| When electronic vacuum devices develop to millimeter wave and terahertz bands,the advantages of Extended Interaction klystron have gradually emerged,and they have been favored and studied in-depth by research institutions at home and abroad.In the high-operating frequency,klystrons have the problems of high frequency loss,small power capacity,and narrow bandwith.Although traveling wave tube has a broad working bandwidth,output power of TWT is too low,which cannot fulfill the demand for high-power MMW sources in space communication systems.EIK possesses great application value in MMW and terahertz bands.Because EIK own the characteristics of both TWT and klystron,it has the properties of high power,broadband,and miniaturization.So it is necessary to study in these aspects in depth.The sheet beam has a larger current and smaller electron density,and the interaction area between the beam and waves is larger,so that the sheet beam EIK can have the potential of higher output power and electronic efficiency than the cyclic beam EIK.This dissertation focuses on the W-band sheet beam EIK,mainly researches on improving working efficiency,and committed to expanding the bandwidth.Designed sheet beam gun and PCM focusing system.The main work are as follows:The fundamental theory and design method of W-band high-efficiency EIK are analyzed in this dissertation.Analyze the influence of the size parameters of the high-frequency structure on the high-frequency characteristics,frequency by simulation software,and provide a reliable basis for the subsequent design and optimization of the high-frequency structure which conforms to high-efficiency EIK,also analyzed the stability and dispersion characteristics of high-frequency structure.The influence of the intermediate cavity frequency tuning,the phase velocity jump technology and the reduction of perveance on the improvement of the electronic efficiency are studied emphatically by simulating beam-wave interaction process.Finally,a high-efficiency EIK was designed with a bandwidth of 125MHz,an output power of 10.22kW,and an electronic efficiency of 13.62%.The main factors affecting the working bandwidth of the EIK are the bunching bandwidth and the transmission bandwidth.The bunching bandwidth can be expanded by adopting interleaved long and short grid,the frequency staggered tuning of the intermediate cavity and the multiple mode switching operation.However,traditional broadband transmission methods are no longer suitable for working in MMW and terahertz bands.In view of the ultra-large bandwidth of the TWT,this paper proposes to use the traveling wave device as the transmission structure of the EIK to expand the transmission bandwidth.Specifically,the T-shaped interleaved double grid is used as the energy transmission structure,and the intermediate cavities use frequency staggered tuning.The results show that when the input power is 0.06W,the output peak power achieves 1253W,the gain is 43dB,the electronic efficiency attains 10%,the-3dB bandwidth achieves 670MHz,and the relative bandwidth is up to 0.7%.The design is suitable for the sheet beam gun of the high-efficiency EIK.The current of 2A is obtained with the working voltage of 38kV.The beam final cross-section is:3.9mm×0.39mm,and the PCM magnetic focusing system was designed for the gun. |
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