On the design of impedance matching circuits for vehicular power line communication systems

The design of power line communication (PLC) systems for vehicles, i.e., vehicular power line communication (VPLC), is a challenging task as propagation conditions are harsh and devices need to be low cost and highly integrated (to have minimal overhead on vehicle´s cost and weight). One particular challenge, which is common to many PLC application scenarios, is the temporal and spatial variation of the input impedance. In this paper, we investigate on this issue and, based on previous studies and measurements on access impedances for a PLC network in a car, we discuss the design of adaptive impedance matching circuits for VPLC. This includes a study on frequency range of operation, suggestions for impedance matching circuits, and proposing a circuit structure. In particular, since inductors are an integral part of matching circuitry and given that over the typical frequency range of operation for VPLC their integration is challenging, if not impractical, we advocate the use of active inductors in matching circuits. As compared to passive inductors, they occupy a smaller on-chip size and their inductance is adjustable. We also propose an active inductor structure that provides a wide range of inductance values which are suitable for VPLC applications.