周期损耗介质加载波导与均匀圆波导间的模式映射

损耗介质环与金属环间隔加载的周期损耗介质波导能够有效地控制各种模式的衰减特性,这对于抑制毫米波回旋行波管放大器的绝对不稳定性和提高其性能具有重要作用.针对应用于Ka波段、TE01模的回旋行波管放大器的周期损耗介质加载圆波导,系统地分析了该周期系统与均匀系统间的模式映射关系.研究表明,当介质层厚度一定时,均匀介质加载波导中的高阶模式可以映射为光滑波导中的低阶模式,且相互映射的模式在中空区域的场型一致.周期系统中的模式表现出复合模式的分布.在一个周期中,介质段和金属段的模式分别映射为均匀介质波导和金属波导中的模式.明确周期介质加载波导系统与均匀波导系统间的模式映射关系是分析发生在这种复杂的互作用回路中的回旋电子脉塞注波互作用的前提,对简化其物理模型具有指导作用.

Modal Mapping between Periodic Lossy Dielectric-Loaded Waveguide and Uniform Circular Waveguide

A waveguide periodically loaded with lossy dielectric rings and metal rings is able to effectively control the attenuation to each mode, this is important for suppressing the absolute instability and enhancing the performance of a millimeter-wave gyrotron-traveling-wave amplifier (gyro-TWT). The modal mapping between the periodic waveguide and the uniform waveguide was systematically studied for a periodic ceramic-loaded cylindrical waveguide applied in TE01 mode gyro-TWT at Ka-band . It was revealed that, with a proper dielectric thickness, a higher order mode in uniform dielectric-loaded waveguide can be mapped to a lower order mode in smooth waveguide and the field distributions of the inter-mapped modes in vacuum region bear good resemblance to each other. A mode in periodic system exhibits complex mode distribution . In a period, the field distributions in the dielectric section and the metal ring section are mapped to those in uniform dielectric-loaded waveguide and smooth waveguide, respectively. The understanding of the modal mapping between the periodic dielectric-loaded waveguide and smooth waveguide is the precondition for the analysis of the complex electron cyclotron interaction in such a periodic system, which brings helpful guidance to the simplification of the physical model.