复杂航迹和起伏地形条件下SAR极坐标格式算法波前弯曲误差补偿

摘要

极坐标格式算法(PFA)受波前弯曲误差影响,其有效成像场景范围受到一定限制.采用图像域的空变后滤波处理可以有效补偿波前弯曲误差,但该方法基于雷达平台线性运动假设,无法满足大机动条件下的波前弯曲误差补偿要求.本文提出了一种改进的空变后处理方法,该方法通过对相位历史域的波前弯曲误差函数做与PFA成像相同的极坐标格式转换处理,得到波前弯曲误差在两维空间频域的精确表示,因此再通过分块后滤波处理能够精确补偿雷达任意航迹和地形起伏条件下PFA波前弯曲误差,显著提高PFA有效成像场景范围.最后通过仿真数据处理验证了该算法的有效性.%The space-variant defocus effect introduced by wavefront curvature in polar format algorithm (PFA) imagery limits its maximal focused scene size.Several compensation strategies have been developed in literature to solve this problem,e.g., subaperture processing, space-variant post processing and widefield polar format algorithm. However,all these approaches are based on the assumption that radar platform is following an expected linear trajectory. They still can't meet the required precision when imaging from arbitrary radar flight path. In this paper, an improved space-variant post processing method for wavefront curvature compensation is proposed. The method computes wavefront curvature error in original phase history domain, and then transforms it into spatial frequency domain by polar format transformation used in image formation.Using the transformed error, we can accurately compensate wavefront curvature effect by space-variant post filtering. Simulation experiments show that the new algorithm has improved focused scene size when applied to phase history generated by non-ideal radar flight path.