An Improvement of Communication Environment for ETC System by using Circular-Polarizations'EM Wave Absorber

Abstract

The electronic toll collection (ETC) system is now beginning to widely use as part of the ITS which aims for the new environment in Japan road traffic. However, it is not fully prepared the environment for ETC system because of the communication interference caused by the multiple reflections from the constructions, such as the tollgate canopy and the elevated highway. In this paper, we propose a new improvement method to suppress the multiple reflections from the constructions by using EM wave absorber. We present the necessary absorption of EM wave absorber in the oblique incidence at 5.8GHz circular-polarized wave, abbreviated as CP wave, by using a basic radio propagation principle. Then, we develop the CP' EM wave absorber. Moreover, we experiment at the ETC system under the elevated highway in order to demonstrate the effectiveness of the CP' EM wave absorber. As a result, we were able to confirm effectiveness of the proposed new method.