射頻辨識讀取器受到多重路徑衰減(Multi-path fading)影響，導致其標籤讀取率下降。因此可使用具天線分集之RFID標籤來改善此問題。
本論文以美商國家儀器所開發之軟體無線電平台－NI 5644R vector signal transceiver (VST) 實現天線分集射頻辨識標籤之對應讀取器。在順向鏈結方面，使用具天線分集標籤進行選擇性合併以提高接收信號功率；反向鏈結方面，標籤反向散射空時區塊編碼(Space-Time Block Code, STBC)信號，讀取器端則使用最大比合併技術獲得分集增益，以改善接收反向散射信號之位元錯誤率。
訊號同步在UHF RFID系統中為一重要的議題。若是訊號同步上出現了問題，將會導致後續的通道估測、訊號解調及解碼錯誤。本論文嘗試應用兩種不同的同步序列於天線分集之RFID標籤上，並且比較兩種同步序列的效能。
本論文也改善了通道估測的效能。先前文獻沒有考慮到非理想的實際反向散射訊號問題。此問題乃因實作標籤原型的偏差，致使實際回傳的反向散射係數與理想反向散射係數存在著相位及增益誤差。為了解決此問題，可先量測該相位及增益校正誤差，將其補償後再進行通道估測。模擬結果也證明進行校正誤差補償後再進行通道估測，能夠有效改善通道估測之效能。

Muti-path fading degrades the tag read rate of a UHF Radio Frequency Identification (RFID) reader. An RFID tag with antenna diversity is proposed to mitigate this problem.
This work proposes a reader design for RFID tags with antenna diversity. The reader is implemented using National Instrument 5644R software defined radio (SDR) platform.
In the forward (reader to tag) link, an RFID tag with antenna diversity uses selective combining technique to improve its received signal power. In the reverse (tag to reader) link, the tag backscatters space-time block coded signals, and the reader uses maximum ratio combining technique to obtain diversity gain and to improve the bit error rate (BER) of received backscatter signal.
Synchronization is an important issue in a UHF RFID system. If synchronization error occurs, it will result in channel estimation, signal demodulation, and decoding errors. In this thesis, we compare the synchronization performance of two different synchronization sequences for RFID tag with antenna diversity.
In addition, this work also improved the channel estimation performance for RFID tag with antenna diversity. Prior related studies do not take imperfect practical backscatter signal into account. Due the deviation of prototype RFID tag realization, there are unavailable phase and gain differences between the practical backscatter coefficients and the idea backscatter coefficients. To mitigate this problem, we measure the phase and gain calibration errors and compensate the error before channel estimation. Simulation results verify the effectiveness of calibration error compensation in channel estimation.

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