Analysis of mode characteristic of guided electromagnetic wave in mine tunnels

According to the surface impedance method, the equations of both monofilar mode and bifilar mode of guided electromagnetic waves in mine tunnels were presented, the distribution of synthesized electromagnetic field in tunnels was given by utilizing image approach. The attenuation constant of monofilar mode in a circular tunnel was solved. The simulation results show that propagation attenuation of monofilar mode of low frequency would increase as increasing of frequency. The skin effect and attenuation would be fearful as cable closing tunnel wall nearby, and the attenuation would be reduced if cable was located in tunnel locate. The field of bifilar mode is concentrated in space between double cable and around area, the effects are stronger due to space between double cables than space between double cables and tunnel wall, in same time that attenuation of monofilar mode would be increasing with the decreasing of space between cables and tunnel wall.