# Design of a Ku-Band Monopulse Antenna with a Truncated Reflector and an Open-Ended Waveguide Feed
## 4 Conclusions  
The design of a monopulse antenna consisting of a simple coax-fed monopulse feed and a truncated parabolic reflector has been presented for Ku band radar applications at 14-17 GHz requiring asymmetric beamwidths in the elevation and azimuth planes. The feed is an array of four open-ended rectangular waveguides fed by a coaxial probe. The first stage of the work presents the arrangement of the radiators and the design of the coaxial probe.  
Figure 14: Diagonal-plane cross-polarization directivity of the sum channel (\(-180^{\circ}\) to \(180^{\circ}\)).  
Figure 15: Diagonal-plane cross-polarization directivity of the elevation-difference channel (**a**) and of the azimuth-difference channel (**b**) (\(-180^{\circ}\) to \(180^{\circ}\)).  
\begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline
**Ref.** & \(f\) **(GHz)** & \(a\)**GSUM (dBi)** & \(G\)**Diff (dBi)** & \(D\) **(mm)** & \(\text{BW}_{E}\) **(deg.)** & \(\text{BW}_{H}\) **(deg.)** & \(\text{SLL}\) **(dB)** \\ \hline
[9] & 34.5–35.5 & 32 & 28 & 140 & 4.24 & 4.24 & \(-25\) \\ \hline
[11] & W-band & 42.2 & 38.6 & - & 1.41 & 1.61 & \(-35\) \\ \hline
[19] & 9.2 & 34.4 & - & \(1200\times 300\) & 6.10 & 1.60 & \(-22.7\) / \(-18.9\) \\ \hline This work & 14–17 & 30.9–32.1 &
\begin{tabular}{c} 28.1–29.9/ 26.4–27.8 \\ \end{tabular} & 452 \(\times\) 213 & 2.6–3.2 & 4.6–5.2 & \(-20.0\) to \(-12.6\)/ \(-20.0\) to \(-18.8\) \\ \hline \hline \end{tabular}
\end{table}
Table 3: Comparative Analysis.  
The second stage detailed a final design that combines the monopulse feed with a truncated parabolic reflector. The \(E\)- and \(H\)-plane angles of the feed illuminating the reflector have been optimized for balanced directivities of the sum and difference channels. The designed reflector antenna has the following characteristics. The co-polarization directivity of the sum channel, elevation, and azimuth difference channels are 30.9-32.1 dB, 28.1-29.9 dB, and 26.4-27.8 dB at 14-17 GHz, respectively. The cross-polarization directivity of the sum channel, elevation, and azimuth difference channels are \(-\)1.50-1.16, 1.84-4.82, and 6.42-6.97 dB at 14-17 GHz, respectively. The \(E\)- and \(H\)-plane beamwidths of the sum channel are 2.6-3.2 and 4.6-5.3 degrees at 14-17 GHz, respectively. The \(E\)- and \(H\)-plane sidelobe levels of the sum channel are \(-\)20.0 to \(-\)12.6 dB and \(-\)20.0 to \(-\)18.8 dB at 14-17 GHz. The proposed design of a monopulse reflector antenna may find applications where asymmetric beamwidths are required, such as projectile tracking radars, airport surveillance radars, and vehicle tracking radars.  
Conceptualization: A.M.M., B.-C.A.; methodology: A.M.M., B.-C.A.; validation: A.M.M., B.-C.A.; formal analysis: A.M.M., B.-C.A.; formal data curation A.M.M., B.-C.A., S.-G.C., C.-S.L.; writing--original draft: A.M.M.; writing--review and editing: A.M.M., B.-C.A. All authors have read and agreed to the published version of the manuscript.  
This research was supported by the MSIT (Ministry of Science and ICT), Korea, under the Grand Information Technology Research Center support program (IITP-2022-2020-0-01462) supervised by the IITP (Institute for Information & communications Technology Planning & Evaluation). This research was supported by Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education (No. 2020R1A6A1A12047945).  
Not applicable.  
The authors declare no conflict of interest.