Biomedical Engineering Reference
In-Depth Information
Index
Real (
a
n
)
Imaginary(
jb
n
)
0
2
0
DC offset
1
0.5
0.95
Fundamental (
f
0
)
2
3
2.1
2nd Harmonic
3
1.1
−
6
.
2
3
×
f
0
4
0.25
−
6
.
7
Center fold
5
1.1
6.2
Conjugate 3 ×
f
0
6
3
−2
.
1
Conjugate 2 ×
f
0
7
0.5
−0
.
95
Conjugate
f
0
FIGURE 13.6
:
Output values for an eight-sample FFT
signal flow diagram with the number of complex computation Stages as,
V
=
Log2
N
,
since
N
2
V
. In general, computation of a subsequent stage from the previous butterfly
is given by the basic butterfly equations, which reduce the number of complex operations
from
N
2
=
2
m
, and
m
is a positive
integer. The output of the FFT is shown in Fig. 13.6. Note that the first index output
is the DC value of the signal. Note that the spectrum folds about the center (index 4)
and the output values for indices, 5 through 7, are the conjugate of the output values for
indices, 1 through 3.
for the DFT to
N
Log2
N
for the FFT; where
N
=
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