A study of the reactions between rooftop test and expansion functions in inhomogeneously-filled stripline structures

Formulates closed-form expressions for the method of moment (MoM) reaction elements associated with x-directed, roof-top expansion and test functions that reside in inhomogeneously-filled stripline structures. This paper describes the first step in the extension of the capabilities of a recently developed full-wave layered interconnect simulator (UA-FWLIS). This simulator could previously only handle MoM reaction element evaluations associated with expansion and test functions in homogeneously-filled stripline structures. After a robust algorithm was developed for the computation of all the TM_z and TE_z modes for the inhomogeneous case, the Green´s functions were incorporated into UA-FWLIS to allow for the evaluation of the MoM reaction elements in inhomogeneously layered stripline structures. In this paper, we use the resulting closed-form expressions for the reaction elements to compare the behavior of the reaction elements for the homogeneously-filled and inhomogeneously-filled stripline cases. These computational results for the reaction elements provide a better understanding of the physical phenomenology associated with coupling in stripline structures.