Wireless Power Transfer System with High Misalignment Tolerance for Bio-medical Implants

A hybrid array resonator structure for Wireless Power Transfer (WPT) is presented. The proposed structure exploits an array of four identical coils surrounded by a larger coil to generate uniform magnetic field. As a result, a nearly constant and high efficiency is achieved over a large misalignment region. The quasi-uniform magnetic field distribution of the proposed structure is analytically derived. For demonstration, one prototype operating at 40 MHz is designed for implantable medical devices (IMDs). According to experimental results, the developed WPT system exhibits an efficiency of 53% when the receiver and the transmitter are aligned, while the efficiency is 44% when they operate with a lateral misalignment of 10 mm. As per a conventional WPT system using a single spiral resonator as transmitter and receiver, the efficiency is 47.2% in aligned condition, while, it is 30.5% for a 10 mm lateral misalignment. The reported results demonstrate that the proposed design approach provides a high misalignment tolerance. This represents an attractive future for applications, such as the recharge of embedded devices, where the alignment between the transmitter and the receiver is difficult to guarantee.