Design of Novel Miniature E-Shape Koch Fractal Antenna for Multiband Characteristics

Transcription

1 Indian Journal of Science and Technology, Vol 9(44), DOI: /ijst/2016/v9i44/98904, November 2016 ISSN (Print) : ISSN (Online) : Design of Novel Miniature E-Shape Koch Fractal Antenna for Multiband Characteristics P. Prabhu * and E. Elamaran SRM University, Chennai , Tamil Nadu, India;prabhu. beece66@gmail.com, elamgame@gmail.com Abstract In this study, the new E-shape fractal multi-band antenna with Koch fractal structure is presented. Omni-directional radiation pattern and better radiation characteristics is achieved by E-shape rectangular patch. Space filling and self-affine property of Koch fractal structure is applied to achieve the compact size and multi-band characteristics. The antenna had the compact size of 44*22mm3 and antenna printed on Rogers_RO4003 with 1.2 mm thickness. The proposed E-shape Koch fractal geometry is flexible in optimizing the bandwidth and resonance. Various factors such as radiation pattern, polarization, directivity, gain and bandwidth for the proposed antenna is simulated. The proposed E-shape Koch fractal antenna resonates at 1830MHz, 2.83GHz, 5.15GHz and 7.70GHz for DCC, WiMAX, WLAN and C-band applications respectively with broad bandwidth. Keywords: E-shape Koch Fractal, Multiband, Miniature, Novel, WLAN Antenna, WiMAX Antenna. 1. Introduction The recent development in wireless communication and the need for frequency band have accelerated the growth of multiband characteristics and broadband antennas. Moreover, antenna industries expect low-profile antennas. Hence, miniaturization of an antenna is the unavoidable task while optimizing the design of antenna for various modern wireless communication operations such as GSM/ WiMAX/WLAN. The fractal antenna is an emerging area in antenna design engineering because of self similarity and space filling properties of fractals. These features support the realization of a small-sized multiband with highly improved radiation characteristics. Fractals imply an irregular pattern geometry. They consist of self-similar structures with the irregular patterns. A fractal structure is created by connecting numerous replicas of a single structure of various sizes. Hence, the fractal structure does not have a defined scale. The self-similar comprises of downsized duplicates of original structures. The self -similarity property of a fractal structure can be used to design a multiband with characteristics antenna. Because the space-filling property of fractals, the area occupied by an antenna gets filled as the order of iteration increases. Hence, this provides malleability in design, selecting appropriate scaling factors which facilitates in minimizing the size of an antenna. In literature, the fractal and Koch fractal antenna both have been reported. The fractal technique was used for developing a multiband antenna using self-similar property 1,2. An E-shaped antenna was designed using the fractal property for multiband applications 3. Fractal geometry has been used to design monopole antennas 4,5 ; Fractal was used for rectangular and circular patch antennas 6 - array antennas, dipole antennas and slot antennas 7 9. A Multiband antenna with re-configurable feed using Koch fractal geometry was examined 10. Koch-fractal circularly polarized antenna for handheld UHF RFID reader application using a Koch fractal with a micro strip feed was Evaluated 11. An asymmetrical Koch fractal for a tri-band application was implemented 12. Dimension comparison of the proposed antenna and other *Author for correspondence

2 Design of Novel Miniature E-Shape Koch Fractal Antenna for Multiband Characteristics existing antenna for multiband applications using Koch fractal is indicated in table 1. In this paper, the design of novel miniature E-shape Koch fractal antenna for multiband characteristics is proposed. The E-shape slot Koch fractal structure is designed and simulated using the Agilent advanced design system method of momentum (MOM) simulator. Koch fractal iteration methods have been used to E-shape slot rectangular patch to acquire Zero th, first and second iterations of fractal structure. The proposed antenna parameters presented in forthcoming chapters. Table 1. Dimension comparison of the proposed antenna and other existing antennas for multiband applications using Koch fractal Reference Dimension of antenna [2] 55 *45 [3] 41*47 [4] 39*41 [5] 55*36 Proposed 34*30 2. Antenna Design Koch fractal is one of the fractal geometries, which can be created with space filling and self-similarity of fractals and geometry can be engendered by iterative function method 13,14. The Koch fractal can be implemented directly, it has initiator and generator. It begins with the straight line which is called Initiator. This Initiator is divided into three identical segments and the part at the center substituted by two other areas of the equal size 13,14. The modified iteration of initiator is called generator 13,14. The higher iteration of Koch fractal geometry can be generated by reprocessing of the previous process Iterative function of fractal is given below: w a b x e = + y c d y f Or (1) w( x, y) = ( ax + by + e, cx + dy + f ) (2) where a, b, c, d, e, f real numbers coefficients. Movements of fractal element in space only based on these factors ad, is scaling factors, bcare, rotation factors by θ 1,θ 2 and e, f are linear translation.it can be written as, a= d cos f ; d = d cos f ; (3) b= d sin f ; c= d sin f ; (4) Koch fractal Iterative transform function (IFS) given below w x dq1cosqq1 dq2sinqq2 x tq1 q = + y d sinq + d cosq y t q1 q1 q2 q2 q2 Scaling factor for Koch fractal given below, d q (5) 1 = (6) 2 + 2cosq q Where, θ q is the inclination angle between the two generators of segmented Koch fractal. In Koch fractal θ qi =60 0 and, tqi is part movement on the coordinate plane. From the above equations, Iterative transfer function coefficients matrix for Koch fractal is given below, 1/ /3 1/6 3/6 3/6 1/6 1/6 3/6 3/6 1/6 1/ /3 2.1 Proposed E-shape Koch Fractal Geometry The Koch fractal iteration applied to E-shape slot rectangular patch antenna is shown in figure.1(a). In the initiator of E-shape slot segmented into three parts with length l /3 and center part is replaced by triangle which has length of two parts ( ls /3 + ls /3) with angle 60 0 angles between two lines. The Second Koch fractal iteration achieved by repeating the same procedure on the first iteration E-shape slot antenna. The E-shape slot is created on the rectangular patch. Koch fractal iteration is applied on the E-shape slot of an antenna and iteration generated by downsizing the initial structure ohm Impedance matching is achieved by using micro strip feed method Miniaturization of maximum surface and multiband is achieved by applying Koch iterative process on the E-shape slot. The initiator length of E-shape of proposed antenna is 23mm, and generator length is 6.6 mm 3. The rectangular patch with E-shape slots is shown in figure.1 (a). Eventually, miniaturization (7) 2 Indian Journal of Science and Technology

3 P. Prabhu and E. Elamaran 1(a) 1(b) 1(c) Figure 1(a), Figure 1(b), Figure 1(c). itration, respectivly. Geomtry of the proposed E-shape koch fractal antenna for 0 th itration,1 st itration,2 nd is achieved by employing Koch fractal. The dimension of proposed Rectangular patch is 31*39 mm 3, and other dimensions of a proposed antenna are given in table.2. The proposed E-shape slot Koch fractal antenna printed on the 1.6 mm thickness Rogers substrate and dielectric constant of the substrate is 3.4. The geometry first iteration and the second iteration of E-shape slot Koch fractal antenna have shown in figure.1(b), figure.1(c) respectively. The proposed antenna simulated results are discussed in results and discussions section. Table 2. W Dimensions of the proposed antenna W1 Wg H H1 H2 H3 H Results and Discussions 3.1 Return Loss The proposed novel E-shape slot Koch fractal antenna is simulated in advanced design system software. The size of the proposed ground plane is 31*39 mm 3 and simulated return loss of initiator (0 th iteration), first iteration and the second iteration of the antennas are shown in figure.2, figure.3 and figure.4 respectively. The simulated return loss for E-shape Koch fractal of 0 th iteration is -15 db, db, db and db return losses at resonant frequencies GHz, 3.50GHz,4.79 GHz and 7.66GHz respectively. For 1 st iteration is db, db, db and db return loss at resonant frequencies 1.531GHz,2.9GHz,4.68 GHz and 6.9 GHz respectively. For the 2 nd iterations Koch fractal, simulated return loss db at 1.8GHz, db return loss at the resonant frequency of 2.9GHz, return loss at the resonant frequency of 5.15GHz and db return loss at resonant frequency 7.73GHz. The return loss performance comparison plot of zero, first and second iterations is shown in figure.5. and that resonant frequency comparison given in table.3. It can be interpreted from the return loss graph of Koch fractal that notable change in the operating frequency was witnessed between 0th iteration and the 1st iteration of Koch fractal. From the 1st iteration and 2nd iteration return loss graph can be observed that significant change in lower resonant frequency and higher resonant frequency in the 2nd iteration compare to that of the 1st iteration of E-shape Koch fractal antenna. Since second iterations exhibit better, return loss characteristics compare to that of other iterations. Hence the proposed novel E-shape slot Koch fractal iterative antenna suitable for multiband antenna applications. Indian Journal of Science and Technology 3

4 Design of Novel Miniature E-Shape Koch Fractal Antenna for Multiband Characteristics Table 3. Comparisons of return loss for various Iterations Figure 2. Return loss of 0 th Iteration of E-shape Koch fractal antenna. Resonant frequency K 0 K 1 K 2 Resonant Return nant Reso- Return frequency (db) uency loss freq- loss (db) Return loss (db) BW Figure 3. Return loss of 1 st Iteration of E-shape Koch fractal antenna. Figure 4. Return loss of 2 nd Iteration of E-shape Koch fractal antenna. 3.2 Radiation Pattern Radiation patterns of the proposed E-shape Koch fractal antenna are shown in the figure.6 and figure.7. It shows the E-theta, E-phi, E-cross and E-co polarization of the proposed antenna at the resonant frequencies 1.8GHz, 2.8GHz, 5.15GHz, and 7.9GHz respectively. From the radiation pattern can be observed that the radiation pattern of the proposed antenna exhibits omnidirectional radiation pattern, and it exhibits consistent radiation response over entire operating frequency band (1.8 GHz-7.9 GHz). The gain of the Koch fractal antenna E-shape antenna is 6 dbi, 7.4 dbi, 6.5dBi and 8.2 dbi at center frequencies 1.8GHz, 2.82GHz, 5.15GHz and 7.9 GHz respectively. The antenna has linear polarization at 1.82 GHz and 5.15GHz, since current density at the center of the antenna and it exhibits circular polarization at 2.8GHz and 7.6 GHz since it exhibits high current distribution at the corners of an antenna. Figure 5. Return loss comparison of three iterations of proposed E-shape Koch fractal antenna. Figure 6. The Simulated E-theta, E-phi, E-cross and E-co polarization radiation patterns of third iterated E-shape Koch fractal antenna at 1.8 GHz, and 2.8 GHz respectively. 4 Indian Journal of Science and Technology

5 P. Prabhu and E. Elamaran Figure 7. The Simulated E-theta, E-phi, E-cross and E-co polarization radiation patterns of third iterated E-shape Koch fractal antenna at 5.1 GHz, and 7.6 GHz respectively. 3.3 Current Distribution The surface current of the proposed E-shape Koch fractal antenna is shown figure.8(a), figure.8(b), figure.8(c). From the Figures it can be interpreted that surface current distribution of 2 nd iteration of E-shape slot Koch fractal antenna is more than that of 0 th Koch fractal iteration and 1 st Koch fractal iteration, since higher order iterations introduce more discontinuities on the patch due to the discontinuities current flow increase in the 2 nd iterations of the E-shape slot Koch fractal antenna. Therefore, the radiation efficiency of the proposed antennas has been improved. 4. Conclusion The novel miniature E-Shape Koch fractal antenna for multiband characteristics was proposed with simulated results. The Koch fractal applied for E-shape rectangular patch to obtain miniaturization in antenna size, improved the number of resonant frequency bands and enriched the bandwidth. Multiband antenna characteristics are achieved by increasing iterations of the antenna. The vital antenna characteristics of antenna such as far-field radiation characteristics return loss, and impedance bandwidth have been simulated at functional resonant frequencies, and the proposed E-shape Koch fractal antenna operates at 1.8GHz, 2.9GHz, 5.1GHz and 7.9 GHz with better return loss. Hence, the proposed E-shape slot Koch fractal is antenna most suited for multiband characteristics antenna also, it can be used for PCS, DCS, WiMAX, WLAN and C-band applications. 5. References 1. Chou YJ, Lin GS, Chen JF, Houng LSCMP. Design of GSM/ LTE multiband application for mobile phone antennas. Electronics Letter. 2015; 51(17): Ban YL, Qiang YF, Chen Z, Kang K, Guo JH. A Dual-Loop Antenna Design for Hepta-Band WWAN/LTE Metal- Rimmed Smartphone Applications. IEEE Antennas And Wireless Propagation Letters. 2015; 63(1): Lian R, Wang Z, Yin Y, Wu J, Song X. Design of a Low- Profile Dual-Polarized Stepped Slot Antenna Array for Base Station. IEEE Antennas and Wireless Propagation Letters. 2016; 15: Wojciech J, Krzysztofik K. Fractal Geometry in Electromagnetics Applications - from Antenna to Metamaterials. Microwave Review. 2013; 9(2): Manimegalai B, Raju S, Abhaikumar V. IEEE A Multifractal Cantor Antenna for Multiband Wireless Applications. 8.(a) 8.(b) 8.(c) Figure 8(a), Figure 8(b), Figure 8(c). itration, 2 nd itration, respectively. Current distribution of the proposed E-shape koch fractalantenna for 0 th itration, 1 st Indian Journal of Science and Technology 5

6 Design of Novel Miniature E-Shape Koch Fractal Antenna for Multiband Characteristics IEEE Antennas and Wireless Propagation Letters. 2009; 8: Bayatmaku N, Lotfi P, Azarmanesh M. Member, IEEE, and Saber Soltani Design of Simple Multiband Patch Antenna for Mobile Communication Applications using New E-Shape Fractal. IEEE Antennas and Wireless Propagation Letters. 2011; 10: Sundaram A, Maddela M, Ramadoss R. Koch-Fractal Folded-Slot Antenna Characteristics. IEEE Antennas and Wireless Propagation Letters. 2007; 2(6): Puente C, Romeu J, Pous R, Ramis J, Hijazo A. Small but long Koch fractal monopole. Inst Elect Eng Electron Lett. 1998; 34(1): Borja C, Romeu J. On the behavior of Koch island fractal boundary microstrip patch antenna. IEEE Trans Antennas Propagat. 2003; 51(6): Cohen N. Fractal and shaped dipoles. Commun Quart, Spring. 1996; 45(1): Anagnostou D, Chryssomallis MT, Lyke JC, Christodoulou CG. A CPW Koch dipole slot antenna. Proc IEEE Topical Conf Wireless Commun Technol. 2003; 337 pp. 12. Puente C, Pous R. Fractal design of multiband and low side-lobe arrays. IEEE Trans Antennas Propagat. 1996; 44(5): Kumar AMM, Amalendu Patnaik A, Christos G, Christodoulou C. Design and Testing of a Multifrequency Antenna With a Recon Figureurable Feed. IEEE Antennas and Wireless Propagation Letters. 2014; 13: Farswan A, Gautam AK, Kanaujia BK, Rambabu K. Design of Koch Fractal Circularly Polarized Antenna for Handheld UHF RFID Reader Applications. IEEE Transactions on Antennas and Propagation. 2016; 64(2): Reddy VV, Sarma NVSN. Triband circularly polarized Koch fractal boundary microstrip antenna. IEEE Antennas Wireless Propag Lett. 2014; 13: Werner DH, Ganguly S. An overview of fractal antenna engineering research. IEEE Antennas Propagat Mag. 2003; 45(1): Vinoy KJ. Fractal Shaped Antenna Elements for Wide and Multi-Band Wireless Applications, Ph.D. dissertation, Dep Elec Eng, Pennsylvania State University, University Park, Prabhu P, Elamaran E, Lenein Desai S. Design of self-similarity multifractal antenna for WiMAX applications Apr; 9(15). 6 Indian Journal of Science and Technology