## 5 Conclusions  
A novel frequency-scanning antenna with wide beam scanning and consistent gain in the sub-THz frequency range was presented in this paper. The antenna system uses a layered dielectric waveguide, in which a 15-element linear array of radiating overlapped discs was designed to mitigate the OSB problem fed by the mentioned waveguide. The dominant mode of the layered dielectric waveguide is perturbed by the infinite space harmonics generated by two sets of overlapped discs periodically sandwiched between the layers. Specific properties of the proposed design in terms of radiation characteristics, feeding network, and fabrication and measuring challenges were discussed. A gain of 13.6 dBi in the broadside direction was obtained. The antenna demonstrated a good radiation performance over the working frequency band and enabled continuous wide-beam scanning from \(-23^{\circ}\) to \(38^{\circ}\) through the broadside with the peak gain of 15 dBi. The  
\begin{table}
\begin{tabular}{c c c c c c c} \hline  & **Frequency Range** & **Scanning Range** & **Peak Gain** & **Broadside** & **Size** & **Efficiency (\%)** \\  & **(GHz)** & **(Degree)** & **(dBi)** & **Radiation** & **Size** & **Efficiency (\%)** \\ \hline [25] & 75–85 & \(-10^{\circ}\)–\(8^{\circ}\) & 12.7 & Yes & 11.1 \(\lambda_{0}\) & Not mentioned \\ \hline \multirow{2}{*}{[50]} & \multirow{2}{*}{55 to 67} & Forward only & \multirow{2}{*}{6} & \multirow{2}{*}{No} & \multirow{2}{*}{12 \(\lambda_{0}\)} & \multirow{2}{*}{79} \\  & & & \(4^{\circ}\)–\(18^{\circ}\) & & & \\ \hline \multirow{2}{*}{[51]} & \multirow{2}{*}{230–245} & \multirow{2}{*}{\(-25^{\circ}\)–\(25^{\circ}\)} & \multirow{2}{*}{29} & \multirow{2}{*}{Yes} & \multirow{2}{*}{8 \(\lambda_{0}\)} & \multirow{2}{*}{55} \\  & & & & & & \\ \hline \multirow{2}{*}{[1]} & \multirow{2}{*}{220–300} & Backward only & \multirow{2}{*}{28.5} & \multirow{2}{*}{No} & \multirow{2}{*}{10 \(\lambda_{0}\)} & \multirow{2}{*}{75.8} \\  & & \(-75^{\circ}\)—\(30^{\circ}\) & & & & \\ \hline \multirow{2}{*}{[27]} & \multirow{2}{*}{86–106} & \(-31^{\circ}\)–\(10^{\circ}\) & 11 & Yes & 6 \(\lambda_{0}\) & 58 \\ \hline \multirow{2}{*}{[26]} & \multirow{2}{*}{58–67} & Forward only & \multirow{2}{*}{11.7} & \multirow{2}{*}{No} & \multirow{2}{*}{2.6 \(\lambda_{0}\)} & \multirow{2}{*}{85} \\  & & \(7^{\circ}\)–\(38^{\circ}\) & & & & \\ \hline This work & 157.5–206 & \(-23^{\circ}\)–\(38^{\circ}\) & 15 & Yes & 6.9 \(\lambda_{0}\) & 60 \\ \hline \end{tabular}
\end{table}
Table 1: Performance comparison with the prior literature.  
technique proposed in this work can be easily adapted to realize and implement antennas in the higher mm-wave frequency.  
All authors provided critical feedback and helped shape the research, analysis and manuscript and contributed to the final manuscript. Conceptualization, Y.T.; methodology, Y.T.; investigation, Y.T.; software, Y.T. and M.H.; validation, G.D., Y.T. and M.H.; formal analysis, Y.T.; resources, H.O. and A.L.; data curation, H.O. and A.L.; writing--original draft preparation, Y.T.; writing--review and editing, Y.T. and A.L.; supervision, G.D. and H.O.; project administration, G.D. and H.O. All authors have read and agreed to the published version of the manuscript.  
This research received no external funding.  
The authors declare no conflict of interest.