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

Title: Synthetic Aperture Radar Image Formation in Reconfigurable Logic

Abstract

This paper studies the implementation of polar format, synthetic aperture radar image formation in modern Field Programmable Gate Arrays (FPGA's). The polar format algorithm is described in rough terms and each of the processing steps is mapped to FPGA logic. This FPGA logic is analyzed with respect to throughput and circuit size for compatibility with airborne image formation.

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:
782724
Report Number(s):
SAND2001-1827
TRN: AH200126%%119
DOE Contract Number:
AC04-94AL85000
Resource Type:
Technical Report
Resource Relation:
Other Information: PBD: 1 Jun 2001
Country of Publication:
United States
Language:
English
Subject:
47 OTHER INSTRUMENTATION; 99 GENERAL AND MISCELLANEOUS//MATHEMATICS, COMPUTING, AND INFORMATION SCIENCE; ALGORITHMS; COMPATIBILITY; IMPLEMENTATION; RADAR; IMAGE PROCESSING

Citation Formats

DUDLEY,PETER A. Synthetic Aperture Radar Image Formation in Reconfigurable Logic. United States: N. p., 2001. Web. doi:10.2172/782724.
DUDLEY,PETER A. Synthetic Aperture Radar Image Formation in Reconfigurable Logic. United States. doi:10.2172/782724.
DUDLEY,PETER A. Fri . "Synthetic Aperture Radar Image Formation in Reconfigurable Logic". United States. doi:10.2172/782724. https://www.osti.gov/servlets/purl/782724.
@article{osti_782724,
title = {Synthetic Aperture Radar Image Formation in Reconfigurable Logic},
author = {DUDLEY,PETER A.},
abstractNote = {This paper studies the implementation of polar format, synthetic aperture radar image formation in modern Field Programmable Gate Arrays (FPGA's). The polar format algorithm is described in rough terms and each of the processing steps is mapped to FPGA logic. This FPGA logic is analyzed with respect to throughput and circuit size for compatibility with airborne image formation.},
doi = {10.2172/782724},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Fri Jun 01 00:00:00 EDT 2001},
month = {Fri Jun 01 00:00:00 EDT 2001}
}

Technical Report:

Save / Share:
  • Spotlight synthetic aperture radar images can be formed from the complex phase history data using two main techniques: (1) polar-to-cartesian interpolation followed by two-dimensional inverse Fourier transform (2DFFT), and (2) convolution backprojection (CBP). CBP has been widely used to reconstruct medical images in computer aided tomography, and only recently has been applied to form synthetic aperture radar imagery. It is alleged that CBP yields higher quality images because (1) all the Fourier data are used and (2) the polar formatted data is used directly to form a 2D Cartesian image and therefore 2D interpolation is not required. This report comparesmore » the quality of images formed by CBP and several modified versions of the 2DFFT method. We show from an image quality point of view that CBP is equivalent to first windowing the phase history data and then interpolating to an exscribed rectangle. From a mathematical perspective, we should expect this conclusion since the same Fourier data are used to form the SAR image. We next address the issue of parallel implementation of each algorithm. We dispute previous claims that CBP is more readily parallelizable than the 2DFFT method. Our conclusions are supported by comparing execution times between massively parallel implementations of both algorithms, showing that both experience similar decreases in computation time, but that CBP takes significantly longer to form an image.« less
  • IFP V4.0 is the fourth generation of an extraordinarily powerful and flexible image formation processor for spotlight mode synthetic aperture radar. It has been successfully utilized in processing phase histories from numerous radars and has been instrumental in the development of many new capabilities for spotlight mode SAR. This document provides a brief history of the development of IFP, a full exposition of the signal processing steps involved, and a short user's manual for the software implementing this latest iteration.
  • Most producing geothermal fields and known geothermal resources in the Basin and Range province are associated with Quaternary active fault systems, within which hydrothermal fluids are presumed to circulate from depth to relatively shallow production levels through high permeability fractures. Research at the Dixie Valley field by Barton et al. (1997) indicates that hydraulically conductive fractures within the Stillwater fault zone are those that have orientations such that the fractures are critically stressed for normal shear failure under the regional tectonic stress field. In general, therefore, we might expect geothermal resources to occur in areas of high inter-seismic strain accumulation,more » and where faults are favorably oriented with respect to the regional strain tensor; in the case of Basin and Range normal faults, these would generally be faults striking normal to the direction of maximum extension. Expanding this hypothesis, Blewitt et al. (2003), based on preliminary, broad-scale analysis of regional strain and average fault strike in the northwestern Basin and Range, have proposed that geothermal resources occur in areas where fault-normal extension associated with shear strain is the greatest. Caskey and Wesnousky (2000) presented evidence that the Dixie Valley field occupies a 10 km-long gap between prehistoric Holocene ruptures of the fault segments on either side. Modeled maximum shear and Coulomb failure stress are high within the gap owing to the stress concentrations at the ends of the ruptures. These results suggest that a major contributing factor to the enhanced permeability at fault-hosted geothermal systems may be localized stress and strain concentrations within fault zone segments. This notion is generally consistent with the common occurrence of geothermal fields within fault offsets (pull-aparts) along strike-slip fault systems, where the local strain field has a large extensional component (e.g., Salton Sea and Coso). Blewitt et al. (2003) suggested that resources correlate with abrupt changes in fault orientation and with changes in the direction of extensional strain.« less
  • An acousto-optic processor which forms synthetic aperture radar images in real-time is described. It employs a space and time integrating architecture to perform the required two dimensional matched filtering operation as a sequence of one dimensional processes. The matched filtering in range is performed on each radar return pulse using the acousto-optic device. The azimuthal matched filtering is performed using a fixed reference mask and a charge-coupled device operating in the time delay and integrate mode. This fixed mask architecture has been modified to include a background subtraction capability to reduce the effects of unwanted bias terms on image quality.more » The effectiveness of this technique will be analyzed for two different time bandwidth product cases. SAR imagery formed using the real-time optical processor is also presented.« less
  • Radar non-acoustic anti-submarine warfare (NAASW) became the subject of considerable scientific investigation and controversy in the West subsequent to the discovery by the Seasat satellite in 1978 that manifestations of underwater topography, thought to be hidden from the radar, were visible in synthetic aperture radar (SAR) images of the ocean. In addition, the Seasat radar produced images of ship wakes where the observed angle between the wake arms was much smaller than expected from classical Kelvin wake theory. These observations cast doubt on the radar oceanography community's ability to adequately explain these phenomena, and by extension on the ability ofmore » existing hydrodynamic and radar scattering models to accurately predict the observability of submarine-induced signatures. If one is of the opinion that radar NAASW is indeed a potentially significant tool in detecting submerged operational submarines, then the Soviet capability, as evidenced throughout this report, will be somewhat daunting. It will be shown that the Soviets have extremely fine capabilities in both theoretical and experimental hydrodynamics, that Soviet researchers have been conducting at-sea radar remote sensing experiments on a scale comparable to those of the United States for several years longer than we have, and that they have both an airborne and spaceborne SAR capability. The only discipline that the Soviet Union appears to be lacking is in the area of digital radar signal processing. If one is of the opinion that radar NAASW can have at most a minimal impact on the detection of submerged submarines, then the Soviet effort is of little consequence and poses not threat. 280 refs., 31 figs., 12 tabs.« less