A novel EBG structure in the form of a square spiral cell with a via at its middle is presented in this work to improve the isolation between the antenna elements and also enhance the overall parameters of the proposed MIMO system. Wide BW is achieved for the 6-elements MIMO system operating in the frequency range from 3 GHz to 5 GHz which is suitable for 5G mobile applications. The single antenna element consists of four coupled sections printed on an FR4 substrate. To improve the performance and maintain the BW, the EBG structure is employed to increase the isolation between the antenna elements. The proposed EBG is designed to have a bandgap from 2.5 GHz to 6.5 GHz. The addition of the EBG structure between the radiating elements reduces the envelope correlation coefficient across the whole operating BW. SAR calculations are also performed using head and hand models. The performance of the proposed EBG loaded MIMO antenna is suitable to be a potential competitor for future 5G applications.
2. Sim, C.-Y.-D., H.-Y. Liu, and C.-J. Huang, "Wideband MIMO antenna array design for future mobile devices operating in the 5G NR frequency bands n77/n78/n79 and LTE band 46," IEEE Antennas and Wireless Propagation Letters, Vol. 19, 74-78, 2020.
3. Dicandia, F. A. and S. Genovesi, "Exploitation of triangular lattice arrays for improved spectral efficiency in massive MIMO 5G systems," IEEE Access, Vol. 9, 17530-17543, 2021.
4. Desai, A., T. Upadhyaya, M. Palandoken, and C. Gocen, "Dual band transparent antenna for wireless MIMO system applications," Microwave and Optical Technology Letters, Vol. 61, 1845-1856, 2019.
5. Garg, P. and P. Jain, "Isolation improvement of MIMO antenna using a novel flower shaped metamaterial absorber at 5.5 GHz WiMAX band," IEEE Transactions on Circuits and Systems II: Express Briefs, Vol. 67, 675-679, 2019.
6. Khade, S. S. and S. Badjate, "Square shape MIMO antenna with defected ground structure," 2018 4th International Conference on Recent Advances in Information Technology (RAIT), 1-5, 2018.
7. Cai, X. and K. Sarabandi, "A compact broadband horizontally polarized omnidirectional antenna using planar folded dipole elements," IEEE Transactions on Antennas and Propagation, Vol. 64, 414-422, 2015.
8. Molins-Benlliure, J., M. Cabedo-Fabrés, E. Antonino-Daviu, and M. Ferrando-Bataller, "Effect of the ground plane in UHF Chip antenna efficiency," 2020 14th European Conference on Antennas and Propagation (EuCAP), 1-5, 2020.
9. Pikale, R., D. Sangani, P. Chaturvedi, A. Soni, and M. Munde, "A review: methods to lower specific absorption rate for mobile phones," 2018 International Conference On Advances in Communication and Computing Technology (ICACCT), 340-343, 2018.
10. Tu, D. T. T., N. T. B. Phuong, P. D. Son, and V. Van Yem, "Improving characteristics of 28/38 GHz MIMO antenna for 5G applications by using double-side EBG structure," J. Commun., Vol. 14, 1-8, 2019.
11. El May, W., I. Sfar, J. M. Ribero, and L. Osman, "Design of low-profile and safe low SAR tri-band textile EBG-based antenna for IoT applications," Progress In Electromagnetics Research Letters, Vol. 98, 85-94, 2021.
12. Palandoken, M., Metamaterial-based Compact Filter Design, Intech Open, 2012.
13. Hediya, A. M., A. M. Attiya, and W. S. El-Deeb, "Multiple-input multiple-output antenna for sub-six GHz 5G applications using coupled folded antenna with defective ground surface," Progress In Electromagnetics Research C, Vol. 114, 13-29, 2021.
14. Parchin, N. O., H. J. Basherlou, Y. I. Al-Yasir, A. M. Abdulkhaleq, R. A. Abd-Alhameed, and P. S. Excell, "Eight-port MIMO antenna system for 2.6 GHz LTE cellular communications," Progress In Electromagnetics Research C, Vol. 99, 49-59, 2020.
15. Saleem, R., M. Bilal, H. T. Chattha, S. U. Rehman, A. Mushtaq, and M. F. Shafique, "An FSS based multiband MIMO system incorporating 3D antennas for WLAN/WiMAX/5G cellular and 5G Wi-Fi applications," IEEE Access, Vol. 7, 144732-144740, 2019.
16. Bhavarthe, P. P., S. S. Rathod, and K. Reddy, "A compact dual band gap electromagnetic band gap structure," IEEE Transactions on Antennas and Propagation, Vol. 67, 596-600, 2018.
17. Kulkarni, J., A. Desai, and C.-Y. D. Sim, "Wideband Four-Port MIMO antenna array with high isolation for future wireless systems," AEU-International Journal of Electronics and Communications, Vol. 128, 153507, 2021.
18. Khalid, M., et al., "4-port MIMO antenna with defected ground structure for 5G millimeter wave applications," Electronics, Vol. 9, 71, 2020.
19. Jiang, W., Y. Cui, B. Liu, W. Hu, and Y. Xi, "A dual-band MIMO antenna with enhanced isolation for 5G smartphone applications," IEEE Access, Vol. 7, 112554-112563, 2019.
20. Rao, T., A. Sudhakar, and K. Raju, "Novel technique of MIMO antenna design for UWB applications using defective ground structures,", 2018.
21. Kumar, J., "Compact MIMO antenna," Microwave and Optical Technology Letters, Vol. 58, 1294-1298, 2016.
22. Kumar, N. and U. K. Kommuri, "MIMO antenna H-plane isolation enhancement using UC-EBG structure and metal line strip for WLAN applications," Radio Engineering, Vol. 29, 2019.
23. Saxena, G., P. Jain, and Y. Awasthi, "High isolation EBG based MIMO antenna for X-band applications," 2019 6th International Conference on Signal Processing and Integrated Networks (SPIN), 97-100, 2019.
24. Modak, S. and T. Khan, "Cuboidal quad-port UWB-MIMO antenna with WLAN rejection using spiral EBG structures," International Journal of Microwave and Wireless Technologies, 1-8, 2021.
25. Desai, A., et al., "Transparent 2-element 5G MIMO antenna for sub-6 GHz applications," Electronics, Vol. 11, 251, 2022.
26. Desai, A., M. Palandoken, J. Kulkarni, G. Byun, and T. K. Nguyen, "Wideband flexible/transparent connected-ground MIMO antennas for sub-6 GHz 5G and WLAN applications," IEEE Access, Vol. 9, 147003-147015, 2021.