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Patch diameter limits for tiered subaperture SAR image formation algorithms

Description: Synthetic Aperture Radar image formation algorithms typically use transform techniques that often requires trading between image resolution, algorithm efficiency, and focussed image scene size limits. This is due to assumptions for the data such as simplified (often straight-line) flight paths, simplified imaging geometry, and simplified models for phase functions. Many errors in such assumptions are typically untreatable due to their dependence on both data domain positions and image domain positions. The result is that large scenes often require inefficient multiple image formation iterations, followed by a mosaicking operation of the focussed image patches. One class of image formation algorithms that performs favorably divides the spatial and frequency apertures into subapertures, and perhaps those subapertures into sub-subapertures, and so on, in a tiered subaperture fashion. This allows a gradual shift from data domain into image domain that allows correcting many types of errors that limit other image formation algorithms, even in a dynamic motion environment, thereby allowing larger focussed image patches without mosaicking. This paper presents and compares focussed patch diameter limits for tiered subaperture (TSA) image formation algorithms, for various numbers of tiers of subapertures. Examples are given that show orders-of-magnitude improvement in non-mosaicked focussed image patch size over traditional polar format processing, and that patch size limits increase with the number of tiers of subapertures, although with diminishing returns.
Date: December 31, 1994
Creator: Doerry, A.W.
Partner: UNT Libraries Government Documents Department

Proceedings of the environmental technology through industry partnership conference. Volume 2

Description: The overall objective of this conference was to review the latest environmental and waste management technologies being developed under the sponsorship of METC. The focus of this conference was also to address the accomplishments and barriers affecting private sector, and lay the groundwork for future technology development initiatives and opportunities. 26 presentations were presented in: Mixed waste characterization, treatment, and disposal; Contaminant plume containment and remediation; and Decontamination and decommissioning. In addition there were 10 Focus Area presentations, 31 Poster papers covering all Focus Areas, and two panel discussions on: Mixed waste characterization, treatment, and disposal issues; and the Application, evaluation, and acceptance of in-situ and ex-situ plume remediation technologies. Volume 2 contains 16 papers in a poster session and 8 papers in the contaminant plume containment and remediation and landfill stabilization Focus Areas. Selected papers are indexed separately for inclusion in the Energy Science and Technology Database.
Date: October 1, 1995
Creator: Kothari, V.P.
Partner: UNT Libraries Government Documents Department

Advanced product realization through model-based design and virtual prototyping

Description: Several government agencies and industrial sectors have recognized the need for, and payoff of, investing in the methodologies and associated technologies for improving the product realization process. Within the defense community as well as commercial industry, there are three major needs. First, they must reduce the cost of military products, of related manufacturing processes, and of the enterprises that have to be maintained. Second, they must reduce the time required to realize products while still applying the latest technologies. Finally, they must improve the predictability of process attributes, product performance, cost, schedule and quality. They must continue to advance technology, quickly incorporate their innovations in new products and in processes to produce them, and they need to capitalize on the raw computational power and communications bandwidth that continues to become available at decreasing cost. Sandia National Laboratories initiative is pursuing several interrelated, key concepts and technologies in order to enable such product realization process improvements: model-based design; intelligent manufacturing processes; rapid virtual and physical prototyping; and agile people/enterprises. While progress in each of these areas is necessary, this paper only addresses a portion of the overall initiative. First a vision of a desired future capability in model-based design and virtual prototyping is presented. This is followed by a discussion of two specific activities parametric design analysis of Synthetic Aperture Radars (SARs) and virtual prototyping of miniaturized high-density electronics -- that exemplify the vision as well as provide a status report on relevant work in progress.
Date: March 1995
Creator: Andreas, R. D.
Partner: UNT Libraries Government Documents Department

Treaty on Open Skies sensor technologies with potential international safeguards applications

Description: The Treaty on Open Skies is a precedent-setting agreement that allows signatory states to fly aircraft over each other`s territory with sensor systems. The purpose of the Treaty is to improve confidence and security with respect to military activities of the signatories. This paper reviews the sensor technology that is currently allowed by the Treaty on Open Skies and potential future sensor technology. The Treaty on Open Skies does have provisions to allow for the improvement of the technology of the current sensor systems and for the proposal of new sensors after a period of time. This can occur only after the Treaty has been ratified and has entered into force. If this regime was to be used for other than Treaty on Open Skies applications some modifications to the allowed sensor technology should be examined. This paper presents some ideas on potential improvements to existing allowed sensor technology as well as some suggested new advanced sensor systems that would be useful for future potential monitoring of safeguard`s related activities. This paper addresses advanced imaging sensors and non-imaging sensors for potential use in aerial remote sensing roles that involve international data sharing.
Date: December 1, 1996
Creator: Sandoval, M.B.
Partner: UNT Libraries Government Documents Department

Development of a folded compact range and its application in performing coherent change detection and interferometric ISAR measurement

Description: A folded compact range configuration has been developed at the Sandia National Laboratories` compact range antenna and radar cross section measurement facility as a means of performing indoor, environmentally controlled far-field simulations of synthetic aperture radar (SAR) measurements of distributed target samples (i.e. gravel, sand, etc.). In particular, the folded compact range configuration has been used to perform both highly sensitive coherent change detection (CCD) measurements and interferometric inverse synthetic aperture radar (IFSAR) measurements, which, in addition to the two-dimensional spatial resolution afforded by typical interferometric SAR (ISAR) processing, provides resolution of the relative height of targets with accuracies on the order of a wavelength. This paper describes the development of the folded compact range, as well as the coherent change detection and interferometric measurements that have been made with the system. The measurement have been very successful, and have demonstrated not only the viability of the folded compact range concept in simulating SAR CCD and IFSAR measurements, but also its usefulness as a tool in the research and development of SAR CCD and IFSAR image generation and measurement methodologies.
Date: September 1, 1996
Creator: Sorensen, K.W.; Zittel, D.H. & Littlejohn, J.H.
Partner: UNT Libraries Government Documents Department

Determination of absolute interferometric phase using the beam-amplitude ratio technique

Description: Determination of the absolute phase difference (i.e., not modulo 2{pi}) is a key problem in interferometric synthetic aperture radar (IFSAR) for topographic mapping. One way of solving this problem requires use of a technique different from the basic interferometry to resolve a `coarse` angle measurement that lies within the IFSAR ambiguity angle. The method investigated in this paper involves taking advantage of the difference in the amplitude ratio versus elevation angle that occurs when the elevation beams of the two IFSAR antennas are pointed in slightly different directions. The performance of the technique is a function of the angular separation of the two beams, the elevation beamwidth, and the symmetry of the two beam-amplitude patterns. The performance required of the technique is set by the ambiguity angle of the interferometer. This paper presents an analysis of the beam-amplitude ratio technique and shows experimental results.
Date: March 1, 1996
Creator: Bickel, D.L. & Hensley, W.H.
Partner: UNT Libraries Government Documents Department

Fusion of LADAR with SAR for precision strike

Description: This paper presents a concept for fusing 3-dimensional image reconnaissance data with LADAR imagery for aim point refinement. The approach is applicable to fixed or quasi-fixed targets. Quasi-fixed targets are targets that are not expected to be moved between the time of reconnaissance and the time of target engagement. The 3-dimensional image data is presumed to come from standoff reconnaissance assets tens to hundreds of kilometers from the target area or acquisitions prior to hostilities. Examples are synthetic aperture radar (SAR) or stereoprocessed satellite imagery. SAR can be used to generate a 3-dimensional map of the surface through processing of data acquired with conventional SAR acquired using two closely spaced, parallel reconnaissance paths, either airborne or satellite based. Alternatively, a specialized airborne SAR having two receiving antennas may be used for data acquisition. The data sets used in this analysis are: (1) LADAR data acquired using a Hughes-Danbury system flown over a portion of Kirtland AFB during the period September 15--16, 1993; (2) two pass interferometric SAR data flown over a terrain-dominated area of Kirtland AFB; (3) 3-dimensional mapping of an urban-dominated area of the Sandia National Laboratories and adjacent cultural area extracted from aerial photography by Vexcel Corporation; (4) LADAR data acquired at Eglin AFB under Wright Laboratory`s Advanced Technology Ladar System (ATLAS) program using a 60 {mu}J, 75 KHz Co{sub 2} laser; and (5) two pass interferometric SAR data generated by Sandia`s STRIP DCS (Data Collection System) radar corresponding to the ATLAS LADAR data. The cultural data set was used in the urban area rather than SAR because high quality interferometric SAR data were not available for the urban-type area.
Date: March 1, 1995
Creator: Cress, D.H. & Muguira, M.R.
Partner: UNT Libraries Government Documents Department

Buried mine detection using ground-penetrating impulse radar

Description: LLNL is developing a side-looking, ground-penetrating impulse radar system that can eventually be mounted on a robotic vehicle or an airborne platform to locate buried land mines. The system is described and results from field experiments are presented.
Date: March 1995
Creator: Sargis, P. D.
Partner: UNT Libraries Government Documents Department

Consistent 2-D phase unwrapping guided by a qualtiy map

Description: The problem of 2-D phase unwrapping arises when a spatially varying quantity is measured modulo some period. One needs to reconstruct a smooth unwrapped phase, consistent with the original data, by adding a multiple of the period to each sample. Smoothness typically cannot be enforced over all of the scene, due to noise and localized jumps. An unwrapping algorithm may form a mask within which phase discontinuities are allowed. In interferometry a quality map is available, indicating the reliability of the measurements. In this case, the mask should be contained as much as possible in areas of low quality. This paper presents an algorithm for phase unwrapping in which the mask design is guided by the quality map. The mask is grown from the residues (as defined by Goldstein et al.) into areas where the quality is below a threshold. A connected component of the mask stops growing when its residue charge becomes balanced. The threshold is raised as necessary to allow growth. This stage terminates when all components are balanced. The mask is then thinned by removing points that are not needed to cover the residues correctly. The unwrapped phase is found by simple I-D unwrapping along paths that avoid the mask. We present an example solution found by the algorithm and discuss possible modifications.
Date: 1995
Creator: Flynn, T. J.
Partner: UNT Libraries Government Documents Department

Imaging radar for bridge deck inspection

Description: Lawrence Livermore National Laboratory (LLNL)l is developing a prototype imaging radar for inspecting steel reinforced concrete bridge decks. The system is designed to acquire Synthetic Aperture Radar (SAR) data and provide high-resolution images of internal structure, flaws, and defects enabling bridge inspectors to nondestructively evaluate and characterize bridge deck condition. Concrete delamination resulting from corrosion of steel reinforcing bars (rebars) is an important structural defect that the system is designed to detect. The prototype system uses arrays of compact, low-cost Micropower Impulse Radar (MIR) modules, supported by appropriate data acquisition and storage subsystems, to generate and collect the radar data, and unique imaging codes to reconstruct images of bridge deck internals. In this paper, we provide an overview of the prototype system concept, discuss its expected performance, and present recent experimental results showing the capability of this approach to detect thin delamination simulations embedded in concrete.
Date: April 13, 1995
Creator: Warhus, J.; Mast, J. & Nelson, S.
Partner: UNT Libraries Government Documents Department

Ambiguity resolution in SAR interferometry by use of three phase centers

Description: 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 that 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.
Date: March 1, 1996
Creator: Jakowatz, C.V. Jr.; Wahl, D.E. & Thompson, P.A.
Partner: UNT Libraries Government Documents Department

Lossless compression of synthetic aperture radar images

Description: Synthetic Aperture Radar (SAR) has been proven an effective sensor in a wide variety of applications. Many of these uses require transmission and/or processing of the image data in a lossless manner. With the current state of SAR technology, the amount of data contained in a single image may be massive, whether the application requires the entire complex image or magnitude data only. In either case, some type of compression may be required to losslessly transmit this data in a given bandwidth or store it in a reasonable volume. This paper provides the results of applying several lossless compression schemes to SAR imagery.
Date: February 1, 1996
Creator: Ives, R.W.; Magotra, N. & Mandyam, G.D.
Partner: UNT Libraries Government Documents Department

Preliminary results of the LLNL airborne experimental test-bed SAR system

Description: The Imaging and Detection Program (IDP) within Laser Programs at Lawrence Livermore National Laboratory (LLNL) in cooperation with the Hughes Aircraft Company has developed a versatile, high performance, airborne experimental test-bed (AETB) capability. The test-bed has been developed for a wide range of research and development experimental applications including radar and radiometry plus, with additional aircraft modifications, optical systems. The airborne test-bed capability has been developed within a Douglas EA-3B Skywarrior jet aircraft provided and flown by Hughes Aircraft Company. The current test-bed payload consists of an X-band radar system, a high-speed data acquisition, and a real-time processing capability. The medium power radar system is configured to operate in a high resolution, synthetic aperture radar (SAR) mode and is highly configurable in terms of waveforrns, PRF, bandwidth, etc. Antennas are mounted on a 2-axis gimbal in the belly radome of the aircraft which provides pointing and stabilization. Aircraft position and antenna attitude are derived from a dedicated navigational system and provided to the real-time SAR image processor for instant image reconstruction and analysis. This paper presents a further description of the test-bed and payload subsystems plus preliminary results of SAR imagery.
Date: January 16, 1996
Creator: Miller, M.G.; Mullenhoff, C.J.; Kiefer, R.D.; Brase, J.M.; Wieting, M.G.; Berry, G.L. et al.
Partner: UNT Libraries Government Documents Department

A high-resolution, four-band SAR testbed with real-time image formation

Description: 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.
Date: March 1, 1996
Creator: Walker, B.; Sander, G.; Thompson, M.; Burns, B.; Fellerhoff, R. & Dubbert, D.
Partner: UNT Libraries Government Documents Department

A survey of early warning technologies

Description: This paper presents a survey of technologies useful in providing early warning in physical security systems. Early warning is important in virtually all types of security systems whether they are used for temporary (tactical, portable, or semi-permanent) applications, border warning, fixed-site detection, or standoff surveillance detection. With the exception of the standoff surveillance detection systems, all systems discussed in this paper usually involve a moving target. The fact that a person(s) to be detected in a standoff surveillance scenario is not moving presents challenging problems and requires different applications of technology. The technologies commonly used to detect moving targets and some suggestions for detection of stationary targets are addressed in this paper.
Date: July 1, 1995
Creator: Smith, G.D.; Arlowe, H.D. & Williams, J.D.
Partner: UNT Libraries Government Documents Department

The single antenna interferometer

Description: Air and space borne platforms using synthetic aperture radars (SAR) have made interferometric measurements by using either two physical antennas mounted on one air-frame or two passes of one antenna over a scene. In this paper, a new interferometric technique using one pass of a single-antenna SAR system is proposed and demonstrated on data collected by the NASA-JPL AirSAR. Remotely sensed L-band microwave data are used to show the sensitivity of this technique to ocean surface features as well as a baseline for comparison with work by others using two-antenna systems. 7 refs., 3 figs.
Date: January 15, 1990
Creator: Fitch, J.P.
Partner: UNT Libraries Government Documents Department

Three-dimensional subsurface imaging synthetic aperture radar

Description: The objective of this applied research and development project is to develop a system known as `3-D SISAR`. This system consists of a ground penetrating radar with software algorithms designed for the detection, location, and identification of buried objects in the underground hazardous waste environments found at DOE storage sites. Three-dimensional maps of the object locations will be produced which can assist the development of remediation strategies and the characterization of the digface during remediation operations. It is expected that the 3-D SISAR will also prove useful for monitoring hydrocarbon based contaminant migration after remediation. The underground imaging technique being developed under this contract utilizes a spotlight mode Synthetic Aperture Radar (SAR) approach which, due to its inherent stand-off capability, will permit the rapid survey of a site and achieve a high degree of productivity over large areas. When deployed from an airborne platform, the stand-off techniques is also seen as a way to overcome practical survey limitations encountered at vegetated sites.
Date: March 1, 1995
Creator: Moussally, G. J.
Partner: UNT Libraries Government Documents Department

A comparative evaluation of SAR and SLAR

Description: Synthetic aperture radar (SAR) was evaluated as a potential technological improvement over the Coast Guard`s existing side-looking airborne radar (SLAR) for oil-spill surveillance applications. The US Coast Guard Research and Development Center (R&D Center), Environmental Branch, sponsored a joint experiment including the US Coast Guard, Sandia National Laboratories, and the Naval Oceanographic and Atmospheric Administration (NOAA), Hazardous Materials Division. Radar imaging missions were flown on six days over the coastal waters off Santa Barbara, CA, where there are constant natural seeps of oil. Both the Coast Guard SLAR and the Sandia National Laboratories SAR were employed to acquire simultaneous images of oil slicks and other natural sea surface features that impact oil-spill interpretation. Surface truth and other environmental data were also recorded during the experiment. The experiment data were processed at Sandia National Laboratories and delivered to the R&D Center on a computer workstation for analysis by experiment participants. Issues such as optimal spatial resolution, single-look vs. multi-look SAR imaging, and the utility of SAR for oil-spill analysis were addressed. Finally, conceptual design requirements for a possible future Coast Guard SAR were outlined and evaluated.
Date: November 1, 1993
Creator: Mastin, G. A.; Manson, J. J.; Bradley, J. D.; Axline, R. M. & Hover, G. L.
Partner: UNT Libraries Government Documents Department

Imaging targets embedded in a lossy half space with Synthetic Aperture Radar

Description: This paper addresses theoretical aspects of forming images from an airborne Synthetic Aperture Radar (SAR) of targets buried below the earth`s surface. Soil is generally a lossy, dispersive medium, with wide ranging variability in these attributes depending on soil type, moisture content, and a host of other physical properties. Focussing a SAR subsurface image presents new dimensions of complexity relative to its surface-image counterpart, even when the soil`s properties are known. This paper treats the soil as a lossy, dispersive half space, and presents a practical model for the radar echo-delay time to point scatterers within it. This model is then used to illustrate effects of refraction, dispersion, and attenuation on a SAR`s phase histories, and the resulting image. Various data collection geometries and processing strategies are examined for both 2-Dimensional and 3-Dimensional SAR images. The conclusions from this work are that (1) focussing a SAR image must generally take into account both refraction and dispersion, (2) resolving targets at different depths in lossy soils requires perhaps unprecedented sidelobe attenuation, that for some soils may only be achievable with specialized window functions, (3) the impulse response of the soil itself places a practical limit on the usable bandwidth of the radar, and (4) dynamic ranges and sensitivities will need to be orders of magnitude greater than typical surface-imaging SARs, leading to significant impact on SAR parameters, for example compressing the usable range of pulse repetition frequencies (PRFs).
Date: May 1, 1994
Creator: Doerry, A. W.; Brock, B. C.; Boverie, B. & Cress, D.
Partner: UNT Libraries Government Documents Department

New formulation for interferometric synthetic aperture radar for terrain mapping

Description: The subject of interferometric synthetic aperture radar (IFSAR) for high-accuracy terrain elevation mapping continues to gain importance in the arena of radar signal processing. Applications to problems in precision terrain-aided guidance and automatic target recognition, as well as a variety of civil applications, are being studied by a number of researchers. Not unlike many other areas of SAR processing, the subject of IFSAR can at first glance appear to be somewhat mysterious. In this paper we show how the mathematics of IFSAR for terrain elevation mapping using a pair of spotlight mode SAR collections can be derived in a very straightforward manner. Here, we employ an approach that relies entirely on three-dimensional Fourier transforms, and utilizes no reference to range equations or Doppler concepts. The result is a simplified explanation of the fundamentals of interferometry, including an easily-seen link between image domain phase difference and terrain elevation height. The derivation builds upon previous work by the authors in which a framework for spotlight mode SAR image formation based on an analogy to three-dimensional computerized axial tomography (CAT) was developed. After outlining the major steps in the mathematics, we show how a computer simulator which utilizes three-dimensional Fourier transforms can be constructed that demonstrates all of the major aspects of IFSAR from spotlight mode collections.
Date: April 1, 1994
Creator: Jakowatz, C. V. Jr.; Wahl, D. E.; Eichel, P. H. & Thompson, P. A.
Partner: UNT Libraries Government Documents Department

New approach to strip-map SAR autofocus

Description: Means for removing phase errors induced in spotlight mode synthetic aperture radar (SAR) imagery are now well-established. The Phase Gradient Autofocus (PGA) algorithm has been shown to be robust over a wide range of spotlight mode imagery and phase error functions. These phase errors could have their origin either in uncompensated platform motion or random propagation delays incurred, for example, from tropospheric turbulence. The PGA technique, however, cannot be directly applied to imagery formed in the conventional strip-mapping mode. In this paper we show that if the fundamental ideas of PGA are modified in an appropriate way, the phase errors in strip-map imagery can be effectively estimated and compensated.
Date: May 1, 1994
Creator: Wahl, D.; Jakowatz, C.; Thompson, P. & Ghiglia, D.
Partner: UNT Libraries Government Documents Department

Interferometric SAR phase difference calibration: Methods and results

Description: This paper addresses the steps necessary to determine and maintain the phase calibration of a two-channel interferometric synthetic aperture radar (IFSAR). The method, setup, and accuracy of four different calibration techniques are compared. The most novel technique involves pointing the interferometric baseline at nadir and imaging a lake surface. The other techniques include measuring various flat surfaces in traditional side-looking IFSAR maps, in-flight closed-loop calibration path measurements, and static laboratory measurements. Initial results indicate that, using combinations of these measurements, it is possible to maintain the interferometric phase calibration of Sandia National Laboratories` K{sub U} Band IFSAR to better than 3 degrees. The time variability of various parts of the calibration and requirements for recalibration are also discussed.
Date: December 31, 1993
Creator: Bickel, D. L. & Hensley, W. H.
Partner: UNT Libraries Government Documents Department

Radially combined 30 W, 14-16 GHz amplifier

Description: The paper describes a highly integrated 30 W power amplifier for a Synthetic Aperture Radar, operating in the 14--16 GHz band. The use of a waveguide radial combiner, a microstrip power divider and direct microstrip to waveguide miniaturized ceramic technology, leads to an unusually compact and accessible structure, well suited for commercial production.
Date: April 1, 1994
Creator: Sechi, F.; Bujatti, M.; Knudson, R. & Bugos, R.
Partner: UNT Libraries Government Documents Department

Factors governing selection of operating frequency for subsurface- imaging synthetic-aperture radar

Description: A subsurface-imaging synthetic-aperture radar (SISAR) has potential for application in areas as diverse as non-proliferation programs for nuclear weapons to environmental monitoring. However, subsurface imaging is complicated by propagation loss in the soil and surface-clutter response. Both the loss and surface-clutter response depend on the operating frequency. This paper examines several factors which provide a basis for determining optimum frequencies and frequency ranges which will allow synthetic-aperture imaging of buried targets. No distinction can be made between objects at different heights when viewed with a conventional imaging radar (which uses a one-dimensional synthetic aperture), and the return from a buried object must compete with the return from the surface clutter. Thus, the signal-to-clutter ratio is an appropriate measure of performance for a SISAR. A parameter-based modeling approach is used to model the complex dielectric constant of the soil from measured data obtained from the literature. Theoretical random-surface scattering models, based on statistical solutions to Maxwell`s equations, are used to model the clutter. These models are combined to estimate the signal-to-clutter ratio for canonical targets buried in several soil configurations. Results indicate that the HF spectrum (3--30), although it could be used to detect certain targets under some conditions, has limited practical value for use with SISAR, while the upper VIHF through UHF spectrum ({approximately}100 MHz - 1 GHz) shows the most promise for a general purpose SISAR system. Recommendations are included for additional research.
Date: December 31, 1993
Creator: Brock, B. C. & Patitz, W. E.
Partner: UNT Libraries Government Documents Department