A 125-MHz mixed-signal echo canceller for Gigabit Ethernet on copper wire

A discrete-time analog echo canceller is described that reduces the echo in the front end of Gigabit Ethernet twisted-pair interfaces. Echo cancellati on in the analog domain by means of four taps reduces the complexity of the digital echo canceller and crosstalk cancellers. Designed in a 0.4-mum CMO S technology, the circuit employs an LMS algorithm to adapt to the cable le ngth and impedance discontinuities, providing an echo suppression of 10 dB. The design operates at 125 MHz while consuming 43 mW from a 3-V supply.