AntSelDualpolunit6.docx

AntSelDualpolunit6.docx

《AntSelDualpolunit6.docx》由会员分享，可在线阅读，更多相关《AntSelDualpolunit6.docx（14页珍藏版）》请在冰豆网上搜索。

AntSelDualpolunit6

Unit6:

AntennaSelectionConsiderations

Author

Department

PhoneNumber

ScottTran

CDMAGlobalNetworkDesign

（Dept.2779）

（972）6842796

ESN444-2796

6.AntennaSelectionConsiderationsandExperimentalResultsofDualPolarizationDiversityPerformance

Thissectionhastwomainsubections.Thefirstsubsectionisantennaselectionconsiderationsandthesecondsub-sectionistheexperimentalresultsofdualpolarizationdiversityperformanceatPCSBand.

6.1AntennaSelectionConsiderations

Thissub-sectioncoverswhatshouldbeconsideredwhenevaluatingorselectingbasestationantennasbasedonantennaspecificationsandtesting.Thissectionalsocovershowthehorizontalandverticalpatterncanimpactthesystemperformanceassociatedwithsofthandoffandsystemnoiseandhowtocombinemechanicaldowntiltandelectricaldowntiltforoptimizingthesystemperformance.ThissectionalsointroducesalistofantennavendorsthatisselectedbyNortelfortheantennausage.

6.1.1SelectionBaseStationAntennaperSpecificationandTestResults

ItisimportanttoconsiderthefollowingpointswhenselectingantennasforPCS（1900MHz）andDCS（800MHz）systems.

1.Electricaldesignspecifications

2.Mechanicaldesignspecifications

3.Environmentaldurabilitytestresults

6.1.1.1ElectricaldesignSelection

6.1.1.1.1HorizontalBeamwidthConsiderations

HorizontalbeamwidthtypicalusedonCDMA,TDMA,andAMPSsystemsare33o,65o,85o,and90o.

Fortri-sectorsiteapplication,ahorizontalbeamwidthof85o（atthe–3dBpoints）isusuallyspecifiedtoprovidetherightoverlapandcoverageareaforthesuburbanandruralareas.Forthedenseurban,urban,andinnercityareas,anantennabeamwidthof65oisconsideredtobeabetterchoicesincethecellradiusofdenseurbanandurbanareasisabout1Kmto2Km.Withthedeploymentof65ohorizontalbeamwidthantennafordenseurbanandurbansites,theexcessiveoverlapbetweensectorscanbereduced.Theseresultinreducingsofthandoff,channelelementusage,andsystemnoise.

Bi-sectorsitewithtwoantennasmountingbacktobackisnormallydeployedalongthehighwayintheruralareas.Anantennabeamwidthof65oisusuallyusedforhighwayinthesuburbanarea.Theusageof65ohorizontalbeamwidthinsteadof85obeamwidthcanincreasethelinkbudgetbyabout1.5dB.Forlongnarrowinterstatehighway,normallythecoverageisthemainconcern.Thelongerthecoveragecanextendalongthelongnarrowhighwaythelessrevenueneedtospendonthehardware（i.e.BTS）.Thisresultsinusingantennaswith33ohorizontalbeamwidth.

6.1.1.1.1.2FronttoBackRatioConsideration

Thefront-to-backratioisalsoneededtobeconsidered.Thefront-to-backratioofhorizontalpatternnormallyvariesbetween20dBto35dB.Anantennawithfront-to-backratioof25dBistypicallybeenused.

6.1.1.1.1.3VerticalBeamwidthConsideration

Thehighergainthenarrowerverticalbeamwidthandthelongerlengthofanantennacanonlybedesigned.Averticalbeamwidthof4oisaboutasnarrowaverticalbeamwidthasshouldbeusedsinceantennawithverticalbeamwidthlessthan4oishardtolevelitaccuratelyandrequiresaverystablemountingstructurefortheantenna.Alsoantennawithverticalbeamwidthlessthan4oisveryeasysufferwinddeflectionandvibration.

Theselectionofverticalbeamwidthdependsonparticularapplications.Anantennawithverticalbeamwidthbetween7oto10oistypicallydeployedfordenseurban,urban,andinnercityareas.Anantennawithverticalbeamwidthbetween4oto7oisoftenusedforsuburbanandruralarea.

6.1.1.1.1.4UpperSidelobeConsideration

Almostanyoptimizednetworkrequiredsiteswithdowntilteitherwithmechanicalorelectricalorboth.Antennawithoutuppersidelobesuppressioncancreateunpredictableinterference,pilotpollution,systemnoiseincrease,andunnecessarysofthandtotheneighborsectororsometimesover-shoottothesecondtiercellsasaresultofmechanicaltilt.Therefore,allverticalsidelobeswithin20oofthemainbeamareoftenrequiredtosuppresstoatleast–19dBrelativetothemainbeam.

6.1.1.1.1.5VSWR（VoltageStandingWaveRatio）Consideration

VoltageStandingWaveRatio（VSWRorreturnloss）isanotherfactorneedtobeconsidered.ThetypicalvalueforVSWRisbetween1.2:

1to1.5:

1

issuggestusingbothmechanicaltiltandelectricaltilttogether.

6.1.1.1.1.6IntermodulationProductGenerationConsideration

Duplexingtransmittersandreceiversontothesameantennaareoftenbeendeployedtosaveantennaandmountingcostandtoimprovethevisualprofile.ThelevelofPassiveIntermodulationProduct（PIP）thatgeneratedbythemutiplexingofmultifrequencycarrierontransmissionandreceptiononanantennamustbeconsidered.

TypicallythePIPslevelisspecifiedtobeabout–110dBmfortwo+43dBm（20W）carriersformostantennamanufactures.ThePIPatthelevelof–110dBmissufficientforavoidinginterferenceintermodulationsincethe3rdintermodulationthataregeneratedbybasestationTXisfelloutthepass-bandofthemobileRXandviceversaforboth800MHzand1900MHz.Pleaserefertotables:

6.1and6.2belowforthedetails.

Table6.1:

3rdPIPgeneratedbyBaseStationandMobileStation（1900MHzSystem）

Table6.2:

3rdPIPgeneratedbyBaseStationandMobileStation（800MHzSystem）

6.1.1.2AntennaHardwareandEnvironmentaldurabilityConsideration

Alongwiththeseelectricalissues,mechanicalissuesarealsoimportanttoconsider.Theantennashouldhaslesscablesandsolderjointinthedesignsincethesolderedjointishardtocontrolandmaybreakdownoverlongperiodoftime.Thepassiveintermodulationisintroducedwhenthesesolderedjointsarelosingorbreakdown.

Anotherkeymechanicalissueistheantennaconnector.The7/16Dinconnectorshouldbeusedsinceitdurableandishardtohaveinnerpintobedamageduringtheinstallation.Iftheinnerpinispartialdamage,itcanhavepoorTxpowerandcreateintermodulation.

Downtiltclampsshouldbeconsidered.Theseclampsmustholdupto125-mphwind.Theantennamusthavethedrainhole.

Environmentaldurabilityalsoneedstobeconsidered.Whenselectingantennas,theenvironmentaltestingsuchastheIEC（InternationalElectroTechnical）testingmustbeobtainfromtheantennamanufacture.ThefollowingaretheminimalIECtestingamanufacturerneedtoperform.

IECTestCode

Description

IEC68-2-1

ColdTest:

16hoursat–40oC

IEC68-2-2

DryHeatTest:

16hoursat+70oC

IEC68-2-11

SaltMistTest:

48hoursinsalttank@5%saltsolution

IEC68-2-14

ChangeofTemperatureTest:

+70oCto–40oCtwocycles,2hoursdwell.ItshouldbedoneinconjunctionwithVSWRmeasurement.

IEC68-2-18

RainTest:

10mm/houratvariousangle

ICE68-2-26

Vibration:

Variedfrequenciesandmultipleaxes.

IEC-68-2-3

HumidityTest:

24hours@55oCand95%humidity,sixcycles.

6.1.2OptimizingSystemPerformancebydowntilting

Downtiltingbasestationantennaisakeyfactorfordesigningandoptimizingthesystemperformance.Asite（basestation）withantennalocatedinahighhillnormallycreatesindeadspotatdistanceclosetothebasestation.Onewaytocorrectthatistoapplysmall（2oto3o）mechanicaldowntilt.

DowntiltingthemainbeambelowthehorizoncanreduceRFsignalpropagatingbeyondthedesiredcoverageorreducetheRFpowerblastingtoadjacentsitesandtothesecondtiersites.Asaresult,systemnoise,unnecessarysofthandoff,pilotpollutioncanbereducedorcontrolled.

Downtiltingtheantennashouldbehandlewithcaresinceverysitehasspecificheightabovetheaverageterrain.Anestimatevalueofdowntiltcanbecalculatedbyusingthefollowingformula.

Mainbeamdistance=（H/tan（DT））/5280

Dmin=（H/tan（DT+0.5*VBW））/5280

Dmax=（H/tan（DT–0.5*VBW）/5280

WhereDT=downtiltangleandVBW=verticalbeamwidth.

Sitesthatrequiremechanicaltiltingwithmorethan6oshouldbeverifiedwhethertheboresideofthehorizontalpatternisdistorted.Electricaltiltcanbeusedinconjunctionwithmechanicaltiltforbetterresultsincemechanicaltiltonlyaffectonthehorizonbutnotthetwosidesofthehorizontalpattern.Thereforeifmechanicaltiltrequiresmorethan9o.Itissuggestusingbothmechanicaltiltandelectricaltilttogether.

6.1.3ListofAntennaVendorsSelectedbyNortelfortheantennausage

1.ALLGON

2.ANDREWS

3.COMSATRSI

4.CELWAVE

5.DAPA

6.DECIBLE（ALLENTELECOMGROUP）

7.

SCALA

6.1.4Appendices

6.2DualPolePolarizationAntenna

Dualpolarizationantennahasbeenpaidmuchattentionforitsdiversityperformancesincethesamesectorwhichisusedtwoantennasforspacediversitycannowbereplacedwithoneantennafordual-polepolarizationdiversity.

Dual-polepolarizationantennaisidealfordeployinginareaswithzoningrestrictionsindenseurban,urban,andsuburbansincethehighertheantennaofabasestationisthewidertheseparationoftwodiversityantennasisrequired.TheseparationDofthespacediversityschemecanbedeterminedwiththefollowing.

h/D=11,wherehistheantennaheight.

Theaboveequationhasbeendeterminedexperimentallythattheoptimumvalueis11asindicatedinLee[2].Forexample,iftheaverageantennaheightofbasestationsininnercityis30mor100feet,andthentheoptimumseparationDisabout3mor9feet.

Asmentionedabove,thedeploymentofdualpolarizationantennafordiversitywillreducetheantennacount.Atri-sectorsite（basestation）requires9antennas,3foreachsectorwhensimplexantennasystemconfigurationisusedandrequires6antennasforduplexantennaconfiguration.T