This paper presents a new approach to rejection of complex-valued sinusoidal disturbances acting at the output of a discrete-time linear stable plant with unknown and possibly time-varying dynamics. It is assumed that both the instantaneous frequency of the sinusoidal disturbance and its amplitude may be slowly varying with time and that the output signal is contaminated with wideband measurement noise. The proposed disturbance rejection algorithms are extensions of the algorithm proposed earlier for the constant-known-frequency case. The main purpose of this study is to compare cancellation efficiency under two approaches to frequency tracking: parametric (model-based) and nonparametric (based on decomposition of the signal space). We show that, rather surprisingly, a simple parametric scheme yields results that are of similar quality to those obtained using a high-resolution, computationally much more involved, nonparametric (ESPRIT) scheme.
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