印刷電路板之微小型RFID標籤天線

Abstract

本論文提出一個透過第零階諧振天線概念所設計並且用於RFID標籤天線的電小天線(electrically small antenna(ESA))。此天線為製作在厚度為0.8mm的FR4基板且具有雙層銅箔的天線結構，上下銅箔層分別為饋入結構與輻射結構體，天線保持相當小的大小使之具備了容易整合於印刷電路板中的特點。而為了增加小天線的輻射效率，透過負導磁係數(MNG)的機制來建立具備諧振電路之雙層結構，而此架構具備相同方向的感應電流，這能夠降低在遠場輻射機制中會相互抵銷的輻射效應，並且在天線的饋入結構與輻射體的結構設計則可以增加互感效應，使得能量的耦合量增加以提高輻射效率，透過數值模擬軟體得到在頻段902~928 MHz具有相當好的匹配程度，而整體天線的大小保持在20 × 5 × 0.8 mm^3，在如此小的RFID標籤天線結構並且能在測得實際的讀取距離為5.2公尺為相當具備實際應用價值的標籤天線設計。本天線的設計細節及實驗結果在論文中有詳細討論。

This thesis presents an electrically small (ka<0.2) tag antenna(ESA), which is designed as a zeroth-order resonator (ZOR) with a two-layer structure of copper. It is also easily integrated with a PCB (Printed Circuited Board). To enhance the radiation efficiency of the small antenna, mechanism of negative permeability is implemented to keep induced current of the feeding and radiation parts to have the same direction. Furthermore, the mutual coupling between the feeding and radiation parts increases due to a spiral structure of the radiation part, which increases the efficiency. The simulated result demonstrates good impedance matching in the frequency range of 902~928 MHz. Although the antenna volume is quite small and is of 20 × 5 × 0.8 mm^3 , the measured read range is long and reaches 5.2 meters. The design details for the proposed antenna are described, and the experimental results of the antenna performances are presented and discussed.