A mu‐zero resonator with an effective zero permeability is presented for efficient wireless power transfer (WPT) using resonant inductive coupling (RIC). An N‐cell mu‐zero resonator is modified to maintain a fixed size and resonance frequencies that are important design factors of WPT using RIC because they are related to the magnetic coupling coefficient and Q‐factor. The resonator has many resonant modes with the extraordinary phenomena of metamaterials such as an infinite wavelength wave and backward‐wave propagation. An analysis of the resonant modes and a design of the N‐cell mu‐zero resonator is performed by theory and full‐wave simulation based on a dispersion diagram and magnetic field distribution. The power transfer efficiencies of one‐cell and two‐cell mu‐zero resonators are simulated and measured. To optimise the transfer efficiency of the WPT system using the mu‐zero resonance (MZR) mode, which supports stronger coupling than the other modes, an equivalent circuit of mu‐zero resonator is analysed for a high Q‐factor. The theoretical, simulated, and measured results of a one‐cell resonator with optimum values confirm that an efficient WPT system can be successfully designed by the MZR mode.

In this paper, various spiral zeroth-order resonators are proposed for wireless power transmission. Since a zerothorder resonance(ZOR) mode of meta-material transmission lines has the characteristic of an infinite wavelength, its frequency is independent of physical length. Also, to obtain high transmission efficiencies high-Q resonators and strong coupling coefficient between coupled resonators are required. Therefore, the resonators consist of spiral inductor and lumped capacitor to use the ZOR mode and they are optimized via parametric study and circuit analysis for a high-Q resonator design. The optimized resonators are simulated and compared with a conventional spiral resonator and one of them was fabricated and measured. The fabricated one has a dimension of 20 cm×20 cm×8 cm(0.009 λ0×0.009λ0 ×0.004 λ0) and the transmission efficiency of 80 % is measured at 13.56 MHz at transmitted distance of 40 cm.