Heri Rakouth

"Driving concepts for automotive EMC testing."

SYNOPSIS

The global automotive EMC community has been very productive over the past decade. In particular, in 1994 the ISO organization published the first versions of the ISO 11451 series and ISO 11452 series respectively for the vehicle and the component immunity test methods. And in 1995, the IEC introduced the CISPR 25 document combining both component and vehicle emissions test methods for the protection of receiver used on board vehicles. This presentation is aimed at analyzing the most innovative concepts, which have been developed to provide the technical foundations the immunity testing. Another presentation will be set up in the near future to address topics related to emissions testing will be addressed during a presentation. Accordingly, the following outlines the selected concepts.

Amplitude modulation and constant peak method

For both component and vehicle immunity testing automotive EMC requirements involve radiated electric field as high as several hundreds volt/m and injected current in the range of several hundred milliamps. In addition, the tests are done for both CW and AM modulation. For budget optimization, most EMC labs use power amplifiers rated for the CW power requirements. Therefore, most of them run in non-linear mode as soon as the low frequency signal is superimposed for the AM modulation. This situation results in an unacceptable measurement uncertainty associated with the unintended generation of harmonic frequencies. The constant peak calibration method has been introduced to eliminate this issue and is extensively described in the ISO 11451-1 and ISO 11452-1 documents.

Substitution method and ground reflection

For the purpose of rendering the worst case of road electromagnetic characteristics, most EMC labs run their vehicle immunity tests in a semi-anechoic chambers, whereby the ground is the only part of the chamber that is not lined with absorbing material. For radiated immunity, the electric field is calibrated by means of the substitution method, which entails two main steps. Step 1, the vehicle is removed from the test site and the field is measured at the reference point while the driving power is recorded for each test frequency. The associated power calibration file displays peaks and minimums corresponding respectively to destructive and constructive and interferences, which result from the superposition of the direct and ground reflected waves. Step 2, the actual test is run with the vehicle installed in the chamber, and the field intensity controlled by the power calibration file. The presence of the vehicle significantly alters the propagation of the waves involved in step 1. As a result, the test object will be either over-tested or under-tested. Several new calibration procedures have been introduced to offset the interference problems, as presented in the ISO 11451-2 test procedure.

Bulk current injection: need for multiple positions of the injection probe

For the purpose of component immunity testing, the automotive community has widely adopted the so-called Bulk Current Injection (BCI) method. Here again, the substitution method is used to calibrate the injected current. Similarly to the vehicle radiated immunity testing described above, this method involves two steps, whereby the current is first calibrated through a 50 W fixture prior to being effectively injected into the actual harness, while keeping the power as a reference. For each test frequency, the current effectively injected in the actual harness is subject to the impedance seen by the injection probe. By virtue of the transmission line properties, the concerned impedance can vary from zero to infinity over the test frequency range for a given position of the injection probe. As a result, like for the vehicle situation, the test object will be either over-tested or under-tested. ISO 11452-4 uses the multiple positions method to mitigate the issue.

BIOGRAPHY

Heri Rakouth currently is the manager of the EMC and Connection Systems group at Delphi Automotive Systems located in Saginaw, Michigan. He received the BS degree in mechanical and electronic engineering from Ecole Spéciale de Mécanique et D'Electricité of Paris, France in 1978, and the MS and PhD degrees in electrical engineering, from the University of Pierre and Marie Curie of Paris, France in 1979 and 1982 respectively. Dr. Rakouth also holds an MBA from Saginaw Valley State University, Saginaw Michigan, and a MS in manufacturing management from Kettering University, Flint Michigan. Dr. Rakouth was an Assistant Professor of Electrical Engineering at Ecole Supérieure de Physique et Chimie Industrielles de Paris in France, associated primarily with the Acoustics and Electronics Departments until 1982. He then joined Thomson CSF, where he started to deal with EMC for the aerospace and military applications, and took the leadership for HAEMP and EMC/Tempest protections of the radio system in the Mobile Subscriber Equipment project, a joint program shared with GTE for the U.S army in 1985. Dr. Rakouth started working for the automotive industry, when he joined Renault in 1989. Since then, he has been very active in the arena of EMC standardization. In particular, he was the technical pivot for the build of the European Directive 95/54/CE and has fostered a sustained momentum for a scientific EMC practice in the automotive industry. For the European directive and for the current versions of the ISO 11451, ISO 11452 as well as CISPR 25 standards, Dr. Rakouth has championed several innovative concepts such as constant peak amplitude calibration for AM testing, time saving technique for vehicle radiated narrowband emissions measurement, and mitigation of the ground reflection for vehicle radiated immunity testing. Dr. Rakouth was member of different advisory boards such as UTAC in France, ATA in Italy and Era Technology in Great Britain and chaired different EMC symposia sessions. He has published over twenty scientific papers and tens of classified and non-classified reports. He joined Delphi Automotive Systems in 1996, and currently represents Delphi at the SAE-EMR standardization group. In addition, Dr. Rakouth has always been very active in the academic arena. Currently, he serves as an adjunct faculty at Saginaw Valley State University, Kettering University, and Central Michigan University, where he teaches among other topics, Applied Electronics, Communication Systems and Electromagnetics.

Dr. Rakouth
EMC-Connection Systems Group
Manager Delphi Automotive Systems
3900 Holland Road
Saginaw, Michigan 48601-9494
(989) 757 3065 Phone
(989) 757 3039 Fax

heritianarisoa.rakouth@delphiauto.com

Southeastern Michigan Chapter of the IEEE EMC Society Link.