fftm.m

实现快速傅里叶变换

 
function x=FFTM(x)
N=length(x);
n=log2(N);
x=code(x);
  
for i=1:n
    for m=1:N/(2^i)
        for k=1:2^(i-1)
           swap=x(k+(m-1)*(2^i));
           x(k+(m-1)*(2^i))=x(k+(m-1)*(2^i))+exp(-2*pi*j*(k-1)/(2^i))*x(k+(m-1)*2^i+2^(i-1));
           x(k+(m-1)*(2^i)+2^(i-1))=swap-exp(-2*pi*j*(k-1)/(2^i))*x(k+(m-1)*2^i+2^(i-1));
        end
    end
end
x
xx=0:N-1
plot(xx,abs(x),'*')
return