Analysis and design of asymmetric mid-range wireless power transfer system with metamaterials

Abstract

In a wireless power transfer (WPT) system, the power transfer efficiency (PTE) decreases sharply with the increase in transfer distance. Metamaterials (MMs) have shown great potential to enhance PTE in mid-range WPT systems. In this paper, we propose two MM slabs of a 3 × 3 array to enhance the magnetic coupling. The MM unit cell was designed by using square spiral patterns on a thin printed circuit board (PCB). Moreover, the asymmetric four-coil WPT system was designed and built based on the practical application scenario of wireless charging for unmanned devices. The simulation and experimental results show that two MM slabs can enhance power transmission capability better than one MM slab. By optimizing the position and spacing of two MM slabs, the PTE was significantly improved at a mid-range distance. The measured PTEs of a system with two MM slabs can reach 72.05%, 64.33% and 49.63% at transfer distances of 80, 100 and 120 cm. When the transfer distance is 100 cm, the PTE of a system with MMs is 33.83% higher than that without MMs. Furthermore, the receiving and load coils were integrated, and the effect of coil offset on PTE was studied.