Motion estimation and compensation in SAR/ISAR imaging

The authors present a synthetic aperture radar (SAR) coherent system model and inversion (ISAR) to image a target moving with an unknown constant velocity in a stationary background. It is shown that SAR imaging of a moving target can be converted into imaging the target in a stationary squint-mode SAR problem where the parameters of the squint-mode geometry depend on the target´s velocity. A method for estimating the moving target´s velocity that utilizes a spatial Doppler analysis of the SAR data within overlapping subapertures is presented. On estimating a moving target´s velocity, unlike the temporal Doppler processing methods, the spatial Doppler technique does not require the radar signal to be narrowband. Thus, the reconstructed image´s resolution is not sacrificed to improve the target´s velocity estimator