A modified version of the mosaic phase gradient autofocus

High resolution radar and sonar images can be constructed using either spotlight or stripmap synthetic aperture systems. In the presence of residual phase errors, the respective images are blurred and their quality degrades dramatically. Typically, autofocus techniques are applied in spotlight operation to correct the degradation. However, for stripmap modes, the use of autofocus methods is not straightforward due to a spatially variant point spread function. We propose modifications to the existing mosaic phase gradient algorithm to overcome its drawbacks and to make it more applicable for stripmap synthetic aperture systems.