Full-Wave Synthesis of Modulated Metasurface Antennas

A full-wave synthesis algorithm for modulated metasurface antennas is presented. It is able to provide arbitrary radiation patterns, with any polarization. The algorithm does not use the local periodicity approximation, but is directly based on the electric field integral equation (EFIE). Using Fourier-Bessel basis functions (FBBFs), one can efficiently discretize the surface currents. An inverse problem based on the EFIE is then formulated to derive the surface impedance from the knowledge of the currents. It has been observed that the FBBFs are also more suited than the Zernike basis for the surface impedance discretization. In the case of antenna applications, only the visible part of the surface currents spectrum is known from pattern specifications. This visible part can be combined with the nearfield of the average reactance (SW contribution) to derive the required impedance boundary condition (IBC); this latter is constrained to be anti-Hermitian as required for implementation in the absence of losses. An example of shaped beam design is presented and numerically validated.