The Optimal Location and Size of an Intermediate Coil in a Magnetic Resonant Coupling Wireless Power Transfer System

To increase the transmission distance of Wireless Power Transfer (WPT) systems, we provide guidelines on choosing the optimal location of an Intermediate Coil with respect to size within a standard five-coil axially aligned experimental setup. From our results, for maximum magnitude of S21 at the resonant frequency we found the optimal location to exist where the coupling coefficient between the Transmitter and the Intermediate Coil and the coupling coefficient between the Receiver and the Intermediate Coil are identical. Additionally, the optimal outer diameter for the maximum magnitude of S21 at the resonant frequency of the Intermediate Coil in the given symmetric and asymmetric setup are found to be larger than both TX and RX.