Optimal TX multi-coil beamforming and RX coil selection in a magnetic MIMO wireless power transfer system

Abstract

The interest in magnetic resonance coupling for wireless power transfer has increased in recent years. It is known that utilizing multiple transmit and receive coils can improve the power transfer efficiency, but a bit surprisingly, utilization of multiple transmit and receive coils at the same time, i.e., magnetic multiple input multiple output (MIMO), has not been well studied in literature. In this paper, we jointly optimize transmit multi-coil beamforming and receive coil selection in a magnetic MIMO wireless power transfer system to minimize the total transmit power, while satisfying a required level of the charged power. The optimal current allocation for transmit multi-coil beamforming is derived for an arbitrary number of receive coils, and then it is shown that using only a subset of the receive coils can be more beneficial than using all the receive coils in some conditions when mutual couplings among receive coils exist. Based on our analysis, we develop an algorithm to find the optimal subset of the receive coils. Our simulation results verify that the proposed scheme with multi-coil transmit beamforming and receiver coil selection requires the lowest transmit power to meet the constraint on the charged power.