> On a sunny day (Wed, 03 Sep 2008 09:42:57 -0400) it happened Stevea
> > wrote in :
>
> >>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. =A0Is there an
> >>analog design that uses a single potentiometer or perhaps is voltage
> >>controlled ? =A0Low 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.
>
> =A0 =A0NOT analog.
> =A0 =A0Use a ramp oscillator for constant amplitude; one stage generates =
square wave for integrating to the ramp.
> =A0 =A0Run a comparitor off the ramp (triangle); that will be 90 degrees =
WRT
the square wave.
> =A0 =A0The 2 square waves can be filtered with a simple 3-stage phase ret=
ard
filter.- Hide quoted text -
>
> - Show quoted text -
I was going to sugest a ramp generator also... as a analog solution..But I din't know if you can build the filter to work at 0.05 Hz! How much distortion can you handle? George