afd_butt.m

西交大刘树棠写的《数字信号处理》那本书的所有源代码

function [b,a]=afd_butt(Wp,Ws,Rp,As)
if Wp<=0
      error('Passband edge  must  be larger than 0')
end
if Ws<=Wp
      error('Stopband edge must be larger than Passband edge')
end
if (Rp<=0)|(As<0)
      error('PB ripple and/or SB attenuation ust be larger than 0')
end
N=ceil((log10((10^(Rp/10)-1)/(10^(As/10)-1)))/(2*log10(Wp/Ws))); 
fprintf('\n***Butterworth Filter Order=%2.0f\n',N)
OmegaC=Wp/((10^(Rp/10)-1)^(1/(2*N)));
[b,a]=u_buttap(N,OmegaC);