射頻辨識標籤之後散射場分析及其在金屬表面標籤天線之應用

本論文以R. B. Green所推導之天線散射場公式為基礎，提出一套簡易的方法來擷取天線的散射特性，包含其結構模態與天線模態。文中分別以塊狀天線與平面偶極天線為例，分析其天線散射特性，進而驗證天線散射場公式的基本物理意義：其一，結構模態與天線的物理結構高度相關；其二，天線模態與該天線的輻射能力高度相關。此一方法將有助於分析射頻辨識標籤天線之工作效能。此外，本論文亦提出一款適用於金屬物體之標籤天線設計，為一微型化之塊狀天線。吾人首先以HFSS進行該天線之參數分析，瞭解結構參數與天線阻抗特性的關係。接著，參考市售的射頻辨識標籤晶片之阻抗值，適當地設計該天線，使之與晶片阻抗達共軛匹配，並利用吾人所提出之方法分析該天線之散射特性。最後，於微波暗室中進行標籤天線讀取效能之量測，並與市售之標籤天線效能作比較。經由實驗證實，吾人提出之標籤天線設計，其讀取距離確實不受金屬物體的影響。

關鍵字

射頻辨識；標籤天線；後散射；結構模態；天線模態

並列摘要

In this thesis, a simple method to extract the structure-mode and antenna-mode scattered fields of an antenna is proposed based on the antenna scattering formula derived by R. B. Green. The back-scattering properties of the microstrip patch antenna and the printed dipole antenna are characterized respectively using the proposed method. In addition, the physical interpretation of the antenna scattering formula is also verified. The structure-mode scattered field of an antenna depends only on its physical structure, while the antenna-mode scattered field is highly related to the radiation performance of the antenna, such as the gain. The proposed method would be of great help in the design of RFID tag antennas. Additionally, a miniaturized patch antenna suitable for use in the metal-mount RFID tags is presented in this study. First of all, the antenna is analyzed using the Ansoft HFSS, and some parametric analyses on its impedance characteristics are performed. Given the input impedance value of a commercial RFID tag chip, the proposed antenna is properly designed to be conjugately matched to the tag chip. The back-scattering properties of the resulting antenna are then characterized using the above method. Finally, the read range of the proposed antenna is measured in the anechoic chamber. During the measurement, the antenna is integrated with a commercial RFID tag chip. For comparison, the same experimental setup is also employed to test a commercial RFID tag. The results show that the reading performance of the proposed antenna is not affected by the presence of the metallic object. Therefore, the proposed antenna may be used in the metal-mount RFID tags.

並列關鍵字

RFID ； Tag antenna ； Backscattering ； Structure mode ； Antenna mode

參考文獻

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[3] K. Penttila, M. Keskilammi, L.Sydanheimo , M. Kivikoski, “Radar cross-section analysis for passive RFID systems”, IEE Proc.-Microw. Antennas Propag., Vol.153, No. 1, February 2006.

[5] H. J. Li, C. Y. Lo, and J. Y. Chen, “Impedance Loading State Determination for UHF Passive RFID Applications,” submitted for publication.

Ohio State University, Report No. 223-17, November 1963

[7] Nikitin, P.V., Rao, K.V.S., “Theory and measurement of backscattering from RFID tags”, IEEE Antennas and Propagation Magazine, Vol. 48, pp. 212 – 218, Dec. 2006

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射頻辨識標籤之後散射場分析及其在金屬表面標籤天線之應用

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