The use of reverberation chambers in the quantitative assessment of the risk associated with the installation of electronic systems on vehicles.

The EU SAFETEL Project was concerned with the safety implications of installing electronic equipment on vehicles. Part of the project concerned the development of a risk assessment model suitable for predicting an upper bound on the probability of failure of an electronic system installed inside a vehicle that is irradiated externally or internally. Only limited information on the immunity of the device and associated cabling is required. As an example, the model is used to demonstrate the probability of failure of a system due to irradiation from Digital Audio Broadcast (DAB) transmitters in the United Kingdom (UK). The failure probability is found to be highly sensitive to the clearance above the vehicle chassis of wire looms attached to the system, and to the accuracy with which the electric field is measured during an immunity test for the system/cable combination. The failure probability predicted by the risk assessment model is consistent with common observations of a log-normal distribution in the terminating power of receiving cables inside an irradiated vehicle confirmed by measurements in a reverberation chamber. In this paper we describe the experiments undertaken in the reverberation chamber and present the results of the experiments which illustrate their correspondence with the theoretical and observed statistics of the power received by cable terminations in a lossy enclosed space such as a vehicle. The rotational positions of the stirrer substitute for the statistical nature of the excitation fields in the vehicle and the variations of positioning of the cables within the vehicle. An example system comprising a multisensor ultrasonic parking warning system was used in the experiments and good agreement was achieved between the predictions and the observed failures of the system when under test. This paper is illustrates the potential for the use of reverberation chambers for testing systems that may be installed on vehicles and integrating the test results with a quantitative risk assessment of the vehicle operated in a real environment.