IIR Filter Design

The direct design of IIR filer is not possible hence analog filter must be connected into digital filter. The analog filter design is in laplace domain.
Where,
             $s=\sigma +j\omega$

To mark laplace domain into z-domain following are the desired property -

1. The imaginary axis of s-plane should map on unit circle of z-plane.
   Thus, there will be direct relationship between in the two frequency variable in two domain.
2. The half of the s-plane should map into interior of unit circle in the z-plane.
   Thus, a stable analog filter will be converted into stable digital filter.

To convert analog filter to digital filter various techniques are available following method are widely used-

1. Impulse Invarience Method
2. Bilinear Transformation(BLT) Method