Synthetic Aperture Radar Processing Using Flexible and Seamless Factorized Back-Projection

This paper describes a flexible and seamless processor for Unmanned Aerial Vehicle (UAV)-borne Synthetic Aperture Radar (SAR) imagery. When designing a focusing algorithm for large-scale and high-resolution SAR images, efficiency and accuracy are two mandatory aspects to consider. The proposed processing scheme is based on a modified version of Fast Factorized Back-Projection (FFBP), in which the factorization procedure is interrupted on the basis of a computational cost analysis to reduce the number of complex operations at its minimum. The algorithm gains efficiency in the case of low-altitude platforms, where there are significant variations in azimuth resolution, but not in the case of conventional airborne missions, where the azimuth resolution can be considered constant in the swath. The algorithm's performance is derived by assessing the number of complex operations required to focus an SAR image. Two scenarios are tackled in a numerical simulation: a UAV-borne SAR with a short synthetic aperture and a wide field of view, referred to as the ground-based-like (GBL) scenario, and a classical stripmap scenario. In both cases, we consider mono-static and bi-static radar configurations. The results of the numerical simulations show that the proposed algorithm outperforms FFBP in the stripmap scenario while achieving the same performance as FFBP in the GBL scenario. In addition, the algorithm is validated thanks to an experimental UAV-borne SAR campaign in the X-band.