Single Channel (Univariate) Signal
Katarzyna J. Blinowska, Jarosław Żygierewicz · 2021
Signals may contain many frequency components. Some of them may be of interest, like frequency bands of electroencephalogram rhythms; others, like power line artifacts, may be undesired. To remove the unwanted part of the spectral content of the signal one usually uses filters. In order to be implementable the filter must be causal. That is, the filter response must only depend on the current and past inputs. If the filter has to depend also on the past outputs it still can be causal by introducing the feedback with appropriate delays. The requirements concerning filter characteristics are usually contradictory, e.g., for a given filter order the increase of steepness of the filter results in bigger ripples. Therefore some optimization process has to be applied and the resulting filter is a compromise between the set of the conditions. A decision must be made which of the possible filter designs is best for the planned use.