Power efficient line driver with high performance echo cancellation for 1000BASE-T

摘要

A 1000BASE-T transceiver linked to an unshielded twisted pair (UTP) through a transformer currently transmits and receives outgoing and incoming signals via the UTP. The transceiver employs an energy efficient class B or AB line driver supplying asymmetric output currents to the transformer's primary winding terminals so that the transformer's secondary winding induces the outgoing signal on the UTP. Resistors couple the transformer's primary winding terminals to inputs of separate amplifiers producing a differential output signal mimicking the incoming 1000BASE-T signal. Since both the incoming and outgoing signals contribute to voltages appearing at the transformer's primary winding terminals, echo cancellation circuits provide additional compensating signals to the amplifier inputs for canceling echo in each amplifier input due to the resistive and reactive loading on each driver output current and arising from the asymmetric nature of the class B or AB driver's output currents.