Controlling the resonances of indefinite materials for maximizing efficiency in wireless power transfer

In this paper, we investigate the possibility of improving efficiency in wireless power transfer (WPT) using metamaterials. Our analysis differs from previous works as we focus on the design of thin metamaterial slabs. Specifically, three types of metamaterial are considered: the double negative material (DNG), the μ-negative material (MNG), and the indefinite material (IM). Although in general all three types of material are capable of amplifying evanescent waves, when the thickness is small, the slab formed by IM offers the best performance in enhancing WPT efficiency. We also propose a tuning method by varying its material parameters to maximize the WPT efficiency. Full-wave simulations of a WPT system equipped with a thin IM slab show that the system efficiency can be enhanced by an order of magnitude, comparing with the conventional design. As an example implementation of the thin IM slab, the capacitively loaded split-ring resonators (CLSRR) are considered, and the enhancement of WPT efficiency shows a similar performance to the ideal homogeneous IM slab.