Analysis of propagation characteristics of radio waves in tunnels using a surface impedance approximation


  • K. Yasumoto,

  • H. Shigematsu


A simple approximate method to analyze the propagation of radio waves in tunnels is proposed, based on a surface impedance assumption. This method is used, as a basic application, to determine the propagation constants of normal modes in circular tunnels bounded by a uniform lossy dielectric or bounded by two lossy dielectric layers. From the comparison of numerical results it is shown that our approximate solutions agree with the exact ones obtained from the general dielectric waveguide theory, with enough precision for practical purpose.