Design and optimization of decoupled concentric and coplanar coils for WPT systems

This paper presents the analysis and design of two decoupled, concentric and coplanar PCB coils. Decoupled coils could be used as two independent receivers sensing the same field and not interfering with each other. In order to nullify the mutual inductance, one of the coils is split into two segments and the segments are wound in different directions, while the second coil is inserted in between those two segments. Since wireless power transfer systems operate at high frequencies, the coil efficiency suffers mainly due to the losses caused by skin and proximity effects. Optimizing a coil to reduce the AC conduction losses and increase the inductance can help improve system efficiency. One of the methods presented in the paper involves splitting the coil turns into multiple parallel traces to reduce the losses due to proximity or current crowding effect. The design methodology includes the optimization of coils to achieve a high quality factor and find an arrangement where two circular spiral coils are coaxial, coplanar and decoupled at the same time. The proposed method is verified through simulations and experiments on a selected PCB design.