Boundary conditions for finite element analysis combined with geometrical theory of diffraction

In this paper a method is presented to enforce boundary conditions for a Finite Element (FE) analysis when free space or large external scatterers are present. The equivalence theorem is used to divide the original problem into an internal and an external part via introduction of equivalent sources. FE analysis solves the internal problem with standard metallic or magnetic boundary conditions while an asymptotic method, here the uniform version of the Geometrical Theory of Diffraction (GTD), deals with the external scatterers. A time harmonic variation of the fields is assumed