植入式人体通信中电磁波在不同组织分界面上的传播特性研究

通过计算电磁波在不同人体组织分界面的入射情况，研究人体信道电磁波跨越不同组织分界面时的传播特性.文章首先利用电磁场边界条件推导均匀平面电磁波向单层与多层导电媒质入射时的反射系数、透射系数及电磁波表达式；然后以人体手臂为研究对象，采用4阶Cole-Cole模型获取10 Hz~100 GHz人体组织介电参数，计算向单层、多层组织入射时各个分界面上的最大入射角、反射系数、透射系数与平均能流密度，结果显示，垂直入射是电磁波透射多层人体组织的主要路径，皮肤与空气分界面的反射系数最大，频率小于1 MHz或大于10 GHz的电磁波能量比较难在人体内外传播，电磁波平均能流密度传播随频率呈带通特性，带宽及中心频率与器件植入位置有关等；最后采用COMSOL Multiphysics建立电磁波向3层人体组织垂直入射的有限元仿真模型，仿真结果与理论计算结果相比误差小于0.000 08，验证了理论推导与计算的正确性.

Electromagneticwave transmission characteristics on different tissue boundaries for implantable human body communication

Transmission characteristics of signal crossing the boundary of different tissues in human body are studied through calculating the incidence of electromagnetic wave at the tissue boundaries.Reflection coefficient, transmission coefficient and the expression of electromagnetic field are deduced from the boundary conditions firstly when the uniform plane electromagnetic wave incidence to the single layer and multi-layer mediums.Then the human arm is taken as a research object, and the fourth-order Cole-Cole model issued to obtain the dielectric parameters of body tissues in 10 Hz-100 GHz.After that, the maximum incident angle, reflection coefficient, transmission coefficient and average energy flux density on the boundaries are calculated when electromagnetic wave incidence to 1-layer, 2-layer and 3-layer tissues.The results show that electromagnetic wave is propagating through the multi-layer tissues mainly with the vertical incidence, the reflection coefficient on the boundary of skin and air is larger than any other tissues, the energy of electromagnetic wave is difficult to be transmitted inside and outside the body with a frequency less than 1 MHz or larger than 10 GHz, the average energy flux density of electromagnetic wave presents band-pass characteristic with frequency, and the bandwidth and center frequency are related to the implantation position of device.Finally, a finite element simulation model of vertical incidence to the 3-layer human body tissues is built by using COMSOL Multiphysics.The differences between the simulation results and calculation results are less than 0.000 08, which verify the accuracy of the theoretical deduction and calculation.