移动通信调制技术.pdf

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

2、mphasisisplacedonexplainingonedecreases,becomesmorecomplex,ordoesnotthetradeoffsthataremadetooptimizeefficienciesperformwellinapoorenvironment.Costisadom-insystemdesign.inantsystempriority.Low-costradioswillalwaysbeindemand.Inthepast,itwaspossibletomakeMostcommunicationss

3、ystemsfallintooneofthreearadiolow-costbysacrificingpowerandband-categories:bandwidthefficient,powerefficient,orwidthefficiency.Thisisnolongerpossible.Thecostefficient.Bandwidthefficiencydescribestheradiospectrumisveryvaluableandoperatorswhoabilityofamodulationschemetoacco

4、mmodatedonotusethespectrumefficientlycouldlosetheirdatawithinalimitedbandwidth.Powerefficiencyexistinglicensesorloseoutinthecompetitionfordescribestheabilityofthesystemtoreliablysendnewones.Thesearethetradeoffsthatmustbeinformationatthelowestpracticalpowerlevel.considered

5、indigitalRFcommunicationsdesign.Inmostsystems,thereisahighpriorityonband-widthefficiency.TheparametertobeoptimizedThisapplicationnotecoversdependsonthedemandsoftheparticularsystem,ascanbeseeninthefollowingtwoexamples.•thereasonsforthemovetodigitalmodulation;•howinformatio

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

7、ndarenotconcernedwith•waysoflookingatdigitallymodulatedsignals;powerefficiency.Theyarenotespeciallycon-•multiplexingtechniquesusedtosharethecernedwithreceivercostorcomplexitybecausetransmissionchannel;theydonothavetobuildlargenumbersofthem.•howadigitaltransmitterandreceiv

8、erwork;•measurementsondigitalRFcommunicationsOntheotherhand,designersofhand-heldcellularsystems;