The LabVIEW Digital Filter Design Toolkit contains several filter design tools that are similar to the filtering tools included with the LabVIEW Full or Professional Development System. For example, the Butterworth Coefficients VI in LabVIEW Full or Professional Development System is similar to the Butterworth Design functionality from the Digital Filter Design Toolkit. Also, the Parks-McClellan VI in LabVIEW Full or Professional Development System is similar to the Remez Design VI from the Digital Filter Design Toolkit.
In general, the Digital Filter Design Toolkit provides greater capabilities including, but not limited to, support for arbitrary phase and magnitude specifications and fixed-point filter design.
Although the two sets of VIs have similar functionality, their results might not be the same because the design algorithms are different. This document explains the major differences between the two sets of VIs, lists the similar VIs, and provides examples that demonstrate how to convert filters designed with the LabVIEW Full or Professional Development System for use in the Digital Filter Design Toolkit and vice versa.
The following list explains the main differences between the filtering VIs in the LabVIEW Full or Professional Development System and the Digital Filter Design Toolkit.
The following table lists the names of similar VIs in the LabVIEW Full of Professional Development System and the Digital Filter Design Toolkit. Although the VIs listed in the table have similar functions, their results might not be the same.
LabVIEW Full or Professional Development System
|
LabVIEW Digital Filter Design Toolkit
|
Butterworth Coefficients | DFD Butterworth Design |
Chebyshev Coefficients | DFD Chebyshev Design |
Inv Chebyshev Coefficients | DFD Inverse Chebyshev Design |
Elliptic Coefficients | DFD Elliptic Design |
Bessel Coefficients | DFD Bessel Design |
FIR Windowed Coefficients | DFD Windowed FIR Design |
Parks-McClellan | DFD Remez Design |
FIR Narrowband Coefficients | DFD Narrowband Filter Design |
Convolution | DFD Filtering |
IIR Filter | DFD Filtering |
IIR Filter with I.C. | DFD Filtering with State |
IIR Cascade Filter | DFD Filtering |
IIR Cascade Filter with I.C. | DFD Filtering with State |
FIR Narrowband Filter | DFD Narrowband Filtering |
Cascade->Direct Coefficients | DFD Convert Structure |
Because the filtering VIs in LabVIEW Full or Professional Development System are coefficients-oriented and the DFD VIs are object-oriented, you must use the DFD Utilities VIs to convert filters you designed in LabVIEW Full or Professional Development System to filters you can use with the Digital Filter Design Toolkit. Likewise, you can use the Utilities VIs to retrieve filter information from filters you designed with the Digital Filter Design Toolkit to filter signals you can use with the filtering VIs in LabVIEW Full or Professional Development System.
The following block diagram demonstrates how to apply the coefficients computed for a finite impulse response (FIR) filter in LabVIEW Full or Professional Development System to create a digital FIR filter in the Digital Filter Design Toolkit using the DFD Build Filter from TF VI.
The following block diagram demonstrates how to apply the coefficients computed for an infinite impulse response (IIR) filter in LabVIEW Full or Professional Development System to create a digital IIR filter in the Digital Filter Design Toolkit using the DFD Build Filter from Cascaded Coef VI.
The following block diagram demonstrates how to retrieve filter coefficients from a filter you designed with the Digital Filter Design Toolkit using the DFD Get TF VI and then use the coefficients to filter a signal with the IIR Filter VI in LabVIEW Full or Professional Development System.
The following block diagram demonstrates how to convert a filter from the Digital Filter Design Toolkit to an IIR filter cluster that is compatible with the IIR Filter Cluster output in the LabVIEW Full or Professional Development System filtering VIs.