| Vacuum electronic device is a device that uses charged particles to interact with electromagnetic waves in a vacuum environment and converts the moving energy of charged particles into electromagnetic energy for output.In recent years,with the development of vacuum electronic devices in military applications to high frequency band and miniaturization,the size of devices and the radius of electron beam channels gradually decrease,and the current also decreases,which severely limits the output power.Usually,the smaller the size of the device,the more difficult it is to process.Higher requirements are put forward for the accuracy of assembly.At the same time,small size devices increase the difficulty of focusing electron beams.In this case,the band beam vacuum electronic devices show great advantages in high frequency microwave applications.The planar microstrip slow-wave structure is a two-conductor slow-wave structure,which is different from the traditional helix slow-wave structure.Besides the advantages of good bandwidth,small size,easy processing,good heat dissipation and low working voltage,it can interact with banded electron beams with large width-height ratio without designing other electron beam channels.The main research contents of this thesis are as follows:(1)The X-band microstrip slow-wave structure traveling wave tube is studied.Firstly,the HFSS eigenmode solver is used to analyze the high frequency characteristics of slow wave structure,and the high frequency structure is designed according to the design requirements of low voltage and small size.Then the input/output coupling structure of coaxial rotating rectangular waveguide is designed,and the transmission characteristics of the whole slow wave system are simulated.In the frequency band from 8 GHz to 12 GHz,S11 is below-18 dB and S21 is between-1 dB and-2 dB.Next,CST is used to analyze beam-wave interaction.The results are as follows: in the 8-12 GHz band,the working voltage is 6.5 kV,the current is 50 mA,the maximum output power is 56 W at 10.8 GHz,the electronic efficiency is 16.3%,and the maximum gain of the structure is 19.1 dB.(2)Processing the designed slow-wave structure and exploring a series of assembly test schemes.Firstly,Ti-Ag-Cu solder was used to encapsulate the structural components.After testing the assembly structure,it was found that the transmission was poor.After that,the structure of the microstrip line is improved,and the copper plating process is added.After welding,the microstrip line is cut twice.The test data obtained is better than that of the former.Finally,the structure is optimized again,and the transmission characteristics meet the practical standards.(3)An electronic optical system for X-band microstrip slow-wave structure traveling wave tube(TWT)is studied and designed.The cathode and anode structure of Pierce electron gun was modified,elliptical cathode and focusing pole were adopted,and the electronic gun with 6.5 kV voltage,50 mA current and 7 mm x 0.3 mm cross section at the waist of electron beam was designed by CST tracking studio.Finally,a focused band electron beam periodic tangent(PCM)focusing system is designed,and the flow rate of electron beam in slow wave structure is 100% by simulation. |
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