Sparse-Array Metasurface for Beam Scanning

Beam scanning is traditionally achieved with phased arrays, whose application often faces the challenge of high density of antennas and associated electronic components. Metasurfaces (MTS) allow the tailoring of pencil and shaped beams with a low-profile radiator, but scanning with MTSs remains difficult, e.g., reconfiguring each subwavelength patch of the MTS defeats the initial purpose of simplicity. This communication proposes a novel design approach to beam scanning with surface-wave (SW)-based MTS antennas. Both the feeding and the MTS are made periodic at a scale of a few wavelengths. To avoid grating lobes, the unit cell of the periodic MTS is designed, such that the embedded element pattern (EEP) has a nearly rectangular shape with proper width. The sparsity of the feeding system enables a drastic reduction of the density of electronics at the expense of a smaller field of view. The resulting antenna, demonstrated here in 2-D (uniform antenna versus one space coordinate), has low profile (including the feeder) and enables continuous beam scanning with high gain. With a spacing of two wavelengths between feeds, the scan range is +/-10 degrees. The MTS is first designed at the surface impedance level, and the resulting structure has then been validated through full-wave simulation of a MTS implemented with subwavelength patches. Numerical analysis versus frequency indicates a pattern bandwidth of the order of 5%.