雙頻槽形天線與印刷式分集天線

Abstract

本論文的主旨在發展一製程簡單，功能優良且創新思維的雙頻天線結構—雙頻槽形天線(Notch antenna)。大部份的雙頻天線是以patch天線之變形，提昇或降低雙頻天線之頻率比(frequency ratio)，或增加阻抗頻寬，或天線微小化等為該結構應用之工程目的。然這些結構不管在饋入方式或製程上都有其複雜度。本論文的雙頻天線設計，希望跳脫以patch天線為基本結構的模式，強調簡單製程，且同時具有寬頻，微小化，彈性的頻率比，以及應用於分集式天線(Diversity antenna)的潛力。 本論文以程序性的發展方式，探討槽形天線結構。首先以單端短路槽線(short-end slotline)為基礎結構，採微帶線轉槽線(microstrip-slotline)的饋入方式，基於簡化製程，以共平面波導轉槽線(cpw-slotline)的方式饋入。為微小化天線結構，將槽線作九十度的轉折，即產生獨立分明的兩個共振頻率點。由於第一共振點的阻抗頻寬(impedance bandwidth)僅約3%，於是提出兩個新式寬頻應用的槽形天線。第一個寬頻結構利用功率分向器(power divider)同時激發二合一的槽形天線組，利用兩個鄰近共振點合併加大頻寬，可將第一共振點的阻抗頻寬提昇到約43%。第二個寬頻結構，利用槽線的特性，亦成功完成另一寬頻槽形天線;該結構在幾乎不加大結構尺寸的情況下，達到逾30%的頻寬百分比。 由於槽線形天線具有良好的抗電磁干擾性，所以當兩個獨立的槽形天線靠得很近，甚至結合為一時，天線間的關聯性低，適合開發分集式天線。本論文在最後以一組pin diode設計單刀雙擲(Single Pole Double Throw)開關，配合一組槽形天線，完成分集天線設計。 在本論文中將針對槽形天線的基本工作原理與設計方法做詳盡的討論，此外對於寬頻效應的設計，亦有所著墨。槽形天線具有許多優於patch 天線的特性，其場形可設計成單向或雙向輻射，良好的抗干擾性(EMI immunity)，寬頻及不錯的增益(Gain)表現，透過對槽線特性的了解，亦可以施行相當程度的天線微小化。文中亦將針對所提槽形天線的幾項特性，做透徹的比較與分析。最後將歸納槽形天線可能發展應用的潛力與可延續的研發工作。

The thesis aims at developing an innovative dual-band antenna structure with simple fabrication and excellent performances, named “ dual-band notch antenna.” Major port of dual-band applications in antenna design is based on the extensions of patch antenna. The merits of applying patch antennas to dual-band applications include promoting or lowering the frequency ratio for specific utilizations, enhancing impedance bandwidth and miniaturizing dimensions. However, utilizing patch antenna as a basis of dual-band antennas involves complexities in feedline network and fabrication. The goal of designing dual-band antennas in this thesis is is exploring a innovative scheme to design dual-band antennas, instead of utilizing patch antennas as a basis. Simple fabrication, wide-band, miniaturization, flexible frequency ratios and potential to design diversity antennas are all the main advantages and emphases in this thesis. A sequential approach is adopted to investigate notch antenna. Two kinds of feeding structure are presented in this thesis. The first one is microstrip-slotline transition. The other one proposed to upgrade the fabrications is cpw-slotline counterpart.。 Turning slotline with right angle for miniaturization produces two distinct resonant frequencies. It merely has about 3% in impedance bandwidth of proposed dual-band notch antennas at the first resonant frequency. Two creative wide-band, dual-band antennas are proposed to solve the problem of narrow bandwidth. The first one wide-band geometry utilizes power divider to excite 2-in-1 notch antenna set simultaneously. Combining the two adjacent resonant frequencies to extend bandwidth significantly promote the impedance bandwidth to 43%. The second wide-band one employ the inherent characteristic of slotline and successfully enhance impedance bandwidth to over 30% without applying larger dimension. Notch antenna has excellent EMI immunity than other types of antennas. Taking two notch antennas closer or even combining them into a single one causes low correlation between them. Therefore, employing notch antennas to design a compact diverity antenna is suitable. Designing notch divesity antnna Applying two pin diodes to switch two different notch antennas are presented in the thesis when designing notch diversity antenna. Detailed discussions on design rules and principals of dual-band notch antennas are reported in the thesis. Additionally, wide-band geometries are addressed also. Notch antenna has many advantages over patch antenna. Providing thorough comparisons and analyses on some characteristics of notch antenna and inducing some continuous works and possible applications by utilizing notch antennas in the conclusion of thesis.