Research On The Key Techniques Of Two-octave Ultra-Wideband TWT

The helix traveling wave tube(TWT)has the advantages of wide bandwidth,high power and high gain.TWT has become one of the most important vacuum devices.With the continuous development of TWT techniques,the requirements of its bandwidth and output power are increasing.For TWT,expanding the frequency band and increasing the output power can not only improve the performance,but also reduce the number of tubes used in the electronic warfare system.In this way,economic cost can be saved and significant economic benefits can be produced.TWT is more and more inclined to have wider bandwidth,higher power,smaller volume,higher electronic efficiency and so on.Based on the above reasons,this paper studies a variety of key techniques of ultra-wideband(UWB)TWT.In order to suppress the second harmonic of the beam wave interaction and improve the output power,the high-frequency characteristics,the beam-wave interaction characteristics and the structure of the input and output devices of the 2.7-12 GHz UWB TWT are studied in this paper.The main work of this paper is shown as follows:1.In order to achieve ultra-wideband,the influence of the slow wave structure of UWB TWT on the high-frequency characteristics has been researched systematically.In the slow wave structures,the helix inner diameter,the vane inner diameter,vane angle and pitch have obvious influence on high frequency characteristics,which have been simulated and analyzed in this paper.After analyzing the slow wave structure parameters in the working frequency band,the proper parameters have been determined.2.Research of the key techniques of UWB TWT,the methods of back wave oscillation suppression,second harmonic suppression and improving electronic efficiency are deeply discussed.For the suppression of second harmonic of UWB TWT,the method of vane tapering combined with pitch tapering is adopted.Combined with phase velocity tapering,which effectively improves the electronic efficiency of the UWB TWT.3.Combined with the key techniques of UWB TWT,a new type of interaction distribution is designed to optimize the output power.The output power of all frequency points in the working frequency-band is greatly improved.The high-frequency characteristics of the input section is optimized to have high coupling impedance and the output section has abnormal dispersion.The simulation design of the quadruple frequency ultra-wide band TWT in the working frequency band of 2.7-12 GHz is completed.The output power and the second harmonic suppression ratio were simulated and calculated.The output power in the entire frequency band range was greater than 160 W,the second harmonic suppression ratio was less than-4.7dBc and electronic efficiency was greater than 16%.4.The input and output structure of the UWB TWT has been designed.In the input and output system of TWT,the coaxial input and output window and the coaxial impedance conversion section have been designed.The influence of some key parameters on the transmission performance is analyzed.Finally,the optimization results show that in the whole 2.7-12 GHz working band,its VSWR is less than 1.85.