User Manual

SystemDescription
6
Base Station Interface Unit (BIU)
TheBaseStationInterface Unit(BIU)istheinterfacebetweentheoperator’sbasestationandtheFiber‐DASsystem.
ThismodulehasseveralRFconnectorsonthefrontpanelanditcontainsduplexfilters(optional)orseparateuplink/
downlinkpathswhichcanbechosendependingontheneedsfortheconnec tiontotheba
sestation.In mostcases
theduplexedversionwithacombinedDL/ULportisused.
Figure 2 Base Station Interface Unit (BIU)
Functional description
TheBIUha
sfourSMAports(femaletype)toconnecttheRBS/BTS.Intheduplexedversioncombine dDL/UL
connectorsareusedtoconnecttotheRBS,andthereareULtest(TP)connectorspresentthatcanbeusedto
monitorthesignaloutfromtheBIU.Intheversionwithoutduplexfi
ltersthetestconnectorsreplacedbyUL
connectorsandthenormally combinedUL/DLconnector sarereplacedbyDLonlyconnectors.
TheBIUha
sfourQMAports(femaletype)thatarenormallyusedtoconnectittoaPOI.Therearetwouplink(input)
portsandtwodownlink(output,TX)ports.Thesearetwoseparatepaths,theisolationbetweenDL1andDL2is> 
50dBandtheisolationbetweentheUL1an
dUL2portsisalso>50dB.
Therear
etwoseparateRFpathsintheBIUandtheBIUisconfiguredatthefactoryforthespecificfrequencybandit
willserve.ThetwopathsintheBIUcannothavedifferentfrequencies;aGSM900BIUwillhavetwoGSM900paths
andcannotbecombinedwithan18
00path.SeparatefrequenciesrequireanadditionalBIUcardtobeinserted.
RFpatc
hcablesareusedtopatchtheDLandULpathstothePOI.
ThereisanalarmportontheBIUwh
ich(futureupgrade)canbeusedtoconnectexternalalarms.ThisisaDB9
femaleconnector.
TheBIUiste
chnologyneutralandthedownlinkpathcontainssettableattenuatorsthatcanbeused toadjustthe
signalstrengthtoproperlevelsbeforefeedingthemintothePOI.Intheuplinkthereisanamplifierfollowedbya
settableattenuatorusedtoadjustthesignalandthenoiselevelin
tothebasestationuplink.
AllRFc
onnectionsaremadeonthefrontoftheBIU.ThemaximumrecommendedinputpowertotheBIUis30dBm
andtherearehighpoweralarmsthatactivateat>30dBmandlowpoweralarms at<10dBminputpower.Ahigher
inputpowerthantherecommendedca
ncausetheunittofailpermanentlythusneedingreplacement.Itistherefore
recommendedthatforhighpowerbasestationanattenuatorisusedtoensurethattheinputpowertotheBIUcan
neverexceedspecifications.
Thereisa0dB
minputversionoftheBIUavailableonrequest.