Envelope approach based on special knots for empirical mode decomposition

An alternative envelope approach for empirical mode decomposition (EMD) is proposed. The new approach constructs the envelope by cubic spline interpolation, not using the extrema directly but some special knots calculated from the extrema. Owing to the particular property of the knots, the intrinsic mode function is the constant envelope signal so that the EMD with this envelope is suitable for sinusoid signal decomposition, which is also validated by simulation.