Research On G-band Folded Waveguide Traveling Wave Tube

There is a huge demand for terahertz technology in broadband communication,medical imaging,non-destructive testing,etc.,and the current problem that limits the development of terahertz technology is the lack of terahertz radiation sources.Folded waveguide traveling wave tube has the advantages of wide frequency band,high power and easy processing,and it is one of the choices for the development of terahertz sources.The low frequency band of the G-band in the terahertz frequency band is an atmospheric window frequency band with practical application value,which has attracted the attention of many scholars at home and abroad.In this thesis,the G-band folded waveguide traveling wave tube is mainly studied,and the operating frequency is 214-224 GHz.The G-band folded waveguide traveling wave tube is designed and processed.The purpose is to verify the design scheme through testing and provide a certain reference for subsequent corresponding theoretical research.The main work of this thesis includes:1.Based on the working parameters of the electron gun,Opera-3D software is used to design a circular injection electron gun working in the G-band;according to the focusing requirements,a matching periodic permanent magnet focusing system is designed;finally,the electron gun and the periodic permanent magnet focusing system are jointly built.The design of the electronic optical system of the G-band folded waveguide traveling wave tube is completed.2.Using the equivalent circuit theory to analyze the dispersion and coupling impedance characteristics of the slow-wave structure,a single-segment folded waveguide slow-wave structure is designed by using FWGTWT4.0 software.The output power is greater than 11.9W and the gain is greater than 27.8d B,the CST software was used to calculate the note-wave interaction to verify the design scheme,and the HFSS software was used to design the energy transmission window and transition waveguide that matched the slow-wave structure.3.Process and cold test each part of the single-segment folded waveguide traveling wave tube,complete the whole tube assembly and thermal test,and the test result shows self-excited oscillation.4.Based on the previous experience of pipe making,the two-stage folded waveguide high-frequency system scheme was redesigned by using the attenuator.The output power is greater than 15 W and the gain is greater than 30.63 dB within the operating frequency range of 214-224 GHz,and the phase speed jump technology is used.Optimized design.5.Process the two-section folded waveguide traveling wave tube,assemble the whole tube after passing the cold test,build a test platform,test the flow rate,output power and gain of the sample tube,record and analyze the experimental results.