圆极化rfid天线的分析

《圆极化rfid天线的分析》由会员上传分享，免费在线阅读，更多相关内容在行业资料-天天文库。

1、摘要AbstractOwingtotheexponentialgrowthintheapplicationsofradiofrequencyidentification(RFID)，thedesignofRFIDantennawithperfectcharacteristicispresentlyoneofthemostchallengingtopics．TheuseofcommercialRFIDsysteminpracticalenvironmentusuallyrequirescircularlypolar

2、ized(CP)readerantennafororientationdiversity．Atpresent，commerciallyavailableRFIDtagsarecommonlydesignedasdipoleormicrostrip—typewitlllinearpolarization(LP)，thus，thepolarizationmismatchbetweenthereaderandtagwillresultsinonlyhalfofthetransmittedpowerreceivedbyt

3、heLPtag．Theoretically,themaximumreadingrangeofaCPtagCanbeimprovedgreatlywhenthereaderisalsoaCPtype(exhibitingthesamerotation)．ThedesignforcircularpolarizationRFIDantennahasagreatsignificance．Basedonantennaandmicrowavecircuittheories，circularlypolarizedRFIDant

4、ennasarestudiedinthisdissertation．Themainacademiccontributionsaresummarizedasfollows．1)Basedontheradiationcharacteristicsofdipoleantenna,acircularpolarizedRFIDtagantennaisproposed．Byusinggroovingtechnology,twodipoleantennasCanachievesamelengthsandunequalembed

5、slots．Oneofdipoleshasequalrealandimaginarypartsofimpedance，whileanotherdipolehasthecomplex-conjugatedimpedance．Thusthedifferenceimpedanceangleofthedipolesis90。．Then，thecircularlypolarizedradiationisattained．Amodifiedinductivelycoupledloopisappliedfortheimpeda

6、ncematchbetweentheantennaandtag．Theequivlentcircuitsofinductivelyandcapacitivelycoupledfedareproposed．ThiscouplingfeedCanisolatetherealpartandimaginarypartoftheimpedance，whichmadetheantennadesignsimpler．Finally,thecircularpolarizedradiationandimpedancematchin

7、ghavebeenwellexplainedandthedesignprocedureoftheantennashasbeensummarized．2)Basedonmicrostripantenna,acompactcircularlypolarizedtagantennainUHFbandformetallicobjectapplicationisproposed．Theprocessfortheformationofcircularlypolarizedwaveandimpedancematchingise

8、xplainedindetail．ThecompactCPoperationisachievedbyonlyadjustingtwopairsofunequalcrossd-slitlengths．Thecompleximpedancematchingoftheproposedtagantennacanbeeasilyobtainedbyselectingtheprope