% Author: Dr. Matthias Jung, DL9MJ
% Year: 2020
\begin{circuitikz}
    \pgfdeclarelayer{fg} % declare background layer
    \pgfsetlayers{main,fg}
    \draw (0,0)
        node [allpassshape, anchor=west](all){};
    \draw (all.east)
        to [short, name={l1}] ++(1,0) node[inputarrow](){}
        node [twoportsplitshape,anchor=west,t1=f,t2={2\,f}](f1){};
    \draw(f1.east)
        to [short, name={l2}] ++(1,0) node[inputarrow](){}
        node [twoportsplitshape,t1=f,t2={2\,f},anchor=west](f2){};
    \draw(f2.east)
        to [short, name={l3}] ++(1,0) node[inputarrow](){}
        node [twoportsplitshape,t1=f,t2={2\,f},anchor=west](f3){};
    \draw(f3.east)
        to [short, -o] ++(0.5,0) coordinate(e0);
    \begin{pgfonlayer}{fg}
        \draw(e0)
            to [open,-o] ++(0,-0.75) coordinate(e1) node[anchor=west](){} 
            to [open,-o] ++(0,-0.75) coordinate(e2) node[anchor=west](){a}  
            to [open,-o] ++(0,-0.75) coordinate(e3) node[anchor=west](){}  
            to [open,-o] ++(0,-0.75) coordinate(e4) node[anchor=west](){};
    \end{pgfonlayer}

    %Help connector:
    \draw(l3.center) to [open] ++(-0.15,0) coordinate(l3l);
    \draw(l3.center) to [open] ++(+0.15,0) coordinate(l3r);

    \draw(l2.center)
        to [short, *-] ++(0,2) coordinate(l22);
    \draw(l3r.center)
        to [short] ++(0,2) coordinate(l33)
        |- (e1);
    \draw(l22)
        to [twoportsplit,t1=f,t2={3\,f},>] (l33);
    \draw(l3l)
        to [short, *-] ++(0,0)
        |- (e2);
    \draw(l2.center)
        |- (e3);
    \draw(l1.center)
        to [short, *-] ++(0,0)
        |- (e4);
    \draw(all.south) node[anchor=north](){VFO};
\end{circuitikz}