Rigorous design of magnetic-resonant wireless power transfer links realized with two coils

Magnetic resonant wireless power transfer has been typically realized by using systems of coupled resonators. We show that the essential elements are only the coupled inductances. In fact, by starting from coupled inductances, and by introducing their conjugate image impedances, we can derive the series and parallel matching topologies that realize maximum wireless power transfer. By sacrificing some efficiency we show that we can realize a matched (lossless case) mid-range wireless power transfer link by using just one inductive coil on the secondary side and having the required capacitances all on the primary side (or viceversa). The proposed topology greatly simplifies the design; in addition, when tuning is required due to coils misalignment or to link distance variation, it can be attained without the need for a feed-back through the communication link. A preliminary experimental verification of the proposed approach is also presented.