單端饋入可切換式寬頻圓極化E型塊狀天線

Abstract

本論文提出一種可應用於無線通訊系統之單端饋入可切換式寬頻圓極化天線。此設計利用二極體的開關切換，極性可自由切換於左右圓極化之間，並且具有寬頻的特性，使其更具實用性。 為使用單端饋入架構並具備寬頻圓極化切換的特性，我們提出主體為E型的塊狀天線，在其平行的槽孔上焊上PIN二極體。二極體在正向偏壓時可視為等效的小電阻，逆向偏壓時為等效的電容，其阻抗變化可改變天線上的共振模態，進而達到圓極化的特性。 基於以上的設計架構，我們同時提出一種長度縮減版本的設計。此設計運用邊緣縮減與寄生塊狀平板兩種不同的機制來達到長度縮減的目的。 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 single-feed reconfigurable antenna which is proposed to achieve wide-band circular polarization diversity for wireless communication systems. Turning the diodes on or off, this antenna can radiate with either wide-band left hand circular polarization (LHCP) or right hand circular polarization (RHCP), which is more applicable than other narrow-band designs. In order to achieve wide-band circularly polarized performance with single-feed structure, two parallel slots with PIN diodes are incorporated into the E-shaped patch antenna. Since a diode can be regarded as an equivalent low resistance under forward bias and capacitance under reverse bias, changing the impedance of diodes can simply alter the resonant modes, obtaining circular polarization. Base on the structure above, a length-reduced design is also presented. Two different length-reduced mechanisms, edge reduction and parasitic patch, are applied in this modified design. 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.