A Three Element Yagi Uda Antenna for RFID Systems

Transcription

1 2014 IJEDR Volume 2, Issue 1 ISSN: A Three Element Yagi Uda Antenna or RFID Systems Pristin K Mathew Department o Eletronis and Communiation Karunya University, Coimbatore, India pristinkmathew@karunya.edu.in Abstrat This paper presents a simple broad band printed Yagi Uda antenna operating at a resonant requeny o 400 MHz that an be used or Ultra High Frequeny (U.H.F) appliations like Radio Frequeny Identiiation (R.F.I.D) Systems. The antenna is horizontally polarized and onsists o a dipole, a reletor and a set o three diretors whih are plaed 3 m above the ground. The impedane bandwidth o the proposed antenna is about 21.5 % and the maximum gain in the pass band requeny range is 16.3 dbwith a return loss o -19 db.the design ormulas and various antenna parameters like Return loss, Voltage Standing Wave Ratio (V.S.W.R), Input impedane, Gain et o the proposed antenna is observed and the simulation is arried out using an eletromagneti simulation tool, CADFEKO. The results show that the designed antenna is well suited or Ultra High Frequeny appliations like RFID systems. IndexTerms Printed YagiUda antenna, Reletors, Diretors, Driven element, Parasiti elements, CADFEKO. I. INTRODUCTION Yagi Uda antenna was disovered by ShintaroUda and Hidetsugu Yagi and was simply known as the Yagi antenna. It is a highly diretional antenna that onsist o an array o dipoles (Driven Element) and a set o parasiti elements behind the driven element having more than one diretor and a reletor that improves the radiation properties o the antenna when properly aligned. It is a highly diretional antenna in the sense that it radiates greater power in one diretion thereby reduing the intererene rom all other soures. Yagi Uda antenna is very widely used due to various advantages like low ost, high gain, easy struture et. During the early days o its disovery the antenna was mainly used in Televisions but later, suh antennas ound appliations in all other ields like Radars, RFID s, Satellites et. Yagi Uda antenna an also be used or radio requeny identiiation in whih a tag attahed to an objet will be identiied at the radiorequenies. Suh tags may ontain muh useul inormation and may emit mirowave or ultra high requeny waves. A Driven element or Dipole is the point where the eeding is provided. The eeding is usually provided towards the entre o the dipole so that maximum power transer takes plae rom transmitters to antennas. A dipole is said to be resonant when its length is hal the wavelength o operation. The dipoles need not be always linear in struture, it may be olded also. The geometry o the dipole greatly determines the gain o the antenna in orward and bakward diretions. Eah o these dipole elements are arranged on a supporting boom struture. The ield provided by the driven element indues urrents in the parasiti elements o the array through mutual oupling and determines most o the parameters o the antenna. The shortest parasiti element is alled a Diretor. It is a highly resonant struture and operates at a requeny less than the driven element. Diretors provide a diretional position to the struture with high gain. The length o a diretor is less than that o a driven element and may vary eah time depending on the spaing between the diretors whih is o the range λ. The number o diretors used may depend on the physial size o the antenna and inreasing the number o diretors may enhane the diretivity (Gain) o the antenna. The length and spaing o a diretor has signiiant eet on the orward and bakward gain and provides the antenna with a diretional radiation pattern. Diretors are the most important elements present in the array. A reletor is usually plaed at the ends o the driven element. The length o a reletor is more than that o a driven element but its requeny o operation is less than the driven element. The length o a reletor depends on the dimensions o eah element in the array whereas the spaing between the reletors will be o the order o λ. The length and spaing o a reletor also aets the gain and input impedane o an antenna. The reletor and the diretor are designed to be in parasiti mode, sine no eeding is provided to these elements. These elements may vary the radiation properties o the driven element. Varying the length between the driven element and parasiti element auses the radiation pattern to be reversed in the array. A low ost Yagi Uda antenna operating at short range (1-100 m) Radio Frequeny Identiiation System operating in the Ultra High requeny (UHF) bands (300MHz 3000 MHz) is proposed in this paper. Setion II disusses the proposed antenna design while setion III analyses the results and the paper end with a onlusion in setion IV. II. ANTENNA DESIGN The geometry o the proposed antenna is shown in Fig 1. It onsist o a dipole, reletor and a set o 3 diretors designed to operate at a resonant requeny o 400 MHz and is said to be horizontally polarized. Table I shows the parameters o the designed antenna. A port is attahed to the middle o the dipole element and is ed by a voltage soure. IJEDR International Journal o Engineering Development and Researh ( 30

2 A Three Element Yagi Uda Antenna or RFID Systems Figure 1. Geometry o the proposed antenna The general rules o design or a Yagi Uda antenna operating at 400 MHz is given by Reletor Length, L (1) R Ative Element Length, L (2) i Diretor Length, L (3) D Spaing between elements, d = 0.25 (4) λ is the wavelength in metres, is the veloity o light in reespae (3x10 8 m/s), is the operating requeny in MHz. TABLE I PARAMETERS OF THE PROPOSED ANTENNA Parameters L R L i L D d Value (mm) When the diretor is plaed lose to the driven element its length should inrease but does not derease when they are moved away rom the driven element. Length o the array is onsidered to be most important than the atual number o elements present in the array. The position o irst diretor element and the spaing o reletors deides the mathing o the Yagi. Antenna gain depends on the number o array elements. As the number o elements inreases, the gain inreases provided the elements are not separated ar apart and they are equal in length. Fig 2 shows the three dimensional view o the designed antenna using CADFEKO. Figure 2.Antenna designed using CADFEKO IJEDR International Journal o Engineering Development and Researh ( 31

3 A Three Element Yagi Uda Antenna or RFID Systems III. RESULTS AND DISCUSSION The proposed antenna is simulated using CADFEKO and various parameters suh as Return loss, VSWR, Gain, Input impedane et are observed. Fig 4 shows the return loss o the Yagi Uda antenna that operates at a requeny o 400MHz. Return loss indiates the amount o power lost to the load and does not return as radiation. I Pr and Pi indiates the power releted and suppied by the soure respetively, P r Return Loss = 10 log (5) Pi The bandwidth o the antenna is measured rom the return loss urve. The Yagi Uda antenna has an impedane bandwidth o 84 MHz with return loss <-10 db. Impedane Bandwidth is given by h l Impedane Bandwidth (%) = 100 (6) l, h and 2 l h (7) are the upper ut o, lower uto and entre requenies o the antenna with return loss <-10dB. Figure 3. Return loss o the proposed antenna VSWR o the Yagi Uda antenna is less than 2 or all the requenies between 400 and 440 MHz and is shown in ig 4. VSWR desribes the level o impedane mathing to a radio or transmission line o 50Ω to whih it is onneted. It is expressed in terms o Reletion oeiient and is given by VSWR = 1 1 (8) Figure 4 VSWR o the designed antenna Fig 5 shows the 3D plot o gain (in db) o the Yagi Uda antenna element at 400 MHz. The observed gain at resonant requeny o the proposed antenna is 16.3 db whih is shown in ig 6. Antenna gain is the ability o an antenna to diret radiations in a partiular diretion. Gain o an isotropi antenna is unity. IJEDR International Journal o Engineering Development and Researh ( 32

4 A Three Element Yagi Uda Antenna or RFID Systems Figure 5. 3-D plot o gain o the antenna at 400 MHz The radiation pattern plot o the Yagi Uda antenna in E plane (XZ) and H plane (YZ) at 400 MHz is plotted in ig 6 a) and 6b)) and ig 6) shows a 3 dimensional view o the pattern. Antenna radiation pattern is deined as a graphial representation o radiation o an antenna as a untion o spae o-ordinates and is usually expressed in terms o ar ield pattern. Figure 6. a) Radiation pattern in XZ plane b) Radiation pattern in YZ planec) 3D view o Radiation pattern at 400 MHz Fig 8 plots the impedane graph o the Yagi Uda antenna. It is observed that the input impedane o the Yagi Uda antenna at entre requeny o 400 MHz is 52 Ω whih is very lose to 50Ω. Hene good impedane mathing is ahieved between the antenna and the transmitter and maximum power is transerred. Figure 7. Impedane plot o the antenna Current distribution plot at 400 MHz is illustrated in ig 8. Most o the radiation ields are onentrated near the dipole element sine it ats as the driven element. IJEDR International Journal o Engineering Development and Researh ( 33

5 A Three Element Yagi Uda Antenna or RFID Systems IV. CONCLUSION Figure 8. Current distribution o the antenna at 400 MHz A printedyagi Uda antenna with 3 diretors, a reletor and a driven element is designed using CADFEKO sotware. The antenna operates in the Ultra High Frequeny Band ( MHz) and the bandwidth o operation an be inreased by inreasing the reletor length and by reduing the diretor length. Eet o these antenna elements on various antenna parameters are observed and evaluated. A return loss o -19 db, gain o 16.3 db, and VSWR<2 is ahieved or the proposed antenna when operated at 400 MHz. so the designed antenna is well suited or RFID systems operating in the Ultra High Frequeny bands. REFERENCES [1] K.D.Prasad Antenna and wave propogation [2] Warren L. Stutzman, Antenna Theory And Design, Chapter 5.4.Yagi-uda Antenna [3] C. A.Balanis Antenna theory analysis and design 2nd Edition, John Wiley and Sons, New-York [4] Sun, B.H., S.G Zhou, Y.Fwei, and Q.-Z Liu, Modiied two elements and Yagi-uda-antenna with tunable beams with tunable beams progress,progress eletromagneti researh, Vol. 16, pp , 2009 [5] H. Yagi, Beam Transmission o ultra short waves proeeding o the IRE vol. 16, pp , June [6] Bemani, M. and S. Nikmeh, \A novel wide-band mirostripyagi-uda array antenna or WLAN appliations," Progress InEletromagnetis Researh B, Vol. 16, , [7] Bayderkhani, R. and H. R. Hassani, Wideband and low side lobe linear series FED Yagi-link antenna array," Progress In Eletromagnetis Researh B, Vol. 17, , [8] Chou, H. T., K. L. Hung, and C. Y. Chen, Utilization o a Yagi antenna diretor array to synthesize a shaped radiation pattern or optimum overage in wireless ommuniations," Journal o Eletromagneti Waves and Appliations, Vol. 23, No. 7, , [9] Misra, I. S., R. S. Chakrabarty, and B. B. Mangaraj, Design,analysis and optimization o V -dipole and its three-element Yagi-Uda array," Progress In Eletromagnetis Researh, PIER 66, , 2006 [10] Q. Xin,F.-S.Zhang, B.H.Sun,Y.l-Zou,and Q.-Z.Liu, Dual band Yagi-Uda Antenna or wireless ommuniation Progress in Eletromegnati researh,vol.16, ,2010 [11] Teisbaek, H. B. and K. B. Jakobsen, Koh-ratal Yagi-Uda antenna," Journal o Eletromagneti Waves and Appliations, Vol. 23, , [12] Zheng, G., A. A. Kishk, A. B. Yakovlev, and A. W. Glisson, Simpliied eed or a modiied printed Yagi antenna," Eletronis Letters, Vol. 40, No. 8, , [13] Cheng, D. K., Gain optimization or Yagi-Uda arrays," IEEE Antennas and Propagation Magazine, Vol. 33, No. 3, 42-46, Jun [14] Mao, J. Y., Z. R. Li, Q. X. Guo, H. Zhang, X. Q. Zhang, X. F. Wu, and Y. Yang, A wideband quasi-yagi antenna with arrow-shaped dipoles or digital TV band appliations," Journal o Eletromagneti Waves and Appliations, Vol. 26, No. 13, , [15] Majid, H. A., M. K. A. Rahim, M. R. Hamid, and M. F. Ismail, Frequeny and pattern reonigurable Yagi antenna," Journal o Eletromagneti Waves and Appliations, Vol. 26, Nos. 23, , IJEDR International Journal o Engineering Development and Researh ( 34