Time-frequency transforms for radar imaging and signal analysis

This text is a hands-on guide to time-frequency transforms for radar imaging and signal analysis. It explores more efficient ways to: extract dispersive scattering features; detect and extract weak signals in noise; form clear radar images; estimate parameters and perform motion compensation; detect and track moving targets in the synthetic aperture radar; and analyze vibration and rotation induced micro-Doppler. This resource introduces an image formation algorithm based on time-frequency-transforms, showing its advantage over the more conventional Fourier-based image formation. Referenced with over 170 equations and 80 illustrations, the book presents algorithms that help improve the result of radar imaging and signal processing. Moreover, the authors discuss future trends in time-frequency to analyze micro-Doppler, and provide a newly developed time-frequency approach to radar signal and image processing to help solve problems associated with conventional approaches.

Author Notes

Victor C. Chen received his Ph.D. and, M.S. Degree in Electrical Engineering from the Case Western Reserve University, Cleveland, OH.

Mr. Chen, an electronic engineer in the Radar Division of the Naval Research Laboratory in Washington, DC, is a senior member of the IEEE, and a member of the SPIE.

050

Foreword	p. xi
Preface	p. xiii
Acknowledgments	p. xvii
1 Introduction	p. 1
1.1 Electromagnetic Back-Scattering from Targets	p. 6
1.2 Radar Signal and Noise	p. 9
1.2.1 Signal Waveforms	p. 9
1.2.2 The SNR	p. 11
1.3 Radar Ambiguity Function and Matched Filter	p. 13
1.3.1 Radar Ambiguity Function	p. 13
1.3.2 Matched Filter	p. 17
1.3.3 Pulse Compression	p. 19
1.4 Synthetic Aperture Radar Imaging	p. 20
1.4.1 Range Profile	p. 21
1.4.2 Range Resolution	p. 21
1.4.3 Cross-Range Resolution	p. 22
References	p. 22
2 Time-Frequency Transforms	p. 25
2.1 Linear Time-Frequency Transforms	p. 26
2.1.1 The STFT	p. 28
2.1.2 The CWT	p. 32
2.1.3 Adaptive Time-Frequency Representation	p. 33
2.2 Bilinear Time-Frequency Transforms	p. 36
2.2.1 The WVD	p. 37
2.2.2 Cohen's Class	p. 39
2.2.3 The TFDS	p. 42
References	p. 45
3 Detection and Extraction of Signal in Noise	p. 47
3.1 Introduction	p. 48
3.2 Time-Varying Frequency Filtering	p. 48
3.3 SNR Improvement in the Time-Frequency Domain	p. 51
3.3.1 SNR Definition Suitable for Signal Detection and Extraction	p. 54
3.3.2 SNR in the Joint Time-Frequency Domain	p. 56
3.4 CFAR Detection in the Joint Time-Frequency Domain	p. 57
3.5 Signal Extraction in the Joint Time-Frequency Domain	p. 61
3.5.1 Time-Frequency Expansion and Reconstruction	p. 61
3.5.2 Time-Frequency Masking and Signal Extraction	p. 62
References	p. 63
4 Time-Frequency Analysis of Radar Range Profiles	p. 65
4.1 Electromagnetic Phenomenology Embedded in Back-Scattered Data	p. 66
4.2 Time-Frequency Representation of Range Profiles	p. 70
4.3 Application of High-Resolution Time-Frequency Techniques to Scattering Data	p. 77
4.3.1 Use of the CWT	p. 77
4.3.2 Use of the TFDS	p. 79
4.3.3 Windowed Superresolution Algorithm	p. 81
4.3.4 Adaptive Gaussian Representation	p. 83
4.4 Extraction of Dispersive Scattering Features from Radar Imagery Using Time-Frequency Processing	p. 85
References	p. 89
5 Time-Frequency-Based Radar Image Formation	p. 93
5.1 Radar Imaging of Moving Targets	p. 94
5.2 Standard Motion Compensation and Fourier-Based Image Formation	p. 102
5.3 Time-Frequency-Based Image Formation	p. 104
5.4 Radar Imaging of Maneuvering Targets	p. 107
5.4.1 Dynamics of Maneuvering Targets	p. 107
5.4.2 Radar Imaging of Maneuvering Target Using Time-Frequency-Based Image Formation	p. 108
5.5 Radar Imaging of Multiple Targets	p. 113
5.5.1 Multiple-Target Resolution Analysis	p. 113
5.5.2 Time-Frequency-Based Phase Compensation for Multiple Targets	p. 117
5.5.3 Time-Frequency-Based Image Formation for Radar Imaging of Multiple Targets	p. 119
5.6 Summary	p. 120
References	p. 120
6 Motion Compensation in ISAR Imaging Using Time-Frequency Techniques	p. 123
6.1 Motion Compensation Algorithms	p. 124
6.2 Time-Frequency-Based Motion Compensation	p. 126
6.2.1 Estimating Phase Using Adaptive Time-Frequency Projection	p. 128
6.2.2 Motion Error Elimination	p. 129
6.3 Motion Compensation Examples of Simulated and Measured Data	p. 131
6.4 Presence of 3D Target Motion	p. 135
References	p. 144
7 SAR Imaging of Moving Targets	p. 147
7.1 Radar Returns of Moving Targets	p. 148
7.1.1 Range Curvature	p. 149
7.1.2 Clutter Bandwidth	p. 150
7.1.3 Analysis of Radar Returns from Moving Targets	p. 152
7.2 The Effect of Target Motion on SAR Imaging	p. 155
7.3 Detection and Imaging of Moving Targets	p. 157
7.3.1 Single-Aperture Antenna SAR	p. 157
7.3.2 Multiple-Antenna SAR	p. 161
7.4 SAR Imaging of Moving Targets Using Time-Frequency Transforms	p. 165
7.4.1 Estimation of Doppler Parameters Using Time-Frequency Transforms	p. 166
7.4.2 Time-Frequency-Based SAR Image Formation for Detection of Moving Targets	p. 168
References	p. 170
8 Time-Frequency Analysis of Micro-Doppler Phenomenon	p. 173
8.1 Vibration-Induced Micro-Doppler	p. 174
8.1.1 Time-Frequency Signature of a Vibrating Scatterer	p. 177
8.1.2 An Example of Micro-Doppler Signatures of Moving Targets	p. 179
8.2 Rotation-Induced Micro-Doppler	p. 181
8.2.1 Rotor Blade Motion	p. 181
8.2.2 Radar Returns from Rotor Blades	p. 181
8.2.3 Time-Domain Signatures of Rotation-Induced Modulations	p. 184
8.2.4 Frequency-Domain Signatures	p. 188
8.2.5 Time-Frequency Signatures	p. 190
References	p. 192
9 Trends in Time-Frequency Transforms for Radar Applications	p. 193
9.1 Applications of Adaptive Time-Frequency Transforms	p. 193
9.2 Back-Scattering Feature Extraction	p. 194
9.3 Image Formation	p. 195
9.4 Motion Compensation	p. 195
9.5 Moving Target Detection	p. 196
9.6 Micro-Doppler Analysis	p. 198
References	p. 199
List of Acronyms	p. 203
About the Authors	p. 205
Index	p. 207

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