Research Of Low-voltage Power Line Carrier Communication Based On OFDM

Low-voltage power line carrier communication technology is an economical and doable communication technology.With high economic returns and social benefits,nowadays it receives more and more widespread attention.However,at present,using the low-voltage power line to set up the data access still has many difficulties,mainly reseason is that it is opened for user,and the impedance will change unpredictable without any forecast. which will seriously affect the quality of communications.In view of the communication problems which caused by the impedance changes on signal access points of the low-voltage power line,the author has done an in-depth study on the low-voltage power line communication coupe technology.It involves three main aspects:The analysis of the impedance of the low-voltage power line,the research of communication technology based on OFDM and the design of the automatic impedance matching system.When analyzing the impedance of the low-voltage power line,the author summarized the impedance test methods,analyzed the testing principle of the precision impedance analyzer and the test method of the impedance of the low-voltage power line,analyzed the impedance change of the low-voltage power line which caused by the architecture of the low-voltage power line.At last,through analyzing the test results of the impedance on each communications site,the author researched the characteristics of the impedance of the low-voltage power line.It gives the principle of orthogonal frequency division multiplexing modulation and demodulation and discuss the advantages and disadvantages of OFDM. Combination of OFDM technology and impedance matching, it can achieve a good matching resultsIn designing the automatic impedance matching system,on the basis of analysis on the impedance of the low-voltage power line ,the author raised one kind of model for the automatic impedance matching system,then designed the hardware electric circuit which used AD9288 and AVR chip,studied the following key parts: the impedance measurement,the calculation control,the reactance compensation and the resistance transformation.In the end,the author did the experimental confirmation to the impedance test and the impedance matching results of the entire automatic impedance matching system..