How to compute the short time Fourier transform of a signal z(n) in a time frame that is centered at n?

I want to do the periodicity analysis of a signal using the short time ACF based method. The equations which I have says that I need to compute the short time fourier transform in a time frame that is centered at n. Can anybody help??

Answer 1

[Youssef Khmou]

The Short time Fourier transform use overlapping fragments of the signal, the computed transformations are concatenated into single columns to represents a spectro gram, you can start with basic non overlapping example;a signal with 1000 points where each 10 points we compute the FF with 512 resolution :

t = 0:0.001:1-0.001;          
f = chirp(t,0,2,150);
N=length(f);
T=N/100;
k=1:T:N;
NFFT=512;
for n=1:length(k)-1

    F(n,:)=abs(fft(f(k(n):k(n+1)-1),NFFT));
end