overgangsbands

Overgangsbanden, in the context of signal processing and filter design, refer to the frequency range between the passband and the stopband where the filter’s amplitude response transitions from near unity to the specified attenuation in the stopband. In other words, it is the region where the filter gradually reduces signal strength rather than cutting off frequencies instantly.

This transition is defined by the passband edge frequency (f_p), the stopband edge frequency (f_s), and the corresponding allowed ripple in the passband as well as the minimum attenuation in the stopband. The width of the overgangsbanden is typically f_s minus f_p (in absolute terms) or a normalized transition width when expressed relative to the bandwidth or Nyquist frequency. In a practical filter, the magnitude response in this region rises or falls smoothly rather than changing abruptly.

The existence and width of overgangsbanden are a result of trade-offs in filter design. A steeper transition (narrow overgangsbanden) generally requires a higher-order filter, which increases computational load, delay, and potential passband/stopband ripple. Design methods such as windowing, equiripple (Parks–McClellan), or optimization aim to meet specific specifications for both passband ripple and stopband attenuation, while controlling the transition width.

Applications of overgangsbanden include digital and analog filters used in audio processing, communications, and instrumentation. The concept also appears in optical filters and other domains where a system moves from a region of high transmission or low attenuation to one of low transmission, with a transitional region in between.