Efficient wireless power transfer system by using highly sub-wavelength negative-index metamaterials

In this paper, we present a kind of highly sub-wavelength negative refractive index metamaterials for operation at radio frequencies. A dual layer design consisting of planar spiral and meandering line with metallic strips enables the metamaterials with the properties of effective negative permittivity and permeability simultaneously, i.e. negative refractive index. Moreover, its cell size is about 330 times smaller than the resonant wavelength. By applying one or two metamaterial slabs between the two traditional inductive coupling copper rings, the transfer mechanism will be changed to be resonant coupling. Therefore, both of the transfer distance and the transfer efficiency are improved significantly. Full-wave simulation results show that the miniature WPT system with proposed metamterials can work perfectly in improving the transfer efficiency and transfer distance.