Research On Theory Of Low-frequency Through-the-earth Communication System

An emergency security communication system is needed for the exploitation of mine and other underground buildings. In order to solve this problem, the best way should be penetration stratum communication, only by which can meet the needs of communication in the non-free space. Low-frequency Trough-the-Earth communication whose channel is the stratum earth medium for mine is seen as the most secure way of production and emergency communication because of its channel character not affected by emergency. Therefore, it is very essential to study the characteristic of the radio wave transmitting through the earth.This paper "Research on Theory of Low-frequency Through-the-earthCommunication System" is funded by Sichuan province research project "The Theory and Method Study on Disaster Life Search and Rescue" and the Minister of Education fundamental Doctor's Degree research subject "Research on the Theory of new kind of Disaster Search and Rescue Methods". The present situations in domestic and foreign of the wireless communication for the coal mine is narrated, many kinds of methods of wireless communication and its trend of development for mine are discussed. The earth medium's characteristic is analyzed in detail in this paper, and the work frequency and all kinds of stratum parameters tied closely to the propagation of the radio wave are discussed, then the suitable frequency band for the through-the-earth communication is obtained; the multi-layer structure of the earth medium is proposed, and under this model the reflection coefficient, the transmission coefficient and the absorption (loss) coefficient along with the radio wave's propagation are calculated; each coefficient's influence factors are analyzed by the graphic method. The antenna shaping which suitable for the through-the-earth communication is discussed here, and the antenna parameters are calculated either. The transmission/receiver principle of the through-the-earth communication system is analyzed, and the through-the-earth communication system organization plan which is based on the Software-Defined Radio (SDR) is proposed, meanwhile, the communication system's error rate is simulated withthe tools of Matlab/Simulink.The conclusion obtained can provide theory basis for the design of the through-the-earth communication system, has certain practical significance.