Applications of time‐frequency signature analysis to target identification

The overlapping subjects of target identification, inverse scattering, and active classification have many applications that differ depending on specific sensors. Many useful techniques for these relevant subjects have been developed in the frequency and the time domains. A more recent approach views target signatures in the combined or coupled time‐frequency (t‐f) domain. For either ultra‐wideband (UWB) projectors, or UWB processing these joint t‐f domain techniques are particularly advantageous. Such analysis requires the use of some of the scores of nonlinear distributions that have been proposed and studied over the years. Basic ones, such as the Wigner distribution [E. Wigner, Phys. Rev. 40, 749 (1932)] and its many relatives, have been shown to belong to the well‐studied ‘‘Cohen Class’’ [L. Cohen, J. Math. Phys. 7, 781–786 (1966)]. Half‐a‐dozen of these distributions will be selected to review applications that the authors have addressed and solved in several areas such as: (a) sonor [Appl. Mech. Re...