Simulation-based Prediction of System-Level RF Immunity Test Results for Automotive Open-Loop Bulk Current Injection Tests

This work describes a methodology for RF immunity prediction for automotive component- or system-level EMC tests on the example of an open-loop Bulk Current Injection (BCI) (ISO 11452-4) up to 1 GHz.

The research mainly focuses on the typical automotive configurations with the equipment under test (EUT) being locally ungrounded and therefore floating for RF signals. Accurate characterisation and modelling of such floating structures and of the notorious CM-DM mode conversion using plain RLC- and MTL-based models represent the main challenges covered in this work.

A straightforward modelling procedure with the necessary key concepts and tools is developed. Two independent direct and indirect measurement techniques to access the nodes at the floating structures with the virtual S-parameter measurement ports are proposed and discussed.

The method extension for realistic complex EUT layouts using MoM field solvers is proposed. The corresponding challenges and solutions are discussed.

The final validation is performed on a case study with an active demonstrator EUT consisting of a mass-market voltage regulator DUT IC and a minimal amount of external passive components. A very good correlation or RF immunity prediction to the measurements is confirmed.

The work proposes the decomposition into two independent top and bottom modes (TM/BM) as an efficient method for the analysis of floating structures. The assumptions necessary to apply such decomposition, its limitations, advantages and disadvantages vs. common and differential (CM/DM) mixed modes are discussed.

The maximum effective RF noise levels that can be reached locally at DUT ICs in the open-loop BCI test are analysed with parametric sweeps. A very good correlation to the RF immunity classes of the IC-level Direct Power Injection (IEC 62132-4) tests is observed.