| Synthetic Aperture Radar (SAR) was a new type of radar developed since 1950s. Based on the principle of synthetic aperture and pulse compression technology, SAR broke through the limitation of real antenna aperture and realized 2-D high-resolution imaging to distant targets, hence SAR got widely used in both military and civil fields besides its all-time, all-condition and proactive attributes.This thesis focused on SAR large squint mode imaging algorithms and Real-time processing technologies.Chapter Ⅱ introduced the conception of synthetic aperture and pulse compression technology, analyzed SAR imaging mechanism from the view of the relationship of coordinates' transform, and emphasized that the key to obtain high quality SAR image was to remove range-azimuth coupling existing in echo signals.Chapter Ⅲ introduced SAR imaging algorithms in orthogonal mode. The principle and implementation methods of Range-Doppler algorithm and Chirp Scaling algorithm were deduced and compared in detail. The imaging results of simulated signal and real data were given.Chapter Ⅳ researched in deep on new and fundamental challenges caused by badly range-azimuth coupling with the increase of squint angle and proposed counterpart resolutions. Algorithms for large squint mode imaging, such as Improved Range-Doppler (IRD) and Extended Chirp Scaling (ECS) were analyzed and derived minutely, the simulations in a squint angle up to ±45° degree were given at last.Chapter Ⅴ summarized algorithms to estimate Doppler centroid from echo signals, which was the key to resolve azimuth spectral folding in squint mode imaging. Hardware implementation of real-time Doppler centroid estimation based on DSPs was discussed and simulation results were shown.Chapter Ⅵ calculated the computation and hardware cost needed to realize squint-mode SAR Real-time Processor under system requirements, allotted tasks and verified real-time feasibility for key nodes of ECS, outlined hardware frame based on TI TMS320C6415T DSP chip. |
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