特徵模態分析中輻射效率之計算-以金屬機殼天線為例

Calculation of Radiation Efficiency in Characteristic Modes Analysis-Case Study of Chassis Antenna

邱健豪(Chien-Hao Chiu)

指導教授 ： 陳士元

國立臺灣大學/電機資訊學院/電信工程學研究所/碩士(2016年)

https://doi.org/10.6342/NTU201601084

摘要

本論文提出了一款採用特徵模態分析設計的全金屬背蓋機殼天線。特徵模態分析能夠分析金屬結構上的電流模態，因此有助於將任意形狀的金屬結構設計成天線。
由於現有的特徵模態分析方法無法計算天線的輻射效率，吾人使用波因亭定理推導如何以特徵模態分析的結果計算介質損耗、導體損耗及天線輻射效率。所提出的方法經過不同條件的塊狀天線驗證，無論是在以完美導體或以有損耗的非理想導體當作邊界的塊狀天線上，吾人的方法計算得到的天線輻射效率和一般模擬方法的結果有很好的一致性。
吾人以此方法分析一手機背蓋大小的金屬片，並用一個立在側邊的電容耦和結構激發金屬背蓋上的電流模態。搭配阻抗匹配電路，金屬背蓋能在低頻(698-960MHz)輻射，並在不同的匹配元件值下可以任意調整操作頻率。其最佳輻射效率為35%，在操作頻率邊緣處的效率為20%。在中頻(1710-2170MHz)，藉由電容耦和結構的自振以及額外的PIFA 天線，可以達到同時涵蓋全頻段，其輻射效率為60-70%。

關鍵字

特徵模態分析 ； 機殼天線 ； 電容耦合元件

並列摘要

In this thesis, the design of complete metallic back cover chassis antenna is presented. The design method is characteristic mode analysis. The existing characteristic mode analysis for conducing bodies, dielectric bodies,lossy dielectric bodies are reviewed. Since existing characteristic mode analysis couldn’t be used to calculated radiation efficiency of antenna, we start from the Poynting theorem to inspect the formulation of conductor loss and dielectric loss and deduce how to calculate dielectric loss and conductor loss based on the characteristic mode analysis. The proposed method is evaluated on patch antenna at both the cases of PEC and lossy conductor co-existed with lossy dielectric. The calculated radiationefficiency is close to that in ordinary driven simulation. Proposed method is applied on chassis antenna design. It is used to analyze the current on metallic chassis. And capacitive-coupling element vertical on the side wall is utilized to excite the need mode. Integrated with tuning matching circuits, the chassis antenna radiate and adjust operating frequency at low-band (698-960 MHz). The self-resonance of CCE and extra PIFA are used to cover the mid-band (1710-2170 MHz). Overall, we designed a complete metallic back cover chassis antenna. It is frequency tunable at low-band. The peak antenna efficiency is 35% and the efficiency at edge is 20%. At mid-band, it covers whole band at a time with antenna efficiency 60-70 %.

並列關鍵字

Characteristic mode analysis ； Chassis antenna ； Capacitive-coupling element (CCE)

參考文獻

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