© National Instruments
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3-7
Figure 3-5.
1 V Range, Sampled at 20 MS/s
Figure 3-6.
0.5 V Range, Sampled at 20 MS/s
1/n Decimation
Data comes in and out of the digital filter at a rate of 20 MS/s. Depending on the sample rate
requested by the user, the filtered data may be decimated by hardware to achieve a slower sample
rate than 20 MS/s.
When hardware decimates, it does so by returning every nth sample coming out of the filter. For
example, to produce a sample rate of 5 MS/s (n = 4), the hardware drops the first three samples
coming from the digital filter and then returns the fourth sample. After sending a sample, the
count starts over and the next three samples are dropped before sending the fourth. This pattern
A
m
p
lit
u
d
e
(V)
1.2
–0.2
0
0.2
0.4
0.6
0.
8
1.0
8
0
1
2
3
4
5
6
7
Time (µ
s
)
Amplit
u
de (V)
0.6
–0.1
0
0.1
0.2
0.
3
0.4
0.5
8
0
1
2
3
4
5
6
7
Time (µ
s
)
