Radio transmission in an elliptical tunnel with a contained axial conductor

摘要

Electromagnetic transmission in a straight cylindrical tunnel with imperfectly conducting walls is considered when the cross section is in elliptical form. The presence of a thin axial conductor is also allowed for in the boundary‐value formulation. The general matrix solution is simplified by invoking the quasistatic approximation which is shown, at least for circular tunnel geometry, to be valid for frequencies up to 20 MHz. The results of the quasistatic calculations indicated that the attenuation rate of the dominant mode is relatively insensitive to the ellipticity if the cross‐section area and the cable‐to‐wall separation is kept constant.