A Novel Wideband Dual-Circularly Polarized Array Antenna for Millimeter-Wave Communication

In this letter, a novel millimeter-wave (mm-wave) dual-circularly polarized (dual-CP) array antenna based on a gap waveguide is proposed. By cascading septum polarizer and turnstile orthomode transducer (OMT), the simple feeding network is first proposed to achieve dual-circular polarization conditions. The +/- 90 degrees phase differences are generated between the TE10 and TE01 modes by the septum polarizer, and the turnstile OMT is employed to separate the two orthogonal modes into four mutually orthogonal subarrays, respectively. For validation, an 8 x 8 dual-linearly polarized (dual-LP) array is introduced to realize a dual-CP array antenna and a prototype of the dual-CP array antenna has been fabricated and measured. The measurement results show that the overlap bandwidth for impedance bandwidth |S-11| < -14 dB, coupling coefficient |S-21| < -13.5 dB, and axial-ratio (AR) bandwidth < 3 dB are 18% from 92 GHz to 110 GHz, and maximum measured gain value is 23.7 dBic with radiation efficiency up to 82.64%. The proposed dual-CP array antenna would be a promising candidate for millimeter-wave communication systems.