14. BUTTERWORTH ANALOG FILTER

BUTTERWORTH ANALOG FILTER

rp=input('enter the passband ripple');

rs=input('enter the stopband ripple');

wp=input('enter the passband freq');

ws=input('enter the stopband freq');

fs=input('enter the sampling freq');

w1=2*wp/fs;

w2=2*ws/fs;

[n,wn]=buttord(w1,w2,rp,rs,'s');

[z,p,k]=butter(n,wn);

[b,a]=butter(n,wn,'s');

w=0:.01:pi;

[h,om]=freqs(b,a,w);

m=20*log10(abs(h));

an=angle(h);

subplot(2,1,2);

plot(im/pi,m);

ylabel('gain in dB');

xlabel('Normalised frequency');

subplot(2,1,2);

plot(om/pi,an);

xlabel('normalised frequency');

ylabel('phase in radians');

RESULT

enter the passband ripple   0.15

enter the stopband ripple       60

enter the passband freq      1500

enter the stopband freq       3000

enter the sampling freq       7000