On the design of adaptive notch filters

In instrumentation and other applications, the on-line estimation of the frequency and amplitude of a noise-corrupted sinewave is of great practical interest. Recently an adaptive notch filter (ANF) with global convergence properties has been developed, and is a candidate approach to our problem. This paper analyses the transient and noise properties of this ANF and equips the method with design equations. Using frequency ranges greater than (up to 2 decades) and signal/noise ratios less than (down to -16 dB) those commonly found in the ANF literature, it is verified by extensive simulations that the new frequency estimator has excellent tracking and noise-rejection properties, provided that the signal/noise ratio is not too small. A comparison is made of its behaviour with that of a phase-locked loop, a method commonly used in practice. Copyright (C) 2001 John Wiley & Sons, Ltd.