Metasurface Antennas: Efficiency versus Bandwidth

Two methods are proposed for the accurate and fast analysis of the efficiency of arbitrarily modulated metasurface (MTS) antennas. The surface current on the MTS is expanded into entire-domain basis functions. The first method uses a Fourier-Bessel basis and relies on the Poynting theorem, while the second approach is based on the calculation of the surface-wave residue with a Gaussian-Ring expansion for the current. Both methods allow one to compute the efficiency of MTS antennas in a few minutes, which represents a drastic reduction of the computation time in comparison with any commercial software. The algorithms are then used to analyze the frequency dependence of the efficiency of MTS antennas in two different cases: 1) anisotropic MTS with uniform periodicity, 2) anisotropic MTS with non-uniform periodicity. The latter case corresponds to an active region MTS and provides a larger bandwidth. Validation with commercial software and measurements data is provided.