以加载衰减器的螺旋线慢波结构作为研究对象,采用螺旋导电面模型,用真空层模拟螺旋带的厚度,用均匀介质层等效分立的介质夹持杆,并考虑到各横向区域横向传播常数的不同,得到了任意次模式的色散方程和耦合阻抗的表达式。在此基础之上,分析了衰减器对主模和-1次模式的衰减常数、相位常数和耦合阻抗的影响,所得结果对设计衰减器具有理论指导意义,为螺旋线慢波系统高频特性的改善以及反射振荡和返波振荡的抑制提供了理论依据。
The sheath-helix model is used to analyze the helical slow-wave structure in which the helix turns are considered effectively shorted by the resistive coating on dielectric helix-support rods. Meanwhile, a gap is introduced to simulate the helix tape thickness, and the helix support rods are emulated by an effective dielectric tube and the difference of the radical propagation constant in different regions is taken into consideration. The dispersion equation and interaction impedance of arbitrary field modes are derived. On this basis, the effects of attenuation coating on the attenuation constant, phase constant and interaction impedance are discussed. The results presented here are useful for designing attenuator and improving the high-frequency characteristics of helical slow-wave structure as well as preventing the reflection oscillation and backward-wave oscillation of traveling-wave tubes.