Design and characterization of a miniaturized patch antenna for passive UHF RFID applications

A low profile RFID (radio frequency identification) tag consisting of a compact microstrip patch antenna for operation at the ultra high frequency (UHF) RFID band, ranging from 860–960 MHz, is proposed. The patch is backed by a mushroom-type Electromagnetic Band Gap (EBG) structure in order to achieve an area reduction of 29.11% in comparison with a conventional patch design. The RFID chip is integrated on the patch via an inset feed line that is positioned in a way to deliver the conjugate impedance matching between the antenna and the chip. The frequency response of the assembled tag was obtained by measuring the reflected power in the ON and OFF states of the chip and subtracting them. The maximum reading range of the tag was found to be around 11 m in two test scenarios of free standing tag and tag attached on a metallic surface.