一种适于弹载平台的PFA波前弯曲补偿方法

Wavefront Curvature Correction for Missile Borne Spotlight SAR Polar Format Image

极坐标格式算法(Polar format algorithm,PFA)将球面波前近似为平面波前,由此引入的误差会造成SAR图像出现严重的边缘模糊和几何失真。之前的波前弯曲补偿方法都是基于雷达平飞假设,然而由于弹载SAR平台大俯冲、大斜视的机动特点,使得现有的滤波器设计方法无法直接应用于雷达平台俯冲等机动条件,波前弯曲误差补偿方法的应用范围因此受到很大限制。本文根据导弹飞行末端大斜视、大俯冲的机动特点,推导了雷达俯冲机动条件下波前弯曲空间频域相位误差的精确表达式,通过空变后滤波等处理实现了弹载SAR极坐标格式算法波前弯曲误差的精确补偿,有效地解决了弹载SAR俯冲机动条件下PFA图像的模糊和几何失真问题。该方法扩展了图像后处理补偿极坐标格式算法波前弯曲误差的应用范围,进一步完善了极坐标格式算法的波前弯曲补偿理论。最后通过仿真验证了公式和方法的正确性。

The polar format algorithm(PFA)for spotlight synthetic aperture radar(SAR)is influenced by wavefront curvature e rror.The error introduced will cause the missile borne SAR image edge blur and geometric distortion seriously.The previous wavefront curvature compensation me thods are all assumed that the height of the radar is constant.These compensati on methods cannot be directly applied to the case of missile borne SAR where the platform always has large dive angle.The application range of wavefront curvat ure error compensation method is restricted greatly.In this paper,the precise expression of wavefront curvature phase error in the frequency domain of missile borne SAR is derived.After image domain post processing steps,the problems of distortion and defocus of PFA image in the missile borne SAR are solved effecti vely.This method further improves the precision of wavefront curvature compensa tion.At last,the correctness of formula and method is verified by simulation.