Design of an embedded-feed type microstrip patch antenna for UHF radio frequency identification tag on metallic objects

The design of an embedded-feed type microstrip patch antenna, which can be mounted on metallic objects for radio frequency identification (RFID), is presented. The structure consists of an embedded feed with T-matching networks and a symmetrical radiating rectangular loop patch. The proposed antenna has no shorting plate or via hole and consists of a very thin structure of microstrip patch antenna compared with the conventional metallic tag antennas. The impedance of the presented antenna can be changed to match the impedance values of tag chips by using the T-matching network. The gain radiation pattern performance of the proposed antenna on metal surface is improved so that it can be used for a tag antenna mountable on metal surface in ultra-high frequency (UHF) band RFID applications. The antenna is analysed by full wave simulations, and experimental results are provided for the manufactured prototype.