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Re: delay added by matlab butterworth filter

Started by Jerry Avins January 24, 2011
Dirk,

I think it depends on how one construes "delay". A _real_ Butterworth filte=
r (as distinguished from a digital approximation) exhibits a response as so=
on as an input is applied. It may be small enough to go unnoticed, but it's=
 there. Was Rune splitting hairs?

Jerry
On Jan 24, 1:39&#2013266080;pm, Jerry Avins <j...@ieee.org> wrote:
> Dirk, > > I think it depends on how one construes "delay". A _real_ Butterworth filter (as distinguished from a digital approximation) exhibits a response as soon as an input is applied. It may be small enough to go unnoticed, but it's there. Was Rune splitting hairs? > > Jerry
Jerry, If you put an impulse into the filter and look at the response you see the most impulsive part of the output delayed. Based on the OPs comments about a delay of 1/Wn it appears that is what he is referring to. That is an effective 'delay' (granted, a function of freq), and the OP should be getting it. When we talk about typical linear-phase filters we don't talk about them having no delay because the first output point is non-zero. Dirk