US 7,068,726 B1Granted

Near end cross-talk and echo avoider for bi-directional digital communications

Assignee3Com Corporation

InventorAnthony Eugene Zortea

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Abstract

A bi-directional communication link has plural channels with respective masters and slaves at respective ends of respective channels, in which each master issues a Master Tx clock, each slave constructs a Slave Rx clock frequency locked to the Master Tx clock, and a Slave Tx clock frequency locked to the Slave Rx clock. A metric processor for each master produces a metric signal indicative of resolution of a signal received by the master from the corresponding slave. A decision processor responsive to the metric processor changes the phase of the Slave Tx clock relative to the Slave Rx clock so as to maximize the metric signal. In one embodiment, the resolution is a resolution between leading and trailing edges of the received signal. In another embodiment, the resolution is a resolution between allowed amplitude levels of the received signal.

Claims11

Dependent claims

Apparatus for a bi-directional communication link having a plurality of channels, each of said channels comprising:

a master connected at a near end of the channel and a slave connected at an opposite end of the channel, said master comprising:
(a) a first transmitter coupled to the channel and having a master Tx clock signal;
and
(b) a first receiver coupled to the channel and comprising;
(i) an analog-to-digital (A/D) converter that periodically samples a signal incoming over the channel to yield a received signal;
(ii) a clock recovery circuit that generates a master Rx clock from a clock signal embedded in the received signal;
and
(iii) a metric processor, connected to an output of said A/D converter, that produces a metric signal reflective of amplitude differences between the received signal and allowed amplitude levels for the received signal;
and
said slave comprising:
(a) a second receiver coupled to the channel and comprising a clock recovery circuit for generating a Slave Rx clock from a signal received over the channel and transmitted from the master;
(b) a second transmitter coupled to the channel and having a Slave Tx clock signal, said master Rx clock signal being frequency locked to said Slave Tx clock signal;
and
(c) a first delay element for generating said Slave Tx clock signal by controllably delaying said Slave Rx clock signal;
and
wherein said apparatus further comprises a decision processor, connected to said master and responsive to said metric signal, for determining a delay value to be provided by said first delay element in the slave which will maximize the metric signal and issuing a command, via the first transmitter and the channel, to said second receiver in order to set a delay provided by said first delay element to said delay value, so as to reduce distortion caused by near end cross-talk and echo in signals received over the channel, by the first receiver and thus facilitate clock and data recovery by the first receiver.

13 more elements

Apparatus for a bi-directional communication link having a plurality of channels with a master and a slave at respective ends of each one of the channels so as to define respective pluralities of masters and slaves, the master issuing a Master Tx clock, the slave constructing both a Slave Rx clock frequency-locked to the Master Tx clock and a Slave Tx clock frequency-locked to the Slave Rx clock, said apparatus comprising:

a metric processor, situated within said master, which produces a metric signal reflective of amplitude differences between a signal received by the master from a corresponding one of the slaves and allowed amplitude levels of the received signal;
and
a decision processor, connected to the master and responsive to the metric processor, for changing phase of the Slave Tx clock relative to the Slave Rx clock in the corresponding one of the slaves in order to maximize the metric signal produced by the metric processor and thereby reduce distortion caused by near end cross-talk and echo in signals received over the channel by a receiver in the master and thus facilitate clock and data recovery by the receiver.

Dependencies are inferred from the claim text.