A Minimized 2-D Left-Handed Material Spiral Unit Cell With Rotation Symmetry for Midrange Wireless Power Transfer

Abstract

This letter presents a technique for designing left-handed material (LHM) unit cell, and a minimized 2-D low-loss LHM square spiral unit cell ( $38~ \text {mm} \times 38 ~\text {mm} \times 1.6 ~\text {mm}$ ) with rotation symmetry is developed in the frequency band 13.56–14 MHz. Two LHM slabs with $5 \times 5$ unit cell array are added to the transmission and receiving antennas, respectively, and the power transfer efficiency has increased greatly.