Recent Progress on Design Method of Microwave Power Amplifier and Applications for Microwave Heating


IEICE TRANSACTIONS on Electronics   Vol.E103-C    No.10    pp.404-410
Publication Date: 2020/10/01
Publicized: 2020/03/19
Online ISSN: 1745-1353
DOI: 10.1587/transele.2020MMI0002
Type of Manuscript: Special Section INVITED PAPER (Special Section on Microwave and Millimeter-Wave Technologies)
Category: Microwaves, Millimeter-Waves
GaN power amplifier,  pulse-mode operation,  active load-pull,  microwave heating,  frequency and phase control,  medical instrument,  

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Recently, GaN devices are often adopted in microwave power amplifiers to improve the performances. And many new design methods of microwave power amplifier were proposed. As a result, a high-efficiency and super compact microwave signal source has become easily available. It opens up the way for new microwave heating systems. In this paper, the recent progress on design methods of microwave power amplifier and the applications for microwave heating are described. In the first, a device model of GaN transistor is explained. An equivalent thermal model is introduced into the electrical non-linear equivalent device model. In the second, an active load-pull (ALP) measurement system to design a high-efficiency power amplifier is explained. The principle of the conventional closed-loop ALP system is explained. To avoid the risk of oscillation for the closed-loop ALP system, novel ALP systems are proposed. In the third, a microwave heating system is explained. The heating system monitors the reflection wave. Then, the frequency of the signal source and the phase difference between antennas are controlled to minimize the reflection wave. Absorption efficiency of more than 90% was obtained by the control of frequency and phase. In the last part, applications for a medical instrument is described.