Research And Design Of Wireless Magnetic Induction Through-the-Earth Communication

With the development and utilization of deeper underground resources,the energy industry has put forward higher requirements for improving the detection of underground facilities,disaster emergency rescue,and environmental safety monitoring.The reliable through-the-earth communication can effectively connect the ground and underground,and transmit the ground control,monitoring and alarm signals to the underground.It has been the focus of domestic and foreign experts and scholars.The communication medium for wireless ground-penetrating communication is not air but soil,water,and rock.Traditional electromagnetic waves attenuate faster when they penetrate through the earth's medium,and the need for long-distance Through-the-Earth Communication(TEC)cannot be realized.This article focuses on wireless magnetic induction through-the-ground communications,and the specific research content is as follows.First,this paper analyzes the reasons why the distance of traditional electromagnetic wave penetrates through the earth is short.The electromagnetic wave is greatly degraded when it penetrates through the earth.The multipath effect caused by the layered soil and rock causes the electromagnetic wave to refract and reflect.It also disturbs the propagation of electromagnetic waves.Then the paper models the magnetic induction through-the-earth communication of the coil,the characteristics of the magnetic field generated by the coil are analyzed,and the feasibility of magnetic induction communication for long-distance through-the-earth communication is verified.According to the coupling relationship between transmitting and receiving coils,an equivalent circuit model of magnetic induction communication is established in this paper.The characteristics of the channel are analyzed to calculate the transmitted and received power of the coil.In this paper,the path loss,channel bandwidth and noise of the coil magneto-optical transmission are further studied.Finally,the channel capacity of magnetic induction TEC is analyzed.It is pointed out that increasing the quality factor of the system and the coupling coefficient between the coils can increase the channel capacity of the system.Based on the software radio equipment USRP N210,a magnetic induction ground penetration communication platform was built to verify the theoretical analysis,and the modulation and demodulation modes of the magnetic permeability ground communication were tested.The experimental results are consistent with theoretical analysis.The coil magnetic induction communication has the problems of high path loss and small channel capacity.Also,in order to conduct long-distance through-the-earth communication,the coil size is large and it is not suitable for layout in a space-limited underground manner.In order to solve the problem of magnetic induction TEC of coils,this paper proposes magnetic induction TEC based on magneto-resistive sensors,that is,tunnel magneto-resistance(TMR)is used instead of coil as the receiver of magnetic induction through-the-earth communication.Firstly,the principle of the linear TMR sensor receiving the magnetic field signal is studied,and the linear working area of the TMR sensor is analyzed.The TMR magnetic induction through-the-ground communication model is studied,and the relationship between the transmit power and the received power is established.The bandwidth and noise of the channel model are also studied.Finally,a TMR sensor chip was used to build a communication experiment platform to realize the transmission and reception of TMR magnetic induction communication signals.By comparing the channel capacity of conventional coils with TMR magnetic induction TEC systems,it is found that the performance of the TMR sensor magnetic communication is relatively poor.But as the magnetic resistance sensor's own noise is reduced,the sensitivity is improved and the linear range is expanded,based on TMR magnetic induction TEC will occupy an increasingly important position.