An Improved Polar Formation Imaging Algorithm for Squinted TOPS SAR

For squinted terrain observation by progressive scans (TOPS) synthetic aperture radar (SAR) imaging mode, the generalized polar formation algorithm (PFA) is improved and an imaging algorithm, which firstly carries out linear range walk correction (LRWC) and then applies the PFA interpolation, is proposed in this paper. The LRWC can effectively mitigate the range-azimuth coupling effect and simplify range cell migration (RCM) correction. Besides, after performing LRWC, the azimuth sampling interval is still uniform, as such, the azimuth interpolation can be completed by Chirp-Z transform. For the azimuth-variation of Doppler rate induced by the antenna beam steering and LRWC, the azimuth nonlinear chirp scaling (ANCS) is implemented. Therefore, the azimuth focus depth is improved greatly and the scene size which can be well-focused is increased. Both simulation and real data results are provided to demonstrate the effectiveness of the proposed method.