Broadband Impedance Matching Circuit Design Using Numerical Optimisation Techniques and Field Measurements

After a pre-study of the feasibility of impedance matching circuit design for broadband power line (BPL) communication system, EDF R&D division decided to go ahead in this field. This gave the opportunity to launch a PhD thesis at the University of Manchester. This paper presents a method of designing an optimal broadband impedance matching circuit for maximising a BPL communication equipment (or modem) signal injection into its load at any power line connection port. This optimal broadband impedance matching (BIM) circuit design is achieved in two phases. The first phase uses ´real frequency technique´ (with any kind of known load circuit or field load impedance measurement) to find the BIM circuit topology and its initial parameters. This is done by studying the frequency response of the BIM matching circuit that matches to the load. In the second phase, an optimisation method is applied to calculate optimal parameters for the BIM circuit. This is done by maximising the power transfer gain from the BPL modem to the load. This proposed method has been tested using some field load impedance measurements obtained from substations at EdF, France. The results give good confidence on the method in order to be able to have an optimized PLC system.