Compact size annular-ring slot antenna with broad circularly polarized bandwidth

A novel microstrip-line fed circularly polarized (CP) annular-ring slot antenna (ARSA) is investigated. To achieve broad CP bandwidth, a simple method of loading a lightning-shaped slot into the bottom section of the ARSA is proposed. Measured results show that the proposed antenna has wide 10-dB impedance bandwidth of 41.15% (2.20-3.34 GHz), and its corresponding CP bandwidth was approximately 12.94% (2.24-2.55 GHz).