[SOLVED]Chebyshev Filters - example

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matusel

Member level 1
Hello everybody i'm studiing the Chebyshev Filters and i would like to know if someone can post an example of a third order Chebyshev Filter.

rfmemo

Newbie level 3
what is the frequency specification of your filter?

Staff member
Just an example

matusel

matusel

points: 2

matusel

Member level 1
Ok thankyou very much I needed this example because I have a doubt. In my book they say that the amplitude of a cebyshev filter oscillates in the pass band but the question is, if the transfer function has just poles how can the module (bode plot) oscillate (see ripple) ?
To oscillate there should be also zeroes!! In the oscillation the poles move the amplitude down of 20dB and the zeroes move it up...what is my mistake?

FvM

Super Moderator
Staff member
A Chebyshev type I filter has only poles, one real and a complex pair in case of 3rd order. Your simplified assumption about relation of poles/zeros and magnitude characteristic doesn't aplly to complex pole pairs, I think.

matusel

matusel

points: 2

matusel

Member level 1
Thank you FvM And there is no way/rules to draw a bode diagram of amplitude of a couple of complex poles ?

FvM

Super Moderator
Staff member
I think, you can't sketch the magnitude without considering the pole quality factor. Below is an example of a second order Cheybyshev, which represents basically one complex pole pair.

matusel

matusel

points: 2

matusel

Member level 1
Thank I think I've finally undersood

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