## 4 Conclusions  
In this work, wide-angle beam steering has been shown for the purpose of on-the-move satellite communication through the utilization of an innovative closed-form pillbox antenna system. The complete wide-angle beam steering antenna system includes three main parts: fixed-feed SIW-based horn, novel quasi-optical system, and leaky-wave radiating part. A transition made by a single coupling slot alongside and without spacing from the parabolic reflector has been proposed for the quasi-optical system to have effective coupling and extend the bandwidth. Through the utilization of the mechanical rotation of  
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Angle of Rotation \(\omega\)** & \(-\mathbf{20}^{\circ}\) & \(-\mathbf{10}^{\circ}\) & \(\mathbf{0}^{\circ}\) & \(\mathbf{10}^{\circ}\) & \(\mathbf{20}^{\circ}\) \\ \hline Simulated Gain (dBi) & 24 & 25.5 & 26.5 & 25.5 & 24 \\ \hline Measured Gain (dBi) & 20.21 & 22.1 & 23.2 & 22.5 & 20.18 \\ \hline \hline \end{tabular}
\end{table}
Table 2: The simulated and measured peak gain at 20 GHz for different rotation angles.  
\begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**Ref.** & **Antenna Height \(\lambda_{0}\)** & **BW (GHz)** & **Beam Coverage (Degree)** & **Measured Gain (dBi)** & \multicolumn{2}{c}{**SLL (dB)**} \\ \cline{4-7}  & & & & **@ BS** & **@ MSA** \\ \hline [35] & 0.08 & 23.9–24.9 & \(\pm 36\) & 17.7 & \(-15\) & \(-8.8\) \\ \hline [40] & 0.08 & 23.5–25.7 & \(\pm 30\) & 23.8 & \(-12\) & \(-16\) \\ \hline [39] & 4.39 & 27.5–31.0 & \(\pm 40\) & 28.9 & \(-32\) & \(-11\) \\ \hline [36] & 0.08 & 23.5–24.6 & \(\pm 40\) & 25 & \(-15\) & \(-10\) \\ \hline [21] & 0.32 & 10.2–13.9 & \(\pm 40\) & 19.6 & \(-30\) & \(-15.6\) \\ \hline [45] & 9 & 28.5–31.0 & \(\pm 24\) & 31.3 & \(-20\) & \(-10\) \\ \hline [46] & 0.1 & 23.8–24.3 & \(\pm 39\) & 21.6 & \(-23\) & \(-10\) \\ \hline [47] & 0.1 & 23.8–24.4 & \(\pm 40\) & 24.2 & \(-24\) & \(-11\) \\ \hline [48] & 0.1 & 23.5–24.5 & \(\pm 35\) & 22 & \(-20\) & \(-15\) \\ \hline [49] & 0.25 & 74–78 & \(\pm 40\) & 24 & \(-25\) & \(-10\) \\ \hline This Work & 0.3 & 19.0–20.4 & \(\pm 60\) & 23.2 & \(-20\) & \(-17.8\) \\ \hline \hline \end{tabular}
\end{table}
Table 3: Performance comparison of the proposed and previous quasi-optical antenna system.  
the metallic patterns, beam scanning is accomplished. The experimental results show that the antenna can provide a beam-scanning capability of 120\({}^{\circ}\) in the azimuth plane. The antenna terminal demonstrates directive radiation pasters with a maximum measured gain of 23.2 dBi with an antenna height of 0.3\(\lambda_{0}\) and low SLL of \(-\)17.8 dB at a maximum scan angle of 60\({}^{\circ}\). The antenna operates in the frequency range from 19.2 GHz to 20.4 GHz with a reflection coefficient less than \(-\)10 dB. This concept has the potential to be extended to achieve circular polarization, which might be accomplished by incorporating a superstrate layer of a thin polarizer.  
Conceptualization, M.I., A.T.M. and A.A.; design, M.I. and K.S.; software, K.S.; validation, M.I. and M.M.; analysis, K.S. and M.I; investigation, A.T.M. and M.M.; writing--original draft preparation, M.I. and K.S.; writing--review and editing, A.T.M., M.M. and A.A.; supervision A.A. All authors have read and agreed to the published version of the manuscript. This research was supported by the Australian Research Council under ARC Grant LP160100917.  
All data has been included in the paper.  
The authors declare no conflicts of interest.