用于X波段模块化相对论速调管放大器在线测量的紧凑型定向耦合器设计

为实现模块化相对论速调管放大器功率、频率和相位的在线测量，对紧凑型高定向性高带宽的定向耦合器进行了仿真和实验研究。利用小孔耦合理论和相位叠加原理进行理论分析，设计了一种双孔紧凑型定向耦合器，在此基础上采用主、副波导正交连接，耦合孔沿轴向和角向二维分布的方法，进一步缩短了耦合器的长度。通过电磁仿真对耦合器各参数进行优化，模拟结果表明：当中心频率为10 GHz时，普通双孔定向耦合器对TM01模式的耦合度为-60.68 dB，在250 MHz的带宽内定向性大于20 dB，此时耦合区长度为3.49 cm。改进型定向耦合器对TM01模式的耦合度为-58.1 dB，在300 MHz的带宽内定向性大于20 dB，此时耦合区长度仅为1.8 cm（约0.6λ）。耦合器的冷腔实验测量结果与仿真结果符合较好。

Design of compact directional coupler for X-band relativistic triaxial klystron amplifier

To realize the on-line measurement of power, frequency and phase of modular relativistic triaxial klystron amplifier, a compact directional coupler with high directivity and bandwidth is simulated and experimentally studied. Based on the theoretical analysis of the pinhole coupling theory and the phase superposition principle, a dual-hole compact directional coupler is designed. On this basis, the main and auxiliary waveguides are connected orthogonally, and the coupling holes are distributed along the axial and angular directions, which further shortens the length of the coupler. The parameters of the coupler are optimized by electromagnetic simulation. The simulation results show that when the center frequency is 10 GHz, the coupling degree of the ordinary dual-hole directional coupler to the TM₀₁ mode is ?60.68 dB, and the directivity is greater than 20 dB in the bandwidth of 250 MHz, and the coupling area length is 3.49 cm. The coupling degree of the improved directional coupler to the TM₀₁ mode is ?58.1 dB, and the directivity is greater than 20 dB in the bandwidth of 300 MHz. At this time, the length of the coupling zone is only 1.8 cm (about 0.6λ）. The cold cavity experimental results of the coupler are in good agreement with the simulation results.