The port plane is defined as the cross-section of the simulation domain that is coplanar with the port, excluding any parts of the plane that are electromagnetically isolated from the port. The port solve involves structures and boundary conditions that touch or cross the port plane. Only the parts of the structures that are physically in the plane of the port are considered in the port solve. If two conductors are connected by a via, the via must physically intersect the port plane for the port solve to treat the conductors as connected. Otherwise, the port solve will treat the conductors as isolated.
Once the port plane has been defined within the solver, RF3p runs an eigenanalysis on the 2D domain. This eigenanalysis determines one or more modes of the waveguiding system, ordered by propagation constant (smallest to largest). RF3p returns the eigenmode with the lowest cutoff frequency that satisfies the voltage constraints indicated by the port assignment; for details on using voltage constraints see Port Indices.