> Fourier tells you that a sine wave is an infinite
> series of even harmonics,

Huh!?  Sine waves are the basis functions in Fourier analisys.  A sine wave
IS a pure single frequency.

> and a square wave is an infinite series of odd harmonics.  You're trying
to
> make a sine purse out of a square ear. :)
>
> You need a filter, with fair Q, on the frequency of interest,

You can make a filter with a sharp enough rollof to reduce the harmonics of
a square wave below the level you care about.  However, the amplitude of the
resulting sine wave will be very dependent on frequency.  This will probably
be an issue since he has to vary the frequency on the fly.


********************************************************************
Olin Lathrop, embedded systems consultant in Littleton Massachusetts
(978) 742-9014, olin@embedinc.com, http://www.embedinc.com

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