usrp相关通信实验室频移键控.pdf

RFCommunicationsDemos

FrequencyShiftKeying:StepbyStep

ThistutorialispartoftheNationalInstrumentsRFandCommunicationsdemoseries.

Eachtutorialinthisseries,willteachaspecificconceptofRFandcommunications,by

explainingthetheoryandprovidinganexampleVIthatgivesapracticalexample.This

tutorialcoversanintroductiontoRF,wirelessandhigh-frequencysignalsandsystems.

Forthecompletelistoftutorials,returntotheNIMeasurementFundamentalsMainpage

orformoreRFtutorialsrefertotheNIRFFundamentalsMainsubpage.Formore

informationonNationalInstrumentsRFproducts,visit

Introduction:

Thisstep-by-stepdemoisdesignedtoexaminetherelationshipbetweentheM-aryofan

FSKtransmitterandtheresultingfrequencydomain.FrequencyShiftKeying(FSK)isa

digitalmodulationschemeinwhichdigitalinformationistransmittedthroughchangesin

acarriersinusoid’sfrequency.Indigitalcommunication,thereareseveraltypesof

modulationschemeswhichbuildonthesamefundamentalconceptsofamplitude,

frequency,orphasemodulation.Here,informationistransmittedthoughshiftsin

frequency.Inaddition,astheterm“ShiftKeying”implies,changesinfrequencyare

usedtorepresentdiscretedigitalvalues.OthervariationsofFSKincludeprefixesthat

indicatesymbolnumber(B=2,Q=4,M=any).However,youcanoftenomitthe

acronymprefixifM=2.Therefore,BFSKissynonymouswithFSK.FSKisasimple

modulationparadigmusedinRFID,cordlessphones,callerID,andmanyother

applications.

FSKCoherency:

Frequencyshiftkeyingcanbedividedintotwotypes,coherentandnoncoherent.In

coherentformsofFSK,thereisnophasediscontinuityintheoutputsignal.