GaN transistor large-signal characterization under multi-frequency excitation

Transmitters for high peak-to-average power ratio communication, including Doherty, outphasing, and envelope tracking, are increasingly using supply modulation to improve efficiency. This paper describes a technique to measure multi-frequency excitation of a transistor under supply modulation conditions. The measurement setup is used to characterize GaN transistors in large signal operation at X-band with 1-500MHz low frequency excitation on the drain and is useful for supply modulator design.