# Transmission Line as a Quadrupole in Circuitikz

How do I realize a circuit with a trasmission line as a quadrupole (quadripole?) like the one in the picture (from Wikipedia)?

The standard versione is just a single cylinder which means I would have to do something like done here, which is not ideal since I think is "too abstract" for my purpose and doesn't really represent the situation I'm studying.

Thanks for any help!

The main problem here is that you do not want a symbolic circuit, but something which is a mix between a drawing (better done with pure TikZ) and a circuit. I propose to split the things; after all, a circuitikz is also a tikzpicture. Like this:

\documentclass[border=10pt]{standalone}
\usepackage[siunitx, RPvoltages]{circuitikz}
\usetikzlibrary{shapes, calc}
%\usepackage[siunitx, RPvoltages]{circuitikzgit}
\begin{document}
\begin{circuitikz}[
]
% this is a cylinder with an axial line
\node [cylinder, draw, minimum height=4cm, minimum width=1cm, xscale=-1](CYL){};
\draw [gray, dashed] (CYL.before bottom) arc(270:90:0.125cm and 0.5cm);
\draw [gray] (CYL.west) -- (CYL.east);
\coordinate (CYL top center) at ($(CYL.before top)!0.5!(CYL.after top)$);
\coordinate (CYL bottom center) at ($(CYL.before bottom)!0.5!(CYL.after bottom)$);
\node [color=gray, circ] at (CYL bottom center) {};
\node [circ] at (CYL top center) {};
% these are the connections, almost simmetrical
\draw (CYL top center) -- ++(-0.5,0) coordinate(top hot);
\draw (CYL.west) -- ++(0.5,0) coordinate(bottom hot);
\draw (CYL.after top) -- ++(0,-0.5) coordinate(tmp) -- (tmp -| top hot) coordinate(top shield);
\draw (CYL.before bottom) -- ++(0,-0.5) coordinate(tmp) -- (tmp -| bottom hot) coordinate (bottom shield);
% and then you add  the circuit
\draw (top hot) to [R, o-] ++(-2,0) to[sV] ++(0,-2) node[ground](GND){};
\draw (GND) to[short, *-] (GND-|top shield) to[short, -o] (top shield);
\draw (bottom hot) to[short, o-] ++(1,0) to[R] ++(0,-2) -| (bottom shield) node[ocirc]{};
\end{circuitikz}
\end{document}


which gives

You can find the details about the cylinder shape in the section dedicated to the "shape" library of the TikZ manual, and about the gimmick for the terminals, look at section 4.6 of the circuitikz manual, a recent version).

• Thank you! Great answer! Now I've just got to understand to code a little bit better in order to use it in other circuits. Commented Jul 3, 2019 at 9:32