DFD Butterworth Design VI

	filter type specifies the type of filter that this VI creates. 0 Lowpass (default) 1 Highpass 2 Bandpass 3 Bandstop
	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 VI or function runs. The default is no error. If an error occurred before this VI or function runs, the VI or function passes the error in value to error out. This VI or function runs normally only if no error occurred before this VI or function runs. If an error occurs while this VI or function runs, it runs normally and sets its own error status in error out. Use the Simple Error Handler or General Error Handler VIs to display the description of the error code. Use error in and error out to check errors and to specify execution order by wiring error out from one node to error in of the next node. status is TRUE (X) if an error occurred before this VI or function ran or FALSE (checkmark) to indicate a warning or that no error occurred before this VI or function ran. The default is FALSE. code is the error or warning code. The default is 0. If status is TRUE, code is a nonzero error code. If status is FALSE, code is 0 or a warning code. source specifies the origin of the error or warning and is, in most cases, the name of the VI or function that produced the error or warning. The default is an empty string.
	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. If error in indicates that an error occurred before this VI or function ran, error out contains the same error information. Otherwise, it describes the error status that this VI or function produces. Right-click the error out front panel indicator and select Explain Error from the shortcut menu for more information about the error. status is TRUE (X) if an error occurred or FALSE (checkmark) to indicate a warning or that no error occurred. code is the error or warning code. If status is TRUE, code is a nonzero error code. If status is FALSE, code is 0 or a warning code. source describes the origin of the error or warning and is, in most cases, the name of the VI or function that produced the error or warning.

DFD Butterworth Design Details

Butterworth filters have the following characteristics:

• Smooth frequency response at all frequencies and monotonically decreasing or increasing magnitude response in the transition band.
• Maximally flat at frequencies of zero and one-half the sampling frequency.

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.

Examples

Refer to the following VIs for examples of using the DFD Butterworth Design VI:

• Extract the Sine Wave - DFD VI: labview\examples\Digital Filter Design\AALXMPL

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• IIR Filter Design - DFD VI: labview\examples\Digital Filter Design\AALXMPL

   Open example  Browse related examples