Research on Characteristics of the Loss of UHF Propagation in Rectangular Tunnels

When UHF propagation in a rectangular tunnel, the wavelengths are much smaller than the tunnel dimensions, so the fundamental (1, 1) modes and some lower order modes can realize long distant propagation together. Therefore, the effect of lower modes could not be negligible, when analyzing the characteristics of the attenuation of UHF propagation. A multi-mode theory of waveguides was educed in this paper, based on the mode theory of dielectric waveguides. Of prime interest are the loss natures for E
^h
and E
^v
modes along with frequency and with the shape of the tunnel section. This work would perfect part of theoretical results of the analysis of the dominant mode.