Hfc Access Network Modulation And Demodulation Of The Dvb-c Technology - The Realization Of Complex Adaptive Equalizer

In this paper, HFC and its technical standard DVB-C are introduced. And then study the modulation and demodulation technology in accord with DVB-C has been completed, which are QAM applied in transmission of digital video signal (downstream) and QPSK (upstream) used for interactive communication. After analyzing the characteristic of QAM signal and explaining the effect due to the channel and the noise, the scheme, which can improve the quality of QAM, is put forward. Completely comparing adaptive equalizer with blind equalizer, LMS is selected for the equalizer. The hardware has been completed with the CPLD devices of Altere. The design of the core circuit is finished with MAX+PLUS II. The astringency of equalizer proved by a simulation of wave in the end. The flexibility and credibility of system are improved very much by the technology of CPLD. The complex filter is composed of four transversal filters. This kind of design make equalizer work more quickly and its structure more simple. To save the system resource, when designing the transversal filter of complex filter, a scheme of combine global parallel with part serial is adopted. So the project can be completed with fewer devices. At present, the equalizer in the CABLE MODEM is a blind equalizer or adaptive equalizer. The equalizer completed in the task is a project of equalizing QAM signal.