Definition of instantaneous frequency on real signals

This paper introduces a definition of the instantaneous frequency (IF) on real signals. Basically the definition ωt = xt/√1 − x²t avoids some pitfalls associated with the corresponding definition on analytic signals. It readily applies to the class of monocomponent frequency modulated signals and also accommodates the class of amplitude and frequency modulated signals. An interpretation of the IF is given for the latter and an extension of it to instantaneous parameters is discussed.