Fast overlapped subaperture algorithm for high-squint spotlight SAR imaging

The overlapped subaperture algorithm (OSA) is popular for high-squint spotlight synthetic aperture radar (SAR) imaging due to its ability of dealing with a much larger swath than the primary polar format algorithm. However, the traditional OSA suffers from the problem of low efficiency because of the high subaperture overlapping ratio (SOR) required to get rid of spurious targets. The contribution of this study is to loosen the original SOR limit by embedding an additional spatially variant apodization (SVA) into the architecture, resulting in a new fast OSA with lighter computational load and hence higher processing efficiency. Specifically, the algorithm is modified mainly from two aspects: First, a new spatial variant quadratic phase error (QPE) filter is induced to enable effective SVA implementation; Second, a new squint subaperture stitch method is induced to accommodate the subaperture extraction with the new data format led by the new QPE filter. The proposed approach is evaluated by both the point target simulations and the real airborne SAR data in aspects of spurious target suppression, image quality and processing efficiency.