標籤間的碰撞是無線射頻辨識系統(Radio Frequency Identification, RFID)面臨的問題之一，近來將直序展頻技術應用到RFID以解決碰撞問題的研究漸多，然而對同步問題或多個標籤的碰撞偵測較少說明；在本文裡，我們以EPCglobal Class-1 Generation-2規範為藍本，引進CDMA的技術以解決少量標籤碰撞的情形，建立起低複雜度的展頻化RFID系統，因為增加資料的利用率，減少時槽的浪費，而縮短對所有標籤識別碼的讀取時間。
我們將重點放在系統的多重存取偵測上，在文中提出結合匹配濾波器波封檢測法(matched filter envelope detection)與連續干擾消除法(Successive Interference Cancellation, SIC)的多重存取偵測架構，然後針對此系統的特性，進行多重存取偵測的分析；在信號偵測裡，臨界值的設定是很重要的系統參數，藉由對臨界值的適當設定，可以使系統發揮最佳的偵測效能；最後以模擬結果呈現所提出的偵測架構在系統裡的運作概況；由模擬結果中亦可看出結合連續干擾消除法的偵測架構較僅用臨界值判定法來得穩定，因為提升偵測的正確率，故能提高資料正確解碼率，使展頻化RFID系統有較好的效能表現。

Collision of tags is one of the problems RFID systems encounter. Recently, the researches of applying direct-sequence spread spectrum technique to RFID are published frequently, but the portion about synchronization and detection of multiple tags is not mensioned. In the thesis, we build up a low-complexity spread-spectrum RFID system on the basis of EPCglobal Gen-2 protocol, and we utilize CDMA to resolve the collision of few tags. Since the data utility rate is improved, the waste of slot is alleviated and then the read time of all the identification code of tags could be reduced.
Under the construction, we focus on the multiple access detection portion of the new system. In the context, a multiple access detection architecture which combines matched filter envelope detection and successive interference cancellation (SIC) is proposed. Then the analyses of the detection method are presented. In the signal detection, the setting of threshold is a very important system parameter. A system could perform well by giving an adequate threshold. In the end, we figure the operation characteristics of the new system’s multiple access detection by computer simulation. From the simulation results, we could find that the proposed detection method is more feasible than the method that just uses threshold comparator with matched filter detection. Since the performance of detection is improved, the correct data decoding rate increases so that the spread-spectrum RFID systems could have better performance.

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