Sensitivity Analysis of RF Current Injection Techniques for Immunity Testing of Automotive Ethernet

Resorting to point-to-point communication between two devices over an unshielded twisted-wire pair (UTP), the BroadR-Reach (R) Physical Layer has the potential to assure very high transmission speeds. However, ensuring immunity of such high-speed data lines in the harsh electromagnetic environment of modern car architectures is a challenging task, requiring repeatable and reliable test procedures for immunity assessment. This work investigates and compares the performance of the Bulk Current Injection (BCI) and of the Tubular Wave Coupler (TWC) techniques-currently foreseen by the ISO standard up to 400 MHz and from 400 MHz up to 3 GHz, respectively-in testing the immunity of an UTP. The focus is on the sensitivity of the test outcome to poor positioning of the injection device on the cable harness. Indeed, preliminary measurement on canonical wiring structures revealed a more pronounced sensitivity to possible misalignment in the case of TWC rather than BCI setups, which is here investigated by means of a specific set of full-wave numerical simulations and interpreted by the light of simplified circuit models.