提出采用分段变参数型折叠波导慢波结构提高器件增益的新方法。结合小信号理论分析和束-波互作用的三维PIC数值模拟，进行分段变参数型慢波结构的理论设计研究。通过0.345 THz两段式折叠波导慢波结构的设计实现和模拟验证，结果证明,相同的电子注工作条件下，两段式慢波结构的电子转化效率和饱和功率相对于传统均匀型慢波结构提高了94%，并可以推广应用到多段式。

This paper proposes a new type of folded waveguide slow-wave structure with variable parameters, which can greatly increase the device’s saturation gain. Combining small-signal theory analysis and three-dimensional PIC numerical simulation of beam-wave interaction process, the paper also proposes a theoretical design method for this variable-parameter slow-wave structure. A 0.345 THz two-stage folded waveguide slow-wave structure is designed and simulated, which proves that the two-stage slow-wave structure has higher electron conversion efficiency and saturation gain than the conventional uniform slow-wave structure under the same working conditions and can be widely applied to multi-stage structures.