Radiation-pattern synthesis with uniform nonlocal metasurfaces

One of the main applications of electromagnetic metasurfaces (MSs) is to tailor spatial field distributions. The radiation pattern of a given source can be desirably modified by reflection from an MS having appropriate spatial modulation of its local macroscopic parameters. At the microscopic level, spatial modulation requires individually engineered meta-atoms at different points. In contrast, the present research demonstrates the opportunity for radiation-pattern engineering in the reflection regime without using any spatial modulation. The approach involves the deliberate tailoring of the surface impedance of a uniform but spatially dispersive (nonlocal) MS composed of identical meta-atoms. A two-dimensional synthesis problem with a magnetic line current source is solved analytically by finding the required form of the surface impedance as a function of the tangential wave vector in both the visible and evanescent parts of the spatial spectrum. To validate this concept, three different pattern shapes are implemented via full-wave numerical simulations by tuning the spatial dispersion in a realistic mushroom-type high-impedance electromagnetic surface with loaded vias. This work extends the synthesis methods and application area of spatially dispersive MSs, demonstrating that they represent a promising platform for future antenna designs.