Re: Are harmonics real?

JasonTranter wrote:

...

In response to Julius’ comments:

< You ask a very good question! I would like to caution you that you
< have assumed that the input-output relationship of your system follows
the
< linear, time-invariant rule. Are you sure about this assumption?
< Just food for thought: suppose that you have a saturation effect in
< your system (which makes it nonlinear). Then given a pure sinusoid
input,
< the output may have harmonics since the output may end up looking like
< a square wave, for example.

This is one of the issues that keeps me awake at night. As an experiment
I recorded a signal twice, once correctly and the second time I overloaded
the front-end, therefore clipping the input signal. The FFT of the
saturated signal had more harmonics than I knew what to do with.

So, in that case I could point to the FFT in a non-technical way and say
that it “created the harmonics” – it is showing that there are peaks
(harmonics) at frequencies that do not exist. Of course, we were feeding
the FFT routine dodgy data, so we should not expect perfection.

Not at all. The FFT analyzed the signal correctly. It found and revealed the harmonics created by the saturation.

...

I hate to say that all of these questions have lead me to one more
question – are sidebands real?

You betcha!

...

Jerry
--
Engineering is the art of making what you want from things you can get.
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.

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