Method and apparatus for compensating for an echo signal component in telecommunication systems
View Patent ↗A balanced hybrid circuit for compensating for transmission echo signal in a modem. The hybrid circuit includes transmission echo compensation circuits that approximate the echo signal effects of the line and line transformer, respectively, and produce a transmission echo signal replica. A sample of the transmission signal and the replica of the transmission echo are then subtracted from the signal received on the line to produce a received signal isolated from the transmission signal and the transmission echo signal.
1. An apparatus for compensating for echo signal in a telecommunications device comprising:
a first differential transmitter having an output terminal coupled to a first transmitted signal node;
a second differential transmitter having an output terminal coupled to a second transmitted signal node;
a first current limiting resistor having a first terminal coupled to the first transmitted signal node and a second terminal coupled to a first line transformer node;
a second current limiting resistor having a first terminal coupled to the second transmitted signal node and a second terminal coupled to a second line transformer node;
a first sampling resistor having a first terminal coupled to the first line transformer node and a second terminal connected to a first received signal node;
a second sampling resistor having a first terminal coupled to the second line transformer node and a second terminal connected to a second received signal node;
a first compensation circuit having a first terminal coupled to the first transmitted signal node and a second terminal coupled to the first received signal node;
a second compensation circuit having a first terminal coupled to the first transmitted signal node and a second terminal coupled to the second received signal node;
a third compensation circuit having a first terminal coupled to the second transmitted signal node and a second terminal coupled to the second received signal node; and
a fourth compensation circuit having a first terminal coupled to the second transmitted signal node and a second terminal coupled to the first received signal node.
2. An apparatus for compensating for echo signal in a telecommunications device according to claim 1 wherein,
the first compensation circuit further comprises a first compensation resistor and a first compensation capacitor connected in series;
the second compensation circuit further comprises a second compensation resistor and a second compensation capacitor connected in series;
the third compensation circuit further comprises a third compensation resistor and a third compensation capacitor connected in series; and
the fourth compensation circuit further comprises a fourth compensation resistor and a fourth compensation capacitor connected in series.
3. An apparatus for compensating for echo signal in a telecommunications device according to claim 1 wherein,
the first terminal of the first sampling resistor is coupled to the first transmitted signal node; and
the first terminal of the second sampling resistor is coupled to the second transmitted signal node.