abe2.m

filter design sigma delta filter

l=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=[1 -4 6 -4 1];
    [h,f]=freqz(z,p,6400,12800);%根据降频64换算，前100个属于信号通带
    h=20*log10(abs(h(100)));
    if (h<(-60))%只取衰减大于60db的系数组
        l=l+1;
        mm(l,:)=[a(1) a(2) a(3) a(4) h];%前四个数是系数，最后一个是达到得衰减数
    else
    end
end