function [b,a] = afd_chb2(Wp,Ws,Rp,As);
% 切比雪夫-2型模擬低通濾波器設(shè)計(jì)
% -----------------------------------------
% [b,a] = afd_chb2(Wp,Ws,Rp,As);
%  b = Ha(s) 分子的系數(shù)
%  a = Ha(s) 分母的系數(shù)
% Wp = 以弧度/秒為單位的通帶邊緣頻率; Wp > 0
% Ws = 以弧度/秒為單位的阻帶邊緣頻率; Ws > Wp > 0
% Rp = 通帶中的振幅波動(dòng)的+dB數(shù); (Rp > 0)
% As = 阻帶衰減的+dB數(shù); (As > 0)
%
if Wp <= 0
        error('通帶邊緣必須大于 0')
end
if Ws <= Wp
        error('阻帶邊緣必須大于通帶邊緣')
end
if (Rp <= 0) | (As < 0)
        error('通帶波動(dòng)或阻帶衰減必須大于0')
end

ep = sqrt(10^(Rp/10)-1);
A = 10^(As/20);
OmegaC = Wp;
OmegaR = Ws/Wp;
g = sqrt(A*A-1)/ep;
N = ceil(log10(g+sqrt(g*g-1))/log10(OmegaR+sqrt(OmegaR*OmegaR-1)));
fprintf('\n*** 切比雪夫-2 濾波器階次 = %2.0f \n',N)
[b,a]=u_chb2ap(N,As,Ws);