Research Of 220 GHz TE₀₃ Mode High Frequency System For Gytro-TWT

Gyrotron travelling-wave tube（gyro-TWT）is a kind of electric vacuum device.It has good application prospects in electronic countermeasures,broadband high-speed communication,millimeter wave radar because of its wide bandwidth,high power and high frequency.The traditional gyro-TWTs usually use low-order modes such as TE₁₁,TE₂₁ or TE₀₁ mode as the working mode,and most of them work at the low end of millimeter wave frequency band.With the development of gyro-TWT,the research of it is developing towards the direction of terahertz band.In terahertz band,the use of low-order mode as the operating mode will lead to many problems like the high-frequency structure size and power capacity is too small and so on.Using higher order mode as working mode is an effective way to solve the above problems.However,the higher-order gyro-TWT faces more serious mode competition problem at the same time.At present,the traditional dielectric loaded high-frequency system structure can not solve the mode competition problem of high order mode gyro-TWT perfectly.In order to solve the problem of high order mode gyro-TWT,a novel high frequency system structure of gyro-TWT is proposed in this thesis.Based on this,a TE₀₃ mode gyro-TWT operating in the 210 GHz to 220 GHz frequency band is designed.Specific work contents are as follows:1.Based on the small signal theory of gyro-TWT,the dispersion curve,coupling coefficient,the starting current of the operating mode TE₀₃ and the starting length of the main competitive mode of the high-frequency structure are calculated.2.A new dielectric loaded high-frequency structure is proposed,and a comparative simulation analysis between the new dielectric loaded high-frequency structure and the traditional dielectric loaded high-frequency structure is carried out,laying a foundation for the subsequent PIC simulation in CST.3.Based on the novel dielectric loaded high-frequency structure,a gyrotron traveling wave tube operating at 220 GHz TE₀₃ mode is designed.PIC simulation is carried out to verify the zero-drive stability.After optimization,the gyro-TWT scheme with stable output reaches a peak power of 64.8 k W at 215 GHz,and the gain is 67.1 dB,the efficiency is 21.6%.4.The input coupler and output window of 220 GHz TE₀₃ mode gyro-TWT are studied.TE₀₃ mode input coupler and double-layer window output window which have excellent performance of are designed.In the simulation results of the input coupler,the transmission coefficient of TE₀₃ mode S21 is greater than-2 dB and the relative bandwidth is greater than 5%when in the range of 210 GHz-220 GHz,and the transmission coefficient of main competition modes is less than-14 dB.For the double layers output window,the bandwidth of S11 parameter less than-20 dB is 15.3 GHz,and the relative bandwidth is greater than 7%.In addition,the designed input coupler has been processed and measured,and its performance has been verified.