A Refocusing Method for Ground Moving Target in Circular SAR

Non-cooperative ground moving targets appear smeared and dislocated in synthetic aperture radar (SAR) imagery as they are treated as static targets in the imaging procedure. In this paper, a non-searching method for Circular SAR (CSAR) ground moving target refocusing based on Inverse SAR (ISAR) technique as well as the sub-aperture segmentation is proposed. Firstly, the range migration of the moving target is directly extracted in range-frequency domain and fitted according to a quadratic polynomial. Secondly, a matched filter constructed by the quadratic polynomial is multiplied by sub-aperture echo of moving target in range frequency domain to accomplish motion compensation. Then, map-drift algorithm is performed to compensate for the residual quadratic phase errors to improve imaging quality. The proposed method is non-searching and can avoid the range alignment procedure in conventional ISAR-based techniques. Experimental CSAR data processing results show that the proposed method can achieve satisfied imaging quality of moving targets.