LPF butterworth filter question

On 21-05-2010 at 08:59:00 zs <zsolt.garamvolgyi@gmail.com> wrote:

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> What I'm talking about is filter design and visualization: when
> designing a filter, I think it's useful to see its actual response
(...)

And they are actual and precise.
Fdatool generates digital filters coefficients.

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> without taking 'secondary' effects into account.

What do you mean, there is no secondary effects.
They all are primary.

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> (visualized) response being corrupted below -150 dB won't imply any
> problems during realization,
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Frequency response is just perfectly the same as later realization.

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> but having a correct response in a larger
> dynamic range gives insight on the filter design process:
(...)

Maybe you would like an analog filter.
Then you should use proper tool for that.
My best analog design tool is pen and paper.
The all infinities I plot in my mind because I have only finite sheet of  
paper.

> Zsolt


-- 
Mikolaj