A measurement method based on a modified version of the Chirplet transform for instantaneous frequency estimation

A measurement method for instantaneous frequency estimation is presented in this paper. The method is based on the use of the Chirplet transform, a linear time-frequency representation (TFR) allowing additional modifications of each cell on the time-frequency plane with respect to other TFRs. In particular, a modified version of this transform is proposed here; a bending effect can be further imposed on the cells. Thanks both to this feature and a suitable measurement procedure, properly set up by the authors, the method assures a satisfying accuracy in reconstructing the instantaneous frequency trajectory of monocomponent signals as well as a good resolving capability in the analysis of multicomponent signals whose instantaneous frequency trajectories are strongly nonlinear and very close to one another. Theoretical details concerning the Chirplet transform and its modified version are first given. Then, the proposed measurement procedure for choosing the optimal values of the parameters of the transform according to the local features of the analyzed signal is described. At the end, the results of several experimental tests conducted both on monocomponent and multicomponent signals are presented; advantages over other solutions are also highlighted.