Development of Multilayer Rectangular Coils for Multiple-Receiver Multiple-Frequency Wireless Power Transfer

In this paper, three viable multilayer rectangular coil structures, namely the spiral, concentrated and uneven compound types, are proposed and analyzed. In the multiple-receiver multiplefrequency wireless power transfer system, the compact coil topologies are particularly preferable and should fulfill the required performance of magnetic field with the compact size design. In order to minimize the variation of magnetic fields that can be picked up by multiple receivers, the uneven compound type is newly derived by combining the merits of both the spiral and concentrated types. Because of providing more uniform magnetic flux density distribution, the uneven compound type can achieve better tolerance of misalignment. Without any misalignment, its transmission efficiency can reach up to 92%. Moreover, their electric potential distributions are analyzed to provide guidance for the maximum input current at the desired operation frequency. Both finite element analysis and experimental results are given to verify the validity of the proposed coil structures.