A. K. SHUKLA 1 B.V.V. RAVINDRA BABU 2 UMESH KUMAR 3 1 Assistant Professor and Head, Dept of EC and IC, College of Science & Engineering,Jhansi, (U.P.

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1 PERFORMANCE ANALYSIS OFCURVED U-SLOT PATCH ANTENNA WITH ENHANCED BANDWIDTH AND ISOLATION FOR MIMO SYSTEMS A. K. SHUKLA 1 B.V.V. RAVINDRA BABU 2 UMESH KUMAR 3 1 Assistant Professor and Head, Dept of EC and IC, College of Science & Engineering,Jhansi, (U.P.) 2 Assistant Professor, Dept of EC, Aditya College of Engineering, Madanapalle (AP) 3 PG Student, Dept of EC, College of Science & Engineering, Jhansi, (U.P.) ABSTRACT: The paper presents a compact tri band Curved U-Slot patch antenna with improved bandwidth and isolation characteristics. The proposed antenna excited by coaxial feed resonates at tri band of 2.8 GHz, 4.1 GHz and 5.7 GHz for VSWR 1.5 with an improved bandwidth of 99.7% and also for getting high gain antenna of db. A 2 2 MIMO is developed using the proposed antenna giving an excellent isolation of 28 db between the two antennas. The simulation results of return loss, Mutual Coupling, Gain, VSWR, Surface Current Distribution and Electrical Distribution are presented. By keeping the substrate thickness constant over various dielectric constants, simulations were carried out using MATLAB and HFSS (High Frequency Structure Simulator) software. Keywords: Curved U-slot patch antenna, Impedance bandwidth, Mutual coupling and Dielectric constant. INTRODUCTION Microstrip or patch antennas are most preferred antennas because they can be printed directly onto a circuit board. Microstrip antennas are becoming very popular within the mobile phone market. Patch antennas are low cost, have a low profile and are easily fabricated. The major disadvantage of microstrip antennas is their low bandwidth. The U shaped patch antennas gained popularity due to their wideband nature. In 1995 a broad band single layer probe fed patch antenna with a u-shaped slot was presented by Huynh and Lee [1] and [5]. However, the general microstrip antennas suffer from narrow bandwidth, which limits their application in modern communication systems like MIMO systems etc. Recently, tri-band antennas gained attention as they can be used for various applications including Wi Max [6]. MIMO technology gained popularity in wireless communications as they offer significant data throughput and link range without additional bandwidth or increased transmit power. Also they achieve array gain that improves the spectral efficiency and diversity gain that improves the link reliability with reduced fading.because of these properties, MIMO is an important part of modern wireless communication standards such as IEEE in (Wi-Fi), 4G, 3GPP Long Term Evolution, Wi-MAX and HSPA+. The main parameter regarding MIMO systems is mutual coupling, which depends on the distance between the elements in a MIMO system. If the distance is more, the mutual coupling between antennas becomes less and vice versa. Hence, by increasing the distance between the elements we can reduce the mutual coupling between the antennas. However, the distance between the antennas cannot be maintained too large, since MIMO systems have their major applications in Mobile terminals, laptops, and WLAN Access Points Wireless communications [4], where size of the device can t be maintained too large. The main source of mutual coupling is surface current flowing through ground in order to reduce these, there are several techniques like Electromagnetic band gap structure, defected ground structure [8,9], decoupling techniques, etc However, all these methods make the design of the antenna entangled. In the present work, a Curved U-Slot patch antenna MIMO system is proposed with improved bandwidth and reduced mutual coupling. The desired antenna resonates at a tri-band of 2.8 GHz, 4.1 GHz, and 5.7 GHz frequencies with an improved impedance bandwidth of 99.7% (2.3 GHz-7 GHz) and the obtained mutual coupling between the antenna elements is small and is less than -28 db.in section 2, the proposed antenna geometry is presented and in Section 3 the two element MIMO array system is presented. ANTENNA DESIGN The main objective of the antennas used in MIMO systems is to improve the bandwidth of the patch antenna. The dielectric constant of the substrate decides the bandwidth of the microstrip antennas. Low dielectric constant of the substrate produces larger bandwidth, while high dielectric constant of the substrate results in smaller size and low bandwidth [7]. The bandwidth of microstrip antennas can be increased by several techniques such as keeping parasitic elements on the patches, increasing the substrate thickness, inserting slots and using defected ground structures [9].The patch antennas are fabricated with various shapes and most of them are widely designed antennas are E shaped patch antenna, H shaped patch antenna [10] etc. Among all these antennas, E shaped patch ISSN All Rights Reserved 2014 IJEETE Page 11

2 antennas are widely used as they give better performance in terms of both impedance bandwidth and mutual coupling. The U-Slot patch antenna can be formed by cutting three rectangular slots on a rectangular patch and also using polyline to cut frontends and edges of the rectangular slots as shown in Figure 1.The dimensions of the geometry are given in the Table 1. For better performance, a thick dielectric substrate having a low dielectric constant is desirable as it provides better efficiency, larger bandwidth and better radiation. Here, the substrate selected for the design of the proposed antenna is RT/duroid 5880 of thickness 6.4 mm and with low permittivity (εr=2.2). The dimensions of the substrate are taken as mm3. Simulator) software. The analysis on results obtained for different parameters of proposed antenna is as follows: RETURN LOSS Return loss indicates the amount of delivered power loss due to reflections.it is the ratio of power reflected to the power delivered expressed in negative logarithmic db. The more return loss tends to negative value,the effective is the power delivery.the proposed antenna is operated at the frequency of 3 GHz and it resonates at 2.8 GHz with wide band characteristics. The range of frequencies between 2.3 GHz-7 GHz is covered within a single broad band. The return loss, S11= -25dB can be measured from the plot at the centre frequency of 5.7 GHz.The impedance bandwidth measured from the plot is 99.7% which ismore than the maximum available bandwidth. The return loss plot of the designed antenna is shown in the figure 2. Figure 2:The return loss of the proposed antenna. Figure 1: The top and side views of the proposed Curved U-Slot patch antenna Table 1: The dimensions of the patch and substrate are in millimeters Here, the substrate selected for the design of the proposed antenna is verified by using different materials such asrt/duroid 5880, Epoxy, FR4_epoxy and Rogers RO60006 among all these parameters RT/duroid5880 substrate produces high impedance bandwidth as shown in Table 2 and the return loss plot is sown in Figure3. Table 2:Different bandwidths obtained for different materials. S.NO. Material Dielectric constant Impedance Band Width The proposed antenna resonates at tri-band of 2.8 GHz, 4.1 GHz and 5.7 GHz frequencies for VSWR 1.5 with an improved impedance bandwidth of 99.7% and a reduced mutual coupling of -28 db. The antenna has been simulated by using HFSS software. RESULTS AND ANALYSIS The proposed antenna is simulated using MATLAB and HFSS (High Frequency Structure 1) Rogers RT/Duroid % 2) Epoxy % 3) FR4 epoxy % 4) Rogers RO % As the dielectric constant of the material increases then the bandwidth will decrease we can observe in the ISSN All Rights Reserved 2014 IJEETE Page 12

3 Table 2. Figure 3 shows the return loss plot of different materials with a dielectric constant ranges from 2.2 to 6.2. Figure 3:The return loss plot of Different bandwidths obtained for different materials. RADIATION PATTERN Radiation pattern is a graphical representation of the antenna radiation properties as a function of spherical coordinates in desired direction The radiation or antenna pattern describes the relative strength of the radiated field in various directions from the antenna, at a constant distance. The radiation pattern is a reception pattern as well, since it also describes the receiving properties of the antenna. The radiation characteristics of the designed antenna is represented by the 2D radiation pattern at Phi=0 deg, Phi=90 deg for all theta as observed from the fig-8.the patch's radiation at the fringing fields results in a certain far field radiation pattern. This radiation pattern shows that the antenna radiates more power in a certain direction than another direction. (c) 5.7 GHz Figure 8: Radiation patterns of the proposed antenna The variations of power radiated by the proposed antenna at triple band are shown here. Figure 9: 3D polar plot of the proposed antenna (a) 2.8 GHz (b) 4.1 GHz EXPORT PARAMETERS Peak Directivity Radiated Power Accepted Power Incident Power Radiation Efficiency (W) (W) (W) CONCLUSION In this paper, a novel compact tri band Curved U- Slot patch antenna is proposed and a two element MIMO array is developed using the proposed antenna has a compact size of 60mmx40mm.The proposed antenna excited by coaxial feed resonates at tri band of 2.8 GHz, 4.1 GHz and 5.7 GHz for VSWR 1.5 with an improved bandwidth of 99.7% and also for getting high gain antenna of db was obtained using RT/duroid 5880 substrate material which a dielectric constant of 2.2. A 2 2 MIMO is developed using the proposed antenna giving an excellent isolation of 28 db between the two antennas. In this paper, design of for small-size wide-bandwidth patch antennas has been presented. These designs combine the wideband U-slot ISSN All Rights Reserved 2014 IJEETE Page 13

4 and different substrate material. The results prove that using a substrate material with a lower dielectric constant substrate constant in design of MPA leads to better performance. The proposed antenna is expected to have numerous applications in the modern communication systems such as 4G, WLAN,Wi-MAX, UMTS and Ultra Wide Band applications. The proposed study can be extended by employing more number of antennas in MIMO system for improving the channel capacity of the MIMO systems in future. REFERENCES [1] K. F. Lee, K. M. Luk, K. F. Tong, S. M. Shum, T. Huynh and R. Q. Lee, Experimental and simulation studies of the coaxially fed U-slot rectangular patch antenna, Inst. Elect. Eng. Proc. -Microw. Antennas Propagat., vol. 144, (1997) October, pp [2] ShahramMohanna, Ali Farahbakhsh, and SaeedTavakoli Mutual Coupling Reduction in Two-Dimensional Array of Microstrip Antennas Using Concave Rectangular Patches International Journal of Telecommunications, Volume 2, Issue 2, May [3] K. L. Wong, Compact and Broadband Microstrip Antennas. New York: Wiley, [4] P.Kiran, R.Chiramjeevi, T.Chaitanya Reddy, D.SushmaSree, A Triband U- Slot Patch Antenna with Enhanced Bandwidth and Isolation for MIMO Systems, International Journal of Energy, Information and Communications Vol.4, Issue 5 (2013), pp.1-14 [6] T. Huynh and K. F. Lee, Single-layer single-patch wideband microstrip antenna, Electron.Lett., vol. 31, no. 16, (1995), pp [7] K. J. Babu, K. S. R. Krishna and L. P. Reddy, A triband swastika shaped patch antenna with reduced mutual coupling for wireless MIMO systems, Journal of Electronics (China), SPRINGER, vol. 28, (2011) November, pp [8] D. M. Pozar, Microstrip Antennas, Proc. IEEE, vol. 80, no. 1, (1992) January, pp [9] F. Caminita, S. Costanzo, G. DiMassa, G. Guarnieri, S. Maci, G. Mauriello and I. Venneri, Reduction ofpatch antenna coupling by using a compact EBG formed by shorted strips with interlocked branchstubs, IEEE Antennas and Wireless Propagation Letters, vol. 8, (2009), pp [10] K. J. Babu, K. S. R. Krishna and L. P. Reddy, A Multi Slot Patch Antenna for 4G MIMO Communications, International Journal of Future Generation Communication and Networking, vol. 4, no. 2, (2011). [11] S. C. Gao, L. W. Li, M. S. Leong and T. S. Yeo, Analysis of an H-shaped patch antenna by using the FDTD Method, Progress in Electromagnetics Research, vol. 34, (2001), pp [12] A. K. Shackelford, K. -F. Lee and K. M. Luk, Design of Small-Size Wide-Bandwidth Microstrip-Patch Antennas, IEEE Antennas and Propagation MOQOZine, vol. 4-5, no. 1, (2003) February. [13] L. H. Weng, Y. C. Guo, X. W. Shi and X. Q. Chen, AN OVERVIEW ON DEFECTED GROUND STRUCTURE, Progress In Electromagnetics Research B, vol. 7, (2008), pp [14] K. Siakavara, Methods to Design Microstrip Antennas for Modern Applications, Microstrip Antennas, N. Nasimuddin, (Ed.), ISBN: , InTech, (2011). [15] K. JagadeeshBabu, Dr.K.Sri Rama Krishna, Dr.L.PratapReddy, A Multi Slot Patch Antenna for 4G MIMO Communications, International Journal of Future Generation Communication and Networking Vol. 4, No. 2, June, 2011 AUTHOR S BIBLOGRAPHY UMESH KUMAR Received B.E in Electronics & Communication Engineering from ANNA University, Tamilnadu, INDIA. Presently he is pursuing M.Tech in Electronics & Communication Engineering from UPTU Lucknow (UP) INDIA. He attended so many National Conferences, Workshops and Published Many Papers in National and International Journals. A K. SHUKLA Received B.Tech and M.Tech in Electronics & Communication Engineering from U.P.T.U. LUCKNOW INDIA. Presently Working as Asst. Professor and HOD of EC & IC Departments in SRGI JHANSI (UP). He attended so many National Conferences, Workshops and Published Many Papers in National and International Journals ISSN All Rights Reserved 2014 IJEETE Page 14

5 B.V.V RAVINDRABABU Received B.Tech in Electronics & Communication Engineering from M.I.S.T- SATTUPALLI (JNTU) and M.Tech in VLSI DESIGN from Sathyabama University, Chennai.Presently working as Asst. Professor (ECE Department) in Aditya College of Engineering, Madanapalle (AP). He attended many National Conferences, Workshops and Published Many Papers in National and International Journals. ISSN All Rights Reserved 2014 IJEETE Page 15