\begin{table}%t2
%\centering
\par
\caption{\label{measerr}Beam pattern measurement results for a typical single-mode back-to-back
horn.}
\begin{tabular}{cccc}
\hline\hline
\noalign{\smallskip}
Beam level &  Difference & Rel. diff. & Rel. diff.\\
\hline
$-$1~dB & $-$25~dB & $-$24~dB & 0.4\%\\
$-$3~dB & $-$23~dB & $-$20~dB & 1\%\\
$-$10~dB & $-$30~dB & $-$20~dB & 1\%\\
$-$20~dB & $-$35~dB & $-$15~dB & 3\%\\
$-$30~dB & $-$40~dB & $-$10~dB & 10\%\\
\hline
\end{tabular}
\tablefoot{The difference is computed between the theoretical modal-matching model and experimental measurements according to Eq.~(\ref{diff}). Column 3, relative difference, is the ratio (dB) between the difference and the beam level, while Col.~4 is the same result in \%.}
\end{table}