超高頻射頻辨識標籤之新型雙天線架構

A Novel Dual-Antenna Structure for UHF RFID tags

袁得勝(De-Seng Yuan)

指導教授 ： 李學智

共同指導教授 ： 陳士元(Shih-Yuan Chen)

國立臺灣大學/電機資訊學院/電機工程學研究所/碩士(2010年)

https://doi.org/10.6342/NTU.2010.00804

摘要

在本篇論文中，吾人提出了一種新型射頻辨識標籤架構，其天線與負載阻抗(Loading impedance) 連接方式與傳統標籤不同。傳統標籤僅以一天線進行接收與後散射，無法得到最大後散射場差值(Backscattering level difference)且在短路狀態期間無法接收能量，為瞭解決傳統標籤的限制，吾人提出新型標籤架構，其使用兩支各自獨立天線進行接收與後散射。一支天線負責接收，其天線輸入阻抗與標籤晶片阻抗呈共軛匹配，具有最大能量轉移；另一支天線負責後散射調變訊號，其天線輸入阻抗設計為虛部為零，如此便具有最大後散射場差值，進而提升偵測效能。

因為同時要有最大接收能量且有最大後散射場差值，必須要有兩支天線，故吾人設計一款新型標籤雙天線架構。而根據參考文獻所設計之雙天線架構，有著隔離度不為最佳之設計問題，故吾人改良了此天線架構，不僅微小化天線面積，也增加了射頻辨識系統的讀取效率。

再者，經由模擬與量測，可瞭解所設計之天線特性均有達到預期之要求，無論是天線輸入阻抗、-6dB頻寬、隔離度、場型，以及新型標籤與傳統標籤的散射場觀念，從中可發現新型標籤架構之後散射場差值確實是優於傳統標籤，證明了吾人所提出之新型標籤與所設計雙天線架構之優越性。

關鍵字

射頻辨識 ； 負載阻抗 ； 交叉極化 ； 後散射 ； 隔離度

並列摘要

In this dissertation, we design a novel tag structure for RFID system. The conventional tag has single antenna, which is used for both receiving and backscattering. Input impedance of the conventional tag antenna is designed to match tag IC for receiving and switched between match and short state for backscattering. The maximum backscattering level difference cannot be obtained and also no power be supplied to the tag IC during the short state. The novel tag structure includes two cross-polarized antennas. The receiving antenna is received that is designed to match the tag IC for maximum power transfer. The backscattering antenna is alternatively connected to two optimized impedance states for maximum backscattering level difference. It is expected that the reading range can be much increased.

According to literatures, we know that designed antenna doesn’t have the best isolation, and therefore we improve it. Furthermore, the improved antenna can be easily printed with general PCB to reduce complexity of antenna fabrication, and increased read efficiency of RFID system at the same time.

In addition, we know that antenna performances achieved request on antenna input impedance, -6dB bandwidth, isolation and pattern by simulations and measurement. Level difference of the novel tag structure is excellent than the conventional tag. We don’t doubt superiority of the novel tag structure over the conventional one.

並列關鍵字

Radio Frequency Identification (RFID) ； impedance loading ； cross-polarized ； backscattering ； isolation

參考文獻

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