I. Introduction
Fully-dielectric passive terminals have emerged as a interesting alternative for applications in the millimeter range to design high-gain antennas. Furthermore, the evolution of 3D printing technology has enabled a great tool to bring to reality fully-dielectric antennas that were very costly to manufacture with conventional methods in the past. Among the different types of antennas that can be made with only dielectrics, we can highlight dielectric resonator antennas (DRA) [1], [2], reflectarrays (RA) [3], [4], transmitarrays (TA) [5], [6] and lenses [7]–[20].