Jounal of Applied Science and Agicultue, 9(16) Octobe 214, Pages: 1-15 AENSI Jounals Jounal of Applied Science and Agicultue ISSN 1816-9112 Jounal home page: www.aensiweb.com/jasa A Design of New Bluetooth Antenna fo RFID Application Daiush Toabi, Ahmad khosavi, Vali Ahmadpou, Rohhallah Adelifad Sama technical and vocational taining college, Islamic Azad Univesity, Khoamabad banch, Khoamabad, Ian A R T I C L E I N F O Aticle histoy: Received 11 June 214 Received in evised fom 25 July 214 Accepted 2 Septembe 214 Available online 1 Octobe 214 Keywods: Radio Fequency Identification RFID, TAG, Readable Range R, and BT Antenna A B S T R A C T This pape coves the design and optimization of new antenna fo RFID applications at micowave fequencies. The stuctue is designed to esonate at 2.45GHz one of the FID fequencies. In fact, the development of RFID antenna is of theoetical significance and pactical value fo the RFID system. In this chapte, the RFID technology is biefly intoduced, and the opeating pinciple of the RFID system is descibed. An equivalent esonant model is pesented based on a model of tiangula antenna. Simulation esults given by ou appoach, show that the antenna and its model have the same esonant fequency at 2.45GHz but with a little diffeence in Bandwidth. 214 AENSI Publishe All ights eseved. To Cite This Aticle: Daiush Toabi, Ahmad khosavi, Vali Ahmadpou, Rohhallah Adelifad, A Design of New Bluetooth Antenna fo RFID Application. J. Appl. Sci. & Agic., 9(16): 1-15, 214 INTRODUCTION Radio Fequency Identification is an automatic identification technology of objects. The RFID system is made up of a Reade and a Tag which is attached to objects. The identification does not necessitate a contact between the eade and the tag. The antenna is the main component of RFID system. It epesents the channel between the eade and the tag figue (1). As RFID fequencies aise into micowave egion, the antenna should be caefully designed in ode to educe the tag size and to maximize the tansfe of powe into and out of the tag (Ami Galehda, 27). Fig. 1: RFID system Thus, we should in choosing the antenna consideate some points. Fist, the type of the antenna should diffe fom the eade to the tag and fom an application to anothe. Second, the antenna should be small, easy when made and cheap when poduced. Thid, the RF chaacteistics of the antenna should be acceptable consideing impedance, gain and diectivity. On the one hand, the eduction of the size of the antenna means a possibility to have a small TAG which can be placed anywhee without occupying a lage place. On the othe hand, one of the impotant chaacteistic of RFID system is the eadable ange R. The eadable ange is the maximum distance that the Inteogato can ead fom the TAG. This distance depends essentially on the gain of both the TAG antenna and the eade antenna as shown in the equation 1 (Klaus Finkenzelle, 23): 2. 2 P 4 1. G G R eade T 4 P 3 (1) Coesponding Autho: Daiush Toabi, Sama technical and vocational taining college, Islamic Azad Univesity, Khoamabad banch, Khoamabad, Ian E-mail: toabi.daiush@yahoo.com
11 Daiush Toabi et al, 214 Jounal of Applied Science and Agicultue, 9(16) Octobe 214, Pages: 1-15 With: P3 = Powe eceived in the TAG P1 = Powe tansmitted by the Inteogato G eade = The Gain of inteogato antenna G T = The Gain of TAG antenna In this pape, we popose a new small tag antenna. The patch is based on a bow tie antenna. It simulated using Advanced Design System (ADS 29). The impotance of the new patch is that we educe the oiginal antenna size that esonates at 2.45GHz by moe than 7%. In ode to validate ou wok, we simulated an electical model of the stuctue and we compae the ADS esults of the physical patch. A bt small antenna: Geomety of tiangula antenna: Figue (2) shows the geomety of an equilateal tiangula micostip patch on a dielectic substate with a gound plane. The antenna is mounted on a substate mateial with a thickness h=3.2mm, a dielectic constant 2.6 and loss tangent (tangδ) =.2. Fin. 2: Tiangula Antenna stuctue Electical model of tiangula patch: The ecent study wok of micostip patch have demonstate that the tiangula patch have a adiation chaacteistic simila to a ectangula patch but with a educed dimensions (Nasimuddin and A.K. Vema Ami, 24; Geoge, 1996; Xu-Pu zhang and Shum-Shi Zheng, 22). Fo this eason, to studies ou antenna, we can eplace the tiangula electical model by its equivalent electical ectangula model figue (3). Fig. 3: Electical model of Tiangula antenna. To calculate the model paametes, we use the fomula pesented in (Celal YILDIZ and Keim GÜNEY, 1998) to evey tiangle. Z in R jx (2) f _ f R R T f f Z in j X L 2 2 f _ f 1 2 f _ f T 1 f f T f f Resonant esistance R: The esonant esistance is calculated using equation (3) as in (Celal YILDIZ and Keim GÜNEY, 1998):
12 Daiush Toabi et al, 214 Jounal of Applied Science and Agicultue, 9(16) Octobe 214, Pages: 1-15 T H 2 x R cos ( ) f A a f : Resonant fequency T : uality facto : Dynamic pemittivity X : The distance of the feed point fom the edge of the patch. a: length of tiangle H : thickness of dielectic A: aie of tiangle1 1 1 1 1 T R C D (4) c R 4 f H 1 D Tg.786 fz a ( W ) H c p a R : Radiation quality facto D : Losses in the dielectic C : Losses in the conducto (8) The impedance of an ai filled micostip line W 1.441.82 6 2 2H Z ( w) a ( 1) W 1.451 Ln.94 2 2H Z a ( w) Z a ( w, 1) W W ( H ) H 2 1 H W.94 W 2H p a W 2 W Ln2 exp.94 H 2H W 2 H C ( ) C ( ) 2 (3) (5) (6) (7) (9) (1)
13 Daiush Toabi et al, 214 Jounal of Applied Science and Agicultue, 9(16) Octobe 214, Pages: 1-15 1 (,, ) ( ) A eff HW A C H n m 2 n c Z ( 1, H, W ) H 1, j j 2, j (11) 377 f ( w ) 2 2 (,, 1) H Z W H Ln 1 ( ) 2 w h W H (12).758 3.666 f ( w ) 6 (2 6) exp H W H (13) Capacitance C, Inductance L: To detemine the capacitance C we use the fomula of. To detemine L, we know that: es 2 f 1 1 es L LC 2 esc C. (14) (15) Inductive eactance of Coax: Inductive eactance of Coax is calculated via the equation below: 377 fh c X L Ln c fd (16) The model is simulated and then compaed to physical patch. The esults ae epesented in figue (4). The tiangula patch and its electical model pesent a esonant fequency about 2.45GHz but with a diffeence in Band width because of the diffeence between calculated and simulated losses. The gain and diectivity equal espectively 8.1dB and 8.2dB. Fig. 4: Retun loss of both physical and model of tiangula patch Geomety of poposed bow tie antenna: The poposed patch is constituted of fou tiangle patches disposed on plana stuctue figue (5). This stuctue is inspied fom the bow tie patch antenna. Only one tansmission line links the fou tiangles. The patch is mounted on a dielectic with a thickness h =.65mm and pemittivity 2, 3.
14 Daiush Toabi et al, 214 Jounal of Applied Science and Agicultue, 9(16) Octobe 214, Pages: 1-15 Fig. 5: Poposed bow tie antenna stuctue. Electical model: To analyze this antenna, an electical model is developed. The model is inspied fom the electical model of tiangula patch descibed by Nasimuddin and A. K. Vema in [3] whee they eplaced the tiangula patch by its equivalent ectangula patch and then they built the tiangula electical model. The tansmission line is also modeled by an RLC cicuit. The electical model is epesented in figue (6). Fig. 6: Electical model of poposed bow tie antenna. The RLC paametes ae calculated using the fomulas developed in section 1. RESULTS AND DISCUSSION Dimensions: The poposed patch is designed to esonate at 2.45GHz (one of the RFID fequencies). The odinay dimension of an antenna is about 5.8cm 5.8cm. The dimension of the pesent antenna is about 1.4mm 6.2mm which means that the dimensions of antennas ae educed by moe than 7%. Hence we can obtain a vey small tag with a good chaacteistic. Retun loss: The etun loss is shown in figue (7). The esonant fequency is 2.45 GHz. The antenna epesents a band width about 8 MHz which is acceptable to RFID system. The magnitude S11 attainted 25dB.
15 Daiush Toabi et al, 214 Jounal of Applied Science and Agicultue, 9(16) Octobe 214, Pages: 1-15 Fig. 7: Retun loss of both physical and model of poposed bow tie antenna. Gain and Diectivity: As the eadable ang R depends on and diectivity, we should guaantee suitable ones. Fo ou poposed bow tie antenna, the gain and the diectivity ae successively 2.1dB and 5.2dB which ae acceptable paametes to an RFID system. Finally, when we compae physical patch and electical model we can see that the esonant fequency is the same and thee is a little diffeence in band width due to the diffeence in losses between theoy and eal. Conclusion: The eduction of antenna and tag size is of geat inteest fo many applications. In this way, many techniques ae applied to popose a vey small patch. On the one hand, in this pape we think that educing antenna size by moe than 7% is vey impotant. On the othe hand, amelioating antenna paametes and deceasing antenna cost ae ou pioities in ou futue eseach. REFERENCES Ami Galehda, V. David Thiel and G. Steven O Keefe, 27. Antenna Efficiency Calculations fo Electically Small, RFID Antennas, IEEE Antenna Wieless Popagation Lettes, 6: 156-159. Klaus Finkenzelle, 23. RFID HANDBOOK, Second Edition. Nasimuddin and A.K. Vema Ami, 24. Fast and accuate model fo analysis of equilateal tiangula patch antenna, Jounal of Micowaves and Optoelectonics, 3: 99-11. Celal YILDIZ, Keim GÜNEY, 1998. Simple model fo the impedance of ectangula micostip antenna, jounal of engineeing sciences, pp: 733-738. Geoge, J., M. Deopukuma,, C.K. Aanadan, P. Mohanan and K.G. Nai, 1996. New compact micostip antenna, Electon let, 32(6): 58-59. Xu-Pu zhang, Shum-Shi Zheng, 22. Resonant fequency and dual-fequency opeation of a bow-tie micostip antenna, IEEE AP-S Int Symp, 2: 6-63.