地面数字电视广播车载接收天线的设计

本文简要阐述了用于数字电视地面广播的车载接收天线的特点和测试方法，介绍了三种车载接收天线的设计方案及实测结果。     

浅析数字电视单频网（SFN）组建的几个问题

2006年，国家标准委员会颁布了中国地面数字电视国标方案，并要求自2007年8月起强制执行。目前地面无线数字覆盖作为电视广播的传统手段，由于其具有简单接收和移动接收的能力，能够满足现代信息化社会所要求的“信息到人”的基本需求。数字电视一个频道可以同时收看多套标准清晰度电视节目、调频广播节目及数据广播等，对电视观众来说，是质的进步，而且地面数字电视广播的传输和使用能克服恶劣环境，并从根本上解决了频谱资源紧张的问题。无疑，地面数字电视广播的推广和产业化将带来不可估量的经济增长。     

对数字电视地面广播编码方法的思考

合理利用MPGE-2、MPEG-4编码方法，使数字电视地面广播既能支持多套节目的静态接收又能支持移动电视。一个单频网可以替代现有的无线覆盖，同时解决移动电视的接收问题，实现模拟电视地面广播到数字电视地面广播的转变，真正形成多套频道、多功能的数字地面广播网。     

超紧凑流形合路器

RFS新增了一款领先的UHF合路器,一款超紧凑流形合路器,它是低功率数字电视广播站点的理想选择。这款UHF流形合路器可合路高达250W的数字频道,是替换平衡式合路器的既经济又节约空间的理想选择。     

深圳移动电视"高高挂"

移动数字电视 地面移动数字电视是指"用地面广播传播方式传输数字电视信号的地一种电视系统".它和我们脚底下的这个"地面"没有任何关系,其接收的电视信号是发射端采用地面数字传输技术播出实时节目,接收终端第一类是安装在时速120公里以内的移动车载设备,第二类是供手机、笔记本电脑、PMP等手持移动接收设备(手持移动数字电视)的群体.     

地面数字多媒体电视传输系统的设计与实现

本文介绍了清华大学提出的地面数字多媒体/电视广播传输标准(DMB-T)方案.该传输方案的调制部分采用了自主创新的时域同步正交频分复用(简称TDS-OFDM)的多载波调制方式,适用于具有多径干扰和多普勒频移的地面数字电视广播传输信道.整个DMB-T接收系统集成在“中视一号“专用芯片上,已经批量生产;在额定8MHz带宽的广播频道中,净载数据传输率在4.813-32.486Mbps范围内可选,实现了单天线移动条件下,高清晰度数字电视的广播与接收.     

地面数字电视广播传送技术

地面数字电视广播传送技术覆盖的范围较广,对于信号的接收具有可变动性,但要实现地面数字广播传送,将要面临复杂的工作环境。文章以地面数字电视广播传送技术为切入口,深入研究我国地面数字电视广播技术发展的现状,以及未来地面数字电视广播传送技术的发展趋势。     

浅谈地面数字电视

在中国,大部分城市居民是通过有线电视网收看数字电视,地面数字电视主要面向没有网络覆盖的城郊、乡村等地区,以及移动终端如车载数字电视和手机。按照信息产业部SJ/T11324-2006《数字电视接收设备术语》的定义,地面数字电视是指"用地面广播传播方式传     

有线电视系统前端的载噪比

1开路前端的载噪比开路前端是指用VHF，UHF接收天线接收当地开路发射电视信号，其组成如图1所示。图1开路前端当天线接收到的电视信号，进人等效噪声系数为F的前端。前端设备可能是天线放大器加频道处理器，也可能没有天线放大器而只有频道处理器或频道变换器。前端设备的选用要看接收地点的开路信号场强。信号本身是没有噪声的（或者说信号本身的载噪比高，其影响可以忽略），只有接收天线转移来的基础热噪声和前端设备引人的噪声。引人设备的噪声系数后，前端输出端的载噪比可以在输人端进行计算，这给计算带来很大的方便。设第1级输人…     

浅谈基于AVS+/DTMB的车载移动接收

本文详细介绍了车载移动接收AVS+地面数字电视信号的调试过程及车载接收系统的改装情况,拓宽了地面数字电视的应用,为广播电视公益覆盖探索新模式。     

Finite Mixture Noise Models for Mobile Digital Television Channel on Urban Terrestrial Broadcasting

Since 21st century, the test service for digital TV terrestrial broadcasting has been successively carried out in some Chinese big cities, and bus commuters can watch TV programs while traveling in the signal-covered regions. When the digital mobile TV coverage is planned, the level of radio noise in environments is of considerable concern to designers. In this paper the results of average noise power of a digital TV channel in a UHF band on public transportation courses are introduced. Not only the noise factors but also the K times variance deviation of the upper decile of noise factors under three typical communication environments has been obtained through the analysis of nonlinear regression of cumulative distribution functions on the test results. Through the trials of mobile reception of digital television, two coverage plans have been compared; The results show that the coverage effect for the model based on interference statistical distributions is higher than the one based on AWGN noise.     

重庆市地面数字电视覆盖网络建设项目技术规划

本文介绍了重庆市广电发展基本情况,根据重庆自然条件、收视需求和地面数字电视覆盖系统建设需要,做了一系列有针对性的技术测试,提出了重庆市地面数字电视覆盖网络建设项目各系统的技术规划和实施计划。     

Digital TV comes down to earth

The introduction of digital television, albeit with only modest pretensions to glitz, is bound to invigorate competition among manufacturers and broadcasters. The BBC and commercial TV companies in Britain will launch what looks to be the world's first terrestrial digital TV (DTTV) service intended for nationwide viewing. The British services will be the first to use ground transmitters to send digital pictures and sound to an ordinary Yagi roof antenna of the type used for analog TV in Europe or even to indoor rabbit ears. Plenty of digital receivers should be in the shops, and pay TV services, both satellite and terrestrial, will be wooing hesitant viewers with special incentives. Most other countries in Europe are also getting ready to launch DTTV services. The author discusses the phase out of analog services, digital video broadcasting standards, data rates, encryption standard, and competing digital services     

Testing of digital television broadcasting from the stratosphere

Digital TV broadcasting from the stratosphere was tested using an unmanned aerial vehicle, a Pathfinder Plus. A television transmitter installed under the wing transmitted a UHF band signal as the vehicle flew at an altitude of 20 km. The Japanese digital terrestrial broadcasting standard (ISDB-T) was used for transmission. The 13.5-hour flight time included 3 hours of transmission testing. The transmitting equipment worked as expected in spite of the cold and low-atmospheric-pressure environment. Reception at the ground station was satisfactory even when the ISDB-T parameter set used was the one least robust under poor channel conditions.     

A new wideband high frequency channel simulation system

This paper provides a technical overview of a high frequency (HF) channel simulation system that is applicable to either narrowband or wideband HF channels. Although narrowband models of the HF channel have existed for many years, they are applicable only to a limited set of actual narrowband channel conditions. The need for an HF channel model that is valid for both narrow and wide bandwidths over a more extensive range of channel conditions motivated the research reported in this paper. Wideband propagation, noise, and interference models have been developed and implemented in a real-time digital simulator that utilizes state-of-the-art signal processing hardware with a throughput in excess of 1 mega samples/s. The simulator architecture has the flexibility to permit its application to future simulator designs as faster signal processing components become available. The current simulation system can be used for simulating radio channels other than HF because the propagation, noise, and interference models are implemented in software. This flexibility results in a very powerful test instrument     

数字电视信号的有线传输与接收

介绍了数字电视信号在有线信道中传输和接收所需的信号处理方式以及数字接收终端和模拟接收终端各自所需的解调、解扰、解密的方式方法。     

Study of the required crosspolar protection ratio in G-PAL TV FMsatellite transmissions planning

A study including simulation and a measurement campaign using live TV broadcast satellite signals and receiving commercial equipment has been carried out to investigate the required cross-polar protection ratio at the terrestrial receiving antenna for satellite transmission planning. This experiment provides useful and realistic results for efficient channel allocation in the spectrum band of broadcast satellite systems. Among them is the frequency offset required between cross-polar channels, depending on the cross-polar rejection at the receiving antenna, for a certain degree of video signal impairment due to the cross-polar channel interference effect, and taking into account the noise contribution to the signal. A worst case in frequency offset value, i.e., larger subjective impairment of the picture at equal carrier to noise ratio (CNR), has been detected around 5 MHz (near the chroma carrier in G-PAL system 4.43 MHz) only for high values of CNR. Different subjective degradation of the image due to cross-polar channel interference and noise has been observed, and their particular contributions to impairment have been evaluated     

HFC网络中数字电视信号性能参数测试分析

光纤同轴混合(HFC)网是目前承载数字电视信号的主要传输媒质,HFC网络能否真正满足数字电视传输网络的要求,需要对HFC网络中数字电视信号性能参数进行测试分析.在讨论数字电视信号电平、误码率、调制误差比等主要性能参数的基础上,根据实际运营的有线数字电视HFC网络构建测试模型,测试了数字电视信号的性能参数,分析了数字电视信号在HFC网络中的传输情况.测试分析表明:在目前条件下,HFC网络能适应数字电视信号的传输,有一定的优越性.     

Novel carrier recovery scheme in multicarrier digital TV system

This work is aimed at researching and analyzing the performance of carrier recovery (CR) with two transmit antennas on a multicarrier digital TV system operating in time‐selective fading channel. It is shown in the paper that CR can correct the performance degradation caused by Doppler effect when the terminal is receiving high resolution digital TV signals in a fast moving environment. To have the ability to cover a large frequency range, the CR system should do a frequency sweep first. Then the coarse and fine frequency offset estimation is introduced. Both the theoretical and simulated results give valuable insight that the CR is able to perform well with a certain amount of channel fading. The phase and noise effect on the CR performance is also studied. The CR system and the working procedure concerning CR and timing recovery are also researched to give a full solution on synchronization. Copyright © 2012 John Wiley & Sons, Ltd.     

Study of the reliability of a binary symmetric channel under non‐Gaussian disturbances

The field of digital and data communications is becoming increasingly dominant because digital transmission offers data processing options and flexibilities not available with analog transmission. The main feature of a digital communication system is that during a finite interval of time, it sends a waveform from a finite set of possible waveform. One of the most important and fundamental models of communications channels is the binary symmetric channel (BSC). An important measure of system performance in a digital communication system is the probability of error. In this paper, the probability of error, the reliability, the entropy and the channel capacity of a BSC model are studied under non‐Gaussian noise disturbances. Namely, Cauchy, Laplace and logistic distributions are considered. It is found that the reliability of the signaling system is low under non‐Gaussian noise distributions compared to the Gaussian noise distribution. Several methods were used to reduce the error probability. The amount of improvement in reliability using the reduction methods is higher in the case of Gaussian noise. In order to achieve high reliability under non‐Gaussian noise distribution, it is required to increase signal‐to‐noise ratio (SNR) and increase number of repetitions when sending the same signal different times. Finally, it is observed that increasing the reliability for Cauchy distribution noise has totally failed based on sending the same signal different times and summing the received signals. Copyright © 2003 John Wiley & Sons, Ltd.