\begin{tikzpicture}[->, >=stealth, shorten >= 0pt, draw=black!50, node distance=3.5cm, 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=0pt]
    \tikzstyle{annot} = []

	\node[node] (xc) {};
    \node[block, right=1cm of xc, text width = 1cm, align= center] (DSP) {$~~L$};
    \draw[-latex, shorten >= 15pt, shorten <= 15pt, line width=0.75pt] ($(DSP.south)-(5pt, 0)$) -- ($(DSP.north)-(5pt, 0)$) {};
	\node[block, right of=DSP, text width = 3cm, align= center] (LPF) {Lowpass filter \\ Gain = $L$ \\ Cutoff = $\pi/L$};
	\coordinate (yc) at ($(LPF.east)+(1.5cm, 0)$) {};
		
	\coordinate (mid) at ($(DSP.east)!0.5!(LPF.west)$) {};		
		
    \path (xc) edge (DSP);
    \path (DSP) edge (LPF);
    \path (LPF) edge (yc);
    
    \node[above = 0mm of mid, text width = 1cm, align=center] {$x_e[n]$};
    \node[above = 0mm of xc, text width = 1cm, align=center] {$x[n]$};
    \node[above = 0mm of yc, text width = 3cm, align=center] {$x_i[n]$}; 
    \node[align=center] at ($(DSP.south) - (0, 0.3cm)$) {Upsampling};
    \node[align=center] at ($(LPF.south) - (0, 0.3cm)$) {Interpolation filter};
\end{tikzpicture}