Validity of Geometrical Simplifications in the Application of a Modal Equivalent Circuit for Interconnection Networks in Metallic Enclosures

A broadband Foster-type equivalent circuit to model the electromagnetic behavior of complex interconnection structures in metallic casings of arbitrary geometry is presented. Based on the eigenmodes of the system, this model is inherently stable in the time domain due to its passivity and allows simulation by a conventional circuit simulator with arbitrary linear or nonlinear port terminations. The typically slow convergence of the circuit model is accelerated by the extraction of quasi-static inductances and capacitances. Losses are considered by additional modal resistive elements. As examined by an example, approximations made to the geometry can greatly reduce the simulation time and modeling effort. The validity of such simplifications is demonstrated in the frequency domain by elaborate full-wave reference simulations.