Beam-Wave Interaction Analysis For The Coupling Cavity Traveling Wave Tube

The traveling wave tubes(TWTs)is widely used in radar systems,communication satellites and spacecraft launchers,and electronic warfare systems.Due to the different slow wave structures,the TWTs is divided into many different subclasses.Coupling cavity(CC)TWT is one of the most widely used and widely varied,tubes,so the CC TWTs has become one of the research hotspots because of its advantages in coupling impedance,power,heat dissipation capability and so on.With the popularization of computer technology,the simulation design of the CC-TWTs has gradually evolved from manual deduction to computer computing.So,the researchers has proposed 1-dimension,2-dimension,2.5-dimensional and 3-dimension interaction analysis model of high frequency characteristics,beam wave interaction of the CC-TWTs,and the simulation program is designed and written.Although the output power of coupled cavity TWT is high,its bandwidth is narrow,therefore,expanding the bandwidth is becoming a hot topic.In order to expand the bandwidth of the CC-TWTs,a lot of new structures and new designs have been proposed.As many analysis models are not universal for every structures,each time,a new structure or a new design idea is put forward,a new analysis model which is more consistent with the new characteristics is required.Such as the resynchronization technique,which is a useful way to expand the bandwidth while improving the efficiency and bandwidth meanwhile suppressing oscillation,and it need the beam-wave interaction analysis of the near-cut-off frequency.At present,there are few models to analyze the near cut-off region,and the computation program is rare.In this paper,for expanding the bandwidth and improving the efficiency,the high frequency characteristics of the CC-TWTs and the analysis 2.5 dimensional model of beam-wave interaction are introduced.Moreover,in order to extend the bandwidth and suppress oscillation,the interaction characteristics in the near cut-off region are also studied to optimize the model.The main work is:1.A high frequency characteristic analysis model is proposed.Each period of the coupling cavity is equivalent to the transmission circuit,and each period is divided into several parts,and the divided parts are equivalent to the equivalent parameters of the transmission circuit,and then high frequency characteristics are analyzed.2.A uniform slow wave line analysis model is presented,which can quickly analyze the beam-wave interaction of the CC TWTs.3.A beam-wave interaction analysis model named coupling cavity cascade model is presented to analyze the beam-wave interaction of the CC TWTs in the near cut-off region and the commonly used working band.The analysis methods of transmission matrix,electronic motion equation,gap field equation,R/Q,phase shift and other parameters are given.For the characteristics of the near cut-off region,the optimization analysis is made.4.Based on the uniform slow wave line interaction analysis model and the coupling cavity cascade model,the interaction analysis programs are written.The programs are written by Python with high scalability and compatibility,and the MVC framework has been referenced to.A comparison is made between the measured data of a W-band TWT and the interaction calculation results of the two models.Then the simulation results of the particle simulation program and the coupled cavity cascade model in the near cut-off region are compared.The feasibility and reliability of the two models are verified.