A Broadband Circularly Polarized Patch Antenna for UHF RFID Applications

A broadband circularly polarized patch antenna is proposed for UHF (840 – 960 MHz) RF Identification (RFID) reader applications. The antenna consists of two oblique thin slot cut square patches and a suspended microstrip line with open-circuited at the end. The feed for the main patch is given by four probes which are sequentially connected to the suspended microstrip feed line. It presents a systematic, empirical design technique to obtain optimum return loss, axial-ratio (AR) and gain. The stacked patches and feed line is surrounded by an air medium, the air medium act as a substrate. The conductivity is high. Parametric studies are carried out to demonstrate the effects of antenna geometry parameters on the performance. The proposed antenna can be a good reader for UHF RFID applications.