ZL50233GDC ZARLINK [Zarlink Semiconductor Inc], ZL50233GDC Datasheet - Page 7

• Manufacturer Part Number: ZL50233GDC
• Description: 4 Channel Voice Echo Cancellor
• Manufacturer: ZARLINK [Zarlink Semiconductor Inc]

Data Sheet
Each echo canceller contains the following main elements (see Figure 4).
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Each echo canceller in the ZL50233 has four functional states: Mute, Bypass, Disable Adaptation and Enable
Adaptation. These are explained in the section entitled Echo Canceller Functional States.
1.1
The adaptive filter adapts to the echo path and generates an estimate of the echo signal. This echo estimate is then
subtracted from Sin. For each group of echo cancellers, the adaptive filter is a 1024 tap FIR adaptive filter which is
divided into two sections. Each section contains 512 taps providing 64ms of echo estimation. In Normal
configuration, the first section is dedicated to channel A and the second section to channel B. In Extended Delay
configuration, both sections are cascaded to provide 128ms of echo estimation in channel A. In Back-to Back
configuration, the first section is used in the receive direction and the second section is used in the transmit
direction for the same channel.
Adaptive Filter for estimating the echo channel
Subtractor for cancelling the echo
Double-Talk detector for disabling the filter adaptation during periods of double-talk
Patented Advanced Non-Linear Processor for suppression of residual echo, with comfort noise injection
Disable Tone Detectors for detecting valid disable tones at send and receive path inputs
Narrow-Band Detector for preventing Adaptive Filter divergence from narrow-band signals
Offset Null filters for removing the DC component in PCM channels
0 to -12dB level adjusters at all signal ports
Parallel controller interface compatible with Motorola microcontrollers
PCM encoder/decoder compatible with /A-Law ITU-T G.711 or Sign-Magnitude coding
(channel N)
(channel N)
Path Change detector for fast reconvergence on major echo path changes
Instability Detector to combat instability in very low ERL environments
Rout
Sin
Adaptive Filter
/A-Law/
Linear
Linear/
/A-Law
0 to -12dB
Level Adjust
Disable Tone
Programmable Bypass
Detector
Instability
Detector
0 to -12dB
Level Adjust
Figure 4 - Functional Block Diagram
Offset
Null
Echo Canceller (N), where 0 < N < 3
Zarlink Semiconductor Inc.
-
Narrow-Band
0 to -12dB
Level Adjust
Detector
Non-Linear
Processor
Microprocessor
Double - Talk
Detector
Interface
MuteR
Offset
0 to -12dB
Null
Level Adjust
Path Change
MuteS
Disable Tone
Detector
Detector
/A-Law/
Linear
Linear/
/A-Law
(channel N)
(channel N)
ZL50233
Sout
Rin
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