An apparatus for analyzing a physical signal representing a physical phenomenon is provided. The apparatus comprises an analog-to-digital converter, a slope calculator, a local extrema identifier, a residual signal constructor and an intrinsic mode function (IMF) extractor. The analog-to-digital converter is used to convert the physical signal into a plurality of data points. The slope calculator is used to calculate slope of each data point. The local extrema identifier is used to identify a plurality of local extrema of the slopes. The residual signal constructor is used to construct a residual signal of the physical signal from the data points corresponding to the local extrema of slopes. An IMF extractor is used to extract an intrinsic mode function indicative of an intrinsic oscillatory mode in the physical phenomenon by subtracting the residual signal from the physical signal. A method for analyzing a physical signal representing a physical phenomenon is provided.