%$Id: sffm.tex,v 21.13 2002/03/25 05:37:03 al Exp $
% man behavior sffm .
% Copyright (C) 2001 Albert Davis
% Author: Albert Davis <aldavis@ieee.org>
%
% This file is part of "Gnucap", the Gnu Circuit Analysis Package
%
% This program is free software; you can redistribute it and/or modify
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% the Free Software Foundation; either version 2, or (at your option)
% any later version.
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% but WITHOUT ANY WARRANTY; without even the implied warranty of
% MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
% GNU General Public License for more details.
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% Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA
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%------------------------------------------------------------------------
\section{{\tt SFFM}: Frequency Modulation time dependent value}
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\subsection{Syntax}
\begin{verse}
{\tt SFFM} {\it args}\\
{\tt SFFM} {\it offset amplitude carrier modindex signal}
\end{verse}
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\subsection{Purpose}

The component value is a sinusoid, frequency modulated by another sinusoid.
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\subsection{Comments}

For voltage and current sources, this is the same as the Spice {\tt
SFFM} function, with some extensions.

The shape of the waveform is described by the following equations:

\begin{verbatim}
mod = (_modindex * sin(2*PI*_signal*time));
ev = _offset + _amplitude 
        * sin(2*PI*_carrier*time + mod);
\end{verbatim}
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\subsection{Parameters}

\begin{description}

\item[{\tt Offset} = {\it x}] Output offset.  (Default = 0.)

\item[{\tt Amplitude} = {\it x}] Amplitude.  (Default = 1.)

\item[{\tt Carrier} = {\it x}] Carrier frequency, Hz.  (required)

\item[{\tt Modindex} = {\it x}] Modulation index.  (required)

\item[{\tt Signal} = {\it x}] Signal frequency.  (required)

\end{description}
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%\subsection{Example} 
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%------------------------------------------------------------------------
