Covariance-based frequency reassignment for detection of non-stationary sinusoids

A new approach to the frequency reassignment for sinusoidal energy localization in the time-frequency plane is presented. While the classical reassignment method operates statically on each point in the plane, a more global approach focuses on the dynamics of the frequency reassignment operator along the frequency grid. It is shown that the first mixed moment of the frequency reassignment operator and linear frequency well describes the Discrete-Time Fourier Transform (DTFT) spectral peaks in terms of sinusoids and noise. The new method eludes spurious artifacts in noisy regions, produced by the classical reassignment method randomly clustering noise. The proposed method is shown to have very good behavior for low SNR and it is computationally efficient.