Design And Implementation Of Through-the-earth Communication System Receiver For Mine Based On The Current Field

In recent years,underground emergency communication system has been paid more and more attention due to coal mine safety accidents often happens.Because the serati belongs to semi conductive medium,traditional radio waves can not be transmitted under the ground,and the stratification of strata is obvious,it will produce specular reflections on the electromagnetic wave.In order to reduce the absorption and attenuation of waves,we should use a low communication frequency,but when the communication frequency is low,we need set up a large antenna accordingly,and the communication rate and the radiation efficiency should be lower.However,owing to the advantages of small volume,high efficiency and invunlnerability characteristic,the communication method based on electromagnetic field has become a through-earth communication method with good growth prospects.It great scientific value and practical significance to study the conduction current field propagation and application technology,we are rich in mine resources,the mining accidents happen frequently.In this paper,we studied the conduction current field theory,and complished the design and implementation of emergency communications receiver system in mine through the earth.The main contents and work of this paper is as follows:(1)Founding the mathematical model of the conductive medium conduction current field,and analyse the effects of factors,such as conductive medium parameters and frequency on communication system and communication distance.Finally,we design the electric dipole receiving antenna and the grounding resistance model.(2)Conduting demodulation and decoding according to modulation and encoder mode of emission system.Encoder method is convolutional coder of(2,1,3),the way of decoding is Viterbi decoding algorithm,and demodulation is using coherent demodulation.Decoding and demodulation of the signal are finished mainly on the QuartusII software platform using Verilog HDL language.using the modularization method,it is convenient for language drafting and function adjustment.(3)Completing the design and realization of the hardware circuit of the receiving system,and conduct the simulation of power integrity and signal integrity.(4)Conducting Pspice optimizational simulation on the receiver simulation system and Analysing of the effects of temperature and sensitive device to output value of noise,and optimizing the efficiency of the devices by choosing the reasonable value.(5)Completing system test,laboratory communicating experiments and out-field through-earth communicating experiment,to optimize of the hardware system and demodulation algorithm according to the interference and noise in nature.