Millimeter-Wave Circularly Polarized Tapered-Elliptical Cavity Antenna With Wide Axial-Ratio Beamwidth

A millimeter-wave (mm-wave) circularly polarized (CP) antenna with wide axial-ratio (AR) beamwidth, consisting of L-shaped patches (LSPs) and a tapered elliptical cavity (TEC), is presented. The LSPs are fed by a transverse slot on the top metal surface of a substrate integrated waveguide, to excite two orthogonal modes in the cavity for CP radiation. Experimental results show that the proposed antenna can achieve a bandwidth from 56.9 to 63.4 GHz for both
${\text{axial}}\,{\text{ratio}}\,{\leq}\,3\,{\text{dB}}$
and reflection coefficient
$\vert{{\text{S}}_{11}}\vert{\leq}- 10\,{\text{dB}}$
, and an average broadside gain of 10.4 dBi. In particular, the measured 3-dB AR beamwidths (ARBWs) at 60 GHz in the two orthogonal elevation planes have been extended to 134° in an angular range from
$- 74^\circ $
to 60°. The measured results agree reasonably with the simulated ones.