Complex FIR coefficients
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From: HardySpicer on 28 Mar 2010 18:14 What is the physical significance of having an impulse response with complex coefficients ie {h0,h1,h2...hn} where the h values are complex. Hardy
From: Rune Allnor on 28 Mar 2010 18:21 On 29 Mar, 00:14, HardySpicer <gyansor...(a)gmail.com> wrote: > What is the physical significance of having an impulse response with > complex coefficients Does there have to be one? Rune
From: Randy Yates on 28 Mar 2010 19:19 HardySpicer <gyansorova(a)gmail.com> writes: > What is the physical significance of having an impulse response with > complex coefficients ie > > {h0,h1,h2...hn} where the h values are complex. Hi, You know that the the frequency response of an FIR filter is the Discrete Fourier Transform (DFT) of its impulse response, right? What are the properties of the DFT when the inputs are real versus complex? -- Randy Yates % "Maybe one day I'll feel her cold embrace, Digital Signal Labs % and kiss her interface, mailto://yates(a)ieee.org % til then, I'll leave her alone." http://www.digitalsignallabs.com % 'Yours Truly, 2095', *Time*, ELO
From: Tim Wescott on 28 Mar 2010 20:38 HardySpicer wrote: > What is the physical significance of having an impulse response with > complex coefficients ie > > {h0,h1,h2...hn} where the h values are complex. That your system, as described, is impossible to implement physically. You've asked a question with an absurd answer, and you're not dim. So what are you _really_ doing? The two biggest reasons I could think that you may see this happen are: (1) you've calculated an impulse response from a frequency response using an FFT and you've either not paid proper attention to phase, or you have the inevitable numerical inaccuracies and you haven't noticed that the imaginary parts are minuscule (2) you're modeling a system that's operating on I/Q data, and you've modeled quadrature as imaginary. -- Tim Wescott Control system and signal processing consulting www.wescottdesign.com
From: HardySpicer on 28 Mar 2010 23:18
On Mar 29, 1:38 pm, Tim Wescott <t...(a)seemywebsite.now> wrote: > HardySpicer wrote: > > What is the physical significance of having an impulse response with > > complex coefficients ie > > > {h0,h1,h2...hn} where the h values are complex. > > That your system, as described, is impossible to implement physically. > > You've asked a question with an absurd answer, and you're not dim. So > what are you _really_ doing? > > The two biggest reasons I could think that you may see this happen are: > > (1) you've calculated an impulse response from a frequency response > using an FFT and you've either not paid proper attention to phase, or > you have the inevitable numerical inaccuracies and you haven't noticed > that the imaginary parts are minuscule > > (2) you're modeling a system that's operating on I/Q data, and you've > modeled quadrature as imaginary. > > -- > Tim Wescott > Control system and signal processing consultingwww.wescottdesign.com Oh I saw a paper with an example in it that has complex data points, actually it is matrices but the same principle holds. It was for Quarternary-Quam. So I suppose it is complex because the imaginary part also has frequency-selective properties as well as real. Hardy |