R. Tong¹, O. Bengtsson², J. Olsson³, A. Bäcklund⁴, and D. Dancila¹

Published in:

IEEE Trans. Microwave Theory Tech., vol. 70, no. 2, pp. 1401-1409 (2022).

Abstract:

This article presents a highly efficient solid-state kilowatt level power amplifier implemented in laterally-diffused metal-oxide semiconductor (LDMOS) technology in a single-ended architecture. It is designed for power-combining systems of radioisotope production cyclotrons. To achieve high efficiency at high power as well as output power back-off (OPBO), waveform engineering is adopted to evaluate the performance of alternative efficient narrowband modes of operation in saturation with various drain supply voltages. Based on a large signal model, a multimode with Class-J/Class-F^-1 properties is found to enable a flat 10 dB OPBO-range exceeding 90% drain efficiency. The implemented solid-state RF power amplifier (SSPA) module based on this waveforms analysis achieves 93% efficiency at 980 W output power and more than 90% efficiency over a measured 5 dB OPBO-range. Drain supply-controlled OPBO is shown to improve the efficiency by 15%-points at a 75% full power rating of the system, which is the estimated long-term average output power. The proposed operational mode will enable considerable energy saving for 24-7 cyclotron operation and is a very promising approach for other kilowatt narrowband applications with the need for efficient OPBO operation.

Index Terms:

Drain supply control, high efficiency, kilowatt, laterally-diffused metal-oxide semiconductor (LDMOS), power amplifier, RF energy.

Copyright © 2021 IEEE. Personal use is permitted, but republication/redistribution requires IEEE permission. See https://www.ieee.org/publications/rights/index.html for more information.

Full version in pdf-format.