Efficiency of magnetic resonance WPT with two off-axis self-resonators

In the paper, the characteristics of magnetic resonance wireless power transfer (MR-WPT) system with two off-axis rectangular self-resonators are analyzed. Efficiency and mutual inductance method between two rectangular coils are obtained. Mutual inductance in an off-axis system is derived at an arbitrary spatial point by subdividing the Rx coil and summing the magnetic flux density of each subdivision. For verification, calculation results are compared with simulation by a commercial EM solver. The calculation result is in good agreement with the simulation for a two single loop system. Two identical rectangular self-resonators are also fabricated. The measured mutual inductances and efficiencies are in good agreement with the calculated results. It is also shown that the high efficiency can be achieved in the off-axis system.