abd.m

filter design sigma delta filter

% 从上一程序中选出得系数中 ，选出使通带波纹不超过0.1db得系数组、
s=0;
for i=1:122;
    a=d(i,:);%d为上一节筛选函数输出
    A1=a(1);
    A2=-3*a(1)+a(1)*a(2);
    A3=3*a(1)-2*a(2)*a(1)+a(1)*a(2)*a(3);
    A4=-a(1)+a(1)*a(2)-a(1)*a(2)*a(3)+a(1)*a(2)*a(3)*a(4);
    p=[1 A1-4 A2+6 A3-4 A4+1];
    z=[0 A1 A2 A3 A4];
    [h,f]=freqz(z,p,6400,12800);%根据降频64换算，前100个属于信号通带
    h=h(1:100);
    h=abs(20*log10(abs(h)/abs(h(1))));
    s(i,:)=max(h(2:100));%数组s中存有得通带波纹最大值
end