双基聚束模式合成孔径雷达(SAR)成像中的极坐标格式算法(PFA)是基于平面波前假设建立的。由于该平面波前假设在聚焦过程中引入了相位误差，双基PFA聚焦图像中会出现空变几何失真和散焦现象。因此，实际应用PFA时其有效场景聚焦范围通常受到严格限制。基于双基合成孔径雷达回波信号相位的泰勒展开式，推导双基PFA中波前弯曲误差的解析表达式。基于此表达式，分别应用1维空变滤波和插值来补偿、校正波前弯曲效应引入的散焦和几何失真现象，从而有效改善了双基PFA的聚焦范围。点目标仿真验证了该方法的有效性。

The polar format algorithm (PFA) for the bistatic spotlight-mode synthetic aperture radar (SAR) imaging is based on the planar wavefront assumption. As the unrealistic planar wavefront assumption introduces phase error terms in the focusing process, there will be space-variant geometry distortion and defocusing effect in the image focused via bistatic PFA. Hence, the focused scene size when using bistatic PFA is usually restricted severely to avoid the defocusing effect. Based on the expansion of the received signal’s phase term in bistatic SAR, the analytical expression of the wavefront curvature error in bistatic PFA is derived in our study. Based on the expression, the space-variant filtering and interpolation operation are applied to compensate for the defocusing effect and correct the geometry distortion in the image, respectively, which extends the focused scene size of bistatic PFA effectively. Point target simulation validates the algorithm.