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<blockquote data-quote="Mark DeArman" data-source="post: 147955" data-attributes="member: 950">Re: FIR filtersHaha, well I&#039;m not being very clear. I&#039;m home from work because I hurt my back lifting speakers (damn those ferrite compression drivers!!!). Anyway, whether or not group delay exists in a global sense or not for your distribution, I believe has to do with the marginal properties holding? They do call the inverse of IF, rotation of the t-f plane basically, group delay also, as the concentration is to the FT of the analytic signal in an ideal distribution, but you&#039;re not going to find many references taking this treatment except briefly.Concentration is always described in terms of the expansion of the phase, IF, and higher derivatives. All of these definitions come from the stationary phase (condition) holding, and I&#039;ve never seen that presented in terms of group delay. And I&#039;m not mathematician enough to know whether one implies the other holds.The reason it&#039;s hard to make sense out of the IF is because we are looking at impulse responses. Either by statistical averaging/correlation or via dechirping/matched filtering, we&#039;ve thrown out a lot of data and polluted our measurement with the effective window of the stimulus. Also, an IR typically has poor finite support in the frequency domain, and doesn&#039;t satisfy the stationary phase condition.&nbsp; If you simply play a stimulus with a continuous IF, like a linear chirp with low rate, you&#039;ll see much more informative results. </blockquote>

[QUOTE="Mark DeArman, post: 147955, member: 950"] Re: FIR filters [FONT=Verdana]Haha, well I'm not being very clear. I'm home from work because I hurt my back lifting speakers (damn those ferrite compression drivers!!!). [/FONT] [FONT=Verdana]Anyway, whether or not group delay exists in a global sense or not for your distribution, I believe has to do with the marginal properties holding? They do call the inverse of IF, rotation of the t-f plane basically, group delay also, as the concentration is to the FT of the analytic signal in an ideal distribution, but you're not going to find many references taking this treatment except briefly. Concentration is always described in terms of the expansion of the phase, IF, and higher derivatives. All of these definitions come from the stationary phase (condition) holding, and I've never seen that presented in terms of group delay. And I'm not mathematician enough to know whether one implies the other holds.[/FONT] [FONT=Verdana]The reason it's hard to make sense out of the IF is because we are looking at impulse responses. Either by statistical averaging/correlation or via dechirping/matched filtering, we've thrown out a lot of data and polluted our measurement with the effective window of the stimulus. Also, an IR typically has poor finite support in the frequency domain, and doesn't satisfy the stationary phase condition. [/FONT][FONT=Verdana]If you simply play a stimulus with a continuous IF, like a linear chirp with low rate, you'll see much more informative results. [/FONT] [/QUOTE]

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