Compact and Highly Efficient Lumped Push-pull Power Amplifier at Kilowatt level with Quasi-static Drain Supply Modulation

This paper reports a very compact highly efficient solid-state kilowatt power amplifier (SSPA) design in a push-pull architecture. This SSPA is used as an RF source for cyclotron application at low VHF band. In this work, a lumped LC balun instead of a traditional ferrite transformer is adopted, for it realizes 180 phase shifting to implement push-pull architecture and compact design purpose. This design realized in a compact circuit of only 90 mm × 70 mm. In 24.5-27 MHz band, measured results show more than 960 Watt output power with more than 83% efficiency, it also achieves 89% efficiency with 1150 Watt output power at 26.5 MHz. A quasi-static drain supply modulation success to realize more than 90% efficiencies over more than 5 dB back-off power region. The achieved results show that this design with drain supply modulation is a very promising architecture for very high power RF source design.