縮小型單端饋入且地有環形槽之可切換式圓極化方形貼片天線

Abstract

本論文提出一種可應用於無線通訊系統之縮小型單端饋入可切換式圓極化天線。此設計利用二極體的開關切換，自由地使天線切換於左右圓極化之間，並且具有天線尺寸縮小的特性，使其更具實用性。 為使用單端饋入架構並具備尺寸縮小圓極化切換的特性，我們引入了兩個短路節點以及兩個正方形環形凹槽。凹槽內的二極體在正向偏壓時可視為等效的小電阻，在逆偏壓時圍等校的電容，其阻抗變化可以改變天線上的共振模態，進而達到圓極化的特性。 以上所提出的設計皆有模擬與實驗相互驗證，並對其原理、參數、設計流程有詳細的討論。

This thesis presents a miniaturization of single-feed reconfigurable antenna which is proposed to achieve circular polarization diversity for wireless communication systems. With the state of the diodes, that is ON state and OFF state, this miniaturized antenna radiates with either left hand circular polarization (LHCP) or right hand circular polarization. In order to achieve size reduction on the circularly polarized performance with single-feed structure, two shorting pins and wider square loops slots are incorporated into the square patch antenna. Since a diode can be regarded as an equivalent low resistance under forward bias and capacitance under reverse bias, the impedance of diode changes, which results in different resonant modes and thus the circular polarization can be obtained. Simulated and experimental results of the design are presented to confirm the feasibility. Moreover, the operating mechanism, parametric analysis and design flow are also discussed in detail.