An Improved Compact & Multiband Fractal Antenna Using the Koch Curve Geometry

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1 Wireless and Mobile Technologies, 14, Vol., No. 1, 1-6 Available onle at Science and Education Publishg DOI:1.1691/wmt--1-1 An Improved Compact & Multiband Fractal Antenna Usg the Koch Curve Geometry Manas Ranjan Jena 1,*, B.B. Mangaraj 1, Rajiv Pathak 1 Deparment of ELTCE, VSSUT, Burla, Odisha, India BIT, Durg, Chhatisgadh, India *Correspondg author: manas.synergy@gmail.com Received March 6, 14; Revised May 3, 14; Accepted June, 14 Abstract In this paper, we have achieved an compact & multiband fractal antenna usg a Koch curve geometry. The simulation of the proposed antenna is done by CST Microwave Studio EM simulation software. The proposed Koch curve fractal antenna proves that it is capable to create multiband frequencies. The proposed fractal antenna is designed on FR-4 substrate with ℇr= 4.4. The antenna is fed with the probe feed method. We got two resonant frequencies like 3.84GHz & 34.8GHz which shows multiband characteristics. Simulated results shows that the return loss is better than 15 db, the VSWR is less than 1.3, the directivity is greater than 6dBi & the ga is more than 6dB each band. So this fractal antenna can be suitable for the radio astronomy & space research applications. Keywords: fractal antenna, koch curve, CST, IFS, self similarity, self fillg, multiband Cite This Article: Manas Ranjan Jena, B.B. Mangaraj, and Rajiv Pathak, An Improved Compact & Multiband Fractal Antenna Usg the Koch Curve Geometry. Wireless and Mobile Technologies, vol., no. 1 (14): 1-6. doi: /wmt Introduction. Antenna Design Now-a-days there is a need for more compact and portable communication systems. We know that antenna is an tegral part of all the communication systems. So there is a demand for small antennas for portable communication systems [1]. It is well known that the antenna dimension is a function of its operatg wavelength (λ). i.e if the antenna size is less than the operatg wavelength (λ), the antenna becomes icient as its characteristics like radiation resistance, directivity, ga & bandwidth are dimished []. Fractal geometry is a very good solution for this problem due to its two major characteristics like self similarity & space fillg. so fractal geometry has become an important approach for designg multiband antennas [3,4]. A fractal is a rough or fragmented that can be subdivided to parts, each of which is a reduced copy of whole. Therefore the basic property of a fractal shape is self similarity and structure at all scales [5]. The goal of this paper is to design and characterize a fractal antenna with Koch curve geometry as it has the potential to provide multiband solution [6]. A koch curve is a famous fractal objects mathematics [7]. These are low profile antennas with better return loss, VSWR, directivity and ga. So Koch curve can be made operative at multiple frequency bands and hence are multifunctional [8,9]. w G = for W < λ 9λ w G = for W < λ 1λ k l ε B = z Y + jy tanβ ( L + l) slot Y = Yslot + Y Y + jy slot tan β L + l Design Equations: ( )

2 Wireless and Mobile Technologies Z 1π h = W ε εr + 1 εr 1 1h 1/ = + (1 + ) =.14 W +.3 W l =.41 h( )( h +.64 ).58 W h +.8 f c r= ( L+ l) λg λ ( L+ l) = = ε c εr + 1 W = f r 1/ ( not critical) Here we have designed a 3 GHz antenna usg the followg parameters. Substrate: FR4 (ε r = 4.4, h=1.6 mm). c λ = = 1cm f r 1/ c εr + 1 W = 6mm f = r εr + 1 εr 1 1h 1/ = + (1 + ) =.4 1 W +.3 W l =.41 h( )( h +.64 ) =.4cm.58 W h +.8 c L = l = 6mm ε Y R Z OT 1W 1 = G = = 45λ R = 88 Ω= put impendance = R.5 = 1Ω This proposed fractal antenna is an iterative model to a normal square patch as shown Figure a with a generator of the shape shown the followg Figure 1. Figure 1. proposed generator Figure a shows a normal wire square patch antenna which the length of each side is 6 mm. Iteration 1 is produced by replacg each straight wire with the proposed generator shape as shown figure b. Iteration is produced from iteration 1 by usg IFS (Iterated Function System) as shown figure c [1,11]. Figure. Different iteration stages of the proposed Koch curve fractal antenna. Here One stage is generated by applyg the affe transformation to the previous one 3. Simulation Setup & Results CST Microwave Studio electromagnetic simulator software is used for design & simulation. Antenna is fed with probe feed. Results like Reflection coicient (return loss), VSWR (voltage standg wave ratio), Variation of Impedance Z (real & Imagary part), D radiation patterns, 3D radiation patterns are simulated [1,13]. Simulation results of iteration 1, iteration & iteration 3 are summerised Table 1, Table & Table 3 respectively Simulated Results of Iteration Figure 3. a. Variation of simulated reflection coicient(s11)with frequency Figure 3. b. Variation of VSWR with frequency

3 Wireless and Mobile Technologies 3 Figure 3. c. 3D Radiation pattern (Directivity) at Fr=3.37 GHz Figure 3. D. 3D Radiation pattern (Ga) at Fr=3.37 GHz Table 1. The different results (1) are given below Fr (GHz) RL (db) VSWR Directivity (dbi) Ga (db) Simulated Results of Iteration 1 Figure 4. a. Variation of simulated reflection coicient (S11) with frequency Figure 4. b. Variation of VSWR with frequency

4 4 Wireless and Mobile Technologies Figure 4. c: 3D Radiation pattern (Directivity) at Fr=3.73 GHz Figure 4. d. 3D Radiation pattern (Ga) at Fr=3.73 GHz Table. The different results(1) are given below Fr (GHz) RL (db) VSWR Directivity (dbi) Ga (db) Simulated Results of Iteration Figure 5. a. Variation of simulated reflection coicient (S11) with frequency Figure 5. b: Variation of VSWR with frequency

5 Wireless and Mobile Technologies 5 Figure 5. c. 3D Radiation pattern(directivity) at Fr=3.84 GHz Figure 5. d. 3D Radiation pattern(ga) at Fr=3.84 GHz Figure 5. e. 3D Radiation pattern(directivity) at Fr=34.8 GHz Table 3. The different results (9) are given below Fr (GHz) RL (db) VSWR Directivity (dbi) Ga (db) Figure 5. F. 3D Radiation pattern (Ga) at Fr=34.8 GHz BW Calculation 1. For th iteration =3.37 GHz, f L =31.67GHz & f H =33.83GHz So BW= ( fh fl ) 1%=6.67%

6 6 Wireless and Mobile Technologies. For 1 st iteration =3.73 GHz, f L =3.1GHz & f H =33.19GHz So BW= ( fh fl ) 1%=.99% 3. For nd iteration For 1 st band =3.84GHz, f L =3.91GHz & f H =33.41GHz So BW= ( fh fl ) 1%=7.61% For nd band =34.8GHz, f L =33.9GHz & f H =34.94GHz So BW= ( fh fl ) 1%=.97% Table 4. Comparision of different major parameters for multiple iterations Multiple Parameters th iteration 1 st iteration nd iteration Return loss VSWR Directivity Ga Presence of multiband Nil Nil Yes () BWenhancement 6.67%.99% 7.61%.97% 4. Conclusion A fractal antenna with Koch curve geometry is designed & characterized. The simulated results show that return loss is more than -15 db, VSWR is less than 1.3, directivity is more than 6dBi, ga is more than 6dB. This antenna not only improve return loss, VSWR, directivity & ga, but also can Provide a compact size of radiatg patch. Ga is enhanced with multiple iterations. Bandwidth enhancements for multiple iterations is compared. Antenna size is reduced by usg fractal shapes with multiple iterations. After these comparisons, it is clear that the proposed fractal antenna is superior than the conventional rectangular patch antenna. It follows the multiband characteristics which enables to use a sgle antenna stead of many. So the proposed antenna is suitable for the radio astronomy & space research applications. Acknowledgement The authors scerely thank to the Vice Chancellor & the H.O.D of EL & TCE Dept. VSSUT, BURLA for constant encouragement and support. Authors are thankful to all the staff of EL & TCE Dept. VSSUT, BURLA for their support directly or directly. References [1] Balanis, Constante, Antenna theory-analysis and Design, John Wiley & Sons Ltd, Reprted 8. [] B. B. Mandelbrot, The Fractal Geometry of Nature San Francisco, CA: Freeman, [3] N. Cohen, Fractal Antenna Application In Wireless Telecommunications Proceedgs of Electronics Industries Forum of New England, 1997, pp [4] R.M. Crownover, Introduction to Fractals and Chaos, Boston, MA Jones & Bartlett, [5] D. H. Werner, P. L. Werner, and K. H. Church, Genetically engeered multi-band fractal antennas, Electron. Lett., vol. 37, no. 19, pp , Sep. 1. [6] B. Manimegalai, S. Raju, & V. Abhaikumar, A multi fractal cantor antenna for multiband wireless applications, IEEE Antennas Wireless Propag. Lett., vol. 8, pp , 9. [7] D. H. Werner and S. Ganguly, An overview of fractal antenna engeerg research, IEEE Antennas Propag. Mag., vol. 45, no. 1, pp , Feb. 3. [8] K. J. Voy, Fractal Shaped Antenna Elements for Wide and Multi-Band Wireless Applications Thesis, Pennsylvania, Aug.. [9] Best S.R. The Effectiveness of Space Fillg Fractal Geometry Lowerg Resonant Frequency, Antennas & Propagation Letters, Vol. 1, (), [1] X. Yang, J. Chiochetti, D. Papadopoulos, and L. Susman, Fractal antenna elements and arrays, Appl. Microw. Wireless, vol. 5, no. 11, pp , May [11] Puente, C., Romeu, J., and Cardama, A. (). The Koch Monopo le: A Small Fractal Antenna. IEEE Transactions On Antennas And Propagation 48 (11). [1] Best, S.R. (). On the resonant properties of the Koch fractal and other wire monopole antennas. IEEE Antennas and Wireless Propagation Letters. 1 (1). [13] Voy, K. J., Abraham, J.K., and Varadan, V.K. (3). Fractal dimension & frequency response of fractal shaped antennas. IEEE Antennas &Propagation Society International Symposium. -7 June. Volume 4, -5.