Effect of Phase Gradient and Angle of Incidence Reversal in Phase Gradient Surfaces for IRS Applications

A passive phase gradient surface (PGS) employing a linear reflection phase profile on the surface with unit cells having high reflectivity is being studied. For a fixed angle of incidence of 20°, reversing the direction of phase gradient from positive to negative, the anomalous reflection changes from 42.48° to 0.5°. With consecutive change in positive incident angles, the passive PGS can enable the reflected wave to steer from 19.47° to 90° and $-19.47^{\circ}$ to 41.81° for positive and negative phase gradients respectively. Thus, for all positive incident angles, the PGS can effectively cover all positive anomalous reflection angles by simply changing the phase gradient to either positive or negative. The effect of incident angle reversal is also demonstrated here, where the mirror image of the propagation direction and the flipping of the mode numbers are observed, along with a reversal in the modes themselves. The PGS can be potentially useful to achieve communication by alternate switching of the reflected wave towards two targets.