Acknowledgements .............................................. vii
List of Figures ............................................. xviii
List of Tables ................................................ xix
List of Symbols and Acronyms .................................. xxi
1 Introduction ................................................. 1
1.1 Synthetic aperture radar remote sensing ................. 1
1.1.1 A historical perspective ......................... 3
1.2 Motivation and overview of the thesis ................... 5
1.2.1 Problem formulation .............................. 7
1.2.2 Climbing atop others' shoulders .................. 9
1.2.3 Overview of the thesis .......................... 12
1.3 Original contributions of the thesis ................... 12
2 Fundamentals of bistatic SAR ................................ 13
2.1 Introduction ........................................... 13
2.2 State of the art ....................................... 14
2.3 From monostatic radar to bistatic SAR .................. 15
2.3.1 Side-looking imaging radar ...................... 15
2.3.2 Along-track coherent integration: the SAR
principle ....................................... 16
2.3.3 SAR data acquisition model ...................... 17
2.3.4 Block diagram of a bistatic SAR ................. 18
2.3.5 Bistatic SAR impulse response ................... 19
2.3.6 Operational challenges .......................... 20
2.3.7 A simple classification of bistatic SAR ......... 20
2.4 Geometrical framework of bistatic SAR .................. 21
2.4.1 Bistatic radar geometry ......................... 21
2.4.2 Isorange surfaces ............................... 22
2.4.3 Isodoppler surfaces ............................. 23
2.4.4 Topographic dependence of the ideal bistatic
range history ................................... 24
2.4.5 Imaging geometry ................................ 26
2.5 Performance analysis of bistatic SAR ................... 28
2.5.1 Range resolution ................................ 28
2.5.2 Doppler resolution .............................. 28
2.5.3 Resolution cell size ............................ 30
2.5.4 Sensitivity ..................................... 30
2.6 Bistatic SAR processing: a general approach ............ 33
2.7 Applications of bistatic SAR ........................... 34
2.8 From bistatic to multistatic SAR ....................... 35
3 Bistatic SAR experiments at DLR ............................. 37
3.1 Introduction ........................................... 37
3.2 State of the art ....................................... 38
3.3 DLR-ONERA joint airborne bistatic SAR experiment ....... 39
3.3.1 Motivation and historical background ............ 39
3.3.2 Bistatic configurations ......................... 40
3.3.3 Bistatic acquisitions ........................... 43
3.3.4 Imaged scenes ................................... 45
3.3.5 Performance analysis ............................ 46
3.4 TerraSAR-X/F-SAR spaceborne-airborne bistatic SAR
experiment ............................................. 49
3.4.1 Motivation and historical background ............ 49
3.4.2 Bistatic configuration .......................... 49
3.4.3 Bistatic acquisition ............................ 51
3.4.4 Imaged scene .................................... 52
3.4.5 Performance analysis ............................ 53
3.5 Bistatic SAR experiments during the TanDEM-X pursuit
monostatic commissioning phase ......................... 57
3.5.1 Motivation, historical background and bistatic
configuration ................................... 57
3.5.2 Bistatic acquisitions ........................... 58
3.5.3 Bistatic imaging and repeat-pass SAR
interferometry .................................. 59
3.5.4 Bistatic single-pass SAR interferometry ......... 59
4 Synchronisation of bistatic SAR data ........................ 61
4.1 Introduction ........................................... 61
4.2 State of the art ....................................... 62
4.3 Cooperative versus non-cooperative bistatic systems .... 62
4.4 Clock error model ...................................... 63
4.1 Bistatic SAR impulse response with missing
synchronisation ........................................ 64
4.6 Effect of clock errors on focussed bistatic SAR
images ................................................. 65
4.7 Automatic estimation of clock phase errors ............. 66
4.7.1 Automatic phase error estimation using
autofocus ....................................... 68
4.7.2 Automatic phase error estimation using
a reference image ............................... 70
5 Bistatic SAR image formation ................................ 77
5.1 Introduction ........................................... 77
5.2 State of the art ....................................... 78
5.3 On the symmetry properties of bistatic SAR ............. 81
5.4 Bistatic SAR image formation for the common man ........ 83
5.5 Fourier-domain bistatic SAR image formation ............ 85
5.5.1 Bistatic range-Doppler (BRD) algorithm .......... 86
5.5.2 Bistatic chirp scaling (BCS) algorithm .......... 90
5.5.3 Bistatic omega-K (BωK) algorithm ................ 93
5.6 Efficient time-domain image formation: bistatic fast
factorised backprojection (BFFBP) algorithm ............ 95
5.6.1 Direct versus fast backprojection ............... 96
5.6.2 Geometric model ................................. 98
5.6.3 Definition of the subimage grid ................. 99
5.6.4 Nyquist sampling requirements .................. 100
5.6.5 Implementation ................................. 105
5.6.6 Computational burden and memory consumption .... 107
5.6.7 Results with simulated data .................... 109
6 Experimental results ....................................... 115
6.1 Introduction .......................................... 115
6.2 State of the art ...................................... 116
6.3 DLR-ONERA joint airborne experiment ................... 116
6.3.1 Bistatic airborne SAR processing chain ......... 116
6.3.2 Bistatic SAR imaging ........................... 121
6.3.3 Bistatic cross-platform SAR interferometry ..... 123
6.4 TerraSAR-X/F-SAR spaceborne-airborne experiments ...... 128
6.4.1 Bistatic spaceborne-airborne processing chain .. 128
6.4.2 First bistatic SAR imaging experiment .......... 133
6.4.3 Dual-pol bistatic SAR imaging experiment ....... 139
6.5 Experiments with TanDEM-X in the pursuit monostatic
commissioning phase ................................... l39
6.5.1 Bistatic spacebome processing chain: the TAXI
project ........................................ 139
6.5.2 Bistatic SAR imaging and repeat-pass
interferometry ................................. 144
6.5.3 Bistatic single-pass SAR interferometry ........ 145
7 Conclusion ................................................. 151
7.1 Summary and discussion of the achieved results ........ 151
7.2 Outlook ............................................... 153
References ................................................. 156
A Efficient numerical generation of SAR transfer functions ... 177
A.l Iterative estimation of the time of stationary
phase ................................................. 178
A.2 Method of series reversion ............................ 178
B Oscillator phase noise in bistatic SAR ..................... 181
|
