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Adaptive filter for reducing ingress noise in CATV return signals

  • US 6,757,910 B1
  • Filed: 06/08/2000
  • Issued: 06/29/2004
  • Est. Priority Date: 06/08/2000
  • Status: Expired due to Term
First Claim
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1. A method for reducing ingress noise from upstream signals in a communication network, the method comprising:

  • monitoring frequencies of a desired signal in an upstream path on an ongoing basis;

    detecting a first lowest signal frequency and a second lowest signal frequency used by the desired signal in the upstream path at a first time and at a second time later than the first time, respectively;

    electronically adjusting a first cutoff frequency of a filter circuit in response to detection of the detected first lowest signal frequency, to a frequency below the first lowest signal frequency used by the signals in an upstream spectrum; and

    electronically adjusting a second cutoff frequency of a filter circuit in response to detection of the second lowest signal frequency, to a frequency below the second lowest signal frequency used by the signals in the upstream path, by using a first selected time constant for exponentially lowering the cutoff frequency from the first cutoff frequency to the second cutoff frequency, and by using a second selected time constant for exponentially raising the cutoff frequency from the second cutoff frequency to the first cutoff frequency, thereby blocking a signal component having a frequency below at least one of the first and second cutoff frequencies, to an extent permitted by a frequency plan used in the upstream spectrum, where at least one of the first and second time constants is selected to reduce the likelihood of false or spurious signal detection.

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