Coherent Power Combining of Four-Way Injection-Locked 5.8-GHz Magnetrons Based on a Five-Port Hybrid Waveguide Combiner

• Published in: IEEE Transactions on Microwave Theory and Techniques Vol. 72; no. 7; pp. 4395 - 4404
• Main Authors: Huang, Heping, Yang, Bo, Shinohara, Naoki, Liu, Changjun
• Format: Journal Article
• Language: English; Japanese
• Published: New York IEEE 01.07.2024; Institute of Electrical and Electronics Engineers (IEEE); The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Efficiency; Electromagnetic heating; Five-port waveguide combiner; Frequency locking; hybrid tee; injection locking; magnetron; Magnetrons; Microwave amplifiers; Microwave antenna arrays; Microwave circuits; Microwave communication; Phase control; Phase locked loops; power combining; Scattering parameters; Waveguides; wireless power transmission (WPT)
• ISSN: 0018-9480; 1557-9670
• DOI: 10.1109/TMTT.2023.3347549

A high-efficiency power-combining method for four-way 5.8-GHz magnetrons based on the external injection-locking technique is presented in this article. The method uses a nonisolated, lossless five-port hybrid waveguide combiner for power combining. Meanwhile, the injection-locking technology has been applied to magnetrons for achieving coherent power combining. The phase fluctuation of the injection-locked magnetron, without the presence of a phase-locked loop, measured nearly ±2.5°. In contrast, when a phase-locked loop was introduced, the phase fluctuation reduced significantly to approximately ±0.5°. This phase accuracy can fully meet the requirements of combining experiments. Four magnetrons worked in injection-locked states without phase-locked loop. The proposed power-combining system is designed, measured, and analyzed. Measurement results show that a high-power-combining efficiency of over 95% is achieved by injection-locked magnetron without PLL, with the best efficiency reaching up to 97.7% with phase control of the injected signals. Experimental results reveal that the magnetron phase-pushing effects and the ripple in high-power dc voltage and current have a minor impact of approximately 4% on the combining efficiency.