Abstract
This paper proposes a class-F synchronous rectifier using an independent second harmonic tuning circuit for the power receiver of 2.4 GHz wireless power transmission systems. The synchronous rectifier can be designed by inverting the RF output port to the RF input port of the pre-designed class-F power amplifier based on time reversal duality. The design of the class-F power amplifier deploys an independent second harmonic tuning circuit in the matching networks to individually optimize the impedances of the fundamental and the second harmonic. The synchronous rectifier at the 2.4 GHz frequency is designed and implemented using a 6 W gallium nitride high electron mobility transistor (GaN HEMT). Peak RF-dc conversion efficiency of the rectifier of 69.6% is achieved with a dc output power of about 7.8 W, while the peak drain efficiency of the class-F power amplifier is 72.8%.
Highlights
As interest increases in wireless power transfer techniques and RF energy harvesting systems for various mobile/wearable or wireless sensor applications, highly efficient RF-dc converters or rectifiers are rapidly growing in importance [1,2,3,4]
The high-power GaN HEMT [10] can be an effective choice for the synchronous rectifier design, due to its high-power and high-frequency switching capabilities [11]
We propose a class-F synchronous rectifier employing an independent second harmonic tuning circuit that uses a GaN HEMT with integrated coupler and phase shifter on a module
Summary
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. These previous works employed an external coupler and phase shifter to supply the RF signal to the gate They employed harmonic control circuits that could not be tuned without disturbing the fundamental impedance of the matching network. We propose a class-F synchronous rectifier employing an independent second harmonic tuning circuit that uses a GaN HEMT with integrated coupler and phase shifter on a module. With the ability to independently tune the fundamental and second harmonic impedances of the proposed circuits, it becomes easier to experimentally achieve high efficiency and high output power of the power amplifier and the rectifier, where fine tuning after implementation is inevitable, due to the error in the large-signal model of the transistor, and inaccuracy in the RF simulation of the passive circuits. Experimental results are presented and compared to the results of previous work
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