1,721,205 research outputs found
A novel subgridding scheme based on a combination of the finite-element and finite-difference time-domain methods
No full textA simple and versatile local mesh refinement scheme, based on the hybridization of the finite-element (FE) and the finite-difference time-domain (FDTD) algorithms, is presented in this letter. The scheme achieves considerable flexibility in subgridding by using a transition region between the coarse and fine FDTD grids, meshed according to an unstructured grid, and solved by means of the FE method in TD. An interpolation scheme in the time domain, which allows the use of different time steps in the coarse and fine mesh regions, is included in the paper
A hybrid finite-element finite-difference time-domain (FE/FDTD) technique for solving complex electromagnetic problems
No full textA hybrid finite-element finite-difference time domain (FE/FDTD) technique for solving complex electromagnetic problems is presented in this letter. The method combines the computational simplicity of the structured FDTD scheme with the versatility as well as flexibility of the finite-element method (FEM) and enables us to accurately model curved geometries and those with fine features. Numerical results that illustrate the accuracy of the method are included in the letter
Closed-Form green's functions and their use in the method of moments
No full textDerivation of the spatial-domain, closed-form Green's functions of the vector and
scalar potentials are demonstrated for planar media, and their use in conjunction
with the method of moments (MoM) is presented. As the first step of the derivation,
the Green's functions are obtained analytically in the spectral domain for various
sources viz., horizontal and vertical electric and magnetic dipoles embedded in a
planar stratified media. The spatial-domain Green's function can be obtained from
the Sommerfeld integral which is the Hankel transform of the corresponding Green's
function in the spectral domain. The analytical evaluation of this transformation
yields the closed-form, spatial-domain Green's functions which can be used in the
solution of a mixed-potential integral equation (MPIE) via the MoM. This combination,
i.e., the use of the closed-form Green's functions in conjunction with the
MoM, results in a significant improvement in the fill-time of MoM matrices. In
the conventional application of the spatial-domain MoM, the matrix elements are
double integrals and they require the evaluation of the time-consuming Sommerfeld
integral for the spatial-domain Green's function. In the approach presented
herein, the spatial-domain Green's functions are in closed forms, and the remaining
double-integrals in the matrix elements are evaluated analytically. Thus, there are
two factors in this approach that contribute to the improvement in the computation
time: (i) elimination of the numerical integration to obtain the spatial-domain
Green's functions; (ii) circumventing the need to carry out the numerical integration
in the calculation of the MoM matrix elements
A new genetic algorithm-based frequency selective surface design for dual frequency applications
No full textIn this paper, an optimization procedure based on the genetic algorithm is applied to the design of frequency selective surfaces (FSSs) for dual frequency applications, fabricated by printed circuit technology. The inclusion of the shape of the mask in the set of parameters controlling the optimization scheme enables us to obtain the requisite frequency and polarization performance, while simultaneously reducing the number of layers in some case
CBMOM - An highly scalable MoM approach for electrically large multiscale EM radiation and scattering problems
Full text linkIn this paper, we describe a new and efficient strategy for solving linear system of equations arising in the application of Method of Moments to electromagnetic problems. This new approach is based on the use of Characteristic Basis Functions (CBFs) that are defined on macro domains (blocks), and include a relatively large number of conventional subdomains functions, defined on triangular or rectangular patches. The use CBFs leads to a significant reduction in the number of unknowns, and, as a result, the technique enables us to use a direct solver, as opposed to iteration. Numerical results are presented to demonstrate the accuracy and efficiency of the CBFM when used to solve several test problems
Electromagnetic Scattering from Large Cylindrical Shaped Reflectors by Using the Characteristic Basis Function Method with Analytical Basis Functions
No full text
Hybrid technique combining finite element finite difference and integral equation methods in time domain
No full textA Spectral Domain Integral Equation Method Utilizing Analytically Derived Characteristic Basis Functions for the Scattering from Large Faceted Objects
No full textA novel technique, based on a spectral domain integral equation method with analytically derived characteristic basis functions, is introduced in this paper. It enables us to treat scattering problems from electrically large faceted bodies in a numerically rigorous and computationally efficient manner, in terms of both time and memory. The analytically derived characteristic basis functions include certain desirable features of the asymptotic schemes and are defined on subdomains that can be electrically large, not being bound to the typical discretization size of the conventional method of moments. By properly weighting through a Galerkin procedure the resulting electric field integral equation, the problem is reduced to a matrix equation having dimensions that do not depend on the size of the scatterer but only on its shape. Electrically large problems can be handled in a computationally efficient manner by using the proposed method since the associated matrix size is relatively small; moreover, all the reduced matrix elements are calculated in the spectral domain without evaluating any convolution products
A Sub-Boundary Approach for Enhanced Particle Swarm Optimization and its Application to the Design of Artificial Magnetic Conductors
No full textThe particle swarm algorithm is a newly introduced method for electromagnetic optimization problems that is based on the observation of swarm intelligence and particle behavior. This paper proposes a novel strategy for the initialization of the agents' position within the multidimensional solution domain. In particular, the domain is initially subdivided into subdomains so to have a more uniform distribution of the agents. At a second stage, the sub-boundaries are removed and the best position information of each group is passed to each agent; the agents are therefore allowed to explore the whole search space. This procedure results to be efficient and to improve the convergence rate. A comparison between the performance of this new implementation and that of the basic particle swarm algorithm is presented for several test cases. Finally, this new procedure is successfully applied to the synthesis of artificial magnetic conductors (AMCs)
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