折叠波导以其宽频带、加工方便而成为一类重要的毫米波与太赫兹波段行波管慢波线。针对折叠波导慢波系统与标准波导的匹配过渡连接, 通过等效电路分析与电磁计算软件模拟, 设计出了直渐变波导、双曲圆弧渐变波导、切比雪夫阶梯渐变波导3种输入输出过渡波导结构, 分析了各种过渡波导的优缺点及结构尺寸对性能的影响。计算表明, 经过合理优化的设计, 3种过渡结构均可以使反射系数在28～40 GHz波段小于0.05。

The folded waveguide is widely studied in the world due to its broad band. The transition waveguides between folded waveguide slow-wave structure and 8 mm waveguide are studied by using numerical method. Three transition waveguides, i.e. linearly tapered waveguide, dual-arc waveguide and Chebyshev stepped waveguide, are designed for millimeter wave folded waveguide traveling wave tubes, and their merits and demerits are analyzed. The relationship between the dimensions and performance of the waveguides is obtained. The simulation results show that the reflectivity is below 0.05 within 28~40 GHz for the three structrues with rational optimization.