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i'm trying to use Berchin's FDLS methods (for those that don't know what it is, it's a way to design arbitrary magnitude and phase of an IIR Eq)

I tried different things but neither gave me what i asked:

1) i tried to design an allpass filter with arbitrary phase response (nothing fancy just a linear phase and a short deviation for 5 points) and it didn't worked as planned.

2) i tried a linear phase response for a -12 db notch and the same way it didn't worked (in black the desired response) a http://nsa34.casimages.com/img/2013/08/22/13082211272913316.jpg

i used a samplerate of 316, M=158 points and a filter order of around 50.

Do i need to use more points to increase the filter order or is it just impossible to design my filters using that algorithm?

thanks for you answers

Jeff

IonOne
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1 Answers1

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With FDLS, the parameters to play with to find alternate solutions, are not only the total filter order, but the ratio of zeros to poles. IIRC, more of both isn't always better (possibly for numerical reasons). So try smaller numbers of poles and zeros (only a few of each), increase the numbers separately, and see if you get a more appropriate match to your desired frequency response.

hotpaw2
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