High Quality Content by WIKIPEDIA articles! A time frequency representation (TFR) is a view of a signal (taken to be a function of time) represented over both time and frequency. Time frequency analysis means analysis into a TFR. TFRs are often complex-valued fields over time and frequency, where the modulus of the field represents "energy density" (the concentration of the root mean square over time and frequency) or amplitude, and the argument of the field represents phase.