Analysis and Design of a Multi-hop Resonant Wireless Power Transfer System: Optimal Intermediate Coil Size and Location

To increase the transmission distance of Wireless Power Transfer systems, engineering an intermediate coil (IC) is a common approach. In this paper, we provide methodologies and formulas for choosing the optimal size and location of an IC that provides a required transferred power to the load in a standard four-coil systems. Increasing the size of the IC will result in diminishing returns, so the optimal size depends on the target power ratio. The optimal location depends on the size of the IC and the separation of transmitting and receiving coils.