International Journal of Electronics and Communication Engineering & Technology (IJECET),
INTERNATIONAL JOURNAL OF ELECTRO...
International Journal of Electronics and Communication Engineering & Technology (IJECET),
ISSN 0976 – 6464(Print), ISSN 09...
International Journal of Electronics and Communication Engineering & Technology (IJECET),
ISSN 0976 – 6464(Print), ISSN 09...
International Journal of Electronics and Communication Engineering & Technology (IJECET),
ISSN 0976 – 6464(Print), ISSN 09...
International Journal of Electronics and Communication Engineering & Technology (IJECET),
ISSN 0976 – 6464(Print), ISSN 09...
International Journal of Electronics and Communication Engineering & Technology (IJECET),
ISSN 0976 – 6464(Print), ISSN 09...
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A pattern diversity compact mimo antenna array design for wlan

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A pattern diversity compact mimo antenna array design for wlan

  1. 1. International Journal of Electronics and Communication Engineering & Technology (IJECET), INTERNATIONAL JOURNAL OF ELECTRONICS AND ISSN 0976 – 6464(Print), ISSN 0976 – 6472(Online), Special Issue (November, 2013), © IAEME COMMUNICATION ENGINEERING & TECHNOLOGY (IJECET) ISSN 0976 – 6464(Print) ISSN 0976 – 6472(Online) Special Issue (November, 2013), pp. 134-139 © IAEME: www.iaeme.com/ijecet.asp Journal Impact Factor (2013): 5.8896 (Calculated by GISI) www.jifactor.com IJECET ©IAEME A Pattern Diversity Compact MIMO Antenna Array Design for WLAN Application Prof. S S Khade1, Dr. S L Badjate2 1Dept. 2Dept. of Electronics and Telecommunication Engg., Y.C.C.E, Nagpur, India of Electronics and Telecommunication Engg., S.B.J.I.T., Nagpur, India 1sac_mob@rediffmail.com, 2 s_badjate@rediffmail.com ABSTRACT: In this paper, design of multiple-input multiple-output (MIMO) arrays is presented for WLAN applications. The planar directive antenna is of interest in the proposed work. To enhance channel capacity in rich multipath environment low mutual coupling among radiating elements is necessary. To achieve low mutual coupling among radiating elements, we need orthogonal patterns. In this paper, printed Yagi-Uda antenna with an integrated balun is presented and MIMO array is obtained by placing three printed Yagi-Uda antenna in a triangular configuration to achieve orthogonal patterns. The proposed MIMO array is designed on FR4 substrate. The proposed array exhibit very low mutual coupling less than -20 dB in the impedance bandwidth ranging around 4.8 GHz to 6.2 GHz. KEYWORDS: Multiple-input multiple-output system, multipath channels, Printed Yagi antenna, directive antenna, integrated balun, wireless local area network (WLAN). I. INTRODUCTION MULTIPLE-INPUT–MULTIPLE-OUTPUT (MIMO) wireless systems, characterized by multiple antenna elements at the transmitter and receiver, have demonstrated the potential for increased capacity in rich multipath environments. Such systems operate by exploiting the spatial properties of the multipath channel, thereby offering a new dimension which can be used to enable enhanced communication performance. The technology figures prominently on the list of recent technical advances with a chance of resolving the bottleneck of traffic capacity in future Internet-intensive wireless networks. Perhaps even more surprising is that just a few years after its invention the technology seems poised to penetrate large-scale standards-driven commercial wireless products and networks such as broadband wireless access systems, wireless local area networks (WLAN), third generation networks (3G) and beyond. In wireless environment, signals are scattered from various structures and reach the receiving terminal from any unpredicted direction. An omnidirectional antenna not only receives signal from all directions but also receives noise from all directions. A directional antenna receives noise only from a particular direction, resulting in better communication. Also, for WLAN APs, International Conference on Communication Systems (ICCS-2013) B K Birla Institute of Engineering & Technology (BKBIET), Pilani, India October 18-20, 2013 Page 134
  2. 2. International Journal of Electronics and Communication Engineering & Technology (IJECET), ISSN 0976 – 6464(Print), ISSN 0976 – 6472(Online), Special Issue (November, 2013), © IAEME directional and end fire antennas are promisingly suitable. Also for outdoor-indoor scenarios directive antennas are used to enhance MIMO capacity [1]. The performance of the MIMO antenna is studied by considering some parameters. Mutual coupling is one of the important parameter because higher mutual coupling means lower antenna efficiency, correlation coefficient and total active reflection coefficient are another parameters [2].To achieve low mutual coupling among radiating elements in a MIMO array, diversity techniques are used. There are essentially three antenna diversity techniques commonly employed in MIMO array designs which are space, polarization, and pattern diversity [3-6]. In typical MIMO systems, size and cost constraints often prevent the antennas from being placed far apart therefore space-diversity techniques may be insufficient for next generation wireless handsets. Therefore pattern diversity technique is considered advantageous over other techniques. To exploit pattern diversity, the antennas are designed to radiate with orthogonal radiation patterns as a means to create uncorrelated channels across different array elements. There are many designed to achieve pattern orthogonality for example by exciting orthogonal modes within the same geometrical structure in co-located patch antennas [7] or in spirals [8], pattern synthesis based on properly tailored current distribution in a theoretical array [9], or reconfigurable planar arrays made of combined Landstorfer and Yagi-Uda antennas [10]. In this paper, to exploit pattern diversity or to achieve orthogonal patterns, a very simple and easy to implement design has been developed. In particular, the printed Yagi-Uda antenna with an integrated balun has been designed and MIMO array has been obtained in a triangular configuration. The proposed array has been designed for WLAN application. II. SIMULATED ANTENNA STRUCTURE A. Single Printed Yagi-Uda Antenna The printed Yagi Uda antenna with an integrated balun was designed on both sides of 27.6 mm x 24 mm FR4 with a dielectric constant 4.4 and thickness of 1.6mm as shown in fig. 1. FR4 is more available and much cheaper than any other PCB material and it has good parameters for most applications, mechanical, electrical & climatic stabilities and even economical aspects too. The antenna comprises of an integrated balun feeding, two printed dipoles, a parasitic strip and a ground plane. The two printed dipoles, the larger dipole and the smaller dipole, act as a reflector and driver respectively. The parasitic strip in the proposed structure acts as a director. A printed Yagi-Uda antenna has been presented in [11] where a broadband Microstrip-tocoplanar strips (CPS) transition is employed. The ground plane below the transition acts also as the Yagi-Uda reflector. Here we construct different Microstrip-to-CPS transition with a shaped ground for optimization of the reflector element. The shaped ground also allows reduction of the metallization near the feeding point. The entire structure is excited by proximity coupling, using an open ended microstrip above a rectangular hole in the ground plane. We used a 50Ω impedance microstrip line on a back side of substrate while the coplanar stripline was designed on the front side of the substrate with a characteristic impedance of 100Ω. The antenna was simulated using CADFEKO software. The dimensions of the proposed antenna are as described below. The length of substrate (ls) and width of substrate (ws) is 27.6 mm and 24 mm respectively. Thus the proposed antenna is International Conference on Communication Systems (ICCS-2013) B K Birla Institute of Engineering & Technology (BKBIET), Pilani, India October 18-20, 2013 Page 135
  3. 3. International Journal of Electronics and Communication Engineering & Technology (IJECET), ISSN 0976 – 6464(Print), ISSN 0976 – 6472(Online), Special Issue (November, 2013), © IAEME compact in size. The length of driver (l1) is optimized to 17 mm which is responsible for resonant frequency and bandwidth response of proposed Yagi – Uda antenna. The length of director (l3) value is adjusted to 11.5 mm in order to reach high directivity. The length of reflector (l1) and finite ground plane length (lg) and width (wg) values are 21.5 mm, 6.2 mm and 9 mm respectively which improves back lobe suppression which results in high directivity. The ground plane extension (h1) value is 2.6 mm. The width of director (w0), driver (w1) and reflector (w2) is 2 mm. Separation between reflector and driver (d2) and separation between director and driver (d3) is adjusted to 4.5 mm and 5.5 mm respectively. Length of rectangular slot (a1) and its width (b1) values are 4 mm and 1 mm respectively. The distance (d1) of slot from finite ground plane is 5 mm. The ratio of transition (a2/b2) is maintained to 0.5 mm and magnitude of cut “c” is 1 mm which is also responsible for bandwidth response of proposed antenna. The impedance matching was realized by acting again on the ratio of the transition and on the driven element-to-director distance. (a)Top View (b) Bottom View Fig. 1: Proposed single antenna design B. Array Configuration To achieve orthogonal patterns, MIMO array is obtained by placing three printed Yagi-Uda antenna in a triangular configuration as shown in fig. 2. The ground plane extension of single printed antenna is delimited by a Y-shaped slot whose branches are spaced by 120 degrees, which enhance isolation among radiating elements in an array since each antenna in an array configuration is having separate ground plane. (a) Top View (b) Bottom View Fig. 2: Proposed antenna array design obtained by rotating each printed antenna by 120 degree International Conference on Communication Systems (ICCS-2013) B K Birla Institute of Engineering & Technology (BKBIET), Pilani, India October 18-20, 2013 Page 136
  4. 4. International Journal of Electronics and Communication Engineering & Technology (IJECET), ISSN 0976 – 6464(Print), ISSN 0976 – 6472(Online), Special Issue (November, 2013), © IAEME III. RESULTS AND DISCUSSIONS For a proposed antenna array we got upper WLAN band operation at 5 GHz ranging from 5.15 GHz – 5.825 GHz. The return loss plot of each antenna in an array configuration is below -10 dB in the interested frequency band. The value of mutual coupling is low in an interested frequency range due to separate ground plane of each antenna in an array configuration. It is less than -20 dB in an impedance bandwidth of proposed array. Thus the proposed antenna array is designed and simulated for upper band WLAN application.Simulated results are visualized in the following figures. Fig. 3: Combined Return loss plot for array The performance of all three antennas of a MIMO Array is nearly same. Bandwidth range obtained is from 4.8 GHz to 6.2 GHz which covers upper WLAN band ranging from 5.15 GHz to 5.825 GHz as shown in fig. 3. The operating frequency is 5.69 GHz. Fig. 4: VSWR graph of a MIMO Array Fig. 5: Impedance graph of a MIMO Array International Conference on Communication Systems (ICCS-2013) B K Birla Institute of Engineering & Technology (BKBIET), Pilani, India October 18-20, 2013 Page 137
  5. 5. International Journal of Electronics and Communication Engineering & Technology (IJECET), ISSN 0976 – 6464(Print), ISSN 0976 – 6472(Online), Special Issue (November, 2013), © IAEME VSWR is in between 1 and 2 in the impedance bandwidth and impedance is around 50 Ώ in the bandwidth obtained for an array, as shown in fig. 4 and 5 respectively. Fig. 6: Plot representing transmission coefficients for array The mutual coupling between the radiating elements should be -10 dB below for good performance of an array. The value of mutual coupling is less than -20 dB in the impedance bandwidth of an array, as shown in figure 6. Fig. 7: Gain (3D View) of an array Fig. 8: Directivity plot (2D View) of a MIMO Array Gain of a MIMO array is around 2.29 dBi at operating frequency as shown in figure 7, where red colour indicates maximum value of gain in the particular direction. Directivity of an MIMO International Conference on Communication Systems (ICCS-2013) B K Birla Institute of Engineering & Technology (BKBIET), Pilani, India October 18-20, 2013 Page 138
  6. 6. International Journal of Electronics and Communication Engineering & Technology (IJECET), ISSN 0976 – 6464(Print), ISSN 0976 – 6472(Online), Special Issue (November, 2013), © IAEME array is around 2.97 dBi at the operating frequency. Figure 8 represents polar plot of an array, showing directivity. IV. CONCLUSION In this paper, pattern diversity is exploited to achieve orthogonal patterns. Here, printed YagiUda antenna is of interest since it is directive antenna and has many advantages. Here, we have designed MIMO array by placing three printed antennas in an equilateral triangular configuration to achieve isolation among radiating elements. The proposed array is of size 60 mm x 55 mm and thus compact in nature. The proposed array has been designed for WLAN application and it has low cost. The proposed antenna array is used for indoor applications due to its compact size. Also the proposed antenna design principle can be extended to arrays having a large number of antennas due to compact size of antenna. REFERENCES [1]C. Hermosilla, R. Feick, R. Valenzuela, and L. Ahumada, “Improving MIMO capacity with directive antennas for outdoor-indoor scenarios,” IEEE Trans. Wireless Commun., vol. 8, pp. 2177–2181, May 2009. [2]S. H. Chae, S.-K. Oh, and S.-O. Park, “Analysis of mutual coupling,correlations, and TARC in WiBro MIMO array antenna,” IEEE Antennas Wireless Propag. Lett., vol. 6, pp. 122–125, 2007. [3]M. A. Jensen and J. W. Wallace, “A review of antennas and propagation for MIMO wireless communications,” IEEE Trans. Antennas Propagat., vol. 52, no. 11, pp. 2810–2824, Nov. 2004. [4]A. M. Tulino, A. Lozano, and S. Verdu, “Impact of antenna correlation on the capacity of multiantenna channels,” IEEE Trans. Inf. Theory, vol. 51, no. 7, pp. 2491–2509, Jul. 2005. [5]A. M. Tulino, S. Verdu, and A. Lozano, “Capacity of antenna arrays with space, polarization and pattern diversity,” in Proc. IEEE Inf. Theory Workshop, Mar. 2003, pp. 324–327. [6]S. W. Ellingson, “Antenna design and site planning considerations for MIMO,” in Proc. IEEE Veh. Technol. Conf., Sep. 2005, vol. 3, pp. 1718–1722. [7]A. Forenza and R. W. Heath, “Benefit of pattern diversity via two element array of circular patch antennas in indoor clustered MIMO channels,” IEEE Trans. Commun., vol. 54, pp. 943– 954, May 2006. [8]C.Waldschmidt and W. Wiesbeck, “Compact wide-band multimode antennas for MIMO and diversity,” IEEE Trans. Antennas Propag., vol.52, pp. 1963–1969, Aug. 2004. [9]B. T. Quist and M. A. Jensen, “Optimal antenna radiation characteristics for diversity and MIMO systems,” IEEE Trans. Antennas Propag., vol. 57, pp. 3474–3481, Nov. 2009. [10]A. C. K. Mak, C. R. Rowell, and R. D. Murch, “Lowcost reconfigurable Landstorfer planar antenna array,” IEEE Trans. Antennas Propag., vol. 57, pp. 3051–3061, Oct. 2009.. [11]N.Kaneda,W.R.Deal,Y.Qian,R.Waterhouse,and T. Itoh, A Broadband Planar Quasi Yagi Uda Antenna,IEEE Trans.Antennas Propag.,vol50,pp.1158-1160,Aug.2002. International Conference on Communication Systems (ICCS-2013) B K Birla Institute of Engineering & Technology (BKBIET), Pilani, India October 18-20, 2013 Page 139

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