A fundamental study of acoustic and EM wave absorber using resistive films and glass wool

Abstract

AbstractOver the past few years, the use of electromagnetic (EM) waves on highways has increased due to the spread of Electronic Toll Collection (ETC) systems in Intelligent Transport Systems (ITSs). Conventionally, roadside walls have been set up while considering the sound absorption of noise, but the need has developed for a structure also equipped with an EM wave absorption effect with the objective of preventing unwanted EM waves when EM waves are used. In addition, based on the properties of the EM waves used in Dedicated Short Range Communication (DSRC), the EM wave absorber used in the roadside walls should handle the circularly polarized waves that are second‐order reflections due to the wall surface and have ultrawide angle characteristics. In this paper, we place an EM wave absorber that does not harm the acoustic absorption characteristics behind a commercial acoustic absorber (standard acoustic panel of the Japan Highway Public Corporation) and unify the acoustic absorber and the EM wave absorber in a single structure. We then study the implementation of an acoustic and EM wave absorber having both functions of absorbing sound and EM waves, and wide angle characteristics for circularly polarized waves. © 2004 Wiley Periodicals, Inc. Electron Comm Jpn Pt 1, 87(12): 60–67, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecja.10195