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Shielding Performance of Triply Shielded Coaxial Cables 总被引:1,自引:0,他引:1
Demoulin B. Degauque P. Cauterman M. Gabillard R. 《Electromagnetic Compatibility, IEEE Transactions on》1980,(3):173-180
We determine the shielding effectiveness of a triply shielded coaxial cable and compare it to the performance of a singly shielded cable. Then we apply well-known transmission-line theory to make a parametric study of the shielding performance as a function of the geometrical and electrical parameters of the braids. We suppose that the three braids are homogeneous, in order to use exact expressions relating the transfer impedance to the shield characteristics. We study the influence of the intersheath space on screening effectiveness and on the intersheath resonances. To damp these resonances, a material having a low conductivity could be used between the braids. To improve the shielding at low frequencies, an intermediate copper braid can be replaced by a ferromagnetic material. We take into account the variation of the permeability as a function of frequency and we point out, in this case, the effect of the intersheath space. 相似文献
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A numerical technique is developed that may be used to analyze the shielding characteristics of a cable with a saturable ferromagnetic outer sheath in an intense low-frequency environment. The solution relates the center conductor current to the total current exciting a coaxial cable with a ferromagnetic sheath. Several examples are given to illustrate how saturation effects the shielding properties of a ferromagnetic sheath. 相似文献
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毫米波半柔软射频同轴电缆的研制 总被引:1,自引:0,他引:1
介绍了一种毫米波半柔软射频同轴电缆的结构设计与制造工艺。该电缆可传输毫米波射频信号,具有传输频率高(40GHz)、插入损耗小、弯曲成型能力强等性能特点。微孔聚四氟乙烯绝缘和导电金属层+镀锡铜线编织+热浸锡整体外导体结构是该电缆的主要创新点。 相似文献
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EPON+低频EOC在乡镇广电网双向改造中的应用 总被引:1,自引:1,他引:0
EPON+低频EOC技术接入模式比较适合有线电视双向改造,阐述了EPON+低频EOC的工作特性,认为完全可以做到灵活、快捷、经济地改造现有有线电视网络,介绍了设计、调试、监测直至应用一套组合网络的过程、方法。 相似文献
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李庆和 《光纤与电缆及其应用技术》2011,(5):15-18,34
3GHz宽带漏泄同轴电缆的设计要求是在3GHz宽带频率范围内所有使用频段都具有有效的传输距离(衰减)及良好的辐射特性(足够的耦合损耗及均匀的全向辐射场强图)。通过外导体“八”字槽孔结构参数的设计调整,研制出在3GHz所有的通信频率中均能使用,并具有优良性能的辐射型漏泄同轴电缆。 相似文献
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本文采用嵌入式设计方法,实现了电缆故障检测系统的自动化、集成化、便携化设计,能够完成绝缘阻值测量、电缆长度测量、回路电阻测量和故障定位等功能,可测试各种型号电缆上发生的短路、接地、接触不良等故障,用于实战有线通信和高频电缆的敷设与维护,可有效提高电缆线路故障的排除时间。 相似文献
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Submarine optical-fibre cable design considering low elongation under tension is proposed. Submarine cable using aluminium pressure resistant pipe according to this design can decrease the cable elongation under laying and recovery, and can be used even in deep sea up to a depth of 5000 m. 相似文献
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Heng-Chia Chang 《Microwave Theory and Techniques》2003,51(9):1994-1999
Phase-noise analysis of the self-injection-locked oscillator is presented in this paper. The analysis is developed for different oscillator models and arbitrary self-injection feedback loops. The results are illustrated with specific cases of simple time-delay cable and a high-Q factor resonator. It is shown that the behavior of the phase noise is similar to an oscillator locked to an external low phase-noise source. The output phase noise can be reduced at the noise offset frequency near the carrier frequency, and returning to the free-running oscillator noise far from the carrier frequency for certain stable feedback delay ranges. The phase-noise reduction is affected by the self-injection signal strength and feedback transfer function for different oscillator equivalent-circuit models. The theory is verified by using a self-injection-locked GaAs MESFET oscillator operating at the X-band with delay cable loops. The self-injection-locked technique may be used to improve the phase noise of the existing oscillators. 相似文献
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介绍了一种基于电磁感应原理的电缆路径检测仪的硬件设计。利用发射设备向电缆中注入一定频率和强度的电流信号,根据电缆路径检测仪中的线圈所产生的感应电动势的强弱来判断电缆的具体位置,从而确定电缆的路径。该系统中以单片机和FPGA为核心,由信号处理电路、单片机系统、高速ADC等硬件电路模块组成。文中对该系统的工作原理作了详细描述。 相似文献
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针对分布式光缆防外破监测系统易受降雨振动影响造成系统误报,干扰系统正常运行的问题,文章通过搭建一套分布式外破监测系统用于采集信号,并分析雨水信号与人工光缆作业、机械施工信号的时域与频域特征差异,研究雨水信号识别的可行性,以期分辨出降雨信号,排除干扰。结果表明:雨水信号在低频段区间强度高,在高频段强度低,随着频率增高强度呈明显下降趋势。雨水信号特征在影响范围、频谱特征等方面均与人工光缆作业和机械施工存在较大差异。因此,可通过对雨水信号进行识别,减少外破监测系统误报率。 相似文献
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在射频功放运用中经常会涉及到使用一些低阻抗的同轴电缆的情况,如制作平衡-非平衡轮换的巴伦,以及特定阻抗变换电路? 研究了根据标准同轴电缆的结构,通过改变部分关键结构参数,制备任意非标准的低阻抗同轴电缆技术方法;通过同轴电缆中的电磁传播理论分析和推导,提出准确测试低阻抗同轴电缆的可调电阻测试法? 相似文献
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从ADSS光缆的结构特点入手,分析了光纤余长和抗张元件在ADSS光缆设计中的重要地位,详细阐述了层绞式ADSS光缆中绞合余长的产生机理和控制方法以及加强元件芳纶纱的选取原则和求解过程,并提出了ADSS光缆的发展方向和开发前景。 相似文献
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A theory on the shielding effectiveness of n coaxial metallic tubings which shield a coaxial cable has been developed based on electromagnetic (EM) field theory. The theory holds for all homogeneous, linear, and isotropic shields, magnetic or nonmagnetic, and covers essentially the entire frequency range. When a cable carries an evenly distributed axial current, the dominant mode of propagation is transverse magnetic (TM) and has only three field components, i.e., Ez, H?, and Er. The fields of the dominant mode leaking from the cable, with and without shields, have been determined rigorously from the solutions of Maxwell's equations and boundary conditions. The shielding effectiveness of the tubings, defined as the insertion loss, has thus been readily obtained. To simplify the obtained expressions to a certain degree such that numerical calculations are manageable, various approximations have been introduced and precisely justified. The limitations imposed on the simplified expression due to the approximations have been clearly listed. It has been shown that Schelkunoff's shielding theory is merely a special case of the present work. As an example, the shielding effectiveness of a single copper tubing surrounding an RG-8/U cable has been considered. The data measured from a carefully designed experimental setup show that at high frequencies, i.e., above 10 kHz, the curve predicted by the present work is about 1 dB above the empirical curve, while the curve due to Schelkunoff is about 5 dB below the empirical curve. At low frequencies, i.e. 相似文献
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介绍一种基于时域脉冲回波(TDR)原理的ADSL线缆断点测试系统。该系统设计以STC单片机为控制核心,以FPGA为测试主体发射接收脉冲.采集脉冲往返线缆时间,实现ADSL线缆断点位置的测量。在分析现有测试产品的基础上,首先阐述设计理论。然后介绍系统总体设计框图、硬件实现、软件测试流程以及系统实际测试结果。实验结果表明该测试仪能够快速准确测试出断点位置,并且只需适当剪切,便可作为内嵌模块应用于其他仪表。 相似文献
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Antonini G. Cristina S. Orlandi A. 《Electromagnetic Compatibility, IEEE Transactions on》1997,39(2):114-123
Ferromagnetic grids are becoming more and more popular for electromagnetic shielding applications in avionics, satellite design, and power electronic systems. This paper presents an equivalent homogeneous but anisotropic model of a planar ferromagnetic grid. The nonlinear characteristic and the hysteresis of the material are taken into account. The field source is a low frequency magnetic dipole placed in the proximity of the grid. Both grid and source models are given in the form of multiconductor transmission line (TL) equations. They are solved, in the time domain, by the circuit simulator SPICE 相似文献
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Lancaster M.J. Jiafeng Zhou Maolong Ke Yi Wang Jiang K. 《Microwave Theory and Techniques》2007,55(7):1548-1553
This paper presents the design and performance of a low-loss rectangular air-filled coaxial cable. A high-precision micromachining technique is used to fabricate the cable. It is assembled by bonding together five layers of gold-coated SU-8 photoresist fabricated using the ultraviolet photolithographic technique. As the cable is air filled, both the dielectric and radiation losses are negligible. The cross coupling is also very weak between the cable and other parts of the circuit in a system. These advantages make the proposed cable a very good candidate for low-cost high-performance miniaturized transmission lines. The cable is designed to work in the frequency range of 14-36 GHz, which covers the whole JC-band. The size of the cable is only 8.9 mm times 8.6 mm times 1.5 mm and the measured minimum insertion loss of the as-made cable is approximately 0.6 dB. The return loss is better than 15 dB in the passband. 相似文献