Compact and Highly Efficient Kilowatt Lumped Push-Pull Power Amplifier for Cyclotron in Radioisotopes Production

R. Tong1, O. Bengtsson2, A. Bäcklund3, and D. Dancila1

Published in:

IEEE Trans. Microwave Theory Tech., vol. 69, no. 1, pp. 723-731 (2021).

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This article presents a very compact highly efficient solid-state power amplifier (SSPA) module at kilowatt level in a push-pull architecture. This SSPA is intended to be used as a modular RF source for a 20 kW cyclotron that operates in the low VHF band for radioisotopes production. For a compact design, a lumped LC balun is adopted instead of a traditional ferrite transformer for the 180° phase shift requirement of the push-pull architecture. Lumped harmonic traps are employed as harmonic tuning to achieve higher efficiency. This implementation enables an ultracompact design realized on a 90 mm×70 mm circuit board. Improved efficiency at reduced output power is achieved through a static supply voltage variation, which gives more than 90% efficiency over a 5 dB output power range. This approach enables considerable energy saving when applied to the whole cyclotron system. The achieved results show that the proposed SSPA with drain supply modulation is a very promising architecture for very high-power RF sources in cyclotrons for radioisotope production.

1 Department of Electrical Engineering, Uppsala University, 75236 Uppsala, Sweden
2 Ferdinand-Braun-Institut, Leibniz-Institut für Höchstfrequenztechnik, 12489 Berlin, Germany
3 GEMS PET Systems AB (General Electric: GE Healthcare), 75228 Uppsala, Sweden

Index Terms:

Drain supply modulation, high efficiency, kilowatt, lumped balun, power amplifier, RF energy.