A novel antenna design for UHF RFID tag on metallic objects

Abstract

A novel microstrip patch RFID tag antenna with wideband characteristic is pro-posed. It has less sensitive characteristic against size of metallic object, wide impedance band-width and long reading distance. The antenna consists of shorting strip, open stubs, tag IC and radiating patch having I-shaped slits. The proposed antenna is located on the finite ground plane and is constructed on FR4 substrate (εr = 4:4; tan α = 0:02). Overall dimension of the antenna is 100mm×26mm×6 mm. The tag IC has input impedance of 43-j800- at 915 MHz. The -3 dB impedance bandwidth is from 696MHz to 978 MHz. When the antenna is placed in free space and mounted on 200mm×200 mm, 400mm×400mm and 600mm×600mm metallic plates, the peak gains are 4.7 dBi, 2.4 dBi, 2.3 dBi and 1.7 dBi, respectively. The radiation efficiencies are 69%, 40%, 38% and 38%, respectively, and the maximum reading distances are 5.13 m, 6 m, 5.75m and 4.75 m, respectively.