What does Notch filter depth shows?

Hi

I want to know what does notch filter depth shows? On what parameters does the depth depend on? I think more deeper response is better.

Stopband attenuation is another name for it. Mobetta,
as a rule, but mocostya.

There is the type of notch filter which interacts with an incoming signal. Its frequency components are phase shifted by different amounts. The center frequency goes through a 180 degree phase shift. As a result the center frequency is mostly cancelled - although maybe not entirely since the filter is not 100 percent efficient. This probably has to do with Q factor. As is true with other types of filters, Q is hampered by parasitic resistances.

Another kind of notch filter works by diverting the center frequency to ground. Again Q factor probably has to do with steepness of the rolloff curve, and thus depth of the notch.

student14 said:

Hi
I want to know what does notch filter depth shows? On what parameters does the depth depend on? I think more deeper response is better.

Click to expand...

An ideal 2nd-order notch filter has zero gain at the notch frequency wz. Here, wz is the zero frequency of the transfer functions numerator.
An ideal notch filter with equal gain values for very low and very high frequencies requires the condition wz=wp. The frequency wp is the pole frequency (zero of the denominator).
More than that, similar to the bandpass case, a second-order notch can have different Qp values, which are responsible for the slope of the transfer function for frequencies smaller and larger than wz.
(Comment: There is no phase shift of 180 deg at the notch frequency).

Notch filter transfer function: H(s)=N(s)/D(s)

N(s)=A[1+(1/wzQz)+(s²/wz²)]

D(s)=[1+(1/wpQp)+(s²/wp²)]

For Qz approaching infinity we have a real zero on the imaginary axis (ideal notch). The pole quality Qp determines the steepness of the function in the vicinity of the notch at wz.
Of course, due to some uncertainties and tolerances it is not possible to have an infinite Qz - this "error" determines the achievable depth of the notch.