An Airborne SAR Moving Target Imaging and Motion Parameters Estimation Algorithm With Azimuth-Dechirping and the Second-Order Keystone Transform Applied

In this paper, we propose an algorithm for airborne SAR moving target imaging and motion parameters estimation in Doppler ambiguity situation with azimuth-dechirping and the second-order keystone transform (SOKT) applied. In this algorithm, we use a third-order phase model for the echo signal, and after the compensation of third-order phase, the moving target can be symmetrically focused in azimuth. This algorithm has five major steps. 1) The azimuth-dechirping is conducted to eliminate the Doppler ambiguity. 2) The SOKT is conducted to correct the range curvature. 3) The Radon transform is applied to estimate the trajectory slope for range walk correction and the across-track velocity estimation. 4) The fractional Fourier transform (FrFT) is utilized to estimate the Doppler rate for estimating the along-track velocity. 5) The moving target is focused after azimuth compression and third-order phase compensation. Both simulation and real SAR data are processed to validate the proposed algorithm.