Interactive video distribution systems – Video distribution system with upstream communication – Remote testing of cable system
Reexamination Certificate
2000-07-19
2004-10-12
Tran, Hai (Department: 2611)
Interactive video distribution systems
Video distribution system with upstream communication
Remote testing of cable system
C725S017000, C455S067130, C455S067140, C455S067150
Reexamination Certificate
active
06804826
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to the detection of RF leakage from communication circuits. It is disclosed in the context of an RF leakage detection system for a CATV system, but is believed to be useful in other applications as well.
BACKGROUND OF THE INVENTION
Techniques for the detection of RF leakage from CATV systems are known. There are, for example, the systems described in U.S. Pat. Nos. 5,608,428; 5,294,937; 4,520,508; 4,491,968; 4,413,229; 4,237,486; 4,072,899; 3,711,767. There are also the systems described in U.S. Pat. Nos. 5,585,842; 5,493,210; 5,321,089; 5,210,498; 5,210,497; 4,962,358; 4,814,694; 4,810,961; 4,775,839; 4,731,586; 4,670,789; 4,609,866; 3,882,287; 3,684,823; 3,368,031; 3,345,560; 3,155,897; and, 2,291,533. There is also the disclosure of U.S. Ser. No. 08/690,122, filed Jul. 31, 1996. There is also the disclosure of Archer S. Taylor,
Characterization of Cable TV Networks as the Transmission Media for Data
, IEEE Journal on Selected Areas in Communications, vol. SAC-3, no. 2, March 1985, pp. 255-265. The disclosures of all of these references are hereby incorporated herein by reference. This listing is not intended as a representation that the disclosures listed above are pertinent, or that a thorough search of the prior art has been conducted, or that no more pertinent disclosures than those listed above exist, and no such representations should be inferred.
DISCLOSURE OF THE INVENTION
According to a first aspect of the invention, a communication circuit carries at least one signal including synchronizing intervals by which output of the signal by first apparatus coupled to the communication circuit is to be synchronized. A communication method includes selecting and modulating at least a portion of the duration of at least some of the synchronizing intervals.
Illustratively according to this aspect of the invention, the method further includes transporting along the circuit second apparatus adapted for receiving the signal, detecting the modulation, and producing an indication that the modulation has been detected for determining whether the signal is escaping from the circuit.
Further illustratively according to this aspect of the invention, selecting and modulating at least a portion of the duration of at least some of the synchronizing intervals includes modulating the amplitude of at least a portion of the duration of at least some of the synchronizing intervals.
Additionally illustratively according to this aspect of the invention, selecting and modulating at least a portion of the duration of at least some of the synchronizing intervals includes sinusoidally modulating at least a portion of the duration of at least some of the synchronizing intervals.
Illustratively according to this aspect of the invention, selecting and modulating at least a portion of the duration of at least some of the synchronizing intervals includes generating a first sinusoid having a first frequency, generating a second sinusoid having a second frequency, frequency modulating the first sinusoid with the second sinusoid to produce a frequency modulated signal, and modulating at least a portion of the duration of at least some of the synchronizing intervals with the frequency modulated signal.
Further illustratively according to this aspect of the invention, detecting the modulation includes detecting the frequency modulated signal.
Alternatively illustratively according to this aspect of the invention, detecting the modulation includes detecting the second sinusoid.
Alternatively illustratively according to this aspect of the invention, detecting the modulation includes detecting the first sinusoid.
Additionally illustratively according to this aspect of the invention, selecting and modulating at least a portion of the duration of at least some of the synchronizing intervals includes modulating the amplitude of at least a portion of the duration of a relatively constant portion of the synchronizing intervals.
Illustratively according to this aspect of the invention, selecting and modulating at least a portion of the duration of at least some of the synchronizing intervals includes sinusoidally modulating at least a portion of the duration of substantially all of the synchronizing intervals.
Further illustratively according to this aspect of the invention, selecting and modulating at least a portion of the duration of at least some of the synchronizing intervals includes modulating the amplitude of substantially all of the duration of at least a portion of the synchronizing intervals.
Additionally illustratively according to this aspect of the invention, selecting and modulating at least a portion of the duration of at least some of the synchronizing intervals includes sinusoidally modulating substantially all of the duration of at least a portion of the synchronizing intervals.
According to another aspect of the invention, a communication circuit carries at least one signal including synchronizing intervals by which output of the signal by first apparatus coupled to the communication circuit is to be synchronized. A modulator is provided for selecting and modulating at least a portion of the duration of at least some of the synchronizing intervals.
Illustratively according to this aspect of the invention, the apparatus further includes a detector for transportation along the circuit. The detector is adapted for receiving the signal, detecting the modulation, and producing an indication that the modulation has been detected for determining whether the signal is escaping from the circuit.
Further illustratively according to this aspect of the invention, the modulator includes a modulator for selecting and modulating the amplitude of at least a portion of the duration of at least some of the synchronizing intervals.
Additionally illustratively according to this aspect of the invention, the modulator includes a modulator for sinusoidally modulating at least a portion of the duration of at least some of the synchronizing intervals.
Illustratively according to this aspect of the invention, the modulator includes a modulator for generating a first sinusoid having a first frequency, generating a second sinusoid having a second frequency, frequency modulating the first sinusoid with the second sinusoid to produce a frequency modulated signal, and modulating at least a portion of the duration of at least some of the synchronizing intervals with the frequency modulated signal.
Further illustratively according to this aspect of the invention, the detector includes a detector for detecting the frequency modulated signal.
Alternatively illustratively according to this aspect of the invention, the detector includes a detector for detecting the second sinusoid.
Alternatively illustratively according to this aspect of the invention, the detector includes a detector for detecting the first sinusoid.
Additionally illustratively according to this aspect of the invention, the modulator includes a modulator for modulating the amplitude of at least a portion of the duration of a relatively constant portion of the synchronizing intervals.
Illustratively according to this aspect of the invention, the modulator includes a modulator for sinusoidally modulating at least a portion of the duration of substantially all of the synchronizing intervals.
Further illustratively according to this aspect of the invention, the modulator includes a modulator for modulating the amplitude of substantially all of the duration of at least a portion of the synchronizing intervals.
Additionally illustratively according to this aspect of the invention, the modulator includes a modulator for sinusoidally modulating substantially all of the duration of at least a portion of the synchronizing intervals.
According to yet another aspect of the invention, a communication circuit carries at least a first signal including frequencies in at least a first frequency band. A method of determining whether the first signal is escaping from the circuit includes transporting along the circuit apparatus adapted fo
Bush Terry W.
Rodgers Gregg S.
Barnes & Thornburg
Saltarelli Dominic
Tran Hai
Trilithic, Inc.
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