matlab具体实现的FFT

function myfft=Myfft(N)   %N点采样 
f1=200;
f2=300;
f=150;
fs=3*f;
t=0:1/fs:(N-1)/fs;
u=5*cos(2*pi*f*t);
%u=2+3*cos(2*pi*f1*t+60*pi/180)+4*cos(2*pi*f2*t+120*pi/180);


M=0;%分为M级
%N=2^M
tempN=N;
while(tempN~=1)
    tempN=tempN/2;
    M=M+1;
end

%%%码位倒置
a=zeros(1,N);
n=1:N;
m=bitrevorder(n);
i=1:N;
a(i)=u(m(i));

WN=exp(-1i*2*pi/N);

for L=1:M
    B=2^(L-1);
    for J=0:2^(L-1)-1