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Operation
6
Statistical Power
Mostmodernwirelesscommunicationsystemsemploy
complexmodulationmethodslikeorthogonalfrequency
divisionmultiplexing(OFDM)orQuadratureAmplitude
Modulation(QAM).Thesemethodsuseacombination
amplitude,frequency,orphasetocreatesymbolbased
multichannelormulti‐carriersystemsthatresultin
pseudorandomornoise‐likepowerenvelops.Thepeak‐to‐
average
powerratioofsuchawaveformcanbeacomplex
functionofthedatastr eamcontentratherthanjust
amplitude.Sincedigitallymodulatedsignalsoftenappear
noise‐like,statisticalanalysismaybeusedinorderto
characterizethem.
TheStatisticalPowerSensorcollectssamplesoftheenvelope
ofacarrierandaccumulatestheminaseriesofbins.This
informationisusefulforqualitativeassessmentofcomplex
waveformsthathaveafinitenumberofdiscreteamplitude
levels,likeQAM.
Amoreusefulmeasurementisonethatshowshowoften
variouspowerlevelsoccurasa percentageofdataensemble
length.Thisisdonebycalculatingthecumulativedistribution
function(CDF)fromthePDF.
CDF‐Showstheprobabilityinpercentthatthe
measuredpowerislessthanorequaltoaspecified
powerlevel.
ComplementaryCDF(CCDF)‐Theprobabilitythat
themeasuredpowerisgreaterthanaspecified
powerlevel.
CrestFactor‐Peak‐to‐averageratio,orCrestFactor ,
displaysthenumberofsamplesanalyzed,elapsed
time,andconfidenceband.