超寬頻(UWB)天線是一個無線超寬頻系統的關鍵元件，本論文研究一個平面單極UWB天線的優化設計，且以0.8mm厚的FR4基板(相對介電係數為4.4)來進行模擬與實驗驗證。優化過程乃是以一個長方形單極當作初始結構，並將其細分成多個(例如10個)細長條的金屬strip，且以strip的長度當作待優化變數。 本論文的目的在使用一個系統性的優化設計方法(結合等差田口優化法與響應表面模型技巧)來探究上述平面單極UWB天線的特性，包括只改變單極輻射體的下緣、只改變接地面的上緣，或同時改變上述兩者的的上緣與下緣所產生的效果。 除此之外，我們還探討了將細長條的寬度，以及接地面的寬度也一起加入做為變數所產生的效果。實驗與模擬結果顯示經此方法設計出來的平面單極UWB天線的|S11|max較之前的研究設計結果還要低3dB左右(達-13dB)。 Ultra-wideband (UWB) antenna is a key element for a wireless ultra-wideband system. In this thesis, the optimization of the UWB planar monopole antennas is considered, for which the UWB antenna is assumed to reside on an FR4 board of 0.8mm thick (relative dielectric constant=4.4) and the simulation and experimental verification are carried out. The optimization process starts with a rectangular monopole structure, and the metallic monopole structure is subdivided into many (eg. 10) thin strips such that the lengths of the strips are used as variables to be optimized.
The purpose of this thesis is to employ a systematic optimization method (combination of Taguchi optimization method and response surface modeling techniques) to explore the S11 characteristics of the above planar UWB monopole antenna. The examples tested include those by changing only the lower edge of the monopole radiator, and those by changing only the upper edge of the ground plane, in addition to those by changing both the lower edge and the upper edge, respectively, of the above mentioned edges. Furthermore, we also investigate the performance by adding two more variables , that is, the width of the strips and the width of the ground plane. Simulated and experimental results show that the achieved | S11 | max (about -13dB) for the optimized UWB planar monopole antenna is lower than those of previous studies by ~3dB.