Contents
Preface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . III
Foreword . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . V
CHAPTER 1
Theoretical Basis of Laser Coherent Detection . . . . . . . . . . . . . . . . . . . . . . . 1
1.1 Overview of Laser Detection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
1.2 Principles of Laser Coherent Detection . . . . . . . . . . . . . . . . . . . . . . . . 2
1.2.1 Square-Law Characteristic of Photoelectric Detectors . . . . . . . . 3
1.2.2 Characterization of Laser Coherent Detection Signals . . . . . . . . 3
1.3 Signal-to-Noise Ratio of Laser Coherent Detection . . . . . . . . . . . . . . . 5
1.3.1 Noise of Photoelectric Detectors . . . . . . . . . . . . . . . . . . . . . . . . 5
1.3.2 Signal-to-Noise Ratio of Coherent Detection . . . . . . . . . . . . . . . 7
1.4 Coherence Efficiency of Laser Coherent Detection . . . . . . . . . . . . . . . . 9
1.4.1 Signal and LO Optical Fields . . . . . . . . . . . . . . . . . . . . . . . . . . 9
1.4.2 Coherence Efficiency Analysis. . . . . . . . . . . . . . . . . . . . . . . . . . 11
1.5 Basic Characteristics of Laser Coherent Detection . . . . . . . . . . . . . . . . 11
1.6 Overview of Typical Applications of Laser Coherent Detection . . . . . . 13
1.6.1 Laser Detection of Atmospheric Disturbances . . . . . . . . . . . . . . 13
1.6.2 Laser Ranging and Velocity Measurement . . . . . . . . . . . . . . . . 17
1.6.3 Laser Detection Based on the Micro-Doppler Effect . . . . . . . . . 20
1.6.4 High-Resolution Synthetic Aperture Laser Imaging . . . . . . . . . 23
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
CHAPTER 2
Laser Coherent Detection of Atmospheric Disturbances . . . . . . . . . . . . . . . . 29
2.1 Fundamental Principles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
2.1.1 Radar Equation for Laser Detection of Atmosphere . . . . . . . . . 29
2.1.2 Fundamental Principles of Laser Coherent Atmospheric CO2 Detection . . . . . . . . .. 32
2.1.3 Fundamental Principles of Laser Coherent Detection of Wind-Field Disturbances. . . .. 39
2.2 Experimental System for Laser Coherent Detection of Atmospheric Disturbances . . . . . . . 42
2.2.1 Overall Structure of the Detection System . . . . . . . . . . . . . . . . 42
2.2.2 Parameter Design of the Detection System . . . . . . . . . . . . . . . . 46
2.2.3 Pulse Data Processing of Detection Echoes . . . . . . . . . . . . . . . 57
2.3 Laser Coherent Detection Experiments of Atmospheric Disturbances. . 62
2.3.1 Atmospheric CO2 Detection Experiments . . . . . . . . . . . . . . . . . 62
2.3.2 Atmospheric Wind-Field Detection Experiments . . . . . . . . . . . 68
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 74
CHAPTER 3
Chirped AM Laser Coherent Detection of Range and Velocity . . . . . . . . . . . 77
3.1 Fundamental Principles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77
3.1.1 Principle of Chirped AM Ranging . . . . . . . . . . . . . . . . . . . . . . 79
3.1.2 Principle of Chirped AM Velocity Measurement . . . . . . . . . . . . 79
3.2 Characteristics of Chirp Signals and De-Chirping . . . . . . . . . . . . . . . . 80
3.2.1 Chirp Signals and Their Ambiguity Function . . . . . . . . . . . . . . 80
3.2.2 Pulse Compression by a Matched Filter . . . . . . . . . . . . . . . . . . 83
3.2.3 Frequency-Domain Pulse Compression of Chirp Signals . . . . . . 84
3.2.4 Range-Velocity Coupling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 86
3.3 Balanced Coherent Detection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 87
3.4 Chirped AM Laser Coherent Detection Experiment of Range and Velocity . . . . . . 88
3.4.1 Chirped AM Laser Heterodyne Coherent Detection Experiments of Range . . . . . . 89
3.4.2 Chirped AM Laser Homodyne Coherent Detection Experiments of Range and Velocity . . 95
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 102
CHAPTER 4
Laser Coherent Detection Based on the Micro-Doppler Effect . . . . . . . . . . . . 103
4.1 Fundamental Principles of the Micro-Doppler Effect for Laser Detection . . . . . 103
4.1.1 Doppler and Micro-Doppler Effects . . . . . . . . . . . . . . . . . . . . . 103
4.1.2 Modeling of Echoed Photocurrent Signals in Target Vibration Detection . . . . 105
4.1.3 Modeling of Echoed Photocurrent Signals of Targets with Multiple Scattering Points. . . . 108
4.1.4 Influencing Factors of Characteristics of Laser Micro-Doppler Signals . . . . . . . . 112
4.2 Target Micro-Doppler Signal Acquisition and Experimental System for Laser Coherent Detection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 119
4.3 Target Micro-Motion Feature Extraction Based on TFA . . . . . . . . . . . 121
4.3.1 TFA of Micro-Doppler Signals of Targets . . . . . . . . . . . . . . . . . 121
4.3.2 Decomposition of Time–Frequency Features of Multi-Component Signals Based on Curve Tracking . . . . . . . 125
4.3.3 Separation and Extraction of Time–Frequency Features of Micro-Motions Based on Empirical Mode Decomposition . . . 128
4.4 Micro-Motion Parameter Estimation Based on Signal Models . . . . . . . 132
4.4.1 Micro-Motion Parameter Estimation Using PF Based on SPM . 132
4.4.2 Micro-Motion Parameter Estimation Based on ML. . . . . . . . . . 136
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 152
CHAPTER 5
Laser Coherent Detection Using Synthetic Aperture Technology . . . . . . . . . . 155
5.1 Fundamental Principles of SALs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 155
5.1.1 Intuitive Concept of Synthetic Aperture in Lidars . . . . . . . . . . 155
5.1.2 Echo Signal Model of SALs . . . . . . . . . . . . . . . . . . . . . . . . . . . 157
5.1.3 Fundamental Principles of Coherent Mixing of Chirp Signals . . 160
5.2 SAL Imaging Algorithms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 162
5.2.1 R-D Imaging Algorithm . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 162
5.2.2 Phase Gradient Autofocus Algorithm . . . . . . . . . . . . . . . . . . . . 170
5.3 Laser Coherent Detection Experiments Using Synthetic Aperture Technology. . . . . . . . 173
5.3.1 Structure of the Experimental System . . . . . . . . . . . . . . . . . . . 173
5.3.2 Data Processing Flow . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 177
5.3.3 Analysis of Experimental Results . . . . . . . . . . . . . . . . . . . . . . . 178
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 194
