A Frequency Selective Zero-permeability Metamaterial Shield for Reduction of Near-field Electromagnetic Energy

Wireless power transfer and other near-field applications can generate large magnetoquasistatic fields that can potentially be harmful to humans or interact negatively with the environment. Several shields have been proposed for the magnetic near-field, such as ferrite sheets or metallic shields. While each can be effective, there are tradeoffs to each, namely loss, weight and cost. In addition, metallic and ferrite shields are broadband and block large portions of the electromagnetic spectrum. In this Letter we introduce a new type of magnetic near-field shield, a zero-permeability near-field metamaterial (NF-MM) shield. This shield operates by canceling the incident magnetic flux without significant additional loss to the system. Moreover, the zero-permeability shield is frequency selective, blocking only a single or small bandwidth of frequencies, enabling shielding only at the desired frequency while allowing the remainder of the electromagnetic spectrum through. We show that a zeropermeability NF-MM shield can reduce magnetic field strength by 22.84 dB in simulation and demonstrate 77 % reduction in an experimental prototype.