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参数资料
| 型号： | CS6422-CS |
| 厂商： | CIRRUS LOGIC INC |
| 元件分类： | 无绳电话/电话 |
| 英文描述： | Enhanced Full-Duplex Speakerphone IC |
| 中文描述： | SPEAKER PHONE CIRCUIT, PDSO20 |
| 封装： | 0.300 INCH, MS-013, SOIC-20 |
| 文件页数： | 34/48页 |
| 文件大小： | 873K |
| 代理商： | CS6422-CS |
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CS6422
34
characteristics than white noise because of its qua-
si-periodic nature.
Research at Crystal has shown that quasi-periodic
signals cause the formation of spurious non-zero
coefficients within the adaptive filter at tap inter-
vals determined by the periodicity of the signal.
This results in small changes in period being very
destructive to the adaptive filter
’
s performance.
One mechanism the CS6422 uses to prevent this
filter corruption with speech is to pre-emphasize
the signal sent to the adaptive filter so that much of
the low frequency content is removed.
The CS6422 works very well with a speech training
signal because of the pre-emphasis filter. White
noise training signals, however, result in sub-opti-
mal performance, so when testing with white noise,
it is recommended that the pre-emphasis filters be
disabled.
4.1.1.2.2 Graded Beta
The update gain of an adaptive filter, sometimes
called the
“
beta
”
, is the rate at which the filter co-
efficients can change. If beta is too low, the adap-
tive filter will be slow to adapt. Conversely, if it is
too high, the filter will be unstable and will create
unwanted noise in the system.
In most echo canceller implementations, the beta is
a fixed value for all the filter coefficients. In some
situations, though, through knowledge of the char-
acteristics of echo path response, the beta can be
varied for groups of coefficients. This preserves
stability by allowing the beta to be higher for some
coefficients and compensating by reducing beta be-
low nominal for others.
For example, acoustic echo tends to decay expo-
nentially, so the first taps need to be larger than the
later taps. Having a beta profile that matches the
expected response path enhances the echo cancel-
ler
’
s ability to correctly and accurately model the
acoustic path. Furthermore, this has an added ben-
efit of suppressing the spurious taps mentioned in
Section 4.1.1.2.1,
“
Pre-Emphasis
”
.
The Microcontroller Interface allows four settings
for graded beta: none, 0.19 dB/ms, 0.38 dB/ms,
and 0.75 dB/ms. Use 0.75 dB/ms for acoustically
dead rooms or cars, and 0.19 dB/ms or no grading
of beta for large, or acoustically live rooms.
4.1.1.3
Update Control
As mentioned in Section 4.1.1.1,
“
Theory of Oper-
ation
”
, the update control algorithms are the heart
of any useful echo canceller implementation. Aside
from telling the adaptive filter when to adapt, they
are responsible for correcting performance when
the path changes more quickly than the filter can
respond. For example, if the adaptive filter is actu-
ally adding signal power instead of cancelling it,
the update control algorithms will reset the adap-
tive filter to cleared coefficients, forcing it to re-
start.
4.1.1.4
Speech Detection
The CS6422 detects speech by using power estima-
tors to track deviations from a background noise
power level. The power estimators filter and aver-
age the raw incoming samples from the ADC.
A background noise level is established by a regis-
ter that increases 3 dB at intervals determined by
NseRmp (Register 2, bits 11 and 10). When the
power estimator level rises, the background noise
level will slowly increase to try to match it. When
the power estimator level is below the background
noise level, the background noise level adjusts
quickly to match the power estimator level. This
method allows significant flexibility in tracking the
background noise level.
Speech is detected when the power estimator level
rises above the background noise level by a given
threshold. The half-duplex receive speech detector
threshold is set by RHDet (Register 2, bits 15 and
14), the half-duplex transmit speech detector
threshold is set by THDet (Register 1, bits 15 and
DS295F1
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相关代理商/技术参数 |
参数描述 |
|---|---|
| CS6422-CSZ | 功能描述:音频放大器 Enhanced Full-Duplex Speakerphone IC RoHS:否 制造商:STMicroelectronics 产品:General Purpose Audio Amplifiers 输出类型:Digital 输出功率: THD + 噪声: 工作电源电压:3.3 V 电源电流: 最大功率耗散: 最大工作温度: 安装风格:SMD/SMT 封装 / 箱体:TQFP-64 封装:Reel |
| CS6422-CSZ | 制造商:Cirrus Logic 功能描述:ICTelephone Speech CircuitSOP20PINPL |
| CS6422-CSZ | 制造商:Cirrus Logic 功能描述:IC TELEPHONE SPEECH CIRCUIT 20SOP |
| CS6422-CSZ/A | 功能描述:IC SPEAKERPHONE ENHANCED 20SOIC 制造商:cirrus logic inc. 系列:* 零件状态:过期 标准包装:37 |
| CS6422-CSZR | 功能描述:电信集成电路 IC Enhanced Full-Duplx Spkrphone RoHS:否 制造商:STMicroelectronics 类型:Telecom IC - Various 工作电源电压:4.75 V to 5.25 V 电源电流: 工作温度范围:- 40 C to + 85 C 安装风格:SMD/SMT 封装 / 箱体:PQFP-100 封装:Tray |
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