Interior resonance problems associated with hybrid integral equation/partial differential equation methods

Various methods have been proposed to employ a hybrid surface integral equation/partial differential equation approach, or finite element/boundary element method for electromagnetic scattering problems involving inhomogeneous scatterers. Few investigators, however, have discussed possible problems associated with fictitious interior resonances. It is demonstrated that certain formulations exhibit the interior resonance problem, and that a combination of the finite element method (FEM) and the combined field integral equation (CFIE) can eliminate such problems. In addition, it is demonstrated that the interior and exterior regions can be partially decoupled in a resonance-free manner by using the CFIE/FEM.<>