At millimeter and sub-millimeter wavelengths lens-antennas are a valuable alternative to reflect-antennas, since at these working frequencies they come in more compact configurations. As for reflect-antennas, lens-antennas are able to increase the gain of a primary feed antenna positioned in a focal point or, reciprocally, to focus parallel rays, describing an incident plane wave, in a specific point. The law describing the behaviour of reflect- and lens- antennas is the Snell’s law for reflection and refraction, respectively. Moreover, both lens- and reflect-antennas allow the possibility of reshaping the amplitude and phase distribution of the electromagnetic field at the aperture and, thus, the radiated pattern. However, the possibility of manufacturing lenses with a spatially variable refractive index adds more degrees of freedom in the design. In particular, dielectric metamaterials (DMTM) comprised of resonating or sub-resonating elements can form low-loss graded index (GRIN) media. These media can be easily fabricated by 3D printing, enabling a significant cost-reduction without decreasing performances.

     

Fig. 1 – Lens Antenna transforming spherical wave fronts in planar ones (plane wave), allowing the enhancement of radiation parameters (high gain and low Side-Lobe-Level)*