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With80years of development and change, RFID technology becomes radiatevitality, especially in recent years information technology and industrializationtechnology integration needs, RFID technology is placed on a higher level, however,the sensitivity of the metal environment greatly limited its application areas.So,thestudy of the metal environment UHF RFID tag has a very important significance.In this paper, studied the UHF RFID tag performance variation in metalenvironment. See through the appearance to the essence, found that the declineperformance of RFID tags is two aspects together results: multipath interferencewhich caused by the metal plate reflected electromagnetic wave and the metal affectstag antenna parameters. To solve this problem, RFID tags theoretical was depthstudied, energy and signal transmission of the RFID system was analysied, a largenumber of the latest solutions papers were refered, formulate design process, the finaldesign and manufacture the anti-metal plane of RFID tag which size is8.0cm×1.5cm×0.16cm. And after different views of practical applications test shows that the tag’sworking performance is stability, the final measurement shows that the anti-metalRFID tag has1.20m-1.30m stable reading distance.Follows are the original points of this paper:(1)From UHF RFID tag antenna practical application, studies why the RFIDtag performance deterioration in the metal environment. The results show that thepresence of metal environment brings the entire RFID system with multipathtransmission problems; meanwhile when RFID tag antenna near metal, its radiationpattern, gain, radiation efficiency, input impedance, directivity parameters and so onserious changes, thereby affecting the actual work performance. Through simulationanalysis, the distance between the RFID tag and the area of metal plate were theimportant factor about affecting the restore performance of the RFID tag.With themethod which added air cushion between the metal and the tag, measurement reslutsshow that can recover the tag antenna parameters and tag regain reading performance,and at a distance of2cm place, the read ability was regained;meanwhile themeasurement also showed that the larger size of the metal plate had a bad influence onthe restore performance of RFID tag. (2)Combined with my own practice, this paper analyzed different solutions ofthe current anti-metal RFID, especially the different impedance matching techniques,tried to find the basis of the circuit principles. Meanwhile, with the analysis of gooddesign, summarized anti-metal RFID tag design methods and processes for moredesigners with provide guidances.(3)Using combination design scheme which is microstrip patch technique andT-type matching technology, this paper deduced tag antenna impedanceexpression,which function model was Z in F (L p, w p, r, l, w ’, H, s), in the functionL pis radiating body length,w pis width, l is the T-type matching length and w ’iswidth, H is the distance between the double row structure, ris dielectric;Using theprofessional software HFSS for simulation optimization as well as control variablesfor analysis of the characteristics of this kind of tag structure，got the function ofchanges table about best working frequency f F (L, w, L1, s, w1)and return lossS11F (w, L, L1, s, w1);optimization of the RFID tag antenna works at9l5MHz whichhas the lowest return loss is31.85dB, VSWR is1.025, the reflection coefficient is0.012, matching efficiency up to99.98%, band of-10dB is860-939MHz;Finaly,theoptimized antenna was to be manufactured, tested and verified, at last the completeRFID tag was tested in many application areas.
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