Wireless power transfer in the presence of a conducting interface: Analytical solution

A comprehensive model of wireless power transfer (WPT) between a pair of inductively coupled loop resonators in the vicinity of a conducting slab is developed by combining electromagnetic (EM) theory with an equivalent circuit representation of the system. The model incorporates all EM interactions occurring between the coils both directly and through the slab. The design of an optimal WPT regime for two coils in the presence of a conducting slab with variable conductivity is demonstrated by exploiting the model to predict the coil detuning produced by the slab. It is further shown that the model also constitutes an effective tool to estimate the losses in the conducting material solely in terms of the parameters of the generalised equivalent circuit and to analyse the power flow in a WPT system. The validity of the analytical results is proved by comparison with rigorous full-wave simulations. The proposed analytical method can have particular relevance in the field of wireless charging of electric vehicles and WPT for supplying implanted medical devices and body sensor networks, where it can be instrumental for the design and optimisation of the system to be compliant with existing RF exposure safety levels