Design of MIMO Antenna for WiMAX Applications based on DGS Technique for Bandwidth Enhancement N.LAKSHMI TEJASWI [1], M.V.S.PRASAD [2] [1] COMMUNICATION AND SIGNAL PROCESSING, M.TECH [2] ASSOCIATE PROFESSOR, ECE DEPARTMENT RVR AND JCCE COLLEGE OF ENGINEERING, GUNTUR, A.P, INDIA nagasaraputeja@gmail.com, mvsprasad@rvrjc.ac.in Abstract: In this paper, a new design of microstrip patch antenna is proposed, which can be used in WiMAX communication systems. In this we use MIMO (multiple input multiple output) antenna for antenna design. Nowadays, WiMAX communication applications are widely using microstrip patch antenna. The proposed antenna design uses 1-10GHz frequency band and it is working at narrowband within this band. The substrate material is RT/DUROID 5880 for the microstrip patch antenna. The proposed antenna shows advantages in terms of bandwidth and gain. In this paper, we use DGS technique for increasing the bandwidth of the antenna. Keywords: Microstrip patch antenna, DGS, MIMO, WiMAX. 1. INTRODUCTION Microstrip antenna was proposed in early 1970 [3] and it provides a great revolution in the field of antenna design. Nowadays microstrip patch antenna has become very popular and is widely used in various types of applications. A microstrip patch antenna consists of a radiating patch on one side of a dielectric substrate and other side is ground plane [4]. The patch is generally made of conducting material such as copper or gold. In modern wireless communication systems, multiband antenna has been playing a very important role for wireless service requirements. Some applications of the wireless communication system such as cellular phones, laptops, PC wireless cards, and various remote-sensing devices require miniaturized antennas. For these applications, the microstrip patch antenna has special advantages because of its simple structure. The microstrip antenna has several advantages such as low profile, lightweight, simple structure and easy fabrication. The topology used for making microstrip patch antenna is U-shaped, which is single narrowband patch antenna [1]. Dual wideband stacked patch antenna is used for both WLAN and WiMAX applications [6]. Due to these properties, the microstrip patch antenna has become very popular in many applications s uch as in WiMAX communication system and mobile applications. This antenna is designed for WiMAX communication system. WiMAX belongs to IEEE 802.16 family of standards. The full form of WiMAX is worldwide interoperability for microwave access. DGS technology is used in this paper for better antenna performance [6,9]. DGS means defected ground structure. It helps to absorb the waves which propagate through ground plane. These waves are known as surface waves. DGS basically helps in shrinking the size of patch antenna due to change in current distribution. This motivates to use DGS to reduce the coupling between antenna arrays and also the size of the patch along with enhancement in the bandwidth. Etched slots or defects on the ground plane of microstrip circuits are referred to as Defected Ground Structure. Single or multiple defects on the ground plane may be considered as DGS. 259
2. ANTENNA DESIGN This microstrip patch antenna was designed for WiMAX communication system with MIMO technology. The result comes out that the antenna bandwidth can be increases. The proposed antenna was designed for WiMAX communication system with MIMO antenna with different dimensions of height and length. The substrate material is RT/DUROID 5889 with permittivity 2.2and dielectric tangent loss 0.0009. The thickness of the substrate is 2.4mm. The thickness of the ground is 0.1mm. The length of the substrate is 70mm and width is 90mm. The width of the patch is 50mm and length is 50mm. The length of the feed is 28mm and width is 3mm. List of parameters used in the design of U- shaped microstrip patch antenna are given below in table C. L1(l1,w1) L2(l2,w2) W2(l,w) S1(l,w) S2(l,w) S3(l,w) S4(l,w) S5(l,w) S6(l,w) S7(l,w) 20,3mm 20,3mm -29,-0.7mm 4,1.4mm 4,2mm 4,1.4mm 4,2mm The S1, S2, S3, S4, S5, S6, S7 are the stubs in the U-shaped patch antenna starting from the left one and so on. The MIMO antenna can be designed in CST studio site. The antenna design is shown below Fig 1. Fig 1: The MIMO antenna In this paper, the result is to increase the performance of MIMO antenna for using in WiMAX communication application system. This antenna gives the result is increase in bandwidth and maximum gain at 9GHz. The microstrip antenna is operating in between 1-10GHz frequency. The geometric shape of single microstrip antenna is shown in Fig 2. Fig2: Geometric shape of the single antenna. 260
The DGS technique is applied to microstrip antenna. Etched slots or defects on the ground plane of microstrip circuits are referred to as Defected Ground Structure. The design of the microstrip antenna after applying the DGS technique is in figure 3. Fig 3: Antenna with DGS technique The ground can be cut into with some dimensions for better performance of antenna. 3. SIMULATION RESULTS In this paper, our aim is to increase the antenna performance such as return loss, bandwidth and gain. The simulated return loss result of the proposed antenna is shown in Figure 4. The operating frequency of MIMO antenna is 1-10GHz. It can be used for multiband for WiMAX applications. The resonant bands are at 2.5GHz, 5GHz, 7GHz, and 9GHz. Fig 4: Return loss of MIMO antenna VSWR is a function of the reflection coefficient, which describes the power reflected from the antenna. The smaller the VSWR is, the better antenna is matched to the transmission line and more power is delivered to the antenna. From the VSWR plot, VSWR of multiband antenna is closely equals to unity. VSWR of the proposed antenna is shown in Fig 5. Fig 5: VSWR of MIMO antenna Radiation pattern is the one of the most important property of the microstrip antenna. In this we absorb the gain of the MIMO antenna. The far field radiation patterns in terms of 3D view for the proposed multiband antenna are shown in below figures at the resonant frequencies 5GHz, 7GHz and 9GHz respectively. 261
Fig 6: Radiation pattern of antenna at 5GHz Fig 7: Radiation pattern of antenna at 7GHz Fig 8: Radiation pattern of antenna at 9GHz Figure 6, 7 and 8 shows the simulated result of gain of the MIMO antenna. The gain of the proposed antenna is at 5GHz is 6.94dB, at 7GHz is 6.208dB and at 9GHz is 8.225dB. 4. CONCLUSION The MIMO antenna is most widely used antenna design in the WiMAX communication systems. In this paper, the antenna performance can be improved using multiple antenna for gain, returnloss and bandwidth. The simulation has been carried out by using CST studio software. The performance of single patch antenna is improved by using MIMO antenna by increasing the data rates for WiMAX communication applications. Using MIMO antenna the maximum gain obtained is 8.2dB at 9GHz. The bandwidth of the antenna is improved to 10GHz. REFERENCE [1] Kumari Nidhi Lal and Ashutosh Kumar Singh, Modified Design of Microstrip Patch Antenna for WiMAX Communication System,,2014. [2] Singh, V.K.; Ali, Z.; Singh, A.K., "Dual Wideband Stacked Patch Antenna for WiMAX and WLAN Applications," Computational Intelligence and Communication Networks (CICN), 2011 [3] Ali, Z.; Singh, V.K.; Singh, A.K.; Ayub, S., "E-Shaped Microstrip Antenna on Rogers Substrate for WLAN Applications," Computational Intelligence and Communication Networks (CICN), 2011 262
[4] Sanjeev Dwivedi,Abhishek Rawat and R.N Yadav, Design of U-shaped Microstrip patch antenna For WIMAX Applications at 2.5GHz IEEE WiMAX sys. applications and comm.,2013. [5] S.-C. Pan and K. L. Wong, Dual-frequency triangular microstrip antenna with a shorting pin, IEEE Trans. Antennas Propagat., 1997. [6] Aditi Kumar and satish devane, DGS based mutual coupling reduction between microstrip patch antenna arrays for WiMAX Applications,,2016. [7] K. Guney, Resonant frequency of a tunable rectangular microstrip patch antenna, Microw. Opt. Tech. Lett.,1994. [8] Balanis C.A., Antenna Theory Analysis and Design, John Wiley & Son, 2005. [9] Mukesh Kumar Khandelwal, Bino d Kumar Kanaujia and Sachin Kumar, Defected Ground Structure: Fundamentals, analasys, and Applications in modern wirelesstrends,. [10] Deming sun, Peng Wang and Peng Gao, Single radiator four-port MIMO antenna for WLAN and WIMAX applications with high isolation,. [11] Rakesh Roshan and Rajat Kumar Singh, Dual-ISM Band MIMO Antenna for WiFi and WiMAX applications, 263