Highly Efficient Multiband Harmonic-Tuned GaN RF Synchronous Rectifier

This article presents a highly efficient GaN-based harmonic-tuned multiband RF rectifier for wireless power transfer (WPT) applications. The rectifier has been implemented by incorporating a microstrip coupler and a transmission line-based phase shifter to convert a power amplifier (PA) into a synchronous rectifier based on the time-reversal duality principle. The proposed rectifier provides a compact solution for wireless power charging systems while supporting dual-bands. The microstrip coupler is used to derive the gate driving signal for the device, which requires a weak coupling from the input RF signal. The coupler has been characterized separately for wideband operation from 1 to 3 GHz with only 0.3-dB insertion loss. Measurement results show that the rectifier has 77% and 75% efficiencies at 1.17 and 2.4 GHz, respectively, when the input RF power is 10 W. The rectifier shows > 50% efficiency for input power levels down to 1.5 W. To the best of the authors' knowledge, this rectifier presents one of the highest RF-to-dc rectification efficiencies in dual-band operation for a watt-level RF input power.