PSB21384HV1.3 Infineon Technologies, PSB21384HV1.3 Datasheet - Page 150

• Manufacturer Part Number: PSB21384HV1.3
• Description: Telecom ICs AMuLaw/Speech CODEC w/ ST Transceiver
• Manufacturer: Infineon Technologies

Specifications of PSB21384HV1.3

• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

Data Sheet
Figure 80
Speech Comparator at the Acoustic Side
At the SCAE-input, logarithmic amplifiers compress the signal range. Hence after the
required signal processing for controlling the acoustic echo, pure logarithmic levels on
both paths are compared.
Principally, the main task of the comparator is to control the echo. The internal coupling
due to the direct sound and mechanical resonances are covered by GAE. The external
coupling, mainly caused by the acoustic feedback, is controlled by GDAE/PDAE.
The Gain of the Acoustic Echo (GAE) corresponds to the terminal couplings of the
complete telephone: GAE is the measured or calculated level enhancement between
both receive and transmit inputs of the SCAE (see figure Chapter 78). It equals the sum
of the amplification of ALS plus the gain due to the loudspeaker/microphone coupling
plus the TX-amplification of AMIC1 and GX1. To succeed in a sure differentiation
between original speech and echo, it must be guaranteed that the TX-signal does not
run into saturation due to the loudspeaker/microphone coupling. Therefore, it is
recommended to reduce the TX-gain by 10 dB in front of the SCAE at least in the loudest
loudspeaker volume step. To fulfill the sending loudness rating, this gain is realized by
the LGAX/AGCX which follows the SCAE. Of course, the GAE has to be reduced by the
same amount.
140
PSB 21381/2
PSB 21383/4
2001-03-12
Codec