Design of Dual-Polarized 3-D Slotline Reflective Metasurface to Improve Millimeter-Wave Coverage

This paper proposes a dual-polarized slotline unit cell for designing reflective metasurface at millimeter waves. The unit cell consists of a three-dimensional (3-D) assembly of PCB layers. The metallic pattern of each PCB layer implements an orthogonal short-circuited slotlines whose length can be varied independently to control the phase in reflection of each incident polarization. The performance has been studied for normal and oblique incidences, showing high levels of co-polar and a linear phase between 37 GHz and 44 GHz. Using the proposed unit cell, a use case is presented where a reflective metasurface is needed to improve the coverage at various positions of an NLOS scenario. Two design options for the phase distribution in the metasurface are discussed. Through their radiation patterns, a comparison is performed. The advantages of using a metasurface with a broad-beam for coverage over a large bandwidth and for different angularly separated positions are demonstrated.