Balanced Electric-Magnetic Absorber Greens Function Method for MoM Matrix Thinning and Conditioning

Author(s): Naor R. Shay, Raphael Kastner and Daniel S. Weile
Source: FERMAT, Volume 20, Communications 14, Mar.-Apr., 2017

Abstract: A new numerical approach to solving the classic problem of electromagnetic (EM) scattering off a perfect electric object is studied with the objective of substantially reducing computation times. The method considered here is the in the frequency domain Method of Moments (MoM) formulation involving the use of a dyadic Green’s function (GF). Traditionally, this GF is formulated in free space, as afforded by the equivalence principle. However, since the resultant equivalent sources generate a null filed inside the scatterer volume, the door is open for the inclusion of arbitrary fillers therein.

We suggest the usage of balanced absorbers as fillers and using their Green’s function instead of the free space one. To this end, the solution of the essentially volumetric problem of the absorber is required as a preprocessing stage. Balanced absorbers have both electric and magnetic Weston-like or Perfect Matched Layers (PML) loss mechanisms. Many interactions between pairs of basic functions are then virtually eliminated. As a result, the MoM matrix, representing the GF, is significantly thinned.

The cost of calibrating this modified GF using the volumetric representation of the absorber is investigated. The effort incurred in the pre-processing stage can be alleviated by choosing absorber configurations that apply to many problems with high degrees of symmetry, thin absorbing shells rather than volumetric scatterers or homogeneous absorbers that lend themselves to surface formulations.

It is shown that this form of thinning has little effect on the accuracy. Moreover, most of the thinned elements need not be computed at all.

Keywords: Method of Moments, matrix thinning, spurious resonances.

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Balanced Electric-Magnetic Absorber Greens Function Method for MoM Matrix Thinning and Conditioning

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