Design of Low-Loss Electromagnetic Metamaterial with Non-uniform Linewidth for Magnetic Field Convergence in WPT System

Electromagnetic metamaterial (EM metamaterial) with a double-layer spiral structure is often used to enhance the transmission efficiency of wireless power transfer (WPT). When EM metamaterial is used as an array, its AC resistance and loss cannot be ignored due to the high-frequency magnetic field of WPT. This paper decreases EM metamaterial's loss by increasing its quality factor according to the quality factor theory and proposes a novel structure. This structure adopts a non-uniform linewidth, which can decrease the proximity effect resistance of the EM metamaterial as well as maintain its high inductance. When using the proposed EM metamaterial to form an array, to enhance its effect in modulating the magnetic field, a hybrid EM metamaterial slab (HMS) is constructed by adjusting the series resonance capacitor. The corresponding samples of EM metamaterial with the non-uniform linewidth structure are developed. The experiment results prove that compared to the uniform linewidth structure, the equivalent resistance and loss of the non-uniform linewidth structure respectively are decreased by about 5.48% and 19.73%, and the quality factor is enhanced to 556.874. The HMS constructed by the proposed EM metamaterial can enhance the transmission efficiency of the experimental WPT system to 59.8%, which is about 2.1% higher than the HMS constructed by the normal EM metamaterial. © 2024 Institute of Electrical Engineers of Japan and Wiley Periodicals LLC.