Imaging moving targets using the second-order keystone transform

The use of synthetic aperture radar (SAR) for moving target imaging has recently attracted a great deal of interest. The ability to obtain focused images of moving targets makes it possible to maximise the use of existing single-channel SAR systems, without upgrading to more complex and expensive multi-channel systems. In this study, a novel technique is presented for moving target imaging utilising a single-channel SAR operating in Spotlight mode. First, the second-order keystone transform is applied to remove range curvature. Next, a non-linear phase correction is applied to correct the remaining range walk. Finally, the nominally quadratic phase in azimuth is estimated and corrected to provide focused imagery. An experimental result is presented to demonstrate the performance of this approach.