电子类专业毕业外文翻译文献

HindawiPublishingCorporationJournalofElectricalandComputerEngineeringVolume2013,ArticleID146986,[e-mail]6June2013;Accepted6July2013AcademicEditor:SandraCostanzoCopyright©2013G.GalatiandG.Pavan.ThisisanopenaccessarticledistributedundertheCreativeCommonsAttributionLicense,whichpermitsunrestricteduse,distribution,andreproductioninanymedium,providedtheoriginalworkisproperlycited.Insomeapplications,suchasautomotiveandmarine/navigation,hundredsofradarsmayoperateinasmallenvironment(e.g.,aroadcomplexorastrait)andinanallocatedfrequencybandwithlimitedwidth.Therefore,acompatibilityproblembetweendifferentradarsarisesthatisnoteasilysolvedbytime,frequency,space,orpolarizationdiversity.Theadventoffastdigitalsignalprocessingandsignalgenerationtechniquesmakesitpossibletousewaveformdiversitytosolvethisproblemthatwillbeexacerbatedinthenextfuture.IdealwaveformsforthediversityaresuppliedbyNoiseRadarTechnology(NRT),whoseapplicationispromisinginsomemilitaryapplicationsaswellasinthecivilianapplicationsconsideredinthispaper.Inadditiontobeingorthogonalasmuchaspossible,therandomsignalstobetransmittedhavetosatisfyrequirementsconcerningsidelobelevelandcrestfactor,callingfornovel,originaldesignandgenerationprocesses.1.IntroductionInspiteofitsmilitaryorigin,datedbacktothe1930s,radartechnologyisbeingmoreandmoreappliedintheciviliandomainforthesafetyofair,sea,andlandtraffic.Inseaandroadapplications,thistechnologyisenteringthemassmarketwithasignificantyearlyreductionofcosts,mainlyduetothelargerandlargerintegrationofthehardwareandtothescaleeconomy.Forexampleintheautomotiveradarthefactorycosthasfallenbyoneorderofmagnitude(fromhundredstotensofdollars)inafewyears.Asimilarsituationistobeexpectedinthefieldofmarineradar[1,2],presentinmostvessels,asthey(X-bandradar)aremandatoryforallpassengervesselsandforallvesselsabove500tonsGT(GrossTonnage),withadouble-bandrequirement(X-bandradar+S-bandradar)above3000tonsGT.Theallocatedbandsare9.3to9.5GHz(X)and2.9to3.1GHz.Mostmarineradarsusethesimpleandcheapmagnetrontransmitter,a1940stechnology,generatingshortpulses(from50–80nsintheshort-rangemodeto800–1000nsinthelong-rangemode,upto96NM)andpeakpowerfromaveryfewkWto12.5–25kW(and50kWincoastalapplicationsforVesselTrafficSystems).Thelargenumberofmarineradarsinagivenarea,simultaneouslypresentabovethehorizon,makesthemutualinterferenceaverylikelyevent.Forageneraloverviewofpotentialsolutiontothisproblem,see[3,4].Inmarineradarsthemostusedsolutionisbasedontheirrelativelyshortpulsesthatcanbesuppressed(videoblankingorthresholding)becausetheyarereceivedasynchronouslywithrespecttothetransmissionfromthevictim(theown)radar.Suchasuppressioncausestolerabledetectionlossesforsmalltargetsandnegligiblelossesforlargetargets.Asinmanyotherradarapplications,forexample,inAirTrafficControl(ATC),solid-statetransmittertechnologyisattractiveformarineradars.Itpermits(i)theimplementationofhighlystable,coherentRx-TxchainscompatiblewithDopplerprocessing,(ii)thetransmissionofsophisticatedwaveforms[5],(iii)abetteravailability,and(iv)theabsenceofhighvoltages.UnlikeATCradarsthathavebeenusingsolidstatetransmittersforovertwodecades,solid-statemarineradarsareappearingonthemarketjustnow,mostofthem,intheS-band.Whilemaintainingapproximatelythesameaveragetransmittedpowerasmagnetrontransmitters,thesenew(orexperimental)solid-statemarineradarshavethreeordersofmagnitudelargerdutycycle,thatis,intherangeof10%–12%.Theselongpulses(about10or20microseconds,insomecasesupto100microseconds)arenotcompatiblewiththecurrentinterferencesuppressiontechniques.In2JournalofElectricalandComputerEngineeringtheremainingpartofthispaperanewtechniqueisproposedtosolvethisinterferenceproblem,whosegeneralframeworkissynopsizedintheappendix.2.SignalRequirementsandAdvantagesofNoiseRadarTechnology(NRT)Mitigationtechniquesforinterferencesfromsimilarradarscanbebasedondiversityin(i)frequency,(ii)polarization,(iii)direction(antennapatternadaptation),and(iv)wave-form.Inthemarineradarcontext,asconsideredhere,thelimitedallocatedbandwidth(only200MHzinX-bandandthesameintheS-band)andtheuseofstandardantennaewithfixedpolarizationpreventtheuseof(i),(ii),and(iii).There-foreapossiblesolutionhastobebasedonwaveformdiversity,thatis,thetransmission(bythevariousradarsinpotentialinterferenceconditions)ofpairwiseorthogonalwaveforms,suchthatthematchedfilteroutputismainlyduetothe“own”waveform,withanoisefloorduetothe“otherradars”waveforms.Thelargenumberofradarsinbusymaritimeenvironmentssuchasstraitsandseaareasaroundharbors,makesitnecessarytoexploitalargenumberoforthogonalwaveforms,whichcanonlybeobtainedbypolyphasecodes[3]or,asproposedhere,bysuitableprocessingofsamplesofrandomprocesses,leadingtoNoiseRadarTechnology.Themainrequirementsforapairofsignalswithcomplexenvelope𝑠�