Filtercharakter

Filtercharakter (literally "filter character") is a term used in signal processing to describe the overall effect a filter has on a signal's spectral content. It encompasses the type of filtering (low-pass, high-pass, band-pass, or band-stop), the filter order, and the specific realization (analog or digital). The Filtercharakter is most directly observed in the filter's magnitude and phase response versus frequency.

The magnitude response specifies how amplitudes at different frequencies are attenuated or passed. Common characteristics include the cutoff or corner frequency, a passband in which the signal is passed with little attenuation, a stopband where frequencies are suppressed, and the transition band between these regions. Passband ripple and stopband attenuation quantify deviations from ideal behavior. The phase response describes how different frequency components are shifted in time; in linear-phase filters this shift is proportional to frequency, yielding constant group delay.

Filter characterization also depends on implementation. Analog filters (resistor–capacitor networks, inductors, or active op-amps) have continuous-time responses, while digital filters use discrete-time processing and depend on sampling rate, quantization, and numerical precision. FIR and IIR are common digital classes; FIR filters can be designed with linear phase at the cost of higher order, while IIR filters approximate analog prototypes with potentially higher efficiency but less predictable phase.

In design practice, the Filtercharakter guides choices such as filter type, order, and topology to satisfy specifications for audio, communications, or instrumentation. It provides a concise summary of how a filter will affect a signal, beyond its mathematical definition.