A compact four-element multiple-input-and-multiple-output (MIMO) antenna system is proposed based on substrate-integrated-waveguide (SIW) cavities. By bisecting a square SIW cavity, two rectangle half-mode cavities with opened edges are formed. They are arranged side by side sharing a row of metallic vias. Then two narrow T-shaped slots are etched along symmetry planes to divide these two cavities into four quarter-mode sub-cavities. Excited by feeding ports, four antenna elements with compact size are constructed, which radiate incident wave through opened cavity edges and etched slots. Moreover, antenna isolation can be easily improved by adjusting slot length though these elements interconnect. A prototype with the cavity size of 0.22λ0 × 0.86λ0 has been fabricated. The fabricated MIMO antenna system exhibits the center frequency of 3.51 GHz, port isolation of 14 dB, envelope correlation coefficient of 0.03, peak gain of 4.9 dBi, and high efficiency of 77.4%. The compact size and effective isolation improvement make the proposed design attractive for practical applications.
2. Sun, L., H. Feng, Y. Li, and Z. Zhang, "Compact 5G MIMO mobile phone antennas with tightly arranged orthogonal-mode pairs," IEEE Transactions on Antennas and Propagation, Vol. 66, No. 11, 6364-6369, 2018.
3. Niu, B. and J. Tan, "Compact four-element MIMO antenna using T-shaped and anti-symmetric U-shaped slotted SIW cavities," Electronics Letters, Vol. 55, No. 19, 1031-1032, 2019.
4. Hong, Y., J. Tak, and J. Choi, "An all-textile SIW cavity-backed circular ring-slot antenna for WBAN applications," IEEE Antennas and Wireless Propagation Letters, Vol. 15, 1995-1999, 2016.
5. Sboui, F., J. Machac, and A. Gharsallah, "Tunable slot antenna backed by substrate integrated waveguide cavity," International Journal of RF and Microwave Computer-Aided Engineering, e21591, 2018.
6. Niu, B. and J. Tan, "Compact two-element MIMO antenna based on half-mode SIW cavity with high isolation," Progress In Electromagnetics Research Letters, Vol. 85, 145-149, 2019.
7. Liu, F., Z. Xu, D. Ranasinghe, and C. Fumeaux, "Textile folded half-mode substrate-integrated cavity antenna," IEEE Antennas and Wireless Propagation Letters, Vol. 15, 1693-1697, 2016.
8. Tian, H. and T. Itoh, "Development of a circularly polarized HMSIW antenna," Progress In Electromagnetics Research Letters, Vol. 87, 81-87, 2019.
9. Deckmyn, T., et al., "A novel 60GHz wideband coupled halfmode/ quarter-mode substrate integrated waveguide antenna," IEEE Transactions on Antennas and Propagation, Vol. 65, No. 12, 6915-6926, 2017.
10. Casula, G. A., "A quarter mode SIW antenna for short-range wireless communications," Journal of Electromagnetic Waves and Applications, Vol. 33, No. 7, 853-864, 2019.
11. Yan, S., P. J. Soh, and G. A. E. Vandenbosch, "Dual-band textile MIMO antenna based on substrate-integrated waveguide (SIW) technology," IEEE Transactions on Antennas and Propagation, Vol. 63, No. 11, 4640-4647, 2015.
12. Zhai, G., Z. N. Chen, and X. Qing, "Mutual coupling reduction of a closely spaced four-element MIMO antenna system using discrete mushrooms," IEEE Transactions on Microwave Theory and Techniques, Vol. 64, No. 10, 3060-3067, 2016.
13. Boukarkar, A., et al., "A miniaturized extremely close-spaced four-element dual-band MIMO antenna system with polarization and pattern diversity," IEEE Antennas and Wireless Propagation Letters, Vol. 17, No. 1, 134-137, 2018.
14. Sharawi, M. S., A. T. Hassan, and M. U. Khan, "Correlation coefficient calculations for MIMO antenna systems: A comparative study," International Journal of Microwave and Wireless Technologies, Vol. 9, No. 10, 1991-2004, 2017.
15. Ren, Z. and A. Zhao, "Dual-band MIMO antenna with compact self-decoupled antenna pairs for 5G mobile applications," IEEE Access, Vol. 7, 82288-82296, 2019.