RS8973 Mindspeed Technologies, RS8973 Datasheet - Page 83

• Manufacturer Part Number: RS8973
• Description: Single-chip Sdsl/hdsl Transceiver
• Manufacturer: Mindspeed Technologies

RS8973
Single-Chip SDSL/HDSL Transceiver
4.1.1 Compromise Hybrid
N8973DSD
transmission line. This model generates an approximation of the transmitted
signal’s echo. The echo replica is then subtracted from the signal on the line
transformer to generate a first order approximation of the received signal. The
RS8973 includes a dual differential analog input to accommodate a hybrid using
only passive components.
simulations that optimize the echo cancellation functions at the frequencies of
interest for the loops as specified in the ETS TS 101 135 (formerly ETR 152)
standards. In addition, maximum reach was taken into consideration for the
hybrid design.
the compromise hybrid transfer function be highly linear. Therefore, we
recommend that all capacitors used in the hybrid be NPO ceramic capacitors
because of their highly linear characteristics.
needed to reduce the signal level input to the ADC. This eliminates ADC
overflow for short loops and increases the resolution of the digitized receive
signal for better digital signal processing performance. In addition, because the
digital EC cannot cancel out very low frequency signals, it is very important that
the analog EC cancel out most of the low frequency echo.
Table 4-1. Compromise Hybrid Component Values
NOTE:
The purpose of the compromise hybrid is to model the impedance of the
Hybrid component values have been determined by means of calculations and
To maximize digital echo cancellation within the RS8973, it is important that
Although the RS8973 contains a digital echo canceller (EC), the hybrid is
Table 4-1
All capacitors in the signal path should be film or NPO ceramic capacitors.
lists compromise hybrid component values.
Hybrid Components
Preliminary Information
R11, R12
R1, R4
C1, C4
R2, R3
C2, C3
R5, R6
Conexant
4.0 Interconnection Information
4.1 Transmission Line Interface
1.58 k
6.04 k
2.0 k
5.1 k
Value
2.3 nF
1 nF
4-3