6

I'm using the Smithchart library with PGF/TikZ, and I'm trying to add a simple circle in the middle of the chart. However, the circle is plotted using the "smithchart coordinate system" so it looks flatted out.

Code:

\documentclass[preview]{standalone}
\usepackage{tikz}
\usepackage{pgfplots}
\usepgfplotslibrary{smithchart}
\pgfplotsset{compat=1.11}

\begin{document}
    \begin{tikzpicture}
        \begin{smithchart}
            \draw (1,0) circle[radius=0.5];
        \end{smithchart}
    \end{tikzpicture}
\end{document}

Result:

Imgur

I tried digging into the PGFplots manual but found nothing similar.

  • 1
    Do you need the circle for highlighting a particular point, or is the size of the circle meaningful in terms of the axis units? – Jake Nov 10 '14 at 19:06
  • The size is meaningful. For example, I would like to draw the circle in which the arc crossing the x-axis at 1 is in. – Lorenzo Gasparini Nov 10 '14 at 20:32
6

Take a look at 5.10 Smith Charts of pgfplots manual, there are many examples and notes about your question.

Please note that by changing \path[draw=red] (0pt,0pt) circle (1.5cm); to \path[draw=red] (0,0) circle (1.5cm); you can use the smith's coordinates instead.

enter image description here

\documentclass[preview]{standalone}
\usepackage{tikz}
\usepackage{pgfplots}
\usepgfplotslibrary{smithchart}
\pgfplotsset{compat=1.11}

\begin{document}
    \begin{tikzpicture}
        \begin{smithchart}
        \path[draw=red] (0pt,0pt) circle (1.5cm);
        \path[draw=blue] (0.2,0.5) circle (0.75cm);
        \path[draw=blue,fill=blue] (0.2,0.5) circle (0.05cm);
        \end{smithchart}
    \end{tikzpicture}
\end{document}
| improve this answer | |
  • What if I would like to plot circle for SWR = 1.5 similiar to yours like \path[draw=blue] (0,0) circle (1.5); with no cm handling? Is it possible too? – Jan Filip Dec 4 '17 at 14:53
  • Doesn't work. The coordinates are plotted in the wrong coordinate system. Drawing a circle in the middle of the chart requires me to write the coordinate (0,0) and not (1,0). – GNA Oct 7 '18 at 16:44

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