Research On Testing Environment Of Low Voltage Power Line Carrier Communication

Power line network is a kind of physical network, which connects thousands of families and extends in all directions. People have a dream of realizing data communication by this kind of huge network. But the low voltage power line is mainly used for power transmission, not for communication. Therefore, the channel environment is quite rough. In order to communicate via low voltage power line, it is necessary to conduct the research to its channel characteristics. The research work in this thesis is carried on just under this background.At first, transmission characteristics of low voltage power line are analyzed based on transmission line theory. Definition and solution of high-frequency low voltage power line parameters are discussed. Then the solution of the transmission line equation in complex frequency domain is obtained based on this foundation. By two-port network theory, the circuit equation of power line transmission characteristics are calculated. Meanwhile the multi-path propagation characteristics of low voltage power line are analyzed. A network coupler is designed to test the power line transmission characteristics cooperated with the network analyzer. The data is analyzed and the transmission characteristics are presented briefly.Secondly, noise, a principal aspect of communications interference, has also been analyzed. Only three important kinds of noise have been analyzed in the thesis since noise is complex in power line. At the same time, the actual noise of low voltage power line is measured by the spectrum analyzer (GW GSP-810) and the network coupler designed in this thesis. The noise characteristics of low voltage power line have been qualitative analyzed according to the experimental data. At last, to prevent the noise of the low voltage grid from interferencing the testing device, an isolation equipment, named electrical network power source, is connected between the testing device and the low voltage grid. The designing method of the electrical network power source has thoroughly been studied in this part based on the electromagnetic compatibility theory. The network component parameters have also been analyzed qualitative and precisely. Finally the simulation waveform of LISN (Line Impedance Stable Network) shows that the design is conformed to the measurement standard of radio jamming and anti-jamming equipment.