Guided electromagnetic waves along an axial conductor in a circular tunnel

A method to calculate the propagation characteristics of the guided modes in a circular tunnel bounded by lossy dielectric media is presented. The effect of an axial thin. wire within the tunnel is also accounted for in the boundary value treatment of the problem. It is found that the attenuation of the transverse electromagnetic (TEM) or coax type mode is greatly increased when the conductor is moved toward the tunnel wall.