Method and design for increasing signal to noise ratio in xDSL modems
AssigneeNortel Networks Limited
InventorsDan V. Gorcea, Carl C. Anderson, Gyula G. Jakab
Life of this patent
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Abstract
A DSL modem comprises an additional transformer and additional coils on a coupling transformer to couple a received signal on a transmission line to a receive path without loss due to an active impedance. The ratio of windings on the coils allows gain to be introduced to improve the signal to noise ratio.
Claims27
A modem comprising:
- a first transformer comprising a first coil, a second coil and a third coil;
- a second transformer comprising a fourth coil and a fifth coil;
- said fifth coil and said third coil comprising a receive path operatively coupled to a receive port;
- said fourth coil and said second coil comprising a transmit path operatively coupled to a transmit port;
- said transmit path further comprising an active impedance element introducing a loss onto said receive path;
- and
- said third and fifth coils introducing a gain into said receive path.
A method of using a modem, comprising:
- receiving a signal over a transmission line;
- coupling the signal through a first transformer to a transmit path and a receive path;
- and
- coupling the signal from the transmit path to the receive path with a second transformer to reduce losses introduced by an active impedance element in the transmit path.
The method of clam 15, wherein coupling the signal from the transmit path to the receive path comprises coupling the signal from a first coil to a second coil.
A transformer positioned in a modem, said transformer comprising:
- a first coil comprising a set of first windings;
- a second coil comprising a set of second windings;
- a third coil comprising a set of third windings;
- said first, second, and third windings having a ratio of 1:1:α, wherein cα is greater than 1 and said third coil is positioned in a receive path of the modem wherein a signal from a transmit path is coupled to the receive path with the second coil to reduce losses introduced by an active impedance element in the transmit path.
A modem comprising:
- a first transformer having first, second, and third coils, the first coil for coupling to a network having a load impedance with a value, ZL;
- a second transformer having a fourth and fifth coil, the fifth coil operatively coupled to the third coil and forming a receive port,
- a transmit power amplifier having an output coupled to the second coil through a first impedance and to the fourth coil through a second impedance;
- and
- a third impedance coupled in parallel with the fourth coil.
Dependencies are inferred from the claim text.