Mutual coupling analysis for 2*2 MIMO antenna using DGS

Mutual coupling analysis for 2*2 MIMO antenna using DGS

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  International Research Journalof Engineering and Technology (IRJET) e-ISSN: 2395-0056 Volume: 09 Issue: 07 | July 2022 www.irjet.net p-ISSN: 2395-0072 © 2022, IRJET | Impact Factor value: 7.529 | ISO 9001:2008 Certified Journal | Page 2806 Mutual coupling analysis for 2*2 MIMO antenna using DGS Anand1 and Vijaya K2 1M. Tech Scholar, Dept of ECE, BMSCE, Bengaluru, Karnataka, India 2Professor, Dept. of ECE, BMSCE, Bengaluru, Karnataka, India ---------------------------------------------------------------------***--------------------------------------------------------------------- Abstract - Mutual coupling significantly lowers MIMO (multiple input multiple output) antennas' system performance and radiation patterns. In this paper, mutual coupling analysis of two element MIMO antenna operating at 28 GHz with various spacing between them is carried out. The analysis was done with and without applying DGS to the proposed structure. The spacing of λ/2, λ/4 and λ/8 is considered between the antennaelementsformutualcoupling analysis, where λ is the wavelength at frequency of 28GHz. It has been found that mutual coupling is greater when there is less space between the two antenna components, i.e., the mutual coupling obtained is greater when the spacing between the antenna elements is λ /8 in both the presenceand absence of DGS. All the simulationscarriedoutinthiswork has been done on HFSS v.15.0 tool. Key Words: MIMO Antenna, Mutual Coupling, DGS, Inter element spacing, Reflection and Transmission Co-efficient. 1. INTRODUCTION Numerous disciplines, including realistic Ultra High Definition, Artificial Intelligence,Block-chain,andInternetof Things services like Smart Cities, Smart Transportation, and Smart Grids, will be much improved as a result of the phenomenal rise in mobile data speeds brought on by 5G. Carriers are likely to employ the 28, 38, and 73 GHz bands, which will be made accessible for future technologies, asthe mobile industry moves toward using the millimeter-wave spectrum. Multiple-input-multiple-output (MIMO) technology can be used to accomplish these goals [1]. MIMO (multiple input multiple output) antenna is represented by M*N, where M represent multiple antennas at transmitter side and N represent multiple antennas at receiver. Isotropic antenna radiates signals in all directions equally but in case of point-to-point communication like satellite, radar applications need to send signals in only one direction for that purpose researchers start designing the MIMO antenna. Two things needtomaintainwhiledesigning MIMO antennas are spacing and feeding method. As separation between antennas get decreases the mutual coupling between them got increases. The presence of this mutual coupling reduces the radiation pattern,increasesthe co-channel interference and changes the input characteristics of the antenna. So, to overcome this drawback there are many technologies like EBG structure [2], PCR method [3], 3D EIW cells [4], DGS [5], and other hybrid techniques [6]. In this paper, we used DGS (defective ground structure) because it is easier to design, and cost required for designing purpose also less compared to other methods. In this work, the mutual coupling analysis of 2*2rectangular patch antenna with inter-element spacing of λ/2, λ/4 and λ/8 respectively is done using Defective Ground Structure (DGS), where λ is a wavelength at frequency of 28GHz. The antenna was built on RT duroid and has a compact dimension of 15.7 x 5.8 x 0.5 mm3. The antenna operates at 28 GHz (27.22 to 28.84 GHz) satisfying the need of future 5G applications. 2. ANTENNA CONFIGURATION The Proposed configuration of 2*2 MIMO antenna is illustrated in Fig 1. The antenna is built on RT duroid with a thickness h = 0.5mm and relative permittivity ɛr = 2.2 with compact dimension of 15.7 x 5.8 mm2. The proposed structure mainly consists of two rectangular patches placed apart from each other used as a single MIMO antenna as shown in Fig 1. The inset feed method is used to excite the proposed antenna. Firstly, an antenna withfull groundplane is designed at 28GHz with S11 < -10 dB, as shown inFig1(a), and corresponding mutual couplinghasbeenanalyzed.Next, the antenna with partial ground plane (DGS) is designed with same frequency of 28GHz, as shown in Fig 1(b), and the corresponding mutual coupling parameter is analyzed. The detailed dimensions of the antenna designedinthiswork are tabulated in Table 1 and its point by point dimensions are presented in Fig 2 (a) (b) Fig -1: Proposed 2*2 MIMO Antenna: (a) Without DGS and (b) With DGS
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  International Research Journalof Engineering and Technology (IRJET) e-ISSN: 2395-0056 Volume: 09 Issue: 07 | July 2022 www.irjet.net p-ISSN: 2395-0072 © 2022, IRJET | Impact Factor value: 7.529 | ISO 9001:2008 Certified Journal | Page 2807 (a) (b) Fig -2: Proposed 2 * 2 MIMO Antenna with DGS: (a) Radiating Patch (b) Ground Plane. Table -1: Detailed Dimension of proposed antenna 3. DESIGN ANALYSIS In this work the mutual coupling between the patchesof2*2 MIMO antenna is analyzed by varying the distance between them(D) in both cases of with DGS and without DGS. Without DGS: The patches are placed apart at a distance of λ/2, λ/4 and λ/8 respectively, where λ is the wavelength of operating frequency at 28GHz. At first case, when D=λ/2 theReflection co-efficient S11 obtained is -42.32 dB and transmission co- efficient S12, which represents mutual coupling is -40.0382. At second case, when D=λ/4 S11 obtained is -35.443 dB and S12 is -43.3795. At third case, when D=λ/8, S11 obtained is - 52.3425 dB and S12 is -22.27dB.ThecorrespondingS11and S12 plots are shown Fig 3 and Fig 4 respectively. With DGS: As shown in Fig 5 and Fig 6, by applying DGS to the antenna designed with D=λ/2, S11 obtainedis -39.1895dBandS12is -36.5569. At second case, when D=λ/4 the S11 obtained is - 38.4209 dB and S12 is -42.1844. At third case, when D=λ/8 the S11 obtained is -41.8286 dB and S12 is -21.1390 dB. By the analysis shown above it is observed that, as distance between the elements of MIMO antenna gets reduces, the mutual coupling between them increases. Fig -4: S12 plots of proposed 2*2 MIMO Antenna without DGS for various inter element spacing. Fig -5: S11 plots of proposed 2*2 MIMO Antenna with DGS for various inter element spacing. Parameter Dimension (mm) W 15.7 W1 3.7 L 5.8 L1 3.2 D 5.3 F 1.8 F1 0.75 I1,I2 0.1 P 1.7
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  International Research Journalof Engineering and Technology (IRJET) e-ISSN: 2395-0056 Volume: 09 Issue: 07 | July 2022 www.irjet.net p-ISSN: 2395-0072 © 2022, IRJET | Impact Factor value: 7.529 | ISO 9001:2008 Certified Journal | Page 2808 Fig -6: S12 plots of proposed 2*2 MIMO Antenna with DGS for various inter element spacing. 4. RESULTS AND DISCUSSIONS: The Table summarizes the overall results obtained from proposed 2*2 MIMO antenna. As discussed above the antenna operates at 28GHz with spacing of λ/2, λ/4 and λ/8 respectively. The better S11 was obtained by spacing of λ/8 between the elements of MIMO antenna, i.e., -52.34 dB was obtained without DGS and while applying DGS a maximum S11 is -41.82 dB. The more mutual coupling which is represented in terms of S12 parameter is observed at by spacing of λ/8. In order to show the significance ofproposed structure, the VSWR, gain and directivity was found and is illustrated in Table 2. The VSWR values obtained lies nearer to 1 which shows that better impedance matching was obtained. The gain of 6.03, 6.18, and 5.99 was obtained without DGS with inter element spacing of λ/2, λ/4 and λ/8 respectively, the gain of 6.04, 6.17 and 6.06 was obtained with DGS with inter element spacing of λ/2, λ/4 and λ/8 respectively. Similarly, directivity of 6.07,6.21,and6.05 was obtained without DGS with inter element spacing ofλ/2, λ/4 and λ/8 respectively, the directivity of 6.07, 6.20 and 6.11 was obtained with DGS with inter element spacing of λ/2, λ/4 and λ/8 respectively. The 3D polar plot of proposed antenna with and without applying DGS for various inter element spacing is shown in Fig 7. Table 2: Summarized Results of Proposed Antenna (c) (d) (e) (f) Fig -7: 3D Polar plot of Proposed Antenna: (a)(b)and(c)are without DGS, (d) (e) and (f) are with DGS: (a) and (d) for /2 spacing, (b) and (e) for /4 spacing, and (c) and (f) for /8 spacing. 3. CONCLUSIONS In this paper, a 2*2 MIMO antenna is designed operating at a center frequency of 28 GHz for 5G applications. The mutual coupling of two antenna elementswasanalyzedwithrespect to various distance between them and further theantenna is analyzed by applying DGS. Along with mutual coupling, the analysis of reflection co-efficient, VSWR, gain and directivity for various cases was done in this paper. It is observed that the mutual coupling is more when distance betweenthetwo antenna elements is less i.e., the mutual coupling obtained is more when the spacing betweentheantenna elementsis /8 in both with and without DGS condition. The results confirm that the antenna operates well because better S11, acceptable gain and directivity, and stable radiation pattern was obtained. REFERENCES [1] Paulraj, A.J, Gore, D.A, Nabar, R.U, Bo¨lcskei, H, “An overview of MIMO communications-a key to gigabit,” wireless. Proc. IEEE, 92 (2) (2004), 198– 218. [2] Alaa H. Radhi, Nur Ab Aziz, R. Nilavalan and H. S. Al- Raweshidy, “Mutual Coupling Reduction Between Parameters Without DGS With DGS /2 /4 /8 /2 /4 /8 S11(dB) -42.32 -35.44 -52.34 -39.18 -38.42 -41.82 S12 (dB) -40.03 -43.37 -22.27 -36.55 -42.18 -21.13 VSWR 1.01 1.03 1.00 1.02 1.02 1.01 Gain (dB) 6.03 6.18 6.06 6.04 6.18 5.99 Directivity(dB) 6.07 6.21 6.05 6.07 6.20 6.11
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  International Research Journalof Engineering and Technology (IRJET) e-ISSN: 2395-0056 Volume: 09 Issue: 07 | July 2022 www.irjet.net p-ISSN: 2395-0072 © 2022, IRJET | Impact Factor value: 7.529 | ISO 9001:2008 Certified Journal | Page 2809 Two PIFA Using Uni-Planar Fractal Based EBG for MIMO Application” Loughborough Antennas & Propagation Conference (LAPC), 2016 [3] Kuttathati Srinivasan Vishvaksenan, Kaliyappa Mithra, Ramalingam Kalaiarasan, Kaliyappa Santhosh Raj, “Mutual Coupling Reduction in Microstrip Patch Antenna Arrays Using Parallel Coupled-Line Resonators”, IEEE Antennas and Wireless Propagation Letters, 2017 [4] Tianqi Jiao, Tao Jiang, Yingsong Li, “A Low Mutual Coupling MIMO Antenna Using3-DElectromagnetic Isolation Wall Structures” IEEE, 978-1-5386-1608 6/17/2017 [5] Subuh Pramono, Budi Basuki Subagio, “Mutual Coupling Reduction & Bandwidth Enhancement Using a Simple Folded Slot-Partial Ground Plane in DualbandMIMOAntenna”,International Seminaron Intelligent TechnologyandItsApplications(ISITIA), 2018. [6] Lingaraj Duggani, Dr. Udaykumar Naik, VijayRayar, “Review of Mutual Coupling ReductioninMicrostrip Patch Antenna Array for MIMO Applications”,Third International Conference on Intelligent Sustainable Systems, 2020.