Expanding bandwidth of class-F power amplifier with harmonic structures

This paper presents a methodology for designing compact broad-band RF power amplifiers with stretched harmonic tuning output networks. Rather than adopting a conventional output matching for wideband class-F operations, which is bulky in its size, this paper suggests a simpler way to achieve small-sized but wideband class-F operation. The proposed idea is achieved by stretched harmonic tuning circuits, and is verified by implementing a power amplifier at 1.9 GHz with a 10 W GaN HEMT transistor. It showed 50 % of drain efficiency over the bandwidth of 250 MHz with significantly smaller size than the conventional continuous-mode class-F designs. The maximum output power is 14.45 W and a peak gain is 12.9 dB at 1.9 GHz.