Design and Optimization of the Low-Frequency Metasurface Shield for Wireless Power Transfer System

This article presents an optimized kilohertz (kHz) shielding metasurface (MTS) for wireless power transfer (WPT) system. Recently, the working frequencies of reported MTSs are concentrated in the megahertz range, which limits its application in low-frequency WPT system. Accordingly, the model of
$3\times 3$
matrix MTS shield (M-MTSS) with resonance frequencies of 65 and 190 kHz is proposed to eliminate the influence of fundamental (85 kHz) and harmonic (255 kHz) leakage magnetic flux density on the human body, respectively. A circuit model is established to consider all coupling of the system structure. Meanwhile, an exhaustive fitting analysis is carried out on the electromagnetic parameters of the application model. The winding of the M-MTSS is optimized to achieve a tradeoff between the efficiency and the magnetic field. Moreover, the calculated magnetic flux density distribution and the principle of the M-MTSS are illustrated. Finally, a test platform is set up to evaluate the performance of suppressing the emission of magnetic flux density. The experimental results showed that the magnetic flux of the fundamental and harmonic is reduced in the entire plane. These results verify the feasibility of the proposed method.