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A novel slotted helix slow-wave structure (SWS) is proposed to develop a high power, wide-bandwidth, and high reliability millimeter-wave traveling-wave tube (TWT). This novel structure, which has higher heat capacity than a conven- tional helix SWS, evolves from conventional helix SWS with three parallel rows of rectangular slots made in the outside of the helix tape. In this paper, the electromagnetic characteristics and the beam-wave interaction of this novel structure operating in the Ka-band are investigated. From our calculations, when the designed beam voltage and beam current are set to be 18.45 kV and 0.2 A, respectively, this novel circuit can produce over 700-W average output power in a frequency range from 27.5 GHz to 32.5 GHz, and the corresponding conversion efficiency values vary from 19% to 21.3%, and the maximum output power is 787 W at 30 GHz. 相似文献
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科技人才观是科技人才发展的重要指南,是我国科技创新的指导思想之一。科技人才政策是落实科技人才观的首要载体,科技人才观蕴含在科技人才政策中。总结梳理科技人才政策的演变历程和实践情况,有助于探析中国特色科技人才观的内涵。我国70年的科技人才政策经历了摸索、发展和深化3个阶段,"如何界定科技人才""如何看待科技人才""如何评价科技人才""如何培养科技人才"和"如何使用科技人才"等思想观念在这3个阶段中不断发展和完善,并在政策实践的检验下形成了结构完整、内容科学、环环相扣、互相作用的中国特色科技人才观内涵。 相似文献
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提出了一种角度对数周期微带曲折线慢波结构,该结构具有微带型慢波结构尺寸小、易加工的特点,同时特殊的结构使得它可以工作在极低的电压下,可用于低工作电压、宽频带毫米波径向束行波管。给出了这种慢波结构在Ka波段的色散特性和传输特性,并进行了注波互作用的分析。计算结果表明:该新型慢波结构的工作电压可低至809 V,输出功率26 W,3 dB带宽约为19 GHz (27~46 GHz),虽然单个角度对数周期微带曲折线慢波结构的输出功率较小,但是这种结构通过功率合成,可以达到数百W的功率输出。 相似文献
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The photonic crystal structure has attracted much attention due to its ability to confine light. In this paper, we present our study on an improved Smith-Purcell radiation from a simple metal photonic crystal excited by moving electrons. Different from the wide-band Smith-Purcell radiation from a single metal grating, the results show that the injected electrons could induce more dipole oscillations inside the multi-grating structure, and it leads to the enhancement of the radiation intensity. In addition, there are strong resonances in metal multi-grating structure, and the resonance characteristics may narrow the radiation band, which leads to a radiation with an obvious peak in the spectrum. Therefore, the multi-grating structure has the ability to enhance the radiation intensity and shape the radiation frequency band. By optimizing the structure parameters, coherent and tunable Smith-Purcell radiation can be realized, and it provides a potential way to develop band-controllable light or THz radiation source. 相似文献
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自我国创立环境科学这门学科以来,我国的环境科学研究体系经过这几十年的发展已经逐渐形成并取得了丰硕的科研成果,然而在我国的经济发展与环境、资源矛盾日益加重,政府大力发展绿色环保产业,并不断加大环境保护方面的投入背景之下,高校环科毕业生在就业市场却面临有价无市的尴尬局面。相信随着环保和可持续发展作为国家一项战略性任务的提出,必将推动环境科学这门学科的迅速发展。环境科学专业的毕业生也一定会受到更多用人单位的青睐。 相似文献
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