A hybrid time-domain technique that combines the finite element, finite difference and method of moment techniques to solve complex electromagnetic problems (original) (raw)
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An integral equation is developed for determining the time-dependent current distribution on a wire structure excited by an arbitrary time-varying electric field. The sub-sectional collocation form of the method of moments is used to reduce this integral equation to a form that can be evaluated on a digital computer as an initial value problem. A Lagrangian interpolation scheme is introduced so that the dependent variables can be accurately evaluated at any point in the spacetime cone; thus, only mild restrictions on the space and time sample density are required. The integral equation relating present values of the current to previously computed values is presented in a form that can be directly converted into a computer code. Expressions are developed for the computer time and the relative advantages of time-domain and frequency-domain calculations are discussed, providing impetus for analyses in the time domain in certain cases. Part II of this paper will present well-validated numerical results obtained using the technique described.
Presented here are the numerical results from a computer solution of the time-dependent thin-wire electric-field integral equation described in Part I of this paper. Both radiation and scattering problems are considered. The present results are validated by their Fourier transform to the frequency domain, where they are compared with independently computed data. A space—time sampling criterion is derived for predicting the highest frequency to which the time-domain calculations are accurate and found to be in accord with the numerical results. The time domain results are also shown to grovide informative insights into the radiation characteristics of specific structures. Recommendations for further work are also presented.
A hybrid technique combining the method of moments in the time domain and FDTD
IEEE Microwave and Guided Wave Letters, 1998
This letter presents a new hybrid method that efficiently combines two versatile numerical techniques, viz., the finite difference time domain (FDTD) and the method of moments in the time domain (MoMTD). The hybrid method is applicable to complex geometries comprising arbitrary thin-wire and inhomogeneous dielectric structures. It employs the equivalence theorem to separate the original problem into two subproblems: 1) the region containing the wires, which is analyzed by using the MoMTD, and 2) the dielectric zone that is modeled with the FDTD. The application of the method is illustrated by analyzing two canonical problems involving thin wires and inhomogeneous media.
ACCELERATED WIDE-BAND FREQUENCY/TIME-DOMAIN HYBRID COMPUTATIONAL ELECTROMAGNETIC TECHNIQUE
ABSTRACT A hybrid technique is proposed for computation of broadband characteristics of an antenna in the presence of a dielectric scatterer. The technique links the frequency domain Method of Moments (MoM) and the Finite Difference Time Domain (FDTD) method. The coupling of these methods is achieved by using the Equivalence Principle, applied over the intervening surface. A great reduction in computation time is achieved in the MoM domain by using an impedance interpolation technique.
IEEE Transactions on Magnetics, 2008
For the modeling of electromagnetic scatter of thin metal wires located above or under real ground, a new numerical method based on time domain integral equations is presented. The influence of lossy ground is taken into account via Fresnel space-time reflection coefficient. The integral equations are solved efficiently by method of moments combined with marching on in time procedure. The calculated results agree with those of references. The method is also verified by the experiment in near field. Index Terms-Half-space, time-domain integral equation (TDIE), wire structure.
Time Domain Boundary Element Analysis OfResistively Loaded Wire
1998
The analysis of the resistively loaded dipole antenna radiating in homogeneous dielectric medium is performed directly in the time domain. The problem is formulated by means of the time domain Hallen integral equation. The integral equation is solved by the time domain boundary element procedure which enables space and time discretization to be handled separately. Numerical results for the transient antenna current are presented.
1997
Abstract A hybrid formulation is presented, which combines the method of moments (MOM) with the edge-based vector finite element method (FEM) to solve electromagnetic radiation problems from structures consisting of an inhomogeneous dielectric body of arbitrary shape attached to one or more perfectly conducting bodies. While either method alone fails to model these structures efficiently, a combination of both finite element and moment methods provides an excellent way to solve these problems.