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Scattering Problem (scattering + problem)
Kinds of Scattering Problem Selected AbstractsA study of uniform approximation of equivalent permittivity for index-modulated gratingsELECTRONICS & COMMUNICATIONS IN JAPAN, Issue 11 2008Shota Sugano Abstract It is well known that surface-relief dielectric gratings with rectangular profile can be treated by uniform approximation of the equivalent permittivity when the periodicity is very small compared with the wavelength. In optics, this phenomenon is the equivalent anisotropic effects or the form birefringence. When the periodicity is very small, the equivalent anisotropic effects will be shown in index-modulated gratings. In this paper, the uniform approximation is described for the electromagnetic scattering problem of index-modulated gratings. The scattering properties of dielectric slabs are calculated by transmission-line theory and the equivalent permittivity obtained from our proposed formulation of the uniform approximation. Scattering by index-modulated gratings is analyzed rigorously by matrix eigenvalue calculations using the Fourier expansion method and spatial harmonics expansions. When the periodicity is very small, the results are in good agreement. By investigating the difference between the equivalent permittivity and the numerical values corresponding to the permittivity of the index-modulated gratings, the conditions of applicability of the uniform approximation are shown. The equivalent anisotropic effects of various profiles are compared. © 2009 Wiley Periodicals, Inc. Electron Comm Jpn, 91(11): 28,36, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecj.10181 [source] Numerical accuracy of a Padé-type non-reflecting boundary condition for the finite element solution of acoustic scattering problems at high-frequencyINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, Issue 10 2005R. Kechroud Abstract The present text deals with the numerical solution of two-dimensional high-frequency acoustic scattering problems using a new high-order and asymptotic Padé-type artificial boundary condition. The Padé-type condition is easy-to-implement in a Galerkin least-squares (iterative) finite element solver for arbitrarily convex-shaped boundaries. The method accuracy is investigated for different model problems and for the scattering problem by a submarine-shaped scatterer. As a result, relatively small computational domains, optimized according to the shape of the scatterer, can be considered while yielding accurate computations for high-frequencies. Copyright © 2005 John Wiley & Sons, Ltd. [source] Image reconstruction for a partially immersed imperfectly conducting cylinder by genetic algorithmINTERNATIONAL JOURNAL OF IMAGING SYSTEMS AND TECHNOLOGY, Issue 4 2009Wei Chien Abstract This article presents a computational approach to the imaging of a partially immersed imperfectly conducting cylinder. An imperfectly conducting cylinder of unknown shape and conductivity scatters the incident transverse magnetic (TM) wave in free space while the scattered field is recorded outside. Based on the boundary condition and the measured scattered field, a set of nonlinear integral equations, and the inverse scattering problem are reformulated into an optimization problem. We use genetic algorithm (GA) to reconstruct the shape and the conductivity of a partially immersed imperfectly conducting cylinder. The genetic algorithm is then used to find out the global extreme solution of the cost function. Numerical results demonstrated that, even when the initial guess is far away from the exact one, good reconstruction can be obtained. In such a case, the gradient-based methods often get trapped in a local extreme. In addition, the effect of random noise on the reconstruction is investigated. © 2009 Wiley Periodicals, Inc. Int J Imaging Syst Technol, 19, 299,305, 2009 [source] Microwave imaging of parallel perfectly conducting cylindersINTERNATIONAL JOURNAL OF IMAGING SYSTEMS AND TECHNOLOGY, Issue 6 2000Anyong Qing This paper considers microwave imaging of parallel perfectly conducting cylinders using a solution of the scattering problem by the point-matching method. A cubic B-spline, real-coded genetic algorithm and an adaptive hybrid algorithm are proposed to solve the inverse problem. Previous shape functions in trigonometric series with arbitrary coefficients are nondefinite, which intensify the ill-posedness and slow the early time convergence of the algorithm. A novel shape function based on cubic B-splines is developed and the real-coded genetic algorithm is modified accordingly. Numerical simulation examples show that the early time convergence of the real-coded genetic algorithm is improved significantly. Next, the adaptive hybrid algorithm is developed to improve the late time convergence of the cubic B-spline real-coded genetic algorithm. © 2001 John Wiley & Sons, Inc. Int J Imaging Syst Technol 11, 365,371, 2000 [source] A global time domain circuit simulation of a microwave rectennaINTERNATIONAL JOURNAL OF NUMERICAL MODELLING: ELECTRONIC NETWORKS, DEVICES AND FIELDS, Issue 1-2 2007Brahim Essakhi Abstract The paper presents a global time domain simulation of a microwave rectenna studied for wireless energy transfer. The novelty of the work is to take into account both distributed electromagnetic parts of the antenna and the rectifier circuit including lumped elements. From a 3D finite element time domain electromagnetic modelling of the structure an equivalent circuit of the antenna is deduced: the input impedance is obtained as a function of frequency over a broad band. Then a rational approximation gives a corresponding PSPICE representation. The electromotive force induced between the ports of the antenna during the microwave illumination is directly computed from the 3D transient scattering problem. The resulting equivalent circuit of the antenna is finally incorporated into the electronic simulator PSPICE, together with the lumped components of the rectenna (ideal diodes and load). Thus a global non-linear time domain analysis of the whole structure becomes available. The results obtained with the methods presented in the paper are compared with those resulting from other techniques. The approach developed in the work could efficiently improve the design stage of rectennas devoted to microwave power transfer. Copyright © 2006 John Wiley & Sons, Ltd. [source] Structure Determination in Colloidal Crystal Photonic Bandgap StructuresJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 6 2002John Ballato Structure/optical property relationships in photonic bandgap structures are evaluated by a novel combination of sample sectioning, microscopy, and image analysis. Disordered colloidal crystals of solution-derived, monosized SiO2 particles were sectioned by focused ion beam (FIB) milling and then imaged using field emission scanning electron microscopy (FE-SEM). Pair correlation and radial distribution functions of the particulate arrangement were generated directly from a binary color scale rendering of the FE-SEM images, therein defining the level of order or disorder in the structure. These experimentally obtained spatial correlation functions were used to compute the scattering spectral properties in an analogous, although inverse (i.e., solving the inverse scattering problem), method to that used in X-ray diffraction for structure determination. Using a first-order approximation to the scattering from a disordered structure, the bandwidth and midgap values for the colloidal crystal photonic bandgap materials were within 15% of those measured. This new methodology promises to provide a simple and direct approach for quantifying the structure/optical property relationships in ordered and disordered photonic crystals directly from standard microstructural imaging techniques. [source] Reconstruction of cracks of different types from far-field measurementsMATHEMATICAL METHODS IN THE APPLIED SCIENCES, Issue 8 2010Jijun Liu Abstract In this paper, we deal with the acoustic inverse scattering problem for reconstructing cracks of possibly different types from the far-field map. The scattering problem models the diffraction of waves by thin two-sided cylindrical screens. The cracks are characterized by their shapes, the type of boundary conditions and the boundary coefficients (surface impedance). We give explicit formulas of the indicator function of the probe method, which can be used to reconstruct the shape of the cracks, distinguish their types of boundary conditions, the two faces of each of them and reconstruct the possible material coefficients on them by using the far-field map. To test the validity of these formulas, we present some numerical implementations for a single crack, which show the efficiency of the proposed method for suitably distributed surface impedances. The difficulties for numerically recovering the properties of the crack in the concave side as well as near the tips are presented and some explanations are given. Copyright © 2009 John Wiley & Sons, Ltd. [source] Modified wave operators for the fourth-order non-linear Schrödinger-type equation with cubic non-linearityMATHEMATICAL METHODS IN THE APPLIED SCIENCES, Issue 15 2006Jun-ichi Segata Abstract We consider the scattering problem for the fourth-order non-linear Schrödinger-type equation: (1) We show the existence of the modified wave operators for the above equation with cubic case by imposing the mean zero condition for the final data. Copyright © 2006 John Wiley & Sons, Ltd. [source] A time-marching finite element method for an electromagnetic scattering problemMATHEMATICAL METHODS IN THE APPLIED SCIENCES, Issue 12 2003Tri Van Abstract In this paper, Newmark time-stepping scheme and edge elements are used to numerically solve the time-dependent scattering problem in a three-dimensional polyhedral cavity. Finite element methods based on the variational formulation derived in Van and Wood (Adv. Comput. Math., to appear) are considered. Existence and uniqueness of the discrete problem is proved by using Babuska,Brezzi theory. Finite element error estimate and stability of the Newmark scheme are also established. Copyright © 2003 John Wiley & Sons, Ltd. [source] Combined far-ield operators in electromagnetic inverse scattering theoryMATHEMATICAL METHODS IN THE APPLIED SCIENCES, Issue 5 2003Fioralba Cakoni Abstract We consider the inverse scattering problem of determining the shape of a perfect conductor D from a knowledge of the scattered electromagnetic wave generated by a time-harmonic plane wave incident upon D. By using polarization effects we establish the validity of the linear sampling method for solving this problem that is valid for all positive values of the wave number. We also show that it suffices to consider incident directions and observation angles that are restricted to a limited aperture. Copyright © 2003 John Wiley & Sons, Ltd. [source] The Schrödinger equation and a multidimensional inverse scattering transformMATHEMATICAL METHODS IN THE APPLIED SCIENCES, Issue 16-18 2002Swanhild Bernstein Abstract The Schrödinger equation is one of the most important equations in mathematics, physics and also engineering. We outline some connections between transformations of non-linear equations, the Schrödinger equation and the inverse scattering transform. After some remarks on generalizations into higher dimensions we present a multidimensional ,¯ method based on Clifford analysis. To explain the method we consider the formal solution of the inverse scattering problem for the n -dimensional time-dependent Schrödinger equations given by A.I. Nachman and M.J. Ablowitz. Copyright © 2002 John Wiley & Sons, Ltd. [source] Existence of solution in elastic wave scattering by unbounded rough surfacesMATHEMATICAL METHODS IN THE APPLIED SCIENCES, Issue 6 2002T. Arens We consider the two-dimensional problem of the scattering of a time-harmonic wave, propagating in an homogeneous, isotropic elastic medium, by a rough surface on which the displacement is assumed to vanish. This surface is assumed to be given as the graph of a function ,,C1,1(,). Following up on earlier work establishing uniqueness of solution to this problem, existence of solution is studied via the boundary integral equation method. This requires a novel approach to the study of solvability of integral equations on the real line. The paper establishes the existence of a unique solution to the boundary integral equation formulation in the space of bounded and continuous functions as well as in all Lp spaces, p,[1, ,] and hence existence of solution to the elastic wave scattering problem. Copyright © 2002 John Wiley & Sons, Ltd. [source] Inverse scattering for the non-linear Schrödinger equation: Reconstruction of the potential and the non-linearityMATHEMATICAL METHODS IN THE APPLIED SCIENCES, Issue 4 2001Ricardo Weder In this paper we consider the inverse scattering problem for the non-linear Schrödinger equation on the line \def\dr{{\rm d}}$$i{\partial\over\partial t}u(t,x)=-{\dr^2\over\dr x^2}u(t,x)+V_0(x)u(t,x)+\sum_{j=1}^{\infty}V_j(x)|u|^{2(j_0+j)}u(t,x)$$\nopagenumbers\end We prove, under appropriate conditions, that the small-amplitude limit of the scattering operator determines uniquely Vj, j=0,1,, . Our proof gives also a method for the reconstruction of the Vj, j=0,1,, . Copyright © 2001 John Wiley & Sons, Ltd. [source] Surface integral methods for high-frequency electromagnetic scatteringPROCEEDINGS IN APPLIED MATHEMATICS & MECHANICS, Issue 1 2007M. Ganesh Surface integral equation based methods are advantageous for simulation of electromagnetic waves scattered by three dimensional obstacles, because they efficiently reduce the dimension of the problem and are robust for high-frequency problems. However, the cost of setting up the associated discretized dense linear systems is prohibitive due to evaluation of highly oscillatory magnetic and electric dipole surface integral operators using standard cubatures. The computational complexity of evaluating such integrals depends on the incident wave frequency, and the size and shape of the obstacles. In this work we discuss a surface integral reformulation of the scattering problem that involves evaluation of surface integrals with a highly oscillatory physical density, and discuss methods for efficient evaluation of such integrals for a class of smooth three dimensional scatterers whose diameter is a large multiple of the incident wavelength. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Semiclassical expansion of quantum characteristics for many-body potential scattering problemANNALEN DER PHYSIK, Issue 9 2007M.I. Krivoruchenko Abstract In quantum mechanics, systems can be described in phase space in terms of the Wigner function and the star-product operation. Quantum characteristics, which appear in the Heisenberg picture as the Weyl's symbols of operators of canonical coordinates and momenta, can be used to solve the evolution equations for symbols of other operators acting in the Hilbert space. To any fixed order in the Planck's constant, many-body potential scattering problem simplifies to a statistical-mechanical problem of computing an ensemble of quantum characteristics and their derivatives with respect to the initial canonical coordinates and momenta. The reduction to a system of ordinary differential equations pertains rigorously at any fixed order in ,. We present semiclassical expansion of quantum characteristics for many-body scattering problem and provide tools for calculation of average values of time-dependent physical observables and cross sections. The method of quantum characteristics admits the consistent incorporation of specific quantum effects, such as non-locality and coherence in propagation of particles, into the semiclassical transport models. We formulate the principle of stationary action for quantum Hamilton's equations and give quantum-mechanical extensions of the Liouville theorem on conservation of the phase-space volume and the Poincaré theorem on conservation of 2p -forms. The lowest order quantum corrections to the Kepler periodic orbits are constructed. These corrections show the resonance behavior. [source] Identification and removal of above-ground spurious signals in GPR archaeological prospecting,ARCHAEOLOGICAL PROSPECTION, Issue 2 2005Luigia Nuzzo Abstract Ground-penetrating radar (GPR) is a shallow geophysical method increasingly used in archaeological prospecting to detect buried remains and to map the stratigraphy of the uppermost earth layers embodying the archaeological features. The GPR sections, however, can be contaminated by spurious correlated signals caused by above-ground obstacles (buildings, trees, fences, power lines) placed either in-line or off-line with respect to the profile (surface scattering). In the case study presented this problem is analysed for a 35,MHz GPR survey carried out for stratigraphical purposes in the archaeological site of the Roman Ships near Pisa (Italy). The investigation inside the archaeological excavation, when the level was about 5,m below the ground surface, produced a severe surface scattering problem caused by the iron sheet-piling protecting the excavation walls and bordering some of the partly excavated boats. An attempt to interpret the profiles was carried out in a zone where the relatively simple geometry of the metallic enclosure allowed understanding of the possible origin of spurious events, also thanks to the high density of profiles acquired along two orthogonal directions. Migration at the air velocity and geometrical considerations helped the identification of hyperbolic and slightly slanted features as surface scattering phenomena from different sides of the iron sheet-piling. A simple but original subtraction procedure was successful for the attenuation of some of the spurious reflections. After this partial removal, other spurious signals could be recognized more easily as well as two weak subhorizontal reflections of probable stratigraphical meaning. Subsequently, filtering procedures based on f-k and Radon transform methods were tried to further reduce the spurious signals, thus enhancing the visibility of the interesting reflections. Copyright © 2005 John Wiley & Sons, Ltd. [source] On semiclassical (zero dispersion limit) solutions of the focusing nonlinear Schrödinger equationCOMMUNICATIONS ON PURE & APPLIED MATHEMATICS, Issue 7 2004Alexander Tovbis We calculate the leading-order term of the solution of the focusing nonlinear (cubic) Schrödinger equation (NLS) in the semiclassical limit for a certain one-parameter family of initial conditions. This family contains both solitons and pure radiation. In the pure radiation case, our result is valid for all times t , 0. We utilize the Riemann-Hilbert problem formulation of the inverse scattering problem to obtain the leading-order term of the solution. Error estimates are provided. © 2004 Wiley Periodicals, Inc. [source] Numerical accuracy of a Padé-type non-reflecting boundary condition for the finite element solution of acoustic scattering problems at high-frequencyINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, Issue 10 2005R. Kechroud Abstract The present text deals with the numerical solution of two-dimensional high-frequency acoustic scattering problems using a new high-order and asymptotic Padé-type artificial boundary condition. The Padé-type condition is easy-to-implement in a Galerkin least-squares (iterative) finite element solver for arbitrarily convex-shaped boundaries. The method accuracy is investigated for different model problems and for the scattering problem by a submarine-shaped scatterer. As a result, relatively small computational domains, optimized according to the shape of the scatterer, can be considered while yielding accurate computations for high-frequencies. Copyright © 2005 John Wiley & Sons, Ltd. [source] Improved accuracy for the Helmholtz equation in unbounded domainsINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, Issue 15 2004Eli Turkel Abstract Based on properties of the Helmholtz equation, we derive a new equation for an auxiliary variable. This reduces much of the oscillations of the solution leading to more accurate numerical approximations to the original unknown. Computations confirm the improved accuracy of the new models in both two and three dimensions. This also improves the accuracy when one wants the solution at neighbouring wavenumbers by using an expansion in k. We examine the accuracy for both waveguide and scattering problems as a function of k, h and the forcing mode l. The use of local absorbing boundary conditions is also examined as well as the location of the outer surface as functions of k. Connections with parabolic approximations are analysed. Copyright © 2004 John Wiley & Sons, Ltd. [source] A fictitious domain decomposition method for the solution of partially axisymmetric acoustic scattering problems.INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, Issue 1 2003Part 2: Neumann boundary conditions Abstract We present a fictitious domain decomposition method for the fast solution of acoustic scattering problems characterized by a partially axisymmetric sound-hard scatterer. We apply this method to the solution of a mock-up submarine problem, and highlight its computational advantages and intrinsic parallelism. A key component of our method is an original idea for addressing a Neumann boundary condition in the general framework of a fictitious domain method. This idea is applicable to many other linear partial differential equations besides the Helmholtz equation. Copyright © 2003 John Wiley & Sons, Ltd. [source] Physics-based preconditioner for iterative algorithms in multi-scatterer and multi-boundary method of moments formulationsINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, Issue 3 2002Jürgen v. Hagen Abstract An efficient method to solve electromagnetic scattering problems involving several metallic scatterers or bodies composed of dielectric and metallic regions is proposed. So far, the method of moments has successfully been applied to large arrays of identical scatterers when it was combined with preconditioned iterative algorithms to solve for the linear system of equations. Here, the method is generalized to geometries that are composed of several metallic elements of different shapes and sizes, and also to scatterers that are composed of metallic and dielectric regions. The method uses in its core an iterative algorithm, preferably the transpose-free quasi-minimum residual (TFQMR) algorithm, and a block diagonal Jacobi preconditioner. For best performance, the blocks for the preconditioner are chosen according to individual scatterers or groups of scatterers for the array case, and according to the electric and magnetic current basis functions for dielectric/metallic scatterers. The iterative procedure converges quickly for an optimally chosen preconditioner, and is robust even for a non-optimal preconditioner. Reported run times are compared to run times of an efficiently programmed LU factorization, and are shown to be significantly lower. Copyright © 2002 John Wiley & Sons, Ltd. [source] On the spectrum of the electric field integral equation and the convergence of the moment methodINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, Issue 1 2001Karl F. Warnick Abstract Existing convergence estimates for numerical scattering methods based on boundary integral equations are asymptotic in the limit of vanishing discretization length, and break down as the electrical size of the problem grows. In order to analyse the efficiency and accuracy of numerical methods for the large scattering problems of interest in computational electromagnetics, we study the spectrum of the electric field integral equation (EFIE) for an infinite, conducting strip for both the TM (weakly singular kernel) and TE polarizations (hypersingular kernel). Due to the self-coupling of surface wave modes, the condition number of the discretized integral equation increases as the square root of the electrical size of the strip for both polarizations. From the spectrum of the EFIE, the solution error introduced by discretization of the integral equation can also be estimated. Away from the edge singularities of the solution, the error is second order in the discretization length for low-order bases with exact integration of matrix elements, and is first order if an approximate quadrature rule is employed. Comparison with numerical results demonstrates the validity of these condition number and solution error estimates. The spectral theory offers insights into the behaviour of numerical methods commonly observed in computational electromagnetics. Copyright © 2001 John Wiley & Sons, Ltd. [source] Multi-region ADI DD-FDTD algorithm for the analysis of three-dimensional sparse multi-objects scattering problemINTERNATIONAL JOURNAL OF NUMERICAL MODELLING: ELECTRONIC NETWORKS, DEVICES AND FIELDS, Issue 1-2 2008Feng Xu In this paper, a multi-region domain decomposition finite-difference time-domain (DD-FDTD) algorithm is proposed and developed for the analysis of multiple-objects electromagnetic (EM) problems. A significant number of mesh nodes between objects are removed since only local meshes are generated for each object. All the separated sub-domains are interconnected by the use of a 3-D time-domain Green's function. The coupling between objects can be regarded as the equivalent spherical wave irradiations. Incident signals of the equivalent spherical waves are expressed as a spherical wave input field array according to the Huygens principle. The near-field to far-field transformation is introduced to obtain the equivalent spherical wave. Moreover, the alternating direction implicit FDTD (ADI-FDTD) scheme is applied to overcome the limit of the stability condition and increase the speed of the simulation. The new algorithm has been demonstrated and applied to solve typical 3-D multi-objects EM scattering problems. Copyright © 2007 John Wiley & Sons, Ltd. [source] Multilevel fast multipole algorithm enhanced by GPU parallel technique for electromagnetic scattering problemsMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 3 2010Kan Xu Abstract Along with the development of graphics processing Units (GPUS) in floating point operations and programmability, GPU has increasingly become an attractive alternative to the central processing unit (CPU) for some of compute-intensive and parallel tasks. In this article, the multilevel fast multipole algorithm (MLFMA) combined with graphics hardware acceleration technique is applied to analyze electromagnetic scattering from complex target. Although it is possible to perform scattering simulation of electrically large targets on a personal computer (PC) through the MLFMA, a large CPU time is required for the execution of aggregation, translation, and deaggregation operations. Thus GPU computing technique is used for the parallel processing of MLFMA and a significant speedup of matrix vector product (MVP) can be observed. Following the programming model of compute unified device architecture (CUDA), several kernel functions characterized by the single instruction multiple data (SIMD) mode are abstracted from components of the MLFMA and executed by multiple processors of the GPU. Numerical results demonstrate the efficiency of GPU accelerating technique for the MLFMA. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52: 502,507, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24963 [source] Shifted SSOR preconditioning technique for electromagnetic wave scattering problemsMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 4 2009J. Q. Chen Abstract To efficiently solve large dense complex linear system arising from electric field integral equations (EFIE) formulation of electromagnetic scattering problems, the multilevel fast multipole method (MLFMM) is used to accelerate the matrix-vector product operations. The symmetric successive over-relaxation (SSOR) preconditioner is constructed based on the near-field matrix of the EFIE and employed to speed up the convergence rate of iterative methods. This technique can be greatly improved by shifting the near-field matrix of the EFIE with the principle value term of the magnetic field integral equation (MFIE) operator. Numerical results demonstrate that this method can reduce both the number of iterations and the computational time significantly with low cost for construction and implementation of preconditioners. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 1035,1039, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24254 [source] Further comments on the performances of finite element simulators for the solution of electromagnetic problems involving metamaterialsMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 12 2006Gaia Cevini Abstract In this paper, we analyze the performances of three-dimensional finite element (FE) simulators in handling electromagnetic scattering problems involving metamaterials. It has already been proved that the performances of the FE method are worse than usual, when metamaterials are considered. In this work, we extend our previous analysis by providing some additional results on the precision of the FE solution and on the performances of the iterative and direct solvers typically used with FE simulators. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 48:2524,2529, 2006; Published online in Wiley InterScience (www.interscience.wiley.com).DOI 10.1002/mop.22008 [source] Assessment of the performances of first- and second-order time-domain ABC's for the truncation of finite element gridsMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 1 2003Salvatore Caorsi Abstract In this paper we investigate the performances of first- and second-order time-domain absorbing boundary conditions (ABCs) when introduced in a finite-element algorithm to solve electromagnetic scattering problems. Attention is focused on the analysis of the ABC's absorbing characteristics when different geometries are considered for the truncation of the computational domain. Numerical results will be given by considering, as a first analysis, two-dimensional scattering problems. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 38: 11,16, 2003 [source] Use of wavelet transform to the method-of-moments matrix arising from electromagnetic scattering problems of 2D objects due to oblique plane-wave incidenceMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 2 2002Jin Yu Abstract An efficient method is presented for transforming the matrix of the method of moments obtained by the expansion of the unknown surface currents with pulse basis function and the use of point match testing to a matrix with wavelet basis and testing functions. When the electromagnetic scattering object is a dielectric or object under oblique plane-wave incidence, more than one equivalent surface current component exists at the object surface. When these currents are connected into one current vector in the method of moments, there must be some discontinuities between the current components. These discontinuities make the direct wavelet transform to the whole MoM matrix inefficient and not equivalent to the use of the wavelet functions in the expansion of the unknown currents and the testing. Therefore, the wavelet transform must be constructed in a different way to avoid these discontinuities. Here, the proper wavelet transform that is equivalent to the use of the wavelet functions in the MoM, which avoids such discontinuities, is presented. This transform is referred to as wavelet subtransform. © 2002 Wiley Periodicals, Inc. Microwave Opt Technol Lett 34: 130,134, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10394 [source] The hybrid FEM,MOL approach for the analysis of scattering problemsMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 2 2002Ying Xiao Abstract In this Letter a hybrid approach combining the finite-element method and the method of lines is presented for solving the scattering problems of irregular geometry and inhomogeneity. In this approach, the FEM is used to treat the region with complicated geometry and inhomogeneous material profile, and the MoL acts as a radiation boundary condition for the FEM. The MoL can also treat layered regions. Because of the flexibility of the FEM and the semianalytical nature of the MoL, the flexibility, efficiency, and accuracy of these two methods are maintained. © 2002 Wiley Periodicals, Inc. Microwave Opt Technol Lett 34: 134,138, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10395 [source] Electromagnetic scattering problems solved by an improved spectral iteration techniqueMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 6 2001Sandra Costanzo Abstract The spectral iteration technique is used to solve electromagnetic scattering problems. A detailed analysis is carried out to investigate the convergence properties of the procedure, and a static solution is proposed as an initial estimate of the current to solve divergence problems. Diffraction by strips is considered to validate the method. © 2001 John Wiley & Sons, Inc. Microwave Opt Technol Lett 29: 384,388, 2001. [source] | ||||||||||||||||