Empirical mode decomposition frequency resolution improvement using the pre-emphasis and de-emphasis method

Empirical mode decomposition (EMD) is a time-frequency analysis technique that has gained popularity in recent times due to its adaptivity and applicability to non-stationary signals. Paired with the Hilbert transform it yields a timefrequency spectrum and is called the Hilbert-Huang transform (HHT). The empirical nature of EMD has resulted in a lack of theoretical analysis so far. Issues regarding its ability to resolve different frequencies have been largely ignored in the past as have been questions regarding optimum choice of some control parameters based on the signal. In this paper we propose a new pre-emphasis/de-emphasis technique to improve the frequency resolving ability of EMD for a particular configuration of tonal signals with unequal amplitudes. The dependence of the frequency resolving ability of this technique on the number of sifting iterations and stopping criterion threshold setting is pointed out.