Design of Simultaneously Transmitting and Reflecting Bianisotropic Metasurfaces

This article presents a rigorous procedure for the design of space-fed omega-type bianisotropic metasurfaces enabling independent beam-forming in transmission and reflection. It is first demonstrated that, when illuminated by a normally incident plane wave, the metasurface can generate refracted and reflected fields with equal amplitudes and apply independent phase shifts to each. Semi-analytical solutions for the surface parameters are derived. Then, a preliminary design of 32 unitcells is presented, achieving a 2-bit and 3-bit uniform phase quantization in transmission and reflection, respectively. The cells comprise three stacked sheet impedances, spaced by two dielectric slabs. Two metasurfaces are synthesized using the designed cells to individually control the scan angles of the transmitted and reflected beams. The radiation characteristics are numerically evaluated and validate the design.