Wideband Dual Circularly Polarized Substrate-Integrated Cavity Antenna Array for Millimeter-Wave Applications

This letter presents a novel design of a wideband dual circularly polarized (dual CP) substrate-integrated cavity (SIC) antenna array operating in millimeter-wave (MMW) bands. To realize
$\mathrm{T}{{\mathrm{M}}_{211}}$
mode in the SIC and maintain it over a wide spectrum, a circular patch functioning as an electrical wall is loaded in the center of the aperture. The impedance matching can be improved by tuning the dimensions of the slots on the patch. For obtaining wideband dual circular polarizations, a substrate-integrated waveguide (SIW) sequential rotating (SR) network utilizing self-compensating phase shifters is designed. A 2 × 2 array prototype is fabricated and measured, which exhibits a wide impedance bandwidth of 33.4% and a wide axial ratio bandwidth of 33.8% for both polarizations, with a peak gain of 15.6 dBic. The satisfactory electromagnetic characteristic of the proposed antenna makes it suitable for scenarios with wide bandwidth and CP requirements in the millimeter-wave bands.