Statistical Signal Extraction and Filtering: Notes for the Ercim

The Impulse Response The sequence {ψj} of the filter’s coefficients constitutes its response, on the output side, to an input in the form of a unit impulse. If the sequence is finite, then ψ(z) is described as a moving-average filter or as a finite impulse-response (FIR) filter. When the filter produces an impulse response of an indefinite duration, it is called an infinite impulse-response (IIR) filter. The filter is said to be causal or backward-looking if none of its coefficients is associated with a negative power of z. In that case, the filter is available for real-time signal processing.