李學智臺灣大學：電信工程學研究所羅啟業Chi-Ya-Lo2007-11-272018-07-052007-11-272018-07-052006http://ntur.lib.ntu.edu.tw//handle/246246/58883隨著自動化程序應用的增加，射頻辨識系統 (RFID system) 的研究更形重要。這本論文主要的目的即是探討阻抗負載 (impedance loading) 對於射頻辨識系統及其辨識能力 (detection ability) 的影響。我們使用一個式子來解釋阻抗負載對於後向散射場 (backscattered field) 的影響，此後向散射場是由殘餘形式部份 (residual mode component) 和天線形式部份 (antenna mode component) 所組成。我們也討論了如何用力矩法 (method of moments) 去計算後向散射場。除此之外，我們發現散射天線的一些性質也和阻抗負載的效應有關，如天線極化方向 (polarization)， 天線增益 (gain)， 以及天線的輻射場型 (radiation pattern)。在一個無線辨識系統裡，我們使用了兩個阻抗值來當作後向散射調變 (backscatter modulation) 的兩個狀態。射頻辨識偵測的主要目的就是要來分辨負載的狀態。因此，調變準位差越大，偵測效率越好。我們發現了兩個阻抗能讓後向散射場的準位差最大。除此之外，我們發現在射頻偵測時，同調的方法 (coherent method) 比非同調的方法 (incoherent method) 來的好。然而，假如一個射頻辨識系統的通道是處在一個多路徑波 (multipath) 的環境中，所收到的訊號將會遭受嚴重的衰退。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.Abstract I Contents III List of Figures V List of Tables IX Chapter 1 Introduction 1 1.1 Overview of Identification Systems 1 1.2 Motivation 2 1.3 Organization of Thesis 3 Chapter 2 Effect of Impedance Loading on Backscattering 5 2.1 Overview of a RFID System 5 2.2 Impedance Loading 6 2.2.1 Concept of Impedance Loading 6 2.2.2 Theoretical Analysis 7 2.3 Another Viewpoint of Impedance Loading by Using Moment Methods 10 Chapter 3 Measurement of Backscattered Field 15 3.1 System Setup 15 3.2 Measurement 19 3.2.1 Measurement Settings 27 3.2.2 Measurement Results 31 3.3 Detection 45 3.3.1 Measurement Settings 48 3.3.2 Measurement Results 50 3.3.3 Measurement Results by using an EPCglobal Generation-1 IC 56 3.4 Effect of Multi-Path 57 Chapter 4 RFID Detection by Using an IC 63 4.1 Link Timing of EPC Class-1 63 4.1.1 Generation-1 63 4.1.2 Generation-2 64 4.2 Theory of Our Measurement 69 4.3 System Setup 72 4.4 Measurement 74 4.4.1 Design and Setting of Measurement for Gen-1 IC 74 4.4.1.1 Part I (original) 76 4.4.1.2 Part II (shunt 1pF) 77 4.4.2 Result for Gen-1 IC 79 4.4.2.1 Part I (original) 80 4.4.2.2 Part II (shunt 1pF) 80 4.4.3 Design and Setting of Measurement for Gen-2 IC 81 4.4.3.1 Part I (original) 82 4.4.3.2 Part II (cascade 18 ) 83 4.4.4 Result for Gen-2 IC 84 4.4.4.1 Part I (original) 85 4.4.4.2 Part II (cascade 18 ohm) 86 Chapter 5 Conclusion 87 Reference 912883899 bytesapplication/pdfen-US天線形式部份後向散射場阻抗負載殘餘形式部份Antenna mode componentBackscattered fieldImpedance loadingResidual mode componentthesishttp://ntur.lib.ntu.edu.tw/bitstream/246246/58883/1/ntu-95-R93942011-1.pdf