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目前,基于Cable Modem技术的HFC接入网已得到较为广泛的应用,但网络中的漏斗噪声限制了系统带宽的充分利用.着重分析上行信道的噪声特性,并根据噪声特性,研究了TDMA,FDMA和CDMA 3种多址接入技术的特点,认为TDMA/FDMA混合方案更适合HFC网络上行信道的传输要求. 相似文献
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目前 ,基于CableModem技术的HFC接入网已得到较为广泛的应用 ,但网络中的漏斗噪声限制了系统带宽的充分利用。着重分析上行信道的噪声特性 ,并根据噪声特性 ,研究了TDMA ,FDMA和CD MA 3种多址接入技术的特点 ,认为TDMA/FDMA混合方案更适合HFC网络上行信道的传输要求 相似文献
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在利用HFC网进行多功能业务的实践中,上行性能的改善,尤其是各种上行噪声的抑制关系到HFC网络整体质量及业务实现的成败。本文重点分析了HFC宽带接入网上行信道的噪声特性及噪声来源,提出了一些抑制上行噪声干扰的方法和措施。 相似文献
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本文详细论述了HFC网上行信道噪声的来源、分类和性质,深入讨论了HFC网络上行信道噪声的形成机理与抑制方案。 相似文献
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针对HFC网络上行信道的噪声和干扰特性,介绍了S—CDMA(同步码分多址)技术。对S—CDMA的技术原理和性能进行分析研究,并详细介绍了S—CDMA技术在HFC网络中的应用情况: 相似文献
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1 引言 HFC交互式有线电视系统同轴电缆接入网络上行信道除了非线性失真外,还存在噪声漏斗效应、回波反射和窄带短波干扰等影响通信的因素,这些因素的存在影响了HFC同轴电缆网络双向通信系统的设计和实现。 在上行信道中,具有比下行信道更高的热噪声和其它随机噪声电平,这可以用噪声漏斗效应因子来衡量;另外,存在的窄带调幅短波干扰对HFC的双向通信具有较大的影响,这两个因素将影响到上行信道调制技术的选择。 本文主要研究和分析了上行信道调制技术的选择问题。 相似文献
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DingYaogen 《电子科学学刊(英文版)》2002,19(4):441-444
Recent research progresses in Multi-Beam Klystron(MBK)in IECAS are briefly introduced in the letter,The S-band MBKs of IECAs have peak power of 120-250kW,average power of 4-9kW,efficiency of 35-45%,gain of 41-46dB.beam voltage of 15-19kV,and weight of 40-45kg.Some key technical problem of MBK are also described and discussed.Among them,improving the design of MBK to botain the required bandwidth,raising beam transmission to increase average power,eliminating oscillation and spray spectrum,overcoming window breakdown caused by magic mode,reducing breakdown times of electron gun,are most important things for the practical MBK.Besides,further research owrk in MBK in IECAS is commented. 相似文献
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《Digital Communications & Networks》2018,4(4):244-257
This paper presents a review of recent investigational studies on exciting Surface Plasmon Polaritons (SPPs) in MicroWave (MW) and TeraHertZ (THz) regimes by using subwavelength corrugated patterns on conductive or metal surfaces. This article also describes SPP Microstrip (MS) structures at microwave and terahertz frequencies, and compares their significance with that of conventional MS Transmission Lines (TL), in order to tackle the key challenges of high gain, bandwidth size, compactness, TL losses, and signal integrity in high-end electronic devices. Because they have subwavelength properties, surface plasmon polaritons are gaining attention for their improved performance and ability for miniaturization in high-speed dense circuits. They possess comparably minuscule wavelength compared to incident light (photons). Consequently, they can demonstrate stronger spatial confinement and higher local field intensity at optical frequencies. In addition to engineering spoof SPP waveguides, which are created by engraving grooves and slits on metal surfaces to allow operation on at low frequencies (microwave and terahertz), semiconductors with smaller permittivity values and thus lower free charge carrier concentration have been demonstrated as a potential candidate in plasmonic devices. If necessary, further tuning of semiconductor-based SPP structures is aided by controlling the charge carrier concentration through doping, or by external stimuli such as optical illumination or thermal excitation of charge carriers from valence to conduction bands. This article conclusively covers previously elucidated perspectives on manipulating SSPPs in the MW and THz ranges, and emphasizes how these could steer next-generation plasmonic devices. 相似文献
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The Digital Gap has been recognized as one important issue to develop a country. This paper reviews the most important concepts and parameters that take place in the information and communications technologies and Digital Gap matter. Also reports a survey made in Maracaibo, the second largest city of Venezuela in order to determine the access level to such technologies and discuss the government policies in order to reduce the Digital Gap. 相似文献
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模电教学中的形象思维 总被引:1,自引:0,他引:1
赵青梅 《电气电子教学学报》2001,23(6):104-105,108
阐述了形象思维在认识客观世界时的重要作用,同时以大量的实例说明形象思维在模电课程中的应用,并论述了如何在模电教学中利用形象思维提高教学质量,同时培养学生的形象思维能力。 相似文献
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域名系统面临的安全威胁和风险不断加大,安全事件增多主要是缺乏有效的监管和相应的更积极的技术手段和措施。因此,转变对互联网非传统安全问题的认识.充分研究域名系统面临的新情况、新问题和新威胁,切实增强保障域名系统安全的责任感和紧迫感,是保证我国互联网稳定发展的前提。 相似文献
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《Electron Devices, IEEE Transactions on》1972,19(4):524-531
A review is given of the progress in electrophotographic science and technology in Western Europe during the years 1967 to early 1971. University research work is mainly directed towards two areas: 1) the electrical and physical properties of photoconductors, such as selenium, chalcogenides, oxides, and organic materials; and 2) the sensitization of these photoconductors. Industrial research teams report on the preparation of electrophotographic layers on development and on image evaluation. A bibliography including scientific papers and patents published on this subject during said period completes this review. 相似文献
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本文介绍了DDN的基本结构和作用,分析了DDN设备的几个特点,指出了DDN在惠州市电信业务中的几种主要的应用,最后还指出了DDN设备使用中存在的问题。 相似文献