当采用相位聚焦技术提高行波管的互作用效率时,应求解考虑阻抗和耦合函数变化的非线性方程组。本文从自由螺旋导面的耦合阻抗公式出发,考虑了变节距段的螺旋带、介质及金属屏蔽筒的影响,得出了实际螺旋线慢波结构变节距段的阻抗和耦合函数的变化规律,并用实验验证了此规律,取得了较好的一致性。本文还列出了Rowe和Cutler提出的结果,并进行了比较。 When using phase-focusing technique to improve the interaction efficiency of traveling-wave tubes, a nonlinear system of equations that takes into account changes in impedance and coupling functions should be solved. In this paper, based on the formula of the coupling impedance of the free helical surface, the influence of the helical strip, the dielectric and the metal shielding tube in the variable pitch section is taken into account. The variation of the impedance and the coupling function of the pitch- The experiment verified the law and achieved a good consistency. This article also lists the results presented by Rowe and Cutler and compares them.