In this paper, a three-dimensional diagonalized transmitting coil (DAG-Tx) structure is proposed for improving angular free-positioning in a wireless power transfer (WPT) system. The magnetic field distribution is analyzed to transfer power effectively to a rectangular receiver (Rx) in spatial freedom. A mathematical method is adopted to calculate mutual inductance between the proposed Tx and rectangular Rx. In addition, the inductor-capacitor-capacitor (LCC) and capacitor-capacitor (CC) impedance matching networks are proposed and implemented on the Tx and Rx sides to improve the power transfer efficiency (PTE). Experimental results show that the WPT system can transfer with PTE of up to 80% in a face-to-face transmission distance of 100 mm. Moreover, the PTE maintains above 70% by rotating Rx from 0 o to 135 o around three coordinate axes.

This letter presents a hybrid transmitting coil (HBRTx) for angular-freedom wireless power transfer. The rotating magnetic field is analyzed and obtained in different charging planes by three coil configurations to adapt the Rx rotations. Furthermore, the CLC (capacitor-inductor-capacitor) impedance matching networks (IMN) are implemented on the Tx and Rx side to match the coil impedance to the source and load impedance and improve the power transfer efficiency (PTE). Experimental results show that our proposed WPT system can supply power effectively to a distance of up to 51 mm with a maximum PTE of 80.35%. Moreover, the PTE maintains above 70% regardless of the Rx’s rotations around Ox, Oy and Oz axes, which shows the system’s flexibility and mobility.