共平面波導饋入槽孔天線之縮小化及阻抗匹配設計

Miniaturization and Impedance Matching of Coplanar Waveguide-fed Slot Antennas

賴建伯(Chien-Pai Lai)

指導教授 ： 陳士元

共同指導教授 ： 李學智(Hsueh-Jyh Li)

國立臺灣大學/電機資訊學院/電信工程學研究所/博士(2013年)

https://doi.org/10.6342/NTU.2013.00771

摘要

在本論文中，吾人先提出了共振型天線的阻抗匹配技術及其設計公式。從微波共振電路的觀點，吾人探討了品質因子、半功率頻寬及輸入阻抗(導納)對頻率的微分三者之間的關係。利用此關係及共振特性，串聯及並聯共振器的阻抗匹配可分別利用集總電感和電容去完成。吾人也提出了相對應的設計公式，而這些設計公式有助於預測所使用的集總元件的感值。此外，論文中也進一步探討匹配後共振電路的品質因子，但發現其增加量非常些微。
本論文的第二部份是聚焦於共平面波導饋入的槽孔型天線的微小化，而這些天線的阻抗匹配可以前述的技術完成。當吾人利用電抗性負載，共平面波導饋入的末端短路及開路的半波長槽孔天線可以被有效地縮小。而共平面波導的雙側接地面則被裁切用來放置這些所使用的電抗性負載。因此整個天線的面積，包含槽孔輻射體及接地面，可以大幅縮小。以2.4-GHz的原型天線為例，整個天線的面積只有0.088λ0 × 0.062λ0 (λ0為2.4 GHz時的空氣波長)。
最後，當吾人再度利用微波共振器的觀點及同樣的阻抗匹配技術，共平面波導電感性饋入的環形槽孔天線的基礎共振模態可以被匹配至五十歐姆，而此模態也是第一次被運用在天線設計當中。因為操作在基礎共振模態的環型槽孔輻射體的周長只有半個導波波長，故可達微小化之目的。此外，此環型槽孔輻射體的高階共振模態也同時被匹配用的電感有效抑制。其原型天線在設計的頻率(2.5 GHz)可以達到很好的匹配，且其寬頻的諧振抑制效果可達至少20 GHz。

關鍵字

共平面波導 ； 共振型天線 ； 槽孔天線 ； 微小化天線

並列摘要

The impedance matching technique and design formulas for resonant-type antennas are first proposed in this dissertation. From the viewpoint of microwave resonant circuit, we investigate the relation among quality factor, half-power bandwidth, and frequency derivate of input impedance (admittance). By using this relation and the resonant characteristics, the lumped inductor and capacitor are added to accomplish the input impedance matching of series and parallel resonators, respectively. The corresponding design formulas are also proposed, and they are of great help to estimate the reactance values of the used lumped components. Besides, the quality factor of the matched resonant circuit is further examined, but it is found that the increase in quality factor is insignificant.
The second part of this dissertation focuses on the miniaturization of coplanar waveguide-fed slot type antenna, in which the impedance matching of these proposed antennas is achieved by the aforementioned technique. Employing the reactive terminations, the short- and open-ended half-wavelength slot antennas fed by coplanar waveguide can be effectively miniaturized. The bilateral ground plane of the feeding coplanar waveguide is truncated to accommodate the used reactive terminations. As a result, the total antenna area, including slot radiator and ground plane, can be greatly reduced. For the 2.4-GHz prototype antenna, its antenna area is only 0.088λ0 × 0.062λ0, where λ0 is the free space wavelength at 2.4 GHz.
At last, when we again apply the design concept of microwave resonator and the impedance matching technique, the fundamental resonant mode of the inductively coplanar waveguide-fed slot loop antenna can be matched to 50-Ω and it is utilized in antenna design for the first time. Since the perimeter of the slot loop radiator operated at fundamental mode is a half guided-wavelength, the area of the slot loop radiator is also relatively smaller as compared to the conventional designs. Moreover, the higher-order resonant modes of this slot loop radiator are accordingly suppressed by the added quasi-lumped inductors for impedance matching. The prototype antenna is well matched at 2.5 GHz and a wideband harmonic suppression up to at least 20 GHz is achieved.

並列關鍵字

Coplanar waveguides ； resonant-type antennas ； slot antennas ； miniaturized antennas

參考文獻

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