太赫兹光子带隙双模级联行波管的研究

Traveling wave tubes are facing large transmission loss and low intrinsic interaction efficiency problem in development to the terahertz frequency. The key to solving this problem lies in an exploration of a high frequency circuit based on a new interaction mechanism. Operating at a higher order mode, can increase the transverse circuit size of high frequency circuit, improve the power capacity, but will bring very serious problem of the mode competition. Another disadvantage of operating at a higher order mode is the coupling impedance is not high, and the interaction efficiency is low. In order to solve the problems above, a novel cascade interaction mechanism is proposed, which can be summarized as the modulation and demodulation of an electron beam by interaction with two separated Slow Wave Structures (SWSs). The first SWS working at lower mode modulates the beam current at some extent with the input RF signal. The resulting velocity modulation is then converted into a longitudinal density modulation as the electron beam traverses a drift space. In the second SWS, whose operating mode is higher mode, and the microbunched current is reinforced by the interaction with SWS, and a stronger amplification is established. The operation mode of the pre bunching and radiation sections are selected by loading Photonic Band Gap Structures (PBGs).. The band gap properties of photonic crystals are to be analyzed. A theoretical analysis model and simulation model of photonic crystal slow-wave structure will be fond. An interaction theories and simulations of photonic crystal slow wave structure will to be researched, to reveal the physical mechanism of mode competition. A novel property of interaction in a dual-mode cascade photonic crystals circuit will to be researched. As the certification, this project will design a 0.22THz photonic band gap dual-mode cascade Traveling Wave Tube. This project has the potential to solve the problem of low efficiency and small transverse dimension in THz wave interaction tube, improve the output power of a THz TWT, and promote the process of its practical use..

行波管在向太赫兹频段的发展中将面临传输损耗大、电子注和波互作用效率低的问题，解决这个难题的关键在于探索一种基于新型互作用机制的高频电路。若采用高次模式工作，可增大互作用电路的横向尺寸，提高功率容量，但将带来十分严重的模式竞争问题。采用高次模式工作的另一个缺点是：耦合阻抗的绝对值不大，互作用效率通常较低。为了解决上述难题，本项目提出一种预群聚段和辐射段采用采用光子带隙加载选择不同工作模式的互作用电路。分析光子晶体的禁带特性，建立光子带隙加载慢波结构的理论分析模型和仿真模型；研究光子晶体慢波结构中非线性互作用理论与模拟，揭示模式竞争的物理机制；研究双模级联光子晶体互作用的新特性。作为对理论的验证，本项目将设计一支0.22THz光子带隙双模级联行波管。本项目有可能解决太赫兹行波管所面临的互作用效率低、横向尺寸小的问题，推动太赫兹行波管向更大功率发展，促进其实用化进程。