基于强点目标的条带SAS自聚焦研究

摘要

合成孔径成像中，主要通过自聚焦校正剩余相位误差。相位曲率自聚焦是一种典型的条带SAR自聚焦方法，算法利用不同强点目标估计不同孔径相位误差曲率，对整个孔径相位曲率进行二次积分得到相位误差。侧摆偏差幅度较大时，条带SAS合成孔径图像中强点目标在距离向和方位向都会散焦，导致传统基于强点的条带SAR自聚焦算法无法直接用于条带SAS自聚焦。该文提出在距离压缩后利用强点目标的运动轨迹提取强点目标对应的存在误差的线性调频信号，对强点目标对应的信号进行解线频调处理得到相位误差函数并计算相位曲率。通过二次积分得到整个孔径的相位误差，从而提取侧摆误差。仿真结果表明改进算法可用于条带SAS中聚焦。%In synthetic aperture imaging,autofocus is used to correct the residual phase error. Phase curvature autofocus is a typical autofocus method for stripmap SAR The algorithm estimates phase curvature of the aperture of each strong target, and phase error is derived via double integration of the phase curvature of the whole aperture In SAS imaging, strong targets are blurred in both azimuth and range direction which leads to the failure of PCA use in stripmap gAS autdocus. In this paper LFM signal with phase error is derived according to the range migration trajectory of the strong target, and phase curvature can be got after the signal related to strong target is dechirped. The phase curvatures are double integrated and sway error can be derived. Simulation result shows that the improve algorithm can he applied in stripmap SAS autofocus.