Field-based scattering-matrix extraction scheme for the FVTD method exploiting a flux-splitting algorithm

This paper introduces a novel field-based scheme for the extraction of a generalized-scattering matrix. A flux-splitting (FS) algorithm that separates the total electromagnetic field into an incident and a reflected part is used for a new definition of power waves. This flux-separation scheme, based on a plane-wave approach of the split waves, originates from finite-volume techniques. However, it can be applied locally in any numerical scheme that uses a volume discretization. To yield correct S-parameters, the FS matrix needs to be adapted through introduction of modified wave velocities to match the plane-wave condition. The introduced extraction scheme is applied to the finite-volume time-domain method and compared successfully to reference solutions for TEM and non-TEM structures, both with homogeneous and inhomogeneous cross sections.