VHF Doherty amplifier with GaN FETs and independent drive-signal control

A VHF Doherty amplifier with independent drive-signal control is presented. An I-Q modulator/up-converter is used to produce the driving signals at a carrier frequency of 144-MHz. The amplifiers of the Doherty transmitter are designed using GaN FETs and lumped-element networks. The carrier amplifier operates in class-B with a drain efficiency of 63% while the peaking amplifier operates in class-C with an efficiency of 73%. Independent drive control allows access to one or both amplifiers at a time controlling their performance individually with amplitude and phase predistortion. This both enhances system linearity and ensures that the peaking amplifier does not consume power during the generation of lower-level signals, further enhancing overall efficiency.