Space-variant filtering for correction of wavefront curvature effects in spotlight-mode SAR imagery formed via polar formatting

Charles V. Jakowatz Jr.; Daniel E. Wahl; Paul A. Thompson; Neall E. Doren

doi:10.1117/12.281576

28 July 1997 Space-variant filtering for correction of wavefront curvature effects in spotlight-mode SAR imagery formed via polar formatting

Charles V. Jakowatz Jr., Daniel E. Wahl, Paul A. Thompson, Neall E. Doren

Author Affiliations +

Proceedings Volume 3070, Algorithms for Synthetic Aperture Radar Imagery IV; (1997) https://doi.org/10.1117/12.281576
Event: AeroSense '97, 1997, Orlando, FL, United States

Abstract

Wavefront curvature defocus effects can occur in spotlight- mode SAR imagery when reconstructed via the well-known polar formatting algorithm under certain scenarios that include imaging at close range, use of very low center frequency, and/or imaging of very large scenes. The range migration algorithm, also known as seismic migration, was developed to accommodate these wavefront curvature effects. However, the along-track upsampling of the phase history data required of the original version of range migration can in certain instances represent a major computational burden. A more recent version of migration processing, the frequency domain replication and downsampling (FReD) algorithm, obviates the need to upsample, and is accordingly more efficient. In this paper we demonstrate that the combination of traditional polar formatting with appropriate space-variant post- filtering for refocus can be as efficient or even more efficient than FReD under some imaging conditions, as demonstrated by the computer-simulated results in this paper. The post-filter can be pre-calculated from a theoretical derivation of the curvature effect. The conclusion is that the new polar formatting with post filtering algorithm should be considered as a viable candidate for a spotight-mode image formation processor when curvature effects are present.

Citation Download Citation

Charles V. Jakowatz Jr., Daniel E. Wahl, Paul A. Thompson, and Neall E. Doren "Space-variant filtering for correction of wavefront curvature effects in spotlight-mode SAR imagery formed via polar formatting", Proc. SPIE 3070, Algorithms for Synthetic Aperture Radar Imagery IV, (28 July 1997); https://doi.org/10.1117/12.281576

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