Novel Rigorous Multimode Equivalent Network Formulation for Boxed Planar Circuits with Arbitrarily Shaped Metallizations

The Multimode Equivalent Network (MEN) formulation has been traditionally employed for the efficient and accurate analysis of waveguide devices. In this paper, we extend the use of the MEN to the analysis of zero thickness, multilayer planar circuits in a metallic enclosure. The formulation is developed for arbitrary shape metallic areas and includes both internal and external ports in the transverse plane. The BI-RME method is applied to analyze the arbitrary shaped metallizations and to compute the coupling integrals needed to solve the corresponding integral equations. On this basis, typical shielded microstrip circuits of complex geometries, are analyzed in the common frame of the MEN technique. To validate the theoretical formulation, several shielded filtering microstrip structures are analyzed, showing good agreement with respect to both other commercial tools and experimental measurements.