Additive Manufacturing of Variable Density Lenses for Radio Frequency Communications in the X Band

This paper presents three realizations of a whole set of horn antenna and focusing Gradient Index (GRIN) lens in X band. The set was specifically designed for getting advance of additive manufacturing (AM) of polymers with different materials and techniques. The set has three constructive parts: a horn antenna, a support and a lens. The horn antenna is the active element and must be electrically conductive, it was manufactured with Rigid10K acrylic resin and subsequently metallised using an electroless process. The support needed to be light, robust and electrically transparent, so that Polyamide 11 (PA11) was used. The lens realization intended a dielectric material whose permittivity varies with its density. So that, we measured both dielectric permittivity and loss tangent of different polymeric materials used in AM at 2.45, 6.25 and 24.5 GHz. In addition, stochastic and gyroid mesh structures have been studied. These structures allow printing a volume that presents porosity, enabling control over the material density. Measuring the dielectric characteristics of each material with each density enables establishing graphs that relate them. The sets were then manufactured and their frequency response and radiation diagram were measured, showing excellent results when compared with literature.