Effects of Impedance Loading on RFID Detection

• Main Authors: Chi-Ya-Lo, 羅啟業
• Other Authors: Hsueh-Jyh Li
• Format: Others
• Language: en_US
• Published: 2006
• Online Access: http://ndltd.ncl.edu.tw/handle/22234947678781730850

碩士 === 國立臺灣大學 === 電信工程學研究所 === 94 === With the increasing applications of automatic procedures, the researches on the RFID system will become more indispensable. In this thesis, the main purpose is to discuss the effects of impedance loading on a RFID system and its detection ability. We use an equation to explain the effects of impedance loading on the backscattered field, which is contributed by the residual mode component and the antenna mode component. We also discuss how to use the method of moments to calculate the backscattered field. In addition, we found that the tag scattering antenna’s properties are related to the effects of impedance loading, such as polarization, antenna gain, and antenna’s radiation pattern. In a RFID system, we use two loading values as the two states of backscatter modulation. The main purpose of RFID detection is to differentiate between the loading states. As a result, the larger the modulation level difference is, the better the detection performance is. We have found that two loadings with opposite reflection coefficients can give the maximum variation of the backscattered field. We also found that the coherent detection method can perform better than the incoherent detection method on RFID detection. If the channel of a RFID system is in a multipath environment, the signals received will suffer severe fading.