Field-circuit Finite Element Method Modeling And Experiment Of Intra-body Communication

Intra-body communication(IBC)is a novel method to achieve the "last meter"information sharing in mobile health by capitalizing on good conductivity of human body,which has the advantages of low power consumption,being easy to connect,better anti-noise performance,less radiation etc.Recently,most of researches focus on geometry models,equivalent circuit models and theoretical models.The paper deeply discussed the signal transmission principal inside the human body by establishing the thorough field-circuit model of body channel based on authentic test environment.A novel human phantom with realistic anatomy and spatially varying conductivity was developed to verify the validity and accuracy of the field-circuit model by in vivo and in vitro experiments.Exploratory experiments were carried out to explore the consistency,bi-directionality and linearity of the human channel.The specific contents of this paper are as follows:Governing equations based on the quasi-static electric field approximation in intra-body communication were derived in this paper.Then,combined with the profile of human body and boundary conditions via visual 3D reconstruction and the dielectric properties of the tissues,an electric field model of galvanic coupling IBC channel was established.The input and output impedance of measurement device,parasitic impedance between electrodes and the coupling relationship of channel were also taken into consideration as a circuit model.Moreover,a more complete field-circuit model of intra-body communication was established by combining the electric field model and the circuit model,both of which were on the basis of the design of the interface module.The parameters of the field-circuit model were estimated and finite element analysis was also carried out.Simulation results showed that muscle had greater influence on signal transmission of IBC from 10 kHz to 1MHz,and more than 65%of the current was transmitted through the muscle layer.Different materials were selected and combined together according to the difference of tissue's electrical conductivity,to simulate human skin,fat and muscle.Because of the complexity and irregularity of human tissue,digital human data were used to produce mold.A novel human phantom with realistic anatomy and spatially varying conductivity was developed,which was served as one of effective ways of the field-circuit model validation.The experiments in this thesis were divided into two parts.One was the verification experiment,the other was exploratory experiment.The validity of the field-circuit model and the universality of the phantom model were verified via verification experiments,while the consistency,bi-directionality,and linearity of the human channel were validated via exploratory experiments.Experiment results showed that the characteristics of field-circuit model were much closer to the human channel than those electric field models,the error between field-circuit model and human channel was less than 9dB.Characteristic curves of the phantom model were similar to those of the human body,which means that phantom model could be an effective supplement to validate the accuracy of the field-circuit model.The exploratory experiments proved the consistency,bidirectional and linearity of human body through the in vivo experiments,which could provide theoretical guidance for the design of the hardware circuit in intra-body communication.In conclusion,the investigation of IBC field-circuit model revealed the transmission characteristics of electrical signal in human body.The work of this thesis offered theoretical basis for practical application of IBC in mobile medical equipment.