US 5,333,194 A · Autoequalizing bidirectional-to-unidirectional hybrid network

Abstract

An autoequalizing hybrid circuit for providing a cancelation path to minimize the two-wire receive path signals that are reflected onto a two-wire transmit path from a subscriber line interface circuit is disclosed. The hybrid circuit includes a variable impedance balance network. A tone generator injects a set of equalization signals into the receive path which are used to control the setting, or equalization, of the balance network. The tone generator also generates a supervisory signal into the receive path used to monitor the performance of the balance network. A detect circuit monitors the level of the reflected equalization sidetone signals and produces balance signals whenever the equalization signals fall to a null level. The detect circuit also monitors the supervisory sidetone signals and produces a recalibration signal whenever an abrupt change in the signals indicates that the balance network is no longer adequately cancelling their reflected signals. A microprocessor controls the generation of the equalization and supervisory signals and is connected to the detect circuit for monitoring production of the balance and the recalibration signals. When the hybrid is first activated, the microprocessor initially sets the balance network impedance with reference to the balance signals. After the balance network is equalized the microprocessor directs the tone generator to produce the supervisory sidetone signals. The microprocessor then monitors the detect circuit for recalibration signals and if they are produced, reequalizes the impedance of the balance network.

Claims41

Dependent claims

A hybrid circuit for separating incoming signals on a receive path from outgoing signals on a transmit path, including:

a balance network having an adjustable impedance connected between the receive path and the transmit path;
a tone generator connected to the receive path for selectively injecting at least one equalization signal and a supervisory signal into the receive path;
a detect circuit connected to the transmit path for receiving reflected sidetone signals produced as a consequence of said signals being injected into said receive path said detect circuit producing a balance signal when a measured equalization signal sidetone is at approximately a null level, said detect circuit producing a recalibration signal when a measured supervisory sidetone signal level has an abrupt change in magnitude;
and
processor means that is connected to said balance network for controlling the adjustable impedance of said balance network impedance, that is connected to said tone generator for controlling the injection of said equalization and supervisory signals, and that is connected to said detect circuit for receiving said balance signal and said recalibration signal, said processor means equalizing an impedance of said balance network by directing said tone generator to inject said at least one equalization tone into the receive path, changing the impedance of said balance network adjustable impedance, and in response to receiving said balance signal, setting said balance network impedance, said processor means further directing said tone generating to inject said supervisory signal into said receive path and in response to receiving and recalibrate signal, reequalizing said balance network impedance.

2 more elements

A method of equalizing the impedance of a hybrid circuit having a balance network and having an adjustable impedance connected between a receive path and a transmit path including the steps of:

injecting equalization signals into the receive path and changing a balance network impedance;
measuring equalization sidetone signals that appear on the transmit path as a consequence of said equalization signals being injected into the receive path and determining a balance network impedance when said equalization sidetone signals are approximately at a null level;
setting the balance network impedance;
injecting supervisory signals into the receive path;
monitoring supervisory sidetone signals that appear on the transmit path as a consequence of said supervisory signals being injected into the receive path;
and
when a select supervisory sidetone signal characteristic is detected, reequalizing the balance network impedance.

4 more elements

A hybrid circuit for separating incoming signals on a receive path from outgoing signals on a transmit path, including:

a balance network having an adjustable impedance and a variable resistor connected between the receive path and the transmit path;
a tone generator connected to the receive path for selectively injecting equalization tones into the receive path;
a detect circuit connected to the transmit path for receiving reflected sidetone signals produced as a consequence of said equalization tones being injected into said receive path, said detect circuit producing a balance signal when said measured equalization signal sidetone is approximately at a null level;
and
processor means that is connected to said balance network for controlling said balance network impedance and said variable resistor, that is connected to said tone generator for controlling the injection of said equalization tones, and that is connected to said detect circuit for receiving said balance signal, said processor means equalizing said balance network impedance by directing said tone generator to inject a first equalization tone into the receive path, adjusting said variable resistor until said balance signal is produced to obtain a first equalization sidetone null impedance level, said first equalization sidetone null impedance level forming at least part of a first impedance component, injecting a second equalization tone into the receive path, adjusting said variable resistor until said balance signal is produced to obtain a second equalization sidetone null impedance level, said second equalization sidetone null impedance level forming at least part of a second impedance component, comparing said first and second impedance components, and based on said comparison, setting said balance network impedance.

2 more elements

A method of equalizing an impedance of a hybrid circuit imcluding a balance network having an adjustable impedance connected between a receive path and a transmit path comprising the steps of:

injecting a first equalization tone into the receive path, adjusting the balance network impedance and measuring equalization sidetones that appear on the transmit path to obtain a first equalization sidetone null impedance level forming at least part of a first impedance component;
injecting a second equalization tone into the receive path, adjusting the balance network impedance and measuring equalization sidetones that appear on the transmit path to obtain a second equalization sidetone null impedance level different from said first equalization sidetone null impedance level forming at least part of a second impedance component;
comparing said first and second impedance components;
and
setting the balance network impedance based on the comparison.

2 more elements

Dependencies are inferred from the claim text.

Autoequalizing bidirectional-to-unidirectional hybrid network

Life of this patent

Autoequalizing bidirectional-to-unidirectional hybrid network

Life of this patent

Abstract

Claims41