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參數資料
| 型號： | ZL38002QDG |
| 廠商： | ZARLINK SEMICONDUCTOR INC |
| 元件分類： | 數字傳輸電路 |
| 英文描述： | Low-Voltage Acoustic Echo Canceller With Noise Reduction |
| 中文描述： | DATACOM, ISDN ECHO CANCELLER, PQFP48 |
| 封裝： | 7 X 7 MM, 1 MM HEIGHT, MS-026ABC, TQFP-48 |
| 文件頁數： | 7/47頁 |
| 文件大?。?/td> | 440K |
| 代理商： | ZL38002QDG |
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ZL38002
Data Sheet
7
Zarlink Semiconductor Inc.
1.3 Adaptation Speed Control
The adaptation speed of the acoustic echo canceller is designed to optimize the convergence speed versus
divergence caused by interfering near-end signals. Adaptation speed algorithm takes into account many different
factors such as relative double-talk condition, far end signal power, echo path change and noise levels to achieve
fast convergence.
1.4 Advanced Non-Linear Processor (ADV-NLP)
After echo cancellation, there is likely to be residual echo which needs to be removed so that it will not be audible.
The ZL38002 uses an NLP to remove low level residual echo signals which are not comprised of background noise.
The operation of the NLP depends upon a dynamic activation threshold, as well as a double-talk detector which
disables the NLP during double-talk periods.
The ZL38002 keeps the perceived noise level constant, without the need for any variable attenuators or gain
switching that causes audible “noise gating”. The noise level is constant and identical to the original background
noise even when the NLP is activated.
The NLP can be disabled by setting the NLP- bit to 1 in the AEC control registers.
1.5 Narrow Band Signal Detector (NBSD)
1
Single or multi-frequency tones (e.g,. DTMF, or signalling tones) present in the reference input of an echo canceller
for a prolonged period of time may cause the adaptive filter to diverge. The Narrow Band Signal Detector (NBSD) is
designed to prevent this divergence by detecting single or multi-tones of arbitrary frequency, phase, and amplitude.
When narrow band signals are detected, the filter adaptation process is stopped but the echo canceller continues to
cancel echo.
The NBSD can be disabled by setting the NB- bit to 1 in the MC control registers.
1.6 Howling Detector (HWLD)1
The Howling detector is part of an Anti-Howling control, designed to prevent oscillation as a result of positive
feedback in the audio paths.
The HWLD can be disabled by setting the AH- bit to 1 in the (MC) control register.
1.7 Programmable High Pass Filter
Programmable high pass filters are place at the Sin and Rin ports. These filters have two functions, one to remove
any DC offset that may be present on either the Rin or the Sin port and two, to filter low frequency noise such as
road noise (below 300 Hz).
The offset null filters can be disabled by setting the HPF- bit to 1 in the AEC control registers.
1.8 Limiters
To prevent clipping in the echo paths, two limiters with variable thresholds are provided at the outputs.
1.9 User Gain
The user gain function provides the ability for users to adjust the audio gain on all paths. This gain is adjustable
from -24 dB to +21 dB in 3 dB steps for the Sout and Rout paths. It is important to use ONLY this user gain function
to adjust the speaker volume. The user gain function in the ZL38002 is optimally placed outside the echo path such
1. Patented
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| ZL38003GMG2 | 制造商:Microsemi Corporation 功能描述:ECHO CANCELLER CHIP 1CH G.711/G.712 W/OUT TONE DETECTION 81C - Trays 制造商:MICROSEMI CONSUMER MEDICAL PRODUCT GROUP 功能描述:IC ECHO CANCEL DUAL CODEC 81CBGA 制造商:Microsemi Corporation 功能描述:IC ECHO CANCEL DUAL CODEC 81CBGA |
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