A Novel UHF RFID Tag Antenna for Metallic Operations

應用於金屬物體的新穎超高頻無線辨識標籤天線

本論文提出了一個小型化的RFID 標籤天線，尺寸僅有36 × 36 × 0.8 mm3，並可直接貼附於金屬物體上使用而不受影響。此天線是使用FR4 板製作而成，使用偶極天線兩臂之輻射而產生應用頻寬，再利用兩條曲折金屬線使天線尺寸得以縮小，另外還有兩條L 型金屬線來改善匹配提高阻抗頻寬之用。其中我們在雙輻射路徑末端打孔並連接到背面的接地面，藉由此機制可以有效防止當貼附於金屬物體上使用時所受的干擾。本天線在10dB 阻抗頻寬定義之下，操作頻帶為898 到930 MHz，符合台灣(922 到928 MHz)與南美(902 到928 MHz)的RFID 通訊協定規範。此外，天線的最大讀取範圍，在自由空間之下為2.2 公尺，貼附於金屬物體上時為1.2 公尺。以此天線的小型化尺寸與其擁有的效能；相信此天線非常適合應用在貼附於金屬物體上的標籤天線。

This paper proposes a compact RFID tag antenna with size of 36 × 36 × 0.8 mm3 for metallic object applications. The proposed tag antenna, which is fabricated on FR4 substrate, consists of two radiating patches and two meandered lines to reduce the antenna size. Two L-shaped strips is added to increase impedance bandwidth. The two radiating patches are connected to ground plane located on the back side through two shorting pins for increasing immunity from metallic objects. The 10 dB impedance bandwidth from 898 to 930 MHz or 3.5 % of 915 MHz is suitable for Taiwan (922 to 928 MHz) and North America (902 to 928 MHz) RFID applications. The maximum reading ranges about 2.2 m and 1.2 m are tested in free space and mounted on metallic plate, respectively. Equipping with the advantages of dimension and performance, the proposed antenna appears as a promising candidate for RFID application in metallic objects.