TY - JOUR
T1 - Highly efficient microwave power system of magnetrons utilizing frequency-searching injection-locking technique with no phase shifter
AU - Lai, Chao
AU - Zhao, Chaoxia
AU - Li, Kang
AU - Cai, Danli
AU - Zhang, Yi
AU - Yang, Yang
AU - Zhu, Huacheng
AU - Agrawal, Dinesh K.
AU - Slawecki, Tania
AU - Wu, Li
AU - Zhou, Yanping
AU - Chen, Qian
AU - Zhou, Lin
AU - Huang, Kama
N1 - Funding Information:
Manuscript received May 5, 2020; accepted May 11, 2020. Date of publication July 15, 2020; date of current version October 5, 2020. This work was supported by the National Natural Science Foundation of China under Grant 61901286 and Grant 61731013. (Corresponding author: Yi Zhang.) Chao Lai, Chaoxia Zhao, Kang Li, Danli Cai, Yi Zhang, Yang Yang, Huacheng Zhu, Li Wu, Yanping Zhou, Qian Chen, and Kama Huang are with the College of Electronics and Information Engineering, Sichuan University, Chengdu 610017, China, and also with the Key Laboratory of Wireless Power Transmission of Ministry of Education, Chengdu 610064, China (e-mail: yizhang_ee@163.com).
PY - 2020/10
Y1 - 2020/10
N2 - A microwave power-combining technique based on magnetrons has been widely researched to solve the urgent demands for high-power, low-cost microwave sources in microwave industrial applications. To achieve high resultant efficiency, conventionally, injection locking with static frequency is utilized to drag the output frequency of each magnetron source to the exact same frequency, and a phase shifter is required to adjust the output phase of each combining source. In this article, we propose a novel phase shifterless microwave power system with two magnetrons utilizing a frequency-searching injection-locking technique. Coaxial cables with different physical lengths are used to realize phase adjustment under different injection frequencies. By sweeping the injection frequency in a small band, the phase difference between combining signals can be adjusted. Thus, high resultant efficiency can be obtained. When the injection frequency is swept, the phase difference between the output and injection signals has been analyzed theoretically, the phase difference between the different-length coaxial injection cables has also been analyzed. Furthermore, the relationship between the sweeping frequency bandwidth and requirements of the minimum length difference of the coaxial injection cables has been derived and analyzed. Experimental results show that a high resultant efficiency of 94.6% can be obtained with the proposed phase shifterless system. The system could maintain high resultant efficiency even when the free-running frequency and power of one magnetron are changed by adjusting its anode current. The experiments reveal that the proposed method works for different combining sources.
AB - A microwave power-combining technique based on magnetrons has been widely researched to solve the urgent demands for high-power, low-cost microwave sources in microwave industrial applications. To achieve high resultant efficiency, conventionally, injection locking with static frequency is utilized to drag the output frequency of each magnetron source to the exact same frequency, and a phase shifter is required to adjust the output phase of each combining source. In this article, we propose a novel phase shifterless microwave power system with two magnetrons utilizing a frequency-searching injection-locking technique. Coaxial cables with different physical lengths are used to realize phase adjustment under different injection frequencies. By sweeping the injection frequency in a small band, the phase difference between combining signals can be adjusted. Thus, high resultant efficiency can be obtained. When the injection frequency is swept, the phase difference between the output and injection signals has been analyzed theoretically, the phase difference between the different-length coaxial injection cables has also been analyzed. Furthermore, the relationship between the sweeping frequency bandwidth and requirements of the minimum length difference of the coaxial injection cables has been derived and analyzed. Experimental results show that a high resultant efficiency of 94.6% can be obtained with the proposed phase shifterless system. The system could maintain high resultant efficiency even when the free-running frequency and power of one magnetron are changed by adjusting its anode current. The experiments reveal that the proposed method works for different combining sources.
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U2 - 10.1109/TMTT.2020.3006488
DO - 10.1109/TMTT.2020.3006488
M3 - Article
AN - SCOPUS:85092584518
VL - 68
SP - 4424
EP - 4432
JO - IEEE Transactions on Microwave Theory and Techniques
JF - IEEE Transactions on Microwave Theory and Techniques
SN - 0018-9480
IS - 10
M1 - 9141437
ER -