FFT快速傅里叶变换Matlab自编程序

% fft function;

%

%

function y=fft_new(x);

M=length(x);

n=log2(M);

K=M/2;

even_no=zeros(1,K);

odd_no=zeros(1,K);

f_valve=zeros(1,M);

for i=0:K-1

for x1=0:K-1

even_no(i+1)=even_no(i+1)+( x(2*x1+1)*exp(-j*2*pi*x1*i/K ) )/K;

odd_no(i+1)=odd_no(i+1)+( x(2*x1+1+1)*exp( -j*2*pi*x1*i/K) )/K;

end

end

for i=0:K-1

f_valve(i+1)=(even_no(i+1)+odd_no(i+1)*exp(-j*2*pi*i/M))/2;

end

for i=0:K-1

f_valve(i+K+1)=(even_no(i+1)-odd_no(i+1)*exp(-j*2*pi*i/M))/2;

end

y=f_valve.*M;

程序运行结果