Broadband planar antenna with circular polarization for RFID readers

A novel planar antenna with broadband and circular polarization characteristics is reported which can be easily fabricated and embedded into RFID readers. Circular polarization radiation is achieved by introducing a cross branch at its corner. And the modified PIFA structure gives the antenna a broadband impedance bandwidth characteristic. For ease in integration with active devices and design facilitation, the radiating element and ground are etched on the same layer of the substrate. Simulated and measured parameters including return loss, axial ratio, and radiation patterns are presented to validate the proposed design.