Wide-Band High-Efficiency GaN HEMT Amplifier Based on Dual-Band Multi-Harmonic Treatments

A 4.5-4.9-GHz high-efficiency GaN HEMT amplifier has been developed based on a dual-band design regarding a multi-harmonic treatment technique considering up to third-order harmonics. To prevent narrowing of the high-efficiency bandwidths due to many reactance control transmission lines connected in cascade for the harmonics, T-shaped stubs which terminate four harmonics at one point on a transmission line were used instead of lambda/4 open-ended stubs terminating the harmonics for each of the reactance control lines. The fabricated GaN HEMT amplifier exhibited a maximum power-added efficiency of 65% and a maximum drain efficiency of 71% at 4.6 GHz with a saturation output power of 36 dBm. In addition, a drain efficiency of more than 60% was obtained over a wide frequency range from 4.52 to 4.94 GHz.