Transfer impedance of braided coaxial cables under applied longitudinal torsion

The surface transfer impedance ZT of several braided coaxial cables was measured under applied longitudinal torsion to determine the electromagnetic shielding characteristics of the cables under such conditions. The results cover the frequency range 100 kHz to 150 MHz with torsion angles varying between 0°, +360° m?1 and ?180°m?1. It was found that ZT increases with torsion angle and depending on the degree of optimisation in the braid, increases of up to 800% can occur at a torsion angle of 360° m?1. Further, when a cable is returned to its original position, after being subjected to torsion, the resulting value of ZT is higher than the original value.     

High-frequency coaxial cables

It is shown that simple transmission-line theory leads to agreement with Millington and radical conflict with Barlow concerning the effect of dielectric layers on the conducting walls of a high-frequency coaxial cable. Suggestions are given of possible sources of error in Barlow's analysis of the power-flow method, and mention is made of the Riccati equation satisfied by the ratio Ex/H?, with an approximate solution agreeing with Millington's results. The experimental values of attenuation reported by Barlow and Sen are therefore, as yet, unexplained theoretically.     

Current flow in coaxial braided cable shields

In the last few years, much effort has been made to describe the behavior of shielded cables. Many researchers have attempted to understand how an electromagnetic field couples into a braided coaxial cable. There are some important publications on this topic. Nevertheless, up to now, it has not been possible to predict analytically the coupling through a braid shield. An electromagnetic field outside a cable induces a disturbance current in the cable shield. The coupling from the current in the shield into the cable can be described by the transfer impedance. How the current flows in the cable shield is an important quantity in this coupling process. Therefore, to understand the coupling mechanism into a cable, it is necessary to understand the behavior of the current flow in such a braided shield. The paper discusses the current flow in a braided cable shield. The assumption often made in the literature, that a braided shield behaves like a homogeneous tube with apertures, is shown to be inaccurate. It is also shown that the standard braid of the shield used had the same properties as a braid made with insulated wires.     

Structural return loss phenomenon in coaxial cables

This paper presents a study of the structural return loss (SRL) phenomenon pertaining to coaxial cables. Basic equations are developed, the effect of periodic changes in the physical structure of the cables is analyzed, measuring principles and techniques are discussed, and a method of fault location using the SRL test technique is given.     

Attenuation coefficient of dielectric-lined coaxial cables

Recent experimental results for the attenuation coefficient of dielectric-lined coaxial cables have been analysed in terms of a dominant TM01 surface-wave mode. It is shown that there is no conclusive evidence of a possible reduction in the attenuation coefficient below that of the unlined cable.     

辐射型漏泄同轴电缆的设计

总结了漏泄同轴电缆的理论研究现状。围绕使用频带和耦合损耗这两个重要电气参数，讨论辐射型漏泄同轴电缆的设计方法。基于周期性槽孔结构的空间谐波的分析，讨论了抑制高次谐波以拓展使用频带的方法。利用时域有限差分方法和Matlab软件计算耦合损耗。     

Nonlinear effects in coaxial cables at microwave frequencies

A study of the generation of intermodulation products due to nonlinearities in braided coaxial cables at L-, S-and C-band frequencies is in progress and some results are presented. The different cable parameters responsible for intermodulation products at microwave frequencies have been examined and their relative contributions towards the total nonlinearities assessed.     

Use of the hybrid TEM-dual surface wave in coaxial cables and resonators to reduce attenuation

Experimental evidence is given of the reality of this hybrid wave in a coaxial guide having supporting surfaces of deliberately enhanced reactance. Moreover it is shown that a very significant reduction in attenuation is obtainable by this technique.     

Propagation characteristics of inhomogeneous dielectric-filled coaxial cables

A general program has been written for calculating the attenuation and phase characteristics of the first TM surface-wave mode in an inhomogeneous dielectric-filled coaxial cable. As an example, the program has been used to study the special case of a coaxial cable with a very thin dielectric layer on the inner conductor.     

Electrical design requirements for low-loss high-frequency coaxial cables

Arrangements for electric loading of the inner conductor of a coaxial cable as a means of reducing attenuation have been shown experimentally to be effective at 3GHz. It is now proposed to extend the technique to submarine telephone cables working at a few megahertz, and electrical design criteria are given.     

Full-wave modelling of coaxial cables by FDTD technique

Coaxial cables are commonly used in microwave systems but are difficult to model rigorously in the finite-difference time-domain (FDTD) method, particularly with coarse meshes. Various techniques are investigated and the optimum method identified. In addition, attention is paid to strategies for the computation of the characteristic impedance.     

Theory and analysis of leaky coaxial cables with periodic slots

Frequency band and coupling loss are the two important parameters of leaky coaxial cables with periodic slots. The frequency band can be predicted by analyzing the arrangement of the slots on the outer shield of the cable, but the coupling loss is not so easy to determine by classical methods. In this paper, the finite-difference time-domain (FDTD) method is used to calculate the electric field distribution in the slot cut in the outer conductor of the coaxial cable. The dyadic Green's function is then used to calculate the radiation field of the equivalent surface magnetic current densities. By these two methods, the coupling losses of the leaky coaxial cables with different periods, sizes and shapes of the slots can be accurately obtained. Some results in this paper were verified by the experimental results of leaky coaxial cables designed for railway mobile communications with a frequency band of 100-500 MHz     

Propagation characteristics of the TM01 surface-wave mode in dielectric-lined coaxial cables

Accurate calculations of the propagation coefficients of the TM01 surface-wave mode in coaxial cables with dielectric linings on the inner, outer or both conductors were carried out using a perturbation method, and were checked by solving the exact characteristic equations. The calculations show that the perturbation method yields very accurate results, and that the attenuation coefficients cannot be reduced below that of the quasi-TEM mode in the unlined cable.     

An improved model for the transfer impedance calculations ofbraided coaxial cables

A new model is presented for the accurate prediction of transfer impedances of braided coaxial cables. This model is compared with earlier models proposed by E. F. Vance (1972, 1975) and M. Tyni (1975). A large number of measurements were carried out on several braided cable samples, and the accuracy of the new model is evaluated using transfer impedance values obtained from these measurements     

Circuit model for bulk current injection test on shielded coaxial cables

A SPICE circuit model for the evaluation of the effects of the bulk current injection test on coaxial shielded cables is developed. The proposed equivalent circuits do not need the usual subdivision of the circuits in elementary cells, it is valid in both frequency and time domain and is based on the exact solution of the equations stemming from a lossless transmission line model. The intermediate and final results are validated by means of comparison with others, evaluated by independent methods.     

Through-pulse measurements on installed 1.2/4.4 mm coaxial cables: two examples

Through-pulse measurements have been performed on several installed 1.2/4.4 mm coaxial cables to record their forward, echo characteristics for possible operation up to 565 Mbit/s- Two typical examples are presented that illustrate the effects of both the random and periodic irregularities within such cables.     

采用双漏缆覆盖的轨道交通LTE-M系统信道的测量研究

下一代轨道交通系统将采用LTE-M系统, 并采用多根漏泄电缆(简称漏缆)组成多入多出(Multiple Input Multiple Output,MIMO)系统.因此,需要研究漏缆设置与系统性能之间的关系。依据时域信道测量方法与MIMO信道相关理论, 在典型的类地铁隧道环境中, 测量并分析了1.8 GHz频段下基于双根漏缆覆盖的MIMO系统性能, 通过测量不同极化方式下的漏缆和接收天线以及不同漏缆间距下的信道信息,分析了信道相关性,发现当接收机天线垂直极化而双漏缆同采用水平极化时MIMO性能最优, 相关性大小并不太依赖于漏缆间距.这些结果可对今后LTE-M系统部署提供参考.