Dplc Communications Dual Digital Mediation And Its Dsp Implementation

PLC is the communication means of transmitting carrier wave signal with multiplexing high voltage power lines, which is special communication technology in electric power systems. PLC has been used widely in electric power industry in long-term development. Traditional PLC is single tone channels structure. At the precondition that the modern communications are developing along with ISDN of wide band and intelligence, PLC is facing challenge of frequency resource utilization, anti-intervening characteristic, connection to LSDN, intelligent management of networks and electric power distribution. DPLC just emerge as times require. Because DPLC overcomes some disadvantages of PLC and improves many characteristics of PLC, it is importance and become rapidly the mainstream of PLC communication in world. DPLC is communication system, which converts information into data signals and transmits in power lines by using many advanced technologies. DPLC doesn抰 send data signals to power lines directly, but modulates the carrier wave to analog signals and then transmits it in power lines Modulation, demodulation and baseband signals processing are the core of DPLC, the dual modem we designed just realize the core of DPLC. First, we discusse the relevant theory of data communication from the basal model of data communication systems in this paper, and then stress on the scheme of the modulation and demodulation, the design of filter and the technology of code synchronization in system. Based on the theory that the data of base band embody timing information in zero point of intersection, we put forward the method of code synchronization by using information of the cross-zero point. We discusse the protocol of controlling errors based on ITU-T V.42 and the essential of DSP realization. The dual modem use LSI and realize the modulation of DPSK and QPSK by using DSP technology, and offer the coupling transformer interface of counterpoise four lines, which connects the carrier equipment, and fit in channel by using the root raised cosine-shaping filter.