LNB本振频率偏移的校正

数字卫星电视接收系统在使用过程中 ,经常遇到LNB本振频率偏移的情况 ,轻者可造成马赛克不断或节目错位 ,重者致使接收系统完全不能收看节目。本文介绍两种常用的校正方法 ,供参考。1　问题的提出无论是正常收视的系统还是新安装的卫视接收套站 ,由于市售的非品牌LNB良莠不齐 ,往往引发以下故障 :在室外系统和接收机完全正常的情况下 ,当模拟接收机接入LNB时节目尚能满意收看 ,但数字接收机接入时试收出厂时预存的节目 ,只能收看少数节目 ,且有马赛克和停顿现象 ,有的仅能勉强收看个别节目并有节目错位现象 ,有的根本收不到任何节目。大…     

LNB本振频率的漂移及调整方法

1999年入冬以后,吉林化纤集团公司电视台接收的数字卫星电视节目经常出现马赛克现象,有时图像信号还会发生中断,严重影响收看效果。为解决这些故障,经过翻阅大量的资料,并作了多次实验,最终判断是ＬＮＢ本振频率发生了漂移。众所周知,本振频率=下行频率 接收频率。所以有时接收不到节目图像的原因是ＬＮＢ本振频率偏离下行频率较多的缘故。如青海电视台下行频率是3713ＭＨｚ,因5150=3713 1437,若本振频率偏离4ＭＨｚ的话,下行频率也要偏离4ＭＨｚ才能收到信号,即本振频率变为5154ＭＨｚ的话,下行频率可变为3717ＭＨｚ,除此别无他法。高频头…     

卫星电视接收机的新型室外设备

近十年来,随着卫星电视机的不断改进,用于接收卫星电视节目的室外设备(卫星接收天线、低噪声变频器LNB、天线分配系统及其附件等)也在不断地改进。本文概述几种新型极化器、LNB和天线分配系统 一、磁性极化器 早期卫星电视接收天线使用的LNB通常都在输入波导管法蓝盘     

彩色电视机中的调谐器

由天线接收的电视广播信号，首先经过调谐器进行频率变换成为中频信号，这是它的主要作用。彩色电视机还要求调谐器具有良好的选择性，较高的信噪比，本振频率应稳定、增益控制范围大、寄生辐射小。     

一种Ku双本振多输出高频头的设计

高频头是一种数字卫星电视信号接收装置,它能对卫星接收信号进行变频和放大.介绍一种Ku双本振多输出高频头的工作原理、性能指标、仿真结果、技术难点、实测结果,并在工程实践中实现批量化生产.     

基于注频锁相技术的接收天线本振阵列

文中以注频锁相技术为基础,提出一维和二维注频锁相耦合本振阵列基本结构,分析了注频锁相本振阵列的相位动力学方程,推导了稳定同步状态本振信号间的相对相移与振荡器自由振荡频率的关系,为注频锁相技术在接收天线本振阵列的应用提供理论基础.     

两根分布式接收天线载波频偏的联合估计

该文在平坦瑞利衰落信道下,针对一根发射天线、两根分布式接收天线场景,提出了一种缩小频率搜索范围的最大似然准则载波频偏联合估计方法。该方法利用载波频率、收发天线晶振精度和移动台最大运动速度的先验信息,确定了两个载波频偏之差的取值区间;联合各接收天线的相关值滑动此取值区间进行搜索,相比已有方法缩小了搜索范围。仿真结果表明,在信噪比为5 dB,载波频率为2 GHz,发射天线晶振精度为10 ppm,接收天线晶振精度为1 ppm,移动台最大运动速度为120 km/h的条件下,载波频偏联合估计的均方误差性能高出已有方法一个数量级。     

DVB机本振频率的设置

用DVB机接收卫视节目,首先要对相关参数进行设置。其中：高频头本振频率的设置是重要的一项,如本振频率设置有误,与外接的高频头不匹配,则无法接收到信号,这一点对于初涉卫视圈的烧友尤其应引起注意。     

DM46U6微波设备收发信本振频率的调节方法

收发信机的本拓是微波设备的心脏,及时判断本振故障并调节本振频率,对于微波维护人员来说很重要。     

雷达接收机混频交扰抑制的研究

设计实现了一个雷达接收机用的二次变频接收前端组件,考虑了主要技术指标及本振和信号通道寄生频率的影响,解决了一本振和二本振交调在信号通道内产生的交调干扰问题.通过理论计算预先确定了频率干扰点,合理选择多次混频组件中频,从而减少了组合频率干扰,对交调与互调起到一定的抑制作用.同时对接收前端组件因频率干扰、交调失真、噪声调制等因素引起噪声系数变差的原因进行了分析,提出抑制交扰的措施,解决了组件噪声系数恶化的技术问题.结果表明,该接收机前端组件在S波段、工作频率400 MHz带宽范围噪声系数小于1.0 dB.     

MMIC family for DBS down-converter with pulse-doped GaAs MESFETs

A monolithic microwave integrated circuit (MMIC) family was demonstrated as a low-noise block (LNB) downconverter for use in direct broadcast satellite (DBS) receivers operating from 11.7 to 12 GHz. A 12-GHz low-noise amplifier (LNA), a 12-GHz mixer (MIX), a 10.7-GHz dielectric resonator oscillator (DRO), and a 1-GHz IF amplifier (IFA) were designed with GaAs MMIC technology. These MMIC chips were designed to form a complete LNB downconverter function with the exception of the dielectric resonator. The most significant result of this work is that practical low-noise performance can be achieved without the use of high-electron-mobility transistors (HEMTs) in a preceding stage of the MMIC LNB downconverter. Almost noise-free satellite broadcast TV pictures were seen by using a parabolic antenna, 40 cm in diameter, without needing any additional circuit adjustment     

卫星电视接收天线的极化匹配问题探析

接收天线的极化调整影响卫星电视的接收效果,极化匹配问题越来越受到人们的重视.文章根据极化波的合成与分解规律以及前馈、后馈式天线的结构区别,分析探讨极化波的接收与极化调整问题.     

C波段下变频器的设计与实现

下变频器是微波接收机的关键组件,其性能优劣将影响整个系统的指标。采用至上而下的模块化设计方法研制了一款C波段下变频器,首先进行下变频器的系统搭建和分立器件的指标分配,然后完成分立模块的原理设计、仿真优化和功能实现,最后实现系统集成和调试封装。该下变频器主要包括低噪声放大器、镜像抑制微带滤波器、锁相环本振源、混频器和功分器等元器件,体积小且便于集成,其射频输入为4.65±0.25 GHz,中频输出为1.3±0.25 GHz,测试噪声系数为4 d B,增益为1 d B,镜像频率和杂散信号抑制性能良好,各项指标满足系统要求。     

基于VB的卫星电视接收天线定位系统的研究与开发

卫星电视信号接收天线定位的主要参数是方位角、仰角和极化角。以VisualBasic语言为工具开发了卫星电视信号接收天线定位系统,系统界面友好、功能强大,用户在选择接收地和卫星的基础上,系统输出天线定位参数并以图示方式显示,还可显示被选择卫星的主要参数及转发的电视节目,供接收卫星电视信号时参考。     

Measurement of the required cross-polar protection ratio in G-PALTV FM satellite transmissions planning

A measurement campaign using live TV broadcast satellite signals and receiving commercial equipment has been carried out to study the required cross-polar protection ratio at the receiving antenna in satellite transmission planning. This experiment provides useful and realistic conclusions for the optimum spectrum allocation of TV channels in broadcasting satellite systems, as for example, the frequency offset required between cross-polar channels depending on the cross-polar rejection at the receiving antenna, for a certain grade of video signal impairment due to the cross-polar channel interference effects, and taken also into account the noise contribution on the signal     

数字卫星电视信号的接收调试及天线维护

通过实例的计算，阐述了作为有线电视系统信号源的数字电视信号余量与接收天线口径的关系，另外介绍了在卫星接收调试及天线维护方面的一些经验体会。     

The European system for digital multi-programme television bysatellite

The general concepts of the system for digital television transmission by satellite developed within the European DVB (digital video broadcasting) project and standardised by ETSI (European Telecommunications Standards Institute) are described. The system, named DVB-S, is intended to provide DTH (direct-to-home) multi-programme TV services in the BSS (broadcasting satellite service) and FSS (fixed satellite service) bands and is addressed to consumer IRDs (integrated receiver decoders), as well as collective antenna systems (SMATV, satellite master antenna TV) and cable television head-end stations, with a likelihood of remodulation. The exploitation of the multiplex flexibility allows the use of the transmission capacity for a variety of TV service configurations. The use of flexible and advanced error protection techniques, based on the concatenation of Reed-Solomon and convolutional codes (with Viterbi decoding), allows optimum adaptation to different satellite transponder characteristics, i.e. bandwidth and power, providing high service quality and availability with small receiving antennas. For example, in climatic zone E (in Europe) on a 33 MHz transponder a data-rate of 38.1 Mbit/s can be transmitted, adequate to provide five standard definition TV programmes (SDTV) or, alternatively three to four enhanced definition programmes (EDTV), while ensuring 99.90% service availability (in the average year) with 50-cm receiving antenna within the 51 dBW EIRP (equivalent isotropic radiated power) service area contour     

Coexistence conditions of LTE-advanced at 3400–3600 MHz with TVRO at 3625–4200 MHz in Brazil

In Brazil, the 3625–4200 MHz frequency band (C-band) is widely used by TV receive-only (TVRO) application in the fixed satellite service (FSS). The 3400–3600 MHz adjacent band can be used by International Mobile Telecommunications (IMT) systems, but many low noise block downconverters (LNB) of TVRO sold in Brazil have not a C-band filter. Thus, it is likely that the low cost LNB used in TVRO receivers would be overloaded by the IMT-systems emissions within the LNB wideband receiver, even the IMT stations operating accordingly to international standards. This paper shows that both systems can coexist harmoniously depending on the characteristics of the IMT system and on the FSS receiver specifications.

     

Ultimate Subjective Quality of a Satellite Television Network Covering Europe and Africa

The distribution of television programs over Europe and Africa via a geostationary satellite is considered on the basis of the satellite-earth liaison. The subjective quality of the image to be expected on the domestic TV receiver is expressed in terms of the ground antenna diameter for values of the satellite output power ranging from 10 to 100 watts, for different values of the RF bandwidth and several locations of the ground terminals in Europe, Africa, and the Middle East. The modulation technique used is the standard FM and the values considered for the carrier frequency are 4, 8, and 12 GHz. The effect of the dimensions of the ground receiving antenna on the subjective quality is given graphically for black-and-white and color television systems in both high and low field strengths relative to the local distribution station.     

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