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I'm currently studying "Data Acquisition".

I read that when we have frequency/spectral resolution equal to a natural number, there will be no spectral leakage, for none of the harmonics.

However the text I read makes a parenthesis about a situation where the harmonics frequency is greater than half the sampling frequency but it doesn't explain on detail what happens. I was wondering if someone could give me some explanation please.

I'm also testing this phenomena on lab.

On one experiment I'm sampling a triangular signal with frequency 600 Hz and sampling frequency 24000 with 5600 samples. I'm studying the first 11 harmonics. In this case 11*600= 6600<12000 so I assume no spectral leakage.

On the other hand I have a square wave with frequency 500 Hz and sampling frequency 9500 with 1710 samples. I'm studying again the first 11 harmonics and then again theoretically we would have no spectral leakage. However in this case the 10th and 11th harmonic will have a frequency greater than fs/2 so spectral leakage?

But now that I think about it, while I was writing this. Isn't f>fs/2 a condition for aliasing? So I'm getting aliasing instead of spectral leakage. I'm confused.

If someone who understands about this could explain me I would thank you very much!

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    \$\begingroup\$ no, that's not spectral leakage, that's aliasing. You're right about that! Nothing much to explain about that – if you understand aliasing, you're understanding what happens to the harmonics that end up at or above \$f_s/2\$. \$\endgroup\$ Nov 6, 2019 at 21:02
  • \$\begingroup\$ Hey Marcus! Ok, got it, thank you very much. What did confuse me was that in the book that appears in the paragraph where they talk about spectral leakage (way after than talking about aliasing), therefore I was confused! \$\endgroup\$ Nov 6, 2019 at 21:52
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    \$\begingroup\$ Definitely go look first at a visual introduction to Fourier. You will have a much better feel. Then go look at what is a Fourier series?. Both of these are Youtube videos, with audio, and worth the time. \$\endgroup\$
    – jonk
    Nov 6, 2019 at 22:33

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No, that's not spectral leakage, that's aliasing. You're right about that!

Nothing much to explain about that – if you understand aliasing, you're understanding what happens to the harmonics that end up at or above.

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