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Digital set-top box modem module



Digital set-top box modem module


Digital STB working in the state of cable television network, cable television network using analog transmission, it must be digital signal modulation and demodulation can be transmitted in the analog channel, the modem is a key component of the system, technically similar to the principle of telephone modems, But using a higher modulation method, the downlink use 64QAM or 256QAM, DVB-C (Digital Video Broadcast by Cable) and DAVIC use 64QAM as the standard modulation method to Motorola's MC92305QAM demodulator chip, for example, 7M Analog signal bandwidth using 64QAM modulation of up to 42Mbit / S, the uplink using two ways, one is the use of telephone lines as the uplink channel, the other is the use of bidirectional HFC network uplink channel, the use of HFC network QPSK as a modulation scheme. The QAM or QPSK modulator modulates the MPEG-formatted data stream in a standard PAL channel and combines it with other video-modulated signals.