通信网络（通信简易教程）-Agilent_Digital_Modulation_in_Communications_Systems-An_Introduction.pdf

《通信网络（通信简易教程）-Agilent_Digital_Modulation_in_Communications_Systems-An_Introduction.pdf》由会员上传分享，免费在线阅读，更多相关内容在学术论文-天天文库。

1、AgilentDigitalModulationinCommunicationsSystems—AnIntroductionApplicationNote1298IntroductionThisapplicationnoteintroducestheconceptsofEverytimeoneoftheseefficiencyparametersdigitalmodulationusedinmanycommunications(bandwidth,power,orcost)isincreased,anothersystemstoday.Emphas

2、isisplacedonexplainingonedecreases,becomesmorecomplex,ordoesnotthetradeoffsthataremadetooptimizeefficienciesperformwellinapoorenvironment.Costisadom-insystemdesign.inantsystempriority.Low-costradioswillalwaysbeindemand.Inthepast,itwaspossibletomakeMostcommunicationssystemsfall

3、intooneofthreearadiolow-costbysacrificingpowerandband-categories:bandwidthefficient,powerefficient,orwidthefficiency.Thisisnolongerpossible.Thecostefficient.Bandwidthefficiencydescribestheradiospectrumisveryvaluableandoperatorswhoabilityofamodulationschemetoaccommodatedonotuse

4、thespectrumefficientlycouldlosetheirdatawithinalimitedbandwidth.Powerefficiencyexistinglicensesorloseoutinthecompetitionfordescribestheabilityofthesystemtoreliablysendnewones.Thesearethetradeoffsthatmustbeinformationatthelowestpracticalpowerlevel.consideredindigitalRFcommunica

5、tionsdesign.Inmostsystems,thereisahighpriorityonband-widthefficiency.TheparametertobeoptimizedThisapplicationnotecoversdependsonthedemandsoftheparticularsystem,ascanbeseeninthefollowingtwoexamples.•thereasonsforthemovetodigitalmodulation;•howinformationismodulatedontoin-phase(

6、I)Fordesignersofdigitalterrestrialmicrowaveandquadrature(Q)signals;radios,theirhighestpriorityisgoodbandwidth•differenttypesofdigitalmodulation;efficiencywithlowbit-error-rate.Theyhaveplenty•filteringtechniquestoconservebandwidth;ofpoweravailableandarenotconcernedwith•waysoflo

7、okingatdigitallymodulatedsignals;powerefficiency.Theyarenotespeciallycon-•multiplexingtechniquesusedtosharethecernedwithreceivercostorcomplexitybecausetransmissionchannel;theydonothavetobuildlargenumbersofthem.•howadigitaltransmitterandreceiverwork;•measurementsondigitalRFcomm

8、unicationsOntheotherhand,designersofhand-heldcellularsystems;