This paper describes a new approach for the analysis of signals containing fluctuating harmonics. It is based on the Fourier transform, using windowing to reduce the error arising from analysing the signal over a non integer number of signal periods and an iterative process intended to estimate and correct the errors. Some simulations have been performed to prove the efficiency of the method and showed that the final error arising from the computation generally ranges between a few parts in 1010 and a few parts in 1015.
