Research on propagation characteristics of electromagnetic wave in tunnels with arbitrary cross sections

The attenuation constant has the similar calculating expression, but different coefficients in different tunnels, like circular tunnel, rectangular tunnel, arched tunnel and ellipse tunnel. An analysis of the relationship between the attenuation rate in tunnels with arbitrary cross sections is given in the paper after the equivalence of the cross section area, the effects of tunnel dimensions on the attenuation rate also be discussed. The result shows that the attenuation rate of electromagnetic wave in rectangular tunnel and ellipse tunnel can be calculated by the attenuation constant in circular tunnel, while to arched tunnel, the attenuation constant in circular tunnel only can be used at high frequency. It is consistent with the measured data in related literature. On the other hand, the conclusions are proved theoretically.