In Japan, ETC, the electronic toll collection system, is now about to go operational as part of the intelligent transportation systems (ITS) which aims for the new environment in road traffic. However, the environment for the ETC systems is not fully prepared because of the communication interference caused by the multiple reflections from the construction, such as the toll gate canopy or the elevated highway. In this paper, the authors propose a new countermeasure method to suppress the multiple reflections from the constructions. They investigate the new radio wave absorber to suppress the multiple reflections. By using the basic radio propagation principle, the necessary absorption level of the radio wave absorber against the circular polarized wave and oblique incidence is obtained. They develop the circularly-polarized radio wave absorber. The absorbing panel by using the developed circularly-polarized radio wave absorber is presented. After, they experiment with the absorber panel. Experimental results prove the validity of a new countermeasure method.
Samenvatting