Rapid measurement of digital instantaneous frequency

A new method is proposed for estimating the frequency domain structure of digital signals which may be characterized as having a narrow-band, rapidly time-varying spectrum. The estimated parameter is termed the digital instantaneous frequency of the input and is defined in a manner similar to that used previously to describe frequency-modulated, continuous-time signals. Instantaneous frequency estimates are derived from a spectral computation based on the use of an adaptive linear prediction filter. The proposed method differs from previous techniques in that the coefficients of this filter are continuously updated as each new input data sample is received using a simple time-domain algorithm, A derivation of the algorithm and its properties are presented. Numerical examples are included which illustrate the properties of the procedure.