Design aspects and field trial results of a subscriber loop transceiver for the ISDN basic access

The authors deal with activities and developments carried out in Italy concerning the subscriber loop transceiver and transmission system structure for the ISDN basic access. The ECBM (echo canceller burst model) transceiver is implemented (in the present introductory solution) by a dual-chip version: an analog section and a digital one. The analog section is implemented by a full custom technique using 1.5 μm double polysilicon layer CMOS technology. It contains filtering/equalization structures for transmission/receiving functions, a line driver to drive the line coupling transformer directly, and an 11 bit D/A converter used, in conjunction with the processing section, to perform the echo cancellation and the digital line equalization. The digital section implements the digital signal processor to perform the echo cancellation and DFE algorithm, timing extraction, frame formatting and decoding, and the activation/deactivation procedures. The transmission system structure and functionalities of the ISDN basic access are described. Laboratory and field trial results are summarized