A Sandwich Structure for Cost-Effective Printed-Circuit-Board Wireless Power Resonator

This paper presents a cost-effective and high-performance design of printed-circuit-board (PCB) wireless power resonators. Unlike traditional PCB resonators that have inherent parallel LC configuration, the new PCB resonator structure can be flexibly configurated as either a parallel LC or a series LC resonator. Instead of using expensive high-frequency PCB materials to reduce the dielectric loss, we propose to use a sandwiched structure to form a low-loss resonant capacitance. The sandwiched structure comprises two layers of variable trace width PCB inductors and one layer of low-loss dielectric. Due to the utilization of low-loss dielectric, the displacement current is "redirected" from flowing through high-loss PCB substrate to low-loss dielectric. In turn, it is possible to achieve high quality factor at the designated resonant frequency with cost-effective PCB materials such as FR-4. The principles and design considerations to reduce inter-capacitance of the PCB resonators are discussed. Hardware prototypes are built, and the comparative study shows that the proposed design method can significantly increase the quality factor and transmission efficiency of wireless power resonators.