low_mu_bmax.m

信号处理－滤波器设计（基于matlab和Mathmatica的设计方法）中关于无乘法器椭圆IIR滤波器设计的原创程序。

function result=Low_Mu_Bmax(e)
%  Low_Mu_Bmax.m 计算关于Bmax的表达式
%  $date 4/10/2005
%
%   作者：赵泽平
%      [e-mail]
%   
%
%   References:
%        Miroslav D. Lutovac, Dejan V. Tosic, Brian L. Evans
%           Advanced Filter Design for Signal Processing
%                   Using MATLAB and Mathematica
global n f3dB Bmax 
%n=9;f3dB=0.5/3;Bmax=0;
if e>=sqrt(2)
    t=(1-(1-1/e^2)^0.25)/(2*(1+(1-1/e^2)^0.25));
    q=t+2*t^5+15*t^9+150*t^13;
else
    t=(1-1/e^0.5)/(2*(1+1/e^0.5));
    qp=t+2*t^5+15*t^9+150*t^13;
    q=exp(pi^2/log(qp));
end
L=0.25*sqrt(1/q^n-1);
ap=10*log10(1+1/L);
as=10*log10(1+L);
fp=atan(sqrt((tan(pi*f3dB)^2/e)))/pi;
[z,p,c]=ellip(n,ap,as,2*fp);
Bmax1=max(abs(p).^2);
result=Bmax1-Bmax;