螺旋线行波管慢波结构设计及注波互作用模拟

通过模拟计算,分析螺旋线内径和螺距变化对色散和耦合阻抗的影响,优化慢波结构,初步设计了Ku波段螺旋线行波管慢波结构。模拟行波管输入输出结构,得到输入端反射系数小于-19 dB,电压驻波比小于1.24。电子聚焦系统采用周期永磁聚焦,磁场周期为8.5 mm,计算得到磁场峰值为0.17 T。为提高注波互作用效率,采用具有动态速度渐变特性的慢波结构,使得电子注与高频场有足够的互作用时间,从而保证电子不断地将能量交给高频场。运用三维PIC粒子模拟软件分析行波管的注波互作用,得到在12.5~16 GHz频率范围内输出功率大于88.7 W,电子效率大于14.8%,增益大于34.6 dB。

Design of slow-wave structure and beam-wave interaction simulation for helix traveling-wave tube

A Ku-band helix traveling-wave tube (TWT) is designed using theoretical analysis and simulation. The effect of the variation in inner radius on dispersion and coupled impedance is analyzed to optimize the slow-wave structure of helix TWT. The input and output structure of TWT is simulated, the input reflecting coefficient is less than -19 dB and the voltage standing wave ratio (VSWR) is less than 1.24. Periodic permanent-magnetic field is used as electromagnetic focusing system, the magnetic system period is 8.5 mm and the magnetic peak value is 0.17 T. The slow-wave circuit with property of dynamic velocity tapper (DVT) is used to increase the interaction efficiency, it can provide enough time for the interaction of beam and high-frequency field and make electrons continuously transport energy to high-frequency field. The helix TWT is simulated using a three-dimensional particle-in-cell (PIC) code. The simulation results demonstrate that the output power is bigger than 88.7 W, the electron efficiency is bigger than 14.8% and the saturated gain is bigger than 34.6 dB in the frequency range from 12.5 to 16.0 GHz.