基于超大幅宽的高轨SAR加速BP成像方法

在高轨(GEO)合成孔径雷达(SAR)成像中，超大的成像幅宽导致成像区域不满足平面近似，使得基于平面网格的快速BP算法失效。该文提出一种基于地表网格的快速BP算法来精确高效地处理高轨SAR信号。首先针对轨道弯曲和地表弯曲所带来的信号复杂空变问题，采用一种基于实际地表的曲面网格布置方法。针对子孔径BP图像的频谱混叠问题，提出基于曲面网格的两步频谱压缩函数，将子孔径图像在合成之前实现频谱解混叠。同时采用多级子孔径图像合成的方法提高成像效率。最后，通过对比仿真，证明了该文所提算法的精确性以及高效性。

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.