A time domain phase-gradient based ISAR autofocus algorithm

Autofocus is a well known required step in ISAR (and SAR) processing to compensate translational motion. This research proposes a time domain autofocus algorithm and discusses its relation to the well known phase gradient autofocus (PGA) technique. Results on simulated and measured data show that the algorithm performs well. Unlike many other ISAR autofocus techniques, the algorithm does not make use of several computationally intensive iterations between the data and image domains as part of the autofocus process. As such, the proposed algorithm could prove to be faster than other techniques. Observations are made regarding the type of phase errors that can be handled, and it is argued that the technique could be posed either as parametric or non-parametric depending on the type of phase errors expected.