Electric Field Simulations around a Car of the Tire Pressure Monitoring System

Kouichi TANOSHITA
Koji NAKATANI
Yoshihide YAMADA

Publication
IEICE TRANSACTIONS on Communications   Vol.E90-B    No.9    pp.2416-2422
Publication Date: 2007/09/01
Online ISSN: 1745-1345
DOI: 10.1093/ietcom/e90-b.9.2416
Print ISSN: 0916-8516
Type of Manuscript: Special Section PAPER (Special Section on 2006 International Symposium on Antennas and Propagation)
Category: Electromagnetics
Keyword: 
TPMS,  electromagnetic simulation of a car,  method of moment,  multilevel fast multipole method,  radiation from a tire,  

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Summary: 
In order to support driving safety, TPMS (Tire Pressure Monitoring System) has been introduced in U.S.A. and Europe. In Japan, the AIRwatch system has been developed and commercialized. Some studies were made to clarify the electric field environment of this system. However, no detailed calculation of the electric field between the transmitter in the tire and the receiving antenna has been published. This paper clarifies the electric field environment of the Japanese system through electromagnetic simulations by a high performance MoM simulator that utilizes the MLFMM scheme. First of all, electric wave emissions from an antenna mounted in a tire are shown to be larger than that of the same antenna in free space. The tire rubber effects are also investigated. Next, electric field distributions on the windshield holding the receiving antenna are calculated. By comparing calculated electric field levels with those in the free space condition, car body interruptions are clarified. Because car body interruptions are not so severe, it is shown that the free space electric field levels can be used as rough design parameters. Moreover, electric field changes due to tire rotation are also clarified. Calculation accuracy is confirmed by the good agreement with measured data collected from a 1/5 scale car model. To permit estimations to be made in actual situations, the effects of the ground are also investigated. This simulation study introduces a lot of important data useful in TPMS system design.