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。前人探討平面式超寬頻單極天線一直受限於H-平面輻射場型不均勻(non-isotropic)的缺點，本研究從簡單方形單極天線的特性分析，衍生出單極天線寬頻匹配的原理，並提出兩個技巧，以完成平面式超寬頻單極天線結構的縮小化設計及改善H-平面輻射場型特性的目的。其一是適當設計gap的形狀以達到寬頻匹配目的，並進一步發展成Triangular型結構以改善H-平面輻射場型；其二則提出將金屬單極多層彎繞使天線同時達成寬頻及縮小化的目的，同時有效的改善H-平面輻射場型的不均勻特性。本研究設計的三種天線實例，在最佳化後，其金屬單極的寬度皆小於10mm，而接地面的寬度皆在20mm左右，比起簡單方形單極天線，新結構的尺寸明顯縮小許多。最後進行天線實作和時域及頻域特性的量測，量測的天線特性包含S參數、系統轉換函數以及時域波形，模擬和量測結果的一致性印證了這些實例的實用性。 The goal of this thesis is to design a compact fully planar antenna that satisfies the ultra wide band (UWB) (3.1GHz~10.6GHz) released by the Federal Communication Committee (FCC). The applicatons of planar UWB monopole antennas are limited due to the non-isotropic property of the H-plane radiation patterns. This research starts with the investigation of the characteristics for a simple square monopole antenna of the planar type, by which the concept of introducing certain parallel capacitance to achieve broadband matching is obtained. Two techniques are proposed to realized the compact design of the planar UWB monopole antennas and to improve the isotropic characteristics of the H-plane radiation patterns. One technique is to design the gap shape between the monopole and the ground plane to achieve for broadband matching, in addition, a triangular shape for the monopole is employed to improve the isotropic characteristics of the H-plane radiation pattern. The other is to utilize a meander monopole in a multi-layered printed circuit board environment to achieve the goals of the broadband matching and miniaturization, simultaneously. Meanwhile, the characteristics of the H-plane radiation patterns are improved at the same time. Three designs are tested in this research, it is found that, after optimization, the patch widths are all less than 10mm, and the ground widths are all about 20mm. The overall sizes of the new structures are much smaller than that of the simple square monopole antenna. Finally the antenna prototypes are fabricated and the antenna characteristics are measured in both the time domain and the frequency domain. The antenna characteristics measured includes the S parameter, the radiation patterns, the system transfer function and the time domain waveform, etc. The consistency between the simulated results and the measurement results confirm the practicability of these techniques.