exam1_2.m

基2ditfft的matlab源程序

function XK=exam1_2(xn,N)
%it is a function of 2N points FFT by both of N points FFT.
%the argument 'xn'is the sample sequence input,
%the argument 'N'is the length of the sample sequence input.
%------------------add zeros----------------------------%
if length(xn)<N    
    xn=[xn,zeros(1,N-length(xn))];    
end
k=1;
for m=0:N-1
    t=mod(m,2);
    if t==0
        xn1(m/2+1)=xn(m+1);
    else
        xn2(k)=xn(m+1);k=k+1;
    end
end
xn1=ditfft(xn1,N/2);
xn2=ditfft(xn2,N/2);
u=exp(0);
w=exp(-pi*i*2/N);
for j=0:N/2-1
    xn3(j+1)=xn1(j+1)+xn2(j+1)*u;
    xn3(j+N/2+1)=xn1(j+1)-xn2(j+1)*u;
    u=u*w;
end
XK=xn3;