Passive Reflective Metasurfaces for Far-Field Beamforming

A single-layer, passive metasurface is designed that controls the amplitude and phase of an aperture using the method of moments and gradient descent optimization. The single layer metasurface is backed by a grounded dielectric substrate. An integral equation is used to model the mutual coupling between surface currents on the homogenized elements, ground plane, and the polarization currents in the dielectric. The integral equation is solved by the method of moments. The metasurface is designed to transform an incident cylindrical wave into a scattered far field beam with a Taylor distribution sidelobe envelope that is scanned to 30° off broadside. Surface waves are introduced through the optimization to obtain a purely reactive and thus passive metasurface. Back-projection of the optimized far field shows both the amplitude and phase are reshaped in the near field.