Electronically tuned UHF power amplifier

This electronically tunable UHF power amplifier (PA) is based upon a gallium-nitride (GaN) HEMT operated in class C. The gate input is tuned by two arrays of varactor diodes. The drain output is tuned by a three-stub tuner whose stub lengths are controlled by pin diodes. From 325 to 800 MHz (factor of 2.5:1), the PA delivers an output of 34 to 50 W with an overall efficiency of 47 to 65 percent.