Metasurface-enabled high-gain circularly polarized antenna array for sensing in dust-laden environments

This work presents a millimetre-wave (mm-wave) antenna array designed for object detection in dust-laden environments. The proposed circularly polarized antenna structure consists of two substrate layers: the upper layer accommodates a 16-element radiating array, while the lower layer incorporates the feeding network. A single-port feeding configuration is employed, where input power is uniformly distributed across the array using a power divider. A square slot is created in the centre of the resonating patch, into which a rotated U-shaped element is introduced, and the corners of the square patch are truncated to achieve circular polarization. The network is realized through multiple junctions that ensure equal power allocation to each radiating element. The coupling mechanism transfers energy efficiently without requiring a direct electrical connection, thereby reducing conductor losses and improving impedance matching at mm-wave frequencies. In addition, a metasurface layer is integrated with the antenna array to suppress mutual coupling between elements and enhance overall gain. The metasurface is created by arranging the proposed unit cells in a periodic manner at a distance of 0.66 mm (0.078 λ_g), and it is configured as a 9 × 9 periodic structures with dimensions matching those of the antenna array, facilitates the propagation of leaky-wave modes between the patch layer and the superstrate. This interaction leads to a notable improvement in the radiation performance of the array. The performance of the proposed mm-wave antenna array is further evaluated in two representative dusty conditions, namely beach sand and gray sand. With the inclusion of the metasurface layer, the array achieves a peak gain of 17.2 dB in free space, which reduces to 14.7 dB under dusty conditions. The antenna maintains an impedance bandwidth spanning 35.5-38.5 GHz in both environments. Owing to its stable radiation characteristics and consistent performance, the proposed design demonstrates strong potential for object detection in dust-laden scenarios.