Adaptive chirplet representation of signals on time-frequency plane

Dynamic spectra, which exhibit the spectral content of a signal as time elapses, are based on subdivision of the time-frequency plane into minimum-area rectangular cells. The cell dimensions in time and frequency are usually held constant throughout. A more general spectral analysis would allow the cells to change aspect ratio with time. Elementary cells assuming oblique forms (chirplets) are proposed, together with an adaptive method for selecting their aspect ratio and obliquity to suit the data.