Re: PWM -> Audio



MooseFET wrote:


PWM is the nonlinear operation, and this makes the things complicated.
How do you conclude it must be non-linear?

PCM(x) + PCM(y) == PCM(x+y)
PWM(x) + PWM(y) != PWM(x+y)

I can think of ways it can
be but it seems that it needn't be.

Imagine a DC + small sinewave on the top of it. At the PWM output, the phase shift of the sinewave will be dependent on the DC level. With two sinewaves you will get all sorts of harmonics and intermods.

Even if it is non-linear, since
it is before the filter, you can correct the data to make it produce
the linear result.

It doesn't matter before or after filter. This is a dynamic nonlinearity problem; it is fairly difficult to correct.

Vladimir Vassilevsky
DSP and Mixed Signal Design Consultant
http://www.abvolt.com
.

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