MULTICHANNEL SPACEBORNE SAR SQUINTED SLIDING SPOTLIGHT IMAGING WITH NONLINEAR CHIRP SCALING

The multichannel Synthetic Aperture Radar (SAR) squinted sliding spotlight data is difficult to process due to the extended Doppler spectrum and the spatial varied range cell migration. Conventional algorithms solve this problem by spectrum reconstruction and nonlinear chirp scaling to achieve a low resolution imaging with a three-order slant range model. However, in the case of a higher resolution case, e.g. 0.5 m, most existing conventional algorithms will fail due to insufficient accuracy. In this paper, a modified imaging algorithm based on a fourth-order slant range model is presented for the high-resolution multichannel spaceborne SAR squinted sliding spotlight imaging. Azimuth preprocess is firstly applied to recover an unambiguous azimuth spectrum. Based on the more accurate slant range model, a novel azimuth nonlinear chirp scaling process is proposed to compensate the phase more precisely, achieving a higher resolution imaging. The accuracy of the proposed algorithm is verified by the point simulation.