abe.m

filter design sigma delta filter

l=0;
for i=1:5
    a=d(i,:);%d为上一节筛选函数输出
    A1=a(1);
    A2=-4*a(1)+a(1)*a(2) ;
    A3=6*a(1)-3*a(1)*a(2)+a(1)*a(2)*a(3);
    A4=-4*a(1)+3*a(1)*a(2)-2*a(1)*a(2)*a(3)+a(1)*a(2)*a(3)*a(4)  ;
    A5=a(1)-a(1)*a(2)+a(1)*a(2)*a(3)-a(1)*a(2)*a(3)*a(4)+a(1)*a(2)*a(3)*a(4)*a(5);
    p=[1 A1-5 A2+10 A3-10 A4+5 A5-1];
    z=[0 A1 A2 A3 A4 A5 ];
    [h,f]=freqz(z,p,3200,6400);%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)a(5) h];%前四个数是系数，最后一个是达到得衰减数
    else
    end
end