volume | PIER Journals

Abstract

This work presents a compact four-port low-profile multi-input multi-output(MIMO) antenna designed for wideband wireless communication over the S(2-4 GHz), C(4-8 GHz), and lower X-band(8-12 GHz) spectrum. The proposed antenna initially exhibits a broad impedance bandwidth extending from 2.5 to 9 GHz under the standard -10 dB matching condition. To improve spectral selectivity and mitigate unwanted interference, U-shaped slots are embedded in the feeding line and radiator, generating two distinct rejection bands at 3.5-3.9 GHz and 5.1-5.9 GHz, corresponding to WiMAX and WLAN frequencies, respectively. Including these slots slightly shifts the upper operating limit to 8.5 GHz. Implemented on an FR4 dielectric substrate (ε_r = 4.4) with a thickness of 1.6 mm, the antenna occupies an overall footprint of 40 × 34 mm². Additionally, circular polarization is achieved across the 6.1-7.9 GHz region, enhancing communication reliability in multipath propagation environments. A common-ground decoupling structure is employed to improve port isolation and suppress mutual coupling, resulting in isolation greater than 20 dB. The antenna demonstrates favorable diversity characteristics, with an envelope correlation coefficient below 0.05 and a diversity gain exceeding 9.95 dB. Moreover, a maximum realized gain of 6.2 dBi is obtained within the operational band. Experimental validation of the fabricated prototype confirms close agreement with simulated results, highlighting its potential for compact wideband multi-antenna wireless systems.

1. FCC, "First Report and Order in the Matter of Revision of Part 15 of the Commission’s Rules Regarding Ultra-Wideband TransmissionSystems," ET-Docket 98-153, 2002.

2. See, Terence S. P. and Zhi Ning Chen, "An ultrawideband diversity antenna," IEEE Transactions on Antennas and Propagation, Vol. 57, No. 6, 1597-1605, Jun. 2009.
doi:10.1109/tap.2009.2019908 Google Scholar

3. Chandel, Richa, Anil Kumar Gautam, and Karumudi Rambabu, "Tapered fed compact UWB MIMO-diversity antenna with dual band-notched characteristics," IEEE Transactions on Antennas and Propagation, Vol. 66, No. 4, 1677-1684, Apr. 2018.
doi:10.1109/tap.2018.2803134 Google Scholar

4. Ko, S. C. K. and R. D. Murch, "Compact integrated diversity antenna for wireless communications," IEEE Transactions on Antennas and Propagation, Vol. 49, No. 6, 954-960, Jun. 2001.
doi:10.1109/8.931154 Google Scholar

5. Ismail, Nuraiza and Ermeey Abd Kadir, "A co-planar waveguide ultra-wideband antenna for ambient Wi-Fi RF power transmission and energy harvesting applications," International Journal of Engineering and Technology Innovation, Vol. 13, No. 4, 265-283, 2023.
doi:10.46604/ijeti.2023.11444 Google Scholar

6. Pandey, Utkarsh, Parulpreet Singh, Raghvendra Singh, Vivek Kumar, Kanad Ray, Saurav Mallik, Haya Mesfer Alshahrani, E. Elshiekh, Mohamed Abbas, and Ben Othman Soufiene, "Ultra-wideband microstrip folded antenna for wireless LAN, 5G and Internet of Things applications," Scientific Reports, Vol. 14, No. 1, 29319, 2024.
doi:10.1038/s41598-024-65502-6 Google Scholar

7. Nie, Nian-Sheng, Xue-Song Yang, and Bing-Zhong Wang, "A compact four-element multiple-input-multiple-output antenna with enhanced gain and bandwidth," Microwave and Optical Technology Letters, Vol. 61, No. 7, 1828-1834, 2019.
doi:10.1002/mop.31787 Google Scholar

8. Deng, Jing-Ya, Li-Xin Guo, and Xiang-Long Liu, "An ultrawideband MIMO antenna with a high isolation," IEEE Antennas and Wireless Propagation Letters, Vol. 15, 182-185, 2016.
doi:10.1109/lawp.2015.2437713 Google Scholar

9. Lin, Guo-Sheng, Che-Hui Sung, Jing-Lun Chen, Lih-Shan Chen, and Mau-Phon Houng, "Isolation improvement in UWB MIMO antenna system using carbon black film," IEEE Antennas and Wireless Propagation Letters, Vol. 16, 222-225, 2017.
doi:10.1109/lawp.2016.2570301 Google Scholar

10. Zhao, Xing, Swee Ping Yeo, and Ling Chuen Ong, "Planar UWB MIMO antenna with pattern diversity and isolation improvement for mobile platform based on the theory of characteristic modes," IEEE Transactions on Antennas and Propagation, Vol. 66, No. 1, 420-425, Jan. 2018.
doi:10.1109/tap.2017.2768083 Google Scholar

11. Nirmal, Sanket, Sumit Kumar, and Richa Chandel, "Quad-port staircase U-shaped wideband MIMO antenna for 5G new radio applications," Progress In Electromagnetics Research Letters, Vol. 125, 43-50, 2025.
doi:10.2528/pierl24121204 Google Scholar

12. Ali, Wael and Mohamed Abdel Azeem, "Dual band Notched 2-port UWB MIMO antenna reconfiguration using lumped capacitors," Scientific Reports, Vol. 16, No. 1, 5265, 2026.
doi:10.1038/s41598-026-35976-7 Google Scholar

13. Saraswat, Ritesh K. and Mithilesh Kumar, "A vertex-fed hexa-band frequency reconfigurable antenna for wireless applications," International Journal of RF and Microwave Computer-Aided Engineering, Vol. 29, No. 10, e21893, 2019.
doi:10.1002/mmce.21893 Google Scholar

14. Mallani, Hareetaa, Archana Agrawal, and Ritesh K. Saraswat, "Implementation of fractal metamaterial inspired antenna for multi-standard wireless applications," Progress In Electromagnetics Research B, Vol. 108, 121-137, 2024.
doi:10.2528/pierb24072905 Google Scholar

15. Ji, Luyi, Chengzhu Du, Yongkang Yang, and Fangrui Zhang, "Characteristic mode-inspired ultra-wideband dual-band notched four-port MIMO antenna," Progress In Electromagnetics Research C, Vol. 171, 75-86, 2026.
doi:10.2528/pierc26042904 Google Scholar

16. Wang, Zixiang, Zhonggen Wang, Wenyan Nie, and Han Lin, "A compact ultra-wideband MIMO antenna with triple band-notched characteristics," Progress In Electromagnetics Research C, Vol. 169, 279-289, 2026.
doi:10.2528/pierc26032005 Google Scholar

17. Dhasarathan, Vigneswaran, Truong Khang Nguyen, Manish Sharma, Shobhit K. Patel, Sudesh Kumar Mittal, and M. Thurai Pandian, "Design, analysis and characterization of four port multiple-input-multiple-output UWB-X band antenna with band rejection ability for wireless network applications," Wireless Networks, Vol. 26, No. 6, 4287-4302, 2020.
doi:10.1007/s11276-020-02343-x Google Scholar

18. Hatami, Nazir, Javad Nourinia, Changiz Ghobadi, Maryam Majidzadeh, and Burhan Azarm, "High inter-element isolation and WLAN filtering mechanism: A compact MIMO antenna scheme," AEU --- International Journal of Electronics and Communications, Vol. 109, 43-54, 2019.
doi:10.1016/j.aeue.2019.07.001 Google Scholar

19. Gorai, Abhik and Rowdra 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.
doi:10.1016/j.aeue.2019.152978 Google Scholar

20. Sharma, Manish, Vigneswaran Dhasarathan, Shobhit K. Patel, and Truong Khang Nguyen, "An ultra-compact four-port 4 × 4 superwideband MIMO antenna including mitigation of dual notched bands characteristics designed for wireless network applications," AEU --- International Journal of Electronics and Communications, Vol. 123, 153332, 2020.
doi:10.1016/j.aeue.2020.153332 Google Scholar

21. Abdpour, S. S., N. Azadi-Tinat, H. Oraizi, and J. Ghalibafan, "Design of WLAN/WiMAX band notch super-wideband microstrip fractal antennas," International Journal of Microwave and Wireless Technologies, Vol. 11, No. 8, 844-850, 2019.
doi:10.1017/s1759078719000540 Google Scholar

22. Arora, Sapna, Sharad Sharma, and Rohit Anand, "Ultra-wideband antenna with quintuple band notches integrated with metamaterials," Progress In Electromagnetics Research M, Vol. 122, 41-52, 2023.
doi:10.2528/pierm23090601 Google Scholar

23. Singh, K. and Rajan Mishra, "Design of a circular microstrip patch antenna with single band notch characteristic for UWB applications," 2017 IEEE International WIE Conference on Electrical and Computer Engineering (WIECON-ECE), 262-265, Dehradun, India, 2017.
doi:10.1109/WIECON-ECE.2017.8468902

24. Pozar, D. M., Microwave Engineering, 4th Ed., Wiley, 2011.

25. Balanis, C. A., Antenna Theory: Analysis and Design, 4th Ed., Wiley, 2016.

26. Garg, R., P. Bhartia, I. Bahl, and A. Ittipiboon, Microstrip Antenna Design Handbook, Artech House, 2001.

27. Amari, S., U. Rosenberg, and J. Bornemann, "Adaptive synthesis and design of resonator filters with source/load-multiresonator coupling," IEEE Transactions on Microwave Theory and Techniques, Vol. 50, No. 8, 1969-1978, Aug. 2002.
doi:10.1109/tmtt.2002.801348 Google Scholar

Dr. Pandillapalli Janardhana Reddy

Prof. Gummadi Kameswari