Low-permittivity EBG materials for antenna superstrates

Suitability of low-permittivity EBGs to implement superstrates of high-gain resonator antennas is explored. Unit cell of the EBG is a square lattice with circular cross-section rods, with band-gap in the X-band. Permittivity of the rods is typical of PLA plastic filament used in 3D printing, with ε_r = 2.76 and tan δ = 0.014. EBG cavity made by two identical mirrors separated by a resonating spacing is used to derive the antenna layout. The primary radiator is a rectangular patch, covered by the EBG mirror at a resonating distance, displaying a good gain enhancement. A further resonator antenna is devised, introducing a non-uniform spacing in the EBG rods along each layer of the superstrate. In this new layout, antenna gain and Side Lobe Level are considerably improved.