模拟电视信号加解扰系统的故障现象及排除

1 模拟电视加解扰系统介绍 有线电视模拟加解扰系统按原理可分为多种类型,目前国内使用的主流产品有两种,一是单加群解分段系统,一是群加群解系统,群加群解系统的前端只需要1台加扰器,对混合后的射频信号进行处理,此类前端设备的费用较低,但加解扰后的图像还原质量不尽如人意,所以此类系统仅适用于规模不大用户较少且对信号质量要求不高的网络.     

有线电视分级条件接收系统

有线电视节目收费采用机顶盒是一种性价比较高的方案.介绍了一种采用机顶盒方案的有线电视条件接收系统,它是基于射频处理的同步抑制分级群加解扰系统,具有群加扰系统的相对低成本和多级别利于收费节目开发的优点.     

有线电视加解扰技术系统介绍之三──PM射频加解扰可寻址技术系统

有线电视加解扰技术系统介绍之三──ＰＭ射频加解扰可寻址技术系统李福祥（广电部科技司）美国某公司的ＰＭ可寻址加解扰技术系统，是一种对已调制的射频电视信号进行处理的系统。该系统使用了ＰＲＯＣＥＳＳ专利技术。ＰＲＯＣＥＳＳ是指对载波相位反转和同步脉冲抑制而...     

有线电视的射频加解扰

介绍有线电视射频加解扰技术的发展，重点介绍射频幅度调制型加解扰系统，简单介绍射频幅度调制的工作原理，分析高频电子开关和数字处理部分的电路，最后为用户提供一些应用建议。     

声音加解扰系统在CATV/MMDS/MUDS中的应用

介绍声音加解扰系统的特点、功能和原理，以及该系统在CATV／MMDS／MUDS中的应用。     

黔江区有线电视网模拟加解扰系统方案

模拟有线电视网落后的管理方式,严重制约了有线电视的发展。本文通过对几种模拟加解扰原理的阐述,结合本地的实际情况选择了射频群加解扰方式,使有线电视网络管理规范化、科学化,为有线电视的进一步发展打下了基础。     

一种改进的射频加解忧方法

文中提出了一个改进的射频加解扰新方法，采用视频加扰与射频解扰相结合的技术，利用（Ｎ＋１）个电视射频频道实验对Ｎ格电视信号的加扰。     

一种改进的射频加解扰方法

文中提出了一种改进的射频加解扰新方法，采用视频加扰与射频解扰相结合的技术，利用（Ｎ＋１）个电视射频频道实现对Ｎ路电视信号的加扰。     

可寻址射频加解扰技术

提出了一种有线电视射频加扰新技术，给出了一种可寻址射频加解扰和管理系统的实现方案，系统采用射频随机捷变技术实现电视信号的加扰，并详细讨论了系统的硬件组成及软件实现。     

基于伪随机算法的有线电视加解扰系统设计

提出了利用伪随机线性叠加算法产生多种码组合加扰射频电视信号的设计方案,给出了加解扰机的软硬件设计与实现,通过上位机管理软件设计,完成了对解扰机的控制和管理,解决了目前有线电视加解扰系统成本高,安全性差的问题。目前系统已在国内许多地区得到成功应用,具有实际应用的价值。     

卫星网络管理系统控制信道设计

设计了一套用于卫星网络管理系统的控制信道。采用TDM/TDMA专用控制信道和复接控制信道互为备份的方式保证信息传输的畅通,2种信道都可保证卫星网管所有功能的完成。主用TDM/TDMA专用控制信道,一旦专用信道中断,采用复接控制信道。复接控制信道与业务复接在一起利用业务信道传输网管信息。TDM/TDMA专用控制信道由链路适配器和突发卫星调制解调器组成,重点描述其设计方案。     

Capacity, Cutoff Rate, and Coding for a Direct-Detection Optical Channel

It is shown that When Pierce's pulse-position modulation scheme with 2^Lpositions is used on a self-noise-limited directdetection optical communication channel, there results a 2^L-ary erasure channel that is equivalent to the parallel combination ofL"completely correlated" binary erasure channels. The capacity of the full channel is the sum of the capacities of the component channels, but the cutoff rate of the full channel is shown to be much smaller than the sum of the cutoff rates. An interpretation of the cutoff rate is given that suggests a complexity advantage in coding separately on the component channels. It is shown that if short-constraint length convolutional codes with Viterbi decoders are used on the component channels, then the performance and complexity compare favorably with the Reed-Solomon coding system proposed by McEliece for the full channel. The reasons for this unexpectedly fine performance by the convolutional code system are explored in detail, as are various facets of the channel structure.     

Multiuser receiver scheme for full‐rate space–time coded CDMA system with imperfect estimation

By introducing a full‐rate space–time coding (STC) scheme, a synchronous CDMA (code division multiple access) system with full‐rate STC is given, and the corresponding uplink performance is investigated in Rayleigh fading channel with imperfect estimation. Considering that existing STC‐CDMA system has high decoding complexity, low‐complexity multiuser receiver schemes are developed for perfect and imperfect estimations, respectively. The schemes can make full use of the complex orthogonality of STC to reduce the high decoding complexity of the existing scheme, and have linear decoding complexity compared with the existing scheme with exponential decoding complexity. Moreover, the proposed schemes can achieve almost the same performance as the existing scheme. Compared with full‐diversity STC‐CDMA, the given full‐rate STC‐CDMA can achieve full data rate, low complexity, and partial diversity, and form efficient spatial interleaving. Thus, the concatenation of channel coding can effectively compensate for the performance loss due to partial diversity. Simulation results show that the full‐rate STC‐CDMA has lower bit error rate (BER) than full‐diversity STC‐CDMA systems under the same system throughput and concatenation of channel code. Moreover, the system BER with imperfect estimation are worse than that with perfect estimation due to the estimation error, which implies that the developed multiuser receiver schemes are valid and reasonable. Copyright © 2010 John Wiley & Sons, Ltd.     

TDD/CDMA移动通信系统的一种信道分配方案

未来的TD/CDMA移动通信系统中存活话音及上下行业务量不等、优先级不同的数据业务，为适应新业务的特点，充分发挥TDD/CDMA移动通信系统自身的优势，本文提出了TDD/CDMA移动通信的一种新的信道分配方案。仿真结果表明，该方案可大大降低低优先级业务的掉线概率，充分利用有限的信道资源。     

A novel duplex WDM-PON with DPSK modulated downstream and re-modulation of the downlink signal for OOK upstream

We experimentally demonstrate and analyze a 10 Gbit/s full duplex wavelength division multiplexing passive optical network (WDM-PON) system. A non-return-to-zero differential phase shift keying (NRZ-DPSK) modulation technique is first utilized for downlink direction, and then the downlink signal is re-modulated for the uplink direction using intensity modulation technique of on-off keying (OOK) with a data rate of 10 Gbit/s per channel. An effective colorless WDM-PON full duplex transmission system is achieved for the data rate of 10 Gbit/s per channel with a channel spacing of 60 GHz over the distance of 25 km with low power penalty.     

信道估计误差对MIMO系统信道容量的影响研究

为了分析信道估计误差对信道容量的影响,结合MIMO系统接收端信道估计误差的特点,重新构建了MIMO信道的统计模型。利用Wishart分布的性质,推导了当MIMO信道矩阵满秩时,仅接收端已知信道CSI情况下系统信道容量的下限。仿真结果表明,MIMO系统信道容量对信道估计误差比较敏感。     

基于小波阈值去噪的UFMC信道估计算法

通用滤波多载波(Universal Filtered Multi-Carrier,UFMC)技术是一种新型多载波技术,是5G备选波形技术之一.对UFMC系统进行了介绍,再针对该系统的信道估计问题,提出一种基于小波阈值去噪的最小二乘(Least Square,LS)信道估计算法.首先利用LS算法获得导频处的信道响应,再用...     

发射分集OFDM系统中一种基于Turbo迭代的判决反馈信道估计

本文对频率选择性衰落信道条件下发射分集OFDM系统的信道估计进行了研究,提出了一种基于Turbo迭代的判决反馈信道估计方法.该方法充分利用Turbo迭代信息来改善信道估计性能,且因无需求逆运算,使得整个系统的复杂度增加不多.仿真结果表明,所提方法在较高信噪比条件下,明显提高了系统信道估计的性能,且适合于高速移动的信道环境.     

Source coding, channel coding and modulation techniques used in theDigiCipher system

The DigiCipher high-definition television (HDTV) system, an all-digital approach that achieves full HDTV performance with error-free reception in a single 6-MHz television channel is described. The DigiCipher HDTV system is based on discrete cosine transform coding and uses motion prediction techniques to eliminate redundancy in the digital signal, channel equalization to defeat multipath, and error correction to defeat noise and interference. The source signal, source coding, channel coding, modulation, and performance of the system are discussed