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

近年来，无线局域网系统在写字楼和住宅中得到了越来越广泛的应用。另一方面，由于担心电磁(EM)波泄漏对安全的风险，或由于用于通信的电磁波的多径和/或衰落而降低无线通信的质量，无线局域网的通信环境已成为讨论的主题。在这样的背景下，为了防止多径，在房间的某一部分应用电磁波吸波材料是最好的方法。本研究通过实验和解析的方法，将研制的三层式吸波材料制成普通建筑材料，对改善无线局域网通信的房间传播进行了研究。结果表明，其平均吸收性能为10.4dB(2.4-2.5 GHz)，平均时延展宽仅为反射良好环境的一半。此外，还利用光线追踪法在该房间进行了模拟，计算得到的归一化延迟扩展的位置数与实验结果基本一致。此外，还对无线局域网(IEEE 802.11a，b/g)中添加了电磁波吸收功能的分区类型的电磁波吸收器进行了理论和实验验证。计算结果表明，在2.45 GHz和5.2 GHz频率下，垂直入射时的吸声系数分别达到20dB或以上。根据计算结果制作了吸波材料样品，并在暗室中对吸波材料的性能进行了测试。在入射角度为5到20度时，TE、TM和圆偏振波对15db或以上的吸收。都是通过实验获得的。

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.