Get STFT plot with matrix Input

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Nour on 16 Sep 2019
Edited: nur dsc on 6 Apr 2021
I am working with a radar output Q/ I matrix and I want to apply stft on the complex matrix (I + j Q) using matlab.
The stft function didn't accept Matrix Input. Is there a way to do it ?
Thank you so much in advance :)

Answers (2)

Priyanshu Mishra
Priyanshu Mishra on 19 Sep 2019
Hi Nour,
In the documentation page of stft, under the input argument section, it is mentioned that x can take vector and matrix both. You may refer to examples given in the documentation page of stft.
Sara James
Sara James on 21 Oct 2019
The stft function in 2019b only supports plotting of vector inputs. If you want to use the convenience plot of stft for your matrix input, you could do so within a for loop. Alternatively, you could specify your own plots using pcolor and subplot like in the following example:
fs = 1e3; % Sampling frequency (Hz)
t = 0:1/fs:1-1/fs; % Time (sec)
x = [chirp(t,100,1,300,'quadratic',45,'concave');
chirp(t,300,1,500,'logarithmic')]'; % Multi-channel signal
[S,F,T] = stft(x,fs,'Window',hamming(128,'periodic'),'OverlapLength',50);
smag = mag2db(abs(S)); % Convert to dB
caxisLims = max(smag(:)) + [-60 0]; % Color axis limits
numChannels = size(x,2);
for ii = 1:numChannels
xlabel('Time (s)')
ylabel('Frequency (Hz)')
shading flat
title(sprintf('Channel %d',ii))

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nur dsc
nur dsc on 6 Apr 2021
Edited: nur dsc on 6 Apr 2021
Hi Nour,
You do not need a matrix format actually. I+j*Q is also in vector format and you can apply stft this complex data.
If you have orijinal x signal you can use hilbert(x).
result = hilbert(x)
then you can apply stft to result.

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