共查询到20条相似文献,搜索用时 125 毫秒
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芯线供电即通过同轴电缆的芯线与外屏蔽传输安全交流低电压,对网络中的有源器件进行供电。采用芯线供电,就必须考虑,电缆的外导体质量、抗腐馈性能、环路电阻及电缆连接的可靠性和接头的抗腐蚀性能,随着国产优质器材的成功生产(如QR540,MC~2500,铝管—12等),芯线供电由于其可靠性和安全性能,成为有线电视网升级改造中最 相似文献
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1 同轴电缆的衰减频率特性同轴电缆对所传输的信号有衰减作用 ,其衰减量不仅与同轴电缆的内外导体直径和绝缘材料的相对电容率 (介电常数 )有关 ,还与信号频率有关 ,并且电缆越长衰减量越大。把单位长度 (如 10 0m)电缆对信号衰减的分贝值称作同轴电缆的衰减常数 ,常温下 (2 0℃ )其大小为 :l=2 .6 3εf1d+ 1Dlg Dd (dB/ 10 0m) (1)式中 d———内导体 (芯线 )外径 (mm) ;D———外导体 (屏蔽层 )内径 (mm) ;ε———绝缘层相对电容率 (介电常数 ) ;f———传输信号频率 (Hz)。当电缆的型号和规格确定之后 ,(1)… 相似文献
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屏蔽电缆的屏蔽层主要是作为电磁辐射、电磁干扰和接地保护的作用。屏蔽层悬浮电位的接地主要有单点接地、多点接地、交叉互联和连续交叉互联等方式。对于接地的屏蔽电缆是由电容效应和电感效应组成的。本文通过仿真模拟137/220 kV屏蔽电缆单端接地与双端接地的电容效应,研究不同高压输电线路下屏蔽电缆的电压电流分布特性,进而分析220、330、500 kV屏蔽电缆屏蔽层的电压电流特性和损耗特性。 相似文献
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Jung L. Luiken ter Haseborg J. 《Electromagnetic Compatibility, IEEE Transactions on》1999,41(4):460-468
Besides the knowledge of the primary line parameters per unit length, the determination of the complex transfer impedances and transfer admittances of shielded multiconductor cables is the prerequisite for the calculation of the propagation of disturbing currents on the inner wires of the cable. With a measurement procedure based on triaxial measurement setups using multiconductor transmission line theory for evaluation, it is possible to determine individual transfer impedances and admittances for each inner conductor of a shielded multiconductor cable over a broad frequency range. This paper shows the measurement procedure, the method of evaluation: and from measurement results, the determination of the location and the calculation of the area of single-shield inhomogeneities by the evaluation of measured transfer impedances and transfer admittances 相似文献
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This paper presents the study of coupling between multiconductor cables from the multiconductor lines theory and the assumption of perfectly conducting ground. The cables can be excited by generators of arbitrary waveforms and terminated by arbitrary impedances. The medium surrounding the conductors can be homogeneous or inhomogeneous and the conductors can have finite conductivity. Once the used assumptions indicated, we formulate the complete solutions of induced currents and voltages at the ends of the multiconductor line, by using the state variable theory. We give numerous comparisons of numerical results, obtained by our numerical code, with literature (microstrip lines) and experimental results (shielded cables, unshielded RNIS bus). 相似文献
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Homentcovschi D. Manolescu A. Manolescu A.M. Kreindler L. 《Microwave Theory and Techniques》1988,36(6):1002-1007
An analytical method is presented for determining the Maxwell's capacitance matrix of multiconductor shielded microstrips with coupled conductors of arbitrary widths, spacings, and inhomogeneous media, in terms of elliptic integrals. The method is based on conformal mapping and the theory of singular integral equations. Two kinds of problems are presented as examples: the first consists of simple structures with one or two coupled striplines; the other type concerns the general case of multiconductor coupled structures for which simple analytical expressions are not available 相似文献
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V. V. Tyurnev 《Journal of Communications Technology and Electronics》2006,51(7):788-791
A method is proposed for calculating a shielded homogeneous multiconductor transmission line containing conductors of circular cross section. Formulas are obtained for the matrix of the conductor capacitance per unit length and the electric parameters of transverse electromagnetic waves. 相似文献
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V. V. Tyurnev 《Journal of Communications Technology and Electronics》2007,52(11):1252-1258
For the first time, a method is proposed for numerical calculation of a monolithic multiconductor shielded transmission line integrated with planar coupling circuits. Formulas for the matrix of the per-unit-length capacitance of coupled conductors are derived. The electric parameters of fundamental modes are calculated in the quasi-static approximation. The computation results can be used for designing monoblock microwave filters. 相似文献
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Theethayi N. Thottappillil R. 《Electromagnetic Compatibility, IEEE Transactions on》2007,49(4):924-927
This paper investigates the importance of a follow-on buried bare earth wire for the lightning protection of buried shielded cables. The use of follow-on bare wires for lightning protection of communication towers was suggested as a recommendation in certain standards, without being complemented either by theory or experiments. When lightning transients couple to the cable shields, it induces large currents (depending on the type of coupling) causing transient overvoltages between the inner conductors and the shield. It is shown by simulations based on multiconductor transmission line theory that if the follow-on bare earth conductor is placed in parallel with the shielded cable with the bare earth wire connected to the shield at the current injection end, then the shield current, and thereby, the internal transient voltages of the cable are reduced considerably. 相似文献
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An exact analytical expression for the capacitance matrix of a shielded or open multiconductor microstrip structure is derived by solving the system's dual integral equations by constructing a Volterra boundary-value problem (BVP). The solution is expressed in terms of infinite matrices with very good convergence properties. This new approach uses a series of Bessel functions rather than trigonometric series to approximate the solution which results in an efficient algorithm. Simplified formulas are given for the even and odd capacitance of symmetric coupled microstrip lines and compared to the results given by the finite analytical solution available in this particular case. Numerical examples demonstrate that the method yields accurate results and is computationally effective for structures having a large number of conductors 相似文献
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外部电磁场对屏蔽多导体电缆系统耦合影响的分析 总被引:4,自引:0,他引:4
本文给出了一个有效的、用以分析外部电磁场对屏蔽多导体电缆系统电耦合影响的方法,适用于电缆的频域或时域电磁兼容分析。 相似文献
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SPICE-like models for the analysis of the conducted and radiated immunity of shielded cables 总被引:2,自引:0,他引:2
The aim of this work is the development and validation of compact SPICE models suitable to analyze the conducted and radiated immunity of shielded cables. The reference structures are coaxial cables, and shielded cables with two parallel wires (i.e., twinax cable). The conducted and radiated immunity of the shielded cables are evaluated considering as source a known injected current on the cable shield, and the coupling with an external plane wave electromagnetic field, respectively. The circuit models are validated by comparing the results with those obtained by other approaches. The developed models are then used to quantify the main grounding practices of shielded cables. 相似文献