Apparatus and method for locating nonlinear impairments in a communication channel by use of nonlinear time domain reflectometry
First Claim
1. A method of determining the presence or absence of one or more nonlinear impairments in a linear medium, comprising:
- setting one or more pulse transmission parameter values;
applying a first sequence of one or more first transmit pulses to the medium for transmission through the medium under the one or more pulse transmission parameter values;
receiving from the medium a first sequence of one or more echo signals reflected from impairments in the medium in response to the first sequence of transmit pulses;
digitizing the echo signals for each transmit pulse of the first sequence of first transmit pulses to produce a set of digital values for each transmit pulse of the first sequence of first transmit pulses;
averaging the digital values for corresponding echo signals of the first sequence of echo signals to produce a first digitized set representing the average of the first sequence of echo signals;
changing the one or more pulse transmission parameter values;
applying a second sequence of one or more second transmit pulses to the medium for transmission through the medium under the one or more changed pulse transmission parameter values;
receiving from the medium a second sequence of one or more echo signals reflected from impairments in the medium in response to the second sequence of transmit pulses;
digitizing the echo signals for each transmit pulse of the second sequence of second transmit pulses to produce a set of digital values for each transmit pulse of the second sequence of second transmit pulses;
averaging the digital values for corresponding echo signals of the second sequence of echo signals to produce a second digitized set representing the average of the second sequence of echo signals;
combining the first and the second digitized sets to produce a residual digitized set; and
examining the residual digitized set for a residual pulse indicating the presence of one or more nonlinear impairments.
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Accused Products
Abstract
A series of time domain reflectometry (tdr) measurements are made on a channel having nonlinear impairments as well as linear impairments. In a given measurement, the reflected signals from the impairments are digitized and sequentially stored in memory. The parameters characterizing the channel are then changed, preferably by biasing the line by means of a dc current. The changed bias condition modifies the impedance of nonlinear impairments in a nonlinear manner, while the impedance of linear impairments are unchanged by the bias. A second tdr measurement is initiated, and the reflected signals digitized and sequentially stored. The two sets of stored reflected signals are then sequentially compared, and corresponding signals having either the same amplitudes or linearly proportional amplitudes are identified as reflected from linear impairments, while those not the same, nor proportional, are identified as from nonlinear impairments.
16 Citations
38 Claims
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1. A method of determining the presence or absence of one or more nonlinear impairments in a linear medium, comprising:
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setting one or more pulse transmission parameter values; applying a first sequence of one or more first transmit pulses to the medium for transmission through the medium under the one or more pulse transmission parameter values; receiving from the medium a first sequence of one or more echo signals reflected from impairments in the medium in response to the first sequence of transmit pulses; digitizing the echo signals for each transmit pulse of the first sequence of first transmit pulses to produce a set of digital values for each transmit pulse of the first sequence of first transmit pulses; averaging the digital values for corresponding echo signals of the first sequence of echo signals to produce a first digitized set representing the average of the first sequence of echo signals; changing the one or more pulse transmission parameter values; applying a second sequence of one or more second transmit pulses to the medium for transmission through the medium under the one or more changed pulse transmission parameter values; receiving from the medium a second sequence of one or more echo signals reflected from impairments in the medium in response to the second sequence of transmit pulses; digitizing the echo signals for each transmit pulse of the second sequence of second transmit pulses to produce a set of digital values for each transmit pulse of the second sequence of second transmit pulses; averaging the digital values for corresponding echo signals of the second sequence of echo signals to produce a second digitized set representing the average of the second sequence of echo signals; combining the first and the second digitized sets to produce a residual digitized set; and examining the residual digitized set for a residual pulse indicating the presence of one or more nonlinear impairments. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. A method for differentiating at least one nonlinear impairment from any linear impairments present in an electrically conductive line, the method comprising:
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performing a first measurement on the line by a time domain reflectometry apparatus to detect the presence of at least one nonlinear impairment in the line; receiving a first data sequence in the first measurement, the first data sequence including echo signals reflected from impairments in the line, in which first echo signals reflected from at least one nonlinear impairment are not distinguishable from first echo signals reflected from any linear impairment in the line; storing the first data sequence obtained in the first measurement; altering the impedance of at least one nonlinear impairment in the line without altering the impedance of any linear impairment in the line; performing a second measurement by the time domain reflectometry apparatus on the line; receiving a second data sequence in the second measurement, the second data sequence including second echo signals reflected from the impairments in the line, in which second echo signals reflected from the at least one nonlinear impairment in the line have characteristics which are distinguishable from corresponding characteristics of second echo signals reflected from the any linear impairment in the line, the characteristics resulting from altering the impedance; storing the second data sequence obtained in the second measurement; and combining the first data sequence and the second data sequence to distinguish echo signals reflected from the at least one nonlinear impairment in the line from any linear impairment in the line based on the characteristics. - View Dependent Claims (12, 13, 14, 15, 16, 17, 18, 19)
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20. A time domain reflectometry apparatus, comprising:
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a pulse amplifier with an output for producing sequences of transmit pulses for application to an electrically conductive line; a switch circuit connected to the pulse amplifier output for controlling transmission parameters of the transmit pulses applied to the line; a digitizer with an input for receiving echo signals reflected from impairments in the line in response to the sequences of transmit pulses; storage connected to the digitizer for storing sets of digitized echo signals, a first set including at least one digitized echo signal representing an echo signal reflected from an impairment in the line in response to a first sequence of transmit pulses applied to the line under first transmission parameters and a second set including at least one digitized echo signal representing an echo signal reflected from an impairment in the line in response to a second sequence of transmit pulses applied to the line under second transmission parameters; and an arithmetic unit connected to the storage for; averaging amplitudes of the signals in the first set of digitized echo signals and magnitudes of the signals of the second set of digitized echo signals; combining the average amplitudes of the signals of the first set of digitized echo signals with the average amplitudes of corresponding signals of the second set of digitized echo signals; and distinguishing at least one nonlinear impairment in the line based upon the combination. - View Dependent Claims (21, 22, 23, 24, 25, 26, 27, 28)
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29. An apparatus for differentiating at least one nonlinear impairment from any linear impairments present in an electrically conductive line, the apparatus comprising:
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a time domain reflectometry apparatus for performing a first measurement and a second measurement on the line to detect the presence of the at least one nonlinear impairment in the line; a switch connected to the time domain reflectometry apparatus for altering the impedance of the at least one nonlinear impairment after the first measurement without altering the impedance of the any linear impairments; storage for sequentially storing a first data sequence in the first measurement and a second data sequence in the second measurement, the first data sequence including echo signals reflected from impairments in the line, in which first echo signals reflected from at least one nonlinear impairment are not distinguishable from first echo signals reflected from any linear impairment in the line, the second data sequence including second echo signals reflected from the impairments in the line, in which second echo signals reflected from the at least one nonlinear impairment in the line have characteristics which are distinguishable from corresponding characteristics of second echo signals reflected from the any linear impairment in the line, the characteristics resulting from altering the impedance; and a processor connected to the storage for combining the first data sequence and the second data sequence to distinguish echo signals reflected from the at least one nonlinear impairment in the line from any linear impairment in the line based on the characteristics. - View Dependent Claims (30, 31, 32, 33, 34, 35, 36, 37)
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38. A method of determining the presence or absence of one or more nonlinear impairments in a linear medium, comprising:
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setting one or more pulse transmission parameter values; applying a first sequence of one or more first transmit pulses to the medium for transmission through the medium under the one or more pulse transmission parameter values; receiving from the medium a first sequence of one or more echo signals reflected from impairments in the medium in response to the first sequence of transmit pulses; digitizing the echo signals for each transmit pulse of the first sequence of first transmit pulses to produce a set of digital values for each transmit pulse of the first sequence of first transmit pulses; averaging the digital values for corresponding echo signals of the first sequence of echo signals to produce a first digitized set representing the average of the first sequence of echo signals; changing the one or more pulse transmission parameter values; applying a second sequence of one or more second transmit pulses to the medium for transmission through the medium under the one or more changed pulse transmission parameter values; receiving from the medium a second sequence of one or more echo signals reflected from impairments in the medium in response to the second sequence of transmit pulses; digitizing the echo signals for each transmit pulse of the second sequence of second transmit pulses to produce a set of digital values for each transmit pulse of the second sequence of second transmit pulses; averaging the digital values for corresponding echo signals of the second sequence of echo signals to produce a second digitized set representing the average of the second sequence of echo signals; combining the first and the second digitized sets to produce a residual digitized set; and determining the distance to at least one of the one or more nonlinear impairments based upon the location of displacements in the residual digitized set.
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Specification