INHERENT PHASE DISTORTION IN RECTANGULAR FORMAT FFT PROCESSING ALGORITHMS FOR SYNTHETIC APERTURE RADAR.

An important class of digital processing algorithms for synthetic aperture radar (SAR) is based on the computational efficiency of the FFT. Since the FFT algorithm simultaneously processes all targets within a single azimuthal resolution cell, it cannot be perfectly focus on all targets. An analysis is presented of phase mismatch for targets displaced from the reference position. The results provide a quantative evaluation of patch size limitations for spotlight mode SARs that achieve high speed operation by means of rectangular format FFT algorithms.