Study On Imaging Algorithm And Motion Compensation For Bistatic Forward-looking SAR

As a specific mode of bistatic SAR, bistatic forward-looking SAR(BFSAR) system can achieve imaging with high resolution, and breaking through the limitations of traditional SAR. Therefore, BFSAR has broad application prospects in both civilian and military fields.The thesis thoroughly studies on the fundamental theory, imaging algorithm and motion compensation of BFSAR based on the research of BISAR. Focus ability with range variable of Chirp Scaling algorithm is improved by the means of curve-fitting, and the performance of ISFFT algorithm is improved by canceling the high-order phase error. Extended imaging algorithm with motion compensation is investigated, which effectively compensate the impact on BFSAR imaging of motion error. The main contents of the thesis can be concluded as follows:1. The fundamental theory of BFSAR is investigated particularly. The model of BFSAR is established. The range history, Doppler and resolution characteristics are analyzed. Finally, the echo signal model of point target is deduced in detail based on the geometry mode and range history.2. An improved Chirp Scaling imaging algorithm for BFSAR is proposed. The two-dimensional spectrum is expensed in high order, so that the impact of high-order phase on BFSAR focusing can be compensated directly. The curve-fitting method is adopted to get an accurate analytical expression of two-dimensional spectrum. The range-migration correction and azimuth Doppler modulation compensation are better completed. The focus ability of algorithm is improved effectively.3. An improved ISFFT imaging algorithm for BFSAR is proposed. The high-order phase impact on BFSAR is compensated. The range compression, second range compression and phase compensation of the reference point can be accomplished. The two-dimensional spectrum of echo signal can be expanded to the analytical expression of the range variable by the means of curve-fitting. Moreover, Inverse Scaled Fast Fourier Transform(ISFFT) is chosen to complete the range migration correction and azimuth Doppler modulation compensation. The performance of algorithm is improved effectively.4. The motion compensation method for BFSAR is studied particularly, and an extended imaging algorithm with motion compensation is deduced. The echo signal model with motion error is established. The effect of motion error on imaging in range and azimuth direction is analyzed in detail, and the compensation function is deduced. The extended imaging algorithm with motion compensation is investigated, which effectively compensate the impact of motion error on BFSAR imaging.