## 6 Conclusions  
The main goal of this study was the development of a compact multi-antenna system operating in the 3.1-10.6 GHz frequency band and covering a wide range of wireless applications and satellite communications. The proposed designed antenna exhibits an ultra-wide frequency band, a high level of isolation, and a good diversity performance. To meet the FCC UWB requirements, two rectangular parasitic elements are incorporated into the radiating structure. Additionally, the isolation is enhanced through the utilization of metamaterial CSRR structures etched into the L-shaped defected ground plane, and an important low-frequency shifting is achieved. The fabricated antenna prototype exhibits performances that closely align with the simulation predictions. The designed antenna presents an ultra-wide frequency band spreading from 3.01 to 12.3 GHz, quite high mutual coupling (exceeding 22 dB), a quasi-ommidirectional radiation pattern, and good diversity parameters, including the EDG, ECC, TARC, CCL, and ratio of MEGs. These results collectively meet the UWB-MIMO system requirements.  
\begin{table}
\begin{tabular}{c c c c c c c c c c c c} \hline \hline
**Year** & **Ref.** & **Size** & **Bandwidth** & **No. of** & **Isolation** & **Gain** & **Efficiency** & **ECC** & **DG** & **CCL** & **TARC** & **MEG** \\  & **(mm2)** & **(GHz)** & **Ports** & **(dB)** & **(dB)** & **(\%)** & & **(dB)** & **(bits/Hz/s)** & **(dB)** & **(dB)** \\ \hline
2019 & [8] & 24 \(\times\) 32 & 3.1–12.5 & 2 & \(\geq\)16 & 4.8 & NG & \(\leq\)0.05 & \(\geq\)9.9 & 0.4 & NG & \(\leq\)\(-3\) \\
2019 & [13] & 55 \(\times\) 28 & 2.01-3.9 & 2 & \(\geq\)15 & 2 & NG & \(\leq\)0.01 & \(\geq\)9.8 & 0.2 & \(<\)0 & \(<\)\(-2\) \\
2020 & [9] & 33 \(\times\) 48 & 2–13.7 & 2 & \(\geq\)20 & 4.3 & 96 & \(\leq\)0.15 & \(>\)9.85 & 0.06 & NG & NG \\
2021 & [24] & 27.9 \(\times\) 38 & 1.5–3.5 & 2 & \(\geq\)20 & NG & NG & \(<\)0.2 & NG & NG & NG \\
2022 & [20] & 70 \(\times\) 25 & 4.65–4.97 & 2 & \(\geq\)15 & 1.65 & 45 & \(<\)0.03 & \(>\)9.8 & 0.15 & \(>\)\(-12\) & 1 \\
2022 & [33] & 29.5 \(\times\) 60 & 3–20 & 2 & \(\geq\)23 & NG & 98 & \(<\)0.001 & \(>\)9.995 & 0.3 & NG & NG \\
2023 & [23] & 30 \(\times\) 60 & 3–12 & 2 & \(\geq\)25 & 5 & 90 & NG & NG & NG & NG & NG \\
2023 & [23] & 46 \(\times\) 46 & 3.1–11.7 & 2 & \(\geq\)16.5 & NG & 55 & \(<\)0.057 & \(>\)9.78 & \(<\)0.25 & \(\leq\)\(-10\) & NG \\
2023 & [37] & 29.5 \(\times\) 60 & 3–15.7 & 2 & \(\geq\)20 & 6.2 & NG & \(<\)0.045 & \(>\)9.998 & 0.3 & NG & NG \\
2023 & [43] & 52 \(\times\) 26 & 2.3–11.5 & 2 & \(\geq\)16 & 5.9 & 98 & \(<\)0.012 & 10 & NG & NG & NG \\ Proposed & & 30 \(\times\) 20 & 3.01–12.34 & 2 & \(\geq\)22 & 5.5 & 70 & \(<\)0.0025 & 10 & 0.15 & \(<\)\(-12\) & \(-3\) \\ \hline \hline \end{tabular}
\end{table}
Table 2: Performance comparison with reported two-element MIMO antennas.  
Figure 17: Simulated MEGs of proposed antenna.  
**Author Contributions:** Conceptualization, Y.T., C.B., R.Z., P.S. and D.S.; methodology, Y.T., C.B., I.E. and S.M.; software, Y.T., C.B., M.L.B. and C.Z.; validation, I.E., R.Z. and P.S.; formal analysis, M.L.B. and R.Z.; investigation, I.E. and J.R.; writing--original draft preparation, Y.T., C.B. and S.M.; writing--review and editing, R.Z., D.S. and P.S.; visualization, S.M.; supervision, I.E. and R.Z.; project administration, I.E.; funding acquisition, I.E. and P.S. All authors have read and agreed to the published version of the manuscript.  
**Funding:** This project received funding, in part, from the DGRSDT (Direction Generale de la Recherche Scientifique et du Developpement Technologique), MESRS (Ministry of Higher Education and Scientific Research), Algeria and in part, by the National Research Foundation of Korea (NRF) grant funded by the Korean government (NRF-2022R1G1A1004799).  
**Data Availability Statement:** The data presented in this study are available in the article.  
**Conflicts of Interest:** The authors declare no conflict of interest.