A Millimeter-wave Wideband Dual Circularly Polarized Antenna

Abstract

A wideband dual circularly polarized antenna working in millimeter-wave band is proposed in this paper. The antenna is composed of three substrate layers, a round radiation patch on the top of the 1 ^st substrate layer, a three-stub 3-dB directional coupler planted between the 2 ^nd and 3 ^rd substrate layers, and two capacitive disks in the air layer between the 1 ^st and 2 ^nd substrate layers connected to the coupler through two probes. The proposed antenna has both wide impedance bandwidth of 25.6-34.1 GHz (30%) and wide 3-dB axial ratio bandwidth of 24.1-34.1 GHz (33.3%) simultaneously, with the isolation between two input ports better than 15 dB within the operating band. The proposed antenna is able to achieve left-hand circular polarization (LHCP) or right-hand (RHCP) in a wide bandwidth of about 26-34 GHz (26.7%) and can be used as the units for an antenna array.