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 structure, such design is used for an RF source of particle accelerator in low VHF band. In this work, lumped LC balun instead of traditional ferrite transformer, is adopted here for good 180° phase shifting to push-pull structure and compact design purpose. Finally, such design realized in a compact 90mm × 70mm circuit. In 24.5-27 MHz band, measured results show it achieves more than 960 Watts output power with more than 83 % efficiency, especially it achieves about 89 % efficiency with 1150 Watts output power at 26.5 MHz. Meanwhile, collaborating with measurement bench, quasi-static drain supply modulation also 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.