Printed spiral coils with multiloop technique for planar magnetically coupled resonant wireless power transfer system

In this paper, a planar magnetically coupled resonant wireless power transfer (MCR-WPT) system is proposed to achieve high efficiency over a distance by using printed spiral coils with multiloop technique. The multiloop technique of applying several loops with different sizes allows the adjustment of the coupling coefficient depending on the distance between the transmitter and the receiver. It enables the optimum efficiency to be obtained where one of the three loops is selected. The fabricated MCR-WPT system maintains high efficiency across a range of 0–25cm. The efficiency is 46.2% at a distance of 25cm, which is 36% higher than the conventional system. The maximum efficiency is 88.7% at a distance of 10cm.