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# How to calculate the SNR of a jittered Sine Wave?

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#### sixth

##### Member level 4
sine wave frequency cacluate

For a sine wave generated by PLL, can anyone tell me how to calculated its SNR?
In the frequency spectrum , I can not distingguish what's the signal and what's the noise because the signal spectrum is not a single line but with a lot of phase noise.
As a common method, in FFT analysis, we often pick some bins beside the signal and add them together as the signal energy and the sum of the remainder part as the noise energy. But for a jittered sine wave, how many bins should i pick up as the signal energy?

sixth

calculate noise in a sine wave

sixth said:
For a sine wave generated by PLL, can anyone tell me how to calculated its SNR?
In the frequency spectrum , I can not distingguish what's the signal and what's the noise because the signal spectrum is not a single line but with a lot of phase noise.
As a common method, in FFT analysis, we often pick some bins beside the signal and add them together as the signal energy and the sum of the remainder part as the noise energy. But for a jittered sine wave, how many bins should i pick up as the signal energy?

sixth

Hi sixth,
The signal energy is usually only in one bin. If you choose equal bins to the either side of the signal frequency, the middle bin (only one bin) will be your signal frequency.

Bharath

you must add amplitudes of sidelobes which are significant with respect to main sinewave frequency.

say which are more than 1% of the main lobe

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