Optimization of Magnetic Field Focusing and Null Steering for Selective Wireless Power Transfer

Wireless power transfer (WPT) has recently emerged as a prominent technology to liberate various applications with small devices from limited mobility and design constraints. Among various techniques, magnetic field focusing (MFF) with multiple transmit (Tx) coils have been known as a powerful solution to enhance the efficiency of power transfer to multiple receivers (Rxs) in midrange WPT. However, in such MFF techniques, even unintended Rx may suffer from unwanted power due to leakage, which may disrupt the operations of the devices. Motivated by this issue, in this article, we consider selective magnetic resonance coupling (MRC)-based WPT, which enables WPT systems to better shape power distribution only focusing on the intended Rxs while leakages to the unintended Rx are suppressed. To this end, we first formulate the selectivity requirement of WPT as an optimization problem. Then, we propose a method to obtain the optimal Tx voltage vector for simultaneous MFF and null-steering optimization. Simulation and experimental results validate the theoretical analysis and the proposed method in practical scenarios.