A set of related methods of demodulating amplitude and frequency modulated signals. T'he emphasis is on using an iterative approach to separate an envelope signal and a possibly frequency modulated signal from which a physically meaningful, non-negative instantaneous frequency can be derived. Three schemes are presented. The first scheme represents signals as the single product of an envelope signal and a possibly frequency modulated signal with a constant envelope, derived by iterative methods. The remaining schemes involve repeatedly smoothing the signal prior to demodulation. The signal is represented as being the sum of a set of component signals, each of which is the product of an envelope signal and a frequency modulated signal. For all three schemes the envelope and instantaneous frequency values can be presented in the form of the Demodulated Signal time-frequency representation.
