Current-based design of metasurface antennas with tensorial surface impedance

In this paper, a current-based algorithm for the synthesis of metasurface antennas is adapted to deal with tensorial surface impedance. The surface current is obtained through the minimization of an objective function that takes into account all constraint related to a tensorial impedance. A non-linear conjugate gradient algorithm is applied to minimize an objective function that includes both realizability and far field requirements. The proposed surface impedance distribution is then implemented through a suitable choice of anisotropic unit cells, either through local optimization or from a database of precomputed shapes. Results are shown for the case of a circular metasurface antenna radiating a linearly-polarized broadside beam.