Wireless Power Transfer System Using Sub Wavelength Toroidal Magnetic Metamaterials

In recent years, the traditional four-coil magnetic resonance coupled wireless power transfer (WPT) system has been applied to wireless charging of mobile electronic devices and electric vehicles. However, it remains a fundamental challenge to maintain a high power transfer efficiency in a resonance system with magnetic radiation. Here, by using sub-wavelength toroidal magnetic metamaterials, we reconstruct the magnetic field and improve the power transfer efficiency to a considerable value. Dual-layer metamaterial spirals are employed to design the resonators of a toroidal magnetic mode system (TMMS) in which one can obtain a magnetic resonant mode dominated by the toroidal magnetic moment. This mode provides a concentrated magnetic field distribution and reduces the far-field radiation which are both observed in our simulations and experiments. We propose such method as a practical strategy to turn useless radiation into effective energy and solve the leakage of electromagnetic field in WPT systems.