SAR Image Formation via Subapertures and 2D Backprojection

Radar imaging requires the use of wide bandwidth and a long coherent processing interval resulting in range and Doppler migration throughout the observation period. This migration must be compensated in order to properly image a scene of interest at full resolution and there are many available algorithms having various strengths and weaknesses. Here, a new subaperture-based imaging algorithm is proposed, which first forms range-Doppler (RD) images from slow-time sub-intervals, and then coherently integrates over the resulting coarse-resolution RD maps to produce a full resolution SAR image. The novelty is in the use of a two-dimensional backprojection approach to perform distortion-free integration of the RD maps, and in the application of the Keystone Transform to make the subaperture processing compatible with subsequent processing to detect and/or image moving targets.