Efficient Foster-Type Macromodels for Rectangular Planar Interconnections

A novel macromodeling technique for passive linear multiport interconnecting structures is presented. It is based on an inherently stable Foster-type equivalent-circuit realization of the Greens function, given in the form of an infinite eigenfunction expansion. In order to obtain a finite number of equivalent-circuit elements, a rapidly convergent double sum representation of the corresponding port transfer-impedance function is cast into a newly modified Foster-type equivalent circuit with additional inductive elements. For a time-domain analysis, a system-theory based model-order estimation is presented and evaluated for trapezoidal excitation functions. Numerical computations are shown for a rectangular parallel-plate example structure, and validated by the results of full-wave field simulations, based on the finite-integration theory and method of moments. The suggested macromodeling technique provides a computationally very efficient and versatile approach for system analysis in the frequency- and time-domain with linear/nonlinear passive and active components.