Improved calculation of the inductive and capacitive interactions of vertical sheet currents in a multilayered medium

The mixed potential formulation for multilayered microstrip-slotline structures is extended to incorporate the effect of vertical vla-sheet currents in the analysis. The vertical via currents are incorporated in the mixed potential Green's functions, keeping the discretisation of the currents essentially restricted to the horizontal interfaces. The paper focuses on an improved representation of the singular behaviour of this modified Green's functions and the calculation of the corresponding system matrix elements. The latter follow from the application of the method of Galerkin to discretise the mixed potential integral equations. Our approach allows for a more accurate calculation of the inductive and capacitive effects of via's, airbridges and bond wires. A practical example of the bond wire modelling in the design of a packaged high power transistor with integrated prematch circuit is given.