Butterworth Filter Design

The objective of this experiment was to design a digital butterworth filter from analog filter. program for this filter design was develop on scilab based on the algorithm taught in the class i.e 

• from the given data calculate the necessary data for digital filter design 
• calculate the order (N)
• find out normalized LPH filter
• from that calculate De-normalized filter
• and after that by BLT or IIM we can calculate the H(z)

In this experiment we have studied that,

1.  response in butterworth filter is monotonic. 
2. As the order increases the response becomes more sharpen in both high pass filter and low pas filter.
3.  In this designing we intially find order through passband and stopband frequency.and find normalized and denormalized transfer function and the find actual transfer function in z transform

from the image below we can understand about how filter behaves as the order increase and the difference between ideal and actual filter

 

scilab code for Butterworth filter design :

https://drive.google.com/open?id=0B-US8fsfaFQxbDhHMGdQMWRzRlE