A hybrid Synthetic Aperture Radar autofocus approach based on FRFT and PGA

In order to obtain high-resolution images, autofocus are widely used in Synthetic Aperture Radar (SAR) imaging. In this paper, a hybrid SAR autofocus approach is proposed, which estimates the quadratic phase error by using the fractional Fourier transform (FRFT) and the residual phase error by the phase gradient autofocus (PGA). The proposed approach combines the parametric and non-parametric autofocus techniques and its performance is superior to that of the PGA alone. Experimental results of simulated and real data demonstrate the validity of this hybrid approach.