外文翻译原文-汽车防撞雷达系统

CarCollision-PreventionRadarSystemNiGuoqiLiuChangmanGuanYongjunWangManshengDepartmentofFireControl&Command,GuilinAirForceAcademyModulatorAbstract:Intheseyears,thereisahighrateofcarchain-collisionaccidentsonthehighways,especiallyontheexpressways.Yet,untilrecentlynogoodsolutiontothisproblemhasbeenworkedout.Inthispaper,anattempttosolvetheproblemcompletelyispresented,thatis,thecar-carriedrangefindingradar,whichcanautomaticallycontrolthedrivingspeedandkeepagivenspacebetweenthecars.4OscillationSourceKeywords:car,collision-prevention,radar1.IntroductionItisover100yearssincethecarcameintobeinginGermanyin1886.Sincethen,thedevelopmentofcarindustryhasbroughtradicalchangestothehumanlifeallovertheworld.Inrecentyears,withthedevelopmentofthenationaleconomyinchina,theroadtraffichasbeengrowingrapidlyandtheconstructionofexpresswaysisinitsprime,whichhasplayedanimportantroleintherapiddevelopmentofournationaleconomy.But,forsomereasonslikelowcadroadrate,lowgradedroads,mixedpedestrian/cartrafficandpoormanagement.Trafficaccidentshavebeenhappeningatahighrate.Forexample,ontheexpresswayfromShanghaitoNanjing,thereismorethanonecarchaincollisionaccidenteachyear.Theaccidentsresultedingreatlossoflivesandproperty,thenwhatisthewaytopreventallthis?Theauthorsofthisarticlebelievethat,inadditiontoattachingmoreimportancetotrafficsafety,strictertrafficlawsandbettermanagement.Weshouldsetupanadvancedcarcarriedcollision-preventionradarsystemtoautomaticallylimitthecarspeedandreducetrafficaccidents.2.GeneralPlanandBasicPrinciples2.1BlockDiagramofGeneralStructureThegeneralplanisdesignedaccordingtotheabovedesignprinciples,asshowninthefollowingdiagram.SpeedRegulatorIndicationII-Figure1:Generalstructureofcarcollision-preventionradarWeadoptthedesignofthetraditionalgun-controlradar,thatis,oneantennaissharedforbothtransmissionandreception,andamono-pulsesystemisemployed.Inthisway,thecostisloweredandsignalprocessingissimplified.Therangingaccuracyofthistypeofradarislessthan5meters.Theantennafortransmissionandreceptionissetatthefrontofthecartotransmitelectromagneticwavesforward.Anelectromagneticreflectionplateissetatthebackofthecarinfrontsoastoreflectthewavecomingfromthecarbehind.Thecarbehindreceivessignalfromthecarinfront,whichisamplified,detectedandcollated,inordertoworkoutthespacebetweenthetwocars.Thespacesignalissentbothsystem0-7803-h677-8/01/$10.000200IIEEE.872totheindicatorfordisplay,andtothecontroldevicewherethesignaliscomparedwiththethresholdsignalpresetforthespacebetweenthetwocars.Accordingtothedifferencebetweenhetoosignals,thecontroldeviceautomaticallycontrolthespeedregulatorofthecartokeepaconstantspacebetweenthetwocars.Anotheradvantageofthisplanisitslowcost.Becauseonlyarangingradarisneededandthedetectingrangeisfixed(120”),theactingdistanceneednotbelong(aboutIkm).Thepowerofthetraditionsourceneedntbehighandthereisalmostnoantennacontrolpart,therefore,thecostisgreatlylowered.CharacteristicsForm1.ComparisonoffunctionsbetweenradarsystemofdifferentbandMicrowaveOpticalMillimeterradarradarradarUnderpoorcircumstanceGoodITracking/accuracyIPoorIGood1MediumIPoorMediumSortingI11(33;1MediumIidentificationConcealmentMediumMediumAirsearchingGoodUnderfogordust1Good/Medium/Good/circumstance2.2Transmitter2.2.1FrequencySelectionThemajorfactorthataffectsfrequencyselectionistheradarfunctions,whatisrequiredhereoftheradarisgoodsearching,highrangingaccuracyadoptmillimeterwaver2,highrangingaccuracyadoptmillimeterwavebecause(1)Ithasshorterwavelength.Thesystemwillbecompactandwillpossesshighrangingaccuracy;(2)Itsbandwidthisverywide.Therearefour“windows”foratmospherictransmissionnear8.6mm,3.2mm,2.lmmand1.4mm,withinthemillimetertheband.Thebandwidthofeachwindowisverywide.Theyarerespectively16GHz,23GHz,26GHzand70GHz;(3)Atmosphericattenuationanddissipationofthetransmissionwindowsarequitelow.Theattenuationislowunderthecircumstanceofsuspendedparticlesanddustandsmokeandfogandairpollution.Becauseoftheirlowgroundscattering,thegroundclutterandmulti-channelinterferenceislow,TwoAmericans,WickerandWebbhavemadeacomparisonbetweenmicrowaveradarandmillimeterradarandopticalradar.Theirconditionisasshowninthefollowingform.2.2.2OscillationSourceRadartransmitterismainlycomposedofradiofrequencypowersourceandmodulatorandpowersource.Therearetwomethodofgeneratetheradiofrequencypower:thepoweroscillatorandmainvibrationamplifier.Fortheconvenienceofsignalprocessingandlightweighandsmallvolume,themainpoweramplifieradoptedinthissystemisusedasoscillationsource.Themainoscillatorthatmaybeappliedinthissystemarecrossed-fieldamplifierandklystronandtravelingwavetubeandtransistoramplifieretc.Whichareusuallyappliedinsuchaoccasionswherethestablelowpowerdevicesareneeded.Forexample,theycanbeusedastheterminalpoweramplifierincoherentmovementtargetindicationsystem,pulsecompressionradarandpulseDopplersystem.2.2.3TransmittineAntennaFollowingthedesignprincipleofonecertaintracingradar,theorientationantennaisadoptedtotrytocentralizeitsenergy,andcausethelightbeamintoanacicularbeam.ThematuretechnicalCastiglianoantennaistheidealone.Theselectionofanantennadependsonthesystematicrequirementsthemaximumnumberoftargetstobedetectedatanytime;thenumberoftargetstobetracked;thespeedandmaneuveroftargetsandpossiblescopeofanglesofazimuthandelevationoftargets.Thesescannersrangefromthesimplestandcheapestmechanicalscannerstocomplicatedandexpensiveelectronicscanners.Theformercanbeusedunderanotdemandingconditionwhilethelattercanbeusedunderahighlydemandingcondition.Theonesbetweenthetwoaremixedscannersandelectromechanicalscanners.Thesimplestscanningtypeisthefixedbeamsystem.Thistypeofsystem,suchaswakerangingradar,doesnotrequireantennabeamscanning.Weadoptthistypeofscanning.2.3SignalProcessingSystem73.1Receiver873Throughthereceptionandtransmissiontransformationswitch,thereflectedmagneticwavesignalentersthereceiverchannelandgetstheintermediatefrequencyafterfrequencymixinginthemixerandthentheintermediatefrequencysignalissentintotherectifiertodetectoroutthevideosignalafterbeingbipolarityamplification.Thesuperheterodynereceiverusedinthissystemworkssmoothlywithahighersensibilityandamodestcost.Inthissystem,weadopttheno-coolingmillimeterwaveheterodynereceiverinwhichthebeamleadGaAssemi-conductordevicesareadopted.Itisverysuitforthereceiverwhichfrequencyrangeisbetween30to100gigahertz.Atpresentthewave-guidecomponentfrequencyover100gigahertzanditstechnologyhavefoundawideapplication.So,manydifferenttransmittingvectorsandtechnologyalsohavefounditsapplicationwiththedevelopmentofmillimeterwaveintegratedcircuit.Manymultifunctioncomponentshavebeenadoptedonsuspension-bandedlineandmicro-bandedlineandfin-lineandnotchedlineandwave-guide.Theirfrequencyisbetween35and100gigahertz.Themillimeterwavereceivercanbemadeasthesameasthestructureofordinarymicrowavereceiver.Generalspeaking,themillimeterwavereceiverusethehigherintermediatefrequency,butthemillimeterwavereceiveronthelowfrequency(30gigaherz)isadoptedasthesameastechnologyofthemicrowavereceiver.Suchasintegratedcircuitreceiver,gasdischargetubereceptionandtransmissionswitch,receiverprotectiondevice,wavefilter,amplitudelimitedcirculator,isolatorandPINswitchandsoon5J.2.3.2.DiPitalProceaNow,theradarsignaldigitalprocessingisbecomingverypopular.Itbecomestherealityforustogeneratethedigitalsignalandtobefiltered,withthedevelopmentofanalog/digitalconverterandintegratedcircuittechnologyandtheappearanceofthefastFourierCalculation.Thedigitalprocessinghasshownitsadvantagesinitsstabilityandrepeatabilityandflexibility.Intheory,norestrictionisputonwavepatternandwavefilterfunction.Withtheappearanceofthedigitalcomputer,wecaneffectivelydealwiththecontinuousradarssignalaccordingtothesampledtheorem.Thefrequencyspectrumiscalculatedbasedonthesampled-signalgroup.2.3.3,DigtalPulseCompressionThedigitalsystemprovideuswithalargecapabilitytodoprocessingineffectivetime.Thehandleddatacanbestoredinthememoryafteranalogytodigitalconversionprocessingandcontinuetocarryouttheprocessinginno-realtimerate(fasterorslower).Whythepulsecompressiontechnologyisadopted?Itismainlybecauseofitsgreatimprovedtestabilityandlessinterference.Itwillbecomeseriousproblemforradartointerferenceoneanotherinaverydenseactiveelectromagneticenvironment.Sothepulsecompressionradarcanbedesignedtoreduceitinterferencebyusingdifferentmodulationcodesanddifferentmatchedwavefilter.2.3.4DieitwhedFiltaigTheidealmethodofdigitalmatchedfilteringistoadopttheweightedmethodofcalculatingtappeddelayline.ButitisreplacedrecentlybythefastFouriortransformforitsperipheralconvolution.ThewidedynamicstaterangeandthehighspeedmatchedfilterprocessingdeviceshavecomeintobeingwiththedevelopmentoftheassemblylinefasterFouriertransformtechnologyandthedevelopmentofthefloatingpointequipment.AnewmatchedfilterprocessingmethodcalledsteptransformusetheSubapertureprocessingandreducethefasterFouriertransformscale,itshardwareisnotmorethanthehalfofthefasterFourierconvolutionprocessing.2.4IndicatorInthissystem,theradarindicatorisjustkindofaccessoryequipment.Whichprovidedriversthedistancebetweentwocars,anddisplaythespeed.Weadoptthemorepopularplasmaindicator,whichcancompletetheclassicalprogramwiththemicroprocessorandprecompiledprogram.Thisplasmaindicatorcangeneratethedotlineandspecialsymbols,suchassmallcirclesandblocks.Theplasmaindicatorhaslotsofadvantages:tohavehigherstabilityandlongerlifetimethanthecathedrastube,tohavebrighterbrightnessthansomecathode-raytube.Takethecostintoconsiderationanotherdesigntodisplaysortsofdatasistoadoptthelightemittingdiodearray.2.5ControllingandReadjustmentSpeedThecarloaderradarmeasuresoutthedistancebetweentwocarsandconvertsitintodigitalsignalandcomparewithhesafedistance(150m).Ifmeasureddistanceisshorterthanthesafedistance.Theradarwilloutputapositiveerrorsignaltocontroltheregulatingsystemtoreducecarsspeeduntilthetwocarsisatthesetupdistanceotherwise.Theradarwilloutputanegativeerrorsignaltocontrolandadjustthecarsmovingspeed.Thecarss