Ingress Noise Inhibiting Network Interface Device and Method for Cable Television Networks
First Claim
1. A network interface device for connecting subscriber equipment to a cable television (CATV) network over which downstream signals in a first frequency band from a headend of the CATV network are transmitted to the subscriber equipment and valid upstream signals in a second different frequency band are transmitted from the subscriber equipment to the headend, the network interface device having an upstream noise mitigation circuit which mitigates ingress noise into the CATV network in the second frequency band, comprising:
- an upstream filter which filters upstream signals before delivery to the CATV network;
a detector connected to the upstream filter which determines an instantaneous level of power of the upstream signals filtered by the upstream filter, and which supplies a power signal related to the instantaneous power of the upstream signals;
a threshold circuit which establishes a threshold level of power which characterizes valid upstream signals, and which supplies a threshold signal related to the established threshold level of power;
a comparator connected to the detector and the threshold circuit which compares the power signal to the threshold signal, and which asserts a trigger signal when the power signal exceeds the threshold signal;
a switch connected to the upstream filter and having a normal position and an activated position, the normal position isolating and terminating signals from the upstream filter and the activated position conducting the upstream signals from the upstream filter to the CATV network, the switch assuming the activated position in response to the assertion of a control signal and assuming the normal position in response to the de-assertion of the control signal; and
a control circuit connected to the comparator and to the switch, the control circuit asserts a control signal to the switch immediately upon assertion of the trigger signal and de-asserts the control signal to the switch at or after de-assertion of the trigger signal.
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Accused Products
Abstract
Ingress noise from subscriber equipment is mitigated or prevented from reaching a cable television (CATV) network. All upstream signals including ingress noise are initially transmitted to the CATV network whenever their instantaneous power exceeds a threshold which typically distinguishes ingress noise from a valid upstream signal. Whenever the instantaneous power is below the threshold, ingress noise is blocked from reaching the CATV network. A gas tube surge protection device is included to resist component destruction and malfunction arising from lightning strikes and other high voltage, high current surges.
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Citations
20 Claims
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1. A network interface device for connecting subscriber equipment to a cable television (CATV) network over which downstream signals in a first frequency band from a headend of the CATV network are transmitted to the subscriber equipment and valid upstream signals in a second different frequency band are transmitted from the subscriber equipment to the headend, the network interface device having an upstream noise mitigation circuit which mitigates ingress noise into the CATV network in the second frequency band, comprising:
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an upstream filter which filters upstream signals before delivery to the CATV network; a detector connected to the upstream filter which determines an instantaneous level of power of the upstream signals filtered by the upstream filter, and which supplies a power signal related to the instantaneous power of the upstream signals; a threshold circuit which establishes a threshold level of power which characterizes valid upstream signals, and which supplies a threshold signal related to the established threshold level of power; a comparator connected to the detector and the threshold circuit which compares the power signal to the threshold signal, and which asserts a trigger signal when the power signal exceeds the threshold signal; a switch connected to the upstream filter and having a normal position and an activated position, the normal position isolating and terminating signals from the upstream filter and the activated position conducting the upstream signals from the upstream filter to the CATV network, the switch assuming the activated position in response to the assertion of a control signal and assuming the normal position in response to the de-assertion of the control signal; and a control circuit connected to the comparator and to the switch, the control circuit asserts a control signal to the switch immediately upon assertion of the trigger signal and de-asserts the control signal to the switch at or after de-assertion of the trigger signal. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12)
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13. A network interface device comprising components which conduct upstream and downstream signals to and from a cable television (CATV) network and subscriber equipment, the network interface device further comprising:
a gas tube surge protection device connected within the network interface device where the upstream and downstream signals are conducted to and from the CATV network, the gas tube surge protection device operative to shunt high voltage and high current surges from the components and subscriber equipment.
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14. A method of mitigating upstream ingress noise to a cable television (CATV) network, comprising:
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transmitting downstream signals in a first frequency band from a headend of the CATV network to subscriber equipment; transmitting valid upstream signals in a second different frequency band from the subscriber equipment to the headend; filtering the upstream signals including ingress noise to confine the frequency of the upstream signals to the second frequency band; determining an instantaneous power content of the upstream signals; establishing a threshold power level which characterizes valid upstream signals from the subscriber equipment; comparing the instantaneous power content to a threshold power level; conducting the filtered upstream signals to the CATV network whenever the instantaneous power content is equal to or greater than the threshold power level; and preventing the filtered upstream signals from reaching the CATV network when the instantaneous power content is less than the threshold power level. - View Dependent Claims (15, 16, 17, 18, 19, 20)
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Specification