Characteristics of Arbitrarily-Shaped Helical Groove Slow-Wave Structure Loaded with a Concentric Dielectric-Rod
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Characteristics of Arbitrarily-Shaped Helical Groove Slow-Wave Structure Loaded with a Concentric Dielectric-Rod Yu-Bin Gong & Yan-Yu Wei & Hong-Tao Liu
Received: 6 July 2010 / Accepted: 24 September 2010 / Published online: 13 October 2010 # Springer Science+Business Media, LLC 2010
Abstract The dielectric-rod is loaded on the central axis of the arbitrarily-shaped helical groove slow-wave structure. Meanwhile, the profile of the groove is replaced by a series of continuous rectangular steps. The unified dispersion equation of the arbitrarily-shaped helical groove waveguide loaded with a concentric dielectric-rod is obtained by means of a combination of filed-matching method and admittance-matching technique. Then, the effect of the change of groove shape and the dielectric-rod parameters on the dispersion and coupling impedance is approached by theory calculation. The results show that: loaded with dielectric-rod, the bandwidth of the helical groove traveling wave tube (TWT) is effectively broadened, but the coupling impedance is reduced. Among the five different groove shapes, the triangle-type groove has the widest bandwidth but the smallest coupling impedance, and the swallow-tailed-type groove has the narrowest bandwidth but the largest coupling impedance. Keywords Arbitrarily-shaped helical groove . Slow-wave structure . Dispersion characteristics . Coupling impedance . Traveling wave tube
1 Introduction With the rapid development of modern military information technology, the requirement of superior performance microwave devices, which can provide wider bandwidth, higher gain and operating frequency for future electronic-war and space applications, has become more
This work was supported by the Fundamental Research Funds for the Central Universities under ZYGX2009Z003. Y.-B. Gong (*) : Y.-Y. Wei : H.-T. Liu National Key Laboratory of High Power Vacuum Electronics, University of Electronic Science and Technology of China, Chengdu 610054, China e-mail: [email protected] Y.-Y. Wei e-mail: [email protected]
J Infrared Milli Terahz Waves (2010) 31:1412–1421
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and more urgent. The traveling wave tube (TWT) is widely applied in electronic counter measures (ECM), radar [1–4] and satellite communications for its capability of high efficiency and high power in microwave frequency [5–8]. The slow-wave structure (SWS) [9, 10], as a key component of beam-wave interaction in TWT, directly determines the performance of the TWT. Therefore, it has become a main direction to search for novel SWSs [11–18], which can not only improve higher power capacity but also operate over a wider frequency bandwidth. Among these SWSs, the helical groove waveguide has been extensively investigated due to its peculiarities: the superior wholeness stability in structure, the high precision of manufacturing and assembling, large transverse size, low cost, especially applicability for millimeter wave TWT. While, the phase velocity of the electromagnetic wave in the present helical groove structure is still high. For working at a lo
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