编织参数对电缆辐射特性的影响

从屏蔽电缆的共模辐射机理引出转移阻抗,结合某型动车组线槽和屏蔽电缆结构,通过仿真软件对不同编织参数电缆的屏蔽性能做出了规律性的分析,并与编织层覆盖率计算公式相互验证了计算结果.结果表明:编织束数、编织束内的导线数、单位长度上编织层交叉的股数的增加会导致转移阻抗减小、屏蔽效能增大,但电缆的低耗和柔韧性降低.电缆参数优化,需综合考虑各参数对电缆整体性能的影响.     

从“部标”看我国聚四氟乙烯绝缘同轴射频电缆水平

本文从F_4电缆的规格、工艺和主要性能(工作温度,特性阻抗,试验电压,电晕电压)等方面分析指出,我国F_4电缆基本接近IEC标准规定的水平。但是,在镀银铜包钢线、衰减等方面还有差距。今后需进一步开展铜包钢线、编织密度与屏蔽系数、电缆使用寿命、标记、原材料标准等方面的研制工作。     

超屏蔽电缆

本文讨论了编织电缆屏蔽中所涉及的基本现象,说明了解这些现象有助于改善这种屏蔽的表面转移阻抗。叙述了在两层编织之间采用磁性材料,再结合所述最佳技术知识,就能大大改善屏蔽性能,磁性材料以磁性带的形式适当地加到电缆结构中去,从而保证了这样的屏蔽性能。     

编织屏蔽同轴射频电缆的屏蔽效率

本文叙述按照电磁耦合机理试验研究编织蔽同轴电缆屏蔽的泄漏特性。用改进三同轴法(加计算机程序)在扩散作用可以略去不计的频率下,能间接测出屏蔽电缆的转移电感与几何转移比(L_T和GTR)。这两个量只与屏蔽结构有关,而与实验条件无关。它们代入相应方程后可表示屏蔽泄漏特性。端接三同轴法,用平衡-不平衡变换器端接。围绕试样端部安装铁氧体园环,使沿电缆外表面向平衡-不平衡盒子流动的电流变为最小。测定了电容耦合阻抗并在导出的完整的转移阻抗数学表达式中考虑了它的影响。四同轴法测出屏蔽效率(S、E)=Z_0logR_L-Z_T与编织物理参数(编织角、编织线尺寸、锭子数及编织密度)的关系,这对进行最佳屏蔽计具有重要的实际指导意义。     

电缆屏蔽效率测试

本文讨论了一种经过改进的电缆屏蔽系数测试方法,并叙述了单支及多分支电缆的试验结果。也提到了影响电缆屏蔽参数的主要因素。它们是:编织层数、编织材料、编织角,复盖率、电缆长度及线径,本方法允许测量长的样品,并可采用大电流,但沿电缆屏蔽应有均匀的电缆分布。测量是在频率为0.5～100兆赫范围内进行的.本方法被提议为屏蔽电缆屏蔽效率测试的一项标准技术。     

安德鲁公司新品频出

美国安德鲁公司(Andrew Corporation)近期不断推出新品,仅在一个多月的时间里就有3种新产品面市。 安德鲁全新5/8"LDF4.5-50HELIAX同轴电缆。该电缆适用于对性能和成本效益要求较高的无线应用系统,以及要求低衰减和短电缆的站点。此电缆由可降低衰减率的泡沫介质、易于连接的实心导线和波纹外护套实心铜线组成,该护套比编织屏蔽电缆具有更高的屏蔽性能。     

水密电缆的结构分类及特性分析

引言随着现代化建设的需求,近年来水密电缆(要求纵向阻水)应用越来越多,但我国当前对该类电缆没有完善的标准对其进行控制,因此我国当前生产的水密电缆种类繁多,性能参差不齐。本文对当前应用的水密电缆设计特点进行了分类归纳和简要评述,希望通过本文对该种结构电缆发展能够起到一些帮助。一水密电缆分类目前常用的水密电缆按照用途及特性分类可分为六大     

多芯屏蔽视频电缆转移阻抗的测试研究

本文讨论了基于"三同轴法"的多芯屏蔽视频电缆转移阻抗的测试原理和方法,据此方法我们设计给出了使用矢量网络分析仪作为信号源及接收器实现多芯屏蔽视频电缆转移阻抗测试的测量装置和测试结果,最后基于测试结果我们对多芯屏蔽视频电缆的屏蔽效能进行了验证,从而证明了多芯屏蔽视频电缆转移阻抗对信息安全的重要意义.     

超小型同轴电缆表面转移阻抗的测量

为了确定电磁屏蔽特性,对 RG-174/U,RG-188/U 及小型同轴屏蔽线等几种柔软超小型同轴电缆的表面转移阻抗进行了测量。测量在0.1～50兆赫频率范围内进行的。得出的结果与以前的理论模式一致,并且 RG-58那样的大电缆的实验值一致.铜编织超小型电缆的表面转移阻抗值比 RG-58的值大2～5倍。     

屏蔽特性

㈠外界干扰的种类射频电缆在高功率雷达、广播电台、电力线或其它工业用电装置附近使用时,如果电缆的屏蔽性能不好,则它会从这些外界干扰场吸收噪声讯号而影响其正常工作,一般说来,同轴或屏蔽线缆可以通过如下三种途径来接收外界噪声:     

Surface Transfer Impedance Measurements on Subminiature Coaxial Cables

The surface transfer impedances (STI) of several flexible subminiature coaxial cables, such as RG-174/U and RG-188/U, plus smaller coaxial shielded wires, were measured to determine EM shielding characteristics. The results cover the frequency range 0.1-50 MHz and correlate well with previous theoretical models and with experimental values for larger cables, such as RG-58. Copperbraided subminiature cables had STI values 2-5 times larger than those for RG-58     

Present status and outlook of line transmission systems in China

The various line transmission media, including open wires, symmetrical pair cables, coaxial cables, and optical fiber cable, that are used in the different regions of China are described. Both analog transmission systems and the newer digital transmission systems are discussed. The standardized physical transmission media deployed throughout China-symmetrical pair cables, coaxial cables, and optical fiber cables-are also discussed     

镀镍铜粉填充型电磁屏蔽硅橡胶性能研究

研究了镀镍铜粉填充型电磁屏蔽硅橡胶的力学性能、电性能、电磁屏蔽效能及耐电化腐蚀性能。结果表明,在保证其良好的力学性能前提下,镀镍铜粉填充型硅橡胶在30 MHz～18 GHz的频段范围内具有良好的屏蔽效能,并且可提供极好的耐电化腐蚀性能。在高温高湿环境中具有良好的电性能和屏蔽效能稳定性。通过与镀银铜粉填充型的硅橡胶相比较,发现材料体积电阻率的大小和屏蔽性能的优劣没有直接的相关关系。     

Cable shielding measurements at microwave frequencies

A matched triaxial device is developed and constructed to measure the transfer impedance of braided coaxial cables at microwave frequencies. Full-design principles of the device have been developed and given in detail in the paper. The device is particularly suited for shielding measurements at frequencies up to 3.5 GHz, for which no comparable technique exists. The performance of the device is fully evaluated both theoretically and by measurements. The accuracy of the device is studied by comparing the results against those obtained from the low-frequency International Electrotechnique Committee triple-coaxial apparatus, and using well-known theoretical models.     

射频同轴电缆屏蔽衰减测试方法的比较

屏蔽衰减是表征射频同轴电缆电磁兼容性的重要指标。随着电缆相关理论的发展和应用,国际上出现了各种不同的针对射频同轴电缆屏蔽衰减的测试方法。介绍了当前各类典型的测试方法,并对其进行了比较。     

Economic Analysis of Fiber Versus Alternative Media

The paper presents economic analysis of single-mode and multimode fiber optic cables in the telecommunications environment. Fiber optic cables are economically compared to alternative transmission media including twisted pair copper cables, screened copper cables, coaxial cables, and various radio facilities. Economic sensitivity to growth rates and digital office integration is performed to investigate variables influencing the economic study.     

Modélisation de l’impédance de transfert des câbles coaxiaux à blindages multiples

The shielding effectiveness of multishielded coaxial cables is determinated through the concept of the equivalent transfer impedance. The transfer impedance is computed from the main parameters of the coaxial structure. We describe in this paper the theoretical formulation to evaluate the amplitude of the disturbing voltage at the end of the cable flowed by the disturbing current. This result is used for the computation of the equivalent transfer impedance when the cable is made of various shields for exemple: homogeneous screens or braids. A comparison with the experimental results is also described.     

Undersea fiber cable technology

Compared with the conventional coaxial undersea cable systems, an optical fiber undersea cable system has a great technical and economical advantage. It is also suitable for digital transmission. In this paper, the optical fiber undersea cable technology (including optical fiber cables and repeaters), which is now in the research and development stage in several countries, is reviewed.     

Shielded Microstrip Array for 7T Human MR Imaging

The high-frequency transceiver array based on the microstrip transmission line design is a promising technique for ultrahigh field magnetic resonance imaging (MRI) signal excitation and reception. However, with the increase of radio-frequency (RF) channels, the size of the ground plane in each microstrip coil element is usually not sufficient to provide a perfect ground. Consequently, the transceiver array may suffer from cable resonance, lower Q-factors, and imaging quality degradations. In this paper, we present an approach to improving the performance of microstrip transceiver arrays by introducing RF shielding outside the microstrip array and the feeding coaxial cables. This improvement reduced interactions among cables, increased resonance stability, and Q-factors, and thus improved imaging quality. An experimental method was also introduced and utilized for quantitative measurement and evaluation of RF coil resonance stability or “cable resonance” behavior.      

同轴电缆线和测量夹具对滤波器性能的影响

研究了在测量时同轴电缆线和测量夹具对微波滤波器性能的影响。实验结果表明:同轴电缆线的特性阻抗对微波滤波器的通带影响很大,而测量夹具的夹持和固定对整个滤波器的性能也有影响。作者通过实验研究提出了减小该类影响的有效措施。