frequency tracking

[Ethan Robert Duni]

>Well, this could work with an ideal sine wave input signal, but I'm
>shure you want to use the pitch2volt converter also for real world
>applications, and in this case the incomming signal has not at all
>constant amplitude or shape, so the above mentioned idea won't work.
>
>All pitch2volt converters I have seen so far convert the incomming
>signal into a pulse train. The "magic" is to isolate the fundamental
>which may be very weak for some instruments. 
>There are two basic methods:
-of course; i was thinking in terms of sinusoidal excitation.. silly me..
however, assuming you could get the input signal to something close to a
sine wave, it would seem that my method would work pretty well.. i don't
want to do anything quite as ornate as the Moog or Bode methods (though the
Bode method sounds very useful; thanks for including them).  

i'm thinking it might be workable to turn the input into a pulse via a
comparator (which would eliminate the problem of notes being at different
volumes.. also probably low-pass filter the signal pretty heavily first to
get rid of possible higher-frequency glitches in the zero-crossing points)
and then use it with the RC/buffer/rectifier circuit?  while the output
voltages certainly wouldn't be quite so easy to predict as in the case of a
sine, there would still be frequency-dependent amounts of energy in the
output signal, so the rectified (and filtered) output would vary with
frequency.. of course, beneath the cutoff of the filter, it'd be useless and
too far above it the signals would get lost in the noise, but it seems
reasonable that it would be usable over a sufficient range for use with,
say, a guitar?  i suppose i'll have to build a prototype and find out.. 


any thoughts?


Ethan Duni
http://ieng9.ucsd.edu/~ee20waf/file.html