An integrated adaptive analog balancing hybrid for use in (A)DSL modems

摘要

For high speed data modems, such as those for ADSL/HDSL, full-duplex transmission at bit-rates in the range of 10 Mb/s on 2-wire copper lines requires sophisticated designs. Complex data pump algorithms, as well as high performance analog front ends are required. Transmitting data simultaneously in both directions (full duplex) over a two wire twisted pair means that modems have to handle strong echo signals (transmit signal that comes back via receive path), while the received signal is strongly attenuated by the line itself. For transmit data in frequency division mode, transmit and receive signals can be well separated by high-order analog filtering. For overlapping bandwidths, the strong echo has to be suppressed either by an analog hybrid or digitally which requires extremely high resolution A/D converter (<15 b). This paper describes an integrated analog hybrid, which reduces the resolution needed in the ADC by more than 2b.