Design of Metamaterial for Efficiency Improvement of Magnetic Resonant WPT System

This paper proposes the design of a metamaterial for improving the efficiency of the magnetic resonant wireless power transmission (WPT) system. The transmission efficiency in the magnetic resonant WPT technique decreases as the transmission distance between the transmitting and receiving coils becomes longer. To improve this, a planar spiral metamaterial having a negative permeability at the operating frequency has been designed. The structure of the proposed metamaterial unit cell is compared with the characteristics obtained by parametric analysis, and a structure with a high Q-factor value is selected. The size of the planar spiral resonator can be reduced as compared to the size of the resonator at the same frequency. In addition, by using chip capacitors, it is easy to have a negative permeability characteristic at the resonance frequency, thus gives a convenient design method. The metamaterial slab fabricated through this method has an improved transmission efficiency of 62.4% at a distance of 13 cm from the transmitter, which is more than about 20.5% compared to the transmission efficiency of the conventional method.