Investigation of angular log-periodic folded groove waveguide slow-wave structure for low voltage Ka-band TWT

• Main Authors: Wang, Hexin, Wang, Shaomeng, Wang, Zhanliang, Li, Xinyi, Xu, Duo, He, Tenglong, Tang, Tao, Gong, Huarong, Lu, Zhigang, Duan, Zhaoyun, Aditya, Sheel, Gong, Yubin
• Other Authors: School of Electrical and Electronic Engineering
• Format: Article
• Language: English
• Published: 2021
• Subjects: Engineering::Electrical and electronic engineering; Slow Wave Structure; Traveling-wave Tube Amplifier
• Online Access: https://hdl.handle.net/10356/147323
• Institution: Nanyang Technological University

In this paper, a novel angular log-periodic folded groove waveguide (ALFGW) slow-wave structure (SWS) has been investigated theoretically and experimentally for application in Ka-band traveling-wave tubes (TWTs). The dispersion relation for the ALFGW is derived analytically, and the dispersion characteristics are calculated for a Ka-band design. The designed SWS is fabricated using oxygen-free-copper that is silver electroplated. The measured cold-test parameters show good agreement with the simulation results, with S varying from -2.7 dB to -4.8 dB and S better than -13.6 dB over the frequency range of 30-38 GHz. Simulations of beam-wave interactions using a 4850 V and 0.4 A sheet beam with a high aspect ratio of 28:1 indicate an output power of 128 W, corresponding to a maximum gain and electronic efficiency of 18.1 dB and 6.6%, respectively. Due to the log-periodic form, a higher output power, higher efficiency, wider bandwidth, and lower operating voltage are achieved as compared to a TWT based on the conventional folded groove waveguide (FGW) SWS. These results show that the proposed ALFGW SWS has good potential for application in relatively high-power wideband TWTs.