High efficiency GaN HEMT class-F synchronous rectifier for wireless applications

In this paper, experimental results are shown for a synchronous class-F RF to DC rectifier. The rectifier design is obtained by transforming a class-F amplifier into a rectifier using the theory of time reversal duality. The amplifier and rectifier are tested under identical source power conditions to demonstrate the duality between the circuits. A 10W Cree HEMT device is used in the designs at a frequency of 985 MHz. The class-F amplifier delivers 8.3W with an efficiency of 77.5% for a DC source power of 10.7W. The time reversed dual, a class-F rectifier, delivers 8.7W of DC load power for a RF input source power of 10.7W with an efficiency of 81.3%. The rectifier circuit has slightly higher efficiency than the amplifier and lower losses in the rectifier are attributed to device operation in both quadrants I and III compared to an amplifier which operates exclusively in quadrant I. The rectifier has a peak output power of 11.3W with an efficiency of 78% and this is the highest reported power for a synchronous RF class-F amplifier.