An iterative approach for spectrogram reassignment of frequency modulated multicomponent signals

In this paper, an evolution law for the modulus of the Short Time Fourier Transform, referred as spectrogram, of a frequency modulated multicomponent signal is proposed. Based on this result, an iterative reallocating method for the enhancement of spectrogram resolution is proposed. Compared to the standard reassignment method, the presented procedure allows us to obtain a time–frequency representation which better localizes the individual modes of a multicomponent signal even in the non separable case. The proposed method is computationally advantageous and robust to modes interference, then it could be employed for accurate instantaneous frequency estimation, which is a fundamental goal in applications dealing with non stationary signals such as radar, surveillance and audio signals.