Time-Frequency reassignment: from principles to algorithms

Time–frequency analysis (TF) is a field that has experienced a number of qualitative and quantitative changes during the last two decades. Whereas most of classical signal processing studies of the 1970s were aimed at stationary signals and processes, many efforts were devoted to less idealized situations during the 1980s, and the idea of TF progressively emerged as a new paradigm for nonstationarity. It is now well recognized that many signal processing problems can be advantageously phrased in a TF language, and the issue may no longer be designing brand new methods from scratch, but instead in adequately using some of the many tools that we have at our disposal, or in improving them for specific tasks. In some sense, the purpose of this chapter has to be understood from this second generation perspective, because what is discussed here essentially builds on the methods that have already been extensively studied and used. New advances nevertheless are to be provided, thanks to fresh interpretations that have been made possible by recent developments in TF analysis.