Contents 7
Foreword 19
Preface 21
Acknowledgments 29
PART I: FUNDAMENTALS OF LPI RADAR DESIGN 31
Chapter 1 To See and Not Be Seen 33
1.1 The Requirement for LPI 33
1.2 Characteristics of LPI Radar 35
1.2.1 Antenna Considerations 35
1.2.2 Achieving Ultra-Low Side Lobes 37
1.2.3 Antenna Scan Patterns for Search Processing 40
1.2.4 Advanced Multifunction RF Concept 43
1.2.5 Transmitter Considerations 44
1.2.6 Power Management 46
1.2.7 Carrier Frequency Considerations 47
1.3 Pulse Compression\u2014The Key to LPI Radar 48
1.4 Radar Detection Range 54
1.5 Interception Range 57
1.6 Comparing Radar Range and Interception Range 59
1.7 The Pilot LPI Radar 61
1.8 Concluding Remarks 66
References 67
Problems 69
Chapter 2 LPI Technology and Applications 71
2.1 Altimeters 71
2.1.1 Introduction 71
2.1.2 Fielded LPI Altimeters 72
2.2 Landing Systems 75
2.2.1 Introduction 75
2.2.2 Fielded LPI Landing Systems 76
2.3 Surveillance and Fire Control Radar 78
2.3.1 Battlefield Awareness 78
2.3.2 LPI Ground-Based Systems 78
2.3.3 LPI Airborne Systems 86
2.4 Antiship Capable Missile and Torpedo Seekers 88
2.4.1 A Significant Threat to Surface Navies 88
2.4.2 Fielded LPI Seeker Systems 88
2.5 Summary of LPI Radar Systems 92
References 94
Problems 95
Chapter 3 Ambiguity Analysis of LPI Waveforms 97
3.1 The Ambiguity Function 98
3.2 Periodic Autocorrelation Function 98
3.3 Periodic Ambiguity Function 99
3.3.1 Periodicity of the PAF 100
3.3.2 Peak and Integrated Side Lobe Levels 100
3.4 Frank Phase Modulation Example 101
3.4.1 Transmitted Waveform 101
3.4.2 Simulation Results 102
3.5 Reducing the Doppler Side Lobes 105
References 108
Problems 108
Chapter 4 FMCW Radar 111
4.1 Advantages of FMCW 111
4.2 Single Antenna LPI Radar for Target Detection 113
4.3 Transmitted Waveform Design 116
4.3.1 Triangular Waveform 116
4.3.2 Waveform Spectrum 119
4.3.3 Generating Linear FM Waveforms 121
4.4 Receiver-Transmitter Isolation 124
4.4.1 Transmission Line Basics 125
4.4.2 Single Antenna Isolation Using a Circulator 126
4.4.3 Single Antenna Isolation Using a Reflected Power Canceler 127
4.5 The Received Signal 130
4.6 LPI Search Mode Processing 131
4.7 Track Mode Processing Techniques 134
4.8 Effect of Sweep Nonlinearities 135
4.9 Moving Target Indication Filtering 137
4.10 Matched Receiver Response 138
4.11 Mismatched Receiver Response 140
4.12 PANDORA FMCW Radar 143
4.13 Electronic Attack Considerations 145
4.14 Technology Trends for FMCW Emitters 145
References 149
Problems 152
Chapter 5 Phase Shift Keying Techniques 155
5.1 Introduction 155
5.2 The Transmitted Signal 156
5.3 Binary Phase Codes 158
5.4 Polyphase Codes 163
5.5 Polyphase Barker Codes 164
5.6 Frank Code 169
5.7 P1 Code 178
5.8 P2 Code 182
5.9 P3 Code 182
5.10 P4 Code 187
5.11 Polytime Codes 193
5.11.1 T1(n) Code 193
5.11.2 T2(n) Code 195
5.11.3 T3(n) Code 199
5.11.4 T4(n) Code 199
5.12 Omnidirectional LPI Radar 209
5.13 Summary 212
References 212
Problems 213
Chapter 6 Frequency Shift Keying Techniques 217
6.1 Advantages of the FSK Radar 217
6.2 Description of the FSK CW Signal 219
6.3 Range Computation in FSK Radar 219
6.4 Costas Codes 221
6.4.1 Characteristics of a Costas Array or Sequence 221
6.4.2 Computing the Difference Triangle 222
6.4.3 Deriving the Costas Sequence PAF 222
6.4.4 Welch Construction of Costas Arrays 223
6.5 Hybrid FSK/PSK Technique 225
6.5.1 Description of the FSK/PSK Signal 225
6.6 Matched FSK/PSK Signaling 229
6.7 Concluding Remarks 231
References 235
Problems 236
Chapter 7 Noise Techniques 237
7.1 Historical Perspective 237
7.2 Ultrawideband Considerations 240
7.3 Principles of Random Noise Radars 242
7.4 Narayanan Random Noise Radar Design 245
7.4.1 Operating Characteristics 246
7.4.2 Model of RNR Transmitter 249
7.4.3 Periodic Ambiguity Results 249
7.5 Random Noise Plus FMCW Radar 252
7.5.1 RNFR Spectrum 253
7.5.2 Model of RNFR Transmitter 255
7.5.3 Periodic Ambiguity Results 255
7.6 Random Noise FMCW Plus Sine 257
7.6.1 Model of RNFSR Transmitter 259
7.6.2 Periodic Ambiguity Results 260
7.7 Random Binary Phase Modulation 264
7.7.1 Model of RBPC Transmitter 266
7.7.2 Periodic Ambiguity Results 266
7.8 Millimeter Wave Noise Radar 268
7.9 Correlation Receiver Techniques 268
7.9.1 Ideal Correlation 269
7.9.2 Digital-Analog Correlation 269
7.9.3 Fully Digital Correlation 271
7.9.4 Acousto-Optic Correlation 272
7.10 Concluding Remarks 273
References 274
Problems 277
Chapter 8 Over-the-Horizon Radar 279
8.1 Two Types of OTHR 279
8.2 Sky Wave OTHR 282
8.2.1 Characteristics of the Ionosphere 283
8.2.2 Example of F2-Layer Propagation 289
8.2.3 Doppler Clutter Spectrum 289
8.2.4 Example Sky Wave OTHR System 291
8.2.5 Sky Wave Processing 291
8.3 Sky Wave LPI Waveform Considerations 295
8.3.1 Phase Modulation Techniques 295
8.3.2 Costas Frequency Hopping 296
8.3.3 Reducing the CIT 296
8.3.4 Multiple Waveform Repetition Frequencies 296
8.3.5 Out-of-Band Emission Suppression 300
8.4 Sky Wave Maximum Detection Range 301
8.5 Sky Wave Footprint Prediction 304
8.6 Surface Wave OTHR 306
8.6.1 Example Surface Wave OTHR System 311
8.7 Surface Wave LPI Waveform Considerations 312
8.7.1 FMICW Characteristics 312
8.7.2 FMICW Ambiguity Space 317
8.8 Surface Wave Maximum Detection Range 318
8.9 Concluding Remarks 325
References 325
Problems 329
Chapter 9 Case Study: Antiship LPI Missile Seeker 331
9.1 History of ASCM Seeker Technology 331
9.2 The Future for ASCM Technology 332
9.3 Detecting the Threat 335
9.4 ASCM Target Scenario 336
9.4.1 Low RCS Targets 336
9.4.2 Sea Clutter Model 338
9.4.3 Linear FMCW Emitter Power Management 340
9.4.4 Target-to-Clutter Ratio 342
9.5 ASCM Ship Target Model 345
References 345
Problems 346
Chapter 10 Network-Centric Warfare and Netted LPI Radar Systems 349
10.1 Network-Centric Warfare 349
10.1.1 NCW Requirements 352
10.1.2 Situational Awareness 353
10.1.3 Maneuverability 353
10.1.4 Decision Speed and Operational Tempo 354
10.1.5 Agility 355
10.1.6 Lethality 355
10.2 Metrics for Information Grid Analysis 356
10.2.1 Generalized Connectivity Measure 356
10.2.2 Reference Connectivity Measure 358
10.2.3 Network Reach 359
10.2.4 Suppression Example 361
10.2.5 Extended Generalized Connectivity Measure 363
10.2.6 Entropy and Network Richness 363
10.2.7 Maximum Operation Tempo 366
10.3 Electronic Attack 367
10.4 Information Network Analysis Using LPIsimNet 368
10.5 Netted LPI Radar Systems 372
10.5.1 Advantages of the Netted LPI Radar Systems 376
10.5.2 Netted LPI Radar Sensitivity 378
10.5.3 Signal Model 379
10.5.4 Netted Radar Electronic Attack 382
10.6 Netted Radar Analysis Using LPIsimNet 383
10.6.1 Monostatic LPI Emitter and the SNR Contour Chart 383
10.6.2 Three Netted LPI Emitters 384
10.6.3 Two Netted LPI Emitters with Jammer 388
10.7 Orthogonal Waveforms for Netted Radar 388
10.7.1 Orthogonal Polyphase Codes 392
10.7.2 Addressing Doppler Shift Degradation 395
10.7.3 Orthogonal Frequency Hopping Sequences 400
10.7.4 Noise Waveforms 404
10.8 Netted Over-the-Horizon Radar Systems 407
References 408
Problems 410
PART II: INTERCEPT RECEIVER STRATEGIES AND SIGNAL PROCESSING 415
Chapter 11 Strategies for Intercepting LPI Radar Signals 417
11.1 EW Intercept Receiver Techniques 417
11.1.1 Traditional Approach 417
11.1.2 The Look-Through Problem 418
11.1.3 Modern Network-Centric Concepts Arriving 419
11.2 Detecting the LPI Radar with UAVs 421
11.3 Noncooperative Intercept Receivers 422
11.3.1 Comparison of Classic Receiver Architectures for Detecting LPI Waveforms 422
11.3.2 Digital EW Receivers 426
11.3.3 Direct RF Sampling 428
11.4 Demodulation of the LPI Waveform 430
11.5 EW Receiver Challenges 430
11.6 Concluding Remarks 432
References 433
Chapter 12 Wigner-Ville Distribution Analysis of LPI Radar Waveforms 435
12.1 Wigner-Ville Distribution 436
12.1.1 Continuous WVD 436
12.1.2 Example Calculation: Real Input Signal 439
12.1.3 Example Calculation: Complex Input Signal 441
12.1.4 Two-Tone Input Signal Results 444
12.2 FMCW Analysis 449
12.3 BPSK Analysis 451
12.4 Polyphase Code Analysis 456
12.5 Polytime Code Analysis 459
12.6 Distinguishing Between Phase Codes 461
12.7 FSK and FSK/PSK Analysis 468
12.8 Summary 468
References 472
Problems 474
Chapter 13 Choi-Williams Distribution Analysis of LPI Radar Waveforms 475
13.1 Mathematical Development 476
13.2 LPI Signal Analysis 478
13.2.1 FMCW Analysis 479
13.2.2 BPSK Analysis 479
13.2.3 Polyphase Code Analysis 485
13.2.4 Polytime Code Analysis 485
13.2.5 FSK and FSK/PSK Analysis 488
13.3 Summary 488
References 494
Problems 494
Chapter 14 LPI Radar Analysis Using Quadrature Mirror Filtering 497
14.1 Time-Frequency Wavelet Decomposition 498
14.1.1 Basis Functions 498
14.1.2 Short-Time Fourier Transform Decomposition 499
14.1.3 Wavelets and the Wavelet Transform 499
14.1.4 Wavelet Filters 502
14.2 Discrete Two-Channel Quadrature Mirror Filter Bank 504
14.3 Tree Structure to Filter the Lowpass Component 506
14.4 Tree Structure to Filter the Highpass Component 507
14.5 QMFB Tree Receiver 508
14.6 Example Calculations 512
14.6.1 Complex Single-Tone Signal 512
14.6.2 Complex Two-Tone Signal 515
14.7 FMCW Analysis 517
14.8 BPSK Analysis 519
14.9 Polyphase Code Analysis 524
14.10 Polytime Code Analysis 525
14.11 Costas Frequency Hopping Analysis 529
14.12 FSK/PSK Signal Analysis 529
14.13 Noise Waveform Analysis 529
14.14 Summary 536
References 539
Problems 540
Chapter 15 Cyclostationary Spectral Analysis for Detection of LPI Radar Parameters 543
15.1 Introduction 543
15.1.1 Cyclic Autocorrelation 544
15.1.2 Spectral Correlation Density 545
15.2 Spectral Correlation Density Estimation 546
15.3 Discrete Time Cyclostationary Algorithms 550
15.3.1 The Time-Smoothing FFT Accumulation Method 550
15.3.2 Direct Frequency-Smoothing Method 552
15.4 Test Signals 555
15.5 BPSK Analysis 558
15.6 FMCW Analysis 561
15.7 Polyphase Code Analysis 565
15.8 Polytime Code Analysis 569
15.9 Costas Frequency Hopping Results 570
15.10 Random Noise Analysis 573
15.11 Summary 575
References 577
Problems 578
Chapter 16 Antiradiation Missiles 581
16.1 Suppression of Enemy Air Defense 581
16.1.1 The Beginning of SEAD 583
16.1.2 Early ARM Developments 584
16.1.3 Vietnam 585
16.1.4 Post Vietnam 586
16.1.5 Miniature Air-Launched Decoys 588
16.2 Antiradiation Missile Seeker Design 589
16.2.1 Antenna Design 589
16.2.2 Receiver and Signal Processing 596
16.2.3 Dual-Mode Design 597
16.2.4 Signal Processing 601
16.2.5 Future ARMs\u2013Addressing the LPI Emitter 602
16.3 ARM Performance Metrics 607
16.4 Former Soviet Union and Warsaw Pact Allies 608
16.4.1 AA-10 Alamo 608
16.4.2 AS-4 Kitchen 609
16.4.3 AS-5 Kelt 610
16.4.4 AS-6 Kingfish 611
16.4.5 AS-9 Kyle 612
16.4.6 AS-11 Kilter 614
16.4.7 Kh-27 615
16.4.8 AS-12 Kegler 615
16.4.9 AS-16 Kickback 617
16.4.10 AS-17 Krypton 617
16.5 United States 619
16.5.1 Shrike 619
16.5.2 Standard ARM 621
16.5.3 HARM 621
16.5.4 AARGM 622
16.5.5 Affordable Reactive Strike Missile 623
16.5.6 Sidearm 623
16.5.7 Rolling Airframe Missile 624
16.5.8 Army UAVs 625
16.6 France 626
16.7 United Kingdom 627
16.8 Taiwan 628
16.9 Germany 630
16.10 Israel 631
16.10.1 Harpy 631
16.10.2 STAR-1 633
16.11 China 634
16.12 Anti-ARM Techniques 636
16.12.1 Decoys 637
16.12.2 Gazetchik 640
16.12.3 AN/TLQ-32 ARM-D Decoy 641
References 642
Problems 646
Chapter 17 Autonomous Classificationof LPI Radar Modulations 649
17.1 Classification Using Time-Frequency Imaging 650
17.2 Classification Authority and Automation 651
17.2.1 Human-Computer Interface Considerations 651
17.2.2 Automation and the Human Operator 652
17.2.3 Autonomous Modulation Classification 653
17.3 Nonlinear Classification Networks 654
17.3.1 Single Perceptron Networks 655
17.3.2 Multilayer Perceptron Networks 659
17.3.3 Radial Basis Function 662
17.4 Feature Extraction Signal Processing 664
17.4.1 Marginal Frequency Adaptive Binarization 664
17.4.2 Classification Results with Multilayer Perceptron 668
17.4.3 Classification Results with Radial Basis Function Network 672
17.4.4 Discussion of Classification Results 677
17.5 Modified Feature Extraction Signal Processing 678
17.5.1 Lowpass Filtering for Cropping Consistency 678
17.5.2 Calculating the Marginal Frequency Distribution 681
17.5.3 Principal Components Analysis 686
17.5.4 Classification Using Modified Feature Extraction 690
17.5.5 Classification Results with the Multilayer Perceptron 697
17.5.6 Classification Results with the Radial Basis Function 704
17.6 Summary 712
References 712
Problems 715
Chapter 18 Autonomous Extraction of Modulation Parameters 717
18.1 Emitter Clustering 717
18.2 Polyphase Parameters Using Wigner-Ville Distribution\u2013Radon Transform 718
18.2.1 Time-Frequency Algorithm Description 719
18.2.2 Testing the Algorithm 724
18.3 Polyphase Parameters from Quadrature Mirror Filtering 725
18.3.1 Wavelet Decomposition Algorithm Description 725
18.3.2 Testing the Algorithm 729
18.4 FMCW Parameters from CyclostationaryBifrequency Plane 729
18.4.1 Cyclostationary Algorithm Description 730
18.4.2 Testing the Algorithm 733
18.5 Concluding Remarks 735
References 735
Problems 735
Appendix A Low Probability of Intercept Toolbox 739
A.1 Introduction to the LPIT 739
A.2 Naming Convention and Example 740
Appendix B Generating PAF Plots Using the LPIT Files 743
Appendix C Primitive Roots and Costas Sequences 745
C.1 Primes 745
C.2 Complete and Reduced Residue Systems 746
C.3 Primitive Roots 747
Appendix D LPIsimNet 751
D.1 Overview of LPIsimNet Architecture 751
D.1.1 Loading the Default Sensor Network 752
D.1.2 Building a Scenario File and Running the Simulation 752
D.2 Setting the Node Properties 756
D.3 Viewing the Simulation Results 758
D.4 Adding a Moving Jammer to the Scenario 761
D.5 Netted Radar with a Jammer 763
Appendix E PWVD for FMCW with 螖F = 500 Hz 771
Appendix F PWVD for Frank Code with T = 64 ms 775
Appendix G PWVD Results for P1, P2, P3, and P4 Codes 779
G.1 P1 Code Analysis 779
G.2 P2 Code Analysis 779
G.3 P3 Code Analysis 782
G.4 P4 Code Analysis 782
Appendix H PWVD Results for Polytime Codes T2, T3, and T4 789
H.1 T2(2) Polytime Code 789
H.2 T3(2) Polytime Code 793
H.3 T4(2) Polytime Code 793
Appendix I QMFB Results for FMCW with 螖F = 500 Hz 801
Appendix J QMFB Results for 11-Bit BPSK 803
Appendix K QMFB Results for Frank Signal with Nc = 16 807
Appendix L QMFB Results for P1, P2, P3, and P4 811
L.1 P1 Analysis 811
L.2 P2 Analysis 812
L.3 P3 Analysis 812
L.4 P4 Analysis 818
Appendix M QMFB Results for T2, T3, and T4 827
Appendix N Cyclostationary Processing Results with FMCW 螖F = 500 Hz 835
Appendix O Cyclostationary Processing Results with Frank Signal, Nc = 16 839
Appendix P Cyclostationary Processing Results for P1, P2, P3, and P4 843
P.1 P1 Code Analysis 843
P.2 P2 Code Analysis 846
P.3 P3 Code Analysis 846
P.4 P4 Code Analysis 846
Appendix Q Cyclostationary Processing Results for T2, T3, and T4 Polytime Codes 851
Q.1 Polytime T2(2) Code Analysis 851
Q.2 Polytime T3(2) Code Analysis 851
Q.3 Polytime T4(2) Code Analysis 853
List of Symbols 859
Glossary 871
About the Author 877
Index 879