0
Problem with visualisatioin of output of chebyshev type one filter.

Respected Sir / Madam I am presently working with design of digital IIR Chebyshev type One LPF. The problem I am facing is that I am not observing ripple in pass band as we observe in general textbook. Please help. I am posting the code as well. Thank you T.V.Chandra Shekar

//Low Pass IIR Chebyshev Type I Filter
clc;
clear;
close;
fs = 8000;
omegap = 500;
omegas = 2000;
wp = 500/8000;
ws = 2000/8000;
A1_dB = -3 ;
A2_dB = -40;
A1 = (10)^(A1_dB/20);
A2 = (10)^(A2_dB/20);
disp(A1,A2);
epslon = sqrt((1/A1)^2 -1);
num = ((sqrt(1- A2^2))+(sqrt(1-((A2^2)*(1+epslon^2)))))/(epslon*A2);
den = (omegas/omegap)+sqrt((omegas/omegap)^2-1);
N = log10(num)/log10(den);
N = ceil(N);
hz=iir(N,'lp','cheb1',[0.0625 .25],[0.01 0.7]);
[hzm,fr]=frmag(hz,256);
subplot(2,1,1);
plot2d(fr',hzm');xgrid(color("green"));
xtitle('Chebyshev Type One LPF','f Frequency','Magnitude');
n = 0:1023;
x = 2*sin(2*%pi*2200*n/fs);
y = flts(x,hz);
Y = abs(fft(y))/1024;
f = (0:1023)*fs/1024;
subplot(2,1,2);
plot2d(f,Y);xgrid(color("green"));
xtitle('Magnitude Spectrum Of Output','Frequency f','Magnitude');


Scilab 24-12-17, 8:26 a.m. chandrashekar

Answers:

0

Hello, As you can see in the attached picture, there is a small ripple in the pass band.

It is visible when we zoom in a little.

01-01-18, 4:18 p.m. Abhinav

Thanks a million Sir. Your word of support was priceless.


05-01-18, 5:58 a.m. chandrashekar

Login to add comment


Log-in to answer to this question.