Tapered All-Dielectric EBGs with 3D Additive Manufacturing for High-Gain Resonant-Cavity Antennas

A resonant-cavity antenna is implemented assembling on an open-ended rectangular waveguide a wideband EBG, designed as a multilayer. Two different implementations of the multilayer are proposed, labelled as Case A and Case B. As to Case A, a high-permittivity layer is embedded between two slabs of low permittivity, whereas, a single layer of low permittivity, surrounded by two high-permittivity slabs is employed in Case B. Successful performances of the broadband behavior are also dependent on the side length of the EBG, that is truncated to small footprints, with an effect of high Side Lobe Level. Therefore, grid layouts with non-uniform air holes are proposed for in-plane realization of the dielectric slabs. Their effect in the EBG superstrate is a non-uniform spatial reflectivity, that reduces the Side Lobe Level keeping a good wideband response. In the EBG manufacturing, both numerically controlled machining techniques and 3D printing have been employed. 3D printing has been used for the low permittivity layers, realized in the PLA filament, allowing more flexibility in the fabrication of the grid slabs to custom layouts. Results of two antenna prototypes assembling the EBGs, with the parameters of Case-A and Case-B and grid layout, to the waveguide source are reported.