电子通信系统原理

出版时间：2010-7  出版社：清华大学出版社  作者：（美）弗伦泽尔 著，刘家康 改编  页数：592  
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前言

　　ThisnewthirdeditionofPrinciplesofElectronicCommunicationSystemsisfullyrevisedandupdatedtomakeitoneofthemostcurrenttextbooksavailableonwireless,networking,andothercommunicationstechnologies.Becausethefieldofelectroniccommunicationschangessofast,itisanever-endingchallengetokeepatextbookuptodate.Whileprinciplesdonotchange,theiremphasisandrelevancedoastechnologyevolves.Furthermore,studentsneednotonlyafirmgroundinginthefundamentalsbutalsoanessentialunderstandingoftherealwordcomponents,circuits,equipment,andsystemsineverydayuse.Thislatesteditionattemptstobalancetheprincipleswithanoverviewofthelatesttechniques.　　Oneofthemajorgoalsofthislatestrevisionistoincreasetheemphasisonthesystemlevelunderstandingofwireless,networking,andothercommunicationstech-nologies.Becauseoftheheavyintegrationofcommunicationscircuitstoday,theengi-neerandthetechniciannowworkmorewithprintedcircuitboards,modules,plug-incards,andequipmentratherthancomponentlevelcircuits.Asaresult,olderobsoletecircuitshavebeenremovedfromthistextandreplacedwithmoreintegratedcircuitsandblockdiagramlevelanalysis.Modemcommunicationsengineersandtechniciansworkwithspecificationsandstandardsandspendtheirtimetesting,measuring,installing,andtroubleshooting.Thiseditionmovesinthatdirection.Detailedcircuitanalysisisstillincludedinselectedareaswhereitprovesusefulinunderstandingtheconceptsandissuesincurrentequipment.

内容概要

本书是关于通信系统的经典著作，全面覆盖了各种主要的电子通信系统。全书采用丰富的插图和浅显的语言描述最新的通信技术，避免了高深的数学公式，特别适合用作大学本科的通信系统的双语教材。本书采用国内流行的每一章介绍一种主要通信系统的方式，便于学生自学以及教学内容的讲授。本书共分14章，包括通信系统导论、多路复用、通信系统中的二进制传输、网络和局域网导论、传输线、天线与电波传播、因特网技术、微波通信、卫星通信、电信系统、光纤通信、蜂窝电话技术、无线技术、通信测试与测量等，最后还给出了部分习题的答案以及术语表。    本书可作为通信工程专业、电子信息工程专业、信息工程专业的本科生，以及通信与信息系统、信号与信息处理、电磁场与微波技术等专业研究生的教材。

书籍目录

Preface Chapter 1 Introduction to Electronic Communication   1-1 The Significance of Human Communication   1-2 Communication Systems   1-3 Types of Electronic Communication   1-4 Modulation and Multiplexing   1-5 The Electromagnetic Spectrum   1-6 Bandwidth   1-7 A Survey of Communication Applications   1-8 Careers in the Communication Industry Chapter 2 Multiplexing and Demultiplexing   2-1 Multiplexing Principles   2-2 Frequency-Division Multiplexing   2-3 Time-Division Multiplexing   2-4 Pulse-Code Modulation   2-5 Duplexing Chapter 3 The Transmission of Binary Data in Communication Systems   3-1 Digital Codes   3-2 Principles of Digital Transmission   3-3 Transmission Efficiency   3-4 Modem Concepts and Methods  3-5 Wideband Modula1:ion   3-6 Broadband Modem Techniques   3-7 Error Detection and Correction   3-8 Protocols Chapter 4 Introduction to Networking and Local-Area Networks   4-1 Network Fundamentals   4-2 LAN Hardware   4-3 Ethernet LANs   4-4 Token-Ring LAN Chapter 5 Transmission Lines   5-1 Transmission Line Basics   5-2 Standing Waves 168   5-3 Transmission Lines as Circuit Elements   5-4 The Smith Chart Chapter 6 Antennas and Wave Propagation   6-1 Antenna Fundamentals   6-2 Common Antenna Types   6-3 Radio Wave Propagation Chapter 7 Internet Technologies Chapter 8 Microwave Communication Chapter 9 Satellite Communication Chapter 10 Telecommunication Systems Chapter 11 Optical Communication Chapter 12 Cell Phone Technologies Chapter 13 Wireless Technologies Chapter 14 Communication Tests and Measurements Answers to Selected Problems Glossary

章节摘录

　　ThephasedetectorcomparesthephaseoftheincomingPAMsinewavetotheVCOsinewave.Ifaphaseerrorexists,thephasedetectorproducesanoutputvoltagewhichisfilteredtoprovideavaryingdirectcurrent.ThesystemisstabilizedorlockedwhentheVCOoutputfrequencyisidenticaltothatofthesinewavefrequencyderivedfromthePAMinput.Thedifferenceisthatthetwoareshiftedinphaseby90.　　IfthePAMsignalfrequencychangesforsomereason,thephasedetectorpicksupthevariationandgeneratesanerrorsignalwhichisusedtochangethefrequencyoftheVCOtomatch.Becauseoftheclosed-loopfeatureofthesystem,theVCOautomaticallytracksevenminutefrequencychangesinthePAMsignal,ensuringthattheclockfre-quencyusedinthedemultiplexerwillalwaysperfectlymatchthatoftheoriginalPAMsignal.　　TheoutputsignaloftheVCOisappliedtoaone-shotpulsegeneratorwhichcreatesrectangularpulsesattheproperfrequency.Theseareusedtostepthecounterinthedemul-tiplexer;thecountergeneratesthegatingpulsesfortheFETdemultiplexerswitches.　　Asimpler,open-loopclockpulsecircuitisshowninFig.2-19（b）.Again,thePAMsignalisappliedtoanamplifier/limiterandthenabandpassfilter.Thesinewaveoutputofthebandpassfilterisamplifiedandappliedtoaphase-shiftcircuitwhichproducesa90~phaseshiftatthefrequencyofoperation.Thisphase-shiftedsinewaveisthenappliedt　　apulsegenerator,which,inturn,createstheclockpulsesforthedemultiplexer.Onedisadvantageofthistechniqueisthatthephase-shiftcircuitisfixedtocreatea90~shiftatonlyonefrequency,andsominorshiftsininputfrequencyproduceclockpulseswhosetimingisnotperfectlyaccurate.However,inmostsystemsinwhichfrequencyvariationsarenotgreat,thecircuitoperatesreliably.

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