Design Of MSK-based Power Line Digital Carrier Communication System

Along with the pace of global networking quickening, information networking and control automation have become the pressing requirements of every industry for improving efficiency and realizing modernization. So it has very wide application prospect using power line as channel to realize data transmission and information exchanging. Power line carrier communication technology adopts power line as communication medium and possesses the merits of making full use of resources on hand, easy construction, low comprehensive cost, being unrestricted by environmental conditions. But power line is characteristic of violent change in amplitude-frequency peculiarity, narrow effective band, complex channel character, which needs to using modulation technology with higher comprehensive characteristics. At the same time, with the continuous perfection and maturity of large-scale , very large-scale integrated circuit technology and the further development of digital circuit design, using DSP and CPLD to establish all digital application system has become development trend.This paper brings forward the idea of using MSK with high frequency efficiency, fast power descent outside band, constant wrap, successive phase as carrier communication system of modulation and demodulation technology and designs all digital communication module based on DSP, CPLD, digital frequency synthesis and software demodulation to implement the reliable middle & low speed data transmission. The field tests and analyses show that the system has excellentperformance , strong anti-interference capability, good reliability and high performance-price-ratio, and can be used in such middle & low speed data transmission occasions with higher demand of communication reliability such as Distribution Automation, Automatic Meter Reading System, Industry Control.This paper first analyzes the low-voltage power line channel character and establishes the corresponding channel model. Then introduces principles of MSK technique, methods of implementation and the feasibility and superiority of taking MSK technique for the modulation plan of power line carrier communication in details. Subsequently the system architecture and the hardware & software implementation including modulation loop based on DSP'VC5416 & AD9851 , demodulation loop made up of ADS803 & FIFO IDT72245, DSP'VC5416 and RS232/485 interface, system clocking and logical control circuit using CPLD XC95144 , the whole system operation control using DSP and its realization by C and assembly programs are provided. The system debug and performance analysis are also listed in the paper.