# A Low-Profile Dielectric Resonator Antenna Array for OAM Waves Generation at 5G NR Bands
## 4 Conclusions  
A rectangular DRA with an inset-fed technique and uniform circular array configuration was designed to generate OAM mode +1 at 3.5 GHz for the 5G NR band. Moreover, a mirror image arrangement of the feeding network was adopted to make the structure simple and less complex. The proposed antenna indicates that the dielectric resonator element has low metallization and can increase the gain and radiation efficiency of the antenna. In addition, the array DRA with a cross slot at the ground plane manages to enhance the bandwidth of the antenna. Moreover, the implementation of the dielectric resonator successfully contributes to antenna miniaturization, yielding its compact size of 2.16\(\lambda\)\(\times\) 1.87\(\lambda\). To further validate the performance of the proposed design, the 2D far-field radiation patterns are measured using a standard horn antenna, and the measured results coincide well with the simulated ones. The measured results show that the antenna arrays \begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline \multirow{2}{*}{**Ref.**} & \multirow{2}{*}{\(f_{r}\) **(GHz)**} & \multirow{2}{*}{**Imp. BW (\%)**} & \multirow{2}{*}{\begin{tabular}{c} **Antenna** \\ **Dimension** \\ \end{tabular} } & \multirow{2}{*}{**Gain (dBi)**} & \multirow{2}{*}{\begin{tabular}{c} **Mode** \\ **Number** \\ \end{tabular} } & \multirow{2}{*}{\
\begin{tabular}{c} **Mode** \\ **(\%)** \\ \end{tabular} } & \multirow{2}{*}{
\begin{tabular}{c} **Wave and** \\ **Intensity** \\ **Distributions** \\ \end{tabular} } \\ \hline
[25] & 4.5–7 & 43.5 & 5.83\(\times\) 5.83\(\lambda\) & NA & +1 and +2 & NA & Yes \\
[26] & 4.9–6.5 & 28.1 & 1.4\(\times\) 1.4\(\lambda\) & 15.19 & 0 and \(\pm\)1 & NA & Yes (Phase only) \\
[27] & 5.72–5.95 & 3.94 & \(R\) = 1.46\(\lambda\) & NA & \(\pm\)1 & NA & Yes (Phase only) \\
[28] & 1.54–1.56 & 1.29 & NA & NA & \(\pm\)1 & NA & No \\
[29] & 2.25–2.4 & 6.45 & 3.5\(\times\) 3.5\(\lambda\) & NA & +1 and +2 & NA & Yes (Phase only) \\
[30] & 10–10.7 & 4.78 & NA & 4.6 & –1 & NA & No \\
[31] & 9.25–10.5 & 12.66 & \(R\) = 0.19\(\lambda\) & NA & +1 & NA & Yes (Phase only) \\
[32] & 5.07–5.14 & 1.37 & \(R\) = 0.37\(\lambda\) & 1.08 & \(\pm\)1 and \(\pm\)3 & NA & Yes (Phase only) \\
[33] & 2.8–4.55 & 47.6 & NA & NA & +1 and +2 & NA & No \\ This work & 3.2–3.66 & 13.4 & 2.16\(\lambda\) \(\times\) 1.87\(\lambda\) & 7.3 & +1 & 53.87 & Yes \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Comparison between various OAM antennas. Figure 10: Mode purity of OAM mode +1 at 3.56 GHz. can cover the 3.5 GHz band of the 5G NR spectrum. The electric field phase patterns confirm the generation of OAM beams. The proposed antenna generated an OAM mode of high purity and achieved a wide bandwidth of 460 MHz with a purity of 53.87%. Future work could include different shapes of the dielectric resonator to increase the bandwidth of the antenna. In addition, a modified slot in the ground plane could also be used to achieve wide bandwidth performance. Using the different shapes of the slot is advantageous as it simplifies the process. In comparison with previous studies, this method is believed to be a significant development in producing a compact size, simple structure, and wide bandwidth to generate OAM waves at the 5G NR band. Lastly, the mode purity analysis of this work shall guide future researchers and engineers in selecting the receiver size of the OAM wave-based wireless communication system. Conceptualization, N.A.A.R., M.N.M.Y. and S.K.N. ; methodology, N.A.A.R. ; writing--original draft preparation, N.A.A.R. ; writing--review and editing, N.A.A.R. ; M.N.M.Y., S.K.N., M.N.O. and S.B.I. ; supervision, M.N.M.Y. and A.M.L; funding acquisition, M.N.M.Y. and I.M.I. All authors contributed equally to this work. All authors have read and agreed to the published version of the manuscript. This research was funded by a publication incentive grant from the Universiti Malaysia Perlis (UniMAP).