Conduct STFT analysis for chirp signal for 25% overlapping

Hello everyone, I really could use some help with chirp signal in matlab.. I need to visualize the result on spectogram, however i have no idea how to do the overlapping part. I really would be grateful for every hint :)

That is the code i got to import the chirp signal:

N = 4096;

N_DFT = 256;

n = 0:N-1;

fs = 8000;

t = n/fs;

f0 = 0;

f1 = 100;

x = chirp(t,f0,t(150),f1);

spectrogram(x, hamming(N_DFT), 3*N_DFT/4);

Answer 1

[Bjorn Gustavsson]

From the help for spectrogram:

S = spectrogram(X,WINDOW,NOVERLAP) NOVERLAP is the number of samples

each segment of X overlaps. NOVERLAP must be an integer smaller than

WINDOW if WINDOW is an integer. NOVERLAP must be an integer smaller

than the length of WINDOW if WINDOW is a vector. If NOVERLAP is not

specified, the default value is used to obtain a 50% overlap.

So if you want 25% overlap you should use something like this:

spectrogram(x, hamming(N_DFT), N_DFT*1/4);

Remember to read the help and documentation carefully, then play around with the different inputs and look at the results.

HTH

[Magdalena Bartoszek]

Thank you very much, I'm so grateful! :)