The U.S. Army Research Laboratory (ARL) is investigating an efficient SAR image formation algorithm to support its mission-funded Ultra-Wideband BoomSAR program. The traditional Back-projection technique produces images, requires no memory resources and allows arbitrary motion; however it is very computationally intensive and is therefore appropriate only for postprocessing applications. ARL invented a new recursive backprojector that reduces the computational load from an order N3 to N2Log(N). This new algorithm is competitive in speed with the frequency domain WK processing but requires less memory, and produces fewer artifacts. We compare both algorithms and presents the results of using simulation data and real data.