Notch filter

• Notch filter are used to remove the specific frequency components from the total frequency response.

• The notch filter contains ideally nulls in the frequency response characteristics.

• The nulls are obtained at the frequencies $ω_0$and$ ω_1$. To obtain null at $ω_0$a pair of complex conjugate zero is introduced on unit circle.

  $Z_1,2=e^{±jω_0}$

  $H(z)=b_0 (z_1 z^{-1})(1-z_2 z^{-1})$

  $H(z)=b_0 (1-e^{jω_0 } z^{-1})(1-e^{-jω_0 } z^{-1})$

Limitation:

Bandwidth is relatively large. So that frequency components round the nulls are also affected.