## 5 Conclusions  
A novel concept of a Dual-Mode Conical Horn Antenna (DM-CHA) has been introduced in this paper for monopulse systems. It is designed for 5G millimeter-wave applications operating at 37.5-39 GHz. The DM-CHA system has been achieved by integration of a Dual-Mode Converter (DMC) network to a conical horn antenna (CHA). The DMC network includes two mode converters modules (\(TE_{10}{}^{rec}\)-\(TE_{11}{}^{cir}\) and \(TE_{10}{}^{rec}\)-\(TE_{01}{}^{cir}\)). The CHA connected to the DMC is used to excite either the \(TE_{11}{}^{cir}\) or the \(TE_{01}{}^{cir}\) modes, which radiate the sum (\(\Sigma\)) and difference (\(\Delta\)) radiation patterns, respectively, involved in the monopulse system operation. The proposed DM-CHA has been evaluated experimentally. It has been manufactured using two techniques. The DMC has been fabricated by subtractive manufacturing using Computer Numerical Control (CNC) technology. The CHA has been fabricated by additive manufacturing using Direct Metal Laser Sintering (DMLS) technology. After manufacturing the whole system, experimental measurements have been obtained for the S-parameters and for the normalized sum (\(\Sigma\)) and difference (\(\Delta\)) radiation patterns. The measured results have been compared with the simulated results, with a very good agreement. Finally, the measured realized gain and directivity of the sum (\(\Sigma\)) radiation patterns have been compared. About 0.3 dB average loss in the frequency range has been observed for the measured results. This can be explained by the associated roughness of the DMLS process of the inner wall of the CHA. Monopulse antennas operating in the millimeter-wave frequency band play a crucial role in advanced radar systems, particularly for tracking and guiding high-speed, precision-targeted objects. Furthermore, monopulse antennas in this frequency band fulfill a critical role in the detection and tracking of elusive targets, a task that proves challenging for lower-frequency radar systems. This capability holds paramount importance in countering the advanced technologies employed by potential adversaries. Overall, monopulse antennas in the millimeter-wave frequency band are essential components in modern technology, \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Ref.** & [35] & [28] & [19] & [20] & **This Work** \\ \hline \multirow{2}{*}{Technology} & Horn + mode & Gap waveguide & & & \\  & converter & array & & & \\ \hline \(f_{0}\) (GHz) & 35 & 30 & 33.5 & 31.25 & 38 \\ \hline \multirow{2}{*}{Directivity [dBi]} & \multirow{2}{*}{24.08} & \multirow{2}{*}{27} & \multirow{2}{*}{31.2} & \multirow{2}{*}{18.74} & \multirow{2}{*}{21.8} \\ \cline{1-1}  & & & & & \\ \hline \multirow{2}{*}{\
\begin{tabular}{c} Radiation \\ efficiency (\%) \\ \end{tabular} } & \multirow{2}{*}{\(NA\)} & \multirow{2}{*}{80} & \multirow{2}{*}{42} & \multirow{2}{*}{\(NA\)} & \multirow{2}{*}{85} \\ \hline Size (\(\lambda_{0}{}^{3}\)) & \(14.93\times 13.53\times 35.35\) & \(12\times 12\times 2.6\) & \(16.78\times 16.78\) & \(14.6\times 13.55\) & \(4.84\times 4.84\times 13.9\) \\ \hline \multirow{2}{*}{
\begin{tabular}{c} Full metal \\ structure \\ \end{tabular} } & \multirow{2}{*}{_Yes_} & \multirow{2}{*}{_Yes_} & \multirow{2}{*}{_No_} & \multirow{2}{*}{_No_} & \multirow{2}{*}{_Yes_} \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Comparison of the characteristics of this work with other state-of-the-art works. enabling precise and reliable tracking and guidance in complex and dynamic scenarios. According to the full set of experimental results, the novel monopulse antenna concept proposed in this work has shown its potential for future 5G millimeter-wave applications requiring monopulse operation. Conceptualization, A.P., M.H.R., J.L.M.-C., J.L.C.-R. and J.A.R.-C.; methodology, A.P., M.H.R., J.L.M.-C., J.L.C.-R. and A.R.-C.; software, A.P., M.H.R. and J.L.C.-R., validation, A.P., M.H.R., J.L.M.-C., J.L.C.-R. and J.A.R.-C.; writing--original draft preparation, A.P., M.H.R. and J.L.M.-C.; writing--review and editing, A.P., M.H.R.