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Butterworth Filters

LabVIEW 2013 Help

Edition Date: June 2013

Part Number: 371361K-01

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Butterworth filters have the following characteristics:

  • Smooth response at all frequencies
  • Monotonic decrease from the specified cut-off frequencies
  • Maximal flatness, with the ideal response of unity in the passband and zero in the stopband
  • Half-power frequency, or 3 dB down frequency, that corresponds to the specified cut-off frequencies

The advantage of Butterworth filters is their smooth, monotonically decreasing frequency response. The following figure shows the frequency response of a lowpass Butterworth filter.



As shown in the previous figure, after you specify the cut-off frequency of a Butterworth filter, the steepness of the transition is proportional to the filter order. Higher order Butterworth filters approach the ideal lowpass filter response.

Butterworth filters do not always provide a good approximation of the ideal filter response because of the slow roll-off between the passband and the stopband.


 

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