Metamaterial cavity and RF rectifier for wireless powering system

Two critical components for a wireless charging system of mobile handset, i.e. a metamaterial cavity using artificial magnetic conductor surfaces and a RF rectifier with high-power and high-effieency characteristics, are presented. This wireless charging system demonstrates the advantages of broad bandwidth, small size, long transmitting range, high transferring efficiency and EMI-free feature. To overcome the low breakdown voltage limit of silicon-based Schottky diode, the 1-to-4 series dividing transformer is employed to couple the high input RF power into four differential-type bridge diodes. The proposed rectifier is developed to withstand up to 36 dBm of input power before reaching the breakdown limint of Schottky diode, and their corresponding RF-to-DC power conversion efficiency is 58.9 % at the load resistance 10 Ω and operating frequency 920 MHz.