# Fourier series/transform of an amplitude-limited sinusoid

I am trying to estimate the amplitude of an original unlimited sine wave from a measurement of the power spectral density (PSD) of an amplitude-limited version. I expect that I may be able to do so by measuring the amplitude of the fundamental and a few of the harmonics.

As a side question, what is the relationship between the coefficients of the Fourier series and the amplitude of the harmonics of the PSD?

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I thought sine waves were always amplitude-limited?! – Igor Rivin Nov 25 '11 at 12:23
Sorry for the confusion. What I meant was a sinusiod that was amplitude limited below it's true maximum value A. As an example, consider a signal x(t) = Asinωt as input to a limiter with max output L. Therefore, it's output y(t) = x(t) for x(t) ≤ L; y(t) = L for x(t) > L. I would like to know the power of the fundamental and first two harmonics as a function of the paramaters A and L (or its ratio), with L ≤ A. Also, I still have the side question relative the coefficients of the Fourier series and the amplitude of the fundamental and harmonics of the PSD. – Joe Nov 26 '11 at 0:03