Research On The Input And Output System Of Dual-band Gyro-TWT

The Gyro-TWT is an important high power millimeter wave source,it has the characteristics of high output power,high gain,wide working frequency band and so on.Therefore,it is widely concerned at home and abroad.The input-output system is an important part of the Gyro-TWT.Its performance directly affects the efficiency,gain and bandwidth of the whole tube.The input system consists of an input coupler and an input window.The function of the input coupler is to convert the TE₁₀ mode of the rectangular waveguide into the mode required by the Gyro-TWT,and thus realize the velocity modulation.The function of the input window is to isolate the outer atmosphere and keep the vacuum environment,and to realize the broadband input of the driving signal.The design requirements of the input system are low reflection and high mode purity.The output taper waveguide is an important part of the output system of the Gyro-TWT.It is a taper waveguide that connects the high frequency interaction system with the collector.It is used to achieve the high mode purity and low reflection output of the high-power electromagnetic wave.Moreover,it realizes the fast detuning of the output cyclotron electron injection and improves the interaction efficiency of the whole tube.The radius of the output taper waveguide gradually increases in the axial direction,which makes the competitive modes coupling when the high-power electromagnetic wave passes through the output gradient section,thus affecting the output mode purity of the high-power electromagnetic wave.The design requirements of output gradient section are compact structure,small reflection and high output mode purity.In order to meet the demand of dual-band radar system for high-power broadband dual-band power source,a new dual-band Gyro-TWT structure is proposed.The research on the dual-band input and output system is the basis and premise for the development of the dual-band Gyro-TWT.Different from the traditional single-band and single-mode Gyro-TWT,the double-band Gyro-TWT puts forward a new requirement for the input and output systems design.In this paper,the input and output systems of the double-band Gyro-TWT are studied,and the main contents are as follows:In the first chapter,the working principle and development status of Gyro-TWT are briefly introduced,and the research background and significance of double-band Gyro-TWT and input-output system are expounded.In the second chapter,a new type of input coupler for dual-band and dual-mode Gyro-TWT is proposed.The new type of input coupler has two input ports to satisfy the requirements of inputting TE₁₁ and TE₀₁ mode respectively,and Bragg reflector is adopted between the two input ports.The Bragg reflector has a mode selection feature,TE₁₁ mode can be transmitted in the Bragg reflector,but TE₀₁ mode is completely reflected in the Bragg reflector.In the design of TE₁₁ input system,the E-bend waveguide is used to replace the H-bend waveguide to reduce the transverse scale of the input system.In addition,to suppress the self-excited oscillation of operated mode,a lossy medium is loaded in the dual-band input coupler.Finally,a pressure drop input structure is designed and applied to the dual-band Gyro-TWT which has a buck collector.In the third chapter,a new design method of dual-band output taper waveguide is presented.Firstly,the commonly used linear output taper waveguide and the rising sine output taper waveguide are applied to the dual band.Then,according to the design requirements of the dual band output taper waveguide,the contour line of the Chebyshev output taper waveguide is adjusted,and an improved Chebyshev dual band output taper waveguide is designed.Finally,by fitting the contour of the rising sine type and improving Chebyshev type taper waveguide,a new dual-band output taper waveguide is designed.In the fourth chapter,the novel wide-band rectangular waveguide TE₁₀ mode to circular waveguide TE₀₁ mode converter and rectangular waveguide TE₁₀ mode to circular waveguide TE₂₁ mode converter are proposed,which are applied to the cold test of input and output systems.HFSS high frequency electromagnetic simulation software was used to optimize the structural parameters of these mode converters,and the experimental samples were produced for experimental verification.Chapter five briefly summarizes the research work done in this paper.