Optimization of wireless power transmission through resonant coupling

We investigated an optimization condition for a maximum power transmission between coils wirelessly. Due to the resonant coupling nature of the system, for the highest power transmission, there is an optimum distance between the power (receiving) coil and sending (load) coil for a fixed distance between the sending coil and receiving coil. This effect cannot be explained by a conventional magnetic induction theory. We made a model of a four-coil system employing a complex coupling constant to explain the effect.