satelliteand terrestrialnarrow ... · (i 3.4. jpl indoor (building. 161)-satellite and terrestrial...
TRANSCRIPT
Satellite and TerrestrialNarrow-BandPropagationMeasurementsAt 2.05 GHz
A. Vaisnys Jet PropulsionLaboratory,CaliforniaInstitute of Technologyw. Vogei EE~niversitY of Texasat Austin
1.~
A SeliCSof satelliteandtenestn“alpropagationmeasurementswereconducklon 15and 16December,1994in the vicinityof theJet PropulsionLaboratory(JPL),PasadeU Califomi&in supportoftheVOMPL DBS-Radioprogram.Thereasonfor includingterrestrialmeasurementswas the possibleuseof terrestrialboostersto improvereceptionin somesatellitedigitalaudiobroadcastingsystemserviceareas.
The signalsourcesusedweretheNASATDRSsatellitelocatedat 171degreesWestand aterrestrialtransmitterlocatedon a highpointon JPLproperty.Bothsignalswereunmodulatedctiers near2.05GHz, spaceda few lcHzapartso thatbothcouldbereceivedsimultaneouslyby a singlereceiver.Anunmodulatedsignalwas usedin orderto maximizethedynamicrangeof thesignalstrengthmeasurement.Arangeof greaterthan 35 dB wasachievedwiththesatellitesignal,andover50 dB wasachievedwith thetemestrialsignalmeasurements..
Three testcourseswereusedto conductthemeasurements:●
A 33 km roundtrip drivefromJPL throughPasadenawasusedto remeasurethepropagationof thesatellitesignalover thepathpreviouslyusedin DBS-Radioexperimentsin mid 1994.A shortenedportionof this test course,approximately20 km,wasusedto measurethesatelliteand temestrialsignalssimultaneously.
A 9 km roundtrip drivethroughJPLproperty,goingbehindbuildingsandotherobstacles,was used tomeasurethe satelliteandterrestrialsignalssimultaneously. “
A path throughoneof thebuildingsat JPL,handcamyingthe receiver,wasalsousedto measurethes~ellite and temestrialsignalssimultaneously.
Belowis a photographof the viewfkomtheterrestrialtransmitsitedownto JPL andtowardPasa-dena. The horizonis ColoradoBoulevard,whichmarksthefar pointof thePasadenaruns. Building161,whichwas the siteof the indoormeasurement,is indicated.
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2. Test Confisruration
Thereceivingsystemconjuration for theautomobilemountedequipmentis shownin Figure 1.Thereceivingantema wasa bifilarhelixwitha gainof 8 dBiat25 degrees’elevation.Thiswas followedbya lownoisearnp~ler and a receiverwhichconvertedthesignalto theaudiofkquency rangebetween2.5kHzand 7.5 kHz.This signalwasrecordedon a digitalaudiotape (DAT’)recorderat a samplingrate of 48kHz.Postprocessingwas thenusedto falteranddetectthesignalamplitudeandphase.The resultantdatawasprovidedat a samplerateof 1000samplesper second.
Theconfigurationusedindoorswasthesameexceptthat theantennawasomnidirectional,withapproximatelyOdBi gain.
Allof the outdoortestsalso includedrecordingwithtwo vehiclemountedvideocameras,onefacingforwardand theothera fisheyelensfacingup.A globalpositioningsystem(GPS)receiverwas usedto recordvehicleposition,speedand heading.
l%e directionto thesatellitewas248compassdegrees(SouthofWest)andthe elevationanglewas22 degrees.Thedirectionto theterrestrialtransmitterwasgenerallyto theNorthor Northwest,
TerrestrialSignalat Oto 10 deg.Eiev.
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at 22 deg.Elev.2049.9975MHz
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Figure1.ReceivingSystemConfiguration
3. Test Results -.
‘he completeset of testdata isdocumentedin UniversityofTexasReportEERL-95-B1,10February,1995.Thispaperpresentsa selectionof the testresultsandsomeconclusionson the differencesin propagationof satelliteandterrestrialsignals.
3.1.Pasadena Run 1- SatelliteSismal.
ThePasadenalongpathwas usedin a previoustesh in mid 1994,to test theperformanceof theVOA/JPLDBSReceiverwith‘IT)RS.Signaldrop-outswereexperienceddue to blockageby buildingsandtrees.The signalstrengthmeasurementshowedsharpsignaldropsduringblockage,butbeinga wide bandmeasuremen~it couldnotachievea dynamicrangeof morethanabout10dB. The mainpurposeof theDecember1994testrun 1wasto retestthispath witha muchwiderdynamicrangesignalmeasurement.
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Figure2 showsa mapof thetest route,witha shortdescriptionof the temaingivenin Table 1.Figure3 showsa GPSderivedplotof the vehiclepositionduringthe testrun.
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Table 1.Test RouteDescription
Longitude“*g
Figure3. GPSDerivedVehiclePosition
BuildingsandtreesonJPL property 1Mediumwidth,4 lane, streetwith treesat vqing distancefkom 2roadwayAbovestreetIevelfkeewaywithoccasionaloverpasses 3Wide,4 lane,streetwithtreesat varyingdistancefromroadway 4
Wide,4 lane,streetwithtreesat varyingdistancefromroadway 5(south)commercialwith10W buildings 6Abovestreetlevelkeway withoccasionaloverpasses 7Twolongtunnels 8Belowstreetlevelfreewaywithoccasionaloverpasses 9Commercial,mostly3 story,but sometallbuildings 10MixedOpen andsometreescloseto road 11Residentialheavilyshadedby trees 12Mediumwidth,4 lane, streetwith treesat varyingdistancefkom 13roadwayBuildingsandtreesonJPLproperty I 14 1
Figure4 is a plotof thereceivedsignalpower,at 100samplesper second,relativeto a line-of-sightvaluereferencedto OdB. Themeasurementindicatesthat thereis verylittlemultipathunderline-of-sightconditions.Mostimpairmentsaredue to signalblockageby buildingsandtrees.Figure5 showsthehistogramandcumulativeprobabilityof thereceivedsignalpowersamples,whichindicate that signalattenuationunderthe testconditionsexceeded15dB about 10percentof thetimeand 30 dB about2percentof the time.
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Becauseof transmkion at a lowerelevationangle, the terrestrialsignalsuffersmuchmoremultipaththanthe satellitesignal.In additionthereis a greaterchanceof terrainblockage.Run 6 startedonthehillnearthe terrestrialtransmitsite.In the initialparLhorn 10:43to 10:49,thesignalwas blockedbythe ridgeuponwhichthe transmitterwas located.Thereare also indicationsof signalblockageby terrainat11:12and at 11:19.
Run6 includedseveral360degreeloopsin a parkinglot.Figure8 showsa plot of @esatelliteand\k
terrestrialsignalduringtheparkinglotcalibrationcircles.Thisplotalsoindicatesthat thereis muchmore..
fnuitipathfor the temestrialsignalpath.
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Figure8. SatelliteandTenestrialSignalMeasurementDuringCalibrationTurnson Run 6.
Run 7 was conductedoverthesametest courseas run 6, exceptthat it wasstartedpasttheinitialarea of terrestrialsignalblockage.Run 7 also inciudeda segmentwiththe temestrialsignalturnedoff.whichprovideda calibrationof thenoisefloorof thereceiverfor the terrestrialsignalmeasurement.
Figures9 and 10showthereceivedsatelliteand terrestrialsampledsignalsfor run 7.
Figure11showsthereceivedterrestrialsignalaveragedwitha onesecondrunningaverage.Thisshowsthatmuchof the signalfluctuationstructureseen in Figure10is of a shorttermnature,a goodindicationthat signalfluctuationsare causedby multipath.Multipatheffectscan be overcometo someextentbyantennadiversity.
The averageattenuationof the terrestrialsignalover the testcoursewasnot excessive. Since it ispossibleto have largertemestrialsignaltransmitterpower,the useof wideareaterrestrialboostersforaugmentingsatellitesignalreceptionat S-bandappearspromising.
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Figure 12showthesignalstatisticsfor thesatelliteand terrestrialsignalmeasurementsof run 7.
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Figure10.ReceivedTerrestrialSignalPower
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Figure-l1.ReceivedTerrestrialSignalPowerfor Run7- OneSecondAverages
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Figure 12.HistogramsandCumulativeProbabilitiesofReceivedSignalPowerfor Run 7
186
3 JPL Run 5- SatelliteandTerrestrialSimmlson JPLTestRun.
Run 5 wasalsoa simultaneousmeasurementof thesatelliteandterrestrialsignal,exceptthat it wasconductedover a shortercoursewithinJPL.Figure13showsa map ofJPL,whileFigure14showsthe GPSderivedvehiclepositionduringthetest loop.Somedrift in the latitudedeterminationis apparentfkomthisplot.
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EERUUTAURoutefor Run 1218as05
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Figures 15through17showthesignalmeasurementsandsignalstatisticsfor Run5.
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Figure 17.HistogramsandCumulativeProbabilityof the ReceivedSignalPowerSamplesfor Run
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3.4. JPL Indoor (Building. 161)- Satellite and Terrestrial Signals.
Run 8 of the measurements was conducted indoors, walking throughbelow is a close-up photo of Building 161, looking from the general direction
JPL building 161. Shownof the temestrial transmit site.
The receiver was carried into the second floor East entrance to the building, carried through theNorth corridor, out through the West door (at 14:35:30), back in and down the West corridor, then back allthe way to the East entrance and outside (at 14:39:40).
Figure 18shows the signal statistics. Figures 19 through 20 show the signal power measurements.including one second averages.
Run 8- Terrestrialand SatelliteSignal Statistics(Bid. 161)100.00
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Figure 18. Signal Statistics for Run 8
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Figure20b.ReceivedTerrestrialSignal- OneSecondAverages
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