**IIR Butter worth Filter Design**

**AIM**

**:-**To design IIR Butterworth digital filters.

**THEORY: -**IIR filters can be expanded as infinite impulse response filters. In designing IIR filters, cutoff frequencies of the filters should be mentioned. The order of the filter can be estimated using butter worth polynomial. That’s why the filters are named as butter worth filters. Filter coefficients can be found and the response can be plotted.

**PROGRAM: -**

fs = 1000;

wpn = 2 * wp / fs;

wqn = 2 * wq / fs;

[ n wn ] = buttord( wpn, wqn, rp, sp )

[ b a ] = butter( n, wn )

[ h w ] = freqz( b, a, 128);

plot( (w/pi) * ( fs/2 ), abs(h) )

**RESULT: -**A Butterworth LPF is designed and response is plotted.

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