Design And Application Of Magnetic Metamaterials In Wireless Power Transfer

Artificially constructed materials,as a research hotspot in recent years,have been applied in various fields and the construction of new devices in almost all frequency ranges.The split-ring resonators(SRRs)and spiral resonators(SRs)are the most widely used metamaterial cells,especially in telemetry and antenna systems.The performance of the wireless power transfer system can be greatly improved by a magnetic metamaterial slab composed of respective SRRs and SRs,which has the advantage of simple fabrication process at a low cost.In this paper,a magnetic metamaterial slab is designed with low loss and-1 permeability at 29.8 MHz by means of numerical simulation,and a 40-centimeterdistance wireless power transmission system is built in HFSS.The power transfer effiency of the system can be optimized by using this magnetic metamaterial slab.After the improvement of the efficiency caused by the slab,another method of improving the efficiency is further discussed where the SR unit cells in the center of slab are replaced with the cells with near zero permeability.The effects of the modified magnetic metamaterial slab and metamaterial slab combined with ferrite slabs are explored.The equivalent analytical models are also established for WPT system and metamaterials.Based on the S-parameter retrieval method,the influence of geometrical parameters on the resonant frequency and permeability of double-sided square spiral resonator is studied and a method for adjusting the resonant frequency and the permeability of the SR structure is concluded.