基于距离Keystone变换的改进的多普勒调频率估计方法

多普勒调频率估计是SAR成像处理中的一个重要步骤。针对聚束、滑动聚束SAR采用全孔径算法进行成像时的调频率估计问题，该文提出一种改进的平移相关(SAC)算法。将距离Keystone变换引入到SAC算法中，去除了互相关峰值位置与目标距离间的耦合关系，从而消除了聚焦深度的限制。由于没有时域补零操作，调频率估计过程中将会出现模糊，针对此，给出了一种基于最小熵准则的模糊数估计方法。仿真及实测数据处理结果验证了所提方法的有效性。

An Improved Doppler Rate Estimation Approach Based on the Range-Keystone Transform

Doppler rate estimation is an essential procedure in Synthetic Aperture Radar (SAR) signal processing. For the Doppler rate estimation in spotlight and sliding spotlight SAR focused with the full-aperture imaging algorithm, this paper proposes an improved Shift-And-Correlation (SAC) approach. The range-Keystone transform is introduced into the original SAC algorithm to eliminate the coupling effect between the cross-correlation peak position and the targets distance. Thus, the constraint of the focus depth can be avoided. Due to no zero padding in the proposed approach, aliasing will occur in the Doppler rate estimation. For this problem, an ambiguity number estimation method based on minimum entropy is presented. Finally, both simulation and results of real data are provided to demonstrate the effectiveness of the proposed approach.