Electromagnetic Effects of Cellular Radiotelephone on Motor Vehicles and Their Standards

Today, a lot of numeric modelling studies are carried out in the car industry to determine the electromagnetic condition in the vehicle. The purpose of these studies is to determine the car passenger cell effects on the coupling level and mode of electromagnetic disturbances. The passenger cell is an enclosed environment, pratically a Faraday cage, which an anechoic chamber test does not simulate properly. The present state of motor vehicle standards reflect this problem, since bench tests (ISO 11452) and complete motor vehicle tests (ISO 11451) are different. The study presented here deals with the correlation problem between anechoic chamber and passenger cell car testing for the particular case of cellular radiotelephone electromagnetic disturbances. Considering the increased use of this communication tool, for which one of the main uses is in cars, cellular radiotelephone disturbances have to be differentiated by a specific motor vehicle test. Now, the present ENV 50204 standard (immunity to electromagnetic field generated by numeric radiotelephone) does not take into account this specificity. Similarly, the complete motor vehicle test ISO 11451 does not take into account the cellular radiotelephone disturbances specificity. There is therefore a problem to which the present study tries to answer with an easy experimental simulation. Many practical results of coupled current and voltage to a test D.U.T. (Device Under Test), and taking into account the interaction cellular radiotelephone antenna/ D.U.T., are given for different bench and car test configurations. The electric field generated near the cellular radiotelephone antenna is also measured. Finally, a synthesis allows to give a first answer concerning the correlation between present standards (ENV 50204 / ISO 11451) and the particular cellular radiotelephone disturbances in the motor vehicle environment.