Research On The Analysis Method Of The Seawater Channel Transmission Characteristics Of Inductively Coupled Mooring Chain

With human understanding and exploration of the oceans,in view of the demand for high speed and real-time transmission of a large number of multi element monitoring data in deep-sea environment,it is of great significance to improve the inductive coupled data transmission technology.Using the electromagnetic induction principle,the bi-directional data transmission from the overwater control equipment to the underwater sensor can be realized.However,due to attenuation in marine environment,it is difficult to realise the long distance and efficient transmission.From the point of view of improving the transmission efficiency and speed of inductively coupled data transmission technology,this paper focuses on analyzing the key factors that restrict the inductively coupled channel to improve the transmission efficiency and speed.In order to accurately analyse the channel transmission characternstics of inductive coupling temperature-salinity-depth chain,an three level distributed prototype of the transmission channel using COMSOL Multiphysics is constructed.The transmission characteristics of the channel are analysed at various depths?parameter.The analysis of three level simulation model demonstrates that the transmission efficiency of the single node transmission channel is 2.9%.The transmission efficiency is reduced to 2.6%,when the sensor nodes in the transmission channel are 10,while it may be less than 1%with the decrease of the inductance.Moreover,the seawater resistivity is calculated,which is about 39?.This paper summarizes the influence of Magnetic parameters and the sensor nodes on transmission efficiency.The attenuation and restriction of seawater on transmission efficiency are emphasized.In this paper,attenuation characteristics are analyzed from two aspects,including multipath effect and frequency-selective.The seawater is an important transmission medium in the inductive coupling channel.The transmission of the electrical signal has multipath effect in the infinite seawater.When the signal transmission frequency is increased,multipath delay spread effect is enhanced.Meanwhile,the effect of inter code crosstalk and selective fading of the received signals will be enhanced.Then,the signal-to-noise ratio of the transmitted signal will be reduced.However,the research on this problem is still a blank.In this project,the method of finite element simulation and numerical calculation is used to determine the key parameters,such as the number of paths,time delay and amplitude attenuation,and establish the multipath channel model.The relationship between these key parameters and the transmission rate is studied through the time-frequency method.On this basis,a set of a series of seawater measurement systems is set up in this paper.The amplitude-frequency and phase-frequency characteristics in seawater are measured using the frequency-sweep method in laboratory and establish the actual measurement channel model.Finally,the mathematical models established in two different ways are compared and analyzed.The results of this study provides an optimized solution for the transmission performance of the inductive coupling data transmission system,which provides theoretical and experimental basis for solving the common problems of the inductive coupling channel transmission technology.