% Digital Filter Specifications:
wp=0.2*pi;        %       digital Passband freq in rad 
ws=0.3*pi;        %       digital Stopband freq in rad
Rp=1;             %       Passband ripple in dB
As=15;            %       Stopband attenuation in dB
%Analog Prototype Specifications:Inverse mapping for frequencies
T=1;                   %        Set T=1
OmegaP=wp/T;           %        Prototype Passband freq
OmegaS=ws/T;           %        Prototype Stopband freq
%Analog Chebyshev-1 Prototype Filter Calculation:
[cs,ds]=afd_chb1(OmegaP,OmegaS,Rp,As);
%  ***Chebyshev-1 Filter Order=4
%  Impulse Invariance transformation:
[b,a]=imp_invr(cs,ds,T);
[C,B,A]=dir2par(b,a);
[db,mag,pha,grd,w]=freqz_m(b,a);