Low-complexity tracking and estimation of frequency and amplitude of sinusoids

Formulas are proposed for estimating and tracking the (time-dependent) frequency and amplitude of a sinusoidal signal. These formulas are recursive in nature, and use only the instantaneous values of the signal, in a low cost and low complexity manner; in particular, there is no need to take square roots or to carry out divisions. Special attention is paid to the convergence behavior of the algorithm for stationary signals and the dynamic behavior in case of a transition to another stationary state. The latter issue is considered to be important to assess the tracking abilities for non-stationary signals.