Source Impedance (Zco); Balance Impedance (Echo Canceller); Fig. 11: 3-Element Zco Model; Table 9: Examples Of Zco Coëfficients - Alcatel MTK-40131 Datasheet And User Manual

Source Impedance (Zco)

The central-office impedance, Zco, is
synthesised using digital signal proces-
sing techniques. This renders it very sta-
ble, and moreover programmable by
the user by means of coefficients which
are loaded via the GCI. Real or com-
plex Zco's can be synthesised, using the
common 3-element model (Rs, Rp, Cp;
see fig 11). The Zco setting is common
for both lines. Both real and complex
Zco's can be programmed to address
the local requirements of specifications
world-wide, and cover the range:
Rs

Fig. 11: 3-element Zco model.

Balance Impedance
(Echo Canceller)
The balance impedance (model of the
line+set impedance used to separate
the receive and transmit signals in the
'hybrid') is independently programma-
ble (though is the same for both
Table 9: Examples of ZCO Coefficients
Rs Rp Cp
Belgium 600 0 0
Germany 220 820 115nF 0
Europe 270 750 150nF 0
ZCO850 850 0 0
ZCO900 900 0 0
h0 h1 h2
Belgium 4 -22 105
Germany -31 48 1
Europe 3 -23 118
ZCO850 4 -22 105
ZCO900 4 -22 105
Using the default coefficient values, the
return loss when measured against
600Ω (using 0dBm input signal level) is
better than 20dB in the 300 to 3400
Hz band, and better than 10 dB at 10
kHz.
Real impedances: 600Ω to 900Ω
Complex impedances:
Rs from 160Ω to 500Ω
Rp from 300Ω to 1000Ω
Rp//Cp pole from 725 Hz to 5kHz
Cp
Rp
channels). Default values offer echo
return loss of better than 20dB, though
optimization to specific line and set
characteristics may yield further
improvement.
ZcoSh Alfa3 ZcoA2 Rzco
0 0 3
40 9
19 7
0 0 0
0 0 0
h3 a0 c5 b0
95 0 0 0
156 0 0 0
88 0 0 0
95 0 0 0
95 0 0 0
19
MTK-40131
ZcoGamma ZcoAlfa3 Ftx
0 0 237
9 5 52
15 4 122
0 0 282
0 0 290
Dzd0 Dzd1
1 1
0 0
0 0
1 1
1 1
Ap Nan ACG
0 0 103
346 512 125
388 -179 125
0 0 123
0 0 126