Current-based design of tensor metasurfaces

In this work, the design of tensor surface impedances is addressed by adapting a current-based technique for the synthesis of metasurface antennas. An objective function that incorporates both far field and realizability constraints associated with a tensor impedance is minimized using a non-linear conjugate gradient algorithm in order to determine the optimal surface current. From it, the corresponding surface impedance is retrieved and implemented through a suitable selection of anisotropic unit cells. The design of a circular metasurface antenna radiating a squinted beam with linear polarization is demonstrated.