BIRD 5009 - Chapter 1 Introduction; Description; Element Types; 43 Type Elements

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Chapter 1 Introduction
Description
TheDPSPowerSensorsareintendedforuseincoaxialtransmissionlinesof50
ohmnominalimpedance.Thesensorsutilizeelementsinordertomakepower
measurements.Eachelementhasanarrowonitthatrepresentsthedirectionin
whichitmeasurespower.Theelementsignorepowerintheoppositedirection

withadirectivityofatleast25dB.TheDPSseriescanmakepower
measurementsusingeither43typeorAPM/DPMelements,andthereadings
availablevary,basedonwhichelementsarebeingused.
SincetheDPSusestwoelements,itcanmeasurethequalityofthesystemby
comparingtheforwardandthereflectedpower.Thisisusuallypresentedinthe
formofVSWR(voltagestandingwa veratio)orReturnLoss.
Element Types
43 Type Elements
The43typeelementsarenormallyusedtomeasurepeakpower.These
elementscanmeasurethepeakpowerofasystemwithanaccuracyof+/‐8%of
fullscaleaslongasthesignalmeetsthefollowingrequirements:
 Atleast15pulsespersecond(PPS
 Minimumpulsewidthof15µs(800nsiffrequencyisgreaterthan100
MHz)
 MinimumDutyCycleof0.01%
Inaddition,43typeelementscanbeusedtomeasureaveragepowerinsignals
withapeak‐to‐averageratiocloseto1,likeaCWorFMsignals.Inthesecases,
theaveragepowerismeasuredwithanaccuracyof+/‐5%offullscale.
APM/DPM Elements
TheAPM/DPMelementsareusedtomeasuretrueaveragepower.Trueaverage
powermeansthesensorprovidesequivalentheatingpowerofthesignal,
regardlessofmodulationornumberofcarriers.Theseelementscanmeasure
averagepowerwithanaccuracyof+/‐5%ofreadingfromfullscaledownto
2.5%of
fullscale.
Note: Theequivalentheatingpowerisdependentontheduty
cycleofasignal.Ifasystemputsout50wattswitha50%duty
cycle,theAPM/DPMelementswillmeasure25watts.