Alexey Lukin wrote: ... > Just take the magnitude response of lin-phase filter, substitute some > phase response, and take the inverse FFT. If you subst. the phase > resp. of the min-phase filter - you get the min. phase filter. If you > subst. the phase resp. of the lin-phase filter - you get the lin. > phase filter. But if you subst. some intermediate phase response (an > average, for example), you won't get any good filter, due to time > domain aliasing (?) the magnitude response will be altered too. > So the phase response must be carefully designed somehow, and not just > thought out. Zeros in the right-half s plane reduce a filter's "promptness" -- the concentration of its impulse response early on. Moving a zero to its conjugate location -- reflecting it about the jw axis -- leaves the response for real frequencies unchanged. For a filter of N zeros, there are exactly [(2^n) - 1] other filters with the same frequency response but different impulse responses. For small N, you can try them all. Jerry -- Engineering is the art of making what you want from things you can get. �����������������������������������������������������������������������
Between min. phase and lin. phase filters
Started by ●November 8, 2003
Reply by ●November 11, 20032003-11-11
Reply by ●November 11, 20032003-11-11
Alexey Lukin wrote:> an2or@mailcircuit.com (Andor) wrote in message news:<ce45f9ed.0311110717.7308ed8b@posting.google.com>... > >>I was suggesting an approach which tries to reduce pre-ringing for >>linear-phase filters. What are you aiming at? You didn't specify how >>and why you wanted the phase response to lie "between" linear and >>minimum. >> >>Perhaps if you state your goal there are better ways. > > > Yes, my goal is the same: trying to reduce the pre-ringing. > The windowing of the pre-ringing is not a solution, because it heavily > distorts the frequency response of the filter. Isn't it the case in > your experiments? > > AlexYou're keeping too much in your head. Pre ringing of what? If sound, what means do you use yo associate a particular amount of pre-ringing with a given coloration or lack of that? To "what are you trying to do?", you're answering "Climb onto the bus" instead of "Get to Miami." Jerry -- Engineering is the art of making what you want from things you can get. �����������������������������������������������������������������������
Reply by ●November 12, 20032003-11-12
Jerry Avins <jya@ieee.org> wrote in message news:<bormb0$gtt$1@bob.news.rcn.net>...> > Yes, my goal is the same: trying to reduce the pre-ringing. > > The windowing of the pre-ringing is not a solution, because it heavily > > distorts the frequency response of the filter. Isn't it the case in > > your experiments? > > > > Alex > > You're keeping too much in your head. Pre ringing of what? If sound, > what means do you use yo associate a particular amount of pre-ringing > with a given coloration or lack of that? To "what are you trying to > do?", you're answering "Climb onto the bus" instead of "Get to Miami."Sorry if I made it unclear, but both Andor and me are talking about pre-ringing of FIR filters in the sound equalizers. As Andor pointed out, there are evidences that amount of (pre-)ringing affects the sound coloration. What I'm trying to do is just making some experiments with different phase responses of the filters. So I'm asking about the ways to design filters with different phase responses. Alex
Reply by ●November 12, 20032003-11-12
Jerry Avins <jya@ieee.org> wrote in message news:<bor2ci$34q$1@bob.news.rcn.net>...> Zeros in the right-half s plane reduce a filter's "promptness" -- the > weighting of its impulse early on. Moving a zero to its conjugate > location -- reflecting it about the jw axis -- leaves the response for > real frequencies unchanged. For a filter of N zeros, there are exactly > [(2^n) - 1] other filters with exactly the same frequency response but > different impulse responses. If N is not too large, you can try them all.Thanks for the idea. Could you direct me to some good factorization algorithms? I've never worked with direct factorization, so I have no idea how the existing algorithms behave for the filters that are long enough. How about several hundred taps? Alex
Reply by ●November 12, 20032003-11-12
Alexey Lukin wrote: ...> Sorry if I made it unclear, but both Andor and me are talking about > pre-ringing of FIR filters in the sound equalizers. As Andor pointed > out, there are evidences that amount of (pre-)ringing affects the > sound coloration. What I'm trying to do is just making some > experiments with different phase responses of the filters. So I'm > asking about the ways to design filters with different phase > responses. > > AlexThanks. Jerry -- Engineering is the art of making what you want from things you can get. �����������������������������������������������������������������������
Reply by ●November 12, 20032003-11-12
Alexey Lukin wrote:> Jerry Avins <jya@ieee.org> wrote in message news:<bor2ci$34q$1@bob.news.rcn.net>... > >>Zeros in the right-half s plane reduce a filter's "promptness" -- the >>weighting of its impulse early on. Moving a zero to its conjugate >>location -- reflecting it about the jw axis -- leaves the response for >>real frequencies unchanged. For a filter of N zeros, there are exactly >>[(2^n) - 1] other filters with exactly the same frequency response but >>different impulse responses. If N is not too large, you can try them all. > > > Thanks for the idea. Could you direct me to some good factorization > algorithms? I've never worked with direct factorization, so I have no > idea how the existing algorithms behave for the filters that are long > enough. How about several hundred taps? > > Alex"In theory, there's no difference between theory and practice. In practice, there is." In a word: no. If an approximate solution will do, you might look at IIR "equivalents". There, the factoring is done. Jerry -- Engineering is the art of making what you want from things you can get. �����������������������������������������������������������������������
