Analysis of inhomogeneously filled waveguide devices by a hybrid mode matching-finite element technique

A new Hybrid Mode Matching (MM)/Finite Element (FE) Method for the rigorous analysis of discontinuities between inhomogeneous filled waveguides is presented. The proposed hybrid approach combines the numerical efficiency of MM with the capability of FEM to reconstruct the electric field where a modal expansion is not available, e.g., at the transverse plane of arbitrarily shaped cross-section waveguides and in the presence of inhomogeneous filling. Moreover, the problem of the spurious solutions is avoided by the use of both Whitney's Edge elements to interpolate transverse field components and Lagrange polynomials to reconstruct the longitudinal ones. The analysis automatically includes the complete set of hybrid modes and takes complex and backward waves into account. Some examples are presented to demonstrate the effectiveness of the method.