Abstract
In this paper, an improved U-shaped microstrip meander-line slow wave structure (SWS) for low-voltage high-efficiency miniature G-band traveling wave tubes (TWT) is presented. To increase the TWT efficiency, the synchronization between electromagnetic (EM) wave and the electron beam should be maintained. Since the velocity of the electron beam passing along the tube is gradually reduced, the EM wave phase velocity should be also slowed down. Therefore, we gradually lengthen the width of meander-line to make longer the EM wave path for decreasing the EM wave phase velocity. Meanwhile, a simple analysis for calculating the dispersion properties of this kind of SWS is presented and the analytical results are compared with those obtained from simulation using CST-microwave studio. In addition, the scattering parameters of the SWS and the interaction between electron sheet beam and the electromagnetic fields are investigated with the help of CSTmicrowave studio and CST-Particle Studio, respectively. Our study shows that the G-band TWT is capable of delivering several tens of watts output power with 3-dB frequency bandwidth of 17GHz, ranging from 210GHz to 227GHz. Additionally, the peak output power is about 50 W with the corresponding gain of 40 dB at 218 GHz.
Keywords: Beam-wave interaction, microstrip meander line (MML), slow-wave structure (SWS), transfer matrix, travelingwave tube (TWT).
Graphical Abstract
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