Filter design with 'freqsamp' method?
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From: Steve Pope on 2 Jul 2010 15:39 Pete Fraser wrote: > I'd rather not deal with Butterworth's phase issues. A good thing to remember is that any filter that is as selective as a given Butterworth filter will have a similar RMS delay spread as the Butterworth filter. So no free lunch on phase issues in many cases. Steve
From: Pete Fraser on 2 Jul 2010 16:33 "Steve Pope" <spope33(a)speedymail.org> wrote in message news:i0lfa3$rk9$1(a)blue.rahul.net... > A good thing to remember is that any filter that is as > selective as a given Butterworth filter will have a > similar RMS delay spread as the Butterworth filter. > So no free lunch on phase issues in many cases. But I'm doing a symmetric FIR with the Butterworth amplitude response.
From: Steve Pope on 2 Jul 2010 16:42 Pete Fraser <pfraser(a)covad.net> wrote: >"Steve Pope" <spope33(a)speedymail.org> wrote in message >> A good thing to remember is that any filter that is as >> selective as a given Butterworth filter will have a >> similar RMS delay spread as the Butterworth filter. >> So no free lunch on phase issues in many cases. >But I'm doing a symmetric FIR with the Butterworth >amplitude response. Linear phase is overrated. :-) S.
From: robert bristow-johnson on 2 Jul 2010 19:05 On Jul 2, 4:42 pm, spop...(a)speedymail.org (Steve Pope) wrote: > Pete Fraser <pfra...(a)covad.net> wrote: > >"Steve Pope" <spop...(a)speedymail.org> wrote in message > >> A good thing to remember is that any filter that is as > >> selective as a given Butterworth filter will have a > >> similar RMS delay spread as the Butterworth filter. > >> So no free lunch on phase issues in many cases. > >But I'm doing a symmetric FIR with the Butterworth > >amplitude response. so then you'll get even *more* phase shift delay. (Butterworths are minimum phase and linear phase is not minimum phase unless it's a wire or a simple gain.) > Linear phase is overrated. :-) yeah, and what Steve said. r b-j
From: robert bristow-johnson on 2 Jul 2010 19:09
On Jul 1, 10:59 am, Fred Marshall <fmarshallx(a)remove_the_xacm.org> wrote: > > r b-j, > > Well, maybe I've had it wrong all these years but I'd say that the > windowing method starts with N frequency samples where N is the length > of the filter you want. so then, since the DFT and iDFT are bijective (i love using fancy- pants words), why window? if h[n] has N samples and N degrees of freedom, so does H[k]. you specify your N frequency samples and you can hit it perfectly with no windowing. so, that seems curious to me. r b-j |