Table Of Contents
Filter Design (Butterworth) (G Dataflow)
Designs an IIR cascade filter as specified by the Butterworth filter model.
Programming Patterns
To filter a sequence of data, wire the filter output to the Filtering node.
filter structure option
The order of the IIR cascade filter.
| Name | Value | Description |
|---|---|---|
| IIR 2nd Order | 0 | Returns IIR second-order filter stages. |
| IIR 4th Order | 1 | Returns IIR fourth-order filter stages. |
| Auto Select | 10 | Returns either IIR second-order or IIR fourth-order filter stages according to filter type. If filter type is Lowpass or Highpass, this node returns IIR second-order filter stages. If filter type is Bandpass or Bandstop, this node returns IIR fourth-order filter stages. |
Default: Auto Select
filter type
The passband of the filter.
| Name | Description |
|---|---|
| Lowpass |
Uses a lowpass filter. |
| Highpass |
Uses a highpass filter. |
| Bandpass |
Uses a bandpass filter. |
| Bandstop |
Uses a bandstop filter. |
Default: Lowpass
low cutoff frequency
The low cutoff frequency, in Hz.
This value must be greater than zero but less than half the sampling frequency. If this input is less than zero or greater than half the sampling frequency, this node returns an error as well as an empty array for reverse coefficients and forward coefficients.
Default: 0.125
high cutoff frequency
The high cutoff frequency, in Hz. This value must observe the Nyquist criterion.
The node places the following restrictions on this parameter according to filter type:
| filter type | Restrictions |
|---|---|
| Lowpass or Highpass | The node ignores this input. |
| Bandpass or Bandstop | This value must be greater than low cutoff frequency and less than half of sampling frequency. |
Default: 0.45
order
The order of the IIR filter.
This input must be greater than zero. If it is not, the node returns an error as well as an empty array for Reverse Coefficients and Forward Coefficients in the output.
error in
Error conditions that occur before this node runs.
The node responds to this input according to standard error behavior.
Standard Error Behavior
Many nodes provide an error in input and an error out output so that the node can respond to and communicate errors that occur while code is running. The value of error in specifies whether an error occurred before the node runs. Most nodes respond to values of error in in a standard, predictable way.
Default: No error
sampling frequency
The sampling frequency, in Hz.
sampling frequency must be greater than zero. If this input is less than or equal to zero, this node returns an error as well as an empty array for reverse coefficients and forward coefficients.
Default: 1
filter
Output IIR cascade filter.
filter structure
Structure of the output filter.
forward coefficients
The forward coefficients of the IIR cascade filter.
reverse coefficients
The reverse coefficients of the IIR cascade filter.
sampling frequency
The sampling frequency in Hz.
error out
Error information.
The node produces this output according to standard error behavior.
Standard Error Behavior
Many nodes provide an error in input and an error out output so that the node can respond to and communicate errors that occur while code is running. The value of error in specifies whether an error occurred before the node runs. Most nodes respond to values of error in in a standard, predictable way.
Where This Node Can Run:
Desktop OS: Windows
FPGA: Not supported
Web Server: Not supported in VIs that run in a web application