Instantaneous frequency and wave shape functions (I)

Hau Tieng Wu

Research output: Contribution to journalArticlepeer-review


Although one can formulate an intuitive notion of instantaneous frequency, generalizing "frequency" as we understand it in e.g. the Fourier transform, a rigorous mathematical definition is lacking. In this paper, we consider a class of functions composed of waveforms that repeat nearly periodically, and for which the instantaneous frequency can be given a rigorous meaning. We show that Synchrosqueezing can be used to determine the instantaneous frequency of functions in this class, even if the waveform is not harmonic, thus generalizing earlier results for cosine wave functions. We also provide real-life examples and discuss the advantages, for these examples, of considering such non-harmonic waveforms.

Original languageEnglish (US)
Pages (from-to)181-199
Number of pages19
JournalApplied and Computational Harmonic Analysis
Issue number2
StatePublished - Sep 2013


  • Heart rate variability
  • Instantaneous frequency
  • Reassignment
  • Respiratory rate variability
  • Sleep stage
  • Synchrosqueezing transform
  • Wave shape function

ASJC Scopus subject areas

  • Applied Mathematics


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