US 7,212,627 B2 · Line interface with analog echo cancellation

Abstract

A line interface performs echo cancellation without the use of a hybrid filter network and includes a transmit path having a line driver, a single matching network terminating the line, and a single transformer. The transformer uses split windings on both the primary side and the secondary (line) side. Each half of the primary side is tapped to obtain a turns ratio of N1:N2, while each half of the secondary side of the transformer has N windings. The single matching impedance is coupled in parallel between the first winding and the second winding on each half of the primary side. Either the voltage across the matching impedance or the voltage across the receive terminals is bootstrapped to the receive signal through multiple negative feedbacks. The transfer function of the line driver is shaped as a first-order high-pass filter (HPF) to reject any out-of-band noise and distortion components.

Claims18

Dependent claims

A line interface for use in a transceiver system, the line interface comprising a hybrid circuit including a single transformer and a single matching circuit, the transformer couplable on a primary side to a transmit amplifier and to a receive amplifier and couplable on a secondary side to a communication medium, each side of the transformer having split windings, each half of the primary side further split into a first winding having a first number of turns and a second winding having a second number of turns, the first winding and the second winding coupled in series on each half of the primary side, the single matching circuit having a matching impedance less than a line impedance and coupled in parallel between the first windings and the second windings on each half of the primary side, the line interface further comprising a multiple negative-feedback network for causing the matching impedance to appear larger than its actual value as seen by the communication medium on the secondary side and to appear with its actual value at the output of the transmit amplifier.

A transceiver system for use in a communication device, the transceiver system comprising:

a transmit circuit including a transmit amplifier having differential inputs and differential outputs;
a receive circuit including a receive amplifier having differential inputs and differential outputs;
and
a hybrid circuit coupled to the differential outputs of the transmit circuit and to the differential inputs of the receive circuit, the hybrid circuit including a single transformer and a single matching circuit, the transformer coupled on a primary side to the differential outputs of the transmit amplifier and to the differential inputs of the receive amplifier and coupled on a secondary side to a communication medium, each side of the transformer having split windings, each half of the primary side further split into a first winding having a first number of turns and a second winding having a second number of turns, the first winding and the second winding coupled in series on each half of the primary side, the single matching circuit having a matching impedance less than a line impedance and coupled in parallel between the first windings and the second windings on each half of the primary side, the transceiver system further comprising a multiple negative-feedback network for causing the matching impedance to appear larger than its actual value as seen by the communication medium on the secondary side and to appear with its actual value at the output of the transmit amplifier.

1 more element

Dependencies are inferred from the claim text.

Line interface with analog echo cancellation

Life of this patent

Line interface with analog echo cancellation

Life of this patent

Abstract

Claims18