Swept frequency domain relectometry enhancement
First Claim
1. A method of locating a discontinuity in a cable under test using a spectrum analyzer, the spectrum analyzer having an input/output terminal coupled to one end of the cable, comprising the steps of:
- inserting a test signal into the cable;
receiving a return signal from the cable resulting from the test signal;
detecting a first maximum amplitude of an intermediate frequency obtained by mixing the return signal with a local oscillator and a reference signal;
varying the frequency of the test signal as a function of an offset frequency;
detecting a second maximum amplitude of the intermediate frequency resulting from the variation of the frequency of the test signal;
measuring the intermediate frequency at the first maximum value;
measuring the offset frequency at the second maximum value;
determining from the measured intermediate frequency and the measured offset frequency a distance to the discontinuity; and
displaying the distance to the discontinuity.
1 Assignment
0 Petitions
Accused Products
Abstract
An improved swept frequency domain reflectometry instrument has an input/output terminal coupled to one end of a cable. A radio frequency at the input/output terminal is converted to an intermediate frequency using a swept local frequency. The radio frequency is derived from the swept local frequency and a variable offset frequency. A controller controls the variable offset frequency, monitoring the amplitude of the intermediate frequency. A period counter counts the intermediate frequency at a first maximum response of the intermediate frequency and further counts the offset frequency at a second maximum response of the intermediate frequency. The location of a discontinuity in the cable is calculated from the counted frequencies.
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Citations
5 Claims
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1. A method of locating a discontinuity in a cable under test using a spectrum analyzer, the spectrum analyzer having an input/output terminal coupled to one end of the cable, comprising the steps of:
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inserting a test signal into the cable; receiving a return signal from the cable resulting from the test signal; detecting a first maximum amplitude of an intermediate frequency obtained by mixing the return signal with a local oscillator and a reference signal; varying the frequency of the test signal as a function of an offset frequency; detecting a second maximum amplitude of the intermediate frequency resulting from the variation of the frequency of the test signal; measuring the intermediate frequency at the first maximum value; measuring the offset frequency at the second maximum value; determining from the measured intermediate frequency and the measured offset frequency a distance to the discontinuity; and displaying the distance to the discontinuity. - View Dependent Claims (2)
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3. An apparatus for locating a distance to a discontinuity in a cable under test, the apparatus having means for generating a test signal for insertion into the cable and for receiving in response to the test signal a return signal, comprising:
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means for generating an intermediate frequency from the return signal as a function of a local oscillator signal and a reference signal; means for offsetting the frequency of the test signal from the test signal generating means; means for detecting a first maximum amplitude of the intermediate frequency with no frequency offset for the test signal from the offsetting means, and for detecting a second maximum amplitude of the intermediate frequency as the frequency of the test signal is offset by the offsetting means; means for measuring the intermediate frequency at the first maximum amplitude and the offset frequency of the offsetting means at the second amplitude as a function of the reference signal; means for calculating from the measured frequencies determined by the measuring means the distance; and means for displaying the distance. - View Dependent Claims (4, 5)
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Specification