PSB21383HV13XP Lantiq, PSB21383HV13XP Datasheet - Page 151

• Manufacturer Part Number: PSB21383HV13XP
• Manufacturer: Lantiq

Specifications of PSB21383HV13XP

• Number Of Line Interfaces: 1
• Control Interface: HDLC
• Lead Free Status / Rohs Status: Compliant

To control the acoustic feedback two parameters are necessary: GDAE-features the
actual reserve on the measured GAE. Together with the Peak Decrement (PDAE) it
simulates the echo behaviour at the acoustic side: After RX-speech has ended there is
a short time during which hard couplings through the mechanics and resonances and the
direct echo are present. Till the end of that time (
be at least equal to GAE to prevent clipping caused by these internal couplings. Then,
only the acoustic feedback is present. This coupling, however, is reduced by air
attenuation. For this in general the longer the delay, the smaller the echo being valid.
This echo behaviour is featured by the decrement PDAE.
Figure 81
Interdependence of GDAE and PDAE
According to figure 81, a compromise between the reserve GDAE and the decrement
PDAE has to be made: a smaller reserve (GDAE) above the level enhancement GAE
requires a longer time to decrease (PDAE). It is easy to overshout the other side but the
intercommunication is harder because after the end of the speech, the level of the
estimated echo has to be exceeded. On the contrary, with a higher reserve (GDAE*) it
is harder to overshout continuous speech or tones, but it enables a faster
intercommunication because of a stronger decrement (PDAE*).
Two pairs of coefficients, GDSAE/PDSAE when speech is detected, and GDNAE/
PDNAE in case of noise, offer a different echo handling for speech and non-speech.
Data Sheet
141
t
) the level enhancement VAE must
PSB 21381/2
PSB 21383/4
2001-03-12
Codec