A full duplex analog front-end chip set for split-band and echo-canceling modems

Abstract

This paper will report on an analog CMOS three-chip set which interfaces to an associated modem digital-signal processor. The chip set performs A/D and D/A conversion, analog subtraction of replicated echo signal, filtering, automatic gain control, and analog carrier detection for split-band modems up to 2400b/s and echo-canceling modems up to 16,800b/s. Implementation was in 4μ CMOS.