Underwater Wireless Communication Technology Based On Magnetic Induction

With the increasing frequency of ocean exploration,in order to ensure the safety of ocean exploration activities and the transmission of relevant exploration information,the communication capability is increasingly required.However,in the underwater multi-path environment,the communication technology of traditional underwater acoustic,electromagnetic wave and laser technology has complex channels,fast attenuation of distance,and is affected by Doppler effect,wave refraction and scattering.Due to the complexity of the underwater environment,the traditional wireless communication has certain technical limitations when applied underwater.Therefore,it is urgent to seek a new underwater acoustic signal processing technology to adapt to the application requirements of wireless data transmission in underwater environment.As a new wireless communication technology,wireless magnetic induction communication technology has attracted much attention.This technology uses the change of magnetic field to transmit information,which has unique advantages and application potential in underwater environment.By using specific transmitting and receiving devices,wireless magnetic induction communication can realize reliable data transmission underwater,which provides a new solution for wireless communication needs in underwater field.Magnetic induction communication has the advantages of no multipath interference,fast propagation speed,low delay,low cost,easy modulation and demodulation,strong confidentiality,carrying relative distance direction information,and can be used for underwater communication applications in short and medium distance.In this paper,the underwater wireless magnetic induction communication technology is studied in combination with the actual application scenarios in underwater environment.This paper intends to carry out the basic theoretical research of underwater acoustic electromagnetic communication.According to the distance between the observation station and the field source,the underwater acoustic electromagnetic communication is divided into near field area and far field area,the transmission model of magnetic signal is established,and the influence of coil parameters and position on the underwater acoustic electromagnetic communication is simulated.In the two cases of single and omnidirectional coil communication,the working frequency of the receiving device and the working voltage of the receiving device are compared theoretically and experimentally through the method of combining theory and experiment,and the optimal working frequency is obtained through calculation.At the same time,the transmission path loss and eddy current loss in the ocean under various modes are studied.The results show that unidirectional electromagnetic interference can easily lead to communication interruption when the antenna position and direction change,which seriously affects the performance of underwater wireless magnetic induction communication.The omnidirectional magnetic field transmission mode can better suppress the interference caused by the change of antenna position and direction.Secondly,through the analysis of the common signal modulation and demodulation modes,the binary phase shift keying(BPSK)technology is selected as the signal modulation solution mode of the experimental system.The basic structure of the magnetic communication circuit system is designed,and then according to the basic principle of each part of the circuit,the RLC resonance circuit is deeply studied and analyzed,and the transmission power amplifier is designed.The design parameters of each component are analyzed in detail.The hardware circuits of transmitting,receiving and signal processing of magnetic communication system are developed.The transmitted signal is TTL level generated by the signal generator,which is used as baseband signal;the digital frequency generator AD9854 generates 1.6MHz analog sine wave signal,which is used as carrier signal;then the current is amplified through the power amplifier module to drive signal transmission on the transmitting coil;the serial port is used to receive the module at the receiving end.The received signal is received and stored.Finally,an underwater magnetic induction communication platform based on an orthogonal phase keying modulator with a code rate of 500 Baud and a carrier frequency of1.6MHz is realized.Through the communication test and verification in air,indoor and fresh water environment,the wireless magnetic induction communication system designed by omnidirectional antenna can reduce the interference caused by the change of antenna position and Angle to a certain extent,and realize omnidirectional underwater magnetic field communication with a distance of 1.0m.The comparison of the receiving load model and the analysis of the circuit parameters,and the determination method of the optimal working frequency of the communication signal proposed in this paper provide the basis for the design of the underwater magnetic induction communication system.