隧道中低频导行电磁波的传播特性

Propagation characteristic of low-frequency guided electromagnetic waves in tunnel

在低频段上 ,导行电磁波的衰减率很小 ,随频率的升高而缓慢增加 ,不论单线波模还是双线波模其近壁效应都很小。用数值分析方法求解了单线波模方程和双线波模方程 ,得出的主要结论为它们的衰减率与隧道壁电导率和隧道半径有微弱依赖关系。理论分析含单导体的任意横截面隧道可知低频段上导行电磁波的衰减率与隧道横截面积大小有微弱依赖关系 。

In low frequency band, the attenuation rate of guided electromagnetic waves are very low and increases slowly as frequency. The response of near-wall is very small for either monofilar mode or bifilar mode, In this paper, the equations of both monofilar and bifilar mode are solved using numerical method. It is concluded from the presented results that the attenuation rate is weakly related to radius of tunnel and conductivity of tunnel wall. For a tunnel with arbitrary cross-section containing an axial conductor, the propagation characteristic of guided electromagnetic waves are weakly depended on area of tunnel cross sections, not related to the tunnel cross sections shape.