Realization of EM-wave absorbers for improving EM field environment between ETC lane

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In recent years, wireless LAN systems have been increasingly used more widely in office buildings as well as houses. On the other hand, the communication environment for wireless LAN has become a subject of discussion, due to concerns about risks to security by leakage of electromagnetic (EM) waves or reduction of the quality for wireless communication by multipath and/or fading of the EM wave for communication. In such a background, there is the best way to apply EM-wave absorbers to a certain portion of the room in order to prevent multipath.In this study, the improvement of propagation in the room for wireless LAN communication is investigated experimentally and analytically by making the developed three-layer-type wave absorber consist of common building materials. As a result, the average absorption performance is found to be 10.4dB (2.4-2.5GHz) that makes the average delay spread one-half of that of the well-reflected environment. Moreover, simulation using the ray-tracing method is also performed in this room and the results for number of positions the normalized delay spread calculated by the simulation are similar to those obtained from the experiment.Furthermore, EM wave absorber with partition type add the function of EM wave absorption for wireless LAN (IEEE 802.11a,b/g) is also examined theoretically and experimentally. As a result, the absorption of 20dB or more for vertical incident is obtained at 2.45GHz and 5.2GHz in calculation, respectively. The wave absorber sample is fabricated based on the calculated results and the performance of this absorber is examined in anechoic chamber. The absorption of 15dB or more for TE, TM, and circularly polarized wave at the incident angle ranging between 5 and 20 deg. are obtained experimentally.