A mixed finite-element formulation for the modal analysis of electromagnetic waveguides featuring improved low-frequency resolution of transmission line modes

This paper presents an improved finite-element formulation for axially uniform electromagnetic waveguides. It allows for both dielectric and conduction losses and covers the entire range from optics down to the static limit. Propagation coefficients of small magnitude, particularly those of transmission line modes in the low-frequency regime, are computed much more accurately than with previous approaches.