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|Title:||Bistatic synthetic aperture radar data processing and analysis.|
|Author:||Goh, Alvin Soonlien|
|School/Discipline:||School of Electrical and Electronic Engineering|
|Abstract:||Synthetic Aperture Radar (SAR) operation in a bistatic configuration offers various advantages over its now well-established monostatic counterpart but also poses various challenges, among which are the inversion of the raw bistatic SAR data into imagery, the maintenance of time and phase synchronisation between the separated transmitter and receiver, the application of interferometric techniques to bistatic data, and the polarimetric calibration of field-based bistatic systems in constant motion (particularly those with airborne/spaceborne components). As part of a research programme into the potential benefits and challenges of bistatic SAR, the Ingara fully polarimetric X-band airborne imaging radar system, developed and operated by the Australian Defence Science and Technology Organisation, was upgraded to conduct experimental SAR data collections in a bistatic geometry. Experimental trials of the new bistatic SAR system were conducted in 2007 and 2008 in which the existing airborne radar was operated in a fine-resolution (600 MHz bandwidth) circular spotlight-SAR mode, in conjunction with a newly developed fully polarimetric stationary ground-based bistatic receiver. These trials produced a set of fully polarimetric simultaneously collected monostatic and bistatic SAR data, collected over a wide range of bistatic angles, for research purposes. The work reported in this thesis is motivated by the various processing challenges presented by these data sets. Herein, image formation from raw spotlight-mode bistatic SAR data using the Polar Format Algorithm (PFA), particularly as it pertains to a circling-transmitter-stationary-receiver bistatic geometry, is discussed. The limitations of the first-order (plane-wave) phase approximation employed in deriving the PFA are examined for the case of a stationary-receiver bistatic collection geometry with co-planar transmitter, receiver and scatterers: expressions for the size of the focussed region are derived by restricting the magnitude of the second order phase term, and the complicated behaviour of the shape of this region in this bistatic case (which is not encountered in the monostatic case) is discussed. Fine-resolution imagery results from the PFA-based processing of simultaneously collected monostatic and bistatic data sets are shown, and results from the interferometric processing of single-pass simultaneously collected monostatic and bistatic SAR data with a relatively large (approx. 5°) grazing-angle difference and of repeat-pass bistatic data with a temporal delay of hours, both demonstrating interferometric coherence in the fine-resolution interferograms, are presented. Finally, the polarimetric calibration of a field-based bistatic SAR with an airborne component is addressed: minor variants of three previously published distributed-target-based polarimetric calibration algorithms are derived; the results of Monte Carlo numerical studies to compare their accuracies are discussed; a new calibration approach involving a hybrid of two of these algorithms which takes account of channel noise is proposed; the use of standard calibration targets (dihedrals, trihedrals etc.) potentially supplemented by the direct-path signal for polarimetric calibration is considered; and calibration results from the Ingara data are presented.|
|Advisor:||Gray, Douglas Andrew|
Stacy, N. J. S.
|Dissertation Note:||Thesis (Ph.D.) -- School of Electrical and Electronic Engineering, 2012|
|Keywords:||bistatic radar; bistatic SAR; imaging radar; synthetic aperture radar|
|Appears in Collections:||Research Theses|
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|01front.pdf||144.04 kB||Adobe PDF||View/Open|
|02whole.pdf||7.14 MB||Adobe PDF||View/Open|
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