Dynamic Over-Voltage Operation of a Discrete-Level Supply-Modulated GaN-based RF PA

In this paper an investigation for increasing the peak output power of a GaN-based RF power amplifier (PA) by dynamically operating it at a higher supply voltage is presented. The PA is operated with a high peak-to-average power ratio signal with 100 MHz instantaneous modulation bandwidth and discrete-level (class-G) supply modulation. For the peak power levels the supply voltage is switched by the class-G modulator from 40 to 60 V. This increases the peak output power by 1 dB but has a very low negative impact, since the high-voltage pulses are too short to cause self-heating in the GaN-HEMT device. Modulated measurements with digital predistortion linearization also show a 1 dB increase in average output power without linearity degradation. With this over-voltage operation, the peak output power density of the GaN HEMT can be increased from 4.9 W/mm to 6.4 W/mm.