Detecting Moving Targets in SAR Imagery by Using a Phase-Error Correction Algorithm

Motion of a target induces phase errors in a synthetic-aperture radar (SAR) signal (phase) history that cause the image of the moving target to be smeared in azimuth. We can detect the presence of a moving target by sensing the smearing, as follows. We divide the complex image of a scene that includes a moving target into a grid of patches, and apply a phase-error correction algorithm to each patch. We have used the shear averaging phase-error correction algorithm. Patches that have large phase errors are likely to contain the image of a moving target. We also compute the sharpness of the image in the patch before and after phase-error correction; an increase in sharpness indicates the presence of a moving target, and it is a better indicator than the magnitude of the phase error. This approach requires just a single-antenna conventional SAR system. It is highly sensitive to the azimuth component of target velocity and to radial acceleration.