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The metamaterial (MA) has been proved to enhance the efficiency of the wireless power transfer (WPT) system considerably in many studies. This study presents an equivalent circuit model using a qualitative and even quantitative simple explanation for the behaviour of MA in WPT. For this purpose, the electromagnetic field simulation of WPT system with MA is carried out by the high-frequency structure simulation three-dimensional electromagnetic simulator. Also, the authors propose the circuit structure of the WPT system based on MA and explore its characteristics by numerical calculation and advanced design system simulation. The transmission efficiency of the simulator is characterised by reflection coefficient here. Although some methods, such as interference theory, transmission line circuit model, and effective medium theory, have been put forward to explain the physics mechanism of WPT system with MA, some of reactive parameters and the basic physical interpretation have not been expounded clearly so far. Differ from the existing theoretical model, the proposed approach focuses on the effect of the system parameters of MA and transfer coils on the transfer characteristics and is beneficial to the analysis of the complicated system. [ABSTRACT FROM AUTHOR]

Featured Application: The proposed Wireless Power Transfer (WPT) system with metamaterials using Class-E amplifier can be applied for mid-range high-power energy transfer. In this paper, a mid-range wireless power transfer (WPT) system based on metamaterials (MMs) has been presented. It has been shown that the MMs are positioned in the WPT system to focalize the electromagnetic field for distance enhancement and efficiency improvement theoretically and experimentally. The MMs were fabricated by using a single layer printed-circuit board (PCB) with the negative magnetic permeability, μr. An applicable impedancetuning technology was implemented by changing the operating distance between the drive (load) resonator and the internal resonator, which can achieve the optimal load of the system. In addition, the Class-E RF (radio frequency) power amplifier is firstly proposed as the high frequency excitation source of the WPT system based on the MMs due to its simple design and high efficiency. The proposed technology can achieve efficiency improvements of 4.26% and 9.13% at distances of 100 cm and 200 cm around the 2.80 MHz WPT system with the MMs, respectively. Specially, it is worth mentioning that the system efficiency is enhanced by 18.58% at 160 cm. The measured results indicate the WPT system based on the MMs can assure a stable output power of 5W at a transfer distance of 200 cm. [ABSTRACT FROM AUTHOR]