PSB4860HV4.1 Lantiq, PSB4860HV4.1 Datasheet - Page 45

• Manufacturer Part Number: PSB4860HV4.1
• Manufacturer: Lantiq

Specifications of PSB4860HV4.1

• Lead Free Status / Rohs Status: Supplier Unconfirmed

2.1.4
The contains an adaptive line echo cancellation unit for the cancellation of near end
echoes. The unit has three modes.
Normal mode: The maximum echo length considered is 4 ms. This mode is always avail-
Extended mode: The maximum echo length considered is 24 ms. This mode cannot be
Superior mode: The maximum echo length considered is 4 ms. This mode is always
The line echo cancellation unit is especially useful in front of the various detectors
(DTMF, CPT, etc.). A block diagram is shown in figure 22.
Figure 22 Line Echo Cancellation Unit - Block Diagram
Input I
signal.
In normal mode the adaptation process is controlled by the three parameters MIN, ATT
and MGN. Adaptation takes place only if both of the following conditions hold:
1.
2.
With the first condition, adaptation to small signals can be avoided. The second condition
avoids adaptation during double talk. The parameter ATT represents the echo loss
provided by external circuitry. The adaptation stops if the power of the received signal
(I2) exceeds the power of the expected signal (I1-ATT) by more than the margin MGN.
In extended mode, adaptation is enabled all the time.
Data Sheet
I1
I1 I2
>
–
2
MIN
is usually connected to the line input while input I
I
able.
used while the speech encoder, the acoustic echo cancellation unit or slow
playback is active.
available. By using an additional shadow filter, the echo cancellation quality is
improved.
2
–
ATT
Line Echo Canceller
+
MGN
>
0
Adaptive
+
Filter
-
Σ
45
1
is connected to the outgoing
I
S
1
15
PSB 4860
2000-01-14