I am considering using a 50Hz active filter such as the first one illustrated here:
However, I would like to keep phase delay to a minimum. Is this a suitable circuit for this criteria, or is there something more suitable?
I have heard Bessel filters are superior in this regard, but the notch is notch as sharp. Has anyone seen an online caluclator for these?
How does the number of poles affect the phase linearity?
Any suggestions?
Martin Greaves
The phase delay increases with the number of poles. The phase linearity depends on the filter design, but component tolerances build up as you add poles and you have to keep that in mind as well.
If you wanted a notch with phase linearity you might be stuck with doing something horrid like making two phase-linear all-pass filters with phase delays that differed by 10msec at 50Hz and adding the two outputs.
-- Bill Sloman, Nijmegen
Here is a better, easy to tune, notch filter...
The phase rolls smoothly from 0° into -90° then snaps to +90° in the notch, then rolls smoothly back to 0°.
By "phase delay" did you actually mean "group delay"? ...Jim Thompson
"Martin Greaves"
FFS tell us what you are trying to do so an alternative solution can be suggested.
..... Phil
opa...
I don't think that a pair of linear-phase filters in parallel necessarily makes a linear-phase filter. In fact, I'm pretty sure it doesn't.
But I'd have to actually think to demonstrate that, and I'm feeling lazy.
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