Improved focusing approach for highly squinted beam steering SAR

For different applications with diverse requirements, many synthetic aperture radar (SAR) modes have been developed in the literature, such as, spotlight SAR, terrain observation by progressive scans (TOPS) SAR, and sliding spotlight SAR. For highly squinted beam steering SAR (BS-SAR; spotlight SAR, sliding spotlight SAR, and TOPS SAR), the main challenge is to develop an efficient full-aperture focusing approach since the mostly traditional algorithms fail to process the highly squinted BS-SAR data without subaperture technique. In this study, a unified full-aperture focusing algorithm is presented for BS-SAR modes in the case of highly squint angle. The key of the algorithm lies in the linear multiplications applied in the range-wavenumber and azimuth-space domain, which can remove the azimuth spectral folding effect and the geometrical distortion caused by spectrum skewing. Moreover, there is no any approximation in the focusing procedure; thus, the presented algorithm can perform well. Since the subaperture is avoided, this improved focusing approach is highly efficient. Simulation results are presented to validate the proposed method.