From the nimble fingers of Herbie Gluender (H.Gluender@...)
(19/12/2001 6:56 AM) came...

> The Optimum filter proposed by Norbert Wiener is a linear filter that
> reconstructs a signal that suffers from additive noise so that the sum of the
> squared differences between the original undisturbed signal from the
> reconstructed one in the average becomes a minimum. From this idea you may
> realize the main problem with this approach. You need to know the original
> signal which in most cases is unkown. So you have to estimate essentially the

A noteable case where it IS known is the GLONASS/GPS thing (and
spread-spectrum systems in general), and this sort of filtering is used to
considerable effect to retrieve a signal from well below the noise floor.

Here, the receiver decides that it's looking for a specific pattern (say
11010001) in a signal, so it twiddles and tweaks at its filter and
autocorrelator until it finds it. Or not...
-- 
Ted Spencer; ted@...
--
To fully appreciate the grandeur of a thunderstorm, one must be alone, in a
small boat, on open water. Being the highest point - however low - for
kilometers merely clarifies the sensation.