用於人體區域網路之縮小化超寬頻寬槽天線之設計與性能分析

Abstract

本篇論文主旨在於開發一種超寬頻（Ultrawideband, UWB ）天線，以有效提升在人體區域網絡（Body Area Network, BAN）中on-body通訊(收發天線皆配戴於人體上)的效能。 在on-body通訊的情境下，使用者的身體會對天線的特性造成很大的影響。特別是，當平面天線貼於人體時（天線平行於身體表面），無論該天線在自由空間的場型為何，由於受到人體的影響，最終都會變成方向性的場型，其主波束會朝著人體往外的方向，因此大部分的電磁（EM）能量往遠離人體的方向發射(而非朝著配戴於人體上的接收天線)，而電波傳播也高度依賴附近散射體的反射波，這樣的傳播模式會造成很高的路徑損耗(Path Loss)，而且通道的特性也容易受到環境的影響。在本論文的研究中，提出一個6 -10 GHz具方向性的超寬頻縮小化寬槽天線（Reduced-size Wide Slot Antenna, RWSA），用於on-body的無線通信的傳播研究。RWSA的設計特點為寬度窄，因此可以裝置在無線元件的側邊。當一個側置的RWSA配戴在人體上時，天線的主波束會自然地朝著身體表面的方向，因此大部分的能量可以透過直接或繞射波，有效地傳送至接收天線，進而大幅改善on-body通訊的效能。經過一系列的on-body通道測量，結果顯示使用側置的RWSA，相較於先前國際上的研究結果，可以大幅改善(降低)通道的路徑損耗(高達 20 dB以上)，而且可以有效地降低通道對人體和環境的敏感度。本研究也提出一種測試方法，可以估計天線在實際環境中的效能，使用這種方法，再次驗證RWSA在頻域和時域上，具有優越的特性表現。最後，本研究也使用RWSA進行天線分集(Antenna Diversity)的研究。

This dissertation presents a study on developing an ultrawideband (UWB) antenna for improving the efficiency of on-body communications in body area network (BAN). In scenarios involving the use of on-body communication devices, the human body can exert a strong influence on the characteristics of the antennas used in the devices. Particularly, when a planar antenna is worn parallel to the body surface, the body can alter the radiation pattern considerably. Typically, the resultant pattern is directional, and the main beam is oriented away from the body. Therefore, most of the electromagnetic (EM) energy is radiated away from the body, and the signal propagation between the on-body antennas is highly dependent on reflections from nearby scatterers. Consequently, the path loss of on-body channel is high, and the channel is sensitive to environmental influences. In this study, a 6–10-GHz UWB directional reduced-size wide slot antenna (RWSA) is proposed for applications involving on-body wireless communication systems. The proposed RWSA is based on a narrow-width design, and it can be mounted on the side of a wireless device. When a side-mounted RWSA is worn on a body, the antenna boresight is naturally directed along the body surface, and most of the EM energy can be efficiently transmitted by direct or diffracted waves. Consequently, the performance of the on-body communication channel can be effectively improved. A series of on-body channel measurements were performed in various environments. Compared with previous studies, the results show that using side-mounted RWSAs can markedly improve the path loss (>20 dB) and reduce the sensitivity of the channel to the human body and environments. This study also proposes an approach for estimating the performance of antennas in real environments. With the proposed approach, the superior performance of the proposed RWSA is verified again in both the frequency and time domains. Furthermore, the antenna diversity of using multiple RWSAs is investigated.