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Wednesday, December 7, 2011

DSP To design analog filters (low pass, high pass, band pass, band stop)


AIM: - To design analog filters (low pass, high pass, band pass, band stop)

PROGRAMS: -

Low Pass: -

%Program for the design of butterworth low pass analog filter
clc;
close all;
clear all;
format long 
rs=input('enter the stopband ripple...');  
rp=input('enter the passband ripple...');
ws=input('enter the stopband freq...');     
wp=input('enter the passband freq...');
fs=input('enter the sampling freq...');
w1=2*wp/fs;
w2=2*ws/fs;                     
[n,wn]=buttord(w1,w2,rp,rs);
[z,p,k]=butter(n,wn);
[b,a]=zp2tf(z,p,k);
[b,a]=butter(n,wn);
w=0:0.01:pi;
[h,om]=freqs(b,a,w);
m=20*log10(abs(h));
an=angle(h);
subplot(2,1,1);
plot(om/pi,m);
ylabel('GainindB-->');
xlabel('(a)Normalised frequency-->');
subplot(2,1,2);
plot(om/pi,an)
xlabel('(b)Normalised frequency-->');
ylabel('Phase in radians-->'); 

Output: -

enter the stopband ripple...60
enter the passband ripple...0.15
enter the stopband freq...3000
enter the passband freq...1500
enter the sampling freq...7000





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