縮小型寄生接地天線

Abstract

本論文主要研究適用於無線區域網路的新型寄生接地天線。本論文的前半段，將針對一種前人設計的寄生接地天線提出改良的方法，使其更易於製作且有較佳的阻抗匹配。此架構是利用上層的T形驅動單極線段以激發下層的倒L形寄生元件，以免除連通柱之製作成本。我們利用此架構去設計一雙頻雙極化分集天線，並探討天線分支間的波封相關度。本論文的後半段，提出了兩種新型的寄生接地天線，此架構乃是利用上層金屬之驅動元件去控制共振的部位，我們將透過電流分佈與參數分析來探討其共振的機制。這兩種天線皆具有雙頻操作的特性，其頻寬能有效地涵蓋無線區域網路WLAN (IEEE 802.11a/b/g)的工作頻段，因其場型類似於單極天線，非常適用於室內無線通訊使用。最後，我們以此架構去設計一雙頻雙極化分集天線，並分析其效能。

This thesis presents several novel designs of the grounded parasitic antennas with applications for Wireless Local Area Network (WLAN) systems. In the first half of this thesis, we investigate a previously designed grounded parasitic antenna and propose an improved design to enhance the manufacturing simplicity and the impedance matching performances. Fed by a microstrip line, the antenna uses the T-shaped driven monopole stub on the top layer to excite the inverted-L-shaped parasitic element on the backed layer, omitting the via hole complexity. We extend this structure to a dual-band dual-polarized diversity antenna for mini-PCI application. We also investigate the envelope correlation between two branches of the diversity antenna. In the second half of this thesis, two new kinds of grounded parasitic antenna are presented. Fed by a microstrip transmission line, the antenna contains a T- or double T-shaped driven stub on the top layer and a grounded parasitic element on the bottom layer. We investigate the resonant modes of the antenna through the current distribution and systematic parametric study on some key dimensions. The proposed antennas are successfully designed, implemented, and measured. The antennas perform dual band resonances with sufficient bandwidth covering all the frequency bands of IEEE 802.11a/b/g WLAN applications. In addition, the monopole-like radiation patterns make the proposed antennas very suitable for indoor wireless communication system. At last, we also extend the structure with T-shaped driven stub case to a dual-band dual-polarized diversity antenna for further analysis.