Discrete-Time, Discrete-Frequency Reassignment Method
The reassignment method is a non-linear, postprocessin technique which cans improve the localization of a time-frequency distribution by moving its values according to a suitable vector field. The reassignment method’s scheme assumes that the energy distribution in the time-frequency plane resembles a mass distribution and moves each value of the time-frequencyplane located at a point (𝒕𝒕𝒕𝒕, 𝒇𝒇𝒇𝒇)to another point,(𝒕𝒕𝒕𝒕℘,𝒇𝒇𝒇𝒇 ℘), which is the center of gravity of the energy distribution in the area of (𝒕𝒕𝒕𝒕, 𝒇𝒇𝒇𝒇). The result is a focused representation with very highintensity [11]. During this research it was investigated and determined that the frequency reassignment corrections derived from the Flandrin reassignment method have undesired noise sensitivity at very small noise levels as well as undesired observed distortions. In order to address these issues, a novel approach was derived-the discrete-time, discrete-frequency formulation of frequency reassignment. It is shown that in noise-free tone scenarios, this novel approach eliminates ambiguity and provides less distortion than the Flandrin reassignment method.
