US 6,208,732 B1 · Switched hybrid circuit for use with digital subscriber lines

Abstract

The present invention provides a switched impedance matching network which may be implemented in a hybrid circuit of a digital subscriber line (DSL) system, or in any other wire-bound communications system for which two-wire-to-four-wire conversion, and vice versa, must be accomplished. In accordance with the preferred embodiment of the present invention, the matching network comprises switchable circuit modules of discrete-valued resistor and capacitor components. Preferably, the circuit modules are assembled into an array of buffered first-order RC circuits. The buffers comprise amplifiers that are switched on or off to control the switching of the circuit modules. The buffer amplifiers also isolate the individual circuit modules from each other and eliminate the need to implement transmission switches between the modules. The switching of the buffer amplifiers clears or blocks the transmission paths between the individual modules, thereby providing the optimum path through the module array. By controlling the transmission paths through the circuit module array, the balancing impedance of the matching network is optimized to match the impedance of the subscriber line in use, thus maximizing transhybrid loss and minimizing near-end echo.

Claims24

Dependent claims

A hybrid circuit for performing two-wire-to-four-wire conversion, and vice versa, the hybrid circuit comprising:

a first interface for coupling a transmitter and a receiver to a bridge circuit comprised in the hybrid circuit, the bridge circuit comprising a bridge resistance Rt;
a second interface for coupling the bridge circuit of the hybrid circuit to the subscriber loop, the subscriber loop having an input impedance ZL;
an impedance matching network comprised in the bridge circuit, the impedance matching network having a balancing impedance, the impedance matching network comprising a plurality of circuit modules;
a controller comprising logic for switching the circuit modules on and off, wherein the controller switches at least one of the circuit modules on during a period of time, the circuit module switched on during the period of time having a transfer function H(s) that substantially matches a transfer function T(s) of the bridge resistance Rt and of the input impedance of the subscriber loop ZL, whereby the balancing impedance of the matching network substantially matches the impedance of the subscriber loop.

1 more element

A hybrid circuit for performing two-wire-to-four-wire conversion, and vice versa, the hybrid circuit comprising:

means for coupling a transmitter and a receiver to a bridge circuit comprised in the hybrid circuit,
means for coupling the bridge circuit of the hybrid circuit to the subscriber loop, the subscriber loop having an impedance;
an impedance matching network comprised in the bridge circuit, the impedance matching network comprising a plurality of circuit modules, each circuit module having a predetermined impedance;
means for switching the circuit modules on and off, wherein said means for switching the circuit modules on and off switches at least two of the circuit modules on during a period of time to form a cascade circuit, whereby the impedance matching network is provided with a balancing impedance, the balancing impedance substantially matching the impedance of the subscriber loop.

1 more element

A method for setting a balancing impedance for a hybrid circuit, the hybrid circuit connecting a subscriber loop to a central office, the bridge circuit comprising a bridge resistance Rt the balancing impedance substantially matching an input impedance ZL of the subscriber loop, the method comprising the steps of:

switching on different combinations of circuit modules comprised in an impedance matching network of the hybrid circuit to alter the impedance of the impedance matching network, wherein the combination of circuit modules switched on at any given instant in time has a transfer function H(s);
measuring a transhybrid power loss of the hybrid circuit for each combination of circuit modules that have been switched on;
selecting the combination of circuit modules that result in the maximum transhybrid power loss and thus the minimum near-end echo;
and
switching on the selected combination of circuit modules to form a cascade circuit having a transfer function H(s) that substantially matches a transfer function T(s) formed by the bridge resistance Rt and by the input impedance ZL of the subscriber loop.

2 more elements

Dependencies are inferred from the claim text.

Switched hybrid circuit for use with digital subscriber lines

Life of this patent

Switched hybrid circuit for use with digital subscriber lines

Life of this patent

Abstract

Claims24