Advanced mmWave Slot-Ring Phased Array Antenna with Polarization Reconfigurability

Polarization reconfiguration in phased array antennas is gaining attention due to its ability to reduce multipath fading, which is crucial in mmWave frequency bands. This paper presents a 2×2 slot-ring phased array antenna designed for mmWave 5G NR (n257 and n258) bands. At these higher frequencies, the small size of the radiation aperture and the narrow spacing between antenna elements present design challenges. To address this, a novel feeding technique is proposed for the antenna array. The antenna comprises six layers-three metal and three dielectric layers. The top-layer microstrip line is connected via a metalized hole with a diameter of 0.2 mm, while the antenna aperture is connected through several ground vias with a diameter of 0.15 mm. This feeding technique provides flexibility for integrating surface-mounted phase shifters, enabling the generation of appropriate phase shifts at each array port, which are necessary for polarization state changes. The antenna operates from 24.5 to 29.5 GHz, achieving a 20% fractional bandwidth and 8.5 dBi gain. Additionally, the array is capable of beam steering within a ±20-degree range without creating any grating lobes.