Wideband Unidirectional Circularly Polarized Antenna With L-Shaped Radiator Structure

This letter presents a wideband unidirectional circularly polarized (CP) antenna of a simple structure that is suitable for array application. The antenna has twofold bends that form an L-shaped radiator connecting with a probe over a ground plane. Circular polarization is achieved due to traveling wave excitation producing currents with quadrature phase difference on the L-shaped sections. Meanwhile, the ground plane, which is a quarter-wavelength away from the L-shaped radiator, produces a directional radiation pattern. A 2 × 2-element array prototype based on the proposed element was fabricated using two layers of printed circuit board. Measured results of the antenna array exhibit a 3-dB axial-ratio bandwidth of 55% (5.2-9.1 GHz) within its -10-dB impedance bandwidth and a 3-dB right-handed CP gain bandwidth of 49% (5.3-8.8 GHz) with a peak gain of 12.1 dBic.