ANALOG PRE-CIRCUIT IN DIGITAL SUBSCRIBER LINE COMMUNICATION SYSTEM AND ITS PROCESSING METHOD

摘要

PROBLEM TO BE SOLVED: To simplify the constitution of an analog pre-function for a asynchronous digital subscriber line communication modem and to integrate it in a single integrated circuit. SOLUTION: An analogue pre-function 12 is integrated in a single integrated circuit and it contains a transmission side and a reception side. The transmission side contains an over sampler 44C and a digital filter 46C and they operate to improve the sampling rate of digital data. Consequently, down stream analog LPF 50C is realized by a comparatively simple low-order filter since a DA converter 48C operates by an over-sampling method. For reducing the complicated reception side analog LPF 58C, a digital filter 64C is contained in the down stream of an AD converter 62C. For conquering the influence of line attenuation to high frequency down stream transmission, a remote DSL modem contains an equalizer function boosting signal amplitude as the frequency becomes higher.