Question

How do you calculate the notch frequency of a notch filter?

Answer 1

The notch frequency of a notch filter can be calculated using the following formula:


notch
=

center

f
notch
    ​

=
Q
f
center
    ​

    ​


where:


notch
f
notch
    ​

 is the notch frequency,


center
f
center
    ​

 is the center frequency of the notch filter, and


Q is the quality factor of the notch filter.

The center frequency

center
f
center
    ​

 is the frequency at which the notch filter provides maximum attenuation, and the quality factor

Q determines the bandwidth and depth of the notch.

In some cases, the notch frequency is also expressed as the angular frequency

notch
ω
notch
    ​

 (in radians per second) instead of the regular frequency

notch
f
notch
    ​

. The formula remains the same, but you'll use the angular frequency instead.

For certain notch filter designs, the quality factor

Q might be given, or you can calculate it using the following formula:


=

center

bandwidth
Q=
f
bandwidth
    ​

f
center
    ​

    ​


where

bandwidth
f
bandwidth
    ​

 is the bandwidth of the notch filter, which is the range of frequencies around the center frequency where the notch effect is significant.

It's important to note that the above formulas are general approximations, and for more complex filters, especially those involving higher-order filter designs or digital implementations, the calculations can be more involved. Additionally, for practical applications, some factors like component tolerances and non-ideal characteristics may need to be considered.