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

• US 9,647,851 B2
• Filed: 10/13/2008
• Issued: 05/09/2017
• Est. Priority Date: 10/13/2008
• Status: Active Grant

• Current Assignee: PPC Broadband Incorporated (Belden Inc.)
• Original Assignee: PPC Broadband Incorporated (Belden Inc.)
• Inventors: Newby, Charles F., Halik, Gregory F., Kellogg, Matthew
• Primary Examiner(s): Pendleton, Brian T
• Assistant Examiner(s): LUONG, ALAN H
• Application Number:
  US12/250,229
• Publication Number:
  US 20100095344A1
• Time in Patent Office: 3,130 Days
• Field of Search: 725124, 725 78, 725125-130, 725149
• CPC Class Codes: H04L 12/2801 Broadband local area networks
• CPC Class Codes: H04L 12/2898 Subscriber equipments DSL modems H04M11/062; cable modems H04L12/2801
• CPC Class Codes: H04N 21/2402 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 Class Codes: H04N 21/2408 Monitoring of the upstream path of the transmission network, e.g. client requests monitoring data switching networks utilization H04L43/0876; scheduling or organising the servicing of application requests H04L67/60
• CPC Class Codes: H04N 21/6118 involving cable transmission, e.g. using a cable modem
• CPC Class Codes: H04N 21/6168 involving cable transmission, e.g. using a cable modem
• CPC Class Codes: H04N 7/104 Switchers or splitters

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.

Claims

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 voltage and high current surges from the components and subscriber equipment.

35. The network interface device as defined in claim 1, wherein the switch is configured to change from the normal position to the activated position with radio frequency speed.

12. A method of mitigating upstream ingress noise to a cable television (CATV) network, comprising:

transmitting downstream signals in a first frequency band from a headend of the CATV network to subscriber equipment; and

performing a plurality of steps comprising;

transmitting upstream signals in a second different frequency band from the subscriber equipment to the headend;

filtering the upstream signals including ingress noise;

delivering the upstream signals to a detector;

determining a power level associated with each of the upstream signals;

establishing a threshold power level which characterizes valid upstream signals from the subscriber equipment;

comparing each determined power level to the threshold power level;

generating a trigger signal when one of the determined power levels is equal to or greater than the threshold power level; and

instantaneously conducting the filtered upstream signals to the CATV network in response to the trigger signals without demodulating, analyzing, comparing or isolating any of the frequencies within the upstream signals, wherein conducting one of the filtered upstream signals to the CATV network occurs for a predetermined time period based on a timing signal activated by the trigger signal after the associated determined power level equals or exceeds the threshold power level,

wherein the steps are performed without demodulating the upstream signals.

13. The method as defined in claim 12, further comprising:

conducting one of the filtered upstream signals to the CATV network for a predetermined time period after the associated determined power level equals or exceeds the threshold power level.

14. The method as defined in claim 12, wherein none of the steps include analyzing, comparing or isolating any frequencies within the upstream signals.

15. The method as defined in claim 12, wherein determining the power levels includes processing a logarithm function.

16. The method as defined in claim 15, which includes producing signals based on the logarithm function, each signal being proportionate to one of the determined power levels.

17. The method as defined in claim 12, wherein the steps are performed without adding a delay which would be necessary for demodulation or comparison of frequency components.

18. The method as defined in claim 12, further comprising:

dividing downstream signals from the CATV network into active downstream signals and passive downstream signals at premises of a subscriber;

transmitting the passive downstream signals to passive subscriber equipment;

transmitting the active downstream signals to active subscriber equipment;

conditioning the active upstream signals from the active subscriber equipment;

not conditioning the passive upstream signals from the passive subscriber equipment;

combining non-conditioned passive upstream signals and the conditioned active upstream signals into upstream signals transmitted to the CATV network;

determining power levels of the active upstream signals; and

preventing noise in the second frequency band originating from active subscriber equipment from reaching the CATV network when the power levels of the active upstream signals are less than the threshold power level.

19. The method of claim 12, which includes continuing the conduction of one of the filtered upstream signals to the CATV network until the filtered upstream signal is transmitted to the CATV network without truncation of information contained in the filtered upstream signal.

34. The method as defined in claim 12, further comprising the step of preventing the filtered upstream signals from reaching the CATV network when the determined power levels are less than the threshold power level.

20. A network interface device comprising:

a first port configured to receive downstream signals from a communication network;

a second port configured to receive upstream signals from a subscriber device, each one the upstream signals comprising at least one frequency component;

a first signal path operatively coupled to the first and second ports, the first signal path configured to pass the downstream signals to the subscriber device;

a second signal path operatively coupled to the first and second ports, the second signal path configured to pass the upstream signals to the communication network; and

circuitry operatively coupled to the second signal path, the circuitry configured to;

evaluate linear magnitudes of the upstream signals;

maintain a switch at a default position to block the upstream signals which have linear magnitudes below a designated linear magnitude so that the blocked upstream signals are not transmitted to the communication network; and

assert a timing signal having a time period in response to the linear magnitudes that are evaluated greater than the designated linear magnitude;

activate the switch to an activated position for the duration of the time period to pass the upstream signals which have linear magnitudes greater than the designated linear magnitude so that the passed upstream signals are transmitted to the communication network,

wherein the circuitry is configured to transmit the upstream signals to the communication network, wherein the switch is configured to change to the activated position based only on the evaluation of the linear magnitudes of the upstream signals.

21. The network interface device of claim 20, wherein the evaluation excludes any demodulation of the upstream signals, and the evaluation also excludes any analysis, comparing or isolation of any frequencies within the upstream signals.

22. The network interface device of claim 20, wherein the circuitry includes a log amplifier detector.

23. The network interface device of claim 22, wherein the log amplifier detector is configured to generate a DC voltage signal that is proportional to the logarithm of input power to the log amplifier detector.

24. A communication system comprising:

a house amplifier comprising;

a first port configured to connect to a cable network;

a second port configured to connect directly to a home coaxial outlet;

a forward signal path coupled between the first port and the second port to pass a forward signal received through the first port; and

a reverse signal path coupled between the first port and the second port to pass a reverse signal received through the second port, wherein the reverse signal path comprises;

a gate coupled between the first port and the second port and configured to control a selective passing of the reverse signal; and

a detector circuit configured to detect when the reverse signal is received from the second port and to activate the gate when the reverse signal is present and to deactivate the gate when the reverse signal is not present, the detector circuit being operatively coupled to a timing circuit configured to assert a timing signal having a time period that activates the gate when the reverse signal is detected and to enable a delay corresponding to the time period before deactivating the gate when the reverse signal is no longer detected,

wherein at least one of the forward signal path or the reverse signal path includes a radio frequency signal amplifier.

25. The communication system of claim 24, which includes an RF switch operatively coupled to the gate.

26. The communication system of claim 25, wherein the gate is an OR gate configured to respond by applying a control signal to the RF switch.

27. The communication system of claim 24, wherein the reverse signal is received from a cable modem, eMTA, or settop box inside a house.

28. The communication system of claim 24, further comprising a house.

29. The communication system of claim 24, wherein the forward signal path comprises a forward signal amplifier configured to amplify the signal received through the first port.

30. The communication system of claim 24, wherein the reverse signal path comprises an operational amplifier configured to affect the reverse signal.

31. The communication system of claim 24, wherein the detector circuit includes a log amplifier detector that is configured to generate a signal that configures the communication system to allow the reverse signal to impress on the second port, wherein the generated signal is proportional to a power content of the reverse signal.

32. The communication system of claim 24, wherein the communication system is configured to connect subscriber equipment to a cable television (CATV) network over which the forward signal in a first frequency band from a headend of the CATV network is transmitted to the subscriber equipment and a valid reverse signal in a second different frequency band is transmitted from the subscriber equipment to the headend, the communication system configured to mitigate ingress noise into the CATV network in the second frequency band, the communication system comprising:

an upstream filter which filters reverse signals before delivery to the CATV network, the reverse signals including a plurality of frequency components, wherein the detector circuit is connected to the upstream filter, the detector circuit determining a level of power corresponding to each of the reverse signals filtered by the upstream filter, and wherein the detector circuit supplies a power signal related to each level of power;

a threshold circuit which establishes a threshold level of power which characterizes valid reverse signals, and which supplies a threshold signal related to the established threshold level of power;

a comparator connected to the detector circuit 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 operatively coupled to the gate, wherein the switch is configured to change from a normal position to an activated position, the normal position isolating and terminating the reverse signals from the upstream filter, and the activated position conducting the reverse signals from the upstream filter to the CATV network, wherein the conducted reverse signals include information;

wherein the detector circuit, the threshold circuit and the comparator operate without delaying an activation of the gate due to any analysis of the frequency components within the upstream signals;

wherein the switch assumes the activated position in response to the assertion of one of the trigger signals; and

wherein the switch returns to the normal position after the information has been fully transmitted to the CATV network.

33. The communication system of claim 32, wherein the detector, the threshold circuit and the comparator operate without demodulating the upstream signals and without comparing or isolating any of the frequency components of the upstream signals.

36. 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:

a first port configured to receive downstream signals from the CATV;

a second port configured to receive upstream signals from the subscriber equipment, each one the upstream signals comprising at least one frequency component;

a first signal path operatively coupled to the first and second ports, the first signal path configured to pass the downstream signals to the subscriber equipment;

a second signal path operatively coupled to the first and second ports, the second signal path configured to pass the upstream signals to the CATV network;

an upstream filter which filters the upstream signals before delivery to the CATV network;

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 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;

a switch connected to the upstream filter wherein the switch is configured to change from a normal position to an activated position for the duration of the time period, 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;

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,

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, 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.