High-resolution Geosynchronous SAR Imaging of Ship Target

Due to high orbit and low relative speed, the integration time of geosynchronous synthetic aperture radar (GEO SAR) for a fine resolution reaches up to hundreds of seconds. However, during the long integration time, ship targets have complex motions such as significant angular motions (roll, pitch, and yaw), which makes the coherent integration of echo signals difficult to achieve. Aim at solving this problem, a subaperture inverse SAR (ISAR) imaging approach is proposed in this paper. Instead of compensating the angular motions for long time coherent integration, we use it for ISAR imaging during short subaperture time. Firstly, the achievable resolution is analyzed by ambiguity function (AF) to validate our proposition, then the complete flowchart of ISAR processing is presented, in which a modified discrete chirp Fourier transform (DCFT) approach is applied for high-order phase compensation. The processing results of simulated data illustrate the effectiveness of our proposed method.