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Integration of the finite-difference time-domain (FDTD) method into the iterative multiregion (IMR) technique, an iterative approach used to solve large-scale electromagnetic scattering and radiation problems, is presented in this paper. The idea of the IMR technique is to divide a large problem domain into smaller subregions, solve each subregion separately, and combine the solutions of subregions after introducing the effect of interaction to obtain solutions at multiple frequencies for the large domain. Solutions of the subregions using frequency domain solvers has been the preferred approach as such; solutions using time domain solvers require computationally expensive bookkeeping of time signals. In this paper, we present an algorithm that makes it feasible to use the FDTD method, a time domain numerical technique, in the IMR technique to obtain solutions at a prespecified number of frequencies in a single simulation. A hybrid method integrated into the IMR technique is also presented in this paper. This hybrid method combines the desirable features of the FDTD method and the method of moments (MoM) to solve radiation problems more efficiently. As a result, a considerable reduction in memory storage requirements and computation time is achieved. [ABSTRACT FROM PUBLISHER]

An axisymmetric chiral radome has been analyzed numerically by using the method of moments. The chiral body is illuminated by a plane wave and the surface equivalence principle is used to replace the body by equivalent electric and magnetic surface currents. The effect of adding chirality to a dielectric radome of revolution is investigated throughout numerical results obtained for bodies of different shapes and material parameters. Chiral materials can be used to design anti-reflective structures to control scattering cross section patterns of bodies. A computer program is developed for the chiral radome of revolution and examples of numerical calculations are given for a chiral spherical radome, a chiral cylindrical radome, and a chiral Von Karman radome. Numerical results for the chiral spherical radome are in excellent agreement with the exact ones obtained by the eigenfunction solution. Moreover, the numerical results of the chiral Von Karman radome are in excellent agreement with the published results. [ABSTRACT FROM AUTHOR]

A chiral body of revolution (BOR) which is partially covered by a thin conducting shield is analyzed using the Method of Moments (MOM). The axisymmetric system is excited by a plane wave. The internal fields and the far scattered fields are computed. The problem is solved using the surface equivalence principle. The scattered fields outside the structure are assumed to be produced by an equivalent magnetic surface current that exists on the unshielded part of BOR surface and an external equivalent electric surface current that exists over the entire BOR surface. These two currents are assumed to radiate in the unbounded external medium. Similarly, the internal fields are assumed to be produced by the negative of the above magnetic current and an internal electric surface current that exists over the entire BOR surface, but is an independent unknown only on the shielded part of the BOR surface. These two currents radiate in the unbounded internal medium. Enforcing the boundary conditions at the surface of the BOR results in a set of coupled integral equations for the three equivalent surface currents. These equations are solved numerically using the MOM. The computed results for the partially shielded spherical chiral body are in excellent agreement with other data. [ABSTRACT FROM AUTHOR]

The problem of electromagnetic transmission through an arbitrarily shaped aperture in an arbitrarily shaped 3-D conducting surface enclosing homogeneous chiral material is investigated. To solve the problem numerically, the surface equivalence principle and the method of moments are used. The validity of the procedure has been checked by comparing the numerical results to other available solutions whenever possible. Numerical results for the physical electric current on the surface of the obstacle, the internal field, and the bistatic radar cross section are presented for the examples of a sphere and a finite cylinder with circular apertures. These results are computed for various electrical sizes, permittivity values, chirality values, and aperture sizes. [ABSTRACT FROM PUBLISHER]

Abstract-A method of moments (MoM) solution is presented for the problem of electromagnetic scattering by a three-dimensional (3-D) inhomogeneous chiral scatterer illuminated by an arbitrary incident field. The volume equivalence principle was used to obtain coupled integral equations for equivalent volume currents. These integral equations were then solved numerically using MoM. The volume of the scatterer was modeled by tetrahedral cells, and face-based expansion functions were used to approximate the equivalent currents. Computed results are in very good agreement with exact data or other published data. [ABSTRACT FROM AUTHOR]