Filter design with 'freqsamp' method?
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From: Greg Berchin on 3 Jul 2010 07:10 On Sat, 03 Jul 2010 06:48:57 -0400, Greg Berchin <gberchin(a)comicast.net.invalid> wrote: >Possibly useful: see US Patent 5375067 for a discussion of Central Time and RMS >Delay. I gotta stop typing before my brain is awake. Make that Central Time and RMS *Duration*.
From: robert bristow-johnson on 3 Jul 2010 14:34 On Jul 3, 6:48 am, Greg Berchin <gberc...(a)comicast.net.invalid> wrote: > On Fri, 2 Jul 2010 20:37:14 -0700 (PDT), robert bristow-johnson > > <r...(a)audioimagination.com> wrote: > >> ... but Steve and I were talking about RMS delay spread. > > >"spread" from what? zero? or some mean delay? how is the mean > >defined? > > >"RMS delay spread" hasn't been a parameter i've been familiar with. > >is it a measure of overall phase nonlinearity? > > Possibly useful: see US Patent 5375067 for a discussion of Central Time and RMS > Duration. > Greg, i didn't know about this patent of yours. good show! well, i'm still trying to pin these guys down. if their r.m.s. delay parameter ("spread" or whatever it's called) is a measure of deviation from phase linearity, then nothing can beat a phase linear FIR. but if it's a measure of phase delay or group delay (from zero), then a minimum-phase filter will beat linear-phase. that's all i wanted to say about it. r b-j
From: Steve Pope on 3 Jul 2010 14:35 robert bristow-johnson <rbj(a)audioimagination.com> wrote: >well, i'm still trying to pin these guys down. if their r.m.s. delay >parameter ("spread" or whatever it's called) is a measure of deviation >from phase linearity, then nothing can beat a phase linear FIR. but >if it's a measure of phase delay or group delay (from zero), then a >minimum-phase filter will beat linear-phase. It is neither. Steve
From: Pete Fraser on 3 Jul 2010 14:55 "robert bristow-johnson" <rbj(a)audioimagination.com> wrote in message news:c2f65e9b-74e2-41e3-85f0-61684db85f48(a)k39g2000yqd.googlegroups.com... > well, i'm still trying to pin these guys down. if their r.m.s. delay > parameter ("spread" or whatever it's called) is a measure of deviation > from phase linearity, then nothing can beat a phase linear FIR. I don't know if there's a formal definition. I just assumed it was a measure of the dispersiveness (frequency dependent delay) of the filter. > but if it's a measure of phase delay or group delay (from zero), > then minimum-phase filter will beat linear-phase. True, but I'm not sure why anybody would refer to that as "spread". Pete
From: Steve Pope on 3 Jul 2010 15:04
Steve Pope <spope33(a)speedymail.org> wrote: >robert bristow-johnson <rbj(a)audioimagination.com> wrote: >>well, i'm still trying to pin these guys down. if their r.m.s. delay >>parameter ("spread" or whatever it's called) is a measure of deviation >>from phase linearity, then nothing can beat a phase linear FIR. but >>if it's a measure of phase delay or group delay (from zero), then a >>minimum-phase filter will beat linear-phase. >It is neither. Here's a reference: Ibnkahla, _Signal Processing for Mobile Communications Handbook_, section 1.2.2.1.4. It is viewable on Google Books. He used the same expression for average delay I stated, but his expression for RMS Delay Spread is a little different, and I don't like it as much, but I think his expression is as close to a standard definition as you will get. RMS delay spread must be used carefully; there are responses with large RMS delay spreads which do not have bad phase qualities for a most signals, i.e. something like h(t) = 1*(t) + 100*(t - 20) - 100*(t - 20.0001) S. |