Range- and Aperture-Dependent Motion Compensation Based on Precise Frequency Division and Chirp Scaling for Synthetic Aperture Radar

The complicated vibrations of the radar sensor, referred to as motion error, generally produce extra range cell migration (RCM) along the range direction as well as spectral replicas along the azimuth direction, which severely impairs the quality of a focused synthetic aperture radar (SAR) image. This paper concerns the compensation of motion error that is deemed to be range- and aperture-dependent. To this end, two pairs of relations, such as shift range and angle frequency, are analyzed. Based on the derived relations, we propose a chirp scaling-based range envelope correction to cope with the range-dependent position shifts (i.e., RCM) and a precise frequency division approach to account for the residual aperture-dependent motion error. The proposed algorithm can compensate bulk and complicated motion error completely before RCM correction and ensure the focusing quality of an SAR image without autofocus. Both simulated and real data experiments validate the effectiveness of the proposed algorithm.