Owning Palette: Advanced IIR Filter Design VIs
Requires: Digital Filter Design Toolkit
Creates a digital Butterworth infinite impulse response (IIR) filter.
You can use the DFD Butterworth Order Estimation VI to estimate order.
|filter type specifies the type of filter that this VI creates.
|order specifies the digital filter order. The value of order must be greater than zero. The default is 2. If you set filter type to Lowpass or Highpass, the digital filter order you specify must equal the analog prototype filter order. If you set filter type to Bandstop or Bandpass, the digital filter order you specify must be an even number that equals two times the analog prototype filter order. Increasing the value can narrow the transition band.|
|high cutoff freq specifies the high cutoff frequency in hertz. The value must be greater than low cutoff freq. The default is 0.45. This VI uses this input only for bandpass and bandstop filter design. The cutoff frequency that you specify corresponds to the half-power frequency or the 3 dB frequency.|
|low cutoff freq specifies the low cutoff frequency in hertz. The default is 0.12. The cutoff frequency that you specify corresponds to the half-power frequency or the 3 dB frequency.|
|error in describes error conditions that occur before this node runs. This input provides standard error in functionality.|
|fs specifies the sampling frequency in hertz. The value must be greater than zero. The default is 1, which is the normalized sampling frequency.|
|filter out returns a new filter.|
|error out contains error information. This output provides standard error out functionality.|
Butterworth filters have the following characteristics:
Butterworth filters do not always provide an acceptable accurate approximation of the ideal frequency response because the filter has slow roll off in the transition band. Use Chebyshev, Inverse Chebyshev, or Elliptic filters to achieve a sharper roll off.
Refer to the following VIs for examples of using the DFD Butterworth Design VI: