# Shape Optimization of an Integrated Mast for RCS Reduction of a Stealth Naval Vessel
## 3 Analysis Results
(**a**) HH polarization at an elevation angle of 0\({}^{\circ}\), (**b**) VV polarization at an elevation angle of 0\({}^{\circ}\), (**c**) HH polarization at an elevation angle of 10\({}^{\circ}\), (**d**) VV polarization at an elevation angle of 10\({}^{\circ}\). Figure 7: RCS pattern of the integrated mast in the azimuth plane in the S-band. (**a**) HH polarization at an elevation angle of 0\({}^{\circ}\), (**b**) VV polarization at an elevation angle of 0\({}^{\circ}\), (**c**) HH polarization at an elevation angle of 10\({}^{\circ}\), (**d**) VV polarization at an elevation angle of 10\({}^{\circ}\). The RCS of a naval vessel equipped with each mast was also analyzed to evaluate its stealth performance. Figure 9 shows the geometry and dimension of the naval vessel used in the simulation. The length, width and height of the naval vessel were 152.1 m, 18.14 m and 24.9 m, respectively. The RCS patterns (red and solid line) of the naval vessel equipped with the initial mast in the azimuth plane for the elevation angles of 0\({}^{\circ}\) and 10\({}^{\circ}\) in the L-, S- and X-band were plotted and are shown in Figures 10-12, respectively. The results with the optimized mast (blue and dashed line) and without the mast (black and dotted line) were also plotted and can be seen in the same Figures, respectively. The naval ship generally had large RCS values in the regions of the bow, the starboard, the port and the stern. The physical size of the naval ship was very large but the RCS of the naval ship itself was relatively very small due to the superstructure and the hull form, which had sloping sides. Although the integrated mast was mounted on the naval ship, the RCS results with and without the mast were very similar as seen in Figures 9a and 10b. However, the RCS was seen to be larger in the order of no mast, optimization mast and initial mast. Additionally, the RCS pattern for the initial mast was found to have four additional spikes in the threat regions at an elevation angle of 10\({}^{\circ}\) (see Figure 10c,d, Figure 11c,d and Figure 12c,d). From these results, it could be seen that the scattered field was mainly composed of the influence by the integrated mast with a relatively small physical size rather than the naval ship. In the \begin{table}
\begin{tabular}{c c c c c c} \hline \hline \multirow{2}{*}{**Frequency**} & **Elevation** & \multicolumn{2}{c}{**Initial Mast**} & \multicolumn{2}{c}{**Optimized Mast**} \\  & **Angle** & **HH** & **VV** & **HH** & **VV** \\ \hline \multirow{6}{*}{L-band} & 0\({}^{\circ}\) & 1.69 & 1.75 & \(-\)4.04 & \(-\)4.13 \\  & 3\({}^{\circ}\) & 11.23 & 10.40 & \(-\)2.78 & \(-\)2.15 \\  & 5\({}^{\circ}\) & 15.74 & 16.32 & \(-\)1.37 & \(-\)4.90 \\  & 7\({}^{\circ}\) & 18.02 & 17.55 & 3.28 & 4.89 \\  & 10\({}^{\circ}\) & 16.91 & 17.00 & 6.02 & 4.89 \\  & 0\({}^{\circ}\) & \(-\)1.21 & 0.03 & \(-\)5.03 & \(-\)3.91 \\  & 3\({}^{\circ}\) & 5.68 & 7.08 & \(-\)8.94 & \(-\)11.60 \\  & 5\({}^{\circ}\) & 14.92 & 15.37 & \(-\)4.49 & \(-\)8.07 \\  & 7\({}^{\circ}\) & 20.05 & 20.34 & \(-\)2.31 & \(-\)0.37 \\  & 10\({}^{\circ}\) & 11.50 & 13.60 & 0.57 & 3.78 \\  & 0\({}^{\circ}\) & \(-\)3.99 & \(-\)3.63 & \(-\)11.12 & \(-\)9.88 \\  & 3\({}^{\circ}\) & \(-\)2.21 & \(-\)12.35 & \(-\)9.18 & \(-\)10.69 \\ X-band & 5\({}^{\circ}\) & 6.41 & 7.92 & \(-\)8.85 & \(-\)4.24 \\  & 7\({}^{\circ}\) & 20.22 & 20.14 & \(-\)5.17 & \(-\)1.99 \\  & 10\({}^{\circ}\) & 1.87 & \(-\)0.54 & \(-\)4.99 & \(-\)4.32 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Geometric mean of the integrated mast.