本篇論文探討一符合FCC要求3.1GHz ~ 10.6GHz超寬頻(UWB)單極小天線之設計。前人探討超寬頻天線大多屬三維結構（準2維）的半平面式寬頻單極（monopole），真正全平面二維的共平面或微帶激發的超寬頻平面單極天線仍不多，S11和輻射場型皆適用於超寬頻頻段的全平面天線目前尚無，所以本研究針對全平面式的結構，採用厚0.8mm的FR4基板，以相對介電係數為4.4來進行模擬並和實作相驗証，並進一步將此一全平面式天線結構縮小化，使擁有更小的單極面，更容易和印刷電路整合。吾人首先利用經驗公式得到初始之方形單極天線結構，並探討天線結構參數對 之影響，模擬結果顯示其中以gap的大小對 參數影響最大，本研究遂提出改變gap的形狀來同時達成寬頻及縮小化的目的，最佳化的結果顯示在H-plane上的全方向性輻射特性及E-plane之輻射特性也同時得到改善。 The goal of this thesis is to design a miniature fully-planar antenna that satisfies for UWB (3.1GHz~10.6GHz) released by the FCC. Most of the planar monopoles reside on a large orthogonal ground plane, and thus the antennas are not fully planar structures.. The fully planar coplanar waveguide-fed or microstrip-fed UWB monopole antennas have attracted the attention of many researchers. None of them has both the impedance bandwidth and radiation bandwidth covering the UWB simultaneously. In this study, the UWB antennas are fabricated on an FR4 board of thickness 0.8mm, for which the relative dielectric constant 4.4 is used for design. In this paper, the miniature ultra wideband (UWB) fully-planar monopole antennas fed by microstrip line are investigated in order to take full advantages of the planar antenna structure, such as the light weight, small size, low cost, conformal and ease of integration with the microwave networks. The empirical formula is employed to determine the initial size of a square monopole, by which the influences of the dimensions upon the reflection coefficient are investigated. It is found that the reflection coefficient is very sensitive to the gap. It is thus proposed to change the shape and size of the gap between the monopole and the ground in order to achieve the goal of miniature wideband antenna. The optimized results show that the radiation patterns in the E plane and the omni-directional characteristic in the H-plane are improved.
