太赫兹折叠波导慢波电路及功率合成技术

Slow-wave circuits and power synthesis techniques of folded waveguides for terahertz applications

针对太赫兹频段行波管输出功率较小的瓶颈以及对紧凑型设计的明确需求,提出一种管内功率合成的0.34 THz折叠波导行波管结构。首先,对太赫兹折叠波导慢波结构的高频特性进行了研究,通过仿真计算得到了其色散特性和耦合阻抗,0.34 THz处归一化相速度为0.248,耦合阻抗为0.46Ω;其次,提出了用于管内功率合成的3 dB定向耦合器结构设计,分析表明,其在0.31~0.368 THz范围内,幅度平衡度在±0.19 dB以内,隔离度优于24 dB;最后,完成了基于3 dB定向耦合器管内功率合成的折叠波导行波管基本结构设计并构建了仿真模型,仿真结果表明,最大输出功率为9.16 W,增益为26.6 dB,3 dB带宽达到21 GHz。作为对比,单个折叠波导行波管输出功率为6.18 W,故管内合成的折叠波导行波管的输出功率是单个行波管输出功率的1.48倍;此外,与采用常规外置功率合成结构的双行波管组件设计相比,管内功率合成折叠波导行波管的横向尺寸至少缩减了56.5%。

Aiming to address the bottleneck of low output power in terahertz band traveling wave tubes and responding to the distinct demand for compact design,this paper proposes a 0.34 THz folded waveguide traveling wave tube structure with power combination inside the tube.Firstly,the high-frequency characteristics of the folded waveguide slow-wave structure are investigated.Electromagnetic full-wave simulations are used to obtain its dispersion characteristics and coupling impedance.The normalized phase velocity at 0.34 THz is 0.248 and the coupling impedance is 0.46Ω.Secondly,a 3 dB directional coupler structure for in-tube power combination is designed.The analysis indicates that its amplitude balance is within±0.19 dB in the range of 0.31–0.368 THz,and the isolation exceeds 24 dB.Finally,the basic structure of the folded waveguide traveling wave tube based on the in-tube combination of the 3 dB directional coupler is demonstrated.The simulation model is constructed,and the results show a maximum output power of 9.16 W,a gain of 26.6 dB,and a 3 dB bandwidth of 21 GHz.For comparison,the output power of a single folded waveguide traveling wave tube is 6.18 W.The output power of the in-tube synthesized folded waveguide traveling wave tube is 1.48 times that of the single traveling wave tube.Moreover,compared with the design of a dual-tube assembly using conventional external power combination structure,the lateral size is reduced by at least 56.5%.