% 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 atenuation in dB
% Analog Prototype Specifications:
T=1;                   %              Set T=1
OmegaP=(2/T)*tan(wp/2); %             Prewarp Prototype Passband freq
OmegaS=(2/T)*tan(ws/2);%             Prewarp Prototype Stopband freq
% Analog Prototype  Order Calculation:
ep=sqrt(10^(Rp/10)-1);      %          Passband Ripple Factor 
A=10^(As/20);              %          Stopband Attenuation Factor
OmegaC=OmegaP;             %          Analog Prototype Cutoff freq
OmegaR=OmegaS/OmegaP;      %          Analog Prototype Transition Rat
g=sqrt(A*A-1)/ep;          %          Analog Prototype Intermediate c
N=ceil(log10(g+sqrt(g*g+1))/log10(OmegaR+sqrt(OmegaR*OmegaR-1)));
fprintf('\n***Chebyshev-2 Filter Order =%2.Of\n',N)
% ***Chebyshev-2 Filter Order = 4
% Digital Chebyshev-II Filter Design:
wn=ws/pi;            %                     Digital Stopband freq in pi uni
[b,a]=cheby2(N,As,wn);
[b0,B,A]=dir2cas(b,a)