Method for detecting leakage in digitally modulated systems
First Claim
1. A method for detecting leakage in a digital cable system, the method comprising:
- inserting at least one first signal with an amplitude multiple tens of dB below a digital channel power of digital channels carried on the digital cable system;
receiving a second signal containing the at least one first signal;
converting the second signal to an intermediate frequency (IF) signal;
digitizing the IF signal to create a digitized IF signal;
obtaining samples of the digitized IF signal;
providing a set of digitized samples of a third signal at a nominal frequency or nominal frequencies of the at least one first signal at maximum amplitude converted to the IF;
correlating the digitized IF signal and the digitized samples of the third signal at the nominal frequency or nominal frequencies of the at least one first signal at maximum amplitude converted to the IF; and
,detecting the presence of the inserted at least one first signal based upon the result of the correlation.
4 Assignments
0 Petitions
Accused Products
Abstract
In a method for detecting leakage in a digital cable system, at least one first signal is inserted on the cable system. The at least one first signal has an amplitude multiple tens of dB below the digital channel power of the digital channels carried on the cable system. A second signal containing the first signal is received. The second signal is converted to an intermediate frequency (IF) signal. The IF signal is digitized and samples of the digitized IF signal are obtained. Digitized samples of a third signal at the nominal frequency of the first signal at maximum amplitude converted to the IF are provided. The digitized IF signal and the digitized samples of a third signal at the nominal frequency of the first signal at maximum amplitude converted to the IF are correlated. The presence of the inserted first signal is detected based upon the result of the correlation. In another method, a pair of first signals are inserted on the cable system. The pair of first signals are spaced apart a fixed frequency and with amplitudes multiple tens of dB below the digital channel power of the digital channels carried on the cable system. A second signal containing the first signal is received and converted to an intermediate frequency (IF) signal. The IF signal is digitized, samples of the digitized IF signal are obtained, and a large scale Fast Fourier Transform (FFT) is applied to the samples to generate an FFT output. The FFT output is examined for generally equally sized signals separated from each other by the fixed frequency in the FFT output. If generally equally sized signals separated from each other by the fixed frequency are detected in the FFT output, a decision is made that the second signal represents detected leakage from the digital cable system.
46 Citations
18 Claims
-
1. A method for detecting leakage in a digital cable system, the method comprising:
- inserting at least one first signal with an amplitude multiple tens of dB below a digital channel power of digital channels carried on the digital cable system;
receiving a second signal containing the at least one first signal; converting the second signal to an intermediate frequency (IF) signal; digitizing the IF signal to create a digitized IF signal; obtaining samples of the digitized IF signal; providing a set of digitized samples of a third signal at a nominal frequency or nominal frequencies of the at least one first signal at maximum amplitude converted to the IF; correlating the digitized IF signal and the digitized samples of the third signal at the nominal frequency or nominal frequencies of the at least one first signal at maximum amplitude converted to the IF; and
,detecting the presence of the inserted at least one first signal based upon the result of the correlation. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12)
- inserting at least one first signal with an amplitude multiple tens of dB below a digital channel power of digital channels carried on the digital cable system;
-
13. A method for detecting leakage in a digital cable system, the method comprising:
- inserting a pair of first signals spaced apart a fixed frequency and with amplitudes multiple tens of dB below a digital channel power of digital channels carried on the digital cable system;
receiving a second signal containing the first signals; converting the second signal to an intermediate frequency (IF) signal; digitizing the IF signal to create a digitized IF signal; obtaining samples of the digitized IF signal; applying a large scale Fast Fourier Transform (FFT) to the second signal to generate an FFT output; examining the FFT output for generally equally sized signals separated from each other by a fixed frequency in the FFT output; and
,if generally equally sized signals separated from each other by the fixed frequency of the FFT output are detected in the FFT output, deciding that the second signal represents detected leakage from the digital cable system. - View Dependent Claims (14, 15, 16, 17, 18)
- inserting a pair of first signals spaced apart a fixed frequency and with amplitudes multiple tens of dB below a digital channel power of digital channels carried on the digital cable system;
Specification
-
- Resources
-
Current AssigneeViavi Solutions, Inc. (Lumentum Holdings Inc.)
-
Original AssigneeTrilithic Incorporated (Lumentum Holdings Inc.)
-
InventorsStelle, Raleigh Benton IV, Orndorff, Dennis Lee
-
Primary Examiner(s)Bayard, Emmanuel
-
Application NumberUS14/128,908Publication NumberTime in Patent Office1,204 DaysField of Search375/340, 375/343, 375/373, 375/224US Class Current1/1CPC Class CodesH04B 3/46 Monitoring; TestingH04N 17/004 for digital television systemsH04N 21/235 Processing of additional da...
