Detecting signal leakage in cable networks
AssigneeJDS Uniphase Corporation
InventorsAl RUTH, Rodney Harbison WEAVER, Koji OKAMOTO
Life of this patent
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Abstract
A signal leakage in a cable network may be detected by using a test device to obtain a spectrum of an electromagnetic wave propagating in vicinity of the cable network, and automatically detecting QAM channels in the obtained spectrum by detecting characteristic spectral roll-offs at boundary frequencies between QAM channels of the cable network. A test device may be used to determine which QAM channels are currently active on the cable network, thereby facilitating automatic QAM signal leakage detection.
Claims21
A testing device for detecting a QAM channel signal leaking at a first location of a cable network, which propagates QAM channel signals at a QAM channel frequency spacing, the testing device comprising:
- memory configured to store high and low boundary frequencies of a QAM channel of the QAM channel signal;
- a receiver configured to detect an electromagnetic wave propagating in air proximate the first location, and to obtain a frequency spectrum of power density of the electromagnetic wave in a frequency band comprising the high and low boundary frequencies of the QAM channel;
- and
- a controller operably coupled to the memory and the receiver and configured to detect the QAM channel signal in the electromagnetic wave by determining that:
- a drop in the power density of the electromagnetic wave, between a frequency higher than the low boundary frequency by a first step frequency and the low boundary frequency, is above a first threshold;
- and a drop in the power density of the electromagnetic wave, between a frequency lower than the high boundary frequency by a second step frequency and the high boundary frequency, is above the first threshold.
A method of detecting a QAM channel signal leaking at a first location of a cable network, which propagates QAM channel signals frequency-separated at a QAM channel frequency spacing, the method comprising:
- obtaining high and low boundary frequencies of a QAM channel of the QAM channel signal;
- detecting an electromagnetic wave propagating in air proximate the first location, and obtaining a frequency spectrum of power density of the electromagnetic wave in a frequency band comprising the high and low boundary frequencies of the QAM channel;
- and
- determining that:
- a drop in the power density of the electromagnetic wave, between a frequency higher than the low boundary frequency by a first step frequency and the low boundary frequency, is above a first threshold;
- and a drop in the power density of the electromagnetic wave, between a frequency lower than the high boundary frequency by a second step frequency and the high boundary frequency, is above the first threshold;
- detecting that the QAM channel signal is leaking from the cable network.
Dependencies are inferred from the claim text.