Tlm-Based Explicit Eigenvalue Approach to the Determination of the Complete Spectrum of Inhomogeneous, Closed Waveguide

In the recent past we introduced a new approach for the analysis of the propagation of hybrid modes in closed inhomogeneous waveguides of complex shape. The essential point of the method is the discretization of the Maxwell's equations by means of the modes taken at cutoff which leads to an explicit linear eigenvalue matrix equation. A requisite for improving the efficiency of the method is the fast calculation and storage of the modes at cutoff. This is obtained by using the flexible TLM method. The resulting TLM-based eigenvalue matrix algorithm is very efficient in finding the characteristics of a large number of modes as it requires very low computational effort and is free from spurious solutions. Numerical results are provided for the unilateral finline, showing very good agreement with existing data.