Hybrid metamaterial with zero and negative permeability to enhance efficiency in wireless power transfer system

Metamaterials with negative relative permeability can change magnetic field in the opposite direction. It can also change the magnetic field direction to straight if it has zero relative permeability. Previously reported metamaterials use only single characteristic which is a negative or a zero permeability to enhance efficiency by field confinement in wireless power transfer (WPT) systems. In this paper, we combined two kinds of structures of metamaterial cells, which have the negative and zero permeability. The hybrid metamaterial slab (HMS) is designed by using two spiral type patterns on a double layered PCB. It has the negative permeability at the edge of the slab and the zero permeability at the center of the slab. The HMS can confine greater magnetic fields around and inside transmit and receive coils. Therefore, the hybrid metamaterials can increase the power efficiency by 21.4% at 20 cm distance in 6.78 MHz WPT systems compared to the previous single permeability metamaterial slab (SMS).