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The following statement is an excerpt from the book EMI filter design:

"if the filter is not optimized for characteristic impedance the filter will be prone to peaking at the points of impedance mismatch. If the EMI filter design is left unchecked, this phenomenon may lead to corresponding elevations in noise amplitude around the pole-Q frequency, causing EMC test failure"

What is the "pole-Q frequency"?

enter image description here

enter image description here From EMI filter design by Richard Lee Ozenbaugh, 3rd edition, page 1-4

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    \$\begingroup\$ As far as I know there is no such thing as pole-Q frequency. There is Q-factor and, there is pole frequency of course. More details needed; maybe use your camera and post a screen shot. \$\endgroup\$
    – Andy aka
    Commented Aug 29, 2022 at 11:47
  • \$\begingroup\$ @Andy aka, yes this is exactly what I'm confused about. I've attached the whole paragraph to the question. \$\endgroup\$
    – WeTech
    Commented Aug 29, 2022 at 11:59
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    \$\begingroup\$ @WeTech If it's only that occurence then it's possible the author had a temporary crossed neuron (pole frequency with Q factor). It can be confusing but you can ignore that one blooper. \$\endgroup\$
    – a concerned citizen
    Commented Aug 29, 2022 at 18:52
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    \$\begingroup\$ @WeTech I don't know what the author was thinking but, personally, I haven't met this description-- it's either pole frequency, or Q (quality) factor [of the pole]. When you say "this is used frequently in literature", do you mean in this book, or in general, in literature? Because, if the latter, I haven't seen it. \$\endgroup\$
    – a concerned citizen
    Commented Aug 30, 2022 at 6:58
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    \$\begingroup\$ I cannot confirm that this term is used "frequently" - for me it is the first time within the last 40 years that I have seen this term here in the forum. A pole is characterized by its position in the s-plane - and this is described by the pole frequency wp (length of the pointer between pole and origin) and the angle (expressed as Qp) \$\endgroup\$
    – LvW
    Commented Aug 30, 2022 at 7:24

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As @LvW comment pointed out, It seems that "pole-Q frequency" is well based on this picture.
It's only ... just a "shortcut"...

Same book, page 18.7, nothing strange.
This picture gives effectively ... poles position, Q or zeta=1/(2*Q), and wd or wn.

Based on a single r-L/C filter. (wn=1/sqrt(L*C) ...)

enter image description here

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