Development of high power 20 dB directional coupler for Ion Cyclotron Resonance frequency system of Tokamak

Abstract

ABSTRACT This article presents the design and fabrication of 20 ± 0.3 dB directional coupler having 2 kW power handling capability in the frequency range of 140–200 MHz. The developed coupler has an important application in the prototype of the Ion Cyclotron Resonance Frequency (ICRF) system of Tokamak. The directional coupler used to couple the forward and reflected power for measurement and provide the feedback to the existing matching network responsible for protecting the high-power RF source. The developed coupler is compact in size, robust, and capable of handling 2 kW, continuous wave (CW) RF power. This paper also analyses the dielectric breakdown strength using electric field distribution inside the coupler, and the average power handling capability is determined using numerical analysis. The test results using Vector Network Analyser (VNA) are obtained as, the coupling flatness of 20 ± 0.3 in 140–200 MHz frequency range, return loss and isolation are −30 dB and −35 dB, respectively. The work presented in this paper is helpful for the development of high-power coupler in radio frequency (RF) range and may be applied in various applications such as RF Plasma, Radar, navigation, satellite, and research, etc.