Digital Signal Processing Reference
In-Depth Information
This new set of weights represents only the values after one complete cycle. These
weight values can be verified using a training program for this project. For this pro-
cedure of training the network, readjusting the weights is continuously repeated
until the output values converge to the set of desired output values. For this project,
the training program is such that the training process can be halted by the user, who
can still use the resulting weights.
This project was implemented on the C30 and can be transported to the C6x.
Two sets of inputs were chosen: a sinusoidal and a square wave input. The FFT (128-
point) of each input signal is captured and stored in a file, with a total of 4800 points:
200 vectors, each with 64 features (retaining one-half of the 128 points). Another
program scales each set of data (sine and square wave) so that the values are
between 0 and 1.
To demonstrate this project, two output values for each node are displayed on
the PC screen. Values of
+
1 for node 0 and
-
1 for node 1 indicate that a sinusoidal
input is recognized, and values of
-
1 for node 0 and
+
1 for node 1 indicate that a
square wave input is recognized.
This project was successful but was implemented for only the two sets of chosen
data. Much work remains to be done, such as training more complex sets of data
and examining the effects of different training rules based on the different signals
to be recognized.
10.23.4 Adaptive Temporal Attenuator
An adaptive temporal attenuator (ATA) suppresses undesired narrowband signals
to achieve a maximum signal-to-interference ratio. Figure 10.66 shows a block
diagram of the ATA. The input is passed through delay elements, and the outputs
from selected delay elements are scaled by weights. The output is
m
1
(
)
1
[]
[]
[
]
Â
n
i
-
=
1
0
T
C
k
,
d
=
r
k
ƒ
r
k
-
d
N
m
2
[
]
[ ]
C
,
[]
k
d
=
0
◊
m
k
=
l
D
S
Output
y
(
[
]
)
-
1
m
k
=
l
C
k
,
d
=
0
D
m
3
r
1
r
2
r
3
r
N
Input
D
1
D
2
D
N
-1
FIGURE 10.66.
Block diagram of an adaptive temporal attenuator.
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