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Chapter 2
NI-DSP Analysis VI Reference
NI-DSP SRM for LabVIEW for Windows
2-23
Part 3: NI-DSP Function Reference
DSP Equi-Ripple BandPass
Generates a bandpass FIR filter
with equi-ripple characteristics
using the Parks-McClellan
algorithm and the number of taps,
lower stop frequency, higher stop
frequency, lower pass frequency,
higher pass frequency, and
sampling frequency. The VI then
filters the input sequence X to
obtain the bandpass filtered linear-
phase sequence Filtered Data.
with equi-ripple characteristics
using the Parks-McClellan
algorithm and the number of taps,
lower stop frequency, higher stop
frequency, lower pass frequency,
higher pass frequency, and
sampling frequency. The VI then
filters the input sequence X to
obtain the bandpass filtered linear-
phase sequence Filtered Data.
The first stopband of the filter
region goes from zero (DC) to the
lower stop frequency. The passband region goes from the lower pass frequency to the higher pass frequency, and
the second stopband region goes from the higher stop frequency to the Nyquist frequency.
region goes from zero (DC) to the
lower stop frequency. The passband region goes from the lower pass frequency to the higher pass frequency, and
the second stopband region goes from the higher stop frequency to the Nyquist frequency.
higher pass freq must be greater than lower pass freq frequency. If higher pass freq is less than or
equal to lower pass freq, the VI returns an error. higher pass freq defaults to 0.3.
equal to lower pass freq, the VI returns an error. higher pass freq defaults to 0.3.
lower pass freq must be greater than the lower stop freq. If lower pass freq is less than or equal to
lower stop freq, the VI returns an error. lower pass freq defaults to 0.2.
lower stop freq, the VI returns an error. lower pass freq defaults to 0.2.
X is a DSP Handle Cluster that indicates the memory buffer on the DSP board that contains the input
data array.
data array.
# of taps must be greater than 0. If the number of taps is less than or equal to zero, the VI returns an
error. # of taps defaults to 32.
error. # of taps defaults to 32.
lower stop freq must be greater than zero. If lower stop freq is less than or equal to zero, the VI
returns an error. lower stop freq defaults to 0.1.
returns an error. lower stop freq defaults to 0.1.
higher stop freq must be greater than higher pass freq and must observe the Nyquist criterion:
0 < f
0
< f
1
< f
2
< f
3
≤
0.5f
s
,
where f
0
is lower stop freq, f
1
is lower pass freq, f
2
is higher pass freq, f
3
is the higher stop freq, and
f
s
is the sampling frequency. If any of these conditions is violated, the VI returns an error. higher stop
freq defaults to 0.4.
sampling freq: fs defaults to 1.0.
Filtered Data in is a DSP Handle Cluster that indicates the memory buffer on the DSP board that will
contain the filtered data output.
contain the filtered data output.
Filtered Data out is a DSP Handle Cluster that is identical to Filtered Data in, but with the filtered
data already stored in the memory buffer on the DSP board. Because the VI filters via convolution, the
number of elements, k, in Filtered Data is as follows:
data already stored in the memory buffer on the DSP board. Because the VI filters via convolution, the
number of elements, k, in Filtered Data is as follows:
k = n + m - 1,
where n is the number of elements in X, and m is the number of taps.