Wireless Transmission in Tunnels With Non-Circular Cross Section

We study wireless communication via the free modes in a uniform tunnel with non-circular cross section. The dominant modes propagating in such tunnel are considered as perturbed versions of corresponding modes in the well studied circular tunnels. Of particular practical interest are tunnels whose cross section comprise an incomplete circle with flattened base. It is shown that in these tunnels, a vertically polarized mode is more attenuated than its horizontally polarized counterpart. We also investigate the approximation of a non-circular tunnel with an equivalent rectangular tunnel regarding the attenuation of the dominant modes. Comparison is made with experimental attenuation measurements available in the literature.