3-D FEM/BEM-hybrid approach based on a general formulation of Huygens´ principle for planar layered media

Huygens´ principle is used to exclude inhomogeneous regions and ideal conducting regions from planar layered structures. The fields in the inhomogeneous regions are modeled by the finite-element method (FEM) with tetrahedral edge elements in terms of the electric-field strength E&oarr;. The fields in the layered structure are described by an integral representation of the electric-field strength E&oarr; in terms of equivalent electric and magnetic Huygens´ surface current densities for the inhomogeneous regions, and in terms of electric Huygens´ surface current densities for ideal conducting regions. It is formulated with the help of electromagnetic (EM) potentials resulting in low-order singular integral kernels to facilitate the numerical handling of the integral representation. A general formulation of the integral representation is given for observation points lying in the Huygens´ surface. As compared to the homogeneous-space case, additional terms in the integral representation have to be considered if parts of the Huygens´ surface lie in an interface of layers with different material properties. An integral equation is formulated and discretized by a Galerkin testing procedure (boundary-element method), together with the finite-element (FE) system resulting in an unequivocal discretized description of the entire field problem. The method is validated with the help of a canonical test problem. Further numerical results are presented for dielectric resonators coupled to microstrip circuits