In this paper, a hexagonal-shaped multiple-input multiple-output (MIMO) patch antenna is presented. It covers the S band (2-4 GHz), WLAN (2400-2480 MHz & 5150-5350/5725-5875 MHz), UWB (3.1-10.6 GHz), and X band (8-12 GHz) applications. The proposed structure is simulated and fabricated on an FR4 substrate with overall dimensions of 0.186λ0 x 0.373λ0 and separation of two patches with a distance of 0.053λ0 (where λ0 is the wavelength at 2 GHz). The single UWB patch antenna is derived from the triangular-shaped edge cuttings in the bottom of the rectangular patch antenna with partial & defected ground. The proposed MIMO structure produces simulated results from 2 GHz to 13.3 GHz and measured results from 2.1 GHz to 12.9 GHz, with good agreement. The proposed structure resonates at 3.4 GHz, 5.8 GHz, 10.2 GHz and 11.8 GHz. Isolation improved to below -20 dB by placing an E-shaped tree structure and parasitic element. The radiation efficiency and peak gain values are 78-94% and 1.4-6.6 dB, respectively. Diversity performance of the proposed structure is verified with low envelope correlation coefficient (ECC < 0.04), high diversity gain (DG > 9.985), and acceptable total active reflection coefficient (TARC < -10 dB) values.
2. Zarrabi, F. B., A. M. Shire, M. Rahimi, and N. P. Gandji, "Ultra-wideband tapered patch antenna with fractal slots for dual notch application," Microwave and Optical Technology Letters, Vol. 56, No. 6, 1344-1348, 2014.
3. Khanjari, S. P., S. Jarchi, and M. M. Taheri, "Compact and wideband planar loop antenna with microstrip to parallel strip balun feed using metamaterials," International Journal of Electron and Communications, Vol. 111, 152883, 2019.
4. Kaiser, T., Z. Feng, and E. Dimitrov, "An overview of ultra-wide band systems with MIMO," Proceedings of IEEE, Vol. 97, No. 2, 285-312, 2009.
5. Nadeem, I. and D.-Y. Choi, "Study on mutual coupling reduction technique for mimo antennas," IEEE Access, Vol. 7, 563-586, 2019.
6. Liu, L., S. W. Cheung, and T. I. Yuk, "Compact MIMO antenna for portable devices in UWB applications," IEEE Transactions on Antennas and Propagation, Vol. 61, No. 8, 4257-4264, 2013.
7. Radhi, A. H., R. Nilavalan, Y. Wang, H. S. Al-Raweshidy, A. A. Eltokhy, and N. A. Aziz, "Mutual coupling reduction with a wideband planar decoupling structure for UWB-MIMO antennas," International Journal of Microwave and Wireless Technologies, Vol. 10, No. 10, 1143-1154, 2018.
8. Chacko, B. P., G. Augustin, and T. A. Denidni, "Uniplanar slot antenna for ultra wide band polarization --- diversity applications," IEEE Antennas and Wireless Propagation Letters, Vol. 12, 88-91, 2013.
9. Ren, J., W. Hu, Y. Yin, and R. Fan, "Compact printed MIMO antenna for UWB applications," IEEE Antennas and Wireless Propagation Letters, Vol. 13, 1517-1520, 2014.
10. Naderia, M., F. B. Zarrabib, F. S. Jafaric, and S. Ebrahimid, "Fractal EBG structure for shielding and reducing the mutual coupling in microstrip patch antenna array," International Journal of Electronics and Communications, Vol. 93, 261-267, 2018.
11. Ouahabi, M. E., A. Zakriti, M. Essaaidi, A. Dkiouak, and H. Elftouh, "A miniaturized dual-band MIMO antenna with low mutual coupling for wireless applications," Progress In Electromagnetics Research C, Vol. 93, 93-101, 2019.
12. Veeramani, A., A. S. Arezomand, J. Vijayakrishnan, and F. B. Zarrabi, "Compact S-shaped EBG structures for reduction of mutual coupling," IEEE, Fifth International Conference on Advanced Computing & Communication Technologies, 21-25, 2015.
13. Babashah, H., H. R. Hassani, and S. Mohammad-Ali-Nezhad, "A compact UWB printed monopole MIMO antenna with mutual coupling reduction," Progress In Electromagnetics Research C, Vol. 91, 55-67, 2019.
14. Gao, P., S. He, X. Wei, Z. Xu, N. Wang, and Y. Zheng, "Compact printed UWB diversity slot antenna with 5.5 GHz band-notched characteristics," IEEE Antennas and Wireless Propaga Letters, Vol. 13, 376-379, 2014.
15. Wong, K. L., S. W. Su, and Y. L. Kuo, "A printed ultra-wideband diversity monopole antenna," Microwave and Optical Technology Letters, Vol. 38, No. 4, 257-259, 2003.
16. Park, J.-D., M. U. Rahman, and H. N. Chen, "Isolation enhancement of wide-band MIMO array antennas utilizing resistive loading," IEEE Access, Vol. 7, 81029-81026, 2019.
17. Li, Q., M. Abdullah, and X. Chen, "Defected ground structure loaded with meandered lines for decoupling of dual-band antenna," Journal of Electromagnetic Waves and Applications, Vol. 33, No. 13, 1764-1775, 2019.
18. Li, Z., C. Yin, and X. Zhu, "Compact UWB MIMO vivaldi antenna with dual band-notched characteristics," IEEE Access, Vol. 7, 38696-38701, 2019.
19. Wang, L., Z. Du, H. Yang, R. Ma, Y. Zhao, X. Cui, and X. Xi, "Compact UWBMIMO antenna with high isolation using fence-type decoupling structure," IEEE Antennas and Wireless Propagation Letters, Vol. 18, No. 8, 1641-1645, 2019.
20. Tang, T. C. and K. H. Lin, "An ultra wideband MIMO antenna with dual band-notched function," IEEE Antennas and Wireless Propagation Letters, Vol. 13, 1076-1079, 2014.
21. Mao, C. X., Q. X. Chu, Y. T. Wu, and Y. H. Qian, "Design and investigation of closely-packed diversity UWB slot-antenna with high isolation," Progress In Electromagnetics Research C, Vol. 41, 13-25, 2013.
22. Mao, C. X. and Q. X. Chu, "Compact coradiator UWB-MIMO antenna with dual polarization," IEEE Transactions on Antennas and Propagation Letters, Vol. 62, No. 9, 4474-4480, 2014.
23. Bhattacharya, A., B. Roy, S. K. Chowdhury, and A. K. Bhattacharjee, "An isolation enhanced, printed, low-profile UWB-MIMO antenna with unique dual band-notching features for WLAN and WIMAX," IETE Journal of Research, 1-8, 2019.
24. Mathur, R. and S. Dwari, "Compact CPW-fed ultra wide band MIMO antenna using hexagonal ring monopole antenna elements," International Journal of Electronics and Communications, Vol. 93, 1-6, 2018.
25. Balanis, C. A., Antenna Theory Analysis and Design, 3rd Ed., a John Wiley & Sons, Inc., Publication, Copyright 2005 by John Wiley & Sons, Inc. All rights reserved.
26. Jetti, C. R. and V. R. Nandanavanam, "Trident-shape strip loaded dual band-notched UWB MIMO antenna for portable device applications," International Journal of Electronics and Communications, Vol. 83, 11-21, 2018.
27. Jetti, C. R. and V. R. Nandanavanam, "A very compact MIMO antenna with triple band-notch function for portable UWB systems," Progress In Electromagnetics Research C, Vol. 82, 13-27, 2018.
28. Chandel, R. and A. K. Gautam, "Design and packaging of an eye-shaped multiple-input-multiple-output antenna with high isolation for wireless UWB applications," IEEE Transactions on Components, Packaging and Manufacturing Technology, Vol. 8, No. 4, 635-642, 2018.
29. Malviya, L. and K. Machavaram, "MIMO antennas with diversity and mutual coupling reduction techniques: A review," International Journal of Microwave and Wireless Technologies, Vol. 9, No. 8, 1763-1780, 2017.
30. Chae, S. H., W. I. Kawk, S. Park, and K. Lee, "Analysis of mutual coupling in MIMO antenna array by TARC calculation," Asia-Pacific Microwave Conference, 2090-2093, 2006.
31. Jafri, S. I., R. Saleem, M. F. Shafique, and A. K. Brown, "Compact reconfigurable multiple-input-multiple-output antenna for ultra wideband applications," IET Microwaves, Antennas & Propagation, Vol. 10, No. 4, 413-419, 2015.