An Absorbing Boundary Condition Based on Anechoic Absorber For EM Scattering Computation

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Abstract
A novel absorbing boundary condition (ABC), to be used with finite difference and finite element electromagnetic radiation and scattering problems is described. It is based on anechoic chamber absorber foam geometry, with specified complex permittivity and permeability. The advantage of this absorbing boundary is that it prevents reflections from much wider incident angles than currently used lattice termination conditions. Since incident waves need not be normal to this boundary for absorption, the boundary can be placed much closer than previously possible. This new type of ABC can be used to absorb scattered waves in a local sense, so the electrical size of the scattering object does not effect the distance from it to the ABC. Since even a modest decrease in the required separation distance yields a huge savings in the number of required matrix elements for three dimensional geometries, this novel ABC may greatly improve the general applicability of computational electromagnetics.