\begin{table}%t3
%\centering
\par
\caption {\label{main_beam_chars}Main beam characteristics at the central frequency.}
%\centerline
 {\begin{tabular}{c c c c c c c c c c c c c c c}
\hline\hline
\noalign{\smallskip}
& &\multicolumn{2}{c}{{\sc hw} at $-3$dB} & \multicolumn{2}{c}{{\sc hw} at $-10$dB} & \multicolumn{2}{c}{{\sc hw} at $-20$dB} & & & & & & & \\
Beam & & \multicolumn{2}{c}{(deg)} & \multicolumn{2}{c}{(deg)} & \multicolumn{2}{c}{(deg)} & 
{\it FWHM} & $e$ & $\tau$ & $\cal D$ & XPD & $d$ & $\cal S$ \\
\cline{3-8}
          &   & min   &  max  & min   & max   & min   & max   & (arcmin) & & ($^\circ$) & (dBi) & (dB) & (\%) & (\%) \\
\hline
18 and 23 & X & 0.0969 & 0.1235 & 0.1702 & 0.2212 & 0.2247 & 0.3147 & 13.22 & 1.27 &  --0.1 & 58.80 & 28.01 & 0.38 & 0.55 \\
          & Y & 0.0989 & 0.1219 & 0.1725 & 0.2176 & 0.2273 & 0.3096 & 13.25 & 1.23 & --89.8 & 58.83 & 28.54 & 0.40 & 0.50 \\
19 and 22 & X & 0.0969 & 0.1219 & 0.1667 & 0.2167 & 0.2229 & 0.3013 & 13.13 & 1.26 &    0.0 & 59.02 & 29.73 & 0.26 & 0.64 \\
          & Y & 0.0969 & 0.1203 & 0.1690 & 0.2131 & 0.2247 & 0.2967 & 13.03 & 1.24 & --90.0 & 59.06 & 30.21 & 0.28 & 0.58 \\
20 and 21 & X & 0.0949 & 0.1203 & 0.1643 & 0.2140 & 0.2264 & 0.2981 & 12.91 & 1.27 &    0.0 & 59.17 & 31.20 & 0.21 & 0.73 \\
          & Y & 0.0949 & 0.1187 & 0.1655 & 0.2112 & 0.2256 & 0.2941 & 12.82 & 1.25 &   89.9 & 59.22 & 30.99 & 0.23 & 0.69 \\
24        & X & 0.1655 & 0.2176 & 0.2880 & 0.3927 & 0.3815 & 0.5539 & 22.99 & 1.31 &    0.0 & 54.14 & 29.98 & 0.31 & 0.14 \\
          & Y & 0.1619 & 0.2229 & 0.2839 & 0.4025 & 0.3779 & 0.5654 & 23.09 & 1.38 &   90.0 & 54.09 & 29.97 & 0.29 & 0.16 \\
25 and 26 & X & 0.2229 & 0.2727 & 0.4001 & 0.5260 & 0.5370 & 0.7923 & 29.74 & 1.22 &    0.5 & 51.71 & 24.90 & 0.99 & 0.16 \\
          & Y & 0.2112 & 0.2639 & 0.3790 & 0.5170 & 0.5211 & 0.7948 & 28.51 & 1.25 &   89.7 & 51.97 & 25.32 & 0.96 & 0.16 \\
27 and 28 & X & 0.2349 & 0.3208 & 0.4093 & 0.5706 & 0.5392 & 0.7808 & 33.34 & 1.37 &    0.2 & 50.97 & 28.21 & 0.44 & 0.58 \\
          & Y & 0.2299 & 0.3239 & 0.4015 & 0.5757 & 0.5301 & 0.7891 & 33.23 & 1.41 &   89.9 & 51.00 & 28.31 & 0.41 & 0.58 \\
\hline
\end{tabular}}
\tablefoot{The half width ({\sc hw}, minimum and maximum) at $-3$, $-10$, $-20$ dB, the full width half maximum ({\it FWHM}), the ellipticity ($e$), the rotation angle of the polarization ellipse~($\tau$), the main beam directivity ($\cal D$), the cross polar discrimination factor (XPD), the main beam depolarization parameter~($d$), and the spillover~($\cal S$) are reported.}
\end{table}