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

Abstract

Wavefront curvature defocus effects can occur in spotlight-mode SAR imagery when reconstructed via the well-known polar formatting algorithm (PFA) 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 (RMA), 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 the authors 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 (PF2) should be considered as a viable candidate for a spotlight-mode image formation processor when curvature effects are present.

Authors:
; ; ;
Publication Date:
Research Org.:
Sandia National Labs., Albuquerque, NM (United States)
Sponsoring Org.:
USDOE, Washington, DC (United States)
OSTI Identifier:
463669
Report Number(s):
SAND-96-2376C; CONF-970465-9
ON: DE97004442; TRN: AHC29709%%106
DOE Contract Number:
AC04-94AL85000
Resource Type:
Conference
Resource Relation:
Conference: SPIE international conference, Orlando, FL (United States), 21-25 Apr 1997; Other Information: PBD: [1996]
Country of Publication:
United States
Language:
English
Subject:
44 INSTRUMENTATION, INCLUDING NUCLEAR AND PARTICLE DETECTORS; 99 MATHEMATICS, COMPUTERS, INFORMATION SCIENCE, MANAGEMENT, LAW, MISCELLANEOUS; RADAR; IMAGE PROCESSING; DIGITAL FILTERS; ALGORITHMS; MODIFICATIONS; CORRECTIONS

Citation Formats

Jakowatz, C.V. Jr., Wahl, D.E., Thompson, P.A., and Doren, N.E. Space-variant filtering for correction of wavefront curvature effects in spotlight-mode SAR imagery formed via polar formatting. United States: N. p., 1996. Web.
Jakowatz, C.V. Jr., Wahl, D.E., Thompson, P.A., & Doren, N.E. Space-variant filtering for correction of wavefront curvature effects in spotlight-mode SAR imagery formed via polar formatting. United States.
Jakowatz, C.V. Jr., Wahl, D.E., Thompson, P.A., and Doren, N.E. Tue . "Space-variant filtering for correction of wavefront curvature effects in spotlight-mode SAR imagery formed via polar formatting". United States. doi:. https://www.osti.gov/servlets/purl/463669.
@article{osti_463669,
title = {Space-variant filtering for correction of wavefront curvature effects in spotlight-mode SAR imagery formed via polar formatting},
author = {Jakowatz, C.V. Jr. and Wahl, D.E. and Thompson, P.A. and Doren, N.E.},
abstractNote = {Wavefront curvature defocus effects can occur in spotlight-mode SAR imagery when reconstructed via the well-known polar formatting algorithm (PFA) 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 (RMA), 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 the authors 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 (PF2) should be considered as a viable candidate for a spotlight-mode image formation processor when curvature effects are present.},
doi = {},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Tue Dec 31 00:00:00 EST 1996},
month = {Tue Dec 31 00:00:00 EST 1996}
}

Conference:
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