2019 IEEE International Symposium on Antennas and Propagation and USNC-URSI Radio Science Meeting, 2019
Millimeter-wave imaging radar is becoming increasingly popular for sensing and security applicati... more Millimeter-wave imaging radar is becoming increasingly popular for sensing and security applications. Usually full phased arrays, synthetic apertures, or focusing reflect-arrays are employed to sense a given image space. One new approach is to generate an axially-scanning focal spot using an axial nearfield bifocal dual reflector. The bifocal has two perfect foci on the symmetry axis, each corresponding to the two perfect feed points on the axis, made possible when two degrees of freedom – two reflectors – are employed. With two perfect foci, the optical aberrations for other image points between them must be of even order, which leads to a reasonable focal region bounded by the perfect foci. It is envisioned that a small feed moving along the axis might interrogate the image region, with better precision and speed, and less force than the full focusing stage. Alternatively, an electronically selective line source could scan the image space at nanosecond rates using only one dimension of sensing hardware. The concept is referred to as a microscope, because it maps rays diverging from the image space to rays converging at the observation points much like an optical microscope.
IEEE Antennas and Propagation Society International Symposium 1992 Digest, 1992
A novel ABC has been proposed, based on anechoic chamber absorber foam geometry, with specified c... more A novel ABC has been proposed, based on anechoic chamber absorber foam geometry, with specified complex permittivity and permeability. The advantage of this absorbing boundary, based on carbon-loaded anechoic chamber absorber foam pyramids, is that it prevents reflections from much wider incident angles than currently used techniques. Preliminary FDTD (finite-difference time-domain) results on this ABC are presented. A two-dimensional FDTD simulation of an equilateral triangle saw-tooth absorbing layer, with a modulated Gaussian pulse plane wave, is shown.<<ETX>>
2020 14th European Conference on Antennas and Propagation (EuCAP), 2020
In this work, we investigate the application of the phase coherence method for improving the qual... more In this work, we investigate the application of the phase coherence method for improving the quality of reconstructed images of small isolated objects with our Advanced Imaging Technique (AIT) nearfield millimeter-wave radar security scanning system. Based on the phase diversity of the reconstructed solutions for different transmitters, a phase coherence factor (PCF) is designed to weight the coherent sum. We verify its effectiveness with both numerical simulation and experimental measurement. In both simulation and experiment results, the artifacts like side-lobes, grating lobes or clutter in the original images are reduced in the processed images after applying the phase coherence method.
2016 10th European Conference on Antennas and Propagation (EuCAP), 2016
High bit-rate RF communication is shown to be possible in deep oil wells using the air gap betwee... more High bit-rate RF communication is shown to be possible in deep oil wells using the air gap between the steel cladding and exterior rock as a dielectric waveguide to propagate TE signals in the kHz to MHz range. Computational modeling analysis in both the frequency and time domains validate the ideal analytic cylindrical guidance condition. Efficient propagation is also possible for asymmetric borehole geometries, even when the casing comes in contact with the surrounding rock wall.
A novel handheld time-domain array GPR antipersonnel mine detection system using an offset parabo... more A novel handheld time-domain array GPR antipersonnel mine detection system using an offset paraboloidal reflector antenna is described. The reflector collimates rays from an ultra-wideband transmitting feed, directing the microwave impulse forward, in front of the antenna structure. As such, much of the ground reflected wave is directed further forward, away from the operator, the reflector, and the receiving antennas, and thereby reducing the major source of clutter. The wave transmitted into the ground that interacts with the target, generating significant backscatter returning toward the receiving antennas. These receiving antennas are configured in a 2 by 2 array to provide spatial focusing in both the along- and cross-track directions. This system has been built and tested at both Lawrence Livermore National Laboratory, and GeoCenters, Inc. In both cases, custom-built wideband antenna elements generate narrow pulse shapes, which allow for resolving small non-metallic targets buried at shallow depths. The LLNL's Micro-Power Impulse Radar (MIR) operates in the 1.5 to 5 GHz range a very narrow pulse shape. The Geo-Centers wideband TEMR antenna elements have higher power, though lower frequency range (850 to 1700 MHz), and generate less residual ringing in the time signal. Preliminary measured data from both systems indicate thatmore » the surface clutter is indeed reduced relative to the target signal, and that small non-metallic anti-personnel mines can be reliably detected at burial depths as shallow as 1 inch in both dry sand and dry vegetative clay loam soil.« less
2015 IEEE International Symposium on Antennas and Propagation & USNC/URSI National Radio Science Meeting, 2015
Synthetic Aperture Radar (SAR) Imaging is able to detect not only conducting but also weak dielec... more Synthetic Aperture Radar (SAR) Imaging is able to detect not only conducting but also weak dielectric objects. When a dielectric is affixed to a conducting surface, reflection of the dielectric can be difficult to distinguish from the sidelobes from the surface, since they have similar magnitude and range. The ability to distinguish imaging artifacts and target surfaces is necessary to enable automated feature analysis and threat detection of unknown targets. Our new methods varies the imaging bandwidth, which changes the range of the sidelobe position without changing the range of the dielectric peak reflection, which distinguishes the front surface dielectric reflectivity from sidelobe artifacts. Experimental data is used to demonstrate the effectiveness of this approach.
2015 USNC-URSI Radio Science Meeting (Joint with AP-S Symposium), 2015
Effective communication in oil wells is challenging because of partially-conductive soil and rock... more Effective communication in oil wells is challenging because of partially-conductive soil and rock, and inhomogeneities in the ground. An alternative approach to communicating with the drill head, or electronics associated with it, is to use the drilled hole itself as a path for communication. The typical well hole is cased with a steel lining and surrounded by air or cement. The electrically-conductive casing, along with a second conductor consisting of the earth itself, acts like a dielectric waveguide used in fiber optics to guide light. The earth is not very conductive, but as long as it has a different dielectric constant than air, it can act to guide waves axially through the gap between the steel and the ground.
Symposium on the Application of Geophysics to Engineering and Environmental Problems 2007, 2007
Soil is a material of interest in a number of disciplines such as geotechnical, environmental, mi... more Soil is a material of interest in a number of disciplines such as geotechnical, environmental, military and agricultural engineering. Precise knowledge of dielectric properties of soil provides information about the interactions between the soil and applied electromagnetic (EM) fields. Detecting anomalies of interest in heterogeneous soil media without enough information about the background media is very challenging, if not impossible. Dielectric properties are considerably intricate, can exhibit frequency dependent behavior, and correlate with many physical and chemical properties. Measuring dielectric properties can therefore be used to estimate those physical and chemical properties, if the correlation between the dielectric properties and other physical and chemical properties is well investigated and understood. In this study, laboratory measurements and theoretical modeling of dielectric properties of sandy soils are carried out. Dielectric property measurements are executed using a minimally invasive cross-borehole microwave measurement technique. An in-situ technique to measure dielectric properties of a sandy soil at different densities and moisture contents, and their frequency dependence over a wideband of frequency (0.4 GHz to 2.2 GHz) is implemented and evaluated. Then, the correlation between variations of dielectric and physical properties of the soil (e.g. density and water content) is studied. Dielectric mixing models were used to ascertain these correlations as a forward model for future inversion. Finally, a comparison between the forward model and experimental results was undertaken to seek the level of agreement. Introduction Soils are media composed of interacting discrete solid elements with voids filled with air and/or fluids. These three phases have different physical, chemical and dielectric properties. Soil materials are considerably intricate and can exhibit significantly dispersive (i.e. frequency dependent) behavior. Therefore, soil dielectric properties must be treated as complex quantities. These complex quantities are dependent on physical and chemical conditions (e.g. temperature, crystal mineralogy in case of clay). The complex-plane representation of the complex dielectric permittivity can be presented to reveal the frequency and temperature behaviors of dielectric materials (Trabelsi and Nelson, 1997; and Trabelsi et al. 1998 and 2001). This behavior is of utmost significance in subsurface imaging. The accuracy of indirect measurement of dielectric properties by full-wave inversion of electromagnetic signals relies on the appropriateness of the model describing their frequency-dependence. At microwave frequencies, dispersion arises from factors such as relaxation mechanisms due to the presence of free water and the water bound to mineral surfaces, and interactions between ions and soil particles. To have a realistic model of propagation of electromagnetic waves in the subsurface, it is necessary to account for this phenomenon. Therefore, characterizing the frequency and physical state dependence of dielectric properties of saturated and unsaturated soils is of a prime importance. The propagation of EM waves through materials is dependent on dielectric properties, which are in turn controlled by many geologic parameters. Previous research has illustrated the potential of using
IEEE Antennas and Propagation Society International Symposium. 1996 Digest
The bifocal dual reflector antenna system is an important wide-angle scanning antenna configurati... more The bifocal dual reflector antenna system is an important wide-angle scanning antenna configuration, offering an extra degree of design freedom over single reflectors. Although bifocal subreflectors tend to be large, offset configurations can be designed to minimize this effect. The article examines a relatively unknown bifocal configuration, one having a concave, Gregorian subreflector. Also, design formulas for all types of
An analytic algebraic formulation has been derived to find the ground surface refraction point fo... more An analytic algebraic formulation has been derived to find the ground surface refraction point for rays originating at a source point in air and arriving at a specific underground destination point. Finding precise refraction points is useful for air-coupled GPR underground imaging. The procedure is based on finding the parent hyperbola from which unbent rays originate, then finding initial guesses for ray intersection points based on the best fit asymptote or circle, then finding an improved intersection point using second-order perturbation analysis. The resulting approximations for a typical geometry are below 2% error.
Proceedings of the First Joint BMES/EMBS Conference. 1999 IEEE Engineering in Medicine and Biology 21st Annual Conference and the 1999 Annual Fall Meeting of the Biomedical Engineering Society (Cat. No.99CH37015)
2014 USNC-URSI Radio Science Meeting (Joint with AP-S Symposium), 2014
Summary form only given. Ground-penetrating radar is a mature technology which has a promising ap... more Summary form only given. Ground-penetrating radar is a mature technology which has a promising application in humanitarian demining. The technology is fast, inexpensive, and capable of detecting both metallic and non-metallic target casings. However, the efficacy of conventional air-coupled GPR has been limited by the rough air-soil interface, below which landmines are typically buried. Much of the recent literature focuses on advanced signal processing techniques in an attempt to remove the effects of the rough surface. Conversely, this work proposes the use of ground-contact antennas, which greatly improves signal penetration and reduces the rough ground clutter, thereby simplifying data analysis. Achieving contact between the surface and antennas can be done by integrating the antennas onto the feet of a non-articulated walking robotic platform. Finally, rather than imaging the subsurface, this localization method implements a robust geometric analysis to detect and localize a target with a minimal number of GPR scans. By using fewer scans and simpler data processing techniques, this method is capable of increasing the surveying speed of traditional GPR methods. Experimental data is collected using an ultra-wideband radar from Time Domain (Huntsville, AL, USA), which has a bandwidth of 3.1 to 5.3GHz. The antennas are circularly polarized compact spiral antennas, which operate from 2GHz to 6GHz. These antennas were designed and fabricated for this application, and the diameter of only 2cm achieves complete contact with the ground for each GPR scan. Additionally, the polarization and directivity of the antennas minimizes the direct signal, and therefore simplifies the identification of target reflections. The time-of-flight is determined by the maximum correlation between the reflection and a reference signal. Scans which satisfy both an amplitude and correlation threshold are analyzed with a localization algorithm, which utilizes time-difference of arrivals to geometrically determine the target location. A minimum of four unique bistatic GPR scans are necessary to evaluate for the target's position in three-space in soil with unknown permittivity, and an increased number of GPR scans improves the accuracy and reliability of the results. Using the proposed localization method, metallic cylindrical targets, 4cm in height and 4cm in radius buried in dry sand at depths varying between 5 and 15cm, were successfully located. Although this method has not yet been evaluated experimentally for non-metallic targets, previous computational work shows evidence that this method can be viable for plastic mine targets as well. Furthermore, theoretical simulations have demonstrated acceptable localization results for dispersive and wet soils for both casing types.
2014 IEEE Antennas and Propagation Society International Symposium (APSURSI), 2014
Borehole ground penetrating radar systems probe at varying depths below the surface to determine ... more Borehole ground penetrating radar systems probe at varying depths below the surface to determine soil properties and search for anomalies. Current detection approaches use time of flight estimations or tomography to determine the properties of the soil. These methods use the inaccurate assumption that the signal propagates in a straight direct path from transmitter to receiver in layered soil media. We propose a novel eigenmode method, similar to dielectric waveguide analysis, to estimate soil layer boundaries, permittivity, and conductivity, taking into account the true propagation of waves in layered medium.
2014 USNC-URSI Radio Science Meeting (Joint with AP-S Symposium), 2014
Describes our latest results in the design of new 3D breast cancer imaging system that combines M... more Describes our latest results in the design of new 3D breast cancer imaging system that combines Microwave Nearfield Radar Imaging (NRI) and Digital Breast Tomosynthesis (DBT).
Illegal immigrants and smugglers have frequently used underground tunnels to avoid border securit... more Illegal immigrants and smugglers have frequently used underground tunnels to avoid border security and checkpoints. The threat of international terrorism also warrants the effort to detect tunnels a national security priority. The goal of this research is to study and evaluate the ...
2019 IEEE International Symposium on Antennas and Propagation and USNC-URSI Radio Science Meeting, 2019
Millimeter-wave imaging radar is becoming increasingly popular for sensing and security applicati... more Millimeter-wave imaging radar is becoming increasingly popular for sensing and security applications. Usually full phased arrays, synthetic apertures, or focusing reflect-arrays are employed to sense a given image space. One new approach is to generate an axially-scanning focal spot using an axial nearfield bifocal dual reflector. The bifocal has two perfect foci on the symmetry axis, each corresponding to the two perfect feed points on the axis, made possible when two degrees of freedom – two reflectors – are employed. With two perfect foci, the optical aberrations for other image points between them must be of even order, which leads to a reasonable focal region bounded by the perfect foci. It is envisioned that a small feed moving along the axis might interrogate the image region, with better precision and speed, and less force than the full focusing stage. Alternatively, an electronically selective line source could scan the image space at nanosecond rates using only one dimension of sensing hardware. The concept is referred to as a microscope, because it maps rays diverging from the image space to rays converging at the observation points much like an optical microscope.
IEEE Antennas and Propagation Society International Symposium 1992 Digest, 1992
A novel ABC has been proposed, based on anechoic chamber absorber foam geometry, with specified c... more A novel ABC has been proposed, based on anechoic chamber absorber foam geometry, with specified complex permittivity and permeability. The advantage of this absorbing boundary, based on carbon-loaded anechoic chamber absorber foam pyramids, is that it prevents reflections from much wider incident angles than currently used techniques. Preliminary FDTD (finite-difference time-domain) results on this ABC are presented. A two-dimensional FDTD simulation of an equilateral triangle saw-tooth absorbing layer, with a modulated Gaussian pulse plane wave, is shown.<<ETX>>
2020 14th European Conference on Antennas and Propagation (EuCAP), 2020
In this work, we investigate the application of the phase coherence method for improving the qual... more In this work, we investigate the application of the phase coherence method for improving the quality of reconstructed images of small isolated objects with our Advanced Imaging Technique (AIT) nearfield millimeter-wave radar security scanning system. Based on the phase diversity of the reconstructed solutions for different transmitters, a phase coherence factor (PCF) is designed to weight the coherent sum. We verify its effectiveness with both numerical simulation and experimental measurement. In both simulation and experiment results, the artifacts like side-lobes, grating lobes or clutter in the original images are reduced in the processed images after applying the phase coherence method.
2016 10th European Conference on Antennas and Propagation (EuCAP), 2016
High bit-rate RF communication is shown to be possible in deep oil wells using the air gap betwee... more High bit-rate RF communication is shown to be possible in deep oil wells using the air gap between the steel cladding and exterior rock as a dielectric waveguide to propagate TE signals in the kHz to MHz range. Computational modeling analysis in both the frequency and time domains validate the ideal analytic cylindrical guidance condition. Efficient propagation is also possible for asymmetric borehole geometries, even when the casing comes in contact with the surrounding rock wall.
A novel handheld time-domain array GPR antipersonnel mine detection system using an offset parabo... more A novel handheld time-domain array GPR antipersonnel mine detection system using an offset paraboloidal reflector antenna is described. The reflector collimates rays from an ultra-wideband transmitting feed, directing the microwave impulse forward, in front of the antenna structure. As such, much of the ground reflected wave is directed further forward, away from the operator, the reflector, and the receiving antennas, and thereby reducing the major source of clutter. The wave transmitted into the ground that interacts with the target, generating significant backscatter returning toward the receiving antennas. These receiving antennas are configured in a 2 by 2 array to provide spatial focusing in both the along- and cross-track directions. This system has been built and tested at both Lawrence Livermore National Laboratory, and GeoCenters, Inc. In both cases, custom-built wideband antenna elements generate narrow pulse shapes, which allow for resolving small non-metallic targets buried at shallow depths. The LLNL's Micro-Power Impulse Radar (MIR) operates in the 1.5 to 5 GHz range a very narrow pulse shape. The Geo-Centers wideband TEMR antenna elements have higher power, though lower frequency range (850 to 1700 MHz), and generate less residual ringing in the time signal. Preliminary measured data from both systems indicate thatmore » the surface clutter is indeed reduced relative to the target signal, and that small non-metallic anti-personnel mines can be reliably detected at burial depths as shallow as 1 inch in both dry sand and dry vegetative clay loam soil.« less
2015 IEEE International Symposium on Antennas and Propagation & USNC/URSI National Radio Science Meeting, 2015
Synthetic Aperture Radar (SAR) Imaging is able to detect not only conducting but also weak dielec... more Synthetic Aperture Radar (SAR) Imaging is able to detect not only conducting but also weak dielectric objects. When a dielectric is affixed to a conducting surface, reflection of the dielectric can be difficult to distinguish from the sidelobes from the surface, since they have similar magnitude and range. The ability to distinguish imaging artifacts and target surfaces is necessary to enable automated feature analysis and threat detection of unknown targets. Our new methods varies the imaging bandwidth, which changes the range of the sidelobe position without changing the range of the dielectric peak reflection, which distinguishes the front surface dielectric reflectivity from sidelobe artifacts. Experimental data is used to demonstrate the effectiveness of this approach.
2015 USNC-URSI Radio Science Meeting (Joint with AP-S Symposium), 2015
Effective communication in oil wells is challenging because of partially-conductive soil and rock... more Effective communication in oil wells is challenging because of partially-conductive soil and rock, and inhomogeneities in the ground. An alternative approach to communicating with the drill head, or electronics associated with it, is to use the drilled hole itself as a path for communication. The typical well hole is cased with a steel lining and surrounded by air or cement. The electrically-conductive casing, along with a second conductor consisting of the earth itself, acts like a dielectric waveguide used in fiber optics to guide light. The earth is not very conductive, but as long as it has a different dielectric constant than air, it can act to guide waves axially through the gap between the steel and the ground.
Symposium on the Application of Geophysics to Engineering and Environmental Problems 2007, 2007
Soil is a material of interest in a number of disciplines such as geotechnical, environmental, mi... more Soil is a material of interest in a number of disciplines such as geotechnical, environmental, military and agricultural engineering. Precise knowledge of dielectric properties of soil provides information about the interactions between the soil and applied electromagnetic (EM) fields. Detecting anomalies of interest in heterogeneous soil media without enough information about the background media is very challenging, if not impossible. Dielectric properties are considerably intricate, can exhibit frequency dependent behavior, and correlate with many physical and chemical properties. Measuring dielectric properties can therefore be used to estimate those physical and chemical properties, if the correlation between the dielectric properties and other physical and chemical properties is well investigated and understood. In this study, laboratory measurements and theoretical modeling of dielectric properties of sandy soils are carried out. Dielectric property measurements are executed using a minimally invasive cross-borehole microwave measurement technique. An in-situ technique to measure dielectric properties of a sandy soil at different densities and moisture contents, and their frequency dependence over a wideband of frequency (0.4 GHz to 2.2 GHz) is implemented and evaluated. Then, the correlation between variations of dielectric and physical properties of the soil (e.g. density and water content) is studied. Dielectric mixing models were used to ascertain these correlations as a forward model for future inversion. Finally, a comparison between the forward model and experimental results was undertaken to seek the level of agreement. Introduction Soils are media composed of interacting discrete solid elements with voids filled with air and/or fluids. These three phases have different physical, chemical and dielectric properties. Soil materials are considerably intricate and can exhibit significantly dispersive (i.e. frequency dependent) behavior. Therefore, soil dielectric properties must be treated as complex quantities. These complex quantities are dependent on physical and chemical conditions (e.g. temperature, crystal mineralogy in case of clay). The complex-plane representation of the complex dielectric permittivity can be presented to reveal the frequency and temperature behaviors of dielectric materials (Trabelsi and Nelson, 1997; and Trabelsi et al. 1998 and 2001). This behavior is of utmost significance in subsurface imaging. The accuracy of indirect measurement of dielectric properties by full-wave inversion of electromagnetic signals relies on the appropriateness of the model describing their frequency-dependence. At microwave frequencies, dispersion arises from factors such as relaxation mechanisms due to the presence of free water and the water bound to mineral surfaces, and interactions between ions and soil particles. To have a realistic model of propagation of electromagnetic waves in the subsurface, it is necessary to account for this phenomenon. Therefore, characterizing the frequency and physical state dependence of dielectric properties of saturated and unsaturated soils is of a prime importance. The propagation of EM waves through materials is dependent on dielectric properties, which are in turn controlled by many geologic parameters. Previous research has illustrated the potential of using
IEEE Antennas and Propagation Society International Symposium. 1996 Digest
The bifocal dual reflector antenna system is an important wide-angle scanning antenna configurati... more The bifocal dual reflector antenna system is an important wide-angle scanning antenna configuration, offering an extra degree of design freedom over single reflectors. Although bifocal subreflectors tend to be large, offset configurations can be designed to minimize this effect. The article examines a relatively unknown bifocal configuration, one having a concave, Gregorian subreflector. Also, design formulas for all types of
An analytic algebraic formulation has been derived to find the ground surface refraction point fo... more An analytic algebraic formulation has been derived to find the ground surface refraction point for rays originating at a source point in air and arriving at a specific underground destination point. Finding precise refraction points is useful for air-coupled GPR underground imaging. The procedure is based on finding the parent hyperbola from which unbent rays originate, then finding initial guesses for ray intersection points based on the best fit asymptote or circle, then finding an improved intersection point using second-order perturbation analysis. The resulting approximations for a typical geometry are below 2% error.
Proceedings of the First Joint BMES/EMBS Conference. 1999 IEEE Engineering in Medicine and Biology 21st Annual Conference and the 1999 Annual Fall Meeting of the Biomedical Engineering Society (Cat. No.99CH37015)
2014 USNC-URSI Radio Science Meeting (Joint with AP-S Symposium), 2014
Summary form only given. Ground-penetrating radar is a mature technology which has a promising ap... more Summary form only given. Ground-penetrating radar is a mature technology which has a promising application in humanitarian demining. The technology is fast, inexpensive, and capable of detecting both metallic and non-metallic target casings. However, the efficacy of conventional air-coupled GPR has been limited by the rough air-soil interface, below which landmines are typically buried. Much of the recent literature focuses on advanced signal processing techniques in an attempt to remove the effects of the rough surface. Conversely, this work proposes the use of ground-contact antennas, which greatly improves signal penetration and reduces the rough ground clutter, thereby simplifying data analysis. Achieving contact between the surface and antennas can be done by integrating the antennas onto the feet of a non-articulated walking robotic platform. Finally, rather than imaging the subsurface, this localization method implements a robust geometric analysis to detect and localize a target with a minimal number of GPR scans. By using fewer scans and simpler data processing techniques, this method is capable of increasing the surveying speed of traditional GPR methods. Experimental data is collected using an ultra-wideband radar from Time Domain (Huntsville, AL, USA), which has a bandwidth of 3.1 to 5.3GHz. The antennas are circularly polarized compact spiral antennas, which operate from 2GHz to 6GHz. These antennas were designed and fabricated for this application, and the diameter of only 2cm achieves complete contact with the ground for each GPR scan. Additionally, the polarization and directivity of the antennas minimizes the direct signal, and therefore simplifies the identification of target reflections. The time-of-flight is determined by the maximum correlation between the reflection and a reference signal. Scans which satisfy both an amplitude and correlation threshold are analyzed with a localization algorithm, which utilizes time-difference of arrivals to geometrically determine the target location. A minimum of four unique bistatic GPR scans are necessary to evaluate for the target's position in three-space in soil with unknown permittivity, and an increased number of GPR scans improves the accuracy and reliability of the results. Using the proposed localization method, metallic cylindrical targets, 4cm in height and 4cm in radius buried in dry sand at depths varying between 5 and 15cm, were successfully located. Although this method has not yet been evaluated experimentally for non-metallic targets, previous computational work shows evidence that this method can be viable for plastic mine targets as well. Furthermore, theoretical simulations have demonstrated acceptable localization results for dispersive and wet soils for both casing types.
2014 IEEE Antennas and Propagation Society International Symposium (APSURSI), 2014
Borehole ground penetrating radar systems probe at varying depths below the surface to determine ... more Borehole ground penetrating radar systems probe at varying depths below the surface to determine soil properties and search for anomalies. Current detection approaches use time of flight estimations or tomography to determine the properties of the soil. These methods use the inaccurate assumption that the signal propagates in a straight direct path from transmitter to receiver in layered soil media. We propose a novel eigenmode method, similar to dielectric waveguide analysis, to estimate soil layer boundaries, permittivity, and conductivity, taking into account the true propagation of waves in layered medium.
2014 USNC-URSI Radio Science Meeting (Joint with AP-S Symposium), 2014
Describes our latest results in the design of new 3D breast cancer imaging system that combines M... more Describes our latest results in the design of new 3D breast cancer imaging system that combines Microwave Nearfield Radar Imaging (NRI) and Digital Breast Tomosynthesis (DBT).
Illegal immigrants and smugglers have frequently used underground tunnels to avoid border securit... more Illegal immigrants and smugglers have frequently used underground tunnels to avoid border security and checkpoints. The threat of international terrorism also warrants the effort to detect tunnels a national security priority. The goal of this research is to study and evaluate the ...
Uploads
Papers by CAREY RAPPAPORT