Circularly polarized near field for resonant wireless power transfer

In this paper, we propose a near field coupling based wireless power transfer (WPT) system with circularly polarized magnetic field. With a pair of orthogonal resonant coils arranged to generate a circularly polarized near field, we show that the power transfer efficiency is largely maintained in case of rotational misalignment. Furthermore, by arranging the coils close to a metal surface, the power transfer efficiency is actually improved, rather than decreased as in the case of WPT system made with conventional coils. Depending on the application, the receiving coil can be either a pair of orthogonal coils, or conventional coils with flat structures. We believe that the proposed technology offers a great option toward flexible WPT applications.