A Low-Profile Dual-Circularly Polarized Wide-Axial-Ratio-Beamwidth Slot Patch Antenna With Six-Port Feeding Network

A low-profile dual-circularly polarized (CP) substrate integrated waveguide (SIW)-cavity-backed slot patch antenna with wide axial ratio beamwidths (ARBWs) is proposed. First, two orthogonal slots are etched on a square patch, and a SIW cavity is backed under the patch. Evolution of the SIW-cavity-backed cross-slot antenna is analyzed, and its beamwidths are enhanced by using the E-plane omnidirectional radiation of the slots. In order to broaden the ARBWs, four different SIW-cavity-backed slot patch antennas are also compared. Then, two rat-race couplers and two Wilkinson power dividers are skillfully cascaded together, and a novel six-port feeding network for the dual-CP antenna with high isolations is designed. Finally, a compact dual-CP slot patch antenna with dimensions of 0.53 λ
₀
×0.53 λ
₀
×0.035 λ
₀
is fabricated. Its measured results reveal that the antenna achieves 180°/194° left-handed CP ARBWs and 203°/200° right-handed CP ARBWs in two orthogonal principal planes at the center frequency of 5.2 GHz. Its measured isolation between two ports is greater than 16 dB in the entire bandwidth.