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Bidirectional trunk amplifier and cable modem for cable hybrid fiber and coax network which utilizes an upstream pilot signal

  • US 6,678,893 B1
  • Filed: 12/28/1998
  • Issued: 01/13/2004
  • Est. Priority Date: 12/26/1997
  • Status: Expired due to Fees
First Claim
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1. A cable modem for bidirectional services in an HFC (Hybrid Fiber and Coax) network, comprising:

  • a central processing unit (CPU);

    a tuner for downconverting upconverted downstream signals into IF (Intermediate Frequency) signals having constant frequency, by utilizing RF (Radio Frequency) signals;

    a saw filter for filtering a specified band frequency of the IF signals received from the tuner;

    a mixer and AGC (Automatic Gain Controller) for converting the filtered IF signals into base band signals and for outputting a gain control signal;

    a LPF (Low Pass Filter) for passing only low band signals and removing high band signals from the signals generated by the mixer and AGC;

    a gain controller for controlling the level of the signals received from the mixer and AGC so that the level of the signals output by the mixer and AGC is constant;

    a downstream demodulator for recovering and converting the base band signals from the LPF into pre-modulated digital signals by demodulating the modulated signals;

    a MAC (Media Access Controller) for dividing the demodulated signals into control signals and data signals and for transmitting upstream data signals to the transceiver under the control of the CPU;

    an upstream modulator for modulating the upstream data signals received from the MAC to be transmitted to the headend;

    a programmable attenuator for controlling the level of the modulated upstream signals;

    a pilot signal generator for generating a pilot signal; and

    a switch for connecting said tuner and said pilot signal generator under the control of the CPU.

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