搞好CATV系统的节目频道规划

本文介绍了在不使用机上变换器的条件下，如何提高ＣＡＴＶ系统节目０容量，做好节目频道规划的系统设计施工方法。     

甘肃农村央视频道收视状况调查分析

通过对甘肃8个地市300个农村家庭电视收视状况调查,发现甘肃农村对央视频道的收视状况是不均衡的,综合频道的收视率远远高于其他频道,收看军事农业频道的观众不少,但喜欢的不多.这说明央视各频道的节目对农村观众而言,没有太明确的针对性,农村观众仍然是沉默的大多数.     

CATV系统的抗干扰分析

随着我国电视广播事业的发展，彩色电视机的数量越来越多。同时，逐年增多的高层建筑对无线电波的屏蔽与反射以及工业，通讯干扰严重地影响了收视效果。因此，CATV(其用无线电视)系统应运而生。但CATV系统仍然存在着干扰问题，如何避免各种干扰，提高接收机的图象质量，这就是本文的出发点。     

CATV增补频道干扰的来源与对策

巴彦县在ＣＡＴＶ网络建设初期就使用了增补频道,过了一段时间个别频道出现了干扰现象。为此,我们在有线电视网上进行测试,对实测数据进行研究分析,找到了ＣＡＴＶ增补频道产生干扰的原因和避免干扰的对策。１ 增补频道的干扰现象 １９９４年我县建起了ＣＡＴＶ网络,播出ＤＳ－１～ＤＳ－１２ １２个标准电视频道和 Ｚ－１～Ｚ－７ ７个增补频道。建网初期,各频道信号正常。随着时间的推移,有的片区用户就不能正常收看,个别增补频道的伴音出现“嘟嘟”干扰声,无规律反复。同时,电视机屏幕出现一层白色较亮的网纹,覆盖整个画面,…     

关于在CATV网络中设置广告频道的思考

1 引言 全面推进广播影视“数字化、网络化”(以下简称“两化”)是顺应全球广电业发展趋势的重大举措,也是我国广电事业的建设重点。西方发达国家实现地面无线数字电视不顺利的一个重要原因,就是资金缺口大。以法国为例,覆盖40％的人口,需要3200万欧元,该国政府拨款1500万欧元,占所需资金的近47％。这     

频道混合器和λ／4开路线在CATV中的巧用两则

在共用天线安装中,如果输入到放大器两路以上的信号电平不等.则会引起交调。因此,很少采用一副宽频带天线将接收到的几路信号直接输入到放大器的方法。我在一个小型CATV系统工程中,利用特有条件采用一副天线解决了两路信号场强不等的问题,这样既降低了成本,又给安装和调试带来方便。 1.巧用频道混合器在接收端测得同一方向的9、11频道场强分别为85dB、65dB,因9、11频道为隔频道,且9频道场强比11频道高20dB,故采用一副ll频道接收天线便将两路信号同时接收下来,因天线是按11道波长设     

CATV系统频道容量及其计算

在有线电视系统中 ,随着频道的增加 ,前端载噪比将会减小 ,当频道增加到一定数量时 ,前端载噪比将无法满足系统指标要求。在ＣＡＴＶ系统中 ,频道数量主要由前端调制器的数量确定 ,因而系统能容纳多少台调制器将反映系统的频道容量有多大。对给定的调制器 ,要满足前端载噪比指标要求 ,其数量不能超过一定值。由调制器复合载噪比公式可求得调制器的最大容量。调制器的复合载噪比公式为 :(Ｃ/Ｎ) 合 =-10ｌｇ [10 -(Ｃ/Ｎ) 内/ 10 +(ｎ -1) 10 -(Ｃ/Ｎ) 外/ 10 ] (ｄＢ) ( 1)式中 :(Ｃ/Ｎ) 合 ———调制器复合载噪比分贝值 ;(Ｃ/Ｎ) 内 ——…     

有线电视系统的频带宽度与频道设置

目前有线电视参向乡镇一级发展，为了让更多的从事有线电视工作的人认识到系统带宽和频道设置的重要性，特发表本文。文中叙述了选用宽频带系统的理由和设置频道时应该注意的事项。     

CATV系统前端接收的性能要求

我国国家标准GB/T6510-1996电视和声音信号的电缆分配系统,规定了在系统输出口处衡量CATV系统的性能要求。但是,在系统输出口的信号     

30路FM－TV光纤CATV传输系统

本文介绍一个设计研制的能传输３０路ＦＭ－ＴＶ光纤系统。系统的频率范围是１～２．５ＧＨ２。对光纤键路的光发射机设计作了详细的论述；系统的信道间隔设计成非等间隔的频率配置，减少了落入信道的二阶和三阶失真产物。实际测试系统的ＣＮＲ＞１８ｄＢ，ＣＳＯ、ＣＴＢ优于５０ｄＢｃ，传输距离＞３０ｋｍ。系统可以用于ＣＡＴＶ的干线或分配传输。     

在宏分集接收技术下扩频信道的容量分析

研究的是在服从瑞利分布受阴影效应影响的衰减信道中。采用直接序列扩频方式的CDMA无线移动通信系统的信道容量。用到的模型是以多用户检测宏分集(MDM)接收技术为基础建立的，他的特点是在阴影衰落信道中．在误码率较低的条件下,取得较高的数据传输速率。其信道容量可由每个小区中的用户数量来确定。     

Performance Analysis of System with Micro- and Macrodiversity Reception in Correlated Gamma Shadowed Rician Fading Channels

In this paper, the performance of wireless system employing microdiversity to mitigate the effects of short-term fading and macrodiversity to reduce long-term fading (shadowing) effects is studied. The system model assumes implementation of maximal-ratio combining (MRC) at the microlevel and selection combining (SC) at the macrolevel. The received signal envelope follows a Rician distribution and it also suffers gamma shadowing. Novel expressions for the probability density function (PDF), cumulative distribution function (CDF), and moment-generating function (MGF) of the output signal-to-noise ratio (SNR) are obtained. Several useful performance criteria, such as the moments of the output SNR and outage probability are analytically derived. Moreover, the average bit error probability (ABEP) for noncoherent binary differential phase-shift keying (BDPSK) is calculated using the MGF based approach while the ABEP for coherent binary phase-shift keying (BPSK) is studied by averaging the conditional bit error probability over the PDF. Numerical results are graphically presented to show the effects of various system parameters to the system performance, as well as the enhancement due to use of the combination of micro- and macrodiversity. Some of numerical results are complemented by equivalent computer simulated results which validate the accuracy of the proposed analysis. The agreement between the Rician-gamma and Rician-lognormal fading model is also established.     

相关衰落信道采用MRC接收的MQAM性能分析

利用Q(x)和Q2(x)的另一种表达式及衰落信道上数字信号传输的归一化性能研究的结果,通过一种一般性方法分析了两种实用天线设置时相关衰落信道下采用MRC接收的MQAM的性能,得到误码率的解析表达式。比较了相关瑞利和赖斯衰落信道的信噪比损失情况。结论对多天线MQAM系统在性能和空间范围之间如何采取折衷有着重要的指导作用。     

Effective Capacity Analysis Over Fisher-Snedecor F Fading Channels with MRC Reception

In contrary to Shannon’s ergodic capacity, the delay-constrained effective rate is used to define the maximum data rate of the real-time applications in 5G and beyond networks. The effective capacity (EC) performance of the delay sensitive communication system over Fisher-Snedecor F fading channel with maximum ratio combining is studied. The closed-form mathematical expressions for the EC are derived in terms of Meijer G-function and the effect of different fading parameters on the effective throughput of the system is demonstrated. The simplified asymptotic expression for high signal-to-noise ratio (SNR) and low SNR regimes are provided to gain more insight into the system. The effect of different system parameters on the EC performance is also demonstrated. Simulation results are corroborated along with the numerical results to verify the correctness of the proposed formulations.

     

有线电视系统故障分析与排除

CATV系统是由大量的器材、部件经电缆连接组合而成,无论设备、器材或施工、调试中哪一环节出现问题,都将给系统造成影响。另外,外界电波干扰、供电系统、自然灾害、人为因素等也将对系统产生影响,严重的出现故障,影响用户收视效果。     

酒店有线数字电视系统工程建设方案技术分析

宾馆酒店作为营业性场所,电视节目是比较重要的服务内容.通过对比分析,提出宾馆有线电视系统建设技术分析,根据目前的实际情况与未来的发展趋势,结合国家关于有线电视网络发展的规定,为酒店行业提供先进的前端中心机房建设方式,该建设方案可为宾馆的有线数字电视系统提供优良的性能,同时为将来实现综合数据业务等增值业务打好基础,体现了有线数字宽带的优点.     

Another Look at Performance Analysis of Energy Detector with Multichannel Reception in Nakagami-m Fading Channels

Energy detection is the most dominant method used for reliable wireless detection owing to its non-coherent structure and low implementation complexity. The main challenge for performance analysis of energy detection comes from the generalized Marcum \(Q\) -function involved. To overcome this hurdle, this paper revisits the detection problem and introduces a new framework based on the incomplete Toronto function that allows analyzing the performance for non-fading and fading scenarios in a very simple way. Based on newly-derived expressions for the incomplete Toronto function, performance analysis of energy detection is firstly formulated for unfaded Gaussian noise channels. Second, novel closed-from expressions are derived for the average probability of detection over Nakagami- \(m\) fading channels. The analyses are based on two approaches: the probability density function-based and the moment generating function-based (MGF). The former uses the canonical series representation of the incomplete Toronto function while the latter employs MGF-derivative method which is based on the \(n\) th order derivative of the MGF. The analysis is then extended to cases with diversity receptions including maximal ratio combining and switch and stay combining (SSC). For the SSC diversity case, an analytical expression that can be used to determine optimum switching thresholds in a maximum average detection probability is also derived. The analytical results are verified by numerical computations and Monte-Carlo simulations.     

有线电视系统前端噪波干扰产生的原因分析及排除方法

目前,我国大部分的有线电视台均使用550MHz邻频传输系统,最多能传送59套模拟电视节目,其中包括22个标准频道和37个增补频道。 一个优良的有线电视前端,应该能把清晰的图像和悦耳的伴音送入系统,通过网络传送到千家万