Example: Minimum shift keying modulator

% Example for an interconnection of signal flow diagrams.
%
% Author: Dr. Karlheinz Ochs, Ruhr-University of Bochum, Germany
% Version: 0.1
% Date: 2007/01/05
\documentclass{article}
\usepackage{signalflowdiagram}
\begin{document}

% Note: The following macros are also defined in the macros.sty file

%
% Creates the signal flow diagram of a minimum shift keying coder.
%
% #1 = global label
% #2 = parameter for placement
\newcommand{\mskCoder}[3]{%
   % building blocks
   \node[modulator]  (#1-in)  [#2] {};
   \node[multiplier] (mul)    [below from=#1-in] {$\mathrm{j}$};
   \node[delay]      (del)    [right from=#1-in] {$T$};
   \node[node]       (#1-out) [right from=del]   {};
   % signal paths
   \path[c>] (#1-in)  -- (del);
   \path[c>] (del)    -- (#1-out);
   \path[c>] (#1-out) |- (mul);
   \path[c>] (mul)    -- (#1-in);
}%

% Creates the signal flow diagram of a pulse shaper.
%
% #1 = global label
% #2 = parameter for placement
\newcommand{\pulseShaper}[4]{%
   % building blocks
   \node[modulator]  (#1-in)  [#2] {};
   \node[coordinate] (pam)
      [above from = #1-in,
       label=above:$\sum\limits_{\nu=-\infty}^{\infty} \delta(t-t_\nu)$] {};
   \node[filter]     (#1-out) [right from = #1-in] {$q(t)$};
   % signal paths
   \path[r>] (pam)   -- (#1-in);
   \path[c>] (#1-in) -- (#1-out);
}%

% interconnection of an MSK symbol encoder with a pulse shaper
\begin{signalflow}{Minimum shift keying modulator}%
   \node[input]  (in)                      {$x(t)$};
   \mskCoder     {mC}  {right from=in}     {};
   \pulseShaper  {pS}  {right from=mC-out} {};
   \node[output] (out) [right from=pS-out] {$z(t)$};
   % signal paths
   \path[c>] (in)     -- (mC-in);
   \path[c>] (mC-out) -- (pS-in);
   \path[c>] (pS-out) -- (out);
   \textaboveof{mC-out}{$y(t)$}
\end{signalflow}

\end{document}