Modeling multiport using a three-dimensional coupled analytical/finite element method application to microwave characterization of material

This paper addresses a general method of analysing the propagation in multiports with a perturbed area (which can be a sample of anisotropic material for example) and computation of the scattering parameters. To this end, the electromagnetic fields in the perturbed area are expressed by a finite element formulation, and are connected to those in the accesses of the multiport, expressed as an eigenmode expansion. To give a specific example, this method is applied to the characterization of a biaxial material in a rectangular waveguide, and in a circular coaxial line. In the first case, the obtained results are compared to analytical results and in the latter to experimental results. In both cases, a close correlation can be observed