Compact Broadband Planar Resonator With a Viaed Double Spiral for Robust Wireless Power Transfer

Abstract

A common problem for most strongly coupled magnetic resonance (SCMR) wireless power transfer (WPT) systems is the dramatic efficiency drops by surrounding high-dielectric objects, e.g., people, caused by the narrow bandwidth of the systems due to a high quality factor ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$Q$</tex-math></inline-formula> ). In this paper, a compact broadband planar double-spiral resonator with a via is proposed to obtain a robust SCMR system with a stable efficiency where interference from high-dielectric surrounding objects is mitigated. The increased bandwidth is obtained without compromising power transfer efficiency by introducing coupling enhancement to the structure while <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$Q$</tex-math></inline-formula> is reduced. The bandwidth of the system is increased by over 15% compared to a conventional system with single-sided resonators, and the efficiency is comparable. In this paper, it is found that the location of the via affects both the efficiency and bandwidth of the SCMR system. Meanwhile, this paper reports an experiment with human hand phantom and a simulation study with multi-layered tissue model, both of which mimic a real human-involved environment, and successfully demonstrate the stability and high efficiency of power transfer of the proposed broadband resonators in a WPT system. Moreover, the proposed structure is tested to be less sensitive to misalignment between the transmitter and the receiver, and the proposed method is compared to the systems proposed for similar human-involved environments. This proposed viaed double-spiral resonator is a promising candidate for a robust WPT system for human-involved environments.