煤岩介质中无线通信频率及衰减机制研究

Radio frequency and attenuation mechanism in coal and rock medium

为给矿井煤岩体介质中无线传感器网络技术开发提供理论依据,基于麦克斯韦方程,建立了煤岩体介质中电磁信号衰减模型,采用理论分析和数值计算方法,得到煤岩体介质中电磁波的合理通信频段、衰减系数及趋肤深度等参数。结果表明:煤岩体的电性参数、孔隙率、温度、湿度是影响电磁信号衰减的主要因素;为保证电磁波在煤岩体介质中良好的传输性,通信频率≤1MHz;在单一有耗煤岩体介质中,电磁信号衰减系数大小为无烟煤>褐煤>肥煤>焦煤>贫煤,石灰岩>泥岩>粗砂岩>砂岩>细砂岩;井下电磁信号传输的有耗媒质为多元混合介质,为保证趋肤深度δ≥5 m,通信频率需满足f≤0.21 MHz.研究结果对确定适用于采空区的WSN最佳通信频率具有重要的应用价值。

In order to provide a theory basis for wireless communication technology development in rock- coal mass, electromagnetic signal attenuation model based on Maxwell Equations was established. The parameters of electromagnetic wave including frequency, attenuation coefficients and skin depthes were obtained through the theoretical analysis and numerical calculation. The results show that coal-rock elec- trical parameters, porosity, temperature and humidity are main factors influencing the electromagnetic signal attenuation. To ensure good transmission of electromagnetic wave in coal-rock medium, communi- cation frequency need less than 1 MHz. Attenuation coefficients of electromagnetic wave in single compo- nent coal or rock medium tend to follow the order of anthracite coal 〉 brown coal 〉 fat coal 〉 coking coal 〉 lean coal and limestone 〉 mudstone 〉 gritstone 〉 sandstone 〉 fine sandstone. The electromagnetic wave is actually muhicomponent mixture, so the good choice of communication frequency is less than 0. 21MHz to ensure the skin depth more than 5 m. The results of research have important application value to determine WSN best communication frequency suitable for the goaf.