Research Of Key Technology Of GMTI In Distributed SAR

A new space-borne SAR system—Distributed SAR or Constellation SAR was put forward by the United States in the 1990s. This SAR system immediately became a new research hotspot of the radar domain, and was emphasized all around the world. In theory, this radar system could overcome the insurmountable difficulties of the traditional SAR system: The traditional SAR cannot acquire wide swath and high resolution SAR image simultaneously; The traditional SAR-GMTI system cannot acquire long enough baseline to meet the requirement of minimum detectable velocity; The traditional InSAR system cannot acquire long enough space baseline to meet the requirement of height measurement accuracy or cannot obtain high related interferometry data. Distributed SAR could acquire wide swath and high resolution SAR simultaneously and acquire higher height measurement accuracy and lower minimum detectable velocity at single pass. But there are many difficulties to solve to realize the Distributed SAR system, such as highly sparse array distribution, Range and/or Doppler blur of echo signal, baseline measurement error of distributed array, transmitting power limit. There is not Distributed SAR system at work at present, so we have to overcome these problems to translate the theoretical system to engineering realization.In this master thesis, Ground Moving Target Indication is studied for Distributed SAR system. The main results of this thesis are listed as follows.(1) This dissertation introduced the basic theory and imaging algorithm, consisting of the principle of synthetic aperture and SAR imaging algorithm(RD algorithm, CS algorithm, NCS algorithm); Simulated a point target SAR raw data at side looking mode and deal it with RD algorithm and CS algorithm; Simulated a point target SAR raw data at squint mode and deal it with NCS algorithm. And deal the real airborne SAR data with RD algorithm and CS algorithm. The echo character of SAR moving target was researched, consisting of the influence of SAR moving target to the Doppler center frequency and Doppler modulation frequency of SAR echo and to SAR image.(2) This paper researched the method of simulating the raw echo data of Distributed SAR. Firstly, the method of simulating SAR real scene raw signal was researched. SAR real scene raw data was simulated with the time domain method and the frequency domain method. Then used the time domain method simulating the Distributed SAR real scene raw data for the dealing process of the time domain method being analogous to the real SAR process of transmitting and receiving signal. The dissertation put forward a method of simulating Distributed SAR based on the non-simultaneous space-time samples, and synthesized this data and the moving point target raw data to get the Distributed SAR real data containing moving target.(3) The dissertation researched the multi-channel and multi-pixel adaptive signal processing in image domain. Here we used the simulated raw data based on the non-simultaneous space-time samples to simulate the process of Ground Moving Target Indication for the raw data of different SAR being high related. The multi-channel and multi-pixel adaptive signal processing use the multi-pixel of multi-channel construct the clutter covariance matrix and use the principle of optimal space time adaptive processing and spatial steering vector to construct filtering weight and get the result of GMTI.