梯形隧道中电磁波的传播特性

梯形巷道是煤矿井下常见的一种巷道，用解析法求解梯形隧道中的Maxwel方程存在很大困难，应用有限元方法研究了梯形隧道中的波导场问题，并以微扰法为基础推导了波模衰减率的计算公式，编制了计算程序，根据计算结果，随工作频率的增加，衰减率减小，随隧道壁电导率的增加，衰减率减小，在工作频率f=500-1000MHz时，梯形隧道中主次波模的衰减率很小，结合实际情况，采用900MHz作为井下移动通信的工作频率是比较理想的。

Propagation Characteristic of Electromagnetic Wave in Trapezium Tunnel

Trapezium tunnel is a sort of familiar tunnel in coal mine.But it is difficulty to solve the Maxwell equation in trapezium tunnel by using analytic method. To make use of finite element method, the field of electromagnetic wave propagating in trapezium tunnel was studied. The attenuation rate and its numerical analysis were deduced on the foundation of tiny-intervene method and the calculating program was also compiled. According to numerical results, the attenuation rate will be reduced when the working frequency or the conductivity of tunnel wall is increased. The attenuation rate of primary mode in trapezium is very low when the working frequency is about 500 to 1000 MHz. On the foundation of practical condition, it is reasonable to choose 900 MHz as the working frequency of mobile communications in mine well.