Minimum phase delay notch filter

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

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| James E.Thompson, CTO                            |    mens     |
| Analog Innovations, Inc.                         |     et      |
| Analog/Mixed-Signal ASIC's and Discrete Systems  |    manus    |
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I love to cook with wine.     Sometimes I even put it in the food.

"Martin Greaves"

** I you need to avoid phase shifts in the wanted signal then forget using notch filters altogether. ** In general - the phase response of a filter is a function of the amplitude response.

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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http://www.wescottdesign.com