Re: Dual sine wave generator with variable frequency and 90 degree phase difference

Jan Panteltje wrote:
On a sunny day (Wed, 03 Sep 2008 09:42:57 -0400) it happened Steve
<steve@xxxxxxxxxx> wrote in <205tb41td5tfa5n3esvim42940ikvhh09l@xxxxxxx>:


I'm looking for a waveform generator that outputs two sine waves of
the same frequency with 90 degree phase difference (sine and cosine).
I need a variable frequency between 0.05 Hz and 10 Hz. Is there an
analog design that uses a single potentiometer or perhaps is voltage
controlled ? Low distortion is not a requirement.

Steve


2 x EPROM sine and cosine lookup table,
4046 VCO variable clock generator,
binary counter on EPROM address lines,
2 x 8 bits wide DA converter, 2 x lowpass.

For a 256 values per sine wave form, your clock should be max 2560 Hz.
NOT analog.
Use a ramp oscillator for constant amplitude; one stage generates a square wave for integrating to the ramp.
Run a comparitor off the ramp (triangle); that will be 90 degrees WRT the square wave.
The 2 square waves can be filtered with a simple 3-stage phase retard filter.
.

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