Ingress noise inhibiting network interface device and method for cable television networks

Patent metadata

Field	Value
Publication number	US-9647851-B2
Application number	US-25022908-A
Country	US
Kind code	B2
Filing date	Oct 13, 2008
Priority date	Oct 13, 2008
Publication date	May 9, 2017
Grant date	May 9, 2017

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.

First claim

The invention claimed is:

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, the upstream signals including a plurality of frequencies;
a detector connected to the upstream filter wherein the detector determines a level of power corresponding to the upstream signals filtered by the upstream filter, and wherein the detector supplies a power signal proportionate to the power level 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 each power signal to the threshold signal, and which asserts a trigger signal when one of the power signals exceeds the threshold signal;
a switch connected to the upstream filter wherein the switch is configured to change from a normal position to an activated position, the normal position isolating and terminating the upstream signals from the upstream filter, and the activated position conducting the upstream signals from the upstream filter to the CATV network, wherein the conducted upstream signals include information;
a control circuit configured to assert a control signal in response to the trigger signal, the control circuit comprising a timer receptive of the trigger signal and operative to assert a timing signal for a time period commencing upon the assertion of the trigger signal,
wherein the detector, the threshold circuit and the comparator operate without demodulating the frequencies within the upstream signals;
wherein the switch is changed to the activated position in response to the comparator's determination that power level of the upstream signals exceeds the power of the threshold signal for the duration of the time period, wherein the threshold circuit and the comparator operate instantaneously without demodulating, analyzing, comparing or isolating any of the frequencies within the upstream signals; and
wherein the switch returns to the normal position after the information has been transmitted to the CATV network.

2. The network interface device as defined in claim 1 , wherein the control circuit responds to the timing signal to cause the trigger signal to be de-asserted only after expiration of an amount of time required to fully transmit the information of one of the upstream signals.

3. The network interface device as defined in claim 2 , wherein the control circuit de-asserts the control signal after the trigger signal is de-asserted and upon expiration of the time period.

4. The network interface device as defined in claim 1 , wherein the detector includes a log amplifier detector.

5. The network interface device as defined in claim 4 , wherein each power signal supplied by the log amplifier detector is proportionate to one of the levels of power corresponding to one of the upstream signals.

6. The network interface device as defined in claim 1 , wherein the switch is changed to the activated position without incurring any delay due to any comparison amongst the frequencies of any of the upstream signals.

7. The network interface device as defined in claim 1 , wherein: the upstream filter constitutes a first upstream filter; the switch constitutes a first switch; the first upstream filter is connected to the first switch; and the noise mitigation circuit further comprises: a second upstream filter which filters upstream signals before delivery to the CATV network; a second switch connected to the first switch and to the second upstream filter, the second switch configured to change from a normal position to an activated position, the normal position of the second switch terminating the second upstream filter, and the activated position of the second switch conducting the upstream signals from the first switch and the first upstream filter through the second upstream filter to the CATV network; and wherein: the first and second switches assume activated positions in response to the assertion of the trigger signal and assume normal positions in response to the de-assertion of the trigger signal.

8. The network interface device as defined in claim 7 , further comprising: a signal splitter/combiner connected to the first and second upstream filters which divides downstream signals from the CATV network into active and passive downstream signals within the network interface device and which combines passive upstream signals from passive subscriber equipment and active upstream signals from active subscriber equipment into upstream signals transmitted to the CATV network; and wherein: the passive downstream signals are transmitted through the network interface device without substantial conditioning to the passive subscriber equipment and the passive upstream signals are transmitted through the network interface device without substantial conditioning to the CATV network; the active downstream signals are conditioned when transmitted through the network interface device to the active subscriber equipment and the active upstream signals are conditioned when transmitted through the network interface device to the CATV network; the active upstream signals are conducted through the first and second upstream filters to the signal splitter/combiner for transmission to the CATV network when the first and second switches are in their activated positions; and ingress noise in the second frequency band originating from active subscriber equipment is conducted through the first upstream filter and is isolated and terminated when the first switch is in the normal position.

9. The network interface device as defined in claim 7 , wherein a drop cable connects the network interface device to the CATV network and the drop cable has a characteristic impedance value, and the upstream noise mitigation circuit further comprises: a first termination resistor connected to terminate the first upstream filter when the first switch is in the normal position; a second termination resistor connected terminate to the second upstream filter when the second switch is in the normal position; and wherein: the first and second termination resistors have impedance values substantially equal to a characteristic impedance of the drop cable.

10. The network interface device as defined in claim 1 , 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.

11. The network interface device as defined in claim 1 , further 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 volt

Assignees

• Newby Charles F
• Halik Gregory F
• Kellogg Matthew
• Ppc Broadband Inc

Inventors

• Newby Charles F
• Halik Gregory F
• Kellogg Matthew

Classifications

• H04L12/2898 Primary

  Subscriber equipments (DSL modems H04M11/062; cable modems H04L12/2801) · CPC title

• H04N7/104

  Switchers or splitters · CPC title

• H04L12/2801 Primary

  Broadband local area networks · CPC title

• H04N21/2402

  Monitoring of the downstream path of the transmission network, e.g. bandwidth available (traffic monitoring in data switching networks H04L43/00; monitoring data switching networks utilization H04L43/0876) · CPC title

• H04N21/6118

  involving cable transmission, e.g. using a cable modem · CPC title