## 4 Conclusions  
This article presents the design and validation of a wideband antenna for Ka-band 5G applications. The initial design is comprised of a rectangular printed antenna, whose performance is enhanced using an additional circular patch along with the loading of two open-ended stubs. The resultant antenna offers wideband ranges from 26.5 GHz to 43.7 GHz having a peak gain of >6 dBi in the operational band. The unit element had a compact size of \(10\times 15\) mm\({}^{2}\). Furthermore, to meet the requirements of the modern-day devices, a MIMO antenna is constructed using elements. The consecutive elements are placed orthogonal to achieve a low mutual coupling. Moreover, the presence of the open-ended stubs further helps to lower mutual coupling. The edge-to-edge space between consecutive elements is \(4\) mm and the maximum mutual coupling is less than \(-30\) dB. Other performance parameters of the MIMO antenna are also studied, which show acceptable values in all terms. At last, the performance comparison is performed with recently reported works and the proposed work overperforms all the works by offering wideband, compact size, high gain, and low mutual coupling, making the proposed work a potential candidate for ka-band applications. The future extension of the proposed work is to deploy it for massive MIMO applications requiring the low mutual coupling among the element placed in close range. Conceptualization, methodology, software, validation, S.A.H., F.T., M.S.A. and I.H. ; formal analysis, investigation, resources, data curation, R.M.G., M.F.A.S. and A.L. ; writing--original draft preparation, S.A.H., I.H. and F.T. ; writing--review and editing, M.S.A., R.M.G., M.F.A.S. and A.L. ; visualization, R.M.G. ; supervision, A.L. ; project administration, funding acquisition, R.M.G. and A.L. All authors have read and agreed to the published version of the manuscript. Princess Nourah bint Abdulrahman University Researchers Supporting Project number (PNURSP2023R138), Princess Nourah bint Abdulrahman University, Riyadh, Saudi Arabia. \begin{table}
\begin{tabular}{c c c c c c c c c c} \hline \hline \multirow{2}{*}{**Ref**} & **Dimensions** & \multirow{2}{*}{**Ports**} & **Bandwidth** & **Operating** & **Peak** & \multicolumn{2}{c}{**Mini.**} & **Max.** & \multirow{2}{*}{**MIMO Antenna Type**} \\  & **(mm \(\times\)mm \(\times\)mm)** & & **(GHz)** & **Frequency** & **Gain** & & & **Esolation** & **Isolation** \\  & & & **(GHz)** & **(GHz)** & & & **(dB)** & **(dB)** & \\ \hline
[18] & \(115\times 60\times 0.76\) & 5 & 27.5–28.7 & 28.3 & 5 & 0.056 & \(-30\) & \(-13\) & Monopole antenna \\
[19] & \(50.8\times 125\times 0.8\) & 4 & 26–36 & 27 & 5.23 & – & \(-45\) & \(-22\) & CPW-fed patch antenna \\
[20] & \(19.25\times 26\times 0.79\) & 4 & 27–30.5 & 28.5 & 7.58 & 0.001 & \(-35\) & \(-12\) & EBG-based antenna \\
[23] & \(24\times 20\times 1.85\) & 4 & 33–44.1 & 38 & 4.56 & 0.1 & \(-32\) & \(-16\) & Patch antenna over transparent substrate \\
[24] & \(53\times 20\times 0.203\) & 2 & 22–50 & \(36/45\) & 15 & 0.12 & \(-40\) & \(-20\) & Slot array antenna \\
[25] & \(110\times 55\times 1.6\) & 6 & 27.7–28.7 & 28 & 5.13 & 0.005 & \(-55\) & \(-22\) & Air-filled sloted loop (AFSJ) antenna \\
[26] & \(125\times 125\times 0.8\) & 4 & 33–36 & 35 & 6 & 0.02 & \(-33\) & \(-23\) & Hexagonal patch antenna \\
[27] & \(60\times 100\times 0.965\) & 2 & 27.6–28.3 & 28 & 4.5 & 0.134 & \(-30\) & \(-17\) & Modified monopole antenna \\
[29] & \(48\times 31\times 0.254\) & 4 & 26-31 & 28 & 10 & 0.0015 & \(-38\) & \(-21\) & Patch antenna loaded with array of metamaterials \\
[30] & \(80\times 80\times 1.57\) & 4 & 23–40 & 30 & 12 & 0.0014 & \(-40\) & \(-20\) & Arc-shaped patch antenna \\
[31] & \(20.5\times 12\times 0.79\) & 2 & 25.5–30 & 28 & 8.75 & – & \(-40\) & \(-30\) & E-shaped patch antenna \\ Prop. Work & \(27\times 27\times 1.52\) & 4 & 26.5–43.7 & 30/38 & 8.4 & 0.001 & \(-42\) & \(-30\) & Stub loaded monopole antenna \\ \hline \hline \end{tabular}
\end{table}