN4OPOGRAPHY3CIENCE7ORKING'ROUP-EETING $#HELTONED #ORVALLIS /REGON/REGON3TATE5NIVERSITY 23CHARROOAND06ISSER h0RECISEORBITDETERMINATIONANDGRAVITYFIELDIMPROVEMENTFORTHE%23 SATELLITES v*OF'EOPHYSICAL2ESEARCH VOL PPn ! 2 :IEGER $ 7 (ANCOCK ' 3 (AYNE AND # , 0URDY h.!3! RADAR ALTIMETER FOR THE 4/0%80OSEIDONPROJECT v0ROCEEDINGSOFTHE)%%% VOL PPn *UNE 0 # -ARTH * 2 *ENSEN # # +ILGUS * ! 0ERSCHY * , -AC!RTHUR $ 7 (ANCOCK '3(AYNE #,0URDY ,#2OSSI AND#*+OBLINSKY h0RELAUNCHPERFORMANCEOFTHE.!3! ALTIMETER FOR THE 4/0%80OSEIDON 0ROJECT v )%%% 4RANSACTIONS ON 'EOSCIENCE AND 2EMOTE 3ENSING VOL PPn $"#HELTON %*7ALSH AND*,-AC!RTHUR h0ULSECOMPRESSIONANDSEA LEVELTRACKINGIN SATELLITEALTIMETRY v*OURNALOF!TMOSPHERICAND/CEANIC4ECHNOLOGY VOL PPn 7**#APUTI h3TRETCHATIME TRANSFORMATIONTECHNIQUE v)%%%4RANSACTIONSON!EROSPACEAND %LECTRONIC3YSTEMS VOL!%3 PPn $43ANDWELL h!NTARCTICMARINEGRAVITYFIELDFROMHIGH DENSITYSATELLITEALTIMETRY v'EOPHYS *)NT VOL PPn 7 ( & 3MITH AND $ 4 3ANDWELL h#ONVENTIONAL BATHYMETRY BATHYMETRY FROM SPACE AND GEODETICALTIMETRY v/CEANOGRAPHY VOL PPn - - 9ALE $ 4 3ANDWELL AND 7 ( & 3MITH h#OMPARISON OF ALONG TRACK RESOLUTION OF STACKED 'EOSAT %23 AND 4/0%8 SATELLITE ALTIMETERS v * 'EOPHYS 2ES VOL PPn , 0HALIPPOU , 2EY 0 $E#HATEAU 4HIERRY % 4HOUVENOT . 3TEUNOU # -AVROCORDATOS AND 2 &RANCIS h/VERVIEW OF THE PERFORMANCES AND TRACKING DESIGN OF THE 3)2!, ALTIMETER FORTHE#RYO3ATMISSION vIN0ROCEEDINGS)%%%)NTERNATIONAL'EOSCIENCEAND2EMOTE3ENSING 3YMPOSIUM PPn 2+2ANEY h4HEDELAYDOPPLERRADARALTIMETER v)%%%4RANSACTIONSON'EOSCIENCEAND2EMOTE 3ENSING VOL PPn * 2 *ENSEN h$ESIGN AND PERFORMANCE ANALYSIS OF A PHASE MONOPULSE RADAR ALTIMETER FOR CONTINENTALICESHEETMONITORING vIN0ROCEEDINGS )%%%)NTERNATIONAL'EOSCIENCEAND2EMOTE 3ENSING3YMPOSIUM)'!233g &LORENCE )TALY )%%% PPn 2 + 2ANEY AND * 2 *ENSEN h!N!IRBORNE #RYO3AT 0ROTOTYPE 4HE $0 2ADAR!LTIMETER v IN 0ROCEEDINGS OF THE )NTERNATIONAL 'EOSCIENCE AND 2EMOTE 3ENSING 3YMPOSIUM )'!233 4ORONTO )%%% PPn 3 ,AXON . 0EACOCK AND $ 3MITH h(IGH INTERANNUAL VARIABILITY OF SEA ICE THICKNESS IN THE !RCTICREGION v,ETTERSTO.ATURE VOL PPn
£n°Èn
2!$!2(!.$"//+
! * "UTRICA 4O 3EE THE 5NSEEN ! (ISTORY OF 0LANETARY 2ADAR $ARBY 0! $IANE 0UBLICATIONS 3 * /STRO h0LANETARY RADAR ASTRONOMY v IN 4HE %NCYCLOPEDIA OF 0HYSICAL 3CIENCE AND 4ECHNOLOGY RD%DITION 2!-EYERSED 3AN$IEGO !CADEMIC0RESS PPn $ " #AMPBELL 2 3 (UDSON AND * , -ARGOT h!DVANCES IN PLANETARY RADAR ASTRONOMY v #HAPTER IN 2EVIEW OF 2ADIO 3CIENCE n 2 3TONE ED /XFORD 523) PPn 33LAVNEY 2%!RVIDSON +"ENNETT %!'UINESS AND4#3TEIN h2ECENTANDPLANNED 0LANETARY$ATA3YSTEMGEOSCIENCESNODEACTIVITIES v0APERPDF 0ROCEEDINGS ,UNARAND 0LANETARY3CIENCE8886)) (OUSTON 48 VOL '(0ETTENGILL 0'&ORD AND"$#HAPMAN h6ENUSSURFACEELECTROMAGNETICPROPERTIES v *'EOPHYS2ES VOL PP "!)VANOV h6ENUSIANIMPACTCRATERSON-AGELLANIMAGES6IEWFROM6ENERA v%ARTH -OON0LANET VOL PPn '(0ETTENGILL 0'&ORD 74+*OHNSON 2+2ANEY AND,!3ODERBLOM h-AGELLAN 2ADARPERFORMANCEANDDATAPRODUCTS v3CIENCE VOL PPn 74+*OHNSON h-AGELLANIMAGINGRADARMISSIONTO6ENUS v0ROCEEDINGSOFTHE)%%% VOL PPn #%LACHI %)M ,%2OTH AND#,7ERNER h#ASSINI4ITANRADARMAPPER v0ROCEEDINGSOFTHE )%%% VOL PPn 3 .OZETTE # , ,ICHTENBERG 0 3PUDIS 2 "ONNER 7 /RT % -ALARET - 2OBINSON AND % - 3HOEMAKER h4HE #LEMENTINE BISTATIC RADAR EXPERIMENT v 3CIENCE VOL PPn .OVEMBER "(APKE h#OHERENTBACKSCATTERANDTHERADARCHARACTERISTICSOFOUTERPLANETSATELLITES v)CARUS VOL PPn $ECEMBER 2!3IMPSONAND',4YLER h2EANALYSISOF#LEMENTINEBISTATICRADARDATAFROMTHELUNAR 3OUTH0OLE v*'EOPHYS2ES VOL PPn &EBRUARY $"#AMPBELL "!#AMPBELL ,-#ARTER * ,-ARGOT AND.*33TACY h.OEVIDENCE FORTHICKDEPOSITSOFICEATTHELUNARSOUTHPOLE v.ATURE VOL PPn -4:UBERAND)'ARRICK "ETHELL h7HATDOWENEEDTOKNOWTOLANDONTHE-OONAGAIN v 3CIENCE VOL PPn + * 0ETERS h#OHERENT BACKSCATTER EFFECT ! VECTOR FORMULATION ACCOUNTING FOR POLARIZATION ANDABSORPTIONEFFECTSANDSMALLORLARGESCATTERERS v0HYSICAL2EVIEW" VOL PPn *ULY 0$3PUDIS #,,ICHTENBERG "-ARINELLI AND3.OZETTE h-INI 3!2!NIMAGINGRADAR FORTHE#HANDRAYAAN MISSIONTOTHE-OON v0APER 0ROCEEDINGS ,UNARAND0LANETARY 3CIENCE8886) (OUSTON 48 VOL 2 + 2ANEY h(YBRID POLARITY 3!2 ARCHITECTURE v IN 0ROCEEDINGS )%%% 'EOSCIENCE AND 2EMOTE3ENSING3YMPOSIUM $ENVER #/ )%%% $ * -UDGWAY "IG $ISH "UILDING !MERICAgS $EEP 3PACE #ONNECTION TO THE 0LANETS 'AINESVILLE5NIVERSITYOF&LORIDA0RESS 2 + -OORE h4RADE OFF BETWEEN PICTURE ELEMENT DIMENSIONS AND NONCOHERENT AVERAGING IN SIDE LOOKINGAIRBORNERADAR v)%%%4RANSACTIONSON!EROSPACEAND%LECTRONIC3YSTEMS VOL PPn 2+2ANEY h4HEMAKINGOFAPRECEDENTTHESYNTHETICAPERTURERADAR3!2 ON-AGELLAN v 6 '2!-*ET0ROPULSION,ABORATORY VOL PPn 2+WOKAND74+*OHNSON h"LOCKADAPTIVEQUANTIZATIONOF-AGELLAN3!2DATA v)%%% 4RANSACTIONSON'EOSCIENCEAND2EMOTE3ENSING VOL PPn ''3TOKES h/NTHECOMPOSITIONANDRESOLUTIONOFSTREAMSOFPOLARIZEDLIGHTFROMDIFFERENT SOURCES v4RANSACTIONSOFTHE#AMBRIDGE0HILOSOPHICAL3OCIETY VOL PPn 32#LOUDEAND%0OTTIER h!REVIEWOFTARGETDECOMPOSITIONTHEOREMSINRADARPOLARIMETRY v )%%%4RANS'EOSCIENCEAND2EMOTE3ENSING VOL PPn 2 + 2ANEY h3TOKES PARAMETERS AND HYBRID POLARITY 3!2 ARCHITECTURE v )%%% 4RANSACTIONS 'EOSCIENCEAND2EMOTE3ENSING VOL PPn
30!#% "!3%$2%-/4%3%.3).'2!$!23
£n°È
91UILFEN "#HAPRON &#OLLARD AND$6ANDEMARK h2ELATIONSHIPBETWEEN%23SCATTEROM ETER MEASUREMENT AND INTEGRATED WIND AND WAVE PARAMETERS v * !TMOSPHERIC AND /CEANIC 4ECHNOLOGY VOL PPn 2+-OOREAND!+&UNG h2ADARDETERMINATIONOFWINDSATSEA v0ROCEEDINGSOFTHE)%%% VOL PPn *+ERKMANN 2EVIEWON3CATTEROMETER7INDS $ARMSTADT 'ERMANY%UROPEAN/RGANIZATIONFOR THE%XPLOITATIONOF-ETEOROLOGICAL3ATELLITES%5-%43!4 P !-OUCHE $(AUSER AND6+UDRYAVSTEV h/BSERVATIONSANDMODELLINGOFTHEOCEANRADAR BACKSCATTERAT# BANDIN(( AND66 POLARIZATIONS vIN0ROCEEDINGS)NTERNATIONAL'EOSCIENCE AND2EMOTE3ENSING3YMPOSIUM 3EOUL +OREA )%%% --IGLIACCIO h3EAWINDFIELDRETRIEVALBYMEANSOFMICROWAVESENSORSAREVIEW vIN0ROC 523)#OMMISSION&3YMPOSIUM )SPRA )TALY %-"RACALENTE $("OGGS 7,'RANTHAM AND*,3WEET h4HE3!33SCATTERINGCOEF FICIENTALGORITHM v)%%%*OURNALOF/CEANIC%NGINEERING VOL/% PPn 2 % &ISCHER h3TANDARD DEVIATION OF SCATTEROMETER MEASUREMENTS FROM SPACE v )%%% 4RANSACTIONSON'EOSCIENCE%LECTRONICS VOL'% PPn 0 7 'AISER AND # 3 2UF h&OREWORD TO THE SPECIAL ISSUE ON THE 7IND3AT 3PACEBORNE 0OLARIMETRIC2ADIOMETERCALIBRATIONVALIDATIONANDWINDVECTORRETRIEVAL v)%%%4RANSACTIONS ON'EOSCIENCEAND2EMOTE3ENSING VOL PPn ) ( 7OODHOUSE AND $ ( (OEKMAN h$ETERMINING LAND SURFACE PARAMETERS FROM THE %23WINDSCATTEROMETER v)%%%4RANSACTIONSON'EOSCIENCEAND2EMOTE3ENSING VOL PPn $',ONG -2$RINKWATER "(OLT 33AATCHI AND#"ERTOIA h'LOBALICEANDLANDCLIMATE STUDIES USING SCATTEROMETER IMAGE DATA v %/3 4RANS!MERICAN 'EOPHYSICAL 5NION VOL PP - 2 $RINKWATER $ ' ,ONG AND!7 "INGHAM h'REENLAND SNOW ACCUMULATION ESTI MATESFROMSATELLITERADARSCATTEROMETERDATA v*OF'EOPHYSICAL2ESEARCH VOL$ PPn ,"+UNZAND$',ONG h#ALIBRATING3EA7INDSAND1UIK3#!4SCATTEROMETERSUSINGNATURAL LANDTARGETS v)%%%'EOSCIENCEAND2EMOTE3ENSING,ETTERS VOL PPn 2+-OORE h3IMULTANEOUSACTIVEANDPASSIVEMICROWAVERESPONSEOFTHE%ARTH4HE3KYLAB 2!$3#!4 EXPERIMENT v IN 0ROCEEDINGS OF THE TH )NTERNATIONAL 3YMPOSIUM ON 2EMOTE 3ENSING !NN!RBOR -ICHIGAN PPn - 3HIMADA AND! &REEMAN h! TECHNIQUE FOR MEASUREMENT OF SPACEBORNE 3!2 ANTENNA PATTERNSUSINGDISTRIBUTEDTARGETS v)%%%4RANSACTIONSON'EOSCIENCEAND2EMOTE3ENSING VOL PPn 7,'RANTHAM %-"RACALENTE ,7*ONES AND*7*OHNSON h4HE3EASAT !SATELLITESCAT TEROMETER v)%%%*OURNALOF/CEANIC%NGINEERING VOL/% PPn *7*OHNSON ,!7ILLIAMS *R %-"RACALENTE &""ECK AND7,'RANTHAM h3EASAT ! SATELLITESCATTEROMETERINSTRUMENTEVALUATION v)%%%*OURNALOF/CEANIC%NGINEERING VOL/% PPn *&IGA 3ALDANA **77ILSON %!TTEMA 2'ELSTHORPE -2$RINKWATER AND!3TOFFELEN h4HE ADVANCED SCATTEROMETER !3#!4 ON THE METEOROLOGICAL OPERATIONAL -ET/P PLATFORM A FOLLOW ON FOR %UROPEAN WIND SCATTEROMETERS v #ANADIAN * OF 2EMOTE 3ENSING VOL PPn &-.ADERI -(&REILICH AND$',ONG h3PACEBORNERADARMEASUREMENTOFWINDVELOCITY OVERTHEOCEANnn!NOVERVIEWOFTHE.3#!4SCATTEROMETERSYSTEM v0ROCEEDINGSOFTHE)%%% VOL PPn #7U *'RAF -(&REILICH $',ONG -73PENCER 7 94SAI $,ISMAN AND#7INN h4HE3EA7INDSSCATTEROMETERINSTRUMENT vIN0ROCEEDINGS )%%%)NTERNATIONAL'EOSCIENCEAND 2EMOTE3ENSING3YMPOSIUM 0ASADENA #! PPn -73PENCER #7U AND$',ONG h4RADEOFFSINTHEDESIGNOFASPACEBORNESCANNINGPENCIL BEAMSCATTEROMETER!PPLICATIONTO3EA 7INDS v)%%%4RANSACTIONSON'EOSCIENCEAND2EMOTE 3ENSING VOL PPn
£n°Çä
2!$!2(!.$"//+
#7U 9,IU +(+ELLOGG +30AK AND2,'LENISTER h$ESIGNANDCALIBRATIONOFTHE 3EA7INDSSCATTEROMETER v)%%%4RANSACTIONSON!EROSPACEAND%LECTRONIC3YSTEMS VOL PPn -73PENCER #7U AND$',ONG h)MPROVEDRESOLUTIONBACKSCATTERMEASUREMENTSWITHTHE 3EA7INDSPENCIL BEAMSCATTEROMETER v)%%%4RANSACTIONSON'EOSCIENCEAND2EMOTE3ENSING VOL PPn 3(9UEH h-ICROWAVEREMOTESENSINGMODELINGOFOCEANSURFACESALINITYANDWINDSUSING AN EMPIRICAL SEA SURFACE SPECTRUM v IN 0ROCEEDINGS )%%% 'EOSCIENCE AND 2EMOTE 3ENSING 3YMPOSIUM !NCHORAGE !+ 3'OGINENI $4AMMANA $"RAATEN #,EUSCHEN 4!TKINS *,EGARSKY 0+ANAGARATNAM *3TILES #!LLEN AND+*EZEK h#OHERENTRADARICETHICKNESSMEASUREMENTSOVER'REENLAND ICESHEET v*OURNALOF'EOPHYSICAL2ESEARCH VOL PPn 3(7ARD '2*IRACEK AND7),INLOR h%LECTROMAGNETICREFLECTIONFROMAPLANE LAYERED LUNARMODEL v*OURNALOF'EOPHYSICAL2ESEARCH VOL PPn ,*0ORCELLO 2,*ORDAN *3:ELENKA '&!DAMS 2*0HILLIPS 7%"ROWN *R 3(7ARD AND0,*ACKSON h4HE!POLLOLUNARSOUNDERRADARSYSTEM v0ROCEEDINGSOFTHE)%%% VOL PPn 7*0EEPLES 723ILL 47-AY 3(7ARD 2*0HILLIPS 2,*ORDAN %!!BBOTT AND 4*+ILLPACK h/RBITALRADAREVIDENCEFORLUNARSUBSURFACELAYERINGIN-ARIA3ERENITATISAND #RISIUM v*OF'EOPHYSICAL2ESEARCH VOL PPn $"ICCARI &#IABATTONI '0ICARDI 23EU 74+*OHNSON 2,*ORDAN *0LAUT !3AFAEINILI $!'URNETT 2/ROSEI /"OMBACI &0ROVVEDI AND%:AMPOLINI h-ARSADVANCEDRADARFOR SUBSURFACEANDIONOSPHERESOUNDING-!23)3 vIN0ROC)NTERNATIONAL#ONFERENCEON 2ADAR "EIJING #HINA * &ARRELL * 0LAUT ! 'URNETT AND ' 0ICARDI h$ETECTING SUB GLACIAL AQUIFERS IN THE .ORTH 0OLAR LAYERED DEPOSITS WITH -ARS %XPRESS-!23)3 v 'EOPHYSICAL 2ESEARCH ,ETTERS VOL PP, *UNE -+ATO 94AKIZAWA 33ASAKI ANDTHE3%,%.%0ROJECT4EAM h3%,%.% THE*APANESELUNAR ORBITINGSATELLITEMISSIONPRESENTSTATUSANDSCIENCEGOALS vIN0ROCEEDINGS ,UNARAND0LANETARY 3CIENCE8886)) (OUSTON 48 PPPDF 4 /NO 4 +OBAYASHI AND ( /YA h)NTERIM REPORT OF THE ,UNAR 2ADAR 3OUNDER ON BOARD 3%,%.%SPACECRAFT vIN0ROCEEDINGS TH#/30!2!SSEMBLY 0ARIS &RANCE PP %)M % 3,$URDEN 34ANELLI AND+0AK h%ARLYRESULTSONCLOUDPROFILINGRADARPOST LAUNCHCALIBRATIONANDOPERATIONS vIN0ROCEEDINGSOFTHE)%%%)NTERNATIONAL'EOSCIENCEAND 2EMOTE3ENSING3YMPOSIUM $ENVER #/ ',3TEPHENSAND$'6ANE h4HE#LOUD3ATMISSION vIN0ROCEEDINGS)%%%)NTERNATIONAL 'EOSCIENCEAND2EMOTE3ENSING3YMPOSIUM 4OULOUSE &RANCE !2OITMAN $"ERRY AND"3TEER h3TATE OF THE ART7 BANDEXTENDEDINTERACTIONKLYSTRONFOR THE#LOUD3ATPROGRAM v)%%%4RANSACTIONSON%LECTRON$EVICES VOL PPn 93ENBOKUVA 33ATOH +&URUKAWA -+OIIMA ((ANADO .4AKAHASHI 4)QUCHI AND + .AKAMURA h$EVELOPMENT OF THE SPACEBORNE DUAL FREQUENCY PRECIPITATION RADAR FOR THE 'LOBAL0RECIPITATION-EASUREMENTMISSION vIN0ROCEEDINGS)NTERNATIONAL'EOSCIENCEAND 2EMOTE3ENSING3YMPOSIUM !NCHORAGE !LASKA PPn 2 3EU $ "ICCARI 2 /ROSEI , 6 ,ORENZONI 2 * 0HILLIPS , -ARINANGELI ' 0ICARDI !-ASDEA AND%:AMPOLINI h3(!2!$THE-2/SHALLOWRADAR v0LANETARYAND3PACE 3CIENCE VOL PPn 4 +OZU 4 +AWANISHI ( +UROIWA - +OJIMA + /IKAWA ( +UMAGAI + /KAMOTO -/KAMURA (.AKATUKA AND+.ISHIKAWA h$EVELOPMENTOFPRECIPITATIONRADARONBOARDTHE 4ROPICAL2AINFALL-EASUREMENT-ISSION42-- SATELLITE v)%%%4RANSACTIONSON'EOSCIENCE AND2EMOTE3ENSING VOL PPn $!'URNETT $,+IRCHNER 2,(UFF $$-ORGAN !-0ERSOON 4&!VERKAMP & $URU %.IELSEN !3AFAEINILI **0LAUT AND'0ICARDI h2ADARSOUNDINGSOFTHEIONOSPHERE OF-ARS v3CIENCE VOL PPn $ECEMBER
#HAPTER
iÌiÀ}V>Ê,>`>À ,°ÊivvÀiÞÊ iiiÀÊ>`Ê,LiÀÌÊ°Ê-iÀ>v .ATIONAL#ENTERFOR!TMOSPHERIC2ESEARCH
£°£Ê /," 1 /" 3TANDARD OPERATIONAL METEOROLOGICAL DOPPLER RADARS HAVE BECOME FAMILIAR OBSERVA TIONALTOOLSTORADARENGINEERSASWELLASTHEGENERALPUBLICSINCETHEIRINTRODUCTIONBY THE5NITED3TATES.ATIONAL7EATHER3ERVICE.73 INTHESANDAREWIDELYUSED BYWEATHERFORECASTERSINTHEPUBLICANDPRIVATESECTORS-AJORTECHNICALIMPROVEMENTS WEREINTRODUCEDINTHESWHENTHE.73 THE&EDERAL!VIATION!GENCY&!! AND THE53!IR&ORCEJOINEDTOGETHERTOINSTALLTHENEXTGENERATIONNATIONALNETWORKOF 732 $DOPPLERRADARSCOMMONLYCALLED.EXRADRADARS !LSOINTHESTHE&!! INSTALLEDTHE4ERMINAL$OPPLER7EATHER2ADAR4$72 SYSTEMATMAJORAIRPORTSINTHE 534HEFEDERALAGENCIESHAVESUBSEQUENTLYIMPLEMENTEDMANYTECHNICALUPGRADES TOTHE.EXRADAND4$72NETWORKSTOIMPROVETHEIRPERFORMANCEFORPUBLICWARNINGS ANDAVIATIONSAFETY )NCONTRASTTOTHE732 AND732 #RADARSTHEYREPLACED THE732 $SYSTEMSPROVIDEQUANTITATIVEANDAUTOMATEDREAL TIMEINFORMATIONON STORMS PRECIPITATION HURRICANES TORNADOES ANDAHOSTOFOTHERIMPORTANTWEATHERPHE NOMENAWITHHIGHERSPATIALANDTEMPORALRESOLUTIONTHANEVERBEFORE )NTHEAVIATION COMMUNITY 4$72RADARSPROVIDECRUCIALINFORMATIONFORPROVIDINGSAFEDEPARTURES ANDLANDINGSATTHEMAJORAIRPORTSBYDETECTINGHAZARDOUSWINDSHEAREVENTSSUCHAS MICROBURSTS STRONGGUSTFRONTS ANDOTHERPERFORMANCEREDUCINGWINDHAZARDS 6ARIOUSOTHERTYPESOFMETEOROLOGICALRADARSEXIST4HE.EXRADLONG RANGEWEATHERSUR VEILLANCERADARSAREFREQUENTLYSUPPLEMENTEDBYTYPICALLY SMALLERMEDIUM RANGEWEATHER RADARSOPERATEDBY46STATIONSFORLOCALOBSERVATIONS)NADDITIONTOTHEFAMILIARCOM MERCIALAIRBORNEWEATHERAVOIDANCEANDOBSERVATIONRADARS AIRBORNEHURRICANEMONITORING PROVIDESDETAILEDFORECASTSANDWARNINGSFORAPPROACHINGCOASTALHURRICANES!NDVERTI CALPOINTINGWINDPROFILINGFIXED BEAMSYSTEMSAREROUTINELYUSEDTOOBTAINCONTINUOUS PROFILESOFHORIZONTALWINDSWHEREASSPACED BASEDMETEOROLOGICALRADARSAREMEASURING WIDESPREADEQUATORIALPRECIPITATIONFIELDSANDCLOUDPROPERTIES-ETEOROLOGICALRESEARCH RESULTSAREREGULARLYTRANSFERREDTOTHEOPERATIONALWEATHERRADARCOMMUNITYFORACHIEV INGHIGHERSPACEANDTIMERESOLUTION FORIMPROVEDDATAQUALITY ANDFORTHEPRODUCTIONOF NEWWEATHERRADARPRODUCTSALLOFWHICHHAVELEDTODRAMATICIMPROVEMENTSINWEATHER FORECASTING$OPPLERWEATHERRADARSMEASUREDETAILEDVECTORWINDFIELDSASWELLASPRECIPI TATIONFIELDS3MALL HIGHLYMOBILERESEARCHRADARSPROVIDEMANYOFTHESAMECAPABILITIES ASTHEFIXEDRADARS$UALPOLARIZATIONTECHNIQUES AREUSEDFORIMPROVEDQUANTITATIVE
4HE.ATIONAL#ENTERFOR!TMOSPHERIC2ESEARCHISSPONSOREDBYTHE.ATIONAL3CIENCE&OUNDATION £°£
£°Ó
2!$!2(!.$"//+
PRECIPITATIONMEASUREMENT FORDETECTINGHAIL ANDFORDISCRIMINATINGICEPARTICLESSNOW FROMWATERRAIN &URTHERMORE GROUND BASEDRESEARCHRADARSCANNOWMEASUREATMO SPHERICMOISTUREINTHESURFACEBOUNDARYLAYER!IRBORNERESEARCHRADARSPROVIDEMANY OFTHESESAMECAPABILITIESWITHINCREASEDCOVERAGEANDGREATERMOBILITY4HISVARIETYOF APPLICATIONSINBOTHRESEARCHANDOPERATIONSILLUSTRATESTHEVITALITYOFMETEOROLOGICALRADAR TECHNOLOGYANDITSEVOLUTION 4HISCHAPTERISINTENDEDTOINTRODUCETHEREADERTOMETEOROLOGICALRADAR PARTICULARLY THOSE SYSTEM CHARACTERISTICS THAT ARE UNIQUE TO METEOROLOGICAL APPLICATIONS )N THIS REGARD ITSHOULDBENOTEDTHATMOSTMETEOROLOGICALRADARSAPPEARSIMILARTORADARSUSED FOROTHERPURPOSES0ULSEDDOPPLERSYSTEMSAREFARMOREPREVALENTTHAN#7RADARS 0RIMARILY CENTER FED PARABOLIC DISH ANTENNAS WITH FOCAL POINT FEED AND LOW NOISE SOLID STATEDIGITALRECEIVERSAREUSED-AGNETRONS KLYSTRONS TRAVELING WAVETUBES AND OTHERFORMSOFTRANSMITTERFORMSAREROUTINELYUSED 4HEDISTINGUISHINGFACTORBETWEENMETEOROLOGICALRADARANDOTHERKINDSOFAVIATION ORMILITARYRADARSLIESINTHENATUREOFWEATHERTARGETS THERESULTINGCHARACTERISTICSOF THERADARSIGNAL ANDTHEMEANSBYWHICHTHESEWEATHERECHOESAREPROCESSEDTOSUP PRESS ARTIFACTS AND GENERATE ONLY THE SIGNIFICANT AND ESSENTIAL WEATHER INFORMATION )MPORTANTMETEOROLOGICALTARGETSOCCUPYAWIDERANGEOFSCATTERINGECHOINTENSITIES TOD": THATAREDISTRIBUTEDINSPACEFROMSHORTRANGE KM TOLONGRANGE KM CLOSETOTHESURFACEM TOTHETOPOFTHEATMOSPHEREWHEREWEATHER IS IMPORTANT KM AND TYPICALLY OCCUPY A LARGE FRACTION OF THE SEVERAL MILLIONS OFSPATIALRESOLUTIONCELLSOBSERVEDBYTHERADAR-OREOVER ITISNECESSARYTOMAKE QUANTITATIVEMEASUREMENTSOFTHERECEIVEDSIGNALCHARACTERISTICSINEACHOFTHESECELLS ORhWEATHERTARGETS vTOESTIMATESUCHPARAMETERSASPRECIPITATIONRATE PRECIPITATION TYPE AIRMOTION TURBULENCE ANDWINDSHEAR)NADDITION BECAUSEAHIGHPERCENTAGE OFRADARRESOLUTIONCELLSCONTAINUSEFULINFORMATION METEOROLOGICALRADARSREQUIREFAST DIGITALSIGNALPROCESSORS EFFECTIVEMEANSFORSUPPRESSINGARTIFACTSCAUSEDBYTHEDATA DENSITY HIGHDATA RATERECORDINGSYSTEMS ANDINFORMATIVEDISPLAYSOFTHISINFORMA TION4HUS WHEREASMANYNON WEATHERRADARAPPLICATIONSCALLFORDETECTION TRACKING ANDDETAILEDCHARACTERIZATIONOFRELATIVELYFEWERNUMBEROFDESIREDTARGETSINAFIELD OFWIDESPREADWEATHER GROUND SEA DECOY ANDBIRDCLUTTER THEMETEOROLOGICALRADARS FOCUSONMAKINGACCURATEESTIMATESOFTHENATUREOFTHEhWEATHERCLUTTERvITSELF"OTH AVIATIONMILITARYANDWEATHERRADARSREQUIREHEAVYPROCESSINGACTIVITY BUTTHEVOLUME OFDATAFORASSIMILATION RECORDING ANDDISPLAYOFWEATHERRADARSISOFTENMUCHLARGER SINCEDIFFERENTESSENTIALINFORMATIONMUSTBEEXTRACTEDFORALARGENUMBEROFANTICI PATEDUSERSWHENMEASURINGWIDESPREADWEATHERSYSTEMS 4HEDISCUSSIONHEREINREFERSTOANUMBEROFUSEFULTEXTSANDREFERENCESFORTHEREADER (OWEVER THE CLASSIC 2ADAR /BSERVATION OF THE!TMOSPHERE BY ,OU "ATTAN DESERVES SPECIALMENTIONFORITSCLARITYANDCOMPLETENESSANDREMAINSASTANDARDFORCOURSESIN RADAR METEOROLOGY 4HE "ATTAN -EMORIAL AND TH !NNIVERSARY 2ADAR -ETEOROLOGY #ONFERENCEPRODUCEDACOLLECTIONOFREVIEWPAPERS 2ADARIN-ETEOROLOGY COVERING THEFIRSTFOURDECADESOFRADARMETEOROLOGYFROMTHEHISTORICAL TECHNOLOGICAL SCIENTIFIC ANDOPERATIONALPERSPECTIVES"EANETALIN3KOLNIKSFIRST2ADAR(ANDBOOKADDRESSED THEPROBLEMOFWEATHEREFFECTSONRADAR$OVIAKAND:RNIC|PLACESPECIALEMPHASISON DOPPLER ASPECTS OF METEOROLOGICAL RADAR WHEREAS "RINGI AND #HANDRA EMPHASIZE ALL ASPECTSOFPOLARIMETRICRADARSAND,HERMITTEFOCUSESONMILLIMETERWAVECLOUD RADARS 2INEHARTS 2ADAR FOR -ETEOROLOGISTS GIVES A BROAD AND EASILY COMPREHENDIBLE OVER VIEWOFALLASPECTSOFWEATHERRADAR4HE)%%%'EOSCIENCEAND%LECTRONICS3PECIAL)SSUE ON 2ADAR -ETEOROLOGY !TLASS 2ADAR IN -ETEOROLOGY 7AKIMOTO AND 3RIVASTIVAS 2ADARAND!TMOSPHERIC3CIENCE!#OLLECTIONOF%SSAYSIN(ONOROF$AVID!TLAS AND
-%4%/2/,/')#!,2!$!2
£°Î
-EISCHNERS7EATHER2ADARPROVIDEANEVOLVINGPERSPECTIVEONMANYASPECTSOFMETEO ROLOGICALRADARSBYTECHNOLOGICALANDSCIENTIFICLEADERS&INALLY PERHAPSTHEBROADESTAND MOSTCOMPLETESETOFREFERENCESONPROGRESSINTHEFIELDCANBEFOUNDINTHESERIESOF 0ROCEEDINGSAND0REPRINTSOFTHE)NTERNATIONAL #ONFERENCESON2ADAR-ETEOROLOGY SPONSORED BY THE !MERICAN -ETEOROLOGICAL 3OCIETY !-3 4HESE DOCUMENTS CAN BEFOUNDINMANYTECHNICALLIBRARIESANDALSOCANBEOBTAINEDONLINE)NADDITION THE 0ROCEEDINGSOFTHE%UROPEAN#ONFERENCESON2ADAR-ETEOROLOGYPROVIDESEXCELLENT REFERENCEMATERIAL
£°ÓÊ / Ê, ,Ê +1/" Ê",Ê / "," " Ê/, /4HERECEIVEDPOWER0RFROMARADARPOINTTARGETCANBEDERIVEDFROMANYOFAVARIETY OFEXPRESSIONSTHATAREAPPLICABLETORADARINGENERAL &ORASINGLEPOINTTARGET A SIMPLEFORMTHATISREADILYDERIVEDIS
0R
BS
R
WHEREAISACONSTANTDEPENDENTUPONRADARSYSTEMPARAMETERSTRANSMITTEDPOWER0T ANTENNASYSTEMGAIN' ANDWAVELENGTHK RISTHERANGETOTHEPOINTTARGET ANDRIS THERADARCROSSSECTION2#3
)T IS IN THE CALCULATION OF R FOR DISTRIBUTED METEOROLOGICAL TARGETS THAT THE RADAR EQUATIONDIFFERSFROMTHATFORPOINTTARGETS&ORDISTRIBUTEDTARGETSLIKERAINFALLTHE2#3 MAYBEWRITTEN
R G6
WHEREGISTHERADARREFLECTIVITYINUNITSOFCROSS SECTIONALAREAPERUNITVOLUMEAND6 ISTHEVOLUMESAMPLEDBYTHERADARGCANITSELFBEWRITTENAS .
H £S I
I
WHERE.ISTHENUMBEROFSCATTERERSPERUNITVOLUMEANDR IISTHEBACKSCATTERINGCROSS SECTIONOFTHEITHPOINTSCATTERER)NGENERAL THEMETEOROLOGICALSCATTERERSCANTAKEON AVARIETYOFFORMS WHICHINCLUDEWATERDROPLETS ICECRYSTALS HAIL SNOW ANDMIXTURES OFTHEABOVE -IEDEVELOPEDAGENERALTHEORYFORTHEENERGYBACKSCATTEREDBYANOPTICALPLANE WAVEIMPINGINGONCONDUCTINGSPHERESINCOLLOIDALSUSPENSION4HESAMETHEORYAPPLIES TOSPHERICALRAINDROPSFALLINGTHROUGHTHEATMOSPHEREFORWHICHTHEBACKSCATTEREDENERGY ISAFUNCTIONOFTHEWAVELENGTHK OFTHEINCIDENTENERGYANDTHERADIUSA ANDCOMPLEX INDEXOFREFRACTIONM OFTHEPARTICLE4HERATIOO AKDETERMINESTHEDOMINANTSCATTER INGPROPERTIESOFTHEPARTICLE3PHERICALWATERDROPLETSINAIRTHATARELARGERELATIVETOTHE WAVELENGTHSCATTERINTHESOCALLEDOPTICALREGIONDROPLETSONTHEORDEROFTHESAMESIZE ASTHEWAVELENGTHSCATTERINTHESOCALLEDRESONANTSCATTERINGREGIONANDDROPLETSSMALL RELATIVETOTHEWAVELENGTHSCATTERINTHESO CALLED2AYLEIGHREGION
"YCONVENTIONINTHISCHAPTER WESHALLUSERFORRANGEAND2FORRAINFALLRATE
£°{
2!$!2(!.$"//+
7HENTHERATIOPAL THE2AYLEIGHAPPROXIMATIONMAYBEAPPLIED ANDRI BECOMES
P \ + \ $I L
SI
WHERE$IISTHEDIAMETEROFTHEITHDROPAND
\ + \
M
M
WHEREMISTHECOMPLEXINDEXOFREFRACTION!TTEMPERATURESBETWEENANDn#AND CENTIMETERWAVELENGTHS \+\yFORTHEWATERPHASEAND\+\yFORTHEICE PHASE %QUATIONCANNOWBEWRITTENAS
H
P \ + \ L
.
£ $I
I
ANDWEDEFINETHERADARREFLECTIVITYFACTOR:AS .
: £ $I I
)NRADARMETEOROLOGY ITISCOMMONTOUSETHEDIMENSIONSOFMILLIMETERSFORDROP DIAMETER$IANDTOCONSIDERTHESUMMATIONTOTAKEPLACEOVERAUNITVOLUMEOFSIZE MTOYIELDAVOLUMEDENSITYEXPRESSION4HEREFORE THECONVENTIONALUNITOF:IS INMMM&ORICEPARTICLES $IISSOMETIMESEXPRESSEDASTHEDIAMETEROFTHEWATER DROPLETTHATWOULDRESULTIFTHEICEPARTICLEWERETOMELTCOMPLETELY(OWEVER THERADAR SCATTERINGPROCESSFORTHEMANYSHAPESANDTEMPERATURESOFICEPARTICLESISEXTREMELY COMPLICATEDANDADEFINITIVEGENERALIZEDEXPRESSIONCANNOTBEGIVEN )TISOFTENCONVENIENTTOTREATTHEDROPORPARTICLESIZEDISTRIBUTIONASACONTINUOUS FUNCTION WITH A NUMBER DENSITY .$ WHERE .$ IS THE NUMBER OF DROPS PER UNIT VOLUMEHAVINGDIAMETERSBETWEEN$AND$ D$)NTHISCASE :ISGIVENBYTHESIXTH MOMENTOFTHEPARTICLESIZEDISTRIBUTION
c
: ¯ N $ $ D$
)F THE RADAR BEAM IS FILLED WITH SCATTERERS THE SAMPLE VOLUME OF 6 IS GIVEN APPROXIMATELYBY
6y
P QF R CT
WHEREPANDEARETHEAZIMUTHANDELEVATIONBEAMWIDTHS CISTHEVELOCITYOFLIGHT AND SISTHERADARPULSEWIDTH3UBSTITUTING%QSANDINTO%Q WESEETHATTHE 2#3FORTHEDISTRIBUTEDWEATHERSCATTERERISDIRECTLYPROPORTIONALTOTHEPULSEVOLUME ASDETERMINEDBYTHEPULSELENGTHANDANTENNABEAMATTHETARGETRANGE 4HEN COMBINING%QS ANDANDSUBSTITUTINGINTO%QGIVES
-%4%/2/,/')#!,2!$!2
0R
B P QF R CT P \ + \ L R
BP QF C T \ + \ : L R
B `: R
£°x
.
£ $I I
4HISEXPRESSIONILLUSTRATESTHATFORTHEDISTRIBUTEDWEATHERTARGETTHERECEIVEDPOWER IS AFUNCTIONONLYOFA`ACONSTANTDEPENDENTUPONALLTHERADARSYSTEMANDPHYSI CALPARAMETERS DIRECTLYPROPORTIONALTOTHERADARREFLECTIVITYFACTOR: ANDMOST SIGNIFICANT INVERSELYPROPORTIONALTORNOTRASINTHECASEOFPOINTTARGETS 4HERADARSYSTEMPARAMETERSINCLUDEDINAIN%QINCLUDETHEPEAKTRANSMIT POWER0T THEANTENNASYSTEMGAIN'TWICEONCEFORTRANSMITTINGANDONCEFORRECEIV ING ANDTHEWAVELENGTHK7EINCLUDEALLANTENNASYSTEMLOSSESINTHISANTENNASYS TEMGAINFACTORRADOME WAVEGUIDE ROTARYJOINTS ETC SINCEALLTHEMEASUREMENTS MUSTBEREFERENCEDTOTHESAMEPOINTINTHERADARSYSTEMUSUALLYATACOUPLERNEAR THECIRCULATOR"ECAUSETHEANTENNAGAINISNOTUNIFORMOVERTHEBEAMWIDTH ASSUMING AUNIFORMGAINCANLEADTOERRORSINTHECALCULATIONOF:5SINGASIMILARDERIVATION 0ROBERT *ONESTOOKTHISINTOACCOUNT ASSUMEDAGAUSSIANSHAPEFORTHEANTENNABEAM ANDDERIVEDTHEFOLLOWINGEQUATIONFORTHERECEIVEDPOWER
0R
0' L QF CT . T SI LN P R £ I
WHERELNISTHECORRECTIONFORTHEGAUSSIAN SHAPEDBEAM"YSUBSTITUTING%QS ANDINTO%Q THERECEIVEDPOWERCANBEEXPRESSEDINTERMSOFTHE REFLECTIVITYFACTOR:ANDRANGERAS
0R
0' QF CTP \ + \ : T LN L R
"ECAUSETHERECEIVINGFILTERSUPPRESSESSOMEOFTHERECEIVEDSIGNALPOWER 0RMUST BEREDUCEDBY,R WHICHDEPENDSONTHEDETAILSOFTHETRANSMITTEDSPECTRUMANDTHE RECEIVERFILTERBUTISUSUALLYAFACTOROFABOUTD" FORATYPICALWAVEFORMAND hMATCHEDFILTERv3OLVINGFORTHERADARREFLECTIVITYFACTOR:GIVES
: ;LNK,R 0T'PECSO\+\=0RR
WHERETHEREFLECTIVITYFACTORISEXPRESSEDINTERMSOFTHERECEIVEDPOWERANDRANGE /NEMUSTBECAREFULTOUSECONSISTENTUNITSIN%Q)FMETER KILOGRAM SECONDS MKS UNITSAREUSED THECALCULATIONOF:WILLHAVEDIMENSIONSOFMM#ONVERSION TOTHEMORECONVENIENTUNITSOFMMMREQUIRESTHAT:BEMULTIPLIEDBYTHEFACTOR &URTHERMORE EXPRESSING0RANDRINCOMMONUNITSOFD"MD"RELATIVETOMILLIWATT ANDKMREQUIRESTHAT:ALSOBEMULTIPLIEDBY"ECAUSE:VALUESOFINTERESTCANRANGE OVERSEVERALORDERSOFMAGNITUDE ALOGARITHMICSCALEISOFTENUSED4HUS
D": # 0RD"M LOGRKM
£°È
2!$!2(!.$"//+
WHERE#ISOLATEDINBRACKETSIN%Q ISTHESOCALLED7EATHER2ADAR#ONSTANT WITH0REXPRESSEDIND"MANDRINKM4YPICALVALUESOF#ARETOD"FORTHE OPERATIONALWEATHERRADARS)TISCLEARTHATFORFIXEDRANGEANDRECEIVEDPOWER ALOWER VALUEOFTHERADARCONSTANT#ALLOWSASMALLERREFLECTIVITYVALUEIND":TOBEOBSERVED 4HUS SMALLERVALUESOF#CORRESPONDTOMORESENSITIVERADARS 4HISEQUATIONCANBEUSEDTOMEASURETHEREFLECTIVITYFACTOR:WHENTHEANTENNA BEAMISFILLED WHENTHESMALLSCATTERINGPARTICLE2AYLEIGHAPPROXIMATIONISVALID AND WHENTHESCATTERERSAREINEITHERTHEICEORTHEWATERPHASE"ECAUSEALLTHESECONDI TIONSARENOTALWAYSSATISFIED ITISCOMMONTOUSETHETERM:E THEEFFECTIVEREFLECTIVITY FACTOR INPLACEOF:7HEN:EISUSED ITISGENERALLYUNDERSTOODTHATTHEABOVECONDI TIONSAREASSUMED0RACTITIONERSINTHEFIELDOFRADARMETEOROLOGYOFTENUSE:EAND: INTERCHANGEABLY ALBEITINCORRECTLY !NOTHERFACTORWEHAVEIGNOREDINTHEDERIVATIONOFTHERADAREQUATIONISATTENUA TIONBYPRECIPITATIONANDATMOSPHERICGASSES!TCMWAVELENGTHSTHEATTENUATIONIS USUALLYNOTSIGNIFICANTHOWEVER AT ANDCMANDESPECIALLYTHEYETSHORTERMM WAVELENGTHS ATMOSPHERICATTENUATIONMUSTBEACCOUNTEDFORINTHERADAREQUATIONBY ADDINGANADDITIONALRANGEDEPENDENTTERM,A4HEFOLLOWINGSECTIONGIVESDETAILSON ESTIMATINGTHISATTENUATIONINCOMMONLYENCOUNTEREDCONDITIONS &INALLY IT IS IMPORTANT TO NOTE THE : VALUES ARE OF METEOROLOGICAL SIGNIFICANCE BECAUSE THEY ARE DIRECTLY RELATED TO CLOUD PROPERTIES AND ACTUAL RAINFALL RATES 2 AS DESCRIBED LATER IN THIS CHAPTER : VALUES IN NONPRECIPITATING CLOUDS AS SMALL AS nD":AREOFINTERESTFORCLOUDPHYSICSSTUDIES)NTHEOPTICALLYCLEAR LOWERATMO SPHERICBOUNDARYLAYER hCLEARAIRv:VALUESOFTHEORDERnD":TOD":ARETYPICAL ANDFREQUENTLYORIGINATEFROMINSECTSANDBIRDS )NRAIN:MAYRANGEFROMABOUT nD":TOASMUCHASD": WITHATOD":RAINBEINGOFTHETYPETHATCAN CAUSESEVEREFLOODING3EVEREHAILSTORMSMAYPRODUCE :VALUESHIGHERTHAND": -ANYOPERATIONALRADARTYPESAREDESIGNEDTODETECTTHOSE:VALUESTHATPRODUCEMEA SURABLEPRECIPITATIONTOD": ANDhCLEARAIRvECHOESTOKMWHERETHE%ARTHS CURVATUREPREVENTSSURFACE BASEDMEASUREMENTS4HUS BEINGABLETOMEASURESTRONG PRECIPITATIONECHOESATSHORTRANGEANDALSOWEAKPRECIPITATIONECHOESATLONGRANGE REQUIRESRADARRECEIVERSHAVINGATOTALDYNAMICRANGEOFnD"WHEREASMEASURING WEAK ECHOES IN THE PRESENCE OF STRONG GROUND CLUTTER REQUIRES AS LARGE AN INSTANTA NEOUSDYNAMICRANGE D" ASPOSSIBLE-ORERECENTOPERATIONALRADARSANDMOST RESEARCHRADARSATTEMPTTOACHIEVETHEMOSTSENSITIVITYPOSSIBLEANDCANDETECTMINI MUMREFLECTIVITYVALUESOFnD":ORLESSATSHORTRANGESEG KM /PERATIONAL RADARS IN THE PAST HAVE EMPLOYED SENSITIVITY TIME CONTROL 34# TO REDUCEGAINATSHORTRANGEANDCOMPENSATEFORSTRONGNEARBYECHOESHOWEVER RECENT RADARSTENDNOTTOUSE34#TECHNIQUESSINCERECEIVERDYNAMICRANGESAREADEQUATETO COVERIMPORTANTWEATHERECHOINTENSITIESATTHENECESSARYRANGES2ESEARCHRADARSHAVE RARELYUSED34#OWINGTOTHEATTENDANTLOSSOFSENSITIVITYATSHORTRANGES
£°ÎÊ - Ê " - ,/" &OUROFTHEMORESIGNIFICANTFACTORSTHATAFFECTTHEDESIGNOFMETEOROLOGICALRADARSARE ATTENUATION RANGEAMBIGUITIES VELOCITYAMBIGUITIES ANDGROUNDORSEACLUTTER4HE COMBINATIONOFTHESEFACTORS ALONGWITHTHENEEDTOOBTAINADEQUATESPATIALRESOLU TION LEADSTOAWAVELENGTHSELECTIONINTHERANGEOFTOCMFORMOSTPRECIPITATION BASEDAPPLICATIONS
-%4%/2/,/')#!,2!$!2
£°Ç
!TTENUATION%FFECTS !TTENUATIONHASATLEASTTWONEGATIVEEFFECTSONMETEORO LOGICALRADARSIGNALS&IRST MAKINGACCURATEQUANTITATIVEMEASUREMENTSOFTHEBACK SCATTEREDENERGYFROMPRECIPITATIONATRANGESFARTHERTHANANYINTERVENINGPRECIPITATION BECOMESVERYDIFFICULT4HISINABILITYTOPRECISELYMEASURETHETRUEBACKSCATTERINGCROSS SECTIONREQUIRESTHATQUANTITATIVEMEASUREMENTSOFPRECIPITATIONRATESBECORRECTEDFOR ATTENUATIONWHENPOSSIBLE 3ECOND IFTHEATTENUATIONDUETOPRECIPITATIONORTHEINTERVENINGMEDIUMISSUF FICIENTLYGREAT THESIGNALFROMAPRECIPITATIONCELLBEHINDAREGIONOFSTRONGABSORP TIONMAYBETOTALLYSUPPRESSED/NEEXAMPLEOFTHEPOTENTIALLYSERIOUSCONSEQUENCES OF VERY STRONG ABSORPTION IS THE IMPACT IT MIGHT HAVE ON AVIATION STORM AVOIDANCE RADARS MOSTOFWHICHAREINTHE CMBAND)TISCOMMONFORSHORTWAVELENGTHON BOARDAVIATIONWEATHERRADARSTONOTDETECTINTENSECONVECTIVECELLSBEHINDCLOSER HIGH ATTENUATIONTHUNDERSTORMS3EVERESTORMSWITHHIGHPRECIPITATIONRATESALSOCAUSEHIGH ATTENUATIONEVENAT CMWAVELENGTHS ASNOTEDBY(ILDEBRANDAND!LLENETAL )N SOME METEOROLOGICAL RADAR APPLICATIONS IT IS DESIRABLE TO ATTEMPT TO MEASURE ATTENUATION ALONG SELECTED PROPAGATION PATHS 4HIS IS DONE BECAUSE ABSORPTION IS RELATEDTOLIQUID WATERCONTENTANDCANPROVIDEUSEFULINFORMATIONFORTHEDETECTIONOF SUCHPHENOMENAASHAIL INACCORDANCEWITHTHEDUAL WAVELENGTHTECHNIQUEDESCRIBED BY%CCLESAND!TLASAND6IVEKETAL )N THE FOLLOWING SUBSECTIONS QUANTITATIVE EXPRESSIONS RELATING ATTENUATION TO PRECIPITATIONAREGIVEN-UCHOFTHISISTAKENFROM"EAN $UTTON AND7ARNERAND ,HERMITTE"ATTANAND/GUCHIAREALSOEXCELLENTSOURCESFORADDITIONALINFORMA TIONONTHEABSORBINGPROPERTIESOFPRECIPITATION !TTENUATIONBY7ATER6APOR !TMOSPHERICWATERVAPORMAYTAKEONVALUESUPTO GMANDGIVEVARIABLEATTENUATIONDEPENDINGONTHEWATERVAPORCONTENT(OWEVER ATTYPICALWEATHERRADARWAVELENGTHSLONGERTHANCM THEATTENUATIONISLESSTHANA FEW HUNDREDTHS D"KM AND IS USUALLY IGNORED 'ASEOUS OXYGEN CONTRIBUTES ONLY A MINORABSORPTIONEFFECTATTHESECENTIMETERWAVELENGTHSANDISALSOUSUALLYIGNORED !TTENUATION IN #LOUDS #LOUD DROPLETS ARE REGARDED HERE AS THOSE WATER OR ICE PARTICLES HAVING RADII SMALLER THAN MM CM &OR WAVELENGTHS OF INCIDENT RADIATIONWELLINEXCESSOFCM THEATTENUATIONDEPENDSPRIMARILYONTHELIQUID WATERCONTENTANDISINDEPENDENTOFTHEDROP SIZEDISTRIBUTION4HEGENERALLYACCEPTED EQUATIONSFORATTENUATIONBYCLOUDSUSUALLYSHOWTHEMOISTURECOMPONENTOFTHEEQUA TIONSINTHEFORMOFTHELIQUID WATERCONTENTGRAMSPERCUBICMETER /BSERVATIONS INDICATE THAT THE LIQUID WATER CONCENTRATION IN CLOUDS GENERALLY RANGES FROM TO GM ALTHOUGH7EICKMANNAND+AMPEHAVEREPORTEDISOLATEDINSTANCESOFCUMU LUSCONGESTUSCLOUDSHIGHTOWERINGCONVECTIVECLOUDSTHATFREQUENTLYPRODUCEHEAVY PRECIPITATION WITHWATERCONTENTSOFGMINTHEUPPERLEVELS)NICECLOUDS THE WATERCONTENTRARELYEXCEEDSANDISOFTENLESSTHANGM4HEATTENUATIONDUE TOCLOUDDROPLETSMAYBEWRITTEN
+ +-
WHERE + ATTENUATION D"KM
+ ATTENUATIONCOEFFICIENT D"KMGM
- LIQUID WATERCONTENT GM
-
PR . AI £ I
£°n
2!$!2(!.$"//+
+
P ¤ M ³ )M ¥ L ¦ M ´µ
WHERETHEAIAREDROPLETRADII QISTHEDENSITYOFWATER AND)MISTHEIMAGINARYPART 6ALUESOF+FORICEANDWATERCLOUDSAREGIVENFORVARIOUSWAVELENGTHSANDTEMPERA TURESBY'UNNAND%ASTIN4ABLE 3EVERALIMPORTANTFACTSAREDEMONSTRATEDBY4ABLE4HEDECREASEINATTENUA TIONWITHINCREASINGWAVELENGTHISCLEARLYSHOWN4HEVALUESCHANGEBYABOUTANORDER OFMAGNITUDEFORACHANGEOFKFROMTOCM4HEDATAPRESENTEDHEREALSOSHOWS THAT ATTENUATION IN WATER CLOUDS INCREASES WITH DECREASING TEMPERATURE )CE CLOUDS GIVE ATTENUATIONS ABOUT TWO ORDERS OF MAGNITUDE SMALLER THAN WATER CLOUDS OF THE SAMEWATERCONTENT4HEATTENUATIONOFMICROWAVESBYICECLOUDSCANBENEGLECTEDFOR PRACTICALPURPOSES !TTENUATIONBY2AIN 2YDEAND2YDECALCULATEDTHEEFFECTSOFRAINONMICROWAVE PROPAGATIONANDSHOWEDTHATABSORPTIONANDSCATTERINGEFFECTSOFRAINDROPSBECOME MOREPRONOUNCEDATTHEHIGHERMICROWAVEFREQUENCIES WHERETHEWAVELENGTHSAND THERAINDROPDIAMETERSAREMORENEARLYCOMPARABLE)NTHE CMBANDANDATSHORTER WAVELENGTHS THEEFFECTSAREAPPRECIABLE BUTATWAVELENGTHSINEXCESSOFCM THE EFFECTSAREGREATLYDECREASED)TISALSOCLEARTHATSUSPENDEDWATERCLOUD DROPLETSAND RAINHAVEANABSORPTIONRATEINEXCESSOFTHATOFTHECOMBINEDOXYGENANDWATER VAPOR ABSORPTION )NPRACTICE ITHASBEENCONVENIENTTOEXPRESSRAINATTENUATIONASAFUNCTIONOFTHE PRECIPITATIONRATE2 WHICHDEPENDSONTHELIQUID WATERCONTENTANDTHEFALLVELOCITYOF THEDROPS THELATTERINTURNDEPENDINGONTHESIZEOFTHEDROPS2YDESTUDIEDTHEATTENU ATION OF MICROWAVES BY RAIN AND DEDUCED BY USING ,AWS AND 0ARSONSS DROP SIZE DISTRIBUTIONS THATTHISATTENUATIONINDECIBELSPERKILOMETERCANBEAPPROXIMATEDBY R
+ 2 ¯ + ; 2R =A DR
WHERE +2 TOTALATTENUATION D" 2R RAINFALLRATEALONGPATHR
R LENGTHOFPROPAGATIONPATH KM
+ CONSTANTDEPENDENTONFREQUENCYANDTEMPERATURE
A CONSTANTDEPENDENTONFREQUENCY 4!",% /NE WAY!TTENUATION#OEFFICIENT+IN#LOUDSIND"KMPERGM,IQUID7ATER
7AVELENGTH CM 4EMPERATURE n# 7ATERCLOUD
)CECLOUD
EXTRAPOLATEDVALUE
n n n
rn rn rn
rn rn rn
rn rn rn
rn rn rn
-%4%/2/,/')#!,2!$!2
£°
-EDHURSTSHOWSTHATA ISAGOODASSUMPTIONINMANYCASES4HEPATHLOSS PERMILEFORTHETHREEFREQUENCYBANDSOF AND'(ZISSHOWNIN&IGURE ,HERMITTEEXTENDSTHISEARLYWORKTOHIGHERFREQUENCIES CONFIRMINGTHERELATIONSHIP ANDDESCRIBINGTHEEFFECTOFTHEDROP SIZEDISTRIBUTIONONTHEATTENUATIONRATE(EALSO REVIEWSMORERECENTEMPIRICALDATA 4HE GREATEST UNCERTAINTY IN PREDICTION OF ATTENUATION RATES CAUSED BY RAINFALL WHENTHEORETICALFORMULASAREUSEDASABASISFORCALCULATION ISTHEEXTREMELYLIM ITEDKNOWLEDGEOFDROP SIZEDISTRIBUTIONSINRAINOFVARYINGFALLRATESUNDERDIFFER INGCLIMATICANDWEATHERCONDITIONS,HERMITTEAND5IJLENHOETETALTHOROUGHLY REVIEWTHEEVOLUTIONOFANALYTICEXPRESSIONSFORDROP SIZEDISTRIBUTIONS DESCRIBING THE-ARSHALL 0ALMEREXPERIMENTANDTHEIRRESULTINGEXPONENTIALDISTRIBUTIONANDTHE MORE GENERAL THREE PARAMETER 'AMMA DISTRIBUTION 4HEY ALSO REVIEW THE DEPEN DENCE OF THE PARAMETERS DEFINING THE DISTRIBUTION TO THE RAIN RATE AND TO THE TYPE OFRAINFALL4HEREISLITTLEEVIDENCETHATRAINWITHAKNOWNRATEOFFALLHASAUNIQUE DROP SIZEDISTRIBUTION ALTHOUGH"URROWSAND!TTWOODSSTUDIESSEEMTOINDICATETHAT ACERTAINMOSTPROBABLEDROP SIZEDISTRIBUTIONCANBEATTACHEDTORAINOFAGIVENRATE OFFALL2ESULTSOFTHISSTUDYARESHOWNIN4ABLE WHICHGIVESTHEPERCENTAGE OFTOTALVOLUMEOFRAINFALLOCCUPIEDBYRAINDROPSOFDIFFERENTDIAMETERSANDVARYING RAINFALLRATESMILLIMETERSPERHOUR )NTHEBASISOFTHESERESULTS THEABSORPTIONCROSS SECTIONOFDIFFERENTRAINRATESISSHOWNIN4ABLE4HISTABLEGIVESTHEDECIBEL ATTENUATIONPERKILOMETERFORDIFFERENTRAINFALLRATESFORRADARWAVELENGTHSBETWEEN ANDCM
&)'52% 4HEORETICAL RAIN ATTENUATION IN D"MILE STATUTE VERSUSRAINFALLRATEAFTER*72YDEAND$2YDE
£°£ä
2!$!2(!.$"//+
4!",% $ROP3IZE$ISTRIBUTIONSAT$IFFERENT0RECIPITATION2ATES
0RECIPITATION2ATE2 MMH $ROP$IAMETER$ CM
0ERCENTAGEOFA'IVEN6OLUME#ONTAINING$ROPSOF$IAMETER$
3INCETHETOTAL ATTENUATIONCROSSSECTIONDEPENDSONTHETEMPERATUREBECAUSEOF ITSEFFECTSONTHEDIELECTRICPROPERTIESOFWATER ITISIMPORTANTTOEVALUATETHEATTENU ATIONOFRAINSWHOSEDROPSAREATDIFFERENTTEMPERATURESFROMTHOSEINTHEPRECEDING TABLES4ABLECONTAINSTHENECESSARYDATARELATIVETOTHECHANGEOFATTENUATIONWITH TEMPERATUREANDCANBEUSEDWITH4ABLE 4ODETERMINETOTALATTENUATIONCAUSEDBYRAINFALLTHROUGHAPARTICULARPRECIPITATION PATH SOMETHINGMUSTBEKNOWNORASSUMEDABOUTTHENATUREOFTHEPRECIPITATIONITSELF AND CONSEQUENTLY ABOUTHOWITSRAINFALLRATESANDDROPSIZESAREDISTRIBUTEDINTHREE DIMENSIONS !SYSTEMATICVERTICALVARIATIONOF2 DECAYINGWITHHEIGHTABOVEAMEASUREDSUR FACE VALUE SEEMS TO BE APPROPRIATE IN STRATIFORM RAINFALL WHICH IS RAIN HAVING A WIDESPREADANDCONTINUOUSNATURE3UCHWIDESPREADRAINFALLISUSUALLYTRIGGEREDBY 4!",% !TTENUATIONIN$ECIBELSPER+ILOMETERFOR$IFFERENT2ATESOF2AIN0RECIPITATIONATA
4EMPERATUREOFn#5SINGTHE$ROP SIZE$ISTRIBUTIONSIN4ABLE 7AVELENGTHK CM 0RECIPITATION 2ATE2 MMH K K K K K K K
K K
-%4%/2/,/')#!,2!$!2
£°££
4!",% #ORRECTION&ACTOR-ULTIPLICATIVE FOR2AINFALL!TTENUATION
0RECIPITATION 2ATE2 MMH
K CM
n#
n#
n#
n#
n#
ARELATIVELYLARGE SCALEMECHANISM SUCHASAFRONTALORMONSOONSITUATION!VERTICAL VARIATIONOF2OFTHEFORM
2 2 E DH
CANBEASSUMEDTOBEAPPROPRIATEUNDERCONTINUOUSRAINFALLCONDITIONS2ISTHESUR FACERAINFALLRATE HISTHEHEIGHTABOVETHE%ARTHSSURFACE ANDDISACONSTANT EQUAL TOABOUT#ONVECTIVEPRECIPITATION HOWEVER SHOWSAQUITEDIFFERENTNATURE&OR EXAMPLE THEPRESENCEOFVIRGAPRECIPITATIONALOFTBUTEVAPORATINGBEFOREREACHING THESURFACE ASSOCIATEDWITHSOMANYSHOWER TYPECLOUDSINDRYCLIMATESINDICATESTHAT CONVECTIVESHOWERRAINFALLPROFILESAREMUCHMOREDIFFICULTTOMODEL !TTENUATION BY (AIL 2YDE CONCLUDED THAT THE ATTENUATION CAUSED BY HAIL IS ONE HUNDREDTH OF THAT CAUSED BY RAIN AND THAT ICE CRYSTAL CLOUDS CAUSE NO SENSIBLE ATTENUATIONANDSHOWVERYSMALLATTENUATIONEVENATTHEEXCESSIVERATEOFFALLOFINH (OWEVER THESCATTERINGBYICESPHERESSURROUNDEDBYACONCENTRICFILMOFLIQUIDWATER HAVINGADIFFERENTDIELECTRICCONSTANTDOESNOTGIVETHESAMEEFFECTTHAT2YDESRESULTS FORDRYPARTICLESWOULDINDICATE&OREXAMPLE WHENONE TENTHOFTHERADIUSOFANICE SPHEREOFRADIUSCMMELTS SCATTERINGOF CMRADIATIONISAPPROXIMATELYOF THEVALUETHATWOULDBESCATTEREDBYANALL WATERDROP !TWAVELENGTHSOFANDCMWITHA A RADIUSOFDROP +ERKER ,ANGLEBEN AND'UNNFOUNDTHATPARTICLESATTAINEDTOTALATTENUATIONCROSSSECTIONSCORRESPONDINGTO ALLMELTEDPARTICLESWHENLESSTHANOFTHEICEPARTICLESWASMELTED7HENTHEMELTED
£°£Ó
2!$!2(!.$"//+
MASSREACHEDABOUTTO THEATTENUATIONWASABOUTTWICETHATOFACOMPLETELY MELTEDPARTICLE4HESECALCULATIONSSHOWTHATTHEATTENUATIONINTHEMELTINGOFICEIMME DIATELYUNDERTHEn#ISOTHERMCANBESUBSTANTIALLYGREATERTHANINTHESNOWREGIONJUST ABOVEAND UNDERSOMECIRCUMSTANCES GREATERTHANINTHERAINBELOWTHEMELTINGLEVEL &URTHERMELTINGCANNOTLEADTOMUCHFURTHERENHANCEMENT APPARENTLY ANDMAYLEADTOA LESSENINGOFTHEREFLECTIVITYOFTHEPARTICLEBYBRINGINGITTOSPHERICITYORBYBREAKINGUP THEPARTICLE-ELTINGOFICEPARTICLESPRODUCESENHANCEDBACKSCATTER ANDTHISEFFECTGIVES RISETOTHEOBSERVEDELEVATEDBRIGHTBANDNEARTHEn#ISOTHERM ,HERMITTEDISCUSSESHAILATTENUATIONFORSHORTERWAVELENGTHRADARSWHENRESONANT REGION -IE SCATTERING IS THE DOMINANT SCATTERING MECHANISM 5SING ACCEPTED SIZE DISTRIBUTIONS OF DRY HAIL HE SHOWS ATTENUATION RATES OVER THE FREQUENCY INTERVAL OF n'(ZTHATARENEGLIGIBLEATTHELOWERFREQUENCIESBUTRISEASYMPTOTICALLYTOABOUT D"KMATFREQUENCIESABOVE'(Z !TTENUATIONBY&OG 4HECHARACTERISTICFEATUREOFAFOGISTHEREDUCTIONINVISIBIL ITY6ISIBILITYISDEFINEDAShTHEGREATESTDISTANCEINAGIVENDIRECTIONATWHICHITISJUST POSSIBLETOSEEANDIDENTIFYWITHTHEUNAIDEDEYE INTHEDAYTIME APROMINENTDARK OBJECTAGAINSTTHESKYATTHEHORIZONAND ATNIGHTAKNOWN PREFERABLYUNFOCUSED MODERATELYINTENSELIGHTSOURCEv!LTHOUGHTHEVISIBILITYDEPENDSUPONBOTHDROPSIZE ANDNUMBEROFDROPSANDNOTENTIRELYUPONTHELIQUID WATERCONTENT INPRACTICETHE VISIBILITYISANAPPROXIMATIONOFTHELIQUID WATERCONTENTAND THEREFORE MAYBEUSED TOESTIMATERADIO WAVEATTENUATION /NTHEBASISOF2YDESWORK 3AXTONAND(OPKINSGIVETHEFIGURESIN4ABLE FORTHEATTENUATIONINAFOGORCLOUDSATn#TEMPERATURE4HEATTENUATIONVARIESWITH THE TEMPERATURE BECAUSE THE DIELECTRIC CONSTANT OF WATER VARIES WITH TEMPERATURE THEREFORE ATn#ANDn#THEFIGURESIN4ABLESHOULDBEMULTIPLIEDBYAND RESPECTIVELY)TISIMMEDIATELYNOTEDTHATCLOUDORFOGATTENUATIONISANORDEROF MAGNITUDEGREATERATCMTHANATCMANDTHATNEARLYANOTHERORDEROFMAGNITUDE INCREASEOCCURSBETWEENANDCM 2ANGEAND6ELOCITY!MBIGUITIES 7EATHERRADARSUTILIZEASEQUENCEOFPULSES TOMEASURETHERADARREFLECTIVITYANDDOPPLERCHARACTERISTICS"ECAUSETHEPULSINGRATE TYPICALLYDETERMINESTHESAMPLINGFREQUENCYFORDOPPLERQUANTITIESONACONSTANTPULS ING RATE RADAR THE UNAMBIGUOUS DOPPLER FREQUENCY .YQUIST FREQUENCY FOR A FIXED PULSE REPETITION FREQUENCY02& RADARISGIVENBY
&.YQ o02&
WHERE02&ISTHEPULSEREPETITIONFREQUENCY3IMULTANEOUSLY THEUNAMBIGUOUSRANGE INTERVALISGIVENBY
2A
C
02&
4!",% !TTENUATION#AUSEDBY#LOUDSOR&OG4EMPERATURE n#
!TTENUATION D"KM 6ISIBILITY M
K CM
K CM
K CM
-%4%/2/,/')#!,2!$!2
£°£Î
ANDTHEPRODUCT&.YQ2AISSIMPLY C 3INCE THE DOPPLER SHIFT F AND THE TARGET RADIAL VELOCITY V ARE LINEARLY RELATED THE UNAMBIGUOUSVELOCITYISRELATEDTOTHE.YQUISTFREQUENCYBY
&.YQ 2A
6A
L & .YQ
)TFOLLOWSTHATTHEPRODUCTOFUNAMBIGUOUSVELOCITYANDUNAMBIGUOUSRANGEIS
6A 2A
LC
&ORCONSTANT02&RADARS THISPRODUCTISMAXIMIZEDBYMAXIMIZINGK THETRANSMIT TEDWAVELENGTH4HUS USINGLONGERWAVELENGTHSALLOWSOPTIMIZINGTHE02&BYTRAD INGUNAMBIGUOUSRANGEFORUNAMBIGUOUSVELOCITY&ORSTANDARDCONSTANT02&RADARS CM WAVELENGTHS HAVE BEEN WIDELY CHOSEN FOR MOST PRECIPITATION MEASUREMENTS OFINTERESTINWHICHDESIGNPARAMETERSSUCHASRADARBEAMWIDTH SIZEOFANTENNA AND ATTENUATIONEFFECTSMAYBEMADEACCEPTABLE 'ROUND #LUTTER %FFECTS -ANY METEOROLOGICAL RADAR APPLICATIONS CALL FOR THE DETECTIONOFPRECIPITATIONECHOESINTHEPRESENCEOFGROUNDCLUTTER3PECIFICALLY PRE CIPITATIONMEASUREMENTSNEARTHEGROUNDAREOFEXTREMEINTERESTINAGRICULTURALAND HYDROLOGICALAPPLICATIONSASWELLASINFORMATIONFORTHEGENERALPUBLIC!PPLICATIONS INWHICHGROUNDCLUTTERISSERIOUSRELATESTOTHEGROUND BASEDRADARDETECTIONOFLOW LEVELWINDSHEARATAIRPORTSANDMEASURINGPRECIPITATIONNEARTHEGROUNDINMOUNTAIN OUSTERRAINFORFLASHFLOODWARNINGS"OTHTHE.EXRADAND4ERMINAL$OPPLER7EATHER 2ADAR4$72 NETWORKRADARSHAVEBEENDESIGNEDTOASSURECLUTTERSUPPRESSIONIN EXCESSOFD" !LTHOUGHGROUNDCLUTTERCANNOTBEELIMINATED ITSEFFECTCANBEMITIGATEDTHROUGH CAREFULDESIGN4HEPRIMARYAPPROACHISTOUSEANANTENNAWITHLOWSIDELOBES PAR TICULARLY IN ELEVATION WHICH WILL SUPPRESS THE CLUTTER COMPONENT OF THE INPUT ECHO WHENTHEMAINBEAMISSLIGHTLYABOVETHEHORIZON!SECONDAPPROACHISUSINGSHORTER WAVELENGTHS 3HORTER WAVELENGTHS RESULT IN IMPROVED SIGNAL TO CLUTTER RATIOS OWING TOTHEFACTTHATTHE2AYLEIGHSCATTEREDWEATHERSIGNALPOWERISINVERSELYPROPORTIONAL TOK WHEREASTHEGROUNDCLUTTERRETURNISONLYWEAKLYDEPENDENTONWAVELENGTH)F ONEASSUMESTHATTHECLUTTERSIGNALISWAVELENGTHINDEPENDENTANDTHEANTENNABEAM WIDTHISFIXED ITCANBESHOWNTHATTHEWEATHER SIGNAL POWERTOCLUTTER POWERRATIOIS INVERSELYPROPORTIONALTOK 7EATHER RADARS TYPICALLY USE DIGITAL SIGNAL PROCESSING TECHNIQUES TO IMPLEMENT CLUTTERFILTERSTHATSUPPRESSNEARZEROVELOCITYCLUTTERECHOES4HESEFILTERSMAYBE IMPLEMENTED USING EITHER A TIME DOMAIN CLUTTER FILTER APPLIED TO THE ) AND 1 RADAR VIDEODATAONEFORMOFWHICHISSOMETIMESCALLEDADELAYLINECANCELERFROMITSEARLY ANALOGIMPLEMENTATION TOSUPPRESSTHEZEROVELOCITYGROUNDCLUTTERCOMPONENTSORA FREQUENCYDOMAINDOPPLERPOWERSPECTRUMADIGITALhFILTERBANKv TOACHIEVETHESAME EFFECT4HETIMEDOMAINFILTERSFORMECHANICALLYSCANNEDWEATHERRADARSAREUSUALLY INFINITEIMPULSERESPONSE))2 FILTERSWITHNARROW BUTADJUSTABLE WIDTHSUPTOAFEW MSANDHAVINGSUPPRESSIONLEVELSOFnD"ANDVERYSTEEPTRANSITIONREGIONS 4HESETIMEDOMAINFILTERSWITHAFREQUENCYNOTCHCENTEREDATZEROVELOCITYFREQUENCY
£°£{
2!$!2(!.$"//+
WILLALSOSUPPRESSWEATHERECHOPOWERTHATMAYEXISTINTHESAMEVELOCITYREGIONAND BIASALLTHEESTIMATESOFREFLECTIVITY VELOCITY ANDWIDTH 3PECTRALDOMAINCLUTTERFILTERSIMPLEMENTEDBYADISCRETE&OURIERTRANSFORM$&4 ONTHEOTHERHAND SUPPRESSTHENEARZEROCLUTTERCOMPONENTSINTHEFREQUENCYDOMAIN ANDMAYINTERPOLATETHEREMAININGSPECTRUMACROSSTHISREGIONTORETAINMOSTOFTHE UNDERLYING SIGNAL OR NOISE SPECTRAL INFORMATION!N ALTERNATIVE FREQUENCY DOMAIN TECHNIQUE FOR THE .EXRAD RADAR SEPARATELY MODELS THE CLUTTER AND WEATHER SIGNAL AS GAUSSIAN SHAPEDSPECTRAANDSEPARATESTHESETWOCOMPONENTSOFTHEDOPPLERSPECTRUM USINGDIGITALSEARCHALGORITHMSANDTHENREMOVESTHESECLUTTERCOMPONENTSWHILELEAV INGTHEUNDERLYINGWEATHERSIGNALUNPERTURBED4HUS WHENTHEGAUSSIANASSUMPTIONS APPLY THEREMAININGWEATHERSIGNALSPECTRUMPROVIDESANUNBIASEDESTIMATORFORALL THEWEATHERPARAMETERSPECTRUMMOMENTESTIMATES 4YPICAL7EATHER2ADAR$ESIGNS 4HEREISNOUNIVERSALWEATHERRADARSYSTEM DESIGNTHATCANSERVEALLPURPOSES!IRBORNEWEATHERRADARSARECONSTRAINEDBYSIZE ANDWEIGHTLIMITATIONS'ROUND BASEDRADARSMAYBECONSTRAINEDBYCOSTANDSITING CONSIDERATIONS3EVERESTORMWARNINGRADARSREQUIRELONGRANGEANDHIGHUNAMBIGU OUSVELOCITYANDTHENMUSTPENETRATEVERYHEAVYRAIN THUSDICTATINGLONGWAVELENGTHS 2ADARS DESIGNED FOR STUDIES OF NONPRECIPITATING CLOUDS TYPICALLY USE SHORT WAVE LENGTHS MMANDMM INORDERTOACHIEVESUFFICIENTSENSITIVITYTODETECTSMALL CLOUDPARTICLESOFTHEORDEROFnMMATSUFFICIENTLYSMALLRESOLUTIONVOLUMES 3ENSITIVE SHORT RANGE &- #7 RADARS HAVING HIGH AVERAGE POWER CAN BE USED TO OBTAINVERYHIGHRANGERESOLUTIONFORDETECTINGVERYTHINSCATTERINGLAYERSINTHECLEAR AIRBOUNDARYLAYER -OSTMETEOROLOGICALRADARSAREPULSEDRADARSHAVINGDOPPLERCAPABILITY'ROUND BASED RADARS USED FOR SEVERE STORM RESEARCH AND WARNINGS NORMALLY USE 3 BAND ^'(Z OR# BAND^'(Z TRANSMITTERS!IRBORNEWEATHERAVOIDANCEANDPRECIP ITATIONRADARSPRIMARILYUSE8BAND^'(Z DUETOSIZELIMITATIONSANDOCCASIONALLY # BANDTRANSMITTERSTOMINIMIZEATTENUATION!IRBORNEANDGROUNDCLOUDRADARSAND SPACEBORNERADARSENCOMPASSTHEMM WAVELENGTHSAT+UBAND^'(Z +ABAND ^'(Z AND7BAND^'(Z "EAMWIDTHSOFanARECOMMONLYUSEDFORLONGER RANGERADARS!DMITTEDLY THIS ISSOMEWHATARBITRARY BUTTHECHOICEOFnISBASEDUPONSEVERALDECADESOFEXPERI ENCE!nBEAMWILLPROVIDEACROSS RANGERESOLUTIONOFKMATARANGEOFKM "ECAUSE THUNDERSTORMS CONTAIN IMPORTANT SPATIAL FEATURES SUCH AS HEAVY PRECIPITA TIONSHAFTSANDUPDRAFTCORES WITHHORIZONTALDIMENSIONSOFTHEORDERTOKM An BEAMISREASONABLYWELLMATCHEDTOTHESEATMOSPHERICPHENOMENABEINGOBSERVEDOUT TORANGESOFAFEWHUNDREDKM3HORTER RANGEAIRBORNEWEATHERRADARSOFTENEMPLOY BEAMWIDTHSOFnnASACOMPROMISEBETWEENWAVELENGTHREQUIREMENTSANDANTENNA SIZECONSTRAINTSWHEREASSPACEBORNERADARSMAYUSEAFRACTIONOFADEGREEBEAMWIDTH TORETAINUSABLEHORIZONTALRESOLUTIONATTYPICALLONGRANGESnKM /PERATIONALWEATHERRADARSNORMALLYARECAPABLEOFSHORTANDLONGPULSEOPERATION INTHERANGEOFMSTOABOUTMSAND02&SBETWEENAND(ZFORLONG RANGEPRECIPITATIONRADARS4HROUGHPULSE WIDTHDIVERSITY HIGHRESOLUTIONISOBTAINED USUALLY AT SHORT RANGE WHEREAS FOR LONG RANGE DETECTION LONGER PULSES PROVIDE INCREASEDSENSITIVITYANDTENDTOEQUALIZETHEALONG BEAMANDCROSS BEAMRESOLUTIONS 4HESHORTERWAVELENGTH+U +A AND7 BANDRADARSTYPICALLYUSEPULSELENGTHSLESS THANMSTOACHIEVEIMPROVEDRANGERESOLUTIONAND02&SBETWEENAND (Z BECAUSE OF THE SHORT RANGE CLOUD MEASUREMENTS THAT ARE LIMITED BY ATTENUATION
-%4%/2/,/')#!,2!$!2
£°£x
ATTHESEWAVELENGTHS3PACE BORNERADARSALSOUSETHESEHIGHER02&SBUTKEEPTRACK OFMULTIPLEPULSESEN ROUTETOTHEIRWEATHERREGIONSFARBELOWTHEORBITALALTITUDES %QUATIONSHOWSTHATTHERECEIVEDPOWERISDIRECTLYPROPORTIONALTOTHEPULSE LENGTHS4HENOISEPOWER0NISCONVENTIONALLYGIVENBY
0N J 4"
WHERE J "OLTZMANNSCONSTANT rn7(Z+
4 RECEIVERNOISETEMPERATURE +
" RECEIVERNOISEBANDWIDTH (Z &ORARECEIVERFILTERMATCHEDTOTHEPULSELENGTH T 3OMETIMESWEATHERRADARSWILLUSEASHORTPULSEFORHIGH02&DOPPLERPROCESSING ATSHORTRANGESANDALONGERPULSEATLOW02&FORGREATERSENSITIVITYWHENPERFORM ING LONG RANGE SURVEILLANCE SCANS TO MONITOR DISTANT WEATHER 3INCE THE TRANSMITTED PEAKPOWERISTYPICALLYCONSTRAINEDTOBEFIXED THENTHETRANSMITTEDAVERAGEPOWER INCREASES LINEARLY WITH S!LSO THE MATCHED FILTER BANDWIDTH AND ASSOCIATED NOISE POWER DECREASES INVERSELY WITH S )F THE RADAR PULSE VOLUME IS FILLED WITH DISTRIB UTEDMETEOROLOGICALSCATTERERS THENTHERADARCROSSSECTIONOFTHEWEATHERTARGETALSO INCREASESWITHSASDETERMINEDBY%QUATIONSAND ANDTHESIGNAL TO NOISE RATIO3.2 OFRECEIVEDPOWERISPROPORTIONALTOS
"y
0R T T s y
0N K 4" K 4
4HUS UNDERTHESECOMMONCONDITIONSINCREASINGTHEPULSELENGTHWILLINCREASETHE 3.2ANDTHEEFFECTIVERADARRANGE)TISIMPORTANTTONOTETHATTHEDISTRIBUTEDTARGET RADARDEPENDENCEOF3.2ONS ISDIFFERENTFROMTHEPOINTTARGETRADARINWHICHTHE MATCHEDFILTER3.2EQUALSTHERATIOOFPULSEENERGYTONOISESPECTRALDENSITY%. 0TS . ALINEARDEPENDENCEONS 4HESQUAREDDEPENDENCEFORDISTRIBUTEDSCATTER ERSISBECAUSETHETRANSMITPULSESCATTERSPOWERFROMALLSCATTERERSINTHECS PULSE VOLUMENOTJUSTASINGLEPOINTTARGET THEREBYINCREASINGTHERADARCROSSSECTIONOFTHE WEATHERSCATTERER 02&SFORMETEOROLOGICALRADARSRANGEFROMASLOWASSEVERALHUNDREDSnFORLONG RANGEDETECTIONTOSEVERALTHOUSANDSnFORSHORTER WAVELENGTHSYSTEMSATTEMPTINGTO ACHIEVEHIGHUNAMBIGUOUSVELOCITIES'ENERALLYSPEAKING MOSTMETEOROLOGICALDOP PLERRADARSAREOPERATEDINASINGLE02&MODE COMPROMISINGTHERADARSABILITYTO UNAMBIGUOUSLYRESOLVEEITHERRANGEORVELOCITY(OWEVER THEPULSINGSEQUENCEMAY USEAhDUAL02&vMODEINWHICHGROUPSOFCONSTANT02&PULSESARETRANSMITTEDOR AhDUALSTAGGERED 024vPULSEREPETITIONTIME TORESOLVEBOTHRANGEANDVELOCITY AMBIGUITIES!NOTHERAPPROACHISTOEMPLOYATRANSMITTEDPULSESEQUENCEWITHRAN DOMORDETERMINISTICPHASESFROMPULSETOPULSE WHICHALLOWSOVERLAIDECHOESTO BESEPARATED-ULTIPLE024TECHNIQUESHAVEALSOBEENEXPLOREDBUTARENOTINCOMMON USE2ANGEAMBIGUITIESCANNOTBETOTALLYELIMINATED BUTTHEIREFFECTSCANBESIGNIFI CANTLYMITIGATEDTHROUGHTHESEAPPROACHES 4ODISCUSSDESIGNDETAILSOFTHECOMMONTYPESOFMETEOROLOGICALRADARSISBEYOND THESCOPEOFTHISCHAPTER2INEHARTGIVESADETAILEDTABLEOFSYSTEMCHARACTERISTICSOF
£°£È
2!$!2(!.$"//+
4!",% 2ELEVANT.EXRAD3YSTEM#HARACTERISTICS
4RANSMITTED0EAK!VERAGE0OWERKLYSTRON 0ULSELENGTH 0OLARIZATION 7AVELENGTH 2ECEIVERNOISETEMPERATURE $YNAMICRANGE !NTENNAGAIN "EAMWIDTH 3IDELOBELEVELS -AXIMUMRANGEREFLECTIVITYDATA -AXIMUMRANGEDOPPLERDATA 5NAMBIGUOUSVELOCITY #LUTTERSUPPRESSIONMAXIMUM 3YSTEMSENSITIVITY 2OTATIONRATE
K77 M MS ,INEARHORIZONTAL CM + D" D" n nD" KM KM oMS D" nD":ATKM nDEGSEC
AVARIETYOFWEATHERRADARS(OWEVER ITWILLBEUSEFULHEREINTOINCLUDESOMEOFTHE IMPORTANTCHARACTERISTICSOFTHE.EXRAD732 $RADAR WHICHILLUSTRATETHEPERFOR MANCEOFMODERNOPERATIONALWEATHERRADARS4ABLECONTAINSSOMEOFTHEMORE RELEVANTORIGINAL.EXRADDESIGNFEATURES &IGURESHOWSATYPICAL.EXRADINSTALLATIONAT-ISSOULA -ONTANA4HEANTENNAIS MOUNTEDONATOWERTOCLEARSURROUNDINGOBSTACLESSUCHASBUILDINGSANDTREES4HEELEC TRONICEQUIPMENTISHOUSEDINONESHELTERANDTHESTANDBYGENERATORISHOUSEDINANOTHER
&)'52% .EXRAD 732 $ RADAR AT -ISSOULA -ONTANA MOUNTEDON MTOWERWITH TWOEQUIPMENTSHELTERSONECONTAININGTHETRANS MITTER RECEIVER PROCESSOR AND COMMUNICATIONS EQUIPMENT ANDTHEOTHERCONTAININGASTANDBYGEN ERATOR0HOTOCOURTESYOF./!!.73
-%4%/2/,/')#!,2!$!2
£°£Ç
&)'52% .EXRAD REFLECTIVITY DATA FROM &REDERICK /KLAHOMA RADARON!PRIL SHOWINGLINEOFINTENSECON VECTIVE CELLS AND SURROUNDING PRECIPITATION 0HOTO COURTESY OF ./!!.73
&IGURESHOWSANEXAMPLEOFRADARREFLECTIVITYDATAFROMTHE&REDERIC /KLAHOMA RADARASALINEOFINTENSETHUNDERSTORMSANDASSOCIATEDRAINFALLPASSTHROUGHTHECOVER AGEAREA4HEPROCESSINGTECHNIQUESUSEDTOGENERATETHEVARIOUSWEATHERIMAGESAND PRODUCTSAREDISCUSSEDLATERINTHISCHAPTER &IGURE SHOWS THE 3 BAND CM AND +A BAND CM DUAL POLARIZATION DOPPLERRESEARCHRADAROPERATEDBYTHE.ATIONAL#ENTERFOR!TMOSPHERIC2ESEARCH .#!2 4HESYSTEMPERMITSSIMULTANEOUSMEASUREMENTSOFTHEREFLECTIVITYFACTORON TWOWAVELENGTHS DOPPLERPARAMETERSONTHE3 BANDWAVELENGTH ANDEXTENSIVEPOLARI METRIC MEASUREMENTS AT BOTH WAVELENGTHS4HE TECHNICAL CHARACTERISTICS ARE SIMILAR TOTHE.EXRADSPECIFICATIONS4HEANTENNABEAMSAREMATCHEDWITHAPPROXIMATELYn BEAMWIDTHANDTHELARGE3 BANDDISHISMINDIAMETER4HEPEAKTRANSMITTEDPOWER
&)'52% 3 0OL4HEMULTI PARAMETER3 BANDAND+A BANDPOLARIMETRICRESEARCHRADARPOINTINGATTHESUNFORASOLAR CALIBRATIONATTHE.ATIONAL#ENTERFOR!TMOSPHERIC2ESEARCH "OULDER #OLORADO #OURTESY OF 5NIVERSITY #ORPORATION FOR !TMOSPHERIC2ESEARCHÚ "OULDER #/
£°£n
2!$!2(!.$"//+
IS-7AT3BANDAND+7AT+ABAND4HEPULSEWIDTHSAREAPPROXIMATELYMS 4HE 02& IS TYPICALLY Sn AT 3 BAND AND A FEW TIMES LARGER AT +A BAND 4HIS RADAR SYSTEM IS CHARACTERISTIC OF THE TECHNOLOGIES CURRENTLY IN PLACE IN THE RESEARCH COMMUNITY 0OLARIMETRIC2ADAR -ETEOROLOGICALRADARSUSINGDUALPOLARIZATIONTRANSMITAND RECEIVEBOTHHORIZONTALANDVERTICALPOLARIZATIONSTOESTIMATEADDITIONALCHARACTERIS TICSOFTHEWEATHERTARGETS 4RANSMITTINGTHETWOORTHOGONALPOLARIZATIONSEITHER SIMULTANEOUSLY3(6 ORTRANSMITTINGTHEMSEPARATELYINAPREDETERMINEDSEQUENCE ANDUSINGDUALPARALLELDIGITALRECEIVERSONEONEACHPOLARIZATIONCHANNEL ALLOWESTI MATIONOFTHEDIFFERENTIALQUANTITIESBETWEENECHOESFROMTHETWOPOLARIZATIONS/NE CANDERIVEIMPROVEDRAINFALLRATESASWELLASOTHERPHYSICALINFORMATIONONTHETYPEOF PRECIPITATION ASFUNCTIONSOFPOLARIMETRICMEASUREMENTSTHATRELATETHEDIFFERENCESIN THEHORIZONTALLYANDVERTICALLYPOLARIZEDSIGNALS"YFARTHEMOSTCOMMONPOLARIMET RICPARAMETERSARETHEhDIFFERENTIALREFLECTIVITYv:DR ANDhDIFFERENTIALPHASEv&DP WHICHGIVEBULKSCATTERINGANDPROPAGATIONCHARACTERISTICSOFTHEMETEOROLOGICALTAR GETS,ETTING%HAND%VDENOTETHECOMPLEXRECEIVEDSIGNALVOLTAGESTHATALSOREPRE SENTTHERECEIVEDELECTRICFIELDSATHORIZONTALANDVERTICALPOLARIZATIONS THEIMPORTANT POLARIMETRICPARAMETERSTOBEESTIMATEDAREGIVENBELOW
$IFFERENTIALREFLECTIVITY:DR :H :V
$IFFERENTIALPHASE&DP &V &H
3PECIFICDIFFERENTIALPHASE+DP D &DP DR
#O POLARCORRELATIONRATIOQHV \ %H %V \ % H%H % V%V ,INEARDEPOLARIZATIONRATIO,$2 :CXV :COH
:HAND :VARETHEMEASUREDREFLECTIVITIESOFTHEHORIZONTALANDVERTICALCO POLAR IZEDRECEIVEDSIGNALSAND:DRISEXPRESSEDIND" WHEREAS&HAND&VARETHEMEASURED PHASES OF THE SAME POLARIZED RECEIVED SIGNALS +DP IS THE SUITABLY SMOOTHED RANGE DERIVATIVEOFTHEMEASUREDDIFFERENTIALPHASE &DP ANDISUSUALLYEXPRESSEDINDEGKM QHVISTHECO POLARCORRELATIONCOEFFICIENTOF%HAND%VWHERETHEPHASEMEASUREMENTS AREASSUMEDTOBETIMECOINCIDENT WHICHISTHECASEWITH3(6TRANSMISSIONANDRECEP TION,$2ISARATIOOFTHECROSS POLARVERTICALREFLECTIVITY:CX V NORMALIZEDBYTHE CO POLARHORIZONTALREFLECTIVITY:CO H "ECAUSEPOLARIMETRICMEASUREMENTSADDNEW DIMENSIONSOFRADARINFORMATIONANDBECAUSETHESEMEASUREMENTSARERELATEDTOTHE PHYSICALCHARACTERISTICSOFTHESCATTERERS SUITABLECOMBINATIONSOFTHESEDATAGIVEA STRONGINDICATIONOFPRECIPITATIONTYPERAIN SNOW ICEPARTICLES SLEET HAIL ETC AS WELLASRADARECHOCLASSIFICATIONINTOVARIOUSCATEGORIESPRECIPITATION GROUNDORSEA CLUTTER BIRDSANDINSECTS CHAFF ETC 2ADAR #ALIBRATION 4O EFFECTIVELY USE RADARS FOR ACCURATE PRECIPITATION ESTI MATES THE CONVERSION OF MEASURED REFLECTIVITY FACTOR TO RECEIVED ECHO POWER MUST BEWELLKNOWN4HEGAINSORCONVERSIONCONSTANTS OFTHEVARIOUSRADARCOMPONENTS CANBEMEASUREDUSINGENGINEERINGTESTEQUIPMENT MANUFACTURERSPECIFICATIONS AND FIELD MEASUREMENTS #ALIBRATING WEATHER RADAR USUALLY MEANS TO ACCURATELY SPECIFY THERADARCONSTANTINTHERADAREQUATIONANDTOACCURATELYESTIMATETHERECEIVEDPOWER
-%4%/2/,/')#!,2!$!2
£°£
MEASUREDBYTHERADARSYSTEM)TALSOENCOMPASSESITEMSSUCHASKNOWINGWHERETHE SCATTERINGVOLUMEISIN$SPACEBYKNOWINGANTENNAPOINTINGANGLESANDACCURATELY DETERMININGRANGE !LTHOUGHFLOATINGSPHERES TETRAHEDRALREFLECTORS ANDOTHERTARGETSOFKNOWNRADAR CROSSSECTIONMAYBEUSED THEIMPORTANThSOLARCALIBRATIONvTECHNIQUEUSESTHE SOLAR POSITION TO ADJUST ANTENNA POINTING AND THE RADIATED SOLAR FLUX TO DETERMINE ANTENNA GAIN !LONG WITH OTHER RADAR PARAMETER MEASUREMENTS ONE CAN READ ILYDETERMINETHERADARCONSTANT"YINJECTINGTESTSIGNALSOFKNOWNPOWER ONECAN DETERMINE THE RECEIVER GAIN TRANSFER FUNCTION &OR POLARIMETRIC RADARS SPECIAL CARE ISREQUIRED)THASBEENDEMONSTRATEDTHATBYMEASURINGTHECROSS POLARPOWERSIN ADDITION TO THE SOLAR FLUX AN ACCURATE ESTIMATE OF THE DIFFERENTIAL CHANNEL CALIBRA TIONCANBEOBTAINED4HE!-3HELDAVERYSUCCESSFUL7EATHER2ADAR#ALIBRATION 3YMPOSIUMDOCUMENTINGALLASPECTSOFMETEOROLOGICALRADARCALIBRATION
£°{Ê - Ê*,"
-- 4OCOMPUTETHEVARIOUSWEATHERPRODUCTSNECESSARYFORFORECASTING WARNING ANDOTHER OPERATIONAL ACTIVITIES THE FIRST THREE SPECTRUM MOMENTS CORRESPONDING TO RECEIVED POWER MEANRADIALVELOCITY ANDDOPPLERSPECTRUMORVELOCITYWIDTHMUSTBEESTIMATED +EELERAND0ASSARELLIREVIEWSTANDARDESTIMATIONTECHNIQUESANDERRORSFORSPECTRUM MOMENTESTIMATION&ORTHEHIGHESTRESOLUTIONMEASUREMENTS THESESPECTRALMOMENTS MUSTBECOMPUTEDATEACHRANGEGATESENSEDBYTHERADARANDCONVERTEDINTOMEANINGFUL METEOROLOGICALINFORMATION4HENATUREOFTHEDISTRIBUTEDMETEOROLOGICALTARGET WHICH SHALLBEDISCUSSEDNEXT IMPOSESSOMESPECIALREQUIREMENTSNOTGENERALLYCONSIDEREDFOR HARD NONFLUCTUATINGTARGETSONTHEPROCESSINGTECHNIQUESTOESTIMATETHESEMOMENTS )TCANBESHOWNTHATTHERECEIVEDSIGNALFROMMETEOROLOGICALTARGETSISWELLREPRE SENTEDBYANARROWBANDGAUSSIANPROCESS4HISISADIRECTCONSEQUENCEOFTHEFACT THAT THENUMBEROFSCATTERERSINTHEPULSEVOLUMEISLARGE THEPULSE VOLUME IS LARGE COMPARED WITH THE TRANSMITTED WAVELENGTH THE PULSE VOLUME CONTAINSMULTIPLEPOINTSCATTERINGSOURCES CAUSINGALLPHASESONTHERANGEFROMTO OTOBECOMBINEDANDRETURNEDAND THEPARTICLESAREINRELATIVEMOTIONDUETO TURBULENCE WINDSHEAR ANDTHEIRVARYINGFALLSPEEDS 4HESUPERPOSITIONOFTHESCATTEREDELECTRICFIELDSFROMSUCHALARGENUMBEROFPAR TICLESEACHWITHDIFFERENTAMPLITUDEANDRANDOMPHASE GIVESRISE THROUGHTHECENTRAL LIMITTHEOREM TOASIGNALWITHBIVARIATE ORATWODIMENSIONAL GAUSSIANPROBABILITY DENSITYFUNCTION4HUS THEFLUCTUATINGAMPLITUDEOFTHERETURNSIGNALHASA2ALEIGHSTA TISTICALDISTRIBUTIONANDITSPHASEISUNIFORMLYDISTRIBUTEDBETWEENnO&URTHERMORE ITSINTENSITYPOWER ISEXPONENTIALLYDISTRIBUTED "ECAUSEALLTHEPARTICLESWITHIN THESAMPLEVOLUMEAREMOVINGWITHSOMEMEANORAVERAGERADIALVELOCITY THEREIS A MEAN FREQUENCY OF THE DOPPLER SPECTRUM THAT IS SHIFTED FROM THE TRANSMITTED FRE QUENCY&INALLY SINCETHEPARTICLESAREINMOTIONWITHRESPECTTOONEANOTHER THEREIS ALSOADOPPLERSPREAD OFTENREFERREDTOASTHEWIDTHOFTHEDOPPLERSPECTRUM:RNIC DESCRIBES A STRAIGHTFORWARD TECHNIQUE OF SYNTHESIZING DIGITAL WEATHER RADAR SIGNALS FROM A PARAMETERIZED DOPPLER SPECTRUM CHARACTERIZING A SPECIFIC PULSE VOLUME $OVIAKAND:RNICASWELLAS"RINGIAND#HANDRASEKARGIVEDETAILEDDERIVATIONSOF THESERELATIONSHIPS WHEREAS+EELERAND0ASSARELLISUMMARIZEDISTRIBUTEDTARGETDATA CHARACTERISTICSANDRELATETHEMTOTHESAMPLEDDATASETSREPRESENTATIVEOFWEATHERRADAR ANDOTHERATMOSPHERICSOUNDINGSYSTEMS
£°Óä
2!$!2(!.$"//+
3PECTRUM -OMENT %STIMATION ! COMMON 'AUSSIAN MODEL OF THE MEAN RECEIVEDPOWERSPECTRALDENSITYOFAMETEOROLOGICALSIGNALISDEPICTEDIN&IGURE ANDCANBEINTERPRETEDASFOLLOWS4HERECEIVEDPOWERISSIMPLYTHEINTEGRALUNDERTHE CURVETHEZEROTHMOMENT ANDISGIVENBY
0R ¯ 3 F DF ¯ 3 V DV
WHEREFANDVARERELATEDBYF K V 4HEMEANVELOCITYV ISGIVENBYTHEFIRSTMOMENTOFTHESPECTRUM
V
¯ V3V DV ¯ 3V DV
4HESPECTRUMVELOCITY WIDTHR V ISGIVENBYTAKINGTHESQUAREROOTOFTHESECOND CENTRALMOMENT
S V
¯ V V 3V DV ¯ 3V DV
2ADARMETEOROLOGISTSSOMETIMESREFERTO S V ASTHESPECTRUMVARIANCEBECAUSEOF ITSCOMPUTATIONALEQUIVALENCETOTHEVARIANCEOFACONTINUOUSLYDISTRIBUTEDRANDOM VARIABLE)NSHORT 3V ISANALOGOUSTOAPROBABILITYDENSITYFUNCTIONFORVSINCEITIS ACTUALLYAREFLECTIVITYWEIGHTEDDISTRIBUTIONOFPARTICLEVELOCITIESWITHINTHESCATTERING VOLUME4HETERMSPECTRUMWIDTHWILLBEUSEDTOREFERTORV)TISCLEAR THEREFORE THAT THEDOPPLERSPECTRUMCONTAINSTHEINFORMATIONNECESSARYTOMEASUREMETEOROLOGICALLY IMPORTANTSIGNALPARAMETERS4HESEFIRSTTHREEMOMENTSAREUSUALLYREFERREDTOASBASE DATAANDOFTENLABELED: 6 AND7WITHTHEAPPROPRIATECONVERSIONSANDUNITS )NTHEMOSTGENERALCASE QUADRATUREPHASEDETECTIONISUSEDTOOBTAINTHEREALAND IMAGINARYPARTSOFTHECOMPLEXSIGNAL4HESEAREUSUALLYDIGITIZEDINALARGENUMBER OFRANGEGATESy ATTHERADARSPULSEREPETITIONFREQUENCY4HERESULTANTCOMPLEX TIMESERIESINEACHGATECANTHENBEPROCESSEDBYUSINGAFAST&OURIERTRANSFORM&&4 TOOBTAINANESTIMATEOFTHEDOPPLERPOWERSPECTRUMFROMWHICHTHEECHOPOWER MEANVELOCITY ANDSPECTRUMWIDTHCANBEOBTAINED
&)'52% 'AUSSIANMODELOFTHEMEANDOPPLERPOWER SPECTRUM 4HE THREE SPECTRAL MOMENTS RECEIVED POWER RADIALVELOCITY ANDSPECTRUMWIDTH CANBEESTIMATEDFROM THE SPECTRUM AND ARE DIRECTLY RELATED TO THE METEOROLOGICAL VARIABLESOFINTEREST
-%4%/2/,/')#!,2!$!2
£°Ó£
!NEFFICIENTMOMENTESTIMATIONTECHNIQUEWASORIGINALLYDESCRIBEDBY2UMMLER ANDREINTERPRETEDBY$OVIAKAND:RNIC4HISESTIMATORMAKESUSEOFTHEFACTTHATTHE COMPLEXAUTOCORRELATIONFUNCTIONOFTHERECEIVEDSIGNALHASTHEGENERALFORM
§ P V ¶ 2 N4 0R R N4 EXP ¨ J N4 · © L ¸
WHERE QN4 IS THE CORRELATION COEFFICIENT OF THE TIME SERIES DATA AND N4 IS THE TIMELAG )TCANBESHOWNTHAT V THEMEANVELOCITY ISAFUNCTIONOFTHEFIRSTLAG24
V
L ARG; 24 = P 4
)TCANALSOBESHOWNTHAT
S V y
L P 4
24 ¶ § ¨ 2 0N · © ¸
WHERE0NISTHENOISEPOWER 4HISESTIMATORHASBEENWIDELYUSEDINTHEPASTFORMEAN FREQUENCYESTIMATIONWITH DOPPLER METEOROLOGICAL RADARS4HE ESTIMATES ARE UNBIASED IN THE PRESENCE OF NOISE WHENTHEDOPPLERSPECTRUMISSYMMETRICAL)TSGREATESTAPPEAL HOWEVER ISDUETOITS COMPUTATIONALSIMPLICITY&ORAPULSEDRADAR WITHAPULSEREPETITIONPERIOD4 24 IS OBTAINEDFROMADJACENTPAIRSOFPULSESUSINGTHESIMPLEEXPRESSION
24
.
.
£ SK SK K
WHERETHESKARETHECOMPLEXIN PHASE) ANDQUADRATURE1 SIGNALSAMPLESSAMPLED ATTHERADAR024 ATAGIVENRANGEAND SK ISITSCOMPLEXCONJUGATE)TISCLEARTHATTHIS ALGORITHMREQUIRES.COMPLEXMULTIPLICATIONSFORATIMESERIESOF.SAMPLESWHEREAS THE&&4REQUIRES.LOG.4HISSO CALLEDPULSE PAIRALGORITHM THEREFORE ISANEFFI CIENTSPECTRALMOMENTESTIMATIONTECHNIQUE(OWEVER ITSHOULDBEAPPLIEDONLYWHEN ONEISCERTAINTOHAVEAPUREWEATHERSIGNALINWHITENOISEOTHERWISE OTHERSPECTRAL COMPONENTSORNON WHITENOISEWILLBIASTHESPECTRALMOMENTESTIMATES &OR MANY PAST OPERATIONAL RADARS THE PULSE PAIR PROCESSOR WAS THE TECHNIQUE OF CHOICE(OWEVER INMANYRESEARCHAPPLICATIONS ITREMAINSADVANTAGEOUSFORIMPROVED DATAQUALITYCONTROLPURPOSESTOACCESSTHEFULLDOPPLERSPECTRUMANDREMOVEARTIFACTS PRIOR TO COMPUTING THE SPECTRAL MOMENTS CORRESPONDING TO THE METEOROLOGICAL DATA OFINTEREST 4HEWINDPROFILINGRADARCOMMUNITYHASMADEEXTENSIVEUSEOFSPEC TRALPROCESSINGFORARTIFACTREMOVALANDSENSITIVITYIMPROVEMENT/NEOFTHEMORE IMPORTANTTASKSISESTIMATINGTHENOISEFLOORSOASTOREMOVEITSEFFECTONTHESPECTRAL MOMENTESTIMATES4WOOBJECTIVETECHNIQUESARECOMMON #ONSTANTLYIMPROVING PROGRAMMABLEDIGITALSIGNALPROCESSINGCHIPSANDSIGNALPROCESSINGCOMPUTERSMAKE ITPOSSIBLEFORRADARMETEOROLOGISTSTOIMPLEMENTVARIOUSTYPESOFSPECTRUMPROCESS INGTECHNIQUESTHATVASTLYIMPROVEDATAQUALITYOVERTHESIMPLEPULSEPAIRPROCESSING ALGORITHM&URTHERMORE PROCESSORSTHATADAPTTHEMSELVESTOAVARIABLEENVIRONMENTIN WHICHTHEYUSUALLYOPERATEAREFEASIBLE&LEXIBLEPROGRAMMINGOFDIGITALSIGNALPROCES SORSPERMITSTAILORINGOFTHEPROCESSORSCHARACTERISTICSTOTHEAPPLICATIONFROMDAYTO DAYOREVENBEAMTOBEAMANDGATETOGATE
£°ÓÓ
2!$!2(!.$"//+
-EASUREMENT !CCURACY "ECAUSE THE RECEIVED SIGNALS ARE SAMPLE FUNCTIONS FROM GAUSSIAN RANDOM PROCESSES THE DOPPLER SPECTRUM AND ITS MOMENTS CANNOT BE MEASUREDEXACTLYINANYFINITEPERIODOFTIME#ONSEQUENTLY ALLMEASUREMENTSWILLBE SOMEWHATINERROR WITHTHEERRORBEINGAFUNCTIONOFTHEPROPERTIESOFTHEATMOSPHERE THERADARWAVELENGTH ANDTHETIMEALLOCATEDTOTHEMEASUREMENT 4HE THEORETICAL DEVELOPMENT OF SIGNAL ESTIMATOR STATISTICS IS FOUND IN $ENENBERG 3ERAFIN AND0EACHFORTHE&&4TECHNIQUE$OVIAKAND:RNIC` COVERTHESUBJECTQUITE COMPLETELYWHILE+EELERAND0ASSARELLIPROVIDEAGOODSUMMARYOFALLTHESEESTIMATION TECHNIQUESANDTHERESPECTIVEMEASUREMENTERROREXPRESSIONS&OLLOWINGARESOMEUSE FULEXPRESSIONSFORTHEMEANSQUAREERROROFMEANPOWERANDMEANVELOCITYESTIMATES 0OWER%STIMATION )TISWELLKNOWNTHATFORAGAUSSIANRANDOMPROCESSUSING SQUARE LAWSIGNALDETECTION SAMPLESOFTHEMEANPOWER0ROFTHEPROCESSAREEXPO NENTIALLYDISTRIBUTEDWITHVARIANCE 0R 4HEVARIATIONISDUETOTHEPROCESSITSELF NOTANY NOISEASSOCIATEDWITHTHEMEASUREMENT'IVENATIME4SEC ALLOCATEDTOTHEMEASURE MENTANDASIGNALBANDWIDTHR F (Z THEREWILLBEAPPROXIMATELYR F4INDEPENDENT SAMPLESOFTHESQUAREOFTHESIGNALENVELOPE)TFOLLOWS THEREFORE THATFORTHEHIGH 3.2CASEANESTIMATEOFTHEMEANPOWERFORTHISPROCESS 0}R WILLHAVEAVARIANCEOR MEANSQUAREERRORGIVENBY
VAR 0}R y
0R
S F 4
3UBSTITUTINGFORR FFROMTHEEXPRESSIONR F R V K WHERER VISTHEWIDTHOFTHE DOPPLERSPECTRUM %QBECOMES
VAR 0}R y
L 0R
S V4
4HISEXPRESSIONISVALIDFORHIGHSIGNAL TO NOISECASES 6ELOCITY%STIMATION 4HEVARIANCEOFTHEMEANFREQUENCYESTIMATEOFTHEDOPPLER SPECTRUMIS
VAR F}
0R4
¯ F 3 F F DF
} 4HISISANINTERESTINGRESULTSHOWINGTHATTHEVARIANCEOFTHEESTIMATE F ISAFUNC TIONONLYOFTHESHAPEOFTHEDOPPLERSPECTRUMPRIMARILYITSSPECTRUMWIDTH ANDTHE INTEGRATIONTIME4ALLOCATEDFORPROCESSING)FTHESPECTRUMCANBEACCURATELYMODELED BYAGAUSSIANSHAPEWITHVARIANCE S F %QREDUCESTO
VAR F}
SF
LS V P 4
P 4
.OTINGTHAT VAR V} L VAR F} WECANWRITE
VAR V}
-%4%/2/,/')#!,2!$!2
£°ÓÎ
)FWEMULTIPLYTHENUMERATORANDDENOMINATORBYR V %QBECOMES VAR V
LS V S V
P S V4 P S F 4
4HUS ITISSEENTHATTHEVARIANCEOFTHEMEANVELOCITYESTIMATE V} ISDIRECTLYPROPOR TIONALTOTHEVARIANCEOFTHEDOPPLERSPECTRUMANDINVERSELYPROPORTIONALTOTHENUMBER OFINDEPENDENTSAMPLES R F 4.OTEALSOTHATVAR V} ISPROPORTIONALTOK INDICATING THAT FORTHESAMEPROCESSINGTIME4ANDFORTHESAMER V THEVARIANCEOFTHEESTIMATE CANBEREDUCEDBYREDUCINGTHEWAVELENGTH WHICHINCREASESTHENUMBEROFINDEPEN DENTSAMPLES %QUATIONS n ARE APPLICABLE IN HIGH SIGNAL TO NOISE RATIO CASES 5NCERTAINTIES IN THE SPECTRAL MOMENT ESTIMATES RESULT FROM THE LIMITED OBSERVATION TIMEOFTHENARROWBANDRANDOMPROCESSCHARACTERIZINGTHEMETEOROLOGICALECHO!NY NOISE IN THE MEASUREMENT FURTHER INCREASES THE UNCERTAINTY :RNIC` GIVES THE MORE GENERALFOLLOWINGEXPRESSIONFORTHEVARIANCEOFTHEMEANFREQUENCYESTIMATEFFORTHE PULSE PAIRESTIMATIONTECHNIQUEANDAGAUSSIAN SHAPEDSPECTRUM ª ¹ . . «P S F 4 3 ; R 4 =º 3 ¬ » WHERE QIS THE CORRELATION COEFFICIENT AND .3 IS THE NOISE TO SIGNAL RATIO %QUATION APPLIESASINGLE02&WITHINTERPULSEPERIOD4ANDASSUMESTHATALLPULSESINTHE INTERVAL4AREUSEDINTHEESTIMATIONALGORITHM)TREDUCESEXACTLYTO%QFORA LARGE3.2ANDFORNARROWSPECTRA IE Q4 y4HEREADERISREFERREDTO:RNIC` FOR FURTHERDETAILSREGARDINGTHEESTIMATIONOFOTHERMOMENTSOFTHEDOPPLERSPECTRUM
VAR F}
P 4 R 4 4
0ULSE#OMPRESSION 0ULSECOMPRESSIONHASBEENINFREQUENTLYUSEDFORMETEO ROLOGICAL APPLICATIONS BECAUSE SHORT PULSE PEAK POWER HAS NOT BEEN A LIMITATION ON WEATHERRADARSYSTEMPERFORMANCE+EELERAND&RUSH HOWEVER DESCRIBEDHOWATMO SPHERICDISTRIBUTEDTARGETSMAYBETREATEDASFROZENFIXED hSLABSvOFSCATTERINGCENTERS SUCHTHATTHEYAPPROXIMATELAYERSOFNONFLUCTUATINGSCATTERERSASTHECODEDRADARPULSE PROPAGATESTHROUGHTHEM4HUS EACHSCATTERINGSLABPRODUCESARETURNSIGNALTHATCAN BECOMPRESSEDBYTHECOMPRESSIONFILTERINTHESAMEWAYASFORINDIVIDUALPOINTTARGETS 4HEYPOINTEDOUTTHATPULSECOMPRESSIONCANBENEFITRAPID SCANNINGRADARAPPLICATIONS INWHICHTHEDESIREDDWELLTIMEOFEACHSCATTERINGVOLUMEISMUCHSHORTERTHANTHE DECORRELATIONTIMEOFTHEWEATHERECHOES)NTHESECASES AVERAGINGPULSECOMPRESSED RANGE MEASUREMENTS INSTEAD OF INTEGRATING OVER A LONGER DWELL TIME PROVIDES THE LARGENUMBEROFINDEPENDENTSAMPLESNEEDEDFORACCURATEMEASUREMENTINAVERYSHORT BEAMOBSERVATIONTIME3IMILARLY THEEFFECTIVERANGERESOLUTIONOVERWHICHAVERAG INGISPERFORMEDCANBEFLEXIBLETOMEETCHANGINGOBSERVATIONALREQUIREMENTSSHORT RANGEINTERVALSFORHIGHLYSTRUCTUREDHEAVYRAINFALLSTORMSTYPICALLYCONVECTIVE AND LONGERRANGEINTERVALSFORMOREUNIFORMBUTWEAKERRAINFALLTYPICALLYSTRATIFORM )N OTHERSITUATIONSWHERESIGNALSAREVERYWEAKSUCHASFORWINDPROFILERAPPLICATIONS ANDCLEARAIRBOUNDARYLAYEROBSERVATIONS PULSECOMPRESSIONMAYBEUSEDTOINCREASE SYSTEMSENSITIVITYBYINCREASINGTHEAVERAGEPOWEROFTHESYSTEMUSINGLONGPULSES WHILEPROCESSINGFORANYDESIREDRANGERESOLUTION2ANGERESOLUTIONAND3.2AREINDE PENDENTLYDETERMINEDBYTHEPULSECOMPRESSIONWAVEFORMDESIGNPARAMETERS ! NOTE OF CAUTION IS IN ORDER WHEN CONSIDERING PULSE COMPRESSION FOR METEORO LOGICAL RADARS RELATING TO THE MATTER OF RANGE SIDELOBES #AREFUL DESIGN IS NECESSARY TOMINIMIZETHESESIDELOBES JUSTASANTENNASIDELOBESSHOULDBEMINIMIZED INORDER
£°Ó{
2!$!2(!.$"//+
TOMITIGATETHEEFFECTSOFINTERPRETIVEERRORSCAUSEDBYWIDEDYNAMICRANGEDISTRIBUTED WEATHERTARGETS !MPLITUDE FREQUENCY ANDPHASESHAPINGOFTHETRANSMITTEDPULSE ALONGWITHSPECIALSIDELOBESUPPRESSIONCOMPRESSIONFILTERSINTHERECEIVERPROCESSOR ALLOWRANGESIDELOBESTOBESUPPRESSEDBYMORETHAND"OVERASIGNIFICANTDOPPLER INTERVALTENSOFMETERSPERSECOND4HESECOMPRESSIONFILTERSARENOTMATCHEDTOTHE TRANSMITWAVEFORMTHEREFORE THE3.2DEGRADESSOMEWHATANDPOSSIBLELOSSOFRANGE RESOLUTIONINTHEMAINBEAMMAYOCCUR(OWEVER THESELOSSESARETOLERABLEFORMANY METEOROLOGICALMEASUREMENTSOFINTEREST 7HITENING 0ULSE COMPRESSION INVOLVES INCREASED TRANSMIT BANDWIDTH THAT IS FREQUENTLYDIFFICULTTOHAVEALLOCATEDANDMAYLIMITITSUSEAT3BANDAND#BANDFOR OPERATIONALAPPLICATIONS!FIXEDBANDWIDTHTECHNIQUEFORINCREASINGRANGERESOLUTION ANDTHENUMBEROFINDEPENDENTSAMPLESISTHEPROCESSOFSAMPLINGTHETRANSMITPULSEAT ANINTERVALSEVERALTIMESSHORTERTHANITSDURATIONANDUSINGALINEARPREDICTIVEWHITENING FILTERTOREMOVETHECORRELATEDINFORMATIONFROMTHEOVERSAMPLEDDATA 4HISWHIT ENINGPROCESSINCREASESTHENUMBEROFINDEPENDENTSAMPLESFORRANGEAVERAGINGTHAT ALLOWSIMPROVEDPARAMETERESTIMATIONACCURACYBUTATACOSTOFSIGNIFICANTLYREDUCED 3.24HEHIGHERNOISEBANDWIDTHINTHERECEIVERREQUIREDBYTHEHIGHERRATESAMPLING ANDTHEWHITENINGFILTERNOISEENHANCEMENTCAUSETHE3.2TOBEREDUCEDBYAFACTOROF APPROXIMATELY,WHERE,ISTHEINCREASEDSAMPLINGFACTOR3TATEDANOTHERWAY THE WHITENINGFILTEREFFECTIVELYSHORTENSTHETRANSMITPULSEBY, WHILEPASSINGTHEINCREASED RECEIVERNOISEPOWERBY, THEREBYTRADINGRANGERESOLUTIONFOR3.2&ORTUNATELY FOR PRECIPITATIONECHOESANDTYPICALWEATHERRADARS THE3.2ISQUITEHIGH ANDEVENAFTER THEWHITENINGPROCESS ITREMAINSHIGHENOUGHTOEFFECTIVELYUTILIZETHELARGERNUMBER OFINDEPENDENTSAMPLESFORIMPROVEDBASEDATAESTIMATESORIMPROVEDRANGERESOLU TIONMEASUREMENTS/NTHEOTHERHAND IFTHESIGNALISWEAK NOISEENHANCEMENTWILL DOMINATETHEWHITENINGPROCESSANDANYADVANTAGEISLOST(IGHLYIMPORTANTISTHEFACT THATTHETRANSMITPULSEANDITSBANDWIDTHARENOTCHANGEDCONSEQUENTLY INCREASEDFRE QUENCYALLOCATIONTOMAKEUSEOFTHEHIGHERRANGERESOLUTIONISNOTANISSUE 3HORT $WELL 4IME 3PECTRA -AXIMUM %NTROPY 3PECTRAL PROCESSING OF WEATHERECHOESADDSANOTHERDEGREEOFFREEDOMTHEFREQUENCYDIMENSION TOTHEABIL ITYTODISCRIMINATESIGNALFROMGROUNDCLUTTER OTHERARTIFACTS ANDNOISE ANDTOESTIMATE METEOROLOGICAL PARAMETERS OF INTEREST -OST FREQUENCY DOMAIN PROCESSING REQUIRES RELATIVELYLONG)1DATASAMPLESETSFORDISCRETE&OURIERTRANSFORMANALYSES WINDOW FUNCTIONS AND POSSIBLE SPECTRAL AVERAGING TO OBTAIN SPECTRA SUITABLE FOR QUANTITA TIVEPROCESSING&ASTERSCANNINGRADARSUSEDFORSAMPLINGRAPIDLYEVOLVINGSTORMS REQUIRESSPECTRUMANALYSISTECHNIQUESTHATUSESHORTDWELLTIMEDATASETSOFMANYFEWER )1DATASAMPLES-ODERNSPECTRUMANALYSISTECHNIQUESSUCHASTHE"URGMAXIMUM ENTROPYANDTHE#APONMAXIMUMLIKELIHOODESTIMATORSALLOWUSINGSHORTDWELL SAMPLED DATA TO OBTAIN STABLE SPECTRUM ESTIMATORS 4HESE TECHNIQUES BELONG TO THE GENERALCLASSOFAUTOREGRESSIVE!2 ESTIMATORSWHEREBYTHEOBSERVEDDATAAREMOD ELEDASALL POLEFILTEREDWHITENOISERATHERTHANAWEIGHTEDSUMOFSINUSOIDSACCORDING TOTHE&OURIERMODEL-ULTIPLESIGNALSANDGROUNDCLUTTERMAYBERESOLVEDTHESAME ASUSING&OURIERESTIMATORS4HESESHORTDWELLTIME!2SPECTRAMAYTHENBEUSEDTO ESTIMATEWEATHERSPECTRALMOMENTSTHESAMEASTHE&OURIERDATAMODELSPECTRUMESTI MATORSFROMWHICHTHEWEATHERPARAMETERSAREDERIVED 0ROCESSOR )MPLEMENTATIONS -ODERN METEOROLOGICAL RADARS USE DIGITAL SIGNAL PROCESSING TECHNIQUES ON PROGRAMMABLE PLATFORMS AND INTERACTIVE COLOR DISPLAYS
-%4%/2/,/')#!,2!$!2
£°Óx
FORQUANTITATIVEPRECISIONININTERPRETINGTHEWEATHERECHOES-ODERNWEATHERRADARS REQUIRE LARGE DYNAMIC RANGE TO SENSE STRONG ECHO AT SHORT RANGE AND WEAK ECHO AT LONGRANGE4HUS THERECEIVERANDPROCESSORDESIGNSATTEMPTTOMAINTAINAMPLITUDE ANDPHASELINEARITYTHROUGHOUTTHATRANGEBYUSINGADYNAMICAUTOMATICGAINCONTROL !'# WHEREBY THE RECEIVER GAIN AND PHASE ARE ADJUSTED ALONG THE RANGE INTERVAL THROUGHTHEUSEOFRAPIDLYSWITCHEDATTENUATORSOR MOREOFTEN DIGITALCOMPENSATION #LEARLY SUCHRAPIDSWITCHINGINTHERECEIVERREQUIRESCAREFULDESIGNINORDERTOAVOID THEAFFECTSOFSWITCHINGTRANSIENTS!NAPPROACHTHATAVOIDSTRANSIENTEFFECTSISTOUSE TWOPARALLEL)&RECEIVERCHANNELS EACHWITHMODERATEDYNAMICRANGEANDFIXEDGAINS ANDTOSAMPLETHESIGNALINTHECHANNELTHATISBESTMATCHEDTOTHESIGNALSTRENGTH )NALLTHOSEAPPROACHES ITISPOSSIBLETOACHIEVELINEARDYNAMICRANGEOFGREATERTHAN D"ANDTOUSEFLOATING POINTDIGITALPROCESSING4HEREFLECTIVITY MEANDOPPLERVELOCITY ANDSPECTRUMWIDTHCANALLBEESTIMATEDDIGITALLYFROMTHEFLOATING POINTSAMPLES4HE PROCESSINGCANBEPERFORMEDWITHADEDICATEDDIGITALSIGNALPROCESSINGCOMPUTERORBYFAST GENERAL PURPOSECOMPUTERSCOMBINEDWITHSPECIALSIGNALPROCESSINGCOMPONENTSUSING $IGITAL3IGNAL0ROCESSING$30 CHIPSORFIELDPROGRAMMABLEGATEARRAY&0'! DEVICES #ONTINUEDTECHNOLOGYADVANCESWILLPERMITADVANCED BUTMATURE SIGNALPROCESSINGALGO RITHMSSUCHASMODERNSPECTRALPROCESSINGANDADAPTIVEFILTERINGTOBEIMPLEMENTED
£°xÊ "* ,/" Ê** /" !S HAS BEEN DEMONSTRATED METEOROLOGICAL RADARS MEASURE BACKSCATTERED POWER AND RADIALVELOCITYPARAMETERS4HECHALLENGETOTHERADARMETEOROLOGISTISTOTRANSLATETHESE MEASUREMENTS THEIRSPATIALDISTRIBUTIONS ANDTHEIRTEMPORALEVOLUTIONINTOQUANTITATIVE ASSESSMENTS OF THE WEATHER 3ERAFIN AND 7ILSON AMONG OTHERS SHOW HOW MODERN METEOROLOGICALRADARSAREUSEDFORFORECASTINGTHEWEATHER4HELEVELOFSOPHISTICATION USEDININTERPRETATIONVARIESBROADLY RANGINGFROMHUMANINTERPRETATIONOFRUDIMEN TARYDISPLAYSTOAUTOMATICALGORITHMSANDMODERNMULTIDIMENSIONALDISPLAYSTOASSIST HUMANINTERPRETATION%XPERTSYSTEMAPPROACHES THATATTEMPTTOREPRODUCEHUMAN INTERPRETIVE LOGICAL PROCESSES HAVE BEEN EMPLOYED EFFECTIVELY 4HE DEGREE TO WHICH AUTOMATIONCANBEAPPLIEDISEVIDENTINTHE.EXRADRADARSYSTEMDESIGNTHATPRODUCES THEAUTOMATEDMETEOROLOGICALPRODUCTSSHOWNIN4ABLE 4!",% 0ARTIAL,ISTOF.EXRAD!UTOMATED0RODUCTS
"ASERADARREFLECTIVITYALLRANGES EACHSCAN "ASERADIALVELOCITY "ASESPECTRUMWIDTH #OMPOSITEMAXIMUMATALLHEIGHTS REFLECTIVITY 0RECIPITATIONECHOTOPS 3EVEREWEATHERPROBABILITY 6ELOCITY!ZIMUTH$ISPLAY6!$ 7IND0ROFILE 3TORMRELATIVEMEANRADIALVELOCITY 6ERTICALINTEGRATEDLIQUID 3TORMTRACKINGINFORMATION (AILPOTENTIAL -ESOCYCLONEAND4ORNADO6ORTEX3IGNATURE 3URFACERAINFALLACCUMULATIONHR HR TOTALSTORM 2ADAR%CHO#LASSIFIER
£°ÓÈ
2!$!2(!.$"//+
0RECIPITATION -EASUREMENT !MONG THE MORE IMPORTANT PARAMETERS TO BE MEASUREDISRAINFALL HAVINGSIGNIFICANCETOANUMBEROFWATERRESOURCEMANAGEMENT PROBLEMSRELATEDTOAGRICULTURE FRESH WATERSUPPLIES STORMDRAINAGE ANDWARNINGOF POTENTIALFLOODING4HERAINFALLRATECANBEEMPIRICALLYRELATEDTOTHEREFLECTIVITYFACTOR BYANEXPRESSIONOFTHEFORM
: A2B
WHEREAANDBARECONSTANTAND2ISTHERAINFALLRATE USUALLYINMILLIMETERSPERHOUR "ATTANDEVOTESTHREEFULLPAGESOFHISBOOKTOTHELISTINGOFDOZENSOF: 2RELATION SHIPSDERIVEDBYINVESTIGATORSATVARIOUSLOCATIONSTHROUGHOUTTHEWORLD FORVARIOUS WEATHERCONDITIONS ANDINALLSEASONSOFTHEYEAR4HEFACTTHATNOUNIVERSALEXPRESSION CANBEAPPLIEDTOALLWEATHERSITUATIONSISNOTSURPRISINGWHENONENOTESTHATRAINFALL DROP SIZEDISTRIBUTIONSAREHIGHLYVARIABLE&ORMANYCONDITIONS THEDROP SIZEDISTRI BUTIONCANBEREPRESENTEDBYANEXPONENTIALFUNCTION
.$ .En,$
WHERE.AND,ARECONSTANTSAND,$ WHERE$ISTHEMEDIANDROPDIAMETER )F.$ ISKNOWN THEREFLECTIVITYFACTORCANBECALCULATEDFROM%Q"YUSINGTHE TERMINAL FALLSPEEDDATAOF'UNNAND+INZER THERAINFALLRATECANALSOBEOBTAINED AND:RELATEDTO2ASSHOWNIN%Q4HEEXPONENTIALFORMOFTHEDROP SIZEDISTRI BUTIONGENERALLYFITSTHEAVERAGEOFSEVERALDROP SIZEDISTRIBUTIONSTHATOCCUROVERDIF FERENTPHASESOFCONVECTIVEANDTROPICALRAINFALLANDAREAVERAGEDOVERSPACEORTIME (OWEVER THEhGAMMAvDROP SIZEDISTRIBUTIONREPRESENTSABETTERFITTOINSTANTANEOUS NATURALVARIATIONSOFTHEDROP SIZEDISTRIBUTIONUNDERDIFFERENTCONDITIONS4HEGAMMA DROP SIZEDISTRIBUTIONISGIVENAS
.$ .$LEn,$
WITHL nAND,$ L4HELPARAMETERCONTROLSTHESHAPEOFTHEDISTRIBUTION ANDWHENL THEDISTRIBUTIONISEXPONENTIAL #LEARLY ASINGLE WAVELENGTH SINGLE POLARIZATIONRADARCANMEASUREONLYASINGLE PARAMETER:ANDMUSTASSUME2AYLEIGHSCATTERING3INCETHERAINFALLRATEDEPENDSUPON TWOPARAMETERS .AND, ITISNOTSURPRISINGTHAT%QISNOTUNIVERSAL$ESPITE THISFACT "ATTANLISTSFOUREXPRESSIONSASBEINGhFAIRLYTYPICALvFORTHEFOLLOWINGFOUR TYPESOFRAIN
3TRATIFORMRAIN: 2
/ROGRAPHICRAIN: 2
4HUNDERSTORMRAIN: 2
3NOW: 2
3TRATIFORMREFERSTOWIDESPREAD RELATIVELYUNIFORMRAINANDUSESTHEWELL KNOWN -ARSHALL 0ALMER DROP SIZE DISTRIBUTION /ROGRAPHIC RAIN IS PRECIPITATION THAT IS INDUCEDORINFLUENCEDBYHILLSORMOUNTAINS WHEREAS4HUNDERSTORMRAINISTYPICALOF CONVECTIVEPRECIPITATIONSYSTEMS)NEACHOFTHEABOVEEXPRESSIONS :ISINMMMAND 2ISINMMH)N%Q 2ISTHEPRECIPITATIONRATEOFTHEWATER EQUIVALENTMELTED SNOW"ATTANGIVESAMORECOMPLETETREATMENTOFTHISIMPORTANTTOPIC
-%4%/2/,/')#!,2!$!2
£°ÓÇ
7ILSON AND "RANDES GIVE A COMPREHENSIVE TREATMENT OF HOW RADAR AND RAIN GAUGEDATACANBEUSEDTOCOMPLEMENTONEANOTHERINMEASUREMENTSOFPRECIPITATION OVERLARGEAREAS4HEYSTATETHATTHERADARDETERMINEDSTORMCUMULATIVEPRECIPITATION MEASUREMENTSAREEXPECTEDTOBEACCURATEWITHINAFACTOROFFOROFTHETIME !CCURACIES OVER LARGE AREAS CAN BE IMPROVED TO ABOUT WITH THE ADDITION OF A SURFACERAIN GAUGENETWORK!LTHOUGHRADARMEASURESREFLECTIVITYALOFT THEPRIMARY CONCERNISRAINFALLESTIMATIONATTHESURFACE2AINGAUGEMEASUREMENTSAREFREQUENTLY USEDTOADJUSTTHERADARREFLECTIVITYVALUES:AWADZKIDESCRIBESMANYFACTORSTHAT INFLUENCE RAINFALL MEASUREMENT BY RADAR *OSS AND ,EEAND OTHERS USE THE 6ERTICAL0ROFILEOF2EFLECTIVITY602 TOESTIMATETHESURFACERAINFALLRATEWITHSOME SUCCESS"RIDGESAND&ELDMANDISCUSSHOWTWOINDEPENDENTMEASUREMENTSREFLEC TIVITYFACTORANDATTENUATION CANBEUSEDTOOBTAINBOTHPARAMETERSOFTHEDROP SIZE DISTRIBUTIONANDMOREPRECISELYDETERMINETHERAINFALLRATE 0OLARIMETRIC%STIMATES $UALPOLARIZATIONRADARHASBEENPROVENTOYIELDIMPROVED RAINFALLESTIMATESASWELLASOTHERADVANTAGESFORWEATHERRADAR0OLARIMETRICRADAR MEASUREMENTS TAKE ADVANTAGE OF THE FLATTENED RAINDROP SHAPE APPROXIMATED BY AN OBLATESPHEROIDAFLATTENEDSPHEREHAVINGAHORIZONTALDIMENSIONGREATERTHANITSVERTI CALDIMENSION ANDITSPROPAGATIONANDSCATTERINGCHARACTERISTICS TOOBTAINACCURATE RAIN RATEESTIMATORS3ELIGAAND"RINGIAND3ACHIDANANDAAND:RNICSHOWHOWTHE CO POLARMEASUREMENTSOF:ATHORIZONTAL:H ANDVERTICAL:V POLARIZATIONSCANPRO DUCETWOINDEPENDENTMEASUREMENTSAND THEREFORE PROVIDEMOREACCURATERAINFALL RATE MEASUREMENTSTHANTHOSERELATEDTOSIMPLEREFLECTIVITY"RINGIAND#HANDRAGIVETHE FOLLOWINGRAIN RATEESTIMATORSFORMEASUREMENTSATCM3BAND /THERWAVELENGTHS HAVEDIFFERENTCONSTANTSBECAUSEOF-IEFACTORSENTERINGINTOTHECALCULATIONSANDTHE WAVELENGTHDEPENDENCEOFPHASEMEASUREMENTS
2:H :DR :H:DRn
2+DP +DP
2+DP :DR +DP:DRn
4HEREFLECTIVITY BASEDRAIN RATEESTIMATORSCORRESPONDINGTOTHE-ARSHALL 0ALMER : 2 ANDTHECOMMON.EXRAD732 $: 2 RELATIONSARE
2-0: : FOR-ARSHALL 0ALMER
2$: : FOR.EXRAD732 $
4HE POLARIMETRIC PRECIPITATION MEASUREMENTS BRING UNIQUE CHARACTERISTICS THAT ADDRESSNOTONLYIMPROVEDPRECIPITATIONMEASUREMENTS BUTALSOIMPROVEDDATAQUAL ITY CHARACTERISTICS 4HE DIFFERENTIAL REFLECTIVITY BETWEEN THE HORIZONTAL AND VERTI CALPOLARIZATIONS:DR ALLOWSESTIMATINGTHEEFFECTIVEDROPSIZE WHEREASDIFFERENTIAL PHASE +DP GIVES ADDITIONAL SOMEWHAT INDEPENDENT INFORMATION ON ESTIMATION OF RAINFALLRATES+DPISANESPECIALLYIMPORTANTPARAMETERWHENTHERADARISCONFRONTED WITHTYPICALCONTAMINANTSASBEAMBLOCKAGE GROUNDCLUTTERDOMINATION ANDCALIBRA TION ERRORS &URTHERMORE 2YZHKOV AND :RNIC HAVE SHOWN THAT +DP BASED RAINFALL MEASUREMENTS ARE LESS DEPENDENT ON THE UNKNOWN AND VARIABLE DROP SIZE DISTRIBU TION$3$ THANPOWER BASEDMEASUREMENTS&URTHERMORE OTHERINFERENCESFROMTHE
£°Ón
2!$!2(!.$"//+
POLARIMETRICMEASUREMENTSALLOWONETOESTIMATETHEPARAMETERSOFTHEGAMMAFUNC TION FORM OF THE $3$ WHICH MAY FURTHER IMPROVE RAINFALL ESTIMATION!ND SELF CONSISTENCY CONSTRAINTS OF THE POLARIMETRIC PRECIPITATION COVARIANCE MATRIX IMPOSE RELATIVELY STRICT BOUNDS ON THE ABSOLUTE REFLECTIVITY MEASUREMENTS ALLOWING ONE TO CALIBRATETHEREFLECTIVITYMEASUREMENTANDMAKEIMPROVEDRAINFALLRATEESTIMATES &ORSHORTWAVELENGTHRADARS ONEMUSTCONSIDER-IESCATTERINGEFFECTSWHENMEASUR INGRAINFALLRATEBYREFLECTIVITYMEASUREMENT,HERMITTEAND+OLLIASETALGIVEAN ANALYSISOF-IESCATTERINGANDSHOWTHATIFTHESCATTERINGISPROPERLYACCOUNTED THE RAINFALLMEASUREMENTSAREACCURATE 0OLARIMETRIC RADARS MAY BE CONFIGURED IN DIFFERENT WAYS FOR DIFFERENT MEASURE MENTS2ESEARCHRADARSEXPLORETHEDEPOLARIZATIONRATIOSBYALTERNATINGHORIZONTALLY AND VERTICALLY POLARIZED PULSES (OWEVER THE PREFERRED CONFIGURATION FOR OPERA TIONALRADARSISTOTRANSMITBOTHHORIZONTALANDVERTICALPOLARIZATIONSSIMULTANEOUSLY WHILEINDEPENDENTLYRECEIVINGBOTHORTHOGONALSIGNALSFORPOLARIMETRICPROCESSING ALLOWINGRECEPTIONOFTHEIMPORTANTCO POLARQUANTITIES4HERELATIVEPHASEOFEACH TRANSMITTED POLARIZATION IS ARBITRARY BUT THE DIFFERENTIAL MAGNITUDE AND PHASE OF THECO POLARRECEIVEDSIGNALSINEACHPOLARIZATIONARESUFFICIENTFORTHEPOLARIMETRIC MEASUREMENTS )T IS OUR OPINION THAT NO SINGLE TOPIC IN RADAR METEOROLOGY HAS RECEIVED MORE ATTENTIONTHANRAINFALLRATEMEASUREMENT!LTHOUGHUSEFULEMPIRICALEXPRESSIONSHAVE EVOLVED AND DUAL POLARIZATION TECHNIQUES SHOW SIGNIFICANT IMPROVEMENTS IN ACCU RACY ACOMPLETELYSATISFACTORYAPPROACHREMAINSTOBEDEVELOPED 0OLARIMETRIC MEASUREMENTS BY THE 732 $ RADARS WILL ALLOW MORE ACCURATE PRECIPITATION MEASUREMENTS AND ICE WATER PHASE KNOWLEDGE THAT IS IMPORTANT FOR MAKINGIMPROVEDFORECASTS SEPARATINGWINTERPRECIPITATIONINTOREGIONSOFRAINAND SNOW ANDDETECTINGHAZARDOUSAIRCRAFTICINGCONDITIONS)MPLEMENTATIONOFPHASE CODING ALGORITHMS ALLOW THESE RADARS TO SEPARATE MULTIPLE TIME AROUND OR MULTI PLETRIP ECHOES ANDTOCOMPUTEDEALIASEDVELOCITIESINTHERANGEDEALIASED ECHOESTOCLASSIFYANDSEPARATEPRECIPITATIONECHOESFROMARTIFACTSASGROUNDCLUT TER SEACLUTTER ANDINSECTSECHOESTOACCOMMODATEFLEXIBLESCANSTRATEGIESAND TOINCORPORATEIMPROVEDDATARESOLUTIONINRANGEANDAZIMUTH4HESEPERFORMANCE ENHANCEMENTSAREREADILYACHIEVEDBYINSTALLINGGREATERANDMOREFLEXIBLESIGNALAND DATAPROCESSINGPOWER 3EVERE3TORM7ARNING /NEOFTHEPRIMARYPURPOSESOFWEATHERRADARSISTO PROVIDETIMELYWARNINGSOFSEVEREWEATHERPHENOMENASUCHASTORNADOES DAMAGING WINDS FLASHFLOODS ANDLANDFALLINGHURRICANES!CCURATELONG TERMFORECASTINGOFTHE PRECISELOCATIONANDLEVELOFSEVERITYOFTHESEPHENOMENA THROUGHDATAASSIMILATION ANDNUMERICALWEATHERPREDICTIONTECHNIQUES ISBEYONDTHEPRESENTSTATEOFTHEART /PERATIONALRADARS HOWEVER CANDETECTTHESEPHENOMENAANDPROVIDELOCALWARN INGS OF APPROACHING SEVERE EVENTS THEY CAN ALSO DETECT THE ROTATING MESOCYCLONES INSEVERESTORMSTHATAREPRECURSORSTOTHEDEVELOPMENTOFTORNADOESATTHE%ARTHS SURFACE'ROUND BASEDCOASTALANDAIRBORNERADARSCANALSOMEASURETHESEVERITY OFAPPROACHINGHURRICANESANDDEFINETHEIRMOSTINTENSELANDFALLPOSITIONSFOREVACU ATIONWARNINGS 4ORNADO$ETECTION !SINGLEDOPPLERRADARCANMEASUREONLYTHERADIALCOMPO NENTOFTHEVECTORWINDFIELD(ENCE EXACTMEASUREMENTSOFVECTORWINDSATAPOINT AREGENERALLYNOTPOSSIBLE(OWEVER ROTATINGWINDSORVORTICESCANBEDETECTEDAND
-%4%/2/,/')#!,2!$!2
£°Ó
THEIR INTENSITIES MEASURED BY SIMPLY MEASURING THE CHANGE IN RADIAL VELOCITY WITH AZIMUTH ANGLE AS SHOWN IN &IGURE 4HE RADAR SCANS IN AZIMUTH AND DETECTS A COUPLETINRADIALVELOCITYATCONSTANTRANGE4HEAZIMUTHSHEARISGIVENSIMPLYBYTHE EXPRESSION
DVR VR y
DX RA
WHEREXISINTHEDIRECTIONORTHOGONALTOTHERADIUSOFTHECIRCULATIONAND@ISTHEANGLE SUBTENDEDBYTHECIRCULATIONATRANGER "ECAUSEMESOCYCLONESMAYSPAWNTORNADOESANDCANBEMANYKILOMETERSINDIAM ETER RADARS WITH ABOUT n BEAMWIDTH HAVE THE SPATIAL RESOLUTION TO DETECT MESOCY CLONESATRANGESINEXCESSOFKM)TSHOULDBECLEARTHATANYMEANTRANSLATIONAL MOTIONWOULDCHANGETHEABSOLUTEVALUESOFTHEMEASUREDRADIALVELOCITIESBUTWOULD NOT AFFECT THE SHEAR MEASUREMENT!ZIMUTHAL SHEAR VALUES OF THE ORDER OF n Sn ORGREATERANDWITHVERTICALEXTENTGREATERTHANTHEDIAMETEROFTHEMESOCYCLONEARE DEEMEDNECESSARYFORATORNADOTOOCCUR $ETECTIONOFTHETORNADOVORTEXITSELFISNOTGENERALLYPOSSIBLEBEYONDABOUTKM USINGTYPICALWEATHERRADARBEAMWIDTHS SINCEITSHORIZONTALEXTENTMAYBEONLYAFEW HUNDREDMETERS$ETECTIONOFTHERADIALSHEAR THEREFORE ISNOTPOSSIBLEUNLESSTHETOR NADOISCLOSEENOUGHTOTHERADARTOBERESOLVEDBYTHEBEAMWIDTH(OWEVER INCASES WHERETHETORNADOFALLSENTIRELYWITHINTHEBEAM THEDOPPLERSPECTRUMWIDTHMAYBE USEDTOESTIMATETORNADICINTENSITY)NSOMECASES BOTHAMESOCYCLONEANDITSINCIPIENT TORNADOCANBEDETECTED7ILSONAND2OESLISHOWANEXCELLENTEARLYEXAMPLEOFA TORNADOVORTEXSIGNATURE463 EMBEDDEDWITHINALARGERMESOCYCLONE -ICROBURSTS &UJITAAND#ARACENAFIRSTIDENTIFIEDTHEMICROBURSTPHENOMENON ASTHECAUSEOFANAIRLINERCRASHTHATTOOKPLACEIN4HEMICROBURSTANDITSEFFECTS ONANAIRCRAFTDURINGTAKEOFFORLANDINGAREDEPICTEDIN&IGURE4HEMICROBURSTIS SIMPLYASMALL SCALE SHORT DURATIONDOWNDRAFTEMANATINGFROMACONVECTIVESTORM 4HIS hBURSTv OF AIR SPREADS OUT RADIALLY AS IT STRIKES THE GROUND FORMING A RING OF DIVERGINGAIRABOUTTOKMDEEPANDOFTHEORDEROFTOKMINDIAMETERWITH DIVERGENTWINDSGREATERTHANMSANDLASTINGLESSTHANMINUTES!IRCRAFTPEN ETRATINGAMICROBURSTFIRSTEXPERIENCEANINCREASEINHEADWINDANDTHENACONTINU OUS PERFORMANCE ROBBINGDECREASEINHEADWIND WHICHCANCAUSETHEPLANETOCRASH IF ENCOUNTERED SHORTLY BEFORE TOUCHDOWN OR JUST AS THE AIRCRAFT IS TAKING OFF -ORE COMPLETEDESCRIPTIONSOFMICROBURSTSANDTHEIREFFECTSONAVIATIONSAFETYAREGIVENBY &UJITA AND-C#ARTHYAND3ERAFIN
&)'52% -EASUREMENT OF ROTATION OR AZIMUTHAL WIND SHEAR IN A MESOCYCLONE AROTATINGWINDPARCEL4HEAZIMUTHALSHEARISGIVENBY#V#X VR R@#OURTESYOF 5NIVERSITY#ORPORATIONFOR!TMOSPHERIC2ESEARCHÚ "OULDER #/
£°Îä
2!$!2(!.$"//+
&)'52% $EPICTIONOFAMICROBURSTANDITSEFFECT ONANAIRCRAFTDURINGTAKEOFF4HELOSSOFAIRSPEEDINTHE DIVERGENTWINDFIELDNEARTOTHEGROUNDISEXTREMELYHAZ ARDOUS!SIMILARLOSSOFAIRSPEEDNEARTHEGROUNDOCCURS DURINGLANDING#OURTESYOF5NIVERSITY#ORPORATIONFOR !TMOSPHERIC2ESEARCHÚ "OULDER #/
-ICROBURSTDETECTION LIKETORNADODETECTION ISACCOMPLISHEDBYESTIMATINGSHEAR (OWEVER INTHECASEOFTHEMICROBURST ITISTHERADIALSHEAROFTHERADIALVELOCITYTHATIS TYPICALLYMEASURED(UMANINTERPRETATIONOFMICROBURSTSIGNATURESINCOLOR ENHANCED RADIALVELOCITYDISPLAYSISEASILYACCOMPLISHEDWITHTRAINEDOBSERVERSANDAUTOMATIC DETECTIONHASBEENIMPLEMENTEDONTHE4$72RADARSYSTEM2ADIALVELOCITYDIFFER ENCESOFTOMSAREOBSERVEDINMICROBURSTS!RADIALVELOCITYDIFFERENCEOFMORE THANMSOVERTHELENGTHOFAJETRUNWAYyKM ISASERIOUSCONCERN /NEPRINCIPALPROBLEMCONCERNINGMICROBURSTSISTHEIRSHORTLIFETIMES WHICHARE ONTHEORDEROFnMINUTESBUTTHEDURATIONOFPEAKINTENSITYISONLYORMIN UTES&IELDRESEARCHHASCLEARLYDEMONSTRATEDTHATAFEWMINUTESADVANCEWARNING USINGDOPPLERRADARCANBEACHIEVED/PERATIONALMICROBURSTDETECTIONRADARSUSETHIS AUTOMATEDDETECTIONALGORITHMWITHHIGHPERFORMANCEGROUNDCLUTTERMITIGATIONTECH NIQUESSINCETHEPHENOMENONOCCURSNEARTHEGROUNDANDOFTENTIMESINVERYLIGHTOR NOPRECIPITATION #BANDISTHEPREFERREDOPERATIONALFREQUENCYFORSEVERALREASONS&IRST A# BAND ANTENNA WILL HAVE A SMALLER BEAMWIDTH THAN AN 3 BAND ANTENNA OF THE SAME SIZE ANDALLOWIMPROVEDAIRFLOWMEASUREMENTSWITHSTRONGCLUTTERSUPPRESSIONNEARTHE AIRPORT SURFACE 3ECOND SINCE SHORTRANGEDETECTIONISIMPORTANT RADARATTENUATION EFFECTS ARE NOT A PRIMARY CONCERN4HIRD # BAND OFFERS IMPROVED SIGNAL TO CLUTTER
-%4%/2/,/')#!,2!$!2
£°Î£
PERFORMANCESINCETHELARGECLUTTERTARGETSARELIMITEDINRADARCROSSSECTIONBY-IE SCATTERING WHEREASTHEATMOSPHERE BORNEWINDTRACINGSCATTERERSARESMALLANDOBEY 2AYLEIGH SCATTERING CROSS SECTION PHYSICS 8 BAND RADARS HAVE BEEN CONSIDERED TO SOMEDEGREEBUTTHEMORESEVEREATTENUATIONTHATCANOCCURINVERYHEAVYRAINWILL LIMIT PERFORMANCE UNLESS THE RADAR IS LOCATED VERY NEAR TO THE AIRPORT RUNWAYS )N THE MID S THE # BAND4ERMINAL $OPPLER7EATHER 2ADAR 4$72 SYSTEM WAS INSTALLED AT MAJOR AIRPORTS TO DETECT AND WARN AIRCRAFT OF HAZARDOUS WIND SHEAR CONDITIONS APPROACHINGGUSTFRONTSTHATMAYAFFECTTHEAIRPORTAPPROACHANDDEPARTURE CONFIGURATION ANDMICROBURSTS4HISNETWORKOFRADARSALONGWITHMUCHIMPROVED PILOTTRAININGANDAWARENESSHASALLBUTELIMINATEDAIRCRAFTACCIDENTSCAUSEDBYMICRO BURSTSANDSTRONGWINDSHEAR (AIL 4HE.EXRADRADARMAKESUSEOFAHAIL DETECTIONALGORITHMTHATCOMBINES AHIGHREFLECTIVITYFACTORWITHECHOHEIGHTANDUPPER LEVELDIVERGENTRADIALVELOCITY WINDSTODETECTTHEOCCURRENCEOFHAIL0OLARIMETRICRADARTECHNIQUESIMPROVEQUANTITA TIVEHAILDETECTION"RINGIETAL !YDINETAL AND)LLINGWORTHETALPROPOSEDA HAILDETECTIONTECHNIQUEUSINGDIFFERENTIALREFLECTIVITYMEASUREMENTS4HISTECHNIQUE DEPENDSUPONTHEFACTTHATFORTUMBLINGHAILTHEDIFFERENTIALREFLECTIVITY THERATIOOF HORIZONTAL TO VERTICAL REFLECTIVITY IS NEAR UNITY y D" 4HIS DIFFERS SHARPLY FROM HEAVYRAIN WHERETHISRATIOCANBEASLARGEASD"BECAUSELARGEWATERDROPLETSARE HORIZONTALLY ORIENTED 4HE COMBINATION OF ABSOLUTE REFLECTIVITY FACTOR AND THE DUAL POLARIZATIONDIFFERENTIALREFLECTIVITYGIVESUNIQUESIGNATURESFORHAILANDHEAVYRAIN EACHOFWHICHISCHARACTERIZEDBYAHIGHREFLECTIVITYFACTOR4HEDIFFERENCEINTHEDIFFER ENTIALREFLECTIVITYSIGNATURESISEASILYEXPLAINED,ARGERAINDROPSASSUMEFLATTERSHAPES APPROXIMATED BY OBLATE SPHEROIDS AS THEY FALL AND THUS SCATTER BACK THE HORIZON TALLYPOLARIZEDELECTRICFIELDMORESTRONGLYTHANTHEVERTICALLYPOLARIZEDELECTRICFIELD (AILSTONES HAVINGANIRREGULARSHAPE PHYSICALLYTUMBLEWHILETHEYFALLAND THEREFORE EXHIBITNOPREFERREDORIENTATIONONAVERAGE4HUS THEHORIZONTALANDVERTICALSCATTERED FIELDSHAVENEARLYTHESAMEAVERAGEVALUE 7IND-EASUREMENT ,HERMITTEAND!TLASWERETHEFIRSTTOSHOWHOWASINGLE DOPPLERRADARCANBEUSEDTOMEASUREVERTICALPROFILESOFTHEHORIZONTALWINDFIELDWHEN PRECIPITATIONISPRESENT4HISTECHNIQUEISMOSTACCURATEIFTHEWINDFIELDISUNIFORMIN THEREGIONSCANNEDBYTHERADAR4HEMETHODDEPENDSUPONANANALYSISOFTHERADIAL VELOCITY MEASURED DURING A COMPLETE SCAN IN AZIMUTH WITH A SINGLE FIXED ELEVATION ANGLE!TANYSLANTRANGER THEHEIGHTOFTHEMEASUREMENTISRSIN@ANDTHERADIUSOF THEREGIONSCANNEDISRCOS@ WHERE@ISTHEELEVATIONANGLEASDEPICTEDIN&IGURE )FAISTHEAZIMUTHANGLE 6HISTHEHORIZONTALWINDSPEED AND6FISTHEFALLSPEEDOFTHE PARTICLES THENTHERADIALVELOCITYATRANGERISGIVENBY
6RA 6HCOSACOS@ 6FSIN@
!HARMONICANALYSISLEASTSQUAREFITTINGTHEAMPLITUDE PHASE ANDOFFSETOFASINU SOID CANBEUSEDTOOBTAIN6H THEHORIZONTALWINDSPEED THEWINDDIRECTIONWHERECOS AISMAXIMUM AND6F THEMEANPARTICLEFALLSPEEDALLPLOTTEDASAFUNCTIONOFHEIGHT 4HISTECHNIQUEISREFERREDTOASTHE6ELOCITY !ZIMUTH $ISPLAY6!$ "ROWNINGAND 7EXLERLATERSHOWEDHOWTHE6!$TECHNIQUECOULDBEEXTENDEDTOMEASUREOTHER PARAMETERSOFTHEWINDFIELDINCLUDINGWIND FIELDDIVERGENCEANDWIND FIELDDEFORMA TIONBYEMPLOYINGANEXTENDEDHARMONICOR&OURIERSERIESANALYSIS4HE6!$HASBEEN IMPLEMENTEDONTHE.EXRADASASTANDARDPRODUCTTHATCANBEUSEDINPRECIPITATIONAND
£°ÎÓ
2!$!2(!.$"//+
&)'52% 6ELOCITY !ZIMUTH $ISPLAY GEOMETRY FOR MEASURING HORIZONTAL WIND WITH A SINGLE DOPPLER RADAR -EASUREMENTOFTHERADIALVELOCITYFORACOMPLETEAZIMUTHAL SCAN A AT ELEVATION ANGLE @ PERMITS AN ESTIMATE OF THE VERTICAL PROFILE OF HORIZONTAL WINDS #OURTESY OF 5NIVERSITY #ORPORATIONFOR!TMOSPHERIC2ESEARCHÚ "OULDER #/
FREQUENTLYINCLEARAIR4HE6!$TECHNIQUEISMOSTOFTENAPPLIEDTOWINDPROFILERRADARS THATPOINTVERTICALLYANDSTEPSCANATRELATIVELYLARGEELEVATIONANGLES!NALTERNATIVE DETERMINATIONOFBOUNDARYLAYERWINDFIELDSUSINGASINGLEWEATHERRADARHASFOUND SUCCESSUSINGANECHOTRACKINGTECHNIQUE 4HUNDERSTORM0REDICTION 7ILSONAND3CHREIBERILLUSTRATEHOWMETEOROLOGI CALDOPPLERRADARCANBEUSEDTODETECTLOCATIONSWHERENEWTHUNDERSTORMDEVELOP MENT IS LIKELY TO OCCUR -ANY WEATHER RADARS HAVE SUFFICIENT SENSITIVITY TO DETECT DISCONTINUITIESOFCLEARAIRECHOESINTHELOWERTOKMOFTHEATMOSPHEREOUTTO OR KM4HIS DETECTION OCCURS PRINCIPALLY IN THE SUMMER MONTHS WHEN THE BACKSCATTERINGMECHANISMISCAUSEDBYINSECTSINTHELOWERLEVELSOFTHEATMOSPHERIC BOUNDARYLAYERANDSOMETIMESMAYALSOBEDUETO"RAGG SCATTEREDREFRACTIVEINDEX INHOMOGENEITIES7ILSONAND3CHREIBERHAVEFOUNDTHATABOUTOFTHETHUNDER STORMS THAT OCCUR IN THE &RONT 2ANGE OF THE 2OCKIES IN THE SUMMERTIME DEVELOP OVERSUCHhBOUNDARIESvBETWEENTWODIFFERENTAIRMASSES3INCETHESEBOUNDARIES CANBEDETECTEDBEFOREANYCLOUDSAREPRESENTANDITISPOSSIBLETOINFERTHEAIRMASS CONVERGENCE OR COMING TOGETHER OF TWO AIR MASSES WHERE INSECTS ARE FORCED TO ACCUMULATE ALONG THESE BOUNDARIES BY DOPPLER RADAR MEASUREMENTS MORE PRECISE PREDICTIONOFTHUNDERSTORMOCCURRENCEISPOSSIBLE&ROMTHERADARDESIGNERSSTAND POINT SUCHAPPLICATIONSDICTATETHEUSEOFANTENNASWITHVERYLOWSIDELOBESALONG WITHLOW PHASENOISETRANSMITTERSANDRECEIVERCOMPONENTS ANDSIGNALPROCESSORS HAVINGSIGNIFICANTGROUNDCLUTTERREJECTIONCAPABILITY4HE.EXRADRADARSYSTEM WITH ITSHIGHQUALITYANTENNAANDD"OFCLUTTERREJECTION ISWELLSUITEDTOTHISIMPORTANT OPERATIONALTASK 2EFRACTIVITY AND7ATER 6APOR -EASUREMENTS #ONVENTIONAL WEATHER RADAR PRO CESSINGISGENERALLYDESIGNEDTOEMPHASIZEPRECIPITATIONANDWIND FIELDMEASUREMENTS
-%4%/2/,/')#!,2!$!2
£°ÎÎ
ANDTOSUPPRESSGROUNDCLUTTER(OWEVER ITISKNOWNTHATRADARBEAMBENDINGCAUSED BY ATMOSPHERIC REFRACTION AND THE RESULTING ANOMALOUSLY PROPAGATED GROUND CLUTTER ECHOGIVESANINDICATIONOFTHEVERTICALPROFILESOFTEMPERATUREANDMOISTUREINTHE INTERVENING LOWER ATMOSPHERE -OREOVER MEASURING THE PROPAGATION SPEED OF THE RADAR PULSE BETWEEN NORMALLY PROPAGATED CLUTTER TARGETS THOSE DIRECTLY VIEWED BY THERADAR GIVESANESTIMATEOFTHEREFRACTIVEINDEXOFAIRALONGTHISPROPAGATIONPATH "YMEASURINGTHEABSOLUTEPHASEOFTHERADARSIGNALRECEIVEDFROMSTATIONARYGROUND CLUTTERTARGETSANDCOMPARINGTHEMWITHREFERENCEABSOLUTEPHASEMEASUREMENTSUNDER KNOWN REFRACTIVE CONDITIONS ONE CAN MEASURE THE NEAR SURFACE PROPAGATION SPEEDS OFTHERADARPULSEALONGTHESEPATHS4HEN THEREFRACTIVEINDEX ORREFRACTIVITY OFTHE ATMOSPHEREOFTHESEATMOSPHERICPATHSMAYBEDETERMINED2EFRACTIVITYISAFUNC TION OF TEMPERATURE PRESSURE AND MOISTURE CONTENT #ONSEQUENTLY IF SURFACE TEM PERATURE AND PRESSURE ARE INDEPENDENTLY AVAILABLE AS THEY FREQUENTLY ARE THEN THE REFRACTIVEINDEXMEASUREMENTSMAYBECONVERTEDTOSPATIALFIELDSOFWATERVAPORINTHE SURFACE BOUNDARY LAYER 3UCH WATER VAPOR MEASUREMENTS ARE CRITICAL FOR OBTAINING ACCURATEFORECASTSUSINGNUMERICALMODELSANDSIMULATIONSOFTHEATMOSPHERE4HIS EXPERIMENTALMEASUREMENTTECHNIQUECANBEUSEDTORANGESOFABOUTKMWHERETHE %ARTHSCURVATUREPREVENTSROUTINEOBSERVATIONOFGROUNDCLUTTERTARGETSANDISBEING CONSIDEREDFOROPERATIONALUSEIN.EXRAD
£°ÈÊ , - , Ê** /" /PERATIONALMETEOROLOGICALRADARSAREDESIGNEDFORRELIABILITYANDSIMPLICITYOFOPERA TIONWHILEPROVIDINGTHEPERFORMANCENEEDEDFOROPERATIONALAPPLICATIONS2ESEARCH RADARS ARE CONSIDERABLY MORE COMPLEX SINCE CUTTING EDGE RESEARCH REQUIRES MORE DETAILED AND MORE SENSITIVE MEASUREMENTS OF A MULTIPLICITY OF VARIABLES SIMULTANE OUSLY)NTHERESEARCHCOMMUNITY MULTIPLE PARAMETERPOLARIZATIONANDWAVELENGTH RADARSTUDIES MULTIPLEDOPPLERRADARNETWORKSTUDIES ANDANEWGENERATIONOFAIRBORNE ANDSPACEBORNERADARSARERECEIVINGCONSIDERABLEATTENTION $UAL 0OLARIZATION7AVELENGTH 2ADAR )T IS CLEAR THAT POLARIMETRIC DOPPLER RADARS PROVIDE A SIGNIFICANT INCREASE IN THE USEFUL INFORMATION THAT CAN BE OBTAINED FROM METEOROLOGICAL TARGETS 4HE DETECTION OF HAIL AND MORE ACCURATE RAINFALL ESTI MATES HAS PRIMARY SIGNIFICANCE $UAL POLARIZATION MEASUREMENTS AT MULTIPLE WAVE LENGTHS PROVIDE EVEN MORE INFORMATION RELATED TO THE EVENTUAL INTERPRETATION OF THE SIZEDISTRIBUTIONS WATER PHASESTATES ANDHYDROMETEORWATERORICEPARTICLES TYPES INDIFFERENTCLASSESOFPRECIPITATIONANDCLOUDS4HECAPABILITIESOFMULTIPLE PARAMETER METEOROLOGICALRADARSAREPRESENTEDIN"RINGIAND(ENDRY "RINGIAND#HANDRA AND INTHECOLLECTIONOFPAPERSEDITEDBY(ALL7HEREASLONGER WAVELENGTHRADARSARE NECESSARYFORTHESTUDYOFSEVERESTORMS SHORTERWAVELENGTHMILLIMETER WAVERADARS AREUSEFULFORSENSINGANDPROBINGNEWLYDEVELOPINGCLOUDS2ESEARCHERSOFTENNEED AWIDERANGEOFTHESECAPABILITIESSIMULTANEOUSLY&ROMTHERADARENGINEERINGSTAND POINT THE CHALLENGE IS CONSIDERABLE REQUIRING RADAR DESIGNERS TO DEVELOP COHERENT WAVEFORM POLARIZATION DIVERSE ANDWAVELENGTH DIVERSERADARS!SNOTED THEREEXIST SEVERALPOLARIMETRICRESEARCHRADARSANDOPERATIONALRADARSINTHEWORLD -ULTIPLE2ADARS !SINGLEDOPPLERRADARMEASURESONLYASINGLERADIALCOMPO NENTOFVELOCITY,HERMITTEWASAMONGTHEFIRSTTODESCRIBEHOWTWOORMOREDOPPLER RADARSCOULDBEUSED SCANNINGTOGETHER TOOBTAINTHEFULLTHREE DIMENSIONALAIRMOTION
£°Î{
2!$!2(!.$"//+
FIELDSINPRECIPITATION4HISPIONEERINGWORKLEDTHEWAYTOWARDTHEUSEOFNETWORKS OFDOPPLERRADARSFORSTUDIESOFINDIVIDUALCLOUDSTOEXAMINETHETHREE DIMENSIONAL STRUCTUREOFVECTORAIRMOTIONINPRECIPITATION!POINTSHOULDBEMADEHEREREGARDING THEUSEOFTWODOPPLERRADARSFORMEASUREMENTSOFTHREE DIMENSIONALWINDS3INCE INPRINCIPLE TWOINDEPENDENTLOOKSCANMEASUREONLYTWOCOMPONENTSOFVECTORAIR MOTION THEASSUMPTIONOFATMOSPHERICMASSCONTINUITYISINVOKED4HISEQUATIONOF MASSCONTINUITY 6 ISUSEDTOOBTAINTHETHIRD DIMENSIONALCOMPONENT WHERE 6 ISTHEVECTORAIRMOTIONANDISCONSTRAINEDTOBEZEROATTHESURFACE4HEVERTICALAIR MOTIONISCALCULATEDFROMVERTICALINTEGRATIONOFTHEMASSCONTINUITYEQUATION &IGUREILLUSTRATESANAIRMOTIONFIELDOBTAINEDBYTWODOPPLERRADAROBSERVA TIONSINANINDIVIDUALCONVECTIVESTORMCELL3HOWNARETHEHORIZONTALVECTORFIELDSIN APLANEAPPROXIMATELYMABOVETHESURFACE4HEPHENOMENONBEINGMEASUREDIS ALOW LEVELDIVERGENTOUTFLOWORMICROBURST JUSTTORIGHTOFTHECENTER&IGURE SHOWSANOTHEREXAMPLEOFPRECIPITATIONINTENSITYANDAIRMOTIONFIELDSSUPERPOSEDON APHOTOGRAPHOFACONVECTIVETHUNDERSTORMCELL4HEDATAARETAKENFROMTHREEDOPPLER RADARSSPACEDABOUTKMAPART !DEVELOPINGNETWORKOFSHORTRANGEDOPPLERRADARSNOTRANGELIMITEDBYTHE%ARTHS CURVATUREWILLPROVIDEMOREDETAILEDOBSERVATIONSCLOSETOTHESURFACETHANTHERELA TIVELYWIDELYSPACED732 $NETWORK4HE#OLLABORATIVE !DAPTIVE3ENSINGOFTHE !TMOSPHERE#!3! RADARNETWORKWILLINCLUDEMANYINEXPENSIVE LOWPOWER SCAN NING SHORTWAVELENGTHRADARSMOUNTEDONTOWERSOFOPPORTUNITY PRIMARILYCELLPHONE TOWERSTHATBLANKETMUCHOFTHE53 %XISTINGEQUIPMENTONTHESETOWERSWILL
&)'52% 6ECTOR WIND FIELDS IN A HORIZONTAL PLANEDERIVEDFROMDUAL DOPPLERRADAROBSERVATIONSOFA SUMMERTIMECONVECTIVESTORMNEAR$ENVER #OLORADO 4HEDARK SOLIDLINEISSHOWNTOINDICATETHELENGTHOFA TYPICALJETAIRCRAFTRUNWAY4HEDIVERGENTOUTFLOWFROM A MICROBURST SHOWS A STRONG MS HEADWIND CHANG INGTOASIMILARLYSTRONGTAILWINDOVERTHELENGTHOFTHE RUNWAY #0 IS THE FORMER RESEARCH RADAR OPERATED BY .#!2 #OURTESY OF 5NIVERSITY #ORPORATION FOR !TMOSPHERIC2ESEARCHÚ "OULDER #/
-%4%/2/,/')#!,2!$!2
£°Îx
&)'52% 2ADAR REFLECTIVITY CONTOURS AND AIRFLOWVECTORSSUPERPOSEDONPHOTOGRAPHOFARAP IDLY GROWING!LABAMA THUNDERSTORM CELL 4HE DATA DEPICTSAMSUPDRAFTORIGINATINGINANEXTREMELY STRONGD":RAINORHAILCORE4HEWINDVECTORSARE TAKENFROMCOMBININGDATAFROMTHREENEARBYDOP PLER RADARS #OURTESY OF !MERICAN -ETEOROLOGICAL 3OCIETY&ROM$%+INGSMILLAND2-7AKIMOTO h+INEMATIC $YNAMIC AND4HERMODYNAMIC!NALYSIS OF A 7EAKLY 3HEARED 3EVERE 4HUNDERSTORM OVER .ORTHERN !LABAMA v -ONTHLY 7EATHER 2EVIEW VOL P
PROVIDEASHAREDINFRASTRUCTUREFORTHE#!3!RADARS4HISRADARSYSTEMWILLINCLUDE INTELLIGENTDECISIONMAKINGFORSCANNINGANDTRACKINGIMPORTANTLOW LEVELATMOSPHERIC FEATURESTHATAREDEEMEDCRITICALFORTHEAVIATION WEATHERFORECASTING TRANSPORTATION ANDLOCALEMERGENCYRESPONSEUSERS4HE#!3!RADARSCANCOMMUNICATEWITHEACH OTHERFORCOLLABORATIVEUSEOFTHEDATAANDADAPTIVELYCHANGETHEIROPERATINGPARAM ETERSTOBESTMEETTHEPRESCRIBEDNEEDSATAGIVENTIME$EPENDINGONTHEFINALCOSTS OFDEPLOYMENTANDOPERATION #!3!NETWORKSMAYBEDEVELOPEDONLYAROUNDCRITICAL AREASSUCHASURBANAREAS AIRPORTS ETC 2APID3CAN0HASED!RRAY 2ADAR $OPPLERWEATHERRADARSTHATUSEPHASEDARRAY ANTENNASANDCOMPLEXWAVEFORMDESIGNMAYBEAPPLIEDTOSOMEOFTHEMOREDIFFICULT RADARMETEOROLOGYOBSERVATIONS4HEUSEOFMULTIPLEDOPPLERRADARSHASPROVIDEDDRA MATICNEWINFORMATIONONTHEINTERNALWINDSINLARGEPRECIPITATINGSYSTEMSINFORMATION THATCANBEOBTAINEDINNOOTHERWAY$ESPITETHEPOWEROFTHISTECHNIQUE THESPATIAL RESOLUTION IN THE DERIVED THREE DIMENSIONAL MOTION FIELDS IS GENERALLY NOT BETTER THAN
£°ÎÈ
2!$!2(!.$"//+
OFTHEORDEROFKM4HEREARESEVERALREASONSFORTHIS4HEFINITEBEAMWIDTHLIMITSTHE RESOLUTIONAVAILABLEATLONGERRANGES!TSHORTERRANGES THELARGESOLIDANGLETHATMUST BESCANNEDINORDERTOCOVERALLREGIONSOFASTORMREQUIRESTOTALSCANNINGTIMESOFTHE ORDEROFTOMINEVENFORWELL SITUATEDSTORMS4HISISACONSEQUENCEOFTHEON TARGET DWELLTIMENECESSARYFORACCURATEMEASUREMENTS&INALLY THESTORMITSELFISEVOLVINGAND MOVINGDURINGTHISMEASUREMENTTIME THUSCOMPLICATINGTHEDATAREGISTRATIONINSPACE ANDTIME 3OME OPERATIONAL AND MANY RESEARCH APPLICATIONS REQUIRE FASTER SCANNING THAN CONVENTIONALMECHANICALLYSCANNEDRADARSCANPROVIDE4HESEAPPLICATIONSINCLUDE LONGERLEADTIMESFORTORNADOWARNINGS THESTUDYOFFINERSCALESTORMFEATURES INTERAC TIONSBETWEENTHEINTERNALMOTIONSANDHYDROMETEORGROWTHPROCESSESINTHESTORMS ANDSTUDIESOFELECTRICCHARGESEPARATIONINCLOUDS"ROOKAND+REHBIELWEREAMONG THEFIRSTTODISCUSSAVERYRAPID SCANNINGRADARALTHOUGHNONDOPPLER FOREFFECTIVELY OBTAININGSNAPSHOTSOFCONVECTIVESTORMS+EELERAND&RUSHDISCUSSDESIGNCONSID ERATIONSFORAMORECAPABLERAPID SCANNINGDOPPLERRADAR !NYRAPID SCANNINGAPPROACHGENERALLYMUSTENCOMPASSTWOFEATURES THETRANS MITWAVEFORMMUSTHAVEARELATIVELYLARGEBANDWIDTHTOINCREASETHENUMBEROFINDE PENDENTSAMPLESAVAILABLEINTHEDESIREDSPATIALRESOLUTIONCELLAND THEANTENNAMUST BERAPIDLYSCANNEDTHROUGHOUTTHEDESIREDATMOSPHERICVOLUMEEITHERMECHANICALLYOR ELECTRONICALLY-ECHANICALLYSCANNEDSINGLEFREQUENCYSTANDARD WEATHERRADARSUSEA LONGDWELLTIMETOACQUIREANADEQUATENUMBEROFINDEPENDENTSAMPLESTOACCURATELY ESTIMATE THE SPECTRAL MOMENT DATA USED FOR METEOROLOGICAL MEASUREMENTS! LARGE BANDWIDTHSYSTEMEG PULSECOMPRESSIONRADAR CANACQUIREINDEPENDENTSAMPLESIN RANGEINASHORTDWELLTIMETHATCANBEAVERAGED THUSREDUCINGTHEDWELLTIMEFOREACH BEAMANDREDUCINGTHETOTALVOLUMECOVERAGESCANTIME&ASTMECHANICALSCANNING DEGSEC PRODUCESDELETERIOUSSPECTRUMBROADENINGEFFECTSTHATELECTRONICSTEP SCANNINGEASILYAVOIDSSINCETHEBEAMISFIXEDINSPACEDURINGTHEDWELLTIME!FAVORED APPROACHISTOUTILIZEAONE DIMENSIONALPHASEDARRAYTHATISELECTRONICALLYSCANNEDIN ELEVATIONWHILESLOWLYROTATINGINAZIMUTH)NTHISWAY AFULLHEMISPHERICVOLUME CANBECOVEREDINnMINUTESANDSMALLERSECTORVOLUMESMAYBECOVEREDINLESSTHAN MINUTE3EVERALMILITARYRADARSANDAVIATIONRADARSUTILIZEELECTRONICALLYSCANNED BEAMSBUTTHEEXPENSEOFAFULLYCAPABLESYSTEMHASPREVENTEDMORETHANONLYAFEW METEOROLOGICAL RADAR SYSTEMS FROM BEING DESIGNED AND BUILT 2APID SCANNING PHASEDARRAYRADARSHAVEALSOBEENSTUDIEDEXTENSIVELYIN%UROPE !NALTERNATIVEAPPROACHISTOEMPLOYDIGITALBEAMFORMINGORFREQUENCY STEERING TECHNIQUES TO TRANSMIT AND SIMULTANEOUSLY RECEIVE MULTIPLE BEAMS USING PARALLEL RECEIVERS3UCHMILITARYRADARSHAVEBEENOPERATEDFORSEVERALDECADESBUTNONEOF THESESYSTEMSWEREEVERDESIGNEDORUSEDFORWEATHERMEASUREMENTS!MECHANICALLY SCANNEDMULTIPLEBEAMWEATHERRADARSYSTEMUSINGSIMULTANEOUSFREQUENCYSCANNED BEAMS HAS BEEN DESIGNED AND CONSTRUCTED ON A SMALL TRUCK4HE 2APID $OPPLER ON 7HEELS2APID $/7 8 BANDRADAR SHOWNIN&IGURE USESSIXSIMULTANEOUS FREQUENCY STEEREDBEAMSSEPARATEDBYAFEWDEGREESEMANATINGFROMASLOTTEDWAVE GUIDE PHASED ARRAY AND INDEPENDENT RECEIVERS TO ACQUIRE A VOLUMETRIC COVERAGE OF CONVECTIVESTORMSINnMINUTES0ULSECOMPRESSIONISNOTUSED4HERAPIDDATA ACQUISITIONSPEEDOFTHISSYSTEMHASTHEPOTENTIALTOGIVENEWINSIGHTSINTOTHUNDER STORMEVOLUTION HURRICANESATLANDFALL HAILFORMATIONPLUSMICROBURST GUSTFRONTAND TORNADOGENESISMECHANISMSTHATMAYLIKELYEVOLVEINTOANOPERATIONALCAPABILITY )NTHEEARLYS THE&!!LEDANEFFORTTODEVELOPDUAL USEWEATHERANDAIRCRAFT SURVEILLANCERADARBASEDONELECTRONICSCANNINGANDPULSECOMPRESSIONTECHNIQUES
-%4%/2/,/')#!,2!$!2
£°ÎÇ
&)'52% 2APID $/7$OPPLERON7HEELS ISAMOBILE8 BANDRADAR THATUSESSIXSIMULTANEOUSBEAMSTOCOVERAVOLUMEOFATMOSPHEREINAMUCH SHORTERVOLUMECOVERAGETIMETHANAMECHANICALLYSCANNEDSINGLEBEAMRADAR 4HISRAPIDUPDATESCANISIMPORTANTFORMEASURINGVIOLENTCONVECTIVESTORMS ESPE CIALLYTORNADOESASSHOWNINPHOTO0HOTOCOURTESYOF5NIVERSITY#ORPORATION FOR!TMOSPHERIC2ESEARCHÚ "OULDER #/
AND AN EFFORT BEGINNING A DECADE LATER CONTINUED THE DEVELOPMENT OF PHASED ARRAY RADARS FOR CIVIL APPLICATIONS 2ADARS INITIALLY DESIGNED FOR MILITARY APPLICATIONS WEREMODIFIEDFORWEATHERDETECTIONANDSUCCESSFULLYDEMONSTRATEDTHECONCEPT)N THEEARLYS AJOINTEFFORTBETWEENTHE53.AVY THE.ATIONAL7EATHER3ERVICE THE.ATIONAL3EVERE3TORMS,ABORATORY ANDTHE5NIVERSITYOF/KLAHOMALEDTOTHE DEVELOPMENT OF THE SO CALLED .ATIONAL 7EATHER 2ADAR 4ESTBED FACILITY IN .ORMAN /KLAHOMA BYCOMBININGASINGLEPANEL309 PHASEDARRAYRADARONAROTATINGPEDES TALWITHA732 $TRANSMITTERANDCUSTOMRECEIVER!LTHOUGHTHISPARTICULARRADAR ISNOTLIKELYTOBETHEPREFERREDDESIGNFORAFUTUREWEATHERRADAR THE/KLAHOMA0HASED !RRAY2ADARTESTBEDCANBEUSEDTOEXPLOREELECTRONICSCANNINGSTRATEGIESTOGETHERWITH NEWPULSINGANDPROCESSINGCONCEPTSTHATMAYLEADTOFUTUREDEVELOPMENTOFAPHASED ARRAYWEATHERRADARSYSTEM !IRBORNE 2ADARS 7HEREAS COMMERCIAL AVIATION WEATHER RADARS ARE NOSE MOUNTED8 BANDRADARSFORSEVEREWEATHERANDTURBULENCEDETECTIONANDAVOIDANCE AIRBORNERESEARCHRADARSMUSTHAVERELATIVELYMORECOMPLEXARCHITECTURESINORDERTO MAKEMORESENSITIVE HIGH RESOLUTIONMEASUREMENTS4HISPOWERFULTECHNIQUEPERMITS THEUSEOFAMOBILEPLATFORM WHICHTHEREFOREALLOWSMEASUREMENTSOVERREGIONSNOT ACCESSIBLEBYGROUND BASEDSYSTEMS-OREOVER THEMOBILITYOFTHEAIRCRAFTPERMITS LONGERTERMOBSERVATIONSOFRAPIDLYMOVINGBUTLONG LIVEDSTORMSANDCLOUDSYSTEMS THEREBY ALLOWING MORE COMPLETE STUDIES OF EVOLUTION DURING VARIOUS PHASES OF THE SYSTEM .#!2S%LDORAAIRBORNEDOPPLERRADARSYSTEM SHOWNIN&IGURE CONSISTS OF TWO SLOTTED WAVEGUIDE FIXED BEAM ANTENNAS MOUNTED IN THE TAIL OF THE 0 AIR CRAFT WHICHISOPERATEDBYTHE.AVAL2ESEARCH,ABORATORYANDCOVEREDBYAROTATING
£°În
2!$!2(!.$"//+
&)'52% 4AIL MOUNTED%,$/2!DOPPLERWEATHERRADAR OPERATED BY THE .ATIONAL #ENTER FOR!TMOSPHERIC 2ESEARCH ON THE.AVAL2ESEARCH,ABORATORY0 RESEARCHAIRCRAFT#OURTESY OF 5NIVERSITY #ORPORATION FOR !TMOSPHERIC 2ESEARCH Ú "OULDER #/
RADOMEAROTO DOME/NEBEAMPOINTSFORWARDABOUTnANDTHEOTHERAFTBYTHE SAMEANGLE THEREBYOBTAININGTWORADIALCOMPONENTSOFCOMMONTARGETVOLUMES7ITH SUCHASYSTEM EACHANTENNASCANSINACONICALSURFACEONECONEPOINTINGFORWARD THE OTHER ONE REARWARDTHUS PERMITTING SYNTHESIS OF A DUAL DOPPLER RADAR SYSTEM ALONGTHEAIRCRAFTTRACK4HEAIRCRAFTISFLOWNALONGSIDESTORMSTOSYNTHESIZEDUAL DOP PLEROBSERVATIONSAND THEREFORE TOOBTAINVECTORWINDS"ECAUSETHEAIRCRAFTNEEDNOT FLYORTHOGONALTRACKS THETIMEREQUIREDFORMEASUREMENTSOFCLOUDSYSTEMSISDRAMATI CALLYREDUCEDASARETHEERRORSINTHESEMEASUREMENTS-OREOVER SEVERESTORMSWHICH COULDOTHERWISENOTBEPENETRATEDALONGANORTHOGONALTRACK ANDHURRICANESWHICH CANBEPENETRATEDBYSUCHAIRCRAFT CANBEOBSERVEDFULLYBYANAIRCRAFTOUTSIDETHE REGIONSOFSEVEREWEATHER 6ARIOUSAIRBORNERADARSEXISTINTHERESEARCHCOMMUNITYFORDIFFERENTAPPLICATIONS ANDUSERGROUPS.!3!HASDEVELOPEDTHEDUALWAVELENGTHCMANDMM %$/0 RADARFORTHEHIGHALTITUDE%2 AIRCRAFTANDA7 BAND '(ZAIRBORNECLOUDRADAR FORTHE$# RESEARCHAIRCRAFT./!!HASOPERATEDTWO8 BANDRADARSSIMILARTO THE%,$/2!RADARFORHURRICANETRACKINGANDRESEARCH*0,DEVELOPEDTHE!2-!2 RADARTOTESTSPACERADARCONCEPTSFORTHE4ROPICAL2AINFALL-EASUREMENTS-ISSION 42-- 4HE5NIVERSITYOF7YOMINGUSESA MMCLOUDRADARMOUNTEDONA+ING !IRAIRCRAFT)NTHEMID S .#!2ACQUIREDTHE(IGH PERFORMANCE)NSTRUMENTED !IRBORNE0LATFORMFOR%NVIRONMENTAL2ESEARCH(!)0%2 A'ULF3TREAM' MEDIUM SIZEJETAIRCRAFT ANDDESIGNEDADUALWAVELENGTHANDMM REMOVABLEPOD MOUNTED RADARFORCLOUDSTUDIES4HE#ANADIAN.ATIONAL2ESEARCH#OUNCILHASDEVELOPEDA SIMILARAIRBORNERADARSYSTEM 3PACEBORNE2ADARS !MONGTHEMORESIGNIFICANTCHALLENGESFACINGRESEARCHERS TODAYISTHENEEDTOMAKEGLOBALMEASUREMENTSOFPRECIPITATION5NDERSTANDINGGLOBAL CLIMATEREQUIRESTHATQUANTITATIVEMEASUREMENTSOFPRECIPITATIONBEMADETHROUGHOUT THEWORLD PARTICULARLYINTHETROPICSANDOVERTHEOCEANS3ATELLITEOBSERVATIONSAPPEAR
-%4%/2/,/')#!,2!$!2
£°Î
TOOFFERTHEONLYPRACTICALMECHANISMFOROBTAININGTHESEMEASUREMENTS4HE42-- SATELLITE WAS LAUNCHED IN CARRYING THE +U BAND SINGLE FREQUENCY 0RECIPITATION 2ADAR02 ANDAMSINGLEBEAMARRAYANTENNATHATISSTEEREDnONEITHERSIDE OFTHESPACECRAFTTRACK)TSRELATIVELYLOWINCLINATIONORBITATKMALTITUDEPROVIDES TROPICALPRECIPITATIONMEASUREMENTSWITHMRANGERESOLUTIONANDAKMFOOT PRINT OVER A KM SWATH!42-- FOLLOW ON PROGRAM THE 'LOBAL 0RECIPITATION -EASUREMENT '0- PROGRAM ENVISIONS EXTENDING PRECIPITATION COVERAGE TO THE MID LATITUDEn.AND3LATITUDE FLYINGINAKMALTITUDEORBITANDUSINGDUAL WAVELENGTHPRECIPITATIONRADAR$02 AT+UAND+ABANDSFORMOREACCURATERAINFALL ESTIMATESUSINGATTENUATIONTECHNIQUES 4HETWORADARSWILLHAVEMATCHEDBEAMS FROMTWOSLOTTEDWAVEGUIDEARRAYANTENNASANDPROVIDECOVERAGEUNDERTHESPACECRAFT TRACKSIMILARTO42-- #LOUD3ATISASATELLITELAUNCHEDINFLYINGA7BANDMM CLOUDPROFILING RADAR #02 ORBITING THE %ARTH IN A SUN SYNCHRONOUS ORBIT AT AN ALTITUDE OF ABOUT KM 4HE TRANSMITTER IS AN %XTENDED )NTERACTION +LYSTRON %)+ HIGH POWER AMPLIFIERGENERATINGALSECMONOCHROMATICPULSEHAVINGPEAKPOWEROFK7 4HEANTENNAISAMDIAMETERREFLECTOROFFSETFEDBYAQUASI OPTICALTRANSMISSION LINE AND PRODUCES A n BEAM WITH EXTREMELY LOW SIDELOBES 4HESE RADAR DESIGN PARAMETERSALLOWANEXCEPTIONALSENSITIVITYOFnD":ATTHE%ARTHSURFACE#LOUD3AT ORBITSINFORMATIONWITHFOUROTHERSATELLITESASPARTOFTHESO CALLED! TRAINCONSTEL LATIONOFSATELLITESTHATPROVIDECOMBINEDRADAR LIDAR ANDRADIOMETRICMEASUREMENTS FOR%ARTHSTUDIES4HE#02ON BOARD#LOUD3ATHASMVERTICALRESOLUTIONWITHA KMFOOTPRINTANDISSIMILARTOTHE.!3!!IRBORNE#LOUD2ADARTHATHASFLOWNFOR SEVERALYEARSONBOARDTHE.!3!$# AIRCRAFT#OMBININGTHESEHIGH RESOLUTION CLOUDMEASUREMENTSWITHHIGHSENSITIVITYISONEOFTHETECHNICALGOALSFORACQUIRING NEWINFORMATIONREGARDINGCLOUDEFFECTONTHE%ARTHSCLIMATE #LEAR !IR 7IND 0ROFILING 2ADARS !NOTHER FORM OF DOPPLER RADAR THAT HAS BECOMEWIDELYUSED ESPECIALLYINTHERESEARCHCOMMUNITY ISTHESO CALLEDWINDPRO FILING RADAR OR hWIND PROFILERv7IND PROFILERS USUALLY TAKE THE FORM OF6(& AND 5(& MULTIPLE FIXED BEAM SYSTEMS POINTING VERTICALLY AND AT ANGLES APPROXIMATELY nFROMTHEZENITHTOINFERPROFILESOFTHEHORIZONTALWINDAVERAGEDOVERTHEAREAOF MEASUREMENT3UCHRADARSCANMAKEDOPPLERMEASUREMENTSTHROUGHOUTTHERANGEOF ALTITUDESFROMAFEWHUNDREDMETERSTOKMORMOREABOVETHESURFACE DEPENDING UPONTHEWAVELENGTHSELECTEDANDTHEPOWER APERTUREPRODUCTAVAILABLE4HESERADARS HAVE THE ABILITY TO MEASURE HIGH RESOLUTION WINDS CONTINUOUSLY WHICH PERMITS THE OBSERVATIONOFSMALLERSCALETEMPORALANDSPATIALWIND FIELDFEATURESTHATCANNOTBE OBTAINEDFROMTHEGLOBAL HOURRAWINSONDEBALLOONLAUNCH NETWORK4HESESMALLER SCALEMEASUREMENTSAREIMPORTANTFORUNDERSTANDINGLOCALANDREGIONALWEATHERAND FOREFFECTIVEFORECASTINGONTHESESCALES 6ERY POWERFUL RADARS OF THIS TYPE ARE REFERRED TO AS -ESOSPHERE 3TRATOSPHERE 4ROPOSPHERE-34 RADARSBECAUSEOFTHEIRABILITYTOMAKEMEASUREMENTSTHROUGHOUT MOSTOFTHESEATMOSPHERICREGIONSUPTOnKMINALTITUDE3EVERALMAJOR-34 RADARFACILITIESLOCATEDATFACILITIESAROUNDTHEWORLDOPERATEAT6(&FREQUENCIESAROUND -(ZANDOBSERVEUPPERATMOSPHERICTROPOSPHERICANDLOWERSTRATOSPHERIC WINDS ORTHEHIGHERLEVELSTRATOSPHERICANDMESOSPHERICWINDS3HORTERWAVELENGTH5(&WIND PROFILERSOPERATINGATn-(ZSENSEATMOSPHERICWINDSUPTOnKMANDTHESE hTROPOSPHERICWINDPROFILERSvARETHEMOSTWIDELYUSEDFOROPERATIONALWEATHEROBSER VATIONS5(&WINDPROFILERSOPERATINGAT-(ZINTHE53ANDn-(Z
£°{ä
2!$!2(!.$"//+
IN%UROPECOVERTHELOWERATMOSPHERICWINDSUPTOnKMORAFEWKMHIGHERWITH LARGER ANTENNAS WHERE THE STRONG MOISTURE FLUCTUATIONS PRESENT IN THE ATMOSPHERIC BOUNDARY LAYER PROVIDE STRONG SCATTERING SIGNATURES AT THESE SHORTER WAVELENGTHS 4HESE5(&BOUNDARY LAYERWINDPROFILERSARETYPICALLYUSEDFORAIRPOLLUTIONMONI TORINGANDWARNINGSASWELLASVARIOUSRESEARCHAPPLICATIONS 4HESECLEAR AIRRADARSRECEIVEENERGYBACKSCATTEREDFROMREFRACTIVEINDEXINHO MOGENEITIESCAUSEDBYNATURALLYOCCURRINGATMOSPHERICTURBULENCE4HEANTENNA SYSTEMS USUALLY TAKE THE FORM OF PHASED ARRAYS THAT FORM BEAMS SEVERAL DEGREES WIDETHATARESWITCHEDTO ORNEARLYVERTICALBEAMSFORnMINUTESEACHAND MEASUREVERTICALPROFILESOFWINDEVERYnMINUTES4HEANTENNASAREFREQUENTLY OFTHECOAXIALCOLLINEARCO CO STYLEFORTHOSERADARSAND9AGIARRAYELEMENTSFOR THOSEATTHEHIGHERFREQUENCIES4HEHIGHERFREQUENCY5(&PROFILERSTYPICALLYUSE EITHER9AGI OR MICROSTRIP PATCH ARRAY ANTENNAS 4RANSMITTERS ARE GENERALLY IN THE FORMOFHIGH POWERED COHERENTTRANSMITTINGTUBESORSOLID STATEAMPLIFIERS!TTHE 5NIVERSITYOF+YOTO *APAN THEANTENNA TRANSMITTERSYSTEMCONSISTSOFCROSSED 9AGIRADIATINGELEMENTS EACHWITHITSOWNSOLID STATETRANSMITTER4HISAPPROACH ALLOWS FOR VERY FLEXIBLE ELECTRONIC SCANNING OF THE BEAM ./!! OPERATES A NET WORKOFOVERTHIRTYAND-(ZWINDPROFILERSINTHECENTRAL5NITED3TATES USINGSOLID STATETRANSMITTERSTHATSUPPLYCONTINUOUSWINDPROFILESUPTOKMFOR IMPROVED WEATHER FORECASTS AND CURRENT UPPER AIR WIND INFORMATION FOR AVIATION APPLICATIONS )T IS IMPORTANT TO RECOGNIZE THAT THREE BEAM DOPPLER SYSTEMS CAN ACCURATELY MEASUREHORIZONTALWINDSINALLTHREEVELOCITYCOMPONENTSIFTHEWINDISUNIFORM &OUR AND FIVE BEAM SYSTEMS ALLOW ONE TO DETERMINE THE QUALITY OF THE MEASURE MENTSBYDETECTINGTHEPRESENCEOFANONUNIFORMWINDFLOW#ARBONE 3TRAUCH AND (EYMSFIELD AND 3TRAUCH ET AL ADDRESS THE ISSUE OF WIND MEASUREMENT ERROR INDETAIL4HEREADERISREFERREDTOTHEREVIEWPAPERBY2TTGERAND,ARSENFORA THOROUGHTREATMENTOFWIND PROFILERTECHNOLOGYANDTOTHESEQUENCEOF4ROPOSPHERIC 0ROFILING3YMPOSIAFORTROPOSPHERICPROFILINGAPPLICATIONSOFWINDSANDOTHERMETE OROLOGICALPARAMETERS 3PACED!NTENNA4ECHNIQUES !NADDITIONALADVANTAGEOFTHESELONGWAVELENGTH RADARSISTHEIRABILITYTOMEASURENOTONLYTHERADIALVERTICALWINDCOMPONENTSDIRECTLY BUT ALSO THE MEAN HORIZONTAL WIND THAT IS TRANSVERSE TO THE VERTICAL BEAM WITHOUT SCANNINGTHATBEAMOFFZENITH4HESEPROFILERSUSETHESO CALLEDSPACEDANTENNATECH NIQUES WITH MULTIPLE RECEIVERS TO PROCESS THE AMPLITUDE AND PHASE DIFFERENCES OF THEECHOSTRUCTURESASTHEYTRANSLATEOVERTWOADJACENTANTENNASUSUALLYSUBARRAYS OF THE SAME ARRAY ANTENNA TO MEASURE COMPONENTS OF THE HORIZONTAL OR TRANSVERSE WIND)NTHISMANNER TWOORTHOGONALSUBARRAYSCANMEASURECOMPONENTSOFTHE HORIZONTAL WIND USING CROSS SPECTRAL OR CORRELATION PROCESSING TECHNIQUES 3INCE THEMEASUREMENTISMADEINPAIRSOFOVERLAPPINGBEAMSDIRECTLYABOVETHERADAR ITIS NOLONGERNECESSARYTOASSUMEORREQUIREHORIZONTALHOMOGENEITYOFTHEWINDFIELDIN THELARGERAREAABOVETHERADARANDORTHELONGINTEGRATIONTIMESNECESSARYTOASSURE THISHOMOGENEITY4HESESPACEDANTENNATECHNIQUESAREMOSTFREQUENTLYUSEDWHEN HIGHSPATIALANDTEMPORALRESOLUTIONMEASUREMENTSAREREQUIREDSUCHASESTIMATING DETAILEDBOUNDARYLAYERTURBULENCEFIELDS:HANGAND$OVIAKHAVEINVESTIGATEDUSING THEDUALBEAMnSPACEDANTENNATECHNIQUEIMPLEMENTEDWITHANELECTRONICALLYSCANNED PHASEDARRAYRADARTOESTIMATETHETRANSVERSE ASWELLASTHERADIAL WINDCOMPONENTS ATARBITRARYSCANANGLES
-%4%/2/,/')#!,2!$!2
£°{£
, ,
2*3ERAFINAND*77ILSON h/PERATIONALWEATHERRADARINTHE5NITED3TATES0ROGRESSAND OPPORTUNITY v"ULL!M-ETEOROL3OC VOL PPn !-3 "OSTON 2 * 3ERAFIN h.EW NOWCASTING OPPORTUNITIES USING MODERN METEOROLOGICAL RADAR v IN 0ROC -ESOSCALE!NALYSIS&ORECAST3YMP %UROPEAN3PACE!GENCY 0ARIS PPn 4$#RUMAND2,!LBERTY h4HE732 $ANDTHE732 $/PERATIONAL3UPPORT&ACILITY ;.OW2ADAR/PERATIONS#ENTER= v"ULL!M-ETEOROL3OC VOL PPn 4$#RUM 2%3AFFLE AND*77ILSON h!NUPDATEONTHE.EXRADPROGRAMANDFUTURE732 $SUPPORTTOOPERATIONS v7EATHERAND&ORECASTING VOL PPn *-C#ARTHY *7ILSON AND44&UJITA h4HE*OINT!IRPORT7EATHER3TUDIES*!73 PROJECT v "ULL!M-ETEOROL3OC VOL PPn --ICHELSON 773HRADER AND*'7IELER h4ERMINALDOPPLERWEATHERRADAR v-ICROWAVE* VOL PPn *'7IELERAND773CHRADER h4ERMINAL$OPPLER7EATHER2ADAR4$72 SYSTEMCHARACTER IZATIONSANDDESIGNCONSTRAINTS vINTH)NT#ONFON2ADAR-ETEOROL!-3 PP*n* .ATIONAL2ESEARCH#OUNCIL !SSESSMENTOF.EXRAD#OVERAGEAND!SSOCIATED7EATHER3ERVICES 7ASHINGTON $#.ATIONAL!CADEMY0RESS (7"AYNTON 2*3ERAFIN #,&RUSH '2'RAY 06(OBBS 2!(OUZE *R AND*$ ,OCATELLI h2EAL TIMEWINDMEASUREMENTINEXTRATROPICALCYCLONESBYMEANSOFDOPPLERRADAR v *!PPL-ETEOROL VOL PPn * 2TTGER AND - & ,ARSEN h5(&6(& RADAR TECHNIQUES FOR ATMOSPHERIC RESEARCH AND WIND PROFILER APPLICATIONS v #HAPTER IN 2ADAR IN -ETEOROLOGY !TLAS ED "OSTON !-3 PPn 6#HANDRASEKAR 2-ENEGHINI AND):AWADZKI h'LOBALANDLOCALPRECIPITATIONMEASUREMENTS BYRADAR v#HAPTERIN2ADARIN!TMOSPHERIC3CIENCE!COLLECTIONOFESSAYSINHONOROF$AVID !TLAS 27AKIMOTOAND23RIVASTAVAEDS -ETEOROLOGICAL-ONOGRAPH VOL "OSTON!-3 PPn * 7URMAN * 3TRAKA % 2ASMUSSEN - 2ANDALL AND! :AHRAI h$ESIGN AND DEPLOYMENT OF A PORTABLE PENCIL BEAM PULSED CM DOPPLER RADAR v * !TMOS /CEANIC 4ECHNOL VOL PPn $ 3 :RNIC h7EATHER RADAR POLARIMETRY4RENDS TOWARD OPERATIONAL APPLICATIONS v "ULL!MER -ETEOROL3OC VOL PPn 6 . "RINGI AND ! (ENDRY h4ECHNOLOGY OF POLARIZATION DIVERSITY RADARS FOR METEOROLOGY v #HAPIN2ADARIN-ETEOROLOGY !TLASED "OSTON!-3 PPn 6."RINGI 4!3ELIGA AND+!YDIN h(AILDETECTIONWITHADIFFERENTIALREFLECTIVITYRADAR v 3CIENCE VOL PPn *6IVEKANANDAN $3:RNIC 3-%LLIS 2/YE !62YZHKOV AND*3TRAKA h#LOUDMICRO PHYSICS RETRIEVAL USING 3 BAND DUAL POLARIZATION RADAR MEASUREMENTS v "ULL !-3 VOL PPn & &ABRY # &RUSH ) :AWADZKI AND! +ILAMBI h/N THE EXTRACTION OF NEAR SURFACE INDEX OF REFRACTIONUSINGRADARPHASEMEASUREMENTSFROMGROUNDTARGETS v*!TMOS/CEAN4ECH VOL PPn 0((ILDEBRANDAND2+-OORE h-ETEOROLOGICALRADAROBSERVATIONSFROMMOBILEPLATFORMS v #HAPTERIN2ADARIN-ETEOROLOGY !TLASED "OSTON!-3 PPn 2*3ERAFINAND23TRAUCH h-ETEOROLOGICALRADARSIGNALPROCESSINGIN@AIRQUALITYMETEOROLOGYAND ATMOSPHERICOZONE v!MERICAN3OCIETYFOR4ESTINGAND-ATERIALS PPn 0HILADELPHIA ,*"ATTAN 2ADAR/BSERVATIONOFTHE!TMOSPHERE #HICAGO5NIVERSITYOF#HICAGO0RESS $!TLASED 2ADARIN-ETEOROLOGY "OSTON!-3 "2"EAN %*$UTTON AND"$7ARNER h7EATHEREFFECTSONRADAR vIN2ADAR(ANDBOOK ST %D -3KOLNIKED .EW9ORK-C'RAW (ILL"OOK#OMPANY PP n
£°{Ó
2!$!2(!.$"//+
2*$OVIAKAND$3:RNIC` $OPPLER2ADARAND7EATHER/BSERVATIONS ND%D -INEOLA .9 $OVER0UBLICATIONS 6 . "RINGI AND 6 #HANDRASEKAR 0OLARIMETRIC $OPPLER 7EATHER 2ADAR 0RINCIPLES AND !PPLICATIONS #AMBRIDGE 5+#AMBRIDGE5NIV0RESS 2-,HERMITTE #ENTIMETER-ILLIMETER7AVELENGTH2ADARSIN-ETEOROLOGY -IAMI,HERMITTE 0UBLICATIONS 2%2INEHART 2ADARFOR-ETEOROLOGISTS TH%D #OLUMBIA -/2INEHART0UBLICATIONS h3PECIALISSUEONRADARMETEOROLOGY v)%%%4RANS'EOSCI%LECTRON '% )%%% /CTOBER 2-7AKIMOTOAND2#3RIVASTAVAEDS 2ADARAND!TMOSPHERIC3CIENCE!#OLLECTIONOF %SSAYIN(ONOROF$AVID!TLAS -ETEOROLOGICAL-ONOGRAPHS 6OL "OSTON!-3 0 -EISCHNER ED 7EATHER 2ADAR 0RINCIPLES AND !DVANCED !PPLICATIONS "ERLIN 3PRINGER 6ERLAG 0REPRINTSAND0ROCEEDINGSOF#ONFERENCESON2ADAR-ETEOROLOGY nPRESENT "OSTON!-3 0ROCEEDINGSOF%UROPEAN#ONFERENCESON2ADARIN-ETEOROLOGYAND(YDROLOGY nPRESENT "ERLIN 'ERMANY#OPERNICUS'MB( -)3KOLNIK )NTRODUCTIONTO2ADAR3YSTEMS RD%D .EW9ORK-C'RAW (ILL P '-IE h"EITRÅGEZUR/PTICTRÓBER-EDIEN SPEZIELLKOLLOIDALER-ETALLÕSUNGEN;#ONTRIBUTIONTO THEOPTICSOFSUSPENDEDMEDIA SPECIFICALLYCOLLOIDALMETALSUSPENSIONS= v!NN0HYS VOL PPn * 2 0ROBERT *ONES h4HE 2ADAR %QUATION IN -ETEOROLOGY v 1 * 2 -ETEOROL 3OC VOL PPn *77ILSON 4-7ECKWERTH *6IVEKANANDAN 2-7AKIMOTO AND272USSELL h"OUNDARY LAYERCLEARAIRRADARECHOESORIGINOFECHOESANDACCURACYOFDERIVEDWINDS v*!TMOS/CEANIC 4ECHNOL VOL PPn 272USSELLAND*77ILSON h2ADAR OBSERVEDFINELINESINTHEOPTICALLYCLEARBOUNDARYLAYER REFLECTIVITY CONTRIBUTIONS FROM AERIAL PLANKTON AND ITS PREDATORS v "OUNDARY ,AYER -ETEOROL VOL PPn 0((ILDEBRAND h)TERATIVECORRECTIONFORATTENUATIONOFCMRADARINRAIN v*!PPL-ETEOROL VOL PPn 2(!LLEN $7"URGESS AND2*$ONALDSON *R h3EVERE CMRADARATTENUATIONOFTHE7ICHITA &ALLSSTORMBYINTERVENINGPRECIPITATION vINTH#ONF2ADAR-ETEOROL !-3 "OSTON PPn 0*%CCLESAND$!TLAS h!DUAL WAVELENGTHRADARHAILDETECTOR v*!PPL-ETEOROL VOL PPn 2 % #ARBONE $ !TLAS 0 %CCLES 2 &ETTER AND % -UELLER h$UAL WAVELENGTH RADAR HAIL DETECTION v"ULL!MER-ETEOR3OC VOL PPn 4/GUCHI h%LECTROMAGNETICWAVEPROPAGATIONANDSCATTERINGINRAINANDOTHERHYDROMETEORS v 0ROC)%%% VOL PPn 2*$ONALDSON *R h4HEMEASUREMENTOFCLOUDLIQUID WATERCONTENTBYRADAR v*-ETEOROL VOL PPn (+7EICKMANNAND(*AUFM+AMPE h0HYSICALPROPERTIESOFCUMULUSCLOUDS v*-ETEOROL VOL PPn +,3'UNNAND472%AST h4HEMICROWAVEPROPERTIESOFPRECIPITATIONPARTICLES v1*2 -ETEOROL3OC VOL PPn * 7 2YDE AND $ 2YDE !TTENUATION OF #ENTIMETER 7AVES BY 2AIN (AIL &OG AND #LOUDS 7EMBLEY %NGLAND'ENERAL%LECTRIC#OMPANY " 2 "EAN AND 2!BBOTT h/XYGEN AND WATER VAPOR ABSORPTION OF RADIO WAVES IN THE ATMO SPHERE v'EOFTS 0URA!PPL VOL PPn *72YDE h4HEATTENUATIONANDRADARECHOESPRODUCEDATCENTIMETREWAVELENGTHSBYVARIOUS METEOROLOGICAL PHENOMENA v IN -ETEOROLOGICAL &ACTORS IN 2ADIO7AVE 0ROPAGATION ,ONDON 0HYSICAL3OCIETY PPn
-%4%/2/,/')#!,2!$!2
£°{Î
*/,AWSAND$!0ARSONS h4HERELATIONSHIPOFRAINDROPSIZETOINTENSITY vINTH!NN-EET 4RANS!M'EOPHYS5NION PPn 2'-EDHURST h2AINFALLATTENUATIONOFCENTIMETERWAVESCOMPARISONOFTHEORYANDMEASURE MENT v)%%%4RANS!NT0ROP VOL!0 PPn 25IJLENHOET -3TEINER AND*!3MITH h6ARIABILITYOFRAINDROPSIZEDISTRIBUTIONSINASQUALL LINEANDIMPLICATIONSFORRADARRAINFALLESTIMATION v*(YDROMETEOROL VOL PPn #2"URROWSAND33!TTWOOD 2ADIO7AVE0ROPAGATION #ONSOLIDATED3UMMARY4ECHNICAL 2EPORTOFTHE#OMMITTEEON0ROPAGATION .$2# .EW9ORK!CADEMIC0RESS P 7*(UMPHREYS 0HYSICSOFTHE!IR .EW9ORK-C'RAW (ILL"OOK#OMPANY P 'LOSSARYOF-ETEOROLOGY ND%D "OSTON!-3 P $!TLASAND%+ESSLER))) h!MODELATMOSPHEREFORWIDESPREADPRECIPITATION v!ERONAUT%NG 2EV VOL PPn -+ERKER -0,ANGLEBEN AND+,3'UNN h3CATTERINGOFMICROWAVESBYAMELTINGSPHERICAL ICEPARTICLE v*-ETEOROL VOL P !#"EST 0HYSICSIN-ETEOROLOGY ,ONDON3IR)SAAC0ITMAN3ONS ,TD *!3AXTONAND('(OPKINS h3OMEADVERSEINFLUENCESOFMETEOROLOGICALFACTORSONMARINE NAVIGATIONALRADAR v0ROC)%%,ONDON VOL PT))) P *.#HRISMANAND#!2AY h!FIRSTLOOKATTHEOPERATIONALDATAQUALITY IMPROVEMENTSPROVIDED BYTHE/PEN2ADAR$ATA!CQUISITION/2$! SYSTEM vINST)NT#ONFON)NFOR0ROCESSING3YS ))03 FOR-ETEOROL /CEANOG AND(YDROL 3AN$IEGO #! 02 - 3ACHIDANANDA AND $ 3 :RNIC h#LUTTER FILTERING AND SPECTRAL MOMENT ESTIMATION FOR DOP PLER WEATHER RADARS USING STAGGERED PULSE REPETITION TIME 024 v *!TMOS /CEAN4ECH PPn ,"*ACKSON $IGITAL&ILTERSAND3IGNAL0ROCESSING ND%D .ORWELL -!+LUWER !$3IGGIAAND2%0ASSARELLI *R h'AUSSIANMODELADAPTIVEPROCESSING'-!0 FORIMPROVED GROUNDCLUTTERCANCELLATIONANDMOMENTCALCULATION vINRD%UROPEAN#ONFON2ADAR-ETEORO 6ISBY )SLANDOF'OTLAND 3WEDEN PPn &0ASQUALUCCI "7"ARTRAM 2!+ROPFLI AND72-ONINGER h!MILLIMETER WAVELENGTH DUAL POLARIZATION DOPPLER RADAR FOR CLOUD AND PRECIPITATION STUDIES v * #LIM !PPL -ETEOROL VOL PPn 2 ,HERMITTE h! '(Z DOPPLER RADAR FOR CLOUD OBSERVATIONS v * !TMOS /CEAN 4ECHNOL VOL PPn * ( 2ICHTER h(IGH RESOLUTION TROPOSPHERIC RADAR SOUNDING v 0ROC #OLLOQ 3PECTRA -ETEOROL 6ARIABLES 2ADIO3CI VOL PPn 2*+EELER $3:RNIC AND#,&RUSH h2EVIEWOFRANGEVELOCITYAMBIGUITYMITIGATIONTECH NIQUES vINTH#ONFON2ADAR-ETEOROL !-3 -ONTREAL PPn " ' ,AIRD h/N AMBIGUITY RESOLUTION BY RANDOM PHASE PROCESSING v IN TH #ONF 2ADAR -ETEOROL "OSTON !-3 P -3ACHIDANANDAAND$3:RNIC h3YSTEMATICPHASECODESFORRESOLVINGRANGEOVERLAIDSIGNALS INADOPPLERWEATHERRADAR v*!TMOS/CEANIC4ECHNOL VOL PPn *0IRTTILÅAND-,EHTINEN h3OLVINGTHERANGE DOPPLERDILEMMAWITHTHE3-02&PULSECODE vIN TH#ONF2ADAR-ETEOROL -UNICH !-3 PPn .ATIONAL2ESEARCH#OUNCIL 7EATHER2ADAR4ECHNOLOGYBEYOND.EXRAD 7ASHINGTON $#.ATIONAL !CADEMY0RESS 2 * +EELER * ,UTZ AND * 6IVEKANANDAN h3 0OL.#!2S POLARIMETRIC DOPPLER RESEARCH RADAR v IN 0ROC )NT 'EOSCI 2EMOTE 3ENS 3YMP ;)'!233 = )%%% (ONOLULU PPn (,IUAND6#HANDRASEKAR h#LASSIFICATIONOFHYDROMETEORSBASEDONPOLARIMETRICRADARMEA SUREMENTS DEVELOPMENT OF FUZZY LOGIC AND NEURO FUZZY SYSTEMS AND IN SITU VERIFICATION v * !TMOS/CEAN4ECHNOL VOL PPn
£°{{
2!$!2(!.$"//+
#*+ESSINGER 3-%LLIS AND*6AN!NDEL h4HERADARECHOCLASSIFIERAFUZZYLOGICALGORITHMFOR THE732 $ vPRESENTEDATRD!-3!NNUAL-EETINGRD!)#ONF 0 ,ONG"EACH $ !TLAS h2ADAR CALIBRATION SOME SIMPLE APPROACHES v "ULL !M -ETEOROL 3OC VOL PPn *&0RATTAND$'&ERRARO h!UTOMATEDSOLARGAINCALIBRATION PREPRINTS vINTH#ONF2ADAR -ETEOROL !-3 4ALLAHASSEE PPn $3IRMANSAND"5RELL h/NMEASURING732 $ANTENNAGAINUSINGSOLARFLUX v.732/# %NGINEERING"RANCH2EPORT %'ORCUCCI *3CARCHILLI AND6#HANDRASEKAR h#ALIBRATIONOFRADARSUSINGPOLARIMETRICTECH NIQUES v)%%%4RANS'EOSCI2EM3ENS VOL PPn *#(UBBERT 6."RINGI AND$"RUNKOW h3TUDIESOFTHEPOLARIMETRICCOVARIANCEMATRIX 0ART)#ALIBRATIONMETHODOLOGY v*!TMOS/CEAN4ECHNOL VOL PPn 2ADAR CALIBRATION WORKSHOP PRESENTED AT ST !NNUAL -EETING OF THE !M -ETEOROL 3OC !LBUQUERQUE 2*+EELERAND2%0ASSARELLI h3IGNALPROCESSINGFORATMOSPHERICRADARS v#HAPTERIN2ADAR IN-ETEOROLOGY !TLASED "OSTON!-3 PPn *3-ARSHALLAND7(ITSCHFELD h4HEINTERPRETATIONOFTHEFLUCTUATINGECHOFORRANDOMLYDISTRIB UTEDSCATTERERS v0T) #AN*0HYS VOL PPn 027ALLACE h4HEINTERPRETATIONOFTHEFLUCTUATINGECHOFORRANDOMLYDISTRIBUTEDSCATTERERS v0T )) #AN*0HYS VOL PPn $3:RNIC h3IMULATIONOFWEATHER LIKEDOPPLERSPECTRAANDSIGNALS v*!PPL-ETEOROL VOL PPn $3:RNICAND2*$OVIAK h6ELOCITYSPECTRAOFVORTICESSCANNEDWITHAPULSE DOPPLER v*!PPL -ETEOROLO VOL PPn 7$2UMMLER h)NTRODUCTIONOFANEWESTIMATORFORVELOCITYSPECTRALPARAMETERS v4ECH-EMO -- "ELL4ELEPHONE,ABORATORIES 7HIPPANY .* $3:RNIC` h%STIMATINGOFSPECTRALMOMENTSFORWEATHERECHOES v)%%%4RANS'EOSC%LECTRON VOL'% PPn ! 6 /PPENHEIM AND 2 7 3CHAEFER $IGITAL SIGNAL PROCESSING %NGLEWOOD #LIFFS .* 0RENTICE (ALL & &ABRY AND 2 * +EELER h)NNOVATIVE SIGNAL UTILIZATION AND PROCESSING v #HAPTER IN 2ADAR IN!TMOSPHERIC3CIENCE!#OLLECTIONOF%SSAYSIN(ONOROF$AVID!TLAS 27AKIMOTOAND2 3RIVASTAVAEDS -ETEOROLOGICAL-ONOGRAPHS 6OL "OSTON!-3 PPn 4,7ILFONG $!-ERRITT 2*,ATAITIS ",7EBER $"7UERTZ AND2'3TRAUCH h/PTIMAL GENERATION OF RADAR WIND PROFILER SPECTRA v * !TMOS /CEAN 4ECHNOL VOL PP n 0 ( (ILDEBRAND AND 2 ( 3EKHON h/BJECTIVE DETERMINATION OF THE NOISE LEVEL IN DOPPLER SPECTRA v*!PPL-ETEOROL VOL PPn (5RKOWITZAND*0.ESPOR h/BTAININGSPECTRALMOMENTSBYDISCRETE&OURIERTRANSFORMWITH NOISEREMOVALINRADARMETEOROLOGY v0ROC)NT'EOSCI2EMOTE3ENS3YMP;)'!233 = )%%% (OUSTON PPn *.$ENENBERG 2*3ERAFIN AND,#0EACH h5NCERTAINTIESINCOHERENTMEASUREMENTOFTHE MEANFREQUENCYANDVARIANCEOFTHEDOPPLERSPECTRUMFROMMETEOROLOGICALECHOES vINTH#ONF 2ADAR-ETEOROL !-3 "OSTON PPn 2 * +EELER AND # , &RUSH h#OHERENT WIDEBAND PROCESSING OF DISTRIBUTED TARGETS v IN0ROC )NT 'EOSCI AND 2EMOTE 3ENSING 3YMP ;)'!233 = 3AN &RANCISCO )%%%523) PPn 2'3TRAUCH h!MODULATIONWAVEFORMFORSHORT DWELL TIMEMETEOROLOGICALDOPPLERRADARS v* !TMOS/CEANIC4ECHNOL VOL PPn 2*+EELERAND#!(WANG h0ULSECOMPRESSIONFORWEATHERRADAR vIN)%%%)NT2ADAR#ONF 7ASHINGTON $# PPn
-%4%/2/,/')#!,2!$!2
£°{x
! -UDUKUTORE 6 #HANDRASEKAR AND 2* +EELER h0ULSE COMPRESSION FOR WEATHER RADARS v )%%%4RANSON'EOSCI2EM3ENS VOL PPn &/(ORAAND*+EELER h#OMPARISONOFPULSECOMPRESSIONWHITENINGTRANSFORMSIGNALPRO CESSING vINTH%UROPEAN2ADAR#ONF "ARCELONA PPn %!2OBINSON h0REDICTIVEDECOMPOSITIONOFTIMESERIESWITHAPPLICATIONTOSEISMICEXPLORA TION v'EOPHYSICS VOL PPn 2*+EELERAND,*'RIFFITHS h!COUSTICDOPPLEREXTRACTIONBYADAPTIVELINEARPREDICTIONFILTER ING v*!COUST3OC!MER VOL PPn !#+OIVUNENAND!"+OSTINSKI h&EASIBILITYOFDATAWHITENINGTOIMPROVEPERFORMANCEOF WEATHERRADAR v*!PPL-ETEOROL VOL PPn 3-4ORRESAND$3:RNIC h7HITENINGINRANGETOIMPROVEWEATHERRADARSPECTRALMOMENT ESTIMATES0ARTFORMULATIONANDSIMULATION v*!TMOS/CEANIC4ECHNOL VOL PPn 499U ':HANG !"#HALAMALASETTI 2*$OVIAK AND$3:RNIC h2ESOLUTIONENHANCEMENT TECHNIQUEUSINGRANGEOVERSAMPLING v*!TMOS/CEAN4ECHNOL VOL PPn !6/PPENHEIMAND273CHAEFER $ISCRETE4IME3IGNAL0ROCESSING %NGLEWOOD#LIFFS .* 0RENTICE (ALL * 0 "URG h4HE RELATIONSHIP BETWEEN MAXIMUM ENTROPY SPECTRA AND MAXIMUM LIKELIHOOD SPECTRA v'EOPHYSICS VOL PPn * #APON h(IGH RESOLUTION FREQUENCY WAVENUMBER SPECTRUM ANALYSIS v 0ROC )%%% VOL PPn 3-+AY -ODERN3PECTRAL%STIMATION4HEORYAND!PPLICATION .EW9ORK0RENTICE (ALL 3$#AMPBELLAND3(/LSON h2ECOGNIZINGLOW ALTITUDEWINDSHEARHAZARDSFROMDOPPLERWEATHER RADARANARTIFICIALINTELLIGENCEAPPROACH v*!TMOS/CEAN4ECHNOL VOL Pn ! , 0AZMANY * " -EAD 3 - 3EKELSKY AND $ * -C,AUGHLIN h-ULTI FREQUENCY RADAR ESTIMATIONOFCLOUDANDPRECIPITATIONPROPERTIESUSINGANARTIFICIALNEURALNETWORK vINTH)NT #ONFON2ADAR-ETEOROL -UNICH !-3 PPn $!TLAS h!DVANCES IN RADAR METEOROLOGY v IN !DVANCES IN 'EOPHYSICS 6OL .EW9ORK !CADEMIC0RESS 2'UNNAND'$+INZER h4HETERMINALVELOCITYOFFALLFORWATERDROPLETSINSTAGNANT!IR v *-ETEOROL VOL PPn *3-ARSHALLAND7-+0ALMER h4HEDISTRIBUTIONOFRAINDROPSWITHSIZE v*-ETEOROL VOL PPn $ # "LANCHARD h2AINDROP SIZE DISTRIBUTION IN (AWAIIAN RAINS v * -ETEOROL VOL PPn $-!*ONES hCMANDCMWAVELENGTHRADIATIONBACKSCATTERFROMRAIN vINTH7EATHER 2ADAR#ONF !-3 "OSTON PPn + , 3 'UNN AND * 3 -ARSHALL h4HE DISTRIBUTION WITH SIZE OF AGGREGATE SNOWFLAKES v *-ETEOROL VOL PPn * 7 7ILSON AND % ! "RANDES h2ADAR MEASUREMENT OF RAINFALLA SUMMARY v "ULL !M -ETEOROL3OC VOL PPn ):AWADZKI h/NRADAR RAINGAGECOMPARISON v*!PPL-ETEOROL VOL PPn ) :AWADZKI h&ACTORS AFFECTING THE PRECISION OF RADAR MEASUREMENTS OF RAIN v IN CD #ONF 2ADAR-ETEOROL !-3 "OSTON PPn **OSSAND2,EE h!PPLICATIONOFRADAR GAUGECOMPARISONTOOPERATIONPRECIPITATIONPROFILE CORRECTIONS v*!PPL-ETEOROL VOL PPn 5 'ERMANN AND * *OSS h-ESOBETA PROFILES TO EXTRAPOLATE RADAR PRECIPITATION MEASUREMENTS ABOVETHE!LPSTOGROUNDLEVEL v*!PPL-ETEOROL VOL PPn "6IGNAL ''ALLI **OSS AND5'ERMANN h4HREEMETHODSTODETERMINEPROFILESOFREFLECTIV ITYFROMVOLUMETRICRADARDATATOCORRECTPRECIPITATIONESTIMATES v*!PPL-ETEOROL VOL PPn
£°{È
2!$!2(!.$"//+
&&-ARZANO %0ICCIOTTI AND'6ULPIANI h2AINFIELDANDREFLECTIVITYVERTICALPROFILERECONSTRUCTION FROM# BANDRADARVOLUMETRICDATA v)%%%4RANS'EOSCI2EM3ENS VOL PPn * "RIDGES AND * &ELDMAN h!N ATTENUATION REFLECTIVITY TECHNIQUE TO DETERMINE THE DROP SIZE DISTRIBUTIONOFWATERCLOUDSANDRAIN v*!PPL-ETEOROL VOL PPn $3:RNICAND!2YZHKOV h0OLARIMETRYFORWEATHERSURVEILLANCERADARS v"ULL!MER-ETEORO 3OC VOL PPn 4!3ELIGAAND6."RINGI h0OTENTIALUSEOFRADARDIFFERENTIALREFLECTIVITYMEASUREMENTSATORTHOGO NALPOLARIZATIONSFORMEASURINGPRECIPITATION v*!PPL-ETEOROL VOL PPn -3ACHIDANANDAAND$3:RNIC h2AIN2ATEESTIMATIONFROMDIFFERENTIALPOLARIZATIONMEASURE MENTS v*!TMOS/CEAN4ECH VOL PPn $.-OISSEEV #-(5NAL (7*2USSCHENBERG AND,0,IGTHART h)MPROVEDPOLARIMETRIC CALIBRATIONOFATMOSPHERICRADARS v*!TMOS/CEAN4ECH VOL PPn !2YZHKOVAND$:RNIC h!SSESSMENTOFRAINFALLMEASUREMENTTHATUSESSPECIFICDIFFERENTIAL PHASE v*!PPL-ETEOROL PPn ':HANG *6IVEKANANDAN AND%"RANDES h!METHODFORESTIMATINGRAINRATEANDDROPSIZE DISTRIBUTIONFROMPOLARIMETRICRADARMEASUREMENTS v)%%%4RANS'EOSCI2EMOTE3ENS VOL PPn *6IVEKANANDAN ':HANG 3-%LLIS $2AJOPADHYAYA AND3+!VERY h2ADARREFLECTIVITY CALIBRATIONUSINGDIFFERENTIALPROPAGATIONPHASEMEASUREMENT v2ADIO3CI VOL PPnTO n 0+OLLIAS "!!LBRECHT AND&-ARKS *R h7HY-IE v"ULL!MER-ETEOR3OC VOL PPn 2*$OVIAK 6"RINGI !2YZHKOV !:AHRAI AND$:RNIC h#ONSIDERATIONSFORPOLARIMETRIC UPGRADESTOTHEOPERATIONAL732 $RADARS v*!TMOS/CEAN4ECHNOL VOL PPn #&RUSH 2*$OVIAK -3ACHIDANANDA AND$3:RNIC h!PPLICATIONOFTHE3:PHASECODE TOMITIGATERANGE VELOCITYAMBIGUITIESINWEATHERRADARS v*!TMOS/CEAN4ECHNOL VOL PPn *#(UBBERT '-EYMARIS AND2*+EELER h2ANGE VELOCITYMITIGATIONVIA3:PHASECODING WITHEXPERIMENTAL3 BANDRADARDATA vINST#ONFON2ADAR-ETEOROL !-3 3EATTLE PPn -3ACHIDANANDAAND$3:RNIC h#LUTTERFILTERINGANDSPECTRALMOMENTESTIMATIONFORDOPPLER WEATHERRADARSUSINGSTAGGEREDPULSEREPETITIONTIME024 v*!TMOS/CEAN4ECHNOL VOL PPn $"URGESSETAL h&INALREPORTONTHE*OINT$OPPLER/PERATIONAL0ROJECT*$/0 vn ./!!4ECH-EMO%2,.33, 7 # ,EE AND - - "ELL h2APID INTENSIFICATION EYEWALL CONTRACTION AND BREAKDOWN OF (URRICANE#HARLEY NEARLANDFALL v'EOPHYS2ES,ETT VOL , DOI ', 2! (OUZE *R 3 3 #HEN 7 # ,EE 2 & 2OGERS *! -OORE ' * 3TOSSMEISTER * , #ETRONE 7:HAO AND--"ELL h4HE(URRICANE2AINBANDAND)NTENSITY#HANGE%XPERIMENT 2!).%8 /BSERVATIONSANDMODELINGOF(URRICANES+ATRINA /PHELIA AND2ITA v"ULL !MER-ETEORO3OC VOL PPn 2 * $ONALDSON *R h6ORTEX SIGNATURE RECOGNITION BY A DOPPLER RADAR v * !PPL -ETEOROL VOL PPn *7ILSONAND(02OESLI h5SEOFDOPPLERRADARANDRADARNETWORKSINMESOSCALEANALYSISAND FORECASTING v%3!* VOL PPn 4&UJITAAND&#ARACENA h!NANALYSISOFTHREEWEATHER RELATEDAIRCRAFTACCIDENTS v"ULL!M -ETEOROL3OC VOL PPn 4&UJITA h4HEDOWNBURST v3ATELLITEAND-ESOMETEOROLOGY2ESEARCH0ROJECT $EPARTMENTOFTHE 'EOPHYSICAL3CIENCES 5NIVERSITYOF#HICAGO 4&UJITA h4HE$&7MICROBURST v3ATELLITEAND-ETEOROLOGY2ESEARCH0ROJECT $EPARTMENTOF THE'EOPHYSICAL3CIENCES 5NIVERSITYOF#HICAGO
-%4%/2/,/')#!,2!$!2
£°{Ç
* -C#ARTHY AND 2 3ERAFIN h4HE MICROBURST HAZARD TO AVIATION v 7EATHERWISE VOL PPn 2 $ 2OBERTS AND *77ILSON h! PROPOSED MICROBURST NOWCASTING PROCEDURE USING SINGLE DOPPLERRADAR v*!PPL-ETEOROL VOL PPn +!YDIN 4! 3ELIGA AND 6 "ALAJI h2EMOTE SENSING OF HAIL WITH DUAL LINEAR POLARIZATION RADAR v*#LIM!PPL-ETEOROL VOL PPn !*)LLINGWORTH *7&'ODDARD AND3-#HERRY h$ETECTIONOFHAILBYDUALPOLARIZATION RADAR v.ATURE VOL PPn 2-,HERMITTEAND$!TLAS h0RECIPITATIONMOTIONBYPULSEDOPPLERRADAR vINTH7EATHER 2ADAR#ONF !-3 "OSTON PPn +!"ROWNINGAND27EXLER h!DETERMINATIONOFKINEMATICPROPERTIESOFAWINDFIELDUSING DOPPLERRADAR v*!PPL-ETEOROL VOL PPn *$4UTTLEAND'"&OOTE h$ETERMINATIONOFTHEBOUNDARYLAYERAIRFLOWFROMASINGLEDOPPLER RADAR v*!TMOS/CEAN4ECHNOL VOL PPn *77ILSONAND7%3CHREIBER h)NITIATIONOFCONVECTIVESTORMSATRADAR OBSERVEDBOUNDARY LAYERCONVERGENCELINES v-ON7EATHER2EV VOL PPn 477ECKWERTH #20ETTET &&ABRY 3*0ARK -!,E-ONE AND*77ILSON h2ADAR REFRACTIVITYRETRIEVAL6ALIDATIONANDAPPLICATIONTOSHORT TERMFORECASTING v*!PPL-ETEORO VOL PPn -(ALLED h3PECIALPAPERS-ULTIPLEPARAMETERRADARMEASUREMENTSOFPRECIPITATION v2ADIO 3CI VOL 2-,HERMITTE h$UAL DOPPLERRADAROBSERVATIONSOFCONVECTIVESTORMCIRCULATIONS vINTH #ONF2ADAR-ETEOROL !-3 "OSTON PPn $*-C,AUGHLIN 6#HANDRASEKAR +$ROEGEMEIER 3&RASIER *+UROSE &*UNYENT "0HILIPS 3#RUZ 0OL AND*#OLOM h$ISTRIBUTED#OLLABORATIVE!DAPTIVE3ENSING$#!3 FORIMPROVED DETECTION UNDERSTANDINGANDPREDICTIONOFATMOSPHERICHAZARDS vPRESENTEDATTH!-3!NNUAL -EETING 3AN$IEGO !-3 &*UNYENT 6#HANDRASEKAR $"RUNKOW 0#+ENNEDY AND$*-C,AUGHLIN h6ALIDATION OFFIRSTGENERATION#!3!RADARSWITH#35 #(),, vPRESENTEDATCD#ONF2ADAR-ETEOROL 02 !-3 !LBUQUERQUE 2%#ARBONE -#ARPENTER AND#"URGHART h$OPPLERRADARSAMPLINGLIMITATIONSINCONVEC TIVESTORMS v*!TMOS/CEAN4ECHNOL VOL PPn -"ROOKAND0+REHBIEL h!FAST SCANNINGMETEOROLOGICALRADAR vINTH#ONF2ADAR-ETEOROL !-3 "OSTON PPn 2*+EELERAND#,&RUSH h2APID SCANDOPPLERRADARDEVELOPMENTCONSIDERATIONS 0ART)) TECHNOLOGYASSESSMENT vINST#ONF2ADAR-ETEOROL!-3 "OSTON PPn 0 , 3MITH h!PPLICATIONS OF RADAR TO METEOROLOGICAL OPERATIONS AND RESEARCH v )%%% 0ROC VOL PPn #,(OLLOWAYAND2*+EELER h2APIDSCANDOPPLERRADARTHEANTENNAISSUES vINTH#ONF ON2ADAR-ETEOROL !-3 .ORMAN PPn ,*OSEFSSON h0HASEDARRAYANTENNATECHNOLOGYFORWEATHERRADARAPPLICATIONS vINTH#ONF ON2ADAR-ETEOROL !-3 0ARIS PPn 2*+EELER h7EATHERRADARSOFTHESTCENTURYATECHNOLOGYPERSPECTIVE vINTH#ONFON 2ADAR-ETEOROL !USTIN !-3 PPn 0-EISCHNER ##OLLIER !)LLINGWORTH **OSS AND72ANDEU h!DVANCEDWEATHERRADARSYS TEMSIN%UROPE4HE#/34 ACTION v"ULL!MER-ETEORO3OC VOL PPn % "ROOKNER ED 0RACTICAL 0HASED !RRAY !NTENNA 3YSTEMS .ORWICH -! !RTECH (OUSE *7URMANAND-2ANDALL h!NINEXPENSIVE MOBILE RAPIDSCANRADAR vINTH)NT#ONFON 2ADAR-ETEOROL -UNICH !-3 PPn *72OGERS ,"UCKLER !#(ARRIS -+EEHAN AND#*4IDWELL h(ISTORYOFTHE4ERMINAL !REA 3URVEILLANCE 3YSTEM 4!33 v IN TH #ONF 2ADAR -ETEROL !-3 !USTIN PPn
£°{n
2!$!2(!.$"//+
7"ENNER 7'4OROK .'ORDNER +ALANI -"ATISTA #ARVER AND4,EE h-0!2PROGRAM OVERVIEWANDSTATUS vPRESENTEDATRD)NT#ONFON)NTERACT)NFO0ROC3YS))03 !-3 3AN !NTONIO 4 -AESE * -ELODY 3 +ATZ - /LSTER 7 3ABIN ! &REEDMAN AND ( /WEN h$UAL USE SHIPBORNE PHASED ARRAY RADAR TECHNOLOGY AND TACTICAL ENVIRONMENTAL SENSING v IN 0ROC )%%% .ATIONAL2ADAR#ONF !TLANTA PPn $%&ORSYTH +*+IMPEL $3:RNIC 33ANDGATHE 2&EREK *&(EIMMER 4-C.ELLIS *% #RAIN !-3HAPIRO *$"ELVILLE AND7"ENNER h4HENATIONALWEATHERRADARTESTBEDPHASED ARRAY vPRESENTEDATTH)NT#ONFON)NTERACT)NFO0ROC3YS))03 !-3 /RLANDO 2 , 4ROTTER h$ESIGN CONSIDERATIONS FOR THE ./!! AIRBORNE METEOROLOGICAL RADAR AND DATA SYSTEM vINTH#ONFON2ADAR-ETEOROL !-3 !TLANTA PPn (""LUESTEINAND2-7AKIMOTO h-OBILERADAROBSERVATIONOFSEVERECONVECTIVESTORMS v #HAPTERIN2ADARIN!TMOSPHERIC3CIENCE!COLLECTIONOFESSAYSINHONOROF$AVID!TLAS 2 7AKIMOTOAND23RIVASTAVAEDS -ETEOROLOGICAL-ONOGRAPH 6OL "OSTON!-3 PPn 0 ( (ILDEBRAND # ! 7ALTHER # , &RUSH * 4ESTUD AND & "AUDIN h4HE %,$/2! !342!)!AIRBORNEDOPPLERWEATHERRADARGOALS DESIGNANDFIRSTFIELDTEST v0ROC)%%% VOL PPn '-(EYMSFIELDETAL h4HE%$/0RADARSYSTEMONTHEHIGHALTITUDE.!3!%2 AIRCRAFT v* !TMOS /CEANIC4ECHNOL VOL PPn ,,I '-(EYMSFIELD 0%2ACETTE ,4IAN AND%:ENKER h! '(ZCLOUDRADARSYSTEMON A.!3!HIGH ALTITUDE%2 AIRCRAFT v*!TMOS/CEANIC4ECHNOL VOL PPn $0*ORGENSEN 423HEPHERD AND!3'OLDSTEIN h!DUAL PULSEREPETITIONFREQUENCYSCHEME FORMITIGATINGVELOCITYAMBIGUITIESOFTHE./!!0 AIRBORNEDOPPLERRADAR v*!TMOS/CEANIC 4ECHNOL VOL PPn 3,$URDEN %)M &+,I 72ICKETTS !4ANNER AND77ILSON h!2-!2!NAIRBORNE RAINMAPPINGRADAR v*!TMOS/CEANIC4ECHNOL VOL PPn !0AZMANY 2-C)NTOSH 2+ELLY AND'6ALI h!NAIRBORNE'(ZDUAL POLARIZEDRADARFOR CLOUDSTUDIES v)%%%4RANS'EOSCI2EMOTE3ENS VOL PPn '&ARQUHARSON %,OEW 7#,EE AND*6IVEKANANDAN h!NEWHIGH ALTITUDEAIRBORNEMILLI METER WAVERADARFORATMOSPHERICRESEARCH vPRESENTEDAT0ROC)NT'EOSCI2EMOTE3ENS3YMP ;)'!233= )%%% "ARCELONA -7OLDE AND! 0AZMANY h.2# $UAL FREQUENCY AIRBORNE RADAR FOR ATMOSPHERIC RESEARCH v PRESENTEDATCD#ONF2ADAR-ETEOROL 02 !LBUQUERQUE 4+OZUETAL h$EVELOPMENTOFPRECIPITATIONRADARON BOARDTHE4ROPICAL2AINFALL-EASURING -ISSION42-- SATELLITE v)%%%4RANS'EOSCI2EMOTE3ENS VOL PPn %)METAL h3ECOND GENERATIONPRECIPITATIONRADAR02 v&INAL2EP*0,$ .!3! %ARTH3CIENCE)NSTRUMENT)NCUBATOR0ROGRAM *0, #ALIF)NST4ECH 0ASADENA #! 2-ENEGHINIAND$!TLAS h3IMULTANEOUSOCEANCROSS SECTIONANDRAINFALLMEASUREMENTSFROM SPACEWITHANADIR LOOKINGRADAR v*!TMOS/CEAN4ECHNOL VOL PPn ,,IANGAND2-ENEGHINI h!STUDYOFAIRSPACE BORNEDUAL WAVELENGTHRADARFORESTIMATIONOF RAINPROFILES v!DVANCESIN!TMOS3CI VOL PPn ',3TEPHENS $'6ANE 2*"OAIN ''-ACE +3ASSEN :7ANG !*)LLINGWORTH %* /#ONNOR 7"2OSSOW 3,$URDEN 3$-ILLER 24!USTIN !"ENEDETTI #-ITRESCU ANDTHE #LOUD3AT3CIENCE4EAM h4HE#LOUD3ATMISSIONANDTHE! TRAINANEWDIMENSIONOFSPACE BASED OBSERVATIONSOFCLOUDSANDPRECIPITATION v"ULL!M-ETEOROL3OC VOL PPn %%'OSSARDAND2'3TRAUCH 2ADAR/BSERVATIONSOF#LEAR!IRAND#LOUDS !MSTERDAM %LSEVIER 3+ATO44SUDA -9AMAMATO 43ATO AND3&UKAO h&IRSTRESULTSOBTAINEDWITHAMIDDLEAND UPPERATMOSPHERE-5 RADAR v*!TMOS4ERR0HYS VOL PPn
-%4%/2/,/')#!,2!$!2
£°{
3'"ENJAMIN "%3CHWARTZ %*3ZOKE AND3%+OCH h4HEVALUEOFWINDPROFILERDATAIN 53WEATHERFORECASTING v"ULL!MER-ETEOR3OC VOL PPn 2%#ARBONE 23TRAUCH AND'-(EYMSFIELD h3IMULATIONOFWINDPROFILERSINDISTRIBUTED CONDITIONS vINRD#ONF2ADAR-ETEOROL VOL) !-3 "OSTON PPn 2'3TRAUCH ",7EBER !3&RISCH #',ITTLE $!-ERRITT +0-ORAN AND$#7ELSH h4HEPRECISIONANDRELATIVEACCURACYOFPROFILERWINDMEASUREMENTS v*!TMOS/CEAN4ECHNOL VOL PPn 0ROCEEDINGSOF)NTERNATIONAL3YMPOSIAON4ROPOSPHERIC0ROFILING nPRESENT 2*$OVIAK 2*,ATAITIS AND#,(OLLOWAY h#ROSSCORRELATIONSANDCROSSSPECTRAFORSPACED ANTENNAWINDPROFILERS v2ADIO3CI VOL PPn *36AN"AELENAND!$2ICHMOND h2ADARINTERFEROMETRYTECHNIQUE4HREE DIMENSIONALWIND MEASUREMENTTHEORY v2ADIO3CI VOL PPn ':HANGAND2*$OVIAK h3PACED ANTENNAINTERFEROMETRYTOMEASURECROSSBEAMWIND SHEARAND TURBULENCE4HEORYANDFORMULATION v*!TMOS/CEAN4ECHNOL VOL PPn
#HAPTER
Ê"ÛiÀÌ
iÀâÊ,>`>À >iÃÊ °Êi>`ÀV .AVAL2ESEARCH,ABORATORYRETIRED
-ÌÕ>ÀÌÊ°Ê`iÀÃ !USTRALIAN$EFENCE3CIENCEAND4ECHNOLOGY/RGANISATION
Óä°£Ê /," 1 /" "EYOND THE HORIZONDETECTIONOFTERRESTRIALTARGETSATRANGESOFTHOUSANDSOFKILOMETERS CANBEACHIEVEDBYRADARSOPERATINGINTHEHIGH FREQUENCY(& BANDTO-(Z 4HIS VERYLONGRANGECOVERAGEISOBTAINEDBYUSINGSKYWAVEPROPAGATION THATIS REFLECTING THE RADAR SIGNALS FROM THE IONOSPHERE (& GROUND WAVE SURFACE WAVE PROPAGATION OVERTHESEAHASBEENUSEDFORINTERMEDIATEBUTSTILLOVER THE HORIZONDISTANCES UPTO SEVERAL HUNDRED KILOMETERS /CCASIONALLY (& RADAR SYSTEMS ALSO FIND APPLICATIONS IN LINE OF SIGHTAPPLICATIONSATSHORTRANGE4HISCHAPTERFOCUSESPREDOMINANTLYONSKYWAVE RADAR THOUGHMUCHOFTHEDISCUSSIONAPPLIESEQUALLYTOSURFACEWAVERADAR2ATHERTHAN AMALGAMATE DISCUSSION OF THE TWO RADAR CONFIGURATIONS THROUGHOUT THE CHAPTER THE DISTINCTIVEFEATURESOF(&SURFACEWAVERADARARETREATEDSEPARATELYINANAPPENDIXAT THEENDOFTHECHAPTER )NONESENSETHEDEVELOPMENTOF(&SKYWAVERADARCANBETRACEDBACKTOTHES WHENSKYWAVEECHOESWEREIDENTIFIED BUTTHEFIRST(&RADARSYSTEMSWERENOTDEPLOYED UNTILTHES3INCETHEN SKYWAVERADARHASEVOLVEDTOADDRESSAPPLICATIONSSUCH ASTHEDETECTIONANDTRACKINGOFAIRCRAFT BALLISTICANDCRUISEMISSILES ANDSHIPSn)N ADDITIONTODETECTINGhSKINvECHOESFROMTARGETSOFINTEREST (&RADARISUSEFULFOROBSERV INGVARIOUSFORMSOFHIGH ALTITUDEATMOSPHERICIONIZATION BOTHNATURAL INCLUDINGTHOSE ASSOCIATEDWITHAURORAEANDMETEORS ANDARTIFICIAL INCLUDINGTHEINTERACTIONOFSPACE CRAFTANDBALLISTICMISSILESWITHTHEIONOSPHERICPLASMAn&URTHER THEWAVELENGTHS USEDAREOFTHESAMEORDERASOCEANSURFACEGRAVITYWAVES ANDTHISCORRESPONDENCECAN BEEXPLOITEDTOPROVIDEINFORMATIONONTHEWAVEDIRECTIONALSPECTRUM OCEANCURRENTS AND BYINFERENCE SURFACEWINDS)NDEED SCATTERINGFROMTHESEACANOFTENBEEMPLOYED ASARADARCROSSSECTION2#3 AMPLITUDEREFERENCEANDISAWIDELYUSEDDIAGNOSTICTOOL 4HENARROW BANDWAVEFORMSEMPLOYED THELOWFREQUENCIES ANDTHENATUREOFTHETRANS MISSIONPATHMAKETHESPATIALRESOLUTIONCOARSEWHENCOMPAREDWITHHIGHER FREQUENCY RADARS BUTTHEDOPPLERRESOLUTIONCANBEEXCEEDINGLYFINE4HEMAGNITUDEANDDOPPLER DISTRIBUTION OF THE ECHOES FROM THE DISTANT %ARTHS SURFACE OFTEN TERMED BACKSCATTER THOUGHTHATTERMSHOULDBERESERVEDFORMONOSTATICRADARS AREMAJORFACTORSINSETTING SYSTEMDYNAMICRANGE SPECTRALPURITY ANDSIGNALPROCESSINGREQUIREMENTS Óä°£
Óä°Ó
2!$!2(!.$"//+
&)'52% 2AY TRACINGTHROUGHAMODELIONOSPHERE SHOWINGTHEVARIATIONOFTHERADARFOOTPRINT WITHCARRIERFREQUENCY4HECONTOURSMAPTHEPLASMAFREQUENCYORELECTRONDENSITY
&OREFFECTIVERADAROPERATION ENVIRONMENTALPARAMETERSTHATAFFECTRADARPERFORMANCE NEEDTOBEDETERMINEDINREALTIME DEFINEDASTHATINTERVALINWHICHTHEREARENOLARGE SCALE CHANGESINTHEIONOSPHERE4YPICALLY THISISOFTHEORDEROFnMINUTES4RANSMISSION PATHINFORMATIONISGENERALLYDERIVEDFROMADJUNCTVERTICALANDOBLIQUESOUNDERSASWELL ASBYUSINGTHERADARITSELFASASOUNDER!NIONOSPHERICELECTRONDENSITYMODELCOMPLEX ENOUGHTOENABLEADEQUATESOUNDINGINTERPRETATIONISREQUIRED)ONOSPHERICORTRANSMIS SIONPATHSTATISTICALCLIMATOLOGIESANDFORECASTSARENECESSARYFORRADARDESIGNANDFOR DEVELOPMENTOFSITE SPECIFICMODELS)NADDITION OTHERUSERSINTHE(&SPECTRUMMUSTBE OBSERVEDCONTINUOUSLYANDOPERATINGFREQUENCIESSELECTEDTOAVOIDINTERFERENCE 4HE ESSENTIAL FEATURES OF SKYWAVE PROPAGATION CAN BE SEEN IN &IGURE 4HE IONOSPHERE BEINGANIONIZEDGASWITHFREEELECTRONS WILLREFLECTALLRADARSIGNALSWHEN THERADARFREQUENCYISLESSTHANTHEPLASMAFREQUENCYGIVENBY
F0
r . E
(&/6%2 4(% (/2):/.2!$!2
Óä°Î
&)'52% .UMERICALLYCOMPUTEDRAYSILLUSTRATINGMULTIPLEHOPPROPAGATIONACROSSTHEEQUATORIALZONE 4HEELEVATEDPEAKELECTRONDENSITYNEARTHEEQUATORAT^KMISTHE!PPLETONANOMALY
WHEREF0ISIN-(ZAND.EISINELECTRONSPERCUBICMETER&ORAGIVENELEVATIONANGLE@ IF THERADARFREQUENCYEXCEEDS F P SIN A ATTHEHEIGHTOFMAXIMUMIONIZATION RAYSLAUNCHED ATHIGHERELEVATIONANGLESWILLESCAPE RESULTINGINASO CALLEDSKIPORDEADZONEWITHIN WHICHTHE%ARTHSSURFACEISNOTILLUMINATED"EYONDTHISSKIPZONE ENERGYISRETURNEDTO THE%ARTH REACHINGAMAXIMUMRANGEWHENTHERAYSLEAVINGTHEANTENNAAREHORIZONTAL 5SEFULRANGECOVERAGEWILLLIEBETWEENTHESELIMITS WHICHDEFINETHEONE HOPZONE !SSHOWNIN&IGURE AMULTIPLICITYOFHOPSMAYEXIST ANDENERGYMAYEVEN CIRCLE THE EARTH CLUTTER ECHOES FROM THESE LONG RANGES CAN SERIOUSLY DEGRADE RADAR PERFORMANCE!COMPARISONOF&IGURESA B ANDCREVEALSTHATDIFFERENT RANGE EXTENTS ARE ILLUMINATED BY USING DIFFERENT OPERATING FREQUENCIES WITH LONGER STARTINGRANGESREQUIRINGHIGHERFREQUENCIES)NTHEEXAMPLESSHOWN -(ZILLUMI NATESRANGESFROMTOKM WHEREAS-(ZILLUMINATESRANGESFROMTO KMWHEREAS-(ZILLUMINATESFROMTOKM(ENCE THEFARTHESTEDGE OFTHEFOOTPRINTNEEDNOTINCREASEWITHFREQUENCY DEPENDINGONTHEPREVAILINGIONO SPHERICCONDITIONS)NTHISEXAMPLE ASINGLEIONOSPHERICLAYERISCONSIDERED.ORMALLY THEREARETWOORTHREEDISTINCTLAYERSSUCHTHATSIGNALSMAYPARTIALLYPENETRATETHELOWER LAYERSTOBEREFLECTEDBYAHIGHERLAYER!SACONSEQUENCE THERELATIONSHIPBETWEEN THERANGETOATARGETANDTHEMEASUREDECHOTIMEDELAYBECOMESMULTIVALUED WITH UNKNOWN PARAMETERS SUCH AS LAYER HEIGHTS THAT MUST BE ESTIMATED BY VARIOUS TECH NIQUESASDESCRIBEDLATERINTHISCHAPTER 4O ILLUSTRATE THE OPERATING PRINCIPLES OF A SKYWAVE RADAR &IGURE PRESENTS A MAPSHOWINGMULTIPLESURVEILLANCETASKSASSIGNEDTOAHYPOTHETICALRADARWITHn AZIMUTHAL COVERAGE &IVE SECTORS OF CURRENT SURVEILLANCE ACTIVITY ARE SHOWN EACH ADDRESSINGAPARTICULARMISSIONASINDICATED EACHMISSIONCONSISTINGOFANUMBEROF DWELL INTERROGATION REGIONS $)2S 4HE ELECTRONICALLY STEERED RADAR TRANSMIT BEAM STEPSTHROUGHTHESE$)2S INSOMEASSIGNEDSEQUENCE ILLUMINATINGEACH$)2WITHAN APPROPRIATEWAVEFORMFORACORRESPONDINGINTERVALDURINGWHICHTHERECEIVINGSYSTEM ACQUIRESACOHERENTTIMESERIESOFECHOSAMPLES4HECOHERENTINTEGRATIONTIME#)4 DEPENDSONTHETYPEOFOBSERVATIONBUTISALMOSTALWAYSINTHERANGEOFnSECONDS %ACH TRANSMITTER FOOTPRINT IS ANALYZED BY FORMING SIMULTANEOUS CONTIGUOUS RECEIVE BEAMS ONTHEORDEROFnWIDEAT-(ZINTHECASEOFTHE53.AVY2/4(2AND THE!USTRALIAN*INDALEEAND*/2.RADARS WHICHEQUATESTOAKMCROSS RANGERESOLU TIONATAKMRANGE4HETASK SPECIFICREQUIREMENTSON$)2REVISITRATESDETERMINE THESEQUENCINGOFTHE$)2INTERROGATIONSAND OFCOURSE SETTHELIMITONHOWMANY TASKSCANBEADDRESSED
Óä°{
2!$!2(!.$"//+
n.
n.
2ADAR
n.
n n7
n7
n7
n7
n n7
n7
&)'52% 3OME COVERAGE AND TASKING OPTIONS FOR HYPOTHETICAL (& RADARS ON A FICTITIOUS MID !TLANTICISLAND4HECOVERAGEREGIONSNUMBEREDnCORRESPONDTOSKYWAVERADARMISSIONSASFOLLOWS AIRROUTEMONITORING BARRIERSURVEILLANCE STRATEGICWATERWAYMONITORING BALLISTICMISSILELAUNCH DETECTIONAND REMOTESENSINGANDHURRICANETRACKING4HESECTORDESIGNATEDISREPRESENTATIVEOF(& SURFACEWAVERADARCOVERAGE
#ONSIDERTHESETOFTASKSAND$)2SSHOWNIN&IGURE4ASKWOULDREQUIREONLY SHORT#)4S nS SAY IFTHEAIRCRAFTISASSUMEDTOBELARGE ANDWOULDNEEDREVISITS PERHAPSEVERYMINUTE ASTHEFLIGHTISNOTEXPECTEDTOMANEUVERSOTHETRACKWILLBE WELL BEHAVEDANDOBSERVEDPOSITIONERRORSWOULDBEDUETOIONOSPHERICFLUCTUATIONS /NLYTHESINGLE$)2CONTAININGTHEAIRCRAFTNEEDBEINTERROGATED4ASK BARRIERSUR VEILLANCE IF CONCERNED WITH SHIP TRAFFIC CAN AFFORD TO RELAX THE REVISIT TIME TO TENS OFMINUTESASSHIPSMOVESOSLOWLY BUTINORDERTOACHIEVEDETECTION LONG#)4SOF nSAREREQUIREDTOSEPARATETHESHIPECHOESFROMTHESEACLUTTERINTHEDOPPLER SPECTRUM%VENSO THERADARCANSTEPACROSSTHEBARRIERARC WITHPLENTYOFTIMETO INTERLEAVEA4ASKDWELLBETWEENADDRESSINGSUCCESSIVE$)2SIN4ASK)FTHEBARRIER 4ASKWERECONCERNEDWITHAIRCRAFT WITHA#)4OFnS THEREVISITSWOULDNEEDTO BEFREQUENTENOUGHTOACHIEVETHEDESIREDPROBABILITYOFDETECTIONBEFORETHEAIRCRAFT HADTIMETOCROSSTHEBARRIER/NEAPPROACHISTOWIDENTHEBARRIERBYPROCESSINGMORE RANGECELLSORBYREDUCINGTHEWAVEFORMBANDWIDTHANDALLOWINGTHERANGECELLSTO GROWWIDER BUTTHISMAYFAILIFTHEIONOSPHEREDOESNOTSUPPORTPROPAGATIONOVERTHE INCREASED RANGE DEPTH!NOTHER POSSIBILITY IS TO INCREASE THE REVISIT INTERVAL OVER A SUBSETOFTHE$)2S4HERELATIVEPRIORITYOF4ASKSANDWOULDALSONEEDTOBETAKEN INTOACCOUNT 4ASKBALLISTICMISSILELAUNCHDETECTION WOULDREQUIREMUCHMOREFREQUENTSUR VEILLANCEIFALAUNCHWEREBELIEVEDTOBEIMMINENT ORELSETHEMISSILEMIGHTESCAPE FROM THE RADAR FOOTPRINT WITHOUT BEING DETECTED!SSUME A #)4 OF SECONDS AND A TOLERABLEREVISITINTERVALOFS4ASKSANDCOULDBEINTERLEAVED FOREXAMPLE BY CARRYINGOUTFIVEDWELLSOF4ASK ANDTHENONEOF4ASK ANDTHENREPEATINGTHISPAT TERN4ASKISCONCERNEDWITHSLOW MOVINGSHIPS SOTHEREVISITINTERVALCOULDBETENS
(&/6%2 4(% (/2):/.2!$!2
Óä°x
OFMINUTES BUTALONG#)4OFPERHAPSnSISREQUIREDINORDERTOSEPARATETHESHIP ECHOESFROMTHESEACLUTTERINTHEDOPPLERSPECTRUM$URINGTHISTIME 4ASKSREQUIRE MENTSWOULDBEVIOLATED4ASKSAND ASDEFINED AREINCOMPATIBLE 4ASKREMOTESENSINGOFOCEANCONDITIONS WOULDHAVEAMUCHLOWERPRIORITYAS ITDEALSWITHSLOWLYVARYINGPHENOMENA SOITWOULDNEEDONLYOCCASIONALREVISITING 4HESMALLERSECTORSHOWNAS4ASK EXTENDINGTOARANGEOFKM ISREPRESENTATIVE OFTHECOVERAGEOFAN(&SURFACEWAVERADAR ASUSEDFORPROTECTINGTHEAPPROACHESTO APORT FOREXAMPLE 4HISEXAMPLEISTYPICALOFTHESCHEDULINGANDRESOURCEALLOCATIONPROBLEMTHATIS CENTRAL TO (& SKYWAVE RADAR OPERATIONS #OMPROMISES ARE OFTEN UNAVOIDABLE 4HE SITUATIONISFURTHERCOMPLICATEDBYTHECONTINUOUSVARIATIONOFIONOSPHERICPROPAGA TION CONDITIONS WHICH MUST BE MONITORED AND USED TO GUIDE TASKING AS WHEN BAD IONOSPHERIChWEATHERvISLIKELYTOPRECLUDECERTAINMISSIONS !LMOSTINVARIABLY THESECTORSAND INDEED THEINDIVIDUAL$)2SWITHINASECTORWILL REQUIREDIFFERENTCARRIERFREQUENCIES EVENFORAGIVENRANGE ASTHEIONOSPHEREMAY VARY SUBSTANTIALLY ACROSS THE FULL RANGE AND AZIMUTH EXTENT OF THE ACTIVE COVERAGE 4HEDEFININGCHARACTERISTICOF(&SKYWAVERADARISTHATTHERADAROPERATORMUSTSELECT FREQUENCIESTHATAREOPTIMUMFORTHEVARIOUSTASKSANDADAPTTHESEFREQUENCIESTOTHE EVER CHANGINGIONOSPHERE 4HISCHAPTERSETSOUTTOEXPLAINTHEPRINCIPALFEATURESOF(&SKYWAVERADARASITIS PRESENTLYIMPLEMENTED EMPHASIZINGTHEPHYSICALCONSIDERATIONSTHATGOVERNSYSTEM DESIGNANDPERFORMANCE
Óä°ÓÊ / Ê, ,Ê +1/" !FORMOFTHERADAREQUATION %Q CANBEUSEDTOPOINTTOASPECTSOF(&RADAR THATARESIGNIFICANTLYDIFFERENTFROMRADARSTHATUSEHIGHERFREQUENCIES4HESEDIFFER ENCESINCLUDEADAPTATIONTOENVIRONMENT FREQUENCYANDWAVEFORMSELECTION RADAR CROSSSECTION PATHLOSSES MULTIPATHEFFECTS NOISE INTERFERENCE ANTENNAGAIN SPATIAL RESOLUTION AND CLUTTER &OR THE CASE OF NOISE LIMITED DETECTION THE RADAR EQUATION TAKESTHEFORM 3 0AV 'T 'R 4K S &P
. P , P ,S . 2
WHERE
3. OUTPUTSIGNAL TO NOISERATIO 0AV AVERAGETRANSMITTEDPOWER 'T TRANSMITTERANTENNAGAIN 'R RECEIVERANTENNAGAIN 4 COHERENTPROCESSINGTIME K WAVELENGTH R TARGETRADARCROSSSECTION &P PROPAGATION PATHFACTOR . NOISEPOWERPERUNITBANDWIDTH ,P ,S TRANSMISSION PATHANDSYSTEMLOSSES 2 DISTANCEBETWEENRADARANDTARGET
Óä°È
2!$!2(!.$"//+
4HESEPARAMETERSAREEXPLAINEDBRIEFLYASFOLLOWS !NTENNAS 'TAND'R!COMMONCONVENTIONFOR(& BANDRADARSISTOINCLUDETHE EFFECT OF THE GROUND IN THE ANTENNA PERFORMANCE CHARACTERIZATION AND THAT CON VENTION WILL BE USED HERE &OR EXAMPLE A HALF WAVE DIPOLE IN FREE SPACE HAS A MAXIMUMGAINOVERANISOTROPEOFD")FTHATANTENNAISORIENTEDVERTICALLY JUSTABOVEBUTNOTTOUCHINGAPERFECTLYCONDUCTINGEARTH ITSMAXIMUMGAINWILL BEINCREASEDBYAFACTOROF ORD" TOD"ATnELEVATIONANGLE"ECAUSE THE %ARTH IS NEVER PERFECT ITS CONDUCTIVITY AND DIELECTRIC CONSTANT ARE FACTORS IN DETERMININGANTENNAPERFORMANCE4HEELECTRICALPROPERTIESOFTHE%ARTHAREAMUCH STRONGERFACTORFORVERTICALPOLARIZATIONTHANFORHORIZONTALHOWEVER TERRAINFEA TURESANDSURFACEROUGHNESSAREIMPORTANTFORBOTHPOLARIZATIONS #OHERENTPROCESSINGTIME 4&ORRANGESBEYONDTHESKIPDISTANCE (&RADARRETURNS ALMOSTINVARIABLYCONTAIN%ARTHBACKSCATTERATTHESAMERANGESASTARGETS$OPPLER PROCESSINGISUSEDTOSEPARATETARGETSFROM%ARTHBACKSCATTERHENCE COHERENTSAM PLESAREACQUIREDOVERANINTERVAL4 WHICHMAYEXCEEDS THOUGHITISUSUALLY INTHERANGEOFnS 7AVELENGTHK 4HEWAVELENGTHOROPERATINGFREQUENCYMUSTBESELECTEDSOTHAT THETRANSMITTEDENERGYISREFLECTEDBYTHEIONOSPHERETOILLUMINATETHEDESIREDAREA OFTHE%ARTH4HESPECTRUMOFTHEEMISSIONSMUSTBECONSTRAINEDNOTTOINTERFERE WITHOTHERUSERS"ECAUSEBOTHTHEIONOSPHEREANDTHE(& BANDOCCUPANCYDISTRIBU TIONSARETIME VARYINGPARAMETERS ADAPTIVERADARMANAGEMENTISREQUIRED 2ADARCROSSSECTION2#3 R4HERADARCROSSSECTIONOFCONVENTIONALTARGETSWILL GENERALLYBEAFUNCTIONOFFREQUENCY POLARIZATION ANDASPECTANGLE BUTAT(& THE TARGET DIMENSIONS ARE TYPICALLY OF THE SAME ORDER AS THE WAVELENGTH SO SCATTER INGBEHAVIORISDIFFERENTFROMTHATOBSERVEDATHIGHERFREQUENCIES3CATTERINGALSO OCCURSFROMTHEENVIRONMENTCLUTTERSOMODELSOFTHESCATTERINGCOEFFICIENTPER UNITAREAOFLANDANDOCEANSURFACES ORPERUNITVOLUMEOFTHETURBULENTIONOSPHERE AREUSEDTOPROVIDEEFFECTIVE2#3VALUESFOR%QWHENTHOSENATURALSCATTER ERSARETHEhTARGETSvOFINTEREST4HUS FORTHE2#3OF%ARTHCLUTTER THENORMALIZED SURFACE SCATTERING COEFFICIENT Rn IS MULTIPLIED BY THE RESOLUTION CELL SIZE !4HE IMPORTANTRESOLUTIONCELLSIZEFACTORS VIZRECEIVERANTENNABEAMWIDTHANDSPECTRAL BANDWIDTH ARENOTEXPLICITLYCONTAINEDIN%Q#LUTTERFREQUENTLYSETSTHELIMIT TOTARGETDETECTABILITYINWHICHCASE ITISTHESIGNAL TO CLUTTERRATIORATHERTHANTHE SIGNAL TO NOISERATIOTHATISOFINTEREST!CCORDINGLY ADIFFERENTFORMOFTHERADAR EQUATIONMUSTTHENBEEMPLOYED 0ROPAGATION FACTORS &P 3EVERAL PROPAGATION PHENOMENA INCLUDING &ARADAY POLARIZATIONROTATION GROUND REFLECTIONMULTIPATH MULTIPLEHOPPROPAGATION AND IONOSPHERICFOCUSINGMAYNEEDTOBEINCLUDEDINTHEEQUATION DEPENDINGONTHE SCENARIOOFINTEREST&ARADAYROTATIONREFERSTOTHEVARIATIONOFTHEPOLARIZATIONOF THESIGNALINCIDENTONTHETARGETASAFUNCTIONOFTIMEANDDISTANCE ARISINGFROMITS PROPAGATIONTHROUGHTHEMAGNETIZEDIONOSPHERICPLASMALINEARLYPOLARIZEDTRANS MITTEDSIGNALSOFTENARRIVEINTHETARGETZONEWITHAROTATEDAXISOFPOLARIZATIONBUT STILL ESSENTIALLY LINEARLY POLARIZED 3INCE MANY TARGETS HAVE 2#3 THAT VARY WITH POLARIZATION ANIMPORTANTRESULTISTHATTHEMOSTFAVORABLEPOLARIZATIONWILLILLU MINATETHETARGETRECURRENTLY4HESPATIALSCALEOFTHEPOLARIZATIONhFRINGESvINTHE RADARFOOTPRINTISTYPICALLYINTHERANGEnKM ANDTHECHANGEOFFREQUENCY NEEDEDTOROTATETHEPLANEOFPOLARIZATIONBYnATAGIVENLOCATIONINTHERADAR FOOTPRINTTHEPOLARIZATIONBANDWIDTH ISOFTHEORDEROFK(Z SODIFFERENTIAL
(&/6%2 4(% (/2):/.2!$!2
Óä°Ç
EFFECTSMAYBESIGNIFICANT/FCOURSE POLARIZATIONWILLALSOFLUCTUATEATTHERECEIV INGANTENNAASACONSEQUENCEOFTHETIME VARYINGRETURNPATH .OISE.O &ORRADARSOPERATINGINTHE(&BAND THERECEIVERINTERNALNOISEISALMOST ALWAYSLESSTHANTHEEXTERNALNOISE ,OSSES ,P ,S 4HE LOSS TERM ,P CONTAINS THE TWO WAY LOSSES ALONG THE PATH TRAVERSED INCLUDINGIONOSPHERICABSORPTIONANDGROUND REFLECTIONLOSSES,SREPRE SENTSANYRADARSYSTEMLOSSES)ONOSPHERICLOSSES WHILEPREDICTEDONASTATISTICAL BASIS CANCONSTITUTEAMAJORUNKNOWNINREAL TIMERADAROPERATION 2ANGE2 4HERANGEIN%QISTHEhSLANTRANGE vTHATIS THELENGTHOFTHESKY WAVEPATHBETWEENTARGETANDRADAR NOTTHEDISTANCEASMEASUREDALONGTHE%ARTHS SURFACE4HE IONOSPHERIC REFLECTION HEIGHT NEEDS TO BE USED TO CONVERT THIS SLANT RANGETOGREAT CIRCLEGROUNDDISTANCE4HEAPPARENTRANGETOAPARTICULARTARGETMAY TAKEONMORETHANONEVALUESINCEMULTIPLEPATHSMAYEXIST 7ITHTHESEINTERPRETATIONS THERADAREQUATION%Q CANBEUSEDTOMODEL THEPERFORMANCEOFSKYWAVERADARSWHENNOISE NOTCLUTTER ISSETTINGTHELIMITTO TARGETDETECTABILITY NOTINGTHATTHECOMPLEXITYANDSTATISTICALNATUREOFIONOSPHERIC PROPAGATION AND THE EXTERNAL NOISE ENVIRONMENT MEANS THAT IT IS OFTEN NECESSARY TOAPPLYTHEEQUATIONTOPROBABILITYDISTRIBUTIONS NOTSCALARVALUESOFTHEPARAM ETERS7HENTHETARGETSVELOCITYPLACESITSDOPPLERSHIFTBEYONDTHOSEOFANYCLUT TER RETURNS THE NOISE LIMITED MODEL IS APPROPRIATE BUT THERE ARE TWO IMPORTANT SITUATIONSWHERETHISISNOTTHECASE4HEFIRSTISSHIPDETECTION WHERETHEINTRINSIC DOPPLERSPREADOFSEACLUTTERROUTINELYEXTENDSBEYONDTHETYPICALDOPPLERSHIFTSOF MOSTSHIPECHOES4HE SECONDCASEISTHEPHENOMENONOFSPREADDOPPLERCLUTTER WHICHARISESFROMPLASMAINSTABILITIESANDTURBULENCE ESPECIALLYPOST SUNSETAND ATHIGHANDLOWLATITUDES4HEEQUIVALENTVELOCITYOFTHISTYPEOFCLUTTERCANEXTEND TOHUNDREDSOFMETERSPERSECOND MASKINGEVENFASTAIRCRAFTRETURNS4HESETOPICS AREADDRESSEDIN3ECTION$EALINGWITHCLUTTER LIMITEDSITUATIONSISAVITALPART OFTHERADARDESIGNERSTASK REQUIRINGADETAILEDUNDERSTANDINGOFTHEPHENOMENA ANDTHEIRDISTRIBUTIONS
Óä°ÎÊ /",-Ê 1 ÊÊ - 976 Ê, ,Ê - 0RINCIPAL$IFFERENCES"ETWEEN(&AND-ICROWAVE2ADAR "EFOREANALYZING (&SKYWAVERADARSYSTEMSINDETAILINTHESECTIONSTHATFOLLOWANDDESCRIBINGTHOSE PROPERTIESOFTHEENVIRONMENTTHATIMPACTTHEIRDESIGNANDPERFORMANCE ITISINSTRUC TIVETOSUMMARIZETHEPRINCIPLEDIFFERENCESBETWEENSKYWAVERADARANDCONVENTIONAL MICROWAVERADAR4HISPROVIDESACAUTIONARYREMINDERNOTTOEXTRAPOLATETOOREADILY FROMTHEFAMILIARCHARACTERISTICSOFTHEMICROWAVEDOMAINTOTHE(&BAND (& SKYWAVE RADARS OPERATE AT RANGES ABOUT AN ORDER OF MAGNITUDE GREATER THAN MICROWAVELONG RANGEAIRSURVEILLANCERADARS4HE(&RADARWAVELENGTHISHUNDREDS OFTIMESGREATER SOTHEANTENNASAREPROPORTIONATELYLARGER ASMUCHASTWOORTHREE KILOMETERSINLENGTHIFTHEYARETOSEESHIPS BUTCONSIDERABLYLESSIFONLYAIRCRAFTARE TOBEDETECTED4RANSMITTERAVERAGEPOWERMIGHTBEONTHEORDEROFSEVERALHUNDRED KILOWATTSFORASKYWAVERADAR BUTONTHEORDEROFAFEWKILOWATTSFORAMICROWAVE !4#RADAR4HEOBSERVATIONTIME#)4 FORSKYWAVESYSTEMSCANRANGEFROMONETO MANYTENSOFSECONDS BUTISONTHEORDEROFTENSOFMILLISECONDSFORMICROWAVERADAR
Óä°n
2!$!2(!.$"//+
4HELONGOBSERVATIONTIMEFORASKYWAVERADARISNEEDEDTOOBTAINTHENECESSARYECHO SIGNALENERGYTOENSURERELIABLETARGETDETECTIONASWELLASTOOBTAINTHELONGINTEGRA TIONTIMESNEEDEDFOREFFECTIVEDOPPLERPROCESSING4HEIONOSPHEREHASADOMINATING INFLUENCEONSKYWAVERADAR WHEREASTHENORMALATMOSPHEREHASVERYLITTLEEFFECTON MICROWAVE RADAR 4HE SKYWAVE RADARS FREQUENCY AND OTHER PARAMETERS ARE DRIVEN PRIMARILYBYTHENEEDTOPROPAGATEVIATHEIONOSPHERE#ONSTRAINTSIMPOSEDBYPROPA GATION AND THE AVAILABILITY OF UNOCCUPIED FREQUENCY CHANNELS DICTATE THAT THE RANGE RESOLUTIONOF(&RADARSISNOTNEARLYASGOODASTHATOFMICROWAVESYSTEMS4HE(& TRANSMITTERHASTOMAINTAINSTRINGENTCONTROLOFITSRADIATEDSIGNALSPECTRUMSOASTO AVOIDINTERFERENCETOOTHERUSERSOFTHE(&SPECTRUM!SIMILARCONSIDERATIONAPPLIES TOMICROWAVERADARS BUTNOTTOTHEEXTENTTHATITDOESAT(&-ILITARYMICROWAVERADARS LIKETOHAVEAVAILABLEAWIDESPECTRALWIDTHFORPURPOSESOFELECTRONICPROTECTIONANDTO EXTRACTMOREDETAILEDTARGETINFORMATION BUTTHEINCREASINGDEMANDSOFCIVILIANWIRE LESSSERVICESHAVEREDUCEDTHEAVAILABLESPECTRUMAVAILABLETOMICROWAVERADARSTOTHE POINTWHEREITISLIMITINGPERFORMANCE 4HESENSITIVITYOFMICROWAVERADARSISLIMITEDBYRECEIVERNOISE BUTTHESENSITIVITYOF (&RADARSISLIMITEDBYEXTERNALNOISETHATENTERSTHERECEIVERTHROUGHTHEANTENNA4HIS EXTERNALNOISEISDUENOTONLYTONATURALMECHANISMSSUCHASTHUNDERSTORMSBUTTOTHESIG NALSFROMTHEMANY(&TRANSMITTERSTHROUGHOUTTHEWORLD"OTHMICROWAVEAND(&RADARS CANBELIMITEDBYTHELARGEECHOSIGNALSFROMLANDORSEA THOUGHIN(&SKYWAVERADARS THEPROBLEMISPARTICULARLYSEVERE$OPPLERPROCESSINGISESSENTIALUNDERSUCHCONDITIONS &ORSOMEAIRCRAFT THERADARCROSSSECTIONAT(&ISSIGNIFICANTLYLARGERTHANTHATATMICRO WAVES-ANY(&/4(RADARSUTILIZEAN&- #7WAVEFORM SOWIDELYSEPARATEDSITESARE NEEDEDTOMINIMIZETHELEAKAGEOFTHETRANSMITTERINTOTHERECEIVER-ICROWAVERADARS HAVEUSED&- #7WAVEFORMSINTHEPAST BUTINMOSTCASES THESEHAVEBEENREPLACEDBY WAVEFORMSTHATDONTREQUIRESEPARATETRANSMITTERANDRECEIVERSITES 4ABLEPRESENTSACOMPARISONOFSOMEKEYRADARPARAMETERSFORREPRESENTATIVE RADARSYSTEMSOFEACHTYPE ANDCONTRASTSTHEWAYSINWHICHTHERESPECTIVEMODESOF PROPAGATION SCATTERING NOISE AND DEPLOYMENT CONSTRAIN THE FORM AND FUNCTION OF RADARSYSTEMS )MPLICATIONSFOR3KYWAVE2ADAR$ESIGN &ROMANEXAMINATIONOF4ABLE ITISCLEARTHATASKYWAVERADARISNOTSIMPLYAMICROWAVERADARSCALEDUPINSIZEBY AFACTOROF^ THATIS INPROPORTIONTOTHEWAVELENGTH2EFERRINGTOTHERADAR EQUATION THE2nLOSSTERMMEANSTHAT FORAREPRESENTATIVETENFOLDINCREASEINDETEC TIONRANGEOF(&OVERMICROWAVE D"EXTRARANGELOSSACCUMULATES4HISCANNOT ALLBERECOVEREDBYRADIATINGMOREPOWERANDINCREASINGANTENNAGAIN FORPRACTICAL ENGINEERINGREASONSANDCOST APARTFROMCONSTRAINTSIMPOSEDBYIONOSPHERICPROPA GATION#OHERENTDOPPLER PROCESSINGPROVIDESTHENECESSARYPROCESSINGGAIN BUTTHE PROCESSINGTIMESREQUIREDFROMTOSMEANTHATREVISITRATESWHENCONDUCTING SURVEILLANCEOVERANEXTENDEDREGIONWILLFALLBELOWACCEPTABLELEVELSUNLESSMULTIPLE RECEIVEBEAMSAREPROCESSEDINPARALLEL$ESIGNERSHAVEEXPLOREDDIFFERENTTRADE OFFS IN MOST CASES CONVERGING ON SCHEMES IN WHICH n RECEIVE BEAMS ARE FORMED WITHINABROADERTRANSMITTEDBEAMFOOTPRINT4HEREDUCEDTRANSMITTINGANTENNAGAIN MAYBECOMPENSATEDBYINCREASINGPOWERORCOHERENTPROCESSINGTIME %VEN UNDER BENIGN CONDITIONS THE IONOSPHERE SELDOM SUPPORTS HIGHLY COHER ENTPROPAGATIONOVERBANDWIDTHSGREATERTHAN^K(Z EVENWHENCLEARCHANNELS WIDEENOUGHTOACCOMMODATESUCHWAVEFORMSAREAVAILABLE WHICHISINFREQUENTLY -ORETYPICALLY CLEARCHANNELSRANGEFROMnK(Z SOTHEWAVEFORMBANDWIDTH ISNORMALLYCHOSENTOLIEINTHISRANGE4HECORRESPONDINGRANGERESOLUTIONSEXTEND
(&/6%2 4(% (/2):/.2!$!2
Óä°
FROM n KM4HE CROSS RANGE RESOLUTION CELL DIMENSION ,2 AT RANGE 2 IS GIVEN BY , y 2$K WHERE $ IS THE RECEIVING ARRAY APERTURE AND K IS THE RADAR WAVELENGTH 4!",% +EY$IFFERENCES"ETWEEN-ICROWAVE2ADARAND(&3KYWAVE2ADAR
4HEPARAMETERVALUESQUOTEDHEREAREINTENDEDTOBEBROADLYREPRESENTATIVE RATHER THANANATTEMPTTOSPANALLKNOWNSYSTEMS ) -)#2/7!6%2!$!2 4YPECHOSENFORCOMPARISON
,ONG RANGEAIRTRAFFIC CONTROLSUCHAS!232
)) (&3+97!6%2!$!2
*OINTAIRCRAFTANDSHIPDETECTION TWO SITERADARSUCHAS*INDALEE */2. AND 2/4(2 -AJORANTENNADIMENSIONM n n !VERAGETRANSMITPOWERK7 !NTENNARADIATIONPATTERN &ULLYDEFINEDBYANTENNA 3TRONGLYINFLUENCEDBYGROUND CONSTRUCTION PROPERTIESAROUNDANTENNA 4YPICALOPERATINGRANGEKM n n -INIMUMRANGEKM 2ANGERESOLUTIONM n u 3 TRUCTUREDHORIZONTALLYAND 0ROPAGATIONMEDIUM u (OMOGENEOUSOR VERTICALLY BOTHDETERMINISTICALLYAND STRATIFIED RANDOMLY ONMANYSCALES u &REQUENCYDISPERSIVE u .ONDISPERSIVE u !NISOTROPICMAGNETOIONIC u )SOTROPIC u (IGHLYDYNAMIC u 3TABLE u 7EAKLYNONLINEAR u ,INEAR u 6 ARIESDRAMATICALLYWITHTIMEOF u .EARLYCONSTANT DAY SEASON ETC u 2EFLECTEDFROMIONOSPHERE 2ADARSIGNALPROPAGATIONPATH u ,INE OF SIGHT u ULTIPLEPATHS RESULTINGINMULTIPLE u 5SUALLYUNIQUEMAY ECHOESFROMASINGLETARGET AT HAVESIMPLEGROUND DIFFERENTAPPARENTRANGES BEARINGS REFLECTIONMULTIPATH ELEVATIONANGLES ANDDOPPLERSHIFTS u 2ELATIVELYSTABLE u 5NSTABLE u 0 OORLYKNOWN MUSTBEINFERRED FROMANCILLARYSOUNDINGSYSTEMS $OMINANTPROPAGATIONEFFECTS u -ULTIPATHINTERFERENCE u !TTENUATION u &OCUSINGANDDEFOCUSING ONTHERADARSIGNAL BETWEENDIRECTAND SURFACE REFLECTEDSIGNALS u 0OLARIZATIONTRANSFORMATION u 0HASEMODULATION u 7AVEFRONTDISTORTION 4ARGETSCATTERINGREGIME /PTICALHIGHFREQUENCY 2AYLEIGHnRESONANCE IE TARGETSIZE OR^RADARWAVELENGTH IE TARGETSIZERADAR WAVELENGTH ,OOK DOWNVIEWINGGEOMETRY #LUTTER u #ANBESERIOUS INEVITABLYRESULTSINSTRONGGROUND ESPECIALLYATSHORT ECHOESATTHESAMERANGEASTHETARGET RANGES u -INIMIZEDBYNARROW TYPICALLYnD"STRONGERTHANTHE BEAM SHORTPULSE AND TARGETECHO DOPPLERPROCESSING $OPPLERPROCESSING 7IDELYUSEDFORDETECTION %SSENTIALTOSEPARATEMOVINGTARGETS OFMOVINGTARGETSINCLUTTER FROMSTRONGCLUTTERRETURNS
Óä°£ä
2!$!2(!.$"//+
4!",% +EY$IFFERENCES"ETWEEN-ICROWAVE2ADARAND(&3KYWAVE2ADAR
4HEPARAMETERVALUESQUOTEDHEREAREINTENDEDTOBEBROADLYREPRESENTATIVE RATHER THANANATTEMPTTOSPANALLKNOWNSYSTEMS #ONTINUED ) -)#2/7!6%2!$!2 &REQUENCYCONSTRAINTS
.OISEFLOORDOMINATEDBY 3ITINGCONSTRAINTS
)) (&3+97!6%2!$!2
u "OUNDEDABOVEBYTHESTATISTICAL #ANBESERIOUS AVAILABILITYOFSKYWAVEPROPAGATION BECAUSEOFTHENEEDFOR TORANGESOFINTEREST WIDEBANDRADARSYSTEMS u "OUNDEDBELOWBYSPECTRUM ANDBYCOMPETITION AVAILABILITY ANTENNASIZE ANDTHE FORTHEMICROWAVE RAPIDFALL OFFINTARGET2#3 FREQUENCYSPECTRUMBY COMMUNICATIONSANDOTHER u -USTNOTINTERFEREWITHOTHERUSERS INTHECROWDED(&SPECTRUM THUS ELECTROMAGNETICSERVICES LIMITINGCHOICEOFFREQUENCYAND BANDWIDTH u -USTADAPTCONTINUALLYTOTHE CHANGINGIONOSPHERESOASTO MAINTAINILLUMINATIONOFCURRENT TARGETREGION )NTERNALRECEIVERNOISE 3OURCESATMOSPHERIC GALACTIC THERMAL ETC ANTHROPOGENIC ETC u 5NOBSTRUCTED ELEVATED u 2ECEIVEARRAYSITEMUSTBE%- SITESPREFERRED QUIET GENERALLYRURAL TOAVOID CITYANDINDUSTRIALNOISEAT(& FREQUENCIES u (UGEARRAYSREQUIREFLAT OPEN SPACESTOMINIMIZETOPOGRAPHIC EFFECTSONBEAMPATTERNS u )FABISTATICORTWO SITEQUASI MONOSTATICDESIGNISADOPTED IT NEEDSTWOSITESWITHADEQUATE SEPARATION^KM ANDTHE CORRECTGEOGRAPHICALRELATIONSHIP RELATIVETOTHECOVERAGEARC u ,OCATIONONTHE%ARTHMUSTBESUCH THATAURORALANDEQUATORIALSPREAD DOPPLERECHOESDONTMASKTARGETS
(ENCE TOACHIEVE, KMATKMRANGEWHENTHEFREQUENCYIS-(Z AND THUSARESOLUTIONCELLNOTTOOECCENTRICINSHAPE REQUIRESANARRAYAPERTUREOFABOUT M&EEDINGARRAYSOFTHISSIZECANREQUIREHUNDREDSOFKILOMETERSOFCABLESOR IN SOMESYSTEMS FIBEROPTICS ANDRAISESCHALLENGINGPROBLEMSINARRAYCALIBRATION4HE TRANSMITTINGARRAYAPERTURE ASSUMINGyRECEIVEBEAMSTOBEFITTEDINTOTHETRANSMIT BEAM NEEDBEONLY^MATTHISFREQUENCY )TFOLLOWSFROMTHERADAREQUATIONANDTHECONSIDERATIONSJUSTDISCUSSEDTHATTRANS MITPOWERINTHERANGEOFnK7ISGENERALLYAPPROPRIATEFORDETECTINGSMALL AIRCRAFTTARGETSOVERAWIDERANGEOFCONDITIONS)NORDERTORADIATEPOWEREFFICIENTLY THETRANSMITTINGANTENNAELEMENTSTENDTOBELARGE RESONANTSTRUCTURESFOREXAMPLE THEVERTICALLOG PERIODICANTENNASUSEDINTHE*/2.SYSTEMAREUPTOMTALL)N CONTRAST THECHOICEOFRECEIVINGANTENNAELEMENTHASTRADITIONALLYBEENBASEDONTHE
(&/6%2 4(% (/2):/.2!$!2
Óä°££
PRECEPTTHATEFFICIENCYISOFLOWIMPORTANCEFOR(&RECEPTIONBECAUSEEXTERNALNOISE ISALMOSTALWAYSFARSTRONGERTHANINTERNALNOISE!MOREEFFICIENTRECEIVINGELEMENT ACCEPTSMORESIGNALPOWERBUTEQUALLYMOREEXTERNALNOISESO PRIMAFACIE NOTHINGIS GAINEDINTERMSOFTHESIGNAL TO NOISERATIO#OSTISTHUSREDUCEDBYEMPLOYINGASMALL RECEIVINGANTENNAELEMENT(EIGHTSOFnMARECOMMON 4HELOOK DOWNGEOMETRYOFSKYWAVEILLUMINATIONRESULTSINSTRONGCLUTTERRETURNS INTHESAMERANGECELLASTHETARGET DEMANDINGAHIGHDYNAMICRANGEABLETOSUPPORT CLUTTER TO TARGETENERGYRATIOSINEXCESSOFD"4HISPLACESSEVEREDEMANDSONTHE SPECTRALPURITYANDDYNAMICRANGEOFTHERADARWAVEFORMGENERATOR TRANSMITTING AND RECEIVINGSYSTEMS(IGHSENSITIVITYHASTHESIDEEFFECTOFREVEALINGTHEECHOESFROM MANYNATURALSCATTERERSINTHEIONOSPHERE ASWELLASTHESPECTRUMOFGROUNDCLUTTERTHAT HASBEENSPREADINDOPPLERBYTHEFLUCTUATIONSOFTHESIGNALPROPAGATIONPATH)NORDER TORECOGNIZEANDSUPPRESSTHESEUNWANTEDRETURNS WHICHCANOBSCURETARGETECHOES ANUNDERSTANDINGOFTHEUNDERLYINGPHYSICSISESSENTIAL !DISTINCTIVEREQUIREMENTOFASKYWAVERADARISASUITEOFAUXILIARYSYSTEMSTOMON ITORTHESTATEOFTHEIONOSPHEREANDTHEAVAILABILITYOFUNOCCUPIEDCHANNELSINWHICH TOOPERATE4HISRELIANCEONCONTINUOUSENVIRONMENTALMONITORINGANDTHEASSOCIATED ABILITYTOADAPTTHERADARPARAMETERSANDTASKINGTOMAKEBESTUSEOFTHEPREVAILING CONDITIONS CANNOT BE SATISFIED WITH SIMPLE LOW DYNAMIC RANGE EQUIPMENT FOR THAT WOULDFAILTOREVEALMANYOFTHEPHENOMENATHATARESETTINGTHETHRESHOLDFORTARGET DETECTIONANDTRACKING&URTHER AHIGHDEGREEOFAUTOMATIONISESSENTIALTOKEEPUP WITHTHECHANGINGENVIRONMENT !COMPARISONOFPRINCIPLEDESIGNPARAMETERSOFSEVERALCURRENTANDFORMEROPERA TIONAL(&SKYWAVERADARSISPRESENTEDIN4ABLE ILLUSTRATINGTHEDIVERSITYOFENGI NEERING SOLUTIONS THAT HAVE BEEN IMPLEMENTED TO MEET SPECIFIC MISSION OBJECTIVES
4!",% 0RINCIPAL$ESIGN0ARAMETERSFOR3OME-AJOR(&3KYWAVE2ADAR3YSTEMS
0ASTAND0RESENT 4HISINFORMATIONHASBEENCOMPILEDFROMSOURCESTHAT INSOMECASES AREINCOMPLETE7HEREONLY PARTIALINFORMATIONISPROVIDED ITMAYSTILLBEUSEFULFORCOMPARISONPURPOSES.OTESI 6,0! DENOTESVERTICALLOG PERIODICANTENNAANDII BANDN BAND LINEARARRAYSAREUSUALLYCONSTRUCTEDAS CONTIGUOUSCOLLINEARARRAYS
$EVELOPER
*/2. ,AVERTON
$34/ !USTRALIA
4ELECOM 'ENERAL%LECTRIC 2AYTHEON !USTRALIA 53! 53! '%# -ARCONI 5+2,- 53! !USTRALIA
/.%2! &RANCE
.))$!2 2USSIA
1UASI MONOSTATIC
1UASI MONOSTATIC
1UASI MONOSTATIC
4RUE MONOSTATIC
1UASI MONOSTATIC
NA
n D"7
D"7
D"7
9EAROFFIRST TARGETDETECTIONS #ONFIGURATION 1UASI MONOSTATIC 4Xn2XSITE SEPARATIONKM -AXTRANSMITTER POWERK7 4XGAIND" %20 D"7
!.&03 %#237#23
!.403 2/4(2
3TEEL9ARD +OMSOMOLSK .OSTRADAMUS NA!MUR
*INDALEE 3TAGE"
Óä°£Ó
2!$!2(!.$"//+
4!",% 0RINCIPAL$ESIGN0ARAMETERSFOR3OME-AJOR(&3KYWAVE2ADAR3YSTEMS
0ASTAND0RESENT 4HISINFORMATIONHASBEENCOMPILEDFROMSOURCESTHAT INSOMECASES AREINCOMPLETE7HEREONLY PARTIALINFORMATIONISPROVIDED ITMAYSTILLBEUSEFULFORCOMPARISONPURPOSES.OTESI 6,0! DENOTESVERTICALLOG PERIODICANTENNAANDII BANDN BAND LINEARARRAYSAREUSUALLYCONSTRUCTEDAS CONTIGUOUSCOLLINEARARRAYS #ONTINUED *INDALEE 3TAGE" 4XARRAYDESIGN BANDLINEAR ARRAYOF LOWBAND ANDHIGH BAND 6,0! ANTENNAS
&REQUENCY n RANGE-(Z 4XAPERTURESM
*/2. ,AVERTON
ADJACENT CONTIGUOUS BANDLINEAR BANDLINEAR ARRAYSOF6,0! ARRAYSOF ANTENNAS CANTEDDIPOLES ARRAYSORIENTED WITH MTALL ATnTOEACH BACKSCREENS OTHER ELEMENTSPER BANDARRAYS ORIENTEDATn n n
4XAZIMUTH on on BEAMSTEERDEG 2XARRAYDESIGN ,INEARARRAY LINEARARRAYS OF MFAN OFTWIN MONOPOLEPAIRS MONOPOLE GROUPEDAS ELEMENTS OVERLAPPED ARRAYSATn SUBARRAYS 2XAPERTUREM
!.&03 %#237#23
!.403 2/4(2 BANDLINEAR ARRAYOFr 6,0! ANTENNAS
9 SHAPED ARRAYOFr BICONICAL ELEMENTS RANDOMLY DISTRIBUTED
rVERTICAL CURTAINARRAYS OFMASTSr VERTICALLY STACKED HORIZONTAL CAGEDIPOLES
n n
n
n
ARMSr LONG r WIDE n
on
on
CONTIGUOUS LINEARARRAYS OFr MVERTICAL MONOPOLES WITHM BACKSCREENS ARRAYSATn
,INEARARRAY 9 SHAPED rVERTICAL OFrM ARRAYOFr CURTAINARRAYS VERTICALTWIN MBICONICAL OFMASTSr MONOPOLES ELEMENTS VERTICALLY GROUPEDASr STACKED SUBARRAYS HORIZONTAL WITHRANDOM CAGEDIPOLES DISTRIBUTION LONG r ARMSr LONG r HIGH WIDE
.OOFRECEIVE CHANNELS 2XAZIMUTH on on on on BEAMSTEER 7AVEFORMTYPE ,INEAR&-#7 ,INEAR&-#7 ,INEAR&-#7 ,INEAR&- #7,INEAR &-#7 7AVEFORM ^n ^n n n REPETITION FREQUENCY(Z 7AVEFORM nTYPICAL nTYPICAL n n BANDWIDTHK(Z #OHERENT n!IR n!IR n n INTEGRATION MODE MODE TIMES n3HIP n3HIP MODE MODE 0RIMARYMISSION !IRCRAFT !IRCRAFT !IRCRAFT !IRCRAFT DETECTION DETECTION DETECTION DETECTION 3ECONDARY MISSIONS
3TEEL9ARD +OMSOMOLSK .OSTRADAMUS NA!MUR
3HIPDETECTION 3HIPDETECTION #RUISEMISSILE 2EMOTE 2EMOTE DETECTION SENSING SENSING
3HIP DETECTION
n #ODEDPULSE
"INARYPHASE CODEDPULSE
!IRCRAFT DETECTION
"ALLISTIC MISSILE DETECTION 3HIPDETECTION !IRCRAFT 2EMOTE DETECTION SENSING #RUISEMISSILE DETECTION
(&/6%2 4(% (/2):/.2!$!2
Óä°£Î
4HETERMQUASI MONOSTATICISUSEDTODENOTECONFIGURATIONSINWHICHTHETRANSMITAND RECEIVE SITES ARE SEPARATED AS IS OFTEN DONE WITH RADARS EMPLOYING &- #7 WAVE FORMS BUTNOTSOFARAPARTTHATTHEANGLESUBTENDEDATTHETARGETISMORETHAN^n SO THESCATTERINGBEHAVIORISCLOSETOWHATISOBSERVEDFOREXACTLYMONOSTATICGEOMETRY
Óä°{Ê / Ê" "-* , ÊÊ Ê, "76 Ê*,"*/" 4HESOLARACTIVITYTHATDRIVESTHEIONIZATIONOFTHE%ARTHSUPPERATMOSPHEREISVARIABLE ONADIURNAL SEASONAL ANDLONG TERMBASISWITHASUPERIMPOSEDRANDOMCOMPONENTAND OCCASIONALMAJORSTORMSANDOTHERDISTURBANCES&URTHER THE%ARTHSLOWERATMOSPHERE ISCOUPLEDTOTHEIONOSPHEREBYAVARIETYOFUPWARD PROPAGATINGWAVEANDRADIATION PROCESSES WHEREASTHE%ARTHSMAGNETOSPHERE THEREGIONBEYONDTHEIONOSPHEREWHERE THESOLARWINDINTERACTSWITHTHE%ARTHSMAGNETICFIELD ISTHESOURCEORCONDUITFOR CORRESPONDINGPERTURBATIONSFROMABOVE4HEIONOSPHERICRESPONSETOALLTHESEEXTERNAL FORCESISGOVERNEDNOTONLYBYINERTIALEFFECTSBUTALSOBYCHEMICALREACTIONSANDBYTHE EMBEDDEDTIME VARYINGELECTRICANDMAGNETICFIELDSTHATLINKTHEIONOSPHERICPLASMA TOTHE%ARTHANDTOTHEINTERPLANETARYMEDIUM!SACONSEQUENCE THESTRUCTUREOFTHE IONOSPHEREUNDERGOESCHANGESONAWIDEVARIETYOFSPATIALANDTEMPORALSCALES WHICH DRASTICALLYAFFECTITSPROPERTIESASAMEDIUMFORRADIOWAVEPROPAGATION 4HEPRIMARYREQUIREMENTFORRADARSYSTEMDESIGNISAQUANTITATIVEDESCRIPTIONOF THEPROPAGATIONCHARACTERISTICSOVERTHEPROPOSEDCOVERAGEREGION3PECIFICALLY THE RADARDESIGNERNEEDSASTATISTICALDESCRIPTIONTHATWILLENABLEMATCHINGTHETRANSMITTED SIGNAL POWERLEVEL ANDANTENNAGAINPATTERNTOTHESUPPORTEDFREQUENCYSPAN NOISE LEVELS PROPAGATIONLOSSCHARACTERISTICS ANDRAYPATHSTOTHETARGETREGION)NADDITION THERADAROPERATORNEEDSAMODELWITHENOUGHSOPHISTICATIONTOPERMITFULLINTERPRETA TIONOFTHEREAL TIMESOUNDINGSFOROPERATINGPARAMETERSELECTION SIGNALPROCESSING ANDDATAANALYSIS7ITHTHISLATTERREQUIREMENT ASTATISTICALDESCRIPTIONISUSUALLYNOT ADEQUATE AS IMPORTANT FEATURES MAY BE LOST &OR EXAMPLE UNDER RAPIDLY CHANGING IONOSPHERICCONDITIONS THERADARECHOESWILLEXPERIENCEATIME VARYINGDOPPLERSHIFT !VERAGINGOVERTIMEWOULDRESULTINADOPPLERSHIFTTENDINGTOZERO#LEARLY THISISOF NOVALUETOTHEOPERATORWISHINGTOCOMPENSATEFORIONOSPHERICMOTIONANDHENCETO RETRIEVEAMEANINGFULESTIMATEOFTARGETRADIALVELOCITY!SASECONDEXAMPLE CONSIDER THESITUATIONWHEREANATMOSPHERICGRAVITYWAVE!'7 ISPROPAGATINGTHROUGHTHE IONOSPHERE IN THE VICINITY OF THE CONTROL POINT IONOSPHERIC REFLECTION POINT WHILE ATARGETISBEINGTRACKED4HEIONOSPHEREISONLY^IONIZEDATTHEALTITUDESOF INTERESTTO(&RADAR BUTWAVESINTHENEUTRALGAS UNDERTHERESTORINGFORCEOFGRAVITY TRANSFERTHEIRMOTIONTOTHEFREEELECTRONSVIACOLLISIONS!STHEDISTRIBUTIONOFELECTRONS DEFINESTHEhREFLECTINGSURFACEvEXPERIENCEDBYTHERADARSIGNALS THEAPPARENTBEARING ANDRANGEOFTHETARGETWILLFLUCTUATEASTHEIONOSPHERIChREFLECTINGSURFACEvUNDULATES INRESPONSETOTHE!'74HISUNDULATIONISKNOWNASATRAVELINGIONOSPHERICDISTUR BANCE4)$ 4)$SMAYHAVEWAVELENGTHSOFHUNDREDSOFKILOMETERSANDSPEEDSUPTO KILOMETERSPERHOUR5NLESSTHERADARMAKESAPPROPRIATEREAL TIMECORRECTIONSTO THETARGETCOORDINATES TRACKINGACCURACYWILLBESEVERELYIMPAIRED 4OADDRESSTHESEVARIOUSNEEDS ITISADVANTAGEOUSTOADOPTCORRESPONDINGDESCRIP TIONSORMODELS EMPHASIZINGDIFFERENTASPECTSOFTHEIONOSPHEREANDITSINFLUENCEON RADIOWAVEPROPAGATIONAND HENCE (&RADARPERFORMANCE)NMANYCASESOFPRACTICAL INTEREST IONOSPHERICMODELSDEVELOPEDORIGINALLYFOR(&COMMUNICATIONSPURPOSES
Óä°£{
2!$!2(!.$"//+
CANBEADAPTEDTOTHERADARCONTEXT WHERETHEMAINDIFFERENCEISTHEGREATERSENSITIV ITYOFRADAROBSERVATIONSTODYNAMICALPROCESSES4HISARISESPRIMARILYBECAUSEOFTHE EXTREMELYHIGHDYNAMICRANGEREQUIREDTOACCOMMODATEANDPRESERVETARGETECHOESIN THEPRESENCEOFSTRONGCLUTTERANDEXTERNALNOISE )ONOSPHERIC3TRUCTURE 4HEBASICPHYSICSOFIONIZATIONANDRECOMBINATIONPRO CESSESLEADSTOANATURALDIVISIONOFTHEIONOSPHEREINTOANUMBEROFREGIONS $2EGION 4HISREGIONOCCUPIESTHELOWESTALTITUDESCONSIDERED)TEXTENDSFROM TO KM WITH ELECTRON DENSITY INCREASING RAPIDLY WITH ALTITUDE IN THE DAYTIME )TS PROPERTIES REFLECT THE BALANCE BETWEEN FREE ELECTRON PRODUCTION BY THE INCIDENT SOLARRADIATIONFLUXANDFREEELECTRONLOSSVIAVARIOUSELECTRON IONANDELECTRON NEUTRAL RECOMBINATIONPROCESSES!CCORDINGLY THEMAXIMUMIONIZATIONINTHE$REGIONOCCURS NEARTHESUBnSOLARPOINTANDWILLBEGREATESTDURINGPERIODSOFHIGHESTSOLARACTIVITY SUNSPOTMAXIMUM THOUGHITDOESNOTACHIEVEDENSITIESSUFFICIENTTOREFLECTOREVEN SIGNIFICANTLYREFRACT(&RADIOWAVES4HEKEYROLEOFTHE$REGIONIN(&RADIOWAVE PROPAGATION IS SIGNAL ATTENUATION VIA ELECTRON NEUTRAL COLLISIONS THAT ARE FREQUENT AT THESEMODERATEALTITUDESWHERETHENEUTRALSPECIESDENSITYISSTILLRELATIVELYHIGH)TIS NOTREPRESENTEDEXPLICITLYINSOMEIONOSPHERICMODELSWHEREITSEFFECTSAREACCOUNTED FORWITHANEMPIRICALLYDERIVEDPATH LOSSCALCULATION %2EGION 4HISIONIZATIONREGIONEXTENDSBETWEENABOUTANDKMINALTI TUDEWITHAMAXIMUMNEARKMWHENSUNLIT)NADDITION THEREMAYBEANOMALOUS IONIZATIONREFERREDTOASSPORADIC%4HISLATTERIONIZATIONLAYERISTYPICALLYONLYAFEW KILOMETERSTHICKANDUSUALLYSHORT LIVED OFTENLASTINGLESSTHANANHOURITMAYBEEITHER SMOOTHORPATCHY ISSEASONALLYANDDIURNALLYVARIABLE WEAKLYCORRELATEDWITHSOLAR ACTIVITY SHOWINGATENDENCYTOFAVORLOWSUNSPOTNUMBERS ANDHASMARKEDVARIATION WITHLATITUDE&ROMTHEPROPAGATIONPERSPECTIVE SPORADIC%HOLDSASPECIALPLACEASTHE LAYERPROVIDINGTHEMOSTSTABLEPROPAGATIONOVERCOHERENTINTEGRATIONTIMESTYPICALOF SKYWAVERADAR"ECAUSEITISONLY^KMABOVETHE%ARTHSSURFACE THEMAXIMUM RANGETHATCANBEREACHEDVIAONE HOP% LAYERPROPAGATIONISONLY^KM THOUGH NORMALLYTHELAYERISNOTTOTALLYREFLECTING SOSOMEENERGYCONTINUESUPWARDTOTHE & LAYERWHEREITISREFLECTEDTOREACHTHE%ARTHSSURFACEATMUCHGREATERRANGES &2EGION 4HISISTHEHIGHEST ALTITUDEREGIONOFINTERESTFORSKYWAVEPROPAGATION ANDITISALSOTHEREGIONOFGREATESTELECTRONDENSITY)NTHEDAYLIGHTHOURS THE®ION SOMETIMESMANIFESTSTWOCOMPONENTLAYERS ESPECIALLYINSUMMER4HE&LREGIONLIES BETWEEN AND KM AND LIKE THE % REGION IS DIRECTLY DEPENDENT UPON SOLAR RADIATIONITREACHESMAXIMUMINTENSITYABOUTHAFTERLOCALNOON4HE®IONIS VARIABLEINBOTHTIMEANDGEOGRAPHICALLOCATION4HEALTITUDEOFTHE®IONPEAKLIES TYPICALLYBETWEENANDKMATMIDDLELATITUDES4HE& REGIONIONIZATIONSHOWS MARKEDDAY TO DAYVARIATIONSAND INGENERAL ISNOTTHEREGULARSUNFOLLOWERTHATTHE %AND®IONSARE 4HESIMPLEPHYSICALPICTUREOFTHEIONOSPHEREASCONSISTINGOFSEVERALMOREORLESS CONCENTRIC LAYERS MUST BE MODIFIED SUBSTANTIALLY AT BOTH LOW AND HIGH LATITUDES TO TAKEINTOACCOUNTTHEEFFECTSOFTHEIMPRESSEDELECTRICANDMAGNETICFIELDS4OBEGIN WITH THEDISPLACEMENTOFTHE%ARTHSMAGNETICAXISFROMITSROTATIONALAXISMEANSTHAT THEIONOSPHEREDOESNOTPRESERVEAMOREORLESSCONSTANTFORMENVELOPINGAROTATING EARTH .EAR THE MAGNETIC EQUATOR WHERE THE GEOMAGNETIC FIELD IS CLOSE TO HORIZON TAL ATMOSPHERICTIDESANDASSOCIATEDWINDSDRIVETHESO CALLED% REGIONAND& REGION
(&/6%2 4(% (/2):/.2!$!2
Óä°£x
DYNAMOS RESULTINGINANUPWARDDRIFTOFTHEIONOSPHERICPLASMAANDITSSUBSEQUENT DESCENTALONGTHEGEOMAGNETICFIELDLINES4HERESULTINGELECTRONDENSITYDEPLETIONAT THEEQUATORANDROUGHLYSYMMETRICENHANCEMENTSINTHEVICINITYOF^n.3LATITUDE ISKNOWNASTHE!PPLETONOREQUATORIALANOMALY"ESIDESCAUSINGERRORSINESTIMATED TARGETRANGEANDBEARING THETILTEDIONOSPHERIChREFLECTINGSURFACEvNEARTHEEQUATOR CANSUPPORTSCATTERINGOFINCIDENTRADIOWAVESINTOLOW LOSSELEVATEDTRANS EQUATORIAL MODESCHORDALMODES THATRETURNSTRONGCLUTTERFROMTHEOPPOSITEHEMISPHERE OFTEN WITHHIGHLYUNSTABLEPHASECHARACTERISTICS )N THE POLAR ZONES THE NEAR VERTICAL GEOMAGNETIC FIELD LINES PROVIDE A PATHWAY FOR CHARGED PARTICLES AND DISTURBANCES OF SOLAR AND MAGNETOSPHERIC ORIGIN TO REACH IONOSPHERICHEIGHTSANDCONTRIBUTETOIONIZATIONPROCESSESANDPLASMATRANSPORT4HE BESTKNOWNPHENOMENAHEREARETHEAURORAE WHICHARECONCENTRATEDINOVALSPOLE WARDOFTHEBOUNDARYWHERETHE%ARTHSGEOMAGNETICFIELDLINESCHANGEFROMCLOSED CONNECTEDTOTHEIRIMAGESINTHEOPPOSITEHEMISPHERE TOOPEN THATIS CONNECTEDTO THE INTERPLANETARY MAGNETIC FIELD! WIDE VARIETY OF PLASMA WAVES AND INSTABILITIES POPULATE THESE REGIONS PRODUCING IRREGULARITIES THAT ACHIEVE HIGH ELECTRON DENSITIES ANDHENCE PROVIDESTRONGSOURCESOFSPREAD DOPPLERCLUTTER4HEYHAVEBEENKNOWNTO IMPACTSKYWAVERADARSYSTEMSSEVERELY )ONOSPHERIC6ARIABILITY 7HILEALLIONOSPHERICPROPERTIESARETIME VARYING FROM AN/4(2PERSPECTIVE ITISUSEFULTOSEPARATETHEhFASTvPROCESSESORhDYNAMICSvFROM THEhSLOWvORhSTRUCTURALvVARIABILITY!PHENOMENONISTERMEDDYNAMICALRELATIVETO ARADAROBSERVATIONPROCESSIFITOCCURSONATIMESCALECOMMENSURATEWITHTHECORRE SPONDINGPROCESSTIMESCALE SUCHASI PULSEWAVEFORMREPETITIONINTERVAL II COHERENT INTEGRATION DWELL TIME III SCAN REVISIT TIME OR IV MISSION TRACK LIFETIME $YNAMICALPROCESSESIMPACTDIRECTLYONHOWONESHOULDPROCESSTHERECEIVEDSIGNALS ORPERFORMTRACKING3LOWPROCESSES SUCHASTHE YEARSOLARCYCLE SEASONALCHANGES ANDTHEDIURNALCYCLEOFTHE% AND& LAYERSCANGENERALLYBETREATEDASQUASI STATIONARY BACKGROUNDPROCESSESTHATSETUPTHEIONOSPHERICSTRUCTUREATANYGIVENTIME WITHIN WHICH FAST PROCESSES MAY OCCUR!N EXCEPTION TO THIS CLASSIFICATION ARISES WITH THE DAWN AND DUSK TERMINATORS THAT IS THE DAY NIGHT BOUNDARIES SWEEPING AROUND THE %ARTHATKMHR THEYPRODUCEABRUPTCHANGESINTHEIONOSPHEREANDTRIGGERLARGE SCALEINSTABILITIES 3TRUCTURAL6ARIABILITY 4HEDAY NIGHTCYCLEPRODUCESDRASTICCHANGESINTHEION IZATIONDISTRIBUTIONWITHINTHEIONOSPHERE!TNIGHT THE$ LAYERDISAPPEARS THE%AND ®IONSEXPERIENCEASUBSTANTIALDECREASEINIONIZATION ANDTHEEQUATORIALANDPOLAR REGIONSAREMOREPRONETOLARGE SCALEPERTURBATIONS4HEEXTENTOFDIURNALVARIATIONCAN BESEENBYEXAMINING&IGURE WHICHSHOWSMEASUREDELECTRONDENSITYEXPRESSED INTERMSOFPLASMAFREQUENCYASDEFINEDIN%Q VERSUSVIRTUALHEIGHTANDTIME OF DAYATAMID LATITUDELOCATION 4YPICALLY THEDIURNALVARIATIONREQUIRESARADARTO VARYITSOPERATINGFREQUENCYBYMORETHANANOCTAVEINFREQUENCYTOMAINTAIN HOUR SURVEILLANCEOVERAFIXEDTARGETLOCATION
6IRTUALHEIGHTISTHEREFLECTIONHEIGHTCOMPUTEDFROMSIGNALTIMEDELAYBYASSUMINGTHATTHERADIOWAVETRAVELSAT THESPEEDOFLIGHTASIFINFREESPACEINFACT THERADIOWAVEGROUPVELOCITYINTHEPLASMAISLOWER SOTHETRUEHEIGHT ISLESS&ORMOSTPURPOSES ITISMORECONVENIENTTODEALWITHVIRTUALHEIGHT BECAUSETHEREARETWOTHEOREMSTHAT DRAMATICALLYSIMPLIFYPRACTICALCALCULATIONS-ARTYNSTHEOREMSHOWSTHATCOMPLICATEDOBLIQUESKYWAVERAYPATHS VIATHETRUEREFLECTIONPOINTCANBEREPLACEDTOGOODAPPROXIMATIONWITHSIMPLERECTILINEARGEOMETRYVIATHEVIRTUAL REFLECTIONPOINT4HETHEOREMOF"REITAND4UVEDEMONSTRATESTHAT TOGOODAPPROXIMATION THETIME OF FLIGHTIS UNCHANGEDBYTHISSUBSTITUTION$AVIESPROVIDESACLEAREXPLANATIONOFTHESEUSEFULTHEOREMS
Óä°£È
2!$!2(!.$"//+
&)'52% $IURNALVARIATIONOFTHEELECTRONDENSITYPROFILE ASMEASUREDBYTHEPLASMAFREQUENCY PLOTTEDFORVARIOUSVIRTUALHEIGHTSINKM 4HEDATAWASRECORDEDBYAVERTICALINCIDENCESOUNDERAT LATITUDE3 LONGITUDE%ON3EPTEMBER 33.
7HATISMORESURPRISINGISTHEDAY TO DAYVARIABILITY EVENATMID LATITUDES WHICH IMPACTSSIGNIFICANTLYON(&RADARPERFORMANCE4HEINABILITYTOPREDICTRELIABLYEVEN ADAYINADVANCEISASERIOUSCONSIDERATIONINRADARDESIGNANDSCHEDULING !NILLUSTRATIONOFDAY TO DAYVARIABILITYISPRESENTEDIN&IGURE WHICHOVER LAYSVERTICALINCIDENCESOUNDINGSRECORDEDATTHESAMETIMEOFDAYFORAMONTH
&)'52% #OMPARISONOFMEASUREDVERTICALINCIDENCEIONOGRAMS FORAFIXEDTIMEOFDAYOVERAMONTHWITHAMODEL BASEDPREDICTIONOFTHE MEDIAN DENOTEDBYTHESMALLCIRCLES
(&/6%2 4(% (/2):/.2!$!2
Óä°£Ç
4HETRACESPLOTTHEVIRTUALHEIGHTVERSUSRADIOWAVEFREQUENCYFORTHEORDINARYRAYSEE SUBSECTIONBELOWONRADIOWAVEPROPAGATION 3OUNDINGSOFTHISTYPEIONOGRAMS MEASURETHERETURNTRIPTIMEDELAYFORASIGNALTOTRAVELUPTOTHEHEIGHTATWHICHTHE ELECTRONDENSITYISSUFFICIENTTOREFLECTIT THATIS WHERETHEPLASMAFREQUENCYFPEQUALS THEINCIDENTRADIOWAVEFREQUENCY !LSOSHOWNIN&IGUREISTHECORRESPONDINGMONTHLYMEDIAN TAKENFROMTHE MODELOF4HOMASONETAL#ONSIDERTHECRITICALFREQUENCY THATIS THEHIGHESTREFLECTED FREQUENCY CORRESPONDING TO THE IONOSPHERES PEAK ELECTRON DENSITY 4HE UPPER AND LOWERDECILESDEPARTFROMTHEMEDIANBYTYPICALLYo/VERSUCHARANGEOFFRE QUENCY TERMSINTHERADAREQUATIONSUCHASANTENNAGAINS TARGET2#3 ANDSLANTRANGE MAY VARY SUBSTANTIALLY SO RADAR PERFORMANCE IS INEVITABLY STATISTICALLY DISTRIBUTED !LTHOUGHITMAKESSENSETOUSEMEDIANVALUESFORMANYRADARPERFORMANCEMODELING CALCULATIONS THERADARDESIGNERSHOULDADOPTACONSERVATIVEAPPROACHANDASSUMETHE LOWESTCRITICALFREQUENCY 0ERHAPS THE MOST INTRIGUING MAJOR CAUSE OF SYSTEMATIC VARIATION IS THE YEAR CYCLEOFSOLARACTIVITY6ARIOUSCORRELATEDPARAMETERSHAVEBEENDEFINEDTOMEASURE THISACTIVITY INCLUDINGTHECMSOLARFLUX SUNSPOTNUMBER ANDVARIOUSMAGNETIC INDICES&IGURESHOWSTHESMOOTHEDAVERAGESUNSPOTNUMBERPLOTTEDFROM THEYEAROFTHEFIRSTVALIDATED/4(2DETECTIONSOFMILITARYTARGETSACHIEVEDBYTHE -53)#RADARAT.2, %NHANCEDSOLARACTIVITYIMPACTSONTHEIONOSPHEREINMANYWAYS BUTITSMOSTSIG NIFICANTACTIONFROMARADARPERSPECTIVEISTOPRODUCESUBSTANTIALLYHIGHERIONIZATION LEVELSTHATPERSISTATUSABLELEVELSTHROUGHTHENIGHT SOHIGHERRADARFREQUENCIESCANBE EMPLOYEDANDTHEMINIMUMACHIEVABLERANGEDECREASES)NADDITION THEHEIGHTOFTHE MAXIMUMELECTRONDENSITYINCREASES SOONE HOPPROPAGATIONCANREACHGREATERRANGES
&)'52% 4HEVARIATIONOFTHEMONTHLYMEDIANSUNSPOTNUMBERSINCE THEYEAROFTHEFIRSTOPERA TIONALSKYWAVERADARDETECTIONS
Óä°£n
2!$!2(!.$"//+
$AYTIMEABSORPTIONINCREASESFORAGIVENFREQUENCYBECAUSEOFHIGHER$ LAYERDENSI TIES BUTTHISISCOMPENSATEDBYACCESSTOHIGHEROPERATINGFREQUENCIES!NINCREASEIN THENUMBERANDSEVERITYOFMAGNETICSTORMSANDSUDDENIONOSPHERICDISTURBANCESIS ANOTHERCONSEQUENCEOFHIGHERSOLARACTIVITY ASAREINCREASEDPOST SUNSETPLASMABUB BLEACTIVITYANDASSOCIATEDSCINTILLATIONINEQUATORIALREGIONS SOLARFLARES ANDCORONAL MASSEJECTIONSALLOFWHICHDISRUPTSTABLEPROPAGATION3OLARFLARESAREGIANTEXPLOSIONS ONTHESUNSSURFACE GENERALLYOCCURRINGNEARSUNSPOTS WHICHEMITIONIZINGRADIATION THATPENETRATESINTOTHE$REGIONANDDRAMATICALLYINCREASESABSORPTION4HERESULTING SUDDEN IONOSPHERIC DISTURBANCE 3)$ OR SHORT WAVE FADE OUT CAN COMPLETELY INCA PACITATEASKYWAVERADARFORAPERIODFROMMINUTESTOHOURS0ERHAPSMOREIMPORTANTLY ALTHOUGHTHEFLAREITSELFISNOTPREDICTABLE THEASSOCIATEDBURSTOFPARTICLESWILLSTARTTO ARRIVEAFEWHOURSLATER WITHMOSTEJECTEDMATERIALREACHING%ARTHSEVERALDAYSLATER SERIOUSLYDISRUPTING(&PROPAGATION4HECRITICALIMPORTANCEOFSOLARACTIVITYWILLBE DEMONSTRATEDIN3ECTIONINTHECONTEXTOFRADARPERFORMANCEPREDICTION )ONOSPHERIC$YNAMICS !STHERADARSIGNALSTRAVERSETHEIONOSPHERE MOTIONSOFTHE PLASMAMEDIUMALONGTHEPROPAGATIONPATHIMPRINTTHEMSELVESONTHESIGNALSINWAYS THATCANDEGRADEOROBLITERATETHETARGETINFORMATIONOFINTEREST3KYWAVERADARSCANBE DESIGNEDTORECOGNIZETHESIGNATURESOFTHESEPHENOMENA ADJUSTINGTHERADARFREQUENCY CHOICEOFWAVEFORM ANDPROCESSINGTOMITIGATETHEIREFFECTSWHERENECESSARY3OMETIMES THEIONOSPHERICMOTIONSACTUALLYHELPTHERADAR FOREXAMPLE BYENABLINGITTODISCRIMI NATEBETWEENNATURALNOISEANDSOMEFORMSOFDELIBERATEINTERFERENCE4HUS ITISVITALLY IMPORTANTTOUNDERSTANDNOTONLYTHESTRUCTUREOFTHEIONOSPHEREANDTHEOPPORTUNITIESIT PROVIDESFORPROPAGATION BUTALSOTHEMOTIONSANDDISTURBANCESTHATINHABITIT 4HEVARIETYOFWAVETYPESANDIRREGULARITYOFPRODUCTIONMECHANISMSINTHEION OSPHERE IS ENORMOUS AND INCLUDES NOT ONLY THOSE ARISING NATURALLY BUT ALSO MANY INDUCEDPHENOMENASUCHASTHOSERESULTINGFROMGROUND BASEDIONOSPHERIC2&HEAT ERSORROCKETINTERACTIONSWITHTHEAMBIENTPLASMA!MONGTHEMOSTIMPORTANTFROM THERADARPOINTOFVIEWARETHEFOLLOWING u4RANSIENTPLASMASTRUCTURESASSOCIATEDWITHIONIZEDMETEORTRAILSATANYGIVENLOCA TION METEORSHAVEASTRONGDIURNALVARIATIONANDDIRECTIONALITY4HEYAREEVER PRES ENTANDCONSTITUTEAMAJORSOURCEOFCLUTTERFOR(&RADARS u,ARGEANDMEDIUMSCALEATMOSPHERICGRAVITYWAVES!'7 PRODUCEDBYENERGETIC PHENOMENA IN THE LOWER ATMOSPHERE PROPAGATE UPWARD WITH INCREASING AMPLITUDE UNTILNONLINEARPROCESSESBEGINTODOMINATE RESULTINGINWAVEBREAKING,ARGE!'7S MAYPERSISTFORHOURSANDPROPAGATEOVERGLOBALDISTANCES CAUSINGSERIOUSDEVIATION OFINCIDENTRADIOWAVES4HEYARESOMETIMESTHEMAJORCAUSEOFTRACKINGERRORS u-AGNETICDISTURBANCESORIGINATINGWHERETHESOLARWINDIMPACTSONTHEMAGNETO SPHERETHEYPROPAGATEEARTHWARDANDCAUSERESONANTOSCILLATIONSOFTHEGEOMAGNETIC FIELDLINESPERMEATINGTHEIONOSPHERE4HEFIELDLINESAREhFROZENINvTOTHEIONO SPHERICPLASMAAND HENCE THEIONOSPHEREVIBRATESLOCALLYATFREQUENCIESTYPICALLY INTHERANGEOFnn(Z IMPOSINGACORRESPONDINGMODULATIONONANYTRANSITING RADIOWAVES3HIPECHOESCANBEOBSCUREDBYTHISMODULATION u4HEEQUATORIALELECTROJET PARTOFTHEGLOBALSYSTEMOFFIELDSANDCURRENTSDRIVENBY THEDYNAMOACTIONOFWINDSANDTIDES ISHOSTTOSMALLSCALEFIELD ALIGNEDIRREGULARI TIESWITHCHARACTERISTICVELOCITYDISTRIBUTIONS3OMESMALL SCALEPLASMAINSTABILITIES MAYENDUREFORAFRACTIONOFASECOND OTHERSFORTENSOFSECONDS EVIDENTTORADARSAS SPREAD DOPPLERCLUTTERTHATPREVENTSTHEDETECTIONOFSMALLTARGETS
(&/6%2 4(% (/2):/.2!$!2
Óä°£
u%QUATORIALPLASMABUBBLESOFTENAPPEARAFTERSUNSETANDCONVECTUPWARDTHROUGHTHE ®IONWHERETHEYCONTRIBUTETOSTRONGDIFFUSEDOPPLER SPREADSCATTERINGREFERRED TOASSPREAD &$ETECTIONOFALLTARGETSISDIFFICULTWHENTHISEFFECTOCCURS u4HEAURORAEAREDYNAMICSTRUCTURESGOVERNEDBYFIELDSANDPLASMAFLOWSINTHEMAG NETOSPHERESTRONGELECTRICFIELDSALIGNEDWITHTHEMAGNETICFIELDACCELERATEELECTRONS DOWNINTOTHEIONOSPHEREWHERETHEYPRODUCEHIGHLYIONIZEDFORMATIONSTHATREFLECT RADIOWAVESVERYEFFICIENTLY4HERESULTINGDOPPLER SPREADECHOESARESOSTRONGTHEY CANINCAPACITATEARADARTHROUGHITSSIDELOBES u'EOMAGNETICSTORMSANDSUB STORMSRESULTFROMSOLARFLARESANDCORONALMASSEJEC TIONS!SMENTIONEDEARLIER HARD8 RAYSANDULTRAVIOLETRADIATIONRAISE$ LAYERION IZATIONDRAMATICALLYWITHCONSEQUENTINCREASESINRADIOWAVEABSORPTION7ITHINAN HOURANDFORADAYORSOAFTER FLARE GENERATEDPARTICLEBURSTSSTARTTOARRIVEANDARE CHANNELEDDOWNTHEMAGNETICFIELDLINESATHIGHLATITUDES CAUSINGIONOSPHERICHEAT INGANDASSOCIATEDDIFFUSIONTOLOWERLATITUDES TOGETHERWITHAVARIETYOFMAGNETIC FIELDPERTURBATIONS(&PROPAGATIONISOFTENSEVERELYDISRUPTED -ODELSAND4HEIR5SES +NOWLEDGEOFTHECONDITIONSTOBEEXPECTEDFORAPAR TICULARRADARDEPLOYMENTISVITALTORADARDESIGN ASWELLASPROVIDINGAGUIDETOECHO INTERPRETATION AND A MEANS TO SIMULATION AND PERFORMANCE PREDICTION 4HIS TYPE OF INFORMATION BASEDONDECADESOFIONOSPHERICOBSERVATIONSANDTHEORY ISCONVENIENTLY DISTILLED IN MODELS THAT ARE WIDELY AVAILABLE AND USED EXTENSIVELY "UT EVEN MORE IMPORTANTLY FROM THE OPERATIONAL PERSPECTIVE (& RADARS MUST MAINTAIN A REAL TIME IONOSPHERICMODEL24)- THATISINTIMATELYLINKEDWITHTHERADARSUBSYSTEMS SERVING TOGUIDEFREQUENCYSELECTION RADIATEDPOWER TASKSCHEDULING COORDINATEREGISTRATION CONVERTINGFROMTHERADARCOORDINATESOFTIMEDELAYANDANGLE OF ARRIVALTOGEOGRAPHI CAL COORDINATES IONOSPHERIC MODE STRUCTURE INTERPRETATION AND ASSOCIATION OF MUL TIPLE TRACKS FROM A SINGLE TARGET 5NLIKE THE CLIMATOLOGICAL MODELS 24)-S MUST BE UPDATEDCONTINUOUSLYWITHINFORMATIONFROMANAUXILIARYNETWORKOFBEACONS/BLIQUE ANDVERTICALINCIDENCESOUNDERSANDTRANSPONDERSHAVEBEENDEPLOYEDFORTHISPURPOSE &ORINSTANCE THE*/2.RADARSEXPLOITAPPROXIMATELYSOUNDERSANDRELATEDFACILITIES DISTRIBUTEDAROUNDTHECOASTOF!USTRALIA2ADARPERFORMANCEINMOSTOPERATIONALROLES ISGOVERNEDBYTHEFIDELITYOFTHEADOPTED24)- )T IS IMPORTANT TO DIFFERENTIATE BETWEEN MODELS THAT DESCRIBE THE PHYSICAL OR PHYSICO CHEMICAL STATEOFTHEIONOSPHEREANDMODELSTHATDESCRIBERADIOWAVEPROPA GATIONCHARACTERISTICS THOUGHTHELATTERAREOFTENDERIVEDFROMTHEFORMERBYAPPLY INGRAY TRACINGMETHODS ANDTHEFORMERAREPREDOMINANTLYDERIVEDFROMRADIOWAVE PROPAGATIONMEASUREMENTSSUCHASPOINT TO POINTLINKSTATISTICSANDVERTICALINCIDENCE SOUNDINGS"OTHCLASSESAREOFGENERALAPPLICABILITYTO(&COMMUNICATIONSANDGEO PHYSICALINVESTIGATIONS ASWELLASSKYWAVERADAR -ODELS OF THE )ONOSPHERIC -EDIUM -ODELS OF THE IONOSPHERE FALL INTO TWO CATEGORIES u#LIMATOLOGICALMODELSBASEDONSOUNDER ROCKET ANDSATELLITEMEASUREMENTS"EING DERIVEDFROMSTATISTICS THEYPROVIDENOEXPLICITINFORMATIONONREAL TIMEh@WEATHERv THATIS IRREGULARITIES WAVES ANDOTHERDYNAMICPROCESSES THOUGHMEASURESOFVARI ABILITYMAYBEPROVIDED-ANYEARLYMODELSHADTHEIRGENESISINTHELARGEDATABASEOF RECORDEDIONOSPHERICSOUNDINGSMADEDURINGTHE)NTERNATIONAL'EOPHYSICAL9EAROF nANDTHE)NTERNATIONAL9EAROFTHE1UIET3UNOFn4HESEMODELS
Óä°Óä
2!$!2(!.$"//+
WHICHFOCUSEDONTHESPATIALDISTRIBUTIONOFELECTRONDENSITY WEREUSEDEXTENSIVELY IN EARLY (& RADAR PERFORMANCE ANALYSES AND INCLUDE )43! )43 2!$!2 # )/.#!0 AND!-"#/-n ,UCAS PROVIDES DETAILS OF THESE MODELS AND THEIR ORIGINS3OMEOFTHEPREDICTIONMETHODSHAVENOTBEENWELLDOCUMENTEDALTHOUGH WIDELY DISTRIBUTED ALSO USERS FREQUENTLY hIMPROVEv UPON A MODEL AND PREDICTION METHODTOSUITTHEIRSPECIFICNEEDS!SANEXAMPLE THEMODEL2!$!2#ISTHEBASIC BUILDINGBLOCKOF4HOMASONETALIN.2,2EPORTHOWEVER THEYADDEDA$ REGION ACOLLISION FREQUENCYDISTRIBUTION AN%ARTHSMAGNETICFIELD ATOPSIDEELEC TRONDISTRIBUTION ANAURORALELECTRON DENSITYMODIFICATION ANDOTHERFEATURESTHAT MAKETHEMODELMOREGENERALLYUSEFUL4HEIONOSPHERICMODELASDESCRIBEDIN.2, 2EPORTHASBEENUSEDFORSOMEOFTHEEXAMPLESPRESENTEDIN3ECTION 4HE)NTERNATIONAL2EFERENCE)ONOSPHERE)2) ISPERHAPSTHEFOREMOSTMODERNEXAM PLE PRESENTLYAVAILABLEASVERSION)2) n/THERCLIMATOLOGICALMODELSUSED IN(&RADARAPPLICATIONSARE0)- 02)3- AND&!)- u0HYSICS BASEDORFIRSTPRINCIPLESMODELS SUCHAS535'!)- *0,53#'!)- 3!-)DEVELOPEDBY(UBAAND*OYCE AND+HATTATOVSMODEL SOLVETHEPLASMA DYNAMICSANDCOMPOSITIONEQUATIONSGOVERNINGEVOLUTIONOFDENSITY VELOCITY AND TEMPERATUREFORVARIOUSIONSPECIESONAGLOBAL$GRID SUBJECTTOTHE%ARTHSMAG NETICFIELDANDPREVAILINGSOLARINDICES4HESEMODELSREQUIREDSEEDINGWITHINITIAL CONDITIONS OFTENALIMITINGCONSIDERATION &OR BOTH CLASSES IMPROVED ACCURACY OF FORECASTING IS ACHIEVED BY ASSIMILATING DATAFROMGROUND BASEDSOUNDERS TOTALELECTRONCONTENT4%# DERIVEDFROM'03 56 AIRGLOWDATA ANDINSITUMEASUREMENTSOFELECTRONDENSITYFROMSATELLITESANDOTHER SOURCES/FTENTHEASSIMILATIONISPERFORMEDWITHINANEXTENDED+ALMANFILTERFRAME WORK SOACCURACYESTIMATESAREABYPRODUCT&URTHER SITE SPECIFICAPPLICATIONSMAY BENEFITFROMADAPTATIONOFTHEUNDERLYINGMODELPARAMETERSANDCOEFFICIENTS 4HECOMPLEXSTRUCTUREANDDYNAMICSOFTHEIONOSPHERICMEDIUMGOVERN(&SKY WAVE PROPAGATION PRIMARILY THROUGH THE SPACE TIME VARIATION OF THE FREE ELECTRON DENSITY DISTRIBUTION! USEFUL SIMPLIFICATION IS TO REGARD THE LARGE SCALE IONOSPHERIC STRUCTUREASDEFININGTHEPROPAGATIONGEOMETRYTHROUGHOUTTHEILLUMINATIONVOLUME WHEREASTHEDYNAMICALPROCESSESIMPOSETHEIRRESPECTIVEMODULATIONSONTHETRANSIT INGSIGNALS #OMPUTATIONAL!SPECTSAND2AY TRACING &ORMANY/4(2PURPOSES ITSUFFICES TOEMPLOYARAY THEORETICREPRESENTATIONOFTHERADIOWAVEFIELD2AY TRACINGTECHNIQUES FALLINTOTWOCATEGORIESANALYTICANDNUMERICAL!NALYTICMETHODSAREFASTBUTRELYONFIT TINGPARAMETRICMODELSTOTHEELECTRONDENSITYPROFILESANDARE HENCE OFLIMITEDUSEFOR OPERATIONALAPPLICATIONSWHEREACCURACYISCRITICAL4HEYAREALSOLIMITEDBYTHEIRINABILITY TOHANDLEMAGNETOIONICEFFECTSONPROPAGATION.EVERTHELESS THEYPROVIDECLOSEDFORM EXPRESSIONSFORGROUPRANGE PHASEPATH GROUNDRANGE ANDOTHERPARAMETERS ANDTHERE FORE CANBEVERYUSEFULFORCOMPUTATIONALLYINTENSIVESTUDIESSUCHASSYSTEMOPTIMIZA TION4HEMULTI QUASI PARABOLIC-10 MODELOF(ILLBASEDON#ROFTS10TECHNIQUE ISWIDELYUSED WHILEQUASI CUBICMODELSHAVEBEENPROPOSEDBY.EWTONETAL .UMERICALRAY TRACINGCODESAREVERSATILEANDABLETOACCOMMODATEALMOSTARBI TRARY IONOSPHERIC STRUCTURE AT THE EXPENSE OF COMPUTATIONAL BURDEN /F THE MANY NUMERICALRAY TRACINGCODESDEVELOPEDOVERTHEYEARS THEIMPLEMENTATIONBY*ONES AND3TEPHENSONBASEDONINTEGRATIONOFTHEFIRST ORDER(ASELGROVEEQUATIONSREMAINS THEMOSTWIDELYUSED#OLEMANHASDEVELOPEDANALTERNATIVEIMPLEMENTATION
(&/6%2 4(% (/2):/.2!$!2
Óä°Ó£
-ODELSOF)ONOSPHERIC2ADIOWAVE0ROPAGATION &ROMTHE(&SKYWAVERADARPER SPECTIVE INTERESTISUSUALLYCENTEREDNOTONTHEIONOSPHEREPERSEBUTONHOWITDETER MINES RADIOWAVE PROPAGATION -ODELS SUCH AS 6/!#!0 AND!3!03 GENERATE PREDICTIONSOFPOINT TO POINTCIRCUIT PARAMETERS INCLUDINGMAXIMUMANDMINIMUM USABLEFREQUENCY ELEVATIONANGLE GROUPPATH MODEPROBABILITY PATHLOSS ANDSIGNAL TO NOISERATIO FORUSER SPECIFIEDTERMINALCHARACTERISTICS!MOREGENERALCAPABILITYIS AVAILABLEWITH0ROPLAB !STHESEMODELSAREBASEDONTHEIRRESPECTIVECLIMATOLOGICALDATABASES THEYAREOF NOUSEFORREAL TIMEAPPLICATIONSSUCHAS24)-ANDAREINADEQUATEFORSERIOUSRADAR DESIGN WHICHSHOULDBEBASEDONMEASUREMENTSTAKENATTHEPROPOSEDDEPLOYMENT SITE BUTTHEYCANBEUSEFULFORANSWERINGCERTAINQUESTIONS SUCHASh#ANMYSIGNALBE HEARDAT8ANDIFSO ATWHAT3.2 v &OR CALCULATIONS REQUIRING MODERATE ACCURACY GEOMETRICAL OPTICS OR VIRTUAL RAY TRACINGBASEDON-ARTYNS4HEOREMCANBEAPPLIEDTOSTOREDSEMI EMPIRICALELECTRON DENSITYPROFILES ORBETTER STOREDhSNAPSHOTSvOFTHEIONOSPHEREGENERATEDBYAN24)- !LTERNATIVELY ANALYTICRAY TRACINGCANBEPERFORMEDONANALYTICPROFILESFITTEDTO24)- DATABASES4HEMOSTACCURATEPREDICTIONSCOMEFROMTHEAPPLICATIONOFSOPHISTICATED RAY TRACING ROUTINES TO A DATABASE OF 24)- SNAPSHOTS7HEN A RADIOWAVE PROPAGA TIONMODELISCOMBINEDWITHRADARSYSTEMPARAMETERS TARGETSCATTERINGCHARACTERISTICS AND(&NOISEDISTRIBUTIONS THERADAREQUATION%Q CANBESOLVEDTOPREDICTTHE RADARSPERFORMANCE ASTREATEDIN3ECTION4HISISTHEBASICAPPROACHEMPLOYED WITHIN2!$!2# FORINSTANCE&ROMTHEOPERATIONAL(&RADARVIEWPOINT USE OFTHESEPROPAGATIONMODELSISLIMITEDTOSTATISTICALSTUDIESOFRADARPERFORMANCE NOT REAL TIME RADAR SUPPORT APPLICATIONS SUCH AS COORDINATE REGISTRATION BECAUSE OF THE POOR FIDELITY OF THE ASSUMED ELECTRON DENSITY DISTRIBUTIONS AND THE SHORTCOMINGS OF GEOMETRICRAY TRACING /THER -ODELS AND 0ROPAGATION )SSUES 3TUDIES OF (& RADAR PERFORMANCE AT LOWLATITUDESHAVESHOWNTHATITISOFTENNECESSARYTOINCORPORATEMODELSOFDYNAMICAL PROCESSES EITHERBECAUSETHEYMANIFESTTHEMSELVESDIRECTLYINTHEDOPPLERSTRUCTURE OF RADAR ECHOES OR BECAUSE THEY ARE INDICATORS OF OTHER PHENOMENA THAT DO 5SEFUL MODELSINTHISCATEGORYINCLUDE(7- WHICHDESCRIBESTHESTRUCTUREOFTHEZONAL AND MERIDIONAL NEUTRAL WINDS THROUGHOUT THE IONOSPHERE AND 7"-/$ WHICH DESCRIBESSCINTILLATIONARISINGFROMSMALLSCALEIRREGULARITIESSUCHASTHOSEASSOCIATED WITHSPREAD &INTHEPOST SUNSETIONOSPHERE4HESEMODELSFINDIMPORTANTAPPLICATIONS TOTHEANALYSISANDINTERPRETATIONOFDOPPLER SPREADCLUTTER !NUMBEROFPHENOMENAHAVEBEENIGNOREDINTHEPRECEDINGDISCUSSION THOUGH THEIREFFECTSCANBEOBSERVEDINSOMESKYWAVERADARSYSTEMS4HEYINCLUDEI AVARIETY OFNONLINEARPROCESSESTHATCANOCCURDURINGIONOSPHERICPROPAGATION II DELAYED ECHOES FOCUSINGATTHEANTIPODE ANDIII ROUND THE WORLDPROPAGATION4HEMOST SIGNIFICANT PRACTICAL EXPLOITATION OF SUCH PHENOMENA CAN BE FOUND IN EXPERIMENTS DIRECTEDATIONOSPHERICMODIFICATION
Óä°xÊ 76 ", -Ê",ÊÊ, , 4HEFACTORSTHATGOVERNTHECHOICEOFWAVEFORMIN(&RADARSYSTEMSCANBEGROUPED INTOTWOCLASSES&IRST THEREARETHECONSIDERATIONSCOMMONTOMICROWAVERADAR THAT IS RANGEANDDOPPLERRESOLUTIONASDESCRIBEDBYTHEAMBIGUITYFUNCTIONANDOPTIMIZED
Óä°ÓÓ
2!$!2(!.$"//+
FORTARGETDETECTIONANDESTIMATION REALIZABILITYINHARDWARE SUSCEPTIBILITYTOINTERFER ENCE EFFICIENCY ANDTHEELECTRICALPROPERTIESOFTHESCATTERERSOFINTEREST)NADDITION u(&RADARWAVEFORMSMUSTFITWITHINAVAILABLECLEARCHANNELSINTHE(&FREQUENCY BAND COMPLYING WITH STRINGENT CONSTRAINTS ON LEAKAGE INTO CHANNELS OCCUPIED BY OTHERUSERS u4HEYMUSTBECOMPATIBLEWITHTHEFACTTHATTHERADARISOPERATINGINAhWAVEGUIDE v NAMELY THE VOLUME BETWEEN THE %ARTHS SURFACE AND THE IONOSPHERE WITH UNIQUE POSSIBILITIESFORMULTIPLEPROPAGATIONPATHSINCLUDINGROUND THE WORLDPROPAGATION SIGNIFICANTLYMODIFYINGTHEEFFECTIVEAMBIGUITYFUNCTION u4HEYMUSTBEABLETOACHIEVETHEDESIREDMEASUREMENTCAPABILITYINTHEPRESENCEOF EXTREMELYSTRONGGROUNDCLUTTER u4HEYMUSTBEDESIGNEDSOASTOMINIMIZEDISTORTIONORCORRUPTIONBYTHEIONOSPHERIC MEDIUMOR ATLEAST ENABLESUCHDISTORTIONTOBEESTIMATEDANDMITIGATEDBYSIGNAL PROCESSINGAFTERRECEPTION u4HEYMUSTHEEDTHECONSTRAINTSONPEAKVERSUSAVERAGEPOWERIMPOSEDBYTHE(& TRANSMITTINGEQUIPMENTANDANTENNAS 4HEWAVEFORMSUSEDINMOSTOPERATIONAL(&SKYWAVERADARSAREVARIATIONSONTHE PERIODICLINEARFREQUENCY MODULATEDCONTINUOUSWAVE,&- #7 SIGNAL/FTEN THERE IS SOME PROVISION FOR AMPLITUDE SHAPING NORMALLY AT THE COMMENCEMENT AND END OF EACH SWEEP 4HE *INDALEE RADAR WAS DESIGNED WITH THE FACILITY TO APPLY A NUM BER OF AMPLITUDE NOTCHES WITHIN THE SWEEP THEREBY ENABLING THE RADAR TO SWEEP AT ZEROAMPLITUDEACROSSNARROW BANDUSERSINTHESAMEFREQUENCYBANDWITHOUTCAUSING INTERFERENCE!NOTHERCLASSOFVARIATIONSINVOLVESDEPARTINGFROMALINEARFREQUENCY MODULATION"YVARYINGTHEFREQUENCY TIMECHARACTERISTICOFTHEWAVEFORM RANGESIDE LOBESCANBEREDUCEDANDSPECTRALLEAKAGECANBECONTROLLED#ONTROLLINGTHEPHASE DISCONTINUITYFROMTHEENDOFONESWEEPTOTHEBEGINNINGOFTHENEXTPROVIDESANOTHER DIMENSIONINWHICHTHEWAVEFORMPROPERTIESCANBEOPTIMIZED&URTHERGENERALIZATION OFTHE&- #7WAVEFORMISPOSSIBLEBYRELAXINGTHECONDITIONTHATTHEWAVEFORMBE PERIODIC4HISISAPOWERFULTOOLFORCONTROLLINGRANGE AMBIGUOUSECHOES WHICHCANBE SHIFTEDABOUTINTHERANGE DOPPLERPLANETOUNCOVERPREVIOUSLYOBSCUREDTARGETECHOES !NDPERHAPSMOSTIMPORTANTLY INTHECONGESTED(&SPECTRUMWHERECLEARCHANNELSOF ADEQUATEBANDWIDTHTOACHIEVETHEDESIREDRESOLUTIONMAYBESCARCE &- #7WAVE FORMSDEFINEDOVERTWOORMORESEPARATESUBBANDSAREREADILYSYNTHESIZED -OSTEARLY(&SKYWAVERADARSEMPLOYEDPULSEWAVEFORMS INPARTBECAUSETHETECH NOLOGYOFTHEDAYDIDNOTSUPPORT&- #7WAVEFORMSWITHTHEREQUIREDLEVELOFSPEC TRALPURITYFORTHISDEMANDINGAPPLICATIONBUTALSOBECAUSEPULSEWAVEFORMSENJOYSOME UNDENIABLEADVANTAGES&IRST THEYCANBEEMPLOYEDFROMASINGLETRANSMIT RECEIVESITE AVOIDINGTHECOSTANDCOMPLEXITYOFACQUIRINGSUITABLELAND DUPLICATINGMANYFACILITIES ANDSYNCHRONIZINGTWOWIDELYSEPARATEDSITES3ECOND THEABILITYTOGATETHEECHOESIN TIMEMEANSTHATTHEONLYCLUTTERPOWERTHATIMPACTSONTHERANGEFOOTPRINTSPANNEDBYA PULSEISCLUTTERORIGINATINGINTHATFOOTPRINT4HISRELAXESTHEWAVEFORMGENERATORDYNAMIC RANGEREQUIREMENTSSOMEWHAT ESPECIALLYWHENPHENOMENASUCHASAURORALCLUTTERMAY CAUSEPROBLEMS THOUGHTOACHIEVETHESAMEPROBABILITYOFDETECTION PEAKPOWERMUST INCREASETOMAINTAINEQUIVALENTAVERAGEPOWER4HIRD ASACONSEQUENCEOFREDUCEDDYNAMIC RANGEREQUIREMENTSANDASSUMINGFORTHEMOMENTTHATSTRICTSPECTRALEMISSIONCONTROLSARE NOTANISSUE MOREEFFICIENTAMPLIFIERSCANBEUSED ASDISCUSSEDINTHEFOLLOWINGSECTION &OURTH PULSEWAVEFORMSMAYBELESSSUSCEPTIBLETOSOMEFORMSOFJAMMING
(&/6%2 4(% (/2):/.2!$!2
Óä°ÓÎ
"UTTHEREAREDISADVANTAGES&IRST EMISSIONCONTROLSAREALMOSTINVARIABLYASERI OUSMATTERWHENITCOMESTOOBTAININGALICENSETORADIATE3ECOND THEREARERADAR APPLICATIONSBEYONDBASICTARGETDETECTIONWHEREEXTREMELYHIGHSPECTRALPURITYIS ESSENTIAL ASWITHDETECTIONOFSMALLSHIPSATLOWSPEEDS4HIRD THEANTENNADESIGN MUSTBEABLETOHANDLEHIGHERFIELDSTRENGTHSWITHOUTARCINGANDSPARKING WHICH INTRODUCES NOISE &OURTH UNLIKE THE &- #7 CASE IT IS NOT GENERALLY FEASIBLE TO SYNTHESIZESUITABLEPULSEWAVEFORMSFROMSEPARATESUBBANDSOFTHE(&SPECTRUM WHENWIDECLEARCHANNELSARENOTAVAILABLE&IFTH THEREAREFEWEROPTIONSFORRADI ATINGMULTIPLEWAVEFORMSSIMULTANEOUSLYFROMTHESAMETRANSMITTINGFACILITY!ND SIXTH FORHIGHPOWER(&RADARS THEADDITIONALPOWERDENSITYASSOCIATEDWITHPULSE WAVEFORMSINTHEIONOSPHEREMAY INPRINCIPLE CAUSESELF MODULATIONFROMNON LINEAREFFECTS
Óä°ÈÊ / Ê/, - // Ê-9-/ 4RANSMITTERS -OSTOFTHERADARDESIGNSANDMISSIONSREQUIRETRANSMITTERAVER AGEPOWERLEVELSBETWEENK7AND-7!NTENNASAREGENERALLYARRAYSOFRADIAT INGELEMENTS ANDTHECOMMONPRACTICEWITH(&RADARISTODRIVEEACHELEMENTWITH ASEPARATEAMPLIFIER4HISAPPROACHPERMITSBEAMSTEERINGATALOWPOWERLEVELINTHE AMPLIFIERCHAIN4HEACTIVEELEMENTINEACHFINALTRANSMITTERSTAGECANBEEITHERATRA DITIONALVACUUMTUBEORASOLID STATEDEVICE -OSTOPERATIONAL(&RADARSEMPLOY SOLID STATEAMPLIFIERSBASEDONAHIERARCHYOFMODULES STARTINGWITHELEMENTALAMPLI FIERSOFPERHAPS7ANDCOMBININGTHESEPROGRESSIVELYVIAPASSIVENETWORKSUNTIL THEFINALOUTPUTPOWERISATTAINED2ELATIVEPHASESHIFTSORTIMEDELAYSAREINSERTEDIN THEAMPLIFIERCHAIN DRIVINGEACHANTENNAELEMENTTOSTEERTHERESULTANTBEAM4HIS ARCHITECTURE ENHANCES RELIABILITY AND PROVIDES GRACEFUL DEGRADATION IN THE EVENT OF MODULEFAILURE 3OLID STATE (& RADAR TRANSMITTERS OPERATE AT POWER EFFICIENCIES LOWER THAN THOSE BASEDONVACUUMTUBEAMPLIFIERS6ACUUMTUBEAMPLIFIERSAREALSOMOREROBUSTAND HAVEBEENUSEDSUCCESSFULLYINANUMBEROF(&SKYWAVERADARSINCLUDINGTHE!.&03 4HEADOPTIONOFSOLID STATEAMPLIFIERSINRADARSSUCHAS2/4(2AND*INDALEE */2.ISDRIVENBYTHENEEDTOACCOMMODATEINSTANTANEOUSFREQUENCYSWITCHINGOVER WIDEBANDWIDTHSWHILEMAINTAININGHIGHLINEARITYANDSPECTRALPURITY4HESERADARS ROUTINELYINTERLEAVEDIFFERENTSURVEILLANCETASKSWITHWIDELYSEPARATEDCARRIERFREQUEN CIESAND-(Z FOREXAMPLESWITCHINGASOFTENASEVERYONEORTWOSECONDS WHILECONFORMINGTOSTRICTSPECTRALEMISSIONSTANDARDS3UCHINSTANTANEOUSFREQUENCY CHANGESWOULDPLACEUNACHIEVABLESWITCHINGDEMANDSONTHEHIGH LEVELVACUUMTUBE RADIOFREQUENCYCIRCUITS-EETINGPOWERCONTROLANDAMPLITUDE SHAPINGOFWAVEFORM REQUIREMENTSDICTATESLINEAROPERATIONOFAMPLIFIERS !PART FROM THE REQUIREMENT TO MEET EMISSION GUIDELINES LAID DOWN BY NATIONAL ANDINTERNATIONALSPECTRUMMANAGEMENTAUTHORITIES HIGHSPECTRALPURITYISESSENTIAL BECAUSESKYWAVERADARUSESDOPPLERPROCESSINGTOSEPARATETHETARGETSFROMTHECLUT TER ANDHENCE THECLUTTERRETURNEDONTHEPHASEANDAMPLITUDENOISESIDEBANDSRADI ATEDBYTHETRANSMITTERMUSTBEKEPTBELOWTHEECHOPOWEROFDESIREDTARGETS4HIS CANIMPOSEASTRINGENTCONDITIONONTHEEMITTEDSIGNAL TO NOISERATIOOFTHETRANSMIT TER ANDHENCE ONTHESIGNAL TO NOISERATIOOFTHEWAVEFORMGENERATOR&OREXAMPLE NOISESPECTRALDENSITYAT(ZFROMACARRIERMAYNEEDTOBEASLOWASnD"CIN ORDERTODETECTSOMETARGETSOFINTEREST&ORDESIGNSEMPLOYINGANAMPLIFIERFOREACH
Óä°Ó{
2!$!2(!.$"//+
ANTENNAELEMENT THERADIATEDPHASENOISEWILLGENERALLYADDNONCOHERENTLYANDTHUS BESUPPRESSEDBY^D"RELATIVETOBEAMFORMEDNOISEPOWERFORA ELEMENTARRAY "UTTHATISNOTTHEENDOFTHEMATTERTRANSMITTERPHASENOISEWILLBEREFLECTEDBYTHE DISTANT%ARTHSURFACEANDINTEGRATEDACROSSTHERECEIVERPASSBAND RAISINGTHEPHASE NOISECONTRIBUTIONSTOTHENOISEFLOORBYAFACTORTHAT FORAN&- #7WAVEFORM IS ROUGHLY EQUAL TO THE RATIO OF THE WAVEFORM BANDWIDTH TO THE WAVEFORM REPETITION FREQUENCY4HELOWER LEVELSTAGESOFSIGNALAMPLIFICATIONCANGENERALLYBEDESIGNED TOADDESSENTIALLYZERONOISE BUTMECHANICALVIBRATIONINTHEHIGH POWERAMPLIFIERS CANADDAPPRECIABLEAMOUNTSSOCAREMUSTBEEXERCISEDINTHEAIRORLIQUIDCOOLANT FLOWSYSTEMDESIGN )FTHERADARISTOPERFORMWIDE AREASURVEILLANCE FREQUENTFREQUENCYCHANGESARE REQUIREDINORDERTOCOVERTHEVARIOUSRANGEEXTENTS)NADDITION RELATIVEPHASEORTIME DELAYCHANGESAREREQUIREDINEACHAMPLIFIERCHAINTOACCOMPLISHAZIMUTHALSTEERING !BROAD BANDWIDTHPERFORMANCEANDATOLERANCETOAVARIABLEVOLTAGESTANDING WAVE RATIOLOADARE THEREFORE ESSENTIALFEATURESINAN(&RADARTRANSMITTER4YPICALLY ONE MIGHTSPECIFY6372 ATFULLPOWEROVERANOPERATINGRANGEOFn-(Z SAY WITH ANABILITYTOTOLERATEHIGHER6372SATFRACTIONALPOWEROUTPUTS3INCETHEANTENNAELE MENTSWILLBEWIDEBAND HARMONICFILTERSMAYBEREQUIRED&OREXAMPLE ONETRANSMIT TERANDHARMONICFILTERCOMBINATIONMIGHTHAVEATO-(ZPASSBANDANDASTOPBAND FOR-(ZANDHIGHERFREQUENCIESASECONDCOMBINATIONMIGHTPASSUPTO-(Z ANDREJECT-(ZANDHIGHER ANDTHEDESIGNWOULDCONTINUEINTHISMANNERTOTHE HIGHESTFREQUENCYOFOPERATION3OMESKYWAVERADARDESIGNSCALLFORUPTOSIXBANDS !RELATEDISSUEISTHEOCCURRENCEOFMUTUALCOUPLINGBETWEENANTENNAELEMENTSINTHE TRANSMITARRAY%NERGYCOUPLEDBACKINTOANAMPLIFIERFROMITSNEIGHBORSCANREACH LEVELSTHATRESULTININTERMODULATIONDISTORTION ASWELLASCAUSINGLOADRESONANCESTHAT STRESSTHEAMPLIFIERCHAIN !NTENNAS 4HECHOICEOFANTENNACONFIGURATIONISINTIMATELYLINKEDTOTHERADAR MISSION GENERALLYDEFINEDINTERMSOFTARGETTYPES RADARCOVERAGE ANDCOVERAGERATE 4HE .AVAL 2ESEARCH ,ABORATORY MAGNETIC DRUM RECORDING EQUIPMENT -!$2% RADAR EMPLOYEDASINGLEANTENNA DUPLEXEDANDUSEDFORBOTHTRANSMITANDRECEIVE 4HIS M WIDEBY M HIGHAPERTUREPROVIDEDSUFFICIENTGAINANDANGULARRESOLU TIONFORAIRCRAFTTRACKINGINTHEUPPERPARTOFTHE(&BAND4HEEXPERIMENTAL&RENCH /4(RADAR.OSTRADAMUSnLIKEWISEEMPLOYSASINGLEANTENNAARRAY CONFIGUREDAS THREEHORIZONTALARMSOFLENGTHMRADIATINGFROMACENTRALCONTROLCENTER THOUGH ONLYASUBSETOFELEMENTSAREUSEDTOTRANSMIT WHEREASALLOFTHEELEMENTSAREUSED FORRECEPTION3UCHTRULYMONOSTATICDESIGNSHAVETHESPECIALADVANTAGETHATTHEOUT BOUNDPROPAGATIONPATHTOATARGETISALMOSTIDENTICALTOTHEIN BOUNDPATH-ONOSTATIC RADARSWITHSEPARATETRANSMITANDRECEIVEANTENNASEXPERIENCEDECORRELATIONBETWEEN THE PATHS AS THE SEPARATION INCREASES AND DIFFERENT PARTS OF THE IONOSPHERE BECOME INVOLVED%ITHERFORMOFMONOSTATICRADARAVOIDSTHECOSTSOFMULTIPLESITESANDASSO CIATEDCOMMUNICATIONSINFRASTRUCTURE ANDTHECHALLENGEOFFINDINGSUITABLESITESWITH ANAPPROPRIATEGEOGRAPHICALRELATIONSHIP BUTTHEYARECONSTRAINEDINWAVEFORMCHOICE ANDORRADIATEDPOWERBYTHENEEDTOAVOIDSIMULTANEOUSTRANSMISSIONANDRECEPTION ASWELLASBEINGPOTENTIALLYSUSCEPTIBLETORANGE FOLDEDCLUTTER)NPARTICULAR THECLASS OF&- #7WAVEFORMSHASBEENWIDELYADOPTED DRIVENMAINLYBYCONSTRAINTSONSPEC TRALEMISSIONSOUTSIDETHENOMINALRADARBANDWIDTH&ORTHESEREASONS CONFIGURATIONS EMPLOYINGSEPARATETRANSMITANDRECEIVEANTENNASITESAREEMPLOYEDINRADARSSUCHAS *INDALEE */2. AND2/4(2 USUALLYINAQUASI MONOSTATICARRANGEMENTWHERETHE
(&/6%2 4(% (/2):/.2!$!2
Óä°Óx
INTERSITESEPARATIONISABOUTnNAUTICALMILES MUCHLESSTHANTHERANGETOTHE TARGETZONEBUTSUFFICIENTTOPREVENTSELF JAMMINGWHENUSINGCONTINUOUSWAVEFORMS ANDTOSEPARATETHETRANSMITANDRECEIVERANGEAMBIGUITYZONESINAZIMUTH 4RANSMITRADIATINGELEMENTCHOICEISDRIVENPRIMARILYBYTHERANGEOFFREQUENCIES TOBERADIATEDANDTHEWAVEFORMBANDWIDTH BUTITMUSTALSOTAKEINTOACCOUNTTHE RANGE AND AZIMUTH COVERAGE REQUIRED THE ASSOCIATED COVERAGE RATE AND CONCERNS ABOUT CLUTTER ESPECIALLY SPREAD DOPPLER CLUTTER 4HE VERTICAL RADIATION PATTERN CON TROLSTHESEISSUES4HEPOWER HANDLINGCAPABILITIESOFTHEANTENNAELEMENTSAREALSO ACONSIDERATION !LOWERBOUNDONTHETRANSMITARRAYAPERTUREISSETBYTHENEEDTOACHIEVEADEQUATE DIRECTIVITYANDHENCEPOWERDENSITYONTHETARGETTHESENSITIVITYREQUIREDDEPENDS ON THE SIZE OF THE TARGETS OF INTEREST 4HE UPPER BOUND IS OFTEN SET BY THE REVISIT REQUIREMENTIN GENERAL THE RADAR WILL STEP OVER A WIDE ARC BUT IT MUST SAMPLE EACH REGION FREQUENTLY TO MAINTAIN TRACKS ON MANEUVERING TARGETS SO THE TRANSMIT BEAMWIDTHSHOULDNOTBETOONARROW4HENEEDTOKEEP6372TOMODESTLEVELSIS USUALLYADDRESSEDBYHAVINGTOARRAYSADDRESSINGSUBBANDSOFABOUTONEOCTAVE OFFREQUENCYEACH 3OMEOFTHESECONSIDERATIONSAREINFLUENCEDBYTHEADVANTAGESTHATATTACHTOEMPLOY INGMULTIPLESIMULTANEOUSRECEIVEBEAMS SOABROADBUTWELL SHAPEDTRANSMITBEAM THATCANBEFILLEDBYPERHAPSTONARROWRECEIVEBEAMSISAPOPULARCHOICE)NTHE LIMITINGCASE THETRANSMITARRAYMAYFLOODLIGHTTHEENTIRESECTOROFCOVERAGE WHICHIS FILLEDWITHRECEIVEBEAMSTHATSTARECONTINUOUSLY4HENONUNIFORMITYOFCLUTTERSOURCES CANCAUSESERIOUSPROBLEMSWITHANYDESIGNTHATDOESNOTHAVECONTROLOVERTHEARRAY PATTERN&URTHER (&ANTENNASSELDOMACHIEVEHIGHFRONT TO BACKRATIOS SOTHERISKOF SIGNALMASKINGBYBACKLOBECLUTTERCANNOTBEIGNORED&ORLINEARARRAYS OFFSETTINGTHE TRANSMITANDRECEIVEARRAYBORESIGHTSISAMODERATELYEFFECTIVEMEASURETHATMUSTBE TRADEDOFFAGAINSTTHECONCOMITANTREDUCTIONINMAINBEAMOVERLAP,INEARARRAYSOF VERTICALLYPOLARIZEDLOG PERIODICANTENNAS VERTICALPLANARARRAYSOFHORIZONTALDIPOLES STACKED9AGIANTENNAS ELEVATEDRHOMBICELEMENTS LINEARARRAYSOFTILTEDMONOPOLES ANDATWO DIMENSIONALARRAYOFBICONICALANTENNASHAVEALLBEENUSEDINSKYWAVERADAR TRANSMITSYSTEMS INSOMECASES WITHBACKSCREENSTOIMPROVETHEOTHERWISEMEDIOCRE FRONT TO BACKRATIOS )NTHEELEVATIONPLANE DESIRABLERADIATIONANGLESRUNBETWEENnANDnFORCOM MONVALUESOFRANGEANDREFLECTIONHEIGHT4HEVERTICALBEAMWIDTHNEEDSTOBESUF FICIENTTOILLUMINATETHEREQUIREDRANGEDEPTHINGENERAL THISISAUTOMATICALLYSATISFIED OWINGTOTHECOSTANDCOMPLEXITYOFANANTENNAABLETOFORMABEAMNARROWERTHAN THIS IN THE VERTICAL PLANE &OR MOST SCENARIOS ANY SENSITIVITY GAINED BY DIRECTIVITY INELEVATIONDIRECTLYIMPROVESRADARPERFORMANCE SINCEINSTANTANEOUSRANGEDEPTHIS GENERALLYLIMITEDBYIONOSPHERICEFFECTS4HISISINCONTRASTWITHAZIMUTHDIRECTIVITY FORTRANSMITTING WHEREANINCREASEINDIRECTIVEGAINISACCOMPANIEDBYADECREASEIN AREACOVERAGE&ORNOISE LIMITEDDETECTION THISCANBECOMPENSATEDBYAREDUCTIONIN DWELLTIME BUTFORCLUTTER LIMITEDDETECTIONTHEREMAYBEAPENALTYFORCOVERAGERATE 3OMERADARSUSEHORIZONTALTWO DIMENSIONALARRAYSWITHUPTO^RECEIVECHANNELS TO ACHIEVE QUITE HIGH VERTICAL DIRECTIVITY ON BOTH TRANSMIT AND RECEIVE )N THE PAST OTHERS SUCHAS-!$2%ANDSOMEFORMER3OVIET5NIONSKYWAVERADARS EMPLOYED VERTICALTWO DIMENSIONALARRAYS UPTOMHIGHANDMWIDEINTHECASEOFTHE 3OVIETRADARS !TLOWELEVATIONANGLES THEANTENNAPATTERNISSTRONGLYINFLUENCEDBYTHEELECTRI CALANDMAGNETICPROPERTIESOFTHEGROUNDAROUNDANDINFRONTOFTHEARRAY4OACHIEVE
Óä°ÓÈ
2!$!2(!.$"//+
GAINATLOW ANGLES ITISSTANDARDPRACTICETOINSTALLAGROUNDMESHSCREENTHISHASTHE SECONDARYBENEFITOFAVOIDINGPATTERNDISTORTIONDUETOINHOMOGENEITIESINTHESOIL&OR EXAMPLE THE*INDALEETRANSMITARRAYSSITON^HECTARES^ACRES OFSTEELMESH EXTENDING^MINFRONTOFTHEARRAYS .OTWITHSTANDING THE MERITS OF VERTICAL DIRECTIVITY MOST SKYWAVE RADARS DO NOT EMPLOYSTEERABLEDIRECTIVITYINELEVATIONBUTCOVERALLNECESSARYRADIATIONANGLESWITH ONEBROADELEVATIONBEAM4HISCHOICEPERMITSTHEANTENNATOHAVEARELATIVELYSMALL VERTICAL DIMENSION AND HENCE REDUCED COST THOUGH DEMANDS ON ANTENNA RADIATION EFFICIENCYIMPOSEALOWERLIMIT !NOTHERISSUEISTHECHOICEOFTRANSMITPOLARIZATION.EARLYALLOPERATIONALSKYWAVE RADARSRADIATEWITHVERTICALPOLARIZATION BASEDONTHEEASEOFACHIEVINGGOODVERTI CALCOVERAGEATMODERATECOSTBYMEANSOFTHEWIDELYUSEDLOG PERIODICBROADBAND ANTENNA4HELARGECURTAINARRAYSOFTHEFORMER3OVIETRADARSUSEDHORIZONTALDIPOLE ELEMENTSWHEREASTHE53!&!.!03 USEDINCLINEDDIPOLESTOADAPTTOGROUND CONDITIONS4HEPOTENTIALBENEFITSOFFULLPOLARIZATIONCONTROLONTRANSMITHAVEBEEN ASSESSEDANDANUMBEROFEXPERIMENTALSTUDIESCARRIEDOUT BUTNOOPERATIONALSYSTEM HASGONEDOWNTHISPATH 4HEANTENNASANDPOWERAMPLIFIERSUSEDIN(&BROADCASTSTATIONSHAVEMUCHIN COMMONWITH(&RADAR THATIS TOMAINTAINASPECIFIEDLEVELOFILLUMINATIONOVERA DESIGNATEDAREA4OACHIEVETHISGOAL MANYMULTIBANDANDSTEERABLEBROADCASTANTEN NASnEMPLOYLARGEVERTICALAPERTURES!NTENNASUSEDFOR(&RADARHAVEANADDITIONAL SEVERECONSTRAINTTHENEEDTOMINIMIZEMECHANICALMOTIONDUETOTHEWIND!EOLIAN VIBRATION THATWOULDCAUSESIGNALPHASEMODULATIONTHATWOULDTHENBEIMPOSEDON THE TRANSMITTED SIGNALS THIS REQUIREMENT IS EASIER TO MEET WITH LOW ANTENNA HEIGHT DESIGNS!NUNDER EXPLOITEDADVANTAGEOFBROADBEAMSINELEVATIONISTHEABILITYTO ILLUMINATEANEXTENDEDRANGEDEPTHWHENCONDITIONSPERMIT PROVIDINGCLUTTERMAPS OUTSIDETHERANGEBANDOFIMMEDIATEINTERESTFORTARGETDETECTIONTHESECANBEUSEDTO SCHEDULESUBSEQUENTSURVEILLANCETASKS
Óä°ÇÊ , ,Ê ,"--Ê- /" 4HE RADAR SCATTERING PROPERTIES OF TARGETS DETERMINE BOTH THEIR DETECTABILITY AND THE PROSPECTSFORTARGETCLASSIFICATIONTHEREFORE MUCHEFFORTHASGONEINTOESTABLISHING PRECISELYHOWTODESCRIBETHOSEPROPERTIESFORAGIVENRADARCONTEXT)NTHE(&SKYWAVE RADARCASE THEINEVITABILITYOF&ARADAYROTATIONTHATOCCURSDURINGIONOSPHERICPROPA GATIONHASBEENUSEDTOARGUETHATAFULLYPOLARIMETRICTREATMENTISUNNECESSARY SOIT ISCOMMONPRACTICETOREPRESENTTHESCATTERINGBEHAVIORINTERMSOFSCALARRADARCROSS SECTION2#3 &ULLYPOLARIMETRICFORMULATIONSARERELEVANTWHENMODELINGCOMPLEX SCATTERINGPROCESSES ANDFORTARGETCLASSIFICATIONSTUDIES )NGENERAL AIRCRAFTANDSHIPSHAVEDIMENSIONSTHATPUTTHEMWITHINTHERESONANT SCATTERING REGIME THOUGH THE SMALLEST AIRCRAFT AND CRUISE MISSILES WILL LIE IN THE 2AYLEIGHSCATTERINGREGIMEFORTHELOWERHALFOFTHE(&BAND(ERE THE2#3DISPLAYS LIMITEDASPECTSENSITIVITYANDASTRONGDEPENDENCEONTHETARGETSGROSSDIMENSIONS &ORANAIRCRAFT THESPANOFTHEWINGS THEFUSELAGELENGTH THETAILANDELEVATORSPAN THE VERTICAL STABILIZER AND RUDDER HEIGHT AND THEIR RELATIVE LOCATIONS ARE THE MAIN FEATURES THAT INFLUENCE THE 2#3 4ARGET SHAPING ON A SCALE SIZE MUCH LESS THAN A WAVELENGTHWILLHAVELITTLEEFFECT!CCURATEMEASUREMENTSOFRADARSCATTERINGAT(& FREQUENCIESISCHALLENGING BUTFACILITIESFORMAKINGSCALEMODELMEASUREMENTSARE
(&/6%2 4(% (/2):/.2!$!2
Óä°ÓÇ
WIDELYAVAILABLE INCLUDINGANECHOICCHAMBERS INDOORCOMPACTRANGES ANDOUTDOOR TEST FIELDS &ULL SCALE EXPERIMENTAL MEASUREMENTS CAN BE MADE IN SOME CIRCUM STANCESBYMEANSOFCALIBRATEDREFERENCESCATTERERSORTRANSPONDERSDEPLOYEDINTHE TARGETZONEANDMODULATEDTOSEPARATETHEIRRETURNSFROMTHETARGETANDCLUTTERECHOES &ORBODIESWITHHIGHLYCONDUCTIVESURFACES THESCATTERINGCROSSSECTIONCANBECALCU LATEDQUITEACCURATELYBYNUMERICALMETHODS SUCHASTHEMETHOD OF MOMENTSCODE .%#!SARULEOFTHUMB THE(&2#3OFAIRCRAFTCANUSUALLYBECOMPUTEDTOAN ACCURACYOFABOUTORD"WITHRESPECTTOMEASUREDVALUES WITHOUTRESORTINGTO HIGHLYSOPHISTICATEDTECHNIQUES 7HENPRECISE2#3INFORMATIONISNOTESSENTIAL ROUGHBUTUSEFUL2#3ESTIMATES CAN BE MADE BY EXAMINING THE SCATTERING BEHAVIOR OF A FEW hCANONICALv SHAPES &IGUREISAFAMILYOFPLOTSGIVING2#3VERSUSRADARFREQUENCYFORANOBLONG SHAPEDCONDUCTINGBODY4HESTRAIGHTLINEMARKEDnLDIPOLEGIVESTHE2#3OFA RESONANT CONDUCTINGHALF WAVELENGTHROD WHERETHERODISPARALLELWITHTHEELECTRIC FIELD4HISGEOMETRYGIVESTHEMAXIMUM2#3FORTHEROD4HEUPPERSCALEOFTHE ABSCISSA GIVES THE ONE HALF WAVELENGTH DIMENSION OF THE FREQUENCY GIVEN ON THE LOWERSCALE4HECURVEMARKEDnISTHE2#3OFTHEOBLONG SHAPEDCONDUCTINGBODY OFMLENGTHANDMTHICKNESSAGAIN THETARGETLONGDIMENSIONISALIGNEDWITH THEELECTRICFIELD4HEMAXIMUM2#3COINCIDESWITHTHENOMINALHALF WAVELENGTH DIMENSIONORWITHTHEFIRSTRESONANCE
&)'52% 4HEFREQUENCYDEPENDENCEOFTHE2#3FORANMLONGBYMDIAMETER PERFECTLY CONDUCTINGCYLINDER PRESENTEDFORVARIOUSILLUMINATIONGEOMETRIES4HE%VECTORANDTHEMDIMEN SIONAREINTHESAMEPLANEnNOSE ON n ANDnBROADSIDE CURVESARESHOWN4HETOPDASHED CURVEISFORARESONANTDIPOLEATn4HESMALLSKETCHESATTHEFIRST SECOND ANDTHIRDRESONANCESSHOW THE2#3ANGULARPATTERNNEARTHESEFREQUENCIES
Óä°Ón
2!$!2(!.$"//+
&)'52% 2#3FREQUENCYDEPENDENCEOFARODMONOPOLE ANDAHEMISPHEREONAPERFECTLYCONDUCTING PLANEFORVERTICALINCIDENTANDSCATTEREDPOLARIZATION
4HECURVESMARKED ANDnGIVETHE2#3ASTHETARGETISROTATEDTOTHESE ANGLESINTHEPLANETHATCONTAINSTHEELECTRICVECTOR4HELITTLESKETCHESGIVE ATTHELEFT THEBODYSHAPE ANDTHENTHE2#3PATTERNSATNOMINALWAVELENGTH WAVELENGTH ANDWAVELENGTH INORDERTOHELPVISUALIZEHOWTHE2#3WILLCHANGEASTHEASPECT ANGLEISVARIED&ORTARGETSOFOTHERLENGTHSWITHAPPROXIMATELYTHESAMESHAPEFACTOR THERESPONSECANBEDETERMINEDBYSLIDINGTHECURVEALONGTHELLINEANDMAKINGTHE FIRSTRESONANCECOINCIDEWITHTHELINEATTHEWAVELENGTHPOINT!SHASBEENMEN TIONED &ARADAYROTATIONRESULTSINVARYINGINCIDENTPOLARIZATION SOOVERTIMEATARGET WILLEXPERIENCEBOTHFAVORABLEANDMISMATCHEDPOLARIZATION WITHRESULTANTFADINGOF THESCATTEREDSIGNAL/FCOURSE ADDITIONALFADINGOFTHESCATTEREDSIGNALOCCURSDUETO TIME VARYINGPOLARIZATIONMISMATCHATTHERECEIVINGANTENNA &IGUREGIVESTHEVERTICAL POLARIZATION2#3OFARODANDAHEMISPHEREMOUNTED ONAPERFECTLYCONDUCTINGSURFACE7ITHTHESECANONICALSHAPES ANESTIMATEOF2#3 CANBEMADEFORSURFACECRAFTBYMATCHING,AND2TOTHEPRINCIPLEDIMENSIONSTOTHE TARGET&ORSMALLVESSELS THEMASTHEIGHTWILLBEOFMOSTIMPORTANCE&ORSURFACE TARGETS WHERETHEMAXIMUM2#3OCCURSWITHVERTICALPOLARIZATION AD"SKYWAVE 2#3ENHANCEMENTRESULTSFROMTHEIMAGEFIELD 4OILLUSTRATETHE2#3BEHAVIOROFATYPICALAIRCRAFTINMOREDETAIL &IGURE SHOWSTHE2#3OFTHE& FIGHTER ASCOMPUTEDHEREBY.%#APPLIEDTOAWIRE GRIDREPRESENTATIONOFTHEAIRCRAFTDERIVEDFROMAPLASTICKITMODEL4HE2#3SHOWN ISFORMONOSTATICBACKSCATTER GEOMETRYANDHORIZONTALCOPOLAR(( POLARIZATION #ALCULATIONSAREPRESENTEDFORFREQUENCIESOF AND-(Z !LTHOUGHTHEFIDELITYOFSUCH2#3CALCULATIONSOFCONVENTIONALPLATFORMSHASBEEN CONFIRMED ON MANY OCCASIONS IT IS NOT CLEAR THAT STANDARD COMPUTATIONAL METHODS AREAPPLICABLETOTHEPROBLEMOFESTIMATINGTHE2#3OFAIRCRAFTTARGETSTHATCANNOTBE MODELEDASSIMPLEPERFECTELECTRICALCONDUCTORS0%# ORTOSMALLhGO FASTvBOATSIN DYNAMICINTERACTIONWITHTHESEASURFACE
(&/6%2 4(% (/2):/.2!$!2
Óä°Ó
&)'52% -ONOSTATIC2#3OFTHE& FIGHTERAIRCRAFTAT AND-(Z COMPUTEDFOR((POLAR IZATIONATALOOK DOWNANGLEOF
Óä°nÊ 1// ,\Ê " -Ê," ÊÊ / Ê 6," / %ARTH3URFACE#LUTTER 4HEGEOMETRYOFSKYWAVEILLUMINATIONENSURESTHATTAR GETECHOESWILLBEIMMERSEDINRETURNSFROMTHE%ARTHSSURFACE THATIS CLUTTER)NORDER TODETECTTHETARGETS THEPROPERTIESOFTHISCLUTTERNEEDTOBEUNDERSTOODSOTHATTHE CHOICEOFFREQUENCY WAVEFORM ANDSIGNALPROCESSINGARECOMPATIBLEWITHTHENEEDTO SEPARATETARGETECHOESFROMCLUTTER ANDALSOSOTHATTHEREQUIREDDYNAMICRANGEOFTHE RADARCANBECORRECTLYSPECIFIED %ARLY (& RADAR EXPERIMENTS ESTABLISHED THAT THE STRONG GROUND CLUTTER OBSERVED VIASKYWAVEPROVIDEDANINDICATIONOFTHEPHYSICALCHARACTERISTICSOFTHEILLUMINATED TERRESTRIAL SURFACE %XTENSIVE OBSERVATIONS MADE AT THE .AVAL 2ESEARCH ,ABORATORY VIEWING ALTERNATELY!TLANTIC /CEAN AREAS AND CENTRAL 5NITED 3TATES AREAS INDICATED THAT AVERAGEDOVERAWIDEAREA SEACLUTTERPOWERLEVELSWEREUSUALLYABOUTANORDEROF MAGNITUDEHIGHERTHANTHOSEFROMANAREAOFSIMILARSIZEINTHECENTRAL5NITED3TATES ,ATEROBSERVERSNOTEDEXTREMELYLOWBACKSCATTERFROMICE COVEREDAREASOF'REENLAND 4HESERESULTSARECONSISTENTWITHPREDICTEDSCATTERINGCOEFFICIENTVARIATIONSBASEDON THETOPOGRAPHYANDTHEELECTRICALPROPERTIESOFTHESURFACES3UBSEQUENTLY OBSERVA TIONSOVERTHE)NDIAN/CEANWITHTHE*INDALEERADAR EMPLOYINGCAREFULLYCALIBRATED TRANSPONDERS REVEALED^D"VARIATIONSINTHEOCEANSCATTERINGCOEFFICIENT DEPEND INGONSEASTATE ,AND#LUTTER -APPINGOFSKYWAVEBACKSCATTERFROMTERRESTRIALLAND SURFACES ISOFINTERESTFORTWOMAINREASONS&IRST ALOCALIZEDAREAOFENHANCEDBACKSCATTER SUCHASACITYINTHECENTRALPLAINSOFTHE53ORAMOUNTAINRISINGFROMATROPICAL
Óä°Îä
2!$!2(!.$"//+
RAINFOREST PROVIDES A GEOGRAPHICAL REFERENCE THAT CAN ASSIST WITH THE EVER PRESENT PROBLEMOFCOORDINATEREGISTRATIONUNCERTAINTIESINTHERAYPATHTRAVERSEDBYTHE RADARSIGNALSCANLEADTOTARGETPOSITIONINGERRORSOFOVERKMUNDERSOMECIRCUM STANCES 3ECOND SOMEREGIONSEXPERIENCESTRONGSEASONALVARIATIONSINVEGETATION ANDSOILMOISTURECONTENT WHICHMAYBEREFLECTEDINMEASURABLECHANGESTOSCATTERING BEHAVIOR)TISALSOIMPORTANTTOUNDERSTANDTHEEFFECTOFTHEGROUNDSCATTERINGCOEF FICIENTANDTHETOPOGRAPHYWHENINTERPRETINGECHOESFROMTARGETSABOVETHEGROUND 3EA #LUTTER )N CONTRAST WITH THE ABRUPT CHANGES IN SCATTERING BEHAVIOR THAT OCCURATCOASTLINESOROVERCOMPLEXTERRAIN THEMAGNITUDEOFTHERADARECHOFROM THEOPENOCEAN THATIS THESCATTERINGCOEFFICIENTRnTENDSTOVARYSLOWLYWITHRANGE ANDAZIMUTHASACONSEQUENCEOFTHESCALELENGTHSOFTYPICALOCEANICMETEOROLOGICAL SYSTEMSANDTHERESPONSETIMEOFTHEOCEANSURFACETOVARYINGWINDSTRESS-OREOVER MUCH OF THE TIME TO A REASONABLE APPROXIMATION THE ECHO POWER IS PROPORTIONAL TO THE RESOLUTION CELL AREA AND CAN BE USED AS AN ABSOLUTE AMPLITUDE REFERENCE WHENCAREISEXERCISED4HEREASONFORTHISISEXPLAINEDLATERINTHEDISCUSSIONOF RADAROCEANOGRAPHY /FFARGREATERINTERESTTHANTHE AVERAGEMAGNITUDEOF THESEAECHOISTHEWEALTH OF INFORMATION EMBEDDED IN ITS DOPPLER SPECTRUM 4HE WAVES ON THE SEA SURFACE INTRODUCEACOMPLEXMODULATIONONTHEREFLECTEDRADARSIGNAL WHICHISMANIFESTEDIN THESIGNALSDOPPLERSPECTRUM%STIMATIONANDINTERPRETATIONOFTHISMODULATIONYIELDS INFORMATIONONTHETIME VARYINGSEASURFACEGEOMETRYWITHMAJORIMPLICATIONSFORSHIP DETECTIONASDISCUSSEDBELOW )TTRANSPIRESTHATARELATIVELYSIMPLEMODELACCOUNTSFORTHEOBSERVEDPROPERTIESOF SEACLUTTERWITHREMARKABLEFIDELITY PROVIDEDTHESEAISNOTTOOROUGH4HISMODELIS BASEDONTWOASSUMPTIONS 4HESEASURFACECANBEREPRESENTEDTOAGOODAPPROXIMATIONASASUPERPOSITIONOR F SPECTRUM3J OFSURFACEGRAVITYWAVESSATISFYINGTHEDISPERSIONRELATION
V GJ TANHJ D
WHEREVISTHEWAVEANGULARFREQUENCY GISTHEACCELERATIONDUETOGRAVITY JIS THEWAVENUMBEROFTHEWATERWAVE ANDDISTHEWATERDEPTH&ORDEEPWATER THIS REDUCESTO V GJ
FROMWHICHTHEWATERWAVEPHASEVELOCITYCANBEWRITTEN
Vx
V § G, ¶ J ¨© P ·¸
WHERE,ISTHEWAVELENGTHOFTHEWATERWAVE )NTERMSOF(&WAVELENGTHS THESEASURFACECANBEREGARDEDASONLYSLIGHTLYROUGH THEREFOREADMITTINGANAPPROXIMATESOLUTIONFORTHESCATTEREDFIELDINTHEFORMOFA PERTURBATIONSERIESEXPANSIONINTHEPARAMETERKA WHEREKISTHERADIOWAVENUM BERANDAISAREPRESENTATIVEOCEANWAVEAMPLITUDE4HISAPPROACH FORMULATEDBY 2ICEFORTHECASEOFASTATICSURFACEANDEXTENDEDBY"ARRICK TOTHECASEWHERE THESURFACEISEVOLVINGACCORDINGTOTHEDISPERSIONRELATION%Q LEADSTOAN EQUATIONFORTHEDOPPLERSPECTRUMOFTHEREFLECTEDRADIOWAVES
(&/6%2 4(% (/2):/.2!$!2
R V P K
F
Óä°Î£
F
£ 3 MKSCAT KINC C V V "
M o
P K
F
F
F
F F C V M GJ M GJ DJ DJ
F
£ ¯¯ 'MJ MJ 3MJ 3MJ M M o
F F F WHERE KINC AND KSCAT ARETHEINCIDENTANDSCATTEREDRADIOWAVEVECTORS K \ KINC \ F VISTHEDOPPLERFREQUENCY 3J ISTHESEADIRECTIONALWAVESPECTRUM C ISTHE F F $IRACDELTAFUNCTION ANDTHE"RAGGFREQUENCYV "ISGIVENBYV " G K K 4HE F F KERNEL ' J J ISDISCUSSEDBELOW%QREVEALSTHATTHE"ARRICK 2ICESOLU TIONHASASIMPLEINTERPRETATIONINTERMSOFSPATIALRESONANCEOR"RAGGSCATTERING !LTHOUGHTHEDISORGANIZED LOOKINGOCEANSURFACEISREPRESENTEDASTHE&OURIERSUM OFANINFINITENUMBEROFSINUSOIDALWAVETRAINS EACHWITHITSCHARACTERISTICWAVE NUMBERANDDIRECTION THEPRINCIPALhFIRST ORDERvCONTRIBUTIONSTOTHESCATTEREDFIELD ARISEFROMONLYTWOOCEANWAVETRAINS NAMELYTHOSEWHOSEWAVEVECTORSSATISFY THERELATION SCAT
F F F J o o KSCAT KINC
INC
&ORTHESIMPLECASEOFBACKSCATTERATGRAZINGINCIDENCE THEGEOMETRYFORMONO F F STATICSURFACEWAVERADAR KSCAT KINC SOTHESERESONANTOCEANWAVESHAVEAWAVE LENGTH EQUAL TO ONE HALF OF THERADARWAVELENGTH WITHONESOLUTIONCORRESPONDING TOAWAVEDIRECTLYAPPROACHINGTHERADARANDTHEOTHERRECEDINGFROMIT4HECORRE SPONDINGDOPPLERSHIFTSARETHOSEASSOCIATEDWITHTHEPHASEVELOCITYOFTHERESONANT WAVES THATIS
FD o
G GF o y o F -(Z PK PC
WHERETHEDOPPLERSHIFTFDISIN(ZGISTHEGRAVITATIONALACCELERATIONMS FISTHE RADARFREQUENCY ANDCTHEVELOCITYOFLIGHT 7ITHTHISINSIGHT THESECOND ORDERTERMIN%QCANBEINTERPRETEDAShDOUBLE BOUNCEvPROCESSESINVOLVING"RAGGSCATTERFROMFIRSTONEANDTHENANOTHERWAVETRAIN WITHTHETWICE SCATTEREDRADIOWAVEDIRECTEDTOWARDTHERECEIVER/FCOURSE THEREARE INPRINCIPLE INFINITELYMANYPAIRSOFWAVETRAINSTHATCANSATISFYTHISCONDITION HENCE THEINTEGRAL!NDTHEREISANOTHERCOMPLICATION4HEINDIVIDUALOCEANWAVETRAINSARE NOTCOMPLETELYINDEPENDENTTHEYINTERACTWEAKLYANDPRODUCEEVANESCENTNONLINEAR PRODUCT WAVES THAT WHILE NOT FREELY PROPAGATING CHANGE THE GEOMETRY OF THE SEA SURFACEANDCONTRIBUTETOTHESCATTEREDFIELDATSECONDORDER ALSOVIA"RAGGSCATTERING 4HUS ASSHOWNFIRSTBY"ARRICK THESECOND ORDERSCATTERINGKERNELISMADEUPOF ELECTROMAGNETICANDHYDRODYNAMICTERMS ' ' %- ' (9$4HERESULTINGPIECEWISE CONTINUOUSSECOND ORDERDOPPLERSPECTRUMISUSUALLYSOMEnD"WEAKERTHANTHE FIRST ORDER"RAGGPEAKSBUT BEINGSPREADINDOPPLER HASTHEPOTENTIALTOMASKSHIP ECHOESOVERMUCHMOREOFDOPPLERSPACE&IGUREISANEXAMPLEOFTHENUMERICAL EVALUATIONOF%QFORASPECIFICOCEANWAVESPECTRUM 0OLARIZATIONDEPENDENCEARISESTHROUGH' &ORAHIGHLYCONDUCTINGMEDIUMSUCH AS SEAWATER VIEWED AT TYPICAL (& RADAR GEOMETRIES THE COPOLAR SURFACE SCATTERING
Óä°ÎÓ
2!$!2(!.$"//+
&)'52% #OMPUTEDDOPPLERSPECTRAOFSEACLUTTERFORVARIOUSPOLARIZATIONSTHERADARFREQUENCY HEREIS-(ZWHILETHEDIRECTIONALWAVESPECTRUMADOPTEDISA0IERSON -OSKOWITZWAVE NUMBER SPECTRUMCOMBINEDWITHACOSI ANGULARSPREADINGPATTERN
COEFFICIENT OR2#3PERUNITSURFACEAREA ISMUCHLARGERFORVERTICALTHANFORHORIZONTAL POLARIZATION WITHTHECROSSPOLARSCATTERINGCOEFFICIENTSTYPICALLYASSUMINGINTERMEDI ATEVALUESFORMODERATEBISTATICSCATTERINGGEOMETRIES RnVVRnHV yRnVH RnHH AS ILLUSTRATEDIN&IGURE %QISOFFUNDAMENTALIMPORTANCETOMANY(&RADARAPPLICATIONS INCLUDINGSHIP DETECTION REMOTESENSINGSEEFOLLOWINGSECTION WAVEFORMSELECTION ANDOTHERRADAR MANAGEMENT FUNCTIONS &OR EXAMPLE &IGURE SHOWS A MEASURED DOPPLER SPEC TRUMAND SUPERIMPOSED REPRESENTATIVEESTIMATESOFTHEMAGNITUDESOFTHEECHOESTHAT MIGHTBERECEIVEDFROMANUMBEROFDIFFERENTSHIPTYPESFORTHESAMERADARDESIGNAND WAVEFORMPARAMETERS!LSOSHOWN ATLEFT ARETHESPEEDBANDSWITHINWHICHTHESHIP ECHOESWOULDBEOBSCUREDBYTHECLUTTER4HEABILITYTOPREDICTTHESEOBSCUREDBANDSBY MEANSOF%QCANBEEXPLOITEDFOR(&RADARDESIGNANDSITINGANDFORSCHEDULING SHIPDETECTIONOPERATIONS4HUSCOMBINING%QWITHANOCEANWAVECLIMATOLOGY FORANYREGIONENABLESTHESTATISTICALPREDICTIONOFRADARSHIPDETECTIONPERFORMANCE
(&/6%2 4(% (/2):/.2!$!2
Óä°ÎÎ
&)'52% 3CHEMATICREPRESENTATIONOFBLINDSPEEDBANDSINWHICHSHIPECHOESAREOBSCURED BYSEACLUTTER
3IMILARLY CHOICEOFTHEWAVEFORMFREQUENCYANDBANDWIDTHCANBEGUIDEDBYCALCULA TIONOFTHECLUTTERPOWERSPECTRALDENSITYASAFUNCTIONOFTHESEPARAMETERSFORANYGIVEN SEASTATE TAKINGINTOACCOUNTANYINFORMATIONABOUTTARGETCOURSE SPEED AND2#3 !VERYIMPORTANTOPERATIONALCONSIDERATIONHEREISTHEPOTENTIALFORANADVERSARY TOEXPLOITTHESEACLUTTERSPECTRUMBYCONTRIVINGTOPLACEHISSHIPECHOATTHE"RAGG FREQUENCYWHEREITWOULDBEOBSCUREDBYSEACLUTTER4HEADVERSARYCANACHIEVETHIS BYCHOOSINGANYCOMBINATIONOFCOURSEANDSPEEDTHATMAKESTHEVELOCITYCOMPONENT TOWARDTHERADAREQUALTOTHEEQUIVALENTPHASEVELOCITYOFTHE"RAGGPEAK4HERADAR OPERATORMUSTCOUNTERTHISBYEXPLOITINGHISUNDERSTANDINGOFTHEDETAILEDSTRUCTUREOF THESPECTRUMANDITSVARIATIONWITHRADARFREQUENCYTOUNMASKTHETARGET 2ADAR /CEANOGRAPHY 4HE EXISTENCE OF THE RELATION EXPRESSED INF %Q BETWEENTHESEASURFACEREPRESENTATIONASADIRECTIONALWAVESPECTRUM3J ANDTHE DOPPLERSPECTRUMMEASUREDBYAN(&RADARPROVIDESANOPPORTUNITYTODETERMINETHE DETAILEDSTATEOFTHESEASURFACEBYREMOTESENSINGWITHSKYWAVEORSURFACEWAVE RADAR)NORDERTOEXTRACTSEAPARAMETERSFROMRADARDOPPLERSPECTRA ANDTOOPTIMIZE THECHOICEOFRADARPARAMETERSFORTHERADARSSURVEILLANCEMISSIONS ITISHELPFULTO UNDERSTANDSOMEELEMENTARYOCEANOGRAPHY 4HEOCEANWAVESTHATCONTRIBUTEMOSTTOTHE(&RADARRETURNSHAVEWAVELENGTHSIN THERANGEOFnMTHESEWAVESAREEXCITEDBYTHESURFACEWINDS)FAWINDBLOWSAT ACONSTANTVELOCITYLONGENOUGHANDOVERSUFFICIENTFETCHTHEDISTANCEOVERWHICHTHE WINDISBLOWING ASTEADY STATECONDITIONWILLBEACHIEVEDWHERETHEWINDPROVIDES JUSTENOUGHENERGYTOTHEWAVESTOBALANCETHATLOSTBYBREAKINGANDOTHERDISSIPATION MECHANISMS-OREOVER INTHISSTATEOFDYNAMICEQUILIBRIUM ENERGYWILLBETRANSFERRED
Óä°Î{
2!$!2(!.$"//+
&)'52% .ONDIRECTIONALWAVEHEIGHTPOWERSPECTRALDENSITY ASMEASUREDWITHAWAVEBUOY SHOW INGPOWERLAWBEHAVIOR4HESTRAIGHTLINEISTHEORIGINAL0HILLIPSSATURATIONASYMPTOTE WHICHISAPPROACHED ATHIGHFREQUENCIESINTHISEXAMPLE4HESCALEMARKEDhWINDVELOCITYvCANBEUSEDTODEDUCETHATWINDSUP TOKTHAVEEXCITEDWAVESWITHFREQUENCIESASLOWAS(Z BUTTHATEITHERTHEDURATIONORFETCH ORBOTH HAVENOTBEENSUFFICIENTFORFULLDEVELOPMENT4HESCALEACROSSTHETOPGIVESTHERADARFREQUENCYCORRESPOND INGTORESONANTBACKSCATTER
PREDOMINANTLYTOWAVESWHOSEVELOCITIESAREFAIRLYCLOSELYMATCHEDTOTHEWINDVELOC ITY AND UNDERGO REDISTRIBUTION ACROSS WAVENUMBER SPACE THROUGH THE MECHANISM OF NONLINEARWAVEINTERACTIONSTOPRESERVETHEEQUILIBRIUMSPECTRALFORM 4HEREAREANUMBEROFMODELSTHATHAVEBEENPROPOSEDTODESCRIBETHEEQUILIBRIUM SPECTRALFORM ANDINDEED MODELSTHATATTEMPTTHEMOREAMBITIOUSTASKOFMODELING NONEQUILIBRIUM SPECTRA -OST OF THESE MODELS ARE BASED ON EXPERIMENTAL MEASURE MENTS ILLUSTRATED HERE BY &IGURE WHICH SHOWS AN EXAMPLE OF THE FREQUENCY SPECTRUMDERIVEDFROMWAVEBUOYMEASUREMENTS!COMMONFEATUREOFSUCHWAVE SPECTRAISTHATWAVESOFAGIVENWAVELENGTHTENDTOREACHALIMITINGSPECTRALDENSITY BEYONDWHICHTHEPROCESSESOFDISSIPATIONANDNONLINEARTRANSFEROFENERGYTOOTHER WAVENUMBERSPREVENTSFURTHERGROWTH4HISCONDITIONKNOWNASSATURATION ORBEING FULLYDEVELOPEDISREACHEDATQUITEMODESTWINDSPEEDSFORTHOSEWAVESRESPONSIBLE FORFIRST ORDERSCATTERAT(& THATISnKNOTS /FTHEVARIOUSNONDIRECTIONALOCEANWAVEMODELSREPORTEDINTHELITERATURE THAT OF0IERSONAND-OSKOWITZHASBEENMOSTWIDELYUSEDBYTHERADARCOMMUNITY4HEY DERIVED THE FOLLOWING RELATION FOR A FULLY DEVELOPED NONDIRECTIONAL SPECTRUM BASED UPONEMPIRICALDATA
& J
§ ¤J ³ ¶ AE C EXP ¨ N ¥ J ´ · P J ¦ µ · ©¨ ¸
(&/6%2 4(% (/2):/.2!$!2
Óä°Îx
OREQUIVALENTLY INTERMSOFWAVEFREQUENCY
§ ¤ G ³ ¶ A G & V E EXP ¨ N ¥ ´ · V ¨© ¦ V Uµ ·¸
WHERE
U WINDSPEED JC GU M ANDAE
4HE EXPONENTIAL TERM APPROXIMATES THE DECAY IN THE SPECTRUM FOR WAVE SPEEDS ABOVETHEWINDMAXIMUMVELOCITY-ODELSTHATTAKEACCOUNTOFTHECONSEQUENCESOF FINITEFETCHANDFINITEDURATIONOFTHEWINDSTRESSINCLUDETHE*/.37!0SPECTRUM ANDTHEMODELOF%LFOUHAILYETALSUCHEFFECTSCANLEADTOSUBSTANTIALCHANGESINTHE (&DOPPLERSPECTRUMANDHENCETARGETDETECTABILITY SOTHESEMODELSSHOULDBEUSED WHENAPPLICABLE 4HEDECREASEOFWAVESPECTRALDENSITYWITHWAVENUMBERISOBSERVEDTOLIECLOSE TOAKnPOWERLAW ASADOPTEDBYMOSTMODELS ANDBYANATURALCOINCIDENCE THISIS BALANCEDBYTHEKFACTORINTHEFIRST ORDERSCATTERINGCOEFFICIENTIN%Q SOTHE RESULTING S IS ROUGHLY INDEPENDENT OF FREQUENCY OVER THE RANGE OF FREQUENCIES FOR WHICHTHEPOWERLAWBEHAVIORISOBSERVED!NIMPORTANTCONSEQUENCEISTHATWITHSUCH AREFERENCE PROPAGATIONPATHLOSSESMAYBEESTIMATED 4OTESTTHISIDEA THEMAGNITUDEANDVARIABILITYOFRVVnWASEXAMINEDWITHTHE3AN #LEMENTE)SLAND(&SURFACEWAVERADAR4HISRADARFACILITYHADSEVERALVALUABLEAND UNIQUEFEATURESATRANSMISSIONPATHOUTOVERTHEOPENSEA MULTIPLE FREQUENCYOPERATION WITHINAREPETITIONPERIOD CALIBRATEDANTENNAS KNOWNTRANSMITTERPOWER ANDGROUND TRUTHINTHEFORMOFOCEANWAVEHEIGHTRECORDINGS7HENLOOKINGINTOANAPPROXIMATELY KNOTWIND VALUESOFRVVnWEREFOUNDTOBECONSTANTWITHINAFEWDECIBELSFOROPERAT ING FREQUENCIES WHERE THE OCEAN WAVE SPECTRUM WAS APPROXIMATELY FULLY DEVELOPED THESEOBSERVATIONSPROVIDEDACONFIRMATIONOF"ARRICKSFIRST ORDERTHEORY"YUSING THEANTENNAGAINCONVENTIONSSTATEDEARLIERANDASSUMINGASEMI ISOTROPICSEADIRECTIONAL SPECTRUM THEVALUEOFRVVnWASCALCULATEDASnD"THEMEASUREDVALUESWEREGROUPED BETWEEN AND D"OFTHISVALUEOVERATO-(ZFREQUENCYSPAN4HISEXPERIMENT PROVIDEDTHEFIRSTDIRECTMEASUREMENTSOFTHESEASURFACESCATTERINGCOEFFICIENT /FCOURSE WHENTHE"RAGGRESONANTWAVESARENOTFULLYDEVELOPED THESCATTERING COEFFICIENTWILLBEPROPORTIONATELYLESS ASSHOWNIN&IGURE COMPILEDFROMDATA SETSRECORDEDLOOKINGUPWINDORDOWNWINDWITHTHE*INDALEERADAR/CCASIONSWHEN THEWINDSPEEDWASINSUFFICIENTTOAROUSETHE"RAGGRESONANTWAVESTOSATURATIONLEVELS YIELDEDSCATTERINGCOEFFICIENTVALUESUPTOD"BELOWTHEPEAKVALUES ,OWSCATTERINGCOEFFICIENTVALUESCANALSOARISEBECAUSETHEANGULARSPECTRUMOF THEWAVESYSTEMISNOTBEINGSAMPLEDALONGADIRECTIONTHATPRESENTSTHEMAXIMUM AMPLITUDECOMPONENTATTHE"RAGGRESONANTWAVENUMBER4HEDIRECTIONALWAVESPEC TRUMCANBEWRITTENAS F
3 K x 3 K E & K ' E K WHERE&K ISTHENONDIRECTIONALSPECTRUM
& K ¯
P
3 K E DE
Óä°ÎÈ
2!$!2(!.$"//+
&)'52% #ALIBRATED MEASUREMENTS OF THE RATIO OF THE MEASURED SCATTERING COEFFICIENT TO THE SATURATEDSEASCATTERINGCOEFFICIENT PLOTTEDASAFUNCTIONOFTHERATIOOFWINDSPEEDTOTHEPHASESPEEDOF THE"RAGG RESONANTWAVESFORUPWINDDOWNWINDOBSERVATIONS
AND'E K ISTHENORMALIZEDANGULARSPREADINGFUNCTIONTHATDESCRIBESHOWTHEWAVE ENERGYISDISTRIBUTEDINAZIMUTH
P
¯
' E K DE
4HENON ZEROWAVESPECTRUMISNOTCONFINEDTODIRECTIONSHAVINGACOMPONENTPAR P P ALLELTOTHEWINDDIRECTIONE IE 'E K FOR a E a NORISITSEMI ISOTROPIC ' E K P FOR P a E a P )NGENERAL THEANGULARSPECTRUMISNON ZEROTHROUGHn WITHTHESPREADINGFUNCTIONDEPENDINGONMANYVARIABLES INCLUDINGTHERECENTSURFACE WINDHISTORY(&RADARHASSUFFICIENTSENSITIVITYTOMEASURETHERELATIVEAMPLITUDEOF THE WAVES RUNNING AGAINST THE WIND EVEN THOUGH THEY MAY HAVE A POWER SPECTRAL DENSITYANDHENCEAN2#3 SEVERALORDERSOFMAGNITUDEBELOWTHOSERUNNINGWITH THEWIND4HESEUPWIND PROPAGATINGOCEANWAVESARECAUSEDPREDOMINANTLYBYTHIRD ORDER NONLINEAR WAVE WAVE INTERACTIONS REFLECTION PROCESSES WAVE CURRENT INTERAC TIONS ANDPROPAGATIONFROMNEIGHBORINGREGIONSWITHDIFFERENTWINDSTRESS4HEYARE VERYIMPORTANTFORREMOTESENSINGANDIMPACTSTRONGLYONTARGETDETECTIONBECAUSETHE SECOND ORDERSCATTERINGPROCESSESAREHEAVILYDEPENDENTON'E K 4HEYALSOSERVE ASASENSITIVEINDICATOROFBACKSCATTERCOEFFICIENTESTIMATIONSINCE TAKINGACCOUNTOF ONLYTHEFIRST ORDERSCATTEREDFIELD
R s ;' E E7 K ' E E7 P =
WHEREE7ISTHEWINDDIRECTION4OQUANTIFYTHIS IFTHEWAVEANGULARSPECTRUMMODEL OF,ONGAND4RIZNAISUSED THEMAXIMUMVALUEOFRnFORASATURATEDSEAISnD"IN THEUPWINDORDOWNWINDDIRECTIONLONGITUDINALSEA ANDONLYnD"INTHECROSSWIND DIRECTIONTRANSVERSESEA &IGURESHOWSTHESCATTERINGCOEFFICIENTFORTHISAND SOMESIMPLEPARAMETRICANGULARSPREADINGFUNCTIONSVERSUSANGLEWITHRESPECTTOWIND DIRECTION ASCOMPUTEDFROMTHEFIRST ORDERCONTRIBUTIONS
(&/6%2 4(% (/2):/.2!$!2
Óä°ÎÇ
&)'52% 6ARIATIONOFTHEPEAKBACKSCATTERCOEFFICIENTASAFUNCTIONOFWINDDIRECTIONRELATIVETOTHE RADARLOOKDIRECTIONFORVARIOUSSPREADINGFUNCTIONS ASSUMINGASEAFULLYDEVELOPEDATTHE"RAGG RESONANT WAVEFREQUENCY
)NSUMMARY THESEAECHOPOWERINARESOLUTIONCELL ISGENERALLYTHELARGESTECHO SIGNAL GENERALLYEXISTSINTHEOPENOCEANEVENINRELATIVECALM VARIESASTHE SQUAREOFRESONANTWAVEHEIGHT WHICHISFREQUENTLYSATURATEDATTHEHIGHERFREQUEN CIESAND VARIESWITHDIRECTION BEINGGREATESTFORSEASRUNNINGTOWARDORAWAY FROMTHERADAR4HEDOPPLERSPECTRUMOFTHEECHOHASSHARPVARIATIONSTHATREQUIRE CAREFUL PROCESSING TO PRESERVE4HE RECEIVER AND PROCESSOR MUST BE ABLE TO HANDLE BOTHTHEHIGH LEVELSIGNALDUETOTHISLARGE2#3ANDTHOSEMUCHSMALLERSIGNALSDUE TOTARGETS ESPECIALLYWHENTHELATTERAREADJACENTTOTHESTRONGESTCLUTTERCOMPONENTS !N(&RADARMUSTBEDESIGNEDTOACCOMMODATESUCHCLUTTERLEVELSEVENTHOUGH THEY WILLNOTEXISTALLTHETIME ORATANYONETIME OVERALLAREAS ESPECIALLYATTHELOWER OPERATINGFREQUENCIES %STIMATIONOF3EA3TATE 7AVE3PECTRA AND3URFACE7INDS 4ECHNIQUESFOR EXTRACTINGOCEANWAVEFIELDINFORMATIONFROMMEASUREDDOPPLERSPECTRAHAVEBEEN REPORTEDBYNUMEROUSAUTHORS WORKINGINALMOSTALLCASESFROMTHE"ARRICKSOLUTION FOR THE SCATTERED FIELD AND DEALING ALMOST EXCLUSIVELY WITH (& SURFACE WAVE RADAR DATA UNCORRUPTEDBYIONOSPHERICPROPAGATION)NVERSIONOFTHERELATIONIN%Q F TOOBTAINANESTIMATEOF3J ISMATHEMATICALLYNONTRIVIAL REQUIRINGSOMEADDITIONAL ASSUMPTIONSTOOBTAINAUNIQUE STABLESOLUTION3OMEOFTHESEMETHODSADDRESSTHE PROBLEM OF FULL DIRECTIONAL WAVE SPECTRUM ESTIMATION n WHEREAS OTHERS PROPOSE ESTIMATORSFORINTEGRATEDMEASURESOFSEAROUGHNESSSUCHASSIGNIFICANTWAVEHEIGHT
Óä°În
2!$!2(!.$"//+
/CEANCURRENTSCANBEDETERMINEDWHENAZERODOPPLERREFERENCESUCHASANISLAND IS IN THE RADAR FOOTPRINT 4HE ./!! 7AVEWATCH WEBSITE PROVIDES ACCESS TO ARCHIVEDMAPSOFSIGNIFICANTWAVEHEIGHT DOMINANTWAVEPERIOD ANDOTHERPARAM ETERSSUCHINFORMATIONISEXTREMELYHELPFULWHENDESIGNINGARADARFORREMOTESENS INGAPPLICATIONS )NADDITIONTOPROVIDINGINFORMATIONABOUTTHESEASURFACE (&RADARCANBEUSED TOINFERSURFACEWINDSPEEDANDDIRECTION 7INDDIRECTIONISCOMMONLYESTIMATED BYTAKINGTHERATIOOFTHEFIRST ORDERRESONANT"RAGGPEAKSANDEMPLOYINGANEMPIRICAL RELATIONSHIPBETWEENTHISRATIOANDTHEWINDDIRECTIONRELATIVETOTHERADARLOOKAXIS AS PIONEEREDBY,ONGAND4RIZNA"YSCANNINGOVERARADARSCOVERAGEAREA AMAPOF INFERREDWINDDIRECTIONCANBECONSTRUCTEDSURFACE WINDDIRECTIONMAPSAREAROUTINE BYPRODUCTOFTHE*INDALEERADAR 7HILE WAVEHEIGHT AND WAVE SPECTRUM ESTIMATES CAN IN PRINCIPLE BE EXTRACTED FROM HIGHER ORDER FEATURES OF SKYWAVE RADAR SEA ECHO SPECTRA A MAJOR DIFFICULTY ARISES DUE TO THE MYRIAD FORMS OF CONTAMINATION AND DISTORTION INTRODUCED BY THE IONOSPHERE4HISHASLEDTOTHEDEVELOPMENTOFNUMEROUSTECHNIQUESFORESTIMATING ANDREMOVINGTHEVARIOUSFORMSOFSIGNALCORRUPTIONn!SANALTERNATIVE 4RIZNA AND0ILONAND(EADRICKHAVEREPORTEDAMETHODFORESTIMATINGRnFROMSIMPLEMEA SUREMENTSMADEDIRECTLYONTHECORRUPTEDRADARECHOSPECTRUM7HILETHISAPPROACH MAYBERELATIVELYINSENSITIVETOSOMEFORMSOFCORRUPTION ITISNOTAPPLICABLETOSEAS FARFROMEQUILIBRIUM !LL THE METHODS FOR ESTIMATING SEA STATE OR SCATTERING COEFFICIENTS REQUIRE LONG COHERENTINTEGRATIONTIMES USUALLYCOMBINEDWITHNONCOHERENTAVERAGINGOFANUMBER OF#)4SINORDERTOACHIEVEADISTINCTANDSTABLESPECTRUM4HISTYPEOFRADAROPERATION WILLFREQUENTLYBEINCOMPATIBLEWITHOTHERRADARMISSIONS"UTBECAUSETHESEAECHO ISGENERALLYAVERYLARGESIGNAL ITMAYBEOBTAINEDWITHANADJUNCTOBLIQUESOUNDER OPERATINGINANAPPROPRIATERADARMODE 3CATTERING FROM -ETEOR 4RAILS AND /THER )RREGULARITIES IN THE )ONOSPHERE #LUTTER FROM IONOSPHERIC IRREGULARITIES SUCH AS THOSE MENTIONED IN 3ECTION CAN SEVERELY LIMIT RADAR PERFORMANCE 5NLIKE THE TERRESTRIAL OR OCEAN ENVIRONMENTSWHEREVELOCITIESOFNATURALSCATTERERSTENDTOBELOW THEIONOSPHEREIS HOMETOPHENOMENAWITHAPPARENTSPEEDSOFnMSnANDMORE OBSCURINGMUCH OFTHERELEVANTDOPPLERDOMAINWHEREMANMADETARGETSMIGHTBEFOUND-ANYOFTHESE SCATTERERSHAVEATRANSIENTEXISTENCE MUCHLESSTHANTHECOHERENTINTEGRATIONTIME SO CONVENTIONALSIGNALPROCESSINGCAUSESTHEIRECHOESTOAPPEARSPREADINDOPPLER ASWELL ASDOPPLERSHIFTED4HEGENERICTERMSPREAD DOPPLERCLUTTERISUSEDTOCOVERALLTHESE PHENOMENAWHERETHESCATTERERSRESPONSIBLEFORTHECLUTTERDONOTHAVEAWELL DEFINED DOPPLER SHIFT 4HE SAME TERM IS USED TO DESCRIBE THE ENTIRELY DIFFERENT MECHANISM WHERECLUTTERSMEARINGINDOPPLEROCCURSASACONSEQUENCEOFRAPIDVARIATIONSINTHE PROPAGATIONPATHRATHERTHANINTHEMOTIONOFTHESCATTERER -ETEORS AND THEIR TRAILS ARE THE MOST UBIQUITOUS SOURCE OF TRANSIENT ECHOESn 4HEYDISPLAYAREASONABLYWELL DEFINEDDIURNALANDGEOGRAPHICALDISTRIBUTIONSPECIFIC TOANYGIVENRADARSITE BUTTHEYCANCAUSEPROBLEMSOVERAWIDERANGEEXTENTBECAUSE THEYCANBEILLUMINATEDBYAVARIETYOFPROPAGATIONMODES ASSHOWNSCHEMATICALLYIN &IGURE.ORMALINCIDENCEASSHOWNYIELDSTHELARGESTECHO BUTOBLIQUEINCIDENCE ECHOESANDSCATTERINGFROMTHEMETEORhHEADvAREALSOOBSERVED&IGURECOMPARES ASIMPLEPREDICTIVEMODELWITHMEASUREMENTS CONFIRMINGTHATTHEOBSERVEDBEHAVIORIS UNDERSTOODANDTHUSCANBETAKENINTOACCOUNTINRADARDESIGNANDOPERATIONS
(&/6%2 4(% (/2):/.2!$!2
Óä°Î
&)'52% -ETEORTRAILSPECULARSCATTERINGGEOMETRYFORSEVERALPROPAGA TIONMODES
-ETEORSAREUSUALLYCLASSIFIEDASSPORADIC OCCURRINGMOREORLESSRANDOMLYASTHE %ARTHMOVESAROUNDTHESUN ANDSHOWERS SUCHASTHE,EONIDSANDTHE%TA!QUARIDS WHICH OCCUR ON PREDICTABLE DATES WHERE THEIR ORBITS INTERSECT THE %ARTHS ORBIT #%'#$&$ $&# &%%#$%#&% $
) %
#"& ) *
! (#
&)'52% 0REDICTEDRANGEDEPENDENCEOFMETEORECHOSTRENGTHCOMPAREDWITHMEASUREMENTSGROUND CLUTTERRETURNSAREALSOSHOWN4HEDISTRIBUTIONOFMETEORRADIANTSDETERMINESTHISVARIATION
Óä°{ä
2!$!2(!.$"//+
/NTHESEOCCASIONS THEFLUXOFMETEORSCANBESOHIGHTHATTHEYCANCAUSESERIOUS OBSCURATIONOFTARGETECHOES!SRADARSBECOMEMORESENSITIVE THEYREGISTERSMALLER ANDSMALLERMETEORS WHICHAREFARMOREABUNDANT SOATTIMES THEFLUXOFCOUNTLESS SMALLMETEORTRAILSSETSTHEEFFECTIVEDETECTIONTHRESHOLD -ETEORECHOSUPPRESSIONCANBEATTEMPTEDINTHESPATIALDOMAINIFTHERECEIVING ARRAYHASVERTICALDIRECTIVITY BUTFORMOSTRADARS THEONLYOPTIONISREJECTIONBYSIGNAL PROCESSING EXPLOITINGTHETRANSIENTNATUREOFTHEECHOESTODETECTANDCENSORTHEMIN THETIMEDOMAIN %CHOESFROMTHEAURORAESIMILARLYINVOLVETRANSIENTSCATTERINGPROCESSESTHATAPPEAR INTHERADARDATAASHIGHLYDOPPLER SPREADECHOESWITHTHEPOTENTIALTOOBSCURETARGETS 3CATTERINGFROMTHEAURORALREGIONHASBEENSTUDIEDEXTENSIVELYUSINGTHE3UPER$!2. (&RADARNETWORKINITIATEDBY'REENWALD ANDANAURORALECHO SCATTERINGMODELHAS BEENDEVELOPEDBY%LKINSTHISCANBEUSEDTOPREDICTTARGETOBSCURATIONWHENTHE TRANSMISSIONPATHISTHROUGHTHEAURORALREGION0ROVIDEDTHERADARISWELLREMOVED FROMTHEAURORALZONE THEWAVEFORMCANOFTENBECHOSENSOASTOMANIPULATETHECLUT TER ECHOES WITHIN RANGE DOPPLER SPACE UNMASKING TARGETS HITHERTO OBSCURED /FTEN SEVERALWAVEFORMSWITHDIFFERENTREPETITIONFREQUENCIESAREINTERLEAVEDTOACHIEVETHIS &ORRADARSCLOSETOTHEAURORALZONE THEOPTIONSAREGENERALLYMORELIMITED )ONOSPHERICIRREGULARITIESTHATSCATTERBACKTOTHERADARRECEIVEROCCURMUCHMOREOFTEN ATNIGHTTHANBYDAYATANYLATITUDE3ENSIBLESITINGOFTHERADAR ENSURINGGOODFRONT TO BACKRATIOSONTHEANTENNAS EMPLOYINGVERTICALNULLINGIFAVAILABLE ANDUSINGADAPTIVE SIGNALPROCESSINGTECHNIQUESORATLEASTMAINTAININGLOWRECEIVEARRAYSIDELOBES AREALL EFFECTIVETOOLSFORMITIGATINGAURORAL METEOR ANDOTHERIONOSPHERICCLUTTER
Óä°Ê "- ]Ê / , ,
]ÊÊ Ê-* /,1 Ê"
1* 9 )NTHE(&BAND THEAVERAGENOISEPOWERSPECTRALDENSITYATMID BAND NEAR-(Z SAY MAYEXCEEDnD"7(ZANDWILLGENERALLYEXCEEDnD"7(Z COMPARED WITHTYPICALRECEIVERINTERNALNOISESPECTRALDENSITIESOFPERHAPSnD"7(Z4HUS UNLIKETHEMICROWAVERADARCASE EXTERNALNOISEISALMOSTALWAYSDOMINANT4HISHAS FUNDAMENTALIMPLICATIONSFORRECEIVINGSYSTEMDESIGNANDSIGNALPROCESSING!NOTHER CRITICALISSUEISTHEOBSERVEDSYSTEMATICVARIATIONOFTHEEXTERNALNOISELEVEL WHICHHAS ADIRECTIMPACTONRADARPERFORMANCE 4HEMAJORSOURCEOFQUASI CONTINUUMBACKGROUNDNOISEATTHELOWERFREQUENCIES ISLIGHTNINGDISCHARGESIONOSPHERICALLYPROPAGATEDFROMALLOVERTHEWORLDSFERICS !TTHEHIGH ENDOFTHEBAND EXTRATERRESTRIALORGALACTICNOISEMAYBEGREATERTHANTHAT DUETOSFERICS2ECEIVESITESINANAREAOFEXTENSIVEELECTRICALEQUIPMENTUSECANFIND ANTHROPOGENICNOISEDOMINANT"UTMOSTIMPORTANTLY THE(&BANDISDENSELYOCCUPIED BY OTHER USERS ESPECIALLY POWERFUL (& BROADCASTERS RELYING ON THE PREVAILING FRE QUENCYWINDOWFORSATISFACTORYPROPAGATION%VENOUT OF BANDSIGNALLEVELSAREACON SIDERATIONINRECEIVERFRONT ENDDESIGN WHEREITISCOMMONTOHAVEBANDWIDTHSMUCH WIDERTHANTHATOFTHERADARSIGNAL4HEREAREALARGENUMBEROFBROADCASTSTATIONSTHAT HAVE K7TRANSMITTERSANDANTENNASWITHMORETHAN D"GAIN-EASUREMENTS MADEONTHEMIDDLE!TLANTICCOASTOFTHE5NITED3TATESSHOW(&BROADCAST BANDSIG NALSWITHSTRENGTHSOFTOM6M4HESEAMBIENTLEVELSMUSTBEACCOMMODATED INRECEIVERDESIGNBECAUSEAWIDEBANDFRONTENDISDESIRABLEFORRAPIDANDFREQUENT FREQUENCYCHANGES
(&/6%2 4(% (/2):/.2!$!2
Óä°{£
4HEPRACTICEINALLOCATIONSFOR(&RADAROPERATIONISTOPERMITUSEOFBROADBANDS OFTHESPECTRUMWITHAREQUIREMENTTOCAUSENODISCERNIBLEINTERFERENCETOANEXISTING SERVICEANDTOPROVIDEALOCKOUTFEATUREFORCHANNELSTHATNEEDPROTECTION4HUS AN INTEGRALPARTOFAN(&RADARISACHANNELOCCUPANCYANALYZERTHATPROVIDESAREAL TIME DESCRIPTIONOFSPECTRUMAVAILABILITY ASILLUSTRATEDIN&IGURESAND
&)'52% !SNAPSHOTOFTHE(&SPECTRUMATNOONINSUMMERANDATALOWSUNSPOTNUMBER ZOOM INGINPROGRESSIVELYTOSHOWASECTIONOFTHESPECTRUMWHEREAK(ZCLEARCHANNELISEVIDENT CENTERED ON-(Z4HEDATAWASRECORDEDATLATITUDE3 LONGITUDE%
Óä°{Ó
2!$!2(!.$"//+
!LMOSTWITHOUTEXCEPTION (&RADARSHAVEOPERATEDONTHISPRINCIPLEOFNONINTER FERENCE MAKINGDOWITHhCLEARvCHANNELSBETWEENOTHERUSERS 0ATTERNSIN3PECTRUM/CCUPANCY 7HENTHE(&BANDISSCANNEDWITHASPEC TRUMANALYZER ITCANBESEENTHATTHEGROSSFEATURESOFOCCUPANCYATANYPARTICULARHOUR AREREMARKABLYSTATIONARYOVERTHEDAYSOFASEASON4HISISDUETOBROADCASTSTATIONS FIXED SERVICEPOINT TO POINTTRANSMITTERS ANDMANYOTHERSPECTRUMUSERSHAVINGREGULAR SCHEDULES ASISEVIDENTFROM&IGURE WHICHPLOTSTHEPOWERSPECTRALDENSITYAT K(ZRESOLUTIONFORHIGHANDLOWSOLARACTIVITY SUMMERANDWINTER DAYANDNIGHT
&)'52% (&ACTIVITYOVERTHEn-(ZFORLOWANDHIGHSUNSPOTNUMBERSL H SUMMERAND WINTERS W ANDDAYANDNIGHTD N ASMEASUREDATLATITUDE3 LONGITUDE%4HEDATAIS TAKENFROM*ULIANDAYSANDOFAND
(&/6%2 4(% (/2):/.2!$!2
Óä°{Î
!SREMARKEDEARLIER THEMAXIMUMFREQUENCYTHATWILLREFLECTENERGYBACKTOTHE %ARTHDURINGTHEDAYMAYBEMORETHANTWICETHATATNIGHTTHEREFORE THEOCCUPANCY TENDSTOBEDENSERATNIGHTTHANDURINGTHEDAYAPROBLEMCOMPOUNDEDBYTHELOWER ABSORPTIONAND HENCE RECEPTIONOFMOREDISTANTSIGNALS ,OOKEDATOVERLONGERTIMESCALES VARIOUSPATTERNSANDTRENDSEMERGE-OSTOBVI OUSLY THE YEARSOLARCYCLEFORCESCHANGESTOSPECTRUMUSAGEANDTHEDENSITYOFUSERS WITHARESULTANTIMPACTON(&RADARCHANNELSELECTION!NOTHERTRENDTHATHASBECOME APPARENTINRECENTYEARSISTHEGRADUALREDUCTIONIN(&USERSASSERVICESMOVETOSATEL LITECOMMUNICATIONS MICROWAVELINKS FIBEROPTICS ANDOTHERMEDIA.EVERTHELESS THE INCREASEDNUMBEROF(&RADARSHASLEDTOANEWCHALLENGEINTER RADARINTERFERENCEAND THENEEDFORFREQUENCYARBITRATION .OISE-ODELS 4HEWIDELYUSEDREFERENCEONNOISEISTHE)NTERNATIONAL2ADIO #ONSULTATIVE #OMMITTEE ##)2 2EPORT 4HIS REPORT IS BASED UPON MEA SUREMENTS MADE AT LOCATIONS THROUGHOUT THE WORLD 4HE MEASUREMENT AND DATA ANALYSISWEREPERFORMEDTOEXCLUDEINDIVIDUALCOLLECTIONSITELOCALTHUNDERSTORMCON TRIBUTIONS3PAULDINGAND7ASHBURNADDEDDATAFROMTHEFORMER5332FORTWO REVISED##)2REPORTS.OISE LEVELMEDIANSASAFUNCTIONOFFREQUENCYAREGIVENIN THEFORMOFWORLDWIDEMAPSBYSEASONAND HTIMEBLOCKS,UCASAND(ARPERHAVE PROVIDEDANUMERICALREPRESENTATIONOF##)22EPORT WHICHISUSEFULFORCOM PUTERCOMPUTATIONS ANDTHISHASBEENREVISEDBYADDINGTHEWORKOF3PAULDINGAND 7ASHBURN4HEMAPSOFMEDIANVALUESAREACCOMPANIEDBYDECILEVALUESTOINDICATE DISTRIBUTIONSOVERDAYSOFTHESEASON##)22EPORT HASASIGNIFICANT DISCREPANCY ASPOINTEDOUTBY3AILORS SOITSHOULDBEUSEDWITHCAUTION 4HESE NOISEMAPSPROVIDETHELEVELTHATANOMNIDIRECTIONALANTENNAWOULDRECEIVE%VEN THOUGHASSUMINGISOTROPIC##)2NOISEHASLIMITATIONS ITDOESPROVIDEAREFERENCE LEVELFORINITIALRADARDESIGN!NUMBEROFOPERATIONALANDEXPERIMENTAL(&SYSTEMS HAVEACCUMULATEDTHEIROWNNOISEDATABASESANDCOMPAREDTHEMWITH##)2MODEL DATATHEREPORTOF.ORTHEYAND7HITHAMGIVESADETAILEDANALYSIS !N(&RADARISGENERALLYDESIGNEDTOTAKEADVANTAGEOFWHATTHEENVIRONMENTPER MITSTHATIS THERECEIVERNOISEFIGURESHOULDBEGOODENOUGHTOMAKEENVIRONMENTAL NOISETHELIMITATION !N EXAMPLE OF THE ##)2 2EPORT DATA WILL NOW BE DISCUSSED &IGURE WASDRAWNFROM,UCASAND(ARPER.OISEPOWERINA (ZBANDRELATIVETO7 D"7 ISGIVENASAFUNCTIONOFFREQUENCYFORTHREEDIFFERENTSOURCESOFNOISEGALACTIC ATMOSPHERIC ANDANTHROPOGENIC4HEPRACTICEINUSEISTOSELECTTHELARGEST4HISISA WINTERDAYTIMEEXAMPLEATA5NITED3TATESEASTCOASTLOCATION4HETHREESTRAIGHTLINES AREESTIMATESOFANTHROPOGENICNOISEFORTHREEDIFFERENTTYPESOFSITES4HESHAPEOFTHE ANTHROPOGENICCURVESISDESCRIBEDBYTHEEQUATIONS
.O nnLNF RESIDENTIAL .O nnLNF RURAL .O nnLNF REMOTE
WHERETHEFREQUENCYFISINMEGAHERTZANDLNINDICATESTHENATURALLOGARITHM 4HESE FREQUENCY TRENDS APPROXIMATE MANY MEASUREMENTS OF HUMAN MADE NOISE BUTIDEALLYTHECURVEWOULDBEBASEDONMEASUREMENTSATTHEPARTICULARRADARSITE4HE GALACTIC NOISECURVESHOULDBESELECTEDWHENITISTHELARGESTANDWHENTHEREISAPATH THROUGHTHEIONOSPHERETHEPATHWILLNOTEXISTFORTHELOWEROPERATINGFREQUENCIESIN THEDAYTIME4HEATMOSPHERICNOISERISESFROMLOWFREQUENCIESTOABOUT-(ZAND
Óä°{{
2!$!2(!.$"//+
&)'52% .OISEPOWERPERHERTZISGIVENFORgNORTHLATITUDEANDgWESTLONGITUDEINWINTER A 54#ISGIVENASADAYTIMEEXAMPLEANDB 54#ISGIVENASANIGHTTIMEEXAMPLE
THENRAPIDLYFALLS&IGUREBISFORNIGHTTIME!LLTHECURVESARETHESAMEASIN &IGUREAEXCEPTFORATMOSPHERICNOISE!T-(Z THENIGHTANDDAYLEVELSARE THESAMEBELOW-(Z THENOISEDECREASESWITHDECREASINGFREQUENCYINDAYTIME ANDINCREASESATNIGHT!BOVE-(Z DAYTIMELEVELSAREGREATERTHANTHOSEATNIGHT 4HESE EFFECTS CAN BE PARTIALLY EXPLAINED BY THE VERY LOSSY LONG RANGE PATHS IN DAY THATATTENUATETHELONG RANGENOISEATTHELOWERFREQUENCIESANDBYTHEREBEINGFEW ORNOSKYWAVEPATHSTONOISETERRESTRIALSOURCESATTHEHIGHERFREQUENCIESATNIGHT)N GENERAL NIGHTTIMENOISEWILLBEGREATERTHANDAYTIMENOISEFORSKYWAVEILLUMINATION OFASELECTEDRANGE4HISISEVIDENTIN&IGURE RECORDEDATTIMEZONE54 4HEGENERALTRENDSOFATMOSPHERICNOISEINOTHERSEASONSARESIMILARTOTHOSEINWINTER (OWEVER THERECANBELARGEDIFFERENCESINLEVELSATOTHERLOCATIONSONTHE%ARTH &ORMOREDETAILEDANALYSISANDSYSTEMOPTIMIZATION ITISNOLONGERACCEPTABLETO TREATTHENOISEASANISOTROPICFIELD3TRONGAZIMUTH ANDELEVATION ANGLEDEPENDENCE OFTHESFERICSFIELDISINEVITABLEEXAMINATIONOFMAPSPRODUCEDBYSATELLITES INDI CATESTHATTROPICALRAINFORESTSANDOTHERREGIONSOFCONCENTRATEDTHUNDERSTORMACTIVITY AREMAJORSOURCESOFNOISE ANDTHESEREGIONSARECONNECTEDWITHAGIVENRADARSITE BY THE CONSTRAINTS OF SKYWAVE PROPAGATION #OLEMAN COMBINED THE THUNDERSTORM ACTIVITYMAPSOF+OTAKIWITHNUMERICALRAY TRACINGANDMODELEDANTENNAPATTERNS TODEMONSTRATETHATTHEDIRECTIONALVARIABILITYOFNOISE COUPLEDWITHTHEDIRECTIONAL CHARACTERISTICSOFDIFFERENTANTENNAS CANLEADTOMARKEDCHANGESINNOISEOUTCOMES ANDHENCEINOPTIMALRADARDESIGN !NOTHERIMPORTANTISSUEISTHEBEHAVIOROFTHEEXTERNALNOISEFIELDASAFUNCTIONOF TIME THATIS WITHINTHECOHERENTINTEGRATIONINTERVALSINCETHISIMPACTSSTRONGLYON SIGNALPROCESSINGFORINTERFERENCEREJECTION/THEREFFECTSTHATCANINFLUENCERADAR PERFORMANCEARESOMETIMESMISTAKENFORTHEADDITIVENOISEDISCUSSEDABOVE/NEOF
(&/6%2 4(% (/2):/.2!$!2
Óä°{x
&REQUENCY-(Z
4IMEOFDAY54
&)'52% $IURNAL VARIATION OF (& NOISE MEASURED IN D"7(Z AT LATITUDE 3 LONGITUDE % .OVEMBER
THESEISTHESPREADDOPPLERCLUTTERDISCUSSEDIN3ECTION SOMETIMESREFERREDTOAS ACTIVEORMULTIPLICATIVENOISE4HEOCCURRENCEOFTHISTYPEOFCLUTTERISGREATERATNIGHT ANDISMUCHMOREPREVALENTINTHEAURORALZONESANDAROUNDTHEMAGNETICEQUATOR
Óä°£äÊ / Ê,
6 Ê-9-/ 4HERECEIVINGSYSTEMISDEFINEDHERETOEMBRACEONLYTHERECEIVINGANTENNAARRAYAND THERECEIVERSTHATCONVERTTHEANTENNAOUTPUTSTODISCRETETIMESERIES USUALLYATBASE BAND &OR EASE OF REFERENCE THE CONVENTIONAL SIGNAL PROCESSING STAGES RESPONSIBLE FORTRANSFORMINGTHERECEIVEROUTPUTSINTOSTANDARDRADARPRODUCTSAREDISCUSSEDIN 3ECTION TOGETHERWITHMORESPECIALIZEDTECHNIQUES !NTENNAS &ROMTHERECEPTIONVIEWPOINT ITISDESIRABLETOHAVEFINEAZIMUTHAL RESOLUTIONFORSEVERALREASONS INCLUDINGI TOIMPROVETARGETLOCATIONACCURACYAND TRACKINGPERFORMANCE II FORDETAILEDCLUTTERMAPPING ANDIII TOREDUCETHECLUTTER AMPLITUDELEVELSTOVALUESPERMITTEDBYSYSTEMDYNAMICRANGEANDSLOW TARGETDETEC TION REQUIREMENTS!S MENTIONED EARLIER MOST (& SKYWAVE RADARS EMPLOY A BROAD TRANSMITBEAMTOILLUMINATEAZONEOFINTEREST ANDTHENPROCESSTHEECHOESVIAANUM BEROFMUCHHIGHERRESOLUTIONSIMULTANEOUShFINGERvBEAMS)TISWELLKNOWNTHATTHE CLASSICALRESOLUTIONOFANARRAYIMPROVESLINEARLYWITHAPERTUREUPTOSOMELIMITING VALUEDETERMINEDBYTHEENVIRONMENT(ORIZONTALAPERTURESOFnKMANDEVENGREATER
Óä°{È
2!$!2(!.$"//+
HAVEBEENSHOWNTOSUPPORTSPATIALLYCOHERENTPROCESSING (ENCE THERECEIVING ARRAYAPERTURESOFSKYWAVERADARSMAYRANGEFROM^KMFORSYSTEMSCONCERNED ONLYWITHAIRCRAFTANDBALLISTICMISSILESTOMORETHANKMINSYSTEMSDESIGNEDFORSHIP DETECTIONANDTRACKING4AKINGKMASARECEIVEAPERTURE CONVENTIONALBEAMWIDTH AT-(ZIS^ SOSIMULTANEOUSBEAMSSPAN^ WHICHSETSTHEREQUIRED TRANSMITAPERTUREINTHISEXAMPLEATnM DEPENDINGONTHEVARIATIONINGAIN THATCANBETOLERATEDACROSSTHESETOFRECEIVEBEAMS4HEMOSTVERSATILEBEAMFORM INGTECHNIQUESRELYONHAVINGARECEIVERFOREACHARRAYELEMENT BUTASTHENUMBEROF ELEMENTSMAYAPPROACH THECOSTOFSUCHASOLUTIONMAYBEPROHIBITIVE)TISTHEN ADVANTAGEOUSTOCONFIGURETHEARRAYELEMENTSINTOSUBARRAYS POSSIBLYOVERLAPPEDOR SHARINGELEMENTS WITHONERECEIVERPERSUBARRAY&ORINSTANCE THEORIGINAL*INDALEE RADARGROUPEDELEMENTSSPANNINGKMINTOOVERLAPPEDSUBARRAYS7HILE THISCONSTRAINSTHERESULTANTBEAMSTOLIEWITHINTHESUBARRAYANGULARRESPONSEPATTERN ITHASTHEADVANTAGEOFREDUCINGRECEIVERDYNAMICRANGEREQUIREMENTSBYSUPPRESSING INTERFERENCEFROMOTHERANGULARSECTORS ,INEARARRAYSPROVIDETHEMOSTECONOMICALROUTETOHIGHSPATIALRESOLUTIONINAZI MUTH BUTTHEEXISTENCEOFMULTIPLEPATHSFORSIGNALRECEPTION TYPICALLYVIATHE% & AND&LAYERS HASMOTIVATEDSOMEDESIGNERSTOEMPLOYTWO DIMENSIONALARRAYS HORI ZONTALLYOR ATGREATERCOST VERTICALLYDEPLOYED4HERELATIVEMERITSOFTHESEDESIGNS CANBEMEASUREDONLYWITHRESPECTTOTHEPRIORITIESACCORDEDTOTHEVARIOUSMISSIONS ASSIGNEDTOAGIVENRADAR 4HECHOICEOFRECEIVINGANTENNAELEMENTHASTRADITIONALLYBEENBASEDONTHEPRECEPT THAT AT(& THEEXTERNALNOISEALMOSTALWAYSEXCEEDSTHEINTERNALNOISEBYASUBSTANTIAL MARGIN/NTHISLOGIC IMPROVINGANTENNAEFFICIENCYINCREASESTHEOUTPUTEXTERNALNOISE ANDINTERFERENCEAMPLITUDEATTHESAMERATETHATITIMPROVESTHEWANTEDSIGNALS THEREBY GAININGNOADVANTAGEIN3.23ELECTIONOFANTENNAELEMENTTYPE SUCHASMONOPOLES DIPOLES "EVERAGEANTENNAS PHASEDENDFIREROWSOFMONOPOLES ORBICONICALANTEN NAS FORINSTANCE CANTHENBEBASEDONFREQUENCYRESPONSEOVERTHEANTICIPATEDBAND OFINTERESTANDSUITABILITYFORTHECHOSENARRAYGEOMETRY ASWELLASTERRAINCONSTRAINTS SUCH AS THE SOIL CONDUCTIVITY 3TUDIES HAVE SHOWN THAT THIS ARGUMENT IS NOT NECES SARILYVALIDWHENADVANCEDADAPTIVESPATIALANDTEMPORALPROCESSINGTECHNIQUESARE EMPLOYEDBECAUSEINTERFERENCEREJECTIONEFFICACYISENHANCEDBYHIGHERINTERFERENCE TO INTERNALNOISERATIOS )THASBEENWIDELYARGUEDTHATTHEINEVITABILITYOFTIME VARYINGPOLARIZATIONTRANS FORMATIONINTHECOURSEOFIONOSPHERICPROPAGATIONGREATLYREDUCESTHEPOSSIBLEUTILITY OFBEINGABLETOMEASURETHEPOLARIZATIONSTATEOFTHESIGNALSARRIVINGATTHERECEIVING ARRAY4HISISANOPENQUESTIONATTHISTIME THOUGHEXPERIMENTSAIMEDATASSESSING SKYWAVERADARPOLARIMETRYAREUNDERWAY 2ECEIVERS 4HEREAREMANYDEMANDSONTHERECEIVERSFOR/4(RADAR INCLUDING HIGH DYNAMIC RANGE LINEARITY WIDE BANDWIDTH AND UNIFORMITY BETWEEN RECEIVERS WHEN USED IN MULTIRECEIVER SYSTEMS &OR MOST CIVIL AIRCRAFT AND SHIPS TARGET RADAR CROSSSECTION2#3 AT(&ISROUGHLYOFTHESAMEORDERASTHEMICROWAVE2#3 THATIS ^nD"SMFORAIRCRAFTAND^nD"SMFORSHIPS BUTTHERANGEISnTIMES GREATER SOTHEEXTRALOSSASSOCIATEDWITH2nISINTHERANGEnD"-OREOVER EACH TARGET ECHO IS IMMERSED IN CLUTTER FROM THE ILLUMINATED FOOTPRINT WHICH MAY HAVE ANAREAOFMANYTHOUSANDSOFSQUAREKILOMETERS&URTHER THE(&SIGNALENVIRONMENT INCLUDESONE WAY TRANSMISSIONSFROMPOWERFULRADIOSTATIONSAROUNDTHEWORLD AS DISCUSSEDINTHEPREVIOUSSECTION)MPERFECTIONSINTHERECEIVERRESULTINSOMEOFTHIS
(&/6%2 4(% (/2):/.2!$!2
Óä°{Ç
NOISEANDCLUTTERENERGYBEINGSUPERIMPOSEDONTHEWANTEDRADARECHOES EITHERADDI TIVELYORMULTIPLICATIVELY(ENCE CAREFULATTENTIONTORECEIVERDESIGNISIMPERATIVEIF THERADARDESIGNERWISHESTOAVOIDSELF INFLICTEDPERFORMANCELIMITATIONS !TTEMPTSTOREDUCECONTAMINATIONFROMEXTERNALBROADCASTSIGNALSBYINSERTINGNAR ROW BANDFILTERSATTHERECEIVERFRONT ENDSACRIFICETHEHIGHAGILITYTHATISNEEDEDWHEN THERADARISCHANGINGFREQUENCY TYPICALLYBYSEVERAL-(Z SECONDBYSECOND ASIT JUMPSBETWEENTASKS4HEREAREALSOPENALTIESFROMI FILTERSWITCHINGTIME II SET TLINGTIME III DISTORTIONCAUSEDBYGROUPDELAYDISPERSION ANDIV REDUCEDRELIABILITY WHENTHEREAREHUNDREDSOFRECEIVERS&URTHER EACHCHANNELWILLNEEDTOACCOUNTFOR THEGAINANDPHASEVARIATIONFOREACHFILTER INCREASINGTHEOVERHEADSONBANDSWITCH ING)TISBETTERTOZEROINONTHEBANDWIDTHOFINTERESTBYNONSWITCHEDFILTERSLATERINTHE RECEIVER USINGAVARIABLEFREQUENCYLOCALOSCILLATORTOPOSITIONTHEDESIREDSUBBANDS OVERTHESELECTIVEFILTERS/FCOURSETHESWITCHED,/CANALSOSUFFERFROMIMPERFEC TIONS BUT ONLY ONE LOCAL OSCILLATOR IS NEEDED AS OPPOSED TO HUNDREDS OF RECEIVERS 7HICHEVERDESIGNPATHISFOLLOWED THEDEMANDSONRECEIVERLINEARITYANDSPURIOUS FREEDYNAMICRANGEAREEXTREME 4HERE ARE FIVE DOMINANT MECHANISMS KNOWN TO DEGRADE (& RADAR RECEIVERS THE NONLINEAR PROCESSES OF ANALOG TO DIGITAL CONVERSION OUT OF BAND INTER MODULATION )-$ CROSS MODULATION AND IN BAND INTER MODULATION AND THE PSEUDO LINEAR PRO CESSOFRECIPROCALMIXING !NALOG TO DIGITAL#ONVERSION !NALOG TO DIGITALCONVERSIONINVOLVESTWOSTAGES SAMPLINGANDQUANTIZATIONEACHWITHPOTENTIALFORDISTORTINGTHERECEIVEDSIGNAL 4HERECEIVEDSIGNALSMUSTBESAMPLEDWITHSUFFICIENTPRECISIONANDUNIFORMITYTO PRESERVETHEINHERENTSPECTRALCONTENTACROSSTHEDYNAMICRANGESPANNEDBYTHESIG NALCOMPONENTSTARGETECHOES CLUTTER ANDEXTERNALNOISEAFTERTAKINGACCOUNTOF THEARTIFACTSINTRODUCEDBYQUANTIZATIONANDTIMINGJITTER ESPECIALLYINMULTI RECEIVER SYSTEMS /UT OF BAND)NTER MODULATION /UT OF BAND)-$ARISESFROMNONLINEARMIXING OF TWO OR MORE STRONG INTERFERERS SUCH AS BROADCAST STATIONS WHERE THE POWERFUL SIGNALSENTERTHEFRONTENDOFTHERECEIVINGSYSTEMANDGENERATE)-$PRODUCTSWITHIN THERADARSIGNALBANDWIDTHBEFORETHEY THEORIGINALINTERFERERS AREREJECTEDBYSELEC TIVEFILTERING #ROSS MODULATION #ROSS MODULATION INVOLVES NONLINEAR MIXING OF A STRONG INTERFERERWITHTHERECEIVEDRADARECHOES TRANSFERRINGTHEINTERFERERMODULATIONONTO THERADARSIGNAL )N BAND)NTER MODULATION !SINGLERESOLUTIONCELLINTHERADARFOOTPRINTMAY HAVE AN AREA OF n SQUARE KILOMETERS AND THERE MAY BE HUNDREDS OF CELLS INTHERADARFOOTPRINT SOUSINGREPRESENTATIVEVALUESOFTARGET2#3&IGURE AND SURFACE SCATTERING COEFFICIENT Sn &IGURE THE SIGNAL TO CLUTTER RATIO IN AN/4(RADARRECEIVERMAYBEASLOWASnD"FORSYSTEMSEMPLOYING&- #7 WAVEFORMS .ONLINEARITY AT ANY STAGE HAS THE POTENTIAL TO MASK TARGET ECHOES BY MIXING THE CLUTTER ECHO WITHITSELF GENERATING)-$PRODUCTSTHATEXTENDBEYOND THEINTRINSICDOPPLERBANDOFTHECLUTTER5NLIKETHEOUT OF BAND)-$ IN BAND)-$ CANOCCURATANYSTAGETHROUGHTHERECEIVER ANDHENCEEVENSECOND ORDERPRODUCTS MAYCAUSEPROBLEMS
Óä°{n
2!$!2(!.$"//+
2ECIPROCAL -IXING !NALOG RECEIVERS OF HETERODYNE DESIGN GENERALLY INVOLVE A NUMBEROFLOCALOSCILLATORSFORSIGNALMIXINGANDPERHAPSAWAVEFORMGENERATORUSED TOIMPLEMENTAMATCHEDFILTER4HESEANCILLARYSOURCESAREINEVITABLYOFFINITESPECTRAL PURITY WITHAPHASENOISEFLOORTHATMAYEXTENDOVERAWIDEBANDOFFREQUENCIES ALBEIT ATAVERYLOWLEVEL!NYPOWERFULINTERFERINGSIGNALSENTERINGTHEFIRSTMIXERSTAGEOF THERECEIVERWILLCOMBINEWITHTHEPHASENOISEFLOORANDPOTENTIALLYGENERATEPRODUCTS INTHERADARSIGNALBANDWIDTH )NTHECASEOFDIGITALRECEIVERS SAMPLINGNOISEWILL HAVEANEQUIVALENTEFFECT $IGITAL2ECEIVER4ECHNOLOGY (&RECEIVERSCANEMPLOYDIRECTDIGITALCONVER SIONAT2& AVOIDINGSOMEOFTHELIMITATIONSOFANALOGDEVICES)SSUESSUCHASRECIP ROCALMIXINGARESTILLPRESENT THOUGHINSLIGHTLYMODIFIEDFORM#OMPARISONSWITH ANALOGRECEIVERSHAVEDEMONSTRATEDTHATLITTLEORNOPENALTYISINCURREDWITHSUCH DESIGNSIFABANDPRESELECTORFILTERISINSTALLEDATTHEFRONT END/NTHEOTHERHAND THERE ARE MAJOR ADVANTAGES TO BE HAD SUCH AS SIMULTANEOUS RECEPTION OF SEVERAL RADARSIGNALSONDIFFERENTFREQUENCIES SOASINGLERECEIVERCANSERVICEMORETHAN ONERADARTRANSMITTER #ALIBRATION 4HECONVENTIONALBEAMFORMINGPROCESSINANIDEALMULTI CHANNEL RECEIVINGSYSTEMSHOULDDELIVERASINGLEOUTPUT ASSIGNEDTOTHECORRECTDIRECTION FORA PLANEWAVEINCIDENTONTHEANTENNAARRAY)NEVITABLEVARIATIONSINGAINANDPHASEARIS INGFROMSMALLANTENNAPOSITIONINGERRORS GROUNDSCREENINHOMOGENEITIES DIFFERENCES BETWEENPREAMPLIFIERS MUTUALCOUPLING CABLEMISMATCH THERMALANDOTHERVARIATIONS OFCABLECHARACTERISTICS ANDALLTHEANALOGSTAGESOFTHERECEIVERRESULTINDISTORTIONOF THEBEAMSHAPEANDHENCEDEGRADEDRADARRESOLUTION ELEVATEDSIDELOBESANDHENCE VULNERABILITYTOCLUTTERANDINTERFERENCE POINTINGERRORSANDHENCEINCREASEDTRACKING ERRORS ANDINTERFERERWAVEFRONTGEOMETRYPERTURBATIONSANDHENCEWASTEDDEGREESOF FREEDOMINADAPTIVEBEAMFORMING 4OMITIGATETHESEEFFECTS (&RADARSMUSTEMPLOYSOPHISTICATEDCALIBRATIONSCHEMES 3EVERALAPPROACHESHAVEBEENTRIED u5SE OF AN EXTERNAL RADIATING ELEMENT IN THE NEAR FIELD IN FRONT OF THE ARRAY 4HIS SCHEMEISVULNERABLETOVARIATIONSINTHESOILELECTRICALANDMAGNETICPROPERTIES SUCH ASTHOSERESULTINGFROMSEASONALCHANGESINSOILMOISTURELEVELS u)NJECTIONOFACALIBRATIONWAVEFORMATTHEANTENNAS ORATTHERECEIVERINPUTSBEHIND THEANTENNAARRAY BYMEANSOFANINDEPENDENThOPENLOOPvSIGNALFEEDERNETWORK 4HISSCHEMECANNOTCALIBRATETHEANTENNASANDINITIALFEEDERSITAPPLIESONLYFROM THEPOINTWHERETHESIGNALISINJECTED u5SEOFADISTANTRADIATINGSOURCETHATILLUMINATESTHEARRAYVIASKYWAVEOREVEN ADISCRETETARGETECHO4HISSCHEMEPRESUMESTHATTHEARRIVINGSIGNALWAVEFRONTS AREESSENTIALLYPLANARORSMOOTHAFTERIONOSPHERICREFLECTION WHICHISNOTALWAYS THECASE u*OINTANALYSISOFMULTIPLEDISCRETEMETEORECHOES 4HISSCHEMEISAPPEALINGBUT RELIESONHAVINGENOUGHIDENTIFIABLEDISCRETEECHOES&ORA ELEMENTARRAYITMAY BEGENERALLYVIABLE BUTLESSFREQUENTLYFORA ELEMENTARRAY u2ECEIVERANDPLANEWAVEREJECTIONTESTSAPPLIEDTOINJECTEDBROADBANDNOISE 4HISAPPROACHPROVIDESUSEFULMETRICSOFCALIBRATIONPERFORMANCEANDRELATIVE PERFORMANCE BUT DOES SO ONLY DOWNSTREAM FROM THE RECEIVER INPUTS AS WITH II ABOVE
(&/6%2 4(% (/2):/.2!$!2
Óä°{
%ACHOFTHESEAPPROACHESHASITSADVANTAGESANDDRAWBACKSINTHECONTEXTOFCON VENTIONAL &OURIER BEAMFORMING 7HEN ADAPTIVE PROCESSING TECHNIQUES ARE BEING EMPLOYED ITISALSOIMPORTANTTHATTHEEFFECTIVELOOKDIRECTIONMATCHESTHEARRAYSTEER INGVECTORORELSECANCELLATIONOFTHEWANTEDSIGNALWILLOCCUR
Óä°££Ê - Ê*,"
-- Ê Ê/, 3IGNAL!NALYSISAND4ARGET$ETECTION 4HEOBJECTIVEOFSIGNALPROCESSINGISTO DETECTANDCHARACTERIZEECHOESFROMSCATTERERSOFINTEREST EITHERDISCRETEAIRCRAFTOR SHIPS OREXTENDEDTHESEASURFACE ANDTHISISCUSTOMARILYACHIEVEDBYDECOMPOS INGTHETIMESERIESDATAFROMTHERECEIVERSINTOTHENATURALRADARDOMAINDIMENSIONS OFGROUPRANGEBASEDONTIMEDELAY DIRECTIONOFARRIVALBEAMSPACE ANDDOPPLER FREQUENCY HOPEFULLYSEPARATINGTHEECHOESOFINTERESTFROMUNWANTEDCLUTTERANDNOISE 4HESTANDARDTOOLFORTHISDECOMPOSITIONISTHE&&4 ATLEASTINOPERATIONALSKYWAVE RADARS INPARTBECAUSEITISCOMPUTATIONALLYQUITEFEASIBLETOANALYZETHEINCOMINGSIG NALINTOTYPICALLY^RANGEBINS nBEAMS AND^DOPPLERCELLS INPERHAPS ^SECONDS USINGGENERALPURPOSECOMPUTINGHARDWARE4HUS THE&&4OR$&4FOR SHORTTRANSFORMS ISCOMMONLYUSEDFORTHETHREEDIMENSIONSOFANALYSIS!LTERNATIVE ANALYSISTECHNIQUESHAVEBEENIMPLEMENTEDINSOMESYSTEMSFORAPPLICATIONSSUCHAS DETECTIONOFACCELERATINGTARGETS nTHEDETECTIONOFHARMONICALLYRELATEDSIGNALS ANDWHENHIGHDOPPLERRESOLUTIONISREQUIREDBUTONLYSHORTCOHERENTINTEGRATIONTIMES CANBEACCOMMODATEDINTHERADARTIMELINE 3OME IMPORTANT PROCESSOR DESIGN CONSIDERATIONS EMERGE FROM AN ANALYSIS OF HIGHQUALITY(&RADARDATA ASILLUSTRATEDBYTHEFOLLOWINGEXAMPLE&IGURE SHOWSASEQUENCEOFSEACLUTTERDOPPLERSPECTRAFROMTHE!.&03 RADAR PRE SENTEDASRECEIVEDPOWERAMPLITUDEVERSUSDOPPLERFREQUENCY4OGENERATETHISPLOT POWERSPECTRAFROMASINGLERANGEBINWERECOMPUTEDFROMNONOVERLAPPINGTIME INTERVALS AND THEN GROUPED INTO BLOCKS OF FIVE AND AVERAGED NONCOHERENTLY4HE WAVEFORMREPETITIONFREQUENCY72& INTHISCASEWAS(Z WITHACOHERENTINTE GRATIONTIMEOFS RESULTINGINANOMINALDOPPLERFILTERBANDWIDTHOF(Z .OISE. SAMPLESWERETAKENFROMTHEMAXIMUMDOPPLERBIN TARGETSAMPLES4 ONTHETARGETPEAK AND"RAGGLINEAMPLITUDES! AND2 FROMTHECLUTTERPEAKS CORRESPONDINGTOTHEAPPROACHINGANDRECEDINGRESONANTOCEANWAVES ASDESCRIBED IN3ECTION. 4 ! AND2AREPLOTTEDIN&IGUREA4HESUB CLUTTERVIS IBILITY3#6 WIDELYUSEDIN(&RADARASAMEASUREOFSENSITIVITYANDDEFINEDAS 2. ISD"INTHISEXAMPLE)NMICROWAVERADAR THETERMSUB CLUTTERVISIBILITY ISSENSIBLYDEFINEDASTHERATIOBYWHICHTHETARGETECHOPOWERMAYBEWEAKERTHAN THECLUTTERPOWERANDSTILLBEDETECTED)NTHE(&RADARLITERATURE HISTORICALLYTHE DETECTION THRESHOLD COMPONENT HAS NOT BEEN INCLUDED SO 3#6 IS ESSENTIALLY THE CLUTTER TO NOISERATIO &ORAREPRESENTATIVEEFFECTIVECLUTTER2#3OFD"SMPERRESOLUTIONCELL THETARGET 2#3CANBEESTIMATEDAS
2#3 2D" 4D" D"SM
ANDSUPPOSINGTHATTHE3.2REQUIREDFORREGISTERINGADETECTIONISD" THEMINIMUM DETECTABLE2#3-$2#3 INTHISEXAMPLECANBECOMPUTEDAS
-$2#3 2 . D"SM
Óä°xä
2!$!2(!.$"//+
&)'52% .ONCOHERENTLYAVERAGEDPOWERSPECTRAFROMTHREECONTIGUOUSTIMEINTERVALS PLOTTEDWITH ANOFFSETFORCLARITY4HETARGETLIESWELLOUTSIDETHECLUTTERREGIONWHERETHE"RAGGLINESARECLEARLYVISIBLE SO THESIGNAL TO NOISERATIO NOTTHESIGNAL TO CLUTTERRATIO DETERMINESDETECTABILITY.OTETHE^D"VARIATION INTARGETECHOSTRENGTHDUETOCHANGESINTHEIONOSPHEREOVERSECONDS
4HISISAQUITELOW2#3AT(& INDICATINGTHATWHENCONDITIONSAREFAVORABLE VERY SMALLTARGETSAREPOTENTIALLYDETECTABLE 4HE EXPERIMENTAL DEMONSTRATION THAT ON OCCASION THE ENVIRONMENT SUPPORTS ^D" SUB CLUTTER VISIBILITY OBLIGES THE RADAR DESIGNER TO ENSURE THAT THE RECEIVING SYSTEMANDSIGNALPROCESSINGOPERATIONSDONOTUNWITTINGLYDEGRADETHERADARPERFOR MANCE3OMEAPPROPRIATEDESIGNCONSIDERATIONSARE u!NANALOG TO DIGITAL!$ CONVERTEROFATLEAST BITPRECISIONISINORDERFOR(& RADARSWITHHIGHPOWER GAINPRODUCTS 0AV'4'2 u2ECEIVINGAPERTURES WAVEFORMBANDWIDTHS ANDCOHERENTINTEGRATIONTIMESSHOULD PROVIDEENOUGHSAMPLESANDHIGHENOUGHSAMPLINGRATESTORESOLVEUNAMBIGUOUSLY DISTINCT FEATURES OF THE CLUTTER SPECTRUM WHERE SUCH RESOLUTION IMPACTS ON TARGET DETECTABILITYORTHEEXTRACTIONOFIMPORTANTINFORMATION u4HEWINDOWFUNCTIONSUSEDTOCONTROLLEAKAGEDURINGCONVENTIONALSPECTRUMANALY SISMUSTHAVESUFFICIENTLYLOWSIDELOBESWHENTRANSFORMSARETOBEAPPLIEDDIRECTLY TOHIGHDYNAMICRANGEDATA 4HEBASICSTEPSOFRANGE AZIMUTH ANDDOPPLERANALYSISARENOTTHEONLYSTAGESOF SIGNALPROCESSING!SEXPLAINEDIN3ECTION (&SKYWAVERADARSIGNALSARESUBJECT
(&/6%2 4(% (/2):/.2!$!2
Óä°x£
&)'52% A 4EMPORALFADINGANDB DISTRIBUTIONPROPERTIESOFTHETARGET CLUTTERPEAKS ANDNOISE FEATURESINTHEDOPPLERSPECTRUMOF&IGURE COMPUTEDFROMANEXTENDEDDATASEQUENCE
TO VARIOUS FORMS OF CONTAMINATION AND DISTORTION MANY IONOSPHERICALLY INDUCED SO METHODS TO DEAL WITH THESE HAVE LONG BEEN PART OF THE RADAR SIGNAL PROCESSING TOOLBOX -OREOVER THENEEDTODEALWITHTHESEDELETERIOUSEFFECTSHASBECOME MOREPRESSINGASTHEACHIEVABLEDYNAMICRANGEOFRECEIVINGSYSTEMSHASINCREASED REVEALINGAGREATERVARIETYOFSIGNALDISTORTIONMECHANISMS(ENCE INADDITIONTOPER FORMINGTHEBASICDECOMPOSITIONDESCRIBEDABOVE ANDCALIBRATINGTHERECEIVERCHAIN FORTHECURRENTWAVEFORM THESIGNALPROCESSINGSTAGEMAYBETASKEDWITHANUMBEROF SIGNALCONDITIONINGOPERATIONS3IGNALCONDITIONINGHEREREFERSTOFILTERINGANDSCALING PROCESSESAIMEDATREMOVINGCONTAMINATIONANDDISTORTIONTHAT IFLEFTONTHESIGNAL WOULDDEGRADETHERESULTSOFTHEPRIMARYPROCESSINGOPERATIONS SUCHASDOPPLERANALY SIS ANDBEMOREDIFFICULTTOREMOVEAFTERTHATPRIMARYPROCESSING4YPICALLY THEREARE OPTIONAL PROCESSINGALGORITHMSAVAILABLETOREMOVEIMPULSIVENOISEORIGINATINGFROM LIGHTNING TRANSIENTECHOESFROMMETEORS ANDFIELD ALIGNEDIRREGULARITIESINTHEIONO SPHERE STRONGDIRECTIONALINTERFERENCE ANDCLUTTERECHOESFROMBEYONDTHEMAXIMUM UNAMBIGUOUSRANGE)NADDITION THERADARDESIGNERNOWHASTHEOPTIONTOCOMPENSATE FOR SIGNAL PATH FLUCTUATIONS IN BOTH SPATIAL AND TEMPORAL DOMAINS WITHIN LIMITS BY EMPLOYINGPROCESSINGSCHEMESTHATDIAGNOSETHENATUREOFTHESIGNALCORRUPTIONONA FIRSTPASSANDTHENREPROCESSWITHALGORITHMSTHATCOMPENSATEFORTHEOBSERVEDCORRUPT INGMECHANISMS 4HESIGNALPROCESSINGSTAGEMAYALSOBETASKEDWITHEXTRACTING ENVIRONMENTALINFORMATIONFROMTHERADARECHOES ASMENTIONEDIN3ECTION4HIS INCLUDES REMOTE SENSING OF OCEAN WINDS AND SEA STATE LAND SEA MAPPING FOR COAST LINERECOGNITIONTOASSISTWITHCOORDINATEREGISTRATION MEASUREMENTSOFTHEIONOSPHERE FORASSIMILATIONINTOIONOSPHERICMODELS EXTRACTIONOFECHOESFROMREMOTEBEACONS DEPLOYEDTOASSISTWITHCOORDINATEREGISTRATIONANDCALIBRATION ANDMANYOTHERBYPROD UCTSOFTHEBASICDETECTIONMISSION
Óä°xÓ
2!$!2(!.$"//+
!TPRESENT THEMOSTPOWERFULTOOLSFORDEALINGWITHADDITIVEINTERFERENCE ASWELL ASSOMECLASSESOFSPREAD DOPPLERCLUTTER ARETHETECHNIQUESOFADAPTIVEPROCESSING /RIGINALLY THESETECHNIQUESWEREDEVELOPEDFORAIRBORNEMICROWAVERADARS BUTTHEY HAVEBEENSHOWNTOHAVEWIDEAPPLICABILITYIN(&RADARn4HEPRIMARYDOMAIN WHEREMAJORPERFORMANCEGAINSAREREALIZEDISSPATIALANALYSIS THATIS BEAMFORMING )NTHISCONTEXT AhSNAPSHOTvOFTHEOUTPUTSFROMTHEALLTHERECEIVERSACROSSTHEARRAY ISTAKENANDUSEDTOCOMPUTEASETOFCOMPLEX VALUEDWEIGHTSFOREACHDESIREDBEAM DIRECTIONTHESEARETHENAPPLIEDTOTHERECEIVEROUTPUTSBEFORESUMMINGTOFORMTHE ADAPTED BEAMS 4HE REASON FOR THE EFFICACY OF ADAPTIVITY HERE IS THAT AS REMARKED PREVIOUSLY (&RADARSAREALMOSTALWAYSEXTERNALNOISEnLIMITED4HEAZIMUTHALDIS TRIBUTIONOFNOISEFROMTHUNDERSTORMS INDUSTRIALSITESANDOTHERSOURCESISFARFROM UNIFORMLYDISTRIBUTED&URTHERMORE EVENSO CALLEDCLEARCHANNELSSELECTEDFORRADAR OPERATIONSARECONTAMINATEDWITHDIRECTIONALNOISEOFNATURALORINDUSTRIALORIGIN ALBEIT ATAMUCHLOWERLEVEL#ONVENTIONAL&&4 TYPEBEAMFORMINGMAKESNOALLOWANCEFOR THIS SOALOTOFNOISEENERGYLEAKSINTOEACHCOMPUTEDBEAMTHROUGHTHOSEOFITSREGU LARLYSPACED SIDELOBESTHATAREPOINTINGTOWARDSTRONGNOISESOURCES3PATIALLYADAP TIVEPROCESSING3!0 REDUCESTHISPROBLEMBYADJUSTINGTHEAMPLITUDEANDPHASEOF THESAMPLEDRECEIVEROUTPUTSINSUCHAWAYASTOMINIMIZETHEINTEGRATEDNOISEPOWER LEAKAGE WHILEPRESERVINGTHEGAINSENSITIVITYOFTHEBEAMBEINGSYNTHESIZED &IGURECOMPARESCONVENTIONALPROCESSINGAND3!0APPLIEDTOTHESAMEBLOCK OFRADARDATA!REDUCTIONOFSOMED"ISACHIEVEDINTHISEXAMPLE WHERENOISE NOTCLUTTER ISTHEPROBLEM4HEPATTERNHEREHASADAPTEDTOMINIMIZETHETOTALENERGY COLLECTEDINTHEDOPPLERBANDS;n n=(ZAND; =(Z WHILSTMAINTAININGTHEARRAY
&)'52% #OMPARISONOFDOPPLERSPECTRAESTIMATEDBYI CONVENTIONALBEAM FORMING#"& ANDII SPATIALLYADAPTIVEPROCESSINGDESIGNEDTOMINIMIZEENERGYOUT SIDETHELOW DOPPLERCLUTTER4HENOISEANDANYFASTCLUTTER HASBEENREDUCEDBY^D" WHICHIMPROVESDETECTABILITYOFFASTTARGETSNOTETHATTHESEACLUTTERSPECTRUMCHANGES ASACONSEQUENCEOFTHENEWARRAYPATTERN IE THECLUTTERSPECTRUMDOESNOTNECESSARILY REPRESENTTHECLUTTERSPECTRUMFROMTHECELLOFINTEREST
(&/6%2 4(% (/2):/.2!$!2
Óä°xÎ
RESPONSEINTHESPECIFIEDDIRECTION/FCOURSE DEPENDINGONTHEANGULARDISTRIBUTION OFTHENOISESOURCES THEARRAYRESPONSEPATTERNMAYHAVEVERYHIGHSIDELOBES BUTTHEY WILLLIEINDIRECTIONSWHERETHENOISELEVELSARELOWEST4HESAMEMAYNOTBETRUEOF THECLUTTERTHATOCCUPIESTHELOWDOPPLERBAND ;n =(Z WHICHHASNOTBEENUSEDTO GUIDETHEADAPTATIONOFTHEARRAYRESPONSE)NDEED THERESULTANTCLUTTERSPECTRUMMAY WELLHAVECHARACTERISTICSVERYDIFFERENTFROMTHOSEFOUNDINTHESTEERDIRECTION4HISIS THECASEINTHEEXAMPLESHOWNIN&IGURE WHERETHE"RAGGLINERATIOHASCHANGED DRAMATICALLYANDEVENREVERSEDINSIGN )N THE EXAMPLE JUST GIVEN THE 3!0 WEIGHTS WERE KEPT FIXED FOR THE ENTIRE #)4 7HENTHEEXTERNALNOISEFIELDISCHANGINGRAPIDLY ASHAPPENSWHENTHEIONOSPHERE ISDISTURBED ITISNECESSARYTOADAPTTHEWEIGHTSDURINGTHE#)4TOMAINTAINEFFECTIVE REJECTIONOFTHENOISEASITSAZIMUTHALDISTRIBUTIONCHANGES EVENFORSHORT^S DWELLS ASUSEDFORAIRCRAFTDETECTION4HISISTHEPROVINCEOFSPACE TIMEADAPTIVEPROCESSINGOR 34!0(ERE THEDATAUSEDTODETERMINETHEWEIGHTSREQUIRESNOTJUSTASINGLESNAP SHOTORAVERAGEOFSNAPSHOTSBUTANUMBEROFSNAPSHOTSOFTHEARRAYOUTPUTSTHISBLOCK OFDATAISTHENUSEDTOCONSTRUCTWEIGHTSTHATAREAPPLIEDTOTHEBLOCKOFDATABEFORE BEAMFORMINGANDDOPPLERANALYSIS34!0ISOFPARTICULARIMPORTANCETOSHIPDETECTION WHERETHEEXTERNALNOISEFIELDALMOSTINVARIABLYCHANGESSUBSTANTIALLYDURINGTHELONG #)44HECOMPLEXITYOF34!0INTHISCONTEXTARISESFROMTHEFACTTHATEACHTIMETHE WEIGHTSARECHANGEDACCORDINGTOTHE3!0RULES THEMAINBEAMEXPERIENCESAPHASE SHIFT EVEN THOUGH ITS AMPLITUDE GAINSENSITIVITY IS PRESERVED4HUS OVER THE ENTIRE #)4 ASEQUENCEOFPHASESHIFTSISAPPLIED THATIS AMODULATION WHICHISIMPOSEDON THERECEIVEDSIGNAL!SACONSEQUENCE THESTRONGCLUTTERECHOESARESPREADINDOPPLER MASKINGTARGETS4OOVERCOMETHISPROBLEM !BRAMOVICHETALDEVELOPEDATECH NIQUEKNOWNASTHEMETHODOFSTOCHASTICCONSTRAINTS WHICHUSESDIFFERENTRULESFOR WEIGHTADJUSTMENT PRESERVINGNOTONLYTHEGAINBUTALSO TOAGOODAPPROXIMATION THE PHASEOFTHECLUTTERRECEIVEDVIATHEMAINBEAMRESPONSE !LTHOUGHTHESEMODERNSPATIO TEMPORALADAPTIVEPROCESSINGTECHNIQUESHAVEBEEN PROVENTOBEHIGHLYEFFECTIVE THECOMPUTATIONALANDDATAREQUIREMENTSARESOHIGH THATMOSTOFTHEMCANNOTBEIMPLEMENTEDINTHEIRMOSTPOWERFULFORMSFORREAL TIME PROCESSING)NSTEAD SIMPLIFIEDALGORITHMSWITHIMPRESSIVEBUTNONETHELESSSUBOPTI MUMPERFORMANCEAREEMPLOYED )NVIEWOFTHENUMBEROFSIMULTANEOUSSPATIALCELLSTOBECONSIDERED DETECTION ISGENERALLYBASEDONACONSTANTFALSEALARMRATE#&!2 ALGORITHMADAPTEDTOTHE PARTICULARCLUTTERENVIRONMENT)NMOSTIMPLEMENTATIONS THE#&!2DETECTIONTHRESH OLDISCOMPUTEDFOREACHRESOLUTIONCELLASALINEARCOMBINATIONOFORDERSTATISTICS EXTRACTED FROM RANKED SAMPLE VALUES OVER A WINDOW SPANNING NEIGHBORING RANGE BINS ANTENNA BEAMS AND DOPPLER CELLS WITH PROVISIONS FOR ADAPTING THE WINDOW SHAPENEARSTRONGVARIATIONSINNOISEORCLUTTERPOWER/FTENTHERESULTSARESIMILARTO THOSEPREDICTEDBYTHELOG NORMALDISTRIBUTION ASEVIDENCEDBYTHEEXPERIMENTALDATA SHOWNIN&IGUREB WHICHGIVESTHEPOWER LEVELDISTRIBUTIONSFORTHEEXAMPLE SHOWNIN&IGURE4HESEAPPROXIMATELYLOG NORMALDISTRIBUTIONSARETYPICALFOR BENIGNCONDITIONS 4RACKING 0ERHAPS THE MOST FUNDAMENTAL DIFFERENCE BETWEEN SKYWAVE RADAR ANDOTHERRADARSISTHEEXISTENCEOFMULTIPLEPROPAGATIONPATHS WITHDISTINCTTIME DELAYS ANGLESOFINCIDENCE DOPPLERSHIFTS ANDFLUCTUATIONPROPERTIES4HETRACKING STAGEMUSTDEALWITHTHEMULTIPLICITYOFECHOESASSOCIATEDWITHEACHINDIVIDUALTARGET AND BY EXTRACTING AND ASSIMILATING INFORMATION ABOUT THE PREVAILING IONOSPHERE INFERTHENUMBEROFGENUINETARGETS THEIRTRUELOCATIONSANDVELOCITIES ANDPERHAPS
Óä°x{
2!$!2(!.$"//+
OTHERINFORMATIONSUCHASTARGETALTITUDE%STIMATESOFAIRCRAFTTARGETALTITUDEARE VERYUSEFUL BUTSKYWAVERADARHASNOTPROVEDTOBEARELIABLEMEANSOFOBTAINING ACCURATEESTIMATES 4HE PROBLEM OF CONVERTING FROM RADAR COORDINATES TO GEOGRAPHICAL COORDINATES IS REFERREDTOASCOORDINATEREGISTRATION#2 $OZENSOF#2TECHNIQUESHAVEBEENEXPLORED INCLUDINGI INFERENCEFROMAREGIONALIONOSPHERICMODEL II DEPLOYINGANETWORKOF REPEATERSORBEACONSINTHERADARFOOTPRINT III CORRELATINGCOASTLINESWITHLANDCLUTTER SEACLUTTERBOUNDARIESINTHERADARDATA IV CORRELATINGOTHERPARAMETERSSUCHASSCATTER INGCOEFFICIENT V USINGKNOWNTARGETINFORMATIONSUCHASREPORTSFROMSHIPSANDCOM MERCIALAIRLINEFLIGHTS ANDVI REGISTERINGAIRPORTS WHERETRACKSORIGINATEORTERMINATE 4HEKEYTOROBUST#2ISTHEFUSIONOFALLAVAILABLEINFORMATIONINACONSISTENTPROBABILIS TICFRAMEWORK-OSTRADARSIMPLEMENTTARGETTRACKINGASASEPARATESTAGETHATOPERATES ONTHECANDIDATETARGETSAFTERTHEYHAVEBEENREGISTERED INITIATING UPDATING ORTERMINAT ING TRACKS AS APPROPRIATE %XPERIENCE WITH MANY DIFFERENT TYPES OF TRACKING SCHEMES HASLEDANUMBEROFOPERATIONALRADARSTOCONVERGEONALGORITHMSBASEDONVARIANTSOF PROBABILISTICDATAASSOCIATION0$! SOMETIMESGENERALIZEDTOMAINTAINMULTIHYPOTH ESISMODELS5NLIKETRADITIONALTRACKINGFILTERSSUCHASTHE+ALMANFILTER WHICHSELECTS ASINGLEDETECTIONIE PEAKORPLOT TOASSOCIATEWITHEACHMAINTAINEDTRACK 0$!FILTERS COMBINETHEINFLUENCEOFALLTHECANDIDATEPEAKSWITHINAPRESCRIBEDRADIUSTOCOMPUTEA TRACKUPDATE)NTHESKYWAVERADARCONTEXT THISHASYIELDEDSUPERIORRESULTS !NIMPORTANTDECISIONRELATESTOWHERETHECOORDINATEREGISTRATIONISIMPLEMENTED 3OMESYSTEMSESTABLISHTRACKSINRADARCOORDINATESANDTHENPASSTHETRACKS INCLUDING MULTIPLETRACKSFROMASINGLETARGET TOTHE#2SYSTEM WHICHMUSTIDENTIFYANDRECON CILEANYMULTIPLETRACKSASWELLASPERFORMTHEREGISTRATION!LTERNATIVELY THEPROBLEM OFTARGETTRACKINGCANBEINTEGRATEDWITHTHEPROBLEMOFDETERMININGTHEIONOSPHERIC PROPAGATIONPATHS"YAUGMENTINGTHESTATEVECTORUSEDFORREPRESENTINGATARGETWITH ADDITIONALPARAMETERSTHATCHARACTERIZETHEPROPAGATIONPATHSTRUCTURE AJOINTESTIMA TIONPROBLEMCANBEFORMULATEDANDSOLVEDn)NTHISWAY THETARGETSCONTRIBUTETO REGISTERINGTHEIROWNCOORDINATES
Óä°£ÓÊ , ,Ê, -"1,
Ê / 4HE COMPLEXITY OF THE (& RADAR OPERATING ENVIRONMENTTHE IONOSPHERE CLUTTER NOISE ANDOTHERUSERSOFTHEBANDNECESSITATESACOMMENSURATECOMPLEXITYINSYS TEMDESIGNSOTHATTHERADARCANADAPTTOPREVAILINGCONDITIONSBYSELECTINGTHEBEST FREQUENCYORCOMBINATIONOFFREQUENCIES WAVEFORM SIGNALPROCESSING DETECTION THRESHOLDS ANDSOON FORTHETASKATHAND!CHIEVINGTHISOPTIMUMCONTROLISIMPORTANT BECAUSEEXPERIENCEHASSHOWNTHAT(&SKYWAVERADARPERFORMANCEMAYDEGRADEDRA MATICALLYWITHONLYMODESTDEPARTURESFROMOPTIMUMSETTINGS4HUS THEREISADEMAND FORTWOINGREDIENTSI INFORMATIONABOUTTHEENVIRONMENTANDII AMECHANISM ORAT LEASTASTRATEGY FORUSINGTHATINFORMATIONTOCONTROLTHERADARPARAMETERS !TTHEVERYMINIMUM (&SKYWAVERADARSMUSTMAINTAINAREAL TIMEAWARENESSOF PROPAGATIONCONDITIONSASAFUNCTIONOFFREQUENCY RANGE ANDBEARINGAZIMUTH AS WELLASADETAILEDKNOWLEDGEOFSPECTRUMOCCUPANCY4HISISUSUALLYACHIEVEDBYPRO VIDINGAUXILIARYFACILITIES INCLUDINGSOMEORALLOFTHEFOLLOWINGI #ONVENTIONALION OSPHERICSOUNDERSVERTICALANDOBLIQUEINCIDENCE WHICHDETERMINETHEIONOSPHERIC ELECTRONDENSITYPROFILEBYMEASURINGTHETIMEOFFLIGHTOFREFLECTEDRADIOWAVESOVER A RANGE OF FREQUENCIES THIS ELECTRON DENSITY PROFILE INFORMATION IS ASSIMILATED INTO
(&/6%2 4(% (/2):/.2!$!2
Óä°xx
LOCALREAL TIMEIONOSPHERICMODELSII !WIDEBANDBACKSCATTERSOUNDER THATIS ALOW POWER LOW RESOLUTIONRADARTHATSWEEPSACROSSTHE(&BAND MEASURINGECHOSTRENGTH VERSUSTIMEDELAYGROUPRANGE TOSEEWHICHFREQUENCIESAREILLUMINATINGANYGIVEN REGIONIII !MINI RADAR SIMILARTOABACKSCATTERSOUNDER THATEMPLOYSANARROWBAND WAVEFORMTOSTUDYTHEDOPPLERSTRUCTUREOFTHEECHOESASAFUNCTIONOFGROUPRANGE FORSELECTEDFREQUENCIESIV !NETWORKOFREMOTEBEACONSORTRANSPONDERSTOPROVIDE COORDINATEREGISTRATIONV 3PECTRUMMONITORINGRECEIVERSTOLOCATECLEARCHANNELSFOR POSSIBLEUSEANDTOASSESSTHEIRPROPERTIES!DETAILEDDESCRIPTIONOFTHESUITEOFAUXIL IARIESFORTHE*INDALEERADARCANBEFOUNDIN%ARLAND7ARD 4RADITIONALLY THECONTROLMECHANISMHASBEENTHEEXPERTRADAROPERATOR&ORMANY REASONS THIS IS NOT WHOLLY SATISFACTORY SO VARIOUS ALTERNATIVES HAVE BEEN EXPLORED INCLUDINGPACKAGEDhRECIPESvTHATCANBEINVOKEDBYLESSSKILLEDOPERATORSANDEXPERT SYSTEMSIMPLEMENTEDWITHARTIFICIALINTELLIGENCECONSTRUCTS !PARTFROMTHENEEDTOADAPTTOTHECHANGINGIONOSPHEREANDNOISEENVIRONMENT (&RADARSAREFREQUENTLYTASKEDWITHAVARIETYOFMISSIONSTOBECONDUCTEDMOREOR LESSCONCURRENTLY WITHTIME VARYINGPRIORITIES4HESEWILLGENERALLYINVOLVEDIFFERENT WAVEFORMS TASK SPECIFIC CONSTRAINTS ON FREQUENCY IN ADDITION TO PROPAGATION CON SIDERATIONS DIFFERING REQUIREMENTS IN TERMS OF ACCEPTABLE PROPAGATION QUALITY AND SOON!COMMONEXAMPLEISTHEDESIRETOSEARCHFORSHIPSANDAIRCRAFTCONCURRENTLY !CCORDINGLY OPTIMIZATIONOFTHEALLOCATIONOFRESOURCESBECOMESACRITICALISSUE WITH SIGNIFICANTIMPLICATIONSFORTHEWAYSKYWAVERADARSOPERATE /NEAPPROACHTOFITTINGMORETASKSINTOTHETIMEAVAILABLEISTOPARTITIONTHERADAR TRANSMITANDRECEIVEARRAYS TOGETHERWITHTHETRANSMITTERMODULESANDRECEIVERS SO THATWHENCONDITIONSAREFAVORABLE THEPARTITIONSCANOPERATEASINDEPENDENTRADARS WITHREDUCEDSENSITIVITYANDRESOLUTION&OREXAMPLE THE*INDALEEAND*/2.RADARS AREDYNAMICALLYRECONFIGURABLEASFULLORHALFRADARS!LTERNATIVELY ITMAYBEACCEPT ABLETOEMPLOYADUAL PURPOSEWAVEFORM ABLETOSUPPORTTWODISTINCTMISSIONS THOUGH WITHSUBOPTIMALPERFORMANCE ORFORTHETRANSMITSYSTEMTORADIATEMULTIPLEORTHOGONAL WAVEFORMSFORSIMULTANEOUSRECEPTIONANDPROCESSINGATAPROPORTIONALLOSSOFAVERAGE POWERONEACHTRANSMISSIONBUTWITHOUTLOSSOFSPATIALDIRECTIVITY"UTEVENIFTHESE APPROACHESARESOMETIMESAPPLICABLE ITISALMOSTALWAYSNECESSARYTOSCHEDULETHE VARIOUSTASKSSUCHTHATACCEPTABLEREVISITTIMESAREMAINTAINEDONIMPORTANTMISSIONS WITH LOW PRIORITY TASKS SUCH AS WEATHER MONITORING ACTIVATED LESS FREQUENTLY AND CHALLENGINGTASKSACTIVATEDWHENSUITABLEPROPAGATIONCONDITIONSOCCUR /NEOTHERIMPORTANTISSUEARISESWITHRESOURCEMANAGEMENTANDTHATISTHEABIL ITYTODIAGNOSEFAULTSANDFAILURESASSOONASTHEYOCCUR.OTONLYISTHISNECESSARY TOHASTENTHEREPAIRPROCEDURE BUTALSOITENABLESTHERADARTOADAPTITSCONFIGURATIONTO DOTHEBESTITCANWITHIMPAIREDEQUIPMENT&OREXAMPLE IFTHERECEIVERCONNECTEDTO THEMIDDLEELEMENTINANANTENNAARRAYWERETOFAIL BEAMFORMINGWOULDBEMORESERI OUSLYDEGRADEDTHANIFTHEFAILUREWERETOOCCURINARECEIVERCONNECTEDTOANELEMENT ATTHEENDOFTHEARRAY!UTOMATICDETECTIONOFSUCHAFAILUREANDREALLOCATIONOFANEND ELEMENTRECEIVERTOTHEMIDDLEELEMENTOFTHEARRAYWOULDMINIMIZETHEDEGRADATION
Óä°£ÎÊ , ,Ê* ,",
Ê " -ODELINGISANESSENTIALPARTOFTHERADARDESIGNPROCESSANDALSOASAMEANSTOPREDICT THEPERFORMANCEOFEXISTINGORPROPOSEDRADARSTOWHICHONEDOESNOTEXPECTACCESS )NTHESEROLES THEEMPHASISISONFIDELITY)N(&SKYWAVERADARSYSTEMS MODELINGHAS
Óä°xÈ
2!$!2(!.$"//+
ANOTHERROLEASAREAL TIMEMONITOROFWHATISEXPECTEDUNDERTHEPREVAILINGCONDI TIONS SOASTOALERTTHERADAROPERATORIFADISCREPANCYEMERGES WHICHMIGHTBEINDICA TIVEOFNATURAL EQUIPMENT RELATED ORINTENTIONALEVENTSWARRANTINGATTENTION !NISSUEONEENCOUNTERSWHENDISCUSSINGRADARPERFORMANCEISTHECHOICEOF PERFORMANCECRITERION&ROMTHEUSERSPERSPECTIVE ITMAYSEEMLOGICALTOMEASURE PERFORMANCEINTERMSOFTIMETAKENTOESTABLISHATRACKONAGIVENTARGET AVERAGED OVERTIMEANDCOVERAGE SINCETRACKSARETHEESSENTIALPRODUCTDELIVEREDTOUSERS BYTHERADAR/FCOURSE THISPLACESTHEONUSONTHETRACKINGSYSTEM SOONEMIGHT STEPBACKALITTLEANDCHOOSEINSTEAD3.2ACHIEVABLEONAGIVENTARGET AGAINAVER AGEDOVERTIMEANDCOVERAGE"UTTHISIGNORESTHEPRECISIONOFTHEMEASUREMENT ASSOCIATEDWITHBOTHRESOLUTION WHICHMAYIMPACTONTHEUTILITYOFTHEDETECTIONS ANDACCURACY INTHESENSEOFREGISTRATIONINABSOLUTEGEOGRAPHICAL COORDINATES !ND WHAT OF THE SMALLEST DETECTABLE TARGET #OVERAGE AND COVERAGE RATE 3HIP DETECTIONCAPABILITYVERSUSAIRCRAFTDETECTIONCAPABILITY #LEARLY THEREISNOSINGLE PREFERREDMETRIC 4HE MEASURE ADOPTED HERE FOR ILLUSTRATIVE PURPOSES IS THE ACHIEVABLE SIGNAL TO NOISE RATIO 3.2 AS DEFINED BY THE RADAR EQUATION %Q 4HE CONSTITUENT VARIABLES THAT APPEAR IN THE EQUATION HAVE BEEN DISCUSSED IN 3ECTIONS n EMPHASIZINGTHEUNIQUECONSIDERATIONSTHATARISEWITH(&SKYWAVERADAR SOTHETOOLS FOR PERFORMANCE MODELING AND ANALYSIS ARE AVAILABLE "Y CONSIDERING THE CASE OF NOISE LIMITEDDETECTION ASAPPLIESESPECIALLYTOAIRCRAFTTARGETS THEADDITIONALCOM PLICATIONSOFCLUTTER LIMITEDDETECTIONAREAVOIDED)NTHEFOLLOWINGPARAGRAPHS TWO DIFFERENTAPPROACHESTOPERFORMANCEMODELINGFORTHECASEOFNOISE LIMITEDDETECTION AREDESCRIBEDINSOMEDETAIL 4HE.2, )432ADAR0ERFORMANCE-ODEL 4HE.2, )432ADAR0ERFORMANCE -ODEL DEVELOPED BY ,UCAS ET AL PROVIDES A NUMBER OF TOOLS FOR RADAR PER FORMANCE ESTIMATION )T DOES NOT EMPLOY FULL $ RAY TRACING SUCH AS THE CODE DESCRIBEDBY*ONESAND3TEPHENSON WHICHCANPROVIDEPATHSINTHREEDIMENSIONS INCLUDINGDELAYSANDLOSSESFORBOTHORDINARYANDEXTRAORDINARYRAYSSEE3ECTION !RGUINGTHATSUCHCOMPREHENSIVECALCULATIONSAREEXCESSIVEWHENTHEREARE SIGNIFICANT UNCERTAINTIES IN THE ELECTRON DENSITY DISTRIBUTION .2, -EMORANDUM 2EPORTDESCRIBESTHEBASICTECHNIQUEUSEDFORPATHDETERMINATIONS!SIMPLE CLOSED FORM VIRTUAL PATH TRACE 3NELLS LAW FOR A SPHERICALLY SYMMETRIC MEDIUM ISSEQUENCEDTHROUGHELEVATIONRADIATIONANGLESINnINCREMENTS4HISPROCESSIS INCREMENTEDIN -(ZSTEPSOVERTHERADARSOPERATINGBAND)NTHEPRESENTEXAM PLE AVERTICALSOUNDINGOFTHEIONOSPHEREKMDOWNRANGEHASBEENUSEDASTHE ELECTRONDISTRIBUTIONFORALLONE HOPPATHS ANDASOUNDINGKMDOWNRANGEIS USEDFORTWO HOPPATHS&IGUREGIVESNIGHTANDDAYEXAMPLESOFIONOGRAMS SHOWINGTHEIONOSPHEREKMDOWNRANGEFROMARADARLOCATEDATn.AND n7 LOOKING EAST IN SUMMER AT A MEDIAN SUNSPOT NUMBER OF 4HE COR RESPONDING WINTER CASE IS PRESENTED IN &IGURE 3UCH PLOTS CAN BE USED TO DETERMINE THE MAXIMUM FREQUENCYTHATWILLPROPAGATETOAGIVENRANGEINMOST CASES THEOPTIMUMFREQUENCYISJUSTBELOWTHEMAXIMUMFREQUENCY&ORTHELITTLE TABLESSHOWNIN&IGUREAND &#ISTHECRITICALFREQUENCY INMEGAHERTZ (#ISTHEHEIGHTOFMAXIMUMIONIZATIONORTHENOSEOFTHEPARABOLA INKILOMETERS AND9-ISTHESEMILAYERTHICKNESS INKILOMETERS%SDESCRIBESTHESTATISTICALRANGE OFVARIATIONOFSPORADIC %AS-MEDIAN ,LOWERDECILE AND5UPPERDECILE CRITICALFREQUENCIES INMEGAHERTZ
(&/6%2 4(% (/2):/.2!$!2
&)'52% 4HEVIRTUALSOLIDLINE ANDTRUEDASHEDLINE REFLECTIONHEIGHTSAREGIVEN FOR *ULY 33. AND A MID !TLANTIC COAST REFRACTION AREA A 54 IS A DAYTIME EXAMPLE SINGLEHOPANDB 54ISANIGHTTIMEEXAMPLE3EETEXTFORANEXPLANATIONOF THETABLEINTHELOWERRIGHTOFTHEFIGURE
Óä°xÇ
Óä°xn
2!$!2(!.$"//+
&)'52% 0REDICTEDIONOGRAMSASIN&IGURE BUTFOR*ANUARYA 54# FORDAYANDB 54#FORNIGHT3EETEXTFORANEXPLANATIONOFTHETABLEINTHELOWER RIGHTOFTHEFIGURE
#ONSTANTPLASMA FREQUENCYCONTOURSVERSUSRANGEFROMTHERADARFOR54# 33. *ANUARYNIGHT AND54#DAY AREPRESENTEDIN&IGURESAND TO ILLUSTRATE THE TILT OF THE IONOSPHERE &OR THE NIGHT CASE THE CONCENTRIC
(&/6%2 4(% (/2):/.2!$!2
&)'52% 0LASMA FREQUENCYCONTOURSAREGIVENIN-(Z EXTENDINGFROMTHERADAR TOAPOINTEASTNMIDOWNRANGE FORA*ANUARYNIGHTEXAMPLE
&)'52% 0LASMA FREQUENCYCONTOURSAREGIVENIN-(Z EXTENDINGFROMTHERADAR TOAPOINTEASTNMIDOWNRANGE FORA*ANUARYDAYEXAMPLE
Óä°x
Óä°Èä
2!$!2(!.$"//+
SPHERICALASSUMPTIONFROMTHE KMDOWNRANGEPOSITIONWILLGIVEPATHSTHATARE SLIGHTLYLONGFORONE HOPRANGES)NTHETWO HOPRANGES THENO GRADIENTASSUMP TIONCAUSESMOREDISTORTION)NGENERAL ERRORSOFTHISNATUREHAVELITTLEIMPACTON PERFORMANCE PREDICTION (OWEVER NEAR REAL TIME ANALYSIS FOR VIRTUAL RANGE AND AZIMUTHCORRECTIONTOGREAT CIRCLEDISTANCEANDBEARINGGRIDREGISTRATION REQUIRES THATTILTORGRADIENTEFFECTSBETAKENINTOACCOUNT4HEDAYTIMEEXAMPLEHASLITTLE HORIZONTALGRADIENT ANDTHESIMPLIFYINGASSUMPTIONMAKESLITTLEDIFFERENCE7HEN BETTERACCURACYISDESIRED THECORRECTVERTICALPROFILECANBEUSEDFOREACHRADIATION ANGLE ALSO GRADIENTS CAN BE SIMULATED BY MAKING THE IONOSPHERE NONCONCENTRIC WITHTHE%ARTH!MORECOMPLETEPATHANALYSISSHOULDBEUSEDINRADARPERFORMANCE ASSESSMENT AND MANAGEMENT BUT THESE PLASMA DENSITY CONTOURS CAN BE USED TO ESTIMATETHEMAGNITUDEOFTHEERRORSINTRODUCEDBYTHEASSUMPTIONOFASPHERICALLY SYMMETRICIONOSPHERE &IGURESHOWSAPERFORMANCEPREDICTIONFORAHYPOTHETICALRADARINTHEFORM OFANOBLIQUESOUNDING!TYPICALSKYWAVERADARISSUPPORTEDBYONEORMOREVERTI CALSOUNDERSANDOBLIQUEBACKSCATTERSOUNDERSFORTRANSMISSION PATHANALYSISANDTO AIDINRADAR FREQUENCYMANAGEMENT/FCOURSE THERADARITSELFISANOBLIQUESOUNDER BUTITSSOUNDINGDATAISRESTRICTEDTOTHEFREQUENCY WAVEFORM ANDSCANPROGRAMOF ITSPRIMARYSURVEILLANCETASK!NADJUNCTOBLIQUESOUNDERCANPROVIDEINFORMATIONIN
&)'52% 4HENUMBERSINTHISFIGURESHOWTHE3.2IND"ASAFUNCTIONOFFREQUENCYANDRANGEIN THEFORMOFATYPICALOBLIQUEBACKSCATTERSOUNDING*ANUARY '-4DAY 33. LOCATIONn.AND n7 BEARINGn3EETHETEXTFORADESCRIPTIONOFRADARPARAMETERS
(&/6%2 4(% (/2):/.2!$!2
Óä°È£
THEFORMOF&IGUREON%ARTHBACKSCATTERECHOPOWER%STIMATESFORNOISEPOWER SPECTRALDENSITYAREDERIVEDFROM##)22EPORT ASDESCRIBEDIN3ECTION )NTHISPREDICTION 3.2INDECIBELSISPLOTTEDASAFUNCTIONOFOPERATINGFREQUENCYAND GREAT CIRCLETIMEDELAYORGROUNDRANGE4HENUMBERSJUSTABOVETHEABSCISSAAT MS DELAY ARETHENOISEPOWERSINDECIBELSBELOW7(Z&ORTHISPLOT THE54#TIMEIS 33. 0AV K7 'T'R D" 4 S ANDR D"SM&IGURE GIVESTHECORRESPONDINGNIGHTPLOT 4HESHAPEOFTHESEDISPLAYSISQUITESIMILARTOWHATWOULDBESEENWITHADIAGNOSTIC OBLIQUESOUNDINGTHELEVELSWOULDGENERALLYBEGREATERBECAUSETHERESOLUTIONCELLAREA TIMESTHESURFACESCATTERINGCOEFFICIENTISGENERALLYMUCHLARGERTHAND"SM3OME OFTHENIGHT DAYCONTRASTS SUCHASAVAILABLEFREQUENCIESANDDIFFERENCEINNOISELEVEL FORTHESAMERANGE AREEVIDENT!LSONOTETHATATNIGHTTHE -(ZLOWERFREQUENCY LIMITDOESNOTPROVIDECOVERAGECLOSERTHANABOUTKM)TSHOULDBEREMEMBERED THATTHISISAMEDIAN33.CALCULATION ANDIFCONSISTENTPERFORMANCEFORRANGESAS CLOSEASKMISREQUIREDDURINGNIGHTS ALOWERFREQUENCYLIMITSHOULDBESELECTED TODEALWITHPERIODSOFLOWERSOLARACTIVITYANDTHECRITICALFREQUENCYDISTRIBUTION4HE PLOTSSHOWTHATOPERATIONONASINGLEFREQUENCYMAYEXPERIENCELESSTHANoD"VARIA TIONOVERARANGEINTERVALOFKM!LSO IFFREQUENCYSELECTIONHADBEENMADEWITH A -(ZGRANULARITYINSTEADOFTHE-(ZUSED THE3.2WOULDBEREDUCEDBYONLY ADECIBELORSO
&)'52% 4HENUMBERSINTHISFIGURESHOWTHE3.2IND"ASAFUNCTIONOFFREQUENCYANDRANGEIN THEFORMOFANOBLIQUESOUNDING ASIN&IGURE BUTFOR'-4NIGHT 3EETHETEXTFORADESCRIPTION OFRADARPARAMETERS
Óä°ÈÓ
2!$!2(!.$"//+
4HEPERFORMANCEESTIMATIONCHARTSTHATFOLLOWCOMEFROMANALYSESASDESCRIBED ABOVE !FTER PERFORMING OBLIQUE SOUNDING CALCULATIONS A RANGE INDEXED TABLE OF PROPAGATIONANDNOISEPARAMETERSISCOMPILED0ARAMETERSELECTIONSAREMADEONTHE BASISOFTHEBEST3.2INEACHNOMINAL NMIINTERVAL BUTTHESELECTIONISADJUSTEDTO COMEFROMTHEADJACENTLOWERFREQUENCYTOAVOIDANOPTIMISTICBIAS4HENPARAMETER PLOTSAREGENERATEDASAFUNCTIONOFRANGE4HEVARIABLESADOPTEDHEREASPARAMETERS AREPROPAGATIONLOSSES FREQUENCY NOISE ANDELEVATIONRADIATIONANGLE4HECHOICEOF RANGEASTHEINDEPENDENTVARIABLEMAYSEEMARTIFICIAL BUTITISAUSEFULAPPROACHFOR PERFORMANCEEXAMINATION7ITHTHESECURVES THEIMPACTONRADAR3.2PERFORMANCE CANBEESTIMATEDFORSELECTEDANTENNAGAINPATTERNS TRANSMITTEDPOWERS TARGET2#3 ANDCOHERENTINTEGRATIONTIMES#)4 &IGUREISANEXAMPLEFOR*ANUARYWITHMODERATESOLARACTIVITY 33. IN DAYTIME4HE2LOSSISTHEFOURTHPOWEROFRANGETOTHETARGETINMETERS EXPRESSEDIN DECIBELS2 ,ADDSNONDEVIATIVEABSORPTION DEVIATIVEABSORPTION SPORADIC %OBSCU RATION ANDGROUND REFLECTIONLOSSESIFTHEREISMORETHANONEHOP4HESHARPINCREASEIN LOSSJUSTBEFORENMIISCAUSEDBYTRANSITIONFROMONETOTWOHOPSFORTWOHOPS THELOSSY$REGIONISTRANSITEDTWICEASMANYTIMES GROUND REFLECTIONLOSSISADDED AND REQUIREDOPERATIONATALOWERFREQUENCYINCREASESLOSS4HEJAGGEDCURVEINTHETRANSI TIONREGIONISDUETOTHEPARAMETERSELECTIONPROCESSINRADAROPERATION THEFREQUENCY WOULDBESELECTEDTOMINIMIZETRANSITIONEFFECTS4HEFREQUENCY RADIATIONANGLE AND NOISEPOWERPERHERTZTHATGOWITHTHISSITEANDLOOKDIRECTIONAREALSOPLOTTED
&)'52% 2ADARPERFORMANCE CONTROLLINGVARIABLESPLOTTEDASAFUNCTIONOF RANGEFOR*ANUARY 54# 33.
(&/6%2 4(% (/2):/.2!$!2
Óä°ÈÎ
!NEXAMPLEWILLSERVETOILLUSTRATETHEUSEOFSUCHPLOTS3ELECTNMIASTHE RANGE4HEN THEFREQUENCYIS-(ZWAVELENGTH MANDL D" NOISE POWER nD" AND2 , D"#HOOSED"7FOR0AV D"FOR'T D" FOR'R D"SFOR4 D"SMFOR2#3 ANDD"FOR&P3UBSTITUTINGIN%Q
3.2 D"
&IGURESHOWSTHEPERFORMANCEINDICATEDWITHTHESEASSUMPTIONSFORALLRANGES !PATHFACTORENHANCEMENTOFD"HASBEENCHOSENASAREPRESENTATIVEVALUEOFCONSTRUC TIVEMULTIPATHINTERFERENCEFORANAIRCRAFTTARGET4HEBEAMWIDTHHASBEENTAKENTOBE nANDTHESURFACESCATTERINGCOEFFICIENTTOBEnD" ANDWITHAD"PATHENHANCE MENT THECLUTTERLEVELHASBEENPLOTTED4HECLUTTER TO NOISERATIO#.2 ATNMIIS ABOUTD"&ORTHECONSTANTBEAMWIDTHASSUMED THECLUTTER TO SIGNALRATIOINCREASES WITHRANGEANDISD"ATNMI,ARGECLUTTER TO SIGNALRATIOSARETYPICALOF(& RADARSOMEFORMOFDOPPLERFILTERINGISUSEDTOSEPARATETARGETSFROMCLUTTER )N&IGURES AND PERFORMANCEESTIMATIONCURVESAREGIVEN FOR WINTER AND SUMMER SEASONS NIGHT AND DAY AND LOW SOLAR ACTIVITY4HE PERMIS SIBLEFREQUENCYSELECTIONISSETBETWEENAND-(Z ANDANTENNARADIATIONISNOT CONSIDEREDBELOWANELEVATIONANGLEOFn4HEANALYSESWEREMADEFORARADAROFF THEMID !TLANTICCOASTOFTHE5NITED3TATESANDSHOULDBEAGOODAPPROXIMATIONFOR ANY LOCATION WHERE TRANSMISSION PATHS ARE THROUGH THE MIDDLE MAGNETIC LATITUDES
&)'52% !SPECIFICEXAMPLEOF3.2ANDCLUTTER TO NOISERATIO#.2 ASDETERMINEDBYUSING&IGURE4HETARGET2#3ISLABELEDhSIZEvANDIS TREATEDASCONSTANT
Óä°È{
2!$!2(!.$"//+
&)'52% 2ADAR PERFORMANCE ESTIMATE FOR *ANUARY 54# 33.
&)'52% 2ADAR PERFORMANCE ESTIMATE FOR *ANUARY 54# 33.
(&/6%2 4(% (/2):/.2!$!2
&)'52% 2ADAR PERFORMANCE ESTIMATE FOR *ULY 54# 33.
&)'52% 2ADAR PERFORMANCE ESTIMATE FOR *ULY 54# 33.
Óä°Èx
Óä°ÈÈ
2!$!2(!.$"//+
4HESEPERFORMANCEESTIMATIONCURVESCANBEUSEDTOSHOWEXTREMESIN3.2VARIATION ANTENNAELEVATIONANGLESREQUIRED ANDEXPECTEDCLUTTER TO NOISERATIOS4HEEXPECTED PERFORMANCEOFAPARTICULARRADARDESIGNCANBEEXPLOREDWITHTHESEGRAPHSBECAUSE SUMMER AND WINTER DO GIVE GOOD COVERAGE OF THE IMPORTANT VARIABLES 4HE PERFOR MANCECURVESHAVEBEENLIMITEDINALMOSTALLEXAMPLESTOTHECASEOFLOWSOLARACTIVITY SINCE INGENERAL THISISTHEMOSTDIFFICULTTIME4HEHIGHERFREQUENCYAVAILABILITYAND PERFORMANCEAFFORDEDATHIGHSOLARACTIVITYISILLUSTRATEDIN&IGURE WHICHTREATS THECASEOF*ULY54#FOR33. !NALYSISOFPERFORMANCEESTIMATIONCURVESFORALLCOMBINATIONSOFI THEFOUR SEASONS II DAYANDNIGHT ANDIII HIGHANDLOWSOLARACTIVITYREVEALSCONSISTENT BEHAVIOR I 3UMMERSHOWSMUCHGREATERLOSSESTHANWINTER II %XCEPTFORSUMMER NIGHTLOSSESAREONLYSLIGHTLYLESSTHANDAYLOSSES III .IGHTNOISEISMUCHGREATERTHANDAYNOISE IV &ORASPECIFICRANGE OPTIMUMFREQUENCIESVARYBY 4HIS/4(PERFORMANCEPRESENTATIONFORMATCANBEUSEDTODECIDEONTHEANTENNA PATTERNSANDPOWERSREQUIREDFORSPECIFICTARGETSANDMISSIONS ORITCANBEUSEDTO EXHIBITPERIODSOFENHANCEDORDEGRADEDPERFORMANCEFORANEXISTINGDESIGN
&)'52% 2ADARPERFORMANCEESTIMATEFOR*ULY54# 33.
(&/6%2 4(% (/2):/.2!$!2
Óä°ÈÇ
3EVERALQUALIFIERSSHOULDBEKEPTINMIND!TOTHERGEOGRAPHICLOCATIONS THEAPPRO PRIATE##)2NOISESHOULDBESELECTEDOR BETTERYET NOISEMEASUREMENTSMADEINSITU &ORRADARSTHATUSEAURORALZONEPATHS SPECIFICANALYSESAREREQUIREDANDTARGETOBSCURA TIONBYSPREAD IN DOPPLERCLUTTERMUSTBECONSIDERED4HEPERFORMANCEESTIMATESSHOWN INTHEFIGURESASSUMETHATTHERADARDESIGNANDWAVEFORMSARESUCHTHATEXTERNALNOISEIS THECONTROL4HEUSEOFASINGLEDESCRIPTIONFORNIGHTANDDAYGIVESAFAIRREPRESENTATION BUTTHETRANSITIONFROMNIGHTTODAYISVERYABRUPTANDREQUIRESCAREFULFREQUENCYMAN AGEMENTINRADAROPERATION4HEIONOSPHERICDESCRIPTIONTHATHASBEENUSEDISFORWHAT HASBEENTERMEDTHEQUIETIONOSPHERE CONDITIONSTHATAPPLYMOSTOFTHETIME5NDER DISTURBEDCONDITIONS PERFORMANCEMAYBEMARKEDLYINFERIORTOTHATPREDICTED 4HE *INDALEE 2ADAR 0ERFORMANCE -ODEL 4HE *INDALEE 2ADAR 0ERFORMANCE -ODEL DRAWS ON SEVERAL UNIQUE DATABASES 3INCE OBLIQUE BACKSCATTER SOUND INGSHAVEBEENRECORDEDONAMINUTECYCLE SCANNINGFROMTOOROPTIONALLY -(Z %IGHTSIMULTANEOUSBEAMSSPANNINGAnARCAREFORMED0RIORTO THESYSTEMUSEDASINGLERECEIVERSCANNINGTHERECEIVEBEAMS SERVICINGEACHRECEIVE BEAMFORK(ZOFEACHK(ZPORTIONOFABACKSCATTERIONOGRAM0OST EACH BEAMHASBEENSERVICEDCONTINUOUSLYWITHITSOWNRECEIVER"ACKGROUNDNOISEDATA USEDINCONJUNCTIONWITHTHEBACKSCATTERDATAFORTHE%XCESS0OWERANALYSISISCOL LECTEDUSINGTHESAMEEIGHTDIRECTIONALBEAMSASTHEBACKSCATTERSOUNDER 7HILE THERE ARE A FEW SIGNIFICANT GAPS IN THESE TIME SERIES THEY SPAN TWO SOLAR CYCLES FURTHER INTEGRITY HAS BEEN MAINTAINED BY EXTENSIVE VETTING BEFORE ENTERING NEWDATAINTOTHEDATABASE4HEUNIQUEADVANTAGEOFTHISDATABASEISTHATTHENOISEAND PROPAGATIONDATAARERECORDEDUNDERIDENTICALIONOSPHERICCONDITIONS WHEREASCOM BININGINDEPENDENTCLUTTERANDNOISESTATISTICALMODELSSUCHAS)2) WITH##)2 PRESERVESNOCORRELATIONS HOWEVERSTRONGTHEYMAYBE 3EVERALFORMSOFDATAANALYSISANDDISPLAYAREACCESSIBLE BUTPERHAPSTHEMOSTUSE FULARETHEMAPSOFI %XCESS0OWERANDII /PTIMUM&REQUENCY4HE%XCESS0OWER PARAMETERISCONSTRUCTEDASFOLLOWS#ONSIDERASPECIFICTARGETWHOSE2#3ISKNOWN ORESTIMATEDASAFUNCTIONOFFREQUENCY3UPPOSEAPREDICTIONOFMEDIANRADARDETEC TIONPERFORMANCEISREQUIREDFORASPECIFICMONTHOFTHEYEARANDAPARTICULARSUNSPOT NUMBERORYEAROFSOLARCYCLE !NALYSIS IS INITIATED BY SELECTING FROM THE DATABASE A MONTH THAT MATCHES THE REQUIREMENTS)NDIVIDUALBACKSCATTERIONOGRAMSAREPAIREDWITHTHECONCURRENTBACK GROUNDNOISEDATAANDTHERATIOTAKENTOYIELDAPOPULATIONOFESTIMATESOFTRUESUB CLUTTERVISIBILITY3#6 FOREACHFREQUENCYSTEP EACHBEAM ANDEACHRANGEBIN.EXT USINGASPECIFIEDTIMEGRANULARITYTYPICALLYONEHOURMEDIANVALUESOF3#6ARE CALCULATED FOR EACH SPATIAL CELL AND TIME INTERVAL FROM THE STATISTICAL POPULATION OF INDIVIDUAL3#6ESTIMATES.OTEAGAINTHATTHESEMEDIANVALUESARETHEMEDIANVALUES OFTHE3#6POPULATION NOTASTATISTICDERIVEDBYCOMBININGMEDIANVALUESOFCLUTTER WITHMEDIANVALUESOFNOISE 4HE MEDIAN 3#6 VALUES ARE RELATED DIRECTLY TO THE BACKSCATTER SOUNDER TRANSMIT POWERANDTHETRANSMITANTENNAGAIN&ROMTHERADAREQUATION%Q THE3#6CAN BESCALEDTOTHATWHICHWOULDBEEXPECTEDFORTHEMAINRADAR WITHITSDIFFERENTRADIATED POWER04 APERTURE RADARBANDWIDTH ETC#OMBININGTHESESCALED3#6VALUESWITH I AMODELOFTHESURFACEBACKSCATTERINGCOEFFICIENTVERSUSFREQUENCYALMOSTALLTHE /4(RADARCOVERAGEISOCEAN SOBASEDONREGIONALWAVESTATISTICS THECONSTANTVALUE nD"ISUSED II THETARGET2#3VERSUSFREQUENCYMODELANDIII ANESTIMATEOF THETARGETECHOSIGNALPROCESSINGLOSS TYPICALLY^D" WHICHARISESPREDOMINANTLY FROM&&4ANALYSIS YIELDSTHEPREDICTEDMEDIANTARGET3.2ATEACHSPATIALLOCATIONAS
Óä°Èn
2!$!2(!.$"//+
AFUNCTIONOFFREQUENCY4HISCANBEUSEDDIRECTLY BUTITISCONVENIENTTODEFINETHE %XCESS0OWERATEACHFREQUENCYASFOLLOWS 3UPPOSE u!N3.2THRESHOLDOF-D"ISREQUIREDBEFORETHESIGNALPROCESSINGWILLREGISTERA DETECTIONAND u4HE3.2CALCULATEDFORAPARTICULARRANGE AZIMUTHCELLINTHECOVERAGEIS3.2F D"WHICHMAYBENEGATIVE 4HEN IND"
%XCESS0OWERF - 3.2F 04 02%&
ISTHEAMOUNTOFEXTRAPOWER RELATIVETOANYCHOSENREFERENCEPOWER02%& NEEDEDTO ACHIEVEDETECTIONASAFUNCTIONOFFREQUENCY!NEGATIVEVALUEINDICATESTHATTHERADAR HASGREATERSENSITIVITYTHANREQUIRED&IGURESHOWSANEXAMPLEPRESENTEDASA CONTOURPLOT4HESECONDPARAMETEROFSPECIALINTERESTISOPTIMUMFREQUENCY DEFINED ASTHEVALUEOFTHEFREQUENCYATEACHRANGE TIMELOCATIONTHATMAXIMIZESTHE3.2FOR THEGIVENTARGET TAKINGALLRADAREQUATIONFACTORSINTOACCOUNT!GAIN ACONTOURPLOT FORMATISUSEDHEREIN&IGURE /THER-ODELING!PPROACHES 4HEMODELSDESCRIBEDABOVEAREFORMULATEDINTHE CONTEXTOFTHERADAREQUATION%Q !NALTERNATIVEISTOEMPLOYACOHERENThPRO CESSMODEL vINWHICHTHEFIELDAMPLITUDEANDPHASEARETRACKEDFROMTRANSMITTERTO RECEIVER4HISAPPROACHHASBEENUSEDTOSIMULATETHEEFFECTSOFMULTIPATH DIFFUSESCAT TERING POLARIZATIONEFFECTS ANDNONLINEARITY &OREXAMPLE &IGURESHOWS
&)'52% 2ANGE TIMEMAPOFPOWERREQUIRED RELATIVETOA02%&OFK7 TODETECTASPECIFIC TARGET ASAFUNCTIONOFRANGEANDTIME OF DAY FORAPARTICULARMONTHANDLEVELOFSOLARACTIVITY
(&/6%2 4(% (/2):/.2!$!2
Óä°È
&)'52% 2ANGE TIME MAP OF OPTIMUM FREQUENCY IN -(Z TO DETECT A SPECIFIC TARGET AS A FUNCTIONOFRANGEANDTIME OF DAY FORAPARTICULARMONTHANDLEVELOFSOLARACTIVITY
THE PREDICTED DISTRIBUTION OF THE RESULTANT RADAR CROSS SECTION WHEN MULTIPATH AND &ARADAYROTATIONARETAKENINTOACCOUNT4HERELEVANTPHYSICSROUGHSURFACEFORWARD SCATTERINGCOEFFICIENT BISTATICINTHEVERTICALPLANE FREE SPACETARGETSCATTERINGCROSS
! !!%
"% "
#
$
#
'&*)(
&)'52% 0REDICTED DISTRIBUTION OF EFFECTIVE 2#3 FOR THE!ERMACCHI -"( TRAINER JET AIRCRAFTVIEWEDNOSE ONATAHEIGHTOFFEETWHENGROUND REFLECTIONMULTIPATHAND&ARADAYROTA TIONARETAKENINTOACCOUNT
Óä°Çä
2!$!2(!.$"//+
SECTIONFORHYBRIDMULTIPATH &ARADAYROTATION ANDDIFFERENTIAL&ARADAYROTATIONARE INCORPORATED VIA PARAMETRIC MODELS DERIVED FROM MEASUREMENTS OR COMPUTATIONAL ELECTROMAGNETICSANDTHEDISTRIBUTIONOBTAINEDBY-ONTE#ARLOSIMULATION
** 8\ÊÊ-1,
Ê76 Ê, , 'ENERAL #HARACTERISTICS AND #APABILITIES !LTHOUGH SKYWAVE PROPAGATION PROVIDESTHEUNIQUECAPABILITYOFLOWALTITUDETARGETDETECTIONATRANGESOFTHOUSANDS OFKILOMETERS OTHERFORMSOFPROPAGATIONAT(&CANBEEXPLOITEDINRADARAPPLICATIONS "YFARTHEMOSTCOMMONOFTHESEISGROUNDWAVEORSURFACEWAVEPROPAGATION WHICH ISMOSTEFFECTIVEFORVERTICALLYPOLARIZEDRADIOWAVESTRAVELINGOVERHIGHLYCONDUCTIVE SURFACESSUCHASSEAWATER)NADDITION THEREAREAPPLICATIONSFORWHICHLINE OF SIGHT OR SPACEWAVE PROPAGATION IS APPROPRIATE SUCH AS MEASUREMENT OF THE (& 2#3 OF AEROSPACE VEHICLES &URTHERMORE IN MANY INSTANCES BISTATIC CONFIGURATIONS CAN BE EMPLOYED WITHTHEPOSSIBILITYOFUSINGDIFFERENTPROPAGATIONMECHANISMSFORTRANS MITTER TARGETANDTARGET RECEIVERPATHS)NVIEWOFTHEFAMILIARITYOFSPACEWAVEPROPA GATIONANDTHEPRECEDINGDISCUSSIONOFSKYWAVESYSTEMS ITSUFFICESHERETOADDRESSTHE MAINFEATURESOF(&SURFACEWAVEORGROUNDWAVE RADAR(&372 (&372SYSTEMSTENDTOFALLINTOTWOCATEGORIESI LOW POWERRADARSINTENDED PRIMARILY FOR OCEANOGRAPHIC REMOTE SENSING ESPECIALLY OF OCEAN CURRENTS AND II LARGERANDMOREPOWERFULSYSTEMSWITHTARGETDETECTIONASTHEIRPRIMARYMISSION 4HEFORMERAREINWIDESPREADOPERATIONAROUNDTHEWORLDONLYAFEWOFTHELATTERARE OPERATIONALINSURVEILLANCEROLES4HEABILITYOFTHELOW POWERREMOTESENSINGRADARS TO DETECT SHIPS AT OVER THE HORIZON RANGES ALTHOUGH MODEST HAS BEEN EXPLOITED IN SOMEDUAL PURPOSEDEPLOYMENTS 4HEPRINCIPALVIRTUEOF(&372ASANOCEANSURVEILLANCERADARLIESINITSABILITYTO DETECTSMALLSURFACEVESSELSANDLOW FLYINGAIRCRAFTATRANGESFARBEYONDTHEVISIBLE HORIZON!SWITHSKYWAVERADAR PERFORMANCEDEPENDSSTRONGLYONENVIRONMENTALAND TARGET PARAMETERS AS WELL AS RADAR DESIGN THE DETECTION RANGES CITED IN4ABLE PROVIDESOMEINDICATIONOFCAPABILITYAGAINSTSURFACEVESSELSANDLOW FLYINGAIRCRAFT ASCLAIMEDORREPORTEDFORSEVERALESTABLISHED(&372SYSTEMS 4!",% .OMINALOR#LAIMED-AXIMUM$ETECTION2ANGESKILOMETERS OF3OME(&372
3YSTEMS 3EA3ONDEISACOMPACTLOW POWERRADARDESIGNEDPRIMARILYFORREMOTESENSINGITISAVAILABLEWITH ANUPGRADEDPERFORMANCEOPTION4HEOTHERRADARSSHOWNWEREDESIGNEDFORSURVEILLANCE)NALL CASES PERFORMANCEMAYFALLFARSHORTOFTHECITEDVALUESUNDERINCLEMENTENVIRONMENTALCONDITIONS
4!2'%4490% &RIGATE /FFSHORETRAWLER 3MALLFISHINGBOAT 'O FASTSPEEDBOAT 2IGIDINFLATABLEBOAT ,OW FLYINGFIGHTER SIZEDAIRCRAFT
3%#!2 372 (&372 2AYTHEON "!%3YSTEMS $ARONMONT 0ODSOLNUKH % 3EA3ONDE !USTRALIA .IIDAR2USSIA #ODAR53 5+ #ANADA
(&/6%2 4(% (/2):/.2!$!2
Óä°Ç£
-UCHOFTHEDISCUSSIONRELATINGTOSKYWAVERADARCARRIESOVERDIRECTLYTO(&372 BUTTHEREAREAFEWAREASWHEREDIFFERENCESARESIGNIFICANT u4HE ANTENNAS MUST BE DESIGNED AND POSITIONED TO ACHIEVE HIGH EFFICIENCY IN COUPLING TO THE SURFACE WAVE MODE %XPERIMENTS HAVE SHOWN THAT HIGHER FIELD STRENGTHSAREGENERATEDATOVER THE HORIZONRANGESWHENTHETRANSMITTINGANTENNA ISLOCATEDCLOSETOSEALEVEL RATHERTHANINANELEVATEDPOSITIONPLACINGTHEANTENNA EVEN JUST ONE OR TWO WAVELENGTHS ABOVE SEA LEVEL CAN INTRODUCE SEVERAL D" OF ADDITIONALLOSS u-OST(&372SYSTEMSUSEAVERYBROADhFLOODLIGHTvTRANSMITBEAMTOILLUMINATETHE ENTIRECOVERAGEARCMULTIPLESIMULTANEOUSRECEIVEBEAMSAREFORMEDTOFILLTHEARC ANDUPDATEALLTRACKSSIMULTANEOUSLY4HISREDUCESCOSTANDCOMPLEXITYBUTINCURS SOMELOSSOFSENSITIVITYFORNOISE LIMITEDTARGETDETECTION u#OHERENTINTEGRATIONTIMESMAYEXTENDTOHUNDREDSOFSECONDS AS(&372ISNOT RELIANTONTHEIONOSPHEREASAMEDIUMFORPROPAGATION u/NLYVERTICALLYPOLARIZEDELECTROMAGNETICWAVESPROPAGATEEFFECTIVELYINTHESURFACE WAVEMODEOVERTHESEA SOTHE(&372SIGNAL RECEIVINGANTENNASARENECESSARILY VERTICALLYPOLARIZED/NTHEOTHERHAND UNWANTEDSIGNALSANDINTERFERENCEARRIVING BYSKYWAVEMAYHAVEANYPOLARIZATION4HISPRESENTSAMEANSFORREJECTIONOFINTER FERENCEBYFILTERINGINPOLARIZATIONSPACEANYSIGNALSCORRELATEDWITHTHOSERECEIVED ON AN AUXILIARY HORIZONTALLY POLARIZED RECEIVE ANTENNA CAN BE CANCELLED FROM THE OUTPUTSOFTHEVERTICALLYPOLARIZEDARRAY u4HEINCREASINGLYRAPIDATTENUATIONOFPROPAGATIONTORANGESBEYONDABOUTKM AS SHOWN IN &IGURE MEANS THAT AT LONGER RANGES RELATIVELY LITTLE DETECTION PERFORMANCEIMPROVEMENTISGAINEDBYLARGEINCREASESINTRANSMITTEDPOWER u4HERATEOFDECAYOFTHESURFACEWAVESRISESSHARPLYWITHINCREASINGFREQUENCY AS SHOWNIN&IGURE WHEREASTHE2#3OFSMALLTARGETSTENDSTOINCREASERAPIDLY ANDEXTERNALNOISEDECREASES)TFOLLOWSTHATRADARDESIGNISSENSITIVETOTHECLASSES OFTARGETSTOBEDETECTED u7HILE(&372DOESNOTRELYONTHEIONOSPHERE ECHOESFROMIRREGULARITIESINTHE IONOSPHEREMAYAPPEARATRANGESINEXCESSOF^KM 3IMILARLY GROUNDREFLEC TIONSRECEIVEDVIAOBLIQUESKYWAVEPROPAGATIONMAYAPPEARATRANGESINEXCESSOF ^KM3UCHECHOESMAYBESPREADINDOPPLERANDCANCONSTITUTEASERIOUSPROB LEMFOR(&372SYSTEMS!CCORDINGLY ANTENNASSHOULDBEDESIGNEDWITHLOWGAIN ATHIGHERELEVATIONANGLES 4HEMAINDESIGNPARAMETERSOFAREPRESENTATIVE(&372SYSTEMTHE$ARONMONT 3%#!2RADARARELISTEDIN4ABLE4HECORRESPONDINGVALUESFORSKYWAVERADARS CANBEFOUNDIN4ABLE 0ROPAGATION#ONSIDERATIONSIN(&3723YSTEMS 4OAGOODAPPROXIMATION WHENATARGETOFINTERESTISABOVETHEOPTICALHORIZONOFAN(&372 THEFIELDINCI DENTONTHETARGETCANBEDECOMPOSEDINTOTERMSTHATCORRESPONDTOI DIRECTLINE OF SIGHT II SEA SURFACEREFLECTION ANDIII ALATERALORhSURFACE ATTACHEDvWAVE"EYOND THEHORIZON THESURFACEWAVEISTHEDOMINANTCONTRIBUTOR BUTATSHORTERRANGES ALL THREEMECHANISMSMUSTBETAKENINTOACCOUNT!CCORDINGLY THERELATIONSHIPBETWEEN I TARGET ECHO STRENGTH AND II THE RANGE AND ALTITUDE OF THE TARGET IS NOT A SIMPLE ONE-OREOVER THECALCULATIONOFTHEFIELDDISTRIBUTIONISCOMPUTATIONALLYEXPENSIVEIF
Óä°ÇÓ
2!$!2(!.$"//+
4!",% 3PECIFICATIONSOF3%#!2 AN(&3URFACE7AVE2ADAR$ESIGNEDFOR3URVEILLANCEOF
THENMI%XCLUSIVE%CONOMIC:ONE 2ADAR -ANUFACTURER 4YPE 4X 2XSITESEPARATIONKM 0OWERAVERAGE K7 0OWERPEAK K7 &REQUENCYBAND-(Z 7AVEFORM "ANDWIDTHK(Z 7AVEFORMREPETITIONFREQUENCY(Z 4XANTENNADESIGN 2XANTENNADESIGN 2XAPERTUREM "EAMWIDTH-(Z -(Z .OOFSIMULTANEOUSBEAMS )NSTANTANEOUSRANGEDEPTHKM .OOFRANGEBINS #OHERENTINTEGRATIONTIME#)4 S .OOFDOPPLERCELLS -AXVELOCITYRESOLUTIONMSn 0RIMARYMISSION 2EVISITTIMEFORENTIRECOVERAGEAREA 3ECONDARYMISSIONS .UMBEROFSIMULTANEOUSTARGETSTRACKED
3%#!2 $ARONMONT4ECHNOLOGIES "ISTATIC(&SURFACEWAVERADAR n n LINEAR&- #7 n n 3INGLEVERTICALLOG PERIODICANTENNAWITH GROUNDSCREEN ORENDFIREMONOPOLEDOUBLETSWITH GROUNDSCREEN n n n OR n n n n 3HIPDETECTION %QUALTO#)4 !IRCRAFTDETECTION 2EMOTESENSING
ACCURATEPREDICTIONSAREREQUIRED4HEDIFFICULTIESARECOMPOUNDEDWHENMIXEDPATHS ARE INVOLVED THAT IS WHEN PART OF THE PROPAGATION PATH LIES OVER LAND AS HAPPENS WHEREISLANDSAREPRESENTINTHECOVERAGEAREA &OCUSINGATTENTIONHEREONOVER THE HORIZONDETECTION &IGURESHOWSHOWTHE SURFACEWAVEDECAYSWITHRANGE PARAMETRICINFREQUENCYFORTHECASEINWHICHBOTH THERADARANTENNAANDTHETARGETARENEARTHESEASURFACE4HESECURVESAREFORASMOOTH SURFACEANDUSEAEARTHRADIUSTOAPPROXIMATEATMOSPHERICREFRACTIONEFFECTS4HE PROPAGATIONCODEUSEDHEREISDUETO"ERRYAND#HRISMAN ANDITISQUITEFLEXIBLE PERMITTINGANTENNAANDTARGETALTITUDES SURFACECONDUCTIVITYANDPERMITTIVITY POLARIZA TION ANDFREQUENCYTOBESPECIFIED4HEKEYPOINTSTOBEDRAWNFROMTHISEXAMPLEARE I THEAPPARENTADVANTAGETOBEGAINEDBYOPERATINGATLOWFREQUENCIESWHEREPROPAGA TIONLOSSESAREMINIMIZED THOUGHTHISBENEFITMUSTBEBALANCEDAGAINSTANTENNASIZE THE HIGHER NOISE ENVIRONMENT AND OFTEN REDUCED TARGET 2#3 AND II THE RAPIDLY ACCELERATING FALL OFF IN SIGNAL STRENGTH AT RANGES BEYOND A FEW HUNDRED KILOMETERS WHERED"OFEXTRATRANSMITPOWERMAYBUYONLYONTHEORDEROFKILOMETERSOF ADDITIONALDETECTIONRANGE ! MORE WIDELY USED PROPAGATION CODE IS '27!6% WHICH EMPLOYS DIFFERENT MATHEMATICALREPRESENTATIONSFORTHEFIELD DEPENDINGONRANGEANDOTHERPARAMETERS SO ASTOMAXIMIZECOMPUTATIONALEFFICIENCY3OMEINDICATIONOFTHEACCURACYOFTHISMODEL
(&/6%2 4(% (/2):/.2!$!2
Óä°ÇÎ
&)'52% #URVESOFPROPAGATIONLOSSVERSUSRANGE ASUSEDFORESTI MATINGSURFACEWAVERADARPERFORMANCE4HESURFACEISASSUMEDTOBESMOOTH TARGETANDANTENNAHEIGHTSAREM CONDUCTIVITYISTAKENAS3M ANDTHE DIELECTRICCONSTANTIS
CANBEFOUNDIN&IGURE WHICHCOMPARES'27!6%PREDICTIONSWITHEXPERIMEN TALMEASUREMENTSOFTHESIGNALSTRENGTHRECEIVEDATASHORE BASED(&372WHENTHE TRANSMITTERWASCARRIEDBYASMALLBOATTRAVELINGOUTTOARANGEOF^KM4OAVOID PERIPHERALISSUESCONCERNINGANTENNAS THE'27!6%CURVESHAVEBEENARBITRARILYNOR MALIZEDHERETOALIGNWITHTHEMEASUREMENTSATARANGEOFKM)TISCLEARTHAT WITH THISNORMALIZATION THEPREDICTIONSMATCHREASONABLYWELLOVERTHEWHOLERANGEEXTENT WITH SMALL BUT SYSTEMATIC DEPARTURES '27!6% SEEMS TO UNDERESTIMATE ATTENUATION SLIGHTLYAT-(ZBUTOVER ESTIMATEAT-(Z4HESEAROUGHNESSINTHISCASE WASLOWSEASTATEn 4HEIMPACTOFSEAROUGHNESSONSIGNALAMPLITUDECANBETAKEN INTOACCOUNTBYUSINGTHEEXPRESSIONSFORROUGHNESSLOSSDERIVEDBY"ARRICK !NOTHERSURFACEWAVEPROPAGATIONMODELINGCODEHASBEENDEVELOPEDBY3EVGI PAYINGPARTICULARATTENTIONTOTHECALCULATIONOFPROPAGATIONOVERHYBRIDPATHSWITH MULTIPLEISLANDS 4HEEFFECTOFTHETIME VARYINGSEAROUGHNESSONTHESIGNALPHASEANDWAVEFRONT STRUCTURE MANIFESTED IN THE TIME DELAY DOPPLER SPECTRUM AND DIRECTION OF ARRIVAL SPECTRUMOFTHERECEIVEDSIGNAL CANBECOMPUTEDUSINGTHEMULTIPLESCATTERINGTHEORY OF!NDERSONETAL
Óä°Ç{
2!$!2(!.$"//+
# %$ " %$
$
#"
!" )*
!" "(
+
" "* "& &
+
!" )* "$"' ""$"'
!" #"$"'
&)'52% %XPERIMENTAL MEASUREMENTS OF ONE WAY SURFACE WAVE ATTENUATION COMPAREDWITH'27!6%PREDICTIONS.OTETHEFLUCTUATIONSDUETOSCALLOPINGLOSSASTHE SOURCEMOVEDTHROUGH&&4RANGEBINS
3CATTERING4ARGETSAND#LUTTER 4HEDISCUSSIONOF(&2#3ANDSEACLUTTERIN 3ECTIONSANDAPPLIESEQUALLYTO(&372INDEED THEABSENCEOFTHECOR RUPTINGEFFECTSOFTHEIONOSPHEREPROVIDESEVENGREATERSCOPEFOREXPLOITINGTHESCAT TEREDSIGNALS&URTHERMORE ALTHOUGHTHEINCREASEDRATEOFDECAYOFTHESURFACEWAVEAT HIGHERFREQUENCIESIMPOSESALIMITONTHERANGEOFFREQUENCIESTHATMIGHTBEUSEDTO DETECTATARGETATAGIVENRANGE THESITUATIONISBYNOMEANSASRESTRICTIVEASFORSKY WAVEPROPAGATION4HISRAISESTHEPOSSIBILITYOFEXPLOITINGMULTIPLEFREQUENCIESMORE EFFECTIVELY SO AS TO EXTRACT ADDITIONAL TARGET AND SEA STATE INFORMATION AND UNMASK TARGETSHIDDENINCLUTTER !COMPELLINGEXAMPLEISPRESENTEDIN&IGURE WHEREARANGECELLCONTAININGA SHIPTARGETTRAVELINGATASPEEDOFKNOTSHASBEENINTERROGATEDATEIGHTRADARFREQUEN CIESANDTHERESULTINGDOPPLERSPECTRAPLOTTEDINANESTEDDISPLAY 4HETWOCOLUMNSOFPLOTSSHOWRECEIVEDPOWERVERSUSDOPPLERFREQUENCYFORTHE EIGHT OPERATING FREQUENCIES AS LABELED AND FOR THE TARGET APPROACHING RIGHT COL UMN ANDRECEDINGLEFTCOLUMN 4HEABSCISSAUNITSAREINDOPPLERNORMALIZEDTO
(&/6%2 4(% (/2):/.2!$!2
Óä°Çx
&)'52% -ULTIFREQUENCY (&372 DOPPLER SPECTRA SHOWING THE DIFFERENTFREQUENCYDEPENDENCEOFI TARGETANDII CLUTTERSPECTRUMCHARAC TERISTICS4HETARGET4ISSHOWNWHENAPPROACHINGRIGHT ANDRECEDINGLEFT INTHEPRESENCEOFTHESEAECHO WITH"RAGGPEAKSMARKED!FORAPPROACH ING AND 2 FOR RECEDING 4HE CURVES PLOT RECEIVED POWER VERSUS NORMAL IZEDDOPPLERIE INUNITSOFTHE"RAGGFREQUENCY FOREIGHTRADAROPERATING FREQUENCIES4HEPEAKATZEROFREQUENCYISDUETOASTATIONARYTARGETINAN ANTENNASIDELOBE
THERESONANTWAVEOR"RAGGFREQUENCYTHEREFORE THERESONANTWAVERESPONSESPEAK ATo4HEAMPLITUDERANGEFOREACHPLOTISD"4HENARROWPEAKSATZERODOPPLER FREQUENCYAREDUETOLANDINANANTENNASIDELOBE4HETARGETDOPPLERAND"RAGGLINE FREQUENCYCOINCIDEATARADARFREQUENCYOF-(ZTHETARGETDOPPLERLIESBETWEEN THE "RAGG LINES FOR RADAR FREQUENCIES BELOW THAT FREQUENCY AND OUTSIDE THEM FOR
Óä°ÇÈ
2!$!2(!.$"//+
FREQUENCIESABOVE4HEPOSITIVEDOPPLERRESONANTWAVEPEAKISABOUTD"LARGER THANTHENEGATIVEDOPPLERPEAK INDICATINGASEADRIVENBYWINDSBLOWINGTOWARD THE RADAR 4HE PROCESSING USED IN DEVELOPING THESE DISPLAYS WAS S #)4 AND MINAVERAGING 0ERFORMANCE -ODELING %XAMPLES OF (&372 SYSTEM PERFORMANCE MODEL ING GENERALLYFOLLOWTHEPRECEPTSDESCRIBEDIN3ECTION4HEMAINDIFFERENCE HEREISTHEAVAILABILITYOFPATH LOSSDESCRIPTORSSUCHASTHOSESHOWNIN&IGURE &OREXAMPLE CONSIDERARADARAT-(ZWITHANAVERAGEPOWEROFK7D"7 A TRANSMIT RECEIVEANTENNAGAINPRODUCTOFD" ANDATARGETATNMIWITHAN2#3 OFD"SMTHENTHERECEIVEDPOWERIS
0R D"7 "YUSINGTHE*ANUARYNIGHTTIMENOISEASGIVENIN&IGUREB
3.2 0R . D"
ANDIFSCOHERENTPROCESSINGTIMEISUSED
3.2 D"
!SNOTEDEARLIER PROPAGATIONLOSSACCELERATESRAPIDLYWITHDISTANCE ESPECIALLYAT HIGHER FREQUENCIES WHILE ATMOSPHERIC AND SURFACE ROUGHNESS EFFECTS WILL ACCUMU LATEANDCONTAMINATIONOFTHESURFACEWAVERETURNWITHECHOESRECEIVEDVIASKYWAVE PATHSWILLBECOMEINCREASINGLYSEVERE SOQUANTITATIVEPERFORMANCEPREDICTIONSATLONG RANGES BEYOND^KM SHOULDBETREATEDWITHCAUTION
, ,
!(4AYLORAND%/(ULBERT h4HEPROPAGATIONOFRADIOWAVESOVERTHEEARTH v0HYSICAL2EVIEW VOL &EBRUARY ,!'EBHARD h%VOLUTIONOFNAVALRADIO ELECTRONICSANDCONTRIBUTIONSOFTHE.AVAL2ESEARCH ,ABORATORY v.AVAL2ES,AB2EPT *-(EADRICKAND-)3KOLNIK h/VER THE (ORIZON2ADARINTHE(&"AND v0ROC)%%% VOL PPn *UNE $!"OUTACOFF h"ACKSCATTERRADAREXTENDSEARLYWARNINGTIMES v$EFENSE%LECTRONICS VOL PPn -AY 'UESTEDITORIALANDINVITEDPAPERSINSPECIALISSUEONHIGH FREQUENCYANDICEMAPPINGANDSHIP LOCATION )%%%*/CEANIC%NG VOL/% !PRIL * 2 "ARNUM h3HIP DETECTION WITH HIGH RESOLUTION (& SKYWAVE RADAR v IBID PP n !PRIL *-(EADRICK h,OOKINGOVERTHEHORIZON v)%%%3PECTRUM VOL PPn *ULY $ ( 3INNOTT h4HE *INDALEE OVER THE HORIZON RADAR SYSTEM v #ONF!IR 0OWER IN THE $EFENCE OF!USTRALIA !USTRALIAN.ATIONAL5NIVERSITY 2ESEARCH3CHOOLOF0ACIFIC3TUDIES 3TRATEGICAND $EFENCE3TUDIES#ENTRE #ANBERRA !USTRALIA *ULYn *7YLDER h4HEFRONTIERFORSENSORTECHNOLOGY v3IGNAL VOL PPn 6!9AKUNIN &&%VSTRATOV &)3HUSTOV 6!!LEBASTROV AND9)!BRAMOVICH h4HIRTYYEARS OFEASTERN/4(RADARSHISTORY ACHIEVEMENTSANDFORECAST v,/NDE%LECTRIQUE VOL NO -AYn*UNE
(&/6%2 4(% (/2):/.2!$!2
Óä°ÇÇ
# 'OUTELARD h4HE ./342!$!-53 PROJECT &RENCH /4( " RADAR DESIGN STUDIES v TH !'!2$ 3YMPOSIUM ON @5SE OR 2EDUCTION OF 0ROPAGATION AND .OISE %FFECTS IN $ISTRIBUTED -ILITARY3YSTEMS !'!2$#0 3UPP 'REECE /CTOBER # 'OUTELARD h345$)/ FATHER OF ./342!$!-53 3OME CONSIDERATIONS ON THE LIMITS OF DETECTION POSSIBILITIES OF (& RADARS v )NT #ONF (& 2ADIO 3YSTEMS AND 4ECHNIQUES )%% #ONFERENCE0UBLICATIONNO *ULY 6"AZIN *0-OLINIE *-UNOZ 0$OREY 33AILLANT '!UFFRAY 62ANNOU AND-,ESTURGIE h!GENERALPRESENTATIONABOUTTHE/4( 2ADAR./342!$!-53 v)%%%2ADAR#ONFERENCE 3YRACUSE .9 -AY !LSO REPRINTED IN )%%% !%3 3YSTEMS -AGAZINE VOL NO PPn /CTOBER :HOU7ENYUAND-AO8U h"ISTATIC&-#7/4( "EXPERIMENTALRADAR v0ROC)NT#ONF2ADAR )#2 #HINA)NSTITUTEOF%LECTRONICS PPn 'UEST EDITORIAL AND INVITED PAPERS REVIEWING /4( RADAR TECHNOLOGY WITH EMPHASIS ON RECENT PROGRESS 2ADIO3CIENCE VOL *ULYn!UGUST !!+OLOSOVED &UNDAMENTALSOF/VER THE (ORIZON2ADAR IN2USSIAN 2ADIOISVYAZ !LSOATRANSLATIONBY7&"ARTON .ORWOOD -!!RTECH(OUSE 2!'REENWALD +""AKER 2!(UTCHINS AND#(ANUISE h!N(&PHASEDARRAYRADARFOR STUDYINGSMALL SCALESTRUCTUREINTHEHIGHLATITUDEIONOSPHERE v2ADIO3CIENCE VOL PPn *ANUARYn&EBRUARY 0!"ERNHARDT ''ANGULI -#+ELLEY AND7%3WARTZ h%NHANCEDRADARBACKSCATTERFROM SPACESHUTTLEEXHAUSTINTHEIONOSPHERE v*'EOPHYS2ES VOL PP n 2-4HOMAS 037HITHAM AND7'%LFORD h2ESPONSEOFHIGHFREQUENCYRADARTOMETEOR BACKSCATTER v*!TMOS4ERR0HYS VOL PPn ! #AMERON h4HE *INDALEE OPERATIONAL RADAR NETWORK ITS ARCHITECTURE AND SURVEILLANCE CAPABILITY v0ROC)%%%)NT2ADAR#ONF PPn +$AVIES )ONOSPHERIC2ADIO ,ONDON00EREGRINUS *4HOMASON '3KAGGS AND*,LOYD h!GLOBALIONOSPHERICMODEL v.AVAL2ES,AB2EPT !UGUST +(OCKEAND+3CHLEGEL h!2EVIEWOFATMOSPHERICGRAVITYWAVESANDTRAVELLINGIONOSPHERIC DISTURBANCESn v!NNALES'EOPHYSICAE VOL PPn !"OURDILLON *$ELLOUE AND*0ARENT h%FFECTSOFGEOMAGNETICPULSATIONSONTHEDOPPLERSHIFT OF(&BACKSCATTERRADARECHOES v2ADIO3CIENCE VOL PPn "'&EJERAND-#+ELLEY h)ONOSPHERICIRREGULARITIES v2EV'EOPHYSAND3PACE0HYS VOL PPn # 3(UANG -#+ELLEY AND$,(YSELL h.ONLINEAR2AYLEIGH 4AYLORINSTABILITIES ATMOSPHERIC GRAVITYWAVES ANDEQUATORIALSPREAD& v*'EOPHYS2ES VOL PP n $ , ,UCAS AND ' 7 (AYDON h0REDICTING STATISTICAL PERFORMANCE INDEXES FOR HIGH FRE QUENCYTELECOMMUNICATIONSSYSTEMS v%33!4ECH2EPT)%2)43! 53$EPARTMENTOF #OMMERCE !,"ARGHAUSEN *7&INNEY ,,0ROCTOR AND,$3CHULTZ h0REDICTINGLONG TERMOPERA TIONAL PARAMETERS OF HIGH FREQUENCY SKY WAVE COMMUNICATIONS SYSTEMS v %33! 4ECH 2EPT %2, )43 53$EPARTMENTOF#OMMERCE *-(EADRICK *&4HOMASON $,,UCAS 3-C#AMMON 2(ANSON AND*,,LOYD h6IRTUAL PATHTRACINGFOR(&2ADARINCLUDINGANIONOSPHERICMODEL v.AVAL2ES,AB-EMO2EPT -ARCH , 2 4ETERS * , ,LOYD ' 7 (AYDON AND $ , ,UCAS h%STIMATING THE PERFORMANCE OF TELECOMMUNICATIONSYSTEMSUSINGTHEIONOSPHERICTRANSMISSIONCHANNELIONOSPHERICCOMMU NICATIONSANALYSISANDPREDICTIONPROGRAMUSERSMANUAL v.AT4ELECOM)NF!DM.4)!2EPT n *ULY 6%(ATFIELD h(&COMMUNICATIONSPREDICTIONS!NECONOMICALUP TO DATECOMPUTER CODE !-"#/- v 3OLAR4ERRESTRIAL 0RODUCTION 0ROC VOL IN 0REDICTION OF4ERRESTRIAL %FFECTS OF 3OLAR !CTIVITY 2 & $ONNELLEY ED .ATIONAL /CEANIC AND !TMOSPHERIC !DMINISTRATION
Óä°Çn
2!$!2(!.$"//+
$,UCAS '0INSON AND20ILON h3OMERESULTSOF2!$!2# EQUATORIALSPREADDOPPLERCLUTTER PREDICTIONS v0ROCTH)NT)ONOSPHERIC%FFECTS3YMP !LEXANDRIA 6IRGINIA PP! n! -AY $ , ,UCAS h)ONOSPHERIC PARAMETERS USED IN PREDICTING THE PERFORMANCE OF HIGH FREQUENCY SKYWAVE CIRCUITS v )NTERIM 2EPORT ON .2, #ONTRACT . + !CCOUNT 5NIVERSITYOF#OLORADO "OULDER !PRIL $#-ILLERAND*'IBBS h)ONOSPHERICANALYSISANDIONOSPHERICMODELING v!,4ECH2EPT *ULY $"ILITZA h)NTERNATIONALREFERENCEIONOSPHERE vHTTPMODELWEBGSFCNASAGOVIONOSIRIHTML )NDEXOFMODELSIONOSPHERICIRIIRI HTTPNSSDCFTPGSFCNASAGOVMODELSIONOSPHERICIRIIRI !'+IM :&:UMBRAVA 60'ROZOV '6+OTOVICH 93-IKHAYLOV AND!6/INATS h4HECORRECTIONTECHNIQUEFOR)2)MODELONTHEBASISOFOBLIQUESOUNDINGDATAANDSIMULATION OFIONOSPHERICDISTURBANCEPARAMETERS v0ROC886)))TH523)'ENERAL!SSEMBLY .EW$ELHI /CTOBER 2%$ANIELL *RAND$.!NDERSON h0)-MODEL vHTTPMODELWEBGSFCNASAGOV IONOSPIMHTML 0ARAMETERIZED)ONOSPHERIC-ODEL #OMPUTATIONAL0HYSICS HTTPWWWCPICOMPRODUCTSPIM 2%$ANIELL ,$"ROWN $.!NDERSON -7&OX 0($OHERTY $4$ECKER **3OJKA AND 2 7 3CHUNK h0ARAMETERIZED IONOSPHERIC MODEL! GLOBAL IONOSPHERIC PARAMETERIZATION BASEDONFIRSTPRINCIPLEMODELS v2ADIO3CIENCE VOL PPn 2%$ANIELL h02)3-ASSIMILATINGDISPARATEDATATYPESFORIMPROVEDLOWLATITUDEIONOSPHERIC SPECIFICATION vPRESENTEDATTHE)ONOSPHERIC$ETERMINATIONAND3PECIFICATIONFOR/CEAN!LTIMETRY AND '03 3URFACE 2EFLECTION 7ORKSHOP AT THE *ET 0ROPULSION ,ABORATORY 0ASADENA #! n $ECEMBER $.!NDERSON *-&ORBES AND-#ODRESCU h!FULLYANALYTICAL LOW ANDMIDDLE LATITUDE IONOSPHERICMODEL v*'EOPHYS2ESVOL PPn 'LOBAL!SSIMILATIONOF)ONOSPHERIC-EASUREMENTS 0ARK#ITY 5TAH HTTPGAIMCASSUSU EDU'!)-HTDOCSPRESENTHTM 'LOBAL!SSIMILATIVE)ONOSPHERIC-ODEL *0, HTTPIONOJPLNASAGOVGAIMINDEXHTML *$(UBA '*OYCE AND*!&EDDER h3!-)3AMIISANOTHERMODELOFTHEIONOSPHERE !NEWLOW LATITUDEIONOSPHEREMODEL v*'EOPHYS2ES VOL n "+HATTATOV --URPHY -'NEDIN 4&ULLER 2OWELL AND69UDIN h!DVANCEDMODELINGOF THEIONOSPHEREANDUPPERATMOSPHERE v%NVIRONMENTAL2ESEARCH4ECHNOLOGIES2EPORT ! *UNE *+(ILL h%XACTRAYPATHSINAMULTISEGMENTQUASI PARABOLICIONOSPHERE v2ADIO3CIENCE VOL PPn 4!#ROFTAND((OOGASIAN h%XACTRAYCALCULATIONSINAQUASI PARABOLICIONOSPHEREWITHNO -AGNETIC&IELD v2ADIO3CIENCE VOL PPn 2*.EWTON 0,$YSON AND*!"ENNETT h!NALYTICRAYPARAMETERSFORTHEQUASI CUBIC SEGMENTMODELOFTHEIONOSPHERE v2ADIO3CIENCE VOL PPn 2-*ONESAND**3TEPHENSON h!VERSATILETHREE DIMENSIONALRAYTRACINGCOMPUTERPROGRAM FORRADIOWAVESINTHEIONOSPHERE v/FFICE4ELECOM2EPTn /CTOBER #*#OLEMAN h!GENERALPURPOSEIONOSPHERICRAY TRACINGPROCEDURE v$34/4ECHNICAL2EPORT 32, 42 *ARI 0ERKIMØKI h(IGH FREQUENCY (& IONOSPHERIC COMMUNICATIONS PROPAGATION ANALYSIS AND PREDICTION v6/!#!01UICK'UIDE HTTPWWWVOACAPCOM h!DVANCEDSTANDALONEPREDICTIONSYSTEM v)032ADIOAND3PACE3ERVICES 4HE!USTRALIAN3PACE 7EATHER!GENCY HTTPWWWIPSGOVAU0RODUCTS?AND?3ERVICES 02/0,!" 02/VERSION HTTPWWWSPACEWCOMWWWPROPLABHTML "42OOTAND*-(EADRICK h#OMPARISONOF2!$!2#(IGH FREQUENCYRADARPERFORMANCE PREDICTIONMODELAND2/4(2!MCHITKADATA v.AVAL2ES,AB2EPT.2,-2 *ULY
(&/6%2 4(% (/2):/.2!$!2
Óä°Ç
*-(EADRICK "42OOT AND*&4HOMASON h2!$!2#MODELCOMPARISONSWITH!MCHITKA RADARDATA v2ADIO3CIENCE VOL PPn -AYn*UNE h.EWWINDMODEL v(7- HTTPNSSDCFTPGSFCNASAGOVMODELSATMOSPHERICHWMHWMTXT *!3ECAN 2-"USSEY %*&REMOUW AND3A"ASU h!NIMPROVEDMODELOFEQUATORIAL SCINTILLATION v2ADIO3CIENCE n !6'UREVICH .ONLINEAR0HENOMENAINTHE)ONOSPHERE .EW9ORK3PRINGER 6ERLAG 6!!LEBASTROV !4-ALTSEV 6-/ROS !'3HLIONSKIY AND/)9ARKO h3OMECHARACTERISTICS OFECHOSIGNALS v4ELECOMMAND2ADIO%NG VOL PPn 6 ' 3OMOV 6! ,EUSENKO 6 .4YAPKIN AND '9A 3HAIDUROV h%FFECT OF NONLINEAR AND FOCUSING IONOSPHERIC PROPERTIES ON QUALITATIVE CHARACTERISTICS OF RADAR IN THE DECAMETRIC WAVE BAND v*#OMM4ECHNOLOGYAND%LECTRONICS VOL PPn )44 !VIONICS $IVISION %LECTRO 0HYSICS ,ABORATORIES %0, -ODEL !4, 4RANSMITTER FOR 2ADARAND#OMMUNICATION )2$0ROJECT2EPT 2ESULTSOFPERFORMANCEMEASUREMENTS *ANUARY $*(OFTAND&UAT!GI h3OLIDSTATETRANSMITTERSFORMODERNRADARAPPLICATIONS v#)%)NT2ADAR #ONF2ECORD "EIJING .OVEMBERn PPn &!2AAB 0!SBECK 3#RIPPS 0"+ENINGTON :"0OPOVIC .0OTHECARY *&3EVIC AND ./3OKAL h0OWERAMPLIFIERSANDTRANSMITTERSFOR2&ANDMICROWAVE v)%%%4RANS-ICROWAVE 4HEORAND4ECH VOL PPn -ARCH $*.ETHERWAYAND#ARSON #4 h)MPEDANCEANDSCATTERINGMATRICESOFAWIDEBAND(&PHASED !RRAY v*%LECTRON%NG!UST VOL PPn 'UEST EDITORIAL AND INVITED PAPERS IN SPECIAL ISSUE ON SHORTWAVE BROADCASTING )%%% 4RANS "ROADCAST VOL *UNE 2#*OHNSONAND(*ASIKEDS !NTENNA%NGINEERING(ANDBOOK RD%D .EW9ORK-C'RAW (ILL "OOK#OMPANY !'+URASHOVED 3HORTWAVE!NTENNAS %D IN2USSIAN 2ADIOISVYAZ *ANUARY 3*!NDERSON h,IMITSTOTHEEXTRACTIONOFINFORMATIONFROMMULTI HOPSKYWAVERADARSIGNALS v 0ROC)NT2ADAR#ONF !DELAIDE 3EPTEMBER PPn 3*!NDERSON h4HEDOPPLERSTRUCTUREOFDIFFUSELY SCATTEREDSKYWAVERADARECHOES v0ROC)NT 2ADAR#ONF 4OULOUSE /CTOBER 3*!NDERSON h4ARGETCLASSIFICATION RECOGNITIONANDIDENTIFICATIONWITH(&RADAR PROC.!4/ 2ESEARCHAND4ECHNOLOGY!GENCY v3ENSORSAND%LECTRONICS4ECHNOLOGY0ANEL3YMPOSIUM3%4 2392&4 @4!2'%4 )$%.4)&)#!4)/. !.$ 2%#/'.)4)/. 53).' 2& 3934%-3 /SLO .ORWAY /CTOBER %+7ALTONAND*$9OUNG h4HE/HIO3TATE5NIVERSITYCOMPACTRADARCROSSSECTIONMEASUREMENT RANGE v)%%%4RANS!NT0ROP VOL!0 PPn .OVEMBER ' * "URKE AND ! * 0OGGIO h.UMERICAL ELECTROMAGNETIC CODE NEC METHOD OF MOMENTS v ./3#4ECH$OC 27"OGLEAND$"4RIZNA h3MALLBOATRADARCROSSSECTIONS v.AVAL2ES,AB-EMO2EPT *ULY 2$INGER %.ELSON 3!NDERSON &%ARL AND-4YLER h(IGHFREQUENCYRADARCROSSSECTION MEASUREMENTS OF SURROGATE GO FAST BOATS IN $ARWIN !USTRALIA v 30!7!2 3YSTEM #ENTER4ECH 2EPT 3EPTEMBER 3 * !NDERSON h2EMOTE SENSING WITH THE *INDALEE 3KYWAVE 2ADAR v )%%% * /CEAN %NG VOL/% )) PPn !PRIL * 2 "ARNUM AND % % 3IMPSON h/VER THE HORIZON RADAR TARGET REGISTRATION IMPROVEMENT BY TERRAINFEATURELOCALIZATION v2ADIO3CIENCE VOL PP *ULYn!UGUST $ % "ARRICK * - (EADRICK 2 7 "OGLE AND $ $ #ROMBIE h3EA BACKSCATTER AT (& )NTERPRETATIONANDUTILIZATIONOFTHEECHO v0ROC)%%% VOL PPn *UNE 3/2ICE h2EFLECTIONOFELECTROMAGNETICWAVESFROMSLIGHTLYROUGHSURFACES vIN4HEORY OF %LECTROMAGNETIC 7AVES - +LINE ED .EW 9ORK )NTERSCIENCE 0UBLISHERS PPn
Óä°nä
2!$!2(!.$"//+
$ % "ARRICK h&IRST ORDER THEORY AND ANALYSIS OF -&(&6(& SCATTER FROM THE SEA v )%%% 4RANS VOL!0 PPn *ANUARY $ % "ARRICK h2EMOTE SENSING OF SEA STATE BY RADAR v #HAPTER IN 2EMOTE 3ENSING OF THE 4ROPOSPHERE 6%$ERRED "OULDER #/./!!%NVIRONMENTAL2ESEARCH,ABORATORIES PPn $ $ #ROMBIE h$OPPLER SPECTRUM OF THE SEA ECHO AT -CS v .ATURE VOL PPn *7-ARESCA *RAND*2"ARNUM h4HEORETICALLIMITATIONOFTHESEAONTHEDETECTIONOFLOW DOPPLERTARGETSBYOVER THE HORIZONRADAR v)%%%4RANS!NT0ROP VOL!0 PPn 7*0IERSONAND,-OSKOWITZ h!PROPOSEDSPECTRALFORMFORFULLYDEVELOPEDWINDSEAS BASED ON THE SIMILARITY THEORY OF 3! +ITAIGORDSKII v * 'EOPHYS 2ES VOL NO PPn + (ASSELMANN $ " 2OSS 0 -ULLER AND 7 3ELL h! PARAMETRIC WAVE PREDICTION MODEL v *0HYS/CEANOGR VOL PPn 4%LFOUHAILY "#HAPRON ++ATSAROS AND$6ANDEMARK h!UNIFIEDDIRECTIONALSPECTRUMFOR LONGANDSHORTWIND DRIVENWAVES v*'EOPHYS2ES VOL PPn !%,ONGAND$"4RIZNA h-APPINGOF.ORTH!TLANTICWINDSBY(&RADARSEABACKSCATTER INTERPRETATION v)%%%4RANS!NT0ROP VOL!0 PPn 3EPTEMBER ,27YATT h!RELAXATIONMETHODFORINTEGRALINVERSIONAPPLIEDTO(&RADARMEASUREMENTOFTHE OCEANWAVEDIRECTIONALSPECTRUM v)NT*2EMOTE3ENS VOL PPn !UGUST 9(ISAKI h.ONLINEARINVERSIONOFTHEINTEGRALEQUATIONTOESTIMATEOCEANWAVESPECTRAFROM(& RADAR v2ADIO3CIENCE VOL PPn .(ASHIMOTOAND-4OKUDA h!"AYESIANAPPROACHFORESTIMATIONOFDIRECTIONALWAVESPECTRA WITH(&RADAR v#OASTAL%NG* VOL PPn $%"ARRICK h%XTRACTIONOFWAVEPARAMETERSFROMMEASUREDHFRADARSEA ECHOSPECTRA v2ADIO 3CIENCE VOL NO P 4-'EORGES *!(ARLAN 22,EBEN AND2!,EMATTA h!TESTOFOCEANSURFACECUR RENT MAPPING WITH OVER THE HORIZON RADAR v )%%% 4RANS 'EOSCI AND 2EM 3ENS VOL PPn (,4OLMAN 7!6%7!4#())) .ATIONAL7EATHER3ERVICE HTTPPOLARNCEPNOAAGOVWAVES WAVEWATCHWAVEWATCHHTML *,!HEARN 32#URLEY *-(EADRICK AND$"4RIZNA h4ESTSOFREMOTESKYWAVEMEASURE MENTOFOCEANSURFACECONDITIONS v0ROC)%%% VOL PPn *UNE $ " 4RIZNA AND * - (EADRICK h)ONOSPHERIC EFFECTS ON (& OVER THE HORIZON RADAR v IN 'OODMAN *-ED 0ROC%FFECT)ONOSPHEREON2ADIOWAVE3YSTEMS /.2!&', SPONSORED !PRILn PPn *0ARENTAND!"OURDILLON h!-ETHODTOCORRECT(&SKYWAVEBACKSCATTEREDSIGNALSFORIONO SPHERICFREQUENCYMODULATION v)%%%4RANS!NT0ROP VOL!0 PPn 3 *!NDERSON AND 9)!BRAMOVICH h! UNIFIED APPROACH TO DETECTION CLASSIFICATION AND CORRECTIONOFIONOSPHERICDISTORTIONIN(&SKYWAVERADARSYSTEMS v2ADIO3CIENCE VOL PPn *ULYn!UGUST $"4RIZNA h%STIMATIONOFTHESEASURFACERADARCROSSSECTIONAT(&FROMSECOND ORDERDOPPLER SPECTRUMCHARACTERISTICS v.AVAL2ES,AB2EPT -AY 2/0ILONAND*-(EADRICK h%STIMATINGTHESCATTERINGCOEFFICIENTOFTHEOCEANSURFACEFOR HIGH FREQUENCYOVER THE HORIZONRADAR v.AVAL2ES,AB-EMO2EPT -AY **ONESAND0"ROWN h3PORADICMETEORRADIANTDISTRIBUTIONSORBITALSURVEYRESULTS v-ON.OT 2OY!STR3OC VOL PPn -!#ERVERAAND7'%LFORD h4HEMETEORRESPONSEFUNCTIONTHEORYANDAPPLICATIONTONAR ROWBEAM-34RADAR v0LANET3PACE3CI VOL PPn 0"ROWNAND**ONES h!DETERMINATIONOFTHESTRENGTHSOFTHESPORADICRADIO METEORSOURCES v %ARTH -OONAND0LANETS VOL PPn
(&/6%2 4(% (/2):/.2!$!2
Óä°n£
-!#ERVERA $!(OLDSWORTH )-2EID AND-4SUTSUMI h4HEMETEORRADARRESPONSEFUNC TION!PPLICATIONTOTHEINTERPRETATIONOFMETEORBACKSCATTERATMEDIUMFREQUENCY v*'EOPHYS 2ES VOL! PP 4 * %LKINS h! MODEL FOR HIGH FREQUENCY RADAR AURORAL CLUTTER v 2!$# 2EPT 42 -ARCH h7ORLD DISTRIBUTION AND CHARACTERISTICS OF ATMOSPHERIC RADIO NOISE v ##)2 2EPT ##)2 )NTERNATIONAL2ADIO#ONSULTATIVE#OMMITTEE )NTERNATIONAL4ELECOMMUNICATIONS5NION EDITIONS AND !$3PAULDINGAND*37ASHBURN h!TMOSPHERICRADIONOISE7ORLDWIDELEVELSANDOTHERCHAR ACTERISTICS v.4)!2EPT .ATIONAL4ELECOMMUNICATIONSAND)NFORMATION!DMINISTRATION !PRIL $,,UCASAND*$(ARPER h!NUMERICALREPRESENTATIONOF##)22EPORTHIGHFREQUENCY -CS ATMOSPHERICRADIONOISEDATA v.AT"UR3TAND.OTE !UGUST $"3AILORS h$ISCREPANCYINTHE)NTERNATIONAL2ADIO#ONSULTATIVE#OMMITTEE2EPORT RADIONOISEMODEL4HEPROBABLECAUSE v2ADIO3CIENCE VOL PPn "*.ORTHEYAND037HITHAM h!COMPARISONOF$34/AND$%2!(&BACKGROUND.OISE MEASURINGSYSTEMSWITHTHE)NTERNATIONAL2ADIO#ONSULTATIVE#OMMITTEE##)2 MODELDATA v $34/4ECHNICAL2EPORT$34/ 42 .OVEMBER - +OTAKI AND # +ATOH h4HE GLOBAL DISTRIBUTION OF THUNDERSTORM ACTIVITY OBSERVED BY THE IONOSPHERESATELLITE)33 B v*!TMOS4ERR0HYS VOL PPn # * #OLEMAN h! DIRECTION SENSITIVE MODEL OF ATMOSPHERIC NOISE AND ITS APPLICATION TO THE ANALYSISOF(&RECEIVINGANTENNAS v2ADIO3CIENCE VOL PPn 9U)!BRAMOVICH .+3PENCER AND3*!NDERSON h%XPERIMENTALSTUDYOFTHESPATIAL DYNAMICS OF ENVIRONMENTAL NOISE FOR A SURFACE WAVE /4(2 APPLICATION v 0ROC TH )NT #ONF(&2ADIO3YSTEMSAND4ECHNIQUES )%%#ONFERENCE0UBLICATIONNO 'UILDFORD 5+ *ULY PPn ,%3WEENEY h3PATIALPROPERTIESOFIONOSPHERICRADIOPROPAGATIONASDETERMINEDWITHHALF DEGREEAZIMUTHALRESOLUTION v3TANFORD%LECTRON,AB4ECH2EPT35 3%, 3TANFORD 5NIVERSITY *UNE * 4 ,YNCH h!PERTURE SYNTHESIS FOR (& RADIO SIGNALS PROPAGATED VIA THE & LAYER OF THE ION OSPHERE v 3TANFORD %LECTRON ,AB 4ECH 2EPT 35 3%, 3TANFORD 5NIVERSITY 3EPTEMBER $(3INNOTTAND'2(AACK h4HEUSEOFOVERLAPPEDSUBARRAYTECHNIQUESINSIMULTANEOUS RECEIVEBEAMARRAYS v0ROC!NTENNA!PPL3YMP 5NIVERSITYOF)LLINOIS 3*!NDERSON 9)!BRAMOVICH AND7 -"OERNER h-EASURINGPOLARIZATIONDYNAMICSOFTHE GENERALIZED(&SKYWAVECHANNELTRANSFERFUNCTION v0ROC)NT3YMP!NTAND0ROP )3!0 *APAN !UGUST 4(0EARCE h2ECEIVINGARRAYDESIGNFOROVER THE HORIZONRADAR v'%#*4ECHNOLOGY VOL PPn '&%ARLAND-*7HITINGTON h(&RADAR!$#DYNAMICRANGEREQUIREMENTS vRD)NT#ONFON !DVANCED!$AND$!#ONVERSION4ECHNIQUES *ULY '&%ARL h&-#7WAVEFORMGENERATORREQUIREMENTSFORIONOSPHERICOVER THE HORIZONRADAR v 2ADIO3CIENCE VOL PPn '&%ARL h2ECEIVINGSYSTEMLINEARITYREQUIREMENTSFOR(&RADAR v)%%%4RANS)NSTRUM-EAS VOL PPn '&%ARL 0#+ERR AND0-2OBERTS h/4(RADARRECEIVINGSYSTEMDESIGNUSINGSYNOPTIC (&ENVIRONMENTALDATABASE v0ROCTH)NT#ONF(&2ADIO3YSTEMSAND4ECHNIQUES *ULY PPn 3*!NDERSON h3IMULATIONANDMODELINGFORTHE*INDALEEOVER THE HORIZONRADAR v-ATHAND #OMPIN3IMULATION VOL PPn '&%ARL h#ONSIDERATIONOFRECIPROCALMIXINGIN(&/4(RADARDESIGN v0ROCTH)NT#ONF(& 2ADIO3YSTEMSAND4ECHNIQUES )%%#ONFERENCE0UBLICATIONNO *ULY PPn
Óä°nÓ
2!$!2(!.$"//+
'&%ARL h(&RADARRECEIVINGSYSTEMIMAGEREJECTIONREQUIREMENTS v0ROCTH)NT#ONF(& 2ADIO3YSTEMSAND4ECHNIQUES 3EPTEMBER PPn 4(0EARCE h#ALIBRATIONOFALARGERECEIVINGARRAYFOR(&RADAR v0ROC)NT#ONF(&2ADIO 3YSTEMSAND4ECHNIQUES )%%#ONFERENCE0UBLICATION.O *ULY PPn $ - &ERNANDEZ *6ESECKY AND #4EAGUE h#ALIBRATION OF (& RADAR SYSTEMS WITH SHIPS OF OPPORTUNITY v0ROCOFTHE)%%%)NT'EOSCIENCEAND2EMOTE3ENSING3YMP .EW9ORK *ULY PPn )3$3OLOMON $!'RAY 9)!BRAMOVICH AND3*!NDERSON h/VER THE HORIZONRADARARRAY CALIBRATIONUSINGECHOESFROMIONIZEDMETEORTRAILS v)%%0ROC2ADAR 3ONAR AND.AVIGATION VOL PPn *UNE )3$3OLOMON $!'RAY 9)!BRAMOVICH AND3*!NDERSON h2ECEIVERARRAYCALIBRATION USINGDISPARATESOURCES v)%%%4RANS!NT0ROP VOL PPn -ARCH ' * &RAZER AND 9 )!BRAMOVICH h1UANTIFYING MULTI CHANNEL RECEIVER CALIBRATION v $34/ 4ECHNICAL2EPORT$34/ 42 '*&RAZERAND3*!NDERSON h7IGNER 6ILLEANALYSISOF(&RADARMEASUREMENTSOFANACCELERAT INGTARGET v0ROCTH)NT3YMP3IGNAL0ROC!PPL "RISBANE !UGUST PPn 9 :HANG - ' !MIN AND ' * &RAZER h(IGH RESOLUTION TIME FREQUENCY DISTRIBUTIONS FOR MANEUVERING TARGET DETECTION IN OVER THE HORIZON RADARS v )%% 0ROC 2ADAR 3ONAR AND .AVIGATION VOL PPn 44HAYAPARAN AND 3 +ENNEDY h$ETECTION OF A MANEUVERING AIR TARGET IN SEA CLUTTER USING JOINTTIME FREQUENCYANALYSISTECHNIQUES v)%%0ROC2ADAR 3ONAR AND.AVIGATION VOL PPn &EBRUARY '*&RAZERAND3*!NDERSON h%STIMATINGTHEFREQUENCYINTERVALOFAREGULARLYSPACEDMULTI COMPONENTHARMONICLINESIGNALINCOLOREDNOISE vIN$EFENCE!PPLICATIONSOF3IGNAL0ROCESSING $!#OCHRAN "-ORAN AND,7HITEEDS .EW9ORK%LSEVIER PPn '&ABRIZIO ,3CHARF !&ARINA AND-4URLEY h3HIPDETECTIONWITH(&SURFACE WAVERADAR USINGSHORTINTEGRATIONTIMES v0ROC)NT#ONF2ADAR 4OULOUSE $/#ARHOUN *$2+RAMER*R AND0+2ASHOGI h!DAPTIVECANCELLATIONOFATMOSPHERIC NOISE AND IONOSPHERIC CLUTTER FOR HIGH FREQUENCY RADAR v -)42% 2EPORT -42 " 3EPTEMBER 9 )!BRAMOVICH 3 *!NDERSON !9 'OROKHOV AND . + 3PENCER h3TOCHASTICALLY CON STRAINEDSPATIALANDSPATIO TEMPORALADAPTIVEPROCESSINGFORNONSTATIONARYHOT CLUTTERCANCELLA TION vIN!PPLICATIONSOF3PACE TIME!DAPTIVE0ROCESSING 2++LEMMED ,ONDON3PRINGER PPn 9)!BRAMOVICH 3*!NDERSON !9'OROKHOV AND.+3PENCER h3TOCHASTICCONSTRAINTS METHODINNONSTATIONARYHOTCLUTTERCANCELLATION PART)&UNDAMENTALSANDSUPERVISEDTRAINING APPLICATIONS v)%%%4RANS!%3 VOL PPn /CTOBER 9)!BRAMOVICH 3*!NDERSON AND.+3PENCER h3TOCHASTIC CONSTRAINTSMETHODINNONSTA TIONARYHOTCLUTTERCANCELLATION PART))5NSUPERVISEDTRAININGAPPLICATIONS v)%%%4RANS!%3 VOL PPn *ANUARY 9)!BRAMOVICH 6.-IKHAYLYUKOV AND)0-ALYAVIN h3TABILISATIONOFTHEAUTOREGRESSIVE CHARACTERISTICSOFSPATIALCLUTTERSINTHECASEOFNONSTATIONARYSPATIALFILTERING v3OV*#OMMUN 4ECHNOL%LECTRON VOL PPn TRANSLATIONOF2ADIOTEKNIKA)%LECTRONIKA 2!NDERSON 3+RAUT AND*,+ROLIK h2OBUSTALTITUDEESTIMATIONFOROVER THE HORIZONRADARUSING ASTATE SPACEMULTIPATHFADINGMODEL v)%%%4RANS!%3 VOL PPn *ANUARY $*0ERCIVALAND+!"7HITE h-ULTIPATHCOORDINATEREGISTRATIONANDTRACKFUSIONFOROVER THE HORIZONRADAR vIN$EFENCE!PPLICATIONSOF3IGNAL0ROCESSING $!#OCHRAN "-ORAN AND ,7HITEEDS !MSTERDAM%LSEVIER PPn 9"AR 3HALOMAND4%&ORTMANN 4RACKINGAND$ATA!SSOCIATION .EW9ORK!CADEMIC0RESS *ANUARY 3"#OLEGROVEAND3*$AVEY h0$!&WITHMULTIPLECLUTTERREGIONSANDTARGETMODELS v)%%% 4RANS!%3 VOL PPn *ANUARY
(&/6%2 4(% (/2):/.2!$!2
Óä°nÎ
* , +ROLIK AND 2 (!NDERSON h-AXIMUM LIKELIHOOD COORDINATE REGISTRATION FOR OVER THE HORIZONRADAR v)%%%4RANS3IG0ROC VOL PPn -'2UTTENAND$*0ERCIVAL h*OINTIONOSPHERICANDTRACKTARGETSTATEESTIMATIONFORMULTIPATH OTHR TRACK FUSION v 0ROC 30)% #ONF ON 3IGNAL AND $ATA 0ROCESSING OF 3MALL4ARGETS PPn 2(!NDERSONAND*,+ROLIK h4RACKASSOCIATIONFOROVER THE HORIZONRADARWITHASTATISTICAL IONOSPHERICMODEL v)%%%4RANS3IG0ROC VOL PPn .OVEMBER '70ULFORD h/4(2MULTIPATHTRACKINGWITHUNCERTAINCOORDINATEREGISTRATION v)%%%4RANS !%3 VOL PPn 3*!NDERSON &*-EI AND*0EINAN h%NHANCED/4(2SHIPDETECTIONVIADUALFREQUENCY OPERATION v0ROC#HINA)NSTITUTEOF%LECTRONICS)NT#ONFON2ADAR "EIJING /CTOBER ' & %ARL AND " $ 7ARD h&REQUENCY MANAGEMENT SUPPORT FOR REMOTE SEA STATE SENSING USINGTHE*).$!,%%SKYWAVERADAR v)%%%*OF/CEANIC%NGR VOL/% PPn !PRIL '&%ARLAND"$7ARD h4HEFREQUENCYMANAGEMENTSYSTEMOFTHE*INDALEEOVER THE HORIZON BACKSCATTER(&RADAR v2ADIO3CIENCE VOL PPn 2"ARNES h!UTOMATEDPROPAGATIONADVICEFOR/4(2SHIPDETECTION v)%%0ROC2ADAR 3ONAR AND.AVIGATION VOL PPn &EBRUARY $,,UCAS *,,LOYD *-(EADRICK AND*&4HOMASON h#OMPUTERTECHNIQUESFORPLANNING ANDMANAGEMENTOF/4(RADARS v.AVAL2ES,AB-EMO2EPT 3EPTEMBER * - (EADRICK h(& OVER THE HORIZON RADAR v #HAPTER IN 2ADAR (ANDBOOK - ) 3KOLNIK ED ND%D .EW9ORK-C'RAW (ILL *-(UDNALLAND37$ER h(& /4(RADARPERFORMANCERESULTS v.AVAL2ES,AB4ECH2EPT .2,-2 2&ANTEAND3$HAR h!MODELFORTARGETDETECTIONWITHOVER THE HORIZONRADAR v)%%%4RANS !%3 VOL PPn *ANUARY ,! "ERRY AND - % #HRISMAN h! &/242!. PROGRAM FOR CALCULATION OF GROUND WAVE PROPAGATIONOVERHOMOGENEOUSSPHERICALEARTHFORDIPOLEANTENNAS v.AT"UR3TAND2EPT 3 2OTHERAM h'ROUND WAVE PROPAGATION PARTS AND v )%% 0ROC 0T & VOL PPn 3*!NDERSON 0*%DWARDS 0-ARRONE AND9)!BRAMOVICH h)NVESTIGATIONSWITH3%#!2 !BISTATIC(&SURFACEWAVERADAR v 0ROC)%%%)NT#ONFON2ADAR 2!$!2 !DELAIDE 3EPTEMBER $%"ARRICK h4HEORYOF(&AND6(&PROPAGATIONACROSSTHEROUGHSEA PTS)AND v2ADIO 3CIENCE VOL PPn -AY , 3EVGI #OMPLEX %LECTROMAGNETIC 0ROBLEMS AND .UMERICAL 3IMULATION !PPROACHES (OBOKEN .*)%%%0RESS 3*!NDERSON *0RASCHIFKA AND)-&UKS h-ULTIPLESCATTERINGOF(&RADIOWAVESPROPAGAT INGACROSSTHESEASURFACE v7AVESIN2ANDOM-EDIA VOL PPn !PRIL '(-ILLMANAND'.ELSON h3URFACEWAVE(&RADARFOROVER THE HORIZONDETECTION v0ROC )%%%)NT2ADAR#ONF PPn
#HAPTER
ÀÕ`Ê*iiÌÀ>Ì}Ê,>`>À >Û`Ê >ià %2!4ECHNOLOGY
Ó£°£Ê /," 1 /" 4HETERMSGROUNDPENETRATINGRADAR'02 GROUNDPROBINGRADAR SUBSURFACERADAR ORSURFACEPENETRATINGRADAR302 REFERTOARADAR BASEDELECTROMAGNETICTECHNIQUE DESIGNEDPRIMARILYFORTHELOCATIONOFOBJECTSORINTERFACESBURIEDBENEATHTHE%ARTHS SURFACEORLOCATEDWITHINAVISUALLYOPAQUESTRUCTURE'02ISASUCCESSFULEXAMPLEOF THEEXPLOITATIONOFULTRAWIDEBANDRADARANDTYPICALLYA'02WITHARANGEOFMWOULD OPERATEOVERTHERANGE'(ZTO'(Z !LTHOUGH'02HASMANYSIMILARITIESTORADARSYSTEMS THEREARESOMEKEYDIFFER ENCES WHICHNEEDTOBEAPPRECIATEDWHENCOMPARINGTHEMWITHCONVENTIONALRADAR SYSTEMS'02SYSTEMSAREASPECIALCLASSOFULTRAWIDEBAND57" RADARSYSTEMAND CANRADIATEENERGYINTHERANGEOFFREQUENCIESFROMAFEW-(ZUPTO'(ZWITHA BANDWIDTHOFUPTOADECADE BUTMOREUSUALLYnOCTAVES4HETYPICALAVERAGERADI ATEDPOWER INTEGRATEDOVERTHEBANDOFINTEREST MAYBEINTHEORDEROFAMILLIWATT BUT THEPOWERPER(ZMAYBEASLOWASPICOWATTS '02 IS USUALLY OPERATED SO THAT THE TARGET WHICH IS WITHIN A LOSSY DIELECTRIC IS ONLYAFEWWAVELENGTHSFROMTHEAPERTUREOFANTENNA4HETOTALPATHLOSSESWITHINA FEWWAVELENGTHSMAYREACHD"ORMOREDEPENDINGONTHEMATERIAL-ANY'02 SYSTEMSOPERATEINAREGIONWHERETHEWAVELENGTHSRADIATEDAREGREATERORINTHESAME ORDEROFMAGNITUDEASTHETARGETDIMENSIONS4HUS '02OPERATESBETWEENTHE2AYLEIGH REGIONAND-IEORRESONANCEREGIONOFTHETARGETDIMENSIONS4HISISVERYDIFFERENT FROMCONVENTIONALRADARSYSTEMSWHERETHETARGETDIMENSIONSAREMUCHLARGERTHANTHE WAVELENGTHOFTHEINCIDENTRADIATION IE THEOPTICALREGION 4HETECHNOLOGYOF'02ISLARGELYAPPLICATIONS ORIENTEDANDTHEOVERALLDESIGNPHI LOSOPHY ASWELLASTHEHARDWARE ISUSUALLYDEPENDENTONTHETARGETTYPEANDTHEMATE RIALOFTHETARGETANDITSSURROUNDINGS'02ISVULNERABLETOEXTREMELYHIGHLEVELSOF CLUTTERATSHORTRANGESANDTHIS RATHERTHANSIGNALNOISERECOVERY ISITSMAJORTECHNICAL CHALLENGE4HESYSTEMTOBESPECIFIEDSHOULDTAKETHISINTOACCOUNT!LLTHESEASPECTS POSESPECIALDESIGNPROBLEMSFOR'02 WHICHISDESCRIBEDINDETAILBY$ANIELS4HIS CHAPTERISASUMMARYOFTHATMATERIALANDISREFERENCEDBYCOURTESYOFTHE)%% !TYPICAL'02SYSTEMISSHOWNIN&IGUREANDCONSISTSOFAPAIROFANTENNAS ONEFORTRANSMITANDONEFORRECEIVE CONNECTEDTOTHETRANSMITTERRECEIVERANDPROCES SORANDCONTAINEDWITHINASEALEDENCLOSURE ABATTERYANDCONTROLPROCESSOR ANDDIS PLAYUNIT4HEWHEELSDRIVEASHAFTENCODERTHATTRIGGERSDATAACQUISITIONANDHENCETHE DISPLAYTHATISSYNCHRONISEDTOTHEMOVEMENTOFTHESYSTEM!NEXAMPLEOFTHEDISPLAY Ó£°£
Ó£°Ó
2!$!2(!.$"//+
&)'52% 4YPICAL'02SYSTEM#OURTESY532ADAR
WHICHTAKESTHEFORMOFACROSSSECTIONOFTHEGROUNDSURVEYEDBYTHE'02 ISSHOWN IN&IGURE4HEHORIZONTALSCALEISCMPERMARKERANDTHEVERTICALSCALEISTIME INNANOSECONDSNS !NEXPLANATIONOFTHEIMAGEISPROVIDEDLATERINTHISCHAPTER '02SYSTEMDESIGNCANBECLASSIFIEDINTOTWOGROUPS'02SYSTEMSTHATTRANSMITAN IMPULSEANDRECEIVETHEREFLECTEDSIGNALFROMTHETARGETUSINGASAMPLINGRECEIVERCAN BECONSIDEREDTOOPERATEINTHETIMEDOMAIN'02SYSTEMSTHATTRANSMITINDIVIDUALFRE QUENCIESINASEQUENTIALMANNERANDRECEIVETHEREFLECTEDSIGNALFROMTHETARGETUSINGA FREQUENCYCONVERSIONRECEIVERCANBECONSIDEREDTOOPERATEINTHEFREQUENCYDOMAIN 4HEFIRSTUSEOFELECTROMAGNETICSIGNALSTODETERMINETHEPRESENCEOFREMOTETERRES TRIALMETALOBJECTSISGENERALLYATTRIBUTEDTO(ÓLSMEYERIN BUTTHEFIRSTDESCRIPTION OFTHEIRUSEFORLOCATIONOFBURIEDOBJECTSAPPEAREDSIXYEARSLATERINA'ERMANPATENT BY,EIMBACHAND,WY4HEWORKOF(ÓLSENBECKINAPPEARSTOBETHEFIRSTUSE OFPULSEDTECHNIQUESTODETERMINETHESTRUCTUREOFBURIEDFEATURES(ENOTEDTHATANY
&)'52% 4YPICALDISPLAYFROM'02
'2/5.$0%.%42!4).'2!$!2
Ó£°Î
DIELECTRICVARIATION NOTNECESSARILYINVOLVINGCONDUCTIVITY WOULDALSOPRODUCEREFLEC TIONSANDTHATTHETECHNIQUE THROUGHTHEEASIERREALIZATIONOFDIRECTIONALSOURCES HAD ADVANTAGESOVERSEISMICMETHODS0ULSEDTECHNIQUESWEREDEVELOPEDFROMTHES ONWARDASAMEANSOFPROBINGTOCONSIDERABLEDEPTHSINICE3TEENSONAND%VANS IN FRESH WATER AND SALT DEPOSITS 5NTERBERGER IN DESERT SAND AND ROCK FORMATIONS +ADABAAND-OREY 0ROBINGOFROCKANDCOALWASALSOINVESTIGATEDBY#OOK AS WELLAS2OE ALTHOUGHTHEHIGHERATTENUATIONINTHELATTERMATERIALMEANTTHATDEPTHS GREATERTHANAFEWMETERSWEREIMPRACTICAL.ILSSONGIVESAMOREEXTENDEDACCOUNT OFTHEHISTORYOF'02ANDITSGROWTHUPTOTHEMID S&ROMTHES THERANGEOF APPLICATIONSHASBEENEXPANDINGSTEADILY ANDNOWINCLUDESTHOSEGIVENIN4ABLE 0URPOSE BUILTEQUIPMENTFOREACHOFTHESEAPPLICATIONSHASBEENBEINGDEVELOPED AND THEUSERNOWHASABETTERCHOICEOFEQUIPMENTANDTECHNIQUES '02HASADVANCEDRAPIDLYASARESULTOFAVARIETYOFAPPLICATIONS BUTASTHEREQUIRE MENTSHAVEBECOMEMOREDEMANDING SOTHEEQUIPMENT TECHNIQUES ANDDATAPROCESS INGMETHODSHAVEBEENDEVELOPEDANDREFINED ! '02 TRANSMITS A REGULAR SEQUENCE OF LOW POWER PULSES OF ELECTROMAGNETIC ENERGYINTOTHEMATERIALORGROUNDANDTHENRECEIVESANDDETECTSTHEWEAKREFLECTED SIGNALFROMTHEBURIEDTARGET4HEENERGYISINTHEFORMOFEITHERAVERYSHORTDURA TIONIMPULSE ASWEEPOVERARANGEOFFREQUENCIES RADIATIONOFNOISEOVERADEFINED BAND ORAPSEUDORANDOMCODEDSEQUENCEOFPULSES-OST'02SYSTEMS ALLOFWHICH NEED TO COMPLY WITH THE RELEVANT NATIONAL AND INTERNATIONAL REGULATIONS REGARDING RADIOTRANSMITTERS OPERATEWITHINTHERANGEOFFREQUENCIESFROM-(ZTO'(Z ANDCANHAVEABANDWIDTHOFSEVERAL'(Z4HE&##REQUIREMENTFOR57"LIMITS THERADIATEDPOWERTOnD"M(Zn4HETOPICOFRADARSYSTEMDESIGNISCOVERED IN MANY TEXTS AND USEFUL INFORMATION WILL BE FOUND IN THE FOLLOWING REFERENCES $ANIELS #OOK AND "ERNFELD 3KOLNIK .ATHANSON 7EHNER 'ALATI AND !STANINAND+OSTYLEV 4HEBURIEDTARGETCANBEACONDUCTOR ADIELECTRIC ORCOMBINATIONSOFBOTH4HE SURROUNDINGHOSTMATERIALCANBESOIL EARTHMATERIALS WOOD ROCKS ICE FRESHWATER OR MANMADEMATERIALSSUCHASCONCRETEORBRICK!TYPICAL'02ACHIEVESARANGEOFUPTO AFEWMETERS BUTSOMESPECIALSYSTEMSCANPENETRATEUPTOHUNDREDSOFMETERSOREVEN KILOMETERS!FEW'02SYSTEMSHAVEBEENOPERATEDFROMAIRCRAFTANDFROMSATELLITES TOIMAGEGEOLOGICALFEATURESBURIEDBENEATHTHE3AHARANDESERTSASWELLASMEASURING THEDEPTHOFTHE-OONANDFEATURESON-ARSORCOMETS4HERANGEOFTHE'02INTHE GROUNDISLIMITEDBECAUSEOFTHEABSORPTIONTHESIGNALUNDERGOES WHILEITTRAVELSON ITSTWO WAYPATHTHROUGHTHEGROUNDMATERIAL'02WORKSWELLTHROUGHMATERIALSSUCH ASGRANITE DRYSAND SNOW ICE ANDFRESHWATER BUTWILLNOTPENETRATECERTAINCLAYSTHAT
4!",% -AIN!PPLICATIONSOF'02
!RCHAEOLOGICALINVESTIGATIONS "RIDGEDECKANALYSIS $ETECTIONOFBURIEDMINESANTI PERSONNELANDANTI TANK &ORENSICINVESTIGATIONSDETECTINGBURIEDBODIES 'EOPHYSICALINVESTIGATIONS 0IPESANDCABLEDETECTION 2AILTRACKANDBEDINSPECTION 2OADCONDITIONSURVEY 3NOW ICE ANDGLACIER
Ó£°{
2!$!2(!.$"//+
AREHIGHINSALTCONTENTORSALTWATERBECAUSEOFTHEHIGHABSORPTIONOFELECTROMAGNETIC ENERGYOFSUCHMATERIALS&ORCOMPARISON THETOTALTWO WAYPATHLOSSFROM%ARTHTO THE-OONUSINGA'(ZRADARWOULDBEGREATERTHAND"FORARANGEOF KMANDATARGETRADARCROSSSECTIONINTHEORDEROFM WHEREASA'02RADAROFTEN ENCOUNTERSAPATHLOSSINEXCESSOFD"FORRANGESOFLESSTHANAMETER )NAIR THE'02SIGNALTRAVELSATTHESPEEDOFLIGHT BUTISSLOWEDDOWNINGROUND MATERIALS BY THEIR DIELECTRIC CONSTANT HENCE TRUE RANGE NEEDS CALIBRATING FOR EACH MATERIAL'02WILLNOTPENETRATEMETALBECAUSEOFTHELATTERSCONDUCTIVITY 4HEREARENOWANUMBEROFCOMMERCIALLYAVAILABLEEQUIPMENTS ANDTHETECHNIQUE ISGRADUALLYDEVELOPINGINSCOPEANDCAPABILITY-ANY'02SYSTEMSAREMOBILEAND MOUNTEDONWHEELSORSKIDSTOBEMOVEDBYHAND BUTSYSTEMSCANBEUSEDONVEHICLES FORRAPIDSURVEYBYMEANSOFANARRAYOFANTENNAS/THER'02SYSTEMSAREDESIGNED TOBEINSERTEDINTOBOREHOLESTOPROVIDEIMAGESOFTHEINTERVENINGROCK4YPICAL'02 SYSTEMATTRIBUTESAREGIVENIN4ABLE -OST '02 SYSTEMS USE SEPARATE MAN PORTABLE TRANSMIT AND RECEIVE ANTENNAS WHICHAREPLACEDONTHESURFACEOFTHEGROUNDANDMOVEDINAKNOWNPATTERNOVERTHE SURFACEOFTHEGROUNDORMATERIALUNDERINVESTIGATION ANDANIMAGECANBEGENERATED INREALTIME ONADISPLAYEITHERINGREYSCALEORINCOLOR"YSYSTEMATICALLYSURVEYING THEAREAINAREGULARGRIDPATTERN ARADARIMAGEOFTHEGROUNDCANBEBUILTUP'02 IMAGES ARE DISPLAYED EITHER AS TWO DIMENSIONAL REPRESENTATIONS USING HORIZONTAL XORY ANDDEPTHZ AXESORAHORIZONTALPLANEREPRESENTATIONX Y ATAGIVENDEPTH Z ORASATHREE DIMENSIONALRECONSTRUCTION'02DATAMAYBECLASSIFIEDAS! SCAN " SCAN OR# SCANDEPENDINGONTHEPLANEOFIMAGENOTETHESEARENOTTHESAMEAS CONVENTIONALRADAR! " AND#SCANS !'02! SCANISAMEASUREMENTATASINGLE FIXEDPOINTINSPACEANDISDISPLAYEDINAMPLITUDEY ANDRANGEX !" SCANISA REPRESENTATIONUSUALLYINGRAYSCALEORCOLOR CODEDIMAGEINTENSITYOFAPLANEX ZOR Y Z OFSCANWHEREASA# SCANREPRESENTSAHORIZONTALPLANEX Y ATAGIVENDEPTH Z !LTERNATIVELY THE'02MAYBEDESIGNEDTOPROVIDEANAUDIBLEWARNINGOFTARGET PRESENCEWHILETHE'02ISMOVED 4HE '02 IMAGE OF A TARGET IS VERY DIFFERENT FROM ITS OPTICAL IMAGE BECAUSE THE WAVELENGTHSOFTHEILLUMINATINGRADIATIONARESIMILARINDIMENSIONTOTHETARGET4HIS RESULTSINAMUCHLOWERDEFINITIONINTHE'02IMAGEANDONETHATISHIGHLYDEPENDENT ONTHEPROPAGATIONCHARACTERISTICSOFTHEGROUND4HEBEAMPATTERNOFTHEANTENNAIS WIDELYSPREADINTHEDIELECTRICANDTHISDEGRADESTHESPATIALRESOLUTIONOFTHEIMAGE UNLESS CORRECTED 2EFRACTION AND ANISOTROPIC CHARACTERISTICS OF THE GROUND MAY ALSO DISTORTTHEIMAGE&ORSOMELONGER RANGESYSTEMS SYNTHETICAPERTUREPROCESSINGTECH NIQUESAREUSEDTOOPTIMIZETHERESOLUTIONOFTHEIMAGEANDWILLBEDISCUSSEDLATER 4!",% #HARACTERISTICSOF'023YSTEMSINA3OILOF2ELATIVE$IELECTRIC#ONSTANTOFAND
,OSS4ANGENTOF 0ULSE$URATIONINNS
#ENTER&REQUENCYIN-(Z
2ANGEIN-ETERS
$EPTH2ESOLUTION
'2/5.$0%.%42!4).'2!$!2
Ó£°x
5NPROCESSED '02 IMAGES OFTEN SHOW hBRIGHT SPOTSv CAUSED BY MULTIPLE INTER NALREFLECTIONSASWELLASADISTORTIONOFTHEASPECTRATIOOFTHEIMAGEOFTHETARGET CAUSED BY VARIATIONS IN THE VELOCITY OF PROPAGATION 3YMMETRICAL TARGETS SUCH AS SPHERESORPIPES CAUSEMIGRATIONOFTHEREFLECTEDENERGYTOAHYPERBOLICPATTERN'02 IMAGESCANBEPROCESSEDTOCOMPENSATEFORTHESEEFFECTS ANDTHISISUSUALLYCARRIED OUTOFFLINE!'02CANBEDESIGNEDTODETECTSPECIFICTARGETSSUCHASINTERFACESIN ROADS PIPES ANDCABLESBYMEANSOFPOLARIZEDRADIATIONANDLOCALIZEDOBJECTSSUCH ASCUBES SPHERES ANDCYLINDERS'02ISCAPABLEOFDETECTINGFEATURESMANYHUNDREDS OFYEARSOLDHENCE APROSPECTIVESITESHOULDREMAINUNEXCAVATED PRIORTOSURVEY SO ASTOPRESERVEITSINFORMATION ! SIMPLIFIED DIAGRAM OF THE VARIOUS SOURCES OF CLUTTER IN A '02 ENVIRONMENT IS GIVENIN&IGURE ANDITCANBESEENTHATSEPARATIONOFTHEVARIOUSSIGNALSISTHEKEY TOIDENTIFYINGTHEWANTEDSIGNAL )NEVITABLYTHEREHAVEBEENSOMECLAIMSFOR'02CAPABILITYTHATARESIMPLYOUT SIDETHEREALMSOFKNOWNPHYSICS ANDTHESESEEMTOHAVEBEENSEIZEDONBYSOME SECTIONS OF THE MEDIA! CLAIM WAS MADE THAT A PARTICULAR '02 AND ITS OPERATOR COULD DETECT TARGETS THE SIZE OF GOLF BALLS AT A DEPTH OF EIGHT METERS #LEARLY THE WAVELENGTHSCAPABLEOFPROPAGATINGTOEIGHTMETERSINSOILWOULDBESOMUCHLARGER THANAGOLFBALLnSIZEDTARGETTHATTHERADARCROSS SECTIONALAREAOFTHELATTERWOULD FADEINTOINSIGNIFICANCE EVENNOISE4HEPERSUASIVENESSOFTHECLAIMANTANDTHELACK OFUNDERSTANDINGOFBASICPHYSICSONTHEPARTOFSOMEPOTENTIALUSERSENABLEDTHIS KINDOFCLAIMTOBESERIOUSLYCONSIDERED#LAIMSWEREMADETHATA'02HADBEEN DEVELOPEDhTHATCANPROVIDETHREE DIMENSIONALIMAGESOFOBJECTSUPTOMETERS BELOWTHESURFACEOFLANDANDSEA3UCHADEVICEWOULDALLOWVERIFIERSTOIDENTIFY UNDERGROUND WEAPONS FACILITIES LIKE THOSE OF CONCERN IN ,IBYA )RAQ AND .ORTH +OREA 4HE UNDERWATER DETECTION CAPABILITY COULD ALSO BE USED TO VERIFY TREATIES DEALINGWITHSUBMARINESANDNUCLEARWEAPONSPOSITIONEDONTHESEABEDv(OWWELL
&)'52% 'ENERALSYSTEMOPERATIONOF'02SHOWINGTARGETSANDSOURCESOFCLUTTER#OURTESY)%%
Ó£°È
2!$!2(!.$"//+
'02WOULDPROPAGATETHROUGHSEAWATERISANINTERESTINGQUESTIONGIVENTHEKNOWN ATTENUATIONOFSEAWATERATRADARFREQUENCIES!CAREFULANALYSISOFSOMEOFTHECLAIMS ABOUTTHESAMERADARWASPUBLISHEDBY4ULEYANDISINTERESTINGREADING
Ó£°ÓÊ *9- -Ê"Ê*,"*/" Ê Ê / , )NTRODUCTION #ONVENTIONALRADARSYSTEMSAREGENERALLYNOTSIGNIFICANTLYAFFECTED BYTHEPROPAGATIONCHARACTERISTICSOFTHEMEDIUMTHERADARSIGNALSTRAVELTHROUGH APART FROMRAIN ABSORPTIONSPECTRAOFTHEATMOSPHERE ORIONIZEDATMOSPHERICLAYERS4HISIS DEFINITELYNOTTHECASEWITH'02WHERETHETRANSMISSIONMEDIUMMAYBENON ISOTRO PIC HIGHDIELECTRICANDHIGHLOSS ANDMAYBELAYERED4HEREFORE ANUNDERSTANDINGOF SOILANDMATERIALPROPAGATIONCHARACTERISTICSISIMPORTANT ANDTHISSECTIONDESCRIBES THEKEYFEATURESOFTHEPHYSICSOFPROPAGATIONINMATERIALS -AXWELLSEQUATIONSARETHEFOUNDATIONFORTHECONSIDERATIONOFTHEPROPAGATIONOF ELECTROMAGNETICWAVES)NFREESPACE THEMAGNETICSUSCEPTIBILITYANDELECTRICPERMITTIVITY ARECONSTANTS THATIS THEYAREINDEPENDENTOFFREQUENCYANDTHEMEDIUMISNOTDISPERSIVE )NADIELECTRICWITHAZEROLOSSTANGENT NOLOSSESDUETOATTENUATIONAREENCOUNTERED AND HENCETHEREISNOCONSIDERATIONOFTHEATTENUATION WHICHOCCURSINREALDIELECTRICMEDIA )FANALTERNATINGELECTRICFIELDISAPPLIEDTOAMATERIAL THEINDIVIDUALMOLECULESWILL BEINDUCEDTOROTATEINANOSCILLATORYMANNERABOUTANAXISTHROUGHTHEIRCENTERS THE INERTIA OF THE MOLECULES PREVENTING THEM FROM RESPONDING INSTANTANEOUSLY 3IMILAR TRANSLATIONALEFFECTSCANOCCUR4HEPOLARIZATIONPRODUCEDBYANAPPLIEDFIELDSUCHAS APROPAGATINGRADARWAVE ISCLOSELYRELATEDTOTHETHERMALMOBILITYOFTHEMOLECULES ANDIS THEREFORE STRONGLYTEMPERATUREDEPENDENT.OTETHATPOLARIZATIONINTHISCONTEXT ISDIFFERENTFROMTHEPOLARIZATIONOF%-WAVES)NGENERAL THERELAXATIONTIMEWHICH MAYBEEXPRESSEDASARELAXATIONFREQUENCY DEPENDSONACTIVATIONENERGY THENATURAL FREQUENCY OF OSCILLATION OF THE POLARIZED PARTICLES AND ON TEMPERATURE 2ELAXATION FREQUENCIESVARYWIDELYBETWEENDIFFERENTMATERIALS &OREXAMPLE MAXIMUMABSORPTIONOCCURSATVERYLOWFREQUENCIESINICE(Z WHEREASITTAKESPLACEINTHEMICROWAVEREGIONINWATER(Zn(Z THUS THE EFFECTSOFTHISPHENOMENONCANHAVEADIRECTBEARINGUPONTHEDIELECTRICPROPERTIES OFMATERIALSATTHEFREQUENCIESEMPLOYEDBY'02S ESPECIALLYIFMOISTUREISPRESENT WITHINAMATERIAL4HEREAREANUMBEROFOTHERMECHANISMS WHICHCAUSEASEPARA TIONOFPOSITIVELYANDNEGATIVELYCHARGEDIONSRESULTINGINELECTRICPOLARIZATION4HESE MECHANISMSCANBEASSOCIATEDWITHIONICATMOSPHERESSURROUNDINGCOLLOIDALPARTICLES PARTICULARLY CLAY MINERALS ABSORBED WATER AND PORE EFFECTS AS WELL AS INTERFACIAL PHENOMENONBETWEENPARTICLES 4HEGENERALFORMOFTHEMODELTHATDESCRIBESTHEFREQUENCYDEPENDENCEOFSUCH SYSTEMSISTHE$EBYERELAXATIONEQUATION
E ` I E `` E c
E S Ec
IWT
WHERE
D `ISTHEREALPARTOFTHEDIELECTRICPERMITTIVITY D ` REALPARTOFTHEDIELECTRICPERMITTIVITY D p IMAGINARYPARTOFTHEDIELECTRICPERMITTIVITY D c HIGHFREQUENCYLIMITINGVALUEOFTHEPERMITTIVITY
'2/5.$0%.%42!4).'2!$!2
Ó£°Ç
D S LOWFREQUENCYLIMITINGVALUEOFTHEPERMITTIVITY V RADIANFREQUENCY OF S RELAXATIONTIMECONSTANT
4HEFREQUENCYOFMAXIMUMMOVEMENTANDLOSSOCCURSATV S )N GENERAL SINGLE RELAXATIONS ARE RARELY OBSERVED IN NATURAL SYSTEMS )NSTEAD THERE ARE DISTRIBUTIONS OF RELAXATIONS CORRESPONDING TO DISTRIBUTIONS OF SIZE SCALES THAT INFLUENCE MOVEMENT OF CHARGE 4HERE ARE SEVERAL EQUATIONS DESCRIBING SUCH DISTRIBUTEDSYSTEMS WITHTHEMOSTCOMMONEXPERIMENTALOBSERVATIONSINAGREEMENT WITHTHEMODELFROM#OLEAND#OLE
E ` I E `` E c
E S Ec
IWT A
WHERE@DESCRIBESTHEBREADTHOFTHETIMECONSTANTDISTRIBUTIONFROMASINGLERELAXATION @ TOANINFINITELYBROADDISTRIBUTION @ WITHACOMMONPROCESS$IFFERENT POLARIZATIONPROCESSESMAYBEDESCRIBEDBYASERIESOF#OLE #OLEEQUATIONSWITHDIF FERENTVALUESOF@ANDOTHERPARAMETERS 4HEELECTROMAGNETICPROPERTIESOFABURIEDTARGETMUSTBEDIFFERENTFROMTHESUR ROUNDINGSOILORMATERIAL ANDTHISMEANSTHATTOAFIRSTORDERITSRELATIVEDIELECTRICCON STANTSHOULDBESIGNIFICANTLYLESSERORGREATERTHANTHEHOSTSOIL4YPICALLY MOSTSOILS EXHIBITARELATIVEDIELECTRICCONSTANT WHICHRANGESBETWEENTO&RESHWATERHAS ARELATIVEDIELECTRICCONSTANTOFAPPROXIMATELY)TSHOULDBENOTEDTHATTHEGROUND ANDSURFACEAREQUITELIKELYTOBEINHOMOGENEOUSANDCONTAININCLUSIONSOFOTHERROCKS OFVARIOUSSIZEASWELLASMANMADEDEBRIS4HISSUGGESTSTHATTHESIGNALTOCLUTTERPER FORMANCEOFTHESENSORISLIKELYTOBEANIMPORTANTPERFORMANCEFACTOR#LUTTERMAYBE REGARDEDASANYRADARRETURNTHATISNOTASSOCIATEDWITHTHEWANTEDTARGETANDNEEDSTO BEDEFINEDWITHRESPECTTOAPARTICULARAPPLICATION !TTENUATION %LECTROMAGNETICWAVESPROPAGATINGTHROUGHNATURALMEDIAEXPERI ENCELOSSES TOBOTHTHEELECTRIC% ORMAGNETIC( FIELDS4HISCAUSESATTENUATION OFTHEORIGINALELECTROMAGNETICWAVE0LANEWAVESAREGOODAPPROXIMATIONSTOREAL WAVES IN MANY PRACTICAL SITUATIONS -ORE COMPLICATED ELECTROMAGNETIC WAVEFRONTS CANBECONSIDEREDASASUPERIMPOSITIONOFPLANEWAVES ANDTHISMETHODMAYBEUSED TOGAINANINSIGHTINTOMORECOMPLEXSITUATIONS&ORMOSTSOILSOFINTERESTIN'02 THE MAGNETICRESPONSEISWEAKANDNEEDNOTBECONSIDEREDASACOMPLEXQUANTITY UNLIKE THEPERMITTIVITYANDCONDUCTIVITY(OWEVER INCERTAINSOILTYPES SUCHASTHOSEDERIVED FROMVOLCANICROCKSOROTHERWISEHIGHINIRONCONTENT FULLCONSIDERATIONOFTHEMAG NETICPROPERTIESISNECESSARY)NTHECASEOFLOSSYDIELECTRICMATERIALS BOTHCONDUCTION ANDDIELECTRICEFFECTSCAUSEABSORPTIONOFELECTROMAGNETICRADIATION 4HEELECTROMAGNETICMATERIALPROPERTIESTHATDESCRIBESUCHASYSTEMAREINTHECOM PLEXPROPAGATIONCONSTANTF
G IK A IA
WHEREF PROPAGATIONCONSTANT
K WAVENUMBEROK
@ ATTENUATIONCONSTANT;NEPERSM=
A PHASECONSTANT;RADIANSM=
Ó£°n
2!$!2(!.$"//+
4HEFIELDATADISTANCEZFROMTHESOURCEISGIVENBY % Z T % E A Z E J W T A Z
4HEWAVELENGTH K INTHEMEDIUMISINMETERS
L
P V A F
WHEREFISFREQUENCYIN(ERTZ 4HE LOSSES IN SUCH SYSTEMS ARE DESCRIBED IN TERMS OF TANGENTS OF LOSS ANGLES C BETWEENELECTRICANDMAGNETICFIELDS4HEELECTRICALLOSSTANGENTISGIVENBY
E `` S S TAN D E WHICHCANBESIMPLIFIEDTOTAN D E y FORLOWLOSSMATERIALS E` WE` WE`
REPRESENTINGTHESUMOFTHECHARGETRANSPORTANDPOLARIZATIONRELAXATIONLOSSES ANDTHE PHASEANGLEBETWEENELECTRICFIELDANDCURRENTDENSITY4HESKINDEPTHORATTENUATION LENGTHIS@;M=THEDISTANCEELECTROMAGNETICENERGYTRAVELSWHILEBEINGATTENUATED BYEINAMPLITUDE4HISDISTANCEISKNOWNASTHESKINDEPTH D ANDPROVIDESANINITIAL GUIDETOTHEUSEFULPENETRATIONDEPTHOFA'02SYSTEMALTHOUGHINSOMEMEDIATHE USEFULRANGEMAYBEGREATER 4HEINDIVIDUALPROPAGATIONCONSTANTSCANBEWRITTENAS
WHERE
§ ME ` ¶ ¤ E ``³ A W ¨ ¥ ´ · A W ¦ E` µ ¨ · © ¸
§ ME ` ¶ ¤ E ``³ ¨ ¥ ´ · ¦ E` µ ¨ · © ¸
@ ATTENUATIONFACTOR A PHASECONSTANT
ANDTHEDIMENSIONLESSFACTORD pD `ISMORECOMMONLYTERMEDTHEMATERIALLOSSTANGENT 4HISDISCUSSIONHASNOTCONSIDEREDTHEELECTROMAGNETICANDMAGNETICLOSSTANGENT ANDTHESEMAYNEEDTOBECONSIDEREDINSPECIALCASES )TCANBESEENFROMTHEABOVEEXPRESSIONSTHATTHEATTENUATIONCONSTANTOFAMATE RIALIS TOAFIRSTORDER LINEARLYRELATEDIND"Mn TOFREQUENCY)TISNOTSUFFICIENTTO CONSIDERONLYTHELOWFREQUENCYCONDUCTIVITYWHENATTEMPTINGTODETERMINETHELOSS TANGENTOVERTHEFREQUENCYRANGETO(Z)NTHECASEOFAMATERIALTHATISDRY ANDRELATIVELYLOSSLESS ITMAYBEREASONABLETOCONSIDERTHATTANCEISCONSTANTOVERTHAT FREQUENCYRANGE(OWEVER FORMATERIALSTHATAREWETANDLOSSYSUCHANAPPROXIMATION ISINVALID(OWEVER THEREAREANUMBEROFOTHERFACTORSTHATINFLUENCETHEEFFECTIVE PENETRATIONDEPTH NOTABLYTHESTRENGTHOFREFLECTIONFROMTHETARGETSOUGHT ANDTHE DEGREEOFCLUTTERSUPPRESSIONOFWHICHTHESYSTEMISCAPABLE !FIRSTORDERESTIMATEOFTHEVARIOUSCONTRIBUTIONSTOSIGNALLOSSCANBECARRIEDOUT USINGTHESTANDARDRADARRANGEEQUATION ALTHOUGHTHISISONLYAPPLICABLEFORFAR FIELD CONDITIONSANDTHUSHASRESTRICTIONS
0R
0T !'S K A 2
E P 2
'2/5.$0%.%42!4).'2!$!2
Ó£°
WHERE
0 T 0R ! ' 2 @ K
TRANSMITTEDPOWERINWATTS RECEIVEDPOWERINWATTS ANTENNAGAIN ANTENNAEFFECTIVEAPERTURE RANGEINMETERS TARGETRADARCROSSSECTION CALIBRATIONCOEFFICIENT
4HECUMULATIVELOSSESINCLUDETHETRANSMISSIONCOEFFICIENTSINTOTHEGROUNDTHE SPREADING LOSSES DESCRIBE THE 2n LOSSES FOR A TARGET OF M AND THE ATTENUATION LOSSESAREFORASOILWITHADROFANDTANCOF&IXEDLOSSESINCLUDETHETRANS MISSIONLOSSESINTOTHESOILANDTHEEFFECTIVERADARCROSSSECTIONOFTHETARGET WHICH COMPRISESITSTRUERADARCROSSSECTIONANDREFLECTIONLOSSFROMTHETARGET.OTETHAT ACONDUCTINGREFLECTORWILLHAVELOWRETURNLOSSWHEREASANONCONDUCTINGREFLECTOR WILLHAVEAHIGHRETURNLOSS)N&IGURE THECALCULATIONHASBEENDERIVEDFROM METER TO METERS AS THE RADAR RANGE EQUATION IS NOT AN ACCURATE MODEL IN THIS RANGE LESS THAN METER AND THE PURPOSE OF THE EXPLANATION IS TO PROVIDE A BASIC INTRODUCTIONTOFIRSTORDERSIGNALESTIMATION
#
2EFLECTION )NANYESTIMATIONOFRECEIVEDSIGNALLEVEL ITISNECESSARYTOCONSIDER THECOEFFICIENTSOFREFLECTIONANDTRANSMISSION ASTHEWAVEPASSESTHROUGHTHEDIELECTRIC TOTHETARGETAND3NELLS,AWSDESCRIBETHEASSOCIATEDANGLESOFINCIDENCE REFLECTION TRANSMISSION ANDREFRACTION7HERELOSSYMATERIALSAREINVOLVED COMPLEXANGLESOF REFRACTIONMAYOCCURUNLIKETHESIMPLECLASSICALCASE ANDPOLARIZATIONANDTHE3TOKES MATRIXMAYALSOBEREQUIREDFORORIENTEDHIGH ASPECTRATIOFEATURESLIKEPIPES WIRES ANDFRACTURES
$
!
!! "!
&)'52% ,OSSESFOR'02SIGNALVERSUSRANGE#OURTESY)%%
"!!
Ó£°£ä
2!$!2(!.$"//+
4HE INTRINSIC IMPEDANCE G OF A MEDIUM IS THE RELATIONSHIP BETWEEN THE ELECTRIC FIELD % ANDTHEMAGNETICFIELD ( ANDISACOMPLEXQUANTITYGIVENBY
H
JWM S JWE
!T THE BOUNDARY BETWEEN TWO MEDIA SOME ENERGY WILL BE REFLECTED AND THE REMAINDER TRANSMITTED 4HE REFLECTED FIELD STRENGTH IS DESCRIBED BY THE REFLECTION COEFFICIENT R
R
H H
H H
WHEREGANDGARETHEIMPEDANCESOFMEDIUMAND RESPECTIVELY 4HE REFLECTION COEFFICIENT HAS A POSITIVE VALUE WHEN G G SUCH AS WHERE AN AIR FILLED VOID EXISTS IN A DIELECTRIC MATERIAL 4HE EFFECT ON A PULSE WAVEFORM IS TO CHANGETHEPHASEOFTHEREFLECTEDWAVELETSOTHATTARGETSWITHDIFFERENTRELATIVEDIELEC TRICCONSTANTSTOTHEHOSTMATERIALSHOWDIFFERENTPHASEPATTERNSOFTHEREFLECTEDSIGNAL (OWEVER THEPROPAGATIONPARAMETERSRELATIVEDIELECTRICCONSTANTANDLOSSTANGENT OF THEHOSTMATERIAL THEGEOMETRICCHARACTERISTICSOFTHETARGET ANDITSDIELECTRICPARAM ETERSAFFECTTHEAMPLITUDEOFTHEREFLECTEDSIGNAL #LUTTER ! MAJOR DIFFICULTY FOR OPERATION OF '02 SYSTEMS IS THE PRESENCE OF CLUTTERWITHINTHEMATERIAL#LUTTERISDEFINEDASSOURCESOFUNWANTEDREFLECTIONSTHAT OCCURWITHINTHEEFFECTIVEBANDWIDTHANDSEARCHWINDOWOFTHERADARANDPRESENT ASSPATIALLYCOHERENTREFLECTORS4HEDEFINITIONOFCLUTTERVERYMUCHDEPENDSONTHE WANTEDTARGET4HEOPERATOROFA'02SYSTEMSEARCHINGFORPIPESMAYCLASSIFYTHE INTERFACESBETWEENROADLAYERSASCLUTTER WHEREASTHEOPERATOROFASYSTEMMEASURING ROADLAYERTHICKNESSMIGHTCONSIDERPIPESANDCABLESASSOURCESOFCLUTTER#AREFUL DEFINITIONANDUNDERSTANDINGARECRITICALLYIMPORTANTINSELECTINGANDOPERATINGTHE BESTSYSTEMANDPROCESSINGALGORITHMS#LUTTERCANCOMPLETELYOBSCURETHEBURIED TARGETANDAPROPERUNDERSTANDINGOFITSSOURCEANDIMPACTONTHERADARISESSENTIAL 0OLARIZATION ! COMPLETE DESCRIPTION OF THE RADAR SCATTERING CROSS SECTION OF ATARGETINCLUDESADESCRIPTIONOFITSPOLARIZATIONSCATTERINGCHARACTERISTICSNOTTHE SAMEASMOLECULARPOLARIZATION 4HEPOLARIZINGPROPERTIESOFTARGETSAREDESCRIBED BY THE 3TOKES PARAMETERS AND THE POLARIZATION COORDINATES CAN BE REPRESENTED ON THE0OINCARE3PHERE!LLOFTHESEAREWELLDESCRIBEDINSTANDARDTEXTSONOPTICSAND ELECTROMAGNETICTHEORY)NSUMMARY THESEDESCRIPTIONSALLOWTHESTATEOFANELECTRO MAGNETICWAVETOBEDESCRIBEDINTERMSOFLINEAR ELLIPTICAL ANDCIRCULARPOLARIZATION LEFT HANDEDORRIGHT HANDED )TISWELLKNOWNTHATLINEARTARGETSSUCHASWIRESACT ASDEPOLARIZINGFEATURESANDTHATALINEARLYPOLARIZEDCROSSEDDIPOLEANTENNAROTATED ABOUTANAXISNORMALTOALINEARTARGETSUCHASAWIREORPIPEPRODUCESASINUSOIDAL VARIATION IN RECEIVED SIGNAL (OWEVER THE NULL POINTS ARE A DISTINCT DISADVANTAGE BECAUSETHEOPERATORISREQUIREDTOMAKETWOSEPARATE AXIALLYROTATEDMEASUREMENTS ATEVERYPOINTTOBESUREOFDETECTINGPIPESATUNKNOWNORIENTATIONS!NATTRACTIVE TECHNIQUEISTORADIATEACIRCULARLYPOLARIZEDWAVE WHICHAUTOMATICALLYROTATESTHE POLARIZED VECTOR IN SPACE AND HENCE REMOVES THE DIRECTION OF SIGNAL NULLS 4HESE TECHNIQUESCANBEUSEDTODISCRIMINATEINFAVOROFTHETARGET&OREXAMPLE ARIGHT HANDEDCIRCULARLYPOLARIZED2(#0 WAVEWILLBEREFLECTEDASALEFT HANDEDCIRCULARLY
'2/5.$0%.%42!4).'2!$!2
Ó£°££
POLARIZED,(#0 WAVEFROMAPLANARSURFACE BUTSOMEPROPORTIONOF2(#0WILLBE REFLECTEDFROMATHINPIPEORWIRE4HISENABLESTHEGROUND SURFACEREFLECTIONTOBE REDUCEDWHILEENHANCINGTHATFROMTHETHINPIPEORWIRE 6ELOCITY 4HEVELOCITYOFPROPAGATIONOFELECTROMAGNETICWAVESINFREESPACEIS APPROXIMATELYrMSnBUTSLOWSINAMATERIALDEPENDINGONITSRELATIVEPERMITTIV ITYANDRELATIVEMAGNETICPERMEABILITY4HEVELOCITYOFPROPAGATIONOFELECTROMAGNETIC WAVESINASOILWITHAVALUEFORDROFWOULDBESLOWEDTOrMSn4HETIMETOA TARGETATARANGEOFMETERIS THEREFORE NS AND'02SYSTEMSOPERATEATTIMERANGES BETWEENAFEWNANOSECONDSUPTONS ALTHOUGHSOMESYSTEMSFORPROBINGTHROUGH ICEMAYUSERANGESUPTOSEVERALTENSOFMILLISECONDS )NGENERAL ITISNOTPOSSIBLETOMAKEARELIABLEESTIMATEOFPROPAGATIONVELOCITYORRELA TIVEPERMITTIVITYINAMEDIUMFROMASINGLEMEASUREMENTWITHOUTTRIALHOLINGINSERTINGA PROBEINTOAPREDRILLEDHOLE OROTHERSUPPLEMENTARYINFORMATION%VENINTHECASEWHERE AMEASUREMENTISCARRIEDOUTATONELOCATION ITISOFTENFOUNDTHATSIGNIFICANTVARIATIONSIN VELOCITYWILLOCCURWITHINCOMPARATIVELYSHORTDISTANCESFROMTHEORIGINALLOCATION4HIS CANLEADTOSIGNIFICANTERRORSINTHEESTIMATIONOFDEPTHSOFREFLECTORS/NEPROCEDURETHAT OVERCOMESTHISLIMITATIONISKNOWNASCOMMONDEPTHPOINTSURVEYING WHICHUTILIZESTWO ANTENNASINBISTATICOPERATIONATANUMBEROFTRANSMITANDRECEIVEPOSITIONS 4HEVELOCITYOFPROPAGATIONISGIVENBYM LNLRDNDR nHENCEINAMATERIAL WITHLR THEVELOCITYBECOMESM CER 4HEPHASEVELOCITYISGIVENBYM VAANDAS
§ ³¶ ME ` ¤ ¤ E ``³ ¥ ¥ ´ ´ · A W ¨ ¦ E` µ ¨ ¥ ´µ · ¦ © ¸
4HEPHASEVELOCITYISALSODEPENDENTONTHEFACTORD pD ` WHICHISALSOTANC )TISALSOPOSSIBLETODERIVEVELOCITYFROMMULTIPLEMEASUREMENTSSCANNINGOVERA TARGET BUTTHISWORKSWELLONLYINRELATIVELYUNCLUTTEREDSITUATIONSWHERETHEMEDIAHAS NOANISOTROPICCHARACTERISTICS $ISPERSION 4HEFREQUENCYDEPENDENTNATUREOFTHEDIELECTRICPROPERTIESOFTHEMATE RIALCAUSESTHEPHASEVELOCITYOFTHECOMPONENTFREQUENCIESOFAWIDEBANDSIGNALTOSUFFER DIFFERENTIALPROPAGATIONVALUES(ENCE THEREWILLBEVARIATIONINTHEVELOCITYOFPROPA GATION WITH FREQUENCY $IELECTRICS EXHIBITING THIS PHENOMENON ARE TERMED DISPERSIVE )NTHISSITUATION THEDIFFERENTFREQUENCYCOMPONENTSWITHINABROADBANDRADARPULSEWOULD TRAVELATSLIGHTLYDIFFERENTSPEEDS CAUSINGTHEPULSESHAPETOCHANGEWITHTIME(OWEVER THEPROPAGATIONCHARACTERISTICSOFOCTAVEBANDRADARSIGNALSINMOSTEARTHMATERIALSREMAIN LARGELYUNAFFECTEDBYDISPERSION)NMANYINSTANCES THEPOTENTIALVARIATIONINTHEVELOCITY OFWAVEPROPAGATIONOVERTHEFREQUENCYRANGEOFINTERESTISSMALLANDCANBEIGNORED $EPTH2ESOLUTION &ORTRADITIONALRADARSYSTEMS ITISACCEPTEDTHATTWOIDENTICAL TARGETSCANBESEPARATEDINRANGEIFTHEYAREOFAPULSEWIDTHAPART)NOPTICS ,ORD 2AYLEIGH PROPOSED THAT THE RESOLVING POWER OF AN INSTRUMENT IS WHEN THE PRINCIPAL INTENSITYOFONECOMPONENTCOINCIDESWITHTHEFIRSTINTENSITYMINIMUMOFTHEOTHERCOM PONENT-ANY'02PULSESTAKETHEFORMOFA2ICKERWAVELETTHESECONDDIFFERENTIALOF AGAUSSIANIMPULSE ANDANEXAMPLEOFTWOPULSESFROMTARGETSISSHOWNIN&IGURE WHEREBOTHTHEIMPULSESANDTHEIRENVELOPESARESHOWN7HENTHETARGETSARECLOSER AS
Ó£°£Ó
2!$!2(!.$"//+
&)'52% 4WORESOLVED2ICKERWAVELETS
SHOWNIN&IGURE ALTHOUGHITISPOSSIBLETODISTINGUISHTHEIRENVELOPES ITBECOMES INCREASINGLYDIFFICULTTORESOLVETHEACTUALPULSESBECAUSETHESIGNALMIGHTBEDUETOA RESONANCEGENERATEDBYASINGLETARGETHENCE INTHECASEOFPULSESWITHANENVELOPE THATHASNOMINIMA THEPULSEWIDTHRESOLUTIONCRITERIAMAYNOTBEOPTIMAL %SSENTIALLY RANGERESOLUTIONISDEFINEDBYTHEBANDWIDTHOFTHERECEIVEDSIGNAL! RECEIVERBANDWIDTHINEXCESSOF-(ZANDTYPICALLY'(ZISREQUIREDTOPROVIDE ATYPICALRESOLUTIONOFBETWEENANDCM DEPENDINGONTHERELATIVEPERMITTIVITYOF THEMATERIAL 7HENANUMBEROFFEATURESMAYBEPRESENT ASIGNALHAVINGALARGERBANDWIDTHIS REQUIREDTOBEABLETODISTINGUISHBETWEENTHEVARIOUSTARGETSANDTOSHOWTHEDETAILED STRUCTUREOFATARGET)NTHISCONTEXT ITISTHEBANDWIDTHOFTHERECEIVEDSIGNALTHATIS IMPORTANT RATHERTHANTHATOFTHETRANSMITTEDWAVELET4HEMATERIALACTSASALOWPASS FILTER WHICHMODIFIESTHETRANSMITTEDSPECTRUMINACCORDANCEWITHTHEELECTRICALPROP ERTIESOFTHEPROPAGATINGMEDIUM4HEREARESOMEAPPLICATIONSOF'02 SUCHASROAD LAYERTHICKNESSMEASUREMENT WHERETHEFEATUREOFINTERESTISASINGLEINTERFACE5NDER SUCH CIRCUMSTANCES IT IS POSSIBLE TO DETERMINE THE DEPTH SUFFICIENTLY ACCURATELY BY MEASURINGTHEELAPSEDTIMEBETWEENTHELEADINGEDGEOFTHERECEIVEDWAVELETPROVIDED THEPROPAGATIONVELOCITYISACCURATELYKNOWN !LTHOUGH A GREATER DEPTH RESOLUTION IS ACHIEVED IN WETTER MATERIALS FOR A GIVEN TRANSMITTEDBANDWIDTHBECAUSEOFTHEREDUCEDWAVELENGTHINHIGHDIELECTRICMATERIALS EARTHMATERIALSWITHSIGNIFICANTWATERCONTENTTENDTOHAVEHIGHERATTENUATIONPROPER TIES4HISCHARACTERISTICREDUCESTHEEFFECTIVEBANDWIDTH TENDINGTOBALANCEOUTTHE CHANGESOTHATWITHINCERTAINBOUNDSTHERESOLUTIONISAPPROXIMATELYINDEPENDENTOF LOSSWITHINTHEPROPAGATINGMATERIAL
&)'52% 4WOUNRESOLVED2ICKERWAVELETS
'2/5.$0%.%42!4).'2!$!2
Ó£°£Î
7HEREINTERFACESARESPACEDMORECLOSELYTHANONEHALFWAVELENGTH THEREFLECTED SIGNALFROMONEINTERFACEWILLBECOMEDIFFICULTTORESOLVEWITHTHATFROMANOTHER )TSHOULDBENOTEDTHATTHENORMALRADARCRITERIAFORRANGERESOLUTIONISLESSAPPROPRI ATEFORTHECASEOFAWEAKTARGETADJACENTTOASTRONGTARGET ANDTHEREISNOACCEPTED DEFINITIONOFRESOLUTIONFORTHECASEOFUNEQUALSIZETARGETS 0LAN2ESOLUTION 4HEPLANPLANISDEFINEDASAPLANENORMALTOTHEDIRECTION OFPROPAGATION RESOLUTIONOFA'02SYSTEMISIMPORTANTWHENLOCALIZEDTARGETSARE SOUGHTANDWHENTHEREISANEEDTODISTINGUISHBETWEENMORETHANONEATTHESAME DEPTH 7HERE THE REQUIREMENT IS FOR LOCATION ACCURACY WHICH IS PRIMARILY A TOPO GRAPHICSURVEYINGFUNCTION THESYSTEMREQUIREMENTISLESSDEMANDING 4HE PLAN RESOLUTION IS DEFINED BY THE CHARACTERISTICS OF THE ANTENNA AND THE SIG NALPROCESSINGEMPLOYED)NGENERALRADARSYSTEMSAPARTFROM3!2 TOACHIEVEAN ACCEPTABLEPLANRESOLUTIONREQUIRESAHIGHGAINANTENNA4HISNECESSITATESASUFFICIENTLY LARGE APERTURE AT THE LOWEST FREQUENCY TO BE TRANSMITTED 4O ACHIEVE SMALL ANTENNA DIMENSIONS AND HIGH GAIN THEREFORE REQUIRES THE USE OF A HIGH CARRIER FREQUENCY WHICHMAYNOTPENETRATETHEMATERIALTOSUFFICIENTDEPTH7HENSELECTINGEQUIPMENT FORAPARTICULARAPPLICATION ITISNECESSARYTOCOMPROMISEBETWEENPLANRESOLUTION SIZE OFANTENNA THESCOPEFORSIGNALPROCESSING ANDTHEABILITYTOPENETRATETHEMATERIAL 0LANRESOLUTIONIMPROVESASATTENUATIONINCREASES PROVIDEDTHATTHEREISSUFFICIENTSIG NALTODISCRIMINATEUNDERTHEPREVAILINGCLUTTERCONDITIONS)NLOWATTENUATIONMEDIA THE RESOLUTION OBTAINED BY THE HORIZONTAL SCANNING TECHNIQUE IS DEGRADED BUT ONLY UNDERTHESECONDITIONSDOSYNTHETICAPERTURETECHNIQUESINCREASETHEPLANRESOLUTION %SSENTIALLY THE GROUND ATTENUATION HAS THE EFFECT OF PLACING A hWINDOWv ACROSS THE 3!2APERTURE ANDTHEHIGHERTHEATTENUATIONTHEMORESEVERETHEWINDOW(ENCE IN HIGHATTENUATIONSOILS 3!2TECHNIQUESMAYNOTPROVIDEANYUSEFULIMPROVEMENTTO '02SYSTEMS3!2TECHNIQUESHAVEBEENAPPLIEDTO'02BUTVERYOFTENINDRYSOILS WITHLOWATTENUATION 3!2 TECHNIQUES TYPICALLY REQUIRE MEASUREMENTS MADE USING TRANSMITTER AND RECEIVERPAIRSATANUMBEROFANTENNAPOSITIONSTOGENERATEASYNTHETICAPERTUREORTO FOCUSTHEIMAGE5NLIKECONVENTIONALRADARS WHICHGENERALLYUSEASINGLEANTENNA MOST '02 SYSTEMS USE SEPARATE TRANSMIT AND RECEIVE ANTENNAS TO PROVIDE RECEIVER ISOLATION4HE'02COMMUNITYREFERSTOTHISASABISTATICMODE ALTHOUGHACTUALLYTHE ANTENNA SYSTEM IS CLOSELY SPACED AND MOBILE4HIS IS DIFFERENT FROM THE TRADITIONAL RADARCOMMUNITYTHATASSOCIATESTHETERMBISTATICWITHLARGESEPARATIONS
Ó£°ÎÊ " -ODELS OF THE '02 SITUATION RANGE FROM A SIMPLE SINGLE FREQUENCY EVALUATION OF PATH LOSSES TO COMPLETE $ TIME DOMAIN DESCRIPTIONS OF THE '02 AND ITS ENVIRON MENT-ODELINGTECHNIQUESINCLUDESINGLEFREQUENCYMODELS TIME DOMAINMODELS RAYTRACING INTEGRALTECHNIQUES METHODOFMOMENTS-O- ANDDISCRETEELEMENT METHODS4HE&INITE $IFFERENCE4IME $OMAIN&$4$ TECHNIQUEHASBECOMEONEOF THEPOPULARTECHNIQUESANDCANBEDEVELOPEDTORUNONMOSTDESKTOPCOMPUTERSWITH RELATIVEEFFICIENCY )T SHOULD BE NOTED THAT '02 SYSTEMS OFTEN OPERATE IN INTIMATE CONTACT WITH THE GROUNDANDVERYCLOSETOTHETARGET4HUSTHEANTENNARADIATESINTHENEAR FIELDWHEREAS SOMEGEOPHYSICAL'02SYSTEMSOPERATEATLONGERRANGESMTOKM ANDTHEY
Ó£°£{
2!$!2(!.$"//+
COULDBECONSIDEREDTOOPERATEINTHE&RESNELANDEVEN&RAUNHOFERFAR FIELD REGION 7HENTHETARGETISSOCLOSETOTHEANTENNA ITINTERACTSWITHTHEREACTIVEFIELDSOFTHE ANTENNA ANDACCURATEMODELSWOULDREFLECTTHISMODEOFOPERATION 4HE MOST BASIC MODEL USES THE RADAR RANGE EQUATION AND ENABLES AN ESTIMATE OF RECEIVEDSIGNALLEVEL DYNAMICRANGE ANDPROBABILITYOFDETECTIONTOBEASSESSED)T HASSIGNIFICANTWEAKNESSESINTHATMOSTCLOSE RANGE'02SYSTEMSAREOPERATINGINTHE NEAR FIELDOREVENTHEREACTIVEFIELDOFTHEANTENNAWHEREASTHEMODELASSUMESAFAR FIELDMODEL)TISPROBABLYMORERELEVANTTOTHELONGER RANGEGEOPHYSICALAPPLICATIONS WHERETHETARGETISMANYTENSOFMETERSFROMTHERADAR -ANY'02RECEIVERSWEREORIGINALLYBASEDONSAMPLINGOSCILLOSCOPETECHNOL OGY AND THE USE OF VOLTAGE BECAME EXPERIMENTALLY MORE USEFUL4HE MOST BASIC MODELFORASSESSMENTOFVOLTAGESIGNALLEVELISDERIVEDFROMTHERADARRANGEEQUA TION WHICHDOESHAVETHELIMITATIONSPREVIOUSLYNOTED(OWEVER ITDOESENABLE A FIRST ORDER ASSESSMENT OF ANTICIPATED SIGNAL LEVELS AND AN EXAMPLE IS GIVEN IN THIS SECTION4HE MODEL IS BASED ON THE EQUATION FOR THE VOLTAGE AT THE RECEIVER ASAFUNCTIONOFRANGERANDTARGETRADARCROSS SECTIONRANDGIVENBYREFERENCE 2UTLEDGEAND-UHA )NTHEFIRSTMODELSHOWNIN&IGURE THEANTENNAISSETATAHEIGHTOFCMABOVE THETARGETDIELECTRICCYLINDERSOFCMTHICKNESS RANGINGINSIZEFROMMDIAMETER TOMDIAMETER 4HETARGETHASAVALUEOFDROFANDTHESOILDR ANDTANC 4HERADIATEDPULSEHASACENTERFREQUENCYOF'(ZANDANOUTPUTPULSEPEAKVOLTAGE OFVOLTS4HERADARRECEIVERHASANEQUIVALENTBANDWIDTHOF-(ZTO'(ZAND ANEQUIVALENTRECEIVERNOISEVOLTAGEOFnVOLTS 4HEPROBABILITYOFDETECTION0$ ISDERIVEDFROMTHEERRORFUNCTIONOFTHESIGNAL TO NOISERATIO ASSHOWNIN&IGURE.OTETHATTHESEVALUESONLYRELATETOTHERECEIVER NOISEANDDONOTINCLUDEEXTERNALSOURCESOFFALSEALARMSDUETOCLUTTER 4HEMOSTBASICMODELISTHATOFTHETRANSMISSIONLINEEQUIVALENTANDISUSEFULFOR ASSESSING THE TIME DOMAIN SIGNATURE OF A PHYSICAL SITUATION! CONCEPTUALLY SIMPLE MODELCANBEUSEDTOGAINANINSIGHTINTOTHEOPTIMUMCENTERFREQUENCYOFOPERATION ANDISSHOWNIN&IGURE %ACHLAYERISMODELEDASEQUIVALENTIMPEDANCEANDTHETRANSMISSIONANDREFLEC TIONCOEFFICIENTSARECALCULATEDFOREACHINTERFACE4HEVELOCITYOFPROPAGATIONAND THEMATERIALLOSSESAREINCLUDEDALTHOUGHNOTTHESPREADINGLOSSES4HEREASONFOR THIS IS THAT THE RECEIVED ! SCAN WOULD NORMALLY HAVE TIME VARYING GAIN APPLIED INTHERECEIVERANDSIGNALPROCESSING ANDTOINTRODUCESPREADINGLOSSANDTHENCOM PENSATEISANINEFFICIENTMODELINGEXERCISE)NTHEMODELONLYTHEFIRSTREFLECTIONIS COMPUTED ALTHOUGHMULTIPLEINTERNALREFLECTIONSWITHINEACHLAYERWILLBEGENERATED ANDAFULLREPRESENTATIONSHOULDINCLUDETHESE4HEPARAMETERSOFTHELAYERSAREGIVEN IN4ABLE
&)'52% 0HYSICALLAYOUTOF'02SYSTEM#OURTESY)%%
'2/5.$0%.%42!4).'2!$!2
Ó£°£x
0$
2
r
&)'52% 'RAPHOFPROBABILITYOFDETECTIONASAFUNCTIONOFTARGETRANGEINMILLIMETERSAND TARGETDIAMETERMMLEFT HANDSIDETOMMRIGHT HANDSIDEININCREMENTSOFMM 'ROUND SURFACEISSHOWNASAVERTICALLINE#OURTESY)%%
&)'52% ,AYOUTOFTRANSMISSIONLINEMODELCOURTESY)%%
4!",% ,AYER#HARACTERISTICSFOR4RANSMISSION,INE-ODEL
,AYER
2ANGEIN-ETERS INFINITE
2ELATIVE$IELECTIC#ONSTANTER
,OSS4ANGENT
-ATERIAL !IR ,OSSYLAYER !IRVOID 3UBBASE 7ETBASE 7ETBEDROCK
Ó£°£È
2!$!2(!.$"//+
&)'52% 3IMULATIONOF! SCANUSING-(ZCENTERFREQUENCY#OURTESY)%%
4HEOUTPUTFROMTHEMODELISSHOWNIN&IGUREAND&IGURE &INITE $IFFERENCE4IME $OMAIN&$4$ METHODSCANBEUSEDTOMODELTHEFIELD PROPAGATIONOFATYPICAL'02SYSTEM4HEANTENNAUSEDFORTHISPURPOSEISARESISTIVELY LOADED4%-HORN ASDESCRIBEDBY-ARTELETAL)TISCMLONGWITHANAPERTUREOF CMBYCM4HE4%-HORNHASULTRAWIDEBANDCAPABILITIESFROM-(ZTO'(Z )TISPOSITIONEDABOVEAMETALLICTARGETBURIEDINTHEGROUNDASSHOWNIN&IGURE 4HEDISTANCEBETWEENTHEHORNAPERTUREANDTHEAIR GROUND INTERFACEISCMDIFFERENT FROMTHEEARLIERMODEL 4HEMODELEDTARGETISACYLINDERWITHARADIUSOFCMAND AHEIGHTOFCM)TISSHALLOWLYBURIEDATABOUTCMBELOWTHEAIR GROUNDINTERFACE
&)'52% 3IMULATIONOF! SCANUSING-(ZCENTERFREQUENCY#OURTESY)%%
'2/5.$0%.%42!4).'2!$!2
Ó£°£Ç
&)'52% %LECTRIC FIELD PLOT ON A VERTICAL CUT PLANE AFTER THE MAIN GROUND REFLECTION#OURTESY)%%
4HEGROUNDISMODELEDASAUNIFORMLOSSYMATERIALWITHARELATIVEPERMITTIVITYOF ANDACONDUCTIVITYOF3M3IEMENSMETER 4HEAIR GROUNDINTERFACEISASSUMED TOBEPERFECTLYFLAT &ROMTHEFIELDPLOT ONECANRECOGNIZETHEANTENNASTRUCTUREANDTHESTRONGFIELD REGIONONANDINSIDETHEHORNPLATE4HEBURIEDOBJECTISALSOVISIBLE4HEMAINREFLEC TIONCAUSEDBYTHEAIR GROUNDINTERFACECANCLEARLYBESEENCOMINGBACKTOWARDTHE ANTENNA SYSTEM )N ADDITION A WEAKER REFLECTION COMING FROM THE BURIED OBJECT IS STARTINGTOFORMANDFOLLOWSTHEAIR GROUNDINTERFACEREFLECTIONINTIME4HISISATYPICAL TIME DOMAIN CHARACTERISTIC OF STANDOFF '02 SYSTEM -OREOVER OTHER PHYSICAL PHE NOMENACANBEOBSERVEDSUCHASTHEFREESPACEPATHLOSSANDTHEREDUCTIONINVELOCITY OFPROPAGATIONINTHEGROUND )TSHOULDBENOTEDTHATTHEPROCESSOFPHYSICALLYSCANNINGTHEANTENNASYSTEMOVER THETARGETCREATESAHYPERBOLICIMAGEOFTHETARGET ASSHOWNIN&IGURE&ORTHE TWO DIMENSIONALCASEX POSITIONONSURFACEANDZ DEPTHTOTHETARGET OFAMATERIAL WITHKNOWNCONSTANTVELOCITY THEMEASUREDTIMETOTHEPOINTREFLECTORISGIVENBYT ANDTHENTHEDISTANCETOTHEPOINTREFLECTORISGIVENBYZ VT!TANYPOSITIONALONG THEX AXISTHEDISTANCEZISALSOGIVENBY
ZI XI X Z
Ó£°£n
2!$!2(!.$"//+
&)'52% 4YPICALHYPERBOLICIMAGEOF'02DATAFROMAREFLECTOROFCIRCULAR CROSSSECTION#OURTESY)%%
4HISEQUATIONSHOWSTHATTHEMEASUREDWAVEFRONTAPPEARSASAHYPERBOLICIMAGE OR A CURVE OF MAXIMUM CONVEXITY -IGRATION TECHNIQUE MAY BE USED TO MOVE OR MIGRATE A SEGMENT OF AN! SCAN TIME SAMPLE TO THE APEX OF A CURVE OF MAXIMUM CONVEXITY4HEHYPERBOLICCURVENEEDSTOBEWELL SEPARATEDFROMOTHERFEATURESANDA GOODSIGNAL TO NOISERATIOISNEEDEDFORTHISTECHNIQUETOWORKWELL
Ó£°{Ê *,"* ,/ -Ê"Ê / , 4HEDETERMINATIONOFTHEDIELECTRICPROPERTIESOFEARTHMATERIALSREMAINSLARGELYEXPER IMENTAL2OCKS SOILS ANDCONCRETEARECOMPLEXMATERIALSCOMPOSEDOFMANYDIFFERENT MINERALS IN WIDELY VARYING PROPORTIONS AND THEIR DIELECTRIC PARAMETERS MAY DIFFER GREATLYEVENWITHINMATERIALSTHATARENOMINALLYSIMILAR-OSTEARTHMATERIALSCONTAIN MOISTURE USUALLY WITH SOME MEASURE OF SALINITY 3INCE THE RELATIVE PERMITTIVITY OF WATERISINTHEORDEROF EVENSMALLAMOUNTSOFMOISTURECAUSEASIGNIFICANTINCREASE OFTHERELATIVEPERMITTIVITYOFTHEMATERIAL!LARGENUMBEROFWORKERSHAVEINVESTI GATEDTHERELATIONSHIPSBETWEENTHEPHYSICAL CHEMICAL ANDMECHANICALPROPERTIESOF MATERIALSANDTHEIRELECTRICALAND INPARTICULAR MICROWAVEPROPERTIES)NGENERAL THEY HAVESOUGHTTODEVELOPSUITABLEMODELSTOLINKTHEPROPERTIESOFTHEMATERIALTOITSELEC TROMAGNETICPARAMETERS3UCHMODELSPROVIDEABASISFORUNDERSTANDINGTHEBEHAVIOR OFELECTROMAGNETICWAVESWITHINTHESEMEDIA4HEREALANDIMAGINARYDIELECTRICLOSSES
'2/5.$0%.%42!4).'2!$!2
Ó£°£
&)'52% $IELECTRICPROPERTIESD `UPPER ANDD pLOWER OFLOSSYSOILASA FUNCTIONOFFREQUENCY#OURTESY)%%
ASAFUNCTIONOFFREQUENCYCANBEPLOTTEDOVERAWIDEFREQUENCYRANGEANDATYPICAL RESULTISSHOWNIN&IGURE )NFORMATIONONTHEGEOLOGICALPROPERTIESOFEARTHSOILSCANBEFOUNDINTHE$IGITAL 3OIL-APOFTHE7ORLDAND$ERIVED3OIL0ROPERTIES#$ PUBLISHEDBYTHE&OODAND !GRICULTURE/RGANIZATIONOFTHE5NITED.ATIONS4HISENABLESTHETENMAPSHEETSOF THEWORLDTOBECLASSIFIEDINTERMSOFPARAMETERSSUCHASP(CONCENTRATIONOFHYDRO GEN IONS ORGANIC CARBON CONTENT #. CARBON TO NITROGEN RATIO CLAY MINERALOGY SOILDEPTH SOILMOISTURECAPACITY ANDSOILDRAINAGECLASS3UCHINFORMATIONISUSEFUL INASSESSINGTHEPOTENTIALOF2&TECHNIQUESANDPARTICULARLY'02FORPARTICULARGEO GRAPHICREGIONS 4HEREARETWOBENEFITSTOUNDERSTANDINGSOILPROPERTIESINRELATIONTO'024HEFIRST ISTOUNDERSTANDTHEAPPLICABILITYOF'02TOPARTICULARSOILSANDHENCETHEPOSSIBILITY OFUSING'02TODETECTBURIEDTARGETSSUCHASPIPE CABLES LANDMINES ETC4HESECOND ISTOUSE'02TOCHARACTERIZESOILSANDSOILPROPERTIES '02 CAN PROVIDE A DETAILED MAP OF THE SUBSURFACE WHICH WHEN COMBINED WITH TRADITIONALSOILSURVEYMETHODSCANPROVIDEINFORMATIONONTHETYPEOFSOIL ITSEXTENT LATERALLYANDINDEPTH THEWATERTABLE THELAYERINGANDFEATURESOFTHESOIL ANDHENCE ITSLOCALGEOLOGYANDHISTORY '02 HAS BEEN USED IN THE 53 BY THE $EPARTMENT OF !GRICULTURE .ATURAL 2ESOURCES #ONSERVATION 3ERVICE 53$! .2#3 AS A QUALITY CONTROL TOOL FOR SOIL MAPPINGANDINVESTIGATIONS4HEUSEOF'02INSOILSURVEYACTIVITIESHASPROVIDED INFORMATIONABOUTSOILRESOURCESTHATWOULDHAVEBEENUNOBTAINABLEBYOTHERMEANS ORWOULDHAVEBEENUNECONOMICALTOOBTAIN!NEXAMPLEOFTHERESULTSOFTHISWORK ISSHOWNIN&IGURE
Ó£°Óä
2!$!2(!.$"//+
&)'52% '023OIL3UITABILITY-APOFTHE#ONTINENTAL#ONTERMINOUS 5NITED3TATES#OURTESY OF53$! .2#3
Ó£°xÊ *,Ê-9-/ 4HECHOICEOFSYSTEMDESIGNISTOALARGEEXTENTGOVERNEDBYTHETYPEOFTARGET THERES OLUTIONREQUIRED ANDTHEANTICIPATEDGROUNDATTENUATIONANDCLUTTER4HEDEPTHRANGEOF THERADARSYSTEMISLIKELYTOBEPRIMARILYDEFINEDBYTHESOILATTENUATION ONCEAPARTICU LARRANGEOFFREQUENCIESHASBEENCHOSEN(OWEVER ITCANBESHOWNTHATCONSIDERABLE VARIATIONSnD" INTHESENSITIVITYOFCOMPETINGSYSTEMDESIGNSACTUALLYTRANSLATE TORELATIVELYSMALLCHANGESINDEPTHPERFORMANCEINLOSSYSOILS 4HESELECTIONOFASUITABLEWAVEFORMFORTRANSMISSION ATLEASTINTERMSOFRESOLU TION CANBECONSIDEREDAFUNCTIONOFTHEDURATIONOFTHECOMPLEXENVELOPEOFTHESIG NAL4HEOUTPUTFROMMOSTULTRAWIDEBANDRADARSYSTEMSCANBECOMPAREDINTERMSOFA TIME DOMAINREPRESENTATIONOFTHEWAVEFORM!LMOSTALLTYPESOFRADARCANBEASSESSED NOTJUSTBYTHEIRSIGNAL TO NOISEANDSIGNAL TO CLUTTERRATIOSBUTALSOBYCOMPARINGTHEIR INHERENTRANGESENSITIVITY3UCHAPROCEDUREREVEALSTHECHARACTERISTICSTHATCONTROLTHE RADARPERFORMANCE4HEDESIGNOFA'02SYSTEMISDEFINEDBYTHEMODULATIONTECH NIQUE ANDTIMEDOMAIN FREQUENCYDOMAIN ANDPSEUDO RANDOM CODEDDOMAINRADAR DESIGNSAREMOSTLIKELYTOBEENCOUNTERED&REQUENCYDOMAINRADARSMAYUSEEITHER STEPPEDFREQUENCYORCONTINUOUSLYSWEPTFREQUENCYMODULATION4HEYTRANSMIT ONA REPETITIVEBASIS ANOMINALLYCONSTANTAMPLITUDESIGNALWHOSEFREQUENCYINCREASESINA LINEARPROGRESSIONFROMTHELOWESTTOTHEHIGHESTVALUE 2ECOVERYOFTHERECEIVERSIGNALFROMNOISEMAYBEACHIEVEDBYEITHERCONVENTIONAL BANDPASSFILTERSORBYTHEMATCHEDFILTEROR7IENERFILTER 4HE FUNDAMENTAL OPERATION OF A MATCHED FILTER IS CORRELATION 4HE AMPLITUDE OF EACHPOINTINTHEOUTPUTSIGNALISAMEASUREOFHOWWELLTHEFILTERKERNELMATCHESTHE CORRESPONDINGSECTIONOFTHEINPUTSIGNAL4HEOUTPUTOFAMATCHEDFILTERDOESNOTNEC ESSARILYLOOKLIKETHESIGNALBEINGDETECTED BUTIFAMATCHEDFILTERISUSED THESHAPE OFTHETARGETSIGNALMUSTALREADYBEKNOWN4HEMATCHEDFILTERISOPTIMALINTHESENSE
'2/5.$0%.%42!4).'2!$!2
Ó£°Ó£
THATTHEPEAKSIGNALOUTPUTTOMEANNOISERATIOISGREATERTHANCANBEACHIEVEDWITHANY OTHERLINEARFILTER4HISISNOTALWAYSTHEBESTFILTERTOUSEFORTIME DOMAINWAVEFORMS WHERETHEFIDELITYOFTHEOUTPUTMAYBEAREQUIREMENT 4HE7IENERFILTERSEPARATESSIGNALSBASEDONTHEIRFREQUENCYSPECTRA4HEGAINOF THE7IENERFILTERATEACHFREQUENCYISDETERMINEDBYTHERELATIVEAMOUNTOFSIGNALAND NOISEATTHATFREQUENCY4HE7IENERANDMATCHEDFILTERMUSTBECARRIEDOUTBYCONVOLU TION MAKINGTHEMEXTREMELYSLOWTOEXECUTE 4HEMATCHEDFILTERRADARRECEIVERPROVIDESANOPTIMUMLINEARPROCESSINGOFRADARIN THEPRESENCEOFNOISE4HERADARSIGNALISPROCESSEDBYAFILTERTHATCROSS CORRELATESTHE RECEIVEDWAVEFORMWITHASUITABLYTIME DELAYEDVERSIONOFTHETRANSMITTEDWAVEFORM 4HEOUTPUTRESULTSINANOUTPUTINWHICHTHEAMPLITUDEOFTHELATTERANDITSPOSITIONIN DELAYTIMEISRELATEDTOTHETARGETRADARCHARACTERISTIC4HISTYPEOFRECEIVERISWIDELY USEDTOPROCESSCHIRP STEPFREQUENCY ANDPSEUDO RANDOM CODEDWAVEFORMS ANDTHE DESIGNOFSUCHWAVEFORMSISEXTENSIVELYDESCRIBEDINTHELITERATURE -ANYCOMMERCIALTIME DOMAINRADARSYSTEMSUSEASAMPLINGRECEIVERTODOWN CONVERTTHERADARSIGNALSFROMTHENANOSECONDTIMEFRAMETOAMILLISECONDTIMEFRAME THATISEASIERTOPOSTPROCESS(OWEVER AREALDISADVANTAGEOFTHESAMPLINGRECEIVERIS ITSLIMITEDDYNAMICRANGEDUETOTHESAMPLINGDIODESANDINHERENTLYHIGHNOISELEVEL DUETOITSWIDEBANDWIDTH$ETAILSOFTYPICALSAMPLINGRECEIVERS WHICHAREESSENTIALLY THESAMEASSAMPLINGOSCILLOSCOPES CANBEFOUNDINTHELITERATURE ANDONCEISSUESOF SAMPLINGLINEARITYINTIMEAREADDRESSED THEGENERICDESIGNHASFORMEDTHEBASISFOR THEMAJORITYOFCOMMERCIAL'02SYSTEMS !KEYPARAMETERFORMOST'02SYSTEMSISTHEMEANPOWER4HETIME DOMAINRADAR TRANSMITS ONAREPETITIVEBASIS ASHORTDURATIONIMPULSE#ONSEQUENTLY ITSPEAKPOWER ISSIGNIFICANTLYGREATERTHANITSMEANPOWER4HISISNOTTHECASEWITHSTEPPEDFREQUENCY WHOSERADIATEDPOWERPERSPECTRALLINEISHIGHERTHANTHETIME DOMAINRADARTHATGIVESAN ADVANTAGEINTERMSOFTRANSMITTERPEAKSIGNALCAPABILITYCOMPAREDWITHTHEIMPULSE'02
Ó£°ÈÊ " 1 /" Ê/ +1 4HERE ARE THREE MAIN MODULATION TECHNIQUES TIME DOMAIN FREQUENCY DOMAIN AND PSEUDO RANDOM CODED RADAR '02 SYSTEMS THAT TRANSMIT AN IMPULSE AND RECEIVE THE REFLECTEDSIGNALFROMTHETARGETUSINGASAMPLINGRECEIVERCANBECONSIDEREDTOOPERATEIN THETIMEDOMAIN'02SYSTEMSTHATTRANSMITINDIVIDUALFREQUENCIESINASEQUENTIALMAN NERANDRECEIVETHEREFLECTEDSIGNALFROMTHETARGETUSINGAFREQUENCYCONVERSIONRECEIVER CANBECONSIDEREDTOOPERATEINTHEFREQUENCYDOMAIN4HELATTERSYSTEMSOFTENRECON STRUCTTHEDOWNCONVERTEDFREQUENCIESTORECOVERATIME DOMAINREPLICAOFTHESIGNAL !LL'02SMAYHAVETODETECTSIGNALSFROMATARGETTHATMAYBEnTOnD" LOWERTHANTHERADIATEDSIGNALATRANGESINTHEORDEROFAMETERNSINFREESPACE )N ADDITION THERECEIVEDSIGNALWILLCONTAINTEMPORALSCATTERINGINFORMATIONONTHETARGET THATCANBEEXPLOITED 4HETEMPORALFIDELITYOFRECEIVEDSIGNALNEEDSTOBEPRESERVEDANDTHUSDESIGNERSOF '02HAVETOENSURETHATTHERECEIVERISNOTSATURATEDBYTHETRANSMITTEDSIGNAL THEANTEN NASDONOTCAUSETIMESIDELOBES ANDTHERECEIVERDOESNOTDISTORTTHERECEIVEDSIGNAL 4IME$OMAIN -OSTCOMMERCIALLYAVAILABLE'02SYSTEMSUSESHORTPULSESOR IMPULSESSUCHASTHE2ICKERWAVELET ASSHOWNPREVIOUSLYIN&IGURE4HEHIGH SPEEDSEQUENTIALSAMPLINGAPPROACHUSEDTOACQUIRE2&WAVEFORMSPRODUCESALOW
Ó£°ÓÓ
2!$!2(!.$"//+
3.2 BECAUSE THE SPECTRUM OF THE SAMPLING PULSE IS A POOR MATCH FOR THAT OF THE RECEIVED PULSE )N GENERAL THE DYNAMIC RANGE OF THE SAMPLING RECEIVER IS TYPICALLY D" WITHOUTRANGETIME VARYINGGAIN4HEEFFECTOFTHERANGEVARYINGGAINISTO ENABLETHELOWERAMPLITUDESIGNALSFROMTARGETSATAGREATERRANGETOBEAMPLIFIEDSOAS TOBEABOVETHEMINIMUMSAMPLINGTHRESHOLDSIGNALLEVEL4HISISEQUIVALENTTOALINEAR RECEIVERWITHAD"ORMOREDYNAMICRANGE3IGNALAVERAGINGORINTEGRATIONOFTHE SAMPLESCANINCREASETHEEFFECTIVESENSITIVITYBYTHEAMOUNTOFAVERAGINGANDTHISCAN BETYPICALLYTOD"4HERATIOOFTHEPEAKTRANSMITTEDSIGNALTOTHEMEANRECEIVER NOISELEVELCANBEUPTOD" 4HEANTENNASTHATCANBEUSEDWITHTIME DOMAIN'02ARELIMITEDTOLINEARPHASE DESIGNSSUCHASRESISTIVELYLOADEDDIPOLES 4%-HORNS OR)MPULSE2ADIATING!NTENNAS )2!S )TSHOULDBENOTEDTHATULTRAWIDEBANDANTENNASFALLINTOTWOCLASSES THOSETHAT RADIATEAREASONABLYSHORTIMPULSEWITHLOWTIMESIDELOBESANDFUNDAMENTALLYPOS SESSALINEARPHASE FREQUENCYCHARACTERISTIC4HEALTERNATIVECLASSOFANTENNAS SUCHAS LOGPERIODICS HAVEWIDEBANDFREQUENCYCHARACTERISTICSBUTNONLINEARPHASE FREQUENCY CHARACTERISTICS%SSENTIALLY THELATTERCLASSWILLCAUSETHEDIFFERENTFREQUENCYCOMPO NENTSOFANIMPULSETOBERADIATEDATDIFFERENTTIMES HENCEDISPERSINGTHEIMPULSE )F SUCH ANTENNAS ARE USED WITH TIME DOMAIN RADAR THE DISPERSIVE PROPERTIES OF THE ANTENNAUSEDMUSTBECOMPENSATEDBYSUITABLEPOST PROCESSINGFILTERING 4HETIME DOMAINRADARSYSTEMTRANSMITSASEQUENCEOFPULSES TYPICALLYOFAMPLI TUDES WITHIN THE RANGE BETWEEN 6 TO 6 AND PULSE WIDTHS WITHIN THE RANGE BETWEEN PS TO NS AT A PULSE REPETITION INTERVAL OF BETWEEN SEVERAL HUNDRED MICROSECONDS TO ONE MICROSECOND DEPENDING ON THE SYSTEM DESIGN 4HE IMPULSE GENERATORISGENERALLYBASEDONTHETECHNIQUEOFRAPIDDISCHARGEOFTHESTOREDENERGY INASHORTTRANSMISSIONLINE4HEMOSTCOMMONMETHODOFACHIEVINGTHISISBYMEANS OFATRANSISTOROPERATEDINAVALANCHEBREAKDOWNMODEUSEDASTHEFASTSWITCHANDA VERYSHORTLENGTHOFTRANSMISSIONLINE)TISQUITEFEASIBLETOGENERATEPULSESOFSEVERAL HUNDREDK6ALBEITATLONGREPETITIONINTERVALS4HEOUTPUTFROMTHERECEIVEANTENNA ISAPPLIEDTOAFLASH!$CONVERTERORASEQUENTIALSAMPLINGRECEIVER4HELATTERNOR MALLYCONSISTSOFANULTRAHIGHSPEEDSAMPLEANDHOLDCIRCUIT4HECONTROLSIGNALTOTHE SAMPLEANDHOLDCIRCUIT WHICHDETERMINESTHEINSTANTOFSAMPLETIME ISSEQUENTIALLY INCREMENTEDATEACHPULSEREPETITIONINTERVAL&OREXAMPLE ASAMPLINGINCREMENTOF T PSISADDEDTOTHEPREVIOUSPULSEREPETITIONSAMPLINGINTERVALTOENABLESAM PLINGOFTHERECEIVEDSIGNALATREGULARINTERVALSASINDICATEDIN&IGURE
# $ %%# %
%! %#!
% % &%"&%
&)'52% 4YPICALSAMPLINGRECEIVERUSEDFORTIME DOMAIN'02SYSTEMS
' %
'2/5.$0%.%42!4).'2!$!2
Ó£°ÓÎ
4HEPRINCIPLEOFTHESAMPLINGRECEIVERIS THEREFORE ADOWNCONVERSIONOFTHERADIO FREQUENCYSIGNALINTHENANOSECONDTIMEREGIONTOANEQUIVALENTVERSIONINTHEMICRO ORMILLISECONDTIMEREGION4HEINCREMENTATIONOFTHESAMPLINGINTERVALISTERMINATED ATASTAGEWHEN FOREXAMPLE ORSEQUENTIALSAMPLESHAVEBEENGATHERED 4HEPROCESSISTHENREPEATED4HEREARESEVERALMETHODSOFAVERAGINGORhSTACKINGv THEDATAEITHERACOMPLETESETOFSAMPLESCANBEGATHEREDANDSTOREDANDFURTHERSETS ADDEDTOTHESTOREDDATASET ORALTERNATIVELY THESAMPLINGINTERVALISHELDCONSTANTFORA PREDETERMINEDTIMETOACCUMULATEANDAVERAGEAGIVENNUMBEROFINDIVIDUALSAMPLES 4HEFIRSTMETHODNEEDSADIGITALSTOREBUTHASTHEADVANTAGETHATEACHWAVEFORMSET SUFFERSLITTLEDISTORTIONIFTHERADARISMOVINGOVERTHEGROUND 4HESECONDMETHODDOESNOTNEEDADIGITALSTOREANDASIMPLELOW PASSANALOGUE FILTERCANBEUSED(OWEVER DEPENDINGONTHENUMBEROFSAMPLESTHATHAVEBEENAVER AGED THEOVERALLWAVEFORMSETCANRESULTINBEINGhSMEAREDvSPATIALLYIFTHERADARIS MOVINGATANYSPEED4HESTABILITYOFTHETIMINGINCREMENTISVERYIMPORTANTANDGEN ERALLYTHISSHOULDBEOFTHESAMPLINGINCREMENTHOWEVER PRACTICALLYASTABILITY INTHEORDEROFPSTOPSISACHIEVED4HEEFFECTOFTIMINGINSTABILITYISTOCAUSEA DISTORTION WHICHISRELATEDTOTHERATEOFCHANGEOFTHE2&WAVEFORM%VIDENTLY WHERE THE2&WAVEFORMISCHANGINGRAPIDLY JITTERINTHESAMPLINGCIRCUITSRESULTSINAVERY NOISYRECONSTRUCTEDWAVEFORM7HERETHERATEOFCHANGEOFSIGNALISSLOW JITTERISLESS NOTICEABLE.ORMALLY CONTROLOFTHESAMPLINGCONVERTERISDERIVEDFROMASAMPLEOF THEOUTPUTFROMTHEPULSEGENERATORTOENSURETHATVARIATIONSINTHETIMINGOFTHELATTER ARECOMPENSATEDAUTOMATICALLY4HEKEYELEMENTSOFTHISTYPEOFRADARSYSTEMARETHE IMPULSEGENERATOR THETIMINGCONTROLCIRCUITS THESAMPLINGDETECTOR ANDTHEPEAKHOLD ANDANALOGUETODIGITALCONVERTER &REQUENCY $OMAIN 2ADAR 4HE MAIN POTENTIAL ADVANTAGES OF THE FREQUENCY DOMAINRADARARETHEWIDERDYNAMICRANGE LOWERNOISEFIGURE ANDHIGHERMEANPOWERS THATCANBERADIATED4HEREARETWOMAINTYPESOFFREQUENCYDOMAINRADAR &REQUENCY -ODULATED #ARRIER 7AVE &-#7 AND 3TEPPED &REQUENCY #ARRIER 7AVE 3 &-#7RADARTRANSMITSACONTINUOUSLYCHANGINGFREQUENCYOVERACHOSENFREQUENCY RANGEONAREPETITIVEBASIS4HERECEIVEDSIGNALISMIXEDWITHASAMPLEOFTHETRANSMIT TEDWAVEFORMANDRESULTSINADIFFERENCEFREQUENCY WHICH ALTHOUGHFUNDAMENTALLY RELATEDTOTHEPHASEOFTHERECEIVEDSIGNAL ISAMEASUREOFITSTIMEDELAYANDHENCE RANGEOFTHETARGET4HEDIFFERENCEFREQUENCYORINTERMEDIATEFREQUENCY)& MUSTBE DERIVEDFROMAN)1MIXERPAIRIFTHEINFORMATIONEQUIVALENTTOATIME DOMAINREPRE SENTATIONISREQUIREDIE TORECONSTITUTEANIMPULSE ASASINGLE ENDEDMIXERONLY PROVIDESTHEMODULUSOFTHETIME DOMAINWAVEFORM4HEBASIC&-#7RADARSYSTEM ISPARTICULARLYSENSITIVETOCERTAINPARAMETERS)NPARTICULAR ITREQUIRESAHIGHDEGREE OFLINEARITYOFFREQUENCYSWEEPWITHTIMETOAVOIDSPECTRALWIDENINGOFTHE)&AND HENCEDEGRADATIONOFSYSTEMRESOLUTION$ENNISAND'IBBSMADEANASSESSMENTOFTHE SENSITIVITYOFTIMESIDELOBELEVELTOLINEARITYANDSHOWEDTHERATIOOFSIDELOBETOPEAK LEVELWASDEPENDENTONTHESWEEPLINEARITY0RACTICALLY THEEFFECTOFANONLINEARITYOF AFEWPERCENTISTOCAUSESIGNIFICANTTIMESIDELOBES ASTHISNEEDSTOBECOMPENSATEDIN THETRANSMITTERMODULATORDESIGN 4HE 3 RADAR TRANSMITS A SERIES OF INCREMENTAL FREQUENCIES AND STORES THE RECEIVED)&SIGNALTOTHENCARRYOUTA&OURIERTRANSFORMRECONSTRUCTIONOFTHETIME DOMAIN EQUIVALENT WAVEFORM 4HE 3 HAS FOUND MANY APPLICATIONS IN '02 BECAUSE THE REQUIREMENTS ON SCAN RATE ARE RELATIVELY MODEST4HE IMPACT OF MOBILE COMMUNICATIONSTECHNOLOGYHASHADASIGNIFICANTIMPACTONREDUCINGTHECOSTOFRADAR COMPONENTSFORTHISDESIGN4WOFORMSOFTHESYNTHESIZEDRADARCANBECONSIDERED
Ó£°Ó{
2!$!2(!.$"//+
4HEFIRSTANDSIMPLESTSYSTEMISSTEPPEDFREQUENCYCONTINUOUSWAVERADAR4HESECOND FORMISMORECOMPLEXINTHATEACHINDIVIDUALFREQUENCYISAPPROPRIATELYWEIGHTEDIN AMPLITUDEANDPHASEPRIORTOTRANSMISSION.ORMALLY THERADARISCALIBRATEDBOTHTO ESTABLISHAREFERENCEPLANEFORMEASUREMENTASWELLASTOREDUCETHEEFFECTOFVARIATIONS INTHEFREQUENCYCHARACTERISTICSOFCOMPONENTSANDANTENNAS !MUCHWIDERCLASSOFANTENNAISAVAILABLEFORUSEBYTHEDESIGNEROFFREQUENCY DOMAINRADARS4HENOISEFLOOROFTHERECEIVERISMUCHLOWERTHANTHETIME DOMAIN EQUIVALENT SIMPLYBYVIRTUEOFITSLOWERBANDWIDTHANDHENCELOWERTHERMALNOISE 4YPICALLY ASENSITIVITYOFnD"MISFOUNDANDASYSTEMPEAKTRANSMITTEDSIGNAL TO MEAN RECEIVER NOISE RANGE OF D" IS FEASIBLE )T SHOULD BE NOTED THAT THE )& BANDWIDTHOFTHERECEIVERIN&-#7AND3SYSTEMSCANBEMADERELATIVELYSMALL WHEREASTHESAMPLINGRECEIVERINTHETIME DOMAINRECEIVERHASABANDWIDTHOFMANY '(ZANDHENCEAPOORNOISEPERFORMANCE 4HEMAINPOTENTIALADVANTAGEOFASTEPPEDFREQUENCYOR&-#7'02ISITSABIL ITYTOADJUSTTHERANGEOFFREQUENCIESOFOPERATIONTOSUITTHEMATERIALANDTARGETSAND ELECTROMAGNETICENVIRONMENTUNDERINVESTIGATIONIFTHEANTENNAHASANADEQUATEPASS BANDOFFREQUENCIES)TCANRADIATEAHIGHERMEANPOWERLEVELPERSPECTRALLINETHAN THETIME DOMAINRADAR ANDITSABILITYTOINTEGRATETHERECEIVEDSIGNALLEVELIMPROVES THESYSTEMSENSITIVITY4HECALIBRATIONOFTHERADARDOES OFCOURSE DEPENDONSTABLE SYSTEMCHARACTERISTICSANDANTENNAPARAMETERSTHATAREINVARIANTWITHTHESPACINGOF THEFRONTSURFACEANDTHEANTENNA!LTHOUGHONFIRSTCONSIDERATION FREQUENCYDOMAIN RADARSSHOULDOFFERASUPERIORSENSITIVITYTOTIME DOMAINRADARS BECAUSEOFTHEIRLOWER )&RECEIVERBANDWIDTHANDHENCETHERMALNOISE BOTHTHETYPEOFRECEIVERANDTHERANGE SIDELOBESOFTHERADIATEDSPECTRUMMAYRESULTINANEQUIVALENTORWORSESENSITIVITYIN TERMSOFRANGERESOLUTIONASDISCUSSEDABOVE 0SEUDO RANDOM CODED2ADAR 7ORKHASBEENCARRIEDOUTONPSEUDO RANDOM CODEDMODULATIONTECHNIQUESFOR'024HEMAINADVANTAGEOFTHISMETHODISTHATTHE ENERGYTRANSMITTEDISSPREADMOREEVENLYOVERTHESPECTRUMTHANWITHANYOTHERMODU LATIONMETHODANDHENCETHELIKELIHOODOFINTERFERENCETOOTHERUSERSOFTHESPECTRUM ISMINIMIZED)NADDITION THECHANCESOFOTHERUSERSOF SAY MOBILEPHONESINTERFERING WITHTHE'02OPERATORAREALSOREDUCED4HEMEANPOWERISTHELOWESTOFANYOFTHE MODULATIONSCHEMESANDTHISISHELPFULINMEETINGREGULATORYREQUIREMENTS 4HE TRANSMITTED SIGNAL HAS NOISE LIKE CHARACTERISTICS AND THE RECEIVED SIGNAL IS CROSS CORRELATED WITH A SAMPLE OF THE TRANSMITTED SIGNAL4HE RANGE OF THE TARGET IS GIVENBYTHETIMEPOSITIONOFTHECROSS CORRELATEDSIGNALANDTHEAMPLITUDEBYTHEPEAK OF THE CROSS CORRELATED SIGNAL #ONTROL OF THE CROSS CORRELATION SIDELOBES IS VITAL TO ACHIEVEGOODRANGERESOLUTIONANDTHESIDELOBESAREAFFECTEDBYTHEANTENNAANDSYSTEM CHARACTERISTICSASWELLASTHEDURATIONANDRANDOMNESSOFTHETRANSMITTEDWAVEFORM &URTHERINFORMATIONISGIVENBY.ARAYANANAND3ACHSETAL
Ó£°ÇÊ /
-
)NTHEULTRAWIDEBANDCASE THERADARANTENNASARECONSIDEREDINTERMSOFTHEIRTRANSFER FUNCTIONRATHERTHANTHEIRGAINSOREFFECTIVEAPERTURES)NMANYCASES ASEPARATETRANSMIT ANDRECEIVEANTENNAISUSEDHENCETHEIRTRANSFERFUNCTIONSMAYNOTBEIDENTICAL4HETYPE OFANTENNATHATISUSEDWITHULTRAWIDEBANDRADARHASANIMPORTANTROLEINDEFININGTHE PERFORMANCEOFTHERADAR
'2/5.$0%.%42!4).'2!$!2
Ó£°Óx
%LEMENTANTENNASARECHARACTERIZEDBYLINEARPOLARIZATION LOWDIRECTIVITY ANDRELA TIVELYLIMITEDBANDWIDTH UNLESSEITHEREND LOADINGORDISTRIBUTED LOADINGTECHNIQUES AREEMPLOYEDINWHICHCASEBANDWIDTHISINCREASEDATTHEEXPENSEOFRADIATIONEFFI CIENCY!NELEMENTALANTENNAISADIPOLEINCONTRASTTOAPERTUREANTENNASSUCHASHORNS !NORMALSHORTDIPOLEANTENNAFEDWITHAVERYSHORTCURRENTIMPULSEWILLRADIATEFROM THEFEEDPOINTSANDTHEENDOFTHEELEMENTBECAUSEOFTHELATTERSDISCONTINUITYASFAR ASCURRENTFLOWISCONCERNED4HECURRENTIMPULSEWILLBEREFLECTEDFROMTHEENDOF THEDIPOLEANDTRAVELUPANDDOWNTHEDIPOLECAUSINGASERIESOFIMPULSESOFRADIA TION4HISEXTENDSTHETIMESIGNATUREOFTHERADIATEDWAVEFORMANDDEGRADESTHERANGE RESOLUTIONOFTHESYSTEM4HISEFFECTISSHOWNIN&IGUREWHERETHERADIATIONPAT TERNISSHOWNATATIMESEVERALPULSEDURATIONSAFTERAPPLICATION4HEOUTERPERIMETER REPRESENTSTHEENERGYRADIATEDATTIMEZEROFOLLOWEDATINTERVALSBYTHERADIATIONFROM THEFEEDPOINTSANDTHEENDOFTHEELEMENT !SITISREQUIREDTORADIATEONLYAVERYSHORTIMPULSE ITISIMPORTANTTOELIMINATE THEREFLECTIONDISCONTINUITIESFROMTHEFEEDPOINTSANDENDSOFTHEANTENNAEITHERBY ENDLOADINGORBYREDUCINGTHEAMPLITUDEOFTHECHARGEANDCURRENTREACHINGTHEENDS 4HELATTERCANBEACHIEVEDEITHERBYRESISTIVELYCOATINGTHEANTENNAORBYCONSTRUCTING THEANTENNAFROMAMATERIALSUCHAS.ICHROME WHICHHASADEFINEDLOSSPERUNITAREA )NTHISCASE THEANTENNARADIATESINACOMPLETELYDIFFERENTWAYASTHEAPPLIEDCHARGE BECOMESSPREADOVERTHEENTIREELEMENTLENGTH ANDHENCE THECENTERSOFRADIATIONARE DISTRIBUTEDALONGTHELENGTHOFTHEANTENNA4YPICALRADIATEDFIELDPATTERNSFORARESIS TIVELYLOADEDDIPOLEARESHOWNIN&IGURE(OWEVER THEREDUCTIONINIMPULSE DURATIONISACHIEVEDATTHEEXPENSEOFEFFICIENCYANDLOADEDANTENNASMAYHAVEEFFI CIENCIESASLOWAS 4HETYPESOFANTENNASTHATAREUSEFULTOTHEDESIGNEROFULTRAWIDEBANDRADARFALL INTOTWOGROUPSDISPERSIVEANTENNASANDNONDISPERSIVEANTENNAS$ISPERSIVEANTENNAS HAVE A NONLINEAR PHASEFREQUENCY RESPONSE WHEREAS NONDISPERSIVE ANTENNAS HAVE A SUBSTANTIALLYLINEARPHASEFREQUENCYRESPONSE%XAMPLESOFDISPERSIVEANTENNASTHAT HAVEBEENUSEDINULTRAWIDEBANDRADARARETHEEXPONENTIALSPIRAL THE!RCHIMEDEAN
&)'52% 2ADIATEDFIELDPATTERNFROMACONDUCTINGDIPOLEELEMENTDUE TOANAPPLIEDIMPULSE#OURTESY)%%
Ó£°ÓÈ
2!$!2(!.$"//+
&)'52% 2ADIATED FIELD PATTERN FROM A RESIS TIVELY LOADED DIPOLE ELEMENT DUE TO AN APPLIED IMPULSE #OURTESY)%%
SPIRAL THELOGARITHMICPLANARANTENNA THE6IVALDIANTENNA SLOTANTENNAS ANDTHEEXPO NENTIAL HORN 4HE IMPULSE RESPONSE OF THIS CLASS OF ANTENNAS GENERALLY RESULTS IN A WAVEFORMWHOSETIMEFREQUENCYRESPONSEISEXTENDEDANDISSIMILARTOACHIRP ALBEIT WITHANINCONSTANTAMPLITUDE IFTHEINPUTISANIMPULSE %XAMPLES OF NONDISPERSIVE ANTENNAS ARE THE 4%- HORN THE BICONE THE BOW TIETHERESISTIVE LUMPEDELEMENT LOADEDANTENNA ANDTHECONTINUOUSLY RESISTIVELY LOADEDANTENNA4HEINPUTVOLTAGEDRIVINGFUNCTIONTOTHETERMINALSOFTHEANTENNAIN IMPULSERADARISTYPICALLYANARROWGAUSSIANPULSEOFPS ANDTHISREQUIRESTHE IMPULSERESPONSEOFTHEANTENNATOBEEXTREMELYSHORT4HEMAINREASONFORREQUIR INGTHEIMPULSERESPONSETOBESHORTISTHATITISIMPORTANTTHATTHEANTENNADOESNOT DISTORTTHEINPUTFUNCTIONANDGENERATETIMESIDELOBES4HESETIMESIDELOBESWOULD OBSCURETARGETSTHATARECLOSEINRANGETOTHETARGETOFINTERESTINOTHERWORDS THE RESOLUTIONOFTHERADARCANBECOMEDEGRADEDIFTHEIMPULSERESPONSEOFTHEANTENNA ISSIGNIFICANTLYEXTENDED (OWEVER INPRINCIPLE ALLANTENNASAREDISPERSIVETOSOMEEXTENTBUTNONDISPERSIVE ANTENNASDONOTNEEDCORRECTIONINTHESIGNALPROCESSING WHICHREDUCESTHEOVERALL COMPLEXITY OF THE RADAR PROCESSING 4HE VERY SHORT RANGE OPERATION OF MANY '02 SYSTEMSENABLESOPERATIONOFANTENNASINAWAYTHATDOESNOTCONFORMTOTRADITIONAL ANALYTICMODELSOFANTENNAGAINANDAPERTURE (ORNANTENNASHAVEFOUNDMOSTUSEWITH&-#7ULTRAWIDEBANDRADARSWHERETHE GENERALLYHIGHERFREQUENCYOFOPERATIONANDRELAXATIONOFTHEREQUIREMENTFORLINEAR PHASERESPONSEPERMITTHECONSIDERATIONOFTHISCLASSOFANTENNA&-#7ULTRAWIDE BANDRADARSHAVEUSEDANOFFSETPARABOLOIDFEDBYARIDGEDHORN4HISARRANGEMENTWAS DESIGNEDTOFOCUSTHERADIATIONINTOTHEGROUNDATASLANTANGLETOREDUCETHELEVELOF THEREFLECTIONFROMTHEGROUND#ARENEEDSTOBETAKENINSUCHARRANGEMENTSTOMINI MIZETHEEFFECTOFBACKANDSIDELOBESFROMTHEFEEDANTENNA WHICHCANEASILYGENERATE REFLECTIONFROMTHEGROUNDSURFACE /NE METHOD OF RADIATING CIRCULAR POLARIZATION IS TO USE AN EQUI ANGULAR SPIRAL ANTENNA4HEDISPERSIVENATUREOFTHISTYPEOFANTENNACAUSESANINCREASEINTHEDURA TIONOFTHETRANSMITTEDWAVEFORMS ANDTHERADIATEDPULSETAKESTHEFORMOFAhCHIRPv
'2/5.$0%.%42!4).'2!$!2
Ó£°ÓÇ
INWHICHHIGHFREQUENCIESARERADIATEDFIRST FOLLOWEDBYTHELOWFREQUENCIES!hSPIK INGvFILTER WHICHMAYTAKETHEFORMOFACONVENTIONALMATCHEDFILTER HOWEVER MAY COMPENSATEFORTHISEFFECT ORAMORESOPHISTICATEDFILTERSUCHAS7IENERFILTER WHICH RECOVERSTHEORIGINALSHAPEOFTHEWAVEFORM APPLIEDTOTHEANTENNA )T IS IMPORTANT TO APPRECIATE THE EFFECT OF THE MATERIAL IN CLOSE PROXIMITY TO THE ANTENNA)NGENERALTHISMATERIAL WHICHINMOSTCASESWILLBESOILORROCKSORINDEED ICE CANBEREGARDEDASALOSSYDIELECTRICANDBYITSCONSEQUENTLOADINGEFFECTCANPLAY ASIGNIFICANTROLEINDETERMININGTHELOWFREQUENCYPERFORMANCEOFTHEANTENNAAND HENCE'024HEBEHAVIOROFTHEANTENNAISINTIMATELYLINKEDWITHTHEMATERIALAND INTHECASEOFBOREHOLERADARS THEANTENNAACTUALLYRADIATESWITHINALOSSYDIELECTRIC WHEREASINTHECASEOFTHE'02WORKINGABOVETHESURFACE THEANTENNAWILLRADIATE FROMAIRINTOAVERYSMALLSECTIONOFAIRANDTHENINTOALOSSYHALFSPACEFORMEDBY THE MATERIAL4HE BEHAVIOR OF ANTENNAS BOTH WITHIN LOSSY DIELECTRICS AND OVER LOSSY DIELECTRICSISWELLREPORTED4HEPROPAGATIONOFELECTROMAGNETICPULSESINAHOMOGE NEOUSCONDUCTINGEARTHHASBEENMODELEDBY7AITAND+ING ANDTHEDISPERSIONOF RECTANGULARSOURCEPULSESSUGGESTSTHATTHETIME DOMAINCHARACTERISTICSOFTHERECEIVED PULSECOULDBEUSEDASANINDICATIONOFDISTANCE 4HEINTERACTIONBETWEENTHEANTENNAANDTHELOSSYDIELECTRICHALFSPACEISALSOSIG NIFICANTASTHISMAYCAUSEMODIFICATIONOFTHEANTENNARADIATIONCHARACTERISTICSBOTH SPATIALLYANDTEMPORALLYANDSHOULDALSOBETAKENINTOACCOUNTINTHESYSTEMDESIGN )NTHECASEOFANANTENNAPLACEDONANINTERFACE THETWOMOSTIMPORTANTPARAMETERS ARETHECURRENTDISTRIBUTIONANDTHERADIATIONPATTERN!TTHEINTERFACE CURRENTSONTHE ANTENNAPROPAGATEATAVELOCITY WHICHISINTERMEDIATEBETWEENTHATINFREESPACEAND THATINTHEDIELECTRIC)NGENERAL THEVELOCITYISRETARDEDBYTHE E R 4HENET RESULTISTHATEVANESCENTWAVESAREEXCITEDINAIR WHEREASINTHEDIELECTRICTHEENERGY ISCONCENTRATEDANDPREFERENTIALLYINDUCEDBYAFACTOROFN 4HERESPECTIVECALCULATEDFAR FIELDPOWERDENSITYPATTERNS INBOTHAIRANDDIELECTRIC AREGIVENBY2UTLEDGESEE4ABLE ANDTHESEAREPLOTTEDFORARELATIVEDIELECTRIC CONSTANTOFIN&IGUREAND&IGURE&ORCOMPARISON THEFAR FIELDPATTERN OFADIPOLERADIATINGINTOFREESPACEISSHOWNIN&IGURE 4HEABOVEEXPRESSIONSIN4ABLEASSUMETHATTHECURRENTSOURCECONTACTSTHE DIELECTRIC WHEREAS A MORE GENERAL CONDITION IS WHEN THE ANTENNA IS JUST ABOVE THE DIELECTRIC!SIGNIFICANTPRACTICALPROBLEMFORMANYAPPLICATIONSISTHENEEDTOMAIN TAINSUFFICIENTSPACINGTOAVOIDMECHANICALDAMAGETOTHEANTENNA)TCAN THEREFORE BE APPRECIATEDTHATTHEEFFECTOFCHANGESINDISTANCEBETWEENTHEANTENNAANDHALFSPACEIS TOCAUSESIGNIFICANTVARIATIONINTHERESULTANTRADIATIONPATTERNSINTHEDIELECTRIC !PARTICULARLYUSEFULANTENNACAPABLEOFSUPPORTINGAFORWARDTRAVELING4%-WAVE IS THE 4%- HORN )N GENERAL SUCH ANTENNAS CONSIST OF A PAIR OF CONDUCTORS EITHER 4!",% 0OWER$ENSITY0ATTERNSIN!IRAND$IELECTRIC
0LANE (
%
0OWER
0OWER
2ADIATIONPATTERNINDIELECTRICXDIRECTION
2ADIATIONPATTERNINDIELECTRICYDIRECTION
COSP A ¤ ³ A¥ ¦ COSP A H COSP D ´µ ¤ COSP A COSP D ³ A¥ ¦ H COSP A COSP D ´µ
H COSP D ¤ ³ AH¥ ¦ COSP A H COSP D ´µ
¤ H COSP A COSP D ³ AH¥ ¦ H COSP A COSP D ´µ
Ó£°Ón
2!$!2(!.$"//+
&)'52% % PLANEPLOTOFFAR FIELDPOWERDENSITYOFACURRENTELEMENT RADIATINGINTOALOSSLESSMATERIALOFDIELECTRICCONSTANTOF
FLAT CYLINDRICAL ORCONICALINCROSSSECTION FORMINGA6STRUCTUREINWHICHRADIATION PROPAGATESALONGTHEAXISOFTHE6STRUCTURE!LTHOUGHRESISTIVETERMINATIONISUSED THISTYPEOFANTENNAHASADIRECTIVITYONTHEORDEROFnD"DEPENDINGONSIZE HENCE USEFULGAINCANSTILLBEOBTAINEDEVENWITHATERMINATINGLOSSONTHEORDEROF
&)'52% ( PLANE PLOT OF FAR FIELD POWER DENSITY OF A CURRENT ELEMENTRADIATINGINTOALOSSLESSMATERIALOFDIELECTRICCONSTANTOF
'2/5.$0%.%42!4).'2!$!2
Ó£°Ó
&)'52% ( PLANEPLOTOFFAR FIELDPOWERDENSITYOFACURRENTELEMENT RADIATINGINTOFREESPACE
D"TOD"!FURTHERDEVELOPMENTOFTHE4%-HORNISGIVENBY-ARTELINWHICH THEANTENNAISCOMPOSEDOFASETOFSPREADhFINGERSvFORMINGTHESHAPEOFAHORNAS SHOWNIN&IGURE%ACHFINGERISAWIREWITHADIAMETEROFMMANDISRESIS TIVELYLOADEDATDIFFERENTLOCATIONSALONGTHELENGTHOFTHEANTENNA4HEFEEDCOMPO NENTFORTHEANTENNAISCOMPRISEDOFA/HMCOAX FEEDINGATAPEREDPARALLELPLATE WAVEGUIDEWITHAWIDTHOFMMANDAHEIGHTOFMM!TAPERALONGTHEWIDTHOF THETOPPARALLELPLATEISUSEDASATRANSITIONTOTRANSFORMA/HMUNBALANCEDLINE INTOAOHMBALANCEDLINE
&)'52% !NTENNAANDFEEDGEOMETRYOFLOADED4%-HORN , CM#OURTESY)%%
Ó£°Îä
2!$!2(!.$"//+ "
"
"
! #" $ " " $
"#! #" % "
"
&)'52% 0REDICTEDANDACTUALPULSERESPONSESOFLOADED4%-HORNANTENNA#OURTESY)%%
4HEPREDICTEDANDACTUALTIME DOMAINPULSEOFTHEOPTIMUMDESIGNISSHOWNIN &IGURE4HESHAPEOFTHETIME DOMAINANTENNARESPONSEISSIMILARTOASECOND DERIVATIVEGAUSSIANSIGNAL)TCANBESEENTHATMOSTOFTHEINTERNALREFLECTIONSHAVEBEEN SUPPRESSED4HERATEOFDECREASEFORTHEUNWANTEDRINGINGISBETTERTHAND"NS4HE 6372WASBETTERTHANFROM-(ZTO'(Z 4HEREAREMANYCONFIGURATIONSOFANTENNATHATCANBEUSEDCROSSEDDIPOLESAND PARALLELDIPOLESARETHEMOSTPOPULAR4HEMAINREASONFORTHEUSEOFTWOANTENNASIS THAT42SWITCHESTHATAREFASTENOUGHFOR'02ARENOTYETAVAILABLE
Ó£°nÊ - Ê Ê Ê*,"
-- 4HETHREEBASICPERMUTATIONSOF'02DATAPRESENTATIONARESHOWNIN&IGURE4HE MOSTBASIC'02DATARECORDISAN! SCAN!N! SCANPROVIDESAMPLITUDE TIMERECORD OFASINGLEMEASUREMENTOVERATARGET/NLYAMPLITUDE RANGEINFORMATIONISPLOTTED '02ISGENERALLYUSEDINSUCHAWAYASTOGENERATEASEQUENCEOF! SCANSRELATEDTO THESURVEYPOSITIONONTHEGROUNDSURFACE4HISSEQUENCECANBETERMEDA" SCANAND ANEXAMPLEISSHOWNIN&IGURE4HISEFFECTIVELYREPRESENTSONEAXISZ DEPTHAND THEORTHOGONALAXISXORY LINEARPOSITION4HEAMPLITUDEOFTHESIGNALMAYBESHOWN AS A SERIES OF OVERLAPPING SIGNALS OR ALTERNATIVELY A hWIGGLE PLOTv BORROWED FROM SEISMICTERMINOLOGY ORAGRAYSCALE CODEDINTENSITYPLOTORAPSEUDO COLORIMAGE)N THEMODELEDEXAMPLESHOWN THEHYPERBOLICSPREADINGOFTHETARGETSPATIALRESPONSE CANBESEEN!SSHOWNIN&IGURE A# SCANCONSISTSOFAPLANVIEWX YPLANE OVERADEFINEDRANGEOFDEPTHZ .OTETHATTHESETERMSARENOTTHESAMEASUSEDIN CONVENTIONALRADARDISPLAY 4HERECEIVEDTIMEWAVEFORMCANBEDESCRIBEDASTHECONVOLUTIONOFANUMBEROF TIMEFUNCTIONSEACHREPRESENTINGTHEIMPULSERESPONSEOFSOMECOMPONENTOFTHERADAR SYSTEMINADDITIONTONOISECONTRIBUTIONSFROMVARIOUSSOURCES.OTETHATTWOANTENNAS AREUSEDONETRANSMITSANDONERECEIVES
SR T SS T SAF T SC T SGF T ST T SGR T SAR T NT
WHERE
SST SIGNALAPPLIEDTOTHEANTENNA SADT ANTENNAIMPULSERESPONSE SCT ANTENNACROSSCOUPLINGRESPONSE
'2/5.$0%.%42!4).'2!$!2
Ó£°Î£
SGDT GROUNDIMPULSERESPONSE STT IMPULSERESPONSEOFTARGET NT NOISE
DDENOTESDIRECTIONFBEINGFORWARDANDRREVERSEDIRECTION %ACH CONTRIBUTION HAS ITS OWN PARTICULAR CHARACTERISTICS THAT NEED TO BE CONSID EREDCAREFULLYBEFOREAPPLICATIONOFAPARTICULARPROCESSINGSCHEME)DEALLYTHESIGNAL APPLIED TO THE ANTENNA SHOULD BE A $IRAC FUNCTION BUT PRACTICALLY IT IS MORE LIKE A SKEWED GAUSSIAN IMPULSE OF DEFINED TIME DURATION -OST ANTENNAS USED IN SURFACE PENETRATING APPLICATIONS HAVE A LIMITED LOW FREQUENCY RESPONSE AND TEND TO ACT AS HIGH PASSFILTERS EFFECTIVELYDIFFERENTIATINGTHEAPPLIEDIMPULSEANDHENCECREATINGA TIME LIMITEDFUNCTION)NMOSTCASES NEARIDENTICALANTENNAAREUSED ANDIFTHESEARE SPACEDSUFFICIENTLYFARFROMTHEGROUNDSURFACE THENSAFT SART )NTHECASEOFANTEN NASOPERATEDINCLOSEPROXIMITYTOTHEGROUND THENBOTHSAFT ANDSART AREVARIANTWITH
&)'52% #OORDINATE SYSTEM FOR SCAN DESCRIPTION #OURTESY)%%
Ó£°ÎÓ
2!$!2(!.$"//+
CHANGESINTHEGROUNDSURFACEELECTRICALPARAMETERS%SSENTIALLYTHEIMPEDANCEOFTHE ANTENNAISCHANGEDBYITSPROXIMITYTOTHEGROUNDHENCEITCANNOTBECONSIDEREDTO HAVEASTABLEIMPULSERESPONSE !NYPROCESSINGSCHEMETHATRELIESONINVARIANTANTENNAPARAMETERSSHOULDTAKEINTO ACCOUNTTHEMODEOFOPERATIONOFTHEANTENNASANDTHEDEGREEOFSTABILITYTHATISPRAC TICALLYREALIZABLE4HEANTENNACROSSCOUPLINGRESPONSESCT ISCOMPOSEDOFAFIXED CONTRIBUTIONS`CT DUETOANTENNACROSSCOUPLINGINAIRANDAVARIABLECONTRIBUTIONSpCT DUETOTHEEFFECTOFTHEGROUNDORNEARBYOBJECTS(ENCESCT S`CT SpCT )THASBEEN FOUNDPOSSIBLETOREDUCETHEAMPLITUDEOFSCT TOVERYLOWLEVELS INTHECASEOFCROSSED DIPOLEANTENNASTOBELOWnD"SIMPLYBYATTENTIONTOTHEPRECISIONOFCONSTRUCTION ANDINTHECASEOFPARALLELDIPOLEANTENNASTOBELOWnD"BYTHEINTERPOSINGBETWEEN THEANTENNASOFSUITABLEABSORBINGMATERIAL(OWEVER SpCT CANBESIGNIFICANTLYLARGER ANDDEGRADESTHEOVERALLVALUEOFSCT TOnD"4HEVALUEOFSAT ISDETERMINEDBY ANYLOCALINHOMOGENEITIESINTHESOILORBYANYCOVERINGMATERIALWHETHEROFMINERALOR VEGETABLEORIGIN4HEREISUNFORTUNATELYLITTLETHATCANBEDONETOPREDICTVARIATIONSIN SpCT ANDITISNOTAMENABLETOTREATMENTBYMANYPROCESSINGALGORITHMS4HEVARIATION INSpCT ISMUCHGREATERWITHTHECROSSEDDIPOLEANTENNATHANTHEPARALLELDIPOLE4HE GROUND IMPULSE RESPONSE SGT CAN BE DETERMINED FROM ITS ATTENUATION AND DIELECTRIC CONSTANTACROSSTHEFREQUENCYRANGEOFINTEREST 4HETARGETIMPULSERESPONSECANBECOMPOSEDOFTHECONVOLUTIONOFTHEWANTED TARGETRESPONSE TOGETHERWITHMANYOTHERREFLECTORS WHICHMAYNOTBEWANTEDBYTHE USERBUTWHICHAREVALIDREFLECTINGTARGETSASFARASELECTROMAGNETICWAVESARECON CERNED4HETIMESEPARATIONOFTHETARGETSISRELATEDTOTHEIRPHYSICALSPACINGASWELLAS THEVELOCITYOFPROPAGATION WHICHCANVARYDEPENDINGONTHEMATERIALPROPERTIES 7HERE THE TARGETS ARE WELL SEPARATED IN RANGE IT IS RELATIVELY STRAIGHTFORWARD TO SEPARATETHERADARREFLECTIONS BUTTHISBECOMESPROGRESSIVELYMOREDIFFICULTASTARGETS BECOMECLOSERTOGETHER ASINSTEADOFSEPARABLETIME DOMAINSIGNATURESTHEREFLECTIONS WILLMERGETOGETHER !STHEANTENNASGENERALLYUSEDFOR'02HAVEPOORDIRECTIVITY THEPATTERNOFTHE REFLECTEDWAVEFORMINTHE" SCANREPRESENTEDTHESPATIALCONVOLUTIONOFTHEANTENNA PATTERNWITHTHETARGET4HEREADERISREFERREDTO&IGURE SHOWNPREVIOUSLY WHICH ILLUSTRATESTHISEFFECT4HISSPATIALPATTERNDOESNOTREPRESENTANIMAGEOFTHEOBJECTOF INTERESTANDMUCHEFFORTHASBEENMADETODEVELOPMETHODSTORECONSTRUCTTHETARGET IMAGEFROM'02DATA
&)'52% %NVELOPEOF! SCANSAMPLETIMESERIES#OURTESY)%%
'2/5.$0%.%42!4).'2!$!2
Ó£°ÎÎ
&)'52% " SCANUNPROCESSEDDATA#OURTESY)%%
$ECONVOLVING THE IMAGE USING ANY OF THE FOLLOWING PROCESSES CAN DO THIS SYN THETICAPERTUREPROCESSING CONJUGATEGRADIENTMETHODS ANDREVERSETIMEMIGRATIONARE EXTENSIVELYREPORTEDINTHELITERATURE-ANYOFTHESETECHNIQUESWORKWELLONISOLATED TARGETSSUCHASPIPES WHICHHAVEWELL DEFINEDGEOMETRICALBOUNDARIES4HESITUATION ISMOREDIFFICULTWITHSTRATIFIEDLAYERSAND OFCOURSE ANISOTROPICMATERIALS 7HENARECONSTRUCTEDIMAGEOFTHEBURIEDOBJECTISCREATED WHETHERASA" SCAN OR# SCANAREAATAPARTICULARRANGEOFDEPTHS ITISNECESSARYTOINTERPRETTHERADAR IMAGEASBEINGGENERATEDBYAPHYSICALSTRUCTURE4HISISNOTALWAYSEASYINTHECASEOF ACLUTTEREDIMAGE ANDAGREATDEALSTILLDEPENDSONTHEFIELDEXPERIENCEOFTHEOPERATOR %XAMPLESOFUNPROCESSED" SCANDATAANDTHESAMECORRECTEDFORSPREADINGLOSSAND ATTENUATIONARESHOWNIN&IGUREAND&IGURE !LTHOUGHA# SCANISESSENTIALLYANX YPLANEATASELECTEDVALUEOF:ORRANGEOF VALUESOF: MANYOFTHEPROCESSESDESCRIBEDINTHEPREVIOUSSECTIONCANBEAPPLIED
&)'52% " SCANDATACORRECTEDFORSPREADINGLOSSANDATTENUATION#OURTESY)%%
Ó£°Î{
2!$!2(!.$"//+
2EMEMBERING THAT A '02 " SCAN RESULTS IN A HYPERBOLIC CROSS SECTION FROM A TARGET THENANAREASCAN# SCAN WILLRESULTINAHYPERBOLOIDOFREVOLUTIONWHOSE VERTICALAXISRUNSTHROUGHTHETARGET!PLANEORTHOGONALTOTHEVERTICALAXISWILLGENER ATEACIRCULARFEATUREWHOSERADIUSINCREASESWITHDEPTH!TYPICALEXAMPLEISGIVEN IN&IGURE WHICHSHOWSTHE# SCANSFROMANANTI TANKMINEBURIEDATDIFFERENT DEPTHSWITHTHECENTEROFTHEMINESHOWNASANOVERLAY4HESEIMAGESREPRESENTAN UNFOCUSSEDREPRESENTATIONOFTHETARGETASARESULTOFTHE$SPATIALCONVOLUTIONOFTHE ANTENNAPATTERNWITHTHETARGET 4HEVARIABILITYOFGROUNDCONDITIONS ASWELLASTHEPHYSICSOF%-WAVEPROPA GATIONANDREFLECTION MUSTBECAREFULLYTAKENINTOACCOUNTINATTEMPTINGTOCLASSIFY TARGETSEVENAFTERIMAGEPROCESSING&OREXAMPLE THEDEPTHIMAGEOFAVOIDISALWAYS APPARENTLYSMALLERTHANITSPHYSICALSIZECORNERREFLECTORSOFANYREASONABLESIZEGEN ERATELARGEAPPARENTLYDISCONTINUOUSREFLECTIONIMAGESANDCONDUCTIVETARGETS WHICH REVERBERATEBYMEANSOFSTOREDENERGY CREATEEXTENDEDDEPTHIMAGES4HEIMAGEOF ABURIEDTARGETGENERATEDBYA'02WILLNOT OFCOURSE CORRESPONDTOITSGEOMETRICAL REPRESENTATION4HEFUNDAMENTALREASONSFORTHISARERELATEDTOTHERATIOOFTHEWAVE LENGTHOFTHERADIATIONANDTHEPHYSICALDIMENSIONSOFTHETARGET)NMOSTCASESFOR '02 THERATIOISCLOSETOUNITY4HISCOMPARESVERYDIFFERENTLYWITHANOPTICALIMAGE WHICHISOBTAINEDWITHWAVELENGTHSSUCHTHATTHERATIOISCONSIDERABLYGREATERTHAN UNITYTYPICALLY )N'02APPLICATIONS THEEFFECTOFCOMBINATIONSOFSCAT TERINGPLANES FOREXAMPLE THECORNERREFLECTOR CANCAUSEhBRIGHTSPOTSvINTHEIMAGE ANDVARIATIONSINTHEVELOCITYOFPROPAGATIONCANCAUSEDILATIONOFTHEASPECTRATIOOF THEIMAGE!LTHOUGHMANYIMAGESCANBEFOCUSEDTOREDUCETHEEFFECTOFANTENNABEAM SPREADING REGENERATIONOFAGEOMETRICMODELISAMUCHMORECOMPLEXPROCEDUREAND ISNOTUSUALLYATTEMPTED 4HEGENERALOBJECTIVEOFSIGNALPROCESSINGASAPPLIEDTO'02ISTOPRESENTEITHER ANIMAGETHATCANREADILYBEINTERPRETEDBYTHEOPERATORORTOCLASSIFYTHETARGETRETURN WITHRESPECTTOAKNOWNTESTPROCEDUREORTEMPLATE 4HEGENERALPROCESSINGPROBLEMENCOUNTEREDINDEALINGWITH'02DATAISINTHE WIDESTSENSETHEEXTRACTIONOFALOCALIZEDWAVELETFUNCTIONFROMATIMESERIES WHICH DISPLAYSVERYSIMILARTIME DOMAINCHARACTERISTICSTOTHEWAVELET4HISTIMESERIESIS GENERATEDBYSIGNALSFROMTHEGROUNDANDOTHERREFLECTINGSURFACE ASWELLASINTERNALLY FROMTHERADARSYSTEM5NLIKECONVENTIONALRADARSYSTEMSINWHICHTHETARGETCANGEN ERALLYBEREGARDEDASBEINGINMOTIONCOMPAREDWITHTHECLUTTER INTHE'02CASE THE TARGETANDTHECLUTTERARESPATIALLYFIXEDANDTHERADARANTENNAISMOVEDWITHRESPECT TOTHEENVIRONMENT )TISASSUMEDTHATDATAARERECORDEDTOANADEQUATERESOLUTION-OSTANTENNASUSED INSURFACEPENETRATINGAPPLICATIONSHAVEALIMITEDLOW FREQUENCYRESPONSEANDTENDTO ACTASHIGH PASSFILTERSEFFECTIVELYDIFFERENTIATINGTHEAPPLIEDIMPULSE!STHEGROUND ACTSASALOWPASSFILTER THEGROUNDLARGELYDEFINESTHEBANDWIDTHOFREFLECTEDSIGNAL
&)'52% 3EQUENCE OF UNFOCUSSED # SCANS OF A SET OF A BURIED!4 MINE TARGETS AT DEPTH INCREMENTSOFMM#OURTESY)%%
'2/5.$0%.%42!4).'2!$!2
Ó£°Îx
)NTHECASEOFANTENNASOPERATEDINCLOSEPROXIMITYTOTHEGROUND THEANTENNACHARAC TERISTICSMAYVARYASARESULTOFCHANGESINTHEGROUNDSURFACEELECTRICALPARAMETERS !NYPROCESSINGSCHEMETHATASSUMESTHEANTENNAPARAMETERSREMAINCONSTANTNEEDS TOACCOUNTFORTHEMODEOFOPERATIONOFTHEANTENNASANDTHEDEGREEOFSTABILITYTHATIS PRACTICALLYREALIZABLE4HISISAPARTICULARISSUEFOR'02ANDNEEDSCAREFULATTENTIONTO REDUCETHEEFFECTOFANTENNA GROUNDSURFACEINTERACTION 3OMEOFTHEANCILLARYREQUIREMENTSOFANOPERATIONAL'02SYSTEMNEEDTOBECON SIDERED!CCURATE HIGH RESOLUTION LOW COSTPOSITIONREFERENCINGSYSTEMSFORUSEWITH RADARFORSUBSURFACESURVEYTECHNIQUESARENOWAVAILABLE)TISIMPORTANTTHATDATACAN BERELATEDTOATRUEGEOGRAPHICREFERENCEPARTICULARLYWHENFILEDONDIGITALMAPPING SYSTEMSANDUSEDTODEFINEAREASOFSAFEWORKING !NOTHERCONSIDERATIONISTHEPLANEOFPOLARIZATIONOFTHEELECTROMAGNETICENERGY &ORTARGETSWITHONELARGEAREADIMENSIONSUCHASAPIPE THERADARCROSS SCATTERING SECTIONWILLBELARGERWHENTHEPOLARIZATIONVECTORISINLINEWITHTHEPIPE4HISMEANS THATANYAREATHATISSURVEYEDWITH SAY PARALLELDIPOLESMUSTBESURVEYEDINORTHOGONAL DIRECTIONSTOENSURETHATNOTARGETSAREMISSED4HESAMEREQUIREMENTALSORELATESTO CROSSEDDIPOLEANTENNAS
Ó£°Ê ** /" )TISONLYPOSSIBLETOPROVIDEABRIEFSUMMARYOFTHEWIDEVARIETYOFTHEAPPLICATIONS FOR'02 WHICHHASINSOMECASESBECOMEANESTABLISHEDANDROUTINEMETHODOFSUB SURFACEINVESTIGATION'02 INTHEHANDSOFANEXPERT PROVIDESASAFEANDNONINVASIVE METHODOFCONDUCTINGSPECULATIVESEARCHESWITHOUTTHENEEDFORUNNECESSARYDISRUPTION ANDEXCAVATION!TYPICALEXAMPLEOFA'02IMAGEISSHOWNIN&IGUREWITHTHE VARIOUSFEATURESIDENTIFIED '02HASSIGNIFICANTLYIMPROVEDTHEEFFICIENCYOFTHEEXPLORATORYWORKTHATISFUN DAMENTALTOTHECONSTRUCTIONANDCIVILENGINEERINGINDUSTRIES THEPOLICEANDFORENSIC SECTORS SECURITYINTELLIGENCEFORCES ANDARCHAEOLOGICALSURVEYS '02HASBEENVERYSUCCESSFULLYUSEDINFORENSICINVESTIGATIONS4HEMOSTNOTORI OUSCASEBEINGINTHE5NITED+INGDOMIN WHENTHEGRAVESITES UNDERCONCRETE ANDINTHEHOUSEOF&RED7EST OFTHEVICTIMSOFTHESERIALMURDERERWEREPINPOINTED )N"ELGIUM THEGRAVESITESOFTHEVICTIMSOFTHEPEDOPHILE $UTEOUS WEREDETECTED IN
&)'52% 4YPICALRADARIMAGEOFCONCRETEFLOORSHOWINGREARS JOINTS MESH ETCNSPULSE WIDTH HORIZONTALMARKERSEVERYCM VERTICALSCALEM#OURTESY)%%
Ó£°ÎÈ
2!$!2(!.$"//+
&)'52% 4EMPLESTEPS#OURTESY)%%
!RCHAEOLOGICALAPPLICATIONSOF'02HAVEBEENVARIED RANGINGFROMTHEEXPLORA TIONOF%GYPTIANAND.ORTH!MERICAN)NDIANSITESASWELLASCASTLESANDMONASTERIES IN%UROPE4HEQUALITYOFTHERADARIMAGECANBEEXCEPTIONALLYGOOD ALTHOUGHCORRECT UNDERSTANDING NORMALLY REQUIRES JOINT INTERPRETATION BY THE ARCHAEOLOGISTS AND RADAR SPECIALISTS3INCE THE3QUARE'EOPHYSICAL3URVEY0ROJECT UNDERTHEAUSPICESOF THE.ATIONAL-USEUMOF3COTLANDANDTHE'LASGOW-USEUMS HAVEBEENCARRYINGOUT GEOPHYSICALANDARCHAEOLOGICALSURVEYSAT3QUAREIN%GYPT3QUAREFORMSPARTOFTHE NECROPOLISOFTHEANCIENT%GYPTIANCAPITALCITYOF-EMPHIS4HEBURIALGROUNDSEXTEND FROM!BU2OASH JUSTTOTHENORTHOF#AIRO SOUTHWARDTHROUGH'IZA !BUSIR 3AQQARA AND$AHSHURTO-EIDUMAPPROXIMATELYKMTOTHESOUTH4HEFAMOUS3TEP0YRAMIDOF THERD$YNASTYRULER +ING:OSER DOMINATESTHESITEOF3AQQARA4HEMAINMONUMENT ISKNOWNASTHE'ISREL -UDIR WHICHCONSISTSOFAMETEREASTTOWESTBYMETER NORTHTOSOUTHSTONEENCLOSURE4HEWALLSAREOFEXTREMELYCRUDECONSTRUCTION BUTMAS SIVE4HIS MONUMENT MAY CONSTITUTE ONE OF THE OLDEST STONE BUILDINGS IN %GYPT AND HENCETHEWORLD/NEOFTHEMAINGOALSOFTHEPROJECTHASBEENTODETERMINEWHAT IF ANYTHING LIESWITHINTHEENCLOSURE$ESPITEMANYYEARSOFSURVEYING NOTHINGHASBEEN FOUNDAPARTFROMASMALLAREAOFMUDBRICKPAVEMENT!NUMBEROFRADARSECTIONSHAD BEENMEASUREDOVERTHISAREAPREVIOUSLY ANDINVIEWOFTHEMAGNETOMETRYRESULTS THE RADARPROFILESWEREREEXAMINED4HESECTIONSHAVEBEENMEASUREDONMETERCENTERS SOITWASPURELYBYCHANCETHATONERADARSURVEYLINEWENTSTRAIGHTDOWNTHEFLIGHTOF STEPSEXCAVATED SEENIN&IGUREWITHTHERADARIMAGEIN&IGURE
&)'52% 2ADARSECTIONALONGTHEFLIGHTOFSTEPS#OURTESY)%%
'2/5.$0%.%42!4).'2!$!2
Ó£°ÎÇ
&)'52% %XAMPLEOF'02IMAGEOF4-!!4MINE#OURTESY)%%
!BANDONEDANTIPERSONNELLANDMINESANDUNEXPLODEDORDNANCEAREAMAJORHIN DRANCETOTHERECOVERYOFMANYCOUNTRIESFROMWAR4HEIREFFECTONTHECIVILIANPOPU LATIONISDISASTROUSANDMAJOREFFORTSAREBEINGMADEBYTHEINTERNATIONALCOMMUNITY TOCLEARTHEPROBLEM-OSTDETECTIONISDONEWITHMETALDETECTORS WHICHRESPONDTO THE LARGE AMOUNT OF METALLIC DEBRIS IN ABANDONED BATTLEFIELD AREAS AND HENCE HAVE DIFFICULTYINDETECTINGTHEMINIMUMMETALORPLASTICMINE'02TECHNOLOGYISBEING APPLIED TO THIS PROBLEM AS A MEANS OF REDUCING THE FALSE ALARM RATE AND PROVIDING IMPROVEDDETECTIONOFLOW METAL CONTENTMINES4YPICALEXAMPLESOFRADARIMAGESAT VARIOUSSCALESARESHOWNIN&IGUREAND&IGURE '02HASBEENUSEDFORSURVEYINGMANYDIFFERENTTYPESOFGEOLOGICALSTRATARANG INGFROMEXPLORATIONOFTHE!RCTICAND!NTARCTICICECAPSANDTHEPERMAFROSTREGIONS OF.ORTH!MERICA TOMAPPINGOFGRANITE LIMESTONE MARBLE ANDOTHERHARDROCKSAS WELL AS GEOPHYSICAL STRATA4HE RADAR DATA SHOWN IN &IGURE WERE COLLECTED AT &INSTERWALDERBREEN GLACIER 3VALBARD .ORWAY WHICH IS AN ISLAND ALMOST NORTH OF .ORWAY 4HE GLACIER IS AN KM LONG LAND TERMINATED GLACIER WITH AN AREA OF SQUAREKM4HEGLACIERDEPTHSTARTSATMETERSANDINCREASESDOWNTOMETERS )NTHEBEGINNINGOFTHEPROFILE ONLYTHEBOTTOMECHOISSEEN!TAROUNDKMHORIZONTAL DISTANCE SOMEINTERNALSCATTERINGFROMTHEGLACIERISSEEN4HISISSCATTERINGFROMTHE FREEWATERINSIDETHEGLACIER&ROMKMTOKM THEBOTTOMECHOISDIFFICULTTOSEE DUETOSCATTERING 4HETHICKNESSOFTHEVARIOUSLAYERSOFAROADCANBEMEASUREDUSING'02TECHNIQUES ASSHOWNIN&IGURE4HEGREATADVANTAGEISTHATTHISMETHODISNONDESTRUCTIVE ANDHIGHSPEED KMHR ANDCANBEAPPLIEDDYNAMICALLYTOACHIEVEACONTINUOUS PROFILEORROLLINGMAP4HEACCURACYOFCALIBRATIONTENDSTOREDUCEASAFUNCTIONOF
&)'52% %XAMPLEOF!4MINEIMAGESTAKENOVERAMBYMTESTSITEWITHTHE-).$%2'02 RADARSYSTEM#OURTESY)%%
Ó£°În
2!$!2(!.$"//+
&)'52% 2ADARPROFILESALONGTHECENTERLINEON&INSTERWALDERBREENGLACIERAT n-(ZFROM(AMRANETAL
DEPTHBECAUSEOFTHEATTENUATIONCHARACTERISTICSOFTHEGROUND4HEACCURACYMAYBE QUITEHIGHIE AFEWMILLIMETERS FORTHESURFACE WEARINGCOURSE BUTWILLREDUCETO CENTIMETERSATDEPTHSOFONEMETER "$
#
#
#$
#$
!$
% #
!$
$#
&)'52% 2ADAR IMAGES USING '(Z PULSE DURATION ALONG AN M LONG TRANSVERSAL TRACECLOSETOAJOINTOFAHIGHWAYCONCRETEDECK4OP0OLARIZATIONPARALLELTOTHEDOWELSBOTTOM 0OLARIZATIONPERPENDICULARTOTHEDOWELS#OURTESY)%%
'2/5.$0%.%42!4).'2!$!2
Ó£°Î
&)'52% 57" 3!2 IMAGE OF BURIED!4 MINES IN THE 9UMA $ESERT AIRCRAFT AT M ALTITUDE #OURTESY32))NTERNATIONAL53! $R26ICKERS
)THASBEENSHOWNTHATITISFEASIBLETODETECT!4MINESINDRYSOILCONDITIONSUSING AIRBORNERADARSYSTEMSTHATOPERATEOVERTHEFREQUENCYRANGEn'(Z&IGURE SHOWS A RADAR IMAGE TAKEN FROM AN ALTITUDE OF METERS ABOVE THE9UMA DESERT 4HERADAROPERATEDATADEPRESSIONANGLEOFANDACHIEVEDANOMINALRESOLUTIONOF CM)TWASCAPABLEOFDETECTINGMETAL!4MINESOF CMDIAMETERBURIEDATADEPTH OFnCMINASOILOFCONDUCTIVITYnMMHOSM&URTHERDETAILSCANBEOBTAINED FROM32))NTERNATIONAL53!
Ó£°£äÊ
- !LLCOUNTRIESREQUIRETHAT'02SYSTEMSAREPROPERLYREGULATEDANDOPERATEDINACCOR DANCEWITHNATIONALANDINTERNATIONALREQUIREMENTS5SERSSHOULDCONSULTWITHTHEIR NATIONALAUTHORITIESTODETERMINETHEREGULATORYENVIRONMENT 7ITHINTHE%UROPEAN5NION%5 THEREARETWOMAINCONSIDERATIONSGOVERN INGTHEUSEOF'024HESEARETHEUSEFIRSTOFTHEEQUIPMENTASADELIBERATERADIO FREQUENCYRADIATORANDSECONDASANEQUIPMENTTHATMUSTSATISFYTHE%-#REQUIRE MENTSOFTHE%54HE%UROPEAN4ELECOMMUNICATIONS3TANDARDS)NSTITUTE%43) REGULATORYBODYISINTHEPROCESSOFDRAFTINGSPECIFICATIONSANDINFORMATIONCANBE FOUNDATHTTPWWWETSIORGTHATWILLCOVERTHEUSEOFSUCHEQUIPMENTASADELIBER ATERADIOFREQUENCYRADIATOR,EGISLATIONANDAN%43)PRODUCTSPECIFICATIONMEANS THAT THIS EQUIPMENT WILL NEED TO CONFORM TO THE 2ADIO 4ELECOMMUNICATIONS 4ERMINAL%QUIPMENT244% $IRECTIVE)NTHESHORTTERM UNTILANEWPROD UCTSPECIFICATIONISINTRODUCEDANDFORMALLYPUBLISHEDINTHE/FFICIAL*OURNALOF THE %UROPEAN #OMMUNITIES THE %-# $IRECTIVE SHOULD BE APPLIED !LL EQUIP MENT INCLUDINGULTRAWIDEBANDRADAROR'02 MUSTBE#ONFORMIT£%UROP£ENE #%MARKEDTODEMONSTRATETHATITSATISFIESTHERELEVANTDIRECTIVESOFTHE%UROPEAN 5NION 4HE #% MARK MAY ONLY BE APPLIED WHEN THE REQUIREMENTS OF ALL OTHER RELEVANT%5$IRECTIVES SUCHASSAFETY HAVEALSOBEENDEMONSTRATED)NTHE53 THE &## WEB SITE PROVIDES CURRENT INFORMATION AND THE LIMITS ARE SHOWN IN &IGURE
Ó£°{ä
2!$!2(!.$"//+
%% "!( !
$&$& !* %%& ! * $& &
$#'!) !*
&)'52% &##EMISSIONLIMITS
, ,
$ * $ANIELS 'ROUND 0ENETRATING 2ADAR ND %D )%% 2ADAR 3ONAR .AVIGATION AND!VIONICS 3ERIES ,ONDON)%%"OOKS *ULY "/3TEENSON h2ADARMETHODSFORTHEEXPLORATIONOFGLACIERS v0H$DISSERTATION #ALIF)NST 4ECH 0ASADENA #! 3 %VANS h2ADIO TECHNIQUES FOR THE MEASUREMENT OF ICE THICKNESS v 0OLAR 2ECORD VOL PPn 2 2 5NTERBERGER h2ADAR AND SONAR PROBING OF SALT v IN TH )NT 3YMP ON 3ALT (AMBURG .ORTHERN/HIO'EOLOGICAL3OCIETY PPn 2 - -OREY h#ONTINUOUS SUB SURFACE PROFILING BY IMPULSE RADAR v IN 0ROC #ONF 3UBSURFACE %XPLORATIONFOR5NDERGROUND%XCAVATIONAND(EAVY#ONSTRUCTION !MER3OC#IV%NG PPn 0++ADABA h0ENETRATIONOF'(ZTO'(ZELECTROMAGNETICWAVESINTOTHEEARTHSURFACE FORREMOTESENSINGAPPLICATIONS vIN0ROC)%%%3%2EGION#ONF PPn * # #OOK h3TATUS OF GROUND PROBING RADAR AND SOME RECENT EXPERIENCE v IN 0ROC #ONF 3UBSURFACE%XPLORATIONFOR5NDERGROUND%XCAVATIONAND(EAVY#ONSTRUCTION !MER3OC#IV %NG PPn *##OOK h2ADARTRANSPARENCIESOFMINEANDTUNNELROCKS v'EOPHYS VOL PPn +#2OEAND$!%LLERBRUCH h$EVELOPMENTANDTESTINGOFAMICROWAVESYSTEMTOMEASURECOAL LAYERTHICKNESSUPTOCM v.AT"UR3TDS 2EPORT.O32 "OULDER #/ " .ILSSON h4WO TOPICS IN ELECTROMAGNETIC RADIATION FIELD PROSPECTING v 0H$ DISSERTATION 5NIVERSITYOF,ULEA 3WEDEN $*$ANIELS 3URFACE0ENETRATING2ADAR )%%2ADAR3ONAR.AVIGATIONAND!VIONICS3ERIES ,ONDON)%%"OOKS 3EE2EFERENCE
'2/5.$0%.%42!4).'2!$!2
Ó£°{£
#OOKAND"ERNFELD 2ADAR3IGNALS !N)NTRODUCTIONTO4HEORYAND!PPLICATION .ORWOOD -! !RTECH(OUSE P -3KOLNIK 2ADAR(ANDBOOK ND%D .EW9ORK-C'RAW (ILL #HAP &.ATHANSON 2ADAR$ESIGN0RINCIPLES .EW9ORK-C'RAW (ILL #HAP 7EHNER (IGH2ESOLUTION2ADAR #HAP 'ALATI !DVANCED 2ADAR 4ECHNIQUES AND 3YSTEMS )%% 2ADAR 3ONAR .AVIGATION AND!VIONICS 3ERIES6OL,ONDON)%%"OOKS P !STANIN AND +OSTYLEV 5LTRA WIDEBAND 2ADAR -EASUREMENTS 3YSTEMS )%% 2ADAR 3ONAR .AVIGATIONAND!VIONICS3ERIES 6OL ,ONDON)%%"OOKS #HAP - 4 4ULEY * - 2ALSTON & 3 2OTONDO ! - !NDREWS AND !% - 2OSEN h%VALUATION OF %ARTH2ADAR UNEXPLODED ORDNANCE TESTING AT &ORT!0 (ILL 6IRGINIA v )%%% !EROSPACE AND %LECTRONICS3YSTEMS-AGAZINE VOL ISSUE PPn -AY 0$EBYE 0OLAR-OLECULES .EW9ORK#HEMICAL#ATALOG#O + 3 #OLE AND 2 3 #OLE h$ISPERSION AND ABSORPTION IN DIELECTRICS ) ALTERNATING CURRENT CHARACTERISTICS v*0HYS#HEM VOL PPn $*$ANIELS h2ESOLUTIONOF57"SIGNALS v)%%0ROC2ADAR3ONARAND.AVIGATION VOL PPn !UGUST #-ARTEL -0HILIPPAKIS AND$*$ANIELS h4IMEDOMAINDESIGNOFA4%-HORNANTENNAFOR '02 vPRESENTEDAT-ILLENNIUM#ONFERENCEON!NTENNASAND0ROPAGATION !PRIL $*$ANIELS h!NASSESSMENTOFTHEFUNDAMENTALPERFORMANCEOF'02AGAINSTBURIEDLAND MINES vPRESENTEDAT30)%$ETECTIONAND2EMEDIATION4ECHNOLOGIESFOR-INESAND-INELIKE 4ARGETS8)) /RLANDO &, !PRIL '$ENNISSh3OLID STATELINEAR&-#7SYSTEMSnTHEIRPROMISEANDTHEIRPROBLEMS vIN0ROC)%%% )NT-IC#ONF !TLANTA '! PP n 2-.ARAYANAN 98U 0$(OFFMEYER AND*/#URTIS h$ESIGN PERFORMANCE ANDAPPLICA TIONSOFACOHERENTRANDOMNOISERADAR v/PTICAL%NGINEERING PPn *UNE *3ACHS 00EYERL &4KAC AND-+MEC h$IGITALULTRA WIDEBAND SENSORELECTRONICSINTEGRATED IN3I'E TECHNOLOGY vIN0ROCOFTHE%U-# VOL)) -ILAN )TALY 3EPTEMBER PPn * 3ACHS AND 0 0EYERL h#HIP INTEGRATED 57" RADAR ELECTRONICS v PRESENTED AT 4HIRD $4)& 7ORKSHOP 'ROUND0ENETRATING2ADARIN3UPPORTOF(UMANITARIAN$EMINING *2# )SPRA )TALY 3EPTEMBER *27AIT h0ROPAGATIONOFELECTROMAGNETICPULSESINAHOMOGENEOUSCONDUCTINGEARTH v!PPL 3CI2ES" VOL PPn 270+INGAND44.U h4HEPROPAGATIONOFARADARPULSEINSEAWATER v*!PPL0HYS PPn $"2UTLEDGEAND-3-UHA h)MAGINGANTENNAARRAYS v)%%%4RANS !0 1 PPn &EDERAL#OMMUNICATIONS#OMMISSION HTTPWWWFCCGOVABOUTUSHTML
#HAPTER
ÛÊ >ÀiÊ,>`>À `ÞÊ ÀÀÃ
ÓÓ°£Ê /," 1 /" )NTERMSOFTHENUMBEROFSYSTEMSINWORLDWIDEUSE CIVILMARINERADAR#-2 ISTHE LARGESTRADARMARKETOFALLTIME4HENUMBEROFVESSELSOFALLTYPESCURRENTLYFITTED WITHRADARPROBABLYAMOUNTSTOAROUNDMILLION BUTTHEREARENOOFFICIALRECORDSTO VERIFYTHISESTIMATE #-2BREAKSDOWNINTOTWOMAINAPPLICATIONAREAS4HEVASTMAJORITYAREUSEDAT SEAANDONNAVIGABLEWATERWAYSBYSHIPSANDSMALLERCRAFTTHEOTHERSAREUSEDBYPORT ANDCOASTALAUTHORITIESFORVESSELSURVEILLANCEFROMLAND BASEDSITES4HELATTERGROUP ARENORMALLYKNOWNASVESSELTRACKINGSERVICE643o RADARS2ADARSAREAVAILABLEFOR LEISURECRAFT FISHINGVESSELSANDMERCHANTSHIPS ANDALLOPERATEEITHERINTHE'(Z OR'(ZBANDS-ANYNAVIESALSOUSESTANDARDORSPECIALLYMODIFIED#-2FORNAVI GATIONALPURPOSES.OTONLYDOESITPROVIDEASUITABLENAVIGATIONALTOOLBUTALSOITS TRANSMISSIONSAREIDENTICALTOCONVENTIONALCOMMERCIALTRAFFIC ALLOWINGSAFENAVIGA TIONWITHOUTNECESSARILYHIGHLIGHTINGAVESSELSMILITARYPURPOSE 4HE BIGGEST INFLUENCE ON THE REQUIREMENTS OF SHIPBORNE #-2 COMES FROM THE )NTERNATIONAL -ARITIME /RGANIZATION )-/ ! 5NITED .ATIONS AGENCY BASED IN ,ONDON )-/ISCONCERNEDWITHINTERNATIONALMARITIMESAFETYANDTHEPROTECTIONOF THEMARINEENVIRONMENT)NPARTICULAR )-/ISSUESREQUIREMENTSANDGUIDELINESONTHE INSTALLATION AND USE OF RADAR EQUIPMENT ON COMMERCIAL SHIPS4HESE ARE VIGOROUSLY ENFORCEDBYTHELAWSOFINDIVIDUALMARITIMESTATES4HEPURPOSEOFSHIPBORNERADAR AS DEFINEDBY)-/ ISTOhASSISTINSAFENAVIGATIONANDINAVOIDINGCOLLISIONBYPROVIDING ANINDICATION INRELATIONTOOWNSHIP OFTHEPOSITIONOFOTHERSURFACECRAFT OBSTRUC TIONSANDHAZARDS NAVIGATIONOBJECTSANDSHORELINESv4HE)NTERNATIONAL!SSOCIATION OF-ARINE!IDSTO.AVIGATIONAND,IGHTHOUSE!UTHORITIES)!,! RECOMMENDSOPER ATIONALANDTECHNICALREQUIREMENTSFOR643RADARS 4HISCHAPTEREXPLAINSTHESPECIALREQUIREMENTSOF#-2 BOTHFROMAPRACTICALAND AREGULATORYPOINTOFVIEW ANDLOOKSATTHETECHNOLOGYANDSYSTEMCONCEPTSTHATARE BEINGUSEDTOMEETTHESEREQUIREMENTS5NTILTHEFIRSTDECADEOFTHEPRESENTCENTURY #-2SHIPBORNETECHNOLOGYHADBEENSOLELYBASEDONMAGNETRONSASTHEBASICSOURCE OFTRANSMITTEDPOWER3INCE )-/HASENCOURAGEDTHEUSEOFCOHERENTRADARSOLU TIONSINANATTEMPTTOIMPROVETHEDETECTIONOFTARGETSINHEAVYSEACLUTTERCONDITIONS o!LISTOFALLUSEDMARITIMEABBREVIATIONSISINCLUDEDATTHEENDOFTHECHAPTER
ÓÓ°£
ÓÓ°Ó
2!$!2(!.$"//+
)NTHEMARINEWORLD THESEHAVEBEENCALLED.EW4ECHNOLOGY2ADARS4HEYAREPER MITTED TO TRANSMIT ANY WAVEFORM AT '(Z PROVIDING THE SPECTRUM LIMITATIONS ON MARINERADARARENOTEXCEEDED4HELIMITSHAVEBEENAGREEDWITHINTHE)NTERNATIONAL 4ELECOMMUNICATION5NION)45 A5NITED.ATIONSAGENCYBASEDIN'ENEVA 4HISCHAPTERCONCENTRATESONTHEREQUIREMENTSANDDESIGNOFRADARSFORCOMMER CIALSHIPSNORMALLYINEXCESSOFGTGROSSMETRICTONNAGE WHERERADARFITMENT ISCOMPULSORYANDHIGHLYREGULATED7ORLDWIDE THEREAREABOUT OFTHESEVES SELS ANDMANYAREREQUIREDTOCARRYMORETHANONERADAR4HREEOREVENMORERADARS ARESOMETIMESCARRIEDVOLUNTARILYBYLARGESHIPS2ADARFORMSANIMPORTANTPARTOFA VESSELSTOTALNAVIGATIONEQUIPMENTFIT)NCREASINGLY THEBRIDGEOFASHIPISDESIGNED ASANINTEGRATEDCONCEPT COVERINGNAVIGATION COMMUNICATIONS ENGINECONTROL AND CARGOMONITORINGFACILITIES&IGUREILLUSTRATESAMODERNINTEGRATEDBRIDGESYSTEM )"3 ASFITTEDONACRUISESHIP4HERADARDISPLAYSARESEENTOFORMAPROMINENTPARTOF THESYSTEM2ADARSFITTEDONSMALLERFISHINGVESSELSANDLEISURECRAFTSHAREMANYOFTHE FEATURESOFRADARSDESIGNEDFORSHIPSBUTARENECESSARILYMORECOMPACTATYPICALSMALL BOATRADARISSHOWNIN&IGURE3PECIFICREQUIREMENTSFORTHESERADARS WHERETHEY DIFFERTOANYEXTENTFROMTHEDESIGNOFSHIPBORNERADARS AREDISCUSSEDWITHINRELEVANT PARTSOFTHECHAPTER2ADARFOR643ISSEPARATELYCOVEREDIN3ECTION 4HECHALLENGESFACINGDESIGNERSOFSHIPBORNERADARAREDETAILEDWITHIN3ECTION 4HESE RADARS HAVE TO MEET CERTAIN INTERNATIONAL STANDARDS WHICH ARE DISCUSSED IN 3ECTION3ECTIONCONCENTRATESONTHETECHNOLOGY AND3ECTIONLOOKSAT TARGETTRACKING2ADARTARGETSAREBEINGINCREASINGLYDISPLAYEDWITHELECTRONICCHART DATAASANUNDERLAY4HISISOUTLINEDIN3ECTION TOGETHERWITHOTHERUSERINTERFACE ISSUES3ECTIONLOOKSATTHELINKSBETWEENRADARANDTHERELATIVELYNEW!UTOMATIC )DENTIFICATION3YSTEM!)3 WHICHREPLICATESSOMEFUNCTIONSPREVIOUSLYPROVIDEDSOLELY BYRADAR-ARINERADARBEACONS INCLUDINGRACONS 3EARCHAND2ESCUE4RANSPONDERS 3!24S AND2ADAR4ARGET%NHANCERS24%S AREDESCRIBEDIN3ECTION4HEREIS ASHORTDISCUSSIONIN3ECTIONONSHIPBORNERADARPERFORMANCEVALIDATIONTESTING
&)'52% 3HIPSINTEGRATEDBRIDGESYSTEM#OURTESYOF3!- %LECTRONICS'MB(
#)6),-!2).%2!$!2
ÓÓ°Î
&)'52% 3MALLBOATRADAR#OURTESY&URUNO53! )NC
3HIPBORNERADARHASHADAREMARKABLYLONGHISTORY)TSCONCEPTIONINTHEPERIODFROM TOWASREMARKABLYPROPHETICANDSTILLREVERBERATESINTOTHEPRESENTCENTURY &ORTHISREASON ASHORT!PPENDIXTOTHISCHAPTEROUTLINESTHEEARLYSTEPSINTHEEVOLU TIONOFGLOBALSTANDARDSFORSHIPBORNERADAR
ÓÓ°ÓÊ / Ê %NVIRONMENTAL #IVILMARINERADAR PARTICULARLYSHIPBORNENAVIGATIONRADAR ISA SURPRISINGLYDEMANDINGAPPLICATION4HERADARHEADONA#-2COMPRISESTHEANTENNA ANDTURNINGGEAR THERECEIVERDOWNTO)&ORTODIGITALFORMATANDOFTENTHETRANSMITTER )THASTOOPERATEINEXTREMEENVIRONMENTALCONDITIONSOVERANEXTENDEDTEMPERATURE RANGEDOWNTO #INSOMEPARTSOFTHEWORLD INHIGHLEVELSOFWIND VIBRATION ANDSHOCKANDALSOINHEAVYPRECIPITATIONANDSALTWATERSPRAY%VENWITHINTHENOR MALLYBENIGNCONDITIONSONTHEBRIDGEOFALARGEMODERNSHIP THEDISPLAYANDRADAR PROCESSORCANBESUBJECTTOHIGHLEVELSOFSHOCKANDVIBRATIONANDMUSTMEETHIGH VARIATIONSINTEMPERATURE #TO # /NSMALLCRAFT THEDISPLAYANDRADARPRO CESSORAREOFTENFITTEDINMINIMALLYENCLOSEDAREASANDARESUBJECTTOVERYDAMPAND SALTYCONDITIONS)NTHESEENVIRONMENTS THERADARHASTODETECTTARGETSTHATCANHAVE ECHOINGAREASRANGINGFROMLESSTHANONESQUAREMETERTOMANYTENSOFTHOUSANDSOF SQUAREMETERSIMPORTANTTARGETSCANHAVERELATIVESPEEDSRANGINGFROMSTATIONARYTO KNOTSORMORETHETARGETSCANBESITUATEDINEXTREMEPRECIPITATIONANDSEACLUTTER CONDITIONSANDTHERADARANTENNAISNOTMOUNTEDONASTATICNORASTABLEPLATFORM4HE RADARISUSEDTOPREVENTCOLLISIONSANDGROUNDINGSATSEAANDIS THEREFORE ANIMPORTANT SAFETYRELATEDSYSTEM REQUIRINGINTEGRITYANDRELIABILITY&ORMOSTCOMMERCIALSHIPS THERADARNEEDSTOMEETSTRINGENT INTERNATIONALLYAGREEDPERFORMANCECRITERIA$ESPITE THESEREQUIREMENTS SYSTEMSARESOLDINAHIGHLYCOMPETITIVEMARKETANDPRICESARE THEREFORE KEPTKEEN0RICESRANGEFROMAROUND FORACOMPLETEBUTBASIC'(Z SYSTEMTO ANDABOVEFORAFULLYFEATURED'(ZSYSTEM2ADARSYSTEMSSUIT ABLEFORTHELEISUREMARKETCANSELLFORLESSTHAN
ÓÓ°{
2!$!2(!.$"//+
4!",% )-/2EQUIRED$ETECTION0ERFORMANCEIN#LEAR#ONDITIONS#OURTESYOF)-/
4ARGET &EATURE
4ARGET$ESCRIPTION
(EIGHT!BOVE 3EA,EVEL METERS
$ETECTION2ANGEIN.FORSPECIFIEDTARGETSIZE
'(Z.-
'(Z.-
4ARGET4YPE
3HORELINES 3HORELINES 3HORELINES 3/,!3SHIPSo GT 3/,!3SHIPSo GT 3MALLVESSELWITHRADAR REFLECTORMEETING)-/ PERFORMANCESTANDARDS 3MALLVESSELOFLENGTHM WITHNORADARREFLECTOR 4YPICALNAVIGATIONBUOY
2ISINGTO 2ISINGTO 2ISINGTO
M
$ISTRIBUTED #OMPLEX M 0OINT
M
M #OMPLEX
M
.AVIGATIONBUOYWITH CORNERREFLECTOR 4YPICALCHANNELMARKER
M
M .OTSPECIFIED POINT TARGETASSUMED M 0OINT
M
M .OTSPECIFIED POINT TARGETASSUMED
o3HIPSCONFORMINGTOTHE)-/3AFETYOF,IFEAT3EA3/,!3 REGULATIONS
$ETECTION0ERFORMANCE )N THE CLEARDETECTIONREQUIREMENTSFORSUCHRADARSARE NOTPARTICULARLYDEMANDING!NPROBABILITYOFDETECTIONANDAPROBABILITYOFFALSE ALARMOFnISSPECIFIEDBY)-/ ASSHOWNIN4ABLE 4AKING INTO ACCOUNT ALL PERFORMANCE REQUIREMENTS TYPICAL COMPLIANT SYSTEMS FOR COMMERCIALVESSELSHAVEPEAKTRANSMITPOWERSOFnK7 THELOWERPOWERSBEING CONFINEDTO'(ZSYSTEMS!NTENNAGAINSFROMTOD"ARETYPICAL WITHASSOCI ATEDHORIZONTALBEAMWIDTHSRANGINGFROMABOUTTOLESSTHAN0ULSELENGTHSARE SWITCHABLE GENERALLYINTHERANGEFROMNSTO§S WITH02&SRANGINGFROMTO (ZORMORE0LEASURECRAFTSYSTEMSTYPICALLYHAVEPEAKPOWERSOFnK7AND UTILIZEANTENNASWITHHORIZONTALAPERTURESASSMALLASMMANDGAINSOFABOUTD" 4HESEALLOPERATEAT'(Z4HEGREATESTTECHNICALCHALLENGEINDESIGNINGMARINERADARS ISTOMAINTAINGOODTARGETDETECTIONINHIGHLEVELSOFSEAANDPRECIPITATIONCLUTTER 0RECIPITATION #LUTTER )T IS WELL KNOWN THAT CIRCULAR POLARIZATION #0 CAN BE A COUNTERTORAINCLUTTERBECAUSEITSREFLECTIONISPREDOMINATELYCROSS POLARIZEDTOINCI DENTCIRCULARPOLARIZATION(OWEVER VERYFEWSHIPBORNENAVIGATIONALRADARSUSE#0 EVEN THOUGH n D" IMPROVEMENT IN RAIN CLUTTER REJECTION IS TYPICALLY ACHIEVED FROMITSAPPLICATION4WOIMPORTANTFACTORSHAVECONTRIBUTEDTOTHIS&IRST ITMAKES THEANTENNAMOREEXPENSIVE EXACERBATEDBY)-/SREQUIREMENTSTHAT'(ZRADARS MUSTBEATLEASTSWITCHABLETOHORIZONTALPOLARIZATIONWHENSEARCHINGFORSURVIVALCRAFT FITTED WITH 3EARCH AND 2ESCUE 4RANSPONDERS SEE 3ECTION 3ECOND BY USE OF SMALLRANGECELLSANDBYIMPLEMENTINGCONVENTIONALSIGNALDIFFERENTIATIONTECHNIQUES MODERNRADARS PARTICULARLYAT'(Z GIVEREASONABLEPERFORMANCEINMOSTCOMMONLY EXPERIENCEDPRECIPITATIONCLUTTER4HEREFORE USERSANDMARITIMEAUTHORITIESAREGENER ALLYSATISFIEDWITHTHEPERFORMANCEOFLINEARLYPOLARIZEDSYSTEMSINPRECIPITATION
#)6),-!2).%2!$!2
ÓÓ°x
"ECAUSEPRECIPITATIONCLUTTERISDISTRIBUTEDINARELATIVELYUNIFORMMANNER PASSING THERECEIVEDWAVEFORMTHROUGHADIFFERENTIATORGIVESPROMINENCETOTARGETSEMBEDDED WITHINTHECLUTTERBYENSURINGTHATTHEAVERAGECLUTTERLEVELISKEPTWELLBELOWSATURA TION4HEDIFFERENTIATORHASMINIMALEFFECTONNORMALTARGETSBECAUSEOFTHEIRSMALL EXTENTINTHETIMEDOMAIN4HISMEANSTHATTARGETVISIBILITYISIMPROVED)TSHOULDBE NOTEDTHATTHISTECHNIQUEDOESNOTGIVESUBCLUTTERVISIBILITY4HISPROCESSISCONVENTION ALLYNAMED&AST4IME#ONSTANT&4# 4HETIMECONSTANTOFTHEDIFFERENTIATORISOPERA TOR ADJUSTABLEWITHASO CALLEDRAINCLUTTERCONTROL WHICHALLOWSTHETARGET TO CLUTTER RATIOTOBEOPTIMIZEDFORTHEPARTICULARPRECIPITATIONSCENARIO 4HEVERTICALPATTERNOFASHIPBORNENAVIGATIONALRADARANTENNANEEDSTOBERELA TIVELYWIDETOCOPEWITHTHESHIPSPITCHANDROLL WHICHISASSUMEDTOBEAMAXIMUM OFo5SEOFASTABILIZEDPLATFORMWOULDNOTMEETTHEMARKETSPRICEDEMANDS 4HISLIMITSTHEVERTICALBEAM SHAPINGTHATCANBEUSEDTOREDUCEBOTHPRECIPITATION CLUTTERANDVERTICALLOBINGEFFECTS(OWEVER THERELATIVELYSHORTRANGEOFMOSTTARGETS OFREALINTERESTMEANSTHATTHEVOLUMEOFTHERADAR ILLUMINATEDPRECIPITATIONISRELA TIVELYLOW HELPINGTOMAKETHECLUTTERREJECTIONOFTHEDIFFERENTIATORADEQUATEFORITS PURPOSE3UCHCLUTTERVARIESAPPROXIMATELYWITHTHEFOURTHPOWEROFFREQUENCY AND SOA'(ZSYSTEMINHERENTLYEXPERIENCESD"LESSCLUTTERTHANA'(ZSYSTEM ASSUMING IDENTICALLY SIZED CLUTTER CELLS &OR THIS REASON ON SHIPS FITTED WITH BOTH AND'(ZRADARS THE'(ZRADARISOFTENPREFERABLE EXCEPTWHENMANEUVERING IN CLOSE SITUATIONS FOR EXAMPLE IN HARBORS WHEN THE NORMALLY SUPERIOR AZIMUTH RESOLUTIONOFA'(ZRADARISPREFERRED 3EA#LUTTER 4HEREDUCTIONOFSEACLUTTERTOLEVELSACCEPTABLETOTHEUSERISA FARMOREDIFFICULTPROBLEM ANDASYET COMMERCIALRADARSDONOTMEETALLTHEIDEAL DEMANDSOFUSERS3MALLCRAFTANDBUOYSCANEASILYBEOBSCUREDINSEACLUTTER)N THEDAYSBEFOREPRECISE'LOBAL.AVIGATION3ATELLITE3YSTEMS'.33 SUCHAS'03 THE SAFE NAVIGATION OF A SHIP IN COASTAL WATERS IN POOR VISIBILITY WAS DOMINATED BYTHERADARBEINGABLETODISCERNNAVIGATIONMARKERS SUCHASBUOYS0ASSIVEMARKERS INCLUDING THOSE SUPPLEMENTED BY RADAR REFLECTORS CAN BE NOTORIOUSLY DIFFICULT TO DETECTINHIGHERSEA STATES ANDTHEREFORE SOMEMARKERSARESUPPLEMENTEDBYRADAR BEACONS CALLED RACONSSEE 3ECTION 2ACONS ARE RELATIVELY EXPENSIVE AND NEEDMAINTENANCEINOFTENDIFFICULTTOACCESSLOCATIONS SOTHEIRUSEISRESTRICTED 7HILE'.33 ENHANCEDBYTHEGROWINGUSEOFELECTRONICCHARTS HASHELPEDGREATLY ININFORMINGMARINERSOFTHEPRECISEPOSITIONOFTHEIRVESSEL RADARISSTILLUSEDASAN IMPORTANTSECONDARYSOURCEOFPOSITION2ELIANCEON'.33ALONEHASBEENATTHE ROOTOFMANYMARINEACCIDENTS 4HE MAIN USE OF MARINE RADAR IS TO ASSIST COLLISION AVOIDANCE 6ISUAL OBSERVA TIONANDRADARREMAINTHEPRIMARYMETHODSFORDETERMININGTHERISKOFCOLLISIONWITH OTHERVESSELSANDALSOWITHFLOATINGDEBRISANDICE!UTOMATIC)DENTIFICATION3YSTEMS !)3SEE3ECTION OFFERPOTENTIALTOASSISTWITHCOLLISIONAVOIDANCEOFCOOPERA TIVETARGETS BUTITCANNOTBEASSUMEDTHATALLVESSELSAREFITTEDWITH!)3 PARTICULARLY SMALLCRAFT ORTHATATARGETVESSELS!)3ISOPERATIONAL 4HETRADITIONALWAYFORMARINERSTOOPTIMIZETHEIRRADARFORDETECTIONOFTARGETSINSEA CLUTTERISBYCAREFULADJUSTMENTOFTHEhGAINvANDhSEA CLUTTERvCONTROLS4HEGAINCON TROLEFFECTIVELYALTERSTHEDETECTIONTHRESHOLD/NAMODERNMARINERADAR THESEA CLUTTER CONTROLISBESTDESCRIBEDASAMETHODFORADJUSTINGTHESHAPEOFTHERADARSSENSITIVITY TIMECONTROL34# INORDERTOMATCHITWITHTHEPRESENTLEVELOFCLUTTERRETURNS34#IS OFTENALSOCALLEDSWEPTGAIN4HE34#LAW ANDTHEWAYITVARIESBYUSEOFTHEMANUAL CONTROL CANBECOMPLEX)TISATTEMPTINGTOREDUCETHEDYNAMICRANGEOFTHERECEIVED WAVEFORMANDTOPROVIDE INASSOCIATIONWITHTHEGAINSETTINGS OPTIMIZEDTHRESHOLDS
ÓÓ°È
2!$!2(!.$"//+
.OWADAYS ITNORMALLYINVOLVESSOPHISTICATEDADAPTIVETHRESHOLDINGTECHNIQUES WHICH AREDISCUSSEDIN3ECTION !LTHOUGH THIS HELPS TO SET THE THRESHOLD TO APPROPRIATE LEVELS IT DOES NOT REMOVE THEINTRUSIVEhSPIKYvCOMPONENTOFSEACLUTTERTHATCANMAKEWANTEDTARGETSDIFFICULTTO OBSERVE(OWEVER OVERATYPICALANTENNASCANTIMEOFAMARINERADARnSECONDS THE SPIKESARENORMALLYDECORRELATED WHEREASRETURNSFROMTARGETSAREGENERALLYCORRELATED THEREFORE THE APPLICATION OF SCAN TO SCAN CORRELATION CAN IMPROVE THE TARGET TO CLUTTER RATIO BUTITWILLALSOREMOVEWEAKANDFAST MOVINGTARGETS-ANYYEARSAGO #RONEY SHOWEDTHATSIGNIFICANTIMPROVEMENTSINDETECTINGSMALLTARGETSINSEACLUTTERCOULDBE OBTAINEDBYENSURINGTHATINTEGRATIONWASPERFORMEDATINTERVALSLONGERTHANTHEDECOR RELATIONTIMEPERIODOFTHESEACLUTTER(EUSEDANANTENNAROTATINGATUPTORPMAND A02&OF+(Z4HISGAVETWOCORRELATEDPULSESPERBEAMWIDTH BUTTHEPULSESFROMTHE NEXTSCAN SLATER WEREDECORRELATEDFROMTHEFORMER #RONY NOTED THAT THE RAPID SCANNING OF THE ANTENNA ALLOWED THE EYEBRAIN FUNC TIONSOFTHEOPERATORTOPERFORMSCAN TO SCANCORRELATION!LTHOUGHITISEASYFORMOD ERNSYSTEMSTOPERFORMTHISCORRELATIONDIGITALLY THEDIFFICULTIESINHAVINGANANTENNA ROTATINGATTHISSPEEDMAINLYNOWACOSTISSUE HAVEPREVENTEDTHISFROMBECOMING ESTABLISHEDPRACTICE(OWEVER MORERECENTWORKIN#ANADAHASRESURRECTEDTHISIDEA FORDETECTINGFLOATINGICEHAZARDS WHEREANTENNAROTATIONRATESOFRPMAND02&S OF+(ZHAVEBEENPROPOSED4ERMA!3 A$ANISHCOMPANYINVOLVEDINSUPPLYING HIGHPERFORMANCEMARINERADARS MAINLYINTHENONCOMMERCIALMARKET PRODUCESTHE 3CANTER4-RADAR WHICHHASANOPTIONTHATSIMULTANEOUSLYTRANSMITSONTWOFREQUEN CIESFROMASQUINTINGSLOTTEDWAVEGUIDEARRAY4HISPRODUCESTWOBEAMSSEPARATEDBY AFEWDEGREESINAZIMUTH4HETEMPORALBEAMSEPARATIONISSUCHTHATSEACLUTTERCANBE DECORRELATEDBETWEENTHEBEAMS FURTHERENHANCINGTHEDETECTIONOFTARGETSINCLUTTER 4HISTECHNIQUECOULDPOTENTIALLYBEUSEDBYSOLID STATE#-2S3ECTION /NACONVENTIONALSHIPBORNERADAR ANEXPERIENCEDOPERATORCANMANUALLYSETTHE DETECTIONTHRESHOLDTOGIVETHEBESTSETTINGOVERANYGIVENAREA BUTTHISISOFTENONLY EFFECTIVEOVERASMALLPROPORTIONOFTHETOTALRADARIMAGE4HEUSEOFAUTOMATICTHRESH OLDINGISABLETOGIVEBETTERDETECTIONOVERACOMPLETESCANBUTOFTENCANNOTCOMPETE WITHASKILLEDOPERATOROPTIMIZINGDETECTIONOVERARESTRICTEDAREA)NSOMECONDITIONS NOEXISTINGRADARGIVESTHEPERFORMANCETHATAUSERIDEALLYNEEDS DESPITETHEUSEOF NSPULSESANDSOPHISTICATEDCLUTTERPROCESSINGTECHNOLOGY 3UB CLUTTERVISIBILITYISPOTENTIALLYOBTAINABLEFROMCOHERENT#-2S WHICHHAVE BEENMADEAFFORDABLEBYTHECONTINUEDREDUCTIONINCOSTOFMICROWAVEPOWERSEMICON DUCTORSFORINSTANCE USING'ALLIUM.ITRIDETECHNOLOGY PRECISIONDIGITALLYCONTROLLED SIGNAL GENERATORS AND FAST DIGITAL SIGNAL PROCESSORS #OHERENT #-2S ARE DISCUSSED UNDERh3OLID STATE#-2vIN3ECTION 6ERTICAL ,OBING #LUTTER IS NOT THE ONLY CAUSE OF DETRIMENTAL PERFORMANCE OF MARINERADAR$IRECTREFLECTIONSFROMATARGETARRIVEATTHERADARANTENNAANDCOMBINE VECTORIALLYWITHTARGETREFLECTIONSTHATHAVEALSOBEENREFLECTEDBYTHESEASSURFACE 4HISEFFECTPRODUCESASUMMEDSIGNALATTHERADARANTENNATHATISAFUNCTIONOFBOTHTHE TARGETHEIGHTANDTHERADARANTENNAHEIGHTABOVETHESEA ASTHESEAFFECTTHEPATHLENGTH DIFFERENCEOFTHEDIRECTANDREFLECTEDRADIATION/BVIOUSLY THEEFFECTISRECIPROCALFOR BOTHTRANSMITANDRECEIVEPATHS&ORAPOINTTARGETANDASEAOFDEFINEDROUGHNESS THE CALCULATIONTODETERMINETHERESULTANTEFFECTISRELATIVELYSTRAIGHTFORWARDANDRESULTS INTHECLASSICLOBINGPATTERNSEE FOREXAMPLE "RIGGS &ORATARGETWITHREASONABLE VERTICALEXTENT SUCHASASHIP THELOBINGSTRUCTUREBECOMESVERYCOMPLEXANDISLESS LIKELYTOPRODUCETROUBLESOMENULLS(OWEVER THEDETECTIONOFASMALLTARGET SUCHAS
#)6),-!2).%2!$!2
ÓÓ°Ç
ABUOYORAPLEASURECRAFT ENHANCEDBYARADARREFLECTORCANCREATESIGNIFICANTVERTICAL LOBINGEFFECTSTHATCANBEAPROBLEMTOTHEUSER)NPARTICULAR INVERYCALMSEASPRO NOUNCEDNULLSCANBEEXPERIENCED ANDFORUSERS ITCANBEDISCONCERTINGWHENATARGET CLEARLYEVIDENTFROMTHEBRIDGEWINDOWISNOTVISIBLEONTHERADARDISPLAY DESPITETHE APPARENTLYGOODCONDITIONS 3INCESMOOTHSEASCANALSOBEASSOCIATEDWITHMISTANDFOG VERTICALLOBINGEFFECTS CANBECOMEASIGNIFICANTPROBLEMBECAUSETHEREDUCEDVISIBILITYMEANSTHATRADAROFTEN BECOMESTHESOLEMETHODOFDETECTINGOTHERVESSELS4HEABSENCEOFSEACLUTTERGIVES THEUSERAFALSESENSEOFSECURITYTHATALLTARGETSWILLBEEASILYVISIBLE/NSHIPSFITTED WITHBOTHAND'(ZRADARS FREQUENCYDIVERSITYBECOMESVERYUSEFULASTHESPATIAL FREQUENCIESOFTHEVERTICALLOBESFORTHERADARAREDIFFERENT3URPRISINGLY EVENTHOUGH SOMERADARCOMPANIESPROVIDETHEOPTION VERYFEWSHIPSHAVEFACILITIESTHATALLOW THE AND'(ZSIGNALSTOBECOMBINEDINTOASINGLERADARDISPLAYINANAUTOMATIC PROCESS MAXIMIZING THE BENEFITS OF FREQUENCY DIVERSITY 3OME LARGE SHIPS HAVE AN ADDITIONAL'(ZRADARMOUNTEDONTHEBOWATDECKLEVEL4HISHASTWOADVANTAGES &IRST THEVERTICALLOBINGWILLHAVEADIFFERENTLOWER ANGULARFREQUENCYTOTHEMAIN HIGH MOUNTED'(ZRADAR3ECOND ITSPERFORMANCEINSEACLUTTERWILLBEENHANCED AS THEGRAZINGANGLETOTHESEAWILLBECLOSERTOHORIZONTAL THEREBYLESSENINGTHEREFLECTION COEFFICIENTOFTHECLUTTER4HELONGRANGEPERFORMANCEOFTHEAUXILIARYSYSTEMIS OF COURSE COMPROMISEDBYITSLOWPOSITION -OVING 0LATFORM ! PARTICULAR COMPLICATION OF SHIPBORNE RADAR ARISES BECAUSE THE ANTENNA IS MOUNTED ON AN UNSTABLE MOVING PLATFORM 4HIS MOVEMENT HAS SIX COMPONENTSTHREETRANSLATIONALANDTHREEROTATIONAL ALLOFWHICHARETYPICALLYVARYING 4HEMOTIONSARECOMPLEXTHETRANSLATIONALCOMPONENTSARESURGE SWAY ANDHEAVE AND THEROTATIONALAREROLL PITCH ANDYAW#OMPONENTSCANBEQUASI HARMONICWHENCAUSED BYWAVEMOTION)NPRACTICE THESHIPISNAVIGATEDONNOTIONSBASEDONCOURSE HEADING AND SPEED IN %ARTH AND SEA FIXED COORDINATE SYSTEMS 4HE ADDITIONAL WAVE INDUCED MOTIONSCANPRODUCEUNCOMPENSATEDERRORSINRADAR DERIVEDINFORMATION WHICHADD TOANYMEASUREMENTERRORSINTHECOURSE HEADING ANDSPEEDOFTHEVESSEL4HISAFFECTS THE PRECISION OBTAINED WHEN DISPLAYING RADAR DERIVED DATA WHICH CAN DIFFER WHEN SWITCHINGBETWEENTHEVARIOUSRADARSTABILIZATIONMODESUSEDON#-2&ORINSTANCE INORDERTOFACILITATEBOTHCOLLISIONAVOIDANCEANDPOSITIONFIXINGACTIVITIES SHIPBORNE RADARDISPLAYSHAVEALWAYSHADTWOPARTICULARSTABILIZATIONMODES(EAD UPAND.ORTH UP 4HE hUPv DIRECTION REFERS TO THE VERTICAL Y AXIS DIRECTION OF THE RADAR DISPLAY h(EADvREFERSTOTHESHIPSHEADING(EAD UPMAXIMIZESTHERELATIONSHIPTOTHEVISUAL SCENE AND.ORTH UPAIDSCOMPARISONWITHPAPERCHARTS.OWADAYS #OURSE UPISALSO PROVIDED ASTHISELIMINATESSMALLOSCILLATIONSINTHERADARIMAGEDUETOTHESHIPSYAW THATOCCURWHENTHEDISPLAYISSETTO(EAD UP%ACHOFTHESEDIRECTIONALMODESCANBE SETWITHTARGETTRACKINGVECTORSSHOWNASRELATIVETOTHEMOTIONOFTHESHIP THEGROUND ORTHEAVERAGESEAMOTION
ÓÓ°ÎÊ / , /" Ê-/ , 3PECTRUMUSEASPECTSOFALLRADARS INCLUDINGFREQUENCYBANDOFUSEAND2&EMISSION CONSTRAINTS ARECONTROLLEDBYTHE)45&OLLOWING)45REQUIREMENTS MARINERADARS AREPERMITTEDTOOPERATEINTHETO'(ZBAND8BAND ANDINTHETO'(Z BAND3BAND
ÓÓ°n
2!$!2(!.$"//+
4HE)-/)NTERNATIONAL#ONVENTIONFORTHE3AFETYOF,IFEAT3EA3/,!3 ISAN ESTABLISHEDANDACCEPTEDSETOFPRINCIPLESANDRULESAIMEDATENSURINGTHATSHIPSMEET CERTAINREQUIREMENTSTOENHANCEBOTHSAFETYANDPROTECTIONOFTHEENVIRONMENT4HE MEMBERGOVERNMENTSFLAG3TATES OF)-/HAVEAGREEDTHAT3/,!3REQUIREMENTS AREEMBODIEDWITHINTHEIRNATIONALMARITIMELAWSANDREGULATIONS7ITHIN#HAPTER6 OF 3/,!3 3AFETY OF .AVIGATION THE REQUIREMENTS FOR THE CARRIAGE OF NAVIGATION EQUIPMENTAREDEFINED4HESEVARYACCORDINGTOTHESIZEANDPURPOSEOFASHIP!LL PASSENGER SHIPS AND ALL SHIPS ABOVE GT NEED TO CARRY AT LEAST ONE RADAR WITH TRACKINGFACILITIES &OOTNOTESWITHIN#HAPTER6OF3/,!3IDENTIFYTHERECOMMENDED)-/PERFOR MANCESTANDARDSWITHWHICHTHEEQUIPMENTSHOULDCONFORM)-/HASHADRECOM MENDED RADAR PERFORMANCE STANDARDS SINCE PUBLISHED AS ANNEXES TO )-/ 2ESOLUTIONS (OWEVER BY RADAR MANUFACTURERS WERE REPORTING DIFFICULTIES BECAUSE DIFFERING INTERPRETATIONS BY NATIONAL MARITIME ADMINISTRATIONS MEANT THAT RADARSHADTOBESPECIFICALLYDESIGNEDTOMEETINDIVIDUALFLAG3TATEREQUIREMENTS 4HELEVELOFTECHNICALDETAILREQUIREDTOREMEDYTHISWASOUTSIDETHEREMITOF)-/ AND IT WAS AGREED THAT A 4ECHNICAL #OMMITTEE 4# WITHIN THE )NTERNATIONAL %LECTROTECHNICAL#OMMISSION)%# WOULDDETERMINETECHNICALLYBASEDINTERPRETA TIONSOF)-/RADARPERFORMANCESTANDARDS)NADDITION ITWASAGREEDTHATTHE)%# STANDARDSWOULDINCLUDETESTPROCEDURES WHICHCOULDBEUSEDBYNATIONALMARITIME ADMINISTRATIONSSUCHASTHE#OAST'UARDINTHE5NITED3TATESOF!MERICA TOTESTFOR CONFORMANCEOFSPECIFICDESIGNSBYMANUFACTURERSTO)-/AND)45REQUIREMENTS 4ODAY VIRTUALLYALLNATIONALADMINISTRATIONSUSE)%#STANDARDSTOASSESSRADARAND MOSTOTHER)-/ DEFINEDNAVIGATIONALANDRADIOCOMMUNICATIONSEQUIPMENT )-/PERFORMANCESTANDARDSANDTHE3/,!3#ONVENTIONAREREGULARLYREVISED SOIT ISIMPORTANTTOCHECKTHECURRENTSTATUSOFTHESTANDARDS)%#DEFINESTHETECH NICALANDTESTSTANDARDSBASEDONTHE)-/RADARPERFORMANCESTANDARDS)%#STANDARDS ALSOUNDERGOREGULARREVISION!NAVERAGERADARINSTALLATIONHASALIFENORMALLYEXCEED INGYEARS SORADARSDESIGNEDANDAPPROVEDTOPREVIOUSSTANDARDSWILLCONTINUETOBE USEDFORSOMEYEARSAFTERNEWSTANDARDSHAVEBEENPUTINPLACE2ETROFITTEDEQUIPMENT MUSTMEETTHELATESTSTANDARDS )-/ RADAR PERFORMANCE STANDARDS PREVIOUS TO THOSE IN FORCE ON *ULY REQUIRE COMPATIBILITY WITH EXISTING RACONS RADAR BEACONS AND AT '(Z 3EARCH AND 2ESCUE 4RANSPONDERS 4HIS IMPLIES THE CONTINUED USE OF SHORT PULSE RADARS (OWEVER FORTHESTANDARDS )-/HASENCOURAGEDIMPROVEMENTSINSEACLUT TER PERFORMANCE BY DROPPING THE NEED FOR RACON COMPATIBILITY AT '(Z THEREBY ALLOWING OTHER FORMS OF MODULATION THAT WOULD ENABLE AFFORDABLE COHERENT PRO CESSINGTECHNIQUES"ECAUSEALLSHIPSABOVEGTNEEDTOCARRYATLEASTASINGLE '(ZRADAR ITMEANSTHATRACONAND3!24 DETECTIONCAPABILITYISMAINTAINED 4HISAPPROACHGIVES)-/ANINDEFINITEPERIODTOASSESSTHEIMPACTOFTHENEWREGU LATIONSONTHEDETECTIONOFTARGETSINSEACLUTTERBEFOREDECIDINGWHATSHOULDHAPPEN WITHRADAR RACONS AND3!24SAT'(Z !NOTHERMAJORCHANGEINTHEREQUIREMENTSOFOLDERSTANDARDSISTHATALLNEWRADARS MUSTINCLUDEPROVISIONTODISPLAY!UTOMATIC)DENTIFICATION3YSTEM!)3 TARGETSAND THATTHEIRRELATEDINFORMATIONCANBEACCESSEDONTHERADARDISPLAY4HEREQUIREMENTS FOR TARGET TRACKING HAS ALSO HAD A MAJOR REVISION WITH AUTOMATIC TRACKING FACILITIES BEINGREQUIREDFORALLRADARS4HEINTEGRATIONOFELECTRONICCHARTDATAASABACKGROUND TO RADAR IMAGES IS ALSO EMBODIED WITHIN )-/ STANDARDS 2ADARS WITH THIS OPTIONAL FACILITYAREKNOWNAS#HART2ADARS
#)6),-!2).%2!$!2
ÓÓ°
4HEMINIMUMDETECTIONPERFORMANCEREQUIREDINCLEARCONDITIONSISTABULATEDIN 4ABLE-EASUREMENTSOFRANGEHAVETOBEWITHINMETERSACCURACYORWITHIN OF THE MAXIMUM RANGE SCALE IN USE AND WITHIN BEARING AZIMUTH ANGLE .AVIGATIONALBUOYSWITHTHECHARACTERISTICSGIVENIN4ABLEHAVETOBEDETECTABLE ATAMINIMUMRANGEOFMETERS4WOhPOINTvTARGETSONTHESAMEBEARINGHAVETO APPEARASTWODISTINCTTARGETSIFTHEYARESEPARATEDBYMORETHANMETERSINRANGE! AZIMUTHRESOLUTIONISALSOREQUIRED!LLTHESEPERFORMANCEFIGURESARECONSIDERED TOBEPEAKERRORS WHICHCANBEASSUMEDTOMEANVALUES MEASUREDWITHSTAN DARDIZEDPOINTTARGETS4HE)-/PERFORMANCESTANDARDSRECOGNIZETHATTHEDETECTION PERFORMANCEOFRADARSWORKINGWITHINCONDITIONSOFCLUTTERWILLNOTNECESSARILYGIVE THEPERFORMANCEDEFINEDFORCLEARCONDITIONS-ANUFACTURERSAREREQUIREDTOPROVIDE EFFECTIVEMANUALANDAUTOMATICANTI CLUTTERFUNCTIONSANDMUSTSPECIFYTHEEXPECTED DEGRADATIONINRAINATMMANDMMPERHOURANDFORSEASTATESAND INCLUDING COMBINATIONSOFSEAANDRAINCLUTTER 2ADARS DESIGNED FOR CONVENTIONAL VESSELS NEED TO OPERATE WITH RELATIVE SPEEDS UPTOKT&ORHIGH SPEEDCRAFT SUCHASMULTI HULLFASTFERRIES THERADARSNEEDTO OPERATEWITHRELATIVETARGETSPEEDSUPTOKT/LDERSTANDARDSREQUIREDAMINIMUM ANTENNAROTATIONRATEOFRPM BUTTHISEXPLICITREQUIREMENTHASBEENOMITTEDFROM THE NEW STANDARDS AS OTHER DEPENDENT REQUIREMENTS ARE ADEQUATELY SPECIFIED SUCH ASTHEMAXIMUMRELATIVESPEEDOFTARGETSANDTRACKINGACCURACIES4HE)-/PERFOR MANCESTANDARDSSPECIFYTHATRADAREQUIPMENTSHOULDMEETTHEENVIRONMENTALREQUIRE MENTSANDTESTPROCEDURESDEFINEDWITHIN)%#4HISISACOMPREHENSIVESETOF REQUIREMENTSTHATAREAPPLICABLETOALLSHIPSNAVIGATIONALANDRADIOCOMMUNICATIONS EQUIPMENT4HEYCOVERSUCHASPECTSASTEMPERATURE SHOCK VIBRATION CORROSION AND RESISTANCETOWATERANDOILINGRESS$ETAILEDREQUIREMENTSONELECTROMAGNETICEMIS SIONSANDIMMUNITYTOTHEELECTROMAGNETICENVIRONMENTAREMANDATED)%#ALSO SPECIFIESGENERALREQUIREMENTSONERGONOMICS SOFTWAREDEVELOPMENT ANDSAFETY! FURTHERSETOF)%#STANDARDSCONTAINEDWITHINTHE)%#SERIES DEFINETHEMES SAGESUSEDFORNAVIGATIONANDRADIOCOMMUNICATIONSEQUIPMENTTOINTERCHANGEDIGITAL DATA!SHIPBORNERADARISLIKELYTOBERECEIVINGMESSAGESFROMMANYITEMSOFNAVIGA TIONEQUIPMENT SUCHAS!)3 '03 GYROCOMPASS LOG ANDECHOSOUNDER ANDISALSO LIKELYTOBECOMMUNICATINGTRACKINFORMATIONTOELECTRONICCHARTSYSTEMSANDPOSSIBLY OTHERRADARDISPLAYS ! NUMBER OF MANUFACTURERS PRODUCE RADARS SPECIFICALLY DESIGNED TO BE USED ON VESSELSUSINGTHEWORLDSMAJORINLANDWATERWAYS4HESEAREKNOWNASRIVERRADARS 4HEYAREEPITOMIZEDBYTHEIRSUPERIORSHORT RANGEPERFORMANCEANDBYHAVINGADIS PLAYINhPORTRAITvFORMATINORDERTOGETMAXIMUMLOOK AHEADALONGTHEWATERWAY 4HE MAXIMUM DISPLAY RANGE ON THE SHORTEST SCALE IS TYPICALLY METERS 4HESE RADARSARENORMALLYDESIGNEDTOMEETREQUIREMENTSFORRADARSONVESSELSNAVIGATING THE2IVER2HINE 2ADARSFORTHEFISHINGANDLEISUREMARKETSARENOTCOVEREDBY3/,!35NTIL SUCHRADARSDIDNOTHAVEANINTERNATIONALLYRECOGNIZEDSTANDARDFORMANUFACTURERSTO FOLLOW)%#ISNOWTHEAGREEDINTERNATIONALRADARSTANDARDFORhCRAFTNOTIN COMPLIANCEWITH)-/3/,!3#HAPTER6vANDWASINITIALLYISSUEDATTHEINSTIGATION OF MANUFACTURERS .OW AN INCREASING NUMBER OF NATIONAL MARITIME ADMINISTRATIONS AREINSISTINGTHATALLNEWSMALLCRAFTRADARSSOLDINTHEIRJURISDICTIONCONFORMTOTHIS STANDARD)%#RECOGNIZESTHREECLASSESOFRADAR#LASS!ISINTENDEDFORCOM MERCIALCRAFTUNDERGT#LASS"ISFORRECREATIONALCRAFTAND#LASS#ISFORSMALL RECREATIONALCRAFT4HEMAINPERFORMANCEREQUIREMENTSAREDETAILEDIN4ABLE
ÓÓ°£ä
2!$!2(!.$"//+
4!",% 2ADAR0ERFORMANCE2EQUIREMENTSFOR3MALL#RAFT#OURTESYOF)%#
#OAST ,INE $ETECTION2ANGE
0OINT4ARGET$ETECTION2ANGE
#LASS
"EAMWIDTH
-INIMUM $ISPLAY3IZE
2ISING TOM
2ISING TOM
M MHT
M MHT
M MHT
! " #
a a a
qMM qMM qMM
NM NM NM
NM NM NM
NM NM NM
NM NM NM
NM .! .!
ÓÓ°{Ê / " "9 !NTENNAS !NTENNA MAXIMUM SIDELOBES ARE SPECIFIED FOR 3/,!3 AND NON 3/,!3RADARSIN)%#AND)%# RESPECTIVELY4HESEARESUMMARIZED IN4ABLE /NNON 3/,!3RADARS THEANTENNAROTATIONRATEISSPECIFIEDTOBENOTLESSTHANRPM BUTISNOTDIRECTLYSPECIFIEDFOR3/,!3 APPROVEDRADARS)NPRACTICE ANTENNASFOREXISTING SHIPBORNERADARSNORMALLYROTATEATnRPMONHIGH SPEEDCRAFT THEROTATIONRATEIS TYPICALLYnRPM&OR3/,!3VESSELS THEANTENNAMUSTBEABLETOSTARTANDOPERATEIN RELATIVEWINDSPEEDSUPTOKTOTHERENVIRONMENTALREQUIREMENTSFORTHEANTENNASYSTEM AREDETAILEDIN)%# WHERETHEREARESPECIFICTESTSFORhEXPOSEDvEQUIPMENT 4HERE ARE NO EXPLICIT REQUIREMENTS ON OTHER ANTENNA PARAMETERS FOR 3/,!3 APPROVEDSYSTEMS SUCHASBEAMWIDTHSANDGAIN BUTTHESEOBVIOUSLYNEEDTOBECOM PATIBLEWITHTHETOTALRADARPERFORMANCEREQUIREMENT&ORINSTANCE AZIMUTHRESOLUTION HASTOBEBETTERTHANTARGETBEARINGHASTOBEDETERMINEDTOWITHINANDTHE SYSTEMMUSTOPERATEINCONDITIONSWHENTHESHIPISROLLINGANDPITCHINGo4YPICAL ANTENNAGAINSANDBEAMWIDTHSHAVEBEENOUTLINEDIN3ECTION &ROMTHESONWARDS THEUSEOFASLOTTEDWAVEGUIDELINEARARRAY MOUNTEDIN ALINEARFLAREDHORNHASBEENTHEMOSTCOMMONANTENNASOLUTIONFORSHIPBORNERADARS "ECAUSEATLEASTHORIZONTALPOLARIZATIONHASTOBEPROVIDEDON'(Z3/,!3RADARS SLOTTEDARRAYSOLUTIONSGENERALLYHAVETHEIRSLOTSCUTINTOTHENARROWWALLOFTHEHORIZON TALLYMOUNTEDWAVEGUIDE!VERTICALSLOTPERPENDICULARTOTHEWAVEGUIDEEDGE COUPLES NOPOWER BUTASTHESLOTISINCREASINGLYANGLED MOREPOWERISCOUPLEDOUT4HESLOTS ARENORMALLYOFARESONANTLENGTHHALF WAVELENGTH TOCOUPLEOUTSUFFICIENTPOWER4HIS EXTENDSTHESLOTINTOTHEBROADWALLOFTHEWAVEGUIDE BUTITALSOMAKESTHEMEASIERTO CONSTRUCTCONCEPTUALLYBYASAWINGACTIONINTOTHENARROWWALL2ESIDUALPOWERATTHE ENDOFTHEARRAYTYPICALLYLESSTHAN ISDISSIPATEDINTOAMATCHEDLOAD#ONVENTIONALLY THEARRAYISEND FED ALTHOUGHCENTER FEDALTERNATIVESARESOMETIMESUSED 4!",% !NTENNA3IDELOBE0ERFORMANCE2EQUIREMENTS#OURTESYOF)%#
-AXIMUM3IDELOBE,EVELD" 2ADAR#LASS 3/,!3 .ON 3/,!3#LASS! .ON 3/,!3#LASSES"#
7ITHINo
7ITHINo
n n n
n n n
)%#ED#OPYRIGHTÚ)%# 'ENEVA 3WITZERLANDWWWIECCH
#)6),-!2).%2!$!2
ÓÓ°££
)FSLOTSWERESPACEDATTHEGUIDEWAVELENGTHINANATTEMPTTOGETANEQUI PHASE WAVEFRONTATTHEANTENNAFACE THENLARGEGRATINGLOBESWOULDBEGENERATEDINTHEFAR FIELDPATTERN4HISWOULDOCCURBECAUSETHEYWOULDBESPACEDATAFREE SPACEDISTANCE OFMORETHANONEWAVELENGTH4OOVERCOMETHIS SLOTSARESPACEDATNOMINALLYHALF THEGUIDEWAVELENGTHBUTAREANGLEDALTERNATELYTOTHEVERTICALINORDERTOINDUCETHE NECESSARY PHASE REVERSALS )N PRACTICE THE SLOTS ARE PLACED SLIGHTLY AWAY FROM HALF THEGUIDEWAVELENGTHSPACINGTOAVOIDSLOT GENERATEDMISMATCHESINTHEWAVEGUIDE BECOMINGRESONANT4HISCREATESATILTEDPHASEFRONTACROSSTHEARRAY WHICHCAUSESTHE BEAMTOSQUINTTOANANGLETHATISFREQUENCYDEPENDENT)NDIVIDUALMANUFACTURERSPRO DUCERADARSYSTEMSOPERATINGOVERARESTRICTEDBAND MUCHLESSTHANTHEOVERALLRADAR BAND WHICHREMOVESANYNEEDFORINDIVIDUALSQUINTCOMPENSATIONWHENMAGNETRONS AREREPLACED4HEREQUIREDSIDELOBEPERFORMANCEISNOTDEMANDING4ABLE AND SOSIMPLEAPERTUREDISTRIBUTIONS SUCHASPEDESTAL BASEDCOSINESQUARED ARECOMMON 4HESMALLVERTICALLYPOLARIZEDFIELDSPRODUCEDBYEACHSLANTEDSLOTNEEDTOBESUP PRESSEDASTHEYCANOTHERWISELEADTOHIGHCROSS POLARIZEDSIDELOBESFROMTHEARRAY EXACERBATEDBYTHEPHASEREVERSALOFTHECROSS POLARCOMPONENTFROMSLOTTOSLOT CAUS INGCROSS POLARGRATINGLOBES4HISCANBEACHIEVEDWITHAPRINTEDPOLARIZATIONFILTERIN FRONTOFTHEARRAYORBYEFFECTIVELYCREATING ASPARTOFTHESTRUCTURE ASHORTLENGTHOF OPEN ENDEDWAVEGUIDEINFRONTOFEACHSLOT WITHDIMENSIONSTHATMAKEITBELOWCUTOFF FORVERTICALPOLARIZATION 3LOT CHARACTERIZATION IS NORMALLY PERFORMED BY MEASUREMENT RATHER THAN BY DETAILEDELECTROMAGNETICANALYSIS4HISALLOWSALLCONSTRUCTIONDETAILS INCLUDINGTHOSE REQUIRED FOR POLARIZATION FILTERING TO BE INCORPORATED INTO THE SLOT CHARACTERIZATION SUFFICIENTACCURACYISDIFFICULTTOACHIEVEUSINGNUMERICALANALYSIS0ROVIDEDTHECHAR ACTERIZATIONISDONECAREFULLYANDGOODMANUFACTURINGTECHNIQUESCANGUARANTEETOLER ANCES ITISREASONABLYSTRAIGHTFORWARDTOPRODUCEAFFORDABLEANTENNASTHATMEET)-/ REQUIREMENTS4HEREQUIREDVERTICALBEAMWIDTHISNORMALLYOBTAINEDBYALINEARFLARE 4HEFLAREANGLEISCHOSENSUCHTHATITCREATESAREASONABLYPHASE CONSTANTVERTICALDIS TRIBUTIONATITSAPERTURE4HEVERTICALAMPLITUDEDISTRIBUTIONAPPROXIMATESTOACOSINE BECAUSEOFTHEHORIZONTALLYPOLARIZEDFIELD6ERTICALBEAMWIDTHSARETYPICALLYABOUT WIDEATTHED"POINTS .OTUNNATURALLY COST FORAGIVENPERFORMANCE ISTHEPRIMEDRIVERINTHESYSTEM DESIGNERS CHOICE OF ANTENNA7HILE THE CONVENTIONAL SLOTTED LINEAR ARRAY IS WIDELY USED THEREAREEXAMPLESWHEREDIFFERENTCOSTTRADEOFFSHAVEBEENMADE&ORINSTANCE THEUSEOFADIELECTRICBLOCKMOUNTEDDIRECTLYINFRONTOFTHESLOTTEDWAVEGUIDEARRAY INPLACEOFTHEFLAREDSECTION HASBEENUSEDASANALTERNATIVE4HELEAKINGENERGYFROM THETOPANDBOTTOMFACESOFTHEDIELECTRICBLOCKADDSWITHENERGYEMERGINGFROMITS FRONTFACE GIVINGFORWARDGAIN)TISTHEDEPTHDIMENSIONOFTHEDIELECTRICBLOCKTHAT DETERMINESTHEGAIN SOMEWHATANALOGOUSTOTHELENGTHOFA9AGIANTENNA4HISEFFECT REDUCESTHEHEIGHTOFTHEANTENNACOMPAREDTOACONVENTIONALDESIGNBYABOUTAFACTOR OFTHREE TYPICALLYFROMABOUTMMTOMMAT'(Z4HISMEANSTHATTHEREIS CONSIDERABLYLESSWIND LOADING4HEDIELECTRICCONSTANTOFTHEBLOCKCANBEQUITELOW WHICH WITH THE REDUCED WIND LOADING RESULTS IN A VERY LIGHTWEIGHT STRUCTURE4HIS SAVESCOSTSINTHEANTENNATURNINGGEARANDMAKESTHEINSTALLATIONEASIER!NEXAMPLE OFTHISTYPEOFANTENNA PRODUCEDBY+ELVIN(UGHES ISILLUSTRATEDIN&IGURE 3MALL CRAFT RADARS HAVE USED PRINTED ARRAYS FOR SOME YEARS AS WELL AS SLOTTED WAVEGUIDEARRAYS3MALL HORN FEDPARABOLICREFLECTORSYSTEMSHAVEALSOBEENUSED !NTENNASFORSMALLCRAFTARENORMALLYHOUSEDWITHINARADOME WHICHPROTECTSTHE ANTENNA AND UP MAST ELECTRONICS OF THE RADAR ENVIRONMENTALLY AND PREVENTS THE ANTENNAFROMSNAGGINGTHERIGGING)NPARTICULAR ITASSURESTHATTHEREISNODANGERTO
ÓÓ°£Ó
2!$!2(!.$"//+
&)'52% ,OW PROFILEMETER3 BANDSHIPBORNERADARANTENNA#OURTESYOF+ELVIN(UGHES,TD
USERSFROMROTATINGMECHANISMS SINCETHERADARHEADCANBEMOUNTEDINAREASOPEN TOHUMANACCESS!NTENNASUSINGPRINTEDARRAYSUSEINTEGRAL PRINTEDPOWERDIVIDERS 4HEARRAYSAREUSUALLYTWO DIMENSIONAL DISPENSINGWITHTHENEEDFORAFLAREDSEC TION ANDNORMALLYCONSISTOFRADIATINGPATCHES RATHERTHANPRINTEDDIPOLES(ORIZONTAL APERTURESOFANDMMARECOMMON0RINTEDTECHNOLOGYISNOTGENERALLYUSED FORSHIPBORNEANTENNASSLOTTEDWAVEGUIDEARRAYSREMAINTHECOST EFFECTIVESOLUTION FORLARGERARRAYS PARTICULARLYASTHEHIGHERPOWERCREATESADDITIONALCOMPLICATIONSFOR PRINTEDPOWERDIVIDERS 0OORANTENNASITINGISACOMMONCAUSEOFRADARPERFORMANCEDEGRADATIONONSHIPS ASWELLASONSMALLERCRAFT0ARTICULARLYONSHIPS ITISSURPRISINGTHATINSTALLATIONSARE STILLBEINGIMPLEMENTEDTHATCREATESIGNIFICANTBLOCKAGETOTHERADAR"LINDARCSARE COMMONFROMFUNNELSANDOTHERSUPERSTRUCTURE ANDTHERECANBESIGNIFICANTSIDELOBE DEGRADATIONDUETOSMALLERSTRUCTURES SUCHAS6(&ANTENNAS CAUSINGBLOCKAGECLOSE TOTHERADARANTENNAAPERTURE 2& (EAD 4HE 2& HEAD NORMALLY COMPRISES THE TRANSMITTER AND THE RECEIVER DOWN TO )& OR DIGITAL BASEBAND AS WELL AS THE ANTENNA AND TURNING GEAR )TS DESIGN FORBOTHMAGNETRON BASED3/,!3ANDNON 3/,!3RADARSFOLLOWSCONVENTIONALPRIN CIPLES4HEMAGNETRONISCONNECTEDTOTHEANTENNAVIAADUPLEXERANDAROTATINGJOINT 4HEMAGNETRONHASATYPICALOPERATIONALLIFEOFABOUT HOURSANDISBYFARTHE LOWESTLIFEDCOMPONENTINTHEWHOLESYSTEM4HEDUPLEXERISNOWADAYSATHREE OR FOUR PORTFERRITECIRCULATOR5SEOFAFOUR PORTDEVICEISPREFERREDASITPRESENTSABET TERMATCHEDLOADTOTHEMAGNETRONAND THEREFORE GIVESACLEANER2&SPECTRUM4HE LOW NOISEFRONT END,.&% SUBSYSTEMISCONNECTEDTOTHECIRCULATORVIAA0).DIODE LIMITER WHICHPROTECTSTHE,.&%DURINGPULSETRANSMISSION 4HEMODULATORTOTHEMAGNETRONISTYPICALLYAPULSEFORMINGNETWORK0&. BASI CALLYCOMPRISEDOFCAPACITORSANDINDUCTORS/PERATORCONTROLOFTHEPULSELENGTHEFFEC TIVELYSWITCHESINDIFFERENTCHOICESOFREACTIVECOMPONENTS4HEDISCHARGEOFTHE0&. IS CONTROLLED BY A HIGH VOLTAGE SWITCH WHICH IS OFTEN A SILICON CONTROLLED RECTIFIER THYRISTORSAND&%4SAREALSOUSED&%4MODULATORSARESOMETIMESDRIVENDIRECTLYBY APULSEINPUTRATHERTHANA0&.&INALLY APULSETRANSFORMERMATCHESTHE0&.TOTHE IMPEDANCESEENATTHEMAGNETRONCATHODE!PULSEOFAROUNDK6ISREQUIREDTOFIRE THEMAGNETRON)NORDERTOGETGOODPERFORMANCEOVERAWIDERANGEOFPULSELENGTHS DESIGNSUTILIZEAGREATDEALOFEMPIRICALLYDERIVEDKNOWLEDGE ANDACTUALCIRCUITSCAN BESURPRISINGLYCOMPLEX!NSPULSEHARDLYACHIEVESANYPERIODOFSTABILITYRISE TIMESARENORMALLYRESTRICTEDTOABOUTNSINORDERTOLIMITOUT OF BANDINTERFERENCE
#)6),-!2).%2!$!2
ÓÓ°£Î
ANDFALLTIMESAREUSUALLYLONGER4HEEXTRAHIGHVOLTAGESINVOLVEDCANLEADTOPOOR RELIABILITYIFTHEDESIGNDOESNOTADEQUATELYADDRESSTHEASSOCIATEDPROBLEMS#AREFUL PHYSICALLAYOUTISESSENTIALANDCONSIDERATIONMUSTBEGIVENTOTHEEFFECTSOFOPERATING INAPOTENTIALLYDAMPENVIRONMENT0ULSETIMINGCANBEPURPOSELYJITTEREDONAPULSE TO PULSEBASIS0ULSE TO PULSECORRELATIONINTHERADARPROCESSORTHENVERYEFFECTIVELY BLOCKS INTERFERENCE FROM OTHER RADARS ALBEIT WITH A SMALL BUT GENERALLY ACCEPTABLE DEGRADATIONINDETECTIONPERFORMANCE !FTERTHELIMITER THE,.&%ISPRECEDEDBYABANDPASSFILTERTOREDUCETHEEFFECTS OFOUT OF BANDINTERFERINGSIGNALS4HE,.&%CONSISTSOFAN2&LIFIERTYPICALLY GIVINGABOUTD"GAIN ANDABALANCEDMIXER LOCALOSCILLATOR AND)&HEADAMPLIFIER 4HESEARENORMALLYSUPPLIEDTOTHERADARMANUFACTURERBYSPECIALISTCOMPANIESASA COMPLETESUBUNIT4HEOVERALLSYSTEMNOISEFIGUREISTYPICALLYTOD" BUTLOWER FIGURESAREACHIEVABLE4HEFREQUENCYOFTHELOCALOSCILLATORISGENERALLYDRIVENBYA CONTROLSIGNAL DERIVEDFROMWITHINTHE)&LIFIER)TINCLUDESFACILITIESFORMANUAL FREQUENCYCONTROLBYTHEOPERATOR4HELATTERCANBEUSEFUL FORINSTANCE WHENLOOK INGFOR3!24SINHEAVYSEACLUTTER ASITALLOWSRETURNSFROMOWNTRANSMISSIONSTOBE DESENSITIZED4HELOCALOSCILLATORUSESA'UNNDIODEORAN&%4 GIVINGATYPICALINTER MEDIATEFREQUENCYOF-(Z $ETECTIONAND0ROCESSING !FTERTHE,.&% ALOGARITHMICAMPLIFIERREDUCESTHE DYNAMICRANGEOFTHERECEIVEDSIGNALTOPREVENTLIMITING!DYNAMICRANGEOFAROUND D" IS TYPICALLY ACHIEVED IN PERHAPS AN EIGHT STAGE AMPLIFIER &ILTERING CONSIS TENTWITHTHETRANSMITTEDPULSELENGTH ISAPPLIEDWITHINTHE)&LIFIER4HEOUTPUT FROMTHELOGAMPLIFIERENTERSADIODE BASEDENVELOPEDETECTOR CONVERTINGTHESIGNAL TO BASEBAND FOR SUBSEQUENT THRESHOLD PROCESSING 3ETTING THE THRESHOLD HAS BECOME INTIMATELY CONNECTED WITH THE SENSITIVITY TIME CONTROL 34# OF THE RADAR4HE FUN DAMENTAL USE OF 34# IS TO TAKE OUT THE DISTANCE RELATED DYNAMIC RANGE OF RECEIVED SIGNALS!TCLOSERANGE 34#CLASSICALLYFOLLOWSANINVERSEFOURTHPOWERLAW MERGING TOANINVERSECUBICLAWINTHEREGIONWHERESEACLUTTERDOMINATES INACCORDANCEWITH BASIC THEORY "ECAUSE TRANSITION RANGE IS A FUNCTION OF ANTENNA HEIGHT A SETTING FOR THIS MAY BE NEEDED WHEN THE SYSTEM IS ORIGINALLY INSTALLED4HE OPERATORS MANUAL SEA CLUTTERCONTROLISUSEDTOADJUSTTHETRANSITIONRANGE.OWADAYS THEFORMOFTHE 34#CURVEANDTHEEFFECTSOFTHEMANUALCONTROLAREBASEDONTHEPRACTICALEXPERIENCE OFINDIVIDUALMANUFACTURERS WHICHCONTRIBUTESGREATLYTOTHEACTUALEFFECTIVENESSOF APARTICULARRADARINSEACLUTTER%VENUNDERMANUALCONTROL THEDETAILEDSHAPEOFTHE 34#CURVEMAYHAVEACOMPLEXADAPTIVEELEMENTTOIT INORDERTOOPTIMIZETHRESHOLDS OVERABROADERRANGE 5NDER AUTOMATIC SETTINGS THRESHOLDING BECOMES INCREASINGLY SOPHISTICATED BUT OFTENSTILLALLOWSSOMEMANUALOPTIMIZATION4HECURVEMAYADAPTTOINTERNALCALCULA TIONSMADEONRETURNSFROMTHELASTPULSEORFROMASUCCESSIONOFPULSES)TMAYALSO INCLUDEMORECOMPLEXCLUTTER MAPPINGPROCESSES!LLOFTHISISATTEMPTINGTOCREATE ACONSTANTFALSEALARMRATEACROSSTHERADARDISPLAY3INCETHERADARISSITEDONAMOV ING PLATFORM SUBJECT TO COMPLEX DYNAMICS DIFFICULTIES ARISE WITH CLUTTER MAPPING (OWEVER MODERNPROCESSORSPERMITAFFORDABLETHRESHOLDINGALGORITHMSOFCONSIDER ABLECOMPLEXITY-ANUFACTURERSKEEPTHEIROWNPROCESSESHIGHLYCONFIDENTIALBECAUSE OFTHEEFFORTTHATHASGONEINTOTHEIREMPIRICALOPTIMIZATION4HEORETICALCLUTTERMODELS HAVEBEENGENERALLYFOUNDUNSUITABLETOBEUSEDFOROPTIMIZATION%VENOPTIMIZINGFOR SEACONDITIONSFOUNDINONEPARTICULARAREACANCREATESUBOPTIMALSOLUTIONSINOTHER AREAS ANDTHEREFORE DATAFROMANUMBEROFREGIONSNEEDTOBEUSEDTODESIGNAGLOB ALLYEFFECTIVEPRODUCT
ÓÓ°£{
2!$!2(!.$"//+
34#ANDTHRESHOLDINGISAPROCESSTHATISCONTROLLEDINTHEDIGITALDOMAINBUTOFTEN APPLIESANALOGGAINPROCESSESAT2&AND)&ATBOTHPRE ANDPOST LOGAMPLIFICATION AS WELLASPROCESSESINTHEDIGITALDOMAIN)NTIMATELYCONNECTEDWITHTHRESHOLDINGSTRATE GIESARESIGNALPROCESSING SUCHAS&4# PULSEINTEGRATION ANDCORRELATIONPROCESSES BOTHPULSE TO PULSEANDSCAN TO SCAN-ODERNDIGITALTECHNOLOGY WITHITSPROCESSING SPEED AVAILABLEWORDLENGTH ANDLARGEMEMORYCAPABILITY ALLOWSTHERADARDESIGNER TOHAVEGREATFLEXIBILITYINTHESTRATEGYAPPLIED ANDWHATAREENTIRELYSEPARATEPRO CESSESINTHEANALOGWORLDINCREASINGLYBECOMEANINTEGRATEDDIGITALPROCESS3IMPLE THRESHOLDINGIDEASAREBEINGREPLACEDBYCOMPLEXLOGICALPROCESSES MAKINGADETAILED EVALUATIONOFWHETHERAPOTENTIALTARGETISPRESENTORNOT EVENPOTENTIALLYMERGINGINTO PLOTEXTRACTIONANDTRACKINGPROCESSES -ORECOMPLEXPROCESSINGCANALSOYIELDADDITIONALINFORMATIONTHATISUSEFULTO MARINEOPERATORS&ORINSTANCE BYAPPLYINGSPECTRUMANALYSISTECHNIQUES ITISPOS SIBLETOEXTRACTACCURATESEA STATEINFORMATION INCLUDINGSIGNIFICANTWAVEHEIGHTAND PERIOD DIRECTION ANDSPEED4HE-IROS!37AVEX4-SYSTEMDETERMINESDIRECTIONAL WAVE SPECTRA SCALED IN M(Z AND PARAMETERS SUCH AS SIGNIFICANT WAVE HEIGHT AND AVERAGEWAVEPERIOD!N&&4ISPERFORMEDONDATACOLLECTEDONASCAN BY SCANBASIS SCANSOFDATAARETYPICALLYUSEDINTHEANALYSIS4HERESULTANTINFORMATIONCANBE HIGHLYUSEFULFORLARGEHIGH SPEEDCRAFT PERHAPSTRAVELINGATUPTOKNOTSORMORE )TISALSOPOTENTIALLYUSEFULFORVULNERABLEVESSELSSUCHASCHEMICALCARRIERSTOENSURE THATAPPROPRIATEACTIONINHEAVYWEATHERCANBETAKEN PARTICULARLYATNIGHTORINPOOR VISIBILITY/CEANOILRIGOPERATIONSCANALSOBENEFITFROMSUCHSYSTEMS)NFORMATION CANBEDISPLAYEDTOTHEUSERINTHEFORMOFDIGITALREADOUTSOFTHEPRIMARYPARAMETERS ASWELLASGRAPHICALLYDISPLAYEDDATA)NSTALLEDSYSTEMSNORMALLYEXTRACTTHERAWDATA FROMTHEEXISTING'(ZRADARANDPERFORMWAVEPROCESSINGANDDISPLAYFUNCTIONSON ASEPARATEPROCESSORDISPLAYSYSTEM3PECTRUMANALYSISOFTHISTYPECANALSODETECTOIL SLICKSBECAUSETHEYREDUCETHEAMPLITUDEOFSEASURFACECAPILLARYWAVES3UCHSYS TEMSCANBEVALUABLEONVESSELSASSISTINGWITHCLEAN UPOPERATIONSANDALSOFOREARLY DETECTIONOFSPILLSFROMOILRIGOPERATIONS )THASBEENPROPOSEDTHATADDITIONALPROCESSINGOFTHECROSS POLARCONTENTOFTHE RECEIVEDRADARSIGNALMAYBEOFBENEFITTOMARINEOPERATIONSWHERESEAICEISAHAZARD $UE TO STRUCTURAL CHANGES THAT OCCUR IN OLDER ICE THAT AFFECT THE REFLECTION OF RADAR ENERGY ITISPOSSIBLETODIFFERENTIATEBETWEENPOTENTIALLYDANGEROUSOLDICE INCLUDING GLACIALICEICEBERGS ANDSINGLE SEASONSEAICE WHICHISNORMALLYLESSDANGEROUSTO NAVIGATION4HISISBECAUSETHECROSS POLARCOMPONENTOFTHEREFLECTIONISSIGNIFICANTLY HIGHERFOROLDICECOMPAREDTONEWICE4HEPROBLEMISHOWTOAFFORDABLYDETERMINE THECROSS POLARCOMPONENT )NPRACTICE ITHASBEENFOUNDTHATEXCELLENTICEDETECTIONCANBEMADEBYOPTIMIZED PROCESSINGOFCONVENTIONALMARINERADARSIGNALS"ECAUSEOFTHESLOW MOVINGNATURE OFTHETARGETSOFINTEREST AVERAGINGTHERADARIMAGEOVERMANYANTENNASCANSUSING ANOPTIMIZEDINFINITEIMPULSERESPONSE))2 FILTERCANGIVEAVERYDETAILEDIMAGETHAT ALLOWSTHEUSERTODIFFERENTIATEBETWEENICEANDWATERAREAS)NPARTICULAR SMALLICE FEATURESSUCHASBERGYBITSICEBERGSWITHDIMENSIONSABOVETHEWATERLINEOFLESSTHAN METERSINBREADTHANDGREATERTHANMETERINHEIGHT ANDGROWLERSLESSTHANMETERS INBREADTHANDLESSTHANMETERSHOWINGABOVETHEWATERLINE AREREADILYDETECTED BYSUCHSYSTEMS)NTEGRATIONOVERSECONDSHASBEENFOUNDTOBESUITABLE WITHTHE ANTENNAROTATINGATRPM4HEINCREASEDCAPABILITYOFICE TARGETDETECTIONINSEA CLUTTERWITHHIGHERANTENNAROTATIONRATESHASALSOBEENDEMONSTRATED$RAMATICIMAGES OFICEHAZARDSCANBEPRODUCEDBYSUCHRADARS SUCHASTHATILLUSTRATEDIN&IGURE
#)6),-!2).%2!$!2
&)'52% )CEFEATUREDETECTIONUSING))2FILTERINGON2UTTER3IGMARADARPROCESSOR#OURTESYOF4RANSPORT#ANADA
ÓÓ°£x
ÓÓ°£È
2!$!2(!.$"//+
3OLID STATE#-2 3EVERALFACTORSHAVECOMETOGETHERTOPROMOTETHEINTRODUC TIONOFCIVILMARINERADARSWITHSOLID STATETRANSMITTERS4HEMOSTIMPORTANTOFTHESE ISTHATAFFORDABLEMAGNETRON BASEDRADARSDONOTMEETUSERDEMANDSWHENOPERATING INHEAVYSEAANDPRECIPITATIONCLUTTER3MALLCRAFTANDBUOYSBECOMEINVISIBLEONTHE DISPLAY CREATINGDANGERTOLIFE)-/RECOGNIZEDTHISPROBLEMAND INORDERNOTTOCON STRAINOPPORTUNITIESFORINNOVATIVERADARDESIGN REMOVEDTHEREQUIREMENTTHAT'(Z RADARSBECOMPATIBLEWITHEXISTINGRACONS 'ALLIUM.ITRIDEANDOTHERMICROWAVEPOWERSEMICONDUCTORS DEVELOPEDPRIMAR ILYFORBROADBANDCOMMUNICATIONSLINKS HAVEENABLED#-2MANUFACTURERSTOUSE THESE IN THE RADAR TRANSMITTER TO REPLACE MAGNETRON BASED DESIGNS 0ULSE COMPRES SION TECHNIQUES ARE USED TO REDUCE THE REQUIRED PEAK POWER %VEN SINGLE 'ALLIUM .ITRIDEDEVICESCANGENERATEHUNDREDSOFWATTSOFPEAKPOWER ATMEANPOWERSEASILY SUFFICIENT FOR #-2 APPLICATIONS!LSO ADVANCES IN DIGITALLY CONTROLLED WAVEFORM GENERATORS HAVE GIVEN DESIGNERSTHEABILITYTOCREATEPULSE COMPRESSEDWAVEFORMS WITHHIGHPRECISIONANDATLOWCOST4HESEWAVEFORMSENABLECOHERENTPROCESSINGOF THERECEIVEDSIGNAL GIVINGADDITIONALDOPPLERINFORMATIONTHATCANBEUSEDTOHELP SEPARATETARGETSFROMCLUTTER4HEUSEOFFREQUENCYDIVERSITYTECHNIQUESTOGIVEADDED TARGETDETECTIONPOSSIBILITIESBECOMESPOTENTIALLYAFFORDABLE BECAUSEOFTHEFLEXIBILITY OFTHESIGNALGENERATIONTECHNOLOGY#OSTHASPRECLUDEDTHEUSEOFDUAL MAGNETRON TRANSMITTERSFORTHISPURPOSE $EMANDSFROMOTHERSERVICESFORMOREBANDWIDTH PARTICULARLYFROMMOBILECOM MUNICATIONSOPERATORS CONTINUETOPUTPRESSUREONTHE)45 DETERMINEDMARINERADAR SPECTRUMLIMITSSEE FOREXAMPLE 7ILLIAMS 3INCETHEPEAKTRANSMITTEDPOWERFROM SOLID STATE#-2SISVERYLOWCOMPAREDTOMAGNETRON BASEDRADARS FOREXAMPLE7 COMPAREDTOK7 THESPECTRUMINTERFERENCELEVELSAREMUCHREDUCEDAND THEREFORE EXTENDEDUSEOFTHISTECHNOLOGYCOULDRESULTINBETTERUSEOFTHE2&SPECTRUM!LSO THEHIGHLYCONTROLLEDWAVEFORMSAREEXPECTEDTOCREATELESSSPECTRALNOISETHANTYPICAL MAGNETRON BASED#-2TRANSMITTERS !NEXAMPLEOFASOLID STATECOHERENTRADARISTHE+ELVIN(UGHES3HARP%YE4-THE FIRSTINTRODUCTIONOFSUCHAN)-/ COMPLIANTSYSTEMTOTHE#-2MARKET)THASAPEAK OUTPUTPOWEROF7ANDADUTYCYCLEOF&IGURESHOWSAPHOTOGRAPHOF THETRANSMITTERELECTRONICS)NORDERTOOBTAINTHEREQUIREDSHORT RANGEPERFORMANCE ITTRANSMITSAFRAMEOFPULSESWITHDIFFERINGLENGTHS%ACHPULSEWITHINTHEFRAMEIS OPTIMIZEDTOCOVERASPECIFIEDRANGEBRACKET/VERALL THEPULSESEQUENCECOMPLETELY COVERS THE INSTRUMENTED RANGE AND ENSURES THAT THE )-/ SPECIFIED MINIMUM RANGE REQUIREMENTISMET )NTHERECEIVER FRAMESAREGROUPEDINTOBLOCKSCALLEDBURSTS4HEDURATIONOFA BURSTISAPPROXIMATELYEQUALTOTHETIMETAKENFORTHED"POINTSOFTHEANTENNA AZIMUTHBEAMTOSWEEPPASTAPOINTTARGETCONSEQUENTLY THENUMBEROFPULSESIN ABURSTISDIRECTLYRELATEDTOTHEINSTRUMENTEDRANGEANDTHEANTENNAROTATIONRATE 4HE ECHOES RECEIVED DURING A BURST ARE PROCESSED BY A FILTER BANK TO EXTRACT THE RADIALVELOCITIESOFTARGETSANDCLUTTER7ITHINTHEDIGITALSIGNALPROCESSOR DETECTION THRESHOLDSFOREACHOFTHEFILTERSWITHINTHEBANKARECALCULATEDADAPTIVELY AIMINGAT PROVIDINGOPTIMUMCONTROLOFFALSEALARMSWHILEMAXIMIZINGCLUTTERSUPPRESSIONAND TARGETDETECTION-ANUALCONTROLOFTHETHRESHOLDSISALSOPROVIDEDTOBECOMPLIANT WITH)-/REQUIREMENTS -ODERN FULLYSOLID STATERADARSNEEDLITTLEANALOGCIRCUITRYWITHINTHEIRDESIGNS THEYOPERATEONLOWVOLTAGESANDHAVENOTIME LIFEDCOMPONENTSSUCHASMAGNE TRONS4HIS POTENTIALLY MAKES THEM EXTREMELY STABLE AND RELIABLE WITH A RESULTANT LOWCOSTOFOWNERSHIP THEREFORE MEETINGTHEINCREASINGDEMANDSOFSHIPOPERATORS
#)6),-!2).%2!$!2
ÓÓ°£Ç
&)'52% +ELVIN (UGHES 3HARP%YE4- #-2 3 BAND SOLID STATE TRANSMITTER #OURTESY OF +ELVIN (UGHES,TD
)NPREVIOUSYEARS SHIPSWEREREQUIREDTOHAVEARADIOOFFICER WHOCOULDCARRYOUT RADARREPAIRSATSEA4HISISNOLONGERTHECASE2ELIABILITYISAPRIMECONCERN ASANON OPERATINGRADARCANFORCETHEDELAYOFTHESHIPINPORT ATGREATCOSTTOTHEOPERATOR
ÓÓ°xÊ /, /Ê/, 4HETARGETTRACKINGFUNCTIONOFASHIPBORNENAVIGATIONRADARHASHISTORICALLYBEEN CALLED AN !UTOMATIC 2ADAR 0LOTTING!ID !20! 4HIS TERM IS BECOMING OBSOLETE )-/NOWDEFINESTHISPROCESSAS4ARGET4RACKING44 WHICHINCLUDESTARGETDATA OBTAINEDFROM!)34HEBASICREQUIREMENTCALLSFORAMINIMUMRADARTRACKINGCAPAC ITY OF TARGETS ON SHIPS LESS THAN GT TARGETS ON SHIPS BETWEEN AND GTANDTARGETSONSHIPSOVER GT)NADDITION SHIPSOVER GT MUST HAVE AN AUTOMATIC TARGET ACQUISITION CAPABILITY !CTUAL SYSTEMS COMMONLY EXCEED THESE MINIMUM REQUIREMENTS 4ARGETS WITH A MAXIMUM RELATIVE SPEED OF KTMUSTBETRACKABLETHISREQUIREMENTISINCREASEDTOKTFORRADARSONVESSELS CAPABLEOFMORETHANKT/NTHEBRIDGE THENAVIGATORSREQUIREMENTSTOAIDCOLLI SIONAVOIDANCEINCLUDETHENEEDTOKNOWATARGETSCLOSESTPOINTOFAPPROACH#0! ANDTIMETOCLOSESTPOINTOFAPPROACH4#0! BOTHOFWHICHMUSTBEAVAILABLEFOR ALLTRACKEDTARGETS4HEREQUIREDTRACKEDTARGETACCURACYATLEVELSISGIVENIN 4ABLE
ÓÓ°£n
2!$!2(!.$"//+
4!",% 2EQUIREMENTSFORRADARTRACKEDTARGETACCURACYLEVELS #OURTESYOF)-/
4IMEOF3TEADY 3TATEMINUTES
2ELATIVE #OURSE DEGREES
MINTRENDo
MINMOTIONp
2ELATIVE 3PEEDKN OR WHICHEVER ISGREATER OR WHICHEVER ISGREATER
#0!.-
4#0! MINUTES
4RUE #OURSE DEGREES
4RUE3PEED KN
OR WHICHEVER ISGREATER
o4RENDISANEARLYINDICATIONAFTERMINUTE OFTHETARGETSSPEEDANDDIRECTION p-OTIONISTHEESTABLISHEDASSESSMENTAFTERMINUTES OFTHETARGETSSPEEDANDDIRECTION
4HETRACKINGPROBLEMISCOMPLICATEDBYTHEFACTTHATBASICRADARMEASUREMENTS AREMADERELATIVETOTHESHIPSMOTION BUTTHEDISPLAYMAYBESETTORELATIVEORTRUE MOTION)NADDITION TRUEMOTIONCANBEGROUNDORSEASTABILIZED4ARGETVECTORSAND ASSOCIATEDDATABOXESCANBESHOWNINTRUEORRELATIVEMOTION WHATEVERTHEFRAME REFERENCEOFTHERADARDISPLAY!SHIPSORIENTATIONTONORTHISGIVENBYAGYROCOM PASSORhTRANSMITTINGvMAGNETICCOMPASSACOMPASSWITHADIGITALINTERFACE!LOG GIVES SPEED THROUGH THE WATER 347 4HIS CAN BE EITHER A CONVENTIONAL ROTATING TRANSDUCER DRIVEN BY THE MOVEMENT THROUGH WATER OR ELSE AN ACOUSTIC TRANSDUCER MEASURINGTHEDOPPLEROFTHEREFLECTEDSIGNAL4HELATTERCANBESETTOASSESSSPEED EITHERRELATIVETOTHESURROUNDINGWATER347 ORRELATIVETOTHESEABED IE SPEED OVERGROUND3/' -ANDATORYCARRIAGEOFADUALAXISLOGWHICHMEASURESSPEEDIN THEFORWARDANDTRANSVERSEDIRECTIONS ISREQUIREDONSHIPSABOVE GT4HISIS TYPICALLYADOPPLERLOG/NSMALLERSHIPS '.33ISUSEDTOPROVIDE3/'ANDISOFTEN THEUSER PREFERREDGROUNDSTABILIZATIONSOURCEFORRADAR EVENFORASHIPFITTEDWITHA DOPPLERLOG$OPPLERLOGSDONOTALWAYSGIVEGOODSPEEDREADINGSONSOMETYPESOF SEABED FOREXAMPLE SOFTMUD&ACILITIESMUSTALSOBEPROVIDEDTOALLOWTHEUSEOF STATIONARYTRACKEDTARGETS SUCHASRADARCONSPICUOUSNAVIGATIONMARKS TOPROVIDE THEGROUNDREFERENCE !CCORDINGTOTHEDESIGN THEBASICTRACKINGFUNCTIONCANBECARRIEDOUTINSHIPOR GROUNDSEA REFERENCED FRAMES USING CONVENTIONAL ALGORITHMS4HE TRACKING PROCESS CANBEINITIATEDMANUALLYORAUTOMATICALLY!UTOMATICINITIATIONISBYACONVENTIONAL PLOT EXTRACTION PROCESS CONFINED WITHIN A USER DEFINED AREA WHICH AT ITS SIMPLEST COULDBEACHOSENRANGEENCIRCLINGTHEVESSEL4HEDEFINEDAREAMAYALSOHAVEUSER DEFINEDEXCLUSIONZONES!LGORITHMSFORPREVENTINGPLOTSFROMBEINGFORMEDONTYPI CALLYENCOUNTEREDWAVEFEATURES PERHAPSLASTINGAFEWSCANSSUCHASATRAVELINGWAVE CREST NEEDTOBEEMPLOYED-ANUALSELECTIONISEFFECTIVELYAPLOTEXTRACTIONPROCESS OPERATING OVER A SMALL AREA SURROUNDING THE CURSOR!N ALPHA BETA TRACKER OR OTHER FILTERINGTECHNIQUEISUSEDTOSMOOTHMEASUREMENTNOISE4HECHARACTERISTICSOFTHIS FILTERNEEDTOADAPTTOTHEQUALITYOFTHERECEIVEDTARGETSIGNAL)FTRACKINGISCARRIED OUT IN GROUND REFERENCED COORDINATES THE PROCESS AUTOMATICALLY TAKES INTO ACCOUNT OWN SHIPMOVEMENTS)NRELATIVEMOTION BASEDTRACKINGSYSTEMS THEFILTERNEEDSTOBE AIDEDWITHOWN SHIPDATA $EPENDINGONTHEUSER SETMODE THEDATAHASTOBECONVERTEDTOTHECORRECTREFER ENCE FRAME AND DISPLAYED APPROPRIATELY #0! AND 4#0! ARE CONTINUALLY CALCULATED FOR ALL TRACKED TARGETS SUCH THAT IF LIMITS PRESET BY THE USER ARE BREACHED AN ALARM
#)6),-!2).%2!$!2
ÓÓ°£
CANBEINITIATED!LLTRACKEDTARGETSAREDISPLAYEDONTHESCREENWITHTHEIRASSOCIATED VELOCITYVECTORS4RACKEDTARGETSMAYBESELECTEDBYTHEUSERSUCHTHATALLINFORMATION CONCERNINGTHATTARGET INCLUDING#0!AND4#0! ISDISPLAYEDONTHEDATAPANELOFTHE RADARSCREEN,OSTTARGETSCREATEAVISUALANDANAUDIBLEALARM.ORMALTERMINATIONOF TRACKINGOCCURSWHENATARGETLEAVESTHEACQUISITIONZONEORWHENMANUALLYCANCELLED !GUARDZONEMAYALSOBESETUPBYTHEOPERATOR4HISMAYBEIDENTICALTOTHEACQUISI TIONZONEBUTISTHERETOPROVIDEANALARMIFANYTRACKEDTARGETPASSESINTOTHEZONE )NCOMMONWITHOTHERRADARTRACKERS STRATEGIESHAVETOBEEVOLVEDTOCOPEWITH THETARGETBEINGPOTENTIALLYINVISIBLEINSOMESCANS)-/REQUIRESTHATTHESPECIFIED PERFORMANCEISMAINTAINEDWHENTHETARGETISINVISIBLEINUPTOOFSCANS!LSO FOR ANEFFECTIVESYSTEM STRATEGIESHAVETOBEEVOLVEDTOREDUCETHEPOSSIBILITIESOFTARGET IDENTITIES BEING SWAPPED WHICH CAN HAPPEN WHEN TARGETS MOVE CLOSE TOGETHER AND SUBSEQUENTLYDIVERGE)NPARTICULAR TRACKINGALGORITHMSHAVETOATTEMPTTOCOPEWITH THEPOTENTIALLYLARGEANDFASTCHANGEINTHERADARCENTROIDASATARGETVESSELTURNS)NTHE WORSTCASE THISCANAMOUNTTOALMOSTTHELENGTHOFTHEVESSEL METERSORSO FORA LARGESHIP)TISANARTTOGETAGOODTRACKEROPTIMIZEDFORALLSITUATIONS OVERAVARIETYOF VESSELSPEEDS ANDTOMAINTAINANAPPROPRIATEINDICATIONOFCHANGEINHEADINGWITHOUT EXCESSLATENCY/VER DAMPEDSYSTEMSMAYGIVEANAPPARENTLYSTABLEINDICATIONOFTHE TRACKOFATARGETBUTCANBEVERYINACCURATEWHENATARGETCHANGESHEADING&ROMTHE POINTOFVIEWOFSAFETYOFNAVIGATION THECHANGEINHEADINGISOFTENTHEMOREIMPOR TANTPARAMETER4ARGETTRACKERSFROMINDIVIDUALMANUFACTURERSCANHAVEQUITEDIFFERENT DESIGNANDOPTIMIZATIONSTRATEGIESANDCAN THEREFORE DIFFERINPERFORMANCE7ITHIN )%# THEREAREDEFINEDTESTSCENARIOSTHATALL3/,!3 APPROVEDTRACKINGSYS TEMSMUSTMEET)-/REQUIRESTHATTHETRENDINATARGETSCHANGEOFDIRECTIONISSHOWN WITHINONEMINUTEANDTHEPREDICTIONOFTHETARGETSMOTIONSHOULDBEAVAILABLEWITHIN THREEMINUTES ASGIVENIN4ABLE )N PRINCIPLE TARGET TRACKING COULD BE AIDED BY DATA FROM !)3 3ECTION (OWEVER !)3DATAISBESTLEFTOUTOFTHERADARTRACKINGPROCESSINORDERTOKEEPTHEM ENTIRELY INDEPENDENT /NCE RADAR TRACKS HAVE BEEN FORMED THEY CAN THEN BE AUTO MATICALLYCOMPAREDTO!)3DATAANDASSOCIATEDINTOASINGLETRACK IFDESIREDBYTHE OPERATOR4HISGIVESCOMPLETEINDEPENDENCETORADAR AND!)3 DERIVEDDATA THEREFORE ENHANCINGINTEGRITYCHECKING
ÓÓ°ÈÊ 1- ,Ê / ,
&ROMTHEUSERSPOINTOFVIEW THEMOSTVISIBLEANDIMPORTANTCHANGEINMARINERADAR FROMITSEARLYDAYSHASBEENTHEDEVELOPMENTOFPROCESSOR BASEDDISPLAYTECHNOLOGY )N PARTICULAR MODERN WELL DESIGNED DISPLAYS ARE VIEWABLE OVER A WIDE VARIATION OF AMBIENTLIGHTINGTHEYMAKEEFFECTIVEUSEOFCOLORANDGIVEEASYANDCLEARACCESSTOTHE RADARIMAGEANDASSOCIATEDDATA4HEDAYSWHENTHERADARSCREENWASONLYVIEWABLE INDAYLIGHTONDIMLONG PERSISTENCEMONOCHROME#24STHROUGHTHEAPERTUREOFAHOOD ARELONGGONE-ORERECENTLY HIGHBRIGHTNESSCOLOR#24SAREBEINGREPLACEDBY,IQUID #RYSTAL $ISPLAY FLAT PANEL TECHNOLOGY WHICH IS HELPING TO MAKE THE DISPLAY MORE USERACCESSIBLELARGESTAND ALONERADARCONSOLESARENOLONGERNECESSARY ALLOWING IMPROVEMENTSTOTHEERGONOMICLAYOUTOFASHIPSBRIDGE 5SERINPUTDEVICESVARYBYMANUFACTURER3OMESOLUTIONSRELYONLITTLEMORETHAN ATRACKERBALLANDTHREECONTROLBUTTONS/THERSHAVEANUMBEROFDEDICATEDSWITCHES AND ROTARY CONTROLS AS WELL AS A CURSOR CONTROL SUCH AS A TRACKER BALL OR JOYSTICK
ÓÓ°Óä
2!$!2(!.$"//+
4OUCHSCREENTECHNOLOGYISSOMETIMESEMPLOYED)NCREASINGLY SYSTEMSALSOINCLUDE AFULLALPHANUMERICKEYBOARDTOALLOWEASYINPUTOFUSER SUPPLIEDDATA ESPECIALLYFOR CHARTRADARSRADARSUTILIZINGANELECTRONICCHART BASEDUNDERLAY ANDRADARSINTEGRATED WITH!)32ADARSDESIGNEDFORSMALLERVESSELSTENDTOHAVEACOMPLETELYWATERPROOFED USERINTERFACEASTHEYAREOFTENUSEDINMOREEXPOSEDAREASANDBYOPERATORSWITHWET SALTYHANDS)NGENERAL TRACKERBALLS ALTHOUGHTHEYGIVEMOREPRECISECONTROLANDARE COMMONONSHIPBORNERADARS HAVEBEENFOUNDTOBEUNSATISFACTORYINTHEENVIRONMEN TALCONDITIONSFOUNDONSMALLCRAFT)NSTEAD MINIJOYSTICKSORSIMPLEFOUR WAYROCKER SWITCHESARETYPICALLYUSED 4HE OPERATIONAL AREA OF A RADAR DISPLAY IS NORMALLY CIRCULAR ALTHOUGH THIS IS NO LONGERAMANDATORYREQUIREMENT)TORIGINATESFROMTHEHISTORICALUSEOFCONICALDISPLAY TUBESBUTISRETAINEDBYMOSTMANUFACTURERSASITGIVESADDITIONALSPACEOUTSIDEOFTHE OPERATIONALAREAFORTHEDISPLAYOFDATAANDMENUSSEE&IGURE 4HEMINIMUM OPERATIONALDISPLAYAREAISDEFINEDASADIAMETERMMFORSHIPSLESSTHANGT MMFORSHIPSFROMTO GTANDMMFORSHIPSABOVE GT4HE MINIMUMRECOMMENDEDDISPLAYAREASFORSMALLCRAFTRADARAREGIVENIN4ABLE 4HECOLOROFRADARTARGETSANDBACKGROUNDISNOTMANDATED4HETARGETTRAILSTHATUSED TO BE PROVIDED BY THE DESIGNED IN PERSISTENCE OF ORIGINAL RADAR MONOCHROME #24S HAVETOBEPROVIDEDELECTRONICALLY4HETRAILLENGTHISREQUIREDTOBEUSERSELECTABLEIN UNITSOFTIME7HEN4RUE-OTIONISSELECTED TRAILSCANBECHOSENBYTHEOPERATORTO BESHOWNINEITHERTRUEORSHIP RELATIVEREFERENCEFRAMES4HEPOSITIONOFTHEDISPLAY CURSORISALWAYSAVAILABLEINADATABOXINTERMSOFRANGEANDBEARINGFROMOWNSHIP ANDORLATITUDEANDLONGITUDECOORDINATES)TISTHISCURSORTHATISUSEDTOSELECTANDDE SELECTTARGETSWITHINTHEOPERATIONALDISPLAYAREAANDTODRAWUSER DEFINEDMAPS)TIS ALSOCOMMONLYUSEDTOSETRANGEANDBEARINGMARKERS !CONSISTENTCOMMONREFERENCEPOINT##20 TOWHICHALLRADARANDOTHERNAVIGA TIONALDATANEEDTOBEREFERENCEDISIDENTIFIEDONTHESHIP4HISPOINTCLEARLYBECOMES OFMAJORIMPORTANCEWHENCLOSE INNAVIGATIONALCALCULATIONSAREBEINGMADE(AVING A DEFINED ##20 ALSO ALLOWS A SCALED OWN SHIPS SYMBOL TO BE SHOWN ON THE RADAR DISPLAY WHEN APPROPRIATELY SHORT RANGE SCALES ARE SELECTED 4HE SYMBOLOGY OF THIS GRAPHIC TOGETHERWITHALLOTHERSYMBOLSANDABBREVIATIONSONTHEDISPLAY SHOULDMEET )-/REQUIREMENTS4HISENSURESTHATOPERATORSAREFAMILIARWITHTHERADARPRESENTA TION WHEN WORKING ON DIFFERENT SHIPS 4HE RADAR DISPLAY SHOULD ALSO COMPLY WITH )-/SPERFORMANCESTANDARDSFORNAVIGATIONALDISPLAYS #ERTAINRANGESCALESMAXIMUMDISPLAYEDRANGES AREMANDATORY COVERINGTO NM)NPRACTICE RANGESCALESABOVENMARENORMALLYPROVIDED TYPICALLYUPTO NM2ANGERINGSMAYBEOPTIONALLYSWITCHEDINBYTHEOPERATORTOHELPESTIMATEDIS TANCES0RECISERANGEMEASUREMENTSAREMADEWITHTHEUSEOFAVARIABLERANGEMARKER 62- !TLEASTTWO62-SARENEEDED EACHWITHNUMERICALREADOUTINTHEDATAAREA OFTHEDISPLAY!NACCURACYOFISREQUIREDBUTNOTBETTERTHANMETERS !BEARING SCALEAROUNDTHEPERIPHERYOFTHEOPERATIONALDISPLAYMUSTBEVISIBLE4HISSCALECAN HELPUSERSDETERMINETHESHIPSDIRECTIONFROMVIEWINGTHEHEADINGLINE(, WHICH HASTOBESHOWNONTHEDISPLAYONLYTEMPORARYEXTINGUISHINGOFTHE(,ISPERMITTED )NADDITION ASHIPSHEADINGISNORMALLYAVAILABLEWITHINADATABOXOUTSIDEOFTHE OPERATIONALAREA4HERADARORIGINCANBEOFFSETFROMTHECENTEROFTHEOPERATIONALAREA BYTHEUSERTHEBEARINGSCALEADJUSTSACCORDINGLY 4WOORMOREELECTRONICBEARINGLINES%",S HAVETOBEPROVIDEDWITHCONTINUOUS NUMERICALREADOUT!LTHOUGHTHESEARENORMALLYCENTEREDONTHESHIPATTHE##20 THEY CANALSOBEOFFSETTOANYPOSITION2EADOUTSRELATIVETOOWNSHIPSHEADINGORTRUENORTH CANBESET4HE%",ORIGINCANALSOBESETSUCHTHATITFOLLOWSOWN SHIPMOVEMENTORIS
#)6),-!2).%2!$!2
&)'52% !SHIPSRADARDISPLAY#OURTESYOF.ORTHROP'RUMMAN3PERRY-ARINE"6
ÓÓ°Ó£
ÓÓ°ÓÓ
2!$!2(!.$"//+
GEOGRAPHICALLYFIXED4HEDISTANCEANDBEARINGOFONEPOINTTOANOTHERONTHEDISPLAYCAN BEDETERMINED NORMALLYBYUSEOFASPECIFICMENUITEMANDAPPROPRIATECONTROLOFTHE DISPLAYCURSOR4HEACTUALIMPLEMENTATIONOF%",S 62-S ANDOFFSETMEASUREMENTSIS OFTENEFFECTEDBYACOMMONGRAPHICALTOOL WHICHISUSEDTOPOSITIONANDDRAGLINESAND CIRCLESACROSSTHEDISPLAYBYMEANSOFTHECURSOR-ANYMARINERSFINDTHEUSEOFSHIP REFERENCEDPARALLELINDEX0) LINESTOBEHIGHLYUSEFUL!0)ISASTRAIGHTLINEONTHERADAR DISPLAYTHATISUSER SETTOAFIXEDhCOMPASSvBEARINGANDAFIXEDPERPENDICULARDISTANCE FROMTHERADARORIGIN!TLEASTFOUROFTHESEHAVETOBEPROVIDED4HESECANBEINDIVIDU ALLYSWITCHEDINTOUSEANDSETBYBEARING BEAMRANGE ANDLENGTH0)SARETYPICALLYUSED TOENSURETHATASHIPISMAINTAININGASAFEGROUNDTRACK WITHREFERENCETOAGROUND FIXED CONSPICUOUSRADARTARGET #HART2ADARS 4HECAPABILITYANDRELATIVELYLOWCOSTOFMODERNPROCESSINGAND DISPLAYSYSTEMSALLOWGREATFLEXIBILITYINTHEPRESENTATIONOFINFORMATIONTOUSERS&OR MANYYEARS 3/,!3 COMPLIANTRADARSHAVEHADTHECAPABILITYTOEMPLOYUSER DEFINED MAPSASANUNDERLAYTOTHERADARIMAGE-ANYMAPSCANBECREATEDANDSTOREDFOR FUTUREUSE!LTHOUGHTHISFACILITYISSTILLWIDELYUSED THEUSEOFVECTORIZEDELECTRONIC CHART DATA AS A RADAR UNDERLAY IS BECOMING MORE COMMON )N )-/ TERMS THEY ARE KNOWNASCHARTRADARS!LLAPPROVEDCHARTRADARSHAVETOBECAPABLEOFDISPLAYING OFFICIALLYRECOGNIZEDVECTORDATA4HISDATAISKNOWNASTHE%LECTRONIC.AVIGATIONAL #HART %.# )T IS ISSUED ON NATIONAL AUTHORITY AND COMPLIES WITH AN )NTERNATIONAL (YDROGRAPHIC/RGANIZATION)(/ STANDARDKNOWNAS3%.#DATAISNORMALLY DISPLAYEDONAPPROVEDELECTRONICCHARTSYSTEMSCALLED%LECTRONIC#HART$ISPLAYAND )NFORMATION3YSTEMS%#$)3 ANDMAYBEUSEDBYSHIPSINPLACEOFPAPERCHARTS %.#DATAISKEPTUP TO DATEBYHYDROGRAPHICOFFICESTHATISSUEUPDATEFILESONAREGULAR BASIS!N)-/ APPROVEDCHARTRADARMUSTALSOBEABLETOACCEPTTHESEUPDATES#HARTS ANDTHEIRUPDATESARELOADEDBY#$ 2/-ORVIAASATELLITECOMMUNICATIONSLINK/N SOMESYSTEMS THECHARTRADARMAYHAVEACCESSTOASERVERONTHESHIPTHATCENTRALIZES THEDISTRIBUTIONOFSUCHDATATOALLEQUIPMENTNEEDINGCHARTINFORMATION 4HE USER HAS THE ABILITY TO CHOOSE THE %.# VECTOR LAYERS SHOWN ON THE DISPLAY OFACHARTRADAR&ORINSTANCE THISMAYJUSTINCLUDETHECOASTLINE NAVIGATIONMARKS ANDASINGLEDEPTHCONTOUR CONSIDEREDSAFEFORTHEDRAUGHTOFTHESHIP)FTHESHIPIS NAVIGATING ON %#$)3 RATHER THAN A PAPER CHART IT IS LIKELY THAT BOTH THE RADAR AND THE %#$)3 WILL BE COMMONLY SET TO #OURSE UP OR (EAD UP MODES .ORTH UP IS NO LONGERAPARTICULARADVANTAGEWHENTHECHARTISNOTCONFINEDTOSUCHAPRESENTATION SUCHASPAPERCHARTS-OST%#$)3EQUIPMENTCANOPTIONALLYSHOWRADAR DERIVEDDATA NORMALLYASTRACKEDTARGETVECTORSBUTSOMETIMESASTHERADARIMAGEITSELF4HISDATA ISOBTAINEDFROMTHERADARPROCESSORVIAADIGITALINTERFACE GIVINGANAPPARENTCONVER GENCEOF%#$)3ANDRADARDISPLAYS#ERTAINLY THISISTRUEATABASICDESIGNLEVEL BUT )-/ISKEENTODIFFERENTIATEBETWEENTHETWO!N%#$)3ISUSEDTOPLANANDMONITOR PASSAGESARADARISUSEDPRIMARILYASACOLLISIONAVOIDANCETOOLBUTALSOTOAIDPOSI TIONFIXING PARTICULARLYBYIDENTIFYINGGROUND FIXEDRADARCONSPICUOUSOBJECTSINCLUD INGCOASTLINES4HISRESULTSINMANYDIFFERENCESINTHEDETAILEDREQUIREMENTSOFRADAR AND%#$)3DISPLAYS(OWEVER FROMADESIGNPOINTOFVIEW THEDISPLAYPROCESSING REQUIREMENTSAREVERYSIMILARANDCANTHEREFOREUSEVIRTUALLYIDENTICALHARDWARE!S WELLASSAVINGDESIGNCOSTS THISENABLESANEASYTRANSITIONTOMULTIFUNCTIONDISPLAYS -&$S !N -&$ CAN BE INSTANTLY SWITCHED BETWEEN RADAR AND %#$)3 AS WELL AS OTHERFUNCTIONS ENABLINGDYNAMICRECONFIGURATIONONASHIPTOOPTIMIZEDISPLAYUSE FORPARTICULARCIRCUMSTANCES#LEARINDICATIONOFTHESELECTEDMODEBECOMESNECESSARY FORSAFETYANDSTATUTORYREASONS
#)6),-!2).%2!$!2
ÓÓ°ÓÎ
-OSTSMALLCRAFTRADARSNOWBEINGSOLDINCLUDETHEOPTIONOFACHARTUNDERLAYFACILITY ASARELATIVELYLOW COSTOPTION)NGENERAL THESEUSEUNOFFICIALVECTORCHARTDATA ISSUED BYSPECIALISTPRIVATECOMPANIES4HISDATAISMOREAFFORDABLETHAN%.#SANDISDIRECTED TOTHISPARTICULARMARKET"ECAUSEOFCOSTANDSPACECONSTRAINTS ASINGLEDISPLAYNOR MALLYACTSASBOTHRADARANDELECTRONICCHART4HESESDISPLAYSAREALLEFFECTIVELY-&$S ANDCAN THEREFORE ALSOBEUSEDASANELECTRONICCHARTSYSTEMWITHOUTRADARINPUT
ÓÓ°ÇÊ / ,/" Ê7/Ê4HEMARITIME!UTOMATIC)DENTIFICATION3YSTEM!)3 ISATARGETINFORMATIONSYSTEM THATPERFORMSSIMILARFUNCTIONSTOAIRBORNE3ECONDARY3URVEILLANCE2ADAR332 SUCH AS!IR 4RAFFIC #ONTROL "EACON 3YSTEM !4#2"3 AND )DENTIFICATION &RIEND OR &OE )&& (OWEVER THEVASTMAJORITYOFTRANSMISSIONSARENOTTHERESULTOFANYINTERROGA TION ASITMAINLYOPERATESASABROADCASTSYSTEM BASEDAROUNDA3ELF/RGANIZING4IME $OMAIN-ULTIPLE!CCESS3/4$-! COMMUNICATIONSPROTOCOL4HECOMMUNICATIONS LINK INCLUDINGTHE3/4$-!DEFINITION ISDEFINEDBYTHE)453HIPSAUTOMATICALLY TRANSMITCURRENTNAVIGATIONALDATAANDOTHERINFORMATIONON6(&MARINE BANDCHAN NELSASSIGNEDFOR!)3USE4HETRANSMITTEDINFORMATIONISRECEIVEDBYOTHERSHIPSAND ALSOBYSHORESTATIONS SUCHASCOASTALAUTHORITIESAND643FACILITIES3HORESTATIONS ANDSHIPSALSOHAVETHEABILITYTOSPECIFICALLYINTERROGATESHIPBORNE!)3TRANSPONDERS TO INITIATE THE SENDING OF PARTICULAR DATA!)3 HAS THREE MAJOR USES TO ENHANCE THE BRIDGETEAMSSITUATIONALAWARENESS TOAID643ACTIVITIES ANDTOPROVIDEDATATOASSIST NATIONALSECURITY4HEINTENTIONOF)-/ISTHATSHIPSWILLNORMALLYDISPLAY!)3DATAON THERADARSCREENASITCOMPLEMENTSRADAR DERIVEDDATA ADDINGTOTHEINTEGRITYOFTHE PRESENCE POSITION ANDVELOCITYOFTARGETSANDALSOGIVINGINCREASEDTARGETINFORMATION )N PRINCIPLE A CONVENTIONAL SECONDARY RADAR SOLUTION COULD HAVE BEEN ADOPTED BUT INTERNATIONALCONSENSUSFAVOREDTHE3/4$-!APPROACH ASITWASCAPABLEOFPROVID INGHIGHERLEVELSOFDATAEXCHANGE PARTICULARLYTOAID643ANDSECURITYACTIVITIES!N IMPORTANTADVANTAGEOFTHECHOSEN!)3SOLUTIONISITSRADIOFREQUENCY)TISSUFFICIENTLY LOWSOTHATREASONABLECOMMUNICATIONSAREMAINTAINEDINSITUATIONSWHERETHEREISNO VISUALORRADARLINE OF SIGHT4HISCANBEIMPORTANTINHARBOR RIVER ISLAND ANDESTUARY REGIONS WHERESHIELDINGBYTHETERRAINORBUILDINGSCANAFFECTRADARRANGE ! SHIPBORNE!)3 STATION BROADCASTS INFORMATION DIVIDED INTO A NUMBER OF SETS 4HESECOMPRISESTATICDATA SUCHASTHESHIPSNAME TYPE LENGTH ANDBEAMDYNAMIC DATA INCLUDINGPOSITION 3/' #/' ANDHEADINGANDVOYAGE RELATEDDATA SUCHAS DESTINATIONPORTAND%4! DEPTHUNDERKEEL ANDHAZARDOUSCARGOTYPE4HEDYNAMIC DATAISBROADCASTATARATECONSISTENTWITHTHEVESSELSVELOCITYANDWHETHERITISCHANG INGCOURSE ASSHOWNIN4ABLE3TATICANDVOYAGE RELATEDDATAISNORMALLYBROAD CAST EVERY MINUTES 4O PROVIDE SUFFICIENT BANDWIDTH TWO SPECIFIC 6(& +(Z CHANNELSAREUSED WITHSTATIONSALTERNATINGBETWEENCHANNELSATEACHMESSAGE4HERE ARE MESSAGESLOTSPERCHANNELEVERYMINUTE-INUTESAREALIGNEDTO5NIVERSAL 4IME #OORDINATED 54# WHICH IS OBTAINED FROM AN INTEGRAL '.33 RECEIVER 4HE 3/4$-!ALGORITHMEFFECTIVELYRESERVESFUTURESLOTSFORSTATIONSTHATAREINRECEPTION RANGEOFEACHOTHER PREVENTINGMUTUALINTERFERENCE !)3FOR3/,!3USEISKNOWNAS!)3#LASS!4HEREISA#LASS"SYSTEMTHATIS DESIGNEDFORNON 3/,!3USE4HISSYSTEMUSESTHESAME6(&CHANNELSAS#LASS! ANDTHETRANSMISSIONSARENECESSARILYCOMPATIBLE BUTTOAVOIDOVERLOADINGTHE6(& DATA LINK 6$, #LASS " USES #ARRIER 3ENSING4$-!4HIS IS AIMED AT CONFINING
ÓÓ°Ó{
2!$!2(!.$"//+
4!",% !)30OSITION2EPORTING)NTERVALS#OURTESYOF)-/
3HIP$YNAMICS !TANCHORORMOOREDANDNOTMOVINGFASTERTHANKNOTS 7ITHASPEEDOFBETWEENnKNOTS 7ITHASPEEDOFBETWEENnKNOTSANDCHANGINGCOURSE 7ITHASPEEDOFBETWEENnKNOTS 7ITHASPEEDOFBETWEENnKNOTSANDCHANGINGCOURSE 7ITHASPEEDOFGREATERTHANKNOTS 7ITHASPEEDOFGREATERTHANKNOTSANDCHANGINGCOURSE
2EPORTING)NTERVALSECONDS
#LASS"SYSTEMSTOUSEONLYSLOTSUNALLOCATEDTO#LASS!USERS#LASS"SYSTEMSWILL DELAYTHEIROWNTRANSMISSIONSIFSLOTSARENOTAVAILABLE4HEREISANADDITIONALOPTION OFAN3/4$-! BASED#LASS"SYSTEM )MPORTANTLY #LASS!AND"SYSTEMSRECEIVE EACHOTHERSTRANSMISSIONS 4HECOMBINATIONOF!)3ANDRADAR DERIVEDDATAGIVESBENEFITSTONAVIGATIONBECAUSE OFTHECOMPLEMENTARYNATUREOFTHETWOSYSTEMS4HERELATIVERANGEANDBEARINGSOF A TARGET DERIVED FROM!)3 DATA ARE ENTIRELY INDEPENDENT OF THE RADAR MEASUREMENTS OF THESE PARAMETERS #LEARLY ANY OBSERVED DIFFERENCES IN RADAR AND !)3 POSITIONS WILLTHENINDICATEANERRORINSOMEPROCESS PROVIDEDTHEDIFFERENCESAREOUTSIDETHE EXPECTEDNOISEINTHEMEASUREMENTS4HISCANBEHIGHLIGHTEDFORTHEUSER!HIGHPOSI TIONALCORRELATIONINCREASESTHEINTEGRITYOFTHEOBSERVATION PARTICULARLYASSPEEDAND COURSEMEASUREMENTSCANALSOBEUSEDINTHECOMPARISON,ACKOFANYCORRELATIONCAN ALSOGIVETHEUSERINFORMATIONTHATMAYBEHELPFUL)FONLYRADARDATAISRECEIVED ITMAY BETHATTHETARGETISNOTFITTEDWITH!)3 WHICHMEANSITCOULDBEASMALLCRAFT FLOATING DEBRIS ORICE)TCOULDALSOMEANTHATAVESSELS!)3ISNOTOPERATINGORISTRANSMITTING ERRONEOUSPOSITIONALINFORMATION)FONLY!)3DATAISRECEIVED THERADARIMAGEMAY BEOBSCUREDBYCLUTTER AHEADLAND OREVENAPOORLYSETUPORFAULTYRADARINSTALLATION .ORMALLY JUSTAFEWTARGETSWILLBEUNCORRELATED HIGHLIGHTINGTHATTHESEFEWSHOULD BEGIVENADDITIONALCAUTIONIFTHEYARESIGNIFICANTTOOWN SHIPNAVIGATION ATLEASTUNTIL THEYCANBEPOSITIVELYIDENTIFIED PERHAPSVISUALLY)FNOTARGETSARECORRELATED ITSUG GESTSTHATOWNSHIPHASASIGNIFICANTPROBLEM PERHAPSWITHITSRADAR '.33POSITION ORMORECOMMONLY AGYROCOMPASSOFFSET )FTHEREISGOODPOSITIONALTIE UPOREVENANUNDERSTANDINGOFWHYRADARINFORMA TIONMAYBELACKING FOREXAMPLE DUETOHEAVYSEACLUTTER THEADDITIONALINFORMATION TRANSMITTEDON!)3CANBEEXTREMELYUSEFUL&ORINSTANCE ATARGETSHEADINGISTRANS MITTEDBY!)34HISINFORMATIONISNOTAVAILABLEFROMRADARONLYTHECOURSECANBE DETERMINED ANDYETHEADINGISUSEDASTHEBASISFORDETERMININGCOLLISIONAVOIDANCE ACTION4HE!)3TRANSMITTEDHEADINGSHOULDALIGNWITHTHETARGETSVISUALASPECTAND THEREFORE THENAVIGATIONALLIGHTSONAVESSEL6ESSELNAMESCANBEADDEDAUTOMATICALLY TOTARGETTRACKSONTHERADAR!)3DISPLAY ANDIFTHEREISANEEDTOCOMMUNICATEON6(& WITHAPARTICULARTARGET THERADIOCALLSIGNISALSOAVAILABLEFROMTHE!)3DATA4HE DESTINATIONPORTAND%4!CANSOMETIMESBEUSEFULINDETERMININGTHELIKELYINTENTIONS OFTARGETS ALTHOUGHSUCHASSUMPTIONSMUSTBETREATEDWARILY ! SIGNIFICANT ADVANTAGE OF RADAR IS THAT IT DOES NOT NEED COOPERATIVE TARGETS )T ATTEMPTSTODETECTALLOBJECTSOFPOTENTIALINTEREST)TSINHERENT2ELATIVE-OTIONMODE OFOPERATIONMAKESITIDEALLYSUITEDFORCOLLISIONAVOIDANCEUSEPARTICULARLYASINTHIS MODEITHASNOREQUIREMENTTONEEDOWNSHIPSGEOGRAPHICALPOSITION(OWEVER RADAR IS BASICALLY CONFINED TO LINE OF SIGHT OPERATION ITS PERFORMANCE CAN BE SIGNIFICANTLY
#)6),-!2).%2!$!2
ÓÓ°Óx
DEGRADEDBYCLUTTER ANDITSTRACKINGCAPABILITYISCOMPROMISEDWHENTARGETSARECHANG ING COURSE OR PASSING CLOSE TO OTHER TARGETS!)3 HAS REASONABLY GOOD CAPABILITY IN NON LINE OF SIGHTSITUATIONSBECAUSEOFITSLOWERFREQUENCY)TQUICKLYREPORTSATARGETS CHANGEINHEADINGORCOURSE INCLUDINGRATEOFTURNDATA IFITISAVAILABLEONTHETARGET VESSEL!)3ISNOTAFFECTEDBYSEACLUTTERANDCANREPORTABSOLUTEPOSITIONACCURATELYTO NORMALLYBETTERTHANMETERSOREVENAMETERORTWO IFREPORTINGDIFFERENTIAL'.33 DERIVEDPOSITIONALDATA(OWEVER !)3RELIESONCOOPERATIVETARGETSISPRONETOGROSS ERRORSINDATAACCURACY MAINLYCAUSEDBYSETUPERRORSANDTOTALLYRELIESONREASONABLY ACCURATE'.33DATABEINGAVAILABLE!'.33BLACKOUT PERHAPSCAUSEDBYINTENTIONAL ORUNINTENTIONALJAMMING WOULDPREVENT!)3FROMBEINGANEFFECTIVESYSTEM POSSIBLY OVERAWIDEAREAANDFORANAPPRECIABLETIME &UTURESYSTEMSMIGHTINCREASINGLYEXPLOITTHECOMPLEMENTARYASPECTSOFRADARAND !)34HISCOULDIMPROVETHEOVERALLTARGET TRACKINGCAPABILITYAVAILABLETOSHIPSAND WILLGIVESUPPORTFORDETECTINGCOOPERATIVETARGETSINCLUTTER0OSSIBLY THEKNOWLEDGE FROM!)3THATATARGETISLIKELYTOBEATAPARTICULARRANGEANDAZIMUTHCOULDDIRECT CONCENTRATEDPROCESSINGTECHNIQUESINTHATAREA PERHAPSUSINGPATTERN MATCHINGALGO RITHMSASWELLASOPTIMIZINGTHEFALSE ALARMRATEINTHEIMMEDIATEAREAOFTHE!)3 REPORTEDTARGET)TISIRONICTHATTHEVERYTARGETSTHATMAYBEHIDDENINCLUTTERARESMALLER VESSELSTHATDONOTMANDATORILYCARRY!)3!LSO A#LASS"SYSTEMONLYTRANSMITSONCE EVERYSECONDSATAMAXIMUMANDSOWILLBELESSUSEFULFORAIDINGRADAREVENTHOUGH ITCANUSEFULLYALERTNAVIGATORSTHATASMALLTARGETISPRESENT 4HEUSEOF!)3ASANAID TO NAVIGATION!TO. HASBEENPUTFORWARDASAPOSSIBLE REPLACEMENT FOR RACONS WHICH ARE DESCRIBED IN THE NEXT SECTION )N PRINCIPLE !)3 !TO.S COULD REPLACE RACONS BUT IN PRACTICE IT WOULD BE A RETROGRADE STEP AS THEY CANNOTBEUSEDINDEPENDENTLYOFAPOSITIONFIXSYSTEM SUCHAS'.33(OWEVER THEY CANBEUSEFULLYEMPLOYEDTOINDICATETHEINTEGRITYOFTHEACTUALPOSITIONOFTHEMARK WHICH MAY HAVE DRAGGED OR BECOME UNATTACHED AND OTHER ADDITIONAL DATA SUCH AS SEACURRENTS4HE!)3TRANSCEIVERDOESNOTHAVETOBESITUATEDONTHEACTUALMARKAND COULDBESHORE BASEDTOEASEMAINTENANCE5SEDINTHISWAY THEYAREKNOWNAS6IRTUAL !)3!TO.S 5P TO DATE INFORMATION CONCERNING THE MARK AND ITS INTEGRITY CAN BE AUTOMATICALLYORMANUALLYFED INBYPORTAUTHORITIES3UCHSYSTEMSCANALSOBEUSED FORALERTINGMARINERSOFTHEPOSITIONOFRECENTWRECKSANDOTHERTEMPORARYANDPERHAPS VISUALLYUNMARKEDNAVIGATIONHAZARDS
ÓÓ°nÊ , ,Ê " 2ADARBEACONSHAVEPLAYEDANIMPORTANTROLEINMARINENAVIGATIONEVERSINCETHEEARLY DAYSOFRADAR4HEYBASICALLYDETECTINCIDENTPULSESFROMMARINERADARSANDINSTAN TANEOUSLYTRANSMITADISTINCTIVESIGNALTHATIDENTIFIESTHEBEACONANDITSPOSITIONON ARADARDISPLAY4HEREARETHREEMAINUSESOFSUCHBEACONS4HEFIRSTOFTHESEISFOR ENHANCINGVISUALAIDSTONAVIGATION SUCHASBUOYSANDLANDMARKS TOENABLETHEMTO BEPROMINENTLYIDENTIFIEDONARADARDISPLAY4HESEARENORMALLYCALLEDRACONSASA CONTRACTIONOFRADARBEACONS 3UCHSYSTEMSFORMANIMPORTANTNAVIGATIONALSERVICE THATISWELLLIKEDBYMARINERS4HESECONDUSEISFOR3EARCHAND2ESCUE4RANSPONDERS 3!24S WHICHAREMAINLYDESIGNEDTOBEDEPLOYEDFROMLIFERAFTSAFTERAMARINEACCI DENT4HETHIRDCATEGORYOFUSEISFORRADARENHANCEMENTOFSMALLTARGETS SUCHASPLEA SURECRAFT4HESEARECALLEDRADARTARGETENHANCERS24% ORACTIVERADARREFLECTORS
ÓÓ°ÓÈ
2!$!2(!.$"//+
2ACONS 4HE )NTERNATIONAL !SSOCIATION OF -ARINE !IDS TO .AVIGATION AND ,IGHTHOUSE!UTHORITIES )!,! SETS THE PERFORMANCE STANDARDS FOR RACONS 4HESE INCORPORATETHETECHNICALCHARACTERISTICSSETOUTINASPECIFIC)45 22ECOMMENDATION "ECAUSERACONSNORMALLYFORMONLYONESUBSYSTEMOFAN!TO.THEYTHEREFORENEEDTO BESMALLINSIZEANDPOWEREFFICIENTSINCETHEYARERARELYCONNECTEDTOAMAINPOWER SUPPLY4HEYOFTENOPERATEINANEXTREMEENVIRONMENT SUCHASONABUOYBUFFETEDBY THESEA2ACONSARESPECIFIEDTOMEETANEXTENDEDOPERATIONALTEMPERATURERANGEOF nTO #-ODERNRACONSOPERATEBYDETECTINGANINCIDENTPULSEANDTHENMEASUR INGITSFREQUENCYANDRESPONDINGATTHESAMEFREQUENCY THEREBYREDUCINGTHEINTERFER ENCEPOTENTIALWITHOTHERIN BANDRADARS4HEYAREOFTENDUAL BANDAND'(Z 4HE )45RECOMMENDSTHATFORPULSELENGTHSOF§SORLONGER THEFREQUENCYACCURACYOF THERESPONDINGSIGNALSHOULDBEWITHINo-(Z ANDFORPULSESOFLESSTHAN§S THE FREQUENCY SHOULD BE WITHIN o -(Z 3WEPT FREQUENCY RACONS ARE EFFECTIVELY OBSOLESCENTBUTARESTILLPERMITTED4HESEWORKBYHAVINGANINTERNAL2&SOURCETHATIS SLEWINGINFREQUENCYACROSSTHEENTIRERADARBANDWITHASAW TOOTHWAVEFORMATARATE BETWEENANDSECONDSPER-(Z!LLRECEIVEDPULSESARERESPONDEDTOBUT THEINTERROGATINGRADARWILLRECEIVEARACONBURSTONLYONCEEVERYONETOTWOMINUTES WHENITSRECEIVERISINBANDTOTHEPARTICULARTRANSMISSION )!,!RECOMMENDSTHATRACONSHAVESUPPRESSIONTECHNIQUESTOAVOIDRESPONDING TORADARSIDELOBETRANSMISSIONS4HISISNOTANEASYTASKTOIMPLEMENTANDPROBABLY IMPOSSIBLETOMAKEINFALLIBLE"ASICALLY THERACONNEEDSTOBUILDATABLEOFRADARSIG NATURES THAT IT IS CURRENTLY RECEIVING BASED ON FREQUENCY AND PULSE LENGTH )T THEN IDENTIFIESWHETHERHIGHLEVELANDLOWERLEVELPULSESOFTHESAMESIGNATUREAREBEING RECEIVEDANDMAKESTHEASSUMPTIONTHATTHESEAREFROMTHESAMERADAR)TSETSATHRESH OLDLEVELFORINDIVIDUALRADARSSUCHTHATITONLYRESPONDSTOHIGH POWERMAINBEAM INTERROGATIONS4YPICALLY PEAKTRANSMITPOWERSAREABOUTnWATTS!NTENNASAREUSU ALLY OMNIDIRECTIONAL IN AZIMUTH BUT CAN HAVE A RESTRICTED ELEVATION BEAMWIDTH AND TYPICALLYHAVEANOVERALLGAINOFABOUTD"0RIMEPOWERCONSUMPTIONINAVERAGE TRAFFICCANBELESSTHANWATT 4HEMODULATIONONTHERESPONSESIGNALOFARACONPAINTSA-ORSECODEIMAGEONTHE RADARDISPLAY4HECODEIDENTIFIESAPARTICULAR!TO.ANDAPPEARSINTHERADIALDIRECTION CONVENTIONALLYCOMMENCINGWITHADASH4HISDASHSTARTSASHORTDISTANCEBEYONDTHE ACTUALPOSITIONOFTHE!TO.BECAUSEOFINHERENTDELAYSINTHERESPONSETIMEOFTHERACON (OWEVER DELAYSGIVINGANERROROFLESSTHANMETERSAREREADILYACHIEVABLE)NGOOD CONDITIONS THE!TO.PRIMARYRADARIMAGEWILLBEDISPLAYEDONTHERADARSCREEN HELPEDIF APASSIVERADARREFLECTORISALSOAPARTOFTHE!TO.2ACONSHAVETOINCLUDEMUTINGPERIODS TOALLOWSHIPRADARSTOLOOKFORSMALLTARGETSINTHEVICINITYOFTHERACONIDENTIFIER 4HELONG TERMFUTUREOFRACONSISUNSURE ALTHOUGHMARITIMEAUTHORITIESAREASSESS INGTHESITUATION-ARINERSLIKETHEMASTHEYAREUSEFUL FAMILIAR ANDGIVESHIP RELATIVE DATA(OWEVER ITISDIFFICULTTOSEEHOWTHEYWILLSURVIVEINTHEIRORIGINALFORMASMARINE RADARMOVESAWAYFROMUTILIZINGMAGNETRON BASEDSYSTEMS!LSO COMPAREDWITHEARLIER YEARS WHENRACONSWEREESSENTIAL MANYMORENAVIGATIONALAIDSAREBECOMINGAVAILABLE THATASSISTPOSITIONING4HESEINCLUDEMULTIPLE'.33SERVICES DIFFERENTIAL'.33 !)3 ANDENHANCED643FACILITIES4HEREAREALSOGREATIMPROVEMENTSINONBOARDNAVIGA TIONALAIDSSUCHASELECTRONICCHARTSANDINTEGRATEDNAVIGATIONSYSTEMS 4HERELIANCEOFNAVIGATIONONASINGLESYSTEM SUCHAS'03 OREVENASINGLETECH NOLOGY SUCHAS'.33 ISNOTACCEPTABLETOTHEMARITIMECOMMUNITYANDNEITHERTO AVIATION&ORINSTANCE ITISEASYTOJAMALL'.33USERSOVERAWIDEAREABECAUSEOF THESMALLAMPLITUDEOFTHERECEIVEDSIGNAL4HISMEANSTHATRADARANDOTHERPOSITION INGSYSTEMSARELIKELYTOBEALWAYSUSEDASESSENTIALNAVIGATIONALTOOLS4HEOVERALL
#)6),-!2).%2!$!2
ÓÓ°ÓÇ
REQUIREMENTSFORTHEELECTRONICNAVIGATIONOFSHIPS INCLUDING643REPORTINGSYSTEMS ARE BEING EXAMINED BY )-/ AND )!,! WITH THE INTENTION OF DETERMINING A FUTURE E .AVIGATIONCONCEPTEFORELECTRONICENHANCED 4HECONTINUEDNEEDFORRACONSOR AREPLACEMENTTECHNOLOGYWILLINEVITABLYFORMPARTOFTHISPROGRAM)FTHECONTINUOUS AVAILABILITYOFPRECISEPOSITIONALINFORMATIONCANNOTBETOTALLYRELIEDUPON THENITIS PROBABLY ESSENTIAL THAT SOME FORM OF SHIP RELATIVE SYSTEM TO IDENTIFY FIXED NAVIGA TIONALMARKSISAVAILABLE 3!24S 3EARCHAND2ESCUE4RANSPONDERS3!24 FORMPARTOF)-/S'LOBAL -ARITIME$ISTRESSAND3AFETY3YSTEM'-$33 4HESEARE'(ZRADARTRANSPONDERS THATAREMAINLYDESIGNEDTOBEUSEDONSURVIVALCRAFTSUCHASLIFERAFTS INEMERGENCY CONDITIONS4HEYARERELATIVELYSMALLANDAFFORDABLE/NBEINGTRIGGEREDBYARADAR PULSE A3!24EMITSA CYCLEFREQUENCY SWEPTSAW TOOTHWAVEFORMCOVERINGTO '(Z4HEEXTENSIONDOWNTO'(ZCOVERSTHEBANDUSEDBYSEARCHAIRCRAFT4HE VERYFASTUPWARDFREQUENCYSCANISACCOMPLISHEDIN§STHEDOWNWARDSCANTAKES §S4HISFORMSTHEPOSSIBILITYOFADISPLAYEDTRACEONTHERADARSCREEN CONSISTING OFRADIALDOTSANDDASHESASTHEUPWARDANDDOWNWARDSCANSCROSSTHEPASSBANDOF THERADARRECEIVER WITHTHEFIRSTDOTATASLIGHTLYLONGERRANGETHANTHE3!24POSITION )NPRACTICE THEUPWARDSWEEPISSOFASTTHATTHEDOTSARENORMALLYNOTVISIBLEONTHE DISPLAYANDONLYTHEDASHESCANBESEEN%VENTHESECANBEQUITEDIFFICULTTOLOCATEIN ADVERSESEACLUTTERCONDITIONS 4HEFIRSTDASHDISPLAYEDONTHERADARSCREENCOULDBEUPTONMAWAYFROMTHE ACTUAL3!24POSITIONANDSOSEARCHCRAFTHAVETOTAKEPRECAUTIONSNOTTORUNDOWN THESURVIVALCRAFTWHENBEARINGDOWNONTHESIGNAL!TSHORTRANGES THESWEPTGAIN OFTHERADARMAYTRUNCATETHENEARERDASHES!LSOATSHORTRANGES BECAUSETHEREIS NO SIDELOBE SUPPRESSION CIRCUITRY 3!24S CAN BE TRIGGERED BY RADAR SIDELOBES4O PREVENT ADJACENT 3!24S FROM CONTINUOUSLY TRIGGERING EACH OTHER THERE IS A SHORT DELAYAFTERA3!24TRANSMISSIONBEFOREITMAYBETRIGGEREDAGAIN4ODETECT3!24S IN HEAVY SEA CLUTTER IT IS OFTEN BEST TO DETUNE THE RADAR RECEIVER ELIMINATING ALL OTHERRETURNS3OMERADARMANUFACTURERSPROVIDEA3!24SEARCHMODETHATSETSTHE RADAR OPTIMALLY FOR THEIR DETECTION INCLUDING INHIBITING PULSE TO PULSE CORRELATION ANDOPTIMIZINGFILTERBANDWIDTHS!)3 BASED3!24SHAVENOWBEENPROPOSED4HESE MAYEVENTUALLYREPLACERADAR BASED3!24SBECAUSETHELATTERAREDIFFICULTTODETECT INADVERSECONDITIONS 2ADAR4ARGET%NHANCERS 2ADARTARGETENHANCERS24%S AREUSEDINCREAS INGLYBYSMALLCRAFTBECAUSE FORTHEIRSIZE THEYOFFERABETTERENHANCEMENTINRADAR CROSSSECTIONTHANCANBEGIVENBYAPASSIVEREFLECTOR)NPRINCIPLE THEYARESIMPLE DEVICES)N BANDRECEIVEDSIGNALSAREAMPLIFIEDANDRETRANSMITTEDWITHMINIMUM DELAY$ELAYSCANBEKEPTTOAFEWNANOSECONDS LESSTHANTHEEQUIVALENTDIMEN SIONSOFTHECRAFT ENSURINGCO LOCATEDRETURNSOFTHEENHANCEDSIGNALANDNATURAL RADAR REFLECTION 4O PREVENT POSITIVE FEEDBACK BETWEEN RECEIVER AND TRANSMITTER THETRANSMITANDRECEIVEANTENNASARENORMALLYPHYSICALLYSEPARATE ONEABOVETHE OTHER PROVIDING ISOLATION )SOLATION CAN ALSO BE INCREASED BY TRANSMITTING ON AN ORTHOGONALPOLARIZATIONTOTHATRECEIVED0ROVIDINGTHEYAREOPERATINGWITHLINEAR GAIN THEREARENOADVERSEEFFECTSFROMRADARSIDELOBEINTERROGATION(OWEVER AT CLOSERANGES THESIGNALFROMTHEMAINBEAMOFTHERADARMAYSATURATEWITHINTHE 24% EFFECTIVELYENHANCINGTHELEVELSOFTHE24%RECEIVEDSIGNALTHROUGHTHERADAR SIDELOBES4HE)45REGULATIONSLIMIT24%STOAN%)20OFWATTS WITHAMINIMUM GAINOFD"
ÓÓ°Ón
2!$!2(!.$"//+
ÓÓ°Ê 6 /" Ê/ -/ 4HE FACTORS AFFECTING THE RANGE PERFORMANCE OF A RADAR SYSTEM ARE WELL KNOWN AND INCREASINGLYSOPHISTICATEDDESIGNMETHODOLOGIESHAVEGREATLYIMPROVEDTHEDETECTION OFALLFORMSOFRADAR4HEFINALPROOF HOWEVER ISHOWTHERADARACTUALLYPERFORMSAT SEA!SSTATEDPREVIOUSLY SHIPBORNERADARSAREVALIDATEDASMEETING)-/PERFORMANCE STANDARDSBYBEINGINDEPENDENTLYTYPEAPPROVEDTOTECHNICALSTANDARDSISSUEDBYTHE )%#4HE)%#STANDARDSINCLUDEDEFINEDMETHODSOFTESTING&ORAGIVENTARGETANDRADAR ANTENNAHEIGHT ITISRELATIVELYEASYTODEFINEANDEXECUTEATESTTODETERMINETHATAPOINT SOURCETARGETWITHASPECIFICECHOINGAREAISDETECTEDATAGIVENRANGEINAMINIMAL CLUTTERFIELD)TISVERYDIFFICULTTOEXTENDTHISTODETERMINE INAREPEATABLEANDQUANTI TATIVEMANNER THEPERFORMANCEOFTHERADARAGAINSTPOINTTARGETSINPREDEFINEDCLUTTER CONDITIONS&ORTHISREASON SOMEBASICPERFORMANCETESTSHAVENECESSARILYBEENLOOSELY DEFINEDTOALLOWSCOPEFORAPPROVEDTESTLABORATORIESTOMAKETHEIROWNQUALITATIVEJUDG MENTSONBASICRADARPERFORMANCE NORMALLYBASEDONOPPORTUNISTICALLYTESTINGTHERADAR OVERTHESEAANDINPRECIPITATIONINAVARIETYOFSITUATIONS*UDGMENTSONPERFORMANCE CAN THEREFORE BEQUITESUBJECTIVEANDARENATURALLYAFFECTEDBYTHECONDITIONSACTUALLY ENCOUNTEREDDURINGTHETESTS#OSTCONSIDERATIONSCANSEVERELYLIMITTHELENGTHOFTEST PROGRAMSANDTHEREBYTHERANGEOFSCENARIOSUSED2ADARSUNDERTYPEAPPROVALARETYPI CALLYINSTALLEDONATRIALVESSELFORSUCHTESTSORUSEALANDSITEOVERLOOKINGTHESEA 4HISSCENARIOISBECOMINGINCREASINGLYUNSATISFACTORYASADVANCESINREQUIREMENTS FORSAFETYANDTHEPROTECTIONOFTHEENVIRONMENTMEANTHATITISNECESSARYTOENSURETHAT TYPEAPPROVALISCONSISTENTLYAPPLIEDANDIS THEREFORE MEASUREDINAQUANTITATIVEMAN NER)NANATTEMPTTORESOLVETHIS SOMEWORKHASBEENPERFORMEDTOTRYTOBETTERFORMAL IZEMARINERADARCLUTTERPERFORMANCETESTS INCLUDINGSOMERESEARCHPERFORMEDONBEHALF OFTHE5+-ARITIMEAND#OASTGUARD!GENCY4HISAPPROACHWASAIMEDTOMINIMIZE ANYSPECIALCONFIGURATIONOFTHERADARUNDERTEST)TISBASEDONASYSTEMTHATGENERATES SIMULATEDTARGETANDCLUTTERWAVEFORMS4HESEAREPICKEDUPBYTHEANTENNAOFTHERADAR UNDERTESTFROMANEARBYTRANSMITTINGSOURCE TYPICALLYSITUATEDABOUTMETERSFROM THERADARANTENNA#O LOCATEDWITHTHETRANSMITTINGSOURCEISARECEIVER WHICHDETECTS THETRANSMITTEDRADARSIGNALANDCONTINUALLYANALYSESITSFREQUENCY PULSELENGTH AND AMPLITUDE AS THE RADAR ANTENNA ROTATES &ROM THIS INFORMATION A SIGNAL WAVEFORM IS SYNTHESIZEDONAPULSE TO PULSEBASIS REPLICATINGREFLECTEDSIGNALSFROMTARGETSANDCLUT TER4HESYNTHESISPROCEDURECALCULATESAPPROPRIATEFLUCTUATINGTARGETANDCLUTTERRETURNS FROM ANY DESIRED THEORETICAL MODELWHICH COULD ALSO IN PRINCIPLE INCLUDE MODELS DERIVEDFROMRECORDEDDATAOFREALTARGETANDCLUTTERREFLECTIONS"ECAUSETHESIMULATED SIGNALISPREDOMINATELYENTERINGTHERADARTHROUGHTHESIDELOBESOFTHERADARANTENNA EXCEPTWHENTHERADARMAINBEAMALIGNSWITHTHESIMULATORANTENNATHESYNTHESIZED SIGNAL NEEDS TO BE AUTOMATICALLY ADJUSTED IN AMPLITUDE TO COMPENSATE FOR THE ACTUAL SIDELOBESENSITIVITYINTHEDIRECTIONOFTHESIMULATOR%FFECTIVELY THESYNTHESIZERHASTO AMPLIFYTHETRANSMITTEDSIGNALACCORDINGTOTHEINVERSEOFTHEAMPLITUDEOFEACHPULSE RECEIVEDFROMTHERADAR4HECHALLENGESINDESIGNINGANAFFORDABLESYSTEMINCLUDETHE LARGEDYNAMICRANGESTHATHAVETOBEENCOMPASSEDANDTHEPROCESSINGSPEEDNEEDEDTO DETERMINETHECHARACTERISTICSOFTHETRANSMITTEDSIGNAL )NPRINCIPLE ANUMBEROFCLUTTERANDTARGETMODELSCOULDBEESTABLISHEDBYINTER NATIONALAGREEMENT SUCHTHATTHEYWERECONSIDEREDTOBEREPRESENTATIVEOFCONDITIONS AROUNDTHEWORLDAGREED UPONTESTCRITERIACOULDTHENBEDETERMINED ANDSIMULATOR SYSTEMSCOULDBEBASEDATMARINERADARnTYPEAPPROVALLABORATORIES)THASBEENFOUND
#)6),-!2).%2!$!2
ÓÓ°Ó
THATTHESYSTEMISADVERSELYAFFECTEDIFSETUPCLOSETOLARGERADAR REFLECTINGOBJECTS SUCHASBUILDINGS ANDSONEEDSTOBELOCATEDIDEALLYINRELATIVELYOPENSPACES SIMILAR TOTHATFOUNDONANANTENNAFAR FIELDTESTRANGE4OENABLETESTSTOBEMOREEASILYCARRIED OUT DIRECTINJECTIONOFTESTTARGETSANDCLUTTERINTOTHE2&PATHISFEASIBLE(OWEVER THIS INVOLVES A CERTAIN AMOUNT OF ADAPTATION OF THE RADAR UNDER TEST WHICH MAY BE CONSIDEREDINAPPROPRIATE 4HE POTENTIAL MOVE AT '(Z TO PULSE COMPRESSED RADAR OFFERS ADDITIONAL CHAL LENGES IN THE DESIGN OF A UNIVERSAL SIMULATOR AS THE SYSTEM DESCRIBED IS BASED ON TESTINGNONCOHERENTPULSEDRADARS3YSTEMSBASEDONDIGITAL2&MEMORYMAYHAVETO BEDEVISED STORINGWAVEFORMSTHATCANBESUBSEQUENTLYPROCESSED4ARGETANDCLUTTER MODELSWOULDOBVIOUSLYNEEDTOAPPROPRIATELYTAKEINTOACCOUNTDOPPLEREFFECTSINTRO DUCEDBYTHEMOVEMENTOFTHEIREQUIVALENTSCATTERERS
ÓÓ°£äÊ 6 -- Ê/, Ê- ,6
2ADARHEADSFORPORTCONTROLANDCOASTALSURVEILLANCESYSTEMSHAVESOMEREQUIREMENTS INCOMMONWITHTHOSEFORSHIPBORNERADARS4HISORIGINALLYRESULTEDINMANYOFTHE WELL KNOWN SUPPLIERS OF SHIPBORNE RADAR GETTING INVOLVED IN THIS AREA 4HEY COULD OFFERATTRACTIVEPRICESASTHESUBSYSTEMSWEREDERIVATIVESOFTHERELATIVELYHIGHVOLUME SHIPBORNEMARKET/VERTIME MUCHOFTHEMARKETHASBECOMEMORESOPHISTICATED AND BECAUSEOFTHIS SPECIALISTORGANIZATIONSNOWDOMINATETHESUPPLYOFSYSTEMSFORTHIS APPLICATION4HELARGECOSTSASSOCIATEDWITHAMAJORVESSELTRACKINGSERVICES643 OPERATION INCLUDINGMASSIVEANTENNASUPPORTTOWERS OPERATIONS BUILDINGS SPECIAL IZEDSOFTWARE ANDDISASTER PROOFEDBROADBANDCOMMUNICATIONSYSTEMS MEANTHATTHE COSTS OF A MORE OPTIMIZED RADAR HEAD OFTEN BECOME A RELATIVELY INSIGNIFICANT ADDI TION4HISALSOMEANSTHATSWITCHABLELINEARANDCIRCULARPOLARIZATIONMODESAREMORE COMMONON643SYSTEMS(OWEVER BASICLOW COST643SYSTEMSSTILLCOMMONLYUSE SUBSYSTEMSINTENDEDFORSHIPBORNEUSE GIVINGGOODCOSTSAVINGSCOMPAREDTOCUSTOM MADESYSTEMS 4HERE ARE SIGNIFICANT DIFFERENCES HOWEVER IN THE REQUIREMENTS FOR A643 RADAR COMPAREDTOASHIPBORNESYSTEM4HE643ANTENNAISMOUNTEDONASTATICPLATFORM 4HIS MEANS THAT THE VERTICAL PATTERN CAN BE MORE OPTIMALLY SHAPED!LSO SINCE THE DESIGNDOESNOTHAVETOCOPEWITHTHESHOCK VIBRATIONANDINSTABILITYEXPERIENCEDON SHIPSRADARMASTS LARGERANTENNASBECOMEFEASIBLE4HISALLOWSAZIMUTHBEAMWIDTHS TOBENARROWER THEREFORE REDUCINGTHESIZEOFCLUTTERCELLS4HEREQUIREDCOASTALAREA TOBECOVEREDCANBELARGE ANDGETTINGTHEBESTRANGEOUTOFAFEWRADARHEADSSITUATED ONTALLTOWERSISOFTENMORECOSTEFFECTIVETHANUTILIZINGMANYSMALLERINSTALLATIONS "ECAUSE 643 OFTEN FORMS PART OF A NATIONS SECURITY NETWORK THEN A LONGER RANGE CAPABILITYTHANTHATJUSTREQUIREDFORPORTOPERATIONSMAYBENECESSARY4HISIMPLIES THATVERYHIGHANTENNATOWERSAREOFTENNEEDED INSOMECASESUPTOMETERS4HIS EXACERBATESVERTICALLOBINGEFFECTS WHICHMAYNEEDTOBEREDUCEDBYTHEUSEOFVERTI CALPATTERNSHAPING4HELONG RANGEREQUIREMENTOFTENMEANSTHATGREATERTRANSMITTER POWERTHANTHATUSEDONSHIPBORNERADARSISNEEDED EVENTHOUGH643ANTENNAGAINS CANBEHIGHER0ULSELENGTHSMUSTBEKEPTSHORTTOGETGOODCLUTTERIMMUNITY BUTSIMUL TANEOUSLY LONG RANGEPERFORMANCEISREQUIRED AGAININCREASINGTHEREQUIREDTRANSMIT TEDPOWER643RADARHEADSAREUSUALLYNOTOPERATORCONFIGURABLEBECAUSEANUMBER OFOPERATORSCANTYPICALLYBEUSINGDATAFROMONEHEAD
ÓÓ°Îä
2!$!2(!.$"//+
4HEREAREMOREOPPORTUNITIESTOENHANCEPERFORMANCEBECAUSEOFTHEFIXEDANTENNA POSITIONFORINSTANCE SEACLUTTERMAPPINGBECOMESEASIERBECAUSETHEANTENNAISNOT ONAMOVINGPLATFORM!LSO THECLUTTERCONDITIONSCANBELESSVARIABLEBECAUSEOFTHE RESTRICTEDGEOGRAPHICALAREAOFOPERATION ANDTHEREARENODEGRADATIONSINTHEACCU RACYOFTHEDISPLAYEDRADARIMAGEINHAVINGTOCOMPENSATEFORASHIPSHEADINGWITH COMPASSINPUT)NPARTICULAR TARGETTRACKINGISPERFORMEDFROMASTABLEANDSTATICPLAT FORM(OWEVER ITISGENERALLYNECESSARYTOTRACKMANYMORETARGETSTHANISREQUIRED ONASHIPBORNERADAR ANDNORMALLY643HASFULLYAUTOMATICPLOTEXTRACTIONANDTRACK INITIATION!LSO MOREINFORMATIONONTRACKEDTARGETSMAYNEEDTOBEEASILYAVAILABLE -UCH OF THIS ADDITIONAL DATA CAN BE AUTOMATICALLY SUPPLIED BY!)34HE RADAR DATA OFTEN HAS TO BE RELAYED MANY MILES TO PERHAPS A NUMBER OF OPERATIONAL CENTERS )T MAYNEEDTOBECOMBINEDWITHDATAFROMANUMBEROFRADARHEADSAND THEREFORE WILL BEQUITESYNTHETICWHENDISPLAYEDONOPERATORSSCREENS REDUCINGTHEPOSSIBILITIESOF INDIVIDUALOPERATORADJUSTMENT%XTENSIVEDATACOMMUNICATIONSNETWORKSBECOMEA CRITICALASPECTINTHEPERFORMANCEOFTHE643(IGHRELIABILITYOFTHESYSTEMISREQUIRED BECAUSEOFSAFETY ENVIRONMENTALPROTECTION ANDSECURITYASPECTS!TOTALSYSTEMAVAIL ABILITYOFISNOTUNCOMMONLYSPECIFIED IMPLYINGANAVERAGEDOWNTIMEOFLESS THANMINUTESPERDAY !NOTHER MAJOR DIFFERENCE COMPARED TO SHIPBORNE RADAR IS THE CUSTOM NATURE OF THEINSTALLATION2ADARHEADSAREFIXED ANDTHEREISASPECIFICREQUIREMENTFORCERTAIN PERFORMANCEPARAMETERSTOBEMETINTHEPARTICULARLOCALIZEDENVIRONMENT3EACLUTTER ALTHOUGHVERYVARIABLE WILLHAVECERTAINLOCALCHARACTERISTICS ENABLINGMOREEFFECTIVE OPTIMIZATIONOFTHEPROCESSING)NPARTICULAR THEACTUALPERFORMANCECANBEMOREEAS ILYMEASUREDAGAINSTDESIGNREQUIREMENTS 4HEDESIGNOFHIGH PERFORMANCEANTENNASFOR643APPLICATIONSHASASIMILARITYTO AIRTRAFFICCONTROLANTENNAS INTHATTHEYBOTHIDEALLYREQUIREATAILOREDELEVATIONPATTERN 4HEIDEALPATTERNSHAPINGFORAHIGH MOUNTED643ANTENNAREQUIRESASHARPCUT OFF ABOVE THE HORIZON AND A TAPERED PATTERN BELOW %NERGY DIRECTED ABOVE THE HORIZON INCREASESPRECIPITATIONCLUTTERANDALSOREDUCESTHEANTENNAGAIN!TANGLESBELOWTHE HORIZON THEGAINSHOULDNOMINALLYFOLLOWACOSECANTSQUAREDPOWERLAW4HISISAIMED ATGIVINGACONSTANTSIGNALSTRENGTHFROMATARGETOFFIXED2#3 INDEPENDENTOFRANGE 4HESEAREOFTENKNOWNASINVERTEDORINVERSECOSECSQUAREDANTENNASTODIFFERENTIATE THEMFROMAIRTRAFFICCONTROLRADARANTENNASTHATHAVETHEIRSHAPINGATANGLESABOVETHE HORIZON3UCHSHAPINGOPTIMIZESTHEPATTERNTOTHEAPPLICATION GREATLYENHANCINGOVER ALLPERFORMANCE4YPICALLY THEPATTERNSHAPINGISENABLEDBYADOUBLYCURVEDREFLECTOR FEDFROMAPOINT SOURCEPRIMARYFEED!NEXAMPLEFROM%ASAT!NTENNASISILLUSTRATED IN&IGURE4HISISAMETERREFLECTORANTENNAWITHADBGAINAT'(Z)T HASANINVERSECOSECANT SQUAREDELEVATIONPATTERNANDAAZIMUTHBEAMWIDTH)T ISREMOTELYCONTROLLEDTOGIVEHORIZONTALORCIRCULARPOLARIZATION4HEVERTICALPATTERN SHAPINGINTERACTSWITHTHE34#OFTHERADARRECEIVER ANDITIS THEREFORE NECESSARYTO TAKETHISINTOACCOUNTINTHESYSTEMDESIGN4OIMPROVEDETECTION FREQUENCYDIVERSITY ISOFTENUSEDONPRIMESYSTEMS )!,!HASISSUEDDETAILEDRECOMMENDATIONSONTHEOPERATIONALANDTECHNICALPER FORMANCEREQUIREMENTSFOR643EQUIPMENT4HEREISMUCHUSEFULINFORMATIONINTHE RECOMMENDATIONS AND THEY ARE ESSENTIAL FOR PROCURERS AND DESIGNERS OF643 RADAR EQUIPMENT4HEYCOVERBOTHCOASTALANDWATERWAYINSTALLATIONS-ANYMAJORRIVERS OFTHEWORLDCARRYVASTAMOUNTSOFCARGOONSHIPSTHATCANBESURPRISINGLYLARGE4HE MEANDERINGNATUREOFRIVERSANDRELATIVELYABRUPTTURNSINCANALSYSTEMS TOGETHERWITH THENATURALANDMANMADEOBSTRUCTIONSTORADAR MEANTHATWATERWAYVESSELTRAFFICSYS TEMSAREGENERALLYCOVEREDBYMANYLOW POWERRADARHEADSONRELATIVELYLOWTOWERS
#)6),-!2).%2!$!2
ÓӰΣ
&)'52% $UAL POLARIZEDDOUBLYCURVED643RADARANTENNA#OURTESYOF%ASAT!NTENNAS,TD
"ECAUSEOFTHEIRNUMBER SUCHRADARSTENDTOBEMINIMALLYADAPTEDSHIPBORNERADARS ASTHEYOFFERADEQUATEPERFORMANCEATRELATIVELYLOWCOST )NTERESTINGLY THE)!,!RECOMMENDATIONSALLOW##46SOLUTIONSTOCOMPETEWITH RADARWHENTHEREISVERYLOWTRAFFICDENSITY!UTOMATICTRACKINGOFASINGLETARGETIS THENREQUIRED(OWEVER ONBASICRADAR BASEDSYSTEMS )!,!EXPECTSATARGETTRACK CAPABILITYANDAPLOTEXTRACTORTHATCANDEALWITHMORETHAN PLOTSPERROTATION/N ANADVANCEDSYSTEM MORETHATTARGETSMAYHAVETOBETRACKEDWITHAPOSSIBILITY OFMORETHAN PLOTSPERANTENNAREVOLUTION
** 8Ê / Ê , 9Ê 9-Ê"Ê , 4HE USE OF COMMERCIAL MARINE RADAR AROSE DIRECTLY FROM THE RAPID DEVELOPMENT OF RADARTECHNOLOGYFORMILITARYAPPLICATIONSDURING7ORLD7AR))%VENASEARLYAS SOMEATTENTIONWASBEINGGIVENTOTHEPEACETIMEROLEOFRADARASANAVIGATIONALAID FORCOMMERCIALSHIPPING)N ANh)NTERNATIONALMEETINGONRADIOAIDSTOMARINE NAVIGATIONvWASHELDIN,ONDONANDATTENDEDBYREPRESENTATIVESFROMCOUNTRIES 4HEMEETINGWASCHAIREDBY3IR2OBERT7ATSON 7ATT)TWASSEENTHATRADARONCOM MERCIALVESSELSHADANIMPORTANTPARTTOPLAYINANTI COLLISION COASTALNAVIGATION AND PILOTAGEDECISIONS0ILOTAGEISNAVIGATINGINWATERSWHEREAQUALIFIEDPILOTISREQUIRED TOBEONBOARD 4HEFUTURECOMPULSORYFITTINGOFRADARTOSHIPSWASCONTEMPLATED AS WAS THE DESIRABILITY OF AN INTERNATIONALLY AGREED UPON MINIMUM PERFORMANCE STAN DARD WITHREQUIREMENTSFORNATIONALLYISSUEDCERTIFICATESOFTYPEAPPROVAL4HENEED TOINCLUDETHEUSEOFRADARWITHINTHE)NTERNATIONAL#OLLISION2EGULATIONSWASCLEARLY SEEN TOGETHERWITHTHENEEDFORCERTIFICATIONOFUSERS
ÓÓ°ÎÓ
2!$!2(!.$"//+
)N THE 5+ FAVORED OPERATION AT '(Z PRESUMABLY AS IT MORE AFFORDABLY MET THE 5+ PERCEIVED AZIMUTH REQUIREMENTS OF RESOLUTION AND ACCURACY4HE 5NITED 3TATES IDENTIFIED OPERATIONAL PROBLEMS AT '(Z THAT COULD BE EXPERIENCED INTHEEXTREMERAINFALLCONDITIONSFOUNDONTHE53EASTERNSEABOARD4HESECAUSED hBLACKOUTSvONEARLY'(ZSYSTEMSDEFINEDASANEFFECTIVERANGEOFLESSTHANMILE !SACONSEQUENCE THE53FAVOREDOPERATIONAT'(Z4HESHORTESTPULSELENGTHS THEN COMMONLY AVAILABLE AROUND NS MADE THE CLUTTER CELLS LARGE RESULTING IN '(ZRADARSBEINGVERYSUSCEPTIBLETORAINCLUTTER PARTICULARLYASCLUTTERPROCESSING TECHNIQUESWEREINTHEIRINFANCY)N THEREWASNOQUESTIONTHATACOMMERCIALSHIP COULDAFFORDBOTHAANDA'(ZRADAR ASTHEEXPENSEOFEVENASINGLERADARSYSTEM WASSEENTOBEALIMITINGISSUE"ECAUSEOFCOST ITWASALREADYENVISAGEDTHATFITMENT WOULDBECONFINEDMAINLYTOCERTAINCLASSESOFPASSENGERSHIPSTHATHADADEFINITENEED TOCARRYRADAR PARTICULARLYTHOSEWORKINGINTHENORTH!TLANTIC INCONGESTEDAREASOR AREASSUBJECTTOFOGORICE 4HEEARLYTRIALSINTHE5+CONCENTRATEDONASINGLE'(ZDEMONSTRATIONSYSTEM FITTEDTOANAVALVESSEL)TWASBASEDAROUNDAK7MAGNETRONCAPABLEOFNS PULSESATA02&OF (Z)TWASINTERESTINGTHATTHESPEEDOFROTATIONCOULDBEVAR IEDBETWEENANDRPM$ESPITETHEPERCEIVEDMODERNITYOFTODAYSCHARTRADARS ITWASCONNECTEDTOANOPTIONAL#HART#OMPARISON5NIT WHICHWASANOPTICALSYSTEM ALLOWINGTHERADARIMAGETOBEDISPLAYEDINCOINCIDENCEWITHAPAPERCHART4HEFACILITY TOALLOWh.ORTH UPvOPERATIONWASALWAYSSEENTOBEAVITALREQUIREMENTFORMARINE NAVIGATIONRADAR0ARALLELTRIALSINTHE5NITED3TATESWERECONDUCTEDONANUMBEROF CANDIDATE SYSTEMS USING A BROAD RANGE OF FREQUENCY BANDS 4HE INITIAL TRIALS WERE CONDUCTEDINTHE'REAT,AKESANDWEREOVERSEENBYTHE#OAST'UARD 4HERADARSTANDARDSPROPOSEDINWERENOTADOPTEDINTERNATIONALLY ALTHOUGH THE5+ISSUEDNATIONALPERFORMANCESTANDARDSBASEDONTHEMIN4HE5+STAN DARD WAS ALSO ADOPTED BY A NUMBER OF OTHER COUNTRIES )T WAS NOT UNTIL THAT INTERNATIONALMARINERADARSTANDARDSWEREAGREEDBYTHE)NTERGOVERNMENTAL-ARITIME #ONSULTATIVE/RGANIZATION)-#/ THEORIGINALNAMEOF)-/ (OWEVER THEUSEOF RADAR ON SHIPS WAS FIRST FORMALLY RECOGNIZED BY )-/ IN IN AN!NNEX TO THE )NTERNATIONAL2EGULATIONSFOR0REVENTING#OLLISIONSAT3EA4HEINFLUENCEOFTHE PROPOSEDINTERNATIONALSTANDARDWASEVIDENTINTHEPERFORMANCESTANDARDS EVEN TOTHEEXTENTOFUSINGIDENTICALWORDINGINANUMBEROFPLACES 4HESIMILARITYINPERFORMANCEREQUIREMENTSISSTILLEVIDENTINTHELATESTREVISIONSOF THE)-/PERFORMANCESTANDARD&ORINSTANCE THEPROPOSEDPERFORMANCESPECI FICATIONINCLUDEDTHENEEDTOGIVEACLEARINDICATIONOFCOASTLINESRISINGTOFTAT MILES OFAGROSSREGISTEREDTONh)MPERIALvUNITS VESSELATMILESANDOFA FTFISHINGVESSELATMILES4HEMODERNPERFORMANCEREQUIREMENTS SUMMARIZEDIN 4ABLE STILLUSETHESEFIGURESBUTWITHPARAMETERS EXCEPTRANGES GIVENINEQUIVA LENTMETRICUNITS 4HETECHNICALVISIONOFTHEMEETINGWASREMARKABLE&ORINSTANCE ITWASSEEN THATINTHEFUTUREITWOULDBEPOSSIBLETOOVERLAYRADARDATAAUTOMATICALLYONTOACHART IMAGEDISPLAYEDONAhTELEVISIONvTYPESCREEN4HISWASNOTTOBEREALIZEDONCOM MERCIALSYSTEMSFORYEARS!LSO ITWASOBSERVEDTHATSUCHDISPLAYSYSTEMSCOULD ACCOMPLISHMORETHANONEFUNCTIONANDNOTJUSTBEUSEDFORSHOWINGRADARONACHART 4HISANTICIPATEDTHECONCEPTOFMULTIFUNCTIONDISPLAYS NOWINUSEONSOMEINTEGRATED BRIDGESYSTEMS )T IS INTERESTING TO NOTE THAT +ELVIN (UGHES AND $ECCA OBTAINED THE FIRST TYPE APPROVALFORCOMMERCIALMARINERADARINEFFECTIVELY BOTHARESTILLSUPPLYING
#)6),-!2).%2!$!2
ÓÓ°ÎÎ
MARINERADARTODAY+ELVIN(UGHESHASRETAINEDITSNAMEAND$ECCAISINCORPORATED INTOTHE3PERRY-ARINEORGANIZATIONOF.ORTHROP'RUMMAN#ORPORATION4HE +ELVIN(UGHES4YPERADARHADAPEAKPOWEROFK7 §SPULSEWIDTH ANDA 02& OF (Z4HE FT METER CHEESE ANTENNA HAD HORIZONTAL AND VERTICAL BEAMWIDTHSOFAND RESPECTIVELY ROTATINGATRPM4HEREWASANANTENNA HEATERTOPREVENTICING ANDTHETRANSMITTERANDTHERECEIVERTO)& WEREhUPMASTv INTEGRATEDWITHINTHEANTENNATURNINGUNIT 4HEDISPLAYWASAINCM CATHODE RAYTUBEPLANPOSITIONINDICATOR4HESIMILARITIESWITHSYSTEMSBEINGSOLDINTHEST CENTURYAREPERHAPSMORESURPRISINGTHANTHEOBVIOUSDIFFERENCES
-/Ê"Ê ,/ Ê, ,, / Ê , 6/" !)3 !TO. ##20 #-2 #/' #0! %", %#$)3 %.# &4# '.33 '03 GT (, )!,! )"3 )%# )-/ )45 -&$ 0) .42ADAR NM 3!24 3/' 3/4$-! 347 4#0! 643 54# 62-
!UTOMATIC)DENTIFICATION3YSTEM !IDTO.AVIGATION #ONSISTENT#OMMON2EFERENCE0OINT #IVIL-ARINE2ADAR #OURSE/VER'ROUND #LOSEST0OINTOF!PPROACH %LECTRONIC"EARING,INE %LECTRONIC#HART$ISPLAYAND)NFORMATION3YSTEM %LECTRONIC.AVIGATIONAL#HART4HEDATAFOR%#$)3 &AST4IME#ONSTANTDIFFERENTIATOR 'LOBAL.AVIGATION3ATELLITE3YSTEM 'LOBAL0OSITIONING3YSTEM 'ROSSTONNAGEMETRICTONNES (EADING,INE )NTERNATIONAL!SSOCIATIONOF,IGHTHOUSE!UTHORITIES )NTEGRATED"RIDGE3YSTEM )NTERNATIONAL%LECTROTECHNICAL#OMMISSION )NTERNATIONAL-ARITIME/RGANIZATION )NTERNATIONAL4ELECOMMUNICATIONS5NION -ULTI FUNCTION$ISPLAY 0ARALLEL)NDEXLINE .EW4ECHNOLOGY2ADAR-ARINETERMFORCOHERENTSOLID STATERADARS .AUTICALMILE METERS 3EARCHAND2ESCUE4RANSPONDER 3PEED/VER'ROUND 3ELF/RGANIZING4IME$IVISION-ULTIPLE!CCESS 3PEED4HROUGHTHE7ATER 4IMETO#LOSEST0OINTOF!PPROACH 6ESSEL4RAFFIC3ERVICES 5NIVERSAL4IME#OORDINATED 6ARIABLE2ANGE-ARKER
ÓÓ°Î{
2!$!2(!.$"//+
"7 / -ATERIAL FROM )-/ PUBLICATIONS IS REPRODUCED WITH THE KIND PERMISSION OF THE )NTERNATIONAL-ARITIME/RGANIZATION)-/ WHICHDOESNOTACCEPTRESPONSIBILITY FORTHECORRECTNESSOFTHEMATERIALASREPRODUCEDINCASEOFDOUBT )-/SAUTHENTIC TEXTSHALLPREVAIL 4HEAUTHORTHANKSTHE)NTERNATIONAL%LECTROTECHNICAL#OMMISSION)%# FORPER MISSION TO REPRODUCE INFORMATION FROM ITS )NTERNATIONAL 3TANDARD )%# ED !LLSUCHEXTRACTSARECOPYRIGHTOF)%# 'ENEVA 3WITZERLAND!LL RIGHTS RESERVED &URTHER INFORMATION ON THE )%# IS AVAILABLE FROM WWWIECCH )%#HASNORESPONSIBILITYFORTHEPLACEMENTANDCONTEXTINWHICHTHEEXTRACTSAND CONTENTSAREREPRODUCEDBYTHEAUTHOR NORIS)%#INANYWAYRESPONSIBLEFORTHE OTHERCONTENTORACCURACYTHEREIN
, ,
)NTERNATIONAL-ARITIME/RGANIZATION WWWIMOORG h2EVISED RECOMMENDATIONS ON PERFORMANCE STANDARDS FOR RADAR EQUIPMENT v 2ESOLUTION -3# )NTERNATIONAL-ARITIME/RGANIZATION ,ONDON )NTERNATIONAL !SSOCIATION OF -ARINE !IDS TO .AVIGATION AND ,IGHTHOUSE !UTHORITIES WWW IALA AISMORG h4ECHNICAL CHARACTERISTICS OF MARITIME RADIO NAVIGATION RADARS v )45 2 2ECOMMENDATION - )NTERNATIONAL4ELECOMMUNICATION5NION 'ENEVA )NTERNATIONAL4ELECOMMUNICATION5NION WWWITUINT *#RONY h#IVILMARINERADAR vIN4HE2ADAR(ANDBOOK ST%D -)3KOLNIKED .EW9ORK -C'RAW (ILL #HAPTER *2YANAND#+IRBY h)CEBERGDETECTIONPERFORMANCEANALYSIS v2EPORT40% 4RANSPORTATION $EVELOPMENT#ENTRE 4RANSPORT#ANADA * . "RIGGS h4ARGET DETECTION BY MARINE RADAR v )NSTITUTION OF %LECTRICAL %NGINEERS NOW THE )NSTITUTIONOF%NGINEERINGAND4ECHNOLOGY ,ONDON h4HEINTERNATIONALCONVENTIONFORTHESAFETYOFLIFEATSEA3/,!3 v)NTERNATIONAL-ARITIME /RGANIZATION ,ONDON ASAMENDED )NTERNATIONAL%LECTROTECHNICAL#OMMISSION WWWIECCH h-ARITIMENAVIGATIONANDRADIOCOMMUNICATIONEQUIPMENTANDSYSTEMS3HIPBORNERADAR v)%# )NTERNATIONAL%LECTROTECHNICAL#OMMISSION 'ENEVA h-ARITIMENAVIGATIONANDRADIOCOMMUNICATIONEQUIPMENTANDSYSTEMS'ENERALREQUIREMENTS v )%# )NTERNATIONAL%LECTROTECHNICAL#OMMISSION 'ENEVA h-ARITIMENAVIGATIONANDRADIOCOMMUNICATIONEQUIPMENTANDSYSTEMS$IGITALINTERFACES v)%# SERIES )NTERNATIONAL%LECTROTECHNICAL#OMMISSION 'ENEVA h2EGULATIONSREGARDINGTHEMINIMUMREQUIREMENTSANDTESTCONDITIONSFORRADAREQUIPMENTUSED FOR 2IVER 2HINE AND INLAND WATERWAYS v #ENTRAL #OMMISSION FOR THE .AVIGATION ON THE 2IVER 2HINE 3TRASBOURG h-ARITIME NAVIGATION AND RADIOCOMMUNICATION EQUIPMENT AND SYSTEMS2ADAR FOR CRAFT NOT IN COMPLIANCE WITH )-/ 3/,!3 #HAPTER 6 v )%# )NTERNATIONAL %LECTROTECHNICAL #OMMISSION 'ENEVA 2'ANGESKARAND'RNLIE h7AVEHEIGHTMEASUREMENTSWITHASTANDARDNAVIGATIONSHIPRADAR RESULTS FROM FIELD TRIALS v PRESENTED AT 3IXTH )NTERNATIONAL #ONFERENCE ON 2EMOTE 3ENSING FOR -ARINEAND#OASTAL%NVIRONMENTS #HARLESTON 3OUTH#AROLINA
#)6),-!2).%2!$!2
ÓÓ°Îx
2 'ANGESKAR h!UTOMATIC OIL SPILL DETECTION BY MARINE 8 BAND RADARS v 3EA 4ECHNOLOGY !UGUST 4+"HATTACHARYAETAL h#ROSS POLARIZEDRADARPROCESSING v2EPORT40% 4RANSPORTATION $EVELOPMENT#ENTRE 4RANSPORT#ANADA 20ENGELLY h)MPROVINGTHELINEARITYANDEFFICIENCYOF2&POWERAMPLIFIERS v(IGH&REQUENCY %LECTRONICS 3EPTEMBER 0$,7ILLIAMS h#IVILMARINERADARAFRESHLOOKATTRANSMITTERSPECTRALCONTROLANDDIVERSITY OPERATION v4HE*OURNALOF.AVIGATION VOL PPn h'UIDELINESFORTHEPRESENTATIONOFNAVIGATION RELATEDSYMBOLS TERMSANDABBREVIATIONS v3AFETY OF.AVIGATION#IRCULAR )NTERNATIONAL-ARITIME/RGANIZATION ,ONDON h0ERFORMANCE STANDARDS FOR THE PRESENTATION OF NAVIGATION RELATED INFORMATION ON SHIPBORNE NAVIGATIONAL DISPLAYS v 2ESOLUTION -3# )NTERNATIONAL -ARITIME /RGANIZATION ,ONDON )NTERNATIONAL(YDOGRAPHIC/RGANIZATION WWWIHOSHOMFR h4RANSFERSTANDARDSFORDIGITALHYDROGRAPHICDATA v0UBLICATION3 )NTERNATIONAL(YDROGRAPHIC /RGANIZATION -ONACO ((ECHT ""ERKING '"ÓTTGENBACH -*ONAS AND,!LEXANDER 4HE%LECTRONIC#HART ND%D ,EMMER .ETHERLANDS')4# h/PERATIONALUSEOF!)3 v-ODEL#OURSE )NTERNATIONAL-ARITIME/RGANIZATION ,ONDON h4HETECHNICALCHARACTERISTICSFORAUNIVERSALSHIPBORNEAUTOMATICIDENTIFICATIONSYSTEM!)3 USING TIME DIVISION MULTIPLE ACCESS IN THE MARITIME MOBILE BAND v )45 2ECOMMENDATION - )NTERNATIONAL4ELECOMMUNICATION5NION 'ENEVA h-ARITIME NAVIGATION AND RADIOCOMMUNICATION EQUIPMENT AND SYSTEMS#LASS " SHIP BORNE EQUIPMENT OF THE AUTOMATIC IDENTIFICATION SYSTEM !)3 v )%# )NTERNATIONAL %LECTROTECHNICAL#OMMISSION 'ENEVA h2ECOMMENDATION! ONTHEUSEOFTHEAUTOMATICIDENTIFICATION3YSTEM!)3 INMARINE AIDS TO NAVIGATION v %DITION )NTERNATIONAL!SSOCIATION OF ,IGHTHOUSE!UTHORITIES )!,! 0ARIS h2ECOMMENDATION2 ONMARINERADARBEACONSRACONS v%DITION )NTERNATIONAL!SSOCIATION OF,IGHTHOUSE!UTHORITIES)!,! 0ARIS h4ECHNICALPARAMETERSFORRADARBEACONSRACONS v)452ECOMMENDATION- )NTERNATIONAL 4ELECOMMUNICATION5NION 'ENEVA ! 0 .ORRIS h4HE FUTURE OF RACONS v &INAL 2EPORT #ONTRACT .O 'ENERAL ,IGHTHOUSE !UTHORITIES ,ONDON h'LOBALMARITIMEDISTRESSANDSAFETYSYSTEM'-$33 0ART2ADARTRANSPONDER-ARINESEARCH ANDRESCUE3!24 v)%# )NTERNATIONAL%LECTROTECHNICAL#OMMISSION 'ENEVA '-$33(ANDBOOK ND%D ,ONDON)NTERNATIONAL-ARITIME/RGANIZATION h4ECHNICALPARAMETERSFORRADARTARGETENHANCERSv)452ECOMMENDATION- )NTERNATIONAL 4ELECOMMUNICATION5NION 'ENEVA 40,EONARDAND3*"RAIN h2ADARPERFORMANCETEST-ETHODSFINALREPORT v2ESEARCH0ROJECT 20 5+-ARITIMEAND#OASTGUARD!GENCY 3OUTHAMPTON h2ECOMMENDATION 6 ON OPERATIONAL AND TECHNICAL PERFORMANCE REQUIREMENTS FOR 643 %QUIPMENT v %DITION )NTERNATIONAL !SSOCIATION OF ,IGHTHOUSE !UTHORITIES )!,! 0ARIS h)NTERNATIONALMEETINGONRADIONAVIGATIONAIDSTOMARINENAVIGATION -AY vVOL2ECORD OFTHEMEETINGANDDEMONSTRATIONS (IS-AJESTYS3TATIONERY/FFICE ,ONDON
#HAPTER
ÃÌ>ÌVÊ,>`>À V
>ÃÊ°Ê7Ã 4ECHNOLOGY3ERVICE#ORPORATIONRETIRED
Óΰ£Ê "
*/Ê Ê /" ! BISTATIC RADAR USES ANTENNAS AT SEPARATE SITES FOR TRANSMISSION AND RECEPTION4HE TRANSMITTER AND RECEIVER CAN BE AND USUALLY ARE LOCATED AT THOSE SITES TO MINIMIZE TRANSMISSIONLINELOSSES)NNEARLYALLCASESOFBISTATICOPERATION ANTENNASEPARATION IS SELECTED TO ACHIEVE SOME OPERATIONAL TECHNICAL OR COST BENEFIT AND IS USUALLY A SIGNIFICANT FRACTION OF THE TARGET RANGE "ISTATIC RADARS HAVE BEEN DESIGNED DEVEL OPED TESTED AND IN SOME CASES DEPLOYED FOR MILITARY COMMERCIAL AND SCIENTIFIC APPLICATIONS4YPICALMILITARYAPPLICATIONSINCLUDEAIRANDSPACESURVEILLANCEANDRANGE INSTRUMENTATION#OMMERCIALAPPLICATIONSINCLUDEWINDFIELDMEASUREMENTSANDTRAF FICSURVEILLANCE3CIENTIFICAPPLICATIONSINCLUDEMEASUREMENTOFPLANETARYSURFACESAND ATMOSPHERESANDSTUDYOFIONOSPHERICTURBULENCE%XAMPLESAREGIVENIN3ECTION 7HILETHESEEXAMPLESAREBOTHCREDIBLEANDUSEFUL THEYARENICHEAPPLICATIONSWHEN COMPAREDTOTHEUBIQUITOUSCAPABILITIESOFMONOSTATICRADARS WHICHREMAINTHEPRIN CIPALMETHODFORRADIODETECTIONANDRANGING "ISTATIC RADARS CAN OPERATE WITH DEDICATED TRANSMITTERS WHICH ARE DESIGNED FOR BISTATIC OPERATION AND CONTROLLED BY THE BISTATIC RADAR OR WITH TRANSMITTERS OF OPPORTUNITY WHICHAREDESIGNEDFOROTHERPURPOSESBUTFOUNDSUITABLEFORBISTATICOPER ATIONEVENWHENNOTCONTROLLEDBYTHEBISTATICRADAR7HENTHETRANSMITTEROFOPPOR TUNITYISFROMAMONOSTATICRADAR THEBISTATICRADARISOFTENCALLEDAHITCHHIKER7HEN THE TRANSMITTER OF OPPORTUNITY IS FROM A BROADCAST STATION OR COMMUNICATIONS LINK SOURCESOTHERTHANARADAR THEBISTATICRADARHASBEENCALLEDMANYTHINGSINCLUDING PASSIVERADAR PASSIVEBISTATICRADAR PASSIVECOHERENTLOCATION PARASITICRADAR AND PIGGY BACKRADAR4RANSMITTERS OF OPPORTUNITYINMILITARYSCENARIOSCANBEDESIGNATED EITHERCOOPERATIVEORNONCOOPERATIVE WHERECOOPERATIVEDENOTESANALLIEDORFRIENDLY TRANSMITTERANDNONCOOPERATIVEDENOTESAHOSTILEORNEUTRALTRANSMITTER "ISTATIC TARGET DETECTION USES A PROCESS SIMILAR TO THAT OF A MONOSTATIC RADAR WHERE THE TARGET IS ILLUMINATED BY A TRANSMITTER AND TARGET ECHOES ARE RECEIVED DETECTED ANDPROCESSEDBYARECEIVER7HENOPERATINGWITHTRANSMITTERSUSING#7 OR HIGH DUTY CYCLE WAVEFORMS A BISTATIC RECEIVER MAY NEED TO AUGMENT ITS SPA TIALISOLATIONWITHSPATIALANDORSPECTRALCANCELLATIONTOREDUCETHETRANSMITTERS DIRECT PATH FEED THROUGH TO ACCEPTABLE LEVELS 4HE BISTATIC RADAR CAN ALSO USE A PORTIONOFTHERESIDUALORUNCANCELLEDDIRECT PATHTRANSMITSIGNALASAREFERENCEIN ACORRELATIONRECEIVER WHICHCROSS CORRELATESTHERECEIVEDANDTRANSMITTEDSIGNALS EMULATINGMATCHEDFILTEROPERATION Óΰ£
ÓΰÓ
2!$!2(!.$"//+
"ISTATICTARGETLOCATIONUSESAPROCESSDIFFERENTFROMTHATOFAMONOSTATICRADAR)NA TYPICALIMPLEMENTATION THEBISTATICRADARMEASURESA THETRANSMITTER TO TARGET TO RECEIVER PROPAGATIONTIME CONVERTEDTOATRANSMITTER TO TARGETPLUSTARGET TO RECEIVERRANGE SUM B THE TARGET DIRECTION OF ARRIVAL $/! FROM THE RECEIVER AND C THE TRANSMITTER TO RECEIVERDISTANCE ORBASELINE TOSOLVETHETRANSMITTER TARGET RECEIVERTRIANGLE CALLEDTHE BISTATICTRIANGLE4HISTRIANGLELOCATESTHETARGET USUALLYINTERMSOFARANGEANDANGLE REFERENCEDTOTHERECEIVESITE/THERLOCATIONSCHEMESAREGIVENIN3ECTION 7HENSEPARATETRANSMITANDRECEIVEANTENNASAREATASINGLESITE ASISCOMMONIN #7RADARS THERADARHASCHARACTERISTICSOFAMONOSTATICRADAR ANDTHETERMBISTATIC ISNOTUSEDTODESCRIBESUCHASYSTEM)NSPECIALCASES THEANTENNASCANBEATSEPA RATESITES ANDTHERADARISSTILLCONSIDEREDTOOPERATEMONOSTATICALLY&OREXAMPLE ANOVER THE HORIZON/4( RADARCANHAVEASITESEPARATIONOFKMORMORETO ACHIEVEADEQUATETRANSMITSIGNALISOLATION"UTTHATSEPARATIONISSMALLCOMPAREDTO THETARGETRANGEOFTHOUSANDSOFKILOMETERS ANDTHERADARAGAINOPERATESWITHMONO STATICCHARACTERISTICS !VARIATIONOFTHEBISTATICRADARISTHEMULTISTATICRADAR WHICHUSESMULTIPLEANTEN NASATSEPARATELOCATIONS ONEANTENNAFORTRANSMISSIONANDMULTIPLEANTENNASEACH ATADIFFERENTLOCATIONFORRECEPTION ORVICEVERSA!GAIN TRANSMITTERSORRECEIVERS ARE USUALLY SITED WITH THE ANTENNAS4ARGET DETECTION IS DONE BISTATICALLY WITH EACH TRANSMIT RECEIVEPAIRPERFORMINGINDEPENDENTDETECTIONSWITHINASURVEILLANCEREGION COMMONTOALLSUCHPAIRS4ARGETLOCATIONTYPICALLYMEASURESTHEBASELINEANDTAKES SIMULTANEOUSRANGE SUMMEASUREMENTSFROMMULTIPLETRANSMITTER RECEIVERPAIRS WHICH AREPLOTTEDASELLIPSESWITHATRANSMITTER RECEIVERPAIRATEACHELLIPSEFOCI4HEINTERSEC TIONOFTHESEELLIPSES ORCONSTANTRANGE SUMCONTOURS LOCATETHETARGET)TISSIMILARTO MULTILATERATIONBECAUSEONLYRANGEMEASUREMENTSAREUSEDTOLOCATETHETARGET
!MULTISTATICRADARCANALSOUSETRIANGULATIONFORTARGETLOCATIONBYTAKINGSIMUL TANEOUSTARGET$/!MEASUREMENTSFROMMULTIPLERECEIVESITESATKNOWNLOCATIONS )T IS USED BY 30!352 AS A BRUTE FORCE SATELLITE LOCATION TECHNIQUE (OWEVER BECAUSEOFTHELARGEAPERTURESIZESORARRAYLENGTHS REQUIREDFORSUFFICIENTLYACCU RATE $/! MEASUREMENTS AT USEFUL RANGES TRIANGULATION IS SELDOM CONSIDERED FOR OTHERAPPLICATIONS #ONCEPTS DATA ANDEXPRESSIONSDEVELOPEDFORBISTATICRADARSOFTENAPPLYTOMULTI STATICRADARS FOREXAMPLE THERANGEEQUATION TARGETDOPPLER TARGETRADARCROSSSECTION ANDSURFACECLUTTER4HUS THEREMAINDEROFTHISCHAPTERWILLCONCENTRATEONTHEBISTATIC RADARTOPIC DEVELOPINGMULTISTATICEXCURSIONSANDDEVIATIONSONLYWHENNECESSARY 0ASSIVE RECEIVING SYSTEMS OR ELECTRONIC SUPPORT MEASURE %3- SYSTEMS OFTEN USE TWO OR MORE RECEIVING SITES 4HEIR PURPOSE IS TYPICALLY TO DETECT IDENTIFY AND LOCATETRANSMITTERSSUCHASTHOSEFROMMONOSTATICRADARS4HEYAREALSOCALLEDEMITTER LOCATORS4ARGETLOCATIONISBYMEANSOFCOMBINEDANGLEMEASUREMENTSFROMEACHSITE EG TRIANGULATION ORTIME DIFFERENCE OF ARRIVALANDORDIFFERENTIALDOPPLERMEASURE MENTSBETWEENSITESEG MULTILATERATION 4HESESYSTEMSUSUALLYARENOTDESIGNEDTO DETECTANDPROCESSTHEECHOESFROMTARGETSILLUMINATEDBYTHETRANSMITTER4HEYCAN HOWEVER BEUSEDBYABISTATICHITCHHIKERTOIDENTIFYANDLOCATEASUITABLETRANSMITTER 4HUS ALTHOUGHTHEYHAVEMANYREQUIREMENTSANDCHARACTERISTICSCOMMONTOMULTI STATICRADARS THEYARENOTRADARSANDWILLNOTBECONSIDEREDHERE
4HEFOREGOINGDESCRIBESMULTISTATICOPERATIONTHATCOMBINESDATANONCOHERENTLY#OHERENTDATACOMBININGISALSO POSSIBLEWHEREFOREXAMPLEIN PHASEANDQUADRATUREDATAFROMEACHRECEIVESITEISCOMBINEDTOFORMALARGERECEIVE APERTURE%XAMPLESINCLUDETHINNED RANDOM DISTORTED ANDDISTRIBUTEDARRAYS nINTERFEROMETRICRADARS ANDTHE RADIOCAMERA 4HISSUBJECTISTREATEDFURTHERIN7ILLIS
")34!4)#2!$!2
ÓΰÎ
4HEFOREGOINGDEFINITIONSAREBROADANDTRADITIONALnBUTAREBYNOMEANSUNI FORMLYESTABLISHEDINTHELITERATURE4ERMSSUCHASQUASI BISTATIC QUASI MONOSTATIC PSEUDO MONOSTATIC TRISTATIC POLYSTATIC REAL MULTISTATIC MULTI BISTATIC AND NETTED BISTATICHAVEALSOBEENUSEDn4HEYAREUSUALLYSPECIALCASESOFTHEBROADDEFINI TIONSGIVENABOVE4HETERMPSEUDO MONOSTATICWILLBEUSEDTOCHARACTERIZEBISTATIC GEOMETRIESTHATAPPROXIMATEMONOSTATICOPERATION
ÓΰÓÊ "", / Ê-9-/ !TWO DIMENSIONALNORTH REFERENCEDCOORDINATESYSTEMISUSEDTHROUGHOUTTHISCHAPTER &IGURESHOWSTHECOORDINATESYSTEMANDPARAMETERSDEFININGBISTATICRADAROPERA TIONINTHEX Y PLANE ALSOCALLEDTHEBISTATICPLANE4HEBISTATICTRIANGLELIESINTHE BISTATICPLANE4HEDISTANCE,BETWEENTHETRANSMITTERANDTHERECEIVERISCALLEDTHEBASE LINERANGEORSIMPLYTHEBASELINE24ISTHERANGEBETWEENTRANSMITTERANDTARGETAND22 ISTHERANGEBETWEENRECEIVERANDTARGET4HEANGLESP4ANDP2ARE RESPECTIVELY THETRANS MITTERANDRECEIVERLOOKANGLES WHICHARETAKENASPOSITIVEWHENMEASUREDCLOCKWISE FROMNORTH4HEYAREALSOCALLEDDIRECTION OF ARRIVAL$/! ANGLE OF ARRIVAL!/! OR LINE OF SIGHT,/3 4HEBISTATICANGLE A P4P2 ISTHEANGLEBETWEENTHETRANSMITTER ANDRECEIVERWITHTHEVERTEXATTHETARGET)TISALSOCALLEDTHECUTANGLEORTHESCATTERING ANGLE)TISCONVENIENTTOUSEAINCALCULATIONSOFTARGET RELATEDPARAMETERSANDP4ANDP2 INCALCULATIONSOFTRANSMITTER ANDRECEIVER RELATEDPARAMETERS 4HETRANSMITTER TO TARGET TO RECEIVERRANGEMEASUREDBYABISTATICRADARISTHERANGE SUM24 22 -ETHODSFORMEASURINGTHISSUMAREGIVENIN3ECTION4HERANGE SUMLOCATESTHETARGETSOMEWHEREONTHESURFACEOFANELLIPSOIDWHOSEFOCIARETHE TRANSMITTERANDRECEIVERSITES4HEINTERSECTIONOFTHEBISTATICPLANEANDTHISELLIPSOID
&)'52% "ISTATICRADARNORTHCOORDINATESYSTEMFORTWODIMENSIONS ESTABLISHINGTHEBISTATICPLANE4HEBISTATICTRIANGLELIESINTHEBISTATICPLANE
Óΰ{
2!$!2(!.$"//+
PRODUCESTHEFAMILIARELLIPSESOFCONSTANTRANGESUM ORISORANGECONTOURS!USEFUL RELATIONSHIPISTHATTHEBISECTOROFTHEBISTATICANGLEISORTHOGONALTOTHETANGENTOFTHAT ELLIPSEATTHETARGET4HETANGENTISOFTENAGOODAPPROXIMATIONTOANISORANGECONTOUR WITHINTHEAREACOMMONTOTHETRANSMITANDRECEIVEBEAMS 7HENTHEBISTATICRADARSRECEIVINGANTENNAISAPHASEDARRAY ANDTHEARRAYNORMAL ISALSONORMALTOTHEBASELINE P2 ISMEASUREDDIRECTLYBYTHEANTENNAINANYBISTATIC PLANE4HISFORTUITOUSSITUATIONISCAUSEDBYCONICDISTORTION WHICHISINHERENTINANY PHASEDARRAYANTENNA(OWEVER WHENTHEARRAYNORMALISNOTNORMALTOTHEBASELINE ORWHENTHERECEIVINGANTENNAISMECHANICALLYSTEEREDORSCANNED P2ISNOTMEASURED DIRECTLY/FTEN$/!MEASUREMENTSARETAKENINORCONVERTEDTOAZIMUTHANDELEVA TIONANGLESREFERENCEDTOANX Y ZCOORDINATESYSTEMCENTEREDATTHERECEIVESITE WHERE ZISCO LINEARWITHTHELOCALVERTICAL#ONVERSIONBETWEENANORTHCOORDINATESYSTEM ANDANX Y ZCOORDINATESYSTEMISGIVENIN3ECTIONOF7ILLIS /THER COORDINATE SYSTEMS INCLUDING THREE DIMENSIONAL SYSTEMS HAVE BEEN USED TODEFINEBISTATICRADAROPERATION n!POLARCOORDINATESYSTEMISALSOSHOWNIN &IGURE4HER P COORDINATESARELOCATEDONTHEBISTATICPLANEWITHORIGINATTHE MIDPOINTOFTHEBASELINE)TISUSEFULFORPLOTTINGOVALSOF#ASSINISEE3ECTION AND IS DETAILED IN7ILLIS /N OCCASION THE INCLUDED ANGLES P4g AND P2g ARE USED TO DEFINETRANSMITTERANDRECEIVERLOOKANGLESINTHEBISTATICTRIANGLE SUCHTHATP4g P2g A )NTHISCASE P4g nP4ANDP2g P2CANBEUSEDTOTRANSFORMNORTH REFERENCEDEQUATIONSINTOINCLUDED ANGLEEQUATIONS0LOTSOFBISTATICCLUTTERDATAUSEA SEPARATEANDQUITEARCANECOORDINATESYSTEM WHICHISDEFINEDIN3ECTION 'EOMETRYISAPRINCIPALFACTORDISTINGUISHINGBISTATICFROMMONOSTATICRADAROPERA TION)NEVALUATINGBISTATICRADAROPERATION ITISUSEFULTOSTARTWITHAGEOMETRY INVARIANT PERFORMANCEMEASURE WHICHISOBTAINEDBYSETTING, OR24 22ANDA 4HE RESULTISDEFINEDASANEQUIVALENTMONOSTATICRANGE ORBENCHMARKRANGE ANDISDETAILED IN3ECTION)TISALSOUSEFULASASANITYCHECKBECAUSEATTHESELIMITS ALLBISTATIC RADAREQUATIONSMUSTREDUCETOANEQUIVALENTMONOSTATICEQUATION
ÓΰÎÊ -// Ê, ,Ê +1/" "ENCHMARK2ANGE#ONCEPT 5NLIKEAMONOSTATICRADAR THERANGEPERFORMANCE OFABISTATICRADARISAFUNCTIONOFTHEGEOMETRY SPECIFICALLYTHEBASELINERANGE,AND ANANTENNALOOKANGLE EITHERP4ORP27HENFACTORSSUCHADIFFRACTION REFRACTION MULTIPATH AND MASKING ARE ABSENT OR CAN BE IGNORED BISTATIC RANGE AS A FUNCTION OFTHESEVARIABLESCANBEPLOTTEDONTHEBISTATICPLANEUSINGANOVALOF#ASSINI!N OVALOF#ASSINIISTHELOCUSOFTHEVERTEXOFATRIANGLEWHENTHEPRODUCTOFTHESIDES ADJACENTTOTHEVERTEXISCONSTANTANDTHELENGTHOFTHEOPPOSITESIDEISFIXED7HEN APPLIEDTOTHEBISTATICTRIANGLESHOWNIN&IGURE THEVERTEXISATTHETARGET24AND 22ARETHESIDESADJACENTTOTHEVERTEXANDTHEBASELINE,ISTHELENGTHOFTHEFIXED OPPOSITESIDE 4RADITIONALLY OVALSOF#ASSINIAREDRAWNASCONTOURSOFACONSTANTRECEIVEDSIGNAL POWERORARECEIVEDSIGNAL TO NOISERATIOAROUNDAFIXEDBASELINERANGE ,!LTHOUGH THESESIGNAL DEPENDENTCONTOURSPROVIDEASENSEOFBISTATICRADARPERFORMANCE THEY DO NOT SHOW MAXIMUMMINIMUM DETECTION RANGES AND COVERAGE FOR VARIABLE BASE LINES ALLPARAMETERSOFOPERATIONALINTEREST4OREMEDYTHISPROBLEM THECONCEPTOFA BISTATICBENCHMARKRANGE ORMORESIMPLYBENCHMARK ISINTRODUCED)TISESTABLISHED ASFOLLOWS&IRST THEBISTATICRADARRANGEEQUATIONISDERIVEDINAMANNERCOMPLETELY
")34!4)#2!$!2
Óΰx
ANALOGOUSTOTHATFORAMONOSTATICRADAR4HEEQUATIONISTHENSOLVEDFORTHEBISTATIC MAXIMUMRANGEPRODUCT 2422 MAX.EXT ANEQUIVALENTMONOSTATICMAXIMUMRANGE 2- MAX ISDEFINEDOMITTINGTHEMAXSUBSCRIPTFORCONVENIENCE ASSHOWNHERE 2- 2422
4HISEQUIVALENTMONOSTATICMAXIMUMRANGE ALSOKNOWNASTHEGEOMETRICMEAN RANGE REPRESENTSPERFORMANCEOFTHEBISTATICRADARWHENTRANSMITTERANDRECEIVERARE CO LOCATEDIE WHEN, )TISDEFINEDASTHEBISTATICRADARSBENCHMARKRANGE 3INCE THIS BENCHMARK IS GEOMETRY INVARIANT IT BECOMES USEFUL WHEN COMPARING BISTATICTOMONOSTATICRANGEPERFORMANCE&INALLY ANOVALOF#ASSINIISESTABLISHED ASAFUNCTIONOFTHEBASELINERANGE , NORMALIZEDTOTHEBENCHMARKRANGE 2-"ASED ON THIS OVAL MAXIMUM AND MINIMUM DETECTION RANGES AND THE COVERAGE AREA ARE CALCULATED ALL AS A FUNCTION OF 2- 4HIS PROCEDURE IS ALSO USED TO DEFINE BISTATIC OPERATINGREGIONS 2ANGE%QUATION 4HERADARRANGEEQUATIONFOR#7ORCOHERENTPULSERADARS IS MODIFIED FOR BISTATIC OPERATION AND THEN SOLVED FOR THE BISTATIC MAXIMUM RANGE PRODUCT 2422 MAX
WHERE
§ 0 T ' ' L R " &4 &2 ¶ 24 22 MAX ¨ AV O 4 2 · © P K 4O &N % . O ,4 ,2 ¸
24 4RANSMITTER TO TARGETRANGEM 22 2ECEIVER TO TARGETRANGEM 0AV 4RANSMITTEDAVERAGEPOWER7 TO 3IGNALOBSERVATIONORINTEGRATION TIME '4 4RANSMITTINGANTENNAPOWERGAIN '2 2ECEIVINGANTENNAPOWERGAIN K 7AVELENGTHM R" "ISTATICRADARCROSSSECTIONM &4 0ATTERNPROPAGATIONFACTORFORTRANSMITTER TO TARGETPATH &2 0ATTERNPROPAGATIONFACTORFORRECEIVER TO TARGETPATH K "OLTZMANNSCONSTANT;¾n*+= 4O 3TANDARDTEMPERATURE;+= &N 2ECEIVERNOISEFIGURE %.O 2ECEIVEDENERGYTORECEIVERNOISESPECTRALDENSITYREQUIREDFORDETECTION ,4 4RANSMITTINGSYSTEMLOSSES ,2 2ECEIVINGSYSTEMLOSSES
%QUATIONASSUMESTHATAMATCHEDFILTER ORANEQUIVALENTMATCHEDFILTERSUCHAS ACROSS CORRELATOR ISUSEDONRECEPTION%QUATIONISRELATEDTOTHECORRESPONDING MONOSTATICMAXIMUMRANGEEQUATIONBY2422 2-ANDR- R" WHERER- ISTHE MONOSTATICRADARCROSSSECTION&ORPULSEDRADAROPERATION TO NFP WHERENISTHE NUMBEROFPULSESINTEGRATEDANDFPISTHEPULSEREPETITIONFREQUENCY!LSO THESIGNAL TO NOISERATIOREQUIREDFORDETECTION 3. REQ %.OWHEN"Sy WHERE"ISTHERECEIVER BANDWIDTHANDSISTHEPULSEWIDTH 4HESIGNALPROCESSINGTIME TO ISSOMETIMESSETBYTHEAMOUNTOFDOPPLERSPREAD INGORVELOCITY WALK $FDGENERATEDBYAMOVINGTARGET3PECIFICALLY $FD TO "N
ÓΰÈ
2!$!2(!.$"//+
WHERE "N IS THE NOISE BANDWIDTH OF RECEIVERS PREDETECTION FILTER )N THE MONOSTATIC CASE DOPPLERSPREADINGIS
$FD M ;ARK=
WHERE AR IS THE RADIAL COMPONENT OF TARGET ACCELERATION %QUATION ALSO APPLIES TO THE BISTATIC CASE AT SMALL BISTATIC ANGLES A PARTICULARLY IN AN OVER THE SHOULDER OPERATION WHERETHETARGETLIESNEARTHEBASELINEEXTENDEDBEYONDEITHERTHERECEIVER ORTHETRANSMITTERCALLEDTHEEXTENDEDBASELINE (OWEVER FORLARGERATHEGENERAL CASETHERADIALCOMPONENT WHICHISALIGNEDWITHTHEBISECTOROFTHEBISTATICANGLE WILLBEREDUCED!RULEOFTHUMBFORTHESELARGEACONDITIONSIS
$FD B ;ARK=
%QUATIONISUSEDTOSETTOANDHENCETHENOISEBANDWIDTHOFRECEIVERSPREDETEC TIONFILTER!N3INCE$FD B $FD M THECONSTRAINTONBISTATICSIGNALPROCESSINGTIMEIS SLIGHTLYLESSTHANTHEEQUIVALENTMONOSTATICTIME !SINTHEMONOSTATICEQUATION THETRANSMITTINGANDRECEIVINGPATTERNPROPAGATION FACTORS &4 AND &2 EACH CONSIST OF TWO TERMS THE PROPAGATION FACTORS &g4 AND &g2 ANDTHEANTENNAPATTERNFACTORS F4ANDF2 RESPECTIVELY4HEANTENNAPATTERNFACTORSARE THERELATIVESTRENGTHOFTHEFREE SPACEFIELDRADIATEDBYTHETRANSMITTINGANDRECEIVING ANTENNASASAFUNCTIONOFTHEIRPOINTINGANGLES4HESEFACTORSAREAPPLIEDWHENEVERTHE TARGETISNOTATTHEPEAKOFABEAM 0ROPAGATIONFACTORSCUSTOMARILYINCLUDETHEEFFECTSOFMULTIPATH DIFFRACTION AND REFRACTION WITHATMOSPHERICABSORPTIONEFFECTSINCLUDEDINTHELOSSTERMS!SWITHA MONOSTATICRADAR BISTATICRADARPROPAGATIONREQUIRESASUITABLEPATHFROMTHETRANSMIT TERTOTHETARGETANDTHETARGETTOTHERECEIVER)NCONTRASTTOAMONOSTATICRADAR HOWEVER PROPAGATIONEFFECTSCANBESIGNIFICANTLYDIFFERENTOVERTHETWOBISTATICPATHSANDMUST BETREATEDSEPARATELY-ULTIPATHISTHEPRIMARYEXAMPLE WHERETHETARGETCANBEINA MULTIPATHLOBEONONEPATHANDAMULTIPATHNULLONTHEOTHER DEPENDINGONANTENNA ANDTARGETALTITUDEANDTERRAINCONDITIONS 7HENACORRELATIONRECEIVERUSESTHEDEMODULATEDDIRECTPATH2&SIGNALASITSREFER ENCE THATSIGNALISSUBJECTEDTOINTERFERENCEMULTIPATHAND2&) WHICHISDIFFERENT FROMINTERFERENCEAFFECTINGTHETARGETECHOPATH)FTHECORRELATOROPERATESINITSLINEAR REGION THEECHOPLUSITSINTERFERENCECONVOLVEDWITHTHEREFERENCEPLUSITSINTERFERENCE PRODUCES THE DESIRED ECHO WITH FULL MATCHED FILTER GAIN PLUS INTERFERENCE WITH GAIN REDUCEDBYMISMATCH4HESESIGNALSADDVECTORIALLYTOMODIFYTHEPATTERN PROPAGATION FACTOR(OWEVER IFTHECORRELATOROPERATESINITSNONLINEARREGION WHICHCANFREQUENTLY HAPPEN CROSS PRODUCTS ARE GENERATED WHICH REDUCE THE ECHOS MATCHED FILTER GAIN 4HEAMOUNTOFLOSSDEPENDSONTHEMAGNITUDEOFTHEINTERFERENCEANDISACCOUNTEDFOR INTHESIGNAL PROCESSINGLOSSTERM /VALS OF #ASSINI 4HE FREE SPACE MAXIMUM DETECTION CONTOUR OF A BISTATIC RADARSBENCHMARKRANGEISACIRCLEOFRADIUS2- JUSTASINTHEMONOSTATICCASE3UCH ACIRCLEASSUMESCONSTANTRADARCROSS SECTIONANDPATTERNPROPAGATIONFACTORS WHICH ARESCENARIO ANDGEOMETRY DEPENDENT&ORTHEGENERALBISTATICCASE WHERE, THE FREE SPACEMAXIMUMDETECTIONCONTOURBECOMESTHEFAMILIAROVALOF#ASSINI AGAIN
)NTHEFIRSTCASE THETRANSMITTERILLUMINATESTHETARGETOVERTHERECEIVERSSHOULDERINTHESECONDCASE THERECEIVER VIEWSTHETARGETOVERTHETRANSMITTERSSHOULDER
")34!4)#2!$!2
ÓΰÇ
($)# ** (" * %+)
, (( * %+) *
( *"/ $ %$%,"
) " $ *% )*$ '+ ," $*#%$%)** ($ $ #(!) - ( #. . #+#*% *($ & (# ** %$%," # $ $ #+#*% *($ , "" %$%," , +)% (" - * ( '+"*%( % %$ %," $ * *-%%,") - $ $* *" )%$* ) " $ .* $ /%$* $* *" )%$* ) " $ .* $ /%$*
&)'52% .ORMALIZED OVALS OF #ASSINI LYING IN THE BISTATIC PLANE THE PLANE CONTAINING TRANSMITTER RECEIVER ANDTARGET#OURTESY3CI4ECH)NC
WITH THE MONOSTATIC CAVEATS CITED ABOVE 4HUS THIS OVAL OR OVALS PROVIDES A CONVENIENTBUT AT TIMES OVER SIMPLIFIEDVIEW OF BISTATIC RANGE COVERAGE AND MUSTBEUSEDWITHCARE !NADDITIONALBISTATICCAVEATISNECESSARY7HENTHETARGETISONORNEARTHEBASE LINE IE LOCATEDBETWEENRECEIVERANDTRANSMITTERWHERETHEBISTATICANGLEAl ACOMPLETELYDIFFERENTENVIRONMENTISGENERATEDFORWARDSCATTERFROMBOTHTARGETAND CLUTTER)NTHISCASE THETARGETRADARCROSSSECTION2#3 ANDCLUTTERSCATTERINGCOEF FICIENTRO AREGREATLYENHANCED WHEREASRANGEANDDOPPLERMEASUREMENTSAREGREATLY DEGRADED /FTEN NORMAL BISTATIC OPERATION EXCLUDES THIS REGION SO THAT A WEDGEWITHTHEAPEXATTHERECEIVERANDDIRECTEDATTHETRANSMITTERISEXCISEDFROMTHE OVAL$ETAILSAREGIVENIN7ILLIS &IGURE SHOWS FOUR CASES OF OVALS OF #ASSINI NORMALIZED TO THE BENCHMARK RANGE A BENCHMARK , B ONE OVAL , 2- C LEMNISCATE , 2- AND D TWO OVALS, 2-)NALLCASES THETRANSMITTERISLOCATEDATTHELEFTOVALFOCUS 4HERECEIVERISLOCATEDATTHERIGHTOVALFOCUS /THERTERMSANDSYMBOLSARE DEFINEDINTHEKEYSHOWNWITH&IGURE 4ABLE LISTS EXPRESSIONS FOR CALCULATING OVAL AREA AND MAXIMUMMINIMUM RECEIVERDETECTIONRANGESFORTHESEFOURCASES AGAINREFERENCEDTOTHEBENCHMARKRANGE 2- &OR&IGUREDWHEN, 2- THEOVALSCANCONVENIENTLYBEAPPROXIMATEDAS CIRCLES WITH RADIUS 22AV ^ 2-, AND CORRESPONDING AREA O 2-, %XPRESSIONS FOR
4HEONE OVALAREAFORMULAISDERIVEDFROM%Q$A IN7ILLIS)TISALSOUSEDFORCALCULATINGTHELEMNISCATEAREA &ORMULASFORTHETWO OVALAREAAREDERIVEDFROM%Q$A IN7ILLIS-ORETERMSINTHESESERIESCANBEUSEDIF GREATERACCURACYISREQUIRED
Óΰn
2!$!2(!.$"//+
4!",% !REAAND$ETECTION2ANGESFOR'ENERAL/VALSOF#ASSINI#OURTESY3CI4ECH )NC
#ASE #IRCLE"ENCHMARK /NE/VAL 4WO/VALS
, 2 2 2-
!REAOFONEOVAL O2- ^O;2- ,2- = ^O2-;2-,= ^O2-;2-,=
22MAX ON2XOVAL 22- , , , , 2- ^2-,
22MIN ON2XOVAL 22- , , 2- , , ^2-,
RECEIVERANDTRANSMITTER RANGESONTHEOPPOSITEOVALAREREADILYCALCULATEDTHROUGH MIRROR IMAGESYMMETRY!LSONOTETHATTHEAREAOFEVERYBISTATICOVALISALWAYSLESS THANTHEMONOSTATICCIRCLE 4HEEXPRESSIONSIN4ABLECANALSOBEUSEDTOASSESSFIRST ORDERBISTATICRADAR LINE OF SIGHT,/3 CONSTRAINTS WHERETHE,/3ISDEFINEDASALINEBETWEENTRANSMIT ANDRECEIVEANTENNASTANGENTTOTHE%ARTHSSURFACE3PECIFICALLY FORAGIVENTARGET TRANSMITTERANDRECEIVERALTITUDES THETARGETMUSTSIMULTANEOUSLYBEWITHIN,/3TO BOTHTHETRANSMITTERANDRECEIVERSITES&ORASMOOTH %ARTHMODEL THE,/3RANGE R2BETWEENARECEIVEANTENNAOFALTITUDEH2ANDTARGETOFALTITUDEHTIS
R2 H2 HT
WHERE ALL UNITS ARE IN KILOMETERS 3IMILARLY THE ,/3 RANGE R4 BETWEEN A TRANSMIT ANTENNAOFALTITUDEH4ANDTARGETOFALTITUDEHTIS
R4 H4 HT
4HUS TOPREVENT,/3TRUNCATIONOFTHEOVALS R2q22MAX ANDR4q24MAX 4HESE EXPRESSIONSIGNOREBOTHDIFFRACTIONANDMULTIPATH WHICHCANSIGNIFICANTLYALTERTHESE RANGES SOTHEYMUSTBECONSIDEREDFIRST ORDERAPPROXIMATIONS !TYPICALTASKFORBISTATICAIRSURVEILLANCEISTOSELECTABASELINE,SOTHATARECEIVER WITHANTENNAALTITUDEH2WILLMATCHEXISTING,/3COVERAGEOFATRANSMITTERWITHANTENNA ALTITUDEH4&ORTHEWORSTCASE OVER THE SHOULDERGEOMETRY THEREQUIREMENTWOULDBE TOMATCH,/3COVERAGEONTHEEXTENDEDBASELINE R4 R2 , SOTHAT
, H4 H2
&OREXAMPLE WHENH4 KMANDH2 KM , KM WHICHFROM%Q AND WILL PROVIDE ,/3 TO AN M ALTITUDE TARGET FLYING ABOVE THE EXTENDED BASELINE KMFROMTHERECEIVERANDKMFROMTHETRANSMITTER"ASELINESGREATER THANKMCANPOSESEVERETARGET,/3PROBLEMS&OREXAMPLE IF, KMAND H4 KM THENFROM%Q THETRANSMITTERWOULDONLYILLUMINATEATARGETFLYING DIRECTLYABOVETHERECEIVERATANALTITUDEHT KM4HUS THETARGETCOULDREADILY UNDER FLYTHEILLUMINATION ANDLOW ALTITUDEAIRSURVEILLANCECAPABILITYISLOST!SA CONSEQUENCE THEBISTATICRADARMUSTEITHEREMPLOYAGREATLYELEVATED^KM TRANS MITTERATTHESELONGBASELINESOROPERATEWITHSHORTERBASELINESTOACHIEVEACCEPTABLE LOWALTITUDESURVEILLANCECOVERAGE.OTETHATTHETWO OVALCASECANALSOREQUIREAVERY HIGHALTITUDEFORTHESITELOCATEDINTHEOVALNOTUNDERSURVEILLANCESOHIGHTHATTHE SITEMUSTOFTENBECOMEAIRBORNE &INALLY THETRANSMITANTENNAWILLBEINDIRECT,/3OFTHERECEIVEANTENNAWHEN,a R4 R2WITHHT SOTHAT AGAINWITHALLUNITSINKILOMETERS
,aH4 H2
")34!4)#2!$!2
Óΰ
)F%QISSATISFIED EXTRAORDINARYMEASURESAREUSUALLYREQUIREDTOSUPPRESSTHE DIRECTPATHSIGNALTOALEVELWHERETARGETSCANBEDETECTED ASOUTLINEDIN3ECTION
Óΰ{Ê ** /" /VALSOF#ASSINICANBEUSEDTODEFINETHREEOPERATINGREGIONSFORABISTATICRADAR CO SITE RECEIVER CENTERED ANDTRANSMITTER CENTERED#O SITECORRESPONDSTO&IGUREB RECEIVER CENTERED TO THE RIGHT OVAL IN &IGURE D AND TRANSMITTER CENTERED TO THE LEFT OVAL IN &IGURE D4HE TYPE OF TRANSMITTERDEDICATED COOPERATIVE OR NON COOPERATIVECOMPLETES THE TAXONOMY ! DEDICATED TRANSMITTER IS DESIGNED AND CONTROLLED BY THE BISTATIC OR MULTISTATIC RADAR ANALOGOUS TO A MONOSTATIC RADAR "OTHCOOPERATIVEANDNONCOOPERATIVETRANSMITTERSARETRANSMITTERS OF OPPORTUNITY DESIGNEDFOROTHERFUNCTIONS INCLUDINGRADARANDCOMMUNICATIONS BUTFOUNDSUITABLE FORBISTATICOPERATION4HECOOPERATIVETRANSMITTERISCONTROLLEDBYALLIEDORFRIENDLY FORCESTHENONCOOPERATIVETRANSMITTER BYHOSTILEORNEUTRALFORCES4ABLESUM MARIZESBISTATICRADARAPPLICATIONSINTHESEOPERATINGREGIONS
%NTRIESINTHEDEDICATEDTRANSMITTERCO SITECATEGORYREPRESENTACOMPLETEBISTATIC RADAR SUITERADARS WITH ALL COMPONENTS INCLUDING THE TRANSMITTER DESIGNED FOR BISTATICOPERATION-ANYOFTHESESYSTEMSWEREDEVELOPED TESTED ORDEPLOYEDPRIOR TO%XAMPLESARETHE&RENCH 5332 AND*APANESEFORWARDSCATTERFENCESUSED IN77)) THE!.&03 FORAIR DEFENSEGAPFILLING 0!2!$/0AND-)$/0RANGE INSTRUMENTATION TRACKERS 30!352 FOR SPACE SURVEILLANCE AND 3ANCTUARY FOR AIR DEFENSE 4HE "27, FOR ARTILLERY MORTAR AND ROCKET LOCATION THE 2USSIAN 3TRUNA FORWARDSCATTERFENCE nANDTHE&RENCH'RAVESFORSPACESURVEILLANCE WERELATERDEVELOPMENTS /MITTEDENTRIESINTHEDEDICATEDTRANSMITTERCOLUMNFOROPERATIONINTHERECEIVER AND TRANSMITTER CENTERED OVALS AT LARGE BASELINE RANGES ARE DICTATED BY OPERATIONS ANDCOSTBOTHCOOPERATIVEANDNONCOOPERATIVETRANSMITTERS OF OPPORTUNITYAREOFTEN PRESENTANDCAPABLEOFSUPPORTINGBISTATICOPERATIONINTHESESMALLAREASOFINTEREST
4!",% "ISTATIC2ADAR!PPLICATIONS 2ECEIVER /PERATING 2EGIONS
2ANGE 2ELATIONSHIP
$EDICATED4RANSMITTER
#OOPERATIVE4RANSMITTER
.ONCOOPERATIVE4RANSMITTER
#O SITE
, 2-
s !IRSURVEILLANCE s 2ANGEINSTRUMENTATION s 3ATELLITETRACKING s )NTRUSIONDETECTION
s !IRSURVEILLANCE s 2ANGEINSTRUMENTATION s )ONOSPHERICMEASUREMENT s 7INDMEASUREMENT
s !IRSURVEILLANCE
2ECEIVER CENTERED
, 22422
s 3HORT RANGEAIRSURVEILLANCE s 3ILENTAIR TO GROUNDATTACK s 0LANETARYEXPLORATION
s 3HORTRANGESURVEILLANCE
4RANSMITTER CENTERED
, 22224
s 0LANETARYEXPLORATION
s !IRTHREATMONITORING s -ISSILELAUNCHALERT
!MULTISTATICRADARWITHITSREQUIREMENTFORCOMMONSPATIALCOVERAGENEARLYALWAYSOPERATESINTHECO SITEREGION
Óΰ£ä
2!$!2(!.$"//+
&URTHERMORE THISAPPROACHISLESSCOSTLYANDWHENEXPLOITINGNONCOOPERATIVETRANS MITTERS MORECOVERTANDLESSRISKYTHANUSINGADEDICATEDTRANSMITTER#ONSEQUENTLY DEDICATEDTRANSMITTERSARENOTUSUALLYCONSIDEREDFORTHESEAPPLICATIONS %NTRIES IN THE COOPERATIVE AND NONCOOPERATIVE TRANSMITTER COLUMNS ARE CALLED HITCHHIKERSWHENTHETRANSMITTERISAMONOSTATICRADAR7HENTHETRANSMITTERISFROM ACOMMUNICATIONSORBROADCAST SYSTEM IE NOT FROM A RADAR ENTRIES ARE CALLED A PASSIVEBISTATICRADAR0"2 %XAMPLES OF A HITCHHIKER OPERATING WITH A COOPERATIVE TRANSMITTER IN THE CO SITE REGIONARETHE-ULTISTATIC-EASUREMENT3YSTEMOPERATINGWITH42!$%8FORINCREAS INGBALLISTICMISSILEREENTRYMEASUREMENTACCURACY ANDTHECOMMERCIAL "INET)NC BISTATICRECEIVEROPERATINGWITHMONOSTATICDOPPLERWEATHERRADARSTOMEASURETHREE DIMENSIONALVECTORWINDFIELDS &IGUREISABLOCKDIAGRAMOFTHE"INET)NC DEVELOPEDPROTOTYPE %XAMPLESOFHITCHHIKERSOPERATINGWITHACOOPERATIVETRANSMITTERINTHERECEIVER CENTEREDREGIONARETHE#OVIN2ESTPROGRAM OPERATINGWITHTHESPACE SHUTTLERADARFOR SYNTHETICAPERTURERADAR3!2 GROUNDMAPPINGTHE4")2$PROGRAMOPERATINGWITH *OINT34!23FORSILENTAIR TO GROUNDATTACKVIAFORWARD LOOKINGBISTATIC3!2 AND THE"!#PROGRAMOPERATINGWITH!7!#3FORALERTINGANDCUEINGSHORTRANGE MOBILE AIR DEFENSESYSTEMS
"%"%(!)!%$!$ ) ""!) (
(.!(( "%)) + *! $) $$
,
'$(#!)*"( '! ' , %' '$
%*$) '!# '
%$)'%"%") ,
,$##!,), !-. /&-!
1 )**&!,
, %&&" '
*"( %"'!,)!%$
!())! !+ '
$) $$ %!$)!$ $ " (
)&&$(#!+/!-.
1 ), (#! .$(# ,$##!,-
)(.,)&)&. #!
(.!((
,
)&&$(#!+/!-.
$#( & )/-!%!!*$(# ("),' .$)(
)/-!%!!*$(# ("),' .$)(
$#( &
&)'52% 3IMPLIFIEDBLOCKDIAGRAMOFTHE"INET)NC DEVELOPEDBISTATICWINDMEASUREMENTPROTOTYPE SYSTEM!MODIFIED#0 MONOSTATICWEATHERRADARTRANSMITSANDRECEIVESONANARROWBEAMANTENNA WHILE ONEORMOREBISTATICRECEIVESITESnKMFROMTHE#0 RECEIVEBISTATICALLYSCATTEREDENERGYFROMTHE SAMEILLUMINATEDWEATHERVOLUMEOVERABROADANTENNABEAM!TRANSMITRECEIVETUBEISUSEDTOPROTECTTHE RECEIVER JUSTASINAMONOSTATICRADAR!LLGENERATEDFREQUENCIESARELOCKEDTOTHEMASTER -(Z6#8/ WHICHIS INTURN LOCKEDTO'03TIMINGSIGNALS3YNCHRONIZATIONANDOTHERHOUSEKEEPINGDATAARESENTOVER TELEPHONELINES3IGNALANDDATAPROCESSINGIS0# BASEDAFTER*7URMANÚ)%%%
")34!4)#2!$!2
Óΰ££
(ITCHHIKERSUSINGCOOPERATIVEMONOSTATICRADARTRANSMITTERSALSOHAVETHEINHER ENT CAPABILITY TO COUNTER RETRO DIRECTIVE JAMMERS OPERATING AGAINST THEIR HOST RADAR "ECAUSETHEJAMMERUSESAHIGH GAINANTENNATORETRO DIRECTTHETRANSMITTERSSIGNAL BACKTOTHETRANSMITTERANDTHUSITSMONOSTATICRECEIVER THESPATIALLYSEPARATEDHITCH HIKERCANBEPOSITIONEDINTHESIDELOBESOFTHATANTENNA THUSREDUCINGTHEEFFECTIVENESS OFTHEJAMMER!RULEOFTHUMBISTOANTICIPATEENHANCEDHITCHHIKERPERFORMANCEWHEN EVERTHEBISTATICANGLEISGREATERTHANTHEESTIMATED D"WIDTHOFTHERETRO DIRECTED MAINBEAM %XAMPLESOF0"2SOPERATINGWITHCOOPERATIVEBROADCASTTRANSMITTERSINTHECO SITE REGIONARETHE-ANASTASH2IDGE2ADAROPERATINGWITHAN&-BROADCASTTRANSMITTERFOR TROPOSPHERICSOUNDINGS 3ILENT3ENTRYOPERATINGWITH&-AND46BROADCASTTRANS MITTERS ANDTHE($46 "ASED0ASSIVE2ADAROPERATINGWITHAHIGHDEFINITION 46 BROADCAST TRANSMITTER THE LATTER TWO CONFIGURED FOR AIR SURVEILLANCE %XAMPLES OF 0"2S OPERATING WITH COOPERATIVE COMMUNICATIONS TRANSMITTERS IN THE RECEIVER AND TRANSMITTER CENTERED REGIONS ARE BISTATIC RADARS FOR PLANETARY EXPLORATION 4HEY USE ADATALINKTRANSMITTERONTHEPROBEVEHICLEINTHETRANSMITTER CENTEREDREGIONANDAN %ARTH BASEDCOMMANDTRANSMITTERINTHERECEIVER CENTEREDREGION 4HETERMCOOPERATIVETRANSMITTERISSOMEWHATOFAMISNOMER&OREXAMPLE ACOOP ERATIVE46OR&-STATIONOPERATORWOULDNOTBEINCLINEDTOhCOOPERATEvWITHA0"2BY ALTERINGANTENNACOVERAGEORMODIFYINGBROADCASTMATERIALWITHSPECIALWAVEFORMS &URTHERMORE THEREISALWAYSTHEPOSSIBILITYOFATRANSMITTERFAILUREINTHECOURSEOF NORMALOPERATIONSORFROMANENEMYATTACK4HISEVENTWILLDEGRADEPERFORMANCEOFA 0"2THATOPERATESWITHMULTIPLETRANSMITTERSANDELIMINATEPERFORMANCEOFA0"2THAT OPERATESONLYWITHTHATTRANSMITTER!SARESULT THE0"2ISFREETOEXPLOITCOOPERATIVE ORNONCOOPERATIVE TRANSMISSIONSIFTHEYARESUITABLEHOWEVER COMMERCECONTROLS THEIROPERATIONWITHTHE0"2REMAININGAUSEROFOPPORTUNITY SPECIFICALLYSUFFERING NONOPTIMUMWAVEFORMS3ECTION LIMITEDELEVATIONCOVERAGE ANDOCCASIONALLY REDUCEDORDENIEDPERFORMANCE #ONSTRAINTSALSOAPPLYWHENAHITCHHIKERATTEMPTSTOEXPLOITACOOPERATIVEORNON COOPERATIVEMONOSTATICRADAR SPECIFICALLYWITHTHEHITCHHIKERSUFFERINGANTENNASCAN ON SCANPROBLEMS3ECTION (OWEVER THEPOTENTIALFORENHANCINGPERFORMANCE OFACOOPERATIVEMONOSTATICRADARAGAINSTRETRO DIRECTIVE TYPEJAMMERSWHENUSINGA SUITABLYPOSITIONEDHITCHHIKERNECESSITATESDISTINGUISHINGCOOPERATIVEFROMNONCOOP ERATIVETRANSMITTERS )N THE NONCOOPERATIVE TRANSMITTER COLUMN IF A NONCOOPERATIVE TRANSMITTER AND A HITCHHIKERWERELOCATEDINORNEARABATTLEAREA AHITCHHIKERCOULDUSETHATTRANSMITTER INTHECO SITEREGIONJUSTASITWOULDFORACOOPERATIVETRANSMITTER4HE'ERMAN+LEIN (EIDELBERGHITCHHIKINGOFFTHE"RITISH#HAIN(OMERADARSTOCONDUCTAIRSURVEILLANCE DURING77))ISANEXAMPLE !HITCHHIKERIMPLANTEDINORFLYINGOVERHOSTILEAREAS COULD USE ANY HIGH POWERED SATELLITE TRANSMITTER ILLUMINATING THAT AREA TO CONDUCT SHORT RANGESURVEILLANCEINTHERECEIVER CENTEREDOVAL 4HEMOSTSIGNIFICANTSYSTEMTOUSEADEDICATEDTRANSMITTERISTHE3PACE3URVEILLANCE 30!352 -(ZMULTISTATICRADARFENCE)TWASDEPLOYEDSTARTINGINATSEVEN SITESSPANNINGTHECONTINENTAL5NITED3TATESTODETECTANDTRACKNONCOOPERATIVESATEL LITES 4RANSMITTERSARELOCATEDATTHREESITES THELARGESTOFWHICHTRANSMITS-7 #7FROMALINEARARRAYABOUTKMLONG GENERATINGAFIXEDFANBEAM4HESIXRECEIVE SITESCONSISTOFSEVENOREIGHTLINEARARRAYSWITHDIMENSIONSONTHEORDEROFKM ALSO GENERATINGFIXEDFANBEAMSCOLLINEARWITHTHETRANSMITBEAM&IGURESHOWSTHE DATAFLOWINATYPICALRECEIVINGSTATION
Óΰ£Ó
2!$!2(!.$"//+
$* $* '& !'( " ) %#&
$*
&)'52% 2EAL TIMEDATAFLOWINA.!630!352RECEIVINGSTATIONh4RANSMITTER ENERGY REFLECTED BY THE SATELLITE IS RECEIVED BY VARIOUS COLLINEAR ARRAYS OF DIPOLES AT THERECEIVERSTATIONx;3IGNALS=FROMFOURIN LINEARRAYSFEEDSTHEALERTRECEIVERWHICH DETECTSTHEPRESENCEOFRADIOENERGYINEXCESSOFPRESETTHRESHOLDLEVELS4HEREFLECTED ENERGY IS ALSO SIMULTANEOUSLY RECEIVED ON OTHER ARRAYS THAT ARE SEPARATED IN THE EAST WEST DIRECTION BY VARIOUS DISTANCES BASELINE 3IGNALS FROM ANY TWO CAN BE ADDED TO FORM A BASELINE PAIR 4HE BASELINE RECEIVERS EMPLOY TRIPLE FREQUENCY CONVERSION WHERETHEPHASEDIFFERENCEOFTHESIGNALSRECEIVEDBYTHEANTENNAPAIRISPRESERVEDIN A HERTZDIFFERENCEFREQUENCY;CALLEDAK(ZPHASESIGNALINTHEFIGURE=x4HERE ISARADIORECEIVERANDCONSEQUENTLYA HERTZPHASE;SIGNAL=FOREACHBASELINEPAIR EASTWESTANDNORTHSOUTH 4HISPHASESIGNALISCOMPAREDWITHA HERTZREFER ENCE SIGNAL AND ENCODED DIGITIZED BY THE!$$!3 ENCODING EQUIPMENT 4HE DIGITAL COMBINER CONTAINED WITHIN THE!$$!3 ENCODER RECEIVES THE +(Z PHASE DATA AND GENERATESANUNAMBIGUOUSZENITHANGLESOLUTION4HECOMBINEROUTPUTSALONGWITHDIGI TIZEDPHASEINFORMATIONANDCONTROLBITS FOREMOSTOFWHICHIS@ALERT AREAPPLIEDTOTHE TELEPHONELINESVIAADIGITALDATATRANSMITTERvFROM(ANDBOOKFOR.!630!3523YSTEM /RIENTATION COURTESY53.AVY
4ARGETLOCATIONISESTABLISHEDBYTRIANGULATION IE THEINTERSECTIONOFZENITHANGLE $/! MEASUREMENTSFROMTWOORMORERECEIVESITES3UBSEQUENTLYATHREE SITEFENCE IN3OUTH4EXASWASDEPLOYEDTOEVALUATETHEUSEOFBISTATICRANGEMEASUREMENTSTO IMPROVELOCATIONACCURACY BUTITNEVERENTEREDCONTINUOUSOPERATION
")34!4)#2!$!2
Óΰ£Î
!CCORDINGTO%ASTON THE30!352DESIGNWASDRIVENBYCOSTA NMIDETEC TIONRANGEREQUIREDVERYHIGHAVERAGEPOWER WHICHWASSATISFIEDBYTHELOWESTCOST #7OPERATION"UTTHISSOLUTION INTURN REQUIREDSEPARATESITESFORISOLATIONHENCE MULTISTATIC OPERATION 4HE STATIONARY BEAM LINEAR ARRAYS ALSO MINIMIZED COST WHEN COMPAREDTOSCANNINGARRAYSORREFLECTORANTENNAS)NSHORT FIXTHEBEAMSANDLETTHE SATELLITESFLYTHROUGHTHEM)THASBEENINCONTINUOUSUSESINCE ! HITCHHIKER USING A COOPERATIVE RADAR TRANSMITTER IN THE CO SITE REGION WAS THE -ULTISTATIC-EASUREMENT3YSTEM--3 )TWASINSTALLEDATTHE53+WAJALEIN-ISSILE 2ANGE IN AS AN ADJUNCT TO THE 42!$%8 , BAND MONOSTATIC RADAR 42!$%8 OPERATEDINITSNORMALMONOSTATICMODE ACQUIRING TRACKING ANDILLUMINATINGBALLISTIC MISSILEREENTRYVEHICLES26S 4WOUNMANNED SLAVEDRECEIVESTATIONS LOCATEDABOUT KMFROM42!$%8 RECEIVEDECHOESBISTATICALLYSCATTEREDOFFTHE26ANDRECORDED BISTATICRANGE DOPPLER ANDSIGNATUREDATAFROM26S4HISDATAWASUSEDTOCALCULATE 26POSITIONANDDYNAMICSNEARTHEATMOSPHERICPIERCEPOINTORSTARTOFRE ENTRY4HE SYSTEMWASPROJECTEDTOMEASURETHREE DIMENSIONALPOSITIONANDVELOCITYWITHACCURA CIESBETTERTHANMANDMS RESPECTIVELY THROUGHOUTRE ENTRY &IELD TESTS SHOWED THAT --3 RANGE DATA COMBINED WITH 42!$%8S MONOSTATIC RANGEDATAINATRILATERATIONNETPROVIDEDTHEMOSTACCURATEESTIMATEOFEXO ATMOSPHERIC 26POSITIONSOBTAINEDBYANYOFTHERANGERADARS--3OPERATIONSWERECONCLUDEDIN AFTERTHEMETRICACCURACYOFMONOSTATICRADARSWASIMPROVED )N THE MID S A 0"2 USING A COOPERATIVE &- BROADCAST TRANSMITTER IN THE CO SITE REGION WAS DEVELOPED BY THE 5NIVERSITY OF 7ASHINGTON #ALLED THE -ANASTASH 2IDGE 2ADAR -22 IT IS DESIGNED TO STUDY TURBULENCE IN THE IONO SPHERE SPECIFICALLYAURORAL% REGIONIRREGULARITIES USINGRANGE DOPPLER AND$/! VIAINTERFEROMETRY MEASUREMENTS -OTIVATIONFOR-22DEVELOPMENTINCLUDED LOWERCOST INCREASEDSAFETY SPECTRUMAVAILABILITY ANDPEDAGOGICALOPPORTUNITY -22 PROVIDES RANGE TIME INTENSITY AND RANGE DOPPLER PLOTS TO THE 7ORLD 7IDE 7EBEVERYHALF HOUR!LTHOUGHITISNOTSUBJECTTOTHESTRINGENTAIR DEFENSEREQUIRE MENTSFORACCURATELOCATIONOFMULTIPLETARGETSINREALTIME ITHASDETECTEDMETEORS ANDAIRCRAFTINTHECOURSEOFNORMALOPERATIONS ! SECOND 0"2 CALLED THE ($46 "ASED 0ASSIVE 2ADAR EXPLOITS A COOPERATIVE HIGH DEFINITION46TRANSMITTERFORAIRSURVEILLANCEINTHECO SITEREGION)TUSESRANGE MULTILATERATIONFROMFOURRECEIVERSLOCATEDWITHINKMOFTHETRANSMITTERTOTRACK LOW FLYING AIRCRAFT AND HELICOPTERS AS A GAP FILLER FOR MONOSTATIC AIR SURVEILLANCE RADARS0REDICTEDDETECTIONANDTRACKINGRANGESOFKMONAMTARGETHAVEBEEN DEMONSTRATEDINREALTIMEWITH$TRACKINGERRORSGENERALLYLESSTHANM#OARSE TARGETELEVATIONHASALSOBEENMEASURED$OPPLERDATAHASBEENUSEDTORESOLVEGHOSTS IE FALSEDETECTIONSTHATINEVITABLYARISEWHENUSINGMULTILATERATIONONUNAUGMENTED TARGETS 0"2SHAVEUSEDSATELLITECOMMUNICATIONTRANSMITTERSTOMEASURECHARACTERISTICS OFMOONANDPLANETARYSURFACESANDATMOSPHERESINBOTHTHETRANSMITTER ANDRECEIVER CENTEREDREGIONS4HEFIRSTSUCCESSFULPIGGYBACKOPERATIONINEXPLOITEDDATALINK SIGNALSTRANSMITTEDFROMTHE,UNA PROBE SCATTEREDOFFTHEMOONSSURFACE AND THENRECEIVEDBYAN%ARTH BASEDSTATION INADOWN LINKMODECHARACTERIZEDBYTHE TRANSMITTER CENTEREDOVALOF#ASSINI3UCHSTATIONSINCLUDETHE!RECIBO/BSERVATORY ANDTHE.!3!$EEP3PACE.ETWORK3UBSEQUENTMEASUREMENTSWEREMADEUSING ,UNAR/RBITER %XPLORER AND!POLLOn-ARSBISTATICRADARMEASUREMENTS WERE MADE USING -ARINER 6IKING -ARS 'LOBAL 3URVEYOR AND -ARS %XPRESS6ENUSMEASUREMENTSWEREMADEBY6ENERAS -AGELLAN AND6ENUS %XPRESS &IGUREISASIMPLIFIEDSCHEMATICOFAN%ARTH BASEDRECEIVER
Óΰ£{
2!$!2(!.$"//+
&)'52% "LOCKDIAGRAMOFATYPICAL%ARTH BASEDSYSTEMUSEDFORDOWNLINKBISTATICRADAR4HELOW NOISEAMPLIFIER,.! ISEITHERACOOLEDMASERORAFIELDEFFECTTRANSISTORANDMAYBESWITCHEDBETWEENTHE ANTENNAANDANAMBIENTLOAD ALLOWINGAMPLITUDECALIBRATIONOFTHEINPUT$URINGBISTATICOPERATIONS ASIGNAL FROMTHELOW LEVELNOISEDIODE PREVIOUSLYCALIBRATEDAGAINSTTHEAMBIENTLOAD MAYBEINJECTEDTOMONITOR REAL TIMEPERFORMANCEOFTHESYSTEM-ICROWAVEINPUTSn'(Z AREMIXEDTOA-(ZINTERMEDIATE FREQUENCY)& FORAMPLIFICATION!PROGRAMMABLEOSCILLATOR WHICHCANCORRECTFORFIRST ORDERDOPPLEREFFECTS THENMIXESTHE)&SIGNALTOBASEBAND ANDDIGITALSAMPLESARESTOREDFORLATERPROCESSING!LTHOUGHANANALOG TO DIGITALCONVERSIONISSHOWNATTHEOUTPUT THE!$#MAYACTUALLYTAKEPLACEATANYPOINTINTHESYSTEM #OURTESY3CI4ECH
! RECIPROCAL BUT MORE COMPLEX AND COSTLY UPLINK MODE USES A BISTATIC RECEIVER CARRIEDBYTHEPROBE COLLECTINGHIGHPOWER %ARTH TRANSMITTEDCOMMANDSIGNALSFIRST SCATTEREDOFFTHEPLANETSSURFACEANDCHARACTERIZEDBYTHERECEIVER CENTEREDOVALOF #ASSINI)THASAN^D"GREATERLINKMARGIN WHICHWASFIRSTUSEDFOR-ARS/DYSSEY ANDISPLANNEDFORFUTUREPROBES)NBOTHCONFIGURATIONS EVENTHOUGHTWOLEGSOFTHE BISTATICTRIANGLEAREEXTRAORDINARILYLONG MILES THETHIRDLEGISSUFFICIENTLYSHORT ^MILES TOPRODUCESTRONGECHOESATTHERECEIVER 4HESEPIGGYBACKBISTATICRADARSHAVEPROVIDEDUSEFULDATAINSIMPLE INEXPENSIVE SURVEYSOFPLANETARYSURFACEPROPERTIESASAPRELUDETOROBOTICORHUMANEXPLORATION SPECIFICALLY CENTIMETER TO METER SCALE ROUGHNESS AND MATERIAL DENSITIES IN THE TOP FEWCENTIMETERSOFREGOLITH3PECIALGEOMETRIES SUCHASNEAR BACKSCATTERTOIDENTIFY DEPOSITSOFCLEANWATERICE AREALSOAUNIQUEADVANTAGEOFBISTATICRADAR4HEABILITYTO OBSERVEFORWARDSCATTERINGATLATITUDESAWAYFROMPLANETARYEQUATORSISALSOADVANTA GEOUSFORPROBINGSURFACECHARACTERISTICS
ÓΰxÊ -// Ê "** , &IGURE DEFINES THE GEOMETRY FOR BISTATIC DOPPLER WHEN THE TARGET TRANSMITTER ANDRECEIVERAREMOVING4HETARGETHASAVELOCITYVECTOROFMAGNITUDE6ANDASPECT ANGLECREFERENCEDTOTHEBISTATICBISECTOR4HETRANSMITTERANDRECEIVERHAVEVELOCITY VECTORSOFMAGNITUDE64AND62ANDASPECTANGLESC4ANDC2 RESPECTIVELY REFERENCED TOTHENORTHCOORDINATESYSTEMOF&IGURE!LLVECTORSAREPROJECTIONSOFTHETHREE DIMENSIONVECTORSONTOTHEBISTATICPLANE 4ARGET$OPPLER 7HENTHETRANSMITTERANDRECEIVERARESTATIONARY64 62 THETARGETSBISTATICDOPPLERATTHERECEIVESITEF"IS
F" 6K COSCCOSA
")34!4)#2!$!2
Óΰ£x
&)'52% 'EOMETRYFORBISTATICDOPPLERINTHE BISTATICPLANE
4HETERMF"ALSODEFINESTHEDOPPLERBEATFREQUENCY WHICHISPRODUCEDBYMIX INGTHETARGETSDOPPLERWITHTHEDIRECTPATHSIGNALINTHERECEIVER7ILLISPROVIDESAN EXPRESSIONFORF"WHENALLTHREESITESAREINMOTION%QUATIONSHOWSTHAT 7HENA n F"REDUCESTOTHEMONOSTATICCASEFORAMONOSTATICRADARLOCATEDONTHE BISTATICBISECTOR4HEMAGNITUDEOFTHEBISTATICDOPPLERISNEVERGREATERTHANTHATOF THISMONOSTATICDOPPLER 7HENA n F" FORANYC WHICHISTHEFORWARD SCATTERCASE 7HENC onTHEBISTATICDOPPLERISZERO3INCETHESEVELOCITYVECTORSAREALSO TANGENTTOARANGE SUMELLIPSEATTHISPOINT ALLSUCHELLIPSESINCLUDINGTHEBASELINE BECOMECONTOURSOFZEROTARGETDOPPLER 7HENC n THEBISTATICDOPPLERISAMAXIMUM3INCETHISVELOCITYVECTORISALSO TANGENT TO A HYPERBOLA ORTHOGONAL TO THE RANGE SUM ELLIPSE AT THIS POINT ALL SUCH HYPERBOLASBECOMECONTOURSOFMAXIMUMTARGETDOPPLER 7HENC oAn THEVELOCITYVECTORISPOINTEDATTHETRANSMITTERORRECEIVERAND F" 6K COSA WHICHOCCASIONALLYAPPEARSINTHELITERATUREASASPECIALCASE OF%Q
L
L
L
L
L
)F A MONOSTATIC RADAR IS LOCATED AT THE TRANSMIT SITE AND A BISTATIC HITCHHIKER IS LOCATEDATTHERECEIVESITE BOTHMEASURINGTARGETDOPPLER F- ANDF" RESPECTIVELY THE TWOMEASUREMENTSCANBECOMBINEDTOESTIMATETHETARGETVELOCITYVECTOR6 C INTHE BISTATICPLANE/NESUCHESTIMATEIS
C TAN [;F-F"SINA = COTA ]
6 KF"COSC KF-COSC A
WHEREAISOBTAINEDBYSOLVINGTHEBISTATICTRIANGLE FOREXAMPLE BYUSINGMONO STATICRANGE MONOSTATIC,/3 ANDANESTIMATEOFTHEBASELINE!THIRDHITCHHIKING SITEALLOWSTHETARGETVELOCITYVECTORTOBEMEASUREDINTHREEDIMENSIONS4HISPRO CESSISCALLEDDUAL DOPPLERFORTWOMEASUREMENTSANDMULTIPLE DOPPLERFORTHREEOR MOREMEASUREMENTS ANDHASBEENUSEDTOMEASURETHREE DIMENSIONALVECTORWIND FIELDS
Óΰ£È
2!$!2(!.$"//+
)SODOPPLER #ONTOURS 7HEN THE TARGET IS STATIONARY AND THE TRANSMITTER AND RECEIVER ARE MOVING EG ON AIRBORNE PLATFORMS THE BISTATIC DOPPLER SHIFT AT THE RECEIVERSITEF42IS
F42 64K COSC3 P4 62K COSC2 P2
WHERETERMSAREDEFINEDIN&IGURE 4HELOCUSOFPOINTSFORCONSTANTDOPPLERSHIFTONTHE%ARTHSSURFACEISCALLEDAN ISODOPPLER CONTOUR OR ISODOP #LUTTER RETURNS ARE CHARACTERIZED BY THESE ISODOPS WHICHARECALLEDCLUTTERDOPPLERSHIFT)NTHEMONOSTATICCASEANDAFLAT%ARTH THESE ISODOPSARECONICSECTIONSINTHREEDIMENSIONSANDRADIALLINESEMANATINGFROMTHE RADARINTWODIMENSIONS"ECAUSETHESEISODOPSAREALIGNEDWITHTHERADARSLOOK ANGLE THECLUTTERISCALLEDSTATIONARY)NTHEBISTATICCASE THEISODOPSARESKEWED AWAYFROMTHELOOKANGLE DEPENDINGUPONTHEGEOMETRYANDPLATFORMMOTION AND THECLUTTERISCALLEDNONSTATIONARY"ISTATICISODOPSAREDEVELOPEDANALYTICALLYFOR TWODIMENSIONSANDAFLATEARTHBYSETTINGF42 CONSTANTIN%QANDSOLVING FORP2ORP4 IFAPPROPRIATE &IGUREISAPLOTOFBISTATICISODOPSINATWO DIMENSIONALBISTATICPLANE IE WHERETHETRANSMITTERANDRECEIVERAREATZEROORNEAR ZEROALTITUDE FORTHEFOLLOWING CONDITIONS64 62 MS C4 C2 ANDK M $IMENSIONOFTHEGRIDONTHEBISTATICPLANEISARBITRARYTHATIS THEISODOPSAREINVARI ANTWITHSCALE/NTHELEFTANDRIGHTSIDESOF&IGURE THEISODOPSAREAPPROXIMATELY STATIONARY WHICHAREPSEUDO MONOSTATICOPERATINGPOINTS%LSEWHERE THEISODOPSARE NONSTATIONARY)NTHESENONSTATIONARYREGIONS THEQUALITYOFBISTATIC3!2IMAGERYIS LIMITEDANDMOVINGTARGETINDICATION-4) PERFORMANCEISDEGRADEDWHENUSINGSTAN DARDMONOSTATICRADARPROCESSINGTECHNIQUES
&)'52% "ISTATIC ISODOPPLER CONTOURS FOR TWO DIMENSIONS AND A FLAT EARTH#OURTESY,EE2-OYER 4ECHNOLOGY3ERVICE#ORP
")34!4)#2!$!2
Óΰ£Ç
2ESEARCHWASSTARTEDINTHESTOIMPROVETHEQUALITYOFBISTATIC3!2IMAGES WHICHWERECONSTRAINEDTOCOHERENTINTEGRATIONTIMESOFAFEWSECONDSANDCONSE QUENTLYWEREOFLIMITEDTACTICALINTEREST3PECIFICALLY LOCALOSCILLATORPHASEINSTABILITIES WEREREDUCEDANDBISTATICAUTOMATICFOCUSINGAUTOFOCUS ALGORITHMSWEREDEVELOPED TOIMPROVERANGEMEASUREMENTACCURACYFROMTHEANTENNAPHASECENTERTOTHEIMAGED SCENE"ISTATICAUTOFOCUSREQUIRESTHATTHEPOSITIONOFBOTHTRANSMITANDRECEIVEPLAT FORMSMUSTBETRACKEDWITHSUBWAVELENGTHRELATIVEACCURACYTOCORRECTTIME VARYING PHASEERRORSASPARTOFTHEIMAGEFORMATIONPROCESS4HERESULTALLOWEDANINCREASE INCOHERENTINTEGRATIONTIMESCOMPARABLETOMONOSTATIC3!2 TYPICALLY SECONDS #ONSEQUENTLY BISTATIC 3!2 IMAGE QUALITY WAS GREATLY IMPROVED AS REPORTED BY " 2IGLINGIN#HAPTEROF7ILLISAND'RIFFITHS "ISTATIC SPACE TIME ADAPTIVE PROCESSING 34!0 WAS ALSO DEVELOPED TO IMPROVE -4)PERFORMANCEOFSEPARATELYMOVINGTRANSMITANDRECEIVEPLATFORMS3INCEBISTATIC CLUTTER EXHIBITS NONSTATIONARY SPACE TIME CHARACTERISTICS BISTATIC 34!0 METHODS ARE NOT SIMPLE APPLICATIONS OF MONOSTATIC APPROACHES BUT A NEW CLASS OF ALGORITHMS 3PECIFICALLY THEYAPPLYADATA DEPENDENTWEIGHTINGTOVOLTAGESCOLLECTEDOVERMUL TIPLERECEIVEANTENNACHANNELSANDPULSES4HISWEIGHTINGDYNAMICALLYTAILORSAFILTER RESPONSEINANGLEANDBISTATICDOPPLERTOSUPPRESSGROUNDCLUTTERREFLECTIONS$IGITAL BEAMFORMING IS REQUIRED FOR THIS OPERATION /THER NECESSARY ELEMENTS INCLUDE A MEANSTOESTIMATETHESPATIO TEMPORALCLUTTERCOVARIANCEMATRIXTHEDATA DEPENDENT ELEMENTOFTHEFILTERWEIGHTING ANDHYPOTHESISOFTHETARGETSTEERINGVECTOR)NGENERAL AUXILIARYDATATAKENFROMRANGEBINSOTHERTHANTHECELLUNDERTESTISUSEDTOESTIMATE THEUNKNOWN BUTCRITICAL CLUTTERCOVARIANCEMATRIX7ITHCOMPENSATIONFORNONSTA TIONARYBEHAVIOR BISTATICCLUTTERSUPPRESSIONHASBEENGREATLYIMPROVED ASREPORTEDBY 7-ELVININ#HAPTEROF7ILLISAND'RIFFITHS
ÓΰÈÊ /, /Ê " /" "ISTATIC,OCATION !BISTATICRECEIVERTYPICALLYUSESRANGESUM24 22 FORTAR GETLOCATION WHICHCANBEESTIMATEDBYTWOMETHODS)NTHEDIRECTMETHOD THERECEIVER MEASURESTHETIMEINTERVAL$4RTBETWEENRECEPTIONOFTHETRANSMITTEDSIGNALANDRECEP TIONOFTHETARGETECHO)TTHENCALCULATESTHERANGESUMAS24 22 C$4RT ,4HIS METHODCANBEUSEDWITHANYSUITABLEMODULATEDTRANSMISSIONANDANYTYPEOFTRANS MITTERDEDICATED COOPERATIVE ORNONCOOPERATIVE GIVENANADEQUATE,/3BETWEEN TRANSMITTER AND RECEIVER )N THE INDIRECT METHOD PRESYNCHRONIZED STABLE CLOCKS ARE USEDBYTHERECEIVERANDADEDICATEDTRANSMITTER4HERECEIVERMEASURESTHETIMEINTER VAL$4TT BETWEENTHETRANSMISSIONOFASIGNALANDRECEPTIONOFTHETARGETECHO)TTHEN CALCULATESTHERANGESUMAS24 22 C$4TT!TRANSMITTER TO RECEIVER,/3ISNOT REQUIREDUNLESSPERIODICCLOCKSYNCHRONIZATIONISIMPLEMENTEDOVERTHEDIRECTPATH 4HETRADITIONALMETHODFORCONVERTINGTARGETRANGESUMINTOTARGETRANGEFROMTHE RECEIVER 22 IS
22
24 22 , 24 22 , SINP 2
4HEBASELINE,CANBEDETERMINEDUSING'03OROTHERMETHODSSUCHASANEMITTERLOCA TORFORNONCOOPERATIVETRANSMITTERS!SOUTLINEDIN3ECTION THERECEIVERLOOKANGLE P2 CANBEMEASUREDDIRECTLYWITHAPHASEDARRAYANTENNATHATSCANSINTWODIMENSIONS
Óΰ£n
2!$!2(!.$"//+
ORTARGETAZIMUTHANDELEVATIONMEASUREMENTSCANBECONVERTEDTOP2"EAM SPLITTING TECHNIQUESCANBEUSEDTOREDUCETHEMEASUREMENTERROR%VENWITHBEAM SPLITTING P2IS THECRITICALPARAMETERESTABLISHINGACCURACYOFTHE22ESTIMATE SINCE ASINTHEMONOSTATIC CASE ITSERRORISPROPORTIONALTOTARGETRANGE!FULLERRORANALYSISOF%QISGIVEN IN3ECTIONOF7ILLIS.OBISTATICRADAROPERATINGAUTONOMOUSLYHASBEENSHOWNTO PROVIDEADEQUATELOCATIONOFAIRORSPACETARGETSWITHOUTEMPLOYINGRECEIVEAPERTURES COMPARABLEINSIZETOMONOSTATICRECEIVEAPERTURESUSEDFORTHOSEPURPOSES )NTHESPECIALCASEOFABISTATICRADARUSINGTHEDIRECTRANGESUMESTIMATIONMETHOD WHEN24 22y,%QCANBEAPPROXIMATEDAS
22
C$4RT
SIN P 2
4WOEXAMPLESAREARECEIVEROPERATINGINANOVER THE SHOULDERGEOMETRYANDTHE TRANSMITTEROPERATINGONASATELLITEWITHTHERECEIVERANDTARGETNEARTHEEARTH4HEERROR IN%QISLESSTHANPERCENTFORn P2 nAND, 24 22 ORC$4RT 4HEERRORGROWSRAPIDLYFORP2 n /THER TARGET LOCATION TECHNIQUES ARE POSSIBLE n &OR EXAMPLE WHEN A BISTATICHITCHHIKEREXPLOITSTHETRANSMITTEROFAMONOSTATICRADAR THERADARSLOOKANGLE P4CANBEUSEDINPLACEOFORINCONJUNCTIONWITHP2!NEXAMPLEOFTHELATTERISTHE THETA THETALOCATIONTECHNIQUE WHERE
22 ,COSP4SINP4 P2
ANDP4 P2 A!DEDICATEDORCOOPERATIVEMONOSTATICRADARCANPROVIDEVALUESOF P4DIRECTLYTOTHEHITCHHIKER/THERWISE THEHITCHHIKERMUSTESTIMATETHEVALUE FOR EXAMPLE VIAANEMITTERLOCATORMEASURINGTHERADARSANTENNASCANRATEWHENITISPRE DICTABLE)NTHISCASE TARGETLOCATIONACCURACYISOFTENSETBYTHEP4ESTIMATIONERROR -ULTISTATIC,OCATION -ULTISTATICLOCATIONTYPICALLYUSESMULTIPLETRANSMITTERS OPERATINGWITHONERECEIVERORMULTIPLERECEIVERSOPERATINGWITHONETRANSMITTER%LLIPSES OFCONSTANTRANGE SUM IE ISORANGECONTOURS FROMEACHTRANSMITTER RECEIVERPAIRARECAL CULATEDANDCOMBINEDATACENTRALSITETOPRODUCEINTERSECTINGCONTOURS WHICHLOCATETHE TARGET -ULTISTATICCROSS RANGELOCATIONCANBEMOREACCURATETHANMONOSTATICORBISTATIC CROSS RANGELOCATIONSINCEANGLEDATA WITHITSRANGE DEPENDENTACCURACY ISNOTUSED4HE MULTISTATICRADARMUST HOWEVER USEMULTIPLE PROPERLYLOCATEDSITESWITHBOTHOVERLAP PINGCOVERAGEANDSIMULTANEOUSMEASUREMENTS WHICH INTURN REQUIREBROADTRANSMITAND RECEIVEBEAMSTOACHIEVETHISACCURACY4HESEREQUIREMENTSUSUALLYCOMBINETORESTRICT MULTISTATICAIRSURVEILLANCEPERFORMANCETOSHORTORMEDIUMRANGES 'EOMETRICDILUTIONOFPRECISION'$/0 ESTABLISHESMULTISTATICLOCATIONACCURACY ANDRESOLUTION ANDISDEVELOPEDBY$"ARTONIN#HAPTEROF7ILLISAND'RIFFITHS '$/0ISAFUNCTIONOFTHEANGLEOFINTERSECTION @ BETWEENISORANGECONTOURS"ECAUSE THEBISECTOROFABISTATICANGLEISORTHOGONALTOANISORANGECONTOUR '$/0CANREADILY BEDETERMINEDBYTHEANGLEOFINTERSECTION ALSO@ OFTHESEBISTATICBISECTORS)NTHE SIMPLESTCASE THEDOWN RANGEERRORRDRISPROPORTIONALTO;COS@ = ANDCROSS RANGEERRORRCRISPROPORTIONALTO;SIN@ =
)SORANGECONTOURSINTERSECTATOTHERLOCATIONSASWELL4HESENONTARGETLOCATIONSARECALLEDGHOSTS WHICHMUSTBE EXCISED4HISSUBJECTISTREATEDIN#HAPTEROF7ILLISAND'RIFFITHS
")34!4)#2!$!2
Óΰ£
&OR EXAMPLE WHEN THE TARGET IS SURROUNDED ON THREE SIDES BY A RECEIVE SITE A TRANSMITSITE ANDANOTHERRECEIVESITESUCHTHAT@ RDR RCR 4HISGEOMETRY REPRESENTSTHEOPTIMUMCASEOFAUNITY'$/0FACTOR YIELDINGACIRCULARERRORELLIPSE WITHRADIUSEQUALTOTHERANGEERROROFONETRANSMIT RECEIVEPAIR)NCONTRAST WHENTHE TARGETISLOCATEDSOMEDISTANCEFROMTHETHREESITES @ISREDUCED&OREXAMPLE WHEN @ RDR ANDRCR 4HUS THEDOWN RANGEERRORISSLIGHTLYREDUCEDBUT THECROSS RANGEERRORISGREATLYINCREASED NOTUNLIKETHATOFARADARUSINGANGLEDATATO ESTABLISHCROSS RANGEACCURACY 4HESEEXAMPLESALSOAPPLYWHENGROUND BASEDMULTISTATICSITESATTEMPTTOMEA SURETARGETALTITUDE7HENTHESITESSURROUNDTHETARGET FOREXAMPLE WHENPOSITIONED AROUND THE LAUNCH SITE OF A BALLISTIC MISSILE @ REMAINS RELATIVELY LARGE DURING THE MISSILESLAUNCHPHASE YIELDINGPRECISEALTITUDEESTIMATES7HENTHESITESARESOME DISTANCEFROMTHETARGET FOREXAMPLE WHENCONDUCTINGAIRORMISSILESURVEILLANCE @IS SMALL YIELDINGPOORALTITUDEESTIMATES "OTH BISTATIC AND MULTISTATIC RADARS CAN POTENTIALLY ACHIEVE EVEN BETTER LOCATION ACCURACY BY USING NARROW BAND DOPPLER TRACKING UNDER THE FOLLOWING CONDITIONS 7HENINTEGRATINGDOPPLERDATA INITIALCONDITIONSTHEPESKYCONSTANTOFINTEGRA TION CANBEESTABLISHEDWITHSUFFICIENTACCURACY 7HENTAKINGSEQUENTIALDOPPLER MEASUREMENTS THE TARGETS VELOCITY VECTOR REMAINS CONSTANT OR PREDICTABLE &OR EXAMPLE MANYDOPPLER ONLY PRECISIONRANGEINSTRUMENTATIONSYSTEMSWEREDEVELOPED INTHE53AFTER77))"OTHBEACON AIDEDANDSKIN TRACKSYSTEMSWEREDEVELOPED !LLREQUIREDINITIALIZATIONOFTHETRACKDATA WHICHWASCONVENIENTLYPROVIDEDBYTHE TARGETS LAUNCH COORDINATES (OWEVER IF THE TARGET RETURN MOMENTARILY FADED OR THE TRANSPONDERSIGNALWASINTERRUPTEDDURINGFLIGHTSOTHATTRACKWASLOST THEREWASNO WAYTOREINITIALIZENEWTRACKDATAANDSUBSEQUENTLOCATIONESTIMATESBECAMEBIASEDOR WERELOST4HESESYSTEMSWERESUBSEQUENTLYREPLACEDWITHPRECISIONMONOSTATICRADARS ANDOPTICALTRACKERS
ÓΰÇÊ /, /Ê ,"--Ê- /"
£{]£x]Îä]ÈÈqnÇ
4HEBISTATICRADARCROSSSECTION2#3 OFATARGETR"ISAMEASURE ASISTHEMONOSTATIC RADARCROSSSECTIONR- OFTHEENERGYSCATTEREDFROMTHETARGETINTHEDIRECTIONOFTHE RECEIVER"ISTATICCROSSSECTIONSAREMORECOMPLEXTHANMONOSTATICCROSSSECTIONSIN THEOPTICALREGIONSINCER"ISAFUNCTIONOFASPECTANGLEANDBISTATICANGLEA 4HREE BISTATIC2#3REGIONSAREOFINTERESTINTHEOPTICALREGIONPSEUDO MONOSTATIC BISTATIC ANDFORWARDSCATTER%ACHREGIONISDEFINEDBYTHEBISTATICANGLE4HEEXTENTOFEACH REGIONISSETPRIMARILYBYTHETARGETSPHYSICALCHARACTERISTICS 0SEUDO -ONOSTATIC 2#3 2EGION 4HE #RISPIN AND 3IEGAL MONOSTATIC BISTATIC EQUIVALENCETHEOREMAPPLIESINTHEPSEUDO MONOSTATICREGIONFORVANISHINGLYSMALL WAVELENGTHS THEBISTATIC2#3OFASUFFICIENTLYSMOOTH PERFECTLYCONDUCTINGTARGETIS EQUALTOTHEMONOSTATIC2#3MEASUREDONTHEBISECTOROFTHEBISTATICANGLE3UFFICIENTLY SMOOTH TARGETS INCLUDE SPHERES ELLIPTIC CYLINDERS CONES AND OGIVES ALLOWING THE REGIONTOEXTENDOUTTOA nANDOCCASIONALLYOUTTOA n n
(OWEVERINTHERESONANCEREGION TYPICALLYAT6(&ANDLOW5(&FORMANYAIRTARGETS VARIATIONSINA ^nHAVE LITTLEEFFECTONR" SUCHTHATR"yR-
ÓΰÓä
2!$!2(!.$"//+
&ORTARGETSOFMORECOMPLEXSTRUCTURE THEEXTENTOFTHEPSEUDO MONOSTATICREGION ISREDUCED!VARIATIONOFTHEEQUIVALENCETHEOREMDEVELOPEDBY+ELLAPPLIESTOSMALL BISTATICANGLES INSOMECASESASSMALLASnTHEBISTATIC2#3OFACOMPLEXTARGETIS EQUALTOTHEMONOSTATIC2#3MEASUREDONTHEBISECTOROFTHEBISTATICANGLEATAFRE QUENCYLOWERBYAFACTOROFCOSA +ELLS COMPLEX TARGETS ARE DEFINED AS AN ASSEMBLY OF DISCRETE SCATTERING CENTERS SIMPLE CENTERS SUCH AS FLAT PLATES REFLEX CENTERS SUCH AS CORNER REFLECTORS SKEWED REFLEXCENTERSSUCHASADIHEDRALWITHCORNERwn ANDSTATIONARYPHASEREGIONSFOR CREEPINGWAVES 7HENTHEWAVELENGTHISSMALLCOMPAREDTOTARGETDIMENSIONS THESE COMPLEXTARGETMODELSAPPROXIMATECONVENTIONALAIRCRAFT SHIPS GROUNDVEHICLES AND SOMEMISSILES4HETARGETSCANBECOMPOSEDOFCONDUCTINGANDDIELECTRICMATERIALS !TSMALLBISTATICANGLES THECOSA FREQUENCYREDUCTIONTERMHASLITTLEEFFECTIN +ELLSPSEUDO MONOSTATICREGION&OREXAMPLE AnBISTATICANGLECORRESPONDSTOA SHIFTINWAVELENGTHANDUSUALLYCANBEIGNORED"OTHVERSIONSOFTHEEQUIVALENCE THEOREMAREVALIDWHENTHEPOSITIONSOFTHETRANSMITTERANDRECEIVERAREINTERCHANGED GIVEN THAT THE TARGET SCATTERING MEDIA ARE RECIPROCAL -OST MEDIA ARE RECIPROCAL %XCEPTIONSAREGYROTROPICMEDIA SUCHASFERRITEMATERIALSANDTHEIONOSPHERE "ISTATIC2#32EGION 4HEBISTATICANGLEATWHICHTHEEQUIVALENCETHEOREMFAILS TO PREDICT THE BISTATIC 2#3 IDENTIFIES THE START OF THE SECOND BISTATIC REGION )N THIS REGION THE BISTATIC 2#3 DIVERGES FROM THE MONOSTATIC 2#3 +ELL IDENTIFIED THREE SOURCESOFTHISDIVERGENCEFORCOMPLEXTARGETSANDFORATARGETASPECTANGLEFIXEDWITH RESPECTTOTHEBISTATICBISECTOR4HESESOURCESARE CHANGESINRELATIVEPHASEBETWEEN DISCRETESCATTERINGCENTERS CHANGESINRADIATIONFROMDISCRETESCATTERINGCENTERS AND CHANGESINTHEEXISTENCEOFCENTERSAPPEARANCEOFNEWCENTERSORDISAPPEAR ANCEOFTHOSEPREVIOUSLYPRESENT 4HEFIRSTSOURCEISANALOGOUSTOFLUCTUATIONSINMONOSTATIC2#3ASTHETARGETASPECT ANGLECHANGES BUTNOWTHEEFFECTISCAUSEDBYACHANGEINBISTATICANGLE4HESECOND SOURCEOCCURSWHEN FOREXAMPLE THEDISCRETESCATTERINGCENTER INCLUDINGFLATPLATES RETRO REFLECTSENERGYTOWARDTHETRANSMITTER ANDTHERECEIVERISPOSITIONEDOUTSIDETHE RETRO REFLECTEDBEAMWIDTHTHUS THERECEIVEDENERGYISREDUCED4HETHIRDSOURCEIS TYPICALLYCAUSEDBYSHADOWING FOREXAMPLE BYANAIRCRAFTFUSELAGEBLOCKINGONEOF THEBISTATICPATHSTRANSMITTERORRECEIVER,/3TOASCATTERINGCENTER )NGENERAL THISDIVERGENCERESULTSINABISTATIC2#3LOWERTHANTHEMONOSTATIC2#3 FORCOMPLEXTARGETS&OREXAMPLE %WELLAND:EHNERMEASUREDTHEMONOSTATICAND BISTATIC2#3OFCOASTALFREIGHTERSAT8BANDWHENBOTHTHETRANSMITTERANDTHERECEIVER WERENEARGRAZINGINCIDENCE4HEDATAWASPLOTTEDASARATIOOFBISTATICTOMONOSTATIC 2#3 R"R-4HEMEASUREMENTSGENERALLYMATCH+ELLSMODELOFTHEDATAPOINTS SHOWBISTATIC2#3LOWERTHANMONOSTATIC2#34HEREDUCTIONINBISTATIC2#3STARTS BETWEENA nANDA nANDTRENDSDOWNWARDTOR"R- D"ATA n 4HISRATHERSEVERELOSSWASMEASUREDUNDERSPECIALCONDITIONSLOWGRAZINGANGLES FORTARGETSWITHVERTICALSURFACES ANDDIHEDRALSANDTRIHEDRALS WHICHGENERATEALARGE MONOSTATIC2#34HUS THEBISTATIC2#3BECOMESSIGNIFICANTLYLOWERASTHEBISTATIC ANGLE INCREASES DUE TO SHADOWING AND LOSS OF THESE SPECULARS AND RETRO REFLECTORS "ISTATIC LOSSES SHOULD NOT BE AS SEVERE FOR TARGETS WITH BLENDED SURFACES AND A LESS COMPLEXSTRUCTURE SUCHASCOMBATAIRCRAFT 'LINT2EDUCTIONINTHE"ISTATIC2#32EGION !SECONDEFFECTCANOCCURINTHE BISTATICREGION7HENTHEBISTATIC2#3REDUCTIONISCAUSEDBYALOSSORATTENUATIONOF
")34!4)#2!$!2
Óΰӣ
LARGEDISCRETESCATTERINGCENTERS FOREXAMPLE THROUGHSHADOWING TARGETGLINTISOFTEN REDUCED4ARGETGLINTISTHEANGULARDISPLACEMENTINAPPARENTPHASECENTEROFATARGET RETURNANDISCAUSEDBYTHEPHASEINTERFERENCEBETWEENTWOORMOREDOMINANTSCATTERS WITHINARADARRESOLUTIONCELL!STHETARGETASPECTANGLECHANGES THISPHASEINTERFER ENCE CHANGES SHIFTING THE APPARENT PHASE CENTER OFTEN WITH EXCURSIONS BEYOND THE PHYSICALEXTENTOFTHETARGET4HESEEXCURSIONSCANSIGNIFICANTLYINCREASETHEERRORSIN ANGLETRACKINGORMEASUREMENTSYSTEMS7HENTHERETURNSFROMDOMINANTSCATTERERS AREREDUCEDINTHEBISTATICREGION THESOURCEANDHENCETHEMAGNITUDEOFGLINTEXCUR SIONSISREDUCED-EASUREMENTSWITHTACTICALAIRCRAFTSHOWEDTHATFORAnBISTATIC ANGLE PEAKGLINTEXCURSIONSCOULDBEREDUCEDBYAFACTOROFORMORE WITHMOSTOF THEEXCURSIONSCONTAINEDWITHINTHEPHYSICALEXTENTOFTHETARGET4HISREDUCTIONCAN BEEXPLOITEDINASEMI ACTIVEHOMINGMISSILEBYMODIFYINGITSTRAJECTORYTOMAINTAIN A nnDURINGENDGAME &ORWARD 3CATTER2#32EGION 4HETHIRDBISTATIC2#3REGION FORWARDSCATTER OCCURS WHEN THE BISTATIC ANGLE APPROACHES n 7HEN A n 3IEGEL SHOWED BASEDONPHYSICALOPTICS THATTHEFORWARD SCATTER2#3 R& OFATARGETWITHSILHOUETTE ORSHADOW AREA!IS
R& O!K
WHEREK THEWAVELENGTH ISSMALLCOMPAREDWITHTHETARGETDIMENSIONS4HETARGETS CAN BE EITHER SMOOTH OR COMPLEX STRUCTURES AND FROM THE APPLICATION OF "ABINETS PRINCIPLE CANBETOTALLYABSORBING &ORA n THEFORWARD SCATTER2#3ROLLSOFFFROMR&4HEROLLOFFISAPPROXI MATEDBYTREATINGTHESHADOWAREA!ASAUNIFORMLYILLUMINATEDANTENNAAPERTURE4HE RADIATIONPATTERNOFTHISSHADOWAPERTUREISEQUALTOTHEFORWARD SCATTER2#3ROLLOFF WHENO A ISSUBSTITUTEDFORTHEANGLEOFFTHEAPERTURENORMAL!SPHEREOFRADIUS AWILLROLLOFFD"ATO A yKOA WHENAK4HEROLL OFFCONTINUESAPPROXI MATING*X XDOWNTOAyn WHERE*ISA"ESSELFUNCTIONOFZEROORDER!LINEAR APERTUREOFLENGTH$ WITHASPECTANGLEORTHOGONALTOTHETRANSMITTER,/3 WILLROLLOFF D"ATO A K$ WHEN$K4HEFORWARD SCATTER2#3ROLLOFFCONTINUES WITHSIDELOBESAPPROXIMATINGSINXXOVERTHEFORWARD SCATTERQUADRANTA n &OROTHERASPECTANGLESANDTARGETSWITHCOMPLEXSHADOWAPERTURES CALCULATIONOFTHE FORWARD SCATTER2#3ROLLOFFUSUALLYREQUIRESSIMULATION 4HE FORWARD SCATTER 2#3 OF MORE COMPLEX BODIES HAS BEEN SIMULATED AND MEA SUREDTHEBODIESWEREBOTHREFLECTINGANDABSORBING n&IGURESHOWSA METHOD OF MOMENTSSIMULATIONOFA BY CMCYLINDERWITHFACETSAT'(Z FORTHREEFIXEDTRANSMITTER TO TARGETGEOMETRIESA NEARENDON B nASPECTANGLE ANDC BROADSIDE!LLTHREEBISTATICREGIONSARESHOWNINTHEFIGURE)NTHEBROADSIDE GEOMETRY THEPSEUDO MONOSTATICREGIONOCCURSATA n BISTATICATn A n ANDFORWARDSCATTERATA n4HEOTHERTWOGEOMETRIESSHOWASIMILARBUTBROADER FORWARD SCATTERLOBE ASISEXPECTEDSINCETHESILHOUETTEAREAANDHENCETHESHADOWING APERTUREARESMALLER4HEnASPECTGEOMETRYISOFINTERESTBECAUSETHE2#3INTHE BISTATICREGIONSISLARGERTHANTHEMONOSTATIC2#3FORMOSTBISTATICANGLES4HELARGE SPIKEATA nISTHEBISTATICSPECULARLOBE ANALOGOUSTOTHEMONOSTATICSPECULARLOBE INTHEBROADSIDEGEOMETRY7HILE&IGURESHOWSTHECLEARDEPENDENCYOFBISTATIC 2#3ONBOTHASPECTANDBISTATICANGLES ITALSOSERVESTOCAUTIONAGAINSTATTEMPTSTOUSE OVERSIMPLIFIEDBISTATIC2#3MODELS ESPECIALLYINTHEBISTATICREGION
ÓΰÓÓ
2!$!2(!.$"//+
&)'52% 3IMULATEDBISTATIC2#3 REPLOTTEDASAFUNCTIONOFBISTATICANGLEFORACONDUCTINGCYLINDER BYCMAT'(Z ((POLARIZATIONAFTER2#0ADDISONETAL A NEARENDON B ASPECT ANGLE ANDC BROADSIDE
ÓΰnÊ -1,
Ê 1// , 4HEBISTATICRADARCROSSSECTIONOFSURFACECLUTTER RC ISAMEASURE ASISTHEMONOSTATIC RADARCLUTTERCROSSSECTION OFTHEENERGYSCATTEREDFROMACLUTTERCELLAREA !C INTHEDIREC TIONOFTHERECEIVER)TISDEFINEDAS S C S " !C WHERES " ISTHESCATTERINGCOEFFICIENT ORTHECLUTTERCROSSSECTIONPERUNITAREAOFTHEILLUMINATEDSURFACE4HECLUTTERCELLAREA !CHASBEENDEVELOPEDFORBEAM ANDRANGE LIMITEDCASESANDISREPORTEDELSEWHERE $OPPLER LIMITEDCASESAREAFUNCTIONOFPLATFORMMOTION WHICH INTURN DEPENDONA SPECIFICSCENARIO#ONSEQUENTLY THEYAREMODELEDONACASE BY CASEBASIS "ISTATIC3CATTERING#OEFFICIENT 6ALUESOFTHESCATTERINGCOEFFICIENTS " VARYASA FUNCTIONOFTHESURFACECOMPOSITION FREQUENCY ANDGEOMETRYANDAREOBTAINEDTHROUGH FIELDMEASUREMENTPROGRAMS)N --7EINERDOCUMENTEDANDEVALUATEDALL UNCLASSIFIEDMEASUREMENTSOFS " HOWEVER ITSUSEWASRESTRICTEDTO53GOVERNMENT AGENCIES)N 7ILLISUSED7EINERSREFERENCESTORECONSTRUCTANDEVALUATETYPICAL DATAFROM7EINERSWORK WHICHBECAMEAVAILABLEFORPUBLICUSEIN7ILLIS )N 7EINERSWORKWASCLEAREDFORPUBLICRELEASE MAKINGAVAILABLEINONEDOCUMENTALL UNCLASSIFIEDS " DATAANDANALYSISTHROUGH7EINERTHENUPDATEDHISWORKWITHDATA AVAILABLETHROUGHANDREPUBLISHEDITIN#HAPTEROF!DVANCESIN"ISTATIC2ADAR 4HISSECTIONSUMMARIZESANDCOMMENTSONESSENTIALELEMENTSOF7EINERSWORK
")34!4)#2!$!2
ÓΰÓÎ
4HE AVAILABLE DATABASE FOR TERRAIN AND SEA CLUTTER AT MICROWAVE FREQUEN CIES CONSISTS OF NINE MEASUREMENT
PROGRAMS WHICH ARE SUMMARIZED IN 4ABLE 4HE MEASUREMENT ANGLES SHOWN IN 4ABLE ARE DEFINED IN
&IGURE WHICHISACLUTTER CENTERED COORDINATE SYSTEM SIMILAR TO THOSE
USEDINALLTHEMEASUREMENTPROGRAMS "ECAUSE TERRAIN AND SEA ARE RECIPROCAL MEDIA PIANDPSAREINTERCHANGEABLEIN THESUBSEQUENTDATA 4WOMEASUREMENTSETSAREOFINTER ESTINPLANE WHEREE n ANDOUTOF &)'52% #OORDINATESYSTEMFORBISTATICCLUTTER PLANE WHEREE n7HENE n MEASUREMENTS PI INCIDENT ANGLE IN XZ PLANE A \PS PI\ )N THE MONOSTATIC CASE PS SCATTERING ANGLE IN PLANE CONTAINING Z AXIS AND E n A AND PS PI )N PLANE E OUT OF PLANEANGLEINXYPLANE DATAISSHOWNINBOLDTYPEONTHETABLE /UT OF PLANEDATAISOFTENUSEDINSCATTERJAMMINGHOTCLUTTER CALCULATIONS 4HE BISTATIC ANGLE IS CALCULATED FROM THE ANGLES IN &IGURE BY THE USE OF DIRECTIONCOSINES
A COS COSPICOSPS SINPISINPSCOSE
4RENDSINTHISBISTATICSCATTERINGCOEFFICIENTDATABASEARESUMMARIZEDFROM7ILLIS 7EINER AND#HAPTERIN7ILLISAND'RIFFITHSASFOLLOWS L
L
L
L
L
L
-OSTOFTHER"DATABASEISAT8BAND WITHOUTOFDATACURVESFORBOTHTERRAIN ANDSEACLUTTERTAKENBYOFTHEORGANIZATIONS4HEREMAININGDATABASECONSISTS OFDATACURVESAT,BANDTERRAINONLY AT3BANDTERRAINONLY AT#BANDSEA ONLY ANDAT+ABANDTERRAINONLY EACHPROVIDEDBYONEORGANIZATION.ODATA ISAVAILABLEAT6(&OR5(&4HUSONLY8BANDALLOWSCHOICESINSELECTINGDATA4HE #OST0EAKE AND$OMVILLEnIN PLANEDATASHOWGOODCORRELATION !TTEMPTSTOMODELR"DATAHAVEBEENMADEUSINGGEOMETRICAL STATISTICAL ANDSEMI EMPIRICALTECHNIQUES INCLUDINGVARIATIONSOFTHOSEUSEDTOMODELMONOSTATICDATA -EANINGFULRESULTSHAVEONLYBEENACHIEVEDOVERANARROWRANGEOFIN PLANEDATA E n 6ALUESOFR"FORE ^nARENOTAPPRECIABLYDIFFERENTWITHIN^D" FROMTHE MONOSTATICCASE 6ALUESOFR"INABROADANGULARREGIONCENTEREDONE nARESIGNIFICANTLYLOWER THAN ELSEWHERE AND TYPICALLY TO D" BELOW THE MONOSTATIC VALUE CONSE QUENTLY BISTATICRADARSURVEILLANCECANBEENHANCEDANDHOTCLUTTERCANBEREDUCED INTHESEREGIONS 6ALUESOFR" ARESIGNIFICANTLYLARGERNEARTHEFORWARD SCATTERED SPECULARDIRECTION E n PI PS THANELSEWHEREANDMAY INSOMECASES REDUCEADVANTAGESOFTHE ENHANCED FORWARD SCATTEREDTARGET2#3 PARTICULARLYATFREQUENCIES -(Z 4HEBISTATIC MONOSTATICEQUIVALENCETHEOREMUSEDTOMODELTHE2#3OFSOMETARGETS ISNOTGENERALLYUSEFULFORCLUTTERMODELING EXCEPTTOINDICATEANUPPERLIMITTOR" INSOMEREGIONS
!UTHOR
2URALLAND 5RBANLAND &OREST 3EA 3EMI DESERT WET
$OMVILLE
3EASEASTATES 3EA"EAUFORTWIND
'%# %LECTRONICS ,TD %NGLAND
0IDGEON
3MOOTHSAND ,OAM &OLIAGE SOYBEAN 2OUGHSAND ,OAMWITHSTUBBLE 'RASS
3URFACE#OMPOSITION
*OHNS(OPKINS 5NIV!0,
4HE/HIO3TATE #OST 0EAKE 5NIVERSITY !NTENNA,AB
/RGANIZATION
9EAR REPORTED2EF
AFTER--7EINER #HAPTER COURTESY3CI4ECH
&REQUENCY '(Z
8BAND
8BAND 8BAND
#BAND
8BAND
$ATA #URVES &IGURES
66
66(( 66((
666(
((
66(((6
66(((6
0OLARIZATION
n
n n
n
n
n n
n
PI
n n
n
n
n
n n
n
PS
n
n
E
-EASUREMENT!NGLES DEGREES
4!",% 3UMMARYOF-EASUREMENT0ROGRAMSFOR"ISTATIC3CATTERING#OEFFICIENT S " )N PLANEDATAISSHOWNINBOLDTYPESEESUBSEQUENTTEXT
ÓΰÓ{ 2!$!2(!.$"//+
!UTHOR
4HE5NIVERSITY 5LABYETAL OF-ICHIGAN %%#3$EPT -)4,INCOLN ,AB -! .ORTHEASTERN 5NIV -! .ORTHEASTERN 5NIV -! 5NIVOF-!
'EORGIA)NST OF4ECH%%3
-C,AUGHLIN ETAL
+OCHANSKI
%WELL :EHNER
2AYTHEON#O 7AYLAND -!
#ORNWELL ,ANCASTER
4HE5NIVERSITY ,ARSON (EIMILLER OF-ICHIGAN ETAL %2)-
/RGANIZATION
9EAR REPORTED2EF
&ORESTEDHILLS
3EASEASTATE
6ISUALLYSMOOTHSAND 2OUGHSAND 'RAVEL
3EA M n M WAVEHEIGHTS
"EACHANDSANDDUNES 3EASEASTATE
'RASSWITHCEMENT TAXIWAY
7EEDSANDSCRUBTREES /RCHARD WEEDS SCRUB TREESWSNOWCOVER
3URFACE#OMPOSITION
AFTER--7EINER #HAPTER COURTESY3CI4ECH #ONTINUED
.ONE
$ATA #URVES &IGURES
3BAND
3BAND
&REQUENCY '(Z 0OLARIZATION
&ULLYPOLAR
6((6
66((
6(66
66(( 6((6 6((6
66((
66
(((6
(((6 (((6
,OWGRAZ ANGLE
,OWGRAZ ANGLE
,OWGRAZ ANGLE
n n n
PI
n n n n n n
E
n n n
n
,OWGRAZ n ANGLE n
n
n
,OWGRAZ n ANGLE
,OWGRAZ A n ANGLE
n n
PS
-EASUREMENT!NGLES DEGREES
4!",% 3UMMARYOF-EASUREMENT0ROGRAMSFOR"ISTATIC3CATTERING#OEFFICIENT S " )N PLANEDATAISSHOWNINBOLDTYPESEESUBSEQUENTTEXT
")34!4)#2!$!2
ÓΰÓx
ÓΰÓÈ
2!$!2(!.$"//+
)NADDITIONTOTHISDATABASE BISTATICREFLECTIVITYMEASUREMENTSHAVEBEENMADEAT OPTICALANDSONICWAVELENGTHSANDOFBUILDINGS AIRPORTSTRUCTURES ANDPLAN ETARYSURFACES )NEACHOFTHESEMEASUREMENTS THEREFLECTIVITYDATAISEXPRESSEDIN TERMSOFREFLECTEDPOWER NOTR"
ÓÎ°Ê 1 +1 Ê*," -Ê Ê, +1, /)NTHEPREVIOUSEDITIONOFTHISBOOK THISSECTIONCOVEREDSUCHHARDWAREPROBLEMS ASTIMEANDPHASESYNCHRONIZATIONBETWEENTRANSMITTERANDRECEIVERCONSTRAINEDBY TECHNOLOGY AVAILABLE IN THE S 0HASE STABILITY WAS ALSO AN ISSUE 3INCE THEN MASSIVE ADVANCES IN DIGITAL SIGNAL CORRELATION AND PROCESSING COUPLED WITH GREAT REDUCTIONSINTHECOSTOFHARDWARETOEXECUTESUCHPROCESSING HAVEMITIGATEDTHESE PROBLEMS-ANYRECENTBISTATICRADARPROGRAMSHAVEDEMONSTRATEDQUITEADEQUATE SYNCHRONIZATION AND STABILITYAS WELL AS DETECTION PERFORMANCEUSING OFF THE SHELF COMMERCIALHARDWARE.OTABLEEXAMPLESARETHE.!4/AIRDEFENSETRIALS ANDTHE5NIVERSITYOF7ASHINGTONS-ANASTASH2IDGE2ADARMEASURINGIONOSPHERE TURBULENCE BOTH PASSIVE BISTATIC RADARS EXPLOITING &- BROADCAST TRANSMITTERS THE($46 "ASED0ASSIVE2ADAREXPLOITINGAHIGHDEFINITION 46BROADCASTTRANSMIT TERFORAIRSURVEILLANCE THEINEXPENSIVE COMMERCIALBISTATICRECEIVERHITCHHIKING OFFWEATHERRADARSTOMEASUREFULLVECTORWINDFIELDS ANDTHEBISTATICRADARFOR WEAPONSLOCATION &URTHERMORE MAJORPROGRESSHASBEENMADEINDEVELOPINGSIGNALANDDATAPROCESS INGALGORITHMS INCLUDINGBISTATIC3!2AUTOFOCUSANDIMAGEFORMATIONANDSPACE TIME ADAPTIVEPROCESSINGFORBISTATICAIRBORNE-4)SEE3ECTION (OWEVER TWOPROB LEMS CONTINUE TO PLAGUE BISTATIC AND MULTISTATIC RADARS AND HAVE BECOME THE TOPICS OF THIS SECTION BEAM SCAN ON SCAN FOR BISTATIC RADARS AND RADAR HITCHHIKERS AND NONCOOPERATIVE2&ENVIRONMENTSFORPASSIVEBISTATICRADARS4HESEPROBLEMSAND THEIRPOTENTIALREMEDIESAREDETAILEDNEXT "EAM 3CAN ON 3CAN 7HEN HIGH GAIN NARROW BEAM SCANNING ANTENNAS ARE USEDBYBOTHTRANSMITTERANDRECEIVERINABISTATICSURVEILLANCERADAR INEFFICIENTUSE ISMADEOFTHERADARENERGYBECAUSEONLYTHEVOLUMECOMMONTOBOTHBEAMSCANBE OBSERVEDBYTHERECEIVERATANYGIVENTIME/UTSIDETHISCOMMONBEAMVOLUME TARGETS ARELOSTTOTHERECEIVER&IGURESHOWSTHEGEOMETRY4HISPROBLEMCOMMONLY ARISESWHENATTEMPTINGTOHITCHHIKEOFFMONOSTATICSURVEILLANCERADARS&OURREMEDIES AREAVAILABLETOMITIGATETHEBEAMSCAN ON SCANPROBLEM STEPSCANNING FLOOD LIGHTBEAMS MULTIPLEBEAMS AND TIME MULTIPLEXEDBEAMS WHICHINTHELIMIT ISCALLEDPULSECHASING 3TEP 3CANNING &OR HITCHHIKING THE STEP SCANNING REMEDY CONSISTS OF FIXING THERECEIVEBEAMANDWAITINGFORTHETRANSMITBEAMTOSCANTHROUGHTHESURVEILLANCE SECTOR4HERECEIVEBEAMISTHENSTEPPEDONEBEAMWIDTHFORTHENEXTTRANSMITBEAM SCANANDSOON UNTILTHERECEIVEBEAMHASSTEPPEDACROSSTHEFULLSURVEILLANCESEC TOR&ORADEDICATEDTRANSMITTER THEPROCESSCANBEREVERSEDFIXTHETRANSMITBEAM ANDSCANTHERECEIVEBEAM4HISREMEDYINCREASESTHESURVEILLANCEFRAMETIMEBYTHE NUMBEROFREQUIREDBEAMSTEPSANDISUSUALLYNOTACCEPTABLEFORLARGEAREASURVEIL LANCE)TCANBECONSIDEREDINANOVER THE SHOULDERGEOMETRYORWHENTHEBASELINEIS SMALL)NTHESECASES TRANSMITANDRECEIVEBEAMSBECOMEMORECLOSELYALIGNEDINA
")34!4)#2!$!2
ÓΰÓÇ
&)'52% "EAMSCAN ON SCANCOVERAGEPROBLEMSHOWNIN TWODIMENSIONSINTHEBISTATICPLANE#OURTESY3CI4ECH
PSEUDO MONOSTATICGEOMETRY WHICHREDUCESTHENUMBEROFREQUIREDBEAMSTEPS4HE "ISTATIC2ADARFOR7EAPONS,OCATIONTESTPROGRAMISANEXAMPLE &LOODLIGHT "EAMS ! FLOODLIGHT BEAM CAN BE USED WITH EITHER TRANSMITTER OR RECEIVER4HEFLOODLIGHTTRANSMITTERREMEDYREQUIRESADEDICATEDTRANSMITANTENNATHAT ISDESIGNEDTOFLOODTHESURVEILLANCESECTORCONTINUOUSLY4HERECEIVERTHENSCANSTHE SECTOR WITH A HIGH GAIN ANTENNA 4HIS REMEDY RESTORES THE SURVEILLANCE FRAME TIME LOSTBYSTEPSCANNINGWHILESIMULTANEOUSLYSERVICINGMULTIPLERECEIVERS(OWEVER IT INCURSADETECTIONRANGEPENALTYBYTHEREDUCEDTRANSMITANTENNAGAINANDALSOSUF FERSINCREASEDSIDELOBECLUTTERLEVELS4HEFLOODLIGHTRECEIVERREMEDYCANBEUSEDBY AHITCHHIKERTOFLOODASECTORSCANNEDBYTHETRANSMITBEAM AGAINRESTORINGTHESUR VEILLANCE FRAME TIME )N ADDITION TO THE RANGE PENALTY THE RECEIVER WILL ALSO SUFFER INCREASEDCLUTTERLEVELSANDANGLEMEASUREMENTERRORS$ESPITETHESELIMITATIONS THE "INETFLOODLIGHTRECEIVERWASFOUNDQUITEADEQUATEFORMEASURINGTHREEDIMENSIONAL VECTORWINDFIELDS -ULTIPLE"EAMS !BISTATICRECEIVERCANUSEMULTIPLESIMULTANEOUSFIXEDRECEIVE BEAMSTOCOVERTHESURVEILLANCESECTOR WHICHAGAINRESTORESTHESURVEILLANCEFRAME TIME)FTHEGAINOFEACHRECEIVEANTENNAISMADEEQUALTOTHEGAINOFTHEINITIALSINGLE RECEIVEANTENNA RANGEPERFORMANCEISALSORESTORED(OWEVER THISREMEDYINCREASES THE COST AND COMPLEXITY OF THE RECEIVER SINCE A SPECIAL BEAMFORMING NETWORK IS REQUIRED ALONGWITHARECEIVERANDSIGNALPROCESSOR230 FOREACHBEAM4HEMULTI BEAMRECEIVERCANBEUSEDWITHANYTYPEOFTRANSMITTER INCLUDINGAFLOODLIGHTTRANSMIT TERWHERETHELOSSINRANGEPERFORMANCEMIGHTBEOFFSETBYANINCREASEINDWELLTIME ONTARGET ASDETAILEDSUBSEQUENTLY 4IME MULTIPLEXING )F THE TRANSMITTERS BEAM SCANNING SCHEDULE IS KNOWN THE NUMBER OF RECEIVE BEAMS AND 230S CAN BE REDUCED IN SOME GEOMETRIES BY TIME MULTIPLEXING THEM TO COVER ONLY THE CURRENTLY ILLUMINATED SURVEILLANCE SECTOR
ÓΰÓn
2!$!2(!.$"//+
&OREXAMPLE INANOVER THE SHOULDERGEOMETRY THERECEIVERMIGHTUSEASETOFBEAMSTO COVERTHENORTHSIDEOFTHEBASELINETHEN ASTHETRANSMITBEAMSCANSPASTTHERECEIVER ITSWITCHESTHESETTOTHESOUTHSIDE THUSHALVINGTHETOTALNUMBERREQUIRED4HE"ISTATIC !LERTINGAND#UEINGTESTPROGRAMUSEDTIME MULTIPLEXEDBEAMSWHENHITCHHIKINGOFF THE!7!#3TRANSMITTERFORSHORT RANGEAIRSURVEILLANCE 0ULSE#HASING )FTHETRANSMITTERSBEAMSCANNINGANDPULSETRANSMISSIONSCHED ULEAREKNOWN PULSECHASINGCANBECONSIDEREDTOREDUCETHEMULTIBEAMCOSTPEN ALTY FURTHER n 4HIS WAS SUCCESSFULLY DEMONSTRATED IN THE "ISTATIC 2ADAR FOR 7EAPONS,OCATIONTESTPROGRAM4HESIMPLESTPULSE CHASINGCONCEPTUSESASINGLE BEAMAND230THATRAPIDLYSCANSTHEVOLUMECOVEREDBYTHETRANSMITBEAM CHASING THEPULSEASITPROPAGATESFROMTHETRANSMITTER4HERECEIVEBEAM SCANNINGRATEMUST BEATTHETRANSMITTERSPULSEPROPAGATIONRATE MODIFIEDBYTHEUSUALGEOMETRICCONDI TIONS4HISRATE P2 WASINITIALLYIDENTIFIEDBY*ACKSONANDSUBSEQUENTLYVERIFIEDBY -OYERAND-ORGAN
P2 C TAN A 22
&OROPERATIONINTHECO SITEREGIONSEE4ABLE P2 CANVARYFROMnMSNEARTHE BASELINETOnMSWHEN24 22 ,4YPICAL P2 CONTOURSARESHOWNIN*ACKSON 4HESE RATES AND RATE CHANGES REQUIRE AN INERTIALESS ANTENNA FOR EXAMPLE A PHASED ARRAYWITHDIODEPHASESHIFTERS.ORMALLY APHASEDARRAYANTENNAUSEDFORSURVEILLANCE ISPROGRAMMEDTOSWITCHBEAMSININCREMENTSOFABEAMWIDTH&RACTIONALSHIFTSOFA BEAMWIDTHCANBEACHIEVEDBYCHANGINGTHEPHASEOFAFEWSYMMETRIC PAIRSOFPHASE SHIFTERSINTHEARRAY)NTHISWAY APSEUDO CONTINUOUSBEAMSCANCANBEGENERATEDWITH THEREQUIREDRATESANDRATECHANGES "ECAUSEOFPULSEPROPAGATIONDELAYSFROMTHETARGETTOTHERECEIVER THEPOINTING ANGLEOFTHERECEIVEBEAMP2MUSTLAGTHEACTUALPULSEPOSITION&ORANINSTANTANEOUS PULSEPOSITIONTHATGENERATESABISTATICANGLEA P2 P4 A)NTERMSOFTHEBISTATIC TRIANGLE THEREQUIREDRECEIVEBEAM POINTINGANGLEIS
, COS P 4 ¤ ³
P 2 P 4 TAN ¥ 2 ¦ 4 22 , SIN P 4 ´µ
4HE MINIMUM RECEIVE BEAMWIDTH $P2 M REQUIRED TO CAPTURE ALL RETURNS FROM A RANGECELLINTERSECTINGTHECOMMONBEAMAREAISAPPROXIMATEDBY
$P 2 M y CS U TAN A $P 4 24 22
WHERE SU IS THE UNCOMPRESSED PULSE WIDTH AND $P4 IS THE TRANSMIT BEAMWIDTH4HE APPROXIMATIONASSUMESTHATRESPECTIVERAYSFROMTHETRANSMITANDRECEIVEBEAMSARE PARALLEL 4HE APPROXIMATION IS REASONABLE WHEN 24 22 , OR WHEN , CSU %QUATIONSHOWSTHAT$P2 MCHANGESASTHERECEIVEBEAMSCANSOUTTHETRANSMIT BEAM0HASEDARRAYANTENNASOPERATINGWITHADIGITALBEAMFORMER CANACCOMMO DATETHISCHANGE/THERWISE USEOFAFIXEDBEAMWIDTHINCURSASMALLBEAMMISMATCH LOSS!NEXAMPLEISGIVENIN7ILLIS %VEN THOUGH ONE PULSE MUST BE CHASED AT A TIME A HITCHHIKER OPERATING IN THE CO SITEREGIONHASTIMETOCAPTUREALLPULSESFROMAMONOSTATICRADARTHATUSESRANGE UNAMBIGUOUS02&S&URTHERMORE WHENOPERATINGINTHETRANSMIT ORRECEIVE CENTERED OVALSREFERTO4ABLE AHITCHHIKERCANOPERATEWITHRANGE AMBIGUOUS02&S FOR EXAMPLE WHENTRANSMITTEDFROMANAIRBORNERADAR%XAMPLESAREGIVENIN7ILLIS
")34!4)#2!$!2
ÓΰÓ
/THER IMPLEMENTATIONS OF PULSE CHASING ARE POSSIBLE )N ONE CONCEPT THE FIXED MULTIBEAM RECEIVE ANTENNA IS USED AND TWO 230S ARE TIME MULTIPLEXED ACROSS THE MULTIBEAMS/NE230STEPSACROSSTHEEVEN NUMBEREDBEAMS ANDTHEOTHER230STEPS ACROSSTHEODD NUMBEREDBEAMS SOTHATRETURNSINBEAMPAIRSAREPROCESSEDSIMULTANE OUSLY ETC4HISLEAPFROGSEQUENCEISREQUIREDTOCAPTUREALLRETURNS INTHECOMMON BEAMAREA !SECONDCONCEPTUSESTWOBEAMSANDTWO230SSTEP SCANNINGOVERTHEVOLUMECOV EREDBYTHEMULTIBEAMANTENNA)TUSESANIDENTICALLEAPFROGSEQUENCE"OTHCONCEPTS RELAXTHEFRACTIONALBEAMSCANREQUIREMENTSBYEITHERSAMPLINGORSTEPPINGTHEBEAMS INUNITSOFABEAMWIDTH3INCETHEYBOTHPROCESSRETURNSACROSSTWOBEAMWIDTHSBEFORE SWITCHING THEBEAMDWELLTIME4BISAPPROXIMATELY$P2 M22CANDTHESTEPPINGRATE IS4B 4HEAPPROXIMATIONASSUMESNEGLIGIBLEPHASE SHIFTDELAYSANDSETTLINGTIMES -OVING4ARGET)NDICATION-4) CANBEUSEDWITHANYOFTHESEPULSECHASINGIMPLE MENTATIONS ASLONGASTHERECEIVEBEAMPRECISELYRETRACESITSSCANPATTERNONSUCCES SIVESWEEPSTOCAPTURETHESAMECLUTTERSAMPLESOVERTHE-4)PROCESSINGTIME #OMBINATIONS #OMBINATIONSOFTHESEREMEDIESCANBECONSIDERED&OREXAM PLE AFIXEDMULTIBEAMRECEIVEANTENNACANBEUSEDWITHAFIXEDFLOODLIGHTTRANSMIT ANTENNA4HISCONFIGURATIONALLOWSTHERECEIVERTOINTEGRATELONGER SUBJECTTOTARGET CELLMIGRATIONLIMITS WHICH INTURN CANRECOVERSOMEOFTHELOSTRANGEPERFORMANCEOF THEFLOODLIGHTANTENNA)TALSOHASTHEBENEFITSOFINCREASINGDATARATESANDSIMULTANE OUSLYSERVICINGMULTIPLERECEIVERS)TINCURSINCREASEDSIDELOBECLUTTERLEVELS ASWELLAS COMPLEXITYANDCOST3OMEPASSIVEBISTATICRADARSOPERATEINTHISCONFIGURATION WHERE THEFLOODLIGHTTRANSMITTERISPROVIDEDBYA46OR&-BROADCASTSTATION !SINGLERECEIVEBEAMCANBEUSEDWITHATRANSMITANTENNATHATISADAPTIVELYTAPERED TOFLOODONLYTHEANGULARREGIONCOVEREDBYTHERECEIVEBEAMATAGIVENLOOKANGLE WITHTHETAPERINGSUCHTHATTHESIGNAL TO NOISERATIOATTHERECEIVERISHELDCONSTANTAT ALLPOSITIONSALONGTHERECEIVEBEAM4HISSCHEMEISANALOGOUSTOTHEMONOSTATICAIR SURVEILLANCERADARUSINGACOSECANT SQUAREDANTENNAPATTERN WHERETHEECHOISINDE PENDENTOFRANGEFORACONSTANTALTITUDETARGET)THASTHEPOTENTIALOFRESTORINGMUCH OFTHEFRAMETIMEANDRANGEPERFORMANCE BUTINCURSINCREASEDSIDELOBECLUTTERLEVELS ANDINCREASEDTRANSMITTERCOSTANDCOMPLEXITY!NEXAMPLEISGIVENIN7ILLIS .ONCOOPERATIVE2&%NVIRONMENT -OSTPASSIVEBISTATICRADAR0"2 CONCEPTS ANDDEVELOPMENTSEXPLOITCOMMERCIALBROADCASTTRANSMITTERSASTHEIRSOURCEOFRADAR ILLUMINATION&-AND(IGH$EFINITION($ 46TERRESTRIALBROADCASTTRANSMITTERSARE PARTICULARLY ATTRACTIVE DUE TO THEIR HIGH POWER NOISE LIKE WAVEFORMS AND RELATIVELY WIDE BANDWIDTHSn7HEN THESE BROADCAST TRANSMITTERS ARE APPROPRIATELY SITED AND OPERATING THEYCANSUPPORTMANYTYPESOFSURVEILLANCE PARTICULARLYAIRSURVEILLANCE WHICHISOFTENRESTRICTEDFORMONOSTATICRADARSOPERATINGAT6(&5(&4HESURVEILLANCE CANBECOVERTBECAUSEEVENTHETRANSMITTERISUNAWAREITISBEINGEXPLOITEDANDCANBE COUNTER STEALTHDUETOUNAVOIDABLEAIRCRAFTRESONANCESINTHE6(&5(®ION/THER ATTRACTIVEFEATURESARELOWERPRIMEPOWERREQUIREMENTSANDLOWERCOSTSFORTHE0"2 7HILEA0"2CANEXPLOITBOTHCOOPERATIVEANDNONCOOPERATIVEBROADCASTTRANS MITTERS THE 0"2 HAS NO CONTROL OVER THEIR TRANSMISSION OR WAVEFORM PROPERTIES SPECIFICALLY THE TRANSMISSION SCHEDULE EFFECTIVE RADIATED POWER SPATIAL COVERAGE MODULATIONTYPE MODULATIONCONTENT ANDRESULTINGAUTOCORRELATIONFUNCTION ASOUT LINEDEARLIER&URTHERMORE INTERFERENCEFROMTHEHOSTEMITTERANDOTHEREMITTERS ESPE CIALLYINURBANANDSUBURBANAREAS CANSIGNIFICANTLYDEGRADE0"2PERFORMANCE4HIS SECTION SUMMARIZES THE PROBLEMS AND REMEDIES ENCOUNTERED BY A 0"2 EXPLOITING THESEBROADCASTTRANSMITTERS
ÓΰÎä
2!$!2(!.$"//+
7AVEFORMS 4HEEFFECTIVERADIATEDPOWER%20 OFBROADCASTTRANSMITTERSCANVARY FROMAMAXIMUMOF^-7FOR46TRANSMITTERSTOAMINIMUMOF^7FORCELL PHONE TOWERTRANSMITTERS4HEFORMERCANYIELDEQUIVALENTMONOSTATICDETECTIONRANGESOFAIR TARGETSOFnKMTHELATTER nKM WHICHISOFTHEORDEROFTHECELL PHONEWAVE FORMRESOLUTION TYPICALLYKM#ONSEQUENTLYWHENTHESELOW POWEREDTRANSMITTERS AREEVALUATEDFORSHORT RANGEGROUNDORAIRTARGETLOCATIONONLYDOPPLERANDCOARSE $/! DATA ARE AVAILABLE WHICH SEVERELY RESTRICTS LOCATION CAPABILITY AS OUTLINED IN 3ECTION 4HUS THE LOW %20 OF THESE TRANSMITTERS CONSTRAINED BY THE AVAILABLE BANDWIDTHCONSPIRETOSIGNIFICANTLYREDUCETHEIRUTILITYFOR0"2SURVEILLANCE 4HETYPEOFMODULATIONUSEDBYABROADCASTTRANSMITTERISPARTICULARLYIMPORTANT&OR EXAMPLE THE#RYSTAL0ALACE46TRANSMITTERTRIALSIN,ONDONATTEMPTEDRANGE MEASUREMENTSWITHANALOG46WAVEFORMSBUTFOUNDTHATTHEYGENERATEDHIGHRANGESIDE LOBES^D" RANGEAMBIGUITIESEVERYKM ANDMODESTRANGERESOLUTION^KM AND CONCLUDED THAT SUCH WAVEFORMS WERE MORE SUITABLE FOR DOPPLER MEASUREMENTS 4HIS FINDING ESTABLISHED THE PRECEDENCE FOR SUBSEQUENT 0"2 DEVELOPMENTS DOPPLER EXPLOITATIONOFSTABLE NARROW BANDCARRIERLINESIN46TRANSMISSIONSANDRANGEDOPPLER EXPLOITATIONOFTHEWIDERBAND NOISE LIKESPECTRUMOF&-TRANSMISSIONS 4HEMODULATIONCONTENTOFMANYBROADCASTTRANSMITTERSCHANGESASAFUNCTIONOF TIME THEREBYCOMPLICATINGMATCHEDFILTERINGBYTHE0"2SRECEIVER3PECIFICALLY THE RECEIVERMUSTSAMPLEANDSTOREASEGMENTOFTHEDIRECTPATHWAVEFORMANDTHENCROSS CORRELATEITWITHTHERETURNEDECHO ALLINREALTIME3INCECROSS CORRELATIONMUSTBE PERFORMEDOVERTHERANGEOFEXPECTEDTARGETECHOTIMEDELAYSANDORDOPPLERSHIFTS CORRELATIONRECEIVERCOMPLEXITYISINCREASEDWITHRESPECTTOAMATCHED FILTERRECEIVER TYPICALLYUSEDBYMONOSTATICRADAR3UCHCROSS CORRELATIONISNOWFEASIBLETOIMPLE MENT BUTCOMPLICATESANOTHERWISEWELL DEVELOPEDOPERATIONINTHESTABLE MOREPRE DICTABLEMONOSTATICWORLD !RELATEDMODULATIONCONTENTPROBLEMISDEADAIR WHERENOINFORMATIONISBROAD CASTTHUS THEBROADCASTTRANSMITTERMODULATIONGOESTOZEROANDRANGEMEASUREMENT ERRORSINCREASEWITHOUTLIMIT4HISCONDITIONCANOCCURWHENBROADCASTINGATALKSHOW ORCLASSICALMUSIC BUTOCCURSLESSOFTENWITHPOPULARORROCKMUSIC4HEFREQUENCY OFTHISTYPEOFOUTAGEISNOTINSIGNIFICANT OCCURRINGROUGHLYONCEPERSECONDFORTALK BROADCASTS#ONSEQUENTLY ONCEATRACKHASBEENESTABLISHEDANONLINEARTRACKINGFILTER MAYBENEEDEDTOEDITOUTLARGEERRORSPIKESSEE#HAPTEROF7ILLISAND'RIFFITHS 2ADIO &REQUENCY )NTERFERENCE 0ASSIVE BISTATIC RADAR PERFORMANCE IS SUBJECT TO DEGRADATIONBYRADIOFREQUENCYINTERFERENCE2&) FROMBOTHTHEEXPLOITEDBROADCAST TRANSMITTERANDOTHEREMITTERSINSPATIALORFREQUENCYPROXIMITY4HESEEMITTERSCAN INCLUDE BROADCAST COMMUNICATIONS AND NAVIGATION TRANSMITTERS AS WELL AS POWER TOOLS FLUORESCENTLIGHTS COOLINGFANS ANDOLD AUTOMOBILEIGNITIONS WHICHTYPICALLY GENERATEIMPULSIVENOISE 2&)CANARRIVEVIAADIRECTPATHORMULTIPATHANDINCLUDES SCATTERINGFROMTERRAINORSEASURFACES ALSOCALLEDCLUTTER(OWEVER THESIGNALFROMAN EXPLOITEDTRANSMITTERARRIVINGOVERTHEDIRECTTRANSMITTER TO RECEIVERPATH CALLEDTHE DIRECT PATH IS NEARLY ALWAYS THE DOMINANT 2&) SOURCE -ULTIPATH SIGNALS FROM THAT TRANSMITTERARELESSSEVEREBUTCANALSOCONTRIBUTETO2&) 2&) OVER THE DIRECT PATH FROM THE EXPLOITED TRANSMITTER ALSO CALLED DIRECT PATH BREAKTHROUGH ISCOMMONTOALLBUTTHESIMPLEST LOW POWER#7RADAR)TBECOMES
3KY NOISE CONSISTING OF SUN GALACTIC AND ATMOSPHERIC NOISE IS ANOTHER SOURCE OF 2&) WHICH CAN INCREASE THE RECEIVERSNOISETEMPERATUREBYAFACTOROFnATFREQUENCIESBELOW^-(Z(OWEVER THISINCREASEISUSUALLY ORDERSOFMAGNITUDESMALLERTHAN2&)FROMOTHERSOURCESANDCANBEIGNORED
")34!4)#2!$!2
ÓΰΣ
PARTICULARLYSEVEREWHENTHERECEIVERISLOCATEDINDIRECT,/3OFTHETRANSMITTER WHICH MUSTOCCURWHENSURVEILLANCEOFLOW ALTITUDEAIRTARGETSISREQUIRED%QSn )FTHISDIRECTPATHSIGNALISNOTATTENUATED THERECEIVEDSIGNALBECOMESMASKEDINRANGE ANDOFTENMASKEDINDOPPLERBYSIDELOBESOFTHECORRELATEDDIRECTPATHSIGNAL $IRECT PATHBREAKTHROUGHEFFECTSARESIMILARTOTHOSEOFASPOTNOISEJAMMERAND CANBECHARACTERIZEDBYANINCREASEINTHESYSTEMNOISETEMPERATURE 4S &N4O WHERE &NISTHERECEIVERNOISEFIGUREAND4O +3PECIFICALLY THEAMOUNTOFINCREASEIN 4S ANDHENCETHEAMOUNTOFATTENUATION#DPREQUIREDTOREDUCETHEDIRECTPATHSIGNAL TOTHELEVELOF4S IS
#DP 04'4'2 4KO ",K4S
WHERE04 '4 K ANDKAREDEFINEDWITH%Q'2 4ISTHERECEIVINGANTENNAPOWER GAIN IN THE DIRECTION OF THE TRANSMITTER " IS THE INPUT 2& BANDWIDTH AND , IS THE BASELINERANGE &OREXAMPLE IFTHE0"2EXPLOITSATYPICAL&-BROADCASTTRANSMITTERLOCATEDATA KM,/3FROMTHERECEIVER 04'4 K7 K M " K(Z AND, KM !SSUMINGAFIXEDRECEIVINGANTENNABEAMTAILOREDINELEVATIONANDCOVERINGAWIDE AZIMUTHSECTOR WHICHINCLUDESTHETRANSMITTERSITE '2 4MIGHTBED"I!LSO ASSUM ING THE AMBIENT 2&) ENVIRONMENT DESCRIBED BELOW THE NOISE SPECTRAL DENSITY K4S
D"7(ZTHUS #DP D" #OMBINATIONS OF EARTH MASKING ANTENNA SHIELDING SPATIAL CANCELLATION AND SPEC TRALCANCELLATIONCANBEUSEDTOACHIEVETHEREQUIREDDIRECT PATHATTENUATION!BRUTE FORCEREMEDYISTOPHYSICALLYBLOCKTHETRANSMITSIGNALFROMTHERECEIVERWITHASHROUD ORSTRUCTURE ORIFCOVERAGEALLOWS OVER THE HORIZONSEPARATION7HILEMANYORDERSOF MAGNITUDEATTENUATIONAREPOSSIBLEWITHTHESEMASKINGANDSHIELDINGTECHNIQUES ADDI TIONALREDUCTIONISNEARLYALWAYSNECESSARY(OWLANDREPORTEDATWO STAGE SPATIALNOISE CANCELLERWITHANADAPTIVE- STAGELATTICEPREDICTOR- ASTHEFIRSTSTAGEANDAN ADAPTIVE TAPPED DELAY LINE AS THE SECOND STAGE WHICH ACHIEVED ^ D" CANCELLATION OFTHENARROW BANDSTATIONARYDIRECTPATHSIGNAL 4HISCANCELLATIONCOMBINEDWITH MASKINGACHIEVED D"ATTENUATION WHICHSATISFIESTHE#DPREQUIREMENTINTHEABOVE EXAMPLE(OWLANDALSOOBSERVEDTHATRECEIVERDYNAMICRANGEULTIMATELYLIMITSTHEAVAIL ABLECANCELLATION WHICH INTURN ISSETBYTHERECEIVERSANALOG TO DIGITALCONVERTER .EARBYEMITTERSCANSIGNIFICANTLYRAISETHESYSTEMNOISELEVEL SIMPLYTHROUGHSPEC TRALSPILLOVERFROMADJACENTORNEARBYBANDS)NTHE53THE&##MANDATESAGAUSS IAN SPECTRAL ROLL OFF FOR MANY BROADCAST TRANSMITTERS WHICH IS SUFFICIENT TO PREVENT INTERFERENCEINONE WAYHOMERECEIVERSFROMADJACENTTRANSMISSIONS(OWEVER ITIS NOTSUFFICIENTFORTWO WAYRADARRECEIVERS WHICHNECESSARILYMUSTWORKMUCHFARTHER INTOTHERECEIVERNOISE 4HE SEVERITY OF THIS PROBLEM WAS QUANTIFIED BY IN SITU MEASUREMENTS OF SEVERAL 6(& AND 5(& BANDS IN A DENSE URBAN ENVIRONMENT!MBIENT6(& NOISE LEVELS WEREFOUNDTOBETYPICALLYD"GREATERTHANTHERMALNOISEANDDIRECTPATHILLUMINATOR SIGNALSSOMED"GREATERSTILL%VENWITHROBUSTCANCELLATIONTECHNIQUES THERESIDUE OFTHISUNSUPPRESSED2&)WILLINCREASETHE0"2SSYSTEMNOISEFIGUREBYMANYTENS OFDECIBELSAD"NOISEFIGUREAT6(&INURBANANDSEMI RURALAREASISNOTUNCOM MON4HISVALUETRANSLATESINTOANOISESPECTRALDENSITYOFnD"7(Z3IMILAR MEASUREMENTSHAVEBEENMADEAT5(& WITHnD"NOISEFIGURESBEINGOBTAINED USINGSPECTRALCANCELLATIONBYALEAST SQUARESCHANNELESTIMATOR4HESENOISEFIGURES ARESIGNIFICANTLYHIGHERTHANTHOSEOBTAINEDINTHE53RADAR DESIGNATED6(&5(& CHANNELSANDAREAPENALTYFOREXPLOITINGBROADCASTTRANSMITTERSOFOPPORTUNITY
ÓΰÎÓ
2!$!2(!.$"//+
, ,
. * 7ILLIS "ISTATIC 2ADAR ND %D 3ILVER 3PRING -$ 4ECHNOLOGY 3ERVICE #ORP #ORRECTEDANDREPUBLISHEDBY2ALEIGH .#3CI4ECH0UBLISHING )NC . * 7ILLIS AND ( $ 'RIFFITHS EDS !DVANCES IN "ISTATIC 2ADAR 2ALEIGH .# 3CI4ECH 0UBLISHING)NC 2 # (EIMILLER * % "ELYEA AND 0 ' 4OMLINSON h$ISTRIBUTED ARRAY RADAR v )%%% 4RANS VOL!%3 PPn " $ 3TEINBERG 0RINCIPLES OF !PERTURE AND !RRAY 3YSTEM $ESIGN)NCLUDING 2ANDOM AND !DAPTIVE!RRAYS .EW9ORK*OHN7ILEY3ONS "$3TEINBERGAND%9ADIN h$ISTRIBUTEDAIRBORNEARRAYCONCEPTS v)%%%4RANS VOL!%3 PPn "$3TEINBERG h(IGHANGULARMICROWAVERESOLUTIONFROMDISTORTEDARRAYS v0ROC)NT#OMPUT #ONF VOL 4##HESTONAND*&RANK h0HASEDARRAYANTENNAS v#HAPTERIN2ADAR(ANDBOOK -)3KOLNIK ED ND%D .EW9ORK-C'RAW (ILL ,%-ERTERSAND2(4ABELING h4RACKINGINSTRUMENTATIONANDACCURACYONTHE%ASTERN4EST 2ANGE v)%%%4RANS VOL3%4 PPn -ARCH **3CAVULLOAND&*0AUL !EROSPACE2ANGES)NSTRUMENTATION 0RINCETON .*$6AN.OSTRAND #OMPANY "$3TEINBERG ETAL h&IRSTEXPERIMENTALRESULTSFORTHE6ALLEY&ORGERADIOCAMERAPROGRAM v 0ROC)%%% VOL PPn 3EPTEMBER "$3TEINBERG h2ADARIMAGINGFROMADISTRIBUTEDARRAY4HERADIOCAMERAALGORITHMANDEXPERI MENTS v)%%%4RANS VOL!0 PPn 3EPTEMBER h(ANDBOOK FOR .!630!352 3YSTEM /RIENTATION v VOL .AVAL 3PACE 3URVEILLANCE 3YSTEM $AHLGREN 6! *ULY -)3KOLNIK h!NANALYSISOFBISTATICRADAR v)2%4RANS VOL!.% PPn -ARCH *-#ASPERS h"ISTATICANDMULTISTATICRADAR v#HAPTERIN2ADAR(ANDBOOK -)3KOLNIK ED .EW9ORK-C'RAW (ILL"OOK#OMPANY -)3KOLNIK )NTRODUCTIONTO2ADAR3YSTEMS .EW9ORK-C'RAW (ILL"OOK#OMPANY .*7ILLIS h"ISTATICRADAR v#HAPTER IN2ADAR(ANDBOOK -)3KOLNIKED ND%D .EW9ORK-C'RAW (ILL % & %WING h4HE APPLICABILITY OF BISTATIC RADAR TO SHORT RANGE SURVEILLANCE v IN )%% #ONF 2ADAR 0UBL ,ONDON PPn %&%WINGAND,7$ICKEN h3OME!PPLICATIONSOF"ISTATICAND-ULTI "ISTATIC2ADARS vIN)NT 2ADAR#ONF 0ARIS PPn !&ARINAAND%(ANLE h0OSITIONACCURACYINNETTEDMONOSTATICANDBISTATICRADAR v)%%%4RANS VOL!%3 PPn *ULY % (ANLE h3URVEY OF BISTATIC AND MULTISTATIC RADAR v 0ROC )%% VOL PT & PP n $ECEMBER -#*ACKSON h4HEGEOMETRYOFBISTATICRADARSYSTEMS v)%%0ROC VOL PT& PPn $ECEMBER $%.$AVIES h5SEOFBISTATICRADARTECHNIQUESTOIMPROVERESOLUTIONINTHEVERTICALPLANE v )%%%LECTRON,ETT VOL PPn -AY *2&ORRESTAND*'3CHOENENBERGERh4OTALLYINDEPENDENTBISTATICRADARRECEIVERWITHREAL TIMEMICROPROCESSORSCANCORRECTION v)%%%)NT2ADAR#ONF PPn * ' 3CHOENENBERGER AND * 2 &ORREST h0RINCIPLES OF INDEPENDENT RECEIVERS FOR USE WITH CO OPERATIVERADARTRANSMITTERS v2ADIO%LECTRON%NG VOL PPn &EBRUARY % ' -C#ALL h"ISTATIC CLUTTER IN A MOVING RECEIVER SYSTEM v 2#! 2EV PP n 3EPTEMBER
")34!4)#2!$!2
ÓΰÎÎ
(!#ROWDER h'ROUNDCLUTTERISODOPSFORCOHERENTBISTATICRADAR v)2%.AT#ONV2EC PT .EW9ORK PPn ,*#ANTAFIOED 3PACE "ASED2ADAR(ANDBOOK #HAPTER .ORWOOD -!!RTECH(OUSE !&ARINAAND&!3TUDER 2ADAR$ATA0ROCESSING 6OL !DVANCED4OPICSAND!PPLICATIONS 5+2ESEARCH3TUDIES0RESS,TD )3TEIN h"ISTATICRADARAPPLICATIONSINPASSIVESYSTEMS v*OURNALOF%LECTRONIC$EFENSE PPn -ARCH $+"ARTON -ODERN2ADAR3YSTEM!NALYSIS .ORWOOD -!!RTECH(OUSE $+"ARTON PRIVATECOMMUNICATION *UNE 2 , %ASTON AND * * &LEMING h4HE .AVY SPACE SURVEILLANCE SYSTEM v 0ROC )2% VOL PPn 2*,EFEVRE h"ISTATICRADAR.EWAPPLICATIONFORANOLDTECHNIQUE v7%3#/.#ONF2EC 3AN &RANCISCO PPn & , &LEMING AND . * 7ILLIS h3ANCTUARY RADAR v 0ROC -IL -ICROWAVES #ONF ,ONDON /CTOBERn PPn , "OVINO h"ISTATIC RADAR FOR WEAPONS LOCATION v 53 !RMY #OMMUNICATIONS %LECTRONICS #OMMAND &ORT-ONMOUTH .* 2USSIAS!RMS#ATALOG VOL !IR$EFENSE -OSCOW-ILITARY0ARADE,TD h"ARRIER v "ISTATICAL LOW FLYING TARGET DETECTION SYSTEM .IZHNY .OVGOROD 3CIENTIFIC 2ESEARCH 2ADIOTECHNICAL)NSTITUTE -OSCOW ! ' "LYAKHMAN ET AL h&ORWARD SCATTERING RADAR MOVING OBJECT COORDINATE MEASUREMENT v )%%%)NTERNATIONAL2ADAR#ONFERENCE !4HOMSON !'2!6%33OURCEBOOK VERSIONOF THOMSONA FLASHNET *%3ALAHAND*%-ORRIELLO h$EVELOPMENTOFAMULTISTATICMEASUREMENTSYSTEM vIN)%%% )NTERNATIONAL2ADAR#ONFERENCE PPn h-ULTISTATIC MODE RAISES RADAR ACCURACY v !VIATION7EEK AND 3PACE4ECHNOLOGY PP n *ULY *7URMAN 3(ECKMAN AND$"OCCIPPIO h!BISTATICMULTIPLE DOPPLERRADARNETWORK v*OURNAL OF!PPLIED-ETEROLOGY VOL PPn $ECEMBER *7URMAN -2ANDALL #,&RUSH %,OEW AND#,(OLLOWAY h$ESIGNOFABISTATICDUAL DOPPLERRADARFORRETRIEVINGVECTORWINDSUSINGONETRANSMITTERANDAREMOTELOW GAINPASSIVE RECEIVER vINVITEDPAPER 0ROCOFTHE)%%% VOL NO $ECEMBER PPn &*OHNSON 3YNTHETIC!PERTURE2ADAR3!2 (ERITAGE!N!IR&ORCE0ERSPECTIVE /HIO!IR&ORCE !VIONICS,ABORATORY 7RIGHT0ATTERSON!&" *UNE $ # ,ORTI AND - "ALSER h3IMULATED PERFORMANCE OF A TACTICAL BISTATIC RADAR SYSTEM v )%%% %!3#/.2EC0UBL#( !RLINGTON 6! PP !n h"ISTATIC 2ADARS (OLD 0ROMISE FOR &UTURE 3YSTEM v -ICROWAVE 3YSTEMS .EWS PP n /CTOBER % # 4HOMPSON h"ISTATIC RADAR NONCOOPERATIVE ILLUMINATOR SYNCHRONIZATION TECHNIQUES v IN 0ROCOFTHE)%%%.ATIONAL2ADAR#ONFERENCE $ALLAS 48 -ARCHn *$3AHR h2EMOTESENSINGWITHPASSIVERADARATTHE5NIVERSITYOF7ASHINGTON v)%%%'EOSCIENCE AND2EMOTE3ENSING3OCIETY.EWSLETTER PPn $ECEMBER h0ASSIVESYSTEMHINTSATSTEALTHDETECTIONSILENTSENTRY!NEWTYPEOFRADAR v!VIATION7EEKAND 3PACE4ECHNOLOGY .OVEMBER PPn *"ANIAK '"AKER !-#UNNINGHAM AND,-ARTIN h3ILENT3ENTRY4-0ASSIVE3URVEILLANCE v !VIATION7EEKAND3PACE4ECHNOLOGY *UNE !!NDREWS h($46 BASEDPASSIVERADAR vPRESENTEDAT!/#TH-ULTINATIONAL0#2#ONFERENCE 3YRACUSE .9 /CTOBER 2 ! 3IMPSON h3PACECRAFT STUDIES OF PLANETARY SURFACES USING BISTATIC RADAR v )%%% 4RANS 'EOSCIENCEAND2EMOTE3ENSING VOLNO -ARCH
ÓΰÎ{
2!$!2(!.$"//+
$ 0RICHARD 4HE 2ADAR7AR4HE 'ERMAN!CHIEVEMENT n #AMBRIDGE 5+ 0ATRICK 3TEPHENS,TD ! 0RICE )NSTRUMENTS OF $ARKNESS 4HE (ISTORY OF %LECTRONIC 7ARFARE .EW 9ORK #HARLES 3CRIBNERS3ONS 0*+LASS h.AVYIMPROVESACCURACY DETECTIONRANGE v!VIATION7EEKAND3PACE4ECHNOLOGY PPn !UGUST 4ECHNOLOGYINTHE.ATIONAL)NTEREST ,EXINGTON -!-)4,INCOLN,ABORATORY !"ERNARD PRIVATECOMMUNICATION -)4,INCOLN,ABORATORY *ULY 33ATOHAND*7URMAN h!CCURACYOFWINDFIELDSOBSERVEDBYABISTATICDOPPLERRADARNETWORK v *OURNAL/CEAN!TMOS4ECHVOL PPn !%2UVINAND,7EINBERG h$IGITALMULTIPLEBEAMFORMINGTECHNIQUESFORRADARS vIN)%%% %ASCON2EC PPn % % 3WARTZLANDER AND * - -C+AY h! DIGITAL BEAMFORMING PROCESSOR v 2EAL 4IME 3IGNAL 0ROCESSING))) 30)%0ROC VOL PPn ! &ARINA h4RACKING FUNCTION IN BISTATIC AND MULTISTATIC RADAR SYSTEMS v 0ROC )%% VOL PT& PPn $ECEMBER 2"0ATTON *R h/RBITDETERMINATIONFROMSINGLEPASSDOPPLEROBSERVATIONS v)2%4RANSACTIONS ON-ILITARY%LECTRONICS PPn !PRILn*ULY ! &ARINA h4RACKING FUNCTION IN BISTATIC AND MULTISTATIC RADAR SYSTEMS v )%% 0ROC PT& PPn $ECEMBER -)3KOLNIK )NTRODUCTIONTO2ADAR3YSTEMS .EW9ORK-C'RAW(ILL"OOK#O $+"ARTON 2ADAR3YSTEM!NALYSIS $EDHAM -!!RTECH(OUSE )NC + - 3IEGEL ET AL h"ISTATIC RADAR CROSS SECTIONS OF SURFACES OF REVOLUTION v * !PPL 0HYS VOL PPn -ARCH +-3IEGEL h"ISTATICRADARSANDFORWARDSCATTERING vIN0ROC.AT#ONF!ERONAUT%LECTRON -AYn PPn & 6 3CHULTZ ET AL h-EASUREMENT OF THE RADAR CROSS SECTION OF A MAN v 0ROC )2% VOL PPn &EBRUARY *7#RISPIN *RETAL h!THEORETICALMETHODFORTHECALCULATIONOFRADARCROSSSECTIONOFAIRCRAFT ANDMISSIES v5NIVERSITYOF-ICHIGAN 2ADIATION,AB2EPT ( *ULY 2%(IATTETAL h&ORWARDSCATTERINGBYCOATEDOBJECTSILLUMINATEDBYSHORTWAVELENGTHRADAR v 0ROC)2% VOL PPn 3EPTEMBER 2*'ARBACZAND$,-OFFETT h!NEXPERIMENTALSTUDYOFBISTATICSCATTERINGFROMSOMESMALL ABSORBER COATED METALSHAPES v0ROC)2% VOL PPn *ULY -'!NDREASEN h3CATTERINGFROMBODIESOFREVOLUTION v)%%%4RANS VOL!0 PPn -ARCH #2-ULLINETAL h!NUMERICALTECHNIQUEFORTHEDETERMINATIONOFTHESCATTERINGCROSSSECTIONS OFINFINITECYLINDERSOFARBITRARYGEOMETRICCROSSSECTION v)%%%4RANS VOL!0 PPn *ANUARY 2 % +ELL h/N THE DERIVATION OF BISTATIC 2#3 FROM MONOSTATIC MEASUREMENTS v 0ROC )%%% VOL PPn !UGUST 7)+OCK h2ELATEDEXPERIMENTSWITHSOUNDWAVESANDELECTROMAGNETICWAVES v0ROC)2% VOL PPn *ULY +-3IEGELETAL h2#3CALCULATIONOFSIMPLESHAPESBISTATIC v#HAPTERIN-ETHODSOF2ADAR #ROSS 3ECTION!NALYSIS .EW9ORK!CADEMIC0RESS (7EILETAL h3CATTERINGOFELECTROMAGNETICWAVESBYSPHERES v5NIVERSITYOF-ICHIGAN 2ADIAT ,AB3TUD2ADAR#ROSS3ECTIONS8 2EPT 4 CONTRACT!& *ULY 270+INGAND447U 4HE3CATTERINGAND$IFFRACTIONOF7AVES #AMBRIDGE -!(ARVARD 5NIVERSITIES0RESS 2&'OODRICHETAL h$IFFRACTIONANDSCATTERINGBYREGULARBODIES)4HESPHERE v5NIVERSITYOF -ICHIGAN $EPT%LECTR%NG2EPT 4
")34!4)#2!$!2
ÓΰÎx
- -ATSUO ET AL h"ISTATIC RADAR CROSS SECTION MEASUREMENTS BY PENDULUM METHOD v )%%% 4RANS VOL!0 PPn *ANUARY '7%WELLAND30:EHNER h"ISTATICRADARCROSSSECTIONOFSHIPTARGETS v)%%%*/CEAN%NG VOL/% PPn /CTOBER h2ADARCROSS SECTIONMEASUREMENTS v'ENERAL-OTORS#ORPORATION $ELCO%LECTRON$IV2EPT 2 3ANTA"ARBARA #! #'"ACHMAN 2ADAR4ARGETS ,EXINGTON -!,EXINGTON"OOKS P & # 0ADDISON ET AL h,ARGE BISTATIC ANGLE RADAR CROSS SECTION OF A RIGHT CIRCULAR CYLINDER v %LECTROMAGNETICS VOL PPn *)'LASER h"ISTATIC2#3OFCOMPLEXOBJECTSNEARFORWARDSCATTER v)%%%4RANS VOL!%3 PPn *ANUARY # ##HAETAL h!N2#3ANALYSISOFGENERICAIRBORNEVEHICLESDEPENDENCEONFREQUENCYAND BISTATICANGLE vIN)%%%.AT2ADAR#ONF !NN!RBOR -) !PRIL PPn 7!0IERSONETAL h4HEEFFECTOFCOUPLINGONMONOSTATIC BISTATICEQUIVALENCE v0ROC)%%% PPn *ANUARY h"ISTATIC RADARS HOLD PROMISE FOR FUTURE SYSTEMS v -ICROWAVE 3YST .EWS PP n /CTOBER - - 7EINER h-ULTISTATIC RADAR PHENOMENOLOGY TERRAIN SEA SCATTER v 2!$# 42 VOL -AY NOWUNLIMITEDDISTRIBUTION 3 4 #OST h-EASUREMENTS OF THE BISTATIC ECHO AREA OF TERRAIN AT 8 BAND v 4HE /HIO 3TATE 5NIVERSITY !NTENNA,ABORATORY 2EPORT.O -AY 7(0EAKEAND34#OST h4HEBISTATICECHOAREAOFTERRAINAT'(Z vIN)%%%7%3#/. 3ESSION PPn 6 7 0IDGEON h"ISTATIC CROSS SECTION OF THE SEA v )%%% 4RANS !0 PP n -AY 670IDGEON h"ISTATICCROSSSECTIONOFTHESEAFOR"EAUFORDSEA vIN3CIENCEAND4ECHNOLOGY VOL h5SE OF SPACE SYSTEMS FOR PLANETARY GEOLOGY AND GEOPHYSICS v 3AN $IEGO!MERICAN !STRONAUTICAL3OCIETY PPn !2$OMVILLE h4HEBISTATICREFLECTIONFROMLANDANDSEAOF8 BANDRADIOWAVES 0ART) v'%# %LECTRONICS ,TD 3TANMORE %NGLAND -EMORANDUM3,- *ULY !2$OMVILLE h4HEBISTATICREFLECTIONFROMLANDANDSEAOF8 BANDRADIOWAVES 0ART)) v'%# %LECTRONICS ,TD 3TANMORE %NGLAND -EMORANDUM3,- *ULY ! 2 $OMVILLE v4HE BISTATIC REFLECTION FROM LAND AND SEA OF 8 BAND RADIO WAVES 0ART )) SUPPLEMENT v '%# %LECTRONICS ,TD 3TANMORE %NGLAND -EMORANDUM 3,- 3UPPLEMENT *ULY 27,ARSENAND2#(EIMILLER h"ISTATICCLUTTERDATAMEASUREMENTPROGRAM v%NVIRONMENTAL 2ESEARCH)NSTITUTEOF-ICHIGAN 2!$# 42 .OVEMBER !$ ! 27,ARSEN !,-AFFETT 2#(EIMILLER !&&ROMM %,*OHANSEN 2&2AWSON AND&, 3MITH h"ISTATICCLUTTERMEASUREMENTS v)%%%4RANS!0 PPn .OVEMBER 27,ARSEN !-AFFETT &3MITH 2#(EIMILLER AND!&ROMM h-EASUREMENTSOFBISTATIC CLUTTER CROSS SECTION v %NVIRONMENTAL 2ESEARCH )NSTITUTE OF -ICHIGAN &INAL4ECHNICAL 2EPORT 2!$# 42 -AY !$ ! 0%#ORNWELLAND*,ANCASTER h,OW ALTITUDETRACKINGOVERROUGHSURFACES))%XPERIMENTALAND MODELCOMPARISONS vIN)%%%%!3#/. 2ECORD /CTOBER PPn '7%WELLAND30:EHNER h"ISTATICSEACLUTTERRETURNNEARGRAZINGINCIDENCE vIN)%%)NT #ONF2ADAR 0UBLICATION.O ,ONDON /CTOBER PPn '7%WELL h4ECHNIQUESOFRADARREFLECTIVITYMEASUREMENT v#HAPTERIN"ISTATIC2ADAR#ROSS 3ECTION-EASUREMENTS ND%D .##URRIEED .ORWOOD -!!RTECH(OUSE &45LABY 4%6AN$EVENTER *2%AST 4&(ADDOCK AND-%#OLUZZI h-ILLIMETER WAVE BISTATICSCATTERINGFROMGROUNDANDVEGETATIONTARGETS v)%%%4RANS'23 PPn -AY
ÓΰÎÈ
2!$!2(!.$"//+
4 0 +OCHANSKI - * 6ANDERHILL *6 :OLOTAREVSKY AND 4 &ARISS h,OW ILLUMINATION ANGLE BISTATIC SEA CLUTTER MEASUREMENTS AT 8 BAND v IN )%%% )NT #ONF /CEANS -ASTERING THE /CEANS4HROUGH4ECHNOLOGY 0ROC VOL /CTOBERn PPn $*-C,AUGHLIN %"OLTNIEW 97U AND232AGHAVAN h,OWGRAZINGANGLEBISTATIC.#23 OFFORESTEDCLUTTER v%LECTRONICS,ETTERS PPn 3EPTEMBER $*-C,AUGHLIN %"OLTNIEW 232AGHAVAN AND-*3OWA h#ROSS POLARIZEDBISTATICCLUTTER MEASUREMENTS v%LECTRONICS,ETTERS PPn -ARCH $*-C,AUGHLIN 97U 7'3TEVENS 8:HANG -*3OWA AND"7EIJERS h&ULLYPOLARI METRICBISTATICRADARSCATTERINGBEHAVIOROFFORESTEDHILLS v)%%%4RANS!0 / PPn &EBRUARY 2 % 6ANDER 3CHURR AND 0 ' 4OMLINSON h"ISTATIC CLUTTER ANALYSIS v $ECISION 3CIENCES !PPLICATIONS )NC 2!$# 42 !PRIL '/3AUERMANNAND0#7ATERMAN h3CATTERINGMODELING)NVESTIGATIONOFSCATTERINGBYROUGH SURFACES v-)42%#ORPORATION 2EPT-42 !&!, 42 *ANUARY *':ORNIGETAL h"ISTATICSURFACESCATTERINGSTRENGTHATSHORTWAVELENGTHS v9ALE5NIVERSITY $EPT%NG!PPL3CI2EPT#3 !$ ! *UNE %."RAMLEYAND3-#HERRY h)NVESTIGATIONOFMICROWAVESCATTERINGBYTALLBUILDINGS v0ROC )%% VOL PPn !UGUST !%"RINDLYETAL h!*OINT!RMY!IR&ORCEINVESTIGATIONOFREFLECTIONCOEFFICIENTAT#AND+U BANDSFORVERTICAL HORIZONTALANDCIRCULARSYSTEMPOLARIZATIONS v))42ESEARCH)NSTITUTE &INAL 2EPT 42 !$ ! #HICAGO ), *ULY 0 % (OWLAND $ -AKSIMIUK AND ' 2EITSMA h&- RADIO BASED BISTATIC RADAR v )%% 0ROC 2ADAR3ONAR.AVIG VOL NO PPn *UNE 0 % (OWLAND h&- RADIO BASED BISTATIC RADAR v PRESENTED AT !/# TH -ULTINATIONAL 0#2 #ONFERENCE 3YRACUSE .9 /CTOBER 4!3OAMEAND$-'OULD h$ESCRIPTIONOFANEXPERIMENTALBISTATICRADARSYSTEM vIN)%% )NT2ADAR#ONF0UBL PPn %(ANLE h0ULSECHASINGWITHBISTATICRADAR COMBINEDSPACE TIMEFILTERING vIN3IGNAL0ROCESSING ))4HEORIESAND!PPLICATIONS (73CHUSSLERED .ORTH(OLLAND%LSEVIER3CIENCE0UBLISHERS "6 PPn *'3CHOENENBERGERAND*2&ORREST h0RINCIPLESOFINDEPENDENTRECEIVERSFORUSEWITHCO OPERATIVERADARTRANSMITTERS v2ADIO%LECTRON%NG VOL PPn &EBRUARY . &REEDMAN h"ISTATIC RADAR SYSTEM CONFIGURATION AND EVALUATION v 2AYTHEON #OMPANY )NDEPEND$EV0ROJ$ &INAL2EPT%2 $ECEMBER , 2 -OYER h#OMMENTS ON @2ECEIVER ANTENNA SCAN RATE REQUIREMENTS NEEDED TO IMPLEMENT PULSECHASINGINABISTATICRADARRECEIVER v)%%%4RANSON!EROSPACEAND%LECTRONIC3YSTEMS VOL NO P *ANUARY CORRESPONDENCE *&RANKAND*2UZE h"EAMSTEERINGINCREMENTSFORAPHASEDARRAY v)%%%4RANS VOL!0 PPn .OVEMBER $+04AN (3UN 9,U -,ESTURGIE AND(,#HAN h0ASSIVERADARUSINGGLOBALSYSTEMFOR MOBILECOMMUNICATIONSIGNAL4HEORY IMPLEMENTATIONANDMEASUREMENTS v)%%0ROC 2ADAR 3ONAR.AVIG VOL NO *UNE ($'RIFFITHSAND.27,ONG h4ELEVISION BASEDBISTATICRADAR v)%%0ROC 0T& PPn $ECEMBER -)3KOLNIK )NTRODUCTIONTO2ADAR3YSTEMS RD%D .EW9ORK-C'RAW (ILL ($'RIFFITHSETAL h-EASUREMENTANDANALYSISOFAMBIGUITYFUNCTIONSOFOFF AIRSIGNALSFOR PASSIVECOHERENTLOCATION v%LECTRONICS,ETTERS VOL NO *UNE -!2INGERAND'*'LAZER h7AVEFORMANALYSISOFTRANSMISSIONSOFOPPORTUNITYFORPASSIVE RADAR vIN&IFTH)NTERNATIONAL3YMPOSIUMON3IGNAL0ROCESSINGANDITS!PPLICATIONS "RISBANE !USTRALIA !UGUST PPn 2ICHARD,ODWIG PRIVATECOMMUNICATION ,OCKHEED-ARTIN-ISSION3YSTEMS ($'RIFFITHSAND#*"AKER h0ASSIVECOHERENTLOCATIONRADARSYSTEMS0ART0ERFORMANCE PREDICTION v)%%0ROC 2ADAR3ONAR.AVIG VOL NO PPn *UNE
#HAPTER
iVÌÀVÊÊ
ÕÌiÀ ÕÌiÀi>ÃÕÀià °Ê>À> !NALYSISOF)NTEGRATED3YSTEMS 3%,%83ISTEMI)NTEGRATI
Ó{°£Ê /," 1 /" 3INCE7ORLD7AR )) BOTH RADAR AND ELECTRONIC WARFARE %7 HAVE ACHIEVED A VERY HIGHSTATEOFPERFORMANCE -ODERNMILITARYFORCESDEPENDHEAVILYONELECTROMAGNETIC %- SYSTEMSFORSURVEILLANCE WEAPONCONTROL COMMUNICATION ANDNAVIGATIONTHUS ACCESSTO ANDCONTROLOF THE%-SPECTRUMISVITAL%LECTRONICCOUNTERMEASURES%#- ARELIKELYTOBETAKENBYHOSTILEFORCESTODEGRADETHEEFFECTIVENESSOF%-SYSTEMSn !SADIRECTCONSEQUENCE %-SYSTEMSAREMOREANDMOREFREQUENTLYEQUIPPEDWITHSO CALLEDELECTRONICCOUNTER COUNTERMEASURES%##- TOENSUREEFFECTIVEUSEOFTHE%- SPECTRUMDESPITEANENEMYSUSEOF%7ACTIONS 4HISCHAPTERISDEVOTEDTOTHEDESCRIPTIONOFTHE%##-TECHNIQUESANDDESIGNPRIN CIPLESTOBEUSEDINRADARSYSTEMSWHENTHEYARESUBJECTTOAN%#-THREAT3ECTION STARTSWITHARECALLOFTHEDEFINITIONSPERTAININGTO%7AND%##-4HETOPICOFRADAR SIGNALSINTERCEPTIONBY%7DEVICESISINTRODUCEDIN3ECTIONTHEFIRSTSTRATEGYTO BEADOPTEDBYRADARDESIGNERSISTOTRYTOAVOIDINTERCEPTIONBYTHEOPPONENTELECTRONIC DEVICES3ECTIONISDEDICATEDENTIRELYTOTHEANALYSISOFTHEMAJOR%#-TECHNIQUES ANDSTRATEGIES)TISIMPORTANTTOUNDERSTANDTHE%#-THREATTOARADARSYSTEMINORDER TOBEABLETOEFFICIENTLYREACTTOIT4OFACILITATETHEDESCRIPTIONOFTHECROWDEDFAMILY OF%##-TECHNIQUES3ECTIONSTHROUGH ACLASSIFICATIONISATTEMPTEDIN 3ECTION4HEN THETECHNIQUESAREINTRODUCEDACCORDINGTOTHEIRUSEINTHEVARI OUS SECTIONS OF RADAR NAMELY ANTENNA TRANSMITTER RECEIVER AND SIGNAL PROCESSING ! KEY ROLE IS ALSO PLAYED BY THOSE %##- TECHNIQUES THAT CANNOT BE CLASSIFIED AS ELECTRONIC SUCHASHUMANFACTORS METHODSOFRADAROPERATION ANDRADARDEPLOYMENT TACTICS3ECTION 4HEENSUING3ECTIONSHOWSTHEAPPLICATIONOFTHEAFOREMENTIONEDTECHNIQUES TOTHEMOSTCOMMONRADARFAMILIES NAMELY SURVEILLANCE TRACKING MULTIFUNCTIONAL PHASED ARRAY IMAGING ANDOVER THE HORIZONRADARS4HEMAINDESIGNPRINCIPLESEG SELECTIONOFTRANSMITTERPOWER FREQUENCY WAVEFORM ANDANTENNAGAIN ASDICTATEDBY THE%#-THREATAREALSODISCUSSEDINSOMEDETAIL
!LISTOFACRONYMSISATTHEENDOFTHECHAPTERBEFORETHELISTOFREFERENCES
Ó{°£
Ó{°Ó
2!$!2(!.$"//+
4HE CHAPTER ENDS WITH AN APPROACH TO THE PROBLEM OF EVALUATING THE EFFICACY OF %##-AND%#-TECHNIQUES3ECTION 4HEREISALACKOFTHEORYTOPROPERLYQUAN TIFYTHEENDLESSBATTLEBETWEEN%##-AND%#-TECHNIQUES.EVERTHELESS ACOMMONLY ADOPTEDAPPROACHTODETERMINETHE%#-EFFECTONARADARSYSTEMISBASEDONEVALUATION OFTHERADARRANGEUNDERJAMMINGCONDITIONS4HEADVANTAGEOFUSINGSPECIFIC%##- TECHNIQUESCANBETAKENINTOACCOUNTBYCALCULATINGTHERADARRANGERECOVERY !LISTOFACRONYMSUSEDINTHECHAPTERANDTHEREFERENCESAPPEARATTHEENDOF THECHAPTER
Ó{°ÓÊ / , " "9 %7 IS DEFINED AS A MILITARY ACTION INVOLVING THE USE OF %- ENERGY TO DETERMINE EXPLOIT REDUCE ORPREVENTRADARUSEOFTHE%-SPECTRUMn4HEOPERATIONALEMPLOY MENTOF%7RELIESUPONTHECAPTUREOFRADAR%-EMISSIONSUSINGELECTRONICINTELLI GENCE%,).4 DEVICES COLLATINGTHEINFORMATIONINSUPPORTDATABASESTHATARETHEN USED TO INTERPRET %- EMISSION DATA TO UNDERSTAND THE RADAR SYSTEM FUNCTIONS AND TOPROGRAMREACTIONSAGAINSTTHERADAR%7ISORGANIZEDINTOTWOMAJORCATEGORIES ELECTRONICWARFARESUPPORTMEASURES%3- AND%#-"ASICALLY THE%7COMMUNITY TAKESASITSJOBTHEDEGRADATIONOFRADARCAPABILITY4HERADARCOMMUNITYTAKESASITS JOBTHESUCCESSFULAPPLICATIONOFRADARINSPITEOFWHATTHE%7COMMUNITYDOESTHE GOALISPURSUEDBYMEANSOF%##-TECHNIQUES4HEDEFINITIONSOF%3- %#- AND %##-ARELISTEDBELOW o %3-ISTHATDIVISIONOF%7INVOLVINGACTIONSTAKENTOSEARCHFOR INTERCEPT LOCATE RECORD ANDANALYZERADIATED%-ENERGYFORTHEPURPOSEOFEXPLOITINGSUCHRADIATIONS INTHESUPPORTOFMILITARYOPERATIONS4HUS %3-PROVIDESASOURCEOF%7INFORMATION REQUIREDTOCONDUCT%#- THREATDETECTION WARNING ANDAVOIDANCE%#-ISTHATDIVI SIONOF%7INVOLVINGACTIONSTAKENTOPREVENTORREDUCEARADARSEFFECTIVEUSEOFTHE %-SPECTRUM%##-COMPRISESTHOSERADARACTIONSTAKENTOENSUREEFFECTIVEUSEOF THE%-SPECTRUMDESPITETHEENEMYSUSEOF%7 4HETOPICOF%7ISEXTREMELYRICHINTERMS SOMEOFWHICHAREALSOINGENERALUSE INOTHERELECTRONICFIELDS!COMPLETEGLOSSARYOFTERMSINUSEINTHE%#-AND%##- FIELDSISFOUNDINTHELITERATURE
Ó{°ÎÊ /," Ê7,, ÊÊ -1**",/Ê -1, %3-USUALLYCONSISTSOFSEVERALDETECTIONANDMEASUREMENTRECEIVERSANDREALTIME PROCESSORBOARDSDEDICATEDTOTHEINTERCEPTIONOFRADAREMISSIONS4HEIDENTIFICATIONOF SPECIFICEMITTERSISBASEDONCOMPARISONWITHTACTICALORSTRATEGIC%,).4 n%MITTER LOCATIONCANBEADDITIONALLYPROVIDEDTHROUGHSEVERALMETHODSSUCHASTRIANGULATION o3INCETHEPUBLICATIONOFTHESECONDEDITIONOFTHIS(ANDBOOK THE53!IR&ORCECHANGEDSOMEOFTHE%7TERMSWE HAVEGOTTENUSEDTOOVERTHESEMANYYEARS%#-ISNOW%LECTRONIC!TTACK%! %##-IS%LECTRONIC0ROTECTION %0 AND%3-IS%LECTRONIC3UPPORT%3 4HESETERMSARENOTUSEDINTHISCHAPTERBECAUSETHEYARESELDOMUSED BYTHERADARCOMMUNITYWHOSEEMTOPREFERRETAININGTHEMOREFAMILIAREXPRESSIONS%#- %##- AND%3-
%,%#42/.)##/5.4%2 #/5.4%2-%!352%3
Ó{°Î
FROMREMOTESYSTEMSORSINGLEPLATFORMSEQUENTIALBEARINGMEASUREMENTS DIFFERENCE TIMEOFARRIVAL$4O! ORHYPERBOLATION AND0HASE$IFFERENCE2ATE0$2 -ODERN DIGITAL RECEIVER TECHNOLOGY COUPLED WITH STATE OF THE ART DEINTERLEAVING SIGNAL PRO CESSINGTOCLEANLYISOLATEANDIDENTIFYINDIVIDUAL%-EMITTERS WILLENHANCESITUATION AWARENESS 5SING TECHNIQUES SUCH AS TIME AND FREQUENCY DIFFERENCE OF ARRIVAL WILL IMPROVESINGLEANDMULTIPLEPLATFORMSPATIALLOCATIONTHISWILLALLOW%7TOBEUSED TOCUETARGETINGSYSTEMS 2ADARINTERCEPTION WHICHISOFPARTICULARINTERESTINTHISSECTION ISBASEDONTHE RECEPTIONANDMEASUREMENTSOFTHESIGNALSTRANSMITTEDBYRADARSYSTEMSWHETHERPULSE OR#ONTINUOUS7AVE#7 4HEOPERATIONALSCENARIOINWHICH%3-SHOULDOPERATEIS GENERALLYCROWDEDWITHPULSEDRADARSIGNALSFIGURESOF TOMILLIONPULSESPER SECONDAREFREQUENTLYQUOTEDINTHELITERATURE4HECENTERFREQUENCY AMPLITUDE PULSE WIDTH TIMEOFARRIVAL4O! ANDBEARINGOFEACHDETECTEDPULSEAREMEASURED CON VERTEDINDIGITALFORMAT ANDPACKEDINTOAPULSEDESCRIPTORWORD0$7 4HETRAINOF 0$7SARESENTTOAPULSE SORTPROCESSORTHATDEINTERLEAVESTHESEQUENCESBELONGINGTO DIFFERENTEMITTERSANDIDENTIFIES0ULSE2EPETITION)NTERVAL02) VALUESANDMODULATION LAWSRANDOMJITTER STAGGER SWITCHING &URTHERCOMPARISONAGAINSTANEMITTERDATA BASE WHICHCONTAINSTHERANGEOFCHARACTERISTICPARAMETERSFREQUENCY PULSEWIDTH 02) THERELATEDPATTERNOFAGILITYRANDOM STAGGER ETC FOREACHEMITTER THETYPEOF ANTENNASCANNINGPATTERNANDPERIODSPERMITSTHEGENERATIONOFANEMITTERLISTWITHAN IDENTIFICATIONSCORE4HE%3-RECEIVERISUSEDTOCONTROLTHEDEPLOYMENTANDOPERATION OF%#-THELINKBETWEEN%3-AND%#-ISOFTENAUTOMATIC !SINGLERECEIVEDRADARPULSEISCHARACTERIZEDBYANUMBEROFMEASURABLEPARAME TERS4HEAVAILABILITY RESOLUTION ANDACCURACYOFTHESEMEASUREMENTSMUSTALLBETAKEN INTO ACCOUNT WHEN DESIGNING THE DEINTERLEAVING SYSTEM BECAUSE THE APPROACH USED DEPENDSONTHEPARAMETERDATASETAVAILABLE/BVIOUSLY THEBETTERTHERESOLUTIONAND ACCURACYOFANYPARAMETERMEASUREMENT THEMOREEFFICIENTLYTHEPULSE SORTPROCES SORCANCARRYOUTITSTASK(OWEVER THEREARELIMITATIONSONTHEMEASUREMENTPROCESS FROMOUTSIDETHE%3-SYSTEMEG MULTIPATH FROMINSIDETHESYSTEMEG TIMING CONSTRAINTS DEADTIMEDURINGRECEPTION ANDFROMCOST EFFECTIVENESSCONSIDERATIONS !NGLEOFARRIVALISTHEMOSTIMPORTANTSORTINGPARAMETERAVAILABLETOTHEDEINTERLEAV ING PROCESS SINCE THE TARGET BEARING DOES NOT VARY FROM PULSE TO PULSE 4HEREFORE AMPLITUDE COMPARISON MONOPULSE ANTENNAS OR MULTIPLE BASE INTERFEROMETRIC PHASE COMPARISON SYSTEMSAREOFTENUSEDINORDERTOWARRANTBOTHSPATIALCOVERAGEAND PULSE BASEDANGLEOFARRIVALMEASUREMENT-ONOPULSEROTATINGANTENNASCANALSOBE USEDWHENTHETIMETOINTERCEPTISNOTCRITICALTHISISTHE%,).4CASE ANDITISPOSSIBLE TOSCANSEQUENTIALLYTHEOPERATIONALSCENARIO 4HECARRIERFREQUENCYISTHENEXTMOSTIMPORTANTPULSEPARAMETERFORDEINTERLEAV ING!COMMONMETHODOFFREQUENCYMEASUREMENTISTOUSEASCANNINGSUPERHETERO DYNERECEIVERTHATHASTHEADVANTAGEOFHIGHSENSITIVITY GOODFREQUENCYRESOLUTION AND IMMUNITY WITH RESPECT TO THE INTERFERENCE OF NEARBY EMITTERS 5NFORTUNATELY THISTYPEOFRECEIVERHASAPOORPROBABILITYOFINTERCEPTFORTHESAMEREASONSASTHE ROTATINGBEARINGMEASUREMENTSYSTEM4HESITUATIONISMUCHWORSEIFTHEEMITTERIS ALSO FREQUENCY AGILE RANDOM VARIATION OR FREQUENCY HOPPING SYSTEMATIC VARIA TION !COMMONMETHODTOALLOWFORWIDEBANDFREQUENCYMEASUREMENTSISBASED ONINTERFEROMETRICDEVICESTHATPROVIDEINSTANTANEOUSFREQUENCYMEASUREMENTWITH GOODACCURACYANDAREABLETOREJECTSIGNALINTERFERENCEWITHLOWERINTENSITY4HE HIGHERSENSITIVITYANDPROBABILITYOFINTERCEPTIONAREPROVIDEDBYWIDEINSTANTANEOUS BANDSUPERHETERODYNERECEIVERSFOLLOWEDBYBANKSOFCONTIGUOUSRECEIVERCHANNELS
Ó{°{
2!$!2(!.$"//+
3EVERALTECHNOLOGIESHAVEBEENPROPOSEDINTHEPASTSUCHASSURFACEACOUSTICWAVE 3!7 FILTERSAND"RAGGCELLS4HEPREFERREDAPPROACHISBASEDONDIGITALRECEIVERS THATINTEGRATEWIDEBANDSPECTRALANALYSISANDSEVERALPOST DETECTIONFUNCTIONS SUCH ASINTRAPULSEMODULATIONMEASUREMENTANDWAVEFORMCODERECONNAISSANCE 0ULSEWIDTHISANUNRELIABLESORTINGPARAMETERBECAUSEOFTHEHIGHDEGREEOFCORRUP TIONRESULTINGFROMMULTIPATHTRANSMISSION-ULTIPATHEFFECTSCANSEVERELYDISTORTTHE PULSEENVELOPE FOREXAMPLE BYCREATINGALONGTAILTOTHEPULSEANDEVENDISPLACING THEPOSITIONOFTHEPEAK 4HE4O!OFTHEPULSECANBETAKENASTHEINSTANTTHATATHRESHOLDISCROSSED BUTINTHE PRESENCEOFNOISEANDDISTORTION THISBECOMESAVARIABLEMEASUREMENT.EVERTHELESS THE4O!ISUSEDFORDERIVINGTHE02)OFTHERADAR4HEAMPLITUDEOFTHEPULSEISTAKEN ASTHEPEAKVALUE$YNAMIC RANGECONSIDERATIONSMUSTTAKEINTOACCOUNTATLEASTSOME THREEORDERSOFMAGNITUDEFORRANGEVARIATIONANDTHREEORDERSOFMAGNITUDEFORSCAN PATTERNVARIATIONS)NPRACTICE D"INSTANTANEOUSDYNAMICRANGESOUNDSLIKEAMINI MUMVALUEINMANYAPPLICATIONS ITSHOULDBELARGER4HEAMPLITUDEMEASUREMENTIS USEDALONGWITH4O! FORDERIVINGTHESCANPATTERNOFTHEEMITTER 4HECLASSIFICATIONOFRADARINTERCEPTIONSYSTEMSISBASEDONTHETYPEOFREPRESEN TATIONTHEYPROVIDEOFTHEELECTRONICENVIRONMENT!RADARWARNINGRECEIVER272 INANAIRBORNEINSTALLATIONPROVIDESALERTSOFTHEPRESENCEOFTHREATSSUCHASRADARON AMISSILE SUPPLYINGTHERELATIVEBEARINGONACOCKPIT BASEDDISPLAY3EARCHRADARS ARENOTTHEPRIMARYTARGETFORTHESESYSTEMS THOUGHRANGEADVANTAGEDUETOONE WAY PROPAGATIONWITHRESPECTTOTWO WAYPROPAGATIONALLOWSRADARINTERCEPTIONATFARTHER RANGETHANOWNPLATFORMDETECTION2EQUIREDSENSITIVITYVALUESRANGEFROMnD"M D"MILLI7ATTWITHRESPECTTOTHEISOTROPIC TOnD"M%3-ISTHEMOSTCOMPLEX SYSTEMANDUSUALLYCOMPRISESTHECAPABILITYTOPRODUCEAPICTUREOFTHECOMPLETE ELECTRONIC ORDER OF BATTLE IN ITS DEPLOYMENT AREA AND ALERT FUNCTION 4HIS KIND OF SYSTEMISABLETODETECTANDANALYZEEMITTERWAVEFORMSANDSCANNINGPATTERNS4HE REACTION TIME FOR THE RECONNAISSANCE OF THE OPERATIONAL ENVIRONMENT MAY BE LESS THANS THOUGHDANGEROUSEMITTERSANDALERTFUNCTIONSCALLFORTIGHTERCONSTRAINTS 2EQUIREDSENSITIVITYRANGESFROMnD"MTOBETTERTHANnD"M%,).4SYSTEMS ARESIMILARTO%3- BUTMAYNOTREQUIREPROBABILITYOFINTERCEPT4HEREACTION TIMEMAYBEMINUTESORHOURS4HEPURPOSEISNOTTODETECTEMITTERSASSOONASTHEY SWITCHONINTHEOPERATIONALENVIRONMENT BUTTOPROVIDEDETAILEDCHARACTERISTICSOF EMITTERS TO ALLOW THE GENERATION OF AN IDENTIFICATION DATABASE FOR 272 AND %3- SYSTEMS%,).4SYSTEMSENSITIVITYMAYREACHnD"M BUTTHEYDONTNEEDTOPRO VIDESURVEILLANCE ANDTHEYCANREACHSUCHPERFORMANCEBYMEANSOFSEVERAL DIRECTIVEANTENNAS 4HERANGEATWHICHARADAREMISSIONISDETECTEDBYAN272DEPENDSPRIMARILYON THESENSITIVITYOFTHERECEIVERANDTHERADIATEDPOWEROFTHEVICTIMRADAR4HECALCU LATIONOFTHEWARNINGRANGECANBEOBTAINEDBYTHEBASICONE WAYBEACONEQUATION WHICHPROVIDESTHESIGNAL TO NOISERATIO3.2 ATTHE272
¤ 3³ ¤ 0 ³ ¤ 'R L ³ ¤ ³ ' ¥ ¥¦ . ´µ ¦ P 2 ´µ T ¥¦ P ´µ ¥¦ K43 "´µ , AT 272
WHERE0ISTHERADARRADIATEDPOWER2ISTHERANGEFROMTHE272TOTHERADAR'TISTHE TRANSMITTING ANTENNAGAINOFTHERADAR'RISTHERECEIVING ANTENNAGAINOFTHE272K ISTHERADARWAVELENGTHTHEQUANTITYK4S"ISTHETOTALSYSTEMNOISEPOWEROFTHE272 AND,ISTHELOSSES
%,%#42/.)##/5.4%2 #/5.4%2-%!352%3
Ó{°x
%QUATIONISTHEBASISOFPERFORMANCECALCULATIONFORAN272)TISNOTEDTHAT THE272DETECTIONPERFORMANCEISINVERSELYPROPORTIONALTO2RATHERTHANTO2OFTHE RADARTARGETDETECTIONEQUATION&ORTHISREASON THE272CANDETECTARADIATINGRADAR ATDISTANCESFARBEYONDTHOSEOFARADARSOWNTARGETDETECTIONCAPABILITY4HERADAR VERSUS INTERCEPTORPROBLEMISABATTLEINWHICHTHERADARSADVANTAGELIESINTHEUSE OFMATCHEDFILTERING WHICHCANNOTBEDUPLICATEDBYTHEINTERCEPTORITDOESNOTKNOW THEEXACTRADARWAVEFORM WHILETHEINTERCEPTORSADVANTAGELIESINTHEFUNDAMENTAL 2ADVANTAGEOFONE WAYVERSUSTWO WAYRADARPROPAGATIONn,OWPROBABILITYOF INTERCEPT,0) TECHNIQUESAREAPPLIEDTORADARTOWINTHEBATTLEOFhTOSEEANDNOTTOBE SEENvSEE3CHLEHERANDREFERENCESTHEREIN
Ó{°{Ê /," Ê "1 / , -1, 4HEOBJECTIVESOFAN%#-SYSTEMARETODENYINFORMATIONDETECTION POSITION TRACK INITIATION TRACKUPDATE ANDCLASSIFICATIONOFONEORMORETARGETS THATTHERADARSEEKS ORTOSURROUNDDESIREDRADARECHOESWITHSOMANYFALSETARGETSTHATTHETRUEINFORMATION CANNOTBEEXTRACTEDn %#-TACTICSANDTECHNIQUESMAYBECLASSIFIEDINANUMBEROFWAYS IE BYMAIN PURPOSE WHETHERACTIVEORPASSIVE BYDEPLOYMENT BYPLATFORM BYVICTIMRADAR OR BYACOMBINATIONOFTHESEn !NENCYCLOPEDIAOF%#-TACTICSANDTECHNIQUESCAN BEFOUNDINTHELITERATURE (EREDESCRIPTIONISLIMITEDTOTHEMOSTCOMMONTYPES OF%#- %#-INCLUDESBOTHJAMMINGANDDECEPTION*AMMINGISTHEINTENTIONALANDDELIB ERATE TRANSMISSION OR RETRANSMISSION OF AMPLITUDE FREQUENCY PHASE OR OTHERWISE MODULATEDINTERMITTENT #7 ORNOISE LIKESIGNALSFORTHEPURPOSEOFINTERFERINGWITH DISTURBING EXPLOITING DECEIVING MASKING OROTHERWISEDEGRADINGTHERECEPTIONOF OTHERSIGNALSTHATAREUSEDBYRADARSYSTEMSn!JAMMERISANY%#-DEVICETHAT TRANSMITS A SIGNAL OF ANY DUTY CYCLE FOR THE SOLE OR PARTIAL PURPOSE OF JAMMING A RADARSYSTEMn 2ADIOSIGNALSBYSPECIALTRANSMITTERSINTENDEDFORINTERFERINGWITHORPRECLUDINGTHE NORMALOPERATIONOFAVICTIMRADARSYSTEMARECALLEDACTIVEJAMMING4HEYPRODUCEAT THEINPUTOFAVICTIMSYSTEMABACKGROUNDTHATIMPEDESTHEDETECTIONANDRECOGNITIONOF USEFULSIGNALSANDDETERMINATIONOFTHEIRPARAMETERS4HEMOSTCOMMONFORMSOFACTIVE NOISEJAMMINGARESPOT SWEPT ANDBARRAGENOISES3POTNOISEISUSEDWHENTHECENTER FREQUENCYANDBANDWIDTHOFTHEVICTIMSYSTEMTOBEJAMMEDAREKNOWNANDCONFINEDTO ANARROWBAND(OWEVER MANYRADARSAREFREQUENCY AGILEOVERAWIDEBANDASAN%##- AGAINSTSPOTJAMMING)FTHERATEOFFREQUENCYAGILITYISSLOWENOUGH THEJAMMERCAN FOLLOWTHEFREQUENCYCHANGESANDMAINTAINTHEEFFECTOFSPOTJAMMING"ARRAGEORBROAD BANDJAMMINGISSIMULTANEOUSLYRADIATEDACROSSTHEENTIREBANDOFTHERADARSPECTRUMOF INTEREST4HISMETHODISUSEDAGAINSTFREQUENCY AGILESYSTEMSWHOSERATESARETOOFASTTO FOLLOWORWHENTHEVICTIMSFREQUENCYPARAMETERSAREIMPRECISELYKNOWN *AMMERSIZEISCHARACTERIZEDBYTHEEFFECTIVERADIATEDPOWER%20 'J0J WHERE'J ISTHETRANSMITANTENNAGAINOFTHEJAMMERAND0JISTHEJAMMERPOWER 0ASSIVE%#-ISSYNONYMOUSWITHCHAFF DECOYS ANDOTHERREFLECTORSTHATREQUIRENO PRIMEPOWER4HECHAFFISMADEOFELEMENTALPASSIVEREFLECTORSTHATCANBEFLOATEDOR OTHERWISESUSPENDEDINTHEATMOSPHEREOREXOATMOSPHEREFORTHEPURPOSEOFCONFUSING SCREENING OROTHERWISEADVERSELYAFFECTINGTHEVICTIMELECTRONICSYSTEM%XAMPLESARE METALFOILS METAL COATEDDIELECTRICSALUMINUM SILVER ORZINCOVERFIBERGLASSORNYLON
Ó{°È
2!$!2(!.$"//+
BEINGTHEMOSTCOMMON STRINGBALLS ROPE ANDSEMICONDUCTORS #HAFFCONSISTSOF DIPOLESCUTTOAPPROXIMATELYAHALFWAVELENGTHOFTHERADARFREQUENCY)TISSUITABLY PACKAGED TO CONTAIN A BROAD RANGE OF DIPOLE LENGTHS DESIGNED TO BE EFFECTIVE OVER A WIDE FREQUENCY BAND4HE BASIC PROPERTIES OF CHAFF ARE EFFECTIVE SCATTER AREA THE CHARACTERANDTIMEOFDEVELOPMENTOFACHAFFCLOUD THESPECTRAOFTHESIGNALSREFLECTED BYTHECLOUD ANDTHEWIDTHOFTHEBANDTHATCONCEALSTHETARGET &ROMARADAR VIEWPOINT THEPROPERTIESOFCHAFFAREVERYSIMILARTOTHOSEOFWEATHERCLUTTER EXCEPT THATITSBROADBANDINFREQUENCYCANEXTENDDOWNTO6(&4HEMEANDOPPLERFREQUENCY OFTHECHAFFSPECTRUMISDETERMINEDBYTHEMEANWINDVELOCITY WHILETHESPECTRUM SPREADISDETERMINEDBYWINDTURBULENCEANDASHEARINGEFFECTDUETODIFFERENTWIND VELOCITIESASAFUNCTIONOFALTITUDE $ECOYS WHICHAREANOTHERTYPEOFPASSIVE%#- AREACLASSOFPHYSICALLYSMALL RADARTARGETSWHOSERADARCROSSSECTIONS2#3 AREGENERALLYENHANCEDBYUSINGREFLEC TORSORA,UNEBURGLENSTOSIMULATEFIGHTERORBOMBERAIRCRAFT4HEOBJECTIVEOFDECOYS ISTOCAUSEADILUTIONOFTHEASSETSOFTHEDEFENSIVESYSTEM THEREBYINCREASINGTHESUR VIVABILITYOFTHEPENETRATINGAIRCRAFT(OWEVER WHENTHEDECOYSGROWTOOLARGE THEY HAVETOBEENGAGEDIFTHEYARETHOUGHTLARGEENOUGHTOCARRYAWEAPON 0ENETRATION!ID0ENAIDS COULDBEUSEDBYINCOMINGBALLISTICMISSILES"-S 0ENAID DECOYSAREONLYONEOFSEVERALPOSSIBLEPENAIDS!DECOYPROVIDESANOTHERTARGETTHATTHE DEFENSEHASTOHANDLEIFTHEDEFENSECANNOTDISTINGUISHADECOYFROMARE ENTRYVEHICLE 4HEOTHERMAJORTYPEOFACTIVEJAMMERISDECEPTIVE%#-$%#- $ECEPTIONIS THEINTENTIONALANDDELIBERATETRANSMISSIONORRETRANSMISSIONOFAMPLITUDE FREQUENCY PHASE OROTHERWISEMODULATEDINTERMITTENTOR#7SIGNALSFORTHEPURPOSEOFMISLEAD INGINTHEINTERPRETATIONORUSEOFINFORMATIONBYELECTRONICSYSTEMS 4HECATEGORIES OF DECEPTION ARE MANIPULATIVE AND IMITATIVE -ANIPULATIVE IMPLIES THE ALTERATION OF FRIENDLY%-SIGNALSTOACCOMPLISHDECEPTION WHEREASIMITATIVECONSISTSOFINTRODUCING RADIATIONINTORADARCHANNELSTHATIMITATESAHOSTILEEMISSION$%#-ISALSODIVIDED INTOTRANSPONDERSANDREPEATERS4RANSPONDERSGENERATENONCOHERENTSIGNALSTHATEMU LATETHETEMPORALCHARACTERISTICSOFTHEACTUALRADARRETURN2EPEATERSGENERATECOHERENT RETURNSTHATATTEMPTTOEMULATETHEAMPLITUDE FREQUENCY ANDTEMPORALCHARACTERISTICSOF THEACTUALRADARRETURN2EPEATERSUSUALLYREQUIRESOMEFORMOFMEMORYFORMICROWAVE SIGNALSTOALLOWANTICIPATORYRETURNSTOBEGENERATEDTHISISUSUALLYIMPLEMENTEDBY USINGAMICROWAVEACOUSTICMEMORYORADIGITAL2&MEMORY$2&- )NA$2&-SYSTEM THEINPUT2&SIGNALISGENERALLYFIRSTDOWN SHIFTEDINFREQUENCY ANDTHENSAMPLEDWITHAHIGH SPEEDANALOGUE TO DIGITALCONVERTER!$# 4HESAMPLES STOREDINMEMORY CANBEMANIPULATEDINAMPLITUDE FREQUENCY ANDPHASETOGENERATEA WIDERANGEOFJAMMINGSIGNALS4HESTOREDSAMPLESARELATERRECALLED PROCESSEDBYTHE DIGITAL TO ANALOGUECONVERTER$!# UPCONVERTED ANDTRANSMITTEDBACKTOTHEVICTIM RADAR4HEINFORMATIONCONTENTOFANINTERCEPTEDRADARSIGNALISMAINLYCARRIEDINTHE PHASE OF THE SIGNAL AND THEN THE AMPLITUDE IS USUALLY DISCARDED AND ONLY THE PHASE CONTRIBUTIONISQUANTIZEDANDPROCESSED4HEPHASEQUANTIZATIONISPERFORMEDBYTHE $2&-BYMEANSOF-BITSINTO. -LEVELS!FTERTHEPHASEQUANTIZATION INTRODUCED ONTHESIGNALBYTHE$2&- THEJAMMINGSIGNALISTRANSMITTEDBACKTOTHEVICTIMRADAR WITHANINCREASINGDELAYWITHRESPECTTOTHERECEIVEDRADARSIGNAL4HISDELAYISQUANTIZED BYARANGEGATEPULLOFF2'0/ DEVICE!RANGEGATESTEALERSYSTEMLINEARLYDELAYSTHE QUANTIZEDSIGNALINORDERTOGENERATEACONSTANTRANGE RATEFALSETARGET4HEJOINTEFFECT OFPHASEANDDELAYQUANTIZATIONIN$2&-CANBEANALYZEDASREPORTEDIN'RECO 'INI AND&ARINA/THERARTIFACTSINTHEDECEPTIONSIGNALSCANBEINTRODUCEDBYIMPERFECTIONS INTHEDOWN UPCONVERSIONANDDEMODULATIONMODULATIONOFTHESIGNALPERFORMEDINTHE $2&-DEVICE!DETAILEDANALYSISOFTHISKINDOFERRORSISIN"ERGER
%,%#42/.)##/5.4%2 #/5.4%2-%!352%3
Ó{°Ç
4HE$2&-ISTHEPRINCIPALMEANSTOIMPLEMENTADECEPTIONJAMMERTHERANGE GATE STEALERPULLSTHERADAR TRACKINGGATEFROMTHETARGETPOSITIONTHROUGHTHEINTRODUCTION OFAFALSETARGETINTOTHERADARSRANGE TRACKINGCIRCUITS!REPEATERJAMMERSENDSBACK ANAMPLIFIEDVERSIONOFTHESIGNALRECEIVEDFROMTHERADAR4HEDECEPTIONSIGNAL BEING STRONGERTHANTHERADARSRETURNSIGNAL CAPTURESTHERANGE TRACKINGCIRCUITS4HEDECEP TIONSIGNALISTHENPROGRESSIVELYDELAYEDBYUSINGTHE$2&- THEREBYhWALKINGvTHE RANGEGATEOFFTHEACTUALTARGET2'0/TECHNIQUE 7HENTHERANGEGATEISSUFFICIENTLY REMOVEDFROMTHEACTUALTARGET THEDECEPTIONJAMMERISTURNEDOFF FORCINGTHETRACK INGRADARINTOATARGETREACQUISITIONMODE!NOTHERFORMOFDECEPTIONISTHEVELOCITY GATEPULLOFF6'0/ ACOMBINATIONOF2'0/AND6'0/ISALSOPOSSIBLE !NOTHER$%#-TECHNIQUEISCALLEDINVERSE GAINJAMMINGITISUSEDTOCAPTURETHE ANGLE TRACKING CIRCUITS OF A CONICAL SCAN TRACKING RADAR 4HIS TECHNIQUE REPEATS A REPLICAOFTHERECEIVEDSIGNALWITHANINDUCEDAMPLITUDEMODULATIONTHATISTHEINVERSE OF THE VICTIM RADARS COMBINED TRANSMITTING AND RECEIVING ANTENNA SCAN PATTERNS !GAINSTACONICALLYSCANNINGTRACKINGRADAR ANINVERSE GAINREPEATERJAMMERHASTHE EFFECT OF CAUSING POSITIVE FEEDBACK WHICH PUSHES THE TRACKING RADAR ANTENNA AWAY FROM THE TARGET RATHER THAN TOWARD THE TARGET )NVERSE GAIN JAMMING AND 2'0/ ARE COMBINEDINMANYCASESTOCOUNTERCONICAL SCANTRACKINGRADARS4HEVULNERABILITYOF CONICALSCANTOSUCHCOUNTERMEASURESMOTIVATESTHEUSEOFMONOPULSETRACKERSTHATARE ALMOSTALWAYSUSEDINMILITARYTRACKINGRADARS ! DIFFERENT FORM OF $%#- USED AGAINST THE MAIN BEAM OF SURVEILLANCE RADAR ATTEMPTSTOCOVERTHETARGETSSKINRETURNWITHAWIDEPULSEINORDERTOCONFUSETHE RADARSSIGNAL PROCESSINGCIRCUITRYINTOSUPPRESSINGTHEACTUALTARGETRETURN 7HATTHERADARCANDOAGAINST$%#-ISDISCUSSEDLATERSEE3ECTION )N THE DEPLOYMENT OF %#- SEVERAL CLASSES CAN BE SINGLED OUT )N THE STAND OFF JAMMER3/* CASE THEJAMMINGPLATFORMREMAINSCLOSETOBUTOUTSIDETHELETHALRANGE OFENEMYWEAPONSYSTEMSANDJAMSTHESESYSTEMSTOPROTECTTHEATTACKINGVEHICLES 3TAND OFF%#-SYSTEMSEMPLOYHIGH POWERNOISEJAMMINGTHATMUSTPENETRATETHROUGH THERADARANTENNARECEIVINGSIDELOBESATLONGRANGES%SCORTJAMMINGISANOTHER%#- TACTICINWHICHTHEJAMMINGPLATFORMACCOMPANIESTHESTRIKEVEHICLESANDJAMSRADARS TOPROTECTTHESTRIKEVEHICLES -UTUAL SUPPORT ORCOOPERATIVE %#-INVOLVESTHECOORDINATEDCONDUCTOF%#- BYCOMBATELEMENTSAGAINSTACQUISITIONANDWEAPONCONTROLRADARS/NEADVANTAGEOF MUTUAL SUPPORTJAMMINGISTHEGREATER%20AVAILABLEFROMACOLLECTIONOFPLATFORMS INCONTRASTWITHASINGLEPLATFORM(OWEVER THEREALVALUEOFMUTUAL SUPPORTJAMMING ISINTHECOORDINATEDTACTICSTHATCANBEEMPLOYED!FAVORITETACTICEMPLOYEDAGAINST TRACKINGRADARS FOREXAMPLE ISTOSWITCHBETWEENJAMMERSLOCATEDONSEPARATEAIRCRAFT WITHIN THE RADARS BEAMWIDTH 4HIS BLINKING HAS THE EFFECT OF INTRODUCING ARTIFICIAL GLINTINTOTHERADARTRACKINGCIRCUITS WHICH IFINTRODUCEDATTHEPROPERRATETYPICALLY TO(Z CANCAUSETHERADARTOBREAKANGLETRACK)NADDITION BLINKINGHASTHE DESIRABLEEFFECTOFCONFUSINGRADIATIONHOMINGMISSILESTHATMIGHTBEDIRECTEDAGAINST THEJAMMERRADIATIONS 3TAND FORWARDJAMMINGISAN%#-TACTICINWHICHTHEJAMMINGPLATFORMISLOCATED BETWEENTHEWEAPONSYSTEMSANDTHESTRIKEVEHICLESANDJAMSTHERADARSTOPROTECTTHE STRIKEVEHICLES4HESTAND FORWARDJAMMERISUSUALLYWITHINTHELETHALRANGEOFDEFEN SIVE WEAPON SYSTEMS FOR A CONSIDERABLE TIME4HEREFORE ONLY THE USE OF RELATIVELY LOW COSTREMOTELYPILOTEDVEHICLESMIGHTBEPRACTICALTHEYCANASSISTSTRIKEAIRCRAFT ORMISSILESINPENETRATINGRADAR DEFENDEDAREASBYJAMMING EJECTINGCHAFF DROPPING EXPENDABLEJAMMERSORDECOYS ACTINGASDECOYSTHEMSELVES ANDPERFORMINGOTHER RELATED%#-TASKS
Ó{°n
2!$!2(!.$"//+
!SELF SCREENINGJAMMER33* ISUSEDTOPROTECTTHECARRYINGVEHICLE4HISSITUATION STRESSESTHECAPABILITYOFAN%#-SYSTEMRELATINGTOITSPOWER SIGNAL PROCESSING AND %3-CAPABILITIES 3ELF PROTECTION 30 DECOY JAMMING IS AN OFF BOARD TECHNIQUE INTENDED TO CREATE ANGLEDECEPTIONBYCAUSINGAMISSILESEEKERTOTRANSFERANGLETRACKFROMTHETARGETTO ADECOY#ONSEQUENTLY THEMISSILEGUIDESTOWARDTHEDECOYANDAWAYFROMTHETARGET !SELF PROTECTIONDECOYISMOSTLIKELYTOBEUSEDBYLARGEFIGHTERATTACKANDBOMBER AIRCRAFT4HE30DECOYSAREEXPENDABLEORTOWED%XPENDABLEDECOYSAREEJECTEDOR DROPPED FROM THE AIRCRAFT WHEREAS TOWED DECOYS ARE TETHERED BEHIND THE AIRCRAFT %XPENDABLEDECOYSCONTAINMINIATUREJAMMINGSYSTEMSTHATARESMALLENOUGHTOFITINTO ASTANDARDCHAFFFLAREDISPENSER4HEDECOYORIENTSITSELFTOTHEAIRSTREAMBYDEPLOYING LOW DRAGAERODYNAMICFINSSUFFICIENTTOMAINTAINSTABLEFLIGHT4HEDECOYDIVERGESFROM THEVELOCITYVECTOROFTHELAUNCHAIRCRAFTBYNATURALDECELERATIONASARESULTOFAIRSTREAM ANDFALLINGDUETOGRAVITY4HEDECOYTYPICALLYSTARTSRADIATINGJAMMINGSIGNALSTOWARD THEMISSILESEEKERIMMEDIATELYAFTEREJECTIONFROMTHEAIRCRAFTANDCONTINUESRADIATION THROUGHOUTITSFLIGHT$ECOYEJECTIONISTYPICALLYCOMMENCEDWHENTHE272DETECTS INCOMINGRADAR GUIDEDMISSILES-ULTIPLEDECOYSARESOMETIMESDISPENSEDATPREDETER MINEDRATESINORDERTOIMPROVETHECUMULATIVEPROBABILITYOFAIRCRAFTSURVIVAL !TOWEDDECOYISASMALLAERODYNAMICALLYSTABLEBODYTHATHOUSESAMINIATUREJAM MER4HEDECOYISDEPLOYEDBYREELINGITOUTONACABLEBEHINDTHEAIRCRAFTTOAFIXED DISTANCEOROFFSET4HISOFFSETISCHOSENSUCHTHATEVENIFAMISSILEHITSTHEDECOY THE AIRCRAFTWILLNOTBEDAMAGED4HEDECOYCANEITHERBEPOWEREDBYTHEAIRCRAFTVIATHE CABLEORBESELFPOWERED"ESIDESPROVIDINGPOWERTOTHEDECOY THECABLECANALSOBE USEDASADATALINKTOCONTROLJAMMEROPERATION/NCEDEPLOYED THETOWEDDECOYCAN BEGINRADIATINGJAMMINGSIGNALSTOWARDTHEMISSILESEEKER7HENTHETOWEDDECOYIS NOLONGERNEEDED ITISEITHERREELEDINORJETTISONED4HEMAJORDRAWBACKWITHTOWED DECOYSISTHATTHEYMIGHTSEVERELYDEGRADEAIRCRAFTMANEUVERABILITY !CCORDINGTOTHEPLATFORM THEJAMMERCANBECLASSIFIEDASAIRBORNE MISSILE BORNE NAVAL BASED ORGROUND BASED !SPECIALCLASSOFMISSILE BORNETHREATISTHEANTI RADIATIONMISSILE!2- HAVING THEOBJECTIVEOFHOMINGONANDDESTROYINGTHEVICTIMRADAR4HESORTINGANDACQUISITION OFRADARSIGNALSISPRELIMINARILYMADEBYAN%3-SYSTEMAFTERWARDITCUESTHE!2- WHICHCONTINUESHOMINGONTHEVICTIMRADARBYMEANSOFITSOWNANTENNA RECEIVER AND SIGNALPROCESSOR!CQUISITIONDEPENDSONTHEDIRECTIONOFARRIVAL$O! OPERATINGBAND CARRIERFREQUENCY PULSEWIDTH 02) SCANRATE ANDOTHERPARAMETERSOFTHEVICTIMRADAR !N!2-HOMESONTHECONTINUOUSRADIATIONFROMTHERADARSIDELOBESORONTHEFLASHOF ENERGYFROMTHEMAINBEAM!2-BENEFITSFROMTHEONE WAY ONLYRADARSIGNALATTENUA TION(OWEVER !2-RECEIVERSENSITIVITYISAFFECTEDBYMISMATCHINGLOSSESACCURACYIN LOCATINGTHEVICTIMRADARISAFFECTEDBYTHELIMITEDDIMENSIONOFTHE!2-ANTENNA
Ó{°xÊ " /6 -Ê Ê/8" " 9ÊÊ "Ê
Ê/ +1 4HE PRIMARY OBJECTIVE OF %##- TECHNIQUES WHEN APPLIED TO A RADAR SYSTEM IS TO ALLOWTHEACCOMPLISHMENTOFTHERADARINTENDEDMISSIONWHILECOUNTERINGTHEEFFECTS OFTHEENEMYS%#-)NGREATERDETAIL THEBENEFITSOFUSING%##-TECHNIQUESMAY BESUMMARIZEDASFOLLOWS PREVENTIONOFRADARSATURATION ENHANCEMENTOFTHE SIGNAL TO JAMMINGRATIO DISCRIMINATIONOFDIRECTIONALINTERFERENCE REJECTIONOF
%,%#42/.)##/5.4%2 #/5.4%2-%!352%3
Ó{°
FALSETARGETS MAINTENANCEOFTARGETTRACKS COUNTERACTIONOF%3- AND RADAR SYSTEMSURVIVABILITY 4HEREARETWOBROADCLASSESOF%##-ELECTRONICTECHNIQUES3ECTIONn ANDOPERATIONALDOCTRINES3ECTION 3PECIFICELECTRONICTECHNIQUESTAKEPLACE INTHEMAINRADARSUBSYSTEMS NAMELY THEANTENNA TRANSMITTER RECEIVER ANDSIG NALPROCESSOR4ABLESHOWSACATEGORIZATIONOFSOME%##-TECHNIQUESALONG WITH THE %#- TECHNIQUES THAT ARE USED TO COUNTER 3UITABLE BLENDING OF THESE %##-TECHNIQUESCANBEIMPLEMENTEDINTHEVARIOUSTYPESOFRADARS ASDISCUSSED IN3ECTION 4HEENSUINGDESCRIPTIONISLIMITEDTOTHEMAJOR%##-TECHNIQUESTHEREADERSHOULD BEAWARETHATANALPHABETICALLYLISTEDCOLLECTIONOF%##-TECHNIQUESANDANENCY CLOPEDIAOF%##-TACTICSANDTECHNIQUESCANBEFOUNDINTHELITERATURE -ANYOTHER REFERENCESDESCRIBETHE%##-PROBLEM AMONGWHICH3LOCUMBAND7EST -AKSIMOV ETAL 'ROSETAL AND*OHNSONAND3TONERAREWORTHNOTING 4!",% %##-4ECHNIQUES6ERSUS%#-4ECHNIQUE#OUNTERED2EPRODUCEDWITHPERMISSION
FROM3LOCUMBAND7ESTÚ!RTECH(OUSEAND'6-ORRIS %#-4ECHNIQUE#ATEGORY#OUNTERED 2ADAR 3UBSYSTEM
!NTENNA RELATED
%##-4ECHNIQUE ,OWORULTRA LOWSIDELOBES -ONOPULSEANGLETRACKING ,OWCROSS POLARIZEDRESPONSE 3,"SIDELOBEBLANKING 3,#SIDELOBECANCELER %LECTRONICSCAN !DAPTIVERECEIVEPOLARIZATION #ROSSPOLARIZATIONCANCELLATION
,OWCROSS POLARIZEDANTENNA (IGHPOWER 4RANSMITTER 0ULSECOMPRESSION &REQUENCYDIVERSITY RELATED &REQUENCYAGILITY 02&JITTER
2ECEIVER RELATED
3IGNAL PROCESSING RELATED
2'0/MEMORYNULLING "ANDWIDTHEXPANSION "EATFREQUENCYDETECTOR #OVERPULSECHANNELPROCESSING (OME ON JAM ,EADINGTRAILINGEDGETRACK .ARROWBANDDOPPLERNOISEDETECTOR 6ELOCITYGUARDGATES 6'0/RESET 3IGNALREALISM !CCELERATIONLIMITING #ENSOREDORORDEREDSTATISTIC#&!2 $OPPLERRANGERATECOMPARISON 4IMEAVERAGE#&!2 4OTALENERGYTEST
.OISE
&ALSE 4ARGET
¾
¾
2ANGE 6ELOCITY 'ATE 'ATE 0ULL/FF 0ULL/FF
!NGLE ¾ ¾
¾ ¾
¾ ¾
¾
¾ ¾ ¾ ¾
¾ ¾ ¾ ¾
¾ ¾
¾ ¾
¾ ¾
¾ ¾
¾ ¾ ¾ ¾
¾ ¾ ¾
¾ ¾ ¾ ¾ ¾ ¾
¾ ¾ ¾
¾ ¾ ¾
¾
¾
Ó{°£ä
Ó{°ÈÊ /
2!$!2(!.$"//+
, / Ê
"ECAUSE THE ANTENNA REPRESENTS THE TRANSDUCER BETWEEN THE RADAR AND THE ENVIRON MENT ITISTHEFIRSTLINEOFDEFENSEAGAINSTJAMMING4HEDIRECTIVITYOFTHEANTENNAIN THETRANSMISSIONANDRECEPTIONPHASESALLOWSSPACEDISCRIMINATIONTOBEUSEDASAN %##-STRATEGY4ECHNIQUESFORSPACEDISCRIMINATIONINCLUDEANTENNACOVERAGEAND SCANCONTROL REDUCTIONOFMAIN BEAMWIDTH LOWSIDELOBES SIDELOBEBLANKING SIDE LOBECANCELERS ANDADAPTIVEARRAYSYSTEMS3OMEOFTHESETECHNIQUESAREUSEFULDUR INGTRANSMISSION WHEREASOTHERSOPERATEINTHERECEPTIONPHASE!DDITIONALLY SOME AREACTIVEAGAINSTMAIN BEAMJAMMERS ANDOTHERSPROVIDEBENEFITSAGAINSTSIDELOBE JAMMERS "LANKING OR TURNING OFF THE RECEIVER WHILE THE RADAR IS SCANNING ACROSS THE AZI MUTHSECTORCONTAININGTHEJAMMERORREDUCINGTHESCANSECTORCOVEREDAREMEANSTO PREVENTTHERADARFROMLOOKINGATTHEJAMMER#ERTAINDECEPTIONJAMMERSDEPENDON ANTICIPATIONOFTHEBEAMSCANORONKNOWLEDGEORMEASUREMENTOFTHEANTENNASCAN RATE2ANDOMELECTRONICSCANNINGEFFECTIVELYPREVENTSTHESEDECEPTIONJAMMERSFROM SYNCHRONIZINGTOTHEANTENNASCANRATE THUSDEFEATINGTHISTYPEOFJAMMER!HIGH GAINANTENNACANBEEMPLOYEDTOSPOTLIGHTATARGETANDBURNTHROUGHTHEJAMMERS!N ANTENNAHAVINGMULTIPLEBEAMSCANALSOBEUSEDTOALLOWDELETIONOFTHEBEAMCON TAININGTHEJAMMERANDSTILLMAINTAINDETECTIONCAPABILITIESWITHTHEREMAININGBEAMS !LTHOUGH THEY ADD COMPLEXITY COST AND POSSIBLY WEIGHT TO THE ANTENNA REDUCTION OFMAIN BEAMWIDTHANDCONTROLOFCOVERAGEANDSCANAREVALUABLEANDWORTHWHILE %##-FEATURESOFALLRADARS )FANAIRDEFENSERADAROPERATESINASEVERE%#-ENVIRONMENT THEDETECTIONRANGE CANBEDEGRADEDBECAUSEOFJAMMINGENTERINGTHESIDELOBES/NTRANSMIT THEENERGY RADIATED INTO SPATIAL REGIONS OUTSIDE OF THE MAIN BEAM IS SUBJECT TO BEING RECEIVED BY ENEMY 272S OR!2-S &OR THESE REASONS LOW SIDELOBES ARE DESIRABLE ON BOTH RECEIVEANDTRANSMITSEE3CHRANK 0ATTON AND#HAPTERIN&ARINA 3OMETIMES THEINCREASEINMAIN BEAMWIDTHTHATRESULTSFROMLOWSIDELOBESWORSENSTHEPROBLEM OFMAIN BEAMJAMMINGTHISCONSEQUENCESHOULDBECAREFULLYCONSIDEREDINSPECIFYING THEANTENNARADIATIONPATTERN 5SUALLY SPECIFICATIONOFTHESIDELOBESASASINGLENUMBEREG D" MEANS THAT THE PEAK OF THE HIGHEST SIDELOBE IS D" BELOW THE PEAK OF THE MAIN BEAM 4HE AVERAGE OR ROOT MEAN SQUARE RMS SIDELOBE LEVEL IS OFTEN MORE IMPORTANT &OREXAMPLE IFOFTHERADIATEDPOWERISINTHESIDELOBES THEAVERAGESIDELOBE LEVELIS D" WHERED"REFERSTOTHENUMBEROFDECIBELSBYWHICHTHEAVERAGE SIDELOBELEVELISBELOWTHEGAINOFANISOTROPICIDEAL RADIATOR)NTHEORY EXTREMELY LOWSIDELOBESCANBEACHIEVEDWITHAPERTUREILLUMINATIONFUNCTIONSTHATAREAPPRO PRIATELYTAPERED4HISLEADSTOTHEWELL KNOWNTRADEOFFSAMONGGAIN BEAMWIDTH AND SIDELOBELEVEL)NORDERTOKEEPTHEBEAMWIDTHSMALLWITHLOWSIDELOBES ALARGER ANDCOSTLYTHECOSTCOULDNOTBETHATLARGEUNLESSTHERADARUSESANACTIVEAPERTURE ANTENNAISNEEDED4HECHIEFPROBLEMWITHTHELOWSIDELOBEANTENNAINITSEARLYDAYS WASTHATITHADMOREMECHANICALPROBLEMSBECAUSEITWASAWAVEGUIDEARRAYAND NOT A REFLECTOR /THER DESIGN PRINCIPLES INVOLVED IN LOW ANTENNA SIDELOBES ARE THE USEOFRADAR ABSORBENTMATERIALABOUTTHEANTENNASTRUCTURE THEUSEOFAFENCEON GROUNDINSTALLATIONS ANDTHEUSEOFPOLARIZATIONSCREENSANDREFLECTORS4HISMEANS THAT VERY LOW SIDELOBE ANTENNAS ARE COSTLY IN TERMS OF SIZE AND COMPLEXITY WHEN COMPAREDWITHCONVENTIONALANTENNASOFSIMILARGAINANDBEAMWIDTHCHARACTERISTICS 3ECOND ASTHEDESIGNSIDELOBESAREPUSHEDLOWERANDLOWER APOINTISREACHEDWHERE
%,%#42/.)##/5.4%2 #/5.4%2-%!352%3
Ó{°££
MINORERRORCONTRIBUTIONSTOSCATTEREDENERGYRANDOMERRORS ORMISDIRECTEDRADIA TIONSYSTEMATICERRORS BECOMESIGNIFICANT)NPRACTICE PEAKSIDELOBELEVELSASLOW AS TO D"AVERAGELEVEL TO D" CANBEREADILYREALIZEDWITHPHASED ARRAYANTENNASTHATELECTRONICALLYSCAN4OOBTAINSIDELOBESATLEVELS D"DOWN FROM THE MAIN BEAM AVERAGE LEVEL BELOW D" THE TOTAL PHASE ERROR BUDGET ISREQUIREDTOBEINTHEORDEROFnRMSORLESS4HISISDIFFICULTINARRAYSTHATELEC TRONICALLYSCANTHEERRORSINDUCEDBYPHASESHIFTERS ACTIVECOMPONENTS ANDFEED ELEMENTSMUSTBEINCLUDEDINTHISBUDGET!RRAYSHAVEBEENREALIZEDINPRACTICETHAT HAVEPEAKSIDELOBESINTHEVICINITYOFTHE D"LEVELHOWEVER THESEAREGENERALLY MECHANICALLYSCANNED ANDTHELOWERRORBUDGETSAREACHIEVEDBYUSINGALL PASSIVE FEED COMPONENTS 0HASED ARRAY DEVELOPMENTS WHICH DO SCAN ELECTRONICALLY ALSO FORESEE FAIRLY GOOD SIDELOBE PERFORMANCE SEE THE FOLLOWING REFERENCESn FOR A VIEWOFRELEVANTDEVELOPMENTS 4WOADDITIONALTECHNIQUESTOPREVENTJAMMINGFROMENTERINGTHROUGHTHERADARS SIDELOBESARETHESO CALLEDSIDELOBEBLANKING3," ANDSIDELOBECANCELER3,# !N EXAMPLEOFTHEPRACTICALEFFECTIVENESSOFTHE3,"AND3,#DEVICESISPRESENTEDINTHE LITERATURE WHERETHEPLANPOSITIONINDICATOR00) DISPLAYISSHOWNFORARADAR SUBJECT TOAN%#- EQUIPPEDWITHANDWITHOUTTHE3,"AND3,#SYSTEMS /THERDISCRIMINATIONMEANSAREBASEDONPOLARIZATION4HEPOLARIZATIONCHARACTER ISTICSOFARADARCANBEEXPLOITEDAS%##-TECHNIQUESINTWOWAYS&IRST THECROSS POLARIZEDPATTERNIE THEORTHOGONALPOLARIZATIONTOTHEMAINPLANEOFPOLARIZATION OFARADARANTENNASHOULDBEKEPTASLOWASPOSSIBLECONSISTENTWITHRADARSYSTEMCOST 2ATIOSOFCOPOLARIZEDMAIN BEAMPEAKGAINTOCROSS POLARIZEDGAINANYWHEREINTHE ANTENNAPATTERNSHOULDBEGREATERTHAND"TOPROVIDEPROTECTIONAGAINSTCOMMON CROSS POLARIZEDJAMMING4HISISTHOUGHTOFASAN%##-TECHNIQUE BUTITISREALLY NOMORETHANGOODANTENNADESIGN4HECROSS POLARIZEDJAMMINGINTHISCASEATTACKS ADESIGNDEFICIENCYINTHERADAR4HEREQUIREMENTFORGOODCROSS POLARIZATIONDESIGN PRACTICEINARADARANTENNASYSTEMEXTENDSTOANYAUXILIARY%##-ANTENNASASWELL)F THEIRCROSS POLARIZEDGAINSAREHIGH %##-TECHNIQUESSUCHAS3,#AND3,"MAYNOT BEEFFECTIVEAGAINSTCROSS POLARIZEDNOISEORREPEATERJAMMERS )N THE SECOND USE OF POLARIZATION THE RADAR ANTENNA SYSTEM PURPOSELY RECEIVES THE CROSS POLARIZATION COMPONENT OF THE RADAR WAVE IN ADDITION TO THE COPOLARIZED COMPONENT4HETWOORTHOGONALLYPOLARIZEDCOMPONENTSCANBEUSEDTODISCRIMINATE THEUSEFULTARGETFROMCHAFFANDJAMMERONTHEBASISOFTHEIRDIFFERENTPOLARIZATIONS (OWEVER LIMITEDBENEFITSAFEWDECIBELSOFCANCELLATIONRATIO CANBEOBTAINEDAT THE EXPENSE OF A MORE COMPLEX ANTENNA SYSTEM CONSIDER FOR EXAMPLE A PHASED ARRAY WITH RADIATING ELEMENTS ABLE TO SEPARATELY RECEIVE AND POSSIBLY TRANSMIT THE TWOORTHOGONALCOMPONENTSOFARADARWAVE ANDOFADUPLICATIONOFTHERECEIVERAND SIGNALPROCESSING 3IDELOBE"LANKING3," 3YSTEM 4HEPURPOSEOFAN3,"SYSTEMISTOPREVENT THE DETECTION OF STRONG TARGETS AND INTERFERENCE PULSES AS THEY MIGHT APPEAR AFTER PULSECOMPRESSION ENTERINGTHERADARRECEIVERVIATHEANTENNASIDELOBES4HUS 3," ISMAINLYUSEDTOELIMINATEINTERFERENCEFROMOTHERPULSETRANSMISSIONSANDDELIBER ATEPULSE LIKEJAMMING!LSO 3,"ISEFFECTIVEAGAINSTCOHERENTREPEATERINTERFERENCE #2) HEREhCOHERENTvMEANSTHATTHEINTERFERENCETRIESTOMIMICTHECODEDWAVEFORM RADIATED BY THE RADAR APPEARING AS A SPIKE SIGNAL AFTER PULSE COMPRESSIONn ! METHODOFACHIEVINGTHISISTOEMPLOYANAUXILIARYANTENNACOUPLEDTOAPARALLELRECEIV ING CHANNEL SO THAT TWO SIGNALS FROM A SINGLE SOURCE ARE AVAILABLE FOR COMPARISON
Ó{°£Ó
2!$!2(!.$"//+
&)'52% A -AIN AND AUXILIARY ANTENNA PATTERNS FOR THE 3," AFTER ,-AISELÚ)%%%
"YSUITABLECHOICEOFTHEANTENNAGAINS ONEMAYDISTINGUISHSIGNALSENTERINGTHE SIDELOBESFROMTHOSEENTERINGTHEMAINBEAM ANDTHEFORMERMAYBESUPPRESSED &IGURE A ILLUSTRATES THE RADIATION PATTERN OF THE MAIN ANTENNA TOGETHER WITH A LOW GAINAUXILIARYANTENNA!NIMPLEMENTATIONOFTHE3,"PROCESSORISSHOWNIN &IGURE B WHERE THE SQUARE LAW DETECTED OUTPUTS OF THE TWO CHANNELS IDEALLY IDENTICALEXCEPTFORTHEANTENNAPATTERNS ARECOMPARED4HECOMPARISONISMADEAT EACHRANGEBINFOREACHPULSERECEIVEDANDPROCESSEDBYTHETWOPARALLELCHANNELS 4HUS THE3,"DECIDESWHETHERORNOTTOBLANKTHEMAINCHANNELONASINGLE SWEEP BASISANDFOREACHRANGEBIN!TARGET!INTHEMAINBEAMWILLRESULTINALARGESIGNAL INTHEMAINRECEIVINGCHANNELANDASMALLSIGNALINTHEAUXILIARYRECEIVINGCHANNEL! PROPERBLANKINGLOGICALLOWSTHISSIGNALTOPASS4ARGETSANDORJAMMERS*SITUATEDIN THESIDELOBESGIVESMALLMAINBUTLARGEAUXILIARYSIGNALSSOTHATTHESETARGETSARESUP PRESSEDBYTHEBLANKINGLOGIC)TISASSUMEDTHATTHEGAIN'!OFTHEAUXILIARYANTENNA ISHIGHERTHANTHEMAXIMUMGAIN'SLOFTHESIDELOBESOFTHERADARANTENNA 4HEPERFORMANCEOFTHE3,"MAYBEANALYZEDBYLOOKINGATTHEDIFFERENTOUTCOMES OBTAINEDASACONSEQUENCEOFTHEPAIRU V OFTHEPROCESSEDSIGNALSSEE&IGUREB
&)'52%B 3CHEMEOFSIDELOBE BLANKINGSYSTEMAFTER,-AISELÚ)%%%
%,%#42/.)##/5.4%2 #/5.4%2-%!352%3
Ó{°£Î
4HREEHYPOTHESESHAVETOBETESTED THENULLHYPOTHESIS(CORRESPONDINGTOTHE PRESENCEOFNOISEINTHETWOCHANNELS THE(HYPOTHESISPERTAININGTOTHETARGET INTHEMAINBEAM AND THE(HYPOTHESISCORRESPONDINGTOTARGETORINTERFERENCE SIGNALINTHESIDELOBEREGION4HENULLAND(HYPOTHESESCORRESPONDTOTHEUSUALDECI SIONSOFhNODETECTIONvANDhTARGETDETECTION vRESPECTIVELY4HEBLANKINGCOMMANDIS DELIVEREDWHEN(ISDETECTED 3,"PERFORMANCECANBEEXPRESSEDINTERMSOFTHEFOLLOWINGPROBABILITIESI 4HE PROBABILITY0"OFBLANKINGAJAMMERINTHERADARSIDELOBES WHICHISTHEPROBABILITYOF ASSOCIATINGTHERECEIVEDSIGNALSU V WITH(WHENTHESAMEHYPOTHESISISTRUE0" ISAFUNCTIONOFTHEJAMMER TO NOISERATIO*.2 VALUE THEBLANKINGTHRESHOLD& AND THEGAINMARGINA '!'SLOFTHEAUXILIARYANTENNAWITHRESPECTTOTHERADARANTENNA SIDELOBESII 4HEPROBABILITY0&!OFFALSEALARM WHICHISTHEPROBABILITYOFASSOCIAT INGTHERECEIVEDSIGNALSU V WITHTHEHYPOTHESIS(WHENTHETRUEHYPOTHESISIS( 0&!ISAFUNCTIONOFTHEDETECTIONTHRESHOLD@NORMALIZEDTOTHENOISEPOWERLEVELAND OFTHEBLANKINGTHRESHOLD&III 4HEPROBABILITY0$OFDETECTINGATARGETINTHEMAIN BEAM WHICHISTHEPROBABILITYOFASSOCIATINGTHERECEIVEDSIGNALU V WITH(WHEN THESAMEHYPOTHESISISTRUE0$DEPENDS AMONGOTHERTHINGS ONTHESIGNAL TO NOISE POWERRATIO3.2 0&! ANDTHEBLANKINGTHRESHOLD&IV 4HEPROBABILITY0&4OFDETECT INGAFALSETARGETPRODUCEDBYAJAMMERENTERINGTHROUGHTHERADARSIDELOBES0&4IS THEPROBABILITYOFASSOCIATINGU V WITH(WHEN(ISTRUEITISAFUNCTIONOF*.2 THETHRESHOLDS@AND& ANDTHEGAINMARGINAV 4HEPROBABILITY04"OFBLANKING ATARGETRECEIVEDINTHEMAINBEAM4HISISTHEPROBABILITYOFASSOCIATINGU V WITH (WHEN(ISTHETRUEHYPOTHESIS04"ISRELATEDTO3.2 & ANDTHEAUXILIARYGAIN W '!'TNORMALIZEDTOTHEGAIN'TOFTHEMAINBEAM4OCOMPLETETHELISTOFPARAM ETERSNEEDEDTODESCRIBETHE3,"PERFORMANCE THELASTFIGURETOCONSIDERISTHEDETEC TIONLOSS,ONTHEMAIN BEAMTARGET4HISCANBEFOUNDBYCOMPARINGTHE3.2VALUES REQUIREDTOACHIEVEASPECIFIED0$VALUEFORTHERADARSYSTEMWITHANDWITHOUTTHE3," ,ISAFUNCTIONOFMANYPARAMETERSSUCHAS0$ 0&! & '! *.2 ANDA!NUMERICAL EVALUATIONOFTHESEPERFORMANCEPARAMETERSCANBEFOUNDINTHELITERATURESPECIFICALLY #HAPTEROF&ARINA AMONGOTHERSn 4HE3,"DESIGNREQUIRESTHESELECTIONOFSUITABLEVALUESFORTHEFOLLOWINGPARAME TERS#HAPTEROF&ARINA I THEGAINMARGINAANDTHENTHEGAIN'!OFTHEAUXILIARY ANTENNA II THEBLANKINGTHRESHOLD& ANDTHENORMALIZEDDETECTIONTHRESHOLD@4HEA PRIORIKNOWNPARAMETERSAREHYPOTHESIZEDTOBETHERADARSIDELOBELEVEL'SLANDTHEVAL UESOF3.2AND*.24HEDESIGNPARAMETERSCANBESELECTEDBYTRYINGTOMAXIMIZETHE DETECTIONPROBABILITY0$WHILEKEEPINGATPRESCRIBEDVALUESTHEPROBABILITIES0"AND 0&!ANDTRYINGTOMINIMIZE0&4 04" AND,4HECHOICEOFTHEPOSITIONOFTHEAUXILIARY ANTENNAHASANIMPACTON3,"PERFORMANCEINPRESENCE FORINSTANCE OFMULTIPATHTO AVOIDITSEFFECT THEPHASECENTERSOFMAINANDAUXILIARYANTENNASSHOULDBEPOSITIONED ATTHESAMEHEIGHTWITHRESPECTTOTHETERRAINSURFACE )NMODERNRADAR THEBLANKINGOFSIDELOBEIMPULSIVEINTERFERENCEMAYBEACHIEVED BY THE COMPARISON OF SIGNALS PERTAINING TO THE SAME CELLS OF THE RANGE FILTER MAP 2&- OFMAINBEAMAND3,"CHANNELS4HE2&-ISATWO DIMENSIONALMAPCOL LECTINGTHERADARECHOESOFALLRANGECELLSAFTERPULSECOMPRESSION ANDALLDOPPLER FILTERSOFARADARBURST4HETWO2&-SAREINDEPENDENTLYGENERATEDFORTHEMAINAND AUXILIARYSIGNALSANDTHETESTINGOFTHEMAINANDAUXILIARYRECEIVEDPOWERVALUESIS PERFORMEDFORALLRANGECELLSANDALLDOPPLERFILTERS4HISISDIFFERENTFROMACONVEN TIONAL 3," APPROACH SUCH AS THE ONE ILLUSTRATED IN &IGURE OPERATING SO THAT IFINTERFERINGREPEATERJAMMERPOWERISDETECTEDATAPARTICULARRANGECELL THENTHAT RANGECELLHASTOBEEFFECTIVELYBLANKED4HE2&- BASED3,"LOGICGREATLYREDUCES
Ó{°£{
2!$!2(!.$"//+
THERISKOFSUCCESSFULLYEMULATINGAUSEFULTARGETBECAUSEAREPEATERHASTOAPPEARIN THESAMETARGETRANGECELLANDHASTOEMULATETHESAMETARGETDOPPLER 3IDELOBE #ANCELER 3,# 3YSTEM 4HE OBJECTIVE OF THE 3,# IS TO SUPPRESS HIGH DUTY CYCLE OR EVEN CONTINUOUS NOISE LIKE INTERFERENCES .,) EG 3/* RECEIVEDTHROUGHTHESIDELOBESOFTHERADAR4HISISACCOMPLISHEDBYEQUIPPINGTHE RADARWITHANARRAYOFAUXILIARYANTENNASUSEDTOADAPTIVELYESTIMATETHE$O!AND THEPOWEROFTHEJAMMERSAND SUBSEQUENTLY TOMODIFYTHERECEIVINGPATTERNOFTHE RADARANTENNATOPLACENULLSINTHEJAMMERSDIRECTIONS4HE3,#WASINVENTEDBY 0(OWELLSAND3!PPLEBAUMn!SAMPLEOFSUBSEQUENTREFERENCESON3,#ARE ALSOINTHELITERATURE n 4HECONCEPTUALSCHEMEOFAN3,#SYSTEMISSHOWNIN&IGURE4HEAUXILIARY ANTENNAS PROVIDE REPLICAS OF THE JAMMING SIGNALS IN THE RADAR ANTENNA SIDELOBES 4O THIS END THE AUXILIARY PATTERNS APPROXIMATE THE AVERAGE SIDELOBE LEVEL OF THE RADARRECEIVINGPATTERN)NADDITION THEAUXILIARIESAREPLACEDSUFFICIENTLYCLOSETO THEPHASECENTEROFTHERADARANTENNATOENSURETHATTHESAMPLESOFTHEINTERFERENCE THATTHEYOBTAINARESTATISTICALLYCORRELATEDWITHTHERADARJAMMINGSIGNAL)TISALSO NOTEDTHATASMANYAUXILIARYANTENNASARENEEDEDASTHEREAREJAMMINGSIGNALSTO BESUPPRESSED)NFACT ATLEAST.AUXILIARYPATTERNSPROPERLYCONTROLLEDINAMPLITUDE
&)'52% 0RINCIPLE OF 3,# OPERATION CONNECTION A ONLY IN THE CLOSED LOOP IMPLEMENTATIONTECHNIQUES 28RECEIVER
%,%#42/.)##/5.4%2 #/5.4%2-%!352%3
Ó{°£x
ANDPHASEARENEEDEDTOFORCETOZEROTHEMAINANTENNARECEIVINGPATTERNIN.GIVEN DIRECTIONS4HEAUXILIARIESMAYBEINDIVIDUALANTENNASORGROUPSOFRECEIVINGELE MENTSOFAPHASED ARRAYANTENNA 4HEAMPLITUDEANDPHASEOFTHESIGNALSDELIVEREDBYTHE.AUXILIARIESARECONTROLLED BYASETOFSUITABLEWEIGHTSDENOTETHESETWITHTHE. DIMENSIONALVECTOR7 7 7 x 7. 4HEJAMMINGSIGNALISCANCELEDBYALINEARCOMBINATIONOFTHESIGNALSFROMTHE AUXILIARIESANDTHEMAINANTENNA4HEPROBLEMISTOFINDASUITABLEMEANSOFCONTROLLING THEWEIGHTS7OFTHELINEARCOMBINATIONSOTHATTHEMAXIMUMPOSSIBLECANCELLATIONIS ACHIEVED/WINGTOTHESTOCHASTICNATUREOFTHEJAMMINGSIGNALSINTHERADARANDINTHE AUXILIARYCHANNELSANDTOTHEHYPOTHESIZEDLINEARCOMBINATIONOFSIGNALS ITISADVIS ABLETORESORTTOTHETECHNIQUESOFLINEARPREDICTIONTHEORYFORSTOCHASTICPROCESSES $ENOTEWITH6- THERADARSIGNALATACERTAINRANGEBINANDWITH6 6 6 x 6. THE. DIMENSIONALVECTORCONTAININGTHESETOFSIGNALS ATTHESAMERANGEBIN FROMTHE .AUXILIARYANTENNAS)TISASSUMEDTHATALLTHESIGNALSHAVEBANDPASSFREQUENCYSPEC TRATHEREFORE THESIGNALSCANBEREPRESENTEDBYTHEIRCOMPLEXENVELOPES WHICHMODU LATEACOMMONCARRIERFREQUENCYTHATDOESNOTAPPEAREXPLICITLY4HEJAMMINGSIGNALS INTHECHANNELSMAYBEREGARDEDASSAMPLESOFASTOCHASTICPROCESSHAVINGZEROMEAN VALUEANDACERTAINTIMEAUTOCORRELATIONFUNCTION&ORLINEARPREDICTIONPROBLEMS THE SET OF SAMPLES 6 IS COMPLETELY DESCRIBED BY ITS . DIMENSIONAL COVARIANCE MATRIX - %6 64 WHERE% DENOTESTHESTATISTICALEXPECTATION THEASTERISK INDICATES THECOMPLEXCONJUGATE AND64ISTHETRANSPOSEVECTOROF64HESTATISTICALRELATIONSHIP BETWEEN 6- AND 6 IS MATHEMATICALLY REPRESENTED BY THE . DIMENSIONAL COVARIANCE }ISDETERMINEDBYMINIMIZINGTHE VECTOR2 %6-6 4HEOPTIMUMWEIGHTVECTOR7 MEANSQUAREPREDICTIONERROR WHICHEQUALSTHEOUTPUTRESIDUALPOWER } 4 6 \] 0: %[\ : \] %[\ 6- 7
WHERE : IS THE SYSTEM OUTPUT )T IS FOUND THAT THE FOLLOWING FUNDAMENTAL EQUATION APPLIES } L- 2 7
WHERELISANARBITRARYCONSTANTVALUE4HEBENEFITOFUSINGTHE3,#CANBEMEASURED BYINTRODUCINGTHEJAMMERCANCELLATIONRATIO*#2 DEFINEDASTHERATIOOFTHEOUTPUT NOISEPOWERWITHOUTANDWITHTHE3,#
*#2
%[\ 6- \] %[\ 6- \]
4
4 } %[\ 6- 7 6 \ ] %[\ 6- \ ] 2 - 2
"YAPPLYING%QSANDTOTHESIMPLECASEOFONEAUXILIARYANTENNAANDONE JAMMER THEFOLLOWINGRESULTSAREFOUND
} %[6- 6! ] $ R 7 %[\ 6! \ ]
*#2
\ R \
)TISNOTEDTHATTHEOPTIMUMWEIGHTISRELATEDTOTHECORRELATIONCOEFFICIENTQBETWEEN THEMAINSIGNAL 6- ANDTHEAUXILIARYSIGNAL 6!HIGHVALUESOFTHECORRELATIONCOEF FICIENTPROVIDEHIGHVALUESOF*#2 4HEPROBLEMOFIMPLEMENTINGTHEOPTIMUM WEIGHTSET%Q ISESSENTIALLYRELATED TO THE REAL TIME ESTIMATION OF - AND 2 AND TO THE INVERSION OF - 3EVERAL PROCESSING
Ó{°£È
2!$!2(!.$"//+
SCHEMESHAVEBEENCONCEIVEDTHATMAYBECLASSIFIEDINTWOMAINCATEGORIES CLOSED LOOPTECHNIQUES INWHICHTHEOUTPUTRESIDUECONNECTIONAIN&IGURE ISFEDBACKINTO THEADAPTIVESYSTEMAND DIRECT SOLUTIONMETHODS OFTENREFERREDTOASOPEN LOOP WHICH OPERATEJUSTONTHEINCOMINGSIGNALS6-AND6"ROADLYSPEAKING CLOSED LOOPMETHODSARE CHEAPERANDSIMPLERTOIMPLEMENTTHANDIRECT SOLUTIONMETHODSONEOFSEVERALPRACTICAL IMPLEMENTATIONSISDESCRIBEDIN'RIFFITHS"YVIRTUEOFTHEIRSELF CORRECTINGNATURE THEYDO NOTREQUIRECOMPONENTSTHATHAVEAWIDEDYNAMICRANGEORAHIGHDEGREEOFLINEARITY AND SOTHEYAREWELLSUITEDTOANALOGUEIMPLEMENTATION(OWEVER CLOSED LOOPMETHODSSUFFER FROMTHEFUNDAMENTALLIMITATIONTHATTHEIRSPEEDOFRESPONSEMUSTBERESTRICTEDINORDERTO ACHIEVEASTABLEANDNOTNOISYSTEADYSTATE$IRECT SOLUTIONMETHODS ONTHEOTHERHAND DO NOTSUFFERFROMPROBLEMSOFSLOWCONVERGENCEBUT INGENERAL REQUIRECOMPONENTSOFSUCH HIGHACCURACYANDWIDEDYNAMICRANGETHATTHEYCANONLYBEREALIZEDBYDIGITALMEANS/F COURSE CLOSED LOOPMETHODSCANALSOBEIMPLEMENTEDBYUSINGDIGITALCIRCUITRYINWHICH CASE THECONSTRAINTSONNUMERICALACCURACYAREGREATLYRELAXED ANDTHETOTALNUMBEROF ARITHMETICOPERATIONSISMUCHREDUCEDBYCOMPARISONWITHDIRECT SOLUTIONMETHODS4HE MAJORITYOFIMPLEMENTATIONSHASBECOMEOPENLOOPWITHDIGITALTECHNOLOGY 0RACTICAL CONSIDERATIONS SEE #HAPTER OF &ARINA FOR A DETAILED ANALYSIS OFTEN LIMITTHE3,#NULLINGCAPABILITIESTOA*#2OFABOUTTOD" BUTTHEIRTHEORETI CALPERFORMANCEISPOTENTIALLYMUCHHIGHER!DEQUATECANCELLATIONOFTHEDIRECTIONAL INTERFERENCEISOBTAINEDIFTHERECEIVINGCHANNELSAREPROPERLYMATCHEDINAMPLITUDE ANDPHASEACROSSTHERADARRECEIVINGBANDWIDTH4HISCONDITIONISNECESSARYTOATTRI BUTETHEAMPLITUDEANDPHASEDIFFERENCESMEASUREDACROSSTHECHANNELSONLYTOTHE NATUREPOWERAND$O! OFTHEIMPINGINGINTERFERENCE4HEREARESEVERALSOURCESOF MISMATCHINGTHEIMPERFECTMATCHINGOFTHEANALOGUERECEIVINGCHANNELSISONEOFTHE MAINLIMITATIONSTOTHEINTERFERENCECANCELLATION4HEEFFECTOFTHISMISMATCHONTHE *#2HASBEENSTUDIEDINTHELITERATURESEE&ARINAANDREFERENCESTHEREIN &ORCONTEMPORARYPRESENCEOFAMPLITUDEANDPHASEMISMATCHES THE*#2HASAN EXPRESSIONTHATISDERIVEDIN!PPENDIX!NUMERICALAPPLICATIONOFTHISEQUATIONIS SHOWNIN&IGURETHEPARAMETERVALUESOFTHESTUDYCASEAREQUOTEDIN&ARINA &IGURESHOWSTHE*#2CONTOURCURVESVERSUSTHENORMALIZEDAMPLITUDEANANDTHE PHASEBDEGREES MISMATCHESOFTHEANALOGUERECEIVINGCHANNELSSEE&ARINAFORTHE PRECISEDEFINITIONOFTHESEPARAMETERS )TISSEENTHATTOHAVED"OF*#2 ONENEEDSTOSPECIFYTIGHTREQUIREMENTSFOR BOTHAMPLITUDEBELOW ANDPHASEBELOW MISMATCHES4HISFIGUREMOTIVATES THENEEDTORESORTTOEQUALIZATIONDIGITALFILTERSTOCOMPENSATEFORTHEMISMATCHESOF THEAUXILIARYCHANNELSINTHEIRANALOGUEPART WITHRESPECTTOTHEMAINCHANNEL4HIS SUBJECTISCOVEREDIN&ARINAANDREFERENCESTHEREIN%XAMPLESOFOTHERPOSSIBLELIMI TATIONSTOCANCELLATIONARELISTEDBELOW -ISMATCHBETWEENTHEMAINANDAUXILIARYSIGNALSINCLUDINGTHEPROPAGATIONPATHS THEPATTERNSOFTHEMAINANDAUXILIARYANTENNAS THEPATHSINTERNALTOTHESYSTEMUP TOTHECANCELLATIONPOINT ANDTHECROSSTALKBETWEENTHECHANNELSn 4HELIMITEDNUMBEROFAUXILIARYCHANNELSADOPTEDINAPRACTICALSYSTEMASCOM PAREDWITHTHENUMBEROFJAMMINGSIGNALS !PERTURE FREQUENCY DISPERSION OFTEN EXPRESSED IN TERMS OF APERTURE BANDWIDTH PRODUCT 4HELIMITEDBANDWIDTHOFTHEMAJORITYOFTHESCHEMESIMPLEMENTING%Q AS COMPAREDWITHTHEWIDEBANDOFABARRAGEJAMMERTHATCANBEREGARDEDASACLUSTER SPREADINANGLE OFNARROWBANDJAMMERS 1UADRATUREERRORSINSYNCHRONOUSIE ) 1 DETECTORSn
%,%#42/.)##/5.4%2 #/5.4%2-%!352%3
Ó{°£Ç
&)'52% #ONTOURCURVEOF*#2D" VERSUSTHEAMPLITUDEINNATURAL NUMBER ALONGTHEHORIZONTALAXIS ANDPHASEINDEGREES ALONGTHEVERTICALAXIS MISMATCHESOFTHEANALOGUERECEIVINGCHANNELS
$IGITALRECEIVERCHANNELERRORSSUCHAS!$#QUANTIZATION SAMPLEHOLDJITTER AND DIGITALCONVERTEROFFSET 4HEPULSEWIDTHTHATLIMITSTHEREACTIONTIMEOFTHEADAPTIVESYSTEM INORDERTO AVOIDTHECANCELLATIONOFTARGETSIGNAL 4HETARGETSIGNALINTHEAUXILIARYARRAYTHATMAYRESULTINNONNEGLIGIBLESTEERINGOF THEAUXILIARIESTOWARDTHEMAIN BEAMDIRECTION -ULTIPATHDELAY OFTENEXPRESSEDINTERMSOFDELAY BANDWIDTHPRODUCTn 4HEPRESENCEOFCLUTTERTHAT IFNOTPROPERLYREMOVED MAYCAPTURETHEADAPTIVESYS TEM GIVINGRISETONULLSALONGDIRECTIONSDIFFERENTFROMTHOSEOFTHEJAMMERS 4HETRADEOFFTHATHASTOBESOUGHTBETWEENTHEACCURACYOFWEIGHTSESTIMATIONAND THEREACTIONTIMEOFTHEADAPTIVESYSTEM 4HELIMITEDNUMBEROFTIMESAMPLESAVAILABLETOESTIMATETHEJAMMERCOVARIANCE MATRIX USUALLY . SAMPLE SHOULD BE AVAILABLE IF . IS THE NUMBER OF ADAPTIVE CHANNELS 4HE ANTENNA ROTATION RATE THAT MIGHT PRODUCE A FAST TIME VARYING POWER AND JAMMER$O! *OINT3,"AND3,# 3,"ISEFFECTIVEAGAINSTSPIKYSIGNALAFTERPULSECOMPRES SIONLIKE#2) WHEREAS3,#COMBATSTHECONTINUOUS.,)!SPREVIOUSLYSTATED BOTH TECHNIQUES COMBAT THE INTERFERENCES IMPINGING ON THE MAIN ANTENNA SIDELOBES4HE TWOTECHNIQUESCANBEJOINTLYUSEDAGAINSTTHESIMULTANEOUSPRESENCEOF#2)AND.,) !NAPPROACHISTOCASCADETHE3,#AND3,"TECHNIQUESASSHOWNIN&IGURE4HE SCHEMEDEPICTSTHREERECEIVINGCHANNELS EACHONEHAVINGANANTENNA ARECEIVER AND AN!$# THEY PROVIDE THREE SIGNALS LABELED RESPECTIVELY AS 3,# -!). AND 3," 4HELEFT HANDSIDEANTENNAISALOW GAINAUXILIARYPERFORMINGTHE3,#PROCESSINGIN
Ó{°£n
2!$!2(!.$"//+
! "
!
!
!
#
#
#
#
!
# #
&)'52% !PROCESSINGSCHEMEINCORPORATING3,#AND3,"DEVICES
THEMAINANDSIDELOBEBLANKINGCHANNELS4HECENTERANTENNAISTHEHIGH GAINRADAR ANTENNATODETECTTARGETSNOTWITHSTANDINGIMPULSIVEANDNOISE LIKEINTERFERENCES4HE RIGHT HAND SIDE ANTENNA IS A LOW GAIN AUXILIARY THAT IS USED FOR 3," PROCESSING IN THEMAINCHANNEL4HEADAPTIVECANCELLATIONOF.,)RECEIVEDBYTHEMAINANTENNAIS ACHIEVEDBYTHELINEARCOMBINATIONOFTHE3,#AND-!).SIGNALSWITHTHEADAPTIVE WEIGHTS7AND RESPECTIVELYTHERESULTINGADAPTEDSIGNAL-!).gDOESNTCONTAINTHE .,)3IMILARLY THEADAPTIVECANCELLATIONOF.,)RECEIVEDBYTHERHSAUXILIARYANTENNA ISREACHEDBYTHELINEARCOMBINATIONOFTHE3,#AND3,"SIGNALSWITHTHEADAPTIVE WEIGHTS7AND RESPECTIVELYTHEADAPTEDSIGNAL3,"gDOESNTCONTAINTHE.,)/NCE THE.,)ISREMOVEDFROMTHETWOCHANNELS THENTHECLASSIC3,"LOGICCANBEAPPLIED AGAINSTTHE#2)BYCOMPARINGTHEAMPLITUDE\-!).g\OFTHEMAINCHANNELWITHTHAT \3,"g\OFTHEBLANKINGCHANNEL WHICHAREBOTH.,)FREE "ECAUSETHEPHASECENTERSOFTHETHREEANTENNASTHEMAINANDTHETWOAUXILIARIES ARE SPACED IN GENERAL MORE THAN K WHERE K IS THE LENGTH OF THE RADIATED %- WAVE THEADAPTEDPATTERNSOFTHEMAINAND3,"CHANNELSFLUCTUATEAROUNDAVERAGE CURVESDUETOTHEPRESENCEOFGRATINGLOBES.EVERTHELESS AREASONABLEGAINMARGIN ISPRESENTBETWEENTHEPATTERNOFTHEADAPTED3,"ANDTHESIDELOBESOFTHEADAPTED MAINANTENNATHUS ANADEQUATEPROBABILITYOFBLANKINGTHE#2)INTHEPRESENCEOF ADAPTIVELYNULLED.,)SHOULDBEEXPECTED)NORDERTOIMPROVETHEABOVEGAINMARGIN AND CONSEQUENTLY THEBLANKINGPROBABILITYOF#2) THEFOLLOWINGPROCESSINGSTRATEGIES ARESUGGESTED SPATIALANDFREQUENCYDIVERSITY 3PATIAL$IVERSITY 4HERATIONALEISTOUSETWOLOW GAINAUXILIARIESINSTEADOFONE ASSHOWNIN&IGURE FORTHE3,"BECAUSETHEIRPHASECENTERSWILLBEDIFFERENT THE GRATINGLOBESAFFECTINGTHEADAPTEDPATTERNSOFTHETWO3,"ANTENNASWILLBEDIFFERENT TOO4AKINGTHEGREATEROFTHETWOADAPTED3,"SIGNALS THEGAINMARGINBETWEENTHE 3,"ANDTHEMAINANTENNASIDELOBESWILLINCREASEWITHACONSEQUENTIMPROVEMENTOF THEPERFORMANCEOFTHEBLANKINGLOGIC
%,%#42/.)##/5.4%2 #/5.4%2-%!352%3
Ó{°£
&REQUENCY$IVERSITY !NOTHERTECHNIQUETOIMPROVETHEBLANKINGPERFORMANCE ISTORESORTTOTHEDIVERSITYOFTHERADARCARRIERFREQUENCYINTHISCASE WENEEDJUST ONELOW GAINANTENNAASSHOWNIN&IGURE FORTHE3,"4HERADAROPERATES INFREQUENCYDIVERSITYMODE IE ITRADIATESABURSTOF,PULSES4SECONDSAPART WITHSLIGHTLYDIFFERENTCARRIERFREQUENCIES4HEGRATINGLOBESINTHEADAPTEDMAIN ANDTHE,3,"PATTERNSWILLCHANGEASAFUNCTIONOFTHECARRIERFREQUENCY4AKING THEMAXOFTHEOUTPUTOFTHE,3,"SIGNALSISEQUIVALENTTOASMOOTHINGOFTHEGRAT INGLOBES)NASPECIFICEXAMPLEPRESENTEDIN&ARINAAND4IMMONERI TWOCARRIER FREQUENCIESAREUSEDANDTHEVALUESOFDKWHEREhDvISTHEINTER ELEMENTDISTANCE FORTHEARRAYOFRECEIVINGELEMENTSARERESPECTIVELYAND4HEBLANKINGIS SEPARATELYAPPLIEDONTHERECEIVEDDATAATTHETWOCARRIERFREQUENCIESSUBSEQUENTLY THESEPARATEBLANKINGBITSAREPROCESSEDBYALOGIC/2THEGLOBALBLANKINGLOGIC 4HEENSUING&IGUREDISPLAYSTHEBLANKINGCURVESFORTHETWOSEPARATECARRIER FREQUENCIESANDFORTHELOGIC/2)TISNOTEDTHATTHEFREQUENCYDIVERSITYANDTHE LOGIC /2 PROVIDE AN IMPROVEMENT OF THE BLANKING PROBABILITY THIS IS DUE TO THE DIFFERENTSHAPESOFTHEANTENNAPATTERNSATTHETWOSLIGHTLYDIFFERENTCARRIERFREQUEN CIES &IGURE ALSO PRESENTS THE PROBABILITY OF BLANKING A USEFUL TARGET 04" RECEIVEDBYTHEMAINANTENNABEAM4HEPROBABILITIESAREESTIMATEDVIAINDE PENDENT-ONTE#ARLOSIMULATIONS4HETARGET3.2ISD"THE*.2ISD"THE TARGET$O!ISASSUMEDTOBEEVENLYDISTRIBUTEDINTHEMAIN BEAMANGULARINTERVAL ;n = DETAILS ON THE NUMERICAL PARAMETERS USED IN THE STUDY CASE ARE IN THE REFERENCE)TISNOTEDTHAT04"ISNEGLIGIBLEFOR& D" WHILE0"q !FTERACAREFULPERFORMANCEEVALUATIONOFTHESYSTEMDEPICTEDIN&IGURE IT MIGHTBENECESSARYTOALWAYSRESORTTOEITHERSPATIALORFREQUENCYDIVERSITYTOIMPROVE THE3,"PERFORMANCE4HESELECTIONOFONEOFTHETWODIVERSITYTECHNIQUESDEPENDS ONOVERALLSYSTEMCONSIDERATIONSRELATEDTOTHEIMPACTOFADDINGMOREAUXILIARIESAND ORRADIATING WITHTHERADAR PROPERCARRIERFREQUENCIES&URTHERMORE IFCOMPACTAND HIGH SPEEDPROCESSINGAREREQUESTED SPATIALANDFREQUENCYDIVERSITYTECHNIQUESCAN BEFRUITFULLYIMPLEMENTEDRESORTINGTOSYSTOLICSCHEMES
&)'52% "LANKING PROBABILITY 0" AND TARGET BLANKING PROBABILITY 04" VERSUSTHEBLANKINGTHRESHOLD&IND" FORTHEFREQUENCYDIVERSITYSCHEME
Ó{°Óä
2!$!2(!.$"//+
3YSTOLIC3CHEMESFOR3,"AND3,# )NTHEQUESTFOREFFICIENTPARALLELPROCESSING THESYSTOLICSCHEMESCOMEINTOTHESCENETHEIRUSEHASBEENDESCRIBEDFORTHEIMPLE MENTATIONOF3,#ANDMOREGENERALADAPTIVEARRAYPROBLEMSINTHELITERATURE 4HE RATIONALEANDTHEUSEOFASYSTOLICARRAYTHATPROCESSESTHESIGNALSRECEIVEDBY3,#AND MAINCHANNELISREPORTEDONPAGESnOF&ARINAANDIN&ARINAAND4IMMONERI &IGURESTODEPICTTHEUSEOFASYSTOLICPROCESSINGSCHEMETHATINCORPORATESTHE 3,"AND3,#4HEADVANTAGEOFTHESESCHEMESRESIDESINTHEDECOMPOSITIONOFTHE COMPLEX PROCESSING FOR ADAPTIVE CANCELLATION OF THE .,) INTO A NETWORK OF SIMPLE PROCESSINGELEMENTSTHATCANBECONVENIENTLYMAPPEDONTOAPARALLELPROCESSINGARCHI TECTUREBASEDEITHERON#OMMERCIALOFFTHE3HELF#/43 TECHNOLOGYORCUSTOM6ERY ,ARGE3CALE)NTEGRATION6,3) DEVICES)NTHELITERATUREnITHASBEENSHOWNTHAT AWIDESPECTRUMOFTECHNOLOGIESCANBEUSEDLIKE&IELD0ROGRAMMABLE'ATE!RRAYS &0'! #OORDINATE2OTATION$IGITAL#OMPUTER#/2$)# IMPLEMENTEDWITH6,3) AND OPTICAL COMPUTERS 0IONEERING WORK ON THE USE OF #/2$)# FOR ADAPTIVE NULL INGDATESBACKTO#2ADERAT-)4 ,INCOLN,ABORATORY 4HEADVANTAGEOFSYSTOLIC IMPLEMENTATIONISHIGHPROCESSINGSPEEDANDCOMPACT LOWWEIGHT LOWPOWERCON SUMPTIONHARDWARE !DAPTIVE!RRAYS !NADAPTIVEARRAY&IGURE ISACOLLECTIONOF.ANTENNAS WITHTHEIROWNRECEIVERS28 AND!$# FEEDINGAWEIGHTINGANDSUMMINGNETWORK WITHAUTOMATICSIGNAL DEPENDENTWEIGHTADJUSTMENTTOREDUCETHEEFFECTOFUNWANTED
&)'52% 4HEADAPTIVEARRAYSCHEME
%,%#42/.)##/5.4%2 #/5.4%2-%!352%3
Ó{°Ó£
SIGNALS ANDOR TO EMPHASIZE THE DESIRED SIGNAL OR SIGNALS IN THE SUMMING NETWORK OUTPUT /UTPUT SIGNAL : IS ENVELOPE DETECTED AND COMPARED WITH A SUITABLE THRESH OLD@TODETECTTHEPRESENCEOFAUSEFULTARGETSEE#HAPTERIN&ARINAANDOTHER SOURCESn 4HEADAPTIVEARRAYISAGENERALIZATIONOFTHE3,#DESCRIBEDINTHE PRECEDING SUBSECTION4HE BASIC THEORY OF JAMMER CANCELLATION AND TARGET ENHANCE MENTISCONSIDEREDFIRSTATTENTIONISTHENFOCUSEDONTHEFOLLOWINGTOPICSMAIN BEAM JAMMERCANCELLATION TARGET$O!ESTIMATIONINPRESENCEOFJAMMER TWO DIMENSIONAL ADAPTIVEPROCESSINGFORJOINTCLUTTERANDJAMMERCANCELLATION ADAPTIVITYATTHESUBAR RAYLEVEL ANDSUPERRESOLUTION4HEIMPLEMENTATIONOFTHEADAPTIVEARRAYCONCEPTIS MOREANDMORERELATEDTODIGITALBEAMFORMINGnANDTODIGITALARRAYRADAR$!2 TECHNOLOGIES *AMMER #ANCELLATION AND 4ARGET 3IGNAL %NHANCEMENT !DAPTIVE ARRAY PRIN CIPLESHAVEFOUNDATHOROUGHMATHEMATICALTREATMENTSINCETHELATES FORA BRIEFHISTORYOFADAPTIVEARRAYS SEE2EEDFORANOVERVIEWOFLEASTSQUARESADAP TIVE PROCESSING IN MILITARY APPLICATIONS WITH CELEBRATION OF " &RANKLIN MEDAL TO "7IDROWFORPIONEERINGWORKONADAPTIVESIGNALPROCESSING SEE%TTERETAL4HE THEORYANDAPPLICATIONOFADAPTIVEARRAYPRINCIPLESTORADARISWELLESTABLISHEDFOR ALOOKTOPOPULARPUBLICATIONSSEE FORINSTANCE (AYKINAND3TEINHARDT 3MITH AND&ARINAETAL4HEBASICRESULTISGIVENBYTHEEXPRESSIONOFTHEOPTIMUMSET OFWEIGHTS
} M - 3 7
WHERE- %6 64 ISTHE. DIMENSIONALCOVARIANCEMATRIXOFTHEOVERALLDISTURBANCE NOISEANDJAMMER 6RECEIVEDBYTHEARRAY AND3ISTHE. DIMENSIONALVECTORCON TAININGTHEEXPECTEDSIGNALSAMPLESINTHEARRAYFROMATARGETALONGACERTAINDIRECTION OFARRIVAL4HESIMILARITYOF%QTO%QGOVERNINGTHE3,#ISIMMEDIATELY RECOGNIZED 7ITHRESPECTTO3,# ADAPTIVEARRAYTECHNIQUESOFFERTHECAPABILITYOFENHANCING THETARGETSIGNALWHILECANCELINGTHEDISTURBANCE4HEADAPTIVESYSTEMALLOCATESINAN OPTIMUMFASHIONITSDEGREESOFFREEDOMTOTHEENHANCEMENTOFTHETARGETSIGNALANDTO THECANCELLATIONOFJAMMER 3EVERAL GENERALIZATIONS OF THE BASIC THEORY HAVE BEEN CONSIDERED INCLUDING I THETARGETMODEL3ISNOTKNOWNAPRIORI ASITISASSUMEDINDERIVING%QII IN ADDITIONTOSPATIALFILTERING DOPPLERFILTERINGISPERFORMEDTOCANCELCLUTTERANDCHAFF ANDIII THERADARPLATFORMISMOVINGASINSHIPBORNE AIRBORNE OREVENSPACEBORNE APPLICATIONS!RELEVANTADVANCEMENTOFTHEADAPTIVEARRAYCONCEPTISSPACE TIMEADAP TIVEPROCESSING34!0 n 34!0MAYBETHOUGHTOFASATWO DIMENSIONALADAPTIVEFILTERTHATCOMBINESRECEIVE BEAMFORMINGANDDOPPLERFILTERING!BASICILLUSTRATIONOF34!0ISGIVENIN&IGURE OF7ARDWHEREAPICTORIALVIEWOFTHEINTERFERENCEENVIRONMENTSEENBYANAIRBORNE RADARANDTHECORRESPONDINGADAPTEDTWO DIMENSIONALFILTERRESPONSEARESHOWN4HE POWERSPECTRALDENSITYRESULTINGFROMJAMMERANDCLUTTERISDEPICTEDASAFUNCTIONOF THESPATIALIE THESINANGLE ANDTHETEMPORALIE DOPPLER FREQUENCIES"ARRAGE NOISEJAMMINGAPPEARSASAWALLLOCALIZEDINANGLEANDDISTRIBUTEDALLOVERDOPPLER FREQUENCIES4HECLUTTERECHOFROMASINGLEGROUNDPATCHHASADOPPLERFREQUENCYTHAT DEPENDSONTHEANGLEBETWEENTHECLUTTERPATCHANDTHEPLATFORMFLIGHTDIRECTIONCLUTTER FROMALLANGLESLIESONADIAGONALRIDGEACROSSTHESPACE TIMEFREQUENCYPLANE!MAIN BEAMTARGETCOMPETESWITHBOTHMAIN BEAMANDSIDELOBECLUTTERASWELLASJAMMING
Ó{°ÓÓ
2!$!2(!.$"//+
4HE 34!0 GENERATES A SPACE TIME FILTERING RESPONSE WITH A MAIN BEAM ALONG THE EXPECTED DOPPLER FREQUENCY AND ANGLE OF ARRIVAL OF TARGET AND DEEP NULLS ALONG THEJAMMERWALLANDTHECLUTTERRIDGE4OPERFORM34!0 THERADARSHOULDHAVEAN ARRAYOF.ANTENNAS EACHWITHTHEIROWNRECEIVINGCHANNELAND!$#%ACHCHANNEL RECEIVES-ECHOESFROMATRANSMITTEDTRAINOF-COHERENTPULSES!DAPTIVITYINVOLVES THE.-ECHOES 4HEDETECTIONPROBABILITY0$FORTHEOPTIMUMFILTEROF%QISFORACONSTANT CROSSSECTIONTARGETMODEL
0$ 1
;3 4
3
LN 0&!
WHERE1 ISTHE-ARCUM1FUNCTIONpAND0&!ISTHEPRESCRIBEDPROBABILITYOFFALSE ALARM)TISALSOSHOWNTHATTHESETOFWEIGHTSOF%QPROVIDESTHEMAXIMUMVALUE OFTHEIMPROVEMENTFACTOR)F WHICHISDEFINEDASFOLLOWS
)F
SIGNALnTOnINTERFERENCE PLUS NOISE POWER RATIO AT THE OUTPUT
SIGNALnTOnINTERFERENCE PLUS NOISE POWER RATIO AT THE INPUT
4HE)FVALUECORRESPONDINGTOTHEOPTIMUMSETOFWEIGHTSOF%QIS
)F
34 - 3 3).2 )
4HE SIGNAL TO INTERFERENCE PLUS NOISE POWER RATIO 3).2 ) IS MEASURED AT THE INPUT OF A RECEIVING ELEMENT OF THE ARRAY AND REFERS TO ONE ECHO PULSE 4HE )F REPRESENTS THE PERFORMANCE OF THE ADAPTIVE ARRAY IT ACCOUNTS FOR THE TARGET SIGNAL INTEGRATION ANDTHEINTERFERENCECANCELLATION0RACTICALAPPLICATIONSOFTHEEQUATIONABOVEARE FOR INSTANCE IN#HAPTEROF&ARINA#RUCIALFORTHEUNDERSTANDINGOFTHEADAPTEDARRAY PATTERN IS THE CONCEPT OF EIGENVALUE EIGENVECTOR DECOMPOSITION OF THE INTERFERENCE COVARIANCEMATRIX-SEEAGAIN#HAPTEROF&ARINA AND4ESTAAND6ANNICOLA!N IMPORTANTTECHNIQUETHATMITIGATESTHEDELETERIOUSEFFECTSOFTHENOISEEIGENVECTORS THUSCONTINUINGTOMAINTAINAPRESCRIBEDLEVELOFLOWSIDELOBESINTHEADAPTEDARRAY PATTERNISTHESO CALLEDDIAGONALLOADING !DAPTIVEARRAYSCAMEABOUTAFTERTHESUCCESSFULAPPLICATIONOF3,# THEAPPLICA TIONOF%Q ANDOFMOREGENERALANDPOWERFULADAPTIVEARRAYCONCEPTSEG '3,# GENERALIZED 3,# #LEARLY THE EFFICIENCY OF THE ADAPTIVE ARRAY DEPENDS ON THE NUMBER OF DEGREES OF FREEDOM DOF AND THE ACCURACY OF RECEIVING CHAN NELS EG DEGREES OF MATCHING 4HERE IS SOME TRADE OFF BETWEEN ACCURACY AND NUMBEROFCHANNELSASYSTEMWITHONEDOFISLESSEFFICIENTANDREQUIRESMAXIMUM ACCURACY THAN A SYSTEM WITH SAY FOUR DOF!N ADAPTIVE SYSTEM WITH . DOF CAN THEORETICALLYSUPPRESS.n JAMMERS REALISTICALLYASARULEOFTHUMB.OR .)FTHENUMBEROFJAMMERSISHIGHER THEADAPTIVEARRAYISSTILLUSEFULBECAUSE SOMEJAMMERSUPPRESSIONISACHIEVEDWITHANACCORDINGLYREDUCEDDETECTIONRANGE p4HE-ARCUM1FUNCTIONISDEFINEDAS
1 A B
¯
c
B
ª X A ¹ ) O AX DX º ¬ »
X EXP «
WHERE)O ISTHEMODIFIED"ESSELFUNCTIONOFORDER
%,%#42/.)##/5.4%2 #/5.4%2-%!352%3
Ó{°ÓÎ
#ONCERNING THE COMPARISON BETWEEN ADAPTIVE BEAMFORMING AND A VERY LOW SID ELOBE ANTENNA IT IS IN THE IMPORTANT CASE OF CLOSE TO MAIN BEAM JAMMING WHERE ADAPTIVEBEAMFORMINGISSUPERIOR/NTHEOTHERHAND THEADAPTIVEARRAYALLOWSONE TOOBTAINCERTAINLOWEREDSIDELOBESSIMULTANEOUSLYTOJAMMINGNULLING#ONCERNING THEPRACTICALAPPLICABILITYOFADAPTIVEARRAYSSOMECONSIDERATIONSFOLLOW!NUM BEROFOPERATIONALRADARSYSTEMSAREADAPTIVETHEYAREDESCRIBEDINTHETECHNICAL LITERATUREn !MODERNRADARWITHDIGITALPROCESSINGALREADYHASATLEASTFOUR DIGITALCHANNELSSUM DIFFERENCEINAZIMUTH DIFFERENCEINELEVATION ANDGUARD )N GENERAL THENUMBEROFIMPLEMENTEDRECEIVINGCHANNELSISMAINLYAMATTEROFCOST )THASBEENARGUEDTHATRADARSYSTEMSWITHANUMBEROFADAPTIVEDOFOFAFEWTENS AREALREADYINOPERATIONINTHEMICROWAVEBANDTHENUMBEROFADAPTIVEDOFMAYBE MOREINTHEOVER THE HORIZON/4( RADAR &ORTHEFORESEEABLEFUTURE THEFULLYADAPTIVEARRAYIE WITHADAPTIVITYATRECEIVING ELEMENTLEVEL HASONLYTHEORETICALVALUEFORANTENNASWITHATHOUSANDELEMENTS4HERE ARERADARSTHATAREFULLYADAPTIVE BUTTHEYHAVEONLYALIMITEDNUMBEROFELEMENTS THATCANBEECONOMICALLYHANDLEDINANADAPTIVEARRAY!RRAYSWITHALARGENUMBEROF RECEIVINGELEMENTSNEEDSOMEFORMOFPROCESSINGREDUCTION/NEMETHODOFPARTIAL ADAPTIVITYISTOARRANGETHEARRAYELEMENTSINSUBGROUPSTHATFORMTHEINPUTSOFTHE ADAPTIVEPROCESSOR#AREFULSELECTIONOFTHESUBGROUPELEMENTSISNECESSARYTOAVOID GRATINGLOBESTHISTOPICISDISCUSSEDINAFOLLOWINGSECTION!NOTHERSIMPLIFICATIONOF THEFULLYADAPTIVEARRAYISTHEDETERMINISTICSPATIALFILTERING WHEREAFIXEDREDUCTION OFTHESIDELOBESISOPERATEDINTHOSEDIRECTIONSORSOLIDANGLESFROMWHICHTHEINTERFER ENCESAREEXPECTEDTOCOME!SANEXAMPLE APROBABLEREGIONWITHINTERFERENCESIS THEHORIZONORPARTOFITBECAUSEJAMMERSAREMOSTLYGROUND BASEDORATLONGRANGE 4HEWEIGHTSARECOMPUTEDOFFLINE BYASSUMINGANAPRIORIKNOWNCOVARIANCEMATRIX - ANDSTOREDINAMEMORYWHEREAhMENUvOFWEIGHTSISAVAILABLETOANOPERATOROR ANAUTOMATICDECISIONSYSTEMPPnOF&ARINA -AIN"EAM#ANCELLATION-"# 3YSTEMS 4HEOBJECTIVEOFTHE-"#ISTOSUP PRESS HIGH DUTY CYCLE AND .,) RECEIVED THROUGH THE MAIN BEAM OF THE RADAR 4HE CONCEPTUALSCHEMEOF-"#ISANALOGOUSTOTHESCHEMEOF3,#HOWEVER HIGHGAIN BEAMSAREEMPLOYEDINLIEUOFLOWGAINAUXILIARYANTENNAS*AMMINGISCANCELLEDBYA LINEARCOMBINATIONOFTHESIGNALSFROMTHEHIGHGAINBEAMSANDTHEMAINANTENNA4HE WEIGHTSTOBEAPPLIEDCANBECOMPUTEDBY%Q4HECAPABILITYTOCANCELACERTAIN NUMBER OF MAIN BEAM INTERFERENCES DEPENDS ON THE AVAILABLE NUMBER OF HIGH GAIN BEAMS!SO CALLEDFOUR LOBEDPATTERNCANBEUSEDFORMAIN BEAMINTERFERENCECANCEL LATION 4HEUSEOFLOW GAINAUXILIARYANTENNASJOINEDTOHIGHGAINBEAMSALLOWS THECONTEMPORANEOUSCANCELLATIONOFSIDELOBEANDMAIN BEAMINTERFERENCES 4ARGET $O! %STIMATION IN 0RESENCE OF 3IDELOBE AND -AIN "EAM )NTERFERENCES 0HASED ARRAYRADARSAREREQUIREDTODETECT LOCATE ANDTRACKTARGETSINTHEPRESENCEOF NATURALINTERFERENCEANDJAMMING-ONOPULSEISTHETECHNIQUEOFCHOICETODETERMINE THE TARGET ANGULAR COORDINATES WHEN %#- IS ENCOUNTERED SINCE IT IS MUCH HARDER TO DECEIVETHANACONICALSCAN(OWEVER THEAPPLICATIONOFADAPTIVEBEAMFORMINGTOBET TERMITIGATETHEPRESENCEOFANINTENSEJAMMER WITHTHERELATEDDISTORTIONOFSUMAND DIFFERENCEBEAMSHAPESMAYINTRODUCEERRORSINTHECONVENTIONALMONOPULSETECHNIQUE INPARTICULAR IFTHEJAMMERISCLOSETOTHEMAINBEAMTHUS THECONVENTIONALMONO PULSETECHNIQUECANNOTBEAPPLIED!-AXIMUM,IKELIHOOD-, APPROACHFORTARGET $O!ESTIMATIONISCONSIDERED WHICHGENERALIZESTHEMONOPULSECONCEPTn
Ó{°Ó{
2!$!2(!.$"//+
4HETARGETANGULARCOORDINATESAZIMUTHANDELEVATIONP E CANBEESTIMATEDBY -, ALSOINTHEPRESENCEOFMAIN BEAMANDSIDELOBEJAMMING BYPROCESSINGTHEDATA RECEIVEDBYASETOFLOWANDHIGHGAINBEAMS4HESETOFRECEIVEDRADARECHOES 6x B3P4 E4 D DEPENDSONTHEANGULARCOORDINATESOFTHETARGET P4 E4 THECOMPLEX TARGETAMPLITUDEB ANDWHITEGAUSSIANZEROMEANNOISEPLUSJAMMINGDISTURBANCED 3ISAVECTORCONTAININGTHEVALUESOFTHEPATTERNSOFHIGHANDLOWGAINANTENNASINA CERTAINDIRECTIONP E 4HEDATA6ARECHARACTERIZEDBYAGAUSSIANPROBABILITYDENSITY FUNCTIONCONDITIONEDTOTHETARGETUNKNOWNPARAMETERS IE PV6B P4 E4 4HE-, ESTIMATIONOFTHETARGETSUNKNOWNPARAMETERSISOBTAINEDASFOLLOWS
[
]
B} Q}4 F}4 ARG MIN B Q F ;6 B3Q F = - D ;6 B3Q F = ARG MIN B Q F [& B Q F ] (
WHERE -D IS THE DISTURBANCE COVARIANCE MATRIX -D S N ;) *.2 s 3P* E* s 3P* E* (= DEPENDINGONTHEANGULARCOORDINATESOFTHEJAMMINGP* E* eANDONTHE JAMMING TO NOISEPOWERRATIO *.2 0* S N IN%Q (STANDSFORTHECOM PLEXCONJUGATETRANSPOSEOPERATION4HEAMPLITUDEBCANBESEPARATELYESTIMATEDBY NULLINGTHEFIRSTDERIVATIVEOFTHEFUNCTIONTOBEMINIMIZED"YREPLACINGTHEAMPLI TUDEESTIMATION B} INTOTHEFUNCTIONTOBEMINIMIZED THEFOLLOWING$O!ESTIMATOR ISOBTAINED ª 3( Q F ; - ; 6 ¹ D Q}4 F}4 ARGMAXQ F [5 Q F ] ARGMAXQ F « ( º
Q F Q F 3 ; ; 3 D » ¬
)TCANBENOTEDTHATTHENUMERATOROFTHEFUNCTIONAL5P E ISTHESQUAREDADAPTED OUTPUT \ 3 ( Q F ; - D ; 6 \ OFAGENERALIZEDARRAYOFHIGHANDLOWGAINANTENNA PATTERNSTHEDENOMINATOR;3 ( Q F ; - D ; 3 Q F = ISANORMALIZINGTERMTHAT ASWE WILLSEEINAMOMENT PLAYSAKEYROLE4HE5FUNCTIONFORACERTAINPAIROFANGLES P E DETERMINES AFTERCOMPARISONWITHASUITABLETHRESHOLD IFATARGETISDETECTED 4HE SAME 5 FUNCTIONAL WHEN SCANNED ACROSS A SUITABLE SET OF P E ANGLE VALUES PROVIDES BYMEANSOF%Q THETARGET$O!ESTIMATE7EREFERTO%QAND ITSPRACTICALIMPLEMENTATIONASTHEGENERALIZEDMONOPULSETECHNIQUE 4HE ALGORITHM NEEDS THE ESTIMATION OF THE DISTURBANCE COVARIANCE MATRIX -D WHICHISOBTAINEDBYTHERADARECHOESCORRESPONDINGTORANGECELLSADJACENTTOTHE CELLUNDERTESTWHEREAPOTENTIALTARGETISSOUGHT4HEMAXIMUMOFTHE5FUNCTIONAL CANBEESTIMATEDBYANEXHAUSTIVESEARCHINTHERANGEOFVALUESOFINTERESTOFP E ORBYUSINGAFASTRECURSIVEALGORITHM4HERECURSIONCANBEINITIALIZEDWITHTHE ANGULARCOORDINATESOFTHEMAIN BEAMPOINTING"YREPLACINGTHEESTIMATEDDISTUR BANCECOVARIANCEMATRIXINTOTHE5FUNCTIONAL A#ONSTANT&ALSE!LARM2ATE#&!2 DETECTOR IS OBTAINED 4HUS THE COMPARISON OF THE 5 FUNCTIONAL WITH A SUITABLE THRESHOLDPERMITSTHETARGETDETECTIONMAINTAININGTHEPRESCRIBED#&!2/NLYFOR THERANGECELLINWHICHTHEDETECTIONOCCURRED THERADARSIGNALSARETAKENANDFURTHER PROCESSEDBYTHE-,ALGORITHMTOPRODUCETHETARGET$O!ESTIMATE 4HE PERFORMANCE OF THE -, ESTIMATION ALGORITHM OF TARGET $O! CAN BE STUDIED BY RESORTING TO THE #RAMER 2AO ,OWER "OUND #2," ANALYSIS AND -ONTE #ARLO SIMULATIONS n )NTHESESTUDIES ITISSHOWNTHATTHESHAPEOFTHE5FUNCTIONAL e(ERE JUSTONEJAMMERISCONSIDEREDBUTTHEMATHEMATICALAPPROACHISEASILYEXTENDEDTOMORETHANONEJAMMER
%,%#42/.)##/5.4%2 #/5.4%2-%!352%3
Ó{°Óx
DEPICTSTHEPRESENCEOFTHETARGETASWELLASOFTHEJAMMING)THASBEENDEMONSTRATED THAT-ONTE#ARLOSIMULATIONISINCLOSEAGREEMENTWITH#2,"ANALYSIS)THASBEEN FOUNDTHATTHEUSEOFTHEFOUR LOBEDANTENNAPATTERNINADDITIONTOTHECONVENTIONAL MONOPULSEBEAMSSUM DIFFERENCEINAZIMUTH ANDELEVATION CANIMPROVETHEESTIMA TIONOFTHETARGET$O!INPRESENCEOFAJAMMER *OINT !DAPTIVE *AMMER AND #LUTTER #ANCELLATION #LUTTER ALWAYS PRESENT IN A RADAR NEGATIVELY AFFECTS THE PERFORMANCE OF THE ADAPTIVE JAMMER CANCELLATION THEREFORE MEANSHAVETOBEADOPTEDTOEFFECTIVELYCONTRASTTHECONTEMPORANEOUS PRESENCEOFCLUTTERANDJAMMER7HENHEAVYCLUTTERISPRESENT THE3,#ANDADAPTIVE ARRAYWILLATTEMPTTOMINIMIZETHEPOWERINTHEADAPTEDOUTPUTWITHOUTDIFFERENTIAT INGBETWEENCLUTTERANDOTHERFORMSOFINTERFERENCE)NOTHERWORDS THEADAPTEDPAT TERNWILLCONTAINNULLSSTEEREDINTHEDIRECTIONOFTHEMAIN BEAMANTENNA!NUMBER OFTECHNIQUESMAYBEUSEDTOAVOIDTHEPROBLEMSRAISEDBYTHEPRESENCEOFCLUT TER! TECHNIQUE PARTICULARLY SUITABLE FOR LOW 02& 0ULSE 2EPETITION &REQUENCY RADAR AVOIDSTHEINFLUENCEOFCLOSE INCLUTTERRETURNSONADAPTIVEWEIGHTSBYSIMPLY SELECTINGFORADAPTATIONTHECLUTTER FREERANGESATTHEENDOFEACH02)4HISTECH NIQUEDOESNOTAPPLYTORADARSOPERATINGINHIGH 02&RANGE AMBIGUOUSMODESWITH SIGNIFICANTCLUTTERINALLRANGECELLS)FTHECLUTTERANDJAMMERCANNOTBESEPARATED EITHERINRANGEORDOPPLERDOMAINS THENATWO DIMENSIONALINDOPPLERFREQUENCY ANDANGLE ADAPTIVEFILTERMIGHTBEREQUIREDTHISISPARTICULARLYTRUEWHENTHESTATIS TICALFEATURESOFCLUTTERANDJAMMERARENOTKNOWNAPRIORI)NFACT WHENEITHERTHE JAMMINGORCLUTTERSTATISTICSCANNOTBEESTIMATEDINDEPENDENTLYOFONEANOTHER IT BECOMESDIFFICULTTODESIGNANEFFECTIVESPATIALADAPTIVEFILTERFORJAMMINGREJECTION ORATEMPORALADAPTIVEFILTERFORCLUTTERMITIGATIONSINCETHEPRESENCEOFONECON TAMINATESTHEESTIMATIONPROCESSFORTHEOTHER4HISPROBLEMISMOSTACCENTUATED WHENTHECLUTTER TO JAMMINGRATIOAPPROACHESUNITYINWHICHCASE THECASCADEOFA SPATIALANDATEMPORALADAPTIVEPROCESSORSMAYPERFORMPOORLY)NSUCHSITUATIONS AJOINTTWO DIMENSIONALADAPTIVEFILTERINGINDOPPLERANDANGLEDOMAINSREPRESENTS A MEANS TO CANCEL THE COMPOSITE DISTURBANCE IE THE SUPERPOSITION OF JAMMING ANDCLUTTER JOINTLYRATHERTHANSEQUENTIALLY4HEPERFORMANCEADVANTAGESOFTWO DIMENSIONALADAPTIVITYSHALLBETRADED OFFWITHTHECOMPUTATIONALCOST4OREDUCE THE COMPUTATIONAL LOAD DIFFERENT COMPUTATIONAL STRATEGIES MAY BE DEVISED FOR EXAMPLE BYCALCULATINGTHEADAPTEDTWO DIMENSIONALWEIGHTSATARATELOWERTHAN THEINPUTDATAANDAPPLYINGTHEMTOTHERADARSNAPSHOTSATTHEIRNATURALRATE!NEFFI CIENTALGORITHMICPROCEDURETOEXTRACTTHEWEIGHTS NAMED)NVERSE12 ISDETAILEDIN "OLLINIETAL/THERPOSSIBILITIESARETOUSEMODERNCOMPUTINGTECHNOLOGIESLIKETHE &0'! 0OWER0# ORHIGH SPEEDOPTICALPROCESSORTOSUPPORTTHETWO DIMENSIONAL ADAPTIVEPROCESSING !DAPTIVITY AT THE 3UB !RRAY ,EVEL &OR AN OPERATIONAL PHASED ARRAY RADAR 0!2 WITHTHOUSANDSOFELEMENTS ITISNOTPOSSIBLETOADAPTDIRECTLYTHESIGNALSFROM EACH RADIATING ELEMENT )T IS NECESSARY TO REDUCE THE SYSTEM COMPLEXITY BY USING SUB ARRAYS!SUB ARRAYISANAGGREGATIONOFANTENNAELEMENTARYRADIATORSTHEWHOLE ANTENNA CAN BE CONSIDERED AS AN ARRAY OF THESE SUPER ELEMENTS!DAPTIVE PROCESS INGCANBEAPPLIEDATTHEOUTPUTSIGNALSOFEACHSUB ARRAY THUSREDUCINGTHESYSTEM COMPLEXITY0ROVIDEDTHATTHESUB ARRAYSARECONFIGUREDREASONABLY THENUMBEROF SUB ARRAYS AND THE RECEIVING CHANNEL ERRORS EG CHANNEL MISMATCHING DETERMINE THECANCELLATIONPERFORMANCE4HUS THENUMBEROFSUB ARRAYSISATRADE OFFBETWEEN HARDWARECOMPLEXITY COST ANDACHIEVABLEPERFORMANCE
Ó{°ÓÈ
2!$!2(!.$"//+
)TISHIGHLYDESIRABLEIN0!2TOHAVELOWSIDELOBESTHISISOBTAINEDBYI FIXEDWEIGHT INGLAYERWITHANALOGUETECHNOLOGYIE ATTHEMICROWAVEELEMENTSTAGE TOREDUCETHE SIDELOBE LEVEL EVERYWHERE II FIXED WEIGHTS AT THE DIGITAL SUB ARRAY LEVEL TO REACH A PRESCRIBED PEAK TO SIDELOBE RATIO 03,2 AND III AN ADAPTIVE WEIGHTING LAYER WITH DIGITALTECHNOLOGYTOPUTNULLSALONGTHEJAMMER$O!OFHIGHDIRECTIONALBEAMSSUM DIFFERENCE CLUSTEROFHIGHGAINPATTERNS ANDLOWGAIN POSSIBLYOMNIDIRECTIONAL BEAMS EG GUARDCHANNEL7 &IGUREPRESENTSASIMPLIFIEDSCHEMEOFAMODERN0!2 &ORMATIONOF3UMAND$IFFERENCE0ATTERNS #ONSIDERTHEPROBLEMOFHOWTOFORM SUMANDDIFFERENCEBEAMSWITHPRESCRIBEDLOWSIDELOBESINA0!2WITHSUB ARRAYS !STRATEGYISTOAPPLYATAPERINGATELEMENTLEVELIE INTHEANALOGUERECEIVINGSEC TIONWHEREONEATTENUATORISGENERALLYAVAILABLEPERELEMENTTHUSONETAPERFUNCTION ISAVAILABLETOACHIEVEREASONABLELOWSIDELOBESFORBOTHSUMANDDIFFERENCEBEAMS 3UBSEQUENTLYAFIXEDDIGITALTAPER AFTERTHEFORMATIONOFSUB ARRAYS ISAPPLIEDWITHA SETOFWEIGHTSFORTHESUMANDADIFFERENTSETOFWEIGHTSFOREACHDIFFERENCECHANNEL 4HISISSCHEMATICALLYILLUSTRATEDIN&IGUREFORAUNIFORMLINEARARRAY5,! THAT GENERATESASUMANDADIFFERENCECHANNEL4HEFIGUREDEPICTSA5,!WITHRECEIVING ELEMENTSCLUSTEREDINTOFOURNOTOVERLAPPINGANDNOTREGULARSUB ARRAYS 4HECALCULATIONOFANALOGUETAPERISMADEBYRESORTINGTOTHENULLINGOFFICTITIOUS WIDE ANGLE JAMMING WHICH OCCUPIES THE WHOLE ANGULAR SECTOR WHERE SIDELOBES OF SUMANDDIFFERENCEBEAMSHAVETOBEKEPTLOW)N&ARINAETAL ITWASFOUNDTHATTHE ANALOGUETAPERINGISACOMPROMISEBETWEENTHE4AYLORWHICHISTHEBESTTAPERFORTHE SUMBEAM ANDTHE"AYLISSWHICHISTHEBESTTAPERFORTHEDIFFERENCEBEAM THEDEGREE OFCOMPROMISEBEINGREGULATEDBYAMOUNTOFFICTITIOUS*.2SELECTEDFORTHESUMAND DIFFERENCE BEAMS! NUMERICAL EXAMPLE REPORTED IN &ARINA ET AL FOR A 5,! OF . ELEMENTSANDAUNIFORMDISTRIBUTIONOFTHEFICTITIOUSJAMMEROUTOFTHEMAIN BEAMSOFTHESUMANDDIFFERENCEBEAMS GIVESA03,2OFD"ANDD"FORTHE SUMANDDIFFERENCEBEAMS RESPECTIVELY 4HENEXTSTEPISTODERIVETHEFIXEDTAPERSATADIGITALLEVELFORSUMANDDIFFERENCE BEAMSASUITABLETECHNIQUEISDESCRIBEDIN.ICKEL 4HERATIONALEOFTHEAPPROACH
&)'52% 3CHEMEOFA0!2
%,%#42/.)##/5.4%2 #/5.4%2-%!352%3
Ó{°ÓÇ
# $ "
# $ "
# $ "
# $ "
"" !# "
"" "
&)'52% %XAMPLEOFA5,!WITHSUB ARRAYSTHATGENERATESUMANDDIFFERENCECHANNELS
ISTOOBTAINTHESUMBEAMBYCOMPENSATING ATTHESUB ARRAYLEVEL THEANALOGUETAPER ATTHEELEMENTLEVELTOACHIEVEANOVERALLTAPERMORESIMILARTOTHE4AYLORONETHIS ISOBTAINEDBYINCREASINGTHECONTRIBUTIONOFCENTRALSUB ARRAYWEIGHTSIE THESUB ARRAYSANDSHOWNIN&IGURE WITHRESPECTTOTHEWEIGHTSOFTHESIDESUB ARRAYS AND4OOBTAINTHEDIFFERENCEBEAM THEANALOGUETAPERINGATTHEELEMENTLEVELIS COMPENSATED ATTHESUB ARRAYLEVEL TOACHIEVEANOVERALLTAPERFUNCTIONMORESIMILAR TOTHE"AYLISSONETHISISOBTAINEDBYDECREASINGTHECONTRIBUTIONOFTHECENTRALSUB ARRAYSAND !NUMERICALEXAMPLEISREPORTEDIN&ARINAETALWITHAN5,!OF. ELEMENTS AND- SUB ARRAYS4HECHOSENWEIGHTISA4AYLORTAPERINGWITHD"OF03,2 4HEREAREONLYDIGITALDEGREESOFFREEDOMTHISMEANSTHATMARGINALIMPROVEMENTOF PERFORMANCEINTERMSOF03,2CANBEACHIEVED.EVERTHELESS A03,2OFD"WAS OBTAINEDFORTHECOMBINATIONOFANALOGUEWEIGHTSANDDIGITALWEIGHTS&ORTHE SAME5,!ABOUTD"OF03,2WASOBTAINEDFORTHEDIFFERENCECHANNEL #ONSIDERATIONS2ELATEDTO3UB ARRAY!DAPTIVITY 4APERINGATTHEARRAYELEMENTLEVEL PRODUCESUNEQUALNOISEPOWERATSUB ARRAYOUTPUTSBECAUSEOFTHEDIFFERENTNUMBEROF ELEMENTS IN EACH SUB ARRAY!DAPTIVITY WOULD TRY TO EQUALIZE THE NOISE BETWEEN CHAN NELS THUSNEGATINGTHETAPERINGEFFECT4HETRANSFORMATION4THATENCODESTHESUB ARRAY ARCHITECTURE SHOULDBESUCHTHAT4(4 ))NTHISWAY THENOISEPOWERATSUB ARRAYOUTPUTS ISEQUALSUBSEQUENTLYTHEMISSINGTAPERWEIGHTSAREAPPLIEDDIGITALLYATSUB ARRAYOUTPUTS WEIGHTRESCALING !SANEXAMPLECONSIDERALINEARARRAYOFELEMENTSANDRAISED COSINETAPERING&IGUREDEPICTSTHEFOLLOWING#ONTINUOUSCURVEPATTERNOFARRAY
4HESUB ARRAYSARCHITECTURECANBEREPRESENTEDBYAMATRIX4HAVINGANUMBER-OFCOLUMNSEQUALTOTHENUMBER OFSUB ARRAYSANDANUMBER.OFROWSEQUALTOTHENUMBEROFELEMENTARYRADIATORS4HEELEMENTTIJOFTHEMATRIXIS DEFINEDEITHERASWIIFTHEI THELEMENTARYRADIATORBELONGSTOTHEJ THSUB ARRAYORASIFTHEI THELEMENTARYRADIATOR DOESNOTBELONGTOTHEJ THSUB ARRAY WHEREWIISTHETAPERINGWEIGHTINTHEANALOGUELAYEROF&IGURE
Ó{°Ón
2!$!2(!.$"//+
&)'52% %XAMPLESOFTHEANTENNAPATTERNSACHIEVEDINSEVERALCASES
OFSUB ARRAYSWITHOUTNOISENORMALIZATIONATTHEOUTPUTOFSUB ARRAYSITAPPROXIMATELY FOLLOWSTHEUNIFORMTAPERINGDASHEDLINE $OTTEDLINEPATTERNOFARRAYOFELEMENTSAND OFARRAYOFSUB ARRAYSAFTERNOISENORMALIZATIONANDWEIGHTRESCALING 4HENUMERICALEXAMPLEFOLLOWSWITH&IGURE WHICHPORTRAYSTHECANCELLATION OFAJAMMERWITHTHE$O! nANDA*.2OFD"4HECONTINUOUSLINEREFERSTO ANUNADAPTEDPATTERN TAPEREDATTHEELEMENTLEVEL WHEREASTHEDOTTEDLINEPERTAINSTO THEADAPTEDPATTERNATTHESUB ARRAYLEVEL 3UB ARRAYSARE INGENERAL CHOSENTOBEIRREGULARINTHEIRSHAPEANDPOSITIONTO AVOID GRATING LOBES )F A JAMMER IMPINGES ON A GRATING LOBE THE JAMMER WILL BE NULLED BY DISTORTING THE GRATING LOBE AND AS A CONSEQUENCE THE ARRAY MAIN BEAM GRATINGNOTCH &OREXAMPLE CONSIDERA5,!WITH. ELEMENTSTHEN FORMTWO TYPES OF NOT OVERLAPPING SUB ARRAY CONFIGURATIONS BOTH HAVING - SUB ARRAYS
" ! #"
&)'52% *AMMERCANCELLATIONATSUB ARRAYLEVEL
%,%#42/.)##/5.4%2 #/5.4%2-%!352%3
Ó{°Ó
"!
!#!%! " %# !#!% !
!! $!
&)'52% 3).2VERSUSTHEJAMMER$O!*$O!
4HEFIRSTCONFIGURATIONISREGULARWITHTWOELEMENTSFOREACHSUB ARRAY4HESECOND CONFIGURATIONISIRREGULARWITH ANDELEMENTS RESPECTIVELY&IGURE SHOWSTHE3).2ATTHEOUTPUTOFTHEARRAYVERSUSTHEJAMMER$O!4HETARGET$O! ISAT THE3.2ISD" THE*.2ISD"4HREECURVESSUMMARIZETHESYSTEM PERFORMANCE4HEDASHEDLINEISTHEARRAYPATTERNWITHRAISEDCOSINETAPERTHISIS SHOWNFORTHESAKEOFCOMPARISONWITHTHEOTHERTWOCURVESOFTHE3).24HEDOT TEDLINEISTHE3).2FORTHEQUIESCENTABSENCEOFADAPTIVITY PATTERNITMIMICSTHE RECIPROCALOFTHESIDELOBEANDMAIN BEAMPATTERN4HECONTINUOUSLINEISTHE3).2 FORTHEADAPTIVEIRREGULARSUB ARRAYARCHITECTURETHEMAXIMUMVALUEOFTHE3).2IS LOGnTAPERINGLOSSES &IGUREDEPICTSTHE3).2FORTHEREGULARARRAYCONFIGURATIONANDABSENCEOF TAPERING)TISNOTEDTHATWHENTHEJAMMER$O!ISAROUND THE3).2DECREASESTHIS ISBECAUSEOFTHEGRATINGLOBE4HEMAXIMUMVALUEOF3).2ISD" LOG BECAUSETHEREARENOTAPERINGLOSSES
&)'52% 3).2VERSUSTHE*$O!FORAREGULARSUB ARRAYARCHITECTURE ANDNOTAPERING
Ó{°Îä
2!$!2(!.$"//+
3UPERRESOLUTION 4HERESOLUTIONOFACONVENTIONALANTENNAISLIMITEDBYTHEWELL KNOWN2AYLEIGHCRITERION WHICHSTATESTHATTWOEQUAL AMPLITUDENOISESOURCESCANBE RESOLVEDIFTHEYARESEPARATEDINANGLEBYK, INRADIANS WHEREKISTHEWAVELENGTH AND,ISTHEAPERTURELENGTH7HENTHEINCIDENTWAVEISRECEIVEDWITHAHIGH*.2 AN ADAPTIVEARRAYANTENNAMAYINPRINCIPLEACHIEVEANARROWERADAPTIVEBEAMWIDTH GIVINGASHARPERBEARINGESTIMATIONOFTHEINCIDENTWAVE)FACCURATESTROBESOFTHEJAM MERSCANBEOBTAINED THESECANBEEXPLOITEDTOFORMBEAMSINTHEJAMMERDIRECTIONS WHICH ARE USED AS AUXILIARY CHANNELS FOR ADAPTIVE INTERFERENCE SUPPRESSION 4HE INTERFERENCEDIRECTIONSCANALSOBEUSEDFORDETERMINISTICNULLING WHICHISOFINTEREST FORMAIN BEAMNULLING)NADDITIONTOTHEINTERFERENCESOURCEDIRECTIONSANDSOURCE STRENGTHS THISTECHNIQUECANPROVIDEOTHERINFORMATIONASTOTHENUMBEROFSOURCES ANDANYCROSSCORRELATIONSCOHERENCE BETWEENTHESOURCES3UCHINFORMATIONCANBE USEDTOTRACKANDCATALOGUETHEINTERFERENCESOURCESINORDERTOPROPERLYREACTTOTHEM THEJAMMERMAPPINGAFUNCTIONRUNNINGINTHEBACKGROUNDISUSEFULTOSELECTTHE MODES EG ADMISSIBLE POINTING DIRECTIONS AND WAVEFORMS OF MULTIFUNCTION RADAR ANDFORGENERALSITUATIONAWARENESS3UPERRESOLUTIONMIGHTBEABLETORESOLVEMULTIPLE INDEPENDENTSOURCESDUETOSIDELOBESUPERPOSITIONANDMASKINGPROBLEMS SUPERRESO LUTIONMIGHTBEVITALFORJAMMERMAPPINGINCASEOFMULTIPLEJAMMERS3UPERRESOLUTION ISALSOOFINTERESTASAN%##-TOCOUNTERCROSS EYEJAMMINGINSEEKERHEADAPPLICA TIONSSEE3ECTIONOF7IRTH 4HESUPERRESOLUTIONCONCEPTWASMAINLYDEVELOPEDANDANALYZEDBY7&'ABRIEL ATTHE.AVAL2ESEARCH,ABORATORY53 $IFFERENTMETHODSFORBEARINGESTIMATIONWERE DESCRIBED BY 'ABRIEL AND SUBSEQUENTLY BY OTHER AUTHORS n /NE IS THE MAXI MUM ENTROPYMETHOD-%- INVENTEDBY*0"URG)TWORKSWELLWITHA(OWELLS !PPLEBAUM ADAPTIVE BEAMFORMER WHICH HAS AN OMNIDIRECTIONAL RECEIVING PATTERN EXCEPTWHEREJAMMERSAREPRESENT4HEPRESENCEOFJAMMERSISINDICATEDBYNULLSIN THE RECEIVING PATTERN "ECAUSE NULLS ARE ALWAYS SHARPER THAN ANTENNA LOBES JAMMER BEARINGSCANBEOBTAINEDMOREACCURATELYFROMTHEADAPTIVEBEAMPATTERN ANDSUPER RESOLUTIONISTHERESULT4HEDESIREDSPATIALSPECTRUMPATTERNISOBTAINEDASSIMPLYTHE INVERSEOFTHEADAPTEDPATTERN!S'ABRIELPOINTEDOUT THEREISNOTATRUEANTENNAPATTERN BECAUSETHEREISNOLINEARCOMBINATIONOFTHESIGNALSFROMANARRAYTHATCOULDPRODUCE SUCHAPEAKEDSPATIALPATTERN)TISSIMPLYAFUNCTIONCOMPUTEDFROMTHERECIPROCALOF ATRUEADAPTEDANTENNAPATTERN3UPERRESOLUTIONANDADAPTIVEANTENNASFORJAMMERCAN CELLATIONAREINTIMATELYRELATED2OUGHLYSPEAKING THEDIFFERENCEISTHATONEPRODUCES APATTERNWITHTHENULLSDOWNADAPTIVEANTENNAFORJAMMERCANCELLATION ANDTHEOTHER WITHTHENULLSUP IE PEAKSSUPERRESOLUTIONOFJAMMERS /NE LIMITING FACTOR OF SUPERRESOLUTION TECHNIQUES IS THAT THEY OFTEN REQUIRE THE RECEIVEDSIGNALSTOOBEYACCURATEMODELSOFTHEARRAYMANIFOLD4HISCANBEVIOLATED DUETOPROPAGATIONEFFECTSEG SPATIALSPREADINGANDNONSTATIONARITY ASWELLASINSTRU MENTALEFFECTSEG CHANNELMISMATCH 4HESEFACTORSALSOAFFECTTHEPERFORMANCEOF ADAPTIVE ANTENNAS FOR JAMMER CANCELLATION BUT MODEL MISMATCHES CAN DEGRADE THE PERFORMANCEOFSUPERRESOLUTIONTECHNIQUESMORESEVERELY4HEHIGHERPERFORMANCEOF THESUPERRESOLUTIONTECHNIQUESISOFTENOBTAINEDATTHEEXPENSEOFREQUIRINGASTRICTER ADHERENCETOTHEASSUMEDMODELIFTHEMODELISINACCURATE THESETECHNIQUESWHICH RELY ON ITS HEAVY EXPLOITATIONSUBSEQUENTLY BECOME THE MOST SENSITIVE AND MORE PRONETOPERFORMBADLY &OREFFICIENTSUPERRESOLUTION ANARRAYWITHAREASONABLENUMBEROFSUB ARRAYSIS REQUIREDTHISMAYBETHEREASONFORTHELACKOFAPPLICATIONOFTHISTECHNIQUETOPRACTI CALRADARSYSTEMSEXCEPTFOREXPERIMENTALPURPOSES3UPERRESOLUTIONBASEDONASMALL
%,%#42/.)##/5.4%2 #/5.4%2-%!352%3
Ó{°Î£
3,# CONFIGURATION IS NOT EFFICIENT BECAUSE THIS LEADS TO THE MAXIMUM ENTROPY OR AUTOREGRESSIVEMETHODSTHAT BEINGNONLINEARPROCESSING HAVEAHIGHPROBABILITYOF SPURIOUSPEAKS 0RACTICALEXPERIENCESINDICATETHATTHERESOLUTIONLIMITISDETERMINEDRATHERMOREBY IMPLEMENTATIONANDENVIRONMENTALFACTORSTHANBYTHEPURE*.2CONSIDERATIONS
Ó{°ÇÊ /, - // ,, / Ê
4HEDIFFERENTTYPESOF%##-ARERELATEDTOTHEPROPERUSEANDCONTROLOFTHEPOWER FREQUENCY ANDWAVEFORMOFTHERADIATEDSIGNAL/NEBRUTE FORCEAPPROACHTODEFEAT NOISEJAMMINGISTOINCREASETHERADARSTRANSMITTERPOWER4HISTECHNIQUE WHENCOU PLEDWITHhSPOTLIGHTINGvTHERADARANTENNAONTHETARGET RESULTSINANINCREASEOFTHE RADARS DETECTION RANGE 3POTLIGHTING OR BURNTHROUGH MODES MIGHT BE EFFECTIVE BUT APRICEMUSTBEPAID!STHERADARDWELLSINAPARTICULARDIRECTION ITISNOTLOOKING ELSEWHEREWHERE IT IS SUPPOSED TO LOOK )N ADDITION THE BURNTHROUGH MODE IS NOT EFFECTIVEAGAINSTCHAFF DECOYS REPEATERS SPOOFERS ANDSOON -OREEFFECTIVEISTHEUSEOFCOMPLEX VARIABLE ANDDISSIMILARTRANSMITTEDSIGNALSTHAT PLACEAMAXIMUMBURDENON%3-AND%#-$IFFERENTWAYSOFOPERATIONREFERTOTHE CHANGEOFTHETRANSMITTEDFREQUENCYINFREQUENCY AGILITYORFREQUENCY DIVERSITYMODES ORTOTHEUSEOFWIDEINSTANTANEOUSBANDWIDTHn&REQUENCYAGILITYUSUALLYREFERSTO THERADARSABILITYTOCHANGETHETRANSMITTERFREQUENCYONAPULSE TO PULSEORABATCH TO BATCH BASIS 4HE BATCH TO BATCH APPROACH ALLOWS DOPPLER PROCESSING WHICH IS NOT COMPATIBLEWITHFREQUENCYAGILITYONAPULSE TO PULSEBASIS)NAWAVEFORMWITHPULSE TO PULSEFREQUENCYAGILITY THECENTERFREQUENCYOFEACHTRANSMITTEDPULSEISMOVED IN EITHERARANDOMORAPROGRAMMEDSCHEDULE BETWEENALARGENUMBEROFCENTERFREQUEN CIES4HEFREQUENCYOFTHENEXTPULSECANNOTGENERALLYBEPREDICTEDFROMTHEFREQUENCY OFTHECURRENTPULSE&REQUENCYDIVERSITYREFERSTOTHEUSEOFSEVERALCOMPLEMENTARY RADARTRANSMISSIONSATDIFFERENTFREQUENCIES EITHERFROMASINGLERADAREG ARADARHAV INGSTACKEDBEAMSINELEVATIONBYEMPLOYINGDIFFERENTFREQUENCIESONEACHELEVATION BEAM ORFROMSEVERALRADARS4HEOBJECTIVEOFFREQUENCYAGILITYANDDIVERSITYISTO FORCETHEJAMMERTOSPREADITSENERGYOVERTHEENTIREAGILEBANDWIDTHOFTHERADARTHIS CORRESPONDSTOAREDUCTIONOFTHEJAMMERDENSITYANDRESULTING%#-EFFECTIVENESS !GOODEXAMPLEOFTHEUSEOFTHEFREQUENCYDOMAINFORPURPOSEOF%##-ISTHE 3ENRAD ANEXPERIMENTALLONG RANGEAIR SURVEILLANCERADARBUILTANDTESTEDATTHE.AVAL 2ESEARCH,ABORATORY53 3ENRADWASANEXAMPLEOFHOWTOBUILDARADARSOAS TOFORCETHEJAMMERTODILUTEITSRADIATEDENERGYPERUNITBANDWIDTHITINCLUDESBOTH FREQUENCYAGILITYANDFREQUENCYDIVERSITY4HISRADARSHOWSTHATITSUNUSUALLYWIDE BANDWIDTHALLOWSAREDUCTIONOFTHEEFFECTIVENESSOFTHENOISEJAMMERTHATCANSERI OUSLYDEGRADEMORENARROWBANDRADARS &REQUENCY AGILITY DIVERSITY AND INSTANTANEOUS WIDEBAND TECHNIQUES REPRESENT A FORM OF %##- IN WHICH THE INFORMATION CARRYING SIGNAL IS SPREAD OVER AS WIDE A FREQUENCYORSPACEORTIME REGIONASPOSSIBLETOREDUCEDETECTABILITYBY%3-ANDOR !2-ANDMAKEJAMMINGMOREDIFFICULT4HIS%##-TECHNIQUEPERTAINSTOTHEREALM OFWAVEFORMCODING n 4HEAMBIGUITYFUNCTION!& ISTHETOOLTOCHARACTERIZEWAVEFORMCODINGINTERMS OFRESOLUTION SIDELOBELEVEL ANDAMBIGUITY)NSELECTINGAWAVEFORMFORAGIVEN RADARAPPLICATION THE!&SHOULDBETESTEDAGAINSTTHEENVIRONMENTINWHICHTHERADAR
Ó{°ÎÓ
2!$!2(!.$"//+
WILL BE EXPECTED TO OPERATE 4HE SO CALLED ENVIRONMENTAL DIAGRAM DEPICTS SPECTRAL SPATIAL ANDAMPLITUDECHARACTERISTICSOFTHERADARENVIRONMENTCLUTTER %#-SUCHAS CHAFF INTENTIONAL INTERFERENCES ANDPERHAPSINTERFERENCES FROM NEIGHBORING %- APPARATUSES ANDISUSEDTOASSISTTHERADARWAVEFORMDESIGN!NEXAMPLEOFANENVI RONMENTALDIAGRAMISONPOF,EVANONAND-OZESONONTHERANGE DOPPLERPLANE ARE SHOWN THE REGIONS IN WHICH SEVERAL TYPES OF CLUTTER AND HIGH ALTITUDE CHAFF ARE EXPECTED/NTHESAMEDIAGRAMARESUPERIMPOSEDTHEEXPECTEDTARGETTRAJECTORIESAND THE!&CONTOUROFA SAY PULSE BURSTWAVEFORM!STHETARGETFOLLOWSAPARTICULARTRA JECTORY THE!&WILLMOVEACCORDINGLYANDTHESPURIOUS!&PEAKSWILLSLIDEACROSSTHE CLUTTERANDCHAFFREGIONSDETERMININGTHEINTENSITYANDFEATURESOFTHERADARECHOES 7AVEFORMCODINGINCLUDES02&JITTERAND02&STAGGER WHICHAREHELPFULFORSOME DECEPTIONJAMMERBUTDONTHELPAGAINSTNOISEJAMMER7AVEFORMCODINGMAKESDECEP TIONJAMMINGORSPOOFINGOFTHERADARDIFFICULT SINCETHEENEMYSHOULDNOTKNOWOR ANTICIPATETHEFINESTRUCTUREOFTHETRANSMITTEDWAVEFORMASACONSEQUENCE ITGIVES ASSURANCEOFMAXIMUMRANGEPERFORMANCEAGAINSTSUCHTYPESOFJAMMING)NTRAPULSE CODINGTOACHIEVEPULSECOMPRESSIONMAYBEPARTICULARLYEFFECTIVEINIMPROVINGTARGET DETECTION CAPABILITY BY RADIATION OF ENOUGH AVERAGE RADAR POWER WITHOUT EXCEEDING PEAKPOWERLIMITATIONSWITHINTHERADARANDBYIMPROVINGRANGERESOLUTIONLARGERBAND WIDTH WHICH INTURN REDUCESCHAFFRETURNSANDRESOLVESTARGETSTOAHIGHERDEGREE 3OMEADVANTAGECANBEGAINEDBYINCLUDINGTHECAPABILITYTOEXAMINETHEJAMMER SIGNALS FINDHOLESINTHEIRTRANSMITTEDSPECTRA ANDSELECTTHERADARFREQUENCYWITHTHE LOWEST LEVEL OF JAMMING4HIS APPROACH IS PARTICULARLY USEFUL AGAINST PULSED %#- SPOTNOISE ANDNONUNIFORMBARRAGENOISEITSEFFECTIVENESSDEPENDSPRIMARILYONTHE EXTENTOFTHERADARAGILEBANDWIDTHANDTHEACQUISITIONSPEEDANDFREQUENCYTRACKINGOF ANhINTELLIGENTvJAMMER!TECHNIQUESUITEDTOTHISPURPOSEISREFERREDTOASAUTOMATIC FREQUENCYSELECTION!&3 !NOTHERMETHODTOREDUCETHEEFFECTOFMAIN BEAMNOISEJAMMINGISTOINCREASETHE TRANSMITTERFREQUENCYASANALTERNATIVEMEANSTOTHEUSEOFALARGERANTENNA INORDER TONARROWTHEANTENNASBEAMWIDTH4HISRESTRICTSTHESECTORTHATISBLANKEDBYMAIN BEAMJAMMINGANDALSOPROVIDESASTROBEINTHEDIRECTIONOFTHEJAMMER3TROBESFROM AFEWSPATIALLYSEPARATEDRADARSALLOWTHEJAMMERTOBELOCATED 4HEAVAILABILITYOFSOLID STATETRANSMITTERTECHNOLOGYnALLOWSTHEGENERATIONOF HIGHDUTYCYCLEWAVEFORMS WHICHMAYBEOFSOMEHELPTOREALIZE,0)RADAR !SAGENERALREMARK ONEOFTHEFACTORSPREVENTINGGOOD%##-ISTHEREDUCTIONOF %-SPECTRUMALLOCATEDTORADAR!SDISCUSSED OPERATINGOVERAWIDESPECTRALRANGE HASIMPORTANTADVANTAGESFOR%##- BUTTHECIVILIANANDCOMMERCIALTELECOMMUNICA TIONSYSTEMSERODEMOREANDMOREPORTIONSOFTHESPECTRUMATTHEEXPENSEOFMILITARY %##-CAPABILITY
Ó{°nÊ ,
6 ,, / Ê
*AMMING SIGNALS THAT SURVIVE THE ANTENNA %##- EXPEDIENTS CAN IF LARGE ENOUGH SATURATETHERADARPROCESSINGCHAIN7IDEDYNAMICRANGERECEIVERSNEEDTOBEUSEDTO AVOIDSATURATION !LOGARITHMICLOG RECEIVERMIGHTHELPAGAINSTNOISEJAMMING BUTITHASDETRIMEN TALEFFECTSAGAINSTCLUTTERWHENDOPPLERPROCESSINGISUSED!LOGRECEIVERISADEVICE WHOSEVIDEOOUTPUTISPROPORTIONALTOTHELOGARITHMOFTHEENVELOPEOFTHE2&INPUT SIGNALOVERASPECIFIEDRANGE)TMIGHTBEUSEFULINPREVENTINGRECEIVERSATURATIONIN
%,%#42/.)##/5.4%2 #/5.4%2-%!352%3
Ó{°ÎÎ
THEPRESENCEOFVARIABLEINTENSITIESOFJAMMINGNOISE"YCOMPARISONWITHALINEAR RECEIVEROFLOWDYNAMICRANGE MODERATEJAMMINGNOISELEVELSWILLNORMALLYCAUSE THECOMPUTERTOSATURATESOTHATTHETARGETSIGNALWILLNOTBEDETECTED4HEMAINDISAD VANTAGEISTHATALOGCHARACTERISTICCAUSESSPECTRALSPREADINGOFTHERECEIVEDECHOES)T WOULDNOTBEPOSSIBLETOMAINTAINCLUTTERREJECTIONINAN-4)ORPULSEDOPPLERRADARIF THESPECTRUMOFCLUTTERECHOESWERETOSPREADINTOTHESPECTRALREGIONINWHICHTARGET RETURNSWEREEXPECTED 4HEMAINMESSAGEISTHATTHEDYNAMICRANGEPROBLEMISIMPORTANTFORTHEREJECTION OF JAMMER AS WELL AS CLUTTER THE LATTER ALWAYS PRESENT IN A RADAR4HUS THE RECOM MENDATIONISTOIMPLEMENT INAMODERNRADAR ARECEIVERWITHAWIDELINEARDYNAMIC RANGEEG D" 4HISWIDEDYNAMICRANGENEEDSTOBEMAINTAINEDALSOINTHE!$# DEVICESWITHASUITABLENUMBEROFBITSASARULEOFTHUMB EACHBITADDSD"TOTHE DYNAMICRANGECOUNT (ARDORSOFTLIMITERSCANALSOBEUSEDTOCOUNTERJAMMINGSIGNALS4HEYARENONLINEAR MEMORYLESSDEVICESTHATCUTJAMMINGSIGNALSHAVINGWIDEAMPLITUDES4HE$ICKE &IX RECEIVERCOUNTERSHIGHRATESOFSWEPT FREQUENCY#7JAMMINGANDSWEPTSPOTNOISEJAM MERS )NARADARRECEIVER THE$ICKE &IXUSESAWIDEBANDINTERMEDIATE FREQUENCY )& AMPLIFIERANDALIMITERAHEADOFTHENARROW BANDWIDTH)&LIFIER4HEWIDEBAND AMPLIFIERALLOWSARAPIDRECOVERYTIMEFROMTHEEFFECTSOFTHESWEPTJAMMER ANDTHE LIMITERCUTSTHEJAMMINGSIGNAL4HENARROWBANDTARGETSIGNAL AFTERTRANSITTHROUGHTHE WIDEBAND AMPLIFIER AND THE LIMITER WITHOUT REMARKABLE DEGRADATION IS INTEGRATED BY THENARROWBANDFILTERMATCHEDTOTHESIGNAL4HEWORD&IXINTHE$ICKE &IXWASPUTTHERE MANYYEARSAGOTOINDICATEITWASAhFIXvFORAPROBLEMTHATOCCURREDATTHETIMEANDWAS TOBEREPLACEDBYSOMETHINGBETTER)TWASUSUALLYINSTALLEDWITHASWITCHTOTURNITOFF IF NECESSARY4ODAY$ICKE &IXISNOTUSEDINAMODERNRADAR ESPECIALLYONETHATEMPLOYS DOPPLERPROCESSINGTHUS ITISNOLONGEROFINTERESTINMANYRADARAPPLICATIONS /THERSPECIALPROCESSINGCIRCUITSCANBEUSEDINTHERADARTOAVOIDSATURATION IE FAST TIME CONSTANT &4# DEVICES PERHAPS OF LITTLE USE IN MODERN RADAR AUTOMATIC GAINCONTROL!'# AND#&!2 (OWEVER THEYCANNOTBESAIDTOBE%##-TECH NIQUES&OREXAMPLE &4#ALLOWSTHEDETECTIONOFSIGNALSTHATAREGREATERTHANCLUTTER BY PREVENTING THE CLUTTER FROM SATURATING THE COMPUTER &4# DOES NOT PROVIDE SUB CLUTTERVISIBILITY!'#KEEPSTHERADARRECEIVEROPERATINGWITHINITSDYNAMICRANGE PREVENTINGSYSTEMOVERLOADANDPROVIDINGPROPERNORMALIZATIONSOASTOFURNISHSIG NALSOFSTANDARDIZEDAMPLITUDETORADARRANGE VELOCITY ANDANGLEPROCESSING TRACKING CIRCUITS)NCONCLUSION THESEDEVICESHAVEAPLACEINTHERADARBUTNOTASMEANSFOR FIGHTINGTHE%#-BATTLE )NSUMMARY THEREISNTMUCHTHATHASBEENDONEINTHERECEIVERTOCOMBAT%#- OTHERTHANTOINSURETHEREISAGOODRECEIVERTHATDOESITSJOB4ODAY MODERNPHASED ARRAYMULTI CHANNELRADARAREGOINGTOADOPTFULLYDIGITAL SOFTWARECONTROLLEDRECEIVERS ASINTHE$!2CASEHERE THEEXPECTEDADVANTAGESARETHEWIDERLINEARDYNAMICRANGE ANDTHEWITHIN BANDCALIBRATIONOFTHERECEIVERSTHATWILLSUPPORTTHEADAPTIVITYONSEV ERALTENSOFCHANNELSADISTINCTIVEADVANTAGEAGAINSTDIRECTIONALNOISEJAMMERS
Ó{°Ê - *,"
-- , / Ê
$IGITALCOHERENTSIGNALPROCESSINGGREATLYALLEVIATESTHEEFFECTSOFCLUTTERANDCHAFF 4HISISMOTIVATEDBYTHEUSEOFCOHERENTDOPPLERPROCESSINGTECHNIQUESSUCHASFIXED ADAPTIVE -4) OR OPTIMUM PULSE DOPPLER PROCESSING .ONCOHERENT DEVICES ARE ALSO
Ó{°Î{
2!$!2(!.$"//+
REQUIREDBECAUSEOFTHELIMITEDDEGREEOFCLUTTER CHAFF ANDJAMMERSUPPRESSIONPRACTI CALLYACHIEVEDBYCOHERENTDEVICES SOTHATTHECANCELLATIONRESIDUEMAYSTILLBEASIG NIFICANTSOURCEOFFALSEALARM!MONGTHENONCOHERENTDEVICES ITISWORTHMENTIONING THE#&!2DETECTORnANDTHEPULSE WIDTHDISCRIMINATOR THISLATTERBEINGEFFECTIVE AGAINSTPULSEDJAMMERS4HEPULSE WIDTHDISCRIMINATIONCIRCUITMEASURESTHEWIDTHOF EACHRECEIVEDPULSE)FTHERECEIVEDPULSEISNOTOFAPPROXIMATELYTHESAMEWIDTHAS THETRANSMITTEDPULSE ITISREJECTED!PULSE WIDTHDISCRIMINATIONTECHNIQUECANHELP INREJECTINGCHAFFINFACT ECHORETURNSFROMCHAFFCORRIDORSAREMUCHWIDERTHANTHE TRANSMITTED PULSE (OWEVER IF A TARGET IS WITHIN THE CHAFF CORRIDOR THE PULSE WIDTH DISCRIMINATORMIGHTALSOELIMINATETHETARGET #OHERENT0ROCESSING 4HEMOSTEFFECTIVEANTI CHAFFTECHNIQUEAVAILABLETORADAR ISTHEUSEOFDOPPLERFILTERING WHICHEXPLOITSTHEDIFFERENTMOTIONCHARACTERISTICSOFTHE TARGETANDTHECHAFF4HECHARACTERISTICSOFCHAFFARESIMILARTOTHOSEOFWEATHERCLUTTER EXCEPTTHATTHECHAFF SCATTERINGELEMENTSARECUTTORESPONDTOABROADSPECTRUMOFRADAR FREQUENCIES7EATHERCLUTTERANDCHAFFDIFFERFROMGROUNDCLUTTERINTHATBOTHTHEMEAN DOPPLERSHIFTANDTHESPREADAREDETERMINEDBYWINDVELOCITYANDWINDSHEAR THELAT TERARISINGFROMTHEVARIATIONOFWINDVELOCITYWITHHEIGHT#HAFFMOVESWITHTHELOCAL WIND ANDTHEREAREWAYSADAPTIVE-4)ANDOPTIMUMDOPPLERPROCESSINGo TOMAKEAN -4)NULLOUTBOTHMOVINGANDSTATIONARYUNWANTEDECHOES 4HEREARETWOBASIC DOPPLERFILTERINGTECHNIQUESTHATAREUSED4HEFIRSTISTHE-4) WHICHEMPLOYSA02& THATPROVIDESUNAMBIGUOUSRANGECOVERAGEWHILEUSINGACOMBDOPPLERFILTERWHOSE NULLSARETUNEDTOTHEAVERAGERADIALSPEEDOFCHAFF4HESECONDISTHEPULSEDOPPLER WHICHCANUSEAHIGH02&TOPROVIDEUNAMBIGUOUSDOPPLERCOVERAGEINCONJUNCTION WITHADOPPLERFILTERBANK ALLOWINGSEPARATIONOFTARGETFROMTHECHAFF!PROBLEMWITH CHAFFMIGHTBEWHENTHEREISASIGNIFICANTWINDSHEARINTHEATMOSPHERE7ITHWIND SHEAR THEDOPPLERSPECTRUMFROMCHAFFCANHAVEAWIDESPECTRALWIDTHUNLESSTHEELEVA TIONBEAMWIDTHISVERYNARROWASMIGHTOCCURWITHTRI DIMENSIONALRADARWITHSTACKED BEAMSINELEVATION SOTHATITISDIFFICULTTOCANCELMOVINGCHAFFECHOES!PULSEDOP PLERRADARHASABETTERCHANCE BUTITHASPROBLEMSOFITSOWNBECAUSEOFTHEFOLDOVEROF THECLUTTERTHATMIGHTOCCUPYALARGERANGEEXTENT #OHERENTDOPPLERPROCESSORSMIGHTREQUIRERELATIVELYLARGEAMOUNTSOFPULSESEG MORETHAN WHICHMUSTBETRANSMITTEDATASTABLEFREQUENCYAND02&!RESPONSIVE JAMMERCOULDMEASURETHEFREQUENCYOFTHEFIRSTTRANSMITTEDPULSEANDTHENCENTERTHE JAMMERTOSPOT JAMTHEFOLLOWINGPULSES!LSO THEREQUIREMENTFORASTABLE02&PRE CLUDESTHEUSEOFPULSE TO PULSEJITTER WHICHISONEOFTHEMOSTEFFECTIVETECHNIQUES AGAINSTDECEPTIONJAMMERSTHATRELYONANTICIPATINGTHERADARTRANSMITTERPULSE#OHERENT DOPPLERPROCESSORSAREALSOGENERALLYVULNERABLETOIMPULSIVERADIOFREQUENCYINTERFER ENCE ESPECIALLYINRADARSWITHALIMITEDNUMBEROFCOHERENTBURSTSONTARGET !NOTHER %##- TECHNIQUE TO BE CONSIDERED IS PULSE COMPRESSION BY MATCHED FILTERINGITISINTIMATELYRELATEDTOTHEWAVEFORMCODINGDISCUSSEDIN3ECTION 0ULSECOMPRESSION ISAPULSERADARTECHNIQUEINWHICHLONGPULSESARETRANS MITTEDTOINCREASETHEENERGYONTHETARGETWHILESTILLRETAININGTHETARGETRANGERESO LUTIONOFASHORTPULSETRANSMISSION)TISALMOSTALWAYSUSEDINRADARFORACHIEVING o4HEADAPTIVE-4)ESTIMATESTHEMEANDOPPLERFREQUENCYOFAMOVINGCLUTTERSOURCEANDPLACESTHENULLOF SAY A BINOMIAL-4)/PTIMUMDOPPLERPROCESSINGESTIMATESTHEWHOLESPECTRUMOFCLUTTERANDSHAPES BYMEANSOFTHE INVERSEOFTHECLUTTERCOVARIANCEMATRIX THECANCELLATIONFILTERACCORDINGLYFURTHERMORE WITHADOPPLERFILTERBANK ITINTEGRATESTHEECHOSIGNALFROMMOVINGTARGETS4HEOPTIMUMFILTERWEIGHTSARECALCULATEDBYANEQUATIONSIMILAR TO%QAPPLIEDTOTHERADARECHOESRECEIVEDBYACOHERENTPULSETRAINTRANSMITTEDBYTHERADAR
%,%#42/.)##/5.4%2 #/5.4%2-%!352%3
Ó{°Îx
HIGHRANGERESOLUTIONORREDUCINGTHEPEAKPOWER0ULSECOMPRESSIONOFFERSSOME %##-ADVANTAGETHATISDISCUSSEDHEREAFTER 7HENTHEPULSECOMPRESSIONSEARCH RADARISCOMPARED FROMAN%3-STANDPOINT WITHACONVENTIONALSEARCHRADARWITH THESAMEWIDEPULSE THEENEMYRECEIVERONAJAMMINGPLATFORMWILLNOTKNOWIN THEGENERALCASE THEPULSECOMPRESSIONREFERENCECODEANDWILLBEATADISADVANTAGE #OMPAREDWITHARADARTHATUSESANUNCOMPRESSEDWIDEPULSE THEPULSECOMPRESSION TECHNIQUEINCREASESTHERADARSCAPABILITYAGAINSTEXTENDEDSIGNALRETURNSLIKECHAFF AND CLUTTER )N ADDITION NOISE FROM A JAMMER DOES NOT PULSE COMPRESS %XTENDED CLUTTERTENDSTOBENOISELIKEANDWILLNOTPULSE COMPRESS WHICHKEEPSDOWNINTER FERENCEDISPLAYEDTOOPERATORS4HEDISADVANTAGESOFPULSECOMPRESSIONARERELATED TOTHELONGDURATIONOFTHECODEDPULSE WHICHGIVESMORETIMEFORTHE%#-EQUIP MENTTOPROCESSTHEPULSE)NMANYCASES PULSECOMPRESSIONCANPROVIDETHEMEANS FOR EASY RADAR JAMMING FOR THE ENEMY %#- OPERATOR 0ULSE COMPRESSION IS ALSO VULNERABLETOCOVER PULSEJAMMING INWHICHTHE%#-PULSEISRETURNEDTOTHERADAR WITHAHIGH*.2SUCHTHATTHENORMALTARGETRETURNISCOVEREDBYTHEJAMMINGPULSE 4HEWIDTHOFTHE%#-PULSEISNORMALLYWIDERTHANTHERADARSKINRETURN4HISTYPE OFDECEPTIONCANBECOUNTERACTEDBYAN%##-TECHNIQUESUCHASTHECOVER PULSE CHANNEL WHERE THE TRACKING IS ON THE %#- TRANSMISSION RATHER THAN ON THE SKIN RETURNFROMTHETARGET 4HEDIGITALCOHERENTIMPLEMENTATIONOFTHE$ICKE &IXRECEIVERCONCEPTREQUIRESTHE USEOFACOHERENTHARDLIMITERTHATPRESERVESTHEPHASEOFTHESIGNALWHILEKEEPINGTHE AMPLITUDEATACONSTANTVALUEp4HECOHERENTLIMITERISINSERTEDUPSTREAMOFTHEPULSE COMPRESSIONFILTERINARADARTHATUSESPHASE CODEDSIGNALS)NRECEPTION THEJAMMER AND TARGET SIGNALS ARE CUT IN AMPLITUDE4HE PRESERVATION OF THE TARGET SIGNAL PHASE CODING ALLOWS THE INTEGRATION OF TARGET ENERGY BY MEANS OF THE PULSE COMPRESSION FILTERMATCHEDTOTHEPHASECODE4HE$ICKE &IXPROCESSINGSCHEMESUFFERSFROMTHREE LIMITATIONS4HEFIRSTISRELATEDTOTHEDETECTIONLOSSEXPERIENCEDWHENTHETARGETDOES NOTCOMPETEWITHTHEJAMMER4HESECONDDISADVANTAGEREFERSTOTHEMASKINGEFFECT OFAWEAKTARGETSIGNALSUFFICIENTLYCLOSEINRANGECOMPAREDWITHTHESPATIALEXTEN SIONOFTHECODE TOASTRONGTARGET&URTHERMORE ITCANNOTBEUSEDINCONJUNCTIONWITH DOPPLERPROCESSING #&!2 #&!2 IS A TECHNIQUE MADE NECESSARY TO PREVENT THE COMPUTER FROM BEINGOVERLOADEDBYFALSEALARMS WHICHREDUCETHECAPABILITYOFTHERADARTODETECT DESIREDTARGETS4HISPROCESSINGALSOPLAYSAROLEAS%##-THEREARETHREEMOTIVA TIONSFORTHIS &IRST THESCOPEOF%#-TECHNIQUES INABROADSENSE ISTOIMPAIRTHETARGETDETEC TIONANDTRACKINGPERFORMANCEOFARADARSYSTEM$ETECTIONPERFORMANCEISMEASURED BYTHEPROBABILITYOFDETECTIONTRACKINGPERFORMANCEISDETERMINEDBYTHEPROBABILITY OFDETECTIONANDTHEPROBABILITYOFFALSEALARMASWELL#ONVENTIONALCELLAVERAGING #&!2RAISESTHETHRESHOLDINTHEPRESENCEOFNOISEJAMMINGANDREDUCESTHENUMBEROF TARGETSDETECTED(OWEVER THETARGETSTHATSURVIVECANBEEFFECTIVELYTRACKEDBECAUSE THEPROBABILITYOFFALSEALARMHASBEENMAINTAINEDATSUFFICIENTLYLOWLEVELS7ITHOUT #&!2ANDAPPROPRIATETHRESHOLDADJUSTMENTS PERHAPSNOTARGETSWILLBETRACKEDDUETO THEVERYLARGENUMBEROFFALSEPEAKSDETECTIONSONTHEJAMMER MAKINGITTHROUGHTO SATURATETHETRACKER#ONVENTIONAL#&!2ISNOTREALLYREMOVINGTHEINTERFERENCEITIS JUSThHIDINGvITFROMTHERADAROPERATOR(OWEVER ITISALLOWINGTHETRACKERTOOPERATE p4HISISUSEDWITH"ARKERCODES FORINSTANCE WHERETHEAMPLITUDELIMITATIONDOESNTIMPAIRTHEPHASECODE
Ó{°ÎÈ
2!$!2(!.$"//+
EFFECTIVELYFORTHETARGETSTHATSURVIVE ANDSOINTHISWAY ITCANPREVENTTHEOVERALL FAILUREOFTHERADAR)NTHELIMITOFNOTARGETSBEINGDETECTEDIE AVERYPOWERFULJAM MER THENITCOULDSTILLBEARGUEDTHATNOTRACKSAREBETTERTHANMANYFALSETRACKS 3ECOND NOT ALL JAMMERS ARE NOISE JAMMERS 3OME INDEED HAVE A STRUCTURE IN RANGE DOPPLER SPACE AND #&!2 TECHNIQUES CAN POTENTIALLY BE USED TO LOWER THESE UNWANTEDSIGNALSBENEATHTHEDETECTIONTHRESHOLD ONCEAGAINPREVENTINGTHEDETEC TIONOFFALSETRACKS WHICHFROMATACTICALPERSPECTIVECANCAUSESERIOUSDILEMMAS FORARADAROPERATOR 4HIRD THERE ARE THE ADAPTIVE #&!2 DETECTORS !-& OR ADAPTIVE MATCHED FILTER FOREXAMPLE THATREALLYARE%##-TECHNIQUESINTHESENSETHATTHEYENHANCETHE PROBABILITYOFDETECTIONAGAINSTSTRUCTUREDINTERFERENCESINSPACEANDORTIME WHILE MAINTAININGTHECONSTANTFALSEALARMRATEPROPERTYTHATALLOWSTHESEDETECTEDTARGETSTO BEEFFECTIVELYTRACKED RATHERTHANBEINGSEDUCEDBYAHIGHNUMBEROFFALSEDETECTIONS 4HISTYPEOFPROCESSINGORSIMILARLYDERIVEDFROMTHEGENERALIZEDLIKELIHOODRATIO TEST',24 HASBEENUSEDINSOMEPRACTICALRADAR &URTHERMORE ANYSELF RESPECTINGRADARSYSTEMSHOULDMAKETHEOPERATORAWAREOF HIGHERNOISELEVELSDUETOJAMMINGEVENTHOUGHTHEYMAYNOTBEVISIBLEONTHE#&!2 DISPLAYTHEACTOFPERFORMING#&!2SHOULDNOTEXCLUDETHEOPERATORFROMKNOWING THATJAMMINGISPRESENTANDTHATTHEDETECTIONTHRESHOLDHASBEENRAISED
Ó{°£äÊ "* ,/" * "9 /Ê / +1 4OTHISPOINTINTHECHAPTER ONLYELECTRONIC%##-TECHNIQUESHAVEBEENCONSIDERED (OWEVER RADAROPERATIONALPHILOSOPHYANDDEPLOYMENTTACTICSMAYALSOHAVEASIG NIFICANTEFFECTONTHERADARSRESISTANCETO%#- %3- AND!2-4HISGROUPOFTECH NIQUESCANBESUBDIVIDEDINTOTHOSEINVOLVINGTHEOPERATOR THEMETHODSOFOPERATION THERADARDEPLOYMENTTACTICS ANDTHEFRIEND%3-INSUPPORTTO%##-!NOPERATIONAL TECHNIQUEAGAINST%#-ISTOUSEMISSILESWITHHOMEONJAM(/* GUIDANCETOINTER CEPTNOISEJAMMERS(/*ISAMEANSWHEREBYAMISSILEGUIDANCERECEIVERUTILIZESTHE SELF SCREENINGTARGETJAMMINGSIGNALTODEVELOPANGULARSTEERINGINFORMATIONSOTHE MISSILECANHOMEONTHATTARGET 4HEROLEOFTHEOPERATORINTHE%##-CHAINPERTAINSTOTHEMOREGENERALTOPICOF HUMAN FACTOR%##-4HISISAGENERIC%##-TECHNIQUETHATCOVERSTHEABILITYOF ANAIRDEFENSEOFFICER ARADAROPERATOR ACOMMANDINGOFFICER ANDORANYOTHERAIR DEFENSEASSOCIATEDPERSONNELTORECOGNIZETHEVARIOUSKINDSOF%#- TOANALYZETHE EFFECTOFTHE%#- TODECIDEWHATTHEAPPROPRIATE%##-SHOULDBE ANDORTOTAKE THENECESSARY%##-ACTIONWITHINTHEFRAMEWORKOFTHEPERSONSCOMMANDSTRUCTURE (OWEVER THEHUMANOPERATORISLESSEFFECTIVEAGAINSTASIMULTANEOUSATTACKOFMANY ENEMYVEHICLESSUPPORTEDBYASTRONG%#-FORCE!NOPERATORCONFRONTEDWITHALARGE MIXOF%#-TYPESANDALARGENUMBEROF%##-TECHNIQUESISLIKELYTODOTHEWRONG THINGANDORREACTTOOSLOWLY)NTHISSITUATION ITMIGHTBEPROPERTORESORTTOAUTO MATICALLYAPPLIED%##-TECHNIQUESTHISISTHETENDENCYTODAY(OWEVER APOSSIBLE CONCERNISTHATTHISCOULD SOMETIMES HURTTHE%##-CAPABILITYOFTHERADARSINCEA WELL TRAINEDOPERATORCANOFTENFIGUREOUTWHATISHAPPENINGBUTTHEAUTOMATICPROCES SORCANONLYMAKEDECISIONSBASEDONPREPROGRAMMEDLOGICSINSTALLEDINITSCOMPUTER ANDMIGHTNOTRECOGNIZEWHENSOMETHINGUNUSUALASINJAMMING OCCURS4HISISA POSSIBLEADVERSEEFFECTOFTHEABSENCEOFADECISION MAKINGOPERATOR
%,%#42/.)##/5.4%2 #/5.4%2-%!352%3
Ó{°ÎÇ
4HE OPERATIONAL METHODS INCLUDE EMISSION CONTROL %-#/. THE APPROPRIATE ASSIGNMENTOFOPERATINGFREQUENCIESTOVARIOUSRADARS THEUSEOFCOMBINED%##-S TOMEETCOMBINED%#-S THEUSEOFDUMMYTRANSMITTERSTODRAW%#-TOOTHERFRE QUENCIES AND SO ON %-#/. IS A TECHNIQUE FOR THE MANAGEMENT OF ALL %- RADIA TIONSOFAFRIENDLYSYSTEM FORCE ORCOMPLEXTOOBTAINMAXIMUMADVANTAGESINTHE AREASOFINTELLIGENCEDATARECEPTION DETECTION IDENTIFICATION NAVIGATION MISSILEGUID ANCE ETC OVERTHEENEMYINAGIVENSITUATION%-#/.PERMITSESSENTIALOPERATIONS WHILEMINIMIZINGTHEDISCLOSUREOFLOCATION IDENTIFICATION FORCELEVEL OROPERATIONAL INTENTIONSTOENEMYINTELLIGENCERECEPTORS)TINCLUDESTHEAUTHORIZATIONTORADIATE THE CONTROL OF RADIATION PARAMETERS SUCH AS AMPLITUDE FREQUENCY PHASE DIRECTION AND TIME THEPROHIBITIONOFRADIATION ANDTHESCHEDULINGOFSUCHACTIONSFORALLUNITSAND EQUIPMENTOFACOMPLEX4HEON OFFSCHEDULINGOFTHERADARSOPERATION TOINCLUDE ONLYTHOSETIMEINTERVALSWHENSURVEILLANCEISREQUIRED CANREDUCETHEPROBABILITYOF THERADARLOCATIONBEINGFOUNDBYDIRECTIONFINDING$& EQUIPMENTORRADARHOMING ANDWARNINGRECEIVERS2ADARBLINKINGUSINGMULTIPLERADARSWITHCOORDINATEDON OFF TIMES CANCONFUSEAN!2-SEEKERANDGUIDANCEORA$&RECEIVER$ECOYTRANSMITTERS RADIATINGFROMANTENNASNOTLOCATEDATTHERADAR MAYALSOBEEMPLOYEDTOCONFUSE$& RECEIVERSAND!2-STHESEDECOYSCANALSOOPERATEINCONJUNCTIONWITHTHERADARSIN ABLINKINGMODE 0ROPER SITE SELECTION FOR GROUND BASED RADARS IN FIXED INSTALLATIONS CAN PROVIDE A DEGREEOFNATURALSIGNALMASKINGTOPREVENT FOREXAMPLE DETECTIONBYGROUND BASED %3-EQUIPMENT!HIGHDEGREEOFMOBILITYFORTACTICALSYSTEMSALLOWShRADIATEANDRUNv OPERATIONS WHICHAREDESIGNEDTOPREVENTTHERADARFROMBEINGENGAGEDBY$&LOCATION TECHNIQUESANDASSOCIATEDWEAPONS4HEDEPLOYMENTOFARADARNETWORKWITHOVERLAP PINGCOVERAGECOULDPROVIDESOME%##-BENEFITS)NTHENETTEDMONOSTATICCASE THE RADARS HAVE DIFFERENT FREQUENCIES FOR INTERFERENCE REDUCTION PURPOSES CONSEQUENTLY THE%#-HASTOCONSIDERJAMMINGALLRADARSINTHEOVERLAPPINGZONE THUSREDUCINGITS EFFICACY4HISISTHEKINDOFFREQUENCYDIVERSITYDISCUSSEDIN3ECTION &INALLY ITISWORTHNOTINGTHATFRIENDLY%3-CANSUPPORT%##-ACTIONBYWARN ING OF POSSIBLE HOSTILE ACTIVITY PROVIDING ANGULAR LOCATIONS OF HOSTILE JAMMERS AND INFORMATIONCHARACTERISTICSOFJAMMERS4HISINFORMATIONISHELPFULINTHESELECTIONOF ASUITABLE%##-ACTION
Ó{°££Ê ** /" Ê"Ê
Ê/ +1 4HISSECTIONSHOWSTHEAPPLICATIONOFTHEPREVIOUSLYDESCRIBED%##-TECHNIQUESTO SURVEILLANCE TRACKING PHASED ARRAY IMAGING AND OVER THE HORIZON RADARS4HE USE OF%##-TECHNIQUESINOTHERTYPESOFRADARSSUCHASMORTARLOCATIONRADARS MISSILE GUIDANCERADARS ANDNAVIGATIONRADARSISCONSIDEREDINTHELITERATURE 3URVEILLANCE2ADARS 4HEFUNCTIONOFASURVEILLANCERADARISTOSEARCHALARGE VOLUME OF SPACE AND LOCATE THE POSITION OF TARGETS WITHIN THE SEARCH COVERAGE4HE RADARRANGEANDTHEAZIMUTH ELEVATIONCOVERAGEDEPENDONTHESPECIFICRADARAPPLICA TIONS4HETARGETREPORTSGENERATEDBYASURVEILLANCERADARAREPROCESSEDTOFORMTARGET TRACKS4HEKEYFEATURESOFASURVEILLANCERADARARETHEDETECTIONRANGEINCLEAR CLUTTER ANDJAMMINGENVIRONMENTS THEACCURACYANDRATEOFTHEEXTRACTEDDATA ANDTHEFALSE ALARMRATE)NTHEENSUINGDISCUSSION THEDESIGNPRINCIPLES DRIVENBYTHEREQUIREMENTS FORCEDBYTHETHREAT AREMAINLYADDRESSED
Ó{°În
2!$!2(!.$"//+
$ETECTIONINACLEARENVIRONMENTISAFEATUREOFEARLY WARNINGRADARS eWHICHLOOK PRIMARILYFORHIGH ALTITUDETARGETSATLONGRANGESBEYONDTHESURFACEHORIZON WHERETHE EFFECTSOFCLUTTERCANBEIGNORED5NDERTHESECONDITIONS ASIMPLIFIEDANALYSISSTATES THATRADARPERFORMANCEISRELATIVELYINSENSITIVETOTRANSMITTERFREQUENCYANDWAVEFORM SHAPEINPRACTICE THELOWERMICROWAVEFREQUENCIESAREPREFERREDBECAUSEITISEASIER TOOBTAINLARGEANTENNAANDHIGHAVERAGEPOWERATLOWERFREQUENCIES ANDRAINCLUTTER ISNOTIMPORTANT4HEMAXIMUMDETECTIONRANGEONATARGETWITHACERTAIN2#3R IN FREESPACE FORASURVEILLANCERADARTHATMUSTUNIFORMLYSEARCHASPECIFIEDVOLUMEIN AGIVENTIMEPERIOD DEPENDSONTHEPRODUCTOFTHEAVERAGETRANSMITTERPOWER 0 AND THEEFFECTIVEANTENNAAPERTURE!R )TALSODEPENDSONTHEINVERSEOFTHESYSTEMNOISE TEMPERATURE BUTTHISISOFLITTLECONSEQUENCESINCETHENOISETEMPERATUREISNOTAMAJOR DESIGNISSUEANYMORE4HESITUATIONISMORECOMPLEXWHENTHETARGETTOBEDETECTED ISOFTHESTEALTHTYPE 7AVEFORMDESIGNANDOPERATINGFREQUENCYARERELEVANTPARAMETERSINTACTICALAND VOLUMESURVEILLANCERADARS WHICHMUSTBEABLETODETECTLOW FLYINGPENETRATINGTAR GETSTHATATTEMPTTOUSETERRAIN SHIELDINGEFFECTSTOESCAPERADARDETECTION)NTHISCASE THESELECTIONOFWAVEFORMANDFREQUENCYISMADETOTACKLETHEPROBLEMSOFMASKING MULTIPATH CHAFF CLUTTER AND%#- 4HE MAJOR %7 THREATS TO A SURVEILLANCE RADAR ARE I NOISE JAMMING II CHAFF III DECEPTIONJAMMING IV DECOYSANDEXPENDABLES ANDV !2- #OMMON TYPES OF JAMMING ARE MAIN BEAM NOISE JAMMING AND SIDELOBE NOISE JAMMING!GAINSTTHISTHREAT GOODRADAR%##-PERFORMANCEISACHIEVEDBYINCREAS INGTHEPRODUCT 0!R OFAVERAGETRANSMITTERPOWERBYTHEEFFECTIVEANTENNAAPERTURE !MILITARYRADARSHOULDALWAYSHAVED"MOREPOWER APERTUREPRODUCTTHANGIVEN BYSTANDARDDESIGNS YETTHISISSELDOMALLOWED4HEREQUESTFORALOWSIDELOBELEVEL HASTOBETRADEDOFFWITHTHECORRESPONDINGDEGRADATIONOFTHEMAIN BEAMWIDTH THEWIDENINGOFTHEMAIN BEAMWIDTHMAYMAKETHERADARMOREVULNERABLETOMAIN BEAMJAMMING 4HENOISEJAMMERSITUATIONISBASICALLYANENERGYBATTLEBETWEENTHERADARANDTHE JAMMER)NTHEMAIN BEAMNOISE JAMMINGSITUATION THEADVANTAGEISWITHTHEJAMMER BECAUSETHERADAREXPERIENCESATWO WAYPROPAGATIONLOSSOFITSENERGYASCONTRASTED WITHTHEONE WAYPROPAGATIONLOSSBETWEENTHEJAMMERANDTHERADAR7ITHSIDELOBE JAMMING THERADARDESIGNERCANREDUCETHEJAMMERADVANTAGEBYLOWSIDELOBEDESIGN COUPLEDWITHTHEUSEOFSIDELOBECANCELLATIONTECHNIQUES7ITHMAIN BEAMNOISEJAM MING THERADARCANMAXIMIZETHERECEIVEDTARGETENERGYBYTRANSMITTINGMOREAVERAGE POWER DWELLINGLONGERONTHETARGET ORINCREASINGTHEANTENNAGAIN)FTHERADARSDATA RATE IS FIXED AND A UNIFORM ANGULAR SEARCH RATE IS DICTATED BY MECHANICAL OR SEARCH STRATEGY THENTHEONLYOPTIONFORTHERADARISTOINCREASEITSAVERAGETRANSMITTERPOWER 4HENEXTOPTIONISTOMANAGETHEDATARATE THEREBYALLOWINGALONGERDWELLTIMEONTHE TARGETBURNTHROUGHMODE ALONGSPECIFICSPATIALSECTORSWHERENEEDED4HEABILITYTO VARYTHEDATARATEINANOPTIMALMANNERISONEOFTHEPRINCIPALADVANTAGESOFPHASED ARRAYRADARS !NOTHERPRINCIPLEOF%##-DESIGNAGAINSTMAIN BEAMNOISEJAMMINGISTOMINI MIZETHEAMOUNTOFJAMMINGENERGYACCEPTEDBYTHERADAR4HISISACCOMPLISHEDBY SPREADINGTHETRANSMITTEDFREQUENCYRANGEOFTHERADAROVERASWIDEABANDASPOS SIBLE THUSFORCINGTHEJAMMERINTOABARRAGE JAMMINGMODE4HISCANBEOBTAINEDBY e/FCOURSE SUCHRADARSHAVETOSEEALSOTARGETSATSHORTERRANGESWHERECLUTTERECHOESCANMASKTHETARGETSECHOFOR THISREASON ALLLONGRANGECIVILAIRTRAFFICCONTROLRADAREMPLOYDOPPLERPROCESSING
%,%#42/.)##/5.4%2 #/5.4%2-%!352%3
Ó{°Î
RESORTINGTOFREQUENCYAGILITYANDORFREQUENCYDIVERSITY3OMERADARSINCORPORATEAN !&3DEVICETHATALLOWSTHERADARFREQUENCYTOBETUNEDTOTHATPARTOFTHESPECTRUM CONTAININGTHEMINIMUMJAMMINGENERGY )NACCORDANCEWITHTHESEARCH RADAREQUATIONSEE3ECTION %##-PERFOR MANCEAPPEARSEXPLICITLY TOBEINSENSITIVETOFREQUENCY )NCREASINGTHERADARFRE QUENCYDOESNOTAFFECTTHESIGNAL TO INTERFERENCEENERGYRATIOWITHINARADARRESOLUTION CELLWHENTHEANTENNAAPERTUREANDTHERADARDATARATEAREHELDCONSTANT4HEINCREASED FREQUENCYINCREASESBOTHTHEANTENNAGAINANDTHENUMBEROFRADARRESOLUTIONCELLSTHAT MUSTBESEARCHEDBYEQUIVALENTAMOUNTSTHENETEFFECTISTHATTHETARGETRETURNPOWER ISINCREASEDBYTHESAMEAMOUNTBYWHICHTHETARGETDWELLTIMEISDECREASED THEREBY HOLDING THE TARGET TO JAMMING ENERGY RATIO CONSTANT .EVERTHELESS IN PRACTICE THE EFFECTOFMAIN BEAMNOISEJAMMINGCANBEREDUCEDWITHHIGHRADARFREQUENCY(IGHER FREQUENCYRADARSTENDTOHAVENARROWERANTENNABEAMWIDTHSANDLARGEROPERATINGFRE QUENCYBANDWIDTHSTOPERCENTOFRADARCENTERFREQUENCY THANLOWERFREQUENCY RADARS4HUS MAIN BEAMJAMMERSWILLBLANKSMALLERSECTORSOFHIGHFREQUENCYRADARS THAN OF LOW FREQUENCY RADARS )N ADDITION MAIN BEAM JAMMING OF A NARROW BEAM RADARTENDSTOPROVIDEASTROBEINTHEDIRECTIONOFTHEJAMMER WHICHCANBEUSEDTO TRIANGULATEANDREVEALTHEJAMMERLOCATION7IDERRADARBANDWIDTH WITHAPPROPRIATE CODING FORCESTHEJAMMERTOSPREADITSENERGYOVERAWIDERBAND THEREBYDILUTINGTHE EFFECTIVEJAMMINGENERGY %##- DESIGN PRINCIPLES FOR MAIN BEAM NOISE JAMMING ALSO APPLY TO SIDELOBE NOISEJAMMING WITHTHEADDITIONTHATTHESIDELOBERESPONSEINTHEDIRECTIONOFTHE JAMMER MUST BE MINIMIZED 5LTRALOW SIDELOBES IN THE ORDER OF SAY D" BELOW THEANTENNASMAIN BEAMPEAKRESPONSEAREFEASIBLEBYUSINGADVANCEDTECHNOLOGY 3OMETIMESTHECONTROLOFSIDELOBENOISEJAMMINGBYUSINGULTRALOW SIDELOBEANTEN NASISNOTPROPERTHISISTRUEBECAUSETHEMAIN BEAMWIDTHMIGHTBEINCREASEDTWO TO THREETIMES )N ADDITION MOST OPERATIONAL RADARS DO NOT USE ULTRALOW LESS THAN
D" ORLOW TO D" SIDELOBEANTENNASANDHAVEANTENNASIDELOBESINTHE
TO D"REGIONWITHAVERAGESIDELOBESOFTOD"BELOWISOTROPIC3,#HAS THEPOTENTIALOFREDUCINGNOISEJAMMINGTHROUGHTHEANTENNASIDELOBES ANDITISUSED FORTHISPURPOSEINOPERATIONALRADARS !S EXPLAINED IN 3ECTION %##- TECHNIQUES AGAINST CHAFF ARE MAINLY THOSE BASEDONCOHERENTDOPPLERPROCESSING )NPARTICULAR THEREFERENCEDESCRIBESA COMPARISONOFFIXEDANDADAPTIVEDOPPLERCANCELERSAPPLIEDTOCHAFFDATARECORDEDBY AMULTIFUNCTIONALPHASED ARRAYRADAROPERATINGAT3BAND"OTHCANCELERSPROCESSAN PULSECOHERENTBURST4HEFIXEDIE NONADAPTIVE PROCESSINGISA$OLPH #HEBYSHEV FILTERWITHD"OFSIDELOBEATTENUATIONWITHRESPECTTOPEAK4HEADAPTIVEFILTER BASED ONTHEOPTIMUMDOPPLERFILTERINGSEE3ECTIONANDTHELITERATURE HASTHE WEIGHTSBUILTAROUNDTHEESTIMATIONANDINVERSIONOFTHEDISTURBANCECHAFFANDNOISE COVARIANCEMATRIX4HETARGETDETECTABILITYISEVALUATEDAGAINSTADENSECHAFFCLOUD &OR THE PARTICULAR SET OF RECORDED MEASUREMENTS IT HAS BEEN SHOWN A SUBSTANTIALLY ENHANCEDPERFORMANCEOFTHEADAPTIVEFILTEROVERTHENONADAPTIVEFILTER
!SMENTIONEDPREVIOUSLY THELOWERFREQUENCIESMIGHTBEPREFERREDFORLONG RANGESURVEILLANCEBECAUSETHEUSUAL RADAREQUATIONDOESNOTINCLUDEALLTHEPERTINENTFACTORS)NTHEJAMMINGCASE ONESHOULDTAKEACCOUNTTHATTHE JAMMINGANTENNAONANAIRCRAFTHASALOWERGAINATLOWERFREQUENCIESSOTHEJAMMINGPOWERDENSITYMIGHTBELESS ATTHELOWERFREQUENCIES!LSO WHENMULTIPATHISIMPORTANT BYSELECTINGTHERADARFREQUENCYPROPERLY ONEMIGHT REDUCETHEJAMMINGPOWERRECEIVEDBYBEINGINANULLOFTHEJAMMERTRANSMITTINGANTENNA#HAFFMIGHTNOTBEAS EASYTODEPLOYATTHELOWERFREQUENCIES)NCONCLUSION THELOWERRADARFREQUENCIESMIGHTNOTBEASVULNERABLEAS ONEMIGHTTHINKBYEXAMININGTHETRADITIONALRADAREQUATION
Ó{°{ä
2!$!2(!.$"//+
!NOTHER CLASS OF %##- TECHNIQUES IS AIMED TO CONTRAST THE DECEPTIVE %#- $ECEPTION JAMMERS HAVE A NUMBER OF SPECIFIC CHARACTERISTICS THAT CAN BE USED BY RADARSTOIDENTIFYTHEIRPRESENCE4HEMOSTPROMINENTISTHATFALSE TARGETRETURNSMUST USUALLYFOLLOWTHERETURNFROMTHEJAMMER CARRYINGTARGETANDMUSTALLLIEINTHESAME DIRECTIONWITHINARADAR02))FTHEDECEPTIONJAMMERUSESADELAYTHATISGREATERTHAN A02)PERIODTOGENERATEANANTICIPATORYFALSE TARGETRETURN THENPULSE TO PULSE02) JITTER IDENTIFIES THE FALSE TARGET RETURNS4HE GENERATION OF FALSE TARGETS IN DIRECTIONS DIFFERENTFROMTHATOFTHEJAMMER CARRYINGAIRCRAFTREQUIRESINJECTINGPULSE JAMMING SIGNALSINTOTHERADARSSIDELOBES-ANYRADARSEMPLOYTHE3,"SEE3ECTION TO DEFEATTHISTYPEOF%#- 4RUE TARGETRETURNSTENDTOFLUCTUATEFROMSCANTOSCANWITHFIXED FREQUENCYRADARS ANDFROMPULSETOPULSEWITHFREQUENCY AGILITYRADARS4RANSPONDERJAMMERSGENER ALLYSENDTHESAMEAMPLITUDEREPLYTOALLSIGNALSTHEYRECEIVEABOVEATHRESHOLDAND THEREFORE DONOTSIMULATEACTUALTARGETFLUCTUATIONRESPONSES)NADDITION THEYUSUALLY APPEARWIDERINAZIMUTHTHANREALTARGETSOWINGTOTHEMODULATIONEFFECTOFTHERADAR SCANNINGANTENNASRESPONSEONTHEREALTARGET2EPEATERJAMMERSCANBEMADETOSIMU LATETHEACTUALAMPLITUDERESPONSEOFREALTARGETSAND HENCE AREMOREEFFECTIVEOVER TRANSPONDER TYPEJAMMERSFROMAN%#-VIEWPOINT!NOPERATINGMODETOBEINCLUDED INARADARTODISTINGUISHUSEFULTARGETSFROMTRANSPONDERANDREPEATERJAMMERSISBASED ONADOPPLERSPECTRUMANALYSISPROVIDEDENOUGHTIMEONTARGETISAVAILABLE!DDITIONAL EXPENSIVETECHNIQUESAGAINSTDECEPTIVEJAMMINGCANBEBASEDONTHEMEASUREMENT ANDANALYSISOFTHEANGULARANDPOLARIZATIONSIGNATURESOFTHEECHOSIGNALS 4HE SAME %##- CONSIDERATIONS APPLY WITH DECOY TARGETS THAT HAVE THE GENERAL ATTRIBUTESOFREALTARGETSANDAREVERYDIFFICULTTOIDENTIFYASFALSETARGETS!METHOD SOMETIMESEMPLOYEDISTOTESTTHESCINTILLATIONCHARACTERISTICSOFTHEDETECTEDTARGETSTO DETERMINEWHETHERORNOTTHEYFOLLOWTHOSEOFREALTARGETS%XPENDABLESTHATTENDTOBE DESIGNEDUNDERSTRINGENTECONOMICCONSTRAINTSOFTENRETURNONLYASTEADYSIGNALTOTHE RADAR7ITHDOPPLERSPECTRUMANALYSIS ITISPOSSIBLETOLOOKFORRETURNSFROMROTATING COMPONENTSOFTHETARGETTHATANYFORMOFPOWEREDTARGETMUSTPOSSESS%XAMPLESARE JETENGINEORPROPELLERMODULATIONRETURNSASSOCIATEDWITHAIRCRAFTTARGETS !2-SPOSEASERIOUSTHREATTOASURVEILLANCERADAR4HESURVIVABILITYOFASURVEIL LANCERADARTOAN!2-ATTACKRELIESUPONWAVEFORMCODINGTODILUTETHEENERGYINTHE FREQUENCYRANGE THEMANAGEMENTOFRADIATEDENERGYINTIMEANDALONGTHEANGULAR SECTORS ANDTHEADOPTIONOFLOWSIDELOBESINTRANSMISSION4HESEACTIONSMAKEITMORE DIFFICULTFORAN!2-TOHOMEONRADAR7HENAN!2-ATTACKISDETECTED ITMAYBE USEFUL TO TURN ON SPATIALLY REMOTE DECOY TRANSMITTERS TO DRAW THE!2- AWAY FROM THE RADAR SITE "LINKING WITH A NETWORK OF RADARS ACHIEVES BETTER RESULTS4HE!2- TRAJECTORYISUSUALLYSELECTEDTOATTACKTHERADARTHROUGHTHEZENITHHOLEREGIONABOVE THERADAR WHEREITSDETECTIONCAPABILITYISMINIMAL4HUS ASUPPLEMENTALRADARTHAT PROVIDESAHIGHPROBABILITYOFDETECTIONINTHEZENITHHOLEREGIONISREQUIRED4HEREARE CERTAINADVANTAGESINCHOOSINGALOWTRANSMITTINGFREQUENCY5(&OR6(& FORTHE SUPPLEMENTALRADAR4HE2#3OFTHE!2-BECOMESGREATERASTHEWAVELENGTHOFTHE RADARAPPROACHESTHEMISSILEDIMENSIONS CAUSINGARESONANCEEFFECT!LOW FREQUENCY RADARISSOMEWHATLESSVULNERABLETOAN!2-ATTACKOWINGTOTHEDIFFICULTYOFIMPLE MENTINGALOW FREQUENCYANTENNAWITHTHELIMITEDAPERTUREAVAILABLEINTHEMISSILE (OWEVER LOW FREQUENCYRADARHASPOORANGULARRESOLUTION 4RACKING2ADARS 4RACKINGRADARSPROVIDEGOODRESOLUTIONANDPRECISEMEASURE MENTOFTHEKINEMATICPARAMETERSPOSITION VELOCITY ANDACCELERATION OFTARGETS4HE ESTIMATION UPDATED WITH MEASUREMENTS AND PREDICTION OF THE KINEMATIC PARAMETERS
%,%#42/.)##/5.4%2 #/5.4%2-%!352%3
Ó{°{£
ASTHETIMERUNSARETHEPROCESSINGSTEPSUSEDTOBUILDUPTHETRACKSOFTARGETS4RACKS ALLOW GUIDANCE AND CONTROL OF FRIENDLY FORCES THREAT ASSESSMENT AND ENEMY TARGET ENGAGEMENTBYWEAPONS4RACKINGCANBEACCOMPLISHEDINFOURWAYSI 4HEDEDICATED RADARTRACKERSOMETIMESCALLEDASINGLETARGETTRACKERANDDENOTED344 CONTINUOUSLY POINTSITSANTENNAATASINGLETARGETBYSENSINGERRORSFROMTHETRUETARGETPOSITIONAND CORRECTINGTHESEERRORSBYASERVOCONTROLSYSTEM4HENTHEREARETWODIFFERENTTYPESOF RADARSCALLED INTHEPAST TRACK WHILE SCANII /NEISALIMITEDANGLESCANASINSOME AIR DEFENSE RADARS AND AIRCRAFT LANDING RADARS WHICH SEARCH A LIMITED ANGULAR SECTOR ATARAPIDRATEEG ORTIMESASECOND III 4HEOTHERTYPEOFTRACKWHILESCAN 473 WAS WHAT IS NOW CALLED AUTOMATIC DETECTION AND TRACKING !$4 4HE!$4 SYSTEMGENERATESTRACKSOFMORETHANONETARGETBYUSINGASERIESOFSCAN TO SCANTARGET MEASUREMENTSTAKENASTHEANTENNASAMPLESTHETARGETPATHSIV 4HEMULTIFUNCTIONAL PHASED ARRAYRADARTRACKSMULTIPLETARGETSBYMULTIPLEINDEPENDENTBEAMS FORMEDBY THESAMEARRAYAPERTURE THATAREALLOTTEDTODIFFERENTTARGETS4HISSUBSECTIONISLIM ITEDTOTHEDESIGNPRINCIPLES DRIVENBYTHETHREATREQUIREMENTS OFTHEDEDICATEDRADAR TRACKER 4HEENSUINGSUBSECTIONWILLREFERTOMULTIFUNCTIONALPHASED ARRAYRADAR 'OOD%##-PERFORMANCEISACHIEVEDBYRADIATINGASLARGEANAVERAGETRANSMITTER POWERATTHEHIGHESTTRANSMITTERFREQUENCYPRACTICABLE COUPLEDWITHASLOWASIDELOBE LEVEL AS ACHIEVABLE )NCREASING THE TRANSMITTER FREQUENCY FOR A FIXED ANTENNA SIZE INCREASESTHEANTENNAGAIN'T WHICH INTURN INCREASESTHERECEIVEDTARGETPOWERAS 'T&ORMAIN BEAMNOISEJAMMING THERECEIVEDJAMMINGPOWERINCREASESDIRECTLY AS'T RESULTINGINANETINCREASEINSIGNAL TO JAMMINGPOWERBYAFACTORPROPORTIONAL TOTHEANTENNAGAIN'T(ERE ITISNOTEDABASICDIFFERENCEBETWEENSURVEILLANCEAND TRACKINGRADARTHEDETECTIONRANGEOFATRACKINGRADARIMPROVESASTHEFREQUENCYIS INCREASEDFORAFIXED SIZEANTENNA4HEREASONFORTHISIMPROVEMENTISTHATTHEANTENNA GAINISDIRECTLYINCREASEDWITHFREQUENCY THEREBYFOCUSINGMOREPOWERONTHETARGET 4HISINCREASEDPOWERISINTEGRATEDFORATIME WHICHISINVERSELYPROPORTIONALTOTHE BANDWIDTHOFTHESERVOCONTROLLOOP&ORASURVEILLANCERADAR THISINCREASEDPOWERIS COLLECTEDFORAPROPORTIONALLYSHORTERTIME SINCETHERADARMUSTSEARCHMORECELLSIN THESAMETIMEBECAUSEOFTHENARROWERANTENNABEAMWIDTH 7ITHSIDELOBEJAMMING THERECEIVEDJAMMINGPOWERISPROPORTIONALTOTHESIDELOBE ANTENNA GAIN 'SL RESULTING IN A NET INCREASE IN SIGNAL TO JAMMING POWER RATIO BY THEFACTOR'T'SL !SWITHSURVEILLANCERADARS SIDELOBENOISEJAMMINGANDDECEPTION CANBEFURTHERATTENUATEDBYTHEUSEOF3,#INCONJUNCTIONWITH3," ASDESCRIBEDIN 3ECTION 4HEUSEOFHIGHERTRANSMISSIONFREQUENCIESFORTRACKINGRADARSGENERALLYMAKETHEM LESSSUSCEPTIBLETONOISEJAMMINGTHANSURVEILLANCERADARS)NADDITION TACTICALTRACK INGRADARSMAYTRACKTHENOISEJAMMERINANGLE4RACKINGANOISEJAMMERINANGLEFROM TWOSPATIALLYSEPARATEDRADARSPROVIDESENOUGHINFORMATIONTOLOCATEAJAMMERWITH SUFFICIENTACCURACY !MORETHREATENING%#-AGAINSTTRACKINGRADARSIS$%#-4HESETHREATSREQUIRE CONSIDERABLYLESSENERGYTHANNOISEJAMMINGAFEATUREPARTICULARLYIMPORTANTONTACTI CALAIRCRAFT WHEREAVAILABLESPACEISLIMITED .EVERTHELESS THEYAREVERYEFFECTIVEIN CAPTURINGANDDECEIVINGTHERANGEGATEWITHTHE2'0/TECHNIQUE THEVELOCITYGATE WITHTHE6'0/TECHNIQUE ANDTHEANGLE TRACKINGCIRCUITS!PRIMARY%##-DEFENSE AGAINST2'0/ISTHEUSEOFALEADING EDGERANGETRACKER4HEASSUMPTIONISTHATTHE DECEPTIONJAMMERNEEDSTIMETOREACTANDTHATTHELEADINGEDGEOFTHERETURNPULSE WILLNOTBECOVEREDBYTHEJAMMER02)JITTERANDFREQUENCYAGILITYBOTHHELPTOENSURE THATTHEJAMMERWILLNOTBEABLETOANTICIPATETHERADARPULSEANDLEADTHEACTUALSKIN INTERVAL!LTERNATIVELY THE TRACKING RADAR MIGHT EMPLOY A MULTIGATE RANGE TRACKING
Ó{°{Ó
2!$!2(!.$"//+
SYSTEMTOSIMULTANEOUSLYTRACKBOTHTHESKINANDFALSE TARGETRETURNS4HISAPPROACH UTILIZES THE FACT THAT BOTH THE JAMMING SIGNALS AND THE TARGET RETURN COME FROM THE SAMEANGULARDIRECTION SOTHATTHERADARSANGLE TRACKINGCIRCUITSAREALWAYSLOCKED ONTOTHEREALTARGET 4HEMETHODOLOGYOFINTRODUCING6'0/INTOTHERADARSTRACKINGCIRCUITSISANALOGOUS TOTHEMETHODUSEDWITH2'0/4HEFREQUENCYSHIFTISINITIALLYPROGRAMMEDSOTHATTHE REPEATEDSIGNALISWITHINTHEPASSBANDOFTHEDOPPLERFILTERCONTAININGTHETARGETRETURN 4HISISNEEDEDTOCAPTURETHEDOPPLERFILTERCONTAININGTHETARGET THROUGHTHERADARS!'# ACTION4HEREPEATERJAMMERSIGNALISTHENFURTHERSHIFTEDINFREQUENCYTOTHEMAXIMUM EXPECTEDDOPPLERFREQUENCYOFTHERADAR4HEREPEATEDSIGNALISTHENSWITCHEDOFF FORCING THEVICTIMRADARTOREACQUIRETHETARGET#OHERENTTRACKINGRADARSCANCHECKTHERADIAL VELOCITYDERIVEDFROMDOPPLERMEASUREMENTSWITHTHATDERIVEDFROMDIFFERENTIATEDRANGE DATA!NOMALOUSDIFFERENCESPROVIDEAWARNINGOFTHEPROBABLEPRESENCEOFADECEPTION JAMMER7HEN2'0/AND6'0/OPERATESIMULTANEOUSLY THEBESTDEFENSEISTHECONTEM PORARYTRACKINGOFTRUEANDFALSETARGETSINBOTHRANGEANDDOPPLERDIMENSIONS4HEUSEOF MULTIMODEHIGH LOW ANDMEDIUM02& RADARSCANALSOBEANEFFECTIVE%##-MEASURE HELPINGTOCOUNTERRANGE GATEANDVELOCITY GATESTEALERSBYSWITCHINGRADARMODES !NGLE GATESTEALINGISPARTICULARLYEFFECTIVEAGAINSTCONICAL SCANNINGORSEQUEN TIAL LOBING TRACKING RADARS )T IS FOR THIS REASON THAT SUCH TRACKERS CANNOT BE USED IN MILITARY APPLICATIONS4HE FUNDAMENTAL PROBLEM WITH THESE RADARS IS THAT ANGLE TRACKING IS ACCOMPLISHED BY DEMODULATING THE AMPLITUDE MODULATION IMPOSED ON THETARGETRETURNPULSESOVERACOMPLETESCANNINGORLOBINGCYCLE4OJAMTHISTYPEOF RADAREFFECTIVELY THERADARSANGLE TRACKING ERROR SENSINGCIRCUITSMUSTBECAPTURED WITH A FALSE AMPLITUDE MODULATED SIGNAL AT THE SCANNING OR LOBING RATE WHICH IS SIGNIFICANTLYOUTOFPHASEWITHTHATFROMTHETARGETRETURN7HENTHECONICAL SCAN ORLOBINGMODULATIONISIMPOSEDONBOTHTHETRANSMITTERANDTHERECEIVERBEAMS IT ISRELATIVELYSIMPLEFORAJAMMERTOSYNTHESIZETHEAPPROPRIATEJAMMINGSIGNALBY INVERTINGANDREPEATINGTHETRANSMITTERMODULATIONINVERSE GAINREPEATER 4HIS CAN BE PARTIALLY OVERCOME BY A CONICAL SCAN ON RECEIVER ONLY #/32/ SYSTEM WHERETHETRACKINGRADARRADIATESANONSCANNINGTRANSMITTINGBEAMBUTRECEIVESWITH ACONICAL SCANBEAM4HEJAMMERTHENHASNOKNOWLEDGEOFTHEPHASEOFTHECONI CALLYSCANNEDRECEIVINGBEAMANDMUSTADOPTATRIAL AND ERRORMETHODOFSCANNING THE JAMMING MODULATION UNTIL A NOTICEABLE REACTION OCCURS IN THE TRACKING RADAR BEAM 4HIS JAMMING TECHNIQUE IS CALLED JOG DETECTION ! SEQUENTIAL LOBING ON RECEIVEONLY,/2/ SYSTEMCONCEALSTHELOBINGRATEFROMAPOTENTIALJAMMER #ONICALSCANANDSEQUENTIALLOBINGAREGOINGTOBEREPLACEDBYTHEMONOPULSETECH NIQUETHUS #/32/AND,/2/AREBECOMINGOBSOLETE -ONOPULSETRACKINGISINHERENTLYINSENSITIVETOANGLEDECEPTIVEJAMMINGFROMA SINGLEPOINTSOURCE4HISISARESULTOFTHEMONOPULSEANGLE ERROR SENSINGMECHANISM THAT FORMS AN ERROR PROPORTIONAL TO THE ANGLE BETWEEN THE TARGET AND THE ANTENNAS BORESIGHTONEACHRETURNPULSE4HISISACCOMPLISHEDBYCOMPARINGSIGNALSRECEIVED SIMULTANEOUSLYINTWOORMOREANTENNABEAMS ASDISTINGUISHEDFROMTECHNIQUESSUCH ASLOBESWITCHINGORCONICALSCANNING INWHICHANGLEINFORMATIONREQUIRESMULTIPLE PULSES%FFECTIVEMONOPULSEJAMMINGTECHNIQUESGENERALLYATTEMPTTOEXPLOITTHEMON OPULSERADARSSUSCEPTIBILITYTOTARGETGLINTORMULTIPATHSIGNALS /NEJAMMINGAPPROACH KNOWNASCROSS EYE USEDAGAINSTMONOPULSERADARSGENER ATESARTIFICIALGLINTINTOTHEMONOPULSETRACKINGLOOP4HEINVENTORSOFTHECROSS EYE TECHNIQUEARE",EWIS.2, 53! AND$(OWARDSEETHEIRPATENTORIGINALLYFILED THE#ROSS EYEISBASICALLYATWO SOURCEINTERFEROMETERWHOSEANTENNASUSUALLYARE
%,%#42/.)##/5.4%2 #/5.4%2-%!352%3
Ó{°{Î
MOUNTEDONTHEAIRCRAFTSWINGTIPASFARAPARTASPOSSIBLE4HESIGNALSRECEIVEDINEACH WINGTIPANTENNAAREREPEATEDINTHEOPPOSITEWINGTIPANTENNA EXCEPTFORAnPHASE SHIFT WHICHISINSERTEDINONELINETODIRECTANINTERFEROMETRICNULLTOWARDTHEVICTIM RADAR)NEFFECT THISCREATESANAPPARENTCHANGEOFTARGETDIRECTIONASVIEWEDFROMTHE RADAR!LARGEREPEATERGAINISREQUIREDTOGENERATEAHIGHJAMMER TO SIGNALRATIOOTH ERWISE THESKINECHOWILLOVERWHELMTHEJAMMINGSIGNALSINTHEINTERFEROMETERPATTERN NULLS4HEMAXIMUMEFFECTIVENESSOFTHETECHNIQUEIMPLIESACONSIDERABLEDELAYON THEORDEROFNS INTHEREPEATEDSIGNAL OWINGTOTHETRANSMISSIONLINEANDAMPLIFIER BETWEENTHERECEIVERANDTRANSMITTERANTENNAS4HUS LEADING EDGEORMULTIGATERANGE TRACKINGSHOULDBEANEFFECTIVE%##-TECHNIQUEAGAINSTCROSS EYEJAMMING 4ERRAIN BOUNCE JAMMING OR TERRAIN SCATTERED INTERFERENCE 43) OR HOT CLUTTER IS ANOTHERMONOPULSEJAMMINGTECHNIQUETHATISUSEDAGAINSTSEMIACTIVEMISSILESEEKERS ANDAIRBORNETRACKINGRADARS7ITHTHISTECHNIQUE THEJAMMERAIRCRAFTILLUMINATESTHE %ARTHSSURFACEINFRONTOFANDBELOWIT SOTHATTHESEMIACTIVEMISSILEHOMESONTHE ILLUMINATEDGROUNDSPOTANDNOTONTHEJAMMERAIRCRAFT4HEUNCERTAINTYOFTHETERRAIN SCATTERINGPARAMETERSANDTHEPOSSIBLEDEPOLARIZINGEFFECTSOFSURFACEREFLECTIONARE SOMEOFTHEPROBLEMSASSOCIATEDWITHTHISTECHNIQUE 4HE43) AGAINST AIRBORNE RADAR AND THE CORRESPONDING MITIGATION TECHNIQUES ARE DESCRIBEDINDETAILINTHELITERATUREn43)ISASIGNIFICANTPROBLEMTOMILITARYAIR BORNE RADAR IN FACT AN OFTEN WEAK TARGET SIGNAL IN THE MAIN BEAM HAS TO COMPETE WITHJAMMERTHATPROPAGATESNOTONLYVIADIRECT PATHBUTALSOVIAMULTIPATHFROMTHE UNDERLYINGTERRAIN-ITIGATIONTECHNIQUESHAVEBEENFOCUSEDONESTIMATINGTHEDIRECT JAMMERSIGNAL ESTIMATINGTHELINEARSYSTEMCREATEDBYTHEMULTIPATH ANDREMOVING ANESTIMATEOFTHEREFLECTEDJAMMERSIGNALFROMTHEMAINRECEIVEDRADARSIGNALTHIS ISALSOALLOWEDBYUSINGREFERENCEBEAMSPOINTEDATHOTCLUTTER!DAPTIVECANCELLA TIONTECHNIQUESHAVETOBEABLETOACCOUNTFORTHEDOPPLERINDUCEDBYRELATIVEMOTION BETWEENAIRBORNERADARANDJAMMERPLATFORMSANDTHEJAMMERSIGNALNONSTATIONARITY THATISPRODUCEDFROMSUCHABISTATICGEOMETRY43)MITIGATIONFOROVER THE HORIZON /4( RADARISDESCRIBEDIN!BRAMOVICHETAL -ONOPULSERADARSTHATUSEPARABOLICREFLECTORANTENNASARESUSCEPTIBLETOJAMMING THROUGH CROSS POLARIZATION LOBES GENERATED BY THE REFLECTOR SURFACE 4HIS OCCURS BECAUSETHEANGLE ERROR SENSINGDISCRIMINATORHASANINVERSESLOPEFORACROSS POLARIZED SIGNAL WHICHCAUSESTHEANGLE TRACKINGSERVOTOHAVEPOSITIVEFEEDBACKINSTEADOFTHE NEGATIVEFEEDBACKREQUIREDFORTRACKING-ONOPULSEESTIMATESWITHPLANARARRAYANTEN NASUSUALLYHAVEAHIGHRESISTANCETOCROSS POLARIZATIONJAMMINGSEE3ECTIONOF 7IRTH 7ITHARRAYANTENNASINCONTRASTTOREFLECTORANTENNASALLTHESINGLEANTENNA ELEMENTSHAVETHESAMEPOLARIZATION DEPENDENTPATTERN4HISISMULTIPLIEDWITHTHEARRAY FACTORANDALSOAPPLIESFORTHESUMANDDIFFERENCEPATTERNS4HERESULTANTFORMOFTHE BEAMPATTERNWILLTHUSBEINDEPENDENTOFPOLARIZATION4HEREFORE THEMONOPULSEOPERA TIONWILLALSONOTBEDISTURBED 0HASED !RRAY2ADARS )NTHISSUBSECTION WEILLUSTRATE BYANUMERICALEXAM PLE THEROLEPLAYEDBYTHESCHEDULERINAMULTIFUNCTIONAL0!2TOCOMBAT%#-4OTHIS END WERESORTTOABENCHMARKSTUDYDESCRIBEDINTHELITERATURE WHICHDEFINESTYPICAL %#-THREATS OPERATIONALSCENARIOS ANDPHASED ARRAYPERFORMANCEMAINLYINTERMS OF TARGET TRACKING UNDER %#- 4HE SIMULATION BENCHMARK INCLUDES TWO TYPES OF %#- NAMELY3/*AND2'0/4HE3/* MOUNTEDONANAIRCRAFT TRANSMITSBROADBAND NOISETOWARDTHERADAR4HE3/*FLIESANOVALRACECOURSE HOLDINGPATTERNINACLOCK WISEDIRECTIONATANALTITUDEOFMANDASPEEDOFMSITISAPPROXIMATELY
Ó{°{{
2!$!2(!.$"//+
KM FROM THE RADAR 4HE TWO CIRCULAR TURNS ARE PERFORMED AT AN ACCELERATION OF G4HETRANSMITTED3/*NOISEIMPACTSTHERADARWITHPOWERFNOTEXCEEDINGEIGHT TIMESTHERECEIVERNOISEPOWER4HUS A3/*WILLNOTCOMPLETELYHIDEATARGET ANDITCAN BEDEFEATEDWITHAHIGHERENERGYWAVEFORM)N2'0/ THETARGETUNDERTRACKREPEATS WITHDELAYANDAMPLIFICATIONTHERADARPULSESOASTOPULLTHERADARRANGEGATEOFFTHE TARGET4HETIMEDELAYISCONTROLLEDSOTHEFALSETARGETISSEPARATEDFROMTHETRUEONE WITHEITHERLINEARORQUADRATICMOTION&ORTHELINEARCASE THERANGEOFTHEFALSETARGET 2KFTISRELATEDTOTHERANGEOFTHETRUETARGET2KTVIA
2KFT 2KT VPO TK T
WHERE VPOISTHEPULL OFFRATE TK IS THE TIME AT WHICH THE TARGET IS BEING OBSERVED ANDTISTHEINITIALREFERENCETIMEOFTHE2'0/FALSETARGET!LTERNATIVELY FORTHE QUADRATICCASE
2KFT 2KT
A T T PO K
WHEREAPOISTHEPULL OFFACCELERATION 2ADAR 3CHEDULING 4HE SCHEDULING AND THE TRACKING FUNCTIONS CLOSELY COOPER ATEBOTHINTERACTTOUPDATE WITHCURRENTMEASUREMENTS THETARGETSSTATEVECTOR AND MAKETHEPREDICTIONSNECESSARYTOPOINTTHERADARBEAMATTHETARGETTHENEXTTIMEIT ISOBSERVED SELECTTHETYPEOFWAVEFORMTORADIATE ANDSELECTTHETHRESHOLDTOAPPLY FORTARGETDETECTION!CONCEPTUALSCHEMESHOWINGTHEINTERACTIONOFSCHEDULINGAND TRACKINGISSHOWNIN&IGURE WHERERK BK EKARETHERANGE BEARING ANDELEVA TIONMEASUREMENTSATTK3.2KISTHEOBSERVED3.2ATTKTK ISTHECOMMANDEDTIME FORTHENEXTTARGETOBSERVATIONRK \K BK \K EK \KARETHEPREDICTEDRANGE BEARING AND ELEVATIONFORBEAMPOINTINGCONTROLATTK 7K ISTHEWAVEFORMSELECTIONATTK AK ISTHEDETECTIONTHRESHOLDFORTHEDWELLSETATTK AND8K\K 0K\KARETHETARGETFILTERED STATEESTIMATEANDCOVARIANCEMATRIXATTKGIVENALLTHERADARMEASUREMENTSUPTOTK
&)'52% )NTERACTIONOFRADARSCHEDULERANDTRACKINGFILTER
%,%#42/.)##/5.4%2 #/5.4%2-%!352%3
Ó{°{x
4HE SCHEME IS BUILT AROUND TWO CLOSED LOOPS I THE LOOP ENCOMPASSING THE RADAR MODEL THETRACKINGFILTER ANDTHESCHEDULER ANDII THETRACKINGFILTERLOOP4HESCE NARIOISOBSERVEDBYTHERADARATTIMETKTHERADARMODELPROVIDESTHEMEASUREMENTS RK BK EKAND3.2K4HETRACKINGFILTERUPDATESTHEPREVIOUSTARGETSTATEESTIMATE8K \K ANDITSCOVARIANCEMATRIX0K \K ATTIMETKPROVIDINGTHENEWESTIMATES8K\KAND0K\KAND THEVALUESRK \K BK \KANDEK \KATTHENEXTTIMEINSTANTTK 4HESCHEDULERPROVIDESTHE WAVEFORMTORADIATE7K ANDTHETHRESHOLDAK TOAPPLYFORTARGETDETECTIONATTK 3ELECTIONOFTHE3AMPLING0ERIOD 4HESAMPLINGPERIODISCHOSENAMONGAFINITE NUMBEROFPOSSIBLEDIFFERENTVALUESBASEDONKINEMATICCONSIDERATIONSONTHETARGET ESTIMATEDSPEED ASWELLASONWHETHERMISSEDDETECTIONSHAVEOCCURRED)FTHERE ISNOMEASUREMENTTOBEASSOCIATEDTOTHETARGET THESAMPLINGPERIODISSETEQUALTO 4S SANDTHEWAVEFORMOFHIGHESTENERGYISSELECTED SOASTOPOSSIBLYAVOIDA SECONDMISSEDDETECTIONDUETOTHEPOSSIBLYLOWTARGET 2#3#ONVERSELY THESAM PLINGPERIODISSELECTEDASFOLLOWS
4S SFORTARGETSWITHESTIMATEDSPEEDGREATERTHANMS
4S SFORTARGETSWITHESTIMATEDSPEEDBETWEENANDMS
4S SFORTARGETSWITHESTIMATEDSPEEDLESSTHANMS %VENTHOUGHTHETARGETMAYACCELERATEORMANEUVER FORTHESAKEOFSIMPLICITY THE SAMPLINGPERIODISSELECTEDONLYONTHEBASISOFTHETARGETESTIMATEDSPEED 3ELECTION OF THE $ETECTION 4HRESHOLD 4HE PRESENCE OF A JAMMING SIGNAL CAN INCREASETHENUMBEROFFALSEALARMSANDWRONGPLOT TRACKASSOCIATIONSUPTOANUNAC CEPTABLELEVEL THUSINCREASINGSIGNIFICANTLY THEPROBABILITYOFLOOSINGATARGETUNDER TRACK)TIS THEREFORE IMPORTANTTHATTHERADARRECEIVERBEEQUIPPEDWITHA#&!23INCE THEFALSEALARMPROBABILITYISRELATEDTOTHEDETECTIONTHRESHOLD THELATTERSHOULDBE ADAPTEDONLINEBASEDONTHEINTENSITYOFDISTURBANCES 3ELECTIONOFTHE7AVEFORM 4HEBENCHMARKINCLUDESWAVEFORMS INDEXEDBYI ANDCHARACTERIZEDBYADIFFERENTPULSEWIDTHSEI SOTHATTHEWAVEFORMCANBESELECTED INORDERTOPROVIDEA3.2GREATERTHANTHEDETECTIONTHRESHOLDANDTHUSMAINTAINAN ASSIGNEDPROBABILITYOFTARGETDETECTION4HISCANBEACCOMPLISHEDBYFIRSTESTIMATING THEAVERAGETARGET2#3KoATTIMETK ANDTHENCOMPUTINGFOREACHWAVEFORMI THEPRE DICTED3.2KI ANDFINALLYSELECTINGTHEWAVEFORMINDEXISUCHTHATTHECORRESPONDING 3.2KI ISJUSTGREATERTHANTHEDESIREDDETECTIONTHRESHOLDPLUSAGIVENTOLERANCE %##- ! 3/* AND ! 2'0/ (EREAFTER SPECIFIC ANTI 3/* ! 3/* AND ANTI 2'0/! 2'0/ TECHNIQUESWILLBEDESCRIBED ! 3/*ISBASEDONESTIMATINGTHEJAMMERPOSITIONANDPOWERLEVELANDTHENUSING SUCHESTIMATESTOADAPTTHERADARDETECTIONTHRESHOLDONLINE u*AMMERSTATEESTIMATION7HENEVERTHERADAROPERATESINTHEPASSIVEMODE IE WITH OUTEMITTINGPULSES BEARINGBKJANDELEVATIONEKJOFTHEJAMMERASWELLASTHERELATIVE STANDARDDEVIATIONSRKJBANDRKJE ANDTHEJAMMER TO NOISERATIOQKJINTHEFOLLOWING o4HE2#3ISCERTAINLYAFLUCTUATINGQUANTITYVERSUSTIMEITALSODEPENDSUPONTHETARGETASPECTANGLE(OWEVER IF ENOUGHTIME ON TARGETISAVAILABLE THE2#3ESTIMATECANBESUFFICIENTLYACCURATE
Ó{°{È
2!$!2(!.$"//+
EXPRESSEDIND" AREMEASURED4HISALLOWSTHETRACKINGFILTERTOESTIMATETHEJAMMER STATEMADEUPOFFOURSTATECOMPONENTSTHETWOANGULARPOSITIONSBEARINGANDELEVA TION ANDTHERELATIVEANGULARSPEEDS4HEJAMMERTRACKISINITIALIZEDBYUSINGTHEFIRST TWOMEASUREMENTSPROVIDEDBYTHERADAR u*AMMERPOWERLEVELESTIMATION!NESTIMATEOFTHEPOWERLEVELCANBEOBTAINEDBY THEFIRST ORDERLINEARFILTERINITIALIZEDFROMFTJ FORASUITABLEFILTERCOEFFICIENT @J
J
G O TKJ A J G O TKJ A J RK
u!DAPTATIONOFTHEDETECTIONTHRESHOLD&ORAGIVENDETECTIONTHRESHOLDAIND" THE PROBABILITYOFFALSEALARMTURNSOUTTOBE ¤ ³ B 0FA EXP ¥ ´ J ¦ G 'STC 2 3 K µ
(ENCE THEDETECTIONTHRESHOLDCANBESELECTEDATEACHTIMEINSTANT TK INTHEFOLLOW INGWAY
[
]
BK MAX LOG § G TKJ 'STC RK K 3 KJ ¶ LN 0FA © ¸
J ISTHEMOSTRECENTAVAILABLEESTIMATEOFTHEJAMMERPOWERLEVELTHE WHEREFT K VALUEAK D"ISTHEONEWHICHALLOWS INTHEABSENCEOFJAMMERS THEDESIRED FALSEALARMPROBABILITY0FA RK\KISTHEFILTEREDESTIMATEOFTHETARGETRANGE'STC ISTHESENSITIVITYTIMECONTROLGAINAND3KJISTHENORMALIZEDANTENNAGAINFORTHE RECEIVEDSIGNALCOMPUTEDINTHERADARACTIVEMODE
"ECAUSETHEPHASED ARRAYRADARCONSIDEREDHEREISAMULTIFUNCTIONALONE ITHASALSO ATRACKINGMODETHATMIGHTBEAFFECTEDBYTHE2'0/FORTHISREASON AN! 2'0/IS CONSIDEREDAN%##-TECHNIQUE7HENEVER2'0/ISACTIVE TWOHIGH AMPLITUDESIGNALS ARERECEIVEDFROMTHERADARTHETRUETARGETSECHOANDAN2'0/ INDUCEDSIGNAL3INCE THE TIME AT WHICH THE TARGET UNDER TRACK ACTIVATES 2'0/ IS UNKNOWN TO THE TRACKING ALGORITHM THELATTERMUSTFIRSTRECOGNIZETHAT2'0/ISACTIVEANDTHENIMPLEMENTAN APPROPRIATE! 2'0/TECHNIQUE)NORDERTOESTABLISHWHETHER2'0/ISACTIVE THEFOL LOWINGTESTCANBEADOPTED,ET.BETHENUMBEROFMEASUREMENTSEXCEEDINGTHEDETEC TIONTHRESHOLDOFMORETHAND"4HENIF. ITISDECIDEDTHAT2'0/ISNOTACTIVEAND NO! 2'0/ACTIONISUNDERTAKENOTHERWISE IF. THE! 2'0/%##-SDESCRIBED BELOWAREAPPLIED.OTICETHATTHETESTALSOAIMSATDISCRIMINATINGTHETYPEOF%#-BEING ACTIVE IE 3/*OR2'0/)NFACT WHENEVERTHENOISEJAMMERISINTHEANTENNAMAIN BEAM MANY FALSE MEASUREMENTS WITH HIGH JAMMER TO NOISE RATIO ARE INDUCED IN THIS CASE ITTURNSOUTTHAT. AND2'0/ISDECLAREDINACTIVE7HENEVERTHEJAMMERISNO LONGERINTHETARGETSLINE OF SIGHT ITMAYHAPPENTHATMULTIPLEMEASUREMENTSEXCEEDTHE DETECTIONTHRESHOLD BUTTHECONDITIONTHATTHEEXCESSISGREATERTHAND"WILLBEVERY UNLIKELYTOBEFULFILLEDINPRACTICE/NCEITHASBEENESTABLISHEDTHAT2'0/ISACTIVE SEVERALDEVICESCANBEADOPTEDINORDERTOPREVENTTHELOSSOFTHETARGETUNDERTRACK !FIRSTAPPROACHCONSISTSOFMAINTAININGTWOTRACKSUNTILTHE2'0/ISDEACTIVATED ! SECOND APPROACH CONSISTS OF PENALIZING IN THE DATA ASSOCIATION THE MEASURE MENTSWHOSERANGEISGREATERTHANTHEAVERAGERANGEOFMEASUREMENTSWITH3.2 HIGHERTHANTHEDETECTIONTHRESHOLD
%,%#42/.)##/5.4%2 #/5.4%2-%!352%3
Ó{°{Ç
!THIRD MOREDRASTICAPPROACH CONSISTSOFDISCARDINGTHEMEASUREMENTWITHHIGHER RANGEAMONGTHETWOMEASUREMENTSTHATHAVEEXCEEDEDTHEDETECTIONTHRESHOLDOF MORETHAND" )TISIMPORTANTTOGUARANTEE UNDER2'0/ AVERYHIGH3.2FORTHETARGET)NFACT ITMIGHTHAPPENTHATTHESIGNALPRODUCEDBYTHEFALSETARGETOVERCOMESTHEDETECTION THRESHOLDWHEREASTHEONEFROMTHETRUETARGETDOESNOT THUSCAUSINGANASSOCIATION ERROR WITH POSSIBLE SERIOUS CONSEQUENCES IN THE TARGETS TRACKING (ENCE WHENEVER 2'0/ISACTIVE AHIGHENERGYWAVEFORMMUSTBESELECTED!FURTHERPRECAUTIONISTHE FOLLOWINGIFTHEREAREMISSEDDETECTIONSFORATLEASTTWOOUTOFTHELASTTHREESCANS AN IMMEDIATEREVISITWITHSAMPLINGINTERVAL4S SINSEARCHDWELLMODEISPERFORMED )NSEARCHMODE THERANGEGATEISKMINSTEADOFKM SOINTHISWAY ITISPOSSIBLE TOOBTAINANEWTARGETMEASUREMENTFORUPDATINGTHETRACKINGFILTERANDTHUSAVOIDTHE TARGETSLOSS 3IMULATION2ESULTS -ONTE#ARLOSIMULATIONEXPERIMENTSUSINGTHEBENCHMARK HAVEBEENCARRIEDOUTINORDERTOASSESSTHEBENEFITSOFTHEABOVEDESCRIBED%##-S -ORESPECIFICALLY THEADAPTATIONOFTHEDETECTIONTHRESHOLDHASBEENUSEDAS! 3/* WHEREASTHETECHNIQUEBASEDONDISCARDINGTHEMEASUREMENTSWITHHIGHERRANGEHAS BEENADOPTEDAS! 2'0/4HREETYPESOFTARGETSNUMBERED AND HAVEBEEN CONSIDEREDTARGETREPRESENTSACARGOAIRCRAFTWHILETARGETSANDREPRESENTFIGHTER ATTACKAIRCRAFTSWITHAMUCHHIGHERDEGREEOFMANEUVERABILITY&OREACHEXPERIMENT THEFOLLOWINGRESULTSAREDISPLAYEDNUMBEROFLOSTTARGETSOVER-ONTE#ARLOTRIALS 4SRADARSAMPLINGTIME 4AVEAVERAGEFRACTIONOFTIMEREQUIREDBYTHERADARFORTARGET TRACKING 0- AVERAGE POWER POSITION ERROR AND VELOCITY ERROR4ABLE SHOWS SIMULATIONRESULTSFORTHE)NTERACTING-ULTIPLE-ODEL)-- TRACKINGALGORITHMIN THEABSENCEOF%#-S4ABLESANDREPORTTHERESULTSINTHEPRESENCEOF3/* WITHOUTANDRESPECTIVELYWITH! 3/*3IMILARLY4ABLESANDREPORTTHERESULTS INTHEPRESENCEOF2'0/ WITHOUTANDRESPECTIVELYWITH! 2'0/4HEEXAMINATIONOF THESETABLESREVEALSTHATTHEPRESENCEOF%#-SCONSIDERABLYDETERIORATESTHETRACKING PERFORMANCEIFNOAPPROPRIATE%##-SAREUNDERTAKEN#ONVERSELY THEADOPTIONOFTHE ABOVEDESCRIBED! 3/*AND! 2'0/TECHNIQUESALLOWSTHEPERFORMANCETHATWOULD BEATTAINEDINTHEABSENCEOFTHECORRESPONDING%#-STOBERESTORED 4!",% 3IMULATION2ESULTS7ITHOUT%#-
4!2'%4./
,/34 4!2'%43
4SS
4AVES
0-7
0/3 %22M
6%, %22MS
n n n
4!",% 3IMULATION2ESULTS7ITH3/*AND7ITHOUT! 3/*
4!2'%4./
,/34 4!2'%43
4SS
4AVES
0-7
0/3 %22M
6%, %22MS
n n
Ó{°{n
2!$!2(!.$"//+
4!",% 3IMULATION2ESULTS7ITH3/*AND! 3/*
4!2'%4./
,/34 4!2'%43
4SS
4AVES
0-7
0/3 %22M
6%, %22MS
n n n
4!",% 3IMULATION2ESULTS7ITH2'0/AND7ITHOUT! 2'0/
4!2'%4./
,/34 4!2'%43
4SS
4AVES
0-7
0/3 %22M
6%, %22MS
n
4!",% 3IMULATION2ESULTS7ITH2'0/AND! 2'0/
4!2'%4./
,/34 4!2'%43
4SS
4AVES
0-7
0/3 %22M
6%, %22MS
n n n
)MAGING2ADAR 4HEREARETWOTYPESOFIMAGINGRADARTHATWILLBEDISCUSSED SYNTHETICAPERTURERADAR3!2 ANDINVERSE3!2)3!2 3!2 3!2ALLOWSUSTOHAVEAHIGH RESOLUTIONMAPPINGOFTHE%-BACKSCATTER FROMANOBSERVEDSCENE-OREPRECISELY THERADARDATAISOBTAINEDINPOLARCOORDI NATES IE SLANTRANGEANDAZIMUTH WHILEATWO DIMENSIONALIMAGEINTHERECTANGULAR COORDINATES X Y IS PROVIDED (IGH RESOLUTION IN SLANT RANGE IS OBTAINED BY TRANS MITTING A CODED WAVEFORM WITH A LARGE VALUE OF THE TIME BANDWIDTH PRODUCT AND COHERENTLYPROCESSINGINAFILTERMATCHEDTOTHEWAVEFORMTHEECHOSIGNALS(IGH RESOLUTIONALONGTHETRANSVERSALDIRECTIONISACHIEVEDBYFORMINGASYNTHETICAPERTURE 4HIS REQUIRES I TO PUT THE RADAR ONBOARD A MOVING PLATFORM EG AN AIRCRAFT OR A SATELLITEII TORECORDTHE%-SIGNALSFROMEACHSCATTERERTHATISILLUMINATEDBYTHE MOVINGANTENNABEAMINSUCCESSIVEINSTANTSOFTIME ANDIII TOCOHERENTLYCOMBINE THESIGNALSVIAASUITABLEAZIMUTHALMATCHEDFILTERTHUSFOCUSINGTHESLIDINGANTENNA PATTERNINANARROWERSYNTHETICBEAM2ADIOMETRICRESOLUTION ANOTHERKEYPARAMETER IS RELATED TO THE CAPABILITY OF 3!2 OF DISTINGUISHING DIFFERENT OBJECTS IN THE SCENE ONTHEBASISOFTHEIR%-REFLECTIVITY2ADIOMETRICRESOLUTIONDETERMINESHOWFINEA SENSORCANDISTINGUISHBETWEENOBJECTSWITHSIMILAR%-REFLECTIONPROPERTIES)TISA PARAMETEROFGREATIMPORTANCE ESPECIALLYFORTHOSEAPPLICATIONSORIENTEDTOEXTENDED TARGETEXPLOITATIONLIKEPOLARIMETRYANDCLASSIFICATION4HUS THERADIOMETRICRESOLU TIONSHOULDBEOPTIMIZEDMAINLYFORGOODEXTENDEDTARGETINTERPRETATION ACCOUNTING FORALLKINDOFBACK SCATTERERS-ULTILOOKPROCESSINGISCOMMONLYUSEDIN3!2IMAGE
%,%#42/.)##/5.4%2 #/5.4%2-%!352%3
Ó{°{
FORMATIONINORDERTOREDUCETHESPECKLENOISE4RADITIONALDIGITALMULTILOOKPROCESSING CONSISTSOFANINCOHERENTADDITIONOFINDEPENDENTIMAGESLOOKS OFTHESAMESCENE 4HELOOKSCANBEOBTAINEDBYPARTITIONINGTHEAVAILABLESIGNALBANDWIDTHRANGEAND ORAZIMUTH ANDPROCESSINGEACHLOOKINDEPENDENTLY4HEFINALIMAGEISPRODUCEDBY ADDINGTHELOOKSINCOHERENTLY PIXELBYPIXEL4HEDIRECTTRADE OFFBETWEENGEOMETRIC ANDRADIOMETRICRESOLUTIONMUSTBECONSIDEREDWHENCHOOSINGTHENUMBEROFLOOKSFOR PROCESSING/NE LOOKPROCESSINGMEANSAFULLYCOHERENTUSEOFTHEBANDWIDTHBEST GEOMETRICRESOLUTION ANDINTHISCASE THESPECKLENOISEWILLOBEYANEXPONENTIALDIS TRIBUTIONWHERETHESTANDARDDEVIATIONISEQUALTOTHEMEANVALUEINTHEINTENSITYIMAGE MULTIPLICATIVECHARACTERISTIC &ORMULTILOOKPROCESSING THEGEOMETRICRESOLUTIONWILL DEGRADEASTHENUMBEROFLOOKSINCREASESANDTHESPECKLESTATISTICSOFTHEINTENSITY IMAGE OBEY A GAMMA DISTRIBUTION WHERE THE STANDARD DEVIATION DECREASES WITH THE SQUAREROOTOFTHENUMBEROFINDEPENDENTLOOKS 3!2IMAGESAREUSEFULFORSURVEILLANCEANDRECONNAISSANCEAPPLICATIONS(OWEVER JAMMINGCOULDMAKE3!2IMAGESUNUSABLE4HEUSEOF%##-IS THEREFORE ESSEN TIALTOREDUCINGTHEVULNERABILITYOF3!2TOJAMMERS4HESUSCEPTIBILITYTOINTERCEPT SIGNALSFROM3!2ANDVULNERABILITYTOJAMMINGAREDESCRIBEDIN'OJ!SIMULATED NOISEJAMMINGPRODUCESSTRIPESONTHE3!2IMAGESTHATDEMONSTRATETHEEFFECTIVE NESSOFJAMMINGAGAINSTTARGETSLIKESTRONGPOINTSCATTERERSSUCHASELECTRICPOWER LINE TOWERS AS WELL AS LOW REFLECTIVITY AGRICULTURAL PATTERNS AND DESERT LAND4HE REFER ENCES DISCUSS THE SIGNIFICANT VULNERABILITY TO %#- OF SPACEBORNE 3!2 DUR ING MARITIME RECONNAISSANCE MISSIONS )N TYPICAL IMAGERY FROM 3EASAT 3!2 SHOWEDSEVERALFEATURESTHATMADETHE3!2APOWERFULMARITIMESURVEILLANCESENSOR 4HESHIPSANDTHEWAKESPRODUCEDBYTHESHIPMOTIONWEREIMAGED4HESHIPIMAGE ABLOB APPEAREDDISPLACEDFROMITSWAKEDUETOTHEDOPPLERSHIFTCAUSEDBYTHESHIPS MOTIONRELATIVETOTHESPACECRAFT(OWEVER THESHIPSPOSITIONATTHETIMEOFIMAGING ANDITSCOURSECOULDBEDETERMINEDFROMTHEWAKE4HESHIPSPEEDCANBECALCULATED TOOBYTHEDISPLACEMENTOFTHESHIPFROMITSWAKE!LLTHISINFORMATIONISOBTAINABLE ONLYIFENOUGH3.2ISAVAILABLEFORTHEIDENTIFICATIONOFTHESEIMAGEFEATURESEITHER BYAHUMANOPERATORORANAUTOMATICPROCESSOR4HEREEXISTS THEREFORE APOTENTIAL VULNERABILITYTO3!2INTHEMARITIMESURVEILLANCEAPPLICATIONIFAHIGHLEVELOFBACK GROUNDNOISECAUSESDEGRADATIONSOFTHE3!2IMAGETOANEXTENTWHERESHIPANDWAKE CANNOLONGERBEIDENTIFIEDINTHEIMAGE)NTHELITERATURE SOMECRITICALASPECTS IN TERMSOFJAMMERRECEIVERSENSITIVITYANDTRANSMITTEDPOWER FORSPOT NOISEJAMMING ARECONSIDEREDANDTHESYSTEMREQUIREMENTSAREDERIVEDTODETERMINETHEFEASIBILITY ANDPRACTICALITYOFSUCHJAMMER2ESULTSOFACOMPUTERSIMULATIONOFANENGAGEMENT BETWEEN3!2ANDREPRESENTATIVEJAMMINGSYSTEMAREGIVENTOENABLETHEEFFECTIVE NESSOF%#-TOBEASSESSED 4HETHREATSTOA3!2AREBARRAGEJAMMING SPOTJAMMING RANDOMPULSEJAMMING ANDREPEATERJAMMING2EPEATERDECEPTIONJAMMINGISAMAJORTHREATBECAUSEITMIGHT NOTBERECOGNIZABLE WHEREASTHEOTHERSARE ATLEASTINPRINCIPLE RECOGNIZABLE4HE IMPACTOFEACHTHREATANDTHEPOSSIBLECOUNTERMEASURESAREDESCRIBEDINTHEREMAINING PARTOFTHISSECTION u"ARRAGEJAMMER4HEDISTURBANCENOISEEXTENDSOVERTHEENTIRESWATHOFTHE3!2 IMAGE ANDITSHOWSGENERALLYAUNIFORMINTENSITY4HERADARIMAGEOFBARRAGEJAM MERNOISEWILLEXHIBITSPECKLE IE ABRIGHTNESSVARIATIONFROMONERESOLUTIONCELLTO ANOTHER)NADDITION BECAUSEALARGENUMBEROFNOISESAMPLESAREADDEDNONCOHER ENTLY THEMULTIPLELOOKSOFJAMMERNOISETENDTOSMOOTHOUTTHEINTENSITYVARIATION FROMPIXELTOPIXEL JUSTASINTHECASEOFTHERMALNOISE
Ó{°xä
2!$!2(!.$"//+
u3POTJAMMER)TALSOCOVERSTHEENTIRESWATHANDWITHUNIFORMINTENSITYDISTURBING NOISEASFORTHEBARRAGEJAMMERHOWEVER ITSIMAGEWILLDIFFERFROMTHEBARRAGENOISE BECAUSETHE&OURIERTRANSFORMOFNARROWERBANDJAMMERNOISEWILLRESULTINSPECKLE SIZEINTHERANGEDIMENSIONTHATISLARGERTHANTHATOFTHERMALNOISEORCLUTTER4HE PROCESSEDCROSS RANGEDIMENSIONISAGAINEQUALTOTHATOFCLUTTERORTHERMALNOISE 3POTJAMMERNOISEWILLAPPEARTOBESTRETCHEDINRANGE u2ANDOMPULSEJAMMING4HEJAMMERPULSESMAYALSOBETRANSMITTEDATRANDOMINTER VALS SO THAT SUCH NOISE PULSES CAN APPEAR IN ANY PART OF THE RANGE SWATH 7HEN OBSERVEDOVERASUFFICIENTNUMBEROFSAMPLES THENOISEPULSESWILLOCCUPYALLPARTS OFTHERANGESWATHINONESAMPLEORANOTHER4HEAZIMUTHPROCESSORFORMSTHESUM OFTHENOISEPOWERFROMALLSAMPLESWITHINONESYNTHETICAPERTURELENGTH4HATSUM WILLBEEQUALTOTHETOTALNOISEPOWERINTHEAPERTURE WHICHISPROPORTIONALTOTHE AVERAGEJAMMERNOISEPOWER!LSO INTHISCASE THESPECKLEDIMENSIONWILLAPPEAR STRETCHEDINRANGE JUSTASINTHESPOTJAMMERCASE(OWEVER THERANDOMPULSEJAM MERSPECKLEWILLEXHIBITMOREPRONOUNCEDBRIGHTNESSVARIATIONSTHANTHATFROMSPOT ORBARRAGEJAMMING BECAUSEFEWERNOISESAMPLESAREADDEDNONCOHERENTLY THEREBY REDUCINGTHESMOOTHINGEFFECTOFMULTIPLELOOKS u2EPEATERJAMMING4HEENEMYMAYUTILIZETHETRANSMITTINGRADARTOSENDOUTA SIGNALWITHINTHEBANDOFTHE3!2TOCONFUSETHE3!2SYSTEMRECEIVER4HEJAMMING SIGNALCAUSESTHE3!2TORECEIVEANDPROCESSERRONEOUSINFORMATIONTHATRESULTSIN SEVEREDEGRADATIONSINTHE3!2IMAGESANDORFORMATIONOFTHEIMAGEOFNONEXISTENT TARGETS! DECEPTION JAMMING COULD BE COMPOSED OF MANIPULATED REPLICAS OF THE TRANSMITTEDRADARSIGNALSVIA$2&-)N(YBERGTHEPOSSIBILITYOFPREVENTING3!2 MAPPINGTHROUGHCOHERENT$2&-JAMMINGHASBEENINVESTIGATED!SOFTWAREMODEL HASBEENDEVELOPEDANDVERIFIEDINSEVERALFLIGHTTRIALSINTHECASEOFAGROUND BASED $2&-JAMMER %##-TECHNIQUESFOR3!2CANBEDIVIDEDINTOI ANTENNA BASEDTECHNIQUESLOW SIDELOBES ADAPTIVEARRAYS ANDII TRANSMITTERRECEIVERPROCESSINGnBASEDTECHNIQUES FREQUENCYAGILITY PULSECODING u,OW SIDELOBES 3!2 ANTENNAS WITH LOW SIDELOBES REDUCE THE LEVEL OF JAMMING POWER RECEIVED AND IN ADDITION REDUCE THE PROBABILITY OF BEING INTERCEPTED BY %#-STATIONSINTHESIDELOBEREGION )NRELATIONTOLOWSIDELOBES THEFOLLOWING COMMENTISINORDER)NACONVENTIONALRADAR THEEFFECTOFLOWSIDELOBESISCLEAR BUTTHEREISADIFFERENCEIN3!2BECAUSETHEBEAMWIDTHISMUCHWIDERTHANIN OTHERRADARAPPLICATIONS)NPRINCIPLE THEFINERTHERESOLUTIONTHESMALLERTHE3!2 PHYSICALANTENNAANDTHEWIDERISITSBEAMWIDTH4HUS JAMMINGINTHEMAINBEAM ISMORELIKELYINA3!2THANINOTHERRADARSBECAUSEOFTHEWIDEMAINBEAM4O GETFALSETARGETSINTOTHE3!2 ITWOULDHAVETOCOMEFROMTHEMAINBEAM SOLOW SIDELOBESMIGHTNOTBEMUCHINVOLVEDINDECEPTIONJAMMER,IKEWISE MAIN BEAM JAMMINGMAYBEMOREOFATHREATTO3!2THANSIDELOBEJAMMING u!DAPTIVEARRAYS4HEREFERENCESnDEALWITHTHEREJECTIONOFABARRAGENOISE JAMMINGUSINGANADAPTIVESPATIALNULLING%QUIPPINGTHE3!2SYSTEMWITHAN ANTENNA PARTITIONED INTO SEVERAL SUB APERTURES CONNECTED TO PARALLEL CHANNELS IE MULTICHANNEL 3!2 ALLOWS SPATIAL ADAPTIVE PROCESSING TO SUPPRESS THE INTERFERINGSIGNAL)N&ARINAAND,OMBARDO THEPERFORMANCEOFSUCHATECH NIQUEISEVALUATEDINTERMSOF3!2IMPULSERESPONSE DETECTIONPERFORMANCEOF POINTTARGET ANDRADIOMETRICRESOLUTIONOFANEXTENDEDSCENE)N%NDERA3!2 IMAGE TAKENWITHANEXPERIMENTALFOUR CHANNEL3!2JAMMEDBYASMALLWATT
%,%#42/.)##/5.4%2 #/5.4%2-%!352%3
Ó{°x£
NOISEJAMMERLEADINGTOA*.2INTHERAWDATAOFABOUTD"WHENTHEJAMMER PASSESTHECENTEROFTHEMAINBEAM ISDEPICTED4HEDE JAMMEDIMAGEBYADAP TIVESPATIALSUPPRESSIONISALSOSHOWNDEMONSTRATINGTHEGOODPERFORMANCEOF ADAPTIVESPATIALCANCELLATION4HEREFERENCEPROVIDESACOMPREHENSIVESTUDY OFANTI JAMMINGSPATIALADAPTIVETECHNIQUESINCLUDINGALSOTHESPACESLOW TIME ANTI JAMMINGFILTERWITHSUITABLEIMAGERECONSTRUCTIONALGORITHM2ESULTSINDI CATETHATTHESLOW TIME34!0 PROVIDES SUPERIOR INTERFERENCE CANCELLATION THAN SPATIAL ONLYFILTERING3!2USUALLYINVOLVESWIDEBANDPROCESSING REQUIRINGFOR ADAPTIVE NULLING TECHNIQUES PECULIAR ALGORITHMS %FFICIENT BROADBAND JAMMER NULLINGHASTOBECOUNTEREDWITHSPACEFAST TIMEIE RANGECELL PROCESSING 4HEEXPECTEDNUMBEROFSPATIALDOFISNOTHIGHERWEHAVEONLYTOADDTHEDOF INTIME4HEADAPTIVEBEAMFORMINGALGORITHMSHAVETOBEIMPLEMENTEDINTOTHE 3!2PROCESSINGWHICHISALWAYSSPACE TIMEPROCESSINGTYPICALLYPOST DOPPLER 2OSENBERGAND'RAYTACKLETHEPROBLEMOFMITIGATINGTHEEFFECTSOFANAIRBORNE BROADBANDJAMMERPRESENTINTHEMAINBEAMOFA3!2)NADDITIONTOTHIS MUL TIPATHREFLECTIONSFROMTHEGROUND KNOWNASHOT CLUTTER WILLADDANONSTATIONARY INTERFERENCECOMPONENTTOTHEIMAGE4HEAUTHORSSHOWTHEIMAGEDEGRADATIONFROM HOT CLUTTER THELIMITEDRESTORATIONTHATMULTI CHANNELSPATIALIMAGINGANDSLOW TIME 34!0CANPROVIDE ANDHOWFAST TIME34!0CANIMPROVETHEFINALIMAGEQUALITY u&REQUENCYAGILITY3!2PROCESSINGNEEDSPHASECOHERENCEFOROBTAININGTHESYN THETICAPERTURE THUSFREQUENCYAGILITYHASTOBEUSEDWITHCARE&REQUENCYCHANG ING DURING A SYNTHETIC APERTURE LENGTH TIME RESULTS IN A CHANGE OF FOCAL LENGTH DIFFERENTCOEFFICIENTOFTHEQUADRATICPHASETERM OFTHEPHASEHISTORYOFTHEILLU MINATEDTARGETSTHATDEGRADESTHECROSS RANGERESOLUTION3!2OPERATINGINBURST MODE CAN CHANGE ITS CENTRAL FREQUENCY FROM ONE LOOK TO ANOTHER WITHOUT ANY DEGRADATIONINIMAGEQUALITY'IVENTHEEFFICIENCYOFSIMPLEBROADBANDJAMMING ANDMODERN%3- WENEEDTOCONCLUDETHATFREQUENCYAGILITYISNOTOFGREATHELP IN3!2%##- u0ULSECODING!NEFFECTIVE%##-AGAINSTA$2&-REPEATJAMMERISTOCHANGE THERADARTRANSMITTEDPULSECODEFROMONE02)TOANOTHER4HERADARMAINTAINS THESAMECARRIERANDBANDWIDTHHOWEVER THEPULSESARECODEDTOBEAPPROXI MATELY ORTHOGONAL TO EACH OTHER IE THEIR CROSS CORRELATION IS APPROXIMATELY EQUAL TO ZERO 3UCH A RADAR IS LESS SUSCEPTIBLE TO A $2&- REPEATER BECAUSE I THEJAMMERCANNOTADAPTEASILYSINCETHERADARSIGNALISVARYINGINTHE02) DOMAIN ANDII THESIGNALTRANSMITTEDBYA$2&-REPEATERJAMMERATAGIVEN 02)IE THERADARSIGNALTHATISUSEDBYTHE3!2ATTHEPREVIOUS02) ISAPPROXI MATELYORTHOGONALTOTHERADARSIGNALTHATTHE3!2ISUTILIZINGATTHECURRENT02) ANDTHUS AMATCHEDFILTERINGWITHTHECURRENT02)RADARSIGNALWOULDWEAKENTHE $2&-REPEATERJAMMERSIGNAL)N3OUMEKHANOVELMETHODISOUTLINEDTHAT COMBINESTHEABOVEMENTIONEDPULSEDIVERSITYRADARSIGNALINGWITHANEWCOHER ENTTWO DIMENSIONALPROCESSINGOFTHEMEASUREDDATATOEFFECTIVELYSUPPRESSA $2&-REPEATERJAMMER )3!2 4HE INVERSE 3!2 IS A METHOD OF RECONSTRUCTING A HIGH RESOLUTION TWO DIMENSIONAL%-INTENSITYIMAGEOFMOVINGTARGETSEG SHIPS AIRCRAFT INTHERANGE ANDCROSS RANGEDOPPLER DOMAINS)3!2IMAGINGISIMPORTANTINMILITARYAPPLICATIONS SUCHASTARGETRECOGNITIONANDCLASSIFICATIONSINCEITCANUSUALLYRECOGNIZETHECLASSOF TARGET THATCANALSOBEUSEDTOCUEWEAPONSYSTEMS4HENEEDFORCOHERENTCOUNTERING OF THESE IMAGING SENSORS IS A HIGH PRIORITY FOR %74HE REFERENCES PRESENT THE
Ó{°xÓ
2!$!2(!.$"//+
DESIGNOFAPIPELINEDALL DIGITALIMAGESYNTHESIZERCAPABLEOFGENERATINGFALSE TARGET IMAGES FROM A SERIES OF INTERCEPTED )3!2 CHIRP PULSES THUS PROVIDING 2& IMAGING DECOY CAPABILITY4HE IMAGE SYNTHESIZER MODULATES THE PHASE SAMPLES FROM A PHASE SAMPLING$2&-THATSTORESINTERCEPTED)3!2PULSES4HEIMAGESYNTHESIZERMUSTALSO SYNTHESIZE THE TEMPORAL LENGTHENING AND AMPLITUDE MODULATION CAUSED BY THE MANY REFLECTIVESURFACESOFATARGETANDMUSTGENERATEAREALISTICDOPPLERPROFILEFOREACHSUR FACE4HEPOSITIONOFAFALSETARGETIMAGEINRANGECANBECONTROLLEDBYDELAYINGINTIME THEREAD OUTSAMPLESGOINGTOTHEIMAGESYNTHESIZER4HERANGE DOPPLERIMAGEOFASHIP WITHRANGEBINSISSYNTHESIZEDASANEXAMPLEIN0ACEETAL%##-TECHNIQUESTO DEFEATTHISTYPEOFJAMMINGSIGNALSARESIMILARTOTHOSEPROPOSEDFOR3!2 /VER THE (ORIZON2ADAR !NIMPORTANTDEFENSE RELATEDROLEOFHIGHFREQUENCY (& OVER THE HORIZON/4( RADARISTOPROVIDEACAPABILITYFOREARLYWARNINGDETEC TION AND TRACKING OF AIR AND SHIP TARGETS "Y USING THE IONOSPHERE AS A PROPAGATION MEDIUM SKYWAVE/4(RADARSCANOPERATEATVERYLONGDISTANCESTOACHIEVEDETECTION ANDTRACKINGATRANGESOFnKM/NTHEOTHERHAND SURFACE WAVE/4(RADARS EXPLOITVERTICALLYPOLARIZED(&SIGNALSn-(Z ANDTHECONDUCTIVEPROPERTIESOF SEAWATERTODETECTTARGETSATRANGESLIMITEDTOABOUTKM4HISUPPERLIMITGENERALLY APPLIESTOLARGESHIPSANDFREQUENCIESINTHELOWER(&BAND %#-TO/4(2ADAR &ORBOTHSKYWAVEANDSURFACE WAVE/4(RADARSYSTEMS THEIONOSPHEREALSOPROPAGATESUNWANTEDINTERFERENCESIGNALSTOTHERADARSITE PAR TICULARLYATNIGHTWHENTHEIONOSPHEREISPRONETOPROPAGATINGRADIOFREQUENCYINTER FERENCE2&) SOURCESFROMVERYLONGDISTANCES2&)CANARISEFROMUNINTENTIONALAND INTENTIONALANTHROPOGENICEMITTERSINTHEUSER CONGESTED(&BAND ASWELLASJAMMING SOURCES*AMMINGSOURCESMAYBELOCATEDONTHETARGETPLATFORMITSELFSELF SCREENING ANDRECEIVEDBYTHEMAINANTENNABEAMORRADIATEFROMASEPARATELOCATIONSTAND OFF ANDBERECEIVEDMAINLYTHROUGHTHEANTENNABEAMPATTERNSIDELOBES4HEJAMMINGSIG NALMAYBEINCOHERENTWITHTHERADARWAVEFORMANDOPERATEINAhSPOTvORhBARRAGEv FASHIONTORAISETHENOISEFLOORINBOTHRANGEANDDOPPLERSEARCHSPACESTOPOTENTIALLY IMPAIRDETECTIONPERFORMANCE ORITCANBECOHERENTWITHTHERADARWAVEFORM ASINTHE CASEOFDECEPTIONJAMMING WHICHMAYGENERATEFALSETARGETSANDPOTENTIALLYIMPAIR THETRACKINGSYSTEMFROMFOLLOWINGTHETRUETARGET )MPACT OF )ONOSPHERE !N IMPORTANT ASPECT THAT DISTINGUISHES /4( RADAR FROM LINE OF SIGHT SYSTEMS IS THE IMPACT OF THE IONOSPHERIC PROPAGATION MEDIUM ON THE CHARACTERISTICSOFTHERECEIVEDINTERFERENCE4HEIONOSPHEREISSTRATIFIEDWITHDIFFER ENTREFLECTINGLAYERS SOASINGLEINTERFERENCESOURCEISOFTENRECEIVEDASANUMBEROF MULTIPATH COMPONENTS WITH DIFFERENT $O!S BOTH IN ELEVATION DUE TO THE DIFFERENT HEIGHTSOFREFLECTIONPOINTS ANDINAZIMUTHDUETOLAYER DEPENDENTIONOSPHERICTILTS ORGRADIENTS )NADDITIONTOMULTIPATH EACHINTERFERENCECOMPONENTISSUBJECTEDTO TEMPORALANDSPATIALDISTORTIONSCAUSEDBYTHEDYNAMICBEHAVIOROFELECTRONDENSITY IRREGULARITIESPRESENTINTHEINDIVIDUALREFLECTINGLAYERS4HISPHYSICALPHENOMENON ISKNOWNNOTONLYTODEFORMTHEINTERFERENCEWAVEFRONTSRELATIVETOTHEANTICIPATED PLANEWAVEFRONT BUTALSOTOINDUCEASIGNIFICANTLEVELOFSPATIALNONSTATIONARITYONTHE VARIOUSINTERFERENCECOMPONENTSOVERTIMEINTERVALSCOMMENSURATEWITHTHECOHERENT PROCESSINGINTERVALOF/4(RADARSINTHEORDEROFAFEWTOTENSOFSECONDS 2ELEVANCETO)NTERFERING3IGNALS 3OURCESOFINTERFERENCEWITHINTHERADARCOVERAGE EG ONANAIRBORNEPLATFORM CANPOTENTIALLYSCREENTHEPLATFORMINRANGEANDIMPAIR THE DETECTION OF OTHER TARGETS WITH SIMILAR AZIMUTH BUT POSSIBLY AT DIFFERENT RANGES
%,%#42/.)##/5.4%2 #/5.4%2-%!352%3
Ó{°xÎ
3UCHSOURCESCANEXPECTGOODPROPAGATIONTOTHERADARRECEIVERBECAUSETHECHOICEOF OPERATINGFREQUENCYISUSUALLYOPTIMIZEDFORTHECOVERAGEAREA)NTHECASEOFSTAND OFFINTERFERENCESOURCES WHICHARELOCATEDARBITRARILYWITHRESPECTTOTHESURVEILLANCE REGION EG A GROUND BASED EMITTER PROPAGATION CONDITIONS WILL GENERALLY BE SUB OPTIMUM(OWEVER SUCHSOURCESMAYHAVEGREATERPOWERANDANTENNAGAINATTHEIR DISPOSAL ALLOWING THE SIGNALS TO REACH THE RADAR RECEIVER WITH APPRECIABLE STRENGTH SOMETIMESAFTERPROPAGATIONVIAHIGHLYDISTURBEDANDNONSTATIONARYIONOSPHERICPATHS ASCOMMONLYOCCURSINTHEEQUATORIALANDPOLARREGIONS 5NDERNORMALCIRCUMSTANCES /4(RADARSSEEKTOFINDRELATIVELYCLEARFREQUENCYCHANNELSINTHEUSER CONGESTED(& SPECTRUM SOTHEPRESENCEOFINTERFERENCEFROMOTHERMANMADESOURCESISEFFECTIVELY DIMINISHEDBYSUITABLEFREQUENCYSELECTION7HENJAMMINGISPRESENT THERADARMAY NEEDTOOPERATEWITHMUCHHIGHERTHANUSUALLEVELSOFINTERFERENCETHATCANDEGRADE PERFORMANCE&ORTHISREASON PROTECTIONINTHEFORMOF%##-TECHNIQUESBECOMES NECESSARY %##-4ECHNIQUES %LECTRONICPROTECTIONFOR/4(RADARANTENNAARRAYSCANBE PROVIDEDINTHEFORMOFADAPTIVESIGNALPROCESSINGINSPACEANDTIME4HESTOCHASTIC CONSTRAINTSADAPTIVEBEAMFORMINGAND34!0METHODSnWEREDEVELOPEDSPECIFI CALLY FOR THE (& ENVIRONMENT TO ADDRESS THE REJECTION OF NONSTATIONARY INTERFERENCE WHILEPROTECTINGTHECLUTTERDOPPLERSPECTRUMPROPERTIES!METHODFORTIME VARYING SPATIALADAPTIVEPROCESSING46 3!0 THATADDRESSESTHESAMEPROBLEMWASFOUNDTO BEMOREATTRACTIVEFORPRACTICALIMPLEMENTATIONDUETOTHEMUCHLOWERCOMPUTATIONAL COSTINREAL TIMEAPPLICATIONS ASWELLASGREATERROBUSTNESSINPROTECTINGSUB CLUTTER VISIBILITYAFTERDOPPLERPROCESSING4HEPROBLEMOFREDUCINGFALSEALARMSCAUSEDBY STRONG SIDELOBE TARGETS AND SPATIALLY STRUCTURED NON GAUSSIAN DISTRIBUTED 2&) WAS TREATEDIN&ABRIZIOETAL WHERETHEADVANTAGESOFADAPTIVESUBSPACEDETECTORSRELA TIVETOCONVENTIONALAPPROACHESWERESHOWN34!0TECHNIQUESWITHTEMPORALDEGREES OFFREEDOMSPACEDATTHE02)IE SLOW TIME HAVEBEENPROPOSEDIN&ARINAETAL TOJOINTLYCANCEL2&)ANDCLUTTERWHENBOTHAREOFSIMILARSTRENGTHBUTNEITHERCANBE ISOLATEDFORESTIMATION WHEREASANALTERNATIVELOW DIMENSION34!0FORMULATIONWITH TEMPORALTAPSSPACEDATTHERANGECELLINTERVALIE FAST TIME HASBEENPROPOSEDIN &ABRIZIOETAL TOJOINTLYCANCELSIDELOBEANDMAIN BEAM2&)THATEXHIBITSCORRELA TIONINTHERANGEDIMENSION4HE34!0METHODSUSEDIN/4(RADARAREVERYSIMILAR CONCEPTUALLYTOTHOSEADOPTEDFORAIRBORNERADAR ESPECIALLYTHEFORMERTAPARCHITEC TURE4HECHIEFDIFFERENCEISTHATINBENIGNCONDITIONSFREEOFSIGNIFICANTCO CHANNEL INTERFERENCEp 34!0ISNOTINDICATEDFOR/4(RADARBECAUSETHESIDELOBECLUTTERDOES NOT TYPICALLY MASK DOPPLER SHIFTED TARGETS ANY MORE THAN THE MAIN BEAM CLUTTERe !POSSIBLEEXCEPTIONTOTHISISSHIPBORNE(&SURFACE WAVERADAR ALTHOUGHSUCHSYS TEMSHAVEBEENPROPOSED THEYHAVENOTYETDEMONSTRATEDTHEIRPRACTICALUTILITY p#O CHANNELINTERFERENCEFOR/4(RADARREFERSMAINLYTOOTHERTRANSMISSIONSINTHE(&SPECTRUMTHATEITHERFULLYOR PARTIALLYOVERLAPTHERADARBANDWIDTH e4HEMAINBEAMANDSIDELOBECLUTTERRECEIVEDBYAIRBORNERADARSCANHAVEQUITEDIFFERENTDOPPLERSHIFTSDUETO THEMOVEMENTOFTHEPLATFORMWITHRESPECTTOTHEGROUNDRESULTINGINTHEANGLE DOPPLERCOUPLINGOFTHECLUTTER (OWEVER IN /4( RADAR MAIN BEAM AND SIDELOBE CLUTTER FROM A SINGLE IONOSPHERIC MODE TYPICALLY HAVE SIMI LARDOPPLERSPECTRUMCHARACTERISTICSBECAUSETHERADARISSTATIONARY4HISMEANSTHATSIDELOBECLUTTERAPPEARSAT ROUGHLYTHESAMEDOPPLERSHIFTASMAINBEAMCLUTTERANDDOPPLERFILTERINGCANBEUSEDEFFECTIVELYFORDETECTING TARGETSUSUALLYWITHOUTSPECIALNEEDTOREJECTTHESIDELOBECLUTTERSPATIALLY
/BVIOUSLYTHESITUATIONMAYCHANGEINSHIPBORNE(&SURFACEWAVERADARBECAUSETHEPLATFORMISMOVINGWITH RESPECT TO THE SEA SURFACE AND HENCE A CONCEPTUALLY SIMILAR SITUATION ARISES FOR THE CLUTTER AS ENCOUNTERED IN AIRBORNERADAR
Ó{°x{
2!$!2(!.$"//+
Ó{°£ÓÊ
Ê Ê Ê 9 4HEREISANEEDFORAQUANTITATIVEMEASUREMENTOFTHEEFFICACYOFONEORMORE%##- ELECTRONICTECHNIQUESWHENARADAREQUIPPEDWITHTHESEDEVICESISSUBJECTTOAN%#- THREAT/NEPERFORMANCEMEASUREGENERALLYUSEDFORANUNJAMMEDSEARCHRADARISTHE DETECTIONRANGEOFACERTAINTARGETAGAINSTASYSTEMNOISEBACKGROUNDTHISSITUATIONIS REFERREDTOASDETECTIONINCLEARENVIRONMENT7HENTHERADARISJAMMED ITISOFINTER ESTTOCALCULATETHEDEGRADATIONOFTHEDETECTIONRANGEWITHRESPECTTOSELF SCREENING STANDOFF AND ESCORT JAMMERS4HESE CALCULATIONS APPLY TO BOTH SEARCH AND TRACKING RADARS&ORTRACKINGRADARS ITISALSOWORTHWHILETOCONSIDERTHEDEGRADATIONOFMEA SUREMENTACCURACYANDRESOLUTION4HEBENEFITSOFUSING%##-TECHNIQUESSUCHAS FREQUENCYAGILITY COHERENTDOPPLERPROCESSING VERYLOWSIDELOBEANTENNAS AND3,# CANBEEASILYASSESSEDATAFIRSTAPPROXIMATIONBYPROPERLYMODIFYINGTHEPARAMETERS INVOLVEDINTHERADAREQUATION)F FORINSTANCE AN3,#ISADOPTEDAGAINSTAN3/* ITS NETEFFECTISTOREDUCEJAMMINGPOWERBYTHEAMOUNTOFJAMMERCANCELLATIONRATIOTHAT THE3,#CANOFFER 4HEPREDICTIONOFRADARRANGEISDIFFICULTBECAUSEOFTHEMANYFACTORSTHATAREHARD TOREPRESENTWITHMODELSOFTHEREQUIREDACCURACY4HEFACTORSINVOLVETHETARGETTO BE DETECTED TARGET RETURNS OF AN UNKNOWN STATISTICAL NATURE THE NATURAL ENVIRON MENTINWHICHTHETARGETISEMBEDDEDEG CLUTTERRETURNS UNINTENTIONALINTERFERENCE UNCONTROLLABLE ENVIRONMENTAL REFRACTION AND ABSORPTION THE RANDOM NATURE OF THE INTERFERENCE ANDTHERADARITSELFSYSTEMNOISETEMPERATURE SIGNALDISTORTIONS ETC .EVERTHELESS RADARRANGEPREDICTIONMADEUNDERAVERAGECONDITIONSPROVIDESAPRE LIMINARYANDUSEFULINDICATIONOFPERFORMANCEUNDER%#-THREATAND%##-DESIGN EFFECTIVENESSTHATPRODUCESBASELINEVALUESPRIORTOSIMULATIONANDOPERATIONALTESTS !CLASSICALBOOKPRESENTSACCURATEDETECTIONRANGEEQUATIONSINAVARIETYOFPRACTICAL SITUATIONS)NTHESECONDPARTOFTHISSECTION AREVIEWOFSOFTWARETOOLSAVAILABLEFOR THEPREDICTIONOFRANGEEQUATIONINJAMMINGANDCHAFFCONDITIONSISGIVEN /FCOURSE THERADAREQUATIONISASIMPLIFICATIONINASSESSING%#- %##-INTERAC TIONSAMEASUREOF%##-EFFECTIVENESSSHOULDINVOLVETHEWHOLEWEAPONSYSTEMIN WHICHTHERADAROPERATES4HEMEASUREOFEFFECTIVENESSSHOULDBEEXPRESSEDINTERMS OFTHENUMBEROFATTACKERSDESTROYEDORTHEPROBABILITYOFRADARSURVIVAL2EFERENCES INTHELITERATUREATTEMPTTOASSESSTHE%##-EFFICACYn 3IMULATIONISANOTHERMEANSTOASSESSTHE%##-BENEFITSINRADARANDWEAPON SYSTEMS !N ADVANTAGE OF THIS APPROACH RESIDES IN THE CAPABILITY TO ARTIFICIALLY GENERATEDIFFERENTTYPESOFTHREATSANDTOLOOKATTHERADAR ANDWEAPONSYSTEM REACTIONS (OWEVER THE SIMULATION OF SUCH A COMPLEX SYSTEM IS A DIFFICULT TIME CONSUMINGTASKTHATSOMETIMESINVOLVESTHEUSEOFAD HOCPROGRAMMINGLANGUAGES SUITABLEFORSIMULATION 3IMULATIONOFACOMPLEXSYSTEMONADIGITALCOMPUTERISATECHNIQUEUSEDFORTHE ANALYSIS DESIGN ANDTESTINGOFASYSTEMWHOSEBEHAVIORCANNOTBEEASILYEVALUATED BYMEANSOFANALYSISORCOMPUTATION4HEPROCEDUREESSENTIALLYCONSISTSOFREPRODUC INGTHEALGORITHMSOFASUITABLEMODELOFTHEEXAMINEDSYSTEMBYMEANSOFCOMPUTER PROGRAMS0ROPERINPUTSTOTHEMODEL CORRESPONDINGTOTHEMOSTRELEVANTOPERATIONAL CONDITIONSFORTHEREALSYSTEM CANBEGENERATEDBYTHESAMECOMPUTERPROGRAMS4HE OUTPUTSOBTAINEDARECOMPAREDWITHSOMEREFERENCEVALUESEXPECTEDORTHEORETICAL TOASSESSSYSTEMPERFORMANCE7HENRANDOMINPUTSAREPROVIDED ANUMBEROFSTATISTI CALLYINDEPENDENTTRIALSAREPERFORMEDTOACHIEVEASIGNIFICANTSAMPLEOFTHEOUTPUT VALUESFROMWHICHRELIABLESTATISTICSCANBEESTIMATED
%,%#42/.)##/5.4%2 #/5.4%2-%!352%3
Ó{°xx
4HEACCURACYANDDETAILOFTHEMODELMAYVARYFROMACOARSEFUNCTIONALDESCRIPTION OFTHESYSTEMTOAVERYACCURATEONE ACCORDINGTOTHEPURPOSEOFTHESIMULATIONAND THEREQUIREDACCURACYOFTHERESULTS(OWEVER ITISDESIRABLETOLIMITTHECOMPLEXITY OFTHESIMULATIONTOOLSINORDERTOHAVEMANAGEABLEPROGRAMS GIVINGRESULTSTHATARE EASILYINTERPRETED4HEACCURACYINREPRESENTINGEACHSYSTEMFUNCTIONDEPENDSUPON ITSRELEVANCEWITHRESPECTTOSYSTEMPERFORMANCE7HENAVERYCOMPLEXSYSTEMISTO BESIMULATED ITISGENERALLYPREFERREDTORESORTTOSEVERALPROGRAMSOFLIMITEDCOM PLEXITYINLIEUOFASINGLEBULKYSIMULATION4HISAPPROACHCORRESPONDSTOPARTITIONING THE WHOLE SYSTEM INTO SUBSYSTEMS SEPARATELY MODELED IN DETAIL &ROM EACH PARTIAL SIMULATION ALIMITEDNUMBEROFRELEVANTFEATURESAREEXTRACTEDANDEMPLOYEDTOBUILD ASIMPLIFIEDMODELOFTHEOVERALLSYSTEM 3IMULATIONISPARTICULARLYIMPORTANTTOACCOUNTFORTHEADAPTIVENATUREEG #&!2 ADAPTIVEBEAMFORMING AUTOMATICRADARMANAGEMENT ADAPTIVETRACKING ADAPTIVECLUT TERCANCELLATION OFMODERNRADARSYSTEMS)NTHISCASE TRADITIONALSTATICMEASURES SUCH AS DETECTION RANGE AGAINST A GIVEN TARGET WILL NO LONGER ADEQUATELY DEFINE THE CAPABILITIESOFRADARSYSTEMS-EASURESOFRADARDYNAMICCHARACTERISTICS SUCHASTHE SUSCEPTIBILITYTOPROCESSOROVERLOADORTHETIMETOADAPTINCHANGINGCONDITIONS ARE MOREIMPORTANT-ODELINGANDSIMULATIONSTOEVALUATETHERADARRESPONSETOSTANDARD IZEDCHANGINGSCENARIOSREPRESENTANATTRACTIVETECHNICALSOLUTION 3IMULATIONISALWAYSOFVALUEHOWEVER THEEFFECTIVENESSOF%#-AND%##-IS ULTIMATELYDONE WHENPOSSIBLE WITHTESTSOFREAL%7CAPABILITIESAGAINSTREALRADAR SYSTEMSUNDERREAL WORLDCONDITIONS4HISISESPECIALLYIMPORTANTFORRADAREQUIPPED WITHADAPTIVETECHNIQUESSINCETHEYMIGHTNOTBEALWAYSFULLYMODELEDINASIMULATION ASTHEYAREINTHEREAL WORLDENVIRONMENTINWHICHTHEYMUSTOPERATE 4HE2ADAR%QUATIONIN*AMMINGAND#HAFF#ONDITIONS !NEXAMPLEOFRADAR RANGEPERFORMANCEUNDERNOISEJAMMINGISREPORTEDONPPnOF&ARINA WHERE THEIMPORTANTROLEPLAYEDBYARADARWITHLOWSIDELOBEANTENNASISALSONOTED4ODAY THEUSEOFCOMPUTERPROGRAMSFORPREDICTINGRADARPERFORMANCEUNDERJAMMING CLUT TER ANDCHAFF ANDINTHEPRESENCEOFVARIOUSREFINEDPROPAGATIONMODELSISWELLESTAB LISHED THERE ARE PROGRAMS DEVELOPED IN HOUSE BY INDIVIDUAL RADAR COMPANIES OR AVAILABLEONTHEMARKET 4HE2ADAR7ORK3TATION273 ISANEXAMPLEOFADEVELOPEDIN HOUSEPROGRAM 273ORIGINATESFROMTHEMODELINGANDSIMULATIONACTIVITIESCARRIEDOUTFORPREDICTION OFRADARPERFORMANCEINSEVERALSCENARIOS/NEMAINOBJECTIVEOF273ISTOPROVIDE THE RADAR ANALYST OR SYSTEM DESIGNER WITH A FRIENDLY BUT COMPREHENSIVE TOOLKIT FOR PREDICTIONOFRADARPERFORMANCEBASEDONWELLRECOGNIZED FLEXIBLE ANDDOCUMENTED MATHEMATICALMODELS!BROADRANGEOFRADARTYPESBI DIMENSIONAL MULTI BEAMTHREE DIMENSIONAL PHASED ARRAY COMPOSITECLUTTER %#-ANDPROPAGATIONSCENARIOS AND A TARGETS KINEMATICS AND 2#3 FEATURES ARE COVERED )NPUT AND OUTPUT DATA CAN BE SAVED LOADED ANDEXPORTEDTOOTHERSIMILARAPPLICATIONSORFORGENERALUSEIE -3 /FFICETOOLSFORDATAANALYSIS !SECONDPURPOSEISTOPROVIDEAHANDYANDRELIABLE TOOLFORTECHNICIANSANDENGINEERSPERFORMINGSYSTEMSETUPATTHESITEORACCEPTANCE TESTSBYMEANSOFFIELDTRIALS BYPROVIDINGNOTONLYTHESOFTWARETOOLSANDMODELSBUT ALSO WHEREREQUIRED ADATABASEOFPREDICTIONRESULTS ANDALLOWINGSIMPLEPARAMETRIC EXCURSIONSTHEREOF WITHOUTTHENEEDTOCONSULTABULKYREFERENCEDOCUMENTATION)N BRIEF THEMOSTVALUABLEOUTCOMESTHATCANBEOBTAINEDWITHTHE273ARERADARRANGE CALCULATION RADARELEVATIONCOVERAGEDIAGRAMSINCLEAR %#-ANDMULTI PROPAGATION BOTHFORCOHERENTANDNONCOHERENTRADARSRANGEANDVELOCITYRESPONSESINCOMPLEX
Ó{°xÈ
2!$!2(!.$"//+
SCENARIOSMULTIPLECLUTTERSOURCES USERDEFINEDTRAJECTORY INTERMSOFSIGNAL TO DIS TURBANCEPOWERRATIOANDDETECTIONPROBABILITYANDRADARRANGEANDHEIGHTACCURACY CALCULATION RADAR RESOLUTION EVALUATIONS EMPLOYING SUITABLE DATA EXTRACTING LOGICS 4HE273SUITECONSISTSOFTHEFOLLOWINGMAINMODULES#`>ÀÊ }Ì>ÊÊ -}>Ê*ÀViÃÃ} >iÃÊ°ÊÌiÀÊ ivvÀiÞÊ"°Ê i> .AVAL2ESEARCH,ABORATORY
Óx°£Ê /," 1 /" 4HE EXPONENTIAL GROWTH IN DIGITAL TECHNOLOGY SINCE THE S ALONG WITH THE COR RESPONDINGDECREASEINITSCOST HASHADAPROFOUNDIMPACTONTHEWAYRADARSYSTEMS AREDESIGNED-OREANDMOREFUNCTIONSTHATHISTORICALLYWEREIMPLEMENTEDINANALOG HARDWAREARENOWBEINGPERFORMEDDIGITALLY RESULTINGININCREASEDPERFORMANCEAND FLEXIBILITYANDREDUCEDSIZEANDCOST!DVANCESINANALOG TO DIGITALCONVERTER!$# ANDDIGITAL TO ANALOGCONVERTER$!# TECHNOLOGIESAREPUSHINGTHEBORDERBETWEEN ANALOGANDDIGITALPROCESSINGCLOSERANDCLOSERTOTHEANTENNA &OREXAMPLE &IGURESHOWSASIMPLIFIEDBLOCKDIAGRAMOFTHERECEIVERFRONT ENDOFATYPICALRADARSYSTEMTHATWOULDHAVEBEENDESIGNEDAROUND.OTETHAT THIS SYSTEM INCORPORATED ANALOG PULSE COMPRESSION 0# )T ALSO INCLUDED SEVERAL STAGES OF ANALOG DOWNCONVERSION IN ORDER TO GENERATE BASEBAND IN PHASE ) AND QUADRATURE 1 SIGNALS WITH A SMALL ENOUGH BANDWIDTH THAT THE!$#S OF THE DAY COULDSAMPLETHEM4HEDIGITIZEDSIGNALSWERETHENFEDINTODIGITALDOPPLER-4)AND DETECTIONPROCESSORS "Y CONTRAST &IGURE DEPICTS A TYPICAL DIGITAL RECEIVER FOR A RADAR FRONT END 4HE2&INPUTUSUALLYPASSESTHROUGHONEORTWOSTAGESOFANALOGDOWNCONVERSIONTO GENERATEAN)NTERMEDIATE&REQUENCY)& SIGNALTHATISSAMPLEDDIRECTLYBYTHE!$# !DIGITALDOWNCONVERTER$$# CONVERTSTHEDIGITIZEDSIGNALSAMPLESTOCOMPLEXFORM ATALOWERRATEFORPASSINGTHROUGHADIGITALPULSECOMPRESSORTOBACKENDPROCESSING .OTETHATTHEOUTPUTOFTHE!$#HASASLASHTHROUGHTHEDIGITALSIGNALLINEWITHALETTER ABOVE4HELETTERDEPICTSTHENUMBEROFBITSINTHEDIGITIZEDINPUTSIGNALANDREPRESENTS THEMAXIMUMPOSSIBLEDYNAMICRANGEOFTHE!$#!SWILLBEDESCRIBEDLATER THEUSE OF DIGITAL SIGNAL PROCESSING $30 CAN OFTEN IMPROVE THE DYNAMIC RANGE STABILITY ANDOVERALLPERFORMANCEOFTHESYSTEM WHILEREDUCINGSIZEANDCOST COMPAREDTOTHE ANALOGAPPROACH 4HISCHAPTERWILLPROVIDEAHIGH LEVELOUTLINEOFSOMEOFTHEMAJORDIGITALPRO CESSING TECHNIQUES FOR RADAR SYSTEMS THAT HAVE BECOME PRACTICAL SINCE THE 3ECOND %DITIONOFTHIS(ANDBOOKWASPUBLISHED ASWELLASSOMEDESIGNTRADEOFFSTHATNEED TOBECONSIDERED Óx°£
Óx°Ó
2!$!2(!.$"//+
&)'52% 4YPICALRADARRECEIVERFRONT ENDDESIGNFROM
&)'52% 4YPICALDIGITALRECEIVERFRONTEND
Óx°ÓÊ ,
6 Ê
Ê*,"
--
-AJORADVANCESINANALOG TO DIGITALCONVERTERANDDIGITALCOMPONENTTECHNOLOGYHAVE TRANSFORMEDTHERECEIVERFRONTENDSOFRADARSYSTEMS PROVIDINGHIGHERPERFORMANCEAT LOWERCOST4HISSECTIONWILLDESCRIBEHOWTHESENEWTECHNOLOGIESAREBEINGAPPLIEDTO RADARSYSTEMSANDTHEBENEFITSTHEYBRINGTOSYSTEMPERFORMANCE 3IGNAL3AMPLING"ASICS $IGITALSIGNALPROCESSORSARESAMPLEDSIGNALSYSTEMS 3AMPLINGISTHEPROCESSBYWHICHACONTINUOUSANALOG SIGNALISMEASUREDATREGULAR INTERVALSOFTIMETHESAMPLINGINTERVAL PRODUCINGASEQUENCEOFDISCRETENUMBERS SAMPLES THATREPRESENTSTHEVALUESOFTHESIGNALATTHESAMPLINGINSTANTS4HESAM PLINGFREQUENCYISTHEINVERSEOFTHESAMPLINGINTERVALANDISTYPICALLYDESIGNATEDFS 3AMPLEDSYSTEMSARESUBJECTTOTHE.YQUISTLIMIT WHICHLOWERBOUNDSTHESAMPLING RATEATWHICHRECONSTRUCTIONOFTHEUNSAMPLEDSIGNALFROMITSSAMPLESISPOSSIBLEWITH OUTCORRUPTIONBYALIASING THEOVERLAPPINGOFSPECTRALCOMPONENTS4HEBOUND TERMED THE.YQUISTFREQUENCYOR.YQUISTRATE ISEQUALTOTHETWO SIDEDSIGNALBANDWIDTH" THE BANDWIDTH CONSIDERING COMPONENTS AT BOTH POSITIVE AND NEGATIVE FREQUENCIES 3AMPLINGBELOWTHE.YQUISTRATEALWAYSRESULTSINALIASING BUTSAMPLINGABOVEITDOES NOTGUARANTEEALIAS FREEOPERATION7EWILLSEETHATFORBANDPASSSIGNALSASAMPLING RATEHIGHERTHAN.YQUISTMAYBEREQUIREDTOAVOIDALIASINGINSOMESITUATIONS 4HE.YQUISTRATEISOFTENSAIDTOBETWICETHESIGNALBANDWIDTH BUTTHATREFERSTOA ONE SIDEDBANDWIDTH POSITIVEFREQUENCIESONLY OFAREALSIGNAL/URDEFINITIONREFERS TOTHETWO SIDEDBANDWIDTH BOTHPOSITIVEANDNEGATIVEFREQUENCIES OFASIGNALTHAT IN GENERAL ISCOMPLEXWITHAREALSIGNALASASPECIALCASE )STHETWO SIDEDBANDWIDTHALWAYSTWICETHEONE SIDEDBANDWIDTH &ORCOMPLEX SIGNALSINGENERAL NO BUTFORREALSIGNALSINPARTICULAR YES(ERESWHYANYSIGNAL REALORCOMPLEX WHENEXPRESSEDASA&OURIERINTEGRALINVERSE&OURIERTRANSFORM IS
2!$!2$)')4!,3)'.!,02/#%33).'
Óx°Î
SEENTOBEACOMBINATIONOFSPECTRALCOMPONENTSOFTHEFORM!EJOFT3AMPLEDSIGNALS HAVET N4WITH4ASAMPLINGINTERVALANDNANINTEGERTIME BUTSAMPLEDORNOT THE BASICCOMPONENTFORMISTHESAME!NDEITHERWAY COMPLEXAMPLITUDE!ISAFUNCTION OFFREQUENCYF BUTLETSWRITE!INSTEADOF!F FORSIMPLICITY )N THESE TERMS THEN WHATS SPECIAL ABOUT REAL SIGNALS IS THAT AN EASILY DERIVED &OURIER TRANSFORMPROPERTYREQUIRESTHEIR&OURIERCOMPONENTSTOOCCURINCONJUGATE PAIRS SOTHATIFTHEREISACOMPONENT!EJOFTATFREQUENCYFWITHCOMPLEXAMPLITUDE ! THEREISALSOACOMPONENT! E JOFTATFREQUENCY FWITHTHECOMPLEXCONJUGATE!
OFTHATCOMPLEXAMPLITUDE)FABANDOFPOSITIVEFREQUENCIESFROMFTOFISOCCUPIED BYSPECTRALCOMPONENTS THECORRESPONDINGBANDOFNEGATIVEFREQUENCIESFROM FTO
FWILLBEOCCUPIEDBYSPECTRALCOMPONENTSALSO SOTHETWO SIDEDBANDWIDTHMUSTBE TWICETHEONE SIDEDBANDWIDTH 2EALSIGNALSHAVESPECTRALCOMPONENTSINCONJUGATEPAIRSBECAUSEBYUSINGCOM PLEXAMPLITUDEEXPRESSEDINPOLARFORMAS! REJP !EJOFT ! E JOFT 2E[!EJOFT] 2E[REJPEJOFT] R2E[EJOFT P ] RCOSOFT P 4HEIMAGINARYPARTSOFTHECONJUGATESPECTRALCOMPONENTSHAVECANCELEDTOREVEAL THATTHOSECOMPONENTSTOGETHERINDEEDREPRESENTAREALSIGNAL ASINUSOIDWITHAMPLI TUDEANDPHASESPECIFIEDBYTHEMAGNITUDEANDANGLEOFTHECOMPLEXAMPLITUDE4HE LATTERRELATIONSHIPISSOMUCHAPARTOFTHEENGINEERINGCULTURETHATTHETERMSAMPLITUDE ANDPHASEARECOMMONLY IFIMPRECISELY USEDTOREFERTOTHEMAGNITUDEANDANGLEOFA COMPLEXSIGNALATANINSTANTINTIME 4HEFOLLOWINGFIGURESILLUSTRATETHEORIGINOFTHE.YQUISTRATE)MAGINETHATAREAL SIGNALWITHALOWPASSSIGNALSPECTRUMOFTWO SIDEDBANDWIDTH"ISPLOTTEDONALONG PIECEOFPAPER ASSHOWNIN&IGUREA)NTHEFIGURE THEPOSITIVE FREQUENCYSPECTRAL COMPONENTSOFTHESIGNALAREDARKLYSHADED ANDTHENEGATIVE FREQUENCYCOMPONENTS ARELIGHTLYSHADED4OSEETHEEFFECTOFSAMPLINGTHISSIGNALAT.YQUISTRATE" THELONG SHEETISCUTINTOSMALLERSHEETS WITHTHEFIRSTCUTATZEROFREQUENCYANDSUBSEQUENTCUTS ATSAMPLE RATE" INTHISCASE INTERVALSINPOSITIVEANDNEGATIVEFREQUENCY4HESHEETS ARESTACKEDONEONTOPOFTHEOTHERASSHOWNONTHELEFTSIDEOF&IGUREB ANDTHE RESULTINGPORTIONOFTHESAMPLEDSIGNALSPECTRUMFROMTOTHESAMPLINGRATEOF"IS GENERATEDBYADDINGTHESPECTRAOFTHESTACKEDPAGESTOGETHER ASSHOWNONTHERIGHT
&)'52% A "ANDLIMITED REALSIGNALSPECTRUMBEFORESAMPLING B PORTIONOFSAMPLEDSPECTRUM FROMTO" ANDC FULLSAMPLEDSIGNALSPECTRUM
Óx°{
2!$!2(!.$"//+
&)'52% A "ANDLIMITEDLOWPASSSIGNALSPECTRUMBEFORESAMPLING B ALIASEDLOWPASSSIGNAL SPECTRUMAFTERSAMPLINGATRATEFS " ANDC ALIASEDSAMPLEDSIGNALSPECTRUM
.OTETHATTHELIGHTLYSHADEDNEGATIVE FREQUENCYPORTIONOFTHESPECTRUMNOWAPPEARS ONTHERIGHTOFTHESAMPLEDSPECTRUMANDDOESNTOVERLAPTHEDARKERPOSITIVE FREQUENCY PORTION!SLONGASTHETWOPORTIONSOFTHESAMPLEDSIGNALDONTOVERLAP THESIGNALIS NOTALIASED4HEFULLSAMPLED SIGNALSPECTRUMISOBTAINEDBYLAYINGCOPIESOFTHISPAGE END TO END ASSHOWNIN&IGUREC PRODUCINGCOPIESOFTHETO"PORTIONOFTHE SAMPLEDSIGNALSPECTRUMAT"INTERVALS &IGURE SHOWS THE RESULT OF SAMPLING BELOW THE .YQUIST RATE &IGURE A SHOWSTHESAMEBANDLIMITEDSIGNALASTHEPREVIOUSEXAMPLE BUTTHISTIMEITISSAMPLED ATSOMERATETHATISLESSTHAN.YQUISTRATE"4HERESULTINGSAMPLEDSPECTRUM SHOWNIN &IGUREBANDC CONTAINSOVERLAPPED ORALIASED SPECTRALCOMPONENTSTHATADDAND REPRESENTCORRUPTIONOFTHESIGNAL &IGURE REPEATS THIS .YQUIST ANALYSIS FOR A BANDPASS SIGNALA SIGNAL NOT CONTAININGSPECTRALCOMPONENTSATORNEAR(Z&IGUREASHOWSAREALBANDPASS SIGNALWITHTWO SIDEDBANDWIDTH"ANDCOMPOSEDOFPOSITIVE FREQUENCYANDNEGATIVE FREQUENCYSPECTRALCOMPONENTS EACHOFBANDWIDTH" THATARECOMPLEX CONJUGATED MIRRORIMAGES4HE.YQUISTRATEISTHESIGNALSTWO SIDEDBANDWIDTHIRRESPECTIVEOF THEPARTICULARPORTIONOFTHESPECTRUMINWHICHTHESIGNALRESIDES4HEREFORE FORTHIS SIGNALTHE.YQUISTFREQUENCYIS"EVENTHOUGHTHESIGNALCONTAINSCOMPONENTSATACTUAL FREQUENCIESGREATERTHAN"&IGUREBSHOWSTHERESULTOFSAMPLINGTHISSIGNALAT
&)'52% A "ANDLIMITED REALPASSBANDSIGNALSPECTRUMBEFORESAMPLINGANDB SIGNALSPECTRUM AFTERSAMPLING
2!$!2$)')4!,3)'.!,02/#%33).'
Óx°x
&)'52% A .ON REAL SIGNAL SPECTRUM BEFORE SAMPLING BY .YQUIST FREQUENCY " AND B SIGNAL SPECTRUMAFTERSAMPLING
THE.YQUISTBOUND4HESAMPLEDSPECTRAOFTHETWOPORTIONSOFTHESIGNALDONOTOVER LAPTHESAMPLEDSIGNALISNOTALIASED!SWILLBEDESCRIBEDINMOREDETAILLATERINTHE CHAPTER THISTECHNIQUE BANDPASSSAMPLING ISAPOWERFULTOOLTHATALLOWSARELATIVELY HIGH FREQUENCYSIGNALTOBESAMPLEDBYARELATIVELYLOW PERFORMANCEDIGITIZER WHICH CANRESULTINCONSIDERABLECOSTSAVINGS &IGUREASHOWSTHESPECTRUMOFAMOREGENERALCOMPLEXSIGNALOFBANDWIDTH "BEFORESAMPLING.OTETHATTHISSIGNALDOESNOTPOSSESSCOMPLEX CONJUGATESPECTRAL SYMMETRY4HESIGNALSPECTRUMAFTERSAMPLINGBYITS.YQUISTFREQUENCY"ISSHOWNIN &IGUREB4HEREISNOALIASING 4HE .YQUIST RATE IS A MINIMUM SAMPLING FREQUENCY FOR A SIGNAL A BOUND AND MEETINGTHEBOUNDISNECESSARY BUTNOTSUFFICIENT TOENSURETHATNOALIASINGOCCURS #ONSIDERTHECASEPRESENTEDIN&IGUREA WHICHISTHESAMEBANDLIMITEDBANDPASS SIGNALSHOWNIN&IGURE BUTSHIFTEDINFREQUENCYSOTHATITDOESNTBEGINEXACTLY AT"4HESAMPLEDSIGNALSPECTRUMIN&IGUREBSHOWSTHAT ALTHOUGHTHESAMPLING RATESATISFIESTHE.YQUISTBOUND THESAMPLEDSIGNALISSTILLALIASED4OSOLVETHISPROB LEM THE SIGNAL COULD BE MOVED TO A DIFFERENT CENTER FREQUENCY BEFORE SAMPLING OR THESAMPLINGRATECOULDBEINCREASED4HESYSTEMDESIGNERMUSTALWAYSDEVELOPTHE FREQUENCYPLANOFASAMPLINGSYSTEMCAREFULLYTODETERMINEANAPPROPRIATESAMPLING FREQUENCYANDTOENSURETHATALIASINGDOESNOTOCCUR!FULLTREATMENTOFTHISSUBJECTIS PRESENTEDBY,YONS )NANACTUALSYSTEM BEFORESAMPLINGTHESIGNALISTYPICALLYPASSEDTHROUGHANANTI ALIASING FILTER WHICH IS AN ANALOG LOWPASS OR BANDPASS FILTER THAT PLACES AN UPPER LIMITONTHESIGNALBANDWIDTH4HEFILTERNEEDSTOPROVIDEENOUGHSTOPBANDREJECTION THATANYALIASEDCOMPONENTSAREINSIGNIFICANT/FCOURSE PRACTICALFILTERSDONOTHAVE
&)'52% A "ANDLIMITED REALPASSBANDSIGNALSPECTRUMBEFORESAMPLINGANDB SIGNALSPECTRUM AFTERSAMPLING
Óx°È
2!$!2(!.$"//+
PASSBANDS EXTENDING RIGHT UP TO THEIR STOPBAND EDGES SO THE WIDTHS OF INTERVENING TRANSITIONBANDSMUSTBECOUNTEDASPARTOFTWO SIDEDSIGNALBANDWIDTH"FORPURPOSES OFDETERMININGTHE.YQUISTRATE ASTHEFILTEROUTPUTMAYCONTAINCOMPONENTSINTHESE TRANSITIONSBANDSTHATCOULDOTHERWISERESULTINSIGNIFICANTALIASING $IGITAL $OWNCONVERSION $$# 4HE APPLICATION OF DIGITAL TECHNOLOGY TO )1 DEMODULATION WHICHISJUSTDOWNCONVERSIONOFAN)&SIGNALTOACOMPLEXBASEBAND HAS GREATLY IMPROVED THE PERFORMANCE OF COHERENT SYSTEMS (ERE WE EXPLORE TWO FORMSOFSUCHDIGITALDOWNCONVERSION AGENERALFORMTHATISSTRUCTURALLYPARALLELTO TRADITIONALANALOGDOWNCONVERSIONANDARESTRICTEDFORM DIRECTDIGITALDOWNCONVER SION WHICHISMOREECONOMICALWHENITISAPPLICABLE !NALOG$OWNCONVERSIONAND3AMPLING 4HEGENERALAPPROACHTODIGITALDOWN CONVERSIONDERIVESFROMANALOGDOWNCONVERSIONANDSAMPLING ASILLUSTRATEDINTHE FREQUENCYDOMAININ&IGURE4HESPECTRAONTHEFIRSTAND LINESREPRESENTSIGNALS ATVARIOUSPOINTSINTHESYSTEM ANDTHESPECTRAONTHE ANDrLINES RESPECTIVELY REP RESENTSPECTRAL CONVOLUTIONANDPOINT BY POINTSPECTRALMULTIPLICATIONOPERATIONSTHAT RELATETHOSESIGNALS 4HE FIRST LINE IN THE FIGURE DEPICTS SCHEMATICALLY A REAL )& SIGNAL WITH ONE AND TWO SIDEDBANDWIDTHSOF-(ZAND-(Z RESPECTIVELY ANDWITHPOSITIVE AND NEGATIVE FREQUENCYCOMPONENTS RESPECTIVELYCENTEREDAT-(ZAND-(Z4HE SECONDLINEOF&IGURESHIFTSTHE)&SIGNALBY,/FREQUENCY-(ZUSINGSPEC TRALCONVOLUTION7ELLSEESHORTLYHOWTHISISDONEINHARDWARE 4HERESULT ONTHE THIRDLINE HASSPECTRALCOMPONENTSCENTEREDAT-(ZAND-(Z-ULTIPLICATION BYTHELOWPASS FILTERFREQUENCYRESPONSEINLINETHENREMOVESTHELATTERCOMPONENT LEAVINGONLYTHECOMPLEXBASEBANDSIGNALOFLINE WHICHHASATWO SIDEDBANDWIDTH ANDA.YQUISTFREQUENCYOF-(Z4HESPECTRALCONVOLUTIONONLINECORRESPONDS
+
*
*
+
*
*
$
#"& )$ % + * ! ( % #"& )$ % $ '!$$ %# #$! $
! ($ $ ! * ! ! ( $ $
&)'52% !NALOGDOWNCONVERSIONINTHEFREQUENCYDOMAIN
2!$!2$)')4!,3)'.!,02/#%33).'
Óx°Ç
TO TIME DOMAIN MULTIPLICATION OF A UNIFORM IMPULSE TRAIN AT THE -(Z SAMPLING FREQUENCYWITHTHESIGNALREPRESENTEDBYLINE)NTHETIMEDOMAIN THERESULTISA -(ZTRAINOFSAMPLINGIMPULSESWITHAREASTHATAREGIVEORTAKEASCALEFACTORTHAT WEAREIGNORING SAMPLESOFTHELINESIGNALATTHESAMPLINGINSTANTS/FCOURSE WE WILLNOTCREATETHELINEIMPULSESINHARDWAREBUTWILLINSTEADREALIZETHEIMPULSEAREAS DIGITALLYASNUMBERSINREGISTERS !BLOCKDIAGRAMSHOWINGHOWTHISPROCESSMIGHTBEIMPLEMENTEDINHARDWAREIS SHOWNIN&IGURE4HE)&SIGNALISSENTTOTWOMIXERS)NONEMIXER THE)&SIGNAL ISBEATWITHTHE-(Z,/WITHCOSINEPHASING ANDINTHEOTHERMIXER THE)&IS BEATWITHTHESAME,/BUTWITHNEGATIVESINEPHASING SOTHATTHEMIXERSAREOPERATED INQUADRATURE OAPART4HEMIXEROUTPUTSTAKENTOGETHERASACOMPLEXPAIRFORMA COMPLEXSIGNALWITHTHESPECTRUMSHOWNINLINEOFTHEPREVIOUSFIGURE4HESESIG NALSARETHENPASSEDTHROUGHLOWPASSFILTERS,0& TOREMOVETHESPECTRALCOMPONENT CENTEREDAT-(ZTHATWOULDOTHERWISEHAVERESULTEDINALIASINGINTHESAMPLING STEPTOFOLLOW ,ABELS)IN PHASE AND1QUADRATURE ARETRADITIONALLYUSEDTOINDICATETHEREAL ANDIMAGINARYPARTSOFCOMPLEXTIME DOMAINSIGNALS LIKETHOSEHERE THATAREREALIZED ASPAIRSOFREALSIGNALS7HENAVERTICALCUTTHROUGHADIAGRAM SUCHASIN&IGURE PICKSUPONE)SIGNALANDONE1SIGNAL THEREPRESENTEDCOMPLEXSIGNALCROSSINGTHAT CUTIS) J1)NTHEDIAGRAM CUTSJUSTBEFOREANDAFTERTHE,0&BLOCKSPICKUPCOMPLEX SIGNALS WITH THE SPECTRA SHOWN ON LINES AND OF &IGURE RESPECTIVELY 4HE LINESIGNALISCREATEDINTHETIMEDOMAINAS ;LINE= ;LINE=E JOF,/T
;LINE=COSOF,/T nJ;LINE=SINOF,/T
;)
J1=
&)'52% 4YPICALANALOGDOWNCONVERSIONTOBASEBAND ANDDIGITIZER
Óx°n
2!$!2(!.$"//+
WHEREF,/ -(Z3IMILARLY USING FORTIME DOMAINCONVOLUTIONFILTERINGWITH ANIMPULSERESPONSE
;LINE= ;LINE= HT ;) J1= HT ) HT J1 HT ) J1
7HENTHEFILTEROUTPUTSAREVIEWEDASCOMPLEXSIGNAL;LINE= ) J1 !EJP THE COMPLEXMAGNITUDE!ANDANGLEPGIVETHEAMPLITUDEGIVEORTAKEASCALEFACTOR AND PHASEOFTHE)&SIGNAL BECAUSETHEORIGINAL)&SIGNALCOULDBERE CREATEDFROMTHELINE SIGNALINTHETIMEDOMAINAGAINGIVEORTAKEASCALEFACTOR AS;LINE= 2E[;LINE= EJOF,/T] FROMWHICHITFOLLOWSTHAT ;LINE= 2E[!EJPEJOF,/T] !2E[EJOF,/T P ] !COSOF,/T P !SAFINALSTEPTHEBASEBAND)AND1SIGNALSAFTERTHEFILTERSAREDIGITIZEDBY!$#SAT A-(ZSAMPLINGRATE PRODUCING)AND1OUTPUTSAMPLESOR EQUIVALENTLY COMPLEX OUTPUTSAMPLES) J1 4HESLASHTHROUGHTHEOUTPUTOFTHE!$#WITHAhvABOVEITIN&IGUREINDI CATESTHATOUR!$#PRODUCESBITSOFDIGITALOUTPUT!$#SPROVIDEAPPROXIMATELY D"OFDYNAMICRANGEPERBIT SOOUR BIT!$#PROVIDESABOUTD"OFDYNAMIC RANGE ASSUMING!$#NONLINEARITIESARENEGLIGIBLE ! 'ENERAL !PPROACH TO $IGITAL $OWNCONVERSION )N DIGITAL DOWNCONVERSION THEANALOG)&SIGNALISFIRSTSAMPLEDBYAN!$# ANDALLOFTHESUBSEQUENTPROCESSING ISTHENDONEDIGITALLY&IGUREDEPICTSTHEDIGITALDOWNCONVERSIONPROCESSFOROUR PREVIOUSEXAMPLE AGAININTHEFREQUENCYDOMAIN4HETOPLINESCHEMATICALLYREPRE SENTSTHEREAL)&SIGNALWITHPARAMETERSASBEFORE0ERFORMINGTHESAMPLINGANALYSIS DESCRIBEDPREVIOUSLY WEDISCOVERTHATSETTINGTHESAMPLERATETOTHETWO SIDEDSIGNAL BANDWIDTHOF-(ZWOULDPRODUCEALIASING(OWEVER A-(ZSAMPLERATEDOES NOTCAUSEALIASINGANDISUSEDONTHESECONDLINEOFTHEFIGURE3AMPLINGTHEINPUT SIGNALAT-(ZREPLICATESTHESIGNALSPECTRUMAT-(ZINTERVALSASSHOWNON LINE&REQUENCYSHIFTINGISACCOMPLISHEDBYSPECTRALLYCONVOLVINGTHISSIGNALWITH THECOMPLEXn-(Z,/TONESHOWNINLINE PRODUCINGTHEFREQUENCY SHIFTEDSIG NALONLINE4HELATTERSIGNALISSPECTRALLYMULTIPLIEDBYTHEFILTERRESPONSESHOWNON LINETOREMOVETHECOPIESOFTHENEGATIVE FREQUENCYSIGNALCOMPONENT PRODUCING THECOMPLEXBASEBANDSIGNALSHOWNONLINE4HISSIGNAL WHICHNOWHASATWO SIDED BANDWIDTHAND.YQUISTFREQUENCYOF-(Z ISSPECTRALLYCONVOLVEDINLINEWITH IMPULSESATTHESPECTRALORIGINANDAT-(ZTOEFFECTIVELYDECIMATETHESIGNALBYA FACTOROFTWO4HEFINALBASEBANDSIGNALONLINEHASASAMPLERATEOF-(Z &IGUREDEPICTSTHEHARDWAREIMPLEMENTATIONOFTHIS$$#ARCHITECTURE4HE )& SIGNAL CENTERED AT -(Z IS DIGITIZED DIRECTLY BY AN!$#!FTER THE!$# THE ARCHITECTUREISVERYSIMILARTOANALOGDOWNCONVERSION EXCEPTTHATTHEPROCESSINGIS PERFORMED DIGITALLY )N OUR EXAMPLE WE ELECT TO SAMPLE THE )& SIGNAL AT A RATE OF -(ZWITHA BIT!$#4HISARCHITECTUREREALIZESTHE,/WITHANUMERICALLY CONTROLLEDOSCILLATOR.#/ THATGENERATESDIGITALWORDSTOREPRESENTTHECOSINEAND NEGATIVE SINE SIGNALS AT THE ,/ FREQUENCY HERE -(Z AND SAMPLED AT THE!$#
2!$!2$)')4!,3)'.!,02/#%33).'
0
1
0
Óx°
0
")! $"
#&"!$ -, %(# 0 #&" )! $"
1 0%#&" .*%$
( '+ $/) ! * )! $" ""%-&)) !"* ( ( )&%$)
%#&" .) $ )! $" !#* /*-% )#&" 0 %#&" . !#* ) $ )! $"
&)'52% $IGITALDOWNCONVERSIONINTHEFREQUENCYDOMAIN
SAMPLERATE4HESINEANDCOSINESIGNALSFROMTHE.#/ARETHENDIGITALLYMULTIPLIED BYTHEDIGITIZED)&SIGNAL)NTHISPARTICULAREXAMPLE THERELATIONSHIPBETWEENTHE,/ FREQUENCYANDTHESAMPLINGRATEWILLMAKETHEREQUIRED.#/ANDTHEMULTIPLIERSBOTH RATHERTRIVIALBECAUSEEACHREQUIRED.#/OUTPUTVALUEISZEROORo ANDTHATSPECIAL CASEWILLBEADDRESSEDSHORTLY&ORNOW THISARCHITECTURESUPPOSESTHATNOSUCHSPECIAL SITUATIONEXISTSANDTHATAGENERAL.#/MULTIPLIERSTRUCTUREISNEEDED4HEDESIGNOF
&)'52% $IGITALDOWNCONVERSIONARCHITECTURE
Óx°£ä
2!$!2(!.$"//+
AGENERAL.#/WILLBEIN3ECTION&OLLOWINGTHEMULTIPLICATIONS DIGITALLOWPASS FILTERSPREVENTALIASINGWHENTHEIROUTPUTSAREDECIMATEDBYAFACTOROFTWOTOPRODUCE COMPLEXOUTPUTSAMPLESATA-(ZRATE)NTHEFIGURE -#303STANDSFORMILLION COMPLEXSAMPLESPERSECOND 4HELOWPASSFILTERALSOREDUCESOUT OF BANDNOISEANDTHUSINCREASESSIGNAL TO NOISERATIO3.2 )NORDERTOPRESERVETHIS3.2GROWTH THENUMBEROFBITSUSED TOREPRESENTTHEFILTEROUTPUTMIGHTNEEDTOINCREASE)FTHEFILTERREDUCESTHEBAND WIDTHOFTHEDATABYAFACTOR2WITHOUTAFFECTINGTHESIGNALOFINTEREST THENTHE3.2 INCREASEIND"ISGIVENBYLOG2)NOUREXAMPLE A¾REDUCTIONINBANDWIDTH RESULTSINAPPROXIMATELYAD"INCREASEIN3.27ITHEACHBITREPRESENTINGABOUT D"OF3.2 THEMINIMUMNUMBEROFBITSREQUIREDTOREPRESENTTHEFILTEREDSIGNAL COULDGROWFROMTO )NANACTUALAPPLICATION THESYSTEMDESIGNERNEEDSTOANALYZETHEEFFECTSOFSAM PLINGANDDIGITALPROCESSINGANDDETERMINEHOWMANYBITSNEEDTOBECARRIEDTHROUGH THE CALCULATIONS IN ORDER TO PRESERVE 3.2 AND PREVENT OVERFLOW #ONSIDERATIONS INCLUDE FRONT END SYSTEM NOISE WHICH IS TYPICALLY ALLOWED TO TOGGLE TWO OR MORE BITSFOURORMOREQUANTIZATIONLEVELS OFTHE!$#OUTPUT!LSO ANACTUAL. BIT!$# NEVERPROVIDESEXACTLY.D"OF3.2 DUETO!$# INDUCEDERRORS&OREXAMPLE A TYPICAL BIT!$#GENERALLYPROVIDESABOUTBITSORABOUTD"OF3.2#ARRYING BITSTHROUGHTHESIGNALPROCESSINGPROVIDESABOUTD"OFDYNAMICRANGE)NTHIS CASE THEDESIGNERMAYELECTTOALLOWTHEDATAPATHTHROUGHTHELOWPASSFILTERTOREMAIN ATBITS REALIZINGTHATTHEFILTERINGPROCESSHASSIMPLYINCREASEDTHE3.2OFTHE SIGNALTOD" WHICHCOULDSTILLBEACCOMMODATEDBYTHE BITDATAPATH !$$#PROVIDESSEVERALBENEFITSCOMPAREDTOANALOGDOWNCONVERSION4HEANA LOGAPPROACHISSUBJECTTOVARIOUSHARDWAREERRORS INCLUDINGMISMATCHOFTHEMIX ERS ,/SIGNALSNOTEXACTLYOAPART ANDMISMATCHESINTHEGAINS $#OFFSETS OR FREQUENCY RESPONSES OF THE ) AND 1 SIGNAL PATHS! $$# AVOIDS THESE PROBLEMS THOUGHITISVULNERABLETOTHEPHASENOISEOFTHE!$#SAMPLECLOCK !$#NONLIN EARITIES ANDARITHMETICROUND OFFNOISE2EALIZINGMAXIMUMPERFORMANCEREQUIRES CAREFULATTENTIONTODESIGNDETAILS $IRECT$IGITAL$OWNCONVERSION )FTHEDESIGNERHASSOMEFLEXIBILITYINEITHER THE)&CENTERFREQUENCYOR!$#SAMPLERATE ASIMPLIFIED$$#ARCHITECTURE DIRECT DIGITALDOWNCONVERSION CANBECONSIDERED )FTHE!$#SAMPLERATEISFOURTIMES THE CENTER OF THE )& BAND THEN THE SAMPLING PROCESS CAN ALSO SHIFT THE SPECTRUM TOBASEBAND ANDTHE.#/ANDASSOCIATEDMULTIPLIERSOFTHEGENERAL$$#ARENOT NEEDED )N GENERAL DIRECT CONVERSION TO BASEBAND IS A SIMPLE AND COST EFFECTIVE $$#METHODTHATCANBEUSEDWHENTHESIGNALBEINGSAMPLEDISALWAYSCENTEREDAT ASINGLEFREQUENCY4HESTANDARD$$#ARCHITECTUREMIGHTNEEDTOBEUSEDWHENTHE CENTERFREQUENCYOFTHESIGNALBEINGSAMPLEDDYNAMICALLYCHANGES WHICHFORCESTHE $$#S,/TOCHANGEACCORDINGLY ,ETSLOOKATTHEDIRECT$$#INTHETIMEDOMAINFIRST FORINTUITION ANDTHENWECAN CAREFULLYDERIVETHEARCHITECTUREINTHEFREQUENCYDOMAIN3UPPOSETHE$$#ARCHI TECTUREISASSKETCHEDIN&IGURE WITHAN)&CENTEREDAT-(ZANDA-(Z ,/ANDSUPPOSETHE.#/ISSETTO-(ZSOTHATITPRODUCESTHESAMPLEDSINESAND COSINESSHOWNIN&IGUREA WHEREVERTICALLINESANDDOTSINDICATESAMPLETIMES ANDVALUES RESPECTIVELY"ECAUSETHESAMPLERATEISFOURTIMESTHE,/FREQUENCY THE COS SIN ,/SAMPLEPAIRSCYCLEREPEATEDLYTHROUGH n n AND .EXT SUPPOSETHE)&SIGNALISA-(ZSINUSOIDOFARBITRARYPHASEASINLINEB 4HE$$#SMIXEROUTPUTS)AND1 THEPRODUCTSOFTHELINEB )&SIGNALWITHTHETWO
2!$!2$)')4!,3)'.!,02/#%33).'
Óx°££
&)'52% 6ARIOUS SIGNALS SAMPLED AT -(Z A -(Z COSINE AND nSINE ,/ SIGNALS B -(Z)&TONE ANDC RESULTOFMULTIPLYINGA SAMPLESBYB SAMPLES
LINE A ,/ SIGNALS ARE THEN AS IN LINE C "ECAUSE OUR HYPOTHETICAL )& SIGNAL ON LINEB WASEXACTLYATONEQUARTEROFTHESAMPLERATE BOTH)AND1ARECONSTANTS THE SINEANDCOSINEOFTHE)&SIGNALSPHASEANGLE &IGURESHOWSTHESAME-(Z)&TONE BUTSAMPLEDAT-(ZAND-(Z WHICHAREODDINTEGERSUBMULTIPLESAND OFTHEORIGINALSAMPLERATEOF¾THE)& CENTERFREQUENCY -(Z.OTETHATODDSAMPLESSTILLCYCLEBETWEEN)AND) ANDTHE EVENSAMPLESSWITCHBETWEEN1AND1/DDINTEGERSUBMULTIPLESOF¾THE)&CENTER FREQUENCYCAN THEREFORE BEVIABLEALTERNATIVESAMPLERATES!.YQUISTBOUNDAPPLIESAND REQUIRESTHETWO SIDED)&BANDWIDTHTOBELESSTHANTHESAMPLINGRATE .OWLETSDERIVETHEDIRECT $$#ARCHITECTURECAREFULLYINTHEFREQUENCYDOMAIN 3UPPOSEAREAL)&SIGNALISONCEAGAINCENTEREDAT-(ZANDSAMPLEDAT-(Z ASINLINEA OF&IGURE4HEFIRSTTHREELINESOF&IGUREILLUSTRATETHISIN THE FREQUENCY DOMAIN WITH LINE SHOWING THE SAMPLED )& SIGNAL 4HE BANDPASS FILTERRESPONSEONLINEREMOVESTHEUNWANTEDSPECTRALCOMPONENTSTOPRODUCETHE COMPLEXPASSBANDSIGNALOFLINE4HISSIGNALISTHENDECIMATEDBYANDSHIFTED BYn-(ZTOPRODUCE ATA-(ZSAMPLINGRATE THEDESIREDCOMPLEXBASEBAND SIGNALSHOWNONLINE &IGURESHOWSTHECORRESPONDINGBLOCKDIAGRAM4HEMAGNITUDEOFTHEFRE QUENCYRESPONSEONLINEOF&IGUREISNEITHERANEVENNORANODDFUNCTION SOTHECORRESPONDINGIMPULSERESPONSEISNEITHERPURELYREALNORPURELYIMAGINARY
&)'52% -(ZTONESAMPLEDATA -(Zr)& ANDB -(Zr)&
Óx°£Ó
2!$!2(!.$"//+ -
.
-
!' #!
"%! # *) $&" - "%! ' #!
# %'' !( &
$"%! +%''# ' #!
"( ,(*$
$"%! + "( %''# ' #!
. -$"%! +($#
$"%! + "( ' # ' #!
&)'52% $IRECTDIGITALDOWNCONVERSIONINTHEFREQUENCYDOMAIN
7RITINGTHATIMPULSERESPONSEASHN H)N JH1N USINGREALFUNCTIONSH)N AND H1N THELINEOPERATIONBECOMES
;LINE= ;LINE= HN
;LINE= ;H)N
JH1N =
;LINE= H)N
J;LINE= JH1N
)
J1
WHERE THE FACT THAT LINE IS REAL IN THE TIME DOMAIN WAS USED IN THE LAST STEP )N &IGURE THESAMPLED)&SIGNAL THEREFORE PASSESTHROUGHDIFFERENT&)2FILTERS
&)'52% 4IME DOMAINIMPLEMENTATIONOFADIRECTDIGITALDOWNCONVERTER
2!$!2$)')4!,3)'.!,02/#%33).'
Óx°£Î
&)'52% A (ALFBANDBANDPASSFILTERCOEFFICIENTSFORADIRECTDIGITALDOWNCONVERTER B REALODD ANDC IMAGINARYEVEN PARTSOFTHECOMPLEXIMPULSERESPONSE
&)2FILTERSAREDESCRIBEDIN3ECTION WHERETHETOPANDBOTTOMFILTERSAPPLYTHE REALANDIMAGINARYPARTSOFTHECOEFFICIENTS RESPECTIVELY4HEEQUIVALENTCOMPLEX IMPULSE RESPONSEFILTER WITHTHEFREQUENCYRESPONSESHOWNINLINEOF&IGURE ISAHALFBANDFILTERBECAUSETHATFREQUENCYRESPONSEANDAVERSIONSHIFTEDINFREQUENCY BYHALFAPERIODSUMTOACONSTANT4HISPROPERTYCAUSESALMOSTHALFOFITSIMPULSE RESPONSECOEFFICIENTSTOBEZERO&IGUREAILLUSTRATESTHECOEFFICIENTSOFATYPICAL FILTERFORTHISAPPLICATION!LLOFTHEODD NUMBEREDCOEFFICIENTS EXCEPTFORTHEONE INTHECENTER AREZERO SOTHEFILTERISVERYEFFICIENTTOIMPLEMENT ASTHEZEROCOEFFI CIENTSDONTREQUIREMULTIPLIERS4HEFREQUENCYRESPONSESSYMMETRYABOUTOFTHE SAMPLINGRATECAUSESTHEEVEN ANDODD NUMBEREDCOEFFICIENTSTOBEPURELYREALAND PURELYIMAGINARY RESPECTIVELY SOTHEEVEN ANDODD NUMBEREDCOEFFICIENTSAREUSED TO RESPECTIVELY CREATE)AND1 ASSHOWNIN&IGUREBANDC !FTERTHEFILTERS THECOMPLEXSIGNALISDECIMATEDBYTOPRODUCEA-(ZOUTPUT SAMPLERATE4HEFINALSPECTRALCONVOLUTIONBYAn-(ZTONEISACCOMPLISHEDBY NEGATINGEVERYOTHERSAMPLE )N&IGURE WETRANSFORMTHESYSTEMOF&IGURETOMAKEITMORECOMPUTA TIONALLYEFFICIENT7EBEGINWITHTHESTRUCTUREIN&IGUREA WHICHSHOWSTHEFILTERING INDETAILUSINGSTOINDICATEEACHCLOCK INTERVALDELAY4HELOCATIONOFTHEONENONZERO COEFFICIENTINTHEREALPARTH)N OFTHE&IGUREIMPULSERESPONSECORRESPONDSTOAN ODD NUMBEREDDELAY SOH)N ISREALIZEDUSINGASINGLEDELAYANDSOMENUMBEROFDOUBLE DELAYS4HEIMAGINARYPARTH1N OFTHEIMPULSERESPONSE INCONTRAST HASNONZEROCOEF FICIENTSONLYATEVENNUMBERSOFDELAYS SOITISREALIZEDWITHDOUBLEDELAYSONLY 4HEARCHITECTURECANTHENBEFURTHERSIMPLIFIEDBYMOVINGTHEDECIMATIONAHEADOF THESDELAYS ASSHOWNIN&IGUREB4HISCHANGESEACHDOUBLEDELAYTOASINGLE DELAYATTHELOWERCLOCKRATEATWHICHTHEFILTERCOMPUTATIONSARENOWMOREEFFICIENTLY CLOCKED/PTIONALLY THENEGATIONOFALTERNATESAMPLESATTHEOUTPUTCANNOWBERELO CATEDTOTHEDECIMATIONSOUTPUT%ACHDELAYTHATTHENEGATIONCROSSESASITMOVESIN THISTRANSFORMATIONCAUSESANETSIGNCHANGEINTHESIGNAL SOEACHSIGNALPATHBETWEEN THEOLDLOCATIONANDTHENEWTHATCONTAINSODDNUMBERSOFDELAYSREQUIRESCOEFFICIENT NEGATIONTOCOMPENSATE4HERESULTINTHEDESIGNOF&IGURECISNEGATIONOFALTER NATECOEFFICIENTSINTHE1FILTER ASSHOWNIN&IGUREC 4HEOPTIONALNEGATION MOVINGTRANSFORMATIONJUSTDESCRIBEDYIELDSASIMPLEINTER PRETATIONOFSYSTEMOPERATION&IGURESHOWSTHATTHELEADINGSDELAY DECIMA TION AND SIGN NEGATION OPERATIONS OF &IGURE C WORK TOGETHER TO STEER ) AND 1 SAMPLESINTOTHEUPPERANDLOWERFILTERPATHS RESPECTIVELY BUTTHESAMPLESTHATARE
Óx°£{
2!$!2(!.$"//+
&)'52% $IRECTDIGITALDOWNCONVERTERA BASELINEIMPLEMENTATION B DECIMATINGBEFOREFILTERS ANDC INVERTINGEVERYOTHERSAMPLEAFTERDECIMATION
NOWALIGNEDINTIMEASTHEYPASSTHROUGHTHEREMAININGPROCESSINGDONOTACTUALLYCOR RESPONDTOTHESAMEPOINTSONTHE)&SIGNALINPUTSTIMELINE SINCETHE)AND1SAMPLES WEREDERIVEDFROMALTERNATE!$#SAMPLES(OWEVER THE1FILTERWITHALTERNATECOEF FICIENTSNEGATED SHOWNIN&IGURE ACTUALLYAPPROXIMATESTHEHALF SAMPLEDELAY
&)'52% .EGATED ALTERNATE SIGNSVERSIONOF1FILTERCOEFFICIENTS
2!$!2$)')4!,3)'.!,02/#%33).'
Óx°£x
REQUIREDTOREALIGNTHEDATAINTHETWOPATHS ANDTHISCAUSESTHE)AND1OUTPUTVALUES TOBEEFFECTIVELYSAMPLEDATTHESAMEINSTANTS 3IGNAL 3AMPLING#ONSIDERATIONS !CTUALDEVICESANDSIGNALSINTRODUCEERRORS &OREXAMPLE CLOCKJITTERRESULTSINERRORSINTHESAMPLEDOUTPUTOFAN!$# ASSHOWN IN&IGURE)NADDITION REAL!$#SALSOADDINTERNALJITTER ORAPERTUREUNCERTAINTY WHICHMUSTBETAKENINTOACCOUNT)FTHEERRORSINTHEEFFECTIVESAMPLINGINSTANTINTRO DUCEDBYTHESEJITTERSAREUNCORRELATED AREASONABLEAPPROXIMATION THE2-3SAMPLE TIMEJITTERTHEYINTRODUCE T* IS T * §©T * !$# T * #,/#+ ¶¸
WHERET*!$# ANDT*#,/#+ ARETHE2-3SAMPLETIMEJITTERSINTRODUCEDBYTHE!$#AND THECLOCK RESPECTIVELY !SINUSOIDALINPUTSIGNALOFAMPLITUDE!ANDFREQUENCYFISEXPRESSEDAS
VT !SINOFT
WHICHHASDERIVATIVE
DVT DT !OFCOSOFT
4HEMAXIMUMERRORDUETOJITTEROCCURSATT WHENTHEDERIVATIVEOFTHESIGNAL ISATITSPEAK OR
DV DT !OF 4HE2-3ERRORVOLTAGE 6E PRODUCEDBYAN2-3SAMPLETIMEJITTER T* ISGIVENBY 6E !OFT*
!.!,/' 3)'.!, %22/2 6/,4!'%
*)44%2
3!-0,% #,/#+ &)'52% 2-3 JITTER VS 2-3 NOISE
Óx°£È
2!$!2(!.$"//+
4HISERRORVOLTAGELIMITSTHETHEORETICALMAXIMUM3.2OFAN!$#BY 3.2MAX LOG!6E nLOG;OFT*=
4HIS RELATIONSHIP IS PRESENTED IN &IGURE WHICH PLOTS ON THE LEFT AND RIGHT AXES RESPECTIVELY THE3.2ANDTHEEQUIVALENT!$#EFFECTIVENUMBEROFBITSOR%./" y3.2D" BOTHVERSUSANALOGFREQUENCYANDFORDIFFERENTVALUESOF2-3SAMPLE JITTER$UETOAVARIETYOFERRORSOURCESINTERNALTOAN!$#APERTUREUNCERTAINTY NON LINEARITIES ADDEDNOISE ETC THESPECIFIED%./"OFAN!$#ISALWAYSLESSTHANTHE NUMBEROFBITSITPROVIDES&OREXAMPLE A BIT!$#TYPICALLYHASAN%./"OF 7ITHTHEBANDPASSSAMPLINGTECHNIQUEDESCRIBEDEARLIER WHERETHE!$#CANSAM PLEATARATETHATISCONSIDERABLYLOWERTHANTHEANALOGFREQUENCIESBEINGSAMPLED ITMIGHTSEEMATTRACTIVETODOAWAYWITHTHERECEIVERALTOGETHERANDSAMPLETHE2& SIGNALDIRECTLY!LTHOUGHTHISISPOSSIBLE !$#LIMITATIONSRESTRICTTHEPERFORMANCEOF SUCHARCHITECTURES&IRST THEANALOGFRONTENDOFAN!$#HASALOWPASSD"CUTOFF FREQUENCYSPECIFIEDBYTHEMANUFACTURER!$#INPUTFREQUENCIESSHOULDBEKEPTWELL BELOW THIS CUTOFF 3ECOND AS SHOWN PREVIOUSLY IN &IGURE SAMPLING THE 2& SIGNALDIRECTLYWILLDRAMATICALLYINCREASETHESLEWRATEOFTHESIGNALPRESENTEDTOTHE !$# THUSREQUIRINGVERYLOWLEVELSOF2-3CLOCKJITTER!LSO THE!$#HASINHERENT NONLINEARITIESTHATPRODUCESPURSINTHE!$#OUTPUT APROBLEMWHICHTYPICALLYWORS ENSWITHINCREASINGINPUTFREQUENCY!$#DATASHEETSSPECIFYTHESPUR FREEDYNAMIC RANGE3&$2 OFTHEDEVICE WHICHISTYPICALLYDEFINEDASTHED"DIFFERENCEINSIGNAL LEVEL BETWEEN THE DESIRED SIGNAL AND THE LARGEST SPUR MEASURED AT THE!$# OUTPUT WITHASINGLETONEAPPLIEDTOTHEINPUT4HE3&$2OFATYPICAL!$#ISHIGHERTHANITS SPECIFIED3.25NFORTUNATELY THEREAREMANYDEFINITIONSOF3&$2 SOTHEDESIGNER ISADVISEDTOREADMANUFACTURERSDATASHEETSCAREFULLYINTHISREGARD!SMENTIONED EARLIER THE3.2OFASAMPLEDSIGNALCANBEINCREASEDBYFILTERINGTOELIMINATENOISE IN PARTS OF THE SPECTRUM THAT ARE OTHERWISE UNUSED (OWEVER THE SPURS GENERATED BYAN!$#MAYLIEINTHEBANDOFINTEREST WHEREFILTERINGWOULDBEINAPPROPRIATE 4HEREFORE SPURSLOWERTHANTHEUNFILTEREDNOISELEVELCANBECOMERELATIVELYSIGNIFI CANTAFTER!$#NOISEISREDUCEDTHROUGHFILTERING (% &' (%&'
$
(%&'
(%&'
(% &'
(% &'
(%&'
# "! ) &)'52% 3IGNAL TO NOISERATIOVSANALOGFREQUENCYFORVARYINGSAMPLEJITTER
2!$!2$)')4!,3)'.!,02/#%33).'
Óx°£Ç
-ULTI "EAM$IGITAL"EAMFORMING !NIMPORTANTAPPLICATIONOFDIGITALTECHNOL OGYISFORTHEBEAMFORMINGFUNCTIONINAPHASEDARRAYANTENNASYSTEM&IGUREA DEPICTSANANALOGBEAMFORMINGSYSTEM4HEWAVEFRONTSHOWNCANBETHOUGHTOFASTHE RETURNFROMATARGETOFINTEREST.OTETHATTHEWAVEFRONTWILLHITEACHELEMENTOFTHEARRAY ATDIFFERENTTIMES)NORDERTOFORMABEAMINTHATPARTICULARDIRECTION EACHELEMENTOF THEARRAYNEEDSTOBEFOLLOWEDBYATIMEDELAYUNITTHATDELAYSTHESIGNALRECEIVEDAT EACHELEMENTBYTHEAPPROPRIATEAMOUNT SUCHTHATWHENALLOFTHEOUTPUTSOFTHETIME DELAYSARESUMMED THEYADDUPCOHERENTLYTOFORMABEAMINTHEDESIREDDIRECTION )FTHESYSTEMHASANARROWBANDWIDTHBANDWIDTH ^OF2&FREQUENCY ANDTHE ANTENNABEAMWIDTHISNOTTOONARROWSOTHATTHED"BEAMWIDTHINDEGREESISGREATER THANTHEPERCENTBANDWIDTH THETIMEDELAYCANBEAPPROXIMATEDUSINGPHASESHIFTERS 7IDEBANDWIDTHSYSTEMSREQUIREhTRUEvTIMEDELAYSINORDERTOFORMTHEBEAMSAND PRESERVETHEBANDWIDTH4HERECEIVERWOULDFOLLOWTHEANALOGBEAMFORMER ASSHOWNIN THEFIGURE&IGUREBSHOWSANEXTREMEAPPLICATIONOFDIGITALBEAMFORMING WHERE
&)'52% A !NALOGBEAMFORMER B EVERY ELEMENTDIGITALBEAMFORMER ANDC SUBARRAYDIGITAL BEAMFORMER
Óx°£n
2!$!2(!.$"//+
ARECEIVERAND!$#AREBEHINDEVERYELEMENT)NTHISSYSTEM THETIMEDELAYISIMPLE MENTEDEITHERASADIGITALPHASESHIFTORDIGITALTIMEDELAY FOLLOWEDBYADIGITALSUMMER 4HISCONFIGURATIONALLOWSBEAMSTOBEFORMEDINANYDIRECTION ANDMULTIPLEBEAMSCAN BEFORMEDSIMULTANEOUSLY IFDESIRED BYUSINGTHESAMESAMPLEDATAANDIMPLEMENTING DIFFERENTTIMEDELAYSTOFORMTHEDIFFERENTBEAMS(OWEVER ATTHISWRITING PUTTINGA DIGITALRECEIVERBEHINDEVERYELEMENTISEXPENSIVEANDISUSUALLYNOTFEASIBLEFORMOST LARGEANTENNAAPPLICATIONSIE FORSYSTEMSWITHTHOUSANDSOFELEMENTS /NECOMPRO MISESOLUTIONISSHOWNIN&IGUREC WHEREANALOGBEAMFORMINGISUSEDTOIMPLE MENTSUBARRAYS WHICHAREFOLLOWEDBYDIGITALRECEIVERSANDDIGITALTIMEDELAYS $IGITALBEAMFORMINGOFFERSSEVERALADVANTAGESOVERANALOGBEAMFORMING7ITHAN ANALOGBEAMFORMER USUALLYONLYONEBEAMISFORMEDATATIME2ADARSARETYPICALLY REQUIRED TO PERFORM MULTIPLE FUNCTIONS SUCH AS VOLUME SURVEILLANCE TARGET CONFIR MATION TRACKING ETC7ITHONLYONEBEAMATATIME THEREMAYNOTBEENOUGHTIME AVAILABLE TO PERFORM ALL OF THE REQUIRED FUNCTIONS! DIGITAL BEAMFORMER ALLOWS THE FORMATION OF MULTIPLE SIMULTANEOUS BEAMS ALLOWING THE VOLUME SURVEILLANCE FUNC TIONTOBEPERFORMEDMUCHMOREQUICKLY ALLOWINGMORETIMETODOOTHERTHINGS/F COURSE INORDERTOFORMMULTIPLESIMULTANEOUSRECEIVEBEAMS THETRANSMITTEDBEAM MUSTBEMADEBROADERTOENCOMPASSTHERECEIVEBEAMS WHICHMIGHTREQUIREAMORE POWERFULTRANSMITTERORMOREINTEGRATIONONRECEIVETOPROVIDETHESAMEPERFORMANCE ASASINGLE BEAMSYSTEM !NOTHERADVANTAGEHASTODOWITHDYNAMICRANGE)NANANALOGBEAMFORMINGSYS TEM THEREISONLYONERECEIVERAND!$# ANDTHEDYNAMICRANGEPERFORMANCEISLIM ITEDTOTHECAPABILITYOFASINGLECHANNEL)NADIGITALBEAMFORMINGSYSTEM THEREARE MULTIPLERECEIVERSAND!$#S ANDTHENUMBEROF!$#STHATARECOMBINEDDETERMINES THESYSTEMDYNAMICRANGE&OREXAMPLE IFTHEOUTPUTSOF!$#SWERECOMBINED TO FORM A BEAM ASSUMING THAT EACH!$# INDUCES NOISE THAT IS OF EQUAL AMPLITUDE ANDUNCORRELATEDWITHTHEOTHERS THEREWOULDBEAD"INCREASEINSYSTEMDYNAMIC RANGE COMPAREDTOASINGLE RECEIVERSYSTEMUSINGTHESAME!$# &IGURESHOWSABLOCKDIAGRAMOFATYPICALDIGITALBEAMFORMINGSYSTEM%ACH ANTENNA OUTPUT PORT BE IT FROM AN ELEMENT OR A SUBARRAY IS FOLLOWED BY A DIGITAL
&)'52% 4YPICALDIGITALBEAMFORMER
2!$!2$)')4!,3)'.!,02/#%33).'
Óx°£
DOWNCONVERTERANDANEQUALIZATIONFILTER%15&)2 4HEEQUALIZATIONFILTERISTYPI CALLYACOMPLEXFINITEIMPULSERESPONSE&)2 FILTERDESCRIBEDLATER THATADJUSTSTHE FREQUENCYRESPONSEOFEACHCHANNELSOTHATITSPASSBANDMATCHESTHEOTHERCHANNELSIN PHASEANDAMPLITUDEBEFOREITISSUMMEDWITHTHEOTHERCHANNELSINTHEBEAMFORMER 4HE COEFFICIENTS OF THIS FILTER ARE DETERMINED THROUGH A CALIBRATION PROCESS $URING CALIBRATION ATESTSIGNALISPRESENTEDTOTHE2&INPUTOFALLCHANNELS4HISSIGNALISTYPI CALLYASWEPTFREQUENCYTONEORANOISEINPUTTHATCOVERSTHECHANNELBANDWIDTH4HE !$#SAMPLESOFALLCHANNELSARECOLLECTEDSIMULTANEOUSLYANDCOMPLEXWEIGHTSARE CALCULATEDFORTHEEQUALIZATIONFILTERSTHATFORCETHEFREQUENCYRESPONSEOFEACHCHANNEL TOBEMATCHED/NCETHECHANNELISEQUALIZED AUNIQUETIMEDELAYISIMPLEMENTEDFOR EACHBEAMTOBEFORMED!SMENTIONEDEARLIER THISTIMEDELAYCANBEREALIZEDEITHER ASAPHASESHIFTFORANARROWBANDSYSTEMORASATIMEDELAYFORAWIDEBANDSYSTEM! PHASESHIFTCANBEIMPLEMENTEDWITHACOMPLEXMULTIPLYORA#/2$)#OPERATION BOTH OFWHICHWILLBEDESCRIBEDLATER!TIMEDELAYCANBEIMPLEMENTEDWITHA&)2FILTERTHAT IMPOSESALINEARLYCHANGINGPHASESHIFTOVERFREQUENCYONTHESIGNAL/NCETHETIME DELAYISREALIZEDINEACHCHANNEL THEAPPROPRIATECOMPLEXTIME DELAYEDSIGNALSFROM ALLOFTHECHANNELSARESUMMEDTOFORMABEAM-COMPLEXSUMMERSAREREQUIREDTO FORM-BEAMS $IGITAL0ULSE#OMPRESSION 0ULSECOMPRESSIONISANOTHERSIGNALPROCESSING FUNCTIONTHATISPREDOMINANTLYBEINGPERFORMEDDIGITALLYINRADARSYSTEMS(OWEVER ATTHISWRITING MANYSYSTEMSSTILLEXISTWITHANALOG DELAY LINEPULSECOMPRESSORS )NTHESESYSTEMS ANALOGPULSECOMPRESSIONISPERFORMEDATAN)& FOLLOWEDBYTHE !$# IN THE PROCESSING CHAIN "ECAUSE PULSE COMPRESSION INCREASES THE 3.2 OF THESIGNAL PERFORMINGITBEFORESAMPLINGINCREASESTHEDYNAMICRANGEREQUIREMENT OF THE!$# )N A DIGITAL PULSE COMPRESSION SYSTEM THE!$# PRECEDES THE PULSE COMPRESSOR AND ONLY HAS TO ACCOMMODATE THE PRECOMPRESSION DYNAMIC RANGE OF THESIGNAL WHICHCANBEASIGNIFICANTLYLOWERREQUIREMENT4HEDIGITIZEDSIGNALIS CONVERTEDTOBASEBANDANDPASSEDTOTHEDIGITALPULSECOMPRESSOR4HEINCREASED DYNAMICRANGEDUETOTHEPULSECOMPRESSIONGAINISACCOMMODATEDBYINCREASING THENUMBEROFBITSINTHEDIGITALCOMPUTATION #HAPTER IS DEVOTED TOTALLY TO PULSE COMPRESSION RADAR )N SUMMARY THERE ARE TWOBASICAPPROACHESTOIMPLEMENTINGDIGITALPULSECOMPRESSIONTIME DOMAINAND FREQUENCY DOMAINCONVOLUTION!GENERICTIME DOMAINCONVOLVERCONSISTSOFACOM PLEX&)2FILTER WHERETHECOEFFICIENTSARETHECOMPLEXCONJUGATEOFTHETRANSMITTED BASEBANDWAVEFORMSAMPLESINTIME REVERSEDORDERWHICHISALSOTHEDEFINITIONOF THE MATCHED FILTER FOR THE TRANSMITTED SIGNAL 4HIS ARCHITECTURE CAN COMPRESS ANY ARBITRARYWAVEFORM!SIMPLIFIEDVERSIONOFTHEARCHITECTURERESULTSWHENTHEMODU LATIONISABINARYPHASECODE)NTHISCASE THECOEFFICIENTSAREEITHER ORn SOTHE ARITHMETIC PERFORMED FOR EACH SAMPLE IS A COMPLEX SUM OR SUBTRACTION INSTEAD OF AFULLCOMPLEXMULTIPLICATION 0ULSECOMPRESSIONMAYALSOBEACCOMPLISHEDBYOPERATINGINTHEFREQUENCYDOMAIN WHEREITISREFERREDTOASFASTCONVOLUTION)NTHISCASE THEBASEBANDSAMPLESOFTHE RECEIVE DATA AND THE REFERENCE TRANSMIT WAVEFORM ARE PASSED THROUGH FAST &OURIER TRANSFORMS&&4S THEDATA&&4OUTPUTSAREMULTIPLIEDPOINT BY POINTBYTHECOMPLEX CONJUGATEOFTHEREFERENCE&&4OUTPUTS ANDTHENTHERESULTISCONVERTEDBACKTOTHE TIMEDOMAINBYANINVERSE&&4)NGENERAL ITISMOREHARDWAREEFFICIENTTOPERFORM TIME DOMAINCONVOLUTIONFORASMALLNUMBEROFCOEFFICIENTSANDFREQUENCYDOMAIN CONVOLUTIONFORALARGENUMBERMORETHANOR COEFFICIENTS
Óx°Óä
2!$!2(!.$"//+
Óx°ÎÊ /, - /Ê
Ê*,"
--
"EFORE DIGITAL TECHNOLOGY BECAME WIDELY AVAILABLE ANALOG TECHNIQUES WERE EMPLOYEDTOGENERATERADARTRANSMITWAVEFORMS3IMPLEPULSEDSYSTEMSUSEDANALOG 2&SWITCHESTOGATETHE,/ONANDOFF&REQUENCYMODULATEDSIGNALSWEREGENERATED BYSURFACEACOUSTICWAVE3!7 DEVICES3IMPLEBINARYPHASEMODULATIONSCHEMES LIKEPSEUDO RANDOMNOISEWAVEFORMSWEREALSOPOSSIBLE$IGITALTECHNOLOGY HOW EVER PRESENTSTHERADARSYSTEMDESIGNERWITHMANYMOREOPTIONSANDALLOWSARBI TRARILYMODULATEDTRANSMITWAVEFORMSTOBEMODIFIEDPULSE TO PULSEIFDESIRED4HIS SECTION DESCRIBES SEVERAL OF THE TECHNIQUES COMMONLY USED TO GENERATE THE RADAR TRANSMITSIGNALDIGITALLY $IRECT$IGITAL3YNTHESIZER$$3 &IGURESHOWSABLOCKDIAGRAMOFTHIS TECHNIQUE INWHICHANUMERICALLYCONTROLLEDOSCILLATOR.#/ GENERATESADIGITIZED SINUSOIDTHATISCONVERTEDTOANANALOGSIGNALBYADIGITAL TO ANALOGCONVERTER$!# &IGUREDEMONSTRATESHOWAN.#/OPERATESTOPRODUCEASINEWAVE4HEN BIT TUNINGWORDISACTUALLYAPHASEINCREMENTTHATDETERMINESTHEFREQUENCYOFTHESINE WAVE OUTPUT 4HE PHASE INCREMENT IS EXPRESSED IN A FORMAT CALLED "INARY!NGLE -EASUREMENT"!- INWHICHTHEMOSTSIGNIFICANTBIT-3" OFTHEWORDREPRE SENTSO THENEXTBITREPRESENTSO ANDSOON)NTHEPHASEACCUMULATOR THETUN INGWORDISADDEDTOTHEOUTPUTOFARUNNINGSUM IMPLEMENTEDASANADDERFOLLOWED BYAREGISTER2%' 4HISPRODUCESAUNIFORMLYINCREASINGPHASE INCREMENTEDATTHE SYSTEMCLOCKRATE4HEM-3"SOFTHERUNNINGSUMARESENTTOAPHASE TO AMPLITUDE CONVERTER WHICH IS A LOOKUP TABLE THAT PRODUCES A K BIT VALUE THAT REPRESENTS THE AMPLITUDEOFTHESINEWAVEATTHEINPUTPHASE)FWEREPRESENTTHETUNINGWORDBY- THESAMPLEFREQUENCYBYFS ANDTHENUMBEROFBITSINTHEPHASEACCUMULATORBYN THENTHEFREQUENCYOFTHEOUTPUTSINEWAVECANBEEXPRESSEDAS-FSN )NTHISSCHEME THEPHASEREPRESENTEDBYTHERUNNINGSUMWILLOVERFLOWWHENIT CROSSESOVERO4HEADVANTAGEOFEXPRESSINGTHEPHASEIN"!-NOTATIONISTHATIT ALLOWSMODULO OARITHMETICANDOVERFLOWSAREAUTOMATICALLYTAKENCAREOF SINCEA OPHASESHIFTISTHESAMEASO&OREXAMPLE ASSUMEWEHAVEA BIT"!-NOTA TION WHICHMEANSTHATTHELEASTSIGNIFICANTBIT,3" REPRESENTSAPHASESHIFTOFO ,ETSALSOASSUMETHATTHETUNINGWORDISREPRESENTEDBYFORAPHASEINCREMENT OFOEVERYCLOCK4HERUNNINGSUMPHASEWOULDSTEADILYINCREASEONEVERYCLOCK EDGE BECOMINGO O x O ANDO /NTHENEXTCLOCK EDGE THEPHASESHOULDBEREPRESENTEDBYFORO(OWEVER WEAREONLYPRO VIDEDA BITADDER SOTHE-3"ISSIMPLYLOST LEAVINGUSWITHAPHASECODEOF O WHICHISTHESAMEASO4HEREFORE THERESULTINGPHASEWAVEFORMTAKESONA SAWTOOTHPATTERN LINEARLYRAMPINGFROMOTONOTQUITEOANDTHENRESETTINGTOO ANDRAMPINGAGAIN !NIMPORTANTFEATUREOFAN.#/FORARADARAPPLICATIONISTHE#,%!2SIGNALSHOWN GOING TO THE PHASE ACCUMULATOR REGISTER &OR A COHERENT RADAR EXCITER IMPLEMENTA TION THETRANSMITSIGNALMUSTSTARTATTHESAMEPHASEONEVERYPULSE/THERWISE THE
&)'52% $IRECT$IGITAL3YNTHESIZER$$3
2!$!2$)')4!,3)'.!,02/#%33).'
Óx°Ó£
&)'52% .#/BLOCKDIAGRAM
TRANSMITTED SIGNAL WILL HAVE ARBITRARY PHASE FROM PULSE TO PULSE MAKING DOPPLER PROCESSINGDIFFICULTIFNOTIMPOSSIBLE4HE#,%!2CONTROLPROVIDESTHEMEANSTODO THIS)NSOMEAPPLICATIONS LIKEFORATRANSMITBEAMFORMER THESTARTINGPHASEINEACH CHANNELMAYNEEDTOBEDIFFERENTINORDERTOSTEERTHEBEAM)NTHISCASE WECOULD PROVIDEAMECHANISMTOSETTHEPHASETOTHEDESIREDVALUEATTHEBEGINNINGOFAPULSE INSTEADOFSIMPLYCLEARINGIT 4HE$$3CANALSOBEUSEDTOGENERATELINEARANDNONLINEAR&-hCHIRPvWAVEFORMS 4HISISACCOMPLISHEDBYPROVIDINGCIRCUITRYTHATCHANGESTHETUNINGWORDFROMSAMPLE TOSAMPLEINORDERTOPROVIDETHEDESIREDFREQUENCYORPHASE MODULATION&OREXAM PLE ALINEAR&-CHIRPWAVEFORMREQUIRESAPHASETHATCHANGESINASQUARE LAWFASHION WITHTIME4HISCANBEACCOMPLISHEDBYCHANGINGTHETUNINGWORDORPHASESTEPSIZE INALINEARLYINCREASINGORDECREASINGWAYONEVERYSAMPLE $IGITAL5PCONVERTER$5# !NOTHERPOPULARMETHODTOIMPLEMENTATRANSMIT WAVEFORMISTHROUGHDIGITALUPCONVERSION ALSOREFERREDTOASARBITRARYWAVEFORMGEN ERATION)NTHISTECHNIQUE ADIGITALCOMPLEXBASEBANDWAVEFORM USUALLYREADFROMA MEMORY ISFIRSTINTERPOLATEDTOAHIGHERSAMPLERATE ANDTHENMODULATEDWITHDIGITIZED SINEANDCOSINESIGNALSTOPRODUCEAMODULATEDCARRIER&IGUREPROVIDESABLOCK DIAGRAMOFA$5#THATTRANSLATESACOMPLEXBASEBANDSIGNALUPTOA-(Z)&4HE BASEBAND)AND1SIGNALSENTERTHE$5#ATARATEOF-#303ANDAREFIRSTUP SAMPLED BY A FACTOR OF 4HIS IS ACCOMPLISHED BY INSERTING ZEROES BETWEEN EACH INPUT SAMPLEANDINCREASINGTHECLOCKRATETO-(Z4HISSIGNALISTHENPASSEDTHROUGHA DIGITALLOWPASSFILTERTHATPERFORMSTHEINTERPOLATION4HESESIGNALSARETHENMULTIPLIED
&)'52% $IGITALUPCONVERTER$5#
Óx°ÓÓ
2!$!2(!.$"//+
BYDIGITIZEDSINEANDCOSINEWAVEFORMSFORTHEMODULATIONCARRIERFREQUENCY PRODUC INGACOMPLEXMODULATED)&ASANOUTPUT4HESESIGNALSAREDIGITALLYSUMMED CON VERTEDTOANALOGTHROUGHA$!# ANDPASSEDTHROUGHABANDPASSFILTERTOPRODUCEAN )&OUTPUT&ORLARGEUPSAMPLINGRATIOS ACASCADED INTEGRATORCOMB#)# INTERPOLATOR DESCRIBEDINTHENEXTSECTION PROVIDESANEFFICIENTIMPLEMENTATION
Óx°{Ê -*Ê/"" 4HIS SECTION WILL DESCRIBE VARIOUS PROCESSING ARCHITECTURES AND TECHNIQUES THAT ARE AVAILABLETO$30ENGINEERS 0HASE3HIFT 4HEPHASESHIFTISACOREELEMENTIN$30DESIGN ANDTHEREARESEV ERALTECHNIQUESAVAILABLETOIMPLEMENTONE4HEMOSTSTRAIGHTFORWARDAPPROACHISTO SIMPLYPERFORMACOMPLEXMULTIPLY ASSHOWNIN&IGURE)NTHISEXAMPLE THE COMPLEXINPUTSAMPLEISDENOTEDAS! J" WHICHISMULTIPLIEDBYTHECOMPLEXCOEF FICIENT# J$TOPRODUCE!#n"$ J!$ "# INORDERTOEFFECTTHEPHASESHIFT 4HISOPERATIONREQUIRESFOURMULTIPLIERSANDTWOADDERS !FTERSOMEMANIPULATION THEFOLLOWINGCANBESHOWN
) !#n"$ $!n" !#n$
1 !$ "# #! " n!#n$
.OTINGTHATTHEFINALTERMISTHESAMEINBOTHEQUATIONS WESEETHATTHISCOMPLEX MULTIPLIERCANBEIMPLEMENTEDWITHONLYTHREEREALMULTIPLIERSANDFIVEREALADDS4HIS CAN BE IMPORTANT IF REAL MULTIPLIERS ARE AT A PREMIUM &IGURE SHOWS A BLOCK DIAGRAMOFTHISARCHITECTURE #/2$)#0ROCESSOR !NEFFICIENTANDVERSATILEALGORITHMTHATCANIMPLEMENTA PHASESHIFTWITHOUTUSINGMULTIPLIERSISTHE#/ORDINATE2OTATION$)GITAL#OMPUTER #/2$)# FUNCTION FIRSTDESCRIBEDBY6OLDERIN4HE#/2$)#CANIMPLEMENT
&)'52% 3TANDARDCOMPLEXMULTIPLY
Óx°ÓÎ
2!$!2$)')4!,3)'.!,02/#%33).'
&)'52% #OMPLEXMULTIPLYWITHTHREEREALMULTIPLIERS
AVARIETYOFFUNCTIONS INCLUDINGSINE COSINE VECTORROTATIONPHASESHIFT POLAR TO RECTANGULARANDRECTANGULAR TO POLARCONVERSIONS ARCTANGENT ARCSINE ARCCOSINE AND VECTORMAGNITUDE THROUGHANITERATIVEPROCESSTHATJUSTUSESBITSHIFTSANDADDS4HE FOLLOWINGDISCUSSIONDESCRIBESTHE#/2$)#ALGORITHM 4HEEQUATIONSTHATSHIFTTHEPHASEOFCOMPLEXNUMBER) J1BYANANGLEPTO PRODUCE) J1AREASFOLLOWS
) )COSP 1SINP
1 )SINP 1COSP 4HESEEQUATIONSCANBEMANIPULATEDTOPROVIDE
) COSP ;) 1TANP =
1 COSP ;1 )TANP =
4HE#/2$)#ALGORITHMTAKESADVANTAGEOFTHISRELATIONSHIPTOAPPROXIMATEANARBI TRARYPHASESHIFTBYIMPLEMENTINGMULTIPLESTAGESOFPHASESHIFTS WHERETHETANGENTOF THEPHASESHIFTINEACHSUCCESSIVESTAGEISTHENEXTSMALLERFRACTIONALPOWEROF AND MULTIPLICATIONBYTHISNUMBERCANBEIMPLEMENTEDBYSHIFTINGTHEINPUTDATABITSAN INTEGERNUMBEROFPLACES4HEFIRSTFEWSTAGESAREASFOLLOWS
) COSP ;)n1TANP = COSP ;)n1 =
1 COSP ;1 )TANP = COSP ;1 ) =
) COSP ;)n1TANP = COSP ;) 1 = 1 COSP ;1 )TANP = COSP ;1 ) =
4ABLE SHOWS THESE PARAMETERS FOR AN EIGHT STAGE #/2$)# PROCESSOR %ACH ROWOFTHETABLEREPRESENTSSUCCESSIVEITERATIONSOFTHEALGORITHM4HETANPI COLUMN SHOWSTHEFACTORBYWHICHTHE)AND1VALUESAREMULTIPLIEDFOREACHITERATION.OTETHAT THESEVALUESAREFRACTIONALPOWERSOF SOTHEMULTIPLICATIONCANBEREALIZEDBYSHIFTING THEBINARY)AND1VALUESRIGHTBYIPLACES4HEPICOLUMNSHOWSTHEARCTANGENTOFTHIS FACTOR WHICHCANALSOBETHOUGHTOFASTHEPHASESHIFTAPPLIEDDURINGEACHITERATION
Óx°Ó{
2!$!2(!.$"//+
4!",% #/2$)#0ARAMETERSFOR&IRST%IGHT3TAGES
I
TANPI
PIDEG
COSPI
0;COSPI =
4HE COSPI COLUMN SHOWS THE COSINE OF THIS ANGLE WHICH SHOULD BE MULTIPLIED BY THERESULTOFEACHITERATION ASSHOWNINTHEEQUATIONSABOVE)NACTUALAPPLICATIONS HOWEVER THISCOSINEMULTIPLICATIONISNOTPERFORMEDATEVERYITERATION!TEACHSTAGE THEIMPLIEDFACTORTHATNEEDSTOBEMULTIPLIEDBYTHE)1OUTPUTSOFTHESTAGEINORDERTO PROVIDETHECORRECTANSWERISTHEPRODUCTOFALLOFTHECOSINESUPTOTHATPOINT ASSHOWN IN THE 0;COSPI = COLUMN &OR A LARGE NUMBER OF ITERATIONS THIS PRODUCT OF COSINES CONVERGES TO A VALUE OF )N MOSTCASES THISSCALINGCANBECOMPEN SATED FOR IN LATER STAGES OF PROCESSING 4HEINVERSEOFTHISFACTOR FOR ALARGENUMBEROFITERATIONS ISTHEPRO CESSINGGAINIMPOSEDONTHE)1RESULTS
OFTHE#/2$)#)FINTEGERARITHMETICIS PERFORMED ANEXTRABITSHOULDBEPRO VIDEDATTHEMOSTSIGNIFICANTENDOFTHE ADDERS IN ORDER TO ACCOMMODATE THIS INCREASEDSIGNALLEVEL &IGURE IS A FLOW CHART THAT REPRESENTS THE #/2$)# ALGORITHM TO IMPLEMENT A PHASE SHIFT 4HE INPUTS TOTHEALGORITHMARETHE)IN 1IN ANDEIN
THEDESIREDPHASESHIFT 4HEVARIABLEI WILLKEEPTRACKOFTHEPROCESSINGSTAGE BEING PERFORMED AND IS INITIALIZED TO ZERO4HEBASICALGORITHMCANPERFORMA PHASESHIFTBETWEENoO)FTHEDESIRED PHASESHIFTISOUTSIDEOFTHATRANGE THE INPUT)AND1VALUESAREFIRSTNEGATED IMPOSINGAOPHASESHIFT ANDOIS SUBTRACTEDFROMTHEDESIREDPHASESHIFT 4HENEWPHASESHIFTISNOWWITHINoO ANDTHEALGORITHMPROCEEDSNORMALLY .EXT THE ALGORITHM LOOPS THROUGH . ITERATIONS WITH THE GOAL OF DRIVING
THE RESIDUAL PHASE ERROR E TO ZERO )N EACHITERATION ANEWEISCALCULATEDBY SUBTRACTINGORADDINGTHEPHASESHIFTFOR &)'52% #/2$)#ALGORITHMFLOWCHART
2!$!2$)')4!,3)'.!,02/#%33).'
Óx°Óx
THATSTAGEPI FROMTHETABLE TOTHEPREVIOUSVALUEOFE)FE PI ISADDEDTOE /THERWISE PIISSUBTRACTEDFROME)NEACHSTAGE THE1OR) INPUTISDIVIDEDBYAFAC TOROFIBYSHIFTINGTHENUMBERTOTHERIGHTBYIBITS ANDTHENADDEDTOORSUBTRACTED FROMTHE)OR1 INPUT DEPENDINGONTHESIGNOFE4HEVARIABLEIISINCREMENTEDAND THEPROCESSREPEATSUNTILI . ATWHICHPOINTTHEPHASE SHIFTEDRESULTSAREAVAILABLE &IGUREISABLOCKDIAGRAMOFANEIGHT STAGE#/2$)#PROCESSORTHATIMPLE MENTS A PHASE SHIFT WHERE EACH STAGE REPRESENTS AN ITERATION IN THE FLOW CHART!N . STAGEPROCESSORPROVIDESAPHASESHIFTTHATISACCURATETOWITHINoP.DEGREESFROM THETABLE SOTHEMORESTAGESINTHEPROCESSOR THEMOREACCURATETHEANSWER4HEINPUT ) AND 1 VALUES CHANGE ON THE RISING EDGE OF AN ASSUMED SAMPLE CLOCK )N THE FIRST STAGE THE)VALUEISEITHERADDEDTOORSUBTRACTEDFROMTHE1VALUEINTHE!$$35" BLOCK4HECONTROLBLOCKONTHEBOTTOMOFTHEFIGUREDETERMINESWHETHERADDITIONSOR SUBTRACTIONSAREPERFORMEDATEACHSTAGE BASEDONTHEALGORITHMDESCRIBEDPREVIOUSLY )F THE!$$35" BLOCK IN THE 1 CHANNEL PERFORMS AN ADDITION THE SAME BLOCK IN THE)CHANNELWILLPERFORMASUBTRACTION ANDVICE VERSA4HERESULTOFTHE!$$35" BLOCKSISSTOREDINAREGISTER2%' ONTHENEXTCLOCKEDGEANDPASSEDTOTHENEXTSTAGE OF PROCESSING )N THIS IMPLEMENTATION THE LAST BLOCK LABELED 0!33).6 PERFORMS THEREQUIREDINVERSIONOF)AND1IFTHEDESIREDPHASESHIFTISBEYONDTHEoORANGEOF THEALGORITHM4HEFINALMULTIPLICATIONBYACONSTANTISOPTIONAL ASDESCRIBEDEARLIER 4HEARCHITECTURESHOWNIN&IGUREISAGOODEXAMPLEOFAPIPELINEDPROCESSOR INWHICHAPORTIONOFTHECOMPUTATIONISPERFORMEDANDTHERESULTISSTOREDINAREGISTER ONEACHRISINGEDGEOFTHESAMPLECLOCKANDPASSEDTOTHENEXTSTAGEOFPROCESSING4HE PROCESSORWOULDSTILLFUNCTIONIFTHEREGISTERSWEREREMOVED(OWEVER INTHATCASE WHENTHEINPUT)AND1VALUESCHANGED THEFINALOUTPUTWOULDNOTBEUSEABLEUNTILTHE RESULTSOFTHENEWINPUTVALUESRIPPLEDTHROUGHALLOFTHESTAGESOFPROCESSING WHICH WOULDGENERALLYBEANUNACCEPTABLYLONGPERIODOFTIME)NAPIPELINEDPROCESSOR A SMALLPORTIONOFTHETOTALCALCULATIONSISPERFORMEDATATIME ANDTHERESULTISSTOREDIN AREGISTERANDPASSEDTOTHENEXTPROCESSINGSTAGE4HISARCHITECTUREPROVIDESAHIGHER THROUGHPUT THAN THE NONPIPELINED VERSION WHICH MEANS THAT THE FINAL RESULT CAN BE PRODUCEDATAMUCHHIGHERSAMPLERATE WHICHISINVERSELYPROPORTIONALTOTHEDELAY OFASINGLESTAGE4HELATENCYOFAPIPELINEDPROCESSORREFERSTOTHEDELAYEXPERIENCED BETWEENTHETIMEANEWDATASAMPLEISENTEREDINTOTHEPROCESSORANDTHETIMETHAT THE RESULT BASED ON THAT INPUT IS AVAILABLE ON THE OUTPUT4HE EIGHT STAGE PIPELINED #/2$)#PROCESSORSHOWNINTHEFIGUREWOULDHAVEALATENCYEQUIVALENTTOEIGHTCLOCK PERIODSANDATHROUGHPUTEQUIVALENTTOTHECLOCKRATEIE ONCETHEPIPELINEISFILLED ANDTHEFIRSTRESULTISAVAILABLEONTHEOUTPUT SUCCESSIVECLOCKSWILLPRODUCENEWOUT PUTSATTHECLOCKRATE
!
&)'52% %IGHT STAGE#/2$)#PROCESSOR
!
Óx°ÓÈ
2!$!2(!.$"//+
$IGITAL&ILTERSAND!PPLICATIONS 4HISSECTION DESCRIBESSEVERALOFTHEMAJORFORMSOFDIGITALFILTERS ANDHOWTHEYAREUSEDINRADARSIGNALPROCESSING
&INITE )MPULSE 2ESPONSE &)2 AND )NFINITE )MPULSE 2ESPONSE ))2 &ILTERS &IGURE SHOWSABLOCKDIAGRAMOFADIRECT FORMDIGITAL&)2 FILTER4HEINPUTSAMPLEFEEDSASHIFTREGISTER WHERE EACHBLOCKLABELEDS INDICATESAONE SAMPLEDELAY INTHESHIFTREGISTER4HEINPUTSAMPLEANDTHEOUTPUT OFEACHSTAGEOFTHESHIFTREGISTERAREMULTIPLIEDBY UNIQUE COEFFICIENTS AND THE MULTIPLIER OUTPUTS ARE SUMMED TO PRODUCE THE FILTERED OUTPUT 3OFTWARE TOOLSEXISTTHATGENERATETHESECOEFFICIENTSANDTHE NUMBERREQUIREDWHENTHEUSERPROVIDESTHEDESIRED FILTER CHARACTERISTICS SUCH AS FILTER TYPE LOWPASS &)'52% 'ENERAL DIRECT FORM HIGHPASS BANDPASS ETC SAMPLE RATE CUTOFF AND &)2FILTERBLOCKDIAGRAM STOPBAND FREQUENCY DESIRED PASSBAND RIPPLE AND STOPBANDATTENUATION4HEFILTERSHOWNISREFERREDTOASAREAL&)2FILTER SINCETHEINPUT DATAANDCOEFFICIENTSAREREALVALUESANDREALMATHEMATICALOPERATIONSAREPERFORMED )NACOMPLEX&)2FILTER THEDATASAMPLES COEFFICIENTS ANDMATHARECOMPLEX 4HISTYPEOFFILTERISTERMEDFINITEIMPULSERESPONSEBECAUSEANIMPULSEPRESENTED ATTHEINPUTASINGLESAMPLEOFhvSURROUNDEDBYSAMPLESOFZEROES WOULDPRODUCE A FINITE LENGTH OUTPUT CONSISTING OF THE COEFFICIENTS OF THE FILTER OUTPUT IN ORDER AS THEhvPROPAGATESDOWNTHESHIFTREGISTER ASSHOWNIN&IGUREFORA&)2FILTER WITHSEVENCOEFFICIENTSCOMMONLYREFERREDTOASA TAP&)2FILTER )NTHISEXAMPLE ZERO VALUEDSAMPLESAREFIRSTCLOCKEDINTOTHE&)2FILTERSHIFTREGISTER FILLINGTHESHIFT REGISTERWITHZEROESANDFORCINGTHEFILTEROUTPUTTOBEZERO7HENTHESAMPLEWITHA VALUEOFhvISCLOCKEDINTOTHEFILTER THEFILTEROUTPUTPRODUCESTHEFIRSTCOEFFICIENT A SINCETHEOTHERSAMPLESINTHEFILTERARESTILLZERO/NTHENEXTCLOCK THEhvMOVESTO THESECONDTAPOFTHESHIFTREGISTER ANDAhvISCLOCKEDINTOTHEFIRSTTAP FORCINGTHE FILTEROUTPUTTOPRODUCETHESECONDFILTERCOEFFICIENT A/NSUCCESSIVECLOCKS THEhv PROPAGATESTHROUGHTHESHIFTREGISTER WHILEZEROESARECLOCKEDINTOTHESHIFTREGISTER INPUT PRODUCINGALLOFTHEFILTERCOEFFICIENTSONTHEOUTPUTINSEQUENCE4HE&)2FILTER USESFEED FORWARDTERMSONLY MEANINGTHATTHEOUTPUTVALUESONLYDEPENDONTHEINPUT VALUESWITHNOFEEDBACKTERMS &IGUREDEPICTSTHEGENERALFORMFORANINFINITEIMPULSERESPONSE))2 FILTER ))2FILTERSMAKEUSEOFFEED FORWARDANDFEEDBACKTERMS4HEYAREREFERREDTOASINFINITE IMPULSERESPONSEBECAUSEANIMPULSEPRESENTEDATTHEINPUTTOTHEFILTERWILLPRODUCEAN INFINITESTRINGOFNONZEROOUTPUTSINANIDEALSITUATION
&)'52% )MPULSERESPONSEOF TAP&)2FILTER
2!$!2$)')4!,3)'.!,02/#%33).'
Óx°ÓÇ
&)'52% 'ENERAL))2FILTERBLOCKDIAGRAM
#OMPAREDTO&)2FILTERS ))2FILTERSOFFERSEVERALADVANTAGES)NGENERAL THEYREQUIRE LESSPROCESSINGANDMEMORYTOIMPLEMENTSIMILARFUNCTIONS)TISALSOEASIERTOIMPLE MENT SOME FILTER RESPONSES AS ))2 RATHER THAN &)2 FILTERS (OWEVER WITHOUT CAREFUL DESIGN ))2FILTERRESPONSESCANBEVERYSENSITIVETOCOEFFICIENTQUANTIZATIONLIMITATIONS ANDCOULDEXHIBITATENDENCYTOOVERFLOWIE PRODUCEANOUTPUTTHATEXCEEDSTHEPROCES SORDYNAMICRANGE DETERMINEDBYTHENUMBEROFBITSINTHEDATAPATH !LTHOUGH))2FIL TERSAREALMOSTNEVERUSEDINRADARSYSTEMSFORTHESEANDAVARIETYOFHISTORICALREASONS A CAUTIOUSDESIGNERMIGHTFINDANAPPLICATIONWHERETHEYCANBEUSEDTOGOODADVANTAGE "YCONTRAST &)2FILTERSAREINHERENTLYSTABLE2EAL&)2FILTERSWITHSYMMETRICCOEF FICIENTSAUTOMATICALLYPROVIDEALINEARPHASESHIFTOVERFREQUENCY INTRODUCINGLITTLEOR NOPHASEDISTORTIONTOTHEFILTEREDSIGNAL WHICHISHIGHLYDESIRABLEINMANYAPPLICA TIONS"ECAUSE&)2FILTERSREQUIRENOFEEDBACK THEY ARE EASIER TO USE IN VERY HIGH SPEED APPLICATIONS THAN))2FILTERS WHICHTYPICALLYREQUIRETHECOMPU TATION OF AN OUTPUT SAMPLE BEFORE THE NEXT OUTPUT SAMPLECANBEFORMED#OMPLEX&)2FILTERS WHERE ACOMPLEXMULTIPLICATIONISPERFORMEDATEACHTAP CANBEUSEDTOIMPLEMENTEQUALIZATIONFILTERS TIME DELAYS ANDPULSECOMPRESSIONFILTERS &IGURE SHOWS AN ALTERNATIVE FORM FOR A &)2 FILTER CALLED A TRANSPOSED FORM &)2 FILTER )N THISCONFIGURATION EACHINPUTSAMPLEISMULTIPLIED BYALLOFTHECOEFFICIENTSATONCE WITHTHESAMPLE DELAYSBETWEENTHESUMMEROUTPUTS )FTHECOEFFICIENTSOFA&)2FILTERARESYMMETRIC SOTHATTHECOEFFICIENTSONEITHERSIDEOFTHECENTER OFTHEFILTERAREMIRRORIMAGESOFEACHOTHERASIS THECASEWITHLINEARPHASEFILTERS MULTIPLIERSCANBE SAVEDBYADDINGTHESAMPLESTHATGETMULTIPLIEDBY THE SAME COEFFICIENT FIRST THEREBY REQUIRING ABOUT HALFASMANYMULTIPLIERS ASSHOWNIN&IGURE &)'52% 4RANSPOSED FORM FORA TAPEXAMPLE &)2FILTER
Óx°Ón
2!$!2(!.$"//+
&)'52% TAP &)2 FILTER WITH SYMMETRICCOEFFICIENTS
$ECIMATION&ILTERS !SMENTIONEDPREVIOUSLY THECOMPLEXITYANDCOSTOFASIGNAL PROCESSOR INTERMSOFTHEAMOUNTOFSYSTEMRESOURCESREQUIREDTOIMPLEMENTIT GENER ALLYVARIESLINEARLYWITHTHEDATASAMPLERATE&ORTHISREASON INMOSTSYSTEMAPPLICA TIONS ITISCOST EFFECTIVETOREDUCETHEDATASAMPLERATETOAVALUETHATISJUSTADEQUATETO SUPPORTTHEBANDWIDTHOFTHESYSTEM)NAPPLICATIONSWHERETHESAMPLERATEOFASIGNALIS TOBEDECREASEDDECIMATED THEFREQUENCYCONTENTOFTHESIGNALMUSTFIRSTBEREDUCEDSO THATTHE.YQUISTCRITERIONISSATISFIEDFORTHENEWSAMPLERATE4HISCANBEACCOMPLISHED BYFIRSTPASSINGTHESIGNALTHROUGHADIGITAL&)2FILTERTORESTRICTTHEBANDWIDTHOFTHE SIGNALTOLESSTHANHALFOFTHEDECIMATEDSAMPLERATE ANDTHENREDUCINGTHESAMPLERATE OFTHEFILTEREDSIGNALBYAFACTOROF2BYSELECTINGEVERY2THSAMPLE ASDESCRIBEDINTHE PREVIOUS DISCUSSION OF DECIMATION! DESIGNER CAN TAKE ADVANTAGE OF DECIMATION BY REALIZINGTHATONLYTHEFILTEROUTPUTSTHATAREUSEDNEEDTOBECOMPUTED&OREXAMPLE IFTHEOUTPUTOFA&)2FILTERISTOBEDECIMATEDBYAFACTOROF ONLYEVERYFOURTHFILTER OUTPUTNEEDSTOBECOMPUTED WHICHREDUCESTHEREQUIREDPROCESSINGBYAFACTOROF )NTERPOLATION&ILTERS )NTERPOLATIONISTHEPROCESSBYWHICHTHESAMPLERATEOFA SIGNALISINCREASED FOREXAMPLEINPREPARINGTHESIGNALTOBEUPCONVERTEDTOAN)& ASSHOWNIN&IGURE)NTERPOLATORSARETYPICALLY&)2FILTERSWITHALOWPASSFILTER RESPONSE4OINCREASETHESAMPLERATEBYAFACTOR2 2nZEROESAREFIRSTINSERTED BETWEENTHELOW RATEDATASAMPLES CREATINGADATASTREAMATASAMPLERATE2TIMES FASTERTHANTHEINPUTRATEUPSAMPLING 4HISDATASTREAMISTHENPASSEDTHROUGHTHE LOWPASS&)2FILTERTOPRODUCETHEINTERPOLATEDHIGH SAMPLE RATEOUTPUT/FCOURSE THE&)2FILTERMUSTBECLOCKEDATTHEHIGHERDATARATE4HISPROCESSISILLUSTRATEDIN &IGUREFORAFOURTIMESINCREASEINSAMPLERATE
&)'52% )LLUSTRATIONOFINTERPOLATIONFILTERING
2!$!2$)')4!,3)'.!,02/#%33).'
Óx°Ó
#ASCADED)NTEGRATOR #OMB#)# &ILTERS )NDECIMATIONORINTERPOLATIONAPPLI CATIONS WHERE THE RATE CHANGE FACTOR IS LARGE TYPICALLY OR GREATER A &)2 FILTER IMPLEMENTATIONMIGHTBEPROHIBITIVELYCOSTLYDUETOTHELARGENUMBEROFFILTERTAPS THATWOULDBEREQUIRED#)#FILTERSAREACLASSOFFILTERSINTRODUCEDBY(OGENAUER THAT PROVIDE A VERY EFFICIENT MEANS OF IMPLEMENTING THESE FILTER FUNCTIONS THAT DO NOTREQUIREMULTIPLIERS%XCELLENTDESCRIPTIONSOFTHISCLASSOFFILTERAREPROVIDEDBY ,YONSAND(ARRIS WHICHFORMTHEBASISFORTHEFOLLOWINGDISCUSSION &IGUREASHOWSASINGLE STAGE#)#DECIMATOR4HEFILTERCONTAINSANINTEGRATOR STAGECONSISTINGOFASINGLESAMPLEDELAYANDANADDER FOLLOWEDBYACOMBSTAGEWITH A$ STAGESHIFTREGISTERDENOTEDBYTHE$SBLOCK ANDASUBTRACTOR4HECOMBFILTERGETS ITSNAMEBECAUSEITSFREQUENCYRESPONSELOOKSLIKEARECTIFIEDSINEWAVEANDRESEMBLES THETEETHOFACOMB!FTERTHECOMBSTAGE THESIGNALISDECIMATEDBYAFACTOR2DENOTED BYTHEm2BLOCK BYONLYPASSINGEVERY2THSAMPLE)NMOSTAPPLICATIONS THENUMBER OFSTAGESINTHESHIFTREGISTER $ ISEQUALTOTHERATECHANGEFACTOR 2&IGUREB DEPICTSA#)#INTERPOLATOR WHEREUPSAMPLINGBYAFACTOROF2DENOTEDBYTHEk2BLOCK ISFOLLOWEDBYACOMBSECTIONANDANINTEGRATOR4HEUPSAMPLINGISACCOMPLISHEDBY ZEROINSERTIONASDESCRIBEDINTHEPREVIOUSSECTION h)NTERPOLATION&ILTERSv.OTETHATTHE PROCESSINGONLYCONSISTSOFDELAYSANDADDS &IGURE A SHOWS THE SINX X FREQUENCY RESPONSE OF A SINGLE STAGE #)# DECI MATOR WHERE2 $ 4HEDESIREDPASSBANDISTHELIGHTLYSHADEDAREACENTEREDAT (ZWITHBANDWIDTH"74HEDARKERSHADEDAREASWITHBANDWIDTH"7IN&IGUREA INDICATESIGNALSTHATWILLALIASINTOTHEBASEBANDSIGNALAFTERDECIMATIONBY ASSHOWN IN&IGUREBAFTER,YONS .OTETHATUNLESS"7ISVERYSMALL ASIGNIFICANTPORTION OFOUT OF BANDSIGNALSWOULDGETFOLDEDINTOTHEDECIMATEDBASEBANDSIGNAL4HETYPI CALMETHODUSEDTOIMPROVETHISFILTERRESPONSEISTOINCREASETHEFILTERORDERBYADDING MORESTAGES&IGURESHOWSATHREE STAGE#)#DECIMATIONFILTER ANDITSFREQUENCY RESPONSEBEFOREANDAFTERDECIMATIONBYISSHOWNIN&IGUREAANDB RESPECTIVELY .OTETHATTHEALIASEDCOMPONENTSARESIGNIFICANTLYREDUCEDINAMPLITUDE COMPAREDTOTHE SINGLE STAGE#)#FILTERRESPONSE ANDTHEMAINPASSBANDHASMOREATTENUATIONTOWARDTHE EDGES)NTYPICALAPPLICATIONS A#)#DECIMATORISFOLLOWEDBYA&)2LOWPASSFILTERANDA FINALDECIMATIONBY4HATIS ADECIMATE BY FILTERWOULDBECOMPOSEDOFADECIMATE BY #)#FILTERFOLLOWEDBYADECIMATE BY &)2FILTER4HE&)2FILTERCANBETAILOREDTO REMOVETHEUNDESIREDRESIDUALCOMPONENTSBEFORETHEFINALDECIMATION4HE&)2FILTER CANALSOBECONFIGUREDTOCOMPENSATEFORTHEDROOPINTHEPASSBANDRESPONSE &IGURESHOWSANEQUIVALENTFORMFORA#)#DECIMATIONFILTER WHERETHEDECI MATIONOCCURSRIGHTAFTERTHEINTEGRATORSECTIONANDBEFORETHECOMBSECTION4HEDELAY INTHECOMBFILTERBECOMESAVALUE.S WHERE.ISEQUALTO$24HISALLOWSTHECOMB SECTIONTOOPERATEATTHEDECIMATEDSAMPLERATE WHICHMAKESITSIMPLERTOIMPLEMENT $UETOTHISSIMPLIFICATION #)#DECIMATORSAREGENERALLYIMPLEMENTEDINTHISFORM
&)'52% A #)#DECIMATIONFILTERANDB #)#INTERPOLATIONFILTER
Óx°Îä
2!$!2(!.$"//+
&)'52% &REQUENCYRESPONSEOFSINGLE STAGE#)#DECIMATIONFILTERA BEFOREDECIMATION ANDB AFTERDECIMATION
&)'52% 4HREE STAGE#)#DECIMATIONFILTER
2!$!2$)')4!,3)'.!,02/#%33).'
Óx°Î£
&)'52% &REQUENCYRESPONSEOFTHIRD ORDER#)#DECIMATIONFILTERA BEFOREDECIMATION ANDB AFTERDECIMATION
&)'52% #)#FILTERWITH DECIMATION AFTERINTEGRATOR
Óx°ÎÓ
2!$!2(!.$"//+
#AREFULINSPECTIONOFTHEDECIMATORARCHITECTUREREVEALSAPOTENTIALPROBLEMWITH THEINTEGRATOR4HEINPUTSAMPLESCONTINUALLYGETADDEDTOTHERUNNINGSUM PRODUCINGA DEFINITEOVERFLOWCONDITION4HEBEAUTYOFTHEARCHITECTUREISTHATOVERFLOWSAREALLOWED ANDCOMPENSATEDFORBYTHECOMBSECTION ASLONGASTHEREAREENOUGHBITSINTHEADDERS TOREPRESENTTHEMAXIMUMEXPECTEDOUTPUTVALUEANDTHEFILTERISIMPLEMENTEDUSING TWOSCOMPLEMENTARITHMETIC!SDESCRIBEDBY(ARRIS THENUMBEROFBITSREQUIREDIN THEADDERSB!$$%2 ISGIVENBY
B!$$%2 B$!4! #%),;LOG'!). =
WHEREB$!4!ISTHENUMBEROFBITSINTHEINPUTDATAAND#%),;=INDICATESROUNDINGTHE NUMBERINTHEBRACKETSTOTHENEXTHIGHESTINTEGER'!).ISGIVENBY
'!). 2+
WHERE2ISTHEDECIMATIONFACTORAND+ISTHENUMBEROFSTAGESINTHEFILTER RESULTINGIN
B!$$%2 B$!4! #%),;LOG2+ =
&OREXAMPLE ASSUMEWEHAVE BITINPUTDATAB$!4! ANDA STAGE#)#FILTER + THATDECIMATESTHESAMPLERATEBYAFACTOROF2 3UBSTITUTINGINTOTHIS EQUATIONPRODUCES
B!$$%2 #%),;LOG = #%),;=
)NPRACTICE ALTHOUGHTHEFIRSTADDERSTAGEMUSTSUPPORTTHISNUMBEROFBITS LOWER ORDER BITS MAY BE PRUNED FROM THE ADDERS IN SUCCESSIVE STAGES AS DESCRIBED BY (ARRIS ! #)# INTERPOLATING FILTER WOULD BE PRECEDED BY A &)2 FILTER BASED INTERPOLATOR #)#INTERPOLATORSAREDESCRIBEDINDETAILINTHEREFERENCEDLITERATURE 4HE$ISCRETE&OURIER4RANSFORM$&4 )NMANYSAMPLEDDATASYSTEMS SPEC TRALANALYSISISIMPLEMENTEDBYPERFORMINGTHEDISCRETE&OURIERTRANSFORM$&4 4HE $&4 FORMS THE BASIS FOR MANY RADAR SIGNAL PROCESSING ALGORITHMS SUCH AS DOPPLER PROCESSINGANDFASTCONVOLUTIONPULSECOMPRESSIONDESCRIBEDIN#HAPTER ASWELLAS RADARFUNCTIONSSUCHASSYNTHETICAPERTURERADAR3!2 ANDINVERSESYNTHETICAPERTURE RADAR)3!2 4HE$&4TAKES.DATASAMPLESREALORCOMPLEX ASINPUTANDGENER ATES.COMPLEXNUMBERSASOUTPUT WHERETHEOUTPUTSAMPLESREPRESENTTHEFREQUENCY CONTENTOFTHEINPUTDATASEQUENCE&ORASAMPLERATEFS EACHOUTPUTFREQUENCYSAMPLE BIN HASAWIDTHOFFS.4HEMTHOUTPUTSAMPLE 8M REPRESENTSTHEAMPLITUDEAND PHASE OF THE FREQUENCY CONTENT OF THE FINITE LENGTH INPUT SEQUENCE CENTERED AT THE FREQUENCYMFS. )FANINPUTSIGNALISEXACTLYCENTEREDINONEOFTHE$&4FREQUENCYBINS THEOUTPUT WILLHAVEAMAXIMUMVALUEFORTHATBINANDNULLSFORALLOTHERBINS(OWEVER ANYFRE QUENCYOTHERTHANONECENTEREDINABINWILLBLEEDINTOTHEOTHERBINS4HEBASIC$&4 BINHASAFREQUENCYRESPONSESIMILARTOSINX X WHICHMEANSTHATASIGNALINANOTHER BINMIGHTBLEEDINTOA$&4FREQUENCYBINWITHANATTENUATIONASSMALLASD"4O COMPENSATEFORTHIS THEINPUTSAMPLESCANBEWEIGHTEDINAMPLITUDEWITHAWIDESELEC TIONOFWEIGHTS SUCHAS(ANNINGAND(AMMINGWEIGHTS WHICHBROADENTHEMAINLOBE RESPONSEOFTHE$&4OUTPUT BUTREDUCETHEAMPLITUDEOFTHESIDELOBES!THOROUGH TREATMENTOF$&4WEIGHTINGFUNCTIONSANDTHEIREFFECTSISGIVENBY(ARRIS
2!$!2$)')4!,3)'.!,02/#%33).'
Óx°ÎÎ
&)'52% 2ADIX BUTTERFLY
4HE&AST&OURIER4RANSFORM&&4 4HEIMPLEMENTATIONOFA$&4ISCOMPUTA TIONALLYINTENSIVE REQUIRING.COMPLEXMULTIPLIES4HEFAST&OURIERTRANSFORM&&4 ISAVERYEFFICIENTTECHNIQUETOIMPLEMENTTHE$&4 IF.ISAPOWEROF WHICHREQUIRES ONLY. LOG.COMPLEXMULTIPLIES 4HEBASICCOMPUTATIONALELEMENTINAN&&4ISTHEBUTTERFLY SHOWNIN&IGURE )NTHEBUTTERFLYOPERATION ONEINPUTISPHASESHIFTEDANDTHENADDEDTOANDSUBTRACTED FROMASECONDINPUTTOFORMTWOOUTPUTS4HISSTRUCTUREISREFERREDTOASARADIX BUT TERFLYBECAUSEITHASTWOINPUTS&ORCERTAIN&&4CONFIGURATIONS RADIX ANDHIGHER RADIXBUTTERFLIESPROVIDESOMECOMPUTATIONALSAVINGS &IGURE SHOWS A RADIX POINT &&4 4HE PHASE SHIFTS ARE REPRESENTED AS COMPLEXWEIGHTS7.K WHERE.ISTHENUMBEROFPOINTSINTHE&&4ANDKINDICATESTHE PARTICULARPHASESHIFTAPPLIED7.KDENOTESAPHASESHIFTOFKP.4HESEWEIGHTSARE OFTENREFERREDTOASTWIDDLEFACTORS&IGURESHOWSTHEPHASESHIFTSASSOCIATED WITHVARIOUSTWIDDLEFACTORS .OTETHATTHE POINT&&4CONSISTSOFTHREESTAGES!LLOFTHECOMPUTATIONSINEACH STAGEAREEXECUTEDBEFOREPROCEEDINGTOTHENEXTSTAGE!LSONOTETHATTHEPHASESHIFT INTHEFIRSTSTAGE 7 ISZERO WHICHREQUIRESNOCOMPUTATIONATALL
&)'52% %IGHT POINT 2ADIX &&4
Óx°Î{
2!$!2(!.$"//+
&)'52% 0HASESHIFTSINFERREDBYVARIOUSTWIDDLEFACTORS
3INCEADDITIONSAREPERFORMEDINEACHSTAGE THEMAGNITUDEOFEACHOUTPUTSTAGE SAMPLECOULDBEAFACTOROFTWOORMOREGREATERTHANTHEINPUTSAMPLES)FFIXED POINT COMPUTATIONSAREUSED THENTHISINCREASEDDYNAMICRANGERESULTSINAGROWTHINTHE NUMBEROFBITSREQUIREDTOREPRESENTTHEVALUES ANDTHERENEEDSTOBEASTRATEGYTO ACCOMMODATEIT 4HEREARESEVERALTECHNIQUESGENERALLYUSEDTOHANDLETHISINCREASEDDYNAMICRANGE INFIXED POINT&&4S/NESCHEMEWOULDBETOENSURETHATTHECOMPUTATIONSTAGESCARRY ENOUGHBITSTOACCOMMODATETHEBIT GROWTH&OREXAMPLE INOUR POINT&&4EXAMPLE IFWEASSUMETHATTHEINPUTSAMPLESARE BITCOMPLEXNUMBERS ANDIFWEASSUME THATTHEMAGNITUDESOFTHECOMPLEXNUMBERSDONOTEXCEEDBITS THENTHEFINAL&&4 OUTPUTSCOULDGROWBITSCOMPAREDTOTHEINPUTS SOTHE&&4COMPUTATIONSCOULDBE PERFORMEDWITHBITORLARGERADDERS4HISALSOMEANSTHATTHEMULTIPLIERSWOULDHAVE TOHANDLETHELARGERNUMBEROFBITSONTHEINPUTS4HISMETHODCOULDGETUNWIELDYFOR LARGE&&4S !NOTHERTECHNIQUEISTOAUTOMATICALLYSCALETHEOUTPUTSOFEACHSTAGEBYAFACTOROF WHICHWOULDNOTALLOWTHEOUTPUTSTOGROW5NFORTUNATELY THISWOULDALSOLIMIT ANYPROCESSINGGAINTHATTHE&&4MIGHTOFFER !THIRDMETHOD CALLEDBLOCKFLOATINGPOINT CHECKSTHEMAGNITUDESOFALLTHEOUT PUTSAFTEREACHSTAGEISCOMPUTEDANDPROVIDESASINGLEEXPONENTFORALLOUTPUTVALUES )FANYOFTHEOUTPUTSHAVEOVERFLOWEDORCOMENEARTOOVERFLOWING THENALLOFTHE OUTPUTSARESCALEDBYAFACTOROF ANDTHECOMMONEXPONENTISINCREMENTEDBY %NOUGHBITSHAVETOBEPROVIDEDINTHEFINALMANTISSATOACCOMMODATETHEDYNAMIC RANGEGROWTH4HISTECHNIQUEISPOPULARBECAUSEITONLYSCALESTHEOUTPUTVALUESWHEN ABSOLUTELYNECESSARY
Óx°xÊ - Ê " - ,/" 4HISSECTIONADDRESSESTOPICSTHATNEEDTOBECONSIDEREDINTHEDESIGNOFRADAR$30 SYSTEMSASWELLASIMPLEMENTATIONALTERNATIVES 4IMING$EPENDENCIES )NCOHERENTRADARSYSTEMS ALLLOCALOSCILLATORS,/S ANDCLOCKSTHATGENERATESYSTEMTIMINGAREDERIVEDFROMASINGLEREFERENCEOSCILLA TOR(OWEVER THISFACTALONEDOESNOTENSURETHATTHETRANSMITTEDWAVEFORMSTARTS ATTHESAME2&PHASEONEVERYPULSE WHICHISAREQUIREMENTFORCOHERENTSYSTEMS
2!$!2$)')4!,3)'.!,02/#%33).'
Óx°Îx
#ONSIDER A SYSTEM WITH A -(Z REFERENCE OSCILLATOR FROM WHICH IS DERIVED A -(Z)&CENTERFREQUENCYONTRANSMITANDRECEIVE ANDACOMPLEXSAMPLERATE OF-(Z!RULEOFTHUMBISTHATTHECLOCKUSEDTOPRODUCETHEPULSEREPETITION INTERVAL02) NEEDSTOBEACOMMONDENOMINATOROFTHE)&CENTERFREQUENCIESON TRANSMITANDRECEIVEANDTHECOMPLEXSAMPLEFREQUENCYINORDERTOASSUREPULSE TO PULSEPHASECOHERENCY&ORTHISEXAMPLE WITHAN)&CENTERFREQUENCYOF-(ZAND ACOMPLEXSAMPLERATEOF-(Z ALLOWABLE02)CLOCKFREQUENCIESWOULDINCLUDE -(ZAND-(Z (ARDWARE )MPLEMENTATION 4ECHNOLOGY )N THE PAST IMPLEMENTING A REAL TIMERADARDIGITALSIGNALPROCESSORTYPICALLYREQUIREDTHEDESIGNOFACUSTOMCOMPUT ING MACHINE USING THOUSANDS OF HIGH PERFORMANCE INTEGRATED CIRCUITS )#S 4HESE MACHINESWEREVERYDIFFICULTTODESIGN DEVELOP ANDMODIFY$IGITALTECHNOLOGYHAS ADVANCEDTOTHEPOINTWHERESEVERALIMPLEMENTATIONALTERNATIVESEXISTTHATMAKETHE PROCESSORMOREPROGRAMMABLEAND HENCE EASIERTODESIGNANDCHANGE 0ARALLEL 'ENERAL PURPOSE #OMPUTERS 4HIS ARCHITECTURE EMPLOYS MULTIPLE GEN ERAL PURPOSEPROCESSORSTHATARECONNECTEDVIAHIGH SPEEDCOMMUNICATIONNETWORKS )NCLUDED IN THIS CLASS ARE HIGH END SERVERS AND EMBEDDED PROCESSOR ARCHITECTURES 3ERVERS ARE TYPICALLY HOMOGENEOUS PROCESSORS WHERE ALL OF THE PROCESSING NODES ARE IDENTICAL AND ARE CONNECTED BY A VERY HIGH PERFORMANCE DATA BUS ARCHITECTURE %MBEDDEDPROCESSORARCHITECTURESARETYPICALLYCOMPOSEDOFSINGLE BOARDCOMPUTERS BLADES THAT CONTAIN MULTIPLE GENERAL PURPOSE PROCESSORS AND PLUG INTO A STANDARD BACKPLANEARCHITECTURE SUCHAS6-%4HISCONFIGURATIONOFFERSTHEFLEXIBILITYOFSUP PORTINGAHETEROGENEOUSARCHITECTURE WHEREAVARIETYOFDIFFERENTPROCESSINGBLADES ORINTERFACEBOARDSCANBEPLUGGEDINTOTHESTANDARDBACKPLANETOCONFIGUREATOTAL SYSTEM!TTHISWRITING BACKPLANESAREMIGRATINGFROMPARALLELARCHITECTURES WHERE DATAISTYPICALLYPASSEDAS OR BITWORDS TOSERIALDATALINKS WHICHPASSSINGLE BITS AT VERY HIGH CLOCK RATES CURRENTLY IN EXCESS OF GIGABITS PER SECOND 'BPS 4HESESERIALDATALINKSARETYPICALLYPOINT TO POINTCONNECTIONS)NORDERTOCOMMUNI CATEWITHMULTIPLEBOARDS THESERIALLINKSFROMEACHBOARDGOTOAHIGH SPEEDSWITCH BOARDTHATCONNECTSTHEAPPROPRIATESOURCEANDDESTINATIONSERIALLINKSTOGETHERTOFORM ASERIALFABRIC%XAMPLESOFPOPULARSERIALFABRICBACKPLANESATTHISWRITINGINCLUDE 683 608 AND!4#!)TISAPPARENTTHATHIGH SPEEDSERIALLINKSWILLBETHEPRIMARY COMMUNICATION MECHANISM FOR MULTIPROCESSOR MACHINES INTO THE FUTURE WITH EVER INCREASINGDATABANDWIDTHS 4HESE PARALLEL PROCESSOR ARCHITECTURES OFFER THE BENEFIT OF BEING PROGRAMMABLE USINGHIGH LEVELLANGUAGES SUCHAS#AND# !RELATEDADVANTAGEISTHATPROGRAM MERS CAN DESIGN THE SYSTEM WITHOUT KNOWING THE INTIMATE DETAILS OF THE HARDWARE !LSO THESOFTWAREDEVELOPEDTOIMPLEMENTTHESYSTEMCANTYPICALLYBEMOVEDRELA TIVELYEASILYTOANEWHARDWAREARCHITECTUREASPARTOFATECHNOLOGYREFRESHCYCLE /NTHENEGATIVESIDE THESESYSTEMSCANBEDIFFICULTTOPROGRAMTOSUPPORTREAL TIME SIGNALPROCESSING4HEREQUIREDOPERATIONSNEEDTOBESPLITUPAPPROPRIATELYAMONG THEAVAILABLEPROCESSORS ANDTHERESULTSNEEDTOBEPROPERLYMERGEDTOFORMTHEFINAL RESULT! MAJOR CHALLENGE IN THESE APPLICATIONS IS TO SUPPORT THE PROCESSING LATENCY REQUIREMENTSOFTHESYSTEM WHICHDEFINESTHEMAXIMUMLENGTHOFTIMEALLOWEDTO PRODUCEARESULT4HELATENCYOFAPROCESSORISDEFINEDASTHEAMOUNTOFTIMEREQUIRED TOOBSERVETHEEFFECTOFACHANGEATAPROCESSORSINPUTONITSOUTPUT!CHIEVINGLATENCY GOALSOFTENREQUIRESASSIGNINGSMALLERPIECESOFTHEWORKLOADTOINDIVIDUALPROCESSORS LEADINGTOMOREPROCESSORSANDAMOREEXPENSIVESYSTEM!NOTHERCHALLENGEFACING
Óx°ÎÈ
2!$!2(!.$"//+
THESESYSTEMSINARADARAPPLICATIONISRESETTIME)NAMILITARYAPPLICATION WHENA SYSTEMNEEDSTOBERESETINORDERTOFIXAPROBLEM THESYSTEMNEEDSTOCOMEBACKTO FULLOPERATIONINAVERYSHORTPERIODOFTIME4HESEMULTIPROCESSORSYSTEMSTYPICALLY TAKEALONGTIMETOREBOOTFROMACENTRALPROGRAMSTOREAND HENCE HAVEDIFFICULTY MEETINGRESETREQUIREMENTS$EVELOPINGTECHNIQUESTOADDRESSTHESEDEFICIENCIESISAN ACTIVEAREAOFRESEARCH&INALLY THESEPROCESSORSAREGENERALLYUSEDFORNON REAL TIME ORNEAR REAL TIMEDATAPROCESSING ASINTARGETTRACKINGANDDISPLAYPROCESSING3INCE THES THEYHAVESTARTEDTOBEAPPLIEDTOREAL TIMESIGNALPROCESSINGAPPLICATIONS !LTHOUGHTHEYMIGHTBECOST EFFECTIVEFORRELATIVELYNARROWBANDSYSTEMS THEIRUSEIN WIDEBAND$30SYSTEMSINTHEEARLYSTCENTURYISTYPICALLYPROHIBITIVELYEXPENSIVE DUETOTHELARGENUMBEROFPROCESSORSREQUIRED4HISSITUATIONSHOULDIMPROVEOVER TIMEASFASTERANDFASTERPROCESSORSBECOMEAVAILABLE #USTOM DESIGNED (ARDWARE 4HROUGH THE S REAL TIME RADAR $30 SYSTEMS WEREBUILTUSINGDISCRETELOGIC4HESESYSTEMSWEREVERYDIFFICULTTODEVELOPANDMOD IFY BUTINORDERTOACHIEVETHEREQUIREDSYSTEMPERFORMANCE ITWASTHEONLYOPTION AVAILABLE -ANY SYSTEMS WERE BUILT USING !PPLICATION 3PECIFIC )NTEGRATED #IRCUITS !3)#S WHICH ARE CUSTOM DEVICES DESIGNED TO PERFORM A PARTICULAR FUNCTION4HE USE OF!3)#S ALLOWED $30 SYSTEMS TO BECOME VERY SMALL WITH HIGH PERFORMANCE (OWEVER THEYWEREANDSTILLARE DIFFICULTANDEXPENSIVETODEVELOP OFTENREQUIRING SEVERAL DESIGN ITERATIONS BEFORE THE DEVICE WAS FULLY OPERATIONAL )F AN!3)# BASED SYSTEMNEEDSTOBEMODIFIED THE!3)#SNEEDTOBEREDESIGNED INCURRINGSIGNIFICANT EXPENSE4YPICALLY THEUSEOF!3)#SMAKESSENSEIFTENSORHUNDREDSOFTHOUSANDSOF UNITSARETOBESOLD SOTHATTHEDEVELOPMENTCOSTSCANBEAMORTIZEDOVERTHELIFEOFTHE UNIT4HISISRARELYTHECASEFORRADARSYSTEMS(OWEVER MANY!3)#SHAVEBEENDEVEL OPEDTOSUPPORTTHECOMMUNICATIONINDUSTRY SUCHASDIGITALUP ANDDOWNCONVERTERS WHICHCANBEUTILIZEDINRADARSYSTEMS 4HE INTRODUCTION OF THE &IELD 0ROGRAMMABLE 'ATE!RRAY &0'! IN THE S HERALDEDAREVOLUTIONINTHEWAYREAL TIME$30SYSTEMSWEREDESIGNED&0'!SARE INTEGRATED CIRCUITS THAT CONSIST OF A LARGE ARRAY OF CONFIGURABLE LOGIC ELEMENTS THAT ARECONNECTEDBYAPROGRAMMABLEINTERCONNECTSTRUCTURE!TTHETIMEOFTHISWRITING &0'!SCANALSOINCORPORATEHUNDREDSOFMULTIPLIERSTHATCANBECLOCKEDATRATESUP TO A HALF BILLION OPERATIONS PER SECOND AND MEMORY BLOCKS MICROPROCESSORS AND SERIALCOMMUNICATIONLINKSTHATCANSUPPORTMULTIGIGABIT PER SECONDDATATRANSFERS #IRCUITSARETYPICALLYDESIGNEDUSINGAHARDWAREDESCRIPTIONLANGUAGE($, SUCH AS6($,6(3)#(ARDWARE$ESCRIPTION,ANGUAGE OR6ERILOG3OFTWARETOOLSCON VERTTHISHIGH LEVELDESCRIPTIONOFTHEPROCESSORTOAFILETHATISSENTTOTHEDEVICETO TELLITHOWTOCONFIGUREITSELF(IGH PERFORMANCE&0'!SSTORETHEIRCONFIGURATIONIN VOLATILEMEMORY WHICHLOSESITSCONTENTSWHENPOWEREDDOWN MAKINGTHEDEVICES INFINITELYREPROGRAMMABLE &0'!SALLOWTHEDESIGNERTOFABRICATECOMPLEXSIGNALPROCESSINGARCHITECTURESVERY EFFICIENTLY)NTYPICALLARGEAPPLICATIONS &0'! BASEDPROCESSORSCANBEAFACTOROFTEN ORMORE SMALLERANDLESSCOSTLYTHANSYSTEMSBASEDONGENERAL PURPOSEPROCESSORS 4HISISDUETOTHEFACTTHATMOSTMICROPROCESSORSONLYHAVEONEORVERYFEWPROCESSING ELEMENTS WHEREAS&0'!SHAVEANENORMOUSNUMBEROFPROGRAMMABLELOGICELEMENTS ANDMULTIPLIERS&OREXAMPLE TOIMPLEMENTA TAP&)2FILTERINAMICROPROCESSOR WITHASINGLEMULTIPLIERANDACCUMULATOR ITWOULDTAKECLOCKCYCLESTOPERFORMTHE MULTIPLICATIONS)NAN&0'! WECOULDASSIGNMULTIPLIERSANDACCUMULATORSTO THETASK ANDTHEFILTERCOULDBEPERFORMEDINONECLOCKCYCLE
2!$!2$)')4!,3)'.!,02/#%33).'
Óx°ÎÇ
)N ORDER TO USE AN &0'! MOST EFFICIENTLY WE HAVE TO TAKE ADVANTAGE OF ALL OF THERESOURCESITOFFERS4HESEINCLUDENOTONLYTHELARGENUMBERSOFLOGICELEMENTS MULTIPLIERS AND MEMORY BLOCKS BUT ALSO THE RATE AT WHICH THE COMPONENTS CAN BE CLOCKED)NTHEPREVIOUSEXAMPLE ASSUMETHATTHEDATASAMPLERATEIS-(ZANDALSO ASSUMETHATTHEMULTIPLIERSANDLOGICCANBECLOCKEDAT-(Z)FWESIMPLYASSIGN ONEMULTIPLIERTOEACHCOEFFICIENT WEWOULDUSEMULTIPLIERSCLOCKINGAT-(Z 3INCETHEDATARATEISONLY-(Z EACHMULTIPLIERWOULDONLYPERFORMONESIGNIFICANT MULTIPLICATION EVERY MICROSECOND AND THEN BE IDLE FOR THE OTHER CLOCKS IN THE MICROSECOND WHICHISVERYINEFFICIENT)TWOULDBEMUCHMOREEFFICIENT INTHISCASE TOUSEONEMULTIPLIERTOPERFORMASMANYPRODUCTSASPOSSIBLE4HISTECHNIQUE CALLED TIME DOMAINMULTIPLEXING REQUIRESADDITIONALLOGICTOCONTROLTHESYSTEMANDPROVIDE THECORRECTOPERANDSTOTHEMULTIPLIERATTHERIGHTTIME3INCEAN&0'!CANINCORPORATE HUNDREDSOFMULTIPLIERS ONECANAPPRECIATETHEPOWEROFTHISTECHNIQUE /NTHENEGATIVESIDE UTILIZINGAN&0'!TOITSBESTADVANTAGETYPICALLYREQUIRESTHE DESIGNERTOHAVEATHOROUGHUNDERSTANDINGOFTHERESOURCESAVAILABLEINTHEDEVICE 4HIS TYPICALLY MAKES EFFICIENT &0'! BASED SYSTEMS HARDER TO DESIGN THAN SYSTEMS BASEDONGENERAL PURPOSEPROCESSORS WHEREADETAILEDUNDERSTANDINGOFTHEPROCES SORARCHITECTUREISNOTNECESSARILYREQUIRED!LSO &0'!DESIGNSTENDTOBEAIMEDAT APARTICULARFAMILYOFDEVICESANDTAKEFULLADVANTAGEOFTHERESOURCESPROVIDEDBY THAT FAMILY (ARDWARE VENDORS ARE CONSTANTLY INTRODUCING NEW PRODUCTS INVARIABLY INCORPORATING NEW AND IMPROVED CAPABILITIES /VER TIME THE OLDER DEVICES BECOME OBSOLETEANDNEEDTOBEREPLACEDDURINGATECHNOLOGYREFRESHCYCLE7HENATECHNOL OGYREFRESHOCCURSSEVERALYEARSDOWNTHEROAD TYPICALLYTHEAVAILABLERESOURCESINTHE LATEST&0'!SHAVECHANGEDORATOTALLYDIFFERENTDEVICEFAMILYISUSED WHICHPROBABLY REQUIRESAREDESIGN/NTHEOTHERHAND SOFTWAREDEVELOPEDFORGENERAL PURPOSEPRO CESSORSMAYONLYNEEDTOBERECOMPILEDINORDERTOMOVEITTOANEWPROCESSOR4OOLS CURRENTLYEXISTTHATSYNTHESIZE#OR-ATLABCODEINTOAN&0'!DESIGN BUTTHESETOOLS ARETYPICALLYNOTVERYEFFICIENT4HEEVOLUTIONOFDESIGNTOOLSFOR&0'!STOADDRESS THESEPROBLEMSISANAREAOFMUCHRESEARCHANDDEVELOPMENT (YBRID0ROCESSORS !LTHOUGHITWOULDBEVERYDESIRABLETOSIMPLYWRITE#CODE TOIMPLEMENTACOMPLEXRADARSIGNALPROCESSOR THEREALITYINTHEEARLYSTCENTURYIS THAT FORMANYSYSTEMS IMPLEMENTINGSUCHASYSTEMWOULDBEPROHIBITIVELYEXPENSIVE ORINFLICTMAJORPERFORMANCEDEGRADATION!LTHOUGHTHESTEADYINCREASEINPROCESSOR THROUGHPUTMAYSOMEDAYCOMETOTHERESCUE THEREALITYATTHISWRITINGISTHATHIGH PERFORMANCERADARSIGNALPROCESSORSAREUSUALLYAHYBRIDOFAPPLICATION SPECIFICAND PROGRAMMABLEPROCESSORS$EDICATEDPROCESSORS SUCHAS&0'!SOR!3)#S ARETYPI CALLYUSEDINTHEHIGH SPEEDFRONTENDOFRADARSIGNALPROCESSORS PERFORMINGDEMAND ING FUNCTIONS SUCH AS DIGITAL DOWNCONVERSION AND PULSE COMPRESSION FOLLOWED BY PROGRAMMABLEPROCESSORSINTHEREAR PERFORMINGTHELOWER SPEEDTASKSSUCHASDETEC TIONPROCESSING4HELOCATIONOFTHELINETHATSEPARATESTHETWODOMAINSISAPPLICATION DEPENDENT BUTOVERTIME ITISCONSTANTLYMOVINGTOWARDTHEFRONTENDOFTHESYSTEM
Óx°ÈÊ -1 ,9 4HEPURPOSEOFTHISCHAPTERWASTOPROVIDEANOVERVIEWOFHOWDIGITALSIGNALPROCESS INGHASTRANSFORMEDRADARSYSTEMDESIGNANDTOGIVESOMEINSIGHTINTOTHETECHNIQUES ANDTRADEOFFSTHATADESIGNERHASTOCONSIDER7ITHMANUFACTURERSCONTINUALLYPRODUCING
Óx°În
2!$!2(!.$"//+
&)'52% $IRECT SAMPLINGRADARDIGITALRECEIVER
FASTERANDMOREPOWERFUL!$#S $30DEVICES ANDGENERAL PURPOSEPROCESSORS MORE ANDMOREOFTHERADARSYSTEMFRONTENDWILLMOVEFROMANALOGTODIGITALDESIGNS&OR EXAMPLE &IGURESHOWSATYPICALDIGITALRECEIVERFORARADARFRONTEND WHICHREQUIRES TWOSTAGESOFANALOGDOWNCONVERSIONTOBRINGTHE2&SIGNALDOWNTOAN)&THATCANBE SAMPLEDBYAN!$#4HISISREQUIREDBECAUSEOFTHECHARACTERISTICSOFTHE!$# WHICH TYPICALLYHASPOORERSIGNAL TO NOISERATIO3.2 ANDSPUR FREEDYNAMICRANGE3&$2 WHENTHEINPUTANALOGSIGNALISTOOHIGH ASWOULDBETHECASEIFITWEREPRESENTEDWITH THE2&ORHIGH )&SIGNALDIRECTLY(OWEVER WHENFASTER!$#SBECOMEAVAILABLE WHICH CANACCOMMODATEHIGHERANALOGINPUTFREQUENCIESWHILEPROVIDINGADEQUATE3.2AND 3&$2 SYSTEMSWILLBEDESIGNEDTHATSAMPLETHE2&DIRECTLY ASSHOWNIN&IGURE !TTHISWRITING !$#TECHNOLOGYALLOWSDIRECTSAMPLINGSYSTEMSWITHRESPECTABLEPERFOR MANCETOBEDESIGNEDFORRADARSINTHE(&AND6(&BANDS$OUBTLESS FUTURECOMPONENTS WILLEXTENDTHISPERFORMANCETOHIGHER2&FREQUENCIES
"7 /4HEAUTHORSWOULDLIKETOACKNOWLEDGETHEEFFORTSOFANDEXTENDTHEIRSINCEREGRATI TUDETOSEVERALINDIVIDUALSWHOHELPEDTHEMIMMENSELYINTHEPREPARATIONOFTHIS CHAPTER&IRST TO-R'REGORY4AVIKOF.2,FORHISTHOROUGHREVIEWOFTHISCHAPTER ANDTHEMANYEXCELLENTCOMMENTSHEMADE.EXT TO$R&RED(ARRISOF3AN$IEGO 3TATE5NIVERSITYAND-R2ICHARD,YONS WHOGRACIOUSLYREVIEWEDSECTIONSOFTHE CHAPTERANDOFFEREDSEVERALSUGGESTIONS ALLOFWHICHWEREINCORPORATED
, ,
!6/PPENHEIMAND273CHAFER $IGITAL3IGNAL0ROCESSING ND%D %NGLEWOOD#LIFFS .* 0RENTICE (ALL 2 ' ,YONS 5NDERSTANDING $IGITAL 3IGNAL 0ROCESSING ND %D 5PPER 3ADDLE 2IVER .* 0RENTICE(ALL * / #OLEMAN h-ULTI RATE $30 BEFORE DISCRETE TIME SIGNALS AND SYSTEMS v PRESENTED AT &IRST )%%%7ORKSHOPON3IGNAL0ROCESSING%DUCATION30% (UNT 48 /CTOBER 7-7ATERSAND"2*ARRETT h"ANDPASSSIGNALSAMPLINGANDCOHERENTDETECTION v)%%%4RANS /N!EROSPACE%LECTRONIC3YSTEMS VOL!%3 NO PPn .OVEMBER $03CHOLNIKAND*/#OLEMAN h)NTEGRATED) 1DEMODULATION MATCHEDFILTERING ANDSYMBOL RATESAMPLINGUSINGMINIMUM RATE)&SAMPLING vIN0ROCOFTHE3YMPOSIUMON7IRELESS 0ERSONAL#OMMUNICATION "LACKSBURG 6! *UNE
2!$!2$)')4!,3)'.!,02/#%33).'
Óx°Î
""RANNONAND!"ARLOW h!PERTUREUNCERTAINTYAND!$#SYSTEMPERFORMANCE v!NALOG$EVICES !PPLICATION.OTE!. 2EV! -ARCH * % 6OLDER h4HE #/2$)# TRIGONOMETRIC COMPUTING TECHNIQUE v )2% 4RANS ON %LECTRONIC #OMPUTERS VOL%# PPn 2!NDRAKA h! SURVEY OF #/2$)# ALGORITHMS FOR &0'! BASED COMPUTERS v IN !#-3)'$! )NTERNATIONAL3YMPOSIUMON&IELD0ROGRAMMABLE'ATE!RRAYS -ONTEREY #! &EBRUARY PPn %"(OGENAUER h!NECONOMICALCLASSOFDIGITALFILTERSFORDECIMATIONANDINTERPOLATION v)%%% 4RANSON!COUSTICS 3PEECH AND3IGNAL0ROCESSING !330 PPn !PRIL &*(ARRIS -ULTIRATE3IGNAL0ROCESSINGFOR#OMMUNICATION3YSTEMS 5PPER3ADDLE2IVER .* 0RENTICE(ALL &(ARRIS h/NTHEUSEOFWINDOWSFORHARMONICANALYSISWITHTHEDISCRETE&OURIERTRANSFORM v 0ROC)%%% VOL NO *ANUARY PPn *#OOLEYAND*4UKEY h!N!LGORITHMFORTHEMACHINECALCULATIONOFCOMPLEX&OURIERSERIES v -ATHEMATICSOF#OMPUTATION VOL NO PPn !PRIL
#HAPTER
/
iÊ*À«>}>ÌÊ>VÌÀ]ÊÊ «]ÊÊÌ
iÊ,>`>ÀÊ µÕ>Ì 7>ÞiÊ °Ê*>ÌÌiÀÃ 3PACEAND.AVAL7ARFARE3YSTEMS#ENTER !TMOSPHERIC0ROPAGATION"RANCH
ÓÈ°£Ê /," 1 /" 0ARALLELINGTHEDEVELOPMENTOFRADARTECHNOLOGYISTHEDEVELOPMENTOFTHERADAREQUA TION!SENGINEERINGCONSIDERATIONSSUCHASTHEPROBABILITYOFDETECTION PROBABILITY OFFALSEALARM SIGNALLOSSFACTORS ANDSIGNAL TO NOISERATIOALLOWEDTHERADARRANGE EQUATIONTODEVELOPSUFFICIENTLYTOBEUSEFULINRADARPERFORMANCEANALYSIS DEVELOPING COMPUTERTECHNOLOGIESALLOWEDFORMORESOPHISTICATEDRADARRANGEEQUATIONSOLUTION TECHNIQUES4HUS SOLUTIONTECHNIQUESTOTHERADARRANGEEQUATIONMIGRATEDFROMPENCIL ANDPAPERhWORKSHEETSvTOSIMPLECOMPUTERPROGRAMSAUTOMATINGTHEhWORKSHEETvTO HIGHLYSOPHISTICATEDCOMPUTERPROGRAMSACCOUNTINGFORTECHNOLOGYADVANCESINSIGNAL PROCESSINGANDENVIRONMENTALMODELING 4HEINTENTOFTHISCHAPTERISTWOFOLD4HEFIRSTISTOFOCUSONONEPARTICULARTERM OF THE RADAR RANGE EQUATION THE PROPAGATION FACTOR &0 DEFINED IN 3ECTION %NCOMPASSEDWITHINTHEPROPAGATIONFACTORAREALLTHEEFFECTSUPONPROPAGATIONATTRIB UTABLETOTHENATURALENVIRONMENT4HESEEFFECTSAREENERGYABSORPTIONFROMGASSESAND LIQUIDWATER DIFFRACTION REFRACTION MULTIPATHINTERFERENCE EARTH SURFACEDIELECTRICS TERRAININTERFERENCE ANDANUMBEROFOTHERNATURALENVIRONMENTALCONSIDERATIONS 4HESECONDFOCUSOFTHISCHAPTERISTODESCRIBETHECOMPUTERMODELINGOFTHEPROPA GATIONFACTOR&OREASEOFCOMPUTATIONSINEARLYSOLUTIONTECHNIQUES THEPROPAGATION FACTORWASOFTENTAKENASUNITY ACONDITIONREPRESENTINGFREESPACE7ITHCOMPUTER IMPLEMENTED PROPAGATION MODELS HOWEVER THE ASSUMPTION OF FREE SPACE NEED NO LONGERBEALIMITINGFACTOR/NESUCHPROPAGATIONMODEL THE!DVANCED0ROPAGATION -ODEL !0- AND ITS GRAPHICAL USER INTERFACE PROGRAM THE !DVANCED 2EFRACTIVE %FFECTS0REDICTION3YSTEM!2%03 AREFEATUREDHERE7HILETHEFOCUSUPON!2%03 WITHINTHISCHAPTERISFORTHEUNDERSTANDINGOFHOWIMPORTANTTHEPROPAGATIONFACTORIS WITHINTHERADAREQUATION !2%03ISMUCHMORETHANAPROPAGATIONFACTORTOOL!2%03 PROVIDESTHERADARENGINEERANDTHEOPERATIONALRADAROPERATORWITHANEASYTOUSEBUT EXTREMELYPOWERFULMETHODTODEFINETHENATURALATMOSPHERICENVIRONMENTUSINGDATA FROMAWIDERANGEOFSOURCESTOMANAGE CREATE ANDDEFINEVARIOUSELEMENTSOFTER RAINDATATOEXECUTETHEAPPROPRIATEPROPAGATIONMODELFORTHETASKATHANDANDTHEN TO PRESENT THE RESULTS IN A NUMBER OF DIFFERENT AND HIGHLY CONFIGURABLE GRAPHIC AND ÓÈ°£
ÓÈ°Ó
2!$!2(!.$"//+
TEXT DISPLAYS INCLUDING EXPORTING COMPUTED DATA IN SEVERAL FORMATS FOR IMPORT INTO OTHERAPPLICATIONS!2%03ISNOTLIMITEDTOJUSTRADARAPPLICATIONS HOWEVER!2%03 TOGETHERWITH!0-ANDITSOTHEREMBEDDEDPROPAGATIONMODELSCANPROVIDEASSESS MENTSFOR,&TO%(&COMMUNICATIONSGROUNDANDSKYWAVE STRIKEANDELECTRONIC COUNTERMEASURES %LECTRONIC3UPPORT-EASURES%3- VULNERABILITIES ANDMANYOTHER APPLICATIONS!2%03AND!0-AREPRODUCTSOFTHEATMOSPHERICPROPAGATIONBRANCHOF THE3PACEAND.AVAL7ARFARE3YSTEMS#ENTER30!7!2393#%. 3AN$IEGO!2%03 WILLEXECUTEONAPERSONALCOMPUTERDESKTOPORLAPTOP USINGA-ICROSOFT7INDOWS OPERATING SYSTEM SUCH AS .4 80 OR6ISTA AND REQUIRES NO ADDITIONAL SPECIAL HARDWARE!2%03MAYBEFREELYOBTAINEDATTHE52,LISTEDINTHEFIRSTREFERENCE "EFORECONTINUINGWITHTHEDISCUSSIONOFELECTROMAGNETIC%- PROPAGATIONMOD ELSANDASSESSMENTSYSTEMS ITISAPPROPRIATETODISCUSSTHENATURALENVIRONMENTANDITS INFLUENCEUPON%-SYSTEMPERFORMANCE
ÓÈ°ÓÊ / Ê ,/½-Ê/ "-* , £ 3TRUCTUREAND#HARACTERISTICS 4HE%ARTHSATMOSPHEREISACOLLECTIONOFMANY GASES TOGETHER WITH SUSPENDED PARTICLES OF LIQUIDS AND SOLIDS %XCLUDING VARIABLE COMPONENTSSUCHASWATERVAPOR OZONE SULFURDIOXIDE ANDDUST THEGASESOFNITROGEN ANDOXYGENOCCUPYABOUTOFTHEVOLUME WITHARGONANDCARBONDIOXIDEBEINGTHE NEXTTWOMOSTABUNDANTGASES&ROMTHE%ARTHSSURFACETOANALTITUDEOFAPPROXIMATELY KILOMETERS MECHANICALMIXINGOFTHEATMOSPHEREBYHEAT DRIVENAIRCURRENTSEVENLY DISTRIBUTES THE COMPONENTS OF THE ATMOSPHERE !T ABOUT KILOMETERS THE MIXING DECREASESTOTHEPOINTWHERETHEGASESTENDTOSTRATIFYINACCORDANCEWITHTHEIRWEIGHTS 4HELOWER WELL MIXEDPORTIONOFTHEATMOSPHEREISCALLEDTHEHOMOSPHERE WHILE THEHIGHER STRATIFIEDPORTIONISCALLEDTHEHETEROSPHERE7ITHINTHEHETEROSPHERELIESTHE IONOSPHERE4HEBOTTOMPORTIONOFTHEHOMOSPHEREISCALLEDTHETROPOSPHERE 4ROPOSPHERE 4HETROPOSPHEREEXTENDSFROMTHE%ARTHSSURFACETOANALTITUDE OFTOKILOMETERSATPOLARLATITUDES TOKILOMETERSATMIDDLELATITUDES AND UPTOKILOMETERSATTHEEQUATOR)TISCHARACTERIZEDBYATEMPERATUREDECREASEWITH HEIGHT4HEPOINTATWHICHTHETEMPERATURECEASESTODECREASEWITHHEIGHTISKNOWNAS THETROPOPAUSE4HEAVERAGEVERTICALTEMPERATUREGRADIENTOFTHETROPOSPHEREVARIES BETWEENAND#ELSIUSPERKILOMETER 4HECONCENTRATIONSOFGASCOMPONENTSOFTHETROPOSPHEREVARYLITTLEWITHHEIGHT EXCEPTFORWATERVAPOR4HEWATERVAPORCONTENTOFTHETROPOSPHERECOMESFROMEVAP ORATION OF WATER FROM OCEANS LAKES RIVERS AND OTHER WATER RESERVOIRS $IFFERENTIAL HEATINGOFLANDANDOCEANSURFACESPRODUCESVERTICALANDHORIZONTALWINDCIRCULATIONS THATDISTRIBUTETHEWATERVAPORTHROUGHOUTTHETROPOSPHERE4HEWATERVAPORCONTENT OFTHETROPOSPHERERAPIDLYDECREASESWITHHEIGHT!TANALTITUDEOFKILOMETERS THE WATERVAPORCONTENTISAPPROXIMATELYHALFOFTHESURFACECONTENT!TTHETROPOPAUSE THECONTENTISONLYAFEWTHOUSANDTHSOFWHATITISATTHESURFACE )N THE7EATHER"UREAU ATTHEREQUESTOFTHE.ATIONAL!DVISORY#OMMITTEEFOR !ERONAUTICS.!#! PREPAREDASTANDARDATMOSPHEREFORSCIENTIFICANDENGINEERING USEBASEDPRIMARILYONTHEAVERAGECONDITIONSOVERTHE5NITED3TATESATLATITUDE )N THECOMPUTATIONSWEREEXTENDEDTO METERSUSINGCONSTANTSADOPTED BY THE .!#! !N EXTENSION OF THE STANDARD ATMOSPHERE TO METERS WAS PREPAREDIN
4(%02/0!'!4)/.&!#4/2 &0 ).4(%2!$!2%15!4)/.
ÓÈ°Î
4HESTANDARDATMOSPHEREISBASEDPRIMARILYONTHEASSUMPTIONOFALINEARDECREASE INTEMPERATUREWITHHEIGHTUPTOTHETROPOPAUSEANDANISOTHERMALLAYERABOVE)NADDI TION CERTAINOTHERASSUMPTIONSARE A 4HEAIRISDRY B 4HEAIRISAPERFECTGAS OBEYINGTHE,AWSOF#HARLESAND"OYLE C 'RAVITYISCONSTANTATALLALTITUDES D 4HETEMPERATUREOFTHEISOTHERMALATMOSPHEREIS # E 4HELINEARDECREASEOFTEMPERATUREWITHHEIGHTIS #PERKILOMETER 4HE)NTERNATIONAL#OMMISSIONFOR!IR.AVIGATION)#!. USESTHE.!#! STANDARDATMOSPHERE WITHMINORMODIFICATIONS PRIMARILYINTHEVALUEOFGRAVITYAND THE TEMPERATURE OF THE ISOTHERMAL REGION &OR GENERIC RADAR STUDIES AND OTHER RADAR APPLICATIONS SUCHASTARGETHEIGHTCALCULATIONSFORHEIGHT FINDINGRADARS ITISTHEPROP AGATIONTHROUGHTHISSTANDARDATMOSPHERETHATISCONSIDERED
ÓÈ°ÎÊ , , /"
Ó
)NDEX OF 2EFRACTION 4HE TERM REFRACTION REFERS TO THE PROPERTY OF A MEDIUM TOBENDANELECTROMAGNETICWAVEASITPASSESTHROUGHTHEMEDIUM!MEASUREOFTHE AMOUNTOFREFRACTIONISTHEINDEXOFREFRACTION N DEFINEDASTHEVELOCITY C OFPROPAGA TIONINFREE SPACEAWAYFROMTHEINFLUENCEOFTHE%ARTHOROTHEROBJECTS TOTHEVELOC ITY V INTHEMEDIUM4HISIS
N
C V
2EFRACTIVITY AND -ODIFIED 2EFRACTIVITY IN THE 4ROPOSPHERE 4HE NORMAL VALUEOFTHEREFRACTIVEINDEX N FORTHEATMOSPHERENEARTHE%ARTHSSURFACEVARIES BETWEENAND&ORSTUDIESOFPROPAGATION THEINDEXOFREFRACTION IS NOT A VERY CONVENIENT NUMBER THEREFORE A SCALED INDEX OF REFRACTION . CALLED REFRACTIVITY HASBEENDEFINED!TMICROWAVEFREQUENCIESANDBELOW THERELATIONSHIP BETWEENTHEINDEXOFREFRACTION N ANDREFRACTIVITY . FORAIRTHATCONTAINSWATERVAPOR ISGIVENAS
. N
P ES r
4 4
WHEREESISTHEPARTIALPRESSUREOFWATERVAPORINMILLIBARSOR
ES X
RH E X
4 ¤ 4 ³
LOG E ¥ 4 ¦ ´µ
P ATMOSPHERESBAROMETRICPRESSUREINMILLIBARS 4 ATMOSPHERESABSOLUTETEMPERATUREIN+ELVIN RH ATMOSPHERESRELATIVEHUMIDITYINPERCENT
ÓÈ°{
2!$!2(!.$"//+
4HUS THEATMOSPHERICREFRACTIVITYNEARTHE%ARTHSSURFACEWOULDNORMALLYVARY BETWEENAND. UNITS "ECAUSETHEBAROMETRICPRESSUREANDWATERVAPORCONTENTOFTHEATMOSPHEREDECREASE RAPIDLYWITHHEIGHTWHILETHETEMPERATUREDECREASESSLOWLYWITHHEIGHT THEINDEXOF REFRACTION ANDTHEREFOREREFRACTIVITY NORMALLYDECREASESWITHINCREASINGALTITUDE 7HILEARADARENGINEERMAYLIKETOCONSIDERREFRACTIONINTERMSOF. UNITSBECAUSE ITPROVIDESABETTERPHYSICALPOINTOFVIEW AN!2%03USERMAYNOTBEARADARENGINEER BUTATACTICALOPERATORSUCHASACOMBATPILOT)NGRAPHICALLYEXAMININGREFRACTIVEGRA DIENTSANDTHEIREFFECTUPONPROPAGATIONSUCHASDUCTINGDESCRIBEDIN3ECTION AMODIFIEDREFRACTIVITY DEFINEDAS
- . H FORALTITUDEHINMETERSAN
- . H FORALTITUDEHINFEET
ISUSEDINPLACEOFTHEREFRACTIVITY7HILEAGRAPHICAL. UNITVERSUSHEIGHTDISPLAYWILL SHOW A NEGATIVE SLOPE DECREASING . UNITS WITH HEIGHT A GRAPHICAL - UNIT VERSUS HEIGHTDISPLAYWILLSHOWACHANGEINSLOPE FROMPOSITIVEINCREASING- UNITS UNDER STANDARDATMOSPHERICCONDITIONSTOANEGATIVESLOPEDECREASING- UNITS UNDERDUCTING ATMOSPHERICCONDITIONS4HEREFORE A- UNITTYPEDISPLAYISMOREREADILYUNDERSTOODBY THETACTICALRADAROPERATORLOOKINGFORANOPTIMUMFLIGHTALTITUDEFORHISATTACK
ÓÈ°{Ê -/ , Ê*,"*/"
Ó
3TANDARDPROPAGATIONMECHANISMSARETHOSEMECHANISMSANDPROCESSESTHATOCCURIN THEPRESENCEOFASTANDARDATMOSPHERE4HESEPROPAGATIONMECHANISMSARESTANDARD REFRACTION FREE SPACE PROPAGATION MULTIPATH INTERFERENCE OR SURFACE REFLECTION DIFFRACTION ANDTROPOSPHERICSCATTER .ORMAL3TANDARD 2EFRACTION 4HE REFRACTIVITY DISTRIBUTION WITHIN THE ATMO SPHEREISNEARLYANEXPONENTIALFUNCTIONOFHEIGHT4HEDECREASEOF.WITHHEIGHTCLOSE TOTHE%ARTHSSURFACEWITHINKILOMETER ISSUFFICIENTLYSMOOTH HOWEVER TOALLOW ANAPPROXIMATIONOFTHEEXPONENTIALFUNCTIONBYALINEARFUNCTION4HISLINEARFUNC TIONISKNOWNASASTANDARDGRADIENTANDISCHARACTERIZEDBYADECREASEOF. UNITS PERKILOMETER ORANINCREASEOF- UNITSPERKILOMETER!STANDARDGRADIENTWILL CAUSETRAVELING%-WAVESTOBENDDOWNWARDFROMASTRAIGHTLINE'RADIENTSTHATCAUSE EFFECTSSIMILARTOASTANDARDGRADIENTBUTVARYBETWEENAND . UNITSPERKILOMETER ORBETWEENAND- UNITSPERKILOMETERAREKNOWNASNORMALGRADIENTS &REE SPACE0ROPAGATION 4HESIMPLESTCASEOFELECTROMAGNETICWAVEPROPAGA TIONISTHETRANSMISSIONOFAWAVEBETWEENATRANSMITTERANDARECEIVERINFREESPACE &REESPACEISDEFINEDASAREGIONWHOSEPROPERTIESAREISOTROPIC HOMOGENEOUS AND LOSS FREE IE AWAYFROMTHEINFLUENCESOFTHE%ARTHSATMOSPHEREANDSURFACE)NFREE SPACE THEELECTROMAGNETICWAVEFRONTFROMANISOTROPICRADIATORSPREADSUNIFORMLYIN ALLDIRECTIONSFROMTHETRANSMITTER -ULTIPATH )NTERFERENCE AND 3URFACE 2EFLECTION 7HEN AN ELECTROMAGNETIC WAVESTRIKESANEARLYSMOOTHLARGESURFACE SUCHASTHEOCEAN APORTIONOFTHEENERGY ISREFLECTEDFROMTHESURFACEANDCONTINUESPROPAGATINGALONGAPATHTHATMAKESAN
4(%02/0!'!4)/.&!#4/2 &0 ).4(%2!$!2%15!4)/.
ÓÈ°x
ANGLEWITHTHESURFACEEQUAL TOTHATOFTHEINCIDENTWAVE ASSHOWNIN&IGURE
4HE STRENGTH OF THE REFLECTEDWAVEISDETERMINED BYTHEREFLECTIONCOEFFICIENT AVALUETHATDEPENDSUPONTHE FREQUENCY AND POLARIZATION OF RADIATION THE ANGLE OF INCIDENCE ANDTHEROUGHNESS OFTHEREFLECTINGSURFACE &)'52% 3URFACEREFLECTION &OR SHALLOW INCIDENCE ANGLESANDSMOOTHSEAS TYPI CALVALUESOFTHEREFLECTIONCOEFFICIENTARENEARUNITYIE THEREFLECTEDWAVEISALMOST ASSTRONGASTHEINCIDENCEWAVE !STHEWINDSPEEDINCREASES THEOCEANSURFACEGROWS ROUGHERANDTHEREFLECTIONCOEFFICIENTDECREASES&ORATRANSMITTERNEARTHESURFACE THE REFLECTIONPROCESSRESULTSINTWOPATHSTOARECEIVERWITHINTHELINEOFSIGHT !SSTATEDABOVE UPONREFLECTION APORTIONOFTHEENERGYISPROPAGATEDINTHEDIREC TIONOFINITIALWAVEMOTION!PORTIONOFENERGYISALSOREFLECTEDBACKWARDTOWARDTHE TRANSMITTER4HISBACKWARDREFLECTEDENERGYISALSORECEIVEDBYTHERADARANDMAYINTER FEREWITHTHERADARSABILITYTODISTINGUISHADESIREDTARGET4HISBACKWARDREFLECTED ENERGYISCALLEDCLUTTER .OTONLYISTHEMAGNITUDEOFTHEREFLECTEDWAVEREDUCED BUTALSOTHEPHASEOFTHE WAVEISALTERED&ORHORIZONTALLYORVERTICALLYPOLARIZEDWAVESATLOWGRAZINGANGLES THEPHASECHANGEUPONREFLECTIONISAPPROXIMATELY7HENEVERTWOORMOREWAVE TRAINSTRAVELINGOVERDIFFERENTPATHSINTERSECTATAPOINTINSPACE THEYARESAIDTOINTER FERE MULTIPATH INTERFERENCE )F TWO WAVES ARRIVE AT THE SAME POINT IN PHASE THEY CONSTRUCTIVELYINTERFERE ANDTHEELECTRICFIELDSTRENGTHISGREATERTHANEITHEROFTHETWO COMPONENT WAVES TAKEN ALONE )F THE TWO WAVES ARRIVE TOGETHER OUT OF PHASE THEY DESTRUCTIVELYINTERFERE ANDTHERESULTANTFIELDSTRENGTHISWEAKENED !STHEGEOMETRYOFTHETRANSMITTERANDRECEIVERCHANGE THERELATIVELENGTHSOFTHE DIRECTPATHANDREFLECTEDPATHALSOCHANGE WHICHRESULTSINTHEDIRECTANDREFLECTED WAVEARRIVINGATTHERECEIVERINVARYINGAMOUNTSOFPHASEDIFFERENCE4HERECEIVEDSIG NALSTRENGTH WHICHISTHEVECTORSUMOFTHESIGNALSTRENGTHSOFTHEDIRECTANDREFLECTED WAVE MAYVARYUPTOD"ABOVEANDD"ORMOREBELOWTHEFREE SPACEVALUE $IFFRACTION %NERGYTENDSTOFOLLOWALONGTHECURVEDSURFACEOFANOBJECT4HE DEGREEOFREFRACTIONISDEPENDENTUPONTHEPOLARIZATIONOFTHEPROPAGATINGWAVEAND THESIZEOFTHEDIFFRACTINGOBJECTRELATIVETOTHEWAVELENGTH$IFFRACTIONISTHEPROCESS BYWHICHTHEDIRECTIONOFPROPAGATINGRADIATIONISCHANGEDSOTHATITSPREADSINTOTHE GEOMETRICSHADOWREGIONOFANOPAQUEOBJECTTHATLIESINTHERADIATIONFIELD)NTHE EARTH ATMOSPHERESYSTEM DIFFRACTIONOCCURSWHERETHESTRAIGHT LINEDISTANCEBETWEEN THETRANSMITTERANDRECEIVERISJUSTTANGENTTOTHE%ARTHSSURFACE&ORAHOMOGENEOUS ATMOSPHERE THIS POINT OF TANGENCY WITH THE %ARTH IS REFERRED TO AS THE GEOMETRICAL HORIZON&ORANINHOMOGENEOUSATMOSPHEREUSINGANEFFECTIVEEARTHRADIUS ANDAT RADARANDOPTICALFREQUENCIES THISPOINTOFTANGENCYISREFERREDTOASTHERADARAND OPTICALHORIZON RESPECTIVELY 4HEABILITYOFTHEELECTROMAGNETICWAVETOPROPAGATEBEYONDTHEHORIZONBYDIFFRAC TIONISHIGHLYDEPENDENTUPONFREQUENCY4HELOWERTHEFREQUENCY THEMORETHEWAVE ISDIFFRACTED!TMICROWAVERADARFREQUENCIES THEWAVELENGTHISSMALLWHENCOMPARED
ÓÈ°È
2!$!2(!.$"//+
TO THE %ARTHS DIMENSIONS AND LITTLE ENERGY IS DIFFRACTED!T OPTICAL FREQUENCIES OR VERYSHORTRADARWAVELENGTHS THEOPTICALHORIZONREPRESENTSTHEAPPROXIMATEBOUNDARY BETWEENREGIONSOFPROPAGATIONANDNOPROPAGATION 4ROPOSPHERIC3CATTER !TRANGESFARBEYONDTHEHORIZON THEPROPAGATIONLOSS ISDOMINATEDBYTROPOSCATTER0ROPAGATIONINTHETROPOSCATTERREGIONISTHERESULTOF SCATTERINGBYSMALLINHOMOGENEITIESWITHINTHEATMOSPHERESREFRACTIVESTRUCTURE!T RADAR FREQUENCIES TROPOSCATTER IS GENERALLY NOT CONSIDERED FOR RADAR RANGE PERFOR MANCE(OWEVER TROPOSCATTERSCATTERINGCOULDBEANIMPORTANTCONSIDERATIONINTARGET DETECTIONBYARECEIVERNOTCO LOCATEDWITHTHERADARITSELFORDETECTIONOFTHERADARS EMISSIONSBYAN%LECTRONIC3UPPORT-EASURES%3- SYSTEM
ÓÈ°xÊ " "1-Ê*,"*/"
Ó
!NOMALOUSORNONSTANDARDWAVEPROPAGATIONUSUALLYREFERSTOTHECONSIDERATIONOF NONSTANDARDREFRACTIONVERSUSSTANDARDREFRACTION4HESENONSTANDARDREFRACTIVECONDI TIONSLEADTOTRANS HORIZONPATHS DECREASEDHORIZONPATHS ANDDISTORTIONSINSIMPLE SURFACEREFECTIONANDMULTIPATHINTERFERENCE 3UBREFRACTION )FTHEMOTIONSOFTHEATMOSPHEREPRODUCEASITUATIONWHERETHE TEMPERATURE AND HUMIDITY DISTRIBUTION CREATE AN INCREASING VALUE OF . WITH HEIGHT THEWAVEPATHWOULDACTUALLYBENDUPWARDANDTHEENERGYWOULDTRAVELAWAYFROM THE %ARTH4HIS IS TERMED SUBREFRACTION!LTHOUGH THIS SITUATION OCCURS INFREQUENTLY IN NATURE IT STILL MUST BE CONSIDERED WHEN ASSESSING ELECTROMAGNETIC SYSTEMS PER FORMANCE&OREXAMPLE AN!TLANTICCOASTVESSELTRAFFICCONTROLRADARLOCATEDNEARTHE ENTRANCE TO THE $ELAWARE "AY OBSERVED A REDUCTION IN DETECTION RANGE FROM TO KM3OMETIMESSHIPSCANBESEENVISUALLYFROMTHERADARTOWERBEFORETHEYCANBE OBSERVEDONTHERADARSCREEN4HEREDUCTIONINTHERADARDETECTIONRANGEUSUALLYLASTS SEVERALHOURSANDOCCURSOFTENWHENFOGISPRESENT ! SUBREFRACTIVE LAYER OF THE TROPOSPHERE WOULD CAUSE THE PROPAGATING ENERGY TO BENDUPWARDORAWAYFROMTHE%ARTHSSURFACE THEREBYLEADINGTODECREASEDDETECTION RANGESANDSHORTENEDRADIOHORIZONS 3UBREFRACTIVELAYERSMAYBEFOUNDATTHE%ARTHSSURFACEORALOFT)NAREASWHERE THESURFACETEMPERATUREISGREATERTHAN#ELSIUS ANDRELATIVEHUMIDITIESARELESS THAN IE LARGE DESERT AND STEPPE REGIONS SOLAR HEATING WILL PRODUCE A VERY NEARLYHOMOGENEOUSSURFACELAYER OFTENSEVERALHUNDREDSOFMETERSTHICK"ECAUSE THISLAYERISUNSTABLE THERESULTANTCONVECTIVEPROCESSESTENDTOCONCENTRATEANYAVAIL ABLEMOISTURENEARTHETOPOFTHELAYER4HISINTURNCREATESAPOSITIVE.GRADIENTOR SUBREFRACTIVESTRATUMALOFT4HISLAYERMAYRETAINITSSUBREFRACTIVENATUREINTOTHEEARLY EVENINGHOURS ESPECIALLYIFARADIATIONINVERSIONDEVELOPS TRAPPINGTHEWATERVAPOR BETWEENTWOSTABLELAYERS &OR AREAS WITH SURFACE TEMPERATURES BETWEEN AND #ELSIUS AND RELATIVE HUMIDITIESABOVEIE THEWESTERN-EDITERRANEAN 2ED3EA )NDONESIAN3OUTHWEST 0ACIFIC SURFACE BASEDSUBREFRACTIVELAYERSMAYDEVELOPDURINGTHENIGHTANDEARLY MORNINGHOURS4HESELAYERSARECHARACTERISTICALLYCAUSEDBYADVECTIONOFWARM MOIST AIROVERARELATIVELYCOOLERANDDRIERSURFACE7HILETHE.GRADIENTISGENERALLYMORE INTENSETHANTHATDESCRIBEDABOVE THELAYERISOFTENNOTASTHICK3IMILARCONDITIONS MAYALSOBEFOUNDINREGIONSOFWARMFRONTALACTIVITY
4(%02/0!'!4)/.&!#4/2 &0 ).4(%2!$!2%15!4)/.
ÓÈ°Ç
3UPERREFRACTION )F THE TROPOSPHERES TEMPERATURE INCREASES WITH HEIGHT TEM PERATUREINVERSION ANDORTHEWATERVAPORCONTENTDECREASESRAPIDLYWITHHEIGHT THE REFRACTIVITYGRADIENTWILLDECREASEFROMTHESTANDARD4HEPROPAGATINGWAVEWILLBEBENT DOWNWARDFROMASTRAIGHTLINEMORETHANNORMAL!STHEREFRACTIVITYGRADIENTCONTINUES TODECREASE THERADIUSOFCURVATUREFORTHEWAVEPATHWILLAPPROACHTHERADIUSOFCUR VATUREFORTHE%ARTH4HEREFRACTIVITYGRADIENTFORWHICHTHETWORADIIOFCURVATUREARE EQUALISREFERREDTOASTHECRITICALGRADIENT!TTHECRITICALGRADIENT THEWAVEWILLPROPA GATEATAFIXEDHEIGHTABOVETHEGROUNDANDWILLTRAVELPARALLELTOTHE%ARTHSSURFACE 2EFRACTIONBETWEENTHENORMALANDCRITICALGRADIENTSISKNOWNASSUPERREFRACTION 3UPERREFRACTIVE CONDITIONS ARE LARGELY ASSOCIATED WITH TEMPERATURE AND HUMIDITY VARIATIONSNEARTHE%ARTHSSURFACE)NVERSIONSALOFT DUETOLARGE SCALESUBSIDENCEWILL LEADTOSUPERREFRACTIVELAYERSALOFT3UPERREFRACTIVELAYERSWILLLEADTOANINCREASEOF RADARDETECTIONRANGESANDEXTENSIONSOFTHERADIOHORIZON 4HE EFFECTS OF A SUPERREFRACTIVE LAYER UPON A SURFACE BASED SYSTEM ARE DIRECTLY RELATEDTOITSHEIGHTABOVETHE%ARTHSSURFACE&ORAIRBORNESYSTEMS THEEFFECTSOFA SUPERREFRACTIVELAYERDEPENDUPONTHEPOSITIONOFTHETRANSMITTERANDRECEIVERRELATIVE TOTHELAYER"OTHOFTHESEFACTORSARERELATEDTOTHEELECTROMAGNETICWAVESANGLEOF LAYERPENETRATION4HESTEEPERTHEPENETRATIONANGLE THELESSOFANEFFECTTHELAYERWILL HAVEUPONPROPAGATION 4RAPPING 4RAPPINGISANEXTENSIONOFSUPERREFRACTIONBECAUSETHEMETEOROLOGICAL CONDITIONSFORBOTHARETHESAME3HOULDTHEREFRACTIVITYGRADIENTDECREASEBEYONDTHE CRITICALGRADIENT THERADIUSOFCURVATUREFORTHEWAVEWILLBECOMESMALLERTHANTHE%ARTHS CURVATURE4HEWAVEWILLEITHERSTRIKETHE%ARTHANDUNDERGOSURFACEREFLECTION ORENTER AREGIONOFSTANDARDREFRACTIONANDBEREFRACTEDBACKUPWARD ONLYTOREENTERTHEAREAOF REFRACTIVITYGRADIENTTHATCAUSESDOWNWARDREFRACTION4HISREFRACTIVECONDITIONISCALLED TRAPPINGBECAUSETHEWAVEISCONFINEDTOANARROWREGIONOFTHETROPOSPHERE4HECOMMON TERMFORTHISCONFINEMENTREGIONISATROPOSPHERICDUCTORATROPOSPHERICWAVEGUIDE)T SHOULDBENOTEDTHATATROPOSPHERICWAVEGUIDEISNOTAWAVEGUIDEINTHETRUESENSEOFTHE WORDBECAUSETHEREARENORIGIDWALLSTHATPREVENTTHEESCAPEOFENERGYFROMTHEGUIDE 4HE REFRACTIVITY GRADIENTS AND THEIR ASSOCIATED REFRACTIVE CONDITIONS ARE SUMMA RIZEDIN4ABLE !TMOSPHERIC$UCTS !DUCTISACHANNELINWHICHELECTROMAGNETICENERGYCAN PROPAGATEOVERGREATRANGES4OPROPAGATEENERGYWITHINADUCT THEANGLEMADEBY THEELECTROMAGNETICSYSTEMSENERGYWITHTHEDUCTMUSTBESMALL USUALLYLESSTHAN 4HICKER DUCTS IN GENERAL CAN SUPPORT TRAPPING FOR LOWER FREQUENCIES 4HE VERTICAL DISTRIBUTIONOFREFRACTIVITYFORAGIVENSITUATIONMUSTBECONSIDEREDASWELLASTHEGEO METRICALRELATIONSHIPOFTRANSMITTERANDRECEIVERTOTHEDUCTINORDERTOASSESSTHEDUCTS EFFECTATANYPARTICULARFREQUENCY 4!",% 2EFRACTIVE'RADIENTSAND#ONDITIONS
#ONDITION 4RAPPING 3UPERREFRACTION .ORMAL 3TANDARD 3UBREFRACTION
. 'RADIENT
- 'RADIENT
.KMOR .KFT
TO .KMOR TO .KFT
TO.KMOR TO.KFT
.KM .KMOR .KFT
-KMOR -KFT TO-KMORTO-KFT TO-KMORTO-KFT -KM -KMOR -KFT
ÓÈ°n
2!$!2(!.$"//+
!SIMPLERELATIONSHIPBETWEENADUCTSTHICKNESSANDITSABILITYTOTRAPAPARTICULAR FREQUENCYISGIVENBY ¤C . ³ KMAX r ¥
´ ¦ T µ
T
WHERE KMAX IS THE MAXIMUM FREQUENCY TRAPPED C . IS THE REFRACTIVE INDEX CHANGE ACROSSTHEDUCT ANDTISTHEDUCTTHICKNESS )N ADDITION TO EXTENDED RADAR RANGES ATMOSPHERIC DUCTS AND OTHER PROPAGATION EFFECTSSUCHASMULTIPATHINTERFERENCE HAVEOTHERSIGNIFICANTIMPACTSUPONRADARPER FORMANCE4HESEEFFECTSMAYBEVISUALIZEDWITHTHEAIDOFAHEIGHTVERSUSRANGEGRAPHIC AVAILABLE FROM AN ASSESSMENT SYSTEM SUCH AS!2%03 3UCH A GRAPHIC IS SHOWN IN &IGURE)NTHISFIGURE THEDIFFERENTSHADINGSCORRESPONDTODIFFERENTPROPAGATION LOSSVALUESDEFINEDLATERASCOMPUTEDBYTHEPROPAGATIONMODEL 4HEACTUALVALUES AREIMMATERIALTOTHISILLUSTRATIONASTHEIMPORTANTFEATURESTONOTEARETHECONSEQUENCES OF DUCTING )N THIS FIGURE ONE CAN CLEARLY SEE THE NULL AND LOBE STRUCTURE RESULTING FROMMULTIPATHINTERFERENCE7HILEADISCUSSIONOFDUCTINGCONDITIONSUPON%-WAVE PROPAGATIONISUSUALLYCONCERNEDWITHPROPAGATIONBEYONDTHENORMALHORIZON DUCT INGCANHAVEANEFFECTWITHINTHEHORIZON$UCTINGCANALTERTHENORMALLOBEPATTERN CAUSEDBYTHEINTERFERENCEOFTHEDIRECTRAYANDTHESURFACE REFLECTEDRAY4HERELATIVE PHASEBETWEENTHEDIRECTANDREFLECTEDPATHMAYBECHANGEDASWELLASTHERELATIVE AMPLITUDESOFTHETWORAYS4HEEFFECTOFTHEDUCTONTHELINE OF SIGHTPROPAGATIONISTO REDUCETHEANGLEOFTHELOWESTLOBE BRINGINGITCLOSERTOTHESURFACE
& $ !
%%
#! ## !
!$$( )
"'!
&)'52% $UCTINGCONSEQUENCES
4(%02/0!'!4)/.&!#4/2 &0 ).4(%2!$!2%15!4)/.
ÓÈ°
$UCTSNOTONLYGIVEEXTENDEDRADARDETECTIONRANGESFORSYSTEMSWITHINTHEDUCT BUTTHEYMAYALSOHAVEADRAMATICEFFECTUPONTRANSMITTERRECEIVERSYSTEMSTHATTRAN SCENDDUCTBOUNDARIES&OREXAMPLE ANAIRTARGETTHATWOULDNORMALLYBEDETECTEDMAY BEMISSEDIFTHERADARISWITHINORJUSTABOVETHEDUCTANDTHETARGETISJUSTABOVETHE DUCT4HISAREAOFREDUCEDCOVERAGEISKNOWNASARADARHOLEORSHADOWZONE !NOTHERINTERESTINGFEATUREOFSURFACE BASEDDUCTSISTHESKIPZONENEARTHENORMAL HORIZON INWHICHTHEDUCTHASNOINFLUENCE)TSHOULDBENOTEDTHATTHESURFACEDUCTCRE ATEDFROMASURFACE BASEDTRAPPINGLAYERDOESNOTHAVETHISSKIPZONEPHENOMENON (EIGHT FINDING RADARS USUALLY DETERMINE HEIGHT FROM ENERGY PATH ASSUMPTIONS WITHINANORMALENVIRONMENT.ONSTANDARDREFRACTIVECONDITIONSASDISCUSSEDEARLIER WILLCAUSETHEENERGYSPATHTODEVIATEFROMTHESEASSUMPTIONS RESULTINGINERRORSIN ALTITUDECALCULATIONS&IGURESHOWSTHEDOWNWARDDEVIATEDPATHASSOCIATEDWITH ASURFACEDUCTINGCONDITIONCOMPAREDTOTHEPATHUNDERNORMALCONDITIONS)TCANBE SEEN THAT ACTUAL ALTITUDE OF THE RADAR TARGET IS LOWER THAN CALCULATED BY THE HEIGHT FINDINGRADAR4HISERRORCOULDLEADTOSIGNIFICANTTACTICALCONSEQUENCESINASHIPS SELF DEFENSESCENARIO &ORAPRACTICALEXAMPLEOFDUCTINGEFFECTS ONECANREADABOUTTHEh"ATTLEOFTHE 0IPSv $URING THE SUMMER OF TWO 53 .AVY TASK GROUPS WERE DEPLOYED TO REMOVETHE*APANESEOCCUPATIONOF!TTU !LASKA/NTHENIGHTOF*ULYTH THE533 -ISSISSIPPIGAINEDRADARCONTACTWITHWHATWASBELIEVEDTOBE*APANESEFLEETUNITSMOV INGTOWARD!TTUINORDERTOWITHDRAWTROOPS2ADARSONBOARDTHE533.EW-EXICO THE5330ORTLAND ANDTHE5337ICHITACONFIRMEDTHERADARCONTACTS/NTHEORDERSOF !DMIRAL'IFFEN THE53.AVYSHIPSOPENEDFIRE4HEFIRINGCONTINUEDFORABOUTHALF ANHOURDURINGWHICHTIME INCHSHELLSAND INCHSHELLSWEREEXPENDED 'UNFLASHESWEREREPORTEDLYSEENBYTHE*APANESEON+ISKA MILESAWAY4WOOTHER SHIPS THEDESTROYERS5333AN&RANCISCOAND5333ANTA&E COULDNOTGAINRADARCON TACT BUTTHEYDIDDETECTTHESPLASHESMADEBYSHELLSHITTINGTHEWATER.OTHINGWAS EVERFOUND7HEN53AND#ANADIANFORCESLANDEDAT!TTUON!UGUSTTH THEYFOUND THEISLANDABANDONED4HE *APANESETROOPSHADBEENEVACUATEDUNDERCOVEROF FOGANDRAINON*ULYTH,ATERINVESTIGATIONDETERMINEDTHATTHE*APANESEEVACUATION
&)'52% !LTITUDEERRORS
ÓÈ°£ä
2!$!2(!.$"//+
SHIPSWERENAUTICALMILES37OF+ISKADURINGTHEFIRING4HERADARCONTACTSWERE ACTUALLYRETURNSFROMLANDTHATHADBEENDUCTEDOVERTHEHORIZON 3EVERALMETEOROLOGICALCONDITIONSWILLLEADTOTHECREATIONOFDUCTS7HERETHESECON DITIONSEXISTANDWHATTHESECONDITIONSAREDETERMINESTHENAMEANDNATUREOFTHEDUCT 3URFACE$UCTS )FTHEMETEOROLOGICALCONDITIONSCAUSEATRAPPINGLAYERTOOCCUR SUCH THAT THE BASE OF THE RESULTANT DUCT IS AT THE %ARTHS SURFACE A SURFACE DUCT IS FORMED4HEREARETHREETYPESOFSURFACEDUCTSBASEDONTHETRAPPINGLAYERSRELATION SHIP TO THE %ARTHS SURFACE4HE TRAPPING LAYER IS INDICATED GRAPHICALLY BY THE SOLID BLACK- UNITVERSUSHEIGHTLINEWHERETHESLOPEOFTHELINEISNEGATIVE- UNITDECREASE WITHHEIGHT 4HEFIRSTTYPEOFDUCTISASURFACEDUCTCREATEDFROMASURFACE BASEDTRAPPINGLAYER 4HISDUCTISREFERREDTOASASURFACEDUCTANDISILLUSTRATEDIN&IGURE4HEDOTTED LINE IN THE FIGURE SHOWS THE VERTICAL DIMENSION OF THE DUCT FROM BOTTOM TO TOP4HE SECOND TYPE OF SURFACE DUCT IS CREATED FROM AN ELEVATED TRAPPING LAYER4HIS DUCT IS COMMONLYREFERREDTOASASURFACE BASEDDUCTANDISILLUSTRATEDIN&IGURE.OTETHE DUCT IDENTIFIEDBYTHEDASHEDLINE CONTAINSTHETRAPPINGLAYERANDhNORMALvGRADIENT LAYERBELOW4HETHIRDTYPEOFSURFACEDUCTISONECREATEDBYARAPIDDECREASEOFRELATIVE HUMIDITYIMMEDIATELYADJACENTTOTHEAIR SEAINTERFACE4HISDUCTISREFERREDTOASAN EVAPORATIONDUCT"ECAUSETHEEVAPORATIONDUCTISOFGREATIMPORTANCEFOROVER WATER %-PROPAGATION ITWARRANTSADETAILEDDISCUSSION4HISDISCUSSIONAPPEARSINITSOWN SECTIONBELOW 3URFACE BASEDDUCTSOCCURWHENTHEAIRALOFTISEXCEPTIONALLYWARMANDDRYCOM PAREDWITHTHEAIRATTHE%ARTHSSURFACE3EVERALMETEOROLOGICALCONDITIONSMAYLEAD TOTHEFORMATIONOFSURFACE BASEDDUCTS /VERTHEOCEANANDNEARLANDMASSES WARM DRYCONTINENTALAIRMAYBEADVECTED OVERTHECOOLERWATERSURFACE%XAMPLESOFTHISTYPEOFADVECTIONARETHE3ANTA!NA OFSOUTHERN#ALIFORNIA THE3IROCCOOFTHESOUTHERN-EDITERRANEAN ANDTHE3HAMALOF THE0ERSIAN'ULF4HISADVECTIONWILLLEADTOATEMPERATUREINVERSIONATTHESURFACE)N ADDITION MOISTUREISADDEDTOTHEAIRBYEVAPORATION PRODUCINGAMOISTUREGRADIENTTO STRENGTHENTHETRAPPINGGRADIENT4HISTYPEOFMETEOROLOGICALCONDITIONROUTINELYLEADS TOASURFACEDUCTCREATEDBYASURFACE BASEDTRAPPINGCONDITION(OWEVER ASYOUTRAVEL FROMTHECOASTALENVIRONMENTINTOTHEOPENOCEAN THISTRAPPINGLAYERMAYWELLRISE FROMTHESURFACE THEREBYCREATINGTHESURFACE BASEDDUCT3URFACE BASEDDUCTSTEND
&)'52% 3URFACEDUCT
4(%02/0!'!4)/.&!#4/2 &0 ).4(%2!$!2%15!4)/.
ÓÈ°££
&)'52% 3URFACE BASEDDUCT
TOBEONTHELEEWARDSIDEOFLANDMASSESANDMAYOCCURBOTHDURINGTHEDAYANDAT NIGHT)NADDITION SURFACE BASEDDUCTSMAYEXTENDOVERTHEOCEANFORSEVERALHUNDRED KILOMETERSANDMAYBEVERYPERSISTENTLASTINGFORDAYS !NOTHERMETHODOFPRODUCINGSURFACE BASEDDUCTINGCONDITIONSISBYDIVERGENCE SPREADINGOUT OFRELATIVELYCOOLAIRUNDERATHUNDERSTORM7HILETHISMETHODMAYNOT BEASFREQUENTASTHEOTHERMETHODS ITMAYSTILLENHANCESURFACEPROPAGATIONDURING THETHUNDERSTORMACTIVITY USUALLYONTHEORDEROFAFEWHOURS 7ITH THE EXCEPTION OF THUNDERSTORM CONDITIONS SURFACE BASED DUCTING IS ASSOCI ATEDWITHFAIRWEATHERANDWITHINCREASEDOCCURRENCEOFSURFACE BASEDDUCTSDURING THEWARMERMONTHSANDINMOREEQUATORIALLATITUDES!NYTIMETHETROPOSPHEREISWELL MIXED SUCHASWITHFRONTALACTIVITYORWITHHIGHWINDCONDITIONS SURFACE BASEDDUCT INGISDECREASED %VAPORATION $UCTS ! CHANGE IN THE MOISTURE DISTRIBUTION WITHOUT AN ACCOM PANYINGTEMPERATURECHANGECANALSOLEADTOATRAPPINGREFRACTIVITYGRADIENT4HEAIR INCONTACTWITHTHEOCEANSSURFACEISSATURATEDWITHWATERVAPOR!FEWMETERSABOVE THESURFACETHEAIRISNOTUSUALLYSATURATED SOTHEREISADECREASEOFWATERVAPORPRES SURE FROM THE SURFACE TO SOME VALUE WELL ABOVE THE SURFACE4HE RAPID DECREASE OF WATERVAPORINITIALLYCAUSESTHEMODIFIEDREFRACTIVITY - TODECREASEWITHHEIGHT BUT ATGREATERHEIGHTSTHEWATERVAPORDISTRIBUTIONWILLCAUSE-TOREACHAMINIMUMAND THEREAFTER INCREASEWITHHEIGHT4HEHEIGHTATWHICH-REACHESAMINIMUMISCALLED THEEVAPORATIONDUCTHEIGHT ASILLUSTRATEDIN&IGURE %VAPORATIONDUCTSEXISTOVERTHEOCEAN TOSOMEDEGREE ALMOSTALLTHETIME4HE DUCTHEIGHTVARIESFROMAMETERORTWOINNORTHERNLATITUDESDURINGWINTERNIGHTSTOAS MUCHASMETERSINEQUATORIALLATITUDESDURINGSUMMERDAYS/NAWORLDAVERAGE THEEVAPORATIONDUCTHEIGHTISAPPROXIMATELYMETERS)TSHOULDBEEMPHASIZEDTHAT THEEVAPORATIONDUCThHEIGHTvISNOTAHEIGHTBELOWWHICHANANTENNAMUSTBELOCATED INORDERTOHAVEEXTENDEDPROPAGATIONBUTAVALUETHATRELATESTOTHEDUCTSSTRENGTH ORITSABILITYTOTRAPRADIATION4HEDUCTSTRENGTHISALSOAFUNCTIONOFWINDVELOCITY &ORUNSTABLEATMOSPHERICCONDITIONSCONDITIONSWHEREACOOLERLAYEROFAIROVERLIES AWARMERLAYEROFAIR STRONGERWINDSGENERALLYRESULTINSTRONGERSIGNALSTRENGTHS ORLESSPROPAGATIONLOSS THANDOWEAKERWINDS
ÓÈ°£Ó
2!$!2(!.$"//+
&)'52% %VAPORATIONDUCT
"ECAUSETHEEVAPORATIONDUCTISMUCHWEAKERTHANTHESURFACE BASEDDUCT ITSABIL ITYTOTRAPENERGYISHIGHLYDEPENDENTONFREQUENCY'ENERALLY THEEVAPORATIONDUCTIS ONLYSTRONGENOUGHTOAFFECTELECTROMAGNETICSYSTEMSABOVE-(Z &ORSURFACEDUCTINGCONDITIONS THEVERTICALEXTENTOFTHEDUCTISSUFFICIENTTOALLOWFOR ITSMEASUREMENTUSINGANASCENDINGRADIOSONDE ADESCENDINGROCKETSONDE ORAMICRO WAVEREFRACTOMETERONBOARDSOMESORTOFAIRVEHICLE(OWEVER FORANEVAPORATIONDUCT ITISNOTTHEVERTICALEXTENTOFTHEDUCTTHATISIMPORTANTBUTTHEREFRACTIVEGRADIENTWITHIN THEDUCT#HANGESOFREFRACTIVEGRADIENTSOVERVERTICALHEIGHTSLESSTHANAFEWMILLIMETERS MAYHAVEASIGNIFICANTIMPACTUPONTHEDUCTSTRAPPINGABILITY4HUS ASSESSMENTOFTHE EVAPORATIONDUCTISBESTPERFORMEDBYMAKINGSURFACEMETEOROLOGICALMEASUREMENTSAND INFERRINGTHEDUCTHEIGHTFROMTHEMETEOROLOGICALPROCESSESOCCURRINGATTHEAIRSEAINTER FACEANDNOTFROMDIRECTMEASUREMENTSUSINGTHETRADITIONALRADIOSONDE ROCKETSONDE OR MICROWAVEREFRACTOMETER7ITHTHEADVENTOFNEWER HIGH RESOLUTIONSONDESTHATMAYBE LOWEREDTOTHESURFACEFROMASHIP THEIMPRESSIONISGIVENTHATTHEEVAPORATIONDUCTMAY BEMEASUREDDIRECTLY&ORPRACTICALAPPLICATIONS HOWEVER THISIMPRESSIONISFALSEANDA DIRECTMEASUREMENTSHOULDNOTBEATTEMPTED$UETOTHETURBULENTNATUREOFTHETROPO SPHEREATTHEOCEANSURFACE AREFRACTIVITYPROFILEMEASUREDATONETIMEWOULDMOSTLIKELY NOTBETHESAMEASONEMEASUREDATANOTHERTIME EVENWHENTHETWOMEASUREMENTSARE SECONDSAPART4HEREFORE ANYMEASUREDPROFILEWOULDNOTBEREPRESENTATIVEOFTHEAVERAGE EVAPORATIONDUCTINGCONDITIONS THECONDITIONSTHATANASSESSMENTSYSTEMMUSTCONSIDER %LEVATED $UCTS )F METEOROLOGICAL CONDITIONS CAUSE A TRAPPING LAYER TO OCCUR ALOFT SUCH THAT THE BASE OF THE DUCT OCCURS ABOVE THE %ARTHS SURFACE THE DUCT IS REFERREDTOASANELEVATEDDUCT ASILLUSTRATEDIN&IGURE.OTEAGAINTHEADVANTAGE OFSHOWING- UNITGRADIENTSVERSUS. UNITGRADIENTS&ROM&IGURE ITCANBESEEN THATTHEDUCTEXTENDSFROMTHETOPOFTHETRAPPINGLAYERDOWNWARDUNTILITINTERSECTS WITHTHE- UNITLINEWHERETHE- UNITATTHETOPOFTHEDUCTISTHESAMEASTHE- UNIT ATTHEBOTTOMOFTHEDUCTILLUSTRATEDBYTHEDASHEDLINE 'REATSEMIPERMANENTSURFACEHIGH PRESSURESYSTEMS CENTEREDATAPPROXIMATELY NORTHANDSOUTHLATITUDE COVERTHEOCEANAREASOFTHEWORLD0OLEWARDOFTHESESYSTEMS LAYTHEMID LATITUDEWESTERLYWINDS ANDEQUATORWARDLAYTHETROPICALEASTERLIESORTHE TRADEWINDS7ITHINTHESEHIGH PRESSURESYSTEMS LARGE SCALESUBSIDENCEOFAIRCAUSES HEATINGASTHEAIRUNDERGOESCOMPRESSION4HISLEADSTOALAYEROFWARM DRYAIROVERLAY INGACOOL MOISTLAYEROFAIROFTENCALLEDTHEMARINEBOUNDARYLAYER
4(%02/0!'!4)/.&!#4/2 &0 ).4(%2!$!2%15!4)/.
ÓÈ°£Î
&)'52% %LEVATEDDUCT
4HERESULTANTINVERSIONISREFERREDTOASTHETRADEWINDINVERSIONANDMAYCREATEA STRONGDUCTINGCONDITIONATTHETOPOFTHEMARINEBOUNDARYLAYER%LEVATEDDUCTSMAY VARYFROMAFEWHUNDREDMETERSABOVETHESURFACEATTHEEASTERNPARTOFTHETROPICAL OCEANSTOSEVERALTHOUSANDMETERSATTHEWESTERNPART&OREXAMPLE ALONGTHESOUTHERN #ALIFORNIACOAST ELEVATEDDUCTSOCCURANAVERAGEOFOFTHETIME WITHANAVERAGE TOPELEVATIONOFMETERS!LONGTHECOASTOF*APAN ELEVATEDDUCTSOCCURANAVERAGE OFOFTHETIME WITHANAVERAGETOPELEVATIONOFMETERS )TSHOULDBENOTEDTHATTHEMETEOROLOGICALCONDITIONSNECESSARYFORASURFACE BASED DUCTARETHESAMEASTHOSEFORANELEVATEDDUCT)NFACT ASURFACE BASEDDUCTMAYSLOPE UPWARDTOBECOMEANELEVATEDDUCTASWARM DRYCONTINENTALAIRGLIDESOVERCOOL MOIST MARINEAIR4HETRADEWINDINVERSIONMAYALSOINTENSIFY THEREBYTURNINGANELEVATED DUCTINTOASURFACE BASEDDUCT
ÓÈ°ÈÊ *,"*/" Ê " Ó]Ç 2ADIO WAVE MODELING IS IMPORTANT FOR A NUMBER OF REASONS ALL OF WHICH COULD BE SUMMARIZEDINTOTWOLARGECATEGORIESOFENGINEERINGSTUDIESANDOPERATIONALPERFOR MANCE&ORENGINEERINGSTUDIES THEEFFECTSOFPROPAGATIONMAYBECONSIDEREDINNEW SYSTEMDESIGNORINTHEEVALUATIONOFLONG TERMPERFORMANCEOFEXISTINGSYSTEMS&OR OPERATIONALPERFORMANCE CONSIDERATIONOFPROPAGATIONEFFECTSISUSUALLYBASEDUPON ASINGLEMEASUREDORFORECASTEDATMOSPHERESUCHTHATTHESEEFFECTSCANBEEXPLOITED ORMITIGATEDBYALTERINGTHESYSTEMSUSETACTICS/VERTHEYEARS MANYPROPAGATION MODELSHAVEBEENDEVELOPEDTOACCOUNTFORTHEEFFECTSIMPORTANTTOAPARTICULARAPPLI CATION4HESEMODELSSPANTHESPECTRUMOFVERYFASTEXECUTINGBUTWITHLOWFIDELITY SIMPLIFIEDMODELINGOFORTHECOMPLETEIGNORINGOFCERTAINPROPAGATIONMECHANISMS TORELATIVELYSLOWEXECUTINGBUTWITHHIGHFIDELITYPHYSICALLYRIGOROUSMODELINGOF ANDFULLINCLUSIONOFALLPROPAGATIONMECHANISMS 3PHERICAL3PREADINGOR&REE SPACE0ROPAGATION-ODEL 4HESIMPLESTPROPAGA TIONMODELISSPHERICALSPREADINGWHERETHETRANSMITTERANDRECEIVERAREFARREMOVED
ÓÈ°£{
2!$!2(!.$"//+
FROMTHE%ARTHSSURFACEANDTHEATMOSPHERE IE FREESPACE&REESPACEISDEFINEDASA REGIONWHOSEPROPERTIESAREISOTROPIC HOMOGENEOUS ANDLOSS FREE3PHERICALSPREADING MODELSONLYCONSIDERTHEINCREASINGSURFACEAREAOFASPHERECENTEREDONTHETRANSMITTER ANDRADIATINGOUTUNIFORMLYINALLDIRECTIONS4HEFIELDSTRENGTHATANYPOINTISINVERSELY PROPORTIONALTOTHESQUAREOFTHERANGEBETWEENTRANSMITTERANDTHEPOINT4HISISCALLED FREE SPACEPATHLOSS4HEPOWERDENSITY 0A OVERASPHEREATANYPOINTINFREESPACEIS
¤ 0' ³ 0A ¥ T T ´ 7 M ¦ O R µ
WHERE0TISTHEPOWERRADIATEDBYTHETRANSMITTER RISTHERADIUSOFTHESPHERE AND'TIS THETRANSMITTINGANTENNASGAIN&ORALOSS FREE ISOTROPICANTENNA THEGAINISUNITY )NFREESPACE THEPOWERDENSITYATALOSS FREE ISOTROPICRECEIVINGANTENNAISTHE POWERDENSITYOVERTHEENTIRESPHERESSURFACETIMESTHEAREAOFTHESPHERECOVERED BYTHERECEIVERANTENNA ALSOCALLEDTHEANTENNASEFFECTIVEAPERTURE !E4HEEFFECTIVE APERTUREISRELATEDTOTHEWAVELENGTHK OFRADIATIONBY
!E
'K
O
4HUS THEPOWERATTHERECEIVER 0R FORISOTROPICRADIATINGANDRECEIVINGANTENNAS 'T 'R IS
0R 0A !E
0T K
O R
4HEFREE SPACEPATHLOSS ,FS EXPRESSEDINTERMSOFTHESPHERESRADIUS R ANDWAVE LENGTH K WHERERANDKAREINTHESAMEUNITSIS
§ O R ¶ ¤0³ ,FS LOG ¥ T ´ LOG ¨ · ¦ 0R µ © K ¸
&REE SPACEPATHLOSS ,FS EXPRESSEDINTERMSOFRANGEANDFREQUENCYINDECIBELS ISGIVENBY
,FS LOG F LOGR
WHEREFISFREQUENCYIN-(ZANDRISTHEDISTANCEBETWEENTHETRANSMITTERANDRECEIVER INKILOMETERS&REESPACEISINCLUDEDINMANYMODELINGAPPLICATIONSASAREFERENCEFOR OTHERPROPAGATIONEFFECTS )FNONISOTROPICANTENNARADIATIONALPATTERNSARECONSIDEREDWITHINTHELOSSCALCULA TIONS THELOSSISREFERREDTOASAPROPAGATIONLOSSRATHERTHANAPATHLOSS4HEPROPAGA TIONLOSSCANBEDESCRIBEDWITHTHEAIDOFTHEPROPAGATIONFACTOR& WHICHISDEFINED ASTHERATIOOFTHEACTUALFIELDSTRENGTHATAPOINTINSPACETOTHEFIELDSTRENGTHTHATWOULD EXISTATTHESAMERANGEUNDERFREE SPACECONDITIONS WITHTHEBEAMOFTHETRANSMITTER DIRECTEDTOWARDTHEPOINTINQUESTION3YMBOLICALLYTHISIS
&
\%\
\ %O \
WHERE%OISTHEMAGNITUDEOFTHEELECTRICFIELDUNDERFREE SPACECONDITIONSAND%ISTHE MAGNITUDEOFTHEFIELDTOBEINVESTIGATEDATTHESAMEPOINT
4(%02/0!'!4)/.&!#4/2 &0 ).4(%2!$!2%15!4)/.
ÓÈ°£x
4HEPROPAGATIONFACTORISADESIRABLEQUANTITYSINCEITISANIDENTIFIABLEPARAMETERIN MOSTRADAREQUATIONS!SSTATEDEARLIER ITALSOCONTAINSALLTHEINFORMATIONNECESSARYTO ACCOUNTFORNATURALENVIRONMENTALEFFECTS4HUS IFTHEFUNCTIONALFORMOF&ISKNOWN THENTHEPROPAGATIONLOSSATANYPOINTCANBEDETERMINEDBECAUSETHECALCULATIONOFTHE FREE SPACEFIELDISQUITESIMPLE4HEPROPAGATIONLOSS INCLUDINGANTENNAPARAMETERS ISEQUIVALENTTO
, ,FS LOG &
%FFECTIVE EARTH RADIUS-ODEL 3INCETHEMAJORITYOFHUMANACTIVITYTAKESPLACE WITHINTHE%ARTHSATMOSPHERE THEFREE SPACEPROPAGATIONMODELISUSUALLYINADEQUATE FORPROPAGATIONASSESSMENTAPPLICATIONS ANDOTHERPROPAGATIONMECHANISMSNEEDCON SIDERATION 5NDER STANDARD OR NORMAL ATMOSPHERIC CONDITIONS THE RADIO RAY CURVES DOWNWARDWITHACURVATURELESSTHANTHE%ARTHSSURFACE4HEEFFECTIVE EARTH RADIUS CONCEPT REPLACES THE %ARTHS TRUE RADIUS WITH A LARGER RADIUS SUCH THAT THE RELATIVE CURVATUREBETWEENTHERAYANDTHE%ARTHSSURFACEISMAINTAINED ANDTHERAYBECOMES ASTRAIGHTLINE4HEEFFECTIVE EARTH RADIUS AE ANDTHEACTUAL EARTH RADIUS A ARERELATED BYANEFFECTIVE EARTH RADIUSFACTOR K SUCHTHAT AE KA
KMAYBECOMPUTEDUSING
K
; A DN DH =
WHEREDNDHISTHEVERTICALREFRACTIVEINDEXGRADIENT5SINGTHEMEAN EARTH RADIUSOF KILOMETERSANDAREFRACTIVITYGRADIENTOFn.KMGIVESAKOFORABOUT )N ADDITION TO THE CONSIDERATION OF REFRACTION OTHER STANDARD PROPAGATION MECH ANISMS SUCH AS MULTIPATH INTERFERENCE DIFFRACTION TROPOSCATTER AND TERRAIN MAY BE INCLUDED!MONGTHEGENERALCLASSOFEFFECTIVE EARTH RADIUSMODELSARETHE3TANDARD 0ROPAGATION-ODEL& &ACTOR THE4ERRAIN)NTEGRATED2OUGH%ARTH-ODEL4)2%- THE)RREGULAR4ERRAIN-ODEL)4- ALSOKNOWNAS,ONGLEY 2ICE ANDTHE3PHERICAL %ARTH+NIFE%DGE3%+% 7HILE THESE EFFECTIVE EARTH RADIUS MODELS ARE OF THE SAME NATURE THEY DO NOT IMPLEMENT THE VARIOUS PROPAGATION MECHANISMS EQUALLY &OR EXAMPLE THE & FACTOR MODELPROPERLYIMPLEMENTSMULTIPATHPROPAGATIONFOROVER WATERSURFACESWHEREASTHE 4)2%-MODELISBASEDUPONKNIFEEDGEDIFFRACTIONTECHNIQUES MAKINGTHE4)2%- MODEL INAPPROPRIATE FOR OVER WATER APPLICATIONS!GAIN WHILE TROPOSCATTER MAY BE UNIMPORTANTFORACTIVERADARAPPLICATIONS ITSEFFECTSNEEDTOBEINCLUDEDFORAPPLICA TIONSOFRADARINTERCEPTBYOTHERSENSORS 7AVEGUIDE-ODELS !SENGINEERINGREQUIREMENTSDEMANDEDGREATERANDGREATER FIDELITY OTHERMODELINGTECHNIQUESWEREDEVELOPED/NESUCHMODELINGTECHNIQUEIS USING NORMAL MODE THEORY TO COMPUTE FIELD STRENGTH UNDER STANDARD OR NONSTANDARD REFRACTIVECONDITIONS4HISCLASSOFMODELSISREFERREDTOASWAVEGUIDEMODELS4HEUSE OFWAVEGUIDEMODELSDATESBACKTOTHEEARLYSWHENTHEYWEREUSEDTOEXPLAINTHE PROPAGATIONOFLONGWAVELENGTHRADIOWAVESAROUNDTHESURFACEOFTHE%ARTHINAWAVE GUIDEFORMEDBYTHE%ARTHANDTHEIONOSPHERE!DESCRIPTIONOFWAVEGUIDEMODELSIS BEYONDTHESCOPEOFTHISCHAPTERBUTMAYBEFOUNDINAPUBLICATIONBY"UDDEN
ÓÈ°£È
2!$!2(!.$"//+
7HILEWAVEGUIDEMODELSAREMOSTUSEFULFORCONDITIONSWHERETHEVERTICALREFRACTIV ITYPROFILEDOESNOTCHANGEALONGTHEPROPAGATIONPATHHOMOGENEOUSENVIRONMENTS THEYCANBEAPPLIEDTOINHOMOGENEOUSENVIRONMENTSBYBREAKINGTHEWAVEGUIDEUP INTOSLABSINATECHNIQUEKNOWNASMODECONVERSION7HILESUCCESSFUL THISTECHNIQUE IS LESS COMPUTATIONALLY EFFICIENT THAN OTHER MODELING TECHNIQUES AND HENCE WAVE GUIDEMODELSARENOTGENERALLYUSEDFORASSESSMENTSYSTEMSREQUIRINGRAPIDEXECUTION TIMES7AVEGUIDEMODELSSERVEAShLABORATORYBENCHMARKvMODELSAGAINSTWHICHTHE RESULTSOFOTHERMODELINGTECHNIQUESCANBECOMPARED/NESUCHWAVEGUIDEMODELIS THE-,!9%2 DERIVEDFROMTHEORIGINALWORKSOF"AUMGARTNER 0ARABOLIC%QUATION-ODELS )N &OCKUSEDTHEPARABOLICEQUATION0% METHODTODESCRIBEELECTROMAGNETICPROPAGATIONINAVERTICALLYSTRATIFIEDTROPOSPHERE )N (ARDINAND4APPERTDEVELOPEDANEFFICIENTPRACTICALSOLUTIONCALLEDTHESPLIT STEP&OURIERMETHODBASEDUPONFAST&OURIERTRANSFORMS&&4S THATHASBEENWIDELY APPLIEDTOOCEANACOUSTICPROPAGATIONPROBLEMS4HE0%METHODANDITSSOLUTIONBYTHE SPLIT STEP&OURIERTECHNIQUEPROVIDESAVERYROBUSTMODELFORCOMPLICATEDREFRACTIVITY STRUCTURESFORWITHIN NEAR ANDBEYONDTHEHORIZONEFFECTSANDISPARTICULARLYGOODFOR PROPAGATIONOVERIRREGULARTERRAIN4HUS 0%MODELSALLOWFORASINGLEMODELASSESS MENTINMANYIMPORTANTAPPLICATIONS4HREESUCH0%MODELSARETHE4ERRAIN0ARABOLIC %QUATION -ODEL 40%- THE 4ROPOSPHERIC %LECTROMAGNETIC 0ARABOLIC %QUATION 2OUTINE4%-0%2 ANDTHE6ARIABLE4ERRAIN2ADIO0ARABOLIC%QUATION6420% (YBRID-ODELS 7HILE0%MODELSAREVERYATTRACTIVE THEYALSOHAVETHEIRDISAD VANTAGES0ROBABLYTHEBIGGESTDISADVANTAGEISTHATTHEYREQUIREVERYLARGECOMPUTER RESOURCES BOTHINTERMSOFMEMORYANDEXECUTIONTIMES PARTICULARLYFORAPPLICATIONS INVOLVING COMBINATIONS OF HIGH FREQUENCIES HIGH ELEVATION ANGLES HIGH TERMINALS ANDLONGRANGES)NSOMECASES THISCOMPUTATIONALBURDENCANBEREDUCEDBYCOMBIN INGTHEBESTFEATURESOFTHEVARIOUSOTHERMODELSINAHYBRIDMODEL/NCESUCHMODEL ISTHE!DVANCED0ROPAGATION-ODEL!0- DESCRIBEDBY"ARRIOS)N!0- THE0% MODELISCOMBINEDWITHVARIOUSRAYOPTICSANDOTHERPHENOMENAMODELSTOCREATEA HYBRIDMODELTHATCANBEUPTOTIMESFASTERTHANA0%MODELFORSTRESSFULCASES 4HREEOTHERHYBRIDMODELSARE2ADIO0HYSICAL/PTICS20/ 4%20%-AUTHOREDBY 3IGNAL3CIENCE,IMITED ANDAHYBRIDMETHODFORCOMPUTINGTRANSMISSIONLOSSESIN ANINHOMOGENEOUSATMOSPHEREOVERIRREGULARTERRAINBY-ARCUS 7ITHIN!0- THEASSESSMENTSPACEISDIVIDEDINTOFOURREGIONS ORSUBMODELS AS ILLUSTRATED IN &IGURE !T RANGES LESS THAN M AND FOR ALL ELEVATION ANGLES ABOVE !0-USESAFLATEARTH&% MODELTHATIGNORESREFRACTIONANDEARTHCURVATURE EFFECTS&ORRANGESBEYONDTHE&%REGIONWHERETHEGRAZINGANGLESOFREFLECTEDRAYS FROMTHETRANSMITTEREXCEEDASMALLLIMITINGVALUE AFULLRAYOPTIC2/ MODELISUSED THATACCOUNTSFORTHEEFFECTSOFREFRACTIONANDEARTHCURVATURE4HE0%MODELISUSED FORRANGESBEYONDTHE2/REGION BUTONLYFORALTITUDESBELOWAMAXIMUM0%ALTI TUDEDETERMINEDBYAMAXIMUMFAST&OURIERTRANSFORM&&4 SIZEALLOWED&ORRANGES BEYONDTHE2/REGIONANDABOVETHE0%REGION ANEXTENDEDOPTICS8/ METHODIS USEDTHATISINITIALIZEDBYTHE0%MODELATTHEMAXIMUM0%ALTITUDEANDUSESRAYOPTICS METHODSTOPROPAGATETHESIGNALTOHIGHERALTITUDES#ONTINUITYOFTHESOLUTIONSACROSS EACHREGIONSBOUNDARIESISKEPTLESSTHAND"BYCAREFULSELECTIONOFTHELIMITING 2/GRAZINGANGLEANDTHEMAXIMUM0%PROPAGATIONANGLE 4HEPROPAGATIONMODELSWITHIN!0-HAVEALSOBEENCOMBINEDWITHOTHERENVI RONMENTAL EFFECTS MODELS SUCH AS GASEOUS ABSORPTION AND SURFACE CLUTTER TO FORM A COMPLETE PROPAGATION PACKAGE 4HE PHYSICAL PROPAGATION PHENOMENA CONSIDERED BY!0-VERSIONAREILLUSTRATEDIN4ABLE!SCANBESEENFROMTHETABLE
4(%02/0!'!4)/.&!#4/2 &0 ).4(%2!$!2%15!4)/.
ÓÈ°£Ç
4!",% 0ROPAGATION%FFECTS-ODELEDBY!0-
%#$ ' #" '& " &!&
(# ") %#"!"' %% " '!#&$ %
" $""' %%' )#" ' #"& % '%% " ( ' $'
%' #" %% "!& " %#$#&''% #( &(% &(%*) " $""' '% & &' " (% (''%
&#(&#&%$' #" "''"(' #" '' #"
!0-CONSIDERSALMOSTEVERYENVIRONMENTALEFFECT MAKINGITAHIGHLYDESIRABLEMODEL FORUSEINCOMPLEXASSESSMENTSYSTEMS
&)'52% !0-SUBMODELREGIONS
ÓÈ°£n
2!$!2(!.$"//+
ÓÈ°ÇÊ Ê-9-/ Ê-- -- /Ê*,", 5SING THE POWER OF THE PERSONAL COMPUTER IN CONJUNCTION WITH THE MATURITY OF %-SYSTEM AND ENVIRONMENTAL PROPAGATION MODELING ASSESSMENT PROGRAMS AND ASSOCIATED SOFTWARE ALLOW A USER TO DEFINE AND MANIPULATE REFRACTIVITY AND OTHER NATURAL ENVIRONMENT DATA RUN PROPAGATION MODELS ON THAT DATA AND DISPLAY THE RESULTS IN TERMS OF EXPECTED PERFORMANCE ON ACTUAL OR PROPOSED ELECTROMAGNETIC SYSTEMS7HILETHEREARESEVERALASSESSMENTSYSTEMSINUSEWITHINTHE53ANDIN VARIOUS OTHER COUNTRIES THE FOLLOWING DISCUSSION IS LIMITED TO!2%03 )T IS USED EXTENSIVELY THROUGHOUT THE 53 $EPARTMENT OF $EFENSE $O$ AND OTHER FEDERAL GOVERNMENT AGENCIES 53 PRIVATE INDUSTRY THEIR FOREIGN COUNTERPARTS AND BY PRIVATEINDIVIDUALS !2%03GREWOUTOFANURGENTMILITARYOPERATIONALREQUIREMENTFORRADARPERFOR MANCE AND PROPAGATION MODELING WITHIN A TERRAIN EFFECTS DOMINATED ENVIRONMENT 4HE ASSESSMENT SYSTEM REQUIREMENTS INCLUDED MODELING ALL NATURAL ENVIRONMENTAL EFFECTS BEINGQUICKLYEXECUTABLE ANDEXECUTINGONA-ICROSOFT7INDOWSOPERATING SYSTEMPERSONALCOMPUTER!NEVALUATIONOFTHEVARIOUSPROPAGATIONMODELSFORTHEIR STRENGTHSANDWEAKNESSESQUICKLYSHOWEDTHATAHYBRIDMODELWASTHEONLYACCEPT ABLESOLUTION4HE!2%03GRAPHICALUSERINTERFACEWASCREATEDANDINTERFACEDTOTHE !0-TOPROVIDETHEUSERANEND TO ENDRADARPROPAGATIONASSESSMENTTOOL"ECAUSE %-PROPAGATIONEFFECTSARENOTJUSTLIMITEDTORADARFREQUENCIES OVERTIMETHEINITIAL RADARREQUIREMENTSFOR!2%03WEREEXPANDEDBEYONDSIMPLERADARDETECTIONAPPLI CATIONSTOINCLUDEAPPLICATIONSINCOMMUNICATIONSANDELECTRONICWARFARE!2%03IS THEONLYAPPROVED%-SYSTEMASSESSMENTAPPLICATIONWITHINTHE$EPARTMENTOFTHE .AVY#HIEF)NFORMATION/FFICER$/.!PPLICATIONS$ATABASE-ANAGEMENT3YSTEM $!$-3 !0-ISTHEONLYACCREDITEDBYTHE#HIEFOF.AVAL/PERATIONS %-PROPA GATION-(ZTO'(Z MODELFORUSEIN.AVYSYSTEMS"OTH!2%03AND!0-ARE ACCREDITEDWITHINTHE.AVY-ODELINGAND3IMULATION/FFICE.-3/ !2%03ISALSO A.ORTH!TLANTIC4REATY/RGANIZATION.!4/ APPLICATION APPROVEDBYTHE-ILITARY #OMMITTEE -ETEOROLOGICAL 'ROUP7ORKING 'ROUP "ATTLE !REA -ETEOROLOGICAL 3YSTEMSAND3UPPORTPLUSWITH0ARTNERS !2%03VERSIONCONTAINSSEVERAL%-PROPAGATIONMODELSFORAPPLICATIONSAT VARIOUSFREQUENCIES&ORFREQUENCIESOF-(ZTO'(Z !2%03USESTHE!0-&OR (&SKYWAVECOMMUNICATIONS !2%03USESAN(&MODELINGSUITE CONSISTINGOFA FULLY$IONOSPHERERAYTRACEMODEL AN(&FIELDSTRENGTHMODEL ANDAN(&NOISE MODEL)NADDITIONTOTHESE%-PROPAGATIONMODELS !2%03MAYOPTIONALLYUSETWO INTERNATIONALLYRECOGNIZEDIONOSPHEREMODELS THE0ARAMETERIZED)ONOSPHERIC-ODEL 0)- ANDTHE)NTERNATIONAL2EFERENCE)ONOSPHERE)2) )NADDITIONTOTHEPROPAGA TIONMODELS !2%03CONTAINSASYSTEMPERFORMANCERADARMODEL WHICHISDISCUSSED INTHENEXTSECTION !2%03CONSIDERSRANGE ANDAZIMUTHANGLEnDEPENDENTINFLUENCESFROMSURFACE FEATURESTOINCLUDETERRAINELEVATION FINITECONDUCTIVITY DIELECTRICGROUNDCONSTANTS ANDSCATTERINGEFFECTIVENESSFACTORS4HETERRAINELEVATIONDATAMAYBEOBTAINEDFROM THE .ATIONAL 'EOSPATIAL )NTELLIGENCE !GENCYS .'! $IGITAL 4ERRAIN %LEVATION $ATA$4%$ ORFROMANYOTHERSUITABLESOURCE4HEFINITECONDUCTIVITYANDDIELEC TRIC GROUND CONSTANTS MAY BE SELECTED FROM THOSE DEFINED BY THE )NTERNATIONAL 4ELECOMMUNICATION 5NION )NTERNATIONAL 2ADIO #ONSULTATIVE #OMMITTEE ##)2 ORFROMANYOTHERSUITABLESOURCE
4(%02/0!'!4)/.&!#4/2 &0 ).4(%2!$!2%15!4)/.
ÓÈ°£
!2%03CONSIDERSRANGE ANDAZIMUTHANGLEnDEPENDENTATMOSPHERICREFRACTIVITY DATADERIVEDFROMTHEUPPER AIROBSERVATIONSOFRADIOSONDES OTHERSENSORS ORMESO SCALE METEOROLOGICAL MODELS SUCH AS THE 53 .AVY #OUPLED /CEAN!TMOSPHERE -ESOSCALE 0REDICTION 3YSTEM #/!-03 2ADIOSONDE DATA MAY BE MANUALLY ENTEREDORAUTOMATICALLYDECODEDFROMEITHERTHE7ORLD-ETEOROLOGICAL/RGANIZATION 7-/ OBSERVATIONALMESSAGEFORMATORAFREE FORMCOLUMNFORMAT OBTAINEDFROM A NUMBER OF DIFFERENT DATA SOURCES )N ADDITION CLIMATOLOGICAL REFRACTIVE CONDI TIONSMAYBESELECTEDFROMA7-/STATION WORLDWIDEREPORTINGDATABASE&OR OCEANREPORTINGSTATIONSORNUMERICALWEATHERPREDICTIONGRIDPOINTSOVERTHEOCEAN !2%03AUTOMATICALLYCALCULATESANEVAPORATIONDUCTREFRACTIVEPROFILEANDAPPENDS ITTOTHEBOTTOMOFTHEUPPER AIROBSERVATIONFORACOMPLETEDESCRIPTIONOFTHEPROPA GATIONENVIRONMENT !2%03COMPUTESANDDISPLAYSANUMBEROF%-SYSTEMPERFORMANCEASSESSMENT TACTICALDECISIONAIDS4HESEARERADARPROBABILITYOFDETECTION %3-VULNERABILITY ,& TO %(& COMMUNICATIONS SIMULTANEOUS RADAR DETECTION AND %3- VULNERABILITY AND SURFACE SEARCHDETECTIONRANGES!LLDECISIONAIDSAREDISPLAYEDASFUNCTIONSOFRANGE AZIMUTHANGLE ANDORHEIGHT$ETECTIONPROBABILITY %3-VULNERABILITY ANDCOMMUNI CATIONSASSESSMENTSAREBASEDON%-SYSTEMPARAMETERSSTOREDINAUSER DEFINEDAND CHANGEABLEDATABASE)NADDITIONTONORMALRADARPARAMETERS AUSERMAYCOMPLETELY DEFINETHEANTENNARADIATIONPATTERNTOACCOUNTFORSIDELOBECONSIDERATIONS4HEDATA BASEALSOINCLUDESRADARTARGETDESCRIPTIONSANDPLATFORMS%-EMITTERSUITES &IGUREISANILLUSTRATIONOFAN!2%03FOUR PANELDISPLAY4HISDISPLAYWAS CREATEDINSUPPORTOF53HOMELANDDEFENSEFORTHE&EBRUARY 3UPER"OWL 8,4HE3UPER"OWL8,2OMANNUMERALFOR ISACHAMPIONSHIPFOOTBALLGAME
&)'52% !2%03HOMELANDDEFENSEAPPLICATION
ÓÈ°Óä
2!$!2(!.$"//+
PLAYEDINTHE5NITED3TATES)TWASATTENDEDBYOVER PEOPLE ALLCONFINEDIN ONESPORTINGEVENTSTADIUM WHICHPRESENTEDASIGNIFICANTTARGETFORATERRORISMATTACK 4HEDISPLAYSHOWSARADARPROBABILITYOFDETECTIONINARANGEVERSUSHEIGHTDEPICTION RADARPROBABILITYOFDETECTIONVERSUSRANGEATACONSTANTALTITUDEDEPICTION ANDRADAR PROBABILITYOFDETECTIONVERSUSHEIGHTATACONSTANTRANGEDEPICTION4HISDISPLAYIS COURTESYOFTHETH2ADAR%VALUATION3QUADRON (ILL!IR&ORCE"ASE 5TAH4HERADAR DEPICTED IS THE!232 % 53!IR 2OUTE 3URVEILLANCE 2ADAR LOCATED AT #ANTON -ICHIGAN4HETARGETOFINTERESTISASMALLPRIVATEAIRCRAFT !STHEPERSONALCOMPUTERVERSIONOF!2%03DEVELOPED ITALSOTRANSITIONEDINTOAN APPLICATIONCALLEDTHE.AVAL)NTEGRATED4ACTICAL%NVIRONMENTAL3UBSYSTEM.)4%3 A SEGMENTOFTHE'LOBAL#OMMANDAND#ONTROL3YSTEM -ARITIME'##3 - )N.)4%3 THE!2%03 FUNCTIONALITY OF THE PERSONAL COMPUTER WAS CODED IN *AVA AND INTERFACED TO THE #OMMON /PERATING 0ICTURE #/0 4HE #/0 IS A REAL TIME DISPLAY OF TACTICAL INFORMATIONANDCURRENTFORCEPOSITIONING4HUS ARADARASSESSMENTPROVIDEDBY!2%03 MAYBEDISPLAYEDASATACTICALOVERLAYUPONTHEOPERATINGPICTURE&IGUREISAN ILLUSTRATIONOFSUCHA#/0DISPLAY)NTHISILLUSTRATION THERADARCOVERAGEOFTHREECOASTAL SURVEILLANCE RADARS IS SHOWN ALONG WITH THE TRADITIONAL HEIGHT VERSUS RANGE COVERAGE DISPLAYTYPICALOFTHEPERSONALCOMPUTERVERSIONOF!2%03 !S THE .AVY PROGRESSED INTO WEB BASED APPLICATIONS THE DISPLAY OF !2%03 TACTICALDECISIONAIDSFOLLOWEDSUIT/NESUCHWEB BASEDAPPLICATIONISTHE.AVYS #OMPOSABLE&ORCE.ET ANAPPLICATIONSIMILARINNATURETOTHE'##3 -&IGURE ISANILLUSTRATIONOFTHE#OMPOSABLE&ORCE.ETAPPLICATION&ORTHISILLUSTRATION THE BACKGROUNDFORTHE#OMPOSABLE&ORCE.ET#/0ISAHYPOTHETICALOCEANANDISLAND OPERATIONAREA4HESYMBOLOGYSUCHASTHESMALLCIRCLES SQUARES ANDHALFCIRCLES REPRESENTTHEDISPOSITIONOFVARIOUSFORCESSUCHASSHIPSAND AIRCRAFT4HEMULTIPLE ELLIPTICAL AND FAN SHAPED SHADED AREAS CORRESPOND TO A CERTAIN RADAR PROBABILITY OF DETECTIONOFVARIOUSTARGETSBYVARIOUSOPERATIONALRADARS&OREXAMPLE THESMALLFAN SHAPEDSHADEDAREAINTHEUPPER RIGHTCORNEROFTHEDISPLAYREPRESENTSTHEAREAWHERE AGROUND BASEDRADARWOULDBEABLETODETECTWITHACERTAINPROBABILITYOFDETECTION APARTICULARAIRCRAFTTARGET !NOPTIONALCAPABILITYOF!2%03ISTOPROVIDETOANEXTERNALAPPLICATION THECOM PUTEDRADARPROBABILITYOFDETECTION PROPAGATIONLOSS ORPROPAGATIONFACTOR TOANEXTER NALAPPLICATION4HUS ATACTICALAPPLICATIONDEVELOPERNEEDNOTHAVEKNOWLEDGEOFTHE UNDERLYING RADAR PROPAGATION MODELING TECHNIQUES OR OTHER ENVIRONMENTAL CONSIDER ATIONSBUTCANRELYUPON!2%03TOhSERVEUPvDATAFORDISPLAYWITHINHISORHEROWN APPLICATION3UCHANAPPLICATIONISTHE3IMULATIONAND$ISPLAY3YSTEM3)-$)3 AUTHOREDBYTHE.AVAL2ESEARCH,ABORATORY 7ASHINGTON$#&IGUREISANILLUS TRATIONOF!2%03 COMPUTEDDATADISPLAYEDTHREE DIMENSIONALLYWITHIN3)-$)3)N THISFIGURE THEVIEWISLOOKINGNORTHWARDWITHINTHEBYTEOF3OUTHERN#ALIFORNIA4HE EASTERN TERRAIN OF 3AN #LEMENTE )SLAND SHOWS IN THE MIDDLE LEFT OF THE FIGURE &ROM THISCURRENTVIEW ASHIPWITHAPARTICULARAIR SEARCHRADARISLOCATEDBEYONDNORTH OF THEISLAND4HEDARKENEDFAN SHAPEDAREAEXTENDINGUPWARDOVERTHEISLANDREPRESENTS THERADARSPROBABILITYOFDETECTIONOFACERTAINTARGETASTHERADARSWEEPSSOUTHWARD OVERTHEISLAND&ORATARGETLOCATEDINTHEFOREFRONTOFTHEISLANDANDATASUFFICIENTLY LOWALTITUDE THEDISPLAYSHOWSTHETARGETISNOTDETECTABLEBYTHERADARASTHETARGETIS MASKEDBYTHEINTERVENINGTERRAIN
4(%02/0!'!4)/.&!#4/2 &0 ).4(%2!$!2%15!4)/.
ÓÈ°Ó£
&)'52% !2%03DISPLAYUPONTHE#/0WITHIN.)4%3
&)'52% !2%03COMPUTATIONSDISPLAYUPONTHE#OMPOSABLE&ORCE.ET#/0
ÓÈ°ÓÓ 2!$!2(!.$"//+
4(%02/0!'!4)/.&!#4/2 &0 ).4(%2!$!2%15!4)/.
ÓÈ°ÓÎ
&)'52% !2%03COMPUTATIONSDISPLAYWITHIN3)-$)3SHOWINGRADARPROBABILITYOFDETECTIONOFA SMALLTARGETUNDERTHEINFLUENCEOFTERRAIN MASKINGEFFECTS
ÓÈ°nÊ , *-Ê, ,Ê-9-/ ÊÊ -- -- /Ê " 4HEMAINPURPOSEOF!2%03ISTOOFFERRADAROPERATORSTHEABILITYTOVISUALIZETHEIR RADARS DETECTION OF THREAT TARGETS OR THEIR OWN PLATFORMS DETECTION BY THREAT RADARS UNDERVARIOUSNATURALENVIRONMENTALCONDITIONS4HEPRIMARYVISUALIZATIONISAHEIGHT VERSUSRANGEDISPLAYOFRADARPROBABILITYOFDETECTION WHERETHERADARPROBABILITYOF DETECTIONEXPRESSEDINPERCENTCORRESPONDSTOCERTAINENERGYLEVELSINHEIGHTANDRANGE FROMTHERADAR!0-COMPUTESPROPAGATIONLOSSIND"4OMAKEADETERMINATIONOF RADAR PERFORMANCE !2%03 NEEDS TO MAKE A COMPARISON OF FREE SPACE PROPAGATION LOSSANDPROPAGATIONLOSSWITHINTHE%ARTHSENVIRONMENTASCOMPUTEDBY!0-4HUS !2%03CONTAINSAFAIRLYSIMPLISTICPULSED RADARMODELTOCALCULATEFREE SPACEPROPAGA TIONLOSSFROMRADARSYSTEMPARAMETERSSUCHASFREQUENCY PULSELENGTH ETC4HEMODELS TODOTHISCALCULATIONARETAKENFROM"LAKEANDAREFULLYDESCRIBEDWITHINTHE!2%03 ONLINEHELPANDTHE!2%03OPERATORSMANUAL4HUS !2%03RADARSYSTEMASSESSMENT MODELWILLNOTBEREPEATEDHERE4HEINTENTOFTHISSECTIONISTOSHOWTHENECESSARYRADAR SYSTEMANDRADARTARGETINPUTSNEEDEDBYTHE!2%03PROGRAM4HESEINPUTSARESHOWN IN&IGURESAND&ORACOMPLETEDESCRIPTIONOFEACHINPUTPARAMETER YOU MAYREFERTOTHE!2%03ONLINEHELPORTHE!2%03OPERATORSMANUAL
ÓÈ°Ó{
2!$!2(!.$"//+
&)'52% !2%03RADARWINDOW
4O ASSIST THE!2%03 USER THESE AND OTHER INPUT WINDOWS HAVE MANY hCANNEDv DEFAULT VALUES COMBINED WITH MANY UNIT OPTIONS /NE EXAMPLE IS THE TRANSMITTING ANTENNAPATTERN!0-WILLCONSIDERTHEFULLANTENNAPATTERNOFTHETRANSMITTINGANTENNA
&)'52% !2%03TARGETWINDOW
4(%02/0!'!4)/.&!#4/2 &0 ).4(%2!$!2%15!4)/.
ÓÈ°Óx
!2%03PROVIDESSOMEBASIChCANNEDvANTENNAPATTERNSSUCHASOMNI 3IN88 COSE CANT SQUARED ANDAGENERICHEIGHT FINDER7ITHAUSER SPECIFIEDANTENNATYPE THEOPERA TORMAYENTERTHEPATTERNANGLEANDFACTORDIRECTLY)NADDITIONTOENTERINGTHEANTENNA PATTERNDIRECTLYFROMTHEKEYBOARD !2%03ALSOPROVIDESTHECAPABILITYOFIMPORTING ANANTENNAPATTERNFROMAN!3#))TEXTFILETHATYOUMAYHAVECREATEDFROMANOTHER APPLICATION!NEXAMPLEOFMULTIPLEUNITSISTHETRANSMITTERSPEAKPOWER4HEDEFAULT UNITFORPEAKPOWERIS+ILOWATTS"YRIGHT CLICKINGONTHELABELASSOCIATEDWITHPEAK POWER YOUMAYSELECTOTHERUNITSOFINPUT!2%03WILLEVENCONVERTTHEINPUTNUMBER AUTOMATICALLYFROMONEUNITTOTHEOTHERUNIT
ÓÈ°Ê , *-Ê, ,Ê -* 9"YDEFAULT THERESULTSOFTHEPROPAGATIONMODELCALCULATIONSARESHOWNINTERMSAPPRO PRIATEFORATACTICALRADAROPERATOR IE AHEIGHTVERSUSRANGEDISPLAYOFRADARPROBABILITY OFDETECTIONASAPERCENTAGE ASILLUSTRATEDIN&IGURE4HISDISPLAYISREFERREDTO ASATACTICALDECISIONAIDBECAUSEITWILLALLOWTHERADAROPERATORTOMAKESOMESORTOF TACTICALDECISION&OREXAMPLE SUPERIMPOSEDONTHISTACTICALDECISIONAIDISTHEFLIGHT PROFILEOFATARGETMISSILETHESOLIDLINESLOPINGDOWNWARDTOTHEORIGINFROMRIGHTTO LEFT 4HEATMOSPHERICENVIRONMENTISSURFACE BASEDDUCTING4HENONDETECTIONSKIP ZONEISCLEARLYSEENINADDITIONTOTHETARGETSFLIGHTPATTERN ALLOWINGTHEOPERATORTOSEE HOWTHEPROBABILITYOFDETECTIONOFTHETARGETWILLVARYWITHRANGEANDHEIGHT7ITHTHIS KNOWLEDGE ADECISIONABOUTWHENTOATTEMPTANATTACKONTHEMISSILECANBEMADE
&)'52% !2%03HEIGHTVERSUSRANGECOVERAGEFORSURFACE SEARCHRADARANDSMALLMISSILETARGET PROBABILITYOFDETECTION
ÓÈ°ÓÈ
2!$!2(!.$"//+
&ORRADARENGINEERS ADISPLAYSUCHASTHATSHOWNIN&IGUREWILLMOSTLIKELY NOTBEVERYUSEFULSINCEPROPAGATIONFACTOR &P ISTHEDESIREDQUANTITYFORTHERADAR RANGEEQUATIONANDNOTTHEPROPAGATIONLOSSASCOMPUTEDBY!0-(OWEVER THEREISA SIMPLERELATIONSHIPBETWEENPROPAGATIONLOSSANDPROPAGATIONFACTOR4HISIS
&P ,FS ,D"
WHERE,FSISTHEFREE SPACEPROPAGATIONLOSSGIVENBY%QAND,D"ISTHEPROPAGA TIONLOSSIND"ASCOMPUTEDBY!0-!SACONVENIENCEFORTHERADARENGINEER !2%03 WILLALSODISPLAYTHE!0-OUTPUTINTERMSOFPROPAGATIONFACTOR4HUS &IGURE DISPLAYED IN TERMS OF RADAR PROBABILITY OF DETECTION AS A PERCENTAGE WILL APPEAR AS SHOWNIN&IGUREWHENDISPLAYEDINTERMSOFPROPAGATIONFACTOR )NADDITIONTOTHEDEFAULTHEIGHTVERSUSRANGEDISPLAY !2%03CONTAINSMANYOTHER DISPLAYANDDATAOUTPUTOPTIONS&OREXAMPLE &IGURESHOWSFORTHESAMEMISSILE DETECTIONEXAMPLE ASIGNAL TO NOISERATIOVERSUSRANGEDISPLAYSUPERIMPOSEDWITHACLUTTER TO NOISERATIOCOMPUTEDFROMANMETER PER SECONDWINDSPEED4HEDISPLAYALTITUDEIS FEETABOVESEA LEVEL/NECANSEETHEEFFECTSOFMULTIPATHINTERFERENCEBETWEENARANGE OFANDABOUTNAUTICALMILES"EYONDTHEMULTIPATHINTERFERENCEREGION ONECANSEEA MAJORFALLOFFOFSIGNAL TO NOISEANDCLUTTER TO NOISERATIOCOMESWITHINTHESURFACE BASED DUCTSKIP ZONEBETWEENABOUTNAUTICALMILESANDNAUTICALMILES.OTE HOWEVER THE INCREASEINRATIOSFORRANGESBEYONDTHESKIP ZONE)NFACT ITISEVENSEENTHATFORRANGES BETWEENANDNAUTICALMILES THECLUTTER TO NOISERATIOEXCEEDSTHESIGNAL TO NOISE RATIO4HUSFORTHESERANGES THERADARRETURNISOVERWHELMEDWITHCLUTTER
&)'52% !2%03HEIGHTVERSUSRANGECOVERAGEFORSURFACE SEARCHRADARANDSMALLMISSILETARGET PROPAGATIONFACTOR
4(%02/0!'!4)/.&!#4/2 &0 ).4(%2!$!2%15!4)/.
ÓÈ°ÓÇ
" '#"# &
%&$%" %%"
$)#"& " #
' '
" "! #!$('%' #
#!$(' (''%'#"# &%' # &)'52% !2%03SIGNAL TO NOISERATIOVERSUSRANGEFORSURFACE SEARCHRADARANDSMALLMISSILE TARGETCLUTTER TO NOISERATIOSUPERIMPOSED
7HILEAGRAPHICMAYBEUSEFULFORVISUALINSPECTIONS ITMAYNOTBEUSEFULFORAN ENGINEERINGANALYSISTASK!2%03HASMANYOTHERDATADISPLAYFEATURES&OREXAMPLE THE PROPAGATION FACTOR VALUES AS SHOWN IN &IGURE MAY ALSO BE EXPORTED IN A NUMBEROFDIFFERENTTEXTFORMATSFORUSEINOTHERENGINEERINGAPPLICATIONS
, ,
7 , 0ATTERSON h!DVANCED REFRACTIVE EFFECTS PREDICTION SYSTEM v 3PACE AND .AVAL 7ARFARE 3YSTEMS #ENTER 4$ *ANUARY !2%03 MAY BE FREELY OBTAINED AT HTTPAREPS SPAWARNAVYMIL 7 , 0ATTERSON ET AL h%NGINEERS 2EFRACTIVE %FFECTS 0REDICTION 3YSTEM %2%03 v .AVAL #OMMAND #ONTROL AND/CEAN3URVEILLANCE#ENTER4$ -AY %"ROOKNER h2ADARPERFORMANCEDURINGPROPAGATIONFADESINTHE-ID !TLANTICREGION v)%%% 4RANSACTIONSON!NTENNASAND0ROPAGATION VOL .O *ULY - 0 - (ALL h%FFECTS OF THE TROPOSPHERE ON RADIO COMMUNICATIONS v ,ONDON )NSTITUTION OF %LECTRICAL%NGINEERS P + $ !NDERSON h2ADAR DETECTION OF LOW ALTITUDE TARGETS IN A MARITIME ENVIRONMENT v )%%% 4RANSACTIONSON!NTENNASAND0ROPAGATION VOLNO *UNE 3%-ORISON h!LEUTIANS 'ILBERTSAND-ARSHALLS *UNEn!PRIL(ISTORYOF5NITED3TATES .AVAL/PERATIONSIN7ORLD7AR)) 6OLUME6)) v-ILITARY!FFAIRS VOL NO PPn (6(ITNEY h2EFRACTIVEEFFECTSFROM6(&TO%(& PART"PROPAGATIONMODELS v!DVISORY'ROUP FOR!EROSPACE2ESEARCH$EVELOPMENT !'!2$ ,3 PP!n! 3EPTEMBER *20OWELL h4ERRAIN)NTEGRATED2OUGH%ARTH-ODEL4)2%- v2EP4. %LECTROMAGNETIC #OMPATIBILITY!NALYSIS#ENTER !NNAPOLIS -$ 3EPTEMBER !',ONGLEYAND0,2ICE h0REDICTIONSOFTROPOSPHERERADIOTRANSMISSIONLOSSOVERIRREGULAR TERRAIN!COMPUTERMETHOD v%NVIRONMENTAL3CIENCE3ERVICES!DMINISTRATION4ECH2EP%2, )43 53'OVT0RINTING/FFICE 7ASHINGTON $# 3!YASLI h3%+%!COMPUTERMODELFORLOWALTITUDERADARPROPAGATIONOVERIRREGULARTERRAIN v )%%%4RANSACTIONSON!NTENNASAND0ROPAGATION VOL!0 NO !UGUST
ÓÈ°Ón
2!$!2(!.$"//+
+ ' "UDDEN 4HE 7AVE 'UIDE -ODE 4HEORY OF 7AVE 0ROPAGATION )NGLEWOOD #LIFFS .*0RENTICE (ALL )NC !LSO,ONDON,OGOS0RESS ' " "AUMGARTNER h876' ! WAVEGUIDE PROGRAM FOR TRILINEAR TROPOSPHERIC DUCTS v .AVAL /CEAN3YSTEMS#ENTER4$ *UNE 6!&OCK %LECTROMAGNETIC$IFFRACTIONAND0ROPAGATION0ROBLEMS .EW9ORK0ERGAMON 2((ARDINAND&$4APPERT h!PPLICATIONOFTHESPLIT STEP&OURIERMETHODTOTHENUMERICAL SOLUTIONOFNONLINEARANDVARIABLECOEFFICIENTWAVEEQUATIONS v3)!-2EV P !%"ARRIOS h!4ERRAIN0ARABOLIC%QUATION-ODELFOR0ROPAGATIONINTHE4ROPOSPHERE v)%%% 4RANSACTIONSON!NTENNASAND0ROPAGATION VOL NO PPn *ANUARY '$$OCKERY h-ODELINGELECTROMAGNETICWAVEPROPAGATIONINTROPOSPHEREUSINGTHEPARA BOLIC EQUATION v )%%% 4RANSACTIONS ON !NTENNAS AND 0ROPAGATION VOL PP n /CTOBER & * 2YAN h!NALYSIS OF ELECTROMAGNETIC PROPAGATION OVER VARIABLE TERRAIN USING THE PARABOLIC WAVEEQUATION v.AVAL/CEAN3YSTEMS#ENTER42 /CTOBER ! % "ARRIOS h!DVANCED 0ROPAGATION -ODEL !0- #OMPUTER 3OFTWARE #ONFIGURATION )TEM #3#) v3PACEAND.AVAL7ARFARE3YSTEMS#ENTER4$ !UGUST (6(ITNEY h(YBRIDRAYOPTICSANDPARABOLICEQUATIONMETHODSFORRADARPROPAGATIONMODELING v IN2ADAR )%%#ONF0UBVOL /CTOBERn PPn +EN#RAIGAND-IREILLE,EVY HTTPWWWSIGNALSCIENCECOM 3 7 -ARKUS h! HYBRID &INITE $IFFERENCE SURFACE 'REENS &UNCTION METHOD FOR COMPUTING TRANSMISSIONLOSSESINANINHOMOGENEOUSATMOSPHEREOVERIRREGULARTERRAIN v)%%%4RANSACTIONS ON!NTENNASAND0ROPAGATION VOLNO Pn 2"2OSE h!DVANCEDPROPHET(&ASSESSMENTSYSTEM v.AVAL/CEAN3YSTEMS#ENTER 3AN$IEGO *ANUARY 2%$ANIEL *R ,$"ROWN $.!NDERSON -7&OX 0($OHERTY $4$ECKER **3OJKA AND 2 7 3CHUNK h0ARAMETERIZED IONOSPHERIC MODEL! GLOBAL IONOSPHERIC PARAMETERIZATION BASEDONFIRSTPRINCIPALMODELS v2ADIO3CIENCE VOL PPn + 2AWER 3 2AMAKRISHNAN AND $ "ILITZA h)NTERNATIONAL REFERENCE IONOSPHERE v )NTERNATIONAL5NIONOF2ADIO3CIENCE 523)3PECIAL2EPORT PP "RUXELLES "ELGIUM h0ROPAGATION IN .ON IONIZED -EDIA v )NTERNATIONAL 4ELECOMMUNICATION 5NION )NTERNATIONAL 2ADIO#ONSULTATIVE#OMMITTEE##)2 VOL6 2EPORT P h53 .AVY #OUPLED /CEAN!TMOSPHERE -ESOSCALE 0REDICTION 3YSTEM #/!-03 v .AVAL 2ESEARCH,ABORATORY -ARINE-ETEOROLOGY$IVISION .2,0UBLICATION -AY .AVAL 2ESEARCH ,ABORATORY 7ASHINGTON $# HTTPSSIMDISNRLNAVYMIL SIMDIS ENEWSNRL NAVYMIL , 6 "LAKE 2ADAR 2ANGE 0ERFORMANCE !NALYSIS ,EXINGTON -! ,EXINGTON "OOKS $# (EATHAND#O
I_1
INDEX
A A-12 low cross section aircraft, 14.40 Absorbers, 14.32, 14.36 to 14.38 Active aperture, 13.53 to 13.55 Active Electronically Scanned Array (AESA), 5.1, 5.8 to 5.10, 10.28 compared to mechanical scan, 5.9 to 5.10 timing structure, 5.15 to 5.16 typical waveform parameters, 5.13, 5.15 waveform variations for air-to-surface mode, 5.12 to 5.13 Active jamming, 24.5 Active-switch modulator, 10.24 A/D converter and MTI dynamic range, 2.78 to 2.80 Adaptive arrays (ECCM), 24.20 to 24.30 Adaptive jammer and clutter cancellation, 24.25 Adaptive MTI, 2.80 to 2.83 Adaptive thresholding, 7.11 to 7.19 Advanced Propagation Model (APM), 26.16 to 26.17 Advanced Refractive Effects Prediction System (AREPS), 26.1 to 26.2, 26.18 to 26.27 Aid to Navigation (AtoN), 22.25 to 22.26 Air-to-air ground ranging, 5.33 Air-to-air mission profile, 5.12 to 5.14 Air-to-air modes, 5.14, 5.16 to 5.28 medium PRF, 5.16 to 5.20 Air-to-surface mission profile, 5.10 Air-to-surface mode suite, 5.11 to 5.12 Air-to-surface radar modes, 5.28 to 5.42 Air-traffic control (ATC) radar, 1.21 to 1.22 Air Traffic Control Radar Beacon System (ATCRBS), 7.49 Airborne Early Warning, 3.1. See also Airborne Moving Target Indication antenna sidelobes, 3.13 to 3.14 coverage, 3.2 to 3.3 platform motion, 3.3 to 3.14 TACCAR, 3.4 to 3.9 Airborne Moving Target Indication (AMTI) example of, 3.32 to 3.33 improvement factor, 3.8 multiple spectra, 3.31 to 3.32 scanning motion compensation, 3.14 to 3.17 and STAP, 3.23 to 3.31 Aircraft radar cross section, 14.13 to 14.14 Alpha-beta (-) filter, 7.26 to 7.27, 7.30 Altimeters, from space, 18.33 to 18.57 Altitude line, 4.4 to 4.5 Ambiguity function, 8.40 Ambiguity resolution, in MTI, 2.89 to 2.91 Amplitude-comparison monopulse, 9.3 to 9.11 Amplitude noise, in tracking, 9.27 to 9.30 AN/APG-76, 17.25 AN/APY-9, 3.32 to 3.33 AN/FPQ-6, 9.2, 9.9, 9.18, 9.21, 9.44 AN/FPS-23, 23.7 AN/EPS-117, 8.30, 13.63 to 13.64 AN/MPS-39, 9.2, 9.26 AN/SPS-40, 10.27, 11.32 to 11.33 AN/SPY-1, 13.62
AN/SPY-3, 13.69 AN/TPS-59, 8.30, 13.63 to 13.64 AN/TPS-63, 12.18 AN/TPS-77, 13.63 to 13.64 AN/TPS-78, 13.65 to 13.66 Analog-to-digital (A/D) converters, 6.35 to 6.40
I_2
Anechoic chamber, 14.32 Angle accuracy, by beam splitting, 7.5 to 7.7 Angle measurement errors, 9.43 to 9.44 Angle noise, 9.30 to 9.35 Angle scintillation (glint), 9.30 to 9.35, 9.47 Angular direction, 1.8 Anomalous propagation, 26.6 to 26.13 Antenna-related ECCM, 24.10 to 24.31 Antennas, 1.2, 1.4 to 1.5. See also phased arrays, reflector antennas basic principles, 12.3 to 12.15 for civil marine radar, 22.10 to 22.12 for ground penetrating radar, 21.24 to 21.30 phased array, 13.2 to 13.3 for pulse doppler, 4.12 to 4.13 reflector antennas, role of, 12.1 reflector antennas, types of, 12.7 Anti-radiation missile (ARM), 24.40 Anti-range-gate pull-off (A-RGPO), 24.46 Aperture gain, of antennas, 12.4 to 12.5 Apollo Lunar Sounder, 18.60 to 18.61 Aquarius scatterometer, 18.58 Area MTI, 2.84 Array feeds, for reflector antennas, 12.28 to 12.30 ARSR-4, 12.30 ASR-9, 10.27 to 10.28, 12.20 to 12.21 ASR-11 MTI filter design, 2.50 to 2.51 ASR-12, 8.30, 10.27 to 10.28 Atmosphere, of the Earth, 26.2 Atmospheric ducts, 26.7 to 26.10 Attenuation, by clouds, 19.7 to 19.8 by fog, 19.12 by hail, 19.11 to 19.12 by rain, 19.8 to 19.11 Automatic detection, 7.1 to 7.2, 7.20 to 7.22 Automatic gain control (AGC), in monopulse tracker, 9.5, 9.10 to 9.11 Automatic Identification System (AIS) in civil marine radar, 22.23 to 22.25 in search and rescue, 22.27 Automatic noise-level control, 6.23 to 6.24 Automatic Radar Plotting Aid (ARPA), 22.17 Automatic tracking, 7.22 to 7.46 alpha-beta (-) filter, 7.26 to 7.27, 7.30 detection acceptance, 7.25 to 7.26 Interacting Multiple Model (IMM), 7.35 to 7.37 Kalman filter, 7.28 to 7.35 new track formation, 7.41 to 7.46 retrospective processing, 7.42 to 7.43 scheduling and control, 7.46 track association, 7.38 to 7.41 track file, 7.23 to 7.25 updating tracks, 7.26 to 7.30 AWACS, 13.65
B B-2 low cross section aircraft, 14.18, 14.42 Ballistic missile defense, 13.54 Bandwidth importance of, 1.8 to 1.9 of phased arrays, 13.38 to 13.45 receiver, 6.9 Bar, in airborne radar, 5.15 to 5.16 Barker codes, 8.17
Batch processor, 7.8 to 7.11 Battle of the Pips, ducting effects, 26.9 Beacon equation, 24.4 Beacon rendezvous, 5.27 Beam-shape factor, 7.3 Beam-shape loss, 4.40 Beam-splitting angle accuracy, 7.5 to 7.7 Beam steering, 13.15 to 13.19 Beam steering control, 5.10 Binary integrator, 7.7 to 7.8, 7.12 to 7.13 Birds, and MTI, 2.96 to 2.98 Bistatic plane, 23.3 Bistatic radar applications, 23.9 to 23.14 benchmark range, 23.4 to 23.5 concept of, 23.1 to 23.3 coordinate system, 23.3 to 23.4 doppler in, 23.14 to 23.17 floodlight beams, 23.27 forward scatter, 23.21 glint in, 23.20 to 23.21 ground echo, 16.29 hitchhiker, 23.10 with noncooperative transmitter, 23.29 to 23.31 ovals of Cassini, 23.6 to 23.8 passive, 23.10 pseudo-monostatic region, 23.19 to 23.20 pulse chasing, 23.28 to 23.29
I_3
range equation, 23.5 to 23.6 SAR, 23.17 scattering coefficient, 23.22 to 23.25 surface clutter in, 23.22 to 23.26 target cross section, 23.19 to 23.21 target location, 23.17 to 23.19 with TV transmitter, 23.29 to 23.31 Blind speeds, 2.9 to 2.10 Block diagram digital receiver, 25.2 medium PRF air-to-air pulse doppler, 5.17 monopulse tracking radar, 9.4 to 9.5 Moving Target Detection, 2.6 to 2.7 multifunctional fighter aircraft radar, 5.3 pulse compression, 8.1 to 8.2 pulse doppler, 4.11 radar, 1.3 SBR altimeter, 18.40 Bodies of revolution radar cross section, 14.39 to 14.40 Bragg scatter, 15.2, 15.28 to 15.32, 15.38, and ground echo, 16.11 to 16.12 Burst mode, in SBR SAR, 18.23 to 18.24
C C band, 1.16 Calibrate and self-test, 5.42 Calibration of meteorological radar, 19.18 to 19.19 Cascaded Integrator-Comb (CIC) Filters, 25.29 to 25.32 Cassegrain antenna, 12.21 to 12.23, 12.25, 14.34 Cassini, 18.46 Cathode pulser, 10.23 Cell-averaging CFAR, 7.11 to 7.12, 7.17 CFAR, 7.11 to 7.18 and ECCM, 24.35 to 24.36 loss, 4.44 probability of detection, 7.15 target suppression in, 7.16 to 7.17 Chaff, 24.5 to 24.6 Chaff and ECCM, 24.19, 24.34 Chart radars, 22.22 to 22.23 Chebyshev filter bank, 2.54 to 2.55 Civil Marine Radar (CMR), 22.33 and aids to navigation (AtoN), 22.25, 22.26 antennas, 22.10 to 22.12 Automatic Identification System (AIS), 22.2, 22.8 integration with, 22.23 to 22.25 cost of, 22.3 detection performance, 22.4 to 22.6 detection and processing, 22.13 to 22.15 display, 22.21 early days of, 22.31 to 22.33 environmental conditions, 22.3 international standards for, 22.7 to 22.10 magnetrons for, 10.16 precipitation and sea clutter, 22.5 racons and, 22.26 radar beacons and, 22.25 radar target enhancers (RTEs), 22.27 RF head (transmitter and receiver), 22.12 to 22.13 search and rescue transponders, 22.27 solid-state, 22.16 to 22.17 target tracking, 22.17 to 22.19 user interface, 22.19 to 22.22
validation testing of, 22.28 to 22.29 vertical lobing in, 22.6 to 22.7 Class of (amplifier) operation, 11.18 to 11.20 Clouds, attenuation in, 19.7 to 19.8 CloudSat, 18.63, 19.39 Clustered-cavity klystron, 10.12 to 10.13 Clutter amplitude characteristics, 2.17 attenuation, in MTI, 2.20 to 2.21 characteristics for MTI, 2.10 to 2.19 exponential model, 2.12 to 2.16 in ground penetrating radar, 21.5, 21.10 maps, 2.83 to 2.87, 6.23, 7.19 models, for ground echo, 16.29 to 16.34 MTI filter design, 2.33 to 2.46 optimum filter design, 2.25 to 2.33 point scatterers, 2.18 to 2.19 in pulse doppler radar, 4.14 to 4.24 reflectivity, 2.17 to 2.18 Clutter-limited detection in pulse doppler, 4.48 Coaxial magnetron, 10.14 to 10.15 Coaxitron, 10.21 Cobra Dane radar, 8.36 Coherent processing, and ECCM, 24.34 to 24.35 Coherent Processing Interval (CPI), 2.7 Coherent on receive, 10.14
I_4
COHO, 6.3, 6.20 Collapsing loss, 7.3 Compact range, 14.32 to 14.33 Complementary pulse compression waveforms, 8.19 Complex envelope representation, 8.38 to 8.39 Computer codes for reflector design, 12.33 to 12.35 Conformal arrays, 13.3 Conical-scan tracking, 9.16 to 9.17 Conopulse, 9.15 Constant false alarm rate. See CFAR Continuous wave (CW) radar, 1.5 Constant Efficiency Amplifier (CEA), 10.21 to 10.22, 10.26 Cooperative target identification, 5.22 to 5.23 CORDIC processor, 25.22 to 25.25 Corner reflector, radar cross section, 14.9 to 14.11 Corporate feed monopulse phased array, 9.14 Co secant-squared antenna, and STC, 2.98 COSMO-SkyMed SAR, 18.12 Costas codes, 8.25 to 8.26 Counter Battery Radar (COBRA), 13.62 Creeping waves, 14.3, 14.5 Critical frequency, in HE OTH, 20.3 Crossed-field amplifier (CFA), 10.3, 10.16 to 10.17 Crossed-field tubes, 10.2 Cross-eye ECM, 24.42 to 24.43 Cross-polarization jamming, 24.43 Cross-polarization tracking, 9.40 to 9.41 Crossrange resolution, 17.1 Cross section. See radar cross section Crosstalk, in tracking, 9.40 to 9.41 Crowbar, in transmitters, 10.24 CryoSat altimeter, 18.42 to 18.43
D D region, 20.14 Dällenbach layer, 14.37 to 14.38 Data link, missile, 5.26 Data links, in MFAR, 5.24 to 5.27 Data processing, 1.3 dBZ, 19.5 to 19.6 DC operation of CFA, 10.17, 10.24 Deceptive ECM (DECM), and ECCM, 24.6 to 24.7, 24.40 and tracking radar, 24.41 to 24.42 Decimation, 6.41 to 6.42 Decimation filters, 25.28 to 25.32 Decoys, 24.6, 24.8 Delta-Sigma converters, 6.36 Depressed collector, 10.10 Detection acceptance, 7.25 to 7.26 Detectors batch processor, 7.8 to 7.11 binary integrator, 7.7 to 7.8, 7.12 to 7.13 M-out-of-N, 7.7 to 7.8 moving window, 7.4 to 7.7 nonparametric, 7.17 to 7.18 optimal, 7.2 to 7.4 practical, 7.4 to 7.11 rank, 7.17 to 7.18 Dicke fix, 24.33, 24.35 Differential reflectivity, 19.18 Diffraction, 26.5 Digital beamforming, 13.8, 13.56 to 13.57 multiple beams, 25.17 to 25.19
Digital downconversion (DDC), 6.41 to 6.42, 6.44 to 6.45, 25.6 to 25.15 Digital filters, 25.26 to 25.32 Digital pulse compression, 25.19 generation of, 8.28 to 8.30 Digital receiver, 6.40 to 6.46 block diagram, 25.2 direct sampling, 25.38 Digital RF memory (DREM), 24.6 to 24.7 Digital signal processing hardware implementation, 25.35 to 25.37 timing dependence, 25.34 to 25.35 tools, 25.22 to 25.34 Digital upconverter (DUC), 25.21 to 25.22 Diode phase shifter, 13.51 to 13.52 Dipole antenna, 21.25 to 21.26 Direct digital downconversion, 25.10 to 25.15 Direct digital synthesizer (DDS), 6.22, 6.48 to 6.49, 25.20 to 25.21 Direct sampling digital receiver. 25.38 Direction finding (DF) and radar, 7.50 to 7.54 Directive gain, of an antenna, 12.5 Discrete Fourier transform (DFT), 25.32 to 25.34 Displaced Phase Center Antenna (DPCA), 3.10 to 3.13, 3.19 to 3.21, 5.2 to 5.3 Distortion, in receiver, 6.6 to 6.7 Doppler ambiguity resolution, 4.33 to 4.34
I_5
Doppler beam sharpening (DBS), 5.34 to 5.36, 5.37, 17.2, 17.3 Doppler, in bistatic radar, 23.14 to 23.17 Doppler filter bank, 2.7 to 2.9 Doppler filter straddle loss, 4.43 Doppler filter weighting loss, 4.43 Doppler radars, 4.1 Doppler scintillation, in tracking radars, 9.36 to 9.37 Doppler shift, 1.10 Doppler spectra, spurious, 6.11 Doppler spectrum of ground echo, 16.16 to 16.19 of HF sea echo, 20.49 to 20.52, 20.75 Doppler weather radar, 1.7 Ducts atmospheric, 26.7 to 26.10 elevated, 26.12 to 26.13 evaporation, 26.11 to 26.12 surface, 26.10 to 26.11 Duplexer, 1.2, 6.2 Dynamic range, 1.3, 6.4 to 6.8 of A/D converters, 6.38 to 6.39 and ECCM, 24.32 to 24.33 in pulse doppler radar, 24.32 to 24.33
E E-2C, 3.3 E-2D, 3.1 to 3.3 E region, 20.14 Early-late gate range tracking, 9.21 to 9.22 Eclipsing loss, 4.40 to 4.43, 5.18 Effective-earth-radius model, 26.15 Eldora radar, 19.37 to 19.38 EM system assessment, 26.18 to 16.23 Electronic Attack, 24.2 Electronic counter-countermeasures (ECCM) antenna-related, 24.10 to 24.31 decoys, 24.8 efficiency, 24.54 to 24.56 and imaging radar, 24.48 to 24.52 and ISAR, 24.51 to 24.52 operational-deployment techniques, 24.36 to 24.37 and over-the-horizon radar, 24.52 to 24.53 and phased array radar, 24.43 to 24.48 and radar equation, 24.55 to 24.56 receiver related, 24.32 to 24.33 role of the operator with, 24.36 SLB and SLC, 24.17 to 24.20 sidelobe canceler, 24.14 to 24.20 signal-processing related, 24.33 to 24.36 STAP, 24.21 to 24.22 and subarrays, 24.25 to 24.29 and surveillance radars, 24.37 to 24.40 and SAR, 24.48 to 24.51 techniques, 24.8 to 24.9, 24.37 to 24.53 terminology, 24.2 and tracking radars, 24.40 to 24.43 transmitter related, 24.31 to 24.32 Electronic countermeasures (ECM), 24.5 to 24.8 Electronic Protection (EP), 24.2 Electronic-scan monopulse, 9.12 to 9.13 Electronic Support (ES), 24.2 Electronic Warfare Support Measures (ESM), 24.2 to 24.5 Elevated ducts, 26.12 to 26.13
Elint, 24.2, 24.3, 24.4 Emission Control (EMCON), 24.37 ENVIS AT, 18.11 Errors in tracking radar external causes of, 9.37 to 9.43 internal sources of, 9.42 to 9.43, 9.47 reduction techniques, 9.46 to 9.47 sources of, 9.26 target caused, 9.26 to 9.37 ERS SAR, 18.8 to 18.9 Evaporation ducts, 26.11 to 26.12 Exponential model of land clutter, 2.12 to 2.16 Extended Interaction Klystron (EIK), 10.11 External noise at HF, 20.43 to 20.45
F F-117 low cross section aircraft, 14.40 to 14.42 F region, 20.14 to 20.15 Fading, 16.12 False-alarm control, 7.11 to 7.19 Far field, 14.4 Far-field criterion, 14.27 to 14.28 Fast Fourier transform (FFT), 25.33 to 25.34 filter bank, 2.55 to 2.56 Fast Time Constant (FTC), in CMR, 22.5 Fast-wave tube, 10.3 Ferrite phase shifters, 13.52 to 13.53 Fighter aircraft missions, 5.10 to 5.16
I_6
Filter-bank design, 2.52 to 2.59 Filter mismatch loss, in MTI, 2.22 to 2.23 Filters, in radar, 6.24 to 6.29 Finite impulse response (FIR) filters, 2.33, 25.26 to 25.28 FM-CW radar, 1.5, 9.20 Focused SAR, 17.2 Foliage-penetration (FOPEN) SAR, 17.33 to 17.34 Fog, attenuation in, 19.12 Forward scatter, in bistatic radar, 23.21 Fourier transform, 8.38 Frank codes, 8.19 to 8.20 Free-space propagation, 26.13 to 26.15 Frequency agility, 1.9, 24.31 Frequency diversity, 1.9, 24.31 Frequency, effect on radar, 1.14 to 1.18 Frequency multipliers, 6.49 to 6.50 Frequency synthesis, 6.21 to 6.22 Front end, of receiver, 6.10 to 6.14
G GaAs PHEMT FET, 11.12 to 11.16 Geometrical optics, 14.20 to 14.21 and ground echo, 16.8 reflector analysis, 12.33 Geometric theory of diffraction, 14.24 to 14.25 Geosat, 18.41 to 18.42 Ghosts, 2.88, 4.33, 14.35 Glint in bistatic radar, 23.20 to 23.21 in tracking radar, 9.30 to 9.35 Global Nearest Neighbor (GNN), 7.39 to 7.40 Graceful degradation, 13.4 Graded absorber, 14.37 Grating lobes, 13.10 to 13.12 Gregorian antenna, 12.21, 12.25 Gregorian system, 14.33 to 14.34 Grid-controlled vacuum tubes, 10.21 to 10.23, 10.25 Grid locking, 7.49 Ground echo available information from, 16.4 bistatic, 16.29 fading of, 16.12 to 16.19 at HF, 20.29 to 20.30 imaging radar interpretation, 16.55 to 16.56 at low grazing angle, 16.52 to 16.55 measurement techniques for, 16.19 to 16.29 in meteorological radar, 19.13 to 19.14 models for scattering coefficient, 16.29 to 16.34 near-grazing angle, 16.52 to 16.55 near-vertical, 16.25 number of independent samples, 16.24 parameters affecting, 16.4 to 16.7 polarimetry, 16.46 to 16.52 scattering coefficient data, 16.35 to 16.46 scattering coefficients from radar images, 16.28 to 16.29 sea ice, 16.44 to 16.46 snow, 16.42 to 16.44 soil moisture, 16.40 to 16.41 speckle, 16.55 theoretical models, 16.7 to 16.12 vegetation, 16.41 Ground moving target indication (GMTI), 5.38 to 5.42, 17.25 Ground moving target thresholding, 5.39 to 5.40
Ground moving target track (GMTT), 5.38 Ground moving target weapon delivery, 5.40 to 5.41 Ground penetrating radar (GPR) antennas, 21.24 to 21.30 applications of, 21.3, 21.35 to 21.40 archeological applications, 21.36 and land mines, 21.37 AT mines, 21.34, 21.39 attenuation with, 21.7 to 21.9 bandwidth, 21.1 characteristics of, 21.4 clutter in, 21.5, 21.10 comparison with optical image, 21.4 depth resolution, 21.11 description of, 21.1 to 21.6 dispersion in, 21.11 earth material properties, 21.18 to 21.19 example of, 21.2 forensic investigations, 21.35 and frequency domain, 21.23 and glacier, 21.37 image processing, 21.30 to 21.35 licensing of, 21.39 to 21.40 modeling of, 21.13 to 21.18 modulation techniques, 21.21 to 21.24
I_7
polarization, 21.10 to 21.11 propagation, 21.6 to 21.13 reflections in, 21.9 to 21.10 resolution, 21.13 road thickness measurement, 21.37 to 21.38 and SAR, 21.13 signal processing, 21.30 to 21.35 soil suitability map, 21.20 from space, 18.59 to 18.62 systems, 21.20 to 21.21 velocity of propagation, 21.11 Ground plane, 14.31 Guard blanking loss, 4.44 Guard channel, in pulse doppler, 4.19 to 4.22 Gyrotrons, 10.3, 10.17 to 10.19, 10.26
H Hail, attenuation in, 19.11 to 19.12 Hail, detection of, 19.31 Height measurement, with InSAR, 17.30 to 17.33 Height measurement, with SAR, 17.27 to 17.33 HF, 1.15 HF over-the-horizon radar. See over-the-horizon radar High-medium PRF, 4.7 High-PRF pulse doppler, 4.7 to 4.8 High-PRF range-while-search, 4.36 High-PRF ranging, in pulse doppler, 4.34 to 4.35 High-resolution radar, 1.5 Hilbert transform, 6.43 to 6.44 HJ-1-C SAR, 18.13 Hot clutter, 24.43 Hybrid models for propagation, 26.16 to 26.17 Hybrid processors, 25.37
I Identification friend or foe (IFF), integration with radar, 7.50 I/Q channels, 6.31 to 6.35 Image-reject mixer, 6.13 Imaging radar ground echo, 16.55 to 16.56 Improvement factor, for AMTI, 3.8 Improvement factor limitations caused by staggering, 2.42 to 2.44 Improvement factor, for MTI, 2.19 to 2.20, 2.23 to 2.25, 6.17 to 6.18 Inductive output tube, 10.22 Infinite impulse response (IIR) filters, 2.33, 25.26 to 25.27 Insets, radar cross section of, 14.11 to 14.12 Instabilities in MTI, 2.65, 2.73 Instability limitations in MTI, 2.72 Instantaneous bandwidth, 6.9 Interclutter visibility in MTI, 2.22 Interacting multiple model (IMM) in ADT, 7.35 to 7.37 Interferometric SAR (InSAR), 17.5, 17.23 to 17.24 target height measurement, 17.30 to 17.33 International Maritime Organization (IMO), 22.1, 22.4, 22.8, 22.27, 22.28, 22.32 Interpolation filters, 25.28 Inverse Cassegrain, 9.25 Inverse SAR (ISAR), 5.23 to 5.24, 5.31 to 5.33, 9.37, 17.5 and ECCM, 24.51 to 24.52 Ionogram, 20.16 to 20.17 Ionosphere, 20.13 to 20.21 Ionospheric models, 20.19 to 20.20 Isodoppler contours in bistatic radar, 23.16
J Jamming, 5.27, 24.5 Jaumann absorber, 14.36 to 14.37 J-ERS SAR, 18.9 Jet-engine modulation, 5.23 JianBing-5 SAR, 18.12 Jindalee OTH radar, 20.3, 20.22 performance model, 20.67 to 20.70 Joint STARS, 13.66 to 13.67, 17.23 to 17.24 JORN OTH, 20.12, 20.19
K K band, 1.17 Kalman filter, 7.28 to 7.35 Klystrode, 10.22 Klystron, 10.5 to 10.8, 10.26 origin of, 10.2 to 10.3
L L band, 1.16 Land clutter. See ground echo Laser radar, 1.18
I_8
Letter-band nomenclature, 1.13 to 1.14 Lewis and Kretschmer codes, 8.20 to 8.22 Limiters, 6.29 to 6.31 Line-type modulator, 10.23 Linear array antenna, 13.11 to 13.13 Linear-beam vacuum tube, 10.3 Linear-beam amplifier, 10.4 to 10.13 Linear FM pulse compression, 8.3 to 8.11 Liquid crystal display, for CMR, 22.19 Lobing, in elevation, 22.6 to 22.7 Local oscillator, 6.14 to 6.22 Low-earth orbit, 18.2 Low grazing-angle clutter measurements, 16.52 to 16.55 Low-noise amplifier, 6.10 Low radar cross section ships 14.42 to 14.43 vehicles, 14.39 to 14.43 Low-sidelobe antenna, 24.10 to 14.11
M Madre HF OTH radar, 20.24 to 20.45 Magellan Venus mapper, 18.48 to 18.52 Magnetron, 10.2, 10.14 to 10.16, 10.26 for civil marine radar, 10.16, 22.12 Main-beam cancellation, 24.33 MAPSAR, 18.14 to 18.15 Marcum Q-function, 24.22 Marine boundary layer, 26.12 Matched filter, 1.3, 6.25, 8.39 to 8.40 loss in pulse doppler, 4.40 Maximal-length sequences, 8.18 Maxwell’s equations, 14.17 Mechanical design of antenna, 12.35 to 12.41 Medium PRF for air-to-air mode, 5.16 to 5.20 Medium PRF for pulse doppler, 4.8 Medium PRF for range while search, 4.37 to 4.38 Medium PRF selection algorithms, 5.18 to 5.20 Metal plate, radar cross section of, 14.8 to 14.9 Meteor trails, and HF OTH radar, 20.38 to 20.40 Meteorological radar airborne, 19.37 to 19.38 attenuation effects, 19.7 to 19.12 calibration, 19.18 to 19.19 design considerations, 19.6 to 19.19 ground clutter effects, 19.13 to 19.14 measurement accuracy, 19.22 to 19.23 microbursts, 19.29 to 19.31 MTI filter design for, 2.46 to 2.51 multiple radars, 19.33 to 19.35 operational applications, 19.25 to 19.33 phased array, 19.35 to 19.37 polarization, 19.18, 19.27 to 19.28, 19.33 precipitation measurement, 19.26 to 19.28 processor implementation. 19.24 to 19.25 pulse compression, 19.23 to 19.24 pulse-pair algorithm, 19.21 range and velocity ambiguities, 19.12 to 19.13 research applications, 19.33 to 19.40 severe storm warning, 19.28 to 19.33 signal processing, 19.19 to 19.25 spaceborne, 19.38 to 19.39 spaced antenna techniques, 19.40 spectrum moment estimation, 19.20 to 19.21
typical designs, 19.14 to 19.18 whitening filter, 19.24 wind profiler, 19.39 to 19.40 Method of moments, 14.1, 14.18 to 14.19 MFAR. See Multifunctional Fighter Aircraft Radar Microbursts, 19.29 to 19.31 Microwaves, 1.1, 1.14 Microwave monolithic integrated circuits (MMIC) characteristics of, 11.24 to 11.29 power amplifiers, 11.26 low-noise amplifiers, 11.26 phase shifters, 11.27 to 11.29 transmit/receive switching, 11.27 Microwave power module (MPM), 10.13 Military radar, 1.20 Millimeter waves, 1.14, 1.17 to 1.18 Mirror-scanned antenna, 9.25 Missile guidance performance assessment, 5.42 Missile-range instrumentation radar, 9.2 Mixer, image-reject, 6.13 Mixers, performance parameters, 6.14 Mixers, spurious response of, 6.11 to 6.13 MMIC. See Microwave monolithic integrated circuits
I_9
Modeling, of propagation, 26.13 to 26.17 Modified generalized sign test processor, 7.17 to 7.19 Modulators, 10.23 to 10.25 Monopulse-antenna feed techniques, 9.6 to 9.10 Monopulse antenna feeds, 12.26 to 12.28 Monopulse, dual band, 9.24 to 9.25 Monopulse, and ECM, 24.23 to 24.24, 24.42 to 24.43 Monopulse, phased arrays, 13.4 Monopulse tracking, 9.3 to 9.16 Moving Target Indication (MTI), 1.5, 4.2 A/D converter effect on dynamic range, 2.78 to 2.80 adaptive, 2.80 to 2.83 binomial weight cancelers, 2.35 and birds as clutter, 2.85, 2.87 to 2.88, 2.96 to 2.98 blind speeds, 2.9 to 2.10 block diagram, 2.4 to 2.7 canonical filter design, 2.34 clutter attenuation (CA), 2.20 to 2.21 clutter characteristics, 2.10 to 2.19 clutter filter-bank design, 2.52 to 2.59 clutter filter response, 2.9 to 2.10 clutter maps, 2.83 to 2.87 clutter visibility factor (Voc), 2.23 definitions, 2.19 to 2.23 dynamic range, 2.78 to 2.80 environmental considerations, 2.94 to 2.100 feedforward canceler, 2.39 filter design, 2.25 to 2.46 filter design for weather radar, 2.46 to 2.51 filter mismatch loss, 2.22 to 2.23 hardware considerations, 2.92 to 2.94 improvement factor, 2.19 to 2.20, 2.23 to 2.25, 6.17 to 6.18 interclutter visibility (ICV), 2.22 limitation due to scanning, 2.23, 2.38 limiting in receiver, 2.59 to 2.65 one-delay canceler, 2.35 optimum clutter filter design, 2.25 to 2.33 performance degradation due to limiting, 2.59 to 2.65 pulse compression considerations, 2.75 to 2.78 purpose of, 2.2 radial velocity ambiguity resolution, 2.89 to 2.91 range ambiguity resolution, 2.89 to 2.91 rules for, 2.92 to 2.94 in SAR, 17.23 and STC, 2.96 to 2.98 sensitivity velocity control (SVC), 2.87 to 2.91, 2.99 to 2.100 signal-to-clutter ratio improvement (ISCR), 2.21 to 2.22 stability requirements, 2.65 to 2.78 staggered PRF design, 2.39 to 2.46 subclutter visibility (SCV), 2.6, 2.22 superclutter visibility, 2.84 three-delay canceler, 2.37 two-delay canceler, 2.36 unwanted targets, removal of, 2.96 to 2.100 Moving targets, in SAR, 17.23 to 17.27 Moving Target Detection (MTD), 2.6 to 2.9 block diagram, 2.6 to 2.7 ducted propagation, effect of, 2.95 Moving-window detector, 7.4 to 7.7 MTBF, of klystrons, 10.6 to 10.7 Multi-beam digital beamforming, 25.17 to 25.19 Multifunction radar, 1.7, 13.1 Multifunctional Fighter Aircraft Radar (MFAR), 5.2 to 5.7 processing, 5.5 range-doppler situation in, 5.7 to 5.8
software structure, 5.6 to 5.7 Multipath, 26.4 to 26.5 in tracking radar, 9.37 to 9.40, 9.46 to 9.47 Multiple-beam klystron, 10.7 to 10.8 Multiple hypothesis algorithm in track association, 7.40 to 7.41 Multiple Object Tracking Radar (MOTR), 9.2, 9.26 Multiple reflector antenna, 12.21 to 12.24 Multiple scattering in target recognition, 14.35 Multiplicative noise, 4.28, 18.18 in SAR, 17.17 to 17.18
N NCAR dual band radar, 19.17 Networked radar, 7.46 to 7.49
I_10
Nexrad (WSR-88D) weather radar, 19.1, 19.16 to 19.17 automated weather products, 19.25 Noise, in receiver, 6.4 to 6.5 Noise, in tracking, 9.27 to 9.30 Noncooperative air target recognition, 5.22 to 5.24 Nonlinear FM pulse compression, 8.12 to 8.16 Nonparametric detectors, 7.17 to 7.18 Nonspecular absorbers, 14.38 nth-time-around tracking, 9.24 Nyquist, 25.2, 25.4 to 25.6
O Ogive, radar cross section of, 14.7 to 14.8 On-axis tracking 9.25 to 9.26 Operating bandwidth, 6.9 Optics region, 14.5 to 14.6 Optimal detection, 7.2 to 7.4 Orographic rain, 19.26 Oscillator vs. amplifier transmitter, 10.4 Ovals of Cassini, 23.6 to 23.8 Over-the-horizon radar antennas for, 20.24 to 20.26, 20.45 to 20.46 calibration, 20.48 to 20.49 clutter, 20.29 to 20.33 coherent processing for, 20.6 compared to microwave radar, 20.7 to 20.10 doppler spectrum of the sea, 20.49 to 20.52 and ECCM, 24.52 to 24.53 examples of, 20.11 to 20.12 external noise in, 20.40 and meteor trails, 20.38 to 20.40 noise models, 20.43 to 20.45 oceanography, 20.33 to 20.38 performance modeling, 20.55 to 20.70 propagation factor, 20.6 to 20.7 radar cross section, 20.26 to 20.29 radar equation, 20.5 to 20.7 receiving system, 20.45 to 20.49 resource management, 20.54 to 20.55 revisit times, 20.4 to 20.5 signal processing, 20.49 to 20.54 sky wave radar design, 20.8 to 20.13 spectrum occupancy, 20.40 to 20.45 surface-wave radar, 20.70 to 20.76 tracking, 20.53 to 20.54 transmitters, 20.23 to 20.26 waveforms, 20.21 to 20.23
P PALSAR, 18.11, 18.15 to 18.16 Parabolic cylinder antenna, 12.18 to 12.19 Parabolic equation methods, for propagation, 26.16 Parabolic reflector antenna, 12.17 to 12.18 Passive bistatic radar, 23.29 Passive ECM, 24.5 to 24.6 Passive listening, 5.34 Patriot radar, 13.66 to 13.67 Pave Paws radar, 11.31 to 11.32 Penetration aids accompanying ballistic missiles, 24.6 Phase-comparison monopulse, 9.11 to 9.12 Phase instabilities, 2.66 to 2.70
Phase noise in pulse doppler, 4.28 to 4.30 Phase shifters, 13.51 to 13.53 Phased array radar active aperture, 13.53 to 13.55 antennas, 13.2 to 13.3 AN/SPY-1, 13.62 AN/SPY-3, 13.69 aperture matching, 13.20 array simulator for, 13.25 to 13.26 bandwidth of, 13.38 to 13.45 beam switching, 13.8 calibration of active arrays, 13.60 to 13.62 circular polarization, 13.6 constrained feed, 13.46 Counter Battery Radar (COBRA), 13.62 digital beamforming, 13.56 to 13.57 diode phase shifters, 13.51 to 13.52 and ECM, 24.43 to 24.48 element pattern, 13.22 to 13.23 errors in, 13.30 to 13.38 feed networks, 13.46 to 13.50 ferrite phase shifters, 13.52 to 13.53 frequency scan, 13.7 to 13.8 gain, 13.13 to 13.15 grating lobes, 13.10 to 13.12, 13.17 to 13.19 ground-based, 13.63 to 13.65 illumination functions, 13.28 to 13.29 instantaneous bandwidth, 13.42 to 13.45 limited scan, 13.6 to 13.7
I_11
linear array, 13.11 to 13.13 low sidelobes, 13.28 to 13.33 meteorological, 19.35 to 19.37 monitoring of, 13.4 to 13.5 monopulse tracking, 9.12 to 9.13, 13.4 multifunction, 13.1 mutual coupling, 13.20 to 13.22 optical feed, 13.46 parallel feed, 13.48 to 13.49 periodic errors in, 13.35 to 13.38 phase-only control, 13.58 phase quantization, 13.34 phase shifters, 13.51 to 13.53 planar array, 13.15 to 13.19 radiation pattern nulling, 13.57 to 13.60 scanning, 13.7 to 13.9 series feed, 13.47 to 13.48 simultaneous receive beams, 13.54 to 13.56 small arrays, 13.27 solid-state modules for, 13.53 to 13.54 solid-state transmitter for, 11.24 to 11.31 subarrays, 13.43 to 13.44, 13.49 to 13.50 surface waves and mutual coupling, 13.24 to 13.45 Taylor illumination, 13.29 thinned arrays, 13.23 to 13.24 3D search, 13.4 theory, 13.9 to 13.15 time-delay networks, 13.44 to 13.45 time-delay scanning, 13.7 tracking with, 7.46 Volume Search Radar (VSR), 13.62 to 13.63 wide bandwidth operation, 13.6 Phase shift in DSP, 25.22 to 25.25 Physical optics, 14.21 to 14.24 and ground echo, 16.9 to 16.10 reflector analysis, 12.31 to 12.33 Physical theory of diffraction, 14.25 to 14.26 Pilotage and CMR, 27.31 Pioneer Venus, 18.44 Planar array, 13.15 to 13.19 Planetary radars, 18.43 to 18.53 atmospheric sounding, 18.62 to 18.63 Cassini, 18.46 Clementine, 18.46 to 18.47 cloud profiling, 18.63 flight systems, 18.43, 18.56 to 18.58 ice exploration, 18.47 to 18.48 ionospheric sounding, 18.62 Magellan, 18.45 to 18.46, 18.48 to 18.52 polarization, 18.52 rainfall measurement, 18.62 scatterometers, 18.53 to 18.58 sounders, 18.59 to 18.63 table of, 18.44 Venera, 18.43 to 18.45 Plasma frequency, 20.2 Platform motion, in AMTI, 3.3 to 3.14 compensation abeam, 3.10 to 3.14 forward direction, 3.21 to 3.23 and scan compensation, 3.18 to 3.21 P(n,k) polyphase codes, 8.22 to 8.24 Point-clutter scatterers, 2.18 to 2.19 Polarimetric SAR, 17.22 Polarization and ground echo, 16.46 to 16.52
in ground penetrating radar, 21.10 to 21.11 in meteorological radar, 19.18 for planetary radar, 18.52 Polarization-twist reflector, 12.23 Polyphase codes, 8.19 to 8.24 Power-aperture product, 10.1 Power supply, for AESA, 5.10 Practical detectors, 7.4 to 7.11 Precipitation measurement, 19.26 to 19.28 Precision velocity update, 5.33 to 5.34 Probabilistic data association, 7.39 to 7.40 Probability of detection, in pulse doppler, 4.46 to 4.48 Probability of false alarm, in pulse doppler, 4.44 to 4.46 Propagation, anomalous, 26.6 to 26.13 Propagation factor, 26.1 Propagation, in free space, 26.13 to 26.15 Propagation loss, 4.40 Propagation modeling, 26.13 to 26.17 Propagation, standard, 26.4 to 26.6 Pseudo coherent radar, 6.20 Pulse chasing in bistatic radar, 23.28 to 23.29 Pulse compression block diagram, 8.1 to 8.2 comparison of various waveforms, 8.27 digital, 25.19 and ECCM, 24.34 to 24.35 examples of, 8.30 to 8.36 factors affecting choice of, 8.26 to 8.27
I_12
Pulse compression (cont.) implementation of, 8.28 to 8.30 linear FM, 8.3 to 8.11 in meteorological radar, 19.23 to 19.24 and MTI, 2.75 to 2.78 nonlinear FM, 8.12 to 8.16 phase coded, 8.16 to 8.24 radar, 1.5 range sidelobes, 6.29 SAW devices for, 8.10 to 8.11 signal analysis definitions, 8.36 to 8.37 stretch, 8.31 to 8.36 time-frequency coded, 8.25 to 8.26 waveforms, 8.2 to 8.26 Pulse doppler antenna, 4.12 to 4.13 applications, 4.2 to 4.3 basic configuration, 4.10 to 4.14 block diagram, 4.11 clutter, 4.14 to 4.24 clutter-limited detection, 4.48 doppler ambiguity resolution, 4.33 to 4.34 dynamic range, 4.24 to 4.27 high-PRF ranging, 4.34 to 4.35 losses in, 4.39 nomenclature, 4.1 to 4.2 probability of detection, 4.46 to 4.48 probability of false alarm, 4.44 to 4.46 range ambiguity resolution, 4.31 to 4.33 range performance, 4.39 to 4.48 search mode, 4.36 to 4.38 spectrum, 4.4 to 4.6 stability requirements, 4.27 to 4.31 timeline definitions, 4.9 to 4.10 track mode, 4.38 to 4.39 Pulse-pair algorithm for meteorological radar, 19.21 Pulse repetition frequency and ambiguities in pulse doppler, 4.6 to 4.10 and doppler, 4.2 to 4.4 for SAR, 17.13 to 17.15 Pyramidal absorber, 14.37 to 14.38
Q Quadraphase codes, 8.24 Quantization noise, affect on MTI, 2.73 to 2.74
R Racons, and CMR, 22.26 to 22.27 Radar applications of, 1.20 to 1.22 bandwidth in, 1.8 to 1.9 basic parts of, 1.2 beacons, in CMR, 22.25 blinking for ECCM, 24.37 block diagram, 1.3 in brief, 1.1 conceptual system design, 1.22 to 1.23 cross section of aircraft, 14.13 to 14.14 approximate methods, 14.19 to 14.27 approximations for simple scatterers, 14.10
basic echo mechanisms, 14.2 to 14.4 of birds, 14.11 bistatic, 23.19 to 23.21 of bodies of revolution, 14.39 to 14.40 characteristics, 14.5 to 14.16 of complex objects, 14.11 to 14.16 of a corner reflector, 14.9 to 14.11 definition of, 14.4 to 14.5 exact methods, 14.16 to 14.19 at HF, 20.26 to 20.29 general, for various target types, 14.16 of insects, 14.11 to 14.12 of a man, 14.11 to 14.12 measurement ranges, 14.30 to 14.35 measurement techniques, 14.27 to 14.35 of a metal plate, 14.8 to 14.9 of an ogive, 14.7 to 14.8 prediction techniques, 14.16 to 14.27 of ships, 14.13 to 14.15 of a short wire dipole, 14.7 of a sphere, 14.5 to 14.6 of string, 14.6, 14.7, 14.29 and surface traveling waves, 14.7 of target support, 14.29 to 14.30 doppler shift in, 1.10 echo suppression, 14.36 to 14.43 in A-12, 14.40 in B-2, 14.42 in F-117, 14.40 to 14.42 in SR-71, 14.39 to 14.41 in X-45C, 14.42 to 14.43 by absorbers, 14.36 to 14.38
I_13
by shaping, 14.36, 14.38 to 14.39 in ships, 14.42 to 14.43 equation, 1.10 to 1.13 bistatic, 23.4 to 23.6 and chaff, 24.55 to 24.56 in conceptual design, 1.23 ground penetrating radar, 21.8 to 21.9 HF over-the-horizon, 20.5 to 20.7 and jamming, 24.55 for meteorological targets, 19.3 to 19.6 surveillance, 3.1 frequency bands, 1.13 to 1.14 hole, in propagation, 26.9 information from, 1.7 to 1.10 letter-band nomenclature, 1.13 to 1.14 multifunction, for fighter aircraft, 5.1 to 5.10 networked, 7.46 to 7.49 nomenclature, 1.18 to 1.19 oceanography at HF, 20.30 to 20.38 past advances in, 1.19 to 1.20 reflectivity, 19.3 reflectivity factor, Z, 19.4 scheduling and control, 7.46 types of, 1.5 to 1.7 warning receiver (RWR), 24.4 to 24.5 work station, 24.55 to 24.56 RADARS AT, 18.9 to 18.10 Radial velocity, 1.7 Radiating elements, 13.5 to 13.6 Radomes, 12.39 to 12.41 Radome loss, 4.40 Rain, attenuation by, 19.8 to 19.11 Rain, detection of, 19.3 to 19.6 RAMP air traffic control radar, 11.33 to 11.34 Range, as used in radar, 1.2, 1.7 Range ambiguities, in meteorological radar, 19.12 to 19.13 ambiguity resolution in pulse doppler, 4.31 to 4.33 and doppler, in MFAR, 5.7 to 5.8 error, in tracking radar, 9.43 to 9.44 filter map in sidelobe blanking, 24.13 to 24.14 -gate pull-off, 24.6, 24.44 -gate straddle loss, 4.40 to 4.43 -gated high PRF (RGHPRF), 5.20 to 5.22 gates, 4.2 gating in pulse doppler, 4.9 glint, 9.35 to 9.36, 9.47 noise, 9.35 to 9.36 sidelobes, 6.29 tracking, 9.21 to 9.24 Rank detector, 7.17 Rapid Doppler on Wheels (Rapid-DOW) 19.36 to 19.37 Ratio detector, 7.13 to 7.14 Rayleigh region, 14.5, 19.3 to 19.4 Rayleigh scattering, 14.19 to 14.20 Ray tracing, 20.20 to 20.21 Receiver, 1.3 analog-to-digital converter, 6.35 to 6.40 bandwidth, 6.9 channel matching, 6.29 COHO, 6.20 configuration of, 6.1 to 6.4 digital, 6.40 to 6.46 diplex operation, 6.46 to 6.47 dynamic range, 6.4 to 6.8
effect on radiated signal, 6.11 exciter, 6.47 filtering, 6.24 to 6.29 front end, 6.10 to 6.14 gain control of, 6.22 to 6.24 instability, 6.20 to 6.21 I/Q channels, 6.31 to 6.35 limiter, 6.29 to 6.31 local oscillator, 6.14 to 6.22 multi-channel, 6.45 to 6.46 noise, 6.4 to 6.5 and tracking accuracy, 9.42 spurious response, 6.11 to 6.12 STALO, 6.14 to 6.20 upconversion, 6.47 to 6.50 waveform generation, 6.47 to 6.50 Receiver-related ECCM, 24.32 to 24.33 Reentrant structures and cross section, 14.3 Reflectivity, 19.3 Reflectivity factor, Z, 19.4 Reflector antenna analysis, 12.31 to 12.35 applications of, 12.1 to 12.2 architecture, 12.16 to 12.25 array feeds for, 12.28 to 12.30 basic principles of, 12.3 to 12.15 environmental factors, 12.39 feed blockage, 12.6 to 12.8
I_14
Reflector antenna (cont.) feed displacement, 12.14 feeds for, 12.25 to 12.30 gain optimization, 12.8 to 12.10 mechanical design, 12.35 to 12.41 radomes for, 12.39 to 12.41 role in radar, 12.1 spillover loss, 12.6 strut blockage, 12.14 to 12.15 surface ace of, 12.10 to 12.14 surface roughness loss, 12.12 to 12.14 types of, 12.2 Refraction, 14.20, 26.3 to 26.4 Refractivity, 26.3 to 26.4 Refractivity measurements, 19.32 to 19.33 Region of uncertainty (ROU) in target tracking, 7.47 to 7.48 Remote sensing of the environment, 1.21 Remote sensing, with SBR, 18.11 Repeater jammer, 24.6 Resolution, in GPR, 21.11 to 21.13 Resonance region, 14.5 RF receive loss, 4.40 RF transmit loss, 4.40 RGHPRF (Range Gated High PRF) algorithm, 5.22 Ricker wavelet, 21.11, 21.21 RIS AT SAR, 18.14 River radar, 22.9 ROTHR, 20.3
S S-193 altimeter, 18.33 S band, 1.16 Salisbury screen, 14.36 Sampled signal spectrum, 25.3 to 25.5 Sampling period in phased arrays, 24.45 Sampling receiver, 21.23 SAR-Lupe radar, 18.13 to 18.14 SARTs (Search and Rescue Transponders), 22.27 SAW delay line for pulse compression, 8.10 to 8.11 Scan compensation, and platform motion, 3.18 to 3.21 Scan SAR, 18.12 to 18.13, 18.24 Scatterer, 14.4 Scatterometers, 16.19 to 16.24, 16.26 to 16.28 space based, 18.53 to 18.58 table of, 18.56 wind measurement, 18.54 to 18.55 Sea clutter Bragg scatter, 15.28 to 15.32, 15.38 breaking waves, 15.6 to 15.7 composite-surf ace model, 15.30 to 15.32 contaminants, effect of, 15.26 to 15.27 and ducting, 15.24 to 15.25 empirical behavior of, 15.7 to 15.27 as a global boundary-value problem, 15.27 to 15.32 at HF, 15.19, 20.30 to 20.33 at high grazing angles, 15.16 at low grazing angles, 15.16 to 15.18 at millimeter waves, 15.20 numerical methods for, 15.36 rain, effect of, 15.23 to 15.24 sea spikes, 15.2, 15.16 to 15.17, 15.35 shadowing, effect of, 15.25 sigma zero definition, 15.7
spectrum, 15.20 to 15.23 statistics, 15.8 to 15.9 surface currents, effect of, 15.25 to 15.26 surface features, 15.33 to 15.34 theories of, 15.27 to 15.37 wind speed and direction, 15.12 to 15.16 Sea descriptors, general, 15.5 to 15.6 Sea echo. See sea clutter Sea ice, 16.44 to 16.46, 16.48, 22.14 Sea spikes, 15.2, 15.16 to 15.17, 15.35 Sea state, 15.6, 22.14 Sea surface, 15.3 Sea surface search, 5.30 to 5.31 Seawinds scatterometer, 18.58 Sensitivity time control (STC), 2.96 to 2.98, 6.22 to 6.24, 19.6 in CMR, 22.5, 22.13 and cosecant-squared antenna, 2.98 in pulse doppler, 4.22 Sensitivity velocity control (SVC), 2.87 to 2.91, 2.99 to 2.100 Sensor integration, other than radar, 7.49 to 7.54 Senrad broadband radar, 24.31 Sequential lobing, 9.16 to 9.17 Servosystems, for tracking radar, 9.17 to 9.19 Shaped pulses for transmitter, 10.19 to 10.20 Shaped reflector antennas, 12.19 to 12.20
I_15
Shaping, for radar cross-section reduction, 14.38 to 14.39 Ship, radar cross section, 14.13 to 14.15 Ships, low cross section, 14.42 to 14.43 Sidelooking airborne radar (SLAR), 1.6 17.3 Sidelobe blanking (SLB), 24.11 to 24.14 Sidelobe canceler, 24.14 to 24.20 Sigma zero (for clutter echo), 15.7, 16.1 to 16.3 Signal-to-clutter ratio improvement, 2.21 to 2.22 Signal-to-noise ratio, 1.9 in SAR, 17.16 to 17.17 Signal processing, and ECCM, 24.33 to 24.36 Signal processing, for meteorological radar, 19.19 to 19.25 Signal processor, 1.3 Signal sampling, 25.15 to 25.16 Silicon bipolar junction transistor, 11.10 to 11.11 Silicon LDMOS FET, 11.11 to 11.12 Silicon transistor capabilities, 11.13 Simultaneous lobing, 9.3 SIR-C, 16.46 SIR (spaceborne) SARs, 18.8 Skin depth, 21.8 Skip zone, 20.3 Sky wave OTH radar, 20.8 to 20.13 Slip-SAR, 18.14 Slow-wave tubes, 10.3 Sniff (or passive listening), 5.34 Snow, echo from, 16.42 to 16.44 Software structure, in MFAR, 5.6 to 5.7 Soil, dielectric properties of, 21.19 Soil moisture, effect on radar echo, 16.38, 16.40 to 16.41 Solar calibration of radar, 19.19 SOLAS (Safety of Life at Sea), 22.8 Solid-state advantages of, 11.1 to 11.5 amplifier, 10.4, 10.26 to 10.28 amplitude and phase sensitivities, 11.22 to 11.23 AN/SPS-40 transmitter, 11.32 to 11.33 class of (amplifier) operation, 11.18 to 11.20 devices, 11.5 to 11.17 examples of, 11.31 to 11.34 MMIC, 11.24 to 11.29 modulator, 11.24 to 11.25 modules, 13.53 to 13.54 Pave Paws radar, 11.31 to 11.32 performance capability, 11.2 phased array transmitter, 11.24 to 11.31 power combining, 11.20 to 11.22 power limitations, 11.8 to 11.10 RAMP radar, 11.33 to 11.34 spectral emissions, 11.23 transmit/receive modules, 11.29 to 11.31 Sounders, 18.59 to 18.63 Space-based radars (SBR) altimeters, 18.29 to 18.43 block diagram, 18.40 CryoSat, 18.42 to 18.43 flight systems, 18.33 to 18.37 Geosat, 18.41 to 18.42 orbit considerations, 18.37 to 18.38 overview, 18.30 to 18.31 precision, 18.31 theoretical foundations, 18.38 to 18.41 hardware, 18.4 to 18.5 meteorological, 19.38 to 19.39 planetary. See planetary radars
synthetic aperture radars (SAR), 18.5 to 18.29 ambiguities, 18.17 to 18.18 ambiguity limits, 18.22 to 18.24 antennas, 18.19 applications, 18.29 data products, 18.21 to 18.22 data rate, 18.20 design issues, 18.16 to 18.24 interferometry, 18.24 to 18.27 Kosmos, 18.8 list of, 18.6 to 18.7 multiple channels, 18.24 to 18.29 nadir, return from, 18.18 orbit characteristics, 18.2 to 18.4 polarimetry, 18.27 to 18.29 PRF constraints, 18.16 to 18.17 processing, 18.20 to 18.21 Quill (first space-based SAR), 18.6 ScanSAR, 18.12 to 18.13, 18.24 Seasat, 18.7 to 18.8 Shuttle Imaging Radar (SIR), 18.8 spotSAR 18.23 strip map, 18.23 transmitters, 18.19
I_16
Space-time adaptive processing (STAP), 3.23 to 3.31, 3.33, 5.2 to 5.3, 5.17, 24.21 to 24.22 in HF OTH radar, 20.53, 24.52 Spark-gap transmitter, 10.2 SPASUR, 23.2, 23.9, 23.11 to 23.13 Speckle, 16.55 Spectral characteristics of clutter, 2.11 to 2.16 Spectral noise in doppler radars, 10.20 to 10.21 Spectrometers, 16.20, 16.26 to 16.28 Spectrum, of pulse doppler radar, 4.4 to 4.6 Specular point, 14.20 to 14.21 Specular scatterers, 14.3 Sphere, radar cross section of, 14.5 to 14.6 Spherical reflector antenna, 12.24 to 12.25 Spotlight SAR, 17.4 to 17.5 SpotSAR, 18.12, 18.23 Spread-F region, 20.19 Spurious output, in transmitters, 10.19 Spurious response of mixers, 6.11 to 6.13 SR-71 low cross section aircraft, 14.39 to 14.41 Stability requirements in pulse doppler, 4.27 to 4.31 Stagger PRF design for MTI, 2.39 to 2.46 STALO, 6.3, 6.14 to 6.20 Standard atmosphere, 26.3 Stand-off jamming (SOJ), 24.43 to 24.44 Station keeping, airborne, 5.27 Stealth, 14.2, 14.36, 24.38 Stratiform rain, 19.26 Stretch pulse compression, 6.10, 6.22, 8.31 to 8.36 in SBR altimeter, 18.40 to 18.41 String, radar cross section of, 14.6 to 14.7 Strip map, 18.23 Stripmap SAR (or “strip” SAR), 17.3 to 17.4 Subarray adaptivity to ECM, 24.25 to 24.27 Subarrays, 13.43 to 13.44, 13.49 to 13.50 Subclutter visibility, in MTI, 2.22 Subrefraction, 26.6 Sudden ionospheric disturbance, 20.18 Sunspot number, 20.17 Superclutter visibility, 2.84 Superheterodyne, 6.1 Superrefraction, 26.7 Superresolution, 24.30 to 24.31 Surface discontinuities, and radar cross section, 14.3 Surface ducts, 26.10 to 26.11 Surface traveling-wave echoes, 14.36, 14.38 Surface ace-wave absorbers, 14.38 Surface winds, and HF radar, 20.37 to 20.38 Surveillance radar, 1.5 Surveillance radar equation, 1.12 Synthesizer, digital, 25.20 to 25.22 Synthetic aperture radar (SAR) autofocus, 17.15 basic principle of 17.1 burst mode, 18.23 to 18.24 clutterlock, 17.15 comparison with optical imaging, 17.18 to 17.21 comparison with real-aperture radar, 17.9 to 17.10 crossrange resolution, 17.7 to 17.8 design issues for SBR, 18.16 to 18.24 doppler beam sharpening, 5.34 to 5.36, 5.37, 17.2, 17.3 early history of, 17.2 and ECCM, 24.48 to 24.51 fast-time processing, 17.6 focused, 17.3 to 17.5 foliage penetration, 17.33 to 17.34
and ground penetrating radar, 21.4, 21.13 height measurement with, 17.27 to 17.23 image quality, 17.16 to 17.21 interferometric (InSAR), 17.5, 17.23 to 17.24, 17.30 to 17.33 inverse (ISAR), 5.23 to 5.24, 5.31 to 5.33, 9.37, 17.5, 24.51 to 24.52 Joint STARS, 17.23 to 17.24 key aspects of, 17.10 to 17.15 key equations, 17.21 to 17.22 motion compensation in, 17.12 moving targets in, 17.23 to 17.27 multiplicative noise ratio, 17.17 to 17.18 point-spread function, 17.16 polarimetric, 17.22 pulse repetition frequency requirements for, 17.13 to 17.15 range migration, 17.15 range resolution, 17.6 to 17.7 range and velocity contours, 17.10 to 17.12
I_17
resolution, 17.5 to 17.10 resolution (crossrange) examples, 17.5 to 17.6 shadows in, 17.28 signal-to-noise ratio, 17.16 to 17.17 slow-time processing, 17.6 for space applications, 18.5 to 18.29 specific aspects of, 17.22 to 17.34 spotlight, 17.4 to 17.5 squinted stripmap, 17.4 stereo, 17.29 to 17.30 stripmap, 17.3 to 17.4, 17.14 to 17.15 types of, 17.2 to 17.6 vibrating targets in, 17.25 to 17.27 unfocused, 17.3 Washington monument image, 17.18 to 17.21 System instabilities and MTI, 2.65 to 2.73 System noise, 6.5
T TACCAR, 3.4 to 3.9, 3.33 Target acquisition, in tracking radar, 9.20 to 9.21 Target caused errors in tracking, 9.26 to 9.37 Target cross section. See radar cross section Target noise, in tracking radar, 9.26 to 9.37 Target recognition, 1.7 cooperative, 5.22 to 5.23 noncooperative 5.22 to 5.24 Target resolution, in automatic detection, 7.19 to 7.20 Taylor weighting or illumination, 8.7 to 8.9, 13.29 TecSAR, 18.12 TEM horn, 21.27 to 21.30 Terminal Doppler Weather Radar (TDWR), 19.1, 19.30 to 19.31 MTI filter design for, 2.47 to 2.50 Terrain avoidance, 5.28 to 5.29 Terrain-bounce jamming, 24.43 Terrain database and radar, 5.30 Terrain following, 5.28 to 5.29 Terrain height estimation, 5.29 to 5.30 Terrain scattered interference, 24.43 TerraS AR-X, 18.12 Test ranges, indoor, 14.32 to 14.35 Test ranges, outdoor, 14.30 to 14.32 THAAD radar, 13.68 Thunderstorm prediction, 19.32 Time-delay scanning, 13.7 Time-frequency coded waveforms, 8.25 to 8.26 Topex altimeter parameters, 18.35 Tornado detection, 19.28 to 19.29 Towed decoy, 24.8 T/R module, 10.28 Track association, 7.38 to 7.41 Track file, 7.23 to 7.25 Tracking, automatic, 7.22 to 7.46 Tracking radar, 1.6 acquisition with, 9.20 to 9.21 automatic gain control (AGC), 9.33 to 9.35 conical scan, 9.16 to 9.17 dual band, 9.24 to 9.25 and ECCM, 24.43 error reduction techniques, 9.46 to 9.47 errors in, 9.26 to 9.46 external causes of error, 9.37 to 9.42 glint in, 9.30 to 9.35, 9.47
limitations in performance, 9.44 to 9.45 monopulse, 9.3 to 9.16 two-channel, 9.14 to 9.15 multipath error reduction, 9.46 to 9.47 nth-time-around tracking, 9.24 on-axis tracking, 9.25 to 9.26 range tracking in, 9.21 to 9.24 sequential lobing, 9.16 to 9.17 servosystems for, 9.17 to 9.19 sources of error in, 9.26 updating tracks, 7.26 to 7.30 TRAKX, dual band monopulse radar, 9.24 Transmit/receive module characteristics, 11.29 to 11.31 Transmit signal digital processing, 25.20 to 25.22 Transmitter-related ECCM, 24.31 to 23.32 Transmitters, 1.2, 1.4 clustered-cavity klystrons, 10.12 to 10.13 constant efficiency amplifier, 10.21 to 10.22, 10.26 crossed-field amplifiers (CFA), 10.16 to 10.17 extended interaction klystron (EIK), 10.11 grid-controlled tubes, 10.21 to 10.23, 10.25 gyrotrons, 10.17 to 10.19, 10.26 for HF OTH radar, 20.23 to 20.26 linear-beam amplifiers, 10.4 to 10.13
I_18
Transmitters (cont.) klystrons, 10.5 to 10.8, 10.26 multiple-beam, 10.7 to 10.8 magnetrons, 10.14 to 10.16, 10.26 microwave power module (MPM), 10.13 modulators for, 10.23 to 10.24 MTBF of tubes, 10.6 to 10.7, 10.10, 10.15, 10.16 oscillator vs. amplifier, 10.4 role in radar, 10.1 to 10.2 solid-state, 10.26 to 10.28. See also solid-state spectrum control, 10.19 to 10.21 traveling wave tube, 10.3, 10.8 to 10.10, 10.26 Twystron, 10.11 types of, 10.2 to 10.4 variants of klystrons and TWTs, 10.11 to 10.13 which type to use, 10.25 to 10.28 Transponder, 24.6 Trapping, in ducting, 26.7 Tropical Rainfall Measurement Mission (TRMM) SBR, 18.62, 19.39 Troposphere, 26.2 effect on tracking accuracy, 9.41 to 9.42
U UHF, 1.15 Ultralow sidelobes, 24.37 Ultrawideband (UWB), 21.1 Updating tracks, 7.26 to 7.30
V Velocity ambiguities, in meteorological radar, 19.12 to 19.13 Velocity-Azimuth-Display (VAD), 19.31 to 19.32 Velocity estimation, 19.22 Velocity of propagation, in GPR, 21.11 Velocity search, in pulse doppler, 4.36 Venera, 18.43 to 18.45 Vessel tracking service (VTS) radars, 22.1 Vessel tracking services, 22.29 to 22.31 VHF, 1.15 Vibrating targets, in SAR, 17.25 to 17.27 Volume Search Radar (VSR), 13.62 to 13.63
W Wake detection, 5.31 Warloc millimeter-weave radar, 10.18 Washington Monument SAR image, 17.18 to 17.21 Water vapor, attenuation in, 19.7 Water vapor measurement with radar, 19.32 to 19.33 Wave spectrum, of the ocean, 15.3 to 15.5 Waveform upconversion, 6.50 Waveguide models, for propagation, 26.15 to 26.26 Weather avoidance, with fighter radar, 5.24 Weather radar. See meteorological radar Wedgetail AEW radar, 3.3 Wide bandgap semiconductors, 11.15 to 11.17 Wind measurement, 19.31 to 19.32 Wind profiler, 19.39 to 19.40 WSR-88D (Nexrad), 19.1, 19.16 to 19.17
X X-45C low cross section unmanned combat aircraft, 14.42 to 14.43 X band, 1.17 X-Band Radar (XBR), 13.68 to 13.69
Z Z (radar reflectivity factor), 19.4 Ze (effective reflectivity factor), 19.6