Line Equalizer for a Digital Subscriber Loop Employing Switched Capacitor Technology

A new line equalizer system for time compression burstmode digital suhscriber loop transmission that can equalize a line with multiple bridged taps (BT\´s) is developed. Using the developed equalizer, up to 5 km (0.4 mmφ) line length and four BT connections can be equalized at a data rate of 80 kbits/s in each direction. The equalizer is composed of a variable gain step equilizer, a decision feedback automatic equalizer, and a newly developed wave difference method (WDM) timing extraction PLL. In order to fabricate the whole circuit on a single-chip LSI, most of the analog portion is organized using; switched capacitor technology. In this paper, the system design concept, circuit configuration, and results of simulations and experiiments are described.