INTERNATIONAL JOURNAL OF PURE AND APPLIED RESEARCH IN ENGINEERING AND TECHNOLOGY

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1 INTERNATIONAL JOURNAL OF PURE AND APPLIED RESEARCH IN ENGINEERING AND TECHNOLOGY A PATH FOR HORIZING YOUR INNOVATIVE WORK DESIGN OF MICROSTRIP FED UWB-MIMO DIVERSITY ANTENNA USING ORTHOGONALITY IN POLARIZATION GOPAL SURUSHE 1, RAJ KUMAR 2 1. Student, M. Tech., DIAT (DU), Girinagar,Pune ,India 2. ARDE, Pashan, Pune , India Accepted Date: 05/03/2015; Published Date: 01/05/2015 Abstract:In this paper, a compact Ultra wideband diversity antenna is proposed. It consists of the horizontally polarized slot antenna and trapezoidal monopole antenna with round corner ground. The orthogonality of the E-field improves the isolation between the compact antennas. The volume of the antenna is 58 x 57 x 1.6 mm 3 including the ground plane. The measured results show that the antenna can operate from 3.2GHz to 10.6GHz, with the isolation better than 22dB. Furthermore, the radiation pattern, diversity gain, and envelope correlation coefficient are measured and discussed. These characteristics best suit this antenna for the MIMO diversity applications. Keywords: UWB antenna, Microstrip feed, Horizontal Polarized antenna, MIMO and Diversity \ Corresponding Author: MR.GOPAL SURUSHE Access Online On: How to Cite This Article: PAPER-QR CODE 56

2 INTRODUCTION In recent years, there is tremendous growth in wireless communications. Fast communication is the need of time which requires the high data rate and large bandwidth. In 2002, the Federal Communications Commission (FCC) released unlicensed spectrum from 3.1 GHz to 10.6 GHz. This enlighten the research efforts for high data rate on the UWB application like personal area network, satellite communication [1]. The use of multiple antennas helps us to improve the range and capacity of a system, which leads Multi-input Multi-output (MIMO) concept. The performance of MIMO system depends on the inter element spacing, antenna geometry and number of antenna elements. We have to balance the inter element spacing between the radiators along with the antenna size for better performance. So, it is a difficult task to design Multi-input Multi-output antenna for Ultra Wideband with compact size. Several works have been reported on UWB antennas with CPW/Microstrip fed in open literature [2-7]. In MIMO/ diversity applications, two or more UWB antennas have to be implemented to mitigate the multipath effect of the propagating signals. The Multipath effect of signal can be overcome using MIMO/diversity of antenna [8-12]. In [8], proposed diversity antenna with the size of 37mm x 40mm designed for portable devices operating in lower UWB from GHz. The isolation better than 20 db is obtained within the working range by a vertical branch. In [9], a MIMO antenna with two back-to-back monopole antennas of size 40mm x 30mm is proposed. The dual-band antenna is designed for GHz and GHz application; a T shaped stub is added to improve the isolation between antennas. In [10], 2.4 GHz impedance bandwidth achieved by two fictitious shorts using microstrip feed for a rectangular slot. A compact MIMO antenna of size 40mm x 68mm for Ultra Wideband 3.2GHz to 10.6GHz is presented in [11]. Two symmetric circular patch antennas are kept side by side on a common ground & Y shaped stub is used to achieve isolation more than 15dB between two antennas. An UWB slot antenna is presented in [12] for diversity applications, the antenna with size 80 x 80 mm 2 is proposed for the return loss <-10dB within the range 3GHz to more than 12GHz and isolation better than 15dB achieved.. In this paper, Ultra wideband MIMO antenna is presented with a horizontally polarized microstrip fed stepped antenna integrated with the vertically polarized half-hexagonal microstrip antenna. The design is optimized for good return loss (<-10dB) and isolation 22 db within the working range. 2. ANTENNA GEOMETRY The geometry of proposed UWB diversity antenna is shown in Figure 1. The two UWB antenna elements are printed on a 57 mm 58 mm FR4 PCB substrate with thickness of 1.6 mm, a dielectric permittivity ε r = 4.4. Antenna with port 1 is a horizontally polarized UWB antenna 57

3 which is fed by stepped microstrip line. The port 1 has feed line and successively sectioning of the slot in the ground. The central slot section has less width for better coupling with the feed while the width of the remaining sections is more to get enlarged radiation aperture [13]. Fig. 1 Antenna Geometry Antenna at port 2 has trapezoidal patch having dimensions L1=11 mm, L2=16.5 mm separated by 9.7mm and has stepped feed line. Ground of antenna-2 is blended with the radius R=16 mm. Both the antennas are having different grounds are separated by 0.9 mm. The antenna was designed and optimized for optimum performance using CST Microwave Studio software. 3. EXPERIMENTAL RESULTS AND DISCUSSION The simulated and measured S-parameters for both the ports are shown in Figure 2. Both the antennas exhibits ultrawide bandwidth. For antenna-1, the bandwidth starts from 3.2GHz and goes beyond 12GHz while for antenna-2the bandwidth obtained from 3.4GHz to 10.6GHz for S 11 <-10dB as shown in Figure 2(a). The proposed UWB range is validated by both simulation and measured results. The isolation between both the ports is obtained better than 22 db throughout band as shown in Figure 2(b). (a) 58

4 (b) Fig. 2 (a) Simulated & Measured return loss of port 1 and port 2, (b) Simulated & measured isolation (S 21 ) 4. ENVELOPE CORRELATION COEFFICIENT 1) The multipath effect of the propagating signals to the MIMO antenna is given by the envelope correlation coefficient. Envelope correlation coefficient may vary between 0 and 1, where it gives the degree of similarity between the beam patterns. By using the equation (1), the envelope correlation can be calculated [15]. This is the simplest technique to calculate the envelope correlation coefficient using the S-parameters of the diversity antennas. The simulated and measured S-parameters are used in equation (1) to calculate the simulated and measured ρ = S 11 S 21 +S 12 S S 2 11 S S 2 22 S 2 12 Envelope correlation coefficient as shown in the Figure 3. The simulated envelope correlation is below and measured one is below which is well below the required value [16]. (1) Fig. 3 Envelope Correlation Coefficient of the diversity antenna 5. DIVERSITY GAIN Diversity gain gives the amount of the reduced transmitted power when the diversity scheme is used. The envelope correlation coefficient is the affecting factor for the diversity gain as given in equation (2), until it is less than 0.7 at base station and less than 0.5 at mobile [16]. G = 10 1 ρ e 2 (2) 59

5 Maximum diversity gain can be obtained for the minimum envelope correlation coefficient. Fig. 4 shows the simulated and measured diversity gain which is almost equal and closer to 10. It is shown that lower the mutual coupling, higher the diversity gain indicated the higher antenna efficiencies. Fig. 4 Diversity gain of proposed diversity antenna 6. RADIATION PATTERNS The simulated and measured radiation patterns for the proposed diversity antenna is shown in Fig. 5. The radiation patterns are shown at the three different frequencies 4.2GHz, 8GHz and 10GHz. For antenna-1 and antenna-2 radiation patterns are shown for port 1 and port 2 respectively. The nature of E and H plane radiation patterns are figure of eight and omnidirectional respectively as shown in Fig. 5(a) & 5(b). The radiation patterns are different for both the ports as shown in figure as both the antennas used in MIMO are orthogonally placed and different from each other. (a) 60

6 (b) Fig. 5. Radiation Patterns for diversity antenna in (a) E - plane, (b) H - plane 7. CONCLUSIONS A compact UWB diversity antenna is designed, fabricated and validated experimentally. The measured impedance bandwidth of antenna achieved at port 1from 3.2GHz to 12GHz and at port 2 from 3.4GHz to 10.6GHz. The isolation between the port 1 and port 2 is obtained better than 22dB throughout the band. The simulated and measured radiation patterns, diversity gain, envelope correlation coefficient are also found in good agreement. Within the working band, the envelope correlation coefficient is better than while diversity gain is closer to 10. These feature of proposed diversity antenna system is suitable for the MIMO applications. REFERENCES 1. L. Yang and G. B. Giannakis, Ultra-wideband communications An idea whose time has come, IEEE Signal Process. Mag., vol. 21, no. 6, pp , Nov J.Liang, L.Guo, C.C.Chiau and X.Chen, CPW-Fed Circular Disc Monopole Antenna for UWB Application, IEEE Antenna Technology: small Antennas and Novel Metamaterials, IWAT, IEEE Intern. Workshop, pp , March Ritu, K. Sherdia, Microstrip Antenna Design for UWB Application, International Journal of Advanced research in Computer and Communication Engg., Vol. 2, Issue 10, October K. S. Lim, M. Nagalingam, and C.P. Tan, Design and Construction of Microstrip UWB Antenna With Time Domain Analysis, Progress In Electromagnetics Research M, Vol. 3, ,

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