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.