射頻辨識系統圓極化讀碼天線與變容二極體控制切換波束印刷天線陣列設計

Abstract

本論文前半段主要在設計適用於915MHz射頻辨識系統的圓極化讀碼天線，我們分別討論由雙饋入與單饋入架構實現圓極化微帶天線的技巧與面對的限制，並藉由提升天線高度與改變饋入架構來使設計的天線能符合此系統頻段的頻寬要求。 在無線通訊中，常希望能改變天線的波束方向與形狀來使訊號傳播增益與傳輸距離獲得提升，並減少不必要的干擾與降低被干擾的發生率。本論文後半段提出能採用平面印刷電路板技術來實現以變容二極體控制的切換波束式天線，以期能大幅降低硬體成本與縮小天線面積使天線符合輕、薄、短、小的無線通訊潮流。 本論文是使用美商Ansoft公司所出版的HFSS(High Frequency Structure Simulator)，來模擬與設計各式天線架構。

Design of circularly polarized reader antennas suitable for 915MHz radio frequency identification system is proposed in the first half of this thesis. We discuss the techniques and limits to realize circularly polarized microstrip antennas by dual feed and single feed structure separately. By means of increase the height and change the feeding structure to let the design antennas can conform to this system bandwidth requirement. In wireless communication, we often hope we can change the direction and shape of the antennas beams to improve the signal gain and propagate distance, and diminish the unnecessary interference and decrease the percentage of occurrence. Varactor-controlled bam-switching antennas which can be realized by planar printed circuit board is proposed in the second half of this thesis, in order to lower hardware fabrication cost and reduce antenna size to conform to the trend of wireless communication:light,thin,short,and small. In this thesis, Ansoft HFSS is used to simulate and design every kind of antenna structure.