  The Empirical Mode Decomposition (EMD) is a signal analysis method that
separates multi-component signals into single oscillatory modes called
intrinsic mode functions (IMFs), each of which can generally be associated to a
physical meaning of the process from which the signal is obtained. When the
phenomena of mode mixing occur, as a result of the EMD sifting process, the
IMFs can lose their physical meaning hindering the interpretation of the
results of the analysis. In the paper, "One or Two frequencies? The Empirical
Mode Decomposition Answers", Gabriel Rilling and Patrick Flandrin [3] presented
a rigorous mathematical analysis that explains how EMD behaves in the case of a
composite two-tones signal and the amplitude and frequency ratios by which EMD
will perform a good separation of tones. However, the authors did not propose a
solution for separating the neighboring tones that will naturally remain mixed
after an EMD. In this paper, based on the findings by Rilling and Flandrin, a
method that can separate neighbouring spectral components, that will naturally
remain within a single IMF, is presented. This method is based on reversing the
conditions by which mode mixing occurs and that were presented in the map by
Rilling and Flandrin in the above mentioned paper. Numerical experiments with
signals containing closely spaced spectral components shows the effective
separation of modes that EMD can perform after this principle is applied. The
results verify also the regimes presented in the theoretical analysis by
Rilling and Flandrin.
