Use of Double Bulk Current Injection for Susceptibility Testing of Avionics

In this paper, possible applications of double bulk current injection for susceptibility testing of spacecraft are investigated and discussed. Two test procedures are proposed: one is suitable for system-level (i.e., onboard) testing, the other for unit-level assessment of avionic equipment interconnected by multiwire shielded bundles. By enforcing equivalence between radiation and injection, both procedures are designed to inject expected electromagnetic interference (EMI) levels in the equipment under test (EUT), connected at the terminations of a wiring harness. The procedure for system-level testing requires amplitude and phase control of the radio-frequency power sources used to feed the injection probes. It allows to correlate the susceptibility effects obtained by injection with those due to a nonuniform electromagnetic field (such as the field generated by internal EMI sources in metallic enclosures). It is, therefore, suited for radiated intrasystem verifications. The procedure for unit-level testing exploits equivalence between radiation and injection in terms of the current distribution along the overshield, and applies to bundles with an arbitrary number of inner conductors. In the case of vertical polarization, this procedure allows for the reconstruction of the interference effects produced in the EUT by conventional radiated-susceptibility tests (e.g., DO-160), requiring direct radiation of the system.