CHEBYSHEV TYPE 2 LOW PASS FILTER
alphap=input('pass band attenuation in dB=');
alphas=input('stop band attenuation in dB=');
fp=input('pass band frequency in Hz=');
fs=input('stop band frequency in Hz=');
f=input('Sampling frequency in Hz=');
wp=2*fp/f;ws=2*fs/f;
%To find cutoff frequency and order of the filter
[n,wn]=cheb2ord(wp,ws,alphap,alphas);
%system function of the filter
[b,a]=cheby2(n,alphas,wn);
w=0:.01:pi;
[h,ph]=freqz(b,a,w);
m=20*log(abs(h));
an=angle(h);
subplot(2,1,1);
plot(ph/pi,m);
grid;
ylabel('Gain in dB');
xlabel('Normalised frequency');
subplot(2,1,2);
plot(ph/pi,an);
grid;
ylabel('Phase in radians');
xlabel('Normalised frequency');
Observation:
pass band attenuation in dB=1
stop band attenuation in dB=30
pass band frequency in Hz=200
stop band frequency in Hz=600
Sampling frequency in Hz=2000
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