INTERNATIONAL JOURNAL OF ELECTRONICS AND COMMUNICATION ENGINEERING & TECHNOLOGY (IJECET)

Transcription

1 INTERNATIONAL JOURNAL OF ELECTRONICS AND COMMUNICATION ENGINEERING & TECHNOLOGY (IJECET) International Journal of Electronics and Communication Engineering & Technology (IJECET), ISSN (Print), ISSN (Online) Volume 3, Issue 1, January- June (2012), IAEME ISSN (Print) ISSN (Online) Volume 3, Issue 1, January- June (2012), pp IAEME: Journal Impact Factor (2011): (Calculated by GISI) IJECET I A E M E INNOVATIVE DESIGN OF TREE SHAPED FRACTAL ANTENNA USING RECTANGULAR AND TRIANGULAR PATCHES FOR 2.4 GHZ Sanjay V Khobragade 1, Anitha V R 2 1. Department of EXTC, Dr. BATU, Lonere, , Raigad, Maharashtra, India Research Scholar, Rayalaseema University Kurnool Andhra Pradesh, India 2. Professor Sreevidyaniketan COE Tirupati Andhra Pradesh, India Svk2305@gmail.com, anithavr@gmail.com ABSTRACT In this paper, for more antenna miniaturization, we present a Novel fractal tree geometry that allows decrease in the resonance frequency without occupying more space. Also for improving the inherently narrow bandwidth of Fractal antenna a Proximitycoupled feed is implemented. The Proposed Fractal Tree antenna is designed for 2.4 GHz, 3.6 GHz. The -10 db return loss bandwidth could reach about 9.5% for 2.4 GHz band and 31.5% for 3.6 GHz band, which meet the required bandwidth specification of 2.4/3.6 GHz WLAN standard. The radiation pattern of fractal antenna is nearly omnidirectional in azimuth plane throughout the operating frequency. Keywords Microstrip patch fractal antenna, Fractal Tree Antenna, Wide-band, Fractal Geometry INTRODUCTION The microstrip patch antenna (MPA) has attracted wide interest due to its important features, such as light weight, low profile, low cost, simple to manufacture and easy to integrate with RF devices. For reducing the size of antenna, fractal geometries have been introduced. A fractal is a rough or fragmented geometric shape that is generated by starting with a very simple pattern that grows through the application of rules. In many cases the rules to make the figure grow from one stage to next involve taking the original 188

2 figure and modifying it or adding to it. The process can be repeated recursively an infinite number of times. For reducing the size of antenna, fractal geometries have been introduced in the design of antenna. Fractal geometries have two common properties: Self similar property, Space filling property. The self-similarity property of certain fractals results in a multiband behavior. While using space filling properties, a fractal make reduce antenna size. For improving the inherently narrow bandwidth of a microstrip antenna, it is very effective to use an electrically thick substrate. Several studies for feeding the microstrip antenna with a thick substrate have been reported, such as the L-shaped probe and the capacitive probe-fed structure. Recently the proximity-coupled microstrip antenna with a linear slot in ground plane has also been proposed. It should be noted that the proximity-coupled microstrip antenna without a slot in the ground plane is hard to achieve impedance matching. In this paper, we miniaturize a microstrip patch antenna with suitable gain and impedance bandwidth. For increasing the frequency bandwidth, a proximity-coupled feed is used and an H-shaped slot is placed. In this paper, a multiband fractal tree antenna is presented as a candidate for use in applications such as wireless local area network (WLAN system of IEEE b standard-2.4ghz.), industrial scientific medical (ISM-2.4GHz.), and Bluetooth frequency of 2.45GHz. ANTENNA DESIGN AND GEOMETRY The Proposed fractal tree design is similar to tree shape, which is designed for 4th iteration from rectangular and triangular patches. All the rectangular and triangular patches are connected by simple wire. The scale factor for all iteration is 0.5. The geometry of the proposed antenna is shown in figure. A 4th Iteration, tree is applied as the radiation part here. The Fractal tree structure design has following specification Length of main stem L=20mm, width of the stem W=8mm, Substrate height H=3.5mm, permittivity of the substrate =3 and resonant Frequency is 3GHz. The proposed geometry is excited by microstrip line feeding. Figure 1 Design of Novel Tree Shaped Fractal Antenna 189

3 Figure 2 Geometry of microstrip feed line and substrate RESULTS AND DISCUSSION Five iteration with branching half angle of 60 degree and specification discuss in antenna design were simulated to improve the impedance matching without changing the main beam direction or current distribution. S parameter is plotted for all the iterations are showed in figure. It shows the good result for fifth iteration. Bandwidth up to 9.5% and 31.5%can be achieved by making arrays in and proximity feeding method only, which can be further enhanced by using other enhancement techniques. Return loss measurement confirms resonant frequency location, resonance frequency get shifted without occupying more space. Radiation pattern gives change in pattern direction with number of iterations Table 1 Results of fractal iteration Iteration S Parameter VSWR Frequency (db) 1 st 2.4GHz nd 1.8GHz rd 1.5GHz th 1.3GHz st 190

4 Figure 3 Comparison of VSWR Figure 4 Comparison of return loss Figure 5 Radiation pattern for 5 th iteration 191

5 CONCLUSION Figure 6 3-D view of fractal antenna The novel fractal patch geometry was developed with adequate bandwidth and gain and verified by simulation. This structure reduces the resonant frequency considerably with a few decreases in gain. Also for improving the inherently narrow bandwidth of patch fractal antenna, a microstrip feed is implemented. Due to the advantage of simplified configuration, suitable bandwidth and decrease the mutual coupling due to increase spacing between elements; then the proposed antenna is suitable for WLAN application. ACKNOWLEDGMENT The authors would like to thank Dr. Nalbalwar, and faculty member of Electronics and Telecommunication Department. Similarly special thanks to Pradnya Sarvade, Pooja Holkar and Sucheta Pawar for working hard day and night for the different designs of fractals. We would also like to thanks the pass out students of Dr. Babasaheb Ambedkar Technological University who presents so many papers at National and International level based on fractal design and Microstrip Antenna. REFERENCES 1. Werner D.H., Ganguly S. (2003), An overview of fractal antenna engineering research", IEEE, Antennas and Propagation Magazine, Vol Cohen, N. (1997), Fractal Antenna Applications in Wireless Telecommunications, Professional Program Proceedings of Electronics Industry Forum, pp C. L. Mak, K. M. Luk, K. F. Lee, and Y. L.Chow (2000), "Experimental Study of a Microstrip Patch Antenna with an L shaped Probe," IEEE Trans. on Antennas & Propagation, Vol. 48, pp R. Garg, P. Bhartia, I. Bahl and A. Ittipibon (2001), Microstrip Antenna Design Handbook, Artech House, Boston, London. 192

6 5. M. A. Gonzalez de Aza, J Zapata, and J. A. Encinar (2000), "Broad-band Cavity- Backed and Capacitively Probe-Fed Microstrip Antenna Patch Arrays," IEEE Trans. on Antennas & Propagation, Vol. 48, pp S. Y. Ke (2003), "Broadband Proximity-Coupled Microstrip Antenna with an H- shaped Slot in the Ground Plane," IEEE Trans. on Antennas & Propagation, Vol.43, pp , K. J. Vinoy, Jose K. Abraham, and V.K. Varadan, Fractal Dimension and Frequency Response of Fractal Shaped Antennas, IEEE. 8. Sindou, M., Abalrt G., Sournois C. (1999), Multiband and wideband properties of printed fractal branched antennas, Electronics letter, 35(3): AUTHORS 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 Nagpur University in 1996 and post graduated in Electronics Engineering from Mumbai University in 2008 and pursuing PhD form Rayalaseema University Kurnool, Andhra Pradesh. He has been involved in teaching a Microwave, Antenna & Wave Propagation and Electromagnetic 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 teacher award by ISTE sponsored by Maharashtra and Goa in He has around 70 papers at national 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 is graduated in AMIETE in 2003, postgraduate in Engineering in 2005(M. Tech.) from Nagarjuna University Guntur, and PhD in Design and Analysis of a Square Microstrip Planar Antenna Array for Wind Profiling Radars in January She is qualified for Stipend given by TEQIP Government of India during PhD in 2006 to She is Gold medallist of M. Tech. She is Member IEEE and Life member of IETE. She has 25 papers in national and international conferences and journals. 193