Signal‐to‐Interference Maximization for Multiple Users Using Two Large Vertically Oriented Metasurfaces

This paper investigates simultaneous multiuser beamforming using two large, vertically oriented metasurfaces. A 2 × 21 × 21 prototype composed of 1‐bit polarization‐independent unit cells is designed, simulated, and experimentally evaluated at 3.7 GHz. Because the base station and users are located within the radiative near‐field region of the large aperture, a distance‐dependent spherical‐wave model is employed instead of a single global Snell law phase gradient. Candidate phase‐state combinations are screened to identify configurations capable of generating two simultaneous beams with a signal‐to‐interference ratio (SIR) above a 3‐dB proof‐of‐concept threshold for the tested angular pairs. Eight phase‐state configurations are experimentally evaluated for angular coverage, while detailed radiation patterns are reported for three representative configurations. The diode‐based unit‐cell response at 3.5 GHz is subsequently incorporated into a multiuser MIMO channel model for a larger 2 × 100 × 100 configuration. The metasurface states and base station precoding vectors are jointly optimized to maximize the minimum user signal‐to‐interference‐plus‐noise ratio (SINR) subject to a total transmit power constraint. Performance is evaluated for different numbers of users, user–cluster radii, and angles between the two metasurface sheets and is compared with that of a planar metasurface having the same number of elements. The proposed configuration is shown to provide an improved minimum SINR under the investigated scenarios.