National Instruments 320571-01 用户手册
Chapter 2
NI-DSP Analysis VI Reference
NI-DSP SRM for LabVIEW for Windows
2-25
Part 3: NI-DSP Function Reference
DSP Equi-Ripple BandStop
Generates a bandstop FIR digital filter
with equi-ripple characteristics using the
Parks-McClellan algorithm and number
of taps, lower pass frequency, higher
pass frequency, lower stop frequency,
higher stop frequency, and sampling
frequency. The VI then filters the input
sequence X to obtain the bandstop
filtered linear-phase sequence Filtered
Data.
with equi-ripple characteristics using the
Parks-McClellan algorithm and number
of taps, lower pass frequency, higher
pass frequency, lower stop frequency,
higher stop frequency, and sampling
frequency. The VI then filters the input
sequence X to obtain the bandstop
filtered linear-phase sequence Filtered
Data.
The first passband region of the filter
goes from zero (DC) to the lower pass
frequency. The stopband region goes
from the lower stop frequency to the higher stop frequency, and the second passband region goes from the higher
pass frequency to the Nyquist frequency.
goes from zero (DC) to the lower pass
frequency. The stopband region goes
from the lower stop frequency to the higher stop frequency, and the second passband region goes from the higher
pass frequency to the Nyquist frequency.
higher pass freq must be greater than higher stop freq and observe the Nyquist criterion:
0 < f
0
< f
1
< f
2
< f
3
≤
0.5f
s
,
where f
0
is the lower pass freq, f
1
is the lower stop freq, f
2
is the higher stop freq, f
3
is the higher pass
freq, and f
s
is the sampling freq. If any of these conditions is violated, the VI returns an error. higher
pass freq defaults to 0.4.
lower pass freq must be greater than zero. If lower pass freq is less than or equal to 0, the VI returns
an error. lower pass freq defaults to 0.1.
an error. lower pass freq defaults to 0.1.
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 odd and must be greater than 0. If the number of taps is an even number or is less
than or equal to zero, the VI returns an error. # of taps defaults to 31.
than or equal to zero, the VI returns an error. # of taps defaults to 31.
lower stop freq must be greater than lower pass freq. If lower stop freq is less than or equal to lower
pass freq, the VI returns an error. lower stop freq defaults to 0.2.
pass freq, the VI returns an error. lower stop freq defaults to 0.2.
higher stop freq must be greater than lower stop freq. If higher stop freq is less than or equal to
lower stop freq, the VI returns an error. higher stop freq defaults to 0.3.
lower stop freq, the VI returns an error. higher stop freq defaults to 0.3.
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.