EMF Excitation Dependency on the Boundary Condition Due to Mobile Radios - Parallel FDTD Analysis on the Radio Environment in a Train Carriage -

Electromagnetic field (EMF) distributions inside a train carriage caused by the cellular radios of the passengers are analyzed and effects of their electromagnetic interference (EMI) on implantable cardiac pacemakers are evaluated based upon the analysis results. Since portable radios may be used almost everywhere, accurate and reliable estimations of EMC in various environments including special conditions are required. Spaces surrounded with conductive surfaces, e.g. train carriages and cars, are typical environments requiring assessment. Here, we refer to this kind of environments as a semi-echoic environment (SEE). The authors have already reported the results of both precise computer simulations and experiments using 800 MHz and 2 GHz transmitters in an actual train carriage [1]. We employed the FDTD technique [2] and a supercomputer to estimate the EMF distributions excited inside train carriages. Moreover, large-scale parallel computing based upon several node partitions was used because of its memory and speed capabilities. It could give us a good perspective within a reasonable computation time [3]. In Addition, a simplified histogram estimation method for electric field strength in whole area of the train carriage were employed to deal with the complicated electromagnetic field (EMF) distributions. It allowed the EMI risk to pacemakers by cellular radio transmission to be quantitatively evaluated. The obtained results implied that FDTD computer simulation could be used for estimating complicated EMF excitation problems in SEE precisely. Those results confirmed that excessively high EMF, high enough to affect the normal functions of the pacemaker, did not occur inside the train carriage beyond the safe distance of 22 cm [4], the safety specification for pacemaker users. In the above investigations, we assumed the inside surface of train body to be made of perfectly conductive walls in the FDTD analysis because of considerations for really serious case. Admittedly, the inner surface of the carriage body is covered by non-metallic materials. This paper discusses effects of thin lossy dielectric plates used for inner surface of the carriage. We use a typical train carriage now in active service in Japan, and 800 MHz band cellular radio simulators. We examine the EMF histograms of inner space of train carriage when the inside surface of the body is covered by plastic panels made from polypropylene. The realistic and complicated situations wherein humans occupy a train carriage are also examined. In the following sections, the configurations of FDTD analysis for the EMF of the train carriage are described. Section 3 shows the analytical results of the EMF excited in the train carriage. Finally, a brief summary of this paper is provided in the last section.