23 May 2013 An application of backprojection for video SAR image formation exploiting a subaperature circular shift register
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This paper details a Video SAR (Synthetic Aperture Radar) mode that provides a persistent view of a scene centered at the Motion Compensation Point (MCP). The radar platform follows a circular flight path. An objective is to form a sequence of SAR images while observing dynamic scene changes at a selectable video frame rate. A formulation of backprojection meets this objective. Modified backprojection equations take into account changes in the grazing angle or squint angle that result from non-ideal flight paths. The algorithm forms a new video frame relying upon much of the signal processing performed in prior frames. The method described applies an appropriate azimuth window to each video frame for window sidelobe rejection. A Cardinal Direction Up (CDU) coordinate frame forms images with the top of the image oriented along a given cardinal direction for all video frames. Using this coordinate frame helps characterize a moving target’s target response. Generation of synthetic targets with linear motion including both constant velocity and constant acceleration is described. The synthetic target video imagery demonstrates dynamic SAR imagery with expected moving target responses. The paper presents 2011 flight data collected by General Atomics Aeronautical Systems, Inc. (GA-ASI) implementing the video SAR mode. The flight data demonstrates good video quality showing moving vehicles. The flight imagery demonstrates the real-time capability of the video SAR mode. The video SAR mode uses a circular shift register of subapertures. The radar employs a Graphics Processing Unit (GPU) in order to implement this algorithm.
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J. Miller, J. Miller, E. Bishop, E. Bishop, A. Doerry, A. Doerry, "An application of backprojection for video SAR image formation exploiting a subaperature circular shift register", Proc. SPIE 8746, Algorithms for Synthetic Aperture Radar Imagery XX, 874609 (23 May 2013); doi: 10.1117/12.2016417; https://doi.org/10.1117/12.2016417

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