Wireless Power Transfer System using Near Zero Refractive Index Metasurface for ISM Band Applications

This article proposes a new star-shaped spiral meta-atom design having near zero refractive index (RI) and its periodic metasurfaces that enhances the power transfer efficiency (PTE) of a wireless power transfer (WPT) system operating in the industrial, scientific and medical (ISM) band (2.40-2.48 GHz). The proposed meta-atom has double transmission windows in the 1-6 GHz range covering the ISM band in its first transmission window. Due to the near zero RI property, this metasurface can convert any incident waves (spherical/cylindrical) to planar waves upon transmission through it. Two circular microstrip antennas (CMSAs) having resonances at 2.42 GHz and 2.43 GHz in the ISM band are designed to set-up a WPT system. A $3 \times 3$ and a $4 \times 4$ metasurface have been designed using the proposed meta-atom that enhances PTE from 19.14% (−7.18 dB) to 24.66% (−6.08 dB). A step-by-step design procedure starting from the meta-atom up to the WPT system, along with the complete parametric study of the WPT system and a detailed physical analysis of the working of the meta-atom based on electromagnetic (EM) simulations, has been presented.