Frequency tracking by adaptive notch filter structures

A recursive adaptive filter is able to model a high order function with fewer filter coefficients than required by an FIR adaptive filter. Some properties of the recursive-notch adaptive line enhancer (ALE) are investigated, when tracking sinusoidal signals embedded in white Gaussian noise. The initial values of the adaptive weights are found to have a great effect on filter convergence, and hence on tracking performance. A parallel arrangement of notch filter sections is used for an input consisting of multiple sinusoids, and the poles are initialized at various frequencies inside the unit circle. This structure is also capable of tracking a single sinusoid with a rapidly changing frequency