| Microwave electro-vacuum devices are widely used in communication,radar,satellite navigation,electronic countermeasures and other fields.Because these devices have the advantages of wide working band,high output power and high efficiency.Traveling-wave tube(TWT)has become one of the most widely used microwave tubes in the above fields because of its unparalleled broadband characteristics.In order to take advantage of high resolution and miniaturization when working in high frequency band,people gradually study electromagnetic wave from microwave band to millimeter-wave band,even terahertz band.220 GHz,as the central frequency of an important atmospheric window with less attenuation of electromagnetic wave propagation,has become a research hotspot recently.Therefore,it is of great scientific significance and application prospects to study the TWT slow-wave structure(SWS)suitable for G-band.The main task of this paper is to optimize a new type of staggered double-vane SWS suitable for G-band.On this basis,the input and output couplers are designed,which are well matched for this SWS.Then the feasibility of the design is verified by simulation and cold test after processing.This thesis is divided into four parts,as follows:1.Study of G-band T-shape staggered double-vane SWS.A T-shape staggered double-vane SWS is designed and its high frequency characteristics are simulated and analyzed.The structure parameters are optimized by scanning,and the optimum values of each structure parameter are obtained.Then the high frequency characteristics of Tshape staggered double-vane SWS and conventional staggered double-vane SWS are compared.It is concluded that this T-shape staggered double-vane SWS can improve the high frequency characteristics.2.Design of input and output couplers.Two kinds of input-output couplers are designed for the T-shape staggered double-vane SWS in this paper.The first one is the Eplane bend waveguide input-output coupler,and the second one is the H-plane bend double ridge waveguide input-output coupler.Both of them are simulated to verify the feasibility of the designs.Then the second structure design is improved to make it more suitable for the T-shape staggered double-vane TWT.3.Experimental study of cold-test.The cold-test of the T-shape staggered double-vane SWS combined with input and output couplers is carried out.The test results verify the feasibility of the design.But it also found some points that need improvement,and put forward the corresponding improvement methods.4.Study of beam-wave interaction in G-band TWT.In order to solve the problem of self-excited oscillation,three schemes of centralized attenuator are given.And then,the thickness gradient attenuator is adopted,which has a good effect of concentrated attenuation.The beam-wave interaction of the TWT with 70-periods SWS is simulated.At the same time,the influence of different frequencies and input power on the output power of TWT is also studied.Finally,the phase velocity tapering technology is investigated. |
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