In this work

a 2D overlapped sub-aperture polar format algorithm (PFA) based on stepped-chirp signal is proposed. In synthetic aperture radar (SAR) with stepped-chirp signals

instead of using traditional pulse synthesis to conduct preprocess

the presented method integrates the pulse synthesis process into the range sub-aperture processing. Meanwhile

due to the multi-resolution characteristics of sub-aperture processing

this algorithm is able to compensate the space-variant phase error caused by the radar motion during the period of a pulse cluster. Finally

experiments carried out on simulated and measured data confirm the validity of the algorithm.