Measuring shield breaks in coaxial cable by a sheath test current
First Claim
1. A test system for finding a break in a shield of a coaxial cable, the test system comprising:
- a transmitter having an output that supplies a reference test signal;
a transformer for magnetically inducing the reference test signal onto the shield of the coaxial cable comprisinga primary winding connected to the output of the transmitter;
a secondary winding comprising a portion of the shield of the coaxial cable; and
a magnetic coupling device for magnetically coupling the primary and secondary windings; and
a receiver connected to a center conductor of the coaxial cable, for receiving a signal induced from the shield to the center conductor, and for indicating when the magnitude of the induced signal received exceeds the magnitude of the induced signal received from an unbroken coaxial cable, thereby indicating a shield break is present in the coaxial cable.
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Accused Products
Abstract
A system for determining if there is a break in the shield or a compromise in the shielding effectiveness of coaxial cable plant by inducing a reference test signal onto the sheath or outer conductor of a coaxial cable. Concurrent testing is done with a digital sampling receiver for the presence of some of the induced reference signal on the inner or center conductor of the cable. The test current may be introduced directly onto the coax'"'"'s sheath by magnetically coupling with a split ferrite core, or it may be applied indirectly by inducing the current onto a conductor, such as a grounding wire, that attaches to the coaxial cable. The test signal on the center conductor may be received back at the headend, or it may be received near the injection point by breaking the coaxial cable, or by connecting a probe to the center conductor. The invention may employ ranging to determine the distance to the shield break. This system is particularly useful to detect the source of interference on the upstream or reverse portion of the networks.
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Citations
22 Claims
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1. A test system for finding a break in a shield of a coaxial cable, the test system comprising:
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a transmitter having an output that supplies a reference test signal; a transformer for magnetically inducing the reference test signal onto the shield of the coaxial cable comprising a primary winding connected to the output of the transmitter; a secondary winding comprising a portion of the shield of the coaxial cable; and a magnetic coupling device for magnetically coupling the primary and secondary windings; and a receiver connected to a center conductor of the coaxial cable, for receiving a signal induced from the shield to the center conductor, and for indicating when the magnitude of the induced signal received exceeds the magnitude of the induced signal received from an unbroken coaxial cable, thereby indicating a shield break is present in the coaxial cable. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15)
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16. A test system for finding a shield break in a coaxial cable plant, comprising:
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a triggerless reference test signal transmitter having an output that supplies a triggerless reference test signal; a transformer for magnetically inducing the triggerless reference test signal onto a portion of the shield of the coaxial cable plant comprising a primary winding connected to the triggerless reference test signal transmitter output; a secondary winding which is electrically attached to the coaxial cable plant; and a split ferrite core which magnetically couples the primary and secondary windings; and a triggerless receiver connected to a return path of the cable plant; whereby the triggerless reference test signal transmitter transmits the triggerless reference test signal and the triggerless receiver receives a return path signal when there is a break in the shield of the coaxial cable plant. - View Dependent Claims (17, 18, 19, 20)
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21. A method for identifying a shield break in a coaxial cable plant comprising the steps of:
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(a) magnetically coupling a signal to a shield of the coaxial cable; and (b) receiving the coupled signal from a center conductor of the coaxial cable; whereby the presence of a shield break is determined by receiving the coupled signal on the center conductor. - View Dependent Claims (22)
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Specification