d2fft.m

来自「数字信号处理基于matlab 文件内容 /conv(卷积部分) dupco」· M 代码 · 共 27 行

function xw = d2fft( xn )
%UNTITLED1 Summary of this function goes here
%  Detailed explanation goes here
pow=nextpow2(xn);
N=2^pow;
if length(xn)<N;
    xn=[xn , zeros(1,N-length(xn))];
end
n=bin2dec(fliplr(dec2bin([1:N]-1,pow)))+1;
yn=xn(n);
wn=exp(-j*2*pi/N);
wntable=wn.^(0:N/2-1);  %得到wn表
for time=1:pow               %共这么多蝶形运算
     kuaju=2^(time-1);       %对偶结点跨距
    for fenzu=1:2^(pow-time) %分组个数
        jiange=2^time ;        %分组间隔
        for zulei=1:2^(time-1);%组中的元素个数
        position=(fenzu-1)*jiange+zulei;
        p=2^(pow-time)*(zulei-1)+1;
        temp=yn(position)+yn(position+kuaju)*wntable(p);
        yn(position+kuaju)=yn(position)-yn(position+kuaju)*wntable(p);
        yn(position)=temp;
        end
    end
end
xw=yn;