Monopole Antenna Design for UHF Circularly Polarized RFID Applications

Frequency Identification (RFID) technology is one of the simplest forms of wireless communication systems. It is a unique concept that aims at connecting and identifying tagged assets or objects to RFID readers to collect information. This paper presents the design and implementation of a compact dual-band monopole antenna for RFID applications. The proposed design is a microstrip antenna structure composed of two coupled armed meander-lines having 90 between them to achieve circular polarization. The proposed design is mounted on a 1.6 mm thick FR4-epoxy substrate backed by a partial ground plane with the total area of (58 x 80 mm(2)) to ensure compact size of the design. The designed antenna is fed through a 50-ohm transmission line of length 28.5 mm. The antenna is considered dual bands that resonate at 850 MHz and 1.5 GHz and radiates circularly polarized waves with an axial ratio of 1.4. The simulation results using HFSS software showed promising performance with a bandwidth of 141 MHz at centre frequency 850 MHz and 287 MHz at centre frequency 1.5 GHz, respectively. The S11 parameter shows return loss of -21 dB at 850 MHz band while at the higher frequency band the return loss is much better which was -39 dB. The design provides a perfectly omnidirectional radiation pattern and high radiation efficiency of 93%. Fabrication of the proposed design is done with practical results having a similar trend to the simulated ones to convey good performance of the designed antenna.