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MobileSateliteCommunicationSystem High-FunctioningAntenna AmaneMIURAandYoshiyukiFUJINO TheNationalInstituteofInformationandCommunicationsTechnology(NICT)developeda

1 MobileSateliteCommunicationSystem High-FunctioningAntenna AmaneMIURAandYoshiyukiFUJINO TheNationalInstituteofInformationandCommunicationsTechnology(NICT)developeda highlyfunctionalactivephasedarrayantenna(apaa)foralandmobilevehicleasapartofthe mobilesatelitecommunicationssystem experimentusingets-v Isatelite.Theantennaislight weight,low profileandhasacapabilityofautomaticsatelitetrackingbyusingtheelectronic beam scanning.theefectivenessoftheantennawasconfirmedbythetestsofbasicperformance, trackingperformanceandtransmissionperformancebyusingthesatelitesignal. 1 Introduction TheActivePhasedArayAntenna(APAA)isahighfunctioningantennathatelectronicalycontrolsthebeam, changesdirectionalitywithoutmechanicalymovingthe antennaandperformshigh-speedscanning.itisexpected tobeappliedtomobilesatelitecommunicationssinceit can beconfigured tobethin and light-weight.itwas mountedonasateliteintheka-band [1].Withregardto mountingonthemobilestations,itwasmountedona helicopterforcommunication experiment [2].Both cases showedexcelentperformance.however,ithasnotbecome universalduetothehighcost.nict hasaccumulated practicalexamplesforvarioustypeofapaa [2] [4].Inan eforttorealizetheapaa,wehavedevelopedon-boardsbandactivephasedarayantenna(apaa)forexperiments inmobilesatelitecommunicationswithets-v I [5].For evaluatingtheefectivenesofthisapaa,weobtained basiccharacteristicsusingsatelitesignalsofthisantenna, andtrackingcharacteristicsandtransmisionpropertyin on-board drivingtests.thispaperreportstheseresults. ±1ofandelevationangleof48degreesinanticipationof sateliteanglefluctuationanderorduetothemovement ofthevehicle.aself-diplexingantenna [6] fortransmision andreceptionusingacircularpatchandaringpatchwas adoptedintheelementantenna.arayconfigurationusing 18elementsalows12dBiormoregaininthedirectionof satelite.thetrackingspeedis3degrees/secsothatitis operatedcorectlybytheangularspeedinvehicleturning. Figure2showsasingleelementunit.Oneunitconsistsofs transmision/receiver antenna coresponding to one 2 S-bandActivePhasedArayAntenna [5] Figure1showstheappearanceoftheAPAAthatwas developed (with theradomeremoved).thisapaa is suitableformas-productionsinceitismodular.itweighs 18.7kg and has a thicknes of117mm.ithas the characteristicsofalowpositioninviewofmountingiton theroofofavehicleforon-boarduse.astheapaawas usedinanexperimentusingets-v I,itwasdesignedso thatthedesiredgainof12dbiormoreisobtainedwithin Fig.1 S-bandactivephasedarayantenna Fig.2 Oneelementunit 77

2 element,atransmisionsolidstatepoweramplifier(sspa), areceptionlow noiseamplifier(lna)andtransmision/ reception phaseshifters.themodularstructurecan be disasembledintosingleelements,soitiseasytoaddand fixelements.acontinuouslyvariablephaseshifterusinga doublebalanced mixerisadopted forashifter,which aleviatesquantizationeror.sincetheamplitudeofeach elementsignalcanbechangedindividualybychangingthe outputlevelofthephaseshifter,non-uniform amplitude distribution can be given to an aray antenna.this functioncanbeusedforsuppresingsidelobelevelofthe radiationpaternofanarayantenna. ThisAPAAusestheclosedloopmethodfortrackinga satelite,wherethesatelitesignalisautomaticalytracked using the reception signalof the receiver antenna. Transmisionfrom thetransmisionantennaoccursonly when the receiver antenna is tracking the satelite. Transmisionisautomaticalystoppedduringnon-tracking status(e.g.,automaticsearchmode).thedirectionofthe transmisionantennaisthesameasthatofthereceiver antenna. Figure3 showstheoperation flow ofclosed loop tracking.theoperationflow ischaracterizedbymultiple operationmodescorespondingtosignalconditions.at first,initialsearchingisperformedforthedirectionofthe satelitebythewiderangesearchmode.ifthresholdlevel setisdetected,theoperationflowgoestrackingmode.in thetrackingmode,directionalityisfinelychangedwiththe azimuthangleandelevationangletotrackthemaximum receptionleveldirection.ifthereceptionlevelgoesunder thethreshold,itisconsideredthatthesignallevelhasbeen lost.inthatcase,thetrackingrangeisenlargedgradualy bythreesearchingmodes.ifthesignallevelisdetected again,the flow returnsto tracking mode.the three searching modes include the wait mode (antenna directionalityiscorect,however,satelitesignalisstopped; directionalityismaintainedforsometime),thelocalsearch mode(in thecaseofavehicle,thechangeofsatelite elevation angleissmalso theelevation angleisnot changedandonlytheazimuthangleisscannedtosearch forthesignal),andtheglobalsearchmode(thedirectionof thesateliteisdeterminedbythetwoaxesincludingthe azimuthangleandtheelevationangle).therearetwotypes ofsignalfortracking.in sum patern signal,trackingis performedsothattotalsum ofthearayreceptionsignalis maximum.in diferencepatern signal,anaraypatern (nul)isformedinthedirectionoftheboresitedirection andcontroledsothatthesignalleveliszero.otherthan Signal detection Signal detection Fig.4 Appearanceoftheantennaonthevehicle these,openloopautomatictrackingisposible,wherethe satelite sazimuthandelevationissuppliedfrom outside. AsshowninFig.4,thisantennaismountedonthevehicle, andtrackingcharacteristics,etc.areresearchedasshownin Section3. 3 Experiment 3.1 Basiccharacteristics Global search mode Signal detection Tracking mode Wait mode Local search mode Fig.3 Closedlooptrackingoperationflow APAA Signal loss (a)radiationpatern Figure5showsthereceiptofthecontinuouswave beacon transmited from ETS-V I,and the resultof obtainingthesum paternanddiferencepaterninorder to evaluate the radiation patern when the APAA is operated. The peak of the sum patern width is approximately3degrees.thepeakofthesum paternand nulofthediferencepatern arealmostin thesame direction.thus,itwasconfirmedthattheradiationpatern wasnormalyformedinusage. 78 JournaloftheNationalInstituteofInformationandCommunicationsTechnology Vol.61No.1(214)

3-4-2-2Mobilesatelitecommunicationsystem High-functioningantenna [dbm] Azimuth angle [deg] Fig.5 planepatern Fig.

3 Mobilesatelitecommunicationsystem High-functioningantenna [dbm] Azimuth angle [deg] Fig.5 planepatern Fig.6 Anexampleofangularcharacteristicsoftrackingerorof sum patern (b)basictrackingcharacteristics Thecontinuouswavebeacontransmitedfrom ETS- V IwasreceivedbytheAPAAmountedontherotation platform in theazimuth direction ()and elevation direction().trackingcharacteristicswereverifiedby changingtherotationalspeedoftherotation platform. Trackingerorwasdefinedasthediferencebetweenthe rotationaltable indication and angle detected by the APAA.Thetrackingerorforsum paterntrackingand diferencepaterntrackingwasobtained.figure6shows angle vs.tracking eror ata rotation speed of 3 degrees/secofthesum patern asan exampleof measurement.table1showsthermsvalueofthetracking erorintrackingspeed.thetrackingerorinsum patern isapproximately2degrees.thetrackingerorindiference paternis2-3degrees.ineachcase,theerorissmal comparedtothebeam width,andthereisnodependency on tracking speed. Figure 7 shows tracking eror dependency on C/N (received signalpowervs.noise powerdensityratio).thehigherthec/n ofreceived signal,thelowerthetrackingeror.from theseresults,itis confirmed thatthe APAA hasenough basic tracking performance. Trackingeror[deg] Table1 Trackingerormeasurementresults Tracking angular velocity [deg/sec] Tracking error [deg] sum pattern) Fig.7 DependencyoftrackingeroronC/N Tracking error [deg] difference pattern) Trackingcharacteristicsduringdriving Inordertoevaluatethetrackingcharacteristicsofthe APAA usingsatelitesignals,acontinuouswavebeacon wastransmitedfrom theets-v Isateliteandtracking characteristicsofthesignalsreceivedbytheapaa were obtainedfortheclosedloopmethodincludingthesum paternanddiferencepaternmethodsusinganantenna onavehicledrivinginanurbanareaofkashimacity, Ibaraki prefecture.figure 8 shows the test course. N Satellite direction Fig.8 Testcourse(Themapinthefigureisusedbypermissionof yahoo.) 79

4 Environmentsevaluatedwere;aline-of-siteenvironment wherethesateliteisseen to bewithoutobstacles,a blockingenvironmentwhereradiowavesareblockedby buildingsorelevatedbridges,orashadowingenvironment wheresomeofradiowavesfrom thesateliteareblockedby trees.valueswereobtainedforthereceivedpowervalue duringclosedlooptracking,thelevelmetervalueofthe APAA(itiscorelatedwiththereceivedpowervalueand recordedasreferencevalue),andtheandvaluesof antennadirectionality.asthereferencevalueofdirection ofthesateliteduringdriving,thetrackingsystem bythe openloopmethod [8][9] usingsatelitedirectioninformation from themagneticsensorand thevehiclespeed pulse sensorwasconstructed,toobtainthevalueofsatelite direction(anvaluewasnotobtainedsincethevehicle droveonflatland).inthemeasurementvalues,thelevel metervalue,theandvaluesaresynchronized.the levelmetervalueandreceivedpowervaluehaveatimelag of2-4secondsduetothediferencebetweenbothclocks. However,theyarecorelated. (a)visibilityenvironment Figure 9 showsthe tracking characteristicsduring straightdrivingconcerningthevisibilityenvironment.in thefigure,eachofthereceivedsignalpowers,,,and (openloop)indicatesthereceivedpowervalueduring closedlooptracking,the andvaluesofantenna directionalityandthe valueofsatelitedirectionby open loop tracking.in thesum patern methodsand diference patern methods,stable received power is recordedandthesateliteistrackedwel.thefluctuationin receivedpoweroftheclosedloopmethodislargerthan thatoftheopenloopmethod(notshowninthispaper). Thisarisesbecausedirectionalityiscontinuouslychanged bythesteptrackmethodinclosedlooptrackingmode. (b)blockingbybuildingsandelevatedbridges Figure1showsthetrackingcharacteristicsofvarious tracking methods when the satelite was blocked by buildings.thelevelmeterinthefigureindicatesthelevel metervalueoftheapaa (range:-1%).fluctuation characteristicsofthe and ofsum patern and diferencepatern trackingshow activation ofthewait mode(trackingisstoppedatthesameposition),thelocal searchmode(automaticsearchingisperformedonlyby ) and global search mode (automatic search is signal power [dbm] signal power [dbm] (openloop) 17:52:5 17:52:55 17:53: 17:53:5 17:53: (openloop) :36:1 14:36:15 14:36:2 14:36:25 14:36: A ngle, [deg] A ngular [deg/s] Fig.9 Trackingcharacteristicsofstraightdrivinginagoodvisibility environment signal power [dbm] le Level vel meter m e ter [%] signal power [dbm] lev Level el meter m eter [%] (openloop) :5:18 17:5:23 17:5:28 17:5:33 17:5: :34:35 14:34:4 14:34:45 14:34:5 14:34:55 (openloop) Fig.1 Trackingcharacteristicswhenblockedbybuildings JournaloftheNationalInstituteofInformationandCommunicationsTechnology Vol.61No.1(214)

5 Mobilesatelitecommunicationsystem High-functioningantenna performedbyand).theindicationvalueafter receivedpowerisrecoveredisalmostthesameasthe indicationvalueoftheopenloopmeasuredatthesame time.from theresultshownabove,itwasconfirmedthat trackingcontrolofthesum/diferencepaternfunctioned normaly. Figure11showsthetrackingcharacteristicsofvarious tracking methods when the satelite was blocked by elevatedbridges.powerisreducedtwiceasa resultofblockingbytwoelevatedbridges.inthefirst blockingfor1second,thereceivedpowerwasrecoveredby performing one automatic searching (localsearch mode).inthesecondblockingfor4seconds,theand wereautomaticalysearched(globalsearchmode)and thereceivedpowerwasrecovered.theindicationvalue ofsum/diferencepaternwasalmostthesameasthe indicationvalueoftheopenloopmeasuredatthesame time.from theresultshownabove,itwasconfirmedthat tracking control of the sum/diference patern was functioningnormaly. (c)shadowingbytrees Figure12 showsthetracking characteristicsin an environmentshadowedbytrees.powerisreduced byshadowingoftreesforthesum/diferencepatern.inthe laterhalfofthetimeperiodwherereceivedpoweris significantlyreduced,the and areautomaticaly searched(globalsearchmode)andthereceivedpoweris recovered.itwasconfirmedthatthetrackingcontrolofthe sum/diferencepaternwasfunctioningnormaly.itwas alsoconfirmedtherewasnolargediferencefrom the sum/diferencepaternofautomaticsearchoperation. 3.3 Transmisioncharacteristics Inordertoconfirm theoperationofthetransmision function ofthisapaa,thetransmision action from reduced reception levelby blocking to recovery was evaluated. Inordertomeasurethereceptionandtransmision linksatthesametime,theforwardlink(ka-bandkashima earthstation ETS-V I S-bandAPAA)andthereturn link(s-bandapaa ETS-V I S-bandKashimaearth station)wereused.theforwardlinkwasusedfortracking the APAA and tracking conditions (power,antenna directionality)wererecorded.transmisionwasperformed from theapaabythereturnlink.itwasreceivedbythe S-bandKashimaearthstationanditspowerwasrecorded. Anartificialblockingsituationwasmadebydrivingin [dbm] s ignal pow er Level leve l meter m eter [%] signal power [dbm] Level lev el meter m eter [%] (openloop) :53:35 17:53:4 17:53:45 17:53:5 17:53: (openloop) :37:3 14:37:35 14:37:4 14:37:45 14:37:5 Fig.11 Trackingcharacteristicswhenblockedbyelevatedbridges signal power [dbm] Level level meter meter [%] signal power [dbm] Level lev el meter m eter [%] Global search mode (, search) (openloop) -8-1 Global search mode (, search) Level meter 14:33:25 14:33:3 14:33:35 14:33:4 14:33:45 14:33:5 14:33:55 Level meter Fig.12 Trackingcharacteristicsduringshadowingbytrees 5 Angle 81

6 thekashimaspacetechnologycenter,nict.figure13 showstheresultsofevaluationbyclosedlooptracking (diferencepatern)withopenloopasreference.during diferencepaterntracking,theearthstationreceptionlevel folowsshut-ofto recovery ofreception levelofthe onboard APAA.Thisindicatesthattransmision was stoppedduringblockingandre-startedwhen reception levelwasrecovered.basedonthefluctuationcharacteristics ofantennadirectionality,trackingstoppedwhenreception levelwascutof,antennadirectionalitywassearched,and transmisionrestartedafterblockingwasrecovered. Inopenlooptracking,shownasreference,reception levelreductionbyblockingandrecoveryareobservedon thesideoftheonboard APAA.Thisarisesfrom the antenna is always directed to the satelite position calculated by the high functioning antenna using informationfrom magneticsensorandvehiclespeedpulse sensorinthecaseofopenlooptracking.thesamechange ofreceptionlevelisobservedontheearthstationside.that happensbecausetheopenlooptrackingdoesnotstopthe transmisionsignal.meanwhile,theclosedlooptracking enterssearchingmodewhen thereception levelofthe onboard APAA is les than the threshold.so,level fluctuationissteep. Astheaboveresultsshow,thetransmisionfunctionof thisapaaisefective. Rx level [dbm] Vehicle rx level (closed loop (dif.)) Earth station rx level [sec] Vehicle el (closed loop (dif.)) Vehicle az (closed loop (dif.)) [sec] Rx level [dbm] Vehicle rx level (open loop) Earth station rx level [sec] Vehicle az (open loop) [sec] Fig.13 Antennadirectionalityandreceptionlevelduringblocking (a)receiptlevelofclosedlooptracking (b)receiptlevelofopenlooptracking (c)antennadirectionalityofclosedlooptracking (d)antennadirectionalityofopenlooptracking 4 Summary As part of the mobile satelite communication experimentusingets-v I,wedevelopedathinandlight weighthighfunctioningapaa onboardvehicle.inthis APAA,the closed loop tracking method isused for automaticaly tracking satelite direction and multiple searchmodesthatenlargesearchrangegradualytorealize anefectiveresolutionofsatelitedirectionareadopted.in ordertoconfirm thecharacteristicsofthisapaa,basic characteristicsofthisantennawereobtainedusingsatelite signals,andtrackingandtransmisioncharacteristicsbyan on-board drivingtest.withregardtobasiccharacteristics,aradiationpaternwasnormalyformedinusage condition, the tracking eror was acceptably smal comparedtobeam widthinatrackingpropertytestusinga rotationtable,andtheapaadidnothavetrackingspeed dependency.so,itwasconfirmedthatthisapaa had adequatebasicperformance.fortrackingcharacteristics, trackingactionwasevaluatedbydrivingonthetestcourse inkashimacity,ibarakiprefecture.asaresult,thestable receiptpowervaluewasrecordedbothinsum/diference paterntrackingwhenthesatelitecouldbeseenwithout obstacles.inablockingenvironmentwhereradiowaves from thesatelitewereblockedbybuildingsandelevated bridges,orashadowingenvironmentwhereapartofthe radiowavesfrom thesatelitewereblocked,asignalwas recovered through automatic search by shifting three searchmodes(waitmode,localsearchmodeandglobal searchmode).from thisresult,wecanseethatthetracking action ofthisapaa wasfunctioningefectively.with regard to transmision characteristics, the blocking conditionwasmadeartificialyusingbuildingsandclosed looptracking(diferencepatern)wasperformed.asa result,transmisionstoppedwhenblockingoccuredand restartedwhenrecovered,asthedesignofthisapaa.as theaboveresultsshow,itwasconfirmedthatthisapaa functioned welasa mobile satelite communications antenna. References 1 M.Yajima,T.Kuroda,T.Maeda,M,Shimada,T.Hasegawa,S.Kitao,and K.Hariu, Ka-bandActivePhasedArayAntenna, JournaloftheNICT, Vol.53,No.4,pp.49-55,Dec.27.(inJapanese) 2 Y.Fujino,M.Satoh,S.Nagai,S.Taira,Y.Ozaki,E.Watanabe,M.Sawa,and Y.Tanaka, DevelopmentofHelicopterSateliteCommunicationSystem for thedisasterinformationtransmision, IEICETrans.Com.,Vol.J91-B,No. 12,pp ,Dec.28.(inJapanese) 3 S.Kitao,H.Nakaguro,A.Akaishi,andN.Kadowaki, DevelopmentResults 82 JournaloftheNationalInstituteofInformationandCommunicationsTechnology Vol.61No.1(214)

3-4-2-2Mobilesatelitecommunicationsystem High-functioningantenna ofpartialmodelofaka-bandactivephasedarayantennaforgigabit Satelite, TechnicalReportofIEICE,Vol.AP98-114,pp.51-56,Nov.1998. 4 M.

Yamamoto,andM.Satoh, LandMobileStationforETS-V I MobileSateliteCommunicationsExperiments, JournaloftheCRL,Vol.49, Nos.3/4,pp.145-151,Dec.23.(inJapanese) 6 T.Shiokawa,F.Watanabe,M.Yasunaga,N.Goto,Y.

7 Mobilesatelitecommunicationsystem High-functioningantenna ofpartialmodelofaka-bandactivephasedarayantennaforgigabit Satelite, TechnicalReportofIEICE,Vol.AP98-114,pp.51-56,Nov M.Tanaka,S.Yamamoto,N.Obara,andH.Saito, Ka-BandMobile-Vehicular ActivePhasedArayAntennaforMobileSateliteCommunications, Journal ofthecrl,vol.46,no.4,pp ,dec.2.(injapanese) 5 A.Miura,S.Yamamoto,andM.Satoh, LandMobileStationforETS-V I MobileSateliteCommunicationsExperiments, JournaloftheCRL,Vol.49, Nos.3/4,pp ,Dec.23.(inJapanese) 6 T.Shiokawa,F.Watanabe,M.Yasunaga,N.Goto,Y.Chatani,andH.Abe, Microstrip Aray Antenna foraeronauticalsatelitecommunications, TechnicalReportofIEICE,Vol.AP86-6,pp.23-27,1986.(inJapanese) 7 A.Miura,Y.Fujino,S.Taira,N.Obara,M.Tanaka,T.Ojima,andK.Sakauchi, S-bandactivephasedarayantennawithanalogphaseshiftersusingdoublebalanced mixersformobile SATCOM vehicles, IEEE Trans.Antennas Propagat.,Vol.53,No.8,pp Aug S.Yamamoto,K.Tanaka,K.Suzuki,andH.Wakana, AnAntennaTracking Method for Land-Mobile Satelite Communications System, Technical ReportofIEICE,SANE94-54,pp.35-41,Oct.1994.(inJapanese) 9 S.Yamamoto,K.Tanaka,H.Wakana,andS.Ohmori, AnAntennaTracking MethodforLand-MobileSateliteCommunicationsSystem, IEICE Trans. Com.,J77-B-I,No.6,pp ,June.1994.(inJapanese) Am anemiura,ph.d. SeniorResearcher,SpaceCommunication SystemsLaboratory,WirelessNetwork ResearchInstitute SateliteCommunications,Antenna YoshiyukiFUJINO,Dr.Eng. ProfessorofToyoUniversity/Former:Senior Researcher,SpaceCommunicationSystems Laboratory,WirelessNetworkResearch Institute SateliteCommunications,WirelessPower Transfer 83

인문사회과학기술융합학회

인문사회과학기술융합학회 Vol.5, No.5, October (2015), pp.471-479 http://dx.doi.org/10.14257/ajmahs.2015.10.50 스마트온실을 위한 가상 외부기상측정시스템 개발 한새론 1), 이재수 2), 홍영기 3), 김국환 4), 김성기 5), 김상철 6) Development of Virtual Ambient Weather Measurement