1. A synthetic aperture radar (SAR) imaging method, the method comprising: applying range pulse compression to SAR in-phase and quadrature (IQ) data for each image block of a SAR image grid to generate range-compressed IQ data for each image block; applying pulse range frequency (PRF) decimation to the range-compressed IQ data to generate PRF-decimated range-compressed IQ data for each image block; applying motion compensation to the PRF-decimated range-compressed IQ data to generate motion-compensated data for each image block; computing first stage image values at image grid point intersections of iso-range lines and vertical grid lines for each image bock based on the motion-compensated data for each image block; computing second stage image values for the image grid point intersections by interpolation using the first stage image values at the image grid point intersections; correcting image phase of the second stage image values for the image grid point intersections to generate phase-corrected image values for each image block; and generating a full-resolution SAR image by summing the phase-corrected image values for each image block.