Methods and apparatus for detecting and locating leakage of digital signals
First Claim
1. A system for detecting a digital TV signal emitted into free space from the coaxial cable portion of an HFC network, said system operating in connection with a time reference signal, a timestamp, and a communications link, the digital TV signal being transmitted in the HFC network from a headend, said system comprising:
- a headend unit, including—
an input, adapted to be coupled to the headend, for receiving the digital TV signal from the headend for use as a TV reference signal,a first receiver for receiving the time reference signal and timestamp,a first signal sampler, coupled to the input and the first receiver, for sampling the TV reference signal at a rate corresponding to the time reference signal, to produce TV reference signal samples,a first data processor, coupled to the first signal sampler for receiving the TV reference signal samples, and coupled to the first receiver for receiving the timestamp, said first data processor being adapted to associate the timestamp with the TV reference signal samples, anda first communications interface, associated with the first data processor and adapted to interface with the communications link for transmission of the TV reference signal samples and the associated timestamp over the communications link; and
a detector unit, including—
an antenna for receiving the digital TV signal emitted in free space from the coaxial portion of the HFC network, for detection as a TV leakage signal,a second receiver for receiving the time reference signal and timestamp,a second signal sampler, coupled to the antenna and the second receiver, for sampling the TV leakage signal at a rate corresponding to the time reference signal, to produce TV leakage signal samples,a second data processor, coupled to the second signal sampler for receiving the TV leakage signal samples, and coupled to the second receiver for receiving the timestamp, said second data processor being adapted to associate the timestamp with the TV leakage signal samples,a second communications interface associated with the second data processor and adapted to interface with the communications link for reception of the TV reference signal samples and the associated timestamp from the communications link, and adapted to transfer the TV reference signal samples and the associated timestamp to the second data processor, anda cross-correlation processor, coupled to the second data processor and adapted to perform a cross-correlation of the TV reference signal samples, associated with the timestamp, with the TV leakage signal samples, associated with the same timestamp, to produce a cross-correlation function having a peak,whereby the TV leakage signal is detected from the peak of the cross-correlation function.
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Accused Products
Abstract
A system for detecting and locating a digital TV leakage signal in an HFC network. The system comprises a headend unit and a leakage detector. The headend unit receives the TV signal at the headend for use as a reference signal. The reference signal is sampled at a rate corresponding to a time reference signal, to produce reference signal samples. The reference signal samples and timestamp are transmitted to the leakage detector. The detector receives the digital TV signal from a leakage source, for detection as a leakage signal. The detector includes a cross-correlation processor. The leakage signal is sampled at a rate corresponding to the time reference signal, to produce leakage signal samples. The cross-correlation processor performs a cross-correlation of the reference signal samples with the leakage signal samples to produce a cross-correlation function having a peak, and the TV leakage signal is detected from this peak.
69 Citations
27 Claims
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1. A system for detecting a digital TV signal emitted into free space from the coaxial cable portion of an HFC network, said system operating in connection with a time reference signal, a timestamp, and a communications link, the digital TV signal being transmitted in the HFC network from a headend, said system comprising:
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a headend unit, including— an input, adapted to be coupled to the headend, for receiving the digital TV signal from the headend for use as a TV reference signal, a first receiver for receiving the time reference signal and timestamp, a first signal sampler, coupled to the input and the first receiver, for sampling the TV reference signal at a rate corresponding to the time reference signal, to produce TV reference signal samples, a first data processor, coupled to the first signal sampler for receiving the TV reference signal samples, and coupled to the first receiver for receiving the timestamp, said first data processor being adapted to associate the timestamp with the TV reference signal samples, and a first communications interface, associated with the first data processor and adapted to interface with the communications link for transmission of the TV reference signal samples and the associated timestamp over the communications link; and a detector unit, including— an antenna for receiving the digital TV signal emitted in free space from the coaxial portion of the HFC network, for detection as a TV leakage signal, a second receiver for receiving the time reference signal and timestamp, a second signal sampler, coupled to the antenna and the second receiver, for sampling the TV leakage signal at a rate corresponding to the time reference signal, to produce TV leakage signal samples, a second data processor, coupled to the second signal sampler for receiving the TV leakage signal samples, and coupled to the second receiver for receiving the timestamp, said second data processor being adapted to associate the timestamp with the TV leakage signal samples, a second communications interface associated with the second data processor and adapted to interface with the communications link for reception of the TV reference signal samples and the associated timestamp from the communications link, and adapted to transfer the TV reference signal samples and the associated timestamp to the second data processor, and a cross-correlation processor, coupled to the second data processor and adapted to perform a cross-correlation of the TV reference signal samples, associated with the timestamp, with the TV leakage signal samples, associated with the same timestamp, to produce a cross-correlation function having a peak, whereby the TV leakage signal is detected from the peak of the cross-correlation function. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15)
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16. A system for detecting a digital TV signal emitted into free space from the coaxial cable portion of an HFC network, said system operating in connection with a time reference signal, a timestamp, and a communications link, the digital TV signal being transmitted in the coaxial cable portion of the HFC network from a fiber optic node, said system comprising:
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a reference unit, including— an input, adapted to be coupled to a reference point in the HFC network, for receiving the digital TV signal from the reference point for use as a TV reference signal, a first receiver for receiving the time reference signal and timestamp, a first signal sampler, coupled to the input and the first receiver, for sampling the TV reference signal at a rate corresponding to the time reference signal, to produce TV reference signal samples, a first data processor, coupled to the first signal sampler for receiving the TV reference signal samples, and coupled to the first receiver for receiving the timestamp, said first data processor being adapted to associate the timestamp with the TV reference signal samples, and a first communications interface, associated with the first data processor and adapted to interface with the communications link for transmission of the TV reference signal samples and the associated timestamp over the communications link; and a detector unit, including— an antenna for receiving the digital TV signal emitted in free space from the coaxial portion of the HFC network, for detection as a TV leakage signal, a second receiver for receiving the time reference signal and timestamp, a second signal sampler, coupled to the antenna and the second receiver, for sampling the TV leakage signal at a rate corresponding to the time reference signal, to produce TV leakage signal samples, a second data processor, coupled to the second signal sampler for receiving the TV leakage signal samples, and coupled to the second receiver for receiving the timestamp, said second data processor being adapted to associate the timestamp with the TV leakage signal samples, a second communications interface associated with the second data processor and adapted to interface with the communications link for reception of the TV reference signal samples and the associated timestamp from the communications link, and adapted to transfer the TV reference signal samples and the associated timestamp to the second data processor, and a cross-correlation processor, coupled to the second data processor and adapted to cross-correlate the TV reference signal samples, associated with the timestamp, with the TV leakage signal samples, associated with the same timestamp, to produce a cross-correlation function having a peak, whereby the TV leakage signal is detected from the peak of the cross-correlation function. - View Dependent Claims (17, 18, 19)
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20. A method of detecting a digital TV signal emitted into free space from the coaxial cable portion of an HFC network, said method operating in connection with a time reference signal, a timestamp, and a communications link, the digital TV signal being transmitted in the HFC network from a headend, said method comprising the steps of:
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(a) receiving the digital TV signal from the headend for use as a TV reference signal; (b) receiving the time reference signal and timestamp; (c) sampling the TV reference signal at a rate corresponding to the time reference signal, to produce TV reference signal samples; (d) associating the timestamp with the TV reference signal samples; (e) transmitting the TV reference signal samples and the associated timestamp over the communications link to a detector unit situated in the vicinity of the coaxial cable portion of the HFC network; (f) receiving, at the detector unit, the TV reference signal samples and the associated timestamp from the communications link; (g) receiving, at the detector unit, the digital TV signal emitted in free space from the coaxial cable portion of the HFC network, for detection as a TV leakage signal; (h) receiving, at the detector unit, the time reference signal and timestamp; (i) sampling the TV leakage signal at a rate corresponding to the time reference signal, to produce TV leakage signal samples; (j) associating the timestamp with the TV leakage signal samples; and (k) performing a cross-correlation of the TV reference signal samples, associated with the timestamp, with the TV leakage signal samples, associated with the same timestamp, to produce a cross-correlation function having a peak, whereby the TV leakage signal is detected from the peak of the cross-correlation function. - View Dependent Claims (21, 22)
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23. A method of detecting a digital TV signal emitted into free space from the coaxial cable portion of an HFC network, said method operating in connection with a time reference signal, a timestamp, and a communications link, the digital TV signal being transmitted in the coaxial cable portion of the HFC network from a fiber optic node, said method comprising the steps of:
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(a) receiving the digital TV signal from a reference point in the HFC network for use as a TV reference signal; (b) receiving the time reference signal and timestamp; (c) sampling the TV reference signal at a rate corresponding to the time reference signal, to produce TV reference signal samples; (d) associating the timestamp with the TV reference signal samples; (e) transmitting the TV reference signal samples and the associated timestamp over the communications link to a detector unit situated in the vicinity of the coaxial cable portion of the HFC network; (f) receiving, at the detector unit, the TV reference signal samples and the associated timestamp from the communications link; (g) receiving, at the detector unit, the digital TV signal emitted in free space from the coaxial cable portion of the HFC network, for detection as a TV leakage signal; (h) receiving, at the detector unit, the time reference signal and timestamp; (i) sampling the TV leakage signal at a rate corresponding to the time reference signal, to produce TV leakage signal samples, (j) associating the timestamp with the TV leakage signal samples; and (k) performing a cross-correlation of the TV reference signal samples, associated with the timestamp, with the TV leakage signal samples, associated with the same timestamp, to produce a cross-correlation function having a peak, whereby the TV leakage signal is detected from the peak of the cross-correlation function. - View Dependent Claims (24, 27)
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25. A method of detecting a low frequency ingress source in a bi-directional HFC network carrying digital TV signals in a forward path and having a low frequency return path, the low frequency ingress source admitting low frequency ingress into the return path, said method operating in connection with a time reference signal, a timestamp, and a communications link, said method comprising the steps of:
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(a) receiving a digital TV signal having a center frequency in the VHF Low Band of the forward path, and selecting the digital TV signal for use as a TV reference signal; (b) receiving the time reference signal and timestamp; (c) sampling the TV reference signal at a rate corresponding to the time reference signal, to produce TV reference signal samples; (d) associating the timestamp with the TV reference signal samples; (e) transmitting the TV reference signal samples and the associated timestamp over the communications link to a detector unit situated in the vicinity of the coaxial cable portion of the HFC network; (f) receiving, at the detector unit, the TV reference signal samples and the associated timestamp from the communications link; (g) receiving, at the detector unit, the digital TV signal emitted in free space from the source of low frequency ingress, for detection as a TV egress signal; (h) receiving, at the detector unit, the time reference signal and timestamp; (i) sampling the TV egress signal at a rate corresponding to the time reference signal, to produce TV egress signal samples; (j) associating the timestamp with the TV egress signal samples; (k) performing a cross-correlation of the TV reference signal samples, associated with the timestamp, with the TV egress signal samples, associated with the same timestamp, to produce a cross-correlation function having a peak; and (l) detecting the TV egress signal from the peak of the cross-correlation function, whereby the detection of the TV egress signal indicates a detection of the ingress source. - View Dependent Claims (26)
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Specification