Patent ID: 6678893
Filing Date: 2004-01-13
Classification: H04L,H04N

Abstract:
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.