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# Why are the pole-zero frequencies obtained by the notch filter calculator different

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Why are the pole-zero frequencies obtained by the notch filter calculator different in IDE？

Is there any advantage compared to the same pole-zero frequency?

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What IDE version is this image from? It does not look familiar.

What is different from what?

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Hi Eric,

My IDE version is 4.3.0.107

From the image,my system's resonant frequency is 700Hz, but The Notch filter's Lightly Damped Zero Frequency and Heavily Damped Pole Frequency are not 700Hz.

It seemed Lightly Damped Zero Frequency = 0.9 * Resonant Frequency ; Heavily Damped Pole Frequency = 1.45 * Resonant Frequency ;

Generally，for a notch filter, the numerator and denominator frequencies will be set same with resonant frequency; but in IDE , they are different .

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Having the zeros at 90% of the resonant frequency provides more phase lead for stability. Having the poles at 150%, reduces the high-frequency gain and so noise magnification. If you want, you can bypass these automatic values and specify frequencies and damping ratios for both zeros and poles directly.
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That make sense, Thanks, Eric