Abstract: Instantaneous frequency (IF) calculation is a key step for empirical mode decomposition (EMD). But signal analysis accuracy is not very well for practical condition signal analysis based on traditional IF calculation method. Although non-stationary signals can be modeled as polynomial phase signals (PPS), traditional phase model estimation methods are not very suitable for practical application, such as maximum likelihood estimation and the least squares method. In most circumstances, a lot of calculations are needed. Thus, several problems need to be solved during IF calculation for intrinsic mode function obtained from EMD. The boundary effect for signal analysis is very obvious. High-order ambiguity function (HAF) is put forward for IF calculation. Then, Hilbert time-frequency spectrum can be constructed for signal analysis. HAF can reduce computation and improve IF estimation accuracy. Simulation signal and practical monitored signal are used to testify the effectiveness of this method for IF calculation. The research shows that this method can effectively eliminate the influence of boundary effect and improve the reliability of Hilbert time-frequency spectrum.

Key words: Empirical mode decomposition, High-order ambiguity function, Instantaneous frequency, Parameter estimation