中文摘要：

在机载／固定站构型双站合成孔径雷达（Airborne／Stationary Bistatic Synthetic Aperture Radar，A／S—BiSAR）成像中，回波信号方位不变性的假设不再成立；完成距离徙动校正和距离压缩之后，同一距离单元处信号的多普勒调频率具有沿方位向变化的特性。该信号特性导致了传统的相位梯度自聚焦（PhaseGradientAutofocus，PGA）方法对相位误差的估计精度显著下降。针对该问题，该文提出了一种改进PGA方法。与传统PGA方法相比，该方法通过增加对样本信号的剩余二次相位补偿，有效减小了变化的多普勒调频率对相位误差估计的影响，从而提高了对相位误差的提取精度；此外，该方法考虑了对距离空变相位误差的估计和补偿，使之适用于宽测绘带条件下的A／S—BiSAR成像。实测数据的处理和分析验证了该文方法的有效性。

英文摘要：

In Airborne/Stationary Bistatic Synthetic Aperture Radar （A/S-BiSAR）, the assumption of translational invariance is no longer available. After the Range Cell Migration Correction （RCMC）, the range compressed signal in the same range gate exhibits azimuth-variant Doppler rates which make the phase error difficult to be estimated from the echoes by using the available Phase Gradient Autofocus （PGA） algorithms. To deal with this problem, a modified PGA algorithm is proposed. Comparing with the traditional PGA, the Residual Quadratic Phase （RQP） caused by the azimuth-variant Doppler rates is additionally estimated and compensated. As the influence of the azimuth-variant Doppler rates is greatly reduced, a phase gradient estimator is subsequently applied to accurate phase error retrieval. Furthermore, the range-variance of the phase error is also concerned in the phase error estimation and correction, thus the proposed algorithm is suitable for A/S-BiSAR with wide swath in range. Raw data experiments are presented to verify the advantages of the proposed algorithm.