Research On Miniaturized Radial Beam Traveling Wave Tube

With the advantages of high power,efficiency,gain and wide bandwidth,the traveling wave tube(TWT)is the most widely used vacuum electronic device.With the development of radar technology,electronic countermeasures and satellite communications and other applications,high-precision positioning and tracking,highresolution imaging,high-speed communication systems and other technologies are widely used,which puts forward higher requirements for the TWT.The development of miniaturized high-performance TWT to enhance the flexibility of radar and communication equipment,reduce the volume,weight and power consumption has an important strategic significance.In order to realize the miniaturization of the high-performance TWT,various miniaturized slow wave structures(SWS)have been proposed,such as planar helix SWS,microstrip SWS.However,the miniaturized SWSs face several challenges:(1)the interaction impedance of the SWSs are low,and the interaction efficiency is also low;(2)most of the SWS have a large amount of dielectric material,which will produce charge accumulation and lead to unstable work of the TWT;(3)the periodic number of the SWSs is too many,which brings great difficulties to the focusing of the beam.In this dissertation,we propose a variety of miniaturized SWSs based on the characteristics of existing SWSs in miniaturized TWTs and the problems that need to be solved,and use a combination of theoretical analysis,simulation and experimental testing to study the miniaturized SWSs in depth.The main research work and innovations of this dissertation are as follows.1.In order to improve the interaction impedance of microstrip SWS,the suspended dual-microstrip meander-line SWS is proposed,and the analysis of its high-frequency characteristics and beam-wave interaction characteristics are carried out.The calculation results show that this SWS has higher interaction impedance,and the maximum output power is 20 W at 36 GHz with operating voltage and current of 2050 V and 0.2 A,the maximum saturated gain are 26 d B,the 3-d B bandwidth is 8 GHz,the calculated interaction length is less than 30 mm.This SWS is processed by magnetron sputteringlaser ablation process,and it is verified in the experiment that the reflection loss of this SWS was verified to be consistent with the calculated results in the experiments,and the factors affecting the transmission loss of the structure were analyzed.2.In order to improve the interaction impedances and operating stability of SWS,the conformal microstrip angular log-periodic meander line SWS is proposed,which effectively shortens the tube length by reducing the coverage area of the dielectric substrate and alleviates the problems of charge accumulation in the dielectric substrate and difficult focusing of the band electron beam.The high-frequency characteristics and the beam-wave interaction characteristics of the SWS are simulated.The results show that the maximum output power of this SWS can reach 220 W,the electron efficiency is20%,and the 3-d B bandwidth can reach 13 GHz.Finally,the application of ion beam etching in the processing of this SWSs is explored.3.In order to further improve the operating stability of TWT,the angular logperiodic strip-line SWS is proposed.The results of the calculated beam-wave interaction characteristics show that the output power of this SWS can reach up to 320 W with an electronic efficiency of 9.12% and a 3-d B bandwidth of 5 GHz for an interaction length of less than 10 mm.The angular log-periodic strip-line TWT assembly and experimental work are completed.The experimental proof-of-principle of the angular log-periodic strip-line SWS was completed,which proved the feasibility and potential value of the miniaturized radial beam traveling wave tube.4.In order to improve the gain of the angular log-periodic strip-line SWS,the cascade angular log-periodic strip-line SWS is proposed.The high-frequency characteristics and the beam-wave interaction characteristics of this cascaded SWS were theoretical analyzed and simulated.The results show that the maximum gain of this SWS is 32.5 d B,and the gain per unit length is about 2 d B/mm.And electron-optical system for dual radial sheet beams is studied,and the joint simulation calculation with this SWS is carried out.The static transmission efficiency of the dual radial sheet beam can reach100% and the dynamic transmission efficiency can reach 93%,the maximum output power of this SWS is reduced by 30 W,and the corresponding gain is reduced by only1 d B.5.In order to shorten the length of helix TWT,the radial logarithmic double gradient helix TWT is studied.The dispersion characteristics of the logarithmic double gradient helix SWS are analyzed,and the effect of the simultaneous gradient change of pitch and inner diameter on the dispersion characteristics is analyzed.The results show that the power of this TWT is increased by 20% and the electronic efficiency is increased by 50%compared with that of the periodic helix TWT.Through the experimental test of the radial logarithmic double gradient helix TWT,the experimental results match with the simulation results,which verifies the power enhancement capability of logarithmic gradient structure to the helix TWT.