Study Of Radial Sheet Electron Beam Traveling Wave Tube

Being one of the important traveling wave tubes (TWTs), the radial sheet beamTWT has a good development and application prospect in satellite communication,radar systems, for its wide bandwidth, low operating voltage and small size. To meetthe needs of low voltage, small size microwave amplifiers, expand the applicationfields and increase the competitiveness of TWT, it is important to study the radialTWT.The production, focusing and beam wave interaction of radial sheet electron beamare researched in this paper, and based on this, a kind of novel slow wave structure(SWS) has been proposed, which supplying a new way to solve the TWT’s problems.The main work and innovation of this dissertation are as follows:1. The design method of radial electron optical system is given, and based on this,the production, transmission and focusing of the radial sheet electron beam are studiedin detail.The Brillion focusing magnetic for radial sheet beam is obtained from theMaxwell and Lorenz equations. And two kinds of radial optical systems are designed,that are the divergent type with cathode inside the anodes and the convergent type withcathode outside the anodes.2. The calculation methods of the non-periodic SWS’s dispersion characteristicand coupling impedance are proposed, and they were used to the logartithmical helixresearch.The beam wave interaction mechanism of this kind SWS is studied, and themicro-strip type radial logarithmical helix SWS with operating voltage30V isdesigned. Its dispersion characteristic curve and coupling impedance are obtained. Theparticle-in-cell (PIC) simulation results show that it can give an127mW output powerwith the input power40mW, and its3-dB operating bandwidth is about3GHz at Sband.3. To overcome the disadvantages of the micro-strip logarithmical helix, such asthe small operating voltage and current, the low frequency band, the waveguide typelogarithmical helix is proposed. Its dispersion characteristic and coupling impedanceare studied, and the results show that it can be used for W band radial TWT.4. A novel angular log-periodic meander line SWS, with a simple structure andsmall size, is introduced in this dissertation. Improved from the logarithmic helix, thiskind of SWS can work at a higher frequency. Moreover, the operating voltage istunable from hundreds to thousands Volt for different angles. So its beam current could be smaller than the logarithmic helix needed for the same direct current input power.Two TWTs with radial convergent and divergent sheet electron beam, whose operatingvoltages are1600V and800V respectively, are designed with this kind of SWS. Themaximum output power is160W and26W correspondingly, and the bandwidth is71.6%and80%with electron efficiency19.7%and21.7%.5. To increase the output power of this kind of SWS, the conception of angularintegrated angular log-periodic meander line SWS is proposed. The TWT with thiskind of SWS can give an output power as large as the conventional TWTs, and is betterat the bandwidth and operating voltage. Meanwhile, the electron beam of this kindTWT is easier to focus than the single angular log-periodic meander line TWT.6. The symmetric double angular log-periodic meander line SWS is studied toexplore the potential amplifying ability. Both the convergent and divergent electronbeams are studied with the same operating voltage800V. With a radial convergentsheet beam, this kind of TWT can give a maximum output power55W, with the3-dBbandwidth over20~50GHz and the biggest efficiency26%. While for the divergentelectron beam, an output power more than40W over the20~45GHz is abtained, andthe maximum efficiency and gain are26.3%and19.5dB respectively.7. The transmission and reflect characteristics of the angular log-periodic meanderline SWS are studied in detail. The transmission loss for different metals anddielectrics are calculated. The input and output structures for the angular log-periodicmeander line slow wave structure is designed, and the SWS with operating frequency12GHz is fabricated and tested, the S11less than-10dB, S21larger than-1.5dB andthe voltage stand wave ratio less than2are obtained. Based on the results, a new inputand output structure is designed, and is applied to the18GHz SWS. The experimentresults show that the S11is less than-15dB and S21larger than-2.9dB between thefrequency13~22GHz.