Study On G-Band Broadband Sheet Electron Beam Traveling Wave Tube

In recent years, traveling wave tubes(TWTs) as common electronic vacuum devices in microwave and millimeter bands, have a very wide application in many areas, such as communications, millimeter wave radars, radiation measurements, electronic warfare and so on. The research of TWTs gradually ranges from the microwave band to the millimeter wave band, even to the terahertz wave band. On one hand, the most important part of TWT is the slow wave structure, whose high frequency characteristics can directly affect overall TWT’s performance. Thus, a wide variety of slow wave structures have sprung up. On the other hand, compared with conventional circular electron beam, the sheet electron beam can carry bigger current and thus make the TWT have the advantage of miniaturization and high output power.The main task of this thesis is to design a broadband TWT which works at G band. Firstly, using the W-band staggered double vane SWS as the basis structure, the sizes of a staggered double vane SWS working at G-band are presented this thesis. Secondly, according to microwave field distribution of the staggered double vane SWS, an improved SWS, which can improve high frequency characteristics of SWS, is proposed. Thirdly, according to the structural features of slow wave circuit, two input-output coupler and a transition structure between the input-output coupler and SWS are designed in this thesis. Finally, this thesis combines the main parts together to build a sheet beam electron TWT whose central operating frequency is in G-band. This thesis is divided into three parts, as follows:(1) The study on SWS. We get a G-band normal staggered double vane SWS’s size by calculation and optimization. Under this basis, we propose a modified staggered double vane SWS, which is compared with the former.(2) The study on the input-output coupler. At first, a transition structure which is suitable for a staggered double vane SWS is proposed. Then, two input-output couplers are designed, which are double-ridge waveguide with ridge height gradient and multi-sector gradient waveguide respectively. At last, It’s found that both structures have good transmission characteristics through simulation and analysis.(3) The study on G-band TWT. Firstly, we determine the electron beam emitter area and the density of magnetic field. Secondly, in order to solve TWT’s self-excited oscillation problem, a centralized attenuator stack is designed. With adding the attenuator stack, TWT’s particle simulation calculations are completed in this thesis. Thirdly, we study the affection of the number of periods of the slow wave structure against TWT’s output power. Finally, the performance of the G-band sheet electron beam TWT is analyzed.