RFID passive tag antenna for cork bottle stopperRicardo Goncalves1,2, Roberto Magueta2

1Instituto de Telecomunicacoes, Aveiro, Portugal2Universidade de Aveiro, Aveiro, Portugal

rgoncalves@av.it.pt, rlm@ua.pt

Pedro Pinho1,3 and Nuno B. Carvalho1,23Inst. Sup. Eng. Lisboa - ISEL, Lisboa, Portugal

ppinho@deetc.isel.pt, nbcarvalho@ua.pt

Abstract—In this paper we propose a possible design for aRFID tag antenna embedded into cork. The antenna is smalland conformal and intended to be used into bottle stoppers fortracking and logging purposes of wine or other beverages. Theproposed design is based on a inductive ring and an addedresistance in order to modify the current distributions of theantenna. The resulting antenna has a relatively directive radiationpattern and despite the small efficiency it is able to operated witha commercial RFID reader at a reasonable distance.

I. INTRODUCTION

RFID technology is one of the most used by people ev-erywhere in the world even without notice. Its simplicity andlow cost has widespread its applicability to many differentscenarios. From public transport access, inventory and luggagetracking to anti-theft and electronic tolling systems [1]. Thewide variety of scenarios of application rise challenges for thetag designs, which have been shifting to the use of differentmaterials and techniques to create small and conformal anten-nas to be seamless in many different types of targets.

In this work we looked into bottle tagging. It is a greatchallenge to create RFID tags for bottles due to the presenceof the different materials, from the plastic and/or glass of thebottles to the presence of the liquids in the vicinity of the tags.Moreover, given the characteristic geometry of the bottle, theantenna has to be small and conformal so not to create anyvisual impact into the bottle.

Some possible designs include meander monopole placedinside a plastic bottle closure [2], and several designs consist-ing of dipole antennas placed around the bottle plastic or glassbody [3], [4], [5].

In this work we propose a possible design of a very smallconformal RFID tag antenna that can be embedded into acork bottle stopper for identification purposes. For that wedetermined the permittivity of the dielectrics [6] involved inthe designed, namely, the cork and the bottle glasses anddesigned the antenna considering the application scenario,hence, the presence of the glass, plastic and liquids.

The remaining of this paper is organized as follows. SectionII presents the antenna model and prototype and also the an-tenna characteristics and operation limitations. Finally, SectionIII draws the main conclusions.

II. CORK RFID ANTENNA

The proposed RFID antenna is based on a dipole ring foldedaround the RFIC. The RFIC used is a UCODE SL3ICS1002 by

NXP which has an input impedance of 16-j158 Ω at 866 MHz.Given the inductive characteristic of the folded ring dipolematching the input capacitance of the RFIC was doable witha rather small antenna. However, the resistance of the antennawas very small and there was a large impedance mismatchbetween the antenna and the chip. To solve this, we checkedthe current distribution of the antenna and verified that thehighest impedance point of the antenna, this is, the area inwhich the current level were smaller was in the slimmer armupwards of the feed point. Therefore, if we could increasea little more the resistance at this point we woule be ableto match the input resistance without changing the overallbehavior of the antenna. The easiest solution was to createa gap, however, the gap was not enough to reach the desiredmatch, hence we placed an SMD resistance.

The proposed antenna is shown in Fig. 1 and the correspond-ing dimensions are shown in Table I. The physical dimensionsare for the final prototype matched to be inserted in a glasswine bottle, which was simulated as a whole, as shown in Fig.2.

Fig. 1. Simulation model of the roposed RFID tag antenna (a) front view,(b) left side view, (c) right side view and (d) prespective view (e) prototype.

The input impedance of the simulated antenna is shownin Fig. 3. The several traces are respectful to the antennawhen standing alone in empty space, just with the bottle neckaround and inserted inside a bottle with liquid. The last case

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TABLE IPROPOSED RFID TAG ANTENNA DIMENSIONS

Parameters sizes (mm)A, B, C, D 20.0, 1.6, 4.8, 2.0E, F, G 3.0, 6.0, 25.0

Fig. 2. Simulation model of the proposed RFID tag antenna inside a winebottle.

showcasing an input impedance very close the the RFIC inputimpedance being 15+j154 Ω. The resistance used with theantenna was of 6.2 Ω.

Fig. 3. Simulated input impedance of the antenna under different conditions.

The SMD resistance is responsible for dissipating most ofthe energy in the antenna and therefore leading to an efficiencyas small as 2 %. This is the price to pay for the spaceconstraints applied to the antenna. Nevertheless, the RFIDprototype was tested using a Alien ALR8800 commercialRFID reader, with which we were able to read the RFID tag ata maximum distance of 0.3 m with two regards, the prototypeis built upwards and it was tested outside the bottle while it isproperly designed to operate inserted into a bottle. By meeting

these conditions we expect to reach at least 1 m distance ofcommunication at 1 W of output power from the reader.

The radiation pattern is slightly directive which is ratherconvenient for the application envisioned, so the bottle can beread when laying down on shelves. However, with the presenceof liquid the direction changes towards the liquid, as can beseen in Fig. 4.

Fig. 4. Simulated input impedance of the antenna under different conditions.

III. CONCLUSION

In this paper, and RFID tag antenna implemented in corkbased substrate has been presented. This RFID tag aim to beused in wine bottle stoppers to identify the wine characteris-tics. The RFID tag proposed in this paper presents reasonableresults in terms of reading range while showcasing a smallform factor and maintaining conformity with the targetedapplication dimension constraints.

ACKNOWLEDGEMENT

The authors acknowledge the Portuguese FCT/MCTESfor financing the PhD grant SFRH/BD/91249/2012 and theprojects PTDC/EEA-TEL/122681/2010-PROENERGY-WSN-Prototypes and CREATION EXCL/EEI-TEL/0067/2012.

REFERENCES

[1] K. Finkenzeller, RFID Handbook: Fundamentals and Applications inContactless Smart Cards and Identification. John Wiley & Sons, Ltd,2003.

[2] Z. Hu and P. H. Cole, “Bottle packaged wine product detection by uhf rfidsystems,” Proc. Int. Conf. on Electromagnetics in Advanced Applications,pp. 301–304, September 2010, 2010.

[3] Y. D. Kim, “Design of near omnidirectional uhf rfid tag with one-off sealfunction for liquid bottles,” Wiley Microwave and Optical TechnologyLetters, vol. 55, pp. 375 – 379, 2013.

[4] J. Xi and T. T. Ye, “Conbottle uhf rfid tag antenna mountable onwinebottle neck,” in Proc. IEEE Antennas and Propagation Soc. Int.Symp., July 2012.

[5] T. Bjorninen, A. Z. Elsherbeni, and L. Ukkonen, “Low profile conformaluhf rfid tag antenna for integration with water bottles,” IEEE AntennasWireless Propag. Lett., vol. 10, pp. 1147 – 1150, 2011.

[6] R. Goncalves, S. Rima, R. Magueta, A. Duarte, A. Collado, A. Geor-giadis, N. B. Carvalho, and P. Pinho, “Low profile conformal uhf antennasand rfid tags on cork substrate,” IEEE Trans. Antennas Propag., Underrevision.

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