An Accelerated Back-Projection Algorithm Based on Large Swath for Geosynchronous-Earch-Orbit SAR Imaging

In the Geosynchronous-Earth-Orbit (GEO) SAR imaging, the extremely large swath width causes the imaging plane to no longer satisfy the flat plane approximation, which makes the accelerated BP algorithms based on the flat plane grid invalid. In this paper, an accelerated BP algorithm based on ground grid is proposed to process accurately and efficiently the GEO SAR signals. The imaging grids are arranged on the ground surface to correct the complex space variance of the signal caused by orbit and ground surface curvature. To solve the spectrum aliasing of sub-aperture images, a two-step spectrum compressing method is proposed to achieve the sub-aperture spectrum de-aliasing before fusion. And a multi-stage sub-aperture image fusion method is adopted to improve the imaging efficiency. Finally, simulation results are shown to verify the accuracy and efficiency of the proposed focusing approaches