Optimal Coupling for Capacitive Wireless Power Transfer with One Repeater

In order to extend the range of capacitive wireless power transfer, an electric field repeater between transmitter and receiver can be applied. In this work, a network formalism is adopted to analytically describe and maximize the system efficiency of a repeater setup. The resonator components, resistive losses, load and supply impedances are considered fixed and given. The efficiency is varied by acting on the coupling between transmitter, repeater and receiver only. It is found that it is only possible to optimize the system by varying the coupling between repeater and receiver while keeping the coupling between transmitter and repeater fixed. A condition, dependent on the value of the load, is determined for which the maximization solution exists. The analytical solution is verified through circuital simulations.