Inductive and capacitive couplings in automotive harnesses - A crosstalk investigation

This work consists in an investigation about the electromagnetic interaction between two vehicular systems. The specific circuits under investigation are driven by the radio and the airbag Electronic Control Unit (ECU) and have the right rear speaker and pre-tensioner, respectively, as loads. The occurrence of this kind of interaction, known as crosstalk, is sub-divided into two classes: inductive and capacitive coupling. These phenomena are related to magnetic and electric fields couplings, respectively, and they are usually inseparable. Nevertheless, one of these effects can be predominant in relation to the other. Obviously, none of them is desirable and, when noticed, can lead to anomalies in the vehicular operation. The methodology of this work is based on harnesses´ time and frequency domain voltage measurements, monitoring of airbag ECU´s operation and a prediction of inductive and capacitive contributions to the overall coupling between the systems. These tasks have required the use of an oscilloscope, the information from the On-Board Diagnostic (OBD) terminal and the simulation software Ansys^® Q3D Extractor. Some worst-case harnesses´ spatial dispositions schemes have been proposed and tested. Finally, some modifications in the vehicle´s design have been proposed and tested with the purpose of decreasing the probability of error occurrence due to crosstalk.