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Orfanidis prescribed nyquist peak filter parameters

Started by Unknown June 22, 2016
>Back to this project after a long break. > >I've gotten decent behaviour however when the peak frequency approaches >Nyquist the bandwidth expands like so... > >https://s13.postimg.io/pfj6t5tvb/orfanidis_near_nyquist_behaviour.gif > >Any ideas of how to iron this out? > >I've chosen 0.707*peak_gain to be the gain at which the bandwidth is >measured at. I'm presuming something strange is happening when the
rightmost
>bandwidth frequency is hits and exceeds Nyquist? > >Many thanks, >John.
That's how it works with 'low Q' value. I would try other method(s) for filters above fc where Orfandis' method starts give wrong output response. Särkka/Huovilainen paper "Accurate Discretization of Analog Audio Filters with Application to Parametric Equalizer Design" - https://users.aalto.fi/~ssarkka/pub/eq-article.pdf might work if you tweak the method a bit. If you like to test their method in Matlab/Octave you'll find ready to use functions for that paper from https://users.aalto.fi/~ssarkka/pub/ (eq_desifn_demo.zip)). --------------------------------------- Posted through http://www.DSPRelated.com
>I've gotten decent behaviour however when the peak frequency approaches >Nyquist the bandwidth expands like so...
You could try other matching schemes as outlined here: http://vicanek.de/articles/BiquadFits.pdf --------------------------------------- Posted through http://www.DSPRelated.com