This paper proposes a dual-polarized and high gain, four-element based compact multiple-input-multiple-output (MIMO) antenna operating at 5.2 GHz. First, a hammer-shaped antenna has been designed with a gain of 5.3 dBi, impedance bandwidth of 400 MHz, and broadside radiation. A mathematical analysis for radiated electric field and an equivalent circuit model for the hammer-shaped antenna are developed. Using the hammer-shaped antenna as an element, four element MIMO design with shorting walls is proposed. The shorting walls near non-radiating edges improve isolation between the elements by changing the direction of the major lobe. The proposed design has an envelope correlation coefficient (ECC) < 0.15, measured gain of 5.5 dBi, and mean effective gain (MEG) ~ -3 dB. This design has a low profile and single layer planar structure of area 65 mm x 65 mm, which makes it a good contender for portable devices or low-profile hand-held applications in WLAN band.
2. Paul, T. and T. Ogunfunmi, "Wireless LAN comes of age: Understanding the IEEE 802.11n amendment," IEEE Circuitsand Systems Magazine, Vol. 8, No. 1, 28-54, First Quarter 2008.
3. Chen, X., S. Zhang, and Q. Li, "A review of mutual coupling in MIMO systems," IEEE Access, Vol. 6, 24706-24719, 2018.
4. Lee, H. and B. Lee, "Compact broadband dual-polarized antenna for indoor MIMO wireless communication systems," IEEE Transactions on Antennas and Propagation, Vol. 64, No. 2, 766-770, 2016.
5. Zhu, J., S. Li, B. Feng, L. Deng, and S. Yin, "Compact dual-polarized UWB quasi-self-complementary MIMO/diversity antenna with band-rejection capability," IEEE Antennas and Wireless Propagation Letters, Vol. 15, 905-908, 2016.
6. Ramachandran, A., S. Valiyaveettil Pushpakaran, M. Pezholil, and V. Kesavath, "A four-port MIMO antenna using concentric square-ring patches loaded with CSRR for high isolation," IEEE Antennas and Wireless Propagation Letters, Vol. 15, 1196-1199, 2016.
7. Chen, Y. and C. Chang, "Design of a four-element multiple-input–multiple-output antenna for compact long-term evolution small-cell base stations," IET Microwaves, Antennas & Propagation, Vol. 10, No. 4, 385-392, 2016.
8. Hsu, C., L. Hwang, F. Chang, S. Wang, C. Liu, and , "Investigation of a single-plate π-shaped multiple-input-multiple-output antenna with enhanced port isolation for 5 GHz band applications," IET Microwaves, Antennas & Propagation, Vol. 10, No. 5, 553-560, 2016.
9. Deng, J., L. Guo, and X. Liu, "An ultrawideband MIMO antenna with a high isolation," IEEE Antennas and Wireless Propagation Letters, Vol. 15, 182-185, 2016.
10. Qu, L., R. Zhang, and H. Kim, "Decoupling between ground radiation antennas with ground-coupled loop-type isolator for WLAN applications," IET Microwaves, Antennas & Propagation, Vol. 10, No. 5, 546-552, 2016.
11. Hussain, R. and M. S. Sharawi, "Planar meandered-F-shaped 4-element reconfigurable multiple-input-multiple-output antenna system with isolation enhancement for cognitive radio platforms," IET Microwaves, Antennas & Propagation, Vol. 10, No. 1, 45-52, 2016.
12. Gorai, A. and R. Ghatak, "Utilization of shorted fractal resonator topology for high isolation and ELC resonator for band suppression in compact MIMO UWB antenna," AEU — International Journal of Electronics and Communications, Vol. 113, 152978, 2020.
13. Bakariya, P. S., S. Dwari, and M. Sarkar, "Triple band notch UWB printed monopole antenna with enhanced bandwidth," AEU — International Journal of Electronics and Communications, Vol. 69, No. 1, Art. No. 1, 2015.
14. Atallah, H. A., A. B. Abdel-Rahman, K. Yoshitomi, and R. K. Pokharel, "CPW-fed UWB antenna with sharp and high rejection multiple notched bands using stub loaded meander line resonator," AEU — International Journal of Electronics and Communications, Vol. 83, 22-31, 2018.
15. Deng, C., Z. Feng, and S. V. Hum, "MIMO Mobile handset antenna merging characteristic modes for increased bandwidth," IEEE Transactions on Antennas and Propagation, Vol. 64, No. 7, Art. No. 7, 2016.
16. Balanis, C. A., Antenna Theory: Analysis and Design, John Wiley & Sons, In, 2005.
17. Valagiannopoulos, C. A. and N. L. Tsitsas, "On the resonance and radiation characteristics of multi-layered spherical microstrip antennas," Electromagnetics, Vol. 28, No. 4, 243-264, May 2008.
18. Valagiannopoulos, C. A., "Semi-analytic solution to a cylindrical microstrip with inhomogeneous substrate," Electromagnetics, Vol. 27, No. 8, 527-544, Nov. 2007.
19. Sharma, V., A. Goel, M. D. Upadhayay, and A. V. Singh, "A Pi-shaped slot antenna for 5.2 GHz WLANMIMO application," IETE J. Res. , 1-13, Jan. 2021.
20. Yussuf, A. A. and S. Paker, "Design of a compact quad-radiating element MIMO antenna for LTE/Wi-Fi application," AEU — International Journal of Electronics and Communications, Vol. 111, 152893, 2019.
21. Yalavarthi, U. D., R. T. Koosam, M. N. S. D. Venna, and B. S. Thota, "Four element square patch MIMO antenna for DSRC, WLAN, and X-band applications," Progress In Electromagnetics Research M, Vol. 100, 175-186, 2021.
22. Khan, M. K., Q. Feng, and Z. Zheng, "Experimental investigation and design of UWB MIMO antenna with enhanced isolation," Progress In Electromagnetics Research C, Vol. 107, 287-297, 2021.
23. Goud, J. R., N. V. K. Rao, and A. M. Prasad, "Design of triple band U-slot MIMO antenna for simultaneous uplink and downlink communications," Progress In Electromagnetics Research C, Vol. 106, 271-283, 2020.