多注速调管π模双间隙腔截止波导输出回路研究

Research on an MBK output circuit of π-mode double gap cavity loaded by cutoff waveguide filter

用数值模拟的方法研究了多注速调管π模双间隙腔加载截止波导两节滤波器型输出回路的特性,并重点研究了π模双间隙腔与截止段的耦合结构对输出腔间隙阻抗频率特性的影响,以及耦合接头和电容性销钉对截止波导滤波器的调谐作用。研究结果表明:π模双间隙腔连接截止波导段的耦合口的尺寸主要影响输出腔的外观品质因数,而耦合接头的粗细和电容性销钉的大小和插入深度对截止波导滤波器的调谐具有重要影响。另外,由于耦合接头相当于在截止段中引入了一个附加电感,这使滤波器谐振电路的品质因数变大,谐振峰变窄。因此,π模双间隙腔加载截止波导滤波器型输出回路并不比单间隙腔加载截止波导滤波器型输出回路有更好的带宽优势。

The paper analyzes the characteristic of a multiple-beam klystron output circuit, π-mode double gap cavity loaded by cutoff waveguide filter, with 3D simulation method. The research is focused on the influence of the size of the coupling port, coupling line and the capacitive metal rods in cutoff waveguide on the gap impedance. The result shows that, the size of the coupling port has strong influence on the external quality factor of the output cavity, while the size of the coupling line and the capacitive metal rods mainly affect the tuning frequency of cutoff waveguide filter. Since the coupling line brings about an additive inductance in cutoff waveguide filter, which makes the quality factor bigger and resonant band narrower, π-mode double gap cavities are not more advantageous to achieve wider band than the single gap cavities loaded by cutoff waveguide filters.