A HYBRID EQUATION APPROACH FOR THE SOLUTION OF ELECTROMAGNETIC SCATTERING PROBLEMS INVOLVING ARBITRARILY SHAPED INHOMOGENEOUS DIELECTRIC BODIES (MOMENT METHODS, COMPUTER TECHNIQUE).

摘要

A numerical procedure is presented for the solution of electromagnetic scattering problems involving arbitrarily shaped inhomogeneous dielectric bodies. The scattering problems are formulated via a hybrid integral equation/partial differential equation approach in which the inhomogeneous region is modeled by the partial differential equations for the electric or magnetic field directly and the radiation condition is incorporated by enforcing integral equations at the surface of the inhomogeneous region. The surface integral equations are developed in the usual manner via application of the equivalence principle so that the fields exterior to the body are radiated by equivalent electric and magnetic surface currents J and M. The procedure is formulated for general three dimensional cases as well as two dimensional cases. In two dimensional cases the procedure is implemented both for TM and TE problems. Some features that will appear in three dimensional problems and introduce possible difficulties are examined in the two dimensional TE problems so that there will be no conceptually new difficulties in the three dimensional problems. However, the procedures have not been implemented for three dimensional problems because of limited time and resources.; The partial differential equation for the interior region and the surface integral equation are coupled in such a manner that existing surface integral equation computer codes for treating problems involving scattering by homogeneous bodies can be used to generate the block of the matrix corresponding to the surface current interactions via the method of moments, with only some minor alterations. The remaining blocks of the matrix, which comprise the interior differential equation elements and the elements due to coupling between the surface and the interior region, may be generated efficiently and are sparse. The system matrix is therefore largely sparse and should be amenable to specialized matrix solution techniques or iteration. In addition, the procedure has the advantage that more scatterers may be included in the vicinity of the inhomogeneous body with the usual simplicity of moment method formulations, while still retaining the partially sparse nature of the matrix.