FPGA Central

Think of a slowly varying signal. Instead of quantizing each sample of
this signal how about quantizing the difference of two samples. The
dynamic range is lower and you would need fewer bits. Reconstruct the
sampled version of the original signal by doing the inverse of the
difference.

This is in essence what sigma-delta converters do.

Jerry Avins <[email protected]> wrote in message news:<[email protected]>...
> Matt Timmermans wrote:
> >
> > "Randy Yates" <[email protected]> wrote in message
> > news:[email protected]..
> > > The quantization noise power in a digital signal is constant no
> > > matter what the sample rate is.
> >
> > I have tried, but I haven't been able to show this for >= 2 stage S-D
> > modulators. The trouble is that, while the digital stream has limited
> > power, there doesn't seem to be any bound on the *error* signal it's
> > digitizing, and so there is no limit on the difference between the two!
> >
> > I know they don't go too unstable in practice, but how do we get an estimate
> > on the maximum error signal?
>
> Fools rush in, and all that. At the risk of piling foolishness on
> ignorance, I hazard a guess.
>
> Although it may not be possible to know the upper bound of the error in
> any one sample (other than that imposed by dynamic range), the feedback
> and the band-limited input together bound the short-term average error
> to a reasonable amount. After all, the buggers do work!
>
> Jerry