Passband

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Tolerance scheme for a bandpass filter

The pass band is that frequency range of a frequency filter within which it allows the frequencies contained in an electrical signal to pass. An attenuation of 3  dB or a drop in the signal level to around 71% is usually defined as the limit of the pass band .

  • Low pass : The frequency range extends from 0 Hz to its cutoff frequency  f t .
  • High pass : The pass band begins at its cutoff frequency  f h and theoretically extends up to infinitely high frequencies.
  • Bandpass : The pass band lies between the lower limit frequency  f 1 and the upper limit frequency  f 2 and is also called bandwidth , since the filter allows a frequency band of width  f 2 - f 1 to pass through.
  • Notch filter (notch filter) or bandstop: Apart from the cut-off frequency or the cut-off frequency range, all other frequencies to pass the filter.

A common width of the pass band in measurement technology and recording studio technology is 1/3  octave (a third ); such filters are called third-octave filters . Intermediate frequency filter in FM - receivers for example, have a passband of 150 to 250 kHz bandwidth.

literature

  • Helmut Röder, Heinz Ruckriegel, Heinz Häberle: Electronics 3rd part, communications electronics. 5th edition, Verlag Europa-Lehrmittel, Wuppertal 1980, ISBN 3-8085-3225-4
  • Karl Hermann Huber: Filtering and sifting of audio frequencies. 1st edition, Frech Verlag, Stuttgart 1974, ISBN 3-7724-0162-7