I have a complex signal and I'm trying to use Octave to plot a spectrogram. I found the specgram function, and it's close to what I want, but I can't figure out how to get it to display negative frequencies. Can it be done?
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1 Answer
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The specgram function from the signal package does not handle complex input fully and discards the negative frequency information.
However, there is a function called sgram in the ltfat package that does handle complex input properly and produces the expected -Fs/2 to Fs/2 spectrogram.
https://gnu-octave.github.io/packages/ltfat/
Today I saw a few errors installing the ltfat package on octave 8.4.0, but sgram still worked when all was said and done.
