The approximate modal interface—solution space projection method including internal ports for efficient finite-element analysis of multilayer printed circuits

In the simulation of multilayer circuit boards or packages, it is often of interest to know the interaction between different nodes inside the structure, and as a result internal ports have to be employed. In this paper the approximate modal interface (AMI) formulation is presented, including internal ports, which are in the form of a lumped current source assigned along element edges. The resulting numerical scheme can also handle various kinds of frequency-dependent components and numerical boundaries in each subdomain and on subdomain interfaces.