Research On The Propagation Characteristics Of Electromagnetic Wave In Limited Space Of The Underground Coal Mine

Application of Wireless Communication Systems is an important aspect of modern coal production in underground coal mine, and which has important significance in enhancing the level of management, improving productivity, strengthening safety and protecting security of life and property. However, because the coal laneway is a special limited space where the environment is complicated and harsh, the propagation of electromagnetic wave is a complicated problem. So the study on the propagation characteristic of electromagnetic wave in limited space of the underground coal mine is of great theoretical and practical significance for the research and development of Wireless Communication Systems.At first, the general propagation characteristics of electromagnetic (EM) wave in waveguide were introduced, which is a basis for further study on propagation characteristics of EM wave in concrete laneway. Based on Maxwell equations and the boundary conditions under specified conditions, the formulas of EM wave attenuation rate can be obtained through solving the mode equations. And then taking the basic rectangular laneway and the familiar arched laneway to us as the research objects, the propagation characteristics of EM wave were researched systematically. Using the analytical method of solving the mode equations, combining with numerical method and geometrical optics theory, the formulas of EM wave attenuation rate in laneway were given. Based on these formulas, various factors, such as cross sections of laneway, electric parameter, tilt and roughness of laneway walls, and antenna insertion loss, influencing EM wave transmission were discussed. In addition, a preliminary study for the influence of suspending dust particles on EM wave transmission was done. The numerical simulation results show that within 300~3000MHz frequency band, when the frequency is higher, the attenuation rate is smaller, and the loss caused by walls roughness is smaller too, but the loss induced by walls tilt may be greater. With the different polarization mode of electromagnetic wave, the influences of cross sections and electric parameter on propagation characteristics are different. And when antennae are located in the center of laneway, the insertion loss reaches the minimum. Within the certain concentration range, the attenuations caused by dust on EM wave transmission in different aspects, comparing with attenuations caused by the above mentioned factors, can be negligible.