Minimum shift keying modulator

An example of interconnection of signal flow diagrams using the signalflow library by Karlheinz Ochs. Common system blocks like minimum shift keying coders and pulse shapers are defined as macros for easy reuse and interconnection.

Files:

• Download the version of the signalflow library used in this example: signalflow.zip

Edit and compile if you like:

% 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}

\usepackage[active,tightpage]{preview}
\PreviewEnvironment{signalflow}
\setlength\PreviewBorder{5pt}%

\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}