Research On High Efficiency Millimeter Wave Helix Traveling Wave Tube

Traveling wave tubes(TWTs)have considerable competitiveness and wide application in some specific fields such as electronic countermeasures and satellite communication due to their excellent working characteristics such as broadband,high power and high efficiency.Based on the research project of high efficiency millimeter wave helix TWT,this thesis designed a helix traveling wave tube with operating band 26.5GHz-40 GHz.On account of the requirements of broadband and high efficiency,a helix slow wave structure(SWS)with rectangular dielectric rods and fins is designed.In addition,this thesis designed coaxial input structure,ridge loaded waveguide output structure and input/output windows to match the SWS.The beam-wave interaction simulation results are carried out and researched.Some methods to improve the efficiency of TWT are introduced and investigated in this thesis and the design of high efficiency helix TWT is completed.In order to archive the design,the main research methods and contents of this thesis include the following aspects:1.The helix SWS with rectangular dielectric rods and fins is proposed in this thesis.The high-frequency characteristics of helix slow-wave structures with different loading modes are simulated by HFSS and compared.The simulation results show that the helix SWS with rectangular dielectric rods and fins has a broad operating bandwidth and it is easier to machine.The influence of different dimensional parameters on the highfrequency characteristics are compared and the optimum dimensional parameters are selected.2.Based on the designed helix SWS with rectangular dielectric rods and fins,combined with the requirements of the operating waveband and output power in this thesis,the supported coaxial input structure,dual-ridges loaded waveguide output structure and input/output windows are designed and optimized.The simulation results of the optimized high-frequency system show that the reflection parameter of the whole tube keeps below-16 dB and the standing wave ratio is below 1.4 in the frequency band of 26.5GHz-40 GHz,which meets the design requirements.3.The beam-wave interaction effects of the helix TWT under uniform pitch is simulated in the software ORION.The working parameters are optimized and determined according the simulation results.In order to improve the electronic efficiency of the traveling wave tube,pitch tapering technology is used in this thesis.Forms of negativepositive-negative hopping,negative-positive-negative-negative hopping and grading are tried.The best simulation results are as follows: With the optimum working voltage 9350 V and the beam current 140 mA,the electronic efficiency of the negative-positivenegative-negative hopping tube is over 17.8%,and has an increase over 3.6% compared with the tube with uniform pitch.The electronic efficiency of the grading tube is over 19.5%,and has an increase over 5.3%.4.An axisymmetric five-stage depressed collection is designed by CST software.The simulation results of final optimized collector show that collector efficiency can reach 89.43%,which meets the design specifications.