DISPERSIVE MODES IN THE TIME-DOMAIN - ANALYSIS AND TIME-FREQUENCY REPRESENTATION

Four algorithms for time-frequency (TF) distributions are considered f or the processing and interpretation of dispersive time-domain (TD) da ta: The short-time Fourier transform, frequency and time-domain wavele ts, and a new ARMA-based representation. The TF resolutions of the var ious distributions are discussed and compared with reference to result s for the scattered fields from a chirped finite grating excited by a pulsed plane wave. The processing in the TF phase space extracts TD ph enomenology, in particular the instantaneous dispersion relation-with its associated time-dependent frequencies-descriptive of the local TD Floquet modes on the chirped truncated grating.