Comment filtrer 2 signaux en gardant l'info de phase?

[jean-Leost]

Bonjour,
Je dois mesurer la différence de phase entre deux signaux (sinus) provenant d'un scope.
Mes sigaux etant bruités, je dois les filtrer mais sans perdre l'information de phase.
Existe t il un filtre approprié.
Merci

[LocalDSP]

Try to use the Extract Single Tone Information.vi in the analysis>>measurement palette. This VI returns the exact frequency(ies), amplitude(s) and phase(s) of the highest tone in the input signal(s). You can check that the frequencies on both channels is the same (and of course what you expect) and then simply subtract the 2 phase values from each others. You should not need to filter your signals before using the VI. Bonne chance ...

[jean-Leost]

Thank's.
But I must filter the signal for raise the noise with a filter vi. And after, I take a Extract frequency vi. But I loose the phase information before.
Your solution as weel if I have a good signal.

[LocalDSP]

If your sine tone is buried in noise, you can only extract its information (incl. phase) if you have a sufficiently long portion of it, in which case the Extract Single Tone Information.vi will do the best possible job (better than simple filtering!). The VI bases its calculation on the spectrum (FFT) of your signal and the resolution is therefore proportional with the signal length.

A (bandpass) filter would have to settle before returning reliable phase and the noise would probably still be a issue. But if you are using the same filter on both channels, the phase difference should be unaffected.

Can you post a VI with your signals (a sufficient portion of it)?