Digital Signal Processing Reference
In-Depth Information
1
0.5
0
−0.5
−1
0
50
100
150
200
(a) The Original Sequence (1st 225 Samples)
1
0.5
0
−0.5
−1
0
50
100
150
200
(b) The Decimated Sequence (1st 225 Samples)
Figure 3.29:
(a) Original sequence; (b) Result from taking every 2nd sample of sequence at (a), after
suitably lowpass filtering.
• To maintain the same apparent output frequency after decimation, compute the necessary post-
decimation sample rate
SR
New
as follows:
SR
Orig
D
where
D
is the decimation factor and the original, pre-decimation sample rate is
SR
Orig
.
• If the sample rate is not to be changed, then the post-decimation apparent output frequency
F
New
is computed as follows:
SR
New
=
F
New
=
F
Orig
·
D
3.16.3 COMBINING INTERPOLATION WITH DECIMATION
Based on what we've learned about interpolation and decimation, it should be obvious that we can alter
sample rate by (theoretically) any whole number ratio. For example, if the original sample rate is 44,100
