具有可調Q共振器之超寬頻平面帶拒單極天線分析與設計

Abstract

本篇論文主旨在於實現適用於超寬頻無線通訊系統之平面帶拒天線，其天線結構為叉子形狀之平面超寬頻天線(fork‐shaped UWB antenna)與四種新型諧振單元(resonator)。首先，本文提出一種具有叉子形狀之平面超寬頻天線, 其操作頻率為3.1GHz ~ 10.6GHz並具有全方向性的場型、平坦的增益頻率響應及易於製作的特性，而四種可以應用在超寬頻天線的新型諧振單元分別為tapped‐line coupled resonator, square‐looped resonator, end‐coupled resonator和 open‐looped resonator。本論文即探討這些諧振單元與超寬頻天線之整合與最佳化，有別於一般利用四分之一波長槽線(slot)或微帶線(strip)與天線形成共振結構之超寬頻帶拒天線，本論文所提出的超寬頻平面帶拒天線明顯地改善帶拒效果，其帶拒頻率和增益抑制效果分別為5‐6GHz和15‐30dB。除了提出天線結構上的創新，本論文也提出一種將超寬頻平面帶拒天線等效成一集總元件電路(lump circuit)的方法，利用該方法所得到的阻抗響應和HFSS模擬軟體的模擬結果有相當的一致性。

Since the Federal Communication Commission (FCC) allowed unlicensed use of 3.1-10.6 GHz unlicensed band and EIRP less than -41.3dBm/MHz for Ultra-wideband (UWB) communication, UWB technology has been widely investigated and developed for short range wireless applications. However, the exiting wireless local area network (WLAN) is used in 5-6 GHz and interferes with UWB performance such as sensitivity and signal-to-noise ratio. This dissertation is devoted to manifest and analyze new categories of resonators used in UWB antenna to achieve band-notched performance. A fork-shaped UWB antenna is firstly designed for wide bandwidth, omni-directional pattern and flat gain response over 3.1-10.6GHz. Then, four kinds of resonators, i.e., tapped-line coupled resonator, square-looped resonator, end-coupled resonator and open-looped resonator, are designed and used respectively in a fork-shaped UWB antenna to create a notched band. Moreover, the schematic equivalent circuit of each resonator are investigated and discussed along with band-notched performance. The proposed antennas feature flat gain frequency response, small varied group delay and 10 to 25 dB gain suppression in the notched band. Then, an equivalent circuit model illustrates the band-notched behaviors more clearly. The antenna input admittance calculated with the equivalent circuit model reasonably agrees with the HFSS simulated result. Accordingly, the band-notched antenna can effectively select target bands by adjusting these antenna parameters. The purpose of this study provides high performance antennas which is suitable for UWB applications.