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

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 TM11, TM11+, and TM31 mode. An antenna prototype with dimensions of 1.03 lambda(0) x 1.03 lambda(0) x 0.025 lambda(0) (lambda(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 degrees and 220 degrees, respectively.