National Instruments 320571-01 用户手册

The arrays Forward Coefficients in/out and Feedback Coefficients in/out must have a size of at least (order + 1)
for lowpass and highpass filters.  The arrays Forward Coefficients in/out and Feedback Coefficients in/out must
have a size of at least (2*order + 1) for bandpass and bandstop filters.

Generates the set of filter
coefficients to implement an
IIR filter as specified by the
Chebyshev filter model.
You can then pass
coefficients to the DSP IIR
Filter VI to filter a sequence
of data.

filter type specifies the passband of the filter.  It has four options:

0:  lowpass.
1:  highpass.
2:  bandpass.
3:  bandstop.

filter type defaults to lowpass.

sampling freq : fs is the sampling frequency and must be greater than 0.  If it is less than or equal to
zero, the VI returns an error.  sampling Freq : fs defaults to 1.0.

high cutoff freq: fh is the high cutoff frequency.  The VI ignores this parameter when filter type is
lowpass.  high cutoff freq: fh defaults to 0.45.

low cutoff freq: fl is the low cutoff frequency.  The VI ignores this parameter when filter type is
highpass.  low cutoff freq: fl defaults to 0.125.

Note: fh and fl must observe the Nyquist criterion:  0 

≤

 fl 

≤

 fh 

≤

 fs /2.

ripple must be greater than 0.  If ripple is less than or equal to zero, the VI returns an error.  ripple
defaults to 0.1.

order must be greater than zero.  If order is less than or equal to zero, the VI returns an error.  order
defaults to 2.

Forward Coefficients in is a DSP Handle Cluster that indicates the memory buffer on the DSP board
that will contain the forward coefficients.

Feedback Coefficients in is a DSP Handle Cluster that indicates the memory buffer on the DSP board
that will contain the feedback coefficients.

Forward Coefficients out is a DSP Handle Cluster that is identical to the Forward Coefficients in, but
with the forward coefficients already stored in the memory buffer on the DSP board.