Wide-Bandwidth Power-Combining and Inverse Class-F GaN Power Amplifier at X-Band

In this paper, we present a wide bandwidth power amplifier (PA) utilizing a Marchand balun to achieve power combining and inverse class-F (class-F^-1) matching. We have used a 4-to-1 balun and its out-of-band characteristics to achieve matching at the second and third harmonic for differential class-F^-1 operation. Thus, the balun simultaneously acts as a combiner and harmonic matching network. The experimental results demonstrate that the prototype PA achieves an output power of 41.5 dBm at the 1-dB compression point (P_{1 dB}), power-added efficiency of 55%, and gain of 10 dB over a fractional bandwidth of 40% from 8 to 12 GHz. Due to the differential operation, the class-F^-1 PA has also achieved a measured second harmonic distortion of -50 dBc.