msm7603 Oki Semiconductor, msm7603 Datasheet - Page 19
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msm7603
Manufacturer Part Number
msm7603
Description
Echo Canceler
Manufacturer
Oki Semiconductor
Datasheet
1.MSM7603.pdf
(20 pages)
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EXPLANATION OF TERMS
Attenuating Function :
Echo Attenuation :
Echo Delay Time :
Acoustic Echo :
Telephone Line Echo :
Gain Control Function :
Center Clipping Function : This function forces the SOUT output to a minimum value when
Double Talk Detection :
Howling Detection :
Echo Return Loss (ERL) :
PHS :
This function prevents howling and controls the noise level with
the attenuator for the RIN input and SOUT output. Refer to the
explanation of pins (ATT pin).
If there is talking (input only to RIN) in the path of a rising echo
arises, the echo attenuation refers to the difference in the echo
return loss (canceled amount) when the echo canceler is not used
and when it is used.
Echo attenuation = (SOUT level during through mode operation)
– (SOUT level during echo canceler operation) [dB]
This is the time from when the signal is output from ROUT until it
returns to SIN as an echo.
When using a hands-free phone, for example, the signal output
from the speaker echoes and is input again to the microphone. The
return signal is referred to as acoustic echo.
This is a signal which is delayed midway in a telephone line and
returns as an echo, due to reasons such as a hybrid impedance
mismatch.
This function prevents howling and controls the sound level by
with a gain controller for the RIN input. Refer to the explanation
of pins (GC pin).
the signal is below –57 dBm0. Refer to the explanation of pins (NLP
pin).
Double talk refers to a state in which the SIN and RIN signals are
input simultaneously. In a double talk state, a signal other than the
echo signal which is to be canceled can be input to the SIN input,
resulting in malfunction.
The double talk detector prevents such malfunction of the canceler.
This is the oscillating state caused by the acoustic coupling between
the loud speaker and the microphone during hands-free talking.
Howling not only interferes with talking, but can also cause
malfunction of the echo canceler.
The howling detector prevents such malfunction and howling.
When the signal output from ROUT returns to SIN as an echo, ERL
refers to how much loss there is in the signal level during ROUT.
ERL = (ROUT level) – (SIN level of the ROUT signal which returns
as an echo) [dB]
If ERL is positive (ROUT > SIN), acts as an attenuator.
If ERL is negative (ROUT < SIN), acts as an amplifier.
Personal Handyphone System
MSM7603/7603B
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