广播电视数字微波传输

文章就模拟微波干线的数字化改造和数字MMDS的实现提出了切合实际的解决方案。     

对MMDS微波传输系统的优越性和局限性的认识

前言MMDS（MultichannalMicrowaveDistribution＼System）意为多路微波分配系统。是一种独立的信息传输与分配系统。将残余边带调幅的电视信号与调频的声音信号,通过微波电波自接传送到下家万户。MMDS传输网既具有微波干线传输信号的作用,又具有分配到户的功能。MMDS微波传输系统,八十年代初首先由美国发明和使用,九十年代初传入我国。由于MMDS具有许多优点,所以在很短的几年时间里,MMDS在我国得到了迅速的发展和广泛的应用。用于有线电视传输和分配的MMDS与CATV的电缆网、光缆／电缆混合同（HFC网）相比主要有以下特点…     

MMDS微波传输系统的规划与设计(连载Ⅲ)

4MMDS的传输质量要求及其指标分配MMDS联网的CATV系统要求4级以上图像质量。按GYH106－2标准规定,系统要求达到C／N＞43dB,CTB≥54dB,CSO≥54dB。由于MMDS系统设备的功率放大是甲类线性放大,超线性设计,因此H次失真CSO分量很小;另外,采用平衡式混频器、其二次失真也很小;还有,MMDS下变频器的二次失真也在带外,因此在MMDS系统中不考虑复合二次失真CSO分量,仅考虑载噪比C／N和复合三次失真CTB分量。4．1袖标分留根据MMDS传输网及同轴电缆分配网的规模大小不同,其C／N和CTB的分配比例也不同。l）载噪比C／…     

模拟微波电路传输数字压缩电视信号的关键技术

1993年福建省广播电视厅为加强我省有线电视系统的行业管理,提高各地市(县)有线电视网络的质量,完成省委、省政府为民办实事项目,因地制宜采用多种传输手段,在较短的时间,以较少的投资建成联接我省69个市(县)有线电视台的10GHz微波电路,率先在全国实现全省有线电视大联网。因受资金、时间及当时数字压缩技术国际标准尚在制定等多种因素限制,联网微波电路仍采用模拟微波设备,共使用6个信号,12个收发信频率,频率利用低。随着我省广播电视宣传事业发展的要求,联网10GHz微波电路需增加传送3套电视和3套立体声广播节目,如仍采用模拟方式,每个微波     

MMDS多路微波分配系统的设计

论文分析了ＭＭＤＳ多中微波分配系统的组成原理，介绍了ＭＭＤＳ的设计计算，如接收系统对输入信号的要求，有效全向辐射功率的确定，发射天线的选择等，对建台具有一定的参考意义。     

数字电视模拟微波传输系统数字化改造方案

研究了数字电视微波传输技术,根据各项数字化改造指标,使改造后的微波传输系统达到设计要求,可将误码率控制在≤10-6,信号电平储备为＞20 dB,保证了电视广播传输在图像质量方面的稳定性。采用数字信号传输,有效的消除了原有模拟传输所带来的诸多问题,同时还保留了微波自身的优势,如抗击自然灾害能力强和易维护等特点。     

MMDS微波传输系统的规划与设计(连载Ⅱ)

３ＭＭＤＳ传输特性计算３．１电波在大气中传输ＭＭＤＳ信号工作在微波频段,电波传播为直线传输。但由于气象条件的变化及复杂的地形地势,电波在大气中不是真正的直线传播,而是要产生多径反射、折射、散射和绕射,使电波弯曲。在实际传播中这几种传播形式都存在。当地面平滑范围较大时,以反射为主;当地面高低不平起伏较大时,以散射为主;当传输余隙较小或有障碍时,以绕射为主。１）折射由于对流层的密度变化,其温度、湿度和气层均不同,因此微波在这个不均匀大气中传播就会产生各种各样的折射。大多数情况是向下折射,即朝向地球弯…     

基于SDH数字微波的广播电视传输模式

结合SDH数字微波传输的特点，简要地概述了建立在SDH数字微波体系上的广播电视传输模式，提出对现有模拟微波进行数字化改造的可行性。     

数字微波传输在广播电视中的应用分析

在科学技术发展的推动下,广播电视逐渐发展起来,并被广泛的应用.数字电视,已经成为了人们生活中必不可少的工具.它不仅更具视觉效果,还能够切实的满足用户的个性化需求.为了能够更好的应用数字微波技术,就需要针对其在广播电视中的具体应用进行深度的分析.     

广播电视无线数字化覆盖工程信号源传输方案

随着科学技术的不断发展,我国广播事业开始进入一个全新的发展阶段,数字广播、电视等新兴媒体不断出现在人们的生活中.由于广播电视在覆盖网中的主导地位将受到多种因素或层次的影响,因此有必要在新的路径、新的思维方式等方面进行持续优化.以确保数字广播覆盖项目更加优化.     

便携式数字图像微波中继传输的设计

图像信息因其直观、生动、信息量大而获得了广泛应用,图像的处理与传输成为一个重要的研究课题。设计了一种适于野外使用的图像数字化微波再生中继传输系统,叙述了该系统的组成与工作原理,给出了试验结果和应用范围。     

A packet delay analysis for cellular digital packet data

We formulate and analyze a model of voice and data burst traffic for cellular digital packet data (CDPD). To develop a tractible model, we make some reasonable simplifying assumptions to model the voice traffic and one of the logical CDPD channels as an M/M/1 queue in a random environment. Rather than explicitly solve the resulting matrix quadratic equation, we develop an asymptotic analysis that gives us simple approximate formulas (with error bounds) for many performance measures of interest. In particular, one metric that we highlight comes from using our approximate mean data burst delay formula to characterize the performance of a set of interacting logical CDPD channels. We do so by describing it in terms of an equivalent number of independent, dedicated CDPD channels, We can use this metric to suggest what the optimal number of logical CDPD channels for a given system should be     

Cellular digital packet data network

Cellular digital packet data (CDPD) is a data network designed to meet growing mobile data transmission needs. CDPD networks can stand alone or overlay on the cellular voice system by drawing radio resources from the pool of unused or free cellular analog voice channels. Detection as to whether a channel is free or occupied is mechanized through channel sniffers. Once the CDPD network seizes a channel, it continues to use the channel as long as it is free and leaves the channel within 40 ms of initiation of any voice activity on the channel-the CDPD network then hops to another free channel, if available. CDPD follows slotted nonpersistent digital-sense multiple access with collision detection (DSMA/CD). In addition, it performs channel-error detection and channel-error recovery. We investigate several aspects of the CDPD network, namely, the: (1) effect of CDPD on cellular voice and (2) the delay-throughput performance due to DSMA/CD with error detection     

基于开放平台小基站的5G数字室分解决方案

从5G时代室内覆盖的挑战与趋势进行分析,提出应对该现状的基于开放平台小基站的5G数字室分解决方案,并提出该方案的核心设计要素。基于5G技术可能对于各行各业带来的影响,探讨了5G开放平台小基站对几个典型行业应用的技术赋能研究。     

Comparative performance of some polynomial-based lowpass filters for microwave/digital transmission applications

This paper reports on the comparative performances of some polynomial based lowpass filters in the lumped elements, microstrip and defected ground structure (DGS) environment. The microwave designers are normally familiar with Butterworth, Chebyshev and Bessel filters. However, many more polynomials based, ripple and non-ripple types LPF have been suggested for the low-frequency applications. Some of these LPF, such as L-opt, H-type, Transitional Butterworth-Legendre (TBL), Pascal, Legendre group of LPF, are compared for their applications in analog microwaves, digital transmission, efficiency enhancement of the linear power amplifiers and five level partial response modulations. A method is reported to compute the ripple frequency for the Legendre group of LPF and Pascal LPF. Further, a design is suggested to significantly improve group delay performance of high selectivity filters.     

蓝牙分组传输性能分析与自适应分组选择策略

分析了蓝牙2．0＋EDR新规范定义的3种调制方式在AWGN信道下的位错误率与平均接收信噪比的关系，推导了ACL分组的重传概率与平均接收信噪比的函数表达式。通过分组的重传概率与特性分析了ACL分组的传输性能，包括平均吞吐量、平均重传次数、平均传输时延等。提出了AWGN信道下的自适应分组选择策略，通过在不同的信噪比情况下选择合适的分组类型进行传输而获得最大吞吐量，给出了进行分组类型切换的信噪比门限值。分析结果与提出的策略适用于蓝牙数据传输性能的优化。     

Decoder-assisted frame synchronization for packet transmission

This paper proposes a novel frame synchronization methodology for packets with convolutionally encoded data. Rather than by placing sync bits in a separate header, the sync bits are placed in a midamble and encoded as part of the data sequence, using the error correction encoder to resolve time ambiguities. The scheme is based on the principle that an error in trellis termination may result in decoding a wrong information bit sequence, while the starting portion of the sequence can be decoded as error free. This frame synchronization technique is extended to the synchronization of turbo-coded systems using a list-based approach, where the first synchronizer provides a list of potential packet starting positions, and the following synchronizer makes the final decision. The performance improvement over conventional synchronization techniques is quantified via simulation