True Nulls-Free Magnetoinductive Waveguides Using Alternate Coupling Polarities for Batteryless Dynamic Wireless Power Transfer Applications

A dynamic wireless power transfer (DWPT) system using the conventional magnetoinductive (MI) waveguide suffers from periodic power nulls resulting from standing waves. Although numerous methods have been developed to mitigate the nulls, additional active circuitry was required, increasing the complexity. In this article, the MI waveguide with alternate magnetic coupling polarities between successive resonator cells is proposed for a true nulls-free DWPT system with no use of active components. Two configurations of the alternately coupled MI (ACMI) waveguide are developed—one with the incorporation of a quadrature-phase termination for a linear waveguide, and the other with the adoption of a circular waveguide. Extensive analysis of the generalized ACMI waveguide is provided, and the developed configurations are theoretically verified to maintain power transfer efficiency, independent of the free-positioned load. Practical implementation of DWPT systems using the linear and circular ACMI configurations with seven resonator cells at 13.56-MHz operation are experimentally demonstrated to exhibit no power transfer nulls and achieve up to fivefold reduction in efficiency variation, as compared to their MI counterparts. Comparisons with theoretical calculation are given for verification of the analysis integrity. An experimental model of a batteryless DWPT system is also demonstrated using the circular waveguide as accompanied by a video.