UNIVERSITY FOCUS “I believe the general perception within the EMC community is that the conventional ALSE method is outdated” immunity of all electronics inside the vehicle could be tested simultaneously – and foremost – with isotropic radiation, which ensures reliable testing.” The ISO 11451-5 standard, published in 2023, incorporates input from the EMCVERA project. It outlines EMC test methods harnessing a full reverberating chamber or VIRC. “The study raises concerns regarding the accuracy of the OBT method, primarily because the polarization and placement of the transmitter have substantial implications for whether a disturbance is triggered or not,” says Holm. “I believe the general perception within the EMC community is that the conventional ALSE method is outdated and that reverberating chambers are needed for future automotive EMC testing. Novel approaches to OBT testing need to be evaluated – and the ROBT method clearly shows potential.” Research beyond the initiative continues. The ΔDOF measure in particular has undergone further development, the fruits of which will be presented in a research paper, Utilizing the Chi-Distribution for the Assessment of Electric Fields within Reverberation Chambers , at the EMC Europe 2024 Symposium in Bruges, Belgium. In the paper, a threshold criterion is proposed that enables a determination of whether a reverberation chamber can be considered isotropic characterized by uncorrelated electrical field components, or if stirring needs improvement at specific frequencies. This concerns not only vehicle testing but also reverberation chambers in general. It could provide a standardized method for quantifying the attained reverberation within the vehicle and whether it is adequate for OBT testing. ABOVE LEFT: Expected isotropicity at different positions inside the VUT LEFT: Expected isotropicity for the onboard transmitter method (widely used by testers today) versus the reverberating onboard transmitter method developed by Holm and team The electromagnetic field within the reverberating chamber was evaluated via two new methods: expected isotropicity (eiso), which measures the average level of field from all polarizations, and ΔDOF, which quantifies the spatial distribution inside the reverberation chamber. This can be used to define a threshold for isotropicity and suggest where additional stirring is required. Reverberating onboard transmitter approach Vehicle interiors are complex and variable, with differing metal structures and absorbing materials influencing resonance. This means it would not be possible to forge a ‘perfect’ reverberating chamber, and vehicle-by-vehicle calibration would be required. Holm’s ROBT method did, however, produce a more isotropic field – at all six measured locations – than the OBT technique, with lower input power and less need for stirring. This is because the working volume of a vehicle interior is considerably smaller than a full ALSE. Importantly, it was found that the approach could enable cheaper, faster, more reliable and repeatable EMC analysis while ensuring immunity from all directions. Holm elaborates, “The ROBT method is very cost-efficient because wrapping the vehicle in conductive textile provides sufficient shielding. “Furthermore, a complete vehicle test can be performed in a single sweep in a couple of minutes. Naturally, time is required for rigging as well as performing the necessary calibrations beforehand. Potentially the 60 MARCH 2024 RIGHT: Another of the experimental setups explored in the study. Ongoing research focuses on ΔDOF and how this can be used www.AutomotiveTestingTechnologyInternational.com