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Leung Tsang - One of the best experts on this subject based on the ideXlab platform.
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Electromagnetic computation in scattering of electromagnetic waves by Random Rough Surface and dense media in microwave remote sensing of land Surfaces
Proceedings of the IEEE, 2013Co-Authors: Leung Tsang, Kung Hau Ding, Shaowu Huang, Xiaolan XuAbstract:Active and passive microwave remote sensing has been used for monitoring the soil moisture and snow water equivalent. In the interactions of microwaves with bare soil, the effects are determined by scattering of electromagnetic waves by Random Rough Surfaces. In the interactions of microwaves with terrestrial snow, the effects are determined by volume scattering of dense media characterized by densely packed particles. In this paper, we review the electromagnetic full- wave simulations thatwe have conducted for such problems. In volume scattering problems, one needs many densely packed scatterers in a Randommediumsample to simulate the physical solutions. In Random Rough Surface scattering problems, one needsmany valleys and peaks in the sample Surface. In Random media and Rough Surface problems, the geometric character- izations of the media and computer generations of statistical samples of the media are also challenges besides electromag- netic computations. In the scattering of waves by soil Surfaces, we consider the soil to be a lossy dielectric medium. The ran- dom Rough Surface is characterized by Gaussian Random pro- cesses with exponential correlation functions. Surfaces of exponential correlation functions have fine-scale structures that cause significant radar backscattering in active microwave remote sensing. Fine-scale features also cause increase in emission in passive microwave remote sensing. We apply Monte Carlo simulations of solving full 3-DMaxwell’s equations for such a problem. A hybrid UV/PBTG/SMCG method is devel- oped to accelerate method of moment solutions. The results are illustrated for coherent waves and incoherent waves. We also illustrate bistatic scattering, backscattering, and emissivity which are signatures measured in microwave remote sensing. For the case of scattering by terrestrial snow, snow is a dense medium with densely packed ice grains. We have used two models: densely packed particles and bicontinuous media. For the case of densely packed particles, we used the Metropolis shuffling method to simulate the positions of particles. The particles are also allowed to have adhesive properties. The Foldy–Lax equations of multiple scattering are used to study scattering from the densely packed spherical particles. The results are illustrated for the coherent waves and incoherent waves. For the case of bicontinuous media, the method dev- eloped by Cahn is applied to construct the interfaces from a large number of stochastic sinusoidal waves with Random phases and directions. The volume scattering problem is then solved by using CGS–FFT. We illustrate the results of frequency and polarization dependence of such dense media scattering.
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simulation and measurement correlation of Random Rough Surface effects in interconnects
Electrical Performance of Electronic Packaging, 2012Co-Authors: Ruihua Ding, Leung Tsang, Henning Braunisch, Wenmo ChangAbstract:We study the effects of three dimensional (3D) Random Roughness on wave propagation in a parallel plate metallic waveguide with finite conductivity. The Surface Roughness is characterized as a Random process characterized by root mean square (rms) height, correlation length and power spectral density (PSD) function. The second order small perturbation method (SPM2) is applied to compute the coherent wave enhancement factors of absorption. A microstrip line structure is designed for validation of these enhancement factor results. Rough Surface height profiles are measured on the substrate and the PSD is extracted. With the PSD we obtain the enhancement factor for the specific Surface Roughness. The attenuation constant of the microstrip line with Rough Surface can be estimated using a field solution for a smooth Surface and the enhancement factor. The results for waveguides are also compared with the results obtained for a plane wave incident on a metal Surface with 3D Roughness. Comparison between the estimated and measured attenuation constant shows that the enhancement factor derived by SPM2 gives a better estimation than the standard Hammerstad and Bekkadal equation. The waveguide model gives more accurate enhancement factors than the plane wave model at frequencies above 20 GHz, especially for Rough Surfaces with rms heights larger than 2 μm.
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Random Rough Surface effects in interconnects studied by small perturbation theory in waveguide model
Electrical Performance of Electronic Packaging, 2011Co-Authors: Ruihua Ding, Leung Tsang, Henning BraunischAbstract:We study the effects of Random Roughness on wave propagation in a parallel plate metallic waveguide with finite conductivity. The Rough Surface is three dimensional (3D) with Roughness heights varying in both horizontal directions. Integral equations are obtained from the extinction theorem formulated with layered medium Green's function. The second order small perturbation method is then applied to solve the integral equations. A closed form expression for the coherent wave is derived, which is expressed in terms of a three-fold Sommerfeld type integral due to the waveguide structure. Approximate methods are applied to calculate the Sommerfeld integral. The coherent wave enhancement factors of absorption are computed. The results for waveguides are also compared with the results obtained for a plane wave incident on a metal Surface with 3D Roughness. Results are illustrated for 3D Roughness with a variety of power spectra. It is shown that enhancement factors for a waveguide are larger than that of the plane wave case.
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Random Rough Surface effects on wave propagation in interconnects
IEEE Transactions on Advanced Packaging, 2010Co-Authors: Leung Tsang, Henning Braunisch, Ruihua Ding, Xiaoxiong GuAbstract:To address the Rough Surface effects in high-speed interconnects on printed circuit boards (PCBs) and microelectronic packages, we study the electromagnetic wave propagation in a Rough Surface environment. In our model, the Rough Surface is characterized by a stochastic Random process with correlation function or spectral density. This paper reviews the analytical theory, numerical simulations and experimental results based on such a model. We describe the Rough Surface characterization and the extraction of Roughness parameters from 3D profile measurements. Initially we study the 2D case with the Rough Surface height function varying in only one horizontal direction and consider the case of plane wave incidence. Analytic second-order small perturbation method (SPM2) was used to obtain simple closed-form expressions for the absorption enhancement factor. The numerical transfer matrix (T-matrix) method and the method of moments (MoM) were also used. We next consider the case of the 3D problem with the Rough Surface height varying in both horizontal directions. We also used SPM2 to obtain a simple closed form expression for the enhancement factor. In interconnect problems, electromagnetic (EM) waves propagate in a guided wave environment. Thus, we next considered a waveguide model to study the effects of Random Roughness on wave propagation and compare with results from the plane wave formulation. Analytic SPM2 and numerical finite element method (FEM) with mode matching were used to obtain the enhancement factor. We also describe experimental results and correlation with the theoretical models. Finally, we explain how the enhancement factor concept used thRoughout lends itself to direct inclusion of Rough Surface effects in a wide variety of modeling problems.
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a smfsia method for the electromagnetic scattering perfectly conducting Random Rough Surface
2009Co-Authors: Chi Hou Chan, Leung TsangAbstract:With the recent development of the sparse-matrix flat-Surface iterative approach (SMFSIA), the Monte Carlo simulations of scattering from two-dimensional (3-D scattering problem) Random Rough Surface problems have become much more efficient [l]. In SMFSIA, the iterative procedure involves multiplication of a very large square matrix with a column vector. In this paper, we show that this CPU time-consuming procedure can be replaced by the fast Fourier transform (FFT). A numerical example is given by investigating electromagnetic wave scattering using SMFSIA with the fast Fourier transform. This new method provides a faster solution time without sacrificing numerical accuracy. Electromagnetic scattering from a perfectly conducting Surface is based on the magnetic field integral equation.
Chi Hou Chan - One of the best experts on this subject based on the ideXlab platform.
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a smfsia method for the electromagnetic scattering perfectly conducting Random Rough Surface
2009Co-Authors: Chi Hou Chan, Leung TsangAbstract:With the recent development of the sparse-matrix flat-Surface iterative approach (SMFSIA), the Monte Carlo simulations of scattering from two-dimensional (3-D scattering problem) Random Rough Surface problems have become much more efficient [l]. In SMFSIA, the iterative procedure involves multiplication of a very large square matrix with a column vector. In this paper, we show that this CPU time-consuming procedure can be replaced by the fast Fourier transform (FFT). A numerical example is given by investigating electromagnetic wave scattering using SMFSIA with the fast Fourier transform. This new method provides a faster solution time without sacrificing numerical accuracy. Electromagnetic scattering from a perfectly conducting Surface is based on the magnetic field integral equation.
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Parallel analysis of electromagnetic scattering from Random Rough Surfaces
Electronics Letters, 2003Co-Authors: Chi Hou ChanAbstract:An efficient approach for simulation of Random Rough Surface scattering is developed based on using a single integral equation formulation and a multilevel sparse-matrix canonical-grid method. Merits of the scheme are demonstrated using two wind-driven ocean Surfaces, one which is very Rough and the other large in size.
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monte carlo simulations of large scale problems of Random Rough Surface scattering and applications to grazing incidence with the bmia canonical grid method
IEEE Transactions on Antennas and Propagation, 1995Co-Authors: Leung Tsang, Chi Hou Chan, Kyung Pak, H SanganiAbstract:Scattering of a TE incident wave from a perfectly conducting one-dimensional Random Rough Surface is studied with the banded matrix iterative approach/canonical grid (BMIA/CAG) method. The BMIA/CAG is an improvement over the previous BMIA. The key idea of BMIA/CAG is that outside the near-field interaction, the rest of the interactions can be translated to a canonical grid by Taylor series expansion. The use of a flat Surface as a canonical grid for a Rough Surface facilitates the use of the fast Fourier transform for nonnear field interaction. The method can be used for Monte-Carlo simulations of Random Rough Surface problems with a large Surface length including all the coherent wave interactions within the entire Surface. We illustrate results up to a Surface length of 2500 wavelengths with 25000 Surface unknowns. The method is also applied to study scattering from Random Rough Surfaces at near-grazing incidence. The numerical examples illustrate the importance of using a large Surface length for some backscattering problems. >
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studies of large scale Random Rough Surface problems with the sparse matrix flat Surface iterative approach
International Geoscience and Remote Sensing Symposium, 1994Co-Authors: Leung Tsang, Chi Hou ChanAbstract:Scattering of the TE incident wave from a perfectly conducting Random Rough Surface is studied. First, the vector electromagnetic scattering from a two-dimensional Rough Surface with a Surface area of 81 square wavelengths is illustrated. Monte Carlo results show backscattering enhancement for the co-polarized component. Secondly, the TE scattering from a one-dimensional Random Rough Surface with a Gaussian Roughness spectrum is studied. Specifically, a grazing incident angle at 86/spl deg/ with a Surface length of 800 wavelengths is presented. Lastly, backscattering intensities from Gaussian and non-Gaussian Rough Surfaces are compared. Numerical results are illustrated as a function of rms height and slope. >
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a smfsia method for the electromagnetic scattering from a two dimensional 3 d scattering problem perfectly conducting Random Rough Surface
IEEE Antennas and Propagation Society International Symposium, 1994Co-Authors: Chi Hou Chan, Leung TsangAbstract:With the development of the sparse-matrix flat-Surface iterative approach (SMFSIA), the Monte Carlo simulations of scattering from two-dimensional (3-D scattering problem) Random Rough Surface problems have become much more efficient. In SMFSIA, the iterative procedure involves multiplication of a very large square matrix with a column vector. The present authors show that this CPU time-consuming procedure can be replaced by the fast Fourier transform (FFT). A numerical example is given by investigating electromagnetic wave scattering using SMFSIA with the fast Fourier transform. This new method provides a faster solution time without sacrificing numerical accuracy. >
H Sangani - One of the best experts on this subject based on the ideXlab platform.
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monte carlo simulations of large scale problems of Random Rough Surface scattering and applications to grazing incidence with the bmia canonical grid method
IEEE Transactions on Antennas and Propagation, 1995Co-Authors: Leung Tsang, Chi Hou Chan, Kyung Pak, H SanganiAbstract:Scattering of a TE incident wave from a perfectly conducting one-dimensional Random Rough Surface is studied with the banded matrix iterative approach/canonical grid (BMIA/CAG) method. The BMIA/CAG is an improvement over the previous BMIA. The key idea of BMIA/CAG is that outside the near-field interaction, the rest of the interactions can be translated to a canonical grid by Taylor series expansion. The use of a flat Surface as a canonical grid for a Rough Surface facilitates the use of the fast Fourier transform for nonnear field interaction. The method can be used for Monte-Carlo simulations of Random Rough Surface problems with a large Surface length including all the coherent wave interactions within the entire Surface. We illustrate results up to a Surface length of 2500 wavelengths with 25000 Surface unknowns. The method is also applied to study scattering from Random Rough Surfaces at near-grazing incidence. The numerical examples illustrate the importance of using a large Surface length for some backscattering problems. >
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a bmia fft algorithm for the monte carlo simulations of large scale Random Rough Surface scattering application to grazing incidence
IEEE Antennas and Propagation Society International Symposium, 1994Co-Authors: Leung Tsang, Chi Hou Chan, H SanganiAbstract:A banded matrix iterative approach (BMIA) has been developed to study electromagnetic scattering from one-dimensional Random Rough Surfaces. This new method not only provides a faster solution time, but it also allows one to analyze much longer Surfaces that could not be considered before using the conventional integral equation method. The capability of analyzing Random Surfaces of large Surface length is essential in the study of backscattering at near grazing incident angle. We report our refinement of the BMIA. We first identify the inefficient part of the algorithm and then provide a remedy to alleviate the problem which results in further reduction in solution time as well as computer memory requirement. We then apply the new improved BMIA to investigate backscattering from Random Rough Surface near grazing incidence.
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monte carlo simulations of large scale composite Random Rough Surface scattering based on the banded matrix iterative approach
Journal of The Optical Society of America A-optics Image Science and Vision, 1994Co-Authors: Leung Tsang, Chi Hou Chan, H Sangani, Akira IshimaruAbstract:Scattering of a TE incident wave from a perfectly conducting one-dimensional composite Random Rough Surface is studied. A composite Random Surface contains Roughness of more than one scale. With the recently developed efficient numerical technique known as the banded-matrix iterative approach, we are able to study large-scale composite Roughness with two correlation lengths that are many times different from each other. It is shown that small-scale Roughness, with its large rms slope, rather than large-scale Roughness, with its small rms slope, can dominate bistatic scattering. It is also shown that backscattering enhancement can also exist in a composite Rough Surface.
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application of a banded matrix iterative approach to monte carlo simulations of scattering of waves by a Random Rough Surface tm case
Microwave and Optical Technology Letters, 1993Co-Authors: Leung Tsang, Chi Hou Chan, H SanganiAbstract:A banded matrix iterative approach is applied to study scattering of a TM incident wave from a perfectly conducting one-dimensional Random Rough Surface. It is much faster than the full matrix inversion approach. When compared to the Kirchoff iterative approach, it is of comparable CPU time, is more accurate, and works for cases when the Kirchoff iteration fails. © 1993 John Wiley & sons, Inc.
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banded matrix iterative approach to monte carlo simulations of scattering of waves by large scale Random Rough Surface problems tm case
Electronics Letters, 1993Co-Authors: Leung Tsang, Chi Hou Chan, H SanganiAbstract:A banded matrix iterative approach is applied to study the scattering of a TM incident wave from a perfectly conducting one-dimensional Random Rough Surface. It is accurate and is much faster than the full matrix inversion approach or the conjugate gradient method. Applications of this method to large-scale Rough Surface problems are illustrated.
Akira Ishimaru - One of the best experts on this subject based on the ideXlab platform.
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monte carlo simulations of large scale composite Random Rough Surface scattering based on the banded matrix iterative approach
Journal of The Optical Society of America A-optics Image Science and Vision, 1994Co-Authors: Leung Tsang, Chi Hou Chan, H Sangani, Akira IshimaruAbstract:Scattering of a TE incident wave from a perfectly conducting one-dimensional composite Random Rough Surface is studied. A composite Random Surface contains Roughness of more than one scale. With the recently developed efficient numerical technique known as the banded-matrix iterative approach, we are able to study large-scale composite Roughness with two correlation lengths that are many times different from each other. It is shown that small-scale Roughness, with its large rms slope, rather than large-scale Roughness, with its small rms slope, can dominate bistatic scattering. It is also shown that backscattering enhancement can also exist in a composite Rough Surface.
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a banded matrix iterative approach to monte carlo simulations of large scale Random Rough Surface scattering te case
Journal of Electromagnetic Waves and Applications, 1993Co-Authors: Leung Tsang, Chi Hou Chan, H Sangani, Akira IshimaruAbstract:A banded matrix iterative approach is applied to study scattering of a TE incident wave from a perfectly conducting one-dimensional Random Rough Surface. It is much faster than the full matrix inversion approach or the conjugate gradient method. When compared to the Kirchhoff iterative approach, it is of comparable CPU time, and works for cases when the Kirchhoff iteration is erroneous. The method is illustrated for a variety of parameters with particular application to large scale Rough Surface problems. The largest Surface length used is 400 wavelengths with 3200 unknowns, and all the coherent wave interactions are included within the entire Surface length. The accuracy of the banded iterative approach is demonstrated by showing that the results overlie those of the exact matrix inversion and the conjugate gradient method. The numerical method is also easy to implement. With this approach, we are able to compute the new response characteristics of composite Rough Surfaces with much larger scales. The ca...
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monte carlo simulations of scattering of waves by a Random Rough Surface with the finite element method and the finite difference method
Microwave and Optical Technology Letters, 1990Co-Authors: Leung Tsang, Chi Hou Chan, Akira IshimaruAbstract:The finite element and the finite difference methods are applied to Monte Carlo simulations of Random Rough Surface scattering. The advantages of these methods are the banded nature of matrix and the reduction of computer time. These results are also compared with those of Kirchhoff approximation and those of small perturbation theory when applicable.
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a heuristic algorithm for the bistatic radar cross section for Random Rough Surface scattering
IEEE Transactions on Geoscience and Remote Sensing, 1990Co-Authors: Shira L Broschat, Eric I Thorsos, Akira IshimaruAbstract:Examines a heuristic algorithm which guarantees reciprocity in the cross-section equations when the phase perturbation approximation is used. The results obtained using a Gaussian Surface Roughness spectrum are superior to those of either the phase perturbation or the reversed phase perturbation method and agree well with the exact results obtained using a Monte Carlo integral equation technique. >
Xiaobang Xu - One of the best experts on this subject based on the ideXlab platform.
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analysis of scattering from three dimensional objects buried below a Random Rough Surface by monte carlo mpstd method
Progress in Electromagnetics Research B, 2013Co-Authors: Xiaobang XuAbstract:This paper presents a Monte-Carlo multidomain pseu- dospectral time-domain (MPSTD) algorithm developed for the analy- sis of scattering from a three dimensional (3D) object buried below a Random Rough Surface separating two half spaces. In the development, special attention is paid to the 3D computation domain decomposition and subdomain mapping involving the Random Rough Surface as well as the subdomain patching along the Rough Surface. The Mote-Carlo MPSTD algorithm is then employed to determine the scattering of 3D objects of various shapes and electromagnetic properties; embedded in the lower half space with difierent permittivity and the Roughness of the Random Rough Surface may vary. Sample numerical results are presented, validated, and analyzed. ThRough the analysis, it is ob- served that the Roughness of the Random Rough Surface and the elec- tromagnetic properties of the lower half space can signiflcantly afiect the scattered signature of the buried object.
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a monte carlo mpstd analysis of scattering from cylinders buried below a Random periodic Rough Surface
Progress in Electromagnetics Research B, 2013Co-Authors: Xiaobang XuAbstract:The analysis of scattering of objects buried below a Random Rough Surface is of practical interest. In reality, the Random Rough Surface may be of an extensive periodic structure. To deal with this more realistic situation, this paper presents a Monte-Carlo MPSTD numerical technique developed for investigating the scattering of a cylinder buried below a Random periodic Rough Surface. The computation model is formulated in two steps. In the flrst step, only the Random Rough Surface is considered and the periodic boundary condition (PBC) is enforced at the two ends of a period of the Rough Surface. Then, in the second step, a cylinder is placed below the Random Rough Surface and the interaction between the buried cylinder and the Rough Surface is taken into account. In each of the two steps, the flelds are computed employing the MPSTD algorithm developed in the authors' previous work. Sample numerical results are presented and validated.
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scattering of object buried below Random Rough Surface a monte carlo pseudospectral time domain approach
Electromagnetics, 2012Co-Authors: Haiyan Yang, Xiaobang XuAbstract:Absract This article presents a numerical technique combining the multi-domain pseudospectral time-domain method and the Monte Carlo method for determining the scattering of an object buried below a Random Rough Surface separating two half-spaces. The numerical technique is employed to determine the scattering of a cylinder buried below a Random Rough Surface of finite length under various conditions. Sample numerical results are presented, validated, and analyzed. The results illustrate the significant impact of the Roughness of the Surface and the electromagnetic properties of the lower half-space on the scattered signature of the buried cylinder.
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Scattering of Object Buried below Random Rough Surface—A Monte Carlo Pseudospectral Time-Domain Approach
Electromagnetics, 2012Co-Authors: Haiyan Yang, Xiaobang XuAbstract:Absract This article presents a numerical technique combining the multi-domain pseudospectral time-domain method and the Monte Carlo method for determining the scattering of an object buried below a Random Rough Surface separating two half-spaces. The numerical technique is employed to determine the scattering of a cylinder buried below a Random Rough Surface of finite length under various conditions. Sample numerical results are presented, validated, and analyzed. The results illustrate the significant impact of the Roughness of the Surface and the electromagnetic properties of the lower half-space on the scattered signature of the buried cylinder.