Quantification Phase Gradient Near-Field Focusing Metasurface for Microwave Wireless Power Transfer System

This letter proposes a quantification phase gradient near-field focusing metasurface (MS) to improve the transmission coefficient of the microwave wireless power transfer (WPT) system. The quantification phase gradient MS adopts the numerical approximation principle to achieve simplify the design method by the continuous phase gradient. The MS consists of 13 × 13 cross double split ring resonator (CDSRR) units with four layers structure. The CDSRR unit is symmetric, focusing on x -/ y -polarized transmissive waves in wideband. The results show that the quantification phase gradient MS obtains a maximum focusing efficiency of 62.91% and a depth of focus of 61.4 mm, improving the microwave WPT system's maximum transmission coefficient of 12.3 dB. The CDSRR unit can respond to −3 dB transmission amplitude of −0.52 dB and 2π phase shifts at a bandwidth of 6.4 GHz, providing a maximum transmissive efficiency of 94.1%. The proposed quantification phase gradient MS can be applied in near-field focusing metasurface phase simplification and depth of focus enhancement.