volume | PIER Journals

Abstract

To address the problem of increased electromagnetic mutual coupling caused by multi-antenna integration in compact wireless communication terminals, this study presents a compact four-element, high-isolation, ultra-wideband (UWB), multiple-input multiple-output (MIMO) antenna operating in the 6.5-14 GHz frequency band. The proposed antenna is compact measuring 36 mm×36 mm×1.6 mm. The radiating elements adopt an orthogonally symmetric configuration, with chamfered corners and slot-loading techniques used to enhance impedance matching and broaden impedance bandwidth. To effectively reduce mutual coupling between adjacent elements, a composite decoupling structure is developed, which integrates a non-through isolation slot, embedded metallic patches, and a cross-shaped defected ground structure (cross-DGS). The proposed structure effectively enhances in-band isolation by altering coupling current paths and redistributing surface currents on the ground plane. The results demonstrate that, in the 6.5-14 GHz operating band, the antenna achieves S₁₁ < -10 dB, the adjacent-port isolation (S₂₁) exceeding 20 dB, an envelope correlation coefficient (ECC) below 0.0035, and a diversity gain (DG) close to 10 dB. The proposed antenna combines a compact size, wide operating bandwidth, enhanced isolation, and good diversity performance, providing a potential candidate for compact UWB-MIMO terminals requiring low mutual coupling.

1. Ren, Wanying, Zhong-Gen Wang, Ming Yang, Jinzhi Zhou, and Wen-Yan Nie, "Design of a simple four-port UWB-MIMO antenna based on a fan-shaped isolator," Progress In Electromagnetics Research M, Vol. 126, 117-126, 2024.
doi:10.2528/pierm24011101 Google Scholar

2. Sharawi, Mohammad S., "Printed multi-band MIMO antenna systems and their performance metrics [wireless corner]," IEEE Antennas and Propagation Magazine, Vol. 55, No. 5, 218-232, October 2013.
doi:10.1109/map.2013.6735522 Google Scholar

3. Chen, Xiaoming, Shuai Zhang, and Qinlong Li, "A review of mutual coupling in MIMO systems," IEEE Access, Vol. 6, 24706-24719, 2018.
doi:10.1109/access.2018.2830653 Google Scholar

4. Kumar, Praveen, Sameena Pathan, Shweta Vincent, Om Prakash Kumar, Yashwanth N, Pradeep Kumar, Pranav R. Shetty, and Tanweer Ali, "A compact quad-port UWB MIMO antenna With improved isolation using a novel mesh-like decoupling structure and unique DGS," IEEE Transactions on Circuits and Systems II: Express Briefs, Vol. 70, No. 3, 949-953, March 2023.
doi:10.1109/tcsii.2022.3220542 Google Scholar

5. Kumar, Praveen, Tanweer Ali, and M. M. Manohara Pai, "Highly isolated ultrawideband multiple input and multiple output antenna for wireless applications," Engineered Science, Vol. 17, 83-90, 2021.
doi:10.30919/es8d570 Google Scholar

6. Pakala, Raveendrababu and Dasari Ramakrishna, "Mutual coupling reduction in UWB-MIMO antenna using circular slot EBG structure," Progress In Electromagnetics Research M, Vol. 119, 177-188, 2023.
doi:10.2528/pierm23080504 Google Scholar

7. Yang, Fan and Y. Rahmat-Samii, "Microstrip antennas integrated with electromagnetic band-gap (EBG) structures: A low mutual coupling design for array applications," IEEE Transactions on Antennas and Propagation, Vol. 51, No. 10, 2936-2946, October 2003.
doi:10.1109/tap.2003.817983 Google Scholar

8. Li, Min, Min Wang, Lijun Jiang, and Lawrence Kwan Yeung, "Decoupling of antennas with adjacent frequency bands using cascaded decoupling network," IEEE Transactions on Antennas and Propagation, Vol. 69, No. 2, 1173-1178, February 2021.
doi:10.1109/tap.2020.3010956 Google Scholar

9. Luo, Shengyuan, Y. Li, Y. Xia, et al. "A low mutual coupling antenna array with gain enhancement using metamaterial loading and neutralization line structure," Applied Computational Electromagnetics Society Journal (ACES), Vol. 34, No. 3, 411-418, 2019. Google Scholar

10. 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

11. Li, Pai, Jingchang Nan, and Jiani Qian, "Design of a miniaturized dual notch UWB-MIMO antenna," 2024 6th International Conference on Communications, Information System and Computer Engineering (CISCE), 140-143, Guangzhou, China, May 2024.
doi:10.1109/cisce62493.2024.10653284

12. Liu, Shuming, Jingchang Nan, Yifei Wang, Licong Fan, and Jianxin Qi, "Design of notch UWB-MIMO antennas based on RMS-ZINC structure decoupling method," Progress In Electromagnetics Research C, Vol. 161, 142-149, 2025.
doi:10.2528/pierc25081403 Google Scholar

13. Wang, Heming, Qi Zheng, Qiwei Li, and Xue-Xia Yang, "Isolation improvement and bandwidth enhancement of dual-band MIMO antenna based on metamaterial wall," IEEE Antennas and Wireless Propagation Letters, Vol. 24, No. 5, 1144-1148, May 2025.
doi:10.1109/lawp.2025.3527688 Google Scholar

14. Mahto, Santosh Kumar, Ajit Kumar Singh, Rashmi Sinha, Mohammad Alibakhshikenari, Salahuddin Khan, and Giovanni Pau, "High isolated four element MIMO antenna for ISM/LTE/5G (sub-6GHz) applications," IEEE Access, Vol. 11, 82946-82959, 2023.
doi:10.1109/access.2023.3301185 Google Scholar

15. Yang, Qingzhi, Kang Wang, and Yufa Sun, "Quad-port miniaturized ultra-wideband MIMO antenna with metal vias," Progress In Electromagnetics Research Letters, Vol. 97, 95-103, 2021.
doi:10.2528/pierl21020604 Google Scholar

16. Rekha, Vutukuri Sarvani Duti, Pokkunuri Pardhasaradhi, Boddapati Taraka Phani Madhav, and Yalavarthi Usha Devi, "Dual band notched orthogonal 4-element MIMO antenna With isolation for UWB applications," IEEE Access, Vol. 8, 145871-145880, 2020.
doi:10.1109/access.2020.3015020 Google Scholar

17. Kayabasi, Ahmet, Abdurrahim Toktas, Enes Yigit, and Kadir Sabanci, "Triangular quad-port multi-polarized UWB MIMO antenna with enhanced isolation using neutralization ring," AEU --- International Journal of Electronics and Communications, Vol. 85, 47-53, February 2018.
doi:10.1016/j.aeue.2017.12.027 Google Scholar

18. Zha, Xianbiao, Chunhua Li, Shaoxiang Chen, Wenfei Yin, and Xiaohui Zhang, "Compact high isolation CPW fed 4-element UWB-MIMO antenna with special isolation structure," 2022 7th International Conference on Computer and Communication Systems (ICCCS), 465-470, Wuhan, China, April 2022.
doi:10.1109/icccs55155.2022.9846083

19. Yalavarthi, Usha Devi, Ravi Teja Koosam, Monica Naga Sai Durga Venna, and Bhargav Sai Thota, "Four element square patch MIMO antenna for DSRC, WLAN, and X-band applications," Progress In Electromagnetics Research M, Vol. 100, 175-186, 2021.
doi:10.2528/pierm20103101 Google Scholar

20. Janardhana Reddy, Pandillapalli and Gummadi Kameswari, "A compact wideband 4-port MIMO antenna with novel C-shaped radiators and enhanced isolation characteristics," Progress In Electromagnetics Research C, Vol. 162, 130-139, 2025.
doi:10.2528/pierc25091301 Google Scholar

Ms. Qi Li

Dr. Tiegang Zhong

Mr. Songqi Li