CIRCULARLY POLARIZED SLOT ANTENNA DESIGN AND ANALYSIS USING MAGNETIC CURRENT DISTRIBUTION FOR RFID READER APPLICATIONS

摘要

A microstrip-to-slotline transition technique is presented, for the coupling of a circularly polarized circular slot antenna in the ultrahigh frequency band. The fundamental TE11 mode of the circular slot antenna is investigated, using the magnetic current flow in the slot. In the proposed design, circular polarization (CP) is generated using a proper c-strip metal, within the circular slot structure, and connecting a strip metal to the circular slot edge, at -45° to the feeding slotline. The direct slotline feed is coupled to a 50-Ω microstrip line, on the opposite side of the substrate. Simulated and measured results indicate that the proposed structure achieves good CP radiation, in the TE11 mode. The impedance bandwidth and the 3-dB axial-ratio bandwidth for the design are approximately 22.1% and 2.5%, respectively.