Transmission Characteristics of Fast CAN Signals in Flat Cables

For several years flat cables for the use in the automotive wiring harnesses have been attracting attention. Less weight, less space and higher automation degree are the key factors, which promise a benefit from the introduction of the new technology. The well defined electromagnetic properties are also often mentioned as an advantage of flat cables, because of the precise and constant routing in the car. Although it is true, that statistical error due to an unfavorable position of the cables in the harness is reduced, on the other hand the systematical error due to it's geometry is strongly enhanced. Since basic parameters like impedance or crosstalk characteristics are not specified for the cable types for CAN-transmission used in automotive, it is difficult to qualify a selected wiring system in the early development phase of a car model. In this paper we show a practical approach, combining the basic understanding of failure modes and measurements of the real CAN-transmission in a car like structure.