折叠矩形槽波导行波管输入输出过渡波导

为了将槽波导端与标准矩形波导相连接，设计了一种适用于折叠槽波导结构行波管的输入输出过渡波导, 可将其视为槽宽渐变的双槽加载矩形波导。利用电磁仿真软件CST微波工作室对该结构进行仿真计算，讨论了各个结构参数对其性能的影响。对比了直线渐变、抛物线渐变和指数渐变3种槽宽渐变规律在W波段对其传输特性及损耗特性的影响。研究结果表明:指数渐变结构的驻波系数小于1.15的带宽比其他两种结构都要宽，且在90~99 GHz、驻波系数小于1.25时，该结构的整体长度也远小于另外两种结构，能够实现良好的过渡效果; 而直线渐变结构的损耗在90~97 GHz为最低。

Transition waveguide for traveling wave tubes with folded rectangular groove waveguide

The transition waveguides between folded groove guide slow-wave structure and 3 mm standard rectangular waveguide are designed, which are formed by tapered double groove-loaded rectangular waveguides. The influences of structural parameters on transmission performance are discussed based on the simulation results by CST Microwave Studio. Moreover, the transmission performances and loss characteristics of three transition waveguides, i.e. linearly tapered, parabolically tapered and exponentially tapered double groove-loaded rectangular waveguides are analyzed in W band. The simulation results show that the bandwidth of the exponentially tapered transition waveguide is wider than those of the other two structures, while the voltage standing wave ratio (VSWR) is less than 1.15. Furthermore, the whole length of it is much shorter than those of the other two structures when the VSWR is less than 1.25 within 90-99 GHz. However, the loss of the linearly tapered structure is smaller than that of the other structures in 90-97 GHz frequency range.