Experimental Research On W-band Sheet Electron Beam Traveling Wave Tube

Travelling-wave tube(TWT)is one of the most widely used microwave vacuum devices because of its wide band and high gain.With the rapid advancement of military industry,the demand for wide operating band,large output power and high operating frequency of microwave techniques becomes more and more active.When the operating frequency increases,the size of the high-frequency structure becomes smaller and the loss increases because of the size effect.Moreover,the increase of the current density makes it difficult for the circular electron beam to focus.Sheet beam traveling wave tube(TWT)is a kind of high-power vacuum electron devices(VEDs)which operates in millimeter wave and sub-millimeter wave spectra.Compared with the traditional circular electron beam,the sheet electron beam has a larger cross-sectional area,it means sheet electron beam can transmit a larger current in the same current density.Meanwhile,the planar sheet electron beam is conducive to the planarization,miniaturization and integration of device fabrication.In this thesis,the simulation and experimental research on W-band band TWT are carried out.The main work of the thesis is as follows:1.Research on W-band staggered double vane SWS.The dispersion and coupling impedance of the staggered double vane SWS are studied by HFSS and CST.The structure has a wide band and the coupling impedance is above 4(?)in the frequency range of 90-110GHz.Compared with the experimental results,the Bragg structure is added to the input and output terminals of the slow wave system to improve transmission characteristics.2.Research on the sheet electron gun.The anode voltage and the distance between anode and cathode of the electron gun are simulated and optimized respectively.Moreover,calculating the influence of changing channel size on electron beam transmission.3.Research on the periodic cusped magnetic(PCM).To improve the focusing ability of PCM,the magnetization mode of magnetic block in the focusing system and the degree of interlace between adjacent pole boots are studied.Finally,the transmission ratio of electron gun is 97.37%.4.Performing experiments on slow wave systems and PCM.In the cold test,the reflection coefficient S₁₁is below-13.35d B,and the attenuation coefficient S₂₁is above-4.34d B.The experiments on the periodic cusped magnetic shows that the period of the PCM is 6.6mm and the peak of PCM is 3200Gs,which are consistent with the simulation results.Finally,each part of the TWT is assembly and the hot test is carried out.