Finite-element analysis of high-frequency axisymmetric device problems

A finite-element scheme for solving wave propagation problems in devices with complete azimuthal symmetry both in their material properties and in their geometry is presented. The phi -coordinate variation is restricted to sin(n phi + xi ), thus requiring only a two-dimensional space for the complete finite-element analysis. The open radiating boundaries inherent in many propagation problems are tackled through simulated absorption of the radiation by lossy materials. Also proposed for these kinds of boundaries is a hybrid FEM-BEM (finite-element-method-boundary-element-method) formulation, based on the vector Green´s function for the Helmholtz equation. This method has been tested by application to an open-ended circular waveguide and by a comparison with the simulated-absorption results.