A Novel Technique for Broadband Circular Polarized Pifa and Diversity Pifa Systems

In this paper, a novel technique for planar inverted-F antenna (PIFA) with broadband circular polarization and pattern diversity is proposed. A defeated ground structure (DGS) has achieved broadband circular polarized (CP) PIFA by using a square branch at the ground corner with arrow-shaped slot. The pattern diversity PIFA system consists of two CP PIFAs placed symmetrically on the diagonal of DGS. Furthermore, the DGS improves port-to-port isolation by using another smaller square branch at the opposite ground corner. Finally, a prototype is fabricated and measured. The measured results agree well with simulation, and show 10-dB matching bandwidth of 16.3% (825–986 MHz), 3-dB axial ratio (AR) bandwidth of 15.5% (830–982 MHz), and 25-dB isolation bandwidth of 12.4% (848–968 MHz), which shows suitability for radio-frequencyidentification (RFID) application.