基于改进贝叶斯非负Tikhonov正则化方法的同轴电缆信号传输畸变补偿研究

随着信号频率、带宽及传输距离的增大,信号在同轴电缆传输过程中的畸变问题变得越来越严重。特别地,如果同轴电缆在使用过程中还意外地遭受了挤压、拉伸或折叠,信号畸变问题将会变得更加严重。该文基于贝叶斯推理的非负Tikhonov正则化方法,提出一种改进的信号补偿方法。该方法可有效规避逆分析中的病态矩阵问题,利用同轴电缆的冲击响应函数,并结合输出端口的测量信号,即可实现输入信号的重构。并以长度15 m的受挤压同轴电缆为对象,采用此方法对3种不同样式的脉冲信号(双指数脉冲信号、调制方波信号、双极脉冲信号)进行了传输畸变补偿。结果表明:该方法均能实现优异的补偿效果,补偿后信号与输入信号间偏差远远低于传统的衰减补偿法。并且,该方法具有较强的鲁棒性,当信噪比大于30 dB时,即可保持好的稳定性。     

温度变化对同轴电缆有线电视系统的影响

温度变化易造成同轴电缆电视系统非线性失真现象。从理论上用数学公式表述了同轴电缆的各种特性 ,反映了同轴电缆影响射频传输的各种因素 ,分析了温度变化对电视信号的影响程度 ,并用实例进行了理论分析和计算。这对有线电视系统的设计和维护都有很大的帮助。     

Magnetic Field Pickup by Flexible Braid Coaxial Cables

Cabling systems have long been known to be a source of unwanted pickup of radio-frequency interference. A typical source of pickup occurs when the outer sheath of a coaxial cable system forms part of a ground return for potentially interfering electromagnetic energy. Another source of penetration arises from a magnetic field which is perpendicular to the axis of the coaxial cable. A previous study demonstrated that the field emanating from a coaxial cable could be characterized as an equivalent open-wire pair. This particular effect is caused by the eccentricity between the centers of the outer and the inner conductors or because of other asymmetrical characteristics. The susceptibility of a coaxial cabling system to perpendicular magnetic fields can also be characterized in terms of an equivalent open-wire pair for short runs. The purpose of this investigation was to measure the shielding effectiveness of a typical flexible braid coaxial cable to magnetic fields perpendicular to its axis and to demonstrate that a coaxial cable may be considered as an equivalent open-wire pair in a cylindrical shield. A test setup employed a parallel plane transmission line to generate a uniform magnetic field perpendicular to the axis of the coaxial cable. The shielding effectiveness of the braid was measured for several classes of braid conditions. Then, using the same braid, a coaxial cable with an experimentally induced known eccentricity was employed and the overall pickup measured. The results confirmed the objectives of the investigation.     

Network management for residential broadband interactive dataservices

Although coaxial networks and hybrid fiber coaxial (HFC) networks have been in use for delivering television programs to the home, their usage as access networks to provide broadband interactive data services (BIDS) to the home is very recent. In this article, the authors highlight the importance of managing the networking infrastructure for BIDS and explore the unique requirements and challenges in managing HFC networks. Considering the operational requirements of BIDS operators, network maintenance, subscriber support, and planning are identified as the three functional areas that a BIDS network management system must address. It is argued that management support built into BIDS equipment (e.g., cable modems, headend cable termination units, subscriber PCs) can provide a cost-effective way of monitoring the status and performance of HFC networks, and some initial experiences of implementing and deploying network monitors in a real-world BIDS system are presented     

高清晰度电视信号串行传输系统的研究

提出了一种利用同轴电缆串行传输高清晰度电视信号的方法,设计了传输系统的发送和接收模块,并对其工作过程进行了较为详细的分析和讨论.     

基于同轴电缆的多路视频混合传输技术的研究

针对国内深海测控系统能量供给的紧迫性,对国内现有深海有缆监控系统的特点分析,提出功率能源与多路视频信号同缆混合传输技术,主要采用电容耦合的方式,将数据叠加到电源信号上,通过同轴电缆,实现功率能源、多路实时彩色视频图像的传输以及水上位机与水下位机的数据传输。     

An Experimental 560 Mbits/s Repeater with Integrated Circuits

The bandwidth penalty of digital systems is very obvious in the case of transmission over coaxial cables because of the exponential increse of cable attenuation with square root of frequency. From capacity point of view, it is only at very high information rates (> 500 Mbit/s typically) that a digital system might be competitive with an analog system, because the disadvantage of noise accumulation in an analog system ultimately cancels the bandwidth penalty of the digital system. In addition, it is, however, difficult to realize common functions, such as amplification, equalization, regeneration, clock extraction, etc. with electronic components having a frequency range comparable to the frequency range of the information signal, which extends from zero frequency to the microwave range. Besides, the complexity of a regenerative repeater should be kept to a minimum for reliability reasons. It is shown in the paper that with present-day technology a 560 Mbit/s repeater can be constructed, operating in sections of 1.5 km coaxial cable (2.6/9.5 mm). Also, we demonstrate that new technologies exist which may lead to repeaters with a high degree of monolithic integration, even at such a speed, which is important from the reliability viewpoint. The constructed and described repeater is characterized by unconventional and economic design of amplifier/equalizer and clock extractor and by monolithically integrated decision circuits.     

有线电视电缆分配系统的设计

在有线电视信号传输系统中，入户部分主要通过同轴电缆来实现信号传输，同轴电缆质量、规范的设计直接影响到用户的有线电视信号质量，具体介绍有线电视传输系统中同轴电缆的性能指标和施工技术要求，为施工人员提供技术参考。     

脉冲激光引信光电转换系统的设计

为了应对脉冲激光引信回波信号弱、脉宽窄的特性,获得目标尽量多的不失真信息,对光电探测器的特性和放大电路的带宽进行了分析,设计了一套实用的光电转换系统,包括PIN探测电路、前置放大电路和主放大电路。经过TINA和MULTISIM软件模拟仿真和实验验证,设计的光电转换系统的带宽为61.089MHz,增益为72.14dB。结果表明,该系统对于脉宽为十几纳秒的回波脉冲信号进行了很好的低噪声、不失真放大,满足了设计要求,回波信号经光电转换系统后输出的信号与应用需要相匹配,为激光引信的后续信号处理提供了稳定可靠的信号。     

SYV-75—5和SWV-75—5同轴电缆在视频传输中的性能比较分析

SYV75—5和SYWV75—5是两种传输视频信号的同轴电缆,从理论上讲SYV75—5是用于监控系统的视频信号传输,SYWV75—5是用于有线电视的视频信号传输,然而在实际工程中有的工程商却用SY—WV75—5的线缆做视频传输。两种线缆的价格之差影响到工程造价,因此两种线缆在实际工程中能否替换的问题是值得探究的。通过理论分析与实际测试,论证SYV75—5和SM5—5两种同轴电缆在视频传输线路中的性能优劣,由此得出两种线缆正确的选用方法。     

EoC技术中的HomePlug应用与分析

用户接入的最后100 m方案,目前应用最多的解决方案为Ethernet Over Coax技术,即EoC同轴宽带系统,它采用频分复用技术,对同一根同轴电缆通过频率分割,将以太数据信号IP DATA和有线电视信号TV RF在同一根同轴电缆里传输,现有多种技术应用于EoC中,如MoCA、WiFi、HPNA、HomePlug等技术,简单分析HomePlug在EoC技术中的应用。     

Intermodulation distortion of cascaded transistors

Intermodulation distortion performance of cascaded transistors is analyzed using a nonlinear frequency-dependent model for the transistor and with Volterra series as an analysis tool. The objective of this study is to determine the optimum cascade that has high gain and good modulation performance especially for higher frequencies. A particular application is in long-haul, analog, solid-state coaxial systems where intermodulation distortion is a critical problem. Both experimental as well as computer results are used in this analysis. It is shown, for example, that certain low distortion configurations can exhibit high distortion when cascaded. A few optimum cascade configurations are discussed in detail.     

MLAP: a MAC level access protocol for the HFC 802.14 network

Interactive residential broadband/multimedia services are expected to be the next main event in the cyberspace experience. The large excess bandwidth (well over 300 MHz) available in today's cable TV (CATV) hybrid fiber/coaxial (HFC) plants is an ideal candidate to provide the underlying communications infrastructure for interactive digital services to the home; cable operators that have not yet upgraded their all-coaxial plants to HFC are quickly moving in this direction. MLAP is a flexible ATM-friendly MAC protocol that is capable of supporting various types of traffic with diverse quality-of-service requirements. We introduce a very versatile MAC protocol for the HFC 802.14 network. MLAP can provide integrated broadband services to the home, internetwork easily with ATM wide area networks, support QoS constraints for various types of traffic, and operate over a variety of physical layer protocols. Our presentation is only an extended summary of our medium-sharing protocol proposal to the IEEE 802.14 WG. We consider only error-free system operation. MLAP provides for the use of timers for the recovery of error situations in the network. MLAP is also supported by a management suite of protocols for management of the overall system     

稳相电缆弯曲相位稳定性测试方法的比较

稳相电缆的弯曲相位稳定性指标对于相敏系统中的信号传输而言至关重要。为了精确测得电缆弯曲前后相位的变化量,本文介绍三种电缆弯曲相位稳定性的测试方法,并通过实例的测试对其进行比较和分析。     

漏泄同轴电缆的性能参数及其影响因素的研究

本文介绍了漏泄同轴电缆的类型和漏泄原理,以双八字槽漏泄同轴电缆为例．分析和讨论了漏泄同轴电缆的主要性能参数及其影响因素．为漏泄同轴电缆的设计工作提供了参考依据。     

Bit-error rate of M-QAM signal and its analysis model for compositedistortions in AM/QAM hybrid transmission

In cable television (CATV) systems that deliver digital video services by employing a hybrid fiber and coaxial network, it is important to consider digital channel deterioration due to composite distortions, as well as the amplitude-modulation vestigial-sideband channel. Furthermore, it is essential to clearly estimate a digital channel's quality in designing CATV transmission systems. However, there have been few studies on statistical models and an analysis method to estimate the bit-error rate (BER) of M-ary quadrature amplitude-modulation signals for composite distortions. This paper shows statistical properties of composite distortions and a new BER analysis method to handle them. In the evaluations, the amplitude distributions of composite distortions are given by Weibull distributions with skewness levels of 2.3 for composite second-order distortion and 1.5 for composite triple-beat distortion. We propose a new BER analysis method that uses the Weibull distributions for the composite distortion statistical features and demonstrate the effectiveness of the new BER analysis method in estimating BER by comparing its measurement results to calculation results     

射频功率放大器的宽带匹配设计

多倍频程功率放大器具有显著的优点,同轴电缆阻抗变换器能实现射频功率放大器有效的宽带匹配。在给出同轴电缆阻抗变换器方案设计的基础上,详细介绍了其基本原理以及1∶1和1∶4同轴变换器的具体结构及等效电路。针对工程需要,以同轴电缆阻抗变换器为宽带匹配网络的核心,设计了一款超宽带匹配功率放大器,经软件仿真优化及测试验证,阻抗匹配准确,测试结果达到了技术指标要求。     

Creating a network for interactivity

The one most likely system, to serve as the common meeting ground for phone and cable companies, is a hybrid network architecture of optical fibers and coaxial cables. As the industry evolves toward interactive services, three considerations will become paramount. One is the ability to deliver individualized programming to customers, and get responses from them as well. Here, the instantaneous network bandwidth is of less concern than the effective bandwidth per customer. So long as all the programming and services a customer desires are available in a user-friendly way, it is irrelevant how the network delivers them. By its nature, interactivity also implies that the measure of effective bandwidth per customer be extended to bidirectional communication between the customer and the head-end. Several ways of providing that increased effective bandwidth are discussed. A second prime concern is the need for more attention to network reliability in delivering services. Finally, the issues of standards and security must be dealt with     

A digital video system for the CATV industry

A ditigal pulse code modulator (PCM) system is proposed to implement long-haul video system for the CATV industry. A comparison is made between PCM system and wide-band FM system in terms of repeaterability versus additional occupied signal bandwidth. This is followed by a noise analysis of coaxial cable to determine the correct PCM format and bit information rate. An 80- megabit system is selected, which uses an 8-bit code in a four-level, eight-level, eight-level pulse sequence per video sample. The selected PCM system is then evaluated for its performance on both a long-haul cable system and a long-haul microwave system. Performance calculations are made on a 500-mile cable system in terms of error rate and its related video signal-to-noise ratio. Repeater spacings are computad for various configurations, including the replacement of the digital regenerators with analog amplifiers. Additional performance calculations are then made on a 3000-mile microwave system, including the effect of simultaneous Rayleigh fading.     

Cascading of Distortion in CATV Trunk Line

The second-and third-order distortion buildup in a CATV repeater system is analyzed by means of the Volterra series expansion of the output signal in terms of the input signal. Expressions for cascaded distortion products are given in terms of the single amplifier distortion product and the low frequency phase intercepts of the amplifier, cable equalizer, and cable itself. From these expressions it is also seen that the low-frequency phase intercepts are the dominant factors in determining the cascaded distortion. Conditions for cancellation of either the second-or third-order distortion products are then given.