Multistage digital prefiltering of noisy tachometer signals

A multistage digital prefiltering concept is discussed. The prefilter is implemented by using multirate signal-processing techniques, and contains both linear and nonlinear subfilters. The impulsive and wideband noise components are attenuated by a cascade of a standard median filter (SMF) and a low-order Hanning window (HW). A multirate digital filter is used to attenuate the 50/60-Hz power line frequency and its harmonics. The multirate principle with oversampling and decimation is used to reduce the complexity of the required analog antialiasing filter. The multistage filter was tested in a simulation environment and the results were satisfactory.<
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