Focusing Hypersonic Vehicle-Borne SAR Data Using Radius/Angle Algorithm

As a transition platform between aircraft and satellite, hypersonic vehicle-borne (HSV) synthetic aperture radar (SAR) could offer many advantages such as strong survival ability, fast response, and wide detection range. However, due to the complex aerodynamic configuration and flight characteristics of the hypersonic platform, the HSV SAR faces new challenges including serious cross-couplings and spatial variations. In order to deal with these issues, a radius/angle algorithm (RAA) is devised, which has a similar processing flow as that of the conventional polar format algorithm (PFA). In the RAA, a novel 2-D interpolation function, similar to that of the PFA which is performed in the Cartesian coordinates, is derived in the curvilinear coordinate system. Due to the high accuracy of the multi-decomposition by using the polar radius and polar angle, the RAA has a much larger depth-of-focus than that of the PFA. Moreover, the RAA approach is insensitive to the height variations for the HSV SAR with curved trajectory flight, whereas the PFA is not because of the out-of-plane projection effect. Simulation results verify the effectiveness of the proposed approach.