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ABSTRACT: In this paper, a material-classification technique using polarimetric imagery degraded by atmospheric turbulence is presented. The classification technique described here determines whether an object is composed of dielectric or metallic materials. The technique implements a modified version of the LeMaster and Cain polarimetric maximum-likelihood blind-deconvolution algorithm in order to remove atmospheric distortion and correctly classify the unknown object. The dielectric/metal classification decision is based on degree-of-linear-polarization (DOLP) maximum-likelihood estimates provided by two novel DOLP priors (one being representative of dielectric materials and the other being representative of metallic materials) developed in this paper. The DOLP estimate, which maximizes the log-likelihood function, determines the image pixel's classification. Included in this paper is the review and modification of the LeMaster and Cain deconvolution algorithm. Also provided is the development of the novel DOLP priors, including their mathematical forms and the physical insight underlying their formulation. Lastly, the experimental results of two dielectric and metallic samples are provided to validate the proposed classification technique.
IEEE Transactions on Geoscience and Remote Sensing 02/2011; · 2.89 Impact Factor
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ABSTRACT: The purpose of this paper is to demonstrate how the flanged-waveguide material-characterization technique, originally designed to characterize lossy materials only, can be extended to accurately extract permittivity and permeability of low-loss materials. Provided in this paper is a summary of the flanged-waveguide technique. This is followed by a discussion of how time-domain gating can be utilized to mitigate the error introduced by waves reflected from the edges of the flanges. Furthermore, it is demonstrated that by utilizing time-domain gating, the cross-sectional dimensions of the flanges can be significantly reduced. Lastly, material measurement results of plexiglass are provided to validate the time-domain gating technique.
Electromagnetics in Advanced Applications (ICEAA), 2010 International Conference on; 10/2010
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ABSTRACT: A dual-probe rectangular waveguide material-parameter extraction technique capable of accommodating lowloss samples is presented. The technique's ability to easily measure reflection and transmission (R/T) coefficients necessary for simultaneous extraction of permittivity and permeability over all frequencies is discussed. Love's equivalence principle is used to create a system of coupled magnetic field integral equations (MFIEs) for the theoretical R/T coefficients which are subsequently solved using the Method of Moments (MoM). The material parameters are extracted via least squares by minimizing the magnitude of the difference of the theoretical and measured R/T coefficients. It is shown how the signal processing concept of time-domain gating can be utilized to mitigate edge diffraction effects of the finite waveguide flange. Material parameter extraction results, based on a single waveguide mode expansion, for various lossy and lowloss materials are provided to verify the technique.
Electromagnetic Theory (EMTS), 2010 URSI International Symposium on; 09/2010
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ABSTRACT: A two-layer nondestructive method for characterizing the electric and magnetic properties of lossy conductor-backed magnetic materials using a flanged rectangular-waveguide probe is examined. The two reflection measurements necessary to determine both permittivity and permeability are made by first applying the probe to the material under test and then applying the probe to a known-material layer placed on top of the material under test. The theoretical reflection coefficient is obtained using a rigorous full-wave solution, and an extrapolation scheme is used to minimize the error due to truncating the modal expansion of the waveguide fields. An error analysis is performed to compare the performance of the technique to the two-thickness method, which utilizes two different thicknesses of the material under test. The properties of the known material layer that result in the least error due to network analyzer uncertainty are determined. The sensitivity of the two-layer method is also explored and discussed.
Progress In Electromagnetics Research B. 01/2010; 26:1-21.
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ABSTRACT: A polarimetric bidirectional reflectance distribution function (pBRDF), based on geometrical optics, is presented. The pBRDF incorporates a visibility (shadowing/masking) function and a Lambertian (diffuse) component which distinguishes it from other geometrical optics pBRDFs in literature. It is shown that these additions keep the pBRDF bounded (and thus a more realistic physical model) as the angle of incidence or observation approaches grazing and better able to model the behavior of light scattered from rough, reflective surfaces. In this paper, the theoretical development of the pBRDF is shown and discussed. Simulation results of a rough, perfect reflecting surface obtained using an exact, electromagnetic solution and experimental Mueller matrix results of two, rough metallic samples are presented to validate the pBRDF.
Optics Express 11/2009; 17(24):22138-53. · 3.59 Impact Factor
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ABSTRACT: Free-space and rectangular waveguide techniques for determining the effective complex permittivity and, ultimately, the effective sheet impedance of an R-card using the forward transmission coefficient are presented. The advantage of using a transmission coefficient method instead of a more traditional reflection-based technique is discussed. The exact transcendental expressions relating the transmission coefficient and effective complex permittivity are derived and approximated using the Maclaurin series for sine and cosine. It is shown that the Maclaurin series expansion leads to simple closed-form solutions to the effective complex permittivity and avoids the use of sensitive and often unstable root search algorithms, which are necessary to solve transcendental equations. The accuracy of the approximations is directly related to the R-card's thickness and wavenumber. Free-space (4-16 GHz) and waveguide (8.2-12.4 GHz) measurements are made using two R-cards of differing thicknesses and impedances to demonstrate the method and regimes of validity. An uncertainty analysis is also performed to demonstrate the robustness of the technique.
IEEE Transactions on Instrumentation and Measurement 08/2009; · 1.21 Impact Factor
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ABSTRACT: In this paper, a flanged waveguides technique capable of measuring both reflection and transmission coefficients is formulated to allow for the nondestructive, simultaneous extraction of complex permittivities of a two-layer lossy dielectric absorber. The technique introduced here eliminates the need for additional optimization constraints required in reflection-only based methods. Theoretical expressions for the reflection and transmission coefficients are found using a magnetic field integral equation (MFIE) formulation based on Love's Equivalence Principle and subsequently solved via the Method of Moments (MoM). In addition to these expressions, the dyadic Green's function for a magnetically excited, two-layer, parallel-plate waveguide is developed. The technique is verified experimentally and measured results for an absorber consisting of two R-cards are presented. It is discussed that the flanged waveguides technique is well suited for rapid quality control measurement of dual-layered dielectric absorber or single-layered shielding materials having both dielectric and magnetic properties.
Instrumentation and Measurement Technology Conference Proceedings, 2008. IMTC 2008. IEEE; 06/2008
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ABSTRACT: Single rectangular waveguide probes are frequently employed in characterizing the permittivity of dielectric materials. A new dual rectangular waveguide probe is explored here for simultaneously extracting both permittivity and permeability of a lossy shielding material having dielectric and magnetic properties and backed by a conductor. The material characterization process is facilitated using a magnetic field integral equation formulation which is subsequently solved using the method of moments. The effects of an imperfectly-conducting backing is accommodated through the development of a dyadic Green's function based upon an impedance boundary condition. Experimental measurements of various materials will be performed to validate the analysis.
Microwave Conference, 2007. APMC 2007. Asia-Pacific; 01/2008
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ABSTRACT: In this paper, a non-destructive material parameter extraction technique which uses two flanged rectangular waveguides is presented. The technique improves on existing single probe methods, common in the literature, by its ability to easily measure reflection and transmission coefficients necessary for extraction of epsiv<sub>r</sub> and mu<sub>r</sub> over all frequencies. Love's Equivalence Principle is used to create a system of coupled magnetic field integral equations (MFIEs) which are solved using the Method of Moments (MoM). Measurement results for two R-cards and one magnetic shielding material are shown.
Microwave Symposium, 2007. IEEE/MTT-S International; 07/2007
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ABSTRACT: A free-space-backed dual-waveguide probe measurement technique is introduced to determine nondestructively the complex permittivity and permeability of an unknown material. The purpose of this new measurement technique is to complement the existing PEC-backed dual-waveguide probe materialcharacterization method. Provided in this article is the theoretical development of the new technique and its experimental validation. It is shown, by applying Loves equivalence theorem, that a system of coupled magnetic field integral equations can be formulated and subsequently solved for the dominant mode reflection and transmission coefficients using the Method of Moments. Also included in the theoretical development of the new technique is a derivation of the dyadic Greens function for a magnetic current excited two-medium grounded slab environment. Last, experimental complex permittivity and permeability parameters extracted for two magnetic shielding materials are presented and analyzed to validate the new technique.
IEEE Transactions on Antennas and Propagation · 2.15 Impact Factor
