UHF RFID Tag Antenna Using Meander Patch for Metallic Object

The use of radio frequency identification (RFID) system has increased noticeably in recent years. The tag antenna has been particularly influential in the performance of RFID system. Many applications require tag antennas to be of low profile mounted on electrically metallic objects. Several designs have been developed for RFID patch-type antennas or planar inverted-F antennas (PIFAs) mountable on metallic objects [1][4]. Although most of these reported antennas can give the required reading-range performance, they may suffer from inconvenient mounting on metallic object because of their high profile. However, it is inherent for a patch-type antenna that lowering the antenna profile would degrade its radiation efficiency and antenna gain. Hence, an effort is being made to further improve the antenna gain of the low-profile patch antenna needed to provide the applicable reading range in a RFID application. In this paper, we propose novel designs of low-profile meandered patch antennas suitable for UHF band RFID tags mountable on metallic objects. In this design, a long patch is bent to several half-wavelength radiating elements, which makes the surface currents of all radiating elements in phase and thus achieves an enhanced gain. Furthermore, it is shown that higher gain is obtained by an increased number of radiating elements. The details of the proposed designs and obtained experimental results are presented and discussed.