Numerical Analysis of Sparse-Array Metasurface Antennas Using Gaussian Basis Functions

A sparse-array metasurface (MTS) antenna corresponds to a continuously modulated sheet impedance on top of a grounded slab, periodically repeated over many unit cells (with a few wavelengths cell size). The structure is fed with an array of surface-wave feeds placed at the center of each cell. Such structures may be used to provide continuous beam scanning with a sparse feeding network. Given the larger unit cell and the large number of scan angles to be considered, the computation of the embedded element pattern (EEP) in such array may be very intensive. This letter proposes an accelerated method of moments (MoM) tool allowing the efficient analysis of EEPs of modulated MTSs with periodic boundary conditions. To that aim, the unknown current distribution as well as the sheet impedance are expanded into a set of regularly spaced Gaussian basis functions. The sheet impedance expansion is carried out efficiently using the fast Fourier transform (FFT) algorithm. The adopted Gaussian functions along with the mesh regularity are also employed to dramatically accelerate the MoM matrix computation using FFT-based methods. Numerical results are validated with that from the commercial software HFSS.