Chapter 2
NI 5450 Overview
NI PXIe-5450 User Manual
2-24
ni.com
FIR Filter Type: Flat
Passband Value: 0.40
This lowpass filter is designed to give a flat response until the passband
value. The passband value is a fraction of the I/Q Rate coming into the FIR
filter. Use the Flat Filter Passband property or the
NIFGEN_ATTR_OSP_FIR_FILTER_FLAT_PASSBAND
attribute to set the
passband value.
Caution
The Flat filter stopband does not begin until 0.6 ×
I/Q Rate
. If you provide data
that has frequency content above 0.4 ×
I/Q Rate
, then aliasing occurs in the output
spectrum. NI recommends you keep all frequency content below 0.4 ×
I/Q Rate
when using
the Flat filter.
The following diagram shows the Flat Filter response with a passband of
0.4. The frequency axis is scaled as a fraction of the I/Q Rate.
–
–
–
–
–
–
–
–
–
–
–20
–
–10
–
0
–
10
–30
–40
–50
M
a
gnit
u
de (dB)
–60
–70
–80
–90
0
0.1
0.2
0.3
0.4
0.5
Fre
qu
ency (Hz)
0.7
0.8
0.9
0.6
–100
–
–
–
–
–
–
–
–
–
1
–
