[sdiy] harmonic generator

[Scott Bernardi]

That's a tall order.  You can do frequency division fairly easily with
square waves, in which case you would actually start with a high
frequency and derive the subharmonics; the divide-by-10 subharmonic
would become your "derived fundamental". The problem with this method is
that you get a bunch of extra harmonics from the square waves.
Using a fundamental and deriving the upper harmonics is a lot trickier,
because then you need to do frequency multiplication.  Frequency
doubling is pretty easy - you take a symmetrical triangle wave and run
it through an absolute value circuit, which gives you a triangle wave of
double the frequency. There you can get your 2nd, 4th, and 8th (even)
harmonics.  You can run the triangles into tri-to-sine converters to
warp them into sine waves.
To get the other harmonics, you would need to generate the 3rd, 5th, and
7th.  You could get the 6th by doubling the 3rd, and the 10th by
doubling the fifth.
I suppose you could use phase locked loops to do frequency
multiplication, but the problem is getting a PLL to track over a wide
frequency range (they typically only have about a 10:1 frequency range).

I've thought about doing a circuit like this to make a Hammond
organ-like module (you know, the drawbars). Didn't know how to get past
the hurdles, however.


Rob Hukin wrote:

> Can anyone recommend a harmonic generator circuit - I need about the
> first 10 harmonics of a given fundamental.
>
> thanks,
> rob.

--
Scott Bernardi
sbernardi at attbi.com