人造磁導表面之設計與其在天線上的應用

Abstract

本論文旨在探討應用人造磁導材料(artificial magnetic conductor, AMC)來設計印刷式天線。本研究特別專注一種整合設計之方法，可以將天線與AMC整合在同一印刷電路板(PCB)之中,其優點是可降低製作成本、提升組裝的良率、及增進日後運作的可靠度。鑑於一般文獻中之EBG天線大多操作在10 GHz以上之高頻帶, 我們特別將此設計方法展現說明在2.4 GHz頻帶，此頻帶為目前在無線區域網路通訊上所常用。本論文所使用的PCB有四層金屬,總厚度為2.8 mm,其天線面積在一般的AMC下是38×38mm^2而在微型化AMC之下則只占40×15mm^2。第一支天線設計係利用蘑菇狀人造磁導材料與正方孔徑天線(aperture antenna)結合設計出單頻線性極化天線。第二支天線利用饋入方向的改變同時激發兩個方向的極化並利用極化相依(polarization dependent)人造磁導材料的設計來達成雙頻雙極化天線的設計。第三支天線更將極化相依人造磁導材料在雙極化方向的反射相位設計相差90度以達成圓極化天線。第四支天線則是利用本論文提出的新型縮小化人造磁導材料單元結合一開槽較小的槽孔天線(slot antenna)設計。本論文中第一支天線增益可以到達3.75dBi，第二支天線在低頻帶增益可達3.2dBi在高頻帶可達4.2dBi，第三支天線增益可達2.1dBi，第四支天線可達1.2dBi。

This thesis investigates the application of artificial magnetic conductor (AMC) surface to the printed antenna design. In particular, we emphasize an integrated design of the aperture antenna and the AMC structure with the same PCB, which has advantages of low cost in manufacturing, high yield rate in assembling, and reliable in operation. In view of most EBG antennas in the literature are designed at high frequencies (greater than 10 GHz), we illustrated the presented design method in the ISM band of 2.4 GHz which is widely used in WLAN communication system. The PCB employs four metal layers with a total thickness of 2.8 mm, where the antenna has a resultant area of 38×38mm^2 with regular AMC cells and of 40×15mm^2 with miniature AMC cells. The first design combines the mushroom type AMC and the square aperture antenna to realize a single band linearly polarized antenna. The second design employs a diagonal feeding line to excite the vertical and horizontal polarization modes at two different resonant frequencies, leading to a dual-band dual-polarized operation. In the third antenna design, the AMC surface was designed in a way that the reflection phase of the vertical and horizontal mode has a 90-degree out of phase, resulting in a circular polarization operation. The fourth design presents a miniature AMC structure integrated with a slot antenna, which reveals the feasible design of an EBG antenna of compact size using a common PCB process for 2.4 GHz operation. The first three antenna designs perform decent antenna gains range from 2.1 dBi to 4.2 dBi. The fourth antenna, after the miniaturization on the AMC cells and the aperture, still has a realized gain of 1.2dBi.