A compact economical PLC band-pass coupler with impedance matching

Most coupling circuits for PLC make use of the impedance transformation properties of a coupling transformer. Previous attempts to eliminate this costly component, while maintaining impedance adaptation, have not been successful in reducing component cost nor physical size. In this paper, a novel approach is followed: (1) a suitable band-pass matching circuit as for ordinary electronics is designed, and (2) the specifications of the components are upgraded to function safely in the power-grid environment. Therefore a matching circuit is transformed into a PLC coupler, resulting in a compact coupler which further exhibits band-pass filtering and excellent impedance-adapting performance. The design of such a coupler, and its evaluation in the laboratory as well as an office block, is described in this paper.