Patent ID: 6940973

Claim:
A noise cancellation circuit for a communications channel comprising a differential signal path and a common mode signal path connected to respective inputs of a summing device, the differential signal path comprising input means connected to the channel for receiving a differential signal therefrom and supplying the differential signal to a first of the inputs of the summing device, the common mode signal path comprising extraction means coupled to the channel for extracting therefrom a common mode signal, and coupling means for coupling at least part of the extracted common mode signal to a second of the inputs of the summing device as a common mode noise signal, the coupling means comprising a circuit element having a fixed capacitance equivalent to stray capacitance coupling between an input and an output, respectively, of the input means, the circuit further comprising delay means for compensating for phase differences between the differential signal and common mode noise signal before their application to the summing device, the summing device providing as an output signal of the noise cancellation circuit the difference between the differential signal and the common mode noise estimate signal.