Digital Butterworth Filter Design

EXPERIMENT 5: Design of Butterworth Filter

Day five of DSPP practicals. This one was an uphill battle. This was the first experiment which was performed using SCILAB. This meant we had to modify our codes. But this also produced a lot of errors.
The aim of this experiment was designing analog and digital Butterworth filter.

We designed a digital filter from analog filter and studied the aliasing effect due to sampling in Impulse Invariant Method and the frequency warping effect in BLT Method.

The Input Specifications were given as

(1) Pass band Attenuation (Ap< 3 dB)

(2) Stop band Attenuation (As> 40 dB)

(3) Pass band Frequency (Fp) in Hz

(4) Stop band Frequency (Fs) in Hz

(5) Sampling Frequency (F) in Hz     
We arrived at a conclusion that for both low pass and high pass filter, poles lie inside the unit circle. Hence both the filters are stable. But we also observed in the result that the values of Ap and As are not approximately same. Hence for better stability the order of the filter needs to be increased.
After much discussions, debates and flying tempers, we finally obtained the required the output.  

Program code: BUTTERWORTH