Shielding the magnetic field of wireless power transfer system using zero-permeability metamaterial

The wireless power transfer (WPT) has attracted considerable attention due to its convenience and reliability. However, the electromagnetic leakage of WPT can be harmful to humans and environment. In order to meet safety requirements, electromagnetic leakage to the nearby transmission channel should be controlled below a certain level. Beyond ferrite and metallic shields, several researchers have proposed mu-near-zero metamaterial (MNZ MM). However, little work researches the application of MNZ MM in four-coil WPT systems. Here, the authors propose an optimised MNZ MM for shielding leaked electromagnetic field. Next, the authors setup a miniaturised WPT system loaded with MNZ slab at 13.56MHz. It can serve as a frequency selector that reflected a specified frequency of 13.56MHz, while allowing all other frequencies to pass undisturbed. As a result, the transmission efficiency is dramatically reduced at a 30cm distance. The magnetic field magnitude of the receiver has been decreased. Obviously, the proposed MNZ MM has good performance in magnetic field shielding for WPT systems.