Comparison of the Dependence of Wiring Lengths of Radiated Immunity of Harnesses Connecting Automotive Communication Equipment

In this paper, we compared the immunity characteristics of wiring harnesses connecting automotive communication equipment at different wiring lengths. The communication behavior of an automotive harness connected to an evaluation module equipped with automotive Ethernet and exposed to radiated electromagnetic noise was compared for different wiring lengths. The S-parameters were measured under the same wiring conditions, and the frequency characteristics of the amount of noise applied were derived and compared with the length of the wiring. A reverberation chamber was used for the evaluation. From the results of each evaluation, changes in immunity characteristics due to differences in wiring length were confirmed for each frequency of electromagnetic waves, but no correlation was observed between communication quality characteristics and the results of S-parameter measurement. On the other hand, the frequency characteristics of the amount of noise applied also changed with the difference in wiring length, suggesting that a stable evaluation is possible with longer wiring lengths.