【摘要】 地下工业生产过程中需要对地下人员、设备和环境进行必要监测,由于地层对电磁波的衰减作用,合理选择通信系统频率、天线尺寸是实现有效远距离透地通信的关键因素。对磁场耦合的透地通信系统进行建模分析,并通过引入磁矢量位对三层介质中垂直磁偶极子激发的电磁场进行理论推导。针对"地面—地下"和"地下—地面"两种通信模式,使用XFDTD软件建立环形天线仿真模型,分别在单一均匀介质和成层介质条件下对不同频率电磁波的传播进行仿真。结果表明,高频电磁波在地层中衰减迅速,随着频率的降低衰减程度减缓,且甚低频和超低频电磁波在电导率较大的地层介质中也可以实现有效的远距离传播。更多还原

【Abstract】 For underground industrial processes,it is important to provide necessary monitoring for the underground personnel,equipment and environment. Considering the effect of the earth on the electromagnetic waves attenuation,reasonable choices of communication system frequency and antenna size are the key factors to achieve long-distance through- the- earth communication. In the paper,a model of communication system based on the magnetic field coupling was proposed and analyzed and the electromagnetic field excited by a vertical magnetic dipole in the three- layer medium model was derived by using the magnetic vector potential. The propagation simulations for"down- link"and"up- link"circle antenna models were carried out through XFDTD software. Electromagnetic waves of different frequencies were simulated under the single homogeneous medium and the stratified medium conditions. The results show that high frequency electromagnetic waves declines rapidly in the earth,and the attenuation is gradually slower with the lowering of frequency. Moreover,very low and ultra- low frequency electromagnetic waves can achieve effective long- distance communication in the large conductivity medium.更多还原