| Among all kinds of electronic vacuum devices,traveling wave tube(TWT)is one of the most important microwave tubes,which is widely used in military radar,electronic countermeasures,communication satellite and other fields because of its high output power and wide operating frequency band.TWTs can be divided into two main categories: helix TWTs and coupled-cavity TWTs.Helix traveling structures are widely used in medium and small power TWTs because of its very wide frequency band characteristics.However,because the dielectric clamping rod must be used between the helix and the sub-shell,the heat dissipation ability of helix is poor,which limits its output power.However,due to its large size and all-metal structure,coupled-cavity traveling wave tube(CCTWT)has a strong thermal dissipation capability,so it can obtain a larger output power,which is the representative of high-power TWT.In recent years,folded waveguide TWTs,which have developed rapidly,can be regarded as a distortion of coupled-cavity TWTs.Because they have the advantages of both high power and wide bandwidth,and are very easy to fabricate and assemble,they have wide application prospects in millimeter wave and terahertz band.In this paper,Ka-band high-power coupled-cavity traveling wave tube is studied.Slow-wave structure,electron gun,transmission system and other key components are designed.Some components are processed and tested.The aim is to generate more than 5 kW power output in 33-37 GHz band.In addition,two improved schemes are proposed to improve the output power of a new vacuum terahertz source,HHTWT,in the 340 GHz band.The main contents of this paper are as follows:1.The coupled cavity slow wave structure and its related theory are introduced in detail.The influence of various parameters of slow wave structure on its high frequency characteristics is analyzed,and the specific size parameters are determined.2.The electron gun and transmission system matching with the coupled-cavity TWT are designed and simulated.The dual arc transition waveguide and energy transmission window are fabricated and tested.We chose the common Pierce grateless electron gun.The working voltage of the gun is 28 kV,the working current is 2.5 A,and the radius of the electron beam channel is 0.8 mm.The input and output structures are connected with standard waveguides by a step impedance converter.3.The beam-wave interaction process of two coupled cavity slow-wave structures is analyzed in detail.Firstly,the characteristics of power,efficiency and bandwidth are obtained by using the non-linear beam-wave interaction software independently developed by the research group.Then,the particle simulation of the whole tube is carried out by using CST to demonstrate the feasibility of the design.The simulation results show that the two structures can generate 6.5-10.47 kW and 6.1-9.7 kW output power in 33-37 GHz band,respectively.4.This paper introduces the high-order harmonic frequency-doubled traveling wave tube proposed by our research group,and proposes two improved schemes of terahertz double-beam high-order harmonic cascaded traveling wave tube with different structures in view of its low power.CST simulation results show that when input the W-band signal of 84.5-87.5 GHz at 100 mW,the four-fold terahertz output signals with power of 200-923.3 mW and 600-970 mW can be obtained respectively. |
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