Triple-Band Printed Dipole Antenna for RFID/GPS/BLE Applications

Transcription

1 Progrss In Elctromagntics Rsarch M, Vol. 7, 11 2, 218 Tripl-Band Printd Dipol Antnna for RFID/GPS/BLE Applications Khodor Jbbawi *, Matthiu Egls, and Philipp Pannir Abstract Progrss in wirlss communication rquirs antnnas that work on multi-band simultanously. This papr prsnts a dsign mthod for a multi-band antnna using printd dipol with L-slots fd by a singl coaxial cabl. Using this mthod, a tripl-band antnna that oprats at MHz for RFID (radio frquncy idntification), 1575 MHz for GPS (global positioning systm) and 2.45 GHz for BLE (blutooth low nrgy) was dsignd and manufacturd. Th antnna s paramtrs for tripl-band opration ar invstigatd and discussd. In this antnna dsign, ANSYS HFSS softwar using highly accurat finit lmnt mthod (FEM) simulation is mployd to analyz th ntir structur. Th dsignd antnna is manufacturd using an FR-4 substrat with a dilctric constant (ɛ r ) of 4.4 and thicknss (h) of 1.6 mm. Many prototyps hav bn fabricatd, and good agrmnt btwn simulations and masurmnts has bn achivd. Th prformanc of th prototyps has bn masurd in a standard far-fild anchoic chambr. Th proposd tripl-band antnna is also tstd by masuring th rading distanc, and it is found that th proposd antnna can b usd for RFID applications. 1. INTRODUCTION Multi-standards antnnas hav rcivd significant importanc du to th limitd room in modrn portabl wirlss communication dvics which may rquir an antnna to work at svral frquncis simultanously. This antnna should b planar, lightwight, and compact, so that it can b asily mbddd in activ dvics for wirlss communications. Thrfor, thr ar various multi-band antnnas that hav bn dvlopd ovr th yars, which can b utilizd to achiv multi-band oprations, such as PIFA [1], monopol antnna [2] and othrs [3, 4], whil printd dipol antnnas ar attractiv bcaus thy ar simpl, asy to fabricat and asy to intrfac with an Application Spcific Intgratd Circuit (ASIC) microchip [5]. In rcnt yars, svral multi-band printd dipol antnnas hav bn rportd. A tripl-band printd dipol antnna using parasitic lmnts was proposd in [6]. In [7], a tripl-band omnidirctional antnna which compriss thr pairs of dipols placd back to back and printd on a dilctric substrat was prsntd for WLAN applications (2.4 GHz, 5.2 GHz and 5.8 GHz). A coplanar dipol antnna with an invrtd-h slot has alrady bn proposd for.9/1.575/2./2.4/2.45/5. GHz applications [8]. Most of ths dsigns us an lctromagntic simulation softwar (HFSS, CST, FEKO) to analys th ntir structur. [12 14] prsnt dsigns with microstrips, flangs, strips and patchs. Th addd valu of ths paprs is that thy rfr to smi-analytical mthods for trating th dvics and structurs. A systmatic mthod for dsigning a multi-band antnna is an approach that can b applid to any st of targt frquncis. Existing tchniqus such as [5] of dsigning multi-band printd dipol antnna ar not fully systmatic, sinc thy do not allow to control and manag all bands. [5] prsnts Rcivd 2 May 218, Accptd 9 Jun 218, Schduld 22 Jun 218 * Corrsponding author: Khodor Jbbawi (Khodor.jbbawi@im2np.fr). Th authors ar with Institut Matriaux Microlctroniqu Nanoscincs d Provnc, UMR CNRS 7334, Aix-Marsill Univrsit, 5 ru Enrico Frmi, Batimnt Nl, Tchnopol d Chatau Gombrt, Marsill Cdx 13, Franc.

2 12 Jbbawi, Egls, and Pannir an antnna that oprats at thr diffrnt frquncis by conncting two branchs to th prim dipol. Howvr, th goal of that study was not to dfin a systmatic mthodology for dsigning multi-band antnnas but to dsign a spcific multi-band antnna for RFID. Th multi-band antnna dsignd in this work is a typical application of th nw proposd dsign mthodology. In [6], a tripl-band opration is achivd by using a dipol with parasitic lmnts. This dsign is printd on two mtallic layrs which maks it mor complx. Morovr, th parasitic lmnt is fd by coupling from th driving dipol which rducs th prformancs, spcially th gain of th band providd by th parasitic lmnt. This work proposs a systmatic mthod to achiv a multi-band antnna using a dipol with L-slots fd through a singl fding port. This mthod provids a formula in ordr to comput th lngth of th L-slot for any targt frquncy. In addition, th managmnt and control of th rsonant frquncy for ach band without affcting th othr bands is availabl by changing th lngth of th L-slot rsponsibl for that band. This proposd mthod is applid in ordr to dsign a tripl-band printd dipol antnna for RFID ( MHz), GPS (1575 MHz) and BLE (2.45 GHz). Th tripl-band antnna is printd on a singl mtallic layr and prsnts a vry good rturn loss, bandwidth and gain for ach band. A typical application for this typ of antnna can b th monitoring of patints and th tracking of logistics for a larg multi-sid mdical institut. In ach of th branchs, a ntwork of mobil radrs ar implantd, ach of which mbddd with th proposd antnna. Th RFID band is usd for rading th data (tmpratur, puls) stord in UHF RFID tag placd on th arms of patints. Th BLE band is mant for snding th information to th data cntr. Th rlativly xact position of ach radr can b providd by GPS band. In ordr to validat th prformanc of th fabricatd antnna, a functional RFID rading distanc tst is applid on th first band (UHF RFID) of th proposd antnna by using a commrcial Radr modul (Micro ThingMagic [9]) and commrcial tag (Lintrak C [1]). 2. ANTENNA DESIGN This sction prsnts th followd mthodology to dsign a multi-band dipol antnna with L-slots. Th proposd approach bgins with singl rsonant frquncy. Start with th simpl dipol in Figur 1 to show th stps of this mthodology. This dipol has a singl rsonant frquncy at 868 MHz (L is about λ /2 in fr spac) as shown in Figur 2. Figur 2 prsnts th imaginary componnt of th impdanc Im(Z 11 ) against frquncy. It is obsrvd that a mod rsonats whn th valu of Im(Z 11 ) changs sign, whil incrasing. This phnomnon is known as inductiv rsonanc. (c) Figur 1. Gomtry of th simpl dipol without slots, with on L-slot, (c) with two L-slots (units: mm). Aftr th rsonant frquncy has bn achivd xactly at th cntr of th first dsird band, L- shapd slots wr insrtd in th dipol to achiv multiband opration. Ths slots wr insrtd on by on insid th dipol, whr th lngth of ach slot is about λ/2 of th targt frquncy. Figur 1 shows th dipol with on L-slot (L2) for doubl-band opration. Figur 1(c) shows th dipol with two L-slots (L2,L3) for tripl-band opration. Each L-slot adds a nw band as shown in Figur 3. Th

3 Progrss In Elctromagntics Rsarch M, Vol. 7, Rturn Loss [db] -1-2 Dipol rsonant frquncy Dipol without slots First harmonic of dipol rsonant frquncy Im ( Z 11 ) Dipol rsonant frquncy Dipol without slots First harmonic of dipol rsonant frquncy Frquncy [GHz] Frquncy [GHz] Figur 2. S 11,Im(Z 11 ) of th dipol shown in Figur Rsonanc 1 Dipol rsonant frquncy Rsonanc 2 Effct of first slot Rsonanc 3 Effct of scond slot Rturn Loss [db] -1 Rsonanc 1-2 Dipol rsonant frquncy Rsonanc 2 Effct of first slot First harmonic of Rsonanc 1 Rsonanc 3 Effct of scond slot Dipol without slots Dipol with on L-slot Dipol with two L-slots Frquncy [GHz] Im ( Z 11 ) First harmonic of Rsonanc 1-6 Dipol without slots Dipol with on L-slot -8 Dipol with two L-slots Frquncy [GHz] Figur 3. S 11,Im(Z 11 ) of th diffrnt dipols shown in Figur 1. L-shapd slot crats a nw branch lmnt which modifis th profil of th Im(Z 11 ) by incrasing th numbr of inductiv rsonancs at high frquncis as shown in Figur 3. Th approach mntiond abov is usd to dsign a tripl-band antnna for RFID ( MHz), GPS (1575 MHz) and BLE (2.45 GHz). Th lngth of th dipol is th only paramtr that affcts th rsonant frquncy of th first band. On th othr hand, th paramtrs that affct th highr rsonant frquncis of th antnna ar th L-slots lngths. As th antnna is a symmtrical dipol, th lngth of ach of ths branchs L1, L2 andl3 is about a quartr of th ffctiv wavlngth of th targt frquncy. Morovr, th dipol usd is a slot lin of rctangular gomtry, so th formula in [11] of slot transmission lin can b usd to calculat th valu of ɛ ff, λ ff and L ff as follows. Th ffctiv dilctric constant (ɛ ff ) of a slot lin: ɛ ff = (ɛ r +1) (1) 2 Th ffctiv lngth of ach branch of dipol: L ff = λ ff 4 = c ( ɛff f 4 ) (2) whr λ ff = Effctiv wavlngth c = Vlocity of light f = Targt frquncy ɛ r = Diltric Constant Th gomtry and photograph of th proposd antnna ar prsntd in Figur 4. Th optimal gomtrical paramtrs of th proposd antnna ar obtaind by using Ansoft high-frquncy structur

4 14 Jbbawi, Egls, and Pannir Figur 4. Gomtry and photograph of th proposd antnna. Simulatd Masurd Rturn Loss [db] Frquncy [GHz] Figur 5. Simulatd and masurd S 11 of th proposd antnna. Tabl 1. Paramtrs of th proposd antnna (units: mm). L L 1 L 2 L S 1 S 2 W W 1 W 3 g b c simulator vrsion 17. Th discrt port of 5 Ω was placd across a.5 mm gap at th cntr of th antnna. As shown in Figur 4, th tripl-band antnna is dsignd and printd on a singl mtallic layr mm 2 of an FR4 dilctric substrat which has prmittivity of 4.4 and thicknss of 1.6 mm. All dtaild paramtrs of th proposd antnna ar summarizd in Tabl 1. Th dipol which has a rsonanc frquncy at 9 MHz is altrd by two L-shapd slots, L2andL3, which add two additional bands at 1575 MHz and 2.45 GHz, rspctivly. Small rctangular slots wr placd on th dipol in ordr to rduc th siz of th proposd antnna. Th aim of ths rctangular slots is to shift th first rsonant frquncy to lowr frquncis without adding inductiv rsonancs. Th masurmnt of rturn loss is don using a Rohd & Schwarz ZVA24 Ntwork Analyzr. Figur 5 shows simulatd and masurd rturn losss (S 11 ) of th proposd antnna as a function of frquncy. Th masurd rsults ar in good agrmnt with th prdictd simulatd ons. Rsults obtaind indicat that th proposd antnna provids tripl oprating frquncis of 9 MHz, 1575 MHz and 2.45 GHz and thr good bandwidths (S 11 < 1 db) of 61 MHz (at 9 MHz), 83 MHz (at 1575 MHz) and 758 MHz (broadband at 2.45 GHz).

5 Progrss In Elctromagntics Rsarch M, Vol. 7, Th broadband at th third rsonant frquncy (2.45 GHz) is du to th coupling btwn th first harmonic of th first rsonant mod and th third rsonant frquncy. This is achivd by dcrasing b and kping 4 fixd. Th ffct of b on th bandwidth of 2.45 GHz is shown in Figur 6 which dpicts th rturn loss of th proposd antnna against frquncy with diffrnt valus of b. It is obsrvabl that th bandwidth at 2.45 GHz incrass whn th valu of b dcrass, whil 4 rmains fixd. Morovr, th coupling btwn L1andL3 can b found in Figur 6 by plotting th surfac currnt distributions of th proposd antnna at 2.45 GHz. -1 Rturn Loss [db] b = 3 mm b = 7.2 mm b = 12.2 mm b = 17.2 mm Frquncy [GHz] Figur 6. S 11 of th proposd antnna with diffrnt valus of b. Simulatd surfac currnt distributions of th proposd antnna at 2.45 GHz. 3. RESULTS AND DISCUSSION A study on th ffcts of paramtrs L2 andl3 on th impdanc matching for th proposd antnna is conductd, whil L1 rmains fixd at 5 mm. Figur 7 and Figur 8 rspctivly show th simulatd rturn loss and ralisd gain with rspct to th variation of L3. In this cas, L2 isfixd at 26.3 mm, and as w can s in Figur 7 and Figur 8, th third rsonant frquncy is shiftd to lowr frquncis and dcoupld from th harmonic of first rsonant frquncy whn th lngth of L3-slot incrass, whil kping c fixd. Stting L3 to 16.7 mm, th ffct of th variation of L2 canb shown in Figur 7 and Figur 8 which indicat that th GPS band undrgos th sam shift ffct as th 2.45 GHz band whn th lngth of L2-slot incrass, whil kping b fixd. Thrfor, th only paramtr that affcts th rsonanc frquncy of any band is th lngth of th dipol or L-slot which provids that particular band. Graphs of masurd and simulatd gains vrsus frquncy of th proposd antnna ar plottd in Figur 9. It is obsrvd that th antnna has a good gain in th oprating bands and a vry small gain L3 = 15.2 mm L3 = 16.2 mm L3 = 19.2 mm L2 = 28.8 mm L2 = 26.3 mm L2 = 24.8 mm Rturn Loss [db] -1 Rturn Loss [db] Frquncy [GHz] Frquncy [GHz] Figur 7. S 11 of th proposd antnna as th function of frquncy for diffrnt valus of L3, L2.

6 16 Jbbawi, Egls, and Pannir 5 5 Ralisd Gain [db] -1-2 L3 = 15.2 mm L3 = 16.2 mm L3 = 19.2 mm Ralisd Gain [db] -1-2 L2 = 28.8 mm L2 = 26.3 mm L2 = 24.8 mm Frquncy [GHz] Frquncy [GHz] Figur 8. Ralisd gain of th proposd antnna as th function of frquncy for diffrnt valus of L3, L Simulatd Masurd Ralizd Gain [db] Frquncy [GHz] Figur 9. Simulatd and masurd gain of th proposd antnna. Tabl 2. Simulatd and masurd rsults of tripl-band printd dipol antnna. Frquncy (GHz) Simulatd Masurd Simulatd Masurd Simulatd Masurd Rturn Loss (db) Bandwidth (MHz) Gain (db) outsid thos bands. Figur 1 shows th masurd and simulatd gains for ach band. Tabl 2 shows th simulatd and masurd rsults of th proposd tripl-band antnna in trm of input rturn loss, bandwidth and gain. Th masurd bandwidth is rcordd for S 11 < 1 db. Th diffrncs btwn th simulatd and masurd gains of th antnna ar.7 db,.6 db and.38 db at 9 MHz, 1575 MHz and 2.45 GHz, rspctivly. Th radiation pattrns of th fabricatd antnna ar masurd in an anchoic chambr. Th masurd E-plan and H-plan radiation pattrns at 868 MHz, 9 MHz, 92 MHz, 1575 MHz and 2.45 GHz ar prsntd in Figur 11. Th pattrns xhibit 8-shapd omnidirctional pattrns for E- plan. Circular radiation pattrns ar obsrvd for H-plan for th proposd antnna. Tabl 3 shows a comparison btwn th proposd antnna and coplanar dipol antnna with Invrtd-H Slot [8] which oprats at sam frquncis and tchd on th sam typ of substrat as th proposd antnna. This comparison is in trms of antnna siz, total ara occupid by th antnna and masurd pak gains (E-Plan and H-Plan) at 9 MHz, 1575 MHz and 2.45 GHz. From this tabl, it

7 Progrss In Elctromagntics Rsarch M, Vol. 7, Ralizd Gain [db] Simulatd Masurd Frquncy [GHz] Ralizd Gain [db] Simulatd Masurd Frquncy [GHz] Ralizd Gain [db] Simulatd Masurd Frquncy [GHz] (c) Figur 1. Simulatd and masurd gain for ach band, RFID band, GPS band, (c) BLE band. Tabl 3. Comparison of th proposd antnna prformanc with [8]. Antnna Siz (mm 2 ) Publishd litratur [8] Proposd antnna Total ara occupid (mm 2 ) Pak Gain (db) 9 MHz 1575 MHz 2.45 GHz E-Plan H-Plan E-Plan H-Plan E-Plan H-Plan Tabl 4. Rading distanc of proposd antnna in vrtical/horizontal orintation at 868 MHz. Rading distanc (cm) Powr (dbm) Vrtical Horizontal can b sn that th proposd antnna is th smallst and has th highst E-Plan/H-Plan gains for all bands. Th majority of th rportd multi-band antnnas hav th drawbacks of larg siz and/or limitd frquncy of opration compard with th proposd dsign in this papr. This antnna also has a simpl structur with ability of managmnt and tunability of bands which othr dsigns rarly offr. Thn, as shown in Figur 12 th fabricatd antnna is connctd to a UHF RFID radr modul (Micro from ThingMagic) in ordr to masur th rading distanc at diffrnt valus of powr using a

8 18 Jbbawi, Egls, and Pannir commrcial UHF RFID tag (Lintrak C). Th masurmnt is takn in vrtical and horizontal orintations for (tag, proposd antnna). As shown in Tabl 4, th proposd antnna has good rading distanc valus. Hnc, it indicats that th proposd antnna can b usd for UHF RFID systm. Lik th first band, th two othr bands will b tstd with commrcial solution. (c)

9 Progrss In Elctromagntics Rsarch M, Vol. 7, (d) () Figur 11. Simulatd and masurd radiation pattrn of tripl-band printd dipol antnna at 868 MHz, 9 MHz, (c) 92 MHz, (d) 1575 MHz, () 2.45 GHz. Figur 12. Photography of RFID functional rading distanc tst of th proposd antnna in vrtical, horizontal orintation.

10 2 Jbbawi, Egls, and Pannir 4. CONCLUSION In this papr, a dsign mthod for a multi-band antnna using dipol with L-shapd slots is prsntd. This mthod was applid to dsign a compact tripl-band printd dipol antnna that oprats at MHz/1575 MHz/2.45 GHz for tracking and monitoring systm. Prototyps of th proposd antnna wr fabricatd and tstd. A vry good rturn loss, bandwidth and gain hav bn achivd for ach band of th proposd antnna. REFERENCES 1. Elsadk, H. and D. M. Nashaat, Quad band compact siz trapzoidal PIFA antnna, Journal of Elctromagntic Wavs and Applications, Vol. 21, No. 7, , Pan, B., R. L. Li, J. Papapolymrou, J. Laskar, and M. M. Tntzris, Low-profil broadband and dual-frquncy two-strip planar monopol antnnas, IEEE Antnnas and Propagation Socity Intrnational Symposium, , Dpu, V., K. R. Rohith, J. Manoj, M. N. Suma, K. Vasudvan, C. K. Aanandan, and P. Mohanan, Compact uniplanar antnna for WLAN applications, IEEE Elctronic Lttrs, Vol 43, 7 72, Elrazzak, M. M. and M. F. Alsharkh, A compact widband stackd antnna for th tri-band GPS applications, Activ and Passiv Elctronic Componnts, Hindawi Publishing Corporation, Abu, M. and M. K. Abd Rahim, Tripl-band printd dipol antnna for RFID, Progrss In Elctromagntics Rsarch C, Vol 9, , Chang,K.,H.Kim,K.S.Hwang,I.J.Yoon,andY.J.Yoon, Atripl-bandprintddipolantnna using parasitic lmnts, Microwav and Optical Tchnology Lttrs, Vol 47, , Wu, Y.-J., B.-H. Sun, J.-F. Li, and Q.-Z. Liu, Tripl-band omni-dirctional antnna for WLAN application, Progrss In Elctromagntics Rsarch, Vol 76, , Lu, Y.-Y. and E. Lin, Dsign of coplanar dipol antnna with invrtd-h slot for.9/1.575/2./2.4/2.45/5. GHz applications, Journal of Elctrical and Elctronic Enginring, Vol 5, No. 2, ThingMagic, 1. Invngo-Txtil, RFwirlss-world, Valagiannopoulos, C. A., Elctromagntic propagation into paralll-plat wavguid in th prsnc of a Skw mtallic surfac, Elctromagntics, Vol 31, , Oct Valagiannopoulos, C., On smoothning th singular fild dvlopd in th vicinity of mtallic dgs, IJAEM, Bown, P. T., A. Baron, and D. R. Smith, Thory of patch-antnna mtamatrial prfct absorbrs, PRA, 216.