\begin{tikzpicture}[->, >=stealth, shorten >= 0pt, draw=black!50, node distance=3.2cm, font=\sffamily]
    \tikzstyle{node}=[circle,fill=black,minimum size=2pt,inner sep=0pt]
    \tikzstyle{block}=[draw=black,rectangle,fill=none,minimum size=1.5cm, inner sep=2pt]

	\node[node] (xc) {};    
    \node[block, right=1cm of xc, text width = 1.5cm, align= center] (CTD) {C-to-D};
    \node[block, right=1cm of CTD, text width = 1.5cm, align= center] (Q) {Quantizer};
    \node[block, right of=Q, text width = 1cm, align= center] (L) {$~~2$};
    \draw[-latex, shorten >= 15pt, shorten <= 15pt, line width=0.75pt] ($(L.south)-(5pt, 0)$) -- ($(L.north)-(5pt, 0)$) {};
    \node[block, right of=L, text width = 1.5cm, align= center] (H) {$H(z)$};
    \coordinate[right=1cm of H] (yc) {};
    
    \path (xc) edge (CTD);
    \path (CTD) edge (Q);
    \path (Q) edge (L);
    \path (L) edge (H);
    \path (H) edge (yc);
    
    \coordinate (mid1) at ($(Q.east)!0.5!(L.west)$);
    \coordinate (mid2) at ($(L.east)!0.5!(H.west)$);
    
    \node[above = 0.5mm of mid1] {$x[n]$};
    \node[below = 0.5mm of mid1] {$X(e^{j\omega})$};
    \node[above = 0.5mm of mid2] {$x_e[n]$};
    \node[below = 0.5mm of mid2] {$X_e(e^{j\omega})$};
    \node[above = 0mm of xc, text width = 1cm, align=center] {$x_c(t)$};
    \node[below = 0mm of xc, text width = 1cm, align=center] {$X_c(j\Omega)$};
    \node[above = 0mm of yc, text width = 1cm, align=center] {$y[n]$};
    \node[below = 0mm of yc, text width = 1cm, align=center] {$Y(e^{j\omega})$};
    \node[align=center, text width=2cm, below] at ($(CTD.south)$) {$\Omega_s = \frac{2\pi}{T}$};
    
    \draw[dashed] ($(CTD.north west)+(-0.25cm, 0.25cm)$) rectangle ($(Q.south east)+(0.25, -0.75cm)$);
    \node[below] at ($(CTD.south west)!0.5!(Q.south east) -(0, 0.75cm)$) {ADC};
\end{tikzpicture}