Influences of Magnetic Couplings in Transmitter Array of MIMO Wireless Power Transfer System

Wireless power transfer (WPT) based on the magnetic field has a sharply decreasing efficiency as a charging distance increases. The magnetic beamforming, derived from a radio-frequency (RF) beamforming of the communication field, is the technology to overcome its disadvantage. The WPT with the magnetic beamforming controls the magnetic fields induced from the multiple transmitters, which results in transferring much power to the receiver. Furthermore, the magnetic beamforming can be applied to the WPT employing the multiple receivers, which implies that it is possible to efficiently charge multiple devices simultaneously. However, since the magnetic beamforming requires the transmitter array configured as the multiple transmitters, magnetic couplings between the multiple transmitters inevitably occur. The main objective of this paper is analyzing adverse influences of the magnetic couplings in the transmitters to the multiple-inputs and multiple-outputs (MIMO) WPT with the magnetic beamforming. Theoretical analysis and simulation results are provided from various viewpoints.