Table Of Contents
FIR Narrowband Filter Design (G Dataflow)
Designs a digital interpolated FIR (IFIR) filter.
Programming Patterns
You can design narrowband FIR filters using the FIR Narrowband Filter Design node, and then implement the filtering using the FIR Narrowband Filtering node. The design and implementation are separate operations, because many narrowband filters require long design times, whereas the actual filtering is fast and efficient.
filter type
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
passband frequency
stopband frequency
The stopband bandwidth.
The value for this input must be greater than 0 and less than half of sampling frequency.
Default: 0.02
center frequency
The center frequency of the filter.
The value for this input must be greater than 0 and less than half of sampling frequency.
Default: 0.2
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. If sampling frequency is less than or equal to zero, this node returns an empty cluster for IFIR filter as well as an error.
Default: 1.0
passband ripple
The ripple in the passband of the filter.
The value of this input must be greater than 0.
Default: 0.01
stopband attenuation
The attenuation in the stopband of the filter.
The value of this input must be greater than 0.
Default: 60 decibels
IFIR filter
The IFIR filter.
filter type
Filter type of the IFIR filter.
| Name | Description |
|---|---|
| Lowpass |
The IFIR filter is a lowpass filter. |
| Highpass |
The IFIR filter is a highpass filter. |
| Bandpass |
The IFIR filter is a bandpass filter. |
| Bandstop |
The IFIR filter is a bandstop filter. |
| Wideband-Lowpass |
The IFIR filter is a wideband-lowpass filter with cutoff frequencies near Nyquist. |
| Wideband-Highpass |
The IFIR filter is a wideband-highpass filter with cutoff frequencies near zero. |
interpolation
The interpolation factor M.
The model filter in this is stretched by interpolation times.
Model Filter
The coefficients of the model filter.
Image Suppressor
The coefficients of the filter image suppressor.
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.
Algorithm for Calculating the Delay for the Filter
The overall filter is a linear-phase FIR filter. This node calculates the delay for the filter using the following equation:
where
- N G is the number of elements in Model Filter
- N I is the number of elements in Image Suppressor
- M is the value of interpolation
Where This Node Can Run:
Desktop OS: Windows
FPGA: Not supported
Web Server: Not supported in VIs that run in a web application