PFA algorithm for airborne spotlight SAR imaging with nonideal motions

The nonuniform-interpolation polar format algorithm is developed for processing spotlight SAR data with nonideal platform motions. Instead of two uniform interpolations for the conventional polar format algorithm (PFA), this algorithm employs a one-dimensional uniform interpolation in the range direction and a one-dimensional nonuniform interpolation in the azimuth direction to remove effects of nonideal motion. For azimuth-nonuniform interpolation. the output sample spacing depends on the pulse number, range and motion data, and can be easily computed. The output sample spacing can also be precomputed and stored in RAM. The computational load of azimuth-nonuniform interpolation is almost the same as azimuth-uniform interpolation, if the output sample spacing is precomputed and stored. The computational load is the same for both algorithms. Theoretically, for scatterers in the focus target plane (FTP), this algorithm can produce a SAR image with the same quality for the nonideal motion case as for the ideal motion case. Like conventional PFA, it is compatible with autofocus. Computer simulation results validate the algorithm.