% Author: Prof. Dr. Matthias Jung, DL9MJ
% Year: 2024
\begin{circuitikz}
    \fill[DARCblue!50](2,0) rectangle ++(1,1) coordinate(up);
    \fill[DARCblue!50](2,0) rectangle ++(-1,1) coordinate(down);
    %
    \draw(-0.25,0) -- ++(0.5,0) coordinate(h);
    \draw[dashed](h) -- ++(0.5,0) coordinate(h);
    \draw[-Triangle](h) -- ++(3,0) node[anchor=west](){$f$};
    %
    \draw[-Triangle](0,-0.25) -- ++(0,2) node[anchor=north east](){$U_\text{HF}$};
    %
    \draw[thick](2,0) node[anchor=north](ff){$f_\text{T}$} -- ++(0,1) coordinate(ft);
    %
    \DARCmeasure{ft}{up}{0,0.25}{0}{\textDelta $f$}
    %
    \DARCmeasure{down}{ft}{0,0.25}{0}{\textDelta $f$}
    %
    \draw[-Triangle](1,-0.50) --  ++(2.25,0) node[anchor=west](){$U_\text{NF}$};
    \draw[-Triangle](ff.south) -- ++(0,-0.25) coordinate(start) -- ++(0,-1.75) node[anchor=west](){$t$};
    %
    \draw[DARCblue,thick, rotate=90](start)
        sin ++(-0.33,1)
        cos ++(-0.33,-1)
        sin ++(-0.33,-1)
        cos ++(-0.33,1);
\end{circuitikz}