Spread spectrum data transmission system using the earth returning circuit on a low-voltage distribution line

This paper proposes and investigates a spread spectrum data transmission system using the earth returning circuit in a low-voltage power distribution line. Transmission characteristics of data signals which are transmitted or injected between the distribution line and the earth by using the earth returning circuit are measured in our experimental distribution line. It is confirmed that there are some advantages such as stable transmission, robustness against noise from customer loads compared with conventional data transmission between the distribution lines. We designed and implemented the FSK/DS spread spectrum modem with 9000 bps transmission rate for the distribution line data. Performance of the spread spectrum modem is measured by using the experimental distribution line. Moreover, the spread spectrum signal's electromagnetic radiation from the distribution line is investigated to analyze its effect on radio broadcasting and other facilities around the distribution line.