Considerations for autofocus of spotlight-mode SAR imagery created using a beamforming algorithm

Charles V. Jakowatz Jr.; Daniel E. Wahl

doi:10.1117/12.820049

28 April 2009 Considerations for autofocus of spotlight-mode SAR imagery created using a beamforming algorithm

Charles V. Jakowatz Jr., Daniel E. Wahl

Proceedings Volume 7337, Algorithms for Synthetic Aperture Radar Imagery XVI; 73370A (2009) https://doi.org/10.1117/12.820049
Event: SPIE Defense, Security, and Sensing, 2009, Orlando, Florida, United States

Abstract

In recent papers the authors discussed the advantages of forming spotlight-mode SAR imagery from phase history data via a technique that is rooted in the principles of phased-array beamforming, which is closely related to back-projection. The application of a traditional autofocus algorithm, such as Phase Gradient Autofocus (PGA), requires some care in this situation. Specifically, a stated advantage of beamforming is that it easily allows for reconstruction of the SAR image onto an arbitrary imaging grid. One very useful grid, for example, is a Cartesian grid in the ground plane. Autofocus via PGA for such an image, however, cannot be performed in a straightforward manner, because in PGA a Fourier transform relationship is required between the image domain and the range-compressed phase history, and this is not the case for such an imaging grid. In this paper we propose a strategy for performing autofocus in this situation, and discuss its limitations. We demonstrate the algorithm on synthetic phase errors applied to real SAR imagery.

Citation Download Citation

Charles V. Jakowatz Jr. and Daniel E. Wahl "Considerations for autofocus of spotlight-mode SAR imagery created using a beamforming algorithm", Proc. SPIE 7337, Algorithms for Synthetic Aperture Radar Imagery XVI, 73370A (28 April 2009); https://doi.org/10.1117/12.820049

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