Li Renjie, Ruan Cunjun, Fahad Ayesha Kosar, Zhang Chenyu, Li Shasha
School of Electronic and Information Engineering, Beihang University, Beijing, 100191, China.
Sci Rep. 2019 Mar 14;9(1):4584. doi: 10.1038/s41598-019-41087-3.
Terahertz applications require high performance and high reliability terahertz radiation sources, especially the urgent demands of high output power and broad bandwidth. The extended interaction klystron (EIK) has the great potential to generate hundreds of watt output power in terahertz band. The terahertz EIK adopts multiple gap cavities and unequal-width slots structure is proposed with methodological improvement of bandwidth and output power. The unequal-width slots are the key design of the multiple gap cavity, and the influences of unequal-width slots on the electromagnetic field distribution and beam-wave interaction are analyzed in detail. With multiple gap cavities and unequal-width slots structure, EIK has advantages of wider frequency separation and larger effective characteristic impedance. Particle in cell (PIC) simulation indicates that the bandwidth of unequal-width slots structure can reach to 550 MHz in our initial G-band EIK design. Then, we utilize two kinds of resonance cavities with different width ratios to build a six-cavity beam-wave interaction system and make it operate at the state of stagger-tuning, the bandwidth can be extended to 1-1.5 GHz. Our research shows that the unequal-width slots structure has wider tuning frequency range. Furthermore, the bandwidth can be further broadened to over 2 GHz when dynamic-tuning is adopted, while maintains a high output power of 560 W with efficiency of 11.3% and gain of 47.5 dB. Thus, the methods of multiple gap cavities with unequal-width slots structure, stagger-tuning and dynamic-tuning are much important for the bandwidth improvement of EIK in terahertz band.
太赫兹应用需要高性能和高可靠性的太赫兹辐射源，尤其是对高输出功率和宽带宽的迫切需求。扩展互作用速调管（EIK）在太赫兹频段产生数百瓦输出功率方面具有巨大潜力。提出了采用多个间隙腔和不等宽缝隙结构的太赫兹EIK，以在带宽和输出功率方面进行方法上的改进。不等宽缝隙是多个间隙腔的关键设计，并详细分析了不等宽缝隙对电磁场分布和注波互作用的影响。采用多个间隙腔和不等宽缝隙结构，EIK具有频率间隔更宽和有效特性阻抗更大的优点。粒子模拟（PIC）表明，在我们最初的G波段EIK设计中，不等宽缝隙结构的带宽可达550兆赫兹。然后，我们利用两种不同宽度比的谐振腔构建一个六腔注波互作用系统，并使其在交错调谐状态下运行，带宽可扩展到1至1.5吉赫兹。我们的研究表明，不等宽缝隙结构具有更宽的调谐频率范围。此外，当采用动态调谐时，带宽可进一步拓宽到超过2吉赫兹，同时保持560瓦的高输出功率，效率为11.3%，增益为47.5分贝。因此，多个间隙腔与不等宽缝隙结构、交错调谐和动态调谐的方法对于太赫兹频段EIK的带宽改善非常重要。
