thru zero VCO questions

[mbartkow at ET.PUT.Poznan.PL]

Did you guys try to do it in a completely different way ?
This probably sounds very radio, but...

what about modulating the frequency of an ultrasonic VCO
and then shifting its spectrum down by the means of AM ?

Consider a V/oct VCO with a scale shifted by say 20kHz,
i.e. f=k*exp(Uin)+20kHz. You can freely do a FM as deep
as 20kHz without worrying about the thru-zero problem.
Then its output is multiplied by a stable 20kHz sine wave 
and filtered with a 20kHz lowpass in order to reject the 
hf artifacts. Of course, a sinusoidal output of the VCO
is used, otherwise higher harmonics would not retain their
proper relations, but the final output may be freely waves-
haped to your taste.


MB


--

Maciej Bartkowiak, PhD
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