Dispersive modes in the time domain: analysis and time-frequency representation

Four algorithms for time-frequency (TF) distributions are considered for the processing and interpretation of dispersive time-domain (TD) data: the short-time Fourier transform, frequency and time-domain wavelets, and a new ARMA-based representation. The TF resolutions of the various distributions are discussed and compared with reference to results for the scattered fields from a chirped finite grating excited by a pulsed plane wave. The processing in the TF phase space extracts TD phenomenology, in particular the instantaneous dispersion relation /spl minus/ with its associated time-dependent frequencies-descriptive of the local TD Floquet modes on the chirped truncated grating.<>