EMC Aspects of High Speed Powerline Communications

With the cessation of the German Telekom's monopoly significant changes are taking place in the field of fixed network telecommunications. In this context fast communication links over the so-called „last mile“ are of major interest. The electrical power distribution grid could turn out to be an ideal alternative for existing standard communication links. Numerous experiments and theoretical investigations have demonstrated, that power lines generally exhibit the physical properties for rates up to several Mbits/s. Based on these encouraging results, the vision of the INTERNET access via the standard wall-plug was born in industry and strongly supported by major utilities. Most of the frequency band of interest, however, is already in use for different kinds of wireless services, such as broadcasting, amateur radio or air traffic control. Although PLC is intended to be wire-bound, a certain impact on wireless services seems inevitable, because power distribution networks are electromagnetically open. This could invoke different EMC problems, which have to be carefully analyzed and avoided by appropriate measures. Currently the preparation of regulations is under way, defining portions of the spectrum between I...30MHz, which could be opened for PLC. Furthermore allowable levels of the radiated fields have to be defined, including the corresponding measuring procedures. This paper outlines the possibilities and limitations of high speed PLC, providing EMC with existing services. Towards this aim, broadband modulation schemes as well as measures of network conditioning are considered. The latter will reduce possible antenna effects of the power supply wiring system and suppress common mode signal propagation.