This paper presents the first implementation of hybrid 8.8-9.6 GHz X-band class J power amplifier (PA) designed with a GaN HEMT power transistor. High efficiency power amplifiers suffer from nonlinear performance and relatively low bandwidth. The proposed high efficiency class J power amplifier provides larger bandwidth and more convenient linearity performance. The class J PAs should have appropriate matching networks at second harmonic of fundamental frequency which cannot easily realize for high frequency hybrid PAs. In the proposed Class J PA, second harmonic matching network was achieved by using low parasitic GaN HEMT power transistor and precise modeling of transmission lines and passive elements up to 20 GHz. The optimum dimensions of matching networks are determined by employing optimizing algorithm. This PA achieves 14 dB power gain over the frequency range of 8.8-9.6GHz. Drain efficiency and power added efficiency are about 67% and 58% at 9.3 GHZ, respectively that is about 5% higher than class AB X-band power amplifier that is implemented in similar condition.

Keywords