射頻識別技術是一種非接觸的自動識別技術。它是由電子標簽（Tag/Transponder）、讀寫器（Reader/ Interrogator）及中間件（Middle-Ware）bufenzuchengdeyizhongduanjuliwuxiantongxinxitong。shepinshibiezhongdebiaoqianshishepinshibiebiaoqianxinpianhebiaoqiantianxiandejieheti。biaoqiangenjuqigongzuomoshibutongerfenweizhudongbiaoqianhebeidongbiaoqian。zhudongbiaoqianzishenxiedaidianchiweiqitigongduxieqitongxinsuoxudenengliang：被bei動dong標biao簽qian則ze采cai用yong感gan應ying耦ou合he或huo反fan向xiang散san射she工gong作zuo模mo式shi，即ji通tong過guo標biao簽qian天tian線xian從cong讀du寫xie器qi中zhong發fa出chu的de電dian磁ci場chang或huo者zhe電dian磁ci波bo獲huo得de能neng量liang激ji活huo芯xin片pian
，並bing調tiao節jie射she頻pin識shi別bie標biao簽qian芯xin片pian與yu標biao簽qian天tian線xian的de匹pi配pei程cheng度du，將jiang儲chu存cun在zai標biao簽qian芯xin片pian中zhong的de信xin息xi反fan饋kui給gei讀du寫xie器qi。因yin此ci。射she頻pin識shi別bie標biao簽qian天tian線xian的de阻zu抗kang必bi須xu與yu標biao簽qian芯xin片pian的de輸shu入ru阻zu抗kang共gong軛e匹pi配pei
，以yi使shi得de標biao簽qian芯xin片pian能neng夠gou最zui大da限xian度du地di獲huo得de射she頻pin識shi別bie讀du寫xie器qi所suo發fa出chu的de電dian磁ci能neng量liang。此ci外wai

，標biao簽qian天tian線xian設she計ji時shi還hai必bi須xu考kao慮lv電dian子zi標biao簽qian所suo應ying用yong的de場chang合he，如ru應ying用yong在zai金jin屬shu物wu體ti表biao麵mian的de標biao簽qian天tian線xian和he應ying用yong在zai普pu通tong物wu體ti表biao麵mian的de標biao簽qian天tian線xian在zai天tian線xian的de結jie構gou和he選xuan材cai上shang存cun有you很hen大da的de差cha別bie。適shi合he於yu多duo種zhong芯xin片pian、低成本、多用途的標簽天線是射頻識別在我國得到廣泛普及的關鍵技術之一。


射頻識別係統與天線分類

對於采用被動式標簽的射頻識別係統而言，根據工作頻段的不同具有兩種工作模式。一種是感應耦合（Induc.tiveCoupling）工作模式，這種模式也稱為近場工作模式，主要適用於低頻和高頻RFID係統：另一種則是反向散射（Backscattering）工作模式
，這種模式也稱為遠場工作模式
，主要適用於超高頻和微波RFID係統。

感(gan)應(ying)耦(ou)合(he)模(mo)式(shi)主(zhu)要(yao)是(shi)指(zhi)讀(du)寫(xie)器(qi)天(tian)線(xian)和(he)標(biao)簽(qian)天(tian)線(xian)都(dou)采(cai)用(yong)線(xian)圈(quan)形(xing)式(shi)。當(dang)讀(du)寫(xie)器(qi)在(zai)閱(yue)讀(du)標(biao)簽(qian)時(shi)，發(fa)出(chu)未(wei)經(jing)調(tiao)製(zhi)的(de)信(xin)號(hao)。處(chu)於(yu)讀(du)寫(xie)器(qi)天(tian)線(xian)近(jin)場(chang)的(de)電(dian)子(zi)標(biao)簽(qian)天(tian)線(xian)接(jie)收(shou)到(dao)該(gai)信(xin)號(hao)並(bing)激(ji)活(huo)標(biao)簽(qian)芯(xin)片(pian)之(zhi)後(hou)
，由(you)標(biao)簽(qian)芯(xin)片(pian)根(gen)據(ju)內(nei)部(bu)存(cun)儲(chu)的(de)全(quan)球(qiu)唯(wei)一(yi)的(de)識(shi)別(bie)號(hao)（ID）kongzhibiaoqiantianxianzhongdedianliudaxiao。zhegedianliudedaxiaojinyibuzengqianghuozhejianxiaoyueduqitianxianfachudecichang。zheshi，duxieqidejinchangfenliangzhanxianchubeitiaozhidetexing
，duxieqineibudianlujianbei0到這個由於標簽而產生的調製量並解調並得到標簽信息。

在zai反fan向xiang散san射she工gong作zuo模mo式shi中zhong，讀du寫xie器qi和he電dian子zi標biao簽qian之zhi間jian采cai用yong電dian磁ci波bo來lai進jin行xing信xin息xi的de傳chuan輸shu。當dang讀du寫xie器qi對dui標biao簽qian進jin行xing閱yue讀du識shi別bie時shi，首shou先xian發fa出chu未wei經jing調tiao製zhi的de電dian磁ci波bo
，此ci時shi位wei於yu遠yuan場chang的de電dian子zi標biao簽qian天tian線xian接jie收shou到dao電dian磁ci波bo信xin號hao並bing在zai天tian線xian上shang產chan生sheng感gan應ying電dian壓ya，電dian子zi標biao簽qian內nei部bu電dian路lu將jiang這zhe個ge感gan應ying電dian壓ya進jin行xing整zheng流liu並bing放fang大da用yong於yu激ji活huo標biao簽qian芯xin片pian。當dang標biao簽qian芯xin片pian激ji活huo之zhi後hou，用yong自zi身shen的de全quan球qiu唯wei一yi標biao識shi號hao對dui標biao簽qian芯xin片pian阻zu抗kang進jin行xing變bian化hua
，當dang電dian子zi標biao簽qian芯xin片pian的de阻zu抗kang和he標biao簽qian芯xin片pian之zhi間jian的de阻zu抗kang匹pi配pei較jiao好hao時shi則ze基ji本ben不bu反fan射she信xin號hao，而er阻zu抗kang匹pi配pei不bu好hao時shi則ze將jiang幾ji乎hu全quan部bu反fan射she信xin號hao。這zhe樣yang反fan射she信xin號hao就jiu出chu現xian了le振zhen幅fu的de變bian化hua，這zhe種zhong情qing況kuang類lei似si於yu對dui反fan射she信xin號hao進jin行xing幅fu度du調tiao製zhi處chu理li。讀du寫xie器qi通tong過guo接jie收shou到dao經jing過guo調tiao製zhi的de反fan射she信xin號hao判pan斷duan該gai電dian子zi標biao簽qian的de標biao識shi號hao並bing進jin行xing識shi別bie。這zhe類lei天tian線xian主zhu要yao包bao括kuo微wei帶dai天tian線xian、平麵偶極子天線和環形天線。圖二是我們研製的能工作於多種識別環境下的UHF電子標簽天線。

電子標簽天線的設計與測試

如前所述，作於低頻與高頻的射頻識別係統采用感應耦合模式進行通信，所以T作(zuo)於(yu)這(zhe)兩(liang)個(ge)頻(pin)段(duan)的(de)讀(du)寫(xie)器(qi)與(yu)電(dian)子(zi)標(biao)簽(qian)都(dou)采(cai)用(yong)線(xian)圈(quan)形(xing)式(shi)的(de)天(tian)線(xian)。工(gong)作(zuo)在(zai)這(zhe)兩(liang)個(ge)頻(pin)段(duan)的(de)射(she)頻(pin)識(shi)別(bie)係(xi)統(tong)都(dou)受(shou)製(zhi)於(yu)近(jin)場(chang)作(zuo)用(yong)的(de)範(fan)圍(wei)，從(cong)而(er)導(dao)致(zhi)其(qi)識(shi)別(bie)距(ju)離(li)較(jiao)短(duan)。根(gen)據(ju)目(mu)前(qian)的(de)情(qing)況(kuang)來(lai)看(kan)，采(cai)用(yong)近(jin)場(chang)通(tong)信(xin)的(de)射(she)頻(pin)識(shi)別(bie)係(xi)統(tong)最(zui)大(da)的(de)識(shi)別(bie)距(ju)離(li)小(xiao)於(yu)1米。

由於低頻和高頻頻段的射頻識別係統采用的是電磁場耦合模式，所以係統中的天線都采用線圈形式。采用這種形式的主要原因如下： 
   
1.電磁場的耦合在線圈之間比較緊密： 
2.天線采用線圈的形式進一步減小了天線的體積進而減小了標簽的體積： 
3.標簽芯片的特性要求標簽天線具有一定的電抗。

zaichaogaopinheweiboboduanshi，dianzibiaoqianheduxieqizhijiandetongxincaiyongfanxiangsanshegongzuofangshi。zheshihou，lianjiedianzibiaoqianheduxieqizhijiandeqiaoliangbuzaishijincichangershidiancibo。cishi
，beidongxingdianzibiaoqianchuyuduxieqidedianciboyuanchangzhong。genjupindaidebochanghetianxiandekoujingkeyijisuanchugaipindaineishepinshibiexitongdeyuanchangheduxieqizhijiandejuli。yibanlaishuo，beidongxingbiaoqianzaichaogaopinfanweineidedingzuojulikeda10米左有，根據現有資料來看。工作於微波波段（主要指2.45GHz）的被動標簽工作距離僅為1米左右。所以目前采用反向散射下作模式的射頻識別係統主要使用位於860～960MHz的超高頻頻段。
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在zai由you被bei動dong型xing標biao簽qian天tian線xian組zu成cheng的de射she頻pin識shi別bie係xi統tong中zhong，標biao簽qian需xu要yao從cong瀆du寫xie器qi產chan生sheng的de電dian磁ci場chang或huo者zhe電dian磁ci波bo中zhong獲huo取qu能neng量liang激ji活huo標biao簽qian芯xin片pian。所suo以yi在zai電dian子zi標biao簽qian中zhong有you一yi部bu分fen電dian路lu專zhuan門men用yong於yu檢jian測ce標biao簽qian天tian線xian上shang的de感gan生sheng電dian動dong勢shi或huo者zhe感gan應ying電dian壓ya，並bing通tong過guo二er極ji管guan電dian路lu進jin行xing整zheng流liu並bing經jing過guo其qi他ta電dian路lu進jin行xing電dian壓ya放fang大da等deng等deng。這zhe些xie電dian路lu被bei集ji成cheng存cun標biao簽qian芯xin片pian內nei部bu。當dang芯xin片pian進jin行xing封feng裝zhuang時shi通tong常chang還hai會hui引yin入ru一yi部bu分fen分fen布bu式shi電dian容rong。但dan是shi，天tian線xian設she計ji本ben身shen並bing不bu需xu要yao知zhi道dao芯xin片pian中zhong的de具ju體ti電dian路lu而er隻zhi需xu要yao掌zhang握wo芯xin片pian和he經jing過guo封feng裝zhuang之zhi後hou的de芯xin片pian阻zu抗kang，並bing利li用yong最zui大da能neng量liang傳chuan遞di的de法fa則ze設she計ji天tian線xian的de輸shu入ru阻zu抗kang。

youyudianzibiaoqianxinpiandeshuchuzukangjuyoudiankangfenliang
，weiledadaonengliangdezuidachuandi，xuyaojiangtianxiandeshuruzukangshejiweibiaoqianxinpianzukangdegonge。yibaneryan
，dianzibiaoqianxinpiandeshuruzukangweiZ=R_X形式。為了獲得共軛形式的阻抗
，電子標簽天線的阻抗應為Z=R+iX形式。

如ru前qian文wen所suo述shu，工gong作zuo在zai低di頻pin與yu高gao頻pin的de射she頻pin識shi別bie係xi統tong中zhong的de被bei動dong標biao簽qian天tian線xian采cai用yong了le線xian圈quan形xing式shi
，這zhe種zhong線xian圈quan形xing式shi即ji可ke引yin入ru感gan抗kang用yong於yu抵di消xiao等deng效xiao電dian路lu中zhong的de容rong抗kang從cong而er實shi現xian標biao簽qian芯xin片pian和he天tian線xian之zhi間jian的de最zui大da能neng量liang傳chuan遞di。

而er對dui於yu工gong作zuo於yu超chao高gao頻pin和he微wei波bo頻pin段duan的de標biao簽qian天tian線xian而er言yan，為wei了le引yin入ru感gan抗kang以yi抵di消xiao芯xin片pian的de容rong抗kang
，需xu要yao在zai天tian線xian設she計ji中zhong加jia入ru環huan形xing結jie構gou進jin行xing感gan性xing饋kui電dian
，或huo者zhe加jia入ruT型配『31等結構。另外
，為了在規定的等效全向輻射功率（EIRP）下獲得更遠的閱讀距離除了要求電子標簽天線也具有高增益。還要求電子標簽天線和標簽芯片之間能夠有足夠的匹配。

zaibiaoqiantianxianjinxingshejihefangzhenbinghuodelixiangjieguozhihou，xuyaojiangtianxianjiagongbingjinxingceshiyiyanzhengshejihefangzhendezhengquexing。yezhengxiongweiqianwenzhongsuojieshaodebiaoqiantianxianjuyoufushuzukangdetexing
，qiceshifangfahejuyoushishuzukangtianxiandeceshifangfayousuoqubie。lingwai，zaitongyigebiaoqiantianxiandeceshiguochengjin
，genjusuoxushujudebutongqiceshifangfayeyousuobutongtongchangceshitianxiandeguochengzhongbingbuxuyaozhuanmenceshitianxiandeshuruzukang。danbiaoqiantianxiandezukangweifushuzukang，qieqixubuyushibuzhibijiaoda（通常X/R》10）
，這樣的阻抗曲線在smith圓圖中靠近短路圓不易通過smithwangtuguanchatianxiandezukangdaikuan。weilehuodebiaoqiantianxiandeshuruzukang。keyijiangceshishebeideshuchuduankouzhijieyutianxiandeshuruduankouxianglianyouyuzhezhongfangshibingweikaolvbiaoqiantianxianbenshenjuyoufushuzukangzheyitexing。tianxianheceshishebeizhijianbingmeiyouqudegongepipei，cishizhinengdedaotianxiandezukangcanshu
，zhurusanshejuzhencanshuhezhubobidengchangyonglaihengliangtianxiandedianlucanshubunengzhijiehuode。

為(wei)了(le)獲(huo)得(de)是(shi)散(san)射(she)參(can)數(shu)和(he)駐(zhu)波(bo)比(bi)等(deng)電(dian)路(lu)參(can)數(shu)，以(yi)便(bian)對(dui)天(tian)線(xian)的(de)阻(zu)抗(kang)帶(dai)寬(kuan)特(te)性(xing)進(jin)行(xing)評(ping)價(jia)，可(ke)將(jiang)實(shi)測(ce)的(de)阻(zu)抗(kang)參(can)數(shu)帶(dai)入(ru)相(xiang)關(guan)公(gong)式(shi)進(jin)行(xing)計(ji)算(suan)或(huo)者(zhe)采(cai)用(yong)阻(zu)抗(kang)匹(pi)配(pei)的(de)方(fang)法(fa)在(zai)測(ce)試(shi)設(she)備(bei)和(he)天(tian)線(xian)之(zhi)間(jian)加(jia)入(ru)匹(pi)配(pei)電(dian)路(lu)。匹(pi)配(pei)電(dian)路(lu)可(ke)用(yong)兩(liang)種(zhong)方(fang)法(fa)構(gou)成(cheng)，一(yi)是(shi)采(cai)用(yong)工(gong)作(zuo)頻(pin)率(lv)較(jiao)高(gao)的(de)分(fen)立(li)元(yuan)件(jian)構(gou)成(cheng)，二(er)是(shi)采(cai)用(yong)微(wei)波(bo)電(dian)路(lu)構(gou)成(cheng)。需(xu)要(yao)注(zhu)意(yi)的(de)是(shi)配(pei)電(dian)路(lu)應(ying)該(gai)距(ju)離(li)天(tian)線(xian)端(duan)口(kou)足(zu)夠(gou)近(jin)。這(zhe)樣(yang)才(cai)能(neng)獲(huo)得(de)較(jiao)大(da)的(de)帶(dai)寬(kuan)並(bing)避(bi)免(mian)天(tian)線(xian)和(he)配(pei)電(dian)路(lu)之(zhi)間(jian)的(de)連(lian)接(jie)線(xian)路(lu)帶(dai)來(lai)的(de)負(fu)麵(mian)影(ying)響(xiang)。

電路用於標簽天線的測試。不過采用匹配電路具有一些缺點： 
1.bulunshiyongfenliyuanjianhaishishiyongweibodianlulaigouchengzukangpeidianlu，qidaikuanzongshishouxiande，dangtianxianzhenshidaikuandayupeidianludedaikuanshi，suoceshidaodedaikuanjiangbuzaizhunque; 
2.南於配電路總是存在損耗
，所以測試得到的帶寬和回波損耗值等參數和真實的天線參數有一些差別; 
3.引入的配電路總是和天線之間存在距離，從而使得測試現一定誤差。 

采(cai)上(shang)述(shu)使(shi)用(yong)匹(pi)配(pei)電(dian)路(lu)進(jin)行(xing)測(ce)試(shi)的(de)方(fang)案(an)除(chu)了(le)可(ke)以(yi)獲(huo)得(de)一(yi)定(ding)精(jing)度(du)的(de)帶(dai)寬(kuan)和(he)同(tong)波(bo)損(sun)耗(hao)等(deng)參(can)數(shu)之(zhi)外(wai)
，對(dui)於(yu)測(ce)試(shi)天(tian)線(xian)的(de)方(fang)向(xiang)圖(tu)和(he)增(zeng)益(yi)等(deng)輻(fu)射(she)特(te)性(xing)也(ye)是(shi)必(bi)須(xu)的(de)。隻(zhi)有(you)通(tong)過(guo)阻(zu)抗(kang)配(pei)電(dian)路(lu)才(cai)能(neng)將(jiang)天(tian)線(xian)接(jie)收(shou)到(dao)的(de)絕(jue)大(da)部(bu)分(fen)能(neng)量(liang)基(ji)本(ben)無(wu)反(fan)射(she)地(di)傳(chuan)遞(di)到(dao)測(ce)試(shi)係(xi)統(tong)中(zhong)
，從(cong)而(er)測(ce)試(shi)相(xiang)應(ying)的(de)輻(fu)射(she)參(can)數(shu)。

隨sui著zhe射she頻pin識shi別bie技ji術shu的de應ying用yong不bu斷duan擴kuo大da，越yue來lai越yue多duo的de場chang合he要yao求qiu使shi用yong射she頻pin識shi別bie係xi統tong。電dian子zi標biao簽qian天tian線xian作zuo為wei射she頻pin識shi別bie係xi統tong中zhong不bu可ke或huo缺que的de重zhong要yao一yi環huan
，其qi設she計ji、生產
、測試等均是未來研究的主要內容之一。由於電磁波的固有特性
，在諸如臨近金屬
、yetidenghuanjingzhong，shepinshibiexitongdexingnengjiangdadazhekou。zaizheyangdehuanjingzhongchuletigaoduxieqidexingnengzhiwai

，dianzibiaoqiantianxiandexingnengdetigaogengweizhongyao。muqianwomenzhengzaizhenduidianzibiaoqiantianxianzaizhexiefuzahuanjingzhongdeyingyongzhankaiyanjiu。lingwai，rouxingdianzibiaoqiantiefuzaifeipingtanbiaomianshixingnengyehuiyousuoehua。ruhebimianrouxingbiaoqianyingyongdaofeipingtanbiaomiandailaideyingxiangyeshimuqianwomenlingyigeyanjiuzhongdian。

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http://www.0-fzl.cn/rf-art/80013359