Optimized 3-D Polarized H-Field Forming for Orientation-Insensitive Wireless Power Transfer Systems

This article addresses the angular misalignment problem in wireless power transfer (WPT) systems by a magnetic field ( H-field) forming approach using coil antennas. To power up a planar receiver coil in any orientation, 3-D rotating H-field is required. Using the transmitter coil antennas with amplitude-modulated current excitations, 3-D polarization of H-field is achieved. The power transfer efficiency depends on the polarization of the H-field and varies with receiver inclination. This is applicable for a spherically polarized H-field which is otherwise expected to provide uniform induced voltage in the receiver in any orientation. To completely mitigate the misalignment problem, mathematical analysis of H-field forming is presented followed by optimization of the 3-D polarization. This evolves in understanding the effect of various 3-D H-field polarizations on the induced voltage and results in an optimum ellipsoidal polarization achieving performance that is invariant to the receiver orientation. The results are compared for various 3-D polarizations and the best performance is shown by the proposed solution. The analytically obtained results are validated through simulations and experimental studies. The results thus obtained proved the potential of the proposed optimized 3-D H-field polarization in WPT systems where a free-orientation of the receiver is necessary.