An N² log N back-projection algorithm for SAR image formation

We propose a fast algorithm for far-field SAR imaging based on a new fast back-projection algorithm developed for tomography. We also modify the algorithm for the near-field scenario. The fast back-projection algorithm for SAR has computational complexity O(N²logN). Compared to traditional FFT-based methods, our new algorithm has potential advantages: The new algorithm does not need frequency-domain interpolation, which becomes complex for the wide-angle case; the new approach is applicable to the near-field scenario, taking into account wavefront curvature; and the back-projection algorithm can be easily adapted to parallel computing architectures. For some scenarios of interest, the computational cost of the new backprojection approach is similar to or less than that for FFT-based algorithms.