空圆形隧道中电磁波的传播特性

给出了空圆形隧道中电磁波传播的衰减率计算公式及波模方程，采用数值分析的方法求解了波模方程，得出的主要结论有：采用传统的金属波导的处理方法在隧道的电导率较高时得到的电磁波衰减率是正确的：频率越高，空圆形隧道中的电磁波的衰减率越小；隧道半径越大，越有利于电磁波的传播；对于IE波模，隧道的介电常数和磁导率的变化对电磁波衰减率变化的影响不大，对于TM波模，隧道的介电常数或磁导率越大，电磁波衰减率越大。

Propagation Characteristic of Electromagnetic Waves in Empty Circular Tunnels

The formulas of EM wave attenuation rate and the mode equations in an empty circular tunnel are given, and they are solved through numerical analysis method, and the main conclusions we obtain are as follows: when the conductivity of tunnel is high, the attenuation rate obtained from conventional metal wave guide approximation is correct; if frequency is higher, the attenuation rate is smaller; it is beneficial for EM waves to propagate when tunnel radius is larger; for TE modes, the changes of dielectric constant and magnetic permeability of tunnel have little effect on that of the attenuation rate; for TM modes, the dielectric constant or magnetic permeability of tunnel is bigger, the attenuation rate is higher.