Research On SAR Auto-focusing Space-borne ScanSAR Image Processing And SAR Active Phased Array Design

SAR image auto-focusing, ScanSAR image processing and space-borne SAR antenna design were the main three topics of this thesis.In the study of SAR auto-focusing algorithms, the Map-drift algorithm, the PGA algorithm and the maximum contrast algorithm were implemented and validated. A robust genetic auto-focusing algorithm was also put forward and with this new algorithm the L-SAR image was greatly improved. In addition, a scheme using the Mapdrift algorithm in the L-SAR real time processor was designed.Based on the time domain and the frequency domain characters of ScanSAR echo, the study of various imaging algorithms and the understanding of the RadarSAT ScanSAR data, partitioning Range-Doppler algorithm, full aperture R-D algorithm, SPECAN algorithm and Chirp Scaling algorithm were done. In the real data processing, some methods like the side-lobe control of point target echo, the fast range walk correction, the scalloping weakening, the range ambiguity control, the azimuth false target elimination and the Doppler centroid frequency estimation were discussed and realized. A fast no CTM two dimension FFT algorithm was also studied, with its performance simulated and analyzed.According to the effects of SAR antenna pattern, the ambiguities, the spatial resolutions, the signal to noise ratio, the directivity control and beam forming of ScanSAR oriented active phased array were studied. Based on these studies, the phased array for the two swaths high resolution space-borne ScanSAR system was designed and simulated. Furthermore, the reliability of the phased array was studied and a high reliable design with redundancy was proposed, which extended the life ofphased array effectively.