Wideband Circularly Polarized Antenna With Dual-Mode Operation

Abstract

This letter presents a simple structure of a single-fed broadband circularly polarized (CP) antenna. The antenna consists of four L-shaped strips that rotate in sequence and a double vacant-quarter ring. The double vacant-quarter ring primarily contributes to the wide axial-ratio bandwidth, while the L-shaped strip primarily contributes to the wide axial-ratio beamwidth, with the two modes combined to achieve a wideband CP operation. A prototype antenna was designed, fabricated, and measured. The measured results show that the proposed antenna yields a 10 dB impedance bandwidth of 92.8 $\%$ (4.5–12.3 GHz), a 3 dB axial-ratio bandwidth of 67.5 $\%$ (5.3–10.7 GHz), and a 3 dB gain bandwidth of 62.3 $\%$ (5.3–10.1 GHz) with a peak gain of 12.4 dBic.