Table Of ContentDesign of Multi-Frequency
CW Radars
M. Jankiraman
©2007 bySciTech PublishingInc.
Allrights reserved. No partofthis bookmay be reproduced or used in any
form whatsoeverwithoutwrittenpermissionexcept in the caseofbriefquotations
embodiedin critical articles and reviews. Forinformation, contactSciTech Publishing, Inc.
Printedin the U.S.A.
1098 76543 2 1
ISBN: 1891121561
ISBN13:9781891121562
SciTech President: DudleyR. Kay
ProductionDirector: SusanManning
ProductionCoordinator: RobertLawless
CoverDesign: KathyGagne
This bookisavailable atspecial quantitydiscounts to use aspremiums and
salespromotions, or for use in corporatetrainingprograms. Formoreinformation
and quotes, please contact:
DirectorofSpecial Sales
SciTech Publishing, Inc.
911 Paverstone Dr. - Ste. B
Raleigh, NC 27613
Phone: (919)847-2434
E-mail: [email protected]
http://www.scitechpub.com
LibraryofCongress Cataloging-in-PublicationData.
Jankiraman,Mohinder.
Designofmulti-frequencyCWradars/Me Jankiraman.
p. em,
ISBN-13: 978-1-891121-56-2 (hardcover: alk.paper)
ISBN-10: 1-891121-56-1 (hardcover: alk.paper)
1.Radar. I.Title.
TK6575.]352007
621.3848-dc22
2007015687
Preface
One ofthe great properties ofcontinuous wave (CW) radars is its ability to operate stealthily.
This propertylends itselfto designingthe so-calledlow probabilityofintercept(LPI) radars. In
suchradars, stealthisrealizedby bringingtogethermanypropertiesintoplay,such aslow power,
wide bandwidth, and frequency hoppingwhich make it extremely difficult for such radars to be
detected by means of a passive intercept receiver. Moreover CW radars, yield extremely high
resolutions realized easily in terms ofhardware and signalprocessing. However, an unmodulated
CWsignalcannotmeasureatarget'srange.Therefore,thetransmittedsignalneedsto beimparted
abandwidth.Thisisachievedthroughvariousmeanssuchasfrequencymodulation,phasecoding
and manyvariations ofthese. Adetailed analysis ofthesewaveforms and theirproperties anduse
in designingradars has received limited attentionin the literature aswell asthe methodologyof
designing such radars and the hardware considerations which go into it. Thus, the endeavor of
this bookis to impart aworkingknowledge ofthe subjectnotjustfor postgraduate students and
researchers butfor the entireradarcommunity.
It is assumed that the reader is familiar with basic digital signal processing, RF system
engineering, and probabilitytheory. The style ofwritinghas been kept assimple aspossible and
technical jargonhas been kept to aminimum. All efforthas beenmade to explain the basics in a
cogentand conversationalmanner.
The book is organized into three parts. This first part covers the basic CW radar theory.
The second partintroduces the reader into how this theoryis utilized in the design ofan actual
radar called Calypso. The third and final partdiscusses the theoryand design ofamore complex
multifrequency CW radar called the PANDORA. The PANDORA radar was born out ofthe
author's research work done at the International Research Centre for Telecommunications and
Radar (IRCTR) at the Delft University ofTechnology, in the Netherlands. This radar in fact
formed part ofthe author's Master thesis [1]. It is pointed out that to the best ofthe author's
knowledge andbelief, thisisthefirst timesucharadarhasbeendevelopedanywhere.ThePANDORA
radaryields extremelyhighresolutions evenfor CWradars andhas found manyapplications, the
first beingin its use as aground penetratingradar (GPR) for landmine detection, an area where
extremely high resolutions are vitally required. Moreover, the architecture ofthe PANDORA
radar is such that it can also be applied to pulsed radars and is not just confined to CWradars.
Hence, it isexpectedthatthis type ofradarwill find wide application.
The teaching effort in this book is aided by a set ofaccompanying software. This software is
distributed on the basis ofchapters and directlypertains to topics discussed in those chapters.The
entire codinghas been deliberatelykeptsimple and sometimes verylow-tech to enable readers to
clearlyunderstandthevarioussteps involvedin theimplementationoftheprogram.Thesoftwareis
averybasic one and thereaderisencouragedto experimentwithit and modifyit in anymannerto
suitone's convenience.Thisis an excellentmethod to learn the subject. The software presupposes
asound understandingofMATLAB® and has been tested on MATLAB®Version 6.0 (with Signal
ProcessingToolbox) and above. Some software has beenwrittenin C++ and can be run on any C
compilerlikeVisual C++asaconsoleapplication.Itispointedoutthatin atechnologyofthis nature
thebestwayto assimilate asubjectisbyprogramming. Codingan operationforces theuserto look
at allaspects ofthesubject.Thisissimilarto learningmathematicsthroughsolvingproblems.
Aconsistentsetofnotationshas beenusedthroughoutthebookandexcessivemathematicshas
beenavoided. Emphasisisplacedonimpartingaphysicalunderstandingofthesubjectso thatthe
readerhas acleargrasp oftheprocessesinvolved.
xiv Preface
Therewill be errorseventhougheveryefforthas beenmadeto detectand eliminatethem.Any
inconvenienceto thereadersasaresultisdeeplyregretted.Theauthorhas aweb site: http://www.
jankiraman.com/errata_radar.Thisweb site will be keptup to date basedonreaderinputs aswell
assoftware corrections.Thereaders are advised to visit this site from time to time.
Reference
1.Jankiraman,M.,PandoraMultifrequencyRadar-ProjectReport,IRCTR-S-O14-99,Delft,TheNetherlands,
April 1999.
Contents
Preface xii
Acknowledgments xiv
Part I: FundamentalsofCWRadar 1
Chapter 1 Frequency Modulated ContinuousWave Radar 2
1.1 FMCWRadar Characteristics 2
1.2 Range Equationfor FMCWRadar 3
1.3 InterceptRange ofFMCWRadar 7
1.4 CommercialFMCWRadars 8
1.4.1 The PILOTRadar 8
1.5 ExperimentalAir Search CWRadar 9
1.5.1 MiscellaneousUses ofLPIRadars 12
1.6 ASurveyofThis Book 12
Chapter 2 RadarWaveforms and Processing 16
2.1 Radar Signals 16
2.2 CWWaveform 17
2.3 Range Resolution 18
2.3.1 AmplitudeModulation 19
2.3.2 Frequencyand Phase Modulation 20
2.3.2.1 FrequencyModulated ContinuousWave 20
2.3.2.1.1 Derivationofthe Swept Bandwidth 21
2.3.2.1.2 Calculatingthe Range 22
2.3.2.1.3 Effect ofTargetMotion 22
2.3.2.1.4 FMCWGeneration and Reception 23
2.3.2.1.5 Problemswith FMCW 24
2.3.3 SteppedFrequencyWaveform 24
2.3.3.1 SFWGeneration and Reception 25
2.3.3.2 Problemswith SFWSignals 25
2.3.4 Phase-Coded Signal Compression 25
2.3.4.1 Phase-Coded Signal Generation and Reception 25
2.3.4.2 CorrelationDetectionofPhase-Coded Signals 27
2.3.5 Stretch 28
2.3.6 Interrupted FMCW 29
2.3.6.1 Disadvantages 29
2.3.6.2 Optimizingfor aLong-RangeImage Application 29
2.3.7 Side Lobes and Weightingfor LinearFM Systems 30
2.3.8 LinearFrequencyModulationWaveforms 34
2.4 MatchedFilter 37
2.4.1 StoringaReplica 40
Chapter 3 The RadarAmbiguity Function 41
3.1 Introduction 41
3.2 Examples ofAmbiguityFunctions 42
Contents ix
3.2.1 Single-FrequencyPulse 43
3.2.2 LinearFM Pulse 44
3.2.3 Stepped-FrequencyWaveform 44
3.2.4 Digital-CodedWaveforms 54
Chapter4 FMCWWaveform 55
4.1 Introduction 55
4.2 Waveform Compression 55
4.2.2Time-BandwidthProduct 56
4.2.3 LFMWaveform Compression 57
4.2.3.1 Correlationprocessor 58
4.2.3.2 StretchProcessor 60
4.3 FMCWSystem 68
4.4 Advantages ofan FMCWSystem 69
4.5 BasicEquations ofFMCWRadars 69
4.5.1 The FMCWEquation 70
4.6 TriangularWaveform 71
4.7 EffectofSweepTime on Range Resolution 72
4.8 EffectofReceiver FrequencyResolutionandTargetSpectralWidthon Range
Resolution 73
4.9 ConceptofInstrumentedRange 78
4.10 Nonlinearityin FM Waveforms 78
4.10.1 CoherentProcessingInterval 80
4.11 It AllComesTogether.Application: BrimstoneAntitankMissile 84
4.11.1 System Specifications 84
4.11.2 Seeker Specifications(Known) 85
4.11.3 OperationalProcedure (LOAL) 85
4.11.4 System Performance (Speculated) 87
4.12 Summary 96
Chapter5 Phase-CodedWaveform 97
5.1 Introduction 97
5.2 Phase-Coded Radar Signals 97
5.2.1 Barker Coding 97
5.2.2 FrankCodes 100
5.3 PeriodicAmbiguityFunction 104
5.4 PeriodicAutocorrelationFunction 107
5.5 Cuts ofPAFalong Delayand DopplerAxis 109
5.6 PAFand PACF ofFrankCodes 109
5.7 Matched Filterfor Phase-Coded Signals 110
5.8 Polyphase Codes 112
5.8.1 PI Codes 113
5.8.2 P2 Codes 114
5.8.3 P3 Codes 116
5.8.4 P4Codes 117
5.9 PerformanceAnalysisofPhase-Coded Signals 122
Contents x
Chapter 6 Frequency Hopped Waveform 128
6.1 Introduction 128
6.2 FrequencyHopped Signals asLPI Signals 128
6.3 SteppedFrequencyWaveform 129
6.3.1 Range Resolution and Range Ambiguity 132
6.3.2 Effect ofTargetVelocity 139
6.4 Random FrequencyHoppedWaveforms 141
6.5 Technologyfor SFCW 143
6.6 Hybrid FSKILFMTechnique 145
Part II: Theory and DesignofCalypsoFMCWRadar 153
Chapter 7 DesignApproach 154
7.1 Introduction 154
7.2 Calypso DesignParameters 155
7.3 DopplerTolerance 156
7.4 Beam Patterns/CoverageDiagram 157
7.5 FMCWDescription 158
7.6 Receiver Noise Figure 159
7.7 AM Noise Cancellation 159
7.8 FM Noise Cancellation 165
7.9 IF Amplifier 167
7.10 Anti-Alias FilterandADC 168
7.11 Control Circuitry 168
7.12 CalibrationandVerification 169
7.13 Image Reject Mixers 170
7.14 MovingTargetIndication 170
7.15 SingleAntenna Operation 173
7.15.1 Reflected PowerCanceller 174
7.15.1.1 Performanceofthe RPC 175
7.16 Ambiguous Returns 177
7.17 Performance ofCalypso FMCWRadar 180
7.18 Summary 180
Part III:Theory and Designof Pandora MultifrequencyRadar 183
Chapter 8 DesignApproach 184
8.1 BasicEquations ofFMCWRadars 184
8.2 QualitativeRequirements 184
8.2.1 ProblemDefinition 184
8.2.2 ProgramRequirements 185
8.2.3 Overall System Requirements 185
8.2.4 SpecificRadarRequirements 185
8.2.5 Assumed Parameters 185
8.2.6 CostingRequirements 186
8.3 ThePandoraRadarDescription 186
8.4 BasicEquations ofFMCWRadars 189
8.5 DesignApproach 189
8.5.1 Waveform Selection 190
8.6 Discussionon Sub-Systems 195
Contents xi
8.6.1 FMCWWaveformGenerator 195
8.6.2 PowerCombinerBlock 196
8.6.3 Wideband Low NoiseAmplifier 201
8.6.4 PowerResolver Block 201
8.6.5 Heterodyne Receiver and Range ResolutionProblem 202
8.6.6 NoncoherentProcessor 204
8.6.7 High-ResolutionFITor Channel FIT 205
8.6.8 Baseband Filters 206
8.6.9 StretchProcessing 207
8.7 The SamplingQuestion 208
8.8 Needfor aDelayed Sweep Oscillator 209
8.9 FMCWWaveformTrade-Offs 209
8.10 ChannelIsolation and Group DelayProblems 210
8.11 AmbiguityAnalysis:Pandora Radar 212
8.12 SFCWSignals 218
8.13 Conclusionon AmbiguityAnalysis 219
Chapter 9 Implementation ofthe Single-ChannelPandora and Other Issues 221
9.1 BlockSchematicofthe Single-ChannelRadar 221
9.2 Digital Sweep Generator 221
9.3 Sweep Upconverter 222
9.4 Receiver Downconverter 222
9.5 Local Oscillators 222
9.6 DemonstrationModel 222
9.6.1 PandoraVerificationMeasurements 222
9.6.2 MeasurementProcedures 223
9.6.3 SalientResults 223
9.7 Summary 223
9.8 Conclusion 223
Chapter 10 Pandora Radar Multi-Channel Radar 228
10.1 Introduction 228
10.2 BasicParameters 229
10.2.1 Overall SystemApproach 230
10.2.2 DesignProcedure 232
10.2.2.1 Choosingthe FrequencyBand 232
10.2.2.2 Choosingthe FrequencyStep 232
10.2.2.3 DynamicRange 233
10.2.2.4 Antenna Considerations 234
10.3 SystemAnalysis 234
10.3.1 System BlockDiagramand Schematics 234
10.3.2 The Effect ofPhase Noise 239
10.3.3 TheAmbiguityFunction 239
10.3.4 TheAntenna 240
10.3.4.1 Selectionofthe Design 240
10.3.4.2 Coupling 242
10.3.4.3 The Footprintofthe Antennas 242
10.3.4.4 Calibrationofthe Antennas 242
xii Contents
10.4 Experimental Setup 244
10.5 ExperimentalResults 245
10.6 Conclusion 245
10.7 FuturePossibilities ofPandora 247
Appendices 250
AppendixA CWRadar Range Equations 250
Appendix B The Design Process 258
AppendixC A HardwareSolution tothe Range Resolution Problem 269
Appendix D Nonlinearityin FMWaveforms 274
Appendix E Transmitter NoiseLeakage 277
Appendix F Pandora ReceiverChannel-Basic Design 284
AppendixG Direct Digital Synthesis 290
Appendix H Implementation oftheSingle-Channel Radar 307
Appendix I Pandora Radar PerformanceVerification Measurements 313
Appendix] 8-Way CombinerAnalysis Results 337
Appendix K MatlabSimulation Program 342
Appendix L Level Diagram Calculations-SFCW Radar 344
Index 346
PART I
Fundamentals of
CW Radar
