Novel modeling strategy for a BCI set-up applied in an automotive application: An industrial way to use EM simulation tools to help hardware and ASIC designers to improve their designs for immunity tests
Electronics suppliers of automotive industry use BCI (Bulk Current Injection) measurements to qualify immunity robustness of their equipment whereas electronics components manufacturers use DPI (Direct Power Injection) to qualify immunity of their component. Due to harness resonances, levels obtained during a BCI test exceed standard DPI requirements imposed by automotive suppliers onto components' manufacturers. We propose to use BCI set-up modeling to calculate the equivalent DPI level obtained at the component level during equipment testing and to compare results with DPI measurements realized at IC level.
Experimental validation of the generalized accurate modelling method for system-level bulk current injection setups up to 1 GHz
A small-signal model of an automotive system-level bulk current injection (BCI) setup developed with a generalized accurate method shown in the previous publication is verified on a case study with a demonstrator EUT module. The work utilizes an equivalent circuit modelling approach for the floating ungrounded EUT board and a macromodel for an active DUT IC. The simulation-based prediction of the BCI test results using an IC failure threshold and a small-signal simulation of RF levels at floating EUT module under BCI tests is shown. Due to high accuracy and detail of the BCI setup model, the prediction also shows very good correlation to real measurement data, both qualitatively and quantitatively, up to 1 GHz.
Experimental characterization of injection probes for bulk current injection
In this work, a lumped-parameter circuit model of injection probes for bulk current injection (BCI) is derived from probe input-impedance measurement. The model accounts for the effects related to ferrite magnetic-core losses and degradation of the magnetic permeability with frequency. Model assessment is achieved by comparing predictions of currents induced by BCI in the terminations of an electrically-long single-ended interconnection with direct measurements in a real BCI test applied to the same structure. The proposed model provides a precise description of the coupling between the probe and the wiring under test for frequencies up to 500 MHz. INTRODUCTION The assessment of bulk current injection (BCI) versus other conducted susceptibility tests requires precise modeling of injection probes in a bandwidth extending up to hundreds of MHz. This implies the need to improve the canonical model developed in [1], where a low-frequency, lossless, inductive model of the injection probe was developed. In this paper, this problem is addressed by treating the probe as radio-frequency (RF) transformer with both the primary and the secondary windings acting as distributed-parameter magnetically coupled structures. An approximated, three-port lumped-parameter model of the probe is derived, which exploits experimental data of the probe input impedance (measured via a network analyzer (NA) in terms of reflection coefficient). This approach allows for the inclusion into the probe model of the frequency response of the ferrite core, i.e., the effects related to the degradation of the magnetic permeability of the ferrite core with frequency, as well as the core losses. Predictions obtained by the proposed model are assessed by analyzing a simple BCI setup, composed of a commercially available injection probe clamped on a single-ended wiring with known terminal loads. Comparison of the voltage levels actually induced by BCI in the wiring loads (obtained by measurement) with predictions based on the use of the proposed probe model indicates an appreciable agreement up to 500 MHz. LUMPED-PARAMETER CIRCUIT MODEL OF THE INJECTION PROBE The lumped-parameter circuit used to model the injection probe is sketched in Fig. 1(a). In the circuit, the radiofrequency (RF) source feeding the probe is represented by a Thevenin equivalent circuit with open-end voltage source RF V , and internal impedance Ω = 50 S R . The probe model is based on a low-frequency transmission line (TL) interpretation of the two magnetically coupled coils (i.e., the primary winding and the wiring clamped by the probe). Accordingly, lumped equivalent-circuits are used to model the windings and the input connector/adapter of the probe. In particular, 1 C and 0 1w L account for capacitive and inductive coupling between the primary winding and the inner surface of the metallic body of the probe; 2 C describes capacitive coupling between the metallic body of the probe and the clamped conductor; C C and C L are used to model the chain connection of the SMA-to-N adapter and the N connector mounted at the input port of the probe. The inductance C L affects the probe behavior for frequencies above 400 MHz. Conversely, the capacitance C C typically prevails over 1 C and its contribution to the frequency response of the probe extends at lower frequencies. Estimates for these parameters are provided in [2]. The frequency behavior of the ferrite core is accounted in the model of Fig. 1(a) by the complex and frequency-dependent coupled inductances ) ( 1 ω L , ) ( ˆ2 ω L . The probe frequency response is deeply influenced by these parameters, whose frequency dependence is due to magnetic dispersion and core losses. (a) (b) I2 V2 I1 V1 ΦL ΦR Φ'TL l' ΦP FP L C LB L C LB C2 C2 VS ZP Φ'TL l' VRF RS V1 V2 I1 I2 C2 C2 C1 CC