Design and simulation of UHF RFID tag antennas and performance evaluation in presence of a metallic surface

Passive UHF RFID system have drawn considerable attention because it can provide a long reading range, high data rate, and small antenna size. However, a passive UHF RFID system has challenges in tagging a metallic object due to effects of conducting materials on the tag antenna performance. This study presents investigation and analysis of effects of a metallic surface on the performance of commonly used label-type dipole tag antenna. The performance is evaluated based on the return loss and change in resonance frequency of the tag antenna. To conduct the performance analysis, a folded dipole and a meandered dipole antenna are proposed for a passive tag. The proposed antennas are designed on low profile antenna which can operate at 866 MHz in the UK and Europe UHF RFID frequency band. The design also takes into account of impedance matching, feeding techniques, size-reduction, and bandwidth of the passive UHF tag antenna. Finally, simulation result shows that when the tag antenna is mounted closer to a metallic surface, the return loss of tag antenna is significantly increased and the resonance frequency is also shifted from the desired frequency.