| Generally, helix and coupled cavity slow-wave system has been the most widely used in TWT, the bandwidth of helix TWT is very wide, the working voltage is very low,the interaction efficiency is high, but the output power level is limited by the helix heat dissipation ability. Coupled cavity TWT is metal structure,because of strong ability of heat dissipation, the output power can be very high, but the disadvantage is that the instantaneous bandwidth is very narrow, generally about 5%. As the research of high power vacuum electronic devices system is becoming more and more advanced, some new type of slow wave structure with better performance produced,folded wave-guide slow-wave system is one of them. Folded wave-guide slow-wave circuit is a kind of slow wave system that bends the rectangular wave-guide in a certain pitch along axis direction,the bandwidth of the slow wave line is very wide, because of the two-dimensional structure, the processing of the slow wave line and the assembly of the whole tube is relatively simple,and the cost is very low. The technology has very good consistency and repetition, so the production is very easy. With the development of the technology, the satellite t-t&c and communication link has been extended to the millimeter wave band, such as America’s broadband satellite WGS which can provide the business of radio and new W band military. The anti-interference ability of the signal of W band and higher frequency is strong,the intercept is difficult, so it can greatly improve the security of electronic communications system. According to the present research situation of high frequency folded wave-guide TWT and the fact that our laboratory has successfully developed a kind of Q band folded wave-guide TWT which has the ideal performance, this paper designs a kind of W band folded wave-guide TWT which has higher working frequency, within the working frequency of92GHZ-96 GHZ, the electronic efficiency of the tube reached 3.3%, the output power reached 60 W, the average gain of the whole tube reached above 34 dB.This paper mainly researches the content on the following:1. Using TWT voltage, current, the emission current density of cathode and the electron gun injection parameters, we can calculate the appropriate size of electron gun in Matlab, then simulating and optimizing in Ukraine software ORION, we can get an ideal gun that satisfies the requirement of the tube.2. By firstly introducing the equivalent circuit method that can calculate dispersion characteristics of folded wave-guide slow-wave structure, we can do an approximate theoretical analysis for the structure. In order to get the big coupling impedance and the ideal dispersion characteristics within the specified bandwidth, and improve the interaction efficiency and gain at the same time,we will do studies about the affect of each structure parameter of folded wave-guide to the performance of the tube, obtaining wide band and high interaction efficiency for the slow wave structure. These work will be done in HFSS and Ukraine software ORION, through continuous simulation and interaction optimization, it can meet the design requirements. Finally, basing on the theory of nonlinear large signal of slow-wave structure, we can realize the simulation of one dimensional nonlinear large signal of folded wave-guide slow-wave structure in Matlab, which can verify the rationality of the above simulation and design.3. According to the above slow-wave structure, combining with the working voltage of electron gun, and electron beam radius parameters, we can design a suitable periodic permanent magnetic focusing system(PPM). Using HFSS to simulate and optimize on the basis of teacher’s work of our teaching and research section, we designed good input and output structures and concentrated attenuator which can satisfy the work requirement of TWT.4. We assemble each part into a tube, and test the output power and gain of the whole tube, and summarize the result of the test. |
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