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Re: Sine fitting
Posted:
Jun 16, 2012 12:18 AM
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On Jun 15, 12:00 pm, "Star Strider" <skystriderDELETET...@ieee.net>
wrote:
> > but the amplitude is still off. I don't know if I'm still doing something wrong, or if the signal I'm looking for is weaker than I'm expecting. I also still don't know how to get to the phase shift from here.
>
> ------------------------------------------------------
>
> I suggest you consider the (sin, cos) pairs for each your two frequencies (pi/3, pi/6) as phasors. Generically:
>
> A*cos(w*t + phi) = X*cos(w*t) - Y*sin(w*t)
> A = sqrt(X^2 + Y^2)
> phi = atan(Y/X)
>
> If you haven't already (and if I understand your notation), plot Y*Q and HT to see how they compare. It looks as though you did everything correctly, so Y*Q should be a reasonably good fit to HT.
you may want to use
phi = atan2(Y,X)
Hope this helps.
Greg
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