"orien1202" <[email protected]> wrote in
news:[email protected] :

> Hi,
> I have a question about anti-aliasing filters which I thought would
> fit in this discussion thread.
> I have an RC circuit and my ultimate goal is to estimate the value of
> the capacitor using least square estimation. In order to carry out
> this estimation I need to discretize the system transfer function and
> find the ARMA model, however to do that I need to use an anti-aliasing
> filter first to make the transfer function bandlimited.
> I tried using a Butterworth filter, which does very well is preserving
> the magnitude response of the system however the phase is really not
> preserved and since I'm trying to estimate the value of the capacitor
> in the system I thought preserving the phase is important for my
> estimation purposes. However I am now not certain any more.
> So my question is how do I know if preserving phase is important in an
> application or not? and if it is what is the best anti-aliasing filter
> that would preserve phase?
> thanks

The Bessel filter produces linear phase-- i.e., a simple time delay. Best
practice is to filter all your channels through the same filter.

--
Scott
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