Design of Huygens' Cells for Transmit-Reflect-Arrays at 30 GHz

In this paper, it is demonstrated that Huygens' metasurfaces can achieve equi-amplitude reflected and trans-mitted waves and a $360^{\circ}$ phase coverage in transmission and reflection, when illuminated by a normal plane wave. To exploit this property, a procedure for designing unit-cells of transmit-reflect-arrays is presented. First, the optimal surface parameters are analytically determined. N ext, the design at 30 G Hz of four cells with three patterned layers, compatible with printed circuit board technology, is presented. These cells operate with a maximum phase error of a $10^{\circ}$ over a 5 % relative bandwidth at the operating frequency, thus realizing a uniform 2-bit phase quantization in transmission and reflection.