A Focusing Algorithm Based on CSA for Middle-Earth-Orbit SAR Combined with Two-Step Azimuth Compensation

The significant curved characteristics of the medium-Earth-orbit (MEO) SAR systems lead to the 2-dimensional spatial variation, which brings difficulties to the large scene imaging. To solve this problem, this paper proposes a modified chirp scaling algorithm on MEO SAR (MCSoM). The algorithm is based on the idea of two-step azimuth space variation compensation. First, the bulk azimuth variance is removed in the range processing stage, and then combined with CS the algorithm completes the range cell migration (RCM)correction, and finally removes the remaining azimuth space variation in the azimuth processing stage. The proposed algorithm compensates for both RCM and the azimuth modulation term. Combined with the CS operation, the large-scene focused imaging of the MEO SAR can be realized. Simulation results validate the effectiveness of the proposed algorithm.