\begin{tikzpicture}
\begin{axis}[
	name=plot1,
	axis lines*=middle,
	enlargelimits = false,
	clip=false,
	scale only axis,
	width=0.5\textwidth,
	height=0.15\textwidth,
	ymin=0,
	ymax=1,
	xmin=-5,
	xmax=5,
	axis line style={->,>=stealth},
	xlabel={\small $x$},
	ylabel={\small $p_x(x)$},
	every axis x label/.style={
		at={(ticklabel* cs:1)},
		%xshift=0.2cm,
		anchor=north,
	},
	every axis y label/.style={
		at={(ticklabel* cs:1)},
		anchor=south,
	},
	ytick={0.5},
	xtick={-1, 1},
	every outer y axis line/.append style={white!15!black},
	every y tick label/.append style={font=\color{white!15!black}},
	legend style={draw=white!15!black,fill=white,legend cell align=left}]
	\addplot[ycomb, mark=*, fill=white, mark options={scale=0.75, fill=white}, line width=1pt, domain=0:3, samples=4] coordinates {(-1, 0.5) (1, 0.5)};
\end{axis}
\begin{axis}[
	name=plot2,
	at=(plot1.below south east), anchor=above north east,
	axis lines*=middle,
	enlargelimits = false,
	clip=false,
	scale only axis,
	width=0.5\textwidth,
	height=0.14\textwidth,
	ymin=0,
	ymax=2,
	xmin=-5,
	xmax=5,
	axis line style={->,>=stealth},
	xlabel={\small $m$},
	ylabel={\small $\phi_{xx}[m] = \delta[m]$},
	yticklabel style = {yshift=0cm},
	every axis x label/.style={
		at={(ticklabel* cs:1)},
		%xshift=0.2cm,
		anchor=north,
	},
	every axis y label/.style={
		at={(ticklabel* cs:0.8)},
		anchor=south,
	},
	ytick={1},
	xtick=\empty,
	every outer y axis line/.append style={white!15!black},
	every y tick label/.append style={font=\color{white!15!black}},
	legend style={draw=white!15!black,fill=white,legend cell align=left}]
	\addplot[ycomb, mark=*, fill=white, mark options={scale=0.75, fill=white}, line width=1pt, domain=-5:5, samples=11] {x==0};
\end{axis}
\begin{axis}[
	name=plot3,
	at=(plot2.below south east), anchor=above north east,
	axis lines*=middle,
	enlargelimits = false,
	clip=false,
	scale only axis,
	width=0.5\textwidth,
	height=0.14\textwidth,
	ymin=0,
	ymax=2,
	xmin=-5,
	xmax=5,
	axis line style={->,>=stealth},
	xlabel={$\omega$},
	yticklabel style = {yshift=0.2cm},
	ylabel={$\Phi_{xx}(e^{j\omega}) = 1$},
	every axis x label/.style={
		at={(ticklabel* cs:1)},
		%xshift=0.2cm,
		anchor=north,
	},
	every axis y label/.style={
		at={(ticklabel* cs:1)},
		anchor=south,
		xshift=0cm,
	},
	ytick={1},
	xtick={-3.14, 3.14},
	xticklabels={$-\pi$, $\pi$},
	every outer y axis line/.append style={white!15!black},
	every y tick label/.append style={font=\color{white!15!black}},
	legend style={draw=white!15!black,fill=white,legend cell align=left}]
	\addplot[line width=1pt, domain=-3.14:3.14, samples=2] {1};
\end{axis}
\end{tikzpicture}
