Case Study on Crosstalk Prediction of Transients in the Automotive Environment

The automotive EMI environment was studied. Of particular interest was the transient and pulsed signal behaviour of cable harnesses. Transients conducted by the supply lines of a 12 volt automotive environment were studied. The basis for this was ISO standard DIS/7637 part 1, with some additional current transients such as the current interruption in the ignition coil. Measurements of the transfer function of susceptible lines were performed in a car. With the help of the transfer function of a given cable set, the crosstalk from any given culprit pulse into the victim system can be predicted. A new graphical model is introduced to predict the crosstalk effects, which model is called the "L-shape" method. This new model is generally applicable. To investigate different cable set ups the ISO CAPACITIVE COUPLING CLAMP was used. This clamp was developed for immunity testing of automotive wiring systems. Theoretically crosstalk on cables is always a combination of capacitive and inductive coupling, altough in practice one of them is dominating. In automotive practice, both coupling mechanisms can be expected because high δi/δt and high δu/δt will occur.