A Dual-Polarized Shared-Aperture Antenna With Conical Radiation Patterns and High Gain for 5G Millimeter-Wave Ceiling Communications

A dual-polarized (DP) antenna with a conical radiation pattern and high gain characteristics is proposed. It is mainly comprised of a horizontally polarized (HP) array, a vertically polarized (VP) element, a fence, and a feeding network. In the HP direction, a rotatable stacked substrate-integrated waveguide (SIW)-to-coaxial-to-SIW transition (SCST) is meticulously designed to yield omnidirectional radiation with low gain variations and low transmission loss. As for the VP direction, two orthogonal substrates that are arranged above the VP radiating element act as a holder to fix the director, resulting in gain enhancement. Here, the VP element is placed in the center of the HP array to share the aperture for size reduction. Moreover, the top-hat-shaped metal fence collaborates with the large-size ground plane to yield dual conical beams with high gain in DP directions. From the measured results, the HP direction has exhibited desirable bandwidth of 11.4% (24.8–27.8 GHz) with a peak gain of 11.6 dBi, and the VP direction has demonstrated wider bandwidth of 13.7% (24.5–28.1 GHz) with a corresponding gain up to 8.1 dBi. Notably, low gain variations of ±0.65 and ±0.8 dBi are also realized for the HP and VP directions, respectively. Therefore, a DP antenna with high-gain conical beams and low gain variations can be obtained for the fifth-generation (5G) millimeter-wave (MMW) ceiling communications.