A matching circuit in a communication apparatus may comprise a first inductor disposed at a primary side of a transformer; a second inductor disposed at a secondary side of the transformer; and an impedance element connected to the first inductor and the second inductor. Also, a first terminal of the first inductor may be connected to an input terminal of the transformer, a second terminal of the first inductor may be connected to a common node connected to a ground, a first terminal of the second inductor may be connected to an output terminal of the transformer, a second terminal of the second inductor may be connected to the common node, a first terminal of the impedance element may be connected to the common node, and a second terminal of the impedance element may be connected to the ground.

A matching circuit in a communication apparatus may comprise a first inductor disposed at a primary side of a transformer; a second inductor disposed at a secondary side of the transformer; and an impedance element connected to the first inductor and the second inductor. Also, a first terminal of the first inductor may be connected to an input terminal of the transformer, a second terminal of the first inductor may be connected to a common node connected to a ground, a first terminal of the second inductor may be connected to an output terminal of the transformer, a second terminal of the second inductor may be connected to the common node, a first terminal of the impedance element may be connected to the common node, and a second terminal of the impedance element may be connected to the ground.

At least one example embodiment discloses a method of determining crosstalk for at least one first line in a communication system having a plurality of second lines. The method includes obtaining at least one pilot matrix representing a sequence of pilot signals and transmitting pilot signals across the plurality of second lines in accordance with the at least one pilot matrix. The method further includes obtaining measurement vectors for the at least one first line on a plurality of subcarriers, in response to the transmitted pilot signals, determining a weighted vector, the weighted vector being a weighted combination of the measurement vectors and determining a crosstalk coupling vector based on the determined weighted vector.

A communication device includes: a signal generator configured to generate a first signal and supply the first signal to a telephone line; a terminator having a variable terminal impedance as seen from the telephone line; a detector configured to detect a difference between the terminal impedance and a line impedance of the telephone line; and a controller configured to determine the terminal impedance so that the difference is reduced.

A communication device includes: a signal generator configured to generate a first signal and supply the first signal to a telephone line; a terminator having a variable terminal impedance as seen from the telephone line; a detector configured to detect a difference between the terminal impedance and a line impedance of the telephone line; and a controller configured to determine the terminal impedance so that the difference is reduced.