\noindent
\begin{tabularx}{\textwidth}{|c||c||c|}
\hline
Scheme & Architecture & Functionality \\
\hline
Intelligent wall & Active frequency selective surfaces with PIN diodes & Fully transparent reflecting surfaces\\
Spatial microwave modulators & Binary phase state tunable meta-surfaces & Shaping complex microwave fields\\
Coding meta-materials & Meta-surfaces with binary elements (0 or $\pi$ phases) & Reconfigurable scattering patterns\\
Programmable meta-surface & Meta-surfaces with PIN diode-equipped cells & Reconfigurable phase, polarization,
and scattering\\
Reconfigurable reflect-arrays & Reflect-arrays with tunable (varactor-tuned) resonators & Adjustable reflection phase\\
Large intelligent surface & Active contiguous surface for transmission and reception & Gains compared to massive MIMO \\
Software-controlled hypersurface & Meta-surfaces equipped with IoT gateways & Wave absorption, polarization,
and steering\\
\hline
\end{tabularx}\\ \\
答案1
像这样吗？
\documentclass{article}
\usepackage{tabularx,ragged2e}
\newcolumntype{C}{>{\Centering}X}
\begin{document}
\setlength\extrarowheight{3pt}
\setlength{\tabcolsep}{4pt}
\noindent
\begin{tabularx}{\textwidth}{|C||C||C|}
\hline
Scheme & Architecture & Functionality \\
\hline
Intelligent wall & Active frequency selective surfaces with PIN diodes & Fully transparent reflecting surfaces\\
Spatial microwave modulators & Binary phase state tunable meta-surfaces & Shaping complex microwave fields\\
Coding meta-materials & Meta-surfaces with binary elements (0 or $\pi$ phases) & Reconfigurable scattering patterns\\
Programmable meta-surface & Meta-surfaces with PIN diode-equipped cells & Reconfigurable phase, polarization, and scattering\\
Reconfigurable reflect-arrays & Reflect-arrays with tunable (varactor-tuned) resonators & Adjustable reflection phase\\
Large intelligent surface & Active contiguous surface for transmission and reception & Gains compared to massive MIMO \\
Software-controlled hypersurface & Meta-surfaces equipped with IoT gateways & Wave absorption, polarization, and steering\\
\hline
\end{tabularx}
\end{document}