Analysis of longitudinal slots in ridged waveguides using a hybrid finite element-Galerkin technique

A hybrid approach, combining the finite element method (FEM) with an integral equation formulation of the tangential electric field, is developed for the solution of longitudinal slots cut in the broad wall of finite thickness of a ridged waveguide. The system of integral equations formulated at both interfaces of the slot, is solved using the Galerkin approach with sinusoidal basis and testing functions. The Green´s function for the internal waveguide region, as called for in the integral equation formulation, is generated numerically, utilizing the eigenvalues and eigenfunctions of the waveguide as computed by the FEM with Lagrangian fourth order polynomials. This approach is quite general, allowing for arbitrary waveguide cross sections and compositions. Computations of the dot characteristics performed in this way agree very well with previously documented as well as our own experimental results