A modal analysis of TEM mode in circular-rectangular coaxial waveguides

A modal analysis of transverse electromagnetic (TEM) mode in a circular-rectangular coaxial waveguide is presented in this paper. The analysis is based on the modal-expansion technique. Analytic expressions for the characteristic impedance and attenuation coefficient are derived from the solution of the TEM mode. The calculated results are compared with those of the finite-element method, as well as published data. Excellent agreement is observed.