RFID技术外文文献翻译

word文档可自由复制编辑word文档可自由复制编辑word文档可自由复制编辑外文文献CurrentRFIDTechnologyThissectiondescribesoutofwhichpartsRFIDtagsconsistof,howtheyworkinprinciple,andwhattypesoftagsdoexist.Itfocusesonhowtagsarepoweredandwhatfrequencyrangesisused.Thesectionconcludesbycoveringafewimportantstandards.RFIDtransponders(tags)consistingeneralof:Microchip,Antenna,Case,Battery(foractivetagsonly)ThesizeofthechipdependsmostlyontheAntenna.Itssizeandformisdependentonthefrequencythetagisusing.Thesizeofatagalsodependsonitsaofuse.Itcanrangefromlessthanamillimeterforimplantstothesizeofaboocontainerlogistic.Inadditiontothemicrochip,sometagsalsohaverewritablememoryattachedwherethetagcanstoreupdatesbetweenreadingcyclesornewdatalikeserialnumbers.ARFIDtagisshowninfigure1.Theantennaisclearlyvisible.Assaidbeforetantennahasthelargestimpactofthesizeofthetag.Themicrochipisvisibleincenterofthetag,andsinceisapassivetagitdoesnothaveaninternalthi powersourceInprincipleanRFIDtagworksasfollows:thereadingunitgeneratesanelectro-magneticfieldwhichinducesacurrentintothetag'santenna.Thecurrentusedtopowerthechip.Inpassivetagsthecurrentalsochargesacondenserwhichassuresuninterruptedpowerforthechip.Inactivetagsabatteryreplacesthecondenser.Thedifferencebetweenactiveandpassivetagsisexplainedshortly.Onceactivatedthetagreceivescommandsfromthereadingunitandrepliesbysendingitserialnumberortherequestedinformation.Ingeneralthetagdoesnothaveenoughenergytocreateitsownelectro-magneticfield,insteaditusesbackscatteringtomodulate(reflect/absorb)thefieldsentbythereadingunit.Becausemostfluidsabsorbelectro-magneticfieldsandmostmetalreflectthosefieldsthereadingoftinpresenceofthosematerialsiscomplicated.Duringareadingcycle,thereaderhastocontinuouslypowerthetag.Thecreatedfieldiscalledcontinuouswave,andbecausethestrengthofthefielddecreaseswithesquareofthedistancethereadershavetousearatherlargepower.Thatfieldoverpowersanyresponseatagcouldgive,sothereforetagsreplyonside-channelswhicharelocateddirectlybelowandabovethefrequencyofthecontinuouswave.1.EnergySourcesWedistinguish3typesofRFIDtagsinrelationtopowerorenergy:Passive,Semi-passive,ActivePassivetagsdonothaveaninternalpowersource,andtheythereforerelonthepowerinducedbythereader.Thismeansthatthereaderhastokeepupitsfielduntiltransactioniscompleted.Becauseofthelackofabattery,thesetagsarethesmallestandcheatagsavailable;howeveritalsorestrictsitsreadingrangetoarangebetween2mmandafewmeters.Asanaddedbenefitthosetagsarealsosuitabletobeproducedbyprinting.Furthermotheirlifespanisunlimitedsincetheydonotdependonaninternalpowersource.Thesecondtypeoftagsissemi-passivetags.Thosetagshaveaninternalpowersourcethatkeepsthemicrochippoweredatalltimes.Therearemanyadvantages:Becausethechipisalwayspowereditcanrespondfastertorequests,thereforeincreasingthenumberoftagsthatcanbequeriedpersecondwhichisimportanttosomeapplications.Furthermore,sincetheantennaisnotrequiredforcollectingpowitcanbeoptimizedforbackscatteringandthereforeincreasingthereadingrange.Alastbutnotleast,sincethetagdoesnotuseanyenergyfromthefieldthebackscatteredsignalisstronger,increasingtherangeevenfurther.Becauseofthelastreasons,asemi-activetaghasusuallyarangelargerthanapassivetag.Thethirdtypeoftagsisactivetags.Likesemi-activetagstheycontainanintepowersourcebuttheyusetheenergysuppliedforboth,topowerthemicrochipandtogenerateasignalontheantenna.Activetagsthatsendsignalswithoutbeingqueriedarecalledbeacons.Anactivetag'srangecanbetensofmeters,makingitidforlocatingobjectsorservingaslandmarkpoints.Thelifetimeisupto5years.2.FrequencyBandsRFIDtagsfallintothreeregionsinrespecttofrequency:Lowfrequency(LF,30-500kHz),Highfrequency(HF.10-15MHz),Ultrahighfrequency(UHF,850-950MHz,2.4-2.5GHz,5.8GHz)Lowfrequencytagsarecheaperthananyofthehigherfrequencytags.Theyarefastenoughformostapplications,howeverforlargeramountsofdatathetimeataghaststayinareadersrangewillincrease.Anotheradvantageisthatlowfrequencytagsleastaffectedbythepresenceoffluidsormetal.Thedisadvantageofsuchtagsistshortreadingrange.Themostcommonfrequenciesusedforlowfrequencytagsare125-134.2kHzand140-148.5kHz.HighfrequencytagshavehighertransmissionratesandrangesbutalsocostmorethanLFtags.Smarttagsarethemostcommonmemberofthisgroupandtheyworkat13.56MHz.UHFtagshavethehighestrangeofalltags.Itrangesfrom3-6metersforpassivetagsand30+metersforactivetags.Inadditionthetransmissionrateisveryhigh,whichallowstoreadasingletaginaveryshorttime.Thisfeatureisimportantwheretaggedentitiesaremovingwithahighspeedandremainonlyforashorttimeinareadersrange.UHFtagsarealsomoreexpensivethananyothertagandareseverelyaffectedbyfluidsandmetal.ThosepropertiesmakeUHFmostlyusefulinautomatedtollcollectionsystems.Typicalfrequenciesare868MHz(Europe),915MHz(USA),950MHz(Japan),and2.45GHz.FrequenciesforLFandHFtagsarelicenseexemptandcanbeusedworldwide;howeverfrequenciesforUHFtagsdifferfromcountrytocountryandrequireapermit.3.StandardsThewiderangeofpossibleapplicationsrequiresmanydifferenttypesoftags,oftenwithconflictinggoals(e.g.lowcostvs.security).Thatisreflectedintheofstandards.AshortlistofRFIDstandardsfollows:ISO11784,ISO11785,ISO14223,ISO10536,ISO14443,ISO15693,ISO18000.Notethatthislistisnotexhaustive.SincetheRFIDtechnologyisnotdirectlyInternetrelateditisnotsurprisingthatarenoRFCsavailable.TherecenthypearoundRFIDtechnologyhasresultedinanexplosioninpatents.Currentlythereareover1800RFIDrelatedpatentsissued(fro1976to2001)andover5700patentsdescribingRFIDsystemsorapplicationsarebacklogged.4.RFIDSystemsARFIDreaderandafewtagsareingeneraloflittleuse.Theretrievalofasenumberdoesnotprovidemuchinformationtotheusernordoesithelptokeeptrackofitemsinaproductionchain.TherealpowerofRFIDcomesincombinationwithabackendthatstoresadditionalinformationsuchasdescriptionsforproductsandwhereandwhenacertaintagwasscanned.IngeneralaRFIDsystemhasastructureasdepictedinfigure2.RFIDreadersscantags,andthenforwardtheinformationtthebackend.Thebackendingeneralconsistsofadatabaseandawelldefinedapplicationinterface.Whenthebackendreceivesnewinformation,itaddsittothedatabaseandifneededperformssomecomputationonrelatedfields.Theapplicationretrievesdatafromthebackend.Inmanycases,theapplicationiscollocatedwithtreaderitself.Anexampleisthecheckoutpointinasupermarket(NotethatthegivexampleusesbarcodesinsteadofRFIDtagssincetheyaremorecommon;however,thesystemwouldbehaveinexactlythesamewayiftagswereused).Whenthereaderscansthebarcode,theapplicationusesthederivedidentifiertolookupthecurrentprice.Inaddition,thebackendalsoprovidesdiscountinformationforqualifyingproducts.Thebackendalsodecreasesthenumberofavailableproductsofthatkindandnotifiesthemanageriftheamountfallsbelowacertainthreshold.ThissectiondescribeshowRFIDtagsworkingeneral,whattypesoftagsexistandhowtheydiffer.ThethreefrequencyrangesthatRFIDtagstypicallyuseareLFHF,andUHF.Alsothedifferencebetweenpassive,semi-passive,andactivetagswasexplainedandtheiradvantagesanddisadvantageswerecompared.Thesectionconcludedbylookingatdifferentstandardsandshowedthegreatinterestoftheindustrybycountingthenumberofissuedandbackloggedpatents[USPatentOffice].翻译：当前的RFID技术该节描述的是RFID标签由哪些部分组成、工作原理和确实存在的标签类型，关注标签的供电方式和使用频率范围。这部分也总结了一些重要的标准。RFID应答器的一般组成:微芯片、天线、线圈和电池(仅适用于有源标签)。芯片的大小主要取决于天线，它的规模和形式的取决于标签的使用频率，也取决于它的使用面积。它的大小范围可从不到一毫米的植入体大到一本关于集装箱物流的书。除了微型芯片,有些标签也附有可重写内存，这样标签就可储存更新阅读周期之间的或新的数据，如序号。如图1所示的RFID标签。天线清晰可见。正如前面所说的，天线对标签大小的影响最大。在标签的中心可看见的是芯片。因为这是一个无源标签所以无内部的能源。RFID标签工作原理是如下:阅读单元产生电磁场引导电流流进标签的天线。该电流用以给芯片提供能源。在无源标签中该电流还为冷凝器充电，以保证芯片的不间断供电。在有源标签中电池取代了冷凝器。有源和无源标签的区别是短期内的信息阐释。一旦被激活的标签收到阅读的命令它就可以发送序列号或所要求的信息。总的来说,标签没有足够的能量来创造自己的电磁场,相反它可以采用反向散射调制（反映/吸收）来产生由阅读单元发射的电磁场。由于大多数流体吸收电磁场和大多数金属反射这些场，故可使用的标签阅读材料是复杂的在一次循环解读中,阅读器不得不持续给标签供电。它所建立的场将产生连续波,因为磁场的强度随距离的平方而减少，故阅读器必须有一个相当大的能源。该场迅速响应标签给的任何指示,因此标签位于正下方的侧渠道可以响应上述连续波的频率。1.能源我们辨别三种不同的RFID电子标签的能量或能源：被动、半被动和主动。被动式标签没有内部电源,因此它们的能量来源于阅读器。这意味着阅读器必须保持磁场直到转换完成。由于没有电池,故这些都是可用的最小和最便宜的标签。但它的阅读范围可从2毫米和几米。这些标签的另一个好处是适用于印刷生产。此外，因为它不依赖于内部电源，所以它们的寿命是无限的。第二种类型是半被动式标签。这些标签都有内部电源可在任何时候都给微芯片供电。它有许多优点:由于芯片在持续带电的情况下反应迅速,因此可以增加每秒查询的标签数量，这是非常重要的应用。此外,由于天线不需要收集能量，故可以优化用以反向散射和回归来增加阅读范围。最后但并非不重要，因为标签不使用任何磁场能量所以反向散射的信号越强，阅读范围更广。由于最后两个原因，半被动标签通常比被动标签应用范围更广泛。第三种类型是主动式标签。类似于半主动标签，它的内部也有能源但它的能源用于两个方面：给微芯片供电和使天线产生信号。主动式标签发送信号而不被质疑,这被称为信标。主动标签可查询的范围是几十公尺,从而使其适宜于定位对象或理想标志点。寿命长达5年的。2.频带RFID电子标签按照频率分为三个部分:低频(LF,30-500千赫)、高频(HF、10-15兆赫)、超高频(UHF),（850-950兆赫,2.4-2.5兆赫,5.8兆赫)。低频标签比任何高频率的标签都便宜。对于大多数应用程序来讲,它们的响应速度很快。但是，留在阅读器的大量标记数据的时间范围将增加。另一个优点是低频标签由于流体的存在或金属的存在而受到的影响最小。这类标签的缺点是它们识别范围很短。最常见的低频标签频率是125-134.2千赫和140-148.5千赫。高频标签有更高的传输速率和更广的范围，成