Efficiency improvement for RF power amplifiers by employing harmonic injection at the input

This paper presents the experimental analysis of the injection of harmonic signals at the gate of a RF power transistor. The harmonic injection leads to an optimized shape of the waveforms at the inner transistor resulting in an improvement of the efficiency performance. A triplexer, allowing injecting the second as well as the third harmonic into the transistor is designed for these experiments, although in the present work only the second harmonic is used. At 2.6 GHz, the experimental results show that for a 25 W GaN HEMT RF power device, the drain efficiency can be improved by up to 6%.