Improving Power Transfer Efficiency of a Short-Range Telemetry System Using Compact Metamaterials

Wireless power transfer using resonant inductive coupling has been employed in a number of applications, including wireless charging of electronic devices and powering of implanted biomedical devices. In these applications, power is transferred over short distances, which are much smaller (similar to lambda/100) than the wavelength of operation. In such systems, the power transfer efficiency of the link is inversely related to the range of operation. The power transfer efficiency is principally a function of the Q's of the individual coils and the coupling between them. In this paper, we demonstrate improvements in power transfer efficiencies using negative permeability metamaterials by increasing the mutual coupling between coils. A metamaterial slab is designed for operation at 27 MHz and is compact in size. The power transfer efficiency of the telemetry system in free space is compared to that in the presence of the metamaterial placed near one of the coils. The efficiency of the system increased in the presence of the metamaterial even as the free-space separation was held constant. This shows that compact negative permeability metamaterials can be used to increase power transfer efficiency of short-range telemetry systems used in various applications.