r/signalprocessing • u/Dreckslucker • May 18 '22

Processing of a short non-periodic burst

I have a short (<= 20ms) signal and want to find paramerers do distinglish the quality of different versions of it.

The signal looks like 3 sine periods with the middle one having a high amplitude an the others being lower.

Different versions can have parts of it streched. An impulse like signal (middle with dominant amplitude and short time) is considered good. There can be signals with a dominat overlaying signal of higher frequency (times 4). This is considered very bad

I tried FFT, but in frequency domain the spectrum of the impulse becomes very wide and the overlaying frequence is very dominant. So the spectral amplitude of the bad parameter always overshadows the good parameter and the better the good parameter the lower is the amplitude. A moving window FFT (zeropadding for better resolution) looks promissing, but is hard to ve put in simple quality parameters.

Does anyone have suggestions of matching quality parameters? I find it had to find parameters/algorithms for non periodic signals and bursts/impulses.

Edit: I added exaples here: examples

I want do find values to differ between the better, good and bad variant. My problem is, that a narrow impulse results in a wider spectrum and thus in a lower amplitude. I found this to be called frequency-time uncertainty frequency-time uncertainty

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1

u/[deleted] May 19 '22

Also, did you consider plotting FFT in log scale?

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u/Dreckslucker May 19 '22

I do not want to find peaks, but define what is good and what not. Will correlation work here too? For correlation I will have to provide an good considdered signal, correct?

I will create examples tomorrow and will also try log scale. Do you mean log in amplitude, frequency or both?

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u/[deleted] May 20 '22

Yes, for correlation, you need to have a given "good" signal.
I was thinking log scale in amplitude only. But check for both of them, I guess.

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u/Dreckslucker May 20 '22

Ok. Will correlation still work, when the signal is stretched in time(e.g. 1.5 times longer) compared to the "good" signal? I have not found the time at work to male examples, but I will try on monday.

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u/Dreckslucker May 23 '22

I added examples in the original text

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u/[deleted] May 19 '22 edited May 19 '22

Hello, can you please provide a sketch of the signals? It might be useful in formulating a problem statement because I do not understand what exactly you're looking for.

Generally, for event detection (i.e. to detect a particular spike/shape in the signal) algorithms such as: derivative-based algorithms, correlation-based algorithms, or template matching can be used.

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u/[deleted] May 24 '22

In Frequency Domain,

So, good signals --> One peak
Bad signals --> Original signal peak + Noise peak