Research On D-band Folded Waveguide Traveling Wave Tube

The terahertz frequency band belongs between microwave and infrared,and has many advantages,especially with the development of terahertz technology in recent years,it has huge development prospects in the fields of communication,biomedicine,military,aerospace and astronomical observation.However,due to various technical reasons,especially the lack of terahertz sources with moderate power and stable and reliable performance,this undoubtedly greatly limits the promotion of terahertz technology applications.Therefore,finding a terahertz source with higher power and wider frequency band has become the focus of research in domestic and foreign research institutions.As the operating frequency of the traveling wave tube enters the terahertz frequency band,the size of the slow-wave structure becomes very small due to the influence of the size co-transition effect.and other issues,it has been difficult to meet the requirements.In recent years,the slow-wave structure of folded waveguide has been proposed,which has made it possible to develop a traveling wave tube in the terahertz band.Pay close attention and are widely used in the terahertz field.This thesis mainly studies the folded waveguide traveling wave tube in the D-band,and the working frequency band belongs to the terahertz band.The goal is to design and process a traveling wave tube with an operating frequency of 152?165GHz and an output power greater than 10 W.The main contents of this thesis are:1.Firstly,the method of equivalent circuit is used to theoretically deduce the slowwave structure of the folded-waveguide traveling wave tube,and then the HFSS software is used to study the influence of various structural parameters of the slow-wave structure on the high-frequency characteristics.2.Use the FWGTWT software to simulate the injection-wave interaction of the traveling wave tube.Through the simulation results and the study of high frequency characteristics,an optimization process is designed.The simulation results show that the operating frequency is 152?165GHz,the maximum output power is 26.02W;the maximum gain is 48.04 d B,and the corresponding output power is 19.08W;the minimum gain is 28.02 d B,and the corresponding output power is 25.3W.Finally,the slow-wave structure is simulated and verified by CST,which proves the feasibility of the scheme.3.Use HFSS software to simulate and optimize the transmission system that matches the slow-wave structure.This system includes input and output windows,transition waveguides,and attenuators.The input and output window structure is a box-shaped window with a cone,and the voltage standing wave ratio within the operating frequency is less than 1.2.The transition waveguide adopts a linear gradient structure,and the voltage standing wave ratio is less than 1.03.The attenuator simulation results show that the VSWR is less than 1.45.The transmission system meets the design requirements.4.The slow-wave structure and transmission system were processed and cold-tested,and the cold-test results reached expectations.After that,the assembly,exhaust and other steps of the traveling wave tube were carried out,and the thermal measurement experiment was carried out.The experimental results show that the operating frequency is 148?156GHz,the maximum output power is 15.4W,and the maximum gain is 48.37 d B.The reasons for the difference between the experimental results and the simulation results are summarized to provide experience for later pipe making.