%$Id: sffm.tex,v 25.92 2006/06/28 15:06:41 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
%
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% any later version.
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% Foundation, Inc., 51 Franklin Street, Fifth Floor, 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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%------------------------------------------------------------------------
