A structure for representation of localized time-frequency distributions in presence of noise

This paper considers multi-component non-stationary signals contaminated with additive white Gaussian noise and suggests a structure to remove high noise from quadratic time-frequency distribution (QTFD) of these signals while localizing auto-terms. Proposed structure includes three steps. It first reduces some of the noise power by filtering the distribution in ambiguity domain and thus enhances signal-to-noise ratio. In the second step, the regions corresponding to the auto-terms are determined and by presenting a time-varying threshold, the noise out of auto-terms is eliminated in each time interval. Finally, using reassignment principle, the auto-terms are concentrated to local centroids of their energy. The typical reassignment method localizes both auto-terms and noise components while the proposed procedure relocates only the auto-terms to their original positions. Simulation results illustrate the performance of the proposed structure as compared to more standard state-of-the-art QTFDs.