Design and simulation of fractal tree antenna for wireless application


Published on

1 Like
  • Be the first to comment

No Downloads
Total views
On SlideShare
From Embeds
Number of Embeds
Embeds 0
No embeds

No notes for slide

Design and simulation of fractal tree antenna for wireless application

  1. 1. INTERNATIONAL JOURNAL OF ELECTRONICS AND International Journal of Electronics and Communication Engineering & Technology (IJECET), ISSN 0976 – 6464(Print), ISSN 0976 – 6472(Online) Volume 3, Issue 1, January- June (2012), © COMMUNICATION ENGINEERING & TECHNOLOGY (IJECET) IAEME ISSN 0976 – 6464(Print) ISSN 0976 – 6472(Online) Volume 3, Issue 1, January- June (2012), pp. 178-187 IJECET © IAEME: Journal Impact Factor (2011): 0.8500 (Calculated by GISI) ©IAEME DESIGN AND SIMULATION OF FRACTAL TREE ANTENNA FOR WIRELESS APPLICATION Sanjay V Khobragade1, Anitha V R2 1. Department of EXTC, Dr. BATU, Lonere, 402 103, Raigad, Maharashtra, India Research Scholar, Rayalaseema University Kurnool Andhra Pradesh, India 2. Professor Sreevidyaniketan COE Tirupati Andhra Pradesh, India , ABSTRACT Fractal antennas have been shown to demonstrate repetitive multi-band or log- periodic behavior that has been attributed to the self-similar scale factor of the antenna’s geometry. This geometry, which has been used to model complex objects found in nature such as clouds and coastlines, has space filling properties that can be utilized to miniaturize antennas. These unique properties of fractals have been exploited to develop a new class of antenna-element designs to possess several highly desirable properties, including multiband performance, low side lobe levels, and its ability to develop rapid beam forming algorithms based on the recursive nature of fractals. There are several advantages of these fractal devices including reduction of resonant frequencies, smaller size and broadband width. In this paper, a new design of fractal tree antenna based on ternary fractal tree geometry for wireless local-area network (WLAN, 2.4 GHz for wireless operation) is proposed. Keywords Microstrip patch Fractal antenna, Array Antenna, Fractal Tree Antenna, Multi-band, Fractal Geometry INTRODUCTION Currently, the 2.3–3.6 GHz band assignment for WIMAX is considered as one of thebest choices for the transmission of multimedia services (voice, Internet, email, games andothers) at high data rates. The classics wire and patch antenna are intrinsically a narrowband devices. Their behavior is strongly dependent on the report of an antenna size to theworking wavelength. The antenna parameter is (gain, matching and radiation pattern)endure then any working frequency disagreement one promising approach in this regards isto use fractal geometries to find the best distribution of current within a given volume inorder to meet a particular design goal. Fractal geometries have been recently introduced an 178
  2. 2. International Journal of Electronics and Communication Engineering & Technology (IJECET), ISSN0976 – 6464(Print), ISSN 0976 – 6472(Online) Volume 3, Issue 1, January- June (2012), © IAEMEantenna design. It has been shown that fractal associated with the geometric properties ofthe fractals [5] [6]. One property associated with the fractal geometry and used in antenna’sdesign is self similarity [6]. A fractal antenna can be design to receive and transmit over awide range of frequencies using self-similar properties associated with a fractal geometrystructure, because different antenna’s part are similar to each other at different scale. Thesecond property is the efficiency of space filling of some fractal shapes, which gives hopesto reduce the antenna size, comparatively to that of classic antennas. Various fractal shapesthat possess self-similarity have been applied to multiband and miniaturized antennadesign. A promising fractal geometry that ensures a successful design of multiband antennais known as the deterministic fractal tree. Multi resonant behavior of the first iteration treemounted over a large conducting ground plane are describing in many papers [9] [10].However, the conventional fractal tree monopole antenna does not present many resonantfrequencies in the range of 0.2 to 6 GH wireless bands. Further, the poor matching propertyof the resonance frequency has been shown [6]. In 1975, fractal geometry was first defined by B. Mandelbrot describe complexgeometries and it was generated with an iterative procedure. Recently, fractals have beenwidely used in antenna designs to obtain various kinds of small and multiband antenna. Asthe typical representation of fractal in the nature, trees are good study objects inelectromagnetic theory for engineering applications. Tree-shaped fractal antennas havebeen in broadly investigated in recent years. Fractal antennas are mainly divided into fourparts: fractal line antennas, fractal three dimensional antennas, fractal planar antennas andfractal antenna arrays [1], tree-shaped fractal antennas are mainly researched as fractalthree-dimensional antennas or fractal planar antennas. On one hand, as fractal three-dimensional antennas, C. Puente proposed a tree-shaped fractal antenna as early as fractaltheory was firstly proposed in antenna designing [2]. Fractal tree antennas are very attractive because of their low profile, low weight,conformal to the surface of objects and easy production. A large number of microstrippatches to be used in wireless applications have been developed. Various shapes such assquare, rectangle ring, disc triangle, elliptic, etc. have been introduced .In comparison topatch elements; the antennas with slot configurations demonstrate enhanced characteristics,including wider bandwidth, less conductor loss and better isolation. Particularly the multi-slot structure is a versatile approach formulate-band and broadband design. Also, feedingthese structures could be simpler by using suitable points to slot techniques for differentslots [3-4].FRACTALS AS AN ANTENNA All the basic trigonometric shapes are already utilized in antenna design and theirradiation mechanisms are well explored. And we also know that any arbitrarily randomshape can pick up EM waves. So why not have a discipline in chaos. That means, usingfractals as antennas may offer better radiation pattern and may also offer more controllingparameters to designer. Fractal antennas are multi-resonant and smaller in size. Qualitatively, multi-bandcharacteristics have been associated with the self-similarity of the geometry and Hausdorffdimensions are associated with size. Research towards quantitative relation betweenantenna properties and fractal parameters is going on extensively. Any variation of fractalparameters has direct impact on the primary resonant frequency of the antenna, its inputresistance at this frequency, and the ratio of the first two resonant frequencies. In otherwords, these antenna features can be quantitatively linked to the fractal dimension of the 179
  3. 3. International Journal of Electronics and Communication Engineering & Technology (IJECET), ISSN0976 – 6464(Print), ISSN 0976 – 6472(Online) Volume 3, Issue 1, January- June (2012), © IAEMEgeometry. This finding can lead to increased flexibility in designing antennas using thesegeometries. These results have been experimentally validated. A fractal antennas response differs markedly from traditional antenna designs, in thatit is capable of operating with good-to-excellent performance at many different frequenciessimultaneously. Normally standard antennas have to be "cut" for the frequency for whichthey are to be used and thus the standard antennas only work well at that frequency. Thismakes the fractal antenna an excellent design for wideband and multi-band applications.Various Fractal Types used in Antennas are shown below: [2] Fig 1 Various Types of Fractals Used As AntennaFRACTAL GEOMETRY Fractal trees studied here are also known as fractal canopies and Pythagoras trees.Although these have several features common with other fractals such as Koch curves,their branching nature offers a significant variation, and is expected to cause somedifference in antenna performance. In addition the approach taken for the generation of treehere is somewhat different.A. Pythagorean TreeThe Pythagorean tree is a plane fractal constructed from squares. It is named afterPythagoras because each triple of touching squares encloses a right triangle, inconfiguration traditionally used to depict the Pythagorean Theorem. 180
  4. 4. International Journal of Electronics and Communication Engineering & Technology (IJECET), ISSN0976 – 6464(Print), ISSN 0976 – 6472(Online) Volume 3, Issue 1, January- June (2012), © IAEME Fig 2 Pythagorean Tree In microstrip line implementation, the definition is often modified. Here the initialsegment, i.e. generator, is not a square anymore but it is a rectangle. Hence we will refer toas tree. The initial segment is divided by a scale factor, moved at an angle and placed at thetop of the initial segment. The same pattern is repeated to construct the tree of any order.After some order, depending on the scale factor and angle, the branches start overlappingeach other. Such an antenna can be thought of as a virtual combination of capacitors andinductors, loading the previous structure. This makes the antenna so that it has manydifferent resonances which can be chosen and adjusted by choosing the proper fractaldesign. Here different variable parameters of the fractal are the size of the initial segment,scale factor, branching angle and number of iterations. Increasing the number of segments may increase the coupling between branches. Sizeof the first segment determines the one of the resonant frequency of the antenna. Scalefactors may decide the ratio between the successive resonant frequencies. [1] Thebranching angle also affects the coupling. However it does not affect the ratio of resonantfrequency if the lengths and widths of the branches are not dependent on the angle. [1]Fractal geometry are generated in an iterative fashion, leading to self structure .The treegeometry start with a stem allow one of its ends to branch off in two directions .In the nextstage of iteration ,each of these branches allowed to branch off again. The process iscontinued endlessly as shown in fig. 3 Branch angle 600 and 1200 with Branch Stem of 0.6and 0.3 Fig 3 Fractal Tree with different branching angle and Scale ratios It is possible to vary the scale factor between the length of the stem and branches. Thetransformations required to obtain branches of the geometry in such case may be expressedas follows by equations, = 1 181
  5. 5. International Journal of Electronics and Communication Engineering & Technology (IJECET), ISSN0976 – 6464(Print), ISSN 0976 – 6472(Online) Volume 3, Issue 1, January- June (2012), © IAEME = 2Where S = scale factor θ = Branching half angleThe scaling is by a factor of 0.5, and the branching half angle is 600. The fractaldimension D for the geometry shown in fig. 4 is obtained using (3).Since the branchingangle has no direct role in determining the lengths of these segments, the dimension of allsuch geometries remain the same. However, as the scale factors are changed, the fractaldimension is also changed. For a length ratio x: 1 between branches and the stem, thefollowing expression may be satisfied for the fractal dimension. +2 3 Fig 4 Fractal Tree GeometryB. wideband fractal antennaIt is intuitive that the self similarity property of fractals will result in multiple resonances.The multiple resonances can be converted into wide band characteristics by bringing theresonance frequencies closer and letting the bands overlap. If the fractal parameters arecontrolled properly, this can be achieved. In general, for any antenna to have wide bandcharacteristics, the parameters discussed below have to be taken into account. Theimpedance bandwidth of a micro strip antenna can be determined from frequency responseof its equivalent circuit. For parallel-type resonance, the half power bandwidth is given as:Where Y = G + jB is the input impedance at the resonance frequency. This bandwidth isalso defined as VSWR ~ 2 bandwidth. Hence, in terms of VSWR Where, Q is the quality factor use in design for the structure. As Q decreases, thesystem becomes lossier and bandwidth increases. Hence, if εr decreases, BW increases andif thickness of substrate increases, bandwidth again decreases. Further achievement ofantenna bandwidth can be obtained by increasing gap coupling or direct coupling with theground plane. And slow resistance transformation also helps in increasing bandwidth 182
  6. 6. International Journal of Electronics and Communication Engineering & Technology (IJECET), ISSN0976 – 6464(Print), ISSN 0976 – 6472(Online) Volume 3, Issue 1, January- June (2012), © IAEMEANTENNA DESIGN APPROACH Because of their geometric complexity, it is very difficult to predict mathematicallythe fractal antenna radiation pattern properties. The wide availability of the powerfulelectromagnetic simulator makes possible of such problems, which would be otherwiseimpossible to solve. A first step in the utilization of fractal properties in antenna designshould involve the dimension of the geometry. Many numerical methods are available thatpredict the performances of such antennas. All these techniques are based on solving adiscrete form of Maxwells equations. The most often used are the method of moments(MoM) and the Finite Difference Time Domain (FDTD) method. We use Finite ElementMethod for fractal design similar to fig. 4, explained in [6] [8]. The scale factor for alliteration is 0.66 as per (3). A 5-iternation, tree is applied as the radiation part here. In order to increase thedegrees of freedom of the radiator for the optimization of its performance, such a fractal ischosen. The geometry of the proposed antenna is shown in Figure 5. Figure 5 Novel Design for Fractal Tree Antenna The Fractal tree structure design has following specification Length of main stemL=20mm, width of the stem W=8mm, Substrate height h=1.588mm and resonantFrequency is 2.4 GHz. The proposed geometry is excited by probe feeding technique[3].weexploit the iteration factor η = 0.66 and fabricate the proposed antenna on an economical"Rogers RO4232 (tm)"dielectric with a thickness of 1.588mm (h), relative permittivity of3.2 (εr),and loss tangent of 0.0018 .SIMULATION There exists much software such as HFSS, Fidelity, CST, Feko, EMPro, SIMetric,SuperNEC etc. for the simulation of the RF component designs. In this paper, the antennahas been designed and simulated using FEM method based commercial Electromagneticsimulator. The structure has a substrate layer with εr of 3.2 (RO4232 board), thickness of1.588mm and the antenna is probe fed as shown in Fig.6 (with all dimensions in mm only).The size of the board is 100mmX120mm. The antenna is drawn as a microstrip patch layeron the board using copper as material. 183
  7. 7. International Journal of Electronics and Communication Engineering & Technology (IJECET), ISSN0976 – 6464(Print), ISSN 0976 – 6472(Online) Volume 3, Issue 1, January- June (2012), © IAEME First Second Third Fourth FifthRESULT AND ANALYSISFive iteration with branching half angle of θ =60 and specification discuss in antennadesign were simulated. The design of all five iteration of the novel printed on dielectricsubstrate. The antenna has been fed using 50 ohm coaxial probe to main stem. In this study,the permittivity of the substrate is 3.2. Return loss, VSWR, VSWR bandwidth, anddirection pattern is plotted. The Radiation pattern for the fifth iteration is shown in fig. 6.This gives the change in the pattern direction respectively with number of iteration. Fromthis the measured radiation pattern of fractal antenna is nearly omnidirectional in azimuthplane throughout the operating frequency. Figure 6. Radiation pattern for E field for iteration V.Return loss measurement for all the iteration is presented in fig. 7. This curve confirms theresonant frequency location. For the other iteration same behaviour was noticed andconfirms the resonant frequency. 184
  8. 8. International Journal of Electronics and Communication Engineering & Technology (IJECET), ISSN0976 – 6464(Print), ISSN 0976 – 6472(Online) Volume 3, Issue 1, January- June (2012), © IAEME FIGURE 7 RETURN LOSS FOR ITERATION I TO V VSWR for all the iterations are showed in Figure 8. It shows the good result for thirditeration. Bandwidth up to 10.15% can be achieved using probe fed method only, whichcan be further enhanced by using other enhancement techniques. Figure 8 VSWR for iteration I to VCONCLUSION A tree shaped fractal antenna using rectangular structure based on fractal treegeometry is presented in this paper. It is observed that the resultant antenna is compact insize and simple to design. Our aim was, to see the results of antenna using coaxial probefed method. The proposed novel design provides the bandwidth up to 87.78% using probefed technique. The proposed antenna is simulated for 2.4 GHz frequency. This antenna giveomnidirectional property and operate in 2.1GHz-2.8GHz frequency band with acceptableS11<-10dB (VSWR<2).The proposed antenna used for wireless video operation 2.8GHz,Also used in Bluetooth 2.4GHz and Wireless LAN of 3GHz frequency. 185
  9. 9. International Journal of Electronics and Communication Engineering & Technology (IJECET), ISSN0976 – 6464(Print), ISSN 0976 – 6472(Online) Volume 3, Issue 1, January- June (2012), © IAEMEACKNOWLEDGMENTThe authors would like to thank Dr. Nalbalwar, and faculty member of Electronics andTelecommunication Department. Similarly special thanks to Pradnya Sarvade, PoojaHolkar and Sucheta Pawar for working hard day and night for the different designs offractals. We would also like to thanks the pass out students of Dr. Babasaheb AmbedkarTechnological University who presents so many papers at National and International levelbased on fractal design and Microstrip Antenna.REFERENCES1. C. Puente and J. Claret (1996), “Multiband properties of a fractal tree antennagenerated by electrochemical deposition,” Electronics Letters, vol. 32, no.25, pp. 2298-2299.2. Vinoy, K. J. (2002), “Fractal shaped antenna elements for wide and multi-bandwireless applications,” Thesis, Pennsylvania.3. R. K. Gupta (2010) "Printed TRI-BAND Monopole Antenna Structures For WirelessApplications “Issue, Vol. I.4. Raj Kumar, George Mathai and J.P. Shinde (2009) "Design of Compact MultibandEBG and Effect on Antenna Performance” International Journal of Recent Trends inEngineering, Vol2, No. 5.5. Werner D.H., Ganguly S. (2003), “An overview of fractal antenna engineeringresearch", IEEE. Antennas and Propagation Magazine. Vol. 45.6. Cohen, N. (1997), “Fractal Antenna Applications in Wireless Telecommunications”,Professional Program Proc. Of Electronics Industry Forum, pp 43-49.7. Sindou, M., Abalrt G., Sournois C. (1999), “Multiband and wideband properties ofprinted fractal branched antennas”, Electronics letter, 35(3):181-2.8. Puente Claret, Sagues J., Romeu F., Lopezsalvans,J., Pous M.Q. (1996), “Multibandproperties of a fractal tree antenna”, generated by electrochemical deposition,electron. Letter, 1996, pp 2298- 2299.9. Petko, J. S., Werner D. (2004),“ Miniature reconfigurable three dimensional fractaltree antennas”, IEEE Trans. Antennas and Propagation. August 2004.10. H. Kimouche eI, M.Bitchikh, B.Atrouz (2008), “Novel Design of a Fractal MonopoleAntenna for Wireless Communications”, IEEE transaction of Antenna WavePropagation.11. Garg, Bhatia, Bahl, Ittipiboon (2000), “Microstrip Antenna Design Handbook”, ArtechHouse, London.12. Yahui Zhao, Jinping Xu, and Kang Yin, “A Miniature Coplanar Waveguide-Fed Ultra-Wideband Antenna”, State Key Laboratory of Millimeter Waves, Southeast University,Nanjing, Jiangsu, P.R.China, 210096.13. Masahiro Yanagi, Shigemi Kurashima, Takashi Arita, Takehiko Kobayashi, “A PlanarUWB Monopole Antenna Formed on a Printed Circuit Board”AUTHORS 186
  10. 10. International Journal of Electronics and Communication Engineering & Technology (IJECET), ISSN0976 – 6464(Print), ISSN 0976 – 6472(Online) Volume 3, Issue 1, January- June (2012), © IAEME Sanjay V. Khobragade has been working as Assistant Professor in Dr. B. A. Technological University Lonere, Maharashtra, India from last 13 years. He is graduated from NagpurUniversity in 1996 and post graduated in Electronics Engineering from Mumbai Universityin 2008 and pursuing PhD form Rayalaseema University Kurnool, Andhra Pradesh. He hasbeen involved in teaching a Microwave, Antenna & Wave Propagation andElectromagnetic Field. He has received Young Scientist Award in URSI 2004 in Pisa Italy,and Consolation Prize for best paper in ICMARS Jodhpur, 2008 and best Technical teacheraward by ISTE sponsored by Maharashtra and Goa in 2010. He has around 70 papers atnational and International conferences in his credit. Dr. Anitha V R has been working as a professor in Sree Vidyaniketan College of Engineering Tirupati. She is actively involved in teaching Microwave, Optical and Digital communication subjects. She isgraduated in AMIETE in 2003, postgraduate in Engineering in 2005(M. Tech.) fromNagarjuna University Guntur, and PhD in Design and Analysis of a Square MicrostripPlanar Antenna Array for Wind Profiling Radars in January 2010. She is qualified forStipend given by TEQIP Government of India during PhD in 2006 to 2009. She is Goldmedallist of M. Tech. She is Member IEEE and Life member of IETE. She has 25 papers innational and international conferences and journals. 187