 | Gabele M.K. SAR / Ground moving target indication for spacebased radar with two-dimensional antenna arrays: Diss. … Dr.-Ing. / Deutsches Zentrum für Luft-und Raumfahrt, Institut für Hochfrequenztechnik und Radarsysteme, Oberpfaffenhofen. - Köln: DLR, 2013. - xviii, 198 p.: ill. - (Forschungsbericht; 2013-30). - Bibliogr.: p.167-177. - ISSN 1434-8454
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Zusammenfassung ................................................. v
Abstract ...................................................... vii
Acronyms and Symbols ........................................... ix
1 Introduction ................................................. 1
1.1 Synthetic Aperture Radar Principle ...................... 1
1.2 Moving Targets in SAR ................................... 3
1.3 Next Generation Space Based SAR Imaging and GMTI ........ 0
1.4 Thesis Contributions .................................... 8
2 Signal Model for Spacebased SAR and GMTI with Two-
Dimensional Antenna Arrays .................................. 11
2.1 Introduction ........................................... 11
2.2 Background and Literature Review ....................... 11
2.3 Stationary Target Signals .............................. 12
2.3.1 Single-Channel Signals .......................... 13
2.3.2 Along-Track Array Signals ....................... 16
2.3.3 Across-Track Array Signals ...................... 19
2.4 Ambiguities ............................................ 21
2.4.1 Azimuth Ambiguity Signals ....................... 21
2.4.2 Range Ambiguity Signals ......................... 25
2.5 Moving Target Signals .................................. 27
2.5.1 Single-Channel Signals .......................... 27
2.5.2 Multi-Channel Signals ........................... 29
3 Adaption of the SAR Processing to the Moving Target
Signals ..................................................... 31
3.1 Introduction ........................................... 31
3.2 Background and Literature Review ....................... 31
3.3 SAR Compression of Moving Target Signals ............... 32
3.3.1 Wavenumber Domain Algorithm for GMTI ............ 32
3.3.2 Extended Chirp Sealing Algorithm for GMTI ....... 34
3.4 SAR Compression of Moving Target Signals in Case of
Doppler Backfolding .................................... 36
3.4.1 Motion Parameter Estimation of Doppler
Ambiguous Targets ............................... 43
4 Performance Measures ........................................ 47
4.1 Introduction ........................................... 47
4.2 Signal-to-Noise Ratio .................................. 47
4.3 Signal-to-Interference-plus-Noise Ratio ................ 48
4.3.1 Direction of Arrival Problem Analogy ............ 49
4.3.2 Optimal Processor Solution ...................... 49
4.3.3 Optimal Processor Characteristics ............... 52
4.4 Moving Target Detectability ............................ 54
4.4.1 CFAR Detection .................................. 54
4.4.2 Blind Velocity Intervals ........................ 57
4.5 Target Motion Parameter Estimation ..................... 59
4.5.1 Cramer-Rao Lower Bound of Multi-Channel SAR
Signals ......................................... 59
4.5.2 Cramer-Rao Lower Bound in Case of Clutter
Interference .................................... 60
4.5.3 Across-Track Velocity and Azimuth Position
Estimation ...................................... 62
4.5.4 Comparison of the CRLB and the Estimators
Performance ..................................... 65
4.5.5 Ambiguities in Target Motion Parameter
Estimation ...................................... 68
4.6 Timing Constraints and Swath Width ..................... 70
5 System Concepts for Spaceborne SAR/GMTI with Wide Coverage .. 71
5.1 Introduction ........................................... 71
5.2 TerraSAR-X System ...................................... 71
5.2.1 GMTI Performance of the DRA Mode ................ 72
5.3 HRWS SAR System ........................................ 76
5.3.1 Impact of PRF and Antenna Pattern on the GMTI
Capability ...................................... 77
5.3.2 Design of GMTI Operation Modes .................. 81
5.4 Radar System with Extended Sparse Antenna Aperture ..... 95
5.4.1 Two Wings Sparse Antenna Array Configuration .... 95
5.4.2 System Parameters ............................... 97
5.4.3 SAR Performance ................................ 100
5.4.4 GMTI Performance ............................... 101
5.5 Radar System with Extended Beamsteering Capability .... 111
5.5.1 Pulse and Subpulse Timing Definitions .......... 111
5.5.2 Benefits of an Extended Beamsteering
Capability ..................................... 112
5.5.3 System Design .................................. 115
5.5.4 SAR Performance ................................ 117
5.5.5 GMTI Performance ............................... 119
6 TerraSAR-X Dual Receive Antenna Mode Experiment ............ 124
6.1 Introduction .......................................... 124
6.2 Fore and Aft Channel Reconstruction and Calibration ... 125
6.2.1 Imaging Signals ................................ 126
6.2.2 Calibration Signals ............................ 128
6.2.3 Fore/Aft Channel Reconstruction Procedure ...... 130
6.3 Image Data Modelling .................................. 132
6.3.1 Fore/Aft Channel Image Signals ................. 133
6.3.2 ∑/Δ Channel Image Signals ...................... 134
6.3.3 Propagation of Errors in the ∑/Δ to Fore/Aft
Transformation ................................. 136
6.4 Experimental Data Results ............................. 139
6.4.1 DRA Mode Campaigns ............................. 140
6.4.2 Image Data Analysis ............................ 141
6.4.3 Calibration Pulses Analysis .................... 142
7 Airborne Experimental Data Results ......................... 147
7.1 Introduction .......................................... 147
7.2 Convair ............................................... 580
Experimental Data Results ............................. 147
7.2.1 Partial Doppler Backfolding of a Moving Target
Signal ......................................... 147
7.2.2 SAR Compression of a Partially Backfolded
Moving Target Signal ........................... 148
7.3 F-SAR Experimental Data Results ....................... 152
7.3.1 Target Motion Parameter Estimation: Real
Moving Targets in Clutter and Noise ............ 153
7.3.2 Target Motion Parameter Estimation:
Artificial Moving Targets in Real Clutter and
Noise .......................................... 158
8 Summary and Outlook ........................................ 160
8.1 Summary of the Results ................................ 160
8.2 Outlook on Future Research Activities ................. 164
Bibliography ............................................... 167
Appendices .................................................... 178
A. Spherical Earth Model for Orbit Geometries ................. 179
A.l. Example: Sun-Synchronous Low Earth Orbit .............. 182
B Application Areas for Space Based GMTI ..................... 185
B.l. Backscattering Coefficients and Radar Cross Section ... 185
B.2. Delay from Data Acquisition to Processed Image
Delivery .............................................. 187
B.3. Possible Applications for Space Based GMTI ............ 187
B.3.1. Ocean Currents Monitoring ...................... 187
B.3.2. Monitoring of Vessels on the Ocean ............. 188
B.3.3. Traffic Monitoring ............................. 189
С. Appendices ................................................. 192
C.l. Reconstructed Fore Channel SAR linage ................. 192
C.2. Comparison of the Two Data Takes ...................... 193
C.3. Indication of Vessels ................................. 196
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