Study On Nonlinear Characteristics Of High Band TWT

As an important class of vacuum electronic devices,traveling wave tubes have been widely used in various fields such as national defense technology and satellite communications after decades of development.Its high-power,high-efficiency,and high-reliability characteristics have become an important advantage in competition with solid-state devices.With the rapid development of the fifth-generation mobile communication system,and at the same time,the allocation of spectrum resources in the low-frequency range in various fields is becoming more and more tense.The application of millimeter wave technology to modern communication systems can be as the general trend,and it has also injected new vitality into the traveling wave tube,a device with a long history of development.It is not difficult to find that this type of device is a kind of nonlinear device,and various nonlinear characteristics will inevitably occur in the working process.With the continuous increase of high-frequency excitation,phenomena such as amplitude distortion and phase distortion will occur;When two or more signals are simultaneously injected to the traveling wave tube and interact with the electron beam,intermodulation distortion will occur due to the mutual modulation between the signals.These nonlinear distortion characteristics will inevitably affect the normal operation of communication systems and satellite navigation systems.If the nonlinear characteristics of the traveling wave tube mentioned above are not effectively suppressed,it will affect the development prospects of the traveling wave tube and other vacuum electronic devices in the fields of communication and other fields.Therefore,it is urgent to start from the working principle of the traveling wave tube,and derive the working equations that can describe the nonlinear beam-wave interaction of the traveling wave tube under the single signal and multi-signal input conditions.From this,we find some methods to suppress the nonlinear characteristics of the traveling wave tube,so as to provide a theoretical basis for the linearization design of the traveling wave tube.The main work of this paper is as follows:1.Starting from the non-linear modulation of the electron beam and the excitation of the waves,using Wainstein's large-signal theory,the self-consistent ordinary differential equations of the interaction of electromagnetic waves and electron beams under the multi-signal excitation are derived.2.The working equations of multi-signal beam-wave interaction of traveling wave tube deduced in this paper can be solved from the initial conditions by using iterative method.Therefore,the Runge-Kutta numerical solution method is selected,the equations are numerically calculated in Matlab,the main and auxiliary characteristics of the traveling wave tube are obtained through the output results?3.The important nonlinear parameters of the space traveling wave tube are studied.According to the nonlinear characteristics of the traveling wave tube,a structural optimization scheme to improve the linearity of the traveling wave tube is proposed.Finally,the high-frequency design of a certain W-band space traveling wave tube is optimized,and its nonlinear performance is significantly improved while maintaining high electronic efficiency.