TikZ: Wie komplexe Nodes gruppieren und wiederverwemden?

\documentclass{standalone}

\usepackage{tikz}

\usetikzlibrary{decorations,arrows}

\begin{document}

\pgfdeclaredecoration{complete sines}{initial}

{

    \state{initial}[

        width=+0pt,

        next state=sine,

        persistent precomputation={\pgfmathsetmacro\matchinglength{

            \pgfdecoratedinputsegmentlength / int(\pgfdecoratedinputsegmentlength/\pgfdecorationsegmentlength)}

            \setlength{\pgfdecorationsegmentlength}{\matchinglength pt}

        }] {}

    \state{sine}[width=\pgfdecorationsegmentlength]{

        \pgfpathsine{\pgfpoint{0.25\pgfdecorationsegmentlength}{0.5\pgfdecorationsegmentamplitude}}

        \pgfpathcosine{\pgfpoint{0.25\pgfdecorationsegmentlength}{-0.5\pgfdecorationsegmentamplitude}}

        \pgfpathsine{\pgfpoint{0.25\pgfdecorationsegmentlength}{-0.5\pgfdecorationsegmentamplitude}}

        \pgfpathcosine{\pgfpoint{0.25\pgfdecorationsegmentlength}{0.5\pgfdecorationsegmentamplitude}}

}

    \state{final}{}

}

\tikzset{

auto,

node distance=10mm,

>=latex',

block/.style={draw, rectangle, minimum height=10mm, minimum width=10mm},

wave/.style={decorate, draw=black, decoration={complete sines,amplitude=1mm, segment length=6mm}}

}

\begin{tikzpicture}

    % Mixer

    \node[draw,circle,inner sep = 0pt, minimum width=4mm,label={Mixer}] at (0,0)  (x) {};

    \clip (0,0) circle [radius=2mm];

    \draw ([xshift=-5mm,yshift=-5mm]x.center) -- ([xshift=5mm,yshift=5mm]x.center) {};

    \draw ([xshift=-5mm,yshift=5mm]x.center) -- ([xshift=5mm,yshift=-5mm]x.center) {};

\end{tikzpicture}

\begin{tikzpicture}

    \node at (0,0) [block,label={BPF}]     (bpf)  [anchor=center]    {};

    \draw[wave] ([xshift=-3mm, yshift=2mm]bpf.center) -- +(0.6,0) {};

    \draw[wave] ([xshift=-3mm]bpf.center) -- +(0.6,0) {};

    \draw[wave] ([xshift=-3mm, yshift=-2mm]bpf.center) -- +(0.6,0) {};

    \draw[transform canvas={yshift=2mm}] ([xshift=1mm,yshift=0.75mm]bpf.center) -- ([xshift=-1mm,yshift=-0.75mm]bpf.center) {};

    \draw[transform canvas={yshift=-2mm}] ([xshift=1mm,yshift=0.75mm]bpf.center) -- ([xshift=-1mm,yshift=-0.75mm]bpf.center) {};

\end{tikzpicture}

\end{document}

 \draw [bandpass]