RFID技術外文翻譯文獻

RFID技術外文翻譯文獻RFID技術外文翻譯文獻(文檔含中英文對照即英文原文和中文翻譯)原文：CurrentRFIDTechnologyThissectiondescribesoutofwhichpartsRFIDtagsconsistof,howtheyworkinprinciple,andwhattypesoftagsdoexist.Itfocusesonhowtagsarepoweredandwhatfrequencyrangesisused.Thesectionconcludesbycoveringafewimportantstandards.RFIDtransponders(tags)consistingeneralof:Microchip,Antenna,Case,Battery(foractivetagsonly)ThesizeofthechipdependsmostlyontheAntenna.Itssizeandformisdependentonthefrequencythetagisusing.Thesizeofatagalsodependsonitsareaofuse.Itcanrangefromlessthanamillimeterforimplantstothesizeofabookincontainerlogistic.Inadditiontothemicrochip,sometagsalsohaverewritablememoryattachedwherethetagcanstoreupdatesbetweenreadingcyclesornewdatalikeserialnumbers.ARFIDtagisshowninfigure1.Theantennaisclearlyvisible.Assaidbeforetheantennahasthelargestimpactofthesizeofthetag.Themicrochipisvisibleinthecenterofthetag,andsincethisisapassivetagitdoesnothaveaninternalpowersourceInprincipleanRFIDtagworksasfollows:thereadingunitgeneratesanelectro-magneticfieldwhichinducesacurrentintothetag'santenna.Thecurrentisusedtopowerthechip.Inpassivetagsthecurrentalsochargesacondenserwhichassuresuninterruptedpowerforthechip.Inactivetagsabatteryreplacesthecondenser.Thedifferencebetweenactiveandpassivetagsisexplainedshortly.Onceactivatedthetagreceivescommandsfromthereadingunitandrepliesbysendingitsserialnumberortherequestedinformation.Ingeneralthetagdoesnothaveenoughenergytocreateitsownelectro-magneticfield,insteaditusesbackscatteringtomodulate(reflect/absorb)thefieldsentbythereadingunit.Becausemostfluidsabsorbelectro-magneticfieldsandmostmetalreflectthosefieldsthereadingoftagsinpresenceofthosematerialsiscomplicated.Duringareadingcycle,thereaderhastocontinuouslypowerthetag.Thecreatedfieldiscalledcontinuouswave,andbecausethestrengthofthefielddecreaseswiththesquareofthedistancethereadershavetousearatherlargepower.Thatfieldoverpowersanyresponseatagcouldgive,sothereforetagsreplyonside-channelswhicharelocateddirectlybelowandabovethefrequencyofthecontinuouswave.1.EnergySourcesWedistinguish3typesofRFIDtagsinrelationtopowerorenergy:Passive,Semi-passive,ActivePassivetagsdonothaveaninternalpowersource,andtheythereforerelyonthepowerinducedbythereader.Thismeansthatthereaderhastokeepupitsfielduntilthetransactioniscompleted.Becauseofthelackofabattery,thesetagsarethesmallestandcheapesttagsavailable;howeveritalsorestrictsitsreadingrangetoarangebetween2mmandafewmeters.Asanaddedbenefitthosetagsarealsosuitabletobeproducedbyprinting.Furthermoretheirlifespanisunlimitedsincetheydonotdependonaninternalpowersource.Thesecondtypeoftagsissemi-passivetags.Thosetagshaveaninternalpowersourcethatkeepsthemicrochippoweredatalltimes.Therearemanyadvantages:Becausethechipisalwayspowereditcanrespondfastertorequests,thereforeincreasingthenumberoftagsthatcanbequeriedpersecondwhichisimportanttosomeapplications.Furthermore,sincetheantennaisnotrequiredforcollectingpoweritcanbeoptimizedforbackscatteringandthereforeincreasingthereadingrange.Andlastbutnotleast,sincethetagdoesnotuseanyenergyfromthefieldthebackscatteredsignalisstronger,increasingtherangeevenfurther.Becauseofthelasttworeasons,asemi-activetaghasusuallyarangelargerthanapassivetag.Thethirdtypeoftagsisactivetags.Likesemi-activetagstheycontainaninternalpowersourcebuttheyusetheenergysuppliedforboth,topowerthemicrochipandtogenerateasignalontheantenna.Activetagsthatsendsignalswithoutbeingqueriedarecalledbeacons.Anactivetag'srangecanbetensofmeters,makingitidealforlocatingobjectsorservingaslandmarkpoints.Thelifetimeisupto5years.2.FrequencyBandsRFIDtagsfallintothreeregionsinrespecttofrequency:Lowfrequency(LF,30-500kHz),Highfrequency(HF.10-15MHz),Ultrahighfrequency(UHF,850-950MHz,2.4-2.5GHz,5.8GHz)Lowfrequencytagsarecheaperthananyofthehigherfrequencytags.Theyarefastenoughformostapplications,howeverforlargeramountsofdatathetimeataghastostayinareadersrangewillincrease.Anotheradvantageisthatlowfrequencytagsareleastaffectedbythepresenceoffluidsormetal.Thedisadvantageofsuchtagsistheirshortreadingrange.Themostcommonfrequenciesusedforlowfrequencytagsare125-134.2kHzand140-148.5kHz.HighfrequencytagshavehighertransmissionratesandrangesbutalsocostmorethanLFtags.Smarttagsarethemostcommonmemberofthisgroupandtheyworkat13.56MHz.UHFtagshavethehighestrangeofalltags.Itrangesfrom3-6metersforpassivetagsand30+metersforactivetags.Inadditionthetransmissionrateisalsoveryhigh,whichallowstoreadasingletaginaveryshorttime.Thisfeatureisimportantwheretaggedentitiesaremovingwithahighspeedandremainonlyforashorttimeinareadersrange.UHFtagsarealsomoreexpensivethananyothertagandareseverelyaffectedbyfluidsandmetal.ThosepropertiesmakeUHFmostlyusefulinautomatedtollcollectionsystems.Typicalfrequenciesare868MHz(Europe),915MHz(USA),950MHz(Japan),and2.45GHz.FrequenciesforLFandHFtagsarelicenseexemptandcanbeusedworldwide;howeverfrequenciesforUHFtagsdifferfromcountrytocountryandrequireapermit.3.StandardsThewiderangeofpossibleapplicationsrequiresmanydifferenttypesoftags,oftenwithconflictinggoals(e.g.lowcostvs.security).Thatisreflectedinthenumberofstandards.AshortlistofRFIDstandardsfollows:ISO11784,ISO11785,ISO14223,ISO10536,ISO14443,ISO15693,ISO18000.Notethatthislistisnotexhaustive.SincetheRFIDtechnologyisnotdirectlyInternetrelateditisnotsurprisingthattherearenoRFCsavailable.TherecenthypearoundRFIDtechnologyhasresultedinanexplosioninpatents.Currentlythereareover1800RFIDrelatedpatentsissued(from1976to2001)andover5700patentsdescribingRFIDsystemsorapplicationsarebacklogged.4.RFIDSystemsARFIDreaderandafewtagsareingeneraloflittleuse.Theretrievalofaserialnumberdoesnotprovidemuchinformationtotheusernordoesithelptokeeptrackofitemsinaproductionchain.TherealpowerofRFIDcomesincombinationwithabackendthatstoresadditionalinformationsuchasdescriptionsforproductsandwhereandwhenacertaintagwasscanned.IngeneralaRFIDsystemhasastructureasdepictedinfigure2.RFIDreadersscantags,andthenforwardtheinformationtothebackend.Thebackendingeneralconsistsofadatabaseandawelldefinedapplicationinterface.Whenthebackendreceivesnewinformation,itaddsittothedatabaseandifneededperformssomecomputationonrelatedfields.Theapplicationretrievesdatafromthebackend.Inmanycases,theapplicationiscollocatedwiththereaderitself.Anexampleisthecheckoutpointinasupermarket(NotethatthegivenexampleusesbarcodesinsteadofRFIDtagssincetheyaremorecommon;however,thesystemwouldbehaveinexactlythesamewayiftagswereused).Whenthereaderscansthebarcode,theapplicationusesthederivedidentifiertolookupthecurrentprice.Inaddition,thebackendalsoprovidesdiscountinformationforqualifyingproducts.Thebackendalsodecreasesthenumberofavailableproductsofthatkindandnotifiesthemanageriftheamountfallsbelowacertainthreshold.ThissectiondescribeshowRFIDtagsworkingeneral,whattypesoftagsexistandhowtheydiffer.ThethreefrequencyrangesthatRFIDtagstypicallyuseareLF,HF,andUHF.Alsothedifferencebetweenpassive,semi-passive,andactivetagswasexplainedandtheiradvantagesanddisadvantageswerecompared.Thesectionconcludedbylookingatdifferentstandardsandshowedthegreatinterestoftheindustrybycountingthenumberofissuedandbackloggedpatents[USPatentOffice].翻譯：當前的RFID技術該節(jié)描述的是RFID標簽由哪些部分組成、工作原理和確實存在的標簽類型，關注標簽的供電方式和使用頻率范圍。這部分也總結了一些重要的標準。RFID應答器的一般組成:微芯片、天線、線圈和電池(僅適用于有源標簽)。芯片的大小主要取決于天線，它的規(guī)模和形式的取決于標簽的使用頻率，也取決于它的使用面積。它的大小范圍可從不到一毫米的植入體大到一本關于集裝箱物流的書。除了微型芯片,有些標簽也附有可重寫內存，這樣標簽就可儲存更新閱讀周期之間的或新的數據，如序號。如圖1所示的RFID標簽。天線清晰可見。正如前面所說的，天線對標簽大小的影響最大。在標簽的中心可看見的是芯片。因為這是一個無源標簽所以無內部的能源。RFID標簽工作原理是如下:閱讀單元產生電磁場引導電流流進標簽的天線。該電流用以給芯片提供能源。在無源標簽中該電流還為冷凝器充電，以保證芯片的不間斷供電。在有源標簽中電池取代了冷凝器。有源和無源標簽的區(qū)別是短期內的信息闡釋。一旦被激活的標簽收到閱讀的命令它就可以發(fā)送序列號或所要求的信息?？偟膩碚f,標簽沒有足夠的能量來創(chuàng)造自己的電磁場,相反它可以采用反向散射調制（反映/吸收）來產生由閱讀單元發(fā)射的電磁場。由于大多數流體吸收電磁場和大多數金屬反射這些場，故可使用的標簽閱讀材料是復雜的在一次循環(huán)解讀中,閱讀器不得不持續(xù)給標簽供電。它所建立的場將產生連續(xù)波,因為磁場的強度隨距離的平方而減少，故閱讀器必須有一個相當大的能源。該場迅速響應標簽給的任何指示,因此標簽位于正下方的側渠道可以響應上述連續(xù)波的頻率。1.能源我們辨別三種不同的RFID電子標簽的能量或能源：被動、半被動和主動。被動式標簽沒有內部電源,因此它們的能量來源于閱讀器。這意味著閱讀器必須保持磁場直到轉換完成。由于沒有電池,故這些都是可用的最小和最便宜的標簽。但它的閱讀范圍可從2毫米和幾米。這些標簽的另一個好處是適用于印刷生產。此外，因為它不依賴于內部電源，所以它們的壽命是無限的。第二種類型是半被動式標簽。這些標簽都有內部電源可在任何時候都給微芯片供電。它有許多優(yōu)點:由于芯片在持續(xù)帶電的情況下反應迅速,因此可以增加每秒查詢的標簽數量，這是非常重要的應用。此外,由于天線不需要收集能量，故可以優(yōu)化用以反向散射和回歸來增加閱讀范圍。最后但并非不重要，因為標簽不使用任何磁場能量所以反向散射的信號越強，閱讀范圍更廣。由于最后兩個原因，半被動標簽通常比被動標簽應用范圍更廣泛。第三種類型是主動式標簽。類似于半主動標簽，它的內部也有能源但它的能源用于兩個方面：給微芯片供電和使天線產生信號。主動式標簽發(fā)送信號而不被質疑,這被稱為信標。主動標簽可查詢的范圍是幾十公尺,從而使其適宜于定位對象或理想標志點。壽命長達5年的。2.頻帶RFID電子標簽按照頻率分為三個部分:低頻(LF,30-500千赫)、高頻(HF、10-15兆赫)、超高頻(UHF),（850-950兆赫,2.4-2.5兆赫,5.8兆赫)。低頻標簽比任何高頻率的標簽都便宜。對于大多數應用程序來講,它們的響應速度很快。但是，留在閱讀器的大量標記數據的時間范圍將增加。另一個優(yōu)點是低頻標簽由于流體的存在或金屬的存在而受到的影響最小。這類標簽的缺點是它們識別范圍很短。最常見的低頻標簽頻率是125-134.2千赫和140-148.5千赫