\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}