Tracking drifting interferences using simple cascaded second order FIR filters

Tracking multiple sinusoids using Kwan-Martin´s algorithm is a popular approach but suffers from convergence problems due to the use of IIR filters for the notch or bandpass stages. By replacing each IIR filter with a simple FIR 2^nd-order notch filter and slaving the IIR filters to these 2^nd-order filters, many of the convergence problems can be solved. Using this approach a three-notch system using Grey-Markel Notch filters is able to resolve three different signals separated by 6 degrees at various locations on the unit circle.