粗糙度对矩形巷道电磁波传播特性影响的仿真

Simulation of Influence of Wall Roughness on Electromagnetic Wave Propagation Characteristics in Rectangular Tunnel

在多波模损耗模型基础上,为了确定掠射角的大小,采用作图分析的方法,得出结论:在反射过程中,各波模在两侧壁和上下两壁的掠射角保持不变,且掠射角分别等于水平入射面和垂直入射面的初始入射角,同时推导验证了各模次波模的反射次数。不同于以往只考虑频率因素,为了从频率和粗糙度方差σ2两个方面定量的研究巷道壁粗糙对传播损耗及粗糙度损耗的影响,运用公式推导及仿真的方法得出结论:粗糙度损耗和传播损耗随粗糙度的增加而增大;粗糙对传播损耗的影响随传播频率的增大而增大。在上述结论的基础上提出了频率拐点的概念并通过仿真分析得出结论:当频率小于频率拐点时,传播损耗随着频率的升高而减小,大于频率拐点时,传播损耗随着频率的升高而增大;频率拐点的大小与粗糙度有关,与其它因素无关。频率拐点的确定,有助于判断传播损耗的变化趋势,为井下无线传输的最佳频率提供理论依据。

On the basis of the multimode loss model,we adopted the method of drawing to determine the value of grazing angles,and drew the conclusion that in the reflection process of the rays,grazing angles of two sides and top to bottom sides remain unchanged and the grazing angles are respectively equal to the initial incidence angle of horizontal incidence plane and vertical incident plane. At the same time,the number of reflection on each mode was derived and verified. And unlike previous cases that only frequency factor was considered,we quantitatively studied the influence of wall roughness on propagation loss and roughness loss from two aspects of frequency and roughness varianceσ2,used the methods of formula derivation and simulation to draw the following conclusion： the roughness loss and the propagation loss increases with the wall roughness,and the influence of the wall roughness on the propagation loss increases with propagation frequencies increase. On the basis of above conclusions,we put forward the concept of the knee point of frequency and drew the conclusion through simulation： when the frequency is lower than the knee point,the propagation loss decreases with the frequency increases,when larger than the knee point,the propagation loss increases with the frequency increases; the value of knee point is connected with the wall roughness,independent of other factors. The determination of the frequency knee point can help to estimate the variation trend of propagation loss,which provides a theoretical basis for the optimum frequency of underground wireless transmission.