\begin{tikzpicture}
\begin{axis}[
name=plot1,
axis equal,
axis lines*=middle,
enlargelimits = false, clip=true,
xmin=-1.39,
xmax=1.39,
ymin=-1.10,
ymax=1.10,
axis line style={->,>=stealth},
xlabel={$\mathrm{Re}\{z\}$},
ylabel={$\mathrm{Im}\{z\}$},
every axis x label/.style={
at={(ticklabel* cs:1)},
anchor=north,
},
every axis y label/.style={
at={(ticklabel* cs:1)},
anchor=south,
},
xtick=1, ytick=\empty,
xticklabel style={xshift=0.1cm},
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}]
\draw (axis cs:0,0) circle [black!50, dashed, line width=2pt, radius=1];
\addplot [line width=1pt,mark=x, only marks, mark size = 3pt]
table[row sep=crcr]{
	0 0 \\
};

\addplot [line width=1pt,mark=*, only marks, mark size = 3pt, mark options={fill=white}]
table[row sep=crcr]{
	0.6364 0.6364\\
};

\coordinate (axis) at (axis cs: 1, 0);
\coordinate (orig) at (axis cs: 0, 0);
\coordinate (zero) at (axis cs:	0.6364, 0.6364);
\draw[->, >=stealth, shorten >= 2.5pt, thick] (orig) -- (zero);

\pic [draw, <->, "$\theta$", angle eccentricity=1.5] {angle = axis--orig--zero};

\only<1|handout:0>{
\coordinate (eval) at (axis cs:	1, 0);
%\pic [draw, red2, <->, "$\omega$", angle eccentricity=1.25,  angle radius=1cm] {angle = axis--orig--eval};
\draw[->, >=stealth, shorten >= 2.5pt, thick, red2] (orig) -- (eval);
\draw[red2, fill=red2] (eval) circle (3pt);
\draw[->, >=stealth, shorten >= 2.5pt, thick, blue2] (zero) -- (eval);
}

\only<2|handout:1>{
	\coordinate (eval) at (axis cs:	0.707, 0.707);
	\pic [draw, red2, <->, "$\omega$", angle eccentricity=1.25,  angle radius=1cm] {angle = axis--orig--eval};
	\draw[->, >=stealth, shorten >= 2.5pt, thick, red2] (orig) -- (eval);
	\draw[red2, fill=red2] (eval) circle (3pt);
	\draw[->, >=stealth, shorten >= 2.5pt, thick, blue2] (zero) -- (eval);
}

%\node at ($(orig)!0.5!(zero) + (-0.1cm, 0.3cm)$) {$v_2$};
%\node[red2] at ($(orig)!0.5!(eval) + (0.1cm, 0.3cm)$) {$v_1$};
%\node[blue2] at ($(eval)!0.5!(zero) + (-0.1cm, 0.3cm)$) {$v_3$};

\end{axis}

\begin{axis}[
name=plot2,
at= (plot1.east), anchor=west,
xshift=1cm,
axis lines*=middle,
enlargelimits = upper, clip=true,
scale only axis,
axis line style={->,>=stealth},
xlabel={$\omega$},
ylabel={$20\cdot\log_{10}(|H(e^{j\omega})|)$},
every axis x label/.style={
	at={(ticklabel* cs:1)},
	xshift=-0.2cm,
	anchor=north,
},
every axis y label/.style={
	at={(ticklabel* cs:1)},
	xshift=0.4cm,
	%yshift=0.35cm,
	anchor=south,
},
every outer x axis line/.append style={white!15!black},
every x tick label/.append style={font=\color{white!15!black}},
xmin=0, xmax=3.14,
xtick={0, 0.7850, 1.57, 2.3550, 3.14},
xticklabels ={$0$, $\pi/4$, $\pi/2$, $3\pi/4$, $\pi$},
ymajorgrids,
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 [smooth, black, line width=1.5pt, forget plot, domain=0:3.14, samples=101] {20*log10(sqrt(1+0.81 - 2*0.9*cos(deg(x)-45)))};

\only<1|handout:0>{
\addplot [red2, mark=*, mark size=3pt] coordinates {(0,-2.6986)};
}

\only<2|handout:1>{
	\addplot [red2, mark=*, mark size=3pt] coordinates {(0.7854,-20)};
}

\end{axis}
\end{tikzpicture}