Wave Absorber for Improving EM-Wave Environment between ETC Lanes and Its Practical Application

点击翻译按钮获取中文摘要

In recent years, the non stop automatic charge payment system using wireless communication at 5.8GHz as central service of intelligent transport systems (ITS), which is called electronic toll collection (ETC), is spread widely and diffusion rate has reached to 75% in Japan at 2008. When the operation of ETC was started, communication errors were caused in ETC environment due to undesired electromagnetic(EM)waves from walls, ETC gates or other possible nearby objects. The optimal use of wave absorber is a possible way to mitigate this problem, and a variety of absorbers are used in various places, such as a board type used for the ceiling of tollgate, a pavement type used for the road surface. In such a background, the wave absorber for installing between ETC lanes is also required because the number of tollgate, where two or more ETC lanes are possessed, may increase with diffusion rate rise. Certain performance is necessary for this absorber, such as absorption of undesired EM waves, shielding effect of EM wave reaching adjacent lanes, ventilation to avoid the shock of the wind, and visibility to adjacent lanes.In this research, some wave absorbers placed behind the metal mesh as back metal for improving ETC environment is proposed such as the type of reinforced plastic including glass fiber with periodic lattice, cylindrical bars with magnetic loss covers arranged periodically, and magnetic rubber sheet with circular lattice. Various characteristics are evaluated analytically and experimentally. As a result, good characteristics of reflection loss and shielding effect are obtained for circularly polarized wave using ETC system. Therefore, feasibility of proposed wave absorbers can be confirmed quantitatively.