Overgangsfilters

Overgangsfilters, also known as transition filters, are filters used in signal processing to create a controlled transition between two frequency regions, typically a passband in which signal components are preserved and a stopband in which they are attenuated. The transition band is defined by lower and upper edge frequencies, and its width reflects how quickly the filter moves from pass to stop. Designers balance transition width, passband ripple, and stopband attenuation to meet system requirements.

In digital implementations, overgangsfilters are commonly realised as finite impulse response (FIR) or infinite impulse response (IIR) filters. FIR types can achieve linear phase and low phase distortion, while IIR filters often require fewer coefficients for a given attenuation.

Common design methods include windowed-sinc approaches, the Parks–McClellan (Remez) algorithm for equiripple FIRs, and least-squares design. Window selection, such as Kaiser, Hamming, or Blackman, influences the trade-off between transition width and ripple.

Applications span anti-aliasing before sampling rate conversion, channel selection in communications, and subband filtering in multirate systems and filter banks, where smooth transitions help minimize spectral artifacts. The concept is a general part of filter design and is used across both audio and communications contexts.

The term is used in Danish and other Nordic languages; in English it is often referred to as transition filtering or transition-band filtering as part of broader filter design.