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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

__Answers:__

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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.

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

05-01-18, 5:58 a.m.chandrashekarLogin to add comment