Journl of Electricl Engineering & Technology Vol. 6, No. 4 pp. 551~555, 2011 551 DOI: 10.5370/JEET.2011.6.4 551 Design of the Cr lel tg with loop mtching feed nd modified dipole structure t 900 MHz Eui-Sun Choi, Hk-Yong Lee **, Jin-Seong Lee***, Kyounghwn Lee***, S-Won Lee****, nd Young-Hie Lee* Astrct The Cr lel tg with loop mtching feed nd modified dipole ntenn structure ws proposed. The ntenn impednce is conjugted esily to rdio frequency identifiction IC chip impednce y loop mtching feed. The reding rnge of the cr structure tg is 0.9 1.0 m from the upper side of the formul milk cn lid. The fricted lel tg size is 44.0 44.0 mm2. The operting frequency t -3 db return loss is 861.0 929.0 MHz, nd the mximum reding rnge t the nechoic chmer is 1.5 m. Keywords: RFID, Cr, Lel, Tg, Antenn, Milk cn 1. Introduction RFID (Rdio Frequency IDentifiction) is wireless technology for recognizing tg informtion. Therefore, it requires tg, reder, nd reder ntenn. The tg consists of n ntenn nd semiconductor chip tht records informtion on the semiconductor chip memory nd sends it to the reder through the ntenn. This informtion is used to identify n oject to which the tg is ttched. The tg hs similr function to tht of the rcode currently used in wide rnge of services. The difference etween RFID nd the rcode system is tht the former uses rdio wves insted of light. The RFID system not only works on closed ojects s the rcode system does, ut it cn lso recognize tgs in remote distnces. It cn receive informtion from tgs, even through ojects, nd cn recognize lrge numer of tgs t time. Depending on the power source it uses, RFID is clssified into pssive or ctive type. Depending on the frequency, it is clssified into 125/135 khz, 13.56 MHz, 433 MHz, 900 MHz, or 2.4 GHz [1 2]. In ddition, depending on the tg type, it is clssified into lel tg or metl tg [3 5]. RFID technology originted from the equipment developed y Leon Theremin of the former Soviet Union for intelligence wrfre. Therefter, it hs een pplied nd Corresponding Author: Deprtment. of Electronic Mterils Engineering, Kwngwoon Univerity, Kore. (sunsee@kw.c.kr) * Deprtment. of Electronic Mterils Engineering, Kwngwoon Univerity, Kore. (yhlee@kw.c.kr) ** SONOVISION Co., Ltd, Kore. (hyleentenn@hnmil.net) *** Deprtment. of Antenn Reserch, UTRC, Kore. (jslee@utrc.re.kr, khlee@utrc.re.kr) **** Deprtment of Informtion Communiction nd Homenetwork, Chungju College of Kore Polytechnic Ⅳ, Kore. (swlee@kopo.c.kr) Received: My 25, 2010; Accepted: Mrch 4, 2011 developed diversely s militry technology in utomtic nswering mchines nd identifiction of friend or foe. The 1973 ptent y Mrio Crdullo used rdio wve, sonic wve, nd light for communiction. It lso hd uilt-in memory for wireless communiction. Therefore, it is considered the first true RFID system. In the sme yer, Steven Deppetl demonstrted RFID technology with limited output for the first time in Los Almos Ntionl Lortory. Thus fr, this is the technology tht hs een used s the RFID system. Recently, RFID hs een used in very diverse pplictions such s in trcking product history, ttching pssports or ID crds to recognize personl informtion, nd recording thletes dt. In ddition, it is lso used in trffic fre collection systems such s Hi-pss nd trnsit crds, s well s security crds for uilding ccess nd implnttion in humn odies or nimls for certin medicl purposes. Therefore, RFID is ttrcting sustntil ttention s n effective sustitute for rcodes. To expnd further its ppliction, intensive reserch nd development ctivities re eing undertken to reduce fctory inventory mngement time, to mke physicl distriution flow trnsprent, nd to mnge the uthenticity of expensive commodities. In prticulr, RFID is now pplied to food mngement in order to prevent food poisoning or deth from eting expired or decomposed food. This is chieved y mking the mngement of dt such s the expiry dte, nutrient fcts, nd distriution flow efficient nd trnsprent. The current study ims to exmine 900 MHz -nd RFID tgs ttched to powdered infnt formul cns in order to mnge effectively powdered infnt formul products tht re minly consumed y ies. These re mong the mny food items which hve expiry dtes tht ffect humn food sfety significntly.
552 Design of the Cr lel tg with loop mtching feed nd modified dipole structure t 900 MHz 2. Design of the tg ntenn Through the nlysis of formul milk cns currently in the mrket nd user environment to which the RFID system would e pplied, the tg design specifiction ws determined s shown in Tle 1. The formul milk cns hve thin metl plte under their Low Density Poly- Ethylene (LDPE) lids, which must e tken into considertion for the tg design. As the formul milk cns re cylindricl, the tg should e redle regrdless of the direction of its plcement. Tle 1. Tg design specifiction No. Items Spec. Note 1 2 RFID operting frequency Recognition distnce 908.5 914.0 MHz Repulic of Kore > 1.0 m Directionless 3 RFID chip Impinj s Monz 2 53-j160Ω @910 MHz 4 Tg size 44.0 44.0 mm2 Inly(t=0.068 mm ) 5 Attchment loction 6 Reder 7 Reder Antenn On the formul milk cn Alien Co. ALR-9800 Alien Co. ALR-9611-CR Upper side of LPDE 30 dbm(mx) Repulic of Kore 6dBic(Mx), RHCP To stisfy the specifictions presented in Tle 1, simultion using MWS s CST 2008 ws crried out. The impednce of the tg ntenn ws conjugted to tht of Impinj s Monz 2 RFID chip when the tg ntenn is ttched to the formul milk cn lid. Fig. 1 shows the structure of the tg ntenn designed for formul milk cn. For the tg to fit the sticker size ttched to the formul milk cn lid nd e recognized t distnce of 1.0 m or more in ny direction verticl to the reder ntenn, the dipole ntenn prt ws deformed into cr leg shpe. For the impednce of the tg ntenn to e conjugted to tht of Impinj s Monz 2 RFID chip, loop-shped mtching terminl ws used. The proposed tg llows djustments of the width (Fig. 1(c)) nd height (Fig. 1(f)) of the loop mtching terminl, fcilitting esier control of the inductnce nd cpcitnce. This in turn results in the conjugtion of the RFID chip nd tg ntenn. For the current study, the tg for the powered y formul cn is nmed Cr Tg s its ntenn shpe is similr to tht of cr. To investigte the possiility of filter ppliction, the triplexer ws designed, simulted, nd mnufctured using the Advnced Design System nd HFSS which is used in electro-mgnetic nlysis. The frequency response chrcteristics of the mnufctured triplexer were mesured y vector network nlyzer. Return loss[db]=20 log10 z z z : Impednce of the tg ntenn z : Impednce of the RFIC Chip z + z <Formul 1> The simulted tg ntenn is ttched to the formul milk cn. Fig. 2 shows the grph of the chnges in resistnce nd rectnce of impednce depending on the size of f, wheres Fig. 3 shows the grph for the return loss of ech impednce. In Fig. 2, s the vlue of f increses, the resistnce decreses, nd the rectnce () Resistnce Fig. 1. Tg ntenn structure for the powdered milk cn () Rectnce Fig. 2. Impednce vlues of the tg ntenn (simultion)
Eui-Sun Choi, Hk-Yong Lee, Jin-Seong Lee, Kyounghwn Lee, S-Won Lee nd Young-Hie Lee 553 increses. The rnge of increse or decrese ppers to e igger in the rectnce thn in the resistnce. The chip impednce is clculted to use the Monz 2 dtsheet of Impinj Co [6]. Fig. 3 shows the reflection fctors clculted using Formul 1 with reference to chip impednce. When f is 0.3 mm, the reflection fctor ecomes the smllest t 910 MHz s -48.30 db, t which -3 db ndwidth is 67 MHz (872 939 MHz ). The tg size optimized s result of the simultion of the RFID system for the powered y formul cn tg is =44 mm, =44 mm, c=38 mm, d=6.0 mm, e=3 mm, f=0.3 mm, g=37.97 mm, h=0.77 mm, nd i=1.3 mm. Fig. 3. Return loss vlues of the tg ntenn (simultion) 3. Fricted nd mesured the tg Fig. 4 shows tg fricted y forming copper pttern with thickness of 0.018 mm on 0.05 mm -thick Polyethylene Terephthlte with reltive permittivity of 3.3. Through mesurements nd experiments, the tg ntenn size ws optimized s shown in Fig. 4, which is =44 mm, "=44 mm," c=26 mm," d=6 mm, "e=3 mm," nd "f=0.3 mm. Fig. 5. Comprison of the tg ntenn impednce results (mesurement nd simultion) Fig. 5 shows the grph compring the tg impednce mesured from the cr tg ttched to the y formul milk cn lid with the simultion results. When the tg ws ttched to the formul milk cn lid, the resistnce of the tg impednce decresed, nd its rectnce incresed. This implied tht the impednce chnged depending on the medium to which the tg ws ttched nd the metl plte of the formul milk cn. When the tg ntenn ws ttched to the formul milk cn lid nd when its impednce which the test system used in reference [7] ws mesured t 910 MHz, the impednce ws 67.12 Ω t the resistnce nd 166.65 Ω t the rectnce prts, respectively. If the impednce of the RFID chip is 53.97 j160.29 Ω, there might e some error in mesuring the tg ntenn impednce. Fig. 6 shows grph compring the results of simultion nd the mesurement of return loss. The chnge in impednce resulted in chnge in return loss. In the simultion, the return loss ws -48.30 db t 910 MHz ut ws reduced to -18.71 db t the time of the enchmrk test (BMT). During this period, the time frequency lso chnged to 901 MHz. The reflection fctor ws moved to lower frequency ecuse the tg ws ttched to the formul cn. Bsed on -3 db return loss, the operting rnge is 861 929 MHz, nd the ndwidth is out 68 MHz, which includes the entire RFID operting frequency rnge in Kore. Fig. 4. Fricted cr tg Fig. 6. Return loss of cr tg (mesurement nd the simultion)
554 Design of the Cr lel tg with loop mtching feed nd modified dipole structure t 900 MHz To ensure the more ccurte mesurement of the cr tg, its sensitivity nd recognition distnce were mesured t the electromgnetic nechoic chmer in Songdo RFID/USN Center in Incheon (Kore). Sensitivity is the minimum power of the RFID reder when the tg is operted t ech frequency. This mens tht the impednce of the tg ntenn mtches well tht of the RFID IC chip s the sensitivity vlue is lower. Reference 8 descries the sensitivity mesurement method. Fig. 7 shows the sensitivity mesurement system tht consists of TESCOM TC-2600A RFID tester, G94007A RFID highpower mplifier, nd n LG Industril Systems reder ntenn (Mx gin : 6 db ic). With distnce of 1 m etween the tg nd Tx ntenn nd the cr tg ttched to the formul milk cn, the tg sensitivity ws mesured. Fig. 8 shows the recognition distnce mesurement system tht consists of Alien s reder ALR-9800 (KOR) nd circulr polriztion (RHCP) reder ntenn; the cr tg ws ttched to the formul cn. The mximum recognition rnge is 10 m. The sensitivity result is shown in Fig. 9. Tg sensitivity ws mesured y the unit of 10 MHz t the rnge of 860 960 MHz. It ppered to e higher s the reltive mesurement vlue ws lower. According to the mesurement results, the sensitivity of the tg ws 2.1 db m t 910 MHz. A comprison of these results with the chrcteristics in Fig. 9 suggests tht the tg worked properly. The performnce seemed to result from the slight chnge in impednce due to RFID chip onding. The mximum recognition distnce of the cr tg mesured with the recognition distnce mesurement system shown in Fig. 10 ws 1.5 m for ll smple tgs. Fig. 9. Sensitivity nd mx reding rnge of the cr tg However, in BMT, the tg should e plced more prllel to the ground thn the mximum recognition distnce, nd it should e ttched to cylindricl formul milk cns. Therefore, the tg should e recognizle t ny sme distnce regrdless of its tg orienttion. For this reson, the mesurement system ws configured s shown in Fig. 10, nd the formul milk cn to which the tg ws ttched ws rotted 90 clockwise for mesurement. As the result of the mesurement of 50 tgs, uniform distnce of 0.9 1.0 m ws otined. Fig. 7. Sensitivity mesurement system Fig. 10. Tg reding rnge mesurement system showing the ngle of the reder ntenn 4. Conclusion Fig. 8. Reding rnge mesurement system The current study proposed the cr tg using modified dipole ntenn structure tht includes loopshped mtching terminl. This terminl fcilittes n impednce ir-interfce etween the RFID chip nd ntenn. Also, the dipole ntenn structure hs cr
Eui-Sun Choi, Hk-Yong Lee, Jin-Seong Lee, Kyounghwn Lee, S-Won Lee nd Young-Hie Lee 555 shpe tht provides the following structurl dvntge. Although the tg is lel type whose size is 44 44 mm2, nd the tgged surfce nd the metl rim re out 2.0 mm prt from ech other, the cr tg hs reltively long recognition distnce of 0.9 1.0 m when ttched prllel to the ground surfce. When mesured in rdio-wve nonreflecting chmer, the mximum recognition distnce is out 1.5 m, nd under the ctul operting environment, it is sometimes mesured s 2.0 m or longer. This cn e due to the increse in recognition distnce s the reflection of the rdio wve increses. The result of mesurement in the rdio nechoic chmer confirms tht the cr tg mtches the est t Koren RFID frequencies. The proposed cr tg with these chrcteristics fcilittes ntenn shpe chnge nd impednce ir-interfce. Due to its smll size, it is lso suitle for pplictions tht need to e recognized within the distnce of 1.0 m. It is currently used for formul milk cns in Kore in order to promote trnsprency in distriution nd food sfety mngement. Acknowledgement This work ws supported in prt y MKE & NIPA (Uiquitous Technology Reserch Center) References [1] K. Finkenzeller, RFID Hndook, 2nd edition, John Wiley & Sons, Englnd, 2003. [2] G. De Vit nd G. Innccone, "Design criteri for the RF section of UHF nd microwve pssive RFID trnsponders, Microwve Theory nd Techniques," IEEE Trns. Vol. 53. Issue 9, pp. 2978-2990, Sep. 2005. [3] Q, Chen nd B. Hu, "Novel UHF RFID tg ntenn with shorted stus mountle on the metllic ojects," ICMMT 2008. Interntionl Conference, Vol. 4, pp. 1822-1824, Apr. 2008. [4] D. Kim nd J. Yeo, "Low-Profile RFID Tg Antenn Using Compct AMC Sustrte for Metllic Ojects," IEEE AWPL, Pge(s):1 3, 2008. [5] K.H. Lee nd Y.C. Chung, "High gin Ygi-Ud UHF RFID tg ntenns," IEEE AP-S Interntionl Symposium, pp.1753-1756, Jun. 2007. [6] NXP Semiconductors Co., SL3ICS1002 G2XM, Rev. 3.2, Jul. 2008. [7] J.S. Jung, J.S. Lee, K. Lee, J.M. Yng, "900 MHz Common RFID Lel Tg Impednce Anlysis Using Produced Prove Sttion," 2010 Winter Symposium, Koren Informtion nd Communictions Society, Vol. 41, pp.165, Fe. 2010. [8] http://www.epcglolinc.org/, Sttic Test Method, Rev 1.9.4, My 2008 Eui-Sun Choi He received his M.S. nd Ph.D. degrees in Electronic Mterils Engineering from Kwngwoon University. His reserch interests re microwve dielectric cermics, LTCC, ntenn, nd RFID. Hk-Yong Lee He received his M.S. nd nd Ph.D. degrees in Electric Wve Engineering from Kwngwoon University. He is the CEO of SONOVISION Co., LTD. His reserch interests re sensor, ntenn, nd RFID. Jin-Seong Lee He received his M.S. nd Ph.D. degrees in Electric Wve Engineering from Kwngwoon University. He is resercher of the Uiquitous Technology Reserch Center, Kore. His reserch interests re ntenn nd RFID. Kyounghwn Lee He received his B.S. nd M.S. degrees in Computer nd Communiction Engineering from Degu University. He is resercher of the Uiquitous Technology Reserch Center, Kore. His reserch interests re ntenn nd RFID. S-Won Lee He received his B.S. nd M.S. degrees in Electronic Engineering from Cheongju University. He is professor of the Deprtment of Informtion Communiction nd Homenetwork t Chungju College of Kore Polytechnic Ⅳ. His reserch interests re filter, ntenn, nd RFID. Young-Hie Lee He received his M.S. nd Ph.D. degrees in Electricl Engineering from Yonsei University. He is professor of the Deprtment of Electronic Mterils Engineering t Kwngwoon University in Seoul, Kore. His reserch interests re solgel processing, piezoelectric cermics, thin film, microwve dielectric cermics, sensor, nd memory.