A Low-Profile Broadband Circularly Polarized Patch Antenna With Wide Axial-Ratio Beamwidth

Abstract

A low-profile broadband circularly polarized (CP) patch antenna with wide axial-ratio beamwidth (ARBW) is presented in this letter. The proposed antenna adopts two substrates, one of which is printed with a feeding network composed of the Wilkinson power dividers cascaded with the Schiffman phase shifters to contribute to the broadband CP property. A circular patch with four L-shaped branches as a radiator printed on another substrate is employed to obtain wide ARBWs. A wideband CP radiation is achieved by utilizing TM ₁₁ , TM _11+, and TM ₃₁ mode. An antenna prototype with dimensions of 1.03 λ ₀ × 1.03 λ ₀ × 0.025 λ ₀ (λ ₀ is the wavelength at the center frequency) is fabricated. The measurement results reveal that a wide relative impedance bandwidth of about 55.6% can be achieved in the 3.26–6.04 GHz, and the CP bandwidth is 33.0% (3.85–5.50 GHz). At 5.0 GHz, the 3 dB ARBWs of the xoz plane and the yoz plane are 148° and 220°, respectively.