60-GHz aperture-coupled crossed dipoles backed by tapered elliptical cavity for circular polarization with wide axial-ratio beamwidth

A cavity-backed crossed dipoles for circularly polarized (CP) radiation is presented. To improve the 3-dB axial ratio (AR) beamwidth and the broadside gain, a tapered elliptical cavity is introduced. The proposed antenna uses substrate integrated waveguide (SIW) as its feeder. The crossed dipoles is coupled-fed by a transverse slot on the top metallic surface of the SIW. Simulations show that the antenna can present a bandwidth from 56.1 to 62.5 GHz for a reflection coefficient S₁₁ ≤ -10 dB as well as for an axial ratio (AR) =≤3 dB, and a high broadside gain of around 10.4 dBi on average is achieved. Meanwhile, the wide 3-dB AR beamwidth on all azimuth planes can be achieved. This design yields good directional radiation patterns and low fabrication cost.