skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: Bandwidth requirements for fine resolution squinted SAR

Abstract

The conventional rule-of-thumb for Synthetic Aperture Radar is that an RF bandwidth of c/(2{rho}{sub r}) is required to image a scene at the desired slant-range resolution {rho}{sub r}, and perhaps a little more to account for window functions and sidelobe control. This formulation is based on the notion that the total bandwidth required is the same bandwidth that is required for a single pulse. What is neglected is that efficient processing of an entire synthetic aperture of pulses will often require different frequency content for each of the different pulses that makeup a synthetic aperture. Consequently, the total RF bandwidth required of a Synthetic Aperture Radar may then be substantially wider than the bandwidth of any single pulse. The actual RF bandwidth required depends strongly on flight geometry, owing to the desire for a radar to maintain a constant projection of the Fourier space collection surface onto the {omega}{sub y} axis. Long apertures required for fine azimuth resolution, and severe squint angles with steep depression angles may require total RF bandwidths well beyond the minimum bandwidth required of any single transmitted pulse, perhaps even by a factor of two or more. Accounting for this is crucial to designing efficient versatilemore » high-performance imaging radars. This paper addresses how a data set conducive to efficient processing might increase the total RF bandwidth, and presents examples of how a fixed RF bandwidth might then limit SAR geometries.« less

Authors:
Publication Date:
Research Org.:
Sandia National Labs., Albuquerque, NM (US); Sandia National Labs., Livermore, CA (US)
Sponsoring Org.:
US Department of Energy (US)
OSTI Identifier:
752099
Report Number(s):
SAND99-2360C
TRN: AH200018%%441
DOE Contract Number:
AC04-94AL85000
Resource Type:
Conference
Resource Relation:
Conference: SPIE 14th Annual International Symposium on Aerospace/Defense Sensing, Simulation and Control, Orlando, FL (US), 04/24/2000--04/28/2000; Other Information: PBD: 1 Mar 2000
Country of Publication:
United States
Language:
English
Subject:
47 OTHER INSTRUMENTATION; RADAR; IMAGES; GEOMETRY; MOTION; CORRECTIONS; WAVE FORMS; SPECIFICATIONS; SAR; BANDWIDTH; SQUINT; MOTION COMPENSATION

Citation Formats

DOERRY,ARMIN W. Bandwidth requirements for fine resolution squinted SAR. United States: N. p., 2000. Web.
DOERRY,ARMIN W. Bandwidth requirements for fine resolution squinted SAR. United States.
DOERRY,ARMIN W. Wed . "Bandwidth requirements for fine resolution squinted SAR". United States. doi:. https://www.osti.gov/servlets/purl/752099.
@article{osti_752099,
title = {Bandwidth requirements for fine resolution squinted SAR},
author = {DOERRY,ARMIN W.},
abstractNote = {The conventional rule-of-thumb for Synthetic Aperture Radar is that an RF bandwidth of c/(2{rho}{sub r}) is required to image a scene at the desired slant-range resolution {rho}{sub r}, and perhaps a little more to account for window functions and sidelobe control. This formulation is based on the notion that the total bandwidth required is the same bandwidth that is required for a single pulse. What is neglected is that efficient processing of an entire synthetic aperture of pulses will often require different frequency content for each of the different pulses that makeup a synthetic aperture. Consequently, the total RF bandwidth required of a Synthetic Aperture Radar may then be substantially wider than the bandwidth of any single pulse. The actual RF bandwidth required depends strongly on flight geometry, owing to the desire for a radar to maintain a constant projection of the Fourier space collection surface onto the {omega}{sub y} axis. Long apertures required for fine azimuth resolution, and severe squint angles with steep depression angles may require total RF bandwidths well beyond the minimum bandwidth required of any single transmitted pulse, perhaps even by a factor of two or more. Accounting for this is crucial to designing efficient versatile high-performance imaging radars. This paper addresses how a data set conducive to efficient processing might increase the total RF bandwidth, and presents examples of how a fixed RF bandwidth might then limit SAR geometries.},
doi = {},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Wed Mar 01 00:00:00 EST 2000},
month = {Wed Mar 01 00:00:00 EST 2000}
}

Conference:
Other availability
Please see Document Availability for additional information on obtaining the full-text document. Library patrons may search WorldCat to identify libraries that hold this conference proceeding.

Save / Share:
  • Sandia National Laboratories designs and builds Synthetic Aperture Radar (SAR) systems capable of forming high-quality exceptionally fine resolution images. During the spring of 2004 a series of test flights were completed with a Ka-band testbed SAR on Sandia's DeHavilland DHC-6 Twin Otter aircraft. A large data set was collected including real-time fine-resolution images of a variety of target scenes. This paper offers a sampling of high quality images representative of the output of Sandia's Ka-band testbed radar with resolutions as fine as 4 inches. Images will be annotated with descriptions of collection geometries and other relevant image parameters.
  • A level-1 probabilistic risk assessment (PRA) was completed in July 1990 and revised and updated in January 1993 for the U.S. Department of Energy production reactors at the Savannah River site in Aiken, South Carolina. The PRA has since been used several times to guide risk management decisions, as well as to quantify absolute risk and to help in understanding system interactions. This paper describes one of the risk management applications in which PRA analysis determined that a reactor subcriticality issue being considered for inclusion in the safety analysis report (SAR) is low enough in expected frequency that it canmore » be excluded.« less
  • In a typical interferometric synthetic aperture radar (IFSAR) system employed for terrain elevation mapping, terrain height is estimated from phase difference data obtained from two phase centers separated spatially in the cross-track direction. In this paper we show how the judicious design of a three phase center IFSAR renders phase unwrapping, i.e., the process of estimating true continuous phases from principal values of phase (wrapped modulo 2{pi}), a much simpler process than that inherent in traditional algorithms. With three phase centers, one IFSAR baseline can be chosen to be relatively small (two of the phase centers close together) so thatmore » all of the scene`s terrain relief causes less than one cycle of phase difference. This allows computation of a coarse height map without use of any form of phase unwrapping. The cycle number ambiguities in the phase data derived from the other baseline, chosen to be relatively large (two of the phase centers far apart), can then be resolved by reference to the heights computed from the small baseline data. This basic concept of combining phase data from one small and one large baseline to accomplish phase unwrapping has been previously employed in other interferometric problems, e.g., laser interferometry and direction-of-arrival determination from multiple element arrays, The new algorithm is shown to possess a certain form of immunity to corrupted interferometric phase data that is not inherent in traditional two-dimensional path-following phase unwrappers. This is because path-following algorithms must estimate, either implicity or explicity, those portions of the IFSAR fringe data where discontinuities in phase occur. Such discontinuties typically arise from noisy phase measurements derived from low radar return areas of the SAR imagery, e.g., shadows, or from areas of steep terrain slope.« less
  • This paper describes the Twin-Otter SAR Testbed developed at Sandia National Laboratories. This SAR is a flexible, adaptable testbed capable of operation on four frequency bands: Ka, Ku, X, and VHF/UHF bands. The SAR features real-time image formation at fine resolution in spotlight and stripmap modes. High-quality images are formed in real time using the overlapped subaperture (OSA) image-formation and phase gradient autofocus (PGA) algorithms.