'n Ondersoek na die voorkoms en gedrag van intermodulasieprodukte by kraglyndraerstelsels

Abstract

Power line carriers are used throughout the world by electricity supply utilities for telecommunication purposes. These systems are unique as they have the ability to provide communication over distances that can exceed one hundred kilometer without the aid of repeaters. The power line acts as the transmission medium. In the research the occurance and effect of third-order intermodulation products on the signal-to-noise ratio of power line carriers in Eskom, were investigated. Power line carrier manufacturers do not provide adequate specifications about the behavior of their products with regard to the generation of intermodulation products under operational cond itions. This information is required by designers of communication systems utilizing power line carriers to ensure optimal performance of such systems. Detailed specifications might also be valuable in the identification of equipment suitable for specific applications. Power line carriers are often connected to a mismatched load and an important aim of this research project was to determine the effect of a mismatch between a carrier and its load. A test unit, consisting of a bandpass filter and a variable load impedance, was developed to facilitate measuring the generation of intermodulation products under simulated load conditions. The accuracy of these measurements was also investigated. An important conclusion that can be made on completion of the research is that a mismatched load does not impact much on the amplitude of third-order intermodulation products at the two-wire side. However. it has been found that load mismatching has a big influence on the trans hybrid loss. This loss is an important factor in the final signal-to-noise ratio at the receiver.