HYBRID MULTIPOLE-BEAM APPROACH TO ELECTROMAGNETIC SCATTERING PROBLEMS

Abstract

A hybrid technique combining the Complex Multipole Beam Approach (CMBA) with the Method of Moments (MoM) for the solution of the problems of electromagnetic scattering is presented in this paper. In this technique the CMBA provides for a substantial reduction in the matrix size by taking advantage of the essentially band-limited spatial spectrum of the scattered field in the vicinity of smooth surfaces, while the MoM is employed for the modeling of non-smooth or inhomogeneous regions within the problem geometry. The key step in the CMBA is to represent the scattered field in terms of a series of beams produced by multipole sources located in a complex space. The CMBA not only reduces the number of unknowns, but also generates a generalized impedance matrix with a banded structure and a low condition number. In the present hybrid technique, the scattering properties of each complex region, requiring a relatively large number of unknowns per unit volume, are described in terms of a Beam-matrix, which is constructed numerically to relate the amplitudes of outgoing beams to those of incoming ones. The proposed direct solution scheme takes into account the interactions between all of the complex regions and the smooth portions of the scatterer geometry using an algorithm similar to the recursive T-matrix approach. This hybrid technique, that combines the CMBA with other conventional methods, is a versatile tool, and is expected to enhance the scope of application of the CMBA to a much wider class of problems. (Vol. 9, No. 3 (1994), Special Issue on Generalized Multipole Technique (GMT), pp 7- 17]