Estimation of complex permittivity of human body using transmission matrix method and FEM solver

In the context of in-vitro testing of implantable medical devices, multi-layered body phantom development poses significant challenges in terms of complexity, cost and possible formation of unwarranted air gaps between two layers or mixing chemicals of two layers while one layer is placed on other layer in hot semi-solid form. Therefore, it is recommended to use its equivalent homogeneous phantom with same dielectric properties. In this article, equivalent complex permittivity of three-layer human-body-model at 2.45 GHz is estimated by using Transmission Matrix Method (TMM) and FEM solver. The transmission matrix of the required body model is calculated based on the electrical properties of each layer. Solving nonlinear equations from TMM, multiple solutions of complex permittivity values are obtained. A two-antenna system is designed in FEM solver where one of the antennas is placed within homogeneous phantoms with obtained complex permittivity values and other is in free space to choose exact complex permittivity using scattering parameters. To validate the final phantom properties practically, the simulated setup is replicated. The practical results show good agreement with simulated responses. This approach can reduce complexity of designing multilayer-models considering only 0.53% error to estimate complex permittivity of human body.