What are the time-frequency moments of a signal?

摘要

We review recent work on defining the time-frequency moments of a signal. Expressions are given for moments <ω~n>_t, ω, and (t~mω~n) of all orders n, m, in terms of the amplitude and phase of the signal and spectrum. Knowing the time-frequency moments is of interest for a variety of reasons, including their potential utility as features for classification of nonstationary signals, and also because from the moments one can construct the time-varying spectral density, or approximate it using a few moments.