EW 103 Tactical Battlefield Communications Electronic Warfare DISCLAIMEROFWARRANTY Thetechnicaldescriptions,procedures,andcomputerprogramsinthisbook have been developed with the greatest of care and they have been useful to theauthorinabroadrangeofapplications;however,theyareprovidedasis, withoutwarrantyofanykind.ArtechHouse,Inc.andtheauthorandeditors of the book titled EW 103: Tactical Battlefield Communications Electronic Warfare make no warranties, expressed or implied, that the equations, pro- grams,andproceduresinthisbookoritsassociatedsoftwarearefreeoferror, or are consistent with any particular standard of merchantability, or will meet your requirements for any particular application. They should not be relieduponforsolvingaproblemwhoseincorrectsolutioncouldresultinin- jurytoapersonorlossofproperty.Anyuseoftheprogramsorproceduresin such a manner is at the user’s own risk. 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Contents Preface xiii 1 Introduction 1 1.1 Nature of Communications 1 1.2 Frequency Ranges 2 1.3 Roadmap to the Book 3 1.4 dB Math 4 1.4.1 dBValues 5 1.4.2 ConversiontoandfromdBForm 5 1.4.3 ConvertingtodBUsingaSlideRule 7 1.4.4 AbsoluteValuesindBForm 8 1.4.5 dBEquations 9 2 Communications Signals 13 2.1 Analog Modulations 13 2.2 Digital Modulations 16 2.2.1 TransmissionofAnalogorDigitalInformation 16 2.2.2 Digitization 17 2.2.3 DigitalRFModulations 19 v vi EW 103 2.2.4 BandwidthofDigitalSignals 23 2.2.5 DigitalSignalStructure 26 2.3 Noise 27 2.4 LPI Signals 30 2.4.1 Pseudo-RandomCodes 33 2.4.2 FrequencyHoppingSignals 36 2.4.3 ChirpSignals 41 2.4.4 DirectSequenceSpreadSpectrumSignals 43 2.4.5 CombinedTechniqueLPISignals 47 2.4.6 CellPhoneSignals 49 2.5 Error-Correction Codes 51 3 Communication Antennas 55 3.1 Antenna Parameters 55 3.1.1 TypesofAntennas 56 3.1.2 GeneralCharacteristicsofVariousTypesofAntennas 57 3.2 Important Types of Communication Antennas 59 3.3 The Antenna Beam 59 3.4 More About Antenna Gain 62 3.5 Polarization 62 3.6 Phased Arrays 63 3.6.1 PhasedArrayBeamwidthandGain 65 3.7 Parabolic Dish Antennas 66 4 Communications Receivers 75 4.1 Types of Receivers 75 4.1.1 PulseReceivers 76 4.1.2 SuperheterodyneReceiver 79 4.1.3 TunedRadioFrequencyReceiver 81 4.1.4 Fixed-TunedReceiver 82 4.1.5 ChannelizedReceiver 82 Contents vii 4.1.6 BraggCellReceiver 84 4.1.7 CompressiveReceiver 85 4.1.8 TheDigitalReceiver 86 4.2 Digitization 88 4.2.1 SamplingRates 89 4.2.2 DigitalWaveforms 89 4.2.3 DigitizingTechniques 90 4.2.4 I&QDigitization 91 4.3 Digitized Signal Quality Issues 91 4.3.1 ChipDetection 92 4.3.2 CatchingaFrequencyHoppingSignal 93 4.4 Receiver System Sensitivity 95 4.4.1 kTB 97 4.4.2 NoiseFigure 98 4.4.3 RequiredPredetectionSignal-to-NoiseRatio 99 4.5 Receiver System Dynamic Range 105 4.5.1 AnalogVersusDigitalDynamicRange 106 4.5.2 AnalogReceiverDynamicRange 107 4.5.3 DigitalDynamicRange 110 4.6 Typical Receiver System Configurations 111 4.6.1 MultipleReceiverReconnaissanceandElectronic SupportSystems 112 4.6.2 MultipleReceiverSystems 113 4.6.3 RemoteReceivingSystems 116 5 Communications Propagation 119 5.1 One-Way Link 119 5.2 The One-Way Link Equation 119 5.3 Propagation Losses 123 5.4 Line-of-Sight Propagation 124 5.5 Two-Ray Propagation 129 viii EW 103 5.6 Fresnel Zone 134 5.7 Knife-Edge Diffraction 137 5.8 Atmospheric and Rain Losses 140 5.8.1 AtmosphericLoss 140 5.9 HF Propagation 143 5.10 Satellite Links 147 6 Search for Communication Emitters 153 6.1 Probability of Intercept (POI) 154 6.2 Search Strategies 154 6.2.1 GeneralSearch 154 6.2.2 DirectedSearch 154 6.2.3 SequentiallyQualifiedSearch 155 6.2.4 AUsefulSearchTool 155 6.2.5 PracticalConsiderationsAffectingSearch 156 6.3 System Configurations 158 6.3.1 TypesofReceiversUsedforSearch 160 6.3.2 DigitallyTunedReceiver 161 6.3.3 DigitalReceivers 163 6.3.4 FrequencyMeasuringReceivers 163 6.3.5 EnergyDetectionReceivers 164 6.4 The Signal Environment 167 6.4.1 AngularCoverage 168 6.4.2 ChannelOccupancy 169 6.4.3 Sensitivity 169 6.5 Radio Horizon 170 6.6 Search for Low Probability of Intercept Signals 174 6.6.1 LPISearchStrategies 175 6.6.2 FrequencyHoppers 176 6.6.3 ChirpSignals 177 6.6.4 DirectSequenceSpreadSpectrumSignal 177 Contents ix 6.7 Look Through 178 6.8 Fratricide 181 6.9 Search Strategy Examples 181 6.9.1 NarrowbandSearch 181 6.9.2 Hand-OfffromWidebandReceiver 185 6.9.3 SearchwithaDigitalReceiver 185 7 Location of Communications Emitters 187 7.1 Emitter Location Approaches 187 7.1.1 Triangulation 188 7.1.2 Single-SiteLocation 189 7.1.3 AzimuthandElevation 191 7.1.4 OtherLocationApproaches 191 7.2 Accuracy Definitions 193 7.2.1 RMSError 193 7.2.2 CircularErrorProbableandEllipticalErrorProbable 195 7.2.3 Calibration 198 7.3 Site Location and North Reference 198 7.4 Moderate Accuracy Techniques 203 7.4.1 Watson-WattDirectionFindingTechnique 204 7.4.2 DopplerDirection-FindingTechnique 204 7.5 High Accuracy Techniques 207 7.5.1 SingleBaselineInterferometer 207 7.5.2 MultipleBaselinePrecisionInterferometer 211 7.5.3 CorrelativeInterferometer 212 7.6 Precision Emitter Location 212 7.6.1 TimeDifferenceofArrivalMethod 214 7.6.2 PrecisionEmitterLocationbyFrequencyDifference ofArrival 218 7.6.3 CombinedFDOAandTDOA 221 7.7 Emitter Location—Error Budget 222