AN2384 Freescale Semiconductor / Motorola, AN2384 Datasheet - Page 7

• Manufacturer Part Number: AN2384
• Description: Generic Tone Detection Using Teager-Kaiser Energy Operators on the StarCore SC140 Core
• Manufacturer: Freescale Semiconductor / Motorola

Figure 3 and the following pseudo-code show the application of the TK energy operator within a DTMF detection
context. The SC140 core and its parallel ALUs are ideally suited to this application and can take advantage of the
inherent parallelism in this DTMF tone detector.
Freescale Semiconductor
Generic Tone Detection Using Teager-Kaiser Energy Operators on the StarCore SC140 Core, Rev. 1
Approximation
Polynomial
Operator
Energy
LPF
Figure 2. DTMF Digits Represented on a Bi-Dimensional Graph
Figure 3. Four-Branch Parallelism of the DTMF Detector
(Low Frequency)
1633
1477
1336
1209
Notch Filter
High Frequency (Hz)
LPF
*
697
Operator
Average
L
+
+
+
+
Energy
Moving
LPF
770
+
+
+
+
852
+
+
+
+
Sample
941
Closest Reference Point
+
+
+
+
Approximation
Polynomial
Operator
Estimated Point
Energy
LPF
Low Frequency (Hz)
(High Frequency)
Two-Component Tone Detector for DTMF
Notch Filter
LPF
*
H
Operator
Average
Energy
Moving
LPF
7