Second Harmonic Treatment Technique for Bandwidth Enhancement of GaN HEMT Amplifier With Harmonic Reactive Terminations

Source and load impedance conditions for the second harmonics have a great influence on the efficiency of amplifiers. The bandwidth of high-efficiency operation is limited, since efficiency is drastically degraded due to a slight change in source-side second harmonic impedance from the optimum point. For this reason, to avoid steep efficiency degradation, a source-side second harmonic impedance control is introduced. In addition, a harmonic treatment network, which reduces the influence on matching-network design, is also described here. A fabricated GaN HEMT amplifier has achieved a maximum power-added efficiency (PAE) of 79% with a saturated output power of 48.0 dBm at 2.02 GHz. The amplifier has also achieved a high-efficiency characteristic of more than 70% PAE in the frequency range from 1.68 to 2.12 GHz.